Alcohol consumption in the absence of adequate nutrition may lead to activation of the glyoxylate cycle in man

The metabolomic signatures of alcohol consumption in young adults

BACKGROUND

Metabolomic analysis may help us to understand the association between alcohol consumption and cardio-metabolic health. We aimed to: (i) replicate a previous study of alcohol consumption and metabolic profiles, (ii) examine associations between types of alcoholic beverages and metabolites and (iii) include potential confounders not examined in previous studies.

METHODS

Cross-sectional data of 1785 participants (age 26-36 years, 52% women) from the 2004-2006 Childhood Determinants of Adult Health study were used. Consumption of beer, wine and spirits was assessed by questionnaires. Metabolites were measured by a high-throughput nuclear magnetic resonance platform and multivariable linear regression examined their association with alcohol consumption (combined total and types) adjusted for covariates including socio-demographics, health behaviours and mental health.

RESULTS

Alcohol consumption was associated with 23 out of 37 lipids, 12 out of 16 fatty acids and six out of 20 low-molecular-weight metabolites independent of confounders with similar associations for combined total alcohol consumption and different types of alcohol. Many metabolites (lipoprotein lipids in high-density lipoprotein (HDL) subclasses, HDL cholesterol, apolipoprotein A-1, phosphotriglycerides, total fatty acids, monounsaturated fatty acids, omega-3 fatty acids) had positive linear associations with alcohol consumption but some showed negative linear (low-density lipoprotein particle size, omega-6 fatty acids ratio to total fatty acids, citrate) or U-shaped (lipoprotein lipids in very-low-density lipoprotein (VLDL) subclasses, VLDL triglycerides) associations.

CONCLUSIONS

Our results were similar to those of the only previous study. Associations with metabolites were similar for total and types of alcohol. Alcohol consumption in young adults is related to a diverse range of metabolomic signatures associated with benefits and harms to health.

Consuming a small-moderate dose of red wine alone can alter the glucose–insulin relationship

The aim in the present study was to assess the effect of small-moderate red wine ingestion on the level of serum insulin and plasma glucose when nutritional status is varied. Twenty nondiabetic males (19–22 years) participated in the study. In the fasting trial, all participants underwent a 6 h fast prior to consuming 4 standard units of red wine (40 g alcohol) or the equivalent amount of placebo as dealcoholized wine (containing <0.5% alcohol, 0% resveratrol) over a 135 min period. Alternatively, in the feeding trial, participants consumed food for 45 min prior to ingesting 4 standard units of red wine (40 g alcohol) or placebo over 135 min. Serum insulin and plasma glucose were assessed at regular 45 min intervals during all trials. The results showed a significant decrease in the level of serum insulin and no significant change in plasma glucose concentration in the fasting trial. Alternatively, a significant alcohol-induced decrease in plasma glucose and no change in serum insulin occurred when red wine alone was consumed after food. It was concluded that red wine can alter the glucose–insulin relationship and ingesting red wine alone (without food) should not be encouraged in nondiabetic individuals.

The effect of moderate alcohol consumption on adiponectin oligomers and muscle oxidative capacity: a human intervention study

AIMS/HYPOTHESIS

The aim of this study was to investigate whether moderate alcohol consumption increases plasma high molecular weight (HMW) adiponectin and/or muscle oxidative capacity.

MATERIALS AND METHODS

Eleven lean (BMI 18-25 kg/m(2)) and eight overweight (BMI >or=27 kg/m(2)) men consumed 100 ml whisky ( approximately 32 g alcohol) or water daily for 4 weeks in a randomised, controlled, crossover trial. After each treatment period, muscle biopsies and fasting blood samples were collected.

RESULTS

Adiponectin concentrations increased (p < 0.001) by 12.5% after 4 weeks of moderate alcohol consumption. Moderate alcohol consumption tended to increase HMW adiponectin by 57% (p = 0.07) and medium molecular weight adiponectin by 12.5% (p = 0.07), but not low molecular weight (LMW) adiponectin. Skeletal muscle citrate synthase, cytochrome c oxidase and beta-3-hydroxyacyl coenzyme A dehydrogenase (beta-HAD) activity were not changed after moderate alcohol consumption, but an interaction between alcohol consumption and BMI was observed for cytochrome c oxidase (p = 0.072) and citrate synthase (p = 0.102) activity. Among lean men, moderate alcohol consumption tended to increase cytochrome c oxidase (p = 0.08) and citrate synthase activity (p = 0.12) by 23 and 26%, respectively, but not among overweight men. In particular, plasma HMW adiponectin correlated positively with activities of skeletal muscle citrate synthase (r = 0.64, p = 0.009), cytochrome c oxidase (p = 0.59, p = 0.009) and beta-HAD (r = 0.46, p = 0.056), while such correlation was not present for LMW adiponectin. Whole-body insulin sensitivity and intramyocellular triacylglycerol content were not affected by moderate alcohol consumption.

CONCLUSIONS/INTERPRETATION

Moderate alcohol consumption increases adiponectin concentrations, and in particular HMW adiponectin. Concentrations of HMW adiponectin in particular were positively associated with skeletal muscle oxidative capacity.

