BACKGROUND

Several cases of myopathies have been observed in the horse Norman Cob breed. Muscle histology examinations revealed that some families suffer from a polysaccharide storage myopathy (PSSM). It is assumed that a gene expression signature related to PSSM should be observed at the transcriptional level because the glycogen storage disease could also be linked to other dysfunctions in gene regulation. Thus, the functional genomic approach could be conducted in order to provide new knowledge about the metabolic disorders related to PSSM. We propose exploring the PSSM muscle fiber metabolic disorders by measuring gene expression in relationship with the histological phenotype.

RESULTS

Genotypying analysis of GYS1 mutation revealed 2 homozygous (AA) and 5 heterozygous (GA) PSSM horses. In the PSSM muscles, histological data revealed PAS positive amylase resistant abnormal polysaccharides, inflammation, necrosis, and lipomatosis and active regeneration of fibers. Ultrastructural evaluation revealed a decrease of mitochondrial number and structural disorders. Extensive accumulation of an abnormal polysaccharide displaced and partially replaced mitochondria and myofibrils. The severity of the disease was higher in the two homozygous PSSM horses.Gene expression analysis revealed 129 genes significantly modulated (p < 0.05). The following genes were up-regulated over 2 fold: IL18, CTSS, LUM, CD44, FN1, GST01. The most down-regulated genes were the following: mitochondrial tRNA, SLC2A2, PRKCalpha, VEGFalpha. Data mining analysis showed that protein synthesis, apoptosis, cellular movement, growth and proliferation were the main cellular functions significantly associated with the modulated genes (p < 0.05). Several up-regulated genes, especially IL18, revealed a severe muscular inflammation in PSSM muscles. The up-regulation of glycogen synthase kinase-3 (GSK3beta) under its active form could be responsible for glycogen synthase (GYS1) inhibition and hypoxia-inducible factor (HIF1alpha) destabilization.

CONCLUSIONS

The main disorders observed in PSSM muscles could be related to mitochondrial dysfunctions, glycogenesis inhibition and the chronic hypoxia of the PSSM muscles.

Genome-wide association studies (GWAS) have revealed numerous associations between many phenotypes and gene candidates. Frequently, however, further elucidation of gene function has not been achieved. A recent GWAS identified 69 candidate genes associated with elevated liver enzyme concentrations, which are clinical markers of liver disease. To investigate the role of these genes in liver homeostasis, we narrowed down this list to 12 genes based on zebrafish orthology, zebrafish liver expression and disease correlation. To assess the function of gene candidates during liver development, we assayed hepatic progenitors at 48 hours post fertilization (hpf) and hepatocytes at 72 hpf using in situ hybridization following morpholino knockdown in zebrafish embryos. Knockdown of three genes (pnpla3, pklr and mapk10) decreased expression of hepatic progenitor cells, whereas knockdown of eight genes (pnpla3, cpn1, trib1, fads2, slc2a2, pklr, mapk10 and samm50) decreased cell-specific hepatocyte expression. We then induced liver injury in zebrafish embryos using acetaminophen exposure and observed changes in liver toxicity incidence in morphants. Prioritization of GWAS candidates and morpholino knockdown expedites the study of newly identified genes impacting liver development and represents a feasible method for initial assessment of candidate genes to instruct further mechanistic analyses. Our analysis can be extended to GWAS for additional disease-associated phenotypes.

Single nucleotide polymorphisms (SNPs) in two genes regulating insulin secretion, SLC2A2 (encoding GLUT2) and ABCC8 (encoding SUR1), were associated with the conversion from impaired glucose tolerance (IGT) to type 2 diabetes (T2D) in the Finnish Diabetes Prevention Study (DPS). We determined whether physical activity (PA), assessed annually with a questionnaire, modified the association of SNPs in SLC2A2 and ABCC8 with the conversion to T2D in the combined intervention and control groups of the DPS. Finnish overweight subjects with IGT (N = 479) were followed for an average of 4.1 yr. The interaction of the SNPs with the change in PA on the conversion to T2D was assessed using Cox regression with adjustments for the other components of the intervention (dietary changes, weight reduction). The carriers of the common homozygous genotype of rs5393, rs5394, or rs5404 of SLC2A2 and rs3758947 of ABCC8 who were in the lower third of the change in moderate-to-vigorous PA during the follow-up had a 2.6- to 3.7-fold increased risk of developing T2D compared with the upper third, whereas the rare allele carriers seemed to be unresponsive to changes in moderate-to-vigorous PA (for the interaction of genotype with change in PA, P = 0.022-0.027 for the SNPs in SLC2A2, and P = 0.007 for rs3758947). We conclude that moderate-to-vigorous PA may modify the risk of developing T2D associated with genes regulating insulin secretion (SLC2A2, ABCC8) in persons with IGT.

