Non-high-density lipoprotein fractions are strongly associated with the presence of metabolic syndrome independent of obesity and diabetes: a population-based study among Iranian adults

Abstract

Background: Non-HDL-C as a valuable predictor of premature atherosclerosis, coronary events like first Myocardial infarction and cardiovascular mortality has a high accuracy of measurement both in fasting and non-fasting individuals. Metabolic syndrome (MetS) can promote the development of diabetes mellitus, endothelial dysfunction and atherosclerosis. A common pathway for cross linking of metabolic abnormalities and non-HDL-C has been suggested. In this study we aimed to describe the potential association between non-HDL cholesterol fractions and metabolic syndrome.

Methods: Data of third national surveillance of the risk factors of non-communicable diseases (SuRFNCD-2007) were analyzed. We defined metabolic syndrome (MetS) according to the Adult Treatment Panel III (ATPIII) and International Diabetes Federation (IDF) criteria for 2125 subjects aging 25-64 years. The receiver operating characteristic (ROC) curves were used to determine the optimal cut-points for the diagnosis of MetS. The curves were depicted for non-high-density lipoprotein cholesterol (non-HDL-C) and difference of total non-HDL-C and LDL-C (Differential cholesterol or Diff-C) as predictors of MetS. Logistic regression was also performed in a complex sample analysis scheme.

Results: The area under the curve (AUC) with 95% Confidence intervals of total non-HDL-C was computed. Values were 0.693 (0.670-0.715) for IDF-defined MetS and 0.719 (0.697-0.740) for ATPIII criteria. The optimal non-HDL-C cut-point we recommend for both criteria is 153.50 mg/dl (sensitivity: 75.7%, specificity: 57.2%, with ATPIII; sensitivity: 73.2%, specificity: 57.1%, with IDF). Using IDF criteria, the accuracy of predictors were greater in non-diabetic subjects. AUC of Diff-C in DM (-) vs. DM (+) were 0.786 (0.765-0.807) vs. 0.627(0.549-0.705). Adults with high non-HDL-C were 4.42 times more likely to have ATPIII-defined MetS (≥190 vs. < 190 mg/dL). Elevated Diff-C corresponded to increased risk of the MetS (ORs: 10.71 and 26.29 for IDF and ATP III criteria, respectively. All P-values <0.001).

Conclusions: A significant robust association exists between non-HDL-C and MetS whether applying conventional or new thresholds.

Keywords: Cut-points; Diabetes mellitus; Metabolic syndrome; Non-HDL cholesterol; SuRFNCD-2007.

Fig. 1

Prevalence of metabolic syndrome (ATP III and IDF) among different categories of Non-HDL-C fractions and both genders. Columns (a). and (b). refer to total (Non-HDL-C) and differential fractions (Diff-C: total Non-HDL – (LDL)) respectively. The inferior graphs show the compared prevalence of MetS in diabetics against nondiabetics

Fig. 2

Age and sex standardized ROC curves of Non-HDL-C and Diff-C for diagnosis of metabolic syndrome. The diagnostic criteria for metabolic syndrome are ATP III (left) and IDF (right)

Fig. 3

The optimal cut points of Non-HDL-C and Diff-C for diagnosis of metabolic syndrome. The diagnostic criteria for MetS are those recommended by the international diabetes federation (IDF) (right) and Adult Treatment Panel III (ATP III) (left). Panel a shows the distribution of Non-HDL-C and the panel b refers to Diff-C

Fig. 4

Age and sex standardized positive likelihood ratios of Non-HDL-C and Diff-C for metabolic syndrome (IDF and ATP III). Panels (a). and (b). refer to total (total Non-HDL-C) and differential fractions (Diff-C) respectively

Fig. 5

Mean levels of Non-HDL-C and Diff-C based on number of Metabolic syndrome components