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Type 2 diabetes (T2D) is characterized by muscle metabolic dysfunction that exercise can minimize, but some patients do not respond to an exercise intervention. Myokine secretion is intrinsically altered in patients with T2D, but the role of myokines in exercise resistance in this patient population has never been studied. We sought to determine if changes in myokine secretion were linked to the response to an exercise intervention in patients with T2D. The participants followed a 10-week aerobic exercise training intervention, and patients with T2D were grouped based on muscle mitochondrial function improvement (responders versus non-responders). We measured myokines in serum and cell-culture medium of myotubes derived from participants pre- and post-intervention and in response to an in vitro model of muscle contraction. We also quantified the expression of genes related to inflammation in the myotubes pre- and post-intervention. No significant differences were detected depending on T2D status or response to exercise in the biological markers measured, with the exception of modest differences in expression patterns for certain myokines (IL-1β, IL-8, IL-10, and IL-15). Further investigation into the molecular mechanisms involving myokines may explain exercise resistance with T2D; however, the role in metabolic adaptations to exercise in T2D requires further investigation.

Glucagon-like peptide-1 receptor analogs (GLP-1 RAs) have been an innovative and instrumental drug class in the management of both type 2 diabetes and obesity. Tirzepatide is a novel agent that acts as an agonist for both GLP-1 receptors and gastric inhibitory polypeptide (GIP) receptors, another incretin that lowers glucose and appetite. Although previous studies showed a lack of therapeutic benefit for GIP agonists, current studies show that the glucose lowering and weight loss effects of tirzepatide are at least as effective as GLP-1 RAs with a similar adverse effect profile. Some studies, though not conclusive, predict that tirzepatide may in fact be more potent than GLP-1 RAs at reducing weight. A thorough review of the studies that led to tirzepatide's approval allows for comparisons between tirzepatide and GLP-1 RAs; it also allows for predictions of tirzepatide's eventual place in therapy - an agent used preferentially over GLP-1 RAs in patients with or without diabetes desiring to lose weight., (© 2023. The Author(s).)

Insulin resistance and blunted mitochondrial capacity in skeletal muscle are often synonymous, however, this association remains controversial. The aim of this study was to perform an in-depth multifactorial comparison of skeletal muscle mitochondrial capacity between individuals who were lean and active (Active, n = 9), individuals with obesity (Obese, n = 9), and individuals with obesity, insulin resistance, and type 2 diabetes (T2D, n = 22). Mitochondrial capacity was assessed by ex vivo mitochondrial respiration with fatty-acid and glycolytic-supported protocols adjusted for mitochondrial content (mtDNA and citrate synthase activity). Supercomplex assembly was measured by Blue Native (BN)-PAGE and immunoblot. Tricarboxylic (TCA) cycle intermediates were assessed with targeted metabolomics. Exploratory transcriptomics and DNA methylation analyses were performed to uncover molecular differences affecting mitochondrial function among the three groups. We reveal no discernable differences in skeletal muscle mitochondrial content, mitochondrial capacity, supercomplex assembly, TCA cycle intermediates, and mitochondrial molecular profiles between obese individuals with and without T2D that had comparable levels of confounding factors (body mass index, age, and aerobic capacity). We highlight that lean, active individuals have greater mitochondrial content, mitochondrial capacity, supercomplex assembly, and TCA cycle intermediates. These phenotypical changes are reflected at the level of DNA methylation and gene transcription. The collective observation of comparable muscle mitochondrial capacity in individuals with obesity and T2D (vs. individuals without T2D) underscores a dissociation from skeletal muscle insulin resistance. Clinical trial number: NCT01911104. NEW & NOTEWORTHY Whether impaired mitochondrial capacity contributes to skeletal muscle insulin resistance is debated. Our multifactorial analysis shows no differences in skeletal muscle mitochondrial content, mitochondrial capacity, and mitochondrial molecular profiles between obese individuals with and without T2D that had comparable levels of confounding factors (BMI, age, aerobic capacity). We highlight that lean, active individuals have enhanced skeletal muscle mitochondrial capacity that is also reflected at the level of DNA methylation and gene transcription.

Aims/hypothesis: The aim of this study was to assess metabolic flexibility (MetFlex) in participants with type 2 diabetes within the physiologically relevant conditions of sleeping, the post-absorptive (fasting) state and during meals using 24 h whole-room indirect calorimetry (WRIC) and to determine the impact of aerobic training on these novel features of MetFlex., Methods: Normal-weight, active healthy individuals (active; n = 9), obese individuals without type 2 diabetes (ND; n = 9) and obese individuals with type 2 diabetes (n = 23) completed baseline metabolic assessments. The type 2 diabetes group underwent a 10 week supervised aerobic training intervention and repeated the metabolic assessments. MetFlex was assessed by indirect calorimetry in response to insulin infusion and during a 24 h period in a whole-room indirect calorimeter. Indices of MetFlex evaluated by WRIC included mean RQ and RQ kinetic responses after ingesting a standard high-carbohydrate breakfast (RQ BF ) and sleep RQ (RQ sleep ). Muscle mitochondrial energetics were assessed in the vastus lateralis muscle in vivo and ex vivo using 31 P-magnetic resonance spectroscopy and high-resolution respirometry, respectively., Results: The three groups had significantly different RQ sleep values (active 0.823 ± 0.04, ND 0.860 ± 0.01, type 2 diabetes 0.842 ± 0.03; p < 0.05). The active group had significantly faster RQ BF and more stable RQ sleep responses than the ND and type 2 diabetes groups, as demonstrated by steeper and flatter slopes, respectively. Following the training intervention, the type 2 diabetes group displayed significantly increased RQ BF slope. Several indices of RQ kinetics had significant associations with in vivo and ex vivo muscle mitochondrial capacities., Conclusions/interpretation: Twenty-four hour WRIC revealed that physiological RQ responses exemplify differences in MetFlex across a spectrum of metabolic health and correlated with skeletal muscle mitochondrial energetics. Defects in certain features of MetFlex were improved with aerobic training, emphasising the need to assess multiple aspects of MetFlex and disentangle insulin resistance from MetFlex in type 2 diabetes., Trial Registration: ClinicalTrials.gov NCT01911104., Funding: This study was funded by the ADA (grant no. 7-13-JF-53)., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The effects of exercise training on the skeletal muscle (SKM) lipidome and mitochondrial function have not been thoroughly explored in individuals with Type 2 diabetes (T2D). We hypothesize that 10 wk of supervised endurance training improves SKM mitochondrial function and insulin sensitivity that are related to alterations in lipid signatures within SKM of T2D (males n = 8). We employed integrated multi-omics data analyses including ex vivo lipidomics (MS/MS-shotgun) and transcriptomics (RNA-Seq). From biopsies of SKM, tissue and primary myotubes mitochondrial respiration were quantified by high-resolution respirometry. We also performed hyperinsulinemic-euglycemic clamps and blood draws before and after the training. The lipidomics analysis revealed that endurance training (>95% compliance) increased monolysocardiolipin by 68.2% ( P ≤ 0.03), a putative marker of mitochondrial remodeling, and reduced total sphingomyelin by 44.8% ( P ≤ 0.05) and phosphatidylserine by 39.7% ( P ≤ 0.04) and tended to reduce ceramide lipid content by 19.8%. Endurance training also improved intrinsic mitochondrial respiration in SKM of T2D without alterations in mitochondrial DNA copy number or cardiolipin content. RNA-Seq revealed 71 transcripts in SKM of T2D that were differentially regulated. Insulin sensitivity was unaffected, and HbA1c levels moderately increased by 7.3% despite an improvement in cardiorespiratory fitness (V̇o 2peak ) following the training intervention. In summary, endurance training improves intrinsic and cell-autonomous SKM mitochondrial function and modifies lipid composition in men with T2D independently of alterations in insulin sensitivity and glycemic control.

