Marked over expression of uncoupling protein-2 in beta cells exerts minor effects on mitochondrial metabolism

作者：Hals Ingrid K^*; Ogata Hirotaka; Pettersen Elin; Ma Zuheng; Bjorklund Anneli; Skorpen Frank; Egeberg Kjartan Wollo; Grill Valdemar

来源：Biochemical and Biophysical Research Communications, 2012, 423(2): 259-264.

DOI：10.1016/j.bbrc.2012.05.101

• Uncoupling protein-2
• Mitochondria
• Insulin secretion
• Fatty acid oxidation
• Oxygen consumption

Evidence is conflicting as to the impact of elevated levels of uncoupling protein-2 (UCP-2) on insulin-producing beta cells. Here we investigated effects of a fourfold induction of UCP-2 protein primarily on mitochondrial parameters and tested for replication of positive findings at a lower level of induction. %26lt;br%26gt;We transfected INS-1 cells to obtain a tet-on inducible cell line. A 48 h exposure to 1 mu g/ml of doxycydine (dox) induced UCP-2 fourfold (424 +/- 113%, mean SEM) and 0.1 mu g/ml twofold (178 +/- 29%, n = 3). Fourfold induced cells displayed normal viability (MTT, apoptosis), normal cellular insulin contents and, glucose-induced insulin secretion (+27 +/- 11%) as well as D-[U-C-14]-glucose oxidation (+5 +/- 9% at 11 mM glucose). Oxidation of [1-C-14]-oleate was increased from 4088 to 5797 fmol/mu g prot/2 h at 3.3 mM glucose, p %26lt; 0.03. Oxidation of L-[C-14(U)]-glutamine was unaffected. Induction of UCP-2 did not significantly affect measures of mitochondria] membrane potential (Rhodamine 123) or mitochondrial mass (Mitotracker Green) and did not affect ATP levels. Oligomycin-inhibited oxygen consumption (a measure of mitochondrial uncoupling) was marginally increased, the effect being significant in comparison with dox-only treated cells, p %26lt; 0.05. Oxygen radicals, assessed by dichlorofluorescin diacetate, were decreased by 30%, p %26lt; 0.025. Testing for the lower level of UCP-2 induction did not reproduce any of the positive findings. A fourfold induction of UCP-2 was required to exert minor metabolic effects. These findings question an impact of moderately elevated UCP-2 levels in beta cells as seen in diabetes.

• 出版日期2012-6-29