Rosiglitazone and fenofibrate exacerbate liver steatosis in a mouse model of obesity and hyperlipidemia. A transcriptomic and metabolomic study

Antioxidant potential of acerola by-product along the enterohepatic axis of rats fed a high-fat diet

Acerola (Malpighia emarginata DC) by-product (ABP) has bioactive compounds that can provide antioxidant and hypolipidemic effects in vivo. In this study we aimed to evaluate the antioxidant potential of ABP on oxidative damage along the enterohepatic axis of rats fed a high-fat diet for 7 weeks. In addition, we analysed the phenolic compound profile in the enterohepatic axis, and the lipid accumulation in the liver, colon and liver tissue structure of high-fat diet-fed rats treated with fenofibrate drug (100 mg/kg) or ABP (400 mg/kg) via orogastric administration in the 4th to 7th weeks of the experiment. ABP had increased antioxidant potential in vitro and presented ascorbic acid (2022.06 μg/g), carotenoid (2.63 μg/g), and total phenolic compound (5366.44 μg/g) contents. The high-fat diet-fed rats that received ABP (compared to fenofibrate treatment) presented a non-significant reduction of 9.87% in guanine oxidation product, lower relative liver weight, degree of hepatic steatosis, and aspartate aminotransferase level in their blood. ABP also provided high-fat diet-fed rats: an increased amount of total phenolic compounds in caecal digesta (946.42 µg/g), faeces (3299.07 µg/g), colon (256.15 µg/g) and hepatic tissues (454.80 µg/g); higher total antioxidant capacity in plasma and colon; and lower lipid peroxidation in plasma, colonic and hepatic tissues. The results point to the potential antioxidant activity of ABP against oxidative damage along the enterohepatic axis caused by high-fat diet intake. The ABP had a greater protective effect on the healthy liver compared to fenofibrate treatment due to its bioactive compound content.

A novel therapy for hepatic cholestasis treatment-the combination of rosiglitazone and fenofibrate

Hepatic cholestasis can develop into liver fibrosis and eventually liver failure. Currently, ursodeoxycholic acid (UDCA) or UDCA combined with fenofibrate is used for cholestasis treatment. Rosiglitazone inhibited α-naphthyl isothiocyanate (ANIT)-induced cholestasis in mice. In this study, we compared the effect of rosiglitazone, UDCA, fenofibrate, combined rosiglitazone and fenofibrate or UDCA and fenofibrate on ANIT-induced cholestasis. C57BL/6J mice were induced cholestasis by ANIT while treated with rosiglitazone, UDCA, fenofibrate, combination of rosiglitazone and fenofibrate, or combination of UDCA and fenofibrate. Liver and serum samples were collected to determine liver necrosis and serum biochemical parameters. Rosiglitazone alone or combined with fenofibrate demonstrated better effects than UDCA alone or UDCA combined with fenofibrate in reduction of cholestasis-induced serum biochemical parameters and liver necrosis. Surprisingly, UDCA combined with fenofibrate, but not rosiglitazone combined with fenofibrate, potently increased accumulation of free fatty acids (FFAs) in the liver. Mechanistically, the protection of combination of rosiglitazone and fenofibrate against cholestasis was attributed to activated adiponectin pathway to enhance FXR and mitochondrial functions and reduce apoptosis in the liver. The accumulation of FFAs in the liver by combination of UDCA and fenofibrate was caused by activation of fatty acid biosynthesis and uptake, and triglyceride hydrolysis. Taken together, our study not only demonstrates the adverse effect of combination therapy of UDCA and fenofibrate, but also suggests the combination of rosiglitazone and fenofibrate can be another option for cholestasis treatment.

Modulation of hepatic amyloid precursor protein and lipoprotein receptor-related protein 1 by chronic alcohol intake: Potential link between liver steatosis and amyloid-β

Heavy alcohol consumption is a known risk factor for various forms of dementia and the development of Alzheimer’s disease (AD). In this work, we investigated how intragastric alcohol feeding may alter the liver-to-brain axis to induce and/or promote AD pathology. Four weeks of intragastric alcohol feeding to mice, which causes significant fatty liver (steatosis) and liver injury, caused no changes in AD pathology markers in the brain [amyloid precursor protein (APP), presenilin], except for a decrease in microglial cell number in the cortex of the brain. Interestingly, the decline in microglial numbers correlated with serum alanine transaminase (ALT) levels, suggesting a potential link between liver injury and microglial loss in the brain. Intragastric alcohol feeding significantly affected two hepatic proteins important in amyloid-beta (Aβ) processing by the liver: 1) alcohol feeding downregulated lipoprotein receptor-related protein 1 (LRP1, ∼46%), the major receptor in the liver that removes Aβ from blood and peripheral organs, and 2) alcohol significantly upregulated APP (∼2-fold), a potentially important source of Aβ in the periphery and brain. The decrease in hepatic LRP1 and increase in hepatic APP likely switches the liver from being a remover or low producer of Aβ to an important source of Aβ in the periphery, which can impact the brain. The downregulation of LRP1 and upregulation of APP in the liver was observed in the first week of intragastric alcohol feeding, and also occurred in other alcohol feeding models (NIAAA binge alcohol model and intragastric alcohol feeding to rats). Modulation of hepatic LRP1 and APP does not seem alcohol-specific, as ob/ob mice with significant steatosis also had declines in LRP1 and increases in APP expression in the liver. These findings suggest that liver steatosis rather than alcohol-induced liver injury is likely responsible for regulation of hepatic LRP1 and APP. Both obesity and alcohol intake have been linked to AD and our data suggests that liver steatosis associated with these two conditions modulates hepatic LRP1 and APP to disrupt Aβ processing by the liver to promote AD.

Fenofibrate enhances lipid deposition via modulating PPARγ, SREBP-1c, and gut microbiota in ob/ob mice fed a high-fat diet

Obesity is characterized by lipid accumulation in distinct organs. Presently, fenofibrate is a commonly used triglyceride-lowering drug. This study is designed to investigate whether long-term fenofibrate intervention can attenuate lipid accumulation in ob/ob mouse, a typical model of obesity. Our data demonstrated that fenofibrate intervention significantly decreased plasma triglyceride level by 21.0%, increased liver index and hepatic triglyceride content by 31.7 and 52.1%, respectively, and elevated adipose index by 44.6% compared to the vehicle group. As a PPARα agonist, fenofibrate intervention significantly increased the expression of PPARα protein in the liver by 46.3% and enhanced the expression of LDLR protein by 3.7-fold. However, fenofibrate dramatically increased the expression of PPARγ and SREBP-1c proteins by ~2.1- and 0.9-fold in the liver, respectively. Fenofibrate showed no effects on the expression of genes-related to fatty acid β-oxidation. Of note, it significantly increased the gene expression of FAS and SCD-1. Furthermore, fenofibrate modulated the gut microbiota. Collectively, long-term fenofibrate induces lipid accumulation in liver and adipose tissues in ob/ob mice by enhancing the expression of adipogenesis-related proteins and gut microbiota. These data suggest that fenofibrate may have limited effects on attenuating lipid deposition in obese patients.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

PAQR9 regulates hepatic ketogenesis and fatty acid oxidation during fasting by modulating protein stability of PPARα

BACKGROUND

The cycle of feeding and fasting is fundamental to life and closely coordinated with changes of metabolic programs. During extended starvation, ketogenesis coupled with fatty acid oxidation in the liver supplies ketone bodies to extrahepatic tissues as the major form of fuel. In this study, we demonstrated that PAQR9, a member of the progesterone and adipoQ receptor family, has a regulatory role on hepatic ketogenesis.

