Background
Obesity results in increased oxidative stress, which can be manifested by changes in biomarkers of oxidised lipoproteins and chronic elevations in autoantibodies to oxidised LDL and apoB-immune complexes (apoB-IC). 

Aims
To determine the impact of metabolic surgery on IgG and IgM autoantibodies to oxidised LDL and apoB-IC.

Methods
A prospective study of patients with severe obesity undergoing metabolic surgery (n=59, mean age 50.110.0 years, 30% statin-treated) was undertaken. IgG and IgM autoantibodies to malondialdehyde-modified LDL (MDA-LDL) and apoB-IC, and markers of inflammation and glycaemia were measured at baseline and 12months after surgery.

Results
Weight reduction was significant after metabolic surgery [median (interquartile range, IQR) BMI 48 (44–57) to 33 (30–37) kg/m2, P<0.001). Significant declines were noted in IgG and IgM MDA-LDL, and IgG apoB-IC at 6 months [median (IQR) percentage reduction 24 (12–40), 24 (7–39), and 31 (12–44) respectively; P0.001] with further reductions at 12 months. The decrease in IgM apoB-immune complexes was significant at 12 months [44 (21–74)%, P<0.001] but not at 6 months. These reductions were accompanied by reductions in markers of inflammation and glycaemia. Percentage change (%) in IgG autoantibodies to MDA-LDL correlated with both % IgG and % IgM apoB-immune complexes (=0.571, P<0.001 and =0.360, P=0.007 respectively). % IgM autoantibodies to MDA-LDL correlated with % IgM apoB-immune complexes (=0.439, P=0.001). 

Conclusion
Severe obesity is marked by evidence of heightened oxidation of lipoproteins which improves significantly following metabolic surgery.

04 - REDUCTION IN AUTOANTIBODIES TO OXIDISED LDL AND APOB-IMMUNE COMPLEXES FOLLOWING METABOLIC SURGERY