Perinatal determinants of adult cardiovascular disease and cancer

The biological basis and clinical significance of hormonal imprinting, an epigenetic process

The biological phenomenon, hormonal imprinting, was named and defined by us (Biol Rev, 1980, 55, 47-63) 30 years ago, after many experimental works and observations. Later, similar phenomena were also named to epigenetic imprinting or metabolic imprinting. In the case of hormonal imprinting, the first encounter between a hormone and its developing target cell receptor-usually at the perinatal period-determines the normal receptor-hormone connection for life. However, in this period, molecules similar to the target hormone (members of the same hormone family, synthetic drugs, environmental pollutants, etc), which are also able to bind to the receptor, provoke faulty imprinting also with lifelong-receptorial, behavioral, etc.,-consequences. Faulty hormonal imprinting could also be provoked later in life in continuously dividing cells and in the brain. Faulty hormonal imprinting is a disturbance of gene methylation pattern, which is epigenenetically inherited to the further generations (transgenerational imprinting). The absence of the normal or the presence of false hormonal imprinting predispose to or manifested in different diseases (e.g., malignant tumors, metabolic syndrome) long after the time of imprinting or in the progenies.

[Hormonal imprinting--the unforeseeable future]

Hormonal imprinting takes place at the first encounter between the developing receptor and the target hormone, perinatally, causing life-long changes in the binding capacity of the receptor and the indexes influenced by it. Perinatal hormonal imprinting is absolutely needed for the maturation of receptor, however, at the same time, molecules similar to the target hormone (related hormones, synthetic drugs acting at receptor level, chemicals, environmental pollutants etc.) can cause faulty imprinting, also with (morphological, biochemical, receptorial, behavioral) consequences for life. Although imprinting is characteristic and inevitable perinatally, it can be provoked in any period of life in developing cells, especially at the weanling and adolescent age (late imprinting). There is no gene mutation during imprinting, however, the methylation pattern of the genes changes and that inherits epigenetically the imprinting, which is manifested in disposition to diseases or in diseases (e.g. tumor formation, metabolic syndrome). Imprinting is inherited between generations that could cause--in the present chemical world--evolutionary consequences. Thus, medicaments or preventive drugs, e.g. pregnancy protecting drugs or oral contraceptive pills should be given cautiously, especially in the critical periods, considering that consequences are manifested always after a long period (sometimes decades) or in the next generations.

Fetal growth and childhood cholesterol levels in the United States

Research has linked fetal environment to subsequent adult disease. This study examines the extent to which infants born small-for-gestational age (SGA) were at risk for high cholesterol levels in early childhood (ages 4-6 years). Data were obtained from 1727 children aged 4-6 years who participated in the cross-sectional third US National Health and Nutrition Examination Survey and had both birth certificates and blood cholesterol information. The odds of having moderately elevated (170-199 mg/dL) or high (> or =200 mg/dL) serum total cholesterol after being born SGA were determined after controlling for sex, race/ethnicity, education of household head, saturated fat intake, parental history of high cholesterol and overweight status. Approximately 11% of participants were SGA. Proportions of children with moderately elevated and high cholesterol levels were approximately 28 and 8%, respectively. SGA children were almost twice as likely (odds ratio 1.97, 95% confidence interval [0.8, 4.8]) to have high cholesterol vs. low cholesterol than non-SGA children, although the result was not statistically significant. Multiple linear regression demonstrated a similar inverse, non-significant relationship between gestation-adjusted birthweight and cholesterol (beta = -2.3, P = 0.33). These data indicate a possible association between reduced fetal growth, represented by birthweight adjusted for gestational age, and increased cholesterol levels in early childhood.

Major dietary patterns in pregnancy and fetal growth

OBJECTIVES

To investigate possible associations between maternal diet during pregnancy and fetal growth.

METHOD

Factor analysis was used to explore dietary patterns among pregnant women. The association between maternal dietary patterns and fetal growth (in terms of small for gestational age, SGA) was investigated by logistic regression. Prospective cohort study, including information on 44 612 women in Denmark.

