Effects of Immunosuppressive Agents on Glucose Metabolism: Implications for the Development of Post-Transplant Diabetes Mellitus

New-onset diabetes mellitus after renal transplantation

BACKGROUND AND AIM

Diabetes mellitus is a very common metabolic disease with a rising incidence. It is both a leading cause of chronic renal disease and one of the most serious comorbidities in renal transplant recipients. New-onset diabetes after renal transplantation (NODAT) is associated with poor graft function, higher rates of cardiovascular complications and a poor prognosis. The aim of this paper is to review current knowledge of NODAT including risk factors, diagnosis and management.

METHODS

A MEDLINE search was performed to retrieve both original and review articles addressing the epidemiology, risk factors, screening and management of NODAT. We also focused on microRNAs as potential biomarkers of NODAT.

RESULTS AND CONCLUSION

Understanding the risk factors (both modifiable-e.g. obesity, viruses, and unmodifiable-e.g. age, genetics) may help reduce the incidence and impact of NODAT using pre- and post-transplant management. This can lead to better long-term graft function and general transplant success.

New-onset diabetes after transplantation in tacrolimus-treated, living kidney transplantation: long-term impact and utility of the pre-transplant OGTT

Background

To evaluate the role of the oral glucose tolerance test (OGTT) before transplantation and to examine the risk factors for new-onset diabetes after transplantation (NODAT) during long-term follow-up of renal transplant recipients receiving FK-based therapy.

Methods

The study evaluated 378 patients pre-transplantation using the OGTT and assigned them to one of three groups: Group 1, normal pattern; Group 2, impaired fasting glucose (IFG)/impaired glucose tolerance (IGT) pattern (IFG/IGT); and Group 3, DM pattern.

Results

Although the incidence of NODAT was higher in Group 3 than in groups 1 and 2, no significant difference was found between the three groups with regard to graft survival during long-term follow-up. Multivariate analysis showed that only a family history of diabetes was a significant factor determining NODAT progression.

Conclusions

Impaired glucose tolerance appears to be a threshold influencing NODAT; however, it was not a significant factor in graft survival. Careful monitoring and management based on the result of the pre-transplantation OGTT appear to prevent the deterioration of impaired glucose tolerance in renal transplant recipients receiving FK-based therapy, even when a pre-operative OGTT shows impaired glycemic control.

New-onset diabetes after transplantation

New-onset diabetes after transplantation is a serious complication of organ transplantation that is becoming increasingly more common. New-onset diabetes after transplantation has implications for graft and patient survival. This article reviews the pathogenesis, diagnosis and management of new-onset diabetes after transplantation.

Alterations in glucose metabolism associated with liver cirrhosis persist in the clinically stable long-term course after liver transplantation

