Ethanol, its metabolism and hepatotoxicity as well as its gonadal effects: effects of sex

Oxidation of ethanol to acetaldehyde and free radicals by rat testicular microsomes

A large number of epidemiological studies evidencing that excessive alcohol consumption is associated with impaired testosterone production and testicular atrophy are available in the literature. One hypothesis to explain the deleterious action of alcohol involves the in situ biotransformation to acetaldehyde, but it strongly suggests the need to learn more about the enzymatic processes governing alcohol metabolism to acetaldehyde in different cellular fractions since limited information is available in the literature. In this article we report studies on the metabolic conversion of alcohol to acetaldehyde and to 1-hydroxyethyl radicals in rat testicular microsomal fractions. The oxidation of ethanol to acetaldehyde in rat testes microsomal fraction was mostly of enzymatic nature and strongly dependent on the presence of NADPH and oxygen. Several compounds were able to significantly decrease the production of acetaldehyde: SKF 525A; diethyldithiocarbamate; esculetin; gossypol; curcumin; quercetin; dapsone; and diphenyleneiodonium. Microsomal preparations in the presence of NADPH were also able to produce both hydroxyl and 1-hydroxyethyl free radicals. Their generation was modulated by the presence of diphenyleneiodonium, gossypol, and deferoxamine. Results show that rat microsomal fractions are able to metabolize alcohol to deleterious chemicals, such as acetaldehyde and free radicals, that may be involved in ethanol toxic effects. Enzymes involved could include CYP2E1, P450 reductase, and other enzymes having lipoxygenase- /peroxidase-like behavior.

Oxidative damage in alcoholic liver disease

OBJECTIVE

The metabolic effects of alcohol are due both to its direct action and to that of its first metabolite, and can also be connected with the changes in redox state. Differences in ethanol distribution, bioavailability and hepatic metabolism can provide insight into the protective and predisposing factors in alcoholism, as well as gender differences of alcohol toxicity. Oxidative stress occurs following various conditions of ethanol consumption.

DESIGN

Twenty-six Caucasian patients with alcoholism and 32 healthy, abstinent controls of both sexes were investigated with special regard to reduction-oxidation status and ad hoc free-radical-antioxidant balance.

METHOD

Plasma free SH-group concentration, H-donating ability, and reducing power property were measured by simple spectrophotometric methods. Total scavenger capacity was determined by a newly developed chemiluminometric method in plasma and erythrocytes.

RESULTS

Alcoholics showed a decrease of free SH-group concentration, hydrogen-donating ability and an increase of reducing power property in plasma. A decreased total scavenger capacity of erythrocytes and plasma of alcoholic patients, combined with gender differences, could be detected.

CONCLUSIONS

Alcoholic dependence causes gradual exhaustion of the antioxidant capacity of erythrocytes, therefore this non-invasive measurement may be useful as a follow-up of the evolution of alcoholic liver disease. The results also suggest a gender susceptibility of alcohol toxicity.

Alcoholic hypogonadism: hormonal response to clomiphene

To investigate the androgen, weak androgen, estrogen, and gonadotrophin response to clomiphene in alcoholics, we determined in 63 male patients (25 with and 38 without liver cirrhosis) serum testosterone, sexual hormone binding protein (SHBG), dehidroepiandrosterone, androstenedione, LH, FSH, prolactin, and estradiol levels, on the first and the sixth day after admission, and after a course of 8 days of clomiphene 200 mg/day. The same test was performed on 15 healthy volunteers. Cirrhotic patients showed decreased basal testosterone levels and a loss of the circadian rhythm with recovery after clomiphene. Although basal testosterone levels in noncirrhotic alcoholics did not differ from those of the controls, there was a significant improvement after withdrawal. SHBG levels were higher in both groups of alcoholics than in controls, pointing to a worse degree of hypogonadism, because only the free hormone is active. Before the clomiphene test, serum LH and FSH levels were nonsignificantly higher in both groups of alcoholics than in the control group. After clomiphene both LH and FSH increased. Androstenedione and estradiol showed a (parallelism) similar behavior in alcoholic and in cirrhotic groups, showing in both cases higher levels than in the control group, and an increase after clomiphene, perhaps reflecting peripheral conversion of androgens to estrogens. Because clomiphene has no effect on the adrenal cortex, the increase of androstenedione after clomiphene points to its testicular origin (directly or after testosterone conversion) and not to an adrenal one. The highest serum estradiol levels were observed in cirrhotics with ascites or gynecomastia. We have not found any relation between serum hormone levels and alcohol intake nor with nutritional status.

