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How moderate changes in Akt T-loop phosphorylation impact on tumorigenesis and insulin resistance.

Wullschleger S, Sakamoto K, Johnstone L, Duce S, Fleming S, Alessi DR - Dis Model Mech (2010)

Bottom Line: Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity.This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging.Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

View Article: PubMed Central - PubMed

Affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

ABSTRACT
The Akt signalling pathway plays vital roles in controlling cellular responses to insulin as well as in proliferation and survival. Inhibition of Akt signalling leads to insulin resistance and type 2 diabetes, whereas hyperactivation of Akt promotes tumorigenesis. In this study, we investigate how modest changes in the activity of the Akt signalling pathway, to an extent that might be achieved by drug treatment, would impact on insulin resistance and tumorigenesis. Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity. Introducing the PDK1(K465E/K465E) PH domain knock-in mutation into cancer-prone PTEN(+/-) mice, lowered Akt activity only by about 50%, but led to a delay in tumour onset of ∼4 months in a broad range of tumours. This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging. Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

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Improved insulin sensitivity in PDK1K465E/K465EPTEN+/− mice. (A) Glucose tolerance test. Male mice aged 4 months of the indicated genotype were deprived of food overnight and then injected intraperitoneally with glucose (2 mg/g body weight). Blood glucose concentration was measured at the indicated times. Data are shown as mean ± s.e.m. Area under the curve was calculated and shown as mean ± s.e.m. of arbitrary units. Data from one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by the Student’s t-test, #P<0.02 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.005 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. (B) Blood glucose and plasma insulin levels were measured in male mice aged 4 months fed ad libitum. Data are shown as mean ± s.e.m. Data of one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by Student’s t-test, #P<0.05 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.05 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. PDK1+/+ PTEN+/+ n=9, PDK1+/+ PTEN+/− n=4, PDK1K465E/K465E PTEN+/+ n=8, PDK1K465E/K465E PTEN+/− n=8.
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f2-0040095: Improved insulin sensitivity in PDK1K465E/K465EPTEN+/− mice. (A) Glucose tolerance test. Male mice aged 4 months of the indicated genotype were deprived of food overnight and then injected intraperitoneally with glucose (2 mg/g body weight). Blood glucose concentration was measured at the indicated times. Data are shown as mean ± s.e.m. Area under the curve was calculated and shown as mean ± s.e.m. of arbitrary units. Data from one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by the Student’s t-test, #P<0.02 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.005 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. (B) Blood glucose and plasma insulin levels were measured in male mice aged 4 months fed ad libitum. Data are shown as mean ± s.e.m. Data of one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by Student’s t-test, #P<0.05 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.05 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. PDK1+/+ PTEN+/+ n=9, PDK1+/+ PTEN+/− n=4, PDK1K465E/K465E PTEN+/+ n=8, PDK1K465E/K465E PTEN+/− n=8.

Mentions: To investigate whether the modestly enhanced Akt activity observed in the PDK1K465E/K465EPTEN+/− compared with the PDK1K465E/K465EPTEN+/+ mice would be sufficient to counteract the insulin resistance, we performed a glucose tolerance test on these animals. Mice were starved overnight and injected with an intraperitoneal bolus of glucose, and blood glucose levels monitored over a 120-minute period. As reported previously (Bayascas et al., 2008), PDK1K465E/K465EPTEN+/+ animals displayed significant glucose intolerance because their blood glucose levels were markedly higher at all time points compared with PDK1+/+PTEN+/+ wild-type mice (Fig. 2A). The insulin resistance in the PDK1K465E/K465EPTEN+/+ animals was also emphasised by the markedly higher levels of plasma insulin compared with PDK1+/+PTEN+/+ mice (Fig. 2B). Strikingly, however, the PDK1K465E/K465EPTEN+/− mice showed markedly improved glucose tolerance compared with PDK1K465E/K465EPTEN+/+ animals. The rises in blood glucose levels at all time points were similar to the wild-type PDK1+/+PTEN+/+ mice in the glucose tolerance test (Fig. 2A). In addition, plasma insulin levels were not elevated in the PDK1K465E/K465EPTEN+/− animals and were similar to those of wild-type mice (Fig. 2B). As reported previously (Wong et al., 2007), we also observed that the PDK1+/+PTEN+/− mice displayed enhanced insulin sensitivity compared with wild-type PDK1+/+PTEN+/+ animals (Fig. 2A). The PDK1+/+PTEN+/− mice also possessed lower plasma insulin levels than wild-type mice (Fig. 2B). These data indicate that lowering the expression of PTEN by only 50% is sufficient to rescue the insulin resistance phenotype observed in PDK1K465E/K465EPTEN+/+ animals.


How moderate changes in Akt T-loop phosphorylation impact on tumorigenesis and insulin resistance.

