Sexual dimorphism modulates metabolic and cognitive alterations under HFD nutrition and chronic stress exposure in mice. Correlation between spatial memory impairment and BDNF mRNA expression in hippocampus and spleen.

AIMS: The accumulated evidence suggests that lifestyle - specifically dietary habits and stress exposure - plays a detrimental role in health. The purpose of the present study was to analyze the interplay of stress, diet, and sex in metabolic and cognitive alterations. MAIN METHODS: For this purpose, one-month-old C57Bl/6J mice were fed with a standard diet or high-fat diet (HFD). After eight weeks, one subgroup of mice from each respective diet was exposed to 20 weeks of chronic mild stress (CMS), whilst the others were left undisturbed. KEY FINDINGS: After 28 weeks of HFD feeding, mice from both sexes were overweight, with an increase in caloric intake and abdominal and subcutaneous fat pads. Stress exposure induced a decrease in body weight, related to a decrease in caloric efficiency in both males and females. Results indicate that males are more susceptible than the females in modulating metabolic and cognitive functions under HFD and CMS. Although both sexes demonstrated HFD-induced weight gain, fat accumulation, insulin resistance, high cholesterol, only males exposed to CMS but not females have (i) impaired glucose tolerance with higher glucose level; (ii) significant prolonged latency in Barnes test, suggesting cognitive impairment; (iii) increased IFN-gamma expression in hippocampus, suggesting greater neuroinflammatory response; (iv) poorer cognitive performance related to a decrease in hippocampal and spleen BDNF mRNA expression. SIGNIFICANCE: The main finding in this study is the presence of a sexual dimorphism in modulating metabolic and cognitive functions under HFD and CMS, showing males are more susceptible than females. In addition, poorer cognitive performance was related to a decrease in hippocampal BDNF mRNA expression. Interestingly, these changes were observed in the spleen as well.

Relación entre el índice de masa corporal y el nivel de los ácidos grasos circulantes maternos como predictores de la presencia de la macrosomía fetal / Relationship between body mass index and maternal circulating fatty acid levels as predictors of the presence of fetal macrosomia

Introducción: los recién nacidos con peso elevado al nacer presentan mayor riesgo de complicaciones en el parto y problemas de salud a largo plazo. Un factor poco explorado durante la gestación es el nivel de los ácidos grasos circulantes. Materiales y métodos: estudio prospectivo donde se estudiaron mujeres durante el embarazo hasta el parto. Se analizaron las variables antropométricas y la medición de ácidos grasos libres entre las semanas 24-28 de gestación. Resultados: se incluyeron 27 pacientes, de las cuales cuatro (13,8%) dieron a luz a recién nacidos macrosómicos. Las pacientes se agruparon según el índice de masa corporal (IMC) preembarazo en normopeso y sobrepeso u obesidad. Los bebés macrosómicos correspondieron al grupo de madres con sobrepeso y obesidad que, además, tuvieron un incremento significativo de los niveles de ácidos grasos libres (2067 uM, ICC: 947,5-1590 vs 1212 uM, ICC: 13367-2247; p<0,05) en el grupo obesidad y sobrepeso. Los valores de glucemia basal y posteriores a la prueba de tolerancia oral a la glucosa no mostraron diferencias. El análisis multivariado reveló que tener obesidad o sobrepeso al inicio del embarazo resulta en un odds ratio (OR) de ácidos grasos libres de 1,0023 (IC9 5%:1,0000-1,0046), mientras que la prueba de tolerancia oral a la glucosa presentó un OR: 1,0186 (IC 95%: 0,9645-1,0756). Conclusiones: los resultados muestran el rol del IMC pregestacional sobre el riesgo de tener hijos macrosómicos, lo que confirma la necesidad de mejorar el estado nutricional de las mujeres antes y durante el embarazo.

