Mr. Marmo et al., NEONATAL MONOSODIUM GLUTAMATE TREATMENT INCREASES EPIDIDYMAL ADIPOSE-TISSUE SENSITIVITY TO INSULIN IN 3-MONTH OLD RATS, Brazilian journal of medical and biological research, 27(5), 1994, pp. 1249-1253
We determined the response of glucose transport to insulin in isolated
adipocytes and the lipogenic activity of insulin in fragments of epid
idymal 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 mum2 ce
ll 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 differenc
es were observed in maximally insulin-stimulated glucose transport rat
es between groups (72.6 +/- 10.6 for MSG and 101.0 +/- 12.0 for contro
ls, N = 7). In contrast, for adipocytes pre-incubated for 2 h, the bas
al uptake rates were 3.7 times higher and the maximal response to insu
lin 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 0.4
6 +/- 0.10 ng/ml for controls, P<0.01). The rates of incorporation of
labelled substrates (H2O)-H-3 and C-14-glucose) into total lipids show
ed that in vitro lipogenesis was also 79% ((H2O)-H-3) and 250% (C-14-g
lucose) higher in MSG adipose tissue fragments. The MSG animals were c
onsistently hyperinsulinemic. These data suggest that the obesity of 3
-month old MSG rats is a metabolic alteration characterized by an enha
nced adipocyte capacity to transport glucose and to synthetize lipids
resulting in increased insulin sensitivity.