RESULTS

Two major dietary patterns were defined: the first pattern was characterized by red and processed meat, high-fat dairy, and the second pattern was characterized by intake of vegetables, fruits, poultry and fish. Women were classified into three classes according to their diet: the first class had high intake of foods of the first dietary pattern, and was classified as 'the Western diet', the second class preferred foods of the second pattern and was classified as the 'Health Conscious'; and the third one had eaten foods of both patterns, and was classified as the 'Intermediate'. The odds ratio of having a small for gestational-age infant (with a birth weight below the 2.5th percentile for gestational age and gender) was 0.74 (95% CI 0.64-0.86) for women in the Health Conscious class compared with women in the Western Diet class. The analyses were adjusted for parity, maternal smoking, age, height, pre-pregnancy weight and father's height.

CONCLUSIONS

Our results indicated that a diet in pregnancy, based on red and processed meat and high-fat diary, was associated with increased risk for SGA. Further studies are warranted to identify specific macro-, or micronutrients that may be underlying these associations.

Hormonal imprinting: phylogeny, ontogeny, diseases and possible role in present-day human evolution

Hormonal (chemical) imprinting which was first observed (and named) by us in the seventies of the last century, is a general biological phenomenon which takes place when the developing receptor meets its target hormone for the first time. Under the effect of imprinting, receptors mature and reach their maximal binding capacity. It also influences the cells' hormone production and different functions depending on receptors and hormones. Hormonal imprinting is present already at the unicellular level causing the development of specific receptors and helping the easier recognition of useful or harmful surrounding molecules. The phenomenon is an important factor in the survival of the species, as the effect of imprinting is transmitted to the progeny cell generations. At the same time it possibly helps the selection of molecules which are suitable for acting as hormones in higher ranked animals. In mammals, hormonal imprinting takes place perinatally and determines the function of receptor-signal-transduction systems as well as hormone production for life. However, there are other critical imprinting periods for continuously developing cells. Excess of the target hormones or presence of foreign molecules which are able to bind to the receptors, provoke faulty imprinting in the critical periods with life-long morphological, biochemical, functional or behavioural consequences. As many receptor-bound foreign molecules are used as medical treatments and many such molecules are present around us and inside us as environmental pollutants, they--causing faulty imprinting--are able to predispose the (human) organism to cardiovascular, endocrine, metabolic and cancerous diseases. It seems likely that this effect is connected with disturbance of DNA methylation process in the critical periods of life. There are some signs of the transgenerational effect of faulty imprinting and this could be manifested in the evolution of humans by an epigenetic route.

Birth characteristics and adult cancer incidence: Swedish cohort of over 11,000 men and women

Associations between larger size at birth and increased rates of adult cancer have been proposed but few empirical studies have examined this hypothesis. We investigated overall and site-specific cancer incidence in relation to birth characteristics in a Swedish population-based cohort of 11,166 singletons born in 1915-1929 for whom we have detailed obstetric data and who were alive in 1960. A total of 2,685 first primary cancers were registered during follow-up from 1960 to 2001. A standard deviation (SD) increase in birth weight for gestational age (GA) was associated with (sex-adjusted) increases of 13% (95% CI = 0.03-0.23) in the rates of digestive cancers and of 17% (95% CI = 0.01-0.35) in the rates of lymphatic cancers. Women who had higher birth weights also had increased rates of breast cancer under age 50 years (by 39% per SD increase; 95% CI = 0.09-0.79), but reduced rates (by 24%; 95% CI = 0.07-0.38) of endometrial (corpus uteri) cancer at all ages. There was no evidence of associations with other cancer sites. For overall cancer incidence, men had an 8% increased risk at all ages per SD increase in birth weight for GA while women only had an increased risk under age 50 years (mainly driven by the association with breast cancer). These findings provide evidence of a modest association of birth size and adult cancer risk, resulting from positive associations with a few cancer sites and a possible inverse association with endometrial cancer.

Birthweight differences between USA and China and their relevance to breast cancer aetiology

BACKGROUND

There has been renewed interest about determinants of birth size following the propagation of hypotheses that birth size parameters may have long-term consequences on the occurrence of common diseases in adulthood, including breast cancer.

