Skeletal muscle glucose metabolism in obesity-prone and obesity-resistant rats

1993 ◽  
Vol 264 (6) ◽  
pp. R1224-R1228 ◽  
Author(s):  
M. J. Pagliassotti ◽  
K. A. Shahrokhi ◽  
J. O. Hill

Ad libitum access to a high-fat (HF) diet produces a wide range of weight gain in rats. Rats most susceptible to weight gain on such a diet (obesity prone; OP) are more insulin resistant after 4-5 wk of diet exposure than are those most resistant (obesity resistant; OR) to weight gain. To investigate whether skeletal muscle glucose metabolism contributes to insulin resistance in this model, insulin-stimulated glucose metabolism was assessed in the perfused hindquarter of rats exposed to either a low-fat (LF, n = 6) or HF diet for 5 wk. Delineation of OP (n = 6) and OR (n = 6) rats was based on body weight gain. OP rats gained 60% more body weight while eating only 10% more energy than OR rats. Single-pass perfusions were carried out for 2 h in the presence of glucose, insulin, and [U-14C]glucose. Insulin-stimulated glucose uptake (mumol.100 g-1.min-1) was 14.2 +/- 0.9 in LF, 11.1 +/- 0.8 in OR, and 6.2 +/- 0.6 in OP. Glucose oxidation (mumol.100 g-1.min-1) was 1.7 +/- 0.3 and 1.2 +/- 0.3 in LF and OR, respectively, but was 0.2 +/- 0.1 in OP. Net glycogen synthesis was significantly reduced in OP compared with OR and LF despite similar glycogen synthase I activity. Muscle triglyceride concentration was not significantly different in OR and OP rats. These results demonstrate significant defects in skeletal muscle glucose uptake and disposal in rats most susceptible to HF diet-induced obesity. Clearly, the heterogeneous response to a HF diet involves not only body weight gain but also skeletal muscle fuel metabolism.

1997 ◽  
Vol 273 (3) ◽  
pp. E514 ◽  
Author(s):  
C Fürnsinn ◽  
C Noe ◽  
R Herdlicka ◽  
M Roden ◽  
P Nowotny ◽  
...  

Lithium's impact on glucose metabolism was compared with that of insulin in isolated rat soleus muscle. Lithium chloride (20 mmol/l) induced a 4.8-fold more pronounced increment over basal glycogen synthase activity than insulin (10 nmol/l) (nmol UDP-glucose into glycogen in synthase activity assay.g-1.min-1: lithium, +22.1 +/- 1.8 vs. insulin, +4.6 +/- 3.9; P < 0.01). In parallel, lithium was less efficient than insulin in stimulating glucose transport (counts per minute 2-deoxy-D-[3H]glucose.mg-1.h-1: lithium, +211 +/- 19 vs. insulin, +311 +/- 57; P < 0.05) and lactate release (mumol.g-1.h-1: lithium, +1.0 +/- 0.5 vs. insulin, +3.9 +/- 0.5; P < 0.01), and similar increments were induced in glycogen synthesis (mumol glucose into glycogen.g-1.h-1: lithium, +3.32 +/- 0.43 vs. insulin, +3.46 +/- 0.47; not significant). Full additivity of glycogenic effects and divergent dependency on phosphatidylinositol 3-kinase activation provided further evidence for different mechanisms of action. In muscle from insulin-resistant obese Zucker rats (fa/fa), failure of lithium to reverse deficits in glucose metabolism suggested a primary deficit in muscle glucose uptake rather than glycogen synthesis. Hence lithium distinctly stimulates glycogen synthase activity in skeletal muscle and may therefore be regarded as a candidate for the treatment of disorders associated with primary deficits in the glycogenic pathway.


2008 ◽  
Vol 294 (1) ◽  
pp. E28-E35 ◽  
Author(s):  
Michale Bouskila ◽  
Michael F. Hirshman ◽  
Jørgen Jensen ◽  
Laurie J. Goodyear ◽  
Kei Sakamoto