METHODS

We analyzed the phenotype of Paqr9-deleted mice. We also used biochemical methods to investigate the interaction of PAQR9 with PPARα and HUWE1, an E3 ubiquitin ligase.

RESULTS

The expression of Paqr9 was decreased during fasting partly depending on PPARγ. The overall phenotype of the mice was not altered by Paqr9 deletion under normal chow feeding. However, fasting-induced ketogenesis and fatty acid oxidation were attenuated by Paqr9 deletion. Mechanistically, Paqr9 deletion decreased protein stability of PPARα via enhancing its poly-ubiquitination. PAQR9 competed with HUWE1 for interaction with PPARα, thus preventing ubiquitin-mediated degradation of PPARα.

CONCLUSION

Our study reveals that PAQR9 impacts starvation-mediated metabolic changes in the liver via post-translational regulation of PPARα.

Metabolomic analysis of a selective ABCA1 inducer in obesogenic challenge provides a rationale for therapeutic development

BACKGROUND

Therapeutic agents with novel mechanisms of action are needed to combat the growing epidemic of type 2 diabetes (T2D) and related metabolic syndromes. Liver X receptor (LXR) agonists possess preclinical efficacy yet produce side effects due to excessive lipogenesis. Anticipating that many beneficial and detrimental effects of LXR agonists are mediated by ABCA1 and SREPB1c expression, respectively, we hypothesized that a phenotypic optimization strategy prioritizing selective ABCA1 induction would identify an efficacious lead compound with an improved side effect profile over existing LXRβ agonists.

METHODS

We synthesized and characterized a novel small molecule for selective induction of ABCA1 vs. SREBP1c in vitro. This compound was evaluated in both wild-type mice and a high-fat diet (HFD) mouse model of obesity-driven diabetes through functional, biochemical, and metabolomic analysis.

FINDINGS

Six weeks of oral administration of our lead compound attenuated weight gain, glucose intolerance, insulin signaling deficits, and adiposity. Global metabolomics revealed suppression of gluconeogenesis, free fatty acids, and pro-inflammatory metabolites. Target identification linked these beneficial effects to selective LXRβ agonism and PPAR/RXR antagonism.

INTERPRETATION

Our observations in the HFD model, combined with the absence of lipogenesis and neutropenia in WT mice, support this novel approach to therapeutic development for T2D and related conditions.

Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin

Background:

Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway.

Objective:

The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer.

Conclusions:

Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

Laparoscopic sleeve gastrectomy reverses non-alcoholic fatty liver disease modulating oxidative stress and inflammation

BACKGROUND & AIMS

Hepatic alterations, such as in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are frequently associated with obesity. To investigate the molecular mechanisms of these alterations and to identify molecules that could be used as potential therapeutic targets, we investigated the modulation of hepatic indices of oxidative stress and inflammation in obese patients undergoing laparoscopic sleeve gastrectomy (LSG).

METHODS

Patients (n = 436) attending our obesity clinic underwent LSG for weight loss. We obtained a diagnostic intraoperative liver biopsy, and a sub-cohort (n = 120) agreed to a 1-year follow-up that included donation of blood samples and additional liver biopsies. Selected key molecules in blood and liver tissue were used to investigate the hepatic alterations in obesity, and their response to LSG.

RESULTS

One year post-surgery, the prevalence of diabetes, dyslipidemia and hypertension decreased significantly. LSG improved liver histology features in all patients. Improvement was greater in severe cases of NAFLD including those with steatohepatitis, bridging fibrosis or cirrhosis. Significant pre-surgery differences in plasma, and liver markers of oxidative stress and inflammation (including chemokine C-C motif ligand 2, paraoxonase-1, galectin-3, and sonic hedgehog) were observed between patients with, and those without, NASH; post-surgery indicated consistent improvements in these parameters.

CONCLUSION

Our study shows that the histology and liver function of patients with morbid obesity are significantly improved after LSG via mechanisms that involve the reduction of oxidative stress and inflammatory processes. These data encourage the use of LSG as a therapeutic option to improve, or resolve, NAFLD.

Electrophilic nitro-oleic acid reverses obesity-induced hepatic steatosis

Non-alcoholic fatty liver disease (NAFLD) is linked to obesity and insulin resistance and is the most prevalent chronic liver disease. During the development of obesity and NAFLD, mitochondria adapt to the increased lipid load in hepatocytes by increasing the rate of fatty acid oxidation. In concert with this, reactive species (RS) generation is increased, damaging hepatocytes and inducing inflammation. Hepatic mitochondrial dysfunction is central to the pathogenesis of NAFLD via undefined mechanisms. There are no FDA approved treatments for NAFLD other than weight loss and management of glucose tolerance. Electrophilic nitro-oleic acid (NO₂-OA) displays anti-inflammatory and antioxidant signaling actions, thus mitochondrial dysfunction, RS production and inflammatory responses to NO₂-OA and the insulin sensitizer rosiglitazone were evaluated in a murine model of insulin resistance and NAFLD. Mice on HFD for 20 wk displayed increased adiposity, insulin resistance and hepatic lipid accumulation (steatosis) compared to mice on normal chow (NC). The HFD mice had mitochondrial dysfunction characterized by lower hepatic mitochondrial complex I, IV and V activity compared to mice on NC. Treatment with NO₂-OA or rosiglitazone for the last 42 days (out of 20 wk) abrogated HFD-mediated decreases in hepatic mitochondrial complex I, IV and V activity. Notably, NO₂-OA treatment normalized hepatic triglyceride levels and significantly reversed hepatic steatosis. Despite the improved glucose tolerance observed upon rosiglitazone treatment, liver weight and hepatic triglycerides were significantly increased over vehicle-treated HFD mice. These observations support that the pleiotropic signaling actions of electrophilic fatty acids limit the complex hepatic and systemic pathogenic responses instigated by obesity, without the adverse effects of thiazolidinedione drugs such as rosiglitazone.

