In vitro and ex vivo approach for anti-urolithiatic potential of bioactive fractions of gokhru with simultaneous HPLC analysis of six major metabolites and their exploration in rat plasma

CONTEXT

Tribulus terrestris L. (Zygophyllaceae) fruits have long been used in traditional systems of medicine for the treatment of various urinary diseases including urolithiasis.

OBJECTIVE

To explore the anti-urolithiatic potential of gokhru and to develop an analytical method for quantitative estimation of metabolites for its quality control.

MATERIALS AND METHODS

Aqueous extract of gokhru fruit was prepared through maceration followed by decoction to produce a mother extract, which was further used for polarity-based fractionations. In vitro and ex vivo anti-urolithiatic activity of mother extract and fractions at different concentration (100-1000 μg/mL) were carried out using aggregation assay in synthetic urine and in rat plasma, however, nucleation assay for 30 min was done using confocal microscopy. A simultaneous HPLC method has been developed for quantification of diosgenin, catechin, rutin, gallic acid, tannic acid and quercetin in mother extract and in fractions.

RESULTS

The extraction resulted in 14.5% of w/w mother extract, however, polarity-based fractionation yielded 2.1, 2.6, 1.5, 1.3 and 6.1% w/w of hexane, toluene, dichloromethane (DCM), n-butanol and water fractions, respectively. In vitro and ex vivo studies showed a significant anti-urolithiatic potential of n-butanol fraction. Further, HPLC analysis revealed significantly (p < 0.01) higher content of quercetin (1.95 ± 0.41% w/w), diosgenin (12.75 ± 0.18% w/w) and tannic acid (9.81 ± 0.47% w/w) in n-butanol fraction as compared to others fractions.

DISCUSSION AND CONCLUSION

In vitro and ex vivo studies demonstrated potent anti-urolithiatic activity of n-butanol fraction which can be developed as new phytopharmaceuticals for urolithiasis. HPLC method can be used for quality control and pharmacokinetic studies of gokhru.

Kidney damage in acute intermittent porphyria

Acute intermittent and variegate porphyria are an autosomal dominant hereditary diseases caused by the deficient activity of porphobilinogen deaminase in the haem biosynthesis. Acute intermittent porphyria (AIP) in 11 patients (8 women and 3 men) and variegate porphyria (VP) in one patient were diagnosed and long-term treated during 15-22 years. Eleven patients had in acute attack abdominal pain, they were agitated and restless and suffered from insomnia. Besides they had various neurological signs. Examination of kidney function during remission showed hypertension and tubulointerstitial impairment of the kidneys in 10 patients (hyposthenuria and impairment of tubular excretory phase in isotopic renography). Deficiency of serum erythropoietin in 4 patients, significant deficiency of plasma and erythrocyte vitamin B6, significant hyperoxalaemia and hyperoxaluria in all patients were found. Direct relationship between plasma oxalic acid and effect of pyridoxal-5-phosphate (PLP), (effect of PLP was in indirect relationship with the concentration of erythrocyte vitamin B6), in AIP patients was found. Deficiency of vitamin B6 was probably a cause of hyperoxalaemia and hyperoxaluria in those patients. The effective therapy was repeated i.v. administration of haem-arginate during acute attacks (4-5 days). Besides during remission the patients were treated by pyridoxine (40-60 mg/day), by glucose, sodium chloride and phenothiazines. All patients showed significant improvement and had regular ambulatory check-up every three months. Currently, they are in clinical and laboratory remission.

Restrictive cardiomyopathy in a patient with primary hyperoxaluria type II

This is the first report of a cardiac manifestation of a primary hyperoxaluria type II (PH II) with the hemodynamic characteristics of a severe restrictive cardiomyopathy. PH II is a rare inherited metabolic disease characterized by a deficiency of D-glycerate dehydrogenase, which has also glyoxylate reductase activity. This defect causes an accumulation of hydroxypyruvate the precursor of oxalate. The renal excretion of oxalate is impaired causing a deposition of oxalate mainly in the kidneys. To date, less than fifty cases have been reported. Systemic oxalosis in PH II is an occasional finding; thus far, myocardial oxalosis due to PH II has never been reported. Described is the case of a 41 year old male with renal failure and severe neuropathy of unknown cause, who underwent endomyocardial biopsy under the suspicion of cardiac amyloidosis. Echocardiography and cardiac catheterization showed a severe restrictive cardiomyopathy; endomyocardial biopsy established the diagnosis of oxalosis. Plasma oxalate levels were markedly increased, therefore a liver biopsy was performed. Immunoreactivity for D-glycerate dehydrogenase/ glyoxylate reductase was absent and activity of the enzyme was < 5% of normal. In summary, these findings established the diagnosis of a restrictive cardiomyopathy due to PH II.

