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Alterations in microRNA expression contribute to fatty acid-induced pancreatic beta-cell dysfunction.

Lovis P, Roggli E, Laybutt DR, Gattesco S, Yang JY, Widmann C, Abderrahmani A, Regazzi R - Diabetes (2008)

Bottom Line: The latter effect is associated with inhibition of the expression of vesicle-associated membrane protein 2, a key player in beta-cell exocytosis.Higher miR146 levels do not affect the capacity to release insulin but contribute to increased apoptosis.Our findings suggest that at least part of the detrimental effects of palmitate on beta-cells is caused by alterations in the level of specific miRNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.

ABSTRACT

Objective: Visceral obesity and elevated plasma free fatty acids are predisposing factors for type 2 diabetes. Chronic exposure to these lipids is detrimental for pancreatic beta-cells, resulting in reduced insulin content, defective insulin secretion, and apoptosis. We investigated the involvement in this phenomenon of microRNAs (miRNAs), a class of noncoding RNAs regulating gene expression by sequence-specific inhibition of mRNA translation.

Research design and methods: We analyzed miRNA expression in insulin-secreting cell lines or pancreatic islets exposed to palmitate for 3 days and in islets from diabetic db/db mice. We studied the signaling pathways triggering the changes in miRNA expression and determined the impact of the miRNAs affected by palmitate on insulin secretion and apoptosis.

Results: Prolonged exposure of the beta-cell line MIN6B1 and pancreatic islets to palmitate causes a time- and dose-dependent increase of miR34a and miR146. Elevated levels of these miRNAs are also observed in islets of diabetic db/db mice. miR34a rise is linked to activation of p53 and results in sensitization to apoptosis and impaired nutrient-induced secretion. The latter effect is associated with inhibition of the expression of vesicle-associated membrane protein 2, a key player in beta-cell exocytosis. Higher miR146 levels do not affect the capacity to release insulin but contribute to increased apoptosis. Treatment with oligonucleotides that block miR34a or miR146 activity partially protects palmitate-treated cells from apoptosis but is insufficient to restore normal secretion.

Conclusions: Our findings suggest that at least part of the detrimental effects of palmitate on beta-cells is caused by alterations in the level of specific miRNAs.

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Related in: MedlinePlus

Effect of miR34a and miR146 on apoptosis. A: MIN6B1 cells were transfected with a control RNA duplex or RNA duplexes containing miR15b, miR34a, or miR146. The cells were cultured for 3 days in normal DMEM (□ and □) or with DMEM containing 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of three independent experiments. *Conditions significantly different (P < 0.05, n = 3) from control. B: MIN6B1 cells were transfected with control oligonucleotides, anti-miR34a (anti-34a), or anti-miR146 (anti-146). The cells were then cultured for 3 days in normal DMEM (□) or in DMEM supplemented with 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of four to five independent experiments. *Conditions that are significantly different (P < 0.05).
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f5: Effect of miR34a and miR146 on apoptosis. A: MIN6B1 cells were transfected with a control RNA duplex or RNA duplexes containing miR15b, miR34a, or miR146. The cells were cultured for 3 days in normal DMEM (□ and □) or with DMEM containing 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of three independent experiments. *Conditions significantly different (P < 0.05, n = 3) from control. B: MIN6B1 cells were transfected with control oligonucleotides, anti-miR34a (anti-34a), or anti-miR146 (anti-146). The cells were then cultured for 3 days in normal DMEM (□) or in DMEM supplemented with 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of four to five independent experiments. *Conditions that are significantly different (P < 0.05).

Mentions: FFAs are known to sensitize β-cells to apoptosis (3). Under our experimental conditions, incubation of MIN6B1 cells with palmitate increased the number of apoptotic cells by about fourfold (Fig. 5A). A rise in miR34a or miR146 expression significantly augmented the fraction of cells undergoing apoptosis, suggesting that at least part of the effect of palmitate may be mediated through changes in the level of these miRNAs (Fig. 5A). Inhibition of miR34a or miR146 activity was found to partially protect palmitate-treated cells against apoptosis (Fig. 5B).


Alterations in microRNA expression contribute to fatty acid-induced pancreatic beta-cell dysfunction.