Background: There is a direct relationship between bodyweight and risk of diabetes. Lorcaserin, a selective serotonin 2C receptor agonist that suppresses appetite, has been shown to facilitate sustained weight loss in obese or overweight patients. We aimed to evaluate the long-term effects of lorcaserin on diabetes prevention and remission., Methods: In this randomised, double-blind, placebo-controlled trial done in eight countries, we recruited overweight or obese patients (body-mass index ≥27 kg/m 2 ) with or at high risk for atherosclerotic vascular disease. Eligible patients were aged 40 years or older; patients at high risk for atherosclerotic vascular disease had to be aged 50 years or older with diabetes and at least one other risk factor. Patients were randomly assigned to receive either lorcaserin (10 mg twice daily) or matching placebo. Additionally, all patients had access to a standardised weight management programme based on lifestyle modification. The prespecified primary metabolic efficacy endpoint of time to incident diabetes was assessed in patients with prediabetes at baseline. The prespecified secondary outcomes for efficacy were incident diabetes in all patients without diabetes, achievement of normoglycaemia in patients with prediabetes, and change in glycated haemoglobin (HbA 1c ) in patients with diabetes. Hypoglycaemia was a prespecified safety outcome. Analysis was by intention to treat, using Cox proportional hazard models for time-to-event analyses. This trial is registered with ClinicalTrials.gov, number NCT02019264., Findings: Between Feb 7, 2014, and Nov 20, 2015, 12 000 patients were randomly assigned to lorcaserin or placebo (6000 patients in each group) and followed up for a median of 3·3 years (IQR 3·0-3·5). At baseline, 6816 patients (56·8%) had diabetes, 3991 (33·3%) prediabetes, and 1193 (9·9%) normoglycaemia. At 1 year, patients treated with lorcaserin had a net weight loss beyond placebo of 2·6 kg (95% CI 2·3-2·9) for those with diabetes, 2·8 kg (2·5-3·2) for those with prediabetes, and 3·3 kg (2·6-4·0) for those with normoglycaemia (p<0·0001 for all analyses). Lorcaserin reduced the risk of incident diabetes by 19% in patients with prediabetes (172 [8·5%] of 2015 vs 204 [10·3%] of 1976; hazard ratio 0·81, 95% CI 0·66-0·99; p=0·038) and by 23% in patients without diabetes (174 [6·7%] of 2615 vs 215 [8·4%] of 2569; 0·77, 0·63-0·94; p=0·012). Lorcaserin resulted in a non-significant increase in the rate of achievement of normoglycaemia in patients with prediabetes (185 [9·2%] vs 151 [7·6%]; 1·20, 0·97-1·49; p=0·093). In patients with diabetes, lorcaserin resulted in a reduction of 0·33% (95% CI 0·29-0·38; p<0·0001) in HbA 1c compared with placebo at 1 year from a mean baseline of 53 mmol/mol (7·0%). In patients with diabetes at baseline, severe hypoglycaemia with serious complications was rare, but more common with lorcaserin (12 [0·4%] vs four [0·1%] events; p=0·054)., Interpretation: Lorcaserin decreases risk for incident diabetes, induces remission of hyperglycaemia, and reduces the risk of microvascular complications in obese and overweight patients, supporting the role of lorcaserin as an adjunct to lifestyle modification for chronic management of weight and metabolic health., Funding: Eisai., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: Some individuals with type 2 diabetes do not reap metabolic benefits from exercise training, yet the underlying mechanisms of training response variation are largely unexplored. We classified individuals with type 2 diabetes ( n = 17) as nonresponders ( n = 6) or responders ( n = 11) based on changes in phosphocreatine (PCr) recovery rate after 10 weeks of aerobic training. We aimed to determine whether the training response variation in PCr recovery rate was marked by distinct epigenomic profiles in muscle prior to training., Research Design and Methods: PCr recovery rate as an indicator of in vivo muscle mitochondrial function in vastus lateralis ( 31 P-magnetic resonance spectroscopy), insulin sensitivity (M-value; hyperinsulinemic-euglycemic clamp), aerobic capacity ( V o 2peak ), and blood profiles were determined pretraining and post-training. Muscle biopsies were performed pretraining in vastus lateralis for the isolation of primary skeletal muscle cells (HSkMCs) and assessments of global DNA methylation and RNA sequencing in muscle tissue and HSkMCs., Results: By design, nonresponders decreased and responders increased PCr recovery rate with training. In nonresponders, insulin sensitivity did not improve and glycemic control (HbA 1c ) worsened. In responders, insulin sensitivity improved. V o 2peak improved by ∼12% in both groups. Nonresponders and responders were distinguished by distinct pretraining molecular (DNA methylation, RNA expression) patterns in muscle tissue, as well as in HSkMCs. Enrichment analyses identified elevations in glutathione regulation, insulin signaling, and mitochondrial metabolism in nonresponders pretraining, which was reflected in vivo by higher pretraining PCr recovery rate and insulin sensitivity in these same individuals., Conclusions: A training response variation for clinical risk factors in individuals with type 2 diabetes is reflected by distinct basal myocellular epigenomic profiles in muscle tissue, some of which are maintained in HSkMCs, suggesting a cell-autonomous underpinning. Our data provide new evidence to potentially shift the diabetes treatment paradigm for individuals who do not benefit from training, such that supplemental treatment can be designed., (© 2018 by the American Diabetes Association.)

Aims: Pioglitazone (Pio) is known to improve insulin sensitivity in skeletal muscle. However, the role of Pio in skeletal muscle lipid metabolism and skeletal muscle oxidative capacity is not clear. The aim of this study was to determine the effects of chronic Pio treatment on skeletal muscle mitochondrial activity in individuals with type 2 diabetes (T2D)., Materials and Methods: Twenty-four participants with T2D (13M/11F 53.38±2.1years; BMI 36.47±1.1kg/m 2 ) were randomized to either a placebo (CON, n=8) or a pioglitazone (PIO, n=16) group. Following 12weeks of treatment, we measured insulin sensitivity by hyperinsulinemic-euglycemic clamp (clamp), metabolic flexibility by calculating the change in respiratory quotient (ΔRQ) during the steady state of the clamp, intra- and extra-myocellular lipid content (IMCL and EMCL, respectively) by 1 H magnetic resonance spectroscopy ( 1 H-MRS) and muscle maximal ATP synthetic capacity (ATPmax) by 31 P-MRS., Results: Following 12weeks of PIO treatment, insulin sensitivity (p<0.0005 vs. baseline) and metabolic flexibility (p<0.05 vs. CON) significantly increased. PIO treatment significantly decreased IMCL content and increased EMCL content in gastrocnemius, soleus and tibialis anterior muscles. ATPmax was unaffected by PIO treatment., Conclusions: These results suggest that 12weeks of pioglitazone treatment improves insulin sensitivity, metabolic flexibility and myocellular lipid distribution without any effect on maximal ATP synthetic capacity in skeletal muscle. Consequently, pioglitazone-induced enhancements in insulin responsiveness and fuel utilization are independent of mitochondrial function., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: To evaluate the effects of lorcaserin in patients with pre-existing Food and Drug Administration (FDA)-defined valvulopathy., Methods: This is a pooled, post hoc analysis of three Phase 3 studies. BLOOM and BLOSSOM patients were 18 to 65 years of age without diabetes and with a body mass index (BMI) of 27 to 29.9 kg/m 2 and ≥1 weight-related comorbidity or a BMI of 30 to 45 kg/m 2 . BLOOM-DM patients had a BMI of 27 to 45 kg/m 2 and type 2 diabetes. Patients were treated with placebo, lorcaserin 10 mg once daily, or lorcaserin 10 mg twice daily. Serial echocardiographs were obtained at baseline and every 6 months., Results: Included patients (N = 169) had FDA-defined valvulopathy at baseline and a week 52 echocardiogram. At week 52, 35.5% and 52.7% of patients experienced changes from baseline in aortic and mitral regurgitation, respectively. Numerically greater proportions of patients taking lorcaserin versus placebo had decreases in aortic (33.0% vs. 28.3%) or mitral (41.3% vs. 36.7%) regurgitation. Fewer patients taking lorcaserin versus placebo had increases in aortic (2.8% vs. 6.7%) or mitral (8.3% vs. 21.7%) regurgitation. No adverse event-related discontinuation was due to a valve problem., Conclusions: These data suggest that lorcaserin does not adversely affect valvular disease in patients with pre-existing FDA-defined valvulopathy., (© 2016 The Authors. Obesity published by Wiley Periodicals, Inc. on behalf of The Obesity Society (TOS).)

