Hyperuricemia influences tryptophan metabolism via inhibition of multidrug resistance protein 4 (MRP4) and breast cancer resistance protein (BCRP)

Hyperuricemia is related to a variety of pathologies, including chronic kidney disease (CKD). However, the pathophysiological mechanisms underlying disease development are not yet fully elucidated. Here, we studied the effect of hyperuricemia on tryptophan metabolism and the potential role herein of two important uric acid efflux transporters, multidrug resistance protein 4 (MRP4) and breast cancer resistance protein (BCRP). Hyperuricemia was induced in mice by treatment with the uricase inhibitor oxonic acid, confirmed by the presence of urate crystals in the urine of treated animals. A transport assay, using membrane vesicles of cells overexpressing the transporters, revealed that uric acid inhibited substrate-specific transport by BCRP at clinically relevant concentrations (calculated IC₅₀ value: 365 ± 13 μM), as was previously reported for MRP4. Moreover, we identified kynurenic acid as a novel substrate for MRP4 and BCRP. This finding was corroborated by increased plasma levels of kynurenic acid observed in Mrp4^?/? (107 ± 19 nM; P = 0.145) and Bcrp^?/? mice (133 ± 10 nM; P = 0.0007) compared to wild type animals (71 ± 11 nM). Hyperuricemia was associated with > 1.5 fold increase in plasma kynurenine levels in all strains. Moreover, hyperuricemia led to elevated plasma kynurenic acid levels (128 ± 13 nM, P = 0.005) in wild type mice but did not further increase kynurenic acid levels in knockout mice. Based on our results, we postulate that elevated uric acid levels hamper MRP4 and BCRP functioning, thereby promoting the retention of other potentially toxic substrates, including kynurenic acid, which could contribute to the development of CKD.     

Inducible nitric oxide synthase-mediated decrease of intestinal P-glycoprotein expression under streptozotocin-induced diabetic conditions

AimsP-glycoprotein (P-gp), one of the important drug-efflux pumps, is known to be affected by pathological conditions such as inflammation or infection. Recently, it is reported that high glucose or hyperglycemia can alternate P-gp expression levels at the blood-brain barrier or in the kidney, although the details are still unknown. Here, we analyzed the alteration of intestinal P-gp expression and function in the development of diabetes and elucidated the mechanisms.Main methodsType 1 diabetes was induced in male ddY mice by an i.p. injection of streptozotocin (STZ) (230 mg/kg). We analyzed ileal P-gp expression and function using Western blot analysis and an in situ closed loop method, respectively.Key findingsA significant reduction of P-gp expression level in ileum was found 9 days after STZ administration. In contrast, a remarkable decrease in P-gp function was observed on the 3rd and 9th days. Interestingly, nitric oxide synthase (NOS) activity in ilea was significantly increased on the 9th day. The decrease of P-gp expression levels observed on the 9th day was completely suppressed by L-N^G-nitroarginine methyl ester (L-NAME), a broad range NOS inhibitor, or aminoguanidine, a specific inducible NOS (iNOS) inhibitor.SignificanceThese results indicate the possibility that nitric oxide (NO), produced by iNOS in the ileum, is involved in the reduction of ileal P-gp expression under STZ-induced diabetic conditions.     

