Accumulation of endoplasmic reticulum stress and lipogenesis in the liver through generational effects of high fat diets

Pesticide methoxychlor promotes the epigenetic transgenerational inheritance of adult-onset disease through the female germline

Environmental compounds including fungicides, plastics, pesticides, dioxin and hydrocarbons can promote the epigenetic transgenerational inheritance of adult-onset disease in future generation progeny following ancestral exposure during the critical period of fetal gonadal sex determination. This study examined the actions of the pesticide methoxychlor to promote the epigenetic transgenerational inheritance of adult-onset disease and associated differential DNA methylation regions (i.e. epimutations) in sperm. Gestating F0 generation female rats were transiently exposed to methoxychlor during fetal gonadal development (gestation days 8 to 14) and then adult-onset disease was evaluated in adult F1 and F3 (great-grand offspring) generation progeny for control (vehicle exposed) and methoxychlor lineage offspring. There were increases in the incidence of kidney disease, ovary disease, and obesity in the methoxychlor lineage animals. In females and males the incidence of disease increased in both the F1 and the F3 generations and the incidence of multiple disease increased in the F3 generation. There was increased disease incidence in F4 generation reverse outcross (female) offspring indicating disease transmission was primarily transmitted through the female germline. Analysis of the F3 generation sperm epigenome of the methoxychlor lineage males identified differentially DNA methylated regions (DMR) termed epimutations in a genome-wide gene promoters analysis. These epimutations were found to be methoxychlor exposure specific in comparison with other exposure specific sperm epimutation signatures. Observations indicate that the pesticide methoxychlor has the potential to promote the epigenetic transgenerational inheritance of disease and the sperm epimutations appear to provide exposure specific epigenetic biomarkers for transgenerational disease and ancestral environmental exposures.

A lipid-rich gestational diet predisposes offspring to nonalcoholic fatty liver disease: a potential sequence of events

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of metabolic syndrome. It affects 20%–30% of the US population, and it is increasing worldwide. Recently, the role of lipid-rich maternal gestational nutrition in spurring the development of NAFLD among offspring has been indicated. Fetal predisposition to NAFLD involves numerous physiological reroutings that are initiated by increased delivery of nonesterified fatty acids to the fetal liver. Hampered β-oxidation, uncontrolled oxidative stress, increased triacylglycerol synthesis, and the endoplasmic reticulum unfolded protein response are all implicated in sculpting a hepatic phenotype with a propensity to develop NAFLD in the postnatal state. This review suggests a mechanism that integrates outcomes reported by a variety of studies conducted in an analysis of fetal hepatic metabolic capacity amid the maternal consumption of a high-fat diet. Potential preventive measures and therapies for use both as part of prenatal nutrition and for those at risk for the development of NAFLD are also discussed.

Maternal western diet primes non-alcoholic fatty liver disease in adult mouse offspring

AIM

Metabolic programming via components of the maternal diet during gestation may play a role in the development of different aspects of the metabolic syndrome. Using a mouse model, we aimed to characterize the role of maternal western-type diet in the development of non-alcoholic fatty liver disease (NAFLD) in the offspring.

METHODS

Female mice were fed either a western (W) or low-fat control (L) semisynthetic diet before and during gestation and lactation. At weaning, male offspring were assigned either the W or the L diet, generating four experimental groups: WW, WL, LW and LL offspring. Biochemical, histological and epigenetic indicators were investigated at 29 weeks of age.

RESULTS

Male offspring exposed to prenatal and post-weaning western-style diet (WW) showed hepatomegaly combined with accumulation of hepatic cholesterol and triglycerides. This accumulation was associated with up-regulation of de novo lipid synthesis, inflammation and dysregulation of lipid storage. Elevated hepatic transaminases and increased expression of Tnfa, Cd11, Mcp1 and Tgfb underpin the severity of liver injury. Histopathological analysis revealed the presence of advanced steatohepatitis in WW offspring. In addition, alterations in DNA methylation in key metabolic genes (Ppara, Insig, and Fasn) were detected.

CONCLUSION

Maternal dietary fat intake during early development programmes susceptibility to liver disease in male offspring, mediated by disturbances in lipid metabolism and inflammatory response. Long-lasting epigenetic changes may underlie this dysregulation.

