Hypermyoinositolemic polyneuropathy in rats. A possible mechanism for uremic polyneuropathy

The development of a sensitive myo-inositol analyser using a liquid chromatograph with a post-label fluorescence detector

A sensitive liquid chromatographic analysis for myo-inositol was developed using glycocyamine as the post-labelling reagent. The sensitivity was 500 pmol/injection. The system was applied to analyse myo-inositol in sera from eight patients with chronic renal failure. The average concentration of serum myo-inositol was 498.6 +/- 257.0 mumol/L before haemodialysis, and 244.0 +/- 131.1 mumol/L after haemodialysis. These results indicated that the kidney is the main site of myo-inositol metabolism.

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.

Inositol and inositol 1,4,5-trisphosphate content of Down syndrome fibroblasts exhibiting enhanced inositol uptake

Fibroblasts from individuals with Down syndrome (DS; trisomy 21) exhibit increased inositol uptake. Here we examine the relationship between this increase in uptake and mass levels of free inositol and inositol 1,4,5-trisphosphate (IP3) in DS fibroblasts. We report that human fibroblasts contain high levels of free inositol which are not significantly affected by the increase in inositol uptake associated with DS. In addition, increased uptake is accompanied by increased efflux of radiolabelled inositol from DS cells. Neither basal nor bradykinin-stimulated IP3 levels in DS cells differ significantly from normal values. This work highlights the usefulness of the DS cells in uncovering the role of transport across the plasma membrane in cellular inositol homeostasis.

Inositol supplementation in respiratory distress syndrome: relationship between serum concentration, renal excretion, and lung effluent phospholipids

Inositol or placebo was given to 48 small preterm infants with respiratory distress syndrome (mean birth weight 1365 g, gestational age 30.1 weeks) between 48 hours and 10 days of age. The dose of inositol, 40 mg/kg every 6 hours, was at least as high as amounts received in full preterm human milk feedings. Serum inositol concentration increased between days 2 and 3 from a mean of 566 mumol/L to 823 mumol/L in the infants given supplement and fell from 451 mumol/L to 292 mumol/L in the controls. On day 16, serum inositol values remained higher in the infants given supplement than in those given placebo (mean 334 mumol/L vs 146 mumol/L, P = 0.014). The infants who developed bronchopulmonary dysplasia had significantly higher renal inositol clearance, lower inositol intake, and lower serum inositol concentrations. Inositol supplementation increased the saturated phosphatidylcholine/sphingomyelin ratio in tracheal aspirates. According to these results, supplementation with inositol in preterm infants leads to a rise in serum inositol concentration and improvement in the surfactant phospholipids. Inositol deserves further study as a dietary supplement for immature preterm infants who do not receive full human milk feeds.

Profiling of organic acids and polyols in nerves of uraemic and non-uraemic patients

Organic acids, polyols and lipid-bound polyols in the cauda equina nerves of uraemic patients and non-uraemic patients were analysed with high-resolution gas chromatography-mass spectrometry. In the uraemic nervous tissue, the concentrations of myoinositol and 4-hydroxyphenylacetic acid were increased. Levulinic acid was first detected in the nervous tissue as a normal component. 1-Deoxyglucose and free and lipid phosphatide scylloinositol were detected in the nervous tissue as normal components.

Secondary changes in diabetes mellitus with particular reference to retinopathy and neuropathy

It has previously been suggested (1) that respiratory modulation of the action of insulin on glucose metabolism may contribute to macrosomia in neonates from diabetic mothers. It was proposed that this was due to a relative hypoxaemia which resulted in an increase in glucose metabolised through the hexose monophosphate shunt pathway in fetal adipocytes. This could be understood on the basis of the Crabtree-Pasteur Effects. It is now suggested that a similar mechanism may lead, in certain tissues, to an increase in the metabolism of glucose through polyol pathways and that this may play a role in the development of diabetic sequelae.

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.