A metabolome-wide characterization of the diabetic phenotype in ZDF rats and its reversal by pioglitazone

Type 2 diabetes (T2D) is a complex metabolic disease associated with alterations in glucose, lipid and protein metabolism. In order to characterize the biochemical phenotype of the Zucker diabetic fatty (ZDF) rat, the most common animal model for the study of T2D, and the impact of the insulin sensitizer pioglitazone, a global, mass spectrometry-based analysis of the metabolome was conducted. Overall, 420 metabolites in serum, 443 in the liver and 603 in the intestine were identified at study end. In comparison to two control groups, obese diabetic ZDF rats showed characteristic metabolic signatures that included hyperglycemia, elevated β-oxidation, dyslipidemia—featured by an increase in saturated and monounsaturated fatty acids and a decrease of medium chain and of polyunsaturated fatty acids in serum–and decreased amino acid levels, consistent with their utilization in hepatic gluconeogenesis. A 13-week treatment with the PPARγ agonist pioglitazone reversed most of these signatures: Pioglitazone improved glycemic control and the fatty acid profile, elevated amino acid levels in the liver, but decreased branched chain amino acids in serum. The hitherto most comprehensive metabolic profiling study identified a biochemical blueprint for the ZDF diabetic model and captured the impact of genetic, nutritional and pharmacological perturbations. The in-depth characterization on the molecular level deepens the understanding and further validates the ZDF rat as a suitable preclinical model of diabetes in humans.

Impact of obesity on the toxicity of a multi-ingredient dietary supplement, OxyELITE Pro™ (New Formula), using the novel NZO/HILtJ obese mouse model: Physiological and mechanistic assessments

Herbal dietary supplement (HDS)-induced hepato- and cardiotoxicity is an emerging clinical problem. In this study, we investigated the liver and heart toxicity of HDS OxyELITE-PRO™ New Formula (OEP-NF), a dietary supplement marketed for weight loss and performance enhancement that was recently withdrawn from the market. Using a novel NZO/HlLtJ obese mouse model, we demonstrated that administration of clinically relevant mouse equivalent doses (MED) of OEP-NF produced cardio- and hepatotoxic risks following both short- and long-term administration schedules. Specifically, gavaging female NZO/HlLtJ with up to 2X MED of OEP-NF resulted in 40% mortality within two weeks. Feeding mice with either 1X or 3X MED of OEP-NF for eight weeks, while not exhibiting significant effects on body weights, significantly altered hepatic gene expression, increased the number of apoptotic and mast cells in the heart and affected cardiac function. The degree of toxicity in NZO/HlLtJ mice was higher than that observed previously in non-obese CD-1 and B6C3F1 strains, suggesting that an overweight/obese condition can sensitize mice to OEP-NF. Adverse health effects linked to OEP-NF, together with a number of other hepato- and cardiotoxicity cases associated with HDS ingestion, argue strongly for introduction of quality standards and pre-marketing safety assessments for multi-ingredient HDS.

Metabolomic and lipidomic analysis of the effect of pioglitazone on hepatic steatosis in a rat model of obese Type 2 diabetes

BACKGROUND AND PURPOSE

Thiazolidinediones, acting as PPAR-γ ligands, reduce hepatic steatosis in humans and animals. However, the underlying mechanism of this action remains unclear. The purpose of this study was to investigate changes in hepatic metabolites and lipids in response to treatment with the thiazolidinedione pioglitazone in an animal model of obese Type 2 diabetes.

EXPERIMENTAL APPROACH

Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats were orally administered either vehicle (control) or pioglitazone (30 mg·kg^-1 ) and fed a high-fat diet (60% kcal fat) for 12 weeks. Hepatic metabolites were analysed via metabolomic and lipidomic analyses. Gene expression and PLA₂ activity were analysed in livers from pioglitazone-treated and control rats.

KEY RESULTS

OLETF rats that received pioglitazone showed decreased fat accumulation and improvement of lipid profiles in the liver compared to control rats. Pioglitazone treatment significantly altered levels of hepatic metabolites, including free fatty acids, lysophosphatidylcholines and phosphatidylcholines, in the liver. In addition, pioglitazone significantly reduced the expression of genes involved in hepatic de novo lipogenesis and fatty acid uptake and transport, whereas genes related to fatty acid oxidation were up-regulated. Gene expression and enzyme activity of PLA₂ , which hydrolyzes phosphatidylcholines to release lysophosphatidylcholines and free fatty acids, were significantly decreased in the livers of pioglitazone-treated rats compared to control rats.

CONCLUSIONS AND IMPLICATIONS

Our results present evidence for the ameliorative effect of pioglitazone on hepatic steatosis, largely due to the regulation of lipid metabolism, including fatty acids, lysophosphatidylcholines, phosphatidylcholines and related gene-expression patterns.

Dibutyltin Compounds Effects on PPARγ/RXRα Activity, Adipogenesis, and Inflammation in Mammalians Cells

Organotins are a group of chemical compounds that have a tin atom covalently bound to one or more organic groups. The best-studied organotin is tributyltin chloride, which is an environmental pollutant and an endocrine disruptor. Tributyltin chloride has been shown to bind to PPARγ/RXRα and induces adipogenesis in different mammalian cells. However, there are few studies with other organotin compounds, such as dibutyltins. The aim of this study was to investigate the effect of dibutyltins diacetate, dichloride, dilaurate, and maleate on the transcriptional activity of the nuclear PPARγ and RXRα receptors, and on adipogenesis and inflammation. Analogous to tributyltin chloride, in reporter gene assay using HeLa cells, we observed that dibutyltins diacetate, dichloride, dilaurate, and maleate are partial agonists of PPARγ. Unlike tributyltin chloride, which is a full agonist of RXRα, dibutyltins dichloride and dilaurate are partial RXRα agonists. Additionally, the introduction of the C285S mutation, which disrupts tributyltin chloride binding to PPARγ, abrogated the dibutyltin agonistic activity. In 3T3-L1 preadipocytes, all dibutyltin induced adipogenesis, although the effect was less pronounced than that of rosiglitazone and tributyltin chloride. This adipogenic effect was confirmed by the expression of adipogenic markers Fabp4, Adipoq, and Glut4. Exposure of 3T3-L1 cells with dibutyltin in the presence of T0070907, a specific PPARγ antagonist, reduced fat accumulation, suggesting that adipogenic effect occurs through PPARγ. Furthermore, dibutyltins dichloride, dilaurate, and maleate inhibited the expression of proinflammatory genes in 3T3-L1 cells, such as Vcam1, Dcn, Fn1, S100a8, and Lgals9. Additionally, in RAW 264.7 macrophages, tributyltin chloride and dibutyltin dilaurate reduced LPS-stimulated TNFα expression. Our findings indicate that dibutyltins diacetate, dichloride, dilaurate, and maleate are PPARγ partial agonists and that dibutyltins dichloride and dilaurate are also partial RXRα agonists. Furthermore, dibutyltins induce adipogenesis in a PPARγ-dependent manner and repress inflammatory genes in 3T3-L1 and RAW 264.7 cells. Although dibutyltins display some partial PPARγ/RXRα agonistic effects, the translation of cell-based results assays into in vivo effects on inflammation and insulin resistance is not entirely known. Nevertheless, further studies are necessary to address their effects in different periods of life and to elucidate the actions of organostanic compounds in whole-body context.

