High Concentrations of Nucleotides Prevent Capillary Regression during Hindlimb Unloading by Inhibiting Oxidative Stress and Enhancing Mitochondrial Metabolism of Soleus Muscles in Rats.

Prolonged inactivity in skeletal muscles decreases muscle capillary development because of an imbalance between pro- and antiangiogenic signals, mitochondrial metabolism disorders, and increased oxidative stress. Nucleotides have been shown to exert a dose-dependent effect on disuse-induced muscle atrophy. However, the dose-dependent effect on capillary regression in disused muscles remains unclear. Therefore, this study investigated the dose-dependent effect of nucleotides on capillary regression due to disuse. For this purpose, Wistar rats were divided into five groups as follows: control rats fed nucleotide-free diets (CON), hindlimb-unloaded rats fed nucleotide-free diets (HU), and hindlimb-unloaded rats fed 1.0%, 2.5%, and 5.0% nucleotide diets, (HU + 1.0% NT), (HU + 2.5% NT), and (HU + 5.0% NT), respectively. Unloading increased reactive oxygen species (ROS) production and decreased mitochondrial enzyme activity, thereby decreasing the number of muscle capillaries. In contrast, 5.0% nucleotide-containing diet prevented increases in ROS production and reductions in the expression levels of NAMPT, PGC-1α, and CPT-1b proteins. Moreover, 5.0% nucleotide-containing diet prevented mitochondrial enzyme activity (such as citrate synthase and beta-hydroxy acyl-CoA dehydrogenase activity) via NAMPT or following PGC-1α upregulation, thereby preventing capillary regression. Therefore, 5.0% nucleotide-containing diet is likely to prevent capillary regression by decreasing oxidative stress and increasing mitochondrial metabolism.

Protective Effects of Astaxanthin Supplementation against Ultraviolet-Induced Photoaging in Hairless Mice.

Ultraviolet (UV) light induces skin photoaging, which is characterized by thickening, wrinkling, pigmentation, and dryness. Astaxanthin (AST), a ketocarotenoid isolated from Haematococcus pluvialis, has been extensively studied owing to its possible effects on skin health as well as UV protection. In addition, AST attenuates the increased generation of reactive oxygen species (ROS) and capillary regression of the skeletal muscle. In this study, we investigated whether AST could protect against UV-induced photoaging and reduce capillary regression in the skin of HR-1 hairless mice. UV light induces wrinkle formation, epidermal thickening, and capillary regression in the dermis of HR-1 hairless mice. The administration of AST reduced the UV-induced wrinkle formation and skin thickening, and increased collagen fibers in the skin. AST supplementation also inhibited the generation of ROS, decreased wrinkle formation, reduced epidermal thickening, and increased the density of capillaries in the skin. We also found an inverse correlation between wrinkle formation and the density of capillaries. An association between photoaging and capillary regression in the skin was also observed. These results suggest that AST can protect against photoaging caused by UV irradiation and the inhibitory effects of AST on photoaging may be associated with the reduction of capillary regression in the skin.