An ultrasensitive and selective fluorescence assay for Sudan I and III against the influence of Sudan II and IV.

We report on an ultrasensitive and selective fluorescence assay for Sudan I and III against the influence of Sudan II and IV based on ligand exchange mechanism. Calcein as a fluorescence indicator and Sudan I-IV as model analytes were employed to investigate the analytical feature of this assay platform. Results show that the fluorescence of calcein can be efficiently quenched by Cu(II). When the ligand exchange reaction proceeds, calcein is deprived of Cu(II) by Sudan I and III, resulting in the fluorescence recovery of calcein. However, the ligand exchange reaction does not happen in the presence of Sudan II or IV due to the 2-methyl steric effects, which is favorable for selective determination of Sudan I and III against the influence of Sudan II and IV. It was found that the fluorescence enhancement efficiency (FEE) against the concentration of Sudan (c(Sudan), nmol L⁻¹) shows a linear relationship. The calibration equations are FEE(Sudan I)=0.0032 c(Sudan I)-0.02613, and FEE(Sudan III)=0.0033 c(Sudan III)-0.02467 over the corresponding linear range of 11.25-2078.29 and 9.44-1035.78 nmol L⁻¹ with the correlation coefficients (R(2)) of 0.9984 and 0.9955, respectively. And the detection limits (3σ/slope) are calculated to be 211.3 and 208.5 pmol L⁻¹ for Sudan I and III, respectively, showing ultralow detection limit. The Sudan dye in a commercial chilli powder sample was assayed with satisfactory results.

[Serum adiponectin and leptin levels and bone mineral density in 232 men].

OBJECTIVE: To investigate whether adiponectin and leptin levels are associated with bone mineral density (BMD) in 232 men (20~80 years old). METHODS: Serum adiponectin and leptin levels were determined by enzyme-linked immunosorbentassay (ELISA). BMD at various sites was determined using dual energy x-ray absorptiometry (DXA). RESULTS: Adiponectin was negatively correlated with body fat, while leptin had a positively correlation. Significant negative correlations between adiponectin and BMD were found, which remained significant after adjustment of age and body fat. In the multiple linear stepwise regression analysis, adiponectin but not leptin, was independent predictor of BMD. CONCLUSION: Adiponectin was an independent predictor of BMD in Chinese men. Adiponectin may exert a negative effect on bone mass.

[Biochemical markers of age-related changes in bones turnover and bone mineral density in healthy Chinese men].

OBJECTIVE: To determine the relationship between bone alkaline phosphatase (BAP) and cross-linked N-telopeptides of type I collegen(NTX) and bone mineral density in healthy men aged 20-80. METHODS: BAP and NTX of 389 healthy men were measured by ELISA. BMD at the lumbar spine and the hip as measured by dual energy X-ray absorptiometry. The correlation of bone biochemical markers with age and BMD fit 10 regression models. RESULTS: BAP and NTX negatively correlated with age. The cubic regression model was better with age-related changes of bone biochemical markers as compared with the other regression models and the coefficients of determination of fitting curve were 0.013-0.029 (P< 0.05). The value of bone biochemical markers as the highest during 20-29 age groups, then they decreased to a nadir level in the 50-59 years age. After 60 years, bone formation markers remained stable; however resorption marker increased slightly. After adjustment for age, weight, height, BMI, and smoking, bone biochemical markers were negatively correlated with most sites of BMD. CONCLUSION: BAP and NTX may be relatively sensitive and specific markers to evaluate age-related changes of bone turnover. It may benefit the prevention of osteoporosis by monitoring the level of BAP and NTX.

[Serum leptin with bone mineral density and body fat mass in males].

OBJECTIVE: To determine the relationship of serum leptin concentration and bone mineral density(BMD), body fat mass in males. METHODS: Plasma concentrations of leptin in 350 Chinese males, aged 20 to 80 years were measured with ELISA; BMD values at lumbar spine, hip and total body BMD, and body composition, including lean tissue mass (LTM) and fat tissue mass (FTM), were measured using dual-energy-X-ray absorptiometry (DXA). The relationship between changes in serum leptin concentration with age, body weight, body mass index, body fat mass, and BMD values at 5 skeletal sites was fit by 10 regression models, and the models giving the best fit were selected. RESULTS: The S regression model best described the changes in serum leptin level with age (R(2)=0.104, P<0.009), while the compound regression model best described the changes in serum leptin concentration with BMI and weight (R(2)=0.296, P<0.001; R(2) =0.304, P<0.001). Leptin concentration was correlated with FTM (R(2)=0.448, P<0.001) and rate of body fat(R(2)=0.461, P<0.001). The serum leptin level was significantly correlated with BMD of multiple skeletal sites (R(2) was 0.115 for anterior spine BMD, 0.102 for lateral spine BMD,0.098 for femoral neck BMD, 0.112 for total hip BMD, respectively). In a multivariate analysis, leptin concentration was not a significant predictor of BMD at any site. CONCLUSION: Serum leptin concentration correlates with body fat mass and percentage of body fat, but is not a significant predictor of BMD at any site in Chinese males.