Glomerular proteomic profiling reveals early differences between preexisting and de novo type 2 diabetes in human renal allografts.

BACKGROUND: Diabetes mellitus (DM), either preexisting or developing after transplantation, remains a crucial clinical problem in kidney transplantation. To obtain insights into the molecular mechanisms underlying PTDM development and early glomerular damage before the development of histologically visible diabetic kidney disease, we comparatively analysed the proteome of histologically normal glomeruli from patients with PTDM and normoglycaemic (NG) transplant recipients. Moreover, to assess specificities inherent in PTDM, we also comparatively evaluated glomerular proteomes from transplant recipients with preexisting type 2 DM (T2DM). METHODS: Protocol biopsies were obtained from adult NG, PTDM and T2DM patients one year after kidney transplantation. Biopsies were formalin-fixed and embedded in paraffin, and glomerular cross-sections were microdissected. A total of 4 NG, 7 PTDM and 6 T2DM kidney biopsies were used for the analysis. The proteome was determined by liquid chromatography-tandem mass spectrometry. Relative differences in protein abundance and significantly dysregulated pathways were analysed. RESULTS: Proteins involved in cell adhesion, immune response, leukocyte transendothelial filtration, and cell localization and organization were less abundant in glomeruli from PTDM patients than in those from NG patients, and proteins associated with supramolecular fibre organization and protein-containing complex binding were more abundant in PTDM patients. Overall, proteins related to adherens and tight junctions and those related to the immune system, including leukocyte transendothelial migration, were more abundant in NG patients than in transplanted patients with DM, irrespective of the timing of its development. However, proteins included in cell‒cell junctions and adhesion, insulin resistance, and vesicle-mediated transport were all less abundant in PTDM patients than in T2DM patients. CONCLUSIONS: The glomerular proteome profile differentiates PTDM from NG and T2DM, suggesting specific pathogenetic mechanisms. Further studies are warranted to validate these results, potentially leading to an improved understanding of PTDM kidney transplant pathophysiology and to the identification of novel biomarkers.

Endothelial function after pancreas transplantation-A single-center observational study.

BACKGROUND: Patients with diabetes mellitus treated with successful pancreas transplantation (PTX) normalize hyperglycemia, but are exposed to immunosuppressive drugs that may impair endothelial function. This study aimed to evaluate endothelial function in single PTX recipients. METHODS: Flow-mediated dilatation (FMD) in the brachial artery was measured by ultrasound 8 weeks after transplantation in single PTX (n = 27) and compared with healthy controls (n = 58), simultaneous pancreas and kidney recipients (n = 9), and kidney transplant recipients with (n = 41) and without (n = 95) diabetes mellitus. Adjustments for age, gender, blood pressure, and body mass index were included in a linear regression model. Changes in FMD from before to 1 year after transplantation were assessed in a subgroup of PTX recipients (n = 9). RESULTS: Flow-mediated dilatation% in PTX recipients was not inferior to healthy controls (8.7 ± 3.6 vs 7.7 ± 3.3, P = .06) and simultaneous pancreas and kidney recipients (6.7 ± 4.5, P = .24) in an adjusted model, and superior to kidney recipients with and without diabetes (3.0 ± 3.0 and 4.8 ± 3.3, respectively, both P < .005). FMD% improved significantly from eight weeks to one year after PTX, mean 7.9 ± 4.2% vs 11.8 ± 4.8% (N = 9; P = .03). CONCLUSION: Flow-mediated dilatation is well preserved in patients undergoing pancreas transplantation and is not impaired when immunosuppressive drugs are introduced.

Validation of diagnostic utility of fasting plasma glucose and HbA1c in stable renal transplant recipients one year after transplantation.

BACKGROUND: The use of HbA1c ≥6.5% for diagnosis of diabetes has been challenged for post-transplantation diabetes mellitus (PTDM) also known as new onset diabetes after transplantation (NODAT) due to a low sensitivity early after renal transplantation. PTDM diagnosed with an oral glucose tolerance test (OGTT) is highly predictable for long-term patient mortality. HbA1c was introduced for diagnosis based on the risk of developing diabetic retinopathy. The utility of HbA1c measures versus glucose criteria has not been widely assessed in stable transplant patients but still HbA1c is widely used in this population. The aim of the present analyses was to validate the utility of fasting plasma glucose (FPG) together with HbA1c in diagnosing PTDM in stable renal transplant recipients (RTRs). METHODS: OGTT's were performed one year after transplantation in 494 consecutive RTRs without diabetes. FPG and HbA1c were obtained the same day, before starting the OGTT. Validation was performed using C-statistics and logistic regression analyses. RESULTS: PTDM was diagnosed in 51 patients (10.3%) by glucose criteria, 38 (74%) patients were diagnosed by FPG ≥7.0 mmol/L [126.1 mg/dl], and 13 (26%) only by 2-h plasma glucose. Six of the latter had HbA1c ≥6.5%. Only seven patients out of the 51 (13.7%) PTDM patients remained undiagnosed when HbA1c ≥6.5% was used together with FPG, and five of these regressed to normal after a median follow-up of 14 months. ROC curves including FPG and HbA1c versus OGTT derived criteria revealed an AUC of 0.858. CONCLUSIONS: Combining standard diagnostic FPG and HbA1c criteria captured almost all patients with persistent PTDM in stable RTRs. The combined use of the criteria appears to be an applicable diagnostic strategy for PTDM without the need of an OGTT one year post-transplant. TRIAL REGISTRATION: Retrospectively registered.

Mortality risk in post-transplantation diabetes mellitus based on glucose and HbA1c diagnostic criteria.

Current diagnostic criteria for post-transplantation diabetes mellitus (PTDM) are either fasting plasma glucose ≥7.0 mmol/l (≥126 mg/dl) or postchallenge plasma glucose ≥11.1 mmol/l (≥200 mg/dl) 2 h after glucose administration [oral glucose tolerance test (OGTT) criterion]. In this retrospective cohort study of 1632 renal transplant recipients (RTRs) without known diabetes mellitus at the time of transplantation, we estimated mortality hazard ratios for patients diagnosed with PTDM by either conventional glucose criteria or the proposed glycated haemoglobin (HbA1c) criterion [HbA1c ≥6.5% (≥48 mmol/mol)]. During a median follow-up of 7.0 years, 311 patients died. Compared with nondiabetic patients and after adjustment for confounders, patients diagnosed with PTDM based on chronic hyperglycaemia early after transplantation (manifest PTDM) or by the OGTT criterion at 10 weeks post-transplant suffered a higher mortality risk (HR 1.59, 95% CI 1.06-2.38, P = 0.02 and HR 1.56, 95% CI 1.04-2.38, P = 0.03, respectively). In contrast, patients diagnosed with PTDM by the HbA1c criterion at 10 weeks or between 10 weeks and 1 year post-transplant were not associated with mortality (HR 0.96, 95% CI 0.61-1.51, P = 0.86 and 1.58, 95% CI 0.74-3.36, P = 0.24 respectively). After adjustment for confounders and competing risks, only patients with manifest PTDM had a significantly higher cardiovascular mortality risk (subdistributional HR 2.31, 95% CI 1.19-4.47, P < 0.001). Since many cases with PTDM were only identified by the OGTT, we recommend monitoring fasting plasma glucose early after renal transplantation followed by an OGTT at 2-3 months post-transplant in patients without overt diabetes mellitus.

Short-term efficacy and safety of sitagliptin treatment in long-term stable renal recipients with new-onset diabetes after transplantation.

BACKGROUND: New-onset diabetes after transplantation (NODAT) is a common complication after renal transplantation. There are limited available oral drugs to treat hyperglycaemia in this population owing to reduced renal function, potential interactions with immunosuppressive drugs and adverse effects such as hypoglycaemic events that may increase the cardiovascular risk. This study was initiated to investigate efficacy and safety of sitagliptin treatment that may represent a novel alternative in renal transplant recipients. METHODS: Nineteen long-term stable renal transplant recipients with NODAT were included in a controlled, cross-over study and randomized to first receive either sitagliptin 50-100 mg/day or a sitagliptin-free period of 4 weeks. Median age (interquartile range, IQR) was 67 (62-72) years (12 males/7 females), all studied 1 (1-3) year after transplantation. The immunosuppressive regimen was a triple calcineurin inhibitor-based therapy. Oral glucose tolerance test (OGTT) with insulin and C-peptide responses and laser Doppler (LD) flowmetry assessment of endothelial function were performed at baseline and after each treatment period. Home measurements of plasma glucose were performed daily during the study. RESULTS: The median (IQR) first- and second-phase insulin secretion responses increased significantly by 56.3% (45.2-112.6%, P = 0.005) and 39.3% (26.5-81.0%, P = 0.006), respectively, following sitagliptin treatment as compared with no sitagliptin treatment. Fasting and 2-h plasma glucose concentrations fell significantly {0.9 mmol/L [0.5-1.7 mmol/L (16.2 mg/dL), P = 0.003] and 2.9 mmol/L [0.5-6.4 mmol/L (52.3 mg/dL), P = 0.004], respectively}, as did also home measurements of plasma glucose. Endothelial function and plasma markers of cardiovascular risk were unaffected. No serious adverse events were observed. Two mild and asymptomatic hypoglycaemic episodes were observed in combination with glipizide. CONCLUSIONS: Sitagliptin increases insulin secretion and reduces fasting and postprandial plasma glucose in renal transplant recipients with NODAT. The short-term treatment was well tolerated, and sitagliptin seems safe in this population.