Apelin inhibits the development of diabetic nephropathy by regulating histone acetylation in Akita mouse

Diabetic nephropathy is the primary cause of end-stage renal disease. Increasing numbers of patients are suffering from this disease and therefore novel medications and therapeutic approaches are urgently needed. Here, we investigated whether apelin-13, the most active member of the adipokine apelin group, could effectively suppress the development of nephropathy in Akita mouse, a spontaneous type 1 diabetic model. Apelin-13 treatment decreased diabetes-induced glomerular filtration rate, proteinuria, glomerular hypertrophy, mesangial expansion and renal inflammation. The inflammatory factors, activation of NF-κB, histone acetylation and the enzymes involved in histone acetylation were further examined in diabetic kidneys and high glucose- or sodium butyrate-treated mesangial cells in the presence or absence of apelin-13. Apelin-13 treatment inhibited diabetes-, high glucose- and NaB-induced elevation of inflammatory factors, and histone hyperacetylation by upregulation of histone deacetylase 1. Furthermore, overexpression of apelin in mesangial cells induced histone deacetylation under high glucose condition. Thus, apelin-13 may be a novel therapeutic candidate for treatment of diabetic nephropathy via regulation of histone acetylation.

Differential responses of hepatic endoplasmic reticulum stress and inflammation in diet-induced obese rats with high-fat diet rich in lard oil or soybean oil

Scopes

To investigate the effects of high-fat diet enriched with lard oil or soybean oil on liver endoplasmic reticulum (ER) stress and inflammation markers in diet-induced obese (DIO) rats and estimate the influence of following low-fat diet feeding.

Methods and Results

Male SD rats were fed with standard low-fat diet (LF, n = 10) and two isoenergentic high-fat diets enriched with lard (HL, n = 45) or soybean oil (HS, n = 45) respectively for 10 weeks. Then DIO rats from HL and HS were fed either high-fat diet continuously (HL/HL, HS/HS) or switched to low-fat diet (HL/LF, HS/LF) for another 8 weeks. Rats in control group were maintained with low-fat diet. Body fat, serum insulin level, HOMA-IR and ectopic lipid deposition in liver were increased in HL/HL and HS/HS compared to control, but increased to a greater extent in HL/HL compared to HS/HS. Markers of ER stress including PERK and CHOP protein expression and phosphorylation of eIF2α were significantly elevated in HL/HL group while phosphorylation of IRE1α and GRP78 protein expression were suppressed in both HL/HL and HS/HS. Besides, inflammatory signals (OPN, TLR2, TLR4 and TNF-α) expressions significantly increased in HL/HL compared to others. Switching to low-fat diet reduced liver fat deposition, HOMA-IR, mRNA expression of TLR4, TNF-α, PERK in both HL/LF and HS/LF, but only decreased protein expression of OPN, PERK and CHOP in HL/LF group. In addition, HL/LF and HS/LF exhibited decreased phosphorylation of eIF2α and increased phosphorylation of IRE1α and GRP78 protein expression when compared with HL/HL and HS/HS respectively.

Conclusions

Lard oil was more deleterious in insulin resistance and hepatic steatosis via promoting ER stress and inflammation responses in DIO rats, which may be attributed to the enrichment of saturated fatty acid. Low-fat diet was confirmed to be useful in recovering from impaired insulin sensitivity and liver fat deposition in this study.

Nutritional models of foetal programming and nutrigenomic and epigenomic dysregulations of fatty acid metabolism in the liver and heart

Barker's concept of 'foetal programming' proposes that intrauterine growth restriction (IUGR) predicts complex metabolic diseases through relationships that may be further modified by the postnatal environment. Dietary restriction and deficit in methyl donors, folate, vitamin B12, and choline are used as experimental conditions of foetal programming as they lead to IUGR and decreased birth weight. Overfeeding and deficit in methyl donors increase central fat mass and lead to a dramatic increase of plasma free fatty acids (FFA) in offspring. Conversely, supplementing the mothers under protein restriction with folic acid reverses metabolic and epigenomic phenotypes of offspring. High-fat diet or methyl donor deficiency (MDD) during pregnancy and lactation produce liver steatosis and myocardium hypertrophy that result from increased import of FFA and impaired fatty acid β-oxidation, respectively. The underlying molecular mechanisms show dysregulations related with similar decreased expression and activity of sirtuin 1 (SIRT1) and hyperacetylation of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α). High-fat diet and overfeeding impair AMPK-dependent phosphorylation of PGC-1α, while MDD decreases PGC-1α methylation through decreased expression of PRMT1 and cellular level of S-adenosyl methionine. The visceral manifestations of metabolic syndrome are under the influence of endoplasmic reticulum (ER) stress in overnourished animal models. These mechanisms should also deserve attention in the foetal programming effects of MDD since vitamin B12 influences ER stress through impaired SIRT1 deacetylation of HSF1. Taken together, similarities and synergies of high-fat diet and MDD suggest, therefore, considering their consecutive or contemporary influence in the mechanisms of complex metabolic diseases.

