Fermentation Kinetics of Selected Dietary Fibers by Human Small Intestinal Microbiota Depend on the Type of Fiber and Subject.

SCOPE: An underexplored topic is the investigation of health effects of dietary fibers via modulation of human small intestine (SI) microbiota. A few previous studies hint at fermentation of some dietary fibers in the distal SI of humans and pigs. Here the potential of human SI microbiota to degrade dietary fibers and produce metabolites in vitro is investigated. METHODS AND RESULTS: Fructans, galacto-oligosaccharides, lemon pectins, and isomalto/malto-polysaccharides are subjected to in vitro batch fermentations inoculated with ileostomy effluent from five subjects. Fiber degradation products, formation of bacterial metabolites, and microbiota composition are determined over time. Galacto- and fructo-oligosaccharides are rapidly utilized by the SI microbiota of all subjects. At 5h of fermentation, 31%-82% of galacto-oligosaccharides and 29%-89% fructo-oligosaccharides (degree of polymerization DP4-8) are utilized. Breakdown of fructo-oligosaccharides/inulin DP ≥ 10, lemon pectin, and iso-malto/maltopolysaccharides only started after 7h incubation. Degradation of different fibers result in production of mainly acetate, and changed microbiota composition over time. CONCLUSION: Human SI microbiota have hydrolytic potential for prebiotic galacto- and fructo-oligosaccharides. In contrast, the higher molecular weight fibers inulin, lemon pectin, and iso-malto/maltopolysaccharides show slow fermentation rate. Fiber degradation kinetics and microbiota responses are subject dependent, therefore personalized nutritional fiber based strategies are required.

Impact of dietary ingredients on the interpretation of various fecal parameters in rats fed inulin.

In the present study, the influences of diets (i.e. chow and AIN-93 diets) on the interpretation of various fecal parameters including viable microbiota, moisture, weight, and short-chain fatty acids in rats fed different amounts of inulin (0.5-2 g/kg). Eight groups of rats (n = 8/group) were fed, for 4 weeks, chow or AIN-93 diets with or without inulin supplementation. Fecal samples were analyzed for different fecal parameters. After a 2-week adaptation, apparent differences in some fecal parameters were observed between the chow and AIN-93 diet groups. Throughout the 4-week intervention period, significantly (p < 0.05) higher Lactobacillus spp. counts, fecal moisture (∼2.7-fold), and fecal weight (∼5.8-fold) were observed with chow diet over AIN-93 diet. More specifically, significant elevations in the levels of Bifidobacterium spp., Lactobacillus spp., fecal moisture, and fecal weight could be observed at low-dose (0.5 g/kg) of inulin in chow diet groups, while most of these changes could merely be seen at medium-dose (1 g/kg) in AIN-93 diet groups. These results demonstrated that the choice of experimental diets would affect the comparison of fecal parameters as well as the interpretation of effective dosage of prebiotic in intestinal health assessments.

Development and application of bio-sample quantification to evaluate stability and pharmacokinetics of inulin-type fructo-oligosaccharides from Morinda Officinalis.

Inulin-type fructooligosaccharides (FOS) purified from Morinda Officinalis, with degrees of polymerization (DP) from 3 to 9, have been approved in China as an oral prescribed drug for mild and moderate depression episode, while the stability and oral absorption of this FOS mixtures are largely unknown. As the main active component and quality control marker for above FOS, DP5 was selected as the representative FOS in this study. Desalting method by ion exchange resin was developed to treat bio-sample, followed by separation and quantification by high performance liquid chromatography-charged aerosol detector. Results showed that the DP5 was stepwisely hydrolyzed in simulated gastric fluid and gut microbiota, while maintained stable in intestinal fluid. DP5 has poor permeability across Caco-2 monolayer with Papp of 5.22 × 10-7 cm/s, and very poor oral absorption with bioavailability of (0.50 ±â€¯0.12)% in rat. In conclusion, FOS in Morinda Officinalis demonstrated poor chemical stability in simulated gastric fluid and human gut microbiota, and low oral absorption in rats.

