Chondroitin sulphate inhibits NF-κB activity induced by interaction of pathogenic and damage associated molecules.

OBJECTIVE: To evaluate the anti-inflammatory mechanism of action of Chondroitin Sulphate (CS). DESIGN: THP-1 macrophages were cultured with a range of sizes and concentrations of HA fragments with TLR4 (LPS in a physiologically relevant concentration determined by analyses of sera of a community clinic ascertained knee osteoarthritis (OA) cohort) or TLR2 (heat killed listeria bacteria) agonists and varying concentrations of CS in a physiologically relevant range (10-200 µg/ml). We measured IL-1ß release, intracellular IL-1ß, proIL-1ß, caspase-1 and NF-κB activity and DNA binding activity of NF-κB transcription factors from nuclear and cytoplasmic extracts. RESULTS: Serum LPS was significantly associated with radiographic knee joint space narrowing (JSN) (P = 0.02) in the OA cohort (n = 40). The priming dose of LPS used for these experiments (10 ng/ml) was below the lowest serum concentration of the OA cohort (median 47.09, range 14.43-81.36 ng/ml). Priming doses of LPS and HA fragments alone did not elicit an inflammatory response. However, primed with LPS, HA fragments produced large dose-dependent increases in IL-1ß that were inhibitable by CS. CS did not inhibit caspase-1 activity but in physiologically achievable concentrations, attenuated NF-κB activity induced by either the TLR4 (LPS 1000 ng/ml) or TLR2 agonists alone or in combination with HA fragments. LPS induced and CS significantly reduced activity of canonical NF-κB transcription factors, p65, p50, c-Rel and RelB. CONCLUSIONS: Subinflammatory concentrations of pathogenic (LPS, listeria) and damage associated (HA) molecules interact to induce macrophage-related inflammation. CS works upstream of the inflammasome by inhibiting activation of NF-κB transcription factors.

Small synthetic hyaluronan disaccharides afford neuroprotection in brain ischemia-related models.

High molecular weight (HMW) glycosaminoglycanes of the extracellular matrix have been implicated in tissue repair. The aim of this study was to evaluate if small synthetic hyaluronan disaccharides with different degrees of sulfation (methyl 2-acetamido-2-deoxy-3-O-(ß-d-glucopyranosyluronic acid)-O-sulfo-α-d-glucopyranoside, sodium salt (di0S), methyl 2-acetamido-2-deoxy-3-O-(ß-d-glucopyranosyluronic acid)-6-di-O-sulfo-α-d-glucopyranoside, disodium salt (di6S) and methyl 2-acetamido-2-deoxy-3-O-(ß-d-glucopyranosyluronic acid)-4,6-di-O-sulfo-α-d-glucopyranoside, trisodium salt (di4,6S)) could improve cell survival in in vitro and in vivo brain ischemia-related models. Rat hippocampal slices subjected to oxygen and glucose deprivation and a photothrombotic stroke model in mice were used. The three hyaluran disaccharides, incubated during the oxygen and glucose deprivation (15min) and re-oxygenation periods (120min), reduced cell death of hippocampal slices measured as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction, being the most potent di4,6S; in contrast, high molecular hyaluronan was ineffective. The protective actions of di4,6S against oxygen and glucose deprivation were related to activation of the PI3K/Akt survival pathway, reduction of p65 translocation to the nucleus, inhibition of inducible nitric oxide oxidase induction and reactive oxygen species production, and to an increase in glutathione levels. Administered 1h post-stroke, di4,6S reduced cerebral infarct size and improved motor activity in the beam walk test. In conclusion, di4,6S affords neuroprotection in in vitro and in vivo models of ischemic neuronal damage. Our results suggest that its neuroprotective effect could be exerted through its capability to reduce oxidative stress during ischemia. Its small molecular size makes it a more potential druggable drug to target the brain as compared with its HMW parent compound hyaluronan.

