• Energy Research

Ethanol exposure during fetal development can result in behavioral and neurological deficits, including reduced cognitive functions, retarded growth, and craniofacial abnormalities. Adenosine is an endogenous neuromodulator that fine-tunes the release and/or synaptic activities of several neurotransmitters, including glutamate, dopamine, and serotonin. Our aim was to determine whether ethanol exposure during early development affects adenosine receptors, particularly the A1 receptor subtype, in adult rats. Female rats were given water or 15% (vol/vol) ethanol in water prior to mating and throughout gestation and lactation. Sixty-day-old male rat offspring from these dams were randomly selected and assayed for adenosine A1 receptor expression in four brain areas: cortex, cerebellum, hippocampus, and striatum. Our results indicate that ethanol intake by dams decreased body and brain weights of offspring and reduced both A1 receptor mRNA and protein density in cortex and cerebellum. These preliminary findings indicate that ethanol intake by dams during pregnancy and lactation can affect adenosine A1 receptor signalling in the offspring. A pair-fed controlled study is warranted to explore these findings further.

Experiments were carried out to determine the accuracy and validity of estimations of hepatic blood flow from systemic clearances of ethanol during very low dose (8 μmol∙min−1∙kg−1) infusions of ethanol in anesthetized cats. Systemic clearances were compared with directly measured hepatic blood flow using a hepatic venous long-circuit technique. This technique allowed direct measurement and alteration of hepatic blood flow and collection of arterial, portal, and hepatic venous blood samples without depletion of the animal's blood volume. In 18 cats, Vmax for ethanol was 93 ± 7 μmol∙min−1 per 100 g liver or 21 ± 2 μmol∙min−1∙kg·body weight−1 and Km was 144 ± 19 μM in terms of logarithmic mean sinusoidal concentration. At the dose of 8 μmol∙min−1∙kg body weight−1 used for estimation of hepatic blood flow, extraction was 0.95 ± 0.07 (mean ± SD). Systemic clearance of ethanol overestimated directly measured hepatic blood flow by 15 ± 16%. Hepatic blood flow changes expressed as percentages of the control level were accurately estimated from systemic ethanol clearance (100 ± 10%). Since 73 ± 12% of the infused ethanol was eliminated by the liver and 83 ± 11% was eliminated by the splanchnic bed, an extrasplanchnic uptake of 17% accounted for the overestimation of hepatic blood flow. Estimation of hepatic blood flow from systemic clearances of ethanol during very low dose infusions may have advantages over other clearance methods. Its use in cats was illustrated in a separate series of experiments and it was shown that surgery significantly reduced hepatic blood flow. The method may merit trial for estimation of hepatic blood flow in humans.

Insulin causes the release of the hepatic insulin-sensitizing substance (HISS) from the liver. Hepatic parasympathetic nerves play a permissive role in the release of HISS. HISS-dependent insulin resistance (HDIR) occurs in the absence of HISS. Fetal ethanol exposure has been shown to cause dose-dependent HDIR in adult male rat offspring. Since female offspring are more severely affected by in utero ethanol toxicity, we hypothesized that fetal alcohol exposure causes higher incidence and more severe HDIR in adult female offspring. Adult female rat offspring prenatally exposed to different concentrations of ethanol (0%, 15%, and 20%) were tested for insulin sensitivity using the rapid insulin sensitivity test (RIST). The RIST index was significantly reduced in the 15% (134.1 ± 16.1 mg/kg) and the 20% (98.7 ± 9.7 mg/kg) group compared with the 0% (220.9 ± 27.6 mg/kg) group. Administration of atropine produced significant additional HDIR in the 15% group (82.9 ± 14.5 mg/kg) but not the 20% group (83.8 ± 20.5 mg/kg) indicating complete HDIR had been produced in this group, contrary to the adult male offspring in a previous study. The results are consistent with the hypothesis that adult-female offspring are more severely affected by in utero ethanol exposure compared with adult-male offspring.Key words: fetal, alcohol, insulin resistance, gender, HISS, teratology, diabetes.

