Increase in endogenous estradiol in the progeny of obese rats is associated with precocious puberty and altered follicular development in adulthood

Paternal Obesity Induced by High-Fat Diet Impairs the Metabolic and Reproductive Health of Progeny in Rats

Due to the increased incidence of obesity, it is of great importance to identify all the possible consequences in those who suffer from it and their descendants. This study aimed to investigate how paternal obesity, resulting from an 18-week high-fat diet (HFD), affects the metabolic and reproductive health of offspring. In the fathers (F0 generation), the HFD led to significant weight gain, primarily due to increased visceral fat. It also resulted in impaired glucose control and reduced insulin sensitivity. Furthermore, F0 males from the HFD group had reduced sperm concentration and lower sperm viability but were still able to sire litters. F1 offspring were monitored during 18 weeks; F1 offspring from obese fathers displayed increased body weight during the experimental window, especially in males, without significant metabolic disturbances. Additionally, F1 males showed reduced sperm viability, indicating potential reproductive implications. On the other hand, F1 females showed normal estrous cycle patterns but had a reduced number of primordial follicles, suggesting a decrease in their follicular reserve and reproductive potential. This study highlights that metabolic and reproductive issues may be passed down to future generations through the paternal line.

Modafinil Administration to Preadolescent Rat Impairs Non-Selective Attention, Frontal Cortex D2 Expression and Mesolimbic GABA Levels

The misuse of psychostimulants is an increasing behavior among young people, highlighting in some countries the abuse of modafinil (MOD) as a neuropotentiator. However, several clinical trials are investigating MOD as an alternative pharmacological treatment for attentional deficit and hyperactivity disorder (ADHD) in children and adolescents. On the other hand, the early use of psychostimulants and the misdiagnosis rates in ADHD make it crucial to investigate the brain effects of this type of drug in young healthy individuals. The aim of this work was to evaluate the effects of chronic MOD treatment on neurochemicals (γ-aminobutyric acid and glutamate), dopamine receptor 2 (D₂) expression and behavior (non-selective attention "NSA") in the mesocorticolimbic system of young healthy Sprague-Dawley rats. Preadolescent male rats were injected with MOD (75 mg/kg, i.p.) or a vehicle for 14 days (from postnatal day 22 to 35). At postnatal day 36, we measured the GLU and GABA contents and their extracellular levels in the nucleus accumbens (NAc). In addition, the GLU and GABA contents were measured in the ventral tegmental area (VTA) and D₂ protein levels in the prefrontal cortex (PFC). Chronic use of MOD during adolescence induces behavioral and neurochemical changes associated with the mesocorticolimbic system, such as a reduction in PFC D₂ expression, VTA GABA levels and NSA. These results contribute to the understanding of the neurological effects of chronic MOD use on a young healthy brain.

Intergenerational high-fat diet impairs ovarian follicular development in rodents: a systematic review and meta-analysis

CONTEXT

Excessive consumption of high-fat diets has increased in the population over time and is harmful to female fertility.

OBJECTIVE

To investigate and discuss the effects of a high-fat diet on ovarian follicles in rodents.

DATA SOURCE

A systematic literature search of PubMed, EMBASE, Web of Science, and SCOPUS was carried out.

DATA EXTRACTION

Study characteristics, including study design, population, intervention, outcome, and risk of bias were analyzed.

DATA ANALYSIS

Twenty-two articles were included in a systematic review. Given the availability of studies, a quantitative meta-analysis included 12 studies that were performed for outcomes. There was a decrease in primordial follicles in female rodents that received a high-fat diet compared with the standard diet group. The offspring of mothers exposed to a high-fat diet showed an increased number of cystic follicles and a decreased number of secondary follicles and antral follicles, compared with the control diet group. Therefore, these high-fat diet-induced follicular alterations might impair the fertility of dams and their female newborns.

CONCLUSION

The consumption of a high-fat diet causes damage to ovarian follicular development, and this commitment will persist in the next generation.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42019133865.

