Effects of Natural Products on Fructose-Induced Nonalcoholic Fatty Liver Disease (NAFLD)

Curcumin and other dietary polyphenols: potential mechanisms of metabolic actions and therapy for diabetes and obesity

Recent controversy regarding the therapeutic potential of curcumin indicates the challenges to research in this field. Here, we highlight the investigations of curcumin and other plant-derived polyphenols that demonstrate their application to metabolic diseases, in particular, obesity and diabetes. Thus, a number of preclinical and clinical investigations have shown the beneficial effect of curcumin (and other dietary polyphenols) in attenuating body weight gain, improving insulin sensitivity, and preventing diabetes development in rodent models and prediabetic subjects. Other intervention studies with dietary polyphenols have also found improvements in insulin resistance. Recent studies suggest that the metabolic effects of curcumin/polyphenols are linked to changes in the gut microbiota. Thus, research into curcumin continues to provide novel insights into metabolic regulation that may ultimately translate into effective therapy.

Actein ameliorates hepatic steatosis and fibrosis in high fat diet-induced NAFLD by regulation of insulin and leptin resistant

Insulin and leptin resistance are highly involved in metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Presently, no approved treatment is available. Actein is isolated from the rthizomes of Cimicifuga foetida, a triterpene glycoside, exhibiting important biological properties, such as anti-inflammatory, anti-cancer, and anti-oxidant activity. However, its effects on metabolic syndrome are poorly understood. The aims of the study were mainly to investigate the molecular mechanisms regulating insulin and leptin resistance, and lipogenic action of actein in high fat diet-fed mice. Our data indicated that actein-treated mice displayed lower body weight, epididymal and subcutaneous fat mass, as well as serum lipid levels. Also, improved insulin and leptin resistance were observed in actein-treated groups. Liver inflammation and fibrosis triggered by high fat diet were decreased for actein administration. Moreover, hepatic lipid accumulation was also reduced by actein along with reductions of hepatic de novo lipogenesis-linked signals in actein-treated rodents with high fat diet. High fat diet-induced activation of insulin receptor substrate 1/Forkhead box protein O1 (IRS1/FOXO1), Janus kinase 2 gene/signal transducer and activator of transcription (JAK2/STAT3) and Protein Kinase B/Glycogen synthase kinase 3 beta (AKT/GSK3β) pathways in liver was inhibited by actein, a potential mechanism by which hyperinsulinemia, hyperleptindemia and dyslipidemia were attenuated. Thus, the findings above might be of nutritional and therapeutic importance for the treatment of NAFLD.

Hepatoprotective effect of calculus bovis sativus on nonalcoholic fatty liver disease in mice by inhibiting oxidative stress and apoptosis of hepatocytes

Calculus bovis (CB, niu-huang) is a high-class therapeutic drug that is often used in traditional Chinese medicine. CB helps to eliminate heat and toxic components, and prevents the accumulation of phlegm and blood stasis in the liver. In Asian countries, CB Sativus (CBS), an ideal substitute for natural CB, is presently extensively used for long-term treatment of chronic liver diseases. The present study aimed to evaluate the effects and potential mechanism(s) of action of CBS on mice with fructose-induced nonalcoholic fatty liver disease (NAFLD). The NAFLD model was established in C57BL/6 mice by exclusively feeding fluids containing 30% fructose for 8 consecutive weeks. After these 8 weeks, mice were given CBS (50 mg/kg/day or 100 mg/kg/day) for 2 consecutive weeks. Treatment with CBS reversed the fructose-induced impaired glucose tolerance. Compared with the model group, in which mice received 8 weeks of high-fructose diet and 2 weeks of 0.5% sodium carboxymethyl cellulose, CBS treatment significantly decreased the levels of fasting serum glucose, fasting insulin, triglyceride, and total cholesterol, and increased levels of high-density lipoprotein-cholesterol. CBS treatment also significantly decreased the levels of triglyceride, total cholesterol, and free fatty acid in the liver. The activity of superoxide dismutase in the liver was increased after treatment with CBS, however, levels of malondialdehyde and reactive oxygen species decreased. Histopathological examination showed that liver steatosis and injury were significantly reduced in CBS-treated mice. The expression of fatty acid synthase, nuclear factor kappa-light-chain-enhancer of activated B cells, Cysteinyl aspartate-specific proteinase-3, and synonyms B-cell leukemia/lymphoma-2 gene-associated X protein were downregulated after treatment with CBS, whereas the expression of nuclear factor erythroid-2-related factor 2 was upregulated. In conclusion, CBS treatment exerted therapeutic effects in the liver of mice with NAFLD, which may be associated with amelioration of metabolic disorders, enhanced antioxidant effects, and alleviation of apoptosis.

Chronic High Dose Zinc Supplementation Induces Visceral Adipose Tissue Hypertrophy without Altering Body Weight in Mice

The trace element zinc plays an important role in human life. Zinc deficiency impairs growth, reproduction, metabolism and immunity in both human and animals. Thus, zinc supplementation is recommended in daily life. However, the effect of long-term chronic zinc supplementation on adipose homeostasis has not been well elucidated. In the current study, mice were supplemented with zinc sulfate in the drinking water for 20 weeks. The results suggested that chronic zinc supplementation impaired systemic glucose clearance after exogenous insulin or glucose challenges, as compared to the control mice. Further study revealed that chronic zinc supplementation made no difference to body weight, but increased visceral adipose tissue weight and adipocyte size. In addition, gene expression of leptin and IL6 in the visceral adipose tissue of zinc-supplemented mice were higher than those of control mice. Moreover, serum level of leptin of the zinc-supplemented mice was twice as high as that of the control mice. Besides, phosphorylation level of AKT T308 was attenuated in the perirenal adipose tissue of zinc-supplemented mice. In comparison, the expression of macrophage marker genes and lipogenic genes were not affected by chronic zinc supplementation, but the protein levels of FAS and SCD1 decreased or tended to decrease in the perirenal adipose tissue of zinc-supplemented mice, as compared to the control mice. Our findings suggest that chronic high dose zinc supplementation induces visceral adipose tissue hypertrophy and impairs AKT signaling in perirenal adipose tissue.

Aegle marmelos differentially affects hepatic markers of glycolysis, insulin signalling pathway, hypoxia, and inflammation in HepG2 cells grown in fructose versus glucose-rich environment

Fructose consumption is responsible for the onset of insulin resistance (IR), and metabolic syndrome. It possesses no functional utility in body and its detrimental effects on hepatic metabolic milieu are beyond those produced by glucose. The need of the hour is to identify fructose-induced IR as an unique pathological state to be managed differentially. The effect of aqueous leaf extract of Aegle marmelos (AM) on hepatic markers of insulin resistance using HepG2 cells cultured in either fructose or glucose-rich environment is investigated. Human hepatocellular carcinoma cells (HepG2) were grown under standard conditions in either-DMEM without glucose (NC), DMEM with high glucose 25 mM (Glu), DMEM-glucose+0.55 mM fructose (FC1), DMEM-glucose+1 mM fructose (FC2) or DMEM-glucose+1 mM fructose+0.1 µM insulin (FC3). The cells were treated with either AM, rutin, quercetin, metformin or pioglitazone and assessed for levels of hexokinase, phosphofructokinase (PFK), aldehyde dehydrogenase, phosphatidylinositol kinase (PI3K), signal transducer and activator of transcription-3 (STAT-3), mitochondrial target of rapamycin (mTOR), hypoxia-induced factor (HIF-1α), vascular endothelial growth factor (VEGF) and tumour necrosis factor (TNF-α). Summarily, when results from fructose- and glucose-rich environment were compared, then (1) IR was more pronounced in former; (2) AM performed better in former; (3) metformin and pioglitazone were equivocal in either; (4) rutin and quercetin showed deviant effects from AM; and lastly (5) effects of rutin were closer to AM than quercetin. We hypothesize that AM ameliorates fructose-induced IR through a mechanism which is distinct from standard drugs and not shared by individual phytoconstituents in toto.

Serum bile acid level and fatty acid composition in Chinese children with non-alcoholic fatty liver disease

OBJECTIVE

To determine serum bile acid (BA) and fatty acid (FA) profiles in Chinese children with non-alcoholic fatty liver disease (NAFLD).

METHODS

A total 76 children aged 4-17 years were categorized into three groups according to the presence and absence of as well as the severity of NAFLD, that is, non-NAFLD (control), mild and moderate to severe NAFLD groups, respectively, based on their liver ultrasonography findings. Serum BA and FA profiles were quantified separately by mass spectrometry and gas chromatography. General linear models were performed to assess the differences among the groups.

RESULTS

After adjusted for potential confounders, children with NAFLD had higher levels of chenodeoxycholic acid (CDCA), unconjugated primary BAs (CDCA + cholic acid) but lower levels of deoxycholic acid (DCA), taurodeoxycholic acid (TDCA), glycodeoxycholic acid (GDCA), total DCA (DCA + TDCA + GDCA), glycolithocholic acid (GLCA) and total lithocholic acid (GLCA + taurolithocholic acid) than children without NAFLD. As for FAs, children with mild and moderate to severe NAFLD had higher levels of n-7 monounsaturated FA.

CONCLUSIONS

Circulating BA and FA profiles may change in children with NAFLD. Further studies are needed to determine their associations and to understand the underlying mechanism of action.

Soft drinks consumption is associated with nonalcoholic fatty liver disease independent of metabolic syndrome in Chinese population

PURPOSE

Excessive consumption of soft drinks is associated with nonalcoholic fatty liver disease (NAFLD). However, the association between soft drinks consumption and NAFLD is unclear in non-Caucasian adults with relatively low soft drinks consumption. The aim of this study was to assess the association between soft drinks consumption and NAFLD in Chinese adults.

METHODS

A cross-sectional study was conducted with 26,790 adults living in Tianjin, China. NAFLD (with elevated alanine aminotransferase [ALT]) was diagnosed by the liver ultrasonography and serum ALT concentrations. Soft drinks consumption was assessed using a validated self-administered food frequency questionnaire, and it was summarized as three categories for analysis: almost never (reference), <1 cup/week, and ≥1 cups/week. Metabolic syndrome (MetS) was defined according to the criteria of the American Heart Association scientific statements of 2009. The association between soft drinks consumption and NAFLD was assessed by multiple logistic regression analysis.

RESULTS

The prevalence of NAFLD and NAFLD with elevated ALT was 27.1 and 6.5%, respectively. After adjustment for potential confounding variables (including MetS), the odds ratios (95% confidence intervals) for NAFLD or NAFLD with elevated ALT across soft drinks consumption were 1.00 (reference) for almost never, 1.14 (1.02-1.27) or 1.16 (0.98-1.37) for <1 cup/week, and 1.26 (1.14-1.40) or 1.32 (1.13-1.53) for ≥1 cups/week (both P for trend <0.001), respectively.

CONCLUSIONS

This is the first study to demonstrate that soft drinks consumption is associated with NAFLD independent of MetS in Chinese adults with relatively low soft drinks consumption. These results suggest that reducing soft drinks consumption might be beneficial to the prevention of NAFLD.

Morinda citrifolia Linn. (Noni) and Its Potential in Obesity-Related Metabolic Dysfunction

Cultural and economic shifts in the early 19th century led to the rapid development of companies that made good profits from technologically-produced commodities. In this way, some habits changed in society, such as the overconsumption of processed and micronutrient-poor foods and devices that gave rise to a sedentary lifestyle. These factors influenced host-microbiome interactions which, in turn, mediated the etiopathogenesis of “new-era” disorders and diseases, which are closely related, such as obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease, hypertension, and inflammatory bowel disease, which are characterized by chronic dysregulation of metabolic and immune processes. These pathological conditions require novel and effective therapeutic approaches. Morindacitrifolia (noni) is well known as a traditional healing plant due to its medicinal properties. Thus, many studies have been conducted to understand its bioactive compounds and their mechanisms of action. However, in obesity and obesity-related metabolic (dysfunction) syndrome, other studies are necessary to better elucidate noni’s mechanisms of action, mainly due to the complexity of the pathophysiology of obesity and its metabolic dysfunction. In this review, we summarize not only the clinical effects, but also important cell signaling pathways in in vivo and in vitro assays of potent bioactive compounds present in the noni plant which have been reported in studies of obesity and obesity-associated metabolic dysfunction.

