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Background: MicroRNAs (miRNAs) are small noncoding RNAs involved in posttranscriptional regulation. miRNAs can be secreted and found in many body fluids, and although they are particularly abundant in breastmilk, their functions remain elusive. Human milk (HM) miRNAs start to raise considerable interest, but a comprehensive understanding of the repertoire and expression profiles along lactation has not been well characterized., Objectives: This study aimed to characterize the longitudinal profile of HM miRNA between the second week and third month postpartum., Methods: We used a new sensitive technology to measure HM miRNAs in a cohort of 44 French mothers [mean ± SD age: 31 ± 3.5; BMI (in kg/m2) 21.8 ± 2.3] who delivered at term and provided HM samples at 3 time points (17 ± 3 d, 60 ± 3 d, and 90 ± 3 d) during follow-up visits., Results: We detected 685 miRNAs, of which 35 showed a high and stable expression along the lactation period analyzed. We also described for the first time a set of 11 miRNAs with a dynamic expression profile. To gain insight into the potential functional relevance of this set of miRNAs, we selected miR-3126 and miR-3184 to treat undifferentiated Caco-2 human intestinal cells and then assessed differentially expressed genes and modulation of related biological pathways., Conclusions: Overall, our study provides new insights into HM miRNA composition and, to our knowledge, the first description of its longitudinal dynamics in mothers who delivered at term. Our in vitro results obtained in undifferentiated Caco-2 human intestinal cells transfected with HM miRNAs also provide further support to the hypothesized mother-to-neonate signaling role of HM miRNAs. This trial was registered at clinicaltrials.gov as NCT01894893., (© The Author(s) 2021. Published by Oxford University Press on behalf of the American Society for Nutrition.)

Background: Constitutional thinness (CT) is a state of low but stable body weight (BMI ≤18 kg/m2). CT subjects have normal-range hormonal profiles and food intake but exhibit resistance to weight gain despite living in the modern world's obesogenic environment., Objective: The goal of this study is to identify molecular mechanisms underlying this protective phenotype against weight gain., Methods: We conducted a clinical overfeeding study on 30 CT subjects and 30 controls (BMI 20-25 kg/m2) matched for age and sex. We performed clinical and integrative molecular and transcriptomic analyses on white adipose and muscle tissues., Results: Our results demonstrate that adipocytes were markedly smaller in CT individuals (mean ± SEM: 2174 ± 142 μm 2) compared with controls (3586 ± 216 μm2) (P < 0.01). The mitochondrial respiratory capacity was higher in CT adipose tissue, particularly at the level of complex II of the electron transport chain (2.2-fold increase; P < 0.01). This higher activity was paralleled by an increase in mitochondrial number (CT compared with control: 784 ± 27 compared with 675 ± 30 mitochondrial DNA molecules per cell; P < 0.05). No evidence for uncoupled respiration or "browning" of the white adipose tissue was found. In accordance with the mitochondrial differences, CT subjects had a distinct adipose transcriptomic profile [62 differentially expressed genes (false discovery rate of 0.1 and log fold change >0.75)], with many differentially expressed genes associating with positive metabolic outcomes. Pathway analyses revealed an increase in fatty acid oxidation ( P = 3 × 10-04) but also triglyceride biosynthesis (P = 3.6 × 10-04). No differential response to the overfeeding was observed in the 2 groups., Conclusions: The distinct molecular signature of the adipose tissue in CT individuals suggests the presence of augm ented futile lipid cycling, rather than mitochondrial uncoupling, as a way to increase energy expenditure in CT individuals. We propose that increased mitochondrial function in adipose tissue is an important mediator in sustaining the low body weight in CT individuals. This knowledge could ultimately allow more targeted approaches for weight management treatment strategies. This trial was registered at clinicaltrials.gov as NCT02004821., (Copyright © American Society for Nutrition 2019.)

