Phosphatidylcholines as regulators of glucose and lipid homeostasis: promises and potential risks

Lactobacillus plantarum Alters Gut Microbiota and Metabolites Composition to Improve High Starch Metabolism in Megalobrama amblycephala

The aim of this study was to explore the effects of adding Lactobacillus plantarum (LAB) to a high-starch diet on glucose and lipid metabolism, gut microbiota, and the composition of metabolites in Megalobrama amblycephala. This experiment was equipped with three isonitrogenous and isoenergetic feeds as control group (LW), high starch group (HW), and high starch with LAB group (HP). A total of 180 experimental fish (13.5 ± 0.5 g) were randomly divided into three treatments, and three floating cages (1 m × 1 m × 1 m) were set up for each treatment. A total of 20 fish per net were kept in an outdoor pond for 8 weeks. The results showed that both the HW and HP groups had an altered structure and a reduced diversity of gut microbiota. LAB increased the abundance of Cetobacterium and the ratio of Firmicutes/Bacteroidota and decreased PC (16:1/20:5) and taurochenodeoxycholic acid levels. LAB promoted the expression of genes related to the intestinal bile acid cycle (fxr, hmgcr, rxr, shp and hnf4α) and inhibited the expression of pparβ and g6pase (p < 0.05). LAB reduced the expression of genes related to transported cholesterol (lxr and ldlr) (p < 0.05) in the liver. In conclusion, LAB addition could regulate the gut microbiota disorders caused by high starch levels, promote cholesterol metabolism, produce bile acids, and reduce lipid deposition.

ABCB4 disease: Many faces of one gene deficiency

ATP-binding cassette (ABC) subfamily B member 4 (ABCB4), also known as multidrug resistance protein 3 (MDR3), encoded by ABCB4, is involved in biliary phospholipid secretion, protecting hepatobiliary system from deleterious detergent and lithogenic properties of the bile. ABCB4 mutations altering canalicular ABCB4 protein function and expression may have variable clinical presentation and predispose to several human liver diseases. Well-established phenotypes of ABCB4 deficit are: progressive familial intrahepatic cholestasis type 3, gallbladder disease 1 (syn. low phospholipid associated cholelithiasis syndrome), high ɣ-glutamyl transferase intrahepatic cholestasis of pregnancy, chronic cholangiopathy, and adult biliary fibrosis/cirrhosis. Moreover, ABCB4 aberrations may be involved in some cases of drug induced cholestasis, transient neonatal cholestasis, and parenteral nutrition-associated liver disease. Recently, genome-wide association studies have documented occurrence of malignant tumours, predominantly hepatobiliary malignancies, in patients with ABCB4/MDR3 deficit. The patient's age at the time of the first presentation of cholestatic disease, as well as the severity of liver disorder and response to treatment are related to the ABCB4 allelic status. Mutational analysis of ABCB4 in patients and their families should be considered in all individuals with cholestasis of unknown aetiology, regardless of age and/or time of onset of the first symptoms.

The hepatic phosphatidylcholine transporter ABCB4 as modulator of glucose homeostasis

The hepatic phosphatidylcholine (PC) transporter ATP-binding cassette (ABC) B4 flops PC from hepatocytes into bile, and its dysfunction causes chronic cholestasis and fibrosis. Because a nuclear receptor-dependent PC pathway has been determined to exert antidiabetic effects, we now analyzed the role of ABCB4 in glucose metabolism. We bred congenic Abcb4-knockout (Abcb4(-/-)) mice on the fibrosis-susceptible BALB/cJ background. Knockout mice and wild-type controls were phenotyped by measuring plasma glucose concentrations, intraperitoneal glucose tolerance, hepatic RNA expression profiles, and liver histology. In addition, 4 procholestatic ABCB4 gene variants were correlated with blood glucose levels in 682 individuals from 2 independent European cohorts. Systemic glucose levels differ significantly between Abcb4(-/-) mice and wild-type controls, and knockout mice display improved glucose tolerance with significantly lower area under the curve values on intraperitoneal glucose challenge. Of note, hepatic expression of the antidiabetic nuclear receptor 5A2 (LRH-1) is induced consistently in Abcb4(-/-) mice, and its specific rare PC ligands are detected in liver by mass spectrometry imaging. In humans, serum glucose levels are associated significantly with the common ABCB4 variant c.711A>T. In summary, ABCB4 might play a critical role in glucose homeostasis in mice and humans. We speculate that the effects could be mediated via LRH-1-dependent PC pathways.