P2-23 Peri-implantation and late gestation maternal undernutrition differentially alter pathways of insulin and IGF-1 action in fetal sheep skeletal muscle

Fetal skeletal muscle growth requires myoblast proliferation, differentiation, and fusion into myofibers in addition to protein accretion for fiber hypertrophy. Oxygen is an important regulator of this process. Therefore, we hypothesized that fetal anemic hypoxemia would inhibit skeletal muscle growth. Studies were performed in late gestation fetal sheep that were bled to anemic, and therefore hypoxemic, conditions beginning at ~125 days of gestation (term = 148 days) for 9 ± 0 days (n=19) and compared to control fetuses (n=16). A metabolic study was performed on gestational day ~134 to measure fetal protein kinetic rates. Myoblast proliferation and myofiber area were determined in biceps femoris (BF), tibialis anterior (TA), and flexor digitorum superficialis (FDS) muscles. mRNA expression of muscle regulatory factors was determined in BF. Fetal arterial hematocrit and oxygen content were 28% and 52% lower, respectively, in anemic fetuses. Fetal weight and whole-body protein synthesis, breakdown, and accretion rates were not different between groups. Hindlimb length, however, was 7% shorter in anemic fetuses. TA and FDS muscles weighed less and FDS myofiber area was smaller in anemic fetuses compared to controls. The percentage of Pax7+ myoblasts that expressed Ki67 was lower in BF and tended to be lower in FDS from anemic fetuses indicating reduced myoblast proliferation. There was less MYOD and MYF6 mRNA expression in anemic vs. control BF consistent with reduced myoblast differentiation. These results indicate that fetal anemic hypoxemia reduced muscle growth. We speculate that fetal muscle growth may be improved by strategies that increase oxygen availability.

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Maternal undernutrition during the first week after conception results in decreased expression of glucocorticoid receptor mRNA in the absence of GR exon 17 hypermethylation in the fetal pituitary in late gestation

Journal of Developmental Origins of Health and Disease ◽

10.1017/s2040174413000378 ◽

2013 ◽

Vol 4 (5) ◽

pp. 391-401 ◽

Cited By ~ 8

Author(s):

S. Zhang ◽

O. Williams-Wyss ◽

S. M. MacLaughlin ◽

S. K. Walker ◽

D. O. Kleemann ◽

...

Keyword(s):

Glucocorticoid Receptor ◽

Mrna Expression ◽

Hpa Axis ◽

Early Embryo ◽

Late Gestation ◽

Control Group ◽

Fetal Sheep ◽

Maternal Undernutrition ◽

Stress Responsiveness ◽

Periconceptional Period

Exposure to maternal undernutrition during the periconceptional period results in an earlier prepartum activation of the fetal hypothalamo–pituitary–adrenal (HPA) axis and altered stress responsiveness in the offspring. It is not known whether such changes are a consequence of exposure of the oocyte and/or the early embryo to maternal undernutrition in the periconceptional period. We have compared the effects of ‘periconceptional’ undernutrition (PCUN: maternal undernutrition imposed from at least 45 days before until 6 days after conception), and ‘early preimplantation’ undernutrition (PIUN: maternal undernutrition imposed for only 6 days after conception) on the expression of genes in the fetal anterior pituitary that regulate adrenal growth and steroidogenesis, proopiomelanorcortin (POMC), prohormone convertase 1 (PC1), 11β-hydroxysteroid dehydrogenase type 1 and 2 (11βHSD1 and 2) and the glucocorticoid receptor (GR) in fetal sheep at 136–138 days of gestation. Pituitary GR mRNA expression was significantly lower in the PCUN and PIUN groups in both singletons and twins compared with controls, although this suppression of GR expression was not associated with hypermethylation of the exon 17 region of the GR gene. In twin fetuses, the pituitary 11βHSD1 mRNA expression was significantly higher in the PIUN group compared with the PCUN but not the control group. Thus, exposure of the single or twin embryo to maternal undernutrition for only 1 week after conception is sufficient to cause a suppression of the pituitary GR expression in late gestation. These changes may contribute to the increased stress responsiveness of the HPA axis in the offspring after exposure to poor nutrition during the periconceptional period.