LXRα Regulates Hepatic ChREBPα Activity and Lipogenesis upon Glucose, but Not Fructose Feeding in Mice

Liver X receptors (LXRα/β) and carbohydrate response element-binding proteins (ChREBPα/β) are key players in the transcriptional control of hepatic de novo lipogenesis. LXRα/β double knockout (LXRα^−/−/β^−/−) mice have reduced feeding-induced nuclear O-linked N-acetylglucosamine (O-GlcNAc) signaling, ChREBPα activity, and lipogenic gene expression in livers, suggesting important roles for LXRs in linking hepatic glucose utilization to lipid synthesis. However, the role of LXRs in fructose-induced ChREBP activation and lipogenesis is currently unknown. In this study, we studied the effects of high fructose or high glucose feeding on hepatic carbohydrate metabolism and lipogenic gene expression in livers from fasted (24 h) and fasted-refed (12 h) wild type and LXRα knockout (LXRα^−/−) mice. Hepatic lipogenic gene expression was reduced in glucose fed, but not fructose fed LXRα^−/− mice. This was associated with lower expression of liver pyruvate-kinase (L-pk) and Chrebpβ, indicating reduced ChREBPα activity in glucose fed, but not fructose fed mice. Interestingly, ChREBP binding to the L-pk promoter was increased in fructose fed LXRα^−/− mice, concomitant with increased glucose-6-phosphatase (G6pc) expression and O-GlcNAc modified LXRβ, suggesting a role for LXRβ in regulating ChREBPα activity upon fructose feeding. In conclusion, we propose that LXRα is an important regulator of hepatic lipogenesis and ChREBPα activity upon glucose, but not fructose feeding in mice.

Effects of Periconception Cadmium and Mercury Co-Administration to Mice on Indices of Chronic Diseases in Male Offspring at Maturity

BACKGROUND

Long-term exposure to the heavy metals cadmium (Cd) and mercury (Hg) is known to increase the risk of chronic diseases. However, to our knowledge, exposure to Cd and Hg beginning at the periconception period has not been studied to date.

OBJECTIVE

We examined the effect of Cd and Hg that were co-administered during early development on indices of chronic diseases in adult male mice.

METHODS

Adult female CD1 mice were subcutaneously administered a combination of cadmium chloride (CdCl₂) and methylmercury (II) chloride (CH₃HgCl) (0, 0.125, 0.5, or 2.0 mg/kg body weight each) 4 days before and 4 days after conception (8 days total). Indices of anxiety-like behavior, glucose homeostasis, endocrine and molecular markers of insulin resistance, and organ weights were examined in adult male offspring.

RESULTS

Increased anxiety-like behavior, impaired glucose homeostasis, and higher body weight and abdominal adipose tissue weight were observed in male offspring of treated females compared with controls. Significantly increased serum leptin and insulin concentrations and impaired insulin tolerance in the male offspring of dams treated with 2.0 mg/kg body weight of Cd and Hg suggested insulin resistance. Altered mRNA abundance for genes associated with glucose and lipid homeostasis (GLUT4, IRS1, FASN, ACACA, FATP2, CD36, and G6PC) in liver and abdominal adipose tissues as well as increased IRS1 phosphorylation in liver (Ser 307) provided further evidence of insulin resistance.

CONCLUSIONS

Results suggest that the co-administration of Cd and Hg to female mice during the early development of their offspring (the periconception period) was associated with anxiety-like behavior, altered glucose metabolism, and insulin resistance in male offspring at adulthood.

Acanthoic Acid Can Partially Prevent Alcohol Exposure-Induced Liver Lipid Deposition and Inflammation

Aims: The present study aims to detect the effect of acanthoic acid (AA) on alcohol exposure-induced liver lipid deposition and inflammation, and to explore the mechanisms. Methods: C57BL/6 mice were pretreated with single dose of AA (20 and 40 mg/kg) by oral gavage or equal volume of saline, and then exposed to three doses of ethanol (5 g/kg body weight, 25%, w/v) by gavage within 24 h. The mice were sacrificed at 6 h after the last ethanol dosing. Serum and hepatic indexes were detected by western blot, RT-PCR, and histopathological assay. AML-12 cells were pretreated with AA (5, 10, 20 μM), or AICAR (500 μM), GW3965 (1 μM), SRT1720 (6 μM), Nicotinamide (20 mM) for 2 h, respectively, and then following treated with EtOH (200 mM) and lipopolysaccharide (LPS) (10 ng/ml) for additional 48 h. Cell protein and mRNA were collected for western blot and RT-PCR. Cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) release were detected by ELISA assay. Results: It was found that AA significantly decreased acute ethanol-induced increasing of the serum ALT/AST, LDH, ALP levels, and hepatic and serum triglyceride levels, and reduced fat droplets accumulation in mice liver. AA significantly suppressed the levels of sterol regulatory element binding protein 1 (SREBP-1), cytochrome P4502E1 (CYP2E1), IL-1β, and caspase-1 induced by ethanol. Furthermore, a significant decline of sirtuin 1 (Sirt1) and liver X receptors (LXRs) levels was observed in EtOH group, compared with normal group mice. And AA pretreatment increased the Sirt1 and LXRs levels, and also ameliorated phosphorylation of liver kinase B-1 (LKB-1), adenosine monophosphate-activated protein kinase (AMPK), acetyl CoA carboxylase (ACC) proteins, compared with EtOH group. However, the levels of peroxisome proliferator activated receptor -α or -γ (PPAR-α or PPAR-γ) induced by acute ethanol were reversed by AA. In EtOH/LPS cultivated AML-12 cells, AA decreased IL-1β and TNF-α levels, lipid droplets, and SREBP-1 and CYP2E1 expressions, compared with EtOH/LPS treatment. AA also significantly increased protein expressions of Sirt1, p-LKB1, p-ACC, PPARα, and decreased protein expression of PPARγ, compared with EtOH/LPS treatment. Conclusion: Acanthoic acid can partially prevent alcohol exposure-induced liver lipid deposition and inflammation via regulation of LKB1/Sirt1/AMPK/ACC and LXRs pathways.

