Acute ethanol exposure inhibits renal folate transport, but repeated exposure upregulates folate transport proteins in rats and human cells

Epigenetic insight into effects of prenatal alcohol exposure on stress axis development: Systematic review with meta-analytic approaches

We conducted a systematic review with meta-analytic elements using publicly available Gene Expression Omnibus (GEO) datasets to determine the role of epigenetic mechanisms in prenatal alcohol exposure (PAE)-induced hypothalamic-pituitary-adrenal (HPA) axis dysfunctions in offspring. Several studies have demonstrated that PAE has long-term consequences on HPA axis functions in offspring. Some studies determined that alcohol-induced epigenetic alterations during fetal development persist in adulthood. However, additional research is needed to understand the major epigenetic events leading to alcohol-induced teratogenesis of the HPA axis. Our network analysis of GEO datasets identified key pathways relevant to alcohol-mediated histone modifications, DNA methylation, and miRNA involvement associated with PAE-induced alterations of the HPA axis. Our analysis indicated that PAE perturbated the epigenetic machinery to activate corticotrophin-releasing hormone, while it suppressed opioid, glucocorticoid receptor, and circadian clock genes. These results help to further our understanding of the epigenetic basis of alcohol's effects on HPA axis development.

Folate pathways mediating the effects of ethanol in tumorigenesis

Folate and alcohol are dietary factors affecting the risk of cancer development in humans. The interaction between folate status and alcohol consumption in carcinogenesis involves multiple mechanisms. Alcoholism is typically associated with folate deficiency due to reduced dietary folate intake. Heavy alcohol consumption also decreases folate absorption, enhances urinary folate excretion and inhibits enzymes pivotal for one-carbon metabolism. While folate metabolism is involved in several key biochemical pathways, aberrant DNA methylation, due to the deficiency of methyl donors, is considered as a common downstream target of the folate-mediated effects of ethanol. The negative effects of low intakes of nutrients that provide dietary methyl groups, with high intakes of alcohol are additive in general. For example, low methionine, low-folate diets coupled with alcohol consumption could increase the risk for colorectal cancer in men. To counteract the negative effects of alcohol consumption, increased intake of nutrients, such as folate, providing dietary methyl groups is generally recommended. Here mechanisms involving dietary folate and folate metabolism in cancer disease, as well as links between these mechanisms and alcohol effects, are discussed. These mechanisms include direct effects on folate pathways and indirect mediation by oxidative stress, hypoxia, and microRNAs.

Moderate Alcohol Consumption Uniquely Regulates Sodium-Dependent Glucose Co-Transport in Rat Intestinal Epithelial Cells In Vitro and In Vivo

BACKGROUND

Chronic alcohol use often leads to malnutrition. However, how the intestinal absorption of nutrients such as glucose may be affected during moderate ethanol use has not been investigated. Glucose is absorbed via sodium (Na)-dependent glucose co-transport (SGLT1; SLC5A1) along the brush border membrane (BBM) of intestinal absorptive villus cells.

OBJECTIVE

The aim of this study was to investigate how moderate alcohol consumption affects the absorption of glucose via SGLT1.

METHODS

Intestinal epithelial cells (IEC-18; rat) were exposed to 8.64 mM ethanol over 1, 3, 6, and 12 h. Rats (16-wk-old, male, Sprague-Dawley) were administered 2 g/kg ethanol over 1, 3, and 6 h. Na-dependent 3H-O-methyl-d-glucose uptake was measured to assess SGLT1 activity. Na-K-ATPase activity was measured as a function of inorganic phosphate release. Protein expression was analyzed by Western blot analysis and immunohistochemical staining.

RESULTS

Ethanol significantly decreased Na-dependent glucose absorption in enterocytes in vitro (ethanol treatment: 48.4% of controls at 1 h; P < 0.01) and in vivo (ethanol treatment: 60.0% of controls at 1 h; P < 0.01). Na-K-ATPase activity was significantly inhibited in vitro (ethanol treatment: 36.9% of controls at 1 h; P < 0.01) and in vivo (ethanol treatment: 42.1% of controls at 1 h; P < 0.01). Kinetic studies showed that the mechanism of inhibition of Na-glucose co-transport was secondary to a decrease in the affinity (1/Km) of the co-transporter for glucose both in vitro and in vivo. Western blots and immunohistochemistry further demonstrated unaltered amounts of SGLT1 after ethanol treatment.

CONCLUSIONS

Moderate ethanol significantly decreases glucose absorption in IEC-18 cells and in villus cells of Sprague-Dawley rats. The inhibition of SGLT1 is secondary to an altered Na gradient at the cellular level and secondary to diminished affinity of the co-transporter for glucose at the protein level in the BBM. These observations may, at least in part, explain 1 possible mechanism of the onset of malnutrition associated with alcohol consumption.

