Neonatal monosodium glutamate treatment increases epididymal adipose tissue sensitivity to insulin in three-month old rats

• Published in: Brazilian journal of medical and biological research Vol. 27; no. 5; p. 1249
• Main Authors: Marmo, M R, Dolnikoff, M S, Kettelhut, I C, Matsushita, D M, Hell, N S, Lima, F B
• Format: Journal Article
• Language: English
• Published: Brazil 01-05-1994
• Subjects: Adipocytes - drug effects; Adipocytes - metabolism; Adipose Tissue - drug effects; Adipose Tissue - metabolism; Animals; Animals, Newborn; Deoxyglucose - pharmacokinetics; Epididymis - drug effects; Epididymis - metabolism; Glucose - metabolism; Insulin - administration & dosage; Insulin - pharmacology; Insulin Resistance - physiology; Male; Rats; Rats, Wistar; Sodium Glutamate - pharmacology
• ISSN: 0100-879X

We determined the response of glucose transport to insulin in isolated adipocytes and the lipogenic activity of insulin in fragments of epididymal adipose tissue obtained from male MSG-obese rats. Basal glucose transport rates (pmol 3 min-1 10(5) cells-1) were 100% higher in MSG than in control cells (3-month old male Wistar rats) pre-incubated for 30 min (P < 0.01). Nevertheless, when expressed as fmol 3 min-1 microns 2 cell surface area-1, transport rates were similar for the two groups (31.2 +/- 2.6 for MSG and 26.5 +/- 3.2 for controls, N = 7). No differences were observed in maximally insulin-stimulated glucose transport rates between groups (72.6 +/- 10.6 for MSG and 101.0 +/- 12.0 for controls, N = 7). In contrast, for adipocytes pre-incubated for 2 h, the basal uptake rates were 3.7 times higher and the maximal response to insulin was 103% higher in cells from MSG rats compared to control cells. These alterations in MSG rat adipocytes were accompanied by changes in cell sensitivity to insulin (EC50, 0.13 +/- 0.02 ng/ml for MSG vs 0.46 +/- 0.10 ng/ml for controls, P < 0.01). The rates of incorporation of labelled substrates (3H2O and 14C-glucose) into total lipids showed that in vitro lipogenesis was also 79% (3H2O) and 250% (14C-glucose) higher in MSG adipose tissue fragments. The MSG animals were consistently hyperinsulinemic. These data suggest that the obesity of 3-month old MSG rats is a metabolic alteration characterized by an enhanced adipocyte capacity to transport glucose and to synthetize lipids resulting in increased insulin sensitivity.