20-Hydroxyecdysone induces brown adipose tissue glycogen accumulation in obese gerbil model: Histochemical study

Obesity is a major public health problem. It is defined as an abnormal or excessive accumulation of fat harmful to health. Although the majority of obesity studies focus on changes in white adipose tissue, investigations into brown adipose tissue and its activation are becoming an increasingly popular area of interest. In this study, we attempted to examine the effects of 20-hydroxyecdysone (20E) on the glycogen amount stored in interscapular brown adipose tissue (IBAT). 15 gerbils were divided into: control group submitted to natural diet, two experimental groups submitted to high-calorie-diet supplemented or not with 20E. At the end of the experimental period, the animals were sacrificed and the IBAT was fixed in 10% formalin. Sections of 5 micrometers were made and stained with periodic acid-Schiff (PAS), to highlight the polysaccharides. Glycogen quantification in IBAT was performed using ImageJ software (NIH, Bethesda, MD, USA). PAS staining demonstrated that in the control gerbils, IBAT had strong cytoplasmic presence of glycogen. However, in the high-calorie diet group, the microscopy images had weaker PAS staining with lipid droplets infiltration compared to control group. We observed an important IBAT cytoplasm staining with PAS in group treated with 20E, indicating cells glycogen overload with reduction of lipid droplets accumulation. The quantification of glycogen had confirmed the qualitative study. Although the relationship between brown adipose tissue and glycogen storage remains underestimated and misunderstood, these preliminary results show that 20E could activate obese gerbil's brown adipocytes to store more glycogen.