ESPE/LWPES consensus statement on diabetic ketoacidosis in children and adolescents.

Diabetic ketoacidosis (DKA) is the leading cause of morbidity and mortality in children with type 1 diabetes mellitus (TIDM). Mortality is predominantly related to the occurrence of cerebral oedema; only a minority of deaths in DKA are attributed to other causes. Cerebral oedema occurs in about 0.3-1% of all episodes of DKA, and its aetiology, pathophysiology, and ideal method of treatment are poorly understood. There is debate as to whether physicians treating DKA can prevent or predict the occurrence of cerebral oedema, and the appropriate site(s) for children with DKA to be managed. There is agreement that prevention of DKA and reduction of its incidence should be a goal in managing children with diabetes.

Recruitment of a repressosome complex at the growth hormone receptor promoter and its potential role in diabetic nephropathy.

The growth hormone (GH)-GH receptor (GHR) axis modulates growth and metabolism and contributes to complications of diabetes mellitus. We analyzed the promoter region of the dominant transcript (L2) of the murine GHR to determine that a cis element, L2C1, interacts with transcription factors NF-Y, BTEB1, and HMG-Y/I. These proteins individually repress GHR expression and together form a repressosome complex in conjunction with mSin3b. The histone deacetylase inhibitor trichostatin A increases expression of the murine GHR gene, enhances association of acetyl-H3 at L2C1, inhibits formation of the repressosome complex, and decreases NF-Y's association with L2C1. Our studies reveal that murine models of experimental diabetes mellitus are characterized by reduced hepatic GHR expression, decreased acetyl-H3 associated with L2C1, and increased formation of the repressosome complex. In contrast, in the kidney diabetes mellitus is associated with enhanced GHR expression and lack of alteration in the assembly of the repressosome complex, thus permitting exposure of kidneys to the effects of elevated levels of GH in diabetes mellitus. Our findings define a higher-order repressosome complex whose formation correlates with the acetylation status of chromatin histone proteins. The delineation of the role of this repressosome complex in regulating tissue-specific expression of GHR in diabetes mellitus provides a molecular model for the role of GH in the genesis of certain microvascular complications of diabetes mellitus.

Grtp1, a novel gene regulated by growth hormone.

An in vitro model of GH-responsive cells was subjected to microarray analysis to identify a novel gene regulated by GH. This 258 amino acid protein, we term GH Regulated TBC Protein-1 (GRTP1), contains the TBC signature motif of GTPase activator proteins of Rab-like small GTPases. Northern blot analysis revealed a 1.3 kb major mRNA species, most abundant in testes. TaqMan assay confirmed that in the mouse, Grtp1 is expressed at highest levels in testes, with lesser abundance in intestine, kidney, lung, and liver. In the testis, expression of Grtp1 significantly increases post-pubertally. Administration of GH to mice increased levels of GRTP1 mRNA in testes (140%), but decreased GRTP1 mRNA abundance in kidney (50%) and liver (25%). Grtp1 was localized to mouse proximal chromosome 8. Orthologs of this protein are present in human, mouse, rat, and drosophila suggesting that GRTP1 has an important biological role(s).

Demonstration of direct effects of growth hormone on neonatal cardiomyocytes.

The cellular and molecular basis of growth hormone (GH) actions on the heart remain poorly defined, and it is unclear whether GH effects on the myocardium are direct or mediated at least in part via insulin-like growth factor (IGF-1). Here, we demonstrate that the cultured neonatal cardiomyocyte is not an appropriate model to study the effects of GH because of artifactual loss of GH receptors (GHRs). To circumvent this problem, rat neonatal cardiomyocytes were infected with a recombinant adenovirus expressing the murine GHR. Functional integrity of GHR was suggested by GH-induced activation of the cognate JAK2/STAT5, MAPK, and Akt intracellular pathways in the cells expressing GHR. Although exposure to GH resulted in a significant increase in the size of the cardiomyocyte and increased expression of c-fos, myosin light chain 2, and skeletal alpha-actin mRNAs, there were no significant changes in IGF-1 or atrial natriuretic factor mRNA levels in response to GH stimulation. In this model, GH increased incorporation of leucine, uptake of palmitic acid, and abundance of fatty acid transport protein mRNA. In contrast, GH decreased uptake of 2-deoxy-d-glucose and levels of Glut1 protein. Thus, in isolated rat neonatal cardiomyocytes expressing GHR, GH induces hypertrophy and causes alterations in cellular metabolic profile in the absence of demonstrable changes in IGF-1 mRNA, suggesting that these effects may be independent of IGF-1.