Circulating natriuretic peptide (NP) levels are reduced in obesity and predict the risk of type 2 diabetes (T2D). Since skeletal muscle was recently shown as a key target tissue of NP, we aimed to investigate muscle NP receptor (NPR) expression in the context of obesity and T2D. Muscle NPRA correlated positively with whole-body insulin sensitivity in humans and was strikingly downregulated in obese subjects and recovered in response to diet-induced weight loss. In addition, muscle NP clearance receptor (NPRC) increased in individuals with impaired glucose tolerance and T2D. Similar results were found in obese diabetic mice. Although no acute effect of brain NP (BNP) on insulin sensitivity was observed in lean mice, chronic BNP infusion improved blood glucose control and insulin sensitivity in skeletal muscle of obese and diabetic mice. This occurred in parallel with a reduced lipotoxic pressure in skeletal muscle due to an upregulation of lipid oxidative capacity. In addition, chronic NP treatment in human primary myotubes increased lipid oxidation in a PGC1α-dependent manner and reduced palmitate-induced lipotoxicity. Collectively, our data show that activation of NPRA signaling in skeletal muscle is important for the maintenance of long-term insulin sensitivity and has the potential to treat obesity-related metabolic disorders., (© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Objective: The purpose of the study was to determine the effects of passaging on retention of donor phenotypic characteristics in primary human myotubes., Methods: Primary muscle cultures and serial passaged myotubes from physically active, sedentary lean, and individuals with type 2 diabetes were established. Maximal ATP synthesis capacity (ATPmax) and resting ATP flux (ATPase) in vivo were measured by (31) P magnetic resonance spectroscopy, type-I fibers and intramyocelluar lipid (IMCL) in vastus lateralis tissue were determined using immunohistochemistry techniques, and oxidative phosphorylation complexes (OXPHOS) were measured by Western immunoblotting. Similar in vitro measures for lipid and type-I fibers were made in myotubes, along with mitochondrial content measured by MitoTracker., Results: Passage 4 and 5 measures for myotubes correlated positively with in vivo measurements for percent type-I fibers (P4: R(2)  = 0.39, p = 0.02; P5: R(2)  = 0.48, p = 0.01), ATPmax (P4: R(2)  = 0.30, p = 0.03; P5: R(2)  = 0.22, p = 0.05), and OXPHOS (P4: R(2)  = 0.44, p = 0.04; P5: R(2)  = 0.59, p = 0.006). No correlations were observed for IMCL. However, passage 4 measures for myotubes correlated with passage 5 measures for percent type-I fibers (R(2)  = 0.49, p = 0.01), IMCL (R(2)  = 0.80, p < 0.001), and mitochondrial content (R(2)  = 0.26, p = 0.03)., Conclusions: Myotubes through the first two passages following immunopurification (referred to as passage 4 and 5) reflect the mitochondrial and type-I fiber content in vivo phenotype of the donor., (© 2015 The Obesity Society.)

Context: The role of perilipin 3 (PLIN3) on lipid oxidation is not fully understood., Objective: We aimed to 1) determine whether skeletal muscle PLIN3 protein content is associated with lipid oxidation in humans, 2) understand the role of PLIN3 in lipid oxidation by knocking down PLIN3 protein content in primary human myotubes, and 3) compare PLIN3 content and its role in lipid oxidation in human primary skeletal muscle cultures established from sedentary, healthy lean (leans), type 2 diabetic (T2D), and physically active donors., Design, Participants, and Intervention: This was a clinical investigation of 29 healthy, normoglycemic males and a cross-sectional study using primary human myotubes from five leans, four T2D, and four active donors. Energy expenditure, whole-body lipid oxidation, PLIN3 protein content in skeletal muscle tissue, and ex vivo muscle palmitate oxidation were measured. Myotubes underwent lipolytic stimulation (palmitate, forskolin, inomycin [PFI] cocktail), treatment with brefeldin A (BFA), and knockdown of PLIN3 using siRNA., Setting: Experiments were performed in a Biomedical Research Institute., Main Outcome Measures: Protein content, 24-hour respiratory quotient (RQ), and ex vivo/in vitro lipid oxidations., Results: PLIN3 protein content was associated with 24-h RQ (r = -0.44; P = .02) and skeletal muscle-specific ex vivo palmitate oxidation (r = 0.61; P = .02). PLIN3 knockdown showed drastic reductions in lipid oxidation in myotubes from leans. Lipolytic stimulation increased PLIN3 protein in cells from leans over T2Ds with little expression in active participants. Furthermore, treatment with BFA, known to inhibit coatomers that associate with PLIN3, reduced lipid oxidation in cells from lean and T2D, but not in active participants., Conclusions: Differential expression of PLIN3 and BFA sensitivity may explain differential lipid oxidation efficiency in skeletal muscle among these cohorts.

Aims/hypothesis: Exercise benefits most, but not all, individuals with type 2 diabetes mellitus (T2DM). The aim of this study was to determine whether a proportion of individuals with T2DM would fail to demonstrate exercise-induced metabolic improvements. We hypothesized that this lack of response would be related to their skeletal muscle transcriptional profile., Methods: 42 participants with T2DM from the previously reported HART-D study underwent a 9-month supervised exercise intervention. We performed a principal components analysis to distinguish Responders from Non-Responders (n=9 each) based on: decreases in (1) HbA1c, (2) %fat (3) BMI and (4) increase in skeletal muscle mtDNA. mRNA expression patterns in muscle tissue at baseline were assessed by microarray and qRT-PCR analysis in both groups., Results: Of 186 genes identified by microarray analysis, 70% were up-regulated in Responders and down-regulated in Non-Responders. Several genes involved in substrate metabolism and mitochondrial biogenesis were significantly different (fold-change>1.5, p<0.05) between the groups at baseline, indicating a blunted oxidative capacity at baseline in Non-Responders., Conclusions/interpretations: These data suggest that a unique baseline expression pattern of genes involved in muscle fuel metabolism may predict an individual's lack of exercise response in metabolic outcomes, thus allowing exercise interventions to be targeted to these individuals and aid in the identification of novel approaches to treat Non-Responders in the future., Competing Interests: There are no conflicts of interest., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: To identify an early treatment milestone that optimizes sensitivity and specificity for predicting ≥5% weight loss at Week (W) 52 in patients with and without type 2 diabetes on lorcaserin or placebo., Methods: Post hoc area under the curve for receiver operating characteristic analyses of data from three phase 3 trials comparing lifestyle modification+placebo with lifestyle modification+lorcaserin. A total of 6897 patients (18-65 years; BMI, 30-45 or 27-29.9 kg/m(2) with ≥1 comorbidity) were randomized to placebo or lorcaserin 10 mg bid. Changes (baseline to W52) in cardiometabolic parameters were assessed., Results: Response (≥5% weight loss from baseline) at W12 was a strong predictor of W52 response. Lorcaserin patients with a W12 response achieved mean W52 weight losses of 10.6 kg (without diabetes) and 9.3 kg (with diabetes). Proportions achieving ≥5% and ≥10% weight loss at W52 were 85.5% and 49.8% (without diabetes), and 70.5% and 35.9% (with diabetes). Lorcaserin patients who did not achieve a W12 response lost 3.2 kg (without diabetes) and 2.8 kg (with diabetes) at W52. Responders had greater improvements in cardiometabolic risk factors than the modified intent-to-treat (MITT) population, consistent with greater weight loss., Conclusions: ≥5% weight loss by W12 predicts robust response to lorcaserin at 1 year., (Copyright © 2014 The Authors Obesity published by Wiley Periodicals, Inc. on behalf of The Obesity Society (TOS).)

Objective: This study investigated the relationship between in vitro lipid content in myotubes and in vivo whole body phenotypes of the donors such as insulin sensitivity, intramyocellular lipids (IMCL), physical activity, and oxidative capacity., Design and Methods: Six physically active donors were compared to six sedentary lean and six T2DM. Lipid content was measured in tissues and myotubes by immunohistochemistry. Ceramides, triacylglycerols, and diacylglycerols (DAGs) were measured by LC-MS-MS and GC-FID. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp (80 mU min⁻¹ m⁻²), maximal mitochondrial capacity (ATPmax) by ³¹P-MRS, physical fitness by VO₂max and physical activity level (PAL) by accelerometers., Results: Myotubes cultured from physically active donors had higher lipid content (0.047 ± 0.003 vs. 0.032 ± 0.001 and 0.033 ± 0.001AU; P < 0.001) than myotubes from lean and T2DM donors. Lipid content in myotubes was not associated with IMCL in muscle tissue but importantly, correlated with in vivo measures of ATPmax (r = 0.74; P < 0.001), insulin sensitivity (r = 0.54; P < 0.05), type-I fibers (r = 0.50; P < 0.05), and PAL (r = 0.92; P < 0.0001). DAGs and ceramides in myotubes were inversely associated with insulin sensitivity (r = -0.55, r = -0.73; P < 0.05) and ATPmax (r = -0.74, r = -0.85; P < 0.01)., Conclusions: These results indicate that cultured human myotubes can be used in mechanistic studies to study the in vitro impact of interventions on phenotypes such as mitochondrial capacity, insulin sensitivity, and physical activity., (Copyright © 2013 The Obesity Society.)

Aims: This study examined the effects of pioglitazone on body weight and bone mineral density (BMD) prospectively in patients with impaired glucose tolerance as pioglitazone (TZD) increases body weight and body fat in diabetic patients and increases the risk of bone fractures., Methods: A total of 71 men and 163 women aged 49.3 (10.7) years [mean (s.d.)]; body mass index (BMI), 34.5 (5.9) kg/m(2) were recruited at five sites for measurements of body composition by dual energy X-ray absorptiometry at baseline and at conversion to diabetes or study end, if they had not converted., Results: Mean follow-up was 33.6 months in the pioglitazone group and 32.1 months in the placebo group. Body weight increased 4.63 ± 0.60 (m ± s.e.) kg in the pioglitazone group compared to 0.98 ± 0.62 kg in the PIO group (p < 0.0001). Body fat rose 4.89 ± 0.42 kg in the pioglitazone group compared to 1.41 ± 0.44 kg, (p < 0.0001) in placebo-treated subjects. The increase in fat was greater in legs and trunk than in the arms. BMD was higher in all regions in men and significantly so in most. PIO decreased BMD significantly in the pelvis in men and women, decreased BMD in the thoracic spine and ribs of women and the lumbar spine and legs of men. Bone mineral content also decreased significantly in arms, legs, trunk and in the total body., Conclusions: Pioglitazone increased peripheral fat more than truncal fat and decreased BMD in several regions of the body., (© 2013 John Wiley & Sons Ltd.)

Aims: To assess the determinants of exercise training-induced improvements in glucose control (HbA1C) including changes in serum total adiponectin and FFA concentrations, and skeletal muscle peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) protein content., Methods: A sub-cohort (n = 35; 48% men; 74% Caucasian) from the HART-D study undertaking muscle biopsies before and after 9 months of aerobic (AT), resistance (RT), or combination training (ATRT)., Results: Changes in HbA1C were associated with changes in adiponectin (r = -0.45, P = 0.007). Participants diagnosed with type 2 diabetes for a longer duration had the largest increase in PGC-1α (r = 0.44, P = 0.008). Statistical modeling examining changes in HbA1C suggested that male sex (P = 0.05), non-Caucasian ethnicity (P = 0.02), duration of type 2 diabetes (r = 0.40; P<0.002) and changes in FFA (r = 0.36; P<0.004), adiponectin (r = -0.26; P<0.03), and PGC-1α (r = -0.28; P = 0.02) explain ∼65% of the variability in the changes in HbA1C., Conclusions: Decreases in HbA1C after 9 months of exercise were associated with shorter duration of diabetes, lowering of serum FFA concentrations, increasing serum adiponectin concentrations and increasing skeletal muscle PGC-1α protein expression., Trial Registration: ClinicalTrials.gov NCT00458133.

Adiponectin is an adipokine with insulin-sensitizing, anti-inflammatory, and cardiac protective actions. It homo-oligomerizes into trimers, hexamers, and higher molecular weight (HMW) species, which are not fully characterized. We describe high-resolution separation of adiponectin oligomers under native conditions in polyacrylamide gel coupled with methods for producing standards to provide facile and accurate identification of the oligomers. Using these procedures, adiponectin trimers in human and rodent plasma were found to migrate as two distinct populations. Distributions of these two populations are linearly proportional in plasma from type 2 diabetic patients before (R(2)=0.903, P<0.001) and after (R(2)=0.960, P<0.0001) 12weeks of treatment with pioglitazone as well as from control subjects (R(2)=0.891, P<0.0001). In addition, HMW adiponectin could be separated into three distinct oligomers: nonamer (9mer), dodecamer (12mer), and the previously characterized octadecamer (18mer). Plasma concentrations of all oligomers increased on pioglitazone treatment, with the largest fold increase being observed in 9mers and 12mers compared with baseline. Increasing concentrations of adiponectin during oligomerization in vitro led to a disproportionate increase in 18mers. The difference between in vivo and in vitro observations suggests that higher total adiponectin protein concentration contributes to pioglitazone's ability to enhance HMW adiponectin levels, but additional factors likely affect oligomer assembly or turnover independently., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Context: Type 2 diabetes (T2D) has features of disordered lipid and glucose metabolism, due in part to reduced mitochondrial content., Objective: Our objective was to investigate effects of different types of exercise on mitochondrial content and substrate oxidation in individuals with T2D (ancillary study of the randomized controlled trial Health Benefits of Aerobic and Resistance Training in Individuals with Type 2 Diabetes, HART-D)., Intervention: T2D individuals were randomized to aerobic training (AT, n = 12), resistance training (RT, n = 18), combination training (ATRT, n = 12), or nonexercise control (n = 10). Blood draws, peak oxygen consumption tests, dual-energy x-ray absorptiometry scans and muscle biopsies of vastus lateralis were performed before and after 9 months. Ex vivo substrate oxidations ((14)CO2), mitochondrial content, and enzyme activities were measured. Glycated hemoglobin A1c and free fatty acids were also determined., Results: Mitochondrial content increased after RT and ATRT. Octanoate oxidation increased after AT and ATRT, whereas palmitate, pyruvate, and acetate oxidations increased in all exercise groups. Exercise-induced responses in mitochondrial DNA were associated with improvements in peak oxygen consumption, β-hydroxyacyl-coenzyme A dehydrogenase activity, and palmitate oxidation., Conclusions: Nine months of AT and RT significantly improved most aspects of skeletal muscle mitochondrial content and substrate oxidation, whereas the combination improved all aspects. These exercise responses were associated with clinical improvements, indicating that long-term training, especially combination, is an effective lifestyle therapy for individuals with T2D by way of improving muscle substrate metabolism.

The BLOOM-DM (Behavioral Modification and Lorcaserin for Obesity and Overweight Management in Diabetes Mellitus) study evaluated efficacy and safety of lorcaserin for weight loss in patients with type 2 diabetes. Secondary objectives included evaluations of glycemic control, lipids, blood pressure, and quality of life. This 1-year, randomized, placebo-controlled trial enrolled 604 patients 1:1:1 to placebo, lorcaserin 10 mg once daily (QD) or lorcaserin 10 mg twice daily (BID). Patients were treated with metformin, a sulfonylurea (SFU) or both; had glycated hemoglobin (HbA(1c)) 7-10%; were 18-65 years old; and had BMI 27-45 kg/m(2). Patients received diet and exercise counseling. Safety monitoring included serial echocardiograms. Mean (± SD) age was 52.7 ± 8.7; 54.2% were women; 60.5% were white, 20.9% were African American, and 13.8% were Hispanic. Mean (± SD) weight was 103.6 ± 17.8 kg; BMI was 36.0 ± 4.5 kg/m(2). Most patients (91.7%) took metformin; 50.2% took a SFU. More patients lost ≥5% body weight with lorcaserin BID (37.5%; P < 0.001) or lorcaserin QD (44.7%; P < 0.001) vs. placebo (16.1%; modified intent to treat (MITT)/last observation carried forward (LOCF)). Least square mean (± SEM) weight change was -4.5 ± 0.35% with lorcaserin BID and -5.0 ± 0.5% with lorcaserin QD vs. -1.5 ± 0.36% with placebo (P < 0.001 for each). HbA(1c) decreased 0.9 ± 0.06 with lorcaserin BID, 1.0 ± 0.09 with lorcaserin QD, and 0.4 ± 0.06 with placebo (P < 0.001 for each); fasting glucose decreased 27.4 ± 2.5 mg/dl, -28.4 ± 3.8 mg/dl, and 11.9 ± 2.5 mg/dl, respectively (P < 0.001 for each). Symptomatic hypoglycemia occurred in 7.4% of patients on lorcaserin BID, 10.5% on lorcaserin QD, and 6.3% on placebo. Common adverse events were headache, back pain, nasopharyngitis, and nausea. Lorcaserin was associated with significant weight loss and improvement in glycemic control in patients with type 2 diabetes.

