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β-Endorphin stimulates the secretion of insulin and glucagon in diabetes mellitus
Metabolism Clinical and Experimental MARCH 1984
VOL. XXXII, NO. 3
,8-Endorphin
Stimulates
the Secretion of Insulin Diabetes Mellitus
R. L. Reid,
and Glucagon
in
J. A. Sandler, and S. S. C. Yen
Administration of human fl-endorphin (2.5 mg IV bolus) to three subjects with non-insulin-dependent diabetes mellitus (type II) induced prompt and simultaneous increments in the plasma concentrations of insulin and glucagon lasting up to 90 minutes. In contrast to the hyperglycemic response previously observed in normal subjects following &endorphin, these diabetics showed a progressive decline in plasma glucose throughout the study period. This disparity may be related to a relatively greater release of insulin and lesser rise in glucagon observed in diabetic subjects than in nondiabetic subjects. These preliminary findings suggest that further studies to elucidate the role of pancreatic ,&endorphin on glucoregulation may be rewarding.
W
E have recently reported that in normal adult subjects, IV administration of fl-endorphin induces acute release of insulin and glucagon with subsequent hyperglycemia.’ P-endorphin has previously been identified and quantitated in extracts of human pancreatic tissue obtained at autopsy, employing radioimmunoassay and gel chromatography.’ The colocalization of p-endorphin and somatostatin within the D cells of the pancreas in several species, including man,’ suggested the possibility that pancreatic pendorphin may play a role in glucoregulation.’ We report here the effect of exogenous P-endorphin on the release of insulin and glucagon, and on the levels of plasma glucose, in patients with type 11 diabetes mellitus. MATERIALS
AND
METHODS
After an overnight fast, three non-insulin-dependent diabetic patients, off all medications, were admitted to the Clinical Research Center. Characteristics of these individuals are shown in Table 1. Subject I had been receiving tolbutamide up to 2 g/d and a 1000~calorie diet in the 2 years since the discovery of her diabetes. Subject 2 had received insulin therapy (28 U of NPH and 10 U regular) for 3 years, and in the preceding 6 months had been switched to chlorpropamide 250 mg daily. Subject 3 had received chlorpropamide 250 mg daily since the detection of his diabetes 3 years previously. Informed consent was obtained and an IV was introduced into an antecubital vein for frequent blood sampling. After five basal blood samples were obtained at I5 minute intervals, each subject received a 2.5 mg IV bolus injection (over 30 seconds) of synthetic human (3-endorphin (provided by Dr N. Ling. Salk Institute, La Jolla, CA). Blood samples were obtained at 2.5 minute intervals for I5 minutes and then every 15 minutes until 120 Metabolism, Vol 33, No 3 (March). 1984
minutes. All samples were promptly processed on ice for subsequent determination of plasma concentrations of insulin and glucagon by radioimmunoassays.’ Plasma glucose levels were measured by a glucose-oxidase technique (Beckman glucose analyzer). Hemoglobin A, levels were determined by column chromatography.4 RESULTS
Fasting concentrations of glucose insulin and glucagon (Fig. 1) for the three subjects show varying degrees of hyperglycemia, hyperglucagonemia, and hyperinsulinism consistent with type II diabetes mellitus. The mean (k SE) of the five baseline determinations of glucose, insulin, and glucagon for each subject are presented in Table 1. ,f3-endorphin administration elicited prompt simultaneous increments in the concentrations of plasma insulin and glucagon (Fig. 1). Peak increments in levels of insulin and glucagon of 30 + 3.7 pU/mL and 41.3 r 2.4 pg/mL respectively were achieved at 7.5 minutes and were followed by a gradual decline to basal values by 60 to 90 minutes.
FROM the Department of Reproductive Medicine. School of Medicine (T-002). and the General Clinical Research Center. University of California, San Diego, La Jolla, California. This investigation is supported by NICHD Program Project Grant HD-12303 and, in part, by the UCSD General Clinical Research Center NIH Grant RR-00827. Address reprint requests to S. S. C. Yen, Senior Clayton Foundation Investigator, SOM (T-002). UCSD, La Jolla, CA 92093. o 1984 by Grune & Stratton, Inc. 0026-0495/84/3303-OOOl$Ol .OO/O 197
REID, SANDLER, AND YEN
198
300
GLUCAGON
250
= z
150 200 100 Iti -60
-30
0
30
60
90
120
MINUTES Fig. 1. Changes in plasma glucose, insulin, and glucagon concentrations in response to an IV bolus injection of &_-endorphin (2.5 mgj in three non-insulin-dependent diabetic patients. Subject 1 O--O, subject 2 O--O. subject 3 A--A. Note: insulin determinations were not made in subject 3 because of the presence of antibodies.
