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In response to infection or tissue damage, resident peritoneal macrophages (rpMACs) produce inflammatory lipid mediators from the polyunsaturated fatty acid (PUFA), arachidonic acid (AA). Long-chain acyl-CoA synthetase 4 (ACSL4) catalyzes the covalent addition of a CoA moiety to fatty acids, with a strong preference for AA and other PUFAs containing three or more double bonds. PUFA-CoA can be incorporated into phospholipids, which is the source of PUFA for lipid mediator synthesis. In this study, we demonstrated that deficiency of Acsl4 in mouse rpMACs resulted in a significant reduction of AA incorporated into all phospholipid classes and a reciprocal increase in incorporation of oleic acid and linoleic acid. After stimulation with opsonized zymosan (opZym), a diverse array of AA-derived lipid mediators, including leukotrienes, PGs, hydroxyeicosatetraenoic acids, and lipoxins, were produced and were significantly reduced in Acsl4-deficient rpMACs. The Acsl4-deficient rpMACs stimulated with opZym also demonstrated an acute reduction in mRNA expression of the inflammatory cytokines, Il6, Ccl2, Nos2, and Ccl5. When Acsl4-deficient rpMACs were incubated in vitro with the TLR4 agonist, LPS, the levels of leukotriene B4 and PGE2 were also significantly decreased. In LPS-induced peritonitis, mice with myeloid-specific Acsl4 deficiency had a significant reduction in leukotriene B4 and PGE2 levels in peritoneal exudates, which was coupled with reduced infiltration of neutrophils in the peritoneal cavity as compared with wild-type mice. Our data demonstrate that chronic deficiency of Acsl4 in rpMACs reduces the incorporation of AA into phospholipids, which reduces lipid mediator synthesis and inflammation.

The radial head is an important stabilizer of the elbow joint. Radial head fractures are commonly associated with additional injuries to the ligamentous structures of the elbow and can significantly compromise elbow stability. Young patients with radial head fractures are more likely to be male and present after a high-energy mechanism of injury. While not perfect, the Mason classification is the most commonly used classification system and can help to guide the management of radial head fractures. Type I fractures are nondisplaced or minimally displaced (less than 2 mm) and are treated nonoperatively with early mobilization. Type II fractures, which are displaced 2–5 mm, can be treated nonoperatively or with open reduction and internal fixation (ORIF). Type III fractures are comminuted and are most often treated with ORIF or with radial head arthroplasty (RHA). Treatment of fractures with an associated elbow dislocation (Mason type IV) is also with ORIF or RHA depending on the degree of comminution. For all of these injuries, assessment and treatment of associated ligamentous injuries are necessary in conjunction with treatment of the bony injury. Despite a significant body of literature available on radial head fractures, there is controversy regarding the optimal management of type II, III, and IV fractures, especially in young, active patients. Common complications following radial head fractures include stiffness, instability, and posttraumatic osteoarthritis; as such, these injuries can lead to significant disability in young, active patients if not managed appropriately.

Adipose tissue macrophages regulate adipose tissue inflammation and systemic insulin-glucose homeostasis. In a recent study by Ying et al. (2021), M2 polarized bone marrow-derived macrophages secreted exosomes containing miR-690 that, when administered to obese mice, improved glucose-insulin homeostasis. miR-690 reduced expression of Nadk, which decreased inflammation and improved insulin signaling.

ACSL4 is a member of the ACSL family that catalyzes the conversion of long-chain fatty acids to acyl-coenzyme As, which are essential for fatty-acid incorporation and utilization in diverse metabolic pathways, including cholesteryl ester synthesis. Steroidogenic tissues such as the adrenal gland are particularly enriched in cholesteryl esters of long-chain polyunsaturated fatty acids, which constitute an important pool supplying cholesterol for steroid synthesis. The current studies addressed whether ACSL4 is required for normal steroidogenesis. CYP11A1 promoter‒mediated Cre was used to generate steroid tissue‒specific ACSL4 knockout (KO) mice. Results demonstrated that ACSL4 plays an important role in adrenal cholesteryl ester formation, as well as in determining the fatty acyl composition of adrenal cholesteryl esters, with ACSL4 deficiency leading to reductions in cholesteryl ester storage and alterations in cholesteryl ester composition. Statistically significant reductions in corticosterone and testosterone production, but not progesterone production, were observed in vivo, and these deficits were accentuated in ex vivo and in vitro studies of isolated steroid tissues and cells from ACSL4-deficient mice. However, these effects on steroid production appear to be due to reductions in cholesteryl ester stores rather than disturbances in signaling pathways. We conclude that ACSL4 is dispensable for normal steroidogenesis.

Perilipin 2 (PLIN2) is a lipid droplet (LD) protein in β cells that increases under nutritional stress. Downregulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was downregulated in mouse β cells, INS1 cells, and human islet cells. β Cell–specific deletion of PLIN2 in mice on a high-fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Downregulation of PLIN2 in INS1 cells blunted GSIS after 24-hour incubation with 0.2 mM palmitic acid. Downregulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Downregulation of PLIN2 decreased specific OXPHOS proteins in all 3 models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2-deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress, as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells has an important role in preserving insulin secretion, β cell metabolism, and mitochondrial function under nutritional stress.

Collagen VI, an ECM protein up-regulated in triple-negative breast cancer and obese individuals, drives breast cancer metastasis., The extracellular matrix (ECM), a major component of the tumor microenvironment, promotes local invasion to drive metastasis. Here, we describe a method to study whole-tissue ECM effects from disease states associated with metastasis on tumor cell phenotypes and identify the individual ECM proteins and signaling pathways that are driving these effects. We show that decellularized ECM from tumor-bearing and obese mammary glands drives TNBC cell invasion. Proteomics of the ECM from the obese mammary gland led us to identify full-length collagen VI as a novel driver of TNBC cell invasion whose abundance in tumor stroma increases with body mass index in human TNBC patients. Last, we describe the mechanism by which collagen VI contributes to TNBC cell invasion via NG2-EGFR cross-talk and MAPK signaling. Overall, these studies demonstrate the value of decellularized ECM scaffolds obtained from tissues to identify novel functions of the ECM.

Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in β cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was down-regulated in mouse β cells, INS1 cells, and human islet cells. β cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells have an important role in preserving insulin secretion, β cell metabolism and mitochondrial function under nutritional stress.

The extracellular matrix (ECM) is a major component of the tumor microenvironment that supports cellular growth, promotes local invasion from the primary tumor, and contributes to metastatic outgrowth in sites of colonization. Obesity is a systemic disease that causes chronic inflammation which can lead to ECM deposition and ultimately fibrosis in adipose tissues such as the mammary gland. Overweight breast cancer patients have increased metastasis to the lung and liver, exhibit resistance to chemotherapy and have worse outcomes. We found that ECM isolated from the mammary gland of both tumor-bearing and obese mice increased invasion of breast cancer cells and set out to investigate whether obesity-driven changes in ECM could identify novel drivers of invasion and metastasis in breast cancer. We performed proteomics of the mammary fat pads of both lean and obese mice and identified the entire landscape of obesity-driven ECM changes. In particular, we focused on Collagen VI, an ECM protein secreted by adipocytes in mammary tissues. Collagen VI is upregulated in the ECM of obese and tumor-bearing mice and is associated with poor outcome in human breast cancer. We found that Collagen VI drives adhesion, migration and invasion of several human breast cancer cell lines via crosstalk between the adhesion receptor NG2 and the receptor tyrosine kinase EGFR, and activation of MAPK signaling. Overall, these studies demonstrate that obesity can have profound effects on the ECM composition of tissues, which in turn can promote local invasion and metastasis.

