Transgenerational transmission of hedonic behaviors and metabolic phenotypes induced by maternal overnutrition

Palm oil as part of a high-fat diet: advances and challenges, or possible risks of pathology?

Nutritional status disorders have the most significant impact on the development of cardiovascular and oncologic diseases; therefore, the interest in the study of palm oil as among the leading components of nutrition has been increasing. The data examined in this review were sourced from the Scopus, SCIE (Web of Science), PubMed and PubMed Central, MEDLINE, CAPlus/SciFinder, and Embase databases; experts in the field; bibliographies; and abstracts from review analyses from the past 15 years. This review summarizes recent research data focusing on the quantitative and qualitative composition of nutrition of modern humans; concepts of the relationship between high-fat diets and disorders of insulin functioning and transport and metabolism of fatty acids; analyses of data regarding the palmitic acid (16:0) to oleic acid (18:1) ratio; and the effect of diet based on palm oil consumption on cardiovascular risk factors and lipid and lipoprotein levels. Several studies suggest a potential vector contributing to the transmission of maternal, high-fat-diet-induced, addictive-like behaviors and obesogenic phenotypes across generations. The relationship between cholesterol accumulation in lysosomes that may lead to lysosome dysfunction and inhibition of the autophagy process is analyzed, as is the progression of inflammatory diseases, atherosclerosis, nonalcoholic liver inflammation, and obesity with associated complications. Data are discussed from analyses of differences between rodent models and human population studies in the investigated different effects of palm oil consumption as a high-fat diet component. A conclusion is reached that the results cannot be generalized in human population studies because no similar effects were observed. Although there are numerous published reports, more studies are necessary to elucidate the complex regulatory mechanisms in digestive and nutrition processes, because there are great differences in lipoprotein profiles between rodents and humans, which makes it difficult to reproduce the pathology of many diseases caused by different types of the high-fat diet.

Paternal Prenatal and Lactation Exposure to a High-Calorie Diet Shapes Transgenerational Brain Macro- and Microstructure Defects, Impacting Anxiety-Like Behavior in Male Offspring Rats

Prenatal exposure to high-energy diets (HED) increases the susceptibility to behavioral alterations in the male offspring. We addressed whether prenatal HED primes the transgenerational inheritance of structural brain changes impacting anxiety/depression-like behavior in the offspring. For this, we used female Wistar rats exposed to a HED [cafeteria (CAF) diet, n = 6] or chow [control (CON) n = 6] during development. Anxiety and depression-like behavior were evaluated in filial 1 (F1), filial 2 (F2), and filial 3 (F3) male offspring using the open field (OFT), elevated plus maze, novelty suppressed feeding (NSFT), tail suspension (TST), and forced swimming tests. Structural brain changes were identified by deformation-based morphometry (DBM) and diffusion tensor imaging using ex vivo MRI. We found that the F1, F2, and F3 offspring exposed to CAF diet displayed higher anxious scores including longer feeding latency during the NSFT, and in the closed arms, only F1 offspring showed longer stay on edges during the OFT versus control offspring. DBM analysis revealed that CAF offspring exhibited altered volume in the cerebellum, hypothalamus, amygdala, and hippocampus preserved up to the F3 generation of anxious individuals. Also, F3 CAF anxious exhibited greater fractional anisotropy and axial diffusivity (AD) in the amygdala, greater apparent diffusion coefficient in the corpus callosum, and greater AD in the hippocampus with respect to the control. Our results suggest that prenatal and lactation exposure to HED programs the transgenerational inheritance of structural brain changes related to anxiety-like behavior in the male offspring.

A systematic scientometric review of paternal inheritance of acquired metabolic traits

BACKGROUND

The concept of the inheritance of acquired traits, a foundational principle of Lamarck's evolutionary theory, has garnered renewed attention in recent years. Evidence for this phenomenon remained limited for decades but gained prominence with the Överkalix cohort study in 2002. This study revealed a link between cardiovascular disease incidence and the food availability experienced by individuals' grandparents during their slow growth periods, reigniting interest in the inheritance of acquired traits, particularly in the context of non-communicable diseases. This scientometric analysis and systematic review comprehensively explores the current landscape of paternally transmitted acquired metabolic traits.

RESULTS

Utilizing Scopus Advanced search and meticulous screening, we included mammalian studies that document the inheritance or modification of metabolic traits in subsequent generations of unexposed descendants. Our inclusive criteria encompass intergenerational and transgenerational studies, as well as multigenerational exposures. Predominantly, this field has been driven by a select group of researchers, potentially shaping the design and focus of existing studies. Consequently, the literature primarily comprises transgenerational rodent investigations into the effects of ancestral exposure to environmental pollutants on sperm DNA methylation. The complexity and volume of data often lead to multiple or redundant publications. This practice, while understandable, may obscure the true extent of the impact of ancestral exposures on the health of non-exposed descendants. In addition to DNA methylation, studies have illuminated the role of sperm RNAs and histone marks in paternally acquired metabolic disorders, expanding our understanding of the mechanisms underlying epigenetic inheritance.

