Cognitive Function and Vitamin D Status in the Chinese Hemodialysis Patients

Research progress on the kidney-gut-brain axis in brain dysfunction in maintenance hemodialysis patients

Maintenance hemodialysis (MHD) has become the primary renal replacement therapy for patients with end-stage renal disease. The kidney-gut-brain axis represents a communication network connecting the kidney, intestine and brain. In MHD patients, factors such as uremic toxins, hemodynamic changes, vascular damage, inflammation, oxidative stress, and intestinal dysbiosis in MHD patients refers to a range of clinical syndromes, including brain injury, and is manifested by conditions such as white matter disease, brain atrophy, cerebrovascular disease, cognitive impairment, depression, anxiety, and other behavioral or consciousness abnormalities. Numerous studies have demonstrated the prevalence of these brain disorders in MHD patients. Understanding the mechanisms of brain disorders in MHD patients, particularly through the lens of kidney-gut-brain axis dysfunction, offers valuable insights for future research and the development of targeted therapies. This article reviews the brain dysfunction associated with MHD, the impact of the kidney-brain axis, intestinal barrier damage, gut microbiota dysbiosis caused by MHD, and the role of the gut-brain axis in brain dysfunction.

Association between trace elements and cognitive function among hemodialysis patients in Turkey

INTRODUCTION

Cognitive impairment is common among patients with hemodialysis. Hemodialysis patients have theoretical risks for both deficiency and accumulation of trace elements. We aimed to investigate the relationship between cognitive dysfunction and whole blood levels of trace elements in hemodialysis patients. We also aimed to examine the effect of baseline trace element status and cognitive dysfunction on mortality.

METHODS

Maintenance hemodialysis patients and age-and sex-matched controls were included. The whole blood levels of trace elements were measured by inductively coupled plasma mass spectrometry. Cognitive impairment was defined as a score of ≤24 points on the Montreal Cognitive Assessment test. Executive dysfunction was also defined as Trails A score of more than 75 s and Trails B score of more than 180 s.

FINDINGS

Forty-two patients and 35 controls were included. Cognitive impairment was detected in 69% of the patients and 45.7% of the controls (p = 0.039). Cognitively impaired patients had lower education years (p = 0.003) and higher whole blood levels of manganese (Mn) and lead (Pb) (p = 0.026, p = 0.019, respectively) compared to patients without cognitive impairment. Mn levels were also found statistically higher in patients with executive dysfunction compared to patients without executive dysfunction (p = 0.005). Lower education years and higher Pb levels were independent risk factors for cognitive impairment in hemodialysis patients (odds ratio [OR] 0.589 [95% confidence interval, CI 0.400-0.866, p = 0.007] and OR 1.047 [95% CI 1.001-1.096, p = 0.047, respectively]).

DISCUSSION

Cognitive impairment, especially impaired executive function, is common among patients with hemodialysis patients. Cognitive impairment is not found to be associated in cross-sectional analysis with several modifiable end-stage renal disease- and dialysis-associated factors. The accumulation of trace elements especially Mn and Pb might exacerbate the cognitive dysfunction in hemodialysis patients.

1,25-Dihydroxy Vitamin D3 Facilitates the M2 Polarization and β-Amyloid Uptake by Human Microglia in a TREM2-Dependent Manner

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by dementia as the primary clinical symptom. The production and accumulation of aggregated β-amyloid (Aβ) in patient brain tissues is one of the hallmarks of AD pathogenesis. Microglia, brain-resident macrophages, produce inflammatory cytokines in response to Aβ oligomers or fibrils exacerbating Aβ pathology in AD. HMO6 cells were treated with Aβ42 in the presence or absence of 1,25-dihydroxy vitamin D₃ (1,25(OH)₂D₃) to determine its potential immunomodulatory effects, and the expression of pro-/anti-inflammatory cytokines, M1/M2-associated markers, Toll-like receptors (TLRs), and triggering receptor expressed on myeloid cells 2 (TREM2) was examined. 1,25(OH)₂D₃ was found to suppress Aβ-induced expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6), M1 markers (CD86 and iNOS), and TLR2/4, whilst increasing the expression of anti-inflammatory cytokines (IL-4, IL-10, and CCL17) and M2 markers (CD206 and Arg-1). Furthermore, 1,25(OH)₂D₃ promoted TREM2 expression and Aβ uptake by HMO6 cells, and the enhancement of Aβ uptake and M2 polarization was revealed to be TREM2-dependent. The findings of this study suggest that 1,25(OH)₂D₃ facilitates M2 polarization and Aβ uptake in a TREM2-dependent manner.