Creatine supplementation in health and disease: What is the evidence for long-term efficacy?

Creatine supplementation is an established ergogenic aid in sports and is now claimed to have therapeutical applications in a variety of diseases. The available literature mainly covers the short-term (one to several weeks) effects of creatine supplementation on skeletal muscle function in health and disease, which is of little help to evaluate the long-term (two or more months) potential of creatine as a drug in chronic disorders, such as neurodegenerative diseases or muscular dystrophies. Recent findings in healthy humans indicate that the beneficial effect on muscle function and muscle total creatine content may disappear when creatine is continuously ingested for more than two or three months. The mechanism for this habituation to chronic creatine exposure is poorly understood. The primary purpose of the present review article is to critically evaluate the available evidence for long-term efficacy of creatine administration and to hypothesize about ways to optimize creatine administration regimens.     

Stenosis differentially affects subendocardial and subepicardial arterioles in vivo

The presence of a coronary stenosis results primarily in subendocardial ischemia. Apart from the decrease in coronary perfusion pressure, a stenosis also decreases coronary flow pulsations. Applying a coronary perfusion system, we compared the autoregulatory response of subendocardial (n = 10) and subepicardial (n = 12) arterioles (<120 microm) after stepwise decreases in coronary arterial pressure from 100 to 70, 50, and 30 mmHg in vivo in dogs (n = 9). Pressure steps were performed with and without stenosis on the perfusion line. Maximal arteriolar diameter during the cardiac cycle was determined and normalized to its value at 100 mmHg. The initial decrease in diameter during reductions in pressure was significantly larger at the subendocardium. Diameters of subendocardial and subepicardial arterioles were similar 10--15 s after the decrease in pressure without stenosis. However, stenosis decreased the dilatory response of the subendocardial arterioles significantly. This decreased dilatory response was also evidenced by a lower coronary inflow at similar average pressure in the presence of a stenosis. Inhibition of nitric oxide production with N(G)-monomethyl-L-arginine abrogated the effect of the stenosis on flow. We conclude that the decrease in pressure caused by a stenosis in vivo results in a larger decrease in diameter of the subendocardial arterioles than in the subepicardial arterioles, and furthermore stenosis selectively decreases the dilatory response of subendocardial arterioles. These two findings expand our understanding of subendocardial vulnerability to ischemia.     

Dynamics of flow, resistance, and intramural vascular volume in canine coronary circulation

Varying coronary volume will vary vascular resistance and thereby have an effect on coronary hemodynamics. Six ventricular septa were isolated from anesthetized dogs, dispersed in a biaxial stretch apparatus at diastolic stress, and perfused artificially with an oxygenated perfluorochemical emulsion at maximal vasodilation. Flow and thickness were measured continuously by an electromagnetic flow probe and sonomicrometer. Pressure was varied sinusoidally around 30, 50, and 70 mmHg with an amplitude of 7.5 mmHg; frequencies ranged between 0.015 and 7 Hz. Bode plots of admittance (flow/pressure) and capacitance (scaled thickness/pressure) were constructed. A two-compartment model was used in which the resistances vary with volume. Realistic values of microvascular compliance ( approximately 0.3 ml x mmHg(-1) x 100 g(-1)) were found. Values 10 times higher were then found when resistances were forced to be constant. We concluded that volume dependence of resistances have to be taken into account when dynamic or static pressure-flow relations are studied and conceal the effect of a large intramyocardial compliance on arterial hemodynamics.     

Development of a Lipase Fermentation Process That Uses a Recombinant Pseudomonas alcaligenes Strain

Pseudomonas alcaligenes M-1 secretes an alkaline lipase, which has excellent characteristics for the removal of fatty stains under modern washing conditions. A fed-batch fermentation process based on the secretion of the alkaline lipase from P. alcaligenes was developed. Due to the inability of P. alcaligenes to grow on glucose, citric acid and soybean oil were applied as substrates in the batch phase and feed phase, respectively. The gene encoding the high-alkaline lipase from P. alcaligenes was isolated and characterized. Amplification of lipase gene copies in P. alcaligenes with the aid of low- and high-copy-number plasmids resulted in an increase of lipase expression that was apparently colinear with the gene copy number. It was found that overexpression of the lipase helper gene, lipB, produced a stimulating effect in strains with high copy numbers (>20) of the lipase structural gene, lipA. In strains with lipA on a low-copy-number vector, the lipB gene did not show any effect, suggesting that LipB is required in a low ratio to LipA only. During scaling up of the fermentation process to 100 m³, severe losses in lipase productivity were observed. Simulations have identified an increased level of dissolved carbon dioxide as the most probable cause for the scale-up losses. A large-scale fermentation protocol with a reduced dissolved carbon dioxide concentration resulted in a substantial elimination of the scale-up loss.     

Role of Calcineurin in Ca2+-Induced Release of Catecholamines and Neuropeptides

Abstract: Neurotransmission requires rapid docking, fusion, and recycling of neurotransmitter vesicles. Several of the proteins involved in this complex Ca²⁺-regulated mechanism have been identified as substrates for protein kinases and phosphatases, e.g., the synapsins, synaptotagmin, rabphilin3A, synaptobrevin, munc18, MARCKS, dynamin I, and B-50/GAP-43. So far most attention has focused on the role of kinases in the release processes, but recent evidence indicates that phosphatases may be as important. Therefore, we investigated the role of the Ca²⁺/calmodulin-dependent protein phosphatase calcineurin in exocytosis and subsequent vesicle recycling. Calcineurin-neutralizing antibodies, which blocked dynamin I dephosphorylation by endogenous synaptosomal calcineurin activity, but had no effect on the activity of protein phosphatases 1 or 2A, were introduced into rat permeabilized nerve terminals and inhibited Ca²⁺-induced release of [³H]noradrenaline and neuropeptide cholecystokinin-8 in a specific and concentration-dependent manner. Our data show that the Ca²⁺/calmodulin-dependent phosphatase calcineurin plays an essential role in exocytosis and/or vesicle recycling of noradrenaline and cholecystokinin-8, transmitters stored in large dense-cored vesicles.