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Insulin increase in colon cancerogenesis: a case-control study
Archives of Medical Research 35 (2004) 215–219
ORIGINAL ARTICLE
Insulin Increase in Colon Cancerogenesis: A Case-Control Study Ingrid Tripkovic,a Andro Tripkovic,b Zlatko Ivanisevic,b Vesna Capkunc and Ljubinka Zekanc a
b
Public Health Institute of Split and Dalmatia County, Split, Croatia Department of Surgery, cDepartment of Nuclear Medicine, Clinical Hospital Split, Split, Croatia Received for publication June 11, 2003; accepted December 10, 2003 (03/096).
Background. Our aim was to establish whether individuals who develop colon cancer have elevated blood insulin concentrations. Methods. This was a case-control study in which 56 normoglycemic patients with colon cancer and a corresponding control group were investigated at the Clinical Hospital Split from April 1998 to April 1999. Data on age, weight, height, and sex of examinees were recorded and concentrations of glucose, insulin, and C-peptide were measured first in the morning before breakfast and again 90 min after breakfast. Results. In the male group of colon cancer patients, we found statistically significant higher blood insulin concentrations 90 min after breakfast (median 34.7 mIU/L, range 3.3–162.6 mIU/L) in comparison to male control group (median 20.7 mIU/L, range 3.1– 122.1 mIU/L) (p ⫽ 0.044). Concentration of C-peptide in blood 90 min after breakfast (median 3.28 nmol/L, range 0.38–6.1 nmol/L) was higher in the male group of colon cancer patients than in male control group (median 1.68 nmol/L, range 0.26–4.26 nmol/ L) (p ⫽ 0.001). No difference was found in concentrations of insulin, C-peptide, and glucose in blood measured in the morning before breakfast between the male group of colon cancer patients and male control group. Ratio of insulin 90 min after breakfast with respect to insulin in the morning before breakfast was higher in the male group of colon cancer patients (median 4.65, range 0.83–22.1) than in male control group (median 1.78, range 0.38–8.75) (p ⫽ 0.005). Ratio of C-peptide 90 min after breakfast with respect to fasting C-peptide was higher in the male group of colon cancer patients (median 3.22, range 0.74–11.9) than in male control group (median 1.42, range 0.54–6.0) (p ⫽ 0.001). Women with colon cancer also had statistically significant higher ratio of insulin and Cpeptide with respect to female control group. In the female group of colon cancer patients, median for ratio of C-peptide was 2.42 (range 0.43–8.87), while in female control group it was 1.19 (range 0.62–15.4) (p ⫽ 0.025). Median for ratio of insulin in the female group of colon cancer patients was 4.23 (range 0.25–8.54), while in female control group it was 1.17 (range 0.29–26.89) (p ⫽ 0.007). Conclusions. There was a higher increase of insulin 90 min after breakfast in the group of patients with colon cancer than in control group. 쑖 2004 IMSS. Published by Elsevier Inc. Key Words: Insulin, Colon cancer, Hyperinsulinemia, Cancer risk.
Introduction The hypothesis of hyperinsulinemia promoting colon cancerogenesis has appeared in scientific literature since 1995 (1– 4). This hypothesis was examined principally in studies
Address reprint requests to: Ingrid Tripkovic, Driceva #29, Split, Croatia. Phone: (⫹385) (21) 344-266; FAX: (⫹385) (21) 535-318; E-mail: [email protected]
0188-4409/04 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 3 .1 2 .0 03
in vitro, which revealed the growth-promoting effect of insulin on colon cancer (1,5,6). Insulin has a strong anabolic effect independent of its effect on carbohydrate metabolism. This effect includes stimulation of protein synthesis and cell proliferation. Close structural relation of insulin and IGF (insulin-like growth factors) group of growth factors and the ability of insulin to bind to IGF-1 receptors may explain some of these effects of insulin at high levels (7–9). Insulin/colon cancer hypothesis is based on the similarity of factors that increase insulin levels and these are related
쑖 2004 IMSS. Published by Elsevier Inc.
216
Tripkovic et al. / Archives of Medical Research 35 (2004) 215–219
to increased risk of colon cancer: namely, colonic cancer tissue contains both insulin and IGF-1 (insulin-like growth factor-1) receptors. Mitogenic effects of insulin, in contrast to its glycemic control property, occur in part through IGF1 receptors or hybrid IGF-1 insulin receptors (6). Stimulation of IGF-1 receptors by IGF-1 or IGF-2 may increase risk of colon cancer in humans (7,10,11). Epidemiologic evidence supporting the hyperinsulinemia–colon cancer hypothesis is based primarily on the observation that numerous factors causing hyperinsulinemia, particularly central obesity and physical inactivity, appeared related to risk of colon cancer (12,13). This study was designed to test whether patients with colon cancer had higher concentrations of insulin compared to control group.
Control group corresponded to patient group with colon cancer in sex, age, body mass index (BMI), and in monthof-hospitalization. Matching procedure was used in study. As a result, the group of patients with colon cancer and control group were formed. Each group consisted of 56 patients, 22 females and 34 males. Statistics. All data were analyzed using SPSS 9.0 statistical package. Paired Student t test was used to test differences between basic characteristics of men and women with colon cancer and control group. Wilcoxon test was used due to great variability of data obtained by measuring insulin, glucose, and C-peptide concentrations in blood for comparison of colon cancer patients and controls.
