Increased urinary folate excretion and decreased plasma folate levels in the rat after acute ethanol treatment

Tumor suppressor genes are differentially regulated with dietary folate modulations in a rat model of hepatocellular carcinoma

The current study evaluated the outcome of dietary folate modulations on the expression of tumor suppressor genes (TSGs) during developmental stages of hepatocellular carcinoma (HCC) in a Wistar rat model. In addition to dietary folate modulations, male rats were administered diethylnitrosamine (DEN) intraperitoneally once a week upto 18 weeks to induce HCC. Serum folate levels were found to be decreased and increased in folate deficiency (FD) and folate-oversupplemented (FO) groups respectively when compared to folate normal (FN) rats. Apoptosis was observed in FD in fibrosis and HCC stages. mRNA expression analysis by RT-PCR of TSGs (DPT, p16, RUNX3, RASSF1A and SOCS1) and protein expression by western blot (RASSF1A, RUNX3 and p16) depicted differential expression in FD and FO in various stages of HCC development. Bisulfite sequencing for p16 and RASSF1A promoter was performed. The promoter region of p16 gene was hypermethylated at 7th and that of RASSF1A was hypomethylated at 10th CpG in cirrhotic category in FD rats. Hyper and hypomethylation at 10th and 24th CpG respectively in RASSF1A promoter was observed in HCC category in both FD and FO groups. All TSGs showed differential expression at transcript and protein level. Increased expression of DPT, RASSF1A, SOCS1 and decreased expression of RUNX3 could be playing role in HCC development in FD rats. Reduced expression of RUNX3, RASSF1A and SOCS1 in HCC category was demonstrated in FO rats. Thus, the studied TSGs are differentially expressed with dietary folate modulations during the development of HCC in DEN-treated rat model and the promoter methylation might be a contributing mechanism under these conditions.

Association between maternal periconceptional alcohol consumption and neural tube defects: Findings from the National Birth Defects Prevention Study, 1997-2011

BACKGROUND

Neural tube defects (NTD)s are common birth defects with a multifactorial etiology. Findings from human studies examining environmental (non-inherited) exposures tend to be inconclusive. In particular, although animal studies of alcohol exposure and NTDs support its teratogenic potential, human studies are equivocal. Using data from the National Birth Defects Prevention Study (NBDPS), associations between maternal periconceptional (1 month before through 1 month after conception) alcohol consumption and NTDs in offspring were examined.

METHODS

NTD cases and unaffected live born singleton controls with expected dates of delivery from October 1997-December 2011 were enrolled in the NBDPS. Interview reports of alcohol consumption (quantity, frequency, variability, type) from 1,922 case and 11,251 control mothers were analyzed. Crude and adjusted odds ratios (aOR)s and 95% confidence intervals (CI)s for alcohol consumption and all NTDs combined and selected subtypes (spina bifida, anencephaly, encephalocele) were estimated using unconditional logistic regression analysis.

RESULTS

Among mothers in the NBDPS, 28% of NTD case and 35% of control mothers reported any periconceptional alcohol consumption. For each measure of alcohol consumption, inverse associations were observed for all NTDs combined (aORs = 0.6-1.0). Results for NTD subtypes tended to be similar, but CIs for spina bifida and encephalocele were more likely to include the null.

CONCLUSIONS

These findings suggest a lack of positive associations between maternal periconceptional alcohol consumption and NTDs. Future studies should continue to evaluate the association between maternal alcohol consumption and NTDs in offspring accounting for methodological limitations such as potential misclassification from self-reported alcohol consumption.

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.

Periconceptional maternal alcohol consumption and neural tube defects

BACKGROUND

Neural tube defects (NTD)s, which occur when the neural tube fails to close during early gestation, are some of the most common birth defects worldwide. Alcohol is a known teratogen and has been shown to induce NTDs in animal studies, although most human studies have failed to corroborate these results. Using data from the National Birth Defects Prevention Study, associations between maternal reports of periconceptional (1 month prior through 2 months postconception) alcohol consumption and NTDs were examined.

METHODS

NTD cases and unaffected live born control infants, delivered from 1997 through 2005, were included. Interview reports of alcohol consumption (quantity, frequency, variability, and type) were obtained from 1223 case mothers and 6807 control mothers. Adjusted odds ratios (aOR)s and 95% confidence intervals were estimated using multivariable logistic regression analysis.

