Central nervous dysfunction in uremia

Cerebrospinal fluid biomarkers provide evidence for kidney-brain axis involvement in cerebral malaria pathogenesis

Introduction

Cerebral malaria is one of the most severe manifestations of malaria and is a leading cause of acquired neurodisability in African children. Recent studies suggest acute kidney injury (AKI) is a risk factor for brain injury in cerebral malaria. The present study evaluates potential mechanisms of brain injury in cerebral malaria by evaluating changes in cerebrospinal fluid measures of brain injury with respect to severe malaria complications. Specifically, we attempt to delineate mechanisms of injury focusing on blood-brain-barrier integrity and acute metabolic changes that may underlie kidney-brain crosstalk in severe malaria.

Methods

We evaluated 30 cerebrospinal fluid (CSF) markers of inflammation, oxidative stress, and brain injury in 168 Ugandan children aged 18 months to 12 years hospitalized with cerebral malaria. Eligible children were infected with Plasmodium falciparum and had unexplained coma. Acute kidney injury (AKI) on admission was defined using the Kidney Disease: Improving Global Outcomes criteria. We further evaluated blood-brain-barrier integrity and malaria retinopathy, and electrolyte and metabolic complications in serum.

Results

The mean age of children was 3.8 years (SD, 1.9) and 40.5% were female. The prevalence of AKI was 46.3% and multi-organ dysfunction was common with 76.2% of children having at least one organ system affected in addition to coma. AKI and elevated blood urea nitrogen, but not other measures of disease severity (severe coma, seizures, jaundice, acidosis), were associated with increases in CSF markers of impaired blood-brain-barrier function, neuronal injury (neuron-specific enolase, tau), excitatory neurotransmission (kynurenine), as well as altered nitric oxide bioavailability and oxidative stress (p < 0.05 after adjustment for multiple testing). Further evaluation of potential mechanisms suggested that AKI may mediate or be associated with CSF changes through blood-brain-barrier disruption (p = 0.0014), ischemic injury seen by indirect ophthalmoscopy (p < 0.05), altered osmolality (p = 0.0006) and through alterations in the amino acids transported into the brain.

Conclusion

In children with cerebral malaria, there is evidence of kidney-brain injury with multiple potential pathways identified. These changes were specific to the kidney and not observed in the context of other clinical complications.

Bilateral Posterior Fracture-Dislocation of the Shoulders Secondary to Uremic Encephalopathy

Bilateral posterior fracture-dislocation of the shoulder is an uncommon injury pattern usually caused by epileptic seizures. The cause of the seizure activity remains unknown in most cases, although the injury has been associated with several conditions. A 59-year-old man with uncontrolled hypertension presented with new-onset generalized tonic-clonic seizures. He was diagnosed with uremic encephalopathy and bilateral posterior fracture-dislocation of his shoulders. His medical condition required stabilization leading to a delay in definitive surgery and a subsequent poor outcome. This case highlights the previously unknown association between bilateral fracture-dislocation of the shoulders and seizures caused by uremic encephalopathy. In these complex situations with competing clinical priorities, it is important to initiate prompt treatment of the cause in any new-onset seizures, to facilitate expedient surgical management of the orthopaedic injury.

Segmental Abnormalities of White Matter Microstructure in End-Stage Renal Disease Patients: An Automated Fiber Quantification Tractography Study

Background and Purpose: End-stage renal disease (ESRD) results in extensive white matter abnormalities, but the specific damage segment cannot be identified. This study aimed to determine the segmental abnormalities of white matter microstructure in ESRD and its relationship with cognitive and renal function indicators. Methods: Eighteen ESRD patients and 19 healthy controls (HCs) were prospectively recruited. All participants underwent DTI and clinical assessments. Automatic fiber quantification (AFQ) was applied to generate bundle profiles along 16 main white matter tracts. We compared the DTI parameters between groups. Besides, we used partial correlation and multiple linear regression analyses to explore the associations between white matter integrity and cognitive performance as well as renal function indicators. Results: In the global tract level, compared to HCs, ESRD patients had greater MD, AD, and RD values and lower FA value in several fibers (P < 0.05, FDR correction). In the point-wise level, extensive damage existed in specific locations of different fiber tracts, particularly in the left hemisphere (P < 0.05, FDR correction). Among these tracts, the mean AD values of the left cingulum cingulate correlated negatively with MoCA score. Urea and UA level were independent predictors of the AD value of superior component of the left corticospinal. Besides, urea level was the independent predictors of mean MD value of left anterior thalamic radiation (ATR). Conclusion: White matter fiber tract damage in ESRD patients may be characterized by abnormalities in its specific location, especially in the left hemisphere. Aberrational specific located fibers were related to cognitive impairment and renal dysfunction.

Retinal Neurovascular Impairment in Non-diabetic and Non-dialytic Chronic Kidney Disease Patients

Background: Widespread neural and microvascular injuries are common in chronic kidney disease (CKD), increasing risks of neurovascular complications and mortality. Early detection of such changes helps assess the risks of neurovascular complications for CKD patients. As an extension of central nervous system, the retina provides a characteristic window to observe neurovascular alterations in CKD. This study aimed to determine the presence of retinal neurovascular impairment in different stages of CKD. Methods: One hundred fifteen non-diabetic and non-dialytic CKD patients of all stages and a control group of 35 healthy subjects were included. Retinal neural and microvascular parameters were obtained by optical coherence tomography angiography (OCTA) examination. Results: CKD 1-2 group (versus control group) had greater odds of having decreased retinal ganglion cell-inner plexiform layer thickness (GC-IPLt) (odds ratio [OR]: 0.92; 95% confidence interval [CI]: 0.86-0.98), increased ganglion cell complex-focal loss volume (GCC-FLV) (OR: 3.51; 95% CI: 1.27-9.67), and GCC-global loss volume (GCC-GLV) (OR: 2.48; 95% CI: 1.27-4.82). The presence of advanced stages of CKD (CKD 3-5 group versus CKD 1-2 group) had greater odds of having decreased retinal vessel density in superficial vascular plexus (SVP)-WholeImage (OR: 0.77, 95% CI: 0.63-0.92), SVP-ParaFovea (OR: 0.83, 95% CI: 0.71-0.97), SVP-ParaFovea (OR: 0.76, 95% CI: 0.63-0.91), deep vascular plexus (DVP)-WholeImage (OR: 0.89, 95% CI: 0.81-0.98), DVP-ParaFovea (OR: 0.88, 95% CI: 0.78-0.99), and DVP-PeriFovea (OR: 0.90, 95% CI: 0.83-0.98). Besides, stepwise multivariate linear regression among CKD patients showed that β2-microglobulin was negatively associated with GC-IPLt (β: -0.294; 95% CI: -0.469 ∼ -0.118), and parathyroid hormone was positively associated with increased GCC-FLV (β: 0.004; 95% CI: 0.002∼0.006) and GCC-GLV (β: 0.007; 95% CI: 0.004∼0.01). Urine protein to creatinine ratio was positively associated with increased GCC-FLV (β: 0.003; 95% CI: 0.001∼0.004) and GCC-GLV (β: 0.003; 95% CI: 0.001∼0.006). Conclusion: Retinal neuronal impairment is present in early stages of CKD (stages 1-2), and it is associated with accumulation of uremic toxins and higher UACR, while retinal microvascular hypoperfusion, which is associated with worse eGFR, was only observed in relatively advanced stages of CKD (stages 3-5). The results highlight the importance of monitoring retinal neurovascular impairment in different stages of CKD.

