Association between metabolic disorders and seminal plasma miRNA levels: a pilot study.

BACKGROUND: Excess weight and metabolic disorders have a negative impact on male reproductive functions. The mechanisms involved are numerous and complex and epigenetic mechanisms may also be involved, notably through the small non-coding RNAs. Among them, microRNAs (miRNAs) are of particular interest. This preliminary study aimed to identify the miRNAs differentially enriched in seminal plasma related to metabolic disorders and if some are also associated with spermatic parameters alterations. One hundred and sixty men between 18 to 45 years, partners of infertile couple, were included in this cohort. The miRNAs associated with metabolism were selected from the literature and assayed by quantitative real-time PCR using TaqMan gene expression assays. A subset of those with an interesting profile in seminal plasma were secondarily tested in blood. RESULTS: Among the 11 selected miRNAs, seven were detected in seminal plasma (miR10b, miR19a, miR19b, miR34b, miR34c, miR133b, miRlet7c). A negative correlation was observed between seminal miR19a levels and metabolic syndrome, blood glucose and C-peptide. Seminal miR19b levels were also negatively correlated with metabolic syndrome. Seminal miR34c levels were negatively correlated with body mass index (BMI) and waist circumference. Seminal miR133b levels were positively correlated with BMI, waist circumference and leptin levels. Interestingly, modifications of miRNAs in seminal plasma seem specific since highlighted above correlations were not retrieved in the blood plasma for the miR19a, 19b, 10b, 34c. CONCLUSION: Few metabolic and anthropometric disorders are correlated with the level of specific miRNAs in seminal plasma. Further studies will be required to decipher if other small non-coding RNAs may also be correlated with metabolic and anthropometric disorders and to assess their potential implication in the alteration of reproductive functions in men with obesity or metabolic disorders. CLINICAL STUDY: Metabolic Syndrome and Male Infertility (Metasperme): Trial registration:  NCT01974947 . Registered 18 July 2013.

RéSUMé: CONTEXTE: L'excès de poids et les troubles métaboliques ont un impact négatif sur les fonctions de reproduction masculine. Les mécanismes impliqués sont nombreux et complexes, et des mécanismes épigénétiques peuvent également intervenir, notamment par le biais des petits ARN non codants. Parmi eux, les microRNAs (miRNAs) présentent un intérêt particulier. Cette étude préliminaire visait à identifier les miRNAs différentiellement enrichis dans le plasma séminal en relation avec des troubles métaboliques et si certains étaient également associés à des altérations des paramètres spermatiques. Cent soixante hommes âgés de 18 à 45 ans, partenaires de couple infertile, ont été inclus dans cette cohorte. Les miRNAs associés au métabolisme ont été sélectionnés dans la littérature et analysés par PCR quantitative en temps réel à l'aide de tests d'expression génique TaqMan. Un sous-ensemble de ceux présentant un profil intéressant dans le plasma séminal ont été secondairement testés dans le sang. RéSULTATS: Parmi les 11 miRNAs sélectionnés, sept ont été détectés dans le plasma séminal (miR10b, miR19a, miR19b, miR34b, miR34c, miR133b, miRlet7c). Une corrélation négative a été observée entre les niveaux du miR19a séminal et le syndrome métabolique, la glycémie et le C-peptide. Les niveaux de miR19b séminaux étaient également corrélés négativement avec le syndrome métabolique. Les niveaux de miR34c séminaux étaient négativement corrélés avec l'IMC et le tour de taille. Les niveaux de miR133b séminaux étaient positivement corrélés avec l'IMC, le tour de taille et les niveaux de leptine. Il est intéressant de noter que les modifications des miRNA dans le plasma séminal semblent spécifiques puisque les corrélations mises en évidence ci-dessus n'ont pas été retrouvées dans le plasma sanguin pour les miR19a, 19b, 10b, 34c. CONCLUSION: Quelques désordres métaboliques et anthropométriques ont été observés corrélés avec le niveau de certains miRNAs dans le plasma séminal. Des études complémentaires sont nécessaires pour déterminer si d'autres petits ARN non codants sont corrélés aux troubles métaboliques et anthropométriques et pour évaluer leur implication potentielle dans l'altération des fonctions de reproduction chez les hommes souffrant d'obésité ou de troubles métaboliques.

The Essential Role of Pancreatic α-Cells in Maternal Metabolic Adaptation to Pregnancy.

Pancreatic α-cells are important in maintaining metabolic homeostasis, but their role in regulating maternal metabolic adaptations to pregnancy has not been studied. The objective of this study was to determine whether pancreatic α-cells respond to pregnancy and their contribution to maternal metabolic adaptation. With use of C57BL/6 mice, the findings of our study showed that pregnancy induced a significant increase of α-cell mass by promoting α-cell proliferation that was associated with a transitory increase of maternal serum glucagon concentration in early pregnancy. Maternal pancreatic GLP-1 content also was significantly increased during pregnancy. Using the inducible Cre/loxp technique, we ablated the α-cells (α-null) before and during pregnancy while maintaining enteroendocrine L-cells and serum GLP-1 in the normal range. In contrast to an improved glucose tolerance test (GTT) before pregnancy, significantly impaired GTT and remarkably higher serum glucose concentrations in the fed state were observed in α-null dams. Glucagon receptor antagonism treatment, however, did not affect measures of maternal glucose metabolism, indicating a dispensable role of glucagon receptor signaling in maternal glucose homeostasis. However, the GLP-1 receptor agonist improved insulin production and glucose metabolism of α-null dams. Furthermore, GLP-1 receptor antagonist Exendin (9-39) attenuated pregnancy-enhanced insulin secretion and GLP-1 restored glucose-induced insulin secretion of cultured islets from α-null dams. Together, these results demonstrate that α-cells play an essential role in controlling maternal metabolic adaptation to pregnancy by enhancing insulin secretion.

