Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy

Sodium selenite for treatment of Kashin-Beck disease in children: a systematic review of randomised controlled trials

OBJECTIVE

To assess the effectiveness and safety of sodium selenite in treatment of patients with Kashin-Beck disease (KBD).

METHODS

We searched for all publications between January 1966 and October 2011 using seven electronic databases. All randomized controlled trials (RCTs) assessing the effects of sodium selenite on KBD vs no treatment or placebo were included. For dichotomous data, odds ratios (OR) and 95% confidence intervals (CI) were estimated according to the intention-to-treat principles. For continuous data, mean difference (MD) was used for outcomes pooled on the same scale.

RESULTS

A total of 10 RCTs involving 2244 patients were included. The methodological quality of the included studies was low. When comparing the outcome of sodium selenite treatment group vs the control group, the OR of repairing rate of metaphyseal lesions was 5.63 (95% CI: 3.67-8.63) and repairing rate at the distal end of phalanges was 2.98 (95% CI: 1.32-6.70) based on X-ray assessment, which was statistically significant difference in favour of sodium selenite. In one RCT which reported data on clinical improvement, no statistically significant difference was observed in the treatment vs control group (OR 1.50, 95% CI: 0.43-5.30). Se content in hair was (MD 0.11, 95% CI: 0.09-0.13) which was statistically significant higher in selenium group.

CONCLUSIONS

Current evidence suggests that sodium selenite is more effective than placebo or no treatment in patients with KBD. However, the evidence was limited by potential biases; thus, further high quality large-scale RCTs are still needed to evaluate the short term and long term effects of selenium.

Chondroitin sulfate and/or glucosamine hydrochloride for Kashin-Beck disease: a cluster-randomized, placebo-controlled study

OBJECTIVE

To evaluate the efficacy and safety of chondroitin sulfate and/or glucosamine hydrochloride in alleviating symptoms and improving the dysfunction of Kashin-Beck disease (KBD) patients.

METHODS

We undertook a cluster-randomized, placebo-controlled trial in 251 patients with KBD. Participants were randomly allocated to comparing (1) chondroitin sulfate, (2) glucosamine hydrochloride, (3) a combination of chondroitin sulfate and glucosamine hydrochloride, or (4) placebo, for 6 months duration. The primary outcome measures of interest were 20% and 50% reductions in pain from baseline, measured by pain subscale in the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index. Secondary outcome measures included parameters in the WOMAC Index such as pain, stiffness, and physical function, as well as patients' quality of life by the 12-item Short-Form General Health Survey. The trial registration number is ChiCTR-TRC-11001480 (http://www.chictr.org/).

RESULTS

A combination therapy of chondroitin sulfate and glucosamine hydrochloride was effective in reducing WOMAC pain by 20% (differences of 23.4%, P=0.006) and 50% (differences of 15.7%, P=0.016), WOMAC pain (P=0.032), WOMAC stiffness (P=0.043), and WOMAC total score (P=0.035). Chondroitin sulfate used alone was also found to be effective in reducing WOMAC total score and stiffness score (P=0.038 and P=0.023, respectively). No significant positive effects in improving WOMAC Index scores were observed with glucosamine hydrochloride alone.

CONCLUSION

The findings of this study indicate that a combination of chondroitin sulfate and glucosamine hydrochloride was more effective than placebo in treating KBD.

Preventive effects of supplemental selenium and selenium plus iodine on bone and cartilage development in rats fed with diet from Kashin-Beck disease endemic area

The purpose of this study was to investigate the effects of supplemental selenium and selenium plus iodine on bone and growth plate cartilage histology and serum biochemistic parameters in rats. Ninety-six Wistar rats were randomly divided into the following four groups: group A, the rats fed with normal diet; group B, fed with diet from Kashin-Beck disease (KBD) endemic area; group C, fed with diet from KBD endemic area supplemented with selenium; and group D, fed with diet from KBD endemic area supplemented with selenium and iodine. After 4, 8, and 12 weeks, bone and cartilage samples were collected from the rats and were examined for morphological changes in the tibial growth zone and for changes in the plate cartilage and metaphysic. Compared to the rats fed with diet from the KBD endemic area, the rats fed with the supplemental selenium or selenium plus iodine exhibited diminished necrosis of the chondrocytes in the growth plate. In the groups of rats receiving supplemental selenium and selenium plus iodine, the bone volume/tissue volume ratio (BV/TV), the trabecular thickness (Tb.Th), and the trabecular number were increased, while the trabecular separation was decreased. In the 12th week of the experiment, BV/TV and Tb.Th were significantly increased in the selenium plus iodine group compared to the selenium group. It is concluded that feeding the diet from the KBD endemic area caused necrosis of chondrocytes and dysfunctions of bone development similar to the pathological changes that are seen in KBD. Selenium and iodine protected chondrocytes in growth plate and promoted the formation of trabecular bone. The effects of selenium plus iodine on bone formation were more obvious than those of selenium alone.

