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M Buyse

Publications and source records attributed to M Buyse.

At least 19 recordsLinked to original sources
PubMed2006

Dose-dense adjuvant chemotherapy in node-positive breast cancer: docetaxel followed by epirubicin/cyclophosphamide (T/EC), or the reverse sequence (EC/T), every 2 weeks, versus docetaxel, epirubicin and cyclophosphamide (TEC) every 3 weeks. AERO B03 randomized phase II study.

BACKGROUND: Adding a taxane to anthracycline-based adjuvant chemotherapy prolongs survival in node-positive patients but optimal dose and schedule remain undetermined. This study aimed to select a dose-dense regimen for further assessment in phase III studies. PATIENTS AND METHODS: Ninety-nine patients with node-positive invasive breast adenocarcinoma were randomly assigned to docetaxel (Taxotere) (T) 75 mg/m2, epirubicin (E) 75 mg/m2 and cyclophosphamide (C) 500 mg/m2 (TEC)x6, every 3 weeks; E 100 mg/m2, C 600 mg/m2 x 4, then T 100 mg/m2 x 4 (EC-->T) or the reverse sequence (T-->EC), every 2 weeks, with pegfilgrastim support. The primary end point was the incidence of grade 4 toxicity. RESULTS: Dose intensity was almost doubled with dose-dense regimens, compared with TEC. Twenty-seven patients experienced grade 4 toxicity: 26%, 40% and 18% with TEC, EC-->T and T-->EC, respectively, mainly neutropenia, but febrile neutropenia occurred only in 11%, 10% and 3%. Grade 3-4 nail disorders, hand-foot syndrome and peripheral neuropathy occurred in 46%, 73% and 68% of patients with TEC, EC-->T and T-->EC, respectively. CONCLUSIONS: Dose-dense regimens yield more frequent and severe nonhematological toxic effects than standard dose TEC regimen. Though grade 4 toxicity rates appear acceptable with the T-->EC regimen, the incidence of grade 3-4 events makes it difficult to recommend either dose-dense regimen for further investigation.

Adult↗
PubMed2006

Update in methodology and conduct of cancer clinical trials.

Many interesting changes are regularly brought into the methodology of cancer clinical trials. This position paper focuses on three topics which are felt to appear as recurrent problems which deserve more attention from the scientific community. RECIST guidelines were published five years ago and have since then been largely implemented and used in clinical trials. Although the criteria were initially designed for screening phase II trials they have been used also in most phase III studies aiming at determining the efficacy of new treatments. Problems have been identified some of which require further clarifications and others deserve further research which is being undertaken. Overall RECIST is well accepted and a revised version is being considered for 2007. Interim analysis is also an important issue revealed recently through many large adjuvant or advanced trials being prematurely discontinued at the time of an interim analysis. In most instances trials were stopped because of evidence of superiority of the investigational treatment over the standard treatment. Premature discontinuation of trial poses a number of challenges addressed in this paper. Finally, the consequences of the implementation of the EU clinical trial directive are being discussed. The conclusions are without equivoque. There is much less academic research conducted in Europe, there is a lot of discrepancy and inconsistency in the implementation of the directive across member states and there is no apparent direct benefit for the patients.

Antineoplastic Agents↗
PubMed2006

Alternative clinical end points in rectal cancer--are we getting closer?

