Épigénomique nutritionnelle du syndrome métabolique

A 2-decade bibliometric analysis of epigenetics of cardiovascular disease: from past to present

BACKGROUND

Cardiovascular disease (CVD) remains a major health killer worldwide, and the role of epigenetic regulation in CVD has been widely studied in recent decades. Herein, we perform a bibliometric study to decipher how research topics in this field have evolved during the past 2 decades.

RESULTS

Publications on epigenetics in CVD produced during the period 2000-2022 were retrieved from the Web of Science Core Collection (WoSCC). We utilized Bibliometrix to build a science map of the publications and applied VOSviewer and CiteSpace to assess co-authorship, co-citation, co-occurrence, and bibliographic coupling. In total, 27,762 publications were included for bibliometric analysis. The yearly amount of publications experienced exponential growth. The top 3 most influential countries were China, the United States, and Germany, while the most cited institutions were Nanjing Medical University, Harbin Medical University, and Shanghai Jiao Tong University. Four major research trends were identified: (a) epigenetic mechanisms of CVD; (b) epigenetics-based therapies for CVD; (c) epigenetic profiles of specific CVDs; and (d) epigenetic biomarkers for CVD diagnosis/prediction. The latest and most important research topics, including "nlrp3 inflammasome", "myocardial injury", and "reperfusion injury", were determined by detecting citation bursts of co-occurring keywords. The most cited reference was a review of the current knowledge about how miRNAs recognize target genes and modulate their expression and function.

CONCLUSIONS

The number and impact of global publications on epigenetics in CVD have expanded rapidly over time. Our findings may provide insights into the epigenetic basis of CVD pathogenesis, diagnosis, and treatment.

Epigenetics and Cellular Metabolism

Living eukaryotic systems evolve delicate cellular mechanisms for responding to various environmental signals. Among them, epigenetic machinery (DNA methylation, histone modifications, microRNAs, etc.) is the hub in transducing external stimuli into transcriptional response. Emerging evidence reveals the concept that epigenetic signatures are essential for the proper maintenance of cellular metabolism. On the other hand, the metabolite, a main environmental input, can also influence the processing of epigenetic memory. Here, we summarize the recent research progress in the epigenetic regulation of cellular metabolism and discuss how the dysfunction of epigenetic machineries influences the development of metabolic disorders such as diabetes and obesity; then, we focus on discussing the notion that manipulating metabolites, the fuel of cell metabolism, can function as a strategy for interfering epigenetic machinery and its related disease progression as well.

[The new paradigm of the developmental origin of health and diseases (DOHaD)--Epigenetics and environment: evidence and missing links]

According to the new paradigm of the Developpemental Origins of Health and Disease (DOHaD), the environmental factors to which an individual is exposed throughout his life can leave an epigenetic footprint on the genome. A crucial period is the early development, where the epigenome is particularly sensitive to the effects of the environment, and during which the individual builds up his health capital that will enable him to respond more or less well to the vagaries of life. The research challenge is to decipher the modes of action and the epigenetic mechanisms put into play by environmental factors that lead to increased disease susceptibility or resilience. The challenge for health is to translate these scientific discoveries into action through, among others, the establishment of preventive recommendations to slow down the growing incidence of non communicable diseases.

[Interaction between environment and genetic background in type 2 diabetes: lessons from animal models]

The respective roles of predisposing genetic factors and environmental factors in the development of type 2 diabetes (T2D) in obese subjects is poorly documented. Rodent models have been set up in an attempt to better understand of the differential effect of a prolonged metabolic stress induced by a high fat diet on glycaemic control according to the genetic background. In utero growth retardation resulting from a hypocaloric diet in pregnant rats induces a dramatic alteration of the development of islet cells leading to diabetes and insulin secretory defects in adult age. Experimentally induced diabetes in rodents results in hyperglycaemia and hyperinsulinemia in the fetus related to accelerated endocrine pancreas maturation responsible for the onset of diabetes in the adult. Deranged metabolic environment during fetal life may therefore further contribute to the onset of diabetes in the adult. Normal mouse strains with different genetic backgrounds show a wide range of responses to a high fat diet, with strains resistant to the diet and other more or less sensitive to the diet, the most sensitive exhibiting obesity diabetes and, insulin deficiency. The inability of the β cell to respond to the increased insulin demand related to insulin resistance seems to be pivotal in the pathophysiologic process and a new notion is emerging: "nutritional genetics" which studies the influence of nutrients on gene expression.

