Juan Carlos Solís-S

Inhibition of intrathyroidal dehalogenation by iodide

Iodide is a trace element and a key component of thyroid hormones (TH). The availability of this halogen is the rate-limiting step for TH synthesis; therefore, thyroidal iodide uptake and recycling during TH synthesis are of major importance in maintaining an adequate supply. In the rat, the thyroid gland co-expresses a distinctive pair of intrathyroidal deiodinating enzymes: the thyroid iodotyrosine dehalogenase (tDh) and the iodothyronine deiodinase type 1 (ID1). In the present work, we studied the activity of these two dehalogenases in conditions of hypo- and hyperthyroidism as well as during acute and chronic iodide administration in both intact and hypophysectomized (HPX) rats. In order to confirm our observations, we also measured the mRNA levels for both dehalogenases and for the sodium/iodide symporter, the protein responsible for thyroidal iodide uptake. Our results show that triiodothyronine differentially regulates tDh and ID1 enzymatic activities, and that both acute and chronic iodide administration significantly decreases rat tDh and ID1 activities and mRNA levels. Conversely, both enzymatic activities increase when intrathyroidal iodide is pharmacologically depleted in TSH-replaced HPX rats. These results show a regulatory effect by iodide on the intrathyroidal dehalogenating enzymes and suggest that they contribute to the iodide-induced autoregulatory processes involved in the Wolff-Chaikoff effect.

Iodine nutrition in elementary state schools of Queretaro, Mexico: correlations between urinary iodine concentration with global nutrition status and social gap index

OBJECTIVE AND METHODS To estimate median urinary iodine concentration (UIC), and to correlate it with global nutrition indicators and social gap index (SGI) in 50 elementary state schools from 10 municipalities in the State of Queretaro, Mexico. RESULTS 1,544 students were enrolled and an above of requirements of iodine intake was found (median UIC of 297 µg/L). Iodine status was found as deficient, adequate, more than adequate and excessive in 2, 4, 19 and 25 schools, respectively. Seventy seven percent of table salt samples showed adequate iodine content (20-40 ppm), while 9.6% of the samples had low iodine content (< 15 ppm). Medians of UIC per school were positively correlated with medians of body mass index (BMI) by using the standard deviation score (SDS) (r = 0.47; p < 0.005), height SDS (r = 0.41; p < 0.05), and overweight and obesity prevalence (r = 0.41; p < 0.05). Medians of UIC per school were negatively correlated with stunting prevalence (r = -0.39; p = 005) and social gap index (r = -0.36; p < 0.05). Best multiple regression models showed that BMI SDS and height were significantly related with UIC (p < 0.05). CONCLUSIONS There is coexistence between the two extremes of iodine intake (insufficient and excessive). To our knowledge, the observed positive correlation between UIC and overweight and obesity has not been described before, and could be explained by the availability and consumption of snack food rich in energy and iodized salt.

Iodine Nutrition Status in Pregnant Women in Mexico

BACKGROUND Iodine nutrition during pregnancy has become an important public health concern because of the deleterious impact of iodine deficiency on brain development during fetal and early postnatal life. Iodine nutrition status can be assessed in a population by the median urinary iodine concentration (UIC). World Health Organization, the United Nations Childrens Fund, and the International Council for Iodine Deficiency Disorders have established that a median of UIC between 150 and 249 μg/L in pregnant women indicates an adequate iodine intake. The aim of this study was to assess iodine nutrition status in Mexican pregnant women. METHODS Two hundred ninety-four pregnant women receiving prenatal care in the Public Medical Units of the State Ministry of Health for each pregnancy trimester (first, n=60; second, n=103; and third, n=131) in Queretaro, Mexico, were enrolled to assess UIC by the Sandell-Kholtoff method. RESULTS The median of UIC was 273, 285, and 231 μg/L in the first, second, and third trimesters of gestation, respectively. Globally, the median (range) of UIC was 260 (5-1320) μg/L, and the percentage of samples with UIC below 150 μg/L was 28%. There was no significant difference between the UIC of women using iodine-containing multivitamins compared with those who reported the consumption of noniodized multivitamins (p>0.05). In addition, we found no difference between the UIC of women using iodized table salt compared with those who employed noniodized table salt, with those who did not know whether their table salt was iodized (p>0.05). CONCLUSIONS Based on the median UIC, iodine intake in Queretaro, Mexico, is slightly above requirements during the first two trimesters, and adequate in the third trimester. The wide Mexican universal iodized salt program seems to supply adequate dietary iodine to pregnant women without health insurance in this region. However, regular monitoring of iodine status is recommended during pregnancy throughout Mexico.

Iodine nutrition and thyroid function assessment in childbearing age women from Queretaro, Mexico

OBJECTIVE To assess iodine nutrition and thyroid function in Mexican childbearing age women. METHODS 101 childbearing age women (21.7 ± 3.5 years) randomly selected from the university student population participated in this cross-sectional study. TSH, thyroid hormones, anti-thyroid antibodies, thyroid volume, iodine intake, and urinary iodine concentration (UIC) were assessed. The knowledge about the importance of iodine in nutrition was also evaluated by using questionnaires. RESULTS TSH median (interquartile range) value was 1.9 (1.4-2.5) mIU/L, while FT4 median value was 9.0 (8.3- 9.6) μg/dL. The median FT3 and total rT3 values were 3.3 pg/mL and 40.1 ng/dL, respectively. The prevalence of subclinical hypothyroidism (serum TSH >4.5 mIU/L) and of positive anti-thyroid antibodies were 2.9% and <5.9%, respectively. Median thyroid volume was 5.6 mL and none of the subjects were diagnosed with goiter. Median urinary iodine concentration was 146 (104-180) μg/L. As for the knowledge of iodine nutrition, only 37.6% considered that a pregnant woman needs more dietary iodine than a non pregnant woman, while 43.6% recognized that the lack of iodine can cause mental retardation in children. CONCLUSIONS Prevalence of thyroid test function abnormalities was low in this population and the median UIC indicates adequate iodine intake. We also found a poor knowledge about the importance iodine nutrition in the studied population.

