Effects of glycation on human γd-crystallin proteins by different glycation-inducing agents.

Human γd-crystallin (Hγd-crystallin), a major protein component of the human eye lens, is associated with the development of juvenile- and mature-onset cataracts. Evidence suggests that nonenzymatic protein glycation plays an important role in the aetiology of cataract and diabetic sequelae. This research compared the effects of various glycation modifiers on Hγd-crystallin aggregation, by treating samples of Hγd-crystallin with ribose, galactose, or methylglyoxal using several biophysical techniques. To measure advanced glycation end products, an Nε-(carboxyethyl)lysine enzyme-linked immunosorbent assay was performed on the glycating agent-treated Hγd-crystallin samples. Fructosamine production detection was performed for both ribose-treated and galactose-treated samples. Methylglyoxal-treated samples had the highest level of aggregation and the greatest extent of unfolding, and upon incubation for a minimum of 12 days, exhibited a marked enhancement in the amount of Nε-(carboxyethyl)lysine. The molecular profiles and morphological features of the glycated samples were highly correlated to the type of glycation agent used. These findings highlight a close connection between the type of glycation modifier and the various aggregation species that form. Thus, these results may facilitate deciphering of the molecular mechanism of diabetic cataractogenesis.

α-glucosidase and glycation inhibitory effects of costus speciosus leaves.

BACKGROUND: Hyperglycaemia is a salient feature of poorly controlled diabetes mellitus. Rate of protein glycation is increased with hyperglycaemia leading to long term complications of diabetes. One approach of controlling blood glucose in diabetes targets at reducing the postprandial spikes of blood glucose. The objectives of this study were to assess the in vitro inhibitory effects of Costus speciosus (COS) leaves on α-amylase and α-glucosidase activities, fructosamine formation, protein glycation and glycation-induced protein cross-linking. METHODS: Methanol extracts of COS leaves were used. Inhibitory effects on enzyme activities were measured using porcine pancreatic α-amylase and α-glucosidase from Saccharomyces cerevisiae in the presence of COS extract. Percentage inhibition of the enzymes and the IC50 values were determined. In vitro protein glycation inhibitory effect of COS leaves on early and late glycation products were measured using bovine serum albumin or chicken egg lysozyme with fructose. Nitroblue tetrazolium was used to assess the relative concentration of fructosamine and polyacrylamide gel electrophoresis was used to assess the degree of glycation and protein cross-linking in the reaction mixtures. RESULTS: α-Glucosidase inhibitory activity was detected in COS leaves with a IC50 of 67.5 µg/ml which was significantly lower than the IC50 value of Acarbose (p < 0.01). Amylase inhibitory effects occurred at a comparatively higher concentration of extract with a IC50 of 5.88 mg/ml which was significantly higher than the IC50 value of Acarbose (p < 0.01). COS (250 µg/ml) demonstrated inhibitory effects on fructosamine formation and glycation induced protein cross-linking which were in par with 1 mg/ml aminoguanidine were detected. CONCLUSION: Methanol extracts of COS leaves demonstrated in vitro inhibitory activities on α-glucosidase, fructosamine formation, glycation and glycation induced protein cross-linking. These findings provide scientific evidence to support the use of COS leaves for hypoglycemic effects with an added advantage in slowing down protein glycation.

Avaliação dos níveis de frutosamina em gatos sob estresse agudo e crônico / Assessment of fructosamine concentrations in cats with acute and chronic-stress