Results Patients and Methods This is a case-control study in which normoglycemic patients with colon cancer were examined during a 1-year period from April 1998 to April 1999, as were participants in the corresponding control group. All examinees were hospitalized at the Surgical Clinic of the Clinical Hospital Split. All examinees gave oral informed consent for use of their questionnaire data and blood samples for research purposes. Control group consisted of patients hospitalized due to elective surgery for gallstones or abdominal wall hernias. Each patient in the control group was selected within 1 month after our colon cancer patient was hospitalized. Colon cancer patients for whom we did not manage to find controls were excluded from the study. Patient data on age, weight, height, and sex were recorded, including data on medications they were using to be sure that our examinees took no medications known to affect insulin secretion or action. Blood samples were taken from all examinees prior to surgery to measure concentrations of glucose, insulin, and Cpeptide. Blood samples were taken twice a day, first in the morning before breakfast and then again 90 min after breakfast. Breakfast for patients prior to surgery was standardized at 351 calories. Percentage of protein was 12%, fat 19%, and carbohydrates, 69%. Breakfast was served each morning at 8 A.M. All examinees were required to complete the meal within 10 min. Measurements were performed after overnight fast at 7 A.M. and 90 min after patients finished their breakfast. Insulin concentration was measured at the Department of Nuclear Medicine using insulin immunoradiometric assay kit INSI-CTK irma (DiaSorin, Saluggia, Italy). C-peptide concentration was measured at the same Department using C-peptide radioimmunoassay kit C-PEPTIDE-CTK (DiaSorin). Glucose was measured at the Department for medical diagnostic methods using GLUKOZA PAP (Herbos Dijagnostika, Sisak, Croatia).
The male group of colon cancer patients did not differ from male control group in basic characteristics of examined variables as follows: age (t ⫽ 1.23, p ⫽ 0.228); height (t ⫽ 0.29, p ⫽ 0.774); weight (t ⫽ 0.57, p ⫽ 0.573); waist circumference (t ⫽ 0.42, p ⫽ 0.677); hip circumference (t ⫽ 0.07, p ⫽ 0.944), and BMI (t ⫽ 0.64, p ⫽ 0.527). The female group of colon cancer patients also did not differ from female control group in age (t ⫽ 1.81, p ⫽ 0.085), height (t ⫽ 0.92, p ⫽ 0.368), weight (t ⫽ 1.22, p ⫽ 0.237), waist circumference (t ⫽ 0.71, p ⫽ 0.484), hip circumference (t ⫽ 1.04, p ⫽ 0.311), and BMI (t ⫽ 0.92, p ⫽ 0.368). The group of patients with colon cancer corresponded to control group in all measured variables (Table 1). Men. No statistically significant difference was found in blood concentrations of fasting glucose, insulin, and C-peptide between group of patients with colon cancer and corresponding control group (Table 2). Glucose concentration in blood 90 min after breakfast also did not show any statistically significant difference between groups. In the male group of colon cancer patients, median was 6.4 mmol/L (range 4.7–8.2 mmol/L) and in control group was 5.9 mmol/ L (range 4.3–8.0 mmol/L) (p ⫽ 0.773). The difference was found in values of insulin and C-peptide measured 90 min after breakfast: insulin was statistically significantly higher in the male group of colon cancer patients (median 34.7 mIU/L, range 3.3–162.6 mIU/L) in comparison with control group (median 20.7 mIU/L, range 3.1–122.1 mIU/L) (p ⫽ 0.044). C-peptide also showed statistically significant increase in male group of colon cancer patients (median 3.28 nmol/L, range 0.38–6.1 nmol/L) compared with control group (median 1.68 nmol/L, range 0.26–4.26 nmol/L) (p ⫽ 0.001) (Table 2). To determine difference in concentration values of insulin and C-peptide in the group of patients with colon cancer and corresponding control group, we took the ratio between values of insulin and C-peptide in blood measured 90 min after breakfast in comparison with fasting values of
Insulin Increase in Colon Cancerogenesis
217
Table 1. Basic characteristics of men and women with colon cancer and their control groups Men
Women
Examined variables
Control group (n ⫽ 34)
Group with colon cancer (n ⫽ 34)
t
pa
Control group (n ⫽ 22)
Group with colon cancer (n ⫽ 22)
Age (years) Height (cm) Weight (kg) Waist circumference (cm) Hip circumference (cm) BMI (kg/m2)
63.4 ⫾ 10.0 176.3 ⫾ 7.5 77.6 ⫾ 10.2 98.2 ⫾ 9.5 103.1 ⫾ 6.7 22.0 ⫾ 2.7
66.4 ⫾ 8.7 175.7 ⫾ 9.1 79.3 ⫾ 14.5 97.2 ⫾ 10.9 103.2 ⫾ 6.9 22.5 ⫾ 3.2
1.23 0.29 0.57 0.42 0.07 0.64
0.228 0.774 0.573 0.677 0.944 0.527
63.4 ⫾ 10.1 164.8 ⫾ 3.0 73.3 ⫾ 12.7 94.0 ⫾ 11.9 106.4 ⫾ 8.8 22.2 ⫾ 3.7
58.1 ⫾ 10.8 166.0 ⫾ 5.4 77.0 ⫾ 12.3 96.6 ⫾ 12.4 109.2 ⫾ 9.4 23.2 ⫾ 3.4
a
t
pa
1.81 0.92 1.22 0.71 1.04 0.92
0.085 0.368 0.237 0.484 0.311 0.368
Student t test.
