John Mace

Multiple Acyl-CoA Dehydrogenase Deficiency (Glutaric Aciduria Type II) with Transient Hypersarcosinemia and Sarcosinuria; Possible Inherited Deficiency of an Electron Transfer Flavoprotein

Summary: When amino acids were infused at a rate of 4 g/kg/day, an infant with hypoglycemia, metabolic acidemia and chronic regurgitation showed hypersarcosinemia and excreted abnormal amounts of sarcosine, isovalerylglycine, isobutyrylglycine, α-methylbutyrylglycine, and β-hydroxyisovaleric, glutaric, α-hydroxyglutaric, methylsuccinic, and α-hydroxyisobutyric acids in urine. On all other occasions, when protein intake was lower and lipid intake higher, urine organic acids were dominated by methylsuccinic, ethylmalonic, and α-hydroxyglutaric acids, and hypersarcosinemia was absent. Autopsy showed severe fatty changes in liver, kidneys, and skeletal muscle. A previous female sibling had died with similar autopsy findings at 4 days of age. While activity of glutaryl-CoA dehydrogenase was completely deficient in liver and almost completely so in kidney, it was normal in cultured fibroblasts in the presence of flavin adenine dinucleotide (FAD) and only marginally low in its absence. Incorporation of d-(2-14C) riboflavin into flavin mononucleotides (FMN) and FAD by kidney tissue was normal.The authors conclude that this disorder is not due to generalized deficiency of glutaryl-CoA dehydrogenase or to a defect in FAD synthesis. The amino and organic acid abnormalities noted are most consistent with a defect in the flavoprotein which transfers electrons from the FAD of sarcosine and acyl-CoA dehydrogenases into the respiratory chain, although a defect in intercompartmental transfer of C4-5 acyl CoA esters across cell membranes is not excluded.The variability of the organic aciduria, which possibly reflects changes in protein and fat intake, suggests that a previous name for this disorder, i.e., glutaric aciduria type II, is inappropriate and should be replaced, perhaps by “multiple acyl-CoA dehydrogenase deficiency.”Speculation: What appears to be simultaneous deficiency of several acyl-CoA dehydrogenases may be caused by a number of different primary gene defects; the presence of hypersarcosinemia and/or sarcosinuria may delineate a subtype due to deficiency of an electron carrier flavoprotein. Further, the presence of organic aciduria may define a form of hypersarcosinemia more likely to be associated with phenotypic abnormalities than isolated deficiency of the sarcosine dehydrogenase apoenzyme.

Dynamic Production of Hypoxia‐Inducible Factor‐1α in Early Transplanted Islets

More than half of transplanted β‐cells undergo apoptotic cell death triggered by nonimmunological factors within a few days after transplantation. To investigate the dynamic hypoxic responses in early transplanted islets, syngeneic islets were transplanted under the kidney capsule of balb/c mice. Hypoxia‐inducible factor‐1α (HIF‐1α) was strongly expressed at post‐transplant day (POD) 1, increased on POD 3, and gradually diminished on POD 14. Insulin secretion decreased on POD 3 in association with a significant increase of HIF‐1α‐related β‐cell death, which can be suppressed by short‐term hyperbaric oxygen therapy. On POD 7, apoptosis was not further activated by continually produced HIF‐1α. In contrast, improvement of nerve growth factor and duodenal homeobox factor‐1 (PDx‐1) production resulted in islet graft recovery and remodeling. In addition, significant activation of vascular endothelial growth factor in islet grafts on POD 7 correlated with development of massive newly formed microvessels, whose maturation is advanced on POD 14 with gradual diminution of HIF‐1α. We conclude that (1) transplanted islets strongly express HIF‐1α in association with β‐cell death and decreased insulin production until adequate revascularization is established and (2) early suppression of HIF‐1α results in less β‐cell death thereby minimizing early graft failure.

Air pollution and type 1 diabetes in children

Background: Over the past decade, there has been a worldwide largely unexplained increase in the incidence of type 1 diabetes in young children. This study explores the quantitative role of exposure to specific air pollutants in the development of type 1 diabetes in children.