Serum Uric Acid Levels and Risk of Metabolic Syndrome in Healthy Adults

ObjectiveTo investigate the relationship between hyperuricemia and metabolic syndrome in a population of healthy subjects.MethodsWe studied 1,573 healthy adults (25 to 64 years old) in the population laboratory of the Tehran University of Medical Sciences. The study was designed according to the World Health Organization MONICA (Multinational Monitoring of Trends and Determinants in Cardiovascular Disease) project with use of the National Cholesterol Education Program Adult Treatment Panel III criteria for metabolic syndrome.ResultsThe crude prevalence of the metabolic syndrome was 29.9% (age-adjusted, 27.5%). The rate of metabolic syndrome significantly increased in higher quartiles of serum uric acid in both sexes but especially in women (P < .0001 versus P = .026). The bivariate correlation was significant between uric acid levels and age, total serum cholesterol, high-density lipoprotein cholesterol, triglycerides, body mass index, waist and hip circumferences, waist-to-hip ratio, and systolic and diastolic blood pressures; however, there was not a significant correlation between serum uric acid concentrations and fasting plasma glucose.ConclusionThese data indicate that an independent relationship exists between hyperuricemia and the metabolic syndrome. Moreover, hyperuricemia is significantly correlated with hypertriglyceridemia, hypertension, and visceral obesity. Early detection of hyperuricemia seems to be essential for prevention of the metabolic syndrome. (Endocr Pract. 2008;14:298-304)     

Hyperuricemia and metabolic syndrome in children with overweight and obesity

ObjectiveTo study the prevalence of hyperuricemia in children with overweight or obesity and analyze the relation with metabolic syndrome and the diseases that define it.Materials and methodsThis is a cross-sectional prevalence study in 148 children recruited from pediatric endocrinology consultation, with overweight or obesity (12 ± 3 years, 48% boys, BMI 31.8 ± 6.1). We measured BMI, waist-height, waist circumference, blood pressure with standard instrumentation and glucose (fasting and after overload with 75 g), insulin resistance, cholesterol HDL, triglycerides and uric acid.ResultsThe prevalence of hyperuricemia was 53%. Patients with hyperuricemia had greater BMI (33.9 vs 30.6, p = 0.003), plus waist circumference (101.4 vs 91.1 cm, p < 0.001), higher blood pressure: systolic (123.4 vs 111.9 mm Hg, p < 0.001), diastolic (78.2 vs 68.7 mm Hg, p < 0.001). They presented greater blood glucose after overload oral glucose (107.5 vs 100.7 mg/dl, p = 0.03), insulin was higher (29.2 vs 20.7 mg/dl, p = 0.001) as well as HOMA IR (6.5 vs 4.4, p < 0.001) and HDL levels were lower (49.5 vs 54.4 mg/dl, p = 0.02).Uric acid's level which most is the likely diagnosis of metabolic syndrome corresponds to 5.4 mg/dl in our sample (sensitivity: 64% and specificity 62%).ConclusionThe prevalence of hyperuricemia in children with overweight and obesity is high. In the group of patients with obesity and hyperuricemia, we found out that the parameters measured to diagnose with metabolic syndrome were less favorable. Uric acid's level from where there is a higher possibility to see metabolic syndrome is 5.4 mg/dl.     

Different roles of zinc plus arachidonic acid on insulin sensitivity between high fructose- and high fat-fed rats

AimsThis study was to determine the effects of zinc plus arachidonic acid (ZA) treatment on the insulin action in the specific ZA target organs using hyperinsulinemic euglycemic clamp method.Main methods18 Sprague–Dawley rats weighing ~ 130 g were divided into 3 groups of 6 rats and treated them with 1) normal rat chow, 2) high fructose (60.0%) diet only, or 3) the same fructose diet plus drinking water containing 10 mg zinc plus 50 mg arachidonic acid (AA)/L. In a separate study, male Wistar rats weighing ~ 250 g were fed normal rat chow (n = 4) or high fat (66.5%) diet with drinking water containing zero (n = 9) or 10 mg AA plus 20 mg zinc /L (n = 9). After 4 week treatment, insulin action was assessed using the hyperinsulinemic eguglycemic clamp technique.Key findingsHigh fructose feeding impaired suppression of hepatic glucose output by insulin compared to controls during the clamp procedure (4.39 vs. 2.35 mg/kg/min; p < 0.05). However, ZA treatment in high fructose-fed rats showed a significant improvement of hepatic insulin sensitivity compared to non-treatment controls (4.39 vs. 2.18 mg/kg/min; p < 0.05). Glucose infusion rates in Wistar rats maintained on a high fat diet (HFD) were significantly lower compared to control rats (22.8 ± 1.3 vs. 31.9 ± 1.4 mg/kg/min; p < 0.05). ZA treatment significantly improved (~ 43%) peripheral tissue insulin sensitivity in HFD fed animals (26.7 ± 1.3 [n = 9] vs. 22.8 ± 1.3 mg/kg/min; p < 0.05).SignificanceThese data demonstrate that ZA treatment is effective in improving glucose utilization in hyperglycemic rats receiving either a high-fructose or a high-fat diet.     

