The aim of this thesis is to contribute to the understanding of iron metabolism, as a factor associated with cardiometabolic risk, by undertaking secondary data analyses. The objectives were to identify gaps in existing knowledge in terms of populations studied and alternative iron markers, and to attempt to fill the gaps with additional analyses and interpretation. Serum ferritin was the most widely available measure of iron status but the role of serum transferrin and soluble transferrin receptor (sTfR) levels was considered where available. I have taken a life-course approach with analyses in childhood and adulthood, and have included both intermediate factors such as the metabolic syndrome (MetS), and disease diagnoses of diabetes and cardiovascular disease as outcomes. Chapter one presents a review of empirical research literature on the relationship between iron metabolism and cardiometabolic risk, concepts surrounding iron markers and the study outcomes. This chapter also describes the gaps in understanding the iron-cardiometabolic risk relationship, which are subsequently explored in chapters two to six. Chapter two explores the link between serum ferritin and transferrin and MetS in cross-sectional and prospective studies of 725 Spanish children and 567 Chilean adolescents. I found associations between both ends of the ferritin distribution and MetS or glucose metabolism markers in different paediatric populations. For instance, whereas in the Spanish children there was a decrease of 0.02 SD units in the change of MetS score over time for every SD unit increase in ferritin, in the Chilean male adolescents being in the highest tertile of ferritin (v. the lowest) was associated with an increase of 0.25 SD units of MetS score. Furthermore, sustained high ferritin levels at various time points and gradual increase of ferritin during childhood were associated with higher MetS score in adolescence. The third chapter describes the association between serum ferritin status and MetS in adults in two cross-sectional studies of Scottish populations (2,047 individuals from Shetland Islands and 8,563 subjects from the Scottish Health Surveys (SHeS) 1995- 1998). I also examined the overall association between ferritin, MetS and each MetS component in adults, by conducting a meta-analysis and investigating potential relevant sources of heterogeneity for the association. Interestingly, ferritin levels were positively associated with MetS in the Scottish populations, but the association was not independent of the effect of covariates, mainly body mass index (BMI) and transaminase levels [Men Odds ratio (OR) 95% confidence interval (CI) 1.43(0.83- 2.46); Postmenopausal women OR (95%CI) 1.09(0.62-1.90); Premenopausal women OR (95%CI) 1.02(0.42-2.46), P > 0.05]. The meta-analysis supported this finding by describing hepatic injury markers and BMI as the major attenuating factors of the ferritin-MetS association. Chapter four investigates the association between sTfR or ferritin, and MetS in 725 Croatian adults in a cross-sectional study. There was no evidence of an association between sTfR and MetS [Men OR (95%CI) 1.35(0.90-2.02); Postmenopausal women OR (95%CI) 0.73(0.47-1.15); Premenopausal women OR (95%CI) 0.87(0.66-1.17), P > 0.05]. In contrast serum ferritin, was positively and independently associated with MetS in men and postmenopausal women (P < 0.05) [Men OR (95%CI) 1.78(1.31- 2.42); Postmenopausal women OR (95%CI) 1.71(1.12-2.62); Premenopausal women OR (95%CI) 1.24(0.85-1.80)]. These contrasting results suggest that different iron markers reflect different physiological processes other than iron metabolism. Chapter five evaluates the longitudinal association between serum ferritin and several cardiometabolic disease outcomes (CMDs) in the nationally representative SHeS 1995 and 1998 (n = 6,497). I found an independent positive longitudinal association between ferritin and cerebrovascular disease (CEVD), which was strengthened by using higher cut-points for increased ferritin [higher v. lowest sextile fully adjusted Hazard ratio(HR) 95%CI 2.08 (1.09-3.94), P=0.024], and a not significant association with coronary heart disease (CHD) after adjustment for covariates. My analyses confirmed the widely established association with type 2 diabetes (T2D) [whole sample fully adjusted HR 95% CI 1.59(1.10-2.34), P=0.006], even with serum ferritin within the normal range. The above set of observations confirm ferritin as biomarker mainly related to the development of T2D and identifies the need to investigate the association between ferritin and CEVD in other populations. Chapter six investigates whether ferritin is associated with risk for cardiovascular complications among people with T2D using cross-sectional study designs in two populations with differing baseline cardiovascular risk (Spanish study SIDIAP n=38,617) and (Edinburgh Type 2 Diabetes Study (ET2DS) n= 821) with additional analysis of follow-up data for ET2DS. Interestingly, ferritin levels were negatively associated with prevalence of cardiovascular disease, mainly CHD, in people with T2D in both studies [ET2DS OR (95%CI): 0.80(0.67-0.96), P=0.020; SIDIAP study: 0.85(0.83-0.88), P < 0.001). Ferritin was also negatively associated with incident cardiovascular disease in ET2DS: HR 95% CI: 0.39(0.16-0.93), P=0.035. Therefore, the association between iron status and CMD risk in people with T2D appears to differ from that in general populations in which a positive association has been more commonly described. In conclusion, serum ferritin is associated with cardiometabolic risk in different ways in a variety of populations. Inconsistent associations for other iron markers suggest that iron biomarkers reflect factors other than iron homeostasis that influence cardiometabolic risk. The association between iron markers and MetS appears to differ between populations. This thesis illustrates the complex relationship between iron metabolism markers, MetS and CMD, and identifies the need for further research on the topic in order to extend knowledge about pathophysiology and the potential for measures of iron status as biomarkers for CMD.

No description available.

As síndromes talassêmicas (?- e ?-talassemia) são as desordens mais comuns e frequentes associadas com eritropoese ineficaz. O desbalanço na produção das cadeias ?- e ?-globinas resulta no comprometimento da produção de eritrócitos, em anemia e aumento de progenitores eritroides no sangue periférico. Enquanto os pacientes homozigóticos afetados por essas desordens demonstram alterações características dos parâmetros relacionados a eritropoese, a relação entre grau de anemia, eritropoese alterada e disfunção do metabolismo de ferro ainda não foram investigados nos indivíduos com ?+-talassemia heterozigótica ou ?+-talassêmia. Duzentos e vinte seis indivíduos (75 do gênero feminino e 151 do gênero masculino) foram recrutados e divididos em 5 grupos: Controle (n=28), doadores de sangue regulares (DSR, n=23), ?+-talassemia heterozigótica (TAT, n=14), ?+-thalassemia (traço ?-talassêmico, TBT, n=20) e ?0-talassemia, (?-talassemia maior, BTM, n=27). As amostras foram analisadas para parâmetros hematológicos (Micros ABX 60); ferro sérico, capacidade total de ligação ao ferro e saturação de transferrina por método colorimétrico (Pointe Scientific, Inc., Canton, MI, USA), ferritina e proteína C-reativa ultra sensível por imunoensaio (Immulite 1000); receptor solúvel de transferrina, eritropoetina, fator de diferenciação do crescimento 15 (R&D Systems) e hepcidina (Intrinsic LifeSciences, La Jolla, CA) por ELISA. As razões sTfR/log ferritina e (hepcidina/ferritina)/sTfR foram calculadas para avaliar o metabolismo do ferro. sTfR/log ferritina pode distinguir depleção dos estoques de ferro de eritropoese deficiente de ferro, enquanto (hepcidina/ferritina)/sTfR pode avaliar os estímulos contrários (disponibilidade de ferro e atividade eritropoética) que controlam a síntese de hepcidina e a absorção de ferro, na ausência de estímulos inflamatórios. Foi demonstrado que TAT teve significativa redução da hepcidina e aumento do receptor solúvel de transferrina, com parâmetros hematológicos relativamente normais. Em contraste, todos os parâmetros hematológicos de TBT foram significativamente diferentes do Controle, incluindo aumento dos níveis do receptor solúvel de transferrina, ferritina, eritropoetina e fator de diferenciação do crescimento 15. Essas alterações em ambos os grupos sugerem um balanço alterado entre eritropoese e metabolismo de ferro. Os índices sTfR/log ferritina e (hepcidina/ferritina)/sTfR estão, respectivamente, aumentado e reduzido comparados ao Controle, proporcional a severidade de cada grupo talassêmico. Em conclusão, destacamos que, pela primeira vez, foram descritas alterações no metabolismo de ferro em indivíduos com ?+-talassemia heterozigótica. Esses dados demonstram que, no contexto da saúde pública, são necessários identificação e acompanhamento dos portadores de ?+-talassemia. / The thalassemia syndromes (?- and ?-thalassemia) are the most common and frequent disorders associated with ineffective erythropoiesis. Imbalance of ?- or ?-globin chain production results in impaired red blood cell synthesis, anemia and more erythroid progenitors in the blood stream. While patients affected by these disorders show definitive altered parameters related to erythropoiesis, the relationship between the degree of anemia, altered erythropoiesis and dysfunctional iron metabolism have not been investigated in both carriers of ?-thalassemia and ?-thalassemia. 226 subjects (75 females and 151 males) were recruited to this study and divided in 5 groups: Control (n=28), repeat blood donors (DSR, n=23), ?+-thalassemia heterozygous carriers (TAT, n=14), ?+-thalassemia (?-thalassemia trait, TBT, n=20) and ?0-thalassemia, (?-thalassemia major, BTM, n=27). Samples were tested for hematological parameters (Micros ABX 60); serum iron, total iron binding capacity, and transferrin saturation by the colorimetric method (Pointe Scientific, Inc., Canton, MI, USA), ferritin and high sensitive C-reactive protein by immunoassay (Immulite 1000); soluble transferrin receptor, erythropoietin and growth differentiation factor 15 (R&D Systems) and hepcidin (Intrinsic LifeSciences, La Jolla, CA) by ELISA. Were calculated the ratios sTfR/log ferritin and (hepcidin/ferritin)/sTfR to evaluate iron metabolism. sTfR/log ferritin can distinguish storage iron depletion from iron-deficient erythropoiesis, while (hepcidin/ferritin)/sTfR can be utilized to explore and quantify the opposing forces (i.e. iron availability and erythropoietic activity) regulating hepcidin synthesis and iron absorption in absence of inflammatory stimuli. We demonstrate that TAT have a significantly reduced hepcidin and increased soluble transferrin receptor levels but relatively normal hematological findings. In contrast, TBT have all hematological parameters significantly different from controls, including increased soluble transferrin receptor, ferritin, erythropoietin and growth differentiation factor 15 levels. These changings in both groups suggest an altered balance between erythropoiesis and iron metabolism. The indexes sTfR/log ferritin and (hepcidin/ferritin)/sTfR are respectively increased and reduced relative to controls, proportional to the severity of each thalassemia group. In conclusion, we emphasize that, for the first time in the literature, subjects with heterozygous ?+-thalassemia have altered iron metabolism. Our data demonstrate that within the context of public health, identification and monitoring of patients with ?+-thalassemia are needed.

As síndromes talassêmicas (?- e ?-talassemia) são as desordens mais comuns e frequentes associadas com eritropoese ineficaz. O desbalanço na produção das cadeias ?- e ?-globinas resulta no comprometimento da produção de eritrócitos, em anemia e aumento de progenitores eritroides no sangue periférico. Enquanto os pacientes homozigóticos afetados por essas desordens demonstram alterações características dos parâmetros relacionados a eritropoese, a relação entre grau de anemia, eritropoese alterada e disfunção do metabolismo de ferro ainda não foram investigados nos indivíduos com ?+-talassemia heterozigótica ou ?+-talassêmia. Duzentos e vinte seis indivíduos (75 do gênero feminino e 151 do gênero masculino) foram recrutados e divididos em 5 grupos: Controle (n=28), doadores de sangue regulares (DSR, n=23), ?+-talassemia heterozigótica (TAT, n=14), ?+-thalassemia (traço ?-talassêmico, TBT, n=20) e ?0-talassemia, (?-talassemia maior, BTM, n=27). As amostras foram analisadas para parâmetros hematológicos (Micros ABX 60); ferro sérico, capacidade total de ligação ao ferro e saturação de transferrina por método colorimétrico (Pointe Scientific, Inc., Canton, MI, USA), ferritina e proteína C-reativa ultra sensível por imunoensaio (Immulite 1000); receptor solúvel de transferrina, eritropoetina, fator de diferenciação do crescimento 15 (R&D Systems) e hepcidina (Intrinsic LifeSciences, La Jolla, CA) por ELISA. As razões sTfR/log ferritina e (hepcidina/ferritina)/sTfR foram calculadas para avaliar o metabolismo do ferro. sTfR/log ferritina pode distinguir depleção dos estoques de ferro de eritropoese deficiente de ferro, enquanto (hepcidina/ferritina)/sTfR pode avaliar os estímulos contrários (disponibilidade de ferro e atividade eritropoética) que controlam a síntese de hepcidina e a absorção de ferro, na ausência de estímulos inflamatórios. Foi demonstrado que TAT teve significativa redução da hepcidina e aumento do receptor solúvel de transferrina, com parâmetros hematológicos relativamente normais. Em contraste, todos os parâmetros hematológicos de TBT foram significativamente diferentes do Controle, incluindo aumento dos níveis do receptor solúvel de transferrina, ferritina, eritropoetina e fator de diferenciação do crescimento 15. Essas alterações em ambos os grupos sugerem um balanço alterado entre eritropoese e metabolismo de ferro. Os índices sTfR/log ferritina e (hepcidina/ferritina)/sTfR estão, respectivamente, aumentado e reduzido comparados ao Controle, proporcional a severidade de cada grupo talassêmico. Em conclusão, destacamos que, pela primeira vez, foram descritas alterações no metabolismo de ferro em indivíduos com ?+-talassemia heterozigótica. Esses dados demonstram que, no contexto da saúde pública, são necessários identificação e acompanhamento dos portadores de ?+-talassemia. / The thalassemia syndromes (?- and ?-thalassemia) are the most common and frequent disorders associated with ineffective erythropoiesis. Imbalance of ?- or ?