Este artículo se encuentra disponible en la siguiente URL: https://www.mdpi.com/2073-4409/10/5/1016 Este artículo pertenece al número especial "Highlights in Autophagy: From Basic Mechanisms to Human Disorder Treatments". An imbalance in the storage and breakdown of hepatic lipid droplet (LD) triglyceride (TAG) leads to hepatic steatosis, a defining feature of non-alcoholic fatty liver disease (NAFLD). The two primary cellular pathways regulating hepatic TAG catabolism are lipolysis, initiated by adipose triglyceride lipase (ATGL), and lipophagy. Each of these processes requires access to the LD surface to initiate LD TAG catabolism. Ablation of perilipin 2 (PLIN2), the most abundant lipid droplet-associated protein in steatotic liver, protects mice from diet-induced NAFLD. However, the mechanisms underlaying this protection are unclear. We tested the contributions of ATGL and lipophagy mediated lipolysis to reduced hepatic TAG in mice with liver-specific PLIN2 deficiency (PLIN2LKO) fed a Western-type diet for 12 weeks. We observed enhanced autophagy in the absence of PLIN2, as determined by ex vivo p62 flux, as well as increased p62- and LC3-positive autophagic vesicles in PLIN2LKO livers and isolated primary hepatocytes. Increased levels of autophagy correlated with significant increases in cellular fatty acid (FA) oxidation in PLIN2LKO hepatocytes. We observed that inhibition of either autophagy or ATGL blunted the increased FA oxidation in PLIN2LKO hepatocytes. Additionally, combined inhibition of ATGL and autophagy reduced FA oxidation to the same extent as treatment with either inhibitor alone. In sum, these studies show that protection against NAFLD in the absence of hepatic PLIN2 is driven by the integrated actions of both ATGL and lipophagy.

The data presented here are related to the research article entitled “Overexpression of Perilipin1 protects against atheroma progression in apolipoprotein E knockout mice” [1]. This paper describes data that were obtained from perilipin 1 (PLIN1) transgenic mice (Plin1Tg) regarding atherosclerosis. The main aim of collecting the data was to clarify the role of PLIN1 in the pathophysiology of atherosclerosis. The data were collected from C57BL/6J mice, apolipoprotein E knockout mice (ApoeKO) and Plin1Tg/ApoeKO. The atherosclerotic lesion areas of aorta were 3.3 ± 1.2% in C57BL/6J mice, 14.2 ± 3.2% in ApoeKO, and 5.6 ± 1.9% in Plin1Tg/ApoeKO. Body weight, gonadal adipose mass and plasma triglyceride concentrations were comparable among the three groups [1]. Furthermore, PLIN1 overexpression did not affect the gene expressions related to cholesterol influx and efflux in macrophage. Keywords: perilipin1, PLIN1, Macrophage, Atherosclerosis

Objective Regulation of fatty acid (FA) metabolism is central to adipocyte dysfunction during diet-induced obesity (DIO). Long-chain acyl-CoA synthetase-4 (ACSL4) has been hypothesized to modulate the metabolic fates of polyunsaturated FA (PUFA), including arachidonic acid (AA), but the in vivo actions of ACSL4 are unknown. The purpose of our studies was to determine the in vivo role of adipocyte ACSL4 in regulating obesity-associated adipocyte dysfunction. Methods We developed a novel mouse model with adipocyte-specific ablation of ACSL4 (Ad-KO) using loxP Cre recombinase technology. Metabolic phenotyping of Ad-KO mice relative to their floxed littermates (ACSL4floxed) was performed, including body weight and body composition over time; insulin and glucose tolerance tests; and energy expenditure, activity, and food intake in metabolic cages. Adipocytes were isolated for ex vivo adipocyte oxygen consumption by Clark electrode and lipidomics analysis. In vitro adipocyte analysis including oxygen consumption by Seahorse and real-time PCR analysis were performed to confirm our in vivo findings. Results Ad-KO mice were protected against DIO, adipocyte death, and metabolic dysfunction. Adipocytes from Ad-KO mice fed high-fat diet (HFD) had reduced incorporation of AA into phospholipids (PL), free AA, and levels of the AA lipid peroxidation product 4-hydroxynonenal (4-HNE). Additionally, adipocytes from Ad-KO mice fed HFD had reduced p53 activation and increased adipocyte oxygen consumption (OCR), which we demonstrated are direct effects of 4-HNE on adipocytes in vitro. Conclusion These studies are the first to elucidate ACSL4's in vivo actions to regulate the incorporation of AA into PL and downstream effects on DIO-associated adipocyte dysfunction. By reducing the incorporation of AA into PL and free fatty acid pools in adipocytes, Ad-KO mice were significantly protected against HFD-induced increases in adipose and liver fat accumulation, adipocyte death, gonadal white adipose tissue (gWAT) inflammation, and insulin resistance (IR). Additionally, deficiency of adipocyte ACSL4 expression in mice fed a HFD resulted in increased gWAT adipocyte OCR and whole body energy expenditure (EE)., Highlights • ACSL4 expression is upregulated in murine white adipocytes during diet-induced obesity. • Mice with adipocyte-specific ablation of ACSL4 (Ad-KO) are protected against diet-induced obesity, adipocyte death and metabolic dysfunction. • Lipidomics profiling of isolated adipocytes from Ad-KO mice fed a high-fat diet (HFD) had reduced arachidonic acid (AA) in phospholipids. • Adipocytes from Ad-KO mice fed HFD had reduced free AA and levels of the AA lipid peroxidation product 4-hydroxynonenal (4-HNE). • Adipocytes from Ad-KO mice fed HFD had reduced p53 activation and increased adipocyte oxygen consumption (OCR). • P53 activation and inhibited adipocyte OCR are direct effects of 4-HNE on adipocytes in vitro.

Background and aims: Perilipin1 (PLIN1), a lipid droplet-associated protein, plays an important role in the regulation of lipolysis and lipid storage in adipocytes. PLIN1 has recently been reported to be expressed in macrophages within atheroma plaques, suggesting PLIN1 may play a role in the accumulation of lipids at the arterial wall and in the development of atherosclerosis. To clarify the role of PLIN1 in the pathophysiology of atherosclerosis, we assessed the progression of atherosclerosis in PLIN1 transgenic mice (Plin1Tg). Methods: Plin1Tg were crossed with apolipoprotein E knockout mice (ApoeKO). C57BL/6J mice, ApoeKO and Plin1Tg/ApoeKO received a normal chow diet for 20 weeks. Body weight, gonadal fat mass and plasma lipid concentrations were measured. Aortas were collected for quantification of atheroma lesions and histological analysis by Oil Red O staining. Results: Body weight, gonadal adipose mass and plasma triglyceride concentrations were not significantly different among the three groups. In contrast, the atherosclerotic lesion area was significantly increased in ApoeKO (14.2 +/- 3.2%; p

The mechanisms facilitating hypertension in diabetes still remain to be elucidated. Nonalcoholic fatty liver disease (NAFLD), which is a higher risk factor for insulin resistance, shares many predisposing factors with diabetes. However, little work has been performed on the pathogenesis of hypertension in type 2 diabetes (T2DM) with NAFLD. The aim of this study is to investigate the prevalence of hypertension in different glycemic statuses and to analyze relationships between NAFLD, metabolic risks, and hypertension within a large community-based population after informed written consent. A total of 9473 subjects aged over 45 years, including 1648 patients with T2DM, were enrolled in this cross-sectional study. Clinical and biochemical parameters of all participants were determined. The results suggested that the patients with prediabetes or T2DM were with higher risks to have hypertension. T2DM with NAFLD had significantly higher levels of blood pressure, triglyceride, uric acid, and HOMA-IR than those without NAFLD. Data analyses suggested that hypertriglyceridemia [OR = 1.773 (1.396, 2.251)], NAFLD [OR = 2.344 (1.736, 3.165)], hyperuricemia [OR = 1.474 (1.079, 2.012)], and insulin resistance [OR = 1.948 (1.540, 2.465)] were associated with the higher prevalence of hypertension independent of other metabolic risk factors in type 2 diabetes. Further studies are needed to focus on these associations.