CONCLUSIONS

This review serves as a comprehensive resource, shedding light on the current state of research in this critical area of science, and underscores the need for continued exploration to uncover the full spectrum of paternally mediated metabolic inheritance.

Paternal Western diet causes transgenerational increase in food consumption in Drosophila with parallel alterations in the offspring brain proteome and microRNAs

Several lines of evidence indicate that ancestral diet might play an important role in determining offspring's metabolic traits. However, it is not yet clear whether ancestral diet can affect offspring's food choices and feeding behavior. In the current study, taking advantage of Drosophila model system, we demonstrate that paternal Western diet (WD) increases offspring food consumption up to the fourth generation. Paternal WD also induced alterations in F1 offspring brain proteome. Using enrichment analyses of pathways for upregulated and downregulated proteins, we found that upregulated proteins had significant enrichments in terms related to translation and translation factors, whereas downregulated proteins displayed enrichments in small molecule metabolic processes, TCA cycles, and electron transport chain (ETC). Using MIENTURNET miRNA prediction tool, dme-miR-10-3p was identified as the top conserved miRNA predicted to target proteins regulated by ancestral diet. RNAi-based knockdown of miR-10 in the brain significantly increased food consumption, implicating miR-10 as a potential factor in programming feeding behavior. Together, these findings suggest that ancestral nutrition may influence offspring feeding behavior through alterations in miRNAs.

Maternal Over- and Malnutrition and Increased Risk for Addictive and Eating Disorders in the Offspring

Evidence from human and animal studies has shown that maternal overnutrition and/or obesity are linked with neurobehavioral changes in the offspring. This fetal programming is characterized by adaptive responses to changes in the nutritional state during early life. In the past decade, an association has been made between overconsumption of highly-palatable food by the mother during fetal development and abnormal behaviors resembling addiction in the offspring. Maternal overnutrition can lead to alterations in the offspring's brain reward circuitry leading to hyperresponsiveness of this circuit following exposure to calorie-dense foods later in life. Given the accumulating evidence indicating that the central nervous system plays a pivotal role in regulating food intake, energy balance, and the motivation to seek food, a dysfunction in the reward circuitry may contribute to the addiction-like behaviors observed in the offspring. However, the underlying mechanisms leading to these alterations in the reward circuitry during fetal development and their relevance to the increased risk for the offspring to later develop addictive-like behaviors is still unclear. Here, we review the most relevant scientific reports about the impact of food overconsumption during fetal development and its effect on addictive-like behaviors of the offspring in the context of eating disorders and obesity.

Paternal transmission of behavioural and metabolic traits induced by postnatal stress to the 5th generation in mice

Life experiences and environmental conditions in childhood can change the physiology and behaviour of exposed individuals and, in some cases, of their offspring. In rodent models, stress/trauma, poor diet, and endocrine disruptors in a parent have been shown to cause phenotypes in the direct progeny, suggesting intergenerational inheritance. A few models also examined transmission to further offspring and suggested transgenerational inheritance, but such multigenerational inheritance is not well characterized. Our previous work on a mouse model of early postnatal stress showed that behaviour and metabolism are altered in the offspring of exposed males up to the 4th generation in the patriline and up to the 2nd generation in the matriline. The present study examined if symptoms can be transmitted beyond the 4th generation in the patriline. Analyses of the 5th and 6th generations of mice revealed that altered risk-taking and glucose regulation caused by postnatal stress are still manifested in the 5th generation but are attenuated in the 6th generation. Some of the symptoms are expressed in both males and females, but some are sex-dependent and sometimes opposite. These results indicate that postnatal trauma can affect behaviour and metabolism over many generations, suggesting epigenetic mechanisms of transmission.

Transgenerational inheritance and its modulation by environmental cues

The epigenome plays an important role in shaping phenotypes. However, whether the environment can alter an organism's phenotype across several generations through epigenetic remodeling in the germline is still a highly debated topic. In this chapter, we briefly review the mechanisms of epigenetic inheritance and their connection with germline development before highlighting specific developmental windows of susceptibility to environmental cues. We further discuss the evidence of transgenerational inheritance to a range of different environmental cues, both epidemiological in humans and experimental in rodent models. Doing so, we pinpoint the current challenges in demonstrating transgenerational inheritance to environmental cues and offer insight in how recent technological advances may help deciphering the epigenetic mechanisms at play. Together, we draw a detailed picture of how our environment can influence our epigenomes, ultimately reshaping our phenotypes, in an extended theory of inheritance.

