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Phenotypic Cell Classification Tree

Direct interactions between tumor and immune cells mediate the antitumor effect of all modern cancer immunotherapeutic agents. Simultaneously, tumor cells have evolved mechanisms of evasion, including the downregulation of HLA-I, potentially disrupting the mechanism of action employed by many immune checkpoint inhibitors. And yet, the in situ interplay between these cells within the tumor immune microenvironment (TIME) remains elusive. Recent advances in histologic multiplex bioimaging platforms have enabled in-depth molecular characterization of single cells within spatially preserved and clinically archived tumor tissues. Herein, we applied multiplex immunofluorescence to excisional lymph node biopsies from 14 patients with metastatic melanoma who experienced clear objective responses to immunotherapy (7 complete response; 7 progressive disease) to determine distinguishing features of the TIME in the pretreatment setting. Distinct regions of the TIME were evaluated using 35 proteins probing tumor, immune, and vasculature components across 323 fields of view. Single-cell compositional analysis confirmed established prognostic immune cell types including increased prevalence of cytotoxic T cells within the tumor core fields of view of responders. Integrating single-cell quantification with the spatial arrangement of cellular neighborhoods surrounding tumor cells revealed novel, spatial immune signatures capable of stratifying TIME based on clinical response. Our analysis revealed dynamic cellular composition of the tumor-centric cellular neighborhood (TCCN) based on anatomic subregion, functional expression of HLA-I by the index tumor cell and ultimately clinical response to immunotherapy. Overall, this study provides an analytic framework to resolve the cellular complexity of the TIME, increasingly relevant to the outcomes of modern cancer immunotherapy.Significance:Findings from this work propose a novel approach to resolving clinical heterogeneity of the TIME by objectively quantifying the cellular interactions occurring in metastatic melanoma lymph node tissue utilizing multiplex immunofluorescence. This study provides an analytic and biologically derived unit of measure, the TCCN which is customizable for studying critical paracrine interactions within spatially preserved tissue of various cancers and across the spectrum of multiplex imaging modalities.

Antibody reagents and validation for MxIF panel design

Summary data of FOV distribution, single cells segmented, classified and clinical response to therapy

Virtual H&E images for whole excisional lymph node biopsies from each clinical case

Direct interactions between tumor and immune cells mediate the antitumor effect of all modern cancer immunotherapeutic agents. Simultaneously, tumor cells have evolved mechanisms of evasion, including the downregulation of HLA-I, potentially disrupting the mechanism of action employed by many immune checkpoint inhibitors. And yet, the in situ interplay between these cells within the tumor immune microenvironment (TIME) remains elusive. Recent advances in histologic multiplex bioimaging platforms have enabled in-depth molecular characterization of single cells within spatially preserved and clinically archived tumor tissues. Herein, we applied multiplex immunofluorescence to excisional lymph node biopsies from 14 patients with metastatic melanoma who experienced clear objective responses to immunotherapy (7 complete response; 7 progressive disease) to determine distinguishing features of the TIME in the pretreatment setting. Distinct regions of the TIME were evaluated using 35 proteins probing tumor, immune, and vasculature components across 323 fields of view. Single-cell compositional analysis confirmed established prognostic immune cell types including increased prevalence of cytotoxic T cells within the tumor core fields of view of responders. Integrating single-cell quantification with the spatial arrangement of cellular neighborhoods surrounding tumor cells revealed novel, spatial immune signatures capable of stratifying TIME based on clinical response. Our analysis revealed dynamic cellular composition of the tumor-centric cellular neighborhood (TCCN) based on anatomic subregion, functional expression of HLA-I by the index tumor cell and ultimately clinical response to immunotherapy. Overall, this study provides an analytic framework to resolve the cellular complexity of the TIME, increasingly relevant to the outcomes of modern cancer immunotherapy. Significance: Findings from this work propose a novel approach to resolving clinical heterogeneity of the TIME by objectively quantifying the cellular interactions occurring in metastatic melanoma lymph node tissue utilizing multiplex immunofluorescence. This study provides an analytic and biologically derived unit of measure, the TCCN which is customizable for studying critical paracrine interactions within spatially preserved tissue of various cancers and across the spectrum of multiplex imaging modalities.

