Abstract
Atherosclerotic cardiovascular diseases are leading cause of death in the diabetics who have hyperlipidemia.
To study lipoprotein metabolism in diabetics, streptozotocin diabetes was induced in rat as a good model for study of human insulin-dependent diabetics. We attempted to study the in vivo metabolism of esterified cholesterol in plasma high density lipoprotein and also in low density lipoprotein (d<1.063) of the diabetic rats.
Diabetic rats, pre-fed and maintained on a purina chow which contained 4.5% fat by weight, had marked hypertriglyceridaemia and rather increased HDL-cholesterol. HDL obtained from non-diabetic rats and labeled with 3H in the esterified cholesterol moieties was injected to diabetic and non-diabetic rats. Blood samples were obtained from tail vein at 15, 30 min, or 1, 2, 4, 8 hours after the injection.
The decay of 3H in the esterified cholesterol moieties from plasma was bi-exponential in both diabetic and non-diabetic control rats. Also, the decay of labeled HDL in the plasma was biexponential in the two group of rats.
Following injection of labeled HDL, radioactivity recovered from low density lipoprotein at all time interval was less than 2.1% and did not show any peak activity in both groups of rats.
Fractional catabolic rate (FCR) were calculated following the curve peeling technique as described by Matthews at steady-state conditions. FCR and half life of esterified 3H-cholesterol in the diabetic plasma were faster and shorter than those of non-diabetic rats (p<0.01). Also, FCR and half life of esterified 3H-cholesterol in the HDL of diabetic rats were faster and shorter than those of non-diabetic rats (p<0.1).
These results suggest that the synthesis and catabolism of HDL cholesterol ester are enhanced in the untreated streptozotocin diabetic rat.
An increase in HDL cholesterol ester turnover may reflect the enhanced catabolism of body nutritional reserves in uncontrolled diabetes mellitus.
