Assessment of insulin resistance in the skeletal muscle of mice using positron emission tomography/computed tomography imaging.

Measuring glucose uptake in the skeletal muscle in vivo is an effective method to determine glucose metabolism abnormalities as the skeletal muscle is the principal tissue responsible for glucose disposal and is a major site of peripheral insulin resistance. In this study, we investigated the pathological glucose metabolism dynamics of the skeletal muscle of C57BL/6J mice in a noninvasive and time-sequential manner using positron emission tomography/computed tomography (PET/CT), an imaging technique that uses radioactive substances to visualize and measure metabolic processes in the body, with [18F]-fluoro-2-deoxy-D-glucose (FDG). FDG-PET/CT imaging revealed that insulin administration and exercise load significantly increased FDG accumulation in the skeletal muscle of C57BL/6J mice. FDG accumulation was lower in the skeletal muscle of 14-week-old db/db diabetic model mice exhibiting remarkable insulin resistance compared to that of 7-week-old db/db mice. Based on the continuous observation of FDG accumulation over time in diet-induced obese (DIO) mice, FDG accumulation significantly decreased in 17-week-old mice after the acquisition of insulin resistance. Although insulin-induced glucose uptake in the skeletal muscle was markedly attenuated in 20-week-old DIO mice that had already developed insulin resistance, exercise load effectively increased FDG uptake in the skeletal muscle. Thus, we successfully confirmed that glucose uptake accompanied by insulin administration and exercise load increased in the skeletal muscle using PET-CT. FDG-PET/CT might be an effective tool that could noninvasively capture the chronological changes of metabolic abnormalities in the skeletal muscle of mice.

Assessment of postoperative nutritional status and physical function between open surgical aortic valve replacement and transcatheter aortic valve implantation in elderly patients.

Background and aims : Severe aortic stenosis (AS) has been normally treated with surgical aortic valve replacement (AVR) whereas recently, transcatheter aortic valve implantation (TAVI) has been introduced as a minimally invasive operation for patients with high surgical risk and frailty. In this study, we have evaluated postoperative physical function and nutrition intake in the patients following AVR and TAVI. Methods : This prospective observational study involved 9 patients with surgical aortic valve replacement (AVR) and 7 patients with transcatheter aortic valve implantation (TAVI). Body composition was measured one day prior surgery, postoperative day (POD) 1, POD 3, POD 5 and POD 7. Hand grip strength, calf circumference and gait speed were measured one day before surgery and on the day of discharge. Results : Skeletal muscle was significantly decreased in AVR patients at postoperative day 3 and 7, while there was no change in TAVI patients. Patients with TAVI showed higher dietary intake after surgery compared to patients with AVR, and they maintained hand grip strength and calf circumference at discharge. Conclusions : In elderly patients with AS, TAVI can improve post-operative recovery maintaining nutritional status and physical function even. J. Med. Invest. 67 : 139-144, February, 2020.