The effects of increasing blood ethanol levels on hepatic hemodynamics and O2, ethanol, and lactate metabolism were studied in two groups of anesthetized cats: a control group and a group whose prior fluid intake contained 2, 4, then 8% ethanol for 24 days. Within each group, responses were compared in cats with acutely denervated and innervated livers. A hepatic venous long-circuit technique with an extracorporeal reservoir was used to allow hemodynamic measurements and repeated sampling of arterial, portal, and hepatic venous blood without depletion of the cats' blood volume. Vmax for ethanol was 105 +/- 9 and 91 +/- 6 mumol.min-1 g liver-1 and Km was 136 +/- 18 and 168 +/- 24 microM for control and chronic alcohol groups, respectively. There was no stimulation of ethanol metabolism after chronic administration. O2 uptake by the liver was not altered during acute ethanol administration in any group and base-line O2 uptakes before acute administration of ethanol were not different between normal and chronic ethanol groups. No evidence for a hypermetabolic state induced by chronic ethanol administration was seen in innervated or acutely denervated livers. Oxidation of ethanol required 40-45% of normal O2 uptake; thus other oxidative processes must have been suppressed during ethanol metabolism. Hepatic lactate uptake remained unaltered when ethanol metabolism was less than 0.5 Vmax, but was suppressed on an equimolar basis with ethanol metabolism when ethanol metabolism rose to greater than 0.5 Vmax. Thus lactate metabolism is one process that can be suppressed to allow ethanol metabolism without additional O2 uptake by the liver.

Fetal alcohol syndrome is a serious developmental disorder and exposure of the fetal heart to alcohol results in disturbances in the biochemistry of all cellular substructures. Mitochondrial effects include diminished respiratory function and physical alteration of the membrane secondary to interaction of ethanol with the hydrophobic region of the bilayer. Cardiolipin is a major mitochondrial membrane phospholipid in the heart and plays an important role in the function of mitochondrial enzymes involved in cellular respiration. We examined the activity of cardiac monolysocardiolipin acyltransferase, a key enzyme responsible for the molecular remodelling of cardiolipin with new fatty acids, in the newborn and adult rat and in new born rats that were exposed to alcohol in utero. Cardiac monolysocardiolipin acyltransferase activities were 57% lower (p < 0.05) in adult rats compared to newborn rats. Cardiac mitochondrial monolysocardiolipin acyltransferase activities were 36% lower (p < 0.05) in newborn rats that were exposed to alcohol in utero and this was due to reduced mitochondrial monolysocardiolipin acyltransferase expression. The results indicate that cardiac mitochondrial monolysocardiolipin acyltransferase activity declines during postnatal development in the rat and that in utero exposure to alcohol inhibits cardiac monolysocardiolipin acyltransferase activity and expression.

Ethanol has been considered as a lifestyle factor that may influence the risk of type 2 diabetes mellitus. In healthy adults, acute ethanol consumption results in insulin resistance. Acute ethanol consumption causes insulin resistance selectively in skeletal muscle by an indirect mechanism. Possible mediators include triglycerides (TGs), catecholamines, acetaldehyde, alterations in insulin binding, and hepatic insulin sensitizing substance (HISS). Recent studies in rats showed that acute administration of ethanol causes insulin resistance in a dose-dependent manner that is secondary to the blockade of insulin-induced HISS release. Chronic ethanol consumption may improve insulin sensitivity, but the results from the randomized controlled trials are mixed. Differences in ethanol dose, consumption period, and abstention period may account for the discrepant results. Epidemiological studies have suggested that the relationship between ethanol and insulin sensitivity is either an inverted U-shape or a positive linear relationship. Future randomized controlled trials should consider the dose of ethanol and the duration of ethanol consumption and abstention in the experimental design. Chronic prenatal and postnatal (nursing) ethanol exposure results in insulin resistance that is secondary to the absence of HISS release/action with the HISS-independent insulin action and insulin-like growth factor-1 (IGF-1)-mediated glucose disposal action remaining unimpaired. The impaired HISS release may be related to a reduction in hepatic glutathione (GSH) levels. The effect of chronic ethanol consumption on HISS has not been evaluated.