Major factors modulating the serum oxalic acid level in hemodialysis patients

Ascorbic acid overload and vitamin B6 deficiency have been implicated in the development of hyperoxalemia in dialysis patients, but there is still disagreement about this. Hemodialysis patients who are exposed long-term hyperoxalemia may develop secondary oxalosis with an increased risk of cardiac, vascular, and bone disease, and thus may benefit from maintaining a low serum oxalic acid level. In 452 hemodialysis patients, the serum level of oxalic acid was 47.2 +/- 22.9 micromol /l before and 16.9 +/- 10.5 micromol/l after a 4-hour dialysis session, while the ascorbic acid levels were 39.0 +/- 92.7 micromol/l and 6.5 +/- 18.6 micromol/l, the glycolic acid levels were 7.3 +/- 10.1 micromol/l and 0.6 +/- 2.3 micromol/l, and the citric acid levels were 141.3 +/- 54.7 micromol/l and 117.6 +/- 37.2 micromol/l, respectively. Most patients (65.3 percent) had low serum ascorbic acid levels (less than 10 micromol/l) before hemodialysis. The serum level of oxalic acid [Ox] showed a significant positive correlation with the levels of ascorbic acid [AA], glycolic acid [Gly], and creatinine [Cre]: [Ox] = 21.711 + 0.181 x [AA] + 0.174 x [Gly] + 0.171 x [Cre], (all micromol/l, p less than 0.05). In 124 dialysis patients, the 4-pyridoxic acid level was 8.9 +/- 19.6 micromol /l before and 3.9 +/- 8.8 micromol/l after dialysis, and it was not correlated with oxalic acid or glycolic acid. Most dialysis patients (65.3 percent) had low serum levels of ascorbic acid, but a subgroup of patients (12 percent) had high serum ascorbic acid levels (more than 100 micromol/l) associated with hyperoxalemia (88.2 +/- 24.5 micromol/l). High-dose vitamin C supplementation may aggravate hyperoxalemia in hemodialysis patients, so attention should be paid to avoiding this risk.

Human inhalation exposure to ethylene glycol

Two male volunteers (A and B) inhaled 1.43 and 1.34 mmol, respectively, of vaporous (13)C-labeled ethylene glycol ((13)C(2)-EG) over 4 h. In plasma, (13)C(2)-EG and its metabolite (13)C(2)-glycolic acid ((13)C(2)-GA) were determined together with the natural burden from background GA using a gas chromatograph equipped with a mass selective detector. Maximum plasma concentrations of (13)C(2)-EG were 11.0 and 15.8 micromol/l, and of (13)C(2)-GA were 0.9 and 1.8 micromol/l, for volunteers A and B, respectively. Corresponding plasma half-lives were 2.1 and 2.6 h for (13)C(2)-EG, and 2.9 and 2.6 h for (13)C(2)-GA. Background GA concentrations were 25.8 and 28.3 micro mol/l plasma. Unlabeled background EG, GA and oxalic acid (OA) were detected in urine in which the corresponding (13)C-labeled compounds were also quantified. Within 28 h after the start of the exposures, 6.4% and 9.3% (13)C(2)-EG, 0.70% and 0.92% (13)C(2)-GA, as well as 0.08% and 0.28% (13)C(2)-OA of the inhaled amounts of (13)C(2)-EG, were excreted in urine by volunteers A and B, respectively. The amounts of (13)C(2)-GA represented 3.7% and 14.2% of background urinary GA excreted over 24 h (274 and 88 micromol). The amounts of (13)C(2)-OA were 0.5% and 2.1% of background urinary OA excreted over 24 h (215 and 177 micromol). From the findings obtained in plasma and urine and from a toxicokinetic analysis of these data, it is highly unlikely that workplace EG exposure according to the German exposure limit (MAK-value 10 ppm EG, 8 h) could lead to adverse effects from the metabolically formed GA and OA.