BACKGROUND: In rectal cancer a high risk of local recurrence has been reported for patients treated by surgery alone. It is also recognised that 20%-40% of rectal cancer patients continue to develop distant metastases and die, even when a very low risk of local recurrence has been achieved with the use of preoperative radiotherapy and total mesorectal excision (TME). Hence, the current design of randomised trials in rectal cancer continues to use the standard end points of local control and survival. This strategy is time-consuming. The recently published EORTC 22921 trial, which compared radiotherapy with chemoradiotherapy and tested the role of postoperative adjuvant chemotherapy, has taken 14 years from planning to results. The aim of this review was to use the evidence from both phase II and phase III trials to provide a comprehensive survey of alternative clinical trial end points in rectal cancer, where preoperative chemoradiation has now become the standard treatment. We describe their strengths and weaknesses. Some are clearly defined, easy to assess and can be obtained early, because surgical resection usually takes place within 6-8 weeks of the completion of treatment. Some pathological response end points reflect biological activity, although their effect on survival has yet to be validated in randomised controlled trials. We will propose measurement and analytical techniques for minimising bias and intra- and inter-observer variability of the non-validated end points in the hope of basing these judgements on as firm a ground as possible. METHODS: A literature search identified both randomised and non-randomised trials of preoperative radiation therapy (RT) and chemoradiation therapy (CRT) in rectal cancer from 1993 to 2005. The aim was to find those studies that documented potential alternative end points. RESULTS: Pathological parameters have been used as early end points to compare studies of preoperative radiotherapy or chemoradiation. In the light of the German CAO/ARO/AIO-94 study, which demonstrated an improved therapeutic ratio for preoperative treatment, enthusiasm for preoperative chemoradiation in the management of rectal cancer is increasing. Current evidence cannot indicate whether the degree of response to chemoradiation (e.g. complete pathological response; downsizing the primary tumour; sterilizing the regional nodes; tumour regression grades or residual cell density) or the achievement of a curative resection (CRM/R0 resection) is the best early clinical end point. Problems with these end points include lack of structured measurement and analysis techniques to control for intra- and inter-observer variation and lack of validation as surrogates for long-term clinical end points such as local control and survival. However, retrospective studies in rectal cancer have confirmed a strong association between the presence of microscopic tumour cells within 1 mm of the CRM and increased risks of both local recurrence and distant metastases. Further end points of current clinical relevance for which adequate methodologies for assessment are lacking include sphincter sparing end points, and assessment of long-term toxicities, ano-rectal function and their specific impact on quality of life. Recommendations are made as to the most appropriate information, which should be documented in future trials. CONCLUSIONS: Pathological complete response following preoperative chemoradiation does not reliably predict late outcome. There are other events not mediated through this end point and there are also unintended effects (often an excess of non-cancer related deaths). Disease-free survival currently remains the best (because it is relatively quick) primary end point in designing randomised phase III studies of preoperative chemoradiation in rectal cancer, although it is necessary to control for postoperative adjuvant chemotherapy. However, the CRM status can substantially account for effects on disease-free and overall survival after chemoradiation, radiation or surgery alone. Hopefully, randomised controlled trials, which utilise these alternative clinical end points, will in future determine the precise percentages of the effect of different chemoradiation schedules on disease-free and overall survival.

Biomarkers, Tumor↗
PubMed2006

Impact of on-site initiation visits on patient recruitment and data quality in a randomized trial of adjuvant chemotherapy for breast cancer.

PURPOSE: To provide empirical evidence on the impact of on-site initiation visits on the following outcomes: patient recruitment, quantity and quality of data submitted to the trial coordinating office, and patients' follow-up time. PATIENTS AND METHODS: This methodological study was performed as part of a randomized trial comparing two combination chemotherapies for adjuvant treatment of breast cancer. Centers participating to the trial were randomized to either receive systematic on-site visits (Visited group), or not (Non-visited group). RESULTS: The study was terminated after two years, while the main randomized trial continued. Of the 135 centers that had expressed an interest in the trial, only 69 randomized at least one patient (35/68 in the Visited group, 34/67 in the Non-visited group). Almost two-thirds of the patients were entered by 17 centers (10 in the Visited group, seven in the Non-visited group) that accrued more than 10 patients each. None of the prespecified outcomes favored the group of centers submitted to on-site initiation visits (ie, mean number of queries par patient: 6.1 +/- 9.7 versus 5.4 +/- 6.4, respectively for the Visited and Non-visited groups). Spontaneous transmittal of case report forms, although required by protocol, was low in both randomized groups (mean number of pages per patient: 1.5 +/- 2.0 versus 2.1 +/- 2.3, respectively), with investigators submitting about one-third of the expected forms on time (29% and 39%, respectively). LIMITATIONS: This study could not evaluate the impact of repeated on-site visits on clinical outcomes. CONCLUSION: Systematic on-site initiation visits did not contribute significantly to this clinical trial.

Antineoplastic Agents, Phytogenic↗
PubMed2004

Modulation of fluorouracil by leucovorin in patients with advanced colorectal cancer: an updated meta-analysis.

PURPOSE: The modulation of fluorouracil (FU) by folinic acid (leucovorin [LV]) has been shown to be effective in terms of tumor response rate in patients with advanced colorectal cancer, but a meta-analysis of nine trials previously published by our group failed to demonstrate a statistically significant survival difference between FU and FU-LV. We present an update of the meta-analysis, with a longer follow-up and the inclusion of 10 newer trials. PATIENTS AND METHODS: Analyses are based on individual data from 3,300 patients randomized in 19 trials on an intent-to-treat basis. Two trials had multiple comparisons, leading to a total of 21 pair-wise comparisons. FU doses were similar in both arms in 10 pair-wise comparisons, 15% to 33% higher in the FU-alone arm in six comparisons, and more than 66% higher in five comparisons. RESULTS: Overall analysis showed a two-fold increase in tumor response rates (11% for FU-LV v 21% for FU-LV v 11% for FU [corrected] alone; odds ratio, 0.53; 95% CI, 0.44 to 0.63; P <.0001) and a small but statistically significant overall survival benefit for FU-LV over FU alone (median survival, 11.7 v 10.5 months, respectively; hazards ratio, 0.90; 95% CI, 0.87 to 0.94; P =.004), which were primarily seen in the first year. We observed a significant interaction between treatment benefit and dose of FU, with tumor response and overall survival advantages of FU-LV over FU-alone being restricted to trials in which a similar dose of FU was prescribed in both arms. CONCLUSION: This updated analysis demonstrates, on a large data set, that FU-LV improves both response rate and overall survival compared with FU alone and that this benefit is consistent across various prognostic factors.

Aged↗
PubMed2004

Is overall survival a realistic primary end point in advanced colorectal cancer studies? A critical assessment based on four clinical trials comparing fluorouracil plus leucovorin with the same treatment combined either with oxaliplatin or with CPT-11.

BACKGROUND: The adequacy of overall survival (OS) as study end point in phase III trials for advanced solid tumors is questionable. The present review highlights the limits of OS as study end point to evaluate the efficacy of new drugs. METHODS: Four phase III clinical trials comparing a fluorouracil-based regimen with the same regimen plus either CPT-11 or oxaliplatin in advanced colorectal cancer patients were reviewed. The primary aim of the critical assessment was to explain the lack of OS advantage observed in two of the four trials, despite the presence of increased response rate (RR) and time to progression (TTP). Four possible reasons for the lack of OS benefit (i.e. statistical power, cross-over, magnitude of the effect on RR and TTP, non-tumor-related deaths) were systematically reviewed in the trials, and the detectable 1-year OS difference, assuming a statistical power of 80%, was calculated for each. RESULTS: None of these reasons for the lack of OS advantage in presence of RR and TTP benefits convincingly explained the results of the evaluated trials. Three of the four trials had roughly the same statistical power to detect 1-year OS differences, while the fourth trial was underpowered to detect realistic OS differences. The lack of OS advantage observed in the two oxaliplatin trials is therefore likely fortuitous, and due to lack of statistical power. CONCLUSIONS: Although increase in OS remains the ultimate goal of many clinical trials, the choice of OS benefit as a mandatory requirement to register new compounds can lead to a serious underestimation of a drug's real efficacy.

