Physiologic concentrations of inorganic phosphate accelerate fructosamine synthesis

• Published in: Diabetes research and clinical practice Vol. 17; no. 1; pp. 9 - 16
• Main Authors: Kunika, Kiyoshi, Yamashita, Kamejiro, Itakura, Mitsuo
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.07.1992; Elsevier Science
• Subjects: Adult; Associated diseases and complications; Biological and medical sciences; Blood Glucose - metabolism; Diabetes Mellitus, Type 2 - blood; Diabetes. Impaired glucose tolerance; Diabetic complication; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Fructosamine; Glucose Tolerance Test; Glycemic control; Hexosamines - blood; Humans; Inorganic phosphate; Kinetics; Medical sciences; Phosphates - blood; Phosphates - pharmacology; Phosphates - physiology; Protein glycation; Reference Values; Time Factors; Glycemic control; Diabetic complication; Fructosamine; Inorganic phosphate; Protein glycation; Endocrinopathy; Human; Proteins; Pathophysiology; Diabetes mellitus; Biological marker; Complication
• ISSN: 0168-8227; 1872-8227
• DOI: 10.1016/0168-8227(92)90038-S

The effect of physiologic concentrations of inorganic phosphate (Pi) on fructosamine (FRA) synthesis was studied. After 75 g oral glucose administration (OGTT), ‘ ΔFRA 24 h ’, defined as ΔFRA after incubating serum or other specimens at 37°C for 24 h after adding 1000 mg/dl glucose, was significantly decreased in parallel to the decrease of plasma Pi concentrations. ‘The FRA index’, defined as the FRA value divided by the corresponding glucose concentration, both at fasting, correlated significantly with plasma Pi concentrations. In vitro incubation of serum total protein (TP), albumin (ALB), γ-globulin (GLB), free lysine (Lys), and free valine (Val) with glucose at different concentrations of Pi showed a Pi-dependent increase of FRA synthesis throughout 48 h of incubation. The accelerating effect of 5 mg/dl Pi on FRA synthesis from TP, ALB, GLB, Lys, and Val at pH 7.4 was, respectively, as great as 48, 20, 24, 13 or 25% of those without Pi. Increase of pH from 6 to 10 logarithmically increased ΔFRA 24 h in contrast to a logarithmic decrease of the accelerating effect of Pi on ΔFRA 24 h . These data show that physiologic concentrations of Pi accelerate protein glycation by accelerating dehydrogenation during the Amadori rearrangement through the negative charge of Pi. Because this accelerating effect of physiologic Pi presumably exists in vivo, Pi concentration must be taken into account as an accelerating factor for FRA synthesis in evaluating diabetic control, and further studies must be carried out to elucidate whether hyperphosphatemia accelerates glycation-induced diabetic complications.