Adaptation, allometry, and hypertension

Association of linear growth velocities between 0 and 6 years with kidney function and size at 10 years: A birth cohort study in Ethiopia

BACKGROUND

Risk of noncommunicable diseases accrues from fetal life, with early childhood growth having an important role in adult disease risk. There is a need to understand how early-life growth relates to kidney function and size.

OBJECTIVES

This study aimed to assess the association of linear growth velocities among children between 0 and 6 y with kidney function and size among children aged 10 y.

METHODS

The Ethiopian Anthropometric and Body Composition birth cohort recruited infants born at term to mothers living in Jimma with a birth weight of ≥1500 g and without congenital malformations. Participants were followed up with 13 measurements between birth and 6 y of age. The latest follow-up was at ages 7-12 y with measurement of serum cystatin C as a marker of kidney function and ultrasound assessment of kidney dimensions. Kidney volume was computed using an ellipsoid formula. Linear-spline multilevel modeling was used to compute linear growth velocities between 0 and 6 y. Multiple linear regression modeling was used to examine the associations of linear growth velocities in selected age periods with cystatin C and kidney size.

RESULTS

Data were captured from 355 children, at a mean age of 10 (range 7-12) y. The linear growth velocity was high between 0 and 3 mo and then decreased with age. There was no evidence of an association of growth velocity ≤24 mo with cystatin C at 10 y. Between 24 and 48 and 48 and 76 mo, serum cystatin C was higher by 2.3% [95% confidence interval (CI): 0.6, 4.2] and 2.1% (95% CI: 0.3, 4.0) for 1 SD higher linear growth velocity, respectively. We found a positive association between linear growth velocities at all intervals between 0 and 6 y and kidney volume.

CONCLUSIONS

Greater linear growth between 0 and 6 y of development was positively associated with kidney size, and greater growth velocity after 2 y was associated with higher serum cystatin C concentrations.

Secular trends in blood pressure trajectories in Chinese children and adolescents: the impact of changing physical growth

BACKGROUND

Globally, 80% of cardiovascular disease (CVD) occur in low-income /middle-income countries. High blood pressure (BP), a major risk factor for CVD, has its origins in early-life. We investigated how age trajectories of BP (childhood to late-adolescence) have changed recently in China and the mediating roles of physical growth.

METHODS

Using the longitudinal data on 3785 children from the China Health and Nutrition Survey 1991-2015, we estimated mean BP trajectories (7-18 years) for cohorts born in 1981-1985, 1986-1990, 1991-1995 and 1996-2000 using random effect models. Models were adjusted for BMI and/or height growth to assess their impact on BP trends.

RESULTS

BP trajectories shifted upwards across cohorts. Compared with the earliest cohort, mean BP was higher in the latest cohort throughout childhood to late adolescence. For example, the increment in SBP was 4.4 mmHg (95% confidence interval: 2.9-5.8) in boys and 4.0 mmHg (2.6-5.5) in girls at 9 years, narrowed slightly during adolescence, and was 3.0 mmHg (0.7-5.4) and 2.6 mmHg (0.4-4.8) respectively at 17 years. BMI and height trajectories also shifted upwards. The overall increment was greater for height than BMI. When adjusting for physical growth, the increment in BP trajectories reduced (more for height than BMI), but remained in childhood (P < 0.05).

CONCLUSION

The upward shift of BP trajectories among Chinese youths was largely explained by trends in physical growth, especially increasing height. Other early-life factors might have also contributed to the BP trends. Substantial increases in mean BP in children within a short time frame is a public health concern and will affect future CVD, especially in the developing world.

Barker Hypothesis and Hypertension

Early onset hypertension is one of many major medical disorders that have evolved over the current millennium across both the developing as well as the developed world. Though various mechanisms have been postulated for the evolution of hypertension in these individuals, one of the most relevant ones is that of low birth weight and its association with hypertension. Barker from historical evidence has postulated the foetal onset adult disease (FOAD) or Thrifty phenotype on Low Birth Weight (LBW) associated hypertension. Later, Brenner highlighted the importance of low nephron mass and future implications. In this review we elaborate the mechanisms that were postulated for LBW-related hypertension as well the potential antihypertensive therapy that may be used in these individuals.

Muscle mass is the main somatic growth indicator associated with increasing blood pressure with age in children and adolescents

Studies have shown that lean mass must be an important determinant of blood pressure value in children and adolescents. The absence of adjustment for the collinearity between lean and fat mass (FM), restricted age span, and lack of separate analysis by sex leave a gap in the literature. This study determined direct and indirect effects of the somatic growth indicators linked to the association between age and systolic blood pressure (SBP) in boys and girls. This is a cross-sectional study comprising 1,510 participants (6-18 years). Path analysis was used to test a model in which the association between age and SBP would have a direct and independent component, but also indirect mediating paths through muscle mass (MM), FM, and height. There was no significant association between age and SBP (unstandardized β ± SE) for both girls (0.072 ± 0.236, P = .761) and boys (0.238 ± 0.264, P = .368). Height was not a mediator for the association between age and SBP in both girls (-0.291 ± 0.156, P = .062) and boys (-0.015 ± 0.187, P = .935). Mediating effect of MM was significant for both girls (0.909 ± 0.137, P < .001) and boys (1.341 ± 0.161, P < .001), whereas mediating path through FM was significant only for boys (0.069 ± 0.023, P = .003). In conclusion, muscle mass was the strongest somatic growth indicator associated with the blood pressure value in children and adolescents. Further increase in body fat mass may affect systolic blood pressure more in boys than in girls.

Human genome evolution and development of cardiovascular risk factors through natural selection

Impressive advances in molecular genetic techniques allow to analyze the effects of natural selection on the development of human genome. For example, the trend towards blonde hair and blue eyes was documented. The approach to analyze possible effects of natural selection on the evolution of recent phenotypes with high risk of cardiovascular disease has not been described yet. A possible effect on the evolution of two main risk factors - hypercholesterolemia and hypertension - is presented. The close relationship of non-HDL cholesterol blood concentration to the proportion of pro-inflammatory macrophages in human visceral adipose tissue might be a result of long-lasting natural selection. Individuals with higher proportion of this phenotype might also display a higher ability to fight infection, which was very common in human setting from prehistory until Middle Ages. Successful battle against infections increased the probability to survive till reproductive age. Similar hypothesis was proposed to explain frequent hypertension in African Americans. A long-lasting selection for higher ability to conserve sodium during long-term adaptation to low sodium intake and hot weather was followed by a short-term (but very hard) natural selection of individuals during transatlantic slave transport. Only those with very high capability to retain sodium were able to survive. Natural selection of phenotypes with high plasma cholesterol concentration and/or high blood pressure is recently potentiated by high-fat high-sodium diet and overnutrition. This hypothesis is also supported by the advantage of familial hypercholesterolemia in the 19th century (at the time of high infection disease mortality) in contrast to the disadvantage of familial hypercholesterolemia during the actual period of high cardiovascular disease mortality.

