Mechanisms for nutritional programming of hypertension: identification of gatekeeper genes and proteins

The quality of the maternal diet during pregnancy is a powerful influence on the long-term health and well-being of the developing fetus. Individuals exposed to undernutrition in fetal life are at greater risk of coronary heart disease and hypertension. It is remarkable that very different forms of undernutrition in pregnancy, for example low protein diets or high fat diets, produce very similar profiles of disease risk in the resulting offspring. This suggests that a relatively narrow range of changes to the form and function of organs and tissues in the developing fetus, may be triggered by a nutritional stressor. The aim of this project is to identify the basic molecular mechanisms that drive the early life programming of cardiovascular disease risk. The work will utilise two distinct and well-established animal models of programmed hypertension, namely protein restriction and iron deficiency in the rat. Both dietary restrictions will be imposed during critical phases of pregnancy and, having established the common outcomes of the dietary manipulations, we will use powerful modern molecular techniques to identify changes in expression of genes and proteins that may be the central 'gatekeepers' that mediate the association between early life nutrition and later disease risk. This work is of importance in developing an understanding of the mechanistic basis of the link between fetal nutrition and lifelong health and disease. This is of major importance in terms of public health, as it is becoming clear that risk of obesity, diabetes and cardiovascular disease are not just a product of adult lifestyle factors. Risk at any stage of life is the product of cumulative exposures to adverse factors, including poor nutrition, at all stages of life from conception onwards.

Undernutrition during critical phases of development exerts a powerful programming effect upon tissue morphology and later function. In this way exposure to adverse nutritional stimuli in early life can determine lifelong risk of metabolic disorders and cardiovascular disease. Animal models show that diverse nutritional interventions in pregnancy produce the same basic disease phenotypes, suggesting that there are relatively few mechanistic pathways that drive developmental programming. In this project we will study two established rat models of cardiovascular programming, a low protein diet and an iron deficiency approach. Our experimental design will firstly determine the pattern of cardiovascular phenotype across the two strains of rat. We will then use a combination of genomic and proteomic approaches to identify the genes and proteins that exhibit altered expression in response to both dietary manipulations in embryos from both strains. These common candidate genes or proteins will be putative gatekeepers, likely to play a key mechanistic role in developmental programming. After identification of the gatekeepers in whole embryos, we will use immunohistochemistry to localize their expression followed by laser capture microdissection, allowing more detailed investigation at the tissue-specific level. The project will overcome limitations of other studies that have set out to identify mechanisms of developmental programming, by taking a systematic approach focused on the critical period of development. With this focus we will minimise the identification of gene changes secondary to the programmed phenotype, or those that are not in the causal pathway to disease, as is likely when studying adult offspring. This approach will provide a powerful means for identifying some of the early drivers of nutritional programming and will consider whether the gatekeeper genes and proteins are regulated by maternal nutrition at the transcriptional or post-transcriptional level.