insulin and C-peptide; we found significantly higher ratios of insulin and C-peptide in group of colon cancer patients than in control group. Median for ratio of insulin 90 min after breakfast in comparison with fasting values of insulin in male group of colon cancer patients was 4.65 (range 0.83– 22.1) and in control group was 1.78 (range 0.38–8.75) (p ⫽ 0.005). Median for ratio of C-peptide 90 min after breakfast in comparison with fasting values of C-peptide in the group of colon cancer patients was 3.22 (range 0.74– 11.9) and in control group was 1.42 (range 0.54–6.0) (p ⫽ 0.001) (Table 3). Women. There was no statistically significant difference either in blood concentrations of C-peptide and glucose in the morning before breakfast or in concentrations obtained in measurements 90 min after breakfast between the female group of colon cancer patients and corresponding control group. Median for concentration of C-peptide measured in the morning before breakfast in the group of colon cancer patients was 0.62 nmol/L (range 0.25–1.38 nmol/L) and in control group was 0.86 nmol/L (range 0.39–2.19 nmol/L)
(p ⫽ 0.253). Median for concentration of fasting glucose in the group of colon cancer patients was 5.2 mmol/L (range 4.0–6.5 mmol/L) and in control group was 5.6 mmol/L (range 3.5–6.5 mmol/L) (p ⫽ 0.131). Median for concentration of C-peptide 90 min after breakfast in group of colon cancer patients was 1.67 nmol/L (range 0.26–3.37 nmol/L) and in corresponding control group it was 1.16 nmol/L (range 0.57–6.1 nmol/L) (p ⫽ 0.131), while median for concentration of glucose in the group of colon cancer patients was 5.6 mmol/L (range 4.2–8.5 mmol/L) and in corresponding control group was 5.8 mmol/L (range 4.1–8.3 mmol/L) (p ⫽ 0.774). Concentration of fasting insulin differed between the group of colon cancer patients (median 6.0 mIU/L, range 2.0– 29.4 mIU/L) and control group (median 10.4 mIU/L, 2.8–38.0 mIU/L) (p ⫽ 0.014). Women from the control group had higher concentrations of fasting insulin. There were no statistically significant differences in concentration of insulin measured 90 min after breakfast between the female group of colon cancer patients (median 24.5 mIU/L, range 3.3–80.2
Table 2. Concentrations of glucose, insulin, and C-peptide in blood before breakfast and 90 min after breakfast in men and women with colon cancer and their control groups Men Control group (n ⫽ 34) Examined variables Concentration of insulin before breakfast (mIU/L) Concentration of insulin 90 min after breakfast (mIU/L) Concentration of glucose before breakfast (mmol/L) Concentration of glucose 90 min after breakfast (mmol/L) Concentration of C-peptide before breakfast (nmol/L) Concentration of C-peptide 90 min after breakfast (nmol/L) a
Mann-Whitney test.
Women
Group with colon cancer (n ⫽ 34)
Control group (n ⫽ 22)
Group with colon cancer (n ⫽ 22)
Median
Range
Median
Range
z
pa
Median
Range
Median
Range
10.6
2.6–87.3
7.6
2.0–16.7
1.37
0.179
10.4
2.8–38.0
6.0
2.0–29.4
2.51 0.014
20.7
3.1–122.1
34.7
3.3–162.6
2.015 0.044
13.9
8.6–108.6
24.5
3.3–80.2
1.35 0.182
z
pa
5.42
3.9–6.5
5.2
3.7–6.5
0.78
0.442
5.6
3.5–6.5
5.2
4.0–6.5
1.53 0.131
5.9
4.3–8.0
6.4
4.7–8.2
0.29
0.773
5.8
4.1–8.3
5.6
4.2–8.5
0.32 0.774
0.81
0.19–4.0
0.805
0.26–2.12
0.089 0.934
0.86
0.39–2.19
0.62
0.25–1.38
1.14 0.253
1.68
0.26–4.26
3.28
0.38–6.1
3.18
1.16
0.57–6.1
1.67
0.26–3.37
1.54 0.131
0.001
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Tripkovic et al. / Archives of Medical Research 35 (2004) 215–219
Table 3. Ratio of insulin and C-peptide concentrations in blood 90 min after breakfast and fasting concentrations of insulin and C-peptide in men and women with colon cancer and their control groups Men Control group (n ⫽ 34) Examined variables Concentration of after breakfast concentrations Concentration of after breakfast concentrations a
Women
Group with colon cancer (n ⫽ 34)
Median
Range
Median
Range
insulin 90 min and fasting
1.78
0.38–8.75
4.65
0.83–22.1
C-peptide 90 min and fasting
1.42
0.54–6.0
3.22
0.74–11.9
Control group (n ⫽ 22) z
pa
Group with colon cancer (n ⫽ 22) Range
z
pa
Median
Range
Median
2.83 0.005
1.17
0.29–26.89
4.23
0.25–8.54 2.72
0.007
3.31 0.001
1.19
0.62–15.4
2.42
0.43–8.87 2.24
0.025
Mann-Whitney test.
