Case Report: Increased Insulin Sensitivity in Tumor Hypoglycemia in a Diabetic Patient: Glucose Metabolism in Tumor Hypoglycemia

Case Report: Increased Insulin Sensitivity in Tumor Hypoglycemia in a Diabetic Patient: Glucose Metabolism in Tumor Hypoglycemia NIR BARZILAI,* PINCHAS COHEN,* NEIL McINTYRE,t EDDY KARNIELI*

RACHEL BAR-ILLAN,*

ABSTRACT: A 58-year-old man, with primary hemochromatosis, cirrhosis, and diabetes mellitus treated with insulin developed hepatoma. As the tumor grew, he lost his dependence on insulin therapy and experienced episodes of hypoglycemia. His response to infuse insulin was studied using the euglycemic clamp technique. Insulin was infused at rates of 1 and 10 IL/kg/ min. The insulin dose response curve was shifted to the left and at plasma insulin levels of 72 ILU/ mI, steady-state glucose consumption was 9.6 mg/kg/min, 50% more than in normals, and nearly three times greater than that in other cirrhotics. The insulin clearance rate was 4417 m1/ m2/min, almost five and six times more than in normals and cirrhotics, respectively. Basal hepatic glucose production was 3.6 mg/kg/min, two and three times higher than in normal and in cirrhotic subjects, respectively. The decrease in amino acid during hyperinsulinemia was more than 30% higher than in normal and other cirrhotics. IFG-I and II levels were not elevated in this patient. Increased insulin sensitivity and increased insulin clearance and serum amino acid decrease in response to insulin in vivo, suggest that insulin responsive tissues are at last partially responsible for tumor hypoglycemia. The increased glucose disposal rate probably accounted for the disappearance of the diabetes. KEY INDEXING TERMS: Glucose; insulin; insulin sensitivity; tumor; hypoglycemia; hepaFrom "'the Metabolic Unit, Rambam Medical Center and Facility of Medicine, Technion-Israel Institute of Technology, Haifa, Israel and t the Department of Medicine, Royal Free Hospital and School of Medicine, London, United Kingdom. The work was supported, in part, by a research grant from the U.S. National Institutes of Health, NIDDK, Grant No. AM 31489. The authors thank Dr. Ron G. Rosenfeld of the Department of Pediatrics, Stanford University for the IGF determinations. Correspondence: Nir Barzilai, MD, Division of Endocrinology, Department of Medicine, New York Hospital, CorneU University Medical School, 500 York Avenue, New York, NY 10021. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES

toma; cirrhosis; IGF-II. [Am J Med Sci 1991; 302(4):229-234.]

M

uch controversy exists about the mechanism of hypoglycemia in extrapancreatic neoplasms. Hundreds of cases have been described and most of these tumors were mesenchymal in origin.I-4 Hepatoma is an established cause of hypoglycemia, and at least 37 cases were studied for various purposes in the last 2 years.5-7 In the past, elevations peptides with insulinlike activity (NSILA-S) were noted in less than half of the cases of neoplastic hypoglycemia, yet a role of insulin growth factor II (IGF-II), secreted by tumors, such as leiomyosarcoma and hepatoma, has lately been suggested.5,8 Other mechanisms have also been suggested, for example, inhibition of glycogenolysis and gluconeogenesis; destruction of the liver by tumor metastases; suppression of counter regulatory hormones; and glucose consumption by the tumor itself.4 Lately Stuart et al IO have studied a case of tumor hypoglycemia due to colon carcinoma, and observed a marked increase in insulin receptor number in liver, muscle and ' monocytes. 9 A study by Pun et al7 had demonstrated an improvement in glucose tolerance tests in patients with hepatoma compared to cirrhotics. This paper describes metabolic studies on a diabetic patient with hemochromatosis and hepatoma who completely lost his dependence on 72 units/day of insulin concomitantly with tumor growth and development of hypoglycemia. We studied whether in vivo there is an increase in insulin sensitivity, clearance, and amino acid disposal which would support the hypothesis that tumor hypoglycemia is at last partially related to changes in the insulin response of peripheral tissues. Case Report A 58·year-old man with a IS-year history of primary hemochromatosis and cirrhosis, established by biopsy and appropriate biochemical tests, was studied. He was found to be diabetic 10 years

