Effects of Obesity on Serum Calcium and Parathyroid Hormone in Zucker Rat Model (P08-032-19)

Abstract

Abstract Objectives Obesity has been epidemic in the United States and world for more than two decades. Obesity is associated with type 2 diabetes, cardiovascular disease and certain types of cancer. Primary Hyperparathyroidism (pHPT) is also more commonly seen in western societies and is also increasing. Previously, we have reported that obesity caused a significant reduction in serum Vitamin D using obese rat model. The role of obesity on serum Ca and PTH is less known. The main objective of this study was to investigate the effect of obesity on serum calcium (Ca) and parathyroid hormone (PTH) using obese Zucker rat model. Perhaps this could serve as an animal model for pHPT. Methods Five-week-old female lean and obese Zucker rats were used. After one week of acclimation, lean and obese rats were maintained on AIN-93 G diet for 155 days. Rats were weighed twice per week. At the end of the experiment, rats were sacrificed and serum were collected to measure serum protein, Ca and PTH levels. Serum protein was measured by atomic absorbance spectrophotometry, serum calcium was measured by using with Arsenazo III method and serum PTH by a two-site enzyme-linked immunosorbent assay using a commercially available rat intact PTH ELISA kit. Results Our results shows that 1) obese rats gained significantly (P < 0.001) more weight than lean rats; 2) obesity caused a significant increase in serum protein (P < 0.05); 3) obesity increased significantly serum Ca (P < 0.05) and 4) increased a significant decrease PTH levels (P < 0.05). Conclusions Our results show that obesity increased serum Ca and decreased PTH levels. This is a physiologic negative feedback relationship expected in a normal parathyroid system. If this had been a model for pHPT, the calcium and PTH levels would have been simultaneously elevated. It seems this animal model may not be model for pHPT. Funding Sources Arkansas Bioscience Institute.