Selenium in reproductive health

Selenium is an essential trace element of importance to human biology and health. Increasing evidence suggests that this mineral plays an important role in normal growth and reproduction in animals and humans, and selenium supplementation is now recommended as part of public health policy in geographical areas with severe selenium deficiency in soil. This review addresses the biological functions of selenium followed by a detailed review of associations between selenium status and reproductive health. In many countries, selenium dietary intake falls below the recommended nutrient intakes and is inadequate to support maximal expression of the selenoenzymes. Numerous reports implicate selenium deficiency in several reproductive and obstetric complications including male and female infertility, miscarriage, preeclampsia, fetal growth restriction, preterm labor, gestational diabetes, and obstetric cholestasis. Currently, there is inadequate information from the available small intervention studies to inform public health strategies. Larger intervention trials are required to reinforce or refute a beneficial role of selenium supplementation in disorders of reproductive health.

Plasma selenium, zinc, copper and lipid levels in postmenopausal Turkish women and their relation with osteoporosis

It has been shown that the trace elements and lipids play role in the growth, development and maintenance of bones. We aimed to investigate serum selenium (Se), zinc (Zn), copper (Cu) and lipid (total cholesterol, triglyceride (TG), high density lipoprotein-cholesterol, low-density lipoprotein-cholesterol) levels in postmenopausal women with osteoporosis, osteopenia and in healthy controls, and to determine the relationship between Se, Zn, Cu and lipid parameters and bone mineral density (BMD). The study included 107 postmenopausal women; 35 healthy (group 1), 37 osteopenic (group 2) and 35 osteoporotic (group 3). The women in all three groups were carefully matched for body mass index (BMI). Serum concentrations of Se, Zn and Cu were measured by atomic absorption spectrophotometry. Plasma Se, Cu, Zn and lipid levels were similar in all groups (p > 0.05). When we combined the women in each of the three groups, and considered them as one group (n = 107) we found a positive correlation between BMI and lumbar vertebra BMD, femur neck BMD, femur total BMD; a positive correlation between TG and femur neck BMD, femur total BMD; a positive correlation between Zn and lumbar vertebra BMD (total T score) (p < 0.05). There was no correlation between Se, Cu, Zn, P and lipid parameters (p > 0.05). Although BMI has a positive effect on BMD, trace elements and lipids, except Zn and TG, did not directly and correlatively influence BMD. Further studies are needed to clarify the role and relationship of trace elements and lipid parameters in postmenopausal osteoporosis.

Synthesis of vitamin-selenium complex and its effects on proteins and tumor cells

A selenium-vitamin P complex (SEVP) was synthesized and its structure was determined by IR, LC-MS and (1)H NMR. Its biological effects on bovine serum albumin (BSA) and human colon carcinoma tumor cells were studied by molecular spectra, MTT and flow cytometry. The interaction of SEVP and BSA was discussed by fluorescence quenching method and Förster non-radiation energy transfer theory. The thermodynamic parameters ΔH(θ), ΔG(θ), ΔS(θ) at different temperatures were calculated and the results indicate the interaction is an exothermic as well as entropy-driven process. Hydrogen bond and electrostatic force played major role in the reaction. The binding geometry and conformation changes of BSA were investigated by fluorescence probe technique and circular dichroism (CD) spectra. The effects of SEVP on human colon carcinoma tumor cells HT29 were tested by MTT method and flow cytometry (FCM). The MTT results show the proliferation of HT29 tumor cells were inhibited by SEVP and the inhibition was associated with dose and time. The FCM analysis disclosed SEVP interrupted the DNA synthesis of tumor cells at S phase.

Risk factors for incident osteoarthritis of the hip and knee

This article reviews the published risk factors associated with incident osteoarthritis of the lower extremity weight-bearing joints. Systemic risk factors include factors such as age, ethnicity, gender and genetic variables. Local risk factors are variables such as obesity, previous knee injury and occupational activities. Challenges in the study of incident osteoarthritis, and promising potential future study directions are also reviewed.

