Biol Trace Elem Res (2014) 157:211–217 DOI 10.1007/s12011-014-9898-6
Oxidative Stress Increased in Pregnant Women with Iodine Deficiency Zendy Evelyn Olivo Vidal & Sergio Cuellar Rufino & Esteban Hernández Tlaxcalteco & Cirenia Hernández Trejo & Raúl Martínez Campos & Mónica Navarro Meza & Rocío Coutiño Rodríguez & Omar Arroyo-Helguera
Received: 28 August 2013 / Accepted: 14 January 2014 / Published online: 25 January 2014 # Springer Science+Business Media New York 2014
Abstract Iodine is an essential element trace for the synthesis of maternal thyroid hormones needed to support normal fetal development; it also acts as an antioxidant directly or induce antioxidant enzymes indirectly. Iodine deficiency and oxidative stress are associated with pregnancy complications. This study aimed to assess the urinary iodine concentration and its relationship with the antioxidant and oxidative stress status during gestation. Pregnant women were consecutively recruited from an obstetric clinic during all gestation trimesters, and urinary iodine concentration, antioxidant, and oxidative stress were determined. Results showed that 70 % of pregnant women have optimal iodine levels (150–200 μg/L), while approximately 30 % showed mild iodine deficiency (50– 99 μg/L). Oxidative stress was significantly higher, and the Z. E. O. Vidal : S. C. Rufino : E. H. Tlaxcalteco : R. C. Rodríguez : O. Arroyo-Helguera Instituto de Salud Pública, Universidad Veracruzana, Avenida Luís Castelazo Ayala S/N, Col. Industrial Ánimas, Xalapa, Veracruz, México C. H. Trejo : R. M. Campos Hospital Escuela de Ginecología y Obstetricia, Universidad Veracruzana, Calle Ernesto Ortiz Medina esq. Córdoba. Fracc. Veracruz, Xalapa, Veracruz, México C. H. Trejo Facultad de Bioanálisis, Universidad Veracruzana, Calle Médicos S/N, Col. Unidad del Bosque, Xalapa, Veracruz, México M. N. Meza Laboratorio de Biología Molecular e Inmunología, Centro Universitario del Sur. Universidad de Guadalajara, Ciudad Guzmán, México O. Arroyo-Helguera (*) Laboratorio de Ecología y Salud, Public Health Institute, Universidad Veracruzana, Avenida Luís Castelazo Ayala S/N, Xalapa, Veracruz, México 91190 e-mail: [email protected]
antioxidant status was also compromised as evidenced by decreased total antioxidant status and superoxide dismutase (SOD) activity in pregnant women with mild iodine deficiency than pregnant women with optimal iodine levels. Significant positive correlations were noted between optimal iodine levels and total antioxidant status. Oxidative stress was significantly correlated with mild iodine deficiency. However, no significant correlation was found between iodine levels and SOD and catalase activities. In conclusion, for the first time, these data suggest a correlation between iodine levels and the antioxidant status during pregnancy. Keywords Iodine . Antioxidant status . Pregnant women . Oxidative stress . Gestation
Introduction An optimal iodine nutritional intake during pregnancy is a priority because of its impact to the fetus during gestation and postpartum. The recommendations of the International Council for the Control of Iodine Deficiency Disorders (ICCIDD), WHO, and UNICEF [1], set the minimal urinary iodine excretion to 100 μg/L, a mean of 150 μg of iodine daily intake, and the recommended iodine amount for pregnant and lactating women to 200 μg [2, 3], although the ICCIDD raised this recommendation to 250–300 μg/L/day. Iodine metabolism alterations as hypothyroidism during gestation may induce placental abruption, cretinism, miscarriages, and preeclampsia [4–6]. A previous study done in normal and preeclamptic pregnant women showed that iodine deficiency is a preeclampsia risk factor [7, 8]. Iodine is a part of thyroid hormones and has been reported to act directly as an antioxidant [9] or induce indirectly antioxidant enzymes such as superoxide dismutase (SOD) [4, 9–11]. Iodine can be added to the double bonds of some polyunsaturated fatty acids of
212
cellular membranes, making them less reactive to free radicals [9]. Also, iodine competes with free radicals for membrane lipids, protein, and DNA in order to stabilize cells. This antioxidant role can be exerted through oxidized iodine species obtained by the diet or by local deiodination [4, 12]. Then, iodine levels should be important for the balance of antioxidant status during gestation; although, the roll of iodine is unknown. The oxidative metabolism is increased during pregnancy due to high oxygen demand of the mother and fetus; this induces the formation of oxygen free radicals [13–16]. In normal pregnancies, there is a physiological oxidative balance [13–16]; also, uric acid, vitamin C, vitamin D, and vitamin E gradually increase during normal pregnancy [17–21] leading to a maintained oxidative balance throughout pregnancy. However, the levels of