Raised plasma-myoinositol levels in uraemia and experimental neuropathy

Metabolomic insights in advanced cardiomyopathy of chronic chagasic and idiopathic patients that underwent heart transplant

Heart failure (HF) studies typically focus on ischemic and idiopathic heart diseases. Chronic chagasic cardiomyopathy (CCC) is a progressive degenerative inflammatory condition highly prevalent in Latin America that leads to a disturbance of cardiac conduction system. Despite its clinical and epidemiological importance, CCC molecular pathogenesis is poorly understood. Here we characterize and discriminate the plasma metabolomic profile of 15 patients with advanced HF referred for heart transplantation - 8 patients with CCC and 7 with idiopathic dilated cardiomyopathy (IDC) - using gas chromatography/quadrupole time-of-flight mass spectrometry. Compared to the 12 heart donor individuals, also included to represent the control (CTRL) scenario, patients with advanced HF exhibited a metabolic imbalance with 21 discriminating metabolites, mostly indicative of accumulation of fatty acids, amino acids and important components of the tricarboxylic acid (TCA) cycle. CCC vs. IDC analyses revealed a metabolic disparity between conditions, with 12 CCC distinctive metabolites vs. 11 IDC representative metabolites. Disturbances were mainly related to amino acid metabolism profile. Although mitochondrial dysfunction and loss of metabolic flexibility may be a central mechanistic event in advanced HF, metabolic imbalance differs between CCC and IDC populations, possibly explaining the dissimilar clinical course of Chagas' patients.

Serum myo-inositol and valine improve metabolomic-based estimated glomerular filtration rate among kidney transplant recipients

BACKGROUND

Close monitoring of glomerular filtration rate (GFR) is essential for the management of patients post kidney transplantation. Measured GFR (mGFR), the gold standard, is not readily accessible in most centers. Furthermore, the performance of new estimated GFR (eGFR) equations based upon creatinine and/or cystatin C have not been validated in kidney transplant patients. Here we evaluate a recently published eGFR equation using cystatin C, creatinine, myo-inositol and valine as measured by nuclear magnetic resonance (eGFRNMR).

METHODS

Residual sera was obtained from a cohort of patients with clinically ordered iothalamate renal clearance mGFR (n = 602). Kidney transplant recipients accounted for 220 (37%) of participants.

RESULTS

Compared to mGFR, there was no significant bias for eGFRcr or eGFRNMR, while eGFRcr-cys significantly underestimated mGFR. P30 values were similar for all eGFR. P15 was significantly higher for eGFRNMR compared to eGFRcr, while the P15 for eGFRcr-cys only improved among patients without a kidney transplant. Agreement with mGFR CKD stages of <15, 30, 45, 60, and 90 ml/min/1.73 m2 was identical for eGFRcr and eGFRcr-cys (61.8%, both cases) while eGFRNMR was significantly higher (66.4%) among patients with a kidney transplant.

CONCLUSION

The 2021 CKD-EPI eGFRcr and eGFRcr-cys have similar bias, P15, and agreement while eGFRNMR more closely matched mGFR with the strongest improvement among kidney transplant recipients.

Normalization of Cerebral Blood Flow, Neurochemicals, and White Matter Integrity after Kidney Transplantation

BACKGROUND

CKD is associated with abnormalities in cerebral blood flow, cerebral neurochemical concentrations, and white matter integrity. Each of these is associated with adverse clinical consequences in the non-CKD population, which may explain the high prevalence of dementia and stroke in ESKD. Because cognition improves after kidney transplantation, comparing these brain abnormalities before and after kidney transplantation may identify potential reversibility in ESKD-associated brain abnormalities.

METHODS

In this study of patients with ESKD and age-matched healthy controls, we used arterial spin labeling to assess the effects of kidney transplantation on cerebral blood flow and magnetic resonance spectroscopic imaging to measure cerebral neurochemical concentrations (N-acetylaspartate, choline, glutamate, glutamine, myo-inositol, and total creatine). We also assessed white matter integrity measured by fractional anisotropy (FA) and mean diffusivity (MD) with diffusion tensor imaging. We used a linear mixed model analysis to compare longitudinal, repeated brain magnetic resonance imaging measurements before, 3 months after, and 12 months after transplantation and compared these findings with those of healthy controls.

RESULTS

Study participants included 29 patients with ESKD and 19 controls; 22 patients completed post-transplant magnetic resonance imaging. Cerebral blood flow, which was higher in patients pretransplant compared with controls (P=0.003), decreased post-transplant (P<0.001) to values in controls. Concentrations of neurochemicals choline and myo-inositol that were higher pretransplant compared with controls (P=0.001 and P<0.001, respectively) also normalized post-transplant (P<0.001 and P<0.001, respectively). FA increased (P=0.001) and MD decreased (P<0.001) post-transplant.

CONCLUSIONS

Certain brain abnormalities in CKD are reversible and normalize with kidney transplantation. Further studies are needed to understand the mechanisms underlying these brain abnormalities and to explore interventions to mitigate them even in patients who cannot be transplanted.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Cognitive Impairment and Imaging Correlates in End Stage Renal Disease, NCT01883349.

