In this retrospective cross-sectional study encompassing 2,194 Chinese participants and 9,715 American participants, we identified a sustained positive association between TyG and TyG-WC and DKD risk, which remained significant after comprehensive adjustment for various confounding factors. Subgroup analyses further validated the robustness of this association, demonstrating its generalizability across diverse populations. Furthermore, the RCS analysis uncovered a nonlinear relationship between TyG and DKD, characterized by an inverse L-shaped curve. These findings underscore the potential of TyG-related indices as valuable early biomarkers for predicting DKD.
Type 2 diabetes is a chronic condition marked by a gradual onset over an individual's lifetime, with its prevalence among younger populations rising annually21. Upon diagnosis, type 2 diabetes imposes lifelong challenges on patients, encompassing a spectrum of complications such as circulatory and neurological issues, which profoundly affect quality of life and place a significant economic burden on both individuals and the healthcare system22,23. Recent research underscores that proactive prevention and therapeutic strategies can substantially delay the onset and progression of diabetes-related complications, reduce associated healthcare costs, and enhance patients' quality of life24. A substantial body of evidence indicates that lifestyle interventions, including dietary modifications and increased physical activity, may be more effective than pharmacological treatments in slowing disease progression and facilitating early prevention25. With recent advancements in high-throughput detection technologies, researchers are increasingly investigating biomarkers for type 2 diabetes and its complications through approaches such as metabolomics and proteomics26. For instance, the increased conversion of phenylalanine to tyrosine, attributed to improved renal function, is thought to hold potential predictive value for DKD27. Nonetheless, these findings are constrained in their clinical applicability due to the absence of large-scale observational studies.
The TyG index, introduced by Gisela Unger et al. in 2014, is an effective and cost-efficient measure for assessing insulin resistance28. While the Homeostasis Model Assessment (HOMA) is a well-established method for evaluating insulin resistance (IR) and is relatively simple and reliable, its high cost and invasive nature hinder its routine clinical use29. While the Homeostasis Model Assessment (HOMA) is a well-established method for evaluating insulin resistance (IR) and is relatively simple and reliable, its high cost and invasive nature hinder its routine clinical use30. Recent clinical studies have underscored a strong association between the TyG index and both the incidence and mortality of diabetes. Yang et al.31 demonstrated that, among critically ill patients with acute heart failure, a higher TyG index correlates with an elevated risk of acute kidney injury. Pan et al.32identified a close association between TyG and the risk of lower limb vascular stenosis as well as renal microvascular damage in hospitalized patients. Furthermore, a large observational study revealed that an elevated TyG index mediates the relationship between BMI and end-stage renal disease in middle-aged individuals33. The evidence from these studies suggests that the TyG index could serve as a predictive marker for deteriorating renal function across various patient populations. Our study, utilizing multiple population datasets, identified a link between TyG-related indices and DKD. The mechanism underlying this association is likely related to the effect of insulin resistance on renal function. Existing research suggests that insulin resistance can elevate glomerular hydrostatic pressure, leading to increased renal vascular permeability and, ultimately, glomerular hyperfiltration and renal damage34. Moreover, insulin resistance may enhance the bioavailability of vasoactive mediators, including nitric oxide and renin-angiotensin, thereby influencing renal function35. Simultaneously, these vasoactive substances can induce glomerular hypertrophy, glomerulosclerosis, tubulointerstitial inflammation, and fibrosis36.
This study presents several notable strengths. First, in contrast to other studies investigating the relationship between TyG and type 2 diabetes-related complications, we employed two extensive databases from China and the United States, resulting in a larger sample size. Second, the application of RCS and subgroup analyses increased statistical power and validated the robustness of our findings. Third, incorporating the most recent data from MIMIC-IV 3.0 provided additional validation of the results and further enhanced the generalizability of our findings.
Nonetheless, this study has several limitations. First, given the retrospective and observational nature of the study design, it is unable to establish definitive causal relationships. Second, variables not accounted for, such as dietary patterns, racial differences, and lifestyle factors, could potentially introduce bias into the findings. Furthermore, the inherent limitations of the MIMIC-IV database meant that factors such as the severity of type 2 diabetes and DKD, as well as the socioeconomic status of participants, were not accounted for, which could also contribute to potential bias in the findings.