PLIN2 and chronic obstructive pulmonary disease: Furthermore, PLIN2 serum levels did not differ in patients with and without chronic obstructive pulmonary disease (COPD) (3.5 (0.48–48.3) μg/dL vs. 3.74 (1.68–21.3) μg/dL, p = 0.974; Figure 2D).