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Somatostatin secretion in cultured human islet cells from patients with nesidioblastosis: A compensatory mechanism?
S o m a t o s t a t i n Secretion in Cultured Human Islet Cells From P a t i e n t s With N e s i d i o b l a s t o s i s : A Compensatory M e c h a n i s m ? By James R. Upp, Jr, Jin Ishizuka, Thorn E Lobe, Sirnivasan Rajaraman, Courtney M. Townsend, Jr, and James C. Thompson Galveston, Texas 9 T w o patients with nesidioblastosis, one with persistent hypoglycemia and another who was asymptomatic, underwent pancreatic resection. Dispersed pancreatic islets were prepared from each patient. Insulin secretion from cultured islet cells was increased and somatostatin decreased in the symptomatic patient compared with the asymptomatic patient. Immunocytochemistry showed increased somatostatin-containing cells in the asymptomatic patient. W e hypothesize that this may be the mechanism by which some patients with nesidioblastosis maintain normal serum glucose levels. 9 1987 by Grune & Stratton, Inc.
INDEX WORDS: Islets of Langerhans; nesiodioblastosis; somatostatin; insulin; Beckwith-Wiedemann syndrome; hypoglycemia.
HE FUNCTIONAL INTERACTION between T different populations of pancreatic islet cells may be as important as their quantity in the pathogenesis of nesidioblastosis and may regulate the degree of hypoglycemia. We have studied isolated islet cells from two patients; our data suggest a role for somatostatin secretion by islet cells in the clinical course of patients with nesidioblastosis. CASE REPORTS
Case 1 A Latin American female, first diagnosed at 3 months of age with hyperinsulinemie hypoglycemia, was large for her gestational age at birth. In the neonatal period, she would take large quantities of formula at frequent intervals. Her first symptoms were tonic clonic seizures; a simultaneous insulin level of 51.9 tsU/mL and a blood glucose of 23 mg/dL were obtained. She remained hypoglycemic on intravenous infusions of glucose and treatment with diaz'oxide was begun and titrated to 20 mg/kg/d. Attempts at discontinuing diazoxide failed. At 8 years of age, she underwent 85% distal' pancreatectomy. Diazoxide was discontinued and blood glucose remained above 100 mg/dL.
Case 2 A white female with Beckwith-Wiedemann syndrome (exomphalos, macroglossia, viseeromegaly) t weighed 3.6 kg and was limp and cyanotic with a poor respiratory effort at birth. A blood glucose level was 11 mg/dL. Hypoglycemia remained a problem in the neonatal period with blood glucose levels of 20 to 40 mg/dL on glucose infusion rates >0.5 g/kg/h. A simultaneous blood glucose of 37 mg/dL and insulin level of 28 taU/mL were obtained after fasting. With increased feedings and a strict feeding schedule, glucose infusions were discontinued at 3 weeks of age with the patient,, remaining euglycemic. She continued to remain asymptomatic with diet alone. At 2 years and 10 months of age, a new left upper quadrant mass was discovered. At laparotomy, an enlarged pan-
creatic tail with multiple cysts was found, and a 50% distal pancreatectomy was performed.
Pathology Multiple sections at different levels of each formalin-fixed paraffin-embedded pancreatic specimen were examined. Routine H&E stain and immttnohistochemical studies for insulin, somatostatin, glucagon, and pancreatic polypeptide were done. A semiquantitative estimation of specific hormone-secreting cell populations was done by scanning the entire tissue section (approximately x 200 microscopic fields) and expressed as a percentage of the total islet cell mass. Sections from case 1 revealed nesidioblastosis characterized by small packets of 2 to 25 islet cells, scattered throughout aeinar tissue, separate from islets of Langerhans. About 60% to 70% of the islet cell population, including the scattered islet cells, expressed insulin, 20% to 30% somatostatin, 10% glucagon, and <10% expressed pancreatic polypeptide. Sections from case 2 revealed islet hyperplasia, hypertrophy, and nesidioblastosis. In many areas, the islet tissue was confluent and occupied a larger area than the acinar pancreas. In contrast to case 1, there was a great increase in somatostatinsynthesizing cells consisting of about 70% to 80% of the total islet cell mass, and only about 20% of the cells expressed insulin. Ten percent to 20% of the cells expressed glucagon and about 30% of the cells also expressed pancreatic polypeptide.
