St Johns wort modulates the toxicities and parmacokinetics of CPT-11 (Irontecan) in rats

CPT-11 is a DNA topoisomerase I inhibitor for the therapy of colorectal cancer, whereas St. Johnrsquos Wort (Hypericum perforatum, SJW) is a widely used herbal anti-depressant. This study aimed to investigate the effects of co-administered SJW on the toxicities and pharmacokinetics of CPT-11 and the underlying mechanisms. The body weight loss, gastrointestinal and hematological toxicities induced by CPT-11, and the pharmacokinetic parameters of CPT-11 were evaluated in rats pretreated with SJW or vehicle. Rats treated with CPT-11 alone experienced rapid decrease in body weight, whereas co-administration of SJW with CPT-11 resulted in lesser body weight loss. The gastrointestinal and hematological toxicities following CPT-11 injection were both alleviated in the presence of SJW. The rat pharmacokinetics of both CPT-11 and its metabolite SN-38 were significantly altered in presence of SJW. In conclusion, co-administered SJW significantly ameliorated the toxicities induced by CPT-11. The protective effect of SJW may be partially due to pharmacokinetic interaction between CPT-11 and SJW.

Induction of propranolol metabolism by Ginkgo biloba extract EGb 761 in rats

Ginkgo biloba is one of the most popular herbal medicines in the world, due to its purported pharmacological effects, including memory-enhancing, cognition-improving, and antiplatelet effects. When used in the elderly, Ginkgo has a high potential for interactions with cardiovascular drugs. This study aimed to investigate the effects of the standard Ginkgo biloba extract (EGB 761) treatment on the pharmacokinetics of propranolol and its metabolism to form Ndesisopropylpropranolol (NDP) in rats. We also examined the activity and expression of cytochrome P450 (CYP) 1A and other CYPs in rats treated with EGb 761 at 10 and 100 mg/kg/day for 10 days. A single oral dose of propranolol (10 mg/kg) was administered on day 11 and the concentrations of both propranolol and NDP were determined using validated liquid chromatography-mass spectrometry (LC-MS) methods. The levels of mRNA and protein of various CYPs were determined by RT-PCR and Western blotting analysis, respectively. Pretreatment of EGb 761 at 100 mg/kg, but not 10 mg/kg, for 10 days significantly reduced the area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C max) of propranolol, whereas those values of NDP were significantly increased. CYP1A1, 1A2, 2B1/2, and 3A1 activities and gene expression in the rat liver were significantly increased in a dose-dependent manner by pretreatment with EGb 761. The ex-vivo formation of NDP in liver microsomes from rats pretreated with EGb 761 was markedly enhanced. The formation of NDP from propranolol in liver microsomes was significantly inhibited by α- naphthoflavone (ANF, a selective CYP1A2 inhibitor), but not by quinidine (a CYP2D inhibitor). These results indicated that EGb 761 pretreatment decreased the plasma concentrations of propranolol by accelerated conversion of parental drug to NDP due to induction of CYP1A2. EGb 761 pretreatment also significantly induced CYP2B1/2 and CYP3A1, suggesting potential interactions with substrate drugs for these two enzymes. Further study is needed to explore the potential for gingko-drug interactions and the clinical impact.

Retinal sensitivity loss in third-generation n-3 PUFA-deficient rats

A previous study conducted in guinea pigs suggested that ingestion of diets high in EPA and DHA may result in suboptimal retinal function. The aim of the present study was to evaluate retinal function in pigmented (Long-Evans) rats, raised to a third generation on diets that were either deficient in n-3 PUFA or adequate (with the addition of DHA). Electroretinographic assessment employed full-field white flash stimulation. Photoreceptor responses were evaluated in terms of peak amplitudes and implicit times (a-wave, b-wave), intensity-response functions (Naka-Rushton), and the parameters of a model of transduction (P3). Retinal phospholipid FA composition was measured by capillary GLC. DHA levels were reduced by 55% in n-3-deficient animals compared with the n-3-adequate group, whereas the levels of docosapentaenoic acid n-6 were 44 times higher in n-3-deficient animals. The level of arachidonic acid was marginally higher (12.8%) in n-6-adequate animals. The n-3-deficient animals exhibited significantly reduced retinal sensitivity (σ and S values were both affected by 0.29 log units) and increased b-wave implicit times compared with those fed the n-3-adequate diet. These data suggest that n-3 PUFA are required for development of retinal sensitivity, more so than other indices of retinal function assessed by current methods, such as maximal response amplitude. However, the benefit for retinal function of adding preformed DHA to diets already replete in n-3 PUFA remains unclear.

Biliary intervention augments chemotactic reaction and aggravates cholestatic liver injury in rats

Background
Intervention of the biliary system is frequently done in patients with obstructive jaundice and is associated with significant morbidity and mortality. The pathogenesis is unknown.
Materials and methods
A rat model of bile duct ligation (BDL) for 2 weeks was established in which biliary intervention was feasible by injection of normal saline through an indwelling catheter in the bile ducts. Plasma levels of C-C chemokine MCP-1 and C-X-C chemokine MIP-2 were measured by using ELISA. Blood monocytes, Kupffer cells, and neutrophils in the liver were characterized with antibodies to ED1, ED2, and myeloperoxidase (MPO). Lipid peroxidation was measured by malondialdehyde contents and apoptosis by TUNEL stain of the liver.
Results
Biliary intervention resulted in an increase of plasma MCP-1 and MIP-2 proteins by 1 h, which declined to normal level by 3 h in both sham and BDL rats. The levels in BDL rats were significantly higher than in sham at most points. There was a transient increase of ED1- and ED2-positive cells and MPO-staining cells in sham rat liver by 1 h after intervention. ED2-positive cells increased significantly by 1 h, while ED1- and MPO-positive cells decreased, yet insignificantly after intervention in BDL rats. The cell counts in BDL were constantly higher than in sham. Malondialdehyde increased precipitously in BDL by 3 h and was significantly higher than in sham throughout the study period. Parenchymal liver injury, manifested by elevated ALT, as well as apoptosis and necrosis of liver cells, was significantly increased in BDL rats, but not in sham rats.
Conclusion
Biliary intervention augments chemokine expression, precipitates lipid peroxidation, and aggravates liver injury in cholestatic rats.

Selective reduction in body fat mass and plasma leptin induced by angiotensin-converting enzyme inhibition in rats

Objective: There is emerging evidence that angiotensin stimulates adipocyte differentiation and lipogenesis. This study tested the hypothesis that inhibition of angiotensin II by treatment with an angiotensin-converting enzyme inhibitor, perindopril, would reduce fat mass in rats. Design: After a 12-day baseline, rats were divided into two groups: one was untreated and the other received perindopril (1.2 mg kg⁻¹ per day) in drinking water for 26 days.Subjects: In total, 16 male Sprague–Dawley rats aged 10 weeks at the start of the study. Measurements: Plasma leptin was measured in samples collected at baseline, half-way through and at the end of treatment. Body weight, food and water intake were measured daily throughout the experiment. Body fat mass, bone and lean mass were determined by dual energy X-ray absorptiometry (DEXA) at the end of the treatment period. Results: Daily food intake was the same in both groups throughout the study. By the end of treatment, animals receiving perindopril showed a modest reduction in weight gain relative to the untreated animals (62.4±5.0 g vs 73.0±4.0 g; P<0.05). DEXA analysis showed that body composition was greatly altered and the perindopril-treated group had 26% less body fat mass than the untreated group (61.0±5.2 g vs 44.4±4.2 g; P<0.01). The reduction in body fat mass was correlated with reductions in the weight of both the epididymal and retroperitoneal fat pads (P<0.001). Similarly, plasma leptin was reduced by perindopril treatment (4.64±0.56 ng ml⁻¹) compared to the untreated group (8.27±1.03 ng ml⁻¹; P<0.001). In contrast, there were no differences in lean or bone mass between the two groups.Conclusion: Oral treatment with perindopril selectively reduced body fat mass without influencing daily food intake. In contrast, there were no differences in lean or bone mass between the two groups

Undernutrition during suckling in rats elevates plasma adiponectin and its receptor in skeletal muscle regardless of diet composition : a protective effect?

Objective:
Nutrition during critical periods in early life may increase the subsequent risk of obesity, hypertension and metabolic diseases in adulthood. Few studies have focused on the long-term consequences of poor nutrition during the suckling period on the susceptibility to developing obesity when exposed to a palatable cafeteria-style high-fat diet (CD) after weaning.