Acute aerobic exercise increases reactive oxygen species and could potentially damage proteins, but exercise training (ET) enhances mitochondrial respiration irrespective of age. Here, we report a differential impact of ET on protein quality in young and older participants. Using mass spectrometry we measured oxidative damage to skeletal muscle proteins before and after 8 weeks of ET and find that young but not older participants reduced oxidative damage to both total skeletal muscle and mitochondrial proteins. Young participants showed higher total and mitochondrial derived semitryptic peptides and 26S proteasome activity indicating increased protein degradation. ET however, increased the activity of the endogenous antioxidants in older participants. ET also increased skeletal muscle content of the mitochondrial deacetylase SIRT3 in both groups. A reduction in the acetylation of isocitrate dehydrogenase 2 was observed following ET that may counteract the effect of acute oxidative stress. In conclusion aging is associated with an inability to improve skeletal muscle and mitochondrial protein quality in response to ET by increasing degradation of damaged proteins. ET does however increase muscle and mitochondrial antioxidant capacity in older individuals, which provides increased buffering from the acute oxidative effects of exercise.

We determined the effect of hyperandrogenemia as observed in polycystic ovary syndrome (PCOS) on fasting and glucose-stimulated proatherogenic inflammation markers in lean healthy reproductive-age women. Sixteen lean healthy ovulatory reproductive-age women were treated with 130 mg of DHEA or placebo (n=8 each) for 5 days. Interleukin-6 (IL-6) mRNA and IL-6 release from mononuclear cells (MNC), plasma IL-6 and C-reactive protein (CRP), and MNC-derived (matrix metalloproteinase-2) MMP-2 protein were quantified in the fasting state and 2 h after glucose ingestion, before and after treatment. Before treatment, subjects receiving dehydroepinadrosterone (DHEA) or placebo exhibited no differences in androgens, or any proatherogenic inflammation markers while fasting and after glucose ingestion. Compared with placebo, DHEA administration raised levels of testosterone, androstenedione, and DHEA-sulfate (DHEA-S), and increased the percent change from baseline in fasting IL-6 mRNA, IL-6 release, plasma IL-6, and CRP and MMP-2 protein. However, there were no differences in any of the proatherogenic inflammation markers following glucose ingestion after DHEA administration. We conclude that in lean reproductive-age women, proatherogenic inflammation in the fasting state increases after raising circulating androgens to levels observed in PCOS. However, this hyperandrogenemia-induced MNC activation does not provoke a similar response to subsequent glucose ingestion.

Insulin deprivation in type 1 diabetes (T1D) individuals increases lipolysis and plasma free fatty acids (FFA) concentration, which can stimulate synthesis of intramyocellular bioactive lipids such as ceramides (Cer) and long-chain fatty acid-CoAs (LCFa-CoAs). Ceramide was shown to decrease muscle insulin sensitivity, and at mitochondrial levels it stimulates reactive oxygen species production. Here, we show that insulin deprivation in streptozotocin diabetic C57BL/6 mice increases quadriceps muscle Cer content, which was correlated with a concomitant decrease in the body fat and increased plasma FFA, glycosylated hemoglobin level (%Hb A1c), and muscular LCFa-CoA content. The alternations were accompanied by an increase in protein expression in LCFa-CoA and Cer synthesis (FATP1/ACSVL5, CerS1, CerS5), a decrease in the expression of genes implicated in muscle insulin sensitivity (GLUT4, GYS1), and inhibition of insulin signaling cascade by Aktα and GYS3β phosphorylation under acute insulin stimulation. Both the content and composition of sarcoplasmic fraction sphingolipids were most affected by insulin deprivation, whereas mitochondrial fraction sphingolipids remained stable. The observed effects of insulin deprivation were reversed, except for content and composition of LCFa-CoA, CerS protein expression, GYS1 gene expression, and phosphorylation status of Akt and GYS3β when exogenous insulin was provided by subcutaneous insulin implants. Principal component analysis and Pearson's correlation analysis revealed close relationships between the features of the diabetic phenotype, the content of LCFa-CoAs and Cers containing C18-fatty acids in sarcoplasm, but not in mitochondria. Insulin replacement did not completely rescue the phenotype, especially regarding the content of LCFa-CoA, or proteins implicated in Cer synthesis and muscle insulin sensitivity. These persistent changes might contribute to muscle insulin resistance observed in T1D individuals.