A Novel Metabolic Signature To Predict the Requirement of Dialysis or Renal Transplantation in Patients with Chronic Kidney Disease

Identification of chronic kidney disease patients at risk of progressing to end-stage renal disease (ESRD) is essential for treatment decision-making and clinical trial design. Here, we explored whether proton nuclear magnetic resonance (NMR) spectroscopy of blood plasma improves the currently best performing kidney failure risk equation, the so-called Tangri score. Our study cohort comprised 4640 participants from the German Chronic Kidney Disease (GCKD) study, of whom 185 (3.99%) progressed over a mean observation time of 3.70 ± 0.88 years to ESRD requiring either dialysis or transplantation. The original four-variable Tangri risk equation yielded a C statistic of 0.863 (95% CI, 0.831-0.900). Upon inclusion of NMR features by state-of-the-art machine learning methods, the C statistic improved to 0.875 (95% CI, 0.850-0.911), thereby outperforming the Tangri score in 94 out of 100 subsampling rounds. Of the 24 NMR features included in the model, creatinine, high-density lipoprotein, valine, acetyl groups of glycoproteins, and Ca²⁺-EDTA carried the highest weights. In conclusion, proton NMR-based plasma fingerprinting improved markedly the detection of patients at risk of developing ESRD, thus enabling enhanced patient treatment.

Control of Uremic Neuropathy by Equilibrium Peritoneal Dialysis

Motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNVC) and distal motor latencies times (DMLT) were evaluated both in upper and lower limbs in three groups of 15 patients of comparable age, treated respectively by extracorporeal dialysis (HD), continuous ambulatory peritoneal dialysis (CAPD) and combined peritoneal dialysis (CPD) for comparable sufficiently long periods. Moreover, MNCV was monitored longitudinally in two groups of patients shifted from CAPD to HD and vice versa. The results show a significant superiority of peritoneal dialysis and particularly of CAPD with respect to HD in controlling uremic neuropathy.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

Metabolomic Analysis Provides Insights on Paraquat-Induced Parkinson-Like Symptoms in Drosophila melanogaster

Paraquat (PQ) exposure causes degeneration of the dopaminergic neurons in an exposed organism while altered metabolism has a role in various neurodegenerative disorders. Therefore, the study presented here was conceived to depict the role of altered metabolism in PQ-induced Parkinson-like symptoms and to explore Drosophila as a potential model organism for such studies. Metabolic profile was generated in control and in flies that were fed PQ (5, 10, and 20 mM) in the diet for 12 and 24 h concurrent with assessment of indices of oxidative stress, dopaminergic neurodegeneration, and behavioral alteration. PQ was found to significantly alter 24 metabolites belonging to different biological pathways along with significant alterations in the above indices. In addition, PQ attenuated brain dopamine content in the exposed organism. The study demonstrates that PQ-induced alteration in the metabolites leads to oxidative stress and neurodegeneration in the exposed organism along with movement disorder, a phenotype typical of Parkinson-like symptoms. The study is relevant in the context of Drosophila and humans because similar alteration in the metabolic pathways has been observed in both PQ-exposed Drosophila and in postmortem samples of patients with Parkinsonism. Furthermore, this study provides advocacy towards the applicability of Drosophila as an alternate model organism for pre-screening of environmental chemicals for their neurodegenerative potential with altered metabolism.

Uremic solutes and risk of end-stage renal disease in type 2 diabetes: metabolomic study

Here we studied plasma metabolomic profiles as determinants of progression to ESRD in patients with Type 2 diabetes (T2D). This nested case-control study evaluated 40 cases who progressed to ESRD during 8-12 years of follow-up and 40 controls who remained alive without ESRD from the Joslin Kidney Study cohort. Controls were matched with cases for baseline clinical characteristics; although controls had slightly higher eGFR and lower levels of urinary albumin excretion than T2D cases. Plasma metabolites at baseline were measured by mass spectrometry-based global metabolomic profiling. Of the named metabolites in the library, 262 were detected in at least 80% of the study patients. The metabolomic platform recognized 78 metabolites previously reported to be elevated in ESRD (uremic solutes). Sixteen were already elevated in the baseline plasma of our cases years before ESRD developed. Other uremic solutes were either not different or not commonly detectable. Essential amino acids and their derivatives were significantly depleted in the cases, whereas certain amino acid-derived acylcarnitines were increased. All findings remained statistically significant after adjustment for differences between study groups in albumin excretion rate, eGFR or HbA1c. Uremic solute differences were confirmed by quantitative measurements. Thus, abnormal plasma concentrations of putative uremic solutes and essential amino acids either contribute to progression to ESRD or are a manifestation of an early stage(s) of the disease process that leads to ESRD in T2D.