RESULTS

For all NTDs combined, most aORs for any alcohol consumption, one or more binge episodes, and different type(s) of alcohol consumed were near unity or modestly reduced (≥ 0.7 < aOR ≤ 1.1) and were not statistically significant. Findings were similar for individual NTD subtypes.

CONCLUSIONS

These findings suggest no elevated association between maternal periconceptional alcohol consumption and NTDs. Underreporting of alcohol consumption, due to negative social stigma associated with alcohol consumption during pregnancy, and limited reports for mothers with early pregnancy loss of a fetus with an NTD may have affected the estimated odds ratios. Future studies should aim to increase sample sizes for less prevalent subtypes, reduce exposure misclassification, and improve ascertainment of fetal deaths and elective terminations.

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.

Folate malabsorption is associated with down-regulation of folate transporter expression and function at colon basolateral membrane in rats

Folates, an essential component (important B vitamin) in the human diet, are involved in many metabolic pathways, mainly in carbon transfer reactions such as purine and pyrimidine biosynthesis and amino acid interconversions. Deficiency of this micronutrient leads to the disruption of folate-dependent metabolic pathways that lead to the development of clinical abnormalities ranging from anaemia to growth retardation. Folate deficiency due to alcohol ingestion is quite common, primarily due to malabsorption. The present study dealt with the mechanistic insights of folate malabsorption in colonic basolateral membrane (BLM). Wistar rats (n 12) were fed 1 g/kg body weight per d ethanol (20 %) solution orally for 3 months and folate transport was studied in the isolated colonic BLM. The folate exit across colon BLM shows characteristics of carrier-mediated process with the major involvement of reduced folate carrier (RFC). The chronic ethanol ingestion decreased the uptake by decreasing the affinity by 46 % (P < 0·01) and the number of transport molecules by 43 % (P < 0·001) at the colon BLM. The decreased uptake was associated with down-regulation of proton-coupled folate transporter (PCFT) and RFC expression at mRNA and protein levels. The extent of decrease was 44 % (P < 0·01) and 24 % (P < 0·05) for PCFT and 23 % (P < 0·01) and 57 % (P < 0·01) for RFC at mRNA and protein levels, respectively. Moreover, folate transporters were associated with lipid rafts (LR) of colon BLM, and chronic alcoholism decreased the association of these transporters with LR.

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

Deficiency of folate in heavy-drinking alcoholic populations can occur partly because of an increased urinary folate excretion. Ethanol directly reduces the reabsorption of folate in the renal proximal tubule (PT) by acting on either of 2 folate transport proteins, the reduced folate carrier (RFC) and the folate receptor (FR). This study was designed to determine the effects of ethanol on the transport of folate by PT cells and to examine the effects of ethanol on RFC and the FR protein expression. Normal human PT (HPT) cells were cultured on membrane inserts to study intracellular transport of 5-methyltetrahydrofolate from the apical or basolateral direction in the presence of ethanol [11-109 mmol/L (50-500 mg/dL)]. The long-term effect of ethanol on the renal folate transport protein content was determined by western blot in treated HPT cells and in vivo in rats pair-fed control diets or ethanol-containing liquid diets. A 1-h treatment of HPT cells with ethanol (> or = 65 mmol/L) reduced the apically directed transport of folate by 20-25% without affecting the basolateral transport. A 5-d exposure of HPT cells to ethanol dose-dependently increased the content of both the FR and RFC proteins, with a greater effect on the RFC. Similarly, a 14-d exposure of rats to ethanol increased the in vivo expression of both the RFC and FR. These studies demonstrate that ethanol decreases the reabsorptive transport of folate by renal PT cells, which would increase urinary folate excretion. In contrast, subchronic exposure of PT cells, both in vivo and in vitro, to folate-depleting concentrations of ethanol leads to an upregulation of the 2 folate transport proteins. The increase in folate transporters partly counteracts the inhibitory effects of ethanol on folate transport activity, which explains the lower magnitude of ethanol's effect on transport with subchronic exposure compared with that with acute exposure.

