Diabetes Research and Clinical Practice 69 (2005) 249–255 www.elsevier.com/locate/diabres Increased erythropoiesis and subclinical inflammation as part of the metabolic syndrome T. Mardi a,d,e, S. Toker a,b,d,e, S. Melamed c,d,e, A. Shirom b,e, D. Zeltser a,d,e, I. Shapira a,d,e, S. Berliner a,d,e,*, O. Rogowski a,d,e a Department of Medicine ‘‘D’’ and Institute for Special Medical Examinations (MALRAM), Tel Aviv Sourasky Medical Center, Tel Aviv, affiliated to Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 6 Weizman Street, Tel Aviv 64239, Israel b Faculty of Management, Tel Aviv University, Tel Aviv, Israel c National Institute of Occupational and Environmental Health, Raanana, Israel d Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel e Tel Aviv Medical Center Inflammation Survey (TAMCIS) Group, Tel Aviv, Israel Received 7 June 2004; received in revised form 25 November 2004; accepted 10 January 2005 Available online 3 March 2005 Abstract Recent studies have suggested the insulin resistance might be accompanied by enhanced erythropoiesis. We have examined this association in individuals with the metabolic syndrome (MS) who in addition to insulin resistance harbor a chronic low grade inflammation. This study is relevant because chronic inflammation might have a suppressive effect on erythropoiesis. 280 and 554 non-smoking women and men with respective age of 46.4 9.3 (mean S.D.) and 44.0 11.0 years are included. A significant correlation was noted between the numbers of the components of the MS and the inflammatory biomarkers including the white blood cell count, high sensitivity C-reactive protein, fibrinogen concentrations and the erythrocyte sedimentation rate. In addition, a significant correlation (r = 0.157, p = 0.008) was noted between the number of components of the MS and the number of red blood cells in the peripheral blood in women. The same was true for men (r = 0.192, p < 0.0005). We conclude that enhanced erythropoiesis could be a new, hitherto unrecognized component of the MS. The enhanced erythropoiesis could give an erroneous impression of general ‘‘good’’ health in these individuals. # 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Erythropoiesis; Metabolic syndrome; Inflammation Abbreviations: MS, metabolic syndrome; TAMCIS, Tel Aviv Medical Center Inflammation Survey; WBCC, white blood cell count; ESR, erythrocyte sedimentation rate; hs-CRP, high sensitivity C-reactive protein; HOMA, homeostasis model assessment; BMI, body mass index; RBC, red blood cells; PMN, polymorphonuclears; BP, blood pressure * Corresponding author. Tel.: +972 3 6973133; fax: +972 3 6974961. E-mail address: [email protected] (S. Berliner). 0168-8227/$ – see front matter # 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2005.01.005 250 T. Mardi et al. / Diabetes Research and Clinical Practice 69 (2005) 249–255 1. Introduction The metabolic syndrome (MS) conveys a significant risk for future atherothrombotic cardiovascular events. It has been suggested recently that increased erythropoiesis may be a new aspect of the insulin resistance syndrome [1,2]. This is rather unexpected due to the low grade inflammation that accompanies the MS [3] that could contribute to the presence of an anemia of chronic disease. Here, we investigate the existence of enhanced erythropoiesis in individuals with the MS in the presence of low grade inflammation. The results point to the presence of enhanced erythropoiesis in individuals with the MS despite harboring a low grade state of inflammation. These findings have relevance since the enhanced erythropoiesis could give an erroneous impression of general ‘‘good’’ health in these individuals. in the present survey gave their written informed consent according to the instructions of the Institutional Ethics Committee. Recruitment was based on local announcements and advertisements in the monthly pay bill of the medical personnel as well as personal appeal to the patients in the various outpatient clinics to participate in the inflammation survey. Individuals