Antioxidant, antiinflammatory and neuroprotective actions of chondroitin sulfate and proteoglycans.

The antiinflammatory and antiapoptotic effects of chondroitin sulfate (CS) are being used to treat osteoarthritis. Recent evidence has revealed that those peripheral effects of CS may also have therapeutic interest in diseases of the central nervous system (CNS). We review here such evidence. Perineuronal nets (PNNs) formed by chondroitin sulfate proteoglycans (CSPGs) may have a neuroprotective action against oxidative stress potentially involved in neurodegeneration. On the other hand, in human neuroblastoma SH-SY5Y cells CS has antioxidant and neuroprotective effects by activating the signaling pathway PKC/PI3K/Akt and inducing the antioxidant enzyme hemoxygenase-1. Consistent with this is the observation that protein kinase C (PKC) blockade overcomes inhibition of neurite outgrowth elicited by CSPGs. In addition, CS protects cortical neurons against excytotoxic death by phosphorylation of intracellular signals and the suppression of caspase-3 activation. Of interest is the finding that a disaccharide derived from CSPG degradation (CSGP-DS) protects neurons against toxicity both in vitro and in vivo. Furthermore, CSGP-DS efficiently protects against neuronal loss in experimental autoimmune encephalomyelitis and uveitis, decreases secretion of tumor necrosis factor-alpha (TNF-alpha) and block necrosis factor kappa B (NF-kappaB) translocation. In conclusion, CS may have neuroprotective properties linked to its antioxidant and antiinflammatory effects.

Effectiveness of chondroitin sulphate in patients with concomitant knee osteoarthritis and psoriasis: a randomized, double-blind, placebo-controlled study.

OBJECTIVE: The aim of the trial was to assess the efficacy of chondroitin sulphate (CS) on symptomatic knee osteoarthritis (OA) associated to psoriasis. METHODS: In this randomized, double-blind, placebo (PBO)-controlled clinical trial 129 patients with symptomatic knee OA and concomitant psoriasis were randomized into two groups receiving 800 mg daily of CS or PBO for 3 months. The primary efficacy outcome for knee OA was the Huskisson's visual analogue scale (VAS) and for psoriasis was the Psoriasis Area and Severity Index (PASI). Additionally, other secondary efficacy criteria for both conditions were assessed. RESULTS: After 3 months of treatment, CS was more effective than PBO, relieving pain VAS (CS -26.9+/-24.8 vs PBO -14.23+/-20.8mm, P<0.01), decreasing the Lequesne index (CS -4.8+/-3.4 vs PBO -3.3+/-3.5, P<0.05) and reducing the number of patients using acetaminophen as rescue medication (CS 43% vs PBO 64%, P<0.05). Regarding PASI, Overall Lesion Severity Scale and Physician's Global Assessment of Change no statistically significant changes were detected in front of PBO. However, CS improved plantar psoriasis compared to PBO (CS 87% vs PBO 27%, P<0.05). Quality of life improved significantly in CS-treated patients according to the Short Form-36 health survey and the Dermatology Life Quality Index (DLQI). CS tolerability was excellent. Adverse events were infrequent and evenly distributed among groups. The incidence of psoriatic flares did not increase after treatments. CONCLUSIONS: This study confirms the efficacy and safety of CS as a symptomatic slow-acting drug in patients with knee OA and shows that CS improves plantar psoriasis. The use of CS could represent a special benefit in patients with both pathologies since non-steroidal anti-inflammatory drugs have been reported to induce or exacerbate psoriasis.

Chondroitin sulfate inhibits lipopolysaccharide-induced inflammation in rat astrocytes by preventing nuclear factor kappa B activation.