Indoxyl sulfate promotes cardiac fibrosis with enhanced oxidative stress in hypertensive rats

AimsCardiovascular disease (CVD) is common in chronic kidney disease (CKD) patients. Indoxyl sulfate (IS) is a nephrovascular uremic toxin that induces oxidative stress in kidney and vascular system. The present study aimed to examine the effect of IS on fibrosis and oxidative stress in rat heart.Main methodsThe effects of IS on heart were examined by Masson's trichrome (MT) staining and immunohistochemistry using: (1) Dahl salt-resistant normotensive rats (DN), (2) Dahl salt-resistant normotensive IS-administered rats (DN + IS), (3) Dahl salt-sensitive hypertensive rats (DH), and (4) Dahl salt-sensitive hypertensive IS-administered rats (DH + IS).Key findingsDH + IS rats showed significantly increased heart weight and left ventricle weight compared with DN. DH and DH + IS rats showed significantly increased diameter of cardiomyocytes, increased MT-positive fibrotic area, increased staining for transforming growth factor (TGF)-β1, α-smooth muscle actin (SMA), type 1 collagen, NADPH oxidase Nox 4, malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHdG) and decreased staining for nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase-1 (HO-1) in the heart compared with DN. More notably, DH + IS rats showed significantly increased diameter of cardiomyocytes, increased fibrotic area, increased staining for TGF-β1, SMA, type 1 collagen, Nox4, 8-OHdG and MDA, and decreased staining for Nrf2 and HO-1 in the heart compared with DH.SignificanceIS aggravates cardiac fibrosis and cardiomyocyte hypertrophy with enhanced oxidative stress and reduced anti-oxidative defense in hypertensive rats.     

ABCG2 expression and uric acid metabolism of the intestine in hyperuricemia model rat

Abstract

To elucidate roles of the intestine in uric acid (UA) metabolism, we examined ABCG2 expression, tissue UA content and xanthine oxidoreductase (XOR) activity in different intestinal segments. Male SD rats were assigned to control group or oxonic acid-induced hyperuricemia (HUA) group. In control rats, ABCG2 was present both in villi and crypts in each segment. Tissue UA content and XOR activity were relatively high in duodenum and jejunum. However, in HUA rats, tissue UA content was significantly elevated in the ileum, whereas it remained unaltered in other segments. Moreover, ABCG2 expression in the HUA group was upregulated both in the villi and crypts of the ileum. These data indicate that the ileum may play an important role in the extra-renal UA excretion.     

Prevention of diabetic nephropathy in rats through enhanced renal antioxidative capacity by inhibition of the proteasome