OBJECTIVES: We sought to identify the role of gut microbiota in the previously discovered relationship between a high glycemic diet and the development of retinal damage and metabolic health outcomes in aged mice. METHODS: Male C57Bl6/J mice aged 12 months were fed equal amounts of a high glycemic (HG) or low glycemic (LG) diet for 12 months. The compositions of the diets were identical apart from the starch, which was 100% amylopectin in the HG diet and 30% amylopectin/70% amylose in the LG diet. Within each diet, mice were assigned to one of three treatment conditions: antibiotic ablation of gut microbiota (HGabx or LGabx), weekly fecal microbiota transplants (FMT) from donor control mice fed the alternate diet (HG[tLG] or LG[tHG]), or a control group. Mice were weighed weekly and feces and urine were collected at regular intervals for microbiome and metabolome analysis respectively. Mice underwent MRIs to determine body composition, intraperitoneal glucose tolerance tests to determine glycemic responses, and eye fundus imaging and fluorescein angiography to evaluate the health of the retina and retinal vasculature. RESULTS: Compared with LG-fed controls, the HG-fed controls had significantly increased body fat mass, decreased insulin sensitivity, and an increased prevalence of retinal damage including hypopigmentation and vascular tortuosity. There was no significant difference in body weight between the HGabx and LGabx group throughout the study. The LGabx group had a significantly higher body weight and the HGAbx had significantly lower body weight than their respective control groups throughout the study. The LGabx group had the highest prevalence of abnormal retinal findings. Survival was significantly decreased in the HGabx mice compared with mice of all other groups of mice, and most died suddenly and presented with an enlarged and hemorrhagic cecum. There was no significant effect of the FMT on body weight or body composition compared with the control mice. The HG[tLG] group had improved insulin sensitivity relative to the HG controls. CONCLUSIONS: Gut microbiota mediate the relationship between the glycemic response to the diet and health outcomes such as obesity, insulin sensitivity, eye health, and survival. FUNDING SOURCES: BrightFocus Foundation, USDA/NIFA AFRI grant 2015-05470, USDA contract 1950-510000-060-03A from ARS, Stanley N. Gershoff Scholarship.

BACKGROUND: Menaquinone-4 (MK4), a vitamin K metabolite, is converted from phylloquinone through a process that requires intermediates of endogenous cholesterol production. Recent evidence suggests that MK4 is involved in kidney function. OBJECTIVE: The purpose of this study was to determine the effect of atorvastatin treatment on MK4 formation in young and old male mice. METHODS: C57BL/6 male mice (4-mo-old and 20-mo-old) were randomly assigned to either a diet containing 300 mg atorvastatin/kg with 3 mg phylloquinone/kg or a control diet containing 3 mg phylloquinone/kg for 8 wk. During week 8, all mice received deuterium-labeled phylloquinone in the diet. Labeled and unlabeled phylloquinone and MK4 in liver, kidney, brain, and intestine were measured by atmospheric pressure chemical ionization LC/MS. 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase gene expression was quantified by reverse transcriptase-PCR. Tissue MK4 and phylloquinone concentrations were compared between atorvastatin treatment groups with use of general linear models. RESULTS: There was no age-treatment interaction on MK4 tissue concentrations. In atorvastatin-treated mice, total MK4 and percentage of deuterium-labeled MK4 in kidney were both approximately 45% lower compared to values in mice not given atorvastatin (all P

Objective The family of acyl-CoA synthetase enzymes (ACSL) activates fatty acids within cells to generate long chain fatty acyl CoA (FACoA). The differing metabolic fates of FACoAs such as incorporation into neutral lipids, phospholipids, and oxidation pathways are differentially regulated by the ACSL isoforms. In vitro studies have suggested a role for ACSL5 in triglyceride synthesis; however, we have limited understanding of the in vivo actions of this ACSL isoform. Methods To elucidate the in vivo actions of ACSL5 we generated a line of mice in which ACSL5 expression was ablated in all tissues (ACSL5−/−). Results Ablation of ACSL5 reduced ACSL activity by ∼80% in jejunal mucosa, ∼50% in liver, and ∼37% in brown adipose tissue lysates. Body composition studies revealed that ACSL5−/−, as compared to control ACSL5loxP/loxP, mice had significantly reduced fat mass and adipose fat pad weights. Indirect calorimetry studies demonstrated that ACSL5−/− had increased metabolic rates, and in the dark phase, increased respiratory quotient. In ACSL5−/− mice, fasting glucose and serum triglyceride were reduced; and insulin sensitivity was improved during an insulin tolerance test. Both hepatic mRNA (∼16-fold) and serum levels of fibroblast growth factor 21 (FGF21) (∼13-fold) were increased in ACSL5−/− as compared to ACSL5loxP/loxP. Consistent with increased FGF21 serum levels, uncoupling protein-1 gene (Ucp1) and PPAR-gamma coactivator 1-alpha gene (Pgc1α) transcript levels were increased in gonadal adipose tissue. To further evaluate ACSL5 function in intestine, mice were gavaged with an olive oil bolus; and the rate of triglyceride appearance in serum was found to be delayed in ACSL5−/− mice as compared to control mice. Conclusions In summary, ACSL5−/− mice have increased hepatic and serum FGF21 levels, reduced adiposity, improved insulin sensitivity, increased energy expenditure and delayed triglyceride absorption. These studies suggest that ACSL5 is an important regulator of whole-body energy metabolism and ablation of ACSL5 may antagonize the development of obesity and insulin resistance., Graphical abstract, Highlights • Role of acyl CoA synthetase 5 (ACSL5) in systemic metabolism was studied in an ACSL5 deficient mouse. • ACSL5 deficiency reduced total ACSL activity in liver, intestine, and brown adipose tissue. • ACSL5 deficient mice had increased hepatic and circulating FGF21 expression and energy expenditure. • ACSL5 deficient mice demonstrated delayed triglyceride absorption.