Introduction: neonates with high birth weight are at increased risk of birth complications and long term health problems. An unexplored factor during gestation is the level of circulating fatty acids. Materials and methods: prospective study where women were studied during pregnancy until delivery. Anthropometric variables and free fatty acid measurements were analyzed between 24-28 weeks of gestation. Results: we included 27 patients, of whom 4 (13.8%) gave birth to macrosomic newborns. Patients were grouped according to pre-pregnancy mass index (BMI) into normal weight and overweight or obese. Macrosomic neonates corresponded to the group of overweight and obese mothers, who also presented a significant increase in free fatty acid levels (2067 uM, ICC: 947,5-1590 vs 1212 uM, ICC: 13367-2247; p<0.05) was found in the obese and overweight group. Basal and post oral glucose tolerance test showed no differences, Multivariate analysis showed that being obese or overweight at the beginning of pregnancy results in an OR of free fatty acids 1,0023 (95%CI: 1,0000-1,0046), while oral glucose tolerance test presented an OR: 1,0186 (95%CI: 0,9645-1,0756). Conclusions: the results show the role of pre-gestational BMI on the risk of having macrosomic children, confirming the need to improve the nutritional status of women before and during pregnancy

Perinatal taurine exerts a hypotensive effect in male spontaneously hypertensive rats and down-regulates endothelial oxide nitric synthase in the aortic arch.

Essential hypertension is considered to be a result of the interaction between genetic and environmental factors, including perinatal factors. Different advantageous perinatal factors proved to have beneficial long-lasting effects against an abnormal genetic background. Taurine is a ubiquitous sulphur-containing amino acid present in foods such as seafood. The antihypertensive effects of taurine have been reported in experimental studies and in human hypertension. We aimed to investigate the effects of perinatal treatment with taurine in spontaneously hypertensive rats (SHR), a known model of genetic hypertension. Female SHR were administered with taurine (3 g/L) during gestation and lactation (SHR-TAU). Untreated SHR and Wistar-Kyoto rats (WKY) were used as controls. Long-lasting effects in offspring were investigated. Addition of taurine to the mother's drinking water reduced blood pressure in adult offspring. No differences were observed in cardiac hypertrophy. Findings on morphometric evaluations suggest that perinatal treatment with taurine would be partially effective in improving structural alterations of the aorta. Modifications in gene expression of Bcl-2 family members and upregulation of endothelial nitric oxide synthase in the aorta of 22-week-old male offspring were found. No differences were observed on relative telomere length in different cardiovascular tissues between SHR and SHR-TAU. Altogether results suggest that taurine programming, albeit sex specific, is associated with gene expression changes which ultimately may lead to improvement of aortic remodelling and enhanced endothelial function because of augmented nitric oxide (NO) production.

Systematic review and meta-analysis on the relationship between prenatal stress and metabolic syndrome intermediate phenotypes.

BACKGROUND: Metabolic Syndrome (MetS) can be considered as a consequence of a complex interplay between genetic and environmental factors and can be influenced by changes in the environment early in life. Prenatal stress (PS) exposure likely represents an important adverse intrauterine environment that may impact the biology of the developing organism. The aim of this study was to quantitatively synthesize the available data on the effects of PS on offspring's obesity, estimated indirectly by body mass index (BMI) and body fat; blood pressure, plasma glucose and blood lipid concentrations (triglycerides and high-density lipoprotein cholesterol). METHODS: Literature searches for eligible studies on PubMed were conducted until October 8, 2018. Full text review yielded 24 publications for inclusion into the systematic review. Meta-analyses were performed for the outcomes BMI and body fat. 62 effect sizes from 19 studies together with relevant moderators were collected. Summary estimates were calculated by using random-effects model. RESULTS: The combined standardized mean difference (d) for the relation between BMI and PS indicated that despite significant heterogeneity, stress exposure of expectant mothers was associated with increased BMI of their offspring [d (95% CI) = 0.268 (0.191; 0.345)]. Both objective and subjective stress have been linked to increased overweight. Preliminary results of the relationship between PS and body fat suggested that the contribution of PS to body fat should be at least further considered [d (95% CI) = 0.167 (0.016; 0.317)]. Evidence from a limited number of published studies do not sustains an effect on blood pressure, glucose metabolism or circulating lipids, however these outcomes have only been scarcely investigated. CONCLUSIONS: A direct association between PS and BMI was found and further studies are needed to confirm the relationship between maternal stress during gestation and body fat. Overall, findings suggest that PS could contribute to alterations to the post-natal offspring phenotype.