Role of nonalcoholic fatty liver disease as risk factor for drug-induced hepatotoxicity

BACKGROUND

Obesity is often associated with nonalcoholic fatty liver disease (NAFLD), which refers to a large spectrum of hepatic lesions including fatty liver, nonalcoholic steatohepatitis (NASH) and cirrhosis. Different investigations showed or suggested that obesity and NAFLD are able to increase the risk of hepatotoxicity of different drugs. Some of these drugs could induce more frequently an acute hepatitis in obese individuals whereas others could worsen pre-existing NAFLD.

AIM

The main objective of the present review was to collect the available information regarding the role of NAFLD as risk factor for drug-induced hepatotoxicity. For this purpose, we performed a data-mining analysis using different queries including drug-induced liver injury (or DILI), drug-induced hepatotoxicity, fatty liver, nonalcoholic fatty liver disease (or NAFLD), steatosis and obesity. The main data from the collected articles are reported in this review and when available, some pathophysiological hypotheses are put forward.

RELEVANCE FOR PATIENTS

Drugs that could pose a potential risk in obese patients include compounds belonging to different pharmacological classes such as acetaminophen, halothane, methotrexate, rosiglitazone, stavudine and tamoxifen. For some of these drugs, experimental investigations in obese rodents confirmed the clinical observations and unveiled different pathophysiological mechanisms which could explain why these pharmaceuticals are particularly hepatotoxic in obesity and NAFLD. Other drugs such as pentoxifylline, phenobarbital and omeprazole might also pose a risk but more investigations are required to determine whether this risk is significant or not. Because obese people often take several drugs for the treatment of different obesity-related diseases such as type 2 diabetes, hyperlipidemia and coronary heart disease, it is urgent to identify the main pharmaceuticals that can cause acute hepatitis on a fatty liver background or induce NAFLD worsening.

Fenofibrate, but not ezetimibe, prevents fatty liver disease in mice lacking phosphatidylethanolamine N-methyltransferase

Mice lacking phosphatidylethanolamine N-methyltransferase (PEMT) are protected from high-fat diet (HFD)-induced obesity and insulin resistance. However, these mice develop severe nonalcoholic fatty liver disease (NAFLD) when fed the HFD, which is mainly due to inadequate secretion of VLDL particles. Our aim was to prevent NAFLD development in mice lacking PEMT. We treated Pemt^−/− mice with either ezetimibe or fenofibrate to see if either could ameliorate liver disease in these mice. Ezetimibe treatment did not reduce fat accumulation in Pemt^−/− livers, nor did it reduce markers for hepatic inflammation or fibrosis. Fenofibrate, conversely, completely prevented the development of NAFLD in Pemt^−/− mice: hepatic lipid levels, as well as markers of endoplasmic reticulum stress, inflammation, and fibrosis, in fenofibrate-treated Pemt^−/− mice were similar to those in Pemt^+/+ mice. Importantly, Pemt^−/− mice were still protected against HFD-induced obesity and insulin resistance. Moreover, fenofibrate partially reversed hepatic steatosis and fibrosis in Pemt^−/− mice when treatment was initiated after NAFLD had already been established. Increasing hepatic fatty acid oxidation can compensate for the lower VLDL-triacylglycerol secretion rate and prevent/reverse fatty liver disease in mice lacking PEMT.

New microRNA Biomarkers for Drug-Induced Steatosis and Their Potential to Predict the Contribution of Drugs to Non-alcoholic Fatty Liver Disease

Background and Aims: Drug-induced steatosis is a major reason for drug failure in clinical trials and post-marketing withdrawal; and therefore, predictive biomarkers are essential. These could be particularly relevant in non-alcoholic fatty liver disease (NAFLD), where most patients show features of the metabolic syndrome and are prescribed with combined chronic therapies, which can contribute to fatty liver. However, specific biomarkers to assess the contribution of drugs to NAFLD are lacking. We aimed to find microRNAs (miRNAs) responsive to steatotic drugs and to investigate if they could become circulating biomarkers for drug-induced steatosis.

Methods: Human HepG2 cells were treated with drugs and changes in miRNA levels were measured by microarray and qRT-PCR. Drug-induced fat accumulation in HepG2 was analyzed by high-content screening and enzymatic methods. miRNA biomarkers were also analyzed in the sera of 44 biopsy-proven NAFLD patients and in 10 controls.

Results: We found a set of 10 miRNAs [miR-22-5p, -3929, -24-2-5p, -663a, -29a-3p, -21 (5p and 3p), -27a-5p, -1260 and -202-3p] that were induced in human HepG2 cells and secreted to the culture medium upon incubation with model steatotic drugs (valproate, doxycycline, cyclosporin A and tamoxifen). Moreover, cell exposure to 17 common drugs for NAFLD patients showed that some of them (e.g., irbesartan, fenofibrate, and omeprazole) also induced these miRNAs and increased intracellular triglycerides, particularly in combinations. Finally, we found that most of these miRNAs (60%) were detected in human serum, and that NAFLD patients under fibrates showed both induction of these miRNAs and a more severe steatosis grade.

Conclusion: Steatotic drugs induce a common set of hepatic miRNAs that could be used in drug screening during preclinical development. Moreover, most of these miRNAs are serum circulating biomarkers that could become useful in the diagnosis of iatrogenic steatosis.

Browning of White Adipose Tissue with Roscovitine Induces a Distinct Population of UCP1+ Adipocytes

Brown-like adipocytes exist in several adipose depots including white (WAT) as well as brown (BAT). Activation of these UCP1⁺ cells is a potential therapeutic strategy to combat obesity. Studies have shown that posttranslational modifications of PPARγ regulate select adipocyte programs. Deacetylation of K268 and K293 in the ligand-binding domain of PPARγ by Sirt1 induces browning of WAT. Phosphorylation of S273 of PPARγ by CDK5 or ERK stimulates a diabetogenic program of gene expression in WAT. Here, we report that roscovitine, a CDK inhibitor, prevents S273 phosphorylation and promotes formation of UCP1⁺ (brite) adipocytes in WAT. It also enhances energy expenditure as well as prevents diet-induced obesity and insulin resistance. Analysis of fluorescence-activated cell-sorted UCP1⁺ adipocytes shows that the mRNA signature of brite adipocytes is distinct from beige adipocytes, which arise through catecholamine signaling. These results suggest that brown-like adipocytes in WAT may arise from multiple origins.