Glucose transporter 2 (GLUT2; gene name SLC2A2) has a key role in the regulation of glucose dynamics in organs central to metabolism. Although GLUT2 has been studied in the context of its participation in peripheral and central glucose sensing, its role in the brain is not well understood. To decipher the role of GLUT2 in brain development, we knocked down slc2a2 (glut2), the functional ortholog of human GLUT2, in zebrafish. Abrogation of glut2 led to defective brain organogenesis, reduced glucose uptake and increased programmed cell death in the brain. Coinciding with the observed localization of glut2 expression in the zebrafish hindbrain, glut2 deficiency affected the development of neural progenitor cells expressing the proneural genes atoh1b and ptf1a but not those expressing neurod. Specificity of the morphant phenotype was demonstrated by the restoration of brain organogenesis, whole-embryo glucose uptake, brain apoptosis, and expression of proneural markers in rescue experiments. These results indicate that glut2 has an essential role during brain development by facilitating the uptake and availability of glucose and support the involvement of glut2 in brain glucose sensing.

The RNA recognition motif (RRM) is the far most abundant RNA binding domain. In addition to the typical β1α1β2β3α2β4 fold, various sub-structural elements have been described and reportedly contribute to the high functional versatility of RRMs. The heterogeneous nuclear ribonucleoprotein L (hnRNP L) is a highly abundant protein of 64 kDa comprising four RRM domains. Involved in many aspects of RNA metabolism, hnRNP L specifically binds to RNAs containing CA repeats or CA-rich clusters. However, a comprehensive structural description of hnRNP L including its sub-structural elements is missing. Here, we present the structural characterization of the RRM domains of hnRNP L and demonstrate their function in repressing exon 4 of SLC2A2. By comparison of the sub-structural elements between the two highly similar paralog families of hnRNP L and PTB, we defined signatures underlying interacting C-terminal coils (ICCs), the RRM34 domain interaction and RRMs with a C-terminal fifth β-strand, a variation we denoted vRRMs. Furthermore, computational analysis revealed new putative ICC-containing RRM families and allowed us to propose an evolutionary scenario explaining the origins of the ICC and fifth β-strand sub-structural extensions. Our studies provide insights of domain requirements in alternative splicing mediated by hnRNP L and molecular descriptions for the sub-structural elements. In addition, the analysis presented may help to classify other abundant RRM extensions and to predict structure-function relationships.

Assays to monitor the metabolic state or nutrient uptake capacity of immune cells at a single cell level are increasingly in demand. One assay, used by many immunologists, employs 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2-NBDG), a fluorescent analogue of 2-deoxyglucose (2DG), as a substrate for glucose transporters. This molecule has been validated as a substrate for the glucose transporter Glut2 (Slc2a2) in mammalian cells but 2-NDBG selectivity for the glucose transporters expressed by T cells, Glut1 (Slc2a1) and Glut3 (Slc2a3), has never been explored. Nor has the possibility that 2-NBDG might bind to T cells that do not express glucose transporters been assessed. In this technical commentary we interrogate the specificity of 2-NBBG labelling as a readout for glucose transport in T lymphocytes. We compare flow cytometric 2-NBDG staining against well validated radiolabelled glucose transport assays in murine T cells. Our data show there can be a large discordance between glucose transport capacity and 2-NBDG labelling in T cells. We also find that 2-NBDG uptake into murine T cells is not inhibited by competitive substrates or facilitative glucose transporter inhibitors, nor can 2-NBDG competitively block glucose uptake in T cells. Collectively, these data argue that 2-NBDG uptake alone is not a reliable tool for the assessment of cellular glucose transport capacity.