Contributions of relative linear growth and adiposity accretion from birth to adulthood to adult hypertension

While birth weight and weight gain have been associated with hypertension (HT), the association of linear growth, independently of weight gains, has been less well studied. We assessed the independent association of body mass index (BMI) and length at birth and changes in BMI and height during the first two decades of life with adult blood pressure (BP). A birth cohort (n = 1141) was assembled in 1978–79, and followed up at school-age and adulthood. We used conditional length and BMI measures. BMI at birth was inversely associated with HT; c-BMI from school age to adulthood and c-height from birth to school age were positively associated with hypertension. Early adiposity accretion from birth to 9 years and late linear growth from 9 to 24 years were not associated with increased HT. Regarding BP, systolic and diastolic BP presented similar partterns: the lower the BMI at birth the higher the adult BP; the higher the BMI gains in the first 2 decades of life the higher the adult BP; linear accretion only in the first decade of life was associated with adult BP. Linear growth in the first decade of life and fat accretion in the second decade are associated with adults HT.

Developmental Origins and Nephron Endowment in Hypertension

Primary hypertension continues to be one of the main risk factors for cardiovascular disease worldwide. A stable intrauterine environment is critical for the future development and health of the fetus. The developing kidney has been found to be especially vulnerable during this time period, and epidemiological studies have demonstrated that an adverse in utero environment is associated with an increased risk of hypertension and chronic kidney disease. Macro- and micronutrient deficiencies as well as exposure to tobacco, alcohol, and certain medications during gestation have been shown to negatively impact nephrogenesis and reduce one's nephron number. In 1988, Brenner et al. put forth the controversial hypothesis that a reduced nephron complement is a risk factor for hypertension and chronic kidney disease in adulthood. Since then numerous animal and human studies have confirmed this relationship demonstrating that there is an inverse association between blood pressure and nephron number. As our understanding of the developmental programming of hypertension and other non-communicable diseases improves, more effective preventive health measures can be developed in the future.

Kidney volume and ambulatory blood pressure in children

Low nephron number has been shown to be a risk factor for hypertension (HTN) in adulthood. Kidney volume may serve as a surrogate marker for nephron mass. The relationship between kidney volume and ambulatory blood pressure (BP) in the pediatric population is not known. A retrospective chart review of children younger than 21 years who were evaluated for HTN was performed. Twenty-four-hour BP and ultrasonography data were obtained. Multiple regression was used to examine associations between BP and kidney volume. Of 84 children (mean age 13.87 years, 72.6% males), 54 had HTN. Systolic BP index during the awake, sleep, and 24-hour periods (all P≤.05) was found to be positively correlated with total kidney volume. Greater total kidney volume was found to be a positive predictor of 24-hour and sleep systolic index (P≤.05). It failed to serve as a predictor of HTN, pre-HTN, or white-coat HTN. Contrary to expectation, total kidney volume was positively associated with systolic BP indices.

Blood pressure and the capacity-load model in 8-year-old children from Nepal: Testing the contributions of kidney size and intergenerational effects

Objectives

Growth patterns in early life are increasingly linked with subsequent cardio-metabolic risk, but the underlying mechanisms require elucidation. We have developed a theoretical model of blood pressure, treating it as a function of homeostatic metabolic capacity, and antagonistic metabolic load. We sought to differentiate prenatal and postnatal components of metabolic capacity, and to identify intergenerational contributions to offspring capacity and load.

Methods

We followed up at 8 years a cohort of children originally recruited into a randomized trial of maternal micronutrient supplementation in pregnancy. Maternal anthropometry was measured at recruitment. Offspring anthropometry was measured at birth, 2 years and 8 years. Offspring blood pressure, kidney size, and body composition were measured at 8 years. Regression analysis was used to investigate potential associations of maternal phenotype, birth phenotype, and current body composition with kidney size and blood pressure.

Results

Blood pressure was positively associated with body fat, but negatively associated with birth weight and relative leg length. Kidney size was positively associated with birth weight but not with relative leg length. Adjusting for adiposity, blood pressure was independently negatively associated with birth weight, relative leg length, and kidney length. Maternal height and BMI predicted offspring size at birth and at 8 years, but not blood pressure.

Conclusions

Our data provide support for the capacity-load model of blood pressure in Nepalese children. Fetal and postnatal growth and kidney dimensions all contribute to metabolic capacity. Maternal phenotype contributed to offspring capacity and load, but these associations did not propagate to blood pressure.

African Ancestry, Social Factors, and Hypertension Among Non-Hispanic Blacks in the Health and Retirement Study

The biomedical literature contains much speculation about possible genetic explanations for the large and persistent black-white disparities in hypertension, but profound social inequalities are also hypothesized to contribute to this outcome. Our goal is to evaluate whether socioeconomic status (SES) differences provide a plausible mechanism for associations between African ancestry and hypertension in a U.S. cohort of older non-Hispanic blacks. We included only non-Hispanic black participants (N = 998) from the Health and Retirement Study who provided genetic data. We estimated percent African ancestry based on 84,075 independent single nucleotide polymorphisms using ADMIXTURE V1.23, imposing K = 4 ancestral populations, and categorized into quartiles. Hypertension status was self-reported in the year 2000. We used linear probability models (adjusted for age, sex, and southern birth) to predict prevalent hypertension with African ancestry quartile, before and after accounting for a small set of SES measures. Respondents with the highest quartile of African ancestry had 8 percentage points' (RD = 0.081; 95% CI: -0.001, 0.164) higher prevalence of hypertension compared to the lowest quartile. Adjustment for childhood disadvantage, education, income, and wealth explained over one-third (RD = 0.050; 95% CI: -0.034, 0.135) of the disparity. Explanations for the residual disparity remain unspecified and may include other indicators of SES or diet, lifestyle, and psychosocial mechanisms.

Environmental origins of hypertension: phylogeny, ontogeny and epigenetics

Hypertension and renal parenchymal disease are intricately linked. Primary renal parenchymal disease can impact on sodium and volume regulation and lead to hypertension, while arterial hypertension can induce renal parenchymal injury and precipitate renal dysfunction. The examination for clues to the environmental origins of renal disease and hypertension necessitates an approach that integrates epidemiology, clinical medicine, developmental biology, environmental science and epigenetics, such that the manner in which genes and the environment interact can be better understood to pave the way for innovative management paradigms with regards to prevention, diagnosis and treatment. This review summarizes the extant literature and provides cogent arguments for the need to evaluate chronic adult onset disease models such as hypertension and renal disease from the modern perspective that takes into account prenatal exposures, the intrauterine environment and development, postnatal growth and transgenerational epigenetic modifications with their attendant future disease risk from the individual to the population level.

Body composition, leg length and blood pressure in a rural Italian population: a test of the capacity-load model

BACKGROUND AND AIMS

Whereas adult weight or body mass index (BMI) are directly associated with blood pressure (BP), birth weight is inversely associated with BP. The scenario for height is more complex, as both tall and short stature have been associated with higher BP. We used a theoretical model treating sitting height (SH) and tissue masses (fat mass, lean mass) as components of metabolic load, and leg length (LL) as a marker of homeostatic metabolic capacity. We predicted that decreased capacity and increased load would be independently associated with increased BP..

METHODS AND RESULTS

Anthropometry, body composition (bio-electrical impedance analysis) and BP were measured in 601 adults (228 male) aged 20-91 years from three hill villages in southern Italy. Multiple regression analysis was used to investigate associations of body composition and anthropometry with BP. Adjusting for age, systolic BP (SBP) was associated with lean mass in males, and with adiposity in females, whereas diastolic BP (DBP) was associated with fat mass in both sexes. Associations of LL and SH with BP were in opposite directions. LL was inversely associated with SBP and DBP in males, with a similar trend evident in females. SH was directly associated with SBP and DBP in females, and with DBP in males.

CONCLUSIONS

Consistent with our theoretical model, metabolic load is associated with increased BP, though differently between the sexes, whereas metabolic capacity is independently associated with lower BP. Our findings suggest that early growth improves hemodynamic tolerance of high metabolic load in adulthood..

Growth-related disappearance of the childhood relationship between height and blood pressure levels

CONTEXT

Although there is a positive relationship between height and blood pressure (BP) levels in children, there are no reports regarding the association between height and BP levels in adolescents and adults.

OBJECTIVE

This study examined whether there is an association between height and BP levels in Japanese adolescents.

METHODS

The source population was all fifth (10 and 11-year-olds) and ninth graders (14 and 15-year-olds) who attended 11 elementary schools and five junior high schools in the Iwata area from 2002-2008. School-based screenings were conducted annually by the local government from April to June. Data obtained from health examinations were analysed, including anthropometric measurements and BP levels, for 11 780 children (98.7% of the source population).

RESULTS

Height showed significant positive relationships with systolic blood pressure (SBP) and diastolic blood pressure (DBP) in childhood and in adolescent males. In contrast, the relationship between height and SBP was significantly weaker in adolescent females than in childhood and there was no significant relationship between height and DBP in adolescent females.

CONCLUSION

The relationship between height and SBP was attenuated by development in females and the relationship between height and DBP disappeared.

Testing a capacity-load model for hypertension: disentangling early and late growth effects on childhood blood pressure in a prospective birth cohort

BACKGROUND

In 2005, it was estimated that hypertension affected 26.4% of the adult population worldwide. By 2025, it is predicted that it will affect about 60% of adults, a total of 1.56 billion. Both pre- and postnatal growth patterns have been associated with later blood pressure (BP), but in contrasting directions. These inconsistent associations of growth during different developmental periods merit elucidation. We tested a theoretical model treating birth weight as a marker of homeostatic metabolic capacity, and childhood height, lean mass and fat mass as independent indices of metabolic load. We predicted that decreased capacity and increased load would be independently associated with increased BP.

METHODS AND FINDINGS

Data from the ALSPAC cohort on growth from birth to 7 years, and body composition by dual-energy X-ray absorptiometry and BP at 9 years, were analysed (n = 6579). Data were expressed as standard deviation scores (SDS) or standardised regression residuals (SRR). BP was independently and positively associated with each of height, lean mass and fat mass. In a joint model systolic BP was positively associated with conditional weight velocity [males 0.40 (95%CI: 0.37-0.44) & females 0.44 (95%CI: 0.40-0.47) SDS/SRR], but not birth weight [0.00 (95%CI: -0.03-0.04) & 0.03 (95%CI: -0.01-0.07) SDS/SDS]. Adjusting for height, lean mass and fat mass, the association of systolic BP and conditional weight velocity attenuated [0.00(95%CI: -0.09-0.08) & -0.06(95%CI: -0.14-0.03) SDS/SRR], whereas that with birth weight became negative [-0.10 (95%CI: -0.14-0.06) & -0.09 (95%CI: -0.13-0.05) SDS/SDS]. Similar results were obtained for diastolic BP and pulse pressure.

CONCLUSIONS

Consistent with our theoretical model, high metabolic load relative to metabolic capacity is associated with increased BP. Our data demonstrate the contribution of different growth and body composition components to BP variance, and clarify the developmental aetiology of hypertension.

Adipose and height growth through childhood and blood pressure status in a large prospective cohort study

Raised blood pressure (BP) is the world's leading mortality risk factor. Childhood BP substantially predicts adult levels, and although both prenatal and postnatal growth influence it, their relative importance is debated. In a longitudinal study (Avon Longitudinal Study of Parents and Children) of 12 962 healthy children, we aimed to assess the relative contribution of different growth periods and of standardized measures of height versus weight-for-height (an adiposity marker) to BP at age 10 years. Conditional growth modeling was used in the 3230 boys and 3346 girls with BP measurements. Systolic BP was inversely associated with birth weight and weight-for-height but not length (-0.33, -0.27, and -0.12 mm Hg · SD(-1); P=0.003, 0.035, and 0.35, respectively). In infancy, weight, weight-for-height, and height gains were all positively associated with systolic BP (0.90, 0.41, and 0.82 mm Hg · SD(-1), respectively; all P<0.001). After infancy, all of the growth modalities were positively associated with systolic BP (weight, 1.91; weight-for-height, 1.56; height, 1.20 mm Hg · SD(-1); all P<0.001). Similar but weaker associations were found with diastolic BP. Although BP at 10 years was associated with both prenatal and early postnatal growth, their influence was small compared with that of later growth. Because BP ranking relative to the population is substantially determined in the first decade of life, a focus on strategies to reduce the development of adiposity from infancy onward, rather than an emphasis on the nutrition and weight of mothers and infants, should bring greater reductions in population BP.

