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Etienne Larger Department of Diabetology, Hôpital Bichat and University Paris Denis Diderot, Paris, France

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Nicolai J Wewer Albrechtsen Department of Biomedical Sciences
Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Lars H Hansen Department of Molecular Signaling, Hagedorn Research Institute, Gentofte, Denmark

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Richard W Gelling Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore

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Jacqueline Capeau Inserm UMR_S 938, Centre de Recherche Saint-Antoine, Paris, France
Sorbonne University, UPMC, University of Paris 6, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France

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Carolyn F Deacon Department of Biomedical Sciences
Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Ole D Madsen Global Research External Affairs, Novo Nordisk A/S, 2760 Måløv, Denmark

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Fumiatsu Yakushiji Department of Internal Medicine, Tokyo Metropolitan Bokutoh Hospital, Tokyo, Japan
Department of Education Planning and Development, Faculty of Medicine, Toho University, Tokyo, Japan

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Pierre De Meyts Global Research External Affairs, Novo Nordisk A/S, 2760 Måløv, Denmark

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Jens J Holst Department of Biomedical Sciences
Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Erica Nishimura Metabolic Disease Research, Novo Nordisk A/S, Måløv, Denmark

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Summary

Glucagon stimulates hepatic glucose production by activating specific glucagon receptors in the liver, which in turn increase hepatic glycogenolysis as well as gluconeogenesis and ureagenesis from amino acids. Conversely, glucagon secretion is regulated by concentrations of glucose and amino acids. Disruption of glucagon signaling in rodents results in grossly elevated circulating glucagon levels but no hypoglycemia. Here, we describe a patient carrying a homozygous G to A substitution in the invariant AG dinucleotide found in a 3′ mRNA splice junction of the glucagon receptor gene. Loss of the splice site acceptor consensus sequence results in the deletion of 70 nucleotides encoded by exon 9, which introduces a frame shift and an early termination signal in the receptor mRNA sequence. The mutated receptor neither bound 125I-labeled glucagon nor induced cAMP production upon stimulation with up to 1 µM glucagon. Despite the mutation, the only obvious pathophysiological trait was hyperglucagonemia, hyperaminoacidemia and massive hyperplasia of the pancreatic α-cells assessed by histology. Our case supports the notion of a hepato–pancreatic feedback system, which upon disruption leads to hyperglucagonemia and α-cell hyperplasia, as well as elevated plasma amino acid levels. Together with the glucagon-induced hypoaminoacidemia in glucagonoma patients, our case supports recent suggestions that amino acids may provide the feedback link between the liver and the pancreatic α-cells.

Learning points:

  • Loss of function of the glucagon receptor may not necessarily lead to the dysregulation of glucose homeostasis.

  • Loss of function of the glucagon receptor causes hyperaminoacidemia, hyperglucagonemia and α-cell hyperplasia and sometimes other pancreatic abnormalities.

  • A hepato–pancreatic feedback regulation of the α-cells, possibly involving amino acids, may exist in humans.

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Benjamin G Challis Wellcome Trust–MRC Institute of Metabolic Science, University of Cambridge, Cambridge, CB2 0QQ, UK
Wolfson Diabetes and Endocrinology Clinic, Institute of Metabolic Science, Cambridge University Hospitals NHS Foundation Trust, Addenbrookes Hospital, Box 281, Cambridge, CB2 0QQ, UK

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Nicolai J Wewer Albrechtsen Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark
Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark

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Vishakha Bansiya Wolfson Diabetes and Endocrinology Clinic, Institute of Metabolic Science, Cambridge University Hospitals NHS Foundation Trust, Addenbrookes Hospital, Box 281, Cambridge, CB2 0QQ, UK

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Keith Burling Wellcome Trust–MRC Institute of Metabolic Science, University of Cambridge, Cambridge, CB2 0QQ, UK

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Peter Barker Wellcome Trust–MRC Institute of Metabolic Science, University of Cambridge, Cambridge, CB2 0QQ, UK

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Bolette Hartmann Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark
Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark

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Fiona Gribble Wellcome Trust–MRC Institute of Metabolic Science, University of Cambridge, Cambridge, CB2 0QQ, UK

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Stephen O'Rahilly Wellcome Trust–MRC Institute of Metabolic Science, University of Cambridge, Cambridge, CB2 0QQ, UK
Wolfson Diabetes and Endocrinology Clinic, Institute of Metabolic Science, Cambridge University Hospitals NHS Foundation Trust, Addenbrookes Hospital, Box 281, Cambridge, CB2 0QQ, UK

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Jens J Holst Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark
Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark

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Helen L Simpson Wolfson Diabetes and Endocrinology Clinic, Institute of Metabolic Science, Cambridge University Hospitals NHS Foundation Trust, Addenbrookes Hospital, Box 281, Cambridge, CB2 0QQ, UK