Keywords: 2-NBDG; T cells; T lymphocytes; glucose uptake.

Phytase (PHY) improves growth performance, nutrient digestibility and bone structure in pigs; however, little is known about its effects on intestinal nutrient transporter gene expression. In the present study, a 44 d experiment was carried out using forty-eight pigs (11·76 (sem 0·75) kg) assigned to one of three dietary treatment groups to measure growth performance, coefficient of apparent ileal digestibility (CAID), coefficient of apparent total tract nutrient digestibility (CATTD) and intestinal nutrient transporter gene expression. Dietary treatments during the experimental period were as follows: (1) a high-P (HP) diet containing 3·4 g/kg available P and 7·0 g/kg Ca; (2) a low-P (LP) diet containing 1·9 g/kg available P and 5·9 g/kg Ca; (3) a PHY diet containing LP diet ingredients+1000 phytase units (FTU)/kg of PHY. The PHY diet increased the average daily gain (P< 0·05) and final body weight (P< 0·01) and decreased the feed conversion ratio (P< 0·05) compared with the LP diet. Pigs fed the PHY diet had a higher CAID of gross energy compared with those fed the HP and LP diets (P< 0·001). Pigs fed the PHY diet had increased CAID of P (P< 0·01) and CATTD of Ca and P (P< 0·001) compared with those fed the LP diet. The PHY diet increased the gene expression of the peptide transporter 1 (PEPT1/SLC15A1) (P< 0·05) in the ileum compared with the LP diet. The LP diet decreased the gene expression of the sodium-glucose-linked transporter 1 (SGLT1/SLC5A1) and GLUT2/SLC2A2 (P< 0·05) and increased the expression of membrane Ca channel (TRPV6) and calbindin compared with the HP diet (P< 0·001). In conclusion, feeding a diet supplemented with PHY improves growth performance and nutrient digestibility as well as increases the gene expression of the peptide transporter PEPT1.

Pancreatic β-cell failure is central to the development and progression of type 2 diabetes. We recently demonstrated that β-cells become hypoxic under high glucose conditions due to increased oxygen consumption and that the pancreatic islets of diabetic mice but not those of control mice are moderately hypoxic. However, the impact of moderate hypoxia on β-cell number and function is unknown. In the present study, moderate hypoxia induced a hypoxic response in MIN6 cells, as evidenced by increased levels of HIF-1α protein and target genes. Under these conditions, a selective downregulation of Mafa, Pdx1, Slc2a2, Ndufa5, Kcnj11, Ins1, Wfs1, Foxa2, and Neurod1, which play important roles in β-cells, was also observed in both MIN6 cells and isolated pancreatic islets. Consistent with the altered expression of these genes, abnormal insulin secretion was detected in hypoxic MIN6 cells. Most of the hypoxia-induced gene downregulation in MIN6 cells was not affected by the suppression of HIF-1α, suggesting a HIF-1-independent mechanism. Moderate hypoxia also induced apoptosis in MIN6 cells. These results suggest that hypoxia is a novel stressor of β-cells and that hypoxic stress may play a role in the deterioration of β-cell function.

Finding novel causes for monogenic forms of diabetes is important as, alongside the clinical implications of such a discovery, it can identify critical proteins and pathways required for normal beta cell function in humans. It is increasingly apparent that there are significant differences between rodent and human islets. One example that has generated interest is the relative importance of the glucose transporter GLUT2 in rodent and human beta cells. The central role of GLUT2 in rodent beta cells is well established, but a number of studies have suggested that other glucose transporters, namely GLUT1 and GLUT3, may play an important role in facilitating glucose transport into human beta cells. In this issue of Diabetologia Sansbury et al (DOI: 10.1007/s00125-012-2595-0 ) report homozygous loss of function mutations in SLC2A2, which encodes GLUT2, as a rare cause of neonatal diabetes. Evidence for a beta cell defect in these subjects comes from very low birthweights, lack of endogenous insulin secretion and a requirement for insulin therapy. Neonatal diabetes is not a consistent feature of SLC2A2 mutations. It is only found in a small percentage of cases (~4%) and the diabetes largely resolves before 18 months of age. This discovery is significant as it suggests that GLUT2 plays an important role in human beta cells, but the interplay and relative roles of other transporters differ from those in rodents. This finding should encourage efforts to delineate the precise role of GLUT2 in the human beta cell at different developmental time points and is a further reminder of critical differences between human and rodent islets.

