Engineering brown fat into skeletal muscle using ultrasound-targeted microbubble destruction gene delivery in obese Zucker rats: Proof of concept design

Angiotensin 1-7 (Ang 1-7) enhances insulin signaling and glucose transport activity in the skeletal muscle. The aim of our study was to evaluate the effect of AVE0991, a nonpeptide Mas receptor agonist, on the metabolic parameters, expression of RAS components and markers of oxidative stress, and insulin signaling in the skeletal morbidly obese rats. 33-week-old male obese Zucker rats were treated with vehicle and AVE0991 (0.5 mg/kg BW/day) via osmotic minipumps for two weeks. Gene expressions were determined by qPCR and/or Western blot analysis in musculus quadriceps. The enzymatic activities were detected flourometrically (aminopeptidase A) or by colorimetric assay kit (protein tyrosine phosphatase 1B). Administration of AVE0991 enhanced insulin signaling cascade in the skeletal muscle, reflected by improved whole-body glucose tolerance. It has been shown that reactive oxygen species (ROS) have insulin-mimetic action in muscle. The expression of renin receptor, transcription factor PLZF, and prooxidant genes was upregulated by AVE0991 accompanied by elevated expression of genes coding enzymes with antioxidant action. Our results show that AVE0991 administration activates genes involved in both ROS generation and clearance establishing a new prooxidant/antioxidant balance on a higher level, which might contribute to the improved insulin signaling pathway and glucose tolerance of obese Zucker rats.

Download Full-text

The effect of insulin and exercise on c-Cbl protein abundance and phosphorylation in insulin-resistant skeletal muscle in lean and obese Zucker rats

Diabetologia ◽

10.1007/s00125-003-1322-2 ◽

2004 ◽

Vol 47 (3) ◽

pp. 412-419 ◽

Cited By ~ 10

Author(s):

G. D. Wadley ◽

C. R. Bruce ◽

N. Konstantopoulos ◽

S. L. Macaulay ◽

K. F. Howlett ◽

...

Keyword(s):

Skeletal Muscle ◽

Zucker Rats ◽

Protein Abundance ◽

Insulin Resistant ◽

Obese Zucker Rats ◽

Cbl Protein

Download Full-text

Inhibitory Effect of Hypocrellin A on Protein Kinase C in Liver and Skeletal Muscle of Obese Zucker Rats

The American Journal of Chinese Medicine ◽

10.1142/s0192415x03001624 ◽

2003 ◽

Vol 31 (06) ◽

pp. 871-878 ◽

Cited By ~ 6

Author(s):

Xianqin Qu ◽

Lei Dang ◽

J. Paul Seale

Keyword(s):

Skeletal Muscle ◽

Protein Kinase C ◽

Protein Kinase ◽

Inhibitory Effect ◽

Zucker Rats ◽

Dependent Manner ◽

Kinase C ◽

Hypocrellin A ◽

Pkc Isoforms ◽

Obese Zucker Rats

In this ex vivo study, the inhibitory activity of hypocrellin A (HA), a perylene quinonoid pigment isolated from the Chinese medicinal fungus Hypocrella bambuase, on protein kinase C (PKC) enzyme activity in insulin target tissues of obese Zucker rats was assessed. Pre-incubation with HA for 30 minutes significantly inhibited the activity of partially purified PKC enzyme from liver and soleus skeletal muscle in a dose-dependent manner ( IC 50=0.07 and 0.26 μg/ml, respectively). HA produced a greater inhibitory effect in enzyme prepared from the liver than enzyme prepared from soleus muscle. Since total PKC activity in these two insulin target tissues is the net result of several different isoforms of PKC, and PKC-θ is a major isoform expressed in the soleus skeletal muscle, the present data suggest that the naturally occurring compound, HA, may selectively inhibit certain PKC isoforms other than PKC-θ. Further investigations are required to determine which PKC isoforms are most susceptible to HA and whether changes in PKC signaling during treatment with HA can reverse abnormalities of glucose and lipid metabolism in insulin resistant and diabetic states.