Influencia del suplemento con inulina enriquecida con fructooligosacáridos sobre el contenido y la densidad mineral ósea tras el parto y la lactación en ratas / Influence of supplementation with oligofructose-enriched inulin on bone mineral content and density after delivery and lactation in rats

Introducción: la gestación y lactancia están relacionadas con pérdidas temporales en la densidad mineral ósea (DMO) materna. Una suplementación con calcio podría resultar beneficiosa para evitar la pérdida de masa ósea del esqueleto materno. Otros nutrientes como los prebióticos han sido identificados como responsables de un incremento en la absorción de minerales, pudiendo condicionar la mineralización ósea. Objetivo: estudiar el efecto de la suplementación de la dieta materna con el prebiótico inulina enriquecida con oligofructosa, durante la gestación y la lactancia sobre el contenido mineral óseo (CMO) y la DMO al final del periodo de lactancia. Métodos: las ratas gestantes fueron alimentadas con dieta estándar (grupo CC), dieta fortificada en calcio (grupo Ca) o enriquecida con el prebiótico inulina enriquecida con oligofructosa (grupo Pre) hasta el final del periodo de lactancia. Posteriormente se evaluó el CMO y DMO por absorciometría de rayos X (DEXA) y el pH del contenido cecal. Resultados: en términos generales, el grupo Pre presenta los mayores valores absolutos de CMO y DMO de entre los tres grupos, siendo en la tibia significativamente diferentes en los grupos CC y Pre frente al grupo Ca. El pH del contenido cecal del grupo Pre es signifi cativamente inferior al de los grupos CC y Ca. Conclusión: la suplementación con inulina enriquecida con oligofructosa, en condiciones nutricionales no deficientes en calcio, durante la gestación y la lactancia, ejerce una protección del esqueleto materno en las ratas y puede ser considerada como una estrategia nutricional para proteger la masa ósea materna en el periodo perinatal (AU)

Introduction: Pregnancy and lactation are related with temporary decreases in maternal bone mineral density (BMD). Calcium supplementation could be beneficial to prevent bone loss of maternal skeleton. Other nutrients, such as prebiotics have showed to produce an increase of the mineral absorption and therefore affecting bone mineralization. Objective: To study the effect of maternal diet supplementation with prebiotic oligofructose-enriched inulin during gestation and lactation on the maternal bone mineral content (BMC) and BMD at the end of lactation. Methods: Pregnant rats were fed with standard diet (CC group), calcium fortified diet (Ca group) or with prebiotic oligofructose-enriched inulin supplemented diet until the end of the lactation period. At weaning, bone mineral content (BMC) and BMD were determined by dual-energy X-ray absorptiometry and the pH of the cecal content was also determined. Results: In absolute terms, the highest BMD and BMC were found in the Pre group as compared with the other two groups being significant in the tibia when compared Pre group and CC group with Ca group. The pH of the cecal content in the Pre group was also significantly lower as compared with the other two groups. Conclusion: Prebiotic oligofructose-enriched inulin supplementation, in calcium no-deficient conditions, during gestation and lactation exerts a protection on maternal skeleton during pregnancy and lactation in the rats and could be considered as a plausible nutritional option for protecting maternal bone mass during these periods (AU)

Zinc-Excess Intake Causes the Deterioration of Renal Function Accompanied by an Elevation in Systemic Blood Pressure Primarily Through Superoxide Radical-Induced Oxidative Stress.

Using rats fed 22 g/d of a control diet containing 0.005% zinc (Zn) or 2 Zn-excess diets containing 0.05% or 0.2% Zn for 4 weeks, we examined the mechanisms involved in the deterioration of renal function induced by Zn-excess intake. An increase in Zn intake elevated mean blood pressure (BP) and reduced renal blood flow (RBF) and inulin clearance in a dose-dependent manner. This decline in inulin clearance may be derived from a fall in RBF. Administration of the nitric oxide (NO) synthase inhibitor, Nω-nitro-l-arginine methyl ester, markedly increased mean BP and significantly decreased RBF in the 3 groups of rats. Administration of the exogenous superoxide radical (OO-) scavenger, tempol, significantly decreased mean BP and substantially increased RBF in all groups of rats. These observations suggest that both an elevation in systemic BP and a reduction in RBF seen in the 2 Zn-excess diet groups result from a decrease in the action of the vasodilator, NO, through the formation of peroxynitrite based on the nonenzymatic reaction of NO and increased OO- Indeed, the activity of the endogenous OO- scavenger, copper/Zn-superoxide dismutase, was significantly reduced in the vessel wall of rats fed 2 Zn-excess diets versus a control diet. 8-Hydroxy-2'-deoxyguanosine formation caused by OO- generation was notably elevated in the kidneys of rats fed 2 Zn-excess diets relatively to rats fed a control diet. Thus, Zn-excess intake leads to the aggravation of renal function concomitantly with an increase in systemic BP predominantly through the oxidative stress caused by OO^.

