High plasma retinol binding protein 4 (RBP4) is associated with systemic inflammation independently of low RBP4 adipose expression and is normalized by transplantation in nonobese, nondiabetic patients with chronic kidney disease

Summary Objective  Adipose-secreted retinol binding protein 4 (RBP4) circulates in free (active) and transthyretin (TTR)-bound forms and may be associated with obesity-related inflammation. Potential involvement of plasma and adipose RBP4 in systemic inflammation in the absence of obesity and diabetes is unknown. Inflammation reduces survival in chronic kidney disease (CKD) [particularly in maintenance haemodialysis (MHD)], and plasma RBP4 may increase with renal dysfunction. We investigated (i) potential associations between RBP4 and inflammation in CKD and (ii) the role of adipose tissue in this putative interaction. Design  Cross-sectional. Patients  Nonobese, nondiabetic patients with CKD undergoing conservative (CT: n = 10) or MHD treatment (n = 25) and healthy control subjects (C: n = 11). Renal transplant recipients (n = 5) were studied to further assess the impact of restored near-normal renal function. Measurements  Plasma RBP4, TTR and C-reactive protein (CRP), adipose RBP4 expression. Results  Plasma RBP4, TTR and CRP were highest in MHD (P < 0·05). Adipose RBP4 mRNA was, however, comparably low in CT and MHD (P < 0·05 vs C), and all parameters were normalized in transplant recipients (P < 0·05 vs MHD). In all subjects (n = 51), creatinine and TTR (P < 0·05) but not adipose RBP4 mRNA were associated with plasma RBP4. Plasma RBP4 but not its adipose expression was in turn associated positively (P < 0·05) with CRP independently of creatinine-TTR. Conclusions  High plasma RBP4 and inflammation are clustered in CKD in the absence of obesity and diabetes and are normalized by transplantation. Adipose RBP4 expression is not involved in plasma RBP4 elevation, which appears to be mainly because of passive accumulation, or in CKD-associated inflammation.