dietary and cellular antioxidants are abnormally low in women with complications of pregnancy such as preeclampsia and habitual abortion [21], and the maternal blood levels of vitamin C, vitamin E, vitamin A, and β-carotene decreased [8, 17, 19–23] and lipoperoxidation increased [14]. Antioxidants’ enzymatic components include SOD, which detoxifies the superoxide anion, catalase (CAT), and the Glutathione peroxidase (GPx) system; peroxiredoxins, which inactivate H202; and glutathione peroxidase, which detoxifies cellular peroxides [19]. In pregnancy complications, lipoperoxidation products are increased and enzymatic antioxidants SOD and GPx are decreased [24]. In view of these facts, the present study was done in order to estimate the oxidative stress and antioxidant status, in pregnant women, and to establish its correlation with optimal and deficiency iodine levels in pregnant women in each gestation trimester.
Material and Methods Patients A cross-sectional study was done in pregnant women from Xalapa, Veracruz, México, that received antenatal care at Gynecology and Obstetrics Hospital of the University of Veracruz; the study was approved ethically by the hospital ethical committee and bioethical committee of the health institute of the University of Veracruz. In this study, we incorporated 212 pregnant women (74 for 1st trimester, 72 for 2nd trimester, and 66 for 3rd trimester) between 15 and 48 years old; previously, each pregnant woman signed an informed consent letter. The subjects with diabetes mellitus, severe anemia, and thyroid disease were excluded from this study. The blood collection and urinary sampling were carried out from April 2011 to November 2012 in Gynecology and Obstetrics Hospital in the University of Veracruz. Five milliliters of fasting venous blood was collected in BD vacutainer
Vidal et al.
and were preserved using packs of ice blocks and later transported to the laboratory for the assessment of level of conjugated dienes and indicator of oxidative stress; SOD, catalase, and total antioxidant status (TAS) were measurement as indicator of antioxidant status. The blood samples were centrifugated at 5,000 rpm for 5 min to separate plasma. The layer of white blood cells above the packed erythrocytes was discarded. Erythrocyte pellet was washed three times with 0.15 HCL, diluted in 33 % of phosphate buffer saline (mM; NaCL, 136.9; KCL, 2.68; KH2PO4, 1.47; Na2 HPO4, 6.62; and pH 7.4), and kept at 4 °C until use. Similarly, the urine samples were collected and 10 mL were preserved in frozencapped plastic tubes and 20 % of formalin (2 drops) was added in order to minimize iodine volatilization; then, these were frozen and analyzed within 24 h. Determination of Urinary Iodine Concentration Urinary iodine concentration (UIC) was measured using a fast colorimetric method, appropriate for population studies [1, 25]. Briefly, 0.2 ml of serum or iodine calibrator (50–300 μg/L) and 1.0 mL of ammonium persulfate solution were heated for 1 h at 100 °C. After adding arsenious acid solution (10 g of As2C3, 50 g of NaCl, 400 mL of 2.5 mol/L H2SO4) to each tube, it was mixed in a vortex mixer. Then, fresh ferroine–arsenic acid solution (10.8 mol/L H2SO4, arsenious acid, 200 g/L sodium chloride, and 2 mL ferroine) was added. Finally, ceric ammonium sulfate solution was added with the multipipetter, and the content of each glass tube (150 μL) was then transferred to a sterile polystyrene microtiter plate, and iodine was determined by the rate of color disappearance at 504 nm of each well in a microplate reader (Spectramax Plus; Molecular Devices, Sunnyvale, CA). The UIC was determined by subtracting the OD of the blanks and is expressed as μg/L against a standard iodine concentration (50–300 μg/L). The adequate values according to the UNICEF/WHO/ ICCID [1] criteria were excessive UIC >250 μg/L, optimal iodine concentration 150–200 μg/L, mild deficiency 50– 99 μg/L, moderate deficiency 20–49 μg/L, and severe deficiency
Oxidative Stress Increased in Pregnant Women with Iodine Deficiency Zendy Evelyn Olivo Vidal & Sergio Cuellar Rufino & Esteban Hernández Tlaxcalteco & Cirenia Hernández Trejo & Raúl Martínez Campos & Mónica Navarro Meza & Rocío Coutiño Rodríguez & Omar Arroyo-Helguera
Received: 28 August 2013 / Accepted: 14 January 2014 / Published online: 25 January 2014 # Springer Science+Business Media New York 2014