Epigenetics and nutrition-related epidemics of metabolic diseases: Current perspectives and challenges

We live in a world fascinated by the relationship between disease and nutritional disequilibrium. The subtle and slow effects of chronic nutrient toxicity are a major public health concern. Since food is potentially important for the development of "metabolic memory", there is a need for more information on the type of nutrients causing adverse or toxic effects. We now know that metabolic alterations produced by excessive intake of some nutrients, drugs and chemicals directly impact epigenetic regulation. We envision that understanding how metabolic pathways are coordinated by environmental and genetic factors will provide novel insights for the treatment of metabolic diseases. New methods will enable the assembly and analysis of large sets of complex molecular and clinical data for understanding how inflammation and mitochondria affect bioenergetics, epigenetics and health. Collectively, the observations we highlight indicate that energy utilization and disease are intimately connected by epigenetics. The challenge is to incorporate metabolo-epigenetic data in better interpretations of disease, to expedite therapeutic targeting of key pathways linking nutritional toxicity and metabolism. An additional concern is that changes in the parental phenotype are detectable in the methylome of subsequent offspring. The effect might create a menace to future generations and preconceptional considerations.

Polyol accumulation in muscle and liver in a mouse model of type 2 diabetes

AIMS

Type 2 diabetes (T2D) is a complex metabolic disease leading to complications in multiple organs. Diabetic myopathy and liver disease are common complications of T2D, but are incompletely understood. To gain insight into the pathogenesis of these conditions we performed metabolomic analysis of skeletal muscle and liver in a mouse model of T2D.

METHODS

Tissue metabolomics were performed by GC/MS and LC/MS of the skeletal muscle and liver in the MKR mouse model of T2D, compared with control mice. MKR mice were treated with the β-3 adrenergic receptor agonist, CL-316,243 to determine metabolite changes after correcting hyperglycemia.

RESULTS

Blood glucose was higher in MKR vs WT mice, and normalized with CL-316,243 treatment. Compared with WT mice, MKR mice had 2.5 fold higher concentrations of sorbitol and 1.7 fold lower concentrations of reduced glutathione in skeletal muscle. In liver, MKR mice had 2 fold higher concentrations of the pentitol ribitol. CL-316,243 treatment normalized sorbitol and ribitol concentrations in MKR skeletal muscle and liver, respectively to the levels of the WT mice.

CONCLUSIONS

These results demonstrate tissue-specific accumulation of polyols in a mouse model of T2D and provide novel insights into the pathogenesis of myopathy and liver disease in T2D.

GQ-16, a TZD-Derived Partial PPARγ Agonist, Induces the Expression of Thermogenesis-Related Genes in Brown Fat and Visceral White Fat and Decreases Visceral Adiposity in Obese and Hyperglycemic Mice

Background

Beige adipocytes comprise a unique thermogenic cell type in the white adipose tissue (WAT) of rodents and humans, and play a critical role in energy homeostasis. In this scenario, recruitment of beige cells has been an important focus of interest for the development of novel therapeutic strategies to treat obesity. PPARγ activation by full agonists (thiazolidinediones, TZDs) drives the appearance of beige cells, a process so-called browning of WAT. However, this does not translate into increased energy expenditure, and TZDs are associated with weight gain. Partial PPARγ agonists, on the other hand, do not induce weight gain, but have not been shown to drive WAT browning. The present study was designed to investigate the effects of GQ-16 on BAT and on browning of WAT in obese mice.

Methods

Male Swiss mice with obesity and hyperglycemia induced by high fat diet were treated with vehicle, rosiglitazone (4 mg/kg/d) or the TZD-derived partial PPARγ agonist GQ-16 (40 mg/kg/d) for 14 days. Fasting blood glucose, aspartate aminotransferase, alanine aminotransferase and lipid profile were measured. WAT and brown adipose tissue (BAT) depots were excised for determination of adiposity, relative expression of Ucp-1, Cidea, Prdm16, Cd40 and Tmem26 by RT-qPCR, histological analysis, and UCP-1 protein expression analysis by immunohistochemistry. Liver samples were also removed for histological analysis and determination of hepatic triglyceride content.

Results

GQ-16 treatment reduced high fat diet-induced weight gain in mice despite increasing energy intake. This was accompanied by reduced epididymal fat mass, reduced liver triglyceride content, morphological signs of increased BAT activity, increased expression of thermogenesis-related genes in interscapular BAT and epididymal WAT, and increased UCP-1 protein expression in interscapular BAT and in epididymal and inguinal WAT.

Conclusion

This study suggests for the first time that a partial PPARγ agonist may increase BAT activity and induce the expression of thermogenesis-related genes in visceral WAT.

General Significance

These findings suggest that PPARγ activity might be modulated by partial agonists to induce WAT browning and treat obesity.

Systematic review and meta-analysis deciphering the impact of fibrates on paraoxonase-1 status

OBJECTIVE

A significant residual cardiovascular risk is consistently observed in patients treated with statins. A combined treatment with fibrates reduces cardiovascular events in very high-risk patients. Because this is apparently unconnected to an improvement in lipid-related outcomes we hypothesized that the cardioprotective effects of fibrates might be associated with an improvement in paraoxonase-1 (PON1) status.

METHOD

The search for existing evidence, using the Medline, Scopus and Cochrane databases, was systematic and followed the PRISMA statement without restrictions on publication date. We excluded non-clinical and observational studies and we extracted data on baseline and post-treatment values of serum PON1 activity and other measurements of PON1 status.

RESULTS

Nine studies (including 12 treatment arms) in patients with hyperlipidemia, diabetes or metabolic syndrome treated with fibrates, alone or in combination with statins, were included to synthesize results. A meta-analysis of the data using a random-effects model revealed a significant increase in serum PON1 activity following fibrate therapy (WMD: 15.64U/L, 95% CI: 6.94, 24.34, p<0.001), an effect that was robust and not sensitive to any particular study. Subgroup analysis indicated differences in the effect size among types of fibrates and that PON1 alterations were associated with high-density lipoprotein cholesterol changes following fibrate therapy.

CONCLUSIONS

Results indicate a significant PON1-enhancing effect of fibrates. Whether this effect is associated with a clinical benefit, although likely, remains to be further investigated.

Dual Outcomes of Rosiglitazone Treatment on Fatty Liver

In previous studies, it has been reported that rosiglitazone has opposing effects on nonalcoholic fatty liver disease. The purpose of the current study is to test the hypothesis that such opposing effects are related to different levels of peroxisome proliferator-activated receptor gamma (PPAR-γ) in the liver. Using a gene transfer approach and mice fed a high-fat diet (HFD) as an animal model, we demonstrate that mice with low levels of PPAR-γ expression in the liver are resistant to HFD-induced development of fatty liver when treated with rosiglitazone. Conversely, rosiglitazone treatment actually exacerbates liver steatosis in obese mice that have a higher level of PPAR-γ. Mechanistic studies show that an elevated hepatic PPAR-γ level is associated with an increased expression of genes responsible for lipid metabolism in the liver, particularly Cd36, Fabp4, and Mgat1. The concurrent transfer of these three genes into the mouse liver fully recapitulates the phenotypic change induced by the overexpression of PPAR-γ. These results provide evidence in support of the importance of PPAR-γ in the liver when rosiglitazone is considered for the treatment of fatty liver disease. Clinically, our results suggest the necessity of verifying PPAR-γ levels in the liver when rosiglitazone is considered as a treatment option, and indicate that the direct use of rosiglitazone for treatment of nonalcoholic fatty liver may not be desirable when the patient's PPAR-γ level in the liver is significantly elevated.