Selenium, selenoproteins and the thyroid gland: interactions in health and disease

The trace element selenium is an essential micronutrient that is required for the biosynthesis of selenocysteine-containing selenoproteins. Most of the known selenoproteins are expressed in the thyroid gland, including some with still unknown functions. Among the well-characterized selenoproteins are the iodothyronine deiodinases, glutathione peroxidases and thioredoxin reductases, enzymes involved in thyroid hormone metabolism, regulation of redox state and protection from oxidative damage. Selenium content in selenium-sensitive tissues such as the liver, kidney or muscle and expression of nonessential selenoproteins, such as the glutathione peroxidases GPx1 and GPx3, is controlled by nutritional supply. The thyroid gland is, however, largely independent from dietary selenium intake and thyroid selenoproteins are preferentially expressed. As a consequence, no explicit effects on thyroid hormone profiles are observed in healthy individuals undergoing selenium supplementation. However, low selenium status correlates with risk of goiter and multiple nodules in European women. Some clinical studies have demonstrated that selenium-deficient patients with autoimmune thyroid disease benefit from selenium supplementation, although the data are conflicting and many parameters must still be defined. The baseline selenium status of an individual could constitute the most important parameter modifying the outcome of selenium supplementation, which might primarily disrupt self-amplifying cycles of the endocrine-immune system interface rectifying the interaction of lymphocytes with thyroid autoantigens. Selenium deficiency is likely to constitute a risk factor for a feedforward derangement of the immune system-thyroid interaction, while selenium supplementation appears to dampen the self-amplifying nature of this derailed interaction.

The role of iodine in human growth and development

Iodine is an essential component of the hormones produced by the thyroid gland. Thyroid hormones, and therefore iodine, are essential for mammalian life. Iodine deficiency is a major public health problem; globally, it is estimated that two billion individuals have an insufficient iodine intake. Although goiter is the most visible sequelae of iodine deficiency, the major impact of hypothyroidism due to iodine deficiency is impaired neurodevelopment, particularly early in life. In the fetal brain, inadequate thyroid hormone impairs myelination, cell migration, differentiation and maturation. Moderate-to-severe iodine deficiency during pregnancy increases rates of spontaneous abortion, reduces birth weight, and increases infant mortality. Offspring of deficient mothers are at high risk for cognitive disability, with cretinism being the most severe manifestation. It remains unclear if development of the offspring is affected by mild maternal iodine deficiency. Moderate-to-severe iodine deficiency during childhood reduces somatic growth. Correction of mild-to-moderate iodine deficiency in primary school aged children improves cognitive and motor function. Iodine prophylaxis of deficient populations with periodic monitoring is an extremely cost effective approach to reduce the substantial adverse effects of iodine deficiency throughout the life cycle.

SNP and mRNA expression for glutathione peroxidase 4 in Kashin-Beck disease

Kashin-Beck disease (KBD) is a chronic endemic osteoarthropathy, which mainly occurs in West and Northeast China. Epidemiological studies suggest that Se deficiency is an important environmental factor for the incidence of KBD. Glutathione peroxidase 4 (GPx4) belongs to the glutathione peroxidase family, which is crucial for optimal antioxidant defences. Our purpose is to investigate the putative association between GPx4 polymorphisms and the risk of KBD. Restriction fragment length polymorphism-PCR was used to detect two SNP (rs713041, rs4807542) in 219 cases and 194 controls in Han Chinese subjects, and quantitative analysis for the GPx4 mRNA level was performed by the real-time PCR method. The results revealed that linkage disequilibrium existed in the two SNP. A significant difference was observed in the haplotype A-T (P = 0·0066) of GPx4, which was obviously lower in the KBD cases (0·006 v. 0·032 %). Correlation analysis based on a single locus showed no association between each SNP and KBD risk. Furthermore, the GPx4 mRNA level was dramatically lower in the blood of KBD patients. Overall, our finding indicated GPx4 polymorphisms and decreased mRNA level may be related to the development of KBD in the Chinese population, suggesting GPx4 as a possible candidate susceptibility gene for KBD.

Selenium in human health and disease

This review covers current knowledge of selenium in the environment, dietary intakes, metabolism and status, functions in the body, thyroid hormone metabolism, antioxidant defense systems and oxidative metabolism, and the immune system. Selenium toxicity and links between deficiency and Keshan disease and Kashin-Beck disease are described. The relationships between selenium intake/status and various health outcomes, in particular gastrointestinal and prostate cancer, cardiovascular disease, diabetes, and male fertility, are reviewed, and recent developments in genetics of selenoproteins are outlined. The rationale behind current dietary reference intakes of selenium is explained, and examples of differences between countries and/or expert bodies are given. Throughout the review, gaps in knowledge and research requirements are identified. More research is needed to improve our understanding of selenium metabolism and requirements for optimal health. Functions of the majority of the selenoproteins await characterization, the mechanism of absorption has yet to be identified, measures of status need to be developed, and effects of genotype on metabolism require further investigation. The relationships between selenium intake/status and health, or risk of disease, are complex but require elucidation to inform clinical practice, to refine dietary recommendations, and to develop effective public health policies.

