ATIC as a link between antirheumatic drugs and regulation of energy metabolism in skeletal muscle

Chronic inflammatory rheumatic diseases, such as rheumatoid arthritis, psoriatic arthritis, and systemic lupus erythematosus, increase the risk of developing insulin resistance, metabolic syndrome, and/or type 2 diabetes. While inflammation is thought to be a major mechanism underlying metabolic dysregulation in rheumatic diseases, antirheumatic drugs that exert direct metabolic effects in addition to suppressing inflammation, might be particularly useful to prevent metabolic complications. Here we review antirheumatic drugs, such as methotrexate, that inhibit ATIC, the final enzyme in the de novo purine biosynthesis, responsible for conversion of ZMP to IMP. Inhibition of ATIC results in accumulation of ZMP, thus promoting activation of AMP-activated kinase (AMPK), a major regulator of cellular energy metabolism and one of the most promising targets for the treatment of insulin resistance and type 2 diabetes. We focus especially on ATIC inhibition and AMPK activation in skeletal muscle as this is the largest and one of the most metabolically active tissues with a major role in glucose homeostasis. As an important site of insulin resistance, skeletal muscle is also one of the main target tissues for pharmacological therapy of type 2 diabetes. Finally, we review the metabolic effects of ATIC-inhibiting antirheumatic drugs and discuss whether these drugs might improve systemic glucose homeostasis by inhibiting ATIC and activating AMPK in skeletal muscle.</p

Učinci imidazolijevih i kloriranih bispiridinijevih oksima povezani s njihovom toksičnosti na stanicama SH-SY5Y

Current research has shown that several imidazolium and chlorinated bispyridinium oximes are cytotoxic and activate different mechanisms or types of cell death. To investigate this further, we analysed interactions between these oximes and acetylcholine receptors (AChRs) and how they affect several signalling pathways to find a relation between the observed toxicities and their effects on these specific targets. Chlorinated bispyridinium oximes caused time-dependent cytotoxicity by inhibiting the phosphorylation of STAT3 and AMPK without decreasing ATP and activated ERK1/2 and p38 MAPK signal cascades. Imidazolium oximes induced a time-independent and significant decrease in ATP and inhibition of the ERK1/2 signalling pathway along with phosphorylation of p38 MAPK, AMPK, and ACC. These pathways are usually triggered by a change in cellular energy status or by external signals, which suggests that oximes interact with some membrane receptors. Interestingly, in silico analysis also indicated that the highest probability of interaction for all of our oximes is with the family of G-coupled membrane receptors (GPCR). Furthermore, our experimental results showed that the tested oximes acted as acetylcholine antagonists for membrane AChRs. Even though oxime interactions with membrane receptors need further research and clarification, our findings suggest that these oximes make promising candidates for the development of specific therapies not only in the field of cholinesterase research but in other fields too, such as anticancer therapy via altering the Ca2+ flux involved in cancer progression.Praćenjem učinka odabranih imidazolijevih i kloriranih bispiridinijevih oksima utvrđeno je da uzrokuju citotoksičnost i aktiviraju različite mehanizme ili tipove stanične smrti. Kako bismo to detaljnije istražili, analizirali smo aktivaciju nekoliko signalnih putova, kao i interakcije acetilkolinskih receptora (AChR) s navedenim oksimima te procijenili može li se opaženi toksični učinak objasniti njihovim utjecajem na ove specifične mete. Rezultati su pokazali da su klorirani bispiridinijevi oksimi prouzročili vremenski-ovisnu citotoksičnost, bez smanjenja razine ATP-a uz aktivaciju ERK1/2 i p38 MAPK-vezanih signalnih kaskada i inhibiciju fosforilacije STAT3 i AMPK proteina. Imidazolijevi oksimi djelovali su vremenski neovisno, uz značajno smanjenje razine ATP-a i inhibiciju ERK1/2 signalnog puta te fosforilaciju p38 MAPK, AMPK i ACC proteina. Navedeni signalni putovi obično se aktiviraju ili promjenom unutarnjega staničnog statusa, osobito energetskoga, ili vanjskim signalima, što upućuje na moguće interakcije oksima s nekim membranskim receptorima. Zanimljivo, in silico analizom procijenjeno je da je najvjerojatnija interakcija testiranih oksima s porodicom G-protein-spregnutih membranskih receptora (GPCR). K tomu, eksperimentalno je potvrđeno da testirani oksimi djeluju kao mogući antagonisti acetilkolina za vezanje na membranske AChR, potvrđujući tako i računalnu in silico procjenu. Iako interakcije ispitanih oksima s membranskim receptorima treba dodatno potvrditi, takve bi ih interakcije učinile kandidatima za razvoj specifičnih terapija u drugim područjima istraživanja, osim u istraživanjima povezanima s kolinesterazama, npr. kao moguće protutumorske lijekove, putem utjecaja na fluks iona Ca2+ uključenoga u progresiju tumora