With increasing long-term survival rates after orthotopic liver transplantation (OLT), metabolic alterations complicating the clinical course, such as diabetes mellitus (DM), become increasingly important. Liver cirrhosis is associated with severe alterations in glucose metabolism. However, it is currently unclear whether these changes are reversed by successful OLT. We therefore characterized glucose metabolism in patients with liver cirrhosis and normal fasting glucose levels before OLT (cir), in the clinically stable long-term course after OLT (OLT), and control subjects (con) using oral glucose tolerance tests (cir = 100, OLT = 62, con = 32), euglycemic-hyperinsulinemic clamps (cir = 10, OLT = 27, con = 14), and positron emission tomography (PET) scan analysis with 18F-fluorodeoxyglucose (FDG) as a tracer (cir = 7, OLT = 7, con = 5). Fasting insulin and C-peptide levels were significantly elevated in patients with liver cirrhosis compared with both control subjects (P <.001) and patients after OLT (P <.001). After OLT, insulin was normalized, whereas C-peptide remained elevated (P < 0.01). In the patients with liver cirrhosis, 27% had a normal glucose tolerance, 38% had an impaired glucose tolerance (IGT), and 35% were diabetic. After OLT, 34% had a normal glucose tolerance, 29% an IGT, and 37% were diabetic. Comparison of the same patients before and after OLT demonstrated that IGT or diabetes before OLT was the major risk factor for these conditions after OLT, which was independent of either immunosuppression (cyclosporine vs FK506) or low-dose prednisolone. Total glucose uptake was reduced in patients with liver cirrhosis to less than half the values in control subjects (21.2 +/- 2.8 vs 43.7 +/- 2.4 micromol/kg/minute, respectively, P <.001), whereas patients after OLT showed intermediate values (35.7 +/- 1.4 micromol/kg/minute, P < 0.05 vs con, P < 0.01 vs cir). This difference was caused by a reduction in nonoxidative glucose metabolism in patients with liver cirrhosis compared with control subjects (7.4 +/- 1.9 vs 28.7 +/- 1.8 micromol/kg/minute, respectively, P <.01) and patients after OLT (20.1 +/- 1.4 micromol/kg/minute, P < 0.05 vs con and OLT). In the PET study, skeletal muscle glucose uptake was significantly reduced in patients with liver cirrhosis compared with control subjects (3.5 +/- 0.4 vs 11.8 +/- 2.5 micromol/100g/minute, respectively, P <.05). After OLT, muscle glucose uptake improved compared with patients with liver cirrhosis (5.9 +/- 1.0 micromol/100g/minute, P <.05) but remained significantly lower than in control subjects (P <.05). In conclusion, these results demonstrate that preexisting IGT or diabetes are the major risk factors for IGT and diabetes after OLT. This finding was independent of the immunosuppressive medication. The peripheral insulin resistance in cirrhosis is characterized by a decrease in nonoxidative glucose disposal that is improved, but not normalized, after OLT.

Diabetes mellitus in transplantation: 2002 consensus guidelines

Diabetes mellitus is a serious complication following organ transplantation that is underdiagnosed, possibly due to the inadequate definitions used in published literature and the lack of standardized screening. Diabetes in transplantation amplifies the already increased risk of cardiovascular disease among transplant patients, and increases the risk of graft loss and death. Patients at risk of developing diabetes in transplantation should therefore be prospectively identified and given individualized immunosuppressive therapy to minimize the risk of developing this disease. These guidelines are intended to: (1) help identify patients at risk for diabetes after transplantation; (2) set down a standard definition of posttransplant diabetes mellitus (PTDM); (3) create a standard monitoring protocol for the diagnosis of PTDM; and (4) optimize the management of patients at risk of developing or who develop diabetes after transplantation. With improved diagnosis, individualization of therapy, and proper early management, the incidence of diabetes in transplantation, and the accompanying additional burden of illness the disease carries, may be diminished. In turn, this will help achieve the therapeutic goals of reducing the risk of graft complications, improving quality of life, and reducing postoperative morbidity and mortality in transplant patients.

Insulin resistance as putative cause of chronic renal transplant dysfunction

Transplantation is the preferred organ replacement therapy for most patients with end-stage renal disease. Despite impressive improvements over recent years in the treatment of acute rejection, approximately half of all grafts will loose function within 10 years after transplantation. Chronic renal transplant dysfunction, also known as transplant atherosclerosis, is a leading cause of late allograft loss. To date, no specific treatment for chronic renal transplant dysfunction is available. Although its precise pathophysiology remains unknown, it is believed that it involves a multifactorial process of alloantigen-dependent and alloantigen-independent risk factors. Obesity, posttransplant diabetes mellitus, dyslipidemia, hypertension, and proteinuria have all been identified as alloantigen-independent risk factors. Notably, these recipient-related risk factors are well-known risk factors for cardiovascular disease, which cluster within the insulin resistance syndrome in the general population. Insulin resistance is considered the central pathophysiologic feature of this syndrome. It is therefore tempting to speculate that it is insulin resistance that underlies the recipient-related risk factors for chronic renal transplant dysfunction. Recognition of insulin resistance as a central feature underlying many, if not all, recipient-related risk factors would not only improve our understanding of the pathophysiology of chronic renal transplant dysfunction, but also stimulate development of new treatment and prevention strategies.