Epidemiology of osteoarthritis

Osteoarthritis (OA) is the most common joint disorder in the United States. Symptomatic knee OA occurs in 10% men and 13% in women aged 60 years or older. The number of people affected with symptomatic OA is likely to increase due to the aging of the population and the obesity epidemic. OA has a multifactorial etiology, and can be considered the product of an interplay between systemic and local factors. Old age, female gender, overweight and obesity, knee injury, repetitive use of joints, bone density, muscle weakness, and joint laxity all play roles in the development of joint OA, particularly in the weight-bearing joints. Modifying these factors may reduce the risk of OA and prevent subsequent pain and disability.

Selenoprotein P gene r25191g/a polymorphism and quantification of selenoprotein P mRNA level in patients with Kashin-Beck disease

Kashin-Beck disease (KBD) is an endemic and deformable osteoarthrosis. Epidemiological study has revealed that lower Se level is the principal environmental factor in the pathogenesis of KBD. Selenoprotein P (SEPP1) is a special selenoprotein, which is the primary form of Se in vivo. Our aim was to investigate the putative association of SEPP1 r25191g/a single nucleotide polymorphism (SNP) with KBD risk and the SEPP1 transcriptional levels in whole blood and articular cartilage tissue of KBD cases and controls, respectively. One hundred and sixty-seven cases with KBD and 166 control subjects from Shaanxi province of China were included in the present study. The detection of SNP r25191g/a in the 3' untranslated region was performed using an efficient technique, tetra-primer amplification refractory mutation system PCR. A quantitative analysis of SEPP1 mRNA in KBD and control groups by real-time PCR was also performed. The present results show no significant difference in genotype and allele distribution of SNP r25191g/a between individuals with KBD and controls (P = 0·279 and 0·428, respectively). There was also no association between SNP r25191g/a and risk of KBD (OR 1·153; 95 % CI 0·533, 2·496). However, the frequency of the rare genotype AG of SNP r25191g/a was significantly lower in Chinese population than in the Caucasians. It was shown that the SEPP1 mRNA expression in whole blood was lower in KBD patients than in the control group (0·149-fold, P < 0·001), but that it was much higher in articular cartilage tissue (4·53-fold, P = 0·012). Our aim was to lay a foundation for us to further study the association between the pathogenesis of KBD and SEPP1.

Efficacy of celecoxib, meloxicam and paracetamol in elderly Kashin-Beck disease (KBD) patients

The objective of this study was to compare the efficacy and tolerability of celecoxib, meloxicam and paracetamol in late Kashin-Beck disease. Adults (n = 168) with Kashin-Beck disease were randomised in clusters to receive six week courses of celecoxib 200 mg once daily, meloxicam 7.5 mg once daily or paracetamol 300 mg three times daily. Efficacy assessments included overall joint pain intensity and Western Ontario and McMaster Universities Osteoarthritis Index subscales; tolerability was evaluated by adverse event and physician reporting. Celecoxib and meloxicam were efficacious in relieving pain and improving stiffness, but unable to improve physical function after six weeks. Paracetamol was efficacious in relieving pain, but unable to improve morning stiffness and physical function after six weeks. Celecoxib and meloxicam provide predictable and sustained relief from pain and stiffness. Paracetamol can relieve the pain. None of the treatments improved impaired physical function in Kashin-Beck disease.

Association study between polymorphisms in selenoprotein genes and susceptibility to Kashin-Beck disease

OBJECTIVES

Kashin-Beck disease (KBD) is a disabling osteoarthropathy involving growth cartilage endemic to selenium (Se)-deficient regions in China. Associations between genetic variation in selenoprotein genes and susceptibility to many diseases have recently been investigated but few studies have been performed on KBD. We found four genetic polymorphisms in selenoprotein genes and assessed their association with increased susceptibility to KBD.

METHODS

Four polymorphisms including GPX1 (rs1050450), TrxR2 (rs5748469), SEPP1 (rs7579) and DIO2 (rs225014) were analyzed for 161 KBD patients and 312 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or tetra-primer amplification refractory mutation system PCR (Tetra-primer ARMS PCR). Glutathione peroxidase (GPX) activity in whole blood was measured using a GPX assay kit. The mRNA expression of GPX1, nuclear factor-kappaB (NF-kappaB) p65 and p53 in both whole blood and articular cartilage tissue were detected using Real-Time PCR.

RESULTS

The genotypic and allelic frequency of GPX1 Pro198Leu was significantly different between KBD patients and controls (P=0.013, P=0.037). A significant increased KBD risk was observed in individuals with Pro/Leu or Leu/Leu (odds ratio=1.781; 95% confidence interval: 1.127-2.814) compared with Pro/Pro. No association was observed between the other three single nucleotide polymorphisms (SNPs) and KBD risk. In addition, GPX enzyme activity in whole blood was lower in the KBD group (P<0.01), and the GPX activity in whole blood decreased significantly in a subgroup of individuals representing Pro/Leu and Leu/Leu compared to Pro/Pro (P<0.01). In whole blood and articular cartilage tissue samples of KBD patients, GPX1 and NF-kappaB p65 mRNA levels were lower (P<0.01) while p53 levels were higher (P<0.001).