AimsOxidative stress may play an important role in the pathogenesis of diabetic nephropathy (DN). Recent studies have shown that the ubiquitin–proteasome pathway (UPP) and oxidative stress have interaction. We aimed to investigate whether inhibiting the proteasome has a preventive effect on DN through suppression of renal oxidative stress.Main methodsMale Sprague–Dawley rats were randomly divided into three groups: a normal control (NC) group, a streptozotocin-induced DN model group, and a DN plus MG132 (10 μg/kg) treatment group.Key findingsIncreased 24-h urinary protein excretion rate (UPER) and renal pathological changes were all improved after MG132 administration. Furthermore, enhanced renal 26S proteasome activity and concentration in DN rats were effectively reduced after MG132 administration. Increased p47phox and nitrotyrosine (NT) expressions in kidneys of DN rats were decreased after MG132 treatment. Renal mRNA and protein expressions of NF-E2 related factor 2 (Nrf2) were up-regulated by MG132 in comparison to DN alone. Decreased renal mRNA expression of superoxide dismutase 1 (SOD1), catalase (CAT) and glutathione peroxidase (GPx) in DN rats was heightened after MG132 intervention. Depressed activities of renal SOD, CAT and GPx in DN rats were also improved by MG132 treatment. Increased renal nuclear factor κB (NF-κB) activity was inhibited after MG132 administration in DN rats at the end of 12 weeks.SignificanceOur present data suggest that inhibition of the proteasome by low-dose MG132 has a preventive effect on DN development and progression in rats through the up-regulation of antioxidant genes.     

Extra-renal elimination of uric acid via intestinal efflux transporter BCRP/ABCG2

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.     

Hyperuricemia enhances intracellular urate accumulation via down-regulation of cell-surface BCRP/ABCG2 expression in vascular endothelial cells

Hyperuricemia has been recognized as an independent risk factor for cardiovascular disease. Urate stimulates NADPH oxidase and induces production of reactive oxygen species (ROS); consequently, intracellular urate accumulation can induce oxidative stress leading to endothelial dysfunction. Here, we studied the mechanism involved, using human umbilical vascular endothelial cells (HUVEC) as a model. Pretreatment with 15 mg/dL unlabeled uric acid (corresponding to hyperuricemia) resulted in increased uptake of [¹⁴C]uric acid at steady-state by HUVEC, whereas pretreatment with 5 mg/dL uric acid (in the normal serum concentration range) did not. However, the initial uptake rate of [¹⁴C]uric acid was not affected by uric acid at either concentration. These results suggest that efflux transport of uric acid is decreased under hyperuricemic conditions. We observed a concomitant decrease of phosphorylated endothelial nitric oxide synthase. Plasma membrane expression of breast cancer resistance protein (BCRP), a uric acid efflux transporter, was decreased under hyperuricemia, though the total cellular expression of BCRP remained constant. Uric acid did not affect expression of another uric acid efflux transporter, multidrug resistance associated protein 4 (MRP4). Moreover, phosphorylation of Akt, which regulates plasma membrane localization of BCRP, was decreased. These uric acid-induced changes of BCRP and Akt were reversed in the presence of the antioxidant N-acetylcysteine. These results suggest that in hyperuricemia, uric acid-induced ROS generation inhibits Akt phosphorylation, causing a decrease in plasma membrane localization of BCRP, and the resulting decrease of BCRP-mediated efflux leads to increased uric acid accumulation and dysregulation of endothelial function.     

The effect of encapsulated glutamine on gut peptide secretion in human volunteers

ContextWeight loss and improved blood glucose control after bariatric surgery have been attributed in part to increased ileal nutrient delivery with enhanced release of glucagon-like peptide 1 (GLP-1). Non-surgical strategies to manage obesity are required. The aim of the current study was to assess whether encapsulated glutamine, targeted to the ileum, could increase GLP-1 secretion, improve glucose tolerance or reduce meal size.MethodsA single-center, randomised, double blind, placebo-controlled, cross-over study was performed in 24 healthy volunteers and 8 patients with type 2 diabetes. Fasting participants received a single dose of encapsulated ileal-release glutamine (3.6 or 6.0 g) or placebo per visit with blood sampling at baseline and for 4 h thereafter. Glucose tolerance and meal size were studied using a 75 g oral glucose tolerance test and ad libitum meal respectively.ResultsIn healthy volunteers, ingestion of 6.0 g glutamine was associated with increased GLP-1 concentrations after 90 min compared with placebo (mean 10.6 pg/ml vs 6.9 pg/ml, p = 0.004), increased insulin concentrations after 90 min (mean 70.9 vs 48.5, p = 0.048), and increased meal size at 120 min (mean 542 g eaten vs 481 g, p = 0.008). Ingestion of 6.0 g glutamine was not associated with significant differences in GLP-1, glucose or insulin concentrations after a glucose tolerance test in healthy or type 2 diabetic participants.ConclusionsSingle oral dosing of encapsulated glutamine did not provoke consistent increases in GLP-1 and insulin secretion and was not associated with beneficial metabolic effects in healthy volunteers or patients with type 2 diabetes.     