Blocking NMDA receptors delays death in rats with acute liver failure by dual protective mechanisms in kidney and brain.

Treatment of patients with acute liver failure (ALF) is unsatisfactory and mortality remains unacceptably high. Blocking NMDA receptors delays or prevents death of rats with ALF. The underlying mechanisms remain unclear. Clarifying these mechanisms will help to design more efficient treatments to increase patient's survival. The aim of this work was to shed light on the mechanisms by which blocking NMDA receptors delays rat's death in ALF. ALF was induced by galactosamine injection. NMDA receptors were blocked by continuous MK-801 administration. Edema and cerebral blood flow were assessed by magnetic resonance. The time course of ammonia levels in brain, muscle, blood, and urine; of glutamine, lactate, and water content in brain; of glomerular filtration rate and kidney damage; and of hepatic encephalopathy (HE) and intracranial pressure was assessed. ALF reduces kidney glomerular filtration rate (GFR) as reflected by reduced inulin clearance. GFR reduction is due to both reduced renal perfusion and kidney tubular damage as reflected by increased Kim-1 in urine and histological analysis. Blocking NMDA receptors delays kidney damage, allowing transient increased GFR and ammonia elimination which delays hyperammonemia and associated changes in brain. Blocking NMDA receptors does not prevent cerebral edema or blood-brain barrier permeability but reduces or prevents changes in cerebral blood flow and brain lactate. The data show that dual protective effects of MK-801 in kidney and brain delay cerebral alterations, HE, intracranial pressure increase and death. NMDA receptors antagonists may increase survival of patients with ALF by providing additional time for liver transplantation or regeneration.

pH-responsive hydrogels containing PMMA nanoparticles: an analysis of controlled release of a chemotherapeutic conjugate and transport properties.

Biopolymers composed of a pH-responsive, hydrophilic poly(methacrylic acid-grafted-ethylene glycol) network polymerized in the presence of poly(methyl methacrylate) nanoparticles were designed for the oral delivery of chemotherapeutics for the treatment of colon cancer. An inulin-doxorubicin conjugate, designed to target the colon and improve doxorubicin efficacy, was loaded into these polymer carriers at an efficiency of 54%. Release studies indicated these polymer carriers minimized conjugate release in low pH conditions and released the conjugate at neutral pH conditions using a two-step pH experiment modeling the stomach and the small intestine. At lower concentration levels, the presence of the polymer carriers did not disrupt tight junctions as determined by transepithelial electrical resistance studies using Caco-2 and HT29-MTX cell lines which are an accurate model of the GI tract epithelia. Permeability values of unmodified doxorubicin and the inulin-doxorubicin conjugate in the presence of the polymer carriers were also determined using the same cell models and ranged from 1.87 to 3.80 × 10 (-6) cm/s.

Microbiota benefits after inulin and partially hydrolized guar gumsupplementation - a randomized clinical trial in constipated women / Beneficios en la microbiota intestinal después de la suplementación con inulina y la goma guar parcialmente hidrolizada - un ensayo clínico aleatorizado en mujeres con estreñimiento

