Abstract: BACKGROUND: It has been found that the increase of adipocytes is accompanied by the decrease of bone mineral density and bone mass, while the differentiation of adipocytes is affected by extracellular regulated protein kinases (ERK)1/2 signaling pathway. Up to now, there are few studies on the expression characteristics and correlation of ERK1/2 in lipid metabolism of different syndrome types in patients with osteoporosis. Therefore, this study was designed to explore their internal relationship.
OBJECTIVE: To explore the correlation and characteristics between traditional Chinese medicine (TCM) syndrome types and ERK in senile osteoporosis. 
METHODS: A total of 94 eligible patients with senile osteoporosis were divided into three groups according to TCM syndrome types, including 39 cases of liver-kidney deficiency type, 30 cases of spleen-kidney yang deficiency type, and 25 cases of qi stagnation and blood stasis type. Peripheral venous blood samples were collected on an empty stomach in the next morning after admission to detect total cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein, apolipoprotein A1, and apolipoprotein B. Generally, patients underwent artificial hip replacement on the 3rd day after admission and the cancellous bone specimens excavated from the femoral neck were kept in a cryopreservation tube at -80℃. The protein expression of ERK1/2 and p-ERK1/2 in the cancellous bone was then detected and analyzed. 
RESULTS AND CONCLUSION: There were significant differences in serum triglyceride, high-density lipoprotein, and low-density lipoprotein levels among the patients with three types of TCM syndromes (P < 0.05). The serum triglyceride level of the patients with spleen-kidney yang deficiency was higher than that of the patients with liver-kidney deficiency and qi stagnation and blood stasis (P=0.009, P=0.035). The serum high-density lipoprotein level of the patients with liver-kidney deficiency was higher than that of the patients with spleen-kidney yang deficiency and qi stagnation and blood stasis (P=0.004, P=0.017). The serum low-density lipoprotein level of the patients with qi stagnation and blood stasis was lower than that of the patients with spleen-kidney yang deficiency and liver-kidney deficiency (P=0.009, P=0.003). The levels of p-ERK1 and p-ERK2 in the cancellous bone were higher than those in the patients with qi stagnation and blood stasis than those with spleen-kidney yang deficiency and liver-kidney deficiency (p-ERK1: P=0.000, P=0.000; p-ERK2: P=0.024, P=0.000). The level of p-ERK2 in the patients with liver-kidney deficiency was higher than that in the patients with spleen-kidney yang deficiency (P=0.006). In the spleen-kidney yang deficiency group, there was a positive correlation with triglyceride (r=0.124, P=0.006) and a negative correlation with p-ERK1/2 (r=-0.512, P=0.013); in the qi stagnation and blood stasis group, there was a positive correlation with p-ERK1/2 (r=0.331, P=0.000). In conclusion, among the three syndrome types of osteoporosis, the lipid metabolism of spleen-kidney yang deficiency group is significantly different from the other two groups, and is negatively correlated with p-ERK1/2.

Key words: osteoporosis, atrophic debility of bones, bone metabolism, TCM syndrome type, lipid metabolism, blood lipid, ERK1/2, protein, hip replacement