Insights gained from P. falciparum cultivation in modified media

In vitro cultivation of Plasmodium falciparum, the agent of severe human malaria, has enabled advances in basic research and accelerated the development of new therapies. Since the introduction of in vitro parasite culture nearly 40 years ago, most workers have used a medium consisting of RPMI 1640 medium supplemented with lipids and hypoxanthine. While these standardized conditions yield robust parasite growth and facilitate comparison of results from different studies, they may also lead to implicit assumptions that limit future advances. Here, I review recent studies that used modified culture conditions to challenge these assumptions and explore parasite physiology. The findings are relevant to understanding in vivo parasite phenotypes and the prioritization of antimalarial targets.

NMR Metabolomics Analysis of Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disease, which is characterized by progressive death of dopaminergic neurons in the substantia nigra pars compacta. Although mitochondrial dysfunction and oxidative stress are linked to PD pathogenesis, its etiology and pathology remain to be elucidated. Metabolomics investigates metabolite changes in biofluids, cell lysates, tissues and tumors in order to correlate these metabolomic changes to a disease state. Thus, the application of metabolomics to investigate PD provides a systematic approach to understand the pathology of PD, to identify disease biomarkers, and to complement genomics, transcriptomics and proteomics studies. This review will examine current research into PD mechanisms with a focus on mitochondrial dysfunction and oxidative stress. Neurotoxin-based PD animal models and the rationale for metabolomics studies in PD will also be discussed. The review will also explore the potential of NMR metabolomics to address important issues related to PD treatment and diagnosis.

Metabolic profiling of Parkinson's disease: evidence of biomarker from gene expression analysis and rapid neural network detection

Background

Parkinson's disease (PD) is a neurodegenerative disorder. The diagnosis of Parkinsonism is challenging because currently none of the clinical tests have been proven to help in diagnosis. PD may produce characteristic perturbations in the metabolome and such variations can be used as the marker for detection of disease. To test this hypothesis, we used proton NMR and multivariate analysis followed by neural network pattern detection.

Methods & Results

¹H nuclear magnetic resonance spectroscopy analysis was carried out on plasma samples of 37 healthy controls and 43 drug-naive patients with PD. Focus on 22 targeted metabolites, 17 were decreased and 5 were elevated in PD patients (p < 0.05). Partial least squares discriminant analysis (PLS-DA) showed that pyruvate is the key metabolite, which contributes to the separation of PD from control samples. Furthermore, gene expression analysis shows significant (p < 0.05) change in expression of PDHB and NPFF genes leading to increased pyruvate concentration in blood plasma. Moreover, the implementation of ¹H- NMR spectral pattern in neural network algorithm shows 97.14% accuracy in the detection of disease progression.

Conclusion

The results increase the prospect of a robust molecular definition in detection of PD through the early symptomatic phase of the disease. This is an ultimate opening for therapeutic intervention. If validated in a genuinely prospective fashion in larger samples, the biomarker trajectories described here will go a long way to facilitate the development of useful therapies. Moreover, implementation of neural network will be a breakthrough in clinical screening and rapid detection of PD.

Low water-soluble uremic toxins

The uremic syndrome is the result of the retention of solutes, which under normal conditions are cleared by the healthy kidneys. Uremic retention products are arbitrarily subdivided according to their molecular weight. Low-molecular-weight molecules are characterized by a molecular weight below 500 D. The purpose of the present publication is to review the main water soluble, nonprotein bound uremic retention solutes, together with their main toxic effects. We will consecutively discuss creatinine, glomerulopressin, the guanidines, the methylamines, myo-inositol, oxalate, phenylacetyl-glutamine, phosphate, the polyamines, pseudouridine, the purines, the trihalomethanes, and urea per se.

Sympathetic skin response in peritoneal dialysis patients

To determine if there is any difference in nerve conduction studies or sympathetic skin response (SSR) between patients on peritoneal dialysis and those on regular hemodialysis, we did a cross-sectional observational study. The study group consisted of 24 patients on peritoneal dialysis (PD) (12 men, aged 45 +/- 17 years) and 20 patients on hemodialysis (HD) (11 men, aged 50 +/- 22 years). All of these patients were in stable clinical condition, they were receiving adequate dialysis, and none of them had systemic diseases. Motor and sensory nerve conduction studies of the common and medial peroneal nerve and SSR were performed in all patients. There were no differences in motor and sensory nerve conduction velocities between PD and HD patients. All PD patients had detectable SSR. However, six patients on HD (30%) failed to show SSR (p < 0.05). Mean SSR amplitude was higher in PD patients than in HD patients (1233 +/- 843 vs. 605 +/- 771 microv, p < 0.05). There were no differences in mean SSR latency between PD and HD patients. PD modality (continuous ambulatory PD vs. automated PD) or the presence of residual renal function did not influence nerve conduction studies or SSR. In conclusion, using standard nerve conduction studies, no differences could be found between HD and PD. However, a higher proportion of patients on HD showed an impaired SSR, suggesting that subclinical neuropathy may be more common in HD than PD patients.

