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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 mice display altered glucose homeostasis gene transcription in intact islets. (a–f) RT-PCR assessment of gene transcription in PINK1 KO versus WT islets showing a downregulation of HNF4α and an upregulation of GCK, Neurod1, Nkx6.1, PDK1 and FoxA2, respectively. p < 0.05, Mann–Whitney U-test. (g) Illustration of how PINK1 deficiency results in altered insulin secretion and gene regulation in intact islets.
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RSOB140051F4: PINK1 mice display altered glucose homeostasis gene transcription in intact islets. (a–f) RT-PCR assessment of gene transcription in PINK1 KO versus WT islets showing a downregulation of HNF4α and an upregulation of GCK, Neurod1, Nkx6.1, PDK1 and FoxA2, respectively. p < 0.05, Mann–Whitney U-test. (g) Illustration of how PINK1 deficiency results in altered insulin secretion and gene regulation in intact islets.

Mentions: As the final stage of our investigation, we used six month old male PINK1 WT and KO mice to assess the effect of PINK1 deficiency on islet function in vivo. Blood glucose levels of both PINK1 WT and KO mice showed no discernable differences after random feeding or 16 h starvation (figure 3c,d). In addition, body weight was comparable (figure 3e) and preliminary observations indicated no difference in food or water consumption (data not shown). A glucose tolerance test (GTT) revealed that while PINK1 WT and KO mice initially show a comparable increase in blood glucose levels, the levels in PINK1 KO mice peak at a lower level and decrease significantly faster than the WT littermates (figure 3f, p < 0.05). However, the response to an insulin tolerance test (ITT) was comparable and showed an initial drop in blood glucose levels followed by recovery (figure 3g). A glucose-stimulated insulin secretion (GSIS) experiment revealed that, as in our islet experiments, PINK1 KO mice have a higher basal level of insulin in the bloodstream (figure 3h). This, however, did not reach significant levels compared with WT. Upon injection of glucose, the PINK1 KO mice were initially stimulated to secrete insulin into the blood, but after 3 min, the level secreted was lower than that observed in WT animals (figure 3f). At 7 min post-injection, the blood insulin levels in the PINK1 KO mice had returned to baseline, whereas the WT blood insulin levels, although reduced, remained significantly higher than the basal reading (p < 0.05). However, insulin secretion in the KO animals increased to levels comparable to WT littermates 20 min post-injection (figure 3f). These combined results suggest that PINK1 deficiency results in improved glucose tolerance in vivo and also indicate that, in vivo, there appears to be a trend towards increased basal blood insulin levels with a reduced initial secretion response. In addition to these studies, RT-PCR analysis of several key genes involved in glucose homeostasis (GSK3β, Pecam1, HNF1α, HNF4α, ECAD, GCK, Neurod1, Nkx6.1, FoxA2, PDK1, Pfkp, ALDOB, GAPDH and AKT) revealed that while HNF4α was downregulated in PINK1 KO islets, GCK, Neurod1, Nkx6.1, PDK1 and FoxA2 were all upregulated compared with WT age-matched controls (figure 4a–e and f, respectively, n = 4; for HNF4α and GCK p < 0.0006, for FoxA2 and PDK1 p < 0.004, for Nkx6.1 and Neurod1 p < 0.02). The remaining genes examined showed no significant alteration between genotypes (electronic supplementary material, figure S2).Figure 4.


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 mice display altered glucose homeostasis gene transcription in intact islets. (a–f) RT-PCR assessment of gene transcription in PINK1 KO versus WT islets showing a downregulation of HNF4α and an upregulation of GCK, Neurod1, Nkx6.1, PDK1 and FoxA2, respectively. p < 0.05, Mann–Whitney U-test. (g) Illustration of how PINK1 deficiency results in altered insulin secretion and gene regulation in intact islets.
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Related In: Results  -  Collection

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RSOB140051F4: PINK1 mice display altered glucose homeostasis gene transcription in intact islets. (a–f) RT-PCR assessment of gene transcription in PINK1 KO versus WT islets showing a downregulation of HNF4α and an upregulation of GCK, Neurod1, Nkx6.1, PDK1 and FoxA2, respectively. p < 0.05, Mann–Whitney U-test. (g) Illustration of how PINK1 deficiency results in altered insulin secretion and gene regulation in intact islets.
Mentions: As the final stage of our investigation, we used six month old male PINK1 WT and KO mice to assess the effect of PINK1 deficiency on islet function in vivo. Blood glucose levels of both PINK1 WT and KO mice showed no discernable differences after random feeding or 16 h starvation (figure 3c,d). In addition, body weight was comparable (figure 3e) and preliminary observations indicated no difference in food or water consumption (data not shown). A glucose tolerance test (GTT) revealed that while PINK1 WT and KO mice initially show a comparable increase in blood glucose levels, the levels in PINK1 KO mice peak at a lower level and decrease significantly faster than the WT littermates (figure 3f, p < 0.05). However, the response to an insulin tolerance test (ITT) was comparable and showed an initial drop in blood glucose levels followed by recovery (figure 3g). A glucose-stimulated insulin secretion (GSIS) experiment revealed that, as in our islet experiments, PINK1 KO mice have a higher basal level of insulin in the bloodstream (figure 3h). This, however, did not reach significant levels compared with WT. Upon injection of glucose, the PINK1 KO mice were initially stimulated to secrete insulin into the blood, but after 3 min, the level secreted was lower than that observed in WT animals (figure 3f). At 7 min post-injection, the blood insulin levels in the PINK1 KO mice had returned to baseline, whereas the WT blood insulin levels, although reduced, remained significantly higher than the basal reading (p < 0.05). However, insulin secretion in the KO animals increased to levels comparable to WT littermates 20 min post-injection (figure 3f). These combined results suggest that PINK1 deficiency results in improved glucose tolerance in vivo and also indicate that, in vivo, there appears to be a trend towards increased basal blood insulin levels with a reduced initial secretion response. In addition to these studies, RT-PCR analysis of several key genes involved in glucose homeostasis (GSK3β, Pecam1, HNF1α, HNF4α, ECAD, GCK, Neurod1, Nkx6.1, FoxA2, PDK1, Pfkp, ALDOB, GAPDH and AKT) revealed that while HNF4α was downregulated in PINK1 KO islets, GCK, Neurod1, Nkx6.1, PDK1 and FoxA2 were all upregulated compared with WT age-matched controls (figure 4a–e and f, respectively, n = 4; for HNF4α and GCK p < 0.0006, for FoxA2 and PDK1 p < 0.004, for Nkx6.1 and Neurod1 p < 0.02). The remaining genes examined showed no significant alteration between genotypes (electronic supplementary material, figure S2).Figure 4.

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