OBJECTIVE—Heterozygous, gain-of-function mutations of the insulin gene can cause permanent diabetes with onset ranging from the neonatal period through adulthood. The aim of our study was to screen for the insulin gene in patients who had been clinically classified as type 1 diabetic but who tested negative for type 1 diabetes autoantibodies. RESEARCH DESIGN AND METHODS—We reviewed the clinical records of 326 patients with the diagnosis of type 1 diabetes and identified seven probands who had diabetes in isolation and were negative for five type 1 diabetes autoantibodies. We sequenced the INS gene in these seven patients. RESULTS—In two patients whose diabetes onset had been at 2 years 10 months of age and at 6 years 8 months of age, respectively, we identified the mutation GB8S and a novel mutation in the preproinsulin signal peptide (ASignal23S). CONCLUSIONS—Insulin gene mutations are rare in absolute terms in patients classified as type 1 diabetic (0.6%) but can be identified after a thorough screening of type 1 diabetes autoantibodies.

Aims/hypothesisThe aim of this study was to investigate the genetic aetiology of permanent diabetes mellitus with onset in the first 12 months of age.MethodsWe studied 46 probands with permanent, insulin-requiring diabetes with onset within the first 6 months of life (permanent neonatal diabetes mellitus [PNDM]/monogenic diabetes of infancy [MDI]) (group 1) and eight participants with diabetes diagnosed between 7 and 12 months of age (group 2). KCNJ11, INS and ABCC8 genes were sequentially sequenced in all patients. For those who were negative in the initial screening, we examined ERN1, CHGA, CHGB and NKX6-1 genes and, in selected probands, CACNA1C, GCK, FOXP3, NEUROG3 and CDK4. The incidence rate for PNDM/MDI was calculated using a database of Italian patients collected from 1995 to 2009.ResultsIn group 1 we found mutations in KCNJ11, INS and ABCC8 genes in 23 (50%), 9 (19.5%) and 4 (8.6%) patients respectively, and a single homozygous mutation in GCK (2.1%). In group 2, we identified one incidence of a KCNJ11 mutation. No genetic defects were detected in other loci. The incidence rate of PNDM/MDI in Italy is estimated to be 1:210,287.Conclusions/interpretationGenetic mutations were identified in ~75% of non-consanguineous probands with PNDM/MDI, using sequential screening of KCNJ11, INS and ABCC8 genes in infants diagnosed within the first 6 months of age. This percentage decreased to 12% in those with diabetes diagnosed between 7 and 12 months. Patients belonging to the latter group may either carry mutations in genes different from those commonly found in PNDM/MDI or have developed an early-onset form of autoimmune diabetes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-011-2094-8) contains supplementary material, which is available to authorised users.

Regulation of gene expression in response to mitogenic stimuli is a critical aspect underlying many forms of human cancers. The AP-1 complex mediates the transcriptional response to mitogens, and its deregulation causes developmental defects and tumors. We report that the coactivator CRTC1 cyclic AMP response element-binding protein (CREB)-regulated transcription coactivator 1 is a potent and indispensable modulator of AP-1 function. After exposure of cells to the AP-1 agonist 12-O-tetradecanoylphorbol-13-acetate (TPA), CRTC1 is recruited to AP-1 target gene promoters and associates with c-Jun and c-Fos to activate transcription. CRTC1 consistently synergizes with the proto-oncogene c-Jun to promote cellular growth, whereas AP-1-dependent proliferation is abrogated in CRTC1-deficient cells. Remarkably, we demonstrate that CRTC1-Maml2 oncoprotein, which causes mucoepidermoid carcinomas, binds and activates both c-Jun and c-Fos. Consequently, ablation of AP-1 function disrupts the cellular transformation and proliferation mediated by this oncogene. Together, these data illustrate a novel mechanism required to couple mitogenic signals to the AP-1 gene regulatory program.T he cyclic AMP response element-binding protein (CREB)-regulated transcription coactivators (CRTCs, originally called TORCs) are a novel class of signal-dependent CREB coactivators identified using a high-throughput expression screen of a mammalian cDNA library (1, 2). CRTCs associate with the bZIP region of CREB via their N-terminal region and activate transcription through interactions with components of the basal transcriptional apparatus (1, 3). Under resting conditions, CRTCs are phosphorylated by sucrose nonfermenting1/AMP-activated protein kinase (AMP/SNF) kinases and sequestered in the cytoplasm (4, 5). When the intracellular levels of calcium or cAMP rise, CRTCs are dephosphorylated, travel to the nucleus and bind to CREB, thereby activating transcription. Consistent with their role as CREB activators, CRTCs have been shown to be key regulators of gluconeogenesis (5-8), adaptive mitochondrial biogenesis (9), ␤ cell survival (10), and long-term synaptic plasticity (11).Recent observations have suggested that CRTCs also promote activation of other transcription factors besides those of the CREB/ ATF1 family. Indeed, the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) causes CRTC1 nuclear translocation in HeLa cells (12), and deletion of the TPA responsive element (TRE) from the IL-8 promoter abrogates CRTC1-mediated enhancement (2), suggesting that CRTC1 can stimulate transcriptional output of a TPA-regulated pathway. Recently, it was reported that CRTC1 can be phosphorylated and activated by MEKK1 (13), a critical kinase activated by several mitogenic stimuli, including TPA.TPA is a tumor-promoting drug that activates transcription of a number of genes that typically contain a TPA response element (TRE ϭ TGACTCA) in their promoter regions (14). In turn, the TRE is bound by the dimeric AP-1 transcription factor complex, comprising a...

Objective:Epidemiological studies have shown an association between birth weight and future risk of type 2 diabetes, with individuals born either small or large for gestational age at increased risk. We sought to investigate the influence of birth weight on the relation between insulin sensitivity and ␤-cell function in obese children. Subjects and Methods:A total of 257 obese/overweight children (mean body mass index-SD score, 2.2 Ϯ 0.3), aged 11.6 Ϯ 2.3 yr were divided into three groups according to birth weight percentile: 44 were small for gestational age (SGA), 161 were appropriate for gestational age (AGA), and 52 were large for gestational age (LGA). Participants underwent a 3-h oral glucose tolerance test with glucose, insulin, and C-peptide measurements. Homeostasis model of assessment for insulin resistance, insulinogenic index, and disposition index were calculated to evaluate insulin sensitivity and ␤-cell function. Glucose and insulin area under the curve (AUC) were also considered. One-way ANOVA was used to compare the three groups.Results: SGA and LGA subjects had higher homeostasis model of assessment for insulin resistance than AGA subjects, but they diverged when oral glucose tolerance test response was considered. Indeed, SGA subjects showed higher glucose AUC and lower insulinogenic and disposition indexes. Insulin AUC was not different between groups, but when singular time points were considered, SGA subjects had lower insulin levels at 30 min and higher insulin levels at 180 min.Conclusions: SGA obese children fail to adequately compensate for their reduced insulin sensitivity, manifesting deficit in early insulin response and reduced disposition index that results in higher glucose AUC. Thus, SGA obese children show adverse metabolic outcomes compared to AGAs andLGAs. (J Clin Endocrinol Metab 94: 4448 -4452, 2009)

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