Ethanol elimination rates in an ED population

Knowledge of the rate of ethanol elimination is essential in the assessment of the intoxicated patient. Surprisingly little literature is available regarding ethanol elimination rates in emergency department (ED) patients; prior studies almost exclusively examined populations of alcoholics or normal controls. Consequently, this prospective observational study was undertaken to assess the rate of ethanol elimination in an ED population. Twenty-four consecutive adult ED patients clinically suspected of intoxication who had serum ethanol determinations drawn were enrolled. Patients underwent serial ethanol determinations via breathalyzer (Intoxilyzer 1400, CMI Inc., Owensboro, KY). Linear regression analysis of the plot of decrease in ethanol level over time was performed to determine the rate of ethanol elimination. Initial ethanol levels in the 24 patients ranged from 58 to 447 mg/dL (mean, 249 +/- 109 [SD] mg/dL). Patients were observed for a minimum of 2 and a maximum of 9 observations (mean, 3.9 +/- 1.7), over a period of 0.5 to 12.1 hours (mean, 4.4 +/-3.5 h). Clinical features of intoxication were poorly correlated with ethanol level (r < .5). The rate of ethanol elimination in the ED population was 19.6 mg/dL/h (r = .83; 95% confidence interval [CI], 16.9 to 22.3 mg/dL/h). Subgroup analysis found differences that were statistically significant but small. Multiple regression analysis showed that time was the major variable useful in predicting changes in ethanol level (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic profiles of steroids in urine of alcoholics after withdrawal

The metabolic profiles of steroids in urine were analyzed in 13 male alcoholics during long-term abstinence, in most cases exceeding 3 months. The ratios of 5 beta- to 5 alpha-reduced steroid metabolites (etiocholanolone/androsterone and tetrahydrocortisol/allotetrahydrocortisol) were initially elevated but decreased slowly following withdrawal. The half-life of this normalization exceeded 3 weeks. The change was most marked in patients with signs of liver injury, and may reflect a relative decrease of the activity of hepatic 5 alpha-reductase. The ratio between cortisol metabolites carrying a 11 beta-hydroxy and an 11-oxo group was elevated in the patients and showed no tendency to normalize. This might reflect a decrease in the peripheral inactivation of cortisol.

Ethanol-induced contraction of cerebral arteries in diverse mammals and its mechanism of action

Acute ethanol exposure (8-570 mM) induced potent contractile responses of rings in both basilar and middle cerebral arteries, from dogs, sheep, piglets and baboons, in a dose-dependent manner. The contractions were reproducible and not tachyphylactic. The middle cerebral arteries were found to be more sensitive to ethanol than the basilar arteries. No known pharmacological antagonist, tested, exerted any effects on ethanol-induced contractions. No differences in responsiveness to ethanol in canine cerebral arteries were found between male and female animals or between the presence and the absence of endothelial cells. Removal of extracellular Ca2+ ([Ca2+]o) partially attenuated ethanol-induced contractions, while withdrawal of extracellular Mg2+ ([Mg2+]o) potentiated such contractions. In the complete absence of [Ca2+]o, caffeine and ethanol induced similar, transient contractions followed by relaxation in K(+)-depolarized cerebral vascular tissue. Ethanol-induced contractions were completely abolished by pretreatment of tissues with caffeine. Our results suggest that: (a) acute ethanol intoxication can induce direct contractions (independent of amine, prostanoid or opioid mediation) of diverse mammalian cerebral vascular tissues, including those from primates; (b) these contractile responses are heterogeneous along the cerebrovascular tree and independent of endothelial cells; (c) in addition to a need for [Ca2+]o, an intracellular release of Ca2+ is needed for ethanol to induce contractions; and (d) hypomagnesemia or Mg deficiency potentiates the contractile effects of ethanol on brain vessels and may be a risk factor for ethanol-related, ischemic stroke events.