Maternal gut microbiota mediate intergenerational effects of high-fat diet on descendant social behavior

Dysbiosis of the maternal gut microbiome during pregnancy is associated with adverse neurodevelopmental outcomes. We previously showed that maternal high-fat diet (MHFD) in mice induces gut dysbiosis, social dysfunction, and underlying synaptic plasticity deficits in male offspring (F₁). Here, we reason that, if HFD-mediated changes in maternal gut microbiota drive offspring social deficits, then MHFD-induced dysbiosis in F₁ female MHFD offspring would likewise impair F₂ social behavior. Metataxonomic sequencing reveals reduced microbial richness among female F₁ MHFD offspring. Despite recovery of microbial richness among MHFD-descendant F₂ mice, they display social dysfunction. Post-weaning Limosilactobacillus reuteri treatment increases the abundance of short-chain fatty acid-producing taxa and rescues MHFD-descendant F₂ social deficits. L. reuteri exerts a sexually dimorphic impact on gut microbiota configuration, increasing discriminant taxa between female cohorts. Collectively, these results show multigenerational impacts of HFD-induced dysbiosis in the maternal lineage and highlight the potential of maternal microbiome-targeted interventions for neurodevelopmental disorders.

Transgenerational Susceptibility to Food Addiction-Like Behavior in Rats Associates to a Decrease of the Anti-Inflammatory IL-10 in Plasma

Maternal nutritional programming by energy-dense foods leads to the transgenerational heritance of addiction-like behavior. Exposure to energy-dense foods also activates systemic and central inflammation in the offspring. This study aimed to characterize pro- and anti-inflammatory cytokine profiles in blood and their correlation to the transgenerational heritance of the addiction-like behavior in rats. F1 offspring of male Wistar diagnosed with addiction-like behavior were mated with virgin females to generate the F2 and the F3 offspring, respectively. Diagnosis of addiction-like behavior was performed by the operant training schedule (FR1, FR5 and PR) and pro- and anti-inflammatory cytokine profiles in blood were measured by multiplex platform. Multiple linear models between behavior, fetal programming by diet and pro- and anti-inflammatory cytokine profiles were performed. We found that the addiction-like behavior found in the F1 male offspring exposed to energy-dense food (cafeteria, CAF) diet during fetal programing is transgenerational inherited to the F2 and F3 generations. Blood from addiction-like behavior subjects of F2 and F3 generations exposed to CAF diet during maternal programming showed decrease in the anti-inflammatory IL-10 in the plasma. Conversely, decreased levels of the pro-inflammatory MCP-1 was identified in non-addiction-like subjects. No changes were found in plasmatic TNF-α levels in the F2 and F3 offspring of non-addiction-like and addiction-like subjects. Finally, biological modeling between IL-10 or MCP-1 plasma levels and prenatal diet exposure on operant training responses confirmed an association of decreased IL-10 levels on addiction-like behavior in the F2 and F3 generations. Globally, we identified decreased anti-inflammatory IL-10 cytokine in the blood of F2 and F3 offspring subjects diagnosed with addiction-like behavior for food rewards.

Perinatal Combinational Exposure to Bisphenol A and a High-Fat Diet Contributes to Transgenerational Dysregulation of Cardiovascular and Metabolic Systems in Mice

Both bisphenol A (BPA) and high-fat diet (HFD) exert unfavorable effects on animals and humans; moreover, they could affect the health of their offspring. BPA and HFD often coexist in modern lifestyles; however, the long-term effects of simultaneous exposure of mothers to BPA and HFD during the perinatal period on the cardiovascular and metabolic systems of the offspring remain unclear. This study aimed to examine the effect of simultaneous exposure of mothers to BPA and HFD on the risk of metabolic and cardiovascular abnormalities in offspring. Institute of Cancer Research female mice (F0) were exposed to BPA and fed with HFD before and during gestation until the end of lactation. F0 mice were mated with untreated males to produce the first generation (F1); subsequently, adult F1 males/females were mated with normal females/males to produce the second generation (F2). Combined maternal exposure to BPA and HFD caused myocardial hypertrophy and aortic tunica media thickening as well as increased the cross-sectional area of cardiomyocytes and blood pressure in the matrilineal F2 generation. These cardiovascular changes might be associated with reduced endothelial nitric oxide synthase (eNOS) levels. The patrilineal female F2 was more likely to be obese than the patrilineal male F2. Re-feeding with a HFD showed a more significant weight gain and reduced energy expenditure. However, the aforementioned effects were not observed with exposure to HFD or BPA alone during the perinatal period. Our findings suggest that perinatal combinational exposure to BPA and HFD could cause metabolic and cardiovascular disorders in the offspring, Further, our findings demonstrate that the synergistic effects of HFD and BPA could be transmitted to future generations in a sex-dependent manner.