Human difference in the genomic era: Facilitating a socially responsible dialogue

Background

The study of human genetic variation has been advanced by research such as genome-wide association studies, which aim to identify variants associated with common, complex diseases and traits. Significant strides have already been made in gleaning information on susceptibility, treatment, and prevention of a number of disorders. However, as genetic researchers continue to uncover underlying differences between individuals, there is growing concern that observed population-level differences will be inappropriately generalized as inherent to particular racial or ethnic groups and potentially perpetuate negative stereotypes.

Discussion

We caution that imprecision of language when conveying research conclusions, compounded by the potential distortion of findings by the media, can lead to the stigmatization of racial and ethnic groups.

Summary

It is essential that the scientific community and with those reporting and disseminating research findings continue to foster a socially responsible dialogue about genetic variation and human difference.

Maternal capital and the metabolic ghetto: An evolutionary perspective on the transgenerational basis of health inequalities

There is particular interest in understanding socioeconomic and ethnic variability in health status. The developmental origins of disease hypothesis emphasize the importance of growth patterns across the life-course in relation to noncommunicable disease risk. The physiological components of cardiovascular risk, collectively termed the metabolic syndrome, derive in part from a disparity between the homeostatic "metabolic capacity" of vital organs and the "metabolic load" induced by large tissue masses, a rich diet and sedentary behavior. From an evolutionary perspective, the risk of such disparity is decreased by maternal physiology regulating offspring growth trajectory during gestation and lactation. Maternal capital, defined as phenotypic resources enabling investment in the offspring, allows effective buffering of the offspring from nutritional perturbations and represents the environmental niche initially occupied by the offspring. Offspring growth patterns are sensitive to the magnitude of maternal capital during early windows of plasticity. Offspring life-history strategy can then respond adaptively to further factors across the life-course, but only within the context of this initial maternal influence on growth. Maternal somatic capital is primarily gained or lost across generations, through variable rates of fetal and infant growth. I argue that the poor nutritional experience of populations subjected to colonialism resulted in a systematic loss of maternal capital, reflected in downward secular trends in stature. Accelerating the recovery of somatic capital within generations overloads metabolic capacity and exacerbates cardiovascular risk, reflected in increased disease rates in urbanizing and emigrant populations. Public health policies need to benefit metabolic capacity without exacerbating metabolic load.

Synchronization of adolescent blood pressure and pubertal somatic growth

BACKGROUND

Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relationship of the two events has not been well characterized.

OBJECTIVE

The purpose of this current investigation was to examine the rate of BP change in relation to pubertal growth with the intent to shed light on new mechanisms by which BP is regulated.

METHODS

We examined data from a cohort of 182 normotensive children who had measurements made semiannually for up to 12 yr. From the recorded heights, we identified the subject-specific pubertal growth spurt (PGS) using a growth curve model. With the estimated PGS as an anchoring point, we obtained the rates at which BP and weight changed as continuous functions of time for the duration of pubertal growth. Examining BP on a scale relative to PGS placed BP development in the context of pubertal growth.

RESULTS

Average ages at PGS were 11.5 for girls and 13.3 for boys. Fitted spline models estimated that at the time of PGS, the mean systolic BP was 100 mm Hg for girls and 107 mm Hg for boys; the mean diastolic BP at the PGS was 59 mm Hg for girls and 61 mm Hg for boys. The most intriguing observation was that rate of change in systolic BP and weight peaked at precisely the estimated PGS.

CONCLUSION

The time synchronization of rates of change in BP, weight, and height suggests common regulating mechanisms for somatic growth and BP or growth changes that secondarily affect BP.

Historical cohort studies and the early origins of disease hypothesis: making sense of the evidence

The hypothesis that early-life growth patterns contribute to non-communicable diseases initially emerged from historical cohort studies, consistently associating low birth weight and infant weight gain with later disease risk. Cohort studies offer crucial life-course data on disease aetiology, but also suffer from important limitations, including the difficulty of adjusting for confounding factors and the challenge of interpreting data on early growth. Prospective randomised trials of infant diet appear to provide evidence in direct contradiction to cohort studies, associating faster early growth with disease risk. The present article attempts to resolve this contradiction on two grounds. First, insufficient attention has been directed to inconsistency of outcomes between cohort studies and prospective trials. Cohort studies can assess actual mortality, whereas prospective trials investigate proxies for disease risk. These proxies are often aspects of phenotype that reflect the ‘normalisation’ of metabolism in response to growth, and not all those displaying normalisation in adolescence and early adulthood may go on to develop disease. Second, a distinction is made between ‘metabolic capacity’, defined as organ development that occurs in early life, and ‘metabolic load’, which is imposed by subsequent growth. Disease risk is predicted to be greatest when there is extreme disparity between metabolic capacity and metabolic load. Whereas cohort studies link disease risk with poor metabolic capacity, prospective trials link it with increased metabolic load. Infancy is a developmental period in which nutrition can affect both metabolic capacity and metabolic load; this factor accounts for reported associations of both slow and fast infant growth with greater disease risk.

Ignoring temporal trends in genetic effects substantially reduces power of quantitative trait linkage analysis

Linkage analysis has been one of the most widely used methods for identifying regions of the human genome which contain genes responsible for human diseases. Evidence suggests that the effects of some of the trait causing genes may vary with the age of an individual, giving rise to temporal trends in genetic effects. Linkage analysis routinely tends to ignore such gene-by-age interactions. While linkage analysis methods have been proposed for analysis of longitudinal family data for exploring temporal trends, there are no models to characterize such trends nor methods for analysis of cross-sectional family data. We extend variance component linkage analysis methodology by modeling the variance components due to the quantitative trait locus (QTL) and that due to the polygenic effect to be age dependent. With this model, we investigate the power of linkage analysis in the presence of temporal trends. We show that modeling true temporal trends in QTL effects can substantially increase the power of linkage analysis even when the average locus-specific heritabilities (when trends are ignored) are quite low, thereby demonstrating that, ignoring the gene-by-age interactions, when present, could jeopardize gene discovery.

