Disturbed intestinal nitrogen homeostasis in a mouse model of high-fat diet-induced obesity and glucose intolerance.

The oligopeptide transporter peptide cotransporter-1 Slc15a1 (PEPT1) plays a major role in the regulation of nitrogen supply, since it is responsible for 70% of the dietary nitrogen absorption. Previous studies demonstrated that PEPT1 expression and function in jejunum are reduced in diabetes and obesity, suggesting a nitrogen malabsorption from the diet. Surprisingly, we reported here a decrease in gut nitrogen excretion in high-fat diet (HFD)-fed mice and further investigated the mechanisms that could explain this apparent contradiction. Upon HFD, mice exhibited an increased concentration of free amino acids (AAs) in the portal vein (60%) along with a selective increase in the expression of two AA transporters (Slc6a20a, Slc36a1), pointing to a specific and adaptive absorption of some AAs. A delayed transit time (+40%) and an increased intestinal permeability (+80%) also contribute to the increase in nitrogen absorption. Besides, HFD mice exhibited a 2.2-fold decrease in fecal DNA resulting from a reduction in nitrogen catabolism from cell desquamation and/or in the intestinal microbiota. Indeed, major quantitative (2.5-fold reduction) and qualitative alterations of intestinal microbiota were observed in feces of HFD mice. Collectively, our results strongly suggest that both increased AA transporters, intestinal permeability and transit time, and changes in gut microbiota are involved in the increased circulating AA levels. Modifications in nitrogen homeostasis provide a new insight in HFD-induced obesity and glucose intolerance; however, whether these modifications are beneficial or detrimental for the HFD-associated metabolic complications remains an open issue.

Sexual dysfunction in cystic fibrosis.

BACKGROUND: Sexual dysfunction (erectile dysfunction in males, sexual dissatisfaction, sexual interest/arousal disorders, and dyspareunia in females) has not been the subject of indepth research in people with cystic fibrosis (CF). This study aimed to determine the prevalence of sexual dysfunction in adults with CF, factors associated with sexual dysfunction, and the impact of sexual dysfunction on quality of life. METHOD: We conducted a multicentre study in adults with cystic fibrosis followed in specialist centres in Western France. We assessed erectile dysfunction and its severity using the IIEF5 self-questionnaire (International Index of Erectile Function); the FSFI (Female Sexual Function Index) was used to assess sexual function in females, and we evaluated quality of life in both sexes using the CFQ-R14+ questionnaire. RESULTS: In total, 77 males and 74 females completed the sexual function questionnaire (mean age 32+/- 10 and 25+/- 8,5 years respectively). Among them, 21 % of males and 30 % of females reported sexual dysfunction. CFQ-R14+ score was significantly lower in males with erectile dysfunction than those without (p < 0.001). Faecal incontinence was associated with more frequent sexual dysfunction in females and higher severity of erectile dysfunction in males. CONCLUSION: The prevalence of sexual disorders is relatively high in males and females with cystic fibrosis. Therefore, it seems important to train specialist teams to address the issue of sexuality without embarrassment, and to encourage them to seek out and treat faecal incontinence, which is associated with greater severity or frequency of these symptoms.

Prevalence and severity of functional urinary and anorectal disorders and their impact on quality of life in cystic fibrosis.

BACKGROUND: In cystic fibrosis (CF), coughing is associated with a risk of pelvic floor dysfunction. However, data on the prevalence of symptoms (stress urinary incontinence, bladder overactivity, dysuria, and faecal incontinence) are lacking in males and females with CF. The impact of incontinence on adherence to respiratory care has not been studied. METHODS: We conducted a multicentre study in adults with CF followed in the North-West French CF network. Urinary disorders and their severity were assessed using the Urinary Symptom Profile (USP) self-report questionnaire; the impact of urinary disorders on general quality of life was measured using the SF-Qualiveen questionnaire; faecal incontinence was assessed using the Wexner self-report questionnaire; and the CFQ-R14+ questionnaire was used to assess quality of life. A self-administered questionnaire developed for the study assessed the impact of symptoms on respiratory care. RESULTS: Of the 178 people with CF included, 34 % reported stress urinary incontinence, with a large female predominance (63.5 % of females vs. 7.5 % of males), 65 % bladder overactivity (including 16 % urge incontinence) and 50 % faecal incontinence, also with a female predominance. Neither urinary nor faecal incontinence were related to the severity of the respiratory impairment (FEV1). Quality of life was particularly affected in women. Stress urinary Incontinence symptoms affected respiratory care in both sexes. CONCLUSION: The prevalence of functional urinary and faecal disorders was high in adults with CF and impacted on quality of life and respiratory care. Therefore, multidisciplinary teams must have knowledge of symptoms, the diagnostic tools and management strategies to provide specific treatment.

