Metabolic Effects of a Stabilizing Peptide Fusion Protein of Leptin in Normal Mice

Abstract

Leptin is a protein hormone produced by adipocytes. It is secreted into the blood stream and plays a key role in regulating body energy homeostasis by inhibiting feeding behavior followed by decreased body weight. Because protein aggregation is a major problem in therapeutic proteins, we previously demonstrated that a stabilizing peptide (SP) fusion protein of leptin (SP-leptin) appeared to resist aggregation induced by agitation, freezing/thawing, or heat stress. In this study, we fused mouse leptin with the stabilizing peptide and compared the biological activities of leptin and SP-leptin in vivo using a male C57Bl mouse model and ex vivo using MCF7 breast cancer cell lines. Each group of mice was treated with saline, leptin, and SP-leptin for 20 days and the differences in body weight, food intake, abdominal fat contents, and TG concentration were measured. The SP-leptin appeared to decrease the body weight and food intake in male C57Bl mice more significantly than wild type leptin, and the SP-leptin treated MCF7 cells displayed better cell proliferation than leptin. As a consequence of decreased body weight, the SP-leptin treated mouse group showed decreased abdominal fat contents and low triglyceride (TG) concentration. Moreover, the SP-leptin treated mouse group had fewer lipid droplets in liver and reduced lipid droplet size when analyzed by Oil red O and H & E staining. These results demonstrated that SP-leptin is more effective than wild type leptin in normal mice in lowering their body weight and fat contents in the abdominal region, the serum, and the liver.

Evaluation of the Bioefficacy of a Stabilized Form of Human Growth Hormone (SP-hGH)

“…Proliferation of liver cells and IGF-1 levels increased in the hGH and SP-hGH-treated groups (n = 10/group). ***p < 0.001. fusion protein in vivo was signifi cantly improved compared with leptin alone [ 34 ] . We previously confi rmed that SP-hGH bioactivity was improved compared with hGH alone using an Nb2 cell line [ 8 ] .…”