Chronic alcoholism alters the transport characteristics of folate in rat renal brush border membrane

Folic acid transport across the epithelial cell membrane of kidney tubules is an essential step for its reabsorption, conservation, and homeostasis in the body. We characterized [(3)H]-folic acid transport in renal brush border membrane vesicles after 12 weeks of chronic ethanol ingestion to rats. The results demonstrated that chronic ethanol administration decreased the renal tubular reabsorption by a mechanism which involved an increase in the value of K(m) and a decrease in V(max). Importantly, ethanol feeding also interfered with disulfide bond status, temperature sensitivity, and Na(+) and divalent cation dependency of the transport process. The transport was transmembrane pH dependent, and ethanol did not have any effect on the pH optimum of the folate transport. The reduction in uptake in the ethanol-fed group was more pronounced at pH less than 6. In addition, the binding component was found to contribute to an appreciable extent to the total folate uptake; however, the amount of folate binding was less in the ethanol-fed group. Moreover, the folic acid analog methotrexate inhibited the transport to great degrees in control and ethanol-fed rats. These findings highlight the possible mechanism of renal disturbances of folate conservation during chronic alcoholism.

[Alcohol and nutrition]

Alcoholism and alcohol-associated organ injury is one of the major health problems worldwide. Alcohol may lead to an alteration in intermediary metabolism and the relation between alcohol intake and body weight is a paradox. The effect of alcohol intake on resting metabolic rate, assessed by indirect calorimetry, and lipid oxidation, is still controversial. Small quantities of ethanol seem to have no effect on body weight. Ingestion of moderate amounts may lead to an increase in body weight, via a lipid-oxidizing suppressive effect. Chronic intake of excessive amounts in alcoholics leads to a decrease in body weight, probably via increased lipid oxidation and energy expenditure. Chronic ethanol abuse alters lipid-soluble (vitamins A, D and E) and water-soluble (B-complex vitamins, vitamin C) vitamins status, and some trace elements status such as magnesium, selenium or zinc.

Determination of folate transport pathways in cultured rat proximal tubule cells

Deficiency of the vitamin folic acid has recently been linked with increased incidence of neural tube defects and of cardiovascular disease, through elevated plasma homocysteine levels. The kidney has an important role in conserving folate to counteract development of deficiency. Urinary folate excretion is regulated by the degree of reabsorption of folate by the proximal tubule cell. To evaluate an in vitro model for studies of the regulation of urinary folate excretion, the present studies examined the transport of 5-methyltetrahydrofolate (5-CH3-H4PteGlu), the primary form of folate in the glomerular filtrate, by normal rat proximal tubule (RPT) cells in confluent monolayer cultures. Specific binding of 5-CH3-H4PteGlu to the apical membrane was saturable (K(D) = 27 nM), but intracellular transport was not saturated up to 100 nM concentrations. 5-CH3-H4PteGlu transport was decreased 50% by concentrations of folic acid that completely blocked 5-CH3-H4PteGlu binding by the apical folate receptor. Probenecid (10 mM), an anion exchange (reduced folate carrier) inhibitor, reduced 5CH3-H4PteGlu transport by 50% without significantly affecting binding. Aspirin (3 mM) did not alter 5-CH3-H4PteGlu transport, but significantly enhanced the inhibition due to probenecid. Similarly, indomethacin (5 microM) potentiated the inhibition of 5-CH3-H4PteGlu transport by probenecid. These data suggest that RPT cells take up 5-CH3-H4PteGlu by both the folate receptor and the reduced folate carrier, implying a role for both pathways in regulating urinary folate excretion.

Membrane receptors for endocytosis in the renal proximal tubule

The renal proximal tubule exhibits a very extensive apical endocytic apparatus consisting of an elaborate network of coated pits and small coated and noncoated endosomes. In addition, the cells contain a large number of late endosomes/prelysosomes, lysosomes, and so-called dense apical tubules involved in receptor recycling from the endosomes to the apical plasma membrane. This endocytic apparatus is involved in the reabsorption of molecules filtered in the glomeruli. The process is very effective as demonstrated by the fact that although several grams of protein are filtered daily in the human glomeruli, human urine is virtually devoid of proteins under physiological conditions. Several key receptors appear to be involved in this function, which serves not only to conserve protein as such for the organism but also to reabsorb vital substances such as different vitamins in complex with their binding proteins. Recent research has established megalin, a 600-kDa protein belonging to the LDL receptor family, as probably the most important receptor in this process in the proximal tubule mediating endocytosis of a large variety of ligands and therefore classifying it as a scavenger receptor. More specific receptors like the folate receptor, IGF-II/Man-6-P receptor, and gp280/IFR, identical to the intrinsic factor receptor, are also functioning in the apical endocytic pathway of renal proximal tubules. A better understanding of these receptors will give us new insight into these very important processes for the organism.

