Effect of ethanol on amino acids and related compounds in rat plasma, heart, aorta, bronchus, and pancreas

Separate mechanisms regulating accumbal taurine levels during baseline conditions and following ethanol exposure in the rat

Ethanol-induced dopamine release in the nucleus accumbens (nAc) is associated with reward and reinforcement, and for ethanol to elevate nAc dopamine levels, a simultaneous increase in endogenous taurine is required within the same brain region. By employing in vivo microdialysis in male Wistar rats combined with pharmacological, chemogenetic and metabolic approaches, our aim with this study was to identify mechanisms underlying ethanol-induced taurine release. Our results demonstrate that the taurine elevation, elicited by either systemic or local ethanol administration, occurs both in presence and absence of action potential firing or NMDA receptor blockade. Inhibition of volume regulated anion channels did not alter the ethanol-induced taurine levels, while inhibition of the taurine transporter occluded the ethanol-induced taurine increase, putatively due to a ceiling effect. Selective manipulation of nAc astrocytes using Gq-coupled designer receptors exclusively activated by designer drugs (DREADDs) did not affect ethanol-induced taurine release. However, activation of Gi-coupled DREADDs, or metabolic inhibition using fluorocitrate, rather enhanced than depressed taurine elevation. Finally, ethanol-induced taurine increase was fully blocked in rats pre-treated with the L-type Ca2+-channel blocker nicardipine, suggesting that the release is Ca2+ dependent. In conclusion, while astrocytes appear to be important regulators of basal taurine levels in the nAc, they do not appear to be the main cells underlying ethanol-induced taurine release.

Investigation on the combined effect of cocaine and ethanol administration through a liquid chromatography-mass spectrometry metabolomics approach

Alcohol is the most widely consumed legal drug, whereas cocaine is the illicit psychostimulant most commonly used in Europe. The combined use of alcohol and cocaine is frequent among drug-abuse consumers and leads to further exacerbation of health consequences compared to individual consumption. The pharmacokinetic and metabolic interactions leading to an increase in their combined toxicity still remains poorly understood. Here, the first metabolomics study of combined cocaine and ethanol chronic exposure effects is reported. A Liquid Chromatography strategy based on sample derivatization with 9-fluorenylmethyloxycarbonyl chloride and using a C18 column coupled to high resolution Mass Spectrometry (time of flight analyzer) was employed to analyze plasma from rats exposed intravenously to these drugs in a 52-min analysis. Using a combination of non-supervised and supervised multivariate analysis the metabolic differences between our experimental groups were explored and unraveled. A comparative analysis of the individual models and their variable importance in the projection values have shown that every experiment intervention includes a subset of specific metabolites. Eleven of these metabolites were annotated, where eight were unequivocally identified using standards and three were tentatively identified by matching the MS/MS spectra to libraries. The results demonstrated that the affected metabolic pathways were mainly those related to the metabolism of different amino acids.

Epidermal growth factor-induced vacuolar (H+)-atpase assembly: a role in signaling via mTORC1 activation

Using proteomics and immunofluorescence, we demonstrated epidermal growth factor (EGF) induced recruitment of extrinsic V(1) subunits of the vacuolar (H(+))-ATPase (V-ATPase) to rat liver endosomes. This was accompanied by reduced vacuolar pH. Bafilomycin, an inhibitor of V-ATPase, inhibited EGF-stimulated DNA synthesis and mammalian target of rapamycin complex 1 (mTORC1) activation as indicated by a decrease in eukaryotic initiation factor 4E-binding 1 (4E-BP1) phosphorylation and p70 ribosomal S6 protein kinase (p70S6K) phosphorylation and kinase activity. There was no corresponding inhibition of EGF-induced Akt and extracellular signal-regulated kinase (Erk) activation. Chloroquine, a neutralizer of vacuolar pH, mimicked bafilomycin effects. Bafilomycin did not inhibit the association of mTORC1 with Raptor nor did it affect AMP-activated protein kinase activity. Rather, the intracellular concentrations of essential but not non-essential amino acids were decreased by bafilomycin in EGF-treated primary rat hepatocytes. Cycloheximide, a translation elongation inhibitor known to augment intracellular amino acid levels, prevented the effect of bafilomycin on amino acids levels and completely reversed its inhibition of EGF-induced mTORC1 activation. In vivo administration of EGF stimulated the recruitment of Ras homologue enriched in brain (Rheb) but not mammalian target of rapamycin (mTOR) to endosomes and lysosomes. This was inhibited by chloroquine treatment. Our results suggest a role for vacuolar acidification in EGF signaling to mTORC1.

Effects of wine intake on postprandial plasma amino acid and protein kinetics in type 1 diabetes

BACKGROUND

Alcohol may impair protein turnover and insulin sensitivity in vivo.

OBJECTIVE

The acute effects of moderate wine intake on amino acid kinetics and on the fractional synthetic rate (FSR) of albumin and fibrinogen in patients with type 1 diabetes were studied.

DESIGN

Six patients with type 1 diabetes ingested an elementary mixed meal (46 kJ/kg) over 4 h, first without and 3 mo later with approximately 300 mL red wine. Postprandial glucose concentrations were maintained at <10 mmol/L.

