[Hygieno-dietetic recommendations in the prevention of accumulation of advanced glycation products]

Advanced glycation products are proteins whose structural and functional properties have been modified by a process of oxidative glycation. The accumulation of advanced glycation products in most tissues and the oxidative stress and inflammatory reactions that accompany it, account for the multi-systemic impairment observed particularly in the elderly, diabetics and in chronic renal failure. The advanced glycation products endogenous production is continuous, related to oxidative stress, but the most important source of advanced glycation products is exogenous, mainly of food origin. Exogenous advanced glycation products are developed during the preparation of food and beverages. The advanced glycation products content is higher for animal foods, but it is mainly the preparation and cooking methods that play a decisive role. Dietary advice is based on the selection of foods and the choice of methods of preparation. Several randomized controlled studies have confirmed the favorable effect of these recommendations on serum advanced glycation products concentrations. In humans, as in animals, regular physical activity also results in a reduction of serum and tissue concentrations of advanced glycation products. There is a need for prospective clinical study to confirm the effects of hygienic and dietary recommendations that have only been appreciated, so far, on biological markers.

[Advanced glycation end products: A risk factor for human health]

Advanced glycation end products (AGE) result from a chemical reaction between the carbonyl group of reducing sugar and the nucleophilic NH2 of a free amino acid or a protein; lysine and arginine being the main reactive amino acids on proteins. Following this first step, a molecular rearrangement occurs, rearrangement of Amadori resulting to the formation of Maillard products. Glycation can cause the clouding of the lens by inducing reactions crosslinking proteins. Specialized receptors (RAGE, Galectin 3…) bind AGE. The binding to the receptor causes the formation of free radicals, which have a deleterious effect because they are powerful oxidizing agents, but also play the role of intracellular messenger, altering the cell functions. This is especially true at the level of endothelial cells: the attachment of AGE to RAGE receptor causes an increase in vascular permeability. AGE binding to endothelium RAGE and to monocytes-macrophages, led to the production of cytokines, growth factors, to the expression of adhesion molecules, and the production of procoagulant activity. Diabetic retinopathy is related to excessive secretion of vascular growth factor (vascular endothelial growth factor [VEGF]). AGE-RAGE receptor binding causes the synthesis and secretion of VEGF. Increased permeability, facilitation of leukocyte migration, the production of reactive oxygen species, cytokines and VEGF suggest that the AGE could be an element of a cascade of reactions responsible for the diabetic angiopathy and vascular damages observed during aging and chronic renal failure. Balanced diet or some drugs can limit the deleterious effect of AGE.

Skin autofluorescence is associated with past glycaemic control and complications in type 1 diabetes mellitus

As skin autofluorescence (AF) can assess subcutaneous accumulation of fluorescent advanced glycation end-products (AGEs), this study aimed to investigate whether it was linked to glycaemic control and complications in patients with type 1 diabetes mellitus (T1DM). Using the AGE Reader™, AF was measured in T1DM patients referred to Haut-Levêque Hospital (Bordeaux, France); data on their HbA1c levels measured every 6months as far back as the last 5years were also collected. The association of AF with the patients' past glucose control, based on their latest HbA1c values, and the means of the last five and 10 HbA1c values, and with diabetic complications was also examined by linear regression analysis. The sample included 300 patients: 58% were male; the mean age was 49 (SD 17) years and the mean diabetes duration was 21 (SD 13) years. The median skin AF measurement was 2.0 [25th-75th percentiles: 1.7-2.4] arbitrary units (AU), and this was associated with age (β=0.15 per 10years, P<0.001) and diabetes duration (β=0.17 per 10years, P<0.001). After adjusting for age and estimated glomerular filtration rate (eGFR), the skin AF measurement was also related to the means of the last five and 10 HbA1c values (β=0.10 per 1% of HbA1c, P=0.005, and β=0.13 per 1% of HbA1c, P=0.001, respectively). In addition, the skin AF was associated with retinopathy (P<0.001), albuminuria (P<0.001) and decreased eGFR (P<0.001). In conclusion, the skin AF is related to the long-term glucose control and diabetic complications.