Incidence of new-onset diabetes mellitus and association with mortality in childhood solid organ transplant recipients: a population-based study

BACKGROUND

Precise estimates of the long-term risk of new-onset diabetes and its impact on mortality among transplanted children are not known.

METHODS

We conducted a cohort study comparing children undergoing solid organ (kidney, heart, liver, lung and multiple organ) transplant (n = 1020) between 1991 and 2014 with healthy non-transplanted children (n = 7 134 067) using Ontario health administrative data. Outcomes included incidence of diabetes among transplanted and non-transplanted children, the relative hazard of diabetes among solid organ transplant recipients, overall and at specific intervals posttransplant, and mortality among diabetic transplant recipients.

RESULTS

During 56 019 824 person-years of follow-up, the incidence rate of diabetes was 17.8 [95% confidence interval (CI) 15-21] and 2.5 (95% CI 2.5-2.5) per 1000 person-years among transplanted and non-transplanted children, respectively. The transplant cohort had a 9-fold [hazard ratio (HR) 8.9; 95% CI 7.5-10.5] higher hazard of diabetes compared with those not transplanted. Risk was highest within the first year after transplant (HR 20.7; 95% CI 15.9-27.1), and remained elevated even at 5 and 10 years of follow-up. Lung and multiple organ recipients had a 5-fold (HR 5.4; 95% CI 3.0-9.8) higher hazard of developing diabetes compared with kidney transplant recipients. Transplant recipients with diabetes had a three times higher hazard of death compared with those who did not develop diabetes (HR 3.3; 95% CI 2.3-4.8).

CONCLUSIONS

The elevated risk of diabetes in transplant recipients persists even after a decade, highlighting the importance of ongoing surveillance. Diabetes after transplantation increases the risk of mortality among childhood transplant recipients.

Association of low birth weight and prematurity with clinical outcomes of childhood nephrotic syndrome: a prospective cohort study

BACKGROUND

Low birth weight (LBW)/prematurity have been proposed as risk factors for the development of kidney disease in adulthood. Whether there is an association between LBW/prematurity and poor renal outcomes in childhood onset nephrotic syndrome remains unknown.

METHODS

Children with nephrotic syndrome diagnosed between 1 and 18 years of age were followed prospectively from 1996 to 2016 at The Hospital for Sick Children (N = 377). LBW/prematurity was defined as birth weight < 2500 g or gestational age < 36 weeks. Normal birth weight (NBW) was defined as birth weight ≥ 2500 g. Measures evaluating clinical course of nephrotic syndrome include initial steroid-resistant nephrotic syndrome (SRNS), time to first relapse, and frequently relapsing nephrotic syndrome. Kaplan-Meier survival analysis, logistic regression, and Cox proportional hazards regression were used to determine the association of LBW/prematurity with clinical outcomes.

RESULTS

Median birth weights in LBW/premature (n = 46) and NBW (n = 331) children were 2098 g (interquartile range [IQR] 1700-2325 g) and 3317 g (IQR 2977-3685 g), respectively. Odds of having SRNS were 3.78 (95% confidence interval [CI] 1.28-11.21) times higher among LBW/premature children than NBW children. An 8% decrease in odds of developing SRNS was observed for every 100 g increase in birth weight (adjusted odds ratio [OR] 0.92; 95% CI 0.86-0.98). Median time to first relapse did not differ (hazard ratio [HR] 0.89; 95% CI 0.53-1.16).

CONCLUSIONS

LBW/premature children were more likely to develop SRNS but did not have a difference in time to first relapse with NBW children. Understanding the impact and mechanism of birth weight and steroid-resistant disease needs further study.

