Acylcarnitine and Free Fatty Acid Profiles in Primary Biliary Cholangitis: Associations with Fibrosis and Inflammation.

Background: Primary biliary cholangitis (PBC) is a chronic autoimmune liver disease characterized by bile duct destruction, cholestasis, and fibrosis. Acylcarnitines are esters of carnitine responsible for the transport of long-chain fatty acids into mitochondria for β-oxidation, playing a crucial role in energy metabolism and lipid homeostasis. This study aimed to assess acylcarnitine and free fatty acid (FFA) profiles in PBC patients and their associations with fibrosis severity and inflammation. Methods: This cross-sectional study included 46 PBC patients and 32 healthy controls. Acylcarnitines and FFAs were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and enzymatic assays, respectively. Liver stiffness was measured by point shear wave elastography (ElastPQ), and fibrosis was assessed using APRI and FIB-4 scores. Inflammatory markers (IL-6, IL-1β) were also analyzed. Results: PBC patients had significantly higher levels of C18:1-acylcarnitine (median: 165.1 ng/mL) compared with the controls (152.4 ng/mL, p = 0.0036). Similarly, the FFA levels were markedly elevated in the PBC patients (median: 0.46 mM/L) compared with the controls (0.26 mM/L, p < 0.0001). Patients with higher liver stiffness (ElastPQ > 5.56 kPa) had significantly elevated C18:1-acylcarnitine (p = 0.0008) and FFA levels (p = 0.00098). Additionally, FFAs were significantly increased in patients with higher APRI and FIB-4 scores and were associated with elevated inflammatory markers (IL-6, IL-1β) and liver injury markers. Multivariate regression analysis confirmed C18:1-acylcarnitine (OR = 1.031, 95% CI: 1.007-1.057, p = 0.013) and FFAs (OR = 2.25 per 0.1 mM/L increase, 95% CI: 1.20-4.22, p = 0.012) as independent predictors of fibrosis severity in PBC. Conclusions: C18:1-acylcarnitine and FFAs are significantly elevated in PBC and are strongly associated with fibrosis severity and inflammation. These findings suggest a link between lipid metabolism disturbances and PBC. Both metabolites may potentially serve as non-invasive biomarkers of fibrosis progression in PBC, warranting further investigation.