Post-operative effects on insulin resistance and specific tension of single human skeletal muscle fibres

Abstract

Surgery and accidental trauma are associated with a transient period of insulin resistance, substrate catabolism and muscle weakness. In the present study, we evaluated the changes in the force-generating capacity of chemically skinned single muscle fibres following abdominal surgery. Biopsies of the m. vastus lateralis were obtained in three patients 1 day before and 3 or 6 days after surgery. Part of the biopsy was frozen for histochemical analysis of the fibre cross-sectional area (FCSA) and myofibrillar protein content, and another part was used for single-fibre contractile measurements. All patients developed insulin resistance following surgery. The maximum velocity of unloaded shortening of single muscle fibres did not change following surgery. The FCSA did not decrease after surgery, as determined either from histochemical sections or from single fibres measured at a fixed sarcomere length of 2.76+/-0.09 microm (mean+/-S.D.). Further, the force-generating capacity of the single fibres, measured as maximal Ca(2+)-activated force (P(0)) or as P(0) normalized to FCSA (specific tension), remained unchanged, as did the myofibrillar protein content of the muscle. In conclusion, the muscle weakness associated with post-operative insulin resistance is not related to a decreased specific tension or a loss of myofibrillar proteins. Other potential cellular mechanisms underlying post-operative weakness are discussed.

Neuromuscular Electrical Stimulation Reduces Skeletal Muscle Protein Degradation and Stimulates Insulin-Like Growth Factors in an Age- and Current-Dependent Manner

“…This suggestion is supported by publications revealing no significant enhancement in muscle myofibrillar protein breakdown in rats 24 hours after laparotomy 30 and no significant change in human myofibrillar protein content until the 6th postoperative day after major abdominal surgery. 31 Moreover, it has to be mentioned that the sarcoplasma contains mainly soluble proteins, whereas myofilaments are highly conserved protein complexes. While the ubiquitin-proteasome system easily degrades soluble proteins, it does not degrade intact Proteins were subjected to gradient 4% to15% SDS-PAGE, transferred to a nitrocellulose membrane and stained with Ruthenium Red to evaluate whole protein content of each sample.…”

Noninvasive Estimation of Myosin Heavy Chain Composition in Human Skeletal Muscle

“…The %MHC was detennined as described previously (13). In a cryostat, 10-/Lim cross-sections were collected in a centrifiige tube and dissolved in a sample buffer (three sections in 100 ixL) and boiled for 2 min to denature the proteins.…”

Changes in contractile properties of skinned single rat soleus and diaphragm fibres after chronic hypoxia

“…The sarcomere length was set at 2.6 μm at the start of the experiment and was checked at regular intervals thereafter. Fibre diameter was measured at three places while suspended in the air and cross-sectional areas calculated assuming the fibre to have a circular crosssection [11,13]. No correction was made for the swelling of the fibres during skinning.…”