OBJECTIVES: High glycemic index diet has been demonstrated to induce obesity and insulin resistance. The role of gut microbiota, as a key mediator of several metabolic syndromes, has not been elucidated. The objective of this project is to understand the effect of gut microbiota in a high-glycemic diet-induced obesity and associated metabolic complications. METHODS: Male C57Bl6/J mice aged 8–9 weeks were fed with a high-glycemic diet (HG, amylopectin-based) or low-glycemic diet (LG, amylose-based) ad libitum for 8 weeks. Body composition was determined by MRIs. Intraperitoneal glucose tolerance tests were performed after 6 weeks on diet. Mice were euthanized after 8 weeks on diet. RESULTS: After two weeks on diet, the HG group (n = 12) mice had a significantly higher body fat mass by MRI analysis, as compared to the LG group (n = 12) despite having similar body weight and equal food consumption. After 6 weeks, mice in the HG group had a significantly higher fasting glucose level compared to the LG group. There was no difference in fasting triglyceride level. Gonadal, subcutaneous and brown fat adipose tissue weight were significantly higher in the HG group after 8 weeks on diet. 16S rDNA sequencing on feces showed that the HG mice have a significantly higher Shannon diversity and different overall microbiome structure compared to the LG mice. The microbial community in the LG group was predominated by Bacteroidetes, particularly by Bacteroides thetaiotaomicron (Relative abundance 48.65 ± 12.88% versus HG 14.69 ± 0.07%), while the HG group was predominated by Firmicutes. Ongoing analysis will investigate the relative role of key microbial taxa on obesity and glucose homeostasis. CONCLUSIONS: Consuming two weeks of a high-glycemic index diet induced adiposity and hyperglycemia along with a shift of the overall gut microbiota composition compared to a low-glycemic index diet. FUNDING SOURCES: NIH, USDA, Robert C and Veronica Atkins Foundation

Whereas white adipose tissue depots contribute to the development of metabolic diseases, brown and beige adipose tissue has beneficial metabolic effects. Here we show that CDK6 regulates beige adipocyte formation. We demonstrate that mice lacking the CDK6 protein or its kinase domain (K43M) exhibit significant increases beige cell formation, enhanced energy expenditure, better glucose tolerance, and improved insulin sensitivity, and are more resistant to high-fat diet-induced obesity. Re-expression of CDK6 in Cdk6−/− mature or precursor cells, or ablation of RUNX1 in K43M mature or precursor cells, reverses these phenotypes. Furthermore, RUNX1 positively regulates the expression of Ucp-1 and Pgc1α by binding to proximal promoter regions. Our findings indicate that CDK6 kinase activity negatively regulates the conversion of fat-storing cells into fat-burning cells by suppressing RUNX1, and suggest that CDK6 may be a therapeutic target for the treatment of obesity and related metabolic diseases., Beige adipocytes can arise from transdifferentiation of mature white adipocytes. Here the authors identify CDK6 as a key molecule involved in the white-to-beige adipocyte transdifferentiation and, therefore, as a regulator of organismal energy homeostasis in mice.

Chronic and excessive alcohol consumption leads to the development of alcoholic liver disease (ALD) and greatly increases the risk of liver cancer. Induction of the cytochrome p450 2E1 (CYP2E1) enzyme by chronic and excessive alcohol intake is known to play a role in the pathogenesis of ALD. High intake of tomatoes, rich in the carotenoid lycopene, is associated with a decreased risk of chronic disease. We investigated the effects of whole tomato (tomato powder, TP), partial tomato (tomato extract, TE), and purified lycopene (LYC) against ALD development in rats. Of the three supplements, only TP reduced the severity of alcohol-induced steatosis, hepatic inflammatory foci, and CYP2E1 protein levels. TE had no effect on these outcomes and LYC greatly increased inflammatory foci in alcohol-fed rats. To further support the protective effect of TP against ALD, TP was supplemented in a carcinogen (diethylnitrosamine, DEN)-initiated alcohol-promoted mouse model. In addition to reduced steatosis and inflammatory foci, TP abolished the presence of preneoplastic foci of altered hepatocytes in DEN-injected mice fed alcohol. These reductions were associated with decreased hepatic CYP2E1 protein levels, restored levels of peroxisome proliferator-activated receptor-α and downstream gene expression, decreased inflammatory gene expression, and reduced endoplasmic reticulum stress markers. These data provide strong evidence for TP as an effective whole food prevention strategy against ALD.

Women gain weight and their diabetes risk increases as they transition through menopause; these changes can be partly reversed by hormone therapy. However, the underlying molecular mechanisms mediating these effects are unknown. A novel knock-in mouse line with the selective blockade of the membrane-initiated estrogen receptor (ER) pathway was used, and we found that the lack of this pathway precipitated excessive weight gain and glucose intolerance independent of food intake and that this was accompanied by impaired adaptive thermogenesis and reduced physical activity. Notably, the central activation of protein phosphatase (PP) 2A improved metabolic disorders induced by the lack of membrane-initiated ER signaling. Furthermore, the antiobesity effect of estrogen replacement in a murine menopause model was abolished by central PP2A inactivation. These findings define a critical role for membrane-initiated ER signaling in metabolic homeostasis via the central action of PP2A.

Summary: The central mechanisms controlling glucose and lipid homeostasis are inadequately understood. We show that α2δ-1 is an essential regulator of glucose and lipid balance, acting in steroidogenic factor-1 (SF1) neurons of the ventromedial hypothalamus (VMH). These effects are body weight independent and involve regulation of SF1+ neuronal activity and sympathetic output to metabolic tissues. Accordingly, mice with α2δ-1 deletion in SF1 neurons exhibit glucose intolerance, altered lipolysis, and decreased cholesterol content in adipose tissue despite normal energy balance regulation. Profound reductions in the firing rate of SF1 neurons, decreased sympathetic output, and elevated circulating levels of serotonin are associated with these alterations. Normal calcium currents but reduced excitatory postsynaptic currents in mutant SF1 neurons implicate α2δ-1 in the promotion of excitatory synaptogenesis separate from its canonical role as a calcium channel subunit. Collectively, these findings identify an essential mechanism that regulates VMH neuronal activity and glycemic and lipid control and may be a target for tackling metabolic disease. : Felsted et al. show a required role of the calcium channel subunit and thrombospondin receptor α2δ-1 in regulating glucose and lipid homeostasis in the ventromedial hypothalamus (VMH). These effects are caused by regulation of SF1+ neuronal activity in the VMH through non-canonical mechanisms and concomitant influences on sympathetic output. Keywords: diabetes, VMH, hypothalamus, glucose, norepinephrine, serotonin, excitability, lipid, SF1

Sirtuin 1 (SIRT1) has been reported to protect against nonalcoholic fatty liver disease (NAFLD) development. The mechanism of how SIRT1 deacetylase activity affects NAFLD has not been well investigated. The current investigation addressed the causal effect of systemic SIRT1 activity on NAFLD development and the underlying mechanism involved in both liver and mesenteric adipose tissue (MAT). Both SIRT1 homozygous mice ablated the catalytic activity (sirt1Y/Y) and their corresponding wild type littermates (WT) were fed a high fat diet (HFD, 60% calories from fat) for 34weeks. Sirt1Y/Y mice showed significantly higher level of hepatic triglyceride which was accompanied with higher levels of SREBP-1 and SCD1and decreased phosphorylation of LKB1 and AMPK in the liver. Compared with WT mice, mRNA expression of lipogenic genes (lxrα, srebp-1c, scd1 and fas) in the MAT increased significantly in sirt1Y/Y mice. Fatty acid oxidation biomarkers (acox1, acox3, cpt, ucp1, sirt3) in both liver and MAT were comparable between groups. Interestingly, we observed that in sirt1Y/Y mice, the mRNA level of hormone sensitive lipase (hsl), adipose triglyceride lipase (atgl) and perilipin-2 (plin-2), all involved in lipolysis, significantly increased in MAT, but not in epididymal adipose tissue. These changes positively correlated with circulating free fatty acid (FFA) concentrations and higher hepatic mRNA expression of cd36 for FFA uptake. The present study has provided novel evidence to suggest that under HFD-induced metabolic surplus, the lack of SIRT1 catalytic activity promotes release of FFA from MAT and escalate NAFLD by interfering with lipid homeostasis in both liver and MAT.