Somatotype and blood pressure of rural South African children aged 6-13 years: Ellisras longitudinal growth and health study

BACKGROUND

Physique has been useful in assessing the outcome of underlying growth and maturity processes, which leads to a better understanding of variation in child and adult health. However, a high endomorphy rating has been associated with hypertension in adults, posing a serious threat to their health status, while receiving little attention in children.

AIM

The study examined the association between somatotypes, body mass index (BMI) and blood pressure (BP) in 6-13-year-old rural children, in Ellisras, South Africa.

SUBJECTS

A total of 1902 subjects (980 boys and 922 girls) aged 6-13 years were studied as part of the Ellisras Longitudinal Study. Height, weight, four skinfold sites, two breadths, and two girths were measured according to the International Society for the Advancement of Kinanthropometry (ISAK). The Heath-Carter method of somatotyping was used, together with internationally recommended cut-off points for BMI in children. Hypertension, defined as the average of three separate BP readings, where the systolic or diastolic BP is greater than or equal to the 95th percentile for age and sex, was determined.

RESULTS

The prevalence of hypertension ranges from 1 to 5.8% in boys and 3.4-11.4% in girls. The prevalence of overweight ranges from 1.1 to 2.9% in boys and 0.6-4.6% in girls. Systolic BP and BMI showed a significant positive correlation at age 6 years (r = 0.436) and 10-13 years (r = 0.180-0.246 in boys and r = 0.221-0.271 in girls). Diastolic BP showed an insignificant correlation with the BMI and somatotype components in boys and girls.

CONCLUSION

A significant association exists between BP and BMI, and ectomorphy components even after being adjusted for age, gender and height. The need to manage hypertensive individuals is evident in this sample to combat this chronic disease from an early age. Follow-up studies should investigate the relationship between BP and the dietary intake of these children.

Aerobic fitness, body mass index, and CVD risk factors among adolescents: the Québec family study

PURPOSE

The purpose of this study was to examine the association of body mass index (BMI) and aerobic fitness on cardiovascular disease (CVD) risk factors in adolescents.

METHODS

The sample included 416 boys and 345 girls 9-18 y of age from the Québec Family Study. Participants were cross-tabulated into four groups using a median split of age-adjusted physical working capacity (PWC) and body mass index (BMI). Group differences in age-adjusted CVD risk factors (blood pressures, fasting total cholesterol (CHOL), LDL -C, HDL-C, HDL/CHOL, triglycerides, glucose, and a composite risk factor score) were examined by two-way ANOVA.

RESULTS

Several CVD risk factors showed significant main effects for PWC, BMI and/or the PWC by BMI interaction. In general, low fit males and females had higher blood lipids and glucose compared to their high fit counterparts within BMI categories although none of the differences reached statistical significance. The high fit/low BMI group showed the best CVD risk factor profile while the low fit/high BMI showed a poorer profile as evidenced by several significant differences between these two groups. Other significant differences occurred for various risk factors between groups.

CONCLUSION

Both aerobic fitness and BMI show an independent association with CVD risk factors in adolescents.

Age-Dependent Telomere Attrition as a Potential Indicator of Racial Differences in Renal Growth Patterns

BACKGROUND

Racial differences in the predilection to salt sensitivity may arise from different renal growth patterns. To test this idea, we monitored age-dependent telomere attrition rate, reflecting largely the replicative history of somatic cells, in the outer renal cortex and the inner renal medulla of African Americans and Caucasians.

METHODS

Telomere length, determined by the mean length of the terminal restriction fragments (TRF), was measured in specimens from 58 African-American and 63 Caucasian males, ages 1 day to 71 years.

RESULTS

In the outer renal cortex, TRF length attrition rate was significantly slower in African Americans (-0.021 +/- 0.0064 kb/year) than in Caucasians (-0.060 +/- 0.0094 kb/year) (p = 0.0007). In both ethnic groups the TRF length attrition rate was slower in the inner medulla than in the outer renal cortex, but without significant racial differences.

CONCLUSIONS

The proximal tubule is the most abundant nephron structure in the outer renal cortex. Less proliferative growth of proximal tubular cells in kidneys from African Americans may be one factor explaining the slower age-dependent telomere attrition rate in the outer renal cortex of African Americans than in Caucasians.

Body size, fat distribution, menarcheal age and blood pressure in 14-year-old girls

BACKGROUND

The relationships between body size and fatness and blood pressure are generally acknowledged. The majority of the few studies that have examined the effect of fat distribution and maturation rate on blood pressure have used secondary sex characteristics as the measure of maturity. The aim of the present study is to examine the associations between blood pressure and relative weight, fat distribution, recalled menarcheal age and occurrence of menstruation (yes/no) in a sample comprising of 1149 14-year-old girls.

METHODS

Systolic and diastolic blood pressure (DBP), height, weight and body circumferences were measured using standard protocols. Fatness was expressed as body mass index (BMI, kg/m2), whereas fat distribution was estimated by using waist-to-hip ratio. The girls' maturity status was assessed from exact recalled date of menarche. One-way analysis of covariance and multiple linear regression analyses were used to determine the strength of association among systolic blood pressure (SBP), DBP and BMI, menarcheal age and indices of fat distribution.

RESULTS AND CONCLUSION

Height and BMI are significantly associated with SBP. Relative weight is the most important factor related to SBP independently of chronological age and maturity status. Height and age at menarche are significantly associated with DBP. Height of 14-year-old girls shows the same strength of association with SBP and DBP, whereas maturity status negatively correlates with DBP. Fat distribution shows no effect on the level of DBP in girls.

Low birth weight as a risk factor for hypertension

While the geographic and demographic disparities in the prevalence of hypertension have been recognized for decades, the reasons for these differences in disease risks remain unknown. The demographic and geographic patterns of hypertension are similar to those of low birth weight, giving support to the "Barker Hypothesis" which proposes a fetal origin of adult-onset disease. In fact, ecologic and observational studies throughout the world have detected significant associations of low birth weight and increased risks of hypertension. Nonetheless, the mechanisms for the association have not been fully described and documented. With some supportive evidence, proposed mechanisms include reduced nephrogenesis with a higher threshold for pressure natriuresis and greater susceptibility to progressive renal disease, impaired development of the endothelium, and increased sensitivity to glucocorticoids. Still, considerable work needs to be done to explain the birth weight/blood pressure relationship. The findings to date and the clinical significance warrant continued research in this intriguing area of study.