Uric acid and clinical correlates of endothelial function in kidney transplant recipients.

UNLABELLED: Uric acid is associated with increased mortality in kidney transplant recipients (KTRs), but it is uncertain if this involves endothelial dysfunction. We hypothesized, first, that there was an association between uric acid and endothelial function, and second, that there were associations between endothelial function and cardiac and mortality risk scores. METHODS: One hundred and fifty-two patients were examined 10 wk after kidney transplantation by two measures of endothelial function, the brachial artery flow-mediated dilatation (FMD) expressed as percent dilatation (FMD%), and fingertip peripheral arterial tone (PAT) expressed as log-reactive hyperemia index (LnRHI). Risk scores were calculated from a recently validated formula. Other clinical correlates of endothelial function were described in stepwise linear regression models. RESULTS: Uric acid was associated negatively with FMD% in an age- and gender-adjusted model, while not in the multivariable model. No association was shown between uric acid and LnRHI. FMD% was associated negatively with risk scores in both crude and age- and gender-adjusted models (p < 0.01). LnRHI was associated negatively with risk scores in the latter model only (p < 0.05). CONCLUSIONS: Uric acid was neither associated with FMD% nor LnRHI in KTRs. There were significant associations between endothelial function indices and cardiac and mortality risk scores.

Efficacy and Safety of Empagliflozin in Renal Transplant Recipients With Posttransplant Diabetes Mellitus.

OBJECTIVE: Sodium-glucose cotransporter 2 (SGLT2) inhibitors have lately become the recommended treatment in patients with type 2 diabetes and high cardiovascular risk. Patients with posttransplant diabetes mellitus (PTDM) also have high cardiovascular risk. The aim of this study was to investigate the safety and efficacy of empagliflozin in renal transplant recipients with PTDM. RESEARCH DESIGN AND METHODS: Forty-nine renal transplant recipients were included in an investigator-initiated, single-center, prospective, double-blind study and randomized to receive either 10 mg empagliflozin or placebo once daily for 24 weeks. Patients transplanted >1 year ago, diagnosed with PTDM, with stable renal function (estimated glomerular filtration rate [eGFR] >30 mL/min/1.73 m2), and with stable immunosuppressive therapy were studied. RESULTS: Forty-four renal transplant recipients (22 empagliflozin/22 placebo, 34 males) completed the study. Median (interquartile range) change in glycated hemoglobin (HbA1c) was significantly reduced with empagliflozin compared with placebo: -0.2% (-0.6, -0.1) (-2.0 mmol/mol [-6.5, -1.0]) vs. 0.1% (-0.1, 0.4) (1.0 mmol/mol [-0.75, 3.8]) (P = 0.025). The magnitude of glucose reduction was dependent on GFR and baseline HbA1c. The treatment also resulted in a significant reduction in body weight of -2.5 kg (-4.0, -0.05) compared with an increase of 1.0 kg (0.0, 2.0) in the placebo group (P = 0.014). There were no significant differences between the groups in adverse events, immunosuppressive drug levels, or eGFR. CONCLUSIONS: Empagliflozin appeared safe and improved glycemic control in renal transplant recipients with PTDM compared with placebo. A concomitant reduction in body weight was seen.

Associations Between Posttransplantation Diabetes Mellitus and Renal Graft Survival.

BACKGROUND: Previous reports indicate that posttransplantation diabetes mellitus (PTDM) is associated with overall renal graft loss, but not death-censored graft loss. METHODS: In this single-center retrospective cohort study of 2749 adult Norwegian renal transplant recipients, transplanted between 1999 and 2011, we estimated overall and death-censored renal graft loss hazard ratios in patients diagnosed with PTDM, impaired glucose tolerance and diabetes before transplantation, using multivariable Cox proportional hazard regression analysis. RESULTS: A total of 893 renal grafts were lost during the study period, either due to recipient death (n = 540) or death-censored graft loss (n = 353).When the observational time started at time of transplantation, diabetes before transplantation was associated with both overall and death-censored graft loss. Pretransplantation diabetes was also associated with a steeper decline in renal graft function, a higher risk of acute rejections and more renal grafts lost due to acute rejection.In patients with a functional renal graft 1 year after transplantation, PTDM was associated with overall graft loss (hazard ratio, 1.46; 95% confidence interval, 1.13-1.88; P < 0.001), but not death-censored graft loss (hazard ratio, 1.25; 95% confidence interval, 0.80-1.96; P = 0.33). We found no significant associations between PTDM and change in renal function during the first 5 years or acute rejection risk during the first year after renal transplantation.Impaired glucose tolerance was not associated with either overall or death-censored graft loss. CONCLUSIONS: The present study confirms previous findings of an increased risk of overall but not death-censored renal graft loss in renal transplant recipients with PTDM. Longstanding diabetes might increase the risk of acute rejections.

GLP-1 Restores Altered Insulin and Glucagon Secretion in Posttransplantation Diabetes.

OBJECTIVE: Development of posttransplantation diabetes (PTDM) is characterized by reduced insulin secretion and sensitivity. We aimed to investigate whether hyperglucagonemia could play a role in PTDM and to examine the insulinotropic and glucagonostatic effects of the incretin hormone glucagon-like peptide 1 (GLP-1) during fasting and hyperglycemic conditions, respectively. RESEARCH DESIGN AND METHODS: Renal transplant recipients with (n = 12) and without (n = 12) PTDM underwent two separate experimental days with 3-h intravenous infusions of GLP-1 (0.8 pmol/kg/min) and saline, respectively. After 1 h of infusion, a 2-h hyperglycemic clamp (fasting plasma glucose + 5 mmol/L) was established. Five grams of arginine was given as an intravenous bolus 10 min before termination of the clamp. RESULTS: Fasting concentrations of glucagon (P = 0.92) and insulin (P = 0.23) were similar between the groups. In PTDM patients, glucose-induced glucagon suppression was significantly less pronounced (maximal suppression from baseline: 43 ± 12 vs. 65 ± 12%, P < 0.001), while first- and second-phase insulin secretion were significantly lower. The PTDM group also exhibited a significantly lower insulin response to arginine (P = 0.01) but similar glucagon and proinsulin responses compared with control subjects. In the preclamp phase, GLP-1 lowered fasting plasma glucose to the same extent in both groups but reduced glucagon only in PTDM patients. During hyperglycemic clamp, GLP-1 reduced glucagon concentrations and increased first- and second-phase insulin secretion in both groups. CONCLUSIONS: PTDM is characterized by reduced glucose-induced insulin secretion and attenuated glucagon suppression during a hyperglycemic clamp. Similar to the case in type 2 diabetes, GLP-1 infusion seems to improve (insulin) or even normalize (glucagon) these pathophysiological defects.

Limitations of hemoglobin A1c for the diagnosis of posttransplant diabetes mellitus.

BACKGROUND: Posttransplant diabetes mellitus (PTDM) is usually detected 2 to 3 months after transplantation by fasting plasma glucose (fPG) ≥ 7.0 mmol/L (≥ 126 mg/dL) and/or 2 hr post-challenge plasma glucose ≥ 11.1 mmol/L (≥ 200 mg/dL) during an oral glucose tolerance test (OGTT). Recently, glycosylated hemoglobin (HbA1c) of 6.5% or higher (≥ 47.5 mmol/mol) has been proposed as an alternative diagnostic criterion (the HbA1c criterion). We aimed to assess the sensitivity of applying the HbA1c criterion alone or in combination with a single measurement of fPG of 7.0 mmol/L or higher (≥ 126 mg/dL) at 10 weeks after transplantation as screening tests for the diagnosis of PTDM. METHODS: From 1999 to 2011, measurements of fPG, HbA1c, and OGTT were performed in 1,619 nondiabetic renal transplant recipients. RESULTS: The HbA1c criterion detected 38.0% of patients with PTDM diagnosed with the standard diagnostic criteria. The specificity was 86.3%. When the HbA1c threshold value was lowered to 6.2% (44.3 mmol/mol), sensitivity increased to 57.8% with a corresponding reduced specificity of 80.4%. A combination of the HbA1c criterion and fPG of 7.0 mmol/L or higher (126 mg/dL) at 10 weeks after transplantation improved diagnostic precision with a sensitivity of 77.7% and a specificity of 96.1%. CONCLUSION: The proposed diagnostic HbA1c criterion failed to detect most cases of PTDM, and one of four cases of PTDM was detected by OGTT alone. This indicates that the HbA1c threshold value likely needs to be lowered for renal transplant recipients and supports continued use of OGTT as a diagnostic tool for detection of PTDM.