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Journal of Diabetes 7 (2015) 369–377
O R I G I N A L A RT I C L E
Circulating human epidermal growth factor receptor 2 (HER2) is associated with hyperglycaemia and insulin resistance Ashfaque A. MEMON,1,2 Louise BENNET,3 Bengt ZÖLLER,1,2 Xiao WANG,1 Karolina PALMER,1,2 Kristina SUNDQUIST1,2 and Jan SUNDQUIST1,2 1 2
Department of Clinical Sciences, Center for Primary Health Care Research, 3Genetic and Molecular Epidemiology, Lund University, and Region Skåne, Malmö, Sweden
Correspondence Ashfaque A. Memon, Wallenberg Laboratory, Center for Primary Health Care Research, 6th floor, Inga Marie Nilsson’s gata 53, Skåne University Hospital, S-205 02 Malmö, Sweden. Tel: +46 40 331465 Fax: +46 40 391370 Email: [email protected] Received 18 December 2013; revised 16 May 2014; accepted 3 June 2014. doi: 10.1111/1753-0407.12184
Abstract Background: Type 2 diabetes mellitus (T2DM) and human epidermal growth factor receptor 2 (HER2) are associated with cancer, although the role of HER2 in T2DM is not well defined. The aim of this study was to investigate the association between HER2 levels and T2DM and whether that association differed in Swedish people born in Iraq or Sweden. Methods: Circulating HER2 levels were analyzed by the Luminex assay in 95 Iraqi-born and 75 Swedish-born Swedes. Results: There were significant differences in HER2 among those with normal glucose tolerance (NGT), impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT), and T2DM in the entire population after adjusting for age, sex, and body mass index (BMI; P = 0.03). Stratification of data according to country of birth revealed significant differences in HER2 levels among NGT, IFG/IGT, and T2DM groups only in Swedes (P = 0.007). For the entire study population, there was a positive association between HER2 and hyperglycemia (IFG and/or IGT + T2DM; P = 0.011), BMI, waist circumference, serum insulin, homeostatic model assessment of β-cell function, HbA1c, triglycerides, and C-peptide (P < 0.05), and a negative association between HER2 and insulin sensitivity index (ISI; P < 0.0001). Bivariate and multivariate linear regression analyses on the whole study population revealed that the associations between hyperglycemia and HER2, as well as between ISI and HER2, were independent of factors known to be associated with T2DM and insulin resistance (e.g. demographics, obesity, lipids, sedentary lifestyle, a family history of T2DM, C-peptide, and C-reactive protein). Conclusions: There is an independent association between HER2 levels and hyperglycemia and insulin resistance that is not modified by country of birth. Keywords: epidermal growth factor receptor, ethnicity, human epidermal growth factor receptor 2 (HER2), insulin sensitivity, type 2 diabetes mellitus.
Significant findings of the study: This is the first study of its kind in which the role of circulating human epidermal growth factor receptor 2 (HER2) has been investigated in both men and women and in two ethnic groups. The results show that HER2 is associated with insulin resistance and hyperglycemia independent of anthropometric and metabolic risk factors associated with Type 2 diabetes mellitus (T2DM). What this study adds: Circulating HER2 levels may be implicated in the pathophysiology of T2DM. © 2014 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd
369
Circulating HER2 levels and T2DM
A.A. MEMON et al.