Design:
This study examined the impact of early undernutrition, followed by CD exposure, on blood pressure, hormones and genes important for insulin sensitivity and metabolism and skeletal muscle mRNA expression of adiponectin receptor 1 (AdipoR1), carnitine palmitoyl-transferase I (CPT-1), cytochrome c oxidase 4 (COX4) and peroxisome proliferator-activated receptor alpha (PPARalpha). Following normal gestation, Sprague–Dawley rat litters were adjusted to 18 (undernourished) or 12 (control) pups. Rats were weaned (day 21) onto either palatable CD or standard chow.

Results:
Early undernourished rats were significantly lighter than control by 17 days, persisting into adulthood only when animals were fed chow after weaning. Regardless of litter size, rats fed CD had doubled fat mass at 15 weeks of age, and significant elevations in plasma leptin, insulin and adiponectin. Importantly, undernutrition confined to the suckling period, elevated circulating adiponectin regardless of post-weaning diet. Blood pressure was reduced in early undernourished rats fed chow, and increased by CD. Early undernutrition was associated with long-term elevations in the expression of AdipoR1, CPT-1, COX4 and PPARalpha in skeletal muscle.

Conclusion:
This study demonstrates the important role of early nutrition on body weight and metabolism, suggesting early undernourishment enhances insulin sensitivity and fatty-acid oxidation. The long-term potential benefit of limiting nutrition in the early postnatal period warrants further investigation.

Tissue distribution of lignans in rats in response to diet, dose−response, and competition with isoflavones

This paper investigates the occurrence and distribution of the lignan metabolites enterodiol (END) and enterolactone (ENL) and the isoflavone daidzein (DAID) in rat tissues by use of liquid chromatography−electrospray ionization mass spectrometry (LC−ESI/MSn) following a variety of dietary regimes. Furthermore, we examined the dose−response and distribution of END and ENL in liver, testes, prostate, and lung, and we investigated the effects of competition between lignans and isoflavones on metabolite distribution. In liver, testes, prostate, and lung tissue, dose-related increases in END concentration were observed. In the testes, coadministration of 60 mg/kg secoisolariciresinol diglycoside (SDG) with 60 mg/kg isoflavones produced alterations in the resulting metabolite profile, causing increased END concentration and decreased DAID concentration. Results indicate lignan accumulation in tissues occurs, and coadministration of lignans with isoflavones affects the metabolite profile, with effects dependent on tissue type.

Local nitric oxide synthase inhibition reduces skeletal muscle glucose uptake but not capillary blood flow during in situ muscle contraction in rats

OBJECTIVE: We have previously shown in humans that local infusion of a nitric oxide synthase (NOS) inhibitor into the femoral artery attenuates the increase in leg glucose uptake during exercise without influencing total leg blood flow. However, rodent studies examining the effect of NOS inhibition on contraction-stimulated skeletal muscle glucose uptake have yielded contradictory results. This study examined the effect of local infusion of an NOS inhibitor on skeletal muscle glucose uptake (2-deoxyglucose) and capillary blood flow (contrast-enhanced ultrasound) during in situ contractions in rats.

RESEARCH DESIGN AND METHODS: Male hooded Wistar rats were anesthetized and one hindleg electrically stimulated to contract (2 Hz, 0.1 ms) for 30 min while the other leg rested. After 10 min, the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (arterial concentration of 5 µmol/l) or saline was infused into the epigastric artery of the contracting leg.

RESULTS: Local NOS inhibition had no effect on blood pressure, heart rate, or muscle contraction force. Contractions increased (P < 0.05) skeletal muscle NOS activity, and this was prevented by L-NAME infusion. NOS inhibition caused a modest significant (P < 0.05) attenuation of the increase in femoral blood flow during contractions, but importantly there was no effect on capillary recruitment. NOS inhibition attenuated (P < 0.05) the increase in contraction-stimulated skeletal muscle glucose uptake by ~35%, without affecting AMP-activated protein kinase (AMPK) activation.

CONCLUSIONS: NOS inhibition attenuated increases in skeletal muscle glucose uptake during contraction without influencing capillary recruitment, suggesting that NO is critical for part of the normal increase in skeletal muscle fiber glucose uptake during contraction.