In vitro and in vivo improvement of islet survival following treatment with nerve growth factor.

Background. Nerve growth factor (NGF) has been reported to play an important regulatory role in pancreatic beta-cell function. However, the usefulness of NGF in a transplantation setting is unknown. Methods. A marginal number of islet cells (260 islet equivalents/recipient) cultured for 24 hr with NGF (500 ng/ml) was syngeneically transplanted under the kidney capsule of streptozotocin-induced diabetic Balb/c mice. Fluorescence microscopy was used to evaluate islet viability. Islet function was evaluated in vitro and in vivo by static assay and glucose tolerance test, respectively. Results. In vitro, improved viability and survival were found in murine islets cultured in serum-free medium for 96 hr with 500 ng/ml NGF (P<0.05). NGF-treated islets had more insulin secretion than islets cultured without NGF in response to 2.8 mmol/L glucose (P<0.05), and 20 mmol/L glucose conditions. In vivo, 67% of recipients with a submarginal number of islets cultured in NGF attained normoglycemia for more than 120 days, whereas transplanted islets without NGF treatment survived a maximum of 13 days in control mice. At posttransplant day 4, recipients of NGF-cultured islets showed significant improvement of glucose tolerance. On immunohistochemistry, the kidney capsules containing NGF-cultured islets displayed higher insulin content, and more dilated neoplastic microvessels than control renal capsules. The number of apoptotic cells using TUNEL staining decreased by nearly 50% in NGF-cultured islet grafts in comparison to control islet grafts. Conclusions. The above data suggest potential advantages of NGF for islet survival following transplantation. This neurotrophic approach may prove beneficial in human islet transplantation.

Effect of therapy with insulin glargine (lantus) on glycemic control in toddlers, children, and adolescents with diabetes.

To determine the effect of insulin glargine on glycemic control in pediatric type 1 and 2 diabetes, a retrospective repeated-measure analysis of variance was performed of hemoglobin A1C (HbA1C), frequency of hypoglycemia and hyperglycemia, mean blood glucose, body mass index (BMI), and daily weight-adjusted insulin dosage before and after institution of glargine therapy in 72 children and adolescents with diabetes. At glargine start, age range was 1.2-19.6 years, mean age was 12.5 +/- 4.6 years, BMI was 22.48 +/- 6.3 kg/m(2), and mean HbA1C was 9.7 +/- 1.9%. Mean duration of diabetes was 3.58 years, and mean baseline insulin dose was 0.93 U/kg/day. Gender breakdown was 60% female, and the majority (83%) had type 1 diabetes. Average HbA1C decreased from 9.5% pre-glargine to 8.6% post-glargine (p < 0.001). HbA1C decrease was significant in both types of diabetes without a concomitant increase in frequency of hypoglycemia, BMI, or weight-adjusted insulin dose. Hypoglycemia decreased significantly in type 1 diabetes. Thus, glargine therapy may decrease HbA1C and frequency of hypoglycemia in toddlers, children, and adolescents with diabetes, without an increase in BMI or insulin requirements.

Pediatric Post-Transplant Diabetes: Data From a Large Cohort of Pediatric Heart-Transplant Recipients

A retrospective analysis of 381 pediatric heart‐transplant recipients was performed to determine the frequency, characteristics, and risk factors for post‐transplant diabetes. The rate of post‐transplant diabetes was 1.8% with antithymocyte globulin, cyclosporine and azathioprine as primary immunosuppressive therapy. Time from transplant to diabetes was 0.25–13 years. Diabetes was characterized by reversibility, and lack of insulinopenia and autoimmunity. The post‐transplant diabetes rate in tacrolimus‐converted children (n = 45) was 8.8%. In tacrolimus‐converted children, age at transplant, mean and maximum tacrolimus blood levels, and first‐year rejection episodes were higher in the post‐transplant diabetes group, which also consistently had DR‐mismatched transplants and HLA DR3/DR4 haplotypes. Body mass index was not different between diabetic and control tacrolimus‐converted children. In conclusion, pediatric post‐transplant diabetes may be related to reversible insulin resistance. Tacrolimus levels, HLA DR mismatch, and older age at transplant may predispose to post‐transplant diabetes.