Sirtuin 1 (SIRT1) has been reported to protect against nonalcoholic fatty liver disease (NAFLD) development. The mechanism of how SIRT1 deacetylase activity affects NAFLD has not been well investigated. The current investigation addressed the causal effect of systemic SIRT1 activity on NAFLD development and the underlying mechanism involved in both liver and mesenteric adipose tissue (MAT). Both SIRT1 homozygous mice ablated the catalytic activity (sirt1Y/Y) and their corresponding wild type littermates (WT) were fed a high fat diet (HFD, 60% calories from fat) for 34weeks. Sirt1Y/Y mice showed significantly higher level of hepatic triglyceride which was accompanied with higher levels of SREBP-1 and SCD1and decreased phosphorylation of LKB1 and AMPK in the liver. Compared with WT mice, mRNA expression of lipogenic genes (lxrα, srebp-1c, scd1 and fas) in the MAT increased significantly in sirt1Y/Y mice. Fatty acid oxidation biomarkers (acox1, acox3, cpt, ucp1, sirt3) in both liver and MAT were comparable between groups. Interestingly, we observed that in sirt1Y/Y mice, the mRNA level of hormone sensitive lipase (hsl), adipose triglyceride lipase (atgl) and perilipin-2 (plin-2), all involved in lipolysis, significantly increased in MAT, but not in epididymal adipose tissue. These changes positively correlated with circulating free fatty acid (FFA) concentrations and higher hepatic mRNA expression of cd36 for FFA uptake. The present study has provided novel evidence to suggest that under HFD-induced metabolic surplus, the lack of SIRT1 catalytic activity promotes release of FFA from MAT and escalate NAFLD by interfering with lipid homeostasis in both liver and MAT.

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder in women. Gut microbiota has been implicated to play a critical role in metabolic diseases and may modulate the secretion of mediators of the brain–gut axis. Interaction between gut microbiota and the endocrine and biochemical disturbances in PCOS still remains elusive. Here, we showed an altered gut microbiota significantly correlated with PCOS phenotype. There were 33 patients with PCOS (non-obese PCOS individuals, PN, n = 12; obese PCOS individuals, PO, n = 21) as well as 15 control subjects (non-obese control individuals, CN, n = 9; obese control individuals, CO, n = 6) enrolled in our study. The plasma levels of serotonin, ghrelin, and peptide YY (PYY) were significantly decreased in patients with PCOS compared with controls, and have a significantly negative correlation with waist circumference and testosterone. Sequencing of the V3–V4 region of the 16S rRNA gene in fecal samples revealed the substantial differences of gut microbial species between the PCOS and non-obese controls. Bacterial species were clustered into 23 co-abundance groups (CAGs) based on the SparCC correlation coefficients of their relative abundance. The CAGs increased in PCOS, including the bacteria belonging to Bacteroides, Escherichia/Shigella and Streptococcus, were negatively correlated with ghrelin, and positively correlated with testosterone and BMI. Furthermore, the CAGs that were decreased in PCOS, including the bacteria from Akkermansia and Ruminococcaceae, showed opposite relationship with body-weight, sex-hormone, and brain–gut peptides. In conclusion, gut microbial dysbiosis in women with PCOS is associated with the disease phenotypes.

The study is aimed to investigate the pathogenesis underlying the increased prevalence of thyroid nodule (TN) in different levels of metabolic syndrome (MetS) components and analyze the relationships between TN and MetS components. A total of 6,798 subjects, including 2201 patients with TN, were enrolled in this study. Anthropometric, biochemical, thyroid ultrasonographic, and other metabolic parameters were all measured. There was obviously sexual difference in the prevalence of TN (males 26.0%, females 38.5%, resp.). The prevalence of TN in hyperuricemia (45.7% versus 37.4%, P = 0.001), NAFLD (41.2% versus 36.4%, P < 0.05), and MetS (41.4% versus 35.4%, P < 0.001) groups was significantly increased only in females. Insulin resistance [OR = 1.31 (1.15, 1.49)], MetS [OR = 1.18 (1.03, 1.35)], and diabetes [OR = 1.25 (1.06, 1.48)] were all independent risk factors for TN in total subjects, whereas, after stratified analysis of gender, MetS [OR = 1.29, (1.09, 1.53)] and diabetes [OR = 1.47, (1.17, 1.84)] are still strongly and independently associated with the higher risks of TN in female subjects, but not in males. Our results suggest that the components of MetS might associate with the higher risks of TN in women than in men, but further cohort study of this gender disparity in the association between TN and MetS is required.

Nonalcoholic fatty liver disease is a major public health concern in the obese and type 2 diabetic populations. The high-fat lard diet induces obesity and fatty liver in C57BL/6J mice and suppresses expression of the PPAR-target gene, FA elongase 5 (Elovl5). Elovl5 plays a key role in MUFA and PUFA synthesis. Increasing hepatic Elovl5 activity in obese mice lowered hepatic TGs and endoplasmic reticulum stress markers (X-box binding protein 1 and cAMP-dependent transcription factor 6α) and increased TG catabolism and fatty acyl carnitines. Increased hepatic Elovl5 activity did not increase hepatic capacity for β-oxidation. Elovl5 effects on hepatic TG catabolism were linked to increased protein levels of adipocyte TG lipase (ATGL) and comparative gene identification 58 (CGI58). Elevated hepatic Elovl5 activity also induced the expression of some (pyruvate dehydrogenase kinase 4 and fibroblast growth factor 21), but not other cytochrome P450 4A10 (CYP4A10), PPAR-target genes. FA products of Elovl5 activity increased ATGL, but not CGI58, mRNA through PPARβ-dependent mechanisms in human HepG2 cells. Treatment of mouse AML12 hepatocytes with the PPARβ agonist (GW0742) decreased (14)C-18:2,n-6 in TGs but did not affect β-oxidation. These studies establish that Elovl5 activity regulates hepatic levels of FAs controlling PPARβ activity, ATGL expression, and TG catabolism, but not FA oxidation.

Objective To examine the relationship between dietary characteristics of self-selected foods and energy balance in a cafeteria-style dining hall. Methods Ad libitum dietary intake from a self-selection menu was measured over two days in 151 adults (70% female, mean age 41 years, mean BMI 24.9 kg/m2). The associations of dietary variables with energy balance (calculated as measured energy intake/predicted energy requirements, pER) were assessed. Results Measured energy intake was significantly correlated with pER (R2=0.83, P

As a new hormone, betatrophin has gained attention as a potential new target to combat insulin resistance (IR) and diabetes. Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disorder among women of the reproductive age with long term sequelae which include IR and metabolic syndrome. The aim of this study is to evaluate the circulating plasma betatrophin levels in overweight/obese or lean women with or without PCOS and also to elucidate possible correlations with anthropometric and metabolic parameters. Thirty-two patients with PCOS as well as fifty-three control subjects were enrolled after obtaining informed written consent. Clinical and biochemical parameters of all subjects were determined. Plasma adiponectin, GLP-1 and betatrophin levels were measured by ELISA. Plasma betatrophin levels were significantly increased in lean patients with PCOS compared with lean and obese controls. Moreover, in PCOS group, betatrophin levels were significantly negatively correlated with waist hip ratio (WHR), fasting insulin level (FINS) and HOMA-IR, whereas, significantly positively correlated with adiponectin level. Multiple regression analysis showed that HOMA-IR was an independent factor influencing serum betatrophin levels. Further follow-up studies are needed to highlight whether and how increased betatrophin secretion play an important role in IR and carbohydrates metabolism in patients with PCOS.

The cytoplasmic lipid droplet (CLD) protein perilipin-2 (Plin2) is expressed in multiple nonadipose tissues, where it is thought to play a role in regulating their lipid storage properties. However, the extent to which Plin2 functions in nutrient utilization and metabolism, or how it influences the consequences of over-feeding, remains unclear. In this study, we demonstrate that the absence of Plin2 prevents high-fat diet(HFD)-induced obesity in male and female mice. This response is associated with increased formation of subcutaneous beige adipocyte cells with uncoupling protein 1 expression, and amelioration of inflammatory foci formation in white adipose tissue and steatosis in the liver. Experiments demonstrate that Plin2 loss results in reduced energy intake and increased physical activity in response to HFD feeding. Our study provides the first evidence that Plin2 contributes to HFD-induced obesity by modulating food intake, and that its absence prevents obesity-associated adipose tissue inflammatory foci and liver steatosis.

Body weight (BW) and body composition were examined in CD-1 mice exposed perinatally or perinatally and peripubertally to 0, 0.25, 2.5, 25, or 250 μg BPA/kg BW/day. Our goal was to identify the BPA dose (s) and the exposure window(s) that increased BW and adiposity, and to assess potential sex differences in this response. Both perinatal exposure alone and perinatal plus peripubertal exposure to environmentally relevant levels of BPA resulted in lasting effects on body weight and body composition. The effects were dose specific and sex specific and were influenced by the precise window of BPA exposure. The addition of peripubertal BPA exposure following the initial perinatal exposure exacerbated adverse effects in the females but appeared to reduce differences in body weight and body composition between control and BPA exposed males. Some effects of BPA on body weight and body composition showed a non-linear dose response.

Inflammation associated with obesity may play a role in colorectal carcinogenesis, but the underlying mechanism remains unclear. This study investigated whether the Wnt pathway, an intracellular signaling cascade that plays a critical role in colorectal carcinogenesis, is activated by obesity-induced elevation of the inflammatory cytokine tumor necrosis factor-alpha (TNF-α). Animal studies were conducted on C57BL/6 mice, and obesity was induced by utilizing a high-fat diet (60% kcal). An inflammation-specific microarray was performed, and results were confirmed with real-time polymerase chain reaction. The array revealed that diet-induced obesity increased the expression of TNF-α in the colon by 72% (P=.004) and that of interleukin-18 by 41% (P=.023). The concentration of colonic TNF-α protein, determined by ex vivo culture assay, was nearly doubled in the obese animals (P=.002). The phosphorylation of glycogen synthase kinase 3 beta (GSK3β), an important intermediary inhibitor of Wnt signaling and a potential target of TNF-α, was quantitated by immunohistochemistry. The inactivated (phosphorylated) form of GSK3β was elevated in the colonic mucosa of obese mice (P

Heritability estimates of human body fatness vary widely and the contribution of body composition methodology to this variability is unknown. The effect of body composition methodology on estimations of genetic and environmental contributions to body fatness variation was examined in 78 adult male and female monozygotic twin pairs reared apart or together. Body composition was assessed by six methods – body mass index (BMI), dual energy x-ray absorptiometry (DXA), underwater weighing (UWW), total body water (TBW), bioelectric impedance (BIA), and skinfold thickness. Body fatness was expressed as percent body fat, fat mass, and fat mass/height2 to assess the effect of body fatness expression on heritability estimates. Model-fitting multivariate analyses were used to assess the genetic and environmental components of variance. Mean BMI was 24.5 kg/m2 (range of 17.8–43.4 kg/m2). There was a significant effect of body composition methodology (p

This study examined the relative influence of genetic versus environmental factors on specific aspects of eating behavior. Adult monozygotic twins (22 pairs and 3 singleton reared apart, 38 pairs and 9 singleton reared together, age 18-76 years, BMI 17-43 kg/m 2 ) completed the Three Factor Eating Questionnaire. Genetic and environmental variance components were determined for the three eating behavior constructs and their subscales using model-fitting univariate and multivariate analyses. Unique environmental factors had a substantial influence on all eating behavior variables (ex- plaining 45-71% of variance), and most strongly influenced external locus for hunger and strategic dieting behavior of re- straint (explaining 71% and 69% of variance, respectively). Genetic factors had a statistically significant influence on only 4 variables: restraint, emotional susceptibility to disinhibition, situational susceptibility to disinhibition, and internal locus for hunger (heritabilities were 52%, 55%, 38% and 50%, respectively). Common environmental factors did not statisti- cally significantly influence any variable assessed in this study. In addition, multivariate analyses showed that disinhibi- tion and hunger share a common influence, while restraint appears to be a distinct construct. These findings suggest that the majority of variation in eating behavior variables is associated with unique environmental factors, and highlights the importance of the environment in facilitating specific eating behaviors that may promote excess weight gain.

The aim of this study was to assess multifactorial β-cell responses to metabolic perturbations in primary rat and human islets. Treatment of dispersed rat islet cells with elevated glucose and free fatty acids (FFAs, oleate:palmitate = 1:1 v/v) resulted in increases in the size and the number of lipid droplets in β-cells in a time- and concentration-dependent manner. Glucose and FFAs synergistically stimulated the nutrient sensor mammalian target of rapamycin complex 1 (mTORC1). A potent mTORC1 inhibitor, rapamycin (25 nM), significantly reduced triglyceride accumulation in rat islets. Importantly, lipid droplets accumulated only in β-cells but not in α-cells in an mTORC1-dependent manner. Nutrient activation of mTORC1 upregulated the expression of adipose differentiation related protein (ADRP), known to stabilize lipid droplets. Rat islet size and new DNA synthesis also increased under nutrient overload. Insulin secretion into the culture medium increased steadily over a 4-day period without any significant difference between glucose (10 mM) alone and the combination of glucose (10 mM) and FFAs (240 μM). Insulin content and insulin biosynthesis, however, were significantly reduced under the combination of nutrients compared with glucose alone. Elevated nutrients also stimulated lipid droplet formation in human islets in an mTORC1-dependent manner. Unlike rat islets, however, human islets did not increase in size under nutrient overload despite a normal response to nutrients in releasing insulin. The different responses of islet cell growth under nutrient overload appear to impact insulin biosynthesis and storage differently in rat and human islets.

OBJECTIVE To examine in obese young adults the influence of ethnicity and subcutaneous adipose tissue (SAT) inflammation on hepatic fat fraction (HFF), visceral adipose tissue (VAT) deposition, insulin sensitivity (SI), β-cell function, and SAT gene expression. RESEARCH DESIGN AND METHODS SAT biopsies were obtained from 36 obese young adults (20 Hispanics, 16 African Americans) to measure crown-like structures (CLS), reflecting SAT inflammation. SAT, VAT, and HFF were measured by magnetic resonance imaging, and SI and β-cell function (disposition index [DI]) were measured by intravenous glucose tolerance test. SAT gene expression was assessed using Illumina microarrays. RESULTS Participants with CLS in SAT (n = 16) were similar to those without CLS in terms of ethnicity, sex, and total body fat. Individuals with CLS had greater VAT (3.7 ± 1.3 vs. 2.6 ± 1.6 L; P = 0.04), HFF (9.9 ± 7.3 vs. 5.8 ± 4.4%; P = 0.03), tumor necrosis factor-α (20.8 ± 4.8 vs. 16.2 ± 5.8 pg/mL; P = 0.01), fasting insulin (20.9 ± 10.6 vs. 9.7 ± 6.6 mU/mL; P < 0.001) and glucose (94.4 ± 9.3 vs. 86.8 ± 5.3 mg/dL; P = 0.005), and lower DI (1,559 ± 984 vs. 2,024 ± 829 ×10−4 min−1; P = 0.03). Individuals with CLS in SAT exhibited upregulation of matrix metalloproteinase-9 and monocyte antigen CD14 genes, as well as several other genes belonging to the nuclear factor-κB (NF-κB) stress pathway. CONCLUSIONS Adipose tissue inflammation was equally distributed between sexes and ethnicities. It was associated with partitioning of fat toward VAT and the liver and altered β-cell function, independent of total adiposity. Several genes belonging to the NF-κB stress pathway were upregulated, suggesting stimulation of proinflammatory mediators.