Rosiglitazone and metformin have opposite effects on intestinal absorption of oligopeptides via the proton-dependent PepT1 transporter.

The intestinal H(+)/peptide cotransporter 1 (PepT1) plays a major role in nitrogen supply to the body by mediating intestinal absorption of di- and tripeptides. Previous studies have reported that in animal models of type 2 diabetes/obesity, PepT1 activity and expression were markedly reduced. This prompted us to investigate the effects of two antidiabetic drugs, rosiglitazone and metformin, on PepT1 activity/expression in a murine diet-induced obesity model. C57BL/6J male mice were fed a high-fat diet (HFD) or a standard chow for 6 weeks and then were treated for 7 days with metformin (250 mg/kg/day) and/or rosiglitazone (8 mg/kg/day). For in vitro studies, Caco-2 enterocyte-like cells were treated for 7 days with metformin (10 mM) and/or rosiglitazone (10 µM). A 7-day rosiglitazone treatment increased PepT1 activity and prevented the 2-fold HFD-induced reduction in PepT1 transport. Metformin alone did not modify PepT1 activity but counteracted rosiglitazone-induced PepT1-mediated transport. As with the in vivo studies, rosiglitazone treatment up-regulated PepT1 transport activity with concomitant induction of S6 ribosomal protein activation in vitro. Furthermore, metformin decreased PepT1 expression (mRNA and protein) and its transport activity. The effect of metformin was linked to a reduction of phosphorylated S6 ribosomal protein (active form) and of phosphorylated 4E-BP1 (inactive form), a translation repressor. These data demonstrate that two antidiabetic drugs exert opposite effects on the PepT1 transport function probably through direct action on enterocytes. In our type 2 diabetes/obesity model, rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist compensated for the HFD-induced PepT1 down-regulation, whereas metformin reversed rosiglitazone activity at the translational level.

The tripeptide KdPT protects from intestinal inflammation and maintains intestinal barrier function.

Treatment options for inflammatory bowel disease (IBD) are incompletely helpful, and surgery is often needed. One promising class of future therapeutic agents for IBD is melanocortin-related peptides, which exhibit potent immunomodulatory effects. We investigated KdPT, a tripeptide derivative of the C-terminus of α-melanocyte-stimulating hormone, as an anti-inflammatory small molecule in vivo and in vitro. Intestinal inflammation was studied after oral administration of dextran sodium sulfate and in IL-10 gene-deficient mice. The effects of KdPT on key colonic epithelial cell functions were studied in vitro and in vivo by evaluating proliferation, wound healing, transepithelial resistance, and expression of tight junction proteins. Melanin assays were performed to determine the melanotropic effects of KdPT. KdPT-treated animals showed markedly reduced severity of inflammation in both colitis models. In colonic epithelial cells, KdPT increased proliferation, accelerated closure of wounds, and improved transepithelial electrical resistance after stimulation with interferon-γ/tumor necrosis factor-α. Moreover, treatment with KdPT also prevented the loss of tight junction protein expression and improved barrier function in vivo. KdPT acted independently of IL-1 receptor type I in vivo and did not affect melanogenesis in vitro. KdPT is capable of attenuating the course of experimental colitis in different models and maintains epithelial cell function. Furthermore, KdPT does not induce pigmentation, emphasizing the potential of this small molecule for the future treatment of IBD.

Adherence with metreleptin therapy and health self-perception in patients with lipodystrophic syndromes.