Identification and simultaneous determination of p-FHA and p-FBA,two metabolites of anti-tumor agent—Fluorapacin in rat urine

Fluorapacin, bis(4-fluorobenzyl)trisulfide, a small molecule natural product derivative of trisulfide, has revealed a broad spectrum of anti-proliferative activity and in vivo anti-tumor efficacy in human xenograft mice models with excellent safety profile. In the present study, two new metabolites, para-fluorohippuric acid (p-FHA) and para-fluorobenzoic acid (p-FBA), were identified by GC–MS and HPLC as the main metabolites in urine of rats after intravenous administration of fluorapacin. A simple HPLC-UV method for simultaneous determination of these two metabolites in urine has been developed and validated. The newly developed method demonstrated excellent specificity, accuracy, precision, and stability. This method was successfully employed to study the urinary excretion of fluorapacin in rats. The results indicated that p-FHA was the major metabolite in urine, and the total excretion recovery of p-FHA and p-FBA was 67.6 ± 4.9% (mean ± SE, n = 6) of dosage after 48 h of administration.     

Nox1 causes ileocolitis in mice deficient in glutathione peroxidase-1 and -2

We previously reported that mice deficient in two Se-dependent glutathione peroxidases, GPx1 and GPx2, have spontaneous ileocolitis. Disease severity depends on mouse genetic background. Whereas C57BL/6J (B6) GPx1/2-double-knockout (DKO) mice have moderate ileitis and mild colitis, 129S1Svlm/J (1 2 9) DKO mice have severe ileocolitis. Because GPx’s are antioxidant enzymes, we hypothesized that elevated reactive oxygen species trigger inflammation in these DKO mice. To test whether NADPH oxidase 1 (Nox1) contributes to colitis, we generated B6 triple-KO (TKO) mice to study their phenotype. Because the Nox1 gene is X-linked, we analyzed the effects of Nox1 on male B6 TKO mice and female B6 DKO mice with the Nox1^+/− (het-TKO) genotype. We found that the male TKO and female het-TKO mice are virtually disease-free when monitored from 8 through 50 days of age. Male TKO and female het-TKO mice have nearly no signs of disease (e.g., lethargy and perianal alopecia) that are often exhibited in the DKO mice; further, the slower growth rate of DKO mice is almost completely eliminated in male TKO and female het-TKO mice. Male TKO and female het-TKO mice no longer have the shortened small intestine present in the DKO mice. Finally, the pathological characteristics of the DKO ileum, including the high level of crypt apoptosis (analyzed by apoptotic figures, TUNEL, and cleaved caspase-3 immunohistochemical staining), high numbers of Ki-67-positive crypt epithelium cells, and elevated levels of monocytes expressing myeloperoxidase, are all significantly decreased in male TKO mice. The attenuated ileal and colonic pathology is also evident in female het-DKO mice. Furthermore, the male DKO ileum has eightfold higher TNF cytokine levels than TKO ileum. Nox1 mRNA is highly elevated in both B6 and 129 DKO ileum compared to wild-type mouse ileum. Taking these results together, we propose that ileocolitis in the DKO mice is caused by Nox1, which is induced by TNF. The milder disease in female het-TKO intestine is probably due to random or imprinted X-chromosome inactivation, which produces mosaic Nox1 expression.     