STEATOSIS, OR FATTY liver, is a common pathological feature of impaired hepatic metabolism resulting from chronic alcohol consumption, diet, toxin exposure, or metabolic disorders such as obesity and diabetes. Although often benign and reversible, it is widely believed that steatosis contributes to more advanced liver pathologies, including steatohepatitis and fibrosis. However, the precise role of steatosis in development of these pathologies remains poorly understood (Rubin and Farber, 1999). Histologically, steatosis is characterized by the accumulation of lipid droplets, composed chiefly of triacylglycerol (TAG), in the cytoplasm of hepatocytes (Cairns and Peters, 1983; Day and Yeaman, 1994). The size and lobular distribution of these cytoplasmic lipid droplets (CLD) are variable, reflecting the etiology, severity, and duration of steatosis. Large (macrovesicular) CLD are prominent in livers of individuals with chronic metabolic disorders or ethanol exposure, whereas numerous smaller (microvesicular) CLD have been associated with conditions of acute steatosis such as in Reye’s syndrome, in addition to being present in the early stages of some chronic disorders (Day and Yeaman, 1994). Although they have been hypothesized to reflect different stages of steatotic progression and represent different pathogenic risks (Day and Yeaman, 1994), it is unclear whether macrovesicular and microvesicular CLD are pathophysiologically distinct entities because information about their molecular compositions and biologic properties is limited, and the mechanisms regulating their formation and accumulation are incompletely understood. Steatosis associated with alcoholic, and many forms of nonalcoholic liver disease, is described as initiating in centrilobular areas (zone 3), with advancement to intermediate (zone 2) and periportal (zone 1) areas occurring with disease progression (Brunt, 2007; Lefkowitch, 2005). However, in certain malnutrition disorders, infections, and toxic insults, steatosis is described as originating in zone 1 (James and Day, 1998). At present, details about mechanisms underlying zone-dependent initiation and progression of steatosis are limited (Stewart et al., 2001). Activation of cell stress pathways, which can include the microsomal ethanol-oxidizing system (Cyp2E1), hypoxia, endoplasmic reticulum stress, mitochondrial dysfunction, or lipid peroxidation, appears to be a common feature of steatosis in most disorders (French, 1989). However, the individual, or collective, contributions of these processes to zone-specific promotion and progression of steatosis have not been fully established, and detailed knowledge of their specific effects on the cellular processes controlling CLD accumulation is still incomplete. Members of the perilipin (PAT) family of CLD-associated proteins, including perilipin, adipophilin (ADPH), TIP47, and S3–12, regulate TAG accumulation in eukaryotic cells, either through promotion of processes that enhance TAG synthesis and packaging in CLD (Gao and Serrero, 1999; Larigauderie et al., 2006; Robenek et al., 2006) or by controlling TAG lipolysis (Listenberger et al., 2007; Londos et al., 2005; Sztalryd et al., 2006; Wolins et al., 2006). Several lines of evidence suggest that perilipin family members may be important in the initiation and progression of steatosis. ADPH has been shown to be one of the major CLD-associated proteins in mouse livers (Wu et al., 2000), and its expression is required for induction of steatosis in mice fed high fat diets (Chang et al., 2006; Imai et al., 2007). ADPH immunofluorescence has also been shown to correlate with steatosis induced by alcohol consumption in rats (Mak et al., 2008), and ADPH, perilipin, and TIP47 have been detected on CLD in liver biopsies from patients with alcoholic and nonalcoholic liver disease by immunofluorescence (Straub et al., 2008). Evidence of functional linkage between hypoxia and ADPH transcript expression in HepG2 cells (Saarikoski et al., 2002) further suggest that genes of PAT family members may be direct targets of physiological mediators of steatosis. The possibility that PAT proteins differentially affect steatotic progression, and CLD growth is suggested by observations that PAT protein family members appear to differentially coat distinct populations of CLD in human liver biopsies (Straub et al., 2008) and by evidence from differentiating 3T3-L1 adipocytes indicating that CLD become sequentially coated by TIP47, ADPH, and perilipin as they undergo enlargement (Wolins et al., 2006). Importantly, alterations in CLD protein composition (including PAT family members) in response to lipolytic stimulation demonstrate that CLD are dynamic structures responsive to physiological stimuli (Brasaemle, 2007; Clifford et al., 2000; Gross et al., 2006). In this study, we used the well-established Lieber-DeCarli ethanol feeding model (Lieber and DeCarli, 1970) in mice to test the hypotheses that dietary ethanol induction of steatosis involves distinct alterations in CLD properties, including their protein composition, and is mediated by specific metabolic stress processes. We also investigated the relative abilities of perilipin, ADPH, and TIP47 to promote CLD accumulation in response to fat and ethanol in cell culture models in which these proteins were stably expressed. Our results demonstrate that feeding mice the Lieber-DeCarli ethanol diet (LD-Et) only modestly increased hepatic triglycerides over that of calorically matched Lieber-DeCarli control (LD-Co) diet-fed animals after 6 weeks. However, CLD in livers of LD-Et-fed mice differed markedly from those in LD-Co-fed mice in their larger size, their predominant zone 2 distribution, the presence of perilipin on their surface, and their association with ER stress and lipid peroxide adduction in hepatocytes. Our cell culture studies provide evidence that the presence of perilipin on CLD is sufficient to induce formation of large CLD. Together our data indicate that ethanol ingestion induces specific alterations in CLD protein properties that contribute to large CLD formation during hepatosteatosis.

The lipid droplet-associated fat specific protein 27 (FSP27) suppresses lipolysis and thereby enhances triglyceride accumulation in adipocytes. We and others have recently found FSP27 to be a remarkably short-lived protein (half-life, 15 min) due to its rapid ubiquitination and proteasomal degradation. Thus, we tested the hypothesis that lipolytic agents such as tumor necrosis factor-α (TNF-α) and isoproterenol modulate FSP27 levels to regulate FFA release. Consistent with this concept, we showed that the lipolytic actions of TNF-α, interleukin-1β (IL-1β), and IFN-γ are accompanied by marked decreases in FSP27 expression and lipid droplet size in mouse adipocytes. Similar depletion of FSP27 using short interfering RNA (siRNA) mimicked the lipolysis-enhancing effect of TNF-α, while maintaining stable FSP27 levels using expression of hemagglutinin epitope-tagged FSP27 blocked TNF-α-mediated lipolysis. In contrast, we show the robust lipolytic action of isoproterenol is paradoxically associated with increases in FSP27 levels and a delayed degradation rate corresponding to decreased ubiquitination. This catecholamine-mediated increase in FSP27 abundance, probably a feedback mechanism for restraining excessive lipolysis by catecholamines, is mimicked by forskolin or 8-bromo-cAMP treatment and is prevented by the protein kinase A (PKA) inhibitor KT5720 or by PKA depletion using siRNA. Taken together, these data identify the regulation of FSP27 as an important intermediate in the mechanism of lipolysis in adipocytes in response to TNF-α and isoproterenol.

