In this study, the LAP and TyG index were significantly high in young adults with metabolic syndrome, suggesting high visceral adiposity in them (
3). Although total serum cholesterol was higher in females with metabolic syndrome than in females without metabolic syndrome, the difference was not statistically significant. Nevertheless, other lipid parameters, such as serum triglyceride, LDL cholesterol, and VLDL cholesterol, were significantly high in females with metabolic syndrome. Moreover, total cholesterol is not a component of metabolic syndrome. Therefore, it is to be noted that patients with normal or even low total cholesterol can still have metabolic syndrome.
The LAP and TyG index were observed to be significantly associated with metabolic syndrome. Furthermore, in ROC curve analysis, the LAP showed the highest area under the curve (0.882 in male and 0.905 in female subjects), followed by the TyG index (0.875 in male and 0.886 in female subjects), compared to other anthropometric parameters. The cut-off points for the LAP were 45.65 in males with a sensitivity and specificity of 80% and 46.91 in females with a sensitivity and specificity of 88%. The optimal cut-off points for the TyG index were 8.63 in males with 80% sensitivity and 78.9% specificity and 8.54 in females with 83.3% sensitivity and 79.6% specificity.
The LAP is a simple parameter calculated according to two measurements, waist circumference and triglycerides (
2). It is associated with dysfunctional and lipolytic adipose tissue, a key factor in the development of the metabolic syndrome. Waist circumference, a parameter of the LAP, represents abdominal subcutaneous adipose tissue and visceral adipose tissue (
13). The TyG index is more linked with insulin resistance than HOMA-IR (
14), and insulin resistance is the underlying mechanism of metabolic syndrome (
9).
In a study conducted on Indian adults by Ray et al., the LAP was significantly higher in subjects with metabolic syndrome than in controls (
3). Other studies also demonstrated significantly high LAP in polycystic ovary syndrome patients with metabolic syndrome (
15) and in premenopausal and postmenopausal female subjects with metabolic syndrome (
16).
A study conducted on middle-aged and elderly Chinese individuals by Li et al. (
6) also showed a significant association between the LAP and TyG index with metabolic syndrome. In other studies that compared the LAP with BMI and waist circumference, the LAP was observed to be a better marker among Spanish adults (
13), Iranian adults (
17), male subjects in Argentina (
18), and male subjects in Nigeria (
19). However, in a cohort study carried out on Chinese adults, waist circumference was accurate in predicting metabolic syndrome (
1). In another study performed on the Xinjiang population (
20), the WHtR was a better marker than the LAP and BMI. In the two aforementioned studies, metabolic syndrome was defined using International Diabetes Federation criteria which could be a reason for their contradictory findings.
Therefore, the accurate and reliable parameter for metabolic syndrome differs by age, gender, ethnicity, region, and criteria used to define metabolic syndrome. In Brazilian adults (
2), the cut-off points of the LAP were 64.1 and 38 in male and female patients; nevertheless, it was reported as 53.63 in Argentinians (
18). In a study conducted on the pediatric age group, the cut-off value of the TyG index was 8.33 (
14). In another study, the cut-off points of the TyG index were 8.65 and 8.35 in Mexican American adults and non-Hispanic blacks, respectively (
9). These differences in the cut-off points could be due to the differences in populations assessed in various regions and ethnicities.
The major limitation of the current study is a lack of a population-based study design and the non-representative sample. Other limitations include a small sample size and a cross-sectional design, and causal inferences could not be made.
5.1. Conclusions
The LAP and TyG index are significantly associated with metabolic syndrome in young adults. As simple and inexpensive markers, they can be used to identify individuals with metabolic syndrome with high sensitivity and specificity. By the early identification of metabolic syndrome, lifestyle modifications, such as dietary changes and regular physical activity, can be introduced at an early age to avoid the development of type 2 diabetes mellitus and CVD in the future. Further prospective studies are required with a larger sample size to confirm the obtained findings.