A sled dog model for positive health effects of weight management and exercise

Abstract

Hypertrophic white adipose tissue found in obesity leads to chronic inflammation and reduced insulin sensitivity, bringing rise to a myriad of diseases and is a significant risk factor for premature death. Obesity can be combatted with physical activity, dietary restrictions, or a combination of the two. However, exercise training regardless of changes in body weight has been shown to improve metabolic health. Expanding on a previous study of changes in metabolic biomarkers upon weight gain and after a period of athletic conditioning, in this project we used a sled dog model to examine biomarker shifts over a course of sedentary weight gain, exercise training without weight loss, and exercise training accompanied by weight loss. In order to examine the benefits of exercise training both with and without weight loss, a cohort of healthy sled dogs each served as their own controls as we observed changes in metabolic indices in conjunction with moderate body weight gain, exercise training while sustaining the higher body weight, and exercise training with weight loss.We focused on indices specifically linked to type II diabetes - an obesity-linked disease affecting more than 10% of American adults. Biomarkers measured include plasma glucose, glucose transporter 4, insulin, and hemoglobin A1c. We also measured inflammatory cytokines tumor necrosis factor alpha and interleukin 6, as well as hormones leptin, adiponectin, and resistin. Many biomarkers measured produced not significant change or fell outside of our standard concentrations, but plasma glucose, glucose transporter 4, and tumor necrosis factor alpha produced intriguing results. Weight gain increased plasma glucose while exercise training increased glucose transporter 4 present on peripheral blood mononuclear cells. The changes we observed to plasma glucose, glucose transporter 4 and tumor necrosis factor alpha may be indicative of reduced insulin sensitivity with exercise and weight loss. We believe this may be the result of the high energy demand of exercise training coupled with low caloric availability.