Serum ß2-Microglobulin Predicts Time to Recovery of Delayed Graft Function in Kidney Transplant Recipients.

BACKGROUND: Delayed graft function (DGF) after kidney transplantation is associated with adverse patients and allograft outcomes. A longer duration of DGF is predictive of worse graft outcomes compared to a shorter duration. Posttransplant serum ß2-microglobulin (B2M) is associated with long-term graft outcomes, but its relationship with DGF recovery is unknown. METHODS: We included all kidney-only transplant recipients with DGF enrolled in the E-DGF trial. Duration of DGF was defined as the interval between the transplant and the last dialysis session. We analyzed the association of standardized serum creatinine (Scr) and B2M on postoperative Days (POD) 1-7 during the subsequent days of DGF with the recovery of DGF. RESULTS: A total of 97 recipients with DGF were included. The mean duration of DGF was 11.0 ± 11.2 days. Higher Scr was not associated with the duration of DGF in unadjusted or adjusted models. Higher standardized B2M, in contrast, was associated with a prolonged duration of DGF. This association remained in models adjusting for baseline characteristics from POD 2 (3.19 days longer, 95% CI: 0.46-5.93; p = 0.02) through Day 6 of DGF (4.97 days longer, 95% CI: 0.75-9.20; p = 0.02). There was minimal change in mean Scr (0.01 ± 0. 10 mg/dL per day; p = 0.32), while B2M significantly decreased as the time to recovery approached (-0.14 ± 0.05 mg/L per day; p = 0.006), among recipients with DGF. CONCLUSION: B2M is more strongly associated with DGF recovery than Scr. Posttransplant B2M may be an important biomarker to monitor during DGF. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03864926.

Effects of overhydration, Kt/Vurea, ß2-microglobulin on coronary artery calcification and mortality in haemodialysis patients.

AIM: We studied the effects of overhydration (OH), Kt/Vurea and ß2-microglobulin (ß2-MG) on coronary artery calcification and mortality in patients undergoing haemodialysis (HD). METHODS: The Agatston coronary artery calcium score (CACS), postdialysis body composition using bioimpedance analysis, single-pool Kt/Vurea and predialysis ß2-MG at baseline were assessed and followed up for 3 years in patients undergoing HD. We performed logistic regression analyses for a CACS ≥400 and Cox proportional hazard analyses for all-cause and cardiovascular mortality. RESULTS: The study involved 338 patients with a median age of 67 (56-74) years, dialysis duration of 70 (33-141) months and diabetes prevalence of 39.1% (132/338). Patients with a CACS ≥400 (n = 222) had significantly higher age, dialysis duration, male prevalence, diabetes prevalence, C-reactive protein, predialysis ß2-MG, OH, extracellular water/total body water and overhydration/extracellular water (OH/ECW) but significantly lower Kt/Vurea than patients with a CACS <400 (n = 116) (p < .05). OH/ECW, Kt/Vurea and predialysis ß2-MG were significant predictors of a CACS ≥400 (p < .05) after adjusting for age, dialysis duration, serum phosphate and magnesium. In all patients, cut-off values of OH/ECW, Kt/Vurea and predialysis ß2-MG for a CACS ≥400 were 16%, 1.74 and 28 mg/L, respectively. After adjusting for dialysis duration, OH/ECW ≥16%, Kt/Vurea ≥1.74 and ß2-MG ≥28 mg/L were significant predictors of 3-year all-cause mortality but not 3-year cardiovascular mortality. CONCLUSION: Higher OH/ECW, higher predialysis ß2-MG and lower Kt/Vurea values are significant risk factors for a CACS ≥400 and 3-year all-cause mortality in patients undergoing maintenance HD.

Human wild-type and D76N ß2-microglobulin variants are significant proteotoxic and metabolic stressors for transgenic C. elegans.

