Additionally, Zhu et al. demonstrated that the lower CAV1 expression in the monocytes of patients with T2DM and PDN than patients with T2DM but without PDN correlated negatively with TLR4 expression and the levels of pro-inflammatory cytokines (e.g., IL-6 and TNF-α), suggesting that reduced CAV1 could be a predictive marker for PDN [36]. Here, TLR4 is linked to type 2 diabetes mellitus.