An activated sympathetic nervous system affects white adipocyte differentiation and lipolysis in a rat model of Parkinson's disease.

Weight loss is an important nonmotor symptom associated with Parkinson's disease (PD). However, the cellular factors responsible for PD-induced weight loss remain unclear. Because the sympathetic nervous system plays an important role in lipid metabolism and fat cell differentiation, this study investigates whether PD-induced changes to this system are associated with weight loss in a rat model of PD. Body weight and food intake were measured in control and PD-model rats. After 10 weeks, retroperitoneal white adipose tissues (RWAT) were removed and weighed. Markers of the sympathetic nervous system were measured in the brainstem dorsal medulla and RWAT. Free fat acids (FFA), triglycerides (TG), adipocyte differentiation-related genes, and lipolysis-related molecules in the RWAT and serum were analyzed. Differences in body weight and food intake were insignificant in PD-model rats and control rats; however, relative RWAT weight and adipocyte surface area were significantly reduced in the PD group. Changes in markers of the sympathetic nervous system were observed in the brainstem dorsal medulla and RWAT of PD rats. Decreased mRNA expression levels of genes involved in adipocyte differentiation, decreased TG levels in RWAT, increased FFA in RWAT, and increased lipolysis-related molecules in RWAT and serum FFA were observed in PD rats. This study demonstrates that degenerated dopaminergic neurons in the nigrostriatal system correlate with increases in sympathetic nervous system function, resulting in lipolysis and inhibition of fat cell differentiation. These factors ultimately result in the decrease of RWAT in PD-model rats.