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Cardioprotection Resulting from Glucagon-Like Peptide-1 Administration Involves Shifting Metabolic Substrate Utilization to Increase Energy Efficiency in the Rat Heart.

Aravindhan K, Bao W, Harpel MR, Willette RN, Lepore JJ, Jucker BM - PLoS ONE (2015)

Bottom Line: Furthermore, in isolated CMs GLP-1 treatment increased glucose utilization (↑14%, p<0.05) and decreased fatty acid oxidation (↓15%, p<0.05) consistent with in vivo finding.Our results show that this benefit may derive from distinct and complementary roles of GLP-1 treatment on metabolism in myocardial sub-regions in response to this injury.In particular, a switch to anaerobic glycolysis in the ischemic area provides a compensatory substrate switch to overcome the energetic deficit in this region in the face of reduced tissue oxygenation, whereas a switch to more energetically favorable carbohydrate oxidation in more highly oxygenated remote regions supports maintaining cardiac contractility in a complementary manner.

View Article: PubMed Central - PubMed

Affiliation: Heart Failure Discovery Performance Unit, Metabolic Pathways and Cardiovascular Therapeutic Area, GlaxoSmithKline, King of Prussia, Pennsylvania, United States of America.

ABSTRACT
Previous studies have shown that glucagon-like peptide-1 (GLP-1) provides cardiovascular benefits independent of its role on peripheral glycemic control. However, the precise mechanism(s) by which GLP-1 treatment renders cardioprotection during myocardial ischemia remain unresolved. Here we examined the role for GLP-1 treatment on glucose and fatty acid metabolism in normal and ischemic rat hearts following a 30 min ischemia and 24 h reperfusion injury, and in isolated cardiomyocytes (CM). Relative carbohydrate and fat oxidation levels were measured in both normal and ischemic hearts using a 1-13C glucose clamp coupled with NMR-based isotopomer analysis, as well as in adult rat CMs by monitoring pH and O2 consumption in the presence of glucose or palmitate. In normal heart, GLP-1 increased glucose uptake (↑64%, p<0.05) without affecting glycogen levels. In ischemic hearts, GLP-1 induced metabolic substrate switching by increasing the ratio of carbohydrate versus fat oxidation (↑14%, p<0.01) in the LV area not at risk, without affecting cAMP levels. Interestingly, no substrate switching occurred in the LV area at risk, despite an increase in cAMP (↑106%, p<0.05) and lactate (↑121%, p<0.01) levels. Furthermore, in isolated CMs GLP-1 treatment increased glucose utilization (↑14%, p<0.05) and decreased fatty acid oxidation (↓15%, p<0.05) consistent with in vivo finding. Our results show that this benefit may derive from distinct and complementary roles of GLP-1 treatment on metabolism in myocardial sub-regions in response to this injury. In particular, a switch to anaerobic glycolysis in the ischemic area provides a compensatory substrate switch to overcome the energetic deficit in this region in the face of reduced tissue oxygenation, whereas a switch to more energetically favorable carbohydrate oxidation in more highly oxygenated remote regions supports maintaining cardiac contractility in a complementary manner.

No MeSH data available.


Related in: MedlinePlus

Glucose utilization and reserve capacity in cultured CMs.Glucose utilization was assessed by examining percent change in ECAR and the reserve capacity assessed as percent change in OCR following FCCP challenge in the presence of indicated concentrations of GLP-1 or insulin at 70 nM. A typical seahorse plot representing changes in ECAR over time following acute treatment with 100 nM GLP-1 (maximal effective dose) or insulin optimal media (A) or suboptimal media (B). Percentage change in ECAR, 10 min post injection of GLP-1 (1, 10, 100 nM) or insulin with optimal media (C) and suboptimal media (D). Typical seahorse plots representing changes in OCR over time following acute treatment with 100 nM GLP-1 or insulin with optimal (E) or suboptimal (F) media. Percentage change in OCR, 80 min post injection of GLP-1 (1, 10, 100 nM) or insulin in optimal (G) and suboptimal (H) media. ECAR, extracellular acidification rate; OCR, oxygen consumption rate. Data are presented as mean±SEM of 3–5 replicates per treatment from 2–4 individual experiments. ***p<0.001, *p<0.05, vs Control.
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pone.0130894.g005: Glucose utilization and reserve capacity in cultured CMs.Glucose utilization was assessed by examining percent change in ECAR and the reserve capacity assessed as percent change in OCR following FCCP challenge in the presence of indicated concentrations of GLP-1 or insulin at 70 nM. A typical seahorse plot representing changes in ECAR over time following acute treatment with 100 nM GLP-1 (maximal effective dose) or insulin optimal media (A) or suboptimal media (B). Percentage change in ECAR, 10 min post injection of GLP-1 (1, 10, 100 nM) or insulin with optimal media (C) and suboptimal media (D). Typical seahorse plots representing changes in OCR over time following acute treatment with 100 nM GLP-1 or insulin with optimal (E) or suboptimal (F) media. Percentage change in OCR, 80 min post injection of GLP-1 (1, 10, 100 nM) or insulin in optimal (G) and suboptimal (H) media. ECAR, extracellular acidification rate; OCR, oxygen consumption rate. Data are presented as mean±SEM of 3–5 replicates per treatment from 2–4 individual experiments. ***p<0.001, *p<0.05, vs Control.