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Insulin Deficiency Alters the Metabolic and Endocrine Responses to Undernutrition in Fetal Sheep Near Term

Endocrinology ◽

10.1210/en.2012-1063 ◽

2012 ◽

Vol 153 (8) ◽

pp. 4008-4018 ◽

Cited By ~ 5

Author(s):

Abigail L. Fowden ◽

Alison J. Forhead

Keyword(s):

Oxygen Consumption ◽

Metabolic Response ◽

Plasma Concentrations ◽

Late Gestation ◽

Similar Degree ◽

Hepatic Glycogen ◽

Insulin Deficiency ◽

Fetal Sheep ◽

Maternal Undernutrition ◽

Significant Fall

Insulin deficiency affects the adult metabolic response to undernutrition, but its effects on the fetal response to maternal undernutrition remain unknown. This study examined the effects of maternal fasting for 48 h in late gestation on the metabolism of fetal sheep made insulin deficient by pancreatectomy (PX). The endocrine and metabolic responses to maternal fasting differed between intact, sham-operated and PX fetuses, despite a similar degree of hypoglycemia. Compared with intact fetuses, there was no increase in the plasma concentrations of cortisol or norepinephrine in PX fetuses during maternal fasting. In contrast, there was a significant fasting-induced rise in plasma epinephrine concentrations in PX but not intact fetuses. Umbilical glucose uptake decreased to a similar extent in both groups of fasted animals but was associated with a significant fall in glucose carbon oxidation only in intact fetuses. Pancreatectomized but not intact fetuses lowered their oxygen consumption rate by 15–20% during maternal fasting in association with increased uteroplacental oxygen consumption. Distribution of uterine oxygen uptake between the uteroplacental and fetal tissues therefore differed with fasting only in PX fetuses. Both groups of fetuses produced glucose endogenously after maternal fasting for 48 h, which prevented any significant fall in the rate of fetal glucose utilization. In intact but not PX fetuses, fasting-induced glucogenesis was accompanied by a lower hepatic glycogen content. Chronic insulin deficiency in fetal sheep therefore leads to changes in the counterregulatory endocrine response to hypoglycemia and an altered metabolic strategy in dealing with nutrient restriction in utero.

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Chronic Hyperinsulinemia Increases Myoblast Proliferation in Fetal Sheep Skeletal Muscle

Endocrinology ◽

10.1210/en.2015-1744 ◽

2016 ◽

Vol 157 (6) ◽

pp. 2447-2460 ◽

Cited By ~ 5

Author(s):

Laura D. Brown ◽

Stephanie R. Wesolowski ◽

Jenai Kailey ◽

Stephanie Bourque ◽

Averi Wilson ◽

...

Keyword(s):

