Maternal undernutrition during pregnancy and lactation affects testicular morphology, the stages of spermatogenic cycle, and the testicular IGF-I system in adult offspring

Maternal nutrition and fetal imprinting of the male progeny

The global population as well as the demand for human food is rapidly growing worldwide, which necessitates improvement of efficiency in livestock operations. In this context, environmental factors during fetal and/or neonatal life have been observed to influence normal physical and physiological function of an individual during adulthood, and this phenomenon is called fetal or developmental programming. While numerous studies have reported the impact of maternal factors on development of the female progeny, limited information is available on the potential effects of fetal programming on reproductive function of the male offspring. Therefore, the objective for this review article was to focus on available literature regarding the impact of maternal factors, particularly maternal nutrition, on reproductive system of the male offspring. To this end, we highlighted developmental programming of the male offspring in domestic species (i.e., pig, cow and sheep) as well as laboratory species (i.e., mice and rat) during pregnancy and lactation. In this sense, we pointed out the effects of maternal nutrition on various functions of the male offspring including hypothalamic-pituitary axis, hormonal levels, testicular tissue and semen parameters.

Intra-uterine programming of future fertility

The developmental origins of health and disease (DOHaD) shows that a relationship exists between parental environment at large, foeto-placental development and the risk for the offspring to develop non-transmittable disease(s) in adulthood. This concept has been validated in both humans and livestock. In mammals, after fertilization and time spent free in the maternal reproductive tract, the embryo develops a placenta that, in close relationship with maternal endometrium, is the organ responsible for exchanges between dam and foetus. Any modification of the maternal environment can lead to adaptive mechanisms affecting placental morphology, blood flow, foetal-maternal exchanges (transporters) and/or endocrine function, ultimately modifying placental efficiency. Among deleterious environments, undernutrition, protein restriction, overnutrition, micronutrient deficiencies and food contaminants can be outlined. When placental adaptive capacities become insufficient, foetal growth and organ formation is no longer optimal, including foetal gonadal formation and maturation, which can affect subsequent offspring fertility. Since epigenetic mechanisms have been shown to be key to foetal programming, epigenetic modifications of the gametes may also occur, leading to inter-generational effects. After briefly describing normal gonadal development in domestic species and inter-species differences, this review highlights the current knowledge on intra-uterine programming of offspring fertility with a focus on domestic animals and underlines the importance to assess transgenerational effects on offspring fertility at a time when new breeding systems are developed to face the current climate changes.

Maternal high-fat diet during pregnancy and lactation affects factors that regulate cell proliferation and apoptosis in the testis of adult progeny

Context A maternal high-fat diet is thought to pose a risk to spermatogenesis in the progeny. Aims We tested whether a maternal high-fat diet would affect Sertoli cell expression of transcription factors (insulin-like growth factor I (IGF-I); glial-cell line-derived neurotrophic factor (GDNF); Ets variant 5 (ETV5)) and cell proliferation and apoptotic proteins, in the testis of adult offspring. Methods Pregnant rats were fed ad libitum with a standard diet (Control) or a high-fat diet (HFat) throughout pregnancy and lactation. After weaning, male pups were fed the standard diet until postnatal day 160. Males were monitored daily from postnatal day 34 to determine onset of puberty. On postnatal day 160, their testes were processed for morphometry and immunohistochemistry. Key results The HFat diet increased seminiferous-tubule diameter (P P P P P P P P Conclusions A maternal high-fat diet alters the balance between spermatogonia proliferation and spermatid apoptosis. Implications A maternal high-fat diet seems to 'program' adult male fertility.

Differentially methylated regions identified in bovine embryos are not observed in adulthood

The establishment of epigenetic marks during the reprogramming window is susceptible to environmental influences, and stimuli during this critical stage can cause altered DNA methylation in offspring. In a previous study, we found that low levels of sulphur and cobalt (low S/Co) in the diet offered to oocyte donors altered the DNA methylome of bovine embryos. However, due to the extensive epigenetic reprogramming that occurs during embryogenesis, we hypothesized that the different methylation regions (DMRs) identified in the blastocysts may not maintain in adulthood. Here, we aimed to characterize DMRs previously identified in embryos, in the blood and sperm of adult progenies of two groups of heifers (low S/Co and control). We used six bulls and characterized the DNA methylation levels of KDM2A, KDM5A, KMT2D, and DOT1L genes. Our results showed that all DMRs analysed in both groups and tissues were hypermethylated unlike that noticed in the embryonic methylome profiles. These results suggest that embryo DMRs were reprogrammed during the final stages of de novo methylation during embryogenesis or later in development. Therefore, due to the highly dynamic epigenetic state during early embryonic development, we suggest that is essential to validate the DMRs found in embryos in adult individuals.

