Early-life exposure to high-fat diet may predispose rats to gender-specific hepatic fat accumulation by programming Pepck expression

HFD feeding for seven months abolishes STING disruption-driven but not female sex-based protection against hepatic steatosis and inflammation in mice

Stimulator of interferon genes (STING) is positively correlated with the degrees of liver inflammation in human metabolic dysfunction-associated steatotic liver disease (MASLD). In addition, STING disruption alleviates MASLD in mice fed a high-fat diet (HFD) for 3 months (3-m-HFD). Here we investigated the role of the duration of dietary feeding in regulating MASLD in mice and explored the involvement of STING in sex differences in MASLD. Both male and female STING-disrupted (STINGgt) and wild-type C57BL/6J mice were fed an HFD for 3 or 7 months (7-m-HFD). Additionally, female STINGgt mice upon ovariectomy (OVX) and 3-m-HFD were analyzed for MASLD. Upon 3-m-HFD, STINGgt mice exhibited decreased severity of MASLD compared to control. However, upon 7-m-HFD, STINGgt mice were comparable with wild-type mice in body weight, fat mass, and MASLD. Regarding regulating the liver RNA transcriptome, 7-m-HFD increased the expression of genes indicating proinflammatory activation of various liver cells. Interestingly, the severity of MASLD in female mice was much lighter than in male mice, regardless of STING disruption. Upon OVX, female STINGgt mice showed significantly increased severity of MASLD relative to sham control but were comparable with male STINGgt mice. Upon treatment with 17-beta estradiol (E2), hepatocytes revealed decreased fat deposition while macrophages displayed decreases in lipopolysaccharide-induced phosphorylation of Nfkb p65 and Jnk p46 independent of STING. These results suggest that 7-m-HFD, without altering female sex-based protection, abolishes STING disruption-driven protection of MASLD, likely through causing proinflammatory activation of multiple types of liver cells to offset the effect of STING disruption.

Prenatal amoxicillin exposure induces developmental toxicity in fetal mice and its characteristics

Amoxicillin, a widely used antibiotic in human and veterinary pharmaceuticals, is now considered as an "emerging contaminant" because it exists widespreadly in the environment and brings a series of adverse outcomes. Currently, systematic studies about the developmental toxicity of amoxicillin are still lacking. We explored the potential effects of amoxicillin exposure on pregnancy outcomes, maternal/fetal serum phenotypes, and fetal multiple organ development in mice, at different doses (75, 150, 300 mg/(kg·day)) during late-pregnancy, or at a dose of 300 mg/(kg·day) during different stages (mid-/late-pregnancy) and courses (single-/multi-course). Results showed that prenatal amoxicillin exposure (PAmE) had no significant influence on the body weights of dams, but it could inhibit the physical development and reduce the survival rate of fetuses, especially during the mid-pregnancy. Meanwhile, PAmE altered multiple maternal/fetal serum phenotypes, especially in fetuses. Fetal multi-organ function results showed that PAmE inhibited testicular/adrenal steroid synthesis, long bone/cartilage and hippocampal development, and enhanced ovarian steroid synthesis and hepatic glycogenesis/lipogenesis, and the order of severity might be gonad (testis, ovary) > liver > others. Further analysis found that PAmE-induced multi-organ developmental and functional alterations had differences in stages, courses and fetal gender, and the most obvious changes might be in high-dose, late-pregnancy and multi-course, but there was no typical rule of a dose-response relationship. In conclusion, this study confirmed that PAmE could cause abnormal development and multi-organ function alterations, which deepens our understanding of the risk of PAmE and provides an experimental basis for further exploration of the long-term harm.

Prenatal exposure to corn oil, CMC-Na or DMSO affects physical development and multi-organ functions in fetal mice

Corn oil, sodium carboxymethyl cellulose (CMC-Na), and dimethyl sulfoxide (DMSO) are widely used as solvents or suspensions in animal experiments, but the effects of prenatal exposure to them on fetal development have not been reported. In this study, Kunming mice were given a conventional dose of corn oil (9.2g/kg·d), CMC-Na (0.05g/kg·d) or DMSO (0.088g/kg·d) during gestation days 10-18, and the pregnancy outcome, fetal physical development, serum phenotype, and multi-organ function changes were observed. The results showed that corn oil decreased serum triglyceride level in males but increased their serum testosterone and CORT levels, and affected female placenta and female/male multi-organ functions (mainly bone, liver, kidney). CMC-Na increased female/male body lengths and tail lengths, decreased serum glucose and total cholesterol levels in males as well as increased their serum LDL-C/HDL-C ratio and testosterone level, decreased female serum bile acid level, and affected male/female placenta and multi-organ functions (mainly bone, liver, hippocampus). DMSO decreased male body weight and serum glucose level, decreased male/female serum bile acid levels, and affected male/female placenta and multi-organs functions (mainly bone, hippocampus, adrenal gland). In conclusion, prenatal exposure to a conventional dose of corn oil, CMC-Na or DMSO could affect fetal physical development and multi-organ functions, and has the characteristics of "multi-pathway, multi-organ and multi-target". This study provides the experimental basis for the rational selection of solvents or suspensions in pharmacology and toxicology studies. DATA AVAILABILITY: Data will be made available on request.

Protein restriction during lactation causes transgenerational metabolic dysfunction in adult rat offspring

Introduction

Protein restriction during lactation can induce metabolic dysfunctions and has a huge impact on the offspring's phenotype later in its life. We tested whether the effects of a maternal low-protein diet (LP) in rats can be transmitted to the F2 generation and increase their vulnerability to dietary insults in adulthood.

Methods

Female Wistar rats (F0) were fed either a low-protein diet (LP; 4% protein) during the first 2 weeks of lactation or a normal-protein diet (NP; 23% protein). The female offspring (F1 generation) were maintained on a standard diet throughout the experiment. Once adulthood was reached, female F1 offspring from both groups (i.e., NP-F1 and LP-F1) were bred to proven males, outside the experiment, to produce the F2 generation. Male F2 offspring from both groups (NP-F2 and LP-F2 groups) received a standard diet until 60 days old, at which point they received either a normal fat (NF; 4.5% fat) or a high fat diet (HF; 35% fat) for 30 days.