Introduction Neutropenic fever following high-dose chemotherapy and autologous stem cell transplantation (ASCT) is a common (incidence 63-100%) and potentially life-threatening complication. Recommended time to antibiotic (TTA) administration is within 1 hr of fever onset with delays associated with significant morbidity, prolonged hospitalization, and mortality. Standard of care guidelines emphasize patient self-monitoring for fever, with instructions to seek immediate medical attention if body temperature (temp) reaches 100.4°F or higher. In this study, we evaluated if a novel wearable, continuous temp monitor, tPatch, could reliably estimate core body temp and detect fever in an outpatient setting following ASCT. Additionally, we gathered preliminary data to explore early detection and prediction of clinically relevant temp rise in this clinical setting. Methods Patients (N = 86) with hematologic malignancies (62% multiple myeloma) who underwent high-dose chemotherapy followed by ASCT at Mayo Clinic, MN were prospectively enrolled between June 2018 and March 2019. Patients (82% male) wore an axilla-placed tPatch continuously for 7 days in an outpatient setting during the post ASCT period and were asked to record self-measured oral temp in 3-4 hr intervals daily using a standardized thermometer after appropriate training . Patients followed standard of care procedures with daily clinic assessment of temp, blood counts, and vital signs. An optional patient questionnaire was given at end-of-study. A model was trained using both patient- and clinic-assessed oral temp measures to estimate core temp from 2 sensors on the tPatch device. Core temp estimates and trends were then compared to patient- and clinic-assessed measurements. Fever was defined as a temperature ≥100.4°F for at least 1 hr. Results When compared to all oral temp reads, the tPatch estimated core temp within 0.03 ± 0.7℉. Among the 86 patients, clinic-assessed fever incidence was 29.4% while tPatch-assessed incidence was 58.8%. Using all clinic-recorded temp readings as "ground truth," the sensitivity and specificity of the tPatch algorithm in detecting fevers were 88% and 86%, respectively, while patient self fever detection sensitivity was 62% and specificity 93%. With "fever episode" defined as a temp ≥100.4°F for at least 1 hr, tPatch detected 9.6 times the number of fever episodes vs. clinic reads. The average lead time of tPatch detection of clinic-recorded fevers was 3.7 hours. In 25% of all intervals between clinic temp readings, either tPatch or patients detected at least 1 fever episode. The tPatch was well-tolerated, the only adverse events reported were grade 1 skin irritation and discomfort in 4 (5%) patients. Of 65 patients who completed the survey, 95% reported the tPatch as "quite" or "somewhat" comfortable and 94% stated no difficulty in using the tPatch. Exploration of tPatch temp trends over various time intervals for use in fever prediction is ongoing. Conclusions Patient self-monitoring of temp has low sensitivity and is not feasible for long intervals of time (e.g., overnight). Continuous temperature monitoring by a wearable device overcomes these challenges and has the potential to improve early detection and consequently shorten time to antibiotic initiation. A follow-up randomized study is planned to assess the clinical benefits of continuous temp monitoring through patient and clinician alerts triggering early clinical intervention for febrile neutropenia. Figure Disclosures Vera-Aguilera: Verily Life Sciences: Research Funding. Haji-Abolhassani:Verily Life Sciences: Employment. Kulig:Verily Life Sciences: Employment. Heitz:Verily Life Sciences: Employment. Paludo:Verily Life Sciences: Research Funding; Verily Life Sciences: Research Funding; Celgene: Research Funding; Celgene: Research Funding. Ghoreyshi:Verily Life Sciences: Employment. Scheevel:Verily Life Sciences: Research Funding. Schimke:Verily Life Sciences: Research Funding. Markovic:Verily Life Sciences: Research Funding.