Antimetabolites, Antineoplastic↗
PubMed2003

Multimodal therapy with intravenous biweekly leucovorin, 5-fluorouracil and irinotecan combined with hepatic arterial infusion pirarubicin in non-resectable hepatic metastases from colorectal cancer (a European Association for Research in Oncology trial).

BACKGROUND: The purpose of this study was to evaluate the tolerance and efficacy of combining i.v. irinotecan, 5-fluorouracil (5-FU) and leucovorin (LV) with hepatic arterial infusion (HAI) of pirarubicin in non-resectable liver metastases from colorectal cancer. PATIENTS AND METHODS: Thirty-one patients were included in a phase II trial with i.v. irinotecan/5-FU/LV administered every 2 weeks, combined with HAI pirarubicin 60 mg/m(2) on day 1 every 4 weeks. In most cases HAI was administered via a percutaneous catheter. RESULTS: The main grade 3/4 toxicity was neutropenia, encountered in 78% of the patients. When all patients were considered in the analysis, tumour response rate was 15 out of 31 [48%; 95% confidence interval (CI) 32% to 65%]. Liver resection was made possible in 11 patients (35%; 95% CI 21% to 53%). There were no toxic death. Median overall survival was 20.5 months, and median progression-free survival was 9.1 months. In patients with completely resected metastases, median overall survival was not reached and median progression-free survival was 20.2 months. CONCLUSION: The multimodality approach used in the present study was well-tolerated and yielded dramatic responses. An aggressive approach combining i.v. and HAI chemotherapy deserves further investigation.

Adult↗
PubMed2001

Evaluation of surrogate endpoints in randomized experiments with mixed discrete and continuous outcomes.

A statistical definition of surrogate endpoints as well as validation criteria was first presented by Prentice. Freedman et al. supplemented these criteria with the so-called proportion explained. Buyse and Molenberghs pointed to inadequacies of these criteria and suggested a new definition of surrogacy based on (i) the relative effect linking the overall effect of treatment on both endpoints and (ii) an individual-level measure of agreement between both endpoints. Using data from a randomized trial, they showed how a potential surrogate endpoint can be studied using a joint model for the surrogate and the true endpoint. Whereas Buyse and Molenberghs restricted themselves to the fairly simple cases of jointly normal and jointly binary outcomes, we treat the situation where the surrogate is binary and the true endpoint is continuous, or vice versa. In addition, we consider the case of ordinal endpoints. Further, Buyse et al. extended the approach of Buyse and Molenberghs to a meta-analytic context. We will adopt a similar approach for responses of a mixed data type.

Anticholesteremic Agents↗
PubMed2001

Alpha-interferon does not increase the efficacy of 5-fluorouracil in advanced colorectal cancer.

Two meta-analyses were conducted to quantify the benefit of combining alpha-IFN to 5FU in advanced colorectal cancer in terms of tumour response and survival. Analyses were based on a total of 3254 individual patient data provided by principal investigators of each trial. The meta-analysis of 5FU +/- LV vs. 5FU +/- LV + alpha-IFN combined 12 trials and 1766 patients. The meta-analysis failed to show any statistically significant difference between the two treatment groups in terms of tumour response or survival. Overall tumour response rates were 25% for patients receiving no alpha-IFN vs. 24% for patients receiving alpha-IFN (relative risk, RR = 1.02), and median survivals were 11.4 months for patients receiving no alpha-IFN vs. 11.5 months for patients receiving alpha-IFN (hazard ratio, HR = 0.95). The meta-analysis of 5FU + LV vs. 5FU + alpha-IFN combined 7 trials, and 1488 patients. This meta-analysis showed an advantage for 5FU + LV over 5FU + alpha-IFN which was statistically significant in terms of tumour response (23% vs. 18%; RR = 1.26;P = 0.042), and of a borderline significance for overall survival (HR = 1.11;P = 0.066). Metastases confined to the liver and primary rectal tumours were independent favourable prognostic factors for tumour response, whereas good performance status, metastases confined to the liver or confined to the lung, and primary tumour in the rectum were independent favourable prognostic factors for survival. We conclude that alpha-IFN does not increase the efficacy of 5FU or of 5FU + LV, and that 5FU + alpha-IFN is significantly inferior to 5FU + LV, for patients with advanced colorectal cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Leptin decreases feeding and exploratory behaviour via interactions with CCK(1) receptors in the rat.