Results

At 90 days old, LPNF-F2 offspring had increased lipogenesis and fasting insulinemia compared to NPNF-F2, without alteration in insulin sensitivity. HF diet caused increased gluconeogenesis and displayed glucose intolerance in LPHF-F2 offspring compared to LPNF-F2 offspring. Additionally, the HF diet led to damage to lipid metabolism (such as steatosis grade 3), higher body weight, fat pad stores, and hepatic lipid content.

Discussion

We concluded that an F0 maternal protein restricted diet during lactation can induce a transgenerational effect on glucose and liver metabolism in the F2 generation, making the offspring's liver more vulnerable to nutritional injury later in life.

Oxidative Stress Profile of Mothers and Their Offspring after Maternal Consumption of High-Fat Diet in Rodents: A Systematic Review and Meta-Analysis

Maternal exposure to the high-fat diet (HFD) during gestation or lactation can be harmful to both a mother and offspring. The aim of this systematic review was to identify and evaluate the studies with animal models (rodents) that were exposed to the high-fat diet during pregnancy and/or lactation period to investigate oxidative stress and lipid and liver enzyme profile of mothers and their offspring. The electronic search was performed in the PUBMED (Public/Publisher MEDLINE), EMBASE (Ovid), and Web of Science databases. Data from 77 studies were included for qualitative analysis, and of these, 13 studies were included for meta-analysis by using a random effects model. The pooled analysis revealed higher malondialdehyde levels in offspring of high-fat diet groups. Furthermore, the pooled analysis showed increased reactive oxygen species and lower superoxide dismutase and catalase in offspring of mothers exposed to high-fat diet during pregnancy and/or lactation. Despite significant heterogeneity, the systematic review shows oxidative stress in offspring induced by maternal HFD.

Calcium-Deficiency during Pregnancy Affects Insulin Resistance in Offspring

Prenatal malnutrition is known to affect the phenotype of the offspring through changes in epigenetic regulation. Growing evidence suggests that epigenetics is one of the mechanisms by which nutrients and minerals affect metabolic traits. Although the perinatal period is the time of highest phenotypic plasticity, which contributes largely to developmental programming, there is evidence of nutritional influence on epigenetic regulation during adulthood. Calcium (Ca) plays an important role in the pathogenesis of insulin resistance syndrome. Cortisol, the most important glucocorticoid, is considered to lead to insulin resistance and metabolic syndrome. 11β-hydroxysteroid dehydrogenase-1 is a key enzyme that catalyzes the intracellular conversion of cortisone to physiologically active cortisol. This brief review aims to identify the effects of Ca deficiency during pregnancy and/or lactation on insulin resistance in the offspring. Those findings demonstrate that maternal Ca deficiency during pregnancy may affect the epigenetic regulation of gene expression and thereby induce different metabolic phenotypes. We aim to address the need for Ca during pregnancy and propose the scaling-up of clinical and public health approaches that improved pregnancy outcomes.

Caloric restriction following early-life high fat-diet feeding represses skeletal muscle TNF in male rats

Chronic metabolic diseases are on the rise worldwide and their etiology is multifactorial. Among them, inflammatory components like Tumor Necrosis Factor (TNF), contribute to whole-body metabolic impairment. Caloric Restriction (CR) combats metabolic diseases, but how it reduces inflammation remains understudied. We aimed to evaluate the impact of chronic CR on muscle inflammation, in particular TNF. In our study, 4-week old male Sprague-Dawley rats were fed a high-fat diet (HF, 45% Kcal of fat from lard) ad libitum for 3 months. After estimation of their energy requirement (1 month), they were then divided into three groups: HF ad libitum (OL), weight maintenance with AIN93M (9.5% Kcal from fat; ML, 100% of energy requirement), and caloric restriction (CR, AIN93M with 75% of energy requirement). This dietary intervention continued for six months. At this point, rats were sacrificed and gastrocnemius muscle was collected. CR induced a profound shift in fat and lean mass, and decreased growth factor IGF-1. Muscle qPCR analysis showed a marked decrease in inflammation and TNF (premRNA, mRNA, and protein) by CR, accompanied by Tnf promoter DNA hypermethylation. CR increased expression of histone deacetylase Sirt6 and decreased methyltransferase Suv39h1, together with decreased Tnf promoter and coding region binding of NF- κB and C/EBP-β. Following miRNA database mining, qPCR analysis revealed that CR downregulated the proinflammatory miR-19b and increased the anti-inflammatory miR-181a and its known targets. Chronic CR is able to regulate muscle-specific inflammation by targeting the NF-κB pathway as well as transcriptional and post-transcriptional regulation of Tnf gene.

Maternal high-fat diet activates hepatic interleukin-4 in rat male offspring accompanied by increased eosinophil infiltration

Interleukin-4 (IL-4) is activated as an immune response during infection or tissue injury. Epigenetic programming of maternal high-fat (HF) diet has long-term effects in the offspring. In the present study, we investigated the epigenetic regulation of IL-4 in a maternal HF diet model in the liver of adult offspring. Timed-pregnant Sprague-Dawley rats were fed either control (C) or HF diet throughout gestation and lactation. Offspring were placed on a control diet after weaning, generating C/C and HF/C groups. The liver was collected at 12 wk of age, followed by histological and molecular analysis to investigate the maternal programming effects on IL-4 by HF diet. Maternal HF diet significantly induced mRNA expression and protein level of IL-4 and promoted hypomethylation of Il4 compared with the control group. Methylation-selective PCR (MSP) confirmed that maternal HF diet increased RNA polymerase II, acetylation of histone H4, and dimethylation of histone 3 lysine 4 at the +6 kb region of Il4. Moreover, the rat eosinophil marker Siglec-F was increased and colocalized with IL-4 in the liver. In conclusion, our study indicated that IL-4 was increased in liver cells in response to maternal HF diet. This coincides with DNA hypomethylation in combination with chromatin remodeling at the +6 kb region of the 3' downstream region as well as an induced immune cell infiltration, especially eosinophil infiltration, in the liver of offspring.NEW & NOTEWORTHY The present study identifies that maternal high-fat-diet-induced IL-4 upregulation is associated with DNA hypomethylation at the +6 kb region of the 3' downstream region of the gene. Furthermore, our results confirm that the induced Il4 expression in the liver of male offspring corresponds to the induced immune cell, especially eosinophil, infiltration.

