Betaine alleviates nonalcoholic fatty liver disease (NAFLD) via a manner involving BHMT/FTO/m6A/ PGC1α signaling.

Nonalcoholic fatty liver disease (NAFLD) has emerged as a major public health crisis with significant health threats and economic burdens worldwide in the past decades. Betaine, a naturally occurring alkaloid compound present in various dietary sources including spinach and beets, has been shown to ameliorate hepatic lipid metabolism and attenuate (NAFLD), while the underlying mechanism remains elusive. Here, we propose a novel mechanism through which betaine exerts its protective effects against hepatic lipid accumulation and (NAFLD) from an epigenetics perspective. Specifically, we discover that betaine upregulates betaine homocysteine S-methyltransferase (BHMT) expression, leading to increased nicotinamide adenine dinucleotide phosphate (NADPH) production and subsequent upregulation of fat mass and obesity-associated protein (FTO) expression. Increased abundance of FTO targets peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC1α) mRNA and reduces the N6-methyladenosine (m6A) level in the CDS of Ppargc1α transcript, which positively regulates PGC1α expression and subsequently inhibits hepatic lipid accumulation. Overall, our works demonstrate that betaine may be a promising therapeutic strategy for treating (NAFLD) and improving liver function through the regulation of (NADPH) and m6A-mediated pathways.

Branched-chain amino acids prevent obesity by inhibiting the cell cycle in an NADPH-FTO-m6A coordinated manner.

Obesity has become a major health crisis in the past decades. Branched-chain amino acids (BCAA), a class of essential amino acids, exerted beneficial health effects with regard to obesity and its related metabolic dysfunction, although the underlying reason is unknown. Here, we show that BCAA supplementation alleviates high-fat diet (HFD)-induced obesity and insulin resistance in mice and inhibits adipogenesis in 3T3-L1 cells. Further, we find that BCAA prevent the mitotic clonal expansion (MCE) of preadipocytes by reducing cyclin A2 (CCNA2) and cyclin-dependent kinase 2 (CDK2) expression. Mechanistically, BCAA decrease the concentration of nicotinamide adenine dinucleotide phosphate (NADPH) in adipose tissue and 3T3-L1 cells by reducing glucose-6-phosphate dehydrogenase (G6PD) expression. The reduced NADPH attenuates the expression of fat mass and obesity-associated (FTO) protein, a well-known m6A demethylase, to increase the N6-methyladenosine (m6A) levels of Ccna2 and Cdk2 mRNA. Meanwhile, the high m6A levels of Ccna2 and Cdk2 mRNA are recognized by YTH N6-methyladenosine RNA binding protein 2 (YTHDF2), which results in mRNA decay and reduction of their protein expressions. Overall, our data demonstrate that BCAA inhibit obesity and adipogenesis by reducing CDK2 and CCNA2 expression via an NADPH-FTO-m6A coordinated manner in vivo and in vitro, which raises a new perspective on the role of m6A in the BCAA regulation of obesity and adipogenesis.

mRNA m5C inhibits adipogenesis and promotes myogenesis by respectively facilitating YBX2 and SMO mRNA export in ALYREF-m5C manner.

Although 5-methylcytosine (m5C) has been identified as a novel and abundant mRNA modification and associated with energy metabolism, its regulation function in adipose tissue and skeletal muscle is still limited. This study aimed at investigating the effect of mRNA m5C on adipogenesis and myogenesis using Jinhua pigs (J), Yorkshire pigs (Y) and their hybrids Yorkshire-Jinhua pigs (YJ). We found that Y grow faster than J and YJ, while fatness-related characteristics observed in Y were lower than those of J and YJ. Besides, total mRNA m5C levels and expression rates of NSUN2 were higher both in backfat layer (BL) and longissimus dorsi muscle (LDM) of Y compared to J and YJ, suggesting that higher mRNA m5C levels positively correlate with lower fat and higher muscle mass. RNA bisulfite sequencing profiling of m5C revealed tissue-specific and dynamic features in pigs. Functionally, hyper-methylated m5C-containing genes were enriched in pathways linked to impaired adipogenesis and enhanced myogenesis. In in vitro, m5C inhibited lipid accumulation and promoted myogenic differentiation. Furthermore, YBX2 and SMO were identified as m5C targets. Mechanistically, YBX2 and SMO mRNAs with m5C modification were recognized and exported into the cytoplasm from the nucleus by ALYREF, thus leading to increased YBX2 and SMO protein expression and thereby inhibiting adipogenesis and promoting myogenesis, respectively. Our work uncovered the critical role of mRNA m5C in regulating adipogenesis and myogenesis via ALYREF-m5C-YBX2 and ALYREF-m5C-SMO manners, providing a potential therapeutic target in the prevention and treatment of obesity, skeletal muscle dysfunction and metabolic disorder diseases.

Metformin combats obesity by targeting FTO in an m6A-YTHDF2-dependent manner.

Obesity has become a health threat and hard enough to deal with. Evidences show that metformin could inhibit adipogenesis and combat obesity, while its mechanisms remain to be elucidated more comprehensively. In this study, we found that administration of metformin could combat obesity of mice induced by high-fat diet (HFD), indicated by strikingly decreased body weight and weight of inguinal white adipose tissue (iWAT) and epidydimal white adipose tissue (eWAT) compared with the control group. Mechanically, we revealed that metformin could inhibit protein expression of FTO, leading to increased m6A methylation levels of cyclin D1 (Ccnd1) and cyclin dependent kinase 2 (Cdk2), two crucial regulators in cell cycle. Ccnd1 and Cdk2 with increased m6A levels were recognised by YTH m6A RNA binding protein 2 (YTHDF2), causing an YTHDF2-dependent decay and decreased protein expressions. In consequence, mitotic clonal expansion (MCE) process was blocked and adipogenesis was inhibited.

mRNA m5C controls adipogenesis by promoting CDKN1A mRNA export and translation.

5-Methylcytosine (m5C) is a type of RNA modification that exists in tRNAs and rRNAs and was recently found in mRNA. Although mRNA m5C modification has been reported to regulate diverse biological process, its function in adipogenesis remains unknown. Here, we demonstrated that knockdown of NOL1/NOP2/Sun domain family member 2 (NSUN2), a m5C methyltransferase, increased lipid accumulation of 3T3-L1 preadipocytes through accelerating cell cycle progression during mitotic clonal expansion (MCE) at the early stage of adipogenesis. Mechanistically, we proved that NSUN2 directly targeted cyclin-dependent kinase inhibitor 1A (CDKN1A) mRNA, a key inhibitory regulator of cell cycle progression, and upregulated its protein expression in an m5C-dependent manner. Further study identified that CDKN1A was the target of Aly/REF export factor (ALYREF), a reader of m5C modified mRNA. Upon NSUN2 deficiency, the recognition of CDKN1A mRNA by ALYREF was suppressed, resulting in the decrease of CDKN1A mRNA shuttling from nucleus to cytoplasm. Thereby, the translation of CDKN1A was reduced, leading to the acceleration of cell cycle and the promotion of adipogenesis. Together, these findings unveiled an important function and mechanism of the m5C modification on adipogenesis by controlling cell cycle progression, providing a potential therapeutic target to prevent obesity.