Patterns of kidney injury in pediatric nonkidney solid organ transplant recipients

The incidence of acute kidney injury (AKI) and its impact on chronic kidney disease (CKD) following pediatric nonkidney solid organ transplantation is unknown. We aimed to determine the incidence of AKI and CKD and examine their relationship among children who received a heart, lung, liver, or multiorgan transplant at the Hospital for Sick Children between 2002 and 2011. AKI was assessed in the first year posttransplant. Among 303 children, perioperative AKI (within the first week) occurred in 67% of children, and AKI after the first week occurred in 36%, with the highest incidence among lung and multiorgan recipients. Twenty-three children (8%) developed CKD after a median follow-up of 3.4 years. Less than 5 children developed end-stage renal disease, all within 65 days posttransplant. Those with 1 AKI episode by 3 months posttransplant had significantly greater risk for developing CKD after adjusting for age, sex, and estimated glomerular filtration rate at transplant (hazard ratio: 2.77, 95% confidence interval, 1.13-6.80, P trend = .008). AKI is common in the first year posttransplant and associated with significantly greater risk of developing CKD. Close monitoring for kidney disease may allow for earlier implementation of kidney-sparing strategies to decrease risk for progression to CKD.

Incidence of hyperglycemia and diabetes and association with electrolyte abnormalities in pediatric solid organ transplant recipients

Background

Posttransplant hyperglycemia is an important predictor of new-onset diabetes after transplantation, and both are associated with significant morbidity and mortality. Precise estimates of posttransplant hyperglycemia and diabetes in children are unknown. Low magnesium and potassium levels may also lead to diabetes after transplantation, with limited evidence in children.

Methods

We conducted a cohort study of 451 pediatric solid organ transplant recipients to determine the incidence of hyperglycemia and diabetes, and the association of cations with both endpoints. Hyperglycemia was defined as random blood glucose levels ≥11.1 mmol/L on two occasions after 14 days of transplant not requiring further treatment. Diabetes was defined using the American Diabetes Association Criteria. For magnesium and potassium, time-fixed, time-varying and rolling average Cox proportional hazards models were fitted to evaluate the association with hyperglycemia and diabetes.

Results

Among 451 children, 67 (14.8%) developed hyperglycemia and 27 (6%) progressed to diabetes at a median of 52 days (interquartile range 22-422) from transplant. Multi-organ recipients had a 9-fold [hazard ratio (HR) 8.9; 95% confidence interval (CI) 3.2-25.2] and lung recipients had a 4.5-fold (HR 4.5; 95% CI 1.8-11.1) higher risk for hyperglycemia and diabetes, respectively, compared with kidney transplant recipients. Both magnesium and potassium had modest or no association with the development of hyperglycemia and diabetes.

Conclusions

Hyperglycemia and diabetes occur in 15 and 6% children, respectively, and develop early posttransplant with lung or multi-organ transplant recipients at the highest risk. Hypomagnesemia and hypokalemia do not confer significantly greater risk for hyperglycemia or diabetes in children.

Incidence and risk factors of early surgical complications in young renal transplant recipients: A persistent challenge

There is a paucity of data on the rate of urological and vascular complications in very young children after kidney transplant. We conducted a study on the incidence and risk factors for early post-transplant surgical complications in young recipients (<5 years) over three decades. The primary outcome was any urological or vascular complication within 30 days of transplant, and the secondary outcome was incidence rate of graft failure reported as per 1000 person-years. Risk factors associated with surgical complications were analyzed by logistic regression. There were 22 (26.5%) complications in 21 children with vascular thrombosis being the most common complication. There was no significant difference in the number of complications in period 1 (1985-1994) and period 2 (1995-2014) (P=.1). The incidence rate of graft failure was higher in period 1 (IR 70.8, 95% CI 41.1, 121.9) compared to period 2 (IR 20.7, 95% CI 9.3, 46.0). Cumulative incidence of graft survival at 1, 3, and 5 years' post-transplant was 96.5%, 92.6%, and 90%, respectively, in those without compared to 71%, 65.1%, and 58.6%, respectively, in children with complications. In conclusion, early surgical, especially vascular, complications are quite common in young renal transplant recipients and lead to significantly reduced graft survival.

Parental Health Literacy and Outcomes of Childhood Nephrotic Syndrome

OBJECTIVE

Determine the association of parental health literacy with treatment response among children with nephrotic syndrome.

METHODS

This was a cohort study of children aged 1-18 with nephrotic syndrome and their parent. Health literacy was measured using the validated Short Test of Functional Health Literacy in Adults assessing reading comprehension and numeracy. Outcomes included initial relapse-free period, frequently relapsing disease, relapse rate, second-line medication use, and complete remission after therapy.