Obesity is associated with an increased risk of type 2 diabetes (T2D). Pancreatic beta-cell failure is an early event in the development of glucose dysregulation and diabetes. Interventions to halt beta-cell failure in T2D include diet modification, exercise, and use of pharmacologic agents. There is evidence that abdominal obesity may contribute to diabetes through insulin resistance and beta-cell impairment. Pivotal long-term studies into the prevention of T2D have shown the importance of weight loss beside diet, lifestyle, and medication. The Finnish Diabetes Prevention Program (DPP) showed that weight loss gradually reduces the risk of diabetes, and that even modest weight loss can significantly reduce the incidence of T2D. Similarly, in the US DPP, weight loss as part of intensive lifestyle modification was the major factor in reducing the incidence of T2D in high-risk subjects, being more effective than drug intervention. While understanding the relationship between obesity and diabetes is complex, we know that weight loss has positive effects on adipose tissue. It causes an increase in the beneficial fat cell hormone adiponectin, and a decrease in adipose tissue inflammation. Also, it is associated with reduced insulin resistance and a consequential reduction in glucolipotoxicity, which can improve beta-cell function. In summary, weight loss improves glycemic control and thereby mitigates diabetes symptoms and complications, possibly through the preservation of beta-cell function. Therefore, efforts to prevent diabetes and preserve beta-cell function in patients with T2D should more consequently emphasize and target weight loss.

Aim: To study the effect of dipeptidyl peptidase-4 (DPP-4) inhibition with saxagliptin on β-cell function as reflected by the stimulated insulin secretion rate after an enteral glucose load in patients with type 2 diabetes., Methods: Patients in this randomized, parallel-group, double-blind, placebo-controlled study were drug-naïve, aged 43-69 years, with baseline haemoglobin A1c (HbA1c) 5.9-8.1%. Twenty patients received saxagliptin 5 mg once daily; 16 received placebo. Patients were assessed at baseline and week 12 by intravenous hyperglycaemic clamp (0-180 min, fasting state), and intravenous-oral hyperglycaemic clamp (180-480 min, postprandial state) following oral ingestion of 75 g glucose. Primary and secondary endpoints were percent changes from baseline in insulin secretion during postprandial and fasting states, respectively. Insulin secretion was calculated by C-peptide deconvolution., Results: After 12 weeks, saxagliptin significantly increased insulin secretion percent change from baseline during the postprandial state by an 18.5% adjusted difference versus placebo (p = 0.04), an improvement associated with increased peak plasma concentrations of intact glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. In the fasting state, saxagliptin significantly increased insulin secretion by a 27.9% adjusted difference versus placebo (p = 0.02). Saxagliptin also improved glucagon area under the curve in the postprandial state (adjusted difference -21.8% vs. placebo, p = 0.03)., Conclusions: DPP-4 inhibition with saxagliptin improves pancreatic β-cell function in postprandial and fasting states, and decreases postprandial glucagon concentration. Given the magnitude of enhancement of the insulin response in the fasting state, further study into the effect of DPP-4 inhibition on the β-cell is warranted., (© 2011 Blackwell Publishing Ltd.)

Objective: This report examines what is known about the relationship between obesity and type 2 diabetes and how future research in these areas might be directed to benefit prevention, interventions, and overall patient care., Research Design and Methods: An international working group of 32 experts in the pathophysiology, genetics, clinical trials, and clinical care of obesity and/or type 2 diabetes participated in a conference held on 6-7 January 2011 and cosponsored by The Endocrine Society, the American Diabetes Association, and the European Association for the Study of Diabetes. A writing group comprising eight participants subsequently prepared this summary and recommendations. Participants reviewed and discussed published literature and their own unpublished data., Results: The writing group unanimously supported the summary and recommendations as representing the working group's majority or unanimous opinions., Conclusions: The major questions linking obesity to type 2 diabetes that need to be addressed by combined basic, clinical, and population-based scientific approaches include the following: 1) Why do not all patients with obesity develop type 2 diabetes? 2) Through what mechanisms do obesity and insulin resistance contribute to β-cell decompensation, and if/when obesity prevention ensues, how much reduction in type 2 diabetes incidence will follow? 3) How does the duration of type 2 diabetes relate to the benefits of weight reduction by lifestyle, weight-loss drugs, and/or bariatric surgery on β-cell function and glycemia? 4) What is necessary for regulatory approval of medications and possibly surgical approaches for preventing type 2 diabetes in patients with obesity? Improved understanding of how obesity relates to type 2 diabetes may help advance effective and cost-effective interventions for both conditions, including more tailored therapy. To expedite this process, we recommend further investigation into the pathogenesis of these coexistent conditions and innovative approaches to their pharmacological and surgical management.

Objective: This report examines what is known about the relationship between obesity and type 2 diabetes and how future research in these areas might be directed to benefit prevention, interventions, and overall patient care., Research Design and Methods: An international working group of 32 experts in the pathophysiology, genetics, clinical trials, and clinical care of obesity and/or type 2 diabetes participated in a conference held on 6-7 January 2011 and cosponsored by The Endocrine Society, the American Diabetes Association, and the European Association for the Study of Diabetes. A writing group comprising eight participants subsequently prepared this summary and recommendations. Participants reviewed and discussed published literature and their own unpublished data., Results: The writing group unanimously supported the summary and recommendations as representing the working group's majority or unanimous opinions., Conclusions: The major questions linking obesity to type 2 diabetes that need to be addressed by combined basic, clinical, and population-based scientific approaches include the following: 1) Why do not all patients with obesity develop type 2 diabetes? 2) Through what mechanisms do obesity and insulin resistance contribute to β-cell decompensation, and if/when obesity prevention ensues, how much reduction in type 2 diabetes incidence will follow? 3) How does the duration of type 2 diabetes relate to the benefits of weight reduction by lifestyle, weight-loss drugs, and/or bariatric surgery on β-cell function and glycemia? 4) What is necessary for regulatory approval of medications and possibly surgical approaches for preventing type 2 diabetes in patients with obesity? Improved understanding of how obesity relates to type 2 diabetes may help advance effective and cost-effective interventions for both conditions, including more tailored therapy. To expedite this process, we recommend further investigation into the pathogenesis of these coexistent conditions and innovative approaches to their pharmacological and surgical management.

Objective: The objective of this study was to determine the role of maximum mitochondrial capacity on the variation in insulin sensitivity within a population of patients with type 2 diabetes mellitus (T2DM)., Research Design and Methods: Fifty-eight participants enrolled in a cross-sectional design: eight active controls [maximum aerobic capacity (VO(2max)) > 40 ml/kg · min], 17 healthy sedentary controls without a family history (FH-) and seven with a family history (FH+) of diabetes, four obese participants, and 21 patients with T2DM. Mitochondrial capacity was measured noninvasively using (31)P magnetic resonance spectroscopy of the vastus lateralis. Maximal ATP synthetic rate (ATP(max)) was determined from the rate of phosphocreatine (PCr) recovery after short-term isometric exercise., Results: ATP(max) was lower (P < 0.001) in T2DM and higher (P < 0.001) in active as compared with healthy sedentary FH- (active, 1.01 ± 0.2; FH-, 0.7 ± 0.2; FH+, 0.6 ± 0.1; obese, 0.6 ± 0.1; T2DM, 0.5 ± 0.2 mm ATP/sec; ANOVA P < 0.0001). Insulin sensitivity, measured by euglycemic-hyperinsulinemic (80 mIU/m(2) · min) clamp was also reduced in T2DM (P < 0.001) (active, 12.0 ± 3.2; FH-, 7.8 ± 2.2; FH+, 6.8 ± 3.5; obese, 3.1 ± 1.0; T2DM, 3.4 ± 1.6; mg/kg estimated metabolic body size · min; ANOVA P < 0.0001). Unexpectedly, there was a broad range of ATP(max) within the T2DM population where 52% of subjects with T2DM had ATP(max) values that were within the range observed in healthy sedentary controls. In addition, 24% of the T2DM subjects overlapped with the active control group (range, 0.65-1.27 mm ATP/sec). In contrast to the positive correlation between ATP(max) and M-value in the whole population (r(2) = 0.35; P < 0.0001), there was no correlation between ATP(max) and M-value in the patients with T2DM (r(2) = 0.004; P = 0.79)., Conclusions: Mitochondrial capacity is not associated with insulin action in T2DM.

