Whole body and skeletal muscle glutamine metabolism in healthy subjects

We measured glutamine kinetics using L-[5-15N]glutamine and L-[ring-2H5]phenylalanine infusions in healthy subjects in the postabsorptive state and during ingestion of an amino acid mixture that included glutamine, alone or with additional glucose. Ingestion of the amino acid mixture increased arterial glutamine concentrations by approximately 20% (not by 30%; P < 0.05), irrespective of the presence or absence of glucose. Muscle free glutamine concentrations remained unchanged during ingestion of amino acids alone but decreased from 21.0 +/- 1.0 to 16.4 +/- 1.6 mmol/l (P < 0.05) during simultaneous ingestion of glucose due to a decrease in intramuscular release from protein breakdown and glutamine synthesis (0.82 +/- 0.10 vs. 0.59 +/- 0.06 micromol x 100 ml leg(-1) x min(-1); P < 0.05). In both protocols, muscle glutamine inward and outward transport and muscle glutamine utilization for protein synthesis increased during amino acid ingestion; leg glutamine net balance remained unchanged. In summary, ingestion of an amino acid mixture that includes glutamine increases glutamine availability and uptake by skeletal muscle in healthy subjects without causing an increase in the intramuscular free glutamine pool. Simultaneous ingestion of glucose diminishes the intramuscular glutamine concentration despite increased glutamine availability in the blood due to decreased glutamine production.     

Iron metabolism in the yeast

Current data concerning transport, storage and utilization of iron in the yeast cells, particularly Saccharomyces cerevisiae are summarized in the paper. It has been marked that iron uptake in the cells provides by high affinity system, it function is carried out by protein complex Fet3-Ftr1, and Fet4, protein with low affinity to iron ion. The both systems utilize Fe(II). Furthermore, the active site of the protein Fre1 is exposed on the outer side of plasmalemma. This protein, due to ferrireductase activity, provides availability of Fe(III) to the cell. The information regards to participation of siderophores and metal-proton plasma membrane exchangers Smf1 in iron transport is brought. Particular attention is given to regulation of expression of the genes, coding the iron metabolic systems. Some aspects of iron utilization for Fe-S-containing enzymes synthesis are lighted. It has been concluded that the yeast is a perspective subject for studying balance of living organisms between iron essentiality and its ability to trigger free radical reactions.     

Iron imports. IV. Hepcidin and regulation of body iron metabolism

Hepcidin, a small peptide synthesized in the liver, controls extracellular iron by regulating its intestinal absorption, placental transport, recycling by macrophages, and release from stores. Hepcidin inhibits the cellular efflux of iron by binding to and inducing the degradation of ferroportin, the sole iron exporter in iron-transporting cells. In turn, hepcidin synthesis is increased by iron loading and decreased by anemia and hypoxia. Hepcidin is markedly induced during inflammation, trapping iron in macrophages, decreasing plasma iron concentrations, and contributing to the anemia of inflammation. Hepcidin deficiency due to the dysregulation of its synthesis causes most known forms of hemochromatosis.     

Suppressor cells function in healthy persons

The investigations were performed on lymphocytes isolated from peripheral blood of 26 healthy persons aged from 20 to 68 years. The following parameters were evaluated: T suppressor cell activity in two-step culture, concanavalin A (Con A) responsiveness in three-day culture and number of T lymphocytes carrying receptor for Fc portion of immunoglobulin G (TG cells). A slight increase in T suppressor activity and diminished responsiveness to Con A have been shown to be age-dependent. A correlation has been found between suppressor cells activity in vitro and the percentage of TG cells (r = 0.62, p less than 0.05). The level of suppressor activity of lymphocytes was independent of their Con A responsiveness.     