CONCLUSION

GPX1 Pro198Leu is a potential genetic risk factor in the development of KBD and the GPX1 Leu allele is significantly associated with higher KBD risk among the Chinese Han population and with lower GPX enzyme activity. The expression of apoptosis related molecules in KBD patients significantly differs from controls.

The impact of common micronutrient deficiencies on iodine and thyroid metabolism: the evidence from human studies

Deficiencies of micronutrients are highly prevalent in low-income countries. Inadequate intake of iodine impairs thyroid function and results in a spectrum of disorders. Other common deficiencies of micronutrients such as iron, selenium, vitamin A, and possibly zinc may interact with iodine nutrition and thyroid function. Randomised controlled intervention trials in iodine- and iron-deficient populations have shown that providing iron along with iodine results in greater improvements in thyroid function and volume than providing iodine alone. Vitamin A supplementation given alone or in combination with iodised salt can have a beneficial impact on thyroid function and thyroid size. Despite numerous studies of the effect of selenium on iodine and thyroid metabolism in animals, most published randomised controlled intervention trials in human populations failed to confirm an impact of selenium supplementation on thyroid metabolism. Little evidence is available on interactions between iodine and zinc metabolism.

Osteo-chondroprogenitor-specific deletion of the selenocysteine tRNA gene, Trsp, leads to chondronecrosis and abnormal skeletal development: a putative model for Kashin-Beck disease

Kashin-Beck disease, a syndrome characterized by short stature, skeletal deformities, and arthropathy of multiple joints, is highly prevalent in specific regions of Asia. The disease has been postulated to result from a combination of different environmental factors, including contamination of barley by mold mycotoxins, iodine deficiency, presence of humic substances in drinking water, and, importantly, deficiency of selenium. This multifunctional trace element, in the form of selenocysteine, is essential for normal selenoprotein function, including attenuation of excessive oxidative stress, and for the control of redox-sensitive molecules involved in cell growth and differentiation. To investigate the effects of skeletal selenoprotein deficiency, a Cre recombinase transgenic mouse line was used to trigger Trsp gene deletions in osteo-chondroprogenitors. Trsp encodes selenocysteine tRNA^[Ser]Sec, required for the incorporation of selenocysteine residues into selenoproteins. The mutant mice exhibited growth retardation, epiphyseal growth plate abnormalities, and delayed skeletal ossification, as well as marked chondronecrosis of articular, auricular, and tracheal cartilages. Phenotypically, the mice thus replicated a number of the pathological features of Kashin-Beck disease, supporting the notion that selenium deficiency is important to the development of this syndrome.

Kashin-Beck disease (KBD) is a severe, chronic, and deforming musculoskeletal disease affecting millions of individuals in specific regions of Asia. Starting in childhood, the disorder leads to joint and limb deformities, short stature, and delayed skeletal development. Articular cartilage damage due to chondronecrosis and limb deformities then lead to secondary osteoarthritis and severe disability. Factors proposed to cause KBD include selenium deficiency, iodine deficiency, contamination of grain with toxic molds, and humic substances in well water. Soil and water deficiency in selenium (and iodine) are a consistent feature of KBD endemic areas, and affected individuals show profound deficiencies of these two elements. Thus far, there have been no convincing rodent models of KBD based on selenium (and/or iodine) deficiency achieved through dietary manipulation. Our manuscript describes a conditional gene mutation approach in mice that, in effect, mimics severe selenium deficiency, achieving this specifically within skeletal progenitor cells. By deleting selenocysteine tRNA (required for normal selenoprotein activity) in osteo-chondroprogenitors, we found that mice develop post-natal impairment of skeletal growth, dwarfism, delayed ossification, impaired endochondral bone formation, as well as severe chondronecrosis. Our mutant mouse supports the idea that selenium deficiency is key to the skeletal pathology of KBD.

Regulation and function of selenoproteins in human disease

Selenoproteins are proteins containing selenium in the form of the 21st amino acid, selenocysteine. Members of this protein family have many diverse functions, but their synthesis is dependent on a common set of cofactors and on dietary selenium. Although the functions of many selenoproteins are unknown, several disorders involving changes in selenoprotein structure, activity or expression have been reported. Selenium deficiency and mutations or polymorphisms in selenoprotein genes and synthesis cofactors are implicated in a variety of diseases, including muscle and cardiovascular disorders, immune dysfunction, cancer, neurological disorders and endocrine function. Members of this unusual family of proteins have roles in a variety of cell processes and diseases.