Transgenerational effects of obesogenic diets in rodents: A meta-analysis

Obesity is a major health condition that affects millions worldwide. There is an increased interest in understanding the adverse outcomes associated with obesogenic diets. A multitude of studies have investigated the transgenerational impacts of maternal and parental obesogenic diets on subsequent generations of offspring, but results have largely been mixed. We conducted a systematic review and meta-analysis on rodent studies to elucidate how obesogenic diets impact the mean and variance of grand-offspring traits. Our study focused on transgenerational effects (i.e., F2 and F3 generations) in one-off and multigenerational exposure studies. From 33 included articles, we obtained 407 effect sizes representing pairwise comparisons of control and treatment grand-offspring groups pertaining to measures of body weight, adiposity, glucose, insulin, leptin, and triglycerides. We found evidence that male and female grand-offspring descended from grandparents exposed to an obesogenic diet displayed phenotypes consistent with metabolic syndrome, especially in cases where the obesogenic diet was continued across generations. Further, we found stronger evidence for the effects of grand-maternal than grand-paternal exposure on grand-offspring traits. A high-fat diet in one-off exposure studies did not seem to impact phenotypic variation, whereas in multigenerational exposure studies it reduced variation in several traits.

Small Noncoding RNAs in Reproduction and Infertility

Infertility has been reported as one of the most common reproductive impairments, affecting nearly one in six couples worldwide. A large proportion of infertility cases are diagnosed as idiopathic, signifying a deficit in information surrounding the pathology of infertility and necessity of medical intervention such as assisted reproductive therapy. Small noncoding RNAs (sncRNAs) are well-established regulators of mammalian reproduction. Advanced technologies have revealed the dynamic expression and diverse functions of sncRNAs during mammalian germ cell development. Mounting evidence indicates sncRNAs in sperm, especially microRNAs (miRNAs) and transfer RNA (tRNA)-derived small RNAs (tsRNAs), are sensitive to environmental changes and mediate the inheritance of paternally acquired metabolic and mental traits. Here, we review the critical roles of sncRNAs in mammalian germ cell development. Furthermore, we highlight the functions of sperm-borne sncRNAs in epigenetic inheritance. We also discuss evidence supporting sncRNAs as promising biomarkers for fertility and embryo quality in addition to the present limitations of using sncRNAs for infertility diagnosis and treatment.

Paternal environmental exposure-induced spermatozoal small noncoding RNA alteration meditates the intergenerational epigenetic inheritance of multiple diseases

Studies of human and mammalian have revealed that environmental exposure can affect paternal health conditions as well as those of the offspring. However, studies that explore the mechanisms that meditate this transmission are rare. Recently, small noncoding RNAs (sncRNAs) in sperm have seemed crucial to this transmission due to their alteration in sperm in response to environmental exposure, and the methodology of microinjection of isolated total RNA or sncRNAs or synthetically identified sncRNAs gradually lifted the veil of sncRNA regulation during intergenerational inheritance along the male line. Hence, by reviewing relevant literature, this study intends to answer the following research concepts: (1) paternal environmental factors that can be passed on to offspring and are attributed to spermatozoal sncRNAs, (2) potential role of paternal spermatozoal sncRNAs during the intergenerational inheritance process, and (3) the potential mechanism by which spermatozoal sncRNAs meditate intergenerational inheritance. In summary, increased attention highlights the hidden wonder of spermatozoal sncRNAs during intergenerational inheritance. Therefore, in the future, more studies should focus on the origin of RNA alteration, the target of RNA regulation, and how sncRNA regulation during embryonic development can be sustained even in adult offspring.

Prenatal exercise reverses high-fat-diet-induced placental alterations and alters male fetal hypothalamus during late gestation in rats†

Maternal high-fat (HF) diet negatively affects maternal metabolism and placental function. This study aimed to determine whether gestational exercise prevents the effect of HF diet on placental amino acid transporter expression and nutrient-sensing signaling and the fetal response. Pregnant Sprague-Dawley rats were either fed with a CHOW (13.5% fat) or HF (60% fat) diet during gestation and further divided into two subgroups: voluntary exercised and sedentary. Placentae were collected on gestational day (GD) 14 and GD20, and male placentae were used in this study. We found that gestational exercise ameliorated the detrimental effects of HF diet on dams' adiposity, plasma leptin, and insulin concentrations. Maternal exercise did not influence fetoplacental growth but affected male fetal hypothalamic Leprb, Stat3, Insr, Agrp, and Pomc expressions on GD20. Maternal HF diet decreased placental labyrinth thickness and increased system A amino acid transporter SNAT2 expression, while these changes were normalized by exercise. The activation of placental mechanistic target of rapamycin complex 1/4E-BP1 and LepRb/STAT3 signaling might contribute to the increased placental SNAT2 expression in HF-fed dams, which were reversed by exercise on GD20. These data highlight that gestational exercise reverses HF-diet-induced placental alterations during late gestation without influencing fetal growth. However, maternal exercise altered fetal hypothalamic gene expression, which may affect long-term offspring health.

