Effect of neonatal glucocorticoid treatment on bone mineralization of adult nontreated, dexamethasone-treated or vitamin D3-treated rats

Hormonal Imprinting: The First Cellular-level Evidence of Epigenetic Inheritance and its Present State

Hormonal imprinting takes place perinatally at the first encounter between the developing hormone receptor and its target hormone. This process is needed for the normal function of the receptor-hormone pair and its effect is life-long. However, in this critical period, when the developmental window is open, related molecules (members of the same hormone family, synthetic hormones and hormone-like molecules, endocrine disruptors) also can be bound by the receptor, causing life-long faulty imprinting. In this case, the receptors’ binding capacity changes and alterations are caused at adult age in the sexual and behavioral sphere, in the brain and bones, inclination to diseases and manifestation of diseases, etc. Hereby, faulty hormonal imprinting is the basis of metabolic and immunological imprinting as well as the developmental origin of health and disease (DOHaD). Although the perinatal period is the most critical for faulty imprinting, there are other critical periods as weaning and adolescence, when the original imprinting can be modified or new imprintings develop. Hormonal imprinting is an epigenetic process, without changing the base sequence of DNA, it is inherited in the cell line of the imprinted cells and also transgenerationally (up to 1000 generations in unicellulars and up to the 3_rd generation in mammals are justified). Considering the enormously growing number and amount of faulty imprinters (endocrine disruptors) and the hereditary character of faulty imprinting, this latter is threatening the whole human endocrine system.

Bone Manifestation of Faulty Perinatal Hormonal Imprinting: A Review

Hormonal imprinting takes place at the first encounter between the developing receptor and its target hormone and the encounter determines the receptor's binding capacity for life. In the critical period of development, when the window for imprinting is open, the receptor can be misdirected by related hormones, synthetic hormones, and industrial or communal endocrine disruptors which cause faulty hormonal imprinting with life-long consequences. Considering these facts, the hormonal imprinting is a functional teratogen provoking alterations in the perinatal (early postnatal) period. One single encounter with a low dose of the imprinter in the critical developmental period is enough for the formation of faulty imprinting, which is manifested later, in adult age. This has been justified in the immune system, in sexuality, in animal behavior and brain neurotransmitters etc. by animal experiments and human observations. This review points to the faulty hormonal imprinting in the case of bones (skeleton), by single or repeated treatments. The imprinting is an epigenetic alteration which is inherited to the progeny generations. From clinical aspect, the faulty imprinting can have a role in the pathological development of the bones as well, as in the risk of osteoporotic fractures, etc.

Vitamin-caused faulty perinatal hormonal imprinting and its consequences in adult age

Lipid-soluble vitamins (vitamins A, D, E, and K) are actually hormones (exohormones), as they can be directly bound by hormone receptors or are in connection with molecules, which influence hormone receptors. Vitamin D is a transition between endo- and exohormones and the possibility of similar situation in case of other lipid-soluble hormones is discussed. The perinatal exposition with these “vitamins” can cause faulty perinatal hormonal imprinting with similar consequences as the faulty imprinting by the synthetic endohormones, members of the same hormone family or industrial, communal, or medical endocrine disruptors. The faulty imprinting leads to late (lifelong) consequences with altered hormone binding by receptors, altered sexuality, brain function, immunity, bone development, and fractures, etc. In addition, as hormonal imprinting is an epigenetic process, the effect of a single exposure by fat-soluble vitamins is inherited to the progeny generations. As vitamins are handled differently from hormones; however, perinatal treatments take place frequently and sometimes it is forced, the negative late effect of faulty perinatal vitamin-caused hormonal imprinting must be considered.

Protein deficiency and nematode infection during pregnancy and lactation reduce maternal bone mineralization and neonatal linear growth in mice

Using a 2 x 2 factorial design, we investigated the combined impact of protein deficiency (PD) and gastrointestinal nematode infection during late pregnancy and lactation on resting metabolic rate (RMR), body composition and bone mineralization, neonatal growth, and the regulatory hormones [corticosterone, leptin, and insulin-like growth factor-1 (IGF-1)] and proinflammatory cytokines [interleukin (IL)-1 beta and IL-6] that may drive these processes. Pregnant CD1 mice, fed either a protein-sufficient (PS; 24%) or protein-deficient (PD; 6%) isocaloric diet, were infected 4 times with either 0 (sham) or 100 Heligmosomoides bakeri larvae beginning on d 14 of pregnancy. Dams were killed on d 20 postpartum and pups on d 2, 7, 14, and 21. Diet and infection had largely independent effects. The PD diet elevated corticosterone and upregulated leptin concentration in maternal serum, which was associated with reduced food intake leading to lower body mass, RMR, and body temperature. Infection reduced food intake but elevated maternal serum IL-1 beta and IL-6 and did not affect corticosterone, leptin, RMR, or body temperature. The PD diet decreased maternal bone area and bone mineral content. Infection lowered maternal bone mineral density, consistent with elevated IL-1 beta and IL-6. The elevated serum IL-1 beta and lower IGF-1 in pups of PD dams and lower serum leptin and IGF-1 in pups of infected dams were both consistent with the lower pup body mass and shorter crown-rump length. This mouse model provides a novel framework to study the impact of diet and nematode infection on bone.

The impact of corticosteroids on the developing animal

Infants are subjected to both endogenous and exogenous corticosteroids in the pre- and postnatal periods. Stress to the mother before birth, or to the child postpartum, can give rise to high, chronic endogenous corticosteroid levels caused by activation of the hypothalamic-pituitary-adrenal (HPA) axis. Physician-administered exogenous corticosteroids are also used in the management of a wide spectrum of pre- and postnatal conditions. The long-term effects of corticosteroids in developing humans are not well known. Studies in animals, however, indicate that both natural stress and exogenous corticosteroids can have long-lasting and deleterious effects on the body, brain, behavior, and hypothalamic-pituitary-adrenal axis of developing infants. These data suggest that exogenous corticosteroids should be administered with caution, after careful benefit/risk analyses, and that, as far as possible, the developing brain should be protected against the effects of pre- and postnatal stress.