Prenatal stress and later metabolic consequences: Systematic review and meta-analysis in rodents.

BACKGROUND: Numerous rodent studies have evaluated the effects of maternal stress (MS) on later in life susceptibility to Metabolic Syndrome (MetS) intermediate phenotypes with varying results. The aim of this study was to quantitatively synthesize the available data on the effects of MS on offspring obesity, estimated indirectly by body mass (BM), body fat (BF) and plasma leptin; systolic blood pressure (SBP); plasma glucose (and insulin) and blood lipid concentrations. METHODS: Literature was screened and summary estimates of the effect of MS outcomes were calculated by using random-effects models. Data on the effects of exogenous corticosteroid administration (or inhibition of 11ß-HSD2) during pregnancy in rodents was analysed separately to characterize the direct phenotypic effects of prenatal corticosteroid excess (PCE). RESULTS: We conducted 14 separate meta-analyses and synthesized relevant data on outcomes scarcely reported in literature. Both MS and PCE were associated with low birth weight without rapid catch-up growth resulting in decreased body mass later in life. Our analysis also revealed significant and contradictory effects on offspring adiposity. Little evidence was found for effects on glucose metabolism and blood lipids. We identified increased SBP in offspring exposed to PCE; however, there is not enough data to draw any conclusion about effects of MS on SBP. CONCLUSIONS: Neonatal weight proved to be decreased in offspring prenatally exposed to stress or corticosteroids, but laboratory rodents in the absence of a challenging environment did not show catch-up growth. The available evidence is inconclusive regarding the effect on adiposity revealing clear methodological and knowledge gaps. This meta-analysis also confirmed a significant positive association between PCE and SBP. Nevertheless, additional studies should address the association with MS.

Genetic variation in transmembrane 6 superfamily member 2 and the risk of nonalcoholic fatty liver disease and histological disease severity.

UNLABELLED: We explored the role of transmembrane 6 superfamily member 2 (TM6SF2) rs58542926 C/T nonsynonymous (p.Glu167Lys) variant in genetic susceptibility to nonalcoholic fatty liver disease (NAFLD) and disease severity. A total of 361 individuals (135 control subjects and 226 patients with histologically proven NAFLD) were included in a sample with 97% power for the additive genetic model. A discrete trait analysis of NAFLD showed that rs58542926 was associated with a modest risk of fatty liver (P = 0.038; odds ratio [OR]: 1.37; 95% confidence interval [CI]: 1.02-1.84); nevertheless, conditioning on patatin-like phospholipase domain-containing 3 (PNPLA3)-rs738409 abolished this effect. We did not observe an interaction between rs738409 and rs58542926 variants on the risk of NAFLD. We observed a significant association of rs58542926 and disease severity (P = 0.027), but not lobular inflammation or fibrosis; rs58542926 was not associated with levels of liver enzymes. An allelic test showed that the T (Lys167) allele was significantly associated with disease progression (P = 0.021; OR, 1.66; 95% CI: 1.08-2.55). A significant association was found with the histological degree of liver steatosis (ß, 0.15; standard error: 0.06; P = 0.0299) that was independent of rs738409. Homozygous carriers of the C (Glu167) allele showed increased risk for cardiovascular disease. TM6SF2 protein expression was decreased markedly in liver of NAFLD patients, compared to controls. In addition, TM6SF2 immunoreactivity was reduced in subjects carrying at least one copy of the T allele, consistent with a difference in liver allele-specific transcript abundance. CONCLUSION: rs58542926 is a low-frequency variant with a modest effect on NAFLD, suggesting that carriers of the T allele are slightly more likely to accumulate fat in the liver and develop nonalcoholic steatohepatitis than those without. TM6SF2 appears to play a significant role in disease biology.