Neurologic manifestations of renal disease

Mortality and morbidity from kidney disease and the spectrum of renal-associated neurologic disease have changed markedly since the introduction of renal dialysis and with the advent of renal transplantation. This article includes historical studies of the neurologic complications of acute uremia, now fairly uncommon, and recent literature regarding neurologic side effects associated with dialysis and renal transplantation.

Acute effect of hemodialysis on sympathetic skin response

Sympathetic skin response (SSR) is a useful and simple test for unmyelinated axon function in peripheral sensorimotor neuropathies. SSR was tested on a group of patients undergoing chronic regular hemodialysis before and after a single dialysis session. Nineteen patients in hemodialysis for more than three months were included. Nine patients were on dialysis with cellulosic membranes (CA, 3 male and 6 female, aged 57.7 +/- 16.4 years) and ten ones were on dialysis with non-cellulosic membranes (NC, 4 male and 6 female, aged 50.2 +/- 15.9 years) were studied. There were no differences neither in Kt/V values (NC 1.37 +/- 0.34 vs. CA 1.22 +/- 0.27) nor in TAC ones (NC 41.5 +/- 18.2 vs. CA 41.3 +/- 14.1 mg/dL). After hemodialysis with NC amplitude significantly increased (994 +/- 1015 vs. 382 +/- 465 microv baseline, p < 0.05). Latency did not change (1.76 +/- 0.83 vs. 2.07 +/- 0.50 s baseline). After hemodialysis with CA neither amplitude changed (1368 +/- 1074 vs. 1240 +/- 1594 microv baseline), nor did latency (1.79 +/- 0.35 vs. 1.94 +/- 0.59 s baseline). Hemodialysis with non-cellulosic membranes (but not with cellulose acetate) yields a short-term improvement of sympathetic skin response. This effect is similar to those seen in nerve conduction velocities and it may be related to increased middle-molecules depuration.

Acute effect of hemodialysis with polyacrylonitrile membrane on nerve conduction velocities

AIM

Non cellulosic membranes, as polyacrylonitrile (AN69) improves middle-molecules purification through hemodialysis, and this increased clearance of middle-molecules may have benefical effects on uremic polyneuropathy. We have tried to evaluate this effect comparing nerve conduction velocities before and after hemodialysis with either AN69 or cellulose acetate (CA).

PATIENTS AND METHODS

Eight patients in hemodialysis with AN69 for more than three months (4 men and 4 women, mean age 58.4 +/- 12.9 years, mean time in hemodialysis 9.3 +/- 7.5 months). Motor conduction velocities (MCV) and sensory conduction velocities (SCV) were measured predialysis and postdialysis with AN69 and, one week later, predialysis and postdialysis with CA.

RESULTS

There were no differences neither in Kt/V values (AN69 1.27 +/- 0.36 vs CA 1.16 +/- 0.26) nor in TAC ones (AN69 40.8 +/- 17.4 vs CA 40.8 +/- 21.3 mg/dL). After hemodialysis with AN69 MCV significantly increased (42.0 +/- 3.0 vs 40.6 +/- 2.6 m/s baseline, p < 0.05). SCV was also enhanced (45.3 +/- 2.2 vs 41.1 +/- 3.4 m/s baseline, p < 0.05). After hemodialysis with CA neither MCV changed (42.7 +/- 1.6 vs 42.0 +/- 2.3 m/s baseline), nor did SCV (45.8 +/- 5.8 vs 44.8 +/- 3.0 m/s baseline).

CONCLUSIONS

Hemodialysis with AN69 acutely improved SCV and MCV. This effect was not seen with CA hemodialysis.

HPLC fractions of human uremic plasma inhibit the RBC membrane calcium pump

We have reported that uremic plasma filtrates (UF) inhibit the red blood cell (RBC) membrane calcium pump. The inhibitor was dialyzable, smaller than 3,000 molecular weight, heat-stable, and protease-resistant. In the present study, we used reverse-phase preparative HPLC, analytical HPLC, and Sephadex G-25 elution to identify inhibitory fractions. Inhibition was confirmed in three different bioassays: (1) Sr2+ efflux in intact RBC, the primary bio-assay; (2) 45Ca efflux in intact RBC; and (3) calcium ATPase activity in isolated RBC membranes. Active fractions were analyzed by mass spectrometry, capillary electrophoresis, enzymatic analysis, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. These demonstrated a number of compounds, including: sugars, polyols, osmolytes like betaine and myoinositol, amino acids, and other metabolites, such as 3-D-hydroxybutyrate, dimethylglycine, trimethylamine-N-oxide, guanidinoacetic acid and glycine. Many individual compounds were then tested for an effect on the calcium pump. Thus, HPLC was able to separate a substantial number of compounds in inhibitory fractions. Efforts are under way for precise identification of the inhibitor, to advance our understanding of uremic toxicity and/or hypertension in CRF.

