Insulin dysregulation drives mitochondrial cholesterol metabolite accumulation: initiating hepatic toxicity in nonalcoholic fatty liver disease.

CYP7B1 catalyzes mitochondria-derived cholesterol metabolites such as (25R)26-hydroxycholesterol (26HC) and 3ß-hydroxy-5-cholesten-(25R)26-oic acid (3ßHCA) and facilitates their conversion to bile acids. Disruption of 26HC/3ßHCA metabolism in the absence of CYP7B1 leads to neonatal liver failure. Disrupted 26HC/3ßHCA metabolism with reduced hepatic CYP7B1 expression is also found in nonalcoholic steatohepatitis (NASH). The current study aimed to understand the regulatory mechanism of mitochondrial cholesterol metabolites and their contribution to onset of NASH. We used Cyp7b1-/- mice fed a normal diet (ND), Western diet (WD), or high-cholesterol diet (HCD). Serum and liver cholesterol metabolites as well as hepatic gene expressions were comprehensively analyzed. Interestingly, 26HC/3ßHCA levels were maintained at basal levels in ND-fed Cyp7b1-/- mice livers by the reduced cholesterol transport to mitochondria, and the upregulated glucuronidation and sulfation. However, WD-fed Cyp7b1-/- mice developed insulin resistance (IR) with subsequent 26HC/3ßHCA accumulation due to overwhelmed glucuronidation/sulfation with facilitated mitochondrial cholesterol transport. Meanwhile, Cyp7b1-/- mice fed an HCD did not develop IR or subsequent evidence of liver toxicity. HCD-fed mice livers revealed marked cholesterol accumulation but no 26HC/3ßHCA accumulation. The results suggest 26HC/3ßHCA-induced cytotoxicity occurs when increased cholesterol transport into mitochondria is coupled to decreased 26HC/3ßHCA metabolism driven with IR. Supportive evidence for cholesterol metabolite-driven hepatotoxicity is provided in a diet-induced nonalcoholic fatty liver mouse model and by human specimen analyses. This study uncovers an insulin-mediated regulatory pathway that drives the formation and accumulation of toxic cholesterol metabolites within the hepatocyte mitochondria, mechanistically connecting IR to cholesterol metabolite-induced hepatocyte toxicity which drives nonalcoholic fatty liver disease.

Dried blood spot-based newborn screening for bile acid synthesis disorders, Zellweger spectrum disorder, and Niemann-Pick type C1 by detection of bile acid metabolites.

OBJECTIVE: To examine whether it is possible to screen for bile acid synthesis disorders (BASDs) including peroxisome biogenesis disorder 1a (PBD1A) and Niemann-Pick type C1 (NPC1) at the time of newborn mass screening by measuring the intermediary metabolites of bile acid (BA) synthesis. METHODS: Patients with 3ß-hydroxy-ΔSuchy et al. (2021)5-C27-steroid dehydrogenase/isomerase (HSD3B7) deficiency (n = 2), 3-oxo-ΔPandak and Kakiyama (n.d.)4-steroid 5ß-reductase (SRD5B1) deficiency (n = 1), oxysterol 7α-hydroxylase (CYP7B1) deficiency (n = 1), PBD1A (n = 1), and NPC1 (n = 2) with available dried blood spot (DBS) samples collected in the neonatal period were included. DBSs from healthy neonates at 4 days of age (n = 1055) were also collected for the control. Disease specific BAs were measured by newly optimized liquid chromatography-tandem mass spectrometry with short run cycle (5-min/run). The results were validated by comparing with those obtained by the conventional condition with longer run cycle (76-min/run). RESULTS: In healthy specimens, taurocholic acid and cholic acid were the two major BAs which constituted approximately 80% in the measured BAs. The disease marker BAs presented <10%. In BASDs, the following BAs were determined for the disease specific markers: Glyco/tauro 3ß,7α,12α-trihydroxy-5-cholenoic acid 3-sulfate for HSD3B7 deficiency (>70%); glyco/tauro 7α,12α-dihydroxy-3-oxo-4-cholenoic acid for SRD5B1 deficiency (54%); tauro 3ß-hydroxy-5-cholenoic acid 3-sulfate for CYP7B1 deficiency (94%); 3α,7α,12α-trihydroxy-5ß-cholestanoic acid for PBD1A (78%); and tauro 3ß,7ß-dihydroxy-5-cholenoic acid 3-sulfate for NPC1 (26%). *The % in the parenthesis indicates the portion found in the patient's specimen. CONCLUSIONS: Early postnatal screening for BASDs, PBD1A and NPC1 is feasible with the described DBS-based method by measuring disease specific BAs. The present method is a quick and affordable test for screening for these inherited diseases.

Age at surgery and native liver survival in biliary atresia: a systematic review and meta-analysis.

Biliary atresia (BA) is a childhood rare disease of the liver and bile ducts that requires prompt surgical intervention. Age at surgery is an important prognostic factor; however, controversy exists with regard to the benefit of early Kasai procedure (KP). We aimed to conduct a systematic review and meta-analysis to examine the relationship between the age at KP and native liver survival (NLS) of BA patients. We performed the electronic database search using Pubmed, EMBASE, Cochrane, and Ichushi Web and included all relevant studies published from 1968 up to May 3, 2022. Studies that examined the timing of KP at ages 30, 45, 60, 75, 90, 120, and/or 150 days were included. The outcome measures of interest were NLS rates at 5, 10, 15, 20, and 30 years post-KP and the hazard ratio or risk ratio for NLS. The quality assessment was used using the ROBINS-I tool. Among 1653 potentially eligible studies, nine articles met the inclusion criteria for the meta-analysis. Meta-analysis for hazard ratios revealed that there was a significantly faster time to liver transplantation in the group of patients who had KP at later timing as compared with earlier KP (HR = 2.12, 95% CI 1.51-2.97). The risk ratio comparing KP ≤ 30 days and KP ≥ 31 days on native liver survival was 1.22 (95% CI 1.13-1.31). The sensitivity analysis showed that comparing KP ≤ 30 days and KP 31-60 days, the risk ratio was 1.13, 95% CI 1.04-1.22.  Conclusion: Our meta-analysis showed the importance of early diagnosis and surgical interventions ideally before 30 days of life in infants with BA on native liver survival on 5, 10, and 20 years. Therefore, effective newborn screening of BA targeting KP ≤ 30 days is needed to ensure prompt diagnosis of affected infants. What is Known: • Age at surgery is an important prognostic factor. What is New: • Our study performed an updated systematic review and meta-analysis to examine the relationship between age at Kasai procedure and native liver survival in patients with BA.

Profiling of Urinary Glucuronidated Bile Acids across Age Groups.

We investigated the age-dependent changes in urinary excretion of glucuronidated bile acids at the C-3 position. Bile acid 3-glucuronides accounted for 0.5% of urinary bile acids in neonates, and the proportion of bile acid 3-glucuronides plateaued at 1-3 years of age. The 3-glucuronides of secondary bile acids were first secreted at 3 months of age, the same time as the establishment of the gut bacterial flora in infants. A considerable portion of bile acid 3-glucuronides were present as non-amidated forms. Our results indicate dynamic hepatic enzyme activity in which the levels of uridine 5'-diphospho-glucuronosyltransferases (UGTs) differ by age group, with higher glucuronidation activity of UGTs towards nonamidated bile acids than amidated bile acids.