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Abnormalities of AMPK activation and glucose uptake in cultured skeletal muscle cells from individuals with chronic fatigue syndrome.

Brown AE, Jones DE, Walker M, Newton JL - PLoS ONE (2015)

Bottom Line: Control cultures subjected to 16 h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells.IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured.We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Medicine, William Leech Building, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.

ABSTRACT

Background: Post exertional muscle fatigue is a key feature in Chronic Fatigue Syndrome (CFS). Abnormalities of skeletal muscle function have been identified in some but not all patients with CFS. To try to limit potential confounders that might contribute to this clinical heterogeneity, we developed a novel in vitro system that allows comparison of AMP kinase (AMPK) activation and metabolic responses to exercise in cultured skeletal muscle cells from CFS patients and control subjects.

Methods: Skeletal muscle cell cultures were established from 10 subjects with CFS and 7 age-matched controls, subjected to electrical pulse stimulation (EPS) for up to 24h and examined for changes associated with exercise.

Results: In the basal state, CFS cultures showed increased myogenin expression but decreased IL6 secretion during differentiation compared with control cultures. Control cultures subjected to 16 h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells. In contrast, CFS cultures showed no increase in AMPK phosphorylation or glucose uptake after 16 h EPS. However, glucose uptake remained responsive to insulin in the CFS cells pointing to an exercise-related defect. IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured.

Conclusion: EPS is an effective model for eliciting muscle contraction and the metabolic changes associated with exercise in cultured skeletal muscle cells. We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6. The retention of these differences in cultured muscle cells from CFS subjects points to a genetic/epigenetic mechanism, and provides a system to identify novel therapeutic targets.

No MeSH data available.


Related in: MedlinePlus

Measurement of glucose uptake in control and CFS cultures.Glucose uptake was measured in control (A) and CFS (B) cell cultures. Cells from 5 control and 9 CFS cell cultures were subjected to EPS for 16h before rate of glucose uptake was measured. Open bar: basal, closed bar: insulin stimulated. Results are expressed as mean±SEM. *p<0.05, **p<0.005, ***p<0.0005, ****p<0.0001.
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pone.0122982.g003: Measurement of glucose uptake in control and CFS cultures.Glucose uptake was measured in control (A) and CFS (B) cell cultures. Cells from 5 control and 9 CFS cell cultures were subjected to EPS for 16h before rate of glucose uptake was measured. Open bar: basal, closed bar: insulin stimulated. Results are expressed as mean±SEM. *p<0.05, **p<0.005, ***p<0.0005, ****p<0.0001.

Mentions: Contraction increases the uptake of glucose into the muscle cell in an insulin-independent manner therefore, the effect of the EPS protocol on glucose metabolism was examined by measuring uptake of 2-deoxyglucose into the cells in the absence and presence of insulin. In control cells, Fig 3A shows that under non-EPS conditions insulin-stimulated glucose uptake was increased 1.3-fold over basal (447.1±25.3pmol/min/mg vs 333.5±20.2pmol/min/mg, p<0.0005). After 16h EPS, glucose uptake increased to 550.4±35.9pmol/min/mg (p<0.0001 vs basal) while insulin produced an additive effect in combination with EPS, increasing glucose uptake to 746.1±70.9pmol/min/mg (p<0.005 vs insulin alone). Fig 3B shows that under both non-EPS and EPS conditions, the CFS group cultures significantly increased insulin-stimulated glucose uptake (both p<0.0005). However, 16h EPS did not increase glucose uptake in the absence or presence of insulin indicating that the CFS cultures were unable to increase the rate of glucose uptake in response to exercise. This is consistent with the absence of activation of AMPK. Both basal and insulin stimulated glucose uptake were significantly increased in CFS compared to control (p = 0.001 and p<0.05, respectively). However, this does not alter the finding that CFS was unable to increase glucose uptake in response to EPS since an increase in glucose uptake was observed only in the presence of insulin indicating that the cells are not maximally stimulated in the basal state.


Abnormalities of AMPK activation and glucose uptake in cultured skeletal muscle cells from individuals with chronic fatigue syndrome.