BACKGROUND: Although metreleptin replacement therapy was shown to improve metabolic alterations in lipodystrophic syndromes, patients' adherence and satisfaction with treatment have never been evaluated. The 20 patients with lipodystrophic syndromes participating in the French compassionate program of metreleptin therapy filled in a self-questionnaire including an Adherence Evaluation Test, the Treatment Satisfaction Questionnaire for Medication (TSQM®-vII), and items about physical appearance. RESULTS: 15 patients were women, median age was 32.5 years (IQT 25-75 (16.2;49.5), 18 had diabetes. Adherence with metreleptin (one daily subcutaneous injection) was poor in 25%, excellent in 25% and acceptable in 50% of patients. On a 0-to-100 scale, patients' satisfaction scores reached 66.7 (52.1;81.2) for effectiveness, 55.6 (44.4;66.7) for ease/comfort of use, and 83.3 (52.1;83.3) for global satisfaction with metreleptin therapy. Self-reported side effects were frequent injection site reactions 100 (79.2;100). Satisfaction scores did not differ in patients with partial (n = 10) or generalized (n = 10) lipodystrophic syndromes, did not correlate with metabolic improvement, but were significantly higher in compliant patients with fewer side effects. Morphological appearance was reported improved under metreleptin therapy in 13 among 17 patients. CONCLUSIONS: Metreleptin increases health self-perception and decreases morphotype-associated stigmatization in most patients with lipodystrophic syndromes, but poor comfort of use and local side effects weaken adherence.

Adipocyte Glucocorticoid Receptor Deficiency Promotes Adipose Tissue Expandability and Improves the Metabolic Profile Under Corticosterone Exposure.

Widely used for their anti-inflammatory and immunosuppressive properties, glucocorticoids are nonetheless responsible for the development of diabetes and lipodystrophy. Despite an increasing number of studies focused on the adipocyte glucocorticoid receptor (GR), its precise role in the molecular mechanisms of these complications has not been elucidated. In keeping with this goal, we generated a conditional adipocyte-specific murine model of GR invalidation (AdipoGR knockout [KO] mice). Interestingly, when administered a corticosterone treatment to mimic hypercorticism conditions, AdipoGR-KO mice exhibited an improved glucose tolerance and insulin sensitivity. This was related to the adipose-specific activation of the insulin-signaling pathway, which contributed to fat mass expansion, as well as a shift toward an anti-inflammatory macrophage polarization in adipose tissue of AdipoGR-KO animals. Moreover, these mice were protected against ectopic lipid accumulation in the liver and displayed an improved lipid profile, contributing to their overall healthier phenotype. Altogether, our results indicate that adipocyte GR is a key factor of adipose tissue expansion and glucose and lipid metabolism control, which should be taken into account in the further design of adipocyte GR-selective modulators.

Adaptive ß-Cell Neogenesis in the Adult Mouse in Response to Glucocorticoid-Induced Insulin Resistance.

Both type 1 and type 2 diabetes are characterized by deficient insulin secretion and decreased ß-cell mass. Thus, regenerative strategies to increase ß-cell mass need to be developed. To characterize mechanisms of ß-cell plasticity, we studied a model of severe insulin resistance in the adult mouse and defined how ß-cells adapt. Chronic corticosterone (CORT) treatment was given to adult mice and led to rapid insulin resistance and adaptive increased insulin secretion. Adaptive and massive increase of ß-cell mass was observed during treatment up to 8 weeks. ß-Cell mass increase was partially reversible upon treatment cessation and reinduced upon subsequent treatment. ß-Cell neogenesis was suggested by an increased number of islets, mainly close to ducts, and increased Sox9 and Ngn3 mRNA levels in islets, but lineage-tracing experiments revealed that neoformed ß-cells did not derive from Sox9- or Ngn3-expressing cells. CORT treatment after ß-cell depletion partially restored ß-cells. Finally, ß-cell neogenesis was shown to be indirectly stimulated by CORT because serum from CORT-treated mice increased ß-cell differentiation in in vitro cultures of pancreatic buds. Altogether, the results present a novel model of ß-cell neogenesis in the adult mouse and identify the presence of neogenic factors in the serum of CORT-treated mice.