Developmental programming of the female reproductive system-a review

Exposures to adverse conditions in utero can lead to permanent changes in the structure and function of key physiological systems in the developing fetus, increasing the risk of disease and premature aging in later postnatal life. When considering the systems that could be affected by an adverse gestational environment, the reproductive system of developing female offspring may be particularly important, as changes have the potential to alter both reproductive capacity of the first generation, as well as health of the second generation through changes in the oocyte. The aim of this review is to examine the impact of different adverse intrauterine conditions on the reproductive system of the female offspring. It focuses on the effects of exposure to maternal undernutrition, overnutrition/obesity, hypoxia, smoking, steroid excess, endocrine-disrupting chemicals, and pollutants during gestation and draws on data from human and animal studies to illuminate underlying mechanisms. The available data indeed indicate that adverse gestational environments alter the reproductive physiology of female offspring with consequences for future reproductive capacity. These alterations are mediated via programmed changes in the hypothalamic-pituitary-gonadal axis and the structure and function of reproductive tissues, particularly the ovaries. Reproductive programming may be observed as a change in the timing of puberty onset and menopause/reproductive decline, altered menstrual/estrous cycles, polycystic ovaries, and elevated risk of reproductive tissue cancers. These reproductive outcomes can affect the fertility and fecundity of the female offspring; however, further work is needed to better define the possible impact of these programmed changes on subsequent generations.

Chronic modafinil administration to preadolescent rats impairs social play behavior and dopaminergic system

Some clinical trials are investigating modafinil (Mod) as a treatment for attentional deficit and hyperactivity disorder (ADHD) in children and adolescents. Mod increases dopamine (DA) levels in the reward system by blocking dopamine transporter (DAT). Social interactions are rewarding behaviors and evidence reveals the importance of reward circuitry in social interactions. Chronic psychostimulant treatments alter DA neurotransmission and associated behaviors. The aim of this work was to evaluate the effects of chronic Mod treatment during preadolescence on social play behavior, locomotor activity, and DA in nucleus accumbens (NAc). Preadolescent male Sprague-Dawley rats were injected with Mod (75 mg/kg i.p.) or vehicle for 14 days (PND22 to PND35). After that, we measured social play behavior, content and DA release in NAc by HPLC coupled to electrochemical detection, protein levels of DA type 2 receptor (D₂) by Western blot and DA kinetic by fast-scan cyclic voltammetry (FSCV) in NAc. Regarding social play, the total number of pinning events decreased in the Mod group compared with the vehicle. The K⁺-stimulated DA release in NAc was significantly lower in Mod-treated rats compared with vehicle group. Also, Mod increases locomotor activity at the first injection, but this effect is almost completely lost at day 14 of Mod treatment. Chronic Mod treatment during preadolescence in rats impairs dopaminergic neurotransmission in NAc and decreases the capacity of rats to perceive rewarding effects of social play. Importantly, as Mod is being evaluated to treat ADHD in children and adolescents, potential effects on social behavior should be considered since this kind of behavior in this particular stage is crucial for neurodevelopment.

Impacts of obesity, maternal obesity and nicotinamide mononucleotide supplementation on sperm quality in mice

Male fertility and sperm quality are negatively impacted by obesity. Furthermore, recent evidence has shown that male offspring from obese rat mothers also have reduced sperm quality and fertility. Here, we extend work in this area by comparing the effects of both maternal obesity and offspring post-weaning diet-induced obesity, as well as their combination, on sperm quality in mice. We additionally tested whether administration of the NAD⁺-booster nicotinamide mononucleotide (NMN) can ameliorate the negative effects of obesity and maternal obesity on sperm quality. We previously showed that intraperitoneal (i.p.) injection of NMN can reduce the metabolic deficits induced by maternal obesity or post-weaning dietary obesity in mice. In this study, female mice were fed a high-fat diet (HFD) for 6 weeks until they were 18% heavier than a control diet group. Thereafter, HFD and control female mice were mated with control diet males, and male offspring were weaned into groups receiving control or HFD. At 30 weeks of age, mice received 500 mg/kg body weight NMN or vehicle PBS i.p. for 21 days. As expected, adiposity was increased by both maternal and post-weaning HFD but reduced by NMN supplementation. Post-weaning HFD reduced sperm count and motility, while maternal HFD increased offspring sperm DNA fragmentation and levels of aberrant sperm chromatin. There was no evidence that the combination of post-weaning and maternal HFD exacerbated the impacts in sperm quality suggesting that they impact spermatogenesis through different mechanisms. Surprisingly NMN reduced sperm count, vitality and increased sperm oxidative DNA damage, which was associated with increased NAD⁺ in testes. A subsequent experiment using oral NMN at 400 mg/kg body weight was not associated with reduced sperm viability, oxidative stress, mitochondrial dysfunction or increased NAD⁺ in testes, suggesting that the negative impacts on sperm could be dependent on dose or mode of administration.

Nutritional adversity, sex and reproduction: 30 years of DOHaD and what have we learned?