Short-term docosapentaenoic acid (22:5n-3) supplemtation increases tissue docosapentaenoic acid, DHA and EPA concentrations in rats

The metabolic fate of dietary n-3 docosapentaenoic acid (DPA) in mammals is currently unknown. The aim of the present study was to determine the extent of conversion of dietary DPA to DHA and EPA in rats. Four groups of male weanling Sprague–Dawley rats (aged 5 weeks) were given 50 mg of DPA, EPA, DHA or oleic acid, daily for 7 d by gavage. At the end of the treatment period, the tissues were analysed for concentrations of long-chain PUFA. DPA supplementation led to significant increases in DPA concentration in all tissues, with largest increase being in adipose (5-fold) and smallest increase being in brain (1·1-fold). DPA supplementation significantly increased the concentration of DHA in liver and the concentration of EPA in liver, heart and skeletal muscle, presumably by the process of retroconversion. EPA supplementation significantly increased the concentration of EPA and DPA in liver, heart and skeletal muscle and the DHA concentration in liver. DHA supplementation elevated the DHA levels in all tissues and EPA levels in the liver. Adipose was the main tissue site for accumulation of DPA, EPA and DHA. These data suggest that dietary DPA can be converted to DHA in the liver, in a short-term study, and that in addition it is partly retroconverted to EPA in liver, adipose, heart and skeletal muscle. Future studies should examine the physiological effect of DPA in tissues such as liver and heart.

Effects of ovariectomy and estrogen on ischemia-reperfusion injury in hindlimbs of female rats

The effects of estrogen and ovariectomy on indexes of muscle damage after 2 h of complete hindlimb ischemia and 2 h of reperfusion were investigated in female Sprague-Dawley rats. The rats were assigned to one of three experimental groups: ovariectomized with a 17-estradiol pellet implant (OE), ovariectomized with a placebo pellet implant (OP), or control with intact ovaries (R). It was hypothesized that following ischemia-reperfusion (I/R), muscle damage indexes [serum creatine kinase (CK) activity, calpain-like activity, inflammatory cell infiltration, and markers of lipid peroxidation (thiobarbituric-reactive substances)] would be lower in the OE and R rats compared with the OP rats due to the protective effects of estrogen. Serum CK activity following I/R was greater (P < 0.01) in the R rats vs. OP rats and similar in the OP and OE rats. Calpain-like activity was greatest in the R rats (P < 0.01) and similar in the OP and OE rats. Neutrophil infiltration was assessed using the myeloperoxidase (MPO) assay and immunohistochemical staining for CD43-positive (CD43+) cells. MPO activity was lower (P < 0.05) in the OE rats compared with any other group and similar in the OP and R rats. The number of CD43+ cells was greater (P < 0.01) in the OP rats compared with the OE and R rats and similar in the OE and R rats. The OE rats had lower (P < 0.05) thiobarbituric-reactive substance content following I/R compared with the R and OP rats. Indexes of muscle damage were consistently attenuated in the OE rats but not in the R rats. A 10-fold difference in serum estrogen content may mediate this. Surprisingly, serum CK activity and muscle calpain-like activity were lower (P < 0.05) in the OP rats compared with the R rats. Increases in serum insulin-like growth factor-1 content (P < 0.05) due to ovariectomy were hypothesized to account for this finding. Thus both ovariectomy and estrogen supplementation have differential effects on indexes of I/R muscle damage.

Green tea, black tea, and epigallocatechin modify body composition, improve glucose tolerance, and differentially alter metabolic gene expression in rats fed a high-fat diet