Plasma glucose levels showed a slight decrease during the hour of basal sampling and continued to decline in the 2 hours after administration of /3-endorphin with a mean (k SE) maximal decrease of 43 f 6 mg/lOO mL (Fig. 1). DISCUSSION
In non-insulin-dependent diabetics, as in normal subjects,’ fl-endorphin administration (2.5 mg IV pulse) elicits prompt simultaneous increments in the plasma concentrations of insulin and glucagon. In contrast to the observations of previous studies in normal control subjects’ where these changes were associated with a relatively sustained hyperglycemic response (A max 14.0 + 2.5 mg/lOO mL) that lasted up to two hours after P-endorphin injection, plasma glucose levels in the diabetic subjects of the present investigation fell progressively following administration of P-endorphin. These differing glucose responses can best be explained by comparing the relative increments of insulin and glucagon in normal and diabetic subjects. While the rise in plasma glucagon levels was Table 1. Characteristics
lower in diabetics (A max, 41.3 + 2.4 pg/mL) than in controls (56.8 + 3 1.4 pg/mL) the increment in plasma insulin was 3- to IO-fold greater in diabetics (30.0 k 3.7 pU/mL) than in normal female (9.5 * 5.1 pU/ mL) and male (3.2 c .7 pU/mL) controls.’ Sherwin et als have previously demonstrated that hyperglucagonemia causes an increase in basal plasma levels in diabetic subjects only when they are insulin deprived. Thus, indifference to the hyperglucagonemia which followed ,&endorphin administration to our diabetic subjects along with relative hyperinsulinemia may explain the observed decline in plasma glucose. Within the islets of Langerhan, /3-endorphin has been colocalized with somatostatin in the D cell.’ Ipp et al6 have reported that morphine and P-endorphin decrease somatostatin secretion from the isolated perfused dog pancreas-an effect that is accompanied by parallel increments in the release of insulin and glucagon. In accord with the findings that glucagon may increase plasma glucose in insulin-deficient subjects,’ it has been shown that the administration of both morphine’ and enkephalin,’ induced marked hyperglycemia in insulin-deficient alloxandiabetic dogs. The observation by Bruni et al’ that substantial amounts of P-endorphin were detectable in human pancreatic tissue obtained at autopsy in all subjects studied except for a single non-insulin-dependent diabetic suggests that intra-islet regulatory abnormalities may exist. Further studies on the effects of fl-endorphin on glucoregulation in normal subjects and in patients with diabetes mellitus may be revealing. ACKNOWLEDGMENTS We wish to thank the nurses of the clinical research center P. Zabala, T. Morrison, R. Baker, D. Crowe, and B. Graham for their skillful technical and secretarial assistance.
REFERENCES 1. Reid RL, Yen SSC: fl-endorphin stimulates the secretion of insulin and glucagon in humans. J Clin Endocrinol Metab 52:592593,198l 2. Bruni JF, Watkins WB, Yen SSC: (3-endorphin in the human pancreas. J Clin Endocrinol Metab 49:649-651, 1979 3. Watkins WB, Bruni JF, Yen SSC: D-endorphin and somatostatin in the pancreatic D-cell: Co-localization by immunocytochemistry. J Histochem Cytochem 28:1170-l 174, 1980
of Three Subjects With Type II Diabetes Mellitus. Mean + SE Fasting Concentrations
Height
Weight
HbA,
Sex
Age (vd
(cm)
(kg)
(n 5.8 = 8.5%)
1
F
52
167
83
9.9
210.0
+ 1.8
2
F
73
166
50
9.1
139.8
k 2.1
3
M
66
177
83
8.3
138.8
+ 2.9
Subject
*The presence of insulin antibodies precluded insulin measurement in subject 2.
GlUCOSe (mg%l
lnsukn (uU/mL)
27.8
+ 2.1 l
53.4
t 2.2
Glucagon
Iw/mLI 240.4
f 6.3
130.4
+ 6.5
125.8
+ 4.6
&ENDORPHIN
AND DIABETES MELLITUS
199
4. Trivelli LA, Ranney HM, Hong-Tien Lai: Hemoglobin components in patients with diabetes mellitus. N Engl J Med 284:353-357, 1971
5. Sherwin RS, Fisher M, Hendler R, Felig P: Hyperglucagonemia and blood glucose regulation in normal, obese and diabetic subjects. N Engl J Med 294:4555461, 1976 6. Ipp E, Dobbs
R, Unger
RH:
Morphine
and
@endorphin
influence the secretion of the endocrine pancreas. Nature 276:190191, 1978 7. Ipp E, Schusdziarra V, Harris V, Unger RH: Morphineinduced hyperglycemia: Role of insulin and glucagon. Endocrinology 107:461-463, 1980 8. Ipp E, Dhorajiwala JM, Moossa AR, Rubenstein AH: Enkephalin stimulates insulin and glucagon release in vivo and accentuates hyperglycemia in diabetic dogs. Clin Res 28:396A, 1980
VOL. XXXII, NO. 3
,8-Endorphin
Stimulates
the Secretion of Insulin Diabetes Mellitus
R. L. Reid,
and Glucagon
in
J. A. Sandler, and S. S. C. Yen
Administration of human fl-endorphin (2.5 mg IV bolus) to three subjects with non-insulin-dependent diabetes mellitus (type II) induced prompt and simultaneous increments in the plasma concentrations of insulin and glucagon lasting up to 90 minutes. In contrast to the hyperglycemic response previously observed in normal subjects following &endorphin, these diabetics showed a progressive decline in plasma glucose throughout the study period. This disparity may be related to a relatively greater release of insulin and lesser rise in glucagon observed in diabetic subjects than in nondiabetic subjects. These preliminary findings suggest that further studies to elucidate the role of pancreatic ,&endorphin on glucoregulation may be rewarding.