A late episode of post-transplant diabetes mellitus during active hepatitis C infection in a renal allograft recipient using tacrolimus

BACKGROUND

An association between hepatitis C virus and (post-transplant) diabetes mellitus has been reported.

METHODS

We report a patient on tacrolimus-based immunosuppression who developed an episode of post-transplant diabetes mellitus (PTDM) 2 years after renal transplantation, after contracting a hepatitis C infection. Her glucose metabolism was evaluated regularly by intravenous glucose tolerance tests before and after the PTDM episode.

RESULTS

Before contracting hepatitis C, the patient's insulin resistance and insulin secretion were normal. After contracting hepatitis C, tacrolimus exposure increased, insulin resistance increased, and insulin secretion decreased markedly. Despite low tacrolimus exposure in the last 4 years, glucose metabolism did not recover completely. Although PTDM resolved and insulin resistance normalized, pancreatic beta cell secretion remained impaired by approximately 50% compared with the period before hepatitis C infection.

CONCLUSION

After an initial increase in insulin resistance, insulin secretion decreased markedly in a patient who contracted hepatitis C 12 to 22 months after renal transplantation. This change resulted in an episode of PTDM. Increased tacrolimus exposure secondary to reduced cytochrome P-450 metabolism as a result of impaired hepatocellular function at the time of the development of PTDM seems a likely explanation for the marked decrease in insulin secretion. Viral toxicity to the beta cell might be an additional explanation. The latter might be suspected from several reports about an association between diabetes mellitus and hepatitis C in patients who do not use drugs that interfere with glucose metabolism.

Glucose metabolism in renal transplant recipients on tacrolimus: the effect of steroid withdrawal and tacrolimus trough level reduction

The relative role of steroids and tacrolimus in the development of glucose metabolic disorders and hyperlipidemia after renal transplantation has not yet been clearly established. Therefore, glucose metabolism was prospectively evaluated by intravenous glucose tolerance test, as was lipid profile, in fifteen white nondiabetic renal transplant recipients three times: before and after steroid withdrawal and after tacrolimus trough level reduction. After withdrawal of 10 mg of prednisolone, insulin resistance decreased (fasting C-peptide, 0.99 to 0.77 nmol/L [P < 0.0009]; fasting insulin, 9.5 to 8.1 mU/L [P = 0.09]; insulin/glucose ratio, 1.85 to 1.45 mU/mmol [P = 0.10]) and lipid levels decreased (total cholesterol, 5.1 to 4.2 mmol/L [P = 0.006]); HDL cholesterol, 1.4 to 1.1 mmol/L [P = 0.01]; LDL cholesterol, 3.0 to 2.5 mmol/L [P = 0.15]; triglycerides, 1.52 to 0.91 mmol/L [P = 0.02]). After tacrolimus trough level reduction from 9.5 to 6.4 ng/ml, pancreatic beta-cell secretion capacity improved (C-peptide secretion increased from 49.0 to 66.6 nmol x min/L [P = 0.04] and insulin secretion increased from 1134 to 1403 mU x min/L [P = 0.06]). HbA1c improved also, from 5.9 to 5.3% (P = 0.002). Lipids did not change. In conclusion, steroid withdrawal resulted in a decrease in insulin resistance and a reduction in lipids, and tacrolimus trough level reduction resulted in an improved pancreatic beta-cell secretion capacity. Therefore, these therapeutic measurements may contribute to the reduction of the cardiovascular morbidity and mortality in renal transplant recipients.

Glucose metabolism in the first 3 years after renal transplantation in patients receiving tacrolimus versus cyclosporine-based immunosuppression

