Correlates of Nonanemic Iron Deficiency in Restless Legs Syndrome

Genetic Association Studies in Restless Legs Syndrome: Risk Variants & Ethnic Differences

BACKGROUND

Genetic association studies have not produced consistent results in restless legs syndrome (RLS).

OBJECTIVES

To conduct a systematic review on genetic association studies in RLS to highlight the common gene variants and ethnic differences.

METHODOLOGY

We conducted Pubmed, Embase, and Cochrane search using terms "Genetic association studies" and "restless legs syndrome" for candidate gene-based studies. Out of the initial 43 studies, 18 case control studies (from 2012 to 2022) were included. Thirteen studies including 10794 Caucasian subjects (4984 RLS cases and 5810 controls) and five studies involving 2009 Asian subjects (796 RLS cases and 1213 controls) were tabulated and analyzed. In addition, three Genome-Wide Association Studies (GWAS) in Asians and Europeans/Caucasians were included for comparisons.

RESULTS

In the Asian population, gene variants in BST1, SNCA Rep1, IL1B, BTBD9, and MAP2K5/SKOR1 increased the risk of RLS (odds ratio range 1.2-2.8). In Caucasian populations, examples of variants that were associated with an increased risk of RLS (odds ratio range 1.1-1.9) include those in GABRR3 TOX3, ADH1B, HMOX1, GLO1, DCDC2C, BTBD9, SKOR1, and SETBP1. Based on the meta-analysis of GWAS studies, the rs9390170 variant in UTRN gene was identified to be a novel genetic marker for RLS in Asian cohorts, whereas rs113851554 in MEIS1 gene was a strong genetic factor among the >20 identified gene variants for RLS in Caucasian populations.

CONCLUSION

Our systemic review demonstrates that multiple genetic variants modulate risk of RLS in Caucasians (such as MEIS1 BTBD9, MAP2K5) and in Asians (such as BTBD9, MAP2K5, and UTRN).

Sex, lies, and iron deficiency: a call to change ferritin reference ranges

Iron deficiency is a very common and treatable disorder. Of all the tests available to diagnose iron deficiency, the serum ferritin is the most able to discriminate iron deficiency from other disorders. However, the reference range for ferritin in many laboratories will lead to underdiagnosis of iron deficiency in women. Studies have shown that 30%-50% of healthy women will have no marrow iron stores, so basing ferritin cutoffs on the lowest 2.5% of sampled ferritins is not appropriate. In addition, several lines of evidence suggest the body physiologic ferritin "cutoff" is 50  ng/mL. Work is needed to establish more realistic ferritin ranges to avoid underdiagnosing a readily treatable disorder.

Overview of the Current Pathophysiology of Fatigue in Multiple Sclerosis, Its Diagnosis and Treatment Options - Review Article

Fatigue is a common, debilitating and often underestimated symptom in patients with multiple sclerosis (MS). The exact pathophysiological mechanism of fatigue in MS is still unknown. However, there are many theories involving different immunological, metabolic and inflammatory mechanisms of fatigue. Owing to the subjective nature of this symptom, its diagnosis is still very limited and is still based only on diagnostic questionnaires. Although several therapeutic agents have been used in the past to try to influence fatigue in MS patients, no single effective approach for the treatment of fatigue has yet been found. This review article aims to provide the reader with information on the current theories on the origin and mechanism of fatigue in MS, as well as diagnostic procedures and, finally, current therapeutic strategies for the management of fatigue in MS patients.

Pyridoxal Derived AIEgen for Fluorescence Turn-off Sensing of Cu2+ and Fe2+ Ions and Fluorescence Imaging of Latent Fingerprints

