Changes in the sensitivity of lipogenesis in rat hepatocytes to hormones and precursors over the diurnal cycle and during longer-term starvation of donor animals.

Gibbons, Geoffrey F.; Pullinger, Clive R.; Björnsson, O G

doi:10.1016/s0022-2275(20)34453-9

Cited by 23 publications

(2 citation statements)

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“…To compensate for hormone biodegradation (McGarry et al, 1978;Beynen et al, 1979), similar quantities of each hormone were added at 1 h intervals. In those experiments in which the rate of fatty acid synthesis was determined, 3H20 (1 mCi/ml) was present in the incubation medium and the rate of synthesis was measured as described previously (Gibbons et al, 1984).…”

Section: Maintenance Of Animals Preparation Of Hepatocytes and Incubation Conditionsmentioning

confidence: 99%

“…Pronounced diurnal variations in hepatic lipid metabolism occur both in experimental animals (see, e.g., Hems et al, 1975;Gibbons et al, 1984) and in man (Schlierf & Dorow, 1973;Parker et al, 1982), probably as a result of the rhythmic changes in food consumption. In view of this, we wished to determine whether diurnal changes in food intake modified the response of hepatic VLDL secretion to diets high in polyunsaturated fat. Finally, although the relationship between dietary fat intake and plasma lipoprotein composition has been under intense scrutiny for several years (see, e.g., Goldberg & Schonfeld, 1985), no information is available concerning the effect of high-fat-containing diets on the secretion of hepatic VLDL esterified and non-esterified cholesterol.…”

Section: Introductionmentioning

confidence: 99%

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Regulation of hepatic very-low-density lipoprotein secretion in rats fed on a diet high in unsaturated fat

Gibbons¹,

Pullinger²

1987

Biochemical Journal

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Rats were fed ad libitum on either a standard, high-carbohydrate, chow diet or a similar diet supplemented with 15% unsaturated fat (corn oil). Hepatocytes were prepared either during the dark phase (D6-hepatocytes) or during the light phase (L2-hepatocytes) of the diurnal cycle. In hepatocytes from rats fed on the unsaturated-fat-containing diet, secretion of very-low-density lipoprotein (VLDL) triacylglycerol was inhibited to a greater extent in the D6- than in the L2-hepatocytes. Plasma non-esterified fatty acid concentrations were elevated to the same extent at both D6 and L2 in the unsaturated-fat-fed animals. The secretion of VLDL esterified and non-esterified cholesterol was relatively insensitive to changes in the unsaturated-fat content of the diet. This resulted in proportionate increases in the content of these lipid constituents compared with that of triacylglycerol in the nascent VLDL. There was also an increase in the ratio of esterified to non-esterified cholesterol in the nascent VLDL produced by hepatocytes of the unsaturated-fat-fed animals. In the D6-hepatocytes from the unsaturated-fat-fed animals, the decrease in the secretion of VLDL triacylglycerol could not be reversed by addition of exogenous oleate (0.7 mM) to the incubation medium. In contrast, addition of a mixture of lactate (10 mM) and pyruvate (1 mM) stimulated both fatty acid synthesis de novo and the rate of VLDL triacylglycerol secretion. Secretion of esterified and non-esterified cholesterol also increased under these conditions. Insulin suppressed the secretion of VLDL triacylglycerol and cholesteryl ester under a wide range of conditions in all types of hepatocyte preparations. Non-esterified cholesterol secretion was unaffected. In hepatocytes prepared from the fat-fed animals, these effects of insulin were more pronounced at D6 than at L2. Glucagon also inhibited VLDL lipid secretion in all types of hepatocyte preparations. The decrease in cholesterol secretion was due equally to decreases in the rates of secretion of both esterified and non-esterified cholesterol.

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Section: Maintenance Of Animals Preparation Of Hepatocytes and Incubation Conditionsmentioning

confidence: 99%