Beneficial effect of a low dose of ethanol on liver function and serum urate in rats fed a high-fat diet

Effects of Regular Low-Level Alcohol Consumption in Healthy Individuals: A Randomized, Double-Blind, Placebo-Controlled Crossover Study

The effects of alcohol consumption on health are suggested to depend on the amount of alcohol consumed. We investigated the objective and subjective health effects of the daily consumption of a small amount of alcohol in healthy individuals using a randomized, double-blind, placebo-controlled crossover study. Accordingly, 15 male and 27 female Japanese adults with average or lower general well-being schedule (GWBS) scores were asked to consume a beverage with 0.5% (v/v) alcohol (~4 g of alcohol a day; test beverage) and a placebo beverage two times daily for 4 weeks each. Regular low-level alcohol consumption significantly decreased the serum liver function indexes (aspartic aminotransferase, alanine aminotransferase, and lactate dehydrogenase) before and after consumption (p = 0.034, 0.033, and 0.013, respectively). The small amount of alcohol did not affect the participants’ GWBS scores; however, a stratified analysis with poor subjective well-being revealed that these changes differed significantly between low-level alcohol consumption and placebo-treated subjects (16.0 vs. 11.5, p = 0.041). In addition, changes in serum testosterone levels demonstrated a higher trend in the group that received the test beverage compared with the group that received the placebo beverage (p = 0.051). Daily low-level alcohol consumption may have positive effects on liver function and subjective well-being.

Experimental models of metabolic and alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a multi-systemic disease that is considered the hepatic manifestation of metabolic syndrome (MetS). Because alcohol consumption in NAFLD patients is common, there is a significant overlap in the pathogenesis of NAFLD and alcoholic liver disease (ALD). Indeed, MetS also significantly contributes to liver injury in ALD patients. This “syndrome of metabolic and alcoholic steatohepatitis” (SMASH) is thus expected to be a more prevalent presentation in liver patients, as the obesity epidemic continues. Several pre-clinical experimental models that couple alcohol consumption with NAFLD-inducing diet or genetic obesity have been developed to better understand the pathogenic mechanisms of SMASH. These models indicate that concomitant MetS and alcohol contribute to lipid dysregulation, oxidative stress, and the induction of innate immune response. There are significant limitations in the applicability of these models to human disease, such as the ability to induce advanced liver injury or replicate patterns in human food/alcohol consumption. Thus, there remains a need to develop models that accurately replicate patterns of obesogenic diet and alcohol consumption in SMASH patients.

Low-Dose Ethanol Has Impacts on Plasma Levels of Metabolites Relating to Chronic Disease Risk in SAMP8 mice

The effects of low-dose alcohol on experimental animals are unclear. This study examined plasma metabolites in senescence-accelerated mice 8 (SAMP8) given low-dose ethanol, and compared them with aging progress and skeletal muscle strength. Male SAMP8 mice (10-wk-old) were given drinking water containing 0% (control), 1%, 2%, or 5% (v/v) ethanol for 14 wk. Compared with the control group, only mice who consumed 1% ethanol experienced a lower senescence score at 18 and 23 wk, as well as an increased limb grip strength at 21 wk. Plasma metabolites of control, 1% and 2% ethanol groups were analyzed by capillary electrophoresis-time-of-flight mass spectrometry (CE-TOF/MS). Among the 7 metabolites affected by ethanol, notewhorthy is the positive association of the ethanol levels in drinking water with the levels of α-ketoglutarate (antioxidant and anti-inflammatory metabolite) and hippurate (antioxidant and microbial co-metabolite) (p<0.05). Intriguingly, the levels of 2-hydroxyisobutyrate (the biomarker of energy metabolism and microbial co-metabolite) were higher in the 1% ethanol group (p<0.05), but not in the 2% ethanol group as compared to the control. Furthermore, the levels of some of the metabolites affected were correlated with some variables in the grading score of senescence and muscle strength. This study provides a novel insight into how low-dose ethanol in SAMP8 mice modulates the levels of circulating metabolites relating to chronic disease risk.

Consumption of Low-Dose of Ethanol Suppresses Colon Tumorigenesis in 1,2-Dimethylhydrazine-Treated Rats

