Analyzing Bone, Muscle and Adipose Tissue Biomarkers to Identify Osteosarcopenic Obesity Syndrome in Older Women

Osteosarcopenic obesity (OSO) is a recently identified geriatric syndrome characterized by simultaneous presence of osteopenia/osteoporosis, sarcopenia, and increased adiposity either as overt overweight or fat infiltration into bone and muscle. The diagnostic criteria for OSO are just being established, but there are no data on biomarkers that might characterize this syndrome. Our objective was to examine possible biomarkers associated with OSO syndrome, including serum sclerostin (as a hinder of bone formation), skeletal muscle-specific troponin T (sTnT) (as an indicator of muscle turnover/damage) and serum leptin and adiponectin (measurement for fat metabolism). Additionally, we analyzed C-reactive protein (CRP) and serum lipids to evaluate the level of inflammation and lipid profile, respectively. A total of n=59 healthy Caucasian women ≥65 years were classified into 4 groups based on their bone and body composition profile identified by Dual-energy X-ray Absorptiometry (DXA) measurements: 1) Osteopenic obese (N=35); 2) Obese-only (N=10); 3) OSO (N=10); 4) Osteopenic/sarcopenic non-obese (N=4). Osteopenia/osteoporosis was determined by T-score of L1-L4 and/or femoral neck≤-1. Appendicular lean mass adjusted for both height and fat mass. Appendicular lean mass residual value of ≤ -1.43 was used as the cut-off point for diagnosing sarcopenia. Obesity included women with body fat percentage ≥32%. Serum samples were analyzed using ELISA kits for sclerostin, sTnT, leptin and adiponectin. CRP and Lipid profile were analyzed at Tallahassee Memorial Hospital using the latex amino assay and lipoprotein assay, respectively. In addition, diet and habitual physical activity were evaluated by 3-day dietary record and the Allied Dunbar National Fitness Survey, respectively. Data were evaluated by Pearson's correlations and ANOVA followed by Tukey's tests with p≤0.05. Serum sclerostin was significantly higher in OSO and osteopenic obese group in comparison to the obese-only group. The sTnT concentrations were significantly higher in OSO group in comparison to osteopenic obese and obese-only group. Sclerostin was negatively correlated with bone mineral density/content (BMD/BMC) of all skeletal sites, and the relationship was statistically significant with femoral neck BMD/BMC. Moreover, there was a significant positive correlation between serum sclerostin and sTnT, indicating their simultaneous mediation in bone and muscle loss. The highest concentrations of serum leptin were observed among OSO group. Women in OSO group had significantly greater leptin concentration than osteopenic/sarcopenic non-obese group. Serum leptin was significantly negatively correlated with left femoral neck BMD and T-score, total BMC and left femur BMC after adjusting for weight or BMI. Statistically significant negative correlation of serum adiponectin with body fat percentage was noted, as well as with the BMD and T-scores of several skeletal sites, including total femur and femoral neck. The osteopenic/sarcopenic non-obese group had the highest level of adiponectin (µg/mL) in comparison to other groups. These results confirm the negative relationship between adiposity and serum adiponectin. Significant negative correlation between serum leptin and BMD in groups with increased body fat may indicate its mediating role between bone and body adiposity. The CRP concentrations for all participants ranged from 0.01 to 1.43 mg/dL. None of the CRP concentrations were above the high threshold (3.0 mg/dL). Although the highest concentrations of CRP were observed among OSO group, there was no significant difference between groups. The highest concentrations of cholesterol and low density lipoprotein (LDL) were observed in the OSO group. Moreover, the highest concentrations of triglyceride were observed among the osteopenic obese group vs lowest for osteopenic/sarcopenic non-obese group. Although, the lowest amount of energy intake was observed among OSO group, there was no significant difference among groups. Moreover, there was no significant difference in amount of vitamin D and calcium intake among the groups. The lowest amount of protein intake was observed in the OSO group; however, there was no significant difference among groups. There was a significant positive correlation between total calcium intake and lean/fat ratio. Moreover, there was a significant negative correlation between amount of protein intake and waist/hip ratio. In conclusion, women identified with OSO syndrome have presented with the poorest outcomes for each variable. The combination of high concentration of sclerostin, sTnT, leptin and low adiponectin can be used to better identify the metabolic profile of OSO syndrome and possibly apply as measurements for its diagnostic criteria.