METTL3-mediated m6A modification of FUNDC1/IP3R2 pathway facilitates cardiac hypertrophy in obesity hypertension

FUNDC1-mediated mitochondria-associated endoplasmic reticulum membrane (MAM) Ca²⁺ conduction is crucial in cardiac hypertrophy. N6-methyladenosine (m6A) methylation, a crucial mRNA modification, is implicated in this process. We hypothesise that m6A regulation of FUNDC1-mediated MAM-associated Ca²⁺ overload contributes to obesity hypertension (OBH) cardiac hypertrophy.

We investigated OBH in spontaneously hypertensive rats fed a high-fat diet, with WKY rats as controls. Assessments included blood pressure, cardiac hypertrophy, pyroptosis, protein expression of MAM-related (FUNDC1, IP3R2) and m6A-related gene (METTL3, IGF2BP2). MeRIP assay detected m6A methylation in mRNA. We also examined cardiomyocyte morphology, viability, mitochondrial function (mtROS, SOD, MDA and ATP levels), and expression of pyroptosis-related factors (IL-1β, IL-18, NLRP3, GSDMD-N and Caspase-1/p10) in vitro. Silencing and overexpression of FUNDC1 and METTL3 clarified MAM effects on cardiac hypertrophy. FUNDC1 and IP3R2 interaction was assessed by co-immunoprecipitation.

OBH rats exhibited significantly elevated blood pressure, cardiac hypertrophy, MAM dysfunction, elevated FUNDC1, IP3R2 and METTL3 expression, and pyroptosis. Ang II treatment in vitro upregulated FUNDC1, causing mitochondrial dysfunction, inflammation and pyroptosis in cardiomyocytes. FUNDC1 knockdown improved cardiomyocyte morphology and function, reduced mitochondrial Ca²⁺ concentration, enhanced mitochondrial function and attenuated pyroptosis while increasing IP3R2 ubiquitination. Mito Tempo reversed cardiomyocyte hypertrophy, mitochondrial dysfunction, inflammatory response and pyroptosis induced by FUNDC1 overexpression. Additionally silencing METTL3 and IGF2BP2 reduced m6A methylation of FUNDC1, inhibiting its expression.

METTL3 regulates FUNDC1 m6A methylation modification via IGF2BP2, thereby affecting FUNDC1 expression. FUNDC1 binding to IP3R2 regulates MAM-associated Ca²⁺ overload, inducing mitochondrial dysfunction and pyroptosis, leading to cardiac hypertrophy in OBH.