Sex differences in the response of several lipogenic enzymes to chronic ethanol ingestion

Trans fatty acids in maternal diet may impair lipid biosynthesis in mammary gland of lactating rats

Although trans fatty acids are known to influence essential fatty acid (EFA) metabolism and serum levels of lipids and lipoproteins, little is known about their effects on the metabolism of mammary glands (MGs) during lactation. In this study, 5 groups of lactating Wistar rats were fed semisynthetic diets containing 7% soy oil (control); 7% partially hydrogenated vegetable oil (7% PHVO); 13% PHVO +7% soy oil (13% PHVO); 5% PHVO +2% soy oil (5% PHVO), and 3.5% PHVO +3.5% soy oil (3.5% PHVO). Dams were killed on the 12th day of lactation. Weight, lipid content (LC), in vivo lipogenesis rate (LR) and activity of the lipogenic (ATP-citrate lyase and malic) enzymes were evaluated in the MGs. Maternal food intake, weight gain, and total MG weight were not found to be significantly different between the groups. The groups with 13, 7 and 5% PHVO presented a lower (p < 0.05) LR in MGs when compared to controls, whereas MG LC was higher in the 7 and 13% groups than in controls. The observed decrease in MG lipogenesis was accompanied by a diminution (p < 0.05) in the activities of ATP-citrate lyase and malic enzymes. These data indicate a potential impairment of lipid metabolism in the MG by trans isomers in lactating rats.

Alcohol as a nutrient: interactions between ethanol and carbohydrate

This study examined metabolic interactions between two nutrients--ethanol and carbohydrate. Both nutrients are metabolized by a common pathway to fatty acids from acetyl-coenzyme A by lipogenic enzymes. The effects of ethanol and carbohydrate on the induction of lipogenic enzymes in livers of rats were examined using two types of base diets differing in carbohydrate and lipid content and using isocaloric substitutions of ethanol, carbohydrate, and fat. Three nonlipogenic enzymes were used for comparison. Isocaloric substitution of both fat and carbohydrate for ethanol was necessary to show the specific effects of alcohol on the activity of lipogenic or nonlipogenic enzymes. Carbohydrate, and not ethanol, induced lipogenic enzymes. Ethanol specifically reduced the activity of lactate dehydrogenase and malic enzyme, but did not affect those of alcohol dehydrogenase or glycerol 3-phosphate dehydrogenase. Ethanol interacted with carbohydrate to increase the activity of ATP citrate lyase. In addition, we studied the effects of ethanol and different kinds of carbohydrates on the growth of rats and on the morphology of their livers and intestines. Ethanol significantly decreased growth characteristics (weight gain, growth rate, and caloric efficiency). Fructose, either as a monosaccharide or in sucrose, decreased this alcohol effect. Sucrose was better than glucose in lowering lipid accumulation in livers of rats. Fragility of intestinal villi was found with an alcohol, low carbohydrate diet, but was not present in alcohol diets with a higher level of carbohydrate. In contrast to carbohydrate, ethanol lacked some characteristics of a nutrient, namely, it did not induce some enzymes involved in its metabolism and did not promote optimum growth.

Modulation of hepatic glucose-6-phosphate dehydrogenase activity in male and female rats by estrogen

The effect of estradiol-17 beta on the activity of glucose-6-phosphate dehydrogenase was studied in both male and female rats to further characterize the sex differences in the activity of this enzyme. Four groups of intact and castrated rats were implanted subcutaneously with graded doses (2.4, 4.8 and 7.2 micrograms/day) of pelleted estradiol in a physiologically relevant experimental system. After fourteen days the rats were sacrificed and their livers were assayed for G6PD activities. The result indicated that: (i) the enzyme activity was 3-fold higher in normal adult female than in male rats, (ii) low doses of E2 (2.4, 4.8 and 7.2 micrograms/day) increased the activity of G6PD 6-fold in castrated males and over 2-fold in female castrates as well as intact rats (iii) E2 stimulation of G6PD activity appears to be more effective in castrated males than in female rats (IV) sex difference in the activity of G6PD disappeared after treatment with E2 in castrated rats. It is concluded that the activity of G6PD in rats is markedly enhanced by low doses of E2, which appears to be largely responsible for the sex differences in the activity of this enzyme in rats.

