In this case-control study, there was no significant association between serum Cp level and obesity in all subjects and in case and control groups separately. However, in control group, this positive relation was close to significance. Also, we found a significant positive correlation between serum Cp level and serum triglyceride level. So far, the association between serum Cp level and obesity has not been investigated in Iran. Cp is a copper-containing α
-2 glycoprotein which contains seven copper atoms per molecule and accounts for 95% of the total circulating copper in healthy adults. It is involved in coagulation, angiogenesis, defence against oxidant stress and iron homeostasis [8
A limited number of studies have investigated the association between serum Cp and obesity, and most of them have reported a positive correlation between body fat mass and inflammation-sensitive plasma proteins or ISPs, like Cp, along with other inflammatory markers [6
]. Proinflammatory cytokines generated in adipose tissue can increase hepatic synthesis of ISPs. These proteins are recognized as cardiovascular disease risk factors and some of them like haptoglobin, fibrinogen, α1
-antitrypsin, and Cp were used in clinical practice to measure the degree of inflammation [8
]. In this study, there was no significant association between serum Cp level and obesity in all subjects, and Engström et al. study [9
] in (2004) supports this finding. In that study, in addition to Cp, they investigated some of the other ISPs, among which Cp and α1
-antitrypsin, had not any association with BMI. Serum Cp level can be affected by genetic and environmental factors like diet, life style, and diseases [21
]. Thus, we may find different results in the study of different populations. The mechanisms by which Cp is related to obesity has not been identified; however, it is possible that Cp is involved in the inflammatory pathway linked to obesity [8
]. In addition, obesity is associated with oxidative stress. Therefore, elevated serum Cp levels may signal abnormally high oxidant stress [9
]. Göçmen et al. [21
] showed that Cp can act, depending on its concentration, as antioxidant or prooxidant in laboratory conditions. In this study, we tried to investigate the association between serum Cp level and some of the metabolic syndrome elements and also hsCRP, in addition to obesity. Among these indexes, Cp had a significant positive correlation with serum triglyceride level.
One of the limitations of the study is not to measure other ISPs along with Cp, as we explained earlier, the association between obesity and ISPs can differ by their types. Another limitation is the small sample size of this study, due to which, perhaps the association is not significant between Cp and obesity in all subjects. Not measuring the dietary intakes in study subjects is considered the other limitation, because, in one hand, the intake of some micronutrients, like copper, can affect serum ceruloplasmin level, and on the other hand, it has been found that the degree of macronutrient intake affects the severity of inflammation [9
]. Because the use of oral contraceptive pills or OCPs can affect serum ceruloplasmin level the other limitation is not to consider their consumption in the study.
We propose for future studies to consider other ISPs in addition to Cp, to conduct intervening studies in this basis, and also to conduct this kind of investigations in children. As we discussed earlier, serum Cp level is affected by genetic and environmental factors and we may find different results in the study of different populations. This study is the first one to investigate the association between serum cp level and obesity in Iran.