Insulin promotes dephosphorylation and activation of glycogen synthase (GS) by inactivating glycogen synthase kinase (GSK) 3 through phosphorylation. Insulin also promotes glucose uptake and glucose 6-phosphate (G-6- P) production, which allosterically activates GS. The relative importance of these two regulatory mechanisms in the activation of GS in vivo is unknown. The aim of this study was to investigate if dephosphorylation of GS mediated via GSK3 is required for normal glycogen synthesis in skeletal muscle with insulin. We employed GSK3 knockin mice in which wild-type GSK3α and -β genes are replaced with mutant forms (GSK3α/βS21A/S21A/S9A/S9A), which are nonresponsive to insulin. Although insulin failed to promote dephosphorylation and activation of GS in GSK3α/βS21A/S21A/S9A/S9Amice, glycogen content in different muscles from these mice was similar compared with wild-type mice. Basal and epinephrine-stimulated activity of muscle glycogen phosphorylase was comparable between wild-type and GSK3 knockin mice. Incubation of isolated soleus muscle in Krebs buffer containing 5.5 mM glucose in the presence or absence of insulin revealed that the levels of G-6- P, the rate of [14C]glucose incorporation into glycogen, and an increase in total glycogen content were similar between wild-type and GSK3 knockin mice. Injection of glucose containing 2-deoxy-[3H]glucose and [14C]glucose also resulted in similar rates of muscle glucose uptake and glycogen synthesis in vivo between wild-type and GSK3 knockin mice. These results suggest that insulin-mediated inhibition of GSK3 is not a rate-limiting step in muscle glycogen synthesis in mice. This suggests that allosteric regulation of GS by G-6- P may play a key role in insulin-stimulated muscle glycogen synthesis in vivo.


2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Weidong Xu ◽  
Jiayao Li ◽  
Weipeng Qi ◽  
Ye Peng

Apigenin-8-C-glucoside (vitexin), a natural phytochemical contained in hawthorn, has been reported to have versatile beneficial bioactivities, such as antioxidation, anticancer property, and adipogenesis inhibition. The present research aimed to determine the influence of vitexin on insulin resistance elicited by HFD in mice and HepG2 cells. Vitexin markedly alleviated body weight gain and improved glucose and insulin intolerance induced by HFD. Vitexin partially normalized blood glucose, cholesterol, TNF-α, and hepatic lipid content. Moreover, vitexin recovered the reduced glucose uptake induced by glucosamine. The present results indicate that vitexin prevents HFD-induced insulin resistance.


1997 ◽  
Vol 272 (2) ◽  
pp. E288-E296 ◽  
Author(s):  
J. K. Kim ◽  
J. H. Youn

To determine whether an impairment of intracellular glucose metabolism causes insulin resistance, we examined the effects of suppression of glycolysis or glycogen synthesis on whole body and skeletal muscle insulin-stimulated glucose uptake during 450-min hyperinsulinemic euglycemic clamps in conscious rats. After the initial 150 min to attain steady-state insulin action, animals received an additional infusion of saline, Intralipid and heparin (to suppress glycolysis), or amylin (to suppress glycogen synthesis) for up to 300 min. Insulin-stimulated whole body glucose fluxes were constant with saline infusion (n = 7). In contrast, Intralipid infusion (n = 7) suppressed glycolysis by approximately 32%, and amylin infusion (n = 7) suppressed glycogen synthesis by approximately 45% within 30 min after the start of the infusions (P < 0.05). The suppression of metabolic fluxes increased muscle glucose 6-phosphate levels (P < 0.05), but this did not immediately affect insulin-stimulated glucose uptake due to compensatory increases in other metabolic fluxes. Insulin-stimulated whole body glucose uptake started to decrease at approximately 60 min and was significantly decreased by approximately 30% at the end of clamps (P < 0.05). Similar patterns of changes in insulin-stimulated glucose fluxes were observed in individual skeletal muscles. Thus the suppression of intracellular glucose metabolism caused decreases in insulin-stimulated glucose uptake through a cellular adaptive mechanism in response to a prolonged elevation of glucose 6-phosphate rather than the classic mechanism involving glucose 6-phosphate inhibition of hexokinase.


2015 ◽  
Vol 308 (4) ◽  
pp. E315-E323 ◽  
Author(s):  
Kana Ohyama ◽  
Yoshihito Nogusa ◽  
Katsuya Suzuki ◽  
Kosaku Shinoda ◽  
Shingo Kajimura ◽  
...  

Exercise effectively prevents the development of obesity and obesity-related diseases such as type 2 diabetes. Capsinoids (CSNs) are capsaicin analogs found in a nonpungent pepper that increase whole body energy expenditure. Although both exercise and CSNs have antiobesity functions, the effectiveness of exercise with CSN supplementation has not yet been investigated. Here, we examined whether the beneficial effects of exercise could be further enhanced by CSN supplementation in mice. Mice were randomly assigned to four groups: 1) high-fat diet (HFD, Control), 2) HFD containing 0.3% CSNs, 3) HFD with voluntary running wheel exercise (Exercise), and 4) HFD containing 0.3% CSNs with voluntary running wheel exercise (Exercise + CSN). After 8 wk of ingestion, blood and tissues were collected and analyzed. Although CSNs significantly suppressed body weight gain under the HFD, CSN supplementation with exercise additively decreased body weight gain and fat accumulation and increased whole body energy expenditure compared with exercise alone. Exercise together with CSN supplementation robustly improved metabolic profiles, including the plasma cholesterol level. Furthermore, this combination significantly prevented diet-induced liver steatosis and decreased the size of adipocyte cells in white adipose tissue. Exercise and CSNs significantly increased cAMP levels and PKA activity in brown adipose tissue (BAT), indicating an increase of lipolysis. Moreover, they significantly activated both the oxidative phosphorylation gene program and fatty acid oxidation in skeletal muscle. These results indicate that CSNs efficiently promote the antiobesity effect of exercise, in part by increasing energy expenditure via the activation of fat oxidation in skeletal muscle and lipolysis in BAT.