with an underlying inflammatory disease (arthritis, inflammatory bowel disease, etc.) as well as individuals with any infections or other inflammatory condition, including infarction, surgery or angiography during the 6 months before recruitment are excluded. We also excluded individuals with anemia (hemoglobin lower than 13.5 g/dL for men and 11.7 g/dL for women), those treated with steroid or non-steroidal anti-inflammatory medication, except for aspirin (at doses lower then 325 mg/day), smokers as well as females receiving hormone replacement therapy, and any patients taking lipid lowering medications including HMG-CoA Reductase Inhibitors (Statins) and fibrates. 2. Methods 2.2. Definitions of the MS 2.1. The participants We have used the data base of the Tel Aviv Medical Center Inflammation Survey (TAMCIS) [4–6]. The rationale of this survey was to determine the presence of microinflammation in apparently healthy individuals and those with atherothrombotic risk factors in Israel. Large cross sectional studies are being performed in many other countries including Europe and North America but this is the first large scale survey that is currently taking place in Israel. It will enable us to find out if the findings related to low grade inflammation that were reported in other countries are also relevant for ours. TAMCIS is a cross sectional study to which we invited apparently healthy employees of the Tel Aviv Medical Center and Tel Aviv Municipality (Israel) and individuals with atherothrombotic risk factors who are followed up in the outpatient clinics of the Medical Center. Members of the medical staff, retired employees of the medical center and the Tel Aviv Municipality, individuals who are investigated in our outpatient health screening program as well as those who are in routine follow up in diabetes, hypertension and metabolic disorders clinics are also included. All the individuals included The National Cholesterol Education Program (NCEP) Adult Treatment Panel–III guidelines define the MS as the presence of 3 of the following risk determinants: (1) increased waist circumference (>102 cm for men, >88 cm for women), (2) elevated triglycerides of 1.70 mmol/L, (3) low HDL cholesterol (1.03 mmol/L for men, 1.29 mmol/L for women), (4) hypertension (systolic blood pressure 130 mmHg or diastolic pressure 85 mmHg) or antihypertensive medication use, and (5) impaired fasting glucose 6.1 mmol/L [7]. 2.3. Laboratory tests White blood cell count (WBCC) and differential were performed by using the Coulter STKS (Beckman Coulter, Nyon, Swiss) electronic cell analyzer. The erythrocyte sedimentation rate (ESR) was determined by the method of Westergren [8], quantitative fibrinogen by the method of Clauss [9] and a Sysmex 6000 (Sysmex Corporation, Hyaga, Japan) autoanalyzer and the high sensitivity C-reactive protein (hsCRP) was performed by nephelometry using a Boering BN II Nephelometer (DADE Boering, T. Mardi et al. / Diabetes Research and Clinical Practice 69 (2005) 249–255 Marburg, Germany) [10]. The coefficient of variation (CV) for hs-CRP concentrations below 1 mg/L is 0.11 while it is 0.05 for concentrations >1 mg/L. The CV for fibrinogen is 0.06. 2.4. Statistical analyses Statistical analysis was performed separately for men and women. All data was summarized and displayed as mean S.D. for the continuous variables (age, the MS components and the inflammation markers), and as number of patients plus the percentage in each group for categorical variables (cardiovascular risk factors and medication). The crosstabs and descriptive procedures were used to produce frequencies of categorical variables (cardiovascular risk factors and medication) and means S.D. of continuous variables (age, the MS components and the inflammation markers). Participants were divided into four groups according to the number of components of the MS: 0, 1, 2 and 3 or more components. For all continuous variables, a oneway ANOVA analysis was performed to compare the 251 various parameters between the different