Skeletal Muscle ◽

Lean Mass ◽

Biceps Femoris ◽

Late Gestation ◽

Muscle Size ◽

Substrate Uptake ◽

Ki 67 ◽

Fetal Sheep ◽

Umbilical Blood ◽

Myoblast Proliferation

Insulin is an important fetal growth factor. However, chronic experimental hyperinsulinemia in the fetus fails to accelerate linear and lean mass growth beyond normal rates. Mechanisms preventing accelerated lean mass accretion during hyperinsulinemia are unknown. To address potential mechanisms, late-gestation fetal sheep were infused with iv insulin and glucose to produce euglycemic hyperinsulinemia (INS) or saline for 7–9 days. Fetal substrate uptake and protein metabolic rates were measured. INS fetuses had 1.5-fold higher insulin concentrations (P < .0001) and equivalent glucose concentrations. INS fetuses had 20% more Pax7+ nuclei in the biceps femoris, which indicates the potential for hyperinsulinemia to increase the number of myoblasts within late-gestation fetal skeletal muscle. Additionally, the percentage of Pax7+ myoblasts that expressed Ki-67 was 1.3-fold higher and expression of myogenic regulatory factors was 50% lower in INS fetuses (MYF5 and MYOG [myogenin], P < .005), which indicates a shift toward myoblast proliferation over differentiation. There were no differences for fetal body, organ, or muscle weights, although INS placentas weighed 28% less (P < .05). Protein synthesis and accretion rates did not change in INS fetuses, nor did fiber muscle size. Essential amino acid concentrations were lower in the INS group (P < .05) except for tryptophan. Umbilical blood flow, net total amino acids, and O2 uptakes rates did not differ between groups. Arterial O2 content was 33% lower (P < .005) and norepinephrine was 100% higher in the INS fetuses (P < .01), all of which are factors that may counteract fetal protein accretion during hyperinsulinemia despite an increase in myoblast proliferation.

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Thyroid hormones and the mRNA of the GH receptor and IGFs in skeletal muscle of fetal sheep

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00284.2001 ◽

2002 ◽

Vol 282 (1) ◽

pp. E80-E86 ◽

Cited By ~ 16

Author(s):

A. J. Forhead ◽

J. Li ◽

R. S. Gilmour ◽

M. J. Dauncey ◽

A. L. Fowden

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Thyroid Hormones ◽

Gestational Age ◽

Plasma Cortisol ◽

Mrna Abundance ◽

Late Gestation ◽

Fetal Sheep ◽

Igf I ◽

I Gene

Thyroid hormones are required for the normal development of skeletal muscle in utero, although their mechanism of action is poorly understood. The present study examined the effects of the thyroid hormones on the gene expression of the growth hormone receptor (GHR) and the insulin-like growth factors (IGFs) IGF-I and IGF-II, in skeletal muscle of fetal sheep during late gestation (term 145 ± 2 days) and after manipulation of plasma thyroid hormone concentration. Thyroidectomy at 105–110 days of gestation suppressed muscle GHR and IGF-I gene expression in fetuses studied at 127–130 and 142–145 days. Muscle GHR mRNA abundance remained unchanged with increasing gestational age in intact and thyroidectomized fetuses. In the intact fetuses, a decrease in muscle IGF-I gene expression was observed between 127–130 and 142–145 days, which coincided with the normal prepartum surges in plasma cortisol and triiodothyronine (T3). At 127–130 days, downregulation of muscle IGF-I mRNA abundance was induced prematurely in intact fetuses by an infusion of cortisol for 5 days (2–3 mg · kg−1 · day−1 iv), which increased plasma cortisol and T3 concentrations to values seen near term. However, increasing plasma T3 alone by an infusion of T3 for 5 days (8–12 μg · kg−1 · day−1 iv) in intact fetuses at this age had no effect on GHR or IGF-I gene expression in skeletal muscle. In the thyroidectomized fetuses, no additional change in the low level of muscle IGF-I mRNA abundance was seen with increasing gestational age, but at 127–130 days, IGF-I gene expression was reduced further when plasma cortisol and T3 concentrations were increased by exogenous cortisol infusion. Muscle IGF-II mRNA abundance was not affected by thyroidectomy, gestational age, or exogenous hormone infusion. These findings show, in the sheep fetus, that thyroid hormones may influence the growth and development of skeletal muscle via changes in the local activity of the somatotrophic axis.