Maternal and Offspring Sugar Consumption Increases Perigonadal Adipose Tissue Hypertrophy and Negatively Affects the Testis Histological Organization in Adult Rats

Sugar intake has been associated with the development of male reproductive pathologies because of the increase and dysfunction in different adipose tissue depots. The establishment of these dysfunctions in the early stages of development is unknown. We evaluated the effect of maternal (pregnancy and lactation) and male offspring (from weaning to adulthood) consumption of 5% sucrose on perigonadal adipose tissue (PAT) and testis in adulthood. Moreover, two rat groups were compared, both including pregnant and lactating females: Control (C—drinking tap water) and sugar (S—consuming 5% sucrose solution). From weaning to adulthood with male offspring, four subgroups were formed: Control Mother → Control and Sugar offspring (CC, CS) and Sugar Mother → Control and Sugar offspring (SC, SS). At 120 postnatal days, the testes and PAT were collected and morphologically described. Furthermore, we quantified the number and cross-sectional area of perigonadal adipocytes and their distribution. We found that the males from SC and SS groups showed high PAT weight (p < 0.005), a high number (p < 0.05), and a relative frequency of large adipocytes (p < 0.05), establishing these results during gestational and lactation stages, and enhancing in adulthood since postnatal diet and its interaction. More macrophages, mast cells, and Leydig cells were observed in the interstitial space of the testis for the CS, SC, and SS groups, concluding that consumption of a high-carbohydrate maternal diet, program hypertrophy processes in adult PAT, developing and enhancing with sugar consumption during postnatal life. Furthermore, they are associated with inflammatory processes within the interstitial space of the testis.

Early programming of reproductive health and fertility: novel neuroendocrine mechanisms and implications in reproductive medicine

BACKGROUND

According to the Developmental Origins of Health and Disease (DOHaD) hypothesis, environmental changes taking place during early maturational periods may alter normal development and predispose to the occurrence of diverse pathologies later in life. Indeed, adverse conditions during these critical developmental windows of high plasticity have been reported to alter the offspring developmental trajectory, causing permanent functional and structural perturbations that in the long term may enhance disease susceptibility. However, while solid evidence has documented that fluctuations in environmental factors, ranging from nutrient availability to chemicals, in early developmental stages (including the peri-conceptional period) have discernible programming effects that increase vulnerability to develop metabolic perturbations, the impact and eventual mechanisms involved, of such developmental alterations on the reproductive phenotype of offspring have received less attention.

OBJECTIVE AND RATIONALE

This review will summarize recent advances in basic and clinical research that support the concept of DOHaD in the context of the impact of nutritional and hormonal perturbations, occurring during the periconceptional, fetal and early postnatal stages, on different aspects of reproductive function in both sexes. Special emphasis will be given to the effects of early nutritional stress on the timing of puberty and adult gonadotropic function, and to address the underlying neuroendocrine pathways, with particular attention to involvement of the Kiss1 system in these reproductive perturbations. The implications of such phenomena in terms of reproductive medicine will also be considered.

SEARCH METHODS

A comprehensive MEDLINE search, using PubMed as main interface, of research articles and reviews, published mainly between 2006 and 2021, has been carried out. Search was implemented using multiple terms, focusing on clinical and preclinical data from DOHaD studies, addressing periconceptional, gestational and perinatal programming of reproduction. Selected studies addressing early programming of metabolic function have also been considered, when relevant.

OUTCOMES

A solid body of evidence, from clinical and preclinical studies, has documented the impact of nutritional and hormonal fluctuations during the periconceptional, prenatal and early postnatal periods on pubertal maturation, as well as adult gonadotropic function and fertility. Furthermore, exposure to environmental chemicals, such as bisphenol A, and maternal stress has been shown to negatively influence pubertal development and gonadotropic function in adulthood. The underlying neuroendocrine pathways and mechanisms involved have been also addressed, mainly by preclinical studies, which have identified an, as yet incomplete, array of molecular and neurohormonal effectors. These include, prominently, epigenetic regulatory mechanisms and the hypothalamic Kiss1 system, which likely contribute to the generation of reproductive alterations in conditions of early nutritional and/or metabolic stress. In addition to the Kiss1 system, other major hypothalamic regulators of GnRH neurosecretion, such as γ-aminobutyric acid and glutamate, may be targets of developmental programming.

WIDER IMPLICATIONS

This review addresses an underdeveloped area of reproductive biology and medicine that may help to improve our understanding of human reproductive disorders and stresses the importance, and eventual pathogenic impact, of early determinants of puberty, adult reproductive function and fertility.

Maternal undernutrition during pregnancy and lactation increases transcription factors, ETV5 and GDNF, and alters regulation of apoptosis and heat shock proteins in the testis of adult offspring in the rat

We tested whether changes in Sertoli cell transcription factors and germ cell heat shock proteins (HSPs) are linked to the effects of maternal undernutrition on male offspring fertility. Rats were fed ad libitum with a standard diet (CONTROL) throughout pregnancy and lactation or with 50% of CONTROL intake throughout pregnancy (UNP) or lactation (UNL) or both periods (UNPL). After postnatal Day 21, 10 male pups per group were fed a standard diet ad libitum until postnatal Day 160 when testes were processed for histological, mRNA and immunohistochemical analyses. Compared with CONTROL: caspase-3 was increased in UNP and UNPL (P=0.001); Bax was increased in UNL (P=0.002); Bcl-2 (P<0.0001) was increased in all underfed groups; glial cell line-derived neurotrophic factor (P=0.002) was increased in UNP and UNL; E twenty-six transformation variant gene 5 and HSP70 were increased, and HSP90 was diminished in all underfed groups (P<0.0001). It appears that maternal undernutrition during pregnancy and lactation disrupts the balance between proliferation and apoptosis in germ cells, increasing germ cell production and perhaps exceeding the support capacity of the Sertoli cells. Moreover, fertility could be further compromised by changes in meiosis and spermiogenesis mediated by germ cell HSP90 and HSP70.