W
E have recently reported that in normal adult subjects, IV administration of fl-endorphin induces acute release of insulin and glucagon with subsequent hyperglycemia.’ P-endorphin has previously been identified and quantitated in extracts of human pancreatic tissue obtained at autopsy, employing radioimmunoassay and gel chromatography.’ The colocalization of p-endorphin and somatostatin within the D cells of the pancreas in several species, including man,’ suggested the possibility that pancreatic pendorphin may play a role in glucoregulation.’ We report here the effect of exogenous P-endorphin on the release of insulin and glucagon, and on the levels of plasma glucose, in patients with type 11 diabetes mellitus. MATERIALS
AND
METHODS
After an overnight fast, three non-insulin-dependent diabetic patients, off all medications, were admitted to the Clinical Research Center. Characteristics of these individuals are shown in Table 1. Subject I had been receiving tolbutamide up to 2 g/d and a 1000~calorie diet in the 2 years since the discovery of her diabetes. Subject 2 had received insulin therapy (28 U of NPH and 10 U regular) for 3 years, and in the preceding 6 months had been switched to chlorpropamide 250 mg daily. Subject 3 had received chlorpropamide 250 mg daily since the detection of his diabetes 3 years previously. Informed consent was obtained and an IV was introduced into an antecubital vein for frequent blood sampling. After five basal blood samples were obtained at I5 minute intervals, each subject received a 2.5 mg IV bolus injection (over 30 seconds) of synthetic human (3-endorphin (provided by Dr N. Ling. Salk Institute, La Jolla, CA). Blood samples were obtained at 2.5 minute intervals for I5 minutes and then every 15 minutes until 120 Metabolism, Vol 33, No 3 (March). 1984
minutes. All samples were promptly processed on ice for subsequent determination of plasma concentrations of insulin and glucagon by radioimmunoassays.’ Plasma glucose levels were measured by a glucose-oxidase technique (Beckman glucose analyzer). Hemoglobin A, levels were determined by column chromatography.4 RESULTS
Fasting concentrations of glucose insulin and glucagon (Fig. 1) for the three subjects show varying degrees of hyperglycemia, hyperglucagonemia, and hyperinsulinism consistent with type II diabetes mellitus. The mean (k SE) of the five baseline determinations of glucose, insulin, and glucagon for each subject are presented in Table 1. ,f3-endorphin administration elicited prompt simultaneous increments in the concentrations of plasma insulin and glucagon (Fig. 1). Peak increments in levels of insulin and glucagon of 30 + 3.7 pU/mL and 41.3 r 2.4 pg/mL respectively were achieved at 7.5 minutes and were followed by a gradual decline to basal values by 60 to 90 minutes.
FROM the Department of Reproductive Medicine. School of Medicine (T-002). and the General Clinical Research Center. University of California, San Diego, La Jolla, California. This investigation is supported by NICHD Program Project Grant HD-12303 and, in part, by the UCSD General Clinical Research Center NIH Grant RR-00827. Address reprint requests to S. S. C. Yen, Senior Clayton Foundation Investigator, SOM (T-002). UCSD, La Jolla, CA 92093. o 1984 by Grune & Stratton, Inc. 0026-0495/84/3303-OOOl$Ol .OO/O 197
REID, SANDLER, AND YEN
198
300
GLUCAGON
250
= z
150 200 100 Iti -60
-30
0
30
60
90
120
MINUTES Fig. 1. Changes in plasma glucose, insulin, and glucagon concentrations in response to an IV bolus injection of &_-endorphin (2.5 mgj in three non-insulin-dependent diabetic patients. Subject 1 O--O, subject 2 O--O. subject 3 A--A. Note: insulin determinations were not made in subject 3 because of the presence of antibodies.
