AimWe examined the changes in oxidative stress, mitochondrial function and muscle atrophy during aging in mice.MethodsWe used 6‐, 12‐ and 24‐month (6 M, 12 M and 24 M)‐old C57BL/6J mice. Skeletal muscles were removed from the lower limb and used for quantitative real‐time polymerase chain reaction, immunoblotting and histological analyses.ResultsThe muscle weight and myocyte cross‐sectional area were significantly decreased in the 12 M and 24 M mice compared with those of the 6 M mice. The levels of the oxidative stress markers, nicotinamide adenine dinucleotide phosphate oxidase 2, nicotinamide adenine dinucleotide phosphate oxidase 4, mitochondrial 4‐hydroxy‐2‐nonenal and 3‐nitrotyrosine, were significantly higher in the 24 M mice compared with those of the 6 M mice. Furthermore, the 24 M mice had lower levels of mitochondrial markers, peroxisome proliferator‐activated receptor gamma coactivator 1 (PGC)‐α, peroxisome proliferator‐activated receptor gamma coactivator‐1β, sirtuin‐1, adenosine triphosphate synthase mitochondria F1 complex α subunit 1 and mitochondrial cytochrome c oxidase 1. The ubiquitin–proteasome pathway genes muscle ring finger‐1 and atrogin‐1 were significantly upregulated in the 12 M and 24 M mice, and protein synthesis markers (phosphorylated‐Akt and ‐p70 ribosomal S6 kinase) were significantly lower in the 24 M mice compared with the 6 M mice (all P < 0.05).ConclusionsThese findings have important implications for the mechanisms that underlie sarcopenia and frailty processes. Geriatr Gerontol Int 2020; 20: 78–84.

Despite significant reduction of cardiovascular events by statin treatment, substantial residual risk persists, driving emerging needs for the development of new therapies. We identified a novel cholesteryl ester transfer protein (CETP) inhibitor, K-312, that raises HDL and lowers LDL cholesterol levels in animals. K-312 also suppresses hepatocyte expression of proprotein convertase subtilisin/kexin 9 (PCSK9), a molecule that increases LDL cholesterol. We explored the underlying mechanism for the reduction of PCSK9 expression by K-312. K-312 inhibited in vitro human plasma CETP activity (IC50; 0.06 M). Administration of K-312 to cholesterol-fed New Zealand White rabbits for 18 wk raised HDL cholesterol, decreased LDL cholesterol, and attenuated aortic atherosclerosis. Our search for additional beneficial characteristics of this compound revealed that K-312 decreases PCSK9 expression in human primary hepatocytes and in the human hepatoma cell line HepG2. siRNA silencing of CETP in HepG2 did not compromise the suppression of PCSK9 by K-312, suggesting a mechanism independent of CETP. In HepG2 cells, K-312 treatment decreased the active forms of sterol regulatory element-binding proteins (SREBP-1 and -2) that regulate promoter activity of PCSK9. Chromatin immunoprecipitation assays demonstrated that K-312 decreased the occupancy of SREBP-1 and SREBP-2 on the sterol regulatory element of the PCSK9 promoter. PCSK9 protein levels decreased by K-312 treatment in the circulating blood of cholesterol-fed rabbits, as determined by two independent mass spectrometry approaches, including the recently developed, highly sensitive parallel reaction monitoring method. New CETP inhibitor K-312 decreases LDL cholesterol and PCSK9 levels, serving as a new therapy for dyslipidemia and cardiovascular disease. cholesteryl ester transfer protein; proprotein convertase subtilisin/ kexin 9; atherosclerosis; sterol regulatory element-binding protein; lipoproteins; mass spectrometry; parallel reaction monitoring