Introduction: Prebiotics positively affect gut microbiota composition, thus improving gut function. These properties may be useful for the treatment of constipation. Objectives: This study assessed the tolerance and effectiveness of a prebiotic inulin/partially hydrolyzed guargum mixture (I-PHGG) for the treatment of constipation in females, as well as its influence on the composition of intestinal microbiota and production of short chain fattyacids. Methods: Our study enrolled 60 constipated female health worker volunteers. Participants reported less than3 bowel movements per week. Volunteers were randomized to treatment with prebiotic or placebo. Treatment consisted of 3 weeks supplementation with 15 g/d IPHGG (fiber group) or maltodextrin (placebo group).Abdominal discomfort, flatulence, stool consistency, and bowel movements were evaluated by a recorded daily questionnaire and a weekly interview. Changes in fecal bacterial population and short chain fatty acids were assessed by real-time PCR and gas chromatography, respectively. Results: There was an increased frequency of weekly bowel movements and patient satisfaction in both the fiber and placebo groups with no significant differences. Total Clostridium sp significantly decreased in the fibergroup (p = 0.046) and increased in the placebo group (p =0.047). There were no changes in fecal short chain fatty acid profile. Conclusions: Consumption of I-PHGG produced clinical results comparable to placebo in constipated females, but had additional protective effects on gut microbiota by decreasing the amount of pathological bacteria of the Clostridium genera (AU)

Introducción: Los prebióticos influyen positivamente en la composición de la microbiota intestinal, mejorando así la función intestinal. Estas propiedades pueden ser útiles para el tratamiento del estreñimiento. Objetivos: Este estudio evaluó la tolerancia y la eficacia de una mezcla de prebiótico inulina con la goma guar parcialmente hidrolizada (I-PHGG) para el tratamiento de mujeres con estreñimiento, así como su influencia en la composición de la microbiota intestinal y la producción de ácidos grasos de cadena corta. Métodos: Nuestro estudio contó con la participación de60 mujeres voluntarias con estreñimiento y profesionales de la salud. Las participantes informaron tener menos de tres evacuaciones por semana y fueron asignadas aleatoriamente a tratamiento con prebióticos o placebo. El tratamiento consistió en 3 semanas de suplementación con 15 gd I-PHGG (grupo de fibras) o maltodextrina (grupo placebo). Malestar abdominal, flatulencia, consistencia de las heces, y los movimientos intestinales se evaluaron mediante un cuestionario de registro diario y una entrevista semanal. Cambios en la población de bacterias fecales y los ácidos grasos de cadena corta fueron evaluados por PCR entiempo real y cromatografía de gases, respectivamente. Resultados: Hubo un aumento en la frecuencia de las evacuaciones intestinales por semana y la satisfacción del paciente, tanto en la fibra y el grupo placebo, sin diferencias significativas. El total de Clostridium sp disminuyó significativamente en el grupo de fibras (p = 0,046) y aumentó en el grupo placebo (p = 0,047). No hubo cambios en el perfil fecal de ácidos grasos de cadena corta. Conclusiones: El consumo de I-PHGG ha producido resultados clínicos comparables a placebo en mujeres con estreñimiento, pero ofreció otros efectos protectores sobre la microbiota intestinal al disminuir la cantidad de bacterias patológicas de lo género Clostridium (AU)

Supplemental dietary inulin of variable chain lengths alters intestinal bacterial populations in young pigs.

Previously, we showed that supplementation of diets with short-chain inulin (P95), long-chain inulin (HP), and a 50:50 mixture of both (Synergy 1) improved body iron status and altered expression of the genes involved in iron homeostasis and inflammation in young pigs. However, the effects of these 3 types of inulin on intestinal bacteria remain unknown. Applying terminal restriction fragment length polymorphism analysis, we determined the abundances of luminal and adherent bacterial populations from 6 segments of the small and large intestines of pigs (n = 4 for each group) fed an iron-deficient basal diet (BD) or the BD supplemented with 4% of P95, Synergy 1, or HP for 5 wk. Compared with BD, all 3 types of inulin enhanced (P < 0.05) the abundance of beneficial bifidobacteria and lactobacilli in the microbiota adherent to intestinal mucus of various gut segments of pigs. These changes were seen as proximal as in the jejunum with P95 but did not appear until the distal ileum or cecum with HP. Similar effects of inulin on bacterial populations in the lumen contents were found. Meanwhile, all 3 types of inulin suppressed the less desirable bacteria Clostridium spp. and members of the Enterobacteriaceae in the lumen and mucosa of various gut segments. Our findings suggest that the ability of dietary inulin to alter intestinal bacterial populations may partially account for its iron bioavailability-promoting effect and possibly other health benefits.

Dietary inulin supplementation does not promote colonic iron absorption in a porcine model.

