New targets for NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a growing cause of chronic liver disease worldwide. It is characterised by steatosis, liver inflammation, hepatocellular injury and progressive fibrosis. Several preclinical models (dietary and genetic animal models) of NAFLD have deepened our understanding of its aetiology and pathophysiology. Despite the progress made, there are currently no effective treatments for NAFLD. In this review, we will provide an update on the known molecular pathways involved in the pathophysiology of NAFLD and on ongoing studies of new therapeutic targets.

Implications of hydrogen sulfide in liver pathophysiology: Mechanistic insights and therapeutic potential

Background

Over the last several decades, hydrogen sulfide (H₂S) has been found to exert multiple physiological functions in mammal systems. The endogenous production of H₂S is primarily mediated by cystathione β-synthase (CBS), cystathione γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST). These enzymes are widely expressed in the liver tissues and regulate hepatic functions by acting on various molecular targets.

Aim of Review

In the present review, we will highlight the recent advancements in the cellular events triggered by H₂S under liver diseases. The therapeutic effects of H₂S donors on hepatic diseases will also be discussed.

Key Scientific Concepts of Review

As a critical regulator of liver functions, H₂S is critically involved in the etiology of various liver disorders, such as nonalcoholic steatohepatitis (NASH), hepatic fibrosis, hepatic ischemia/reperfusion (IR) injury, and liver cancer. Targeting H₂S-producing enzymes may be a promising strategy for managing hepatic disorders.

Small molecules for fat combustion: targeting obesity

Obesity is increasing in an alarming rate worldwide, which causes higher risks of some diseases, such as type 2 diabetes, cardiovascular diseases, and cancer. Current therapeutic approaches, either pancreatic lipase inhibitors or appetite suppressors, are generally of limited effectiveness. Brown adipose tissue (BAT) and beige cells dissipate fatty acids as heat to maintain body temperature, termed non-shivering thermogenesis; the activity and mass of BAT and beige cells are negatively correlated with overweight and obesity. The existence of BAT and beige cells in human adults provides an effective weight reduction therapy, a process likely to be amenable to pharmacological intervention. Herein, we combed through the physiology of thermogenesis and the role of BAT and beige cells in combating with obesity. We summarized the thermogenic regulators identified in the past decades, targeting G protein-coupled receptors, transient receptor potential channels, nuclear receptors and miscellaneous pathways. Advances in clinical trials were also presented. The main purpose of this review is to provide a comprehensive and up-to-date knowledge from the biological importance of thermogenesis in energy homeostasis to the representative thermogenic regulators for treating obesity. Thermogenic regulators might have a large potential for further investigations to be developed as lead compounds in fighting obesity.

Capsaicinoids improve consequences of physical activity

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Capsaicinoids (CAPs) are active compounds in Capsicum fruits.

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CAPs have anti-inflammatory and antioxidant properties.

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CAPs with regular exercise may enhance lipid metabolism.

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CAPs down-regulate muscle SREBP-1c, LXRs, ACLY, FAS in exercised rats.

The purpose of this study was to investigate the effects of capsaicinoids (CAPs) on lipid metabolism, inflammation, antioxidant status and the changes in gene products involved in these metabolic functions in exercised rats. A total of 28 male Wistar albino rats were randomly divided into four groups (n = 7) (i) No exercise and no CAPs, (ii) No exercise + CAPs (iii) Regular exercise, (iv) Regular exercise + CAPs. Rats were administered as 0.2 mg capsaicinoids from 10 mg/kg BW/day Capsimax^® daily for 8 weeks. A significant decrease in lactate and malondialdehyde (MDA) levels and increase in activities of antioxidant enzymes were observed in the combination of regular exercise and CAPs group (P < 0.0001). Regular exercise + CAPs treated rats had greater nuclear factor-E2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1) levels in muscle than regular exercise and no exercise rats (P < 0.001). Nevertheless, regular exercise + CAPs treated had lower nuclear factor kappa B (NF-κB) and IL-10 levels in muscle than regular exercise and control rats (P < 0.001). Muscle sterol regulatory element-binding protein 1c (SREBP-1c), liver X receptors (LXR), ATP citrate lyase (ACLY) and fatty acid synthase (FAS) levels in the regular exercise + CAPs group were lower than all groups (P < 0.05). However, muscle PPAR-γ level was higher in the regular exercise and CAPs alone than the no exercise rats. These results suggest CAPs with regular exercise may enhance lipid metabolism by regulation of gene products involved in lipid and antioxidant metabolism including SREBP-1c, PPAR-γ, and Nrf2 pathways in rats.