Imaging the Structure and the Saltwater Intrusion Extent of the Luy River Coastal Aquifer (Binh Thuan, Vietnam) Using Electrical Resistivity Tomography

With the growing population and the adverse effects of climate change, the pressure on coastal aquifers is increasing, leading to a larger risk of saltwater intrusion (SI). SI is often complex and difficult to characterize from well data only. In this context, electrical resistivity tomography (ERT) can provide high-resolution qualitative information on the lateral and vertical distribution of salinity. However, the quantitative interpretation of ERT remains difficult because of the uncertainty of petrophysical relationships, the limitations of inversion, and the heterogeneity of aquifers. In this contribution, we propose a methodology for the semiquantitative interpretation of ERT when colocated well data are not available. We first use existing wells to identify freshwater zones and characterize the resistivity response of clayey deposits. Then, we approximate the formation factor from water samples collected in the vicinity of ERT data to derive a resistivity threshold to interpret the saline boundary. We applied the methodology in the shallow aquifers of the Luy River in the Binh Thuan province, Vietnam, where water resources are under pressure due to agricultural, aquacultural, and industrial production. Twenty-one ERT profiles were collected and revealed a much larger intrusion zone, compared to the previous study. Saltwater is present in lowland areas of the left bank over almost the whole thickness of the aquifer, while the right bank is constituted of sand dunes that are filled with freshwater. At a larger distance from the sea, a complex distribution between fresh and saltwater is observed. Our methodology could be applied to other heterogeneous aquifers in the absence of a dense monitoring network.

Maternal obesity as a risk factor for developing diabetes in offspring: An epigenetic point of view

According to the developmental origin of health and disease concept, the risk of many age-related diseases is not only determined by genetic and adult lifestyle factors but also by factors acting during early development. In particular, maternal obesity and neonatal accelerated growth predispose offspring to overweight and type 2 diabetes (T2D) in adulthood. This concept mainly relies on the developmental plasticity of adipose tissue and pancreatic β-cell programming in response to suboptimal milieu during the perinatal period. These changes result in unhealthy hypertrophic adipocytes with decreased capacity to store fat, low-grade inflammation and loss of insulin-producing pancreatic β-cells. Over the past years, many efforts have been made to understand how maternal obesity induces long-lasting adipose tissue and pancreatic β-cell dysfunction in offspring and what are the molecular basis of the transgenerational inheritance of T2D. In particular, rodent studies have shed light on the role of epigenetic mechanisms in linking maternal nutritional manipulations to the risk for T2D in adulthood. In this review, we discuss epigenetic adipocyte and β-cell remodeling during development in the progeny of obese mothers and the persistence of these marks as a basis of obesity and T2D predisposition.

Understanding the Link Between Maternal Overnutrition, Cardio-Metabolic Dysfunction and Cognitive Aging

Obesity has long been identified as a global epidemic with major health implications such as diabetes and cardiovascular disease. Maternal overnutrition leads to significant health issues in industrial countries and is one of the risk factors for the development of obesity and related disorders in the progeny. The wide accessibility of junk food in recent years is one of the major causes of obesity, as it is low in nutrient content and usually high in salt, sugar, fat, and calories. An excess of nutrients during fetal life not only has immediate effects on the fetus, including increased growth and fat deposition in utero, but also has long-term health consequences. Based on human studies, it is difficult to discern between genetic and environmental contributions to the risk of disease in future generations. Consequently, animal models are essential for studying the impact of maternal overnutrition on the developing offspring. Recently, animal models provided some insight into the physiological mechanisms that underlie developmental programming. Most of the studies employed thus far have focused only on obesity and metabolic dysfunctions in the offspring. These studies have advanced our understanding of how maternal overnutrition in the form of high-fat diet exposure can lead to an increased risk of obesity in the offspring, but many questions remain open. How maternal overnutrition may increase the risk of developing brain pathology such as cognitive disabilities in the offspring and increase the risk to develop metabolic disorders later in life? Further, does maternal overnutrition exacerbate cognitive- and cardio-metabolic aging in the offspring?

Western Diet Consumption During Development: Setting the Stage for Neurocognitive Dysfunction

The dietary pattern in industrialized countries has changed substantially over the past century due to technological advances in agriculture, food processing, storage, marketing, and distribution practices. The availability of highly palatable, calorically dense foods that are shelf-stable has facilitated a food environment where overconsumption of foods that have a high percentage of calories derived from fat (particularly saturated fat) and sugar is extremely common in modern Westernized societies. In addition to being a predictor of obesity and metabolic dysfunction, consumption of a Western diet (WD) is related to poorer cognitive performance across the lifespan. In particular, WD consumption during critical early life stages of development has negative consequences on various cognitive abilities later in adulthood. This review highlights rodent model research identifying dietary, metabolic, and neurobiological mechanisms linking consumption of a WD during early life periods of development (gestation, lactation, juvenile and adolescence) with behavioral impairments in multiple cognitive domains, including anxiety-like behavior, learning and memory function, reward-motivated behavior, and social behavior. The literature supports a model in which early life WD consumption leads to long-lasting neurocognitive impairments that are largely dissociable from WD effects on obesity and metabolic dysfunction.