Chondroitin sulfate (CS) is a glucosaminoglycan (GAG) currently used for the treatment of osteoarthritis because of its antiinflammatory and antiapoptotic actions. Recent evidence has revealed that those peripheral effects of CS may also have therapeutic interest in diseases of the CNS. Since neuroinflammation has been implicated in different neuronal pathologies, this study was planned to investigate how CS could modulate the inflammatory response in the CNS by using rat astrocyte cultures stimulated with lipopolysaccharide (LPS). We have evaluated different proteins implicated in the nuclear factor kappa B (NFkappaB) and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways employing RT-PCR, western blot and immunofluorescence techniques. At 10 microM, CS prevented translocation of p65 to the nucleus, reduced tumour necrosis factor alpha (TNF-alpha) mRNA and mitigated cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS) induction by LPS. However, it did not modify LPS-induced IP-10 and SOCS-1 mRNA, proteins that participate in the JAK/STAT pathway. The results of this study indicate that CS can potentially reduce neuroinflammation by inhibition of NFkappaB. Therefore endogenous GAGs could afford neuroimmunomodulatory actions under neurotoxic conditions.

Effect of chondroitin sulphate in a rabbit model of atherosclerosis aggravated by chronic arthritis.

BACKGROUND AND PURPOSE: Among the agents employed to manage osteoarthritis, chondroitin sulphate (CS) is a natural glycosaminoglycan with an anti-inflammatory effect on joint cells. CS might also influence the inflammatory component of atherosclerosis. Our aim was to examine the effect of CS administration on vascular injury and on markers of systemic inflammation in a rabbit model of atherosclerosis aggravated by systemic inflammation provoked by chronic antigen-induced arthritis. EXPERIMENTAL APPROACH: Atherosclerosis was induced in rabbits by maintaining them on a hyperlipidaemic diet after producing an endothelial lesion in the femoral arteries. Simultaneously, chronic arthritis was induced in these animals by repeated intraarticular injections of ovalbumin in previously immunized rabbits. A group of these rabbits were treated prophylactically with CS (100 mg kg(-1)day(-1)) and when the animals were killed, serum and peripheral blood mononuclear cells (PBMC) were isolated. Furthermore, femoral arteries and thoracic aorta were used for gene expression studies and histological examination. KEY RESULTS: CS administration reduced the concentration of the proinflammatory molecules C-reactive protein and IL-6 in serum. Likewise, CS inhibited the expression of CCL2/monocyte chemoattractant protein (MCP)-1 and cyclooxygenase (COX)-2 in PBMC, and reduced the nuclear translocation of nuclear factor-kappaB. In the femoral lesion, CS also diminished the expression of CCL2 and COX-2, as well as the ratio of the intima/media thickness. Moreover, CS decreased the percentage of rabbits with atherosclerosis and chronic arthritis that developed vascular lesions in the aorta. CONCLUSIONS AND IMPLICATIONS: These findings suggest that CS treatment may to some extent impede the progression of atherosclerosis.

Efecto de condroitín sulfato y ácido hialurónico (500-730 kDa) sobre la síntesis de estromelisina (MMP-3) y MMP-1 en cultivo de condrocitos humanos / Effect of chondroitin sulfate and hyaluronic acid (500-730 kDa) on synthesis of stromelysin (MMP-3) and MMP-1 in human chondrocyte cultures

