Effect of creatine on the pancreatic beta-cell

We report on the stimulatory effect of creatine on insulin secretion and ATP concentration in MIN-6 beta-cells. The addition of creatine (5 mM) to MIN-6 cells in the presence of glucose (1-10 mM) elicited a significant (p<0.001) increase in insulin secretion, but no effect was demonstrated in the absence of glucose. The lack of effect of creatine in the absence of glucose suggests that creatine may act as a potentiator of insulin secretion rather than as an initiator. The potentiatory effect of creatine is specific for glucose since no effect was found in the presence of other known initiators of insulin secretion (K(+), 2-ketoisocaproic acid and tolbutamide). Cellular ATP content was markedly increased by glucose (1-15 mM). Creatine (5 and 10 mM) further increased the ATP level at all glucose concentrations, and the effect was observed even in the absence of glucose. The results from this study demonstrate the ability of creatine to increase insulin secretion only in the presence of glucose, while its effect on increased cellular ATP was independent of the presence of glucose. The mechanism whereby creatine potentiates insulin release is yet to be investigated. However, our data suggest possible unique interactions between creatine and the glucose-dependent insulin secretory pathway.

The influence of season on oxidant–antioxidant status in trained and sedentary subjects

The association between oxidative stress and cardiovascular diseases is a widely accepted fact today. Generally, men have a higher risk of cardiovascular incidents and mortality from acute myocardial infarction and strokes. We have examined sport-associated circannual rhythms of oxidant and antioxidant processes by measuring plasma LPO, erythrocyte SOD, CAT, Gpx activity and plasma hormonal status in both sedentary and long-term trained men and women. We have shown seasonal variations in both oxidant and antioxidant status in all examined groups. The largest difference was observed in the oxidant status between sedentary men and women during autumn and winter, which is considered a period of high coronary risk for men. Sport decreased LPO in trained men in autumn, while the same effect in trained women was shifted towards summer. These data state that regular, long-term physical exercise training induces adaptive responses that confer protection against oxidative stress, as well as the beneficial effect of exercise with regard to season, particularly in men during a period of high coronary risk (autumn and winter, respectively) and in women during summer.

Effect of creatine on erythrocyte rheology in vitro

To evaluate how creatine influences erythrocyte deformability, we determined its effect on erythrocyte filterability in 9 subjects with insulin dependent diabetes (IDDM) without complications, 14 diabetics with uremia and 10 non-diabetic controls. The short-term incubation (15 min at 37 degrees C) of diabetic erythrocytes with 3 mM creatine improved cell filterability (assessed according to the Reid method) from IDDM subjects without complications by 28.4% and that from diabetics with uremia by 18.9%. No rheological effect of creatine was found in erythrocytes from non-diabetic controls. However, a significant protective effect against erythrocyte filterability impairment induced by treatment of red blood cells from non-diabetic controls with hydrogen peroxide was observed with 3 mM (p < 0.04) and 5 mM (p < 0.01) creatine, respectively. Measurement of the thiobarbituric acid (TBA) reactivity was used to assess hydrogen peroxide induced formation of malondialdehyde (MDA). We found that creatine inhibits hydrogen peroxide-induced erythrocyte MDA-formation in a dose dependent manner by 20.4%, 22.3% and 41.4% for 1, 3 and 5 mM creatine, respectively. These results suggest that creatine by its ability to inhibit erythrocyte lipid peroxidation may contribute to the maintenance of normal cell deformability.

Semen quality and reproductive endocrine function in relation to biomarkers of lead, cadmium, zinc, and copper in men

Blood lead (BPb), activity of delta-aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin (EP), blood cadmium (BCd), serum zinc (SZn), seminal fluid zinc (SfZn), serum copper (SCu), and parameters of semen quality and of reproductive endocrine function were measured in 149 healthy male industrial workers 20-43 years of age. The group contained 98 subjects with slight to moderate occupational exposure to Pb and 51 reference subjects. All of the subjects lived in Zagreb, Croatia. Significant (p < 0.05) correlations of BPb, ALAD, and/or EP with reproductive parameters indicated a Pb-related decrease in sperm density, in counts of total, motile, and viable sperm, in the percentage and count of progressively motile sperm, in parameters of prostate secretory function (SfZn, acid phosphatase, and citric acid in seminal fluid), and an increase in abnormal sperm head morphology, serum testosterone, and estradiol. These associations were confirmed by results of multiple regression, which also showed significant (p < 0. 05) influence of BCd, SZn, SCu, smoking habits, alcohol consumption, or age on certain reproductive parameters. These effects were mainly of lower rank and intensity as compared to Pb-related reproductive effects, whereas BCd contributed to a decrease in sperm motility and an increase in abnormal sperm morphology and serum testosterone. No significant Pb- or Cd-related influence was found on levels of the lactate dehydrogenase isoenzyme LDH-C(4) and fructose in seminal fluid or on follicle-stimulating hormone, luteinizing hormone, and prolactin in serum. The seminal fluid concentrations of Pb (SfPb) and Cd (SfCd) were measured in 118 of the 149 subjects, and a highly significant (p < 0.0001) correlation was found between BPb and SfPb levels (r = 0.571) and between BCd and SfCd levels (r = 0.490). The overall study results indicate that even moderate exposures to Pb (BPb < 400 microg/L) and Cd (BCd < 10 microg/L) can significantly reduce human semen quality without conclusive evidence of impairment of male reproductive endocrine function.