We assessed the effects of peripheral leptin on anxiety and exploratory behaviour in the elevated plus-maze and in the four-hole box or Y-maze tests, in rats fed 80% of normal daily food intake and rats fed ad libitum. In the Y-maze test, i.p. injection of 0.4 or 1 mg/kg leptin into rationed rats significantly decreased the percentage of spontaneous alternation behaviour and increased the number of visits. In the elevated plus-maze test, rationed rats spent significantly more time in the open arms (aversive part of the maze) than did rats fed ad libitum. This difference in behaviour was abolished by injecting 0.4 mg/kg leptin. In the four-hole box test, i.p. administration of 1 mg/kg leptin significantly reduced the duration and number of hole visits in rationed and ad libitum fed rats. As with leptin inhibition of food intake, these behavioural changes caused by leptin were prevented by a CCK(1) receptor antagonist (L364,718), at a dose that had no effect by itself. Finally, a 20-min stress that increased corticosterone and ACTH levels had no effect on circulating leptin levels and on the leptin content of epididymal fat tissue, stomach and brain. Thus, leptin induces hypoexploration and decreases spontaneous alternation in rats and these effects are partly dependent on nutritional status. These results also suggest that the CCK system may be involved in the induction of these behavioural changes in rats by leptin, via the CCK(1) receptor.

Animals↗
PubMed2001

Should Dukes' B patients receive adjuvant therapy? A statistical perspective.

The benefit of adjuvant therapy, such as 5-fluorouracil (5-FU) combined with leucovorin, is a matter of debate for patients with Dukes' B colon cancer. Several approaches have been taken to address this issue. Initially, studies were conducted to assess treatment benefits in both Dukes' B and Dukes' C patients. These studies identified an overall benefit of adjuvant treatment and enrolled enough Dukes' C patients to determine a treatment benefit for adjuvant 5-FU/leucovorin in this subpopulation. However, the individual studies were insufficiently powered to detect a treatment benefit in Dukes' B patients. An analysis of four separate studies (National Surgical Adjuvant Breast and Bowel project) compared the benefit of adjuvant treatment in Dukes' B patients with that in Dukes' C patients and showed similar relative reductions in mortality and disease-free survival in Dukes' B and in Dukes' C patients. The Liver Infusion Meta-Analysis Group also reported similar relative benefits from a portal vein infusion of 5-FU-based chemotherapy in Dukes' B and Dukes' C patients. The International Multicenter Pooled Analysis of Colon Cancer Trials B2 study, which combined data from patients with Dukes' B colon cancer in five separate trials, failed to show a statistically significant benefit of adjuvant 5-FU/leucovorin compared with surgery alone. We review the advantages and limitations of different approaches to detect treatment benefits in patients with Dukes' B colon cancer, and we argue that there is a need for a meta-analysis of all adjuvant trials to reliably address this question.

Antimetabolites, Antineoplastic↗
PubMed2001

Randomized adjuvant study comparing two schemes of 5-fluorouracil and leucovorin in stage B2 and C colon adenocarcinoma: study design and preliminary safety results. Groupe d'Etude et de Recherche Clinique en Oncologie Radiotherapies.

