Fructose downregulates miR-330 to induce renal inflammatory response and insulin signaling impairment: Attenuation by morin

Scope: Fructose induces insulin resistance with kidney inflammation and injury. MicroRNAs are emerged as key regulators of insulin signaling. Morin has insulin-mimetic effect with the improvement of insulin resistance and kidney injury. This study investigated the protective mechanisms of morin against fructose-induced kidney injury, with particular focus onmiR-330 expression change, inflammatory response, and insulin signaling impairment. Methods and results: miR-330, sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P)/S1preceptor (S1PR) 1/3 signaling, nuclear factor-kappa B (NF-kappa B)/NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome, and insulin signaling were detected in kidney cortex of fructose-fed rats and fructose-exposed HK-2 cells, respectively. Whether miR-330 mediated inflammatory response to affect insulin signaling was examined using SphK1 inhibitor, S1PR1/3 short interfering RNA, or miR-330 mimic/inhibitor, respectively. Fructose was found to downregulate miR-330 expression to increase SphK1/S1P/S1PR1/3 signaling, and then activate NF-kappa B/NLRP3 inflammasome to produce IL-1 beta, causing insulin signaling impairment. Moreover, morin upregulated miR-330 and partly attenuated inflammatory response and insulin signaling impairment to alleviate kidney injury. Conclusion: These findings suggest thatmorin protects against fructose-induced kidney insulin signaling impairment by upregulating miR-330 to reduce inflammatory response. Morin may be a potential therapeutic agent for the treatment of kidney injury associated with fructose-induced inflammation and insulin signaling impairment.