Gabriel S. Dubis

Regulation of fat metabolism during resistance exercise in sedentary lean and obese men

The effect of acute resistance exercise (RE) on whole body energy expenditure (EE) and alpha(2)-adrenergic receptor (alpha(2)-AR) regulation of lipolysis in subcutaneous abdominal adipose tissue (SCAAT) was determined in sedentary lean (LN) and obese (OB) men. Lipolysis was monitored using microdialysis in 10 LN [body mass index (BMI) 20.9 +/- 0.6] and 10 OB (BMI 36.2 +/- 2.7) men before, during, and for 24 h after RE. EE was measured before and immediately after RE for 40 min. Changes in interstitial glycerol were measured in SCAAT with three microdialysis probes perfused with a control solution, phentolamine (alpha(2)-AR antagonist), or propranolol (beta-AR antagonist). EE and fat oxidation (FOX) were significantly (P < 0.001) elevated immediately post-RE compared with pre-RE in LN and OB subjects, with no differences between groups. RE-induced increases in SCAAT glycerol concentrations from rest to peak exercise were greater in LN than in OB men in the control (LN 142.1 +/- 30.8 vs. OB 65.4 +/- 14.2%, P = 0.03) and phentolamine probes (LN 187.2 +/- 29.6 vs. OB 66.7 +/- 11.0%, P = 0.002). Perfusion of propranolol had no effect on interstitial glycerol concentrations over the time course of the experiment in either group. Plasma insulin concentrations were significantly lower (P = 0.002) and plasma growth hormone (GH) was significantly higher (P = 0.03) in LN compared with OB men. The mechanism behind RE contributing to improved body composition may in part be due to enhanced SCAAT lipolysis and improved EE and FOX in response to RE in LN and OB men. The blunted SCAAT lipolytic response to RE in OB compared with LN men is unrelated to RE-induced catecholamine activation of the antilipolytic alpha(2)-ARs and may be due to depressed GH in OB subjects.

Exercise and Weight Loss Improve Muscle Mitochondrial Respiration, Lipid Partitioning, and Insulin Sensitivity After Gastric Bypass Surgery

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.

Clinical trial demonstrates exercise following bariatric surgery improves insulin sensitivity

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 (VO2 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⁻¹/μU/ml, P = 0.019) above that of surgery. Exercise also improved S(G) (ITT: CON vs. EX; +0.0023 vs. +0.0063 min⁻¹, P = 0.009) compared with the CON group. Exercise improved cardiorespiratory fitness (VO2 peak) compared with the CON group. CONCLUSION Moderate exercise following RYGB surgery provides additional improvements in S(I), S(G), and cardiorespiratory fitness compared with a sedentary lifestyle during similar weight loss. TRIAL REGISTRATION clinicaltrials.gov identifier: NCT00692367. FUNDING This study was funded by the NIH/National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK078192) and an NIH/National Center for Research Resources/Clinical and Translational Science Award (UL1 RR024153).

Microvascular Endothelial Dysfunction in Sedentary, Obese Humans Is Mediated by NADPH Oxidase: Influence of Exercise Training.

Objective—The objectives of this study were to determine the impact of in vivo reactive oxygen species (ROS) on microvascular endothelial function in obese human subjects and the efficacy of an aerobic exercise intervention on alleviating obesity-associated dysfunctionality. Approach and Results—Young, sedentary men and women were divided into lean (body mass index 18–25; n=14), intermediate (body mass index 28–32.5; n=13), and obese (body mass index 33–40; n=15) groups. A novel microdialysis technique was utilized to detect elevated interstitial hydrogen peroxide (H2O2) and superoxide levels in the vastus lateralis of obese compared with both lean and intermediate subjects. Nutritive blood flow was monitored in the vastus lateralis via the microdialysis-ethanol technique. A decrement in acetylcholine-stimulated blood flow revealed impaired microvascular endothelial function in the obese subjects. Perfusion of apocynin, an NADPH oxidase inhibitor, lowered (normalized) H2O2 and superoxide levels, and reversed microvascular endothelial dysfunction in obese subjects. After 8 weeks of exercise, H2O2 levels were decreased in the obese subjects and microvascular endothelial function in these subjects was restored to levels similar to lean subjects. Skeletal muscle protein expression of the NADPH oxidase subunits p22phox, p47phox, and p67phox was increased in obese relative to lean subjects, where p22phox and p67phox expression was attenuated by exercise training in obese subjects. Conclusions—This study implicates NADPH oxidase as a source of excessive ROS production in skeletal muscle of obese individuals and links excessive NADPH oxidase–derived ROS to microvascular endothelial dysfunction in obesity. Furthermore, aerobic exercise training proved to be an effective strategy for alleviating these maladies.

Comparison of a field-based test to estimate functional threshold power and power output at lactate threshold.

