Development of an easy-to-set-up multiple heart-cutting achiral-chiral LC-LC method for the analysis of branched-chain amino acids in commercial tablets.

In this paper, the development and application of a multiple heart-cutting achiral-chiral LC-LC method (mLC-LC) for the analysis of dansylated (Dns) branched-chain amino acids in commercial tablets are described. In the first dimension, a Waters Xbridge RP C18 achiral column was used under gradient conditions with buffered aqueous solution and acetonitrile. The elution order Dns-valine (Dns-Val) < Dns-isoleucine (Dns-Ile) < Dns-leucine (Dns-Leu) turned out with full resolution between adjacent peaks: 7.25 and 1.50 for the Val/Ile and the Ile/Leu pairs, respectively. A "research" validation study was performed, revealing high accuracy (Recovery%) and precision (RSD%) using two external set solutions, respectively, in the range 93.7%-104.1% and 0.4%-3.2%. The C18 column was connected via a two-position six-port switching valve to the quinidine-based Chiralpak quinidine-anion-exchange chiral column. A water/acetonitrile, 30/70 (v/v) with 50 mM ammonium acetate (apparent pH of 5.5) eluent allowed getting the three enantiomers' pairs resolved: RS equal to 4.3 for Dns-Val and Dns-Ile, and 1.7 for Dns-Leu. The application of the mLC-LC method confirmed that the content of Val, Ile, and Leu in the tablets was compliant with that labeled by the producer. Only l-enantiomers were found in the food supplement, as confirmed by LC-MS/MS analysis.

Transcriptomics of natural and synthetic vitamin D in human hepatocyte lipotoxicity.

Vitamin D (VD) has been used to prevent nonalcoholic fatty liver disease (NAFLD), a condition of lipotoxicity associated with a defective metabolism and function of this vitamin. Different forms of VD are available and can be used for this scope, but their effects on liver cell lipotoxicity remain unexplored. In this study we compared a natural formulation rich in VD2 (Shiitake Mushroom extract or SM-VD2) with a synthetic formulation containing pure VD3 (SV-VD3) and the bioactive metabolite 1,25(OH)2-D3. These were investigated in chemoprevention mode in human HepaRG liver cells supplemented with oleic and palmitic acid to induce lipotoxicity. All the different forms of VD showed similar efficacy in reducing the levels of lipotoxicity and the changes that lipotoxicity induced on the cellular transcriptome. However, the three forms of VD generated different gene fingerprints suggesting diverse, even if functionally convergent, cytoprotective mechanisms. Main differences were (1) the number of differentially expressed genes (SV-VD3 > 1,25[OH]2-D3 > SM-VD2), (2) their identity that demonstrated significant gene homology between SM-VD2 and 1,25(OH)2-D3, and (3) the number and type of biological functions identified by ingenuity pathway analysis as relevant to liver metabolism and cytoprotection annotations. Immunoblot confirmed a different response of VDR and other VDR-related proteins to natural and synthetic VD formulations, including FXR, PXR, PPARγ/PGC-1α, and CYP3A4 and CYP24A1. In conclusion, different responses of the cellular transcriptome drive the cytoprotective effect of natural and synthetic formulations of VD in the free fatty acid-induced lipotoxicity of human hepatocytes.