Developmental programming of pediatric nonalcoholic fatty liver disease: redefining the"first hit"

The incidence of pediatric nonalcoholic fatty liver disease has increased dramatically, and growing evidence indicates that the pathophysiology may be unique from the adult form, suggesting a role for early-life events. Recent radiologic techniques have now demonstrated that maternal obesity contributes to hepatic fat storage in newborn infants. In this review, we will explore how maternal obesity and a hyperlipidemic environment can initiate liver histopathogenesis in utero, including steatosis, mitochondrial dysfunction, oxidative stress, and inflammatory priming. Thus, early exposure to excess lipids may represent the "first hit" for the fetal liver, placing it on a trajectory toward future metabolic disease.

Adaptive responses by mouse fetus to a maternal HLE diet by downregulating SREBP1: a microarray- and bio-analytic-based study

Maternal diet has long been recognized as a significant factor affecting offspring development and health, but the target genes affected by a maternal high-lipid diet are currently unknown. In this study, the gene expression profile of neonatal mouse liver was analyzed using gene chips to identify genes with significant up- or downregulated expression levels due to maternal high-fat diet during gestation. Real-time PCR and Western blotting were used to measure key genes selected using microarray. Serum lipid, glucose, and insulin levels in adult offspring from dams fed with chow or a high-lipid diet were measured using commercial kits. Results indicate that the expression of genes involved in cholesterol and fatty acid synthesis were significantly inhibited, while the expression of genes involved in glycolysis were significantly decreased by maternal high-lipid diet during gestation. SREBP1 might be the key gene regulating genes involved in fatty acid, glucose, and cholesterol metabolism in response to a maternal high-fat diet.

DNA hypomethylation of inflammation-associated genes in adipose tissue of female mice after multigenerational high fat diet feeding

OBJECTIVE

Maternal obesity significantly increases the susceptibility of offspring to develop obesity and chronic diseases in adulthood. The offspring of obese mothers are shown to prefer high fat diet (HFD) due to their altered neural circuitry, creating a 'feed-forward cycle' across generations. We hypothesized that the 'feed-forward cycle' caused by multigenerational HFD feeding would have exacerbated effects in adipose tissue of the offspring.

METHODS

Three generations (F0, F1 and F2) of HFD (60% Kcal fat)-fed and corresponding normal chow (NC)-fed C57BL/6 mice were generated. Body weight (BW) and food intake were monitored weekly. Parametrial adipose tissue (pAT) weight and endocrine parameters were measured in 9-month-old female offspring. Gene expression microarray, quantitative RT-PCR and bisulfite sequencing were performed using pAT.

RESULTS

BW and pAT weight increased in female mice across generations under continuous HFD stress, with the most severe phenotype found in the F2 generation. Genes involved in inflammatory response showed increased expression across generations in the pAT, accompanied by increased macrophage infiltration. The promoters of Toll-like receptor 1 (Tlr1), Tlr2 and linker for activation of T cells (Lat) were hypomethylated in the HF groups compared with the NC group, with additional hypomethylation on some specific CpG sites in the F2 generation.

CONCLUSIONS

A feed-forward cycle exists in female mice after continuous HFD stress as demonstrated by increased adiposity and progressive inflammation in adipose tissue across generations. DNA hypomethylation over generations lead to epigenetically altered expression of Tlr1, Tlr2 and Lat, which may contribute to the inflammation in adipose tissue. Our study provides a potential mechanism for enhanced inflammation in adipose tissue under multigenerational HFD-fed stress.

Evidence for transgenerational metabolic programming in Drosophila

Worldwide epidemiologic studies have repeatedly demonstrated an association between prenatal nutritional environment, birth weight and susceptibility to adult diseases including obesity, cardiovascular disease and type 2 diabetes. Despite advances in mammalian model systems, the molecular mechanisms underlying this phenomenon are unclear, but might involve programming mechanisms such as epigenetics. Here we describe a new system for evaluating metabolic programming mechanisms using a simple, genetically tractable Drosophila model. We examined the effect of maternal caloric excess on offspring and found that a high-sugar maternal diet alters body composition of larval offspring for at least two generations, augments an obese-like phenotype under suboptimal (high-calorie) feeding conditions in adult offspring, and modifies expression of metabolic genes. Our data indicate that nutritional programming mechanisms could be highly conserved and support the use of Drosophila as a model for evaluating the underlying genetic and epigenetic contributions to this phenomenon.

