TNF and rheumatoid arthritis: The concentrations of acetate, propionate, and butyrate exhibit circadian oscillations and anatomic compartmentalization, with butyrate peaking during early morning hours (04:00–06:00) and demonstrating an inverse correlation with RA-associated morning stiffness severity (r = −0.82, p < 0.01) through suppression of nocturnal interleukin (IL)-6/tumor necrosis factor (TNF)-α surges [42].