Exercise training increases the number of glucose transporters in rat adipose cells

Effect of Exercise-Induced Lipolysis on Serum Vitamin D Level in Obese Children: A Clinical Controlled Trial

BACKGROUND: Low Vitamin D levels associated with obesity have reached an epidemic level all over the world. It has been supposed that the low serum level of Vitamin D3 in obese subjects may be due to an increase in the uptake of Vitamin D3 by adipose tissue. AIM: The current study aimed to investigate the effect of a specially designed exercise program for boosting lipolysis on the Vitamin D level in obese children. METHODS: Thirty obese male children participated in the study. Their age was ranged from 9 to 11 years. The participants were assigned to two groups, Group I (GI) who received endurance exercise (ENE) only and Group II (GII) who received the specially designed exercise for increasing lipolysis (ENE preceded by resistance exercise). Free fatty acids (FFA), glycerol, and 25(OH)D were assessed before and immediately after exercise. RESULTS: FFA and glycerol showed a significant increase in both groups following exercise, while 25(OH)D showed a significant increase only in GII. GII showed significantly higher levels of FFA, glycerol, and 25(OH)D following exercise when it was compared to GI. CONCLUSION: The application of resistance training before ENE could improve the Vitamin D status through increasing the lipolytic activities more than the application of endurance exercise alone.

Creatine Monohydrate Supplementation Increases White Adipose Tissue Mitochondrial Markers in Male and Female Rats in a Depot Specific Manner

White adipose tissue (WAT) is a dynamic endocrine organ that can play a significant role in thermoregulation. WAT has the capacity to adopt structural and functional characteristics of the more metabolically active brown adipose tissue (BAT) and contribute to non-shivering thermogenesis under specific stimuli. Non-shivering thermogenesis was previously thought to be uncoupling protein 1 (UCP1)-dependent however, recent evidence suggests that UCP1-independent mechanisms of thermogenesis exist. Namely, futile creatine cycling has been identified as a contributor to WAT thermogenesis. The purpose of this study was to examine the efficacy of creatine supplementation to alter mitochondrial markers as well as adipocyte size and multilocularity in inguinal (iWAT), gonadal (gWAT), and BAT. Thirty-two male and female Sprague-Dawley rats were treated with varying doses (0 g/L, 2.5 g/L, 5 g/L, and 10 g/L) of creatine monohydrate for 8 weeks. We demonstrate that mitochondrial markers respond in a sex and depot specific manner. In iWAT, female rats displayed significant increases in COXIV, PDH-E1alpha, and cytochrome C protein content. Male rats exhibited gWAT specific increases in COXIV and PDH-E1alpha protein content. This study supports creatine supplementation as a potential method of UCP1-independant thermogenesis and highlights the importance of taking a sex-specific approach when examining the efficacy of browning therapeutics in future research.

Exercise Training Induces Depot-Specific Adaptations to White and Brown Adipose Tissue

Exercise affects whole-body metabolism through adaptations to various tissues, including adipose tissue (AT). Recent studies investigated exercise-induced adaptations to AT, focusing on inguinal white adipose tissue (WAT), perigonadal WAT, and interscapular brown adipose tissue (iBAT). Although these AT depots play important roles in metabolism, they account for only ∼50% of the AT mass in a mouse. Here, we investigated the effects of 3 weeks of exercise training on all 14 AT depots. Exercise induced depot-specific effects in genes involved in mitochondrial activity, glucose metabolism, and fatty acid uptake and oxidation in each adipose tissue (AT) depot. These data demonstrate that exercise training results in unique responses in each AT depot; identifying the depot-specific adaptations to AT in response to exercise is essential to determine how AT contributes to the overall beneficial effect of exercise.