Promoter DNA methylation of farnesoid X receptor and pregnane X receptor modulates the intrahepatic cholestasis of pregnancy phenotype.

The intrahepatic cholestasis of pregnancy (ICP) is a multifactorial liver disorder which pathogenesis involves the interplay among abnormal bile acid (BA) levels, sex hormones, environmental factors, and genetic susceptibility. The dynamic nature of ICP that usually resolves soon after delivery suggests the possibility that its pathobiology is under epigenetic modulation. We explored the status of white blood peripheral cells-DNA methylation of CpG-enriched sites at the promoter of targeted genes (FXR/NR1H4, PXR/NR1I2, NR1I3, ESR1, and ABCC2) in a sample of 88 ICP patients and 173 healthy pregnant women in the third trimester of their pregnancies. CpG dinucleotides at the gene promoter of nuclear receptors subfamily 1 members and ABCC2 transporter were highly methylated during healthy pregnancy. We observed significant differences at the distal (-1890) and proximal promoter (-358) CpG sites of the FXR/NR1H4 and at the distal PXR/NR1I2 (-1224) promoter, which were consistently less methylated in ICP cases when compared with controls. In addition, we observed that methylation at FXR/NR1H4-1890 and PXR/NR1I2-1224 promoter sites was highly and positively correlated with BA profiling, particularly, conjugated BAs. Conversely, methylation level at the proximal FXR/NR1H4-358 CpG site was significantly and negatively correlated with the primary cholic and secondary deoxycholic acid. In vitro exploration showed that epiallopregnanolone sulfate, a reported FXR inhibitor, regulates the transcriptional activity of FXR/NR1H4 but seems to be not involved in the methylation changes. In conclusion, the identification of epigenetic marks in target genes provides a basis for the understanding of adverse liver-related pregnancy outcomes, including ICP.

Fetal metabolic programming and epigenetic modifications: a systems biology approach.

A growing body of evidence supports the notion that epigenetic changes such as DNA methylation and histone modifications, both involving chromatin remodeling, contribute to fetal metabolic programming. We use a combination of gene-protein enrichment analysis resources along with functional annotations and protein interaction networks for an integrative approach to understanding the mechanisms underlying fetal metabolic programming. Systems biology approaches suggested that fetal adaptation to an impaired nutritional environment presumes profound changes in gene expression that involve regulation of tissue-specific patterns of methylated cytosine residues, modulation of the histone acetylation-deacetylation switch, cell differentiation, and stem cell pluripotency. The hypothalamus and the liver seem to be differently involved. In addition, new putative explanations have emerged about the question of whether in utero overnutrition modulates fetal metabolic programming in the same fashion as that of a maternal environment of undernutrition, suggesting that the mechanisms behind these two fetal nutritional imbalances are different. In conclusion, intrauterine growth restriction is most likely to be associated with the induction of persistent changes in tissue structure and functionality. Conversely, a maternal obesogenic environment is most probably associated with metabolic reprogramming of glucose and lipid metabolism, as well as future risk of metabolic syndrome (MS), fatty liver, and insulin (INS) resistance.

Cardiovascular disease is associated with high-fat-diet-induced liver damage and up-regulation of the hepatic expression of hypoxia-inducible factor 1α in a rat model.