Schiff base 4-((E)-((E)-(2-hydroxybenzylidene)hydrazono)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol (HSP) was synthesized by condensing vitamin B₆ cofactor pyridoxal with salicylaldehyde hydrazone, and characterized by standard spectroscopic techniques (FT-IR, ¹H NMR, ¹³C NMR, and ESI-MS). The solution of HSP in DMSO/HEPES (10 mM, pH = 7.4) mixed solvents with varying HEPES fractions (f_w) from 0 to 95% showed aggregation-induced emission (AIE). The AIE active HSP in 95% HEPES gave intense fluorescent emission at 570 nm was employed for the detection of metal ions. The fluorescence of HSP was quenched upon adding Cu²⁺ and Fe²⁺ ions. The association constant (K_a) of the Schiff base HSP with Cu²⁺ and Fe²⁺ ions was estimated as 4.08 × 10⁵ M^-1 and 1.23 × 10⁵ M^-1, respectively by using the online analysis tool BindFit v0.5. The HSP showed the detection limit down to 1.75 µM and 1.89 µM for Cu²⁺ and Fe²⁺ ions, respectively. Further, the aggregates of HSP were applied to visualize latent fingerprints (LFPs) over a non-porous glass slide.

Significance of low ferritin without anaemia in screen-detected, adult coeliac disease patients

BACKGROUND

Low ferritin without anaemia has been linked to adverse health effects.

OBJECTIVES

To investigate the prevalence and clinical significance of low ferritin in screen-detected coeliac disease.

METHODS

Seventy-six screen-detected coeliac disease patients were enrolled in the prospective collection of comprehensive clinical, laboratory and histological data at diagnosis and after 1-2 years on a gluten-free diet (GFD). All variables were compared between patients with different ferritin levels.

RESULTS

At coeliac disease diagnosis, six patients had anaemia. Of the 70 nonanaemic patients, ferritin levels were <15 μg/L in 21%, 15-29 μg/L in 19%, 30-99 μg/L in 36% and ≥100 μg/L in 24%. Those with lower ferritin were more often females, had lower body mass index, haemoglobin and villous height-crypt depth ratio and also had higher intra-epithelial lymphocyte CD3+ levels in duodenal biopsies. The groups did not differ in neurological or gastrointestinal symptoms, health-related quality of life, bone mineral density, liver values, vitamin, albumin or coeliac autoantibody levels or the prevalence of comorbidities. Median ferritin levels increased from 41.5 μg/L to 86.0 μg/L on GFD (p < 0.001). Ferritin remained <30 μg/L in 21% of patients but was not associated with dietary compliance, nor was any correlation between changes in ferritin and quality of life, gastrointestinal symptoms, autoantibody levels or degree of histological damage detected.

CONCLUSION

Decreased ferritin is a frequent finding in screen-detected coeliac disease and may not be fully restored on a GFD. However, low ferritin levels are not associated with more severe symptoms or poorer quality of life.

Restless Legs Syndrome and the Eyes: Spectral-Domain Optic Coherence Tomography Study

BACKGROUND

Restless legs syndrome (RLS) is a movement disorder thought to be caused by impaired dopamine action. This study aimed to evaluate possible changes in ocular biometric and optic coherence tomography (OCT) parameters in RLS patients.

METHODS

This is a prospective, cross-sectional comparative study. Consecutive primary and secondary (with iron-deficiency anemia) RLS patients and age-matched and sex-matched controls were enrolled in the study. All participants underwent comprehensive neurological and ophthalmological examinations. Ocular biometric and OCT parameters, such as choroidal thickness, macular thickness, macular volume, ganglion cell layer thickness, inner nuclear cell layer thickness, and retinal nerve fiber layer thickness, were compared.

RESULTS

Fifty-one RLS patients and 50 healthy controls were included in this study. There was no difference between the groups' refraction status, ocular biometric data (axial length, anterior chamber depth, central corneal thickness), or OCT parameters (choroidal thickness, macular thickness, macular volume, ganglion cell layer thickness, inner nuclear cell layer thickness). Primary and secondary (with only iron-deficiency anemia) RLS patients were compared, and there was no difference in their axial length, anterior chamber depth, central corneal thickness or OCT parameters. No significant relationship was found between disease severity or duration and OCT parameters.

CONCLUSIONS

Disease severity and disease duration do not affect OCT parameters in primary or secondary RLS patients. OCT data do not seem to provide information about the course of this disease.

