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AICAR and Metformin Exert AMPK-dependent Effects on INS-1E Pancreatic β-cell Apoptosis via Differential Downstream Mechanisms.

Dai YL, Huang SL, Leng Y - Int. J. Biol. Sci. (2015)

Bottom Line: Both AICAR and metformin protected INS-1E cells from palmitate-induced apoptosis, as reflected by decreases in both cleaved caspase 3 protein expression and caspase 3/7 activity, and these protective effects were abrogated by AMPK inhibitor compound C.The protective action of AICAR was probably mediated by the suppression of triacylglycerol accumulation, increase in Akt phosphorylation and decrease in p38 MAPK phosphorylation, while metformin might exert its protective effect on INS-1E cells by decreases in both JNK and p38 MAPK phosphorylation.Our results provided new and informative clues for better understanding of the role of AMPK in β-cell apoptosis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zu Chong Zhi Road 555, Shanghai 201203, China.

ABSTRACT
The role of AMP-activated protein kinase (AMPK) in pancreatic β-cell apoptosis is still controversial, and the reasons for the discrepancies have not been clarified. In the current study, we observed the effects of two well-known AMPK activators 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and metformin, on apoptosis in rat insulinoma INS-1E cells, and further explored their possible mechanisms. Both AICAR and metformin protected INS-1E cells from palmitate-induced apoptosis, as reflected by decreases in both cleaved caspase 3 protein expression and caspase 3/7 activity, and these protective effects were abrogated by AMPK inhibitor compound C. The protective action of AICAR was probably mediated by the suppression of triacylglycerol accumulation, increase in Akt phosphorylation and decrease in p38 MAPK phosphorylation, while metformin might exert its protective effect on INS-1E cells by decreases in both JNK and p38 MAPK phosphorylation. All these regulations were dependent on AMPK activation. However, under standard culture condition, AICAR increased JNK phosphorylation and promoted INS-1E cell apoptosis in an AMPK-dependent manner, whereas metformin showed no effect on apoptosis. Our study revealed that AMPK activators AICAR and metformin exhibited different effects on INS-1E cell apoptosis under different culture conditions, which might be largely attributed to different downstream mediators. Our results provided new and informative clues for better understanding of the role of AMPK in β-cell apoptosis.

No MeSH data available.


Related in: MedlinePlus

Effects of AICAR and metformin on palmitate-induced INS-1E cell apoptosis. INS-1E cells were exposed to 0.25 mM palmitate with or without AICAR or metformin for 16 h, followed by evaluation of apoptosis. (A, B) Apoptosis was evaluated by immunoblotting of cleaved caspase 3 (representative immunoblots; quantification of four independent experiments). (C) Apoptosis was evaluated by measuring caspase 3/7 activity (quantification of three independent experiments). **P<0.01 vs control (cells exposed to 0.25% BSA); ##P<0.01 vs cells exposed to 0.25 mM palmitate. Palm, palmitate; Met, metformin.
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Figure 1: Effects of AICAR and metformin on palmitate-induced INS-1E cell apoptosis. INS-1E cells were exposed to 0.25 mM palmitate with or without AICAR or metformin for 16 h, followed by evaluation of apoptosis. (A, B) Apoptosis was evaluated by immunoblotting of cleaved caspase 3 (representative immunoblots; quantification of four independent experiments). (C) Apoptosis was evaluated by measuring caspase 3/7 activity (quantification of three independent experiments). **P<0.01 vs control (cells exposed to 0.25% BSA); ##P<0.01 vs cells exposed to 0.25 mM palmitate. Palm, palmitate; Met, metformin.

Mentions: INS-1E cells were exposed to 0.25 mM palmitate with or without compounds for 16 h. Challenge of INS-1E cells with palmitate resulted in a significant increase of cleaved caspase 3 protein expression, an important biomarker of apoptosis, and this index was markedly reduced by 57% and 34% in the presence of 1 mM AICAR and 2 mM metformin respectively (P<0.01 vs palmitate-exposed cells; Fig. 1A and 1B). Meanwhile, AICAR and metformin showed similar inhibition of palmitate-induced apoptosis in terms of decreased caspase3/7 activity (P<0.01 vs palmitate-exposed cells; Fig. 1C).


