Abstract

Background & Aims: The consumption of sugar and a high-fat diet (HFD) promotes the development of obesity and metabolic dysfunction. Despite their well-known synergy, the mechanisms by which sugar worsens the outcomes associated with a HFD are largely elusive. Methods: Six-week-old, male, C57Bl/6 J mice were fed either chow or a HFD and were provided with regular, fructose- or glucose-sweetened water. Moreover, cultured AML12 hepatocytes were engineered to overexpress ketohexokinase-C (KHK–C) using a lentivirus vector, while CRISPR-Cas9 was used to knockdown CPT1a. The cell culture experiments were complemented with in vivo studies using mice with hepatic overexpression of KHK–C and in mice with liver-specific CPT1a knockout. We used comprehensive metabolomics, electron microscopy, mitochondrial substrate phenotyping, proteomics and acetylome analysis to investigate underlying mechanisms. Results: Fructose supplementation in mice fed normal chow and fructose or glucose supplementation in mice fed a HFD increase KHK–C, an enzyme that catalyzes the first step of fructolysis. Elevated KHK–C is associated with an increase in lipogenic proteins, such as ACLY, without affecting their mRNA expression. An increase in KHK–C also correlates with acetylation of CPT1a at K508, and lower CPT1a protein in vivo. In vitro, KHK–C overexpression lowers CPT1a and increases triglyceride accumulation. The effects of KHK–C are, in part, replicated by a knockdown of CPT1a. An increase in KHK–C correlates negatively with CPT1a protein levels in mice fed sugar and a HFD, but also in genetically obese db/db and lipodystrophic FIRKO mice. Mechanistically, overexpression of KHK–C in vitro increases global protein acetylation and decreases levels of the major cytoplasmic deacetylase, SIRT2. Conclusions: KHK–C-induced acetylation is a novel mechanism by which dietary fructose augments lipogenesis and decreases fatty acid oxidation to promote the development of metabolic complications.

Document Type

Article

Publication Date

7-2023

Notes/Citation Information

© 2023 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.jhep.2023.02.010

Funding Information

This work was supported in part by NASPGHAN Foundation Young Investigator Award, Pediatric Scientist Development Program Award (HD000850) and COCVD Pilot and Feasibility Grant (GM127211) awarded to SS, and the National Institutes of Health grants K01DK128022 and NIH National Center for Advancing Translational Sciences through grant number UL1TR001998 awarded to RNH. We acknowledge the support of instrumentation for the Orbitrap Eclipse Tribrid from the NCRR shared instrumentation grant 1S10 OD028654 (PI: Birgit Schilling)

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