Effects of Vitamin D on Satellite Cells: A Systematic Review of In Vivo Studies.

The non-classical role of vitamin D has been investigated in recent decades. One of which is related to its role in skeletal muscle. Satellite cells are skeletal muscle stem cells that play a pivotal role in skeletal muscle growth and regeneration. This systematic review aims to investigate the effect of vitamin D on satellite cells. A systematic search was performed in Scopus, MEDLINE, and Google Scholar. In vivo studies assessing the effect of vitamin D on satellite cells, published in English in the last ten years were included. Thirteen in vivo studies were analyzed in this review. Vitamin D increases the proliferation of satellite cells in the early life period. In acute muscle injury, vitamin D deficiency reduces satellite cells differentiation. However, administering high doses of vitamin D impairs skeletal muscle regeneration. Vitamin D may maintain satellite cell quiescence and prevent spontaneous differentiation in aging. Supplementation of vitamin D ameliorates decreased satellite cells' function in chronic disease. Overall, evidence suggests that vitamin D affects satellite cells' function in maintaining skeletal muscle homeostasis. Further research is needed to determine the most appropriate dose of vitamin D supplementation in a specific condition for the optimum satellite cells' function.

Calcitriol Inhibits Proliferation and Potentially Induces Apoptosis in B16-F10 Cells.

BACKGROUND Melanoma is one of the most aggressive types of cancer and it has shown a remarkable surge in incidence during the last 50 years. Melanoma has been projected to be continuously rising in the future. Therapy for advanced-type melanoma is still a challenge due to the low response rate and poor 10-year survival. Interestingly, several epidemiological and preclinical studies had reported that vitamin D deficiency was associated with disease progression in several cancer types. In vivo and in vitro studies revealed anti-proliferative, anti-angiogenic, apoptosis, and differentiation induction effects of calcitriol in various cancers. However, information on the effects of calcitriol (1,25(OH)2D3) on melanoma is still limited, and its mechanism remains unclear. MATERIAL AND METHODS In the present study, by utilizing B16-F10 cells, which is a melanoma cell line, we explored the anti-proliferative effect of calcitriol using cell viability assay, near-infrared imaging, expression of apoptosis-related genes using real-time polymerase chain reactions (PCR), and the expression of apoptosis proteins levels using western blot. In addition, we also assessed calcitriol uptake by B16-F10 cells using high-performance liquid chromatography (HPLC). RESULTS We found that calcitriol inhibits melanoma cell proliferation with an IC50 of 93.88 ppm (0.24 µM), as shown by cell viability assay. Additionally, we showed that B16-F10 cells are capable of calcitriol uptake, with a peak uptake time at 60 min after administration. Calcitriol was also able to induce apoptosis-related proteins such as caspase-3, caspase 8, and caspase-9. These effects of calcitriol reflect its potential utility as a potent adjuvant therapy for melanoma. CONCLUSIONS Calcitriol inhibits cell proliferation and induces apoptosis in B16-F10 cells.

Nutmeg Extract Increases Skeletal Muscle Mass in Aging Rats Partly via IGF1-AKT-mTOR Pathway and Inhibition of Autophagy.

The sarcopenic phenotype is characterized by a reduction of muscle mass, a shift in fiber-type distribution, and reduced satellite cell regeneration. Sarcopenia is still a major challenge to healthy aging. Traditional Indonesian societies in Sulawesi island have been using nutmeg for maintaining health condition during aging. Interestingly, nutmeg has been known to stimulate peroxisome proliferator activated receptors γ (PPARγ) which may contribute to myogenesis process in cardiac muscle. There is limited information about the role of nutmeg extract into physiological health benefit during aging especially myogenesis process in skeletal muscle. In the present study, we want to explore the potential effect of nutmeg in preserving skeletal muscle mass of aging rats. Aging rats, 80 weeks old, were divided into two groups (control and nutmeg). Nutmeg extract was administered for 12 weeks by gavaging. After treatment, rats were anaesthesized, then soleus and gastrocnemius muscles were collected, weighted, frozen using liquid nitrogen, and stored at -80°C until use. We observed phenomenon that nutmeg increased a little but significant food consumption on week 12, but significant decrease in body weight on weeks 10 and 12 unexpectedly increased significantly in soleus muscle weight (p<0.05). Nutmeg extract increased significantly gene expression of myogenic differentiation (MyoD), paired box 7 (Pax7), myogenin, myosin heavy chain I (MHC I), and insulin-like growth factor I (p<0.01) in soleus muscle. Furthermore, nutmeg increased serine/threonine kinase (AKT) protein levels and activation of mammalian target of rapamycin (mTOR), inhibited autophagy activity, and stimulated or at least preserved muscle mass during aging. Taken together, nutmeg extract may increase muscle mass or prevent decrease of muscle wasting in soleus muscle by partly stimulating myogenesis, regeneration process, and preserving muscle mass via IGF-AKT-mTOR pathway leading to inhibition of autophagy activity during aging. This finding may reveal the potential nutmeg benefits as alternative supplement for preserving skeletal muscle mass and preventing sarcopenia in elderly.