Dietary myoinositol results in lower urine glucose and in lower postprandial plasma glucose in obese insulin resistant rhesus monkeys

In a previous study, D-chiroinositol added to a meal (0.5 g/kg) resulted in significantly lower postprandial plasma glucose concentrations without an increase in insulin concentrations in obese insulin-resistant monkeys. The present report describes the effects of another isomer of inositol, myoinositol, on postprandial plasma glucose and insulin concentrations and on urine glucose concentrations in 6 similarly insulin-resistant monkeys. The three 5 day study periods included a control period (liquid diet ad libitum) and 2 experimental periods (liquid diet ad libitum with either 1.5 g/kg/day myoinositol or D-chiroinositol added). Twenty-four hour urine samples were collected during each 5 day period. On the sixth day of each period the monkeys were anesthetized 110 min after completing either the control meal (15 ml/kg) or the experimental meals (1.5 g/kg myoinositol or D-chiroinositol) and plasma samples were obtained at 120, 150, 180, 210, 240, 270 and 300 min. The plasma glucose concentration was lower after the meal with myoinositol compared to the control meal at 120, 150 and 180 min (p's < 0.05). The plasma insulin concentration was lower after the meal with myoinositol compared to the control meal at 150 and 180 min (p's < 0.05). In addition, 24 hour urine glucose concentrations were lower during the myoinositol diet compared to the control diet (p < 0.001). The plasma glucose concentration was lower after the meal with D-chiroinositol compared to the control meal at 150, 240, 270 and 300 min (p's < or = 0.05). In obese insulin-resistant monkeys, myoinositol added to the diet lowers urine glucose concentrations and both myoinositol and D-chiroinositol added to a meal lower postprandial plasma glucose concentrations without increasing postprandial insulin concentrations. Therefore, myoinositol, like D-chiroinositol, may be a useful agent for reducing meal-induced hyperglycemia without inducing hyperinsulinemia in insulin-resistant subjects.

Dialysis and transplantation affect cerebral abnormalities of end-stage renal disease

Localized short echo time proton magnetic resonance spectroscopy was performed to determine whether chronic and end-stage renal failure, hemodialysis, continuous ambulatory peritoneal dialysis, or renal transplantation result in alterations of cerebral water and metabolites in humans. Hemodialysis patients show an increased cerebral concentration of myo-inositol (+ 14%; P < .05). Increased metabolite ratios are found for myo-inositol/creatine (+14%; P <.01) and choline containing compounds choline/creatine (+10%; P < .01) and are more marked in gray than in white matter. N-acetylaspartate and total creatine concentrations are unaffected. Compared to hemodialysis, continuous ambulatory peritoneal dialysis patients show a larger increase in choline and less elevated myo-inositol. Acutely, hemodialysis significantly decreases the cerebrospinal fluid content of the examined brain regions, but metabolite changes are small compared to the persistent alterations in patients receiving hemodialysis or continuous ambulatory peritoneal dialysis. Undialyzed patients with chronic renal failure do not differ from patients on hemodialysis, but cerebral metabolite changes are completely reversed by transplantation. Cerebral metabolic effects of end-stage renal disease differ from Alzheimer's disease, which is associated with markedly reduced N-acetylaspartate, increased myo-inositol, and normal choline concentrations. The small but significant cerebral metabolic disorders associated with renal failure and dialysis may be a consequence of osmotic dysregulation.

Polyol profiles in Down syndrome. myo-Inositol, specifically, is elevated in the cerebrospinal fluid

Polyols are reduction products of aldoses and ketoses; their concentrations in tissues can reflect carbohydrate metabolism. Several polyol species were quantitated in cerebrospinal fluid (CSF) and plasma from 10 Down Syndrome (trisomy 21) subjects between the ages of 22 and 63 years (3 of whom were demented) and from 10 healthy age-matched controls, using a gas chromatographic/mass spectrometric technique. The mean CSF concentration and the mean CSF/plasma concentration ratio of myo-inositol were significantly elevated in Down syndrome compared with controls, but were not correlated with the presence of dementia in the Down subjects. Plasma myo-inositol was not significantly altered in these subjects. No significant difference between Down syndrome and controls was found for CSF concentrations of mannitol, sorbitol, galactitol, ribitol, arabitol, or 1,5-anhydrosorbitol, but plasma mannitol, ribitol and arabitol were elevated in Down syndrome. The present observation provides new impetus for studying synthesis and transport of myo-inositol as well as phosphatidylinositol cycle in trisomy 21 disorder.

Alterations of brain metabolites in metachromatic leukodystrophy as detected by localized proton magnetic resonance spectroscopy in vivo

The brain morphology and chemistry of seven children with late infantile (4/7) and juvenile (3/7) forms of metachromatic leukodystrophy (MLD) were investigated by magnetic resonance imaging (MRI) and localized proton magnetic resonance spectroscopy (MRS). Patients who were examined at least 6 months after the onset of symptoms (6/7) had severe leukodystrophic changes on MRI. Proton MRS revealed a marked reduction of the neuronal marker N-acetylaspartate in white and grey matter and elevated lactate in demyelinated areas. In contrast to other leukodystrophies MLD patients showed a generalized increase of brain myo-inositol (2- to 3-fold in white matter), indicating a specific role in the pathophysiology of demyelination in MLD.

