Disease-driven loss of inactive HSD17B13 isoforms enhances enzymatic output in MASH and counters protective...

We investigated whether liver disease alters HSD17B13 isoform expression, identifying selective loss of exon 2-skipped variants and uncovering variant B as a structured, noncoding RNA with silencing potential.

Human liver samples from lean control (n = 6), metabolic dysfunction-associated steatotic liver (MASL, n = 8), and metabolic dysfunction-associated steatohepatitis (MASH, n = 8) participants were analyzed by isoform-specific reverse-transcription PCR and quantitative PCR. HepG2 cells were transfected with HSD17B13 variant A or B constructs. RNA expression, protein production, RNase sensitivity, and RNA structural conformations (RNAfold) were evaluated. Functional effects were tested under oleic acid-induced lipotoxic stress.

We observed a selective reduction in exon 2-skipped HSD17B13 isoforms (variants B and G) in both human MASL (∼63% vs. lean control; p <0.01) and MASH (∼93% vs. lean control; p <0.001), independent of rs72613567:TA genotype. Notably, variant B nearly abolished endogenous HSD17B13 expression in HepG2 cells (∼99% reduction; p <0.001) without generating detectable protein. RNase III sensitivity assays and RNAfold modeling revealed stable, duplex-rich RNA structures, supporting a noncoding regulatory role for these isoforms under oleic acid-induced lipotoxic stress.

Restoration of exon 2-skipped HSD17B13 isoforms, particularly variant B, may offer a genotype-independent therapeutic strategy for MASH by mimicking protective effects through structured RNA-mediated suppression of enzymatic HSD17B13 activity.

These findings support a dual mechanism of HSD17B13 regulation in liver disease through genotype-mediated transcript suppression and disease-driven isoform imbalance. Therapeutic re-expression of exon 2-skipped isoforms, particularly variant B, may offer a novel strategy to replicate the protective effect of the TA allele without enzymatic inhibition.