Interactions between antiparkinsonian drugs and ABCB1/P-glycoprotein at the blood-brain barrier in a rat brain endothelial cell model.

Parkinson's disease is a neurodegenerative disorder that requires treatment by dopaminergic agonists, which may be responsible for central side effects. We hypothesized that the efflux transporter ABCB1/P-glycoprotein played a role in brain disposition of antiparkinsonian drugs and could control central toxicity. We aimed to evaluate antiparkinsonian drugs as ABCB1 substrates and/or inhibitors in rat brain endothelial cells GPNT, in order to predict potential clinical drug-drug interactions. Among the antiparkinsonian drugs tested, levodopa, bromocriptine, pergolide and pramipexole were ABCB1 substrates. However, only bromocriptine could inhibit ABCB1 functionality with an IC(50) of 6.71 microM on Rhodamine 123 uptake and an IC(50) of 1.71 microM on digoxine uptake. Thus, bromocriptine at 100 microM is responsible for an increase of levodopa intracellular transport of about 2.05-fold versus control. Therefore, we can conclude that bromocriptine is a potent drug for medicinal interactions in vitro. Hence, in patients with Parkinson's disease, these results may be considered to optimise treatments individually.

Sleeve Gastrectomy in Morbidly Obese HIV Patients: Focus on Anti-retroviral Treatment Absorption After Surgery.

CONTEXT: Anti-retroviral therapy (ART) dramatically reduced AIDS development, thus enabling patients to live as long as the general population. New challenges have emerged particularly cardiometabolic diseases and weight gain, with some HIV patients seeking bariatric surgery (BS). However, BS outcomes during HIV remain poorly described, with scarce data on ART pharmacokinetic post-BS. OBJECTIVE: Describing sleeve gastrectomy (SG) results in HIV patients in terms of ART pharmacokinetic, HIV control, weight loss, and metabolic outcomes. DESIGN, SETTING, AND PATIENTS: Prospective study of HIV patients undergoing SG in a referral academic center, with at least 6 months follow-up. MAIN OUTCOME MEASURE: Clinical and biological parameters, HIV medical history, and ART pharmacokinetics were gathered before and post-SG. RESULTS: Seventeen patients (mean BMI = 44.2 ± 5.7 kg m-2) and major obesity-related diseases (47% type-2 diabetes, 64% obstructive sleep apnea, 70% hypertension) underwent SG during a mean 2 years of follow-up. They displayed an average of 20% reduction of initial BMI and improved body composition, similarly to obese non-HIV patients. SG improved metabolic status. All patients had undetectable viral load before BS. Upon HIV follow-up, 12 patients had undetectable viral load with correct ART kinetic parameters (3 and 6 months); 4 displayed detectable viral load along with significant decrease in raltegravir and atazanavir treatment exposure, leading to ART change with subsequent undetectable viral load; and 1 had persistent detectable viral load despite ART change. CONCLUSIONS: SG seems effective and safe in obese HIV patients. However, ART treatment should be monitored post-SG to control HIV infection. We suggest that some ART should be adapted before SG conjoints with infectious disease specialists.

Inward translocation of the phospholipid analogue miltefosine across Caco-2 cell membranes exhibits characteristics of a carrier-mediated process.

Miltefosine (hexadecylphosphocholine, HePC) is the first effective oral agent for the treatment of visceral leishmaniasis. The characteristics of HePC incorporation into the human intestinal epithelial cell line Caco-2 were investigated in order to understand its oral absorption mechanism. The results provide evidence for the involvement of a carrier-mediated mechanism, since the association of HePC at the apical pole of Caco-2 cells was (1) saturable as a function of time with a rapid initial incorporation over 5 min followed by a more gradual increase; (2) saturable as a function of concentration over the range studied (2-200 microM) with a saturable component which followed Michaelis-Menten kinetics (apparent K (m) 15.7 micromol/L, V (max) 39.2 nmol/mg protein/h) and a nonspecific diffusion component; (3) partially inhibited by low temperature and ATP depletion, indicating the temperature and energy-dependence of the uptake process. Moreover, we demonstrated, by an albumin back-extraction method, that HePC is internalized via translocation from the outer to the inner leaflet of the plasma membrane and that HePC may preferentially diffuse through intact raft microdomains. In conclusion, our results suggest that incorporation of HePC at the apical membrane of Caco-2 cells may occur through a passive diffusion followed by a translocation in the inner membrane leaflet through an active carrier-mediated mechanism.

