جستجوی مقالات مرتبط با کلیدواژه "فعالیت ورزشی" در نشریات گروه "زیست شناسی"

Irisin is a myokine secreted mostly by muscles after exercise, and its secretion level changes in metabolic disorders. The aim of present study was to investigate the effect of metformin on changes in the levels of plasma irisin, blood glucose and insulin resistance in male Sprague-Dawley rats receiving a high-fat emulsion diet. Twenty-four rats were divided into a normal control group (n = 8) and a high-fat diet group (n = 16). Then, high-fat diet group was divided into two subgroups, including high-fat diet control group (n = 8) and metformin group (n = 8). The normal control group received a standard diet. The high-fat diet control group received a high-fat emulsion diet containing corn oil by gavage on a daily basis for six weeks, and the metformin group received a high-fat emulsion diet with metformin (250 mg/kg/daily). At the end of the six-week period, factors such as glucose, insulin, irisin, Adiponectin, insulin resistance, liver enzymes, tumor necrosis factor α (TNF-α), serum lipid profile, lipid profile and lipid peroxidation in liver were measured and PGC-1α gene expression were examined in adipose tissue by Real-time PCR method. Liver histological tests with hematoxylin-eosin staining were performed to evaluate fat accumulation in liver tissue. Blood glucose level, insulin resistance, adiponectin, serum irisin level and liver lipid profile in the group receiving high-fat diet compared to the normal control group increased significantly (P <0. 05). Treatment with metformin caused a significant decrease in the level of these parameters compared to the high-fat diet group (P <0. 05) and an increase in the expression of PGC-1α gene in adipose tissue was observed in this group. As insulin resistance increased in rats receiving the high-fat diet, serum irisin level also increased, and with improving blood glucose and insulin resistance by metformin, serum irisin level was decreased. These results suggested that the elevated irisin levels may be a compensatory response to insulin resistance and impaired glucose metabolism. Hence, irisin could be considered as a potential target for the treatment of type 2 diabetes.

Skeletal muscle is a heterogeneous tissue composed of fast and slow fibers. One of the features of skeletal muscle is the highly organized structure that provides variety of functional capabilities ofthis tissue. Muscle fibers are also able to regulate their phenotypic properties in response to different functional needs. Types of muscle fibers can be identified by differences in their structural and functional properties. The main difference between muscle fibers is related to the contractile fibers of actin and myosin. Actin is involved in important cellular processes, including muscle contraction. Myosin is a molecular engine that converts the chemical energy released by ATP into mechanical energy. Energy production in myosin occurs through a number of ATPase in the myosin heavy chain. The myosin heavy chain isoform determines the maximum velocity and shortening force with respect to the cross-sectional area of each muscle fiber. Differences in energy costs and ATP phosphorylation potentials in different types of fast and slow fibers can be effective in the exchange of MHC isoforms. It seems that exercise can change the MHC isoforms through various mechanisms and consequently change the muscle fiber phenotype. In this review, we persent the potential effect of exercise on MHC isoforms.

Heart rate variability (HRV) is negatively associated with mortality. Decrease in HRV is common in cancer patients. The association between HRV and general survival in cancer patients has made HRV a valuable biomarker for evaluation of the disease prognosis. Exercise is considered an interventional strategy to improve various outcomes in cancer patients. The present paper provides a descriptive review of the literature regarding the effect of exercise interventions on HRV in cancer patients.

A systematic search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines in PubMed and Google Scholar, from inception since 1950 till October 15, 2018. The terms exercise, training, cancer, neoplasms, heart rate variability, and HRV were used in the search. Eligible studies were those trials using structured exercise intervention and having untrained adult cancer patients. Only English-language papers were included in the review.

Eight studies were included in the review. Of the various HRV parameters, 2 in the time domain (SDNN and RMSSD) and 3 in the frequency domain (LF, HF, and LF/HF) were commonly reported in the studies. Exercise intervention increased SDNN, RMSSD, and HF in all the studies, although the difference did not reach statistical significance in some cases. The results regarding LF and LF/HF were not consistent.

In general, exercise intervention can improve HRV in cancer patients. It is suggested that SDNN, RMSSD, and HF parameters be used in the evaluation of exercise effects on HRV because these parameters a) have prognostic value and b) more suitably reflect the effects of exercise training in these patients.