Effect of different exercise intensities on the pancreas of animals with metabolic syndrome

Muscle Function, Body Composition, Insulin Sensitivity and Physical Activity in Adolescents Born Preterm: Impact of Gestation and Vitamin D Status

Whilst several studies have explored adolescent metabolic and cognitive function after preterm birth, few have explored muscle function and physical activity. We set out to examine the relationship between gestational age and muscle metabolism in a cohort of adolescents who were born preterm. Participants were recruited from the Newcastle preterm birth growth study cohort. They did not have severe neurological disease and were not on daily medication. Participants underwent an assessment of oxidative muscle function using phosphorus magnetic resonance spectroscopy that included the half-time for recovery of equilibrium of phosphocreatine, τ½PCr. In addition, we measured key variables that might affect muscle function including physical activity levels determined by 3-day accelerometry, body composition using air displacement plethysmography, insulin sensitivity using the homeostatic model assessment/Matsuda index and serum vitamin D concentrations. 60 adolescents (35F) median age 15.6 years (range 12.1−18.8) with a median gestation of 31 weeks (range 24 to 34 weeks) underwent a single assessment. Males were more active and spent less time in sedentary mode. Time spent in light activity was associated with insulin sensitivity (IS) (Matsuda Index; p < 0.05) but there were no strong correlations between activity levels and gestational age. Greater fat mass, waist circumference and body mass index were all associated with lower IS. Gestational age was negatively associated with adjusted measures of oxidative muscle function (τ½PCr). In a stepwise multivariate linear regression model, gestational age at birth was the most significant predictor of oxidative muscle function (p = 0.005). Higher serum vitamin D levels were also associated with faster phosphocreatine recovery time (p = 0.045). Oxidative function in the skeletal muscle of adolescents born preterm is associated with gestational age and vitamin D concentrations. Our study suggests that being born preterm may have a long-term impact on muscle metabolism.

Impacts of an Exercise Intervention on the Health of Pancreatic Beta-Cells: A Review

There is an increasing consensus that exercise is a medicine and that regular exercise can effectively improve and prevent metabolic diseases such as diabetes. Islet cells are the endocrine of the pancreas and vital to the development of diabetes. Decades of developmental research in exercise intervention and the health of islet cells confirmed that exercise exerts beneficial effects on the function, proliferation, and survival rate of islet cells. However, the precise exercise reference scheme is still elusive. To accomplish this goal, we searched and analyzed relevant articles, and concluded the precise exercise prescription treatments for various species such as humans, rats, and mice. Each exercise protocol is shown in the tables below. These exercise protocols form a rich pipeline of therapeutic development for exercise on the health of islet cells.

Impact of chronic exercise on counteracting chronic stress-induced functional and morphological pancreatic changes in male albino rats

Chronic stress has been linked to many diseases resulted from dysfunction of both the nervous system and peripheral organ systems. Yet, the effects of chronic stress on the pancreas have received relatively little attention. This work aims to investigate the influence of chronic stress exposure on both the endocrine and exocrine pancreatic function and morphology and its possible mechanism of action, and also to evaluate the impact of chronic exercise with moderate intensity on ameliorating the stress-induced pancreatic changes. Forty adult male albino rats were used and divided into four groups: control group, exercised group (3 weeks of swimming exercise), stressed group (3 weeks of immobilization stress), and stressed group practicing exercise (3 weeks of exercise, concomitant with 21 daily sessions of stress). On the final day of the experiment, all rats were sacrificed. Biochemical, immunohistochemical, and histological studies were conducted. The results showed that chronic immobilization stress produced hyperglycemia, hyperinsulinemia, and increased homeostatic model assessment of insulin resistance index (HOMA-IR) with increasing exocrine pancreatic injury markers by increasing oxidative and inflammatory status of the pancreatic tissue. Histological study showed the injurious effect of stress on the morphology of pancreatic tissue. Physical exercise protected the pancreas from the negative effects of stress through its anti-inflammatory and anti-oxidative effects, evidenced by increasing pancreatic interleukin 10 and total antioxidant capacity and decreasing pancreatic tumor necrosis factor-alpha, and malondialdehyde with ameliorating most of the histological changes induced by stress exposure. Physical exercise effectively counteracts chronic stress-induced pancreatic changes through different mechanisms.

Aerobic Exercise Training Attenuates Tumor Growth and Reduces Insulin Secretion in Walker 256 Tumor-Bearing Rats