Iron metabolism

The understanding of iron metabolism at the molecular level has been enormously expanded in recent years by new findings about the functioning of transferrin, the transferrin receptor and ferritin. Other recent developments include the discovery of the hemochromatosis gene HFE, identification of previously unknown proteins involved in iron transport, divalent metal transporter 1 and stimulator of Fe transport, and expanded insights into the regulation and expression of proteins involved in iron metabolism. Interactions among principal participants in iron transport have been uncovered, although the complexity of such interactions is still incompletely understood. Correlated efforts involving techniques and concepts of crystallography, spectroscopy and molecular biology applied to cellular processes have been, and should continue to be, particularly revealing.     

Iron metabolism

Major aspects of iron metabolism are reviewed including iron absorption, internal iron distribution and iron storage along with the development of laboratory tests for the evaluation of iron status.     

Effect of metaproterenol on ketone body metabolism of the forearm in healthy and diabetic subjects.

Muscular ketone body metabolism was studied by the registration of arterial-deepvenous concentration differences of glycerol, beta-hydroxybutyrate and acetoacetate, and of muscular blood flow in 53 healthy volunteers and 23 juvenile diabetics. In six subjects of each group substrate metabolism was also investigated during the intrabrachial arterial infusion of metaproterenol (0.4 microgram/min). Identical rates of muscular glycerol release and ketone's fractional extraction were obtained in healthy and diabetic subjects during the basal period. A significant correlation between muscular ketone extraction and arterial ketone concentration was calculated in both groups. During the infusion of metaproterenol the diabetics, unlike the controls, revealed enhanced muscular glycerol output and reduced fractional extraction of beta-hydroxybutyrate. These findings are in line with the present view that the impairment of muscular ketone body utilisation in diabetic ketoacidosis may at least partly be due to enhanced muscular lipolysis.     

Iron metabolism in the reticuloendothelial system

Comprised mainly of monocytes and tissue macrophages, the reticuloendothelial system (RES) plays two major roles in iron metabolism: it recycles iron from senescent red blood cells and it serves as a large storage depot for excess iron. Although iron recycling by the RES represents the largest pathway of iron efflux in the body, the precise mechanisms involved have remained elusive. However, studies characterizing the function and regulation of Nramp1, DMT1, HFE, FPN1, CD163, and hepcidin are rapidly expanding our knowledge of the molecular aspects of RE iron handling. This review summarizes fundamental physiological and biochemical aspects of iron metabolism in the RES and focuses on how recent studies have advanced our understanding of these areas. Also discussed are novel insights into the molecular mechanisms contributing to the abnormal RE iron metabolism characteristic of hereditary hemochromatosis and the anemia of chronic disease.     

Glycaemic index of selected foodstuffs in healthy persons

Aims: The aim of this study was to determine glycaemic index (GI) of 10 popular foodstuffs/mixed meals in healthy persons. Methods: Ten tested foodstuffs and glucose standard were consumed in three replicates in the course of a defined 9-day meal plan: puffed rice squares with chocolate, dark chocolate, white bread, honey and glucose for breakfast (at 7 a.m.) and dinner (at 8 p.m.); pasta with meat, fried fish with mashed potatoes, and buttered apricot dumplings for lunch (at 12 a.m.); wafers, puffed spelt squares with chocolate, and tomato soup for snack (at 4 p.m.). Each portion contained 50 g of carbohydrates and was consumed within 30 minutes. Glucose concentrations were measured by means of the Continous Glucose Monitoring System (CGMStrade mark, Medtronic Minimed, Northridge, CA, USA). The results were processed by Solutions Software (Medtronic Minimed, Northridge, CA, USA) and DegifXL4 software, Palacky University, Olomouc, CZ. Twenty healthy persons aged 21.9 +/- 1.39 y (mean +/- SE), BMI 23.6 +/- 0.63 kg/m(2) completed the study. Results: GI of tested foodstuffs ranged from 34.7 % (chocolate) to 105.3 % (puffed rice squares with chocolate). There were more than tenfold differences between minimal and maximal values of the GI for some foodstuffs. Significant interindividual differences were found between GIs of foodstuffs. Conclusions: In twenty healthy persons the glycaemic indexes of ten popular foodstuffs were determined, to be added to the nutritional labels in order to facilitate the optimum meal planning.