Insulin‐stimulated glucose uptake partly relies on p21‐activated kinase (PAK)2, but not PAK1, in mouse skeletal muscle (original) (raw)
Related papers
Physiological Reports, 2020
Aim: Muscle contraction stimulates skeletal muscle glucose transport. Since it occurs independently of insulin, it is an important alternative pathway to increase glucose transport in insulin-resistant states, but the intracellular signaling mechanisms are not fully understood. Muscle contraction activates group I p21-activated kinases (PAKs) in mouse and human skeletal muscle. PAK1 and PAK2 are downstream targets of Rac1, which is a key regulator of contraction-stimulated glucose transport. Thus, PAK1 and PAK2 could be downstream effectors of Rac1 in contraction-stimulated glucose transport. The current study aimed to test the hypothesis that PAK1 and/or PAK2 regulate contraction-induced glucose transport. Methods: Glucose transport was measured in isolated soleus and extensor digitorum longus (EDL) mouse skeletal muscle incubated either in the presence or absence of a pharmacological inhibitor (IPA-3) of group I PAKs or originating from whole-body PAK1 knockout, muscle-specific PAK2 knockout or double whole-body PAK1 and muscle-specific PAK2 knockout mice. Results: IPA-3 attenuated (−22%) the increase in glucose transport in response to electrically stimulated contractions in soleus and EDL muscle. PAK1 was dispensable for contraction-stimulated glucose transport in both soleus and EDL muscle. Lack of PAK2, either alone (−13%) or in combination with PAK1 (−14%), partly reduced contraction-stimulated glucose transport compared to control littermates in EDL, but not soleus muscle. Conclusion: Contraction-stimulated glucose transport in isolated glycolytic mouse EDL muscle is partly dependent on PAK2, but not PAK1.
The role of p-21 activated kinases (PAKs) in glucose homeostasis and skeletal muscle glucose uptake
2019
Skeletal muscle glucose transport is essential for maintaining whole body glucose homeostasis and skeletal muscle accounts for the majority of glucose disposal in response to insulin. Glucose transport into skeletal muscle can be induced by several stimuli, such as insulin and muscle contraction, which all have been shown to activate group I p-21 activated kinases (PAKs). Skeletal muscle expresses two group I PAK isoforms but the role of these in muscle glucose uptake has not been determined. Recent evidence suggests that p-21 activated kinase (PAK) 1 may play a role in insulin-stimulated GLUT4 translocation and that PAK1/2 signaling is markedly impaired in insulin resistant skeletal muscle. To elucidate the role for group I PAKs in skeletal muscle glucose uptake, we determined glucose uptake in mature skeletal muscle from mice treated with a pharmacological inhibitor of group I PAKs, IPA-3, or knockout (KO) of either PAK1, PAK2, or joint KO of both PAK1 and PAK2 (d1/2KO). In contra...
Frontiers in Endocrinology, 2022
Skeletal muscle accounts for~80% of insulin-stimulated glucose uptake. The Group I p21-activated kinase 1 (PAK1) is required for the non-canonical insulin-stimulated GLUT4 vesicle translocation in skeletal muscle cells. We found that the abundances of PAK1 protein and its downstream effector in muscle, ARPC1B, are significantly reduced in the skeletal muscle of humans with type 2 diabetes, compared to the non-diabetic controls, making skeletal muscle PAK1 a candidate regulator of glucose homeostasis. Although whole-body PAK1 knockout mice exhibit glucose intolerance and are insulin resistant, the contribution of skeletal muscle PAK1 in particular was unknown. As such, we developed inducible skeletal muscle-specific PAK1 knockout (skmPAK1-iKO) and overexpression (skmPAK1-iOE) mouse models to evaluate the role of PAK1 in skeletal muscle insulin sensitivity and glucose homeostasis. Using intraperitoneal glucose tolerance and insulin tolerance testing, we found that skeletal muscle PAK1 is required for maintaining whole body glucose homeostasis. Moreover, PAK1 enrichment in GLUT4-myc-L6 myoblasts preserves normal insulin-stimulated GLUT4 translocation under insulin resistance conditions. Unexpectedly, skmPAK1-iKO also showed aberrant plasma insulin levels following a glucose challenge. By applying conditioned media from PAK1-enriched myotubes or myoblasts to b-cells in culture, we established that a muscle-derived circulating factor(s) could enhance b-cell function. Taken together, these data suggest that PAK1 levels in the skeletal muscle can regulate not only skeletal muscle insulin sensitivity, but can also engage in tissue crosstalk with pancreatic b-cells, unveiling a new molecular mechanism by which PAK1 regulates whole-body glucose homeostasis.