Gene amplification is a frequent event in lung cancer, specifically in squamous cell lung carcinoma. Recently, we reported amplifications on chromosomal bands 3q26.1-q26.3 with the genes BCHE and SLC2A2 amplified in 40% of squamous cell lung carcinomas. Here, we identified an amplified domain within chromosomal bands 1pter-p33 in squamous cell lung carcinoma using reverse chromosome painting. A panel of nine genes which have previously been assigned to region 1pter-p33 was tested for amplification using comparative PCR. The ENO1 gene that encodes enolase and the PAX7 gene that encodes a transcription factor were most frequently amplified. Specifically, the gene ENO1 was amplified in six and the gene PAX7 in five out of 37 cases which included both biopsies and paraffin-embedded tissues of squamous cell lung carcinomas. In total, we identified amplifications of at least one gene at bands 1pter-p33 in 10 out of 37 tumors (27%). Together, our data indicate that a novel and frequent amplification unit is present in squamous cell lung carcinoma with the center of the amplified domain in the vicinity of the genes PAX7 and ENO1.

OBJECTIVE

Sirtuin 1 (Sirt1) has been reported to be a critical positive regulator of glucose-stimulated insulin secretion in pancreatic beta-cells. The effects on islet cells and blood glucose levels when Sirt1 is deleted specifically in the pancreas are still unclear.

METHODS

This study examined islet glucose responsiveness, blood glucose levels, pancreatic islet histology and gene expression in Pdx1Cre; Sirt1ex4F/F mice that have loss of function and loss of expression of Sirt1 specifically in the pancreas.

RESULTS

We found that in the Pdx1Cre; Sirt1ex4F/F mice, the relative insulin positive area and the islet size distribution were unchanged. However, beta-cells were functionally impaired, presenting with lower glucose-stimulated insulin secretion. This defect was not due to a reduced expression of insulin but was associated with a decreased expression of the glucose transporter Slc2a2/Glut2 and of the Glucagon like peptide-1 receptor (Glp1r) as well as a marked down regulation of endoplasmic reticulum (ER) chaperones that participate in the Unfolded Protein Response (UPR) pathway. Counter intuitively, the Sirt1-deficient mice did not develop hyperglycemia. Pancreatic polypeptide (PP) cells were the only other islet cells affected, with reduced numbers in the Sirt1-deficient pancreas.

CONCLUSIONS

This study provides new mechanistic insights showing that beta-cell function in Sirt1-deficient pancreas is affected due to altered glucose sensing and deregulation of the UPR pathway. Interestingly, we uncovered a context in which impaired beta-cell function is not accompanied by increased glycemia. This points to a unique compensatory mechanism. Given the reduction in PP, investigation of its role in the control of blood glucose is warranted.

Pancreatic β-cells and the liver play a key role in glucose homeostasis. After a meal or in a state of hyperglycemia, glucose is transported into the β-cells or hepatocytes where it is metabolized. In the β-cells, glucose is metabolized to increase the ATP:ADP ratio, resulting in the secretion of insulin stored in the vesicle. In the hepatocytes, glucose is metabolized to CO(2), fatty acids or stored as glycogen. In these cells, solute carrier family 2 (SLC2A2) and glucokinase play a key role in sensing and uptaking glucose. Dysfunction of these proteins results in the hyperglycemia which is one of the characteristics of type 2 diabetes mellitus (T2DM). Thus, studies on the molecular mechanisms of their transcriptional regulations are important in understanding pathogenesis and combating T2DM. In this paper, we will review a recent update on the progress of gene regulation of glucose sensors in the liver and β-cells.

Fanconi-Bickel syndrome (FBS), or glycogen storage disease type XI, is a rare, well-defined clinical entity. Recently, this disease was elucidated to link mutations in the SLC2A2 gene in many ethnic groups, indicating that FBS is a single gene disease. We report here an 8-month-old Turkish girl who developed characteristic findings of FBS. However, no mutation was detected in the protein-coding region of the SLC2A2 gene. Therefore, we propose that further molecular analysis is needed to determine whether other genes are involved in FBS.