Mentions: The observed substrate switching in ANAR following GLP-1 treatment was further investigated in CMs using an extracellular flux analyzer to measure the oxidation of glucose and fatty acid substrates. ECAR, as a measure of both lactic acid and CO2 formation during glycolysis and glucose oxidation respectively [35], was monitored in CMs cultured in optimal or suboptimal medium to make them either sensitive or insensitive to insulin respectively. In the optimal medium, GLP-1 at all concentrations tested from 1 nM to 100 nM increased ECAR by net 14%, (p<0.05, Fig 5A and 5C). This effect was significantly less than the 58% net increase observed with insulin (p<0.001) and consistent with the different levels of glucose uptake observed in the in vivo 2DG experiments. However, no significant change in ECAR was observed with either insulin or GLP-1 when tested in suboptimal medium (Fig 5B and 5D). CMs were also sequentially challenged with oligomycin, FCCP and rotenone to assess the effect of GLP-1 treatment on ATP turnover/proton leak, reserve capacity and non-mitochondrial respiration, respectively. A slight, but significant improvement in reserve capacity was observed with GLP-1 at 100 nM, but only in CMs maintained in suboptimal media lacking pyruvate (Fig 5F and 5H) and not when maintained in optimal media (Fig 5E and 5G). The reserve capacity or coupling efficiency improved from 124.4±14.2% in control to 235.5±32.0% of basal respiration in GLP-1 (100 nM) treated cells (p<0.05, Fig 5H). No significant change in ATP turnover, proton leak or non-mitochondrial respiration was observed.


Cardioprotection Resulting from Glucagon-Like Peptide-1 Administration Involves Shifting Metabolic Substrate Utilization to Increase Energy Efficiency in the Rat Heart.

Aravindhan K, Bao W, Harpel MR, Willette RN, Lepore JJ, Jucker BM - PLoS ONE (2015)

Glucose utilization and reserve capacity in cultured CMs.Glucose utilization was assessed by examining percent change in ECAR and the reserve capacity assessed as percent change in OCR following FCCP challenge in the presence of indicated concentrations of GLP-1 or insulin at 70 nM. A typical seahorse plot representing changes in ECAR over time following acute treatment with 100 nM GLP-1 (maximal effective dose) or insulin optimal media (A) or suboptimal media (B). Percentage change in ECAR, 10 min post injection of GLP-1 (1, 10, 100 nM) or insulin with optimal media (C) and suboptimal media (D). Typical seahorse plots representing changes in OCR over time following acute treatment with 100 nM GLP-1 or insulin with optimal (E) or suboptimal (F) media. Percentage change in OCR, 80 min post injection of GLP-1 (1, 10, 100 nM) or insulin in optimal (G) and suboptimal (H) media. ECAR, extracellular acidification rate; OCR, oxygen consumption rate. Data are presented as mean±SEM of 3–5 replicates per treatment from 2–4 individual experiments. ***p<0.001, *p<0.05, vs Control.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4476748&req=5

