Normal proinsulin processing despite beta-cell dysfunction in persistent hyperinsulinaemic hypoglycaemia of infancy (nesidioblastosis)

Summary Persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI) is a genetic disorder which causes severe hypoglycaemia in the neonate. The beta cells fail to respond to changes in blood glucose levels in all the stages of the disease, which often ends with NIDDM. Fasting insulin, intact proinsulin and des 31,32 split proinsulin levels were measured in PHHI patients with active disease, patients after partial pancreatectomy, and those in clinical remission. All but one of the pancreatectomized patients developed diabetes and were hyperglycaemic on evaluation. Fasting insulin was comparable in pancreatectomized and medically treated patients. Des 31,32 split proinsulin levels were much higher in pancreatectomized compared to non-pancreatectomized patients (10.7 ± 2.5 vs 3.4 ± 0.8 pmol/l, p = 0.001) and age-matched control subjects (3.8 ± 1.4 pmol/l, p = 0.018). Also the ratio of des 31,32 split proinsulin to total insulin plus proinsulin-like peptides was higher in pancreatectomized patients (18.7 ± 2.8 vs 7.2 ± 0.8 % in non-pancreatectomized patients, p = 0.001, and 6.8 ± 2.1 % in normal control subjects, p = 0.004). Furthermore, des 31,32 split proinsulin was the dominating species of proinsulin-like molecules in the pancreatectomized patients (62.7 ± 1.6 % vs 45.5 ± 3.8 %, and 49.0 ± 3.2 % in non-pancreatectomized patients and control subjects, respectively, p = 0.001 and p = 0.0002). Intact proinsulin levels, and the proinsulin percentage, tended to be higher in pancreatectomized patients; however, the differences did not reach statistical significance. All parameters were similar in non-pancreatectomized patients and age-matched control subjects. Subgroup analysis showed comparable proinsulin-like peptide levels in patients with active disease and those in apparent clinical remission. Fasting levels of insulin and proinsulin-like peptides were also measured in a larger group of healthy children and young adults. Insulin and des 31,32 split proinsulin increased with age, the differences being most prominent when the young age group (0–8 years) was compared to the older groups (8–16 and > 16 years). The fasting levels of plasma insulin were correlated with those of intact proinsulin and des 31,32 split proinsulin (r = 0.82 and 0.81, respectively). Fasting insulin, intact proinsulin and des 31,32 split proinsulin were correlated with BMI (r = 0.55, 0.56 and 0.53, respectively). In summary, relative hyperproinsulinaemia was noted only in PHHI patients with increased secretory demand following pancreatectomy, but not in patients with active disease or those in spontaneous clinical remission. These findings suggest that abnormal proinsulin processing is not an intrinsic feature of PHHI despite the severe beta-cell dysfunction. [Diabetologia (1996) 39: 1338–1344] Received: 28 February 1996 and in revised form: 23 May 1996     

Characterization of genes encoding the pancreatic beta-cell ATP-sensitive K+ channel in persistent hyperinsulinemic hypoglycemia of infancy in Japanese patients

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a genetic disorder characterized by unregulated insulin secretion and profound hypoglycemia. Recently, mutations of SUR1 and Kir6.2, which constitute the pancreatic beta-cell ATP-sensitive potassium (K(ATP)) channel, have been shown to be associated with familial PHHI in certain ethnic groups. In the present study, we examined clinical symptoms, therapy, and variations in the SUR1 and Kir6.2 genes in eight Japanese patients with PHHI. Four patients were being treated with pharmacological agents and the other four had required pancreatectomy to normalize glucose levels. There was no difference in timing of the onset of hypoglycemia between the groups. There also was no difference in severity between the two groups, as assessed by blood glucose levels, plasma insulin levels, and birth weight. However, all of the pancreatectomized patients and none of the medically treated group had presented with seizures. By genetic screening, we found eleven nucleotide substitutions in the SUR1 gene, three of which result in amino acid changes, and three nucleotide substitutions in the Kir6.2 gene, two of which result in amino acid changes, but all of these genetic variants had been previously reported in normal subjects. These results indicate that the mechanism of hypoglycemia in these patients is different from those previously reported in PHHI patients, giving further support to the view that PHHI is a heterogeneous disorder.     

