The effect of renal transplantation on adiponectin, its isoforms and receptors
Background: Pro-atherogenic risk factors, including insulin resistance (IR) associated with uraemia are improved by transplantation. Adiponectin is a protein with insulin-sensitising, anti-inflammatory and anti-atherogenic properties. It exists in several isoforms but the high molecular weight (HMW) isoform correlates best with insulin sensitivity. Paradoxically, the levels of this protein and its HMW isoform are increased in ESKD. We examined the changes which occur in IR, adiponectin, its isoforms and receptors following transplantation.
Methods: We compared 34 patients on haemodialysis with 34 matched controls and 34 transplant recipients in terms of anthropometric data, HOMA-R, adiponectin and its isoforms, and adiponectin receptors (AdipoR1 and AdipoR2) mRNA on peripheral blood mononuclear cells (PBMC).
Results: HOMA-R values in ESKD were significantly higher in ESKD patients compared to controls (p<0.001) but there was no difference between controls and transplanted patients. Adiponectin levels were also higher in ESKD patients compared to controls (p=0.02) but decreased to normal following transplantation. However the proportion (p<0.01) and amount (p=0.01) of the HMW isoform in transplant patients remained elevated relative to controls. The total but not the proportion of the HMW isoform correlated with HOMA-R in all 3 cohorts. AdipoR1 levels following transplantation were significantly lower than those of control and ESKD subjects (p<0.01 for both). AdipoR1 mRNA correlated with AdipoR2 in all 3 cohorts.
Conclusion: IR improves significantly post-transplantation and this correlates with a decrease in adiponectin, the amount of its HMW isoform and AdipoR1 on PBMCs. The decrease in AdipoR1 post transplantation may be secondary to immunosuppression.