Introduction: Obesity is the primary determinant of nonalcoholic fatty liver disease (NAFLD) . Interventions that decrease body weight, such as bariatric surgery and/or calorie restriction (CR) , may serve as effective therapies for NAFLD. The purpose of this study was to compare the effects of Roux-en-Y gastric bypass surgery (RYGB) to CR on hepatic function in mice with obesity and NAFLD. Methods: 6-week-old male C57BL/6J mice were fed a two-choice chow/high-fat diet (HFD) to promote diet-induced obesity. At 16 weeks of age, mice were randomized to (1) sham surgery (Sham) , (2) RYGB, or (3) sham + weight-matched calorie restriction to RYGB (WM) . Mice were euthanized at 36 weeks for determination of NAFLD/NASH and hepatic function. Body weight/composition and food intake were measured weekly during the treatment period. ANCOVA-adjusted energy expenditure (EE) was determined 3 and 17 weeks after treatment. Hepatic lipid content and NAFLD scores were determined from H&E-stained tissue sections. Hepatic enzymes and glycogen content were determined by ELISA. Results: RYGB & WM achieved a similar reduction in body weight relative to baseline. RYGB decreased adiposity to a greater extent than WM relative to baseline and Sham (-4.4±0.6 vs. -1.3±0.6 Δg, P<0.001) . Decreased body weight was attributable to lower food intake in WM compared to RYGB and Sham (P<0.0001) . WM decreased EE relative to RYGB and Sham (WM:8.6±0.4 vs. RYGB:10.4±0.4 vs. Sham:10.5±0.6 kcals/day, P<0.001) . RYGB decreased hepatic lipid content to a greater extent than WM (92.6 vs. 76.5 % reduction, P=0.02) . RYGB and WM similarly decreased AST and ALT activity relative to Sham. RYGB increased hepatic glycogen relative to both Sham and WM (P<0.001) . Conclusions: RYGB and WM improve hepatic function and decrease the severity of NAFLD through shared and discrete mechanisms of action. RYGB decreases hepatic lipid content to a greater extent than WM independent of food intake, indicating that evading the expected metabolic adaptation in EE after weight loss likely accounts for the additive hepatic benefit of RYGB. Disclosure C. L. Axelrod: None. I. M. Langohr: None. W. S. Dantas: None. R. Townsend: None. V. L. Albaugh: None. J. P. Kirwan: None. H. Berthoud: None. Funding National Institutes of Health (U54GM104940)
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 linked to high type 2 diabetes risk. Positive airway pressure (PAP) therapy is the standard of care for OSA, but it inconsistently improves glucose homeostasis. Senescent cells are common in adipose tissue (AT) of patients with OSA and may impair insulin signaling. However, the effects of PAP therapy on AT senescence are not known. Addition of metformin, an insulin-sensitizer with anti-senescent effects, may be a good adjuvant therapeutic strategy to improve glycemic control in patients with OSA. Methods: We randomly assigned 16 nondiabetic participants with OSA (Mean± SD; age: 50.9 ± 6.7 y, BMI: 36.5 ± 2.9 kg/m2) in a 1:1 ratio to receive either 2g metformin or placebo daily along with PAP therapy for 3 months in a double-blind pilot study. Whole body and AT insulin sensitivity was determined by 2h oral glucose tolerance test (OGTT). AT biopsy was obtained to estimate tissue insulin signaling and senescence. Results: The metformin and placebo groups had comparable age, BMI and OSA severity at baseline. PAP compliance was 38% and 75% in the metformin and placebo groups, respectively. Matsuda Index, glucose area under the curve (2h AUC), and free-fatty acid suppression at baseline and follow-up were not different in metformin or placebo treated groups. Compared to baseline, insulin AUC and insulin to glucose AUC ratio during OGTT was unchanged in the metformin but increased in the placebo group. Metformin, but not placebo, was associated with increased insulin mediated AKT phosphorylation and decreased senescence biomarkers (p21 and MCP1) in AT during the follow-up visit. Conclusion: Metformin, as adjunct to PAP therapy, attenuated insulin rises during OGTT, improved AT insulin signaling, and lowered senescence biomarkers in OSA patients. Larger trials of longer treatment duration are needed to determine if metformin can prevent diabetes in OSA patients. Disclosure S. Rodrigues: None. W.S. Dantas: None. R.A. Beyl: None. R.C. Hebert: None. I. Griffith: None. M. Tanksley: None. E.C. Mader: None. J.P. Kirwan: None. C.L. Axelrod: None. E. Ravussin: Research Support; Eli Lilly and Company, Novartis AG. Advisory Panel; Novartis. P. Singh: None. Funding National Institutes of Health (P30DK072476, U54GM104940); CAPES (88887.470405/2019-00 to S.R.)
Exercise is a known intervention to alleviate insulin resistance. This study investigated how a 12-week endurance exercise intervention changes skeletal muscle mitochondrial and lipid droplet architecture in patients with type 2 diabetes. Participants completed 12 weeks of endurance exercise at 70% of their VO2 max five days a week at one hour a day. Muscle biopsies were taken before and 72 hours after the last exercise session. A subset of these muscle biopsies from two participants (58±0 years, 42.3±3.3 BMI, 2.5±0.7 medications, 8.2±0.1% HbA1c) was imaged using focused ion-beam scanning electron microscopy. Due to these results being preliminary, general trends are discussed. A deep-learning model segmented 14,197 mitochondria and 4,400 lipid droplets to assess individual mitochondrial and lipid droplet 3D structures, and mitochondria-to-lipid interactions. Surprisingly, exercise did not change individual mitochondrial and lipid droplet volume, surface area to volume ratio, or sphericity. There was an increase in mitochondria-to-mitochondria and mitochondria-to-lipid droplet interactions after endurance training. These preliminary data suggest that exercise may relieve insulin-resistant skeletal muscle by increasing the connectivity among mitochondria and lipid droplets prior to changing individual organelle morphology. Further analyses are ongoing to confirm these findings. Disclosure H. A. Parry: None. C. L. Axelrod: None. V. Baena: None. W. S. Dantas: None. J. P. Kirwan: None. B. Glancy: None.
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)
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.