Iodine deficiency

Iodine deficiency has multiple adverse effects in humans, termed iodine deficiency disorders, due to inadequate thyroid hormone production. Globally, it is estimated that 2 billion individuals have an insufficient iodine intake, and South Asia and sub-Saharan Africa are particularly affected. However, about 50% of Europe remains mildly iodine deficient, and iodine intakes in other industrialized countries, including the United States and Australia, have fallen in recent years. Iodine deficiency during pregnancy and infancy may impair growth and neurodevelopment of the offspring and increase infant mortality. Deficiency during childhood reduces somatic growth and cognitive and motor function. Assessment methods include urinary iodine concentration, goiter, newborn TSH, and blood thyroglobulin. But assessment of iodine status in pregnancy is difficult, and it remains unclear whether iodine intakes are sufficient in this group, leading to calls for iodine supplementation during pregnancy in several industrialized countries. In most countries, the best strategy to control iodine deficiency in populations is carefully monitored universal salt iodization, one of the most cost-effective ways to contribute to economic and social development. Achieving optimal iodine intakes from iodized salt (in the range of 150-250 microg/d for adults) may minimize the amount of thyroid dysfunction in populations. Ensuring adequate iodine status during parenteral nutrition has become important, particularly in preterm infants, as the use of povidone-iodine disinfectants has declined. Introduction of iodized salt to regions of chronic iodine deficiency may transiently increase the incidence of thyroid disorders, but overall, the relatively small risks of iodine excess are far outweighed by the substantial risks of iodine deficiency.

Effects of physical environment on the evolution of Kashin-Beck disease in Tibet

In previous studies we observed a proximo-distal gradient of lesion frequencies along the limb, with the distal joints being the most often affected. This suggests an associated effect of environmental factors on the most exposed joints. On a population of 820 children (mean age 13 years) of endemic areas distributed in groups of healthy and severity stages I to III of KBD (Kashin-Beck disease), the effects of different working activities were studied. Heavy work like that of a ploughman were compared to light physical work, e.g. school children, and exposure to cold and history of frostbite were also considered. The most severe stages, II and III, were present in 72% of the ploughman vs. 29% of the schoolchildren, 70% of the shepherds vs. 30% (p < 0.001) of the schoolchildren, and in 65% of the shepherds working in winter vs. 40% of those working in the other seasons (p < 0.001). In the group with history of frostbite, 58% present the severest stages vs. 40% without (p < 0.001). The results confirm a highly significant relation between microtrauma and cold and the severity of the KBD alterations.

On the importance of selenium and iodine metabolism for thyroid hormone biosynthesis and human health

The trace elements iodine and selenium (Se) are essential for thyroid gland functioning and thyroid hormone biosynthesis and metabolism. While iodine is needed as the eponymous constituent of the two major thyroid hormones triiodo-L-thyronine (T3), and tetraiodo-L-thyronine (T4), Se is essential for the biosynthesis and function of a small number of selenocysteine (Sec)-containing selenoproteins implicated in thyroid hormone metabolism and gland function. The Se-dependent iodothyronine deiodinases control thyroid hormone turnover, while both intracellular and secreted Se-dependent glutathione peroxidases are implicated in gland protection. Recently, a number of clinical supplementation trials have indicated positive effects of increasing the Se status of the participants in a variety of pathologies. These findings enforce the notion that many people might profit from improving their Se status, both as a means to reduce the individual health risk as well as to balance a Se deficiency which often develops during the course of illness. Even though the underlying mechanisms are still largely uncharacterised, the effects of Se appear to be exerted via multiple different mechanisms that impact most pronounced on the endocrine and the immune systems.

Selenium for preventing Kashin-Beck osteoarthropathy in children: a meta-analysis

OBJECTIVE

To assess the efficacy of selenium supplementation for prevention of Kashin-Beck Osteoarthropathy in children.

METHODS

We searched eight electronic databases and seven journals (upto July 2007) to identify randomized controlled trials (RCTs) and prospective non-RCTs comparing selenium supplementations with placebo or no intervention for preventing Kashin-Beck disease (KBD). The methodological qualities of included studies were assessed according to the guidelines of Cochrane Handbook for Systematic Reviews of Interventions for RCTs and the method described by Deeks et al. for non-RCTs. Outcomes were presented as Peto-odds ratios (Peto-ORs) with 95% confidence intervals (95% CIs) based on fixed effect model. The number needed to treat (NNT) was calculated. Meta-regression was also conducted to explore the possible impacts of potential confounding variables (place of study, age, selenium form, etc.) of included trials on the incidence of KBD.