Effect of ethanol on folate binding by isolated rat renal brush border membranes

Deficiency of folic acid, an essential vitamin involved in critical metabolic pathways, occurs in several conditions, including alcoholism. In humans and animal models, chronic ethanol consumption leads to decreased plasma levels and increased urinary levels of folate. An isolated perfused rat kidney model has shown that ethanol produces increased urinary excretion of folate, suggesting a direct effect of ethanol on the kidney. Because the folate binding protein, located in the brush border membrane (BBM) of proximal tubule cells, is thought to be involved in renal folate reabsorption, the effects of ethanol on BBM binding of folate were assessed. Binding studies were conducted using isolated rat kidney cortex BBM preparations, incubated with 3H-labeled 5-methyltetrahydrofolate (5-CH3H4PteGlu) at varying concentrations (0.1-100 nM). Ethanol at 500 mg/dl did not significantly affect [3H]5-CH3H4PteGlu binding in BBM. The structural analogue, folic acid, decreased [3H]5-CH3H4PteGlu binding under similar conditions. Because of the lack of effect of ethanol on binding to isolated BBM, the effects of ethanol probably occur at other steps in the renal uptake and metabolism of folate.

Effect of chronic alcohol ingestion on hepatic folate distribution in the rat

The mechanism by which ethanol impairs folate metabolism remains uncertain. In the present study, we used our new technique (affinity/HPLC) for folate analysis to study the effect of chronic alcohol ingestion on the content and distribution of folates in livers. Twelve male Sprague-Dawley rats (180 g) were divided into two groups, and fed for 4 weeks with Lieber-DeCarli semi-liquid isocaloric diets, with and without 5% ethanol. Livers were extracted in boiling, pH 9.3 borate buffers containing ascorbate/dithioerythritol. Folates in the supernatant fractions were purified by affinity chromatography and analyzed using ion pair high performance liquid chromatography. The data obtained showed that hepatic folate distribution in alcohol-treated rats differed from that of control animals in two ways. Livers from the ethanol-fed rats, when compared with those from control rats, exhibited increases in the percent concentrations of methylated tetrahydrofolates (21.46 +/- 2.21 vs 14.8 +/- 1.23), decreases in the percent concentrations of formylated tetrahydrofolates (25.62 +/- 4.02 vs 46.18 +/- 2.65) and higher concentrations of unsubstituted tetrahydrofolates (52.91 +/- 3.84 vs 38.88 +/- 2.50). In addition, alcohol ingestion was associated with longer glutamate chains of the folate molecules, characterized by lower relative concentrations of pentaglutamyl folates (29 vs 48%), and higher relative concentrations of hexa- and heptaglutamyl folates (55 vs 46% and 15 vs 6%) when compared with controls. The data are discussed in relation to the possibility that alcohol exerts its effect through: (1) inhibition of B12-dependent methyl transfer from methyltetrahydrofolate to homocysteine; (2) diversion of formylated tetrahydrofolates toward serine synthesis; and (3) interaction of acetaldehyde with tetrahydrofolates, thereby interfering with folate coenzyme metabolism.

Ethanol acutely impairs the renal conservation of 5-methyltetrahydrofolate in the isolated perfused rat kidney

The ethanol-induced increase in urinary folate excretion has been shown to decrease plasma folate levels and may contribute to the development of folate deficiency associated with alcoholism. The mechanism for this effect remains to be elucidated. The present studies were designed to examine the direct effect of ethanol on the renal handling of 5-methyltetrahydrofolate (5-CH3-H4PteGlu), the physiological folate. Rats were given four consecutive hourly doses of ethanol (1 g/kg) or isocaloric doses of glucose solution orally. This treatment generated an average plasma ethanol level of 305 mg/dl. Kidneys from male Sprague-Dawley rats were removed 5 hr after initial treatment and perfused in vitro to eliminate any extrarenal effects that could confound interpretation of results. Ethanol was not added to the perfusate. These treatments had no effect on 5-CH3-H4PteGlu conservation by the isolated perfused rat kidney in comparison to experiments in which the animal received no treatment. Ethanol was then added directly to the perfusate to generate average concentrations of 293 mg/dl. The in vitro addition of ethanol significantly decreased the percentage reabsorption and increased the fractional excretion of 5-CH3-H4PteGlu in comparison to controls (kidneys perfused with or without an isocaloric dose of glucose). This effect did not become significant until the renal tissue was exposed to these levels of ethanol for 1 hr. These results indicate that ethanol directly impairs the renal conservation of 5-CH3-H4PteGlu.