Introduction Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder caused by defects in insulin secretion, insulin action, or both. If poorly controlled, the resulting chronic hyperglycemia is associated with numerous disabling complications.1 The prevalence of T2DM is increasing and it is estimated that, by 2025, 15% of the world’s population will have T2DM, impaired fasting glucose (IFG), or impaired glucose tolerance (IGT).2 In Sweden, the prevalence of T2DM among nonEuropean immigrants is estimated to be two- to threefold higher than among native Swedes.3 In addition, T2DM develops an average of 10 years earlier in immigrants from the Middle East than in native Swedes, and Middle Eastern immigrants diagnosed with T2DM more frequently have a family history of T2DM.4 Type 2 diabetes mellitus is associated with various cancers, and a higher long-term risk of cancer has been observed in patients with diabetes compared with nondiabetic individuals.5 The underlying mechanism for this association is linked to activation of the insulin receptor, insulin-like growth factor receptors (IGFR),6 and human epidermal growth factor receptor (HER) 2.7 Epidermal growth factor (EGF) receptors are commonly deregulated in human cancers.8 The EGF family of receptor tyrosine kinases is comprised of four members: HER1 (EGF receptor 1, ErbB1), HER2 (neu, ErbB2), HER3 (ErbB3), and HER4 (ErbB4).9 These receptors are comprised of an extracellular ligandbinding domain, a transmembrane domain, and an intracellular tyrosine kinase domain. The EGF receptors are commonly active in a dimeric form and interactions between different EGF receptor pairs represent a mechanism for signal diversification and amplification.10,11 The configuration of different dimeric pairs depends on the concentration of the receptors, the concentration of particular ligands, and the affinity of the receptors towards each other.12,13 Ligands binding to the EGF family receptors induce receptor homo- or heterodimerization, which involves a variety of homodimeric and heterodimeric combinations.14 No ligand for HER2 has been identified; therefore, the normal mechanism by which HER2 can signal is through heterodimerization with other EGF receptors.15 During heterodimerization, HER2 is a preferable dimerization partner and therefore plays a pivotal role in signaling through the EGF family.16 It has been reported that HER2 is overexpressed and/or amplified in a range of tumor types, including breast, ovarian, bladder, salivary gland, endometrial, pancreatic, and non-small cell lung cancer.17 Recent studies have demonstrated a protective role for the antidiabetic drug metformin against 370
cancer18 and studies in in vitro models have shown that metformin downregulates HER2.7 The full-length HER2 receptor undergoes proteolytic cleavage, which results in the release of the soluble (circulating) extracellular domain (ECD) and the cell-bound intracellular domain (ICD) containing tyrosine kinase activity.19 Levels of circulating HER2 are proportional to HER2 cellular signalling.19 Concentrations of HER2 can be detected in the serum and have been used as predictive and prognostic markers of breast cancer.20,21 Little is known about HER2 in other diseases, especially T2DM. A crosssectional study performed on 167 male patients found that HER2 concentrations are associated with insulin resistance.22 Racial disparities in treatment patterns and clinical outcomes in patients with HER2-positive cancer have been observed.23 However, the role of circulating HER2 in insulin resistance in different ethnic groups has not been elucidated. Thus, the aim of the present study was to quantify and investigate the role of circulating HER2 concentrations in hyperglycemia and insulin resistance.
Methods Subjects Male and female residents in the Rosengård residential area of Malmö, aged 45–65 years and born in Sweden (Swedes) or Iraq (Iraqis), were randomly selected from the census register. No participant born in Sweden had a parent born in Iraq. We chose the 45–65 year age group because this is the age group of the non-retired population in which there is the highest probability of identifying individuals with prediabetes or diabetes, because the prevalence of diabetes increases with age. The study was performed according to the Declaration of Helsinki.24 The ethics committee at Lund University approved the study (Approval no. 2009/36) and written informed consent was provided by all participants after they had received a full explanation of the purpose and nature of all the procedures used. Assessment of clinical variables Abdominal obesity was defined as waist circumference ≥102 cm in men and ≥88 cm in women.25 Body mass index (BMI), systolic and diastolic blood pressure (SBP and DBP, respectively), and leisure time physical activity were measured as described previously.26 A standard 75-g oral glucose tolerance test (OGTT) was performed and blood glucose was measured in samples collected at 0, 30, 60 and 120 min by a HemoCue photometer (HemoCue AB, Ängelholm, Sweden).27 The
© 2014 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd
A.A. MEMON et al.
