# Impaired hepatic metabolism in Hereditary Fructose Intolerance confers fructose-independent risk for steatosis and hypertriglyceridemia

## TL;DR

This study shows that people with Hereditary Fructose Intolerance can still develop liver and metabolic issues even without fructose, due to impaired fat metabolism.

## Contribution

The study reveals fructose-independent metabolic pathologies in HFI and identifies potential therapeutic targets.

## Key findings

- Aldob deletion in rats caused liver steatosis and hyperlipidemia on a fructose-free diet during fasting.
- Impaired fatty acid oxidation and elevated de novo lipogenesis were observed due to disrupted gluconeogenesis.
- ACC and DGAT2 inhibitors reduced hepatic and plasma triglycerides in AldoB-KO rats.

## Abstract

Hereditary fructose intolerance (HFI), caused by Aldolase B deficiency, is a rare genetic disorder where fructose exposure leads to severe metabolic pathologies including Type-2 diabetes and liver steatosis. Despite adhering to fructose-free diets, some individuals still present with disease. Using a rat model of HFI we demonstrate that fructose independent pathologies exist and identify the molecular pathways driving disease.

Aldob was deleted in Sprague Dawley rats using CRIPSR/Cas9 (AldoB-KO). Phenotypic, metabolomic and transcriptomic studies were conducted to identify mechanisms promoting fructose-independent pathologies. Potential molecular causes were tested using pharmacologic inhibitors and ASOs.

Deletion of Aldob caused hepatic steatosis, fibrosis and stunted growth in rats weaned on low fructose chow recapitulating human HFI. On fructose-free chow, AldoB-KO rats were phenotypically normal. However, upon fasting, male and female AldoB-KO rats developed hepatic steatosis and hyperlipidemia due to impaired fatty acid oxidation (FAOx) and elevated de novo lipogenesis (DNL). Transcriptional and metabolomic profiling revealed increased hepatic Carbohydrate Response Element Binding Protein (ChREBP) activation in AldoB-KO rats due to glycolytic metabolite accumulation caused by impaired gluconeogenesis. Treatment with Acetyl-CoA Carboxylase (ACC) and Diacylglycerol Acyl Transferase 2 (DGAT2) inhibitors reduced hepatic lipids and plasma triglycerides in AldoB-KO rats. Finally, using electronic health records we observed increased metabolic dysfunction-associated steatohepatitis (MASH) diagnosis in individuals with HFI.

Aldob deletion caused fructose-independent hyperlipidemia and steatosis upon fasting in rats. Individuals with HFI may have risk for hepatic disease and hyperlipidemia even upon fructose abstinence suggesting additional therapies may be needed to mitigate disease.

•Aldolase B deficiency causes Hereditary Fructose Intolerance (HFI), a disease where fructose exposure causes severe adverse reactions in people.•Despite fructose abstinence, individuals with HFI are at risk for developing Type-2 diabetes and often have persistent hepatic steatosis and fibrosis.•In rats lacking Aldob maintained on a fructose-free chow, overnight fasting increases plasma and hepatic triglycerides.•Loss of Aldob causes impaired fatty acid oxidation and elevated de novo lipogenesis upon fasting due to a block in hepatic gluconeogenesis and accumulation of metabolites.•Pharmacologic strategies to suppress de novo lipogenesis and enhance fatty acid oxidation partially reversed plasma and hepatic triglycerides in fasted rats lacking Aldob.

Aldolase B deficiency causes Hereditary Fructose Intolerance (HFI), a disease where fructose exposure causes severe adverse reactions in people.

Despite fructose abstinence, individuals with HFI are at risk for developing Type-2 diabetes and often have persistent hepatic steatosis and fibrosis.

In rats lacking Aldob maintained on a fructose-free chow, overnight fasting increases plasma and hepatic triglycerides.

Loss of Aldob causes impaired fatty acid oxidation and elevated de novo lipogenesis upon fasting due to a block in hepatic gluconeogenesis and accumulation of metabolites.

Pharmacologic strategies to suppress de novo lipogenesis and enhance fatty acid oxidation partially reversed plasma and hepatic triglycerides in fasted rats lacking Aldob.