LPL/AQP7/GPD2 promotes glycerol metabolism under hypoxia and prevents cardiac dysfunction during ischemia
Sohta Ishihama, Satoya Yoshida, Tatsuya Yoshida, Yu Mori, Noriyuki Ouchi, Shunsuke Eguchi, Teruhiro Sakaguchi, Takuma Tsuda, Katsuhiro Kato, Yuuki Shimizu, Koji Ohashi, Takahiro Okumura, Yoshiyuki Bando, Hiroaki Yagyu, Nina Wettschureck, Naoto Kubota, Stefan Offermanns, Takashi Kadowaki, Toyoaki Murohara, Mikito Takefuji
Abstract
In the heart, fatty acid is a major energy substrate to fuel contraction under aerobic conditions. Ischemia downregulates fatty acid metabolism to adapt to the limited oxygen supply, making glucose the preferred substrate. However, the mechanism underlying the myocardial metabolic shift during ischemia remains unknown. Here, we show that lipoprotein lipase (LPL) expression in cardiomyocytes, a principal enzyme that converts triglycerides to free fatty acids and glycerol, increases during myocardial infarction (MI). Cardiomyocyte-specific LPL deficiency enhanced cardiac dysfunction and apoptosis following MI. Deficiency of aquaporin 7 (AQP7), a glycerol channel in cardiomyocytes, increased the myocardial infarct size and apoptosis in response to ischemia. Ischemic conditions activated glycerol-3-phosphate dehydrogenase 2 (GPD2), which converts glycerol-3-phosphate into dihydroxyacetone phosphate to facilitate adenosine triphosphate (ATP) synthesis from glycerol. Conversely, GPD2 deficiency exacerbated cardiac dysfunction after acute MI. Moreover, cardiomyocyte-specific LPL deficiency suppressed the effectiveness of peroxisome proliferator-activated receptor alpha (PPARα) agonist treatment for MI-induced cardiac dysfunction. These results suggest that LPL/AQP7/GPD2-mediated glycerol metabolism plays an important role in preventing myocardial ischemia-related damage.