Diabetes is increasing in epidemic proportion, affecting millions adults worldwide. The increasing prevalence of diabetes places an ever-increasing burden on healthcare systems due to the disease and its complications. Diabetic retinopathy (DR) is the most specific microvascular complication of diabetes, with proliferative DR (PDR) and diabetic macular edema representing the vision-threatening form of DR. DR is the leading cause of vision loss and preventable blindness in working age adults (20–65 years).
Currently, optimal glycaemic control is a mainstay in the prevention of DR. Insulin resistance (IR), described by decreased cell sensitivity to insulin, also plays a pivotal role in the development of type 2 diabetes and its associated vascular complications. Diabetic patients with IR have a characteristic dyslipidemia in the form of abnormally high levels of plasma triglycerides (TG) that interfere with glucose metabolism in muscles, fat and pancreatic cells. This is consistent with the hypothesis that TG elevation in serum and tissue is related to a decrease in insulin sensitivity. Moreover, it has been demonstrated that lowering TG, such as fibrates do, can significantly attenuate the process of developing IR, and often helped improve glycemic control. Past studies have demonstrated that the TyG index has a predictive role in identifying patients with type 2 diabetes at elevated risk of developing future macro-vascular complications, particularly cardiovascular event.
The current study by Neelam et al examined the relationship of TyG index with the prevalence and incidence of DR in a multiethnic cohort study.
1339 patients from an ongoing Singapore Study of Macro-angiopathy and Micro-Vascular Reactivity in Type 2 Diabetes (SMART2D) were included in this study. Fasting triglyceride and glucose levels were quantified and color fundus photographs were assessed for DR presence and severity. Logistic regression models were used to evaluate associations of TyG index with DR prevalence and incidence (median follow-up period = 3.2 years).
Mean TyG index was higher in patients with DR than no DR (9.24±0.7 versus 9.04± 0.6, p<0.001). TyG index was significantly associated with DR prevalence (OR=1.4, CI 1.1–1.7, p=0.002) and incidence (OR=1.8, CI 1.04–2.9, p=0.03), after adjusting for confounders. In a stratified analysis, the association between TyG index and DR prevalence reached significance only in the subgroup with HbA1c levels ><0.001) TyG index was significantly associated with DR prevalence (OR=1.4, CI 1.1–1.7, p=0.002) and incidence (OR=1.8, CI 1.04–2.9, p=0.03), after adjusting for confounders.
In a stratified analysis, the association between TyG index and DR prevalence reached significance only in the subgroup with HbA1c levels < 7.0% (OR=2, CI 1.1–3.8, p=0.03). TyG index significantly predicted DR prevalence and incidence with area under receiver operating curve as 0.77 (CI 0.74–0.80, p<0.001) and 0.66 (CI 0.57–0.76, p value<0.01), respectively.
The data showed that there is an independent association of TyG index with prevalence as well as incidence of DR and addition of TyG index into clinical model with established risk factors significantly improved the prediction of DR. Moreover, HbA1c level modified the effect of TyG index on prevalence of DR but not incident DR. These observations suggest that TyG index may be a novel marker for risk stratification of DR in patients with type 2 diabetes.
The TyG index (composed of fasting triglyceride and fasting glucose) is a useful marker that may help optimize risk stratification for DR in patients with type 2 diabetes. It may be beneficial to consider TyG index as a secondary treatment target in patients with optimally controlled HbA1c. Authors suggest that educational interventions should be provided for patients with a high TyG index with regard to lifestyle changes. Future population-based studies with larger sample and longer duration are required to confirm our observations.
Source: Neelam et al; Clinical Ophthalmology 2023:17 https://doi.org/10.2147/OPTH.S382336