High glucose inhibits effect of ascorbic acid on [ 35S] sulphate incorporation in mesangial cell and matrix proteoglycan

• Published in: Diabetes research and clinical practice Vol. 37; no. 2; pp. 101 - 108
• Main Authors: McAuliffe, Aileen V., Fisher, Elizabeth J., McLennan, Susan V., Yue, Dennis K., Turtle, John R.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.08.1997; Elsevier Science
• Subjects: Adrenals. Adrenal axis. Renin-angiotensin system (diseases); Analysis of Variance; Animals; Ascorbic acid; Ascorbic Acid - antagonists & inhibitors; Ascorbic Acid - pharmacology; Biological and medical sciences; Cells, Cultured; Endocrinopathies; Extracellular Matrix - drug effects; Extracellular Matrix - metabolism; Female; Glomerular Mesangium - drug effects; Glomerular Mesangium - metabolism; Glucose; Glucose - pharmacology; Kinetics; Malignant tumors; Medical sciences; Mesangial cells; Mesangium matrix; Proteoglycan; Proteoglycans - biosynthesis; Rats; Rats, Wistar; Sulfates - metabolism; Sulfur Radioisotopes; Proteoglycan; Mesangial cells; Ascorbic acid; Glucose; Mesangium matrix; Endocrinopathy; Kidney disease; Incorporation; Urinary system disease; Rat; Mesangial cell; Pathogenesis; Diabetes mellitus; Rodentia; Vertebrata; Hyperglycemia; Mammalia; Nephropathy; Animal; Extracellular matrix; Biological effect; Inhibition
• ISSN: 0168-8227; 1872-8227
• DOI: 10.1016/S0168-8227(97)00063-6

Expansion of the glomerular mesangium is a consistent finding of diabetic nephropathy. Negatively charged proteoglycans are an integral part of the mesangium and their synthesis and degradation is disturbed in many forms of glomerulosclerosis. The metabolism of ascorbic acid (AA), which plays an important role in extracellular matrix regulation, is known to be abnormal in diabetes. The action of AA has also been shown to be inhibited by high glucose (HG) concentration. In this study we investigated the effect of AA and HG on proteoglycan (PG) synthesis by examining the incorporation of [ 35S] sulphate into PG in the cellular, matrix and media components of rat mesangial cell (MC) cultures. MC were grown in 9 or 25 mM glucose for 8 days, with and without the addition of AA. Sulphation of PG was measured by adding 50 μCi of [ 35S] sulphuric acid to the culture medium and precipitating 35S-labelled PG with cetylpyridinium chloride. In this study AA was shown to have a stimulatory effect on the overall incorporation of [ 35S] sulphate into cell and matrix PG and this was inhibited by 25 mM glucose. Correcting for protein synthesis and specific activity of [ 35S] sulphate showed that HG inhibits AA stimulation by decreasing sulphation of the individual PG molecules. These findings may be of particular importance in the pathophysiology of nephropathy in diabetes, a condition where AA concentration is already compromised.