Sulphate and osteoarthritis: decrease of serum sulphate levels by an additional 3‐h fast and a 3‐h glucose tolerance test after an overnight fast

Background: Low sulphate levels in blood may contribute to osteoarthritis by decreasing cartilage chondroitin sulphation. Objective: To measure serum levels of sulphate during 3 h of fasting or glucose ingestion after overnight fasts to determine how much sulphate lowering may occur during this period. Methods: Sera from 14 patients with osteoarthritis who fasted overnight were obtained every 15–30 min during 3 h of continued fasting and during 3 h after ingestion of 75 g of glucose. Sulphate was assayed by high-performance liquid chromatography with a Metrohm-Peak 761 Compact IC and simultaneously assayed for glucose by high-performance liquid chromatography with a Metrohm-Peak 817 Bioscan. Results: Continuation of overnight fasting for 3 h resulted in a near-linear 3-h decrease in levels for all 14 patients ranging from 3% to 20% with a mean drop of 9.3%, whereas the 3-h decrease after glucose ingestion ranged from 10% to 33% with a mean drop of 18.9%. Conclusion: A 3-h continuation of fasting caused a marked reduction in serum sulphate levels, whereas ingestion of 75 g of glucose in the absence of protein resulted in doubling the reduction. This suggests that fasting and ingestion of protein-free calories may produce periods of chondroitin undersulphation that could affect osteoarthritis.