Determinants of Insulin Resistance in Renal Transplant Recipients

New-Onset Diabetes Mellitus after Kidney Transplantation

New-Onset Diabetes Mellitus after Transplantation (NODAT) emerges as a prevalent complication post-kidney transplantation, with its incidence influenced by variations in NODAT definitions and follow-up periods. The condition's pathophysiology is marked by impaired insulin sensitivity and β-cell dysfunction. Significant risk factors encompass age, gender, obesity, and genetics, among others, with the use of post-transplant immunosuppressants intensifying the condition. NODAT's significant impact on patient survival and graft durability underscores the need for its prevention, early detection, and treatment. This review addresses the complexities of managing NODAT, including the challenges posed by various immunosuppressive regimens crucial for transplant success yet harmful to glucose metabolism. It discusses management strategies involving adjustments in immunosuppressive protocols, lifestyle modifications, and pharmacological interventions to minimize diabetes risk while maintaining transplant longevity. The importance of early detection and proactive, personalized intervention strategies to modify NODAT's trajectory is also emphasized, advocating for a shift towards more anticipatory post-transplant care.

Inflammation on the Waiting List Is a Risk Factor for New-Onset Prediabetes and Post-Transplant Diabetes Mellitus: A Prospective Study

INTRODUCTION

Inflammation is a risk factor for diabetes in the general population. The role of inflammation in prediabetes or post-transplant diabetes mellitus (PTDM) is not clear. We evaluated the association between inflammatory markers in patients on the waiting list for renal transplantation and the onset of prediabetes and PTDM 12 months after transplantation.

METHODS

This is a post hoc analysis of a prospective study that included nondiabetic patients on the waiting list for kidney transplantation who underwent an oral glucose tolerance test (OGTT) and were followed up to 12 months after transplantation. At this time, those patients without PTDM underwent another OGTT. At pre-transplantation, five cytokines: TNFα, IL6, IL1β, CRP, MCP1 were determined. The association between inflammation and prediabetes/PTDM was evaluated using multiple regression models.

RESULTS

110 patients on the waiting list were enrolled: 74 had normal glucose metabolism and 36 had prediabetes or occult diabetes. At 12 months, 53 patients had normal glucose metabolism, 25 prediabetes, and 32 PTDM. In multiple regression analysis, pre-transplant inflammation was not a risk factor for prediabetes or PTDM. This was attributed to the high interrelation between obesity, prediabetes, and inflammation: about 75% of the cases had these conditions. In a sub-analysis, we analyzed only patients without prediabetes and occult diabetes on the waiting list and found that TNFα levels and BMI at pre-transplantation were independently associated with the onset of prediabetes or PTDM 1 year after transplantation.

CONCLUSIONS

Pre-transplant inflammation and BMI are risk factors for prediabetes and PTDM in patients without glucose metabolism alterations.

A Lipotoxic Medium Decreases the Number of Lipid Droplets in β Cells: One Possible Explanation of the β-Cell Failure in Patients With Hyperlipidemia Receiving Tacrolimus

OBJECTIVES

Dyslipidemia is a risk factor for post- transplant diabetes mellitus, especially in patients who are taking tacrolimus. Although lipotoxicity of dyslipidemia leads to β-cell failure, the handling of lipids by β cells is a mystery in molecular endocrinology. Likewise, lipid droplet homeostasis is appreciated as a key component of lipid metabolism in cells like hepatocytes, but its role in β cells remains to be elucidated.

MATERIALS AND METHODS

To evaluate the morphologic changes in β cells with special focus on lipid droplets, we evaluated electron micrographs under metabolic stress conditions of glucotoxicity, lipotoxicity, and glucolipotoxicity in isolated rat insulinoma INS-1E β cells. Cells were treated with palmitic acid (0.5 mM), glucose (33 mM), or both for 16 hours, after which morphologic changes were observed with an electron microscope.

RESULTS

Many lipid droplets were observed in the cytoplasm of healthy β cells in the control group (no treatment). Lipid droplets were also visible in the cytosol, and the cytoplasm was rich in organelles and insulin vesicles under high glucose stimulation. However, after treatment with palmitic acid, almost no lipid droplets were observed. Endocrine vesicles were also depleted, with severe morphologic disruption of other organelles. Under glucolipotoxic conditions, β cells showed a decreased number of lipid droplets and insulin vesicles compared with controls.

CONCLUSIONS

Lipid droplet dynamics seemed important in the homeostasis of β-cell metabolism. In this preliminary study, healthy β cells appeared rich in lipid droplets under normal conditions. However, lipotoxicity depleted and glucolipotoxicity decreased the number of lipid droplets in β cells. Because dyslipidemia causing lipotoxicity is one of the most frequent metabolic problems in transplant patients and increases risk of posttransplant diabetes mellitus, understanding the mystery of lipid droplets in β cells and the pathophysiology of diabetes in transplant patients is important, especially for those taking tacrolimus.