Regulation of insulin release in persistent hyperinsulinaemic hypoglycaemia of infancy studied in long-term culture of pancreatic tissue

Summary Pancreatic tissue was obtained during therapeutic subtotal pancreatectomy from five infants with persistent hyperinsulinaemic hypoglycaemia of infancy (so-called nesidioblastosis). Collagenase digests of the specimens were cultured in RPMI 1640 medium on extracellular matrix-coated plates. Acute insulin secretion showed minimal sensitivity to changes in glucose concentration. Sensitivity to other nutrient secretagogues such as glyceraldehyde, leucine, -ketoisocaproic acid and arginine was variable, showing either diminished or absent response. On the other hand, stimulators of Beta cell cAMP and modulators of the phosphoinositide-protein kinase C pathway were effective inducers of insulin release. The response to cAMP stimulators was independent of the glucose concentration. Although insulin output was high in the absence of glucose, this was not due to passive leak of hormone, since both removal of calcium and addition of somatostatin and epinephrine inhibited the secretion. Beta cells were more sensitive to somatostatin than epinephrine; however, both agents failed to completely suppress the release even at suprapharmacological concentrations. Although it cannot be excluded that the culture conditions affected Beta cell function, the present findings may suggest that cultured Beta cells in persistent hyperinsulinaemic hypoglycaemia of infancy behave like fetal Beta cells at early developmental stages.     

Persistent hyperinsulinaemic hypoglycaemia of infancy: long-term treatment with the somatostatin analogue Sandostatin

Six infants with severe, persistent hyperinsulinaemic hypoglycaemia were treated with the long-acting somatostatin analogue SMS 201-995 (Sandostatin, Sandoz, Basle, Switzerland). Effective control of hypoglycaemia without the need for parenteral glucose was achieved in five of the six cases with doses ranging from 10 to 40 micrograms/kg day given either by four s.c. injections per day, or by continuous subcutaneous infusion (CSI). One has been well controlled on SMS 10 micrograms/kg day for 17 months as an out-patient without requiring surgery, while the five others underwent sub-total pancreatectomy after receiving short courses of the drug. In two patients where hypoglycaemia persisted after sub-total pancreatectomy SMS was effective in inhibiting insulin secretion and preventing hypoglycaemia. Plasma somatomedin concentrations and linear growth were not suppressed in any patient. It is concluded that Sandostatin is useful in the pre and post-operative management of most infants with this syndrome. In selected cases this analogue of somatostatin may also be a long-term treatment option in place of pancreatectomy.     

Heterogeneity in disease severity in a family with a novel G68V GCK activating mutation causing persistent hyperinsulinaemic hypoglycaemia of infancy.

BACKGROUND/AIM: Glucokinase (GCK)-activating mutations cause persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI). GCK-PHHI patients have regulated insulin secretion and can usually be treated with diazoxide. The six reported cases suggest that the severity of the mutation predicts the clinical phenotype. The aim of this study was to relate genotype to phenotype [clinical phenotype, glucose-stimulated insulin release (GSIR) and GCK functional analysis] in a large pedigree with eight affected individuals. METHODS: The genes encoding B-cell GCK and the K(ATP) channel subunits (ABCC8 and KCNJ11) were sequenced to identify mutations for functional analysis. Genetic variants influencing B-cell function were genotyped in affected individuals. Islet secretory capacity was determined by oral glucose tolerance test RESULTS: A novel GCK mutation (G68V) co-segregating with hypoglycaemia was identified in eight family members. Kinetic analysis revealed that G68V-GCK activity is ~16 times more than wild-type-GCK with an increased affinity for glucose [concentration at half maximal activation (S(0.5)) 1.94 +/- 0.16 vs. 7.43 +/- 0.12, mutant vs. wild type, mean +/- sem]. Mathematical modelling predicted a threshold for GSIR of 1.9 mmol/l in the mutant. Oral glucose tolerance tests showed regulated insulin secretion. The severity of hypoglycaemia and related symptoms in affected subjects were heterogeneous. Clinical presentations were asymptomatic (n = 1), extreme hunger (n = 3), seizures (n = 2) and loss of consciousness (n = 2); 7/8 were managed with diet but the proband was treated with diazoxide and octreotide. Phenotypic modification by a second mutation in the K(ATP) channel genes (ABCC8, KCNJ11) or by common genetic variants in KCNJ11, GCK and TCF7L2 was excluded. CONCLUSION: The novel activating GCK mutation G68V is associated with variable phenotypic severity, supporting modification of GSIR by genetic and/or environmental factors.     