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This study investigates the effects of exercise on all adipose tissue (AT) depots

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Exercise training induces unique metabolic changes to BAT, scWAT, and vWAT

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Exercise training differentially affects each AT depot within BAT, scWAT, and vWAT

Muscle-Adipose Tissue Cross Talk

Exercise training results in adaptations to both skeletal muscle and white adipose tissue (WAT) and protects against metabolic disorders including obesity and type 2 diabetes. Exercise-induced adaptations include an altered profile of secreted proteins, both myokines (from skeletal muscle) and adipokines (from adipose tissue). These secreted proteins may act in an endocrine manner to facilitate tissue-to-tissue communication and "cross talk," likely working together to improve overall metabolic health. Some studies suggest that contracting skeletal muscles release myokines that may function to alter the phenotype of WAT, including WAT "beiging," in which there is increased expression of beige marker genes and increased presence of multilocular cells within the WAT.

Exercise-induced adaptations to white and brown adipose tissue

The beneficial effects of exercise on skeletal muscle and the cardiovascular system have long been known. Recent studies have focused on investigating the effects of exercise on adipose tissue and the effects that these exercise-induced adaptations have on overall metabolic health. Examination of exercise-induced adaptations in both white adipose tissue (WAT) and brown adipose tissue (BAT) has revealed marked differences in each tissue with exercise. In WAT, there are changes to both subcutaneous WAT (scWAT) and visceral WAT (vWAT), including decreased adipocyte size and lipid content, increased expression of metabolic genes, altered secretion of adipokines and increased mitochondrial activity. Adaptations specific to scWAT include lipidomic remodeling of phospholipids and, in rodents, the beiging of scWAT. The changes to BAT are less clear: studies evaluating the effect of exercise on the BAT of humans and rodents have revealed contradictory data, making this an important area of current investigation. In this Review, we discuss the exercise-induced changes to WAT and BAT that have been reported by different studies and highlight the current questions in this field.

Lipidomic Adaptations in White and Brown Adipose Tissue in Response to Exercise Demonstrate Molecular Species-Specific Remodeling

Exercise improves whole-body metabolic health through adaptations to various tissues, including adipose tissue, but the effects of exercise training on the lipidome of white adipose tissue (WAT) and brown adipose tissue (BAT) are unknown. Here, we utilize MS/MS^ALL shotgun lipidomics to determine the molecular signatures of exercise-induced adaptations to subcutaneous WAT (scWAT) and BAT. Three weeks of exercise training decrease specific molecular species of phosphatidic acid (PA), phosphatidylcholines (PC), phosphatidylethanolamines (PE), and phosphatidylserines (PS) in scWAT and increase specific molecular species of PC and PE in BAT. Exercise also decreases most triacylglycerols (TAGs) in scWAT and BAT. In summary, exercise-induced changes to the scWAT and BAT lipidome are highly specific to certain molecular lipid species, indicating that changes in tissue lipid content reflect selective remodeling in scWAT and BAT of both phospholipids and glycerol lipids in response to exercise training, thus providing a comprehensive resource for future studies of lipid metabolism pathways.

Exercise regulation of adipose tissue

Exercise training results in adaptations to numerous organ systems and offers protection against metabolic disorders including obesity and type 2 diabetes, and recent reports suggest that adipose tissue may play a role in these beneficial effects of exercise on overall health. Multiple studies have investigated the effects of exercise training on both white adipose tissue (WAT) and brown adipose tissue (BAT), as well as the induction of beige adipocytes. Studies from both rodents and humans show that there are exercise training-induced changes in WAT including decreased cell size and lipid content, and increased mitochondrial activity. In rodents, exercise training causes an increased beiging of WAT. Whether exercise training causes a beiging of human scWAT, as well as which factors contribute to the exercise-induced beiging of WAT are areas of current investigation. Studies investigating the effects of exercise training on BAT mass and function have yielded conflicting data, and hence, is another area of intensive investigation. This review will focus on studies aimed at elucidating the mechanisms regulating exercise training induced-adaptations to adipose tissue.

