Plasma zonulin levels forecast sarcopenia and physical performance in patients with knee osteoarthritis.

Purpose: Knee Osteoarthritis (KOA) is a common disease in the elderly; however, its causative factors remain poorly elucidated. We investigated the potential contribution of intestinal mucosal disruption to the severity of KOA and physical capacity.

Method: We recruited women, healthy controls (age = 65.3 ± 6.6 years, n = 75) and patients with mild (age = 70.5 ± 3.8 years), moderate (age = 68.3 ± 5.5 years), and poor KOA (age = 73.8 ± 4.5 years, n = 43-50/group), characterized on oxford knee scoring (OKS) system. We also measured plasma zonulin as a marker of intestinal mucosal disruption alongwith plasma biochemistry, body composition, short physical performance battery (SPPB) score, gait speed, and hand grip strength (HGS) in control and KOA patients.

Results: KOA patients had elevated plasma zonulin levels, along with lower appendicular skeletal muscle mass (ASMI), and higher body fats than controls (all p < 0.05). Furthermore, KOA patients had lower SPPB scores, gait speed, and HGS than controls (all p < 0.05). Simple regression analysis revealed robust negative correlations of plasma zonulin with OKS, HGS, gait speed, and SPPB scores in KOA patients. These patients also exhibited higher levels of markers of inflammation and oxidative stress. Zonulin also exhibited significant areas under the curve in diagnosing low OKS scores, reduced physical capacity, and muscle weakness in KOA patients.

Significance: Taken together, increased intestinal permeability may contribute to the reduced functional performance in KOA, and plasma zonulin may be a useful diagnostic tool in KOA.