The mechanisms of how tea and epigallocatechin-3-gallate (EGCG) lower body fat are not completely understood. This study investigated long-term administration of green tea (GT), black tea (BT), or isolated EGCG (1 mg/kg per day) on body composition, glucose tolerance, and gene expression related to energy metabolism and lipid homeostasis; it was hypothesized that all treatments would improve the indicators of metabolic syndrome. Rats were fed a 15% fat diet for 6 months from 4 weeks of age and were supplied GT, BT, EGCG, or water. GT and BT reduced body fat, whereas GT and EGCG increased lean mass. At 16 weeks GT, BT, and EGCG improved glucose tolerance. In the liver, GT and BT increased the expression of genes involved in fatty acid synthesis (SREBP-1c, FAS, MCD, ACC) and oxidation (PPAR-α, CPT-1, ACO); however, EGCG had no effect. In perirenal fat, genes that mediate adipocyte differentiation were suppressed by GT (Pref-1, C/EBP-β, and PPAR-γ) and BT (C/EBP-β), while decreasing LPL, HSL, and UCP-2 expression; EGCG increased expression of UCP-2 and PPAR-γ genes. Liver triacylglycerol content was unchanged. The results suggest that GT and BT suppressed adipocyte differentiation and fatty acid uptake into adipose tissue, while increasing fat synthesis and oxidation by the liver, without inducing hepatic fat accumulation. In contrast, EGCG increased markers of thermogenesis and differentiation in adipose tissue, while having no effect on liver or muscle tissues at this dose. These results show novel and separate mechanisms by which tea and EGCG may improve glucose tolerance and support a role for these compounds in obesity prevention.

Age does not influence the bone response to treadmill exercise in female rats

Purpose: Because it is believed that bone may respond to exercise differently at different ages, we compared bone responses in immature and mature rats after 12 wk of treadmill running.

Methods: Twenty-two immature (5-wk-old) and 21 mature (17-wk-old) female Sprague Dawley rats were randomized into a running (trained, N = 10 immature, 9 mature) or a control group (controls, N = 12 immature, 12 mature) before sacrifice 12 wk later. Rats ran on a treadmill five times per week for 60-70 min at speeds up to 26 m[middle dot]min-1. Both at baseline and after intervention, we measured total body, lumbar spine, and proximal femoral bone mineral, as well as total body soft tissue composition using dual-energy x-ray absorptiometry (DXA) in vivo. After sacrificing the animals, we measured dynamic and static histomorphometry and three-point bending strength of the tibia.

Results: Running training was associated with greater differences in tibial subperiosteal area, cortical cross-sectional area, peak load, stiffness, and moment of inertia in immature and mature rats (P < 0.05). The trained rats had greater periosteal bone formation rates (P < 0.01) than controls, but there was no difference in tibial trabecular bone histomorphometry. Similar running-related gains were seen in DXA lumbar spine area (P = 0.04) and bone mineral content (BMC;P = 0.03) at both ages. For total body bone area and BMC, the immature trained group increased significantly compared with controls (P < 0.05), whereas the mature trained group gained less than did controls (P < 0.01).

Conclusion: In this in vivo model, where a similar physical training program was performed by immature and mature female rats, we demonstrated that both age groups were sensitive to loading and that bone strength gains appeared to result more from changes in bone geometry than from improved material properties.

Histological assessment of intermediate - and long-term creatine monohydrate supplementation in mice and rats

Creatine monohydrate (CrM) supplementation appears to be relatively safe based on data from short-term and intermediate-term human studies and results from several therapeutic trials. The purpose of the current study was to characterize pathological changes after intermediate-term and long-term CrM supplementation in mice [healthy control and SOD1 (G93A) transgenic] and rats (prednisolone and nonprednisolone treated). Histological assessment (18-20 organs/tissues) was performed on G93A mice after 159 days, and in Sprague-Dawley rats after 365 days, of CrM supplementation (2% wt/wt) compared with control feed. Liver histology was also evaluated in CD-1 mice after 300 days of low-dose CrM supplementation (0.025 and 0.05 g · kg^-1 · day^-1) and in Sprague-Dawley rats after 52 days of CrM supplementation (2% wt/wt) with and without prednisolone. Areas of hepatitis were observed in the livers of the CrM-supplemented G93A mice (P < 0.05), with no significant inflammatory lesions in any of the other 18-20 tissues/organs that were evaluated. The CD-1 mice also showed significant hepatic inflammatory lesions (P < 0.05), yet there was no negative effect of CrM on liver histology in the Sprague-Dawley rats after intermediate-term or long-term supplementation nor was inflammation seen in any other tissues/organs (P = not significant). Dietary CrM supplementation can induce inflammatory changes in the liver of mice, but not rats. The observed inflammatory changes in the murine liver must be considered in the evaluation of hepatic metabolism in CrM-supplemented mice. Species differences must be considered in the evaluation of toxicological and physiological studies.