Perinatal origin of adult diseases.

Three relevant, interrelated scientific advances are described: the concept of critical periods (CPs), the Barker Hypothesis (BH), and the underlying epigentic mechanisms involved. Critical periods are genetically programmed, highly sensitive time intervals during which the interaction between environment and individuals generates the development of physiological processes related to physical growth and development, survival (breastfeeding), social behavior, and learning. Barker hypothesis is based on the finding that prenatal malnutrition (for example, lowbirthweight) is closely related to mortality due to cardiovascular disease CVD) in the adult, and to the risk conditions leading to it: insuline resistence, metabolic syndrome, obesity, and high blood pressure. This association is no due to genetical causes, but secondary to nutritional deficits which in turn generate epigenetic mechanisms of methylation of DNA basis and cromatine proteines (histones), which do not modify the genetic code but modulate its expresion, reinforcing some genes, inhibiting others, regulating when and where they are expressed. These genes participate in the process called programming, consisting of permanent changes in the response to stimulation of metabolic and hormone regulators, such as, for example, increasing insuline resistence. Epigenetic changes persist even when original conditions (fetal or perinatal malnutrition) are no longer present. This, in turn, affects health of the offspring later in adult life, creating thus the same environmental prenatal conditions to the next generation. This transgenerational effects of early nutritional experiences are more frequent in population groups of por socioeconomic level, and consequently have serious implications in the future health of Latin American populations.