Monitoring of Potentially Inappropriate Prescriptions in Older Inpatients: A French Multicenter Study.

OBJECTIVES: To determine whether potentially inappropriate medications (PIMs) or potentially inappropriate associations (PIAs) prescribed knowingly are associated with patient monitoring. DESIGN: Prospective observational study. SETTING: Geriatric units (n = 56) in 28 hospitals. PARTICIPANTS: Inpatients aged 75 and older (N = 1,327). MEASUREMENTS: Potentially inappropriate prescriptions (PIP) were defined as a PIM or a PIA selected by an expert board from lists of explicit criteria (Beers, Priscus, Laroche, French Health Agency) using a Delphi process. They were considered to be prescribed knowingly if they were maintained after reassessment by the geriatrician and the clinical pharmacist. Primary outcome was the rate of PIPs maintained (prescribed knowingly) and for which a geriatrician declared that specific monitoring was performed. Secondary outcomes were the parameters monitored and the rate of participants receiving knowingly a PIP. RESULTS: One thousand sixty-three PIPs were detected in 607 participants (46%). After reassessment, 826 (78%) PIPs were maintained in 490 participants (37%), the main reasons being participant's regular treatment and lack of alternative. Psychotropic (36%), cardiovascular (including antithrombotics) (29%), and laxative or antiemetic drugs (16%) were the most-frequent classes prescribed knowingly. The geriatricians declared to perform clinical or biological monitoring for 69% (n = 570) of PIMs or PIAs prescribed knowingly. Three types of specific monitoring were identified: clinical, biological, and follow-up with a specialist. CONCLUSION: Approximately three-quarters of PIMs or PIAs were prescribed knowingly, of which 69% were monitored, with wide variations in occurrence and in quality according to drug classes. This underlines the need for accurate guidelines on PIP monitoring.

Luminal leptin induces rapid inhibition of active intestinal absorption of glucose mediated by sodium-glucose cotransporter 1.

The effect of leptin on glucose transport was studied in rat jejunal mucosa in Ussing chambers. Leptin was added in the luminal or the serosal compartment before the tissues were challenged with 1, 10, or 50 mmol/l glucose. In response to 10 mmol/l glucose, the increase in short-circuit current (DeltaIsc) reached 26.8 +/- 2.1 microA/cm(2). Luminal addition of leptin dramatically decreased glucose-induced Isc (90.5% for 10 nmol/l leptin). Inhibition was maximal after 5 min and dose dependent (IC(50) = 0.13 nM). Western blot analysis showed that rapid inhibition of glucose-induced Isc by leptin was associated with a parallel decrease in the abundance of sodium-glucose transporter-1 in brush border membranes. Inhibition by luminal leptin of DeltaIsc was prevented by inhibitor of conventional protein kinase C isoforms. Serosal addition of leptin did not decrease glucose-induced Isc within 5 min and reached maximum after 10 min. The effect of leptin from serosal side was blocked by cholecystokinin (CCK) receptor-2 receptor antagonist YM022. Altogether, these data demonstrate that luminal leptin induces rapid inhibition of glucose entry into enterocyte. The slower action of leptin on the serosal side of mucosa seems indirect and is likely mediated by endogenous CCK. They demonstrate that gut leptin is a major regulator of rapid intestinal glucose transport.

Modulation of intestinal barrier properties by miltefosine.

