Bone marrow metabolism is affected by body weight and response to exercise training varies according to anatomical location.

AIM: High body weight is a protective factor against osteoporosis, but obesity also suppresses bone metabolism and whole-body insulin sensitivity. However, the impact of body weight and regular training on bone marrow (BM) glucose metabolism is unclear. We studied the effects of regular exercise training on bone and BM metabolism in monozygotic twin pairs discordant for body weight. METHODS: We recruited 12 monozygotic twin pairs (mean ± SD age 40.4 ± 4.5 years; body mass index 32.9 ± 7.6, mean difference between co-twins 7.6 kg/m2 ; eight female pairs). Ten pairs completed the 6-month long training intervention. We measured lumbar vertebral and femoral BM insulin-stimulated glucose uptake (GU) using 18 F-FDG positron emission tomography, lumbar spine bone mineral density and bone turnover markers. RESULTS: At baseline, heavier co-twins had higher lumbar vertebral BM GU (p < .001) and lower bone turnover markers (all p < .01) compared with leaner co-twins but there was no significant difference in femoral BM GU, or bone mineral density. Training improved whole-body insulin sensitivity, aerobic capacity (both p < .05) and femoral BM GU (p = .008). The training response in lumbar vertebral BM GU was different between the groups (time × group, p = .02), as GU tended to decrease in heavier co-twins (p = .06) while there was no change in leaner co-twins. CONCLUSIONS: In this study, regular exercise training increases femoral BM GU regardless of weight and genetics. Interestingly, lumbar vertebral BM GU is higher in participants with higher body weight, and training counteracts this effect in heavier co-twins even without reduction in weight. These data suggest that BM metabolism is altered by physical activity.

Bone Marrow Metabolism Is Impaired in Insulin Resistance and Improves After Exercise Training.

CONTEXT: Exercise training improves bone mineral density, but little is known about the effects of training on bone marrow (BM) metabolism. BM insulin sensitivity has been suggested to play an important role in bone health and whole-body insulin sensitivity. OBJECTIVE: To study the effects of exercise training on BM metabolism. DESIGN: Randomized controlled trial. SETTING: Clinical research center. PARTICIPANTS: Sedentary healthy (n = 28, 40-55 years, all males) and insulin resistant (IR) subjects (n = 26, 43-55 years, males/females 16/10). INTERVENTION: Two weeks of sprint interval training or moderate-intensity continuous training. MAIN OUTCOME MEASURES: We measured femoral, lumbar, and thoracic BM insulin-stimulated glucose uptake (GU) and fasting free fatty acid uptake (FFAU) using positron-emission tomography and bone turnover markers from plasma. RESULTS: At baseline, GU was highest in lumbar, followed by thoracic, and lowest in femoral BM (all Ps < 0.0001). FFAU was higher in lumbar and thoracic than femoral BM (both Ps < 0.0001). BM FFAU and femoral BM GU were higher in healthy compared to IR men and in females compared to males (all Ps < 0.05). Training increased femoral BM GU similarly in all groups and decreased lumbar BM FFAU in males (all Ps < 0.05). Osteocalcin and PINP were lower in IR than healthy men and correlated positively with femoral BM GU and glycemic status (all Ps < 0.05). CONCLUSIONS: BM metabolism differs regarding anatomical location. Short-term training improves BM GU and FFAU in healthy and IR subjects. Bone turnover rate is decreased in insulin resistance and associates positively with BM metabolism and glycemic control. CLINICAL TRIAL REGISTRATION NUMBER: NCT01344928.

Physical Activity Associates with Muscle Insulin Sensitivity Postbariatric Surgery.

