Effects of Parathyroid Hormone and 1,25(OH ₂)D ₃ on Protein Glycation in Moderate Uraemia

Abstract

Glucose intolerance in uraemia may be a consequence of secondary hyperparathyroidism. In this study fructosamine and glycated albumin have been used as markers of long-term glycaemic control in a group of pre-end-stage, non-diabetic uraemic patients with secondary hyperparathyroidism. The serum fructosamine level (μmol/l00 g total protein) was significantly higher (p = 0.005) in uraemic patients (364 ± 42) than in a group of 25 non-uraemic controls (332 ± 27), but the content of glycated albumin did not differ (p > 0.05; 1.6 ± 0.5 vs. 1.5 ± 0.3%). In the uraemic patients, there was a significant relationship between serum 1,25-dihydroxycholecalciferol [1,25(OH₂)D] (median 4.2, range 1.0-38 ng/l) and fructosamine (r = -0.66, p < 0.01; fructosamine = -2.76 1,25(OH₂)D + 389), but not glycated albumin (r = -0.22, p > 0.1). No relationship existed between serum parathyroid hormone (median 15.4, range 7.0-55 pmol/l) and either glycated albumin or fructosamine (p > 0.1). In patients treated with oral calcitriol (0.25 μg/day), significant reductions in serum parathyroid hormone after both 4 (p = 0.03) and 8 weeks (p = 0.02) and concomitant increases in serum 1,25(OH₂)D (p < 0.02) after 8 weeks of treatment were not accompanied by any change in fructosamine, glycated albumin, total calcium, or ionized calcium (p > 0.05). Elevation of serum fructosamine in these patients is consistent with the impaired glucose tolerance of uraemia. The evidence presented supports a relationship between long-term glycaemic control and 1,25(OH₂)D₃, but not parathyroid hormone, in moderately uraemic patients with secondary hyperparathyroidism; however, serum fructosamine was not altered by treatment with calcitriol over an 8-week period.