Betaine increases intramuscular fat deposition by promoting the cell cycle via a manner involving NADPH/FTO/m⁶A signaling

Abstract Intramuscular fat (IMF) content is a critical indicator of meat quality in livestock production and possesses significant medical relevance for human health. Betaine, a naturally occurring alkaloid compound, holds considerable potential as a nutritional approach for regulating intramuscular adipogenesis, while its exact efficacy and underlying mechanisms still remain subjects of ongoing debate and investigation. Here, we clarified the enhancing effect of betaine on IMF deposition using porcine, murine, and cellular models. Mechanistically, betaine supplementation leads to a significant increase in nicotinamide adenine dinucleotide phosphate (NADPH) concentration in the liver, serum, and skeletal muscle. Elevated levels of NADPH upregulate the expression of fat mass and obesity-associated (FTO), a well-established N 6 -methyladenosine (m 6 A) demethylase, to diminish m 6 A modification in skeletal muscle and IMF deposition. This process effectively promotes the mitotic clonal expansion and subsequently intramuscular adipogenesis. In summary, our findings expand current understanding of the regulatory role of betaine in IMF deposition and sheds light on the molecular mechanisms underlying its modulation, which is conducive to producing high-quality and healthful pork.