RESULTS

Of 190 parents, 80% had adequate health literacy (score >67 of 100), and higher scores were not correlated with higher education. Almost all achieved perfect numeracy scores (>86%); numeracy was not associated with outcomes. After adjusting for immigration, education, and income, higher reading comprehension scores (tertile 3) compared with lower scores (tertile 1) were significantly associated with lower risk of first relapse (hazard ratio 0.67, 95% confidence interval [CI] 0.48-0.94, P trend = .02), lower odds of frequently relapsing disease (odds ratio [OR] 0.38, 95% CI 0.21-0.70, P trend = .002), lower relapse rate (rate ratio 0.77, 95% CI 0.73-0.80, P trend < .001), and higher odds of complete remission after both initial steroids and cyclophosphamide (OR 2.07, 95% CI 1.36-3.16, P trend = .003; OR 5.97, 95% CI 2.42-14.7, P trend < .001).

CONCLUSIONS

Lower parental health literacy, specifically reading comprehension, is associated with higher relapse rates among children with nephrotic syndrome and fewer achieving complete remission. This underscores the importance of assessing and targeting health literacy for chronic management of childhood-onset diseases.

Ethnic Differences in Incidence and Outcomes of Childhood Nephrotic Syndrome

BACKGROUND AND OBJECTIVES

Ethnic differences in outcomes among children with nephrotic syndrome are unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a longitudinal study at a single regional pediatric center comparing ethnic differences in incidence from 2001 to 2011 census data and longitudinal outcomes, including relapse rates, time to first relapse, frequently relapsing disease, and use of cyclophosphamide. Among 711 children, 24% were European, 33% were South Asian, 10% were East/Southeast Asian, and 33% were of other origins.

RESULTS

Over 10 years, the overall incidence increased from 1.99/100,000 to 4.71/100,000 among children ages 1-18 years old. In 2011, South Asians had a higher incidence rate ratio of 6.61 (95% confidence interval, 3.16 to 15.1) compared with Europeans. East/Southeast Asians had a similar incidence rate ratio (0.76; 95% confidence interval, 0.13 to 2.94) to Europeans. We determined outcomes in 455 children from the three largest ethnic groups with steroid-sensitive disease over a median of 4 years. South Asian and East/Southeast Asian children had significantly lower odds of frequently relapsing disease at 12 months (South Asian: adjusted odds ratio; 0.55; 95% confidence interval, 0.39 to 0.77; East/Southeast Asian: adjusted odds ratio; 0.42; 95% confidence interval, 0.34 to 0.51), fewer subsequent relapses (South Asian: adjusted odds ratio; 0.64; 95% confidence interval, 0.50 to 0.81; East/Southeast Asian: adjusted odds ratio; 0.47; 95% confidence interval, 0.24 to 0.91), lower risk of a first relapse (South Asian: adjusted hazard ratio, 0.74; 95% confidence interval, 0.67 to 0.83; East/Southeast Asian: adjusted hazard ratio, 0.65; 95% CI, 0.63 to 0.68), and lower use of cyclophosphamide (South Asian: adjusted hazard ratio, 0.82; 95% confidence interval, 0.53 to 1.28; East/Southeast Asian: adjusted hazard ratio, 0.54; 95% confidence interval, 0.41 to 0.71) compared with European children.

CONCLUSIONS

Despite the higher incidence among South Asians, South and East/Southeast Asian children have significantly less complicated clinical outcomes compared with Europeans.

Parental attitudes to genetic testing differ by ethnicity and immigration in childhood nephrotic syndrome: a cross-sectional study

Background

Studies in the USA report differences in opinion among parents of different ethnic groups toward genetic testing for their child; however, there are no studies that address this issue in the diverse ethnic and immigrant population in Canada.

Objective

This study aims to determine whether ethnicity and immigration status influences parental interest in clinical genetic testing for a potentially progressive kidney disease.

Design

This is a cross-sectional study.

Setting

Participants were recruited from the Greater Toronto Area, Canada.

Participants

The study included 320 parents of children ages 1–18 years with nephrotic syndrome enrolled in the Insight into Nephrotic Syndrome: Investigating Genes, Health and Therapeutics (INSIGHT) observational cohort study.

