Effects of SGLT2 inhibition with ertugliflozin on myocardial remodeling, energetics and gene expression in the presence and absence of diabetes in mice

Background: Inhibitors of sodium glucose linked transporter 2 (SGLT2i) improve heart failure (HF) outcomes in patients independent of diabetes. While animal studies suggest SGLT2i improve cardiac metabolism, the effect of SGLT2i on mitochondrial function in the heart is not known. Our goal was to assess the effects of SGLT2i on mitochondrial function, high energy phosphates and genes encoding mitochondrial proteins in hearts of mice with and without diet-induced diabetes. Methods & Results: Ertugliflozin (Ertu; formulated to 0.5 mg/g of diet) was given for 4 months to mice fed a high fat, high sucrose (HFHS) diet that causes diabetic cardiomyopathy or control diet (CD). Mitochondrial function was measured in isolated cardiac mitochondria. Myocardial energetics were assessed by NMR spectroscopy simultaneously with systolic function in isolated beating hearts. Myocardial gene expression was assessed by RNA seq using gene set enrichment analysis. HFHS diet caused myocardial hypertrophy and diastolic dysfunction, mitochondrial dysfunction (decreased ATP production, increased reactive oxygen species release) and an impaired energetic response to increased work demand - all of which were prevented by Ertu. Conctractile function, as reflected by the rate x pressure product (RPP), was super-normalized to a value 124% of CD hearts at high work demand. In control mice, Ertu had no effect on isolated mitochondria function or high energy phosphates, but similar to HFHS hearts, caused super-normalization of RPP to 125% of CD hearts. By GSEA the highest scoring gene set for Ertu treatment was oxidative phosphorylation (OXPHOS), which was up-regulated across all groups while controlling for diet with a Normalized Enrichment Score (NES) of +3.71, and was similarly up-regulated in HFHS-fed mice (NES, +3.32) and in CD-fed mice (NES, +3.34). Fatty acid metabolism (FAM) was the second-highest scoring gene set for Ertu, and, like OXPHOS, was up-regulated independent of diet (NES, +2.82). Conclusion: The super-normalization of contractile function and induction of the OXPHOS and FAM gene sets by Ertu are independent of diabetic status. Pro-metabolic remodeling of the myocardium by Ertu may support increased contractile function and contribute to the beneficial actions of Ertu in states such as heart failure that are associated with impaired cardiac mitochondrial function. 4 representative left ventriclar cardiac tissue samples per group (out of 12 total available samples per group in the study) were assessed, for a total of 16 samples in the RNAseq. The reference group is the control diet (CD) group without Ertugliflozin treatment.

【背景】钠-葡萄糖协同转运蛋白2抑制剂（SGLT2i）可在不合并糖尿病的患者中改善心力衰竭（HF）预后。尽管动物研究提示SGLT2i可改善心脏代谢，但目前尚不清楚其对心脏线粒体功能的具体影响。本研究旨在评估SGLT2i对伴或不伴饮食诱导糖尿病的小鼠心脏的线粒体功能、高能磷酸化合物水平以及编码线粒体蛋白的基因表达的影响。
【方法与结果】将依格列净（Ertu；配置为0.5 mg/g饲料浓度）分别给予饲喂高脂高蔗糖（HFHS）饲料（可诱导糖尿病性心肌病）或普通对照饲料（CD）的小鼠，给药周期为4个月。通过分离心脏线粒体检测线粒体功能；在离体搏动心脏中，同步采用核磁共振波谱法评估心肌能量代谢与收缩功能；通过RNA测序（RNA-seq）并结合基因集富集分析（GSEA）评估心肌基因表达情况。
高脂高蔗糖饲料可诱发心肌肥厚、舒张功能障碍、线粒体功能异常（ATP生成减少、活性氧释放增加）以及对工作负荷增加的能量应答受损，上述病理生理改变均可被依格列净阻断。在高工作负荷条件下，以心率-收缩压乘积（RPP）反映的收缩功能可被上调至普通对照饲料组小鼠的124%，达到超正常水平。
在普通饲料喂养的对照组小鼠中，依格列净对离体线粒体功能及高能磷酸化合物水平无显著影响，但与高脂高蔗糖饲料组小鼠类似，可将RPP上调至普通对照饲料组小鼠的125%，实现超正常化。
通过GSEA分析发现，依格列净治疗得分最高的基因集为氧化磷酸化（OXPHOS），在校正饲料因素的所有组别中，该基因集均呈显著上调趋势，标准化富集得分（NES）为+3.71；在高脂高蔗糖饲料喂养小鼠（NES=+3.32）及普通饲料喂养小鼠（NES=+3.34）中，该基因集同样呈现上调。脂肪酸代谢（FAM）为依格列净治疗得分第二高的基因集，与氧化磷酸化类似，其上调不受饲料因素影响（NES=+2.82）。
【结论】依格列净所介导的收缩功能超正常化以及氧化磷酸化与脂肪酸代谢基因集的诱导，均不受糖尿病状态的影响。依格列净对心肌的促代谢重塑，可能有助于增强收缩功能，并为其在心脏线粒体功能受损相关疾病（如心力衰竭）中的获益作用提供机制支撑。
本研究每组共收集12份样本，从中选取4份代表性左心室心肌组织样本进行检测，RNA测序共纳入16份样本。参照组为未接受依格列净治疗的普通对照饲料（CD）组小鼠。