Recent advances in metabolic research have led to the recognition that adipose tissue is an endocrine organ that secretes a variety of adipokines, which offer a connection between adipose tissue and the metabolic function of other organs, for example, bone [
The previous studies suggest that leptin, one of the remarkable adipokines, plays an essential role in osteogenesis and bone metabolism via multiple pathways and supports the possibility that leptin is involved in the onset or progression of various bone diseases, for example, osteoporosis [
Chemerin is a novel adipocyte-secreted factor, which plays an important role in adipogenesis, adipocyte differentiation, and insulin signaling [
In the present study, we investigated the relationship between serum chemerin levels and bone mineral density (BMD) in patients with osteoporosis and healthy controls by conducting a case-control study.
This observational study included 186 participants who were recruited from January 2014 to January 2015 at the outpatient clinic, the People’s Hospital of Jintan. All participants had got BMD scans of their femoral neck and lumbar spines (L2–L4) by dual energy X-ray absorptiometry (Lunar Prodigy; General Electric Medical Systems, Milwaukee, WI, USA) on the purpose of physical examination [
Fasting blood samples were taken for the measurement of serum chemerin levels by using enzyme-linked immunosorbent assay (ELISA) (catalogue number SEA945Hu; Uscn Life Science Inc., China). In the meantime, routine blood chemistry analyses were performed at the laboratory department in our hospital. Data regarding age, sex, body mass index (BMI), having diabetes mellitus (DM) or hypertension, menstrual history, and serum concentrations of alkaline phosphatase (AKP), total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), and insulin were recorded.
Statistical analyses were performed using SPSS software (version 20.0). Continuous data were presented as mean ± standard deviation (SD), while categorical data were presented as absolute numbers. Statistical significance between the groups was evaluated using Student’s
The basic characteristics of the 186 enrolled patients are presented in Table
Characteristics of the subjects.
Osteoporosis | Control |
| |
---|---|---|---|
Number | 93 | 93 | |
Male/female | 34/59 | 34/59 | |
Age | 64.60 ± 10.29 | 64.48 ± 10.29 | 0.443 |
BMI | 26.06 ± 2.74 | 25.24 ± 2.10 | <0.01 |
Number of patients with DM | 34 | 28 | 0.437 |
Number of patients with hypertension | 38 | 35 | 0.764 |
Number of postmenopausal women | 55 | 50 | 0.239 |
Number of patients with bone fracture | 15 | 0 | <0.01 |
Chemerin (ng/ml) | 87.27 ± 5.80 | 71.13 ±5.12 | <0.01 |
FBMD (g/cm2) | 0.63 ± 0.04 | 0.80 ± 0.07 | <0.01 |
LBMD (g/cm2) | 0.78 ± 0.04 | 1.04 ± 0.10 | <0.01 |
TC (mmol/L) | 6.35 ± 0.48 | 6.23 ± 0.45 | 0.077 |
TG (mmol/L) | 1.69 ± 0.23 | 1.60 ± 0.36 | 0.067 |
HDL-C (mmol/L) | 1.47 ± 0.29 | 1.50 ± 0.35 | 0.356 |
LDL-C (mmol/L) | 3.00 ± 0.24 | 3.12 ± 0.24 | <0.01 |
AKP (U/L) | 99.29 ± 21.31 | 92.99 ± 21.03 | 0.047 |
FBG (mmol/L) | 6.04 ± 1.20 | 5.81 ± 1.13 | 0.136 |
Insulin (mU/L) | 17.13 ± 4.52 | 18.12 ± 3.82 | 0.079 |
Data are presented as mean (standard deviation).
BMI: body mass index; DM: diabetes mellitus; FBMD: femoral bone mineral density; LBMD: lumbar bone mineral density; TC: total cholesterol; TG: triglycerides; HDL-C: high-density lipoprotein cholesterol; LDL-C: low-density lipoprotein cholesterol; AKP: alkaline phosphatase; FBG: fasting blood glucose.
Serum chemerin level was positively correlated with age (
Bivariate correlation analyses between serum chemerin levels with anthropometric and laboratory variables.
Osteoporosis group | Control group | |||||||
---|---|---|---|---|---|---|---|---|
Unadjusted | Adjusted |
Unadjusted | Adjusted |
|||||
|
|
|
|
|
|
|
|
|
Age | 0.395 | <0.01 | NA | NA | 0.250 | 0.016 | NA | NA |
BMI | 0.391 | <0.01 | NA | NA | 0.249 | 0.016 | NA | NA |
TC |
|
0.049 |
|
0.263 |
|
|
|
0.287 |
TG |
|
0.393 |
|
0.094 | 0.189 | 0.070 | 0.053 | 0.618 |
HDL-C |
|
0.012 |
|
0.201 | 0.128 | 0.220 | 0.129 | 0.224 |
LDL-C |
|
<0.01 |
|
0.011 | 0.361 | <0.01 | 0.400 | <0.01 |
AKP |
|
0.643 |
|
0.891 | 0.106 | 0.314 | 0.132 | 0.213 |
FBG | 0.428 | <0.01 | 0.342 | <0.01 | 0.340 | <0.01 | 0.300 | <0.01 |
Insulin | 0.459 | <0.01 | 0.440 | <0.01 | 0.085 | 0.420 | 0.051 | 0.633 |
BMI: body mass index; TC: total cholesterol; TG: triglycerides; HDL-C: high-density lipoprotein cholesterol; LDL-C: low-density lipoprotein cholesterol; AKP: alkaline phosphatase; FBG: fasting blood glucose; NA: not applicable.