Limitations of first-phase insulin response to evaluate insulin secretion in children.

UNLABELLED: The first-phase insulin response (FPIR) is a widely used method to evaluate beta-cell function during the prediabetic phase of evolving type 1 diabetes mellitus (DM). The aim of the present study was to evaluate the influence of clinical and methodological variables on FPIR in normal children and adolescents. Children and adolescents who were first-degree relatives of those with type 1 DM and healthy young adults were studied. All subjects were islet cell antibody-negative. A FPIR test was performed on all subjects while fasting. Insulin samples were drawn at 0, 1, 2, 3, 4, 5, 6, 8, and 10 min after 0.3 g/kg of dextrose. FPIR(1-10) was calculated as the area under the FPIR curve corrected for baseline. Eighty-five subjects aged 4-22 yr were studied, 43 of whom were pre-pubertal, 24 pubertal, and 18 post-pubertal. FPIR(1-10) values were lower in the pre-pubertal group when compared to either the pubertal and post-pubertal groups (415 [179-965, 2SD], 756 [256-2 223] and 684 [235-1 180] mU/L, respectively; p<0.05). Obese subjects had a higher FPIR than non-obese subjects (856 vs. 520 mU/L; p<0.005). Despite correcting for the influence of puberty and obesity, there remained considerable unaccounted variability in FPIR(1-10) (R=0.46). Further variables found to influence FPIR(1-10) were: fasting insulin level (r(2)=0.49); weight for length index (r(2)=0.38); peak blood glucose level (r(2)=0.38, all p<0.001); and pre-pubertal age (r(2)=0.20, p<0.05). CONCLUSION: FPIR exhibited wide inter-subject variability and was influenced by a number of clinical and methodological factors that make interpretation more difficult without more specifically defined standards.

Hyperinsulinemic hypoglycemia of infancy. Recent insights into ATP-sensitive potassium channels, sulfonylurea receptors, molecular mechanisms, and treatment.

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI), previously termed "nesidioblastosis," is an important cause of hypoglycemia in infancy and childhood. Recent studies have defined this syndrome at the molecular, genetic, and clinical level. This article reviews the genetic and molecular basis of these entities, describes their clinical manifestations, and discusses the rationales for available therapeutic options.

Relaxation of imprinting in Prader-Willi syndrome.

We describe two Prader-Willi syndrome (PWS) patients who exhibit maternal uniparental disomy (UPD) of chromosome 15 and unusual patterns of gene expression and DNA replication. Both were diagnosed during infancy as having PWS; however, their growth and development were atypical compared with others with this condition. Weight was below normal in the first patient, and height and development were within normal limits in the second individual. Hyperphagia and polyphagia were not evident in either patient. Genotypes at multiple genomic loci, allele-specific methylation, gene expression, and DNA replication were analyzed at D15S9 [ZNF127], D15S63 [PW71], SNRPN, PAR5, IPW, and D15S10 in these patients. The maternal imprint (based on the absence of gene expression, synchronous replication, and methylation of both alleles) was retained at SNRPN in these patients, as is the case in others with UPD. By contrast, cells from the first individual expressed PAR5 and ZNF127, whereas the second expressed a single IPW allele. Asynchronous DNA replication was observed in both patients at all loci, except SNRPN. These findings show that a subset of imprinted genes can be transcribed in some PWS patients with maternal UPD and that asynchronous DNA replication is coordinated with this pattern of gene expression. Relaxed imprinting in these patients is consistent with their milder phenotype.

Aspects of the etiology, prediction, and prevention of insulin-dependent diabetes mellitus in childhood.

This article focuses on recent developments that have defined the autoimmune nature of this entity and its genetic basis, especially the crucial roles of aspartic acid at position 57 of the DQ beta chain and arginine at position 52 of the DQ alpha chain of the HLA complex on chromosome 6 in conferring susceptibility; other genetic markers on other genes are mentioned. These genetic markers help to explain the worldwide differences in prevalence and incidence of type 1 diabetes. Because the autoimmune process may be gradual, markers of beta pancreatic cell damage, such as islet cell antibodies, glutamic acid decarboxylase antibodies, and insulin autoantibodies, coupled with evidence of progressive failure of insulin secretion may be used to predict the future onset of disease. In turn, accurate prediction may permit preventive intervention. Two intervention trials are mentioned: (1) Diabetes Prevention Trial for Type 1, a multicenter trial in the United States using insulin; and (2) European Nicotinamide Diabetes Intervention Trial in Europe using nicotinamide as the preventive or delaying agent. These first steps reflect the remarkable progress and understanding of this major problem of childhood and the hopes for its future prevention.

Isolation of a liver-specific promoter for human growth hormone receptor gene.

The biological actions of growth hormone (GH) are mediated through the growth hormone receptor (GHR). The GHR gene is expressed in a tissue specific manner and multiple variants (V1 to V8) of GHR mRNA have been detected in human tissues. To understand the regulation of GHR gene expression, a human genomic clone containing the 5'-untranslated region (5'UTR) of the V1, V4, V7 and V8 exons of the GHR was isolated. The 2 kilobase (kb) 5' upstream sequence of the V1 specific UTR has promoter activity in transient transfection assays of the human hepatoma cell line, HepG2. The exclusive expression of the V1 variant in adult liver, and the lack of expression of the other variants in this tissue, suggests that the V1 5'UTR represents the liver specific 5' noncoding exon for the human GHR gene. The data are consistent with the first isolation of a liver specific promoter for human GHR.

Insulin resistance in short children with intrauterine growth retardation.

Epidemiological studies have demonstrated an association between intrauterine growth retardation and an increased risk of adult diseases that include essential hypertension, noninsulin-dependent diabetes mellitus, and ischemic heart disease. A common feature of these diseases is insulin resistance. To investigate whether abnormal insulin sensitivity was a characteristic of subjects with intrauterine growth retardation (IUGR), we compared two groups of short prepubertal children: a group with IUGR (birth weight less than the tenth percentile; n = 15) and a normal birth weight group (n = 12). Subjects underwent a modified frequently sampled iv glucose tolerance test that permitted calculation of the acute insulin response, insulin sensitivity index, and glucose effectiveness. A marked difference in the insulin sensitivity index was noted between groups, with the IUGR group being less insulin sensitive [6.9 vs. 16.9 10(-4)min-1.(microU/mL); P = 0.0048]. The acute insulin response was also significantly different between groups, with IUGR subjects having higher insulin levels (445 vs. 174 microU/mL; P = 0.005). There was no difference in glucose effectiveness between groups. Short prepubertal IUGR children have a specific impairment in insulin sensitivity compared to their normal birth weight peers. In short IUGR children, impaired insulin sensitivity is a potential marker for the early identification and intervention in the development of late adult-onset noninsulin-dependent diabetes mellitus.

Induction of mRNAs for the growth hormone receptor gene during mouse 3T3-L1 preadipocyte differentiation.

Adipose tissue is a growth hormone (GH)-responsive tissue in which GH regulates energy metabolism. GH exerts its effect by interacting with its specific GH receptor (GHR). In rodents, alternative splicing of the nascent transcript from the GHR gene produces two major transcripts: GHR mRNA and GHR binding protein (GHBP) mRNA. These two transcripts share the common extracellular ligand-binding domain, but differ in the C-terminal sequence. Since GHR plays an important role in mediating the actions of GH in adipose metabolism, we initiated these studies to examine GHR gene expression in the course of mouse 3T3-L1 preadipocyte-adipocyte conversion. GHR and GHBP transcripts were detected by RNase protection assay (RPA) using the antisense riboprobes complementary either to the specific sequence of the GHR or to the sequence shared by both GHR and GHBP mRNAs. After stimulation of differentiation, mRNA abundance increased 28-fold and reached a maximal level by day 7 of adipogenesis. The GHR mRNA:GHBP mRNA ratio was 1.1 +/- 0.12 and remained unchanged during differentiation. The decay rate for both mRNAs, estimated by treating the cells with actinomycin D, was approximately 24 hours and showed no significant difference between preadipocytes and adipocytes. Thus, GHR gene expression is dramatically upregulated during preadipocyte-adipocyte differentiations.

Insulin as a growth factor.

Various clinical syndromes illustrate the essential role of insulin in modulating somatic growth both in utero and after birth. The effect of insulin on growth is a consequence of direct effects transduced via its homologous receptor and post-receptor signaling pathways and indirect effects on other modulators of growth, such as the growth hormone-IGF axis. Recent insights into the post-receptor mechanisms of insulin signaling provide a scientific framework for the distinction between the traditional role of insulin as a major modulator of metabolism and its role as a promoter of growth.