SUMMARY Transcriptional regulation of circadian rhythms is essential for lipid metabolic homeostasis, disruptions of which can lead to metabolic diseases. Whether N6-methyladenosine (m6A) mRNA methylation impacts circadian regulation of lipid metabolism is unclear. Here, we show m6A mRNA methylation oscillations in murine liver depend upon a functional circadian clock. Hepatic deletion of Bmal1 increases m6A mRNA methylation, particularly of PPaRα. Inhibition of m6A methylation via knockdown of m6A methyltransferase METTL3 decreases PPaRα m6A abundance and increases PPaRα mRNA lifetime and expression, reducing lipid accumulation in cells in vitro. Mechanistically, YTHDF2 binds to PPaRα to mediate its mRNA stability to regulate lipid metabolism. Induction of reactive oxygen species both in vitro and in vivo increases PPaRα transcript m6A levels, revealing a possible mechanism for circadian disruption on m6A mRNA methylation. These data show that m6A RNA methylation is important for circadian regulation of downstream genes and lipid metabolism, impacting metabolic outcomes.

Background: Intrauterine growth retardation (IUGR) is a common problem in human and other species and increases the risk of death of the fetus and newborn during the perinatal period. Objectives: This study was conducted to examine the influences of intrauterine growth retardation (IUGR) on development of the gastrointestinal tract in newborn pigs. Methods: Ten animals from five litters were divided into five piglets with IUGR and five with normal birth-weight (NW). The IUGR category comprised animals with a birth weight 2 SD below the mean birth weight of the total population, while the NW category included animals with a birth weight within one SD of the mean birth weight in the total population. Animals were anesthetized and sampled within 2–4 h after birth and without suckling. The morphological changes of intestine and stomach of IUGR piglets were compared with NW ones. The expressions of IGF-I and receptors for growth hormone and insulin in intestinal mucosa were semiquantified using reverse transcription PCR. Results: The results of our study indicated that the weights of the stomach, small intestine and small intestinal mucosa were significantly lower in IUGR compared with NW piglets (p < 0.01). In addition, the lengths of the small intestine and colon in IUGR pigs were also significantly less than those of NW (p < 0.05). Furthermore, insulin-like growth factor-I (IGF-I) mRNA level in intestinal mucosa of IUGR piglets was increased significantly (p < 0.05), and the expression mRNA levels of insulin receptor and growth hormone (GH) receptor in the mucosa in IUGR piglets showed a tendency to be lower (p = 0.17 and p = 0.11, respectively) than those of the NW animals. Conclusion: We conclude from the data that IUGR affects intestinal growth and morphology and is in associated with altered gene expression of growth-related proteins. We speculate that the morphological change and associated altered endocrine homeostasis contribute to lower growth rates of pigs affected by IUGR.

N -methyladenosine (m A) regulates gene expression and affects cellular metabolism. In this study, we checked whether the regulation of lipid metabolism by curcumin is associated with m A RNA methylation. We investigated the effects of dietary curcumin supplementation on lipopolysaccharide (LPS)-induced liver injury and lipid metabolism disorder, and on m A RNA methylation in weaned piglets. A total of 24 Duroc × Large White × Landrace piglets were randomly assigned to control, LPS, and CurL (LPS challenge and 200 mg/kg dietary curcumin) groups (n = 8/group). The results showed that curcumin reduced the increase in relative liver weight as well as the concentrations of aspartate aminotransferase and lactate dehydrogenase induced by LPS injection in the plasma and liver of weaning piglets (p < 0.05). The amounts of total cholesterol and triacylglycerols were decreased by curcumin compared to that by the LPS injection (p < 0.05). Additionally, curcumin reduced the expression of Bcl-2 and Bax mRNA, whereas it increased the p53 mRNA level in the liver (p < 0.05). Curcumin inhibited the enhancement of SREBP-1c and SCD-1 mRNA levels induced by LPS in the liver. Notably, dietary curcumin affected the expression of METTL3, METTL14, ALKBH5, FTO, and YTHDF2 mRNA, and increased the abundance of m A in the liver of piglets. In conclusion, the protective effect of curcumin in LPS-induced liver injury and hepatic lipid metabolism disruption might be due to the increase in m A RNA methylation. Our study provides mechanistic insights into the effect of curcumin in protecting against hepatic injury during inflammation and metabolic diseases.

