SMPD2 and atrial fibrillation: Sphingolipid metabolism-related DEGs were significantly higher in AF groups, including neuraminidase 3 (NEU3), arylsulfatase A (ARSA), sphingosine phosphate lyase 1 (SGPL1), sphingomyelin phosphodiesterase 2 (SMPD2), ceramide synthase 4 (CERS4), and N-acylsphingosine amidohydrolase 1 (ASAH1).