TY - JOUR

T1 - Denervation and high-fat diet reduce insulin signaling in T-tubules in skeletal muscle of living mice

AU - Lauritzen, Hans P M

AU - Ploug, Thorkil

AU - Ai, Hua

AU - Donsmark, Morten

AU - Prats Gavalda, Clara

AU - Galbo, Henrik

PY - 2008/1

Y1 - 2008/1

N2 - OBJECTIVE: Insulin stimulates muscle glucose transport by translocation of GLUT4 to sarcolemma and T-tubules. Despite muscle glucose uptake playing a major role in insulin resistance and type 2 diabetes, the temporal and spatial changes in insulin signaling and GLUT4 translocation during these conditions are not well described.RESEARCH DESIGN AND METHODS: We used time-lapse confocal imaging of green fluorescent protein (GFP) ADP-ribosylation factor nucleotide-binding site opener (ARNO) (evaluation of phosphatidylinositide 3-kinase activation) and GLUT4-GFP-transfected quadriceps muscle in living, anesthetized mice either muscle denervated or high-fat fed. T-tubules were visualized with sulforhodamine B dye. In incubated muscle, glucose transport was measured by 2-deoxy-D-[(3)H]-glucose uptake, and functional detubulation was carried out by osmotic shock. Muscle fibers were immunostained for insulin receptors.RESULTS: Denervation and high-fat diet reduced insulin-mediated glucose transport. In denervated muscle, insulin-stimulated phosphatidylinositol 3,4,5 P(3) (PIP3) production was abolished in T-tubules, while PIP3 production at sarcolemma was increased 2.6-fold. Correspondingly, GLUT4-GFP translocation to T-tubules was abolished, while translocation to sarcolemma was increased 2.3-fold. In high fat-fed mice, a approximately 65% reduction in both insulin-induced T-tubular PIP3 production and GLUT4-GFP translocation was seen. Sarcolemma was less affected, with reductions of approximately 40% in PIP3 production and approximately 15% in GLUT4-GFP translocation. Access to T-tubules was not compromised, and insulin receptor distribution in sarcolemma and T-tubules was unaffected by denervation or high-fat feeding. Detubulation of normal muscle reduced basal and abolished insulin-induced glucose transport.CONCLUSIONS: Our findings demonstrate, for the first time, that impaired insulin signaling and GLUT4 translocation is compartmentalized in muscle and primarily localized to T-tubules and not sarcolemma during insulin resistance.

AB - OBJECTIVE: Insulin stimulates muscle glucose transport by translocation of GLUT4 to sarcolemma and T-tubules. Despite muscle glucose uptake playing a major role in insulin resistance and type 2 diabetes, the temporal and spatial changes in insulin signaling and GLUT4 translocation during these conditions are not well described.RESEARCH DESIGN AND METHODS: We used time-lapse confocal imaging of green fluorescent protein (GFP) ADP-ribosylation factor nucleotide-binding site opener (ARNO) (evaluation of phosphatidylinositide 3-kinase activation) and GLUT4-GFP-transfected quadriceps muscle in living, anesthetized mice either muscle denervated or high-fat fed. T-tubules were visualized with sulforhodamine B dye. In incubated muscle, glucose transport was measured by 2-deoxy-D-[(3)H]-glucose uptake, and functional detubulation was carried out by osmotic shock. Muscle fibers were immunostained for insulin receptors.RESULTS: Denervation and high-fat diet reduced insulin-mediated glucose transport. In denervated muscle, insulin-stimulated phosphatidylinositol 3,4,5 P(3) (PIP3) production was abolished in T-tubules, while PIP3 production at sarcolemma was increased 2.6-fold. Correspondingly, GLUT4-GFP translocation to T-tubules was abolished, while translocation to sarcolemma was increased 2.3-fold. In high fat-fed mice, a approximately 65% reduction in both insulin-induced T-tubular PIP3 production and GLUT4-GFP translocation was seen. Sarcolemma was less affected, with reductions of approximately 40% in PIP3 production and approximately 15% in GLUT4-GFP translocation. Access to T-tubules was not compromised, and insulin receptor distribution in sarcolemma and T-tubules was unaffected by denervation or high-fat feeding. Detubulation of normal muscle reduced basal and abolished insulin-induced glucose transport.CONCLUSIONS: Our findings demonstrate, for the first time, that impaired insulin signaling and GLUT4 translocation is compartmentalized in muscle and primarily localized to T-tubules and not sarcolemma during insulin resistance.

KW - Animals

KW - Dietary Fats

KW - Femoral Nerve

KW - Glucose Transporter Type 4

KW - Green Fluorescent Proteins

KW - Insulin

KW - Male

KW - Mice

KW - Microtubules

KW - Muscle Denervation

KW - Muscle, Skeletal

KW - Sciatic Nerve

KW - Signal Transduction

KW - Transfection

U2 - 10.2337/db07-0516

DO - 10.2337/db07-0516

M3 - Journal article

C2 - 17914033

VL - 57

SP - 13

EP - 23

JO - Diabetes

JF - Diabetes

SN - 0901-3652

IS - 1

ER -