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Preisler N.,Copenhagen University | Haller R.G.,University of Texas Southwestern Medical Center | Haller R.G.,The Veterans Affairs Medical Center | Haller R.G.,Institute for Exercise and Environmental Medicine of Presbyterian Hospital | Vissing J.,Copenhagen University
Journal of Inherited Metabolic Disease | Year: 2015

Glycogen storage diseases (GSD) are inborn errors of glycogen or glucose metabolism. In the GSDs that affect muscle, the consequence of a block in skeletal muscle glycogen breakdown or glucose use, is an impairment of muscular performance and exercise intolerance, owing to 1) an increase in glycogen storage that disrupts contractile function and/or 2) a reduced substrate turnover below the block, which inhibits skeletal muscle ATP production. Immobility is associated with metabolic alterations in muscle leading to an increased dependence on glycogen use and a reduced capacity for fatty acid oxidation. Such changes may be detrimental for persons with GSD from a metabolic perspective. However, exercise may alter skeletal muscle substrate metabolism in ways that are beneficial for patients with GSD, such as improving exercise tolerance and increasing fatty acid oxidation. In addition, a regular exercise program has the potential to improve general health and fitness and improve quality of life, if executed properly. In this review, we describe skeletal muscle substrate use during exercise in GSDs, and how blocks in metabolic pathways affect exercise tolerance in GSDs. We review the studies that have examined the effect of regular exercise training in different types of GSD. Finally, we consider how oral substrate supplementation can improve exercise tolerance and we discuss the precautions that apply to persons with GSD that engage in exercise. © 2014, SSIEM. Source

Vissing J.,Copenhagen University | Haller R.G.,University of Texas Southwestern Medical Center | Haller R.G.,The Veterans Affairs Medical Center | Haller R.G.,Institute for Exercise and Environmental Medicine of Presbyterian Hospital
Neuromuscular Disorders | Year: 2012

Exertional fatigue early in exercise is a clinical hallmark of muscle glycogenoses, which is often coupled with painful muscle contractures and episodes of myoglobinuria. A fundamental biochemical problem in these conditions is the impaired generation of ATP to fuel muscle contractions, which relates directly to the metabolic defect, but also to substrate-limited energy deficiency, as exemplified by the " second wind" phenomenon in McArdle disease. A number of secondary events may also play a role in inducing premature fatigue in glycogenoses, including (1) absent or blunted muscle acidosis, which may be important for maintaining muscle membrane excitability by decreasing chloride permeability, (2) loss of the osmotic effect related to lactate accumulation, which may account for absence of the normal increase in water content of exercised muscle, and thus promote higher than normal concentrations of extracellular potassium in exercising muscle and (3) exaggerated accumulation of ADP during exercise that may inhibit sodium-potassium and calcium-ATPases. Disorders of muscle glycogenolysis and glycolysis reveal the crucial role of these metabolic processes for supplying both anaerobic and aerobic energy for muscle contraction; and the pathological fatigue that occurs when glycogenolysis and/or glycolysis is blocked imply an important role for theses metabolic pathways in normal muscle fatigue. © 2012 Elsevier B.V. Source

Landazuri N.,Emory University | Joseph G.,Emory University | Guldberg R.E.,Georgia Institute of Technology | Robert Taylor W.,Emory University | And 2 more authors.
American Journal of Physiology - Regulatory Integrative and Comparative Physiology | Year: 2012

