In vitro insulin resistance of human adipocytes isolated from subjects with noninsulin-dependent diabetes mellitus.

Abstract

A B S T R A C T To assess possible cellular mechanisms of in vitro insulin resistance in noninsulin-dependent diabetes mellitus (NIDDM), maximum insulin-stimulated glucose transport and utilization and insulin binding were measured in adipocytes isolated from weight-matched normal glycemic subjects and patients with NIDDM. Glucose transport rate was determined by measuring the amount of [U-'4C]-D-glucose taken up by incubating adipocytes at trace concentrations of glucose (300 nM), and glucose metabolism by estimating the amount of lactate, CO2, triglyceride, and total glucose carbons retained in the cells following incubating at 5.5 mM glucose. Insulin binding was measured at 50, 100, and 200 pM [mono'25 -tyrosinyl A,J4insulin. Both maximum insulin-stimulated glucose transport and utilization in adipocytes from diabetic subjects were 40% (P < 0.01) and 32% (P < 0.05) lower, respectively, than values obtained for subjects with normal glucose tolerance. In addition, the maximum capacity of glucose transport was correlated with the maximum capacity of glucose utilization (r = 0.81, P < 0.001). Furthermore, fasting plasma glucose concentrations of diabetic subjects were negatively correlated with both maximum insulin-stimulated glucose transport (r = -0.56, P < 0.05) and glucose utilization (r = -0.67, P < 0.05). Since basal glucose transport in adipocytes from diabetic subjects was also 33% lower than in adipocytes from normal subjects, there was no change in the relative ability of insulin to stimulate glucose transport. However, there was a 64% decrease in the sensitivity of the glucose transport system to insulin (P < 0.05), unrelated to concomitant Address reprint requests to Dr. James E. Foley.

Regional variation in adipose tissue insulin action and GLUT4 glucose transporter expression in severely obese premenopausal women

“…The stimulation of glucose transport by insulin in this study (2-3-fold) is less important than that commonly reported in rat adipocytes (10-20-fold) [see [33] for review] but similar to that found in previous studies using human fat cells [25,34,35]. This apparent discrepancy is unlikely to be explained by methodological differences in adipocyte isolation since the magnitude of the antilipolytic effect of insulin was comparable to that observed in rat adipocytes.…”

“…Glucose transport was determined using d -[ 14 C(U)]-glucose as previously described by Kashiwagi et al [25] with minor modifications [26] Measurement of adipocyte lipolysis. Extracellular glycerol release was used as the indicator of adipocyte lipolysis and was determined as previously described (21) using a cell concentration of 500-1000 cells/100 m l. NADH concentration was measured by bioluminescence with a luciferase solution, using a 1251 LKB Wallac luminometer.…”

Selective Insulin Resistance in Adipocytes

“…Thus, although we cannot be certain that the same defect causes insulin resistance in each case, it is likely that this represents a convergent defect that is manifested as a change in the maximum response to insulin. Importantly, previous studies in adipocytes and skeletal muscle from humans with T2D or obesity have shown a defect in maximal insulin-stimulated glucose transport and utilization in vitro (56,57). Moreover, hyperinsulinemic glucose clamp studies in individuals with T2D also reveal a defect in whole body glucose utilization even at maximal insulin concentrations (58).…”

Fat cell enlargement is an independent marker of insulin resistance and ‘hyperleptinaemia’

“…Cellassociated radioactivity was determined by scintillation counting. Under these experimental conditions glucose uptake is mainly determined by the rate of transmembrane glucose transport [22] and it is calculated as glucose clearance from the incubation medium according to the following formula:…”