Molecular mechanisms governing offspring metabolic programming in rodent models of in utero stress

The results of different human epidemiological datasets provided the impetus to introduce the now commonly accepted theory coined as 'developmental programming', whereby the presence of a stressor during gestation predisposes the growing fetus to develop diseases, such as metabolic dysfunction in later postnatal life. However, in a clinical setting, human lifespan and inaccessibility to tissue for analysis are major limitations to study the molecular mechanisms governing developmental programming. Subsequently, studies using animal models have proved indispensable to the identification of key molecular pathways and epigenetic mechanisms that are dysregulated in metabolic organs of the fetus and adult programmed due to an adverse gestational environment. Rodents such as mice and rats are the most used experimental animals in the study of developmental programming. This review summarises the molecular pathways and epigenetic mechanisms influencing alterations in metabolic tissues of rodent offspring exposed to in utero stress and subsequently programmed for metabolic dysfunction. By comparing molecular mechanisms in a variety of rodent models of in utero stress, we hope to summarise common themes and pathways governing later metabolic dysfunction in the offspring whilst identifying reasons for incongruencies between models so to inform future work. With the continued use and refinement of such models of developmental programming, the scientific community may gain the knowledge required for the targeted treatment of metabolic diseases that have intrauterine origins.

Intricate Regulation of Phosphoenolpyruvate Carboxykinase (PEPCK) Isoforms in Normal Physiology and Disease

BACKGROUND

The phosphoenolpyruvate carboxykinase (PEPCK) isoforms are considered as rate-limiting enzymes for gluconeogenesis and glyceroneogenesis pathways. PEPCK exhibits several interesting features such as a) organelle-specific isoforms (cytosolic and a mitochondrial) in vertebrate clade, b) tissue-specific expression of isoforms and c) organism-specific requirement of ATP or GTP as a cofactor. In higher organisms, PEPCK isoforms are intricately regulated and activated through several physiological and pathological stimuli such as corticoids, hormones, nutrient starvation and hypoxia. Isoform-specific transcriptional/translational regulation and their interplay in maintaining glucose homeostasis remain to be fully understood. Mounting evidence indicates the significant involvement of PEPCK isoforms in physiological processes (development and longevity) and in the progression of a variety of diseases (metabolic disorders, cancer, Smith-Magenis syndrome).

OBJECTIVE

The present systematic review aimed to assimilate existing knowledge of transcriptional and translational regulation of PEPCK isoforms derived from cell, animal and clinical models.

CONCLUSION

Based on current knowledge and extensive bioinformatics analysis, in this review we have provided a comparative (epi)genetic understanding of PCK1 and PCK2 genes encompassing regulatory elements, disease-associated polymorphisms, copy number variations, regulatory miRNAs and CpG densities. We have also discussed various exogenous and endogenous modulators of PEPCK isoforms and their signaling mechanisms. A comprehensive review of existing knowledge of PEPCK regulation and function may enable identification of the underlying gaps to design new pharmacological strategies and interventions for the diseases associated with gluconeogenesis.

Perinatal and post-weaning exposure to an obesogenic diet promotes greater expression of nuclear factor-κB and tumor necrosis factor-α in white adipose tissue and hypothalamus of adult rats

Aim: To analyze the effects of exposure to a high-fat diet during the perinatal period and after weaning on white adipose tissue accumulation and gene expression of TNF- α and NF- κB.Method: Wistar female rats were fed with high-fat (H) or control (C) diet during pregnancy and lactation. The offspring were allocated into four groups: Control Control (CC), offspring of mothers GC, fed a control diet after weaning; Control High-fat (CH), offspring of mothers GC, fed a hight-fat diet after weaning; High-fat Control (HC), offspring of mothers GH, fed with control diet after weaning; and High-fat High-fat (HH), offspring of mothers GH, fed a H diet after weaning.Results: HH and HC groups showed increased body weight compared to CC group and increases in caloric intake, larger amount of white adipose tissue and adipocyte size compared to CC and CH groups. The HH and CH groups showed higher NF-kB expression in white adipose tissue compared to the CC and HC groups, and the HH group also showed higher TNF- α expression. In the hypothalamus, the HH and HC groups exhibited higher TNF- α expression compared to the CC and CH groups.Conclusion: Perinatal and post-weaning exposure to the high-fat diet increases the amount of white adipose tissue, adipocyte size, and expression of the inflammatory genes TNF-α and NF-kB.

Pemafibrate, a selective PPARα modulator, prevents non-alcoholic steatohepatitis development without reducing the hepatic triglyceride content

Non-alcoholic steatohepatitis (NASH) is characterized by macrovesicular steatosis with ballooning degeneration of hepatocytes, diffused lobular inflammation, and fibrosis. PPAR ligands are promising therapeutic agents in NASH; accordingly, we evaluated the effects of the first clinically available selective PPARα modulator, pemafibrate. We found that pemafibrate improves F4/80-positive macrophage accumulation, ballooning degeneration of hepatocytes, and the non-alcoholic fatty liver disease (NAFLD) activity score without affecting triglyceride (TG) accumulation in the liver of a mouse model of NASH (STAM). A global gene expression analysis indicated that pemafibrate enhances TG hydrolysis and fatty acid β-oxidation as well as re-esterification from dihydroxyacetone 3-phosphate and monoacylglycerol to TG. These changes are accompanied by the induction of genes involved in lipolysis and lipid droplet formation, along with an increased number and reduced size of lipid droplets in pemafibrate-treated livers. Pemafibrate reduced the expression of the cell adhesion molecule Vcam-1, myeloid cell markers, and inflammation- and fibrosis-related genes in STAM mice. Furthermore, pemafibrate significantly reduced VCAM-1 expression induced by high glucose in cultured human umbilical vein endothelial cells. These results suggest that pemafibrate prevents NASH development by reducing myeloid cell recruitment via interactions with liver sinusoidal endothelial cells, without altering hepatic TG accumulation.

