Several studies have indicated the presence of increased oxidative stress as a critical feature in the pathogenesis of chronic obstructive pulmonary disease (COPD). Another biochemical complication leading to pathogenesis is protein glycation. The nexus between oxidative stress and protein glycation in various pathological conditions is being unraveled. Increased oxidative stress can lead to enhanced protein glycation by a process of auto-oxidative glycation. No information is available in the literature regarding protein glycation among COPD patients. Eleven non-diabetic COPD patients were included in the study and equal number of age and sex-matched healthy individuals were enrolled as controls. The whole-blood reduced glutathione was found to be less among the patients while lipid peroxides and fructosamine were elevated in comparison to control. The present study confirmed oxidative stress and enhanced protein glycation among the COPD patients. Antioxidant therapy may be considered as part of the treatment regimen for COPD patients.

Non-enzymatic glycation as the chain reaction between reducing sugars and free amino groups of proteins has been shown to correlate with physiological ageing and severity of diabetes. The process involves oxidative steps (glycoxidation). In this paper, the effect of D-fructose as a reactive sugar on aspartate aminotransferase (AST) as a model protein was monitored by measurements of the enzyme activity and formation of fluorescent advanced glycation end products (AGEs). Change in the AST activity was considered as a measure of the overall protein damage caused by glycation, and total AGEs and pentosidine represent, at least partly, the formation of glycoxidation products. Catalytic activity of AST in an incubation mixture containing D-fructose (50 mmol L(-1)), decreased compared to control values to 42% (p < 0.05) and to 11% (p < 0.05) on the 5th and on 21st day of incubation, respectively. In the presence of fructose, total fluorescent AGEs concentration was significantly higher since 5th day of incubation (110%, p < 0.05) and the fluorescent pentosidine concentration from 15th day of incubation (117%, p < 0.05) compared to control values, respectively. Catalytic activity of AST clearly and quantitatively demonstrated functional changes in the enzyme molecule caused by structural modifications initiated by fructose, while the evaluation of AGE formation and especially that of pentosidine by fluorescence measurement was less reliable.

The accumulation of Maillard reaction products increases with age in long-lived proteins and can be retarded by caloric restriction. Here we determined whether caloric restriction inhibits formation of glycation and glycoxidation products in skin collagen of squirrel and rhesus monkeys between 1990-1997. Restricted monkeys (n = 11, n = 30, respectively) were maintained at 70% of caloric intake of controls (n = 25, n = 32, respectively). Glycation was assessed by furosine and glycoxidation by pentosidine and carboxymethyl-lysine. With age, the rate of furosine formation moderately but nonsignificantly (p >.05) increased in both control monkey groups. It significantly (p =.011) decreased in the caloric-restricted rhesus, but not squirrel monkeys. Caloric restriction did not significantly decrease the pentosidine or carboxymethyl-lysine rates in either species of monkeys. These results suggest that caloric restriction, when maintained long-term in nonhuman primates, tends to decrease glycation, but not glycoxidation.

ABSTRACT.: Tissue content of advanced glycation end products (AGE) increases with age and contributes to the changes in structure and function of the renal and cardiovascular systems. The effect of chronic food restriction on this AGE accumulation was investigated in lean WAG/Rij rats. A 30% food restriction performed from 10 to 30 mo in female rats reduced their mean body weight from 240 +/- 7 to 160 +/- 12 g, but did not modify their survival. AGE collagen content increased from 14.3 +/- 5.5 to 104.7 +/- 13.0 arbitrary units per microgram (AU/microg) of hydroxyproline (OHPro) in kidney between 10 and 30 mo, and from 9.7 +/- 1.2 to 310.6 +/- 34.6 AU/microg OHPro in the abdominal aorta. Food restriction reduced AGE accumulation to 21.4 +/- 3.3 and 74.6 +/- 16.5 AU/microg OHPro in kidney and aorta of 30-mo-old animals. Similar results were found for collagen prepared from isolated glomeruli (7.8 +/- 1.2, 81.2 +/- 16.1, and 10.3 +/- 4.3 AU/microg OHPro in 10-mo, 30-mo, and restricted 30-mo-old rats). Reduction of intrarenal and arterial AGE accumulation by food restriction was confirmed by immunostaining in optical microscopy. Age-related changes in arterial and kidney structures as polyuria and proteinuria were mainly prevented by food restriction. These data indicate that chronic food restriction reduces the accumulation of AGE and preserves the structure and function of the renal and cardiovascular systems in learn rats, although it did not affect survival of the animals between 10 and 30 m.