Prebiotics may enhance iron bioavailability by increasing iron absorption in the colon. Anemic pigs fitted with cecal cannulas were fed a low-iron diet with or without 4% inulin. Over 7 days, pigs were administered 1 mg of (54)Fe in the morning feed followed by cannula infusion of 0.5 mg of (58)Fe to measure total and colonic iron absorption, respectively. Whole blood was drawn prior to the initial dosing and 14 days thereafter for hemoglobin concentration and stable isotope ratio analyses. The prebiotic role of inulin was confirmed by increases in lactobacilli and bifidobacteria with reductions in clostridia using terminal restriction fragment length polymorphism (TRFLP). Total iron absorption was 23.2 +/- 2.7 and 20.7 +/- 3.5% (mean +/- SEM; p > 0.05), while colonic iron absorption was 0.4 +/- 0.1 and 1.0 +/- 0.2% (mean +/- SEM; p > 0.05) in inulin-fed and control pigs, respectively. These results show that the colon does not make a significant contribution to total iron absorption in iron-deficient pigs and that inulin does not affect iron absorption in the colon.

In vivo evidence for the efflux transport of pentazocine from the brain across the blood-brain barrier using the brain efflux index method.

The efflux transport of pentazocine (PTZ) from the brain across the blood-brain barrier (BBB) was investigated using the Brain Efflux Index method. PTZ was eliminated with the apparent elimination half-life of 13.0 min after microinjection into the parietal cortex area 2 region of the rat brain. The apparent efflux clearance of PTZ across the BBB was 137 microl/min/g brain, which was calculated from the elimination rate constant (5.35 x 10(-2) min(-1) and the distribution volume in the brain (2.56 ml/g brain). The efflux transport of PTZ was decreased in the presence of unlabeled PTZ, suggesting that PTZ is eliminated by a carrier-mediated transport system across the BBB. To characterize the efflux transport of PTZ from the brain in vivo, the effects of several compounds on the efflux transport of PTZ were investigated. P-glycoprotein (P-gp) inhibitors (verapamil and quinidine) reduced the PTZ efflux transport. In addition, the efflux transport of PTZ was inhibited by organic cations such as l-carnitine and tetraethylammonium (TEA), whereas organic anions such as p-aminohippuric acid, probenecid and taurocholate did not affect the PTZ efflux transport. The present results suggest that PTZ is transported from the brain across the BBB via l-carnitine/TEA-sensitive carrier-mediated efflux transport system(s) in addition to P-gp.

Influence of age and vitamin E on post-ischemic acute renal failure.

The aging process causes progressive deterioration in kidney structure and function. Aberrant generation of reactive oxygen species has been implicated in both age-related and ischemia-related tissue injury. Vitamin E (VE), one of the most powerful and effective exogenous antioxidants, prevents lipid peroxidation and protects against the effects of oxidative stress. The objective of this study was to determine the influence of age and VE on post-ischemic acute renal failure (ARF). Young adult, middle-aged and aged male Wistar rats were maintained on three different 30-day diets: Normal, VE absent and VE supplemented. On day 30, urinary protein and serum cholesterol and VE were measured. On day 31, rats were subjected to 60' clamping of the left renal artery plus right nephrectomy. Inulin clearance (InCl) was performed 48 h after renal ischemia. Malondialdehyde (MDA) was measured in the cortex of normal and 48-h post-ischemic kidneys. Urinary protein and serum cholesterol were higher in aged rats than in other rats. With aging, InCl decreased progressively. Vitamin E deficiency aggravated ARF. In middle-aged and aged rats, VE supplementation protected against ARF. In the absence of VE, MDA increased with age. In conclusion, our data suggest that ARF becomes more severe with age and that ischemia/reperfusion injury is exacerbated when antioxidant-scavenging ability of the kidney is impaired by VE deficiency. Supplementation with VE is essential for protecting aging kidneys against ischemic ARF.

Amelioration of tacrolimus-induced nephrotoxicity in rats using juniper oil.

