Decreased myocardial glucose uptake precedes cardiac dysfunction in hindlimb unloading mice revealed by dynamic 18F-FDG PET imaging

This study aimed to quantify the changes in myocardial glucose uptake in simulated microgravity hindlimb unloading (HU) mice via dynamic ¹⁸F-FDG PET/CT imaging and explore whether Shenqi Fuzheng injection (SFI) could improve myocardial abnormalities. FDG PET quantification suggested that the LV myocardial glucose uptake of HU mice decreased rapidly during the first week of HU, which rebounded temporarily in the second week but declined again during the third and fourth weeks. LV structure (LVAWd, LVAWs, LVPWd, and LV mass) and function (CO, FS and EF) decreased at the fourth week but not at the first week. The SFI improved myocardial glucose uptake during the first week of HU. A positive correlation between global_Ki and LV EF was found. The serum TG and NEFA levels of HU mice were reduced, whereas glucose, insulin and H&E staining revealed no obvious changes. SFI partially ameliorated glycogen accumulation and myocardial fibrosis. RNA sequencing suggested that the SFI might partially improve cardiac function through the TGF-β and apelin signaling pathways. Our results indicated that decreased myocardial glucose uptake might precede and trigger the onset of heart dysfunction induced by HU and that the SFI ameliorated myocardial glucose uptake at the early stage of HU.