Background: Several studies recently reported contradicting results regarding the link between amylase 1 (AMY1) copy numbers (CNs), obesity, and type 2 diabetes., Objective: The aim of this study was to assess the impact of AMY1 CN on anthropometrics and glycemic outcomes in obese individuals following a 2-phase dietary weight loss intervention., Methods: Using the paralog ratio test, AMY1 CNs were accurately measured in 761 obese individuals from the DiOGenes study. Subjects first underwent an 8-wk low-calorie diet (LCD, at 800 kcal/d) and then were randomly assigned to a 6-mo weight maintenance dietary (WMD) intervention with arms having different glycemic loads., Results: At baseline, a modest association between AMY1 CN and BMI (P = 0.04) was observed. AMY1 CN was not associated with baseline glycemic variables. In addition, AMY1 CN was not associated with anthropometric or glycemic outcomes following either LCD or WMD. Interaction analyses between AMY1 CN and nutrient intake did not reveal any significant association with clinical parameters (at baseline and following LCD or WMD) or when testing gene × WMD interactions during the WMD phase., Conclusion: In the absence of association with weight trajectories or glycemic improvements, the AMY1 CN cannot be considered as an important biomarker for response to a clinical weight loss and weight maintenance programs in overweight/obese subjects. This trial was registered at www.clinicaltrials.gov as NCT00390637., (Copyright © American Society for Nutrition 2019.)

Background: A low-calorie diet (LCD) reduces fat mass excess, improves insulin sensitivity, and alters adipose tissue (AT) gene expression, yet the relation with clinical outcomes remains unclear. Objective: We evaluated AT transcriptome alterations during an LCD and the association with weight and glycemic outcomes both at LCD termination and 6 mo after the LCD. Design: Using RNA sequencing (RNAseq), we analyzed transcriptome changes in AT from 191 obese, nondiabetic patients within a multicenter, controlled dietary intervention. Expression changes were associated with outcomes after an 8-wk LCD (800-1000 kcal/d) and 6 mo after the LCD. Results were validated by using quantitative reverse transcriptase-polymerase chain reaction in 350 subjects from the same cohort. Statistical models were constructed to classify weight maintainers or glycemic improvers. Results: With RNAseq analyses, we identified 1173 genes that were differentially expressed after the LCD, of which 350 and 33 were associated with changes in body mass index (BMI; in kg/m 2 ) and Matsuda index values, respectively, whereas 29 genes were associated with both endpoints. Pathway analyses highlighted enrichment in lipid and glucose metabolism. Classification models were constructed to identify weight maintainers. A model based on clinical baseline variables could not achieve any classification (validation AUC: 0.50; 95% CI: 0.36, 0.64). However, clinical changes during the LCD yielded better performance of the model (AUC: 0.73; 95% CI: 0.60, 0.87]). Adding baseline expression to this model improved the performance significantly (AUC: 0.87; 95% CI: 0.77, 0.96; Delong's P = 0.012). Similar analyses were performed to classify subjects with good glycemic improvements. Baseline- and LCD-based clinical models yielded similar performance (best AUC: 0.73; 95% CI: 0.60, 0.86). The addition of expression changes during the LCD improved the performance substantially (AUC: 0.80; 95% CI: 0.69, 0.92; P = 0.058). Conclusions: This study investigated AT transcriptome alterations after an LCD in a large cohort of obese, nondiabetic patients. Gene expression combined with clinical variables enabled us to distinguish weight and glycemic responders from nonresponders. These potential biomarkers may help clinicians understand intersubject variability and better predict the success of dietary interventions. This trial was registered at clinicaltrials.gov as NCT00390637., (© 2017 American Society for Nutrition.)

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate target mRNAs by binding to their 3' untranslated regions. There is growing evidence that microRNA-155 (miR155) modulates gene expression in various cell types of the immune system and is a prominent player in the regulation of innate and adaptive immune responses. To define the role of miR155 in dendritic cells (DCs) we performed a detailed analysis of its expression and function in human and mouse DCs. A strong increase in miR155 expression was found to be a general and evolutionarily conserved feature associated with the activation of DCs by diverse maturation stimuli in all DC subtypes tested. Analysis of miR155-deficient DCs demonstrated that miR155 induction is required for efficient DC maturation and is critical for the ability of DCs to promote antigen-specific T-cell activation. Expression-profiling studies performed with miR155(-/-) DCs and DCs overexpressing miR155, combined with functional assays, revealed that the mRNA encoding the transcription factor c-Fos is a direct target of miR155. Finally, all of the phenotypic and functional defects exhibited by miR155(-/-) DCs could be reproduced by deregulated c-Fos expression. These results indicate that silencing of c-Fos expression by miR155 is a conserved process that is required for DC maturation and function.