The formation of vascular networks during embryogenesis and early stages of development encompasses complex and tightly regulated growth of blood vessels, followed by maturation of some vessels, and spatially controlled disconnection and pruning of others. The adult vasculature, while more quiescent, is also capable of adapting to changing physiological conditions by remodeling blood vessels. Numerous studies have focused on understanding key factors that drive vessel growth in the adult in response to ischemic injury. However, little is known about the extent of vessel rarefaction and its potential contribution to the final outcome of vascular recovery. We addressed this topic by characterizing the endogenous phases of vascular repair in a mouse model of hindlimb ischemia. We showed that this process is biphasic. It encompasses an initial rapid phase of vessel growth, followed by a later phase of vessel rarefaction. In healthy mice, this process resulted in partial recovery of perfusion and completely restored the ability of mice to run voluntarily. Given that the ability to revascularize can be compromised by a cardiovascular risk factor such as diabetes, we also examined vascular repair in diabetic mice. We found that paradoxically both the initial growth and subsequent regression of collateral vessels were more pronounced in the setting of diabetes and resulted in impaired recovery of perfusion and impaired functional status. In conclusion, our findings demonstrate that the formation of functional collateral vessels in the hindlimb requires vessel growth and subsequent vessel rarefaction. In the setting of diabetes, the physiological defect was not in the initial formation of vessels but rather in the inability to sustain newly formed vessels. © 2012 the American Physiological Society. Source

Ulland T.K.,University of Iowa | Janowski A.M.,University of Iowa | Buchan B.W.,University of Iowa | Faron M.,University of Iowa | And 4 more authors.
Infection and Immunity | Year: 2013

Francisella tularensis is a Gram-negative bacterium and the causative agent of the diseasetularemia. Escape of F. tularensis from the phagosome into the cytosol of the macrophage triggers the activation of the AIM2 inflammasome through a mechanism that is not well understood. Activation of the AIM2 inflammasome results in autocatalytic cleavage of caspase-1, resulting in the processing and secretion of interleukin-1β (IL-1β) and IL-18, which play a crucial role in innate immune responses to F. tularensis. We have identified the 5-formyltetrahydrofolate cycloligase gene (FTL_0724) as being important for F. tularensis live vaccine strain (LVS) virulence. Infection of mice in vivo with a F. tularensis LVS FTL_0724 mutant resulted in diminished mortality compared to infection of mice with wild-type LVS. The FTL_0724 mutant also induced increased inflammasome-dependent IL-1β and IL-18 secretion and cytotoxicity in macrophages in vitro. In contrast, infection of macrophages with a F. tularensis LVS rluD pseudouridine synthase (FTL_0699) mutant resulted in diminished IL-1β and IL-18 secretion from macrophages in vitro compared to infection of macrophages with wild-type LVS. In addition, the FTL_0699 mutant was not attenuated in vivo. These findings further illustrate that F. tularensis LVS possesses numerous genes that influence its ability to activate the inflammasome, which is a key host strategy to control infection with this pathogen in vivo. © 2013, American Society for Microbiology. Source

Parker B.D.,University of California at San Diego | Schurgers L.J.,Maastricht University | Vermeer C.,Maastricht University | Schiller N.B.,University of California at San Francisco | And 4 more authors.
Atherosclerosis | Year: 2010

Objective: Mitral annular calcification (MAC) and aortic stenosis (AS) are associated with systemic calcification and cardiovascular disease (CVD) events. Matrix Gla protein (MGP) is an inhibitor of vascular calcification and lower levels of its precursor - uncarboxylated MGP (ucMGP) - are associated with vascular calcification in pilot studies. Methods and results: In this cross-sectional study of 839 outpatients with stable CVD, we measured serum ucMGP, and evaluated MAC and AS by echocardiography. The association of ucMGP with MAC differed by diabetes status (interaction P<0.001). Among participants without diabetes (n=615), higher ucMGP (per standard deviation [1178. nM] increase) was associated with lower odds of MAC (odds ratio [OR] 0.73; 95% confidence interval [CI] 0.55-0.97) in models adjusted for traditional CVD risk factors, C-reactive protein, and kidney function. Among persons with diabetes (n=221), higher ucMGP was associated with higher odds of MAC (OR 1.89; 95% CI 1.29-2.78). Results were qualitatively similar for the association of ucMGP with AS although not statistically significant. Conclusions: Among outpatients with stable CVD, higher ucMGP is associated with lower odds of MAC in persons without diabetes, and higher odds of MAC in persons with diabetes. Future studies should determine whether ucMGP levels are associated with CVD events, and whether such associations differ by diabetes status. © 2009. Source

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