Tirozin, triiodotironin ve tiroksinin antioksidan etkinliğinin in vitro ve in vivo ortamlarda araştırılması
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Date
2003
Authors
Çolakoğulları, Mukaddes
Journal Title
Journal ISSN
Volume Title
Publisher
Uludağ Üniversitesi
Abstract
Tez projemizde tirozin amino asidinin ve tiroid hormonlarının olası antioksidan etkinliklerinin in vitro ve in vivo ortamlarda incelenmesi amaçlanmıştır. Çalışmanın birinci basamağında, in vitro ortamda, tirozinin, triiodotironin, tiroksin, östradiol ve alfa-tokoferolün serumda bakırla indüklenen lipid peroksidasyonu ve serum protein karbonillenmesi üzerine olan olası antioksidan etkileri incelendi. Bu moleküllerin bakırla indüklenen serum lipid peroksidasyonunu sınırlamada etkinlik sırası 17β-östradiol > T3 > α-tokoferol > T4 > tirozin olarak saptandı. Aynı moleküllerin serumda protein karbonil oluşumu üzerine istatistiksel olarak anlamlı etkisi bulunmadı. İkinci basamakta, in vitro ortamda antioksidan etkinlikleri gösterilen tiroid hormonlarının ve tirozin amino asidinin oksidan-antioksidan denge ile ilişkisinin araştırılması hedeflendi. Hipertiroidi tanısı alan 19 erkek hasta çalışmaya dahil edildi. Hastaların hipertiroidik ve ötiroidik durumda iken eritrosit Süperoksit dismütaz (SOD) ve Glutatyon peroksidaz (GPx) aktiviteleri, plazma non-HDL fraksiyonunun oksidasyona duyarlılığı, serum amino asit, protein karbonil (PK) ve malondialdehit (MDA) miktarlarının yanısıra kolesterol ve protein profilleri belirlendi. Tedavi takibi tamamlanan 15 hastanın tedavi öncesinde ve sonrasında elde edilen verileri eşleştirilmiş t-testi ile, verilerin grup içi istatistiksel analizi Pearson'un korelasyon analizi ile değerlendirildi. Buna göre tiroid hormonları tedavi sonrasında anlamlı olarak düşerken, TSH anlamlı olarak yükselmiştir. Protein profili üzerine hipertiroidizmin etkisi görülmezken, total kolesterol ve HDL kolesterol miktarları tedavi sonrasında artmıştır. Hem antioksidan savunma sisteminde yer alan SOD ve GPx aktivitelerinde, hem de oksidasyon göstergeleri olan MDA ve PK düzeylerinde ve non-HDL fraksiyonunun oksidasyona olan duyarlılığında hipertiroidik durumun tedavisi sonrasında azalma saptanmıştır. Ayrıca tedavi sonrasında tirozinin yanı sıra diğer serum amino asit düzeylerinde de azalma olduğu gösterilmiştir. In vitro ve in vivo basamaklardan oluşan bu çalışmanın sonuçlarına göre, hem tiroid hormonları hem de tirozin in vitro koşullarda konsantrasyona bağımlı olarak lipid peroksidasyonunu durdurarak lipidleri oksidasyondan koruyucu etkiye sahiptir. Diğer taraftan tiroid hormonları sahip oldukları hormonal etki ile oksijenli solunumu uyarıp, oksidasyonu indüklemektedir ve in vitro şartlarda antioksidan etkinlikleri gösterilen bu moleküller, fizyolojik koşullarda oluşan oksidasyonu engeleyememektedir.