Islet Cell Dispersion and Hormone Secretion Islet cells were prepared from a small piece of each pancreatic specimen obtained fresh from the operating room by a previously reported method. 2 Islets were incubated in RPMI media with 10% fetal calf serum at 37~ in a humidified atmosphere of 95% air, 5% CO2 for 4 weeks at which time insulin and somatostatin concentrations were measured by specific radioimmunoassays.3'~Case 1 had a high insulin level of 135 ng/mL and low somatostatin level of 40 pg/mL (Fig 1). In case 2, insulin secretion was much lower at 0.41 ng/mL with a high somatostatin level of 680 pg/mL.
DISCUSSION
Normal pancreatic islet hormone secretion is regulated by glucose levels, extrapancreatic hormones, the autonomic nervous system, and intra-islet regulatory From the Departments of Surgery and Palhology, The University of Texas Medical Branch, Galveston. Supported by grantsfrom the National Institutes of Health (ROI DK 15241, POI DK 35608, and RCDA CA 00854) and from the American Cancer Society (PDT-220). Presented at the 18th Annual Meeting of the American Pediatric Surgical Association, Hilton tlead Island, South Carolina, May 6-9, 1987. Address reprint requests to James C. Thompson, MD, Department of Surgery, The University o f Texas Medical Branch, Galveston, TX 77550. 9 1987 by Grune & Stratton, Inc. 0022-3468/87/2212-0024503.00/0
Journal of Pediatric Surgery, Vo122, No 12 (December), 1987: pp 1185-1186
1185
UPP ET AL
1186 200 100 - 700
50-
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CASE1
CASE 2
Fig 1, Insulin and s o m a t o s t a t i n secretion f r o m c u l t u r e d islet cells. Insulin levels ( n g / m L } a r e p l o t t e d on a logarithmic scale. S o m a t o s t a t i n levels ( p g / m L } a r e p l o t t e d on a linear scale.
mechanisms, s Somatostatin, produced by pancreatic D cells, inhibits release of insulin, glucagon, and pancreatic polypeptide.6 Depletion of pancreatic somatostatin by cysteamine results in increased insulin release from glucose-stimulated rat islet cells in vitro. 7
Increased numbers of D cells are found in the normal human fetal and neonatal pancreas compared with adults, suggesting that somatostatin may regulate pancreatic development and may act as a fetal inhibitor of pancreatic hormone secretion) Patients with nesidioblastosis have been reported to have a five-fold increase in mean total area occupied by pancreatic endocrine tissue compared with agematched controls) Polak and Bloom t~ reported a decrease in the number of D cells and in somatostatin content of pancreatic tissue extracts in patients with nesidioblastosis who had pancreatectomies for severe hypoglycemia. These findings suggest somatostatin deficiency may play a key role in the pathogenesis of nesidioblastosis. The pathogenesis of hyperinsulinemic hypoglycemia in early life is controversial and the clinical spectrum is broadt; some patients have experienced persistent hypoglycemia while others have had only transient hypoglycemia. Our findings suggest that an increased number of D cells and an increased secretion of somatostatin with subsequent decrease in insulin secretion may represent the mechanism by which some patients with nesidioblastosis maintain normal serum glucose levels, obviating the need for continued therapy.
REFERENCES
1. Aynsley-Green A, Soltesz G (eds): Hypoglycaemia due to hyperinsulinism,in Hypoglycaemia in Infancy and Childhood. New York, Churchill Livingstone, 1985, pp 54-102 2. Ishizuka J, Fujimoto WY, Toyota T, et al: A culture method for the isolation of pancreatic islet cells from young rats. Pancreas 1:494-497, 1986 3. Greeley GH Jr, Thompson JC: Insulinotropie and gastrinreleasing action of gastrin-releasing peptide (GRP). Regul Pept 8:97-103, 1984 4. Arimura A, Sato H, Coy DH, et ah Radioimmunoassay for GH-release inhibiting hormone. Proc Soc Exp Biol Med 148:784789, 1975 5. Hirsch H J, Loo SW, Gabbay KH: The development and regulation of the endocrine pancreas. J Pediatr 91:518-520, 1977 6. Newman JB, Lluis F, Townsend CM Jr: Somatostatin, in Thompson JC, Greeley GH Jr, Rayford PL, Townsend CM Jr (eds):
Gastrointestinal Endocrinology. New York, McGraw Hill, 1987, pp 286-299 7. Kanatsuka A, Makino H, Osegawa M, et al: Is somatostatin a true local inhibitory regulator of insulin secretion? Diabetes 33:510515, 1984 8. Oldham KT, Thompson JC: Ontogeny of gut peptides, in Thompson JC, Greeley GH Jr, Rayford PL, Townsend CM Jr (eds): Gastrointestinal Endocrinology. New York, McGraw Hill, 1987, pp 158-177 9. Heitz PU, Kloppel G, Hacki WH, et al: Nesidioblastosis: The pathologic basis of persistent hyperinsulinemic hypoglycemia in infants. Diabetes 26:632-642, 1977 10. Polak JM, Bloom SR: Decrease of somatostatin content, in persistent neonatal hyperinsulinaemiehypoglycaemia, in Adreani D, Lefebvre PJ, Marks V (eds): Current Views on Hypoglycemia and Glucagon. Orlando, FL, Academic, 1980, pp 367-378
INDEX WORDS: Islets of Langerhans; nesiodioblastosis; somatostatin; insulin; Beckwith-Wiedemann syndrome; hypoglycemia.