The effects of oral and intraperitoneal administration of ethanol on the activities of hepatic glucose-6-phosphate and 6-phosphogluconate dehydrogenases in rats

The activities of hepatic glucose-6-phosphate and 6-phosphogluconate dehydrogenases decreased significantly only in male rats, when rats of both sexes were fed a 2% sucrose solution containing 25% ethanol for six weeks. Sucrose (2%) activation of these enzymes was significant only in female rats. The daily administration of ethanol (5 g/kg body wt.) by intraperitoneal injection for two weeks significantly decreased the activities of these enzymes and eliminated the sex differences in the response to ethanol ingestion.

Liver microsomal drug metabolism in ethanol-treated hamsters

Administration of ethanol in drinking water to Syrian golden hamsters for 1-3 weeks caused alterations of microsomal cytochrome P-450-dependent monooxygenase activities in the liver accompanied by a slight elevation in cytochrome P-450 content. Ethanol treatment resulted in an increase in the activities for ethanol oxidation, aniline p-hydroxylation and dimethylnitrosamine N-demethylation. In particular, when dimethylnitrosamine was used as a substrate, the rate of formaldehyde formation was enhanced by 2- to 2.7-fold, while ethanol oxidation and aniline p-hydroxylation were increased by 1.5- to 2- and 1.2- to 1.3-fold, respectively. On the other hand, the activities of 7-ethoxycoumarin O-deethylase, benzphetamine N-demethylase and benzo[a]pyrene 3-hydroxylase were apparently decreased after ethanol treatment. These results for hamsters were significantly different from those reported for rats.

Paradoxical effect of ethanol on liver lipogenesis in the genetically-obese Zucker rat

Sixteen obese (fa/fa) Zucker rats, sixteen lean (Fa/-) Zucker rats and sixteen Wistar rats, all male rats aged 7-8 weeks, were given either a control (C) diet containing no ethanol or an ethanol (E) diet in which 36% of the energy was supplied by ethanol, for a period of 4 weeks. The activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49), glucose-6-phosphatase (EC 3.1.3.9) and glycerol kinase (EC 2.7.1.30) and the glycogen content in the livers of obese (fa/fa) rats were lower in animals given diet E than in those given diet C. As a result, hepatic lipogenesis and fatty degeneration of the liver were reduced in obese (fa/fa) rats given diet E.

Effects of chronic ethanol ingestion on male and female rat liver glycogen phosphorylase phosphatase

The effects of chronic ethanol ingestion on the interconversion of the active to the inactive form of glycogen phosphorylase by phosphorylase phosphatase was studied. Male and female rats also were compared. Chronic ethanol feeding decreased phosphorylase a and total phosphorylase activity in male rats. In females, no change was observed in phosphorylase a, whereas total phosphorylase activity was increased 73%. This was found to correlate with the relative activities of phosphorylase phosphatase. The data show differences between the two sexes with regard to the AMP inhibition of phosphorylase phosphatase and the caffeine stimulation of the phosphatase. Ethanol markedly enhanced the AMP inhibition of the phosphatase in males but had no effect in females. Further studies in females showed that ethanol completely obliterated the well documented stimulation of the phosphatase by caffeine; however, it did not alter the caffeine effect in males. These data suggest possible alterations in the tertiary structure of phosphorylase a.

Genetic effects on various measures of ethanol dependence in mice: a diallel analysis

A complete 5 X 5 diallel cross was performed using mice from 5 highly inbred strains. Five hundred and fifty-five offspring were fed ethanol in a liquid diet for 9 days, then tested during a withdrawal period using a battery of tests designed to measure physical dependence on ethanol ( McClearn et al., Sub. Alcohol Use/Abuse, 3 (1982) 135; Allen et al., Alcohol Clin. Exp. Res., 7 (1983) 443). The analyses were done separately for each sex. The results show significant, but low genetic effects for most of the measures and no maternal effects for any measure. There was also evidence for a sex-by-genotype interaction that was not due to sex-linkage, i.e., the same autosomal genes are acting differently in the two sexes during withdrawal from ethanol. Males tended to exhibit more genetic influence than females for most of the traits measured. The results are discussed in terms of the use of these measures for creating genetically defined models of physical dependence on ethanol.