Association of diuretic use with increased risk for long-term post-transplantation diabetes mellitus in kidney transplant recipients

Background

Post-transplantation diabetes mellitus (PTDM) is a major clinical problem in kidney transplant recipients (KTRs). Diuretic-induced hyperglycaemia and diabetes have been described in the general population. We aimed to investigate whether diuretics also increase PTDM risk in KTRs.

Methods

We included 486 stable outpatient KTRs (with a functioning graft ≥1 year) without diabetes from a prospective cohort study. Participants were classified as diuretic users and non-users based on their medication use verified by medical records.

Results

At the baseline study, 168 (35%) KTRs used a diuretic (thiazide, n = 74; loop diuretic, n = 76; others, n = 18) and 318 KTRs did not use a diuretic. After 5.2 years [interquartile range (IQR) 4.0‒5.9] of follow up, 54 (11%) KTRs developed PTDM. In Cox regression analyses, diuretic use was associated with incident PTDM, independent of age, sex, fasting plasma glucose (FPG) and haemoglobin A_1c (HbA_1c) {hazard ratio [HR] 3.28 [95% confidence interval (CI) 1.84–5.83]; P <0.001}. Further adjustment for potential confounders, including lifestyle, family history of cardiovascular disease, use of other medication, kidney function, transplantation-specific parameters, BMI, lipids and blood pressure did not materially change the association. Moreover, in Cox regression analyses, both thiazide and loop diuretics associated with the development of PTDM, independent of age, sex, FPG and HbA_1c [HR 2.70 (95% CI 1.24–5.29); P = 0.012 and HR 5.08 (95% CI 2.49–10.34); P <0.001), respectively].

Conclusions

This study demonstrates that diuretics overall are associated with an increased risk of developing PTDM in KTRs, independent of established risk factors for PTDM development. The association was present for both thiazide and loop diuretics.

Post-Transplant Diabetes Mellitus and Prediabetes in Renal Transplant Recipients: An Update

Post-transplant diabetes mellitus (PTDM) is a frequent and relevant complication after renal transplantation: it affects 20-30% of renal transplant recipients and increases the risk for cardiovascular and infectious events. Thus, understanding pathogenesis of PTDM would help limiting its consequences. In this review, we analyse novel aspects of PTDM, based on studies of the last decade, such as the clinical evolution of PTDM, early and late, the reversibility rate, diagnostic criteria, risk factors, including pre-transplant metabolic syndrome and insulin resistance (IR) and the interaction between these factors and immunosuppressive medications. Also, we discuss novel pathogenic factors, in particular the role of β-cell function in an environment of IR and common pathways between pre-existing cell damage and tacrolimus-induced toxicity. The relevant role of prediabetes in the pathogenesis of PTDM and cardiovascular disease is also addressed. Finally, current evidence on PTDM treatment is discussed.

Protein Intake, Fatigue and Quality of Life in Stable Outpatient Kidney Transplant Recipients

Fatigue is a frequent complaint in kidney transplant recipients (KTR), often accompanied by poor quality of life (QoL). The role of nutrition as determinant of fatigue in KTR is largely unexplored. The aims of this study are to examine the association of protein intake with fatigue and QoL in KTR and to identify other determinants of fatigue. This cross-sectional study is part of the TransplantLines Cohort and Biobank Study (NCT03272841). Protein intake was calculated from urinary urea nitrogen (UUN) in 24-h urine samples. Fatigue was assessed by the Checklist Individual Strength (CIS) questionnaire; moderate and severe fatigue were defined as a CIS score of 20–34 and ≥ 35, respectively. QoL was assessed with the RAND-36-Item Health Survey (RAND-36). Associations of protein intake with fatigue and QoL were analyzed using multinomial logistic and linear regression analyses. We included 730 stable outpatient KTR (median age 58 year [IQR 48–65], 57% male) with a mean protein intake of 82.2 ± 21.3 g/d. Moderate and severe fatigue were present in 254 (35%) and 245 (34%) of KTR. Higher protein intake was significantly associated with lower risk of moderate fatigue (OR 0.89 per 10 g/d; 95%CI 0.83–0.98, p = 0.01), severe fatigue (OR 0.85; 95%CI 0.78–0.92, p < 0.001) and was associated with higher physical component summary score of QoL (β 0.74 per 10 g/d; 95%CI 0.39–1.09, p < 0.001). Higher BMI, a history of dialysis, glomerulonephritis as primary kidney disease and a history of combined organ transplantation were also associated with severe fatigue. In conclusion, amongst the potential modifiable factors of fatigue, higher protein intake is independently associated with lower risk of moderate and severe fatigue and with better QoL in KTR. These findings underline the need to incorporate nutritional assessment in the diagnostic work-up of fatigue. Intervention studies are needed to assess the benefits and safety of higher protein intake in KTR.