RESULTS

Five RCTs and 10 non-RCTs were included in this review. The methodological quality of included studies was low. The pooled Peto-OR and NNT favoring selenium supplement was 0.13 (95% CI: 0.04-0.47) and 21 in RCTs, and 0.16 (95% CI: 0.09-0.30) and 26 in non-RCTs. Meta-regression indicated that the effect of potential confounding variables on KBD incidence was not statistically significant. One trial reported the side effects of nausea and vomiting in the process of selenium supplementation.

CONCLUSIONS

Current evidence supports the benefits of selenium supplementation for prevention of KBD in children. However, the evidence was limited by potential biases and confounders. Large, well-designed trials are still needed.

The adverse effects of mild-to-moderate iodine deficiency during pregnancy and childhood: a review

Iodine is required for the production of thyroid hormones, which are essential for normal brain development, and the fetus, newborn, and young child are particularly vulnerable to iodine deficiency. The iodine requirement increases during pregnancy and recommended intakes are in the range of 220-250 microg/day. Monitoring iodine status during pregnancy is a challenge. New recommendations from World Health Organization suggest that a median urinary iodine concentration >250 microg/L and <500 microg/L indicates adequate iodine intake in pregnancy. Based on this range, it appears that many pregnant women in Western Europe have inadequate intakes. A recent Swiss study has suggested that thyroid-stimulating hormone concentration in the newborn is a sensitive indicator of mild iodine deficiency in late pregnancy. The potential adverse effects of mild iodine deficiency during pregnancy are uncertain. Controlled trials of iodine supplementation in mildly iodine-deficient pregnant women suggest beneficial effects on maternal and newborn serum thyroglobulin and thyroid volume, but no effects on maternal and newborn total or free thyroid hormone concentrations. There are no long-term data on the effect of iodine supplementation on birth outcomes or infant development. New data from well-controlled studies indicate that iodine repletion in moderately iodine-deficient school-age children has clear benefits: it improves cognitive and motor function; it also increases concentrations of insulin-like growth factor 1 and insulin-like growth factor-binding protein 3, and improves somatic growth.

Treatment of iodine deficiency in school-age children increases insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations and improves somatic growth

CONTEXT

Iodine deficiency in utero impairs fetal growth, but the relationship between iodine deficiency and postnatal growth is less clear.

OBJECTIVE

The objective of the study was to determine whether iodine repletion improves somatic growth in iodine-deficient children and investigate the role of IGF-I and IGF binding protein (IGFBP)-3 in this effect.

DESIGN, PARTICIPANTS, AND INTERVENTIONS

Three prospective, double-blind intervention studies were done: 1) in a 10-month study, severely iodine-deficient, 7- to 10-yr-old Moroccan children (n = 71) were provided iodized salt and compared with children not using iodized salt; 2) in a 6-month study, moderately iodine-deficient, 10- to 12-yr-old Albanian children (n = 310) were given 400 mg iodine as oral iodized oil or placebo; 3) in a 6-month study, mildly iodine-deficient 5- to 14-yr-old South African children (n = 188) were given two doses of 200 mg iodine as oral iodized oil or placebo. At baseline and follow-up, height, weight, urinary iodine (UI), total T4 (TT4), TSH, and IGF-I were measured; in Albania and South Africa, IGFBP-3 was also measured.

RESULTS

In all three studies, iodine treatment increased median UI to more than 100 microg/liter, whereas median UI in the controls remained unchanged. In South Africa, iodine repletion modestly increased IGF-I but did not have a significant effect on IGFBP-3, TT4, or growth. In Albania and Morocco, iodine repletion significantly increased TT4, IGF-I, IGFBP-3, weight-for-age z scores, and height-for-age z scores.

CONCLUSION

This is the first controlled study to clearly demonstrate that iodine repletion in school-age children increases IGF-I and IGFBP-3 concentrations and improves somatic growth.

Nutritional Epidemiology and Thyroid Hormone Metabolism

Severe iodine deficiency was the main cause of endemic goiter and cretinism. Most of the previously iodine-deficient areas are now supplemented, mainly with iodized salt. The geographical distribution of severe endemic areas has been progressively reduced, and at present, approximately 200 million people living in remote places are still at risk of severe iodine deficiency. International public health programs should be focused first on reaching these populations, and second on auditing and monitoring the operational work of supplementation programs. This second point is essential to prevent iodine-induced hyperthyroidism or interruptions of iodine supplement distribution, which could be catastrophic for the fetus and the young infant. Echography brings a complementary tool to clinical assessment of goiter by palpation. Inductively coupled plasma-mass spectrometry brings at least a definitive gold standard for iodine measurement and thyroid hormone measurement. Thiocyanate overload has been clearly documented as a goitrogen in Central Africa, and when associated with selenium deficiency, it may be included as risk factor for endemic myxedematous cretinism. Variable exposure to different environmental risk factors is likely the explanation of the variable distribution of two types of endemic cretinism (neurological and myxedematous), and the clinical overlap of the pathogeny of both syndromes is more important than previously described. It is possible that Kashin-Beck osteoarthropathy is another evanescent endemic disease that will disappear with the correction of iodine deficiency.