Introducción: El condroitín sulfato (CS) y el ácido hialurónico (AH) son fármacos que se utilizan para el tratamiento sintomático de la artrosis (AO). La colagenasa-1 (MMP-1) y la estromelisina-1 (MMP-3) son 2 enzimas proteolíticas encargadas de la degradación de la matriz extracelular en la AO. Pocos estudios han determinado el efecto in vitro de CS y AH sobre la síntesis de MMP-1 y de AH sobre la expresión de MMP-3 en cultivos de condrocitos humanos artrósicos, y en la bibliografía que se ha revisado no hay estudios que evalúen el efecto de CS sobre MMP-3. Objetivos: Analizar el efecto de CS y AH (500-730 kDa) sobre la síntesis de MMP-3 y MMP-1 inducida por interleucina 1â (IL-1â) en condrocitos artrósicos. Material y métodos: Los condrocitos se incubaron durante 48 h con IL-1â (2,5 ng/ml) en presencia o ausencia de diferentes concentraciones de AH (Hyalgan®, Bioibérica Farma) o CS (Condrosan®, Bioibérica Farma) (10, 50, 100, 150, 200 y 1.000 ìg/ml). La valoración funcional de los condrocitos se realizó mediante enzimoinmunoanálisis de los valores de MMP- 1 y MMP-3. Resultados: CS y AH inhiben la síntesis de MMP-3 inducida por IL-1â, sin afectar de forma significativa a los valores de MMP-1. CS y AH redujeron los valores de expresión de la MMP-3 a todas las concentraciones estudiadas, sin que se encontraran diferencias estadísticamente significativas entre dichas concentraciones. Conclusiones: Nuestro estudio demuestra por primera vez que CS inhibe la síntesis de MMP-3 en el cartílago artrósico y corrobora los escasos datos existentes sobre la capacidad de AH de inhibir dicha enzima(AU)

Introduction: Chondroitin sulfate (CS) and hyaluronic acid (HA) are used in the symptomatic treatment of osteoarthritis (OA). Cholagenase-1 (MMP-1) and stromelysin-1 (MMP-3), are responsible for degradation of the extracellular matrix in OA. Few studies have determined the in vitro effect of CS and HA on MMP-1 synthesis and that of HA on MMP-3 expression in human OA chondrocyte culture. In the literature reviewed, there were no studies evaluating the effect of CS on MMP-3. Objectives: To analyze the effect of CS and HA (500- 730 kDa) on MMP-3 and MMP-1 synthesis induced by interleukin-1â (IL-1â) in OA chondrocytes. Material and methods: Chondrocytes were incubated for 48 hours with IL-1â (2.5 ng/ml) in the presence or absence of different HA concentrations (Hyalgan®, Bioibérica Farma) (10, 50, 100, 150, 200 and 1000 ìg/ml). Functional evaluation of chondrocytes was performed by enzyme-immunoanalysis of MMP-1 and MMP-3 levels. Results: CS and HA inhibited IL-1â-induced MMP-3 synthesis, without significantly modifying MMP-1. CS and HA reduced levels of MMP-3 expression at all the studied concentrations, with no statistically significant differences among these concentrations. Conclusions: The results of this study show for the first time that CS inhibits MMP-3 synthesis in OA cartilage. and corroborates the few existing data on the ability of HA to inhibit this enzyme(AU)

Chondroitin sulfate and hyaluronic acid (500-730 kda) inhibit stromelysin-1 synthesis in human osteoarthritic chondrocytes.

Chondroitin sulfate (CS) and 500-730 kDa hyaluronic acid (HA) are symptomatic slow-acting drugs for the treatment of osteoarthritis (OA). In addition, a growing body of evidence suggests a role for CS and this specific HA as modifiers of the course of OA. The therapeutic efficacy of CS and HA lies in their different mechanisms of action. Stromelysin-1 (metalloprotease-3 [MMP-3]) is a cartilage proteolytic enzyme, which induces cartilage destruction and acts as a mediator of the inflammatory response. However, there are few studies evaluating the in vitro effect of CS and HA on MMP-3 synthesis in human chondrocyte cultures from OA patients. Thus, the aim of the present study was to analyze the effect of CS and HA (500-730 kDa) on MMP-3 synthesis induced by interleukin-1beta (IL-1beta) in chondrocytes from patients with hip OA. Chondrocyte cultures were incubated for 48 h with IL-1beta (2.5 ng/ml) in the absence or presence of different HA 500-730 kDa (Hyalgan, Bioibérica Farma, Barcelona, Spain) concentrations, or alternatively, CS (Condro.san, Bioibérica Farma) at concentrations of 10, 50, 100, 150, 200 and 1,000 microg/ml. The results revealed that both CS and HA (500-730 kDa) inhibited MMP-3 synthesis induced by IL-1beta in human OA chondrocytes. Specifically, CS and HA (500-730 kDa) reduced MMP-3 expression levels at all tested concentrations. Therefore, our study provides new data on the mechanism of action of these drugs, which could help to explain their clinical efficacy in OA patients.