Maternal high-fat diet during lactation reprograms the dopaminergic circuitry in mice

The maternal perinatal environment modulates brain formation, and altered maternal nutrition has been linked to the development of metabolic and psychiatric disorders in the offspring. Here, we showed that maternal high-fat diet (HFD) feeding during lactation in mice elicits long-lasting changes in gene expression in the offspring's dopaminergic circuitry. This translated into silencing of dopaminergic midbrain neurons, reduced connectivity to their downstream targets, and reduced stimulus-evoked dopamine (DA) release in the striatum. Despite the attenuated activity of DA midbrain neurons, offspring from mothers exposed to HFD feeding exhibited a sexually dimorphic expression of DA-related phenotypes, i.e., hyperlocomotion in males and increased intake of palatable food and sucrose in females. These phenotypes arose from concomitantly increased spontaneous activity of D1 medium spiny neurons (MSNs) and profoundly decreased D2 MSN projections. Overall, we have unraveled a fundamental restructuring of dopaminergic circuitries upon time-restricted altered maternal nutrition to induce persistent behavioral changes in the offspring.

tRNA Biology in the Pathogenesis of Diabetes: Role of Genetic and Environmental Factors

The global rise in type 2 diabetes results from a combination of genetic predisposition with environmental assaults that negatively affect insulin action in peripheral tissues and impair pancreatic β-cell function and survival. Nongenetic heritability of metabolic traits may be an important contributor to the diabetes epidemic. Transfer RNAs (tRNAs) are noncoding RNA molecules that play a crucial role in protein synthesis. tRNAs also have noncanonical functions through which they control a variety of biological processes. Genetic and environmental effects on tRNAs have emerged as novel contributors to the pathogenesis of diabetes. Indeed, altered tRNA aminoacylation, modification, and fragmentation are associated with β-cell failure, obesity, and insulin resistance. Moreover, diet-induced tRNA fragments have been linked with intergenerational inheritance of metabolic traits. Here, we provide a comprehensive review of how perturbations in tRNA biology play a role in the pathogenesis of monogenic and type 2 diabetes.

Transgenerational modification of dopaminergic dysfunctions induced by maternal immune activation

Prenatal exposure to infectious and/or inflammatory insults is increasingly recognized to contribute to the etiology of psychiatric disorders with neurodevelopmental components. Recent research using animal models suggests that maternal immune activation (MIA) can induce transgenerational effects on brain and behavior, possibly through epigenetic mechanisms. Using a mouse model of MIA that is based on gestational treatment with the viral mimeticpoly(I:C) (= polyriboinosinic-polyribocytidilic acid), the present study explored whether the transgenerational effects of MIA are extendable to dopaminergic dysfunctions. We show that the direct descendants born to poly(I:C)-treated mothers display signs of hyperdopaminergia, as manifested by a potentiated sensitivity to the locomotor-stimulating effects of amphetamine (Amph) and increased expression of tyrosine hydroxylase (Th) in the adult ventral midbrain. In stark contrast, second- and third-generation offspring of MIA-exposed ancestors displayed blunted locomotor responses to Amph and reduced expression of Th. Furthermore, we found increased DNA methylation at the promoter region of the dopamine-specifying factor, nuclear receptor-related 1 protein (Nurr1), in the sperm of first-generation MIA offspring and in the ventral midbrain of second-generation offspring of MIA-exposed ancestors. The latter effect was further accompanied by reduced mRNA levels of Nurr1 in this brain region. Together, our results suggest that MIA has the potential to modify dopaminergic functions across multiple generations with opposite effects in the direct descendants and their progeny. The presence of altered DNA methylation in the sperm of MIA-exposed offspring highlights the possibility that epigenetic processes in the male germline play a role in the transgenerational effects of MIA.

Perinatal exposure to maternal obesity: Lasting cardiometabolic impact on offspring

Evidence from epidemiological, clinical, and animal model studies clearly demonstrates that prenatal and lactational maternal obesity and high-fat diet consumption are associated with cardiometabolic morbidity in offspring. Fetal and offspring sex may be an important effect modifier. Adverse offspring cardiometabolic outcomes observed in the setting of maternal obesity include an increased risk for obesity, features of metabolic syndrome (hypertension, hyperglycemia and insulin resistance, hyperlipidemia, increased adiposity), and non-alcoholic fatty liver disease. This review article synthesizes human and animal data linking maternal obesity and high-fat diet consumption in pregnancy and lactation to adverse cardiometabolic outcomes in offspring. We review key mechanisms underlying skeletal muscle, adipose tissue, pancreatic, liver, and central brain reward programming in obesity-exposed offspring, and how such malprogramming contributes to offspring cardiometabolic morbidity.