HE FUNCTIONAL INTERACTION between T different populations of pancreatic islet cells may be as important as their quantity in the pathogenesis of nesidioblastosis and may regulate the degree of hypoglycemia. We have studied isolated islet cells from two patients; our data suggest a role for somatostatin secretion by islet cells in the clinical course of patients with nesidioblastosis. CASE REPORTS
Case 1 A Latin American female, first diagnosed at 3 months of age with hyperinsulinemie hypoglycemia, was large for her gestational age at birth. In the neonatal period, she would take large quantities of formula at frequent intervals. Her first symptoms were tonic clonic seizures; a simultaneous insulin level of 51.9 tsU/mL and a blood glucose of 23 mg/dL were obtained. She remained hypoglycemic on intravenous infusions of glucose and treatment with diaz'oxide was begun and titrated to 20 mg/kg/d. Attempts at discontinuing diazoxide failed. At 8 years of age, she underwent 85% distal' pancreatectomy. Diazoxide was discontinued and blood glucose remained above 100 mg/dL.
Case 2 A white female with Beckwith-Wiedemann syndrome (exomphalos, macroglossia, viseeromegaly) t weighed 3.6 kg and was limp and cyanotic with a poor respiratory effort at birth. A blood glucose level was 11 mg/dL. Hypoglycemia remained a problem in the neonatal period with blood glucose levels of 20 to 40 mg/dL on glucose infusion rates >0.5 g/kg/h. A simultaneous blood glucose of 37 mg/dL and insulin level of 28 taU/mL were obtained after fasting. With increased feedings and a strict feeding schedule, glucose infusions were discontinued at 3 weeks of age with the patient,, remaining euglycemic. She continued to remain asymptomatic with diet alone. At 2 years and 10 months of age, a new left upper quadrant mass was discovered. At laparotomy, an enlarged pan-
creatic tail with multiple cysts was found, and a 50% distal pancreatectomy was performed.
Pathology Multiple sections at different levels of each formalin-fixed paraffin-embedded pancreatic specimen were examined. Routine H&E stain and immttnohistochemical studies for insulin, somatostatin, glucagon, and pancreatic polypeptide were done. A semiquantitative estimation of specific hormone-secreting cell populations was done by scanning the entire tissue section (approximately x 200 microscopic fields) and expressed as a percentage of the total islet cell mass. Sections from case 1 revealed nesidioblastosis characterized by small packets of 2 to 25 islet cells, scattered throughout aeinar tissue, separate from islets of Langerhans. About 60% to 70% of the islet cell population, including the scattered islet cells, expressed insulin, 20% to 30% somatostatin, 10% glucagon, and <10% expressed pancreatic polypeptide. Sections from case 2 revealed islet hyperplasia, hypertrophy, and nesidioblastosis. In many areas, the islet tissue was confluent and occupied a larger area than the acinar pancreas. In contrast to case 1, there was a great increase in somatostatinsynthesizing cells consisting of about 70% to 80% of the total islet cell mass, and only about 20% of the cells expressed insulin. Ten percent to 20% of the cells expressed glucagon and about 30% of the cells also expressed pancreatic polypeptide.
Islet Cell Dispersion and Hormone Secretion Islet cells were prepared from a small piece of each pancreatic specimen obtained fresh from the operating room by a previously reported method. 2 Islets were incubated in RPMI media with 10% fetal calf serum at 37~ in a humidified atmosphere of 95% air, 5% CO2 for 4 weeks at which time insulin and somatostatin concentrations were measured by specific radioimmunoassays.3'~Case 1 had a high insulin level of 135 ng/mL and low somatostatin level of 40 pg/mL (Fig 1). In case 2, insulin secretion was much lower at 0.41 ng/mL with a high somatostatin level of 680 pg/mL.