[Effect of chondroitin sulfate and hyaluronic acid (500-730 kDa) on synthesis of stromelysin (MMP-3) and MMP-1 in human chondrocyte cultures]. / Efecto de condroitín sulfato y ácido hialurónico (500-730 kDa) sobre la síntesis de estromelisina (MMP-3) y MMP-1 en cultivo de condrocitos humanos.

INTRODUCTION: Chondroitin sulfate (CS) and hyaluronic acid (HA) are used in the symptomatic treatment of osteoarthritis (OA). Cholagenase-1 (MMP-1) and stromelysin-1 (MMP-3), are responsible for degradation of the extracellular matrix in OA. Few studies have determined the in vitro effect of CS and HA on MMP-1 synthesis and that of HA on MMP-3 expression in human OA chondrocyte culture. In the literature reviewed, there were no studies evaluating the effect of CS on MMP-3. OBJECTIVES: To analyze the effect of CS and HA (500-730 kDa) on MMP-3 and MMP-1 synthesis induced by interleukin-1ß (IL-1ß) in OA chondrocytes. MATERIAL AND METHODS: Chondrocytes were incubated for 48 hours with IL-1ß (2.5 ng/ml) in the presence or absence of different HA concentrations (Hyalgan®, Bioibérica Farma) (10, 50, 100, 150, 200 and 1000 µg/ml). Functional evaluation of chondrocytes was performed by enzyme-immunoanalysis of MMP-1 and MMP-3 levels. RESULTS: CS and HA inhibited IL-1ß-induced MMP-3 synthesis, without significantly modifying MMP-1. CS and HA reduced levels of MMP-3 expression at all the studied concentrations, with no statistically significant differences among these concentrations. CONCLUSIONS: The results of this study show for the first time that CS inhibits MMP-3 synthesis in OA cartilage. and corroborates the few existing data on the ability of HA to inhibit this enzyme.

DAG accumulation from saturated fatty acids desensitizes insulin stimulation of glucose uptake in muscle cells.

The increased availability of saturated lipids has been correlated with development of insulin resistance, although the basis for this impairment is not defined. This work examined the interaction of saturated and unsaturated fatty acids (FA) with insulin stimulation of glucose uptake and its relation to the FA incorporation into different lipid pools in cultured human muscle. It is shown that basal or insulin-stimulated 2-deoxyglucose uptake was unaltered in cells preincubated with oleate, whereas basal glucose uptake was increased and insulin response was impaired in palmitate- and stearate-loaded cells. Analysis of the incorporation of FA into different lipid pools showed that palmitate, stearate, and oleate were similarly incorporated into phospholipids (PL) and did not modify the FA profile. In contrast, differences were observed in the total incorporation of FA into triacylglycerides (TAG): unsaturated FA were readily diverted toward TAG, whereas saturated FA could accumulate as diacylglycerol (DAG). Treatment with palmitate increased the activity of membrane-associated protein kinase C, whereas oleate had no effect. Mixture of palmitate with oleate diverted the saturated FA toward TAG and abolished its effect on glucose uptake. In conclusion, our data indicate that saturated FA-promoted changes in basal glucose uptake and insulin response were not correlated to a modification of the FA profile in PL or TAG accumulation. In contrast, these changes were related to saturated FA being accumulated as DAG and activating protein kinase C. Therefore, our results suggest that accumulation of DAG may be a molecular link between an increased availability of saturated FA and the induction of insulin resistance.

Overexpression of protein targeting to glycogen in cultured human muscle cells stimulates glycogen synthesis independent of glycogen and glucose 6-phosphate levels.

