The enhanced hyperglycemic response to hemorrhage hypotension in obese rats is related to an impaired baroreflex

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The aim of the present study was to assess the metabolic adjustments in adult rats with autonomic imbalance induced by hypercaloric diet. Male Wistar rats (4 weeks of age) were fed a chow diet (CD, n = 12) or hypercaloric diet (HD, n = 13) for 19 weeks. Body weight and dietary intake were measured every week and the basal metabolic rate was assessed. After 19 weeks of diet, six animals from each group were anesthetized with a lethal dose of barbital sodium (100 mg/Kg body weight, intraperitoneal; i.p.). Lee index was evaluated and adipose pads weighted. The remaining animals had a silastic cannula placed into the jugular vein for drug administration, blood collecting, and hemorrhage (1.2 mL/100 g bw/2 min). A polyethylene catheter (PE50) was inserted into the abdominal artery through the femoral artery for cardiovascular monitoring. The assessment of autonomic balance was done by evaluation of baroreflex sensitivity (intravenous (IV) injection of phenylephrine and sodium nitroprusside) and hemorrhage (1.2 mL/100 g bw/2 min). As expected, the HD induced obesity; increased weight gain (28%), adipose pads weight, and baroreflex dysfunction. The plasma level of free fatty acids and triacylglycerols were increased in HD rats by about 124% and 424%, respectively, as well as the basal metabolic rate measured at 19th weeks of diet (p < 0.01). We observed that baroreflex sensitivity to phenylephrine was reduced by about 50%, and the hyperglycemic response to hemorrhage hypotension was increased by 128% in HD rats. We found also a negative correlation between the alteration in baroreflex sensitivity and the increase in hyperglycemic response to hemorrhage in the obese rats (r = 0.72, p < 0.01) and a strong positive correlation between the increased Lee index and the hemorrhagic hyperglycemia (r = 0.93, p < 0.01). Our data demonstrate that obesity induced by hypercaloric diet in Wistar rats promotes an autonomic imbalance, which interferes with metabolic responses dependent on baroreflex sensitivity. In addition, we showed the existence of close correlation between the loss of baroreflex sensitivity and the degree of obesity.

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