Cover Story Current Issue

Glucose is a ubiquitous and essential source of energy for all living organisms. Although mammals have evolved ways to convert other nutritional molecules to ATP, the preference for dietary glucose appears to be preserved. In rodents, the immediate detection of ingested glucose potently reinforces intake, hierarchically organizing behaviors towards glucose-yielding substances, and away from other types of food including other sugars. Taste is the primary sense linked to nutrient selection. Until recently, it was thought that most mammalian species utilize a single broadly tuned receptor to detect all simple sugars. Indeed, this “sweet” receptor, which comprises a heterodimer of the T1R2 and T1R3 proteins, binds multiple natural sugars (e.g., glucose, fructose, sucrose, maltose), as well as various other chemicals that yield little to no energy (e.g., low calorie sweeteners, sugar alcohols) and some d-amino acids. The neural signal originating from the sweet receptor is hardwired into brain circuits that drive eating and drinking behaviors, but it is an unreliable indicator of nutrient quality and quantity.

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Current Issue

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

Melissa A. Fulham, John D. Griffin, Sylvie Perez, Zhongyuan Sun, ... Gregory J. Tesz

 

Objectives

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.

Methods

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.

Results

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.

Conclusions

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.

 

 

Articles in Press

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

Melissa A. Fulham, John D. Griffin, Sylvie Perez, Zhongyuan Sun, ... Gregory J. Tesz

 

Objectives

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.

Methods

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.

Results

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.

Conclusions

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.

 

 

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You are what you eat

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