The long-term effects of tacrolimus and cyclosporine on pancreatic islet cell function in renal transplant recipients are unclear. Therefore, a prospective, randomized, longitudinal study was performed that compared glucose metabolism in adult kidney allograft recipients on tacrolimus versus cyclosporine-based immunosuppression. Twenty-three white renal allograft recipients, randomized for either therapy with cyclosporine or tacrolimus, underwent intravenous glucose tolerance tests 6 times during the first 3 yr after transplantation. Concomitant therapy (low-dose steroids and azathioprine) was the same in both groups. Insulin sensitivity index (kG), insulin resistance (insulin/glucose ratio and homeostasis model assessment), and C-peptide and insulin secretion were calculated. Trough levels of tacrolimus and cyclosporine were measured. The occurrence of posttransplantation diabetes mellitus was prospectively monitored. Statistical analysis was performed by ANOVA for repeated measures, and parametric and nonparametric tests were also performed. Although only one patient treated with cyclosporine developed posttransplantation diabetes mellitus, kG levels were below normal in up to one-third of both patients who received tacrolimus and cyclosporine. The only significant difference between patients who received tacrolimus and those who received cyclosporine was in pancreatic secretion capacity at week 3 after transplantation, when the increment of C-peptide secretion was 57% lower and the increment of insulin secretion was 48% lower for patients receiving tacrolimus. In both groups, from week 3 to month 6, there was a tendency toward an increase in kG, despite a significant increase in fasting glucose and insulin resistance calculated by homeostasis model assessment. After month 6, there were no significant changes in any of the parameters of glucose metabolism, indicating that long-term use of either tacrolimus or cyclosporine does not cause chronic, cumulative pancreatic toxicity.

Influence of tacrolimus on glucose metabolism before and after renal transplantation: a prospective study

Most studies concerning the influence of tacrolimus on glucose metabolism have been performed either in animals or after organ transplantation. These clinical studies have largely been transversal with patients who were using steroids. Therefore, this prospective, longitudinal study investigated the influence of tacrolimus on glucose metabolism before and after transplantation. Eighteen Caucasian dialysis patients underwent an intravenous glucose tolerance test before and 5 d after the start of tacrolimus. Insulin sensitivity index (k(G)), insulin resistance (insulin/glucose ratio and homeostasis model assessment), and C-peptide and insulin secretion were calculated. Trough levels of tacrolimus were measured. After transplantation, the occurrence of posttransplantation diabetes mellitus (PTDM) was prospectively monitored. Statistical analysis was performed using the Wilcoxon signed ranks test and Spearman's rho for correlation. Before tacrolimus, k(G) was indeterminate in three patients. During tacrolimus, k(G) decreased in 16 of 18 patients, from a median of 1.74 mmol/L per min to 1.08 mmol/L per min (P<0.0001). The correlation between C-peptide and insulin data was excellent. Insulin secretion decreased from 851.0 mU x min/L to 558.0 mU x min/L (P = 0.014), whereas insulin resistance did not change. Insulin sensitivity correlated negatively with tacrolimus trough level. After transplantation, three patients developed PTDM; before tacrolimus, two had an indeterminate and one a low normal k(G). During tacrolimus administration, k(G) decreased in almost all patients as a result of a diminished insulin secretion response to a glucose load, whereas insulin resistance did not change. Patients with an abnormal or indeterminate k(G) seem to be at risk of developing PTDM while on tacrolimus.

Racial differences in renal transplantation after immunosuppression with tacrolimus versus cyclosporine. FK506 Kidney Transplant Study Group

BACKGROUND

Results of a multicenter, randomized, clinical trial demonstrated that tacrolimus was more effective than cyclosporine in preventing acute rejection in cadaveric renal transplant patients. As African-Americans comprised approximately 25% of the study population, their outcome was analyzed relative to the experience of Caucasian patients.

METHODS

Of the 205 patients randomized to tacrolimus, 56 (27.3%) were African-American and 114 (55.6%) were Caucasian. Of the 207 patients randomized to cyclosporine, 48 (23.2%) were African-American and 123 (59.4%) were Caucasian. The efficacy variables were 1-year patient survival, graft survival, and incidence of acute rejection.