Iron deficiency and common neurodevelopmental disorders—A scoping review

Background

A wealth of human and experimental studies document a causal and aggravating role of iron deficiency in neurodevelopmental disorders. While pre-, peri-, and early postnatal iron deficiency sets the stage for the risk of developing neurodevelopmental disorders, iron deficiency acquired at later ages aggravates pre-existing neurodevelopmental disorders. Yet, the association of iron deficiency and neurodevelopmental disorders in childhood and adolescence has not yet been explored comprehensively.

In this scoping review, we investigate 1) the association of iron deficiency in children and adolescents with the most frequent neurodevelopmental disorders, ADHD, ASD, and FASD, and 2) whether iron supplementation improves outcomes in these disorders.

Method

Scoping review of studies published between 1994 and 2021 using “iron deficiency / iron deficiency anemia” AND “ADHD” OR “autism” OR “FASD” in four biomedical databases. The main inclusion criterion was that articles needed to have quantitative determination of iron status at any postnatal age with primary iron markers such as serum ferritin being reported in association with ADHD, ASD, or FASD.

Results

For ADHD, 22/30 studies and 4/4 systematic reviews showed an association of ADHD occurrence or severity with iron deficiency; 6/6 treatment studies including 2 randomized controlled trials demonstrated positive effects of iron supplementation. For ASD, 3/6 studies showed an association with iron deficiency, while 3/6 and 1/1 systematic literature review did not; 4 studies showed a variety of prevalence rates of iron deficiency in ASD populations; 1 randomized controlled trial found no positive effect of iron supplementation on behavioural symptoms of ASD. For FASD, 2/2 studies showed an association of iron deficiency with growth retardation in infants and children with prenatal alcohol exposure.

Conclusion

Evidence in favor of screening for iron deficiency and using iron supplementation for pediatric neurodevelopmental disorders comes primarily from ADHD studies and needs to be further investigated for ASD and FASD. Further analysis of study methodologies employed and populations investigated is needed to compare studies against each other and further substantiate the evidence created.

Consensus guidelines on the construct validity of rodent models of restless legs syndrome

Our understanding of the causes and natural course of restless legs syndrome (RLS) is incomplete. The lack of objective diagnostic biomarkers remains a challenge for clinical research and for the development of valid animal models. As a task force of preclinical and clinical scientists, we have previously defined face validity parameters for rodent models of RLS. In this article, we establish new guidelines for the construct validity of RLS rodent models. To do so, we first determined and agreed on the risk, and triggering factors and pathophysiological mechanisms that influence RLS expressivity. We then selected 20 items considered to have sufficient support in the literature, which we grouped by sex and genetic factors, iron-related mechanisms, electrophysiological mechanisms, dopaminergic mechanisms, exposure to medications active in the central nervous system, and others. These factors and biological mechanisms were then translated into rodent bioequivalents deemed to be most appropriate for a rodent model of RLS. We also identified parameters by which to assess and quantify these bioequivalents. Investigating these factors, both individually and in combination, will help to identify their specific roles in the expression of rodent RLS-like phenotypes, which should provide significant translational implications for the diagnosis and treatment of RLS.

Fluorescence "Turn-Off" and Colorimetric Sensor for Fe2+, Fe3+, and Cu2+ Ions Based on a 2,5,7-Triarylimidazopyridine Scaffold

Two cyanoimidazopyridine-based sensors (SS1 and SS2) were explored for the colorimetric and fluorometric detection of Fe²⁺, Fe³⁺, and Cu²⁺ ions in the semi-aqueous medium. The "turn-off" fluorescence response of both sensors to these ions was due to the restriction in internal charge transfer. Job's plot and semi-empirical calculations revealed that SS1 and SS2 complexed with Cu²⁺ ions in a 1:1 ratio and Fe^2+/3+ ions in a 2:1 ratio, respectively. The sensors were found to have high binding constant (K _a) values and low detection limit values. FMO analysis using the semi-empirical quantum mechanics method revealed the decrease in energy gap after complexation with metal ions. Sensor-coated filter paper strips were prepared and analyzed, where the color changes in the strips could be utilized for the real-time detection of Fe²⁺, Fe³⁺, and Cu²⁺ ions.