Effects of ethanol on tissue folate incorporation and recovery from folate deficiency in rats

Studies in folate-deficient alcoholics suggest that ethanol interferes with the recovery of folate status and the hematopoietic response to folate. Previous animal studies have suggested diverse effects of ethanol on intestinal absorption, hepatic metabolism, and urinary excretion of folate. In order to examine the effects of ethanol on folate distribution during folate deficiency, tissue incorporation of a tracer dose of folate was studied in rats chronically fed ethanol-containing and/or folate-deficient diets. Rats fed these diets were also used to study the effect of chronic ethanol consumption on the dietary reversal of folate deficiency by changing the diets (adding folate or replacing ethanol) from 12 to 16 weeks. After 16 weeks, tissue folate depletion was severe in rats fed folate-deficient diets. Plasma and whole body retention of the tracer dose of folate was decreased in folate-deficient rats consuming ethanol. In folate-deficient rats, ethanol consumption increased the incorporation of folate by the kidney and brain, but had no effect in other tissues (liver, lung, spleen, intestine, testis). In ethanol-fed folate-deficient rats that continued to consume ethanol, but with added folate in their diets, urine, plasma, liver, and kidney folate levels returned to control levels in 4 weeks. In the rats that stopped ethanol, but continued low folate diet consumption, no recovery of tissue folate levels was seen in 4 weeks. These results suggest that chronic ethanol consumption can exacerbate folate requirements by inhibiting body retention of small doses of folate. However, these effects are minor because ethanol consumption does not block recovery from folate deficiency when rats are fed sufficient amounts of folate.

Alcohol, liver, and nutrition

Until two decades ago, dietary deficiencies were considered to be the major reason why alcoholics developed liver disease. As the overall nutrition of the population improved, more emphasis was placed on secondary malnutrition. Direct hepatotoxic effects of ethanol were also established, some of which were linked to redox changes produced by reduced nicotinamide adenine dinucleotide (NADH) generated via the alcohol dehydrogenase (ADH) pathway. It was also determined that ethanol can be oxidized by a microsomal ethanol oxidizing system (MEOS) involving cytochrome P-450: the newly discovered ethanol-inducible cytochrome P-450 (P-450IIE1) contributes to ethanol metabolism, tolerance, energy wastage (with associated weight loss), and the selective hepatic perivenular toxicity of various xenobiotics. P-450 induction also explains depletion (and enhanced toxicity) of nutritional factors such as vitamin A. Even at the early fatty-liver stage, alcoholics commonly have a very low hepatic concentration of vitamin A. Ethanol administration in animals was found to depress hepatic levels of vitamin A, even when administered with diets containing large amounts of the vitamin, reflecting, in part, accelerated microsomal degradation through newly discovered microsomal pathways of retinol metabolism, inducible by either ethanol or drug administration. The hepatic depletion of vitamin A was strikingly exacerbated when ethanol and other drugs were given together, mimicking a common clinical occurrence. Hepatic retinoid depletion was found to be associated with lysosomal lesions and decreased detoxification of chemical carcinogens. To alleviate these adverse effects, as well as to correct problems of night blindness and sexual inadequacies, the alcoholic patient should be provided with vitamin A supplementation. Such therapy, however, is complicated by the fact that in excessive amounts vitamin A is hepatotoxic, an effect exacerbated by long-term ethanol consumption. This results in striking morphologic and functional alterations of the mitochondria with leakage of mitochondrial enzymes, hepatic necrosis, and fibrosis. Thus, treatment with vitamin A and other nutritional factors (such as proteins) is beneficial but must take into account a narrowed therapeutic window in alcoholics who have increased needs for such nutrients, but also display an enhanced susceptibility to their adverse effects. Massive doses of choline also exerted some toxic effects and failed to prevent the development of alcoholic cirrhosis. Acetaldehyde (the metabolite produced from ethanol by either ADH or MEOS) impairs hepatic oxygen utilization and forms protein adducts, resulting in antibody production, enzyme inactivation, and decreased DNA repair. It also enhances pyridoxine and perhaps folate degradation and stimulates collagen production by the vitamin A storing cells (lipocytes) and myofibroblasts.(ABSTRACT TRUNCATED AT 400 WORDS)