229

Increased Insulin Sensitivity

prior to this study and was treated with daily glibenclamide. Later that same year, he required insulin therapy, and 3 years later,. 72 units of insulin per day were necessary for good control (fastmg glucose < 140 mg/dl). Two years prior to this. study, he seem~d.w~ll with no change in liver function tests, and WIth a serum ferntm m the low-normal range. Subsequently, his urine glucose tests became consistently negative and he developed episodes of early morning wakening, headaches, and sweating, which were found to be due to hypoglycemia (glucose < 40 mg/dl, requiring intravenous glucose). His insulin dosage was reduced to 28 units/day. A year later, he was readmitted after 4-5 months of anorexia, weight loss, lethargy, and malaise. Computed tomography examination revealed several areas of low attenuation in the liver. A liver biopsy was performed and revealed active cirrhosis with grade 3 siderosis and fragments ofhepatoma. Later, he was found to have a serum glucose of 20 mg/dl and his daily insulin was reduced to 10 units and insulin therapy was stopped. Three weeks after insulin was stopped, he had anot.he~ episode of hypoglycemia with glucose levels of 45 mg/dl. At this time, insulin levels were 5 mg/ml and cortisol was 24 mg/dl. With an increase in carbohydrate intake, he was successful in maintaining glucose levels of above 60 mg/dl. His fasting blood glucose level ~he morning of the study while measuring his hepatic glucose production was averaged at 64 mg/dl, his insulin level was 7 IlU/ml and Cpeptide was 0.46 ng/ml. A month later he died, and his tumor was estimated at autopsy to be 1 kg in weight (Table 1).

Materials and Methods Subjects. Clinical and biochemical characteristics of

the patient with hepatoma, cirrhotics, and normal controls are presented in Table 2. All subjects gave informed consent prior to the studies, which were approved by the Rambam Medical Center Human Rights Board and the Royal Free Hospital ethical committee. Normal subjects had no history of liver or metabolic disease and cirrhosis was proven by biopsy. Euglycemic Insulin Clamp Technique. Studies were performed after an overnight fast, as previously described. l1 The infusate was given via an antecubital vein. A dorsal hand vein was canulated and kept in a warming box (55 0 C) to arterialize the venous samples. After the measurement of hepatic glucose production, a bolus of insulin was given, followed by a continuous infusion for 2 hours at each insulin infusion rate. Rates of insulin infusion were 1 and 10 mU/kg/min in all subjects. Serum glucose was maintained between 85

Table 1. Dates of Diagnoses and Treatment for Diabetes in the Hepatoma Patient Date

Diagnosis

1/71 Primary hemochromatosis Cirrhosis 2/76 Diabetes 4/76 5/79 10/84 Hepatoma Hypoglycemia 1/85 2/85 Hypoglycemia 3/85 Death

230

Treatment for Diabetes (not diabetic) Glibenclamide,5 mg Insulin, 10 U regular +8U NPH Insulin, 44 U regular +28U NPH Insulin, 16 U regular +12U NPH Insulin, 10 U NPH No treatment for diabetes Metabolic studies

Table 2. Clinical and Biomedical Characteristics of the Hepatoma Patient, Hepatocellular Cirrhotics, and Normal Controls

Hepatoma Patient Age (yrs) % of Ideal body weight Total bilirubin (IlmollL) Albumin (gIL) Total protein (giL) Alkaline phosphatase (lUlL) SGOT(IU/L) Pasting plasma glucose (mg/dl) Pasting plasma insulin (llU/mi) C-peptide (ng/ml) Cortisol (llg/dL) Epinephrine (Ilg/L) Growth hormone (ng/ml)

58 73 25 30 60 352 1026 64

7 0.46 18 0.08 <0.5

Hepatocellular Cirrhotics (n = 8) 45 ± 86 ± 60 ± 32 ± 65 ± 199 ± 79 ±

13 14 27 2 3 24 10

75 ± 4 16 ± 2 1.36 ± 0.56

Normal Controls (n = 9) 30± 5 110 ± 10 <17 (35-55) (60-SO) <130 <40 85 ±8 6±1 0.7 ± 0.12 (5-25) (0.05-1) (1-10)

SGOT = asparate aminotransferase.

and 95 mg/dl throughout the study period by monitoring the glucose level at 5-minute intervals for 4 hours. The infusion rate of a 50% glucose solution was adjusted by a servo-mechanism negative-feedback principle. Potassium chloride solution was administered during each study to maintain serum potassium between 3.5 and 4.5 mEqf1, thus avoiding the potentially deleterious effects of hypokalemia. The amount of glucose consumed was calculated from the rate of infusion during the last 40 minutes of each 2 hour period. Basal Hepatic Glucose Production. For 120 minutes before starting the clamp studies, the glucose pool was labeled with a primed continuous infusion ofD3-[3H]glucose, 5 Ci/mmol (New England Nuclear, Boston, MA). The priming dose was given as a 25 uCi bolus injection, followed by a continuous infusion at a rate of 0.25 uCi/min. Plasma samples for the determination of steady-state glucose specific activity were taken at 5-minute intervals for 60 minutes before the clamp study was started. A study-state plateau of glucose specific activity was achieved before beginning the insulin infusion. Glucose specific activity was assayed as previously described. l1 Hepatic glucose turnover in the basal state was calculated by dividing the rate of D3[3H]-glucose infusion (CPM/min) times the fasting blood sugar by the steady-state level of glucose specific activity (CPM/mg)Y Instrument and Analytical Methods. Blood for serum glucose determination was drawn and measured using a Glucometer (Ames Division, Miles Laboratories Inc., Elkhart, IN). Blood samples were also sent to the hospitallaboratories, and the results matched those of the Glucometer, and were within ±3% accuracy. Insulin was infused with a Sage Instruments syringe pump, October 1991 Volume 302 Number 4

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Model 341. Fifty percent glucose solution was infused with an IMED pump (Kantor Co., London, England). Blood for determination of serum insulin and C-peptide was collected every 10 minutes during the last 40 minutes of each point and allowed to clot. The specimens were then spun and the serum removed and stored at - 20° C. Insulin and C-peptide levels were determined with radioimmunoassay kits purchased from Biodata (Milan, Italy). Serum was deproteinized with 40 mg/ ml of sulfosalicylic acid and amino acids were measured with an LKB-4400 amino acid analyzer. IGF levels were measured in the pediatric endocrinology laboratory of Stanford University.

presented in Figure 1. The steady state glucose infusion rate was higher at the two insulin levels achieved in the patient with hepatoma than in normals and cirrhotics displaying a marked left shift of the insulin dose response curve. At insulin levels of 72 JLU/ml (Figure 2), glucose disposal rate was 9.6 mg/kg/min in the hepatoma patient, compared to 3.5 ± 0.3 and 6.4 ± 0.2 mg/kg/min in cirrhotic patients and normal controls, respectively. It was 2.5-fold higher in the hepatoma patient than in cirrhotics, and 50% higher than in normal subjects. Insulin Clearance. The ICR at insulin infusion rates of 1 mU/kg/min (Figure 3) was calculated to be 4427 ml/min/M2 in the hepatoma patient, compared to 1050 + 80 and 776 + 128 ml/min/M2 in the normal controls and cirrhotic patients, respectively. The rate in the hepatoma patient was sixfold higher than in cirrhotics and fivefold higher than in normals. The Effect of Insulin on Amino Acid Decrease. All amino acids were two to four times elevated in the basal state in the hepatoma compared to controls. Alanine was 12.4 mg/dl compared to 3.5 ± 0.4 mg/dl in normal and 3.3 ± 3.0 mg/dl in cirrhotic patients. The percentage of decrease in total amino acid from basal levels at insulin levels of 72 JLU/ml was 66% in the hepatic patient, 30 ± 4% in cirrhotics, and 34 ± 5% in normal controls (Figure 4). Hepatic Glucose Production. Basal hepatic glucose production was markedly increased in the patient with hepatoma, being 3.7 mg/kg/min compared to 1.3 ± .4 and 2.1 ± 0.2 mg/kg/min (mean ± SEM) in cirrhotic and normal subjects, respectively (Figure 5). Insulin-like Growth Factors Levels. IGF-I and IGF-II levels were 0.26 U and 100 ng/ml, respectively (low normal).