Download Full-text

Increased levels of peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC-1α) improve lipid utilisation, insulin signalling and glucose transport in skeletal muscle of lean and insulin-resistant obese Zucker rats

Diabetologia ◽

10.1007/s00125-010-1773-1 ◽

2010 ◽

Vol 53 (9) ◽

pp. 2008-2019 ◽

Cited By ~ 82

Author(s):

C. R. Benton ◽

G. P. Holloway ◽

X.-X. Han ◽

Y. Yoshida ◽

L. A. Snook ◽

...

Keyword(s):

Skeletal Muscle ◽

Glucose Transport ◽

Insulin Signalling ◽

Zucker Rats ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Insulin Resistant ◽

Obese Zucker Rats

Download Full-text

Chronic rosiglitazone treatment restores AMPKα2 activity in insulin-resistant rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00096.2005 ◽

2006 ◽

Vol 290 (2) ◽

pp. E251-E257 ◽

Cited By ~ 40

Author(s):

Sarah J. Lessard ◽

Zhi-Ping Chen ◽

Matthew J. Watt ◽

Michael Hashem ◽

Julianne J. Reid ◽

...

Keyword(s):

Skeletal Muscle ◽

Zucker Rats ◽

Control Group ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Ampk Signaling ◽

Palmitate Oxidation ◽

Insulin Resistant ◽

Obese Zucker Rats

Rosiglitazone (RSG) is an insulin-sensitizing thiazolidinedione (TZD) that exerts peroxisome proliferator-activated receptor-γ (PPARγ)-dependent and -independent effects. We tested the hypothesis that part of the insulin-sensitizing effect of RSG is mediated through the action of AMP-activated protein kinase (AMPK). First, we determined the effect of acute (30–60 min) incubation of L6 myotubes with RSG on AMPK regulation and palmitate oxidation. Compared with control (DMSO), 200 μM RSG increased ( P < 0.05) AMPKα1 activity and phosphorylation of AMPK (Thr172). In addition, acetyl-CoA carboxylase (Ser218) phosphorylation and palmitate oxidation were increased ( P < 0.05) in these cells. To investigate the effects of chronic RSG treatment on AMPK regulation in skeletal muscle in vivo, obese Zucker rats were randomly allocated into two experimental groups: control and RSG. Lean Zucker rats were treated with vehicle and acted as a control group for obese Zucker rats. Rats were dosed daily for 6 wk with either vehicle (0.5% carboxymethylcellulose, 100 μl/100 g body mass), or 3 mg/kg RSG. AMPKα1 activity was similar in muscle from lean and obese animals and was unaffected by RSG treatment. AMPKα2 activity was ∼25% lower in obese vs. lean animals ( P < 0.05) but was normalized to control values after RSG treatment. ACC phosphorylation was decreased with obesity ( P < 0.05) but restored to the level of lean controls with RSG treatment. Our data demonstrate that RSG restores AMPK signaling in skeletal muscle of insulin-resistant obese Zucker rats.

Download Full-text

Enhanced arteriolar α-adrenergic constriction impairs dilator responses and skeletal muscle perfusion in obese Zucker rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.01216.2003 ◽

2004 ◽

Vol 97 (2) ◽

pp. 764-772 ◽

Cited By ~ 39

Author(s):

Jefferson C. Frisbee

Keyword(s):

