Dapagliflozin ameliorates high-fat diet-induced, megalin-mediated autolysosomal dysfunction in proximal tubules via suppression of megalin-dependent endocytosis

Megalin, a multiligand endocytic receptor in proximal tubules (PTs), mediates the uptake of glomerular-filtered lipotoxic proteins, contributing to tubuloglomerular injury in high-fat diet (HFD)-fed mice. This process is characterized by pathologic vacuolation in PTs, which arises due to megalin-dependent autolysosomal dysfunction. Vacuolation is observed exclusively in segment 2 of PTs, which is vulnerable to metabolic stress because of its less robust endolysosomal system. Although receptor-mediated endocytosis (RME) predominates in segment 1, fluid-phase endocytosis (FPE) is more active in segment 2. This study investigates the effects of dapagliflozin, a sodium-glucose cotransporter 2 inhibitor, on HFD-induced autolysosomal dysfunction in PTs. In male kidney-specific conditional megalin-knockout mice, both RME and FPE in PTs were diminished compared with controls, as demonstrated by reduced uptake of fluorescent lysozyme and dextran, respectively. Similarly, in male C57BL/6J mice, 5-day dapagliflozin treatment suppressed uptake of both tracers in PTs compared with vehicle treatment, without affecting the glomerular filtration rate. Nine-week-old male C57BL/6J mice were fed an HFD and treated with dapagliflozin or vehicle for 28 days. Dapagliflozin significantly reduced cortical tubule vacuolation and urinary C-megalin excretion, another marker of autolysosomal metabolic overload and dysfunction in PTs. Urinary excretion of the megalin ligand α₁-microglobulin increased following dapagliflozin treatment via the suppression of megalin's endocytic function. However, renal megalin expression levels remained unchanged, as confirmed by immunoblotting, quantitative PCR, and immunohistochemistry. In conclusion, dapagliflozin alleviates HFD-induced, megalin-mediated autolysosomal dysfunction-particularly in segment 2 of PTs-likely by suppressing megalin-dependent RME and, more notably, FPE.NEW & NOTEWORTHY Here, megalin was found to mediate both receptor-mediated and fluid-phase endocytosis in vivo. Dapagliflozin ameliorates high-fat diet-induced autolysosomal dysfunction-particularly in segment 2 of proximal tubules-likely by suppressing megalin-dependent endocytosis without altering megalin expression levels. This suppression reduces metabolic overload in proximal tubules, supporting a renoprotective role for dapagliflozin in chronic kidney disease. These findings highlight a novel mechanism by which dapagliflozin might protect against tubular injury in the context of metabolic stress.

autolysosome; endocytosis; megalin; proximal tubule; sodium-glucose cotransporter 2 inhibitor.