Date Published: March 7, 2019
Publisher: Public Library of Science
Author(s): Jinsook Lim, Jimyung Kim, Sun Hoe Koo, Gye Cheol Kwon, Fernando Guerrero-Romero.
The triglyceride glucose (TyG) index, a product of triglyceride and fasting glucose, is a reliable marker for insulin resistance (IR). Obesity is also known to be closely related with IR. Recently, the efficiency of TyG-related markers that combine obesity markers with TyG index has been studied; however, earlier studies were limited in number and the results were inconsistent. Therefore, in this study, we investigated the efficiency of several combinations of TyG index and obesity indices, namely, body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR), in reflecting IR. Data were obtained from the Korean National Health and Nutrition Examination Survey from 2007–2010. A total of 11,149 subjects (4,777 men and 6,372 women) were included. IR was defined as the homeostasis model assessment for IR (HOMA-IR) of above the 75th percentile for each gender. Logistic regression analysis was performed after adjusting for confounding factors, to compare and identify the associations of the 4 parameters (TyG index, TyG-BMI, TyG-WC, and TyG-WHtR) with IR. For each parameter, odds ratios (OR) and 95% confidence intervals (CIs) of quartiles 2–4 were calculated and compared with quartile 1 as a reference. A receiver operating characteristic (ROC) curve analysis was conducted to evaluate the ability of each parameter to predict IR. The adjusted ORs of quartile 4 in comparison with quartile 1 (95% CIs) for IR were 7.60 (6.52–8.87) for TyG index, 12.82 (10.89–15.10) for TyG-BMI, 16.29 (13.70–19.38) for TyG-WC, and 14.86 (12.53–17.62) for TyG-WHtR. The areas under the ROC curve for each parameter were 0.690 for TyG index, 0.748 for TyG-BMI, 0.731 for TyG-WC, and 0.733 for TyG-WHtR. In conclusion, TyG-BMI was found to be superior to other parameters for IR prediction. We propose TyG-BMI as an alternative marker for assessing IR in clinical settings.
Insulin resistance (IR) is characterized by an inappropriate physiologic response in which insensitivity to insulin results in compensatory hyperinsulinemia . IR is known to be a major risk factor for metabolic syndrome, type 2 diabetes and cardiovascular diseases [2–4]. Rapidly growing population with chronic diseases associated with IR are reported worldwide, including among the Korean population [5,6]. Thus, early detection of IR is crucial to prevent the manifestation of clinical diseases. The glucose clamp technique, first described by DeFronzo is considered as the gold standard for quantification of IR . However, it is difficult to perform in routine laboratory because of its complexity and invasiveness . To overcome these problems, the homeostasis model for IR (HOMA-IR) was developed in 1985  and has been widely used for IR quantification. However, insulin measurement is still not readily available in many routine laboratories and entails standardization issues . Consequently, several studies have explored methods that can easily predict IR in routine laboratory assessments and they proposed various markers such as lipid ratios and visceral adiposity index (VAI) [8,11–16]. The triglyceride glucose (TyG) index, a product of fasting triglycerides and glucose, has also recently been suggested for IR estimation, and this measurement demonstrates improved efficiency compared to previous markers [8,17,18].
A total of 11,149 participants were included in the study, including 8,362 without IR (Non-IR group) and 2,787 with IR (IR group). The anthropometric, biochemical, and clinical characteristics of participants by gender and presence of IR are summarized in Table 1. The mean ages of the non-IR and IR groups were 44.7 ± 14.9 and 44.5 ± 14.3 years, respectively. Age, height, smoking, drinking, and regular exercise were not significantly different between non-IR and IR groups. However, mean body weight, waist circumference, BMI, WHtR, systolic and diastolic BPs, glucose, total cholesterol, TG, LDL, insulin, HOMA-IR, TyG index, TyG-BMI, TyG-WC, and TyG-WHtR, were significantly higher while the mean HDL level was significantly lower in the IR group than in the non-IR group.
In this cross-sectional study, we evaluated and compared four parameters of IR: TyG index, TyG-BMI, TyG-WC, and TyG-WHtR. Overall, the combination of obesity indices with TyG index showed better results than TyG index alone. Moreover, we found that TyG-BMI, a combination of TyG index and BMI, performed better than the other parameters with a higher odds ratio and the largest AUC of 0.748 in all subjects.