Non-anaemic iron deficiency

Iron deficiency without anaemia is common. Patients may present with unexplained, non-specific symptoms. Iron studies will usually show a low ferritin and low transferrin saturation with a normal haemoglobin concentration. The cause of the iron deficiency should be identified and managed. There is limited evidence about the benefits of giving iron to people who do not have anaemia. If there is iron deficiency, most people can be given oral iron supplements. Iron studies are repeated after 60-90 days of oral iron supplements. Further investigations are needed if the iron deficiency has not been corrected. Some patients, including those who have not responsed to oral supplements may benefit from intravenous iron. There is no role for intramuscular injections of iron.

Akathisia and Restless Legs Syndrome: Solving the Dopaminergic Paradox

Akathisia is an urgent need to move that is associated with treatment with dopamine receptor blocking agents (DRBAs) and with restless legs syndrome (RLS). The pathogenetic mechanism of akathisia has not been resolved. This article proposes that it involves an increased presynaptic dopaminergic transmission in the ventral striatum and concomitant strong activation of postsynaptic dopamine D₁ receptors, which form complexes (heteromers) with dopamine D₃ and adenosine A₁ receptors. It also proposes that in DRBA-induced akathisia, increased dopamine release depends on inactivation of autoreceptors, whereas in RLS it depends on a brain iron deficiency-induced down-regulation of striatal presynaptic A₁ receptors.

Pulse Probiotic Superfood as Iron Status Improvement Agent in Active Women-A Review

Active women or women of reproductive age (15–49 years old) have a high risk of suffering from anaemia. Anaemia is not solely caused by iron deficiency, however, the approaches to improve iron status in both cases are greatly related. Improving the iron status of active women can be done by dietary intervention with functional food. This review aims to provide insights about the functional food role to increase iron absorption in active women and the potency of pulse probiotic superfood development in dry matrices. Results showed that the beneficial effect of iron status is significantly improved by the synergic work between probiotic and prebiotic. Furthermore, chickpeas and lentils are good sources of prebiotic and the consumption of pulses are related with 21st century people’s intention to eat healthy food. There are wide possibilities to develop functional food products incorporated with probiotics to improve iron status in active woman.

An anthracene–quinoline based dual-mode fluorometric–colorimetric sensor for the detection of Fe3+ and its application in live cell imaging

A highly sensitive anthracene–quinoline based dual-mode sensor has been synthesized and used for the fluorometric and colorimetric detection of Fe³⁺ and in live cell imaging.

SNCA-Rep1 polymorphism correlates with susceptibility and iron deficiency in restless legs syndrome

BACKGROUND

Brain iron disequilibrium and dopaminergic dysfunction are key pathophysiological features of Restless Legs Syndrome (RLS). Rep1 polymorphism in the promotor region of SNCA is associated with risk of Parkinson's disease, however its association with RLS and iron status is unclear.

OBJECTIVE

To investigate SNCA-Rep1 polymorphism in RLS and its phenotypes.

METHODS

We recruited RLS patients as well as age and gender matched healthy controls. Demographic information and clinical features of RLS were recorded. Laboratory examinations were performed to exclude possible secondary causes.

RESULTS

215 RLS patients and 369 healthy controls were included. We found that the Rep1 allele 0 homozygosity significantly decreased RLS risk (OR: 0.345; P < 0.0001, and remained significant after the Bonferroni correction). Phenotypic analysis demonstrated that longer Rep1 alleles were associated with increased susceptibility to iron deficiency (53.0% vs 36.1%, P = 0.017), however had no phenotypic significant effects on age, gender, onset age, duration, RLS family history, severity, laterality, extra body involvement and seasonal fluctuation. Multivariate logistic regression analyses confirmed long Rep1 allele was associated with higher risk of iron deficiency in RLS after adjusting for potential confounding factors. In detail, Rep1 allele 2 homozygosity was prone to a higher risk of peripheral iron deficiency in RLS (OR: 4.550, P = 0.006, remained significant after the Bonferroni correction).

CONCLUSION

The SNCA-Rep1 variability modified RLS risk and influenced peripheral iron deficiency in this group of Chinese RLS patients. Rep1 allele 0 homozygosity decreased the risk of RLS, while homozygous allele 2 increased the risk of nonanemic iron deficiency in RLS.