Chronic low-frequency stimulation upregulates uncoupling protein-3 in transforming rat fast-twitch skeletal muscle

Putman, Charles T.; Dixon, Walter T.; Pearcey, J.; MacLean, Ian M.; Jendral, M.J.; Kiricsi, Mónika; Murdoch, Gordon K.; Pette, Dirk

doi:10.1152/ajpregu.00421.2004

Cited by 24 publications

(35 citation statements)

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“…Tibialis anterior muscles that were exposed to CLFS as part of another related study (54) were examined in the present study to investigate the short-and long-term effects of forced contractile activity on the adaptive capacity of AMPK. Briefly, under general anesthesia, electrodes were subcutaneously implanted bilaterally to the left common peroneal nerve, externalized dorsally within the intrascapular region, and connected to a small, portable stimulator.…”

Section: Animalsmentioning

confidence: 99%

“…Muscles were exposed to CLFS for short [i.e., 4 Ϯ 1.2 days (n ϭ 5)] or long [i.e., 25 Ϯ 4.8 days (n ϭ 7)] time periods. Muscles were collected during a postexercise period, in which the acute effects of contractile activity are no longer detectable but the chronic adaptive responses are known to prevail (33,54,67). The unstimulated contralateral tibialis anterior muscles served as paired controls.…”

Section: Animalsmentioning

confidence: 99%

“…MHCIId/x was identified as those fibers that remained unstained by this panel of antibodies and was validated by comparison of the staining pattern with monoclonal antibody BF-35, which stains all MHC isoforms, except IID/X (63). MHC isoform contents of the white and red gastrocnemius and the soleus muscles were quantitatively evaluated by SDS-PAGE as previously described by us (21,39,54,58).…”

Section: Animalsmentioning

confidence: 99%

“…Western blot analyses were completed according to our previously reported procedures (54,58). Purified ␣1-or ␣2-recombinant AMPK proteins, and tissue homogenates were denatured in reducing sample buffer and heated for 5 min at 95°C; 5 l of purified recombinant protein or 87 g of total tissue protein were loaded per lane.…”

Section: Animalsmentioning

confidence: 99%

“…A secondary objective was to investigate the effect of enhanced contractile activity on the protein expression levels of the ␣1 and ␣2 catalytic subunits in previously studied rat fast-twitch tibialis anterior muscles known to undergo fast-to-slow fiber type transitions (54). It was hypothesized that expression levels of the ␣1 and ␣2 isoforms would differ between fiber types.…”

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confidence: 99%

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α-Catalytic subunits of 5′AMP-activated protein kinase display fiber-specific expression and are upregulated by chronic low-frequency stimulation in rat muscle

Putman

Martins²,

Gallo³

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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activated protein kinase (AMPK) signaling initiates adaptive changes in skeletal muscle fibers that restore homeostatic energy balance. The purpose of this investigation was to examine, in rats, the fiber-type protein expression patterns of the ␣-catalytic subunit isoforms in various skeletal muscles, and changes in their respective contents within the tibialis anterior (TA) after chronic low-frequency electrical stimulation (CLFS; 10 Hz, 10 h daily), applied for 4 Ϯ 1.2 or 25 Ϯ 4.8 days. Immunocytochemical staining of soleus (SOL) and medial gastrocnemius (MG) showed that 86 Ϯ 4.1 to 97 Ϯ 1.4% of type IIA fibers stained for both the ␣1-and ␣2-isoforms progressively decreased to 63 Ϯ 12.2% of type IID/X and 9 Ϯ 2.4% of IIB fibers. 39 Ϯ 11.4% of IID/X and 83 Ϯ 7.9% of IIB fibers expressed only the ␣2 isoform in the MG, much of which was localized within nuclei. ␣1 and ␣2 contents, assessed by immunoblot, were lowest in the white gastrocnemius [WG; 80% myosin heavy chain (MHC) IIb; 20% MHCIId/x]. Compared with the WG, ␣1 content was 1.6 Ϯ 0.08 (P Ͻ 0.001) and 1.8 Ϯ 0.04 (P Ͻ 0.0001)-fold greater in the red gastrocnemius (RG: 13%, MHCIIa) and SOL (21%, MHCIIa), respectively, and increased in proportion to MHCIIa content. Similarly, ␣2 content was 1.4 Ϯ 0.10 (P Ͻ 0.02) and 1.5 Ϯ 0.07 (P Ͻ 0.001)-fold greater in RG and SOL compared with WG. CLFS induced 1.43 Ϯ 0.13 (P Ͻ 0.007) and 1.33 Ϯ 0.08 (P Ͻ 0.009)-fold increases in the ␣1 and ␣2 contents of the TA and coincided with the transition of faster type IIB and IID/X fibers toward IIA fibers. These findings indicate that fiber types differ with regard to their capacity for AMPK signaling and that this potential is increased by CLFS. myosin heavy chain; fast-twitch muscle; slow-twitch muscle 5Ј-AMP-ACTIVATED PROTEIN KINASE (AMPK) is a heterotrimeric serine/threonine kinase comprising an ␣ catalytic subunit (␣1 or ␣2), and noncatalytic ␤ (␤1 or ␤2) and ␥ (␥1, ␥2, or ␥3) subunits (12,41). This enzyme complex is the central component of a signaling cascade in skeletal muscle that serves as an intracellular energy-sensor by detecting decreases in the intracellular energy potential (i.e., ATP/ADP free ) through related increases in AMP (11,13,26). Being highly sensitive to small reductions in ATP and corresponding increases in AMP (25), AMPK is activated in skeletal muscle during contractile activity (32, 68, 69) to acutely restore energy balance by increasing flux through ATP-generating pathways (24, 25).In contrast, chronic AMPK activation induced by pharmacological agonists (3, 29, 58, 71) regulates long-term adaptive changes similar to exercise training that seem to limit future reductions in the intracellular energy potential and reportedly reduce metabolic disturbances in rats displaying skeletal muscle insulin resistance (9,52,70). Prolonged AMPK activation has, for example, been associated with mitochondrial genesis (3,58,71,74) and greater expression levels of genes involved in glucose uptake and storage (3, 9, 29), as well as lower plasma free fatty acid and trigl...

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Section: Animalsmentioning

confidence: 99%

Section: Animalsmentioning

confidence: 99%