It is well established that early life environmental signals, including nutrition, set the stage for long-term health and disease risk - effects that span multiple generations. This relationship begins early, in the periconceptional period and extends into embryonic, fetal and early infant phases of life. Now known as the Developmental Origins of Health and Disease (DOHaD), this concept describes the adaptations that a developing organism makes in response to early life cues, resulting in adjustments in homeostatic systems that may prove maladaptive in postnatal life, leading to an increased risk of chronic disease and/or the inheritance of risk factors across generations. Reproductive maturation and function is similarly influenced by early life events. This should not be surprising, since primordial germ cells are established early in life and thus vulnerable to early life adversity. A multitude of 'modifying' cues inducing developmental adaptations have been identified that result in changes in reproductive development and impairments in reproductive function. Many types of nutritional challenges including caloric restriction, macronutrient excess and micronutrient insufficiencies have been shown to induce early life adaptations that produce long-term reproductive dysfunction. Many pathways have been suggested to underpin these associations, including epigenetic reprogramming of germ cells. While the mechanisms still remain to be fully investigated, it is clear that a lifecourse approach to understanding lifetime reproductive function is necessary. Furthermore, investigations of the impacts of early life adversity must be extended to include the paternal environment, especially in epidemiological and clinical studies of offspring reproductive function.

Prenatal metformin treatment improves ovarian function in offspring of obese rats

Maternal obesity causes a wide range of impairment in offspring, such as metabolic and reproductive dysfunctions. We previously demonstrated that female offspring of obese rats have increased serum estradiol levels during early postnatal life, probably because of decreased hepatic cytochrome P450 3A2 levels, which could lead to early onset of puberty and polycystic ovary condition in adulthood. Using metformin during pregnancy and nursing to improve the metabolic status of obese mothers could prevent the sequence of events that lead to an increase in postnatal serum estradiol levels in female offspring and, hence, reproductive dysfunction. We found that metformin prevented an increase in serum estradiol levels at postnatal day 14 in female offspring of obese mothers, which was associated with a restoration of hepatic cytochrome P450 3A2 levels to control values. Treatment using metformin could not prevent advanced puberty, but we observed that the number of antral follicles, follicular cysts and multi-oocyte follicles returned to control values in the female offspring of obese mothers treated with metformin. We also observed an increase in the levels of norepinephrine and the norepinephrine metabolite 3-methoxy-4-hydroxyphenylglycol in the ovaries, indicating increased sympathetic activity in female offspring induced by an obesogenic uterine environment. We found that this effect was prevented by metformin administration. From the results of this study, we concluded that metformin administration to obese mothers during pregnancy and nursing partially prevents ovarian dysfunction in female offspring during adulthood.

Role of amygdala kisspeptin in pubertal timing in female rats

To investigate the mechanism by which maternal obesity disrupts reproductive function in offspring, we examined Kiss1 expression in the hypothalamic arcuate (ARC) and anteroventral periventricular (AVPV) nuclei, and posterodorsal medial amygdala (MePD) of pre-pubertal and young adult offspring. Sprague-Dawley rats were fed either a standard or energy-dense diet for six weeks prior to mating and throughout pregnancy and lactation. Male and female offspring were weaned onto normal diet on postnatal day (pnd) 21. Brains were collected on pnd 30 or 100 for qRT-PCR to determine Kiss1 mRNA levels. Maternal obesity increased Kiss1 mRNA expression in the MePD of pre-pubertal male and female offspring, whereas Kiss1 expression was not affected in the ARC or AVPV at this age. Maternal obesity reduced Kiss1 expression in all three brain regions of 3 month old female offspring, but only in MePD of males. The role of MePD kisspeptin on puberty, estrous cyclicity and preovulatory LH surges was assessed directly in a separate group of post-weanling and young adult female rats exposed to a normal diet throughout their life course. Bilateral intra-MePD cannulae connected to osmotic mini-pumps for delivery of kisspeptin receptor antagonist (Peptide 234 for 14 days) were chronically implanted on pnd 21 or 100. Antagonism of MePD kisspeptin delayed puberty onset, disrupted estrous cyclicity and reduced the incidence of LH surges. These data show that the MePD plays a key role in pubertal timing and ovulation and that maternal obesity may act via amygdala kisspeptin signaling to influence reproductive function in the offspring.

