Association of Serum Bile Acid and Unsaturated Fatty Acid Profiles with the Risk of Diabetic Retinopathy in Type 2 Diabetic Patients

Abstract

Aim: We aimed to identify the ability of serum bile acids (BAs) and unsaturated fatty acids (UFAs) profiles to predict the development of diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM) patients.

Methods: We first used univariate and multivariate analysis to compare 15 serum BA and 11 UFA levels in healthy control (HC) group (n = 82), T2DM patients with DR (n = 58) and T2DM patients without DR (n = 60). Forty T2DM patients were considered for validation. Then, the receiver operating characteristic curve (ROC) and decision curve analysis were used to assess the diagnostic value and clinical benefit of serum biomarkers alone, clinical variables alone or in combination, and the area under the curve (AUC), integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were used to further assess whether the addition of biomarkers significantly improved the predictive ability of the model.

Results: Orthogonal partial least squares-discriminant analysis (OPLS-DA) of serum BAs and UFAs separated the three cohorts including HC, T2DM patients with or without DR. The difference in serum BA and UFA profiles of T2DM patients with or without DR was mainly manifested in the three metabolites of taurolithocholic acid (TLCA), tauroursodeoxycholic acid (TUDCA) and arachidonic acid (AA). Together, they had an AUC of 0.785 (0.918 for validation cohort) for predicting DR in T2DM patients. After adjusting for numerous confounding factors, TLCA, TUDCA, and AA were independent predictors that differentiated T2DM with or without DR. The results of AUC, IDI, and NRI demonstrated that adding these three biomarkers to a model with clinical variables statistically increased their predictive value and were replicated in our independent validation cohort.

Conclusion: These findings highlight the association of three metabolites, TLCA, TUDCA and AA, with DR and may indicate their potential value in the pathogenesis of DR.

Keywords: diabetic retinopathy; serum bile acid; type 2 diabetes mellitus; unsaturated fatty acid.

Figure 1

Bile acids and unsaturated fatty acids distribution among Healthy Control (HC), T2DM patients, and Diabetic retinopathy (DR) patients. Serum levels of bile acids and unsaturated fatty acids in three groups were shown in (B and D). (A and C) Wilcoxon rank sum test (*p < 0.05). B and D: Wilcoxon rank sum test (*p < 0.05) when NDR compared with DR, +p < 0.05 when HC compared with DR, #p < 0.05 when HC compared with NDR.

Figure 2

Metabolomic profiling by targeted metabolomics. (A) OPLS−DA 3D models among HC, NDR, and DR groups. R2X = 0.468, R2Y = 0.310, and Q2Y = 0.253. (B) The 200−permutation test demonstrated no overfitting in the OPLS-DA model [Q2 = (0.0, –0.098)]. (C) OPLS−DA 3D models between NDR and DR groups. R2X = 0.404, R2Y = 0.221, and Q2Y = 0.107. (D) The 200−permutation test demonstrated no overfitting in the OPLS-DA model [Q2 = (0.0, –0.125)].

Figure 3

Clustering analysis and levels of serum levels of bile acids and unsaturated fatty acids among Healthy Control (HC), T2DM patients, with Diabetic retinopathy (DR) patients. Bile acids clustering for each patient and each group were shown in (A). (C) was the Spearman correlation analysis between 15 bile acids and 11 unsaturated fatty acids. (B) ratios of bile acids and unsaturated fatty acids distribution between three groups. (D) was the Spearman correlation analysis among bile acids, unsaturated fatty acids, ratios with clinical indicators in T2DM and DR patients. (B) Wilcoxon rank sum test (*p < 0.05). (A and C) *p < 0.05, +p < 0.01.