ß2-microglobulin (ß2-m) is a plasma protein derived from physiological shedding of the class I major histocompatibility complex (MHCI), causing human systemic amyloidosis either due to persistently high concentrations of the wild-type (WT) protein in hemodialyzed patients, or in presence of mutations, such as D76N ß2-m, which favor protein deposition in the adulthood, despite normal plasma levels. Here we describe a new transgenic Caenorhabditis elegans (C. elegans) strain expressing human WT ß2-m at high concentrations, mimicking the condition that underlies dialysis-related amyloidosis (DRA) and we compare it to a previously established strain expressing the highly amyloidogenic D76N ß2-m at lower concentrations. Both strains exhibit behavioral defects, the severity of which correlates with ß2-m levels rather than with the presence of mutations, being more pronounced in WT ß2-m worms. ß2-m expression also has a deep impact on the nematodes' proteomic and metabolic profiles. Most significantly affected processes include protein degradation and stress response, amino acids metabolism, and bioenergetics. Molecular alterations are more pronounced in worms expressing WT ß2-m at high concentration compared to D76N ß2-m worms. Altogether, these data show that ß2-m is a proteotoxic protein in vivo also in its wild-type form, and that concentration plays a key role in modulating pathogenicity. Our transgenic nematodes recapitulate the distinctive features subtending DRA compared to hereditary ß2-m amyloidosis (high levels of non-mutated ß2-m vs. normal levels of variant ß2-m) and provide important clues on the molecular bases of these human diseases.

ß2-microglobulin, cystatin C, and creatinine and risk of symptomatic peripheral artery disease.

BACKGROUND: ß2-Microglobulin and cystatin C may have advantages over creatinine in assessing risk associated with kidney function. We therefore investigated whether emerging filtration markers, ß2-microglobulin and cystatin C, are prospectively associated with risk of the development of peripheral artery disease (PAD). METHODS AND RESULTS: We conducted nested case-control studies among women within the Nurses' Health Study (1990-2010) and among men within the Health Professionals Follow-up Study (1994-2008) with the use of archived blood samples collected before PAD diagnosis. During follow-up, symptomatic PAD was confirmed in 144 women and 143 men. Controls were matched 3:1 based on age, race, smoking status, fasting status, and date of blood sampling. Conditional logistic regression models were used to estimate relative risks (RRs) and were adjusted for plasma creatinine and cardiovascular risk factors. In women, the RRs (95% CI) per 1-SD) increment were 1.16 (0.85 to 1.58) for ß2-microglobulin and 0.94 (0.69 to 1.28) for cystatin C. Corresponding RRs in men were 1.50 (1.08 to 2.09) for ß2-microglobulin and 1.54 (1.07 to 2.22) for cystatin C. There was no association between creatinine and PAD risk in women, whereas the association in men (RR 1.41, 95% CI 1.10 to 1.81) disappeared after adjustment for either ß2-microglobulin or cystatin C. In pooled analyses of men and women, only ß2-microglobulin was associated with PAD risk (RR 1.31, 95% CI 1.04 to 1.64). CONCLUSIONS: In pooled analyses, ß2-microglobulin was associated with an increased risk of symptomatic PAD; a similar association with cystatin C was observed only in men. The findings suggest that ß2-microglobulin may capture the atherosclerosis-promoting or atherosclerosis-related elements of kidney dysfunction better than creatinine.

The impact of renal tubular damage, as assessed by urinary ß2-microglobulin-creatinine ratio, on cardiac prognosis in patients with chronic heart failure.

BACKGROUND: Renal dysfunction was reported to be closely associated with clinical outcomes in patients with chronic heart failure (CHF). Renal tubulointerstitial damage has been shown to be an important factor in the development of renal dysfunction as well as glomerular damage. However, the impact of renal tubular damage on clinical outcomes in patients with CHF remains to be determined. METHODS AND RESULTS: Urinary ß2-microglobulin-creatinine ratio was measured in 315 patients with CHF. Renal tubular damage was defined as a urinary ß2-microglobulin-creatinine ratio ≥ 300 µg/g, as previously reported. Patients were prospectively followed up for a median period of 1097 days. There were 91 cardiac events, including 16 cardiac deaths and 75 rehospitalizations for worsening heart failure. Log10 urinary ß2-microglobulin-creatinine ratio was increased with worsening New York Heart Association functional class. Multivariate analysis revealed that renal tubular damage was an independent predictor of cardiac events. Kaplan-Meier analysis demonstrated that the rate of cardiac events was higher in patients with renal tubular damage compared with those without it. Patients were divided into 4 groups according to the presence of chronic kidney disease and renal tubular damage. The Cox proportional hazard analysis revealed that comorbidity of chronic kidney disease and renal tubular damage was associated with the highest risk for cardiac events compared with other groups. CONCLUSIONS: Renal tubular damage was related to the severity of heart failure and was associated with poor outcomes in patients with CHF. Renal tubular damage could add clinical information to chronic kidney disease in patients with CHF.