Diabetes, Vol 36, Issue 5 620-625, Copyright © 1987 by American Diabetes Association
Insulin-receptor kinase activity of adipose tissue from morbidly obese humans with and without NIDDM
MK Sinha, WJ Pories, EG Flickinger, D Meelheim and JF Caro
We have determined glucose transport, insulin binding, and insulin-receptor
kinase activity in adipose tissue from morbidly obese patients with and
without non-insulin-dependent diabetes mellitus (NIDDM). The insulin
sensitivity and responsiveness of glucose transport in freshly isolated
adipocytes were significantly reduced in NIDDM subjects compared with
nondiabetics. This was due in part to decreased insulin binding in
adipocytes. Reduced specific 125I-labeled insulin binding was also observed
in crude detergent extracts and partially purified insulin receptors from
adipose tissue. In addition, the basal and insulin-stimulated
tyrosine-specific protein kinase activity per milligram of protein was
significantly decreased in NIDDM patients compared with nondiabetics. The
differences between maximally insulin-stimulated and basal kinase
activities expressed by insulin-binding activity were also significantly
reduced in NIDDM subjects. We conclude that insulin resistance in morbidly
obese patients with NIDDM is due to both insulin-binding and postbinding
defects. One of the postbinding defects in NIDDM appears to be impaired
insulin-receptor kinase activity of fat tissue.