-globin chain production results in impaired red blood cell synthesis, anemia and more erythroid progenitors in the blood stream. While patients affected by these disorders show definitive altered parameters related to erythropoiesis, the relationship between the degree of anemia, altered erythropoiesis and dysfunctional iron metabolism have not been investigated in both carriers of ?-thalassemia and ?-thalassemia. 226 subjects (75 females and 151 males) were recruited to this study and divided in 5 groups: Control (n=28), repeat blood donors (DSR, n=23), ?+-thalassemia heterozygous carriers (TAT, n=14), ?+-thalassemia (?-thalassemia trait, TBT, n=20) and ?0-thalassemia, (?-thalassemia major, BTM, n=27). Samples were tested for hematological parameters (Micros ABX 60); serum iron, total iron binding capacity, and transferrin saturation by the colorimetric method (Pointe Scientific, Inc., Canton, MI, USA), ferritin and high sensitive C-reactive protein by immunoassay (Immulite 1000); soluble transferrin receptor, erythropoietin and growth differentiation factor 15 (R&D Systems) and hepcidin (Intrinsic LifeSciences, La Jolla, CA) by ELISA. Were calculated the ratios sTfR/log ferritin and (hepcidin/ferritin)/sTfR to evaluate iron metabolism. sTfR/log ferritin can distinguish storage iron depletion from iron-deficient erythropoiesis, while (hepcidin/ferritin)/sTfR can be utilized to explore and quantify the opposing forces (i.e. iron availability and erythropoietic activity) regulating hepcidin synthesis and iron absorption in absence of inflammatory stimuli. We demonstrate that TAT have a significantly reduced hepcidin and increased soluble transferrin receptor levels but relatively normal hematological findings. In contrast, TBT have all hematological parameters significantly different from controls, including increased soluble transferrin receptor, ferritin, erythropoietin and growth differentiation factor 15 levels. These changings in both groups suggest an altered balance between erythropoiesis and iron metabolism. The indexes sTfR/log ferritin and (hepcidin/ferritin)/sTfR are respectively increased and reduced relative to controls, proportional to the severity of each thalassemia group. In conclusion, we emphasize that, for the first time in the literature, subjects with heterozygous ?+-thalassemia have altered iron metabolism. Our data demonstrate that within the context of public health, identification and monitoring of patients with ?+-thalassemia are needed.

Las hormonas recombinantes eritropoyetina (EPO) y hormona de crecimiento (GH), prácticamente iguales a las endógenas y de corta vida media en circulación, son de difícil detección directa en el control antidopaje. Se determinaron los valores poblacionales de los biomarcadores indirectos EPO, receptor soluble de la transferrina, insulin-like growth factor-I (IGF-I) y procolágeno tipo III péptido (P-III-P), en poblaciones seleccionadas de deportistas, y el efecto del ejercicio y los distintos tipos de entrenamiento sobre su concentración sérica. La comparación de resultados obtenidos mediante distintos ensayos demostró la necesidad de una validación exhaustiva previa a su utilización. A excepción del P-III-P, los biomarcadores séricos propuestos para la detección de rhEPO y rhGH no se encuentran directamente afectados por el nivel atlético, el ejercicio o la distinta carga de entrenamiento realizada a lo largo de la temporada deportiva. La edad es la principal influencia sobre las concentraciones séricas de IGF-I y P-III-P. / Direct detection of recombinant peptidic hormones erythropoietin (EPO) and growth hormone (GH), very similar to endogen molecules and with a short half life in blood, is difficult in antidoping control. The main objective of this work is to determine indirect biomarkers' values of EPO, soluble transferrin receptor, insulin-like growth factor-I (IGF-I) and procollagen type III peptide (P-III-P), in selected populations of athletes, and the effect of exercise and different types of training on their concentration in serum. The comparison of results obtained by the different assays showed the need of extensive validation of the analytical techniques before their use in the antidoping field. Excepting P-III-P, proposed biomarkers for the detection of rhEPO and rhGH abuse are not directly influenced by the athletic level, exercise or different training workload along the sport season. Age is the main factor affecting IGF-I and P-III-P concentrations in serum.