RBP4 and diabetes mellitus: Despite the positive correlation of CTRP1 with BMI, but weak evidence, we found that CTRP1 in critical illness is not associated with a variety of established biomarkers of energy substrate metabolism or diabetes-related cytokines such as insulin, leptin, leptin receptor, ghrelin, adiponectin, resistin or retinol-binding protein 4 (RBP4).