A microarray minisequencing system for pharmacogenetic profiling of antihypertensive drug response

We aimed to develop a microarray genotyping system for multiplex analysis of a panel of single nucleotide polymorphisms (SNPs) in genes encoding proteins involved in blood pressure regulation, and to apply this system in a pilot study demonstrating its feasibility in the pharmacogenetics of hypertension. A panel of 74 SNPs in 25 genes involved in blood pressure regulation was selected from the SNP databases, and genotyped in DNA samples of 97 hypertensive patients. The patients had been randomized to double-blind treatment with either the angiotensin II type 1 receptor blocker irbesartan or the beta 1-adrenergic receptor blocker atenolol. Genotyping was performed using a microarray based DNA polymerase assisted 'minisequencing' single nucleotide primer extension assay with fluorescence detection. The observed genotypes were related to the blood pressure reduction using stepwise multiple regression analysis. The allele frequencies of the selected SNPs were determined in the Swedish population. The established microarray-based genotyping system was validated and allowed unequivocal multiplex genotyping of the panel of 74 SNPs in every patient. Almost 7200 SNP genotypes were generated in the study. Profiles of four or five SNP-genotypes that may be useful as predictors of blood pressure reduction after antihypertensive treatment were identified. Our results highlight the potential of microarray-based technology for SNP genotyping in pharmacogenetics.

Genetics of obesity and type 2 diabetes: tracking pathogenic traits during the predisease period

The modern generalization of sedentary life and caloric abundance has created new physiological conditions capable of changing the level of expression of a number of genes involved in fuel metabolism and body weight regulation. It is likely that the genetic variants or alleles of these genes have in the past participated in the adaptation of human physiology to its evolutionary constraints. The nature and prevalence of polymorphisms responsible for the quantitative variation of complex metabolic traits may have been different among human populations, depending on their environment and ancestral genetic background. These polymorphisms could likely explain differences in disease susceptibility and prevalence among groups of humans. From complex traits to potentially complex alleles, understanding the molecular genetic basis underlying quantitative variation will continue to be a growing concern among geneticists dealing with obesity and type 2 diabetes, the main fuel disorders of the modern era. Genomics and genetic epidemiology now allow high-level linkage and association studies to be designed. But the pooling of large trans-geographic cohorts may in fact increase the genetic heterogeneity of studied traits and dilute genotype-phenotype associations. In this article, we underscore the importance of selecting the traits to be subjected to quantitative genetic analysis. Although this is not possible for most other multifactorial diseases, obesity and type 2 diabetes can be subjected to a pregenetic dissection of complexity into simpler quantitative traits (QTs). This dissection is based on the pathogenic mechanisms, and the time course of the traits, and the individuals' age, within the predisease period rather than on descriptive parameters after disease diagnosis. We defend that this approach of phenotypes may ease future associations to be established between QTs of intermediate complexity and genetic polymorphisms.

Resting and reactive blood pressure. Predictors of ambulatory blood pressure in older adults with hypertension

The study examined whether reactive change scores from a short blood pressure (BP) reactivity protocol, resting BP, or resting pulse pressure (PP) would be predictors of 24-hour ambulatory BP and BP load in cardiac patients. The study used a single-group design, with both an experimental clinical component and an observational field component. Both components used repeated measurement methods. The study population consisted of 45 adult patients with a mean age of 64.6 +/- 8.5 years who were diagnosed with cardiac disease in a cardiac rehabilitation program and who were taking anti-hypertensive medication. Blood pressure reactivity was operationalized with a speech protocol. During the speech protocol, BP was measured with an automatic device (Dinamap) while patients talked about their health and about their usual day. Twenty-four-hour ambulatory BP measurement followed the speech protocol. Resting systolic BP and resting PP were significant predictors of 24-hour ambulatory systolic BP, and resting systolic BP was a significant predictor of systolic BP load. No predictors were significant of 24-hour diastolic BP or diastolic BP load. Initial resting BP and PP may be used in clinical settings to assess hypertension management. Future studies are necessary to confirm the ability of resting BP to predict ambulatory BP and BP load in older adults who are medicated and hypertensive.

Multi-center genetic study of hypertension: The Family Blood Pressure Program (FBPP)

The Family Blood Pressure Program (FBPP) consists of 4 independently established multicenter networks of investigators who have complementary approaches to the genetics of blood pressure levels and hypertension. The program has recruited participants from the African American, Mexican American, Asian, and non-Hispanic white populations. Each network utilized study designs, laboratory measurements, and analytic methods that made efficient use of the unique characteristics of their populations and the investigators' expertise. The individual networks subsequently unified core study components into a single cohesive program. The unified FBPP includes (1) standardized clinic and laboratory protocols for core variables to facilitate direct comparison of results among networks, (2) coordination among laboratories to avoid unnecessary duplication of effort, (3) utilization of a single laboratory for genome-wide marker typing, and (4) a pooled data set containing phenotype and genotype information from >11 000 individuals.

Multilevel integrative analyses of human behavior: social neuroscience and the complementing nature of social and biological approaches

Social and biological explanations traditionally have been cast as incompatible, but advances in recent years have revealed a new view synthesized from these 2 very different levels of analysis. The authors review evidence underscoring the complementing nature of social and biological levels of analysis and how the 2 together can foster understanding of the mechanisms underlying complex behavior and the mind. Specifically, they review the utility of considering social influences on biological processes that are often viewed as outside the social domain including genetic constitution, gene expression, disease, and autonomic, neuroendocrine, and immune activity. This research underscores the unity of psychology and the importance of retaining multilevel integrative research that spans molar and molecular levels of analysis. Especially needed in the coming years is more research on the mechanisms linking social and biological events and processes.

Allometric relationship between body size and peak VO2 relative to age at menarche

The present study examined allometric coefficients relating peak VO2 and body size relative to the time of menarche. Peak oxygen uptake (peak VO2) during exercise on a bicycle ergometer, stature and body mass were measured at annual intervals in a mixed-longitudinal sample of 40 active girls from 11 to 14 years of age. The girls were interviewed about their menarcheal status at each examination. The data were treated relative to the time before and after menarche: 2 years before (n = 18), 1 year before (n = 26), during the year of menarche (+/- 6 months, n = 32), 1 year after (n = 35) and 2 years after menarche (n = 22). Allometric coefficients were calculated for each of the five menarcheal groups based on logarithmic transformations of peak VO2 and body mass and peak VO2 and stature. The major axis of VO2 and body mass or stature (log transformed) was also calculated. This is the most appropriate slope for comparison with theoretical allometry coefficients. Mean peak VO2 increases from 2.1 +/- 0.19 L 2 years before menarche to 2.3 +/- 0.26 L 2 years after menarche. The slope of the major axis for body mass is always higher (0.508-0.926) than that for the allometric coefficient (0.323-0.591) in each of the menarcheal groups. The major axis slope and allometric coefficient are lowest between body mass and peak VO2 during the year of menarche. The slope of the major axis is below the theoretical allometric coefficients assuming geometric or elastic similarity, 2/3 or 3/4, before and at menarche and increases after menarche. Although the differences are not statistically significant, the results suggest that the relationship between body mass and peak VO2 at menarche is lower compared with relationships before and after this maturational landmark. Allometric coefficients for stature relative to peak VO2 show a similar pattern.