Dietary proanthocyanidins boost hepatic NAD(+) metabolism and SIRT1 expression and activity in a dose-dependent manner in healthy rats

Proanthocyanidins (PACs) have been reported to modulate multiple targets by simultaneously controlling many pivotal metabolic pathways in the liver. However, the precise mechanism of PAC action on the regulation of the genes that control hepatic metabolism remains to be clarified. Accordingly, we used a metabolomic approach combining both nuclear magnetic resonance and mass spectrometry analysis to evaluate the changes induced by different doses of grape-seed PACs in the liver of healthy rats. Here, we report that PACs significantly increased the hepatic nicotinamide adenine dinucleotide (NAD(+)) content in a dose-dependent manner by specifically modulating the hepatic concentrations of the major NAD(+) precursors as well as the mRNA levels of the genes that encode the enzymes involved in the cellular metabolism of NAD(+). Notably, Sirtuin 1 (Sirt1) gene expression was also significantly up-regulated in a dose-response pattern. The increase in both the NAD(+) availability and Sirt1 mRNA levels, in turn, resulted in the hepatic activation of SIRT1, which was significantly associated with improved protection against hepatic triglyceride accumulation. Our data clearly indicates that PAC consumption could be a valid tool to enhance hepatic SIRT1 activity through the modulation of NAD(+) levels.

The acute impact of polyphenols from Hibiscus sabdariffa in metabolic homeostasis: an approach combining metabolomics and gene-expression analyses

We explored the acute multifunctional effects of polyphenols from Hibiscus sabdariffa in humans to assess possible consequences on the host's health. The expected dynamic response was studied using a combination of transcriptomics and metabolomics to integrate specific functional pathways through network-based methods and to generate hypotheses established by acute metabolic effects and/or modifications in the expression of relevant genes. Data were obtained from healthy male volunteers after 3 hours of ingestion of an aqueous Hibiscus sabdariffa extract. The data were compared with data obtained prior to the ingestion, and the overall findings suggest that these particular polyphenols had a simultaneous role in mitochondrial function, energy homeostasis and protection of the cardiovascular system. These findings suggest beneficial actions in inflammation, endothelial dysfunction, and oxidation, which are interrelated mechanisms. Among other effects, the activation of the heme oxygenase-biliverdin reductase axis, the systemic inhibition of the renin-angiotensin system, the inhibition of the angiotensin-converting enzyme, and several actions mirroring those of the peroxisome proliferator-activated receptor agonists further support this notion. We also found concordant findings in the serum of the participants, which include a decrease in cortisol levels and a significant increase in the active vasodilator metabolite of bradykinin (des-Arg(9)-bradykinin). Therefore, our data support the view that polyphenols from Hibiscus sabdariffa play a regulatory role in metabolic health and in the maintenance of blood pressure, thus implying a multi-faceted impact in metabolic and cardiovascular diseases.

Exploring the Process of Energy Generation in Pathophysiology by Targeted Metabolomics: Performance of a Simple and Quantitative Method

Abnormalities in mitochondrial metabolism and regulation of energy balance contribute to human diseases. The consequences of high fat and other nutrient intake, and the resulting acquired mitochondrial dysfunction, are essential to fully understand common disorders, including obesity, cancer, and atherosclerosis. To simultaneously and noninvasively measure and quantify indirect markers of mitochondrial function, we have developed a method based on gas chromatography coupled to quadrupole-time of flight mass spectrometry and an electron ionization interface, and validated the system using plasma from patients with peripheral artery disease, human cancer cells, and mouse tissues. This approach was used to increase sensibility in the measurement of a wide dynamic range and chemical diversity of multiple intermediate metabolites used in energy metabolism. We demonstrate that our targeted metabolomics method allows for quick and accurate identification and quantification of molecules, including the measurement of small yet significant biological changes in experimental samples. The apparently low process variability required for its performance in plasma, cell lysates, and tissues allowed a rapid identification of correlations between interconnected pathways. Our results suggest that delineating the process of energy generation by targeted metabolomics can be a valid surrogate for predicting mitochondrial dysfunction in biological samples. Importantly, when used in plasma, targeted metabolomics should be viewed as a robust and noninvasive source of biomarkers in specific pathophysiological scenarios.

Wedelolactone Regulates Lipid Metabolism and Improves Hepatic Steatosis Partly by AMPK Activation and Up-Regulation of Expression of PPARα/LPL and LDLR

Hyperlipidemia is considered one of the greatest risk factors of cardiovascular diseases. We investigated the anti-hyperlipidemic effect and the underlying mechanism of wedelolactone, a plant-derived coumestan, in HepG2 cells and high-fat diet (HFD)−induced hyperlipidemic hamsters. We showed that in cultured HepG2 cells, wedelolactone up-regulated protein levels of adenosine monophosphate activated protein kinase (AMPK) and peroxisome proliferator-activated receptor-alpha (PPARα) as well as the gene expression of AMPK, PPARα, lipoprotein lipase (LPL), and the low-density lipoprotein receptor (LDLR). Meanwhile, administration of wedelolactone for 4 weeks decreased the lipid profiles of plasma and liver in HFD−induced hyperlipidemic hamsters, including total cholesterol (TC), triglycerides (TG), and low-density lipoprotein-cholesterol (LDL-C). The activation of AMPK and up-regulation of PPARα was also observed with wedelolactone treatment. Furthermore, wedelolactone also increased the activities of superoxidase dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreased the level of the lipid peroxidation product malondialdehyde (MDA) in the liver, therefore decreasing the activity of alanine aminotransferase (ALT). In conclusion, we provide novel experimental evidence that wedelolactone possesses lipid-lowering and steatosis-improving effects, and the underlying mechanism is, at least in part, mediated by the activation of AMPK and the up-regulation of PPARα/LPL and LDLR.