Background: Pioglitazone (Pio) treatment induces weight gain in Type 2 diabetes mellitus (T2DM), which could worsen hepatic lipid accumulation, and alter adiponectin and high-sensitivity C-reactive protein (hs-CRP)., Objective: To compare changes in hepatic lipid, serum adiponectin and hs-CRP in diabetics treated with Pio (with and without weight gain) against metformin (Met) treatment, which produces weight loss., Design: Fifty-one men and women with T2DM, naive to thiazolidinediones, entered a 16-week, open-label, parallel arm study, where participants were randomized to one of three groups: (1) Pio plus the American Diabetes Association diet (Pio+ADA); (2) Pio plus a portion control weight loss diet (Pio+PC), or (3) metformin plus ADA diet (Met+ADA)., Methods: Hepatic lipid was assessed with abdominal computed tomography (CT) and the serum adiponectin and hs-CRP by enzyme-linked immunosorbent assay at baseline and study end., Results: Forty-eight subjects completed the study. The Pio+ADA group gained (mean+/-S.E.M.) 2.15+/-1.09 kg, while Pio+PC and Met+ADA group lost -2.59+/-1.25 and -3.21+/-0.7 kg, respectively. Pio-treated groups (Pio+ADA and Pio+PC) significantly decreased hepatic fat as indicated by increased liver density on CT scan [10.1+/-2.4: 11.4+/-1.0 Hounsfield units (HU)], compared with Met+ADA group (-2.4+/-3.1 HU). The Pio groups demonstrated significantly increased serum adiponectin, (8.6+/-1.5; 7.4+/-1.6 microg/ml) independent of weight change, compared to Met+ADA (-0.14+/-0.6 microgm/ml) group which lost weight. Serum hs-CRP decreased in groups showing weight loss (Pio+PC, -3.1+/-1.7 mg/l; Met+ADA, -1.5+/-1.2 mg/l) compared to Pio+ADA (1.8+/-3.0 mg/l) group that gained weight., Conclusions: Pio treatment in T2DM significantly reduced hepatic lipid and increased adiponectin independent of weight change, while decreasing hs-CRP with weight loss.

Objective: To measure ghrelin and energy intake in the laboratory after pioglitazone treatment., Research Design and Methods: This was a parallel, three-arm study with 51 obese diabetic subjects randomized to either 1) pioglitazone plus a portion-controlled diet (Pio+PC), 2) pioglitazone plus American Diabetes Association (ADA) dietary advice (Pio+ADA), or 3) metformin plus ADA advice (Met+ADA). Energy intake and the suppressive response of a meal on ghrelin were measured at weeks 0 and 16. Mixed models tested if changes from week 0 to 16 differed by group., Results: The Pio+ADA group had a significantly larger increase (P < 0.05) in energy intake ([adjusted means +/- SE] 207 +/- 53 kcal) compared with the Pio+PC (50 +/- 46 kcal) and Met+ADA (52 +/- 49 kcal) groups. Change in restraint and disinhibition (variables associated with eating behavior) mediated weight change. Ghrelin suppression increased in the Pio+ADA group, which gained weight., Conclusions: A portion-controlled diet attenuated the increase in energy intake after pioglitazone. Ghrelin responded to weight change not pioglitazone exposure.

Objective: To characterize the relationships among long-term improvements in peripheral insulin sensitivity (glucose disposal rate [GDR]), fasting glucose, and free fatty acids (FFAs) and concomitant changes in weight and adipose tissue mass and distribution induced by lifestyle intervention in obese individuals with type 2 diabetes., Research Design and Methods: We measured GDR, fasting glucose, and FFAs during a euglycemic clamp and adipose tissue mass and distribution, organ fat, and adipocyte size by dual-energy X-ray absorptiometry, CT scan, and adipose tissue biopsy in 26 men and 32 women in the Look-AHEAD trial before and after 1 year of diet and exercise aimed at weight loss., Results: Weight and fasting glucose decreased significantly (P < 0.0001) and significantly more in men than in women (-12 vs. -8% and -16 vs. -7%, respectively; P < 0.05), while FFAs during hyperinsulinemia decreased and GDR increased significantly (P < 0.00001) and similarly in both sexes (-53 vs. -41% and 63 vs. 43%; P = NS). Men achieved a more favorable fat distribution by losing more from upper compared with lower and from deeper compared with superficial adipose tissue depots (P < 0.01). Decreases in weight and adipose tissue mass predicted improvements in GDR but not in fasting glucose or fasting FFAs; however, decreases in FFAs during hyperinsulinemia significantly determined GDR improvements. Hepatic fat was the only regional fat measure whose change contributed independently to changes in metabolic variables., Conclusions: Patients with type 2 diabetes undergoing a 1-year lifestyle intervention had significant improvements in GDR, fasting glucose, FFAs and adipose tissue distribution. However, changes in overall weight (adipose tissue mass) and hepatic fat were the most important determinants of metabolic improvements.

The size of adipocytes influences their function suggesting a differential responsiveness to intervention. We hypothesized that weight loss in patients with type 2 diabetes mellitus (T2DM) predominantly decreases the size of large and very-large adipocyte subfractions in parallel with beneficial changes in serum adipokines and improved insulin sensitivity. A total of 44 volunteers from the Look Action for Health in Diabetes trial, who lost weight after 1-year of intense lifestyle intervention, were included. Insulin sensitivity (hyperinsulinemic-euglycemic clamp), size of subcutaneous abdominal adipocytes (osmium fixation), and selected serum adipokines were measured. A 13% weight loss was accompanied by 46% improvement in insulin sensitivity (increased glucose disposal rate from 5.9+/-2.2 to 8.6+/-2.7 mg/min/kg fat-free mass, P<0.05) in parallel with a 36% increase in plasma adiponectin concentration (6.1+/-3.1 to 8.3+/-3.9 microg/ml, P<0.05], but no changes in the proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha. Change in adiponectin correlated with changes in glucose disposal rate (r=0.34, P<0.05). Mean adipocyte size decreased (0.84+/-0.25 to 0.64+/-0.23 microl, P<0.05), mainly due to changes in the large adipocyte subfraction (size 0.75-0.44 microl, relative number 19-26%; P<0.05). Our data suggest that change in the large adipocyte subfraction may contribute to the improvement in insulin sensitivity via an increase in serum adiponectin. Such a relationship, which does not imply cause and effect, could not be obtained by measuring only mean adipocyte size. These data provide support for the measures of adipocyte size distribution in concert with in vitro adipokine secretion and lipolysis in future studies.

Objective: We hypothesized that, compared with obese subjects, patients with type 2 diabetes have a lower total adipocyte number with fewer small adipocytes., Research Design and Methods: Abdominal subcutaneous adipose tissue was obtained from lean and obese subjects with or without type 2 diabetes matched for BMI. Adipocyte size was measured by osmium fixation and sizing/counting in a Coulter counter. Adipocyte size and number subdistributions (small, medium, large, and very large) were determined., Results: Compared with obese subjects, type 2 diabetic patients had larger mean adipocyte size and 67% bigger very large adipocytes; the total adipocyte number was lower, but the fraction of small adipocytes was increased by 27%., Conclusions: Total adipocyte cellularity is lower in type 2 diabetic subjects than in obese subjects. We found no evidence for depletion of small adipocytes in patients with type 2 diabetes. This suggests the presence of a defect in early maturation of adipocytes in patients with type 2 diabetes.