Adiponectin Promotes Maternal ß-Cell Expansion Through Placental Lactogen Expression.

Hypoadiponectinemia is a risk factor of gestational diabetes mellitus (GDM). Our previous study reported that adiponectin gene knockout mice (Adipoq -/- ) develop GDM due to insulin insufficiency. The main objective of this study was to elucidate the underlying mechanism through which adiponectin controls islet expansion during pregnancy. A significant reduction in ß-cell proliferation rates, ß-cell areas, and blood insulin concentrations was detected in Adipoq -/- mice at midpregnancy. Surprisingly, conditionally knocking down adiponectin receptor 1 (AdipoR1) or AdipoR2 genes in ß-cells during pregnancy did not reduce ß-cell proliferation rates or blood insulin concentrations. In vitro adiponectin treatment also failed to show any effect on ß-cell proliferation of isolated pancreatic islets. It was reported that placental lactogen (PL) plays a crucial role in pregnancy-induced maternal ß-cell proliferation. A significant decrease in phosphorylation of signal transducer and activator of transcription 5, a downstream molecule of PL signaling, was observed in islets from Adipoq -/- dams. The mRNA levels of mouse PL genes were robustly decreased in the placentas of Adipoq -/- dams. In contrast, adiponectin treatment increased PL expression in human placenta explants and JEG3 trophoblast cells. Most importantly, bovine PL injection restored ß-cell proliferation and blood insulin concentrations in Adipoq -/- dams. Together, these results demonstrate that adiponectin plays a vital role in pregnancy-induced ß-cell proliferation by promoting PL expression in trophoblast cells.

Changes in circulating miRNA19a-3p precede insulin resistance programmed by intra-uterine growth retardation in mice.

OBJECTIVE: Individuals born with intrauterine growth retardation (IUGR) are more prone to cardio-metabolic diseases as adults, and environmental changes during the perinatal period have been identified as potentially crucial factors. We have studied in a preclinical model early-onset molecular alterations present before the development of a clinical phenotype. METHODS: We used a preclinical mouse model of induced IUGR, in which we modulated the nutrition of the pups during the suckling period, to modify their susceptibility to cardio-metabolic diseases in adulthood. RESULTS: Mice born with IUGR that were overfed (IUGR-O) during lactation rapidly developed obesity, hepatic steatosis and insulin resistance, by three months of age, whereas those subjected to nutrition restriction during lactation (IUGR-R) remained permanently thin and highly sensitive to insulin. Mice born with IUGR and fed normally during lactation (IUGR-N) presented an intermediate phenotype and developed insulin resistance by 12 months of age. Molecular alterations to the insulin signaling pathway with an early onset were observed in the livers of adult IUGR-N mice, nine months before the appearance of insulin resistance. The implication of epigenetic changes was revealed by ChIP sequencing, with both posttranslational H3K4me3 histone modifications and microRNAs involved. CONCLUSIONS: These two changes lead to the coherent regulation of insulin signaling, with a decrease in Akt gene transcription associated with an increase in the translation of its inhibitor, Pten. Moreover, we found that the levels of the implicated miRNA19a-3p also decreased in the blood of young adult IUGR mice nine months before the appearance of insulin resistance, suggesting a possible role for this miRNA as an early circulating biomarker of metabolic fate of potential use for precision medicine.

Role of miRNA in the Transmission of Metabolic Diseases Associated With Paternal Diet-Induced Obesity.

The concept of Developmental Origins of Health and Diseases (DOHaD) recognizes that an unfavorable maternal environment alters the developmental trajectory of the fetus and can lead to long-term risk of developing chronic noncommunicable diseases. More recently, the concept of a paternal transmission [Paternal Origins of Health and Diseases (POHaD)] has emerged stressing the impact of paternal overweight or obesity on offspring's health and development. While very few examples of paternal epigenetic inheritance of metabolic disorders have been evidenced in human, many experimental mouse models based on high-fat diet (HFD)-induced paternal obesity have been developed to breakdown molecular mechanisms involved in the process. Besides DNA methylation and chromatin structure, sperm short noncoding RNAs have been considered as the main epigenetic vector of inheritance of paternally environmentally induced changes. Among them, sperm miRNAs are one particular subspecies sensitive to environmental changes and obesity can modify the sperm miRNA profile. Once delivered into the zygote, these molecules might induce epigenetic modifications in the embryo, thereby leading to consequences for fetus development and offspring physical and metabolic health later on in life. Furthermore, some data also suggest that metabolic pathologies may be intergenerationally or transgenerationally transmitted.

Regulation of growth: Epigenetic mechanisms?

Organism development is controlled by both genetic programs and the environment to insure a reproductive success as adults. Linear growth is an important part of the development and is mostly controlled by genetic factors. However, the variability of height in a given species does not seem to be specifically associated with SNP. This suggests that environment may play a crucial role. In agreement, an important part of height-related genes present CpG island in their proximal promoter, indicating potential involvement of epigenetic mechanisms. In mammals, the linear growth is regulated by the IGF system, with IGF-I and IGF-II during the fetal period, and IGF-I being included within the somatotropic axis during the postnatal period. Nutrition during the lactating period programs linear growth and adult size through a modulation of the somatotropic axis development and of the setting of its activity later on. The study of underlying mechanisms suggest two waves of programming, which involve both structural adaptation during the early postnatal period and permanent functional adaptation in adulthood. The former may involve a direct stimulation of axon growth of GHRH neurons by IGF-I in first weeks of life while the latter could involve permanent epigenetic modifications in adulthood.