Inositol treatment raises CSF inositol levels

Inositol is a key precursor for synthesis of phosphatidylinositol in a major second messenger signalling system. It is biologically active in syndromes such as respiratory distress syndrome but has been thought to be excluded from CNS by the blood-brain barrier. Oral inositol treatment of 8 patients is shown to significantly increase CSF inositol by almost 70%, suggesting possible CNS therapeutic applications of this compound and possible CNS side-effects of systemic therapy.

Dietary myo-inositol supplementation does not prevent retinal and glomerular vascular structural changes in chronically diabetic rats

To assess effects of dietary myo-inositol supplementation on diabetes-induced vascular structural lesions, diabetes was induced in Sprague-Dawley rats with streptozotocin; one-third of these rats was fed a 2% myo-inositol diet for 9 months, one-third was left untreated for 5 months then treated with myo-inositol for the last 4 months, and one-third was untreated for the entire 9 months. Controls included untreated and myo-inositol-treated groups. Weight gain was impaired and plasma glucose, glycosylated hemoglobin, food consumption, urine volume, and albuminuria were increased significantly in diabetic versus age-matched control rats. Plasma myo-inositol levels were increased approximately fivefold in controls and approximately six- to eightfold in diabetic rats treated with myo-inositol. In general, myo-inositol did not affect any of the above parameters in control or diabetic rats. Retinal capillary basement membrane width (CBMW) was increased significantly (approximately 50% versus controls) after 9 months of diabetes. In the control group myo-inositol increased CBMW to the level of untreated diabetic rats; myo-inositol had no effect on CBMW in each diabetic group. The number of retinal capillaries containing pericyte nuclei and pericyte capillary coverage were increased in untreated as well as myo-inositol-treated diabetic rats and in the myo-inositol-treated control group. Glomerular CBMW was increased after 5 and 9 months of diabetes versus age-matched controls, and was increased even more by myo-inositol. Mesangial fractional volume of the glomerulus was increased 36% by diabetes and was decreased slightly but significantly by myo-inositol. These results indicate that diets supplemented with 2% myo-inositol (1) cause capillary basement membrane (CBM) thickening and pericyte changes in retinal capillaries of normal rats, (2) are ineffective in preventing or reversing diabetes-induced retinal CBM thickening, and (3) cause further thickening of glomerular CBM in diabetic rats.

Analysis of polyols in uremic serum by liquid chromatography combined with atmospheric pressure chemical ionization mass spectrometry

Liquid chromatography with atmospheric pressure chemical ionization mass spectrometry in the negative-ion mode was used to analyse polyols in uremic serum obtained from haemodialysis patients. With post-column addition of 1% chloroform-methanol as an ionization accelerating solvent, the chloride addition ions, [M+Cl]-, were detected as base peaks, and the molecular masses of the polyols were easily determined by comparing [M+Cl]- and [M - H]- ions. Concentrations of erythritol, myoinositol, mannitol and sorbitol were markedly increased, and that of 1,5-anhydroglucitol was markedly decreased in the uremic serum compared with normal serum. After haemodialysis, the serum concentration of these polyols decreased significantly. This method was found to be useful in analysing the profile of polyols.

Down's syndrome fibroblasts exhibit enhanced inositol uptake

The inositol metabolism of Down's syndrome (DS, trisomy 21) skin fibroblasts was examined. We report that DS cells accumulated [3H]inositol 2-3-fold faster than did other aneuploid or diploid controls. In contrast, trisomy 21 did not affect the uptake of choline, serine or glucose. Kinetic analysis demonstrated an increased maximal velocity of high-affinity, Na(+)-dependent, inositol transport, consistent with the expression of higher numbers of transporters by DS cells. Enhanced uptake was accompanied by a proportional increase in the incorporation of radiolabelled inositol into phospholipid. We suggest that an imbalance of inositol metabolism may contribute to plasma membrane abnormalities characteristic of DS cells.

Primary hyperparathyroidism presenting as cervical myelopathy

Quadriplegia as a presenting syndrome in a case of primary hyperparathyroidism is reported. The clinical picture was misdiagnosed as a space-occupying lesion in the cervical spinal canal, for which an unnecessary laminectomy was performed. The neurologic deficits disappeared following the removal of a parathyroid adenoma. The neurologic presentations of hyperparathyroidism are reviewed and discussed.

Progressive, predominantly motor, uraemic neuropathy

A severe rapidly progressive neuropathy is described in 4 young male adults with end-stage renal failure, 3 of whom had accelerated hypertension. The onset of symptoms developed after regular haemodialysis had been started and in all 4 patients was closely associated with a septicaemic illness. In 2 patients, renal transplantation led to considerable clinical improvement, and in a third patient charcoal haemoperfusion halted further clinical progression of the neuropathy. This improvement was not reflected by the nerve conduction studies which remained grossly impaired. A possible ischaemic aetiology related to accelerated hypertension and septicaemia is suggested for this unusual variant of uraemic neuropathy.