Skeletal Muscle ◽

Blood Flow ◽

Gastrocnemius Muscle ◽

Muscle Blood Flow ◽

Zucker Rats ◽

Metabolic Demand ◽

Obese Zucker Rats ◽

Isometric Twitch ◽

Gastrocnemius Muscles

The present study tested the hypothesis that enhanced vascular α-adrenergic constriction in obese Zucker rats (OZR) impairs arteriolar dilation and perfusion of skeletal muscle at rest and with increased metabolic demand. In lean Zucker rats (LZR) and OZR, isolated gracilis arterioles were viewed via television microscopy, and the contralateral cremaster muscle or gastrocnemius muscle was prepared for study in situ. Gracilis and cremasteric arterioles were challenged with dilator stimuli under control conditions and after blockade of α-adrenoreceptors with prazosin, phentolamine, or yohimbine. Gastrocnemius muscles performed isometric twitch contractions of increasing frequency, and perfusion was continuously monitored. In OZR, dilator responses of arterioles to hypoxia (gracilis), wall shear rate (cremaster), acetylcholine, and iloprost (both) were impaired vs. LZR. Treatment with prazosin and phentolamine (and in cremasteric arterioles only, yohimbine) improved arteriolar reactivity to these stimuli in OZR, although responses remained impaired vs. LZR. Gastrocnemius muscle blood flow was reduced at rest in OZR; this was corrected with intravenous infusion of phentolamine or prazosin. At all contraction frequencies, blood flow was reduced in OZR vs. LZR; this was improved by infusion of phentolamine or prazosin at low-moderate metabolic demand only (1 and 3 Hz). At 5 Hz, adrenoreceptor blockade did not alter blood flow in OZR from levels in untreated rats. These results suggest that enhanced α-adrenergic constriction of arterioles of OZR contributes to impaired dilator responses and reduced muscle blood flow at rest and with mild-moderate (although not with large) elevations in metabolic demand.

Download Full-text

Exercise training increases ERK2 activity in skeletal muscle of obese Zucker rats

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.2.454 ◽

2001 ◽

Vol 90 (2) ◽

pp. 454-460 ◽

Cited By ~ 20

Author(s):

Abdullah A. Osman ◽

Joe Hancock ◽

Desmond G. Hunt ◽

John L. Ivy ◽

Lawrence J. Mandarino

Keyword(s):

Skeletal Muscle ◽

Exercise Training ◽

Acute Exercise ◽

Citrate Synthase ◽

Mapk Pathway ◽

Insulin Response ◽

Mitogen Activated Protein Kinase ◽

Zucker Rats ◽

Obese Zucker Rats ◽

Ribosomal S6 Kinase

Acute exercise and training increase insulin action in skeletal muscle, but the mechanism responsible for this effect is unknown. Activation of the insulin receptor initiates signaling through both the phosphatidylinositol (PI) 3-kinase and the mitogen-activated protein kinase [MAPK, also referred to as extracellular signal-regulated kinases (ERK1/2)] pathways. Acute exercise has no effect on the PI3-kinase pathway signaling elements but does activate the MAPK pathway, which may play a role in the adaptation of muscle to exercise. It is unknown whether training produces a chronic effect on basal activity or insulin response of the MAPK pathway. The present study was undertaken to determine whether exercise training improves the activity of the MAPK pathway or its response to insulin in obese Zucker rats, a well-characterized model of insulin resistance. To accomplish this, obese Zucker rats were studied by using the hindlimb perfusion method with or without 7 wk of treadmill training. Activation of the MAPK pathway was determined in gastrocnemius muscles exposed in situ to insulin. Compared with lean Zucker rats, untrained obese Zucker rats had reduced basal and insulin-stimulated activities of ERK2 and its downstream target p90 ribosomal S6 kinase (RSK2). Seven weeks of training significantly increased basal and insulin-stimulated ERK2 and RSK2 activities, as well as insulin stimulation of MAPK kinase activity. This effect was maintained for at least 96 h in the case of ERK2. The training-induced increase in basal ERK2 activity was correlated with the increase in citrate synthase activity. Therefore, 7 wk of training increases basal and insulin-stimulated ERK2 activity. The increase in basal ERK2 activity may be related to the response of muscle to training.