Moderate Alcohol Consumption Inhibits Sodium-Dependent Glutamine Co-Transport in Rat Intestinal Epithelial Cells in Vitro and Ex Vivo

Malnutrition is present in chronic alcoholics. However, how moderate alcohol consumption affects the absorption of nutrients like glutamine has not been investigated. Glutamine, an amino acid, is vital to gastrointestinal health. Glutamine is absorbed via sodium-dependent glutamine co-transport (B0AT1; SLC6A19) along the brush border membrane of absorptive villus cells. Rat intestinal epithelial cells (IEC-18) and sixteen-week-old Sprague Dawley rats were administered the equivalent of a 0.04% blood alcohol content of ethanol (8.64 mM; 2 g/kg) to investigate the effect of moderate alcohol on sodium-glutamine co-transport. Sodium-dependent ³H-glutamine uptakes were performed to measure B0AT1 activity. Inorganic phosphate was measured as a function of Na-K-ATPase activity. Protein expression was analyzed by immunohistochemical and Western blot analysis. Ethanol significantly inhibited sodium-dependent glutamine absorption and Na-K-ATPase activity in enterocytes in vitro and ex vivo. Kinetic studies suggested that the mechanism of inhibition was due to decreased maximal rate of uptake (V_max) of the B0AT1 co-transporter, corresponding to decreased B0AT1 protein expression and secondary to an inhibited sodium-gradient at the cellular level in vitro and ex vivo. In all, moderate ethanol significantly inhibited glutamine absorption at the level of decreased B0AT1 expression at the brush border membrane and a reduced sodium gradient, which may contribute to malnutrition present in chronic alcoholics.

Increased synthesis of folate transporters regulates folate transport in conditions of ethanol exposure and folate deficiency

Excessive alcohol consumption and dietary folate inadequacy are the main contributors leading to folate deficiency (FD). The present study was planned to study regulation of folate transport in conditions of FD and ethanol exposure in human embryonic kidney cell line. Also, the reversible nature of effects mediated by ethanol exposure and FD was determined by folate repletion and ethanol removal. For ethanol treatment, HEK293 cells were grown in medium containing 100 mM ethanol, and after treatment, one group of cells was shifted on medium that was free from ethanol. For FD treatment, cells were grown in folate-deficient medium followed by shifting of one group of cells on folate containing medium. FD as well as ethanol exposure resulted in an increase in folate uptake which was due to an increase in expression of folate transporters, i.e., reduced folate carrier, proton-coupled folate transporter, and folate receptor, both at the mRNA and protein level. The effects mediated by ethanol exposure and FD were reversible on removal of treatment. Promoter region methylation of folate transporters remained unaffected after FD and ethanol exposure. As far as transcription rate of folate transporters is concerned, an increase in rate of synthesis was observed in both ethanol exposure and FD conditions. Additionally, mRNA life of folate transporters was observed to be reduced by FD. An increased expression of folate transporters under ethanol exposure and FD conditions can be attributed to enhanced rate of synthesis of folate transporters.

The Benefits of Administering Folic Acid in Order to Combat the Oxidative Damage Caused by Binge Drinking in Adolescent Rats

AIMS

An important mechanism in alcohol-induced injury is biomolecular oxidative damage. Folic acid is supplied to chronic alcoholic patients in order to prevent this situation, as this is the main vitamin deficiency that they suffer from. Acute alcohol exposure, such as binge drinking, is one of the most widespread ethanol consumption models practiced by adolescents. However, there is no evidence of folic acid body profiles after this pattern of consumption.

METHODS

Four groups of adolescent rats were used: control, alcohol (exposed to intraperitoneal binge drinking), control folic acid-supplemented group and alcohol folic acid-supplemented group. Folic acid levels, protein, lipid and DNA oxidative damage in serum, and liver glutathione (GSH) and reduced/oxidized glutathione ratio (GSH/GSSG) were measured.

RESULTS

Binge-drinking rats had higher lipids and DNA oxidation levels. They also had lower hepatic GSH levels and GSH/GSSG ratio. Folic acid supplementation to binge-drinking rats does not change the serum protein oxidation but decreases lipid and DNA oxidation. Finally, GSH increased to control levels with folic acid supplementation.

CONCLUSION

Folic acid supplementation is an economic and efficient therapy against the oxidative damage in lipids and mainly in DNA stability caused by binge drinking during adolescence. It has also been demonstrated that folic acid increases GSH levels, improving the antioxidant status and revealing a hepatoprotective effect during binge drinking.

Maternal periconceptional alcohol consumption and congenital limb deficiencies

BACKGROUND

Women of childbearing age report high rates of alcohol consumption, which may result in alcohol exposure during early pregnancy. Epidemiological research on congenital limb deficiencies (LDs) and periconceptional exposure to alcohol is inconclusive.

METHODS

Data from the National Birth Defects Prevention Study (NBDPS) were examined for associations between LDs and patterns of maternal periconceptional (1 month before conception through the first trimester) alcohol consumption among LD case (n = 906) and unaffected control (n = 8352) pregnancies with expected delivery dates from 10/1997 through 12/2007. Adjusted odds ratios (aORs) and 95% confidence intervals were estimated from unconditional logistic regression analysis for all LDs combined, specific LD subtypes (preaxial/terminal transverse), and LD anatomic groups (upper/lower limbs); interactions with folic acid (FA) supplementation were tested.