Lovis P, Roggli E, Laybutt DR, Gattesco S, Yang JY, Widmann C, Abderrahmani A, Regazzi R - Diabetes (2008)

Effect of miR34a and miR146 on apoptosis. A: MIN6B1 cells were transfected with a control RNA duplex or RNA duplexes containing miR15b, miR34a, or miR146. The cells were cultured for 3 days in normal DMEM (□ and □) or with DMEM containing 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of three independent experiments. *Conditions significantly different (P < 0.05, n = 3) from control. B: MIN6B1 cells were transfected with control oligonucleotides, anti-miR34a (anti-34a), or anti-miR146 (anti-146). The cells were then cultured for 3 days in normal DMEM (□) or in DMEM supplemented with 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of four to five independent experiments. *Conditions that are significantly different (P < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551683&req=5

f5: Effect of miR34a and miR146 on apoptosis. A: MIN6B1 cells were transfected with a control RNA duplex or RNA duplexes containing miR15b, miR34a, or miR146. The cells were cultured for 3 days in normal DMEM (□ and □) or with DMEM containing 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of three independent experiments. *Conditions significantly different (P < 0.05, n = 3) from control. B: MIN6B1 cells were transfected with control oligonucleotides, anti-miR34a (anti-34a), or anti-miR146 (anti-146). The cells were then cultured for 3 days in normal DMEM (□) or in DMEM supplemented with 1 mmol/l palmitate (▪). The number of cells displaying apoptotic nuclei was scored and divided by the total number of cells analyzed. Data are means ± SE of four to five independent experiments. *Conditions that are significantly different (P < 0.05).
Mentions: FFAs are known to sensitize β-cells to apoptosis (3). Under our experimental conditions, incubation of MIN6B1 cells with palmitate increased the number of apoptotic cells by about fourfold (Fig. 5A). A rise in miR34a or miR146 expression significantly augmented the fraction of cells undergoing apoptosis, suggesting that at least part of the effect of palmitate may be mediated through changes in the level of these miRNAs (Fig. 5A). Inhibition of miR34a or miR146 activity was found to partially protect palmitate-treated cells against apoptosis (Fig. 5B).

Bottom Line: The latter effect is associated with inhibition of the expression of vesicle-associated membrane protein 2, a key player in beta-cell exocytosis.Higher miR146 levels do not affect the capacity to release insulin but contribute to increased apoptosis.Our findings suggest that at least part of the detrimental effects of palmitate on beta-cells is caused by alterations in the level of specific miRNAs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Morphology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.

ABSTRACT

Objective: Visceral obesity and elevated plasma free fatty acids are predisposing factors for type 2 diabetes. Chronic exposure to these lipids is detrimental for pancreatic beta-cells, resulting in reduced insulin content, defective insulin secretion, and apoptosis. We investigated the involvement in this phenomenon of microRNAs (miRNAs), a class of noncoding RNAs regulating gene expression by sequence-specific inhibition of mRNA translation.

Research design and methods: We analyzed miRNA expression in insulin-secreting cell lines or pancreatic islets exposed to palmitate for 3 days and in islets from diabetic db/db mice. We studied the signaling pathways triggering the changes in miRNA expression and determined the impact of the miRNAs affected by palmitate on insulin secretion and apoptosis.

Results: Prolonged exposure of the beta-cell line MIN6B1 and pancreatic islets to palmitate causes a time- and dose-dependent increase of miR34a and miR146. Elevated levels of these miRNAs are also observed in islets of diabetic db/db mice. miR34a rise is linked to activation of p53 and results in sensitization to apoptosis and impaired nutrient-induced secretion. The latter effect is associated with inhibition of the expression of vesicle-associated membrane protein 2, a key player in beta-cell exocytosis. Higher miR146 levels do not affect the capacity to release insulin but contribute to increased apoptosis. Treatment with oligonucleotides that block miR34a or miR146 activity partially protects palmitate-treated cells from apoptosis but is insufficient to restore normal secretion.

Conclusions: Our findings suggest that at least part of the detrimental effects of palmitate on beta-cells is caused by alterations in the level of specific miRNAs.

Show MeSH
Related in: MedlinePlus