There is growing evidence that glycogen targeting subunits of protein phosphatase-1 play a critical role in regulation of glycogen metabolism. In the current study, we have investigated the effects of adenovirus-mediated overexpression of a specific glycogen targeting subunit known as protein targeting to glycogen (PTG) in cultured human muscle cells. PTG was overexpressed both in muscle cells cultured at high glucose (glycogen replete) or in cells incubated for 18 h in the absence of glucose and then incubated in high glucose (glycogen re-synthesizing). In both glycogen replete and glycogen resynthesizing cells, PTG overexpression caused glycogen to be synthesized at a linear rate 1-5 days after viral treatment, while in cells treated with a virus lacking a cDNA insert (control virus), glycogen content reached a plateau at day 1 with no further increase. In the glycogen replete PTG overexpressing cells, glycogen content was 20 times that in controls at day 5. Furthermore, in cells undergoing glycogen resynthesis, PTG overexpression caused a doubling of the initial rate of glycogen synthesis over the first 24 h relative to cells treated with control virus. In both sets of experiments, the effects of PTG on glycogen synthesis were correlated with a 2-3-fold increase in glycogen synthase activity state, with no changes in glycogen phosphorylase activity. The alterations in glycogen synthase activity were not accompanied by changes in the intracellular concentration of glucose 6-phosphate. We conclude that PTG overexpression activates glycogen synthesis in a glucose 6-phosphate-independent manner in human muscle cells while overriding glycogen-mediated inhibition. Our findings suggest that modulation of PTG expression in muscle may be a mechanism for enhancing muscle glucose disposal and improving glucose tolerance in diabetes.

Glycogen depletion rather than glucose 6-P increments controls early glycogen recovery in human cultured muscle.

In glycogen-containing muscle, glycogenesis appears to be controlled by glucose 6-phosphate (6-P) provision, but after glycogen depletion, an autoinhibitory control of glycogen could be a determinant. We analyzed in cultured human muscle the contribution of glycogen depletion versus glucose 6-P in the control of glycogen recovery. Acute deglycogenation was achieved by engineering cells to overexpress glycogen phosphorylase (GP). Cells treated with AdCMV-MGP adenovirus to express 10 times higher active GP showed unaltered glycogen relative to controls at 25 mM glucose, but responded to 6-h glucose deprivation with more extensive glycogen depletion. Glycogen synthase (GS) activity ratio was double in glucose-deprived AdCMV-MGP cells compared with controls, despite identical glucose 6-P. The GS activation peak (30 min) induced by glucose reincubation dose dependently correlated with glucose 6-P concentration, which reached similar steady-state levels in both cell types. GS activation was significantly blunted in AdCMV-MGP cells, whereas it strongly correlated, with an inverse relationship, with glycogen content. An initial (0-1 h) rapid insulin-independent glycogen resynthesis was observed only in AdCMV-MGP cells, which progressed up to glycogen levels approximately 150 micrograms glucose/mg protein; control cells, which did not deplete glycogen below this concentration, showed a 1-h lag time for recovery. In summary, acute deglycogenation, as achieved by GP overexpression, caused the activation of GS, which inversely correlated with glycogen replenishment independent of glucose 6-P. During glycogen recovery, the activation promoted by acute deglycogenation rendered GS effective for controlling glycogenesis, whereas the transient activation of GS induced by the glucose 6-P rise had no impact on the resynthesis rate. We conclude that the early insulin-independent glycogen resynthesis is dependent on the activation of GS due to GP-mediated exhaustion of glycogen rather than glucose 6-P provision.

Expression of glucokinase in cultured human muscle cells confers insulin-independent and glucose concentration-dependent increases in glucose disposal and storage.