mIU/L) and corresponding control group (median 13.9 mIU/ L, range: 8.6–108.6 mIU/L) (p ⫽ 0.182) (Table 2). Ratio of insulin 90 min after breakfast in comparison with fasting insulin showed statistically significant increase in the female group of colon cancer patients. Median for group of colon cancer patients was 4.23 (range 0.25–8.54), while in the control group it was 1.17 (range 0.29–26.89) (p ⫽ 0.007). Median for ratio of C-peptide 90 min after breakfast with respect to fasting values of C-peptide was 2.42 (range 0.43–8.87) in the group with colon cancer and 1.19 (range 0.62–15.4) in corresponding control group and was also significantly higher in the female group of colon cancer patients (p ⫽ 0.025) (Table 3).
Discussion Accumulated evidence now supports the association of colon cancer with insulin resistance. Thus, multiple studies indicated that numerous factors that cause hyperinsulinemia were related to colon cancer risk. Increase of colorectal cancer was confirmed in patients with type 2 diabetes who showed higher levels of circulating insulin (14,15). This risk was particularly high in men (16). Schoen et al. (4) in their investigation also came to the conclusion that individuals with higher levels of fasting glucose and insulin 2 h after oral glucose challenge and having increased waist circumference had a nearly twofold increased risk for colorectal cancer. Nishhii et al. (17) examined cross-sectionally the relation of fasting plasma insulin levels and glucose tolerance status to colon adenomas. Their findings suggested that long-term hyperinsulinemic status associated with NIDDM may increase risk of colon adenomas and, subsequently, of colon cancer. The prospective study of Kaaks et al. (18) showed that elevated levels of C-peptide—a marker of chronic hyperinsulinemia—may increase colorectal cancer risk. In this study we found a higher increase of insulin and C-peptide 90 min after breakfast in a group of colon cancer patients as well as higher insulin and C-peptide concentrations in blood 90 min after breakfast in male group of colon
cancer patients. We also found the difference in fasting insulin concentrations between the female group of colon cancer patients and control group, although we intentionally attempted to choose patients having uniform general characteristics. Concentrations of fasting insulin were higher in female control group than in female group of colon cancer patients. Nevertheless, after breakfast the difference between insulin concentration disappeared between the female group of colon cancer patients and control group, which could indirectly imply that insulin increase in female group of colon cancer patients was higher than in female control group. Our findings might imply that insulin secretion may be more important than insulin resistance. Therefore, further studies might be directed toward that investigation approach. We are aware that our study is limited by the small sample size; thus, our results cannot reach maximum statistical power. Future studies should have larger sample size and in addition to determining blood insulin levels also should investigate IGF-1 levels, due to their role in transformation and proliferation of carcinoma cells. However, further investigations should attempt to collect additional information on the intricate relationship between tumor presence and insulin status.
References 1. Giovannucci E. Insulin and colon cancer. Cancer Causes Control 1995;6:164–179. 2. Yam D, Fink A, Mashiak A, Ben-Hur E. Hyperinsulinemia in colon, stomach and breast cancer patients. Cancer Lett 1996;104:129–132. 3. Yamada K, Araki S, Tamura M, Sakai I, Takahashi Y, Kashihara H, Kono S. Relation of serum total cholesterol, serum triglycerides and fasting plasma glucose to colorectal carcinoma in situ. Int J Epidemiol 1998;27:794–798. 4. Schoen RE, Tangen CM, Kuller LH, Burke GL, Cushman M, Tracy RP, Dobs A, Savage PJ. Increased blood glucose and insulin, body size, and incident colorectal cancer. J Natl Cancer Inst 1999;91:1147–1154. 5. Tran TT, Medline A, Bruce WR. Insulin promotion of colon tumors in rats. Cancer Epidemiol Biomarkers Prev 1996;5:1013–1015. 6. Koenuma M, Yamori T, Tsuruo T. Insulin and insulin-like growth factor 1 stimulate proliferation of metastatic variants of colon carcinoma 26. Jpn J Cancer Res 1989;80:51–58.