Late-pregnancy uterine artery ligation increases susceptibility to postnatal Western diet-induced fat accumulation in adult female offspring

Stressors during the fetal and postnatal period affect the growth and developmental trajectories of offspring, causing lasting effects on physiologic regulatory systems. Here, we tested whether reduced uterine artery blood flow in late pregnancy would alter body composition in the offspring, and whether feeding offspring a western diet (WD) would aggravate these programming effects. Pregnant rats underwent bilateral uterine artery ligation (BUAL) or sham surgery on gestational day (GD)18 (term = GD22). At weaning, offspring from each group received either a normal diet (ND) or a WD. BUAL surgery increased fetal loss and caused offspring growth restriction, albeit body weights were no longer different at weaning, suggesting postnatal catch-up growth. BUAL did not affect body weight gain, fat accumulation, or plasma lipid profile in adult male offspring. In contrast, while ND-fed females from BUAL group were smaller and leaner than their sham-littermates, WD consumption resulted in excess weight gain, fat accumulation, and visceral adiposity. Moreover, WD increased plasma triglycerides and cholesterol in the BUAL-treated female offspring without any effect on sham littermates. These results demonstrate that reduced uterine artery blood flow during late pregnancy in rodents can impact body composition in the offspring in a sex-dependent manner, and these effects may be exacerbated by postnatal chronic WD consumption.

A Low Protein Diet during Gestation and Lactation Increases Hepatic Lipid Accumulation through Autophagy and Histone Deacetylase

The present study examined the mechanism of a low protein (LP) diet on hepatic lipid metabolism during gestation and lactation. Timed-pregnant Sprague-Dawley rats were fed a control or an LP diet during gestation and lactation. LP dams had increased hepatic triglyceride accumulation and significantly higher aspartate/alanine transaminase ratio, accompanied by a decrease in circulating very low-density/low-density lipoprotein ratio. LC3B (Microtubule Associated Protein 1 Light Chain 3 Beta) expression was stimulated in LP dams along with increased histone acetylation. LP diet-induced co-localization of the LC3 binding motif-interacting proteins APOB or MTTP with LC3B, suggesting autophagic degradation. HDAC3 is found necessary to prevent lipid accumulation in response to amino acid deprivation in HepG2 cells. LC3B-mediated APOB protein degradation is related to increases in lipid accumulation. Conclusion: HDAC3 regulated LC3B-induced lipid accumulation potentially through autophagic degradation of APOB and MTTP in response to amino acid limitation caused by a low protein diet.

Prenatal Choline Supplementation during High-Fat Feeding Improves Long-Term Blood Glucose Control in Male Mouse Offspring

Maternal obesity increases the risk of metabolic dysregulation in rodent offspring, especially when offspring are exposed to a high-fat (HF), obesogenic diet later in life. We previously demonstrated that maternal choline supplementation (MCS) in HF-fed mouse dams during gestation prevents fetal overgrowth and excess adiposity. In this study, we examined the long-term metabolic influence of MCS. C57BL/6J mice were fed a HF diet with or without choline supplementation prior to and during gestation. After weaning, their pups were exposed to either a HF or control diet for 6 weeks before measurements. Prenatal and post-weaning dietary treatments led to sexually dimorphic responses. In male offspring, while post-weaning HF led to impaired fasting glucose and worse glucose tolerance (p < 0.05), MCS in HF dams (HFCS) attenuated these changes. HFCS (versus maternal normal fat control) appeared to improve metabolic functioning of visceral adipose tissue during post-weaning HF feeding, preventing the elevation in leptin and increasing (p < 0.05) mRNA expression of insulin receptor substrate 1 (Irs1) that promotes peripheral insulin signaling in male offspring. In contrast, MCS had minimal effects on metabolic outcomes of female offspring. In conclusion, MCS during HF feeding in mice improves long-term blood glucose homeostasis in male offspring when they are faced with a postnatal obesogenic environment.

Epigenetic Programming and Fetal Metabolic Programming

Fetal metabolic programming caused by the adverse intrauterine environment can induce metabolic syndrome in adult offspring. Adverse intrauterine environment introduces fetal long-term relatively irreversible changes in organs and metabolism, and thus causes fetal metabolic programming leading metabolic syndrome in adult offspring. Fetal metabolic programming of obesity and insulin resistance plays a key role in this process. The mechanism of fetal metabolic programming is still not very clear. It is suggested that epigenetic programming, also induced by the adverse intrauterine environment, is a critical underlying mechanism of fetal metabolic programming. Fetal epigenetic programming affects gene expression changes and cellular function through epigenetic modifications without DNA nucleotide sequence changes. Epigenetic modifications can be relatively stably retained and transmitted through mitosis and generations, and thereby induce the development of metabolic syndrome in adult offspring. This manuscript provides an overview of the critical role of epigenetic programming in fetal metabolic programming.