Effect of Chronic Pioglitazone Treatment on Hepatic Gene Expression Profile in Obese C57BL/6J Mice

Pioglitazone, a selective ligand of peroxisome proliferator-activated receptor gamma (PPARγ), is an insulin sensitizer drug that is being used in a number of insulin-resistant conditions, including non-alcoholic fatty liver disease (NAFLD). However, there is a discrepancy between preclinical and clinical data in the literature and the benefits of pioglitazone treatment as well as the precise mechanism of action remain unclear. In the present study, we determined the effect of chronic pioglitazone treatment on hepatic gene expression profile in diet-induced obesity (DIO) C57BL/6J mice in order to understand the mechanisms of NAFLD induced by PPARγ agonists. DIO mice were treated with pioglitazone (25 mg/kg/day) for 38 days, the gene expression profile in liver was evaluated using Affymetrix Mouse GeneChip 1.0 ST array. Pioglitazone treatment resulted in exacerbated hepatic steatosis and increased hepatic triglyceride and free fatty acids concentrations, though significantly increased the glucose infusion rate in hyperinsulinemic-euglycemic clamp test. The differentially expressed genes in liver of pioglitazone treated vs. untreated mice include 260 upregulated and 86 downregulated genes. Gene Ontology based enrichment analysis suggests that inflammation response is transcriptionally downregulated, while lipid metabolism is transcriptionally upregulated. This may underlie the observed aggravating liver steatosis and ameliorated systemic insulin resistance in DIO mice.

Chemokine ligand 2 and paraoxonase-1 in non-alcoholic fatty liver disease: The search for alternative causative factors

The incidence and prevalence of non-alcoholic fatty liver disease (NAFLD) is constantly increasing. Despite this is apparently associated with the growing increase in obesity, insulin resistance and obesity-related metabolic disturbances their presence is not a necessary or sufficient condition to explain the accumulation of fat in the liver. Conversely, NAFLD is a predictor of other metabolic risks. NAFLD is currently the most frequent chronic liver disease but should not be considered benign or anecdotic because a considerable proportion of patients with NAFLD progress to cirrhosis and end-stage liver disease. Consequently, the search for alternative molecular mechanisms with therapeutic implications in NAFLD and associated disorders deserves a careful consideration. Mitochondria are possible targets as these organelles generate energy from nutrient oxidation. Some findings, generated in patients with extreme obesity and in murine models, support the notion that NAFLD could be a mitochondrial disease. This is plausible because mitochondrial dysfunction affects the accumulation of lipids in hepatocytes and promotes lipid peroxidation, the production of reactive oxygen species, the release of cytokines causing inflammation and cell death. Here we discuss basic research and mechanistic studies targeting the role of chemokine ligand 2 in liver inflammation and that of the paraoxonases in the oxidative stress. Their combination and association with mitochondrial dysfunction may uncover mechanisms underlying the progression of NAFLD and may help to identify novel therapeutic targets.

Flavonoids furom Coreopsis tinctoria adjust lipid metabolism in hyperlipidemia animals by down-regulating adipose differentiation-related protein

Background

To identify the chemical structure of Coreopsis tinctoria extracts and their effect and mechanism on reducing blood lipid in hyperlipemia mice.

Methods

The flavonoids were extracted from Coreopsis tinctoria. The chemical structure was identified by HPLC. 59 mice were divided randomly into 5 groups. (group 1: normal diet control; group 2: hyperlipemia model; group 3: hyperlipemia mice treated with Coreopsis tinctoria, low dose 100 mg/kg; group 4: hyperlipemia mice treated with Coreopsis tinctoria high dose group 200 mg/kg; group 5 hyperlipemia mice treated with Fenofibrate. After 2 week of hyperlipid diet, the treatment of Coreopsis tinctoria and Fenofibrate were given for another 6 weeks with continuous hyperlipid diet. The TC, TG, HDL, histology, adipose differentiation-related protein (ADRP) expression in different groups were compared.

Results

Compared with normal diet group, TC, TG in hyperlipemia model group increased ( P < 0. 01). After treatment with Coreopsis tinctoria low dose group, high dose group, TC of the hyperlipemia mice decreased (P < 0. 05) without increasing AST, ALT and ALP. Fenofibrate can also decrease TC and TG but increase AST, ALT and ALP. Expression of hepatic ADRP increased in hyperlipemia mice. Coreopsis tinctoria high dose group 200 mg/kg can inhibit ADRP as Fenofibrate does.

Conclusion

The flavonoids from Coreopsis tinctoria extracts can reduce blood lipid without liver function damage, showing better anti- hyperlipemia effect than Fenofibrate by down-regulating ADRP.

Protopanaxatriol, a novel PPARγ antagonist from Panax ginseng, alleviates steatosis in mice

Obesity is prevalent worldwide, and is highly associated with metabolic disorders, such as insulin resistance, hyperlipidemia and steatosis. Ginseng has been used as food and traditional herbal medicine for the treatment of various metabolic diseases. However, the molecular mechanisms how ginseng and its components participate in the regulation of lipogenesis are still largely unclear. Here, we identified that protopanaxatriol (PPT), a major ginseng constituent, inhibited rosiglitazone-supported adipocyte differentiation of 3T3-L1 cells by repressing the expression of lipogenesis-related gene expression. In high-fat diet-induced obesity (DIO) mice, PPT reduced body weight and serum lipid levels, improved insulin resistance, as well as morphology and lipid accumulation, particular macrovesicular steatosis, in the livers. These effects were confirmed with genetically obese ob/ob mice. A reporter gene assay showed that PPT specifically inhibited the transactivity of PPARγ, but not PPAR α, β/δ and LXR α, β. TR-FRET assay revealed that PPT was specifically bound to PPARγ LBD, which was further confirmed by the molecular docking study. Our data demonstrate that PPT is a novel PPARγ antagonist. The inhibition of PPARγ activity could be a promising therapy for obesity and steatosis. Our findings shed new light on the mechanism of ginseng in the treatment of metabolic syndrome.

Integrative analysis of transcriptomics, proteomics, and metabolomics data of white adipose and liver tissue of high-fat diet and rosiglitazone-treated insulin-resistant mice identified pathway alterations and molecular hubs

The incidences of obesity and type 2 diabetes are rapidly increasing and have evolved into a global epidemic. In this study, we analyzed the molecular effects of high-fat diet (HFD)-induced insulin-resistance on mice in two metabolic target tissues, the white adipose tissue (WAT) and the liver. Additionally, we analyzed the effects of drug treatment using the specific PPARγ ligand rosiglitazone. We integrated transcriptome, proteome, and metabolome data sets for a combined holistic view of molecular mechanisms in type 2 diabetes. Using network and pathway analyses, we identified hub proteins such as SDHB and SUCLG1 in WAT and deregulation of major metabolic pathways in the insulin-resistant state, including the TCA cycle, oxidative phosphorylation, and branched chain amino acid metabolism. Rosiglitazone treatment resulted mainly in modulation via PPAR signaling and oxidative phosphorylation in WAT only. Interestingly, in HFD liver, we could observe a decrease of proteins involved in vitamin B metabolism such as PDXDC1 and DHFR and the according metabolites. Furthermore, we could identify sphingosine (Sph) and sphingosine 1-phosphate (SP1) as a drug-specific marker pair in the liver. In summary, our data indicate physiological plasticity gained by interconnected molecular pathways to counteract metabolic dysregulation due to high calorie intake and drug treatment.