MRI assessment of ischemic liver after intraportal islet transplantation.

Background. There is a recent focus on embolization of the portal vein by transplanted islets as a major cause of early graft loss. The resultant ischemia causes necrosis or apoptosis of cells within the liver. Thus, noninvasive assessment of the liver receiving the islet transplant is important to evaluate the status islet grafts. Methods. This study used noninvasive magnetic resonance imaging (MRI) for assessment of the posttransplant ischemic liver. Syngeneic islets in streprozotocin-induced diabetic mice were used. MRI and morphological liver assessments were performed at 0, 2, and 28 days after transplantation. Histologic assessment of insulin, hypoxia induced factor 1-&agr;, and apoptosis were undertaken at similar time points. Results. Ischemic/necrotic regions in the liver were detected by MRI at 2 days but not at 28 days after transplantation and were confirmed histologically. Liver injury was quantified from high intensity areas on T2-weighted images. Insulin release peaked 2 days after transplantation. Conclusion. Onset and reversal of liver ischemia due to intraportal islet transplantation are detectable using T2-weighted MRI. These changes coincide with periods of maximum insulin release likely due to partial islet destruction. We propose that MRI, as a noninvasive monitor of graft-related ischemia, may be useful in assessment of liver and islet engraftment after intraportal islet transplantation in a clinical setting.

Role of exposure to air pollutants in the development of type 1 diabetes before and after 5 yr of age.

Abstract: Objective:  To assess the role of ambient air pollutants in type 1 diabetes in children.

In vivo imaging demonstrates a time-line for new vessel formation in islet transplantation

Abstract:  Vascularization of transplanted islets must be maintained to provide long‐term graft function. In vivo assessment of new vessel formation in islet grafts has been poorly documented. The purpose of this study was to investigate whether neovascularization was detectable in vivo in a Feridex‐labeled murine syngeneic subcapsular islet mass using DCE MRI over 180 days. Subcapsular transplants could be visualized at post‐transplant days three, seven, 14, and 28 using T2‐weighted MRI and at post‐transplant day 180 by immunohistochemistry. Injection of the contrast agent gadolinium (Gd)‐DTPA for DCE at three, seven, and 14 days showed increased signal in the transplant area consistent with new vessel formation. Areas under contrast enhancement curves suggested peak angiogenesis at 14 days. At 180 days, there was no observable change in signal intensity after contrast injection suggesting established vascularization or islet mass reduction. Immunohistochemistry confirmed MRI and DCE findings. These data suggest that islet angiogenesis occurs early after transplantation and is likely established after one month of transplantation. This study provides an in vivo time‐line of neovascularization in subcapsular islet grafts. We anticipate that contrast extravasation captured by MRI may provide useful monitoring of graft angiogenesis if reproduced in a clinically relevant intraportal model.

In vivo magnetic resonance imaging of vascularization in islet transplantation

To evaluate changes in neovascularization of transplanted islets in vivo, dynamic contrast (gadolinium) enhanced magnetic resonance imaging (MRI) was used. Both iron (Feridex)‐labeled and unlabeled syngeneic murine subcapsular islet grafts were studied. Differences in dynamic contrast enhancement of islet grafts were quantified after gadolinium injection at post‐transplant days 3 and 14. Normalized contrast concentrations at day 14 in transplanted islets were increased relative with that on day 3. Time to peak contrast enhancement was faster by 12 min at day 14 compared to day 3 islets (while kidney and muscle peak times remained the same). Areas under the curve for contrast concentration versus time plots were larger in 14‐day relative to 3‐day islet grafts. In conclusion, noninvasive assessment of neovascularization is achievable. In vivo dynamic contrast‐enhanced MRI can be used to detect and quantify changes in vascularization following islet transplantation. This technique may be useful in developing pro‐angiogenic strategies to improve the transplantation outcome in experimental and clinical settings.