High-Density Lipoprotein Particles and Their Relationship to Posttransplantation Diabetes Mellitus in Renal Transplant Recipients

High concentrations of high-density lipoprotein (HDL) cholesterol are likely associated with a lower risk of posttransplantation diabetes mellitus (PTDM). However, HDL particles vary in size and density with yet unestablished associations with PTDM risk. The aim of our study was to determine the association between different HDL particles and development of PTDM in renal transplant recipients (RTRs). We included 351 stable outpatient adult RTRs without diabetes at baseline evaluation. HDL particle characteristics and size were measured by nuclear magnetic resonance (NMR) spectroscopy. During 5.2 (IQR, 4.1‒5.8) years of follow-up, 39 (11%) RTRs developed PTDM. In multivariable Cox regression analysis, levels of HDL cholesterol (hazard ratio [HR] 0.61, 95% confidence interval [CI] 0.40-0.94 per 1SD increase; p = 0.024) and of large HDL particles (HR 0.68, 95% CI 0.50-0.93 per log 1SD increase; p = 0.017), as well as larger HDL size (HR 0.58, 95% CI 0.36-0.93 per 1SD increase; p = 0.025) were inversely associated with PTDM development, independently of relevant covariates including, age, sex, body mass index, medication use, transplantation-specific parameters, blood pressure, triglycerides, and glucose. In conclusion, higher concentrations of HDL cholesterol and of large HDL particles and greater HDL size were associated with a lower risk of PTDM development in RTRs, independently of established risk factors for PTDM development.

Insulin Resistance in Nonobese Renal Allograft Recipients on Maintenance Doses of Cyclosporine or Tacrolimus

PURPOSE

In comparison to cyclosporine (CsA), tacrolimus (Tac) seems to be more diabetogenic in renal transplant recipients, and post-transplant diabetes mellitus is more common in patients using Tac, especially during the first year after transplantation. However, at maintenance doses, there are no comparative data of insulin resistance (IR) in patients using Tac or CsA. The purpose of this study was to investigate the IR indexes in patients on maintenance doses of CsA or Tac.

METHODS

Forty-five nondiabetic and nonobese renal transplant recipients participated in the study (M:F, 30:15; age, 36 ± 9 years); 27 patients were on CsA, and 18 were on Tac. All had stable graft function, were transplanted at least 6 months previously, and were receiving maintenance doses of steroids (5.0 mg/d), azathioprine or mycophenolate mofetil, and calcineurin inhibitors (CsA [2.14 ± 0.46 mg/kg/d] or Tac [0.06 ± 0.03 mg/kg/d]). IR was evaluated by the homeostasis model assessment (HOMA) index and composite body insulin sensitivity index.

RESULTS

We did not determine any significant difference in the HOMA and composite body insulin sensitivity index levels among patients using CsA or Tac (1.5 ± 1.3 vs 1.5 ± 1.1, P > .05, and 9.9 ± 5.8 vs 14.6 ± 11.7, P > .05, respectively). There was a significant correlation between creatinine and HOMA values.

CONCLUSION

There was no difference in IR indexes in renal transplant recipients receiving maintenance doses of either CsA or Tac.

Assessment of Cotinine Reveals a Dose-Dependent Effect of Smoking Exposure on Long-term Outcomes After Renal Transplantation

BACKGROUND

Smoking is a risk factor for poor late outcomes in renal transplant recipients (RTR). Smoking exposure can be assessed by self-report and cotinine measurements. We investigated whether use of cotinine as a biomarker for smoking exposure can serve as an alternative for self-report and to compare associations of smoking exposure by self-report and cotinine with outcomes in RTR and assess dose dependency.

METHODS

Renal transplant recipients were classified as never, former, light (≤10 cigarettes/day), and heavy smokers (>10 cigarettes/day) according to self-report and analogous categories for urine and plasma cotinine. First, we assessed agreement of self-reported smoking exposure with smoking exposure according urine and plasma cotinine. Second, we compared the associations with graft failure and mortality.

RESULTS

Of 603 RTR (age 51.5 ± 12.1 years, 55% men), 36.0% RTR were never, 42.3% former, 10.6% light, and 11.1% heavy smokers according to self-report. The majority (98.6%) of never smokers had nondetectable cotinine. However, 14 and 13 RTR reporting no active smoking had respective urine or plasma cotinine consistent with active smoking. Cotinine-based measurements were dose-dependently associated with mortality and graft failure.

CONCLUSIONS

Plasma and urine cotinine can serve as an alternative to self-report and were dose-dependently associated with poor late outcomes in RTR.

Management of the hospitalized transplant patient

Significant hyperglycemia is commonly observed immediately after solid organ and bone marrow transplant as well as with subsequent hospitalizations. Surgery and procedures are well known to cause pain and stress leading to secretion of cytokines and other hormones known to aggravate insulin action. Immunosuppression required for transplant and preexisting risk are also major factors. Glucose control improves outcomes for all hospitalized patients, including transplant patients, but is often more challenging to achieve because of frequent and sometimes unpredictable changes in immunosuppression doses, renal function, and nutrition. As a result, risk of hypoglycemia can be greater in this patient group when trying to achieve glucose control goals for hospitalized patients. Key to successful management of hyperglycemia is regular communication between the members of the care team as well as anticipating and rapidly implementing a new treatment paradigm in response to changes in immunosuppression, nutrition, renal function, or evidence of changing insulin resistance.

