Enduring effects of infant feeding experiences on adult blood pressure

Genetic and environmental contributions to phenotypic components of metabolic syndrome: a population-based twin study

The increasing prevalence of metabolic syndrome (MS) poses a serious public-health problem worldwide. Effective prevention and intervention require improved understanding of the factors that contribute to MS. We analyzed data on a large twin cohort to estimate genetic and environmental contributions to MS and to major MS components and their intercorrelations: waist circumference (WC), systolic (SBP) and diastolic blood pressure (DBP), fasting plasma glucose (FPG), triglycerides (TGs), and high-density lipoprotein-cholesterol (HDL-C). We applied structural equation modeling to determine genetic and environmental structure of MS and its major components, using 1,617 adult female twin pairs recruited from rural China. The heritability estimate for MS was 0.42 (95% confidence interval (CI): 0.00-0.83) in this sample with low MS prevalence (4.4%). For MS components, heritability estimates were statistically significant and ranged from 0.13 to 0.64 highest for WC, followed by TG, SBP, DBP, HDL-C, and FPG. HDL-C was mainly influenced by common environmental factors (0.62, 95% CI: 0.58-0.62), whereas the other five MS components were largely influenced by unique environmental factors (0.32-0.44). Bivariate Cholesky decomposition analysis indicated that the clinical clustering of MS components may be explained by shared genetic and/or environmental factors. Our study underscores the importance of examining MS components as intercorrelated traits, and to carefully consider environmental and genetic factors in studying MS etiology.

Developmental windows and environment as important factors in the expression of genetic information: a cardiovascular physiologist's view

Genetic studies in humans and rodent models should help to identify altered genes important in the development of cardiovascular diseases, such as hypertension. Despite the considerable research effort, it is still difficult to identify all of the genes involved in altered blood pressure regulation thereby leading to essential hypertension. We should keep in mind that genetic hypertension and other cardiovascular diseases might develop as a consequence of early errors in well-co-ordinated systems regulating cardiovascular homoeostasis. If these early abnormalities in the ontogenetic cascade of expression of genetic information occur in critical periods of development (developmental windows), they can adversely modify subsequent development of the cardiovascular system. The consideration that hypertension and/or other cardiovascular diseases are late consequences of abnormal ontogeny of the cardiovascular system could explain why so many complex interactions among genes and environmental factors play such a significant role in the pathogenesis of these diseases. The detailed description and precise time resolution of major developmental events occurring during particular stages of ontogeny in healthy individuals (including advanced knowledge of gene expression) could facilitate the detection of abnormalities crucial for the development of cardiovascular alterations characteristic of the respective diseases. Transient gene switch-on or switch-off in specific developmental windows might be a useful approach for in vivo modelling of pathological processes. This should help to elucidate the mechanisms underlying cardiovascular diseases (including hypertension) and to develop strategies to prevent the development of such diseases.

Adult rabbit offspring of mothers with secondary hypertension have increased blood pressure

Preexisting chronic hypertension complicates up to 5% of pregnancies and is associated with an increased risk of low-birth-weight babies. Studies suggest that an adverse intrauterine environment leading to low birth weight is linked to an increased risk of cardiovascular disease, including hypertension, in the adult. In this study, the blood pressure of offspring from mothers with hypertension were followed up into adulthood. Two-kidney, 1-wrapped hypertension was induced in 7 female rabbits; 5 other rabbits underwent sham surgery. Four weeks later, rabbits were mated, at which time mean arterial pressure was 118+/-3 and 87+/-5 mm Hg in the hypertensive and sham groups, respectively (P<0.001). The blood pressure of 30-week-old females was 89+/-2 mm Hg in the offspring of hypertensive (n=14) and 79+/-1 mm Hg in the offspring of normotensive (n=13) mothers (P<0.005). Also, plasma renin activity was significantly lower in the female offspring of hypertensive mothers at 10 weeks of age (P<0.05), suggesting that development of the renin-angiotensin system was altered. In contrast, male offspring from hypertensive and normotensive mothers had similar mean arterial pressure and plasma renin activity. In conclusion, maternal secondary hypertension can "program" hypertension in female adult offspring. The results also suggest that there are gender-specific differences in sensitivity to altered in utero environmental influences.

An historical and critical review of the articles on blood pressure published in Psychosomatic Medicine between 1939 and 1997

Between 1939 and 1997, there have been 59 volumes of Psychosomatic Medicine. Over this period there were 200 articles dealing with blood pressure. About 90% of these were concerned with high blood pressure. This article reviews all of these papers both from an historical perspective and critically. Although there has been a significant growth in the rate of articles published since 1939, there has always been a strong interest in the nature of hypertension, particularly the roles of affects and emotions in the natural history of the disease. For example, volume 1, number 1 of the Journal includes a symposium on high blood pressure in which Franz Alexander stated his well-known hypothesis that the chronic inhibition of rage plays a causal role in the production of hypertension. In various forms, the notion that anger is an important mediator of hypertension has neither been proved nor abandoned. One major conclusion drawn from this review is that the current research on high blood pressure is drifting somewhat aimlessly. It has become preoccupied with demonstrations that various stimuli or situations (usually characterized as stresses) can acutely raise blood pressure. Despite this focus, neither the necessary nor the sufficient conditions for labeling a stimulus as stress has ever been agreed upon. Likewise, there have been many demonstrations of an iatrogenic effect on blood pressure, but neither the behavioral mechanisms underlying this effect nor the strategies for eliminating it have been explicated. Finally, this article identifies several areas where it would be useful to review and integrate current knowledge. Hopefully, such integrations could play a significant role in focusing and shaping future research and clinical practice.

On the nature and consequences of early loss

OBJECTIVE

To describe how an animal model system can be used to explore basic questions about the nature of loss and the effects of early loss on later vulnerability to disease.

METHOD

The physiological and behavioral responses of infant rats to separation from their mothers are first described and then analyzed experimentally into component mechanisms.

RESULTS

These studies have revealed an extensive layer of processes underlying the psychological constructs generally used to understand the response to loss. Hidden within the observable interactions of parent and offspring, we found a number of discrete sensorimotor, thermal, and nutrient-based events that have unexpected long-term regulatory effects on specific components of infant physiology and behavior. Release from all of these inhibitory and excitatory regulators together during maternal separation constitutes a novel mechanism by which the experience of loss can be translated into a complex patterned response. Evidence for early regulatory processes has also been found in monkey and human mother-infant interactions. Here they may well constitute the building blocks from which attachment and object representations develop. We and others have found long-term effects of loss, and of selective replacement of regulators, on behavioral development and on later vulnerability to disease.

CONCLUSIONS

The results give us a new understanding of early attachment as a developmental force and of human grief as a risk to health.