insulin sensitivity index (ISI) was calculated from the OGTT data using the Matsuda index, as described previously.28 Participants were asked not to eat after 2200 h the day before sample collection. Normal glucose tolerance (NGT) was defined as fasting plasma glucose (FPG; 0 h sample) concentrations of
Journal of Diabetes 7 (2015) 369–377
O R I G I N A L A RT I C L E
Circulating human epidermal growth factor receptor 2 (HER2) is associated with hyperglycaemia and insulin resistance Ashfaque A. MEMON,1,2 Louise BENNET,3 Bengt ZÖLLER,1,2 Xiao WANG,1 Karolina PALMER,1,2 Kristina SUNDQUIST1,2 and Jan SUNDQUIST1,2 1 2
Department of Clinical Sciences, Center for Primary Health Care Research, 3Genetic and Molecular Epidemiology, Lund University, and Region Skåne, Malmö, Sweden
Correspondence Ashfaque A. Memon, Wallenberg Laboratory, Center for Primary Health Care Research, 6th floor, Inga Marie Nilsson’s gata 53, Skåne University Hospital, S-205 02 Malmö, Sweden. Tel: +46 40 331465 Fax: +46 40 391370 Email: [email protected] Received 18 December 2013; revised 16 May 2014; accepted 3 June 2014. doi: 10.1111/1753-0407.12184
Abstract Background: Type 2 diabetes mellitus (T2DM) and human epidermal growth factor receptor 2 (HER2) are associated with cancer, although the role of HER2 in T2DM is not well defined. The aim of this study was to investigate the association between HER2 levels and T2DM and whether that association differed in Swedish people born in Iraq or Sweden. Methods: Circulating HER2 levels were analyzed by the Luminex assay in 95 Iraqi-born and 75 Swedish-born Swedes. Results: There were significant differences in HER2 among those with normal glucose tolerance (NGT), impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT), and T2DM in the entire population after adjusting for age, sex, and body mass index (BMI; P = 0.03). Stratification of data according to country of birth revealed significant differences in HER2 levels among NGT, IFG/IGT, and T2DM groups only in Swedes (P = 0.007). For the entire study population, there was a positive association between HER2 and hyperglycemia (IFG and/or IGT + T2DM; P = 0.011), BMI, waist circumference, serum insulin, homeostatic model assessment of β-cell function, HbA1c, triglycerides, and C-peptide (P < 0.05), and a negative association between HER2 and insulin sensitivity index (ISI; P < 0.0001). Bivariate and multivariate linear regression analyses on the whole study population revealed that the associations between hyperglycemia and HER2, as well as between ISI and HER2, were independent of factors known to be associated with T2DM and insulin resistance (e.g. demographics, obesity, lipids, sedentary lifestyle, a family history of T2DM, C-peptide, and C-reactive protein). Conclusions: There is an independent association between HER2 levels and hyperglycemia and insulin resistance that is not modified by country of birth. Keywords: epidermal growth factor receptor, ethnicity, human epidermal growth factor receptor 2 (HER2), insulin sensitivity, type 2 diabetes mellitus.
Significant findings of the study: This is the first study of its kind in which the role of circulating human epidermal growth factor receptor 2 (HER2) has been investigated in both men and women and in two ethnic groups. The results show that HER2 is associated with insulin resistance and hyperglycemia independent of anthropometric and metabolic risk factors associated with Type 2 diabetes mellitus (T2DM). What this study adds: Circulating HER2 levels may be implicated in the pathophysiology of T2DM. © 2014 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd
369
Circulating HER2 levels and T2DM
A.A. MEMON et al.