Genetics of new-onset diabetes after transplantation

New-onset diabetes after transplantation is a common complication that reduces recipient survival. Research in renal transplant recipients has suggested that pancreatic β-cell dysfunction, as opposed to insulin resistance, may be the key pathologic process. In this study, clinical and genetic factors associated with new-onset diabetes after transplantation were identified in a white population. A joint analysis approach, with an initial genome-wide association study in a subset of cases followed by de novo genotyping in the complete case cohort, was implemented to identify single-nucleotide polymorphisms (SNPs) associated with the development of new-onset diabetes after transplantation. Clinical variables associated with the development of diabetes after renal transplantation included older recipient age, female sex, and percentage weight gain within 12 months of transplantation. The genome-wide association study identified 26 SNPs associated with new-onset diabetes after transplantation; this association was validated for eight SNPs (rs10484821, rs7533125, rs2861484, rs11580170, rs2020902, rs1836882, rs198372, and rs4394754) by de novo genotyping. These associations remained significant after multivariate adjustment for clinical variables. Seven of these SNPs are associated with genes implicated in β-cell apoptosis. These results corroborate recent clinical evidence implicating β-cell dysfunction in the pathophysiology of new-onset diabetes after transplantation and support the pursuit of therapeutic strategies to protect β cells in the post-transplant period.

Pancreatic β-cell dysfunction and risk of new-onset diabetes after kidney transplantation

OBJECTIVE

Chronic exposure to calcineurin inhibitors and corticosteroids poses renal transplant recipients (RTR) at high risk for development of new-onset diabetes after transplantation (NODAT). Pancreatic β-cell dysfunction may be crucial to the pathophysiology of NODAT and specific markers for β-cell dysfunction may have additive value for predicting NODAT in this population. Therefore, we prospectively investigated whether proinsulin, as a marker of pancreatic β-cell dysfunction, is associated with future development of NODAT and improves prediction of it.

RESEARCH DESIGN AND METHODS

All RTR between 2001 and 2003 with a functioning graft for ≥1 year were considered eligible for inclusion, except for subjects with diabetes at baseline who were excluded. We recorded incidence of NODAT until April 2012.

RESULTS

A total of 487 RTR (age 50 ± 12 years, 55% men) participated at a median time of 6.0 (interquartile range [IQR], 2.6-11.5) years after transplantation. Median fasting proinsulin levels were 16.6 (IQR, 11.0-24.2) pmol/L. During median follow-up for 10.1 (IQR, 9.1-10.4) years, 42 (35%) RTR had development of NODAT in the highest quartile of the distribution of proinsulin versus 34 (9%) in the lowest three quartiles (P < 0.001). In Cox regression analyses, proinsulin (hazard ratio, 2.29; 95% CI, 1.85-2.83; P < 0.001) was strongly associated with NODAT development. This was independent of age, sex, calcineurine inhibitors, prednisolone use, components of the metabolic syndrome, or homeostasis model assessment.

CONCLUSIONS

In conclusion, fasting proinsulin is strongly associated with NODAT development in RTR. Our results highlight the role of β-cell dysfunction in the pathophysiology of NODAT and indicate the potential value of proinsulin for identification of RTR at increased risk for NODAT.

Insulin resistance in patients with chronic kidney disease

Metabolic syndrome and its components are associated with chronic kidney disease (CKD) development. Insulin resistance (IR) plays a central role in the metabolic syndrome and is associated with increased risk for CKD in nondiabetic patients. IR is common in patients with mild-to-moderate stage CKD, even when the glomerular filtration rate is within the normal range. IR, along with oxidative stress and inflammation, also promotes kidney disease. In patients with end stage renal disease, IR is an independent predictor of cardiovascular disease and is linked to protein energy wasting and malnutrition. Systemic inflammation, oxidative stress, elevated serum adipokines and fetuin-A, metabolic acidosis, vitamin D deficiency, depressed serum erythropoietin, endoplasmic reticulum stress, and suppressors of cytokine signaling all cause IR by suppressing insulin receptor-PI3K-Akt pathways in CKD. In addition to adequate renal replacement therapy and correction of uremia-associated factors, thiazolidinedione, ghrelin, protein restriction, and keto-acid supplementation are therapeutic options. Weight control, reduced daily prednisolone dosage, and the use of cyclosporin decrease the risk of developing new-onset diabetes after kidney transplantation. Improved understanding of the pathogenic mechanisms underlying IR in CKD may lead to more effective therapeutic strategies to reduce uremia-associated morbidity and mortality.

Calcineurin inhibitors acutely improve insulin sensitivity without affecting insulin secretion in healthy human volunteers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

New onset diabetes after transplantation is related to treatment with immunosuppressive medications. Clinical studies have shown that risk of new onset diabetes is greater with tacrolimus compared with ciclosporin. The diabetogenicity of ciclosporin and tacrolimus has been attributed to both beta cell dysfunction and impaired insulin sensitivity.

