Impact of immunosuppressive regimes on posttransplant diabetes mellitus

Therapeutic potential of coenzyme Q10 in mitochondrial dysfunction during tacrolimus-induced beta cell injury

We previously reported that oxidative stress induced by long-term tacrolimus treatment impairs mitochondrial function in pancreatic beta cells. In this study, we aimed to investigate the therapeutic potential of coenzyme Q₁₀, which is known to be a powerful antioxidant, in mitochondrial dysfunction in tacrolimus-induced diabetic rats. In a rat model of tacrolimus-induced diabetes mellitus, coenzyme Q₁₀ treatment improved pancreatic beta cell function. The administration of coenzyme Q₁₀ improved insulin immunoreactivity within islets, which was accompanied by reductions in oxidative stress and apoptosis. Assessment of the mitochondrial ultrastructure by electron microscopy revealed that coenzyme Q₁₀ treatment increased the size, number, and volume of mitochondria, as well as the number of insulin granules compared with that induced by tacrolimus treatment alone. An in vitro study using a pancreatic beta cell line showed that tacrolimus treatment increased apoptosis and the production of mitochondrial reactive oxygen species, while cotreatment with coenzyme Q₁₀ effectively attenuated these alterations. At the subcellular level, tacrolimus-induced impairment of mitochondrial respiration was significantly improved by coenzyme Q₁₀, as evidenced by the increased mitochondrial oxygen consumption and ATP production. Our data indicate that coenzyme Q₁₀ plays an important role in reducing tacrolimus-induced oxidative stress and protects the mitochondria in pancreatic beta cells. These findings suggest that supplementation with coenzyme Q₁₀ has beneficial effects in tacrolimus-induced diabetes mellitus.

Impaired mitochondrial calcium uptake caused by tacrolimus underlies beta-cell failure

BACKGROUND

One of the most common side effects of the immunosuppressive drug tacrolimus (FK506) is the increased risk of new-onset diabetes mellitus. However, the molecular mechanisms underlying this association have not been fully clarified.

METHODS

We studied the effects of the therapeutic dose of tacrolimus on mitochondrial fitness in beta-cells.

RESULTS

We demonstrate that tacrolimus impairs glucose-stimulated insulin secretion (GSIS) in beta-cells through a previously unidentified mechanism. Indeed, tacrolimus causes a decrease in mitochondrial Ca²⁺ uptake, accompanied by altered mitochondrial respiration and reduced ATP production, eventually leading to impaired GSIS.

CONCLUSION

Our observations individuate a new fundamental mechanism responsible for the augmented incidence of diabetes following tacrolimus treatment. Indeed, this drug alters Ca²⁺ fluxes in mitochondria, thereby compromising metabolism-secretion coupling in beta-cells.

Contribution of β-cell dysfunction and insulin resistance to cirrhosis-associated diabetes: Role of severity of liver disease

BACKGROUND & AIMS

This study evaluated the contribution of β-cell dysfunction and insulin resistance to cirrhosis-associated diabetes.

METHODS

One-hundred and sixty cirrhotic patients with normal fasting plasma glucose (FPG), three with impaired fasting glucose and seven with untreated diabetes mellitus (DM) underwent an extended oral glucose tolerance test (OGTT). The OGTT data were analyzed with a Minimal Model to estimate dynamic (derivative) control (DC) and static (proportional) control (PC) of β-cell function, and with the Oral Glucose Insulin Sensitivity (OGIS)-2h index to estimate insulin sensitivity.

RESULTS

Twenty-six patients (15.6%) had normal glucose tolerance (NGT), 60 (35.8%) had impaired glucose tolerance (IGT), and 84 (48.6%) had DM. DC was significantly reduced in DM vs. NGT and IGT patients. PC was significantly impaired in DM and IGT vs. NGT patients and in DM vs. IGT subjects. The OGIS-2h index was significantly reduced to a similar extent in DM and IGT vs. NGT patients. Patients with Child-Pugh class B and C cirrhosis had reduced DC and PC, but not OGIS-2h values, as compared with subjects in class A. Moreover, Child-Pugh class/score was an independent predictor of β-cell function even after adjustment for glucose tolerance.

CONCLUSIONS

Abnormalities of glucose tolerance occur frequently in cirrhosis even in patients with normal FPG, thereby supporting the importance of performing an OGTT. Transition from IGT to DM is driven primarily by β-cell dysfunction. Insulin secretion worsens in parallel with the severity of liver disease, thus suggesting a detrimental effect of liver failure on pancreatic islets on its own.

Betacellulin ameliorates hyperglycemia in obese diabetic db/db mice

We found that administration of a recombinant adenovirus (rAd) expressing betacellulin (BTC) into obese diabetic db/db mice ameliorated hyperglycemia. Exogenous glucose clearance was significantly improved, and serum insulin levels were significantly higher in rAd-BTC-treated mice than rAd-β-gal-treated control mice. rAd-BTC treatment increased insulin/bromodeoxyuridine double-positive cells in the islets, and islets from rAd-BTC-treated mice exhibited a significant increase in the level of G1-S phase-related cyclins as compared with control mice. In addition, BTC treatment increased messenger RNA (mRNA) and protein levels of these cyclins and cyclin-dependent kinases in MIN-6 cells. BTC treatment induced intracellular Ca(2+) levels through phospholipase C-γ1 activation, and upregulated calcineurin B (CnB1) levels as well as calcineurin activity. Upregulation of CnB1 by BTC treatment was observed in isolated islet cells from db/db mice. When treated with CnB1 small interfering RNA (siRNA) in MIN-6 cells and isolated islets, induction of cell cycle regulators by BTC treatment was blocked and consequently reduced BTC-induced cell viability. As well as BTC's effects on cell survival and insulin secretion, our findings demonstrate a novel pathway by which BTC controls beta-cell regeneration in the obese diabetic condition by regulating G1-S phase cell cycle expression through Ca(2+) signaling pathways.

KEY MESSAGES

Administration of BTC to db/db mice results in amelioration of hyperglycemia. BTC stimulates beta-cell proliferation in db/db mice. Ca(2+) signaling was involved in BTC-induced beta-cell proliferation. BTC has an anti-apoptotic effect and potentiates glucose-stimulated insulin secretion.

Hyperglycemic management after solid organ transplantation

Hyperglycemia after solid organ transplantation increases the risk for wound infection, poor healing time, graft rejection, and graft loss. In patients without a history of diabetes, uncontrolled hyperglycemia increases the risk for advancement to diabetes mellitus. Controlling hyperglycemia can reduce the prevalence of new-onset diabetes after transplantation. This article discusses the current literature concerning blood glucose management after solid organ transplantation, the issues surrounding hyperglycemia in the patient with a solid organ transplant, and how to manage hyperglycemia after solid organ transplant.

Calcineurin/nuclear factor of activated T cells and MAPK signaling induce TNF-{alpha} gene expression in pancreatic islet endocrine cells

Cytokines contribute to pancreatic islet inflammation, leading to impaired glucose homeostasis and diabetic diseases. A plethora of data shows that proinflammatory cytokines are produced in pancreatic islets by infiltrating mononuclear immune cells. Here, we show that pancreatic islet α cells and β cells express tumor necrosis factor-α (TNF-α) and other cytokines capable of promoting islet inflammation when exposed to interleukin-1β (IL-1β). Cytokine expression by β cells was dependent on calcineurin (CN)/nuclear factor of activated T cells (NFAT) and MAPK signaling. NFAT associated with the TNF-α promoter in response to stimuli and synergistically activated promoter activity with ATF2 and c-Jun. In contrast, the β-cell-specific transcriptional activator MafA could repress NFAT-mediated TNF-α gene expression whenever C/EBP-β was bound to the promoter. NFAT differentially regulated the TNF-α gene depending upon the expression and MAPK-dependent activation of interacting basic leucine zipper partners in β cells. Both p38 and JNK were required for induction of TNF-α mRNA and protein expression. Collectively, the data show that glucose and IL-1β can activate signaling pathways, which control induction and repression of cytokines in pancreatic endocrine cells. Thus, by these mechanisms, pancreatic β cells themselves may contribute to islet inflammation and their own immunological destruction in the pathogenesis of diabetes.

Comprehensive management of post-transplant diabetes mellitus: from intensive care to home care

Post-transplant diabetes mellitus (PTDM) is a common complication of solid organ and hematopoietic transplantation. This clinically oriented review article briefly summarizes the pathophysiology of PTDM, then presents a comprehensive clinical approach to diagnosis and therapy. Topics include the key clinical aspects of PTDM screening, diagnosis, and management during all phases following transplantation from the intensive care unit, to the inpatient ward, to the outpatient arena.