Insulin Increase in Colon Cancerogenesis 7. Ma J, Pollak MN, Giovannucci E, Chan JM, Tao J, Hennekens CH, Stampher MJ. Prospective study of colorectal cancer risk in men and plasma levels of insulin-like growth factor (IGF)-1 and IGF-binding protein-3. J Natl Cancer Inst 1999;91:620–625. 8. Giovannucci E. Insulin-like growth factor-1 and binding protein-3 and risk of cancer. Horm Res 1999;51(Suppl S3):34–41. 9. Baserga R. The insulin-like growth factor 1 receptor: a key to tumor growth? Cancer Res 1995;55:249–252. 10. Macaulay VM. Insulin-like growth factors and cancer. Br J Cancer 1992;65:311–320. 11. Baserga R, Helman L, Roberts CT Jr. Insulin-like growth factors and cancer. Ann Intern Med 1995;122:54–59. 12. Giovannucci E, Ascherio A, Rimm EB, Colditz GA, Stampher MJ, Willett WC. Physical activity, obesity, and risk for colon cancer and adenoma in men. Ann Intern Med 1995;122:327–334. 13. Kim YI. Diet, lifestyle, and colorectal cancer: is hyperinsulinemia the missing link? Nutr Rev 1998;56:275–279.
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14. La Vecchia C, Negri E, Decarli A, Franceschi S. Diabetes mellitus and colorectal cancer risk. Cancer Epidemiol Biomarkers Prev 1997;6: 1007–1010. 15. Hu FB, Manson JE, Liu S, Hunter D, Colditz GA, Michels KB, Speizer FE, Giovannucci E. Prospective study of adult onset diabetes mellitus (type 2) and risk of colorectal cancer in women. J Natl Cancer Inst 1999;91:542–547. 16. Will JC, Galuska DA, Vinicor F, Calle EE. Colorectal cancer: another complication of diabetes mellitus? Am J Epidemiol 1998;147:816–825. 17. Nishii T, Kono S, Abe H, Eguchi H, Shimazaki K, Hatano B, Hamada H. Glucose intolerance, plasma insulin levels, and colon adenomas in Japanese men. Jpn J Cancer Res 2001;92(8):836–840. 18. Kaaks R, Toniolo P, Akhmedkhanov A, Lukanova A, Biessy C, Dechaud H, Rinaldi S, Zeleniuch-Jacqotte A, Shore RE, Riboli E. Serum C-peptide, insulin-like growth factor (IGF)-I IGF-binding proteins, and colorectal cancer risk in women. J Natl Cancer Inst 2000;92(19): 1592–1600.
ORIGINAL ARTICLE
Insulin Increase in Colon Cancerogenesis: A Case-Control Study Ingrid Tripkovic,a Andro Tripkovic,b Zlatko Ivanisevic,b Vesna Capkunc and Ljubinka Zekanc a
b
Public Health Institute of Split and Dalmatia County, Split, Croatia Department of Surgery, cDepartment of Nuclear Medicine, Clinical Hospital Split, Split, Croatia Received for publication June 11, 2003; accepted December 10, 2003 (03/096).
Background. Our aim was to establish whether individuals who develop colon cancer have elevated blood insulin concentrations. Methods. This was a case-control study in which 56 normoglycemic patients with colon cancer and a corresponding control group were investigated at the Clinical Hospital Split from April 1998 to April 1999. Data on age, weight, height, and sex of examinees were recorded and concentrations of glucose, insulin, and C-peptide were measured first in the morning before breakfast and again 90 min after breakfast. Results. In the male group of colon cancer patients, we found statistically significant higher blood insulin concentrations 90 min after breakfast (median 34.7 mIU/L, range 3.3–162.6 mIU/L) in comparison to male control group (median 20.7 mIU/L, range 3.1– 122.1 mIU/L) (p ⫽ 0.044). Concentration of C-peptide in blood 90 min after breakfast (median 3.28 nmol/L, range 0.38–6.1 nmol/L) was higher in the male group of colon cancer patients than in male control group (median 1.68 nmol/L, range 0.26–4.26 nmol/ L) (p ⫽ 0.001). No difference was found in concentrations of insulin, C-peptide, and glucose in blood measured in the morning before breakfast between the male group of colon cancer patients and male control group. Ratio of insulin 90 min after breakfast with respect to insulin in the morning before breakfast was higher in the male group of colon cancer patients (median 4.65, range 0.83–22.1) than in male control group (median 1.78, range 0.38–8.75) (p ⫽ 0.005). Ratio of C-peptide 90 min after breakfast with respect to fasting C-peptide was higher in the male group of colon cancer patients (median 3.22, range 0.74–11.9) than in male control group (median 1.42, range 0.54–6.0) (p ⫽ 0.001). Women with colon cancer also had statistically significant higher ratio of insulin and Cpeptide with respect to female control group. In the female group of colon cancer patients, median for ratio of C-peptide was 2.42 (range 0.43–8.87), while in female control group it was 1.19 (range 0.62–15.4) (p ⫽ 0.025). Median for ratio of insulin in the female group of colon cancer patients was 4.23 (range 0.25–8.54), while in female control group it was 1.17 (range 0.29–26.89) (p ⫽ 0.007). Conclusions. There was a higher increase of insulin 90 min after breakfast in the group of patients with colon cancer than in control group. 쑖 2004 IMSS. Published by Elsevier Inc. Key Words: Insulin, Colon cancer, Hyperinsulinemia, Cancer risk.