In this project our goal was to investigate the possible antioxidant capacity of tyrosine amino acid and thyroid hormones both in in vitro and in vivo conditions. On the first step of this study, we investigated the antioxidant effect of tyrosine, triidothyronine, thyroxine, estradiol and α-tocopherol on copper induced serum lipid peroxidation and serum protein carbonyl content, in in vitro conditions. The antioxidant effects of these compounds on peroxidation of serum lipids were in order of 17β-estradiol > T3 > α-tocopherol > T4 > tyrosine. No significant difference was found between the antioxidant capacities of these compounds on protein carbonyl formation. On the second stage, we aimed to evaluate the effect of tyrosine amino acid and thyroid hormones on oxidant-antioxidant balance in hyperthyroidic patients. This step was carried on with 19 male hyperthyroidic patients who were diagnosed according to their T4, T3 and TSH hormone levels. Erytrocyte Superoxide dismutase (SOD) and Glutathione peroxidase (GPx) activities, susceptibilty of plasma non-HDL fraction to oxidation, serum amino acids, protein carbonyl (PC) and malondialdehyde (MDA) contents as well as serum lipid and protein profile were determined in these patients before and after medical treatment. Paired t-test and Pearson's correlation test were used to evaluate inter- and intra-group differences. In hyperthyroidic status, thyroid hormones decreased, TSH increased significantly and total cholesterol and HDL cholesterol increased significantly, but no significant change was found in protein profiles compared to euthyroidic status. Indicators of oxidation, as well as SOD and GPx activities were decreased after treatment. Serum amino acids concentrations were increased in hyperthyroidic status compared to euthyroidic status. According to the results of this project, both thyroid hormones and tyrosine amino acid have concentration dependent antioxidant effects on lipid peroxidation in in vitro conditions. On the other hand, thyroid hormones induce oxidative stress by activating aerobic respiration in vivo and the molecules which showed antioxidant effect in in vitro conditions can not prevent hormone-induced oxidation in physiological conditions.
In this project our goal was to investigate the possible antioxidant capacity of tyrosine amino acid and thyroid hormones both in in vitro and in vivo conditions. On the first step of this study, we investigated the antioxidant effect of tyrosine, triidothyronine, thyroxine, estradiol and α-tocopherol on copper induced serum lipid peroxidation and serum protein carbonyl content, in in vitro conditions. The antioxidant effects of these compounds on peroxidation of serum lipids were in order of 17β-estradiol > T3 > α-tocopherol > T4 > tyrosine. No significant difference was found between the antioxidant capacities of these compounds on protein carbonyl formation. On the second stage, we aimed to evaluate the effect of tyrosine amino acid and thyroid hormones on oxidant-antioxidant balance in hyperthyroidic patients. This step was carried on with 19 male hyperthyroidic patients who were diagnosed according to their T4, T3 and TSH hormone levels. Erytrocyte Superoxide dismutase (SOD) and Glutathione peroxidase (GPx) activities, susceptibilty of plasma non-HDL fraction to oxidation, serum amino acids, protein carbonyl (PC) and malondialdehyde (MDA) contents as well as serum lipid and protein profile were determined in these patients before and after medical treatment. Paired t-test and Pearson's correlation test were used to evaluate inter- and intra-group differences. In hyperthyroidic status, thyroid hormones decreased, TSH increased significantly and total cholesterol and HDL cholesterol increased significantly, but no significant change was found in protein profiles compared to euthyroidic status. Indicators of oxidation, as well as SOD and GPx activities were decreased after treatment. Serum amino acids concentrations were increased in hyperthyroidic status compared to euthyroidic status. According to the results of this project, both thyroid hormones and tyrosine amino acid have concentration dependent antioxidant effects on lipid peroxidation in in vitro conditions. On the other hand, thyroid hormones induce oxidative stress by activating aerobic respiration in vivo and the molecules which showed antioxidant effect in in vitro conditions can not prevent hormone-induced oxidation in physiological conditions.
Description
Keywords
Tirozin, Hipertiroidi, Fenolik halka, Oksidatif stres, Protein karbonil miktarı, Tyrosine, Hyperthyroidism, Phenolic ring, Oxidative stress, Protein carbonyl content
Citation
Çolakoğulları, M. (2003). Tirozin, triiodotironin ve tiroksinin antioksidan etkinliğinin in vitro ve in vivo ortamlarda araştırılması. Yayınlanmamış uzmanlık tezi. Uludağ Üniversitesi Tıp Fakültesi.