Maternal Low-Fat Diet Programs the Hepatic Epigenome despite Exposure to an Obesogenic Postnatal Diet

Obesity and metabolic disease present a danger to long-term health outcomes. It has been hypothesized that epigenetic marks established during early life might program individuals and have either beneficial or harmful consequences later in life. In the present study, we examined whether maternal diet alters DNA methylation and whether such modifications persist after an obesogenic postnatal dietary challenge. During gestation and lactation, male Sprague-Dawley rats were exposed to either a high-fat diet (HF; n = 10) or low-fat diet (LF; n = 10). After weaning, all animals were fed a HF diet for an additional nine weeks. There were no differences observed in food intake or body weight between groups. Hepatic DNA methylation was quantified using both methylated DNA immunoprecipitation sequencing (MeDIP-seq) and methylation-sensitive restriction enzyme sequencing (MRE-seq). Overall, 1419 differentially methylated regions (DMRs) were identified. DMRs tended to be located in CpG shores and were enriched for genes involved in metabolism and cancer. Gene expression was measured for 31 genes in these pathways. Map3k5 and Igf1r were confirmed to be differentially expressed. Finally, we attempted to quantify the functional relevance of intergenic DMRs. Using chromatin contact data, we saw that conserved DMRs were topologically associated with metabolism genes, which were associated with differential expression of Adh5, Enox1, and Pik3c3. We show that although maternal dietary fat is unable to reverse offspring weight gain in response to a postnatal obesogenic diet, early life diet does program the hepatic methylome. Epigenetic alterations occur primarily in metabolic and cancer pathways and are associated with altered gene expression, but it is unclear whether they bear consequence later in life.

Maternal and Post-weaning High-Fat Diets Produce Distinct DNA Methylation Patterns in Hepatic Metabolic Pathways within Specific Genomic Contexts

Calorie-dense high-fat diets (HF) are associated with detrimental health outcomes, including obesity, cardiovascular disease, and diabetes. Both pre- and post-natal HF diets have been hypothesized to negatively impact long-term metabolic health via epigenetic mechanisms. To understand how the timing of HF diet intake impacts DNA methylation and metabolism, male Sprague–Dawley rats were exposed to either maternal HF (MHF) or post-weaning HF diet (PHF). At post-natal week 12, PHF rats had similar body weights but greater hepatic lipid accumulation compared to the MHF rats. Genome-wide DNA methylation was evaluated, and analysis revealed 1744 differentially methylation regions (DMRs) between the groups with the majority of the DMR located outside of gene-coding regions. Within differentially methylated genes (DMGs), intragenic DNA methylation closer to the transcription start site was associated with lower gene expression, whereas DNA methylation further downstream was positively correlated with gene expression. The insulin and phosphatidylinositol (PI) signaling pathways were enriched with 25 DMRs that were associated with 20 DMGs, including PI3 kinase (Pi3k), pyruvate kinase (Pklr), and phosphodiesterase 3 (Pde3). Together, these results suggest that the timing of HF diet intake determines DNA methylation and gene expression patterns in hepatic metabolic pathways that target specific genomic contexts.

Tissue-specific changes in Srebf1 and Srebf2 expression and DNA methylation with perinatal phthalate exposure

Perinatal exposure to endocrine disrupting chemicals negatively impacts health, but the mechanism by which such toxicants damage long-term reproductive and metabolic function is unknown. Lipid metabolism plays a pivotal role in steroid hormone synthesis as well as energy utilization and storage; thus, aberrant lipid regulation may contribute to phthalate-driven health impairments. In order to test this hypothesis, we specifically examined epigenetic disruptions in lipid metabolism pathways after perinatal phthalate exposure. During gestation and lactation, pregnant Long-Evans rat dams were fed environmentally relevant doses of phthalate mixture: 0 (CON), 200 (LO), or 1000 (HI) µg/kg body weight/day. On PND90, male offspring in the LO and HI groups had higher body weights than CON rats. Gene expression of lipid metabolism pathways was altered in testis and adipose tissue of males exposed to the HI phthalate dosage. Specifically, Srebf1 was downregulated in testis and Srebf2 was upregulated in adipose tissue. In testis of HI rats, DNA methylation was increased at two loci and reduced at one other site surrounding Srebf1 transcription start site. In adipose tissue of HI rats, we observed increased DNA methylation at one region within the first intron of Srebf2. Computational analysis revealed several potential transcriptional regulator binding sites, suggesting functional relevance of the identified differentially methylated CpGs. Overall, we show that perinatal phthalate exposure affects lipid metabolism gene expression in a tissue-specific manner possibly through altering DNA methylation of Srebf1 and Srebf2.

Perinatal phthalate and high-fat diet exposure induce sex-specific changes in adipocyte size and DNA methylation

Environmental factors such as diet and endocrine-disrupting chemicals have individually been shown to mediate metabolic function. However, the underlying mechanism by which the combination disrupts adipocyte morphology and fat storage remains unknown. The current study evaluated early-life programming by diet and phthalate exposure. During gestation and lactation, pregnant Long-Evans hooded rat dams were fed either a control (C) or high-fat (HF) diet and were orally administered one of three phthalate dosages (0, 200 or 1000 μg/kg/day), yielding six groups of offspring: C-0, C-200, C-1000, HF-0, HF-200 and HF-1000. On postnatal day (PND) 90, gonadal fat pads were collected and analyzed for histology, gene expression and DNA methylation. Differences in body weight were observed only in males. Hematoxylin and eosin staining revealed larger adipocyte size in HF-0 vs. C-0 females. Exposure to 200 or 1000 μg/kg/day phthalates modulated diet-induced changes in adipose morphology. Compared to C-0 females, HF-0 females also had higher expression of the adipogenesis gene Wnt receptor, frizzled 1 (Fzd1) and the triglyceride cleaving enzyme lipoprotein lipase (Lpl). These increases in gene expression were accompanied by lower DNA methylation surrounding the transcription start sites of the two genes. Diet-driven effects were observed in unexposed females but not in phthalate-treated rats. Results suggest a sex-specific association between perinatal HF diet and body weight, adipocyte size and DNA methylation. Perinatal phthalate exposure appears to produce a phenotype that more closely resembles HF-fed animals.