CVD (cardiovascular disease) is associated with abnormal liver enzymes, and NAFLD (non-alcoholic fatty liver disease) is independently associated with cardiovascular risk. To gain insights into the molecular events underlying the association between liver enzymes and CVD, we developed an HFD (high-fat diet)-induced NAFLD in the SHR (spontaneously hypertensive rat) and its control WKY (Wistar-Kyoto) rat strain. We hypothesized that hepatic induction of Hif1a (hypoxia-inducible factor 1α) might be the link between CVD and liver injury. Male SHRs (n=13) and WKY rats (n=14) at 16 weeks of age were divided into two experimental groups: standard chow diet and HFD (10 weeks). HFD-fed rats, irrespective of the strain, developed NAFLD; however, only HFD-SHRs had focus of lobular inflammation and high levels of hepatic TNFα (tumour necrosis factor α). SHRs had significantly higher liver weight and ALT (alanine aminotransferase) levels, irrespective of NAFLD. Liver abundance of Hif1a mRNA and Hif1α protein were overexpressed in SHRs (P<0.04) and were significantly correlated with ALT levels (R=0.50, P<0.006). This effect was not reverted by a direct acting splanchnic vasodilator (hydralazine). Angiogenesis may be induced by the HFD, but the disease model showed significantly higher hepatic Vegf (vascular endothelial growth factor) levels (P<0.025) even in absence of dietary insult. Hif1a mRNA overexpression was not observed in other tissues. Liver mRNA of Nr1d1 (nuclear receptor subfamily 1, group D, member 1; P<0.04), Ppara [Ppar (peroxisome-proliferator-activated receptor) α; P<0.05], Pparg (Pparγ; P<0.001) and Sirt1 (Sirtuin 1; P<0.001) were significantly upregulated in SHRs, irrespective of NAFLD. Sirt1 and Hif1a mRNAs were significantly correlated (R=0.71, P<0.00002). In conclusion, CVD is associated with Hif1a-related liver damage, hepatomegaly and reprogramming of liver metabolism, probably to compensate metabolic demands.

Effect of Neonatal Clomipramine Treatment on consummatory Successive Negative Contrast

La administración neonatal de clomipramina (CLI) produce alteraciones fisiológicas, neuroendocrinas y comportamentales en las ratas adultas, que son similares a las observadas en los modelos animales de depresión. En el Contraste Sucesivo Negativo consumatorio (CSNc), las ratas que recibieron una solución de sacarosa al 32%, consumen menos de una solución de sacarosa al 4%, que los animales que siempre recibieron la solución 4%. Este modelo de devaluación del incentivo produce en los animales una reacción emocional similar al miedo y la ansiedad. En el presente trabajo, estudiamos si el tratamiento neonatal con CLI altera la respuesta de CSNc en ratas adultas. Los hallazgos del presente trabajo sugieren que el tratamiento neonatal con un antidepresivo podría generar un aumento en la tolerancia a la frustración en animales adultos. Los animales a los que se les administró neonatalmente CLI presentaron una recuperación más rápida en el CSNc, que los animales controles sin tratamiento neonatal. Este resultado puede explicarse por una alteración del eje Hipotálamo-Pituitario-Adrenal (HPA), por un deterioro del sistema serotoninérgico, por la formación de una baja expectativa durante la fase de pre-cambio, o por una combinación de estos factores(AU)

Neonatal administration of clomipramine (CLI) produces physiological, neuroendocrinal and behavioral abnormalities in rats when they reach adulthood, which are similar to those observed in animal models of depression. In consummatory successive negative contrast (cSNC), rats that have had experience drinking 32% sucrose solution drink significantly less 4% sucrose solution than rats that have drunk only 4% solution. It triggers an aversive-emotional reaction similar to fear or anxiety. We studied whether neonatal treatment with CLI alters the cSNC’s response in adult rats. The findings of the present work suggest that the neonatal treatment with an antidepressive could generate an increase tolerance to frustration in adult animals. CLI rats showed a faster recovery from the cSNC than control animals, which may be explained by an alteration of the Hypothalamic- Pituitary-Adrenal axis (HPA), a serotonergic system deficit, a low expectative formation during pre-shift phase, or a combination of all these factors(AU)

Liver transcriptional profile of atherosclerosis-related genes in human nonalcoholic fatty liver disease.