Coumarin attenuates hepatic steatosis by down-regulating lipogenic gene expression in mice fed a high-fat diet

Coumarin is a natural compound abundant in plant-based foods such as citrus fruits, tomatoes, vegetables and green tea. Although coumarin has been reported to exhibit anti-coagulant, anti-inflammation and cholesterol-lowering properties, the effect of coumarin on hepatic lipid metabolism remains unclear. In the present study, we evaluated the ability of coumarin to protect against hepatic steatosis associated with a high-fat diet (HFD) and investigated potential mechanisms underlying this effect. C57BL/6J mice were fed a normal diet, HFD and HFD containing 0·05 % courmarin for 8 weeks. The present results showed that coumarin reduced weight gain and abdominal fat mass in mice fed the HFD for 8 weeks (P< 0·05). Coumarin also significantly reduced the HFD-induced elevation in total cholesterol, apoB, leptin and insulin (P< 0·05). In the liver of HFD-fed mice, coumarin significantly reduced total lipids, TAG and cholesterol (38, 22 and 9 % reductions, respectively; P< 0·05), as well as lipid droplet number and size. Additionally, thiobarbituric acid-reactive substance levels, as an indicator of hepatic steatosis, were attenuated by coumarin (P< 0·05). Finally, coumarin suppressed the HFD-induced up-regulation in fatty acid synthase (FAS) activity, and the expression of sterol regulatory element-binding protein-1, FAS, acetyl-CoA carboxylase 1, PPARγ and CCAAT/enhancer-binding protein-α in the liver. Taken together, these results demonstrate that coumarin could prevent HFD-induced hepatic steatosis by regulating lipogenic gene expression, suggesting potential targets for preventing hepatic steatosis.

Hydrocarbons (jet fuel JP-8) induce epigenetic transgenerational inheritance of obesity, reproductive disease and sperm epimutations

Environmental compounds have been shown to promote epigenetic transgenerational inheritance of disease. The current study was designed to determine if a hydrocarbon mixture involving jet fuel (JP-8) promotes epigenetic transgenerational inheritance of disease. Gestating F0 generation female rats were transiently exposed during the fetal gonadal development period. The direct exposure F1 generation had an increased incidence of kidney abnormalities in both females and males, prostate and pubertal abnormalities in males, and primordial follicle loss and polycystic ovarian disease in females. The first transgenerational generation is the F3 generation, and the jet fuel lineage had an increased incidence of primordial follicle loss and polycystic ovarian disease in females, and obesity in both females and males. Analysis of the jet fuel lineage F3 generation sperm epigenome identified 33 differential DNA methylation regions, termed epimutations. Observations demonstrate hydrocarbons can promote epigenetic transgenerational inheritance of disease and sperm epimutations, potential biomarkers for ancestral exposures.

Molecular Interactions between NAFLD and Xenobiotic Metabolism

Non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome, is a complex multifactorial disease characterized by metabolic deregulations that include accumulation of lipids in the liver, lipotoxicity, and insulin resistance. The progression of NAFLD to non-alcoholic steatohepatitis and cirrhosis, and ultimately to carcinomas, is governed by interplay of pro-inflammatory pathways, oxidative stress, as well as fibrogenic and apoptotic cues. As the liver is the major organ of biotransformation, deregulations in hepatic signaling pathways have effects on both, xenobiotic and endobiotic metabolism. Several major nuclear receptors involved in the transcription and regulation of phase I and II drug metabolizing enzymes and transporters also have endobiotic ligands including several lipids. Hence, hepatic lipid accumulation in steatosis and NAFLD, which leads to deregulated activation patterns of nuclear receptors, may result in altered drug metabolism capacity in NAFLD patients. On the other hand, genetic and association studies have indicated that a malfunction in drug metabolism can affect the prevalence and severity of NAFLD. This review focuses on the complex interplay between NAFLD pathogenesis and drug metabolism. A better understanding of these relationships is a prerequisite for developing improved drug dosing algorithms for the pharmacotherapy of patients with different stages of NAFLD.

