The kidney is resistant to chronic hypoglycaemia in late-gestation fetal sheep

The lack of impact of peri-implantation or late gestation nutrient restriction on ovine fetal renal development and function

Unbalanced nutrition during critical windows of development is implicated in determining the susceptibility to hypertension and cardiovascular disease in adult life, but the underlying mechanisms during fetal life have not been fully elucidated. We investigated the effects of moderate nutritional restriction during critical windows in gestation on late gestation fetal sheep growth, cardiovascular and renal renin-angiotensin system function. Ewes were fed 100% nutrient requirements (control), or 40–50% nutrient requirements during the peri-implantation period (1–31 days gestation (dGA), PI40 and PI50), or 50% nutrient requirements in late gestation (104–127 dGA). At 125 ± 2 dGA, fetal cardiovascular and renal function were measured at baseline, and during frusemide, angiotensin II (Ang II), phenylephrine and hypoxia challenges. Maternal undernutrition had no effect on fetal biometry, kidney weight, nephron number, basal cardiovascular function or cardiovascular and renal responses to frusemide. Fetal blood pressure response to Ang II was blunted in PI50 (P< 0.05), but not in PI40 groups. There was no difference between groups in the cardiovascular or endocrine response to hypoxia. The lack of effect of moderate undernutrition within key developmental windows of fetal kidney development on fetal renal structure and function suggests that renal mechanisms do not underlie our previous observations of cardiovascular dysfunction in adulthood following early-life undernutrition.

The late gestation fetal cardiovascular response to hypoglycaemia is modified by prior peri-implantation undernutrition in sheep

Undernourished late gestation fetuses display asymmetric growth restriction, suggestive of a redistribution of nutritional resources. The modification of fetal organ blood supply in response to acute hypoxia is well characterized, but it is not known whether similar responses occur in response to acute reductions in nutrition, or if such late gestation responses can be influenced by early gestation nutrition. In pregnant sheep, total nutrient requirements were restricted during the peri-implantation period (PI40, 40%; PI50, 50% of total, days 1-31) or in late gestation (L, 50% total, days 104-postmortem). Control animals were fed 100% nutrient requirements. Fetal organ blood flows were measured at baseline, and during acute fetal hypoglycaemia induced by maternal insulin infusion at 125 dGA. Baseline heart rate was increased in PI40 fetuses. During hypoglycaemia, an initial rise in fetal heart rate was followed by a slower fall. Fetal femoral artery blood flow decreased, and adrenal blood flow and femoral vascular resistance increased in all fetuses during hypoglycaemia. These changes were accompanied by increased fetal plasma adrenaline and cortisol, and reduced plasma insulin levels. The maximum femoral artery blood flow response to hypoglycaemia occurred earlier in PI50 and PI40 compared with control fetuses. The late gestation fetal cardiovascular response to acute hypoglycaemia was consistent with a redistribution of combined ventricular output away from the periphery and towards central organs. One element of the peripheral vascular response was modified by peri-implantation nutrient restriction, indicating that nutritional challenges early in gestation can have an enduring impact on cardiovascular control.