Muscle glucose uptake of obese Zucker rats trained at two different intensities

1991 ◽  
Vol 70 (1) ◽  
pp. 36-42 ◽  
Author(s):  
M. E. Willems ◽  
J. T. Brozinick ◽  
C. E. Torgan ◽  
M. Y. Cortez ◽  
J. L. Ivy
Keyword(s):  
Insulin Resistance ◽  
Exercise Training ◽  
Glucose Uptake ◽  
Exercise Bout ◽  
Zucker Rats ◽  
Muscle Insulin Resistance ◽  
Obese Zucker Rat ◽  
Training Response ◽  
Obese Zucker Rats ◽  
The Difference

Exercise training reduces the muscle insulin resistance of the obese Zucker rat. The purpose of the present study was to determine whether the magnitude of this training response is exercise intensity specific. Obese Zucker rats were randomly divided into sedentary (SED), low-intensity (LI), and high-intensity (HI) exercise groups. For the LI rats, exercise training consisted of running on a rodent treadmill at 18 m/min up an 8% grade for 90 min. Rats in the HI group ran at 24 m/min up an 8% grade for four 17-min bouts with 3 min between bouts. Both exercise groups performed the same amount of work and trained 5 days/wk for 7 wk. To evaluate muscle insulin resistance, rat hindlimbs were perfused for 30 min with perfusate containing 6 mM glucose (0.15 mu Ci of D-[14C(U)] glucose/ml) and either a maximal (10.0 mU/ml) or a submaximal (0.50 mU/ml) insulin concentration. Perfusions were performed 48–56 h after the last exercise bout and a 12-h fast. In the presence of 0.5 mU/ml insulin, the rate of muscle glucose uptake was found to be significantly faster for the HI (9.56 +/- 0.66 mumol.h-1.g-1) than for the LI (7.72 +/- 0.65 mumol.h-1.g-1) and SED (6.64 +/- 0.44 mumol.h-1.g-1) rats. The difference in glucose uptake between the LI and SED rats was not significant. In the presence of 10.0 mU/ml insulin, the rate of glucose uptake was significantly faster for the HI (16.43 +/- 1.02 mumol.h-1.g-1) than for the LI rats (13.76 +/- 0.84 mumol.h-1.g-1) and significantly faster for the LI than for the SED rats (11.02 +/- 0.35 mumol.h-1.g-1).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Exercise training improves muscle insulin resistance but not insulin receptor signaling in obese Zucker rats

2002 ◽  
Vol 92 (2) ◽  
pp. 736-744 ◽  
Author(s):  
Christine Y. Christ ◽  
Desmond Hunt ◽  
Joe Hancock ◽  
Rebeca Garcia-Macedo ◽  
Lawrence J. Mandarino ◽  
...  
Keyword(s):  
Exercise Training ◽  
Insulin Receptor ◽  
Glucose Uptake ◽  
Exercise Bout ◽  
Pi3 Kinase ◽  
Serine Phosphorylation ◽  
Zucker Rats ◽  
Receptor Signaling ◽  
Insulin Receptor Signaling ◽  
Obese Zucker Rats

Exercise training improves skeletal muscle insulin sensitivity in the obese Zucker rat. The purpose of this study was to investigate whether the improvement in insulin action in response to exercise training is associated with enhanced insulin receptor signaling. Obese Zucker rats were trained for 7 wk and studied by using the hindlimb-perfusion technique 24 h, 96 h, or 7 days after their last exercise training bout. Insulin-stimulated glucose uptake (traced with 2-deoxyglucose) was significantly reduced in untrained obese Zucker rats compared with lean controls (2.2 ± 0.17 vs. 5.4 ± 0.46 μmol · g−1 · h−1). Glucose uptake was normalized 24 h after the last exercise bout (4.9 ± 0.41 μmol · g−1 · h−1) and remained significantly elevated above the untrained obese Zucker rats for 7 days. However, exercise training did not increase insulin receptor or insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation, phosphatidylinositol 3-kinase (PI3-kinase) activity associated with IRS-1 or tyrosine phosphorylated immunoprecipitates, or Akt serine phosphorylation. These results are consistent with the hypothesis that, in obese Zucker rats, adaptations occur during training that lead to improved insulin-stimulated muscle glucose uptake without affecting insulin receptor signaling through the PI3-kinase pathway.

