Abnormal brain iron accumulation in obstructive sleep apnea: A quantitative MRI study in the HypnoLaus cohort

Diagnostic value of quantitative brain synthetic magnetic resonance imaging in patients with obstructive sleep apnoea

AIM

Investigating the diagnostic value of quantitative brain synthetic magnetic resonance imaging (SyMRI) in adult patients with obstructive sleep apnoea (OSA) and brain microstructural injury.

MATERIALS AND METHODS

Fifty untreated OSA patients at initial diagnosis who were diagnosed were collected as the OSA group, with 36 non-OSA patients as the normal group. Afterwards, all subjects underwent cranial scans using GE SIGNA Architect 3.0T magnetic resonance imaging. Meanwhile, the differences in grey matter relaxation values, white matter relaxation values, and proton density (PD) values between the 2 groups were compared, followed by an analysis of the correlation between the above parameters and apnoea-hypopnoea index (AHI).

RESULTS

Compared with the normal group, T2 values of grey and white matter were significantly decreased, and T1 and PD values of grey matter were slightly decreased in the OSA group, with significant differences (P<005). In the meantime, receiver operating characteristic curves suggested the highest area under the curve (AUC) (0.74) and a high sensitivity (92.0%) of T2 values of white matter, along with a low specificity (52.0%). Additionally, the T1 and T2 values of grey matter shared the same AUC (0.69), which exhibited high specificity (75.0%) and high sensitivity (92.0%), respectively. Furthermore, Spearman correlation analysis indicated that T1 values of grey matter were positively correlated with AHI, while T2 values of grey and white matter were negatively correlated with AHI (P<0.05).

CONCLUSION

SyMRI quantitative imaging parameters are of significant clinical value for adult OSA patients, especially T2 relaxation values, which are beneficial for the early diagnosis of brain microstructural injury.

Regional brain iron mapping in obstructive sleep apnea adults

PURPOSE

Obstructive sleep apnea (OSA) subjects show significant white matter injury, including myelin changes in several brain areas, potentially from impaired glial cells, contributing to increased iron levels that escalate neurodegeneration, but brain iron loads are unclear. Our aim was to examine regional brain iron load, using T2∗-relaxometry, in OSA adults before and after continuous positive airway pressure (CPAP) treatment over controls.

METHODS

We performed T2∗-weighted imaging using a 3.0-T MRI scanner on 35 OSA adults, who were followed after 3- and 9- mo CPAP treatment, and 67 controls. Using T2∗-weighted images, R2∗maps were calculated, normalized, and smoothed. The smoothed R2∗ maps, as well as average R2∗ values extracted from different brain regions were compared between OSA and controls using ANCOVA (covariates: age and sex) and paired t-tests in OSA adults.

RESULTS

Multiple brain areas in OSA showed increased R2∗ values before CPAP, indicative of higher iron, over controls and included the amygdala, insula, hippocampus, cerebellum, medulla, and pons nearby areas. The R2∗ values continued to increase in multiple sites at 3-mo CPAP treatment in OSA, and those sites included the cerebellum, thalamus, and cingulate. However, after 9-mo CPAP usage, none of the brain regions showed increased R2∗ values in OSA over baseline.

CONCLUSIONS

OSA patients show increased iron content in multiple sites over controls, which progressively increased in several sites, even after 3-mo CPAP use, and started to clear after 9-mo. The findings suggest a means for intervention to lessen brain injury by interfering with iron accumulation in OSA.

The impact of chronic intermittent hypoxia on enzymatic activity in memory-associated brain regions of male and female rats

BACKGROUND

Obstructive sleep apnea (OSA) is an intermittent hypoxia disorder associated with cognitive dysfunction, including learning and memory impairments. There is evidence that alterations in protease activity and neuronal activation are associated with cognitive dysfunction, are dependent on sex, and may be brain region-specific. However, the mechanisms mediating OSA-induced cognitive impairments are unclear. Therefore, we used a rat model of OSA, chronic intermittent hypoxia (CIH) to investigate protease activity (e.g., calpain and caspase-3) on spectrin, a cytoskeletal protein associated with neurotransmitter release, and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory.