Fanconi-Bickel syndrome is a rare inherited disorder of carbohydrate metabolism. The disease is characterized by the association of a massive hepatomegaly due to glycogen accumulation, severe hypophosphatemic rickets and marked growth retardation due to proximal renal tubular dysfunction. Fanconi-Bickel syndrome is a single gene disease and is caused by defects in the facilitative glucose transporter 2 (GLUT2) gene (SLC2A2) on chromosome 3q26.1-26.3, which encodes for the glucose transporter protein 2 expressed in hepatocytes, pancreatic beta-cells, enterocytes, and renal tubular cells. Several mutations in a gene encoding a glucose transporter have been reported in patients with Fanconi-Bickel syndrome. Here we report a Turkish child who had a novel mutation that has not been described before and we discuss the knowledge regarding genetic mutations in this rare disease.

All forms of diabetes mellitus involve the loss or dysfunction of pancreatic beta cells, with the former predominating in type 1 diabetes and the latter in type 2 diabetes. Deeper understanding of the coupling mechanisms that link glucose metabolism in these cells to the control of insulin secretion is therefore likely to be essential to develop new therapies. Beta cells display a remarkable metabolic specialisation, expressing high levels of metabolic sensing enzymes, including the glucose transporter GLUT2 (encoded by SLC2A2) and glucokinase (encoded by GCK). Genetic evidence flowing from both monogenic forms of diabetes and genome-wide association studies for the more common type 2 diabetes, supports the importance for normal glucose-stimulated insulin secretion of metabolic signalling via altered ATP generation, while also highlighting unsuspected roles for Zn²⁺ storage, intracellular lipid transfer and other processes. Intriguingly, genes involved in non-oxidative metabolic fates of the sugar, such as those for lactate dehydrogenase (LDHA) and monocarboxylate transporter-1 ([MCT-1] SLC16A1), as well as the acyl-CoA thioesterase (ACOT7) and others, are selectively repressed ('disallowed') in beta cells. Furthermore, mutations in genes critical for mitochondrial oxidative metabolism, such as TRL-CAG1-7 encoding tRNALeu, are linked to maternally inherited forms of diabetes. Correspondingly, impaired Ca²⁺ uptake into mitochondria, or collapse of a normally interconnected mitochondrial network, are associated with defective insulin secretion. Here, we suggest that altered mitochondrial metabolism may also impair beta cell-beta cell communication. Thus, we argue that defective oxidative glucose metabolism is central to beta cell failure in diabetes, acting both at the level of single beta cells and potentially across the whole islet to impair insulin secretion. Graphical abstract.

Keywords: Beta cells; Disallowed genes; Insulin secretion; Interconnectivity; Mitochondria; Review; Type 2 diabetes.

The structural organisation of pancreatic β-cells in the islets of Langerhans is relatively unknown. Here, using three-dimensional (3D) two-photon, 3D confocal and 3D block-face serial electron microscopy, we demonstrate a consistent in situ polarisation of β-cells and define three distinct cell surface domains. An apical domain located at the vascular apogee of β-cells, defined by the location of PAR-3 (also known as PARD3) and ZO-1 (also known as TJP1), delineates an extracellular space into which adjacent β-cells project their primary cilia. A separate lateral domain, is enriched in scribble and Dlg, and colocalises with E-cadherin and GLUT2 (also known as SLC2A2). Finally, a distinct basal domain, where the β-cells contact the islet vasculature, is enriched in synaptic scaffold proteins such as liprin. This 3D analysis of β-cells within intact islets, and the definition of distinct domains, provides new insights into understanding β-cell structure and function.