DISCUSSION
Normal pancreatic islet hormone secretion is regulated by glucose levels, extrapancreatic hormones, the autonomic nervous system, and intra-islet regulatory From the Departments of Surgery and Palhology, The University of Texas Medical Branch, Galveston. Supported by grantsfrom the National Institutes of Health (ROI DK 15241, POI DK 35608, and RCDA CA 00854) and from the American Cancer Society (PDT-220). Presented at the 18th Annual Meeting of the American Pediatric Surgical Association, Hilton tlead Island, South Carolina, May 6-9, 1987. Address reprint requests to James C. Thompson, MD, Department of Surgery, The University o f Texas Medical Branch, Galveston, TX 77550. 9 1987 by Grune & Stratton, Inc. 0022-3468/87/2212-0024503.00/0
Journal of Pediatric Surgery, Vo122, No 12 (December), 1987: pp 1185-1186
1185
UPP ET AL
1186 200 100 - 700
50-
-600
E
10-
-500 D.
z
5-
z
-400
,.J
z
p-
- 300
O ,r
p-
1,0,
-200
0.5-
O
-100 0.1
CASE1
CASE 2
Fig 1, Insulin and s o m a t o s t a t i n secretion f r o m c u l t u r e d islet cells. Insulin levels ( n g / m L } a r e p l o t t e d on a logarithmic scale. S o m a t o s t a t i n levels ( p g / m L } a r e p l o t t e d on a linear scale.
mechanisms, s Somatostatin, produced by pancreatic D cells, inhibits release of insulin, glucagon, and pancreatic polypeptide.6 Depletion of pancreatic somatostatin by cysteamine results in increased insulin release from glucose-stimulated rat islet cells in vitro. 7
Increased numbers of D cells are found in the normal human fetal and neonatal pancreas compared with adults, suggesting that somatostatin may regulate pancreatic development and may act as a fetal inhibitor of pancreatic hormone secretion) Patients with nesidioblastosis have been reported to have a five-fold increase in mean total area occupied by pancreatic endocrine tissue compared with agematched controls) Polak and Bloom t~ reported a decrease in the number of D cells and in somatostatin content of pancreatic tissue extracts in patients with nesidioblastosis who had pancreatectomies for severe hypoglycemia. These findings suggest somatostatin deficiency may play a key role in the pathogenesis of nesidioblastosis. The pathogenesis of hyperinsulinemic hypoglycemia in early life is controversial and the clinical spectrum is broadt; some patients have experienced persistent hypoglycemia while others have had only transient hypoglycemia. Our findings suggest that an increased number of D cells and an increased secretion of somatostatin with subsequent decrease in insulin secretion may represent the mechanism by which some patients with nesidioblastosis maintain normal serum glucose levels, obviating the need for continued therapy.
REFERENCES
1. Aynsley-Green A, Soltesz G (eds): Hypoglycaemia due to hyperinsulinism,in Hypoglycaemia in Infancy and Childhood. New York, Churchill Livingstone, 1985, pp 54-102 2. Ishizuka J, Fujimoto WY, Toyota T, et al: A culture method for the isolation of pancreatic islet cells from young rats. Pancreas 1:494-497, 1986 3. Greeley GH Jr, Thompson JC: Insulinotropie and gastrinreleasing action of gastrin-releasing peptide (GRP). Regul Pept 8:97-103, 1984 4. Arimura A, Sato H, Coy DH, et ah Radioimmunoassay for GH-release inhibiting hormone. Proc Soc Exp Biol Med 148:784789, 1975 5. Hirsch H J, Loo SW, Gabbay KH: The development and regulation of the endocrine pancreas. J Pediatr 91:518-520, 1977 6. Newman JB, Lluis F, Townsend CM Jr: Somatostatin, in Thompson JC, Greeley GH Jr, Rayford PL, Townsend CM Jr (eds):
Gastrointestinal Endocrinology. New York, McGraw Hill, 1987, pp 286-299 7. Kanatsuka A, Makino H, Osegawa M, et al: Is somatostatin a true local inhibitory regulator of insulin secretion? Diabetes 33:510515, 1984 8. Oldham KT, Thompson JC: Ontogeny of gut peptides, in Thompson JC, Greeley GH Jr, Rayford PL, Townsend CM Jr (eds): Gastrointestinal Endocrinology. New York, McGraw Hill, 1987, pp 158-177 9. Heitz PU, Kloppel G, Hacki WH, et al: Nesidioblastosis: The pathologic basis of persistent hyperinsulinemic hypoglycemia in infants. Diabetes 26:632-642, 1977 10. Polak JM, Bloom SR: Decrease of somatostatin content, in persistent neonatal hyperinsulinaemiehypoglycaemia, in Adreani D, Lefebvre PJ, Marks V (eds): Current Views on Hypoglycemia and Glucagon. Orlando, FL, Academic, 1980, pp 367-378