WHAT THIS STUDY ADDS

This is the first trial to investigate beta cell function and insulin sensitivity using gold standard methodology in healthy human volunteers treated with clinically relevant doses of ciclosporin and tacrolimus. We document that both drugs acutely increase insulin sensitivity, while first phase and pulsatile insulin secretion remain unaffected. This study demonstrates that ciclosporin and tacrolimus have similar acute effects on glucose metabolism in healthy humans. AIM The introduction of calcineurin inhibitors (CNIs) ciclosporin (CsA) and tacrolimus (Tac) has improved the outcome of organ transplants, but complications such as new onset diabetes mellitus after transplantation (NODAT) cause impairment of survival rates. The relative contribution of each CNI to the pathogenesis and development of NODAT remains unclear. We sought to compare the impact of CsA and Tac on glucose metabolism in human subjects.

METHODS

Ten healthy men underwent 5 h infusions of CsA, Tac and saline in a randomized, double-blind, crossover study. During infusion glucose metabolism was investigated using following methods: a hyperinsulinaemic-euglycemic clamp, an intravenous glucose tolerance test (i.v.GTT), glucose-stimulated insulin concentration-time series and indirect calorimetry.

RESULTS

Clamp derived insulin sensitivity was increased by 25% during CsA (P < 0.0001) and 13% during Tac administration (P = 0.047), whereas first phase and pulsatile insulin secretion were unaffected. Coinciding with the CNI induced improved insulin sensitivity, glucose oxidation rates increased, while insulin clearance rates decreased, only non-significantly. Tac singularly lowered hsCRP concentrations, otherwise no changes were observed in circulating glucagon, FFA or adiponectin concentrations. Mean blood concentrations of CNIs were 486.9 ± 23.5 µg l(-1) for CsA and 12.8 ± 0.5 µg l(-1) for Tac.

CONCLUSIONS

Acute effects of i.v. CsA, and to a lesser degree Tac infusions, in healthy volunteers include increased insulin sensitivity, without any effect on first phase or pulsatile insulin secretion.

PI3K/AKT, MAPK and AMPK signalling: protein kinases in glucose homeostasis

New therapeutic approaches to counter the increasing prevalence of obesity and type 2 diabetes mellitus are in high demand. Deregulation of the phosphoinositide-3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue (AKT), mitogen-activated protein kinase (MAPK) and AMP-activated protein kinase (AMPK) pathways, which are essential for glucose homeostasis, often results in obesity and diabetes. Thus, these pathways should be attractive therapeutic targets. However, with the exception of metformin, which is considered to function mainly by activating AMPK, no treatment for the metabolic syndrome based on targeting protein kinases has yet been developed. By contrast, therapies based on the inhibition of the PI3K/AKT and MAPK pathways are already successful in the treatment of diverse cancer types and inflammatory diseases. This contradiction prompted us to review the signal transduction mechanisms of PI3K/AKT, MAPK and AMPK and their roles in glucose homeostasis, and we also discuss current clinical implications.

Leptin, insulin resistance, and metabolic changes 5 years after renal transplantation

OBJECTIVE

To evaluate leptin, insulin resistance (IR), and changes in body composition and lipid profile within 5 years after renal transplantation.

DESIGN

Longitudinal study.

SETTING

Hospital de Clínicas de Porto Alegre/RS, Brazil.

SUBJECTS

Thirty-two renal transplant recipients were followed up for 5 years after transplantation.

METHODS

Data were collected at transplantation time (T₁) and after 3 months (T₂), 1 year (T₃), and 5 years (T₄). Leptin serum levels, IR assessed by homeostasis model assessment (HOMA) index, lipid profile, and anthropometric measurements were analyzed. Data were compared with a control group at baseline.

RESULTS

At T₁, pretransplant patients had leptin levels (ng/mL) (11.9 [9.2 to 25.2]) higher than the control group (7.7 [5.2 to 9.9]; P < .0001). After transplantation, levels decreased at T₂ and T₃, but increased at T₄ to values similar to those seen at T₁ (T₄: 9.2 [5.7 to 21]; P = 1). HOMA also decreased at T₂, but increased at T₄ to identical levels (T₁: 2.1 [1.63 to 2.23], T₄: 2.1 [1.6 to 2.85]; P = 1). No significant changes in body fat percentage (BF%) were observed; however, the arm muscle circumference increased significantly at T₄ (P < .0001). At T₂, total cholesterol, triglycerides, and low-density lipoprotein cholesterol increased, whereas at T₄, lipid profile moved toward T₁ levels. By linear regression analysis, gender, BF%, and HOMA were independent predictors of leptin levels. A trend toward higher body mass index was observed in woman who also presented higher leptin and lower HOMA levels.

