Effects of monosodium glutamate-induced obesity in spontaneously hypertensive rats vs. Wistar Kyoto rats: Serum leptin and blood flow to brown adipose tissue

We compared the effects of hypothalamic obesity induced by neonatal monosod ium glutamate (MSG) treatment between spontaneously hypertensive rats(SHR) and normotensive Wistar Kyoto rats (WKY). Newborn WKY and SHR were injected intraperitoneally with 4 mg/kg body weight of MSG daily for 5 days. At 6 m onths of age, the obesity of SHR was more advanced than that of WKY, but at 14 months of age the severity of obesity was similar between the two strai ns, Hypertriglyceridemia was enhanced in MSG-treated SHR as compared with M SG-treated WKY, Systolic blood pressure measured by the tail-cuff method wa s consistently lower in MSG-treated SHR than in control SHR, whereas blood pressure was not affected by neonatal MSG treatment in WKY. Food restrictio n reduced body weight more in control SHR than in control WKY, with the for mer also showing enhanced ketogenesis, Neonatal MSG treatment abolished the accelerated reduction of body weight in SHR. Serum leptin concentration wa s markedly increased in MSG-treated obese rats, though no differences were seen between WKY and SHR in the control or MSG-treated groups. Serum leptin was closely correlated with both Lee obese index and mesenteric fat weight over the strain. Blood flow in interscapular brown adipose tissue (BAT) me asured by Laser Doppler flowmetry was significantly increased in response t o beta(3)-adrenoceptor agonist BRL26830A in both the control and MSG-treate d rats. However, the response of blood flow was not affected by MSG treatme nt or strain difference. The present study demonstrated some strain differe nces in response to neonatal MSG treatment between WKY and SHR. These diffe rences could not be explained by the difference in serum leptin level or be ta(3)-adrenergic reactivity in BAT.