Folate binding and transport by rat kidney brush-border membrane vesicles

[3H]Pteroylglutamic acid (PteGlu) uptake was studied using brush-border membrane vesicles isolated from rat kidney. Results on the uptake of [3H]PteGlu by brush-border membrane vesicles incubated in media of increasing osmolarities demonstrated that uptake was contributed by two components, intravesicular transport and membrane binding. Both the components of the uptake exhibited similar pH dependence, with maxima at pH 5.6, and were found to be saturable mechanisms with Km values of 6.7.10(-7) and 11.2.10(-7) M, respectively. These studies show that PteGlu is transported by isolated rat kidney brush-border membrane vesicles in a manner consistent with a saturable system and that a binding component may be functionally associated with this.

Valproic acid-induced neural tube defects: reduction by folinic acid in the mouse

Neural tube defects were induced dose-dependently by single injections of the anticonvulsant drug valproic acid (VPA) as sodium salt in mice on gestational day 8. Folinic acid (5-CHO-THF) coadministration by i.p. injection or by a constant rate infusion via osmotic minipumps, implanted s.c., significantly reduced the exencephaly rates using a randomized double-blind experimental procedure. 5-CHO-THF supplementation cut the exencephaly rates into half even at high maternal plasma levels of VPA (p less than 0.005, chi 2-test); resorption rates were not affected. The VPA plasma kinetics were not changed by any of the application regimens of 5-CHO-THF. The investigation of the folate metabolite pattern (determined by HPLC) showed that 5-CHO-THF and 5-methyl-tetrahydrofolic acid (5-CH3-THF) were the main metabolites in untreated mice. After supplementation with 5-CHO-THF, only the concentrations of this folate vitamer were increased in the plasma from 0.3 microgram/ml (normal) to 0.6 or 1.9 micrograms/ml (after injection of 3 x 1 mg/kg or 3 X 4 mg/kg) and to 4.2 micrograms/ml (after infusion via osmotic minipumps). Our results indicate that VPA-induced exencephaly in mice combined with the investigation of the plasma levels of VPA and the different folate metabolites could be an appropriate animal model to study protective effects of folates on the occurrence of neural tube defects.

Nutritional and dietary influences on liver tumorigenesis in mice and rats

There is evidence that liver tumor development in mice can be increased by diets high in calories or fat and by diets low in lipotropes. Data in rats suggest that dietary sucrose or ethanol may have an influence independent of caloric contribution, but the reported results are not entirely consistent. The lipotropic effect on tumorigenesis has been studied extensively in rats and may be the result of several factors, including increased cell proliferation, alteration of macromolecular methylation, changes in cell membrane composition and in xenobiotic metabolism. Comparative studies in mouse liver tumor models may be useful in further investigations.

Mechanisms of vitamin deficiencies in alcoholism

Chronic alcoholic patients are frequently deficient in one or more vitamins. The deficiencies commonly involve folate, vitamin B6, thiamine, and vitamin A. Although inadequate dietary intake is a major cause of the vitamin deficiency, other possible mechanisms may also be involved. Alcoholism can affect the absorption, storage, metabolism, and activation of many of these vitamins. Possible factors which cause alterations in the absorption, storage, and metabolism of these vitamins are discussed. Suggestions for management of vitamin deficiencies in chronic alcoholics are also discussed.

Study of dose-dependence and urinary folate excretion produced by ethanol in humans and rats

Acute ethanol ingestion by human alcoholic subjects produces a marked decrease in serum folate levels within 16 hr. A similar decrease occurs in rats and can be explained by a marked increase in urinary folate excretion following ethanol treatment. To assess the effects of acute ethanol ingestion on urinary folate excretion in healthy human volunteers, two studies were carried out at initial ethanol dose levels of 0.8 g/kg and 1.0 g/kg, respectively. Blood ethanol levels peaked at 70 mg/dl in the first study, but in the second study were 100 +/- 20 mg/dl through 6 hr. Only in the second study were urinary folate levels significantly increased by ethanol administration, and this 8 hr after ingestion. This increase was accompanied by a decrease in urine volume so that in neither study was the total amount of urinary folate excreted from 0-12 hr increased by ethanol ingestion. Studies with various dose levels of ethanol in rats showed that there was a linear dose-response relationship between the total urinary folate excretion and the dose of ethanol. Peak urinary ethanol levels also correlated with urinary folate excretion. These results suggest that doses of ethanol larger than 1.0 g/kg produce increases in urinary folate excretion and that the inability to observe large increases in studies in human subjects is probably related to the limited doses of ethanol chosen.