Molecular dynamics simulation and binding free energy studies of novel leads belonging to the benzofuran class inhibitors of Mycobacterium tuberculosis Polyketide Synthase 13

In this work, the binding mechanism of new Polyketide Synthase 13 (Pks13) inhibitors has been studied through molecular dynamics simulation and free energy calculations. The drug Tam1 and its analogs, belonging to the benzofuran class, were submitted to 100 ns simulations, and according to the results obtained for root mean square deviation, all the simulations converged from approximately 30 ns. For the analysis of backbone flotation, the root mean square fluctuations were plotted for the Cα atoms; analysis revealed that the greatest fluctuation occurred in the residues that are part of the protein lid domain. The binding free energy value (ΔG_bind) obtained for the Tam16 lead molecule was of -51.43 kcal/mol. When comparing this result with the ΔG_bind values for the remaining analogs, the drug Tam16 was found to be the highest ranked: this result is in agreement with the experimental results obtained by Aggarwal and collaborators, where it was verified that the IC₅₀ for Tam16 is the smallest necessary to inhibit the Pks13 (IC₅₀ = 0.19 μM). The energy decomposition analysis suggested that the residues which most interact with inhibitors are: Ser1636, Tyr1637, Asn1640, Ala1667, Phe1670, and Tyr1674, from which the greatest energy contribution to Phe1670 was particularly notable. For the lead molecule Tam16, a hydrogen bond with the hydroxyl of the phenol not observed in the other analogs induced a more stable molecular structure. Aggarwal and colleagues reported this hydrogen bonding as being responsible for the stability of the molecule, optimizing its physic-chemical, toxicological, and pharmacokinetic properties.

Cissus quadrangularis extract (CQR-300) inhibits lipid accumulation by downregulating adipogenesis and lipogenesis in 3T3-L1 cells

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CQR-300 inhibited lipid accumulation in 3T3-L1 adipocytes.

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CQR-300 inhibited the differentiation of adipocytes by regulating adipogenesis.

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CQR-300 reduced fatty acids and triglyceride accumulation via downregulating lipogenesis.

The objective of this study was to evaluate the anti-obesity activity and the action mechanism of Cissus quadrangularis extracts (CQR-300) in 3T3-L1 adipocytes. Cissus quadrangularis was extracted with hot water, resulting in CQR-300. The anti-obesity activity of CQR-300 in 3T3-L1 adipocytes was examined by Oil-red O staining. Possible mechanisms of CQR-300 in 3T3-L1 adipocytes were determined by real-time PCR and western blot. Treatment with CQR-300 inhibited lipid accumulation without showing cytotoxicity to 3T3-L1 adipocytes. Furthermore, CQR-300 decreased adipogenesis/lipogenesis-related mRNA expression levels of fatty acid binding protein (aP2), fatty acid synthase (FAS), lipoprotein lipase (LPL), stearoyl-CoA desaturase-1 (SCD-1), and acetyl-CoA carboxylase (ACC). CQR-300 also down-regulated expression levels of adipogenesis/lipogenesis-associated proteins, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), sterol regulatory element binding protein-1c (SREBP-1c), and FAS. It’s also up-regulated the expression level of phosphorylated-AMPK (p-AMPK). Collectively, these results suggested that CQR-300 might have an anti-obesity effect by its ability to decrease expression levels of adipogenesis/lipogenesis-related genes and proteins.

