195 Maternal Impact on Fetal Muscle and Adipose Tissue Development

Tissues and organs are actively developing during the fetal stage, which is sensitive to nutritional alteration and exerts long-term impacts on offspring performance. Both muscle and adipose tissue are derived from the dermomyotome during the early embryonic stage, and their common origins provide an opportunity to promote myogenic instead of adipogenic differentiation, which enhances the lean/fat ratio of offspring. In previous studies with sheep and cattle, we found that maternal nutrient deficiency reduces fetal myogenesis and the lean/fat ratio of offspring. Stress is common in animals during pregnancy, and we examined the impacts of maternal stress induced by dexamethasone on fetal muscle and adipose development. We found that maternal stress impairs fetal muscle and brown adipose tissue (BAT) development. Mechanistically, we found that maternal stress suppresses mitochondrial biogenesis during fetal muscle and BAT development by elevating DNA methylation in the promoter of peroxisome proliferator-activated receptor-gamma coactivator α (PGC-1α), which persists in offspring muscle and BAT, generating lasting effects on the functions of muscle and adipose tissue. In short, available data clearly show that maternal nutrition and other physiological factors have profound impacts on fetal development, which programs offspring performance. Understanding related mechanisms are important for effective and precise management of animals during gestation in order to enhance production efficiency of offspring.

302 Vitamin and Mineral Supplementation and Rate of Gain in Beef Heifers: Effects on Fetal Trace Mineral Reserves at Day 83 of Gestation

Thirty-five crossbred Angus heifers (body weight = 359.5 >± 7.1 kg) were randomly assigned to a 2 × 2 factorial design to evaluate the effects of vitamin and mineral supplementation [VMSUP; supplemented (VTM) vs. unsupplemented (NoVTM)] and rate of gain [GAIN; low gain (LG), 0.28 kg/d vs. moderate gain (MG), 0.79 kg/d] during the first 83 d of gestation on trace mineral concentrations in fetal liver, muscle, and allantoic (ALF) and amniotic (AMF) fluids. The VTM treatment (113 g supplement•heifer-1•d-1) was initiated a minimum 71 d before breeding. At breeding, heifers were either maintained on the basal diet (LG) or received the MG diet by adding a protein/energy supplement to the basal diet. On d 83 of gestation, samples of fetal liver, muscle, ALF, and AMF were collected and analyzed for trace mineral concentrations. In fetal liver, Se, Cu, Mn, and Co concentrations were greater (P ≤ 0.04) for VTM than NoVTM, while Mo and Co greater (P ≤ 0.04) for LG than MG. In fetal muscle, VTM increased (P ≤ 0.02) concentrations of Se and Zn, whereas LG increased (P < 0.01) Zn. In ALF, Mo concentrations were affected (P = 0.03) by a VMSUP × GAIN interaction, with VTM-MG greater than NoVTM-MG; while VTM increased (P < 0.01) concentrations of Se and Co. Trace mineral concentrations were not affected (P ≥ 0.13) in AMF. In conclusion, VTM increased fetal liver Se, Cu, Mn, and Co concentrations; fetal muscle Se and Zn; and ALF Se and Co; while LG increased fetal liver Mo and Co concentrations and fetal muscle Zn. Our results confirm that managerial decisions associated with vitamin and mineral supplementation and rate of gain can alter fetal reserves of trace elements during early pregnancy.

Maternal High-Fat Diet Increases Fetal Muscle Fat Metabolism and Fatty Acid Transporter Expression in an Ovine Model

Objectives Excessive maternal dietary fat consumption during pregnancy may be linked to adverse effects on offspring health, including greater risk of developing metabolic syndrome later in life. Metabolic syndrome is generally considered to be a preventable condition, but the extent to which it is “programmed” during fetal development remains unclear. The aim of this study was to determine the effect of a maternal high-fat diet (MHFD) during pregnancy on fetal muscle oxidative metabolism and related protein and mRNA expressions in an ovine model. Methods White-faced ewes were fed either a control diet (Show-rite NewCo Lamb Feed-17% protein, 5% Fat) or a high-fat diet (Show-rite NewCo Lamb Feed + 6% Rumen-protected Fat) from 2–3 weeks before pregnancy until mid-gestation (75 days), when a C-section was performed to collect the placenta and fetal tissues for analysis. Results MHFD tended to increase fetal body and organ weights, but only significantly increased fetal body length and liver mass (P < 0.05). MHFD increased mRNA expression of placental (cotyledon) fatty acid transport protein-1 (FATP-1) and peroxisome proliferator activated receptor gamma, suggesting an upregulation of placental fatty acid metabolism and transport. Fetal muscle fatty acid oxidation capacity was greater in animals from MHFD pregnancies, with no effect on pyruvate oxidation. This was associated with greater fetal muscle mRNA and protein expression of FATP4, while mRNA expression glucose transporters (GLUT1 and GLUT3) decreased. Muscle expression of insulin signaling enzymes reflected a mild decreases in insulin sensitivity, but these did not reach statistical significance. Conclusions These studies indicate that MHFD induces an increase in placental and fetal muscle fatty acid transport and oxidation capacity, and favors lower blood glucose uptake compared to controls. Whether these shifts in fetal metabolism predispose offspring from MHFD pregnancies to elevated blood sugar and Type 2 diabetes later in life merits further investigation. Funding Sources Colorado Agricultural Experiment Station.