BACKGROUND: Calcineurin-inhibitor nephrotoxicity plays a role in the pathogenesis of chronic allograft nephropathy by causing renal ischemia mediated by vasoconstrictive metabolites of the prostanoid pathway. The purpose of our study was to evaluate whether altering the prostanoid profile using juniper oil (JO) would afford renoprotection in rats treated with tacrolimus. METHODS: Diets supplemented with biologic oils (no supplementation, JO, fish oil [FO], safflower oil [SO], and arachidonic acid [AA]) were fed to five groups of rats for 5 weeks; during the last 2 weeks, tacrolimus was administered to all groups except for a control group of animals. At week 5, urinary prostaglandin (PG)F(2-alpha) and inulin clearances were measured. The rat kidneys were harvested to determine the renal cell membrane composition for arachidonic, eicosatrienoic, and eicosapentaenoic acids. RESULTS: Both JO and FO completely reversed the decrease in inulin clearance seen with tacrolimus, the greatest effect being with JO (inulin clearance 15.1+/-3 vs. 6.0+/-1.1 ml/min in the nonsupplemented group; P<0.001); urinary PGF(2-alpha) excretion was also highest in the JO group (328+/-23 pg/mL, P<0.001 vs. the nonsupplemented group). Fatty acid membrane analysis showed greatest incorporation of eicosapentaenoic and eicosatrienoic acids in the JO- (5.7+/-0.6% and 3.1+/-0.4%, respectively) and FO- (8.1+/-0.7% and 2.8+/-0.6%, respectively) treated animals. CONCLUSIONS: JO supplementation in tacrolimus-treated rats was associated with incorporation of vasodilatory prostanoids in the renal-cell membrane and elevated urinary PGF(2-alpha) excretion, and the precipitous fall in inulin clearance induced by tacrolimus was completely prevented. Whether this benefit will translate into a reduction in chronic allograft nephropathy remains to be determined. However, our preliminary data point towards the need for human trials.

Prevention of renal injury after induction of ozone tolerance in rats submitted to warm ischaemia.

On the basis that ozone (O3) can upregulate cellular antioxidant enzymes, a morphological, biochemical and functional renal study was performed in rats undergoing a prolonged treatment with O3 before renal ischaemia. Rats were divided into four groups: (1) control, a medial abdominal incision was performed to expose the kidneys; (2) ischaemia, in animals undergoing a bilateral renal ischaemia (30 min), with subsequent reperfusion (3 h); (3) O3 + ischaemia, as group 2, but with previous treatment with O3 (0.5 mg/kg per day given in 2.5 ml O2) via rectal administration for 15 treatments; (4) O2 + ischaemia, as group 3, but using oxygen (O2) alone. Biochemical parameters as fructosamine level, phospholipase A, and superoxide dismutases (SOD) activities, as well as renal plasma flow (RPF) and glomerular filtration rate (GFR), were measured by means of plasma clearance of p-amino-hippurate and inulin, respectively. In comparison with groups 1 and 3, the RPF and GFR were significantly decreased in groups 2 and 4. Interestingly, renal homogenates of the latter groups yielded significantly higher values of phospholipase A activity and fructosamine level in comparison with either the control (1) and the O3 (3) treated groups. Moreover renal SOD activity showed a significant increase in group 3 without significant differences among groups 1, 2 and 4. Morphological alterations of the kidney were present in 100%, 88% and 30% of the animals in groups 2, 4 and 3, respectively. It is proposed that the O3 protective effect can be ascribed to the substantial possibility of upregulating the antioxidant defence system capable of counteracting the damaging effect of ischaemia. These findings suggest that, whenever possible, ozone preconditioning may represent a prophylactic approach for minimizing renal damage before transplantation.

Muscle potassium content and potassium gluconate supplementation in normokalemic cats with naturally occurring chronic renal failure.

Muscle potassium content and supplementation with potassium gluconate were evaluated in normokalemic cats with chronic renal failure (CRF). Affected cats received standard medical therapy for renal failure and either placebo (sodium gluconate) or potassium gluconate. At the beginning of the study and after 6 months of supplementation, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were estimated using 3H-inulin and 14C-tetraethylammonium bromide (TEA) clearances. Muscle potassium content was determined in biopsy specimens using atomic absorption spectroscopy. Muscle biopsy samples obtained from cats with CRF before treatment had significantly lower muscle potassium content than did those from normal control cats. Over the 6-month period of supplementation, muscle potassium content increased both in cats with CRF that received potassium gluconate and in those that received placebo (sodium gluconate). Serum potassium concentration and fractional excretion of potassium remained relatively unchanged in both groups of cats throughout the treatment period. There were no significant differences in the percentage change in GFR and ERPF between treatment groups over the 6-month time period. Median values for pH, HCO3-, and total CO2 at 6 months were higher than baseline in the potassium gluconate group but lower than baseline in the sodium gluconate group.

