Impact of SGLT2i on Cardiac Remodeling and the Soleus Muscle of Infarcted Rats

Abstract

Skeletal muscle changes occur in heart failure (HF). Despite the cardioprotective effects of sodium-glucose co-transporter 2 (SGLT2) inhibitors in HF, their impact on skeletal muscle remains poorly understood. We investigated the effects of the SGLT2 inhibitor empagliflozin (EMPA) on cardiac remodeling and the soleus muscle of rats with myocardial infarction (MI)-induced HF.

Methods: One week after MI induction, rats were assigned to Sham, Sham + EMPA, MI, and MI + EMPA groups. EMPA was administered (5 mg/kg/day) for 12 weeks.

Results: MI + EMPA and MI had dilated left cardiac chambers; the left atrium diameter and left ventricle end-diastolic area were smaller in MI + EMPA than MI. The ejection fraction did not differ between infarcted groups. MI + EMPA had a larger soleus cross-sectional area and higher Type II myosin heavy chain expression than MI. Carbonylated protein and malondialdehyde levels were lower and superoxide dismutase activity higher in MI + EMPA than MI. Respiratory Complex I expression was higher in MI + EMPA than MI. Metabolic enzyme activities, altered in MI, were normalized in MI + EMPA. EMPA up-regulated anabolic proteins and down-regulated catabolic proteins.

Conclusion: Empagliflozin attenuates infarction-induced cardiac remodeling in rats. In soleus muscle, empagliflozin preserves cell trophism, reduces oxidative stress, normalizes muscle and mitochondrial metabolism, and positively modulates proteins involved in synthesis and degradation-related pathways.

Keywords: IGF-1 pathway; energy metabolism; mitochondrial function; myocardial infarction; oxidative stress; soleus muscle.

Figure 1

Effects of SGLT2 inhibition on the soleus structural parameters. (A) Representative haematoxylin and eosin-stained histological sections. Bar: 50 µm; (B) soleus weight-to-body weight (BW) ratio; (C) cross-sectional area (CSA); (D) Frequency of the fibres according to CSA; (E,F) Type I and II myosin heavy chain (MyHC) isoforms; (G) Western blot representative blots of MyHC isoforms. Sham: control group (n = 5); Sham + EMPA: Sham treated with empagliflozin (EMPA; n = 6); MI: myocardial infarction (n = 7); MI + EMPA: MI treated with EMPA (n = 7). Data are means ± SD and individual values or relative frequency; ANOVA for a 2 × 2 factorial design and Tukey; p < 0.05: * vs. Sham; # vs. Sham + EMPA; ^† vs. MI.

Figure 2

Soleus muscle oxidative stress. (A,B) Concentration of oxidative stress markers malondialdehyde (MDA) and protein carbonylation; (C,D) maximum activity of antioxidant superoxide dismutase and catalase; (E,F) expression of nuclear factor erythroid 2-related factor 2 (Nrf-2) and Kelch-like ECH-associated protein 1 (Keap-1) evaluated by Western blot; (G) representative Western blots of Keap-1, Nrf-2, and GAPDH. Sham: control group (n = 5); Sham + EMPA: Sham treated with empagliflozin (EMPA; n = 6); MI: myocardial infarction (n = 7); MI + EMPA: MI treated with EMPA (n = 7). Data are the means ± SD and individual values; ANOVA for a 2 × 2 factorial design and Tukey; p < 0.05: * vs. Sham; ^† vs. MI.

Figure 3

Muscle energy metabolism. (A–C) Maximum activity of glycolysis pathway enzymes; (D) maximum activity of the citric acid cycle enzyme, citrate synthase; (E) maximum activity of beta-oxidation pathway enzyme, beta-hydroxyacyl dehydrogenase (BHADH). Sham: control group (n = 5); Sham + EMPA: Sham treated with empagliflozin (EMPA; n = 6); MI: myocardial infarction (n = 7); MI + EMPA: MI treated with EMPA (n = 7). Data are the means ± SD and individual values; ANOVA for a 2 × 2 factorial design and Tukey; p < 0.05: * vs. Sham; ^† vs. MI.

Figure 4

Mitochondrial respiratory complex expressions evaluated by Western blot. (A–E) Protein expression of oxidative phosphorylation complexes; (F) protein expression of peroxisomal proliferators-activated receptor γ-coactivator-1α (PGC-1α); (G) representative gels. Sham: control group (n = 5); Sham + EMPA: Sham treated with empagliflozin (EMPA; n = 6); MI: myocardial infarction (n = 7); MI + EMPA: MI treated with EMPA (n = 7). Data are the means ± SD and individual values; ANOVA for a 2 × 2 factorial design and Tukey; p < 0.05: * vs. Sham; # vs. Sham + EMPA; ^† vs. MI.

Figure 5

Protein expression evaluated by Western blot. (A–H) Protein expression of the anabolic IGF-1 pathway; (I–L) protein expression of the catabolic IGF-1 pathway; (M) representative blots. IGF-1: insulin-like growth factor Type 1; IGF-1R: IGF-1 receptor; Akt: protein kinase B; mTOR: mammalian target of rapamycin; p70S6K: ribosomal protein S6 kinase beta-1; FoxO3: forkhead box O3; MuRF-1: muscle RING-finger protein-1; MAFbx: muscle atrophy F-box. Sham: control group (n = 5); Sham + EMPA: Sham treated with empagliflozin (EMPA; n = 6); MI: myocardial infarction (n = 7); MI + EMPA: MI treated with EMPA (n = 7). Data are the means ± SD and individual values; ANOVA for a 2 × 2 factorial design and Tukey; p < 0.05: * vs. Sham; # vs. Sham + EMPA; ^† vs. MI.