CONCLUSION

Leptin levels and HOMA decrease in the immediate posttransplant period and remain reduced for at least 1 year. Five years post transplantation, leptin, IR, BF%, and lipids have a profile similar to those in the pretransplant period. This metabolic profile is possibly associated with the elevated incidence of cardiovascular diseases observed in the late posttransplant period.

Smoking is a risk factor for graft failure and mortality after renal transplantation

BACKGROUND

Smoking in renal transplant recipients (RTR) is an acknowledged cardiovascular risk factor. It is, however, unclear whether smoking also increases the risk of graft failure (GF).

METHOD

In this study, we prospectively assessed the association of current smoking versus past and never smoking with GF and mortality in 604 RTR (age 51.5 ± 12.1 years, 55% male).

RESULTS

At inclusion, 133 (22%) were current smokers, 255 (42%) were past smokers and 216 (36%) never smoked. During follow-up of 5.3 (4.7-5.7) years, 41 (7%) RTR experienced GF and 95 RTR (16%) died. Current smoking RTR had higher risk for GF compared to never smoking RTR (hazard ratio, HR = 3.3, 95% CI 1.5-7.1, p = 0.002). Past smoking RTR had similar risk of GF as never smoking RTR (HR = 1.1, 95% CI 0.5-2.6, p = 0.7). Current smoking RTR and past smoking RTR were at higher risk for death than never smoking RTR (HR = 2.1, 95% CI 1.1-3.8, p = 0.016, and HR = 2.4, 95% CI 1.4-4.0, p = 0.001, respectively).

CONCLUSION

Smoking after renal transplantation is associated with risk for GF and mortality. Since past smoking is a risk factor for mortality but not for GF, smoking cessation may be beneficial to RTR in delaying GF in long term.

Factors associated with insulin resistance after long-term renal transplantation

Insulin resistance (IR) is an early and very strong predictor of posttransplantation diabetes mellitus as well as an important cardiovascular risk factor even in the absence of hyperglycemia. Patients after renal transplantation are insulin resistant compared with a control group with similar demographic characteristics. The aim of this study was to determine the frequency of IR in renal allograft patients without glucose disorders, to correlate IR indexes with the doses of immunosuppressive medications, and to examine other risk factors, such as age, obesity, and antihypertensive therapy used. One hundred six patients who received a kidney transplant at Baskent University Hospital between 1992 and 2006 were enrolled the study. IR was diagnosed by using homeostasis model assessment (HOMA); 53.8% of the patients (n=57) had IR. HOMA-IR was correlated with age, body mass index, and waist-hip ratio (P values .004, .001, and .000, respectively). In regression analysis, only waist-hip ratio was significantly associated with HOMA-IR. Our results indicate that abdominal waist-hip ratio is a major determinant of IR after renal transplantation. Even in the absence of hyperglycemia, renal transplant patients may have IR. If obesity is prevented, long-term patient and graft survival may be improved.

Prevalence of metabolic syndrome and obesity in renal transplanted Mexican children

The purpose of the study was to evaluate the prevalence of MS and obesity in Mexican children with more than one yr post-renal transplantation. Thirty-two children transplanted between January 2004 and February 2006 were included in the study. The weight and height at the time of renal transplant were obtained. A fasting blood sample was drawn for serum creatinine, adiponectin, and complete lipid profile, and a three-h glucose tolerance test was also taken. A complete nutritional evaluation was performed including anthropometry. There was a statistically significant increase in BMI at one yr post-transplant that was maintained at two yr post-transplant. Three patients exhibited obesity and were overweight. Seventeen patients had hypertension, 14 patients had low HDL, 12 patients had hypertriglyceridemia, all had normal fasting glucose, six of them had glucose intolerance, and two had waist circumference higher than 90%. Eight patients (25%) had MS. Patients with MS had higher proportion of deceased donor grafts, acute rejection episodes, and received more methylprednisolone pulses; also they had a statistically significant higher pretransplant BMI than patients without MS. There was a significant relationship between BMI at one yr post-renal transplant and creatinine clearance estimated by Schwartz formula.

Mammalian target of rapamycin and diabetes: what does the current evidence tell us?

New-onset diabetes mellitus after transplantation (NODAT) is a serious complication in organ transplantation; not only does it enhance the risk of graft dysfunction, it also increases cardiovascular morbidity and mortality. The mammalian target of rapamycin (mTOR) is regulated independently by insulin, amino acids, and energy sufficiency. It integrates signal from growth factors, hormones, nutrients, and cellular energy levels to regulate protein translation and cell growth, proliferation, and survival. In addition, mTOR generates an inhibitory feedback loop on insulin receptor substrate (IRS) proteins. Therefore, it was suggested that mTOR might link nutrient excess with both obesity and insulin resistance. In this review, we summarize the role of mTOR and its inhibitor sirolimus (SRL) on chronic hyperglycemia and insulin resistance in beta cells, adipose tissue, liver, and muscle. We further hypothesize, based on data from the literature and generated in our laboratory, that SRL could counteract the development of NODAT in stable glucose homeostasis due to its positive effects on insulin-stimulated glucose uptake, whereas in conditions that require an adaptive beta cell proliferation (such as pregnancy and weight increase), the administration of SRL might have effects that would promote the development of NODAT. Therefore, it seems crucial for patient outcome to consider these potentially contrasting effects of SRL.