Frutosaminas são proteínas séricas glicadas formadas continuamente resultantes da ligação entre a glicose e proteínas circulantes, e correspondem à avaliação glicêmica de aproximadamente uma a duas semanas em gatos. A concentração de frutosamina tem sido utilizada para a diferenciação entre a hiperglicemia persistente e transitória induzida pelo estresse, sendo considerado o teste padrão ouro para o controle da glicemia em gatos diabéticos. O objetivo deste trabalho consistiu em avaliar a influência dos estados de estresse agudo e crônico em gatos sobre os níveis séricos de frutosamina. Foram selecionados 62 felinos provenientes do atendimento no Hospital Veterinário da FMVZ - UNESP Botucatu, distribuídos em três grupos: felinos com histórico de qualquer doença ou condições de estresse, excluindose o diabetes mellitus (DM), por um período máximo de 48 horas (Grupo A, n = 21) ou por um período superior a 120 horas (Grupo B, n = 27). O terceiro grupo (Grupo C = controle) foi formado por 14 felinos saudáveis. Os grupos foram avaliados quanto às dosagens séricas de frutosamina, glicose, proteína e albumina. Foi constatado um aumento significativo nos valores de frutosamina tanto nos animais submetidos ao estresse agudo quanto crônico, porém os níveis mantiveram-se dentro do intervalo de referência. Da mesma forma, os animais, em média, também se encontravam em normoglicemia, apesar da correlação positiva entre as concentrações de glicose e frutosamina. Conclui-se que a concentração de frutosamina sofre influência dos estados de estresse agudo e crônico em gatos, mantendo-se, porém, dentro dos limites de referência, sendo, portanto, útil no diagnóstico do DM.

circulating proteins, and corresponding to the blood glucose control assessment over the last one to two weeks in cats. The fructosamine concentration has been used for differentiation between persistent and transient hyperglycemia. Therefore, the determination of fructosamine is considered the gold standard for monitoring glycemia into control in diabetic cats. The objective of this study was to evaluate the influence of acute and chronic stress of cats on serum fructosamine. 62 cats were selected from the Veterinary Hospital of FMVZ - UNESP, Botucatu campus. They were distributed into three groups: cats with a history of any illness or stress condition, excluding Diabetes Mellitus (DM), for a maximum of 48 hours (Group A, n = 21) or for a period exceeding 120 hours (Group B n = 27). The third group (Group C = control) was formed by 14 health cats. The groups were evaluated for serum fructosamine, glucose, protein and albumin. In this study, there was a significant increase in the values of fructosamine in animals subjected to acute and chronic stress, but these values remained within the reference range. The animals were, on average, normoglycemic, despite the positive correlation between fructosamine and glucose concentrations. We conclude that the fructosamine concentration is influenced by acute and chronic stress in cats, remaining, however, within the reference range, and therefore, still useful in the diagnosis of DM.

[The experimental study of Radix Puerariae inhibiting glycation in rats induced by D-galactose].

OBJECTIVE: To observe the effects of Radix Puerariae on protein glycation in model rats induced by D-galactose. METHODS: The model rats of protein glycatin were induced by intraperitoneal administration of D-galactose (150 mg/kg) for 8 weeks, and all rats were treated by Radix Puerariae (High dose 300 mg/kg, Middle dose 150 mg/kg, Low dose 75 mg/kg) for 6 weeks. The activity of aldose reductase in red blood cells, the content of fructosamine in serum, the amount of glycohaemoglobin and advanced glycation end-products, the level of insulin in serum, the activity of superoxide dismutase and the amount of maleic dialdehyde were measured. RESULTS: High dose and middle dose of Radix Puerariae could decrease the level of blood glucose and the activity of aldose reductase in red blood cells, inhibit the formation of glycation products significantly in model rats induced by D-galactose (P < 0.01), increase insulin sensitivity and activity of superoxide dismutase (P < 0.01) and decrease the amount of maleic dialdehyde (P < 0.01). CONCLUSION: Puerariae can significantly inhibit glycation reaction in rats induced by D-galactose.

[Effect of oral antidiabetic agents on fructose biosynthesis]. / Viianie protivodiabeticheskikh sredtstv dlia priema vnutr' na obrazovanie fruktozamina.

The oral antidiabetic drugs (glyformin, glyclaside, glycvidon, glybenclamide) at a concentration of 10-196 mM affect the synthesis of fructosamine in an incubation medium containing 40 mM of glucose and 5% of human serum albumin. All these drugs decrease the fructosamine yield measured in the medium on the 4th day of incubation at 37-198 degrees C, while the effect of glycvidon is pronounced even on the 7th day. The introduction of glyformin, glycvidon, and glybenclamide at an amount close to the maximum daily dose over a period of one month reduces the level of fructosamine in the blood of rats with experimental diabetes mellitus, while not affecting the level of glucose in the blood of test animals. Thus, the oral antidiabetic drugs reduce the level of fructosamine--an agent known to modify the protein structure, thus favoring the development of complications in the course of diabetes under permanent hyperglycemia conditions.