Calculations

The insulin clearance rate (ICR) was calculated as follows: ICR(mljM2/min) = Insulin Infusion Rate(JLU/M2 /min)

I inf -

I basal

(1)

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I inf and CPinf are the concentrations of insulin and Cpeptide during the insulin infusion; Ibasal and CPbasa1 are the concentrations of insulin and C-peptide before the start of the study, in JLU/mL andng/mL, respectively.12 All calculations and statistical analyses were performed using an IBM personal computer. Data is presented as mean ± SEM. Results Insulin Mediated Glucose Disposal. Insulin levels and

steady state glucose infusion rates achieved in the hepatoma patient and in cirrhotic and normal patients are THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES

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231

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fibroblasts in tissue culture demonstrated no increase in insulin binding, thus suggesting that the receptor alteration was acquired and intrinsic. This data suggests that proliferation of insulin receptors through unknown humoral mechanism is responsible for the tumor hypoglycemia. While these studies10 have failed to demonstrate a humoral factor, other evidence suggests that this humoral factor could be IGF-II. This molecule exhibits a high degree of structural homology to human proinsulin and it does reduce serum glucose levels in normal and hypophysectomized ratsY Serum IGF-II levels are elevated in some cases of tumor hypoglycemia.3 ,14 In one study, only 37% of all tumor hypoglycemia had elevated IGF-I and II titers. Of four previously reported cases of hepatoma associated with hypoglycemia, only two had increased IGF-like material (250% and 400% above normal). Later, it was shown7 that in the presence of normal values of IGF-II in the serum, a leiomyosarcoma removed from the chest of a patient with recurrent hypoglycemia contained a 50-fold higher amount of mRNA for IGF-II than any normal adult tissue known to express the IGF-II gene. The normal IGF-II con-

70

Discussion

We described a case of a patient who had diabetes due to hemochromatosis and gradually lost his insulin dependence, concomitantly with the development of a hepatoma, until finally he had hypoglycemic episodes while not receiving insulin. In in vivo studies, using the euglycemic insulin clamp technique, we have demonstrated a left shift in the insulin dose response curve, ie, increased insulin sensitivity. This is an opposite observation to the insulin resistance and the right shift in the insulin dose response curve observed in diabetic patients after insulininduced hypoglycemia. 26 Also, we have demonstrated increased insulin clearance and increased fall in total amino acid in response to insulin. These findings are particularly dramatic when compared to other cirrhotics. These results are supportive links between two other studies. In the first, glucose tolerance tests comparing patients with cirrhosis, hepatoma, and hepatoma with hypoglycemia have demonstrated improved tolerance in the latter.7 A mechanism for this phenomena was suggested in a second, in vitro study by Stuart et al10 on tissues from a patient with colon carcinoma metastatic to the liver. Mononuclear cells, obtained before death, and liver and muscle membrane obtained at autopsy, were found to have a threefold to fivefold increase in insulin receptor numbers. As for humoral factors, antibodies against the insulin receptor were not present. IGF-I and II were low but the level of nonsuppressible insulin-like protein was elevated. Another important observation in that study was that skin