Introduction Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder caused by defects in insulin secretion, insulin action, or both. If poorly controlled, the resulting chronic hyperglycemia is associated with numerous disabling complications.1 The prevalence of T2DM is increasing and it is estimated that, by 2025, 15% of the world’s population will have T2DM, impaired fasting glucose (IFG), or impaired glucose tolerance (IGT).2 In Sweden, the prevalence of T2DM among nonEuropean immigrants is estimated to be two- to threefold higher than among native Swedes.3 In addition, T2DM develops an average of 10 years earlier in immigrants from the Middle East than in native Swedes, and Middle Eastern immigrants diagnosed with T2DM more frequently have a family history of T2DM.4 Type 2 diabetes mellitus is associated with various cancers, and a higher long-term risk of cancer has been observed in patients with diabetes compared with nondiabetic individuals.5 The underlying mechanism for this association is linked to activation of the insulin receptor, insulin-like growth factor receptors (IGFR),6 and human epidermal growth factor receptor (HER) 2.7 Epidermal growth factor (EGF) receptors are commonly deregulated in human cancers.8 The EGF family of receptor tyrosine kinases is comprised of four members: HER1 (EGF receptor 1, ErbB1), HER2 (neu, ErbB2), HER3 (ErbB3), and HER4 (ErbB4).9 These receptors are comprised of an extracellular ligandbinding domain, a transmembrane domain, and an intracellular tyrosine kinase domain. The EGF receptors are commonly active in a dimeric form and interactions between different EGF receptor pairs represent a mechanism for signal diversification and amplification.10,11 The configuration of different dimeric pairs depends on the concentration of the receptors, the concentration of particular ligands, and the affinity of the receptors towards each other.12,13 Ligands binding to the EGF family receptors induce receptor homo- or heterodimerization, which involves a variety of homodimeric and heterodimeric combinations.14 No ligand for HER2 has been identified; therefore, the normal mechanism by which HER2 can signal is through heterodimerization with other EGF receptors.15 During heterodimerization, HER2 is a preferable dimerization partner and therefore plays a pivotal role in signaling through the EGF family.16 It has been reported that HER2 is overexpressed and/or amplified in a range of tumor types, including breast, ovarian, bladder, salivary gland, endometrial, pancreatic, and non-small cell lung cancer.17 Recent studies have demonstrated a protective role for the antidiabetic drug metformin against 370
cancer18 and studies in in vitro models have shown that metformin downregulates HER2.7 The full-length HER2 receptor undergoes proteolytic cleavage, which results in the release of the soluble (circulating) extracellular domain (ECD) and the cell-bound intracellular domain (ICD) containing tyrosine kinase activity.19 Levels of circulating HER2 are proportional to HER2 cellular signalling.19 Concentrations of HER2 can be detected in the serum and have been used as predictive and prognostic markers of breast cancer.20,21 Little is known about HER2 in other diseases, especially T2DM. A crosssectional study performed on 167 male patients found that HER2 concentrations are associated with insulin resistance.22 Racial disparities in treatment patterns and clinical outcomes in patients with HER2-positive cancer have been observed.23 However, the role of circulating HER2 in insulin resistance in different ethnic groups has not been elucidated. Thus, the aim of the present study was to quantify and investigate the role of circulating HER2 concentrations in hyperglycemia and insulin resistance.
Methods Subjects Male and female residents in the Rosengård residential area of Malmö, aged 45–65 years and born in Sweden (Swedes) or Iraq (Iraqis), were randomly selected from the census register. No participant born in Sweden had a parent born in Iraq. We chose the 45–65 year age group because this is the age group of the non-retired population in which there is the highest probability of identifying individuals with prediabetes or diabetes, because the prevalence of diabetes increases with age. The study was performed according to the Declaration of Helsinki.24 The ethics committee at Lund University approved the study (Approval no. 2009/36) and written informed consent was provided by all participants after they had received a full explanation of the purpose and nature of all the procedures used. Assessment of clinical variables Abdominal obesity was defined as waist circumference ≥102 cm in men and ≥88 cm in women.25 Body mass index (BMI), systolic and diastolic blood pressure (SBP and DBP, respectively), and leisure time physical activity were measured as described previously.26 A standard 75-g oral glucose tolerance test (OGTT) was performed and blood glucose was measured in samples collected at 0, 30, 60 and 120 min by a HemoCue photometer (HemoCue AB, Ängelholm, Sweden).27 The
© 2014 Ruijin Hospital, Shanghai Jiaotong University School of Medicine and Wiley Publishing Asia Pty Ltd
A.A. MEMON et al.
insulin sensitivity index (ISI) was calculated from the OGTT data using the Matsuda index, as described previously.28 Participants were asked not to eat after 2200 h the day before sample collection. Normal glucose tolerance (NGT) was defined as fasting plasma glucose (FPG; 0 h sample) concentrations of