Exercise Effects on White Adipose Tissue: Beiging and Metabolic Adaptations

Regular physical activity and exercise training have long been known to cause adaptations to white adipose tissue (WAT), including decreases in cell size and lipid content and increases in mitochondrial proteins. In this article, we discuss recent studies that have investigated the effects of exercise training on mitochondrial function, the "beiging" of WAT, regulation of adipokines, metabolic effects of trained adipose tissue on systemic metabolism, and depot-specific responses to exercise training. The major WAT depots in the body are found in the visceral cavity (vWAT) and subcutaneously (scWAT). In rodent models, exercise training increases mitochondrial biogenesis and activity in both these adipose tissue depots. Exercise training also increases expression of the brown adipocyte marker uncoupling protein 1 (UCP1) in both adipose tissue depots, although these effects are much more pronounced in scWAT. Consistent with the increase in UCP1, exercise training increases the presence of brown-like adipocytes in scWAT, also known as browning or beiging. Training results in changes in the gene expression of thousands of scWAT genes and an altered adipokine profile in both scWAT and vWAT. Transplantation of trained scWAT in sedentary recipient mice results in striking improvements in skeletal muscle glucose uptake and whole-body metabolic homeostasis. Human and rodent exercise studies have indicated that exercise training can alter circulating adipokine concentration as well as adipokine expression in adipose tissue. Thus, the profound changes to WAT in response to exercise training may be part of the mechanism by which exercise improves whole-body metabolic health.

Preventing and managing cardiometabolic risk: the logic for intervention

Cardiometabolic risk (CMR), also known as metabolic syndrome or insulin resistance syndrome, comprises obesity (particularly central or abdominal obesity), high triglycerides, low HDL, elevated blood pressure, and elevated plasma glucose. Leading to death from diabetes, heart disease, and stroke, the root cause of CMR is inadequate physical activity, a Western diet identified primarily by low intake of fruits, vegetables, and whole grains, and high in saturated fat, as well as a number of yet-to-be-identified genetic factors. While the pathophysiological pathways related to CMR are complex, the universal need for adequate physical activity and a diet that emphasizes fruits and vegetables and whole grains, while minimizing food high in added sugars and saturated fat suggests that these behaviors are the appropriate focus of intervention.

Mechanism of enhanced insulin sensitivity in athletes. Increased blood flow, muscle glucose transport protein (GLUT-4) concentration, and glycogen synthase activity

We examined the mechanisms of enhanced insulin sensitivity in 9 male healthy athletes (age, 25 +/- 1 yr; maximal aerobic power [VO2max], 57.6 +/- 1.0 ml/kg per min) as compared with 10 sedentary control subjects (age, 28 +/- 2 yr; VO2max, 44.1 +/- 2.3 ml/kg per min). In the athletes, whole body glucose disposal (240-min insulin clamp) was 32% (P < 0.01) and nonoxidative glucose disposal (indirect calorimetry) was 62% higher (P < 0.01) than in the controls. Muscle glycogen content increased by 39% in the athletes (P < 0.05) but did not change in the controls during insulin clamp. VO2max correlated with whole body (r = 0.60, P < 0.01) and nonoxidative glucose disposal (r = 0.64, P < 0.001). In the athletes forearm blood flow was 64% greater (P < 0.05) than in the controls, whereas their muscle capillary density was normal. Basal blood flow was related to VO2max (r = 0.63, P < 0.05) and glucose disposal during insulin infusion (r = 0.65, P < 0.05). The forearm glucose uptake in the athletes was increased by 3.3-fold (P < 0.01) in the basal state and by 73% (P < 0.05) during insulin infusion. Muscle glucose transport protein (GLUT-4) concentration was 93% greater in the athletes than controls (P < 0.01) and it was related to VO2max (r = 0.61, P < 0.01) and to whole body glucose disposal (r = 0.60, P < 0.01). Muscle glycogen synthase activity was 33% greater in the athletes than in the controls (P < 0.05), and the basal glycogen synthase fractional activity was closely related to blood flow (r = 0.88, P < 0.001).

IN CONCLUSION

(a) athletes are characterized by enhanced muscle blood flow and glucose uptake. (b) The cellular mechanisms of glucose uptake are increased GLUT-4 protein content, glycogen synthase activity, and glucose storage as glycogen. (c) A close correlation between glycogen synthase fractional activity and blood flow suggests that they are causally related in promoting glucose disposal.

Facilitative glucose transporters: regulatory mechanisms and dysregulation in diabetes

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