On the partial correlation analyses adjusted for age and BMI, plasmatic chemerin level was positively correlated with FBG (
In osteoporosis subjects, femoral bone mineral density (FBMD) was negatively correlated with age (
Bivariate correlation analyses between bone mineral density with serum chemerin levels and anthropometric and laboratory variables.
Osteoporosis group | Control group | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
FBMD | LBMD | FBMD | LBDM | |||||||||||||
Unadjusted | Adjusted |
Unadjusted | Adjusted |
Unadjusted | Adjusted |
Unadjusted | Adjusted |
|||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Age |
|
<0.01 | NA | NA |
|
<0.01 | NA | NA |
|
0.035 | NA | NA |
|
<0.01 | NA | NA |
BMI |
|
0.822 | NA | NA |
|
0.626 | NA | NA |
|
0.963 | NA | NA |
|
0.848 | NA | NA |
Chemerin |
|
<0.01 |
|
<0.01 |
|
<0.01 |
|
0.172 |
|
<0.01 |
|
<0.01 |
|
<0.01 |
|
<0.01 |
TC |
|
0.303 |
|
0.901 |
|
0.262 |
|
0.365 |
|
0.217 |
|
0.243 |
|
0.685 |
|
0.451 |
TG |
|
0.655 |
|
0.056 |
|
0.310 |
|
0.038 |
|
0.203 |
|
0.071 |
|
0.804 |
|
0.191 |
HDL-C |
|
0.039 |
|
<0.01 |
|
0.833 |
|
0.212 |
|
0.013 |
|
0.029 |
|
0.151 |
|
0.491 |
LDL-C |
|
0.976 |
|
0.504 |
|
0.229 |
|
0.945 |
|
0.169 |
|
0.175 |
|
0.733 |
|
0.762 |
AKP |
|
0.082 |
|
0.101 |
|
0.171 |
|
0.047 |
|
0.056 |
|
0.048 |
|
0.111 |
|
0.049 |
FBG |
|
<0.01 |
|
<0.01 |
|
0.030 |
|
<0.01 |
|
0.187 |
|
0.075 |
|
0.220 |
|
0.029 |
Insulin |
|
<0.01 |
|
<0.01 |
|
0.019 |
|
<0.01 |
|
0.234 |
|
0.359 |
|
0.135 |
|
0.346 |
FBMD: femoral bone mineral density; LBMD: lumbar bone mineral density; BMI: body mass index; TC: total cholesterol; TG: triglycerides; HDL-C: high-density lipoprotein cholesterol; LDL-C: low-density lipoprotein cholesterol; AKP: alkaline phosphatase; FBG: fasting blood glucose; NA: not applicable.
After adjusting for age and BMI in partial correlation analyses, there was a negative correlation between both FBMD (
This study has suggested that patients with osteoporosis present higher concentrations of serum chemerin than healthy controls. Furthermore, serum chemerin level has a negative correlation with FBMD and LBMD both in patients with osteoporosis and in healthy controls.
Chemerin is a novel adiponectin, which has been documented to be associated with metabolic syndrome. It is commonly accepted that incidence of osteoporosis is increased in patients with metabolic syndrome [
According to the results of this study, chemerin level was positively correlated with age, BMI, LDL-C, FBG, and fasting insulin, suggesting the relationship of chemerin with obesity, dyslipidemia, and insulin resistance. Furthermore, we have demonstrated that both FBMD and LBMD negatively correlated with chemerin level in osteoporosis patients and normal controls. After the adjustment of age and BMI, the correlation between LBMD and chemerin in patients with osteoporosis disappeared. In addition, in subjects with osteoporosis, partial correlation analyses suggested a negative correlation of BMD with FBG and insulin. It indicated an association among chemerin, insulin resistance, and bone metabolism, through the complex muscle-fat-bone axis.
To our knowledge, it is the first study to investigate whether serum chemerin level is altered in patients with osteoporosis and to evaluate the relationship between serum chemerin level and BMD. Strength of the present study was mainly the case-control design, matched for age and gender. In terms of limitations, it was not a population-based study. The possibility of selection bias had to be taken into consideration. And we did not measure plasmatic levels of other adipokines, such as adiponectin, leptin, and resistin, and did not evaluate the levels of bone metabolic markers, such as osteocalcin. Therefore, we failed to explore the relationship among these variables, BMD, and chemerin levels. Furthermore, this observational study precluded the establishment of a causal relationship between chemerin and osteoporosis. Further studies are needed to explore the causality and the underlying mechanism. Lastly, failure to include patients with osteopenia is also a limitation of our work. Due to being less aware of the bone health, subjects with osteopenia usually refuse to take full physical and biochemical examinations, which leads to limited number of eligible participants with osteopenia.
In conclusion, we reported a significant higher level of serum chemerin in patients with osteoporosis than normal controls. In addition, BMD presented an inverse correlation with serum chemerin levels. Further considerable studies are needed to demonstrate whether chemerin plays a role in the pathophysiology of osteoporosis and whether chemerin is qualified as a marker or predictor of osteoporosis.
The authors declare that there is no conflict of interests regarding the publication of this paper.