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centration in the serum may have been due to a high molecular weight species of nonimmunoreactive IGF11.5.7.15 An alternative explanation is an abnormal IGF binding protein which allows IGF-II to enter the interstitial fluids and, thus, increase the fraction ofIGFs reaching the target cells. I6 Therefore, IGF-II could be involved in this patient's tumor hypoglycemia in spite of normal serum levels. Of note, is the lack of measurable serum levels of growth hormone in the hepatoma patient. Growth hormone levels are known to be decreased in the presence of elevated IGF-II levels. I7 IGFII has not been reported to have an effect on insulin receptor proliferation. Insulin clearance is thought to occur in the liver, secondly in the kidney, and also in peripheral target tissues of insulin. Insulin binding to its receptor is probably an essential step in insulin metabolism. Recently, Cohen et al I2 have demonstrated the correlation between insulin clearance and insulin responsiveness. Therefore, the increased insulin clearance in our patient supports the possibility of the insulin receptor proliferation. Amino acids usage is also insulin-dependent although the role of insulin receptor is not clear. Both increased insulin clearance and amino acid fall in this patient could be accounted for by an increase insulin receptor or postreceptoral events. Hepatic glucose production in this patient was increased twofold compared to control groups, maintaining blood glucose level just above clinical levels of hypoglycemia. Insulin is the major inhibitor of hepatic glucose production; since hepatic insulin resistance is a major feature of diabetes, it is possible that the relatively low insulin level in this patient (secondary to hypoglycemia) were helpful in not shutting off hepatic glucose production in this unique case.26 In hypoglycemia induced by insulin, hepatic glucose production THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES

initially decreases but eventually increases above baseline but not twofold to threefold as in this case.27 It is, therefore, possible that in hypoglycemia that is not clearly insulin-induced, hepatic glucose production increases due to other mechanism triggered by low glucose levels. The normal levels of counterregulatory hormones, such as cortisol and epinephrine, suggests that abnormal counterregulation was not a problem in this patient. As discussed before, low growth hormone levels might indicate the role of IGF-II in this tumor hypoglycemia, and with other counterregulatory hormones within normal levels, it is not a substantial factor in this case. Tumor glucose consumption has been studied in several models. IS.I9 Some quantitative estimates have been made of glucose consumption by human slices in vitro; in two cases, A-V glucose differences were measured across tumor weighing about 1 kg, as in our case. The results suggested that the tumors would metabolize about 50-200 gm of glucose per day.20 This data and the left shift in the insulin dose response curve makes it unlikely that increased usage of glucose by the tumor can wholly account for the hypoglycemia. Cirrhosis, hemochromatosis, and associated diabetes are insulin resistance states.7.21-25 In this case, the humoral factor that caused the changes described in this patient-tumor hypoglycemia-completely reversed the insulin resistance. References 1. Anderson N, Lodich SS: Mesenchymal tumors associated with hypoglycemia: Case report and review of the literature. Cancer 44:785-790,1979. 2. Chowdhury F, Belicher SJ: Studies of tumor hypoglycemia. Metabolism 22:663-673, 1973. 3. Gordon P, Hendricks CM, Kahn CR, Megyesh K, Roth J: Hypoglycemia associated with non-islet cell tumor and insulin-like growth factors. N Engl J Med 305:1452-1455, 1981. 4. Kahn CR: The riddle of tumor hypoglycemia revisited. Clin Endocrinol Metab 9:2:335-360,1980. 5. Shapiro T, Polansky K, Mew M, Rubinstein A, Bell G: Tumor hypoglycemia is associated in increase expression of the gene for insulin-like growth factor II. Clin Res 36:490 (abstract) 1988. 6. Joffe BI, Keiv MC, Pans VR, Kalk WJ, Shives R, Wing S, Seftel HC: Evaluation of the synthetic somatostatin analogue MS 201995 in patient's with hypoglycemia associated with hepatocellular carcinoma. Br J Cancer 58:91-92, 1988. 7. Pun KK, Ho WM, Yeung RTT. C-Peptide in non-alcoholic cirrhosis and hepatocellular carcinoma. J Endocrinol Invest II:337343,1988. 8. Daughaday WH, Imanuelle MA, Brookes MH, Barlato AL, Kapadia M, Rotwein P: Synthesis and secretion of insulin-like growth factor II by a leiomyosarcoma with associated hypoglycemia. N Engl J Med 319:1434-1440, 1988. 9. Chowdhury F, Belicher SS: Studies of tumor hypoglycemia. Metabolism 22:663-673, 1973. 10. Stuart CA, Prince MJ, Peters FJ, Smith FE, Townsend CM, Poffenbarger PL: Insulin receptors proliferation: A mechanism for tumor-associated hypoglycemia. J Clin Endocrinol Metab 63: 879-885, 1986.

