G. Yoshino et al., EFFECT OF LONG-TERM EXOGENOUS HYPERINSULINEMIA AND FRUCTOSE OR GLUCOSE SUPPLEMENTATION ON TRIGLYCERIDE TURNOVER IN RATS, Atherosclerosis, 129(1), 1997, pp. 33-39
We examined the effect of long-term (6 months) hyperinsulinemia on VLD
L-triglyceride turnover in male Wistar rats. Hyperinsulinemia was indu
ced in rats by daily s.c. injection of Ultralente insulin (6 U/day at
19:00). Fructose (F) or glucose (G) was supplied in the drinking water
(10%) in order to prevent hypoglycemia. The rats were divided into 5
groups: (1) hyperinsulinemia with F water: group F+I; (2) hyperinsulin
emia with G water: group G+I; (3) F water alone: group F; (4) G water
alone: group G; and (5) control rats without sugar water group C. Afte
r 6 months of daily insulin injection triglyceride secretion rate (TGS
R) was estimated using Triton WR1339 in all the rats. Groups F+I and G
+I were obese and hypoglycemic compared to the other groups. Fasting p
lasma glucose level of group F was higher than any other group value.
TGSR of group F+I was significantly higher than that of the control gr
oup, while that of group G+I was not, indicating that long-term hyperi
nsulinemia can stimulate hepatic triglyceride production when the rats
were supplemented only with fructose. On the other hand, the rats in
group G+I showed the lowest plasma free fatty acid level of all and th
eir postheparin lipolytic activity was significantly elevated compared
to that of the control rats. Moreover, they had suppressed plasma tri
glyceride levels and its fractional catabolic rate was significantly i
ncreased, suggesting that hyperinsulinemia can still stimulate triglyc
eride removal from the circulation of glucose supplemented rats even a
t month 6. In conclusion, exogenous hyperinsulinemia can stimulate hep
atic triglyceride secretion even after 6 months duration when suppleme
nted with fructose, while its stimulating effect on triglyceride remov
al from the circulation can be seen only with glucose supplementation.
Thus, the effect of long-term hyperinsulinemia on plasma triglyceride
turnover differs depending on the supplemented monosaccharides. (C) 1
997 Elsevier Science Ireland Ltd.