Background: Obesity is associated with an increased risk of cardiometabolic morbidity and mortality, which may be attributable to systemic low-grade inflammation. The impact of bariatric surgery-induced weight loss on low-grade inflammation has not yet thoroughly been described. We investigated the effect of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on the plasma levels of cytokines, chemokines, and cytokine receptors prior to surgery (baseline), and then three and 12 months after surgery. Methods: We recruited 68 individuals (41 females, 27 males) with severe obesity (42.84 ± 6.28) who had been referred for bariatric surgery (RYGB: n = 29, SG: n = 39). Blood samples were collected after an overnight fast at baseline (immediately before surgery), 3 and 12 months after surgery. Eleven patients without obesity or cardiometabolic disease served as controls at baseline. Ninety-two plasma proteins were measured using an Olink Target 96 inflammation panel. Results: We used a linear mixed model to test differences in inflammatory markers at baseline, across time points and between groups. At baseline, 36 cytokines were found to be differentially expressed between the bariatric surgery patients and controls. Of these cytokines, 13 had significantly decreased three months after bariatric surgery and 27 had significantly decreased 12 months after surgery, compared with baseline. Two cytokines (CCL25 and CCL28) increased markedly after 12 months. Only one cytokine (CCL25) was significantly different between the procedures performed, where it increased in the RYGB group 12 months after surgery. Conclusion: Individuals with severe obesity have increased expression of plasma inflammatory cytokines compared to controls, but low-grade inflammation improves following bariatric surgery, regardless of whether it is RYGB or SG.

Bilirubin is the end product of heme catabolism, mainly produced by the breakdown of mature red blood cells. Due to its anti-inflammatory, antioxidant, antidiabetic, and antilipemic properties, circulating bilirubin concentrations are inversely associated with the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality in adults. Some genetic loci associated with circulating bilirubin concentrations have been identified by genome-wide association studies in adults. We aimed to examine the relationship between circulating bilirubin, cardiometabolic risk factors, and inflammation in children and adolescents and the genetic architecture of plasma bilirubin concentrations. We measured fasting plasma bilirubin, cardiometabolic risk factors, and inflammatory markers in a sample of Danish children and adolescents with overweight or obesity (n = 1530) and in a population-based sample (n = 1820) of Danish children and adolescents. Linear and logistic regression analyses were performed to analyze the associations between bilirubin, cardiometabolic risk factors, and inflammatory markers. A genome-wide association study (GWAS) of fasting plasma concentrations of bilirubin was performed in children and adolescents with overweight or obesity and in a population-based sample. Bilirubin is associated inversely and significantly with a number of cardiometabolic risk factors, including body mass index (BMI) standard deviation scores (SDS), waist circumference, high-sensitivity C-reactive protein (hs-CRP), homeostatic model assessment for insulin resistance (HOMA-IR), hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol (LDL-C), triglycerides, and the majority of measured inflammatory markers. In contrast, bilirubin was positively associated with fasting plasma concentrations of alanine transaminase (ALT), high-density lipoprotein cholesterol (HDL-C), systolic blood pressure (SDS), and the inflammatory markers GH, PTX3, THBS2, TNFRSF9, PGF, PAPPA, GT, CCL23, CX3CL1, SCF, and TRANCE. The GWAS showed that two loci were positively associated with plasma bilirubin concentrations at a p-value threshold of <5 × 10⁻⁸ (rs76999922: β = −0.65 SD; p = 4.3 × 10⁻⁸, and rs887829: β = 0.78 SD; p = 2.9 × 10⁻²⁴⁷). Approximately 25% of the variance in plasma bilirubin concentration was explained by rs887829. The rs887829 was not significantly associated with any of the mentioned cardiometabolic risk factors except for hs-CRP. Our findings suggest that plasma concentrations of bilirubin non-causally associates with cardiometabolic risk factors in children and adolescents.