groups. Hochberg’s multiple comparison technique was used for pairwise comparison between patient’s categories. Pearson partial correlations for confounding variables were used to evaluate the association between the number of components of the MS and the different inflammation markers, as well as the different component of the blood count, and between the erythrocyte parameters to the individual components of the MS. All correlations were adjusted for age and cardiovascular risk factors (hypertension and hyperlipidemia). In order to assess which components of the MS contribute to the change in erythrocyte parameters (hemoglobin, hematocrit and red blood cells), we performed linear regression using those three erythrocyte parameters as the dependent variable and all the different components of the MS as the covariates using the stepwise method. The hs-CRP has non normal distribution, thus we used a logarithmic transformation, and the results of hs-CRP are reflected as back transformed geometric means and S.D. and for the correlation the log (hs-CRP) was used. The level of significance used for all of the above analyses was two Table 1 Age, body mass index, hypertension and dyslipidemia as well as hemoglobin, hematocrit and red blood cells and the different inflammatory variables (N, mean and S.D.) for women, in relation to the number of the components of the metabolic syndrome Number of components 0 (N = 123) 1 (N = 82) 2 (N = 44) 3 (N = 31) P-value Hochberg Women (N = 280) Age (years) 43.8 9.9 46.5 8.6 51.1 8.1 50.0 6.5 <0.0005 0–2 0–3 1–2 <0.0005 0.004 0.037 BMI (kg/m2) 23.9 3.2 25.7 3.9 29.3 4.2 30.8 4.6 <0.0005 0–1 0,1–2,3 0.005 <0.0005 Hypertension (%) 2.4 11.0 15.9 32.3 <0.0005 Dyslipidemia (%) 4.9 11.0 14.0 19.4 N.S. Hemoglobin (mmol/L) 8 0.6 7.9 0.7 8.1 0.6 8.3 05 N.S. N.S. N.S. Hematocrit (%) 37.7 2.7 37.5 3.2 38.2 2.7 38.8 2.3 N.S. N.S. N.S. RBC (106 cells/mL) 4.4 0.3 4.4 0.3 4.5 0.4 4.5 0.3 0.016 N.S. N.S. 6.64 1.47 6.68 1.54 6.54 1.36 7.45 1.90 0.048 N.S. N.S. Polymorphonuclears (10 cells/mL) 3.91 1.21 3.89 1.26 3.89 1.14 4.57 1.55 N.S. N.S. N.S. ESR (mm/h) 16.3 6.8 20.1 11.3 21.4 9.6 20.1 11.2 0.003 0–1 0–2 0.027 0.013 Fibrinogen (mmol/L) 8.4 1.41 8.3 1.4 8.8 1.5 9.1 1.8 0.029 N.S. N.S. hs-CRP (mg/L) 1.0 2.9 1.4 2.9 2.3 3.2 3.9 3.1 <0.0005 0–2,3 1–3 <0.0005 <0.0005 3 WBCC (10 cells/mL) 3 252 T. Mardi et al. / Diabetes Research and Clinical Practice 69 (2005) 249–255 tailed, p < 0.05. The SPSS statistical package was used to perform all statistical evaluation (SSPS Inc., Chicago, IL, USA). 3. Results We have examined 554 men and 280 women of mean age 44.8 10.6 years. There were 123 women with no components of the MS, 82 with 1, 44 with 2 and 31 with 3 components; the respective numbers for men being 184, 190, 107 and 73. Several subjects were taking medications but the percentage of individuals taking low dose aspirin did not exceed 8%, 4% for alpha blockers, 16% for beta blockers, 7% for calcium channel blockers, 6% for ACE inhibitors, 3% angiotensin II receptor blockers and 3% for diuretics. The results of the hematological variables and that of the inflammatory Biomarkers are reported in Table 1 for women and Table 2 for men. It is noted that the multiplicity of the components of the MS is associated with low grade inflammation as expressed by the inflammatory biomarkers. These inflammatory biomarkers correlate with the number of components of the MS in both women and men (Table 3). A significant correlation between the number of these components and the number of red blood cells in women (r = 0.157, p = 0.008) and men (r = 0.192, p < 0.0005) is noted. We have further analyzed the correlations between the individual components of the MS and the hematological parameters (Table 4). A significant correlation with the number of erythrocytes was noted for waist in both genders and triglycerides in men. Finally, a linear regression model was performed by using the individual components of the MS as the independent variables, and the hematological variables as the depend ones. The results are reported in Table 2 Age, body mass index, hypertension and dyslipidemia as well as hemoglobin, hematocrit and red blood cells and the different inflammatory variables (N, mean and S.D.) for men, in relation to the number of the components of the metabolic syndrome Number of components 0 (N = 184) 1 (N = 190) 2 (N = 107) 3 (N = 73) P-value Hochberg Men (N = 554) Age (years) 40.4 10.6 44.1 11.0 47.2 10.0 48.3 10.7 <0.0005 0–1 0–2,3 1–3 0.005 <0.0005 0.025 BMI (kg/m2) 24.9 2.7 25.9 2.7 28.0 3.2 30.4 3.5 <0.0005 0–1 0,1–2,3 2–3 0.006 <0.0005 <0.0005 Hypertension (%) 0 6.8 17.8 30.1 <0.0005 Dyslipidemia (%) 5.5 8.4 24.3 23.3 <0.0005 Hemoglobin (mmol/L) 9.2 0.6 9.2 0.6 9.3 0.6 9.3 0.6 N.S. N.S. N.S. Hematocrit (%) 43.2 2.7 43.3 2.7 43.7 2.6 43.9 2.7 N.S. N.S. N.S. 5.0 0.4 5.0 0.4 5.1 0.3 5.1 0.3 0.003 0–3 1–3 0.003 0.035 6.56 1.75 6.59 1.42 7.09 1.48 7.11 1.49 0.004 0–2 0.033 Polymorphonuclears (10 cells/mL) 3.73 1.10 3.82 1.11 4.14 1.15 4.07 1.12 0.011 0–2 0.020 6 RBC (10 cells/mL) WBC (103 cells/mL) 3 ESR (mm/h) 6.4 4.9 9.3 7.4 10.2 7.4 10.9 8.3 <0.0005 0–1,2,3 <0.0005 Fibrinogen (mmol/L) 7.2 1.4 7.7 1.5 7.8 1.4 8.2 1.4 <0.0005 0–1 0–2 0–3 0.004 0.002 <0.0005 hs-CRP (mg/L) 0.9 2.4 1.3 3.0 1.5 2.6 2.2 2.2 <0.0005 0–1 0–2,3 1–3 0.007 <0.0005 <0.0005 T. Mardi et al. / Diabetes Research and Clinical Practice 69 (2005) 249–255 253 Table 3 Results of the age adjusted Pearson partial correlation coefficients between the number of components of the metabolic syndrome and the inflammatory variables for women (upper part) and for men (lower part) ESR Women (N = 280) Number of components Men (N = 554) Number of components Fibrinogen Log (hs-CRP) WBCC PMN Correlation coefficient Significance 0.143 0.017 0.073 N.S. 0.341 <0.0005 0.154 0.010 0.156 0.009 Correlation coefficient Significance 0.184 <0.0005 0.147 0.001 0.250 <0.0005 0.150 <0.0005 0.133 0.002 Table 5 and show that the number of erythrocytes is mainly influenced by waist in both genders and the concentration of triglycerides in men. 4. Discussion It has been realized recently that the MS is associated with an erythrocytotic response [1] and that this might be a hitherto unrecognized feature of the syndrome [2]. In fact, Choi et al. recently reported a study in 1314 non-diabetic subjects over the age of 60, selected from a cross-sectional study in Seoul [2]. The authors measured fasting and post-load 2h plasma glucose, insulin concentrations, lipid profile, and anthropometric as well as hematological parameters. The authors found a positive correlation between insulin resistance also and hemoglobin concentrations in non-smoking men (r = 0.2, p = 0.018). In nonsmoking women, insulin resistance correlated with hemoglobin (r = 0.1, p = 0.001). Hemoglobin concentrations were also associated with other components of the insulin resistance syndrome such as body man index, blood pressure, lipid profile and fasting plasma insulin levels used as a surrogate for insulin resistance. Furthermore, the group in the upper quartile of insulin resistance showed higher hemoglobin concentrations than the lower quartile, independent of smoking status and serum iron concentrations. The authors suggested that increased erythropoiesis and subclinical inflammatory, expressed as the number of white blood cells in peripheral blood, could be part of the MS [2]. In another study, Barbieri et al. [1] found a correlation between insulin resistance and red cell count (r = 0.14, p < 0.0001), plasma hemoglobin Table 4 Results of the age adjusted Pearson partial correlation coefficients between the hemoglobin, hematocrit and red blood cells to the individual components of the metabolic syndrome for women (upper part) and for men (lower part) Waist HDL TG Glucose Systolic BP Diastolic BP Correlation coefficient Significance 0.035 N.S. 0.035 N.S. 0.110 N.S. 0.066 N.S. 0.114 N.S. 0.092 N.S. Hematocrit Correlation coefficient Significance 0.045 N.S. 0.018 N.S. 0.094 N.S. 0.062 N.S. 0.125 N.S. 0.098 N.S. RBC Correlation coefficient Significance 0.177 0.003 0.101 N.S. 0.192 0.001 0.141 