ALKBH5-Dependent m 6 A Demethylation Promotes Cardiac Aging Through SLC38A3 Reduction and Glutamine Metabolic Alteration

BACKGROUND: N 6 -methyladenosine (m 6 A) modification has been linked to various types of physiological and pathological bioprocesses. However, the exact role of m 6 A mRNA methylation in cardiac aging is largely unknown. Here, we show that ALKBH5 (alpha-ketoglutarate-dependent dioxygenase AlkB homolog 5), an m 6 A demethylase, plays a critical role in regulating cardiac aging. METHODS: Physiologically aged and paraquat-induced mouse models of cardiac aging as well as senescent cardiomyocyte cell cultures were used to evaluate the expression and function of ALKBH5 in cardiac aging. The adeno-associated virus serotype 9 and small interfering RNAs were used to modulate ALKBH5 expression in vivo and in vitro, respectively. Cardiac aging and function were evaluated by histological analysis, immunostaining, and echocardiography. Methylated RNA immunoprecipitation sequencing and functional screening were performed to identify potential targets of ALKBH5 in regulating cardiac aging. RESULTS: ALKBH5 expression was increased in aged hearts and in senescent-like cardiomyocyte models, accompanied by reduced m 6 A levels. ALKBH5 knockdown attenuated senescence-associated phenotypes in cardiomyocytes and reduced aging-associated cardiac remodeling and dysfunction in physiological aging and paraquat-challenged mouse models when adeno-associated virus serotype 9–short hairpin RNA targeting ALKBH5 gene was delivered beginning in young adulthood, whereas ALKBH5 knockdown initiated in already aged hearts did not reverse established phenotypes. Mechanistically, ALKBH5-dependent m 6 A demethylation reduced the expression of SLC38A3 (solute carrier family 38-member 3), which suggested a YTHDC2 (YTH domain-containing protein 2)-dependent mechanism, thereby contributing to reduced glutamine accumulation, impaired mitochondrial homeostasis, and increased oxidative stress. SLC38A3 overexpression attenuated aging-associated cardiac phenotypes in vivo. In addition, glutamine supplementation reduced senescence-associated and cardiac aging–related phenotypes. CONCLUSIONS: Our study demonstrates that ALKBH5-SLC38A3 axis is an important regulator of m 6 A-linked, glutamine-associated pathways in aging-related cardiac phenotypes. These findings support a role for ALKBH5 as a contributor to cardiac aging-associated remodeling and dysfunction and suggest this pathway as a candidate target for further mechanistic and translational investigation.