METHODS

In the context of a cohort study, 296 Caucasian pregnant women in Boston, USA and 329 Chinese pregnant women in Shanghai, China were followed to term. Birth size characteristics of the baby and maternal anthropometry were measured using standardized protocols. Analyses were conducted through multiple regression procedures.

RESULTS

No significant difference was found between US and Chinese newborns with respect to gestational age. Among US women, pregravid oral contraceptive use was strongly associated with higher birthweight. In both US and Chinese women, birthweight was positively associated with height, pre-pregnancy body mass index, and weight gain during pregnancy. More importantly, the difference in these three maternal variables between the two samples fully explains the birthweight difference between the two populations.

CONCLUSIONS

We postulate that babies in China may have lower birthweight because their mothers' anthropometry imposes constraints on the growth of the fetus. When Chinese women migrate to the US, they tend to grow taller and heavier so that their babies can reach, on the average, a higher birthweight. The recurrence of this process in successive generations could explain why eventually Chinese Americans tend to have comparable birth and adult anthropometric characteristics, as well as comparable breast cancer rates, to those of Caucasian Americans.

Increased tissue concentrations of arachidonic acid in umbilical artery and placenta in fetal growth retardation

OBJECTIVE

To compare the fatty acid phospholipid composition of the umbilical artery and the placenta in cases of fetal growth retardation (FGR) and of normal growth, as well as in symmetric and asymmetric FGR.

DESIGN

Case-control study.

SETTING

University hospital.

POPULATION

Thirty-nine FGR cases (12 asymmetric, 27 symmetric) and 78 cases with normal growth.

MAIN OUTCOME MEASURES

Thin layer gas-liquid capillary chromatography of phospholipid fatty acids in umbilical artery and placental cotyledons. Newborns were classified as FGR if their weight was under the 10th percentile for our center. FGR was defined as symmetric if the ponderal index was >2.32, and as asymmetric if it was <2.32.

RESULTS

In FGR, arachidonic acid was significantly increased both in placenta (24.05%+/-2.78 vs 22.46%+/-2.93) and in umbilical artery (16.76%+/-2.40 vs 15.58%+/-3.67). Indeed this increase was significantly higher in asymmetric than in symmetric FGR (25.70+/-2.32 vs 23.32+/-2.68 in placenta and 18.06+/-1.46 vs 16.14 +/-2.53 in umbilical artery). On the other hand, in the placenta there were a number of differences in the metabolic ratios analyzed when comparing symmetric and asymmetric FGR, indicating a lower DHA availability and a higher n-6 fatty acid elongation and desaturation in asymmetric FGR.

CONCLUSION

FGR is characterized by an increase in arachidonic acid both in the placenta and umbilical artery phospolipids, probably reflecting a different mobilization from tissue stores. It is speculated that the different arterial composition could be partially responsible for the increased cardiovascular risk of FGR in adulthood. On the other hand the metabolic status of the placenta concerning polyunsaturated fatty acids was very different in symmetric and asymmetric FGR, suggesting a different pathogenesis.

Change in food availability during pregnancy: Is it related to adult sudden death from cerebro- and cardiovascular disease in offspring?

Maternal access to food during pregnancy affects birth weight and other characteristics of offspring. It has been suggested that fluctuations in food availability during infancy, ranging from plentiful to starvation, may influence cerebro-cardiovascular risk factors for the offspring during adult life. This study was designed to test the correlation between food availability changes during life before birth and adult sudden death from disease. This was a follow-up study of ancient cohorts in the parish of Skellefteå, Sweden, comprising 7,572 individuals born between 1805 and 1849 and still alive at age 40. Food availability variations in the parish during their prenatal life were ascertained from historical sources, the main outcome measures being overall mortality and mortality from sudden death in the age range 40-70 years. The risk of sudden death was almost doubled for those whose mothers were struck by a poor harvest during the early stages of pregnancy, but who experienced a good harvest toward the end. Yet almost the same over-risk was evident for the converse case: plentiful food supply in early pregnancy followed by a poor harvest toward the end. A stable maternal access to food during pregnancy is important for the offspring's risk of sudden death from cerebro- and cardiovascular disease as an adult. Am. J. Hum. Biol. 12:447-453, 2000. Copyright 2000 Wiley-Liss, Inc.