Elevated plasma trimethylamine-N-oxide levels are associated with diabetic retinopathy

To determine the relationship between plasma levels of trimethylamine-N-oxide (TMAO) and odds of diabetic retinopathy (DR).

A cross-sectional study was conducted. Blood samples were obtained from 122 type 2 diabetes mellitus (T2DM) patients with or without DR. Multivariable logistic regression analyses were performed to identify the association between plasma TMAO and DR. The diagnostic value of plasma TMAO was assessed by the area under the receiver operating characteristic curve (AUROC) and integrated discrimination improvement (IDI).

In the T2DM patients, plasma levels of TMAO were significantly higher in patients with DR compared with those without DR (P = 0.001). As logarithmic (ln) transformation of TMAO increased per standard deviation (SD), there was higher probability to have DR [odds ratio (OR) = 2.31; P = 0.005]. As ln-transformed TMAO increased per SD, the severity of DR was more likely to get worse (OR = 2.05; P = 0.004). In the diagnostic model, the addition of TMAO contributed to the improvement in AUROC from 0.646 to 0.734 (P = 0.043), and the IDI was 10.7% (P < 0.001).

Elevated levels of plasma TMAO were associated with higher odds and worse severity of DR in T2DM patients, and further investigation is required for the causality of this association.