Biomedical subjects
Publications and source records attributed to R Poledne.
A multicompartmental analysis of the plasma triglyceride kinetics after [3H]glycerol administration revealed that hypertriglyceridemia in vitamin c deficient guinea-pigs was caused by a slowed triglyceride removal from the plasma compartment.
The study summarizes the metabolic effects of increased sucrose or fructose intake. Compared with the traditional carbohydrate source-starch, a high intake of the above two carbohydrates produces a number of metabolic and other changes that can have a pathological effect. A thus induced metabolic and other changes that can have hepatic lipid synthesis, hypertriglyceridaemia and increased tissue lipid utilization, while tissue glucose utilization decreases. Moreover, the increase of these carbohydrates can lead to some pathological organ changes and elevation of blood pressure.
In experiments on two animal species we studied the effect of age, altered motor activity and alimentary experimental atherosclerosis on a variety of variables of lipid metabolism, particularly on cholesterol and fatty acid levels and formation. Fatty acid and cholesterol cumulation in tissues, including the rat aorta, increases with age (from 2 to about 20 months of age), while their formation decreases. A decrease of motor activity seems to be at play in this phenomenon in older animals and is apparently due especially to a faster rate of decrease of lipid degradation with ageing. Enforced increase of motor activity in rats (60 or 120-day adaptation on a treadmill - 18 m/min/3 hr/day) results in a decreased tissue cumulation of lipids including cholesterol despite their increased formation. In animals of the same age but allowed a limited amount of motor activity the situation produces reverse changes in lipid levels and formation. Changes in lipid metabolism are effected also by a higher level of spontaneous activity (induced by a higher number of young in the litter) and by increased motor activity of the dams during pregnancy. Hyperkinetic animals show a uniform exogenous (alimentary) cholesterol turnover. However their alimentary cholesterol absorption and high-density lipoprotein cholesterol turnover are elevated. Two respectively 10 months following the intake of 2% of dietary cholesterol minipigs exhibit elevated cholesterolaemia, reduced endogenous cholesterol synthesis in the liver and the aorta versus a decreased endogenous fatty acid synthesis. Plasma/vascular wall cholesterol transport in hypercholesterolaemic animals is about 50% higher, while the level of cholesterol in the medium remains constant. Most experimental animals show histologic evidence of incipient atheromatous changes not earlier than 10 months following the start of experimental diet.
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Feeding of a glycerine rich diet with sufficient supply of essential amino acids (mixture of casein and gelatine) causes a significant reduction of the serum triglyceride level in rats. To study some aspects of this triglyceride lowering effect the in vivo incorporation of C14-1-acetate and C14-1-palmitate into the serum and liver lipids as well as the lipoprotein lipase and the hormone sensitive lipolytic activity of the epididymal adipose tissue in vitro were estimated. After feeding the gelatine containing diet the incorporation of labelled acetate and palmitate into the serum triglycerides was significantly decreased with no change of the incorporation into the liver triglycerides and without detectable accumulation of liver lipids. The decreased serum triglyceride level of the serum corresponded to a decreased lipoprotein lipase activity in the epididymal adipose tissue, whereas the basal and norepinephrine stimulated lipolysis of this tissue was not affected. From these results it is concluded that due to feeding of a glycine rich diet the triglyceride secretion of the liver is decreased leading to a lower serum triglyceride level.
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Palmitate and glucose oxidation were investigated in isolated hemidiaphragm of rats in which hypertriglyceridemia was induced by dietary fructose. Palmitate oxidation was increased, and glucose oxidation was reduced, in fructose-fed rats, as compared with glucose-fed controls. Glucose incorporation into muscle glycogen was similar in both dietary groups.
In white male Wistar rats aged 2, 4, 6, 9, 12, 18 and 32 months, receiving a standard laboratory diet (25 cal% proteins, 22 cal% fat and 53 cal% glycides) we assessed the total amount of fatty acids in the carcass and in vitro lipogenesis in liver and adipose tissue by the means of glucose-14C(U). The amount of body fat increased with age; the highest rate of increase in the percentage of body fat occurs 2 to 4 months after birth. Incorporation of 14C of glucose into total liver lipids attains maximum values in the group of rats age 2 to 4 months. By the age of 6 months lipogenesis decreased to a level observed in all the remaining age groups. In adipose tissue, the incorporation of 14C into total lipids decreased between the age of 2 to 4 months, a further decrease was observed around the age of 6 months. No appreciable changes were noted in any of the older age groups.
Three weeks of ischemia of the right hind limb in rat produced by ligature and severing of the right common iliac artery, resulted in changes in FFA transport and blood flow in the regenerating tibialis muscle. FFA transport was measured using i.v. administered palmitate-1-14C bound to albumin. Uptake of palmitate-1-14C or 86Rb 90 s after i.v. administration was decreased in ischemic tibialis muscle, whereas no apparent effect of ischemia on the contralateral muscle was seen. Plasma FFA outflow rate measured according Beker and Rostami was not affected by the presence of an ischemic extremity in comparison with control animals. The plasma FFA inflow rate into the ischemic muscle was markedly decreased to values of 6.5 mmumoles FFA/min/g whereas in control animals values were 18.8 mmumoles FFA/min/g wet tissue. Decreased FFA inflow rate to the ischemic tibialis muscle was due to the decreased radioactivity of palmitate-1-14C in the muscle under the conditions of a constant plasma FFA pool. Differences in the uptake of palmitate-1-14C in tibialis muscle were dependent upon the muscle blood flow, which was markedly decreased in the ischemic muscle on indirect measurement with 86Rb or with the 133Xe clearance.
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