Association of arterial hypertension with renal target organ damage in kidney transplant recipients: the predictive role of ambulatory blood pressure monitoring

BACKGROUND

Although arterial hypertension is a powerful predictor of graft failure, only few studies have evaluated 24-hr blood pressure (BP) profile in renal transplant recipients (RTRs).

METHODS

We performed ambulatory blood pressure monitoring (ABPM) in 94 RTRs (65 men; age 28-71 years) with 1-year functioning grafts. Serum biochemical parameters, daily proteinuria, and transplantation-related data were evaluated in all subjects.

RESULTS

ABPM showed that only 5% of RTRs were normotensives (BP<130/80 mm Hg) and identified 29% of patients with nocturnal hypertension. A strong, direct correlation was shown between each set of both systolic BP and diastolic BP measured by ABPM and serum creatinine, daily proteinuria, and serum triglycerides (P at least <0.025 for each). Serum creatinine immediately after transplantation and 1-yr asleep diastolic BP were the only significant predictors of 1-yr creatinine (P<0.0001; r=0.49), whereas awake systolic BP was the only predictor of daily proteinuria (r=0.39; P=0.005) by multiple regression analysis.

CONCLUSIONS

BP assessed by ABPM proved to be a stronger predictor of renal graft damage than traditional immunologic factors. ABPM improved the diagnostic accuracy of arterial hypertension in RTRs and was the only effective tool in disclosing the association of BP with 1-year renal transplant outcome.

The effect of rosuvastatin on insulin sensitivity and pancreatic beta-cell function in nondiabetic renal transplant recipients

Interventions to attenuate abnormal glycemia posttransplantation are required. In addition, surrogate markers of declining glycemic control are valuable. Statins may have pleiotropic properties that attenuate abnormal glucose metabolism. We hypothesized statins would improve glucose metabolism and HbA1c would be advantageous as a surrogate for worsening glycemia. We conducted a prospective, randomized, placebo controlled, crossover study in 20 nondiabetic renal transplant recipients at low risk for NODAT and compared effects of rosuvastatin on insulin secretion/sensitivity. Mathematical model analysis of an intravenous glucose tolerance test determined first-phase insulin secretion, insulin sensitivity and disposition index. Second-phase insulin secretion was determined with a meal tolerance test. Biochemical/clinical parameters were also assessed. Rosuvastatin significantly improved total cholesterol (-30%, p < 0.001), LDL cholesterol (-44%, p < 0.001) and triglycerides (-19%, p = 0.013). C-reactive protein decreased but failed to achieve statistical significance (-31%, p = 0.097). Rosuvastatin failed to influence any glycemic physiological parameter, although an inadequate timeframe to allow pleiotropic mechanisms to clinically manifest raises the possibility of a type II statistical error. On multivariate analysis, glycated hemoglobin (HbA1c) correlated with disposition index (R(2)= 0.201, p = 0.006), first-phase insulin secretion (R(2)= 0.106, p = 0.049) and insulin sensitivity (R(2)= 0.136, p = 0.029). Rosuvastatin fails to modify glucose metabolism in low-risk patients posttransplantation but HbA1c is a useful surrogate for declining glycemic control.

Skin-autofluorescence is an independent predictor of graft loss in renal transplant recipients

BACKGROUND

Skin-autofluorescence (skin-AF) noninvasively measures the tissue accumulation of advanced glycation end products (AGEs). AGEs are nephrotoxic and potential effectors of cardiovascular mortality. We investigated whether skin-AF predicted graft loss after kidney transplantation.

METHODS

A total of 302 renal transplant recipients were enrolled at a median time of 6.1 (2.6-12.1) years after transplantation and were subsequently followed up for first occurrence of graft loss (i.e., graft failure or all-cause mortality) for 5.2 (4.6-5.4) years. The association of baseline skin-AF with graft loss was investigated with univariable and multivariable Cox-regression and receiver-operator-characteristic curve analyses.

RESULTS

Baseline skin-AF was 2.7+/-0.8 arbitrary units. Skin-AF predicted graft loss in a univariable Cox regression analysis (Hazard ratios 2.40 [1.75-3.29], P<0.001) and in a multivariable model (Hazard ratios 1.83 [1.22-2.75], P=0.003), adjusted for other identified risk-factors, including patient age, creatinine clearance, protein excretion, high sensitivity C-reactive protein (hsCRP), and human leukocyte antigen-DR mismatching. The area under the receiver-operator-characteristic curve for skin-AF as predictor of graft loss was significantly different from 0.5. Skin-AF was also a significant predictor of graft failure and mortality as separate end points.