L-Arginine and allopurinol protect against cyclosporine nephrotoxicity.

The role of nitric oxide (NO) and oxygen free radicals in cyclosporine (CsA) nephrotoxicity was investigated using L-arginine, an NO substrate, and allopurinol, a xanthine oxidase inhibitor (involved in the formation of oxygen radicals) in an experimental model with Wistar rats. CsA, administered at 15 mg/kg/body weight (BW) subcutaneously for 10 days, caused a decrease in glomerular filtration rate, with inulin clearance of 0.33+/-0.04 vs. 1.11+/-0.06 ml/min/100 g BW (P<0.01 vs. control). L-Arginine, 1.5% in drinking water 5 days before and during CsA administration, partially protected the animals against this fall in glomerular filtration rate, with inulin clearance of 0.68+/-0.03 ml/min/100 g BW (P<0.01 vs. CsA). Allopurinol, at 10 mg/kg/BW by gavage, also had a protective action, with inulin clearance of 0.54+/-0.04 ml/min/100 g (P<0.01 vs. CsA). CsA caused an elevation in NO production, as assessed by urinary excretion of its metabolites, nitrite and nitrate (NO2 and NO3; 0.836+/-0.358 vs. 0.107+/-0.019 nmol/microg creatinine). NO production was as much as threefold higher in the L-arginine group (1.853+/-0.206 nmol/g creatinine). This CsA effect is probably related to its vasoconstrictive stimulus. Supplementation with L-arginine, which provides more substrate for NO formation, may enhance vasodilatation and consequently reduce the impairment of renal function. The protection provided by allopurinol may be related to the reduced formation of oxygen radicals, preventing the deleterious effects of lipid peroxidation.

Effects of dietary protein and calorie restriction in clinically normal cats and in cats with surgically induced chronic renal failure.

To determine the effects of long-term dietary protein restriction in cats with chronic renal failure (CRF), 4 healthy adult cats and 7 cats with surgically induced CRF were fed a high-protein (HP, 51.7% protein) diet and 4 healthy adult cats and 7 cats with surgically induced CRF were fed a low-protein (LP, 27.6% protein) diet for 1 year. Cats with induced CRF that were fed the LP diet had reduced serum urea nitrogen concentrations, despite lower glomerular filtration rates, compared with cats with CRF fed the HP diet. Despite five-sixths reduction in renal mass, reduced glomerular filtration rate, and azotemia, 13 of the 14 cats with induced CRF retained the ability to concentrate urine and produced urine with a specific gravity > 1.035. Cats fed the HP diet consumed significantly more calories than did cats fed the LP diet, presumably because the HP diet was more palatable. As a result of the lower caloric intake in cats fed the LP diet, these cats were protein and calorie restricted, compared with cats fed the HP diet. Cats fed the HP diet weighed significantly more than did cats fed the LP diet. Mean hematocrit and mean serum albumin concentration were significantly lower in control cats and in cats with CRF fed the LP diet, compared with control cats and cats with CRF fed the HP diet. Hypokalemia developed in 4 of 7 cats with CRF fed the HP diet (containing 0.3% potassium); hypokalemia did not develop in control cats fed the same diet or in cats with CRF fed the LP diet containing 0.4% potassium. Excessive kaliuresis, hypomagnesemia, and metabolic acidosis did not appear to contribute to the hypokalemia. Subsequent supplementation of the HP diet with potassium gluconate prevented hypokalemia in cats with CRF.

Fish oil modifies effect of high cholesterol diet on intestinal absorption in diabetic rats.