The role of cytokines in MET-enkephalin-modulated nitric oxide release

In the present study the in vitro and in vivo effect of Met-enkephalin (MENK) on nitric oxide (NO) release by mouse peritoneal macrophages was evaluated. While in vitro MENK was ineffective unless combined with suboptimal concentrations of recombinant murine interferon gamma, in vivo all the doses (2.5, 5 or 10 mg/kg bw) bimodaly modulated NO release. Only the stimulative (2.5 and 10 mg/kg bw) and not the suppressive (5 mg/kg bw) dose of MENK was opioid receptor-mediated as demonstrated by abolishing the effect by naloxone. The stimulative effect of the low (2.5 mg/kg bw) dose, that was observed only if MENK was injected p.m., was associated with the IL production and IFN gamma as demonstrated by abolishing the effect by specific antibodies. The data additionally support the idea that opioid-mediated responses might be to a large degree mediated by the release of cytokines.

Influence of methionine-enkephalin on stress-induced parameters

This study examines the influence of methionine-enkephalin (MENK) on stress-induced oxidative damage (lipid peroxidation; LPO) in mice liver homogenate, plasma corticosterone concentration (CS) and phagocytic activity of mouse splenocytes. The LPO value increased in the mice subjected to restraint stress and had no correlation to stress duration, while MENK had no effect. The CS concentration was enhanced after 6 h of stress and 6 h after injection of a low (2.5 mg/kg bw) dose of MENK. However, MENK and stress are adjunct modulators of LPO and corticosterone in vivo. LPO was additionally elevated when MENK (10 mg/kg bw) proceeded for 2 h after the onset of stress. However, corticosterone concentration seems to be regulated differently by the same dose of MENK depending on the duration of stress i.e. elevated in cases involving short periods of stress (2 h) and decreased in cases involving prolonged periods of stress (6 h). This modulation of LPO and corticosterone by 10 mg/kg bw of MENK and 2 h of restraint stress was paralleled with elevated phagocytosis.

Superoxide dismutase activity in lymphocytes and polymorphonuclear cells of diabetic patients

Copper-zinc superoxide dismutase (Cu,Zn-superoxide dismutase) activity was evaluated in lymphocytes and polymorphonuclear cells of insulin-dependent (n = 33) and non-insulin-dependent (n = 34) diabetic patients. A commercial method for the measurement of superoxide dismutase activity was adapted for use on a discrete analyser and evaluated for interference by other antioxidants with superoxide anion-scavenging properties. In comparison to healthy control subjects (n = 32), a significantly lower Cu,Zn-superoxide dismutase activity was found in both lymphocytes and polymorphonuclear cells of insulin-dependent (2.08 +/- 0.58 vs. 1.70 +/- 0.46 U/mg protein, p < 0.05, and 1.06 +/- 0.46 vs. 0.64 +/- 0.40 U/mg protein, p < 0.001, respectively) and non-insulin-dependent diabetic patients (2.08 +/- 0.58 vs. 1.61 +/- 0.48 U/mg protein, p < 0.01, and 1.06 +/- 0.46 vs. 0.53 +/- 0.24 U/mg protein, p < 0.001, respectively). There was a week, but significant negative correlation between age and Cu,Zn-superoxide dismutase activity in lymphocytes and polymorphonuclear cells (r = -0.22 and r = -0.28, p < 0.05, respectively), whereas no influence of gender, diabetes duration and glycaemic control was observed. The results indicate that diabetes mellitus could elicit a significant disturbance in superoxide anion-scavenging potential of lymphocytes and polymorphonuclear cells.