Background: Treatment with thiazolidinediones (TZDs) produces weight gain., Objective: To test whether a portion control diet could prevent weight gain during treatment with pioglitazone in patients with type 2 diabetes mellitus (T2DM)., Design: This 16-week randomized, open-label, parallel arm study compared three groups: (i) pioglitazone plus the American Diabetes Association diet (Pio + ADA); (ii) pioglitazone plus a portion control weight loss diet (Pio + PC); (iii) metformin plus the American Diabetes Association diet (Met + ADA). All participants received the same advice about calorie reduction, lifestyle change and exercise., Methods: Fifty-one men and women with T2DM, naive to TZDs, were randomized to a 16-week study. Pioglitazone (Pio) was titrated to a dose of 45 mg/day and metformin (Met) to a dose of 2 g/day. Fasting blood was collected for lipids, insulin and glycosylated haemoglobin A1c (HbA1c) at baseline and 16 weeks., Results: Forty-eight of fifty-one randomized subjects completed the study. Patients treated with Pio + ADA gained 2.15 +/- 1.09 kg (mean +/- SD) compared with a weight loss of 2.59 +/- 1.25 kg (p < 0.05) in the Pio + PC group, and a weight loss of 3.21 +/- 0.7 kg (p < 0.05) in the Met + ADA group. Waist circumference and visceral adipose tissue decreased significantly more in the Pio + PC group than in the Pio + ADA group. High-density lipoprotein cholesterol levels were significantly increased in the Pio + PC group compared with the Met + ADA group. Pioglitazone reduced insulin resistance (homeostasis model assessment of insulin resistance (HOMA-IR)) more than metformin. No significant differences between groups were seen for glucose, insulin, HbA1c or low-density lipoprotein cholesterol levels., Conclusions: Pio + PC, prevented weight gain, reduced waist circumference and visceral fat compared with Pio + ADA diet.

Objective: Compared with nondiabetic subjects, type 2 diabetic subjects are metabolically inflexible with impaired fasting fat oxidation and impaired carbohydrate oxidation during a hyperinsulinemic clamp. We hypothesized that impaired insulin-stimulated glucose oxidation is a consequence of the lower cellular glucose uptake rate in type 2 diabetes. Therefore, we compared metabolic flexibility to glucose adjusted for glucose disposal rate in nondiabetic versus type 2 diabetic subjects and in the latter group after 1 year of lifestyle intervention (the Look AHEAD [Action For Health in Diabetes] trial)., Research Design and Methods: Macronutrient oxidation rates under fasting and hyperinsulinemic conditions (clamp at 80 mU/m(2) per min), body composition (dual-energy X-ray absorptiometry), and relevant hormonal/metabolic blood variables were assessed in 59 type 2 diabetic and 42 nondiabetic individuals matched for obesity, sex, and race. Measures were repeated in diabetic participants after weight loss., Results: Metabolic flexibility to glucose (change in respiratory quotient [RQ]) was mainly related to insulin-stimulated glucose disposal rate (R(2) = 0.46, P < 0.0001) with an additional 3% of variance accounted for by plasma free fatty acid concentration at the end of the clamp (P = 0.03). The impaired metabolic flexibility to glucose observed in type 2 diabetic versus nondiabetic subjects (Delta RQ 0.06 +/- 0.01 vs. 0.10 +/- 0.01, respectively, P < 0.0001) was no longer observed after adjusting for glucose disposal rate (P = 0.19). Additionally, the increase in metabolic flexibility to glucose after weight loss was accounted for by the concomitant increase in insulin-stimulated glucose disposal rate., Conclusions: This study suggests that metabolic inflexibility to glucose in type 2 diabetic subjects is mostly related to defective glucose transport.

We measured gene expression of paracrine regulators involved in adipocyte differentiation within the stromovascular fraction of abdominal subcutaneous adipose tissue from obese individuals with (n=30) and without (n=18) type 2 diabetes mellitus (T2DM). Despite similar adiposity by design, subjects with T2DM had larger adipocytes (0.92+/-0.28 vs. 0.75+/-0.17 microl, p<0.05) than controls. Gene expression of the adipogenic marker aP2 was lower (0.35+/-0.16 vs. 0.58+/-0.27 arbitrary units, p<0.05) whereas the expression of matricellular peptidase, MMP2 was higher (1.65+/-0.17 vs. 1.27+/-0.21, p=0.02) in T2DM vs. controls. The gene expression levels between the aP2 and MMP2 were inversely correlated (r=-0.32, p=0.03). We conclude that early steps of adipogenesis may be impaired in T2DM independently of obesity due, in part, to an upregulation of the MMP2 transcription.

Insulin resistance (IR) is typically more severe in obese individuals with type 2 diabetes (T2DM) than in similarly obese non-diabetics but whether there are group differences in body composition and whether such differences contribute to the more severe IR of T2DM is uncertain. DEXA and regional CT imaging were conducted to assess adipose tissue (AT) distribution and fat content in liver and muscle in 67 participants with T2DM (F39/M28, age 60 +/- 7 yr, BMI 34 +/- 3 kg/m(2)) and in 35 similarly obese, non-DM volunteers (F20/M15, age 55 +/- 8 yr, BMI 33 +/- 2 kg/m(2)). A biopsy of subcutaneous abdominal AT was done to measure adipocyte size. A glucose clamp was performed at an insulin infusion of 80 mU x min(-1) x m(-2). There was more severe IR in T2DM (6.1 +/- 2.3 vs. 9.9 +/- 3.3 mg x min(-1) x kg FFM(-1); P < 0.01). Group comparisons of body composition parameters was performed after adjusting for the effect of age, gender, race, height and total fat mass (FM). T2DM was associated with less leg FM (-1.2 +/- 0.4 kg, P < 0.01), more trunk FM (+1.1 +/- 0.4 kg, P < 0.05), greater hepatic fat (P < 0.05), and more subfascial adipose tissue around skeletal muscle (P < 0.05). There was a significant group x sex interaction for VAT (P < 0.01), with greater VAT in women with T2DM (P < 0.01). Mean adipocyte size (AS) did not significantly differ across groups, and smaller AS was associated with increased leg FM, whereas larger AS was related to more trunk FM (both P < 0.05). Group differences in IR were less after adjusting for group differences in leg FM, trunk FM, and hepatic fat, but these adjustments only partially accounted for the greater severity of IR in T2DM. In summary, T2DM, compared with similarly obese nondiabetic men and women, is associated with less leg FM and greater trunk FM and hepatic fat.

Insulin resistance is associated with metabolic inflexibility, impaired switching of substrate oxidation from fatty acids to glucose in response to insulin. Impaired switching to fat oxidation in response to a high-fat diet (HFD) is hypothesized to contribute to insulin resistance. The objective of this study was to test the hypothesis that defects in substrate switching in response to insulin and a HFD are linked to reduced mitochondrial biogenesis and occur before the development of diabetes. Metabolic flexibility was measured in young sedentary men with (n = 16) or without (n = 34) a family history of diabetes by euglycemic-hyperinsulinemic clamp. Flexibility correlated with fat oxidation measured in a respiratory chamber after a 3-day HFD. Muscle mitochondrial content was higher in flexible subjects with high fat oxidation after a HFD and contributed 49% of the variance. Subjects with a family history of diabetes were inflexible and had reduced HFD-induced fat oxidation and muscle mitochondrial content but did not differ in the amount of body or visceral fat. Metabolic inflexibility, lower adaptation to a HFD, and reduced muscle mitochondrial mass cluster together in subjects with a family history of diabetes, supporting the role of an intrinsic metabolic defect of skeletal muscle in the pathogenesis of insulin resistance.

Objective: Our objective was to delineate the potential role of adipogenesis in insulin resistance and type 2 diabetes. Obesity is characterized by an increase in adipose tissue mass resulting from enlargement of existing fat cells (hypertrophy) and/or from increased number of adipocytes (hyperplasia). The inability of the adipose tissue to recruit new fat cells may cause ectopic fat deposition and insulin resistance., Research Methods and Procedures: We examined the expression of candidate genes involved in adipocyte proliferation and/or differentiation [CCAAT/enhancer-binding protein (C/EBP) alpha, C/EBPdelta, GATA domain-binding protein 3 (GATA3), C/EBPbeta, peroxisome proliferator-activated receptor (PPAR) gamma2, signal transducer and activator of transcription 5A (STAT5A), Wnt-10b, tumor necrosis factor alpha, sterol regulatory element-binding protein 1c (SREBP1c), 11 beta-hydroxysteroid dehydrogenase, PPARG angiopoietin-related protein (PGAR), insulin-like growth factor 1, PPARgamma coactivator 1alpha, PPARgamma coactivator 1beta, and PPARdelta] in subcutaneous adipose tissue from 42 obese individuals with type 2 diabetes and 25 non-diabetic subjects matched for age and obesity., Results: Insulin sensitivity was measured by a 3-hour 80 mU/m2 per minute hyperinsulinemic glucose clamp (100 mg/dL). As expected, subjects with type 2 diabetes had lower glucose disposal (4.9 +/- 1.9 vs. 7.5 +/- 2.8 mg/min per kilogram fat-free mass; p < 0.001) and larger fat cells (0.90 +/- 0.26 vs. 0.78 +/- 0.17 microm; p = 0.04) as compared with obese control subjects. Three genes (SREBP1c, p < 0.01; STAT5A, p = 0.02; and PPARgamma2, p = 0.02) had significantly lower expression in obese type 2 diabetics, whereas C/EBPbeta only tended to be lower (p = 0.07)., Discussion: This cross-sectional study supports the hypothesis that impaired expression of adipogenic genes may result in impaired adipogenesis, potentially leading to larger fat cells in subcutaneous adipose tissue and insulin resistance.