RESULTS

When compared with nondrinkers, inverse associations were found between all LDs combined, preaxial, and upper LDs and any reported periconceptional alcohol consumption (aORs ranged from 0.56-0.83), drinking without binging (aORs: 0.53-0.75), and binge drinking (≥4 drinks/occasion) (aORs: 0.64-0.94); however, none of the binge drinking aORs were statistically significant. Stratification by alcohol type showed inverse associations between all LDs combined, preaxial, transverse, and upper and lower LDs for drinking without binging of wine only (aORs: 0.39-0.67) and between all LDs combined and upper LDs for drinking without binging of combinations of alcohol (aORs: 0.63-0.87). FA did not modify observed associations.

CONCLUSION

Maternal periconceptional alcohol consumption did not emerge as a teratogen for selected LDs in the NBDPS. Future studies should evaluate additional rare LDs among more highly exposed populations.

Folate, alcohol, and liver disease

Alcoholic liver disease (ALD) is typically associated with folate deficiency, which is the result of reduced dietary folate intake, intestinal malabsorption, reduced liver uptake and storage, and increased urinary folate excretion. Folate deficiency favors the progression of liver disease through mechanisms that include its effects on methionine metabolism with consequences for DNA synthesis and stability and the epigenetic regulation of gene expression involved in pathways of liver injury. This paper reviews the pathogenesis of ALD with particular focus on ethanol-induced alterations in methionine metabolism, which may act in synergy with folate deficiency to decrease antioxidant defense as well as DNA stability while regulating epigenetic mechanisms of relevant gene expressions. We also review the current evidence available on potential treatments of ALD based on correcting abnormalities in methionine metabolism and the methylation regulation of relevant gene expressions.

Folate malabsorption and its influence on DNA methylation during cancer development

The folate transport across the epithelial of the intestine, colon, kidney, and liver is essential for folate homeostasis. The relative localization of transporters in membranes is an important determinant for the vectorial flow of substrates across the epithelia. Folate deficiency is a highly prevalent vitamin deficiency in the world, and alcohol ingestion has been the major contributor. It can develop because of folate malabsorption in tissues, increased renal excretion dietary inadequacy, and altered hepatobiliary metabolism. Additionally, folate-mediated one-carbon metabolism is important for various cellular processes, including DNA synthesis and methylation. In this regard, the contribution of alcohol-associated and dietary folate deficiency to methylation patterns is under intense investigation, especially in cancer. The epigenetic events have increasing relevance in the development of strategies for early diagnosis, prevention, and treatment of cancer.

Effects of ethanol consumption on the B-group vitamin contents of liver, blood and urine in rats

Several studies have shown that blood vitamin levels are lower in alcoholic patients than in control subjects. Acute ethanol exposure enhances the release of vitamins from liver cells in vitro. The aim of the present study is to confirm the effects of ethanol consumption on vitamin contents in vivo. We compared the contents of B-group vitamins in the liver, blood and urine between ethanol-fed and control rats fed a diet containing a sufficient- and low-vitamin mixture. The experimental rats were fed a 15 % ethanol solution freely for 28 d, and then 24 h urine samples were collected, after which the animals were killed. The B-group vitamin contents in the liver, blood and urine were measured. No differences in liver, blood and urine contents were observed between the control and ethanol-fed rats fed a diet containing a sufficient-vitamin mixture. On the contrary, in rats fed a diet containing a low-vitamin mixture, consumption of ethanol caused a decrease in the contents of vitamins B1, B2 and pantothenic acid in the liver; however, the contents of the other vitamins did not decrease. In the blood, the contents of vitamins B1, B2, B6 and pantothenic acid were lower in the ethanol-fed rats than in the controls. Urinary excretion of the B-group vitamins, except for niacin, was lower in the ethanol-fed rats. These results show that ethanol consumption affects the absorption, distribution and excretion of each of the vitamins in rats fed a diet containing a low-vitamin mixture.

Renal conservation of folates role of folate transport proteins

Folates play vital roles in one-carbon metabolism that produces the early substrates necessary for nucleotide synthesis and salvage. Folates are essential vitamins in that humans cannot synthesize them and are totally dependent on the diet to obtain them. As water-soluble vitamins, they would be easily filtered by the kidney and lost to the tubular fluid but for a highly efficient renal conservation mechanism. This renal "folate trap" is made up of alpha-folate receptors and reduced folate carriers. The locations of these transporters are such that they direct folate transport from the apical/luminal sides of kidney cells to the basolateral/plasma sides. In addition, other transporters such as organic anion transporters and multidrug resistance proteins are also found in kidney cells and play a role in renal elimination of folate analogues such as antifolate cancer chemotherapy drugs. This chapter discusses how these transporter activities manifest themselves in folate and antifolate pharmacokinetics. It also discusses effects of alcohol on renal reabsorption of folates.