N 6 -methyladenine (m 6 A) is the most prevalent type of internal RNA methylation in eukaryotic mRNA and plays critical roles in regulating gene expression for fundamental cellular processes and diverse physiological functions. Recent evidence indicates that m 6 A methylation regulates physiology and metabolism, and m 6 A has been increasingly implicated in a variety of human diseases, including obesity, diabetes, metabolic syndrome and cancer. Conversely, nutrition and diet can modulate or reverse m 6 A methylation patterns on gene expression. In this review, we summarize the recent progress in the study of the m 6 A methylation mechanisms and highlight the crosstalk between m 6 A modification, nutritional physiology and metabolism. KEYWORDS epitranscriptomic, M 6 A RNA methylation, metabolism, nutrition 1 | INTRODUCTION More than 100 types of chemical modifications have been discovered in cellular RNAs. 1 Reversible RNA modifications are an emerging layer of posttranscriptional gene regulation, 2,3 which exerts a large number of physiological processes and biological functions. 4,5 As a novel epitranscriptomic marker, the dynamic and reversible chemical N 6methyladenine (m 6 A) modification is the most abundant internal modification in mRNA. In mammals, plants and some prokaryotes, m 6 A is widely involved in mRNA metabolism, including mRNA stability, 6 mRNA splicing, 7,8 RNA nucleation, 9 RNA-protein interactions 10 and mRNA translation. 11The m 6 A modification plays an important role in nutritional physiology and metabolism, such as controlling circadian rhythms, 12,13 lipid accumulation 14 and adipogenesis. 15,16 The dysregulation of m 6 A patterns causes abnormal gene expression and functions, aberrant cell differentiation and cellular homeostasis imbalance, leading to the occurrence of certain inflammatory states, metabolic diseases and cancer. 9,17,18 Therefore, the effects of m 6 A RNA methylation on physiology and metabolism have become a research hotspot in the RNA Abbreviations: m 6 A, N 6 -methyladenine; 3'-UTRs, 3'untranslated regions; CDS, coding sequence; MTC, methyltransferase cpmplex; METTL3, methyltransferase-like 3; METTL14, methyltransferase-like 14; WTAP, Wilms' tumour 1-associating protein; ZC3H13, zinc finger CCCH-type containing 13; RBM15/15B, RNA binding motif protein 15/15B; FTO, fat mass and obesity-associated protein; ALKBH5, AlkB homolog 5; YTHDF1/2/3, YTH domain family 1/2/3; YTHDC1/2, YTH domain containing 1/2; SAM, S-adenosylmethionine; hm 6 A, N 6hydroxymethyladenosine; f 6 A, N 6 -formyladenosine; A, adenosine; m 6 A m , N 6 ,2'-O-dimethyladenosine; DCP2, decapping mRNA 2; snRNA, small nuclear RNA; eIF3, eukaryotic initiation factor 3; SRSF3, serine/arginine-rich splicing factor 3; SRSF10, serine/arginine-rich splicing factor 10; HNRNPA2B1, heterogenous nuclear ribonucleoprotein A2B1; HNRNPC, heterogenous nuclear ribonucleoprotein C; DGCR8, DiGeorge syndrome critical region gene 8; IGF2BP1/2/3, insulin-like growth factor 2 mRNA-binding protein 1/2/3; T2DM, type 2 diabetes melli...

Human infants or piglets are vulnerable to intestinal microbe-caused disorders and inflammation due to their rapidly changing gut microbiota and immaturity of their immune systems at weaning. Resveratrol and curcumin have significant anti-inflammatory, bacteria-regulating and immune-promoting effects. The purpose of this study was to investigate whether dietary supplementation with resveratrol and curcumin can change the intestinal microbiota and alleviate intestinal inflammation induced by weaning in piglets. One hundred eighty piglets weaned at 21 ± 2 d were fed a control diet (CON group) or supplemented diet (300 mg/kg of antibiotics, ANT group; 300 mg/kg of resveratrol and curcumin, respectively, HRC group; 100 mg/kg of resveratrol and curcumin, respectively, LRC group; 300 mg/kg of resveratrol, RES group; 300 mg/kg of curcumin, CUR group) for 28 days. The results showed that compared with the CON group, curcumin alone and antibiotics decreased the copy numbers of Escherichia coli. Both curcumin and resveratrol down-regulated the level of Toll-like-receptor 4 mRNA and protein expression in the intestine to inhibit the release of critical inflammation molecules (interleukin-1β, tumor necrosis factor-α), and increase the secretion of immunoglobulin. Our results suggested that curcumin and resveratrol can regulate weaned piglet gut microbiota, down-regulate the TLR4 signaling pathway, alleviate intestinal inflammation, and ultimately increase intestinal immune function.