Total plasma antioxidants in first-degree relatives of patients with insulin-dependent diabetes

Insulin-dependent diabetes mellitus (IDDM) is a chronic disorder that results from autoimmune destruction of the pancreatic beta-cells. Recent evidence suggests that oxidative damage, resulting from both cytokine-induced production of toxic free radicals and low antioxidant capacity of the beta-cell plays a significant role in the pathogenesis of IDDM. Islet cell antibodies (ICA) have been the best validated marker of risk for the development of IDDM in predisposed individuals, i.e. first-degree relatives of patients with IDDM. We investigated the total plasma antioxidant status (TAS) in both ICA-positive and ICA-negative first-degree relatives of patients with IDDM, to assess the level of overall protection against oxidative damage. TAS was significantly lowered in ICA-positive when compared to both ICA-negative and healthy subjects (p < 0.001), while no significant difference was found in comparison to recently diagnosed patients with IDDM. TAS values were not significantly influenced by gender, age and smoking habits in all groups, as well as by ICA titers in the group of ICA-positive subjects. Results indicate that prediabetic condition, apart from well-established immunological and metabolic alterations, could be associated with biochemical changes revealing complex disturbances of the antioxidative defence system. Although TAS is a functional rather than specific marker, its measurement is likely to be a valuable tool for understanding the mechanisms of specific beta-cell injury.

Evaluation of ascorbate and urate antioxidant capacity in human semen

The ascorbate/urate ratio in the seminal plasma was studied in 76 randomly chosen infertile men. The levels of ascorbate and urate were found to vary widely (range: 93-954 mumol l-1 and 127-670 mumol l-1, respectively), while the ascorbate/urate ratio was 1.03 +/- 0.63 (mean +/- SD), indicating almost equimolar concentrations of both compounds in more than 60% of the subjects investigated. No relationship of ascorbate with any biochemical marker of accessory sex gland secretions was observed, whereas an inverse correlation of urate with some prostatic markers, acid phosphatase (-0.37; P < 0.001), zinc (-0.35; P < 0.002) and citric acid (-0.33; P < 0.003), was found. In vitro experiments were conducted on an artificial suspension containing ascorbate and urate at physiological levels and activated polymorphonuclear leukocytes in the normal range (as proposed by WHO) to determine the extent to which the presence of superoxide anion-generating leukocytes contribute to the depletion of ascorbate and urate. The ascorbate level did not change in the presence of 0.2 x 10(6) leukocytes ml-1, while higher amounts of activated polymorphonuclear leukocytes initiated ascorbate oxidation, the intensity of which was in correlation with the extent of leukocyte contamination. After incubation (37 degrees C, 30 min) in the presence of 0.4, 1.0 and 1.5 x 10(6) cells ml-1, the average decline from the initial ascorbic acid level was 24, 43 and 49%, respectively. However, exposure of whole semen, instead of buffer, to oxidants released from the same amount of activated polymorphonuclears led to only 2.6, 11 and 22% decrease of the ascorbic acid, most probably due to the action of other superoxide anion scavenger compounds present in semen. Excessive superoxide anion production due to the presence of activated leukocytes had no influence on urate level either in the artificial suspension or in semen. The ability of ascorbate to afford protection against leukocyte-associated superoxide anions is not hampered in the semen of infertile men, provided that leukocyte contamination does not exceed 1 x 10(6) cells ml-1. The possible role of urate in stabilizing the ascorbate antioxidant activity in seminal plasma should be further investigated.

Relationship of sperm superoxide dismutase-like activity with other sperm-specific enzymes and experimentally induced lipid peroxidation in infertile men

Superoxide dismutase-like activity (SOD-like), isoenzyme lactate dehydrogenase-C4 (LDH-C4) and NADH-diaphorase activities in spermatozoa have been investigated from 58 normozoospermic and 27 oligozoospermic men. Significantly higher SOD-like, LDH-C4 and diaphorase activities (P < 0.01, P < 0.005 and P < 0.0001, respectively) were detected in spermatozoa from oligozoospermic men, compared to the activities found in normozoospermic samples. SOD-like activity (mean +/- SE) in oligozoospermic samples amounted to 8.3 +/- 1.6 U 10(-8) spermatozoa, while in spermatozoa in normozoospermic men with a sperm concentration above 20 million of spermatozoa per ml amounted to 4.2 +/- 0.5 U 10(-8). There was a close correlation between the SOD-like activity and biochemical indicators of the presence of residual cytoplasm i.e. isoenzyme LDH-C4 and NADH-diaphorase (r = 0.53 and r = 0.66 in normozoospermic and r = 0.63 and r = 0.54 in oligozoospermic men, respectively). A positive relationship between SOD-like activity and experimentally-induced lipid peroxidation was detected in 54 infertile men (r = 0.30; P < 0.05). These findings suggest that a higher level of superoxide dismutase-like activity may reflect a defect in the development or maturation of spermatozoa and, thereby, a decreased fertility potential. Hence, determination of SOD-like activity may give information on the state of maturity of human spermatozoa, while its role in the antioxidative protection remains to be determined.

