system
Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Adenocarcinoma, Animals, Bromodeoxyuridine, Carrier Proteins, Colonic Neoplasms, Epithelium, Female, Growth Substances, Humans, Leptin, Mice, Obesity, Protein Kinases, Receptors, Cell Surface, Receptors, Leptin, Reverse Transcriptase Polymerase Chain Reaction, Thymidine, Tumor Cells, Cultured.
user
Is leptin a growth factor for colonic epithelial cells? Context: Obesity increases the risk of colon cancer, whereas physical activity reduces the risk. Plasma levels of leptin increase in proportion to the level of obesity and are reduced by physical activity. Leptin acts as a growth factor for several cell types and thus may provide a biological explanation for the observed epidemiological risk factors. The aim of this study was to investigate whether leptin is a growth factor for colonic epithelial cells. The presence of the leptin receptor in human colon cancer cell lines was assessed using reverse-transcription polymerase chain reaction and immunoblotting, and its presence in human colonic tissue was assessed by immunohistochemistry. The effects of leptin in vitro on HT29 cells were assessed by assessing p42/44 mitogen-activated protein kinase phosphorylation, thymidine incorporation, and cell numbers and in vivo in C57BL/6 mice by colonic bromodeoxyuridine incorporation. The leptin receptor is expressed in human colon cancer cell lines and human colonic tissue. Stimulation with leptin leads to phosphorylation of p42/44 mitogen-activated protein kinase and increases proliferation in vitro and in vivo.
assistant
Leptin is a growth factor in colonic epithelial cells and one that may provide a biological explanation for the observed associations between obesity, physical activity, and colon cancer. Final Decision: yes