Calcineurin/NFAT signaling in the beta-cell: From diabetes to new therapeutics

Pancreatic beta-cells in the islet of Langerhans produce the hormone insulin, which maintains blood glucose homeostasis. Perturbations in beta-cell function may lead to impairment of insulin production and secretion and the onset of diabetes mellitus. Several essential beta-cell factors have been identified that are required for normal beta-cell function, including six genes that when mutated give rise to inherited forms of diabetes known as Maturity Onset Diabetes of the Young (MODY). However, the intracellular signaling pathways that control expression of MODY and other factors continue to be revealed. Post-transplant diabetes mellitus in patients taking the calcineurin inhibitors tacrolimus (FK506) or cyclosporin A indicates that calcineurin and its substrate the Nuclear Factor of Activated T-cells (NFAT) may be required for beta-cell function. Here recent advances in our understanding of calcineurin and NFAT signaling in the beta-cell are reviewed. Novel therapeutic approaches for the treatment of diabetes are also discussed.

Intrinsic regulators of pancreatic beta-cell proliferation

Once thought incapable of significant proliferation, the pancreatic beta-cell has recently been shown to harbor immense powers of self-renewal. Pancreatic beta-cells, the sole source of insulin in vertebrate animals, can grow facultatively to a degree unmatched by other organs in experimental animals. beta-cell growth matches changes in systemic insulin demand, which increase during common physiologic states such as aging, obesity, and pregnancy. Compensatory changes in beta-cell mass are controlled by beta-cell proliferation. Here we review recent advances in our understanding of the intrinsic factors and mechanisms that control beta-cell cycle progression. Dysregulation of beta-cell proliferation is emerging as a fundamental feature in the pathogenesis of human disease states such as cancer and diabetes mellitus. New experimental observations and studies of these diseases suggest that beta-cell fate and expansion are coordinately regulated. We speculate on how these advances may accelerate the discovery of new strategies for the treatment of diseases characterized by a deficiency or excess of beta-cells.

New-onset diabetes after liver transplantation

AIM

The impact of new-onset diabetes (NOD) posttransplantation has been underestimated in the past. The aim of this study was to evaluate the incidence of diabetes after liver transplantation.

METHODS

We retrospectively analyzed the incidence of NOD in 899 patients transplanted in our center. According to International Consensus 2003 Guidelines, criteria for diagnosis of diabetes were: fasting plasma glucose > or =126 mg/dL, symptoms of diabetes plus casual plasma glucose concentrations > or =200 mg/dL, and 2-hour plasma glucose levels > or =200 mg/dL during an oral glucose tolerance test. We considered only patients with follow-up over 10 months. We evaluated the risk factors correlated with NOD (age, hepatitis C virus [HCV] positivity, tacrolimus vs cyclosporine, steatosic graft), and the outcomes of diabetic patient and their grafts.

RESULTS

The incidence of NOD was 10.8% (90/830 patients). Sixty nine patients were diabetic before transplantation. Recipient age >45 years (14.7% vs 6.8%, P = .002, OR = 2.4) and HCV positivity (15.5% vs 7.8%, P = .001, OR = 2.2) significantly correlated with NOD. Multivariate analysis confirmed these variables to be independently associated with diabetic risk. Tacrolimus was associated with an increased risk of NOD (16.2% in HCV-negative patients, 25% in HCV-positive patients), but this difference was not statistically significant. Steatotic grafts (>10%) were associated with an increased risk of NOD (28.6% vs 10%, P = .001, OR = 3.6). The outcome of patients and grafts in the group of diabetic patients was not significantly different from all other patients.

CONCLUSIONS

The incidence of NOD was more relevant in patients older than 45 years and/or HCV-positive. A steatotic graft was an important risk factor, and the match with high-risk patients should be avoided.

New-Onset Diabetes after Kidney Transplantation: An Application of 2003 International Guidelines

BACKGROUND

The 2003 International Consensus Guidelines defined new-onset diabetes after transplantation. This study determined the risk of new-onset diabetes following kidney transplantation using these criteria.

METHODS

Consecutive nondiabetic patients who received kidney transplantation between August 2001 and March 2003 (recent, n=61) and before August 2001 (earlier, n=61) were retrospectively evaluated.