Exercise and diet reduce muscle insulin resistance in obese Zucker rat

1986 ◽  
Vol 251 (3) ◽  
pp. E299-E305 ◽  
Author(s):  
J. L. Ivy ◽  
W. M. Sherman ◽  
C. L. Cutler ◽  
A. L. Katz
Keyword(s):  
Insulin Resistance ◽  
Exercise Training ◽  
Glucose Uptake ◽  
High Fat Diet ◽  
High Carbohydrate Diet ◽  
Carbohydrate Diet ◽  
Muscle Insulin Resistance ◽  
High Carbohydrate ◽  
Obese Zucker Rat ◽  
Obese Rats

Two treatments that increase skeletal muscle insulin action are exercise training and high-carbohydrate diet. The purpose of the present study was to determine whether exercise training and a diet high in carbohydrates could function synergistically to reduce the muscle insulin resistance in the obese Zucker rat. Obese rats 4 wk of age were randomly assigned to an exercise or sedentary group. Each group was subdivided by diet with one-half of the rats fed a high-carbohydrate diet and one-half fed a high-fat diet. Lean Zucker rats fed the high-fat diet were used as controls. Muscle insulin resistance was assessed during hindlimb perfusion with a submaximally stimulating concentration of insulin. Exercise training and the high-carbohydrate diet increased the rate of muscle glucose uptake in the obese rat by 46 and 53%, respectively. More importantly, the combined effect of exercise training and high-carbohydrate diet was greater than the sum of their individual effects. Glycogen synthesis paralleled glucose uptake and was the major pathway for intracellular glucose disposal. Muscle glucose uptake for exercise-trained, high-carbohydrate fed obese rats was comparable with that of lean controls. It is concluded that exercise training and the high-carbohydrate diet functioned synergistically to reduce the muscle insulin resistance in the obese rat.

Glucose transport: locus of muscle insulin resistance in obese Zucker rats

1988 ◽  
Vol 255 (3) ◽  
pp. E374-E382 ◽  
Author(s):  
W. M. Sherman ◽  
A. L. Katz ◽  
C. L. Cutler ◽  
R. T. Withers ◽  
J. L. Ivy
Keyword(s):  
Insulin Resistance ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glycogen Synthase ◽  
Fiber Type ◽  
Zucker Rats ◽  
Muscle Insulin Resistance ◽  
Obese Rats ◽  
Obese Zucker Rats ◽  
Fast Twitch

The purposes of this study were to determine whether the muscle insulin resistance of the obese rat is due to a defect in the glucose transport process and whether the insulin resistance is fiber-type specific. The hindlimbs of fasted, 14-wk-old obese (fa/fa) and lean (fa/?) Zucker rats were perfused with perfusate containing 8 mM glucose and no insulin or 8 mM glucose and either a physiological (0.15 mU/ml), a submaximal (1.50 mU/ml), or a maximal (15.0 mU/ml) insulin concentration. Glucose uptake was determined after which the initial rate of glucose transport was determined using 3-O-methyl-D-glucose (3-OMG). Glucose uptake of the obese rats was depressed by 40, 33, 42, and 47% in the absence of insulin and in the presence of the physiological, submaximal, and maximal insulin concentrations, respectively, when compared with lean littermates. Glucose transport in the absence and in the presence of the three insulin concentrations was significantly lower in the soleus (slow-twitch, oxidative fibers), red quadriceps (fast-twitch, oxidative, glycolytic fibers), and gastrocnemius (mixed fibers) of the obese rats when compared with lean rats. Glucose transport in the white quadriceps (fast-twitch, glycolytic fibers) was significantly lower in the obese rats in the absence of insulin and in the presence of the submaximal and maximal insulin concentrations. The glycogen concentration and the activity of hexokinase were the same and the glycogen synthase activity was higher in the muscles for the obese rats when compared to lean rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of clenbuterol on insulin resistance in conscious obese Zucker rats

