In the present study of 6069 community-dwelling Chinese participants aged 40 years or older with NGT, we found that serum apoB and the apoB/apoA-I ratio were strongly and positively associated with CIMT independently of traditional serum lipids and other conventional risk factors. To some extent, the results might suggest that the measurements of apolipoproteins were stronger predictors in carotid atherosclerosis than routine lipids.
Apolipoproteins are the protein components of plasma lipoproteins 
. Several large prospective studies have showed that apoB is superior to TC or LDL-C to predict the risk of vascular disease 
. In the Apolipoprotein-related Mortality Risk Study (AMORIS) 
, apoB was found to be a stronger marker of cardiovascular disease risk than LDL-C at any LDL-C levels, but especially in those having normal/low LDL-C levels. Moss et al. 
investigated that apoB was significantly associated with increased coronary event rates, whereas LDL-C was not. Similar findings have been found in the Quebec Cardiovascular Study 
, the MONICA/KORA Augsburg cohort study 
and the multi-ethnic US population study 
. In the Cardiovascular Risk in Young Finns Study 
, apoB and apoA-I measured in children and adolescents reflected a lipoprotein profile predisposing to the development of subclinical atherosclerosis in adulthood.
Early detection and intervention of the risk factors of CVD, is of great importance for CVD. Of all the indicators of CVD, CIMT is an early marker and is most widely adopted 
. However, studies evaluating the associations between apolipoproteins and CIMT are limited. We demonstrated that both serum apoB concentrations and the apoB/apoA-I ratio were independently associated with elevated CIMT in middle aged and elderly Chinese with NGT. Furthermore, these associations remained even after adjustment for the conventional risk factors including traditional lipids. This observation indicated that apoB and the apoB/apoA-I ratio gave additional information in predicting risk for atherosclerotic disease, beyond that of LDL-C.
In our study, we also found that the increasing levels of apoB were associated with increased BMI, WC, SBP, DBP, TG, TC, LDL-C, FPG and fasting serum insulin. In the insulin resistance atherosclerosis study (IRAS), it also showed that serum apoB correlated positively to BMI, WC, DBP and fasting serum insulin 
. Wallenfeldt et al 
found that the metabolic syndrome patients had an increased production of small dense LDL particles, which had been shown to correlate with plasma apoB and considerable evidence indicated that these particles were atherogenic and thus, might have effect on the arterial wall.
The pathophysiological basis for why apolipoproteins are better than other conventional lipids is not completely established. According to the Response-to-Retention hypothesis of atherosclerosis, the key initiating process in atherosclerosis is the subendothelial retention of apoB-containing lipoprotein 
. Biological responses to the retained lipoproteins, including a chronic and maladaptive macrophage- and T-cell–dominated inflammatory response, promote subsequent lesion development. The National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III 
recommended initiation of therapy and therapeutic goals within 3 different CHD risk categories based on LDL-C levels. However, LDL particles, which contain most of the cholesterol in plasma, may differ in composition. Small dense LDL species are more atherogenic than larger LDL particles but carry less LDL-C 
. Moreover, St-Pierre AC et al found that increased plasma CRP levels further elevate the risk of CHD associated with having small, dense LDL particles 
. LDL-C therefore is not always equivalent to LDL particle number. By contrast, each VLDL and LDL particle contains 1 molecule of apoB; therefore, plasma apoB is equivalent to the total atherogenic particle number, more than 90% of which are LDL particles. In addition, van Deventer et al 
found that direct LDL-C measurements did not improve the accuracy of CVD risk score classification.
Dysglycemia Current guidelines for CHD prevention emphasize the use of TC and LDL-C in CHD risk assessment 
. However, there has been an ongoing debate on whether apoB, or rather the apoB/apoA-I ratio, would be a more appropriate measure for estimating CHD risk associated with dyslipidaemia. A series of large, prospective epidemiological studies 
has recently shown that apoB is superior to LDL-C as a predictor of the risk of vascular disease. In a cross-sectional analysis of the US population 
, LDL-C was not significantly correlated with history of atherosclerotic disease. Similarly, in the recently published data from the Framingham study 
, LDL-C was also not found to be a significant risk factor of CHD, which suggested that LDL-C was not the best target for lipid-lowering treatment strategies. Meanwhile, apoB was first suggested as an alternative target treatment by the Canadian Working Group 
. At present, the American Diabetes Association and the American College of Cardiology 
have stated that apoB is the test of choice to assess the adequacy of statin treatment and should therefore be introduced into routine clinical practice. Furthermore, the methods can easily be automated and analyses are cheap, it can be performed on previously frozen sera, and importantly, non-fasted samples can be used.
Some limitations of our present study were of concern. First, the cross-sectional design of this study doesn’t provide information as to whether apolipoproteins predict the progression of CIMT, and cannot compare the associations of the different tests with clinical events from CVD. Second, the population included the subjects with dislipidemia, they might have been treated, but we made adjustment for the drug using history to control the bias. Third, we only used one test for apoB and the various apoB assays such as apoB-48 and apoB-100 may not show the same performance, however, apoB measurement was more convenient in laboratory. Finally, because most participants were residents of a rural community from shanghai, there was the possibility of selection bias. Although our study had limitations in generalizing its results to the worldwide population, the present study was meaningful as a first study to clarify the relationship between lipid and lipoprotein profiles and CIMT among an Asian population with NGT.
In conclusion, the present study showed that apoB and the apoB/apoA-I ratio were associated with elevated CIMT in middle-aged and elderly Chinese with NGT. In addition, the associations were independent of conventional lipids and other risk factors. Although more studies are needed to confirm these findings and to elucidate the mechanisms for this associations, our finds support the fact that apolipoprotein measurements may be better biomarkers of atherosclerotic disease than traditional lipids measures.