IGF-I contributes to glucose homeostasis in the Berlin Fat Mouse Inbred line

Abstract

This study aimed to investigate the tissue-specific role of the insulin-like growth factor 1 (IGF-I) on glucose homeostasis in the high-fatness selected Berlin Fat Mouse Inbred (BFMI) line. Therefore, the expression of different IGF-I transcripts and IGF-I protein, IGF-binding proteins, insulin as well as glucose tolerance was analyzed in BFMI in comparison with that in lean mice. In addition, dietary effects were investigated. The BFMI line showed normal blood glucose clearance on standard diet, but on high-fat diet the clearance was impaired, indicating the beginning of insulin resistance. Circulating IGF-I and insulin levels were elevated in BFMI than in lean mice on both diets along with a down-regulation of three IGF-I binding proteins in BFMI mice. Serum IGF-I levels corresponded with the expression pattern for both hepatic and one class II splice variants in reproductive adipose tissue, but not in muscle. High insulin and high IGF-I levels likely prevent BFMI mice from diabetes.

Keywords::

• Obesity
• glucose
• diabetes
• splice variant
• insulin-like growth factor binding protein

Acknowledgment

We thank Katja Schmolz for advice and technical support and Dr. Christina Neuschl for mice dissection.

Declaration of interest: This research was supported by grants from the German National Genome Research Network (NGFN: 01GS0486, 01GS0829) and by the German Research Foundation (GRK1208). The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.