2007 ◽  
Vol 293 (5) ◽  
pp. E1358-E1364 ◽  
Author(s):  
Andrew J. Hoy ◽  
Clinton R. Bruce ◽  
Anna Cederberg ◽  
Nigel Turner ◽  
David E. James ◽  
...  

Hyperglycemia 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 (∼10 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 < 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 < 0.05) and glycogen synthesis rate (52%; P < 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-3β] 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 < 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.


Endocrinology ◽  
2015 ◽  
Vol 156 (11) ◽  
pp. 4047-4058 ◽  
Author(s):  
Yun-Jung Lee ◽  
Conglin Liu ◽  
Mengyang Liao ◽  
Galina K. Sukhova ◽  
Jun Shirakawa ◽  
...  

Prior studies demonstrated increased plasma IgE in diabetic patients, but the direct participation of IgE in diabetes or obesity remains unknown. This study found that plasma IgE levels correlated inversely with body weight, body mass index, and body fat mass among a population of randomly selected obese women. IgE receptor FcϵR1-deficient (Fcer1a−/−) mice and diet-induced obesity (DIO) mice demonstrated that FcϵR1 deficiency in DIO mice increased food intake, reduced energy expenditure, and increased body weight gain but improved glucose tolerance and glucose-induced insulin secretion. White adipose tissue from Fcer1a−/− mice showed an increased expression of phospho-AKT, CCAAT/enhancer binding protein-α, peroxisome proliferator-activated receptor-γ, glucose transporter-4 (Glut4), and B-cell lymphoma 2 (Bcl2) but reduced uncoupling protein 1 (UCP1) and phosphorylated c-Jun N-terminal kinase (JNK) expression, tissue macrophage accumulation, and apoptosis, suggesting that IgE reduces adipogenesis and glucose uptake but induces energy expenditure, adipocyte apoptosis, and white adipose tissue inflammation. In 3T3-L1 cells, IgE inhibited the expression of CCAAT/enhancer binding protein-α and peroxisome proliferator-activated receptor-γ, and preadipocyte adipogenesis and induced adipocyte apoptosis. IgE reduced the 3T3-L1 cell expression of Glut4, phospho-AKT, and glucose uptake, which concurred with improved glucose tolerance in Fcer1a−/− mice. This study established two novel pathways of IgE in reducing body weight gain in DIO mice by suppressing adipogenesis and inducing adipocyte apoptosis while worsening glucose tolerance by reducing Glut4 expression, glucose uptake, and insulin secretion.


2002 ◽  
Vol 173 (3) ◽  
pp. 465-473 ◽  
Author(s):  
MA Luque ◽  
N Gonzalez ◽  
L Marquez ◽  
A Acitores ◽  
A Redondo ◽  
...  

Glucagon-like peptide-1 (GLP-1) has been shown to have insulin-like effects upon the metabolism of glucose in rat liver, muscle and fat, and on that of lipids in rat and human adipocytes. These actions seem to be exerted through specific receptors which, unlike that of the pancreas, are not - at least in liver and muscle - cAMP-associated. Here we have investigated the effect, its characteristics, and possible second messengers of GLP-1 on the glucose metabolism of human skeletal muscle, in tissue strips and primary cultured myocytes. In muscle strips, GLP-1, like insulin, stimulated glycogen synthesis, glycogen synthase a activity, and glucose oxidation and utilization, and inhibited glycogen phosphorylase a activity, all of this at physiological concentrations of the peptide. In cultured myotubes, GLP-1 exerted, from 10(-13) mol/l, a dose-related increase of the D-[U-(14)C]glucose incorporation into glycogen, with the same potency as insulin, together with an activation of glycogen synthase a; the effect of 10(-11) mol/l GLP-1 on both parameters was additive to that induced by the equimolar amount of insulin. Synthase a was still activated in cells after 2 days of exposure to GLP-1, as compared with myotubes maintained in the absence of peptide. In human muscle cells, exendin-4 and its truncated form 9-39 amide (Ex-9) are both agonists of the GLP-1 effect on glycogen synthesis and synthase a activity; but while neither GLP-1 nor exendin-4 affected the cellular cAMP content after 5-min incubation in the absence of 3-isobutyl-1-methylxantine (IBMX), an increase was detected with Ex-9. GLP-1, exendin-4, Ex-9 and insulin all induced the prompt hydrolysis of glycosylphosphatidylinositols (GPIs). This work shows a potent stimulatory effect of GLP-1 on the glucose metabolism of human skeletal muscle, and supports the long-term therapeutic value of the peptide. Further evidence for a GLP-1 receptor in this tissue, different from that of the pancreas, is also illustrated, suggesting a role for an inositolphosphoglycan (IPG) as at least one of the possible second messengers of the GLP-1 action in human muscle.


