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PINK1 deficiency in β-cells increases basal insulin secretion and improves glucose tolerance in mice.

Deas E, Piipari K, Machhada A, Li A, Gutierrez-del-Arroyo A, Withers DJ, Wood NW, Abramov AY - Open Biol (2014)

Bottom Line: The Parkinson's disease (PD) gene, PARK6, encodes the PTEN-induced putative kinase 1 (PINK1) mitochondrial kinase, which provides protection against oxidative stress-induced apoptosis.This was accompanied by higher basal levels of intracellular calcium leading to increased basal levels of insulin secretion under low glucose conditions.For the first time, these combined results demonstrate that loss of PINK1 function appears to disrupt glucose-sensing leading to enhanced insulin release, which is uncoupled from glucose uptake, and suggest a key role for PINK1 in β-cell function.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.

ABSTRACT
The Parkinson's disease (PD) gene, PARK6, encodes the PTEN-induced putative kinase 1 (PINK1) mitochondrial kinase, which provides protection against oxidative stress-induced apoptosis. Given the link between glucose metabolism, mitochondrial function and insulin secretion in β-cells, and the reported association of PD with type 2 diabetes, we investigated the response of PINK1-deficient β-cells to glucose stimuli to determine whether loss of PINK1 affected their function. We find that loss of PINK1 significantly impairs the ability of mouse pancreatic β-cells (MIN6 cells) and primary intact islets to take up glucose. This was accompanied by higher basal levels of intracellular calcium leading to increased basal levels of insulin secretion under low glucose conditions. Finally, we investigated the effect of PINK1 deficiency in vivo and find that PINK1 knockout mice have improved glucose tolerance. For the first time, these combined results demonstrate that loss of PINK1 function appears to disrupt glucose-sensing leading to enhanced insulin release, which is uncoupled from glucose uptake, and suggest a key role for PINK1 in β-cell function.

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PINK1 KO mice suffer from glucose tolerance and altered insulin secretion in vivo. (a) Concentration of insulin secreted by WT and KO PINK1 isolated islets under low and high glucose stimuli. p < 0.005, Mann–Whitney U-test. (b) Residual concentration of insulin extracted from WT and KO islets. p < 0.05, Mann–Whitney U-test. (c,d) Basal blood glucose concentrations in PINK1 WT and KO mice in response to random feeding or overnight starvation, respectively. (e) Comparison of body weight between PINK1 WT and KO animals. (f) Response of PINK1 WT and KO animals to a GTT. Two-way ANOVA with Bonferroni multiple comparison test with repeated measures. p > 0.005, Mann–Whitney U-test. (g) Response of PINK1 WT and KO animals to an ITT. (h) Assessment of blood insulin levels in PINK1 WT and KO animals in response to a GSIS test. p > 0.005, Mann–Whitney U-test.
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RSOB140051F3: PINK1 KO mice suffer from glucose tolerance and altered insulin secretion in vivo. (a) Concentration of insulin secreted by WT and KO PINK1 isolated islets under low and high glucose stimuli. p < 0.005, Mann–Whitney U-test. (b) Residual concentration of insulin extracted from WT and KO islets. p < 0.05, Mann–Whitney U-test. (c,d) Basal blood glucose concentrations in PINK1 WT and KO mice in response to random feeding or overnight starvation, respectively. (e) Comparison of body weight between PINK1 WT and KO animals. (f) Response of PINK1 WT and KO animals to a GTT. Two-way ANOVA with Bonferroni multiple comparison test with repeated measures. p > 0.005, Mann–Whitney U-test. (g) Response of PINK1 WT and KO animals to an ITT. (h) Assessment of blood insulin levels in PINK1 WT and KO animals in response to a GSIS test. p > 0.005, Mann–Whitney U-test.

Mentions: To determine the impact of PINK1 deficiency on insulin release, we measured the level of insulin secreted by WT control and PINK1 KO intact islets under low and high glucose conditions. As expected, the WT islets secreted significantly more insulin in response to the high 20 mM glucose stimulus than the low 2 mM stimulus (n = 6; p < 0.05; figure 3a). By contrast, PINK1 KO islets secreted significantly higher levels of insulin than their WT counterparts in response to 2 mM glucose and, notably, the level secreted was comparable to the WT islet response to 20 mM glucose (n = 6; p < 0.05; figure 3a). When exposed to high glucose, the PINK1 KO islets also secreted significantly more insulin compared with those observed under low glucose conditions (n = 6; p < 0.005; figure 3a). This confirms our previous observations in MIN6 cells and intact islets demonstrating that PINK1-deficient cells can still respond to high concentrations of glucose (figure 1f,g). To determine whether the difference in insulin secretion between WT and PINK1 KO islets was due to altered total levels of insulin, the residual insulin was extracted from the islets by acid ethanol and measured. Notably, the total concentration of insulin (secreted plus extracted) was comparable between WT and PINK1 KO islets (figure 3b, n = 6; p < 0.05).Figure 3.