RESULTS

The incidence of acute rejection was significantly lower in African-American and Caucasian patients treated with tacrolimus than with cyclosporine. Additionally, no African-American patient who was treated with tacrolimus experienced moderate or severe acute rejection, as determined by blinded independent review. The incidence of nephrotoxicity, cardiovascular and gastrointestinal events, malignancies, and opportunistic infections was similar between treatments and race groups. However, there was an increased incidence of posttransplant diabetes mellitus in tacrolimus-treated patients, particularly in African-Americans, and tacrolimus was associated with significantly lower lipid levels in both Caucasians and African-Americans. African-American patients required a 37% mean higher dose of tacrolimus than Caucasian patients to achieve comparable blood concentrations.

CONCLUSIONS

Tacrolimus is more effective than cyclosporine in preventing acute rejection in both African-American and Caucasian patients. However, tacrolimus was associated with an increased risk of posttransplant diabetes mellitus, particularly in African-Americans, which was reversible in some patients.

Primary immunosuppression with tacrolimus and mycophenolate mofetil for renal allograft recipients

BACKGROUND

Studies using tacrolimus and corticosteroids or the combination of cyclosporine, mycophenolate mofetil, and corticosteroids have been shown to reduce the incidence of biopsy-proven acute rejection episodes in cadaveric kidney recipients compared with cyclosporine-based immunosuppression. The current study is a retrospective analysis of our experience with tacrolimus combined with mycophenolate mofetil and steroids as primary immunosuppression for kidney transplant recipients.

METHODS

In a retrospective analysis, 72 patients who received primary therapy with tacrolimus, mycophenolate mofetil, and corticosteroids (triple therapy) were compared with a control group of 98 kidney recipients who received tacrolimus and corticosteroids (double therapy).

RESULTS

There was a significant reduction in the incidence of biopsy-confirmed acute rejection in the triple therapy group (8.2%) compared with the double therapy group (21%; P=0.003). One-year patient and graft survival did not differ between groups. The incidence of posttransplant diabetes mellitus was 18% and 21% in the triple and double therapy groups, respectively. Leukopenia and gastrointestinal side effects were the most common cause for discontinuation of mycophenolate mofetil.

CONCLUSIONS

The combination of tacrolimus with mycophenolate mofetil and corticosteroids is more effective at preventing early acute rejection than tacrolimus and corticosteroids alone. The use of mycophenolate mofetil was associated with a higher incidence of leukopenia and diarrhea, often leading to discontinuation of the drug.

A comparison of tacrolimus (FK506) and cyclosporine for immunosuppression after cadaveric renal transplantation. FK506 Kidney Transplant Study Group

BACKGROUND

Tacrolimus (FK506), a macrolide molecule that potently inhibits the expression of interleukin 2 by T lymphocytes, represents a potential major advance in the management of rejection following solid-organ transplantation. This randomized, open-label study compared the efficacy and safety of tacrolimus-based versus cyclosporine-based immunosuppression in patients receiving cadaveric kidney transplants.

METHODS

A total of 412 patients were randomized to tacrolimus (n=205) or cyclosporine (n=207) after cadaveric renal transplantation and were followed for 1 year for patient and graft survival and the incidence of acute rejection.

RESULTS

One-year patient survival rates were 95.6% for tacrolimus and 96.6% for cyclosporine (P=0.576). Corresponding 1-year graft survival rates were 91.2% and 87.9% (P=0.289). There was a significant reduction in the incidence of biopsy-confirmed acute rejection in the tacrolimus group (30.7%) compared with the cyclosporine group (46.4%, P=0.001), which was confirmed by blinded review, and in the use of antilymphocyte therapy for rejection (10.7% and 25.1%, respectively; P<0.001). Impaired renal function, gastrointestinal disorders, and neurological complications were commonly reported in both treatment groups, but tremor and paresthesia were more frequent in the tacrolimus group. The incidence of posttransplant diabetes mellitus was 19.9% in the tacrolimus group and 4.0% in the cyclosporine group (P<0.001), and was reversible in some patients.

CONCLUSIONS

Tacrolimus is more effective than cyclosporine in preventing acute rejection in cadaveric renal allograft recipients, and significantly reduces the use of antilymphocyte antibody preparations. Tacrolimus was associated with a higher incidence of neurologic events, which were rarely treatment limiting, and with posttransplant diabetes mellitus, which was reversible in some patients.