Abstract
Obesity is an epidemic disease and the expansion of adipose tissue, especially visceral fat, promotes the secretion of factors that lead to comorbidities such as diabetes and cardiovascular diseases. Thus, diet and exercise have been proposed as an intervention to reverse these complications. An adipocytokine, known as irisin, mediates the beneficial effects of exercise. It has been proposed as a therapeutic potential in controlling obesity. In view of the above, this paper attempts to determine the modulation of irisin, visceral adiposity and biochemical markers in response to dietary intervention and aerobic exercise. To do this, 52 diet-induced obese male Wistar rats were divided into the following four groups: high-fat diet and exercise (HFD-Ex); HFD-Sedentary (HFD-Sed); chow-diet and exercise (CD-Exercise); and CD-Sed. The exercise-trained group performed a treadmill protocol for 60 min/day, 3 days/week for 8 weeks. Body mass (BM), body fat (BF), fat mass (FM), and fat-free mass (FFM) were analyzed. Mesenteric (MES), epididymal (EPI), and retroperitoneal (RET) adipose tissue was collected and histological analysis was performed. Biochemical irisin, triglycerides, glucose, insulin and inflammatory markers were determined and, FNDC5 protein expression was analyzed. In this study, the diet was the most important factor in reducing visceral adiposity in the short and long term. Exercise was an important factor in preserving muscle mass and reducing visceral depots after a long term. Moreover, the combination of diet and exercise can enhance these effects. Diet and exercise exclusively were the factors capable of increasing the values of irisin/FNDC5, however it did not bring cumulative effects of both interventions. Prescriptions to enhance the obesity treatments should involve reducing visceral adiposity by reducing the fat content in the diet associated with aerobic exercise.
Highlights
Obesity is the result of an increase in the intake of a highfat and high-carbohydrate diet associated with low levels of physical activity (Romieu et al, 2017)
All the visceral depots (EPI, RET, and MES) were significantly elevated in the high-fat diet (HFD) group compared to chow diet (CD)
Irisin showed an almost threefold increase in the HFD group when compared to the CD group and on the other hand, FNDC5 was increased in the CD group compared to HFD
Summary
Obesity is the result of an increase in the intake of a highfat and high-carbohydrate diet associated with low levels of physical activity (Romieu et al, 2017). Progressive enlargement of visceral adipose tissue (VAT) causes alterations to mitochondrial oxidative function, increases lipolytic activity induced by catecholamine, and the secretion of pro-inflammatory cytokines leading to chronic inflammation and subsequent dysfunction bioenergetics and structural changes in adipocytes (Wajchenberg, 2000; Kusminski et al, 2016). This dysfunction is associated with an array of metabolic complications, such as type 2 diabetes and cardiovascular disease (Bray et al, 2017; Schoettl et al, 2018). The mechanism involved in this regulation is not completely understood, but it can be suggested that the muscle considering high energy demand, secretes factors that stimulate the thermogenesis of WAT (Rodríguez et al, 2017)
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