Impact of acute exacerbations of COPD on patients' health status beyond pulmonary function: A scoping review.

This scoping review summarized the evidence regarding the impact of acute exacerbations of COPD (AECOPD) on patients' health status beyond pulmonary function. PubMed, Embase, and Web of Science were searched. Prospective cohort studies assessing the health status of patients with COPD in a stable phase of the disease and after a follow-up period (where at least one AECOPD occurred) were included. An integrated assessment framework of health status (i.e., physiological functioning, complaints, functional impairment, quality of life) was used. Twenty-two studies were included. AECOPD acutely affected exercise tolerance, quadriceps muscle strength, physical activity levels, symptoms of dyspnoea and fatigue, and impact of the disease. Long-term effects on quadriceps muscle strength, symptoms of dyspnoea and depression, and quality of life were found. Repeated exacerbations negatively impacted the fat-free mass, levels of dyspnoea, impact of the disease and quality of life. Conflicting evidence was found regarding the impact of repeated exacerbations on exercise tolerance and physical activity levels. AECOPD have well-established acute and long-term adverse effects on health status beyond pulmonary function; nevertheless, the recovery trajectory and the impact of repeated exacerbations are still poorly studied. Further prospective research is recommended to draw firm conclusions on these aspects.

Carbon and hydrogen metabolism of xylitol and various sugars in human erythrocytes.

1) Erythrocytes are able to metabolize D-ribose, D-xylitol, D-xylulose, D-fructose and D-glucose; the rates of metabolism increase in that order from 2430 to 26200 ng atom C/ml packed cells per 120 min of incubation. 2) The utilization of the carbon of these substrates and its recovery in the products were found to be in balance, when the change in the 2,3-bisphosphoglycerate concentration was taken into account. 3) The metabolic rates strongly affected the 2,3-bisphosphoglycerate level. Without addition of substrate the decomposition rate of this intermediate was found to be 1030 nmol/ml packed cells per 120 min. 4) The net decrease of the 2,3-bisphosphoglycerate concentration and the conversion of this compound into lactate provides a NAD regeneration system which enables the red blood cells to utilize xylitol. 5) The rate of carbon metabolism via the pentose phosphate cycle is determined by the NADPH requirement of the erythrocytes which was found to be 160 nmol/ml packed cells per 120 min under the experimental conditions employed.

Energy metabolism of various substrates and the 2,3-Bisphosphoglycerate bypass in human erythrocytes.

1. Using different experimental conditions and applying various substrates, a wide range of metabolic rates could be observed in incubations with human erythrocytes. 2. Lower rates of substrate utilization resulted in a decrease of the ATP and, more pronounced, of the 2,3-bisphosphoglycerate concentration while carbon utilization rates beyond 14 mumol C/ml packed cells in 120 min yielded constant levels of ATP and 2,3-bisphosphoglycerate indicating that steady state had been achieved. 3. It can be concluded, that a carbon utilization rate of 14 mumol C/ml cells in 120 min is able to cover the energy requirement of the red cells under steady state conditions which could be calculated to amount to 3.6 mumol ATP/ml cells in 120 min at 37 degrees C. 4. The contribution of the 2,3-bisphosphoglycerate bypass to carbon metabolism could be calculated to range between 15--25% at metabolic rates below 14 mumol C/ml cells in 120 min (presteady state). When steady state has been achieved, the share of this bypass increases up to 61% with increasing metabolic rates.

Interrelationship between energy metabolism from various substrates and the 2,3-bisphosphoglycerate bypass in human erythrocytes.

Metabolism of the substrates D-ribose, xylitol, D-Xylulose, D-fructose, D-glucose and mixtures of these compounds were studied in human erythrocytes. The metabolic rates obtained with the various substrates affected the intracellular levels of ATP and 2,3-bisphosphoglycerate. Small amounts of substrate utilization resulted in a decrease of the ATP and more pronounced of the 2,3-bisphosphoglycerate concentration while carbon utilization rates beyound 14 microgram atom C/ml packed cells/120 min yielded constant levels of ATP and 2,3-bisphosphoglycerate. From these results it can be concluded that a carbon utilization rate of 14 microgram atom C/ml cells/120 min is able to cover the ATP requirement of the red cells under steady state conditions. Based on the carbon utilization rates obtained with the various substrates and the rates of 2,3-bisphosphoglycerate decomposition an attempt is made to calculate the contribution of the 2,3-bisphosphoglycerate bypass to substrate metabolism. In case of xylitol as substrate the decrease in the 2,3-bisphosphoglycerate content provides the regeneration of NAD thus facilitating uptake and metabolism of xylitol.

Comparison of xylitol and glucose metabolism in nonhepatic rat tissues.

Capability and extent of xylitol metabolism in vitro was studied in a variety of non-hepatic tissues of rats, using enzymatic and isotopic methods. Only kidney was found to be able to utilize xylitol at a significant rate while in all other organs tested - lung, brain, heart muscle, skeletal muscle and adipose tissue - no uptake of xylitol was detectable using two independent methods. In accordance with these results the incorporation of radioactivity from [U-14C]-xylitol as substrate into the products CO2 and lactate was found to be very small in all organs with the exception of kidney and when compared to that from [U-14C]-glucose it was less than 5%. From these results it is concluded that besides liver only kidney can utilize xylitol to a significant extent while for the other tissues studied xylitol is not a suitable substrate.

[Xylitol metabolism in human erythrocytes]. / Xylitstoffwechsel im menschlichen Erythrozyten

1. Washed human erythrocytes metabolize 1,14 muMol xylitol in 120 min under the following experimental conditions: pH 7.4 and 37 degrees C. 2. The levels of 2,3-diphosphoglycerate and ATP decrease during the incubation with xylitol. This decrease is not a specific effect of xylitol, but depends on the amount of C-atoms taken up. This could be shown in control experiments with fructose and glucose as substrates given separated or in combination with xylitol. The highest uptake of C-atoms has been observed with glucose plus xylitol as substrate. 3. 99% of the metabolized xylitol was recovered in the products lactate, Co2 and D-xylulose. 4. There was no measurable oxalate production from xylitol.