Iodine deficiency mitigates growth retardation and osteopenia in selenium-deficient rats

Selenium deficiency is associated with impaired bone metabolism and osteopenia in rats. However, it is not known how combined selenium and iodine deficiency affects bone metabolism. Therefore, we investigated the effect of selenium and iodine deficiency on bone metabolism in 2nd-generation selenium- and iodine-deficient rats. Selenium-deficient (Se-), iodine-deficient (I-), selenium- and iodine-deficient (Se-/I-), and control rats (Se+/I+), were pair-fed their respective diets until they were 74 d old. Each pair-fed rat was fed a selenium-adequate diet in the same amount as that consumed the day before by its selenium-deficient counterpart, taking food spillage into account. The skeletal phenotype was analyzed by dual energy X-ray absorptiometry, histomorphometry, and bone metabolism markers. Erythrocyte glutathione peroxidase activity (Gpx) and plasma thyroid hormones were measured to assess selenium and iodine status, respectively. In both Se-/I+ and Se-/I- rats, Gpx was reduced by 99% compared with pair-fed Se+/I+ and Se+/I- rats (P < 0.001). Iodine deficiency reduced plasma thyroxine by 64% in the 2 iodine-deficient groups (P < 0.001). Body weight, tail length, plasma insulin-like growth factor, pituitary growth hormone concentration, and femur and tibia bone mineral density were significantly greater in the Se-/I- rats than in the Se-/I+ rats. This study shows that iodine deficiency mitigated growth retardation and osteopenia in 2nd-generation selenium-deficient rats and suggests that adequate selenium status should be ensured before measures are taken to correct iodine deficiency.

Selenium, the thyroid, and the endocrine system

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.

Selenium and the control of thyroid hormone metabolism

Thyroid hormone synthesis, metabolism and action require adequate availability of the essential trace elements iodine and selenium, which affect homeostasis of thyroid hormone-dependent metabolic pathways. The three selenocysteine-containing iodothyronine deiodinases constitute a novel gene family. Selenium is retained and deiodinase expression is maintained at almost normal levels in the thyroid gland, the brain and several other endocrine tissues during selenium deficiency, thus guaranteeing adequate local and systemic levels of the active thyroid hormone T(3). Due to their low tissue concentrations and their mRNA SECIS elements deiodinases rank high in the cellular and tissue-specific hierarchy of selenium distribution among various selenoproteins. While systemic selenium status and expression of abundant selenoproteins (glutathione peroxidase or selenoprotein P) is already impaired in patients with cancer, disturbed gastrointestinal resorption, unbalanced nutrition or patients requiring intensive care treatment, selenium-dependent deiodinase function might still be adequate. However, disease-associated alterations in proinflammatory cytokines, growth factors, hormones and pharmaceuticals modulate deiodinase isoenzyme expression independent from altered selenium status and might thus pretend causal relationships between systemic selenium status and altered thyroid hormone metabolism. Limited or inadequate supply of both trace elements, iodine and selenium, leads to complex rearrangements of thyroid hormone metabolism enabling adaptation to unfavorable conditions.

Effectiveness of selenium supplements in a low-selenium area of China

BACKGROUND

Selenium is an essential micronutrient with a recommended dietary allowance for adults of 55 mug/d. It functions as an essential constituent of selenoproteins. Although there is no evidence of selenium deficiency in the United States, people in many other areas of the world are selenium deficient, with the consequence that they are unable to express their selenoproteins fully.

OBJECTIVE

We carried out a supplementation trial in a selenium-deficient population in China to assess the requirement for selenium as selenite and as selenomethionine.

DESIGN

One hundred twenty subjects with an average selenium intake of 10 mug/d were randomly assigned and administered tablets containing no selenium or amounts as high as 66 mug Se/d for 20 wk. Plasma was sampled before supplementation and at 4-wk intervals during supplementation and was assayed for the 2 plasma selenoproteins, glutathione peroxidase and selenoprotein P.

RESULTS

Full expression of glutathione peroxidase was achieved with 37 mug Se/d as selenomethionine and with 66 mug/d as selenite. Full expression of selenoprotein P was not achieved at the highest doses of either form.

CONCLUSIONS

Full expression of selenoprotein P requires a greater selenium intake than does full expression of plasma glutathione peroxidase. This suggests that selenoprotein P is a better indicator of selenium nutritional status than is glutathione peroxidase and that the recommended dietary allowance of selenium, which was set with the use of glutathione peroxidase as the index of selenium status, should be revised. Selenium as selenomethionine had nearly twice the bioavailability of selenium as selenite.