HIF-1 alpha response to hypoxia is functionally separated from the glucocorticoid stress response in the in vitro regenerating human skeletal muscle

Pirkmajer S, Filipovic D, Mars T, Mis K, Grubic Z. HIF-1 alpha response to hypoxia is functionally separated from the glucocorticoid stress response in the in vitro regenerating human skeletal muscle. Am J Physiol Regul Integr Comp Physiol 299: R1693-R1700, 2010. First published October 13, 2010; doi:10.1152/ajpregu.00133.2010.-Injury of skeletal muscle is followed by muscle regeneration in which new muscle tissue is formed from the proliferating mononuclear myoblasts, and by systemic response to stress that exposes proliferating myoblasts to increased glucocorticoid (GC) concentration. Because of its various causes, hypoxia is a frequent condition affecting skeletal muscle, and therefore both processes, which importantly determine the outcome of the injury, often proceed under hypoxic conditions. It is therefore important to identify and characterize in proliferating human myoblasts: 1) response to hypoxia which is generally organized by hypoxia-inducible factor-1 alpha (HIF-1 alpha); 2) response to GCs which is mediated through the isoforms of glucocorticoid receptors (GRs) and 11 beta-hydroxysteroid dehydrogenases (11 beta-HSDs), and 3) the response to GCs under the hypoxic conditions and the influence of this combination on the factors controlling myoblast proliferation. Using real-time PCR, Western blotting, and HIF-1 alpha small-interfering RNA silencing, we demonstrated that cultured human myoblasts possess both, the HIF-1 alpha-based response to hypoxia, and the GC response system composed of GR alpha and types 1 and 2 11 beta-HSDs. However, using combined dexamethasone and hypoxia treatments, we demonstrated that these two systems operate practically without mutual interactions. A seemingly surprising separation of the two systems that both organize response to hypoxic stress can be explained on the evolutionary basis: the phylogenetically older HIF-1 alpha response is a protection at the cellular level, whereas the GC stress response protects the organism as a whole. This necessitates actions, like downregulation of IL-6 secretion and vascular endothelial growth factor, that might not be of direct benefit for the affected myoblasts

C-Peptide Increases Na,K-ATPase Expression via PKC- and MAP Kinase-Dependent Activation of Transcription Factor ZEB in Human Renal Tubular Cells

Replacement of proinsulin C-peptide in type 1 diabetes ameliorates nerve and kidney dysfunction, conditions which are associated with a decrease in Na,K-ATPase activity. We determined the molecular mechanism by which long term exposure to C-peptide stimulates Na,K-ATPase expression and activity in primary human renal tubular cells (HRTC) in control and hyperglycemic conditions.HRTC were cultured from the outer cortex obtained from patients undergoing elective nephrectomy. Ouabain-sensitive rubidium ((86)Rb(+)) uptake and Na,K-ATPase activity were determined. Abundance of Na,K-ATPase was determined by Western blotting in intact cells or isolated basolateral membranes (BLM). DNA binding activity was determined by electrical mobility shift assay (EMSA). Culturing of HRTCs for 5 days with 1 nM, but not 10 nM of human C-peptide leads to increase in Na,K-ATPase α(1)-subunit protein expression, accompanied with increase in (86)Rb(+) uptake, both in normal- and hyperglycemic conditions. Na,K-ATPase α(1)-subunit expression and Na,K-ATPase activity were reduced in BLM isolated from cells cultured in presence of high glucose. Exposure to1 nM, but not 10 nM of C-peptide increased PKCε phosphorylation as well as phosphorylation and abundance of nuclear ERK1/2 regardless of glucose concentration. Exposure to 1 nM of C-peptide increased DNA binding activity of transcription factor ZEB (AREB6), concomitant with Na,K-ATPase α(1)-subunit mRNA expression. Effects of 1 nM C-peptide on Na,K-ATPase α(1)-subunit expression and/or ZEB DNA binding activity in HRTC were abolished by incubation with PKC or MEK1/2 inhibitors and ZEB siRNA silencing.Despite activation of ERK1/2 and PKC by hyperglycemia, a distinct pool of PKCs and ERK1/2 is involved in regulation of Na,K-ATPase expression and activity by C-peptide. Most likely C-peptide stimulates sodium pump expression via activation of ZEB, a transcription factor that has not been previously implicated in C-peptide-mediated signaling. Importantly, only physiological concentrations of C-peptide elicit this effect