A trans10-18:1 enriched fraction from beef fed a barley grain-based diet induces lipogenic gene expression and reduces viability of HepG2 cells

Beef fat is a natural source of trans (t) fatty acids, and is typically enriched with either t10-18:1 or t11-18:1. Little is known about the bioactivity of individual t-18:1 isomers, and the present study compared the effects of t9-18:1, cis (c)9-18:1 and trans (t)-18:1 fractions isolated from beef fat enriched with either t10-18:1 (HT10) or t11-18:1 (HT11). All 18:1 isomers resulted in reduced human liver (HepG2) cell viability relative to control. Both c9-18:1 and HT11were the least toxic, t9-18:1had dose response increased toxicity, and HT10 had the greatest toxicity (P<0.05). Incorporation of t18:1 isomers was 1.8-2.5 fold greater in triacylglycerol (TG) than phospholipids (PL), whereas Δ9 desaturation products were selectively incorporated into PL. Culturing HepG2 cells with t9-18:1 and HT10 increased (P<0.05) the Δ9 desaturation index (c9-16:1/16:0) compared to other fatty acid treatments. HT10 and t9-18:1 also increased expression of lipogenic genes (FAS, SCD1, HMGCR and SREBP2) compared to control (P<0.05), whereas c9-18:1 and HT11 did not affect the expression of these genes. Our results suggest effects of HT11 and c9-18:1 were similar to BSA control, whereas HT10 and t-9 18:1 (i.e. the predominant trans fatty acid isomer found in partially hydrogenated vegetable oils) were more cytotoxic and led to greater expression of lipogenic genes.

Sexually dimorphic brain fatty acid composition in low and high fat diet-fed mice

OBJECTIVE

In this study, we analyzed the fatty acid profile of brains and plasma from male and female mice fed chow or a western-style high fat diet (WD) for 16 weeks to determine if males and females process fatty acids differently. Based on the differences in fatty acids observed in vivo, we performed in vitro experiments on N43 hypothalamic neuronal cells to begin to elucidate how the fatty acid milieu may impact brain inflammation.

METHODS

Using a comprehensive mass spectrometry fatty acid analysis, which includes a profile for 52 different fatty acid isomers, we assayed the plasma and brain fatty acid composition of age-matched male and female mice maintained on chow or a WD. Additionally, using the same techniques, we determined the fatty acid composition of N43 hypothalamic cells following exposure to palmitic and linoleic acid, alone or in combination.

RESULTS

Our data demonstrate there is a sexual dimorphism in brain fatty acid content both following the consumption of the chow diet, as well as the WD, with males having an increased percentage of saturated fatty acids and reductions in ω6-polyunsaturated fatty acids when compared to females. Interestingly, we did not observe a sexual dimorphism in fatty acid content in the plasma of the same mice. Furthermore, exposure of N43 cells to the ω6-PUFA linoleic acid, which is higher in female brains when compared to males, reduces palmitic acid-induced inflammation.

CONCLUSIONS

Our data suggest male and female brains, and not plasma, differ in their fatty acid profile. This is the first time, to our knowledge, lipidomic analyses has been used to directly test the hypothesis there is a sexual dimorphism in brain and plasma fatty acid composition following consumption of the chow diet, as well as following exposure to the WD.

MicroRNAs and oncogenic transcriptional regulatory networks controlling metabolic reprogramming in cancers

Altered cellular metabolism is a fundamental adaptation of cancer during rapid proliferation as a result of growth factor overstimulation. We review different pathways involving metabolic alterations in cancers including aerobic glycolysis, pentose phosphate pathway, de novo fatty acid synthesis, and serine and glycine metabolism. Although oncoproteins, c-MYC, HIF1α and p53 are the major drivers of this metabolic reprogramming, post-transcriptional regulation by microRNAs (miR) also plays an important role in finely adjusting the requirement of the key metabolic enzymes underlying this metabolic reprogramming. We also combine the literature data on the miRNAs that potentially regulate 40 metabolic enzymes responsible for metabolic reprogramming in cancers, with additional miRs from computational prediction. Our analyses show that: (1) a metabolic enzyme is frequently regulated by multiple miRs, (2) confidence scores from prediction algorithms might be useful to help narrow down functional miR-mRNA interaction, which might be worth further experimental validation. By combining known and predicted interactions of oncogenic transcription factors (TFs) (c-MYC, HIF1α and p53), sterol regulatory element binding protein 1 (SREBP1), 40 metabolic enzymes, and regulatory miRs we have established one of the first reference maps for miRs and oncogenic TFs that regulate metabolic reprogramming in cancers. The combined network shows that glycolytic enzymes are linked to miRs via p53, c-MYC, HIF1α, whereas the genes in serine, glycine and one carbon metabolism are regulated via the c-MYC, as well as other regulatory organization that cannot be observed by investigating individual miRs, TFs, and target genes.

Fish oil prevents excessive accumulation of subcutaneous fat caused by an adverse effect of pioglitazone treatment and positively changes adipocytes in KK mice

Pioglitazone, a thiazolidinedione (TZD), is widely used as an insulin sensitizer in the treatment of type 2 diabetes. However, body weight gain is frequently observed in TZD-treated patients. Fish oil improves lipid metabolism dysfunction and obesity. In this study, we demonstrated suppression of body weight gain in response to pioglitazone administration by combination therapy of pioglitazone and fish oil in type 2 diabetic KK mice. Male KK mice were fed experimental diets for 8 weeks. In safflower oil (SO), safflower oil/low-dose pioglitazone (S/PL), and safflower oil/high-dose pioglitazone (S/PH) diets, 20% of calories were provided by safflower oil containing 0%, 0.006%, or 0.012% (wt/wt) pioglitazone, respectively. In fish oil (FO), fish oil/low-dose pioglitazone (F/PL), and fish oil/high-dose pioglitazone (F/PH) diets, 20% of calories were provided by a mixture of fish oil and safflower oil. Increased body weight and subcutaneous fat mass were observed in the S/PL and S/PH groups; however, diets containing fish oil were found to ameliorate these changes. Hepatic mRNA levels of lipogenic enzymes were significantly decreased in fish oil-fed groups. These findings demonstrate that the combination of pioglitazone and fish oil decreases subcutaneous fat accumulation, ameliorating pioglitazone-induced body weight gain, through fish oil-mediated inhibition of hepatic de novo lipogenesis.

Roles and regulation of the mucus barrier in the gut

The gastrointestinal tract is coated by a thick layer of mucus that forms the front line of innate host defense. Mucus consists of high molecular weight glycoproteins called mucins that are synthesized and secreted by goblet cells and functions primarily to lubricate the epithelium and protect it from damage by noxious substances. Recent studies have also suggested the involvement of goblet cells and mucins in complex immune functions such as antigen presentation and tolerance. Under normal physiological conditions, goblet cells continually produce mucins to replenish and maintain the mucus barrier; however, goblet cell function can be disrupted by various factors that can affect the integrity of the mucus barrier. Some of these factors such as microbes, microbial toxins and cytokines can stimulate or inhibit mucin production and secretion, alter the chemical composition of mucins or degrade the mucus layer. This can lead to a compromised mucus barrier and subsequently to various pathological conditions like chronic inflammatory diseases. Insight into how these factors modulate the mucus barrier in the gut is necessary in order to develop strategies to combat these disorders.

Improved adipose tissue metabolism after 5-year growth hormone replacement therapy in growth hormone deficient adults: The role of zinc-α2-glycoprotein

Growth hormone (GH) supplementation therapy to adults with GH deficiency has beneficial effects on adipose tissue lipid metabolism, improving thus adipocyte functional morphology and insulin sensitivity. However, molecular nature of these effects remains unclear. We therefore tested the hypothesis that lipid-mobilizing adipokine zinc-α2-glycoprotein is causally linked to GH effects on adipose tissue lipid metabolism. Seventeen patients with severe GH deficiency examined before and after the 5-year GH replacement therapy were compared with age-, gender- and BMI-matched healthy controls. Euglycemic hyperinsulinemic clamp was used to assess whole-body and adipose tissue-specific insulin sensitivity. Glucose tolerance was determined by oGTT, visceral and subcutaneous abdominal adiposity by MRI, adipocyte size morphometrically after collagenase digestion, lipid accumulation and release was studied in differentiated human primary adipocytes in association with GH treatment and zinc-α2-glycoprotein gene silencing. Five-year GH replacement therapy improved glucose tolerance, adipose tissue insulin sensitivity and reduced adipocyte size without affecting adiposity and whole-body insulin sensitivity. Adipose tissue zinc-α2-glycoprotein expression was positively associated with whole-body and adipose tissue insulin sensitivity and negatively with adipocyte size. GH treatment to adipocytes in vitro increased zinc-α2-glycoprotein expression (>50%) and was paralleled by enhanced lipolysis and decreased triglyceride accumulation (>35%). Moreover, GH treatment improved antilipolytic action of insulin in cultured adipocytes. Most importantly, silencing zinc-α2-glycoprotein eliminated all of the GH effects on adipocyte lipid metabolism. Effects of 5-year GH supplementation therapy on adipose tissue lipid metabolism and insulin sensitivity are associated with zinc-α2-glycoprotein. Presence of this adipokine is required for the GH action on adipocyte lipid metabolism in vitro.

Metabolic effects of intestinal absorption and enterohepatic cycling of bile acids

The classical functions of bile acids include acting as detergents to facilitate the digestion and absorption of nutrients in the gut. In addition, bile acids also act as signaling molecules to regulate glucose homeostasis, lipid metabolism and energy expenditure. The signaling potential of bile acids in compartments such as the systemic circulation is regulated in part by an efficient enterohepatic circulation that functions to conserve and channel the pool of bile acids within the intestinal and hepatobiliary compartments. Changes in hepatobiliary and intestinal bile acid transport can alter the composition, size, and distribution of the bile acid pool. These alterations in turn can have significant effects on bile acid signaling and their downstream metabolic targets. This review discusses recent advances in our understanding of the inter-relationship between the enterohepatic cycling of bile acids and the metabolic consequences of signaling via bile acid-activated receptors, such as farnesoid X nuclear receptor (FXR) and the G-protein-coupled bile acid receptor (TGR5).

Study of the effects of cyclooxygenase-2 inhibitor on the promotion of hepatic tumorigenesis in rats fed a high fat diet

BACKGROUND/OBJECTIVE

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. The highest prevalence of hepatitis is an important risk factor contributing to development of HCCs. However, an increasing number of cases are associated metabolic disease and steatohepatitis. Inflammation associated with many liver disease, seems to be a necessary pre-requisite for successful tumor initiation. Mechanisms that link high fat diet and inflammation initial stage of HCC are not completely understood. The present work was designed to investigate the effect of fat, through modulation of the insulin-like growth factors I and II (IGF-I and IGF-II), on the promotion of hepatocellular carcinoma, and the role of cyclooxygenase 2 (COX-2).

METHODS

two main groups of rats were used: control and HCC groups. The HCC group was further sub-divide in to two subgroups, HCC fed with standard diet and HCC fed with high fat diet. The effects of celecoxib were also investigated in HCC fed with high fat diet.

RESULTS

We found that high fat diet was associated with significant increases in COX2 and interleukin 6 (IL6) with significant promotion of HCC progression. The significant increase in IGF could contribute partially to the observed effects of high fat diet. In addition, celecoxib was found to significantly reduce HCC progression.

CONCLUSIONS

We conclude that COX2 could play central role in high prevalence of HCC observed with high fat diet. Several triggering factors such as IGF and IL6, together with the direct modulation of fat metabolism could open several novel preventive strategies of celecoxib treatment, and could be useful biomarkers for assessment of its pharmacological effects.

Maternal high-fat diet consumption impairs exercise performance in offspring

The aim of the present study was to scrutinise the influence of maternal high-fat diet (mHFD) consumption during gestation and lactation on exercise performance and energy metabolism in male mouse offspring. Female C3H/HeJ mice were fed either a semi-synthetic high-fat diet (HFD; 40 % energy from fat) or a low-fat diet (LFD; 10 % energy from fat) throughout gestation and lactation. After weaning, male offspring of both groups received the LFD. At the age of 7·5 weeks half of the maternal LFD (n 20) and the mHFD (n 21) groups were given access to a running wheel for 28 d as a voluntary exercise training opportunity. We show that mHFD consumption led to a significantly reduced exercise performance (P < 0·05) and training efficiency (P < 0·05) in male offspring. There were no effects of maternal diet on offspring body weight. Lipid and glucose metabolism was disturbed in mHFD offspring, with altered regulation of cluster of differentiation 36 (CD36) (P < 0·001), fatty acid synthase (P < 0·05) and GLUT1 (P < 0·05) gene expression in skeletal muscle. In conclusion, maternal consumption of a HFD is linked to decreased exercise performance and training efficiency in the offspring. We speculate that this may be due to insufficient muscle energy supply during prolonged exercise training. Further, this compromised exercise performance might increase the risk of obesity development in adult life.