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) enhance insulin sensitivity and glucose homeostasis in rodent models of insulin resistance. These beneficial effects have been linked with anti-inflammatory properties, but emerging data suggest that the mechanisms may also converge on mitochondria. We evaluated the influence of dietary n-3 PUFAs on mitochondrial physiology and muscle lipid metabolites in the context of high-fat diet (HFD) in mice. Mice were fed control diets (10% fat), HFD (60% fat), or HFD with fish oil (HFD+FO, 3.4% kcal from n-3 PUFAs) for 10 wk. Body mass and fat mass increased similarly in HFD and HFD+FO, but n-3 PUFAs attenuated the glucose intolerance that developed with HFD and increased expression of genes that regulate glucose metabolism in skeletal muscle. Despite similar muscle triglyceride levels in HFD and HFD+FO, long-chain acyl-CoAs and ceramides were lower in the presence of fish oil. Mitochondrial abundance and oxidative capacity were similarly increased in HFD and HFD+FO compared with controls. Hydrogen peroxide production was similarly elevated in HFD and HFD+FO in isolated mitochondria but not in permeabilized muscle fibers, likely due to increased activity and expression of catalase. These results support a hypothesis that n-3 PUFAs protect glucose tolerance, in part by preventing the accumulation of bioactive lipid mediators that interfere with insulin action. Furthermore, the respiratory function of skeletal muscle mitochondria does not appear to be a major factor in sphingolipid accumulation, glucose intolerance, or the protective effects of n-3 PUFAs.

Context:Hyperandrogenism and oxidative stress are related in polycystic ovary syndrome (PCOS), but it is unknown whether hyperandrogenemia can activate oxidative stress.Objective:The purpose of this study was to determine the effect of oral androgen administration on fasting and glucose-stimulated leukocytic reactive oxygen species (ROS) generation, reduced nicotinamide adenine dinucleotide phosphate oxidase p47phox subunit gene expression, and plasma thiobarbituric acid-reactive substances (TBARS) in lean healthy reproductive-age women.Participants, Design, and Setting:Sixteen lean healthy ovulatory reproductive-age women were treated with 130 mg dehydroepiandrosterone (DHEA) or placebo (n = 8 each) for 5 d in this randomized, controlled, double-blind study that was performed at an an academic medical center.Main Outcome Measures:Leukocytic ROS generation, p47phox gene expression, and plasma TBARS were quantified in the fasting state and 2 h after glucose ingestion, before and after treatment.Results:Before treatment, subjects receiving DHEA or placebo exhibited no differences in androgens or any prooxidant markers while fasting and after glucose ingestion. Compared with placebo, DHEA administration raised levels of testosterone, androstenedione, and DHEA-sulfate, increased the percent change in glucose-challenged p47phox RNA content, and increased the percent change in fasting and glucose-challenged ROS generation from mononuclear cells and polymorphonuclear cells, p47phox protein content, and plasma TBARS.Conclusion:Elevation of circulating androgens comparable to what is present in PCOS increases leukocytic ROS generation, p47phox gene expression, and plasma TBARS to promote oxidative stress in lean healthy reproductive-age women. Thus, hyperandrogenemia activates and sensitizes leukocytes to glucose in this population.

To determine biological mechanisms involved in posttransplantation diabetes mellitus caused by the immunosuppressant tacrolimus (FK506).INS-1 cells and isolated rat islets were incubated with vehicle or FK506 and harvested at 24-hr intervals. Cells were assessed for viability, apoptosis, proliferation, cell insulin secretion, and content. Gene expression studies by microarray analysis, quantitative polymerase chain reaction, and motifADE analysis of the microarray data identified potential FK506-mediated pathways and regulatory motifs. Mitochondrial functions, including cell respiration, mitochondrial content, and bioenergetics were assessed.Cell replication, viability, insulin secretion, oxygen consumption, and mitochondrial content were decreased (P0.05) 1.2-, 1.27-, 1.77-, 1.32-, and 1.43-fold, respectively, after 48-hr FK506 treatment. Differences increased with time. FK506 (50 ng/mL) and cyclosporine A (800 ng/mL) had comparable effects. FK506 significantly decreased mitochondrial content and mitochondrial bioenergetics and showed a trend toward decreased oxygen consumption in isolated islets. Cell apoptosis and proliferation, mitochondrial DNA copy number, and ATP:ADP ratios were not significantly affected. Pathway analysis of microarray data showed FK506 modification of pathways involving ATP metabolism, membrane trafficking, and cytoskeleton remodeling. PGC1-α mRNA was down-regulated by FK506. MotifADE identified nuclear factor of activated T-cells, an important mediator of β-cell survival and function, as a potential factor mediating both up- and down-regulation of gene expression.At pharmacologically relevant concentrations, FK506 decreases insulin secretion and reduces mitochondrial density and function without changing apoptosis rates, suggesting that posttransplantation diabetes induced by FK506 may be mediated by its effects on mitochondrial function.

