Adipocyte lipolysis, hormonal and metabolic changes in ethanol-drinking rats

In vitro, in vivo, and in silico analysis of synbiotics as preventive interventions for lipid metabolism in ethanol-induced adipose tissue injury

The risk of alcoholic liver disease (ALD) is increased by excessive ethanol drinking. For the prevention of ALD, the effects of ethanol on the liver, adipose tissue, and gut are crucial. Interestingly, garlic and a few probiotic strains can protect against ethanol-induced hepatotoxicity. However, the relationship between adipose tissue inflammation, Kyolic aged garlic extract (AGE), and Lactobacillus rhamnosus MTCC1423 in developing ALD is unknown. Therefore, the present study explored the effect of synbiotics (a combination of prebiotics and probiotics) on adipose tissue to prevent ALD. To investigate the efficacy of synbiotics administration on adipose tissue in preventing ALD, in vitro (3T3-L1 cells, N = 3) groups: control, control + LPS (lipopolysaccharide), ethanol, ethanol + LPS, ethanol + synbiotics, ethanol + synbiotics + LPS; in vivo (Wistar male rats, N = 6) groups: control, ethanol, pairfed, ethanol + synbiotics and in silico experiments were conducted. Lactobacillus multiplies in accordance with the growth curve when exposed to AGE. Additionally, Oil red O staining and scanning electron microscopy (SEM) demonstrated that synbiotics therapy maintained the morphology of adipocytes in the alcoholic model. In support of the morphological changes, quantitative real-time PCR demonstrated overexpression of adiponectin and downregulation of leptin, resistin, PPARγ, CYP2E1, iNOS, IL-6, and TNF-α after administration of synbiotics compared to the ethanol group. In addition, MDA estimation by high-performance liquid chromatography (HPLC) indicated that the synbiotics treatment reduced oxidative stress in rat adipose tissue. Consequently, the in-silico analysis revealed that AGE inhibited the C-D-T networks as PPARγ acting as the main target protein. The current study demonstrates that using synbiotics improves adipose tissue metabolism in ALD.

Gut Microbiota: Target for Modulation of Gut-Liver-Adipose Tissue Axis in Ethanol-Induced Liver Disease

Consumption of alcohol (ethanol) in various forms has been an integral part of human civilization. Since ages, it also has been an important cause of death and health impairment across the globe. Ethanol-mediated liver injury, known as alcoholic liver disease (ALD), is caused by surplus intake of alcohol. Several studies have proposed the different pathways that may be lead to ALD. One of the factors that may affect the cytochrome P450 (CYP2E1) metabolic pathway is gut dysbiosis. The gut microbiota produces various compounds that play an important role in regulating healthy functions of distal organs such as the adipose tissue and liver. Dysbiosis causes bacteremia, hepatic encephalopathy, and increased intestinal permeability. Recent clinical studies have found better understanding of the gut and liver axis. Another factor that may affect the ALD pathway is dysfunction of adipose tissue metabolism. Moreover, dysfunction of adipose tissue leads to ectopic fat deposition within the liver and disturbs lipid metabolism by increasing lipolysis/decreasing lipogenesis and impaired glucose tolerance of adipose tissue which leads to ectopic fat deposition within the liver. Adipokine secretion of resistin, leptin, and adiponectin is adversely modified upon prolonged alcohol consumption. In the combination of these two factors, a proinflammatory state is developed within the patient leading to the progression of ALD. Thus, the therapeutic approach for treatments and prevention for liver cirrhosis patients must be focused on the gut-liver-adipose tissue network modification with the use of probiotics, synbiotics, and prebiotics. This review is aimed at the effect of ethanol on gut and adipose tissue in both rodent and human alcoholic models.

The sex specific effect of alcohol consumption on circulating levels of CTRP3

The goal of this project was to establish the effect of alcohol consumption on the circulating levels of the adipose tissue derived protein C1q TNF Related Protein 3 (CTRP3). Adipose tissue secretes several adipokines, such as adiponectin and leptin, which exert a multitude of biological effects important for human health. However, adipose tissue is extremely sensitive to alcohol consumption, leading not only to disrupted fat storage, but also to disruptions in adipokine production. Changes to adipokine secretion could have widespread biological effects and potentially contribute to alcohol-induced ailments, such as alcoholic fatty liver disease (ALD). CTRP3 has been previously demonstrated to attenuate fatty liver disease, and suppression of CTRP3 with alcohol consumption could contribute to development of and progression to alcoholic fatty liver disease. To examine the effect of ethanol consumption on circulating adipokine levels, male and female mice were fed an ethanol containing diet (Lieber-DeCarli 5% (v/v) ethanol diet) for 10-days followed by a single gavage of 5 g/kg ethanol (the NIAAA model), or for 6-weeks with no binge added (chronic model). In female mice, adiponectin levels increased ~2-fold in both models of ethanol feeding, but in male mice increased adiponectin levels were only observed after chronic ethanol feeding. On the other hand, in female mice, circulating CTRP3 levels decreased by ~75% and ~50% in the NIAAA and chronic model, respectively, with no changes observed in the male mice in either feeding model. Leptin levels were unchanged with ethanol feeding regardless of model or sex of mice. Lastly, chronic ethanol feeding led to a significant increase in mortality (~50%) in female mice, with no difference in relative ethanol consumption. These findings indicate that ethanol consumption can dysregulate adipokine secretion, but that the effects vary by sex of animal, method of ethanol consumption, and adipokine examined. These findings also indicate that female mice are more sensitive to the chronic effects of ethanol than male mice. Notably, this is the first study to document the effects of ethanol consumption on the circulating levels of CTRP3. Understanding the impact of excessive alcohol consumption on adipokine production and secretion could identify novel mechanisms of alcohol-induced human disease. However, the mechanism responsible for the increased sensitivity remains elusive.

Alcohol, Adipose Tissue and Lipid Dysregulation

Chronic alcohol consumption perturbs lipid metabolism as it increases adipose tissue lipolysis and leads to ectopic fat deposition within the liver and the development of alcoholic fatty liver disease. In addition to the recognition of the role of adipose tissue derived fatty acids in liver steatosis, alcohol also impacts other functions of adipose tissue and lipid metabolism. Lipid balance in response to long-term alcohol intake favors adipose tissue loss and fatty acid efflux as lipolysis is upregulated and lipogenesis is either slightly decreased or unchanged. Study of the lipolytic and lipogenic pathways has identified several regulatory proteins modulated by alcohol that contribute to these effects. Glucose tolerance of adipose tissue is also impaired by chronic alcohol due to decreased glucose transporter-4 availability at the membrane. As an endocrine organ, white adipose tissue (WAT) releases several adipokines that are negatively modulated following chronic alcohol consumption including adiponectin, leptin, and resistin. When these effects are combined with the enhanced expression of inflammatory mediators that are induced by chronic alcohol, a proinflammatory state develops within WAT, contributing to the observed lipodystrophy. Lastly, while chronic alcohol intake may enhance thermogenesis of brown adipose tissue (BAT), definitive mechanistic evidence is currently lacking. Overall, both WAT and BAT depots are impacted by chronic alcohol intake and the resulting lipodystrophy contributes to fat accumulation in peripheral organs, thereby enhancing the pathological state accompanying chronic alcohol use disorder.

Resveratrol alleviates ethanol-induced hormonal and metabolic disturbances in the rat

Resveratrol is a polyphenol found in different plant species and having numerous health-promoting properties in animals and humans. However, its protective action against deleterious effects of ethanol is poorly elucidated. In the present study, the influence of resveratrol (10 mg/kg/day) on some hormones and metabolic parameters was determined in rats ingesting 10 % ethanol solution for two weeks. Blood levels of insulin, glucagon and adiponectin were affected by ethanol, however, resveratrol partially ameliorated these changes. Moreover, in ethanol drinking rats, liver lipid accumulation was increased, whereas resveratrol was capable of reducing liver lipid content, probably due to decrease in fatty acid synthesis. Resveratrol decreased also blood levels of triglycerides and free fatty acids and reduced gamma-glutamyl transferase activity in animals ingesting ethanol. These results show that resveratrol, already at low dose, alleviates hormonal and metabolic changes induced by ethanol in the rat and may be useful in preventing and treating some consequences of alcohol consumption.

