nondiabetic patients following RYGB surgery are typically quite modest compared with the presurgery condition (3). Moreover, there appear to be 2 discrete periods of improvement. The first is immediately after surgery, at which time hepatic, but not peripheral, S I improves in response to acute energy restriction (4-6), while greater, protracted weight loss appears to be more strongly associated with improved peripheral S I (7,8). Even with significant weight loss 1 year following RYBG surgery, peripheral S I is still low compared with that of lean metabolically healthy individuals (3,5,6,9).Exercise is considered a cornerstone for obesity treatment, and while it is not generally viewed to cause substantial body weight reduction (10), it can potently improve peripheral S I and glucose control (11-13) and can reduce the risk of T2D and cardiovascular disease (14,15). There is general consensus that even a single session of moderate intensity exercise can induce an improvement in S I (16). There is also evidence that exercise can BACKGROUND. Roux-en-Y gastric bypass (RYGB) surgery causes profound weight loss and improves insulin sensitivity (S I ) in obese patients. Regular exercise can also improve S I in obese individuals; however, it is unknown whether exercise and RYGB surgery-induced weight loss would additively improve S I and other cardiometabolic factors. METHODS.We conducted a single-blind, prospective, randomized trial with 128 men and women who recently underwent RYGB surgery (within 1-3 months). Participants were randomized to either a 6-month semi-supervised moderate exercise protocol (EX, n = 66) or a health education control (CON; n = 62) intervention. Main outcomes measured included S I and glucose effectiveness (S G ), which were determined from an intravenous glucose tolerance test and minimal modeling. Secondary outcomes measured were cardiorespiratory fitness (VO 2 peak) and body composition. Data were analyzed using an intention-to-treat (ITT) and per-protocol (PP) approach to assess the efficacy of the exercise intervention (>120 min of exercise/week).RESULTS. 119 (93%) participants completed the interventions, 95% for CON and 91% for EX. There was a significant decrease in body weight and fat mass for both groups (P < 0.001 for time effect). S I improved in both groups following the intervention (ITT: CON vs. EX; +1.64 vs. +2.24 min -1 /μU/ml, P = 0.18 for Δ, P < 0.001 for time effect). A PP analysis revealed that exercise produced an additive S I improvement (PP: CON vs. EX; +1.57 vs. +2.69 min

Both Roux-en-Y gastric bypass (RYGB) surgery and exercise can improve insulin sensitivity in individuals with severe obesity. However, the impact of RYGB with or without exercise on skeletal muscle mitochondria, intramyocellular lipids, and insulin sensitivity index (SI) is unknown. We conducted a randomized exercise trial in patients (n = 101) who underwent RYGB surgery and completed either a 6-month moderate exercise (EX) or a health education control (CON) intervention. SI was determined by intravenous glucose tolerance test. Mitochondrial respiration and intramyocellular triglyceride, sphingolipid, and diacylglycerol content were measured in vastus lateralis biopsy specimens. We found that EX provided additional improvements in SI and that only EX improved cardiorespiratory fitness, mitochondrial respiration and enzyme activities, and cardiolipin profile with no change in mitochondrial content. Muscle triglycerides were reduced in type I fibers in CON, and sphingolipids decreased in both groups, with EX showing a further reduction in a number of ceramide species. In conclusion, exercise superimposed on bariatric surgery–induced weight loss enhances mitochondrial respiration, induces cardiolipin remodeling, reduces specific sphingolipids, and provides additional improvements in insulin sensitivity.

