Adaptation of lipogenesis and lipolysis to dietary ethanol.

The effect of dietary ethanol on metabolic fates of glucose and ethanol, and activities of lipoprotein lipase and hormone-sensitive lipase in several tissues of miniature pigs were determined in vitro. Ethanol and glucose were used at similar rates for fatty acid synthesis in liver and brain and CO2 production in liver. Ethanol was preferred over glucose for fatty acid and CO2 production in ileal mucosal cells. Glucose was the preferred substrate for lipogenesis and oxidation to CO2 in adipose tissue and skeletal muscle, and for oxidation to CO2 in brain. Dietary ethanol decreased glucose and ethanol conversion to fatty acids in ileal mucosa and brain, respectively. Dietary ethanol had no effect on the capacity of liver, adipose tissue, and skeletal muscle to convert either glucose or ethanol to long-chain fatty acids. The capacity to oxidize ethanol, but not glucose, to CO2 in liver was increased by dietary ethanol. No dietary ethanol effect was observed in other tissues. The capacity for removal of plasma triglycerides (based on lipoprotein lipase activity) tended to increase in adipose tissue and skeletal muscle of pigs fed ethanol. Mobilization of long-chain fatty acids from adipose tissue (based on hormone-sensitive lipase activity), triglyceride concentration in plasma, and percentage of lipid in liver remained unchanged when ethanol was fed. Livers of ethanol-fed pigs, however, were larger than livers of control pigs. Our results indicate that feeding miniature pigs 21-37% of total caloric intake as ethanol causes significant metabolic adaptations of lipid metabolism in liver and ileal mucosa, but not in adipose tissue, skeletal muscle, and brain. The ethanol feeding, however, did not cause fatty livers or hyperlipidemia.

An enzymatic assay for activity of lipoprotein lipase.

An enzymatic method for the determination of the amount of free fatty acids released from triglyceride by lipoprotein lipase is described. The quantity of free fatty acids present in media before and after incubation is measured spectrophotometrically by the oxidation of NADH in the final reaction of a series of coupled enzymatic reactions. This assay for lipoprotein lipase is unlike previously described assays in that radioactive substrates or titration procedures are not used in the free fatty acid determination. In addition, another method for assay of lipoprotein lipase activity that involves the separation of free fatty acids from triglycerides by adsorption chromatography with Florisil as a stationary phase is described.

Comparative studies on the kinetic parameters and product analyses of chicken and rat liver and yeast fatty acid synthetase.

1. Comparative kinetics and product analyses of chicken and rat liver and yeast fatty acid synthetase. 2. Vmax's for the three enzymes studied decrease with increasing primer chain-length, while Km's (except for yeast) increases. 3. Palmitate is the main product (approximately 90%) of the rat synthetase whereas palmitate (60%) and stearate (40%) are the products of chicken and yeast enzymes. Increasing the primary chain length does not alter palmitate synthesis by rat and chicken enzymes but increases stearate synthesis by the yeast synthetase. 4. The three synthetases could not synthesize fatty acids in the absence of primer acetyl-CoA suggesting that malonyl-CoA decarboxylase is not a component.

Effect of estrogen on fatty acid synthetase in the chicken oviduct and liver.

Estrogen administered to one-month-old female chickens resulted in a 180-fold increase in the amount of fatty acid synthetase, a seven-fold increase in the enzyme activity per gram of tissue and a 25-fold increase in the weight of the oviduct. In contrast, the fatty acid synthetase content in liver increased three-fold; activity per gram of tissue increased two-fold and the weight increased two-fold. The large increase in the fatty acid synthetase activity in the oviduct was due to a corresponding increase in the amount of the fatty acid synthetase protein since the specific activities of highly purified preparations of oviduct and liver fatty acid synthetases were the same and the two enzymes had the same end point as determined by immunoprecipitation. That the increase in activity of the oviduct enzyme is not due to a modification was further supported by physicochemical comparison of the oviduct enzyme with the chicken liver enzyme. Thus, the synthetase complexes have similar size, their subunit composition and size appear to be the same, and both are multifunctional enzymes. Finally, kinetic studies and product analyses indicated no catalytic difference between the enzyme induced by estrogen in the oviduct and the liver enzyme.

Comparative value of L-, and D-methionine supplementation of an oat-based diet for humans.

Total sulfur-containing amino acids have been found to be the first limiting amino acid in several foods in comparison with human amino acid requirements. Addition of methionine in appropriate amounts to these foods might be expected to improve protein value. Economically, DL-methionine would be preferable to L-methionine for this purpose. However, the comparative tuilization of L- DL-, and D-methionine is unclear. The objective of the current project was to compare the effectiveness of L-, DL-, and D-methionine supplementation of diets based on a food product known to be low in methionine value for human subjects. "Instant" oatmeal was fed to adult subjects to provide 4.0 g of nitrogen/day. In randomly arranged periods, these diets were supplemented with L-, DL-, or D-methionine at two levels (0.58 and 1.16 g of methionine/day). An unsupplemented diet was used in a control period. Diets were adequate in vitamins, minerals, and energy. Mean nitrogen balances of subjects while receiving the L-methionine supplements at the 0.58 and 1.16 g levels were minus0.10 and +0.06 g of nitrogen, respectively. At similar levels of DL-methionine supplementation, nitrogen balances were minus0.12 and minus0.15 g of nitrogen, respectively, and minus0.24 and minus0.18 g of nitrogen with D-methionine supplementation. The mean nitrogen balance when no supplement was used was minus0.22 g of nitrogen. Thus, D-methionine is seemingly poorly utilized by the human. Urinary methionine excretion data supported these results.