Clinical predictors of proteinuria after conversion to sirolimus in kidney transplant recipients

Proteinuria following sirolimus conversion is associated with deterioration of kidney function in liver transplant recipients

BACKGROUND

The role of sirolimus (SRL) conversion in the preservation of kidney function in liver transplant (LT) recipients with calcineurin inhibitor (CNI) nephrotoxicity is unclear.

METHODS

Data on 102 LT recipients with deteriorating kidney function after CNI exposure who were later converted to SRL were retrospectively reviewed. Kidney function was assessed using serum creatinine and estimated glomerular filtration rate (eGFR) at time of conversion and serially thereafter. The primary endpoint was stabilization or improvement of kidney function as assessed by eGFR at last recorded follow-up compared with eGFR at the time of conversion.

RESULT

After a median (interquartile range) of 3.1 (1.6-4.5) years of follow-up, serum creatinine decreased from 1.9 ± 0.8 to 1.8 ± 0.7 mg/dL (P=0.25) and eGFR increased from 40.8 ± 16.7 to 44.3 ± 20.0 mL/min (P=0.03). During the same time period, 24-hr urinary protein excretion increased from median (interquartile range) of 72 (0-155) to 382 (169-999) mg/day (P=0.0001). Sixty-five (64%) patients achieved the primary endpoint and 37 (36%) experienced deterioration in kidney function. Independent predictors of deterioration of kidney function after SRL conversion were development of proteinuria ≥ 1000 mg/day (odds ratio [OR]: 3.3, confidence interval [CI]: 1.1-9.5 P=0.03), post-LT diabetes (OR: 4.2, CI: 1.6-11.1, P=0.004), and higher eGFR at time of conversion (OR: 1.6, CI: 1.2-2.2, P=0.003).

CONCLUSION

Improvement or stabilization of kidney function occurred in the majority of LT recipients converted to SRL for CNI nephrotoxicity. Proteinuria ≥ 1000 mg/day, post-LT diabetes, and higher baseline eGFR were independent predictors of kidney function loss after SRL conversion.

Steroid or tacrolimus withdrawal in renal transplant recipients using sirolimus

BACKGROUND

Calcineurin inhibitor (CNI) and steroid (ST) withdrawal are strategies under investigation to reduce long-term toxicities associated with current immunosuppressive regimens. We conducted a single center, prospective trial comparing the efficacy and safety of CNI or ST withdrawal in kidney transplant recipients receiving sirolimus-based immunosuppressive regimen.

METHODS

Forty-seven recipients of first renal transplant with non-HLA-identical living donors received sirolimus (SRL), tacrolimus (TAC), and ST without induction therapy and were randomized to undergo ST (TAC/SRL group, n = 24) or TAC (SRL/ST group, n = 21) withdrawal 3 months after transplantation. Primary efficacy and safety endpoints were the incidence of biopsy-confirmed acute rejection (BCAR) and renal function at 12 months.

RESULTS

No differences were observed in the incidence of BCAR (4.2% vs. 9.5%), graft (95.8% vs. 95.6%), and patient (95.8% vs. 95.6%) survivals or in renal function (60 ± 11.5 vs. 63.4 ± 10.5 ml/min, P = 0.361). Higher mean cholesterol concentration was observed in the SRL/ST group (191.9 ± 63.3 vs. 241.6 ± 61.5 mg/dl, P = 0.019). Treatment discontinuation due to adverse events occurred in 12.5% of patients in TAC/SRL group and 21.7% in SRL/ST group.

CONCLUSION

Within this short period of observation, our study was unable to detect any significant difference in major transplant outcomes comparing CNI and ST elimination strategies.

Low-dose sirolimus combined with angiotensin-converting enzyme inhibitor and statin stabilizes renal function and reduces glomerular proliferation in poor prognosis IgA nephropathy

BACKGROUND

There is a lack of new therapeutic strategies for IgA nephropathy. Low-dose sirolimus inhibits mesangial cell proliferation and renal fibrosis in animal models.

METHODS

We performed a pilot, randomized controlled trial to evaluate the efficacy and safety of low-dose sirolimus in patients with a high-risk IgA nephropathy. Twenty-three patients with a glomerular filtration rate (GFR) within 30-60 mL/min and/or proteinuria >1 g/day were randomly assigned to low-dose sirolimus plus enalapril and atorvastatin (SRL group, n = 14) or enalapril plus atorvastatin (CONTROL group, n = 9). Primary composite end point was variation of haematuria, proteinuria and blood pressure. Secondary end points were isotopic GFR, renal histology evaluated by Oxford classification and safety parameters evaluated at 6 and 12 months.

RESULTS

Primary end point improved significantly in the SRL group at 12 months. Regarding isotopic GFR, patients included in the CONTROL group lost 8 mL/min/1.73 m(2), whereas those in the SRL arm improved 5 mL/min/1.73 m(2) (P = 0.03). Proteinuria decreased similarly in both study groups. At 1 year, SRL treatment was associated with a significant reduction of mesangial and endocapillary proliferation, whereas glomerular sclerosis, tubular atrophy and interstitial fibrosis were similar. Sirolimus was well tolerated; all patients remained on therapy at 12 months.

CONCLUSION

The addition of low-dose sirolimus to enalapril and statin is safe, stabilizes renal function and reduces glomerular proliferative lesions in patients with poor prognosis IgA nephropathy.

The podocyte as a direct target of immunosuppressive agents

Podocytes play a key role in maintaining the blood-urine barrier for high-molecular-weight proteins. They are considered to be terminally differentiated, and podocyte loss cannot be compensated by regenerative proliferation. Various diseases leading to podocyte damage and loss result in proteinuria and cause nephrotic syndrome. Therefore, direct therapeutical strategies to protect podocytes in disease situations are a logical concept to prevent disease or to delay disease progression. Acquired podocytopathies like idiopathic focal segmental glomerulosclerosis and minimal change disease are historically considered as immunological diseases. Therefore, immunosuppressive agents such as steroids and calcineurin inhibitors are the commonly used treatment strategies. However, the causative disease mechanisms behind these treatment strategies remain elusive. Recent evidence shows that immunosuppressive agents, in addition to the effect on the immune system, directly influence the unique structure and function of podocytes. In this context, the actin cytoskeleton of the podocyte and cytokines such as vascular endothelial growth factor play a pivotal role. In this review, we summarize the direct effects on podocytes obtained in vivo and in vitro after treatment with calcineurin inhibitors, mTOR inhibitors and glucocorticoids. These direct effects could play a key role in the treatment concepts of podocytopathies with an important impact on the long-term renal function in patients with pharmacological immunosuppression.