Introduction The hypothesis of hyperinsulinemia promoting colon cancerogenesis has appeared in scientific literature since 1995 (1– 4). This hypothesis was examined principally in studies
Address reprint requests to: Ingrid Tripkovic, Driceva #29, Split, Croatia. Phone: (⫹385) (21) 344-266; FAX: (⫹385) (21) 535-318; E-mail: [email protected]
0188-4409/04 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 3 .1 2 .0 03
in vitro, which revealed the growth-promoting effect of insulin on colon cancer (1,5,6). Insulin has a strong anabolic effect independent of its effect on carbohydrate metabolism. This effect includes stimulation of protein synthesis and cell proliferation. Close structural relation of insulin and IGF (insulin-like growth factors) group of growth factors and the ability of insulin to bind to IGF-1 receptors may explain some of these effects of insulin at high levels (7–9). Insulin/colon cancer hypothesis is based on the similarity of factors that increase insulin levels and these are related
쑖 2004 IMSS. Published by Elsevier Inc.
216
Tripkovic et al. / Archives of Medical Research 35 (2004) 215–219
to increased risk of colon cancer: namely, colonic cancer tissue contains both insulin and IGF-1 (insulin-like growth factor-1) receptors. Mitogenic effects of insulin, in contrast to its glycemic control property, occur in part through IGF1 receptors or hybrid IGF-1 insulin receptors (6). Stimulation of IGF-1 receptors by IGF-1 or IGF-2 may increase risk of colon cancer in humans (7,10,11). Epidemiologic evidence supporting the hyperinsulinemia–colon cancer hypothesis is based primarily on the observation that numerous factors causing hyperinsulinemia, particularly central obesity and physical inactivity, appeared related to risk of colon cancer (12,13). This study was designed to test whether patients with colon cancer had higher concentrations of insulin compared to control group.
Control group corresponded to patient group with colon cancer in sex, age, body mass index (BMI), and in monthof-hospitalization. Matching procedure was used in study. As a result, the group of patients with colon cancer and control group were formed. Each group consisted of 56 patients, 22 females and 34 males. Statistics. All data were analyzed using SPSS 9.0 statistical package. Paired Student t test was used to test differences between basic characteristics of men and women with colon cancer and control group. Wilcoxon test was used due to great variability of data obtained by measuring insulin, glucose, and C-peptide concentrations in blood for comparison of colon cancer patients and controls.
Results Patients and Methods This is a case-control study in which normoglycemic patients with colon cancer were examined during a 1-year period from April 1998 to April 1999, as were participants in the corresponding control group. All examinees were hospitalized at the Surgical Clinic of the Clinical Hospital Split. All examinees gave oral informed consent for use of their questionnaire data and blood samples for research purposes. Control group consisted of patients hospitalized due to elective surgery for gallstones or abdominal wall hernias. Each patient in the control group was selected within 1 month after our colon cancer patient was hospitalized. Colon cancer patients for whom we did not manage to find controls were excluded from the study. Patient data on age, weight, height, and sex were recorded, including data on medications they were using to be sure that our examinees took no medications known to affect insulin secretion or action. Blood samples were taken from all examinees prior to surgery to measure concentrations of glucose, insulin, and Cpeptide. Blood samples were taken twice a day, first in the morning before breakfast and then again 90 min after breakfast. Breakfast for patients prior to surgery was standardized at 351 calories. Percentage of protein was 12%, fat 19%, and carbohydrates, 69%. Breakfast was served each morning at 8 A.M. All examinees were required to complete the meal within 10 min. Measurements were performed after overnight fast at 7 A.M. and 90 min after patients finished their breakfast. Insulin concentration was measured at the Department of Nuclear Medicine using insulin immunoradiometric assay kit INSI-CTK irma (DiaSorin, Saluggia, Italy). C-peptide concentration was measured at the same Department using C-peptide radioimmunoassay kit C-PEPTIDE-CTK (DiaSorin). Glucose was measured at the Department for medical diagnostic methods using GLUKOZA PAP (Herbos Dijagnostika, Sisak, Croatia).
