Study on glyceraldehyde content and its novel reactants on collagen in the body

概要

Glyceraldehyde is an intermediary metabolite in carbohydrate metabolism. G lyceraldehyde has been proposed as one of the primary sources of toxic advanced gl ycation end products (AGEs). AGEs can modify intracellular signalling and gene expression associated with reactive oxygen species and also release pro-inflammatory compounds, contributing to the pathology of diseases such as diabetes or aging. However very little is known of physiological or pathological levels of glyceraldehyde in body, and its effect in the formation and toxicity of these AGEs.

Existing quantification methods of glyceraldehyde are not reliable or sensitive enough. The objectives of the present study were to develop reliable method for glyceraldehyde quantification and examine effects of diets on liver and blood glyceraldehyde contents.

A method using 1-phenyl-3-methyl-5-pyrazolone (PMP) was optimized in order to achieve high and reproducible recovery of derivative for LC-MS/MS quantification. Briefly, strong basic and acid conditions were substituted by 7 % ammonia treatment and removal of ammonia by evaporation. To suppress undesirable absorption of PMP-derivatives to column, 20 mM sodium acetate was used for liquid partition process. These changes extensively increased glyceraldehyde stability during derivatization and improved PMP-glyceraldehyde signal in sample injected in LC-MS/MS system. This method was tested in plasma and liver samples, good linearity was observed and accuracy above 98 %.

Glyceraldehyde was measured in human plasma after the ingestion of 100 g of steamed rice following overnight fasting. Glyceraldehyde remained consistent before and after food consumption. However, the plasma glyceraldehyde level in patients with type 2 diabetes was positively correlated with plasma glucose level (p<0.0001) and glycated hemoglobin (p<0.01) and inversely correlated with HDL levels. These results indicate that glyceraldehyde content in plasma can be affected by diseases such as diabetes and therefore have an effect in protein glycation in the vascular system or other tissues.

Same as in human plasma, the glyceraldehyde levels stayed unchanged between fasting and non-fasting groups in both mice and rats. On the other hand, the liver glyceraldehyde levels significantly increased after food consumption (p<0.05).

Next, mice were fed 60% high fat diet for 10 weeks. Surprisingly, high fat diet (low carbohydrate diet) feeding significantly increased plasma glyceraldehyde level in mice (p<0.005). A concomitant increase in liver damage markers ALT and AST was also found in mice fed with high fat diet. Glyceraldehyde leaking for damaged hepatocytes could be a possible explanation for the elevation in plasma in mice fed with high fat diet.

Mice were also administered a single dose of fructose or glucose andglyceraldehyde was measured in plasma and liver after 30, 60 and 180 min of