The HDL proteome represents a novel, sensitive biomarker of metabolic inflammation and metabolic health in obesity that can track both disease progression and regression

Introduction: Low-grade metabolic inflammation is causally implicated in the development of multiple obesity-related complications, such as cardiovascular disease, chronic kidney disease (CKD) and liver disease. Our previous preclinical studies in mice have shown that changes in the proteome of high-density lipoprotein (HDL) particles in obesity occur independently of changes in HDL-cholesterol. The HDL proteome in obesity has increased pro-inflammatory acute phase proteins and reduced antioxidant/anti-inflammatory proteins. In the current study we hypothesized that the HDL proteome may serve as a novel biomarker of metabolic inflammation in human obesity, and that a reversal in 'adverse' particle protein composition would be evident after weight-loss.

Methods: HDL particles were isolated from serum using a novel two-step extraction and purification method followed by tryptic digestion for LC-MS/MS. Proteins associated with HDL were identified by data-dependent acquisition (DDA) mass spectrometry using a timsTOF Pro (Bruker Daltonics) coupled with an EvoSep One system (EvoSep BioSystems). MS data was analysed using MaxQuant (v2.0.3.0) and Perseus (v2.0.3.1) software. HDL proteome composition was determined in pair-matched individuals ± obesity and in a separate cohort of patients with obesity and CKD at baseline and 1 year post gastric bypass (n=20), sleeve gastrectomy (n=19), or liraglutide±SGLT2 inhibitors treatment (n=18). An algorithm to determine inflammatory profile of the HDL particle (HDL inflammatory index score) was generated, using 20 proteins identified in obesity setting.

Results: LC-MS/MS analysis of HDL protein composition identified a total 194 proteins in ≥70% of the HDL samples. There was a significant (p≤0.05) change in 64 proteins with increase in inflammatory-related proteins and loss of antioxidant/anti-inflammatory proteins in HDL isolated from obese individuals. Surgically induced weight-loss reversed the pro-inflammatory phenotype of HDL particles with changes in 55 proteins, including reductions in Complement factor I (CFI), Complement factor B (CFB), Vitronectin (VTN) and increases in Serum paraoxonase 3 (PON3), Apolipoprotein D (APOD). In contrast, intervention with liraglutide had little impact on the HDL proteome. An HDL-inflammatory index score significantly (p≤0.0001) delineated the non-obese and obese groups. Furthermore, significant (p≤0.0001) recovery of the HDL inflammatory index was evident upon surgically induced weight-loss.

Conclusions: The HDL proteome exhibits a pro-inflammatory phenotype with deteriorating metabolic health independent of static measurements of HDL-C. The adverse effects of obesity on the HDL proteome are reversible with surgical-induced weight-loss. The data presented here suggest that the HDL proteome composition and an associated inflammatory index score can potentially be used to monitor metabolic health and identify patients at highest risk of cardiometabolic complications