Effects of assisted reproduction technology on placental imprinted gene expression

We used placental tissue to compare the imprinted gene expression of IGF2, H19, KCNQ1OT1, and CDKN1C of singletons conceived via assisted reproduction technology (ART) with that of spontaneously conceived (SC) singletons. Of 989 singletons examined (ART n = 65; SC n = 924), neonatal weight was significantly lower (P < .001) in the ART group than in the SC group, but placental weight showed no significant difference. Gene expression analyzed by real-time PCR was similar for both groups with appropriate-for-date (AFD) birth weight. H19 expression was suppressed in fetal growth retardation (FGR) cases in the ART and SC groups compared with AFD cases (P < .02 and P < .05, resp.). In contrast, CDKN1C expression was suppressed in FGR cases in the ART group (P < .01), while KCNQ1OT1 expression was hyperexpressed in FGR cases in the SC group (P < .05). As imprinted gene expression patterns differed between the ART and SC groups, we speculate that ART modifies epigenetic status even though the possibilities always exist.

Stress hormones mediate environment-genotype interactions during amphibian development

Environments experienced by organisms during early development shape the character and timing of developmental processes, leading to different probabilities of survival in the developmental habitat, and often profound effects on phenotypic expression later in life. Amphibian larvae have immense capacity for plasticity in behavior, morphology, growth and development rate. This creates the potential for extreme variation in the timing of, and size at metamorphosis, and subsequent phenotype in the juvenile and adult stage. Hormones of the neuroendocrine stress axis play pivotal roles in mediating environmental effects on animal development. Corticotropin-releasing factor, whose secretion by hypothalamic neurons is induced by environmental stress, influences the timing of amphibian metamorphosis by controlling the activity of the thyroid and interrenal (adrenal; corticosteroids) glands. At target tissues, corticosteroids synergize with thyroid hormone to promote metamorphosis. Thus, environmental stress acts centrally to increase the activity of the two principle endocrine axes controlling metamorphosis, and the effectors of these axes synergize at the level of target tissues to promote morphogenesis. While stress hormones can promote survival in a deteriorating larval habitat, costs may be incurred such as reduced tadpole growth and size at metamorphosis. Furthermore, exposure to elevated corticosteroids early in life can cause permanent changes in the expression of genes of the neuroendocrine stress axis, leading to altered physiology and behavior in the juvenile/adult stage. Persistent effects of stress hormone actions early in life may have important fitness consequences.

Transgenerational hormonal imprinting caused by vitamin A and vitamin D treatment of newborn rats. Alterations in the biogenic amine contents of the adult brain

Biogenic amines (norepinephrine, dopamine, homovanillic acid, serotonin and 5-hyroxyindole acetic acid) were measured by HPLC method in adult F1 generation rats' brain regions (brainstem, hypothalamus, hippocampus, striatum and frontal cortex), whose mothers (P generation) were treated with vitamin A or vitamin D neonatally (hormonal imprinting). Many significant differences were found, related to the maternally untreated controls. In the earlier studied P generation females, vitamin A consistently influenced the serotonerg system (5HIAA), while vitamin D the dopaminerg system (DA or HVA). Vitamin A imprinting always resulted in reduced, while that by vitamin D always in increased tissue levels. In the present case (directly untreated F1 generation) the transgenerational effect was not unidirectional, however biogenic amine tissue levels were strongly disturbed and brain-area dependent. The results call attention to the transgenerational effect of hormonal imprinting in the case of receptor level acting vitamins which are frequently used in the most imprinting-sensitive period (perinatally) of human life and suggests that caution is warranted.

