Euglycemic hyperinsulinemic clamp to assess posthepatic glucose appearance after carbohydrate loading. 2. Evaluation of corn and mung bean starches in healthy men.

BACKGROUND: The rate of absorption of glucose from carbohydrates is important in several aspects of health. We recently validated a noninvasive technique in pigs, euglycemic hyperinsulinemic clamp plus oral carbohydrate loading (OC-Clamp), to quantify the rate of net posthepatic appearance of glucose after ingestion of carbohydrates. OBJECTIVE: The OC-Clamp procedure was performed in 8 healthy men to compare the net posthepatic appearance of glucose after ingestion of 1 of 3 carbohydrates. DESIGN: Human volunteers underwent the OC-Clamp procedure at an insulin infusion rate of 1.5 mU x kg(-1) x min(-1) (n = 5). The oral carbohydrate load (1 g/kg) consisted of glucose, cornstarch, or mung bean starch. During the OC-Clamp procedure, the glucose infusion rate decreased during absorption to maintain plasma glucose steady state and the decrease reflected the net posthepatic appearance of glucose. In addition, carbohydrates were loaded without insulin infusion (n = 6) and glycemic indexes were calculated (with glucose as the reference). RESULTS: The mean (+/-SEM) glycemic index of cornstarch was higher (95 +/- 18) than that of mung bean starch (51 +/- 13). In the OC-Clamp experiments, the posthepatic appearance of glucose and cornstarch did not differ significantly and represented 79.4 +/- 5.0% and 72.6 +/- 4.0%, respectively, of the load after complete absorption (within 3 h). In contrast, the net posthepatic appearance of glucose from mung bean starch was significantly lower (35.6 +/- 4.6% of the load, P < 0.001) than that from glucose and cornstarch, even 4.5 h postprandially. CONCLUSIONS: The OC-Clamp technique allows a continuous assessment of net posthepatic appearance of glucose after ingestion of carbohydrates and significant discrimination between corn and mung bean starches.

Lipid composition of the synaptosome and erythrocyte membranes during chronic ethanol-treatment and withdrawal in the rat.

Male Sprague-Dawley rats were intoxicated by inhalation of ethanol vapor for 21 days. This allowed high tolerance to the hypnotic effect of ethanol and withdrawal syndrome to be developed. The chronic intoxication brought about modifications of the synaptosome and erythrocyte membrane lipid composition which were not due to the reduction in food intake that parallels intoxication. The fatty acid composition of the phospholipids was modified but the level of cholesterol and the level of phospholipid remained unchanged. The modifications concerned the levels of linoleic (18:2) and arachidonic (20:4) acids which decreased in the synaptosomes. In the red blood cell membranes, ethanol affected the levels of the octadecenoic acids (18:1) which rose, and linoleic acid (18:2) which fell. These disturbances were present when the withdrawal syndrome was at its highest and also 3 days after withdrawal when the signs of hyperexcitability were no longer visible in the animal. Modifications in the brain membrane lipid composition parallel the behavioral tolerance to ethanol; however the present results show that the apparent readaptation of the central nervous system to withdrawal of alcohol occurs earlier than the return to normal of the membrane lipid modifications.

[Validity of the method of alcohol administration by the pulmonary route in studies of the alcoholic syndrome in the rat]. / Validite de la méthode d'alcoolisation par voie pulmonaire dans les études du syndrome alcoolique chez le rat.

Alcohol intoxication by the pulmonary route was studied in the rat. This method of continuous alcoholization quickly leads to deep intoxication. After 3 weeks the animals showed metabolic alterations and a strong withdrawal syndrome. Nutritional control was obtained by adjusting the growth of a group of animals (pair-weight animals) with that of the alcoholic rats. It was shown that prolonged periods in an atmosphere rich in ethanol did not cause any alteration of the lungs: neither the constituents nor the histological structure of the lungs were modified. Measurement of the various blood parameters (pH, arterial O2 and CO2 partial pressures, level of haemoglobin, etc.) showed the absence of adverse respiratory effects. This inhalation procedure would therefore seem to be a model which is well adapted to the study of various aspects of alcoholism.

Membrane fatty acid changes and ethanol tolerance in rat and mouse.

Ethanol tolerance and erythrocyte membrane lipids were studied in Sprague-Dawley rats at various times during and after chronic administration, by inhalation, of ethanol vapor. Tolerance increased during the three weeks treatment period and reverted to base line ten days after the treatment was stopped. Chronic ethanol treatment led to changes in the composition of membrane phospholipid fatty acids. These changes partially reverted after treatment ceased. At all times the changes in 16:0, 18:0, 18:1 and 18:2 were correlated with the degree of ethanol tolerance. Analysis of the effect of ethanol treatment (ip injections over a one week period) in three strains of mice showed that the changes of phospholipid fatty acids in erythrocyte membranes were related to whether the strain developed a tolerance to the hypnotic effect of ethanol (DBA, C 57), or not (Swiss). These results show that membrane phospholipid fatty acid composition and ethanol tolerance co-vary during chronic treatment. During the withdrawal period, ethanol sensitivity reverts to control values while the return of the fatty acids to the normal state is incomplete.

Dietary polyenylphosphatidylcholine decreases cholesterolemia in hypercholesterolemic rabbits: role of the hepato-biliary axis.

