The objective of our study was to investigate the link between TyG, a marker of IR, and the risk of microvascular complications (including DKD and DPN) in patients with T2D. Employing logistic regression models, we identified a graded relationship between TyG and the prevalence of DKD. Nevertheless, further prospective and multi-center studies are required to confirm the association between TyG and DPN.

In recent years, the prevalence of diabetes has risen continuously, resulting in an epidemic of diabetes complications. The meta-analysis conducted in China revealed that 21.8% of patients with diabetes have concomitant DKD [22]. Additionally, two population-based studies utilizing door-to-door screening reported prevalence estimates of 1–4% for neuropathy, with 40–55% of cases found to be secondary to diabetes [23, 24]. In this study, the prevalence rates of DKD and DPN were 21.18% and 16.93%, respectively. The prevalence rate of DKD + DPN was 13.21%. Even after adjusting for potential confounding factors, the results showed a strong association between TyG and DKD (OR = 1.581, [95% CI] 1.031–2.424). The findings suggest that TyG may serve as an effective indicator for identifying DKD in patients with T2D. However, no significant relationship was shown with DPN.

Patients with T2D may require hospitalization for various reasons beyond metabolic issues. In our study, participants were hospitalized primarily for metabolic reasons, including poor glycemic control or the onset or worsening of diabetic complications. Consequently, the association analyses conducted are less susceptible to the influence of concurrent acute conditions. Overall, noticeable differences in age, SBP, BMI, WC, HbA1c, FBG, lipid metabolism, and TyG were observed in DKD and DPN group compared with patients with NDKD + NDPN group. These findings are consistent with previous research [5, 8,9,10]. Through the effective management and control of risk factors such as hyperglycemia, elevated blood pressure, obesity, and dyslipidemia, it is plausible to decelerate the progression of diabetic complications and avert the onset of DKD and DPN [25, 26]. However, these baseline data also underscore the significance of the observed disparities in TyG, warranting serious consideration.

TyG, a newly proposed indicator in recent years, has been shown to be a reliable and simple substitute marker of IR [17, 18]. Our results revealed that elevated FBG and TG have been associated with the occurrence of DKD and DPN. Hence, TyG, which comprises FBG and TG, also exhibited differences between the three group in the baseline. In univariate logistic regressions, an elevated TyG index was found to be associated with a higher risk of DKD. However, since TyG is an indicator of metabolism composed of FBG and TG, it can be influenced by various metabolic conditions. Therefore, through quantile regression, we also identified several implicit factors associated with TyG quartiles, including sex, age, SBP, HbA1c, FCP, TC, HDL-C, LDL-C, and drinking habits. These indicators are primarily related to metabolism and can provide further insights into the association between TyG and microvascular complications in patients with T2D. After controlling for confounders, we still observed a significant increase in the risk of diabetic kidney disease DKD.

The original emergence of TyG was for finding an available measure to replace the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) index [17]. IR has been found to be independently associated with DKD [27], extending beyond its indirect connections with glucose levels, blood pressure, body weight, and lipid control. Numerous studies have consistently demonstrated a significant association between a higher TyG index and various conditions, including cardiovascular disease (CVD), obesity, diabetes, non-alcoholic fatty liver disease, and kidney disease [12,13,14,15,16, 28, 29]. As a predictive tool for the occurrence of DKD, TyG reflects not only blood glucose levels and lipid levels but also IR and obesity. It should be noted that TyG is not a single indicator but rather a multifactorial index that takes into account multiple parameters.

Although our multivariable logistic regression analysis did not reveal a significant relationship between TyG and DPN, we maintain the belief that TyG could potentially play a crucial role as a risk factor for DPN. Previous studies have demonstrated a close correlation between DPN and the duration of diabetes as well as HbA1c levels [30]. Furthermore, independent of HbA1c levels, the presence of multiple metabolic syndrome components, such as hypertriglyceridemia, hypertension, abdominal obesity, and low HDL levels, consistently exhibit an association with DPN in patients with T2D [31, 32]. It is worth noting that dyslipidemia is highly prevalent in individuals with T2D [33] and has been linked to the development of DPN [34]. A study involving 200 patients with T2D demonstrated a significant correlation between TC levels exceeding 5.2 mmol/l and the presence of DPN [35]. In our study, the average TG level in the DPN group was normal. Additionally, 1108 participants (57.4%) had received statin therapy, with 540 (57.4%) in the NDKD + NDPN group, 173 (52.7%) in the DPN group, 237 (57.9%) in the DKD group, and 156 (62%) in the DKD + DPN group. There was no statistically significant difference in statin therapy compared to the NDKD + NDPN group. Therefore, considering multiple metabolic factors is essential when evaluating the risk of DPN in individuals with T2D, as each factor could contribute to the occurrence and progression of this complication.

Although we attempted to find the implicit factors of TyG to improve the accuracy of the results, there were still some limitations in our study. First, there is a selection bias in the population studied because the patients with T2D were collected from the inpatient department of Shanghai Tongren Hospital. The sample size of the data obtained is limited, and the data have a certain region, which is not representative. Second, the study included only 30 to 75-year-old Chinese participants, so we should be cautious in extrapolating the present findings to other subjects. Third, TyG, as an indicator of metabolism, can be affected by some metabolic conditions, such as primary triglyceride abnormalities.

Furthermore, measurements of the TyG index in a hospital setting may be influenced by the administration of hypoglycemic agents and lipid-lowering medications, potentially confounding the results. Therefore the TyG has high sensitivity, but low specificity, for screening the onset of diabetic microvascular complications.