Elevated parathyroid hormone levels and cognitive function: A systematic review

OBJECTIVE

To systematically estimate the association between elevated parathyroid hormone (PTH) levels and cognitive function.

METHODS

This review was conducted on ten papers identified through database searches from inception to 31 October 2018. The quality of studies was assessed using the Downs and Black checklist.

RESULTS

There is a low volume of data reporting on the impact of elevated PTH levels on cognitive impairment. The quality of the identified studies ranged from poor (37 %) to good (76 %). Although the results from studies were mixed, one cross-sectional study and one prospective study suggested a link between elevated PTH levels and a decrease in the Mini-Mental State Examination (MMSE) score. Three cross-sectional studies that assessed other cognitive domain in specific domains, such as language, memory and executive function provided mixed results for an association between elevated PTH levels and cognitive function. Two studies showed mixed evidence for a link between elevated PTH levels and poor executive function. One prospective study, one cross-sectional study and three case-control studies provide mixed evidence for an association between higher PTH levels and Alzheimer´s disease (AD). Two studies showed limited evidence for an association between elevated PTH levels and vascular dementia.

CONCLUSION

This review presented that the level of evidence available to support an association between elevated PTH levels and cognitive function was generally weak and inconsistent. Future studies with more better methodological quality are needed.

The Effect of Serum Calcium Levels on Uremic Encephalopathy in Patients with Acute Kidney Injury in the Emergency Department

Background and objectives: Uremic encephalopathy is the most important complication of renal failure and urgent dialysis treatment is required. Parathormone (PTH) contributes to the etiopathogenesis of uremic encephalopathy. PTH is a hormone that acts in the calcium balance in the organism. The aim of our study was to investigate the effect of serum adjusted and ionized calcium on the development of uremic encephalopathy in patients with acute renal injury (acute kidney injury network (AKIN) stage 3). Materials and Methods: Our study was supported by Canakkale Onsekiz Mart University Scientific Research Projects Unit (ID:1278). Three groups were formed for the study. The first group was acute renal failure AKIN stage 3 (N: 23), the second group was AKIN stage 3, and the patients who had emergency hemodialysis (N: 17) and the third group (N: 9) had AKIN stage 3 hemodialysis due to uremic encephalopathy. In these patient groups, 25-hydroxy vitamin D, PTH, calcium, albumin, urea, creatinine, and blood-gas-ionized calcium were observed in their serum during the first application. Calcium, albumin, urea, creatinine, and ionized calcium in blood gas were also examined in serum at 24th and 72th hours. Data were analyzed using SPSS version 19.0. Kruskal–Wallis test and Mann–Whitney U test were applied for the variables that did not comply with normal distribution. p < 0.005 was accepted statistically. Results: A statistically significant difference was found between the measurement creatinine values at the 24th and 72th hours of admission in AKIN stage 3 patients who applied to the emergency department (p = 0.008). A statistically significant difference was found in the measured calcium values (p = 0.013). A statistically significant difference was found in the measured ionized calcium values (p = 0.035). Conclusions: In our study, the effect of ionized calcium level on uremic encephalopathy in serum creatinine, calcium, and blood gas in patients presenting with acute renal injury, AKIN stage 3, was significant, but studies with new and large groups are needed.

Association between abnormal thalamic metabolites and sleep disturbance in patients with end-stage renal disease

Sleep disturbances are common in end-stage renal disease (ESRD) patients. However, the underlying neuropathological mechanisms are largely unclear. Previous studies have revealed the important role of the thalamus in the potential mechanisms of sleep disorders. We hypothesized that the sleep disturbances in ESRD patients may correspond to metabolic changes of thalamus and the uremic factors may have a vital contribution on these changes. We performed multi-voxel ¹H-MRS of bilateral thalami in 27 ESRD patients who currently receiving hemodialysis treatment and 21 age-matched healthy volunteers. ESRD patients underwent Pittsburgh Sleep Quality Index (PSQI) scale and restless legs syndrome (RLS) rating scale assessment. Laboratory blood tests including serum creatinine, serum urea, cystatin-C, serum parathyroid hormone (PTH), calcium and phosphorus levels, hemoglobin and hematocrit were performed in all ESRD patients close to the time of the MR examination. We found correlations among elevated PTH, higher PSQI score and RLS rating score in ESRD patients. ESRD patients displayed decreased N-acetylaspartate and creatine ratio (NAA/Cr) of thalami compared with controls. There were significantly negative correlation between NAA/Cr and serum PTH level or PSQI score. The metabolic changes of thalami played an important role in the neuropathological mechanisms of lower sleep quality in ESRD patients. Secondary hyperparathyroidism as one of the main uremia-related factors was closely related to abnormal metabolites of the thalamus in patients with ESRD, revealing the crosstalk procedure between renal impairment and brain function.

The influences of vitamin D and omega-3 co-supplementation on clinical, metabolic and genetic parameters in women with polycystic ovary syndrome

OBJECTIVE

The aim of this study was to evaluate the effect of the co-administration of vitamin D and omega-3 fatty acid on clinical, metabolic and genetic parameters in women with polycystic ovary syndrome (PCOS).

METHODS

This randomized, double-blinded, placebo-controlled clinical trial was conducted on 60 subjects, aged 18-40 years old with PCOS. Subjects were randomly allocated to take either 50,000 IU vitamin D every 2 weeks plus 2000 mg/day omega-3 fatty acid from fish oil (n = 30) or placebo (n = 30) for 12 weeks. Gene expression analysis of inflammatory cytokines was conducted on peripheral blood mononuclear cells (PBMCs) of PCOS women using RT-PCR method.