OBJECTIVES AND DESIGN: Epidemiological studies have suggested a role of nonalcoholic fatty liver disease (NAFLD) in the development of cardiovascular disease. We evaluated liver mRNA expression of 84 genes encoding proteins involved in the atherosclerosis pathway in patients with NAFLD proven through biopsy in a case-control design, and examined the putative role of the histological disease severity in the molecular events associated with the atherogenic profile. RESULTS: Nonalcoholic steatohepatitis (NASH), when compared with simple steatosis (SS), significantly increases the expression of TGFB1 (6.8, p<0.005), angiotensin I-converting enzyme (ACE) (2.1, p<0.007), LAMA1 (2.1, p<0.007), SERPINB2 (2.1, p<0.007), CSF2 (2.5, p<0.002), IL1A (2.5, p<0.005), IL3 (2.1, p<0.007), IL4 (2.1, p<0.007), LIF (2.1, p<0.007), and MMP1 (2.1, p<0.007), and decreases the transcript levels of genes involved in the negative regulation of cell-death pathways. A post hoc analysis of liver biopsies of NASH patients who were treated with enalapril monotherapy because of arterial hypertension showed a significant association with lower fibrosis scores in comparison with untreated patients. BIRC3, a severe hypoxia-activated gene, was significantly increased in SS (8.2, p<0.004), when compared with the controls. NASH, but not SS, was also associated with a significant increase in platelet abundance of TGFB1 mRNA. Systems biology analysis revealed highly scored pathways involved in the regulation of programmed cell death, angiogenesis, and immune system, in which TGFB1 was mostly involved. CONCLUSION: NASH, but not SS, may increase atherosclerotic and cardiovascular risk by local overexpression of mediators of atherogenesis, endothelial damage, and regulators of blood pressure; this observation may have therapeutic implications, because ACE inhibitors may improve both cardiovascular outcomes and liver fibrosis. Hepatocyte hypoxia seems to have an important role in the molecular events activated by liver steatosis.

Mitochondrial DNA copy number is modulated by genetic variation in the signal transducer and activator of transcription 3 (STAT3).

The regulation of mitochondrial DNA (mtDNA) copy number not only is critical for the maintenance of the normal mitochondrial function but has a strong clinical significance. A recent report revealed that the signal transducer and activator of transcription 3 (STAT3) is involved in the regulation of the mitochondrial function and is required for the optimal function of the electron transport chain. In this study, we explored whether gene variants in the STAT3 influence the leukocyte mtDNA copy number. Clinical data and blood samples were collected from 179 subjects (aged 52.8 ± 0.9 years). Mitochondrial DNA quantification using nuclear DNA (nDNA) as a reference was carried out by a real-time quantitative polymerase chain reaction method; results are presented as the mtDNA/nDNA ratio. We selected 3 tag single nucleotide polymorphisms showing a minor allele frequency greater than 10% (rs2293152 C/G, rs6503695 C/T, and rs9891119 A/C), representing 24 polymorphic sites of the STAT3 (r(2) > 0.8). We observed a significant association between mtDNA/nDNA ratio and both rs6503695 and rs9891119, adjusted by age and homeostasis model assessment index. The proportion of the total variance of the mtDNA/nDNA ratio accounted for by the rs6503695 and rs9891119 genotypes was 4.7% and 6.53%, respectively. Common variation in the STAT3 may influence mtDNA copy number.

Insulin resistance and epigenetic regulation: insights from human studies and prospects for future research.