Evolution of glyoxylate cycle enzymes in Metazoa: evidence of multiple horizontal transfer events and pseudogene formation

BACKGROUND

The glyoxylate cycle is thought to be present in bacteria, protists, plants, fungi, and nematodes, but not in other Metazoa. However, activity of the glyoxylate cycle enzymes, malate synthase (MS) and isocitrate lyase (ICL), in animal tissues has been reported. In order to clarify the status of the MS and ICL genes in animals and get an insight into their evolution, we undertook a comparative-genomic study.

RESULTS

Using sequence similarity searches, we identified MS genes in arthropods, echinoderms, and vertebrates, including platypus and opossum, but not in the numerous sequenced genomes of placental mammals. The regions of the placental mammals' genomes expected to code for malate synthase, as determined by comparison of the gene orders in vertebrate genomes, show clear similarity to the opossum MS sequence but contain stop codons, indicating that the MS gene became a pseudogene in placental mammals. By contrast, the ICL gene is undetectable in animals other than the nematodes that possess a bifunctional, fused ICL-MS gene. Examination of phylogenetic trees of MS and ICL suggests multiple horizontal gene transfer events that probably went in both directions between several bacterial and eukaryotic lineages. The strongest evidence was obtained for the acquisition of the bifunctional ICL-MS gene from an as yet unknown bacterial source with the corresponding operonic organization by the common ancestor of the nematodes.

CONCLUSION

The distribution of the MS and ICL genes in animals suggests that either they encode alternative enzymes of the glyoxylate cycle that are not orthologous to the known MS and ICL or the animal MS acquired a new function that remains to be characterized. Regardless of the ultimate solution to this conundrum, the genes for the glyoxylate cycle enzymes present a remarkable variety of evolutionary events including unusual horizontal gene transfer from bacteria to animals.

Effect of Moderate White Wine Consumption on Serum IgA and Plasma Insulin under Fasting Conditions

BACKGROUND/AIMS

The present study aims to investigate the contribution of alcohol toxicity to the development of malnutrition by assessing the effect of consuming a moderate amount of white wine on plasma insulin and serum IgA under fasting conditions.

METHODS

A total of 5 non-alcoholic males aged between 19 and 22 years participated in the current investigation. The experimental procedure required participants to undergo a 6-hour fast before ingesting 4 standard units of alcohol (40 g) in the form of white wine over a 120-min period. The level of blood alcohol, plasma insulin and serum IgA was assessed at 30-min intervals across the 120-min experimental period.

RESULTS

Consuming alcohol promotes a significant increase in serum IgA in the absence of any change in plasma insulin or ketone production in fasted individuals.

CONCLUSION

White wine prior to a meal does not promote glucose metabolism and utilization and may increase the risk of developing a transient diabetic condition due to an alteration in energy metabolism.

Effect on plasma insulin and plasma glucose of consuming white wine alone after a meal

BACKGROUND

Rodent studies have highlighted the possibility that alcohol may promote a significant decrease in the level of glucose-stimulated plasma insulin concentration. The aim of this study was to investigate whether a similar alcohol-induced decrease in plasma insulin occurs in humans, by assessing the level of plasma insulin and plasma glucose when a moderate amount of commercially available bottled white wine is consumed alone after a meal.

METHODS

Eight nondiabetic men aged 19 to 22 years participated in this investigation. Participants were required to consume some food for 45 min before ingesting three standard units of white wine (30 g of alcohol) over 90 min. Plasma insulin and plasma glucose levels were assessed at regular 45-min intervals across the experimental period.

RESULTS

The data showed a significant alcohol-induced decrease in the level of plasma insulin and a nonsignificant trend for a decrease in plasma glucose concentration in all participants after 15 g of alcohol had been consumed alone after a meal.

CONCLUSIONS

These findings highlight the possibility that white wine, if consumed alone after a meal, may significantly alter energy utilization and possibly cause an alteration in glucose metabolism.

Cytosolic aconitase and ferritin are regulated by iron in Caenorhabditis elegans

Iron regulatory protein-1 (IRP-1) is a cytosolic RNA-binding protein that is a regulator of iron homeostasis in mammalian cells. IRP-1 binds to RNA structures, known as iron-responsive elements, located in the untranslated regions of specific mRNAs, and it regulates the translation or stability of these mRNAs. Iron regulates IRP-1 activity by converting it from an RNA-binding apoprotein into a [4Fe-4S] cluster protein exhibiting aconitase activity. IRP-1 is widely found in prokaryotes and eukaryotes. Here, we report the biochemical characterization and regulation of an IRP-1 homolog in Caenorhabditis elegans (GEI-22/ACO-1). GEI-22/ACO-1 is expressed in the cytosol of cells of the hypodermis and the intestine. Like mammalian IRP-1/aconitases, GEI-22/ACO-1 exhibits aconitase activity and is post-translationally regulated by iron. Although GEI-22/ACO-1 shares striking resemblance to mammalian IRP-1, it fails to bind RNA. This is consistent with the lack of iron-responsive elements in the C. elegans ferritin genes, ftn-1 and ftn-2. While mammalian ferritin H and L mRNAs are translationally regulated by iron, the amounts of C. elegans ftn-1 and ftn-2 mRNAs are increased by iron and decreased by iron chelation. Excess iron did not significantly alter worm development but did shorten their life span. These studies indicated that iron homeostasis in C. elegans shares some similarities with those of vertebrates.