The effect of low-dose of ethanol consumption on the development of colon cancer is unclear. This study aimed to investigate the effects of low-dose ethanol (0.5%, 1%, and 2% [v/v] ethanol in drinking water) for 28 wk on colon tumor incidence in rats injected with 1,2-dimethylhydrazine. Body weight, fluid and food consumption, and the total numbers of colon adenomas (mild-, moderate-, and severe-grade dysplasia) per rat were unaffected by ethanol consumption. However, the numbers of severe-grade dysplasia were significantly reduced by 1% ethanol compared with the control (0% ethanol; -93%) but not by 0.5% and 2% ethanol. Although the numbers of total adenocarcinomas were unaffected, those of total of adenomas and adenocarcinomas together were significantly reduced by 0.5% and 1% ethanol (-39% and -41%, respectively). Intriguingly, real-time PCR assay indicated the abundance of cecal Clostridium leptum (a putative immunosuppressor) was the least in rats received 1% ethanol. Furthermore, 1% ethanol markedly increased colonic mRNA of IL-6, a putative suppressor of regulatory T-cells and cytoprotector. This study provides the first evidence for the potential of 1% ethanol, but not 2% ethanol, to prevent colon tumorigenesis in rats, supporting the J-curve hypothesis of the effect of low-dose alcohol on health. Further, the modulation of C. leptum and expression of IL-6, potentially linking to carcinogenesis, by 1% ethanol may provide an insight into the underlying mechanisms of the anti-colon tumor effect.

Moderate chronic ethanol consumption exerts beneficial effects on nonalcoholic fatty liver in mice fed a high-fat diet: possible role of higher formation of triglycerides enriched in monounsaturated fatty acids

PURPOSE

Several clinical studies suggested that light-to-moderate alcohol intake could alleviate nonalcoholic fatty liver disease (NAFLD), but the underlying mechanism is still poorly understood.

METHODS

Mice fed a high-fat diet (HFD) were submitted or not to moderate ethanol intake for 3 months (ca. 10 g/kg/day) via drinking water. Biochemical, analytical and transcriptomic analyses were performed in serum and liver.

RESULTS

Serum ethanol concentrations in ethanol-treated HFD mice comprised between 0.5 and 0.7 g/l throughout the experiment. NAFLD improvement was observed in ethanol-treated HFD mice as assessed by reduced serum transaminase activity. This was associated with less microvesicular and more macrovacuolar steatosis, the absence of apoptotic hepatocytes and a trend towards less fibrosis. Liver lipid analysis showed increased amounts of fatty acids incorporated in triglycerides and phospholipids, reduced proportion of palmitic acid in total lipids and higher desaturation index, thus suggesting enhanced stearoyl-coenzyme A desaturase activity. mRNA expression of several glycolytic and lipogenic enzymes was upregulated. Genome-wide expression profiling and gene set enrichment analysis revealed an overall downregulation of the expression of genes involved in collagen fibril organization and leukocyte chemotaxis and an overall upregulation of the expression of genes involved in oxidative phosphorylation and mitochondrial respiratory chain complex assembly. In addition, mRNA expression of several proteasome subunits was upregulated in ethanol-treated HFD mice.

CONCLUSIONS

Moderate chronic ethanol consumption may alleviate NAFLD by several mechanisms including the generation of non-toxic lipid species, reduced expression of profibrotic and proinflammatory genes, restoration of mitochondrial function and possible stimulation of proteasome activity.

Increased intestinal ethanol following consumption of fructooligosaccharides in rats

Previous studies have suggested that ethanol is a fermentation product of microflora. However, it is unknown whether this ethanol production is elevated by intake of prebiotics. Prebiotics are considered to enhance the production of short-chain fatty acids (SCFAs) as a fermentation product of beneficial bacteria. In the present study, the effect of fructooligosaccharides (FOS) consumption on intestinal ethanol levels was investigated. Rats were fed a diet with or without 10% FOS for two weeks. Consequently, FOS intake significantly increased ethanol levels per gram of ileum and cecum digesta of the rats (3.5-fold and 1.9-fold, respectively, P<0.01). The numbers of cecum Bifidobacterium (producer of ethanol and lactate) were significantly increased by FOS intake (P<0.05) and correlated with the cecum ethanol levels per gram of cecum (r=0.626, P<0.05). FOS intake also led to a significant increase in the cecum levels of SCFAs, namely lactate, propionate and n-butyrate (P<0.05). Furthermore, ethanol levels were significantly correlated with lactate levels (r=0.691, P<0.01), but not with propionate or n-butyrate levels (r=0.449 and 0.493, respectively, P>0.05). The current study, to the best of our knowledge, is the first to indicate that FOS intake significantly increases the level of intestinal ethanol. Therefore, dietary FOS may affect the intestinal health status of animals by elevating their ethanol levels, without direct ethanol consumption.

Food functionality research as a new national project in special reference to improvement of cognitive and locomotive abilities

In Japan, where a super-aging society is realized, we are most concerned about healthy longevity, which would ascertain the wellness of people by improving their quality of life (QOL). In 2014, the Cabinet Office proposed a strategic innovation promotion programme, launching a national project for the development of the agricultural-forestry-fisheries food products with new functionalities for the next generation. In addition to focusing on a conventional prevention of lifestyle-associated metabolic syndromes, the project targets the scientific evidence of the activation of brain cognitive ability and the improvement of bodily locomotive function. The project also involves the analysis of the foods-sports interrelation of chronic importance, and the development of devices for the verification of QOL-associated maintenance of homeostasis. In this review, we provide an overview of these studies, with special reference to cognition as a case of the gut-brain axis which the author is particularly interested in.