2001 ◽  
Vol 280 (4) ◽  
pp. E554-E561 ◽  
Author(s):  
Shujia J. Pan ◽  
Joe Hancock ◽  
Zhenping Ding ◽  
Donovan Fogt ◽  
Mancheong Lee ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Body Weight ◽  
Glucose Uptake ◽  
Glycogen Synthesis ◽  
Chronic Administration ◽  
Abdominal Fat ◽  
Zucker Rats ◽  
Control Group ◽  
Obese Zucker Rats ◽  
Long Acting

The present study was conducted to determine the effect of chronic administration of the long-acting β2-adrenergic agonist clenbuterol on rats that are genetically prone to insulin resistance and impaired glucose tolerance. Obese Zucker rats ( fa/fa) were given 1 mg/kg of clenbuterol by oral intubation daily for 5 wk. Controls received an equivalent volume of water according to the same schedule. At the end of the treatment, rats were catheterized for euglycemic-hyperinsulinemic (15 mU insulin · kg−1 · min−1) clamping. Clenbuterol did not change body weight compared with the control group but caused a redistribution of body weight: leg muscle weights increased, and abdominal fat weight decreased. The glucose infusion rate needed to maintain euglycemia and the rate of glucose disappearance were greater in the clenbuterol-treated rats. Furthermore, plasma insulin levels were decreased, and the rate of glucose uptake into hindlimb muscles and abdominal fat was increased in the clenbuterol-treated rats. This increased rate of glucose uptake was accompanied by a parallel increase in the rate of glycogen synthesis. The increase in muscle glucose uptake could not be ascribed to an increase in the glucose transport protein GLUT-4 in clenbuterol-treated rats. We conclude that chronic clenbuterol treatment reduces the insulin resistance of the obese Zucker rat by increasing insulin-stimulated muscle and adipose tissue glucose uptake. The improvements noted may be related to the repartitioning of body weight between tissues.

Interaction of exercise training and clenbuterol on GLUT-4 protein in muscle of obese Zucker rats

1996 ◽  
Vol 271 (5) ◽  
pp. E847-E854 ◽  
Author(s):  
C. H. Kuo ◽  
Z. Ding ◽  
J. L. Ivy
Keyword(s):  
Exercise Training ◽  
Adrenergic Receptors ◽  
Protein Concentration ◽  
Chronic Administration ◽  
Zucker Rats ◽  
Beta Adrenergic Receptors ◽  
Beta Adrenergic ◽  
Glut 4 ◽  
Obese Zucker Rat ◽  
Obese Zucker Rats

Chronic administration of clenbuterol, a beta 2-adrenergic agonist, attenuates the exercise training-induced improvement in muscle insulin resistance of the obese Zucker rat. The present study was conducted to determine whether clenbuterol also attenuates the increase in muscle GLUT-4 protein that occurs with exercise training and whether the action of clenbuterol is related to its ability to downregulate the beta-adrenergic receptors. Female obese Zucker rats were randomly assigned to one of the following four groups: control (CON, n = 7), clenbuterol (CL, n = 8), exercise training (TR, n = 8), and clenbuterol with exercise training (CL+TR, n = 8). Rats assigned to the training groups were run on a rodent motor-driven treadmill for 6-7 wk. Rats receiving clenbuterol were intubated with 0.8 mg/kg body weight 30 min before running each day. Red quadriceps (RQ) and white quadriceps (WQ) GLUT-4 protein concentrations of TR rats were significantly greater than those of CON and CL+TR rats. The RQ GLUT-4 protein concentration of the CL+TR rats was significantly greater than that of CON rats, but this difference did not occur in the WQ. GLUT-4 protein concentrations were not different between the CON and CL rats. The patterns of RQ and WQ GLUT-4 mRNA were similar to those of their respective GLUT-4 proteins. Rats receiving daily injections of propranolol (30 mg/kg body wt), a beta-adrenergic receptor antagonist, demonstrated no increase in GLUT-4 protein in RQ or WQ after 6 wk of exercise training. These results indicate that 1) clenbuterol can attenuate the increase in muscle GLUT-4 protein associated with exercise training and 2) this effect is likely mediated by a downregulation of the beta-adrenergic receptors.