Nutrigenomics and personalized nutrition: science and concept

Diet and genomes interact. Nutrition has the most important life-long environmental impact on human health. While nutrigenetics addresses how an individual’s genetic makeup predisposes for dietary susceptibility, nutrigenomics asks how nutrition influences the expression of the genome. Nutrigenomics builds on the three omics disciplines transcriptomics, proteomics and metabolomics. They are a prerequisite for nutritional systems biology, the understanding of the interaction between food components and diet with cells, organs and the whole body. Personalized nutrition is a conceptual analog to personalized medicine. While there are food products available that address requirements or preferences of specific consumer groups, these products are based on empirical consumer science rather than on nutrigenomics and nutrigenetics. The latter two build the science foundation for understanding human variability in preferences, requirements and responses to diet, and may become the future tools for consumer assessment motivated by personalized nutritional counseling for health maintenance and disease prevention.

Report on the IASO Stock Conference 2006: early and lifelong environmental epigenomic programming of metabolic syndrome, obesity and type II diabetes

Now that analysis of the organization of the human genome sequence is reaching completion, studies of the finely tuned chromatin epigenetic networks, DNA methylation and histone modifications, are required to determine how the same DNA sequence generates different cells, lineages and organs, i.e. the phenotype. Maternal nutrition, behaviour and metabolic disturbances as well as other environmental factors have been shown to have major effects on these epigenetic processes, potentially affecting the predisposition of offspring to obesity and related adult disorders. The March 2006 Stock Conference considered the latest evidence from studies in the field of obesity and other related areas that elucidate mechanisms by which the environment can modify gene expression and the resulting individual phenotype. Presentations included evaluation of the molecular basis of epigenetic memory and the nature of relevant sequence targets, windows of susceptibility, and maternal dietary and behavioural factors that determine epigenetic changes. Imprinted genes, age and tissue-related exposures, transgenerational and potential interventions were also discussed. In summary, it is clear that epigenetic alterations can no longer be ignored in evaluations of the causes of obesity and its associated disorders. There is a need for systematic large-scale epigenetic studies of obesity, employing appropriate strategies and techniques and appropriately chosen environmental factors in critical spatio-temporal windows.

Nutri-epigenomics: lifelong remodelling of our epigenomes by nutritional and metabolic factors and beyond

The phenotype of an individual is the result of complex interactions between genotype, epigenome and current, past and ancestral environment, leading to lifelong remodelling of our epigenomes. Various replication-dependent and -independent epigenetic mechanisms are involved in developmental programming, lifelong stochastic and environmental deteriorations, circadian deteriorations, and transgenerational effects. Several types of sequences can be targets of a host of environmental factors and can be associated with specific epigenetic signatures and patterns of gene expression. Depending on the nature and intensity of the insult, the critical spatiotemporal windows and developmental or lifelong processes involved, these epigenetic alterations can lead to permanent changes in tissue and organ structure and function, or to reversible changes using appropriate epigenetic tools. Given several encouraging trials, prevention and therapy of age- and lifestyle-related diseases by individualised tailoring of optimal epigenetic diets or drugs are conceivable. However, these interventions will require intense efforts to unravel the complexity of these epigenetic, genetic and environment interactions and to evaluate their potential reversibility with minimal side effects.