Aclidinium bromide, a novel long-acting muscarinic antagonist for COPD with improved preclinical renal and urinary safety profile

AimsAclidinium bromide is a novel, long-acting, inhaled muscarinic antagonist currently in registration phase for the treatment of chronic obstructive pulmonary disease. Since urinary difficulty and retention have been reported for anticholinergic agents such as tiotropium and ipratropium, it is important to examine the preclinical urinary and renal safety profile of aclidinium.Main methodsThe effect of aclidinium on urine and electrolyte excretion, renal function and voiding cystometry was analysed in conscious water-loaded Wistar rats (10–1000 μg/kg, s.c.), anaesthetised Beagle dogs (1000 μg/kg, i.v.) and anaesthetised guinea pigs (3–100 μg/kg, intratracheally), respectively. Aclidinium plasma levels were determined in an independent study. Active comparators were tiotropium (all studies) and ipratropium (cystometry only).Key findingsAclidinium 1000 μg/kg had no effect on urine excretion in rats, in contrast to tiotropium 100 μg/kg which significantly decreased this parameter (p < 0.05). Aclidinium 1000 μg/kg also had no effect on renal function in Beagle dogs. In guinea pigs, aclidinium 3–100 μg/kg had no effect on urinary bladder function, whereas tiotropium and ipratropium 100 μg/kg decreased the peak micturition pressure (p < 0.05), increased the volume of urine retained in the bladder (p < 0.01) and showed a trend to decrease the volume of urine excreted.SignificanceAclidinium had no significant effect on urinary and renal function in the animal models studied. These results, together with the rapid plasma clearance of aclidinium reported previously, suggest a lower propensity to induce urinary retention in humans than tiotropium and ipratropium.     

The effect of benzoic acid concentration on nitrogen metabolism,manure ammonia and odour emissions in finishing pigs

A complete randomised block design experiment was conducted to investigate the effects of benzoic acid inclusion level on nitrogen (N) metabolism, and manure ammonia (NH₃) and odour emissions in finishing pigs. Sixteen boars (64 kg live weight ± 1.5 kg) were assigned to one of four dietary treatments (T) varying in benzoic acid concentration: (T1) 0 g benzoic acid/kg (as fed); (T2) 10 g benzoic acid/kg; (T3) 20 g benzoic acid/kg; (T4) 30 g benzoic acid/kg. Animals were housed in individual metabolism crates and feed was provided ad libitum. All diets were formulated to have similar concentration of digestible energy and ileal digestible lysine with benzoic acid replacing wheat in the diet. There was a linear decrease in NH₃ emission (P<0.001), as the dietary benzoic acid concentration increased (141.4 mg/g versus 40.5 mg/g N intake (S.E.M. 12.1) over the 240-h storage period). However, there was no effect (P>0.05) of benzoic acid on odour concentration. Urinary nitrogen (N) excretion, total N excretion and the urinary:faecal N ratio were linearly reduced (P<0.05) with increasing benzoic acid inclusion. Furthermore, N retention increased linearly (P<0.05) as benzoic acid concentration increased from 0 g/kg to 30 g/kg in the diet. In conclusion, the inclusion of benzoic acid in the diet of finishing pigs has the potential to reduce total and urinary N excretion and the urinary to faecal N ratio. This was mirrored by reductions in manure NH₃ emissions in the benzoic acid supplemented treatments.     

Effect of naftopidil,an alpha1D/A-adrenoceptor antagonist,on the urinary bladder in rats with spinal cord injury