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11. DeFronzo RA, Tobin JD, Andres R: The glucose clamp technique: A method for quantifying insulin secretion and resistance. Am J Physiol 237:E214-R222, 1979. 12. Cohen P, Barzilai N, Barzilai D, Karnieli E: Correlation between insulin clearance and insulin responsiveness: Studies in normal, obese, hyperthyroid, and Cushing's syndrome patients. Metabolism 35(8):774-794,1986. 13. Zapf J, Hauri C, Waldnogel M, Froesch ER: Acute metabolic effects and half lines in intravenously administered insulin-like growth factor I and Ii in normal and hypophysectomized rats. J Clin Invest 77:1768-1775, 1986. 14. Daughaday WH, Trivedi B, Kapadia M: Measurement of insulin like growth factor I by a specific radioreceptor assay in serum of normal individuals, patients with abnormal growth hormone secretion, and patient with tumor-associated hypoglycemia. J Clin Endocrinol Metab 53:289, 1981. 15. Lowe WL Jr, Roberts CT Jr, LeRoith D, Rojeski MT, Merimee TJ, Tengfui S, Keen H, Arnold D, Mersey J, Gluzman S, Spratt D, Eastman RC, Roth J: Insulin-like growth factor-II in nonislet cell tumors associated with hypoglycemia: Increased levels of messenger ribonucleic acid. J Clin Endocrinol Metab 69:11531159,1989. 16. Daughaday WH, Kapadia M: Significance of abnormal serum binding of insulin-like growth actor II in the development of hypoglycemia in patients with non-islet-cell tumors. Proc Natl Acad Sci 86:6778-6782, 1989. 17. Ron D, Powers AC, Pandian MR, Gopdine JE, Axelrod L: Increased inculsin-like growth factor II production and consequent suppression of growth hormone secretion: A dual mechanism

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24. 25. 26. 27.

for tumor-induced hypoglycemia. J Clin Endocrinol Metab 68: 701-706, 1989. Marks V, Rose FC: Hypoglycemia. Oxford: Blackwell, 1965. Sauer LA, Stayman JW III, Daucny RT: Amino acid, glucose and lactic acid utilization in vivo by rat tumors. Cancer Res 42: 4090-4097,1982. Unger RM: The riddle of tumor hypoglycemia. Am J Med 40: 325-330, 1966 Creutzfeld W, Frerichs H, Sickinger K: Liver disease and diabetes mellitus. Prog Liver Dis 13:371-407, 1970. Proietto J, Nankervis A, Aitken P, Dudley FJ, Crauso, Alford FP: Insulin resistance in cirrhosis: Evidence for a post-receptor defect. Clin Endocrinol21:677-688, 1984. Cavallo-Peni P, Cassader M, Rozzo C, Bruno A, Nuccio P, Dallomo AM, Marucci M, Pagano G: Mechanism of insulin resistance in human liver cirrhosis: Evidence of a combined receptor and post-receptor defect. J Clin Invest 75:1954-1665, 1985. Nygrean P, Adnen N, Sunbald L, Weichel K-L. Insulin uptake by the human alcoholic liver. Metabolism 34:48-52, 1985. Blei AT, Robbins DC, Drobny E: Insulin resistance and insulin receptors in hepatic cirrhosis. Gastroenterology 83:1191-1199, 1982. Clore IN, Brennan JR, Gebhart SP, Newsome HH, Nestler JE, Blackord WG: Prolonged insulin resistance following insulininduced hypoglycemia. Diabetologia 116:314-320, 1987. Frizzell RT, Hendrik GK, Brown LL, Lacy DB, Donaubu EP, Carr RK, Williams TE, Parlow AF, Stevenson RW, Cherrington AD: Stimulation of glucose production through hormone secretion and other mechanisms during insulin-induced hypoglycemia. Diabetes 37:1531-1541, 1988.

October 1991 Volume 302 Number 4