Dubé JJ, Coen PM, DiStefano G, Chacon AC, Helbling NL, Desimone ME, Stafanovic-Racic M, Hames KC, Despines AA, Toledo FG, Goodpaster BH. Effects of acute lipid overload on skeletal muscle insulin resistance, metabolic flexibility, and mitochondrial performance. Am J Physiol Endocrinol Metab 307: E1117-E1124, 2014. First published October 28, 2014; doi:10.1152/ajpendo.00257.2014.-We hypothesized that acute lipid-induced insulin resistance would be attenuated in highoxidative muscle of lean trained (LT) endurance athletes due to their enhanced metabolic flexibility and mitochondrial capacity. Lean sedentary (LS), obese sedentary (OS), and LT participants completed two hyperinsulinemic euglycemic clamp studies with and without (glycerol control) the coinfusion of Intralipid. Metabolic flexibility was measured by indirect calorimetry as the oxidation of fatty acids and glucose during fasted and insulin-stimulated conditions, the latter with and without lipid oversupply. Muscle biopsies were obtained for mitochondrial and insulin-signaling studies. During hyperinsulinemia without lipid, glucose infusion rate (GIR) was lowest in OS due to lower rates of nonoxidative glucose disposal (NOGD), whereas state 4 respiration was increased in all groups. Lipid infusion reduced GIR similarly in all subjects and reduced state 4 respiration. However, in LT subjects, fat oxidation was higher with lipid oversupply, and although glucose oxidation was reduced, NOGD was better preserved compared with LS and OS subjects. Mitochondrial performance was positively associated with better NOGD and insulin sensitivity in both conditions. We conclude that enhanced mitochondrial performance with exercise is related to better metabolic flexibility and insulin sensitivity in response to lipid overload. lipids; mitochondria; skeletal muscle CHRONIC SUBSTRATE OVERLOAD, coupled with physical inactivity, is a key mediator of the development of obesity and insulin resistance (49). It has been suggested that mitochondrial dysfunction (1, 17), perhaps a result of nutrient oversupply, particularly saturated fatty acids and/or physical inactivity, plays a key role in decreased insulin action observed in the obese state. However, there is evidence to suggest that mitochondrial content and performance are normal in insulinresistant obese subjects (14). Although there is controversy regarding the influence of mitochondrial performance on the development of insulin resistance (17,22), there is little debate that increased physical activity (i.e., aerobic exercise) provides a necessary stimulus for increased mitochondrial content (24), capacity for fat oxidation (6), and improved insulin sensitivity (13). Yet few studies have directly assessed the effects of lipid oversupply on skeletal muscle insulin resistance, metabolic flexibility, and mitochondrial performance in high-vs. lowoxidative muscle (9, 40).Using the exogenous lipid infusion model of insulin resistance (7, 26), we hypothesized that excess fatty acids would be preferentially oxidized in enduranc...

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Dietary nitrate (NO3−) and nitrite (NO2−) support nitric oxide (·NO) generation and downstream vascular signaling responses. These nitrogen oxides also generate secondary nitrosating and nitrating species that react with low molecular weight thiols, heme centers, proteins and unsaturated fatty acids. To explore the kinetics of NO3− and NO2− metabolism and the impact of dietary lipid on nitrogen oxide metabolism and cardiovascular responses, the stable isotopes Na15NO3 and Na15NO2 were orally administered in the presence or absence of conjugated linoleic acid (cLA). The reduction of 15NO2− to 15NO was indicated by electron paramagnetic resonance spectroscopy detection of hyperfine splitting patterns reflecting 15NO-deoxyhemoglobin complexes. This formation of 15NO also translated to decreased systolic and mean arterial blood pressures and inhibition of platelet function. Upon concurrent administration of cLA, there was a significant increase in plasma cLA nitration products 9- and 12-15NO2-cLA. Co-administration of cLA with 15NO2− also impacted the pharmacokinetics and physiological effects of 15NO2−, with cLA administration suppressing plasma NO3− and NO2− levels, decreasing 15NO-deoxyhemoglobin formation, NO2− inhibition of platelet activation, and the vasodilatory actions of NO2−, while enhancing the formation of 9- and 12-15NO2-cLA. These results indicate that the biochemical reactions and physiologic responses to oral 15NO3− and 15NO2− are significantly impacted by dietary constituents such as unsaturated lipids. This can explain the variable responses to NO3− and NO2− supplementation in clinical trials and reveals dietary strategies for promoting the generation of pleiotropic nitrogen oxide-derived lipid signaling mediators.