Beneficial Effects of Dietary Tempeh Prepared with Rhizopus stolonifer on Liver Function in Rats Fed with a High-Fat Diet

The regional standard for tempeh established by the Codex Alimentarius defines the use of Rhizopus oligosporus, R. oryzae, and/or R. stolonifer as soybean tempeh starters. However, comparative studies on the functions of tempeh prepared with these Rhizopus species are scarce. In the present study, we examined the effects of dietary tempeh prepared with these three Rhizopus species using rats fed with a high-fat diet. Compared to the control diet, consumption of tempeh prepared with R. stolonifer significantly suppressed serum levels of aspartate transaminase, total bilirubin, and ammonium (indices of liver function). However, less or no suppression was observed with tempeh prepared with R. oligosporus or R. oryzae. Serum levels of triglyceride, total cholesterol, HDL cholesterol, and glucose were unaffected. Liver levels of free cholesterol, a parameter relating to liver injury, were significantly decreased by the three types of the tempeh examined; however, there was no difference in the free cholesterol levels among the tempeh groups. We conclude that the ingestion of tempeh prepared with R. stolonifer might have beneficial effects pertaining to the liver function in rats fed with high-fat diets.

Effects of low dose of ethanol on the senescence score, brain function and gene expression in senescence-accelerated mice 8 (SAMP8)

Accumulating epidemiological evidence suggests light to moderate alcohol intake reduces risk of several chronic diseases. However, there is limited information regarding the effects of low alcohol intake in animal studies. This study investigated the effect of low ethanol dosage on senescence-accelerated mouse (SAMP8), an animal model of aging and neurodegenaration. Male SAMP8 mice (11 weeks old) had free access to a commercial stock diet with drinking water containing 0, 1 or 2% (v/v) ethanol for 15 weeks. The total grading score of senescence in the 1%-ethanol group was, in large part, the lowest among the three groups. Analysis using the open-field test revealed a significant elevation (+77%, P<0.05) in the rearing activity (index of seeking behavior) in the 1%-ethanol group, but not in the 2%-ethanol group. In addition, 2% ethanol elevated spontaneous locomotor activity (+75%, P<0.05), whereas 1% ethanol did not. Scrutiny of serum parameters indicated intake of 1% ethanol significantly decreased serum insulin levels (-13%, P<0.05), whereas 2% did not. Intake of 2% ethanol significantly elevated (2.5-fold, P<0.05) S100a8 mRNA (an inflammatory signal) in the brain, but that of 1% ethanol did not. Intriguingly, 1% ethanol intake remarkably elevated (10-fold, P<0.05) mRNA of brain alcohol dehydrogenase 1 (Adh1), which metabolizes lipid-peroxidation products and is involved in the synthesis of retinoic acid, a neuroprotective factor. Of note, 2%-ethanol intake did not exert this effect. Taken together, intake of 1% ethanol is likely to be beneficial for SAMP8 mice.

Effects of moderate alcohol consumption on gene expression related to colonic inflammation and antioxidant enzymes in rats

Excessive alcohol consumption is a risk factor associated with colorectal cancer; however, some studies have reported that moderate alcohol consumption may not contribute additional risk for developing colorectal cancer while others suggest that moderate alcohol consumption provides a protective effect that reduces colorectal cancer risk. The purpose of this study was to determine the effects of moderate voluntary alcohol (20% ethanol) intake on alternate days for 3 months in outbred Wistar rats on risk factors associated with colorectal cancer development. Colonic gene expression of cyclooxygenase-2, RelA, 8-oxoguanine DNA glycosylase 1, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-S-transferase M1, and aldehyde dehydrogenase 2 were determined. Blood alcohol content, liver function enzyme activities, and 8-oxo-deoxyguanosine DNA adducts were also assessed. Alcohol-treated rats were found to have significantly lower 8-oxo-deoxyguanosine levels in blood, a marker of DNA damage. Alanine aminotransferase and lactate dehydrogenase were both significantly lower in the alcohol group. Moderate alcohol significantly decreased cyclooxygenase-2 gene expression, an inflammatory marker associated with colorectal cancer risk. The alcohol group had significantly increased glutathione-S-transferase M1 expression, an antioxidant enzyme that helps detoxify carcinogens, such as acetaldehyde, and significantly increased aldehyde dehydrogenase 2 expression, which allows for greater acetaldehyde clearance. Increased expression of glutathione-S-transferase M1 and aldehyde dehydrogenase 2 likely contributed to reduce mucosal damage that is caused by acetaldehyde accumulation. These results indicate that moderate alcohol may reduce the risk for colorectal cancer development, which was evidenced by reduced inflammation activity and lower DNA damage after alcohol exposure.