Terminologija klinične prehrane: Motnje prehranjenosti in s prehranjenostjo povezana stanja

Izhodišča: Prehransko stanje posameznika uvrščamo med ključne dejavnike njegovega zdravja. Za učinkovito individualno in multidisciplinarno obravnavo stanj, povezanih s prehranskim stanjem posameznika, moramo dobro poznati terminologijo klinične prehrane. Ker je klinična prehrana kot medicinska stroka razvita tudi pri nas, v tujini pa so tovrstni terminološki dokumenti že na voljo, želimo tudi v Sloveniji na podlagi konsenza oblikovati enotno terminologijo. Metode: Prispevek je osnovan na podlagi eksplicitnega terminološkega dogovora. K sodelovanju smo povabili obsežno skupino relevantnih slovenskih strokovnjakov s kliničnih, predkliničnih in drugih področij, ki so povezana z dejavnostjo klinične prehrane v medicini, pri oblikovanju pa je sodeloval tudi terminolog s področja medicine. Kot izhodišče smo izbrali terminološke smernice Evropskega združenja za klinično prehrano in presnovo ter ob njih upoštevali najnovejša strokovna priporočila za posamezne pojme. Avtorji so bili v stiku prek osebnih srečanj in elektronske pošte. Pri končnem oblikovanju konsenza je sodelovalo 42 avtorjev iz 19 slovenskih ustanov. Rezultati: Predstavljamo temeljne pojme, terminološke definicije in pripadajoče slovenske termine s področja klinične prehrane. Opredelili smo osnovne motnje prehranjenosti – podhranjenost, prekomerno hranjenost, neravnovesje mikrohranil in sindrom ponovnega hranjenja. Poleg tega smo opredelili tudi s prehranjenostjo povezana stanja – sarkopenijo in krhkost. Osnovne pojme smo podprli s kliničnim kontekstom, v katerem nastopajo. Zaključki: Poenoteno razumevanje osnovnih patoloških stanj, ki jih obravnava klinična prehrana, je izhodišče za nadaljnji razvoj stroke, poleg tega pa je podlaga tudi za prehransko obravnavo in učinkovito prehransko oskrbo

Terminologija klinične prehrane: Prehranska obravnava – presejanje prehranske ogroženosti in prehranski pregled

Izhodišča: Pomembno vlogo pri prehranski obravnavi imata tako presejanje prehranske ogroženosti kot prehranski pregled, na podlagi katerega lahko postavimo diagnozo motnje prehranjenosti ali s prehranjenostjo povezane motnje. Ocena posameznikovega prehranskega stanja, ki jo pridobimo s prehransko obravnavo, je namreč ključna za načrtovanje učinkovite prehranske oskrbe. Za razvoj področja je pomembno, da so vsi termini, ki se uporabljajo pri kliničnem delu, usklajeni. Taki terminološki dokumenti v mednarodnem prostoru že obstajajo, smiselni pa so tudi za slovenščino in naše okolje. Metode: Prispevek temelji na eksplicitnem terminološkem dogovoru skupine 42 relevantnih slovenskih strokovnjakov iz 19 slovenskih ustanov. Osnova oblikovanja terminoloških smernic je terminološki dokument Evropskega združenja za klinično prehrano in presnovo, pri čemer so bili upoštevani tudi novejši izsledki klinične prehrane. Rezultati: Predstavljeni so slovenski termini in terminološke definicije s področja klinične prehrane. Opredeljeni so osnovni pojmi s področja prehranske obravnave, ki je praviloma del medicinske obravnave. Predstavljena sta pojma prehranska ogroženost in presejanje prehranske ogroženosti, ob čemer so navedeni tudi različni presejalni testi za presejanje prehranskih motenj in s prehranjenostjo povezanih stanj. Podrobno so opredeljeni tudi prehranski pregled in njegovi sestavni deli. Zaključki: Tako presejanje prehranske ogroženosti kot prehranski pregled sta bistvena za diagnostično obravnavo v okviru klinične prehrane, poenoteno razumevanje terminologije pa omogoča primerno prepoznavo patoloških stanj pri bolnikih in pripravo ustreznega načrta prehranskih ukrepov

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery