RESUMO
BACKGROUND: Fatty infiltration (FI) and muscle atrophy (MA) in the rotator cuff muscles following rotator cuff tears (RCT) persist postrepair, increasing the risk of re-tears. Brown adipocyte-like "beige adipocytes" are expected to have a therapeutic effect on intramuscular FI and MA due to their lipolytic activity and the muscle regenerative effects of their secreted factors. However, whether parathyroid hormone (PTH) ameliorates the already advanced FI and MA remains unknown. Therefore, this study aimed to clarify whether PTH promotes the expression of beige adipocytes and ameliorates advanced FI and MA following chronic RCT in rats. METHODS: Supraspinatus muscles were harvested from rats with chronic RCT after 4 or 8 weeks of PTH treatment and compared to those in the control group or to those at the start of treatment. FI was assessed by Oil Red O staining, and the staining area was evaluated as a percentage of the muscle cross-sectional area. MA was evaluated by measuring muscle wet weight and cross-sectional area of muscle fiber. Beige adipocyte expression was evaluated by immunostaining for uncoupling protein 1 (UCP1). Fibro-adipogenic progenitors (FAPs) were separated from muscle-injured mice. We assessed whether PTH could diminish fat droplet accumulation by promoting the differentiation of FAPs into beige adipocytes. RESULTS: After 4 weeks, PTH reduced the area fraction of FI in the rat supraspinatus muscle following chronic RCT compared with that at the beginning of treatment (P = .028). In addition, PTH increased wet muscle mass (P < .001), and muscle fiber cross-sectional area (P = .018) compared with measurements at the start of treatment. PTH administration promoted the expression of UCP1, a beige adipocyte marker, in the supraspinatus muscle (P = .019). PTH increased gene expression of beige adipocyte-related markers and suppressed fat droplet accumulation even after adipogenic differentiation of FAPs (P = .004) but did not reduce fat droplets that had already accumulated in in vitro experiments. CONCLUSIONS: PTH facilitated beige adipocyte expression and reversibly ameliorated muscle quality and atrophy following chronic RCT by hindering fat droplet accumulation and facilitating muscle regeneration. Therefore, PTH may be a medical treatment for FI and MA following RCT, leading to expanded rotator cuff repair indications.
RESUMO
Background The benefits of vitamin D encompass the augmentation of rotator cuff healing, the enhancement of bone mineral density (BMD), and the fortification of skeletal muscle strength. The vitamin D deficiency in Asian countries appears to be more severe compared to their Western counterparts. This study aims to ascertain the relationship between rotator cuff tears and vitamin D levels in the urban Thai elderly demographic. Our hypothesis posits that vitamin D deficiency will exhibit an association with the occurrence of rotator cuff tears. Materials and methods A prospective clinical trial conducted at a single tertiary was carried out to assess the patients experiencing shoulder pain who were aged 60 years or older. All participants were tested of blood specimens for calciferol concentration and magnetic resonance imaging (MRI). The duration between blood sample collection and magnetic resonance imaging (MRI) did not exceed a two-week window. The assessment of fatty degeneration in the supraspinatus, infraspinatus, and subscapularis muscles, as well as tear dimensions and cartilage thickness, was conducted using magnetic resonance imaging within the outpatient clinic. Results The analysis of serum vitamin D levels within a cohort comprising 59 subjects produced significant observations, indicating that 20.03% of the participants manifested a deficiency in vitamin D and 44.07% exhibited insufficiency in vitamin D levels. There was no observed correlation between serum vitamin D levels and various patient parameters, including age (P = .99), body mass index (P = 0.31), tear size (P = 0.41), cartilage thickness at different locations on the humeral head (superior, middle, inferior, and total) (P = 0.31, 0.40, 0.26, 0.20, respectively), degree of fatty infiltration of the rotator cuff (P = 0.81), and severity of the rotator cuff condition (P = 0.13). A significant positive correlation was established between rotator cuff tear size and both the severity of the rotator cuff condition (P < 0.001) and the degree of fatty infiltration of the cuff (P < 0.001). Conclusion A negative correlation is observed between serum vitamin D levels and various parameters, including tear size, fatty infiltration, cartilage thickness, and the severity of rotator cuff tears within the elderly urban Thai population. To affirm these findings, it is imperative to conduct additional research and integrate vitamin D assessments into the management strategies for aging populations with rotator cuff conditions.