Role of myoinositol in regulation of surfactant phospholipids in the newborn

According to animal studies myoinositol decreases surfactant phosphatidylglycerol and increases phosphatidylinositol. In the present study lung effluent phospholipids and serum myoinositol were analyzed in respiratory distress syndrome (RDS, 19 cases), in other lung disease (6 cases) and in 22 newborn with no lung disease. In addition, myoinositol was studied in amniotic fluid and in serum from umbilical vessels and from maternal vein (15 healthy newborn). There was a significant correlation between the fetal and amniotic fluid levels of myoinositol, but no detectable correlation between fetal and maternal myoinositol. Serum myoinositol was higher in preterm than in term newborns. In healthy newborns there was a negative correlation between lung effluent phosphatidylglycerol (expressed as percent of the phospholipids) and serum myoinositol (r = -0.968), and a positive linear correlation between myoinositol and lung effluent phosphatidylinositol (r = 0.849). In RDS at birth, undetectable phosphatidylglycerol corresponded with high serum myoinositol. During the first 5 neonatal days serum myoinositol either (1) decreased and phosphatidylglycerol appeared, (2) remained high and phosphatidylglycerol correspondingly low in some small preterm infants, or (3) decreased but phosphatidylglycerol did not expectedly increase and disaturated lecithin/sphingomyelin ratio remained low in other small preterm babies. We propose that a premature decrease in serum myoinositol among small preterm infants with RDS is not beneficial, since myoinositol may promote hormone-induced lung maturation and healing of lung damage.

Changes in short-latency somatosensory evoked potentials during hemodialysis in chronic renal failure

Short-latency SEPs were monitored in eight patients undergoing hemodialysis for end-stage renal disease. The peak latencies of EP,N13, and N20 were significantly delayed compared with those of the control group. Because the interpeak latency of N13 - N20 (central conduction time) was not significantly prolonged, there could be no possible subclinical involvement of the ascending sensory fibers in the brainstem. The dialysis did alter the peak latencies of EP,N20, and interpeak latencies of EP-N13 and EP-N20; these changes, however, were not highly significant. The evoked potential changes did not correlate with the routine biochemical data. Monitoring short-latency SEP may lead to early recognition of pathologic involvement of the peripheral nervous system.

The nutritional significance, metabolism, and function of myo-inositol and phosphatidylinositol in health and disease

Recent advances in nutritional and biochemical research have substantiated the importance of inositol as a dietary and cellular constituent. The processes involved in the metabolism of inositol and its derivatives in mammalian tissues have been characterized both in vivo and at the enzyme level. Biochemical functions elucidated for phosphatidylinositol in biological membranes include the mediation of cellular responses to external stimuli, nerve transmission, and the regulation of enzyme activity through specific interactions with various proteins. Inositol deficiency in animals has been shown to produce an accumulation of triglyceride in liver, intestinal lipodystrophy, and other abnormalities. The metabolic mechanisms giving rise to these latter phenomena have been extensively studied as a function of dietary inositol. Altered metabolism of inositol has been documented in patients with diabetes mellitus, chronic renal failure, galactosemia, and multiple sclerosis. A moderate increase in plasma and nerve inositol levels by dietary supplementation has been suggested as a means of treating diabetic neuropathy, although excessively high levels, such as are found in uremic patients, may be neurotoxic. A thorough consideration of the biochemical functions of inositol and a further characterization of various diseases with the aid of appropriate animal models may suggest a possible role for inositol and other dietary components in their prevention and treatment

Conduction velocity through the somesthetic pathway in chronic renal failure

The latencies of evoked potentials recorded at different levels of the peripheral and central nervous system by median nerve stimulation were measured before and after dialysis, and compared with similar recordings in normal volunteers. Abnormally slow conduction velocity was more often found in proximal rather than in distal segments of the peripheral pathway in patients with chronic renal failure. This abnormality was not correlated with the presence of clinical signs of neuropathy or low values of motor conduction velocity, neither was it affected by dialysis. These findings support the hypothesis of peripheral nerve dysfunction secondary to metabolic derangement in uraemic patients.

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.

Screening for peripheral neuropathy in patients treated by chronic hemodialysis

Observations were made on the occurrence of peripheral neuropathy in a series of 139 patients admitted to a chronic dialysis program over a 10-year period. Evidence of neuropathy was obtained in approximately 50% of these patients over the total period. Once dialysis was instituted, distal paresthesiae evident before the inception of dialysis tended to clear rapidly. Occurrence of the symptom of "restless legs" correlated positively with the presence of neuropathy. Persistent neuropathy was more commonly sensory than motor, and its features were consistent with a predominant loss of large myelinated fibers. This analysis suggests that multiple factors may be involved in the origin of uremic neuropathy.

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.

Myo-inositol in physiological concentrations stimulates production of prostaglandin-like material

In physiological concentrations myo-inositol stimulated production of prostaglandin (PG)-like material in a rat mesenteric vascular bed preparation. There were five lines of evidence: 1. Inositol potentiated pressor responses to both norepinephrine and potassium in a manner similar to PGE2. 2. Inositol had no potentiating effect in preparations in which endogenous PG production was blocked by indomethacin. 3. Inositol caused no further potentiation in preparations already potentiated by arachidonic acid, the PG precursor. 4. The inhibitory effect of the PG antagonist chloroquine was reduced in an apparently competitive manner by inositol. 5. As indicated by rat stomach bioassay inositol caused a three fold rise in the outflow of PG-like material from the preparation.