RESULTS

Vitamin D and omega -3 fatty acid co-supplementation significantly decreased serum total testosterone levels (-0.2 ± 0.5 vs. + 0.1 ± 0.4 ng/mL, P = 0.02) compared with the placebo. In addition, vitamin D and omega-3 fatty acid co-supplementation resulted in a significant improvement in beck depression inventory (-1.4 ± 1.6 vs. -0.5 ± 0.6, P = 0.01), general health questionnaire scores (-4.5 ± 4.3 vs. -1.9 ± 2.3, P = 0.005) and depression anxiety and stress scale scores (-5.0 ± 5.1 vs. -2.3 ± 3.5, P = 0.01) compared with the placebo. Additionally, vitamin D and omega-3 fatty acid co-administration significantly decreased serum high-sensitivity C-reactive protein (hs-CRP) (-1.2 ± 1.9 vs. + 0.1 ± 0.7 mg/L, P = 0.001) and malondialdehyde (MDA) levels (-0.4 ± 0.4 vs. + 0.2 ± 0.6 µmol/L, P < 0.001), and significantly increased plasma total antioxidant capacity (TAC) levels (+ 114.6 ± 122.2 vs. -2.4 ± 168.2 mmol/L, P = 0.003) compared with the placebo. Results of RT-PCR demonstrated that vitamin D and omega-3 fatty acid co-supplementation significantly downregulated gene expression of interleukin-1 (IL-1) (P = 0.03), and upregulated vascular endothelial growth factor (VEGF) (P = 0.004) in PBMCs of subjects with PCOS, when compared with placebo.

CONCLUSIONS

Overall, the co-administration of vitamin D and omega-3 fatty acid for 12 weeks had beneficial effects on mental health parameters, serum total testosterone, hs-CRP, plasma TAC and MDA levels, and gene expression of IL-1 and VEGF among women with PCOS.

Neurological and Psychological Changes in Hemodialysis Patients Before and After the Treatment

Neurological, psychological, and cognitive disorders in chronic kidney disease may contribute to poor quality of life in these patients. The aim of this study was to assess the electroencephalographic, psychological, and cognitive changes before and after hemodialysis (HD) compared with healthy controls (HC). Sixteen HD patients and 15 HC were enrolled. Electroencephalogram (EEG), Minnesota multiphasic personality inventory (MMPI-2) Satisfaction profile (SAT-P), and Neuropsychological test Global z-scores (NPZ5) were performed before (T0) and after (T1) HD treatment and in HC. Renal function, inflammatory markers and mineral metabolism indexes were also evaluated. Patients did not show significant differences before and after HD in the absolute and relative power of band of EEG, except in Theta/Alpha index (P < 0.001). At T1, HD patients showed significant differences in Beta, Delta and Theta band, in addition to Theta/alpha index, with respect to HC. Moreover, HD patients showed significant differences in specific MMPI-2 clinical and content scales, SAT-P domains and NPZ5 tests of memory and concentration with respect to HC. We also observed significant correlations between renal function, mineral metabolism, inflammatory markers and psychocognitive alterations. In our sample EEG abnormalities tend to reduce, but not significantly, after HD treatment and differences remain present with respect to HC. In HD patients cognitive and psychological alterations were associated with reduced quality of life and correlated with mineral metabolism and inflammation. Modification in EEG and in psychological and cognitive parameters should be assessed in a larger HD population to confirm our observation.

The nature, consequences, and management of neurological disorders in chronic kidney disease

Perhaps no other organ in the body is affected as often and in as many ways as the brain is in patients with chronic kidney disease (CKD). Several factors contribute to the neurological disorders in CKD including accumulation of uremic toxins, metabolic and hemodynamic disorders, oxidative stress, inflammation, and impaired blood brain barrier among others. The neurological disorders in CKD involve both peripheral and central nervous system. The peripheral neurological symptoms of CKD are due to somatic and cranial peripheral neuropathies as well as a myopathy. The central neurological symptoms of CKD are due to the cortical predominantly cortical, or subcortical lesions. Cognitive decline, encephalopathy, cortical myoclonus, asterixis and epileptic seizures are distinct features of the cortical disorders of CKD. Diffuse white matter disease due to ischemia and hypoxia may be an important cause of subcortical encephalopathy. A special and more benign form of subcortical disorder caused by brain edema in CKD is termed posterior reversible encephalopathy. Subcortical pathology especially when it affects the basal ganglia causes a number of movement disorders including Parkinsonism, chorea and dystonia. A stimulus-sensitive reflex myoclonus is believed to originate from the medullary structures. Sleep disorder and restless leg syndrome are common in CKD and have both central and peripheral origin. This article provides an overview of the available data on the nature, prevalence, pathophysiology, consequences and treatment of neurological complications of CKD.

Renal Denervation Improves the Baroreflex and GABA System in Chronic Kidney Disease-induced Hypertension

Hypertensive rats with chronic kidney disease (CKD) exhibit enhanced gamma-aminobutyric acid (GABA)_B receptor function and regulation within the nucleus tractus solitarii (NTS). For CKD with hypertension, renal denervation (RD) interrupts the afferent renal sympathetic nerves, which are connecting to the NTS. The objective of the present study was to investigate how RD improves CKD-induced hypertension. Rats underwent 5/6 nephrectomy for 8 weeks, which induced CKD and hypertension. RD was induced by applying phenol to surround the renal artery in CKD. RD improved blood pressure (BP) by lowering sympathetic nerve activity and markedly restored the baroreflex response in CKD. The GABA_B receptor expression was increased in the NTS of CKD; moreover, the central GABA levels were reduced in the cerebrospinal fluid, and the peripheral GABA levels were increased in the serum. RD restored the glutamic acid decarboxylase activity in the NTS in CKD, similar to the effect observed for central treatment with baclofen, and the systemic administration of gabapentin reduced BP. RD slightly improved renal function and cardiac load in CKD. RD may improve CKD-induced hypertension by modulating the baroreflex response, improving GABA system dysfunction and preventing the development and reducing the severity of cardiorenal syndrome type 4 in CKD rats.

Brain-kidney cross-talk: Definition and emerging evidence

Cross-talk is broadly defined as endogenous homeostatic signaling between vital organs such as the heart, kidneys and brain. Kidney-brain cross-talk remains an area with excitingly few publications despite its purported clinical relevance in the management of currently undertreated conditions such as resistant hypertension. Therefore, this review aims to establish an organ-specific definition for kidney-brain cross-talk and review the available and forthcoming literature on this topic.