Glucagon-like peptide-1 (GLP-1) receptors are not overexpressed in pancreatic islets from patients with severe hyperinsulinaemic hypoglycaemia following gastric bypass

Aims/hypothesis  

Glucagon-like peptide-1 (GLP-1) receptors are highly overexpressed in benign insulinomas, permitting in vivo tumour visualisation with GLP-1 receptor scanning. The present study sought to evaluate the GLP-1 receptor status in vitro in other pancreatic disorders leading to hyperinsulinaemic hypoglycaemia, specifically after gastric bypass surgery.     

Genotypes and phenotypes of patients in the UK with carbohydrate-deficient glycoprotein syndrome type 1

18 UK patients (14 families) have been diagnosed with the carbohydrate-deficient glycoprotein syndrome (CDGS), type 1, on the basis of their clinical symptoms and/or abnormal electrophoretic patterns of serum transferrin. Eleven out of the 16 infants died before the age of 2 years. Patients from 12 families had a typical type 1 transferrin profile but one had a variant profile and another, who had many of the clinical features of CDGS type 1, had a normal profile. Eleven of the patients (10 families) with the typical type 1 profile had a deficiency of phosphomannomutase (PMM), (CDGS type 1a) but there was no correlation between residual enzyme activity and severity of disease. All these patients were compound heterozygotes for mutations in the phosphomannomutase (PMM2) gene, with 7 out of the 10 families having the common R141H mutation. Eight different mutations were found, including three novel ones. There was no correlation between genotype and phenotype, although siblings had similar phenotypes. Three patients, including the one with the normal transferrin profile, did not have a deficiency of phosphomannomutase or phosphomannose isomerase (CDGS 1b).     

Beneficial effects of K-ATP channel openers in diabetes: an update on mechanisms and clinical experiences

Stresses associated with the diabetic state participate in the demise of β-cells and therapies that eliminate or reduce such stresses are much needed. K-ATP channel openers, of which diazoxide is the most studied, are potentially useful because experimental studies show that they can counteract chronic over-stimulation of β-cells and protect against toxic conditions, including relative hypoxia. Several mechanisms may underlie the beneficial effects of diazoxide; these may include both indirect (counteracting over-stimulation) and direct mitochondrial effects.
Side effects of diazoxide have limited its use in human trials. We have tested lower doses than previously of diazoxide and thereby largely eliminated side effects. In this setting, we demonstrate positive effects on β-cell function in type 2 diabetic patients who were simultaneously treated with bedtime insulin. However, such effects were absent in insulin-naïve patients. In newly diagnosed type 1 diabetic patients, a 6-month intervention with diazoxide failed to result in better preservation of β-cell function. K-ATP channel openers have a potential to improve β-cell function in subgroups of type 2 diabetes patients. Analogues of diazoxide with more potency in relation to side effects would heighten the possibilities for K-ATP channel openers to be of therapeutic use in type 1 diabetes.     

Genotypes,phenotypes and treatment with immunomodulators in the rheumatic diseases

The autoimmune rheumatological diseases rheumatoid arthritis (RA), spondyloarthritis (SpA) and systemic lupus erythematosus (SLE) are treated with conventional immunosuppressive agents and with modern biological immunomodulators. The latter group of medications have brought about a major change in our ability to control RA and SpA, with more modest results for SLE. The biologicals are very specific in their mechanisms of action, targeting one specific cytokine or one particular cellular marker. Because of this, their efficacy can readily be linked to a single immunomodulatory mechanism. This observation has fuelled hopes that the efficacy of these agents can be predicted at the individual level based on the patient's genetic predisposition, immunological profile or disease phenotype. Whilst the biologic therapies have improved the prospects for patients with these diseases very significantly, the hope that they could be targeted to the patient in an individualized manner has not completely born fruit. In this review, I will argue that we are witnessing important progress in this field, and that justified hope exists for true advances in precision medicine in the autoimmune diseases in the coming years.     