The aim of this randomized open-label study was to compare a bimonthly with a monthly regimen of 5-fluorouracil (5-FU) and leucovorin for the adjuvant treatment of colon and high-rectum adenocarcinoma. The bimonthly regimen was administered for 2 consecutive days every 14 days as d,L-leucovorin 200 mg/m2 or L-leucovorin 100 mg/m2 as a 2-hour infusion followed by 5-FU bolus of 400 mg/m2 and a 600 mg/m2 5-FU 22-hour continuous infusion (LVSFU2). In the monthly regimen, d,L-leucovorin 200 mg/m2 or L-leucovorin 100 mg/m2 15-minute infusion followed by a 400 mg/m2 15 minute 5-FU bolus was administered for 5 consecutive days every 28 days (FUFOL). Nine hundred five patients with recently resected stage B2 or C colon or high-rectum adenocarcinoma (inferior pole of the tumor subperitoneal) were recruited into the study. Patients were randomized in a 2 x 2 factorial design to receive either LV5FU2 or FUFOL for 24 or 36 weeks. Characteristics of the patients in the two different treatment groups were similar at baseline. Compliance was good. Mean 5-FU dose intensities were 930 mg/ m2/wk and 463 mg/m2/wk for LVSFU2 and FUFOL, respectively. The incidence of maximal grade III-IV toxicities for LVSFU2 and FUFOL was neutropenia 6% and 16% (P < .001), diarrhea 4% and 10% (P < .001), and mucositis 2% and 7% (P < .001), respectively. Maximum grade III-IV toxicities in the LV5FU2 treatment group were significantly lower than in the FUFOL group (10% v 26%; P < .001). Although patients in the LV5FU2 group received twice the dose of 5-FU compared with those in the FUFOL group, LV5FU2 was shown to be less toxic. Efficacy data will be available in 2001.

Adult↗
PubMed2001

Expression and regulation of leptin receptor proteins in afferent and efferent neurons of the vagus nerve.

Leptin, the product of the ob gene, plays a key role in the regulation of food intake via a cross-talk between hypothalamic leptin receptors and neuropeptides that affect feeding behaviour. Recent studies have shown a synergistic interaction between leptin and cholecystokinin (CCK) leading to suppression of food intake, which involves CCK-1 receptors and capsaicin-sensitive vagal fibres. In this study, we have investigated the presence of leptin receptors in afferent and efferent neurons of the vagus nerve. By using reverse transcription-polymerase chain reaction, mRNAs encoding long (Ob-Rb) and short (Ob-Ra) leptin receptor isoforms were detected in the rat nodose ganglion, which contains the cell bodies of the vagal afferent neurons. Western blot analysis confirmed the presence of leptin receptor-immunoreactive proteins in extracts from the vagal trunk. Immunohistochemistry showed the presence of leptin receptors and the leptin-induced transcription factor STAT3 in the cytoplasm of nodose ganglion cells. In cervical vagal segments, levels of leptin receptor protein displayed physiological regulation, with decreased amounts after feeding and increased levels after food restriction. In addition, leptin receptor and STAT3 immunoreactivities were detected in neurons of the nucleus of tractus solitarius (NTS) and the dorsal motor nucleus of the vagus nerve (DMNX) by immunofluorescence histochemistry. Furthermore, direct double-labelling demonstrated colocalization of Ob-Rb and STAT3 immunoreactivities in cholinergic vagal efferent cell bodies of the DMNX. It is speculated that vagal leptin receptors, apart from being activated by adipocyte-derived leptin, may also be influenced by leptin produced by the stomach. This may explain the synergistic action of leptin and CCK on neuronal activity in the NTS and on food intake.

Afferent Pathways↗
PubMed2001

Taxanes in the adjuvant treatment of breast cancer: why not yet?

