Cholesterol gallstone formation in hypercholesterolemia

FGF15 promotes hepatic NPC1L1 degradation in lithogenic diet-fed mice

BACKGROUND

Cholesterol gallstone disease (CGD) is accompanied by biliary cholesterol supersaturation. Hepatic Niemann-Pick C1-like 1 (NPC1L1), which is present in humans but not in wild-type (WT) mice, promotes hepatocyte cholesterol uptake and decreases biliary cholesterol supersaturation. In contrast, intestinal NPC1L1 promotes intestinal cholesterol absorption, increasing biliary cholesterol supersaturation. Ezetimibe (EZE) can inhibit both hepatic and intestinal NPC1L1. However, whether hepatic NPC1L1 can affect CGD progress remains unknown.

METHODS

Mice expressing hepatic NPC1L1 (NPC1L1^hepatic-OE mice) were generated using Adeno-associated viruses (AAV) gene delivery. The protein level and function of hepatic NPC1L1 were examined under chow diet, high fat-cholesterol diet (HFCD), and lithogenic diet (LD) feeding. Gallstone formation rates were examined with or without EZE treatment. Fibroblast growth factor 15 (FGF15) treatment and inhibition of fibroblast growth factor receptor 4 (FGFR4) were applied to verify the mechanism of hepatic NPC1L1 degradation.

RESULTS

The HFCD-fed NPC1L1^hepatic-OE mice retained the biliary cholesterol desaturation function of hepatic NPC1L1, whereas EZE treatment decreased biliary cholesterol saturation and did not cause CGD. The ubiquitination and degradation of hepatic NPC1L1 were discovered in LD-fed NPC1L1^hepatic-OE mice. Treatment of FGF15 during HFCD feeding and inhibition of FGFR4 during LD feeding could affect the protein level and function of hepatic NPC1L1.

CONCLUSIONS

LD induces the ubiquitination and degradation of hepatic NPC1L1 via the FGF15-FGFR4 pathway. EZE may act as an effective preventative agent for CGD.

An inverse association of weight and the occurrence of asymptomatic gallbladder stone disease in hypercholesterolemia patients: a case-control study

Background

Despite the fact that the majority of gallstones formed in the gallbladder are mainly composed of cholesterol, as they are formed from cholesterol-supersaturated bile, and hypercholesterolemia is a common metabolic disorder, which is closely related to cardiac, hepatic, renal and other oxidative damage inflammation and necrosis, there is still no consensus regarding the contribution of blood serum lipids in the pathogenesis of gallbladder stone disease (GSD). This study aimed to investigate the relationship between hypercholesterolemia and the risk of new-onset asymptomatic GSD, and to determine the prevalence of factors associated with new-onset asymptomatic GSD in patients with hypercholesterolemia.

Methods

In this study, 927 Chinese patients with new-onset asymptomatic gallstone disease and 845 healthy controls were enrolled starting from August 2012. Patients were matched for age, gender, race, occupation, systolic blood pressure, diastolic blood pressure, and fasting blood glucose levels (FBG). Body mass index (BMI), nonalcoholic fatty liver disease (NAFLD) and serum lipids indexes were compared and the relationships between BMI, blood lipid and gallbladder stone hazards were examined by logistic multivariate regression models.

Results

The result showed a significantly higher morbidity with GSD in hypercholesterolemia than non-hypercholesterolemia patients (Χ² = 17.211, P < 0.001). Of hypercholesterolemia patients, low density lipoprotein (OR = 1.493, P = 0.029) and NAFLD (OR = 2.723, P = 0.022) were significant risk factors for GSD, while being male (OR = 0.244, P = 0.033), weight (OR = 0.961, P = 0.022), high density lipoprotein (OR = 0.305, P < 0.001), and FBG (OR = 0.687, P = 0.034) were significantly negatively correlated with GSD in univariate analysis. Multivariate logistic regression indicated weakly positive correlations with NAFLD (OR = 3.284, P = 0.054), and significant negative correlations with weight (OR = 0.930, P = 0.018), HDL-c (OR = 0.144, P < 0.001), and GSD.

Conclusion

Hypercholesterolemia acts as an independent risk factor for new-onset asymptomatic GSD, while obesity and NAFLD are synergistic factors. Interestingly, it is first reported that elevated weight was inversely associated with GSD in patients with hypercholesterolemia. The results of this study suggest that effective control of hyperlipidemia is of greater significance than weight loss, which might make the situation worse, in the prevention of GSD in obese patients with hyperlipidemia.