scholarly journals Ileal interposition improves glucose tolerance and insulin sensitivity in the obese Zucker rat

2010 ◽  
Vol 299 (3) ◽  
pp. G751-G760 ◽  
Author(s):  
Derek M. Culnan ◽  
Vance Albaugh ◽  
Mingjie Sun ◽  
Christopher J. Lynch ◽  
Charles H. Lang ◽  
...  
Keyword(s):  
Body Weight ◽  
Insulin Sensitivity ◽  
Food Intake ◽  
Glucose Tolerance ◽  
Glucose Uptake ◽  
Zucker Rats ◽  
Ileal Interposition ◽  
Obese Zucker Rat ◽  
Obese Zucker Rats ◽  
Glucagon Like Peptide 1

The hindgut hypothesis posits improvements in Type 2 diabetes after gastric bypass surgery are due to enhanced delivery of undigested nutrients to the ileum, which increase incretin production and insulin sensitivity. The present study investigates the effect of ileal interposition (IT), surgically relocating a segment of distal ileum to the proximal jejunum, on glucose tolerance, insulin sensitivity, and glucose transport in the obese Zucker rat. Two groups of obese Zucker rats were studied: IT and sham surgery ad libitum fed (controls). Changes in food intake, body weight and composition, glucose tolerance, insulin sensitivity and tissue glucose uptake, and insulin signaling as well as plasma concentrations of glucagon-like peptide-1 and glucose-dependent insulinotropic peptide were measured. The IT procedure did not significantly alter food intake, body weight, or composition. Obese Zucker rats demonstrated improved glucose tolerance 3 wk after IT compared with the control group ( P < 0.05). Euglycemic, hyperinsulinemic clamp and 1-[14C]-2-deoxyglucose tracer studies indicate that IT improves whole body glucose disposal, insulin-stimulated glucose uptake, and the ratio of phospho- to total Akt ( P < 0.01 vs. control) in striated muscle. After oral glucose, the plasma concentration of glucagon-like peptide-1 was increased, whereas GIP was decreased following IT. Enhanced nutrient delivery to the ileum after IT improves glucose tolerance, insulin sensitivity and muscle glucose uptake without altering food intake, body weight, or composition. These findings support the concept that anatomic and endocrine alterations in gut function play a role in the improvements in glucose homeostasis after the IT procedure.

scholarly journals Skeletal Muscle Insulin Resistance: Roles of Fatty Acid Metabolism and Exercise

2008 ◽  
Vol 88 (11) ◽  
pp. 1279-1296 ◽  
Author(s):  
Lorraine P Turcotte ◽  
Jonathan S Fisher
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Fatty Acid ◽  
Exercise Training ◽  
Aerobic Exercise ◽  
Glucose Uptake ◽  
Muscle Cells ◽  
Aerobic Exercise Training ◽  
Muscle Insulin Resistance ◽  
Skeletal Muscle Insulin Resistance

The purpose of this review is to provide information about the role of exercise in the prevention of skeletal muscle insulin resistance, that is, the inability of insulin to properly cause glucose uptake into skeletal muscle. Insulin resistance is associated with high levels of stored lipids in skeletal muscle cells. Aerobic exercise training decreases the amounts of these lipid products and increases the lipid oxidative capacity of muscle cells. Thus, aerobic exercise training may prevent insulin resistance by correcting a mismatch between fatty acid uptake and fatty acid oxidation in skeletal muscle. Additionally, a single session of aerobic exercise increases glucose uptake by muscle during exercise, increases the ability of insulin to promote glucose uptake, and increases glycogen accumulation after exercise, all of which are important to blood glucose control. There also is some indication that resistance exercise may be effective in preventing insulin resistance. The information provided is intended to help clinicians understand and explain the roles of exercise in reducing insulin resistance.

