Voluntary running of defined distances reduces body adiposity and its associated inflammation in C57BL/6 mice fed a high-fat diet

Authors: Yan, Lin; Sundaram, Sneha

Submitted to: Applied Physiology, Nutrition & Metabolism
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2017
Publication Date: 1/17/2017
Publication URL: http://handle.nal.usda.gov/10113/5852205
Citation: Yan, L., Sundaram, S. 2017. Voluntary running of defined distances reduces body adiposity and its associated inflammation in C57BL/6 mice fed a high-fat diet. Applied Physiology, Nutrition & Metabolism. http://dx.doi.org/10.1139/apnm-2017-0285.

Interpretive Summary: A sedentary lifestyle is a risk factor of obesity, which occurs when there is an imbalance between eating and burning calories. Excessive body fat mass in obesity produces inflammatory chemicals that further contribute to obesity and enhance inflammation and metabolic dysfunction. Physical exercise can reduce the risk of obesity by using the excessive calories ingested. We compared different running levels on changes in body fat and inflammation outcomes in mice consuming an obesity-inducing diet. The obesity-inducing diet, compared to a control diet, increased body fat mass by approximately 50% in sedentary mice. Voluntary running reduced body fat mass in a dose-dependent manner, improved insulin sensitivity and reduced inflammatory chemicals. While the lowest amount of running did not reduce fat mass it did improve some markers of inflammation. Our findings show that physical exercise is useful in reducing body fat mass and that running even at a low level that does not reduce body fat may be beneficial in reducing inflammation.

Technical Abstract: A sedentary lifestyle contributes to obesity. This study determined the effects of quantitative voluntary running on body adiposity and its associated inflammation in mice fed a high-fat diet. Male C57BL/6 mice were assigned to six groups and fed an AIN93G (sedentary) or a high-fat diet (sedentary, unrestricted running, or 75%, 50% or 25% of unrestricted running) for 12 weeks. The average daily running distance was 8.3, 6.3, 4.2, and 2.1 km for the unrestricted, 75%, 50%, and 25% unrestricted runners, respectively. The high-fat diet increased body fat mass by 46% in sedentary mice. Running reduced the fat mass in a dose dependent manner; there was no difference in fat mass between sedentariness and running 2.1 km per day. The high-fat diet in sedentary mice increased insulin resistance, hepatic triglycerides, and adipose and plasma concentrations of leptin and monocyte chemotactic protein-1 (MCP-1). Running, despite consumption of the high-fat diet, reduced these variables in a dose-dependent manner. While the high-fat diet decreased adiponectin in adipose tissue, running increased both adipose and plasma adiponectin in a dose-dependent manner. Running 8.3 and 6.3 km per day had the greatest but similar effects on the aforementioned measurements, but running 2.1 km per day did not affect these outcomes. However, even the lowest amount of running significantly decreased MCP-1 in adipose tissue and plasma. In summary, voluntary running 6.3 km per day is optimal for reducing body adiposity and its associated inflammation in C57BL/6 mice. That running 2.1 km per day decreased adipose MCP-1 indicates a benefit of exercise at a level that does not affect body adiposity. This reduction may be through mechanisms independent from changes in body adiposity.