Characteristics of metabolic changes in adipocytes of growing rats

Adipocytes, cells of white fat tissue, store energy in the form of lipids and have also endocrine functions. Disturbances in adipocyte metabolism lead to decreased or excessive fat tissue accumulation and are associated with numerous diseases. Pathologic alterations in adipose tissue are known to develop with age, however, changes in young, growing subjects are poorly elucidated. In the present study, glucose transport and metabolism, hyperpolarization of the inner mitochondrial membrane and the lipolytic activity were compared in the epididymal adipocytes of 8-week-old and 16-week-old rats. It was demonstrated that glucose conversion to lipids, glucose transport and oxidation was decreased in the adipocytes of the older animals. These effects were accompanied by increase in lactate release and by decrease in hyperpolarization of the mitochondrial membrane. Lipolytic response to epinephrine was increased (at lower concentrations of the hormone) or reduced (at higher concentration) in the adipocytes of the older rats. However, induction of lipolysis by the direct activation of protein kinase A induced similar response. It was also demonstrated that inhibition of phosphodiesterase 3B or adenosine A1 receptor blocking caused lower lipolysis in the cells of the older rats. Moreover, antilipolytic action of insulin was impaired in the adipocytes of these rats, probably due to changes in the initial steps of the insulin signaling pathway. However, the use of the pharmacologic inhibitor of protein kinase A instead of insulin resulted in similar antilipolysis in both groups of cells. These results show that, in spite of relatively small age difference, substantial changes in adipose tissue metabolism develop in these animals. Decreased response to insulin action seems to be particularly relevant finding.

Common effects of fat, ethanol, and nicotine on enkephalin in discrete areas of the brain

Fat, ethanol, and nicotine share a number of properties, including their ability to reinforce behavior and produce overconsumption. To test whether these substances act similarly on the same neuronal populations in specific brain areas mediating these behaviors, we administered the substances short-term, using the same methods and within the same experiment, and measured their effects, in areas of the hypothalamus (HYPO), amygdala (AMYG), and nucleus accumbens (NAc), on mRNA levels of the opioid peptide, enkephalin (ENK), using in situ hybridization and on c-Fos immunoreactivity (ir) to indicate neuronal activity, using immunofluorescence histochemistry. In addition, we examined for comparison another reinforcing substance, sucrose, and also took measurements of stress-related behaviors and circulating corticosterone (CORT) and triglycerides (TG), to determine if they contribute to these substances' behavioral and physiological effects. Adult Sprague-Dawley rats were gavaged three times daily over 5 days with 3.5 mL of water, Intralipid (20% v/v), ethanol (12% v/v), nicotine (0.01% w/v) or sucrose (22% w/v) (approximately 7 kcal/dose), and tail vein blood was collected for measurements of circulating CORT and TG. On day five, animals were sacrificed, brains removed, and the HYPO, AMYG, and NAc processed for single- or double-labeling of ENK mRNA and c-Fos-ir. Fat, ethanol, and nicotine, but not sucrose, increased the single- and double-labeling of ENK and c-Fos-ir in precisely the same brain areas, the middle parvocellular but not lateral area of the paraventricular nucleus, central but not basolateral nucleus of the AMYG, and core but not shell of the NAc. While having little effect on stress-related behaviors or CORT levels, fat, ethanol, and nicotine all increased circulating levels of TG. These findings suggest that the overconsumption of these three substances and their potential for abuse are mediated by the same populations of ENK-expressing neurons in specific nuclei of the hypothalamus and limbic system.

Red wine increases adipose tissue aromatase expression and regulates body weight and adipocyte size

OBJECTIVE

Obesity is an important component of the metabolic syndrome in constituting a risk factor for cardiovascular disease, diabetes, and cancer. Estrogens influence lipid accumulation in adipocytes, acting indirectly or directly on adipose tissue. In this study we aimed to investigate the influence of red wine ingestion on the expression of aromatase (estrogen synthase) in adipose tissue.

METHODS

Red wine or ethanol solution, in the concentration found in red wine, was provided to Wistar rats as the sole drinking fluid for 8 wk. Food and drink intakes and body weight were monitored throughout treatment and adipocyte size and aromatase expression in the adipose tissue were determined at the end of the experimental period.

RESULTS

Red wine and ethanol increased aromatase expression in the adipose tissue and red wine decreased adipocyte size (P < 0.05). In addition, animals treated with red wine or ethanol had significantly lower weight gain than controls, despite a similar energy intake.

CONCLUSION

Thus, the ingestion of red wine may alter the production of estrogens by adipose tissue, body weight gain, and adipocyte size. Some of these red wine effects are attributable to ethanol. This relation among estrogen availability, adipocyte biology, and weight gain is most interesting and deserves further study because it may lead to new strategies to reduce metabolic syndrome incidence.

The effect of red wine on plasma leptin levels and vasoactive factors from adipose tissue: A randomized crossover trial

AIMS

It has been reported that alcohol has multiple effects on appetite. To elucidate potential mechanisms we measured the levels of plasma leptin and the vasoactive factors after red wine intake.