Epigenetic regulation of carnitine palmitoyltransferase 1 (Cpt1a) by high fat diet

Carnitine palmitoyltransferase 1 (Cpt1a) is a rate-limiting enzyme that mediates the transport of fatty acids into the mitochondria for subsequent beta-oxidation. The objective of this study was to uncover how diet mediates the transcriptional regulation of Cpt1a. Pregnant Sprague Dawley rats were exposed to either a high-fat (HF) or low-fat control diet during gestation and lactation. At weaning, male offspring received either a HF or control diet, creating 4 groups: lifelong control diet (C/C; n = 12), perinatal HF diet (HF/C; n = 9), post-weaning HF diet (C/HF; n = 10), and lifelong HF diet (HF/HF; n = 10). Only HF/HF animals had higher hepatic Cpt1a mRNA expression than C/C. Epigenetic analysis revealed reduced DNA methylation (DNAMe) and increased histone 3 lysine 4 dimethylation (H3K4Me2) upstream and within the promoter of Cpt1a in the HF/HF group. This was accompanied by increased peroxisome proliferator activated receptor alpha (PPARα) and CCAAT/enhancer binding protein beta (C/EBPβ) binding directly downstream of the Cpt1a transcription start site within the first intron. Findings were confirmed in rat hepatoma H4IIEC3 cells treated with non-esterified fatty acid (NEFA). After 12 h of NEFA treatment, there was an enrichment of SWI/SNF related matrix associated actin dependent regulator of chromatin subfamily D member 1 (BAF60a or SMARCD1) in the first intron of Cpt1a. We conclude that dietary fat elevates hepatic Cpt1a expression via a highly coordinated transcriptional mechanism involving increased H3K4Me2, reduced DNAMe, and recruitment of C/EBPβ, PPARα, PGC1α, and BAF60a to the gene.

Involvement of glucocorticoid prereceptor metabolism and signaling in rat visceral adipose tissue lipid metabolism after chronic stress combined with high-fructose diet

Both fructose overconsumption and increased glucocorticoids secondary to chronic stress may contribute to overall dyslipidemia. In this study we specifically assessed the effects and interactions of dietary fructose and chronic stress on lipid metabolism in the visceral adipose tissue (VAT) of male Wistar rats. We analyzed the effects of 9-week 20% high fructose diet and 4-week chronic unpredictable stress, separately and in combination, on VAT histology, glucocorticoid prereceptor metabolism, glucocorticoid receptor subcellular redistribution and expression of major metabolic genes. Blood triglycerides and fatty acid composition were also measured to assess hepatic Δ9 desaturase activity. The results showed that fructose diet increased blood triglycerides and Δ9 desaturase activity. On the other hand, stress led to corticosterone elevation, glucocorticoid receptor activation and decrease in adipocyte size, while phosphoenolpyruvate carboxykinase, adipose tissue triglyceride lipase, FAT/CD36 and sterol regulatory element binding protein-1c (SREBP-1c) were increased, pointing to VAT lipolysis and glyceroneogenesis. The combination of stress and fructose diet was associated with marked stimulation of fatty acid synthase and acetyl-CoA carboxylase mRNA level and with increased 11β-hydroxysteroid dehydrogenase type 1 and hexose-6-phosphate dehydrogenase protein levels, suggesting a coordinated increase in hexose monophosphate shunt and de novo lipogenesis. It however did not influence the level of peroxisome proliferator-activated receptor-gamma, SREBP-1c and carbohydrate responsive element-binding protein. In conclusion, our results showed that only combination of dietary fructose and stress increase glucocorticoid prereceptor metabolism and stimulates lipogenic enzyme expression suggesting that interaction between stress and fructose may be instrumental in promoting VAT expansion and dysfunction.

Dietary Modulation of the Epigenome

Epigenetics is the study of heritable mechanisms that can modify gene activity and phenotype without modifying the genetic code. The basis for the concept of epigenetics originated more than 2,000 yr ago as a theory to explain organismal development. However, the definition of epigenetics continues to evolve as we identify more of the components that make up the epigenome and dissect the complex manner by which they regulate and are regulated by cellular functions. A substantial and growing body of research shows that nutrition plays a significant role in regulating the epigenome. Here, we critically assess this diverse body of evidence elucidating the role of nutrition in modulating the epigenome and summarize the impact such changes have on molecular and physiological outcomes with regards to human health.

Effect of diet in females (F1) from prenatally undernourished mothers on metabolism and liver function in the F2 progeny is sex-specific

PURPOSE

Poor maternal nutrition sensitises to the development of metabolic diseases and obesity in adulthood over several generations. The prevalence increases when offspring is fed with a high-fat (HF) diet after weaning. This study aims to determine whether such metabolic profiles can be transmitted to the second generation and even aggravated when the mothers were exposed to overnutrition, with attention to potential sex differences.

METHODS

Pregnant Wistar rats were subjected to ad libitum (control) or 70% food-restricted diet (FR) during gestation (F0). At weaning, F1 females were allocated to three food protocols: (1) standard diet prior to and throughout gestation and lactation, (2) HF diet prior to and standard diet throughout gestation and lactation, and (3) HF diet prior to and throughout gestation and lactation. F2 offspring was studied between 16 and 32 weeks of age.

RESULTS

FR-F2 offspring on standard diet showed normal adiposity and had no significant metabolic alterations in adulthood. Maternal HF diet resulted in sex-specific effects with metabolic disturbances more apparent in control offspring exposed to HF diet during gestation and lactation. Control offspring displayed glucose intolerance associated with insulin resistance in females. Female livers overexpressed lipogenesis genes and those of males the genes involved in lipid oxidation. Gene expression was significantly attenuated in the FR livers. Increased physical activity associated with elevated corticosterone levels was observed in FR females on standard diet and in all females from overnourished mothers.

CONCLUSIONS

Maternal undernutrition during gestation (F0) improves the metabolic health of second-generation offspring with more beneficial effects in females.

