👤 Rob Howes

Metabolic (dysfunction)-associated steatotic liver disease (MASLD), the hepatic consequence of metabolic syndrome, affects 30% of the global population. Studies in animals and humans investigating the effect of fructose on MASLD present conflicting findings, while in vitro methods often fail to add meaningful evidence due to acute exposures (<72 h) and non-physiological concentrations. This study aimed to determine the effect of fructose on triglyceride (TG) accumulation in HepG2 cells following acute and chronic exposures and assess its effect on the expression of genes related to de novo lipogenesis (DNL). TG concentration was measured after 48 h in response to fructose (20 mM) or glucose (20 mM), with or without a fatty acid mixture (oleic acid/palmitic acid 110 µM/55 µM), in low (5.5 mM)- and high (25.5 mM)-glucose media. To model chronic exposure, cells were maintained in fructose, glucose, or fatty acids for 28 days and the TG concentration was determined every 7 days. The effect of fructose on DNL regulators ( Neither fructose nor glucose, with or without fatty acids, changed the TG levels in cells at 48 h and the media glucose concentration had no effect on this result. Similarly, fructose did not increase TG levels after 28 days. While fructose and glucose did not affect key DNL genes at 6 h, the fatty acid mixture reduced This study shows that fructose did not significantly impact TG synthesis or DNL gene expression in the HepG2 cell model. Future studies should consider using primary human hepatocytes or more complex in vitro models. Show less

The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that controls cell cycle transitions. Its regulation by the spindle assembly checkpoint (SAC) is coordinated with the attachment of sister chromatids to the mitotic spindle. APC/C SUMOylation on APC4 ensures timely anaphase onset and chromosome segregation. To understand the structural and functional consequences of APC/C SUMOylation, we reconstituted SUMOylated APC/C for electron cryo-microscopy and biochemical analyses. SUMOylation of the APC/C causes a substantial rearrangement of the WHB domain of APC/C's cullin subunit (APC2 Show less

Dual-agonist molecules combining glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) activity represent an exciting therapeutic strategy for diabetes treatment. Although challenging due to shared downstream signalling pathways, determining the relative activity of dual agonists at each receptor is essential when developing potential novel therapeutics. The challenge is exacerbated in physiologically relevant cell systems expressing both receptors. To this end, either GIP receptors (GIPR) or GLP-1 receptors (GLP-1R) were ablated via RNA-guided clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 endonucleases in the INS-1 pancreatic β-cell line. Multiple clonal cell lines harbouring gene disruptions for each receptor were isolated and assayed for receptor activity to identify functional knockouts (KOs). cAMP production in response to GIPR or GLP-1R activation was abolished and GIP- or GLP-1-induced potentiation of glucose-stimulated insulin secretion (GSIS) was attenuated in the cognate KO cell lines. The contributions of individual receptors derived from cAMP and GSIS assays were confirmed in vivo using GLP-1R KO mice in combination with a monoclonal antibody antagonist of GIPR. We have successfully applied CRISPR/Cas9-engineered cell lines to determining selectivity and relative potency contributions of dual-agonist molecules targeting receptors with overlapping native expression profiles and downstream signalling pathways. Specifically, we have characterised molecules as biased towards GIPR or GLP-1R, or with relatively balanced potency in a physiologically relevant β-cell system. This demonstrates the broad utility of CRISPR/Cas9 when applied to native expression systems for the development of drugs that target multiple receptors, particularly where the balance of receptor activity is critical. Show less