Exercise Intergenerationally Drives Muscle-Based Thermogenesis and Myogenesis in Offspring Impaired Due to Maternal Obesity

Objectives Maternal obesity (MO) predisposes metabolic dysfunction in offspring muscle. Skeletal muscle-dependent non-shivering thermogenesis (NST) is emerging as a critical mechanism for maintaining energy homeostasis, but the effects of maternal exercise on muscle-based thermogenesis in offspring remains unexplored. In addition, the impact of maternal obesity and exercise on fetal muscle development is unclear, which will also be examined. The objective of the current study is to explore the effects of maternal exercise on muscle-based thermogenesis and myogenesis in fetuses impaired due to MO. Methods Female C57BL/6 J mice were randomized and assigned to either control (CON, 10 kcal% from fat) or obesogenic diet (OB, 60 kcal% from fat) for 8 weeks to induce obesity and then mated. Then, pregnant mice in obesogenic diet were further separated into two groups with/without exercise (daily 60 min exercise) during pregnancy, which resulted in three treatments: control (CON), OB, and OB-EX (n = 6 per group). Fetal skeletal muscles were collected at embryonic day 18.5 (E18.5). In another cohort of animals, maternal mice were allowed to give birth and surface temperature of neonates was measured. Statistical analysis were conducted using one way analysis of variance (ANOVA); a pregnancy/litter was considered as an experimental unit. Results OB reduced surface temperature of neonates (P < 0.01). In E18.5 fetal muscle, OB downregulated muscle-based thermogenic gene expression (P < 0.05), including Sln, Serca2, and Ryr1. In addition, the expression of mitochondriogenic genes (P < 0.05), including Ppargc1a and Tfam, was also reduced in OB fetal female and male muscle. These adverse changes were prevented due to exercise during pregnancy. Furthermore, maternal exercise protected against the downregulation of myogenesis-related gene expression, including MyoD, Myogenin, Myf5, and Pax7, due to MO. Conclusions Exercise during pregnancy enhanced muscle-based thermogenic gene expression and myogenesis which were impaired due to MO, suggesting that maternal exercise intergenerationally improves metabolic health of offspring. Funding Sources Supported by NIH Grant R01HD067449.

PSIV-8 Effects of restricted maternal nutrition and re-alimentation on fetal muscle development from mid to late gestation in sheep

Inadequate maternal nutrition during gestation negatively impacts offspring muscle development, which may be attenuated by re-alimentation. We hypothesized that restricted maternal nutrition would alter fetal muscle fiber cross-sectional area (CSA) and the percent of Pax7(+) progenitor cells. To test this, 48 primiparous ewes, pregnant with singletons, were fed 100% of NRC requirements (CON) between days 25 and 50 of gestation. At day 50 of gestation, seven ewes were euthanized for fetal sample collection. The remaining ewes were fed either CON or 60% NRC requirements (RES). At day 90 of gestation, seven ewes per diet were euthanized for fetal sample collection. The remaining ewes were maintained on their current diet (CON-CON, RES-RES) or switched to the alternate diet (CON-RES, RES-CON). At day 130 of gestation, all ewes (n = 6 or 7 ewes/diet) were euthanized, and fetal samples were collected. On days 90 and 130, fetal longissimus (LM) and triceps brachii (TB) were collected and immunostained for enumeration of Pax7(+) cells and muscle fiber CSA. The percent of Pax7(+) cells was determined by dividing the number of Pax7(+) cells by the total number of cells. At day 90 of gestation, the percent of Pax7(+) cells was less (P < 0.01) in the TB of RES compared with CON. At day 130, fiber CSA was greater (P < 0.04) in RES-CON compared with CON-CON, CON-RES, and RES-CON in the TB, and was greater (P < 0.02) in RES-CON compared with RES-RES and CON-RES in the LM. An effect of maternal nutrition was not observed for the percent of Pax7(+) cells in the LM, or for CSA at day 90 in either muscle. Thus, restricted maternal nutrition during early to mid-gestation alters the percent of Pax7(+) cells at mid-gestation in a muscle specific manner. Re-alimentation during late gestation increased fiber CSA, demonstrating that re-alimentation alters fetal muscle development.