Omega-3 fatty acids ('fish oil') reduce the intestinal absorption of glucose and lipids in normal and in diabetic rats, but their effect is altered by the presence of saturated or poly-unsaturated omega-6 fatty acids in the diet. This study was undertaken to test the hypothesis that the influence of fish oil on the intestinal uptake of nutrients in diabetic rats is also influenced by the cholesterol content of the diet. Streptozotocin diabetic rats were raised for 2 wk on semisynthetic diets in which the lipid composition was derived mainly from beef tallow (BT), beef tallow plus cholesterol (BTC), fish oil (FO), or fish oil plus cholesterol (FOC). Food intake and weight gain was similar in the 4 diet groups, although the fasting blood glucose was lowest in diabetic rats fed BT. Cholesterol supplementation increased intestinal wall and mucosal weights when fed with BT, but the opposite effect was seen with FO, with lower wall and mucosal mass with FOC than with FO. Ileal uptake of D-glucose was lower in FO than in BT or FOC. Cholesterol feeding was associated with enhanced jejunal uptake of cholesterol when fed with BT, but the converse was observed with FO. Thus, 1) the reduction of glucose absorption associated with feeding fish oil is blunted in the presence of a supplemented intake of cholesterol; and 2) a fish oil diet reduces cholesterol uptake even in the presence of a high level of dietary cholesterol. It remains to be established what is the optimal ratio of dietary saturated, polyunsaturated omega-3 and omega-6 fatty acids, and cholesterol required to normalize intestinal transport function in diabetic rats.

Chronic effects of omega-3 fatty acids (fish oil) in a rat 5/6 renal ablation model.

It has been proposed that fish oil dietary supplementation in the chronic rat 5/6 renal ablation model may be either protective or toxic. These conflicting hypotheses were tested in rats who underwent renal ablation or sham surgery. Twenty rats received sham surgery, and 40 received 5/6 renal ablation. All rats were fed a regular laboratory diet up to 1 week postsurgery. At that time, one half of the renal ablation group was provided with an isocaloric diet supplemented with 24% MaxEPA (fish oil), 1% safflower oil, and antioxidants. The renal ablation rats developed hypertension, albuminuria, gammaglobulinuria, and a decline in glomerular filtration rate, which was less in the fish oil group compared with that in the regular laboratory diet group at 10 and 20 wk postsurgery. The fish oil renal ablation rats had significantly less glomerulosclerosis than did the regular laboratory diet renal ablation animals, and no more glomerular fibrin deposition than did the sham controls. The renal ablation regular laboratory diet rats had a significant dyslipidemia at 20 wk which was prevented in the fish oil renal ablation cohort. The fish oil renal ablation rats also demonstrated a significant decline in renal tissue arachidonic acid incorporation and a concomitant increase in eicosapentaenoic acid and docosahexaenoic acid incorporation. The mortality of the renal ablation group was greater than that of the sham controls but not significantly different for the fish oil or the regular laboratory diet groups. These results support the hypothesis that the fish oil diet containing specific antioxidant, vitamin E, and essential fatty acid supplementation is protective in the rat remnant nephron model and prevents the evolution of glomerulosclerosis with associated renal functional impairment, while preserving glomerular filtration.

Effects of selective oxidation of 1-34 bovine parathyroid hormone on its renal actions in the rabbit.

Oxidation of both of the methionine residues (positions 8 and 18) in parathyroid hormone (PTH) eliminates many of its biological effects. The present studies were performed to examine the actions of 1,34 bovine PTH and 1-34 bovine PTH oxidized selectively at Met 8, at Met 18, and at both sites on renal electrolyte handling and on adenylate cyclase (AC) stimulation. In clearance studies in anesthetized rabbits, PTH caused a phosphaturia and an anticalciuria. PTH also stimulated renal proximal tubular AC in vitro and increased renal cortical cAMP content in vivo. PTH oxidized at Met 18 was anticalciuric, but not phosphaturic, stimulated renal AC and increased cortical cAMP content. PTH oxidized at Met 8 also produced an anticalciuria without a phosphaturia, but only weakly stimulated AC and did not alter cortical cAMP content. PTH oxidized at both Met 8 and Met 18 was phosphaturic but not anticalciuric, was a weak agonist for AC and decreased cortical cAMP content. In the isolated perfused rabbit proximal straight tubule, PTH inhibited fluid and phosphate transport, whereas the doubly oxidized peptide was inactive. The data are consistent with the possibility that the effects of PTH on renal tubular phosphorus transport are mediated by more than one mechanism and are, in part, independent of the cAMP messenger system.