Miltefosine (hexadecylphosphocholine, HePC) is the first effective oral agent for the treatment of visceral leishmaniasis. This study aimed to determine whether this oral administration alters the integrity and transport capacities of the intestinal barrier. The objectives of this study were: (i) to evaluate the cytotoxicity of HePC, (ii) to investigate the effects of HePC on paracellular and transcellular transport and (iii) to investigate the influence of HePC on three major transporters of the intestinal barrier, namely, P-glycoprotein, the human intestinal peptide transporter (PepT-1) and the monocarboxylic acid transporter (MCT-1) in Caco-2 cell monolayers, used as an in vitro model of the human intestinal barrier. We show that HePC reduced the transepithelial electrical resistance and increased D-[14C]mannitol permeability in a dose-dependent manner but had no effect on [3H]testosterone permeability, demonstrating that HePC treatment enhances paracellular permeability via an opening of the tight junction complex without affecting the transcellular route. Morphological studies using confocal fluorescence microscopy showed no perturbation of the normal distribution of ZO-1, occludin or E-cadherin but revealed a redistribution of the tight junction-associated protein claudin-1 and the perijunctional actin after incubation with HePC. Finally, HePC was found to inhibit the intestinal P-glycoprotein in the Caco-2 cell model after a single short exposure. These results suggest that HePC could modify the oral bioavailability of other therapeutic compounds absorbed via the paracellular route or which are substrates of the intestinal P-glycoprotein.

NOV/CCN3: A New Adipocytokine Involved in Obesity-Associated Insulin Resistance.

Identification of new adipokines that potentially link obesity to insulin resistance represents a major challenge. We recently showed that NOV/CCN3, a multifunctional matricellular protein, is synthesized and secreted by adipose tissue, with plasma levels highly correlated with BMI. NOV involvement in tissue repair, fibrotic and inflammatory diseases, and cancer has been previously reported. However, its role in energy homeostasis remains unknown. We investigated the metabolic phenotype of NOV(-/-) mice fed a standard or high-fat diet (HFD). Strikingly, the weight of NOV(-/-) mice was markedly lower than that of wild-type mice but only on an HFD. This was related to a significant decrease in fat mass associated with an increased proportion of smaller adipocytes and to a higher expression of genes involved in energy expenditure. NOV(-/-) mice fed an HFD displayed improved glucose tolerance and insulin sensitivity. Interestingly, the absence of NOV was associated with a change in macrophages profile (M1-like to M2-like), in a marked decrease in adipose tissue expression of several proinflammatory cytokines and chemokines, and in enhanced insulin signaling. Conversely, NOV treatment of adipocytes increased chemokine expression. Altogether, these results show that NOV is a new adipocytokine that could be involved in obesity-associated insulin-resistance.

Duodenal leptin stimulates cholecystokinin secretion: evidence of a positive leptin-cholecystokinin feedback loop.

Some of the actions of leptin depend on cholecystokinin (CCK). However, it is unknown whether leptin modulates the release of CCK. Here, we demonstrate in vitro that leptin induces the phosphorylation of extracellular signal-related kinase (ERK)-1/2 proteins and increases CCK release (EC(50) = 0.23 nmol/l) in CCK-secreting STC-1 cells. We showed that rat duodenal juice contains leptin that circulates free and bound to macromolecules, suggesting that leptin has a lumenal action on the intestine. In vivo in the rat, duodenal infusion of leptin increased plasma CCK at levels comparable to those induced by feeding. Moreover, meal-induced increases in plasma CCK were markedly reduced in obese fa/fa rats, whereas the mobilization of the gastric leptin pool was similar in lean and obese Zucker rats. The release of CCK by leptin presumably generates a positive feedback loop. Indeed, the blockade of CCK receptors reversed the meal reduction of the stomach leptin pool and the meal-increased plasma insulin, consistent with the previous concept of an entero-insular axis. Collectively, these data support a novel mode of action of leptin where leptin and CCK may potentiate their own effects by cross-stimulating their secretion. The impairment of this leptin-CCK loop may have pathological implications related to obesity and diabetes.

Intestinal inflammation induces adaptation of P-glycoprotein expression and activity.