Neurological, psychological, and cognitive disorders in patients with chronic kidney disease on conservative and replacement therapy

Chronic kidney disease (CKD) is a highly prevalent condition in the world. Neurological, psychological, and cognitive disorders, related to CKD, could contribute to the morbidity, mortality, and poor quality of life of these patients. The aim of this study was to assess the neurological, psychological, and cognitive imbalance in patients with CKD on conservative and replacement therapy.Seventy-four clinically stable patients affected by CKD on conservative therapy, replacement therapy (hemodialysis (HD), peritoneal dialysis (PD)), or with kidney transplantation (KT) and 25 healthy controls (HC), matched for age and sex were enrolled. Clinical, laboratory, and instrumental examinations, as renal function, inflammation and mineral metabolism indexes, electroencephalogram (EEG), psychological (MMPI-2, Sat P), and cognitive tests (neuropsychological tests, NPZ5) were carried out.The results showed a significant differences in the absolute and relative power of delta band and relative power of theta band of EEG (P = 0.008, P < 0.001, P = 0.051), a positive correlation between relative power of delta band and C-reactive protein (CRP) (P < 0.001) and a negative correlation between estimated glomerular filtration rate (eGFR) (P < 0.001) and 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) (P < 0.001), in all the samples. Qualitative analysis of EEG showed alterations of Grade 2 (according to Parsons-Smith classification) in patients on conservative therapy, and Grade 2-3 in KT patients. The scales of MMPI-2 hysteria and paranoia, are significantly correlated with creatinine, eGFR, serum nitrogen, CRP, 1,25-(OH)2D3, intact parathyroid hormone (iPTH), phosphorus, and cynical and hysterical personality, are correlated with higher relative power of delta (P = 0.016) and theta band (P = 0.016). Moreover, all NPZ5 scores showed a significant difference between the means of nephropathic patients and the means of the HC, and a positive correlation with eGFR, serum nitrogen, CRP, iPTH, and vitamin D.In CKD patients, simple and noninvasive instruments, as EEG, and cognitive-psychological tests, should be performed and careful and constant monitoring of renal risk factors, probably involved in neuropsychological complications (inflammation, disorders of mineral metabolism, electrolyte disorders, etc.), should be carried out. Early identification and adequate therapy of neuropsychological, and cognitive disorders, might enable a better quality of life and a major compliance with a probable reduction in the healthcare costs.

Cognitive Changes in Chronic Kidney Disease and After Transplantation

Cognitive impairment is very common in chronic kidney disease (CKD) and is strongly associated with increased mortality. This review article will discuss the pathophysiology of cognitive impairment in CKD, as well as the effect of dialysis and transplantation on cognitive function. In CKD, uremic toxins, hyperparathyroidism and Klotho deficiency lead to chronic inflammation, endothelial dysfunction and vascular calcifications. This results in an increased burden of cerebrovascular disease in CKD patients, who consistently have more white matter hyperintensities, microbleeds, microinfarctions and cerebral atrophy on magnetic resonance imaging scans. Hemodialysis, although beneficial in terms of uremic toxin clearance, also contributes to cognitive decline by causing rapid fluid and osmotic shifts. Decreasing the dialysate temperature and increasing total dialysis time limits these shifts and helps maintain cognitive function in hemodialysis patients. For many patients, kidney transplantation is the preferred treatment modality, because it reverses the underlying mechanisms causing cognitive impairment in CKD. These positive effects have to be balanced against the possible neurotoxicity of infections and immunosuppressive medications, especially glucocorticosteroids and calcineurin inhibitors. A limited number of studies have addressed the overall effect of transplantation on cognitive function. These have mostly found an improvement after transplantation, but have a limited applicability to daily practice because they have only included relatively young patients.

A highly reproducible mice model of chronic kidney disease: Evidences of behavioural abnormalities and blood-brain barrier disruption

AIMS

In the present study, a novel mice model of chronic kidney disease (CKD) was developed, and psycho-motor behavioural abnormalities, blood-brain barrier (BBB) integrity and brain histology were studied.

MAIN METHODS

Swiss albino female mice were given high adenine diet (0.3% w/w mixed with feed) for 4weeks. Serum urea and creatinine levels and renal histological studies were performed to validate the model. Psycho-motor behavioural abnormalities and neurological severity were studied. BBB integrity was assessed using Evans blue extravasation method. Nissl staining was performed to see possible morphological aberrations in brain.

KEY FINDINGS

There was a significant increase in serum urea and creatinine levels in mice given high adenine diet, and the mice had abnormal kidney morphology. Deposition of adenine and 2,8-dihydroxyadenine crystals, and increased collagen deposits in the renal tissues were found, which validate induction of CKD in the mice. Motor behavioural abnormalities, depression-like and anxiolytic behaviour and increase in neurological severity were prevalent in mice with CKD. Evans Blue dye extravasation was found to occur in the brain, which signifies disruption of BBB. However, Nissl staining did not reveal any morphological aberration in brain tissue.

SIGNIFICANCE

The present study puts forward a highly reproducible mice model of CKD validated with serum parameters and renal histopathological changes. The mice showed psycho-motor behavioural abnormalities and BBB disruption. It is a convenient model to study the disease pathology, and understanding the associated disorders, and their therapeutic interventions.

Brain Microstructural Abnormalities Are Related to Physiological Alterations in End-Stage Renal Disease

PURPOSE

To study whole-brain microstructural alterations in patients with end-stage renal disease (ESRD) and examine the relationship between brain microstructure and physiological indictors in the disease.

MATERIALS AND METHODS

Diffusion tensor imaging data were collected from 35 patients with ESRD (28 men, 18-61 years) and 40 age- and gender-matched healthy controls (HCs, 32 men, 22-58 years). A voxel-wise analysis was then used to identify microstructural alterations over the whole brain in the ESRD patients compared with the HCs. Multiple biochemical measures of renal metabolin, vascular risk factors, general cognitive ability and dialysis duration were correlated with microstructural integrity for the patients.

RESULTS

Compared to the HCs, the ESRD patients exhibited disrupted microstructural integrity in not only white matter (WM) but also gray matter (GM) regions, as characterized by decreased fractional anisotropy (FA) and increased mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). Further correlation analyses revealed that the in MD, AD and RD values showed significantly positive correlations with the blood urea nitrogen in the left superior temporal gyrus and significantly negative correlations with the calcium levels in the left superior frontal gyrus (orbital part) in the patients.

CONCLUSION

Our findings suggest that ESRD is associated with widespread diffusion abnormalities in both WM and GM regions in the brain, and microstructural integrity of several GM regions are related to biochemical alterations in the disease.

Kidney disease as a determinant of cognitive decline and dementia

Chronic kidney disease (CKD) has evolved as a possible new determinant of cognitive decline and dementia. This review outlines the presumed pathophysiology of cognitive decline in CKD, which consists of traditional and new vascular risk factors as well as nonvascular risk factors and metabolic and biochemical abnormalities within the central nervous system caused by CKD. The recent major cross-sectional studies and longitudinal studies - including one meta-analysis - that mostly suggest an association of cognitive decline and CKD are discussed. Finally, potential therapeutic strategies are presented.