The male group of colon cancer patients did not differ from male control group in basic characteristics of examined variables as follows: age (t ⫽ 1.23, p ⫽ 0.228); height (t ⫽ 0.29, p ⫽ 0.774); weight (t ⫽ 0.57, p ⫽ 0.573); waist circumference (t ⫽ 0.42, p ⫽ 0.677); hip circumference (t ⫽ 0.07, p ⫽ 0.944), and BMI (t ⫽ 0.64, p ⫽ 0.527). The female group of colon cancer patients also did not differ from female control group in age (t ⫽ 1.81, p ⫽ 0.085), height (t ⫽ 0.92, p ⫽ 0.368), weight (t ⫽ 1.22, p ⫽ 0.237), waist circumference (t ⫽ 0.71, p ⫽ 0.484), hip circumference (t ⫽ 1.04, p ⫽ 0.311), and BMI (t ⫽ 0.92, p ⫽ 0.368). The group of patients with colon cancer corresponded to control group in all measured variables (Table 1). Men. No statistically significant difference was found in blood concentrations of fasting glucose, insulin, and C-peptide between group of patients with colon cancer and corresponding control group (Table 2). Glucose concentration in blood 90 min after breakfast also did not show any statistically significant difference between groups. In the male group of colon cancer patients, median was 6.4 mmol/L (range 4.7–8.2 mmol/L) and in control group was 5.9 mmol/ L (range 4.3–8.0 mmol/L) (p ⫽ 0.773). The difference was found in values of insulin and C-peptide measured 90 min after breakfast: insulin was statistically significantly higher in the male group of colon cancer patients (median 34.7 mIU/L, range 3.3–162.6 mIU/L) in comparison with control group (median 20.7 mIU/L, range 3.1–122.1 mIU/L) (p ⫽ 0.044). C-peptide also showed statistically significant increase in male group of colon cancer patients (median 3.28 nmol/L, range 0.38–6.1 nmol/L) compared with control group (median 1.68 nmol/L, range 0.26–4.26 nmol/L) (p ⫽ 0.001) (Table 2). To determine difference in concentration values of insulin and C-peptide in the group of patients with colon cancer and corresponding control group, we took the ratio between values of insulin and C-peptide in blood measured 90 min after breakfast in comparison with fasting values of
Insulin Increase in Colon Cancerogenesis
217
Table 1. Basic characteristics of men and women with colon cancer and their control groups Men
Women
Examined variables
Control group (n ⫽ 34)
Group with colon cancer (n ⫽ 34)
t
pa
Control group (n ⫽ 22)
Group with colon cancer (n ⫽ 22)
Age (years) Height (cm) Weight (kg) Waist circumference (cm) Hip circumference (cm) BMI (kg/m2)
63.4 ⫾ 10.0 176.3 ⫾ 7.5 77.6 ⫾ 10.2 98.2 ⫾ 9.5 103.1 ⫾ 6.7 22.0 ⫾ 2.7
66.4 ⫾ 8.7 175.7 ⫾ 9.1 79.3 ⫾ 14.5 97.2 ⫾ 10.9 103.2 ⫾ 6.9 22.5 ⫾ 3.2
1.23 0.29 0.57 0.42 0.07 0.64
0.228 0.774 0.573 0.677 0.944 0.527
63.4 ⫾ 10.1 164.8 ⫾ 3.0 73.3 ⫾ 12.7 94.0 ⫾ 11.9 106.4 ⫾ 8.8 22.2 ⫾ 3.7
58.1 ⫾ 10.8 166.0 ⫾ 5.4 77.0 ⫾ 12.3 96.6 ⫾ 12.4 109.2 ⫾ 9.4 23.2 ⫾ 3.4
a
t
pa
1.81 0.92 1.22 0.71 1.04 0.92
0.085 0.368 0.237 0.484 0.311 0.368
Student t test.
insulin and C-peptide; we found significantly higher ratios of insulin and C-peptide in group of colon cancer patients than in control group. Median for ratio of insulin 90 min after breakfast in comparison with fasting values of insulin in male group of colon cancer patients was 4.65 (range 0.83– 22.1) and in control group was 1.78 (range 0.38–8.75) (p ⫽ 0.005). Median for ratio of C-peptide 90 min after breakfast in comparison with fasting values of C-peptide in the group of colon cancer patients was 3.22 (range 0.74– 11.9) and in control group was 1.42 (range 0.54–6.0) (p ⫽ 0.001) (Table 3). Women. There was no statistically significant difference either in blood concentrations of C-peptide and glucose in the morning before breakfast or in concentrations obtained in measurements 90 min after breakfast between the female group of colon cancer patients and corresponding control group. Median for concentration of C-peptide measured in the morning before breakfast in the group of colon cancer patients was 0.62 nmol/L (range 0.25–1.38 nmol/L) and in control group was 0.86 nmol/L (range 0.39–2.19 nmol/L)
(p ⫽ 0.253). Median for concentration of fasting glucose in the group of colon cancer patients was 5.2 mmol/L (range 4.0–6.5 mmol/L) and in control group was 5.6 mmol/L (range 3.5–6.5 mmol/L) (p ⫽ 0.131). Median for concentration of C-peptide 90 min after breakfast in group of colon cancer patients was 1.67 nmol/L (range 0.26–3.37 nmol/L) and in corresponding control group it was 1.16 nmol/L (range 0.57–6.1 nmol/L) (p ⫽ 0.131), while median for concentration of glucose in the group of colon cancer patients was 5.6 mmol/L (range 4.2–8.5 mmol/L) and in corresponding control group was 5.8 mmol/L (range 4.1–8.3 mmol/L) (p ⫽ 0.774). Concentration of fasting insulin differed between the group of colon cancer patients (median 6.0 mIU/L, range 2.0– 29.4 mIU/L) and control group (median 10.4 mIU/L, 2.8–38.0 mIU/L) (p ⫽ 0.014). Women from the control group had higher concentrations of fasting insulin. There were no statistically significant differences in concentration of insulin measured 90 min after breakfast between the female group of colon cancer patients (median 24.5 mIU/L, range 3.3–80.2
Table 2. Concentrations of glucose, insulin, and C-peptide in blood before breakfast and 90 min after breakfast in men and women with colon cancer and their control groups Men Control group (n ⫽ 34) Examined variables Concentration of insulin before breakfast (mIU/L) Concentration of insulin 90 min after breakfast (mIU/L) Concentration of glucose before breakfast (mmol/L) Concentration of glucose 90 min after breakfast (mmol/L) Concentration of C-peptide before breakfast (nmol/L) Concentration of C-peptide 90 min after breakfast (nmol/L) a
Mann-Whitney test.