Measurements

Demographic, ethnicity, immigration, and child specific factors as well as interest in genetic testing were collected through self-reported questionnaires administered at baseline study visit.

Methods

Logistic regression models were used to examine association of ethnicity and immigration status with interest in genetic testing.

Results

The majority of parents (85 %) were interested in genetic testing for their child. South Asian and East/Southeast Asian parents had 74 and 76 % lower odds of agreeing to genetic testing when compared to Europeans (odds ratio (OR) 0.26, 95 % confidence interval (CI) 0.10–0.68; OR 0.24, 95 % CI 0.07–0.79, respectively) after controlling for age and sex of child, age and education level of parent, initial steroid resistance, and duration of time in Canada. Immigrants to Canada also had significantly lower odds (OR 0.29, 95 % CI 0.12–0.72) of agreeing to genetic testing after similar adjustment. Higher education level was not associated with greater interest in genetic testing (OR 1.24, 95 % CI 0.64–2.42).

Limitations

Participants have already agreed to aggregate genetic testing for research purposes as part of enrolment in INSIGHT study.

Conclusion

While majority of parents were interested in genetic testing for their child, immigrants, particularly South Asians and East/Southeast Asians, were more likely to decline genetic testing. Genetic counseling needs to be tailored to address specific concerns in these parental groups to maximize informed decision-making in the clinical setting.

Trial registration

ClinicalTrials.gov, NCT01605266

Functional organization of the GluR1 glutamate receptor promoter

The GluR1 glutamate receptor subunit is expressed in most brain areas and plays a major role in excitatory synaptic transmission. We cloned and sequenced 5 kilobase pairs of the rat GluR1 promoter and identified multiple transcriptional start sites between -295 and -202 (relative to the first ATG). Similar to other glutamate receptor subunit promoters, the GluR1 promoter lacks TATA and CAAT elements in that region but binds Sp1 proteins at two sites. Promoter activity of GluR1 fragments cloned into pGL3 was assessed by immunocytochemistry and by measuring luciferase activity after transfection into primary cultures of rat cortical neurons and glia. GluR1 promoter activity was stronger in neurons, with neuronal specificity appearing to reside mainly within the neuronal expression-enhancing regions, -1395 to -743 and -253 to -48. The latter region contains 4 sites that bound recombinant cAMP-response element-binding proteins and a glial silencing region between -253 and -202. In both neurons and glia, promoter activity was increased by a 64-base pair GA repeat upstream of the initiation sites and reduced by a 57-base pair region that contained an N box. In contrast to the GluR2 promoter the regulatory regions are mainly located outside of the GluR1 initiation region.

Genetic regulation of glutamate receptor ion channels

Transcriptional and translational regulation of glutamate receptor expression determines one of the key phenotypic features of neurons in the brain--the properties of their excitatory synaptic receptors. Up- and down-regulation of various glutamate receptor subunits occur throughout development, following ischemia, seizures, repetitive activation of afferents, or chronic administration of a variety of drugs. The promoters of the genes that encode the NR1, NR2B, NR2C, GluR1, GluR2, and KA2 subunits share several characteristics that include multiple transcriptional start sites within a CpG island, lack of TATA and CAAT boxes, and neuronal-selective expression. In most cases, the promoter regions include overlapping Sp1 and GSG motifs near the major initiation sites, and a silencer element, to guide expression in neurons. Manipulating the levels of glutamate receptors in vivo by generating transgenic and knockout mice has enhanced understanding of the role of specific glutamate receptor subunits in long-term potentiation and depression, learning, seizures, neural pattern formation, and survival. Neuron-specific glutamate receptor promoter fragments may be employed in the design of novel gene-targeting constructs to deliver future experimental transgene and therapeutic agents to selected neurons in the brain.

Blockade of K+ channels induced by AMPA/kainate receptor activation in mouse oligodendrocyte precursor cells is mediated by Na+ entry

AMPA/kainate receptor activation in cultured oligodendrocyte precursor cells from embryonic mouse cortex leads to a blockade of delayed rectifying K+ currents. In the present study, we provide evidence using the patch-clamp technique in the whole-cell configuration that the mechanism linking kainate receptor activation and K+ conductance blockade is due to the receptor-mediated Na+ entry: 1) The blockade was not observed in Na(+)-free bathing solution nor when intracellular [Na+] was elevated by dialzying the cell with a pipette solution containing high [Na+]. 2) Elevation of intracellular [Na+] alone led to a blockade of outward currents in contrast to cells dialyzed by sucrose. High [Li+]i also reduced the outward currents, and in Li(+)-containing bathing solution the kainate-induced blockade of K+ channels was more pronounced. Probably, Li+ accumulates intracellularly after permeation through the receptor pore due to slower extrusion mechanisms. Experiments with GTP gamma S or GDP beta S and pertussis toxin indicated that GTP-binding protein-mediated mechanisms were not of importance for the kainate-induced K+ conductance blockade. Our data suggest that in glial precursor cells AMPA/kainate receptor activation leads to an intracellular [Na+] increase which blocks delayed rectifying K+ channels.

Adult rat optic nerve oligodendrocyte progenitor cells express a distinct repertoire of voltage- and ligand-gated ion channels

Cultured oligodendrocyte progenitor cells derived from the developing central nervous system (CNS) express a pattern of ion channels that is distinct from mature oligodendrocytes and other cell types of the CNS. In the present study, we used the whole-cell patch-clamp technique and the fura-2-based Ca++ imaging system to study the ion channel expression of oligodendrocyte progenitor cells derived from the optic nerves of adult rats. We found that the adult oligodendrocyte progenitor cell membrane is dominated by K+ currents, both delayed outward and inward rectifying. The inwardly rectifying K+ currents were often as large as the outward delayed rectifying K+ currents. The delayed rectifying outward currents were partially blocked by 50 mM tetraethylammonium or 1 mM 4-aminopyridine, but not by 2 or 5 mM BaCl2. This suggests that the delayed rectifier channels expressed by adult progenitor cells are different from those expressed by perinatal cells. Most adult oligodendrocyte progenitor cells showed no or only small A-type K+ currents. Both Ca++ and Na+ channels were also detected in these cells. Furthermore, adult progenitor cells responded to the neurotransmitters GABA and kainate and the pharmacology of these responses indicated that these cells express GABAA receptors and kainate receptors that are Ca(++)-permeable. Our study suggests that adult oligodendrocyte progenitor cells are electrophysiologically distinct and that these cells share electrophysiological characteristics with both perinatal progenitor cells and immature oligodendrocytes.

AMPA/kainate receptor activation in murine oligodendrocyte precursor cells leads to activation of a cation conductance, calcium influx and blockade of delayed rectifying K+ channels

Studies during the last few years have shown that glial cells can express a large repertoire of neurotransmitter receptors. In this study, we have characterized the properties of a glutamate receptor in oligodendrocytes and their precursor cells from cultures of mouse brain, using the patch-clamp technique to measure ligand-activated currents and a fura-2 imaging system to determine changes in free cytosolic Ca2+ concentration ([Ca2+]i). The precursor cells were identified by their characteristic morphology and their voltage-gated currents as described previously [Sontheimer H. et al. (1989) Neuron 2, 1135-1145]. The ligands kainate, domoate and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA), as well as L-glutamate but not trans-1-amino-1,3-cyclopentanedicarboxylate elicited inward currents at a holding potential of -70 mV and the antagonist 6-cyano-7-nitroquinoxaline-2,3-dione blocked the glutamate- and kainate-induced response reversibly, indicating the expression of an AMPA/kainate-type glutamate receptor. The response is due to the activation of a cationic conductance as revealed by analysing the reversal potential of the kainate-activated current. Receptor activation is accompanied by two additional responses: (i) an increase in [Ca2+]i mediated by depolarization and a subsequent activation of voltage-gated Ca2+ channels and (ii) a transient blockade of a delayed rectifying K+ current, but not of the A-type K+ current. The blockade of the K+ current was not due to the increase in [Ca2+]i since it was also observed in Ca(2+)-free bathing solution when no increase in [Ca2+]i was detectable after exposure to kainate. In contrast to precursor cells, oligodendrocytes responded weakly or not at all to glutamate or related ligands. We conclude that glutamate activates a complex pattern of physiological events in the glial precursor cells, which may play a role during the differentiation process of these cells.