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Summary

Pancreatic neuroendocrine tumours (pNETs) secreting proglucagon are associated with phenotypic heterogeneity. Here, we describe two patients with pNETs and varied clinical phenotypes due to differential processing and secretion of proglucagon-derived peptides (PGDPs). Case 1, a 57-year-old woman presented with necrolytic migratory erythema, anorexia, constipation and hyperinsulinaemic hypoglycaemia. She was found to have a grade 1 pNET, small bowel mucosal thickening and hyperglucagonaemia. Somatostatin analogue (SSA) therapy improved appetite, abolished hypoglycaemia and improved the rash. Case 2, a 48-year-old male presented with diabetes mellitus, diarrhoea, weight loss, nausea, vomiting and perineal rash due to a grade 1 metastatic pNET and hyperglucagonaemia. In both cases, plasma levels of all measured PGDPs were elevated and attenuated following SSA therapy. In case 1, there was increased production of intact glucagon-like peptide 1 (GLP-1) and GLP-2, similar to that of the enteroendocrine L cell. In case 2, pancreatic glucagon was elevated due to a pancreatic α-cell-like proglucagon processing profile. In summary, we describe two patients with pNETs and heterogeneous clinical phenotypes due to differential processing and secretion of PGDPs. This is the first description of a patient with symptomatic hyperinsulinaemic hypoglycaemia and marked gastrointestinal dysfunction due to, in part, a proglucagon-expressing pNET.

Learning points

  • PGDPs exhibit a diverse range of biological activities including critical roles in glucose and amino acid metabolism, energy homeostasis and gastrointestinal physiology.

  • The clinical manifestations of proglucagon-expressing tumours may exhibit marked phenotypic variation due to the biochemical heterogeneity of their secreted peptide repertoire.

  • Specific and precise biochemical assessment of individuals with proglucagon-expressing tumours may provide opportunities for improved diagnosis and clinical management.

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Marta Guimarães
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Pedro Rodrigues
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Sofia S Pereira Clinical and Experimental Endocrinology, Department of Anatomy, Multidisciplinary Unit for Biomedical Research (UMIB), Instituto de Ciências Biomédicas Abel Salazar, University of Porto (ICBAS/UP), Rua Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal

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Mário Nora
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Gil Gonçalves
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Nicolai Wewer Albrechtsen NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Bolette Hartmann NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Jens Juul Holst NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark

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Mariana P Monteiro Clinical and Experimental Endocrinology, Department of Anatomy, Multidisciplinary Unit for Biomedical Research (UMIB), Instituto de Ciências Biomédicas Abel Salazar, University of Porto (ICBAS/UP), Rua Jorge Viterbo Ferreira, 228, 4050-313, Porto, Portugal
Endocrine Unit, Centro Hospitalar de Entre o Douro e Vouga, Rua Doutor Cândido Pinho, 4520-211, Santa Maria da Feira, Portugal

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Summary

Post-prandial hypoglycemia is frequently found after bariatric surgery. Although rare, pancreatic neuroendocrine tumors (pNET), which occasionally are mixed hormone secreting, can lead to atypical clinical manifestations, including reactive hypoglycemia. Two years after gastric bypass surgery for the treatment of severe obesity, a 54-year-old female with previous type 2 diabetes, developed post-prandial sweating, fainting and hypoglycemic episodes, which eventually led to the finding by ultrasound of a 1.8-cm solid mass in the pancreatic head. The 72-h fast test and the plasma chromogranin A levels were normal but octreotide scintigraphy showed a single focus of abnormal radiotracer uptake at the site of the nodule. There were no other clinical signs of hormone secreting pNET and gastrointestinal hormone measurements were not performed. The patient underwent surgical enucleation with complete remission of the hypoglycemic episodes. Histopathology revealed a well-differentiated neuroendocrine carcinoma with low-grade malignancy with positive chromogranin A and glucagon immunostaining. An extract of the resected tumor contained a high concentration of glucagon (26.707 pmol/g tissue), in addition to traces of GLP1 (471 pmol/g), insulin (139 pmol/g) and somatostatin (23 pmol/g). This is the first report of a GLP1 and glucagon co-secreting pNET presenting as hypoglycemia after gastric bypass surgery. Although pNET are rare, they should be considered in the differential diagnosis of the clinical approach to the post-bariatric surgery hypoglycemia patient.

Learning points

  • pNETs can be multihormonal-secreting, leading to atypical clinical manifestations.

  • Reactive hypoglycemic episodes are frequent after gastric bypass.

  • pNETs should be considered in the differential diagnosis of hypoglycemia after bariatric surgery.

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