Effect of Renal Transplantation in Restless Legs Syndrome

OBJECTIVES

Restless legs syndrome is a disorder in which patients have irresistible urge to move legs during rest. Restless legs syndrome seems to be common in end-stage renal disease. After a successful renal transplant, symptoms ameliorate with renal function improvement and restless legs syndrome is seen less in this population. Here, we aimed to investigate restless legs syndrome frequency and associated factors in renal transplant patients.

MATERIALS AND METHODS

In a cross-sectional study with 193 patients (116 hemodialysis patients, 45 transplant patients, and 32 controls), the presence of restless legs syndrome was assessed using the Restless Legs Syndrome Questionnaire. Medical history, demographic, and laboratory data were collected from the patients' medical records. Patients were questioned about the presence of restless legs syndrome using the Restless Legs Syndrome Questionnaire. Patients were evaluated with Beck Depression Scale for depression and Pittsburgh tests for sleep disturbances.

RESULTS

While the rate of restless legs syndrome was similar between transplants and controls, it was significantly greater in hemodialysis patients. Hemodialysis patients and controls had similar depression scores that were higher compared with transplant patients. Pittsburgh score was similar in transplant patients and controls and significantly increased in the hemodialysis patients. The rate of insomnia was significantly higher in the hemodialysis patients compared with the other 2 groups. Logistic regression analysis revealed independent correlates of restless legs syndrome as insomnia, Beck depression score, and being on hemodialysis. Linear regression analysis showed that independent correlates of higher Pittsburgh score were higher depression score, higher age, and presence of restless legs syndrome.

CONCLUSIONS

The prevalence of restless legs syndrome is significantly lower in transplant patients than it is in patients on maintenance dialysis. In renal transplant patients, restless legs syndrome frequency was found to be lower because of improved renal functions (normalization of uremia), psychological symptoms, and sleep disturbances.

Reduced white matter integrity and cognitive deficits in maintenance hemodialysis ESRD patients: a diffusion-tensor study

OBJECTIVES

The purpose of this investigation was to examine the association between cognition disorders and microstructural white matter (WM) changes in maintenance hemodialysis end-stage renal disease (ESRD) patients.

METHODS

Twenty-six maintenance hemodialysis ESRD patients and 28 healthy controls underwent diffusion tensor imaging (DTI), Mini Mental State Examination (MMSE), Trial Marking Test-A&B (TMT-A&B), and white matter hyperintensity (WMH) assessment. Tract-based spatial statistics (TBSS) analyses was performed to evaluate WM changes in the patients. Relationships between behavioural performances, clinical data, and the DTI index were tested, respectively, by correlation analysis at the voxel level.

RESULTS

ESRD patients showed significant decreased fractional anisotropy (FA) in 14 WM regions, and increased mean diffusivity (MD) and radial diffusivity (RD) in widespread regions. Significant positive correlations between FA values and MMSE scores were found in the right anterior corona radiata and the left anterior thalamic radiation; significant negative correlations between the TMT-B time consumption and FA values were identified in the bilateral superior longitudinal fasciculus. Positive linear relationships between MD, RD values, and the duration of hemodialysis were found in several WM regions.

CONCLUSION

Structural damages to radiation and associative fibre tracts, caused by brain oedema and WM demyelination, may account for the cognitive deficits in ESRD patients.

Cerebro-renal interactions: impact of uremic toxins on cognitive function

Cognitive impairment (CI) associated with chronic kidney disease (CKD) has received attention as an important problem in recent years. Causes of CI with CKD are multifactorial, and include cerebrovascular disease, renal anemia, secondary hyperparathyroidism, dialysis disequilibrium, and uremic toxins (UTs). Among these causes, little is known about the role of UTs. We therefore selected 21 uremic compounds, and summarized reports of cerebro-renal interactions associated with UTs. Among the compounds, uric acid, indoxyl sulfate, p-cresyl sulfate, interleukin 1-β, interleukin 6, TNF-α, and PTH were most likely to affect the cerebro-renal interaction dysfunction; however, sufficient data have not been obtained for other UTs. Notably, most of the data were not obtained under uremic conditions; therefore, the impact and mechanism of each UT on cognition and central nervous system in uremic state remains unknown. At present, impacts and mechanisms of UT effects on cognition are poorly understood. Clarifying the mechanisms and establishing novel therapeutic strategies for cerebro-renal interaction dysfunction is expected to be subject of future research.

Brain Na+/K+-ATPase α-subunit isoforms and aestivation in the African lungfish, Protopterus annectens

This study aimed to clone and sequence Na (+) / K (+)-ATPase (nka) α-subunit isoforms from, and to determine their mRNA expression levels and protein abundance in the brain of the African lungfish, Protopterus annectens during the induction, maintenance and arousal phases of aestivation in air. We obtained the full cDNA sequences of nkaα1, nkaα2 and nkaα3 from the brain of P. annectens. Phylogenetic analysis of their deduced amino acid sequences revealed that they are closer to the corresponding NKA α-subunits of tetrapods than to those of fishes. The mRNA expression of these three nkaα isoforms showed differential changes in the brain of P. annectens during the three phases of aestivation. After 12 days of aestivation, there was a significant increase in the protein abundance of Nkaα1 in the brain of P. annectens. This could be an important response to maintain cellular Na(+) and K(+) concentrations and regulate cell volume during the early maintenance phase of aestivation. On the other hand, the mRNA expression of nkaα2 decreased significantly in the brain of P. annectens after 6 months of aestivation, which could be a result of a suppression of transcriptional activities to reduce energy expenditure. The down-regulation of mRNA expression of nkaα1, nkaα2 and nkaα3 and the overall protein abundance of Nka α-subunit isoforms in the brain of P. annectens after 1 day of arousal from 6 months of aestivation were novel observations, and it could be an adaptive response to restore blood pressure and/or to prevent brain oedema.

Motor and Behavioral Changes in Mice With Cisplatin-Induced Acute Renal Failure

We have previously shown that chronic renal failure in rats induces changes in motor activity and behavior. Similar work on the possible effects of acute renal failure (ARF) induced by cisplatin (CP) is lacking. This is the subject matter of the current work. CP was injected intraperitoneally (i.p.) at a single dose of 20 mg/kg to induce a state of ARF, and three days later, its effects on motor activity, thermal and chemical nociceptive tests, neuromuscular coordination, pentobarbitone-sleeping time, exploration activity and two depression models were investigated. The platinum concentration in the kidneys and brains of mice was also measured. The occurrence of CP-induced ARF was ascertained by standard physiological, biochemical and histo-pathological methods. CP induced all the classical biochemical, physiological and histopathological signs of ARF. The average renal platinum concentration of CP-treated mice was 5.16 ppm, but there was no measurable concentration of platinum in the whole brains. CP treatment significantly decreased motor and exploration activities, and increased immobility time in depression models, suggesting a possible depression-like state. There was also a significant decrease in neuromuscular coordination in CP-treated mice. CP, given at a nephrotoxic dose, induced several adverse motor and behavioral alterations in mice. Further behavioral tests and molecular and biochemical investigations in the brains of mice with CP-induced ARF are warranted.