Spermatogenesis requires intact, fully competent Sertoli cells. Here, we investigate the functions of Dicer, an RNaseIII endonuclease required for microRNA and small interfering RNA biogenesis, in mouse Sertoli cell function. We show that selective ablation of Dicer in Sertoli cells leads to infertility due to complete absence of spermatozoa and progressive testicular degeneration. The first morphological alterations appear already at postnatal day 5 and correlate with a severe impairment of the prepubertal spermatogenic wave, due to defective Sertoli cell maturation and incapacity to properly support meiosis and spermiogenesis. Importantly, we find several key genes known to be essential for Sertoli cell function to be significantly down-regulated in neonatal testes lacking Dicer in Sertoli cells. Overall, our results reveal novel essential roles played by the Dicer-dependent pathway in mammalian reproductive function, and thus pave the way for new insights into human infertility.

Retinoic acid mediates most of the biological actions of vitamin A. It is oxidized by CYP26A1 to 4-oxoretinoic acid, considered as an inactive catabolite of retinoic acid. However, in the light of studies reporting the presence of 4-oxoretinal or 4-oxoretinol as the predominant retinoids during morphogenesis, we analyzed the retinoid-like biological activity of these oxoretinoids in mouse skin in vivo. Topical 4-oxoretinal and 4-oxoretinol promoted significant epidermal hyperplasia and metaplasia in mouse tail. They induced a moderate response for epidermal inflammation, compared with retinal, whereas neither 4-oxoretinal nor 4-oxoretinol prevented menadione-induced epidermal lipid peroxidation, unlike retinal and retinol. As analyzed by quantitative PCR, 4-oxoretinal and 4-oxoretinol did not reproduce the significant increased expression of genes coding for keratin 4, amphiregulin, heparin-EGF and CYP26A1, that did induce retinal and retinol. However, both retinal and 4-oxoretinal significantly inhibited the lipopolysaccharide-induced maturation of human dendritic cells in vitro. As analyzed in vivo and in vitro, 4-oxoretinal and 4-oxoretinol were not converted into retinoic acid. We conclude that 4-oxoretinal and 4-oxoretinol exert a moderate direct retinoid-like activity in vivo, thus confirming previous in vitro studies in amphibians showing 4-oxometabolites of vitamin A as bioactive agents rather than inactive catabolites.

The primary event in mammalian sexual development is the differentiation of the bipotential gonads into either testes or ovaries. Our understanding of the molecular pathways specifying gonadal differentiation is still incomplete. To identify the initial molecular changes accompanying gonadal differentiation in mice, we have performed a large-scale transcriptional analysis of XX and XY Sf1-positive gonadal cells during sex determination. In both male and female genital ridges, a robust genetic program is initiated pre-dating the first morphological changes of the differentiating gonads. Between E10.5 and E13.5, 2306 genes were expressed in a sex-specific manner in the somatic compartment of the gonads; 1223 were overexpressed in XX embryos and 1083 in XY embryos. Although sexually dimorphic genes were scattered throughout the mouse genome, we identified chromosomal regions hosting clusters of genes displaying similar expression profiles. The cyclin-dependent kinase inhibitors Cdkn1a and Cdkn1c are overexpressed in XX gonads at E11.5 and E12.5, suggesting that the increased proliferation of XY gonads relative to XX gonads may result from the overexpression of cell cycle inhibitors in the developing ovaries. These studies define the major characteristics of testicular and ovarian transcriptional programs and reveal the richness of signaling processes in differentiation of the bipotential gonads into testes and ovaries.