The Association between High Fat Diet around Gestation and Metabolic Syndrome-related Phenotypes in Rats: A Systematic Review and Meta-Analysis

Numerous rodent studies have evaluated the effects of a maternal high-fat diet (HFD) on later in life susceptibility to Metabolic Syndrome (MetS) with varying results. Our aim was to quantitatively synthesize the available data on effects of maternal HFD around gestation on offspring's body mass, body fat, plasma leptin, glucose, insulin, lipids and systolic blood pressure (SBP). Literature was screened and summary estimates of the effect of maternal HFD on outcomes were calculated by using fixed- or random-effects models. 362 effect sizes from 68 studies together with relevant moderators were collected. We found that maternal HFD is statistically associated with higher body fat, body weight, leptin, glucose, insulin and triglycerides levels, together with increased SBP in offspring later in life. Our analysis also revealed non-significant overall effect on offspring's HDL-cholesterol. A main source of variation among studies emerged from rat strain and lard-based diet type. Strain and sex -specific effects on particular data subsets were detected. Recommendations are suggested for future research in the field of developmental programming of the MetS. Despite significant heterogeneity, our meta-analysis confirms that maternal HFD had long-term metabolic effects in offspring.

Environmental contributors to modulation of brain estrogen signaling and male gender bias in autism: A reply to the oral contraceptive use hypothesis by Strifert (2015)

Strifert has recently put forward an interesting hypothesis regarding the role of oral contraceptive (OC) use in mothers and risk of offspring autism spectrum disorder (ASD). First, the author reports that combined oral contraceptives (COCs), containing both estrogen and progesterone, were developed in the late 1950s and early 60s, which is a time-frame distinct from Leo Kanner's documentation of infantile ASD in 1943 that Strifert just briefly mentions. While this important temporal inconsistency of ASD origin does not invalidate the potential role of OC use in contributing to the rise of ASD, it does support the likely possibility of other environmental exposures at play. Second, the epigenetic basis of the hypothesis is that the endocrine-disrupting components (i.e., ethinylestradiol) of OC perturb estrogenic signaling in the fetal brain by triggering aberrant DNA methylation of the estrogen receptor β (ERβ) gene, and such methylation patterns may be imprinted to future generations and could theoretically increase subsequent ASD offspring risk. The premise of the hypothesis is challenged, however, with the recognition that MeCP2, a "reader" of DNA methylation sites, is not only associated with age-dependent alteration in ERβ in females but is also significantly reduced in ASD brain. Furthermore, Strifert does not clearly address how the OC hypothesis accounts for the male bias in ASD. Therefore, the purpose of this correspondence is to address these inconsistencies by proposing a hypothesis that challenges these points. That is, gestational exposure to the agricultural and combustion air pollutant, nitrous oxide (N₂O), may be a leading contributor to the development of an ASD phenotype. The mechanism undergirding this hypothesis suggests that compensatory estrogenic activity may mitigate the effects of fetal N₂O exposure and thereby confer a protective effect against ASD development in a sex-dependent manner (i.e., male bias in ASD).

Detrimental effect of maternal and post-weaning high-fat diet on the reproductive function in the adult female offspring rat: roles of insulin-like growth factor 2 and the ovarian circadian clock

PURPOSE

We evaluate the impact of maternal and post-weaning high-fat (HF) diet on ovarian follicular population, steroidogenesis, and gene expression with a focus on the circadian clock system and insulin-like growth factor 2 (Igf2) in adult offspring ovaries, and to elucidate whether a maternal and post-weaning diet confers similar risks.

METHODS

Virgin Sprague-Dawley rats were fed with normal chow (C) diet or HF diet for 5 weeks before mating, during gestation, and lactation. Female offspring were fed with the C or HF diet from weaning to 6 months of age, resulting in four study groups (n = 6 per group): C/C, C/HF, HF/C, and HF/HF.

RESULTS

Ovaries from offspring exposed to post-weaning HF diet (i.e., the C/HF and HF/HF groups) had a decrease in small follicle numbers, but with similar numbers of antral follicles and corpora lutea. Offspring from HF-fed dams (i.e., the HF/C and HF/HF groups) had increased plasma estradiol concentrations and decreased luteinizing hormone levels at 6 months of age. In addition, Igf2 and each of the circadian rhythm core genes Clock, Per1, Per2, and Per3 were increased in the ovaries of offspring exposed to maternal HF diet (both HF/C and HF/HF groups).

CONCLUSIONS

Maternal and post-weaning HF diet programs the reproductive profile of the female offspring in adult life through different manners. Post-weaning HF intake resulted in the reduction of small follicles in adulthood, whereas maternal HF diet had long-term deleterious consequences on female offspring steroidogenesis and coincided with alteration of the upregulation of the imprinted gene Igf2 and changes in ovarian circadian rhythms.