OBJECTIVE To determine whether dehydroepiandrosterone (DHEA) replacement therapy in hypoadrenal women improves performance, muscle protein accretion, and mitochondrial functions. PARTICIPANTS AND METHODS Thirty-three hypoadrenal women were enrolled in the study from May 1, 2002, through May 31, 2003. Twenty-eight completed a 12-week, prospective, randomized, placebo-controlled, crossover study with either daily placebo or 50 mg of DHEA with a 2-week washout period and then crossed over to the other treatment. Body composition, physical performance, whole-body and muscle protein metabolism, and mitochondrial functions were determined. RESULTS Administration of DHEA significantly increased plasma levels of DHEA sulfate, testosterone, and androstenedione but did not change body composition, muscle strength, peak aerobic capacity, and whole-body protein turnover or synthesis rates of mitochondrial, sarcoplasmic, or mixed muscle proteins. Muscle mitochondrial oxidative enzymes and messenger RNA (mRNA) levels of genes encoding mitochondrial proteins and nuclear transcription factors did not change after DHEA administration. However, mRNA levels of muscle myosin heavy chain 1 (P=.004), which determines muscle fiber type, and those of insulinlike growth factor binding proteins 4 and 5 significantly decreased (P=.02 and P=.03, respectively). CONCLUSION Three months of DHEA administration increased DHEA sulfate and androgen levels but had no effect on physical performance, body composition, protein metabolism, or muscle mitochondrial biogenesis in hypoadrenal women. However, lowering of mRNA levels of binding proteins of insulinlike growth factor 1 and myosin heavy chain 1 suggests potential effects of long-term treatment with DHEA on muscle fiber type. Trial Registration: clinicaltrials.gov identifier: NCT00279929

Insulin and essential amino acids (EAAs) regulate skeletal muscle protein synthesis, yet their independent effects on mitochondrial protein synthesis (MiPS) and oxidative function remain to be clearly defined.The purpose of this study was to determine the effects of high or low insulin with or without EAAs on MiPS.Thirty participants were randomized to 3 groups of 10 each with each participant studied twice. Study groups comprised (1) low and high insulin, (2) low insulin with and without EAAs, and (3) high insulin with and without EAAs.The study was conducted in an in-patient clinical research unit.Eligible participants were 18 to 45 years old, had a body mass index of25 kg/m(2), and were free of diseases and medications that might impair mitochondrial function.Low (∼ 6 μU/mL) and high (∼ 40 μU/mL) insulin levels were maintained by iv insulin infusion during a somatostatin clamp while maintaining euglycemia (4.7-5.2 mM) and replacing GH and glucagon. The EAA infusion was 5.4% NephrAmine. l-[ring-(13)C6]Phenylalanine was infused, and muscle needle biopsies were performed.Muscle MiPS, oxidative enzymes, and plasma amino acid metabolites were measured.MiPS and oxidative enzyme activities did not differ between low and high insulin (MiPS: 0.07 ± 0.009 vs 0.07 ± 0.006%/h, P = .86) or between EAAs and saline during low insulin (MiPS: 0.05 ± 0.01 vs 0.07 ± 0.01, P = .5). During high insulin, EAAs in comparison with saline increased MiPS (0.1 ± 0.01 vs 0.06 ± 0.01, P.05) and cytochrome c oxidase activity (P.05) but not citrate synthase (P = .27). EAA infusion decreased (P.05) the glucose infusion rates needed to maintain euglycemia during low (∼ 40%) and high insulin (∼ 24%).EAAs increased MiPS and oxidative enzyme activity only with high insulin concentrations.

Context:Both training and normal body mass index are associated with high insulin sensitivity, but the mechanism may be different.Objective:The aim of the study was to examine whether lean trained humans may be protected from acute free fatty acid (FFA)-induced insulin resistance compared with lean sedentary humans.Design and Setting:We conducted an interventional trial using either a 6-h lipid (20% Intralipid at 90 ml/h) or glycerol (2.25 g/100 ml at 90 ml/h) infusion along with a concurrent hyperinsulinemic-euglycemic clamp and serial muscle biopsies (0, 120, 360 min) at a clinical research unit at the University of Minnesota.Patients or Participants:The study included lean endurance-trained (n = 14) and sedentary (n = 14) individuals matched for age, gender, and body mass index.Main Outcome Measures:We measured the decline in glucose infusion rate (GIR) during the hyperinsulinemic-euglycemic clamp.Results:The trained group had higher baseline mitochondrial DNA copy number, mRNA of cytochrome C oxidase subunit 3, and insulin sensitivity (as measured by GIR) compared with the sedentary group. When FFA was acutely elevated to the upper physiological range (0.6–0.7 mEq/liter) by lipid infusion, the GIR in both activity groups declined similarly compared with their respective glycerol controls, although insulin signaling, as measured by Ser 473 pAKT/AKT, remained comparable. Specific to the trained group, the stimulatory effect of hyperinsulinemia on mitochondrial mRNA levels during the glycerol infusion was absent during the lipid infusion.Conclusions:Elevated FFA had similar effects in reducing insulin sensitivity in trained and sedentary humans. In trained participants, this decline was associated with alterations in the skeletal muscle mitochondrial mRNA response to hyperinsulinemia.

We thank Mai Persson, Charles Ford, Jaime Gransee, and Melissa Aakre for technical expertise. We are grateful to Drs. Ethan Anderson and Darryl Neufer for guidance on H2O2 production measurements; Caloric restriction (CR) mitigates many detrimental effects of aging and prolongs life span. CR has been suggested to increase mitochondrial biogenesis, thereby attenuating age-related declines in mitochondrial function, a concept that is challenged by recent studies. Here we show that lifelong CR in mice prevents age-related loss of mitochondrial oxidative capacity and efficiency, measured in isolated mitochondria and permeabilized muscle fibers. We find that these beneficial effects of CR occur without increasing mitochondrial abundance. Whole-genome expression profiling and large-scale proteomic surveys revealed expression patterns inconsistent with increased mitochondrial biogenesis, which is further supported by lower mitochondrial protein synthesis with CR. We find that CR decreases oxidant emission, increases antioxidant scavenging, and minimizes oxidative damage to DNA and protein. These results demonstrate that CR preserves mitochondrial function by protecting the integrity and function of existing cellular components rather than by increasing mitochondrial biogenesis.

Hyperandrogenism and chronic low-grade inflammation are related in polycystic ovary syndrome (PCOS), but it is unknown whether hyperandrogenemia can activate inflammation. We determined the effect of oral androgen administration on fasting and glucose-stimulated nuclear factor-κB (NF-κB) activation and expression and related markers of inflammation in mononuclear cells (MNC) of lean reproductive-age women. Sixteen lean, ovulatory reproductive-age women were treated with 130 mg of DHEA or placebo ( n = 8 each) for 5 days in a randomized, controlled, double-blind fashion. Nuclear activation of NF-κB, p65 and p105 NF-κB subunit RNA, TNFα and IL-1β mRNA, and NF-κB p65 and inhibitory-κB (IκB) protein were quantified from MNC obtained while fasting and 2 h after glucose ingestion, before and after DHEA or placebo administration. Before treatment, subjects receiving DHEA or placebo exhibited no differences in androgens or any inflammatory markers while fasting and after glucose ingestion. Compared with placebo, DHEA administration raised levels of testosterone, androstenedione, and DHEA-S, increased the percent change in fasting and glucose-challenged activated NF-κB, p65, p105, TNFα, and IL-1β RNA and p65 protein, and decreased the percent change in fasting and glucose-challenged IκB protein. We conclude that elevation of circulating androgens to the range observed in PCOS upregulates the NF-κB inflammation pathway in lean reproductive-age women. Thus, hyperandrogenemia activates and sensitizes MNC to glucose in this population.