AICAR and Metformin Exert AMPK-dependent Effects on INS-1E Pancreatic β-cell Apoptosis via Differential Downstream Mechanisms.

Dai YL, Huang SL, Leng Y - Int. J. Biol. Sci. (2015)

Effects of AICAR and metformin on palmitate-induced INS-1E cell apoptosis. INS-1E cells were exposed to 0.25 mM palmitate with or without AICAR or metformin for 16 h, followed by evaluation of apoptosis. (A, B) Apoptosis was evaluated by immunoblotting of cleaved caspase 3 (representative immunoblots; quantification of four independent experiments). (C) Apoptosis was evaluated by measuring caspase 3/7 activity (quantification of three independent experiments). **P<0.01 vs control (cells exposed to 0.25% BSA); ##P<0.01 vs cells exposed to 0.25 mM palmitate. Palm, palmitate; Met, metformin.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4582151&req=5

Figure 1: Effects of AICAR and metformin on palmitate-induced INS-1E cell apoptosis. INS-1E cells were exposed to 0.25 mM palmitate with or without AICAR or metformin for 16 h, followed by evaluation of apoptosis. (A, B) Apoptosis was evaluated by immunoblotting of cleaved caspase 3 (representative immunoblots; quantification of four independent experiments). (C) Apoptosis was evaluated by measuring caspase 3/7 activity (quantification of three independent experiments). **P<0.01 vs control (cells exposed to 0.25% BSA); ##P<0.01 vs cells exposed to 0.25 mM palmitate. Palm, palmitate; Met, metformin.
Mentions: INS-1E cells were exposed to 0.25 mM palmitate with or without compounds for 16 h. Challenge of INS-1E cells with palmitate resulted in a significant increase of cleaved caspase 3 protein expression, an important biomarker of apoptosis, and this index was markedly reduced by 57% and 34% in the presence of 1 mM AICAR and 2 mM metformin respectively (P<0.01 vs palmitate-exposed cells; Fig. 1A and 1B). Meanwhile, AICAR and metformin showed similar inhibition of palmitate-induced apoptosis in terms of decreased caspase3/7 activity (P<0.01 vs palmitate-exposed cells; Fig. 1C).

Bottom Line: Both AICAR and metformin protected INS-1E cells from palmitate-induced apoptosis, as reflected by decreases in both cleaved caspase 3 protein expression and caspase 3/7 activity, and these protective effects were abrogated by AMPK inhibitor compound C.The protective action of AICAR was probably mediated by the suppression of triacylglycerol accumulation, increase in Akt phosphorylation and decrease in p38 MAPK phosphorylation, while metformin might exert its protective effect on INS-1E cells by decreases in both JNK and p38 MAPK phosphorylation.Our results provided new and informative clues for better understanding of the role of AMPK in β-cell apoptosis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Zu Chong Zhi Road 555, Shanghai 201203, China.

ABSTRACT
The role of AMP-activated protein kinase (AMPK) in pancreatic β-cell apoptosis is still controversial, and the reasons for the discrepancies have not been clarified. In the current study, we observed the effects of two well-known AMPK activators 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and metformin, on apoptosis in rat insulinoma INS-1E cells, and further explored their possible mechanisms. Both AICAR and metformin protected INS-1E cells from palmitate-induced apoptosis, as reflected by decreases in both cleaved caspase 3 protein expression and caspase 3/7 activity, and these protective effects were abrogated by AMPK inhibitor compound C. The protective action of AICAR was probably mediated by the suppression of triacylglycerol accumulation, increase in Akt phosphorylation and decrease in p38 MAPK phosphorylation, while metformin might exert its protective effect on INS-1E cells by decreases in both JNK and p38 MAPK phosphorylation. All these regulations were dependent on AMPK activation. However, under standard culture condition, AICAR increased JNK phosphorylation and promoted INS-1E cell apoptosis in an AMPK-dependent manner, whereas metformin showed no effect on apoptosis. Our study revealed that AMPK activators AICAR and metformin exhibited different effects on INS-1E cell apoptosis under different culture conditions, which might be largely attributed to different downstream mediators. Our results provided new and informative clues for better understanding of the role of AMPK in β-cell apoptosis.

No MeSH data available.


Related in: MedlinePlus