METHODS

Male and female Sprague Dawley rats were exposed to CIH or room air (normoxic) for 14 days. We quantified protease activity and cleaved spectrin products, along with EGR-1 protein expression in hippocampal subregions (CA1, CA3), cortical regions [entorhinal cortex (ETC), retrosplenial cortex (RSC), cerebellar cortex (CC)], and subcortical regions [raphe nucleus (RN), locus coeruleus (LC)] associated with learning and memory. Within each group, Pearson correlations of calpain activity, caspase-3 activity, and EGR-1 expression were performed between brain regions. Sex differences within normoxic and CIH correlations were examined.

RESULTS

CIH dysregulated calpain activity in male ETC, and female CA1 and RSC. CIH dysregulated caspase-3 activity in male RN, and female CA1 and RSC. CIH decreased calpain and caspase-3 cleavage products in male ETC. CIH decreased calpain-cleaved spectrin in male RSC but increased these products in female RSC. EGR-1 expression was decreased in male and female RN. Correlational analysis revealed CIH increased excitatory connections in males and increased inhibitory connections in females. EGR-1 expression in males shifted from negative to positive correlations.

CONCLUSIONS

Overall, these data indicate CIH dysregulates protease activity and impairs neuronal function in a brain region- and sex-dependent manner. This indicates that males and females exhibit sex-specific vulnerabilities to mild OSA. These findings concur with our previous behavioral studies that demonstrated memory impairment in CIH-exposed rats.

The impact of chronic intermittent hypoxia on enzymatic activity in memory-associated brain regions of male and female rats

Background

Obstructive sleep apnea (OSA) is an intermittent hypoxia disorder associated with cognitive dysfunction, including learning and memory impairments. There is evidence that alterations in protease activity and neuronal activation as associated with cognitive dysfunction, are dependent on sex, and may be brain region-specific. However, the mechanisms mediating OSA-induced cognitive impairments are unclear. Therefore, we used a rat model of OSA, chronic intermittent hypoxia (CIH), to investigate protease activity (e.g., calpain and caspase-3) and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory. We used a rat model of OSA known as chronic intermittent hypoxia (CIH) to investigate protease activity (calpain and caspase-3) and neuronal activation (early growth response protein 1, EGR-1) in brain regions associated with learning and memory.

Methods

Male and female Sprague Dawley rats were exposed to CIH or room air (normoxic) for 14 days. We quantified protease activity and cleaved spectrin products, along with EGR-1 protein expression in hippocampal subregions (CA1, CA3), cortical regions [entorhinal cortex (ETC), retrosplenial cortex (RSC), cerebellar cortex (CC)], and subcortical regions [raphe nucleus (RN), locus coeruleus (LC)] associated with learning and memory. Within each group, Pearson correlations of calpain activity, caspase-3 activity, and EGR-1 expression were performed between brain regions. Sex differences within normoxic and CIH correlations were examined.

Results

CIH dysregulated calpain activity in male ETC and female CA1 and RSC. CIH dysregulated caspase-3 activity in male RN and female CA1 and RSC. CIH decreased calpain and caspase-3 cleavage products in male ETC. CIH decreased calpain-cleaved spectrin in male RSC but increased these products in female RSC. EGR-1 expression was decreased in male and female RN. Correlational analysis revealed CIH increased excitatory connections in males and increased inhibitory connections in females. EGR-1 expression in males shifted from negative to positive correlations.

Conclusions

Overall, these data show that CIH dysregulates protease activity and impairs neuronal function in a brain region- and sex-dependent manner. This indicates that males and females exhibit sex-specific vulnerabilities to mild OSA. These findings concur with our previous behavioral studies that demonstrated memory impairment in CIH-exposed rats.

The interaction between plasma polymetals and lifestyle on cognitive dysfunction in occupational aluminum exposed workers: A cross-sectional study in China

OBJECTIVE

To investigate the interaction between plasma polymetallic exposure and lifestyle factors on cognitive function abnormalities in occupational aluminum workers. The aim is to develop a new occupational health management model that integrates lifestyle behaviors with occupational activities to comprehensively protect the health of these workers.