pone.0130894.g005: Glucose utilization and reserve capacity in cultured CMs.Glucose utilization was assessed by examining percent change in ECAR and the reserve capacity assessed as percent change in OCR following FCCP challenge in the presence of indicated concentrations of GLP-1 or insulin at 70 nM. A typical seahorse plot representing changes in ECAR over time following acute treatment with 100 nM GLP-1 (maximal effective dose) or insulin optimal media (A) or suboptimal media (B). Percentage change in ECAR, 10 min post injection of GLP-1 (1, 10, 100 nM) or insulin with optimal media (C) and suboptimal media (D). Typical seahorse plots representing changes in OCR over time following acute treatment with 100 nM GLP-1 or insulin with optimal (E) or suboptimal (F) media. Percentage change in OCR, 80 min post injection of GLP-1 (1, 10, 100 nM) or insulin in optimal (G) and suboptimal (H) media. ECAR, extracellular acidification rate; OCR, oxygen consumption rate. Data are presented as mean±SEM of 3–5 replicates per treatment from 2–4 individual experiments. ***p<0.001, *p<0.05, vs Control.
Mentions: The observed substrate switching in ANAR following GLP-1 treatment was further investigated in CMs using an extracellular flux analyzer to measure the oxidation of glucose and fatty acid substrates. ECAR, as a measure of both lactic acid and CO2 formation during glycolysis and glucose oxidation respectively [35], was monitored in CMs cultured in optimal or suboptimal medium to make them either sensitive or insensitive to insulin respectively. In the optimal medium, GLP-1 at all concentrations tested from 1 nM to 100 nM increased ECAR by net 14%, (p<0.05, Fig 5A and 5C). This effect was significantly less than the 58% net increase observed with insulin (p<0.001) and consistent with the different levels of glucose uptake observed in the in vivo 2DG experiments. However, no significant change in ECAR was observed with either insulin or GLP-1 when tested in suboptimal medium (Fig 5B and 5D). CMs were also sequentially challenged with oligomycin, FCCP and rotenone to assess the effect of GLP-1 treatment on ATP turnover/proton leak, reserve capacity and non-mitochondrial respiration, respectively. A slight, but significant improvement in reserve capacity was observed with GLP-1 at 100 nM, but only in CMs maintained in suboptimal media lacking pyruvate (Fig 5F and 5H) and not when maintained in optimal media (Fig 5E and 5G). The reserve capacity or coupling efficiency improved from 124.4±14.2% in control to 235.5±32.0% of basal respiration in GLP-1 (100 nM) treated cells (p<0.05, Fig 5H). No significant change in ATP turnover, proton leak or non-mitochondrial respiration was observed.

Bottom Line: Furthermore, in isolated CMs GLP-1 treatment increased glucose utilization (↑14%, p<0.05) and decreased fatty acid oxidation (↓15%, p<0.05) consistent with in vivo finding.Our results show that this benefit may derive from distinct and complementary roles of GLP-1 treatment on metabolism in myocardial sub-regions in response to this injury.In particular, a switch to anaerobic glycolysis in the ischemic area provides a compensatory substrate switch to overcome the energetic deficit in this region in the face of reduced tissue oxygenation, whereas a switch to more energetically favorable carbohydrate oxidation in more highly oxygenated remote regions supports maintaining cardiac contractility in a complementary manner.

View Article: PubMed Central - PubMed

Affiliation: Heart Failure Discovery Performance Unit, Metabolic Pathways and Cardiovascular Therapeutic Area, GlaxoSmithKline, King of Prussia, Pennsylvania, United States of America.

ABSTRACT
Previous studies have shown that glucagon-like peptide-1 (GLP-1) provides cardiovascular benefits independent of its role on peripheral glycemic control. However, the precise mechanism(s) by which GLP-1 treatment renders cardioprotection during myocardial ischemia remain unresolved. Here we examined the role for GLP-1 treatment on glucose and fatty acid metabolism in normal and ischemic rat hearts following a 30 min ischemia and 24 h reperfusion injury, and in isolated cardiomyocytes (CM). Relative carbohydrate and fat oxidation levels were measured in both normal and ischemic hearts using a 1-13C glucose clamp coupled with NMR-based isotopomer analysis, as well as in adult rat CMs by monitoring pH and O2 consumption in the presence of glucose or palmitate. In normal heart, GLP-1 increased glucose uptake (↑64%, p<0.05) without affecting glycogen levels. In ischemic hearts, GLP-1 induced metabolic substrate switching by increasing the ratio of carbohydrate versus fat oxidation (↑14%, p<0.01) in the LV area not at risk, without affecting cAMP levels. Interestingly, no substrate switching occurred in the LV area at risk, despite an increase in cAMP (↑106%, p<0.05) and lactate (↑121%, p<0.01) levels. Furthermore, in isolated CMs GLP-1 treatment increased glucose utilization (↑14%, p<0.05) and decreased fatty acid oxidation (↓15%, p<0.05) consistent with in vivo finding. Our results show that this benefit may derive from distinct and complementary roles of GLP-1 treatment on metabolism in myocardial sub-regions in response to this injury. In particular, a switch to anaerobic glycolysis in the ischemic area provides a compensatory substrate switch to overcome the energetic deficit in this region in the face of reduced tissue oxygenation, whereas a switch to more energetically favorable carbohydrate oxidation in more highly oxygenated remote regions supports maintaining cardiac contractility in a complementary manner.

No MeSH data available.


Related in: MedlinePlus