0.018 0.116 0.052 0.052 N.S. Correlation coefficient Significance 0.052 N.S. 0.046 N.S. 0.163 <0.0005 0.027 N.S. 0.062 N.S. 0.104 0.016 Hematocrit Correlation coefficient Significance 0.070 0.028 0.019 N.S. 0.155 <0.0005 0.011 N.S. 0.099 0.021 0.121 0.005 RBC Correlation coefficient Significance 0.152 <0.0005 0.088 0.040 0.221 <0.0005 0.048 N.S. 0.146 0.001 0.153 <0.0005 Women (N = 280) Hemoglobin Men (N = 554) Hemoglobin 254 T. Mardi et al. / Diabetes Research and Clinical Practice 69 (2005) 249–255 Table 5 Linear regression model coefficients using the individual components of the metabolic syndrome as the independent variables, and the hemoglobin, hematocrit and the red blood cells as the dependent variables in women (upper part) and in men (lower part) Variables entered the model Unstandardized coefficients Standardized coefficients Significance Partial correlation Women Hemoglobin Systolic BP 0.009 0.148 0.013 0.148 Hematocrit Systolic BP 0.030 0.176 0.003 0.176 RBC Triglycerides Waist 0.001 0.004 0.151 0.129 0.017 0.042 0.143 0.122 Triglycerides Glucose 0.002 0.005 0.176 0.093 <0.0005 0.036 0.169 0.090 Hematocrit Triglycerides 0.005 0.149 <0.0005 0.149 RBC Triglycerides 0.001 0.200 <0.0005 0.200 Men Hemoglobin (r = 0.16, p < 0.001), hematocrit (r = 0.15, p < 0.001) and plasma iron (r = 0.1, p < 0.05). Red blood cell count was also associated with other biological markers of insulin resistance syndrome in this Chianti study that included 608 subjects aged 22– 96 years [1]. The notion that insulin and insulin growth factors I and II support in vitro [11–15] and vivo [16–18] erythropoiesis is not new. However, the MS is accompanied by low grade inflammation, a factor that could support potential down regulation of erythropoiesis in these individuals [19]. Thus, it remained to be seen if the factors that prevail are the erythropoietic or the erythrosuppressive ones. This is especially important due to the fact that anemia by itself has been shown to be a risk factor for cardiovascular disease [20]. In fact, the presence of anemia was independently associated with an increased risk of cardiovascular disease in the atherosclerosis risk in communities (ARIC) study, a community cohort of subjects between the ages of 45 and 64 years [20]. In the present study, we evaluated several established inflammatory biomarkers including the WBCC, ESR, fibrinogen and hs-CRP concentrations in addition to the hematological ones. The significant finding is therefore that erythropoiesis was evident, especially in men, despite there being clear indications of chronic inflammation. The erythropoiesis correlated with waist circumference, a classical marker of central obesity and insulin resistance. The limitation of the present study is that it did not included measurements of insulin or the homeostasis model assessment (HOMA) index. In addition, we do not know what effect, if any, this enhanced erythropoiesis might have on the course of the atherothrombotic disease. Another limitation is the lack of IL-6 measurements. This cytokine is probably increased in individuals with multiplicity of components of the MS and could contribute to both the production of inflammation sensitive proteins in the liver [21] and at the same time be involved in erythropoiesis [22]. Finally, it should be stressed that our study is not a truly population based cross sectional one. In fact, we cannot exclude the possibility of a potential selection bias introduced by the recruitment of subjects from TAMCIS. We have included several individuals who were on medication that might have had an effect on inflammation (e.g. ACE inhibitors) or insulin resistance (thiazide diuretics). However, due to the small number of subjects who were taking these medications, it is unlikely that they had a major effect on the results of the present study. We conclude that the multiplicity of components of the MS is associated with erythropoiesis despite of the presence of concomitant low grade inflammation. 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