RESULTS

Postprandially, the FSR of fibrinogen was approximately 30% greater (21.5 +/- 6.6% compared with 14.1 +/- 3.6% of pool/d; P < 0.01) and glucagon concentrations were approximately 40% greater (103 +/- 20 compared with 61 +/- 13 ng/L; P < 0.015) with wine than without wine. However, the FSR of albumin and the rates of appearance of total and endogenous phenylalanine and leucine were not significantly different between treatments. First-pass splanchnic uptake (in micromol*kg(-1)*min(-1)) of dietary phenylalanine (0.22 +/- 0.02 compared with 0.19 +/- 0.02) and leucine (0.25 +/- 0.04 compared with 0.14 +/- 0.02) were greater with wine (P < 0.05), whereas dietary phenylalanine oxidation was lower with wine, by approximately 25% (0.10 +/- 0.02 compared with 0.14 +/- 0.01 micromol.kg(-1).min(-1); P < 0.05). Selected amino acid concentrations were significantly lower but glutamate concentrations were significantly higher with wine.

CONCLUSIONS

In insulin-infused patients with type 1 diabetes, moderate wine intake with a meal resulted in 1) a higher fibrinogen FSR, glucagon concentration, and first-pass splanchnic uptake of leucine and phenylalanine; 2) lower dietary phenylalanine oxidation; 3) selective changes in plasma amino acid concentrations; 4) and no impairment in endogenous proteolysis and albumin synthesis.

Different diets and amino acid supplementation do not affect the voluntary consumption of ethanol by rats

The effects of four different diets (control diet: 19.5% protein, 60.5% carbohydrate, 10% fat; diet I: 65% protein, 10% carbohydrate, 10% fat; diet II: 5% protein, 76% carbohydrate, 10% fat; diet III: 20% protein, 69% carbohydrate, 1% fat; diet IV: 69% protein, 15% carbohydrate, 1% fat) and supplementation with 3 amino acids (tryptophan: 150 mg/kg/d; arginine: 400 mg/kg/d; taurine: 380 mg/kg/d) on the voluntary consumption of ethanol were investigated in rats using the 2 bottle method. First, rats received the control diet and diets I, II, III and IV for 20 days with a choice of ethanol for the last 6 days only. Ethanol consumption was similar in all dietary groups. Second, rats received the control diet for 8 days followed by diets I, II and IV for another 8 days. Ethanol was offered throughout both periods. The switch to the special diets did not affect ethanol consumption. Third, rats received a control diet with arginine, tryptophan or taurine added to the drinking fluids for 16 days with a choice of ethanol for the last 5 days; thereafter supplementation stopped but the ethanol choice remained. No difference in the voluntary intake of ethanol was noted but ethanol consumption fell after cessation of arginine supplementation. In conclusion, diets differing greatly in their composition or supplementation with these 3 amino acids did not affect the voluntary choice of ethanol by rats in a significant manner.

Alcohol myopathy: impairment of protein synthesis and translation initiation

Alcohol consumption leads to numerous morphological, biochemical and functional changes in skeletal and cardiac muscle. One such change observed in both tissues after either acute alcohol intoxication or chronic alcohol consumption is a characteristic decrease in the rate of protein synthesis. A decrease in translation efficiency appears to be responsible for at least part of the reduction. This review highlights advances in determining the molecular mechanisms by which alcohol impairs protein synthesis and places these observations in context of earlier studies on alcoholic myopathy. Both acute and chronic alcohol administration impairs translational control by modulating various aspects of peptide-chain initiation. Moreover, this alcohol-induced impairment in initiation is associated with a decreased availability of eukaryotic initiation factor (eIF) 4E in striated muscle, as evidenced by an increase in the amount of the inactive eIF4E.4E-BP1 complex and decrease in the active eIF4E.eIF4G complex. In contrast, alcohol does not produce consistent alterations in the control of translation initiation by the eIF2 system. The etiology of these changes remain unresolved. However, defects in the availability or effectiveness of various anabolic hormones, particularly insulin-like growth factor-I, are consistent with the alcohol-induced decrease in protein synthesis and translation initiation.

The effect of antecedent acute ethanol ingestion on the pancreas ultrastructure in taurocholate pancreatitis in rats

The rat pancreas ultrastructure was examined 6, 12, and 18 h after (1) taurocholate-induced acute pancreatitis and after (2) pancreatitis preceded 6 h earlier by intragastric acute 40% ethanol ingestion (5 g/kg b.w.). Pancreatic specific trypsin activity and plasma alpha-amylase were assayed at the same time intervals. The antecedent acute ethanol ingestion resulted in the evident aggravation of pancreas ultrastructural alterations. Acute pancreatitis preceded by ethanol resulted in the increase of zymogen granules number, RER channels were more irregularly distributed, autophagosomes were more abundant and degeneration of mitochondria was more advanced when compared to acute pancreatitis without ethanol ingestion. Tryptic activity increased to higher degree in all pancreatitis groups preceded by ethanol, but this difference was statistically significant (P < 0.01) only after 18 h. These morphological (but not biochemical) differences progressed 12 h after pancreatitis induction. After 18 h of acute pancreatitis the number of zymogen granules decreased in previously alcoholized rats, but tryptic activity remained twofold higher that in animals not given ethanol. Other signs of cellular impairment were still more prominent in alcoholized rats. The obtained results suggest that even single acute ethanol abuse prior to acute pancreatitis does aggravate the morphological and biochemical lesions observed in this disease with possible negative consequences for the prognosis.