Acylated and desacyl ghrelin are associated with hepatic lipogenesis, β-oxidation and autophagy: role in NAFLD amelioration after sleeve gastrectomy in obese rats

Bariatric surgery improves non-alcoholic fatty liver disease (NAFLD). Our aim was to investigate the potential role of ghrelin isoforms in the resolution of hepatic steatosis after sleeve gastrectomy, a restrictive bariatric surgery procedure, in diet-induced obese rats. Male Wistar rats (n = 161) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary interventions [fed ad libitum a normal (ND) or a high-fat (HFD) diet or pair-fed]. Obese rats developed hepatosteatosis and showed decreased circulating desacyl ghrelin without changes in acylated ghrelin. Sleeve gastrectomy induced a dramatic decrease of desacyl ghrelin, but increased the acylated/desacyl ghrelin ratio. Moreover, sleeve gastrectomy reduced hepatic triglyceride content and lipogenic enzymes Mogat2 and Dgat1, increased mitochondrial DNA amount and induced AMPK-activated mitochondrial FFA β-oxidation and autophagy to a higher extent than caloric restriction. In primary rat hepatocytes, the incubation with both acylated and desacyl ghrelin (10, 100 and 1,000 pmol/L) significantly increased TG content, triggered AMPK-activated mitochondrial FFA β-oxidation and autophagy. Our data suggest that the decrease in the most abundant isoform, desacyl ghrelin, after sleeve gastrectomy contributes to the reduction of lipogenesis, whereas the increased relative acylated ghrelin levels activate factors involved in mitochondrial FFA β-oxidation and autophagy in obese rats, thereby ameliorating NAFLD.

Pathophysiology of Non Alcoholic Fatty Liver Disease

The physiopathology of fatty liver and metabolic syndrome are influenced by diet, life style and inflammation, which have a major impact on the severity of the clinicopathologic outcome of non-alcoholic fatty liver disease. A short comprehensive review is provided on current knowledge of the pathophysiological interplay among major circulating effectors/mediators of fatty liver, such as circulating lipids, mediators released by adipose, muscle and liver tissues and pancreatic and gut hormones in relation to diet, exercise and inflammation.

Microbes and Oxytocin: Benefits for Host Physiology and Behavior

It is now understood that gut bacteria exert effects beyond the local boundaries of the gastrointestinal tract to include distant tissues and overall health. Prototype probiotic bacterium Lactobacillus reuteri has been found to upregulate hormone oxytocin and systemic immune responses to achieve a wide array of health benefits involving wound healing, mental health, metabolism, and myoskeletal maintenance. Together these display that the gut microbiome and host animal interact via immune-endocrine-brain signaling networks. Such findings provide novel therapeutic strategies to stimulate powerful homeostatic pathways and genetic programs, stemming from the coevolution of mammals and their microbiome.

GUT MICROBIOTA, PREBIOTICS, PROBIOTICS, AND SYNBIOTICS IN MANAGEMENT OF OBESITY AND PREDIABETES: REVIEW OF RANDOMIZED CONTROLLED TRIALS

OBJECTIVE

To review the data from randomized controlled trials (RCTs) for the roles of microbiota, pre-, pro- and synbiotics in metabolic conditions (obesity, prediabetes, and diabetes mellitus type 2 [DM2]).

METHODS

Primary literature was reviewed on the topics including RCTs of pre-, pro- and synbiotics use for metabolic disease.

RESULTS

Gut bacteria (microbiota) benefit digestion and have multiple other functions. Microbiota could increase harvesting of energy from the food and cause subclinical inflammation seen in metabolic disorders. Diet-related interventions including prebiotics, probiotics, and synbiotics (combining pre-and probiotics) may benefit metabolic conditions. Prebiotics are complex carbohydrates (i.e., dietary fiber). Results of RCTs of prebiotics suggested a neutral effect on body weight, decreased fasting and postprandial glucose, and improved insulin sensitivity and lipid profile. Some inflammation markers were reduced, sometimes substantially (20-30%). RCTs for probiotics demonstrated significant but small effects on body weight (<3%) and metabolic parameters. The effect was seen mostly with fermented milk or yogurt compared to capsule form, consumption for at least 8 weeks, and use of multiple rather than a single bacterial strain. Changes in microbiota were seen at times with both pre- and probiotics. Pickled and fermented foods, particularly vegetables and beans, could serve as a dietary source of pre-, pro-, and synbiotics. These foods showed possible benefits for morbidity and mortality in prospective cohort studies.

CONCLUSION

Pre-, pro-, and synbiotics could prove useful, but further research is needed to clarify their clinical relevance for the prevention and management of metabolic disease.

ABBREVIATIONS

A1c = glycohemoglobin A1c CI = confidence interval CVD = cardiovascular disease GMB = gut (large bowel) microbiota DM2 = diabetes mellitus type 2 HOMA-IR = homeostatic model assessment of insulin resistance LDL = low-density lipoprotein LPS = lipopolysaccharide NAFLD = nonalcoholic fatty liver disease RCT = randomized controlled trial SMD = standardized mean difference TG = triglycerides.

Cathelicidin suppresses lipid accumulation and hepatic steatosis by inhibition of the CD36 receptor

BACKGROUND AND OBJECTIVES

Obesity is a global epidemic which increases the risk of the metabolic syndrome. Cathelicidin (LL-37 and mCRAMP) is an antimicrobial peptide with an unknown role in obesity. We hypothesize that cathelicidin expression correlates with obesity and modulates fat mass and hepatic steatosis.

MATERIALS AND METHODS

Male C57BL/6 J mice were fed a high-fat diet. Streptozotocin was injected into mice to induce diabetes. Experimental groups were injected with cathelicidin and CD36 overexpressing lentiviruses. Human mesenteric fat adipocytes, mouse 3T3-L1 differentiated adipocytes and human HepG2 hepatocytes were used in the in vitro experiments. Cathelicidin levels in non-diabetic, prediabetic and type II diabetic patients were measured by enzyme-linked immunosorbent assay.

RESULTS

Lentiviral cathelicidin overexpression reduced hepatic steatosis and decreased the fat mass of high-fat diet-treated diabetic mice. Cathelicidin overexpression reduced mesenteric fat and hepatic fatty acid translocase (CD36) expression that was reversed by lentiviral CD36 overexpression. Exposure of adipocytes and hepatocytes to cathelicidin significantly inhibited CD36 expression and reduced lipid accumulation. Serum cathelicidin protein levels were significantly increased in non-diabetic and prediabetic patients with obesity, compared with non-diabetic patients with normal body mass index (BMI) values. Prediabetic patients had lower serum cathelicidin protein levels than non-diabetic subjects.

CONCLUSIONS

Cathelicidin inhibits the CD36 fat receptor and lipid accumulation in adipocytes and hepatocytes, leading to a reduction of fat mass and hepatic steatosis in vivo. Circulating cathelicidin levels are associated with increased BMI. Our results demonstrate that cathelicidin modulates the development of obesity.

Probiotic Strain Bifidobacterium animalis subsp. lactis CECT 8145 Reduces Fat Content and Modulates Lipid Metabolism and Antioxidant Response in Caenorhabditis elegans

Recently, microbial changes in the human gut have been proposed as a possible cause of obesity. Therefore, modulation of microbiota through probiotic supplements is of great interest to support obesity therapeutics. The present study examines the functional effect and metabolic targets of a bacterial strain, Bifidobacterium animalis subsp. lactis CECT 8145, selected from a screening in Caenorhabditis elegans. This strain significantly reduced total lipids (40.5% ± 2.4) and triglycerides (27.6% ± 0.5), exerting antioxidant effects in the nematode (30% ± 2.8 increase in survival vs control); activities were also preserved in a final food matrix (milk). Furthermore, transcriptomic and metabolomic analyses in nematodes fed with strain CECT 8145 revealed modulation of the energy and lipid metabolism, as well as the tryptophan metabolism (satiety), as the main metabolic targets of the probiotic. In conclusion, our study describes for the first time a new B. animalis subsp. lactis strain, CECT 8145, as a promising probiotic for obesity disorders. Furthermore, the data support future studies in obesity murine models.

Pathophysiological role of host microbiota in the development of obesity

Overweight and obesity increase the risk for a number of diseases, namely, cardiovascular diseases, type 2 diabetes, dyslipidemia, premature death, non-alcoholic fatty liver disease as well as different types of cancer. Approximately 1.7 billion people in the world suffer from being overweight, most notably in developed countries. Current research efforts have focused on host and environmental factors that may affect energy balance. It was hypothesized that a microbiota profile specific to an obese host with increased energy-yielding behavior may exist. Consequently, the gut microbiota is becoming of significant research interest in relation to obesity in an attempt to better understand the aetiology of obesity and to develop new methods of its prevention and treatment. Alteration of microbiota composition may stimulate development of obesity and other metabolic diseases via several mechanisms: increasing gut permeability with subsequent metabolic inflammation; increasing energy harvest from the diet; impairing short-chain fatty acids synthesis; and altering bile acids metabolism and FXR/TGR5 signaling. Prebiotics and probiotics have physiologic functions that contribute to the health of gut microbiota, maintenance of a healthy body weight and control of factors associated with obesity through their effects on mechanisms that control food intake, body weight, gut microbiota and inflammatory processes.

Prevention of NAFLD development in rats with obesity via the improvement of pro/antioxidant state by cerium dioxide nanoparticles

BACKGROUND

One of the pathogenic mechanisms of the nonalcoholic fatty liver disease (NAFLD) is the accumulation of reactive oxygen species, which in turn aggravates the disease progress. We have investigated novel cerium dioxide nanoparticles (nCeO2) due to their promising antioxidant auto-regenerative ability and low toxicity.

METHODS

30 white male Wistar rats were divided into 3 groups: control, monosodium glutamate (MSG)-induced obesity and MSG treated with nCeO2 (MSG+nCeO2) groups. Newborn rats of control group were injected with saline (control). MSG- and MSG+nCeO2 groups were injected with MSG (4 mg/g concentration, 8 μl/g volume) between the 2nd and the 10th days of life subcutaneously [13]. At the age of 1 month, rats of group II were administered water 2.9 ml/kg orally, MSG+nCeO2 group received 1 mM solution of nCeO2 1 mg/kg orally. 4-months rats were sacrificed and the liver was harvested for histological and biochemical analysis. To assess the morphological changes in the liver we used NAS (NAFLD activity score). The content of lipid peroxidation products and enzymatic activity of superoxide dismutase (SOD) and catalase in the liver were studied by standard biochemical methods [Refs].

RESULTS

In 4-month rats we found significantly lower total score (1.3±0.26 vs 3.6±0.34, p<0.001), degree of steatosis (1.1±0.18 vs 2.1±0.18, p<0.001), manifestation of lobular inflammation (0.2±0.13 vs 1.2±0.2, p<0.001) and ballooning degeneration (0.0±0.0 vs 0.3±0.15, p=0.034) due to NAS in the nCeO2 group compared to the MSG-group. nCeO2 significantly decreased lipid peroxidation in the liver tissue, namely it reduced the conjugated dienes content by 27% (p<0.05), TBA-products - by 43% (p<0.05) and Schiff bases - by 21% (p<0.05).

CONCLUSIONS

Due to its antioxidant properties nCeO2 significantly reduces the incidence of NASH and improves the main NAFLD histological features.

Comparative experimental investigation on the efficacy of mono- and multiprobiotic strains in non-alcoholic fatty liver disease prevention

BACKGROUND

To investigate the efficacy of different probiotic strains, their combinations and forms (alive or lyophilized) in nonalcoholic fatty liver disease (NAFLD) prevention.

METHODS

In this study, 70 rats have been used divided into 7 groups of 10 animals in each: I - intact rats, II-VII - rats with monosodium glutamate (MSG)-induced NAFLD. Rats with NAFLD were untreated (group II, MSG-obesity group) and treated with probiotics (groups III-VII). In order to develop NAFLD, newborn rats of groups II-VII were injected with a solution of monosodium glutamate (MSG) (4 mg/g) subcutaneously (s.c.) at 2nd,4th, 6th, 8th,10th postnatal day. The groups III-V received lyophilized monoprobiotics B. animalis VKL, B. animalis VKB, L.casei IMVB-7280, respectively. The group VI received 2.5 ml/kg of an aqueous solution of a mixture of the three probiotic strains (2:1:1 Lactobacillus casei IMVB-7280, Bifidobacterium animalis VKL, Bifidobacterium animalis VKB) at a dose of 50 mg/kg (5 × 10(9) CFU/kg) (g) (intragastrically). The group VII was treated with multiprobiotic "Symbiter" containing biomass of 14 alive probiotic strains (Lactobacillus + Lactococcus (6 × 10(10) CFU/g), Bifidobacterium (1 × 10(10)/g), Propionibacterium (3 × 10(10)/g), Acetobacter (1 × 10(6)/g)) at a dose of 140 mg/kg (1.4 × 10(10) CFU/kg). The treatment with probiotics was started at the age of 1 month. There were 3 courses of treatment, each included 2-week administration and 2-week break. All parameters were measured in 4-month aged rats.

RESULTS

Introduction of MSG during the neonatal period leads to the NAFLD development in the 4-months old rats. For steatosis degree there was no significant difference between MSG-obesity group and lyophilized monocomponent probiotics groups (III-V). The highest manifestation of steatosis was observed for B. animalis VKL group (2.0 ± 0.25) as compared to B. animalis VKB (1.70 ± 0.21) and L. casei IMVB-7280 (1.80 ± 0.20). The steatosis score changes between all monoprobiotics groups (III-V) were insignificant. Administration from birth of both alive (VII) and lyophilized (VI) probiotic mixture lead to a significant decrease by 69.5 % (p < 0.001) and 43.5 % (p < 0.025) of steatosis score respectively as compared to the MSG-obesity group (2.3 ± 0.21 %). For both alive and lyophilized probiotic mixtures, reduction of lobular inflammation was observed. These histological data were confirmed by the significant decrease of total lipids and triglycerides content in the liver approximately by 22-25 % in groups treated with probiotic mixtures (VI, VII) compared to the MSG-obesity group.

CONCLUSION

We established failure of NAFLD prevention with lyophilized monoprobiotic strains and the efficacy of probiotic mixture with the preference of alive probiotic strains.

Probiotics in prevention and treatment of obesity: a critical view

The worldwide prevalence of obesity more than doubled between 1980 and 2014. The obesity pandemic is tightly linked to an increase in energy availability, sedentariness and greater control of ambient temperature that have paralleled the socioeconomic development of the past decades. The most frequent cause which leads to the obesity development is a dysbalance between energy intake and energy expenditure. The gut microbiota as an environmental factor which influence whole-body metabolism by affecting energy balance but also inflammation and gut barrier function, integrate peripheral and central food intake regulatory signals and thereby increase body weight. Probiotics have physiologic functions that contribute to the health of gut microbiota, can affect food intake and appetite, body weight and composition and metabolic functions through gastrointestinal pathways and modulation of the gut bacterial community.

Cardiovascular benefits of probiotics: a review of experimental and clinical studies

The microbiota inhabiting the human gastro-intestinal tract is reported to have a significant impact on the health of an individual.

Probiotics and immunity: provisional role for personalized diets and disease prevention

There is great interest in the interaction between diet and immune system and concomitantly in the potential of probiotic bacteria, especially given recent advances in understanding of gut microbiota effects on health in the context of microbiome research. Following our recent study on bacterial wall elasticity as a predictive measure of phagocytic cellular reactions and related outcomes, a question was raised regarding the scope of the application of these findings in various medical conditions in the context of predictive, preventive, and personalized medicine (PPPM). This summarizing review of the data describes the contributions, both observed and potential, of probiotics to the gut-brain axis and various medical conditions, including immune and atopic states, metabolic and inflammatory diseases-including liver disease and diabetes mellitus-cancer, and more. It also suggests novel insights for a number of beneficial applications of probiotics and advances in development of novel probiotic-based treatments and personalized diets, as well as application of sophisticated imaging techniques and nanobiotechnologies that can be adopted in the near future by innovative medical experts, warranting further research and practical translation.

TLR4 at the Crossroads of Nutrients, Gut Microbiota, and Metabolic Inflammation

Obesity is accompanied by the activation of low-grade inflammatory activity in metabolically relevant tissues. Studies have shown that obesity-associated insulin resistance results from the inflammatory targeting and inhibition of key proteins of the insulin-signaling pathway. At least three apparently distinct mechanisms-endoplasmic reticulum stress, toll-like receptor (TLR) 4 activation, and changes in gut microbiota-have been identified as triggers of obesity-associated metabolic inflammation; thus, they are expected to represent potential targets for the treatment of obesity and its comorbidities. Here, we review the data that place TLR4 in the center of the events that connect the consumption of dietary fats with metabolic inflammation and insulin resistance. Changes in the gut microbiota can lead to reduced integrity of the intestinal barrier, leading to increased leakage of lipopolysaccharides and fatty acids, which can act upon TLR4 to activate systemic inflammation. Fatty acids can also trigger endoplasmic reticulum stress, which can be further stimulated by cross talk with active TLR4. Thus, the current data support a connection among the three main triggers of metabolic inflammation, and TLR4 emerges as a link among all of these mechanisms.

Diagnostic accuracy of acyl-ghrelin and it association with non-alcoholic fatty liver disease in type 2 diabetic patients

BACKGROUND

Ghrelin is a hormone produced mainly by the cells lining the fundus of the stomach, which is involved in regulation of lipid and glucose metabolism. Two major forms of ghrelin can be found in circulation: an acylated form, and non-acylated form. Serum acyl-ghrelin (AG) concentration is significantly increased in patients with visceral obesity and insulin resistance. This study was conducted to evaluate changes in serum AG levels, its diagnostic accuracy and association with NAFLD in patients with type two diabetes (T2D).

METHODS

In this cross-sectional study, 91 T2D patients, age of 40-80 years, were included. All patients were divided into 3 groups. The control group included 28 T2D patients without NAFLD. The main group included 63 T2D patients with NAFLD, which was divided in 2 subgroups depending on transaminase levels: normal (n = 37) and elevated (n = 26) transaminases group. To assess the diagnostic accuracy of AG for NAFLD we used ROC-analysis.

RESULTS

We observed 1.5 (p = 0.016) and 2.5 (p < 0.001) fold increasing of serum AG levels in patients with NAFLD and normal or elevated transaminases compared to control groups. In multivariate logistic regression analysis high AG level was an independent, from transaminases activity, triglycerides (OR 1.791; 95 % CI 1.162-2.759; p = 0.008) and degree of IR (OR 1.599; 95 % CI 1.019-2.508; p = 0.044) predictor that associated with NAFLD. When serum AG used as non-invasive marker for NAFLD detection AUROC was 0.835 (95 % CI 0.752-0.918, p < 0.001). The cut-off value was >0.52 ng/ml, with sensitivity, specificity, PPV and NPV - 60.3 %, 92.8 %, 95.0 %, 50.9 % respectively. For distinguishing patients with NAFLD and elevated transaminases from patients with NAFLD and normal values AG was less effective.

CONCLUSIONS

Our study has demonstrated that elevated AG level were associated with NAFLD. Patients with elevated transaminases had significantly higher AG levels. An increase of AG over 0.52 ng/ml can be used as a diagnostic marker for NAFLD detection in patients with T2D.