Mechanisms of Insulin-Resistant Glucose Utilization in Rat Skeletal Muscle
Mol Genet Metab, 1998
translocation in this model and suggest suppression Defects in glucose uptake are among the primary of GLUT 4 transporter activity. ᭧ 1998 Academic Press defects associated with peripheral insulin resis-Key Words: insulin resistance; hyperglycemia; hytance, but fundamental mechanisms leading to this perinsulinemia; glucose transport; glucose utilizastate are poorly understood. In order to elucidate tion; GLUT 4; translocation. mechanisms leading toward defects in glucose transport, we have used a partially pancreatectomized infusion (PxI) animal model with infusions of
Biochemical Journal, 2001
We previously reported that SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38 MAPK), attenuates insulin-stimulated glucose uptake without altering GLUT4 translocation. These results suggested that insulin might activate GLUT4 via a p38 MAPK-dependent pathway. Here we explore this hypothesis by temporal and kinetic analyses of the stimulation of GLUT4 translocation, glucose uptake and activation of p38 MAPK isoforms by insulin. In L6 myotubes stably expressing GLUT4 with an exofacial Myc epitope, we found that GLUT4 translocation (t "/# l 2.5 min) preceded the stimulation of 2deoxyglucose uptake (t "/# l 6 min). This segregation of glucose uptake from GLUT4 translocation became more apparent when the two parameters were measured at 22 mC. Preincubation with the p38 MAPK inhibitors SB202190 and SB203580 reduced insulin-stimulated transport of either 2-deoxyglucose or 3-Omethylglucose by 40-60 %. Pretreatment with SB203580 lowered the apparent transport V max of insulin-mediated 2-deoxyglucose and 3-O-methylglucose without any significant change in the
2020
AimMuscle contraction stimulates skeletal muscle glucose transport. Since it occurs independently of insulin, it is an important alternative pathway to increase glucose uptake in insulin-resistant states, but the intracellular signalling mechanisms are not fully understood. Muscle contraction activates group I p21-activated kinases (PAKs) in mouse and human skeletal muscle. PAK1 and PAK2 are downstream targets of Rac1, which is a key regulator of contraction-stimulated glucose transport. Thus, PAK1 and PAK2 could be downstream effectors of Rac1 in contraction-stimulated glucose transport. The current study aimed to test the hypothesis that PAK1 and/or PAK2 regulate contraction-induced glucose transport.MethodsGlucose transport was measured in isolated soleus and extensor digitorum longus (EDL) mouse skeletal muscle incubated either in the presence or absence of a pharmacological inhibitor (IPA-3) of group I PAKs or originating from whole-body PAK1 knockout (KO), muscle-specific PAK2...
Acta Physiologica Scandinavica, 2001
This review will provide insight on potential intracellular signalling mechanisms by which insulin and exercise/contraction increases glucose metabolism and gene expression. Glucose transport, the rate limiting step in glucose metabolism, is mediated by glucose transporter 4 (GLUT4) and can be activated in skeletal muscle by two separate and distinct signalling pathways; one stimulated by insulin and the second by muscle contractions. Impaired insulin action on whole body glucose uptake is a hallmark feature of type II (non-insulin-dependent) diabetes mellitus. Defects in insulin signal transduction through the insulin-receptor substrate-1/phosphatidylinositol 3-kinase pathway are associated with reduced insulin-stimulated glucose transporter 4 translocation and glucose transport activity in skeletal muscle from type II diabetic patients. Studies performed using glucose transporter 4-null mice show that this glucose transporter isoform plays a major role in mediating exercisestimulated glucose uptake in skeletal muscle. Level of physical exercise has been linked to improved glucose homeostasis and enhanced insulin sensitivity. Exercise training leads to alterations in expression and activity of key proteins involved in insulin signal transduction. These changes may be related to increased signal transduction through the mitogen-activated protein kinase (MAPK) signalling cascades. Because MAPK is associated with increased transcriptional activity, these signalling cascades are candidates for these exercise-induced changes in protein expression. Understanding the molecular mechanism for the activation of signal transduction pathways will provide a link for defining new strategies to enhance glucose metabolism and improve health in the general population.
