Uncoupling protein 2 regulates glucagon-like peptide-1 secretion in L-cells.
OBJECTIVE
To investigate whether uncoupling protein 2 (UCP2) affects oleic acid-induced secretion of glucagon-like peptide-1 (GLP-1) in L-cells.


METHODS
mRNA and protein expression of UCP2 were analyzed in human NCI-H716 cells, which serve as a model for enteroendocrine L-cells, by quantitative reverse transcription-polymerase chain reaction and Western blotting before and after treatment with oleic acid. Localization of UCP2 and GLP-1 in NCI-H716 cells was assessed by immunofluorescence labeling. NCI-H716 cells were transiently transfected with a small interfering RNA (siRNA) that targets UCP2 (siUCP2) or with a non-specific siRNA using Lipofectamine 2000. The concentrations of bioactive GLP-1 in the medium were measured by enzyme linked immunosorbent assay.


RESULTS
Both GLP-1 and UCP2 granules were expressed mainly in the cytoplasm of NCI-H716 cells. NCI-H716 cells that secreted GLP-1 also expressed UCP2. Time-course experiments revealed that release of GLP-1 from NCI-H716 cells into the medium reached a maximum at 120 min and remained stable until at least 180 min after treatment with oleic acid (the level of GLP-1 increased about 2.3-fold as compared with the level of GLP-1 in the control cells, P < 0.05). In an experiment to determine dose dependence, stimulation of NCI-H716 cells with ≤ 8 mmol oleic acid led to a concentration-dependent release of GLP-1 into the medium; 10 mmol oleic acid diminished the release of GLP-1. Furthermore, GLP-1 secretion induced by oleic acid from NCI-H716 cells that were transfected with siUCP2 decreased to 41.8%, as compared with NCI-H716 cells that were transfected with a non-specific siRNA (P < 0.01).


CONCLUSIONS
UCP2 affected GLP-1 secretion induced by oleic acid. UCP2 plays an important role in L-cell secretion that is induced by free fatty acids.
Department of Gastroenterology, First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, Jiangsu Province, China.
Yan
Y
Chen
Zheng-Yang
ZY
Li
Yan
Y
Yang
Hong-Jie
HJ
Zhang
D002460:Cell Line; D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000378:metabolism; D019858:Enteroendocrine Cells / Q000166:cytology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D008856:Microscopy, Fluorescence / Q000379:methods; D024101:Mitochondrial Proteins / Q000502:physiology*; D019301:Oleic Acid / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D013997:Time Factors; D000071246:Uncoupling Protein 2
D005230:Fatty Acids, Nonesterified; D007473:Ion Channels; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; D019301:Oleic Acid; D052216:Glucagon-Like Peptide 1