Increased pyruvate dehydrogenase activity in skeletal muscle of growth-restricted ovine fetuses

Fetal sheep with placental insufficiency-induced intrauterine growth restriction (IUGR) have lower fractional rates of glucose oxidation and greater gluconeogenesis, indicating lactate shuttling between skeletal muscle and liver. Suppression of pyruvate dehydrogenase ( PDH) activity was proposed because of greater pyruvate dehydrogenase kinase (PDK) 4 and PDK1 mRNA concentrations in IUGR muscle. Although PDK1 and PDK4 inhibit PDH activity to reduce pyruvate metabolism, PDH protein concentrations and activity have not been examined in skeletal muscle from IUGR fetuses. Therefore, we evaluated the protein concentrations and activity of PDH and the kinases and phosphatases that regulate PDH phosphorylation status in the semitendinosus muscle from placenta insufficiency-induced IUGR sheep fetuses and control fetuses. Immunoblots were performed for PDH, phosphorylated PDH (E1α), PDK1, PDK4, and pyruvate dehydrogenase phosphatase 1 and 2 (PDP1 and PDP2, respectively). Additionally, the PDH, lactate dehydrogenase (LDH), and citrate synthase (CS) enzymatic activities were measured. Phosphorylated PDH concentrations were 28% lower (P < 0.01) and PDH activity was 67% greater (P < 0.01) in IUGR fetal muscle compared with control. PDK1, PDK4, PDP1, PDP2, and PDH concentrations were not different between groups. CS and LDH activities were also unaffected. Contrary to the previous speculation, PDH activity was greater in skeletal muscle from IUGR fetuses, which parallels lower phosphorylated PDH. Therefore, greater expression of PDK1 and PDK4 mRNA did not translate to greater PDK1 or PDK4 protein concentrations or inhibition of PDH as proposed. Instead, these findings show greater PDH activity in IUGR fetal muscle, which indicates that alternative regulatory mechanisms are responsible for lower pyruvate catabolism.

Selection against archaic hominin genetic variation in regulatory regions

Traces of archaic hominin DNA persist in the human gene pool, but are systematically depleted around genes and other functionally important genomic regions. This suggests that many Neandertal and Denisovan alleles had harmful effects on hybrid fitness. We hypothesized that if some harmful effects were mediated by gene dysregulation in specific tissues, alleles previously flagged as archaic using a conditional random field (CRF) should be depleted from those tissues’ regulatory enhancers compared to “control” alleles matched for allele frequency and the strength of background selection. By this metric, both Neandertal and Denisovan variation appear depleted from enhancers, particularly enhancers that show pleiotropic activity across tissues. This depletion is driven by young archaic SNPs that the CRF confidently identifies as private to Neandertals or Denisovans; older variants that were likely present in both archaic species are not depleted from enhancers. We found that enhancer pleiotropy is not only a predictor of archaic SNP depletion, but also a predictor of intolerance to new mutations as measured by both phastCons scores and the frequency spectrum of African variation. In other respects, however, the landscape of selection against young archaic alleles appears qualitatively different from the landscape of ordinary purifying selection, suggesting that archaic alleles had a different distribution of fitness effects from ordinary new mutations. Most strikingly, fetal brain and muscle are the tissues most depleted of young archaic variation in their regulatory regions, but only brain enhancers appear commensurately intolerant to new mutations. In contrast, fetal muscle enhancers show no evidence of elevated purifying selection relative to other enhancers. This suggests that epistatic incompatibility between human and archaic alleles is needed to explain the degree of archaic variant depletion from fetal muscle enhancers, perhaps due to divergent selection for higher muscle mass in archaic hominins compared to humans.

Novel ASCC1 mutations causing prenatal-onset muscle weakness with arthrogryposis and congenital bone fractures

BackgroundThe activating signal cointegrator 1 (ASC-1) complex acts as a transcriptional coactivator for a variety of transcription factors and consists of four subunits: ASCC1, ASCC2, ASCC3 and TRIP4. A single homozygous mutation in ASCC1 has recently been reported in two families with a severe muscle and bone disorder.ObjectiveWe aim to contribute to a better understanding of the ASCC1-related disorder.MethodsHere, we provide a clinical, histological and genetic description of three additional ASCC1 families.ResultsAll patients presented with severe prenatal-onset muscle weakness, neonatal hypotonia and arthrogryposis, and congenital bone fractures. The muscle biopsies from the affected infants revealed intense oxidative rims beneath the sarcolemma and scattered remnants of sarcomeres with enlarged Z-bands, potentially representing a histopathological hallmark of the disorder. Sequencing identified recessive nonsense or frameshift mutations in ASCC1, including two novel mutations.ConclusionOverall, this work expands the ASCC1 mutation spectrum, sheds light on the muscle histology of the disorder and emphasises the physiological importance of the ASC-1 complex in fetal muscle and bone development.