Pdx1, a β-cell-specific transcription factor, has been shown to play a crucial role in maintaining β-cell function through transactivation of β-cell-related genes. In addition, it has been reported that the expression levels of Pdx1 are compromised under diabetic conditions in human and rodent models. We therefore aimed to clarify the possible beneficial role of Pdx1 against β-cell failure and generated the transgenic mouse that expressed Pdx1 conditionally and specifically in β cells (βPdx1) and crossed these mice with Ins2Akita diabetic mice. Whereas Pdx1 mRNA levels were reduced in Ins2Akita mice compared with their non-diabetic littermates, the mRNA levels of Pdx1 were significantly recovered in the islets of βPdx1; Ins2Akita mice. The βPdx1; Ins2Akita mice exhibited significantly improved glucose tolerance, compared with control Ins2Akita littermates, accompanied by increased insulin secretion after glucose loading. Furthermore, histological examination demonstrated that βPdx1; Ins2Akita mice had improved localization of SLC2A2 (GLUT2), and quantitative RT-PCR showed the recovered expression of Mafa and Gck mRNAs in the islets of βPdx1; Ins2Akita mice. These findings suggest that the sustained expression of Pdx1 improves β-cell failure in Ins2Akita mice, at least partially through the preserving expression of β-cell-specific genes as well as improved localization of GLUT2.

Mutations in the pancreatic ATP sensitive K(+) channel proteins [sulfonyluea receptor 1 (SUR1) and inward rectifier K(+) channel Kir6.2 (Kir6.2), encoded by ATP-binding cassette transporter subfamily C member 8 (ABCC8) and potassium channel J11 (KCNJ11), respectively], are the most common cause of neonatal diabetes. We describe the clinical presentation and molecular characterization of Asian Indian children with neonatal diabetes mellitus and monogenic syndromes of diabetes. We sequenced KCNJ11, ABCC8 and insulin (INS) genes in 33 unrelated Indian probands with onset of diabetes below one year of age. A total of 12 mutations were identified which included ABCC8 mutations in seven, KCNJ11 mutations in three and INS mutations in two children. The Asp212Tyr mutation in ABCC8 was novel. We also detected two novel mutations (Val67Met and Leu19Arg) in children with syndromic forms of diabetes like Berardinelli Seip syndrome [1-acyl-sn-glycerol-3-phosphate acyltransferase beta (AGPAT2)] and Fanconi Bickel syndrome [solute carrier family 2A2 (SLC2A2)]. Children carrying the KCNJ11 (Cys42Arg, Arg201Cys) and ABCC8 (Val86Ala, Asp212Tyr) mutations have been successfully switched over from insulin therapy to oral sulfonylurea. Our study is the first large genetic screening study of neonatal diabetes in India.

Research suggests that clinical symptom dimensions may be more useful in delineating the genetics of bipolar disorder (BD) than standard diagnostic models. To date, no study has applied this concept to data from genome-wide association studies (GWAS). We performed a GWAS of factor dimensions in 927 clinically well-characterized BD patients of German ancestry. Rs9875793, which is located in an intergenic region of 3q26.1 and in the vicinity of the solute carrier family 2 (facilitated glucose transporter), member 2 gene (SLC2A2), was significantly associated with the factor analysis-derived dimension 'negative mood delusions' (n=927; P=4.65 × 10(-8), odds ratio (OR)=2.66). This dimension was comprised of the symptoms delusions of poverty, delusions of guilt and nihilistic delusions. In case-control analyses, significant association with the G allele of rs9875793 was only observed in the subgroup of BD patients who displayed symptoms of 'negative mood delusions' (allelic χ(2) model: P(G)=0.0001, OR=1.92; item present, n=89). Further support for the hypothesis that rs9875793 is associated with BD in patients displaying 'negative mood delusions' symptom, such as delusions of guilt, was obtained from an European American sample (GAIN/TGEN), which included 1247 BD patients and 1434 controls (P(EA)=0.028, OR=1.27).