Fetal Programming by Methyl Donors Modulates Central Inflammation and Prevents Food Addiction-Like Behavior in Rats

Fetal programming by hypercaloric intake leads to food addiction-like behavior and brain pro-inflammatory gene expression in offspring. The role of methylome modulation during programming on central immune activation and addiction-like behavior has not been characterized. We employed a nutritional programming model exposing female Wistar rats to chow diet, cafeteria (CAF), or CAF-methyl donor’s diet from pre-pregnancy to weaning. Addiction-like behavior in offspring was characterized by the operant training response using Skinner boxes. Food intake in offspring was determined after fasting–refeeding schedule and subcutaneous injection of ghrelin. Genome-wide DNA methylation in the nucleus accumbens (NAc) shell was performed by fluorescence polarization, and brain immune activation was evaluated using real-time PCR for pro-inflammatory cytokines (IL-1β, TNF-1α, and IL-6). Molecular effects of methyl modulators [S-adenosylmethionine (SAM) or 5-azatidine (5-AZA)] on pro-inflammatory cytokine expression and phagocytosis were identified in the cultures of immortalized SIM-A9 microglia cells following palmitic acid (100 μM) or LPS (100 nM) stimulation for 6 or 24 h. Our results show that fetal programming by CAF exposure increases the number of offspring subjects and reinforcers under the operant training response schedule, which correlates with an increase in the NAc shell global methylation. Notably, methyl donor’s diet selectively decreases lever-pressing responses for reinforcers and unexpectedly decreases the NAc shell global methylation. Also, programmed offspring by CAF diet shows a selective IL-6 gene expression in the NAc shell, which is reverted to control values by methyl diet exposure. In vitro analysis identified that LPS and palmitic acid activate IL-1β, TNF-1α, and IL-6 gene expression, which is repressed by the methyl donor SAM. Finally, methylation actively represses phagocytosis activity of SIM-A9 microglia cells induced by LPS and palmitic acid stimulation. Our in vivo and in vitro data suggest that fetal programming by methyl donors actively decreases addiction-like behavior to palatable food in the offspring, which correlates with a decrease in NAc shell methylome, expression of pro-inflammatory cytokine genes, and activity of phagocytic microglia. These results support the role of fetal programming in brain methylome on immune activation and food addiction-like behavior in the offspring.

Epigenetic Programming of Adipose Tissue in the Progeny of Obese Dams

According to the Developmental Origin of Health and Disease (DOHaD) concept, maternal obesity and the resulting accelerated growth in neonates predispose offspring to obesity and associated metabolic diseases that may persist across generations. In this context, the adipose tissue has emerged as an important player due to its involvement in metabolic health, and its high potential for plasticity and adaptation to environmental cues. Recent years have seen a growing interest in how maternal obesity induces long-lasting adipose tissue remodeling in offspring and how these modifications could be transmitted to subsequent generations in an inter- or transgenerational manner. In particular, epigenetic mechanisms are thought to be key players in the developmental programming of adipose tissue, which may partially mediate parts of the transgenerational inheritance of obesity. This review presents data supporting the role of maternal obesity in the developmental programming of adipose tissue through epigenetic mechanisms. Inter- and transgenerational effects on adipose tissue expansion are also discussed in this review.

Nutrition and its role in epigenetic inheritance of obesity and diabetes across generations

Nutritional constraints including not only caloric restriction or protein deficiency, but also energy-dense diets affect metabolic health and frequently lead to obesity and insulin resistance, as well as glucose intolerance and type 2 diabetes. The effects of these environmental factors are often mediated via epigenetic modifiers that target the expression of metabolic genes. More recently, it was discovered that such parentally acquired metabolic changes can alter the metabolic health of the filial and grand-filial generations. In mammals, this epigenetic inheritance can either follow an intergenerational or transgenerational mode of inheritance. In the case of intergenerational inheritance, epimutations established in gametes persist through the first round of epigenetic reprogramming occurring during preimplantation development. For transgenerational inheritance, epimutations persist additionally throughout the reprogramming that occurs during germ cell development later in embryogenesis. Differentially expressed transcripts, genomic cytosine methylations, and several chemical modifications of histones are prime candidates for tangible marks which may serve as epimutations in inter- and transgenerational inheritance and which are currently being investigated experimentally. We review, here, the current literature in support of epigenetic inheritance of metabolic traits caused by nutritional constraints and potential mechanisms in man and in rodent model systems.

Behavioral Feeding Circuit: Dietary Fat-Induced Effects of Inflammatory Mediators in the Hypothalamus

Excessive dietary fat intake has extensive impacts on several physiological systems and can lead to metabolic and nonmetabolic disease. In animal models of ingestion, exposure to a high fat diet during pregnancy predisposes offspring to increase intake of dietary fat and causes increase in weight gain that can lead to obesity, and without intervention, these physiological and behavioral consequences can persist for several generations. The hypothalamus is a region of the brain that responds to physiological hunger and fullness and contains orexigenic neuropeptide systems that have long been associated with dietary fat intake. The past fifteen years of research show that prenatal exposure to a high fat diet increases neurogenesis of these neuropeptide systems in offspring brain and are correlated to behavioral changes that induce a pro-consummatory and obesogenic phenotype. Current research has uncovered several potential molecular mechanisms by which excessive dietary fat alters the hypothalamus and involve dietary fatty acids, the immune system, gut microbiota, and transcriptional and epigenetic changes. This review will examine the current knowledge of dietary fat-associated changes in the hypothalamus and the potential pathways involved in modifying the development of orexigenic peptide neurons that lead to changes in ingestive behavior, with a special emphasis on inflammation by chemokines.

