Variations in plasma apolipoprotein C-III levels are strong correlates of the triglyceride response to a high-monounsaturated fatty acid diet and a high-carbohydrate diet

The effects of a high carbohydrate diet fed to young rats for 24–48 h on phosphoenolpyruvate carboxykinase, malic enzyme, citrate-cleavage enzyme, and fatty acid synthetase could be overcome by injecting the animals with glucagon (1 mg/100 g body weight) or norepinephrine (20 μg/100 g body weight) four times a day. The same effect was achieved with 50 mg ephedrine added to the 24 h diet. The catecholamines were more effective in brown fat, whereas glucagon seemed somewhat more effective in the liver.

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Studies on the biosynthesis of hepatic pyruvate kinase and its correlation with enhanced hepatic lipogenesis in meal-trained rats

Biochemical Journal ◽

10.1042/bj1820383 ◽

1979 ◽

Vol 182 (2) ◽

pp. 383-397 ◽

Cited By ~ 22

Author(s):

T J Hopkirk ◽

D P Bloxham

Keyword(s):

Fatty Acid ◽

Pyruvate Kinase ◽

Fatty Acid Synthesis ◽

Specific Activity ◽

Acid Synthesis ◽

High Carbohydrate Diet ◽

Hill Coefficient ◽

Carbohydrate Diet ◽

High Carbohydrate ◽

Maximum Activation

Metabolic and enzymic changes were measured in meal-trained rats fed on high-carbohydrate diet. Rates of hepatic fatty acid synthesis are probably greater than rates of gluconeogenesis throughout the 24 h day provided that animals are fed. The daily enhancement of fatty acid synthesis on meal feeding coincided with the maximum activation of hepatic pyruvate kinase. Maximum activation of this enzyme was reflected in increased total catalytic activity (Vmax.), increased activity at 0.5 MM-phosphoenolpyruvate (V0.5), decreased Vmax./V0.5 ratio and a decrease in co-operativity of phosphoenolpyruvate binding as measured by the Hill coefficient (h). The latter changes are consistent with a decrease in enzyme phosphorylation during activation of the enzyme. To estimate changes in enzyme protein, quantitative enzyme precipitation with rabbit antisera was used. Giving a high-carbohydrate diet to meal-trained animals induced enzyme synthesis within a few hours. Adaptations in diet that enhanced fatty acid synthesis (chow to high carbohydrate; starved to high carbohydrate) led to an increased steady-state concentration of pyruvate kinase protein. An approximate estimate of the half-life of hepatic pyruvate kinase was 56 h. Whenever pyruvate kinase specific activity was measured in liver tissue extracts it was always considerably less (20–100 mumol/min per mg of protein, depending on dietary status) than the specific activity of pure pyruvate kinase (200 mumol/min per mg of protein). Antigenically active, catalytically inactive protein was removed during enzyme purification from cytosol at the stage of (NH4)2SO4 fractionation. The fraction precipitated by 30–45%-satd. (NH4)2SO4 was enzymically active, antigenically reacting protein was identified in the remaining (NH4)2SO4 fractions (0–30%- and 45–85%-satd.) and this contained no enzyme activity. These may correspond to inactive proteolytic fragments of pyruvate kinase. The rate-determining step in adjusting enzyme concentration seems to be proteolysis.

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The effect of carbohydrate and fat variation in euenergetic diets on postabsorptive free fatty acid release

British Journal Of Nutrition ◽

10.1079/bjn2002578 ◽

2002 ◽

Vol 87 (6) ◽

pp. 555-559 ◽

Cited By ~ 11

Author(s):

Peter H. Bisschop ◽

Mariëtte T. Ackermans ◽

Erik Endert ◽

An F. C. Ruiter ◽

Alfred J. Meijer ◽

...

Keyword(s):

Fatty Acid ◽

Free Fatty Acid ◽

High Fat Diet ◽

Fat Oxidation ◽

High Carbohydrate Diet ◽

The Other ◽

High Fat ◽

Carbohydrate Diet ◽

High Carbohydrate ◽

And Control

Diet composition and energy content modulate free fatty acid (FFA) release. The aim of this study was to evaluate the dose–response effects of euenergetic variations in dietary carbohydrate and fat content on postabsorptive FFA release. The rate of appearance (Ra) of palmitate was measured by infusion of [2,2-2H2]palmitate after an overnight fast in six healthy men on three separate occasions, i.e. after 7 d on euenergetic control, high-carbohydrate and high-fat diets. The protein content and composition was identical for each diet. Postabsorptive plasma fatty acid concentrations were not different between the high-carbohydrate and control diets (0·36 (SE 0·07) V. 0·43 (se 0·04) mmol/l), but were increased after the high-fat diet (0·75 (se 0·09) mmol/l, (P<0·01 compared with the other diets). Ra palmitate was not different between the high-carbohydrate and control diets (1·36 (se 0·20) v. 1·47 (se 0·15) μmol/kg per min). However, Ra palmitate was increased to 2·36 (se 0·26) μmol/kg per min after the high-fat diet (P<0·01 compared with the other diets). The fatty acid flux and whole-body fat oxidation were not affected by the high-carbohydrate diet compared with the control diet, but were increased by 67 and 47 % respectively, on the high-fat diet (P<0·01 compared with the other diets). A euenergetic high-fat diet results in increased postabsorptive FFA release and fat oxidation, whereas a euenergetic high-carbohydrate diet does not affect these variables of fat metabolism.

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