Leucine imparts cardioprotective effects by enhancing mTOR activity and mitochondrial fusion in a myocardial ischemia/reperfusion injury murine model

Atsushi Morio; Rie Tsutsumi; Shiho Satomi; Takashi Kondo; Hirotsugu Miyoshi; Takahiro Kato; Masashi Kuroda; Tadahiro Kitamura; Kenta Hara; Noboru Saeki; Hiroshi Sakaue; Yasuo M Tsutsumi

doi:10.1186/s13098-021-00755-z

Leucine imparts cardioprotective effects by enhancing mTOR activity and mitochondrial fusion in a myocardial ischemia/reperfusion injury murine model

Diabetol Metab Syndr. 2021 Nov 20;13(1):139. doi: 10.1186/s13098-021-00755-z.

Authors

Affiliations

¹ Department of Anesthesiology and Critical Care, Hiroshima University, 1-2-3 Kasumi, Minami, Hiroshima, 734-8551, Japan.
² Department of Nutrition and Metabolism, Institute of Biomedical Sciences, Tokushima University, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan.
³ Laboratory of Metabolic Signal, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma, 371-8512, Japan.
⁴ Kita Harima Medical Center, 926-250 Ichiba, Ono, Hyogo, 675-1392, Japan.
⁵ Department of Anesthesiology and Critical Care, Hiroshima University, 1-2-3 Kasumi, Minami, Hiroshima, 734-8551, Japan. yasuo223@hiroshima-u.ac.jp.

^# Contributed equally.

Abstract

Background: Coronary artery disease is a leading cause of morbidity and mortality among patients with diabetes. Previously, we demonstrated that branched-chain amino acids (BCAAs) showed cardioprotective effects against cardiac ischemia/reperfusion (I/R) injury. A recent study suggested that leucine (Leu), a BCAA, is a key amino acid involved in mammalian target of rapamycin (mTOR) activity and mitochondrial function. However, whether Leu has cardioprotective effects on diabetic hearts is unclear. In this study, we examined the preconditioning effect of Leu treatment on high-fat diet (HFD)-induced obese mouse which simulate prediabetic heart.

Methods: In vivo mice models of I/R injury were divided into the following groups: control, mTOR^+/-, and high-fat diet (HFD)-induced obese groups. Mice were randomly administered with Leu, the mTOR inhibitor rapamycin (Rap), or Leu with Rap. Isolated rat cardiomyocytes were subjected to simulated I/R injury. Biochemical and mitochondrial functional assays were performed to evaluate the changes in mTOR activity and mitochondrial dynamics caused by Leu treatment.

Results: Leu-treated mice showed a significant reduction in infarct size when compared with the control group (34.8% ± 3.8% vs. 43.1% ± 2.4%, n = 7, p < 0.05), whereas Rap-treated mice did not show the protective effects of Leu. This preconditioning effect of Leu was attenuated in mTOR^+/- mice. Additionally, Leu increased the percentage of fused mitochondria and the mitochondrial volume, and decreased the number of mitochondria per cell in isolated cardiomyocytes. In HFD-induced obese mice, Leu treatment significantly reduced infarct size (41.0% ± 1.1% vs. 51.0% ± 1.4%, n = 7, p < 0.05), which was not induced by ischemic preconditioning, and this effect was inhibited by Rap. Furthermore, we observed enhanced mTOR protein expression and mitochondrial fusion with decreased reactive oxygen species production with Leu treatment in HFD-induced obese mice, but not in mTOR^+/- mice.

Conclusions: Leu treatment improved the damage caused by myocardial I/R injury by promoting mTOR activity and mitochondrial fusion on prediabetic hearts in mice.

Keywords: Cardioprotective; High-fat diet; Leucine; Myocardial ischemia/reperfusion injury.

Grants and funding

19K09353/Japan Society for the Promotion of Science