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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

Role of AMPK activation in prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin. (A) Effects of AICAR or metformin on AMPK and ACC phosphorylation in INS-1E cells exposed to 0.25 mM palmitate with or without compounds for 16 h. Representative immunoblots were shown and protein contents were quantified separately from four independent experiments. (B, C) INS-1E cells were preincubated with or without compound C (10 μM) for 30 min, and then exposed to 0.25 mM palmitate with or without 1 mM AICAR (B) or 2 mM metformin (C) for 16 h, followed by immunoblotting of AMPK and ACC phosphorylation and cleaved caspase 3 (representative immunoblots; quantification of cleaved caspase 3 protein levels from four independent experiments). #P<0.05 and ##P<0.01 vs cells exposed to 0.25 mM palmitate; *P<0.05 and **P<0.01 vs corresponding columns as indicated; ns, not significant. Palm, palmitate; Met, metformin.
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Figure 2: Role of AMPK activation in prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin. (A) Effects of AICAR or metformin on AMPK and ACC phosphorylation in INS-1E cells exposed to 0.25 mM palmitate with or without compounds for 16 h. Representative immunoblots were shown and protein contents were quantified separately from four independent experiments. (B, C) INS-1E cells were preincubated with or without compound C (10 μM) for 30 min, and then exposed to 0.25 mM palmitate with or without 1 mM AICAR (B) or 2 mM metformin (C) for 16 h, followed by immunoblotting of AMPK and ACC phosphorylation and cleaved caspase 3 (representative immunoblots; quantification of cleaved caspase 3 protein levels from four independent experiments). #P<0.05 and ##P<0.01 vs cells exposed to 0.25 mM palmitate; *P<0.05 and **P<0.01 vs corresponding columns as indicated; ns, not significant. Palm, palmitate; Met, metformin.

Mentions: Under condition of palmitate-induced apoptosis, both AICAR and metformin increased AMPK and ACC phosphorylation (P<0.05 and P<0.01 vs palmitate-exposed cells; Fig. 2A). Furthermore, in combination with AMPK inhibitor compound C (10 μM), the protective effect of AICAR (Fig. 2B) and metformin (Fig. 2C) were abrogated, as shown by relief of decreased cleaved caspase 3 protein expression. These findings demonstrated that prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin were dependent on their activation of AMPK.


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)

Role of AMPK activation in prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin. (A) Effects of AICAR or metformin on AMPK and ACC phosphorylation in INS-1E cells exposed to 0.25 mM palmitate with or without compounds for 16 h. Representative immunoblots were shown and protein contents were quantified separately from four independent experiments. (B, C) INS-1E cells were preincubated with or without compound C (10 μM) for 30 min, and then exposed to 0.25 mM palmitate with or without 1 mM AICAR (B) or 2 mM metformin (C) for 16 h, followed by immunoblotting of AMPK and ACC phosphorylation and cleaved caspase 3 (representative immunoblots; quantification of cleaved caspase 3 protein levels from four independent experiments). #P<0.05 and ##P<0.01 vs cells exposed to 0.25 mM palmitate; *P<0.05 and **P<0.01 vs corresponding columns as indicated; ns, not significant. Palm, palmitate; Met, metformin.
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Related In: Results  -  Collection

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Figure 2: Role of AMPK activation in prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin. (A) Effects of AICAR or metformin on AMPK and ACC phosphorylation in INS-1E cells exposed to 0.25 mM palmitate with or without compounds for 16 h. Representative immunoblots were shown and protein contents were quantified separately from four independent experiments. (B, C) INS-1E cells were preincubated with or without compound C (10 μM) for 30 min, and then exposed to 0.25 mM palmitate with or without 1 mM AICAR (B) or 2 mM metformin (C) for 16 h, followed by immunoblotting of AMPK and ACC phosphorylation and cleaved caspase 3 (representative immunoblots; quantification of cleaved caspase 3 protein levels from four independent experiments). #P<0.05 and ##P<0.01 vs cells exposed to 0.25 mM palmitate; *P<0.05 and **P<0.01 vs corresponding columns as indicated; ns, not significant. Palm, palmitate; Met, metformin.
Mentions: Under condition of palmitate-induced apoptosis, both AICAR and metformin increased AMPK and ACC phosphorylation (P<0.05 and P<0.01 vs palmitate-exposed cells; Fig. 2A). Furthermore, in combination with AMPK inhibitor compound C (10 μM), the protective effect of AICAR (Fig. 2B) and metformin (Fig. 2C) were abrogated, as shown by relief of decreased cleaved caspase 3 protein expression. These findings demonstrated that prevention of palmitate-induced INS-1E cell apoptosis by AICAR and metformin were dependent on their activation of AMPK.

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