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The Influence of Insulin, Triiodothyronine (T₃) and Insulin-Like Growth Factor-I (IGF-1) on the Differentiation of Preadipocytes in Serum-Free Cultures of Pig Stromal-Vascular Cells

U.S. Department of Agriculture^1,2, Athens, GA 30613

Abstract

Adipose tissue stromal-vascular (S-V) cells were obtained from 1-d-old pigs by enzymatic digestion and then grown to confluence (1 to 4 d) in 10% fetal bovine serum. Cultures then were shifted to serum-free media for 7 d. One and 50 nM insulin with transferrin (5 µg/ml) significantly increased (P < .05) the cytodifferentiation of preadipocytes in serum-free cultures of S-V cells compared with control cultures (no hormones). Fifty nanomolar and 1 µM insulin with transferrin increased the specific activity of glycerol-phosphate dehydrogenase (GPDH) and the soluble protein levels of S-V cultures compared with control cultures. Ten nanomolar insulin-like growth factor-1 (IGF-1) increased (P < .05) GPDH specific activity, soluble protein and preadipocyte cytodifferentiation compared with control cultures. Triiodothyronine (T₃) supplementation (2 to 10 nM) increased (P < .05) GPDH specific activity and increased lipid droplet size in preadipocytes compared with control cultures (no T₃ but with insulin and transferrin). Cytodifferentiation of preadipocytes and soluble protein levels were not enhanced by T₃ supplementation. Furthermore, T₃ did not influence any parameters when added to S-V cultures that did not contain insulin. These data demonstrate that physiological levels of insulin or IGF-I can stimulate porcine preadipocyte differentiation in the absence of other hormones or growth factors.

¹ Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products which may be suitable.

² R. B. Russell Agric. Res. Center.