Motor and behavioral changes in rats with adenine-induced chronic renal failure: influence of acacia gum treatment

Chronic renal failure (CRF) either occurring naturally in humans or induced surgically in rats causes alterations in behavior and motor functions. However, the effect of chemically induced CRF in rats on behavior is not known. We induced CRF in rats by feeding adenine (0.75% w/w, four weeks) and investigated the effect of the ensuing CRF on a depression model (forced swimming test, FST), analgesia (mechanical nociception), neuromuscular coordination (Rota-rod test) and motor activity (activity meter test). Further, we investigated the effect of giving acacia gum (AG, 10% w/v) in the drinking water concomitantly with adenine using the above models. AG has been previously shown to ameliorate the severity of CRF in humans and rats. Adenine-induced CRF significantly increased the plasma concentrations of urea and creatinine, and reduced creatinine clearance. Additionally, it significantly reduced motor activity and increased immobility time in the FST, suggesting a depressant-like effect. Both of these actions were significantly antagonized by AG treatment. Adenine insignificantly reduced the mechanical nociceptive threshold by 15%. The results of the tests for neuromuscular coordination were inconclusive. In conclusion, adenine-induced CRF caused motor and behavioral alterations, and these were significantly mitigated by administration of AG.

[Cognitive impairment and chronic kidney disease: which links?]

Ageing of the population leads to an increase of cognitive disorders and chronic renal failure incidence. Compared to the general population, prevalence of cognitive impairment is more important in renal failure patients, especially in dialyzed patients. No direct link has been established between renal failure and cognitive impairment. The care of older and older patients and the high frequency of vascular risk factors, in particular hypertension and diabetes, partially explain the prevalence of vascular dementia and Alzheimer disease in this population. Other factors as the anemia, phosphocalcic metabolism disorders facilitate the cognitive impairment. The present work reviews the links existing between chronic renal failure and cognitive impairment.

Metabolic and endocrine factors in mild cognitive impairment

Mild cognitive impairment (MCI) is a heterogeneous condition with cognitive changes between normal aging and dementia. Some forms of MCI are regarded as potential preclinical forms of dementia. The control of treatable somatic risk factors is of great relevance in patients with MCI, particularly as there is insufficient evidence for the efficacy of interventions targeting neurodegenerative processes, as used in manifest dementia. The etiology of MCI is varied including cerebrovascular risk factors and is also associated with metabolic and endocrine factors. Chronic kidney disease is a newly identified and independent risk factor for MCI. Testosterone substitution is useful if a low testosterone level is present but general screening for testosterone deficiency is not yet recommended. A relationship between MCI and vitamin D or subclinical thyroid dysfunction may exist, but the value of substitution is doubtful and requires large randomized placebo-controlled trials. Although an association between vitamin B12 deficiency or hyperhomocysteinemia and MCI is present, substitution of vitamin B12 or folate does not appear to prevent cognitive decline. Estrogen-only hormone replacement therapy may be considered only in younger postmenopausal women, but may have detrimental effects on cognitive function in older postmenopausal women. Other less familiar or unknown risk factors contributing to cognitive dysfunction should be identified as they are a potential target of prevention or intervention of MCI or dementia.

Baroreflex sensitivity and sympatho-vagal balance during intradialytic hypotensive episodes

OBJECTIVES

The role of the baroreflex function in the pathogenesis of hemodialysis-associated hypotension is controversial. Complex demodulation technique (CDM), providing continuous assessment of the amplitude of cardiovascular oscillation over time, is particularly suitable to assess dynamic changes in autonomic nervous system and baroreceptor sensitivity (BRS) during dialysis. In the present study, CDM was used to determine the effects of dialysis treatment on BRS and to characterize BRS changes during acute intradialytic hypotension.

METHODS

Continuous beat-to-beat blood pressure and interbeat intervals (IBIs) were monitored in 93 chronic patients without (n = 70) and with (n = 26) hypotension during 96 dialysis sessions. The amplitudes of SBP and DBP, IBIs, and BRS change in the low-frequency (around center frequency of 0.09 Hz) and high-frequency (around center frequency of 0.30 Hz) ranges were followed during the whole dialysis session.

RESULTS

Hemodialysis treatment was associated with increased low-frequency BRS, especially in sessions without hypotension. Hypotensive episodes were associated with significant increases in both low-frequency BRS and high-frequency BRS, mainly in patients with severe hypotension. The magnitude of the increase in baroreflex indices was proportional to the decrease in blood pressure. Low-frequency IBI/high-frequency IBI ratio, a marker of sympatho-vagal balance, did not significantly change during hypotension.

CONCLUSION

Our study shows that the baroreflex mechanism is preserved and adequately activated during intradialytic hypotension. Other factors, such as ischemic heart disease, left ventricular dysfunction, and inadequate arteriolar tone, rather than failure of baroreflex function, are more likely to be responsible for dialysis-induced hypotension.

End-stage renal disease: in vivo diffusion-tensor imaging of silent white matter damage

PURPOSE

To characterize and compare regional differences in anisotropy in patients with end-stage renal disease (ESRD) and in control subjects to understand the effect of ESRD and hemodialysis on the microstructures of white matter.

MATERIALS AND METHODS

This study was approved by an institutional review board; written informed consent was obtained. From March 2007 to December 2007, 34 patients (16 men, 18 women; mean age, 40.0 years; range, 26-50 years) with ESRD who were undergoing dialysis and 35 control subjects (16 men, 19 women; mean age, 38.3 years; range, 25-49 years) were enrolled. There was no significant sex or age difference between the ESRD and control groups. By using a 1.5-T imager, fractional anisotropy (FA) data obtained at diffusion-tensor magnetic resonance (MR) imaging (echo-planar imaging, 33 directions; b value, 1000 sec/mm(2)) and at T2-weighted fluid-attenuated inversion recovery (FLAIR) MR imaging of the bilateral parietal, frontal, occipital, and temporal lobe white matter, as well as the genu and splenium of the corpus callosum, were compared. The Cognitive Abilities Screening Instrument (CASI) was administered to all participants at imaging.

RESULTS

The ESRD group had significantly lower FA values in all regions than the control group. FA values were generally lower in older patients and in those who had been undergoing dialysis for a longer duration. Duration of dialysis was more often than age found to be correlated with differences in FA values. In areas in which there was a significant correlation between age, duration, and FA values, the regression coefficients were greater for those who had been undergoing dialysis longer than for those who were older. Patients with ESRD had significantly lower CASI scores than control subjects (P = .03). There were no significant group differences in FLAIR values (P = .25-.89).

