Effects of Chronic Insulin and High Glucose on Insulin-Stimulated Responses in Human Preadipocytes

Abstract

The preadipocyte is crucial for healthy adipose tissue (AT) remodeling, and insulin resistance in these cells may contribute to AT dysfunction. Chronic exposure to insulin and high glucose induces insulin resistance in the 3T3-L1 mouse adipocyte cell line in vitro, however, whether this occurs in human preadipocytes is not known. To investigate this, human preadipocytes were isolated from subcutaneous AT obtained from 6 female patients undergoing elective surgery (Research Ethics Board-approved). Human preadipocytes were incubated in 5 mM glucose or 25 mM glucose in the presence or absence of 0.6 nM insulin for 48 hours, followed by acute 100 nM insulin stimulation. 25 mM glucose + 0.6 nM insulin inhibited insulin-stimulated tyrosine phosphorylation of IR-β (77%) and IRS-1 (81%) compared to NG (p<0.01), however, insulin-stimulated Ser473 Akt phosphorylation was not affected. 25 mM glucose and/or 0.6 nM insulin did not significantly change levels of pro-inflammatory adipokines. 25 mM glucose and/or 0.6 nM, prior to and/or during 14 days of adipogenic induction, did not affect levels of adipogenic markers or intracellular triglyceride accumulation.