In this study, we review the current knowledge and recent insights on the role of epigenetic factors in the development of human insulin resistance (IR)- and metabolic syndrome (MS)-related phenotypes, and attempt to lay a framework to consider IR as a potentially reversible incapacity to control metabolic homeostasis that is strongly influenced by the interplay between external and internal cues. We summarize the evidence on how tissue-specific epigenetic markers participate either by activating or repressing the gene expression programs to modulate IR- and MS-associated traits. Some additional data are provided about how the exploration of DNA methylation markers in peripheral blood mononuclear cells potentially offers appealing information about the impact of epigenetics in the pathogenesis of IR. Clues about the relation between IR and impaired intrauterine growth explained by fetal metabolic programming and epigenetic modifications are shown, including novel findings about the impact of histone modifications. For instance, we observed that specific epigenetic factors in genes associated with mitochondrial biogenesis may be associated with birth weight. Furthermore, some prospective ideas about the functional consequences of genetic variation modulated by allele-specific epigenetic markers and its impact on MS susceptibility are also illustrated. Finally, we summarize the current knowledge of epigenetics as the biological rationale for potential therapeutic intervention in IR and MS.

High fat diet-induced liver steatosis promotes an increase in liver mitochondrial biogenesis in response to hypoxia.

Mitochondrial DNA (mtDNA) copy number plays a key role in the pathophysiology of metabolic syndrome-related phenotypes, but its role in non-alcoholic fatty liver disease (NAFLD) is not well understood. We evaluated the molecular mechanisms that may be involved in the regulation of liver mtDNA content in a high-fat-induced rat model of NAFLD. In particular, we tested the hypothesis that liver mtDNA copy number is associated with liver expression of HIF-1α. Rats were given either standard chow diet (SCD, n = 10) or high-fat diet (HFD, n = 15) for 20 weeks. Subsequently, mtDNA quantification using nuclear DNA (nDNA) as a reference was carried out using real time quantitative PCR. HFD induced a significant increase in liver mtDNA/nDNA ratio, which significantly correlated with the liver triglyceride content (R: 0.29, P < 0.05). The liver mtDNA/nDNA ratio significantly correlated with the hepatic expression of HIF-1α mRNA (R: 0.37, P < 0.001); liver HIF-1α mRNA was significantly higher in the HFD group. In addition, liver cytochrome c oxidase subunit IV isoform 1 (COX4I1) mRNA expression was also positively correlated with liver mtDNA content. The hepatic expression of mRNA of transcriptional factors that regulate mitochondrial biogenesis, including peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) and PGC-1ß, nuclear respiratory factor-1 (NRF-1), peroxisome proliferator-activated receptor δ and Tfam, was not associated with the liver mtDNA content. Neither hepatocyte apoptosis nor oxidative stress was involved in the HIF-1α-mediated increase in mtDNA copy number. In conclusion, we found that HFD promotes an increase in liver mitochondrial biogenesis in response to hypoxia via HIF-1α, probably to enhance the mitochondrial function as well as to accommodate the metabolic load.

Epigenetic regulation of insulin resistance in nonalcoholic fatty liver disease: impact of liver methylation of the peroxisome proliferator-activated receptor γ coactivator 1α promoter.

UNLABELLED: Insulin resistance (IR) and mitochondrial dysfunction play a central role in the pathophysiology of nonalcoholic fatty liver disease (NAFLD). We hypothesized that genetic factors and epigenetic modifications occurring in the liver contribute to the IR phenotype. We specifically examined whether fatty liver and IR are modified by hepatic DNA methylation of the peroxisome proliferator-activated receptor γ coactivator 1α (PPARGC1A) and mitochondrial transcription factor A (TFAM) promoters, and also evaluated whether liver mitochondrial DNA (mtDNA) content is associated with NAFLD and IR. We studied liver biopsies obtained from NAFLD patients in a case-control design. After bisulfite treatment of DNA, we used methylation-specific polymerase chain reaction (PCR) to assess the putative methylation of three CpG in the PPARGC1A and TFAM promoters. Liver mtDNA quantification using nuclear DNA (nDNA) as a reference was evaluated by way of real-time PCR. Liver PPARGC1A methylated DNA/unmethylated DNA ratio correlated with plasma fasting insulin levels and homeostasis model assessment of insulin resistance (HOMA-IR); TFAM methylated DNA/unmethylated DNA ratio was inversely correlated with insulin levels. PPARGC1A promoter methylation was inversely correlated with the abundance of liver PPARGC1A messenger RNA. The liver mtDNA/nDNA ratio was significantly higher in control livers compared with NAFLD livers. mtDNA/nDNA ratio was inversely correlated with HOMA-IR, fasting glucose, and insulin and was inversely correlated with PPARGC1A promoter methylation. CONCLUSION: Our data suggest that the IR phenotype and the liver transcriptional activity of PPARGC1A show a tight interaction, probably through epigenetic modifications. Decreased liver mtDNA content concomitantly contributes to peripheral IR.

