Objectives:
Nonalcoholic fatty liver disease (NAFLD) is associated with an increased rate of cardiovascular disease (CVD) related mortality. HDL protects against CVD through reverse cholesterol transport, anti-oxidant and anti-inflammatory functions. HDL functions and the proteome composition are altered in CVD. We used
2
H
2
O metabolic labeling approach to test hypothesis that altered HDL proteome dynamics is involved in HDL dysfunction in NAFLD.
Methods:
The kinetics of HDL proteins were measured in patients NAFLD (n=12) and healthy controls (n=8). Each subject consumed
2
H
2
O in their drinking water and blood samples were collected at different time points during one week.
2
H-enrichment of tryptic peptides from HDL proteins were analyzed by mass spectrometry. Oxidase activity of HDL-associated ceruloplasmin (Cp) and HDL’s inflammatory index were quantified using spectrophotometric assays.
Results:
Compared to control, NAFLD had higher BMI, Hba1c, HOMA-IR, plasma AST, ALT and triglycerides, but similar LDL and HDL cholesterol. NAFLD also had higher inflammatory index (1.8±0.5 vs 1.2±0.2 RUF/mgHDLc/min, p<0.05) and oxidase activity of Cp (93.7±61.2 vs 61.2 U/L, p<0.005). This was associated with increased serum actvity of MPO (6.2±1.2 vs 8.4±1.6, p<0.05), a nutrophile-derived protein involved in HDL dysfunction. HDL
NAFLD
was significantly enriched with proteins involved in the acute phase response (complement 3, Cp) but depleted in apoAII and PON1. These changes were associated with increased fractional catabolic rates (FCRs) of apoAI (1.6±0.2 vs 1.1±0.3 %/h), apoAII (1.6±0.2 vs 1.1±0.3 %/h), apoAIV (2.6±0.8 vs 3.9±0.7%/h) and increased relative production rate (RPR) of complement 3 (>4 fold). Oxidase activity of Cp was positively associated with FCR of apoAI (r=0.53, p=0.002) and RPR of C3 (r=0.32, p=0.03).
Conclusions:
HDL dysfunction in NASH could be related to the altered turnover of HDL proteins, including increased degradation of apoAI, apoAII, apoAIV and increased production of C3.
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