Plasma glucose levels showed a slight decrease during the hour of basal sampling and continued to decline in the 2 hours after administration of /3-endorphin with a mean (k SE) maximal decrease of 43 f 6 mg/lOO mL (Fig. 1). DISCUSSION
In non-insulin-dependent diabetics, as in normal subjects,’ fl-endorphin administration (2.5 mg IV pulse) elicits prompt simultaneous increments in the plasma concentrations of insulin and glucagon. In contrast to the observations of previous studies in normal control subjects’ where these changes were associated with a relatively sustained hyperglycemic response (A max 14.0 + 2.5 mg/lOO mL) that lasted up to two hours after P-endorphin injection, plasma glucose levels in the diabetic subjects of the present investigation fell progressively following administration of P-endorphin. These differing glucose responses can best be explained by comparing the relative increments of insulin and glucagon in normal and diabetic subjects. While the rise in plasma glucagon levels was Table 1. Characteristics
lower in diabetics (A max, 41.3 + 2.4 pg/mL) than in controls (56.8 + 3 1.4 pg/mL) the increment in plasma insulin was 3- to IO-fold greater in diabetics (30.0 k 3.7 pU/mL) than in normal female (9.5 * 5.1 pU/ mL) and male (3.2 c .7 pU/mL) controls.’ Sherwin et als have previously demonstrated that hyperglucagonemia causes an increase in basal plasma levels in diabetic subjects only when they are insulin deprived. Thus, indifference to the hyperglucagonemia which followed ,&endorphin administration to our diabetic subjects along with relative hyperinsulinemia may explain the observed decline in plasma glucose. Within the islets of Langerhan, /3-endorphin has been colocalized with somatostatin in the D cell.’ Ipp et al6 have reported that morphine and P-endorphin decrease somatostatin secretion from the isolated perfused dog pancreas-an effect that is accompanied by parallel increments in the release of insulin and glucagon. In accord with the findings that glucagon may increase plasma glucose in insulin-deficient subjects,’ it has been shown that the administration of both morphine’ and enkephalin,’ induced marked hyperglycemia in insulin-deficient alloxandiabetic dogs. The observation by Bruni et al’ that substantial amounts of P-endorphin were detectable in human pancreatic tissue obtained at autopsy in all subjects studied except for a single non-insulin-dependent diabetic suggests that intra-islet regulatory abnormalities may exist. Further studies on the effects of fl-endorphin on glucoregulation in normal subjects and in patients with diabetes mellitus may be revealing. ACKNOWLEDGMENTS We wish to thank the nurses of the clinical research center P. Zabala, T. Morrison, R. Baker, D. Crowe, and B. Graham for their skillful technical and secretarial assistance.
REFERENCES 1. Reid RL, Yen SSC: fl-endorphin stimulates the secretion of insulin and glucagon in humans. J Clin Endocrinol Metab 52:592593,198l 2. Bruni JF, Watkins WB, Yen SSC: (3-endorphin in the human pancreas. J Clin Endocrinol Metab 49:649-651, 1979 3. Watkins WB, Bruni JF, Yen SSC: D-endorphin and somatostatin in the pancreatic D-cell: Co-localization by immunocytochemistry. J Histochem Cytochem 28:1170-l 174, 1980
of Three Subjects With Type II Diabetes Mellitus. Mean + SE Fasting Concentrations
Height
Weight
HbA,
Sex
Age (vd
(cm)
(kg)
(n 5.8 = 8.5%)
1
F
52
167
83
9.9
210.0
+ 1.8
2
F
73
166
50
9.1
139.8
k 2.1
3
M
66
177
83
8.3
138.8
+ 2.9
Subject
*The presence of insulin antibodies precluded insulin measurement in subject 2.
GlUCOSe (mg%l
lnsukn (uU/mL)
27.8
+ 2.1 l
53.4
t 2.2
Glucagon
Iw/mLI 240.4
f 6.3
130.4
+ 6.5
125.8
+ 4.6
&ENDORPHIN
AND DIABETES MELLITUS
199
4. Trivelli LA, Ranney HM, Hong-Tien Lai: Hemoglobin components in patients with diabetes mellitus. N Engl J Med 284:353-357, 1971
5. Sherwin RS, Fisher M, Hendler R, Felig P: Hyperglucagonemia and blood glucose regulation in normal, obese and diabetic subjects. N Engl J Med 294:4555461, 1976 6. Ipp E, Dobbs
R, Unger
RH:
Morphine
and
@endorphin
influence the secretion of the endocrine pancreas. Nature 276:190191, 1978 7. Ipp E, Schusdziarra V, Harris V, Unger RH: Morphineinduced hyperglycemia: Role of insulin and glucagon. Endocrinology 107:461-463, 1980 8. Ipp E, Dhorajiwala JM, Moossa AR, Rubenstein AH: Enkephalin stimulates insulin and glucagon release in vivo and accentuates hyperglycemia in diabetic dogs. Clin Res 28:396A, 1980