Superoxide anion scavenging capacity of human seminal plasma

This study has investigated the antioxidant capacity of human seminal plasma due to the presence of both high and low molecular weight antioxidant factors. Methods for the measurement of superoxide dismutase-like activity (SOD-like) and total antioxidant status (TAS) were automated, and had a within-run coefficient of variation of 7.3% for SOD-like activity and 4.8% for TAS. In 69 semen samples from unselected infertile men, SOD-like activity in seminal plasma ranged from 2 to 16 U/ml, with a mean of 6.9 +/- 2.8 U/ml. As SOD-like activity was correlated positively with levels of citric acid (p < 0.0001), zinc (p < 0.0002) and acid phosphatase activity (p < 0.0005), and there was no correlation with fructose levels, our results suggest that prostatic secretions are an important source of superoxide anion scavengers. Evaluation of SOD-like activity in infertile men with accessory sex gland infections (n = 12) showed significantly lower activity (p < 0.003) compared to values found in 12 infertile men without signs of infection. The values obtained for total antioxidant status (equivalent to the antioxidant capacity of alpha-tocopherol analogue) ranged from 1.7 to 2.3 mmol/L, with a mean of 2.1 +/- 0.1 (n = 40), reflecting the protective activity of ascorbate, urate and albumin, and to a very low extent of glutathione and taurine. The data obtained by TAS assay correlated with fructose, a major marker of vesicular secretion (p < 0.005), suggesting that low molecular weight components with antioxidant capacity derive partly from the seminal vesicles. The results indicate that the relative contribution of antioxidant defence systems capable of counteracting the deleterious action of superoxide anions, depends on the secretory activity of accessory sex glands and is independent of excessive ROS production due to increased oxidative stress.

Interaction of Met-enkephalin and corticosteroids in immunomodulation

The effect of Met-enkephalin (MENK) on several immune functions, corticosterone (CS) and adrenocorticotropin (ACTH) levels in the plasma was studied in adrenalectomized (ADX) and sham-adrenalectomized (SADX) mice. Multiple Met-enkephalin injections (10 mg/kg per day in two injections 12 h apart, for 4 days) increased the plaque-forming cell response to sheep erythrocytes in the spleen and enhanced the proliferation of spleen cells in vitro. These effects were comparable in sham-adrenalectomized and adrenalectomized mice. However, spleen cells of mice immunized with sheep red blood cells and injected with Met-enkephalin, showed suppressed blastogeneic transformation with Con A. The effect was equal in adrenalectomized and sham-adrenalectomized mice. In the absence of Con A in spleen cell cultures, MENK treatment of donor mice resulted in a significant mitogenic effect. NK activity of the spleen cells was suppressed in MENK-treated adrenalectomized mice. Injection of MENK decreased corticosterone levels and increased ACTH levels in the plasma of sham-adrenalectomized mice. In adrenalectomized mice plasma levels of ACTH were decreased by MENK. It seems that corticosteroid secretion, although changed by adrenalectomy and influenced by treatment with MENK, does not influence the modulatory effect of MENK on the PFC response and blastogeneic transformation of mouse spleen cells. However, NK activity of the spleen cells treated with MENK seems to the reflect joint action of MENK and corticosteroids.

The effect of guanidino substances from uremic plasma on insulin binding to erythrocyte receptors in uremia

We have studied insulin binding to erythrocyte receptors in a group of 25 nonobese, nondiabetic uremic patients undergoing maintenance hemodialysis for 2-54 months and 14 healthy controls. Erythrocytes of predialyzed uremics bind significantly less insulin than control erythrocytes (p less than 0.01). Dialysis resulted in a rapid increase of insulin binding (p less than 0.001). The concentrations of plasma insulin and glucose remained essentially unchanged during 5-hour hemodialysis and did not significantly differ from the control values. The down regulation of insulin receptors in undialyzed patients in the presence of normal plasma insulin concentration indicates that factors other than insulin itself could be responsible for insulin receptor activity during uremia. The results demonstrated that creatinine, creatine and glycocyamine have a direct suppressive effect on insulin binding of postdialyzed plasma (p less than 0.05) in concentration of 1 mmol/l. This suggested that specific uremic toxins could play an important role in the mechanisms of altered insulin binding during hemodialysis. Despite the high concentration of these compounds in blood of uremics, the only common feature for these compounds is the presence of the guanidino group in the molecule.