Direct determination of folate monoglutamates in plasma by high-performance liquid chromatography using an automatic precolumn-switching system as sample clean-up procedure

A simple and rapid technique for the simultaneous isolation and analysis of folate monoglutamates (folic acid, 7,8-dihydrofolic acid, 5,6,7,8-tetrahydrofolic acid and 5-formyl-, 5-methyl- and 10-formyl-5,6,7,8-tetrahydrofolic acids) was developed using reversed-phase high-performance liquid chromatography with an automatic precolumn-switching system. The plasma or the dissolved diet samples were directly injected onto a short precolumn flushed with 50 mM phosphate buffer. The folate vitamers absorbed on the precolumn were backflushed onto the analytical column with a 25 mM phosphate buffer containing 5% methanol and then detected by UV absorption at 280 nm. A linear response was found between the injected sample amounts and the integrated areas for all vitamers analysed. The detection limit was 1-10 pmol and the precision ranged from 1.6 to 10%, depending on the metabolite studied. The recovery rates of folates in plasma were 90-95%. Decomposition of the unstable folates was avoided. Our method was applied to the analysis of mouse plasma and animal diets.

Alcohol and cancer

The cancers consistently associated with ingestion of alcohol, the head and neck cancers, are also associated with tobacco use and arise from epithelia that are in direct contact with both agents. Tobacco smoking-related cancers at sites not directly in contact with alcoholic beverages, that is, lung, bladder, and perhaps pancreas, do not consistently show a relationship to alcohol consumption, although lung and pancreatic tumors are associated in some studies. Liver cancer was thought to be strongly related to alcohol consumption on epidemiological grounds and because of its relationship to cirrhosis. As knowledge of the viral etiology of some cirrhoses has evolved and as methods to detect viruses have developed, the significant association between hepatitis B virus and hepatocellular carcinoma has become clear. Alcohol and hepatitis B virus may interact in the etiology of the disease and have important separate roles as well. There are epidemiologic and experimental data showing that malnutrition (resulting from poor food choice), economic deprivation, or alcoholism contributes to the risk for head, neck, and liver cancers. Colon cancers occur about equally in men and women, are found in well-nourished populations, and are not associated with tobacco smoking. Rectal cancers show a preponderance of cases in men but are frequently found in women as well and are not thought to be associated with smoking or malnutrition. The association between colorectal cancers and alcohol consumption, when it is found, apparently occurs at even relatively low alcohol intakes and is often stronger for consumption of beer than of other beverages. Nutritional and metabolic mechanisms proposed for the influence of alcohol on carcinogenesis are supported by studies in human subjects and laboratory animals. Animal models are needed in which effects of ethanol on carcinogenesis can be consistently demonstrated and which can then be used to examine mechanisms.

Acute ethanol ingestion by humans and subacute treatment of rats increase urinary folate excretion

Previous studies with rats showed that acute treatment with ethanol (4 g/kg) produce a marked increase in urinary folate levels, followed by a decrease in plasma folate levels. Analogous studies with human volunteer subjects using a lower dose of ethanol showed that there were small, but statistically significant increases in urinary folate levels after four hours. The initial ethanol dose was 1.0 g/kg with a single supplement of 0.1-0.2 g/kg to maintain ethanol blood levels at about 100 mg/dl for six hours. Further studies with rats were designed to test the cumulative effects of repeated daily doses of ethanol. Male Sprague-Dawley rats were treated for 1, 2, 3, or 4 days either with ethanol orally in 4 doses of 1 g/kg each at 0, 1, 2, and 3 hours or with glucose orally in 4 isocaloric doses. Urine was collected at timed intervals up to 12 hours after each daily dose. The pattern of the increase in urinary folate levels was similar in all groups, whether treated for 1, 2, 3 or 4 days. These results suggest that repeated ethanol treatment can lead to a marked cumulative folate loss via increased urinary excretion and that increased urinary folate excretion may contribute to the development of folate deficiency in humans.