PURPOSE: Bariatric surgery is considered as an effective therapeutic strategy for weight loss in severe obesity. Remission of type 2 diabetes is often achieved after the surgery. We investigated whether increase in self-reported habitual physical activity associates with improved skeletal muscle insulin sensitivity and reduction of fat depots after bariatric surgery. METHODS: We assessed self-reported habitual physical activity using Baecke questionnaire in 18 diabetic and 28 nondiabetic patients with morbid obesity (median age, 46 yr; body mass index, 42.0 kg·m) before and 6 months after bariatric surgery operation. Insulin-stimulated femoral muscle glucose uptake was measured using fluorodeoxyglucose positron emission tomography method during hyperinsulinemia. In addition, abdominal subcutaneous and visceral fat masses were quantified using magnetic resonance imaging and liver fat content using magnetic resonance spectroscopy. Also, serum proinflammatory cytokines were measured. RESULTS: Patients lost on average 22.9% of weight during the follow-up period of 6 months (P < 0.001). Self-reported habitual physical activity level increased (P = 0.017). Improvement in skeletal muscle insulin sensitivity was observed only in those patients who reported increase in their physical activity postoperatively (P = 0.018). The increase in self-reported physical activity associated with the loss of visceral fat mass (P = 0.029). Postoperative self-reported physical activity correlated also positively with postoperative hepatic insulin clearance (P = 0.02) and tended to correlate negatively with liver fat content (P = 0.076). Postoperative self-reported physical activity also correlated negatively with serum TNFα, methyl-accepting chemotaxis protein and interleukin 6 levels. CONCLUSIONS: Self-reported physical activity is associated with reversal of skeletal muscle insulin resistance after bariatric surgery as well as with the loss of visceral fat content and improved postoperative metabolism in bariatric surgery patients. TRIAL REGISTRATION: Clinicaltrials.gov, NCT00793143 (SLEEVEPASS), NCT01373892 (SLEEVEPET2).

Left ventricular vascular and metabolic adaptations to high-intensity interval and moderate intensity continuous training: a randomized trial in healthy middle-aged men.

KEY POINTS: High-intensity interval training (HIIT) has become popular, time-sparing alternative to moderate intensity continuous training (MICT), although the cardiac vascular and metabolic effects of HIIT are incompletely known. We compared the effects of 2-week interventions with HIIT and MICT on myocardial perfusion and free fatty acid and glucose uptake. Insulin-stimulated myocardial glucose uptake was decreased by training without any significantly different response between the groups, whereas free fatty acid uptake remained unchanged. Adenosine-stimulated myocardial perfusion responded differently to the training modes (change in mean HIIT: -19%; MICT: +9%; P = 0.03 for interaction) and was correlated with myocardial glucose uptake for the entire dataset and especially after HIIT training. HIIT and MICT induce similar metabolic and functional changes in the heart, although myocardial vascular hyperaemic reactivity is impaired after HIIT, and this should be considered when prescribing very intense HIIT for previously untrained subjects. ABSTRACT: High-intensity interval training (HIIT) is a time-efficient way of obtaining the health benefits of exercise, although the cardiac effects of this training mode are incompletely known. We compared the effects of short-term HIIT and moderate intensity continuous training (MICT) interventions on myocardial perfusion and metabolism and cardiac function in healthy, sedentary, middle-aged men. Twenty-eight healthy, middle-aged men were randomized to either HIIT or MICT groups (n = 14 in both) and underwent six cycle ergometer training sessions within 2 weeks (HIIT session: 4-6 × 30 s all-out cycling/4 min recovery, MICT session 40-60 min at 60% V̇O2 peak ). Cardiac magnetic resonance imaging (CMRI) was performed to measure cardiac structure and function and positron emission tomography was used to measure myocardial perfusion at baseline and during adenosine stimulation, insulin-stimulated glucose uptake (MGU) and fasting free fatty acid uptake (MFFAU). End-diastolic and end-systolic volumes increased and ejection fraction slightly decreased with both training modes, although no other changes in CMRI were observed. MFFAU and basal myocardial perfusion remained unchanged. MGU was decreased by training (HIIT from 46.5 to 35.9; MICT from 47.4 to 44.4 mmol 100 g-1  min-1 , P = 0.007 for time, P = 0.11 for group × time). Adenosine-stimulated myocardial perfusion responded differently to the training modes (change in mean HIIT: -19%; MICT: +9%; P = 0.03 for group × time interaction). HIIT and MICT induce similar metabolic and functional changes in the heart, although myocardial vascular hyperaemic reactivity is impaired after HIIT. This should be taken into account when prescribing very intense HIIT for previously untrained subjects.