METHOD

476 Participants were recruited from an aluminum factory in Shanxi, China. Cognitive functioning was assessed using the Montreal Cognitive Assessment Scale (MoCA). Plasma polymetallic levels were measured using ICP-MS. Logistic regression analyzed the relationship between nine plasma metals, lifestyle factors, and cognitive abnormalities. A 3D model validated the interaction between metals and analyzed the combined effects of plasma metals and lifestyle on MoCA scores. The Chi-squared Automatic Interaction Detector (CHAID) decision tree was used to identify factors influencing cognitive dysfunction.

RESULTS

High blood aluminum concentration (>47.85 μg/L), high blood lithium concentration(>3.15 μg/L), as well as sleep time(≤7 h and > 8 h), smoking, alcohol consumption, and length of mobile phone use(≥2 h) were risk factors for abnormal cognitive functioning. In addition aluminum and lithium have a multiplicative interaction on cognitive function(OR=1.86,95 %CI:1.14,3.050). There was an interaction between high plasma levels of aluminum and lithium and smoking on cognitive function in workers, and an interaction between high plasma levels of aluminum and lithium and sleep duration ≤7 or >8 h on cognitive function in workers.

CONCLUSION

The levels of blood metal elements aluminum and lithium, as well as sleep time, smoking, drinking, and length of mobile phone use, are risk factors for cognitive dysfunction in occupational aluminum workers. There are the synergetic effect to increase the risk of cognitive dysfunction between blood aluminum concentration ≥50.59μg/L and blood lithium concentration ≥3.44μg/L, sleep duration ≤7h& >8 h, smoking, drinking, mobile phone use ≥2 h.

Associations between quantitative susceptibility mapping with male obstructive sleep apnea clinical and imaging markers

PURPOSE

To quantitatively measure and compare whole-brain iron deposition between OSA patients and a healthy control group, we initially utilized QSM and evaluated its correlation with PSG results and cognitive function.

MATERIALS AND METHODS

A total of 28 OSA patients and 22 healthy control subjects matched in age, education level, and BMI were enrolled in our study. Each participant underwent scanning with 3D T1 and multi-echo GRE sequences. Additionally, PSG results were collected from OSA patients, and they underwent simple cognitive assessments. Finally, we analyzed the relationship between iron content in different brain regions, PSG results, and cognitive ability.

RESULTS

In OSA patients, iron content increased in the left temporal-pole-sup and right putamen, while it decreased in the left fusiform gyrus, left middle temporal gyrus, right inferior occipital gyrus, and right superior temporal gyrus. The correlation analysis between brain iron content and PSG results/cognitive scales is as follows: left fusiform gyrus and MMSE (r = -0.416, p = 0.028); right superior temporal gyrus and MMSE (r = 0.422, p = 0.025); left middle temporal gyrus and average oxygen saturation (r = -0.418, p = 0.027); left temporal-pole-sup and REM stage (rs = 0.466, p = 0.012); the right putamen and N1 stage (rs = 0.393. p = 0.039). Moreover, both MoCA (r = 0.598, p = 0.001) and MMSE (r = 0.456, p = 0.015) show a positive correlation with average oxygen saturation.

CONCLUSION

This study is the first to use QSM technology to show abnormal brain iron levels in OSA. Correlations between brain iron content, PSG, and cognition in OSA may reveal neuropathological mechanisms, aiding OSA diagnosis.

Associations between the multitrajectory neuroplasticity of neuronavigated rTMS-mediated angular gyrus networks and brain gene expression in AD spectrum patients with sleep disorders

INTRODUCTION

The multifactorial influence of repetitive transcranial magnetic stimulation (rTMS) on neuroplasticity in neural networks is associated with improvements in cognitive dysfunction and sleep disorders. The mechanisms of rTMS and the transcriptional-neuronal correlation in Alzheimer's disease (AD) patients with sleep disorders have not been fully elucidated.

METHODS

Forty-six elderly participants with cognitive impairment (23 patients with low sleep quality and 23 patients with high sleep quality) underwent 4-week periods of neuronavigated rTMS of the angular gyrus and neuroimaging tests, and gene expression data for six post mortem brains were collected from another database. Transcription-neuroimaging association analysis was used to evaluate the effects on cognitive dysfunction and the underlying biological mechanisms involved.