Diabetes, 1995
GLUT4 translocation and activation of glucose uptake in skeletal muscle can be induced by both physiological (i.e., insulin, nerve stimulation, or exercise) and pharmacological (i.e., phorbol ester) means. Recently, we demonstrated that high glucose levels may mimic the effects of phorbol esters on protein kinase C (PKC) and insulin receptor function (JBiol Chem 269:3381^3386,1994). In this study, we tested whether the previously described effects of phorbol esters on translocation of GLUT4 in myotubes in culture and also in rat skeletal muscle might be mimicked by glucose. We found that stimulation of C 2 C 12 myotubes with both insulin (10~7 mol/1, 5 min) and glucose (25 mmol/1, 10 min) induces a comparable increase of the GLUT4 content in the plasma membrane. To test whether this effect occurs in intact rat skeletal muscle as weD, two different model systems were used. As an in vitro model, isolated rat hindlimbs were perfused for 80 min with medium containing 6 mmol/1 glucose ± insulin (1.6 X 10~9 mmol/1, 40 min) or 25 mmol/1 glucose. As an in vivo model, acute hyperglycemia (>11 mmol/1 glucose, 20 min) was induced in Wistar rats by intraperitoneal injection of glucose under simultaneous suppression of the endogenous insulin release by injection of somatostatin. In both models, subcellular fractions were prepared from hindlimb skeletal muscle, and plasma membranes were characterized by the enrichment of the marker enzyme ctl Na +-K +-ATPase. Acute hyperglycemia in vivo (n = 5) and in vitro (n = 6) induced an increase of GLUT4 content in the a l Na +-K +-ATPase-enriched fraction (in vivo, 2.45 ± 0.47-fold increase to basal [mean ± SE]; in vitro, 1.71 ± 0.14-fold increase to basal), which was quantitatively similar to that obtained after insulin treatment (in vivo, 2.35 ± 0.62-fold increase to basal; in vitro, 1.91 ± 0.21-fold increase to basal). Glucose-induced GLUT4 translocation in myotubes was prevented by prior addition of the PKC inhibitor l-(5-isoquinolinylsulfonyl)-2-methylpiperazine; in rat skeletal muscle,
AJP: Endocrinology and Metabolism, 2007
cemia is a defining feature of Type 1 and 2 diabetes. Hyperglycemia also causes insulin resistance, and our group (Kraegen EW, Saha AK, Preston E, Wilks D, Hoy AJ, Cooney GJ, Ruderman NB. Am J Physiol Endocrinol Metab Endocrinol Metab 290: E471-E479, 2006) has recently demonstrated that hyperglycemia generated by glucose infusion results in insulin resistance after 5 h but not after 3 h. The aim of this study was to investigate possible mechanism(s) by which glucose infusion causes insulin resistance in skeletal muscle and in particular to examine whether this was associated with changes in insulin signaling. Hyperglycemia (ϳ10 mM) was produced in cannulated male Wistar rats for up to 5 h. The glucose infusion rate required to maintain this hyperglycemia progressively lessened over 5 h (by 25%, P Ͻ 0.0001 at 5 h) without any alteration in plasma insulin levels consistent with the development of insulin resistance. Muscle glucose uptake in vivo (44%; P Ͻ 0.05) and glycogen synthesis rate (52%; P Ͻ 0.001) were reduced after 5 h compared with after 3 h of infusion. Despite these changes, there was no decrease in the phosphorylation state of multiple insulin signaling intermediates [insulin receptor, Akt, AS160 (Akt substrate of 160 kDa), glycogen synthase kinase-3] over the same time course. In isolated soleus strips taken from control or 1-or 5-h glucose-infused animals, insulin-stimulated 2-deoxyglucose transport was similar, but glycogen synthesis was significantly reduced in the 5-h muscle sample (68% vs. 1-h sample; P Ͻ 0.001). These results suggest that the reduced muscle glucose uptake in rats after 5 h of acute hyperglycemia is due more to the metabolic effects of excess glycogen storage than to a defect in insulin signaling or glucose transport. glucotoxicity; glycogen; hyperglycemia; in vivo metabolism; soleus muscle