Fanconi–Bickel syndrome (FBS, OMIM #227810) is a rare autosomal recessive disorder of carbohydrate transport originally described in 1949 [Fanconi and Bickel(1949);Helv Paediatr Acta 4: 359–396]. FBS is caused by mutations in the glucose and galactose transporter gene SLC2A2 (HGNC ID11006) [Santeret al.(1997); Nat Genet 17: 324–326] and is characterized by hepatic glycogen accumulation with hepatomegaly, fasting hypoglycemia, short stature, impaired glucose tolerance, hyperlipidemia, and tubular nephropathy. Although the described complications would not seem to preclude fertility in FBS patients, there has been no report of reproduction in affected individuals to date. We have followed a female with FBS for at least 20 years. She received a clinical diagnosis in adolescence, with recent molecular confirmation of two mutations in trans in the SLC2A2 gene. She has had glucosuria, proteinuria, impaired tubular reabsorption of phosphate, osteopenia, and hypercholesterolemia throughout her life, without any documented episodes of hypoglycemia. Hepatomegaly was initially noticed in infancy and resolved in late adolescence. She became pregnant at 31 years of age, had gestational diabetes treated with diet, and delivered a healthy boy. She had impaired glucose tolerance after her pregnancy.Her adult height was at the lower end of her target height range, and she had evidence of localized osteopenia at the left distal radius on DXA scan. This report describes the clinical history of an affected individual and highlights the importance of continued follow-up in order to extend our understanding of the history of this rare metabolic disorder.

In mammals, the absorption of monosaccharides from small intestinal lumen involves at least 3 sugar transporters (SugT): sodium-dependent glucose transporter 1 (SGLT1; gene SLC5A1) transports glucose and galactose, whereas glucose transporter (GLUT) 5 (GLUT5; gene SLC2A5) transports fructose, across the apical membrane of enterocytes. In contrast, GLUT2 (gene SLC2A2) transports all of these sugars across basolateral and apical membranes. To compare the distribution patterns and sensitivity with nutritional regulation of these 3 SugT mRNA in beef cattle small intestinal tissue, 18 ruminally and abomasally catheterized Angus steers (BW approximately 260 kg) were assigned to water (control), ruminal cornstarch (partially hydrolyzed by alpha-amylase; SH), or abomasal SH infusion treatments (n = 6) and fed an alfalfa-cube-based diet at 1.3 x NE(m) requirement. The SH infusions amounted to 20% of ME intake. After 14- or 16-d of infusion, steers were killed; duodenal, jejunal, and ileal epithelia harvested; and total RNA extracted. The relative amount of SugT mRNA in epithelia was determined using real-time reverse transcription-PCR quantification methods. Basal expression of GLUT2 and SGLT1 mRNA was greater (P < 0.09) by jejunal than by duodenal or ileal epithelia, whereas basal content of GLUT5 mRNA was greater (P < or = 0.02) by jejunal and duodenal than by ileal epithelia. The content of GLUT5 mRNA in small intestinal epithelia was not affected (P>> or = 0.16) by either SH infusion treatment. In contrast, GLUT2 and SGLT1 mRNA content in the ileal epithelium was increased (P < or = 0.05) by 6.5- and 1.3-fold, respectively, after abomasal SH infusion. Duodenal SGLT1 mRNA content also was increased (P = 0.07) by 64% after ruminal SH infusion. These results demonstrate that the ileum of beef cattle small intestine adapts to an increased luminal supply of glucose by increasing SGLT1 and GLUT2 mRNA content, whereas increased ruminal SH supply results in duodenal upregulation of SGLT1 mRNA content. These adaptive responses of GLUT2 and SGLT1 mRNA to abomasal or ruminal SH infusion suggest that beef cattle can adapt to increase their carbohydrate assimilation through small intestinal epithelia, assuming that altered SugT mRNA contents reflect the altered transport functional capacities.

Dynamic PET (dPET) with (18)F-Deoxyglucose (FDG) provides quantitative information about distribution of the tracer in a predefined volume over time. A two-tissue compartment model can be used to obtain quantitative data regarding transport of FDG into and out of the cells, phosphorylation and dephosphorylation rate of intracellular FDG, and fractional blood volume in the target volume, also named vessel density. Aim of the study was the correlation of glucose transporters expression and hexokinases with the corresponding compartment parameters.Patients with colorectal tumors were examined with dynamic PET prior to surgery. Afterwards, tumor samples were obtained during surgery and gene expression was assessed using gene arrays. The dynamic PET data were evaluated to quantify the parameters of a two tissue compartment model for colorectal tumors using a Volume-of-Interest (VOI) technique. A multiple correlation/regression analysis was performed using glucose transporters as independent variables and k1 as the dependent variable. A correlation of r=0.7503 (p=0.03) was obtained for the transporters SLC2A1, SLC2A2, SLC2A4, SLC2A8, SLC2A9, SLC2A10 and k1. The correlation of r=0.7503 refers to an explained variance of data of 56.30 %, therefore more than 50 % of data changes are associated with the gene expression. An analysis of the hexokinases HK1-HK3 and k3 revealed a correlation coefficient of r=0.6093 (p=0.04), which is associated with an explained variance of 37.12 %. Therefore, parameters k1 and k3 reflect gene activity. The results demonstrate that k1 and k3 of the two-tissue compartment model are correlated with glucose transporters and hexokinases.