RESULTS

Distinct variable neuroplasticity in the anterior and posterior angular gyrus networks was detected in the low sleep quality group. These interactions were associated with multiple gene pathways, and the comprehensive effects were associated with improvements in episodic memory.

DISCUSSION

Multitrajectory neuroplasticity is associated with complex biological mechanisms in AD-spectrum patients with sleep disorders.

HIGHLIGHTS

This was the first transcription-neuroimaging study to demonstrate that multitrajectory neuroplasticity in neural circuits was induced via neuronavigated rTMS, which was associated with complex gene expression in AD-spectrum patients with sleep disorders. The interactions between sleep quality and neuronavigated rTMS were coupled with multiple gene pathways and improvements in episodic memory. The present strategy for integrating neuroimaging, rTMS intervention, and genetic data provide a new approach to comprehending the biological mechanisms involved in AD.

Causal Relationship Between Micronutrient and Sleep Disorder: A Mendelian Randomization Study

Background

Sleep played an important part in human health, and COVID-19 led to a continuous deterioration of sleep. However, the causal relationship between micronutrient and sleep disorder was not yet fully understood.

Methods

In this research, the genetic causal relationship between micronutrient and sleep disorder was analyzed utilizing a two-sample Mendelian randomization (MR). Single nucleotide polymorphisms (SNPs) were used as instrumental variables. The analyses were conducted using the MR-Egger, inverse variance weighted, weighted mode, weighted median, simple mode, Cochran's Q test and leave-one-out.

Results

Our results suggested that 8 genetically predicted micronutrients participated in sleep disorders, including liver iron (L-iron) and iron in sleeping too much, spleen iron (S-iron) in sleeplessness/insomnia, trouble falling or staying asleep, sleep duration (undersleepers) and nonorganic sleeping disorders, iron metabolism disorder (IMD) and vitamin B12 deficiency anaemia (VB12DA) in narcolepsy, urine sodium (uNa) in narcolepsy, sleep apnea syndrome and sleep disorder, vitamin D (VD) in sleep duration (oversleepers), 25-Hydroxyvitamin D (25(OH)D) in trouble falling or staying asleep.

Conclusion

Our study used Mendelian randomization methods at the SNP level to explore the potential causal relationship among L-iron, iron, S-iron, IMD, uNa, 25(OH)D, VD, VB12DA with certain sleep disorder subtypes. Our results uncovered a micronutrient-based strategy for alleviating sleep disorder symptoms.

Ferroptosis-related genes are considered as potential targets for CPAP treatment of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common syndrome characterized by upper airway dysfunction during sleep. Continuous positive airway pressure (CPAP) is the most frequently utilized non-surgical treatment for OSA. Ferroptosis play a crucial role in the physiological diseases caused by chronic intermittent hypoxia, but its involvement in the development of OSA and the exact mechanisms have incompletely elucidated. GSE75097 microarray dataset was used to identify differentially expressed genes between OSA patients and CPAP-treated OSA patients. Subsequently, Gene Ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, STRING database, and FerrDb database were conducted to analyze the biological functions of differentially expressed genes and screen ferroptosis-related genes. Finally, GSE135917 dataset employed for validation. There were 1,540 differentially expressed genes between OSA patients and CPAP-treated OSA patients. These differentially expressed genes were significantly enriched in the regulation of interleukin-1-mediated signaling pathway and ferroptosis-related signaling pathway. Subsequently, 13 ferroptosis-related genes (DRD5, TSC22D3, TFAP2A, STMN1, DDIT3, MYCN, ELAVL1, JUN, DUSP1, MIB1, PSAT1, LCE2C, and MIR27A) were identified from the interaction between differentially expressed genes and FerrDb database, which are regarded as the potential targets of CPAP-treated OSA. These ferroptosis-related genes were mainly involved in cell proliferation and apoptosis and MAPK signaling pathway. Furthermore, DRD5 and TFAP2A were downregulated in OSA patients, which showed good diagnostic properties for OSA, but these abnormal signatures are not reversed with short-term effective CPAP therapy. In summary, the identification of 13 ferroptosis-related genes as potential targets for the CPAP treatment of OSA provides valuable insights into the development of novel, reliable, and accurate therapeutic options.