Combined liver-kidney and kidney-alone transplantation in primary hyperoxaluria

Combined liver-kidney and kidney-only transplantation outcomes in primary hyperoxaluria (PH) are described. Strategies for the selection of type and timing of transplantation and pretransplantation and posttransplantation management are reviewed. Records were reviewed for 16 patients with PH who received 9 liver-kidney and 10 kidney-only transplants. Plasma oxalate values declined from 61 +/- 42 micromol/L pretransplantation to 9 +/- 6 micromol/L 1 month after transplantation in liver-kidney transplant recipients and 92 +/- 19 to 9 +/- 5 micromol/L in kidney-only transplant recipients. In most liver-kidney transplant recipients, hyperoxaluria persisted for 6 to 18 months after transplantation. Follow-up was 3.5 +/- 4.1 years in liver-kidney and 4.5 +/- 6.3 years in kidney-alone transplant recipients. Patient survival rates were 78% for liver-kidney and 89% for kidney-only transplant recipients. No hepatic allografts were lost. Three of 9 liver-kidney and 6 of 10 kidney-alone transplants lost renal allograft function. In those with functioning kidneys, renal clearance was 45.1 +/- 19.5 mL/min/1.73 m(2) in liver-kidney transplant recipients and 49.5 +/- 26.1 mL/min/1.73 m(2) in kidney-only transplant recipients at last follow-up. Kaplan-Meier 1-, 2-, 3-, and 5-year renal allograft survival rates for patients undergoing transplantation after 1984 were 78%, 78%, 52%, and 52% in liver-kidney transplant recipients and 86%, 71%, 54%, and 36% in kidney-only transplant recipients. Simultaneous grafting of liver and kidney after the development of renal insufficiency is recommended for the majority of patients with PH type I (PH-I). Kidney-alone transplantation is recommended for those with pyridoxine-responsive type I disease because pharmacological therapy allows favorable management of oxalate production in this situation. Kidney-alone transplantation also is recommended for PH type II (PH-II). This disease is less severe than PH-I, and it is currently unknown whether liver transplantation will correct the metabolic defect responsible for PH-II.

Renal replacement therapy and secondary hyperoxalemia in chronic renal failure

Oxalic acid is one of the well-known uremic toxins that participates in the pathogenesis of uremic syndrome. Secondary hyperoxalemia is a common feature in patients with chronic renal failure, but oxalate removal is not adequately accomplished by renal replacement therapy. In our series of patients, the plasma level of oxalic acid was significantly elevated, while the plasma vitamin C was in the normal range or in the upper margin of the normal range. The peritoneal clearance of oxalic acid was significantly lower in comparison to the peritoneal clearance of urea. Peritoneal clearance and peritoneal transfer of oxalic acid and other examined parameters increased using dialysis solution containing 2.5% glucose in comparison to dialysis solution containing 1.5% glucose. The significant hyperoxalemia of our patients persisted despite the relatively high peritoneal transfer of oxalic acid during continuous ambulatory peritoneal dialysis. The clearance of oxalic acid related to the clearance of urea was 58.1% during hemodialysis, 74.2% during postdilution hemofiltration, and 69.0% during postdilution hemodiafiltration. The sieving coefficient of oxalic acid during postdilution hemofiltration was 74.0% of urea sieving coefficient. The most significant decrease of plasma oxalic acid was observed during postdilution hemodiafiltation (63.3%). These results suggest that currently, renal replacement therapy is not effective enough for a permanent reduction of plasma oxalic acid.

Water-soluble vitamin levels in patients undergoing high-flux hemodialysis and receiving long-term oral postdialysis vitamin supplementation