Piperine, an LXRα antagonist, protects against hepatic steatosis and improves insulin signaling in mice fed a high-fat diet

This study investigated the role of piperine in the transcriptional regulation of liver X receptor α (LXRα) and the effects of dietary piperine on high-fat diet (HFD)-induced hepatic steatosis and insulin resistance in mice. Furthermore, we explored the potential molecular mechanisms through which the protective effects of piperine may work. In the present study, piperine significantly reduced ligand-induced LXRα activity in a dose-dependent manner and gradually disrupted the interaction between ligand-bound LXRα and GST-CBP. In mice, an HFD supplemented with 0.05% piperine (PSD) significantly decreased body and liver weight as well as plasma and hepatic lipid levels. In agreement with our in vitro study, in mice fed an HFD, dietary piperine markedly decreased LXRα mRNA expression and its lipogenic target genes (i.e., SREBP1c, ChREBPα, FAS, and CD36). Piperine also significantly decreased plasma insulin and glucose concentrations, while increasing insulin sensitivity in mice fed an HFD. In addition, piperine downregulated the expression of genes involved in ER stress, including GRP78, activating transcription factor 6, and eukaryotic translation initiation factor 2α, and upregulated GLUT2 translocation from the cytosol to the plasma membrane in the livers of PSD mice. Piperine antagonized LXRα transcriptional activity by abolishing the interaction of ligand-bound LXRα with the co-activator CBP. The effects of piperine on hepatic lipid accumulation were likely regulated via alterations in LXRα-mediated lipogenesis in mice fed an HFD. Dietary piperine also led to reduced ER stress and increased insulin sensitivity and prevented hepatic insulin resistance in mice fed the HFD.

DNA methylation and hepatic insulin resistance and steatosis

PURPOSE OF REVIEW

In this review, we show novel evidence about the role of the liver in the development of insulin resistance and suggest that abnormal hepatic triglyceride accumulation is not an innocent bystander comorbidity but adversely affects the peripheral insulin sensitivity.

RECENT FINDINGS

The core of this review is built up around the concept that liver DNA methylation of the peroxisome proliferative activated receptor gamma coactivator one alpha gene promoter modulates the status of peripheral insulin resistance and is strongly associated with plasma fasting insulin levels. We discuss about other mechanisms associated with peroxisome proliferative activated receptor gamma coactivator one alpha regulation, such as an acetylation and deacetylation switch and how these events impact on the liver metabolic function. We suggest a mitochondrial-centric approach to understand the connection between nonalcoholic fatty liver disease and insulin resistance. We finally show new data about how the liver epigenome is modulated by nutritional cues and introduce the role of epigenetics in liver metabolic programming.

SUMMARY

The implications of these findings for clinical practice are promising, as the inherent plasticity of epigenetic modifications, produced either physiologically or pathologically, suggests that early therapeutic intervention in patients with fatty liver can potentially revert the systemic phenotype associated with insulin resistance.

Inhibition of poly(ADP-ribose) polymerase inhibits ischemia/reperfusion induced neurodegeneration in retina via suppression of endoplasmic reticulum stress

Poly(ADP-ribose) polymerase (PARP) inhibitors have neuroprotective effects after retinal ischemia and reperfusion (I/R) injury, but mechanisms of this action are not clear. A second generation PARP inhibitor, GPI 15427, was administrated to mice to investigate the possible mechanisms underlying its neuroprotective effects after retinal I/R injury. Ischemia was induced by increasing intraocular pressure to 80-90 mm Hg for 60 min followed by reperfusion, and mice were treated with GPI 15427 (40 mg/kg(-1) day(-1), orally) 2 days before or 1 day after injury. Histopathology caused by the retinal I/R injury was estimated by TUNEL assay and histological analyses. Relative gene expressions were evaluated by RT-PCR, Western blotting and immunohistological studies. GPI 15427 inhibited the retinal I/R-induced PARP activation and glial cell activation. GPI 15427 also significantly inhibited the I/R-induced neurodegeneration, as well as increase in TUNEL-positive cells. I/R-induced PERK-eIF2α-CHOP activation and Bip over-expression were inhibited by GPI 15427, while it did not suppress I/R-induced CHOP over-expression and degeneration of retinal capillaries. Our results suggest that GPI 15427 inhibited retinal I/R-induced neurodegeneration and glial cell activation, and this was associated with an effect of the drug to suppress PERK-eIF2α-CHOP activation and Bip over-expression. These results provide evidence that GPI 15427 inhibits retinal I/R injury at least in part via inhibition of endoplasmic reticulum stress.