SREBP1 induction mediates long-term statins therapy related myocardial lipid peroxidation and lipid deposition in TIIDM mice

Statins therapy is efficacious in diminishing the risk of major cardiovascular events in diabetic patients. However, our research has uncovered a correlation between the prolonged administration of statins and an elevated risk of myocardial dysfunction in patients with type II diabetes mellitus (TIIDM). Here, we report the induction of sterol regulatory element-binding protein 1 (SREBP1) activation, associated lipid peroxidation, and the consequent diabetic myocardial dysfunction after statin treatment and explored the underlying mechanisms. In db/db mice, we observed that 40 weeks atorvastatin (5 and 10 mg/kg) and rosuvastatin (20 mg/kg) administration exacerbated diabetic myocardial dysfunction by echocardiography and cardiomyocyte contractility assay, increased myocardial inflammation and fibrosis as shown by CD68, IL-1β, Masson's staining and Collagen1A1 immunohistochemistry (IHC) staining, increased respiratory exchange ratio (RER) by metabolic cage system assessment, exacerbated mitochondrial structural pathological changes by transmission electron microscopy (TEM) examination, increased deposition of lipid and glycogen by TEM, Oil-red and periodic acid-schiff stain (PAS) staining, which were corresponded with augmented levels of myocardial SREBP1 protein and lipid peroxidation marked by 4-hydroxynonenal (4-HNE) staining. Comparable myocardial fibrosis was also observed in KK-ay and low-dose streptozotocin (STZ)-induced TIIDM mice. Elevated SREBP1 levels were observed in the heart tissues from diabetic patients, which was positively correlated with their myocardial dysfunction. To elucidate the role of statin induced SREBP1 in lipid peroxidation and lipid deposition and related mechanism, we cultured neonatal mouse primary cardiomyocytes (NMPCs) and treated them with atorvastatin (10 μM, 24 h), tracing with [U-¹³C]-glucose and evaluating for SREBP1 expression and localization. We found that statin treatment elevated de novo lipogenesis (DNL) and the levels of SREBP1 cleavage-activating protein (SCAP), reduced the interaction of SCAP with insulin-induced gene 1 (Insig1), and enhance SCAP/SREBP1 translocation to the Golgi, which facilitate SREBP1 cleavage leading to its nuclear trans-localization and activation in NMPCs. Ultimately, SREBP1 knockdown or l-carnitine mitigated long-term statins therapy induced lipid peroxidation and myocardial fibrosis in low-dose STZ treated SREBP1^+/- mice and l-carnitine treated db/db mice. In conclusion, we demonstrated that statin therapy may augment DNL by activating SREBP1, resulting in myocardial lipid peroxidation and lipid deposition.