PINK1 deficiency in β-cells increases basal insulin secretion and improves glucose tolerance in mice.

Deas E, Piipari K, Machhada A, Li A, Gutierrez-del-Arroyo A, Withers DJ, Wood NW, Abramov AY - Open Biol (2014)

PINK1 KO mice suffer from glucose tolerance and altered insulin secretion in vivo. (a) Concentration of insulin secreted by WT and KO PINK1 isolated islets under low and high glucose stimuli. p < 0.005, Mann–Whitney U-test. (b) Residual concentration of insulin extracted from WT and KO islets. p < 0.05, Mann–Whitney U-test. (c,d) Basal blood glucose concentrations in PINK1 WT and KO mice in response to random feeding or overnight starvation, respectively. (e) Comparison of body weight between PINK1 WT and KO animals. (f) Response of PINK1 WT and KO animals to a GTT. Two-way ANOVA with Bonferroni multiple comparison test with repeated measures. p > 0.005, Mann–Whitney U-test. (g) Response of PINK1 WT and KO animals to an ITT. (h) Assessment of blood insulin levels in PINK1 WT and KO animals in response to a GSIS test. p > 0.005, Mann–Whitney U-test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4042854&req=5

RSOB140051F3: PINK1 KO mice suffer from glucose tolerance and altered insulin secretion in vivo. (a) Concentration of insulin secreted by WT and KO PINK1 isolated islets under low and high glucose stimuli. p < 0.005, Mann–Whitney U-test. (b) Residual concentration of insulin extracted from WT and KO islets. p < 0.05, Mann–Whitney U-test. (c,d) Basal blood glucose concentrations in PINK1 WT and KO mice in response to random feeding or overnight starvation, respectively. (e) Comparison of body weight between PINK1 WT and KO animals. (f) Response of PINK1 WT and KO animals to a GTT. Two-way ANOVA with Bonferroni multiple comparison test with repeated measures. p > 0.005, Mann–Whitney U-test. (g) Response of PINK1 WT and KO animals to an ITT. (h) Assessment of blood insulin levels in PINK1 WT and KO animals in response to a GSIS test. p > 0.005, Mann–Whitney U-test.
Mentions: To determine the impact of PINK1 deficiency on insulin release, we measured the level of insulin secreted by WT control and PINK1 KO intact islets under low and high glucose conditions. As expected, the WT islets secreted significantly more insulin in response to the high 20 mM glucose stimulus than the low 2 mM stimulus (n = 6; p < 0.05; figure 3a). By contrast, PINK1 KO islets secreted significantly higher levels of insulin than their WT counterparts in response to 2 mM glucose and, notably, the level secreted was comparable to the WT islet response to 20 mM glucose (n = 6; p < 0.05; figure 3a). When exposed to high glucose, the PINK1 KO islets also secreted significantly more insulin compared with those observed under low glucose conditions (n = 6; p < 0.005; figure 3a). This confirms our previous observations in MIN6 cells and intact islets demonstrating that PINK1-deficient cells can still respond to high concentrations of glucose (figure 1f,g). To determine whether the difference in insulin secretion between WT and PINK1 KO islets was due to altered total levels of insulin, the residual insulin was extracted from the islets by acid ethanol and measured. Notably, the total concentration of insulin (secreted plus extracted) was comparable between WT and PINK1 KO islets (figure 3b, n = 6; p < 0.05).Figure 3.

Bottom Line: The Parkinson's disease (PD) gene, PARK6, encodes the PTEN-induced putative kinase 1 (PINK1) mitochondrial kinase, which provides protection against oxidative stress-induced apoptosis.This was accompanied by higher basal levels of intracellular calcium leading to increased basal levels of insulin secretion under low glucose conditions.For the first time, these combined results demonstrate that loss of PINK1 function appears to disrupt glucose-sensing leading to enhanced insulin release, which is uncoupled from glucose uptake, and suggest a key role for PINK1 in β-cell function.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK.

ABSTRACT
The Parkinson's disease (PD) gene, PARK6, encodes the PTEN-induced putative kinase 1 (PINK1) mitochondrial kinase, which provides protection against oxidative stress-induced apoptosis. Given the link between glucose metabolism, mitochondrial function and insulin secretion in β-cells, and the reported association of PD with type 2 diabetes, we investigated the response of PINK1-deficient β-cells to glucose stimuli to determine whether loss of PINK1 affected their function. We find that loss of PINK1 significantly impairs the ability of mouse pancreatic β-cells (MIN6 cells) and primary intact islets to take up glucose. This was accompanied by higher basal levels of intracellular calcium leading to increased basal levels of insulin secretion under low glucose conditions. Finally, we investigated the effect of PINK1 deficiency in vivo and find that PINK1 knockout mice have improved glucose tolerance. For the first time, these combined results demonstrate that loss of PINK1 function appears to disrupt glucose-sensing leading to enhanced insulin release, which is uncoupled from glucose uptake, and suggest a key role for PINK1 in β-cell function.

Show MeSH
Related in: MedlinePlus