Sex-specific Alterations in Serology and the Expression of Liver FATP4 Protein in Offspring Exposed to High-Fat Diet during Pregnancy and/or Lactation

Changes in dietary composition will have a significant impact on the nutritional status of the mother and the offspring. To examine the relevant hormone level changes during lactation and the expression of fatty acid transporters in the placenta and liver under the condition of a high-fat (HF) diet, we established HF animal models and conducted a cross-fostering program to mimic the shift in diet. On gestation day (GD)18, the weight of placenta in the HF group was significantly higher than that in the control group (p < 0.05). HF-fed male pups had a significantly lower serum insulin level, but the same phenomenon was not found in females. On the contrary, serum triacylglycerol (TAG) level presented a tendency to decrease only in female offspring. Oil red O staining showed lipid accumulation in the HF diet offspring livers. The mRNA levels of FATP4 in the placenta in the HF diet group were significantly upregulated compared to the control diet group (p < 0.05). High-fat diet (HFD) consumption also altered the liver mRNA levels of FATP4, SREBP-1, and SCD-1 in the male offspring, while the changes in protein levels of FATP4 were not observed in either sex. In conclusion, maternal HF diet has a profound impact on offspring growth, metabolism, and the risk of metabolic disorders, which would depend on the exposure period of pregnancy and lactation.

TRIENNIAL GROWTH AND DEVELOPMENT SYMPOSIUM: Molecular mechanisms related to bovine intramuscular fat deposition in the longissimus muscle

The intramuscular fat (IMF) content of the LM, also known as marbling, is particularly important in determining the price of beef in Korea, Japan, and the United States. Deposition of IMF is influenced by both genetic (e.g., breed, gender, and genotype) and nongenetic factors (e.g., castration, nutrition, stressors, animal weight, and age). Castration of bulls markedly increases deposition of IMF, resulting in improved beef quality. Here, we present a comparative gene expression approach between bulls and steers. Transcriptomic and proteomic studies have demonstrated that the combined effects of increases in lipogenesis, fatty acid uptake, and fatty acid esterification and decreased lipolysis are associated with increased IMF deposition in the LM. Several peripheral tissues (LM, adipose tissues, and the liver) are involved in lipid metabolism. Therefore, understanding the significance of the tissue network in lipid metabolism is important. Here, we demonstrate that lipid metabolism in LM tissues is crucial for IMF deposition, whereas lipid metabolism in the liver plays only a minor role. Metabolism of body fat and IMF deposition in bovine species has similarities with these processes in metabolic diseases, such as obesity in humans and rodents. Extensive studies on metabolic diseases using epigenome modification (DNA methylation, histone modification, and microRNA), microbial metagenomics, and metabolomics have been performed in humans and rodents, and new findings have been reported using these technologies. The importance of applying "omics" fields (epigenomics, metagenomics, and metabolomics) to the study of IMF deposition in cattle is described. New information on the molecular mechanisms of IMF deposition may be used to design nutritional or genetic methods to manipulate IMF deposition and to modify fatty acid composition in beef cattle. Applying nutrigenomics could maximize the expression of genetic potential of economically important traits (e.g., marbling) in animals.

Postnatal diet remodels hepatic DNA methylation in metabolic pathways established by a maternal high-fat diet

Aim: We investigate how postweaning diet may modify the epigenetic landscape to meet metabolic demands later in life. Methods: Sprague-Dawley rats were exposed to a high-fat (HF) diet during gestation and lactation. At weaning, male offspring were placed either on an HF diet (HF/HF) or a control diet (HF/C). Methylation-dependent immunoprecipitation sequencing and methylation-sensitive restriction enzyme sequencing were used to quantify hepatic DNA methylation. Results: Out of the 3966 identified differentially methylated regions, 37% were mapped to gene bodies while 6% fell within promoter or downstream regions. Differentially methylated genes were clustered in the type II diabetes mellitus and the adipocytokine signaling pathways. Conclusion: Our results indicate that compared with a lifelong HF diet, offspring exposed to a new postweaning control diet are able to remodel the hepatic epigenome, emphasizing the dynamic nature of the methylome even after early life.

Prenatal Exposure to a Maternal High-Fat Diet Affects Histone Modification of Cardiometabolic Genes in Newborn Rats

Infants born to women with diabetes or obesity are exposed to excess circulating fuels during fetal heart development and are at higher risk of cardiac diseases. We have previously shown that late-gestation diabetes, especially in conjunction with a maternal high-fat (HF) diet, impairs cardiac functions in rat-offspring. This study investigated changes in genome-wide histone modifications in newborn hearts from rat-pups exposed to maternal diabetes and HF-diet. Chromatin-immunoprecipitation-sequencing revealed a differential peak distribution on gene promoters in exposed pups with respect to acetylation of lysines 9 and 14 and to trimethylation of lysines 4 and 27 in histone H3 (all, false discovery rate, FDR < 0.1). In the HF-diet exposed offspring, 54% of the annotated genes showed the gene-activating mark trimethylated lysine 4. Many of these genes (1) are associated with the "metabolic process" in general and particularly with "positive regulation of cholesterol biosynthesis" (FDR = 0.03); (2) overlap with 455 quantitative trait loci for blood pressure, body weight, serum cholesterol (all, FDR < 0.1); and (3) are linked to cardiac disease susceptibility/progression, based on disease ontology analyses and scientific literature. These results indicate that maternal HF-diet changes the cardiac histone signature in offspring suggesting a fuel-mediated epigenetic reprogramming of cardiac tissue in utero.

Developmental origins of NAFLD: a womb with a clue

Changes in the maternal environment leading to an altered intrauterine milieu can result in subtle insults to the fetus, promoting increased lifetime disease risk and/or disease acceleration in childhood and later in life. Particularly worrisome is that the prevalence of NAFLD is rapidly increasing among children and adults, and is being diagnosed at increasingly younger ages, pointing towards an early-life origin. A wealth of evidence, in humans and non-human primates, suggests that maternal nutrition affects the placenta and fetal tissues, leading to persistent changes in hepatic metabolism, mitochondrial function, the intestinal microbiota, liver macrophage activation and susceptibility to NASH postnatally. Deleterious exposures in utero include fetal hypoxia, increased nutrient supply, inflammation and altered gut microbiota that might produce metabolic clues, including fatty acids, metabolites, endotoxins, bile acids and cytokines, which prime the infant liver for NAFLD in a persistent manner and increase susceptibility to NASH. Mechanistic links to early disease pathways might involve shifts in lipid metabolism, mitochondrial dysfunction, pioneering gut microorganisms, macrophage programming and epigenetic changes that alter the liver microenvironment, favouring liver injury. In this Review, we discuss how maternal, fetal, neonatal and infant exposures provide developmental clues and mechanisms to help explain NAFLD acceleration and increased disease prevalence. Mechanisms identified in clinical and preclinical models suggest important opportunities for prevention and intervention that could slow down the growing epidemic of NAFLD in the next generation.