Background: Several clinical studies have demonstrated that body weight increases after treatment with thiazolidinediones (TZDs). Prior studies have demonstrated an increase in insulin-stimulated lipid storage in adipose tissue. Some, but not all, studies demonstrate reductions in visceral adipose tissue. Changes in body weight are the result of changes in energy intake, energy expenditure, or both., Objectives: Based on these findings, the primary aim of this study was to evaluate the effect of TZDs on visceral, subcutaneous, and total body fat. Secondary aims were to determine the effects of pioglitazone on (a) energy expenditure, (b) hunger and satiety, (c) blood lipids, and (d) the role of insulinemia/sulfonylurea usage on weight gain in patients with type 2 diabetes., Subjects and Methods: We performed a randomized, double-blind, placebo-controlled trial in 48 men and women with type 2 diabetes who had not previously received treatment with TZDs. Patients were treated for 24 weeks with 45 mg/d of pioglitazone or a matching placebo. Body composition was measured by dual-energy x-ray absorptiometry. Visceral and subcutaneous fat were measured by computed tomography. Resting metabolic rate and thermogenic response to a test meal were measured by indirect calorimetry before and after a standardized meal. Hunger and satiety were measured with visual analog scales before and after the same test meal. Blood was collected for the measurement of fasting glucose and insulin levels, hemoglobin A 1c levels, and lipid content., Results: Pioglitazone treatment resulted in a decrease in hemoglobin A(1c) level by 0.96 +/- 1.1% vs 0.11 +/- 0.8% in the placebo group (P < .005). Body weight and fat increased steadily in the patients treated with pioglitazone during the 6 months of the study (+3.9 +/- 3.1 kg at 6 months in pioglitazone-treated patients vs -0.8 +/- 3.4 kg in the placebo-treated patients). Subcutaneous fat in the trunk, arms, and legs were all increased in the pioglitazone-treated group. Visceral fat did not change significantly in either group. Neither resting metabolic rate nor the thermogenic responses to a meal were altered by pioglitazone. Subjective measures of hunger (visual analog scale) did not change with pioglitazone treatment. Triglycerides fell in the pioglitazone-treated group (-58.5 +/- 124 mg/dL, P < .003). Neither the prior use of sulfonylureas nor the level of insulinemia before treatment was a predictor of weight or fat change., Conclusion: Pioglitazone increased subcutaneous body fat, but not visceral fat. There was no measurable effect on energy expenditure or hunger/satiety. In contrast to the placebo-treated patient with diabetes, weight gain occurs in the face of falling hemoglobin A(1c) and triglyceride levels.

Background: It is widely accepted that increasing adiposity is associated with insulin resistance and increased risk of type II diabetes. The predominant paradigm used to explain this link is the portal/visceral hypothesis. This hypothesis proposes that increased adiposity, particularly in the visceral depots, leads to increased free-fatty acid flux and inhibition of insulin-action via Randle's effect in insulin-sensitive tissues., Objectives: In this review, limitations of this paradigm will be discussed and two other paradigms that may explain established links between adiposity and insulin resistance/diabetes will be presented. (A) Ectopic fat storage syndrome. Three lines of evidence support this concept. Firstly, failure to develop adequate adipose tissue mass (also known as 'lipodystrophy') results in severe insulin resistance and diabetes. This is thought to be the result of ectopic storage of lipid into liver, skeletal muscle and the pancreatic insulin-secreting beta cell. Secondly, most obese patients also shunt lipid into the skeletal muscle, the liver and probably the beta cell. The importance of this finding is exemplified by several studies demonstrating that the degree of lipid infiltration into skeletal muscle and liver highly correlates with insulin resistance. Thirdly, increased fat cell size is highly associated with insulin resistance and the development of diabetes. Increased fat cell size may represent the failure of the adipose tissue mass to expand and therefore to accommodate an increased energy influx. Taken together, these observations support the 'acquired lipodystrophy' hypothesis as a link between adiposity and insulin resistance. Ectopic fat deposition is therefore the result of additive or synergistic effects including increased dietary intake, decreased fat oxidation and impaired adipogenesis. (B) Endocrine paradigm. This concept was developed in parallel with the 'ectopic fat storage syndrome' hypothesis. Adipose tissue secretes a variety of endocrine hormones such as leptin, interleukin-6, angiotensin II, adiponectin and resistin. From this viewpoint, adipose tissue plays a critical role as an endocrine gland, secreting numerous factors with potent effects on the metabolism of distant tissues., Conclusions: The novel paradigms of ectopic fat and fat cell as an endocrine organ probably will constitute a new framework for the study of the links between our obesigenic environment and the risk of developing diabetes.

It is well recognized that the agouti/melanocortin system is an important regulator of body weight homeostasis. Given that agouti is expressed in human adipose tissue and that the ectopic expression of agouti in adipose tissue results in moderately obese mice, the link between agouti expression in human adipose tissue and obesity/type 2 diabetes was investigated. Although there was no apparent relationship between agouti mRNA levels and BMI, agouti mRNA levels were significantly elevated in subjects with type 2 diabetes. The regulation of agouti in cultured human adipocytes revealed that insulin did not regulate agouti mRNA, whereas dexamethasone treatment potently increased the levels of agouti mRNA. Experiments with cultured human preadipocytes and with cells obtained from transgenic mice that overexpress agouti demonstrated that melanocortin receptor (MCR) signaling in adipose tissue can regulate both preadipocyte proliferation and differentiation. Taken together, these results reveal that agouti can regulate adipogenesis at several levels and suggest that there are functional consequences of elevated agouti levels in human adipose tissue. The influence of MCR signaling on adipogenesis combined with the well-established role of MCR signaling in the hypothalamus suggest that adipogenesis is coordinately regulated with food intake and energy expenditure.

It is widely accepted that increasing adiposity is associated with insulin resistance and increased risk of type 2 diabetes. The predominant paradigm used to explain this link is the portal/visceral hypothesis. This hypothesis proposes that increased adiposity, particularly in the visceral depots, leads to increased free fatty acid flux and inhibition of insulin action via Randle's effect in insulin-sensitive tissues. Recent data do not entirely support this hypothesis. As such, two new paradigms have emerged that may explain the established links between adiposity and disease. (A) Three lines of evidence support the ectopic fat storage syndrome. First, failure to develop adequate adipose tissue mass in either mice or humans, also known as lipodystrophy, results in severe insulin resistance and diabetes. This is thought to be the result of ectopic storage of lipid into liver, skeletal muscle, and the pancreatic insulin-secreting beta cell. Second, most obese patients also shunt lipid into the skeletal muscle, the liver, and probably the beta cell. The importance of this finding is exemplified by several studies demonstrating that the degree of lipid infiltration into skeletal muscle and liver correlates highly with insulin resistance. Third, increased fat cell size is highly associated with insulin resistance and the development of diabetes. Increased fat cell size may represent the failure of the adipose tissue mass to expand and thus to accommodate an increased energy influx. Taken together, these three observations support the acquired lipodystrophy hypothesis as a link between adiposity and insulin resistance. (B) The endocrine paradigm developed in parallel with the ectopic fat storage syndrome hypothesis. Adipose tissue secretes a variety of endocrine hormones, such as leptin, interleukin-6, angiotensin II, adiponectin (also called ACRP30 and adipoQ), and resistin. From this viewpoint, adipose tissue plays a critical role as an endocrine gland, secreting numerous factors with potent effects on the metabolism of distant tissues. These two new paradigms provide a framework to advance our understanding of the pathophysiology of the insulin-resistance syndrome.