Sex-Specific Muscular Maturation Responses Following Prenatal Exposure to Methylation-Related Micronutrients in Pigs

Maternal diet induces persistent DNA methylation changes in the muscle of beef calves

Maternal nutrition during pregnancy can induce epigenetic alterations in the fetal genome, such as changes in DNA methylation. It remains unclear whether these epigenetic alterations due to changes in maternal nutrition are transitory or persist over time. Here, we hypothesized that maternal methionine supplementation during preconception and early pregnancy could alter the fetal epigenome, and some of these alterations could persist throughout different developmental stages of the offspring. Beef cows were randomly assigned to either a control or a methionine-rich diet from - 30 to + 90 d, relative to the beginning of the breeding season. The methylome of loin muscle from the same bull calves (n = 10 per maternal diet) at 30 and 200 days of age were evaluated using whole-genome bisulfite sequencing. Notably, a total of 28,310 cytosines showed persistent methylation differences over time between maternal diets (q-value < 0.10, methylation change > 20%). These differentially methylated cytosines were in the transcription start sites, exons, or splice sites of 341 annotated genes. Over-representation analysis revealed that these differentially methylated genes are involved in muscle contraction, DNA and histone methylation, mitochondrial function, reactive oxygen species homeostasis, autophagy, and PI3K signaling pathway, among other functions. In addition, some of the persistently, differentially methylated cytosines were found in CpG islands upstream of genes implicated in mitochondrial activities and immune response. Overall, our study provides evidence that a maternal methionine-rich diet altered fetal epigenome, and some of these epigenetic changes persisted over time.

Genetic regulation and variation of expression of miRNA and mRNA transcripts in fetal muscle tissue in the context of sex, dam and variable fetal weight

BACKGROUND

Impaired skeletal muscle growth in utero can result in reduced birth weight and pathogenesis of intrauterine growth restriction. Fetal and placental growth is influenced by many factors including genetic, epigenetic and environmental factors. In fact, the sex and genotype of the fetus itself, as well as the mother providing it with a suitable environment, influence the growth of the fetus. Hence, our goal was to decipher and elucidate the molecular pathways of developmental processes mediated by miRNAs and mRNAs in fetal muscle tissue in the context of sex, dam, and fetal weight. Therefore, we analyse the variation of miRNA and mRNA expression in relation to these factors. In addition, the coincidence of genetic regulation of these mRNAs and miRNAs, as revealed by expression quantitative trait loci (eQTL) analyses, with sex-, mother- and weight-associated expression was investigated.

METHODS

A three-generation pig F2 population (n = 118) based on reciprocal crossing of German Landrace (DL) and Pietrain (Pi) was used. Genotype information and transcriptomic data (mRNA and miRNA) from longissimus dorsi muscle (LDM) of pig fetuses sampled at 63 days post-conception (dpc) were used for eQTL analyses.

RESULTS

The transcript abundances of 13, 853, and 275 probe-sets were influenced by sex, dam and fetal weight at 63 dpc, respectively (FDR < 5%). Most of significant transcripts affected by sex were located on the sex chromosomes including KDM6A and ANOS1 or autosomes including ANKS1B, LOC100155138 and miR-153. The fetal muscle transcripts associated with fetal weight indicated clearer metabolic directions than maternally influenced fetal muscle transcripts. Moreover, coincidence of genetic regulation (eQTL) and variation in transcript abundance due to sex, dam and fetal weight were identified.

CONCLUSIONS

Integrating information on eQTL, sex-, dam- and weight-associated differential expression and QTL for fetal weight allowed us to identify molecular pathways and shed light on the basic biological processes associated with differential muscle development in males and females, with implications for adaptive fetal programming.

Maternal Methyl-Donor Micronutrient Supplementation During Pregnancy Promotes Skeletal Muscle Differentiation and Maturity in Newborn and Weaning Pigs

Adequate maternal methyl-donor micronutrient (MET) intake is an important determinant of the organ development and metabolic renovation of offspring. The mechanism involved in skeletal myogenesis and the effect of MET supplementation during pregnancy on the maternal body remain unclear. Thus, this study aimed to investigate the potential effect of methyl donor micronutrients (MET) on skeletal muscle development and metabolism in offspring using pig models. Forty-three Duroc × Erhualian gilts were assigned to two dietary groups during gestation: control diet (CON) and CON diet supplemented with MET (folic acid, methionine, choline, vitamin B6, and vitamin B12). The results showed that maternal MET exposure during pregnancy significantly increased the concentrations of protein, triiodothyronine (T3), and thyroxine (T4) in colostrum and methyl metabolites, including S-adenosylmethionine (SAM), S-adenosyl-L-homocysteine (SAH), 5-methyl-tetrahydrofolate (5-MTHF), and betaine, in the maternal and offspring umbilical vein serum. A similar pattern was demonstrated in the body weight gain and myofiber diameters in offspring. In addition, maternal MET supplementation significantly increased the concentration of offspring serum insulin-like growth factor 1 (IGF-1), T3, and T4; upregulated the mRNA expression of IGF-1 and IGF-1 receptor (IGF-1r) and the phosphorylation level of protein kinases in offspring longissimus dorsi muscle; and upregulated the expression of myogenic genes and fast myosin heavy chain (fast MyHC) in offspring skeletal muscle. Supplementing sows with higher levels of MET during gestation may promote skeletal muscle differentiation and maturity and improve the skeletal muscle mass of the piglets.

Gestational Exposure to Bisphenol A and Bisphenol S Leads to Fetal Skeletal Muscle Hypertrophy Independent of Sex

Gestational exposure to bisphenol A (BPA) can lead to offspring insulin resistance. However, despite the role that the skeletal muscle plays in glucose homeostasis, it remains unknown whether gestational exposure to BPA, or its analog bisphenol S (BPS), impairs skeletal muscle development. We hypothesized that gestational exposure to BPA or BPS will impair fetal muscle development and lead to muscle-specific insulin resistance. To test this, pregnant sheep (n = 7-8/group) were exposed to BPA or BPS from gestational day (GD) 30 to 100. At GD120, fetal skeletal muscle was harvested to evaluate fiber size, fiber type, and gene and protein expression related to myogenesis, fiber size, fiber type, and inflammation. Fetal primary myoblasts were isolated to evaluate proliferation and differentiation. In fetal skeletal muscle, myofibers were larger in BPA and BPS groups in both females and males. BPA females had higher MYH1 (reflective of type-IIX fast glycolytic fibers), whereas BPS females had higher MYH2 and MYH7, and higher myogenic regulatory factors (Myf5, MyoG, MyoD, and MRF4) mRNA expression. No differences were observed in males. Myoblast proliferation was not altered in gestationally BPA- or BPS-exposed myoblasts, but upon differentiation, area and diameter of myotubes were larger independent of sex. Females had larger myofibers and myotubes than males in all treatment groups. In conclusion, gestational exposure to BPA or BPS does not result in insulin resistance in fetal myoblasts but leads to fetal fiber hypertrophy in skeletal muscle independent of sex and alters fiber type distribution in a sex-specific manner.

Folate treatment of pregnant rat dams abolishes metabolic effects in female offspring induced by a paternal pre-conception unhealthy diet

AIMS/HYPOTHESIS

Paternal high-fat diet prior to mating programmes impaired glucose tolerance in female offspring. We examined whether the metabolic consequences in offspring could be abolished by folate treatment of either the male rats before mating or the corresponding female rats during pregnancy.

METHODS

Male F0 rats were fed either control diet or high-fat, high-sucrose and high-salt diet (HFSSD), with or without folate, before mating. Male rats were mated with control-diet-fed dams. After mating, the F0 dams were fed control diet with or without folate during pregnancy.

RESULTS

Male, but not female offspring of HFSSD-fed founders were heavier than those of control-diet-fed counterparts (p < 0.05 and p = 0.066 in males and females, respectively). Both male and female offspring of HFSSD-fed founders were longer compared with control (p < 0.01 for both sexes). Folate treatment of the pregnant dams abolished the effect of the paternal diet on the offspring's body length (p ˂ 0.05). Female offspring of HFSSD-fed founders developed impaired glucose tolerance, which was restored by folate treatment of the dams during pregnancy. The beta cell density per pancreatic islet was decreased in offspring of HFSSD-fed rats (-20% in male and -15% in female F1 offspring, p ˂ 0.001 vs controls). Folate treatment significantly increased the beta cell density (4.3% and 3.3% after folate supplementation given to dams and founders, respectively, p ˂ 0.05 vs the offspring of HFSSD-fed male rats). Changes in liver connective tissue of female offspring of HFSSD-fed founders were ameliorated by treatment of dams with folate (p ˂ 0.01). Hepatic Ppara gene expression was upregulated in female offspring only (1.51-fold, p ˂ 0.05) and was restored in the female offspring by folate treatment (p ˂ 0.05). We observed an increase in hepatic Lcn2 and Tmcc2 expression in female offspring born to male rats exposed to an unhealthy diet during spermatogenesis before mating (p ˂ 0.05 vs controls). Folate treatment of the corresponding dams during pregnancy abolished this effect (p ˂ 0.05). Analysis of DNA methylation levels of CpG islands in the Ppara, Lcn2 and Tmcc2 promoter regions revealed that the paternal unhealthy diet induced alterations in the methylation pattern. These patterns were also affected by folate treatment. Total liver DNA methylation was increased by 1.52-fold in female offspring born to male rats on an unhealthy diet prior to mating (p ˂ 0.05). This effect was abolished by folate treatment during pregnancy (p ˂ 0.05 vs the offspring of HFSSD-fed male rats).

CONCLUSIONS/INTERPRETATION

Folate treatment of pregnant dams restores effects on female offspring's glucose metabolism induced by pre-conception male founder HFSSD.