Despite advances in our understanding of the ways in which nutrient oversupply and triacylglycerol (TAG) anabolism contribute to hepatic steatosis, little is known about the lipases responsible for regulating hepatic TAG turnover. Recent studies have identified adipose triglyceride lipase (ATGL) as a major lipase in adipose tissue, although its role in the liver is largely unknown. Thus, we tested the contribution of ATGL to hepatic lipid metabolism and signaling. Adenovirus-mediated knockdown of hepatic ATGL resulted in steatosis in mice and decreased hydrolysis of TAG in primary hepatocyte cultures and in vitro assays. In addition to altering TAG hydrolysis, ATGL was shown to play a significant role in partitioning hydrolyzed fatty acids between metabolic pathways. Although ATGL gain and loss of function did not alter hepatic TAG secretion, fatty acid oxidation was increased by ATGL overexpression and decreased by ATGL knockdown. The effects on fatty acid oxidation coincided with decreased expression of peroxisome proliferator-activated receptor α (PPAR-α) and its target genes in mice with suppressed hepatic ATGL expression. However, PPAR-α agonism was unable to normalize the effects of ATGL knockdown on PPAR-α target gene expression, and this suggests that ATGL influences PPAR-α activity independently of ligand-induced activation. Conclusion: Taken together, these data show that ATGL is a major hepatic TAG lipase that plays an integral role in fatty acid partitioning and signaling to control energy metabolism. (HEPATOLOGY 2011)

Autophagy is a major degradative pathway(s) by which intracellular components are delivered into the lysosomes. It is largely implicated in determining cell death and survival because it eliminates unnecessary, damaged, and/or potentially harmful cellular products and organelles and is an important source for nutrients and energy production under conditions of external nutrient deficiency. As such, autophagy has been suggested to contribute to the regulation of carbohydrate and protein metabolism during fasting. Recently, three papers implicated a role for autophagy in cellular lipid metabolism as well. This Perspectives article presents these novel findings in the context of prior studies on the role of autophagy and lysosomes in metabolic and energy regulation, discusses their points of agreement and opposing propositions, and outlines key outstanding questions.

Nonalcoholic fatty liver disease (NAFLD) occurs in 20–30% of Americans and is the most prevalent form of liver disease (1,2). NAFLD is commonly linked to hepatic and whole-body insulin resistance and, in some individuals NAFLD can lead to steatohepatitis, cirrhosis, and cancer (3). The selective hepatic insulin resistance that typically accompanies NAFLD results in increased hepatic glucose production, hepatic lipogenesis, and very low-density lipoprotein (VLDL) secretion, thereby contributing to the hyperglycemia and triglyceridemia observed in insulin-resistant and type 2 diabetic subjects. Despite their close association, NAFLD and insulin resistance can be uncoupled, suggesting that not all NAFLD is the same (4). Although dietary and environmental factors have a large influence, genetics alone or in combination with external factors also influence NAFLD etiology. A point mutation in PNPLA3 (also known as adiponutrin) is prevalent in ∼20–50% of people depending upon ethnicity and is the single best genetic predictor of NAFLD (5). A recent meta-analysis of nearly 3,000 subjects showed that carriers of the I148M mutant have 73% higher liver triacylglycerol (TAG) content compared with those with the normal I148I allele (6). In addition, the I148M variant has been associated with complications or progression of NAFLD, including development of nonalcoholic steatohepatitis, alcoholic liver disease and its progression to cirrhosis, and the severity of hepatitis C–induced steatosis (7). Despite its important role in NAFLD etiology, the physiological function of wild-type and variant PNPLA3 remains under intense debate. …

Lesions in articular cartilage can result in significant musculoskeletal morbidity and display unique biomechanical characteristics that make repair difficult, at best. Several surgical procedures have been devised in an attempt to relieve pain, restore function, and delay or stop the progression of cartilaginous lesions. Advanced MRI and ultrasonography protocols are currently used in the evaluation of tissue repair and to improve diagnostic capability. Other nonoperative modalities, such as injection of intra-articular hyaluronic acid or supplementary oral glucosamine and chondroitin sulfate, have shown potential efficacy as anti-inflammatory and symptom-modifying agents. The emerging field of tissue engineering, involving the use of a biocompatible, structurally and mechanically stable scaffold, has shown promising early results in cartilage tissue repair. Scaffolds incorporating specific cell sources and bioactive molecules have been the focus in this new exciting field. Further work is required to better understand the behavior of chondrocytes and the variables that influence their ability to heal articular lesions. The future of cartilage repair will probably involve a combination of treatments in an attempt to achieve a regenerative tissue that is both biomechanically stable and, ideally, identical to the surrounding native tissues.

The relative influence of genetics and the environment on factors associated with cardiovascular disease (CVD) and metabolic syndrome (MetS) remains unclear. We performed model-fitting analyses to quantify genetic, common environmental, and unique environmental variance components of factors associated with CVD and MetS [waist circumference, blood pressure, fasting plasma glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and fasting plasma lipids] in adult male and female monozygotic twins reared apart or together. We also investigated whether MetS components share common influences. Plasma cholesterol and triglyceride concentrations were highly heritable (56–77%, statistically significant). Waist circumference, plasma glucose and insulin, HOMA-IR, and blood pressure were moderately heritable (43–57%, statistically significant). Unique environmental factors contributed to the variance of all variables (20–38%, perforce statistically significant). Common environmental factors contributed 23, 30, and 42% (statistically significant) of the variance of waist circumference, systolic blood pressure, and plasma glucose, respectively. Two shared factors influenced MetS components; one influenced all components except HDL cholesterol, another influenced only lipid (triglyceride and HDL cholesterol) concentrations. These results suggest that genetic variance has a dominant influence on total variance of factors associated with CVD and MetS and support the proposal of one or more underlying pathologies of MetS.

Adipose tissue (AT) inflammation promotes insulin resistance (IR) and other obesity complications. AT inflammation and IR are associated with oxidative stress, adipocyte death, and the scavenging of dead adipocytes by proinflammatory CD11c+ AT macrophages (ATMPhi). We tested the hypothesis that supplementation of an obesitogenic (high-fat) diet with whole blueberry (BB) powder protects against AT inflammation and IR. Male C57Bl/6j mice were maintained for 8 wk on 1 of 3 diets: low-fat (10% of energy) diet (LFD), high-fat (60% of energy) diet (HFD) or the HFD containing 4% (wt:wt) whole BB powder (1:1 Vaccinium ashei and V. corymbosum) (HFD+B). BB supplementation (2.7% of total energy) did not affect HFD-associated alterations in energy intake, metabolic rate, body weight, or adiposity. We observed an emerging pattern of gene expression in AT of HFD mice indicating a shift toward global upregulation of inflammatory genes (tumor necrosis factor-alpha, interleukin-6, monocyte chemoattractant protein 1, inducible nitric oxide synthase), increased M1-polarized ATMPhi (CD11c+), and increased oxidative stress (reduced glutathione peroxidase 3). This shift was attenuated or nonexistent in HFD+B-fed mice. Furthermore, mice fed the HFD+B were protected from IR and hyperglycemia coincident with reductions in adipocyte death. Salutary effects of BB on adipocyte physiology and ATMPhi gene expression may reflect the ability of BB anthocyanins to alter mitogen-activated protein kinase and nuclear factor-kappaB stress signaling pathways, which regulate cell fate and inflammatory genes. These results suggest that cytoprotective and antiinflammatory actions of dietary BB can provide metabolic benefits to combat obesity-associated pathology.