CONCLUSION

Changes in FA values may be used to follow-up white matter changes in patients with ESRD who are undergoing maintenance dialysis.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2523080484/DC1.

Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: randomized double blind trial

OBJECTIVES

The objective of the present study was to examine the cross-sectional relation between serum 25-hydroxyvitamin D [25-(OH) D] levels and depression in overweight and obese subjects and to assess the effect of vitamin D supplementation on depressive symptoms.

DESIGN

Cross-sectional study and randomized double blind controlled trial of 20,000 or 40,000 IU vitamin D per week versus placebo for 1 year.

SETTING

A total of 441 subjects (body mass index 28-47 kg m(-2), 159 men and 282 women, aged 21-70 years) recruited by advertisements or from the out-patient clinic at the University Hospital of North Norway.

MAIN OUTCOME MEASURES

Beck Depression Inventory (BDI) score with subscales 1-13 and 14-21.

RESULTS

Subjects with serum 25(OH)D levels < 40 nmol L(-1) scored significantly higher (more depressive traits) than those with serum 25(OH)D levels > or = 40 nmol L(-1) on the BDI total [6.0 (0-23) versus 4.5 (0-28) (median and range)] and the BDI subscale 1-13 [2.0 (0-15) versus 1.0 (0-29.5)] (P < 0.05). In the two groups given vitamin D, but not in the placebo group, there was a significant improvement in BDI scores after 1 year. There was a significant decrease in serum parathyroid hormone in the two vitamin D groups without a concomitant increase in serum calcium.

CONCLUSIONS

It appears to be a relation between serum levels of 25(OH)D and symptoms of depression. Supplementation with high doses of vitamin D seems to ameliorate these symptoms indicating a possible causal relationship.

Role of Parathyroid Hormone in the Downregulation of Liver Cytochrome P450 in Chronic Renal Failure

Chronic renal failure (CRF) is associated with a decrease in drug metabolism secondary to a decrease in liver cytochrome P450 (P450). The predominant theory to explain this decrease is the presence of factors in the blood of uremic patients. This study tested the hypothesis that parathyroid hormone (PTH) could be this factor. The objectives of this study were to determine (1) the role of PTH in the downregulation of hepatocyte P450 induced by rat uremic serum, (2) the role of PTH in the downregulation of liver P450 in rats with CRF, and (3) the effects of PTH on P450 in hepatocytes. For this purpose, (1) hepatocytes were incubated with serum from rat with CRF that was depleted with anti-PTH antibodies or with serum from parathyroidectomized (CRF-PTX) rat with CRF, (2) the effect of PTX on liver P450 was evaluated in rats with CRF, and (3) the effects of PTH on P450 in hepatocytes were determined. The depletion of PTH from CRF serum completely reversed the downregulating effect of CRF serum on P450 in hepatocytes. Addition of PTH (10(-9) M) to depleted CRF serum induced a decrease in P450 similar to nondepleted CRF serum. The serum of CRF-PTX rats had no effect on P450 in hepatocytes compared with CRF serum. Adding PTH to CRF-PTX serum induced a similar decrease in P450 as obtained with CRF serum. Finally, PTX prevented the decrease of liver P450 in rats with CRF. In summary, PTH is the major mediator implicated in the downregulation of liver P450 in rats with CRF.

Ceftazidime overdose-related nonconvulsive status epilepticus after intraperitoneal instillation

We report a case of ceftazidime-related nonconvulsive status epilepticus (NCSE) in a 70-year-old female patient with continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis. She was given ceftazidime intravenously which was then changed to intraperitoneal installation after clinical improvement. She received 11 g of ceftazidime via intraperitoneal installation for two days after being discharged from the hospital. Her consciousness was altered with mutism, asterisxis, and horizontal nystagmus. Her EEG showed continuous generalized three spikes-and-wave per second that were abolished after intravenous diazepam. Ceftazidime-related NCSE was suggested and ceftazidime therapy was stopped. Hemodialysis was done while phenytoin was also given to control the convulsions. Her consciousness improved after hemodialysis. Serum ceftazidime measured before and after hemodialysis on the second and third day were 105.2/39.4, 36.2/5.2 microg/mL (normal peak level 55 microg/mL), respectively. Repeated evaluation on day 6 showed normal EEG without epileptiform activity. She was later discharged with full recovery.

Involvement of organic anion transporters in the efflux of uremic toxins across the blood-brain barrier

Renal failure causes multiple physiological changes involving CNS dysfunction. In cases of uremia, there is close correlation between plasma levels of uremic toxins [e.g. 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), hippurate (HA) and indoleacetate (IA)] and the degree of uremic encephalopathy, suggesting that uremic toxins are involved in uremic encephalopathy. In order to evaluate the relevance of uremic toxins to CNS dysfunction, we investigated directional transport of uremic toxins across the blood-brain barrier (BBB) using in vivo integration plot analysis and the brain efflux index method. We observed saturable efflux transport of [(3)H]CMPF, [(14)C]HA and [(3)H]IA, which was inhibited by probenecid. For all uremic toxins evaluated, apparent efflux clearance across the BBB was greater than apparent influx clearance, suggesting that these toxins are predominantly transported from the brain to blood across the BBB. Saturable efflux transport of [(3)H]CMPF, [(14)C]HA and [(3)H]IA was completely inhibited by benzylpenicillin, which is a substrate of rat organic anion transporter 3 (rOat3). Taurocholate and digoxin, which are common substrates of rat organic anion transporting polypeptide (rOatp), partially inhibited the efflux of [(3)H]CMPF. Transport experiments using a Xenopus laevis oocyte expression system revealed that CMPF, HA and IA are substrates of rOat3, and that CMPF (but not HA or IA) is a substrate of rOap2. These results suggest that rOat3 mediates brain-to-blood transport of uremic toxins, and that rOatp2 is involved in efflux of CMPF. Thus, conditions typical of uremia can cause inhibition of brain-to-blood transport involving rOat3 and/or rOatp2, leading to accumulation of endogenous metabolites and drugs in the brain.