CONCLUSIONS

We conclude that skin-AF is an independent predictor of graft loss in kidney transplant recipients. Although skin-AF is not a direct measurement for AGEs, we believe that our results do support the hypothesis that accumulation of AGEs in renal transplant recipients contributes to the development of graft loss.

Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease

The therapeutic potential for manipulation of glucocorticoid metabolism in cardiovascular disease was revolutionized by the recognition that access of glucocorticoids to their receptors is regulated in a tissue-specific manner by the isozymes of 11beta-hydroxysteroid dehydrogenase. Selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 have been shown recently to ameliorate cardiovascular risk factors and inhibit the development of atherosclerosis. This article addresses the possibility that inhibition of 11beta-hydroxsteroid dehydrogenase type 1 activity in cells of the cardiovascular system contributes to this beneficial action. The link between glucocorticoids and cardiovascular disease is complex as glucocorticoid excess is linked with increased cardiovascular events but glucocorticoid administration can reduce atherogenesis and restenosis in animal models. There is considerable evidence that glucocorticoids can interact directly with cells of the cardiovascular system to alter their function and structure and the inflammatory response to injury. These actions may be regulated by glucocorticoid and/or mineralocorticoid receptors but are also dependent on the 11beta-hydroxysteroid dehydrogenases which may be expressed in cardiac, vascular (endothelial, smooth muscle) and inflammatory (macrophages, neutrophils) cells. The activity of 11beta-hydroxysteroid dehydrogenases in these cells is dependent upon differentiation state, the action of pro-inflammaotory cytokines and the influence of endogenous inhibitors (oxysterols, bile acids). Further investigations are required to clarify the link between glucocorticoid excess and cardiovascular events and to determine the mechanism through which glucocorticoid treatment inhibits atherosclerosis/restenosis. This will provide greater insights into the potential benefit of selective 11beta-hydroxysteroid dehydrogenase inhibitors in treatment of cardiovascular disease.

Insulin resistance, body fat percentage, and lipid abnormalities as risk factors for cardiovascular diseases in renal transplant recipients: a 1-year analysis

The aim of this study was to evaluate changes in body mass index (BMI), body fat percentage (BF%), insulin resistance, and lipid profile in 32 patients during the first year after renal transplantation by anthropometric measures. The homeostasis model assessment index (HOMA) was calculated for insulin resistance estimation. Anthropometric measures and biochemical markers were evaluated at the time of transplantation (T(0)), and prospectively at 3 (T(3)), 6 (T(6)), 9 (T(9)), and 12 (T(12)) months posttransplantation. The HOMA index decreased significantly at 3 months after transplantation (T(3)) (2.4 +/- 1.5 vs 1.5 +/- 1.1; P < .01); however, an increment was observed at T(6) and T(9) (1.8 +/- 0.8 and 2 +/- 1.5, respectively), remaining stable at T(12) (2 +/- 1.7). BMI and BF% increased significantly over 12 months (23.3 +/- 2.7 vs 24.4 +/- 2.7 kg/m(2); P = .001 and 23.7 +/- 7.8 vs 25.6 +/- 7.7 %; P = .002). Total cholesterol, low-density lipoprotein cholesterol and triglyceride levels showed significant increases starting at T(3). In conclusion, insulin resistance decreased transitorily post-renal transplantation. BMI, BF%, and lipid profile showed unfavorable changes during the first year post-renal transplantation.

Influence of lifestyle modification in renal transplant recipients with postprandial hyperglycemia

INTRODUCTION

Lifestyle modification is recommended as first-line therapy to manage new-onset diabetes after transplantation (NODAT) and impaired glucose tolerance (IGT). No data currently demonstrate the efficacy of this approach specifically for transplant recipients. This study aimed to assess the benefit of intensive lifestyle modification in this high-risk group and to contrast this with the natural evolution of glucose metabolism after transplantation.

METHODS

Baseline oral glucose tolerance test (OGTT) stratified 115 patients into two groups. Group 1 had glucose intolerance, IGT (n=28) and NODAT (n=8), and received intensive lifestyle modification (dietician referral, exercise program, weight loss advice). Group 2 had normal glucose tolerance (n=79) and received lifestyle modification leaflets. Both groups had follow-up OGTT after 6 months to assess change in glycemic status.

RESULTS

Excluding all patients who received steroid weaning or withdrawal as part of their management, 111 patients were included in the analysis. Lifestyle modification in group 1 resulted in 15% improvement in 2-hr postprandial glucose versus 12% deterioration in group 2. In group 1, 44% (n=11) of IGT patients developed normal glucose tolerance, whereas only 4% (n=1) developed NODAT. Fifty-eight percent (n=4) of NODAT patients showed improvement (29% to IGT and 29% to normal). Glucose metabolism deteriorated in group 2 with 14% (n=10) developing IGT and 3% (n=2) developing NODAT.

CONCLUSIONS

Glucose metabolism can deteriorate in transplant recipients despite passive lifestyle modification advice. This study shows active lifestyle modification benefits high-risk transplant recipients with glucose intolerance and should be aggressively pursued.