METHODS

We conducted a randomized crossover trial to study the effect of red wine on the levels of leptin, TNF-alpha, TGF- beta(1), IL-6, ICAM-1, and VCAM-1 in healthy, non-smoking individuals. The subjects were randomized to drinking one glass of red wine (150 ml, 15 g alcohol) every day ('wine period') or to undergo a period of total abstention from alcohol ('abstention period'). After 3 weeks they switched the intervention group. Eighty-seven volunteers completed the study (mean age 50 years).

RESULTS

After 3 weeks' daily intake of red wine, plasma leptin was significantly increased (from 6308 pg/ml to 7402 pg/ml, P = 0.05). There was a marked gender difference, as leptin levels increased only in females (P = 0.012). When calculated as leptin/body mass index (BMI) ratio, the trend and results were similar. Red wine consumption had no significant effect on other vasoactive factors measured in this study.

CONCLUSION

Red wine increases levels of the appetite-regulating hormone leptin in females, but not in males. Whether red wine has an effect on appetite-regulation in its own right, remains to be solved.

In vivo metabolic effects of naringenin in the ethanol consuming rat and the effect of naringenin on adipocytes in vitro

Naringenin is a bioactive flavanone involved in the inhibition of drug metabolism which exhibits antioxidant, anti-inflammatory and anticancerogenic properties and which recently appeared to be a factor mitigating the hyperlipidaemic effects in rats and rabbits. In the performed experiment, the effect of naringenin, administered intragastrically (50 mg/kg) for 2 weeks to normal and ethanol drinking rats, on insulin and leptin levels and on some metabolic parameters was investigated. Naringenin did not change the hormone levels in any group of rats. Blood glucose, triglyceride, total, esterified and free cholesterol and high-density lipoprotein-cholesterol concentrations were also unaffected by this compound. Only free fatty acids were elevated after the naringenin treatment in the water-drinking rats. In spite of unchanged glucose and insulin concentrations in blood, the tested flavanone reduced the glucose/insulin ratio in ethanol-receiving rats. Liver triglycerides, elevated due to ethanol ingestion, were partially normalized by naringenin. Other tested parameters like liver glycogen and cholesterol, muscle triglycerides and glycogen were not altered in any group of rats. The influence of naringenin (62.5, 125, 250 and 500 microM) on basal and insulin-stimulated glucose conversion to lipids (lipogenesis) as well as on basal and epinephrine-stimulated glycerol release (lipolysis) in the isolated rat adipocytes was also tested. The basal and the stimulated lipogenesis tended to be decreased in the presence of the flavanone (250 microM). This inhibitory effect intensified and was statistically significant at the highest concentration of naringenin. The tested compound did not evoke any effect on basal lipolysis while the epinephrine-stimulated process was limited at the highest concentration of the flavanone. Naringenin (62.5, 125, 250 and 500 microM) had no effect on leptin secretion from the isolated rat adipocytes. Results obtained in our studies demonstrate that naringenin exerts a very weak influence on carbohydrate and lipid metabolism of normal and ethanol-consuming rats and on metabolism of isolated rat adipocytes.

Chronic ethanol feeding suppresses beta-adrenergic receptor-stimulated lipolysis in adipocytes isolated from epididymal fat

Chronic ethanol consumption disrupts G protein-dependent signaling pathways in rat adipocytes. Because lipolysis in adipocytes is regulated by G protein-mediated cAMP signal transduction, we hypothesized that cAMP-regulated lipolysis may be vulnerable to long-term ethanol exposure. Male Wistar rats were fed a liquid diet containing ethanol as 35% of total calories or pair-fed a control diet that isocalorically substituted maltose dextrins for ethanol for 4 wk. Lipolysis was measured by glycerol release over 1 h with or without agonists in adipocytes isolated from epididymal fat. Chronic ethanol feeding decreased beta-adrenergic receptor-stimulated lipolysis, but had no effect on basal lipolysis. In response to beta-adrenergic activation, the early peak of cAMP accumulation was suppressed after ethanol feeding, although the basal cAMP concentration in adipocytes did not differ between pair- and ethanol-fed rats. The suppression in cAMP accumulation caused by ethanol feeding was associated with increased activity of phosphodiesterase 4. Chronic ethanol feeding also decreased beta-adrenergic receptor-stimulated protein kinase A activation and phosphorylation of its downstream proteins, perilipin A and hormone-sensitive lipase, the primary lipase-mediating lipolysis. In conclusion, these data suggest that chronic ethanol feeding increased phosphodiesterase 4 activity in adipocytes, resulting in decreased accumulation of cAMP in response to beta-adrenergic activation and a suppression of beta-adrenergic stimulation of lipolysis.