RESULTS

In all, 74% in the recent group and 56% in the earlier group developed diabetes by 1 year posttransplant. Median time to diabetes development was 23 days in the recent vs. 134 days in the earlier group (P=0.0304). Most patients developed diabetes within 60 days after transplantation. Immunosuppression was the strongest correlate of diabetes development; tacrolimus and cyclosporine A treatments were associated with increased risk. The rate of development was also greater when rapamycin was added to tacrolimus, compared to when it was not. The risk was double in African-Americans compared to whites. Age, body mass index, family history of diabetes, and etiology of renal failure did not predict diabetes; however, the mean age of patients was greater than previously reported.

CONCLUSIONS

The majority of patients are at risk of developing new-onset diabetes within a short time after kidney transplantation. The risk may be due to preexisting risk factors, immunosuppressive agents, or older age. The significance of these findings is not clear, but demands appropriate follow-up studies related to glycemia, end-organ complications, and graft function. It remains to be determined whether the 2003 International Consensus Guidelines are adequate to appropriately diagnose diabetes in the posttransplant time period, with special emphasis on the first 3 months.

Factors influencing the onset of diabetes mellitus after kidney transplantation: a single French center experience

Posttransplantation diabetes mellitus (PTDM) is a complication arising mostly during the first 6 months after kidney transplantation. Considering the serious outcomes of chronic hyperglycemia in kidney transplant patients, the recognition of factors that contribute to the onset of PTDM is of particular relevance. A retrospective analysis was performed to document the incidence of and the risk factors for diabetes mellitus occurring in the first year after kidney transplantation among 177 adult patients, without previously known diabetes transplanted between January 1998 and December 2000. PTDM, defined as fasting plasma glucose > or = 126 mg/dL confirmed by repeat testing on a different day, occurred in 48 (27.12%) patients of whom 36 showed transient changes during the first year after transplantation. Univariate analysis identified variables to be associated with the onset of PTDM: older recipient age (P = .05), male gender (P = .03), family history of diabetes (P = .04), advanced donor age (P = .008), absence of induction immunosuppression (P = .04), use of tacrolimus (vs cyclosporine; P = .01), one or more than one (steroid-treated) acute rejection episode(s) (P = .000001), cytomegalovirus infection (P = .02), and use of beta-blockers or diuretics (P = .05). By multivariate analysis, five factors were independently associated with the onset of PTDM: two episodes of rejection (odds ratio = 42.69, P = .000025), one episode of rejection (5.01, P = .007), older recipient age (1.06, P = .017), family history of diabetes (7.24, P = .011), and weight at transplantation (1.03, P = .048). Tacrolimus treatment remained of borderline significance (2.77, P = .05). In addition to traditional risk factors predisposing to the development of type 2 diabetes in the general population, episodes of acute rejection significantly influence the incidence of PTDM.

Pharmacological agents that directly modulate insulin secretion

Blood glucose levels are sensed and controlled by the release of hormones from the islets of Langerhans in the pancreas. The beta-cell, the insulin-secreting cell in the islet, can detect subtle increases in circulating glucose levels and a cascade of molecular events spanning the initial depolarization of the beta-cell membrane culminates in exocytosis and optimal insulin secretion. Here we review these processes in the context of pharmacological agents that have been shown to directly interact with any stage of insulin secretion. Drugs that modulate insulin secretion do so by opening the K(ATP) channels, by interacting with cell-surface receptors, by altering second-messenger responses, by disrupting the beta-cell cytoskeletal framework, by influencing the molecular reactions at the stages of transcription and translation of insulin, and/or by perturbing exocytosis of the insulin secretory vesicles. Drugs acting primarily at the K(ATP) channels are the sulfonylureas, the benzoic acid derivatives, the imidazolines, and the quinolines, which are channel openers, and finally diazoxide, which closes these channels. Methylxanthines also work at the cell membrane level by antagonizing the purinergic receptors and thus increase insulin secretion. Other drugs have effects at multiple levels, such as the calcineurin inhibitors and somatostatin. Some drugs used extensively in research, e.g., colchicine, which is used to study vesicular transport, have no effect at the pharmacological doses used in clinical practice. We also briefly discuss those drugs that have been shown to disrupt beta-cell function in a clinical setting but for which there is scant information on their mechanism of action.