The effects of aldose reductase inhibition on nerve sorbitol and myoinositol concentrations in diabetic and galactosemic rats

The interrelationship between sorbitol excess and myoinositol deficiency in the peripheral nerve was examined in acutely diabetic rats. Nerve myoinositol concentration was also studied in galactosemic rats. Polyol pathway blockade with Sorbinil (Pfizer, Connecticut) prevented nerve myoinositol reduction in both groups of animals. This conclusion was independent of alteration in the fluid content of the peripheral nerve. It is likely that myoinositol loss from nerves is causally related to the sorbitol and galactitol accumulation.

An enzymatic fluorimetric assay for myo-inositol

An enzymatic assay for myo-inositol (MI) is described. The method is based on the oxidation of MI by NAD+-dependent myo-inositol dehydrogenase, coupled to reoxidation of NADH with oxalacetate and malate dehydrogenase. The resultant malate is measured fluorimetrically. Several variations of the assay are described for measuring MI in serum and in tissues in amounts ranging from 0.2 pmol to 8 nmol. Highest sensitivity is achieved by applying an oil-well technique for handling small droplets, and by using the principle of enzymatic cycling. The potential of the technique is illustrated by MI measurements in several tissues of normal and diabetic rats and Chinese hamsters.

Gas chromatographic and gas chromatographic—mass spectrometric analysis of organic acids in plasma of patients with chronic renal failure

Apart from increased concentrations of aliphatic dicarboxylic acids and phenolic aromatic acids in plasma from patients with chronic renal failure, there is large elevation of a furanoid acid, 3-carboxy-4-methyl-5-propyl-2- furanpropionic acid, and of hippuric acid. The levels of 3-hydroxy- and 4- hydroxyhippuric acid are also raised. The quantitative results are as follows: furanoid acid in hemodialysis patients, 1.4 +/- 0.6 mg/dl; in healthy individuals, 0.2 +/- 0.1 mg/dl; hippuric acid in hemodialysis patients, 9.8 +/- 6.5 mg/dl; in health individuals, 0.4 +/- 0.5 mg/dl. Both compounds are dialysable, but less effectively than creatinine and urea. The mean elimination rate of the furanoid acid is only 21%.

Peripheral neuropathies associated with chronic renal failure

A variety of peripheral nerve disorders may be associated with chronic renal failure. The polyneuropathy due to uremic toxins is a distal, motor and sensory polyneuropathy in which there is segmental demyelination, axonal degeneration, and segmental remyelination. The nature of the uremic toxin and the underly mechanism of these changes is unknown. The incidence in patients with "end-stage" renal disease has fallen in recent years, severe cases now being rare, perhaps due to refinements in chronic hemodialysis, transplantation, and other therapies. However, while chronic hemodialysis stabilizes uremic neuropathy, manipulation of hemodialysis schedules may not alter its course, according to current assessment. Successful renal transplantation improves both the clinical and electrophysiological signs, even in severe uremic neuropathy.

Profiling of uremic serum by high-resolution gas chromatography-electron-impact, chemical ionization mass spectrometry

A fast and reliable procedure for gas chromatographic profiling of components in ultrafiltrated uremic serum has been developed, using glass capillary columns. Sample pretreatment consists of ultrafiltration, evaporation and silylation. Some twenty components are identified by electron-impact and chemical ionization mass spectrometry. A comparison is made between profiles of sera from a series of uremic patients, before and after hemodialysis, and from non-uremic sera. Significant differences are found between these profiles. A "dialysis ratio" is introduced as a parameter for the removal of retained components by hemodialysis treatment.

Effect of myo-inositol on peripheral-nerve function in diabetes

myo-Inositol, 500 mg twice a day, given to seven diabetic patients for two weeks, increased the amplitude of the evoked action potentials of the median, sural, and popliteal nerves by an average of 76%, 160%, and 40%, respectively. There was no significant change in the conduction velocities of these nerves, myo-Inositol may be valuable in the treatment of diabetic neuropathy.

Rapid improvement in nerve conduction velocity following renal transplantation

In 12 patients with chronic renal failure who received kidney transplants from either cadavers (6) or related living donors (6), rapid improvement in median sensory and motor nerve conduction velocities (NCVs) was observed within a few days after transplantation. The postoperative improvement in median sensory NCV was found to bear a statistically significant negative correlation with creatinine and myo-inositol concentrations. We suggest that metabolic phenomena are responsible for the rapid improvement in median sensory NCV following renal transplantation. The close relationship between myo-inositol and the median sensory NCV following transplantation suggests that elevated plasma myo-inositol concentrations may be related to nerve conduction abnormalities in uremic polyneuropathy.

Myoinositol and function of peripheral nerves in human diabetics. A controlled clinical trial

Fifty-nine diabetic patients participated in a double-blind study in order to evaluate the efficiency of myoinositol to improve the function of peripheral nerves. Myoinositol in the amounts given was not able to change motor conduction velocity or vibratory perception threshold. No change in retinopathy and several biochemical parameters was observed.