The Protective Effects of p-Coumaric Acid on Acute Liver and Kidney Damages Induced by Cisplatin

In this study, we aimed to investigate the effects of p-Coumaric acid (PCA) on cisplatin (CIS)-induced hepatotoxicity and nephrotoxicity in Wistar adult rats for 24 h compared to untreated control groups. In this experiment, 40 Wistar adult rats were utilized and divided randomly into five groups. After 24 h of CIS administration, liver and kidneys were harvested and assessed by H&amp;E staining. Also, markers for oxidative stress and antioxidants were analyzed in theses tissues. Compared to the control group, accumulation of malondialdehyde was increased in groups treated CIS, whereas superoxide dismutase activities and glutathione levels were distinctly diminished in this group. The study's histopathological findings such as hydropic degeneration, vascular congestion, sinusoidal dilatation in hepatocytes and tubular necrosis in kidneys were in accordance with the results of markers for oxidative stress. PCA may prevent hepatotoxicity and nephrotoxicity by increased antioxidant enzymes and reduced oxidant parameters.

The Metalloproteinase ADAM28 Promotes Metabolic Dysfunction in Mice

Obesity and diabetes are major causes of morbidity and mortality globally. The current study builds upon our previous association studies highlighting that A Disintegrin And Metalloproteinase 28 (ADAM28) appears to be implicated in the pathogenesis of obesity and type 2 diabetes in humans. Our novel study characterised the expression of ADAM28 in mice with the metabolic syndrome and used molecular inhibition approaches to investigate the functional role of ADAM28 in the pathogenesis of high fat diet-induced obesity. We identified that ADAM28 mRNA and protein expression was markedly increased in the livers of mice with the metabolic syndrome. In addition, noradrenaline, the major neurotransmitter of the sympathetic nervous system, results in elevated Adam28 mRNA expression in human monocytes. Downregulation of ADAM28 with siRNA technology resulted in a lack of weight gain, promotion of insulin sensitivity/glucose tolerance and decreased liver tumour necrosis factor-α (TNF-α) levels in our diet-induced obesity mouse model as well as reduced blood urea nitrogen, alkaline phosphatase and aspartate aminotransferase. In addition, we show that ADAM28 knock-out mice also displayed reduced body weight, elevated high density lipoprotein cholesterol levels, and reductions in blood urea nitrogen, alkaline phosphatase, and aspartate aminotransferase. The results of this study provide important insights into the pathogenic role of the metalloproteinase ADAM28 in the metabolic syndrome and suggests that downregulation of ADAM28 may be a potential therapeutic strategy in the metabolic syndrome.

Fructose and NAFLD: The Multifaceted Aspects of Fructose Metabolism

Among various factors, such as an unhealthy diet or a sedentarity lifestyle, excessive fructose consumption is known to favor nonalcoholic fatty liver disease (NAFLD), as fructose is both a substrate and an inducer of hepatic de novo lipogenesis. The present review presents some well-established mechanisms and new clues to better understand the pathophysiology of fructose-induced NAFLD. Beyond its lipogenic effect, fructose intake is also at the onset of hepatic inflammation and cellular stress, such as oxidative and endoplasmic stress, that are key factors contributing to the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Beyond its hepatic effects, this carbohydrate may exert direct and indirect effects at the peripheral level. Excessive fructose consumption is associated, for example, with the release by the liver of several key mediators leading to alterations in the communication between the liver and the gut, muscles, and adipose tissue and to disease aggravation. These multifaceted aspects of fructose properties are in part specific to fructose, but are also shared in part with sucrose and glucose present in energy–dense beverages and foods. All these aspects must be taken into account in the development of new therapeutic strategies and thereby to better prevent NAFLD.