The aim of this work was to study the cholesterol-lowering mechanisms induced by dietary soybean lecithin in hypercholesterolemic rabbits. Male New Zealand white rabbits (n = 6 in each group) were fed for 10 weeks either a low-fat control C diet, containing 27 g fat/kg, or high-fat diets enriched with 2 g cholesterol/kg and 77 g fat/kg. The high-fat diets contained 50 g lard (L), 50 g soybean triacylglycerol (SO), or 50 g pure soybean phosphatidylcholine (PLE). PLE diet decreased by 30% beta-VLDL-cholesterol, compared with SO diet. HDL2-, HDL3- and LDL-lipid contents were unchanged in the L, SO and PLE groups. In gallbladder bile, amounts of phospholipids, bile salts and cholesterol were significantly increased in PLE group by respectively 45%, 11% and 44%, in comparison with SO group. Intestinal and hepatic Hydroxy Methyl Glutaryl Coenzyme A reductase activities were not increased by PLE diet. Triacylglycerol hepatic content was lower in PLE group than in L or SO groups. Compared with triacylglycerol enriched diet, phosphatidylcholine enriched diet developed significant higher cholesterol- and triacylglycerol-lowering effects by a two-step mechanism: i) by reducing the beta-VLDLs, ii) by enhancing the secretion of bile cholesterol. Such results constitute promising effects of soybean phosphatidylcholine at the hepato-biliary level, in the treatment or prevention of hyperlipidemia and related atherosclerosis.

The gastro-intestinal metabolism of ethanol in the rat. Effect of chronic alcoholic intoxication.

By collecting the blood coming exclusively from the stomach or intestine of rats, it has been shown that ethanol can be oxidized in the digestive mucosa on the basis of the appearance, during its absorption, of acetaldehyde and acetate. This has been shown to be the result of the action of alcohol- and aldehyde-dehydrogenases present in these tissues. The metabolic ability of these enzymes was tested after chronic alcoholic intoxication in association with various treatments with "anti-alcoholic" drugs. The modifications observed correspond to the effects of the treatments on the levels of the enzyme activities but are less clearcut in the in vivo conditions.

Comparison of rat blood preparation methods for acetaldehyde assay.

A comparison is made of four previously described methods for the preparation of blood for acetaldehyde (AcH) assay in the rat. The spontaneous formation of AcH which occurs during the treatment of blood containing ethanol and the recovery of known amounts of AcH added to the blood were studied. The methods using sodium nitrite-sulfosalicylic acid or perchloric acid (PCA) in saline gave low levels of spontaneous formation (1 to 2 microM AcH for 48 mM ethanol). In the recovery studies it was seen that semicarbazide does not allow displacement of all the AcH; treatment of the blood with the reactant sodium nitrite-sulfosalycilic acid and use of the hemolysis method gave levels of recovery lower than 50%. Only treatment of the blood with perchloric acid in NaCl allowed all the AcH added to the blood to be recovered. In vivo, PCA in saline releases the AcH which was seen to remain bound in the red blood cells with the semicarbazide method. So the recommended procedure for accurate assay of blood AcH in the rat is cold deproteinization in PCA/saline before head-space gas chromatography. The levels of in vivo blood AcH (4.1 +/- 0.33 microM) obtained in the rat using this method for a blood alcohol concentration of 52 mM are lower than those previously described in the literature.

Ethanol sensitivity and membrane lipid composition in three strains of mouse.

Strains of mouse (Swiss OF 1, DBA/2J Ico and C57 BL/6J Ico) with different sensitivities to the hypnotic effects of acute ethanol administration were also found to have differences in fatty acid composition in synaptosomal and erythrocyte membrane phospholipids. Chronic ethanol treatment altered membrane fatty acid composition in quantitatively different ways depending on whether the mice developed tolerance (DBA, C57) or not (Swiss). These results support the hypothesis that membrane lipid composition plays a role in the sensitivity to the effects of ethanol.

Sensitivity of individual erythrocyte membrane phospholipids to changes in fatty acid composition in chronic alcoholic patients.

The erythrocyte membrane levels of total phospholipids and cholesterol and the fatty acid composition of individual groups of phospholipids (phosphatidylethanolamine, phosphatidylserine plus phosphatidylinositol, and phosphatidylcholine) were studied in 10 patients admitted for ethanol detoxification and in 14 control subjects. The fatty acid composition of the patient phospholipids was modified but the level of cholesterol and the level of phospholipids remained unchanged. The fatty acid changes were mainly confined to phosphatidylcholine. The modifications concerned the levels of the octadecenoic acids (18:1) which rose (p less than 0.01), and linoleic acid (18:2) which fell (p less than 0.05). These results suggest that chronic ethanol ingestion may perturb the cell membrane organization with, in consequence, possible effects on cell morphology and functions.

Examination of the esterified fatty acids from mouse erythrocyte and synaptosomal membrane phospholipids and their distribution between the various phospholipid types.

Esterified fatty acids from mouse erythrocyte and synaptosomal membranes were characterised by fused-silica capillary gas-liquid chromatography and gas chromatography-mass spectrometry. Structural information was obtained from the mass spectra of a number of derivatives including trimethylsilyl (TMS), methyl and picolinyl esters together with the TMS ethers of glycols derived from the unsaturated acids. In addition to previously characterised acids, small concentrations of several acids previously unreported from these membranes were identified. These included branched chain acids and several unsaturated acids.