Neuropsychological function in relation to serum parathyroid hormone and serum 25-hydroxyvitamin D levels. The Tromsø study

There are receptors for parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D in the brain, and there are clinical and experimental data indicating that PTH and vitamin D may affect cerebral function. In the present study 21 subjects who both in the 5th Tromsø study and at a follow-up examination fulfilled criteria for secondary hyperparathyroidism (SHPT) without renal failure (serum calcium < 2.40 mmol/L, serum PTH > 6.4 pmol/L, and normal serum creatinine) and 63 control subjects were compared with tests for cognitive and emotional function. Those in the SHPT group had significantly impaired performance in 3 of 14 cognitive tests (Digit span forward, Stroop test part 1 and 2, and Word association test (FAS)) as compared with the controls, and also had a significantly higher depression score at the Beck Depression Inventory (BDI) (items 1-13). In a multiple linear regression model, a high serum PTH level was significantly associated with low performance at the Digit span forward, Stroop test part 1 and 2, and Digit Symbol tests. A low level of serum 25-hydroxyvitamin D was significantly associated with a high depression score. In conclusion, a deranged calcium metabolism appears to be associated with impaired function in several tests of neuropsychological function.

Impact of parathyroidectomy on neutrophil cytosolic calcium in chronic kidney disease patients: a prospective parallel group trial

OBJECTIVES

Polymorphonuclear leucocytes (PMNs) of chronic kidney disease (CKD) patients display elevated basal cytosolic calcium concentrations (iCa(2+)). As parathyroid hormone is considered to substantially contribute to the inappropriate cellular entry of calcium in uraemia, we hypothesized that parathyroidectomy lowers PMN iCa(2+).

DESIGN AND SETTING

Prospective parallel group trial at a tertiary care centre. SUBJECTS, INTERVENTION AND MAIN OUTCOME MEASURES: Two patient cohorts (cohort 1: 14 CKD patients; cohort 2: 14 renal transplant recipients) underwent parathyroidectomy for uncontrolled secondary hyperparathyroidism. We assessed PMN iCa(2+) (primary objective) spectrofluorimetrically 1 day before and 20 days after intervention (secondary objective: PMN glucose uptake). Data were compared with those of 16 matched maintenance haemodialysis patients (cohort 3), and to 15 healthy subjects (cohort 4), by generalized estimating equations.

RESULTS

PMN iCa(2+) of cohort 1 decreased over time and was significantly higher than that of cohort 3 before but not after parathyroidectomy [mean difference before/after parathyroidectomy: 19.1 nmol L(-1) (95% confidence interval: 9.4-22.4), P =0.0003/-3.2 (-20.9-14.5), P = 0.71]. PMN iCa(2+) of cohort 2 decreased over time, but we found no significant difference in comparison with cohort 3 [mean difference before/after parathyroidectomy: 6.5 nmol L(-1) (-9.4-22.4), P = 0.4/-15.8 (-43.6-12.0), P = 0.25]. PMN iCa(2+) of all CKD patients was substantially higher in comparison with that of healthy subjects [cohort 4 vs. 3: -35.3 (-48.9-21.6), P < 0.001]. PMN glucose uptake increased significantly in both interventional cohorts in comparison with cohort 3.

CONCLUSIONS

Parathyroidectomy lowers, but does not normalize PMN iCa(2+) of CKD patients. Further variables, possibly uraemic retention solutes, control both PMN iCa(2+) and functional responses.

Cognitive function in dialysis patients

There are few detailed studies of cognitive function in dialysis patients. However, appreciating the prevalence and risk factors for cognitive impairment is important because cognitive impairment may decrease an individual's quality of life, increase resource utilization, and result in suboptimal medical care because of difficulty following caregiver recommendations. Cognitive impairment also is likely to become more of a problem as the dialysis population ages. In this review, we argue that cerebrovascular disease is an important cause of cognitive impairment in dialysis patients and discuss risk factors specific for vascular disease, as well as other factors that may influence cognitive function. We describe the structural brain abnormalities frequently seen in dialysis patients and the specific neurocognitive changes noted in prior studies. We explore potential measures to reduce cognitive impairment in this population. We conclude that additional research is needed in this area.

Effects of endothelin-1 on hepatic stellate cell proliferation, collagen synthesis and secretion, intracellular free calcium concentration

AIM: To explore the effects of endothelin-1 (ET-1) on hepatic stellate cells (HSCs) DNA uptake, DNA synthesis, collagen synthesis and secretion, inward whole-cell calcium concentration ([Ca²⁺]_i) as well as the blocking effect of verapamil on ET-1-stimulated release of inward calcium (Ca²⁺) of HSC in vitro.

METHODS: Rat hepatic stellate cells (HSCs) were isolated and cultivated. ³H-TdR and ³H-proline incorporation used for testing DNA uptake and synthesis, collagen synthesis and secretion of HSCs cultured in vitro; Fluorescent calcium indicator Fura-2/AM was used to measure [Ca²⁺]_i inward HSCs.

RESULTS: ET-1 at the concentration of 5 × 10^-8 mol/L, caused significant increase both in HSC DNA synthesis (2247 ± 344 cpm, P < 0.05) and DNA uptake (P < 0.05) when compared with the control group. ET-1 could also increase collagen synthesis (P < 0.05 vs control group) and collagen secretion (P < 0.05 vs control group). Besides, inward HSC [Ca²⁺] _i reached a peak concentration (422 ± 98 mol/L, P < 0.001) at 2 min and then went down slowly to165 ± 51 mol/L (P < 0.01) at 25 min from resting state (39 ± 4 mol/L) after treated with ET-1. Verapamil (5 mol/L) blocked ET-1-activated [Ca²⁺]_i inward HSCs compared with control group (P < 0.05). Fura-2/AM loaded HSC was suspended in no Ca²⁺ buffer containing 1 mol/L EGTA, 5 min later, 10^-8 mol/L of ET-1 was added, [Ca²⁺]_i inward HSCs rose from resting state to peak 399 ± 123 mol/L, then began to come down by the time of 20 min. It could also raise [Ca²⁺]_i inward HSCs even without Ca²⁺ in extracellular fluid, and had a remarkable dose-effect relationship (P < 0.05). Meanwhile, verapamil could restrain the action of ET-1 (P < 0.05).

CONCLUSION: Actions of ET-1 on collagen metabolism of HSCs may depend on the transportation of inward whole-cell calcium.

Effect of NaCN on currents evoked by uremic retention solutes in dissociated mouse neurons

Uremic retention solutes possibly contribute to neuronal hypoxia/ischemia and its consequences in patients with renal failure. We examined the in vitro effects of several uremic retention solutes on murine central neurons under chemically induced metabolic hypoxia by application of sodium cyanide (NaCN). Whole cell currents were recorded using the tight-seal whole-cell voltage clamp technique. Application of NaCN caused an inward whole-cell current. From all tested toxins, which included several indoles, guanidino compounds, polyamines, purines, phenols, DL-homocysteine, orotate and myoinositol, only creatinine (CTN), guanidine (G) and guanidinosuccinic acid (GSA) produced a significant current in control and hypoxic neurons. Current evoked by GSA was significantly increased in the chemical hypoxic condition, and a synergistic effect of GSA and spermine was observed in hypoxic neurons.