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Nutrient Excess and AMPK Downregulation in Incubated Skeletal Muscle and Muscle of Glucose Infused Rats.

Coughlan KA, Balon TW, Valentine RJ, Petrocelli R, Schultz V, Brandon A, Cooney GJ, Kraegen EW, Ruderman NB, Saha AK - PLoS ONE (2015)

Bottom Line: The initial decrease in activity at 30min coincided with a significant increase in muscle glycogen.The subsequent decreases at 1h were accompanied by phosphorylation of αAMPK at Ser485/491, and at 2h by decreased SIRT1 expression and increased PP2A activity, all of which have previously been shown to diminish AMPK activity.Thus, the initial decrease in AMPK activity observed at 3h was associated with changes in Ser485/491 phosphorylation and SIRT1 expression and increased PP2A activity was a later event.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Section of Endocrinology and Diabetes, Boston University Medical Center, Boston, Massachusetts, United States of America.

ABSTRACT
We have previously shown that incubation for 1h with excess glucose or leucine causes insulin resistance in rat extensor digitorum longus (EDL) muscle by inhibiting AMP-activated protein kinase (AMPK). To examine the events that precede and follow these changes, studies were performed in rat EDL incubated with elevated levels of glucose or leucine for 30min-2h. Incubation in high glucose (25mM) or leucine (100μM) significantly diminished AMPK activity by 50% within 30min, with further decreases occurring at 1 and 2h. The initial decrease in activity at 30min coincided with a significant increase in muscle glycogen. The subsequent decreases at 1h were accompanied by phosphorylation of αAMPK at Ser485/491, and at 2h by decreased SIRT1 expression and increased PP2A activity, all of which have previously been shown to diminish AMPK activity. Glucose infusion in vivo, which caused several fold increases in plasma glucose and insulin, produced similar changes but with different timing. Thus, the initial decrease in AMPK activity observed at 3h was associated with changes in Ser485/491 phosphorylation and SIRT1 expression and increased PP2A activity was a later event. These findings suggest that both ex vivo and in vivo, multiple factors contribute to fuel-induced decreases in AMPK activity in skeletal muscle and the insulin resistance that accompanies it.

No MeSH data available.


Related in: MedlinePlus

Incubation with elevated glucose levels or leucine or and in vivo glucose infusion increases PP2A activity at 2h (ex vivo) or 8h (in vivo).EDL muscles incubated for 30, 60 and 120 min in media containing 5.5 or 25 mM glucose (A) or 5.5mM glucose with or without 100μM leucine (C) and red gastrocnemius muscles from rats infused with glucose for 0, 3, 5, or 8h (B) were analyzed for PP2A activity as described in the methods section. Results are means + SE (n = 4–6). *P <0.05 compared to 30 min incubation with 5.5 mM glucose (A) and (C) or the 0h group for infusions (B).
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pone.0127388.g004: Incubation with elevated glucose levels or leucine or and in vivo glucose infusion increases PP2A activity at 2h (ex vivo) or 8h (in vivo).EDL muscles incubated for 30, 60 and 120 min in media containing 5.5 or 25 mM glucose (A) or 5.5mM glucose with or without 100μM leucine (C) and red gastrocnemius muscles from rats infused with glucose for 0, 3, 5, or 8h (B) were analyzed for PP2A activity as described in the methods section. Results are means + SE (n = 4–6). *P <0.05 compared to 30 min incubation with 5.5 mM glucose (A) and (C) or the 0h group for infusions (B).

Mentions: PP2A is a major protein serine/threonine phosphatase that regulates AMPK, among other molecules in mammalian cells [22–24]. As shown in Fig 4A, incubation with 25 vs. 5.5mM glucose increased PP2A activity by 1.7-fold; however, as with SIRT1, this change was only observed at the 2h time point.


Nutrient Excess and AMPK Downregulation in Incubated Skeletal Muscle and Muscle of Glucose Infused Rats.

Coughlan KA, Balon TW, Valentine RJ, Petrocelli R, Schultz V, Brandon A, Cooney GJ, Kraegen EW, Ruderman NB, Saha AK - PLoS ONE (2015)

Incubation with elevated glucose levels or leucine or and in vivo glucose infusion increases PP2A activity at 2h (ex vivo) or 8h (in vivo).EDL muscles incubated for 30, 60 and 120 min in media containing 5.5 or 25 mM glucose (A) or 5.5mM glucose with or without 100μM leucine (C) and red gastrocnemius muscles from rats infused with glucose for 0, 3, 5, or 8h (B) were analyzed for PP2A activity as described in the methods section. Results are means + SE (n = 4–6). *P <0.05 compared to 30 min incubation with 5.5 mM glucose (A) and (C) or the 0h group for infusions (B).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4440828&req=5

pone.0127388.g004: Incubation with elevated glucose levels or leucine or and in vivo glucose infusion increases PP2A activity at 2h (ex vivo) or 8h (in vivo).EDL muscles incubated for 30, 60 and 120 min in media containing 5.5 or 25 mM glucose (A) or 5.5mM glucose with or without 100μM leucine (C) and red gastrocnemius muscles from rats infused with glucose for 0, 3, 5, or 8h (B) were analyzed for PP2A activity as described in the methods section. Results are means + SE (n = 4–6). *P <0.05 compared to 30 min incubation with 5.5 mM glucose (A) and (C) or the 0h group for infusions (B).
Mentions: PP2A is a major protein serine/threonine phosphatase that regulates AMPK, among other molecules in mammalian cells [22–24]. As shown in Fig 4A, incubation with 25 vs. 5.5mM glucose increased PP2A activity by 1.7-fold; however, as with SIRT1, this change was only observed at the 2h time point.

Bottom Line: The initial decrease in activity at 30min coincided with a significant increase in muscle glycogen.The subsequent decreases at 1h were accompanied by phosphorylation of αAMPK at Ser485/491, and at 2h by decreased SIRT1 expression and increased PP2A activity, all of which have previously been shown to diminish AMPK activity.Thus, the initial decrease in AMPK activity observed at 3h was associated with changes in Ser485/491 phosphorylation and SIRT1 expression and increased PP2A activity was a later event.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Section of Endocrinology and Diabetes, Boston University Medical Center, Boston, Massachusetts, United States of America.

ABSTRACT
We have previously shown that incubation for 1h with excess glucose or leucine causes insulin resistance in rat extensor digitorum longus (EDL) muscle by inhibiting AMP-activated protein kinase (AMPK). To examine the events that precede and follow these changes, studies were performed in rat EDL incubated with elevated levels of glucose or leucine for 30min-2h. Incubation in high glucose (25mM) or leucine (100μM) significantly diminished AMPK activity by 50% within 30min, with further decreases occurring at 1 and 2h. The initial decrease in activity at 30min coincided with a significant increase in muscle glycogen. The subsequent decreases at 1h were accompanied by phosphorylation of αAMPK at Ser485/491, and at 2h by decreased SIRT1 expression and increased PP2A activity, all of which have previously been shown to diminish AMPK activity. Glucose infusion in vivo, which caused several fold increases in plasma glucose and insulin, produced similar changes but with different timing. Thus, the initial decrease in AMPK activity observed at 3h was associated with changes in Ser485/491 phosphorylation and SIRT1 expression and increased PP2A activity was a later event. These findings suggest that both ex vivo and in vivo, multiple factors contribute to fuel-induced decreases in AMPK activity in skeletal muscle and the insulin resistance that accompanies it.

No MeSH data available.


Related in: MedlinePlus