Transfer of deuterium from [1,1-2H2]ethanol to steroids and organic acids in the rat testis

Rats were given [1,1-2H2]ethanol in a single dose, and the 2H content was determined in testicular steroids and in organic acids of low molecular mass in the testis, liver and blood. The acids were quantified by capillary gas chromatography/mass spectrometry of t-butyldimethylsilyl derivatives with [2H4]lactate as internal standard. In addition to lactate, pyruvate, 3-hydroxybutyrate and acids of the tricarboxylic acid cycle, the testis was shown to contain 2-hydroxybutyrate, 2-hydroxy-2-methylbutyrate, 2-hydroxyisohexanoate and glycerate. No 2H was found in pregnenolone, 5-androstene-3 beta,17 beta-diol or testosterone, whereas the abundance of monodeuterated molecules of 5 alpha-androstane-3 alpha,17 beta-diol and its 3 beta-isomer were 7.6% and 11.2% respectively. The abundance of monodeuterated lactate was 7.0% in the testis and 5.3% in the blood. The other acids were less labelled but 3-hydroxybutyrate had a higher 2H content in the testis (3.1%) than in the liver. These results support the contention that ethanol is oxidized in an alcohol dehydrogenase-catalysed reaction in testis in vivo and that the acute inhibition of the testosterone production is due at least partly to a redox effect. The labelling and increased concentration of 3-hydroxybutyrate in the testis indicate that a change in the mitochondrial redox state might be involved.

Effect of short-term ethanol feeding on rat testes as assessed by 31P NMR spectroscopy, 1H NMR imaging, and biochemical methods

31P Nuclear magnetic resonance (NMR) spectroscopy and 1H NMR imaging were used to examine the effect of short-term ethanol feeding on the rat testis. Weanling rats were pair-fed for 10 weeks either on ethanol containing liquid diet (36% ethanol of total calories) or a diet in which dextrimaltose was isocalorically substituted for the ethanol of the alcohol-containing diet. In vivo 31P NMR of the testes was used to determine the intratesticular pH and the relative concentrations of various phosphorus-containing metabolites. The integrity of the blood-testes barrier was evaluated using 1H NMR imaging following a gadolinium diethylene tetramine pentaacetic acid derivative (Gd-DTPA) administration as a vascular contrast agent. After the completion of NMR studies, the testis and the liver were freeze-clamped to allow for the assay of their adenosine-5'-triphosphate (ATP) contents. Serum was assayed for its content of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alcohol and testosterone. Ethanol feeding resulted in the following: (a) a reduction in the body weight (p less than 0.05), (b) a reduction in the testicular phosphodiesters (PDE) PDE/ATP ratio (p less than 0.05), (c) an increased change in the testis image intensity difference between pre- and post-iv Gd-DTPA images, (c) a reduction in the testicular and hepatic content of ATP, and (d) increased serum levels of AST and ALT.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral and metabolic interaction between gossypol and ethanol

The effects of gossypol on ethanol-elicited responses pertaining to liver ethanol, acetaldehyde-metabolizing enzymes and alcohol preference were studied in rodents. Intraperitoneal injection of a single dose of gossypol, 100 mg/kg, inhibited hepatic alcohol dehydrogenase for 50 h in mice from both sexes. The acute gossypol treatment produced earlier inhibition of mouse liver cytoplasmic aldehyde dehydrogenase in male than female mice. Acute gossypol administration initially inhibited mouse liver subcellular mitochondrial aldehyde dehydrogenase in both sexes which was not evident 50 h later. Administration of gossypol, 10 mg/kg i.p., to male rats with preference for ethanol caused aversion for ethanol drinking. The enzymatic determinations indicate gender sensitivity of subcellular mouse liver aldehyde dehydrogenase to gossypol. The behavioral study suggests adverse metabolic interaction between gossypol and alcohol which may underlie the rat aversion to voluntary ethanol drinking.

Effect of liver transplantation on the hypothalamic-pituitary-gonadal axis of chronic alcoholic men with advanced liver disease

The hormones testosterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) were assayed in blood obtained from men with alcoholic liver disease before and after successful liver transplantation. The frequency and severity of self reported impotence, intercourse, and paternity were assessed before and 18 +/- 3 months post-transplantation. The results obtained were compared with those of age-matched males transplanted within the same month by the same surgical teams for advanced hepatocellular disease other than alcoholism. Little change for any parameter assessed pre- and post-transplantation was noted for the nonalcoholics. In contrast, the FSH, LH, and testosterone levels of the alcoholic men all increased significantly following successful transplantation. These data suggest that the liver disease associated with alcoholism contributes to some of the endocrine effects of alcohol-associated cirrhosis but not all. Because the transplanted alcoholics remain less adequate than controls, it is further suggested that some residual alcohol-induced injury to the hypothalamic-pituitary-gonadal axis persists despite successful liver transplantation.