Bone, fat, and muscle interactions in health and disease

Low-calorie and high-protein diet has diverse impacts on the muscle, bone, and bone marrow adipose tissues

The present study was designed to evaluate the influence of a high-protein diet under conditions of calorie restriction (CR) in the muscle, adipose tissue, bone, and marrow adipose tissue (MAT). It included three groups of 20 female Wistar Hannover rats, fed with the following diets for 8 wk: control group (C) fed with an AIN93M diet, CR group (R) fed with an AIN-93M diet modified to 30% CR, and CR + high-protein group (H) fed with an AIN-93M diet modified to 30% CR with 40% protein. Body composition was determined by DXA. The femur was used for histomorphometry and the estimation of adipocytes. Microcomputed tomography (μCT) was employed to analyze the bone structure. Hematopoietic stem cells from the bone marrow were harvested for osteoclastogenesis. Body composition revealed that the gain in lean mass surpassed the increase in fat mass only in the H group. Bone histomorphometry and μCT showed that a high-protein diet did not mitigate CR-induced bone deterioration. In addition, the number of bone marrow adipocytes and the differentiation of hematopoietic stem cells into osteoclasts were higher in H than in the other groups. These results indicated that under CR, a high-protein diet was beneficial for muscle mass. However, as the μCT scanning detected significant bone deterioration, this combined diet might accentuate the detrimental effect on the skeleton caused by CR. Remarkably, the H group rats exhibited greater MAT expansion and elevated hematopoietic stem cell differentiation into osteoclasts than the CR and control counterparts. These data suggest that a high protein may not be an appropriate strategy to preserve bone health under CR conditions.

Longitudinal association between muscle and bone loss: Results of US and Japanese cohort studies

BACKGROUND

Muscle and bone are physiologically interconnected, but joint changes of muscle and bone with aging, and whether the muscle-bone changes are different by sex and by country has been little studied. We examined longitudinal associations of bone mineral density (BMD) and muscle mass or muscle strength in community-dwelling 65 years or older in the United States and Japan.

METHODS

The present analytic sample included 1129 women and men from the Baltimore Longitudinal Study of Aging (BLSA) (mean age, 74.5 ± 7.5 years; women, 49.8%) and 1998 women and men from the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA) (mean age, 70.0 ± 4.5 years; women, 51.4%). Median follow-up was 4.6 (min-max, 0-15.4) years in the BLSA and 4.0 (min-max, 0-13.4) years in the NILS-LSA. We selected visits at which participants had BMD (whole body, pelvic, femoral neck, trochanter, and Ward's triangle BMDs) and muscle mass [appendicular lean mass, (ALM)] measured by DXA scan. In each bone site, we ran cohort-specific bivariate linear mixed-effects models adjusted for baseline age, sex, body height, body weight, fat mass, education year, and smoking status. Race was an additional adjustment in the BLSA. Additionally, we performed sex-specific analyses.

RESULTS

In the BLSA, the rate of change in ALM positively correlated with the rate of change in the whole body (rho = 0.30, P < 0.0001) and pelvic BMD (rho = 0.24, P < 0.0001), but not in trochanter, femoral neck, or Ward's triangle BMD (P > 0.05). In the NILS-LSA, ALM positively correlated with the rate of change in all bone sites (rho ranged from 0.20 to 0.71, P < 0.01). In women, ALM positively correlated with the rate of change in all bone sites in both cohorts (in the NILS-LSA, rho ranged from 0.35 to 0.91, P < 0.01; in the BLSA, rho ranged from 0.26 to 0.56, P < 0.05) except for femoral neck BMD in the BLSA. In men, ALM positively correlated with pelvic, trochanter, and Ward's triangle BMD in the NILS-LSA (rho ranged from 0.45 to 0.68, P < 0.0001), and whole body and trochanter BMD in the BLSA (both, rho = 0.20, P < 0.05).

CONCLUSIONS

Muscle loss co-occurred with bone loss in both cohorts, but the association in the NILS-LSA tended to be stronger than in the BLSA, and the association was higher in women than in men, implying that the association may differ by sex and country.

The Influence of the Mediterranean Dietary Pattern on Osteoporosis and Sarcopenia

Diet is a modifiable factor in bone and muscle health. The Mediterranean diet (MedDiet) is rich in nutrients and contains key bioactive components with probable protective effects on muscle and bone deterioration. Osteoporosis (OP) and sarcopenia are diseases that increase frailty and susceptibility to fracture, morbidity and mortality. Therefore, it is necessary to combat them in the population. In this regard, MedDiet adherence has proven to be beneficial to bone mineral density (BMD), muscle mass, physical function, OP and sarcopenia. Hence, this diet is proposed as a therapeutic tool that could slow the onset of osteoporosis and sarcopenia. However, there is doubt about the interaction between the MedDiet, strength and fracture risk. Perhaps the amount of EVOO (extra virgin olive oil), fruits, vegetables and fish rich in anti-inflammatory and antioxidant nutrients ingested has an influence, though the results remain controversial.

PCDH7 as the key gene related to the co-occurrence of sarcopenia and osteoporosis

Sarcopenia and osteoporosis, two degenerative diseases in older patients, have become severe health problems in aging societies. Muscles and bones, the most important components of the motor system, are derived from mesodermal and ectodermal mesenchymal stem cells. The adjacent anatomical relationship between them provides the basic conditions for mechanical and chemical signals, which may contribute to the co-occurrence of sarcopenia and osteoporosis. Identifying the potential common crosstalk genes between them may provide new insights for preventing and treating their development. In this study, DEG analysis, WGCNA, and machine learning algorithms were used to identify the key crosstalk genes of sarcopenia and osteoporosis; this was then validated using independent datasets and clinical samples. Finally, four crosstalk genes (ARHGEF10, PCDH7, CST6, and ROBO3) were identified, and mRNA expression and protein levels of PCDH7 in clinical samples from patients with sarcopenia, with osteoporosis, and with both sarcopenia and osteoporosis were found to be significantly higher than those from patients without sarcopenia or osteoporosis. PCDH7 seems to be a key gene related to the development of both sarcopenia and osteoporosis.