The prescription of multivitamin supplements for dialysis patients is routine practice, but the doses prescribed differ greatly from one dialysis center to another. Few data are available concerning long-term vitamin supplementation and its effects on patients either on high-flux hemodialysis or receiving postdialysis supplementation. For several years, we have systematically prescribed to our patients an oral postdialysis multivitamin supplement containing thiamine hydrochloride 100 mg, riboflavin 20 mg, pyridoxine hydrochloride 50 mg, folic acid 6 mg, and ascorbic acid 500 mg. The aim of this study was to perform a cross-sectional long-term evaluation of the vitamin levels in patients who received this vitamin supplement for at least 12 months. We also were interested in investigating the plasma oxalic acid and total homocysteine levels associated with the long-term prescription of these vitamin supplements. Thirty-three patients on high-flux dialysis were studied. Vitamin levels and/or vitamin-dependent enzymatic activities were within the normal range (N) in all patients. The mean results (+/-SD) were plasma ascorbic acid 13.6 +/- 6.4 mg/L (N > 4), plasma folate 14.1 +/- 1.1 microg/L (N > 3), for vitamin B1, alpha-ETK 1.02 +/- 0.02 (N < 1.18) and ETKo 100 +/- 13 U/L (N > 70), for vitamin B2, alpha-EGR 1.00 +/- 0.07 (N < 1.52) and EGRo 1282 +/- 213 U/L (N > 672), and for vitamin B6, alpha-EGOT 1.34 +/- 0.10 (N < 1.8) and EGOTo 380 +/- 84 U/L (N > 228). Plasma oxalic acid was higher than normal in all patients (mean = 61 +/- 15 micromol/L, N < 33). However, all patients had oxalic acid levels within the range reported in the literature for patients not taking extra ascorbic acid. Mean total homocysteine was 24 +/- 8 micromol/L with only 4 patients (12%) having normal levels (N < 15). In conclusion, the postdialysis supplement given provides adequate vitamin levels in almost all patients in the long term. Postdialysis prescription allows an optimal compliance with the treatment, is well accepted by the patients, and is cost-effective.

Intravenous ascorbic acid as an adjuvant therapy for recombinant erythropoietin in hemodialysis patients with hyperferritinemia

BACKGROUND

Inadequate iron mobilization and defective iron utilization may cause recombinant erythropoietin (rEPO) hyporesponsiveness in hemodialysis (HD) patients with iron overload. We have demonstrated that intravenous ascorbic acid (IVAA), but not intravenous iron medication, can effectively circumvent the functional iron-deficient erythropoiesis associated with iron overload in HD patients. However, it is uncertain whether all HD patients with hyperferritinemia will consistently respond to IVAA and which index may indicate functional iron deficiency in the special entity. Therefore, a prospective study was conducted to establish the guidelines for IVAA adjuvant therapy.

METHODS

Sixty-five HD patients with serum ferritin levels of more than 500 microgram/liter were recruited and divided into the control (N = 19) and IVAA (N = 46) groups. IVAA patients with a hematocrit (Hct) of less than 30% received 300 mg of ascorbic acid three times per week for eight weeks. Controls had a Hct of more than 30% and did not receive the adjuvant therapy. Red blood cell and reticulocyte counts, iron metabolism indices, erythrocyte zinc protoporphyrin (E-ZPP), and the concentrations of plasma ascorbate and oxalate were examined before and following the therapy.

RESULTS

Thirteen patients (four controls and nine IVAA patients) withdrew by the end of the study. Eighteen patients had a dramatic response to IVAA with a significant increase in their hemoglobin and reticulocyte index and a concomitant 24% reduction in rEPO dose after eight weeks. This paralleled a significant rise in serum iron and transferrin saturation (TS) and a fall in E-ZPP and serum ferritin (baselines vs. 8 weeks, serum iron 68 +/- 37 vs. 124 +/- 64 microgram/dl, TS 27 +/- 10 vs. 48 +/- 19%, E-ZPP 123 +/- 44 vs. 70 +/- 13 micromol/mol heme, and serum ferritin 816 +/- 435 vs. 587 +/- 323 microgram/liter, P < 0. 05). Compared with responders, mean values of hemoglobin, rEPO dose, iron metabolism parameters, and E-ZPP showed no significant changes in controls (N = 15) and in non-responders (N = 19). Thirty-seven patients (18 responders and 19 non-responders) were further analyzed by receiver operating characteristic curves to seek the criteria for prediction of a response to IVAA treatment. The results showed that E-ZPP at a cut-off level of more than 105 micromol/mol heme and TS at a level of less than 25% were more specific to confirm the status of functional iron deficiency in iron-overloaded patients. The two criterion values had the highest accuracy to predict a response to treatment.

