1 Department of Gastroenterology, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, United States.
2 Merck Research Laboratories, 2015 Galloping Hill Road, Kenilworth, NJ 07033, United States.
3 Department of Family Medicine, Metro Health Medical Center, Cleveland, OH, United States.
4 Department of Pharmaceutical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, United States.
5 Department of Cellular & Molecular Medicine, Cleveland Clinic, Cleveland, OH 44195, United States.
6 Department of Gastroenterology, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; Department of Pharmaceutical Sciences, Northeast Ohio Medical University, Rootstown, OH 44272, United States.
Altered lipid metabolism and inflammation are involved in the pathogenesis of both non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD). Even though high-density lipoprotein (HDL), a CVD protective marker, is decreased, whether HDL metabolism and function are perturbed in NAFLD are currently unknown. We examined the effect of NAFLD and disease severity on HDL metabolism and function in patients with biopsy-proven simple steatosis (SS), nonalcoholic steatohepatitis (NASH), and healthy controls. HDL turnover and HDL proteins dynamics in SS (n=7), NASH patients (n=8), and healthy controls (n=9) were studied in vivo. HDL maturation and remodeling, anti-oxidant, cholesterol efflux properties, and activities of lecithin cholesterol ester acyl transferase (LCAT) and cholesterol ester transfer protein (CETP) were quantified using in vitro assays. All NAFLD patients had increased turnover of both HDL cholesterol (HDLc, 0.16±0.09 vs. 0.34±0.18 day-1, P<0.05) and ApoAI (0.26±0.04 vs. 0.34±0.06 day-1, P<0.005) compared to healthy controls. The fractional catabolic rates (FCR) of other HDL proteins, including ApoAII (and ApoAIV were higher (P<0.05) in NAFLD patients who also had higher CETP activity, ApoAI/HDLc ratio (P<0.05). NAFLD-induced alterations were associated with lower antioxidant (114.2±46.6 vs 220.5±48.2 nml/ml?min) but higher total efflux properties of HDL (23.4±1.3 vs. 25.5±2.3 %) (both P<0.05) which was more pronounced in individuals with NASH. However, no differences were observed in either HDL turnover, antioxidant and cholesterol efflux functions of HDL or HDL proteins' turnover between SS and NASH subjects. Thus, HDL metabolism and function are altered in NAFLD without any significant differences between SS and NASH.