AimsAlpha_1D-adrenoceptors (α_1D-ARs) located in the spinal cord are involved in the control of lower urinary tract function. In order to clarify the effect of α_1D-ARs on storage function in the spinal cord, we examined the effect of oral administration and intrathecal injection of the α_1D/A-AR antagonist, naftopidil, on bladder activity, as well as the effect of naftopidil on bladder wall histology, in female rats with spinal cord injury (SCI).Main methodsAdult female Sprague–Dawley rats with Th9–10 spinal cord transection were used. In SCI rats with or without 5 mg/day of naftopidil for 4 weeks, bladder activity was examined via continuous cystometry. In other SCI rats, bladder activity was examined before and after intrathecal injection of naftopidil. In addition, bladder wall histology was compared between SCI rats with or without oral administration of naftopidil for 4 weeks.Key findingsOral administration of naftopidil decreased the number of non-voiding contractions (NVCs). Intrathecal injection of naftopidil prolonged the interval between voiding contractions, decreased the maximum voiding contraction pressure and the number of NVCs, and increased bladder capacity without affecting the residual urine volume. Oral administration of naftopidil also decreased bladder wall fibrosis.SignificanceThe α_1D/A-AR antagonist naftopidil might act on the bladder and spinal cord to improve detrusor hyperreflexia in the storage state in SCI female rats. Naftopidil also suppressed bladder wall fibrosis, suggesting that it may be effective for the treatment of neurogenic lower urinary tract dysfunction after SCI.     

Evaluation of the effect of glucosamine on an experimental rat osteoarthritis model

AimsTo investigate the in vivo effect of glucosamine on articular cartilage in osteoarthritis (OA), we evaluated serum biomarkers such as CTX-II (type II collagen degradation) and CPII (type II collagen synthesis) as well as histopathological changes (Mankin score, toluidine blue staining of proteoglycans in an experimental OA model using rats.Main methodsOA was surgically induced in the knee joint by anterior cruciate ligament transection (ACLT) in rats. Animals were divided into three groups: sham-operated group (Sham), ACLT group without GlcN administration (? GlcN) and ACLT group with oral administration of glucosamine hydrochloride (+ GlcN; 1000 mg/kg/day for 56 days).Key findingsACLT induced macroscopic erosive changes on the surfaces of articular cartilage and histological damages such as increase of Mankin score. Of note, glucosamine administration substantially suppressed the macroscopic changes, although the effect on Mankin score was not significant. In addition, serum CTX-II levels were elevated in ?GlcN group compared to that in Sham group after the operation. Of importance, the increase of CTX-II was significantly suppressed by GlcN administration. Moreover, serum CP-II levels were substantially increased in + GlcN group compared to those in Sham and ? GlcN groups after the operation.SignificanceGlcN has a potential to exert a chondroprotective action on OA by inhibiting type II collagen degradation and enhancing type II collagen synthesis in the articular cartilage.     

Age-dependent effect of ouabain on renal Na+,K+-ATPase

AimsThis study examines the effect of chronic ouabain-treatment on renal Na⁺ handling in 12-week and 52-week old rats.Main methodsWistar Kyoto rats aged 5 weeks or 45 weeks were treated with ouabain or vehicle during 7 weeks. Blood pressure was measured in conscious animals throughout the study. After 7 weeks of treatment urinary electrolyte concentration, Na⁺,K⁺-ATPase activity and α₁-subunit expression were determined in 12-week and 52-week old rats.Key findingsIn 12-week and 52-week old rats ouabain produced a significant increase in systolic blood pressure. Although no differences were observed in Na⁺ excretion in these animals, 12-week old ouabain-treated rats had lower Na⁺,K⁺-ATPase activity in proximal tubules. However, 12-week old ouabain-treated rats had decreased fractional excretion of Na⁺. In proximal tubules of 52-week old rats Na⁺,K⁺-ATPase activity did not differ between vehicle and ouabain-treated groups.SignificanceOur results show that in Wistar Kyoto rats renal response to ouabain treatment may be age-dependent and that the hypertensive effect of ouabain is independent of the effect on renal Na⁺,K⁺-ATPase.     