Changes in insulin binding during hemodialysis in uremic patients

To investigate factors responsible for altered insulin sensitivity in uremia, we studied 125I-insulin binding to erythrocytes in 20 uremic patients before and after dialysis. In uremic patients, predialysis binding was 50% lower in comparison with healthy controls (4.35 +/- 1.79 vs. 9.37 +/- 1.30%; p less than 0.01). Five-hour dialysis treatment resulted in a rapid increase in binding (on average to 55%; p less than 0.01). During the course of dialysis, binding to erythrocytes from 2 selected patients steadily increased in a time-dependent manner (on average 24%/h). The dialysis-induced increase in binding did not correlate with the changes in plasma insulin levels, but depended on the efficiency of dialysis as assessed by a relative decrease in plasma urea and creatinine. After an intravenous glucose load, the insulin-to-glucose ratio decreased in parallel with the increase in binding after dialysis. The results indicate that uremic plasma contains dialyzable substances which reversibly inhibit insulin binding, leading to altered insulin sensitivity.

Oxidation of uric acid. 4. Synthesis, structure, and diabetogenic action of 5-imino-2,4,6(1H,3H,5H)-pyrimidinetrione salts and their alloxan-like covalent adducts

Three synthetic routes to salts of 5-amino-5-hydroxy-2,4,6(1H,3H,5H)-pyrimidinetrione (10) are described. The key reactions involved acid-catalyzed cleavage of 5-amino-5-ureido-2,4,6(1H,3H,5H)-pyrimidinetrione (7), conversion of uramil (8) to dehydrouramil (9) and subsequent hydration, and the condensation of alloxan (5) with ammonium salts. The carbinol ammonium salt structure 10a was unambiguously established by X-ray crystallography. New alloxan-like compounds 7, 9, and 10 were evaluated for diabetogenic activity in rats. Compound 7 was inactive, whereas compounds 9 and 10 showed the highest activity comparable to that of streptozotocin (12).

Inhibitor of insulin binding to erythrocytes in plasma of uremic patients

Previously, we have shown that insulin binding (IB) to erythrocytes was decreased in uremic patients and that hemodialysis corrected the receptor defect. In the present study cross-incubation experiments were performed using uremic and control erythrocytes and plasma. Incubation of control erythrocytes with uremic plasma resulted in a 60% decrease in specific insulin binding, and progressive dilutions of uremic plasma revealed a parallel decrease in degree of inhibition suggesting the presence of an inhibitor of insulin binding in uremic plasma. Plasma obtained from uremic patients exhibiting lower IB to their erythrocytes was more potent in inhibition of IB to control erythrocytes, i.e. predialysis in comparison with postdialysis plasma. The alteration of IB was reversible since incubation of uremic erythrocytes with normal plasma restored IB towards normal values. Subjects having higher IB to their erythrocytes had more efficient plasma in restoring IB to uremic erythrocytes. The data indicate that alteration of insulin binding in uremia is mediated by dialysable plasma inhibitors. The possibility that humoral factors affecting binding of insulin to its receptors can in this way influence the sensitivity of peripheral tissues to insulin is considered.

[Direct canthorhinostomy--contribution to the surgery of the tear pathways (author's transl)]

The method of choice in the obstruction of the tear pathways is dacryocystorhinostomy (DCR). It is indicated in cases of an obstruction of the lower segment of the lacrimal apparatus. It cannot be applied in cases of the obstruction of the upper segment of the tear pathways. In such pathologic conditions, the new tear pathway is formed from a part of the mucous membrane of the lateral nose wall and from a part of the mucous membrane of the septum. In a form similar to a tube, the mucous membrane of the nose will be sewn up with the mucous membrane of the conjuctiva. Direct suture is made possible by canthotomy, and, therefore, this surgery is called "Direct Cantorhinostomy".

Decreased insulin binding to erythrocytes in subjects with Klinefelter's syndrome

Insulin binding to specific erythrocyte receptors was investigated in group of 25 subjects with Klinefelter's syndrome (47 XXY genotype) and 14 healthy male volunteers. Insulin binding was significantly decreased in Klinefelter subjects (P less than 0.01 at insulin concentrations of 0.051 and 0.136 mmol/liter); however, their fasting glucose concentration was normal (87 +/- 17), and the glucose disappearance rate was slightly increased (2.3 +/- 0.9; P less than 0.2). These data indicated a compensatory, mechanism involved in the glucose metabolism in Klinefelter's syndrome.