Factors influencing blood pressure: development of a risk model

A review of the literature suggests that blood pressure (BP) is multifactorial and is affected by the interactions of genetics, physiology, responses to the environment, and lifestyle factors that have increasing influence as one ages. The effect of these factors on hypertension (HTN) risk as one ages is depicted in the author's Hypertension Risk Model. The model emphasizes HTN risk in the older adult--age 50 and older--and shows the interaction of the factors influencing HTN development and BP assessment methods. Implications of three methods of BP assessment--(1) static BP, (2) 24-hour ambulatory blood pressure monitoring, and (3) clinic blood pressure reactivity (BPR) protocol--are discussed. The model may be useful for understanding factors that contribute to HTN and for guiding BP assessment for clinical researchers. Addressing the factors associated with the sympathetic system activity from various environmental stressors requires assessing dynamic BP, particularly in the older hypertensive adult who has increased BPR. Further research should focus on ambulatory blood pressure studies in older adults that would provide the methods and instrumentation needed to assess HTN and therefore decrease mortality and morbidity in this population.

Relationship between weight at birth and the number and size of renal glomeruli in humans: a histomorphometric study

BACKGROUND

The number of nephrons in humans varies considerably under normal circumstances, and retarded intrauterine growth has been reported to be associated with a significant reduction in nephron number. Low nephron number may be an independent risk factor for the development of hypertension. We therefore decided to evaluate the relationship between body weight at birth and the number and size of nephron units.

METHODS

We examined coronal sections of the kidneys of 35 neonates who died within two weeks of birth because of hyaline membrane, infectious complications, brain hemorrhage, or perinatal hypoxia and had no urinary congenital malformations. Nine of them (5 males and 4 females) were between 36 and 37 weeks of gestation, and the rest had 38 or more weeks of gestation. Eighteen neonates weighed less than 2500 g at birth [low birth weight (LBW); 9 females and 9 males], and 17 had weights above this value [normal birth weight (NBW); 8 females and 9 males]. In each section, glomeruli present in four sequential subcapsular microscopic fields, corresponding to 0.6 mm2, were counted; in addition, the area of each of 65 consecutive glomeruli was determined by a computerized measurement system. Glomerular volume was calculated from the glomerular area. Linear regression analysis was used to test the relationship between glomerular number and size and the weight at birth.

RESULTS

The number of glomeruli per 0.6 mm2 of renal cortex was 92.9 +/- 4.85 in the LBW and 105.8 +/- 3.91 in NBW (P < 0.0001). Glomerular volume (micro(3) x 10(-3)) was 529.1 +/- 187.63 in the LBW group and 158.0 +/- 49.89 in the NBW group (P < 0.0001). The glomeruli occupied 8.59 +/- 1.38% of the kidney area under examination in the LBW group and 14.3 +/- 2.75% in the NBW group (P < 0.0001). There were significant direct correlations between the weight at birth and the number of glomeruli (r = 0.870, P < 0.0001) and area occupied by glomeruli (r = 0.935, P < 0.0001). There were inverse correlations between the number of glomeruli and the volume of the glomeruli (r = -0.816, P < 0.0001) and the weight at birth and glomerular volume (r = -0.848, P < 0.0001). These findings were independent of sex and race (black vs. white). Essential arterial hypertension existed in 38.9% of the mothers of children with LBW and in 5.9% of the mothers of children with NBW (P < 0.05). Smoking habits existed in 50% of the mothers of LBW children and in 11.8% of the mothers of NBW children (P < 0.05).

CONCLUSION

There are strong correlations between glomerular number (direct) and size (inverse) with LBW in this cohort. Endowment with decreased nephron numbers may be a risk factor for hypertension and the rate of progression of renal disease.

Ontogenetic aspects of hypertension development: analysis in the rat

In this review, we attempt to outline the age-dependent interactions of principal systems controlling the structure and function of the cardiovascular system in immature rats developing hypertension. We focus our attention on the cardiovascular effects of various pharmacological, nutritional, and behavioral interventions applied at different stages of ontogeny. Several distinct critical periods (developmental windows), in which particular stimuli affect the further development of the cardiovascular phenotype, are specified in the rat. It is evident that short-term transient treatment of genetically hypertensive rats with certain antihypertensive drugs in prepuberty and puberty (at the age of 4-10 wk) has long-term beneficial effects on further development of their cardiovascular apparatus. This juvenile critical period coincides with the period of high susceptibility to the hypertensive effects of increased salt intake. If the hypertensive process develops after this critical period (due to early antihypertensive treatment or late administration of certain hypertensive stimuli, e.g., high salt intake), blood pressure elevation, cardiovascular hypertrophy, connective tissue accumulation, and end-organ damage are considerably attenuated compared with rats developing hypertension during the juvenile critical period. As far as the role of various electrolytes in blood pressure modulation is concerned, prohypertensive effects of dietary Na+ and antihypertensive effects of dietary Ca2+ are enhanced in immature animals, whereas vascular protective and antihypertensive effects of dietary K+ are almost independent of age. At a given level of dietary electrolyte intake, the balance between dietary carbohydrate and fat intake can modify blood pressure even in rats with established hypertension, but dietary protein intake affects the blood pressure development in immature animals only. Dietary protein restriction during gestation, as well as altered mother-offspring interactions in the suckling period, might have important long-term hypertensive consequences. The critical periods (developmental windows) should be respected in the future pharmacological or gene therapy of human hypertension.

