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Mercury is potent toxicant element, but its toxicity can be reduced by forming a complex with selenium for safe excretion. Considering the impact of mercury exposure in the Amazon region and the possible interaction between these two elements, we aimed to assess the effects of Pro198Leu polymorphism to GPX1 and GSTM1 deletion, on mercury levels in a population from Porto Velho, an urban locality in the Brazilian Amazon region. Two hundred women from the capital city of Rondônia state were recruited for this study with 149 deemed suitable to participate. We assessed dietary intake using 24-hour recall. Selenium levels in plasma and erythrocytes were measured using hydride generation quartz tube atomic absorption spectroscopy and total hair mercury using cold vapor atomic absorption spectrometry. Oxidative stress parameters (GPx activity, oxygen radical absorbency capacity [ORAC] and malondialdehyde [MDA]) were also analyzed. All participants were genotyped for Pro198Leu polymorphism and GSTM1 deletion. We observed that this population presented high prevalence of selenium deficiency, and also low levels of mercury, likely due to food habits that did not include selenium-rich food sources or significant consumption of fish (mercury biomagnifiers) regularly. Univariate statistical analysis showed that Pro198Leu and GSTM1 genotypes did not affect selenium and mercury levels in this population. Pro198Leu polymorphism and GSTM1 deletion had no effect on mercury levels in mildly exposed people, suggesting these genetic variants impact mercury levels only in highly exposed populations.

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BACKGROUND: thyroid function depends on trace mineral selenium (Se), being at the active center of the iodothyronine deiodinase that catalyzes the conversion of the thyroxine (T4) to the active form of thyroid hormone, triiodothyronine (T3). Hemodialysis (HD) patients have reduced T3 levels partly due to impaired hormonal conversion that can be related to Se deficiency, a common feature in these patients. This study evaluated the effect of Brazil nuts (richest Se source) on thyroid hormone levels in HD patients. METHODS: we performed an uncontrolled intervention with 40 HD patients (53.3 ± 16.1 yrs, dialysis vintage 62.0 (8.0 - 207.0) months) that received one nut (≈5g, average 58.1 µg Se/g) per day for three months. Se plasma levels were determined by atomic absorption spectrophotometry with hydride generation and, serum T3, free T4 (FT4), TSH as well as glutathione peroxidase (GPx) activity were measured by ELISA. RESULTS: all patients were Se deficient and presented low T3 levels at baseline. After intervention, Se plasma levels (from 17.6 ± 11.6 to 153.4 ± 86.1 µg/L), GPx activity (from 33.7 ± 5.9 to 41.4 ± 11.2 nmol/min/mL), T3 (from 27.3 ± 8.8 to 50.2 ± 4.8ng/dL) and FT4 levels (0.87 ± 0.2 to 0.98 ± 0.4 ng/dL) were significantly increased (p < 0.05), while TSH levels were reduced (from 2.17 ± 1.3 to 1.96 ± 1.1 uUI/mL), but not significantly. CONCLUSION: in conclusion, increasing Se levels via Brazil nut supplementation was associated with improvement in thyroid hormone levels in HD patients, although the amount of Se given was not able to restore T3 to normal levels.

Introducción: la funcion tiroidea depende de minerales traza de selenio (Se), que esta en el centro activo de la deiodinasa yodotironina, que cataliza la conversion de la tiroxina (T4) a la forma activa de la hormona tiroidea, triyodotironina (T3). Hemodialisis (HD) de los pacientes ha reducido los niveles de T3 de los pacientes, debido en parte a la conversion hormonal alterada que puede estar relacionada con la deficiencia de Se, una caracteristica comun en estos pacientes. Este estudio evaluo el efecto de las nueces de Brasil (la mas rica fuente de Se) en los niveles de hormonas tiroideas en pacientes en HD. Métodos: se realizo una intervencion no controlada con 40 pacientes en HD (53,3 } 16,1 anos, dialisis vendimia 62,0 (8,0 - 207,0 meses)), que recibieron una nuez (≈ 5, promedio 58,1 mg Se/g) por dia durante tres meses. Determinaron los niveles plasmaticos de Se por espectrofotometria de absorcion atomica con generacion de hidruros y los niveles de T3, T4 libre (FT4), TSH en suero, asi como la actividad de la glutation peroxidasa (GPx) por ELISA. Resultados: todos los pacientes tenian niveles bajos de Se y T3 al inicio del estudio. Despues de la intervencion, los niveles plasmaticos de Se (de 17,6 } 11,6 a 153,4 } 86,1 mg/L), actividad GPx (de 33,7 } 5,9 a 41,4 } 11,2 nmol/min/ml), T3 (de 27,3 } 8,8 a 50,2 } 4,8 ng/dL) y T4L (0,87 } 0,2 a 0,98 } 0,4 ng/dL) se incrementaron significativamente (p < 0,05), mientras que los niveles de TSH se redujeron (de 2,17 } 1,3 a 1,96 } 1,1 IUU/ml), pero no de forma significativa. Conclusión: en conclusion, el aumento de los niveles de Se via suplementacion con nuez brasilena se asocia con una mejoria en los niveles de hormonas tiroideas en pacientes en HD, aunque la cantidad de Se dada no fue capaz de restablecer la T3 a los niveles normales.

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Desenvolveu-se um modelo experimental de deficiências de zinco e vitamina A em ratos, no período de lactacâo. logo após o nascimento dos animais. O delineamento consistiu de um período de deplecâo de 4 semanas após o nascimento. Os animalis do grupo teste receberam racâo a base de caseína deficiente em zinco e vitamina A e os do grupo controle a racâo padrâo segundo as recomendacôes do "Committee on Laboratory Animal Diet". Foram utilizadas ratas adultas pó-parto, Rathus norvergicus, var. albinus, (Rodentia Mammalia), com 6 filhotes machos cada, provenientes do biotério da Faculdadae de Ciencias Farmacêticas, da USP. Ao final do período de deplecâo, verificou-se que o peso dos animais do grupo controle (109, 1g ñ 3,9g) foi significativamente superior aos dos grupo teste (40,8g ñ 6,7g). Da mesma forma a concentracâo de zinco nos fêmures dos animais do grupo controle (115,7 µg/g ñ 5,4 µg do osso) foi significativamente superior á dos animais do grupo teste (35,5 µg/g ñ 3,3 µg/g. A concentracâo de vitamina A no plasma dos animais do grupo controle (31,5 µg/dl ñ 2,5 µg/dL) também foi significativamente superior quando comparada ádos animais do grupo teste (8,9 µg/dL ñ 3,4 µg/dL), entretanto a concentracâo de vitamina A hepática foi semelhante para os dois grupos. Pelos resultados obtenidos podemos concluir que house interacâo de zinco e vitamina A a nivel de mobilizacâo de vitamina A do fígado e deplecâo de zinco. Embora a concentracâo plasmática de vitamina A tivesse indicado uma deplecâo, esta nâo pode ser considerada total tendo em vista as reservas hepáticas

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