Our results showed that empagliflozin could mitigate the progression of atherosclerotic plaques in ApoE-/- mice. Body weight and lipid profiles of the empagliflozin-treated group were also lower than those of the untreated group. In addition, we also showed that empagliflozin significantly reduced expressions of norepinephrine (NE) and neuropeptide Y (NPY), as well as renin, angiotensin II, and aldosterone. These results indicate that empagliflozin alleviates the activation of sympathetic activity and RAAS, which contributes to the development of atherosclerosis. However, the anti-inflammatory effects were not significant in our study.
Previous studies have also demonstrated that SGLT2 inhibitors reduce the development of atherosclerotic lesions in diabetic and non-diabetic mice[13–16]. Our results were consistent with these studies. It was reported that SGLT2 inhibitors could inhibit the activation of NLRP3 inflammasome[17], reduce the secretion of vasoconstrictive eicosanoids and pro-inflammatory chemokines in the vasculature[15, 18], playing an anti-inflammation role. A study showed that empagliflozin prevented the development of atherosclerosis and reduced inflammation and fat deposition in non-diabetic ApoE-/- mice[8]. Our study confirmed that inhibition of sympathetic activity and RAAS contributed to the anti-atherogenic effects of empagliflozin.
Excessive lipid deposition promotes the development of atherosclerosis. However, the effect of SGLT2 inhibitors on lipid profiles is not consistent in animal studies. Several previous studies have shown that SGLT2 inhibitors can lower lipid levels[14, 19, 20], while others have not[21–25]. Our results showed that empagliflozin could reduce the levels of triglyceride, total cholesterol and LDL, while there was no significant difference in HDL between the two groups. Given these findings, further studies are warranted to fully elucidate the effects of SGLT2 inhibitors on lipid metabolism. However, the systemic inflammation level of atherosclerosis in the SGLT2 inhibitor group was not significantly different. Two factors can explain this difference: on the one hand, the non-diabetic ApoE-/- mice we used may not have a significant vascular inflammatory response induced by hyperglycemia. Nakatsu et al demonstrated that hyperglycemia rapidly induced vascular inflammatory response, which can be normalized by short-term (7 days) treatment with the SGLT2 inhibitor luseogliflozin[22]. Even though we did not detect the glucose levels in this experiment. However, previous study have confirmed no significant difference in glucose levels between empagliflozin-treated and untreated mice, and empagliflozin did not increase the risk of hypoglycemia in non-diabetic states [26]. On the other hand, systemic inflammation level is likely affected by the duration of treatment with SGLT2 inhibitors. The duration of our experiment was 12 weeks, and the experimental group was treated with SGLT2 inhibitors since the 7th week. Combining previous studies, we found that SGLT2 inhibitors may inhibit inflammatory mediators with a duration of at least 8 weeks[9, 10, 15, 27]. Therefore, we speculated that short-term of empagliflozin treatment was not enough to play an anti-inflammation effect.
In recent years, some mechanisms underlying the beneficial effect of SGLT2 inhibitor on cardiovascular diseases have been proposed. The decreased toxicity of glucose to endothelial cells may be a potential mechanism in preventing diabetic ApoE-/- mice atherosclerosis[27]. And dapagliflozin could improve the differentiation of epicardial adipose tissue and perivascular adipose tissue[28]. In addition, SGLT2 inhibitor could enhance lipoprotein clearance through heparan sulfate proteoglycans (HSPG) and bile acid pathways[14], which could protect from atherosclerosis progression. In our article, we broaden our understanding of beneficial effect of SGLT2 inhibitor empagliflozin on the progression of atherosclerosis.