Early life programming and the risk of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, type 2 diabetes and cardiovascular disease and can be considered the hepatic manifestation of the metabolic syndrome. NAFLD represents a spectrum of disease, from the relatively benign simple steatosis to the more serious non-alcoholic steatohepatitis, which can progress to liver cirrhosis, hepatocellular carcinoma and end-stage liver failure, necessitating liver transplantation. Although the increasing prevalence of NAFLD in developed countries has substantial implications for public health, many of the precise mechanisms accounting for the development and progression of NAFLD are unclear. The environment in early life is an important determinant of cardiovascular disease risk in later life and studies suggest this also extends to NAFLD. Here we review data from animal models and human studies which suggest that fetal and early life exposure to maternal under- and overnutrition, excess glucocorticoids and environmental pollutants may confer an increased susceptibility to NAFLD development and progression in offspring and that such effects may be sex-specific. We also consider studies aimed at identifying potential dietary and pharmacological interventions aimed at reducing this risk. We suggest that further human epidemiological studies are needed to ensure that data from animal models are relevant to human health.

High fat diet and exercise lead to a disrupted and pathogenic DNA methylome in mouse liver

High-fat diet consumption and sedentary lifestyle elevates risk for obesity, non-alcoholic fatty liver disease, and cancer. Exercise training conveys health benefits in populations with or without these chronic conditions. Diet and exercise regulate gene expression by mediating epigenetic mechanisms in many tissues; however, such effects are poorly documented in the liver, a central metabolic organ. To dissect the consequences of diet and exercise on the liver epigenome, we measured DNA methylation, using reduced representation bisulfite sequencing, and transcription, using RNA-seq, in mice maintained on a fast food diet with sedentary lifestyle or exercise, compared with control diet with and without exercise. Our analyses reveal that genome-wide differential DNA methylation and expression of gene clusters are induced by diet and/or exercise. A combination of fast food and exercise triggers extensive gene alterations, with enrichment of carbohydrate/lipid metabolic pathways and muscle developmental processes. Through evaluation of putative protective effects of exercise on diet-induced DNA methylation, we show that hypermethylation is effectively prevented, especially at promoters and enhancers, whereas hypomethylation is only partially attenuated. We assessed diet-induced DNA methylation changes associated with liver cancer-related epigenetic modifications and identified significant increases at liver-specific enhancers in fast food groups, suggesting partial loss of liver cell identity. Hypermethylation at a subset of gene promoters was associated with inhibition of tissue development and promotion of carcinogenic processes. Our study demonstrates extensive reprogramming of the epigenome by diet and exercise, emphasizing the functional relevance of epigenetic mechanisms as an interface between lifestyle modifications and phenotypic alterations.

Role of placental insufficiency and intrauterine growth restriction on the activation of fetal hepatic glucose production

Glucose is the major fuel for fetal oxidative metabolism. A positive maternal-fetal glucose gradient drives glucose across the placenta and is sufficient to meet the demands of the fetus, eliminating the need for endogenous hepatic glucose production (HGP). However, fetuses with intrauterine growth restriction (IUGR) from pregnancies complicated by placental insufficiency have an early activation of HGP. Furthermore, this activated HGP is resistant to suppression by insulin. Here, we present the data demonstrating the activation of HGP in animal models, mostly fetal sheep, and human pregnancies with IUGR. We also discuss potential mechanisms and pathways that may produce and support HGP and hepatic insulin resistance in IUGR fetuses.

Mouse Maternal High-Fat Intake Dynamically Programmed mRNA m⁶A Modifications in Adipose and Skeletal Muscle Tissues in Offspring

Epigenetic mechanisms have an important role in the pre- and peri-conceptional programming by maternal nutrition. Yet, whether or not RNA m⁶A methylation—an old epigenetic marker receiving increased attention recently—is involved remains an unknown question. In this study, mouse high-fat feeding prior to conception was shown to induce overweight and glucose intolerant dams, which then continued to be exposed to a high-fat diet during gestation and lactation. The dams on a standard diet throughout the whole experiment were used as a control. Results showed that maternal high-fat intake impaired postnatal growth in male offspring, indicated by decreased body weight and Lee’s index at 3, 8 and 15 weeks old, but the percentages of visceral fat and tibialis anterior relative to the whole body weights were significantly increased at eight weeks of age. The maternal high-fat exposure significantly increased mRNA N⁶-methyladenosine (m⁶A) levels in visceral fat at three weeks old, combined with downregulated Fat mass and obesity-associated gene (FTO) and upregulated Methyltransferase like 3 (METTL3) transcription, and these changes were reversed at eight weeks of age. In the tibialis anterior muscle, the maternal high-fat diet significantly enhanced m⁶A modifications at three weeks, and lowered m⁶A levels at 15 weeks of age. Accordingly, FTO transcription was significantly inhibited at three weeks and stimulated at 15 weeks of age, and METTL3 transcripts were significantly improved at three weeks. Interestingly, both FTO and METTL3 transcription was significantly elevated at eight weeks of age, and yet the m⁶A modifications remained unchanged. Our study showed that maternal high-fat intake could affect mRNA m⁶A modifications and its related genes in offspring in a tissue-specific and development-dependent way, and provided an interesting indication of the working of the m⁶A system during the transmission from maternal nutrition to subsequent generations.