Aerobic exercise training can improve insulin sensitivity in many tissues; however, the relationship among exercise, insulin, and cancer cell growth is unclear. We tested the hypothesis that aerobic exercise training begun during adolescence can attenuate Walker 256 tumor growth in adult rats and alter insulin secretion. Thirty-day-old male Wistar rats engaged in treadmill running for 8 weeks, 3 days/week, 44 min/day, at 55-65% VO2max until they were 90 days old (TC, Trained Control). An equivalently aged group was kept inactive during the same period (SC, Sedentary Control). Then, half the animals of the SC and TC groups were reserved as the control condition and the other half were inoculated with Walker 256 cancer cells, yielding two additional groups (Sedentary Walker and Trained Walker). Zero mortalities were observed in tumor-bearing rats. Body weight (BW), food intake, plasma glucose, insulin levels, and peripheral insulin sensitivity were analyzed before and after tumor cell inoculation. We also evaluated tumor growth, metastasis and cachexia. Isolated pancreatic islets secretory activity was analyzed. In addition, we evaluated mechanic sensibility. Our results showed improved physical performance according to the final workload and VO2max and reduced BW in trained rats at the end of the running protocol. Chronic adaptation to the aerobic exercise training decreased tumor weight, cachexia and metastasis and were associated with low glucose and insulin levels and high insulin sensitivity before and after tumor cell inoculation. Aerobic exercise started at young age also reduced pancreatic islet insulin content and insulin secretion in response to a glucose stimulus, without impairing islet morphology in trained rats. Walker 256 tumor-bearing sedentary rats also presented reduced pancreatic islet insulin content, without changing insulin secretion through isolated pancreatic islets. The mechanical sensitivity test indicated that aerobic exercise training did not cause injury or trigger inflammatory processes prior to tumor cell inoculation. Taken together, the current study suggests that aerobic exercise training applied during adolescence may mitigate tumor growth and related disorders in Walker 256 tumor-bearing adult rats. Improved insulin sensibility, lower glucose and insulin levels and/or reduced insulin secretion stimulated by glucose may be implicated in this tumor attenuation.

Effects of moderate exercise on biochemical, morphological, and physiological parameters of the pancreas of female mice with estrogen deprivation and dyslipidemia

Menopausal women are at high risk of developing heart disease. However, physical exercise practice can reverse this scenario. We evaluated the biochemical, morphological, and physiological effects of moderate aerobic physical exercise on the pancreas of knockout mice for LDL receptor with estrogen deprivation by ovariectomy. Animals were divided into six groups (n = 5): sedentary non-ovariectomized control; sedentary ovariectomized control; trained ovariectomized control; sedentary non-ovariectomized LDL-R knockout; sedentary ovariectomized LDL-R knockout; and trained ovariectomized LDL-R knockout. Physical exercise practice promoted improvement in biometric and biochemical parameters analyzed, with reduction of visceral adipose tissue and VLDL, triglycerides, total cholesterol, and blood glucose levels. In addition, physical exercise practice altered the morphology of pancreatic islets and improved their response to the effects of menopause. Thus, physical exercise practice was fundamental to minimize the effects of dyslipidemia associated with ovariectomy in the pancreatic tissue of LDL-R knockout animals, contributing to reduce the risk of developing cardiac diseases in the menopause period.

Excessive consumption of fructose causes cardiometabolic dysfunctions through oxidative stress and inflammation

A rapid rise in obesity, as well as physical inactivity, in industrialized countries is associated with fructose-consumption-mediated metabolic syndrome having a strong association with cardiovascular disease. Although insulin resistance is thought to be at the core, visceral obesity, hypertension, and hypertriglyceridemia are also considered important components of this metabolic disorder. In addition, various other abnormalities such as inflammation, oxidative stress, and elevated levels of uric acid are also part of this syndrome. Lifestyle changes through improved physical activity, as well as nutrition, are important approaches to minimize metabolic syndrome and its deleterious effects.

Oxygen uptake, respiratory exchange ratio, or total distance: a comparison of methods to equalize exercise volume in Wistar rats

This study compared strategies to equalize the volume of aerobic exercise performed with different intensities by Wistar rats, based on the distance covered during exercise bouts and energy expenditure (EE, isocaloric sessions) obtained from oxygen uptake (V̇O₂) or respiratory exchange ratio (RER). Thirty-three male rats (270.5±12.8 g) underwent maximal exercise tests to determine V̇O₂ reserve (V̇O₂R), being randomly assigned to three groups: moderate-intensity continuous exercise at speed corresponding to 50% V̇O₂R (MIC; n=11); high-intensity continuous exercise at 80% V̇O₂R (HIC; n=11); and high-intensity intermittent exercise (HII; n=11) at 60% V̇O₂R (3 min) and 80% V̇O₂R (4 min). Exercise duration was calculated individually to elicit EE of 5 kcal in each session. No difference between groups was found for total running distance (MIC: 801±46, HIC: 734±42, HII: 885±64 m; P=0.13). Total EE measured by RER was systematically underestimated compared to values obtained from V̇O₂ (HII: 4.5% and MIC: 6.2%, P<0.05). Total EE (calculated from V̇O₂), and duration of HIC bouts (2.8 kcal and 30.8±2.2 min) were lower (P<0.0001) than in MIC (4.9 kcal and 64.7±1.8 min) and HII (4.7 kcal and 46.9±2.2 min). Predicted and actual values of total V̇O₂, total EE, and duration of isocaloric sessions were similar in MIC and HII (P>0.05), which were both higher than in HIC (P<0.0001). In conclusion, the time to achieve a given EE in exercise bouts with different intensities did not correspond to the total distance. Therefore, the volume of aerobic exercise in protocols involving Wistar rats should be equalized using EE rather than total covered distance.