Wullschleger S, Sakamoto K, Johnstone L, Duce S, Fleming S, Alessi DR - Dis Model Mech (2010)

Improved insulin sensitivity in PDK1K465E/K465EPTEN+/− mice. (A) Glucose tolerance test. Male mice aged 4 months of the indicated genotype were deprived of food overnight and then injected intraperitoneally with glucose (2 mg/g body weight). Blood glucose concentration was measured at the indicated times. Data are shown as mean ± s.e.m. Area under the curve was calculated and shown as mean ± s.e.m. of arbitrary units. Data from one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by the Student’s t-test, #P<0.02 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.005 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. (B) Blood glucose and plasma insulin levels were measured in male mice aged 4 months fed ad libitum. Data are shown as mean ± s.e.m. Data of one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by Student’s t-test, #P<0.05 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.05 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. PDK1+/+ PTEN+/+ n=9, PDK1+/+ PTEN+/− n=4, PDK1K465E/K465E PTEN+/+ n=8, PDK1K465E/K465E PTEN+/− n=8.
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f2-0040095: Improved insulin sensitivity in PDK1K465E/K465EPTEN+/− mice. (A) Glucose tolerance test. Male mice aged 4 months of the indicated genotype were deprived of food overnight and then injected intraperitoneally with glucose (2 mg/g body weight). Blood glucose concentration was measured at the indicated times. Data are shown as mean ± s.e.m. Area under the curve was calculated and shown as mean ± s.e.m. of arbitrary units. Data from one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by the Student’s t-test, #P<0.02 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.005 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. (B) Blood glucose and plasma insulin levels were measured in male mice aged 4 months fed ad libitum. Data are shown as mean ± s.e.m. Data of one experiment are shown; similar results were obtained with a second group of mice. P-values were obtained by Student’s t-test, #P<0.05 for PDK1+/+ PTEN+/+ compared with PDK1+/+ PTEN+/−. *P<0.05 for PDK1K465E/K465E PTEN+/+ compared with PDK1K465E/K465E PTEN+/−. PDK1+/+ PTEN+/+ n=9, PDK1+/+ PTEN+/− n=4, PDK1K465E/K465E PTEN+/+ n=8, PDK1K465E/K465E PTEN+/− n=8.
Mentions: To investigate whether the modestly enhanced Akt activity observed in the PDK1K465E/K465EPTEN+/− compared with the PDK1K465E/K465EPTEN+/+ mice would be sufficient to counteract the insulin resistance, we performed a glucose tolerance test on these animals. Mice were starved overnight and injected with an intraperitoneal bolus of glucose, and blood glucose levels monitored over a 120-minute period. As reported previously (Bayascas et al., 2008), PDK1K465E/K465EPTEN+/+ animals displayed significant glucose intolerance because their blood glucose levels were markedly higher at all time points compared with PDK1+/+PTEN+/+ wild-type mice (Fig. 2A). The insulin resistance in the PDK1K465E/K465EPTEN+/+ animals was also emphasised by the markedly higher levels of plasma insulin compared with PDK1+/+PTEN+/+ mice (Fig. 2B). Strikingly, however, the PDK1K465E/K465EPTEN+/− mice showed markedly improved glucose tolerance compared with PDK1K465E/K465EPTEN+/+ animals. The rises in blood glucose levels at all time points were similar to the wild-type PDK1+/+PTEN+/+ mice in the glucose tolerance test (Fig. 2A). In addition, plasma insulin levels were not elevated in the PDK1K465E/K465EPTEN+/− animals and were similar to those of wild-type mice (Fig. 2B). As reported previously (Wong et al., 2007), we also observed that the PDK1+/+PTEN+/− mice displayed enhanced insulin sensitivity compared with wild-type PDK1+/+PTEN+/+ animals (Fig. 2A). The PDK1+/+PTEN+/− mice also possessed lower plasma insulin levels than wild-type mice (Fig. 2B). These data indicate that lowering the expression of PTEN by only 50% is sufficient to rescue the insulin resistance phenotype observed in PDK1K465E/K465EPTEN+/+ animals.

Bottom Line: Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity.This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging.Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

View Article: PubMed Central - PubMed

Affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

ABSTRACT
The Akt signalling pathway plays vital roles in controlling cellular responses to insulin as well as in proliferation and survival. Inhibition of Akt signalling leads to insulin resistance and type 2 diabetes, whereas hyperactivation of Akt promotes tumorigenesis. In this study, we investigate how modest changes in the activity of the Akt signalling pathway, to an extent that might be achieved by drug treatment, would impact on insulin resistance and tumorigenesis. Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity. Introducing the PDK1(K465E/K465E) PH domain knock-in mutation into cancer-prone PTEN(+/-) mice, lowered Akt activity only by about 50%, but led to a delay in tumour onset of ∼4 months in a broad range of tumours. This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging. Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

Show MeSH
Related in: MedlinePlus