Mitochondria are the primary site of skeletal muscle fuel metabolism and ATP production. Although insulin is a major regulator of fuel metabolism, its effect on mitochondrial ATP production is not known. Here we report increases in vastus lateralis muscle mitochondrial ATP production capacity (32–42%) in healthy humans ( P < 0.01) i.v. infused with insulin (1.5 milliunits/kg of fat-free mass per min) while clamping glucose, amino acids, glucagon, and growth hormone. Increased ATP production occurred in association with increased mRNA levels from both mitochondrial (NADH dehydrogenase subunit IV) and nuclear [cytochrome c oxidase (COX) subunit IV] genes (164–180%) encoding mitochondrial proteins ( P < 0.05). In addition, muscle mitochondrial protein synthesis, and COX and citrate synthase enzyme activities were increased by insulin ( P < 0.05). Further studies demonstrated no effect of low to high insulin levels on muscle mitochondrial ATP production for people with type 2 diabetes mellitus, whereas matched nondiabetic controls increased 16–26% ( P < 0.02) when four different substrate combinations were used. In conclusion, insulin stimulates mitochondrial oxidative phosphorylation in skeletal muscle along with synthesis of gene transcripts and mitochondrial protein in human subjects. Skeletal muscle of type 2 diabetic patients has a reduced capacity to increase ATP production with high insulin levels.

High-fat diets are reported to increase oxidative stress in a variety of tissues, whereas antioxidant supplementation prevents many diseases attributed to high-fat diet. Rodent skeletal muscle mitochondrial DNA has been shown to be a potential site of oxidative damage. We hypothesized that the effects of a high-fat diet on skeletal muscle DNA functions would be attenuated or partially reversed by antioxidant supplementation. Gene expression profiling and measurement of mitochondrial ATP production capacity were performed in skeletal muscle from male rats after feeding one of three diets (control, high-fat diet with or without antioxidants) for 36 wk. The high-fat diet altered transcript levels of 18 genes of 800 surveyed compared with the control-fed rats. Alterations included reduced expression of genes involved in free-radical scavenging and tissue development and increased expression of stress response and signal transduction genes. The magnitude of these alterations due to high-fat diet was reduced by antioxidant supplementation. Real-time PCR measurements confirmed the changes in transcript levels of cytochrome c oxidase subunit III and superoxide dismutase-1 and -2 noted by microarray approach. Mitochondrial ATP production was unaltered by dietary changes or antioxidant supplemention. It is concluded that the high-fat diet increases the transcription of genes involved in stress response but reduces those of free-radical scavenger enzymes, resulting in reduced DNA repair/metabolism (increased DNA damage). Antioxidants partially prevent these changes. Mitochondrial functions in skeletal muscle remain unaltered by the dietary intervention due to many adaptive changes in gene transcription.

Rodent skeletal muscle mitochondrial DNA has been shown to be a potential site of oxidative damage during aging. Caloric restriction (CR) is reported to reduce oxidative stress and prolong life expectancy in rodents. Gene expression profiling and measurement of mitochondrial ATP production capacity were performed in skeletal muscle of male rats after feeding them either a control diet or calorie-restricted diet (60% of control diet) for 36 wk to determine the potential mechanism of the beneficial effects of CR. CR enhanced the transcripts of genes involved in reactive oxygen free radical scavenging function, tissue development, and energy metabolism while decreasing expression of those genes involved in signal transduction, stress response, and structural and contractile proteins. Real-time PCR measurments confirmed the changes in transcript levels of cytochrome- c oxidase III, superoxide dismutase (SOD)1, and SOD2 that were noted by the microarray approach. Mitochondrial ATP production and citrate synthase were unaltered by the dietary changes. We conclude that CR alters transcript levels of several genes in skeletal muscle and that mitochondrial function in skeletal muscle remains unaltered by the dietary intervention. Alterations in transcripts of many genes involved in reactive oxygen scavenging function may contribute to the increase in longevity reported with CR.