Interaction of aerobic exercise training and clenbuterol: effects on insulin-resistant muscle

1993 ◽  
Vol 75 (4) ◽  
pp. 1471-1476 ◽  
Author(s):  
C. E. Torgan ◽  
G. J. Etgen ◽  
J. T. Brozinick ◽  
R. E. Wilcox ◽  
J. L. Ivy
Keyword(s):  
Insulin Resistance ◽  
Exercise Training ◽  
Aerobic Exercise ◽  
Glucose Uptake ◽  
Adrenergic Receptor ◽  
Citrate Synthase ◽  
Aerobic Exercise Training ◽  
Beta Adrenergic Receptor ◽  
Beta Adrenergic ◽  
Muscle Insulin Resistance

The effects of aerobic exercise training, chronic administration of the selective beta 2-adrenergic agonist clenbuterol, and the combination of these two treatments on muscle insulin resistance were compared in female obese (fa/fa) Zucker rats. Rats were randomly assigned to trained, clenbuterol, clenbuterol-trained, or control groups. Training consisted of treadmill running for 2 h/day at 18 m/min up an 8% grade. Clenbuterol was administered by intubation (0.4–0.8 mg.kg body wt-1 x day-1) approximately 30 min before the rats ran each day. After 8 wk of treatment, muscle insulin resistance was assessed via hindlimb perfusion in the presence of 8 mM glucose and a submaximal (500 microU/ml) insulin concentration. Training increased citrate synthase activity (mumol.g wet wt-1 x min-1) by 32–74% and insulin-stimulated glucose uptake by 45%. Clenbuterol ingestion induced a 17–29% increase in muscle mass but decreased citrate synthase activity by 34–42% and had no effect on muscle glucose uptake. Administration of clenbuterol to rats that exercise trained prevented the training-induced improvement in insulin-stimulated glucose uptake and attenuated the increases in citrate synthase activity. In addition, both clenbuterol-treated groups displayed a 42% decrease in beta-adrenergic receptor density. The results indicate that clenbuterol administration, possibly through beta-adrenergic receptor downregulation, attenuated a cellular reaction essential for the exercise training-induced increase in citrate synthase activity and improvement in skeletal muscle insulin resistance of the obese Zucker rat.

Exercise training and clenbuterol reduce insulin resistance of obese Zucker rats

1993 ◽  
Vol 264 (3) ◽  
pp. E373-E379 ◽  
Author(s):  
C. E. Torgan ◽  
J. T. Brozinick ◽  
E. A. Banks ◽  
M. Y. Cortez ◽  
R. E. Wilcox ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Exercise Training ◽  
Glucose Tolerance ◽  
Glucose Uptake ◽  
Adrenergic Receptor ◽  
Aerobic Exercise Training ◽  
Zucker Rats ◽  
Sedentary Control ◽  
Control Groups ◽  
Beta 2

This study compared the effects of aerobic exercise training and chronic administration of the selective beta 2-adrenergic agonist clenbuterol on whole body and skeletal muscle insulin resistance in obese (fa/fa) Zucker rats. Obese rats were randomly assigned to training, clenbuterol, or sedentary control groups. Lean littermates served as a second control group. After 4-5 wk of treatment, an oral glucose tolerance test was performed, followed 1 wk later by hindlimb perfusion, during which time the rates of glucose uptake and 3-O-methyl-D-glucose (3-MG) transport were assessed in the presence of a submaximal (500 microU/ml) insulin concentration. Training resulted in a significant increase in citrate synthase and cytochrome oxidase activity in the recruited muscles. Clenbuterol induced a large increase in muscle mass but provoked a significant decrease in oxidative enzyme activity and beta-adrenergic receptor density. Both treatments increased glucose tolerance and reduced the postglucose insulin response, with the improvements being more pronounced in the clenbuterol group. However, only exercise training improved insulin-stimulated hindlimb muscle glucose uptake (11.37 +/- 0.65, 8.73 +/- 0.77, and 8.27 +/- 0.41 mumol.g-1.h-1 for trained, clenbuterol, and sedentary control groups, respectively) and 3-MG transport. These results suggest that aerobic exercise training attenuated the insulin-resistant condition in the obese Zucker rat by a mechanism other than or in addition to beta 2-adrenergic receptor activation.

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