Acetylcholinesterase (AChE) inhibition aggravates fasting-induced triglyceride accumulation in the mouse liver

Although fasting induces hepatic triglyceride (TG) accumulation in both rodents and humans, little is known about the underlying mechanism. Because parasympathetic nervous system activity tends to attenuate the secretion of very-low-density-lipoprotein-triglyceride (VLDL-TG) and increase TG stores in the liver, and serum cholinesterase activity is elevated in fatty liver disease, the inhibition of the parasympathetic neurotransmitter acetylcholinesterase (AChE) may have some influence on hepatic lipid metabolism. To assess the influence of AChE inhibition on lipid metabolism, the effect of physostigmine, an AChE inhibitor, on fasting-induced increase in liver TG was investigated in mice. In comparison with ad libitum-fed mice, 30 h fasting increased liver TG accumulation accompanied by a downregulation of sterol regulatory element-binding protein 1 (SREBP-1) and liver-fatty acid binding-protein (L-FABP). Physostigmine promoted the 30 h fasting-induced increase in liver TG levels in a dose-dependent manner, accompanied by a significant fall in plasma insulin levels, without a fall in plasma TG. Furthermore, physostigmine significantly attenuated the fasting-induced decrease of both mRNA and protein levels of SREBP-1 and L-FABP, and increased IRS-2 protein levels in the liver. The muscarinic receptor antagonist atropine blocked these effects of physostigmine on liver TG, serum insulin, and hepatic protein levels of SREBP-1 and L-FABP. These results demonstrate that AChE inhibition facilitated fasting-induced TG accumulation with up regulation of the hepatic L-FABP and SREBP-1 in mice, at least in part via the activation of muscarinic acetylcholine receptors. Our studies highlight the crucial role of parasympathetic regulation in fasting-induced TG accumulation, and may be an important source of information on the mechanism of hepatic disorders of lipid metabolism.

Nutraceuticals as potential therapeutic agents for colon cancer: a review

Colon cancer is a world-wide health problem and the second-most dangerous type of cancer, affecting both men and women. The modern diet and lifestyles, with high meat consumption and excessive alcohol use, along with limited physical activity has led to an increasing mortality rate for colon cancer worldwide. As a result, there is a need to develop novel and environmentally benign drug therapies for colon cancer. Currently, nutraceuticals play an increasingly important role in the treatment of various chronic diseases such as colon cancer, diabetes and Alzheimer׳s disease. Nutraceuticals are derived from various natural sources such as medicinal plants, marine organisms, vegetables and fruits. Nutraceuticals have shown the potential to reduce the risk of colon cancer and slow its progression. These dietary substances target different molecular aspects of colon cancer development. Accordingly, this review briefly discusses the medicinal importance of nutraceuticals and their ability to reduce the risk of colorectal carcinogenesis.

Tissue-selective estrogen complexes with bazedoxifene prevent metabolic dysfunction in female mice

Pairing the selective estrogen receptor modulator bazedoxifene (BZA) with estrogen as a tissue-selective estrogen complex (TSEC) is a novel menopausal therapy. We investigated estrogen, BZA and TSEC effects in preventing diabetisity in ovariectomized mice during high-fat feeding. Estrogen, BZA or TSEC prevented fat accumulation in adipose tissue, liver and skeletal muscle, and improved insulin resistance and glucose intolerance without stimulating uterine growth. Estrogen, BZA and TSEC improved energy homeostasis by increasing lipid oxidation and energy expenditure, and promoted insulin action by enhancing insulin-stimulated glucose disposal and suppressing hepatic glucose production. While estrogen improved metabolic homeostasis, at least partially, by increasing hepatic production of FGF21, BZA increased hepatic expression of Sirtuin1, PPARα and AMPK activity. The metabolic benefits of BZA were lost in estrogen receptor-α deficient mice. Thus, BZA alone or in TSEC produces metabolic signals of fasting and caloric restriction and improves energy and glucose homeostasis in female mice.