CONCLUSIONS

Functional iron-deficient erythropoiesis plays a role in rEPO-hyporesponsive anemia in HD patients with hyperferritinemia. IVAA may be an adjuvant therapy for rEPO in these patients, and E-ZPP of more than 105 micromol/mol heme and TS of less than 25% should be used to guide the IVAA treatment.

A parallel, comparative study of intravenous iron versus intravenous ascorbic acid for erythropoietin-hyporesponsive anaemia in haemodialysis patients with iron overload

BACKGROUND

Functional iron deficiency may develop and cause erythropoietin resistance in haemodialysis patients with iron overload. Controversy remains as to whether intravenous iron medication can improve this hyporesponsiveness due to decreased iron availability, or whether iron therapy will aggravate haemosiderosis. Intravenous administration of ascorbic acid has been shown to effectively circumvent resistant anaemia associated with iron overload in a small preliminary study. To elucidate further the possible mechanisms of this resistance, a parallel, comparative study was conducted to compare the effects of intravenous iron and ascorbate therapies in iron-overloaded haemodialysis patients.

METHODS

Fifty haemodialysis patients with serum ferritin of > 500 microg/l were randomly divided into two protocols. They were further stratified into controls (Control I, n = 11) and intravenous iron group (IVFE, n = 15) in protocol I; and into controls (Control II, n = 12) and intravenous ascorbic acid group (IVAA, n = 12) in protocol II. Controls had a haematocrit of > 30% and did not receive any adjuvant therapy. IVFE and IVAA patients were hyporesponsive to erythropoietin and functionally iron deficient. Ferric saccharate (100 mg dose) was administered intravenously postdialysis on five consecutive dialysis sessions in the first 2 weeks; and ascorbic acid (300 mg dose) thrice a week for 8 weeks. Red cell and iron metabolism indices were examined before and following therapy.

RESULTS

Mean values of haematocrit and transferrin saturation were significantly lower, and erythropoietin dose was higher in IVFE and IVAA patients compared to controls. Intravenous iron therapy neither improved erythropoiesis nor reduced erythropoietin dose during 12 weeks. Iron metabolism indices significantly increased at 2 and 6 weeks, but decreased at 12 weeks returning to the baselines. In contrast, mean haematocrit significantly increased from 25.8+/-0.5 to 30.6+/-0.6% with a concomitant reduction of 20% in erythropoietin dose after 8 weeks of ascorbate therapy. Serum ferritin modestly fell but with no statistical significance. The enhanced erythropoiesis paralleled a rise in transferrin saturation from 27+/-3 to 48+/-6% and serum iron from 70+/-11 to 107+/-19 microg/dl (P<0.05).

CONCLUSIONS

Short term intravenous iron therapy cannot resolve the issue of functional iron deficiency in haemodialysis patients with iron overload. Intravenous administration of ascorbic acid not only facilitates iron release from storage sites, but also increases iron utilization in the erythron. Our study draws attention to a potential adjuvant therapy, intravenous ascorbic acid, to treat erythropoietin-hyporesponsive anaemia in iron-overloaded patients.

Peritoneal clearance and peritoneal transfer of oxalic acid, vitamin C, and vitamin B6 during continuous ambulatory peritoneal dialysis

The peritoneal clearance and peritoneal transfer of oxalic acid, vitamin C, and vitamin B6 in 32 patients during continuous ambulatory peritoneal dialysis (CAPD) using peritoneal dialysis solutions containing 1.5% or 2.5% glucose were examined. The plasma level of oxalic acid was significantly elevated in all patients, plasma vitamin C was in the normal range or in the upper margin of the normal range, and plasma vitamin B6 was in the normal range. The peritoneal clearance of oxalic acid was significantly lower, and the peritoneal clearance of vitamin B6 was the lowest in comparison to the peritoneal clearance of urea. With the exception of vitamin B6, the peritoneal clearance and peritoneal transfer of the examined parameters increased using the dialysis solution containing 2.5% glucose. We found direct relationships between the plasma levels of oxalic acid and creatinine as well as plasma vitamin C and between the peritoneal transfer of oxalic acid and the peritoneal transfer of vitamin C as well as vitamin B6. The significant hyperoxalemia of our patients was found to persist despite the relatively high peritoneal transfer of oxalic acid during CAPD. These results suggest that CAPD is not a method effective enough for permanent reduction of the plasma levels of oxalic acid.