Abnormal amino acid and protein metabolism in uremia

The many alterations in amino acid and protein metabolism in renal failure are often poorly defined, and the available data concerning them are usually descriptive. Nonetheless, certain factors play an important role in the altered amino acid and protein metabolism of uremia. These include malnutrition caused by poor nutrient intake, loss of nutrients during dialysis, and abnormal metabolism of nutrients. Other factors include uremic toxins, superimposed catabolic illnesses, endocrine disorders, and the reduced capacity of the failing kidney to synthesize or degrade certain hormones, amino acids, peptides, and small proteins. These aberrations have complex interrelationships which sometimes potentiate each other. It is possible that the administration of sufficient quantities of energy, vitamins, and minerals, as well as the dietary manipulation of protein, amino acid and ketoacid intake may improve the metabolism of amino acids and proteins. Vitamin B6 and zinc have special requirements that may affect protein or amino acid metabolism.

Mortality and morbidity in pretransplant bilateral nephrectomy: analysis of 305 cases

The surgical riks were analyzed in 305 patients with end stage renal failure who underwent bilateral nephrectomy through midabdominal approach in preparation for kidney transplantation. The over-all mortality rate was 3.6 per cent. Age was the most significant risk factor in the mortality. Patients less than fifty years of age had an operative mortality rate of 3.1 per cent while those more than fifty years had an operative mortality of 11.1 per cent. Other pertinent risk factors were preoperative complications of renal failure and additional surgical procedures at the time of bilateral nephrectomy. The leading causes of death were those of cardiovascular complications and infection. The morbidity rate was 58.7 per cent being major in 18 per cent and minor in 40.7 per cent. Bilateral nephrectomy is recommended selectively in patients with (1) chronic pyelonephritis with urinary tract infection, (2) major vesicoureteral reflux, (3) immunologically active glomerulonephritis, (4) severe hypertension uncontrollable by adequate dialysis, and (5) extremely large or infected polycystic kidneys.

Influence of dietary myoinositol on nerve conduction and inositol phospholipids in normal and diabetic rats

Observations have been made on motor conduction velocity in the tibial nerve of rats given 35% myoinositol in the diet. Comparison between the values before and with up to nine weeks of dosing revealed no alteration in conduction velocity. In such animals, the free myoinositol content in the sciatic nerve was increased; there was no detectable alteration in the lipid inositol concentration. In a second series of experiments, tibial motor nerve conduction velocity in rats with streptozotocin-induced diabetes was compared with conduction velocity in diabetic animals given 1% supplementary dietary myoinositol, and with a control group of nondiabetic rats. Conduction velocity was reduced in the diabetic animals, but no influence from the added dietary myoinositol was detected. No statistically significantly difference in sciatic nerve myoinositol was demonstrated, but the sorbitol and fructose concentrations were increased. Those animals fed the myoinositol supplement had a significantly lower lipid inositol content. The significance of these findings is discussed.

Uremic neuropathy: evidence of middle molecule toxicity

Ten dialysis patients were followed in a prospective study to determine the neurotoxicity of metabolites in the middle molecule (MM) molecular weight (mol wt) range of 500-200 daltons/molecule. In the absence of readily available direct serum measurements of MM concentrations, a theoretically calculated dialysis index, D1(MM), which included the combined effects of dialysis and residual glomerular filtration rate (GFR) on MM removal was used to estimate changes in their predialysis concentrations. The ten patients were dialyzed on protocols which yielded a D1(MM) less than 1.0. Evidence of uremic neuropathy developed in six of these ten patients, and five of these six also developed a progression in their anemia. Two additional patients with no signs of neuropathy developed a progression in their anemia. One patient developed pericarditis with tamponade. A total of eight patients developed complications. One additional patient developed increased weakness, tiredness and general malaise without change in objective findings. When the dialysis therapy to reduce MM concentrations by increasing the D1(MM) above 1.0 was instituted, the complications were reversed. Our data support the findings of others, namely, that there are toxic substances in the MM mol wt range of 500-2000 daltons/molecule. However, a synergism between elevated concentrations of small molecules and MM cannot be ruled out.

Polyols in the cerebrospinal fluid and plasma of neurological, diabetic and uraemic patients

Five polyols, arabinitol, anhydroglucitol, mannitol, sorbitol and myoinositol, normally present in the cerebrospinal fluid (CSF), were studied. Quantitative gas-liquid chromatographic analysis of 211 CSF and 112 plasma samples indicated significantly altered concentrations in several clinical conditions. All five polyols were decreased in the CSF of patients suffering from meningitis, cerebral atrophy, sepsis, and in patients receiving intrathecal cytostate therapy. Equilibration between plasma and CSF may explain the changes in sepsis and meningitis, while decreased total number of functioning cells may cause the decrease in cerebral atrophy. Intrathecal cytostates seem to have a destroying effect on the cell metabolism of the central nervous system. Renal failure causes accumulation of polyols in the plasma. Alterations in the metabolism of sorbitol, myoinositol and anhydroglucitol seem to be present in diabetes. The plasma concentration of anhydroglucitol is decreased in renal failure.