Women
Group with colon cancer (n ⫽ 34)
Control group (n ⫽ 22)
Group with colon cancer (n ⫽ 22)
Median
Range
Median
Range
z
pa
Median
Range
Median
Range
10.6
2.6–87.3
7.6
2.0–16.7
1.37
0.179
10.4
2.8–38.0
6.0
2.0–29.4
2.51 0.014
20.7
3.1–122.1
34.7
3.3–162.6
2.015 0.044
13.9
8.6–108.6
24.5
3.3–80.2
1.35 0.182
z
pa
5.42
3.9–6.5
5.2
3.7–6.5
0.78
0.442
5.6
3.5–6.5
5.2
4.0–6.5
1.53 0.131
5.9
4.3–8.0
6.4
4.7–8.2
0.29
0.773
5.8
4.1–8.3
5.6
4.2–8.5
0.32 0.774
0.81
0.19–4.0
0.805
0.26–2.12
0.089 0.934
0.86
0.39–2.19
0.62
0.25–1.38
1.14 0.253
1.68
0.26–4.26
3.28
0.38–6.1
3.18
1.16
0.57–6.1
1.67
0.26–3.37
1.54 0.131
0.001
218
Tripkovic et al. / Archives of Medical Research 35 (2004) 215–219
Table 3. Ratio of insulin and C-peptide concentrations in blood 90 min after breakfast and fasting concentrations of insulin and C-peptide in men and women with colon cancer and their control groups Men Control group (n ⫽ 34) Examined variables Concentration of after breakfast concentrations Concentration of after breakfast concentrations a
Women
Group with colon cancer (n ⫽ 34)
Median
Range
Median
Range
insulin 90 min and fasting
1.78
0.38–8.75
4.65
0.83–22.1
C-peptide 90 min and fasting
1.42
0.54–6.0
3.22
0.74–11.9
Control group (n ⫽ 22) z
pa
Group with colon cancer (n ⫽ 22) Range
z
pa
Median
Range
Median
2.83 0.005
1.17
0.29–26.89
4.23
0.25–8.54 2.72
0.007
3.31 0.001
1.19
0.62–15.4
2.42
0.43–8.87 2.24
0.025
Mann-Whitney test.
mIU/L) and corresponding control group (median 13.9 mIU/ L, range: 8.6–108.6 mIU/L) (p ⫽ 0.182) (Table 2). Ratio of insulin 90 min after breakfast in comparison with fasting insulin showed statistically significant increase in the female group of colon cancer patients. Median for group of colon cancer patients was 4.23 (range 0.25–8.54), while in the control group it was 1.17 (range 0.29–26.89) (p ⫽ 0.007). Median for ratio of C-peptide 90 min after breakfast with respect to fasting values of C-peptide was 2.42 (range 0.43–8.87) in the group with colon cancer and 1.19 (range 0.62–15.4) in corresponding control group and was also significantly higher in the female group of colon cancer patients (p ⫽ 0.025) (Table 3).
Discussion Accumulated evidence now supports the association of colon cancer with insulin resistance. Thus, multiple studies indicated that numerous factors that cause hyperinsulinemia were related to colon cancer risk. Increase of colorectal cancer was confirmed in patients with type 2 diabetes who showed higher levels of circulating insulin (14,15). This risk was particularly high in men (16). Schoen et al. (4) in their investigation also came to the conclusion that individuals with higher levels of fasting glucose and insulin 2 h after oral glucose challenge and having increased waist circumference had a nearly twofold increased risk for colorectal cancer. Nishhii et al. (17) examined cross-sectionally the relation of fasting plasma insulin levels and glucose tolerance status to colon adenomas. Their findings suggested that long-term hyperinsulinemic status associated with NIDDM may increase risk of colon adenomas and, subsequently, of colon cancer. The prospective study of Kaaks et al. (18) showed that elevated levels of C-peptide—a marker of chronic hyperinsulinemia—may increase colorectal cancer risk. In this study we found a higher increase of insulin and C-peptide 90 min after breakfast in a group of colon cancer patients as well as higher insulin and C-peptide concentrations in blood 90 min after breakfast in male group of colon
cancer patients. We also found the difference in fasting insulin concentrations between the female group of colon cancer patients and control group, although we intentionally attempted to choose patients having uniform general characteristics. Concentrations of fasting insulin were higher in female control group than in female group of colon cancer patients. Nevertheless, after breakfast the difference between insulin concentration disappeared between the female group of colon cancer patients and control group, which could indirectly imply that insulin increase in female group of colon cancer patients was higher than in female control group. Our findings might imply that insulin secretion may be more important than insulin resistance. Therefore, further studies might be directed toward that investigation approach. We are aware that our study is limited by the small sample size; thus, our results cannot reach maximum statistical power. Future studies should have larger sample size and in addition to determining blood insulin levels also should investigate IGF-1 levels, due to their role in transformation and proliferation of carcinoma cells. However, further investigations should attempt to collect additional information on the intricate relationship between tumor presence and insulin status.
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