Insulin resistance, as is found in skeletal muscle of individuals with obesity and NIDDM, appears to involve a reduced capacity of the hormone to stimulate glucose uptake and/or phosphorylation. The glucose phosphorylation step, as catalyzed by hexokinase II, has been described as rate limiting for glucose disposal in muscle, but overexpression of this enzyme under control of a muscle-specific promoter in transgenic mice has had limited metabolic impact. In the current study, we investigated in a cultured muscle model whether expression of glucokinase, which in contrast to hexokinase II is not inhibited by glucose-6-phosphate (G-6-P), would have a pronounced metabolic impact. We used a recombinant adenovirus containing the cDNA-encoding rat liver glucokinase (AdCMV-GKL) to increase the glucose phosphorylating activity in cultured human muscle cells by fourfold. G-6-P levels increased in AdCMV-GKL-treated cells in a glucose concentration-dependent manner over the range of 1-30 mmol/l, whereas the much smaller increases in G-6-P in control cells were maximal at glucose concentrations <5 mmol/l. Further, cells expressing glucokinase accumulated 17 times more 2-deoxyglucose-6-phosphate than control cells. In AdCMV-GKL-treated cells, the time-dependent rise in G-6-P correlated with an increase in the activity ratio of glycogen synthase. AdCMV-GKL-treated cells also exhibited a 2.5- to 3-fold increase in glycogen content and a four- to fivefold increase in glycolytic flux, proportional to the increase in glucose phosphorylating capacity. All of these observations were made in the absence of insulin. Thus we concluded that expression of glucokinase in cultured human muscle cells results in proportional increases in insulin-independent glucose disposal, and that muscle glucose storage and utilization becomes controlled in a glucose concentration-dependent manner in AdCMV-GKL-treated cells. These results encourage testing whether delivery of glucokinase to muscle in vivo has an impact on glycemic control, which could be a method for circumventing the failure of insulin to stimulate glucose uptake and/or phosphorylation in muscle normally in insulin-resistant subjects.

Overexpression of glycogen phosphorylase increases GLUT4 expression and glucose transport in cultured skeletal human muscle.

Skeletal muscle glucose utilization, a major factor in the control of whole-body glucose tolerance, is modulated in accordance with the muscle metabolic demand. For instance, it is increased in chronic contraction or exercise training in association with elevated expression of GLUT4 and hexokinase II (HK-II). In this work, the contribution of increased metabolic flux to the regulation of the glucose transport capacity was analyzed in cultured human skeletal muscle engineered to overexpress glycogen phosphorylase (GP). Myocytes treated with an adenovirus-bearing muscle GP cDNA (AdCMV-MGP) expressed 10 times higher GP activity and exhibited a twofold increase in the Vmax for 2-deoxy-D-[3H]glucose (2-DG) uptake, with no effect on the apparent Km. The stimulatory effect of insulin on 2-DG uptake was also markedly enhanced in AdCMV-MGP-treated cells, which showed maximal insulin stimulation 2.8 times higher than control cells. No changes in HKII total activity or the intracellular compartmentalization were found. GLUT4, protein, and mRNA were raised in AdCMV-MGP-treated cells, suggesting pretranslational activation. GLUT4 was immunodetected intracellularly with a perinuclear predominance. Culture in glucose-free or high-glucose medium did not alter GLUT4 protein content in either control cells or AdCMV-MGP-treated cells. Control and GP-overexpressing cells showed similar autoinhibition of glucose transport, although they appeared to differ in the mechanism(s) involved in this effect. Whereas GLUT1 protein increased in control cells when they were switched from a high-glucose to a glucose-free medium, GLUT1 remained unaltered in GP-expressing cells upon glucose deprivation. Therefore, the increased intracellular metabolic (glycogenolytic-glycolytic) flux that occurs in muscle cells overexpressing GP causes an increase in GLUT4 expression and enhances basal and insulin-stimulated glucose transport, without significant changes in the autoinhibition of glucose transport. This mechanism of regulation may be operative in the postexercise situation in which GLUT4 expression is upregulated in coordination with increased glycolytic flux and energy demand.