The taxanes paclitaxel and docetaxel represent the most active chemotherapeutic agents developed for the treatment of advanced breast cancer in the last decade, and they are now being incorporated into adjuvant chemotherapy trials for lymph node-positive breast cancer with the hope of improving on the results achieved with CMF (cyclophosphamide, methotrexate, 5-fluorouracil) or anthracycline-based regimens. So far, three randomized paclitaxel-based adjuvant clinical trials enrolling 3170 women (Cancer and Leukemia Group B [CALGB] 9344), 3060 women (National Surgical Adjuvant Project for Breast and Bowel Cancers [NSABP]-B28), and 524 women (M. D. Anderson), respectively, have been reported with respective median follow-up times of 52, 34, and 43 months. This article critically reviews these three studies and gives an overview of the many other randomized clinical trials, due to accrue more than 17 000 women, which are investigating the potential of taxanes in adjuvant breast cancer therapy. Given that the early promise of taxanes suggested by CALGB 9344 is not yet confirmed by the two other trials, only level 2 evidence has been reached to date in regard to a positive contribution of these agents to breast cancer outcome in the adjuvant setting. It is argued that level 1 evidence is highly desirable before adopting taxane-based regimens in standard practice. It is anticipated that a meta-analysis will be needed to comprehensively define the value of taxanes in early breast cancer, and a new model of international collaboration is proposed to find a balance between the need to offer new, more effective therapies to patients as soon as possible and the danger of drawing wrong, premature conclusions regarding the magnitude of benefit of a new regimen.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Insulin and glucocorticoids differentially regulate leptin transcription and secretion in brown adipocytes.

Leptin, the ob gene product, is produced by adipose tissue and is submitted to a complex hormonal and metabolic regulation. Leptin plays a critical role in the balance of body weight. Here we report on secretion and hormonal regulation of leptin by brown adipocytes. Using the recently established T37i cell line, we show that leptin expression and secretion occurred as a function of cell differentiation. In differentiated T37i cells, insulin induced leptin release ( approximately 0.25 ng/10(6) cells/h) in a concentration-dependent manner (EC50=0.1 nM), and this was totally suppressed by beta3-adrenergic ligand, thiazolidinedione, cycloheximide, or actinomycin D. Insulin induced a strong, rapid (within 2 h) but transient fivefold increase in leptin mRNA levels. This transcriptional control of ob gene expression by insulin involved both phosphatidylinositol 3-kinase- and MAP kinase-dependent pathways. Glucocorticoids inhibited both insulin-stimulated leptin secretion and ob gene expression without affecting leptin mRNA stability (t(1/2)=3h05). Altogether, our results demonstrate that brown adipocytes express and secrete leptin, whose hormonal regulation clearly differs from that described in white adipose tissue. These findings point to tissue-specific molecular mechanisms and suggest that leptin might exert direct effects on energy homeostasis through an autocrine mechanism.

Adipocytes↗
PubMed2001

PepT1-mediated epithelial transport of dipeptides and cephalexin is enhanced by luminal leptin in the small intestine.

Dietary proteins are mostly absorbed as di- and tripeptides by the intestinal proton-dependent transporter PepT1. We have examined the effects of leptin on PepT1 function in rat jejunum and in monolayers of the human enterocyte-like 2 cell Caco-2. Leptin is produced by the stomach and secreted in the gut lumen. We show here that PepT1 and leptin receptors are expressed in Caco-2 and rat intestinal mucosal cells. Apical (but not basolateral) leptin increased Caco-2 cell transport of cephalexin (CFX) and glycylsarcosine (Gly-Sar), an effect that was associated with increased Gly-Sar uptake, increased membrane PepT1 protein, decreased intracellular PepT1 content, and no change in PepT1 mRNA levels. The maximal velocity (Vmax) for Gly-Sar transport was significantly increased by leptin, whereas the apparent Michaelis-Menten constant (Km) did not change. Furthermore, leptin-stimulated Gly-Sar transport was completely suppressed by colchicine, which disrupts cellular translocation of proteins to plasma membranes. Intrajejunal leptin also induced a rapid twofold increase in plasma CFX after jejunal perfusion with CFX in the rat, indicating enhanced intestinal absorption of CFX. These data revealed an unexpected action of gastric leptin in controlling ingestion of dietary proteins.

Amino Acid Sequence↗