Sinoaortic denervation attenuates vasopressin-induced hypothermia and reduction of sympathetic nerve activity innervating brown adipose tissue in rats

It is well known that sympathetic nerve activity innervating brown adipose tissue (BAT sympathetic nerve activity) plays an important role in BAT thermogenesis. We have found that peripheral administration of arginine vasopressin (AVP) induced hypothermia by reduced thermogenesis in BAT. However, little is known about AVP-induced hypothermic response and its relationship with BAT sympathetic nerve activity. Because increases in baroreceptor inputs inhibit peripheral sympathetic nervous activity, we hypothesized that AVP-induced hypothermia is related to baroreceptor reflex suppression of BAT sympathetic nerve activity. To test this hypothesis, Male Sprague-Dawley rats were subjected to sinoaortic denervation or sham denervation, and implanted with radiotelemetry transmitters to assess the effects of peripheral administration of AVP on BAT sympathetic nerve activity, core and BAT temperatures. In sham-operated rats, an intraperitoneal (i.p.) injection of 10 µg/kg AVP led to a significant decrease in core and BAT temperatures. However, sinoaortic denervation significantly reduced the fall of core and BAT temperatures induced by AVP, compared with levels in sham-operated rats. AVP (10 µg/kg i.p.) rapidly decreased BAT sympathetic nerve activity in control and sham-operated rats, with the greatest levels of suppression occurring at 35 min and these lowest levels attained were with 30.6% and 29.24%, respectively. Furthermore, we found that sinoaortic denervation attenuated the suppressive effects of AVP (10 µg/kg i.p.) on BAT sympathetic nerve activity. The greatest level of suppression was only 20.8% occurring at 35 min after AVP. Therefore, these results indicate that the hypothermic effects of peripheral administration of AVP are partially mediated by the arterial baroreceptor reflex suppression of BAT sympathetic nerve activity and BAT thermogenesis.     

The gold nanoparticle size and exposure duration effect on the liver and kidney function of rats: In vivo

Nanoparticles (NPs) offer a great possibility for biomedical application, not only to deliver pharmaceutics, but also to be used as novel diagnostic and therapeutic approaches. Currently, there are no data available regarding to what extent the degree of the toxicity and the accumulation of gold nanoparticles (GNPs) are present in in vivo administration. This study aimed to address the GNP size and exposure duration effect on the liver and kidney function of rats: in vivo.MethodsA total of 30 healthy male Wistar-Kyoto rats of the same age (12 weeks old) and weighing 220–240 g of King Saud University colony were used. Animals were randomly divided into groups, two GNP-treated rat groups and one control group (CG). The 50 μl of 10 and 50 nm GNPs was intraperitoneally administered in rats for exposure duration of 3 days. Then, several biochemical parameters such as aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alanine transaminase (ALT), alkaline phosphatase (ALP), urea (UREA) and creatinine (CREA) were evaluated.ResultsIn this study, the AST values increased with the administration of 10 and 50 nm GNPs compared with the control. The AST values significantly increased with 10 nm GNPs compared with 50 nm GNPs and control. The GGT and ALT values decreased with the administration of 10 and 50 nm GNPs compared with the control. The GGT and ALT values significantly decreased with 50 nm GNPs compared with 10 nm GNPs and control. The ALP values significantly decreased with the administration of 10 and 50 nm GNPs compared with the control. The decrease in ALP values with 10 nm GNPs was higher than those compared with 50 nm GNPs. In this study, the levels of UREA and CREA values increased in a non significant manner after the administration of 10 and 50 nm GNPs compared with the control.ConclusionsThis study demonstrates that the increase in the enzymes AST and the decrease in ALP are smaller GNPs (10 nm) size-dependent for exposure duration of 3 days; while the decrease in the enzymes GGT and ALT are bigger GNPs (50 nm) size-dependent. The levels of UREA and CREA values indicated no significant changes with the administration of 10 and 50 nm GNPs for exposure duration of 3 days compared with the control. The administration of 10 and 50 nm GNPs for short exposure duration of 3 days induced only significant variations with some liver enzymes while kidney showed no significant variations. This study suggests that synthesis and metabolism of GNPs as well as the protection of the liver will be more important issues for medical applications of gold-based nanomaterials in future.