Abstract Iodine is an essential element trace for the synthesis of maternal thyroid hormones needed to support normal fetal development; it also acts as an antioxidant directly or induce antioxidant enzymes indirectly. Iodine deficiency and oxidative stress are associated with pregnancy complications. This study aimed to assess the urinary iodine concentration and its relationship with the antioxidant and oxidative stress status during gestation. Pregnant women were consecutively recruited from an obstetric clinic during all gestation trimesters, and urinary iodine concentration, antioxidant, and oxidative stress were determined. Results showed that 70 % of pregnant women have optimal iodine levels (150–200 μg/L), while approximately 30 % showed mild iodine deficiency (50– 99 μg/L). Oxidative stress was significantly higher, and the Z. E. O. Vidal : S. C. Rufino : E. H. Tlaxcalteco : R. C. Rodríguez : O. Arroyo-Helguera Instituto de Salud Pública, Universidad Veracruzana, Avenida Luís Castelazo Ayala S/N, Col. Industrial Ánimas, Xalapa, Veracruz, México C. H. Trejo : R. M. Campos Hospital Escuela de Ginecología y Obstetricia, Universidad Veracruzana, Calle Ernesto Ortiz Medina esq. Córdoba. Fracc. Veracruz, Xalapa, Veracruz, México C. H. Trejo Facultad de Bioanálisis, Universidad Veracruzana, Calle Médicos S/N, Col. Unidad del Bosque, Xalapa, Veracruz, México M. N. Meza Laboratorio de Biología Molecular e Inmunología, Centro Universitario del Sur. Universidad de Guadalajara, Ciudad Guzmán, México O. Arroyo-Helguera (*) Laboratorio de Ecología y Salud, Public Health Institute, Universidad Veracruzana, Avenida Luís Castelazo Ayala S/N, Xalapa, Veracruz, México 91190 e-mail: [email protected]
antioxidant status was also compromised as evidenced by decreased total antioxidant status and superoxide dismutase (SOD) activity in pregnant women with mild iodine deficiency than pregnant women with optimal iodine levels. Significant positive correlations were noted between optimal iodine levels and total antioxidant status. Oxidative stress was significantly correlated with mild iodine deficiency. However, no significant correlation was found between iodine levels and SOD and catalase activities. In conclusion, for the first time, these data suggest a correlation between iodine levels and the antioxidant status during pregnancy. Keywords Iodine . Antioxidant status . Pregnant women . Oxidative stress . Gestation
Introduction An optimal iodine nutritional intake during pregnancy is a priority because of its impact to the fetus during gestation and postpartum. The recommendations of the International Council for the Control of Iodine Deficiency Disorders (ICCIDD), WHO, and UNICEF [1], set the minimal urinary iodine excretion to 100 μg/L, a mean of 150 μg of iodine daily intake, and the recommended iodine amount for pregnant and lactating women to 200 μg [2, 3], although the ICCIDD raised this recommendation to 250–300 μg/L/day. Iodine metabolism alterations as hypothyroidism during gestation may induce placental abruption, cretinism, miscarriages, and preeclampsia [4–6]. A previous study done in normal and preeclamptic pregnant women showed that iodine deficiency is a preeclampsia risk factor [7, 8]. Iodine is a part of thyroid hormones and has been reported to act directly as an antioxidant [9] or induce indirectly antioxidant enzymes such as superoxide dismutase (SOD) [4, 9–11]. Iodine can be added to the double bonds of some polyunsaturated fatty acids of
212
cellular membranes, making them less reactive to free radicals [9]. Also, iodine competes with free radicals for membrane lipids, protein, and DNA in order to stabilize cells. This antioxidant role can be exerted through oxidized iodine species obtained by the diet or by local deiodination [4, 12]. Then, iodine levels should be important for the balance of antioxidant status during gestation; although, the roll of iodine is unknown. The oxidative metabolism is increased during pregnancy due to high oxygen demand of the mother and fetus; this induces the formation of oxygen free radicals [13–16]. In normal pregnancies, there is a physiological oxidative balance [13–16]; also, uric acid, vitamin C, vitamin D, and vitamin E gradually increase during normal pregnancy [17–21] leading to a maintained oxidative balance throughout pregnancy. However, the levels of dietary and cellular antioxidants are abnormally low in women with complications of pregnancy such as preeclampsia and habitual abortion [21], and the maternal blood levels of vitamin C, vitamin E, vitamin A, and β-carotene decreased [8, 17, 19–23] and lipoperoxidation increased [14]. Antioxidants’ enzymatic components include SOD, which detoxifies the superoxide anion, catalase (CAT), and the Glutathione peroxidase (GPx) system; peroxiredoxins, which inactivate H202; and glutathione peroxidase, which detoxifies cellular peroxides [19]. In pregnancy complications, lipoperoxidation products are increased and enzymatic antioxidants SOD and GPx are decreased [24]. In view of these facts, the present study was done in order to estimate the oxidative stress and antioxidant status, in pregnant women, and to establish its correlation with optimal and deficiency iodine levels in pregnant women in each gestation trimester.