Environmental and Nutritional Effects Regulating Adipose Tissue Function and Metabolism Across Generations

The unabated rise in obesity prevalence during the last 40 years has spurred substantial interest in understanding the reasons for this epidemic. Studies in mice and humans have demonstrated that obesity is a highly heritable disease; however genetic variations within specific populations have so far not been able to explain this phenomenon to its full extent. Recent work has demonstrated that environmental cues can be sensed by an organism to elicit lasting changes, which in turn can affect systemic energy metabolism by different epigenetic mechanisms such as changes in small noncoding RNA expression, DNA methylation patterns, as well as histone modifications. These changes can directly modulate cellular function in response to environmental cues, however research during the last decade has demonstrated that some of these modifications might be transmitted to subsequent generations, thus modulating energy metabolism of the progeny in an inter- as well as transgenerational manner. In this context, adipose tissue has become a focus of research due to its plasticity, which allows the formation of energy storing (white) as well as energy wasting (brown/brite/beige) cells within the same depot. In this Review, the effects of environmental induced obesity with a particular focus on adipose tissue are discussed.

Maternal overnutrition programs hedonic and metabolic phenotypes across generations through sperm tsRNAs

Obesity is a major public health issue worldwide. Easy accessibility of junk food is considered a major contributor to the current obesity epidemic. Thus, the impact of maternal overnutrition in determining disease susceptibility in offspring has received wide attention. It has also been shown that the effects of maternal overnutrition are not limited to the immediate offspring but can also be transmitted to successive generations. Among different epigenetic marks, sperm small noncoding RNAs (sncRNAs) have recently been reported as a direct mediator of acquired traits to the progeny following postnatal trauma or paternal diet. Here, we investigate whether sperm sncRNAs contributes to the transmission of metabolic and hedonic phenotypes across generations following maternal overnutrition.

There is a growing body of evidence linking maternal overnutrition to obesity and psychopathology that can be conserved across multiple generations. Recently, we demonstrated in a maternal high-fat diet (HFD; MHFD) mouse model that MHFD induced enhanced hedonic behaviors and obesogenic phenotypes that were conserved across three generations via the paternal lineage, which was independent of sperm methylome changes. Here, we show that sperm tRNA-derived small RNAs (tsRNAs) partly contribute to the transmission of such phenotypes. We observe increased expression of sperm tsRNAs in the F1 male offspring born to HFD-exposed dams. Microinjection of sperm tsRNAs from the F1-HFD male into normal zygotes reproduces obesogenic phenotypes and addictive-like behaviors, such as increased preference of palatable foods and enhanced sensitivity to drugs of abuse in the resultant offspring. The expression of several of the differentially expressed sperm tsRNAs predicted targets such as CHRNA2 and GRIN3A, which have been implicated in addiction pathology, are altered in the mesolimbic reward brain regions of the F1-HFD father and the resultant HFD-tsRNA offspring. Together, our findings demonstrate that sperm tsRNA is a potential vector that contributes to the transmission of MHFD-induced addictive-like behaviors and obesogenic phenotypes across generations, thereby emphasizing its role in diverse pathological outcomes.

Maternal Overnutrition Induces Long-Term Cognitive Deficits across Several Generations

Ample evidence from epidemiological studies has linked maternal obesity with metabolic disorders such as obesity, cardiovascular disease, and diabetes in the next generation. Recently, it was also shown that maternal obesity has long-term effects on the progeny’s central nervous system. However, very little is known regarding how maternal overnutrition may affect, in particular, the cognitive abilities of the offspring. We reported that first-generation offspring exposed to a maternal high-fat diet (MHFD) displayed age-dependent cognitive deficits. These deficits were associated with attenuations of amino acid levels in the medial prefrontal cortex and the hippocampus regions of MHFD offspring. Here, we tested the hypothesis that MHFD in mice may induce long-term cognitive impairments and neurochemical dysfunctions in the second and third generations. We found that MHFD led to cognitive disabilities and an altered response to a noncompetitive receptor antagonist of the N-Methyl-D-aspartic acid (NMDA) receptor in adult MHFD offspring in both second and third generations in a sex-specific manner. Our results suggest that maternal overnutrition leads to an increased risk of developing obesity in subsequent generations as well as to cognitive impairments, affecting learning and memory processes in adulthood. Furthermore, MHFD exposure may facilitate pathological brain aging which is not a consequence of obesity. Our findings shed light on the long-term effects of maternal overnutrition on the development of the central nervous system and the underlying mechanisms which these traits relate to disease predisposition.