Obesity is a primary cause of hepatic lipid accumulation, leading to nonalcoholic fatty liver disease (NAFLD). As there are no FDA-approved therapies for NAFLD treatment, weight loss through lifestyle intervention is the first-line therapy. Exercise improves hepatic function in patients with obesity related NAFLD. However, the mechanisms whereby exercise mediates the enhancement of liver function are largely unknown. This study evaluated the impact of exercise training on NAFLD in mice with obesity. At 8 weeks of age, mice were randomized to low-fat (LFD) or high-fat diet (HFD). After 4 weeks of dietary intervention, mice were randomized to either control (SED) or exercise training (ExT) with experimental diet for 10 weeks. ExT mice completed 45 minutes of moderate-intensity treadmill running 4 days/week. Body weight was measured weekly, and body composition and maximal treadmill running were evaluated at weeks 0, 4, and 14. Blood lactate accumulation was measured during the final treadmill test. Mice were euthanized 48 hours after the last exercise session for liver histopathology, blood chemistry, and ex vivo mitochondrial function analysis. Liver function was assessed via serum liver panel and quantification of hepatic lipids. High-resolution respirometry was used to determine maximal hepatic fatty acid oxidation, NADH- and succinate-linked oxidative phosphorylation (OXPHOS), and electron transfer capacity in tissue homogenates. HFD increased body mass, which was reduced with ExT. ExT increased maximal running time independent of diet. HFD worsened lactate metabolism, which was improved with ExT. HFD increased liver weight, which was decreased with ExT. HFD-induced increases in hepatic lipid and serum ALT and ALP were reversed with ExT. Hepatic mitochondrial OXPHOS and electron transfer were reduced with HFD relative to LFD. These data suggest that exercise-induced reversal of NAFLD is not mediated by hepatic mitochondrial oxidative capacity. Disclosure E.C. Heintz: None. W.S. Dantas: None. J.E. Stampley: None. G.M. Davis: None. B.A. Irving: None. C.L. Axelrod: None. J.P. Kirwan: None. Funding Nutrition Obesity Research Center (P30DK072476); Louisiana Clinical and Translational Science Center (U54GM104940); Centers of Biomedical Research Excellence (P20GM103528)
Introduction: There is immense dispute as to whether perturbations in skeletal muscle mitochondrial function contribute to the onset and progression of type 2 diabetes (T2D). The purpose of this study was to examine differences in mitochondrial dynamics, structure, and energetic function in humans across the spectrum of insulin sensitivity. Methods: 58 sedentary adults (37±12 years) were enrolled into one of three groups based upon the following criteria: (1) healthy weight without T2D (HW; BMI: 22.6±1.8 kg/m2 and HbA1c: 5.0±1.1 %); (2) overweight/obesity without T2D (Ov/Ob; BMI: 32.6±3.3 kg/m2 and HbA1c: 5.6±0.4 %); or (3) overweight/obesity with T2D (T2D; BMI: 36.1±6.5 kg/m2 and HbA1c: 6.9±0.9 %). Participants underwent a 3-day inpatient stay consisting of body composition (DXA), aerobic capacity (VO2MAX), and insulin sensitivity (hyperinsulinemic euglycemic clamp). Prior to insulin sensitivity testing, a skeletal muscle biopsy was obtained for determination of mitochondrial dynamics (Western blot), DNA content (qPCR), ultrastructure (electron microscopy), and respiratory capacity (respirometry). Comparisons were made using a one-way ANOVA with contrasts. Results: Insulin sensitivity and aerobic capacity were lower in Ov/Ob and T2D compared to HW. Markers of mitochondrial fission were higher in T2D (Drp1Ser616, MiD49), and fusion lower in T2D and Ov/Ob (Mfn2). The mitophagy marker Parkin was higher in T2D only while Pink1 was lower in T2D relative to Ov/Ob but not HW. The autophagy marker LC3II was higher in Ov/Ob. Mitochondrial content was lower in Ov/Ob and T2D relative to HW. Mitochondrial respiratory capacity was similar between groups. Conclusions: T2D is associated with heightened expression of proteins required for mitochondrial quality control and reduced mitochondrial volume despite intact respiratory function. These data support the notion that mitochondria adapt to progressive insulin resistance by increasing fragmentation to maintain bioenergetic capacity. Disclosure C. L. Axelrod: None. C. Fealy: Employee; Mission Therapeutics. C. L. Hoppel: None. J. P. Kirwan: None. W. S. Dantas: None. E. R. M. Zunica: None. K. Belmont: None. E. C. Heintz: None. G. Davuluri: None. J. T. Mey: None. M. Erickson: None. H. Fujioka: None. Funding National Institutes of Health (DK108089, GM104940)
Introduction: Obstructive sleep apnea (OSA) is a prevalent sleep disorder with high type 2 diabetes (T2D) risk. OSA therapy includes positive airway pressure (PAP) treatment, which resolves breathing events but modestly improves metabolic health. Metformin is recommended for T2D prevention but is not advocated in patients with OSA. Our pilot study evaluated the effects of metformin on glucose metabolism and mitochondrial function in OSA patients. Methods: Sixteen adults (50.5±1.6 years, BMI: 36.4±0.8 kg/m2) with OSA (apnea hypopnea index: 53.2±21.1 events/hour) were randomized to receive placebo (n=8) or metformin (n=8) treatment along with PAP for 3 months in a double-blind parallel-group design. Whole body and adipose tissue-specific insulin sensitivity (IS) was determined by oral glucose tolerance test (OGTT) . Skeletal muscle mitochondrial function was determined by high-resolution respirometry using biopsies obtained at baseline and after 3 months of treatment. Results: Change in whole body IS (Matsuda index) was not different in metformin or placebo treated groups (p=0.46) . However, improved acute phase responses during OGTT - glucose uptake (p=0.02) , insulin release (p=0.03) , and suppressed lipolysis (p=0.03) were observed with metformin treatment relative to control. Increased skeletal muscle mitochondrial function was evident with metformin relative to control. Specifically, metformin increased complex I phosphorylation and complex IV electron transfer capacity. Conclusion: Metformin treatment improves acute phase IS and insulin suppression of lipolysis in OSA patients. Strikingly, metformin improved skeletal muscle mitochondrial function independent of changes in second phase glucose disposal and BMI, indicating improved tissue metabolic function. These data suggest that in patients with OSA, improvement in tissue level metabolic function may precede changes in whole-body IS and metformin may improve metabolism. Disclosure E.R.M.Zunica: None. E.C.Heintz: None. R.C.Hebert: None. M.C.Tanksley: None. E.C.Mader: None. J.P.Kirwan: None. C.L.Axelrod: None. P.Singh: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (DK123456789) ;National Institute of General Medical Sciences (GM123456789)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.