Material and Methods Patients A cross-sectional study was done in pregnant women from Xalapa, Veracruz, México, that received antenatal care at Gynecology and Obstetrics Hospital of the University of Veracruz; the study was approved ethically by the hospital ethical committee and bioethical committee of the health institute of the University of Veracruz. In this study, we incorporated 212 pregnant women (74 for 1st trimester, 72 for 2nd trimester, and 66 for 3rd trimester) between 15 and 48 years old; previously, each pregnant woman signed an informed consent letter. The subjects with diabetes mellitus, severe anemia, and thyroid disease were excluded from this study. The blood collection and urinary sampling were carried out from April 2011 to November 2012 in Gynecology and Obstetrics Hospital in the University of Veracruz. Five milliliters of fasting venous blood was collected in BD vacutainer
Vidal et al.
and were preserved using packs of ice blocks and later transported to the laboratory for the assessment of level of conjugated dienes and indicator of oxidative stress; SOD, catalase, and total antioxidant status (TAS) were measurement as indicator of antioxidant status. The blood samples were centrifugated at 5,000 rpm for 5 min to separate plasma. The layer of white blood cells above the packed erythrocytes was discarded. Erythrocyte pellet was washed three times with 0.15 HCL, diluted in 33 % of phosphate buffer saline (mM; NaCL, 136.9; KCL, 2.68; KH2PO4, 1.47; Na2 HPO4, 6.62; and pH 7.4), and kept at 4 °C until use. Similarly, the urine samples were collected and 10 mL were preserved in frozencapped plastic tubes and 20 % of formalin (2 drops) was added in order to minimize iodine volatilization; then, these were frozen and analyzed within 24 h. Determination of Urinary Iodine Concentration Urinary iodine concentration (UIC) was measured using a fast colorimetric method, appropriate for population studies [1, 25]. Briefly, 0.2 ml of serum or iodine calibrator (50–300 μg/L) and 1.0 mL of ammonium persulfate solution were heated for 1 h at 100 °C. After adding arsenious acid solution (10 g of As2C3, 50 g of NaCl, 400 mL of 2.5 mol/L H2SO4) to each tube, it was mixed in a vortex mixer. Then, fresh ferroine–arsenic acid solution (10.8 mol/L H2SO4, arsenious acid, 200 g/L sodium chloride, and 2 mL ferroine) was added. Finally, ceric ammonium sulfate solution was added with the multipipetter, and the content of each glass tube (150 μL) was then transferred to a sterile polystyrene microtiter plate, and iodine was determined by the rate of color disappearance at 504 nm of each well in a microplate reader (Spectramax Plus; Molecular Devices, Sunnyvale, CA). The UIC was determined by subtracting the OD of the blanks and is expressed as μg/L against a standard iodine concentration (50–300 μg/L). The adequate values according to the UNICEF/WHO/ ICCID [1] criteria were excessive UIC >250 μg/L, optimal iodine concentration 150–200 μg/L, mild deficiency 50– 99 μg/L, moderate deficiency 20–49 μg/L, and severe deficiency