Potent and selective activation of the pancreatic beta-cell type KATP channel by two novel diazoxide analogues

Aims/hypothesis We investigated the pharmacological properties of two novel ATP sensitive potassium (K_ATP) channel openers, 6-Chloro-3-isopropylamino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NNC 55-0118) and 6-chloro-3-(1-methylcyclopropyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (NN414), on the cloned cardiac (Kir6.2/SUR2A), smooth muscle (Kir6.2/SUR2B) and pancreatic beta cell (Kir6.2/SUR1) types of K_ATP channel.Methods We studied the effects of these compounds on whole-cell currents through cloned K_ATP channels expressed in Xenopus oocytes or mammalian cells (HEK293). We also used inside-out macropatches excised from Xenopus oocytes.Results In HEK 293 cells, NNC 55-0118 and NN414 activated Kir6.2/SUR1 currents with EC₅₀ values of 0.33 µmol/l and 0.45 µmol/l, respectively, compared with that of 31 µmol/l for diazoxide. Neither compound activated Kir6.2/SUR2A or Kir6.2/SUR2B channels expressed in oocytes, nor did they activate Kir6.2 expressed in the absence of SUR. Current activation was dependent on the presence of intracellular MgATP, but was not supported by MgADP.Conclusion/interpretation Both NNC 55-0118 and NN414 selectively stimulate the pancreatic beta-cell type of K_ATP channel with a higher potency than diazoxide, by interaction with the SUR1 subunit. The high selectivity and efficacy of the compounds could prove useful for treatment of disease states where inhibition of insulin secretion is beneficial.Abbreviations K_ATP channel ATP-sensitive potassium channel - SUR sulphonylurea receptor - KCO K⁺ channel opener - Kir inwardly rectifying K⁺ channel - TEVC two electrode voltage clamp - HEK293 cell Human Embryonic Kidney 293 cell     

Characteristics of pancreatic beta-cell secretion in Type 2 diabetic patients treated with gliclazide and glibenclamide

The aim of the present cross-over study was to compare the beta-cell response to gliclazide and glibenclamide administered orally during and following a hyperglycaemic clamp in sulphonylurea treated Type 2 diabetes. Nine patients (6 males), aged 61.4 (S.D. 6.9) years with a body mass index of 27.5 (3.1) kg m(-2) and HbA(1c) at baseline of 7.2 (0.9)% were included. Eight healthy control subjects underwent the same tests. Patients received 80-240 mg gliclazide or 5-15 mg glibenclamide for 6 weeks. Thirty minutes after administration of 160 mg of gliclazide or 10 mg of glibenclamide a 1-h hyperglycaemic clamp (11.0 mmol l(-1)) was begun, and followed by a 3.5-h observation period. Nadir blood glucose levels were 4.2 (1.0), 4.3 (1.2) and 3.4 (1.0) mmol l(-1) for glibenclamide gliclazide and controls, respectively (both P=0.07 vs. controls). Glucose levels decreased slowly and linearly in people with diabetes and reached nadirs after 204 (8) and 198 (18) min, respectively, after cessation of glucose infusion, while in controls, glucose levels declined steeply to a nadir at 98 (47) min (P<0.003 vs. both drugs). No first phase insulin secretion peak was observed in people with diabetes. Insulin levels remained elevated during the 3-h observation period in SU treated patients but, in control subjects decreased to baseline values within 2 h of the clamp. The proinsulin to C-peptide ratio increased during the observation period. In conclusion, the effects of glibenclamide and gliclazide on insulin secretion are very similar in patients with Type 2 diabetes who are in moderate glycaemic control, with a slow rise to lower amplitude, poor responsiveness to falling glucose levels, and raised proinsulin to C-peptide ratio.     

初诊肥胖2型糖尿病患者短期胰岛素强化治疗的临床研究

目的 研究初诊肥胖2型糖尿病(DM)患者短期胰岛素强化治疗后胰岛β细胞功能变化，探求更好的血糖控制达标方案。方法 将空腹血糖≥11.1mmol／L和(或)餐后2小时血糖≥16mmol／L的120例初诊肥胖2型DM患者分为三组，其中合并酮症19例作为A组，其余随机分为B组和C组(对照组)。A、B组采用胰岛素强化治疗后同C组一样进入研究，观察随访2年时三组血糖达标后胰岛β细胞功能变化和治疗方案。结果 随访2年时，三组间胰岛素分泌指数(HOMA-IS)有显著性差异，C组与A、B组和自身1年时比较HOMA-IS显著降低，但与初诊时无显著性差异，A、B组满1年时仍保持胰岛素分泌功能。A组和B组以食疗和运动疗法以及加二甲双胍治疗为主占78．2％；C组68．6％的患者需加磺脲类药物治疗，11．8％需要胰岛素治疗。结论 2型DM患者经短期胰岛素强化治疗后，对恢复和保持胰岛β细胞功能起到一定作用，2年内多数患者以基础治疗和二甲双胍治疗为丰。