Leptin decreases apoptosis and alters BCL-2 : Bax ratio in clonal rodent pancreatic beta-cells.
OBJECTIVE
The adipocyte derived peptide hormone leptin is known to regulate apoptosis and cell viability in several cells and tissues, as well as having several pancreatic islet beta-cell specific effects such as inhibition of glucose-stimulated insulin secretion. This study investigated the effects of leptin upon apoptosis induced by serum depletion and on expression of the apoptotic regulators B-cell leukaemia 2 gene product (BCL-2) and BCL2-associated X protein (Bax) in the glucose-responsive BRIN-BD11 beta-cell line.


METHODS
BRIN-BD11 cells were cultured in RPMI 1640 and subsequently serum depleted +/- leptin (10 and 50 ng/mL) for 24 h. Cell viability and apoptosis were measured using a modified MTS assay and TUNEL/YO-PRO-1 assays, respectively. BCL-2 and Bax expression were measured by real-time PCR and Western blotting.


RESULTS
Leptin caused a reduction in serum-depleted apoptosis, although it failed to have any effect on the overall cell viability, causing a 68% shift from apoptosis to necrosis. Leptin significantly increased the level of BCL-2 mRNA expression (150% compared to serum depletion alone), without altering Bax mRNA expression. At the protein level, leptin increased BCL-2 and decreased Bax, altering the BCL-2 : Bax ratio.


CONCLUSIONS
We conclude that leptin reduces apoptosis in beta-cells at physiological concentrations, possibly via its ability to up-regulate BCL-2 and Bax expression.
Brown
James E P
JE
Diabetes and Metabolic Disorders Research Group, RIHS, University of Wolverhampton, Wulfruna St, Wolverhampton, WV1 1SB, UK.
Dunmore
Simon J
SJ
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D016895:Culture Media, Serum-Free; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D020738:Leptin / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
D016895:Culture Media, Serum-Free; D020738:Leptin; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein