Nonenzymatic glycation of proteins, leading to chemical
modification and cross-linking are of importance in the
pathology of diabetic complications.We studied the effect of
α-lipoic acid (LA) on the content and characteristics of the
protein collagen from skin of high-fructose fed rats. The
rats were divided into 4 groups of 6 each. Two groups of
rats were fed with a high fructose diet (60 g/100 g diet) and
administered either LA (35 mg/kg b.w., i.p) (FRU+LA) or
0.2 ml vehicle (saline) (FRU) for 45 days. The other 2 groups
were fed with control diet containing starch (60 g/100 g
diet) and administered either saline (CON) or lipoic acid
(CON+LA). The rats were maintained for 45 days and then
sacrificed. Plasma glucose, insulin, fructosamine, protein
glycation, and blood glycated hemoglobin (HbA1C) were
measured. Collagen was isolated from skin and the physicochemical
properties of collagen were studied. Fructose administration
caused accumulation of collagen in skin. Extensive
cross-linking was evidenced by enhanced glycation
and AGE-linked fluorescence. Increased peroxidation and
changes in physicochemical properties such as shrinkage
temperature, aldehyde content, solubililty pattern, susceptibility
to denaturing agents were observed in fructose-fed
rats. SDS gel pattern of collagen from these rats showed
elevated β component of type I collagen. These changes
were alleviated by the simultaneous administration of LA.
Administration of LA to fructose-fed rats had a positive
influence on both quantitative and qualitative properties of collagen. The results suggest a mechanism for the ability
of LA to delay diabetic complications.