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Skeletal muscle amino acid uptake is lower and alanine production is greater in late gestation intrauterine growth-restricted fetal sheep hindlimb

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00115.2019 ◽

2019 ◽

Vol 317 (5) ◽

pp. R615-R629 ◽

Cited By ~ 2

Author(s):

Eileen I. Chang ◽

Stephanie R. Wesolowski ◽

Elizabeth A. Gilje ◽

Peter R. Baker ◽

Julie A. Reisz ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Protein ◽

External Iliac Artery ◽

Late Gestation ◽

Acid Uptake ◽

Sheep Model ◽

Fetal Sheep ◽

Biceps Femoris Muscle ◽

Intrauterine Growth ◽

Uptake Rates

In a sheep model of intrauterine growth restriction (IUGR) produced from placental insufficiency, late gestation fetuses had smaller skeletal muscle mass, myofiber area, and slower muscle protein accretion rates compared with normally growing fetuses. We hypothesized that IUGR fetal muscle develops adaptations that divert amino acids (AAs) from protein accretion and activate pathways that conserve substrates for other organs. We placed hindlimb arterial and venous catheters into late gestation IUGR ( n = 10) and control (CON, n = 8) fetal sheep and included an external iliac artery flow probe to measure hindlimb AA uptake rates. Arterial and venous plasma samples and biceps femoris muscle were analyzed by mass spectrometry-based metabolomics. IUGR fetuses had greater abundance of metabolites enriched within the alanine, aspartate, and glutamate metabolism pathway compared with CON. Net uptake rates of branched-chain AA (BCAA) were lower by 42%–73%, and muscle ammoniagenic AAs (alanine, glycine, and glutamine) were lower by 107%–158% in IUGR hindlimbs versus CON. AA uptake rates correlated with hindlimb weight; the smallest hindlimbs showed net release of ammoniagenic AAs. Gene expression levels indicated a decrease in BCAA catabolism in IUGR muscle. Plasma purines were lower and plasma uric acid was higher in IUGR versus CON, possibly a reflection of ATP conservation. We conclude that IUGR skeletal muscle has lower BCAA uptake and develops adaptations that divert AAs away from protein accretion into alternative pathways that sustain global energy production and nitrogen disposal in the form of ammoniagenic AAs for metabolism in other organs.

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Impact of periconceptional nutrition on maternal and fetal leptin and fetal adiposity in singleton and twin pregnancies

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00127.2004 ◽

2005 ◽

Vol 288 (1) ◽

pp. R39-R45 ◽

Cited By ~ 32

Author(s):

L. J. Edwards ◽

J. R. McFarlane ◽

K. G. Kauter ◽

I. C. McMillen

Keyword(s):

Maternal Plasma ◽

Late Gestation ◽

Relative Mass ◽

Fetal Sheep ◽

Fetal Plasma ◽

Maternal Undernutrition ◽

Functional Development ◽

Plasma Leptin ◽

The Impact ◽

Twin Pregnancies

It has been proposed that maternal nutrient restriction may alter the functional development of the adipocyte and the synthesis and secretion of the adipocyte-derived hormone, leptin, before birth. We have investigated the effects of restricted periconceptional undernutrition and/or restricted gestational nutrition on fetal plasma leptin concentrations and fetal adiposity in late gestation. There was no effect of either restricted periconceptional or gestational nutrition on maternal or fetal plasma leptin concentrations in singleton or twin pregnancies during late gestation. In ewes carrying twins, but not singletons, maternal plasma leptin concentrations in late gestation were directly related to the change in ewe weight that occurred during the 60 days before mating [maternal leptin = 0.9 (change in ewe weight) + 7.8; r = 0.6, P < 0.05]. In twin, but not singleton, pregnancies, there was also a significant relationship between maternal and fetal leptin concentrations (maternal leptin = 0.5 fetal leptin + 4.2, r = 0.63, P < 0.005). The relative mass of perirenal fat was also significantly increased in twin fetal sheep in the control-restricted group (6.0 ± 0.5) compared with the other nutritional groups (control-control: 4.1 ± 0.4; restricted-restricted: 4.4 ± 0.4; restricted-control: 4.3 ± 0.3). In conclusion, the impact of maternal undernutrition on maternal plasma leptin concentrations during late gestation is dependent on fetal number. Furthermore, we have found that there is an increased fetal adiposity in the twins of ewes that experienced restricted nutrition throughout gestation, and this may be important in the programming of postnatal adiposity.

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