Recent studies suggest that P-glycoprotein (Pgp) encoded by MDR1 gene, may be an important factor in the pathogenesis of inflammatory bowel disease (IBD). In this study, we investigated intestinal Pgp expression and activity: (1) in IL10 deficient (IL10(-/-)) mice which spontaneously develop intestinal inflammation affecting the small and large intestine and (2) in DSS (dextran sodium sulfate)-induced rat colitis. In IL10(-/-) enterocolitis mice, rhodamine 123 efflux was reduced by two to three-fold along the small and large intestine. This decrease was associated with a reduction in membrane's Pgp protein levels. A similar three-fold decrease in Pgps activity and expression was observed in the proximal colon in DSS-induced colitis in rats. However, in the non-inflamed ileum in DSS-induced rat colitis, epithelial cell's Pgp activity and protein levels were unexpectedly increased. This effect was specific to local inflammation since LPS induced systemic inflammation did affect neither the intestinal rho 123 efflux transport nor the abundance of the Pgp protein. These data demonstrate for the first time, an impaired function of epithelial Pgp in IL10 deficient enterocolitis mice. They also show an increase in Pgps activity in the non-inflamed ileum in the DSS-induced rat colitis, which may represent an adaptive mechanism to compensate the impaired activity of Pgp in the colon.

Gastric leptin: a new manager of gastrointestinal function.

Leptin, a 16 kDa protein-encoded by the ob gene, is involved in the regulation of food intake, body composition and energy expenditure through a central feedback mechanism. Initially thought to be adipocyte-specific, the ob gene, as well as the leptin receptor, has been found in a variety of other tissues including the stomach. Stomach-derived leptin, mainly secreted in the lumen, remains stable in gastric juice even at pH2. It then enters the intestine where leptin receptors have been identified on the brush border. Recent data also suggest that gut leptin may act locally within the gastrointestinal tract to influence intestinal functions, such as nutrient absorption, and thus have physiopathological implications.

Modulation of exocrine pancreatic secretion by leptin through CCK(1)-receptors and afferent vagal fibres in the rat.

In this report, we determined whether leptin could modify the exocrine pancreatic secretion of anaesthetized rats in vivo. Intravenous injection of recombinant murine leptin resulted in a time- and dose-dependent stimulation of exocrine pancreatic secretion, maximally observed with 30 nmol/kg of leptin. This stimulation of pancreatic water, bicarbonate, and protein output was abolished by atropine, hexamethonium, L364,718 ([3S(-)-N-(1,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepine]), a cholecystokinin CCK(1) receptor antagonist or perivagal capsaicin pretreatment, but unaffected by the CCK(2) receptor antagonist L365,260 ([3R(+)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3yl)-N'-(3-methylphenyl)urea]). In addition, the physiological dose of 3 nmol/kg leptin, ineffective per se, potentiated the secretory effect of 45 pmol/kg of cholecystokinin octapeptide (CCK-8) on exocrine pancreatic secretion. Furthermore, intraperitoneal leptin induced a rapid increase in plasma CCK levels in vivo in the rat. In conclusion, exogenous leptin can modulate exocrine pancreatic secretion through mechanisms involving CCK(1) receptors and capsaicin-sensitive afferent fibres in the rat. Whether this may have a physiological relevance in the postprandial regulation of exocrine pancreatic secretion and thus in nutrient digestion will require further investigations.

Influence of the pro-inflammatory cytokines on P-glycoprotein expression and functionality.

PURPOSE: P-glycoprotein (P-gp) is involved in the transport of many drugs at different barriers with consequence in terms of drug distribution and elimination. The expression and activity of P-gp can be modulated by different factors and pathologies. The present article reviews the knowledge regarding the effect of pro-inflammatory cytokines (TNFalpha, IL-1beta, IL-6, IL-2, IFNgamma) on the expression and the functionality of P-gp at three major sites of drug absorption and disposition: the liver, the blood-brain barrier, and the intestine. METHODS: The various methods used to study the effect of pro-inflammatory cytokines include in vivo models (i.e. animals infected with Staphylococcus sp, animals injected with bacterial lipopolysaccharide or directly with cytokines, ...) and in vitro models (i.e. primary rat hepatocytes, human brain endothelial cells, ...). RESULTS: The data on P-gp expression and/or function may differ according to the compound used to induce inflammation. However, there is a general trend towards a decrease in both the expression of P-gp (mRNA and protein) and its functionality. Transcription factors and nuclear receptors are probably involved in this regulation. CONCLUSION: Cytokines may interfere with P-gp. Hence, in pathological conditions (inflammation, infection, ...), the expression and functionality of P-glycoprotein may be modulated with consequences for drug disposition and, consequently treatment efficacy.