1997 ◽  
Vol 273 (1) ◽  
pp. E185-E191 ◽  
Author(s):  
R. S. Streeper ◽  
E. J. Henriksen ◽  
S. Jacob ◽  
J. Y. Hokama ◽  
D. L. Fogt ◽  
...  

The racemic mixture of the antioxidant alpha-lipoic acid (ALA) enhances insulin-stimulated glucose metabolism in insulin-resistant humans and animals. We determined the individual effects of the pure R-(+) and S-(-) enantiomers of ALA on glucose metabolism in skeletal muscle of an animal model of insulin resistance, hyperinsulinemia, and dyslipidemia: the obese Zucker (fa/fa) rat. Obese rats were treated intraperitoneally acutely (100 mg/kg body wt for 1 h) or chronically [10 days with 30 mg/kg of R-(+)-ALA or 50 mg/kg of S-(-)-ALA]. Glucose transport [2-deoxyglucose (2-DG) uptake], glycogen synthesis, and glucose oxidation were determined in the epitrochlearis muscles in the absence or presence of insulin (13.3 nM). Acutely, R-(+)-ALA increased insulin-mediated 2-DG-uptake by 64% (P < 0.05), whereas S-(-)-ALA had no significant effect. Although chronic R-(+)-ALA treatment significantly reduced plasma insulin (17%) and free fatty acids (FFA; 35%) relative to vehicle-treated obese animals, S-(-)-ALA treatment further increased insulin (15%) and had no effect on FFA. Insulin-stimulated 2-DG uptake was increased by 65% by chronic R-(+)-ALA treatment, whereas S-(-)-ALA administration resulted in only a 29% improvement. Chronic R-(+)-ALA treatment elicited a 26% increase in insulin-stimulated glycogen synthesis and a 33% enhancement of insulin-stimulated glucose oxidation. No significant increase in these parameters was observed after S-(-)-ALA treatment. Glucose transporter (GLUT-4) protein was unchanged after chronic R-(+)-ALA treatment but was reduced to 81 +/- 6% of obese control with S-(-)-ALA treatment. Therefore, chronic parenteral treatment with the antioxidant ALA enhances insulin-stimulated glucose transport and non-oxidative and oxidative glucose metabolism in insulin-resistant rat skeletal muscle, with the R-(+) enantiomer being much more effective than the S-(-) enantiomer.


2007 ◽  
Vol 21 (1) ◽  
pp. 215-228 ◽  
Author(s):  
Mark E. Cleasby ◽  
Tracie A. Reinten ◽  
Gregory J. Cooney ◽  
David E. James ◽  
Edward W. Kraegen

Abstract The phosphoinositide 3-kinase/Akt pathway is thought to be essential for normal insulin action and glucose metabolism in skeletal muscle and has been shown to be dysregulated in insulin resistance. However, the specific roles of and signaling pathways triggered by Akt isoforms have not been fully assessed in muscle in vivo. We overexpressed constitutively active (ca-) Akt-1 or Akt-2 constructs in muscle using in vivo electrotransfer and, after 1 wk, assessed the roles of each isoform on glucose metabolism and fiber growth. We achieved greater than 2.5-fold increases in total Ser473 phosphorylation in muscles expressing ca-Akt-1 and ca-Akt-2, respectively. Both isoforms caused hypertrophy of muscle fibers, consistent with increases in p70S6kinase phosphorylation, and a 60% increase in glycogen accumulation, although only Akt-1 increased glycogen synthase kinase-3β phosphorylation. Akt-2, but not Akt-1, increased basal glucose uptake (by 33%, P = 0.004) and incorporation into glycogen and lipids, suggesting a specific effect on glucose transport. Consistent with this, short hairpin RNA-mediated silencing of Akt-2 caused reductions in glycogen storage and glucose uptake. Consistent with Akt-mediated insulin receptor substrate 1 (IRS-1) degradation, we observed approximately 30% reductions in IRS-1 protein in muscle overexpressing ca-Akt-1 or ca-Akt-2. Despite this, we observed no decrease in insulin-stimulated glucose uptake. Furthermore, a 68% reduction in IRS-1 levels induced using short hairpin RNAs targeting IRS-1 also did not affect glucose disposal after a glucose load. These data indicate distinct roles for Akt-1 and Akt-2 in muscle glucose metabolism and that moderate reductions in IRS-1 expression do not result in the development of insulin resistance in skeletal muscle in vivo.


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