Objective: To investigate the integrated effects of adipocytes on rat beta-cells, differentiated 3T3L1 adipocytes and rat islet cells co-culture system was established.
Methods: There were two groups: control group (SD rat islet cells) and co-culture group (islet cells and 3T3L1 adipocytes coculture system). Islet cells were obtained for determination of (1) insulin secretion and insulin content; (2) mRNA expressions of GLUT2, GCK and Kir6.2; (3) protein expressions of IR-beta, IRS-1 and their tyrosine phosphorylation level.
Results: (1) At low glucose, insulin secretion of co-culture group increased compared with that of control group (0.79 +/- 0.35) ng x h(-1) x ml(-1) islet vs. (0.38 +/- 0.09) ng x h(-1) x ml(-1) x islet, P = 0.028. At high glucose, insulin secretion of those two groups was almost at the same level (P = 0.760). Compared with control group (2.84 +/- 0.92), stimulation index (SI, insulin release at high glucose/ low glucose) of co-culture system decreased to (1.57 +/- 0.61, P = 0.04). And the insulin content of the both groups was almost at the same level (P = 0.102). (2) The mRNA of GCK, GLUT2 and Kir6.2 in co-culture group downregulated to (0.27 +/- 0.11, P = 0.01), (0.34 +/- 0.24, P = 0.009) and (0.41 +/- 0.09, P = 0.003) compared with control group (mRNA = 1). (3) The protein levels of IR-beta, IRS-1 and their tyrosine phosphorylation decreased in co-culture system.
Conclusions: 3T3L1 adipocytes are involved in beta-cell dysfunction, which may facilitate the development of type 2 diabetes. The effects may be mediated by multiple pathways, which include downregulation of GSIS related gene expressions and suppression of islet cell insulin signaling.