The complex dynamics of diabetes modeled as a fractal complex-adaptive-system (FCAS)

An approach is suggested in this paper that has successfully been applied in physics, ecology, and the biomedical sciences. This is called fractal-complex-adaptive-system (FCAS) modeling. The objective of this type of analysis is to reconstruct the dynamics of the pathological process that has been leading to the disease. Diabetes, a complexdisease, has been used to test the methodology. Biometrical analyses were undertaken on subjects diagnosed with overt diabetes (hereafter called IDDM), chemical diabetes (NIDDM), and a group of normal subjects. The studied variables were plasma glucose, insulin concentration, and insulin sensitivity. FCAS modeling consists in fitting a power-law function to the bivariate lognormal distribution of the variables. The power-law exponent is estimated by principal component analysis (PCA). Analyses have shown that glucose disposal can be considered a fractal process, thereby implying a complex hierarchy of interacting scales and mechanisms in glucose handling. The first principal component represents quantitative glucose disposal, and the second component is compatible with insulin efficiency. PCA further retrieved distinct ongoing pathological processes within clinical groups of subjects. The IDDM insulin production defect had a high (absolute value) exponent of -3.5 that confirms a crude defect scanning the whole fractal hierarchy. Definite insulin resistance has been detected in clinically normal subjects with a low exponent of -0.5, thus suggesting a subtle and complex problem possibly due to aging or reduced physical activity. Insulin sensitivity was definitely impaired in the NIDDM clinical group with an exponent of -2.2, thereby suggesting poorly scheduled insulin feedback, possibly due to peripheral insensitivity. NIDDM appeared to result from aggravation of the subtle insensitivity seen in normal subjects. On the whole, the fractal model seemed to be capable of assessing the degree of complexity of a disease. It is concluded that future studies of diabetes using FCAS modeling ought to be undertaken on the basis of multiple-scale biological variables, thereby closely reflecting the complexity of glucose handling. It is further recommended that such analyses be undertaken with dynamic data to track down the precise timing of the various homeostatic disruptions. It would also be important to carry out this type of analysis on less known but equally complex disease processes. The results might point to important new research findings.

The future of genetic epidemiology

Genetic epidemiology is a hybrid discipline whose ultimate aim is to identify and to characterize population-level factors that contribute to disease. Genetic epidemiologists often pursue this aim through the design and implementation of studies that simultaneously invoke principles in population genetics, epidemiology, molecular biology and biostatistics. However, traditional (and much contemporary) research in genetic epidemiology has barely tapped the potential that these disciplines have to work together. It is our view that future genetic epidemiology inquiry will benefit greatly from stronger integration of these disciplines and is likely to converge on themes in fields as diverse as demography, classical population and evolutionary genetics, pharmacoepidemiology, and ecology. The ultimate focus of this research will be evolution and maintenance of disease within and across populations.

Reflections on telomeres, growth, aging, and essential hypertension

Here we review the "telomere hypothesis of cellular aging." We propose that this hypothesis is relevant to our understanding of the roles of genetics as well as growth and development in the etiology of essential hypertension and its cardiovascular complications. Elements of this hypothesis and the speculations that we make can be directly tested using tissues (cells) obtained from human beings.

Genetically complex cardiovascular traits. Origins, problems, and potential solutions

Modern molecular genetic analysis tools are making it possible for researchers to investigate, and in many cases actually disclose, mutations and other genetic factors that contribute to disease susceptibility. However, the ease with which these factors can be identified is dictated by not only the number of factors underlying or influencing the trait, but also by the manner in which these factors interact. Traits that are influenced by multiple genetic and nongenetic factors are termed "complex" genetic traits and are receiving a great deal of attention in the current medical literature. Hypertension and blood pressure regulation are considered paradigmatic complex traits. In this paper, the origin, nature, and dilemmas associated with the analysis of complex traits are considered. Basic biochemical and physiological determinants of blood pressure are described in an effort to show how genetic complexity could arise within an individual, and fundamental concepts in population genetics and evolutionary theory are discussed to expose the reasons certain forms of genetic complexity can emerge and be sustained in the population at large. Methods for approaching the genetic dissection of complex traits and diseases are also enumerated, with simple descriptions of the scientific motivation offered for each. Problems plaguing these approaches are also discussed. Finally, areas for future research are outlined with the hope of sparking further debate on the subject.

Weights at birth and in early infancy, systolic pressure, and left ventricular structure in subjects aged 8 to 24 years

The objective of this study was to determine whether systolic pressure and left ventricular mass in children, adolescents, and young adults are related to fetal and infant growth. Blood pressure measurements and M-mode echocardiography were performed in 210 subjects aged 8 to 24 years whose information on weights at birth and in early infancy, written by physicians, was obtained from the children's health record booklets. Systolic pressure, adjusted for sex and current height or for sex, current age, weight, and height, was the highest in subjects with low birth weight. No association was observed between systolic pressure and weight at either 9 months or 2 years. Left ventricular mass, adjusted for sex and current height or for sex, current age, weight, and height, increased with decreasing weight at 9 months or 2 years, independent of systolic pressure. Increased ventricular mass associated with reduced infant growth was concentric, resulting from a proportionate thickening of the posterior wall and interventricular septum. Left ventricular mass was not related to birth weight. These findings were observed in both sexes and in all age subgroups and were independent of gestational age, birth order, and parental risk factors. This study supports the hypothesis that systolic pressure and left ventricular mass might be partly determined during fetal life and early infancy. The mechanisms that underlie the associations of blood pressure and left ventricular structure with weights at birth and in early infancy should be studied thoroughly.

Effects of neonatal growth on adult blood pressures of borderline hypertensive rats

We conducted this study to test the hypothesis that there are long-term effects of litter-size manipulations during the preweaning period on growth and adult blood pressure of rats. Litter size of genetically homogeneous borderline hypertensive rats, which were produced by cross-mating male Wistar-Kyoto rats with female spontaneously hypertensive rats, was manipulated from 10 to 16 days of age. In addition, a subset of males and females was castrated within the first 30 hours of life. Body weights were measured at several preweaning and postweaning ages, and tail-cuff blood pressures were recorded at 90 days of age. Intact and castrated pups of both sexes that were reared in small (n = 4) litters from 10 to 16 days of age gained nearly twice the weight of animals reared in large (n = 9 to 12) litters during this period. Intact males from small litters had significantly higher adult blood pressures than those from large litters. These long-term effects remained even in groups matched for adult weight and length. Neonatal castration of males completely blocked the consequences of litter-size manipulation on adult blood pressure, suggesting either an organizational or activational role for androgens. Neither intact nor neonatally castrated females exhibited differences in adult blood pressure as a function of litter-size manipulation.