This study aimed to evaluate the effect of
hyperinsulinemia on
hypertriglyceridemia-induced pressor response in normal and
fructose-induced
insulin resistant rats. The rats were divided into six groups of eight rats and were fed a
fructose-enriched diet (FINs, F(INS+TG)) or a regular chow diet (C, C(TG), C(INS), C(INS+TG)) for 8 wks. The acute experiment was conducted at the end of wk 8 and consisted of a 30-min basal period and followed by a 120-min test period. After the basal period,
somatostatin (1.3 microg/kg/ min) combined with
regular insulin (0.6 or 4 mU/kg/min) and variable
glucose infusion were given to clamp euglycemia and euinsulinemia in C and C(TG) or euglycemia and
hyperinsulinemia in CINs, C(INS+TG), F(INS) and F(INS+TG). During test period,
lipofundin (a
triglyceride emulsion) was infused into CTG, C(INS+TG), F(INS+TG) and saline instead was infused into C, C(INS), FINS. Plasma
insulin and
triglyceride levels were significantly higher in
fructose-fed rats than in normal rats. During the test period, the
lipofundin infusion (1.2 ml/kg/hr) increased plasma
triglyceride levels by 368 +/- 39, 351 +/- 71 and 489 +/- 38 mg/dl compared with their baseline levels in
lipid-infused groups. During the test period, low-dose
insulin infusion kept plasma
insulin at basal levels in C and C(TG) and high-dose
insulin infusion increased plasma
insulin levels about 6 times the baseline
insulin level in C.
Glucose infusion rate (GIR) was significantly higher in rats with high
insulin infusion than those with low
insulin infusion. The increase in GIR was lower in
fructose-fed groups than in control groups under similar
hyperinsulinemia. Rats with or without
lipofundin infusion did not alter GIR during the test period. The present results demonstrated that
hypertriglyceridemia-induced pressor response was diminished under hyperinsulinemic condition in both normal and
fructose-induced
insulin resistant rats.