Gavin, TP, Van Meter, JB, Brophy, PM, Dubis, GS, Potts, KN, and Hickner, RC. Comparison of a field-based test to estimate functional threshold power and power output at lactate threshold. J Strength Cond Res 26(2): 416–421, 2012—It has been proposed that field-based tests (FT) used to estimate functional threshold power (FTP) result in power output (PO) equivalent to PO at lactate threshold (LT). However, anecdotal evidence from regional cycling teams tested for LT in our laboratory suggested that PO at LT underestimated FTP. It was hypothesized that estimated FTP is not equivalent to PO at LT. The LT and estimated FTP were measured in 7 trained male competitive cyclists (&OV0312;O2max = 65.3 ± 1.6 ml O2·kg−1·min−1). The FTP was estimated from an 8-minute FT and compared with PO at LT using 2 methods; LTΔ1, a 1 mmol·L−1 or greater rise in blood lactate in response to an increase in workload and LT4.0, blood lactate of 4.0 mmol·L−1. The estimated FTP was equivalent to PO at LT4.0 and greater than PO at LTΔ1. &OV0312;O2max explained 93% of the variance in individual PO during the 8-minute FT. When the 8-minute FT PO was expressed relative to maximal PO from the &OV0312;O2max test (individual exercise performance), &OV0312;O2max explained 64% of the variance in individual exercise performance. The PO at LT was not related to 8-minute FT PO. In conclusion, FTP estimated from an 8-minute FT is equivalent to PO at LT if LT4.0 is used but is not equivalent for all methods of LT determination including LTΔ1.

Randomized trial reveals that physical activity and energy expenditure are associated with weight and body composition after RYGB

This study investigated the associations of both physical activity time (PA) and energy expenditure (EE) with weight and fat mass (FM) loss in patients following Roux‐en‐Y gastric bypass (RYGB) surgery.

Examination of Lifestyle Behaviors and Cardiometabolic Risk Factors in University Students Enrolled in Kinesiology Degree Programs

Abstract Many, GM, Lutsch, A, Connors, KE, Shearer, J, Brown, HC, Ash, G, Pescatello, LS, Gordish-Dressman, H, Barfield, W, Dubis, G, Houmard, JA, Hoffman, EP, and Hittel, DS. Examination of lifestyle behaviors and cardiometabolic risk factors in university students enrolled in kinesiology degree programs. J Strength Cond Res 30(4): 1137–1146, 2016—Preventing physical inactivity and weight gain during college is critical in decreasing lifelong obesity and associated disease risk. As such, we sought to compare cardiometabolic risk factors and lifestyle behaviors between college students enrolled in kinesiology and non-kinesiology degree programs to assess whether health and exercise degree programs may influence health behaviors and associated disease risk outcomes. Anthropometrics, fasting blood glucose, insulin, lipid profiles and HbA1c%, blood pressure, and peak oxygen consumption (V[Combining Dot Above]O2peak) were assessed in 247 healthy college students. The homeostasis model assessment of insulin sensitivity (HOMA) was calculated using glucose and insulin levels. Self-reported physical activity from the Paffenbarger questionnaire was collected to estimate the average caloric expenditure due to different types of physical activities. Despite no significant differences in body mass index or waist circumference between groups, kinesiology majors presented with ∼20% lower fasting insulin levels and HOMA (p = 0.01; p < 0.01, respectively) relative to nonmajors. Kinesiology majors reported increased weekly participation in vigorous-intensity sport and leisure activities and, on average, engaged in >300 metabolic equivalent-h·wk−1, whereas non-kinesiology majors engaged in <300 MET-h wk−1 (p = 0.01). Our data suggest that students enrolled in kinesiology degree programs display improved healthy behaviors and associated outcomes (parameters of glucose homeostasis). Practical outcomes of this research indicate that implementing components of a comprehensive kinesiology curriculum encourages improved health behaviors and associated cardiometabolic risk factors.

Relationship among physical activity, sedentary behaviors, and cardiometabolic risk factors during gastric bypass surgery–induced weight loss

BACKGROUND The impact of daily physical activity (PA) on the cardiometabolic risk of bariatric surgery patients is not known. OBJECTIVE We examined the influence of physical activity and sedentary behavior on modifying cardiometabolic risk after Roux-en-Y gastric bypass (RYGB) surgery. SETTING University of Pittsburgh Medical Center and East Carolina University bariatric surgery centers. METHODS Data from 43 women and 7 men who completed testing at 1-3 months after RYGB surgery and again at 9 months postsurgery were analyzed. Outcomes measured included PA level (min/d), steps/d, sedentary time, and body composition. Insulin sensitivity was determined with an intravenous glucose tolerance test. Weight and blood lipid profiles also were obtained. RESULTS Patients reduced body mass index by a mean of -8.0±3.4 kg/m2 (P<.001), increased moderate-to-vigorous PA by 17.0±47.0 min/d (P = .014), and decreased sedentary time (-47.9±101.0 min/d, P = .002). However, 24% of patients decreased overall PA (P<.001), and 39% increased sedentary behavior (P<.001). Changes in overall PA (rho = -.33, P = .006) and steps/d (rho = -.31, P = .0106) were related to weight loss. Insulin sensitivity was associated with light PA before (rho = .37, P<.001) and after (rho = .37, P = .015) intervention. Increasing overall PA also was related to higher levels of high-density lipoprotein cholesterol (rho = .33, P<.01). Decreasing sedentary time was related to decreased fat mass (rho = .35, P = .012) but not to other cardiometabolic risk factors. CONCLUSIONS The majority of patients increased PA (76%) and decreased sedentary time (61%) after RYGB surgery, but the amount of PA and sedentary time varied substantially. Higher PA, even at low intensity levels, was related to beneficial outcomes in body composition, insulin sensitivity, and high-density lipoprotein cholesterol.