Download Full-text

Increased vascular thromboxane generation impairs dilation of skeletal muscle arterioles of obese Zucker rats with reduced oxygen tension

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00596.2008 ◽

2008 ◽

Vol 295 (4) ◽

pp. H1522-H1528 ◽

Cited By ~ 26

Author(s):

Adam G. Goodwill ◽

Milinda E. James ◽

Jefferson C. Frisbee

Keyword(s):

Nitric Oxide ◽

Skeletal Muscle ◽

Superoxide Dismutase ◽

Arachidonic Acid ◽

Polyethylene Glycol ◽

Nitric Oxide Synthase ◽

Oxidant Stress ◽

Zucker Rats ◽

Obese Zucker Rats ◽

Oxide Synthase

This study determined if altered vascular prostacyclin (PGI2) and/or thromboxane A2 (TxA2) production with reduced Po2 contributes to impaired hypoxic dilation of skeletal muscle resistance arterioles of obese Zucker rats (OZRs) versus lean Zucker rats (LZRs). Mechanical responses were assessed in isolated gracilis muscle arterioles following reductions in Po2 under control conditions and following pharmacological interventions inhibiting arachidonic acid metabolism and nitric oxide synthase and alleviating elevated vascular oxidant stress. The production of arachidonic acid metabolites was assessed using pooled arteries from OZRs and LZRs in response to reduced Po2. Hypoxic dilation, endothelium-dependent in both strains, was attenuated in OZRs versus LZRs. Nitric oxide synthase inhibition had no significant impact on hypoxic dilation in either strain. Cyclooxygenase inhibition dramatically reduced hypoxic dilation in LZRs and abolished responses in OZRs. Treatment of arterioles from OZRs with polyethylene glycol-superoxide dismutase improved hypoxic dilation, and this improvement was entirely cyclooxygenase dependent. Vascular PGI2 production with reduced Po2 was similar between strains, although TxA2 production was increased in OZRs, a difference that was attenuated by treatment of vessels from OZRs with polyethylene glycol-superoxide dismutase. Both blockade of PGH2/TxA2 receptors and inhibition of thromboxane synthase increased hypoxic dilation in OZR arterioles. These results suggest that a contributing mechanism underlying impaired hypoxic dilation of skeletal muscle arterioles of OZRs may be an increased vascular production of TxA2, which competes against the vasodilator influences of PGI2. These results also suggest that the elevated vascular oxidant stress inherent in metabolic syndrome may contribute to the increased vascular TxA2 production and may blunt vascular sensitivity to PGI2.

Download Full-text

Oxidant stress-induced increase in myogenic activation of skeletal muscle resistance arteries in obese Zucker rats

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00379.2002 ◽

2002 ◽

Vol 283 (6) ◽

pp. H2160-H2168 ◽

Cited By ~ 75

Author(s):

Jefferson C. Frisbee ◽

Kristopher G. Maier ◽

David W. Stepp

Keyword(s):

Skeletal Muscle ◽

Superoxide Dismutase ◽

Oxidant Stress ◽

Intraluminal Pressure ◽

Zucker Rats ◽

Radical Scavengers ◽

Resistance Arteries ◽

Obese Zucker Rats ◽

Cytochrome P 450

This study characterized myogenic activation of skeletal muscle (gracilis) resistance arteries from lean (LZR) and obese Zucker rats (OZR). Arteries from OZR exhibited increased myogenic activation versus LZR; this increase was impaired by endothelium denudation or nitric oxde synthase inhibition. Treatment of vessels with 17-octadecynoic acid impaired responses in both strains by comparable amounts. Dihydroethidine microfluorography indicated elevated vascular superoxide levels in OZR versus LZR; immunohistochemistry demonstrated elevated vascular nitrotyrosine levels in OZR, indicating increased peroxynitrite presence. Vessel treatment with oxidative radical scavengers (polythylene glycol-superoxide dismutase/catalase) or inhibition of Ca2+-activated K+(KCa) channels (iberiotoxin) did not alter myogenic activation in LZR but normalized activation in OZR. Application of peroxynitrite to vessels of OZR caused a greater vasoconstriction versus LZR; the response was impaired in OZR by elevated intraluminal pressure and was abolished in both strains by iberiotoxin. These results suggest that enhanced myogenic activation of gracilis arteries of OZR versus LZR 1) is not due to alterations in cytochrome P-450 contribution, and 2) may be due to elevated peroxynitrite levels inhibiting KCa channels following increased intraluminal pressure.

Download Full-text