L Brawley

Dietary protein restriction in pregnancy induces hypertension and vascular defects in rat male offspring.

It is established that dietary protein restriction of pregnant rats results in their offspring developing hypertension. However, to date no studies have investigated peripheral vascular function of offspring using the low protein model. Therefore, the aim of the study was to assess isolated resistance artery function from adult male offspring of control (C, 18% casein) and protein-restricted (PR, 9% casein) pregnant dams at two different ages. The birthweight of PR offspring did not significantly differ from that of C offspring. Systolic blood pressure was significantly elevated in PR compared with C (p < 0.05). Maximal vascular contraction to phenylephrine and the thromboxane analog U46619 were similar in C and PR offspring at postnatal d 87 and 164. Relaxation induced by the endothelium-dependent vasodilators acetylcholine or bradykinin was significantly reduced in the PR group (p < 0.05). Relaxation to the endothelium-independent vasodilator sodium nitroprusside and phosphodiesterase type 3 inhibitor cilostamide was less in the PR offspring compared with C (p < 0.01). Dietary protein restriction in pregnancy induces hypertension and vascular dysfunction in male offspring. Abnormalities in the nitric oxide-cGMP pathway may explain the defect in endothelium-dependent and -independent relaxation. Reduced vasodilation may be a potential mechanism underlying the elevated systolic blood pressure observed in this model.

Folate Supplementation During Pregnancy Improves Offspring Cardiovascular Dysfunction Induced by Protein Restriction

Dietary protein restriction in the rat compromises the maternal cardiovascular adaptations to pregnancy and leads to raised blood pressure and endothelial dysfunction in the offspring. In this study we have hypothesized that dietary folate supplementation of the low-protein diet will improve maternal vascular function and also restore offspring cardiovascular function. Pregnant Wistar rats were fed either a control (18% casein) or protein-restricted (9% casein) diet ±5 mg/kg folate supplement. Function of isolated maternal uterine artery and small mesenteric arteries from adult male offspring was assessed, systolic blood pressure recorded, and offspring thoracic aorta levels of endothelial nitric oxide (NO) synthase mRNA measured. In the uterine artery of late pregnancy dams, vasodilatation to vascular endothelial growth factor was attenuated in the protein-restricted group but restored with folate supplementation, as was isoprenaline-induced vasodilatation (P<0.05). In male offspring, protein restriction during pregnancy led to raised systolic blood pressure (P<0.01), impaired acetylcholine-induced vasodilatation (P<0.01), and reduced levels of endothelial NO synthase mRNA (P<0.05). Maternal folate supplementation during pregnancy prevented this elevated systolic blood pressure associated with a protein restriction diet. With folate supplementation, endothelium-dependent vasodilatation and endothelial NO synthase mRNA levels were not significantly different from either the control or protein-restricted groups. Maternal folate supplementation of the control diet had no effect on blood pressure or vasodilatation. This study supports the hypothesis that folate status in pregnancy can influence fetal development and, thus, the risks of cardiovascular disease in the next generation. The concept of developmental origins of adult disease focuses predominately on fetal life but must also include a role for maternal cardiovascular function.

Maternal protein restriction in the rat impairs resistance artery but not conduit artery function in pregnant offspring

Dietary protein restriction during gestation has been shown to produce vascular dysfunction in pregnant rats and hypertension in their offspring. However, no studies have to date examined the effects of such ‘programming’ on the vascular function of female offspring when they in turn become pregnant. We have therefore studied isolated conduit and resistance artery function from pregnant female offspring of control (C, 18 % casein) and protein‐restricted (PR, 9 % casein) pregnant dams. There were no differences in birth weight, weight gain during pregnancy, litter size, fetal weight, placental weight, fetal : placental weight ratio or organ weights between the C and PR groups. In isolated mesenteric arteries, the vasodilatation in response to the endothelial‐dependent vasodilator acetylcholine (ACh) and the β‐adrenoceptor agonist isoprenaline was decreased in the PR group, while there were no differences in the constriction in response to potassium (125 mm) or the α1‐adrenoceptor agonist phenylephrine (PE). No differences in any responses were seen in the isolated thoracic aorta. We conclude that dietary protein restriction in pregnancy programmes vasodilator dysfunction in isolated resistance arteries of female offspring when they become pregnant, but does not affect conduit arteries.

Mechanisms Underlying the Programming of Small Artery Dysfunction: Review of the Model Using Low Protein Diet in Pregnancy in the Rat

Human and animal studies have shown that unbalanced maternal nutrition is associated with the development of cardiovascular and metabolic disease in adulthood. In the Southampton maternal low protein model (SMLP), protein deprivation (50%) throughout pregnancy in rats leads to elevated blood pressure in adult offspring. Impaired peripheral arterial function may contribute to the cardiovascular dysfunction observed in these offspring. This review discusses the impact of such a dietary insult on the vascular function of resistance arteries from pregnant rats (pF 0), their offspring (F 1), the pregnant offspring (pF 1) and the second generation (F 2). At each stage, disturbances in endothelium-dependent relaxation were observed, implicating changes in endothelial nitric oxide (NO)-guanylate cyclase (GC) signalling pathway in the vascular adaptations to pregnancy and the programmed effects on offspring.

Vasodilation to Vascular Endothelial Growth Factor in the Uterine Artery of the Pregnant Rat Is Blunted by Low Dietary Protein Intake

Pregnancy is associated with a substantial increase in uterine artery blood flow, which may in part result from dilation in response to vascular endothelial growth factor (VEGF). Uterine blood flow is reported to be reduced in globally diet-restricted pregnant rats. Both global and protein dietary restriction in pregnancy produce programmed effects in offspring. In this study we hypothesized that protein restriction in pregnancy impairs maternal uterine artery responses to VEGF. Vascular responses to VEGF were determined in isolated uterine arteries of pregnant (18 or 19 d of gestation) Wistar rats fed a diet containing either 18% or 9% casein throughout pregnancy. For comparison, responses to phenylephrine, potassium chloride, and acetylcholine were determined. In addition, the response of the mesenteric artery to VEGF was studied in the same animals. A significant reduction of the maximal relaxation to VEGF (p = 0.041) and in the overall response (p = 0.004) to VEGF was found in uterine arteries of the 9% compared with the 18% group, but responses to all other agonists were similar. The VEGF response was reduced by cyclooxygenase inhibition (indomethacin) in both groups. In the 18%, but not the 9%, group it was further reduced by nitric oxide synthase inhibition (Nω-nitro-l-arginine methyl ester). VEGF was shown to dilate the mesenteric artery but this effect was not significantly altered by the low-protein diet. These results show an attenuated uterine artery vasodilator response to VEGF produced by a low-protein diet in pregnancy, partly because of a reduction of the nitric oxide component of VEGF-mediated relaxation.