TRIGLYCERIDE-GLUCOSE INDEX AS NOVEL NONINVASIVE INDICATOR OF NONALCOHOLIC FATTY LIVER DISEASE DIAGNOSTICS IN TYPE 2 DIABETES MELLITUS PATIENTS

Abstract

Background. Non-alcoholic fatty liver disease (NAFLD) can be considered as a predictor and one of the earliest and most specific pathogenetic markers of chronic noncommunicable diseases: type 2 diabetes mellitus (DM) and insulin resistance (IR). Triglyceride-glucose (TyG) index (TyG = ln[triglycerides (mmol/L) *18.018 *glycaemia(mmol/L)*18.018/2]) is a parameter by which insulin resistance can be assessed, since it is considered to be an indirect indicator of insulin resistance. The TyG index can be considered as an indicator for identifying individuals at risk for NAFLD, since elevated levels of the indicators that make up the index (fasting triglycerides and fasting blood glucose) are direct pathogenetic factors of NAFLD, as well as components of the metabolic syndrome.

The aim of the study was to determine the presence and nature of the relationship of a new indirect index of insulin resistance with the presence (or absence) of non-alcoholic fatty liver disease in patients with type 2 diabetes, as well as to determine the contribution of the TyG index to the risk of developing non-alcoholic fatty liver disease.

Materials and methods. 61 patients with type 2 diabetes were examined (34/27 men/women; age 53±1.20 years; disease duration 13.36±3.49 years; of them – with NAFLD (n=24) without NAFLD (n=37); and 12 practically healthy individuals comparable in age and sex to the main group. Determination of total cholesterol (TC), high-density lipoprotein cholesterol (HDL), triglycerides was performed by enzymatic method. Free fatty acids (FFA) were measured using a Wako Diagnostics kit (USA). According to the manufacturer's instructions for using enzyme-linked immunosorbent assay (ELISA), levels of adipocytokines, such as adiponectin, leptin, progranulin and others, as well as insulin (DRG, Germany), were determined. IR was calculated using the HOMA-IR (Homeostasis Model Assessment-Insulin Resistance) insulin resistance index, which includes simultaneous determination of individual fasting serum insulin and glucose levels. Insulin sensitivity was determined by the QUICKI index (Quantitative Insulin Check Index). To assess the diagnostic properties of the TyG index, logistic regression analysis was used, including ROC analysis (receiver operation characteristic).

Results. The studied group (except for the control group) consisted exclusively of patients with type 2 diabetes with an insulin-resistant phenotype (body mass index: 32.68±0.77 kg/m², HOMA-IR 8.04±0.77, QUICKI 0.46±0.007) with varying degrees of glycemic control (HbA1c =7.06±0.18). Patients with NAFLD are characterized by a higher TyG index (8.52±0.68) than the group without NAFLD (7.95±0.76; t=2.96; p=0.004), it was also found that the TyG index in patients with type 2 diabetes (8.17±0.78) was significantly higher than in the control group (7.07±0.49; t= 4.70; p=0.00001).

A significant correlation was found between the TyG index and a number of biochemical parameters: indicators of insulin resistance, lipid profile and oxidative stress, adipokines, and parameters of chronic inflammation, which clearly confirms the relationship between the TyG index and the pathogenesis of NAFLD.

Conclusions. The diagnostic model to form risk groups for non-alcoholic fatty liver disease among patients with type 2 diabetes using logistic regression and ROC analysis was developed. The diagnostic criterion is a new indicator – triglyceride-glucose index, the threshold value of the predictor is defined as 8.018.