Tissue culture studies of possible uremic neurotoxins: myoinositol

Organotypic cultures of dorsal root ganglion cells revealed neuronal toxicity when exposed to myoinositol at doses of 1090 to 109 micrometer (500 to 50 microgram/ml). The ultrastructural changes consisted of membranous cytoplasmic bodies at high concentrations and dense bodies at lower concentrations. There were no changes at 0 to 22 micrometer (0 to 10 microgram/ml). This range of neurotoxicity parallels the levels of myoinositol found in the serum of uremic patients. Myelin loss occurred in a pattern suggesting "secondary demyelination," similar to the pattern seen in uremic neuropathy. The relevance as a possible model for uremic neuropathy is discussed.

Plasma-myoinositol concentrations in uraemic neuropathy

In a series of patients with chronic renal failure managed conservatively, the rise in the plasma-myo-inositol (myoinositol) concentration has been found to be related to depression of sural-nerve conduction velocity. There was no correlation with motor-nerve conduction velocity in the peroneal nerve, or with either of these variables in a series of patients receiving chronic haemodialysis. Despite the negative correlation with sural-nerve conduction velocity, there was no correlation between the plasma-myoinositol concentration and the presence of peripheral neuropathy as assessed clinically. It is concluded that hypermyoinositolaemia may depress nerve conduction velocity, but there is no evidence that it is responsible for the development of uraemic polyneuropathy.

Accumulation of myoinositol in plasma and red cells of diabetic patients

The concentration of myoinositol in plasma, cerebrospinal fluid and red cells and its elimination by the kidneys have been studied in 51 diabetic patients with normal or impaired kidney function, 16 non-diabetic patients with renal failure and 37 healthy controls. All diabetic patients who had a glomerular filtration rate considerably below normal, was the plasma concentration of myoinositol higher than in controls. The findings show that the rise in plasma concentration of myoinositol most probably results from a decreased glomerular filtration rate. In diabetic patients, urinary excretion of myoinositol correlated with an exponential increase in glucose excretion. That myoinositol accumulates in red cells of diabetic patients may be the result of its retention within these cells caused primarily by a transient, abnormal increase in the plasma concentration of myoinositol after an average meal.

Neuropsychiatric symptomatology with chronic renal insufficiency in the stage of compensated and decompensated retention. II. Peripheral nerve disturbances

80 strictly selected patients with chronic renal insufficiency with plasma creatinine values of 1.4-14.5 mg% were examined for clinical and electrophysiological signs of nephrogenic polyneuropathy. The motor symptoms complained of were cramps in 43.8% of the patients, "restless leggs" in 18.7%, muscular twitchings in 12.5%. It was emphasized that the first two symptoms do not always indicate the presence of polyneuropathy. 30% complained of paresthesias, 5% of "burning feet". The most frequent clinical finding was the impairment of vibration sense in the feet in 37.5% followed by diminshed appreciation of passive movement of the toes in 30%, weakening or absence of the ankle jerk in 23.8% and finally, weakening of the patellar reflex in 5%...

Variation in polyol levels in cerebrospinal fluid and serum in diabetic patients

Cerebrospinal fluid (CSF) or CSF and plasma levels of sorbitol, 1,5-anhydroglucitol and myoinositol of diabetic and non-diabetic patients with normal kidney function and of diabetic and non-diabetic patients with impaired kidney function were measured by gas-liquid chromatography. The CSF sorbitol level correlated with the plasma glucose level (p less than or equal to 0.05) in diabetic patients with normal kidney function, having received insulin for less than 12 months. The correlation between CSF sorbitol and plasma glucose levels in patients not dependent on insulin was not significant. Sorbitol was not detected in the plasma. The highest sorbitol levels in CSF were seen in insulin-dependent diabetic patients with impaired kidney function. No rise was seen in non-diabetic uremia. 1,5-anhydroglucitol, normally present in plasma, was absent from CSF and plasma in diabetic patients receiving insulin. In non-diabetic uremic patients, 1,5-anhydroglucitol levels in CSF and plasma were lower than in healthy subjects, but htere was no correlation with plasma glucose levels. The myoinositol level was higher in CSF than in the plasma of both non-diabetic and diabetic patients with normal kidney function. Both plasma and CSF levels were significantly (p less than 0.001) elevated in diabetic as well as in non-diabetic uremic patients, the plasma myoinositol increasing relatively more than the CSF levels. The elevation of plasma myoinositol correlated with the elevation of plasma creatinine and thus also with the impairment of kidney function. Plasma and CSF myoinositol levels were not influenced by the plasma glucose level.