Infection or colonization and antimicrobial susceptibility of Enterococcus spp at a regional hospital in Queretaro, Mexico

To the Editor: I read the recent article by Heimbuch et al on decontamination and reuse of of N95 filtering facepiece respirators (FFRs) with great interest. The authors concluded that microwave-generated steam, warm moist heat, or ultraviolet germicidal irradiation could be effective options for decontaminating FFRs to allow reuse. I have some questions regarding this conclusion. First, there is no doubt that the proposed decontamination techniques can destroy viruses, but whether these techniques also threaten the FFRs’ structural integrity is unclear. Alterations in FFR structure might significantly decrease the device’s protective action. Second, the effectiveness of the proposed techniques in destroying other viruses and pathogens that might contaminate FFRs should be assessed as well. Third, there is a chance that some unwanted residual chemicals may remain on FFRs after decontamination. Whether the proposed technique can eliminate these residual chemicals is of concern. These questions should be answered before FFR decontamination and reuse can be deemed safe.

Signals from the caudal diencephalon are required for the projection of the Interstitial Nuclei of Cajal

Axonal projection is controlled by discrete regions localized at the neuroepithelium, guiding the neurite growth during embryonic development. These regions exert their effect through the expression of a family of chemotropic molecules, which actively participate in the formation of neuronal connections of the central nervous system in vertebrates. Previous studies describe prosomere 1 (P1) as a possible organizer of axonal growth of the rostral rhombencephalon, contributing to the caudal projection of reticulospinal rhombencephalic neurons. This work studies the contribution of chemotropic signals from P1 or pretectal medial longitudinal fascicle (MLF) neurons upon the caudal projection of the interstitial nuclei of Cajal (INC). By using in ovo surgeries, retrograde axonal labeling, and immunohistochemical techniques, we were able to determine that the absence of P1 generates a failure in the INC caudal projection, while drastically diminishing the reticulospinal rhombencephalic neurons projections. The lack of INC projection significantly decreases the number of reticulospinal neurons projecting to the MLF. We found a 48.6% decrease in the projections to the MLF from the rostral and bulbar areas. Similarly, the observed decrease at prosomere 2 was 51.5%, with 61.8% and 32.4% for prosomeres 3 and 4, respectively; thus, constituting the most affected rostral regions. These results suggest the following possibilities: i, that the axons of the reticulospinal neurons employ the INC projection as a scaffold, fasciculating with this pioneer projection; and ii, that the P1 region, including pretectal MLF neurons, exerts a chemotropic effect upon the INC caudal projection. Nonetheless the identification of these chemotropic signals is still a pending task.

Thyroid hormones and obesity: a known but poorly understood relationship

Hormony tarczycy (thyroid hormones, TH) są zaangażowane w wiele różnych procesów biologicznych, wliczając rozwój układu nerwowego, regulację metabolizmu pośredniego oraz zużycie energii. Aktywnie uczestniczą w podstawowym zużyciu energii i termogenezie adaptacyjnej i z tego względu mogą mieć wpływ na masę ciała w przebiegu chorób tarczycy. Otyłość to niezakaźna, przewlekła, zapalna choroba metaboliczna, która implikuje dodatni bilans energetyczny. Tkanka tłuszczowa produkuje szereg hormonów i adipocytokin, takich jak leptyna, które mogą wpływać na stan tarczycy na różnych poziomach. Istnieją dowody na to, że dysfunkcja tarczycy może predysponować do otyłości i odwrotnie, istnieją dowody sugerujące, że otyłość powoduje zmiany dotyczące tarczycy. Celem tej pracy było opisanie związku między układem tarczycy a otyłością. Ponadto w pracy zaprezentowano hipotetyczny model podkreślający znaczenie obwodowej dejodynacji hormonów tarczycy i jego rolę w ustanowieniu dodatniego bilansu energetycznego. Podsumowując, możemy stwierdzić, że relacja między układem tarczycy a otyłością i nadwagą jest złożona i obejmuje wiele poziomów interakcji. Ponadto, poddając ocenie otyłego pacjenta, powinno się rozważyć ocenę funkcji tarczycy, aby uzyskać lepsze i spersonalizowane efekty leczenia.

Iodothyronine Deiodinases: Emerging Clinical Crossroads

Iodothyronine deiodinases, a ubiquitous family of selenoenzymes, are key tissue-specific regulators of intracellular thyroid hormone availability and signaling. This chapter reviews current information supporting the notion that the altered expression and/or activity of deiodinases contribute to the pathophysiology of diverse clinical disorders. Experimental and clinical evidence establishes an association of polymorphisms in deiodinase genes with mood, affective and cognitive functioning, as well as type 2 diabetes mellitus and lipid metabolism. Similarly, an imbalance in the activating and inactivating deiodinase pathways may promote cell proliferation and/or invasiveness of different types of neoplasms. Although a clear-cut picture has not yet been achieved, emerging data support the notion that the deiodinase-dependent thyroid hormone transcriptional footprint has a profound functional impact in health and disease.