Endocrine Abstracts

Type I 5'-monodeiodinase (5'-MDI) converts thyroxine (T4) to triiodothyronine (T3). In fetal sheep, hepatic 5'-MDI activity increases near term in association with the prepartum cortisol surge. This study investigated the effect of maternal dexamethasone treatment, in clinically relevant doses, on hepatic and renal type I 5'-MDI activity and plasma thyroid hormone concentrations in fetal sheep.From 125 days of gestation (term 145 pl...

Deiodinase enzymes have an important role in thyroid hormone metabolism. Type I 5′-monodeiodinase (D1) converts thyroxine (T4) to triiodothyronine (T3), while type III 5-monodeiodinase (D3) inactivates T3 and produces reverse-T3 (rT3) from T4. In fetal sheep, plasma T3 rises towards term in association with the prepartum cortisol surge. This study investigated the effect of cortisol on tissue de...

Leptin is a hormone produced mainly from adipose tissue, which plays a major role in energy homeostasis. Its receptor Ob-R exists in five splice variants (Ob-Ra, b, c, d and e) with differing signal transduction abilities. The function of leptin and its receptor in development is not yet fully understood. This study determined the expression of leptin and its receptor in a number of fetal endocrine tissues.Tissue samples were obtained from 7 fetal sheep ...

The enzyme 5β-reductase (AKR1D1) catalyses an essential step in bile acid (BA) synthesis, but in addition, controls intra-cellular steroid hormone availability by inactivation. Steroid hormones and BA are regulators of global lipid and carbohydrate metabolism. As disturbances in steroid hormone and BA metabolism have potent effects on metabolic health, we hypothesize that AKR1D1 may play a role in metabolic homeostasis. The role of AKR1D1 in regulating glucose homeostasis...

Babies born to mothers with diabetes during pregnancy are exposed to high circulating leptin before birth and, in turn, are at increased risk of developing diabetes in later life. In pancreatic islets isolated from fetal sheep, leptin influences β-cell proliferation in a bimodal manner. This study examined the effect of exogenous leptin infusion and leptin receptor antagonism on pancreatic β-cell mass in the sheep fetus in vivo.<...

Babies born to mothers with diabetes during pregnancy are exposed to high circulating leptin before birth and, in turn, are at increased risk of developing diabetes in later life. In pancreatic islets isolated from fetal sheep, leptin influences β-cell proliferation in a bimodal manner. This study examined the effect of exogenous leptin infusion and leptin receptor antagonism on pancreatic β-cell mass in the sheep fetus in vivo.<...

The enzyme 5β-reductase (AKR1D1) controls intra-cellular steroid hormone availability through hormone clearance. Additionally, it catalyses an essential step in bile acid (BA) synthesis. Disturbances in steroid hormones and BA metabolism have potent effects on metabolic health, therefore we hypothesize that AKR1D1 may play a role in metabolic homeostasis; the role of AKR1D1 in regulating glucose homeostasis and pancreatic function remains unexplored. We generated a global...

Hormonal control of pancreatic β-cell development in the fetus during late gestation remains unclear. In fetal sheep hypothyroidism causes an increase in pancreatic β-cell mass in association with increased plasma insulin and leptin concentrations. This study investigated the effects of triiodothyronine (T3), insulin and leptin on proliferation rates in fetal ovine pancreatic β-cells in vitro.All procedures were approve...

Thyroid hormones increase foetal and adult metabolic rates, and, in adult tissues, increase mitochondrial biogenesis. Foetal tri-iodothyronine (T3) concentrations rise towards term in preparation for the increased postnatal energy demands but whether they affect mitochondrial development remains unknown. This study examined mitochondrial development in skeletal muscle of thyroid hormone deficient sheep foetuses near term.At 105–110 days (...

Although leptin is important in the control of appetite and energy expenditure in adulthood, its actions before birth are unclear. This study investigated the effects of leptin on hepatic carbohydrate metabolism and insulin signalling in fetal sheep. Twelve sheep fetuses were chronically-catheterised at 115–120 d of gestation (term 145±2 d), and infused intravenously with saline (0.9% NaCl; n=6) or recombinant ovine leptin (0.5–1.0 mg/kg/d; Protein Labora...