Brown AE, Jones DE, Walker M, Newton JL - PLoS ONE (2015)

Measurement of glucose uptake in control and CFS cultures.Glucose uptake was measured in control (A) and CFS (B) cell cultures. Cells from 5 control and 9 CFS cell cultures were subjected to EPS for 16h before rate of glucose uptake was measured. Open bar: basal, closed bar: insulin stimulated. Results are expressed as mean±SEM. *p<0.05, **p<0.005, ***p<0.0005, ****p<0.0001.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383615&req=5

pone.0122982.g003: Measurement of glucose uptake in control and CFS cultures.Glucose uptake was measured in control (A) and CFS (B) cell cultures. Cells from 5 control and 9 CFS cell cultures were subjected to EPS for 16h before rate of glucose uptake was measured. Open bar: basal, closed bar: insulin stimulated. Results are expressed as mean±SEM. *p<0.05, **p<0.005, ***p<0.0005, ****p<0.0001.
Mentions: Contraction increases the uptake of glucose into the muscle cell in an insulin-independent manner therefore, the effect of the EPS protocol on glucose metabolism was examined by measuring uptake of 2-deoxyglucose into the cells in the absence and presence of insulin. In control cells, Fig 3A shows that under non-EPS conditions insulin-stimulated glucose uptake was increased 1.3-fold over basal (447.1±25.3pmol/min/mg vs 333.5±20.2pmol/min/mg, p<0.0005). After 16h EPS, glucose uptake increased to 550.4±35.9pmol/min/mg (p<0.0001 vs basal) while insulin produced an additive effect in combination with EPS, increasing glucose uptake to 746.1±70.9pmol/min/mg (p<0.005 vs insulin alone). Fig 3B shows that under both non-EPS and EPS conditions, the CFS group cultures significantly increased insulin-stimulated glucose uptake (both p<0.0005). However, 16h EPS did not increase glucose uptake in the absence or presence of insulin indicating that the CFS cultures were unable to increase the rate of glucose uptake in response to exercise. This is consistent with the absence of activation of AMPK. Both basal and insulin stimulated glucose uptake were significantly increased in CFS compared to control (p = 0.001 and p<0.05, respectively). However, this does not alter the finding that CFS was unable to increase glucose uptake in response to EPS since an increase in glucose uptake was observed only in the presence of insulin indicating that the cells are not maximally stimulated in the basal state.

Bottom Line: Control cultures subjected to 16 h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells.IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured.We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Medicine, William Leech Building, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.

ABSTRACT

Background: Post exertional muscle fatigue is a key feature in Chronic Fatigue Syndrome (CFS). Abnormalities of skeletal muscle function have been identified in some but not all patients with CFS. To try to limit potential confounders that might contribute to this clinical heterogeneity, we developed a novel in vitro system that allows comparison of AMP kinase (AMPK) activation and metabolic responses to exercise in cultured skeletal muscle cells from CFS patients and control subjects.

Methods: Skeletal muscle cell cultures were established from 10 subjects with CFS and 7 age-matched controls, subjected to electrical pulse stimulation (EPS) for up to 24h and examined for changes associated with exercise.

Results: In the basal state, CFS cultures showed increased myogenin expression but decreased IL6 secretion during differentiation compared with control cultures. Control cultures subjected to 16 h EPS showed a significant increase in both AMPK phosphorylation and glucose uptake compared with unstimulated cells. In contrast, CFS cultures showed no increase in AMPK phosphorylation or glucose uptake after 16 h EPS. However, glucose uptake remained responsive to insulin in the CFS cells pointing to an exercise-related defect. IL6 secretion in response to EPS was significantly reduced in CFS compared with control cultures at all time points measured.

Conclusion: EPS is an effective model for eliciting muscle contraction and the metabolic changes associated with exercise in cultured skeletal muscle cells. We found four main differences in cultured skeletal muscle cells from subjects with CFS; increased myogenin expression in the basal state, impaired activation of AMPK, impaired stimulation of glucose uptake and diminished release of IL6. The retention of these differences in cultured muscle cells from CFS subjects points to a genetic/epigenetic mechanism, and provides a system to identify novel therapeutic targets.

No MeSH data available.


Related in: MedlinePlus