OBJECTIVE

Zfp69 was previously identified by positional cloning as a candidate gene for obesity-associated diabetes. C57BL/6J and New Zealand obese (NZO) mice carry a loss-of-function mutation due to the integration of a retrotransposon. On the NZO background, the Zfp69 locus caused severe hyperglycaemia and loss of beta cells. To provide direct evidence for a causal role of Zfp69, we investigated the effects of its overexpression on both a lean [B6-Tg(Zfp69)] and an obese [NZO/B6-Tg(Zfp69)] background.

METHODS

Zfp69 transgenic mice were generated by integrating the cDNA into the ROSA locus of the C57BL/6 genome and characterised.

RESULTS

B6-Tg(Zfp69) mice were normoglycaemic, developed hyperinsulinaemia, and exhibited increased expression of G6pc and Pck1 and slightly reduced phospho-Akt levels in the liver. During OGTTs, glucose clearance was normal but insulin levels were significantly higher in the B6-Tg(Zfp69) than in control mice. The liver fat content and plasma triacylglycerol levels were significantly increased in B6-Tg(Zfp69) and NZO/B6-Tg(Zfp69) mice on a high-fat diet compared with controls. Liver transcriptome analysis of B6-Tg(Zfp69) mice revealed a downregulation of genes involved in glucose and lipid metabolism. Specifically, expression of Nampt, Lpin2, Map2k6, Gys2, Bnip3, Fitm2, Slc2a2, Ppargc1α and Insr was significantly decreased in the liver of B6-Tg(Zfp69) mice compared with wild-type animals. However, overexpression of Zfp69 did not induce overt diabetes with hyperglycaemia and beta cell loss.

CONCLUSIONS

Zfp69 mediates hyperlipidaemia, liver fat accumulation and mild insulin resistance. However, it does not induce type 2 diabetes, suggesting that the diabetogenic effect of the Zfp69 locus requires synergy with other as yet unidentified genes.

Heterozygous mutations in the human paired box gene PAX6 lead to impaired glucose tolerance. Although embryonic deletion of the Pax6 gene in mice leads to loss of most pancreatic islet cell types, the functional consequences of Pax6 loss in adults are poorly defined. Here we developed a mouse line in which Pax6 was selectively inactivated in β cells by crossing animals with floxed Pax6 alleles to mice expressing the inducible Pdx1CreERT transgene. Pax6 deficiency, achieved by tamoxifen injection, caused progressive hyperglycemia. Although β cell mass was preserved 8 days post-injection, total insulin content and insulin:chromogranin A immunoreactivity were reduced by ∼60%, and glucose-stimulated insulin secretion was eliminated. RNA sequencing and quantitative real-time PCR analyses revealed that, although the expression of key β cell genes, including Ins2, Slc30a8, MafA, Slc2a2, G6pc2, and Glp1r, was reduced after Pax6 deletion, that of several genes that are usually selectively repressed ("disallowed") in β cells, including Slc16a1, was increased. Assessed in intact islets, glucose-induced ATP:ADP increases were significantly reduced (p < 0.05) in βPax6KO versus control β cells, and the former displayed attenuated increases in cytosolic Ca2+ Unexpectedly, glucose-induced increases in intercellular connectivity were enhanced after Pax6 deletion, consistent with increases in the expression of the glucose sensor glucokinase, but decreases in that of two transcription factors usually expressed in fully differentiated β-cells, Pdx1 and Nkx6.1, were observed in islet "hub" cells. These results indicate that Pax6 is required for the functional identity of adult β cells. Furthermore, deficiencies in β cell glucose sensing are likely to contribute to defective insulin secretion in human carriers of PAX6 mutations.