Role of genetic variation in insulin-like growth factor 1 receptor on insulin resistance and arterial hypertension.

OBJECTIVE: To perform a two-stage study to explore the role of gene variants in the risk of insulin resistance and arterial hypertension. METHODS AND RESULTS: The selection of variants was performed by a first stage of in-silico analysis of the original genome-wide association data sets on genes involved in metabolic syndrome components, granted by the Diabetes Genetics Initiative and the Wellcome Trust Case-Control Consortium. We started by identifying single-nucleotide polymorphisms with a cutoff for association (P < 0.05) in both data sets after the application of a computational algorithm of gene prioritization. Among the more promising variants, six single-nucleotide polymorphisms in IGF1R (rs11247362, rs10902606, rs1317459, rs11854132, rs2684761, and rs2715416) were selected for further evaluation in our population. Altogether, 1094 men, aged 34.4 +/- 8.6 years, were included in a population-based study. Genotypes of rs2684761 showed significant association with insulin resistance (as a discrete trait, odds ratio per G allele 1.27, 95% confidence interval 1.03-1.56, P = 0.026; and homeostasis model assessment-insulin resistance as a continuous trait, P = 0.01). A significant association of rs2684761 with arterial hypertension was also observed (odds ratio per G allele 1.29, 95% confidence interval 1.02-1.64, P = 0.037) after adjusting for age and homeostasis model assessment-insulin resistance. CONCLUSION: Our study suggests for the first time a putative role of IGF1R variants in individual susceptibility to metabolic syndrome-related phenotypes, in particular on the risk of having insulin resistance and arterial hypertension.

The nuclear receptor PXR gene variants are associated with liver injury in nonalcoholic fatty liver disease.

OBJECTIVE: To explore the contribution of gene variants and derived haplotypes of the pregnane X receptor (NR1I2) to the severity of nonalcoholic fatty liver disease (NAFLD). METHODS: A total of 290 individuals were evaluated in a case-control association study, including 188 NAFLD patients with different stages of disease severity and 102 healthy individuals. Four tag single nucleotide polymorphisms (SNPs; rs12488820 C/T, rs2472671 C/T, rs2461823 A/G, and rs1054191 A/G) encompassing 36 kb in chromosome 3 and representing 33 polymorphic sites (r2>0.8) were genotyped. Four additional SNPs (rs3814055, rs3814057, rs6785049, and rs7643645) were also included because they showed earlier evidence of functionality. RESULTS: Genotypic tests for single SNPs showed that rs7643645 and rs2461823 were significantly associated with disease severity by ordinal multinomial analysis (P<0.0015 and 0.039, respectively). A significant association was also observed under the additive model for both variants (P<0.00038 and 0.012, respectively). Consistent with the analysis of individual markers, we observed that the multimarker composed of rs2461823/A-rs7643645/G was significantly associated with disease severity (P<6.9 x 10(-5), beta: 0.45). In addition, the rs7643645/G variant was significantly associated with ALT level (P<0.026), a surrogate marker of severe liver injury. Finally, in univariate analysis rs7643645/G was significantly associated with fatty liver disease (P<0.04), with an odds ratio of 1.457 (95% confidence interval: 1.018-2.086). CONCLUSION: Our study suggests that pregnane X receptor polymorphisms and related haplotypes may contribute to disease severity in NAFLD by influencing the individual susceptibility to progress to more severe stages of the disease.