Abstract
A sporadic case of multiple endocrine neoplasia type I with coexisting insulinoma and hyperparathyroidism was investigated in vivo and in vitro. The insulinoma was localized by somatostatin receptor scintigraphy and these receptors were functionally active. Octreotide administration decreased the basal insulin and glucagon secretion by 90 and 46%, respectively. Immunocytochemistry of the insulinoma tissue was positive for insulin, chromogranin A and neuropeptide Y. The insulinoma cells were also isolated and cultured in vitro. Incubation experiments revealed that a low glucose concentration (1 mmol/l) was sufficient to increase cytosolic free calcium and to produce a maximal glucose-induced insulin release. Northern blot analysis of RNA obtained from the tumor showed a high abundance of the low Km glucose transporter GLUT1 but no transcript for the high Km glucose transporter GLUT2. The abnormal distribution of glucose transporters probably relates to the abnormal glucose sensing of insulinoma cells, and explains their sustained insulin secretion at low glucose concentrations. Whether these abnormalities share a pathogenetic link with the presence of functionally active somatostatin receptors remains to be elucidated.
Publication types
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Case Reports
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Actins / genetics
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Adolescent
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Dose-Response Relationship, Drug
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Follow-Up Studies
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Gene Expression Regulation, Neoplastic / genetics*
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Glucagon / blood
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Glucagon / metabolism
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Glucose / pharmacology
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Glucose Transporter Type 1
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Hormones / administration & dosage
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Hormones / metabolism
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Humans
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Hyperparathyroidism / diagnosis*
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Hyperparathyroidism / pathology
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Hyperparathyroidism / surgery
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Immunohistochemistry
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Injections, Intravenous
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Insulin / blood
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Insulin / genetics
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Insulin / metabolism*
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Insulin Secretion
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Insulinoma / chemistry
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Insulinoma / diagnosis*
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Insulinoma / pathology
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Insulinoma / surgery
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Male
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Monosaccharide Transport Proteins / genetics
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Multiple Endocrine Neoplasia Type 1 / diagnosis*
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Multiple Endocrine Neoplasia Type 1 / pathology
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Multiple Endocrine Neoplasia Type 1 / surgery
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Octreotide / administration & dosage
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Octreotide / metabolism
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Pancreatic Neoplasms / chemistry
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Pancreatic Neoplasms / diagnosis*
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Pancreatic Neoplasms / pathology
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Pancreatic Neoplasms / surgery
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Parathyroid Neoplasms / diagnosis*
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Parathyroid Neoplasms / pathology
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Parathyroid Neoplasms / surgery
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RNA, Messenger / analysis
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RNA, Messenger / genetics
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Receptors, Somatostatin / metabolism*
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Tomography, Emission-Computed, Single-Photon
Substances
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Actins
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Glucose Transporter Type 1
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Hormones
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Insulin
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Monosaccharide Transport Proteins
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RNA, Messenger
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Receptors, Somatostatin
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SLC2A1 protein, human
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Glucagon
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Glucose
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Octreotide