Secreted human adipose leptin decreases mitochondrial respiration in HCT116 colon cancer cells.
Obesity is a key risk factor for the development of colon cancer; however, the endocrine/paracrine/metabolic networks mediating this connection are poorly understood. Here we hypothesize that obesity results in secreted products from adipose tissue that induce malignancy-related metabolic alterations in colon cancer cells. Human HCT116 colon cancer cells, were exposed to conditioned media from cultured human adipose tissue fragments of obese vs. non-obese subjects. Oxygen consumption rate (OCR, mostly mitochondrial respiration) and extracellular acidification rate (ECAR, mostly lactate production via glycolysis) were examined vis-à-vis cell viability and expression of related genes and proteins. Our results show that conditioned media from obese (vs. non-obese) subjects decreased basal (40%, p<0.05) and maximal (50%, p<0.05) OCR and gene expression of mitochondrial proteins and Bax without affecting cell viability or expression of glycolytic enzymes. Similar changes could be recapitulated by incubating cells with leptin, whereas, leptin-receptor specific antagonist inhibited the reduced OCR induced by conditioned media from obese subjects. We conclude that secreted products from the adipose tissue of obese subjects inhibit mitochondrial respiration and function in HCT116 colon cancer cells, an effect that is at least partly mediated by leptin. These results highlight a putative novel mechanism for obesity-associated risk of gastrointestinal malignancies, and suggest potential new therapeutic avenues.
Institute of Biochemistry, Food Science and Nutrition, The Robert H. Smith Faculty of Agriculture, Food and Environment, the Hebrew University of Jerusalem, Rehovot, Israel.
Einav
E
Yehuda-Shnaidman
Lili
L
Nimri
Tanya
T
Tarnovscki
Boris
B
Kirshtein
Assaf
A
Rudich
Betty
B
Schwartz
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000328:Adult; D015153:Blotting, Western; D019069:Cell Respiration / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D020738:Leptin / Q000494:pharmacology*; D008875:Middle Aged; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D024101:Mitochondrial Proteins / Q000378:metabolism; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D017077:Culture Media, Conditioned; D020738:Leptin; D024101:Mitochondrial Proteins; D012333:RNA, Messenger