[Molecular genetics of MTHFR: polymorphisms are not all benign]

Methylenetetrahydrofolate reductase (MTHFR) is a key regulatory enzyme in folate and homocysteine metabolism. Research performed during the past decade has clarified our understanding of MTHFR deficiencies that cause homocystinuria or mild hyperhomocysteinemia. Our cloning of the MTHFR coding sequence was initially followed by the identification of the first deleterious mutations in MTHFR, in patients with homocystinuria and marked hyperhomocysteinemia. Shortly thereafter, we identified the 677C-->T variant and showed that it encoded a thermolabile enzyme with reduced activity. Currently, a total of 41 rare but deleterious mutations in MTHFR, as well as about 60 polymorphisms have been reported. The 677C-->T (Ala222Val) variant has been particularly noteworthy since it has become recognized as the most common genetic cause of hyperhomocysteinemia. The disruption of homocysteine metabolism by this polymorphism influences risk for several complex disorders, including cardiovascular disease, neural tube defects and some cancers. We describe here the complex structure of the MTHFR gene, summarize the current state of knowledge on rare and common mutations in MTHFR and discuss some relevant findings in a mouse model for MTHFR deficiency.

Epigenetics in assisted reproductive technology

It has been reported that the rates of epigenetic disorders such as Angelman syndrome (AS) and Beckwith-Wiedemann syndrome (BWS) are high in offspring conceived by assisted reproductive technology (ART). Angelman Syndrome is characterized by intellectual disability and BWS is known as large offspring syndrome (LOS). Weight abnormalities have also been reported in cloned animals. Possible factors underlying these findings include inherent gamete characteristics, influence of in vitro culture and peculiarity of ART methods. It is important to conclusively determine whether such epigenetic abnormalities are present in children conceived by ART, so as to consider the health of next generations.

Hormonal imprinting: phylogeny, ontogeny, diseases and possible role in present-day human evolution

Hormonal (chemical) imprinting which was first observed (and named) by us in the seventies of the last century, is a general biological phenomenon which takes place when the developing receptor meets its target hormone for the first time. Under the effect of imprinting, receptors mature and reach their maximal binding capacity. It also influences the cells' hormone production and different functions depending on receptors and hormones. Hormonal imprinting is present already at the unicellular level causing the development of specific receptors and helping the easier recognition of useful or harmful surrounding molecules. The phenomenon is an important factor in the survival of the species, as the effect of imprinting is transmitted to the progeny cell generations. At the same time it possibly helps the selection of molecules which are suitable for acting as hormones in higher ranked animals. In mammals, hormonal imprinting takes place perinatally and determines the function of receptor-signal-transduction systems as well as hormone production for life. However, there are other critical imprinting periods for continuously developing cells. Excess of the target hormones or presence of foreign molecules which are able to bind to the receptors, provoke faulty imprinting in the critical periods with life-long morphological, biochemical, functional or behavioural consequences. As many receptor-bound foreign molecules are used as medical treatments and many such molecules are present around us and inside us as environmental pollutants, they--causing faulty imprinting--are able to predispose the (human) organism to cardiovascular, endocrine, metabolic and cancerous diseases. It seems likely that this effect is connected with disturbance of DNA methylation process in the critical periods of life. There are some signs of the transgenerational effect of faulty imprinting and this could be manifested in the evolution of humans by an epigenetic route.

Mechanisms by which poor early growth programs type-2 diabetes, obesity and the metabolic syndrome

Fetal programming is gaining momentum as a highly documented phenomenon which links poor early growth to adult disease. It is backed up by large cohorts in epidemiological studies worldwide and has been tested in various animal models. The root causes of programming link closely with maternal condition during pregnancy, and therefore the fetal environment. Suboptimal fetal environments due to poor or inadequate nutrition, infection, anemia, hypertension, inflammation, gestational diabetes or hypoxia in the mother expose the fetus to hormonal, growth factor, cytokine or adipokine cues. These in turn act to alter metabolic, immune system, vascular, hemodynamics, renal, growth and mitochondrial parameters respectively and most evidently in the later stages of life where they impact on the individual as poor glucose homeostasis, insulin resistance, type 2 diabetes, hypertension, cardiovascular disease, obesity and heart disease. These events are compounded by over-nutrition or lifestyle choices which are in conflict with the programming of the fetus. We and others have utilised various species to test the early life programming hypothesis and to identify key molecular mechanisms. With parallel studies of human cohorts, these molecular markers can be validated as realistic targets for intervention.