Recent advances in the pathogenesis of hereditary fructose intolerance: implications for its treatment and the understanding of fructose-induced non-alcoholic fatty liver disease.

Hereditary fructose intolerance (HFI) is a rare inborn disease characterized by a deficiency in aldolase B, which catalyzes the cleavage of fructose 1,6-bisphosphate and fructose 1-phosphate (Fru 1P) to triose molecules. In patients with HFI, ingestion of fructose results in accumulation of Fru 1P and depletion of ATP, which are believed to cause symptoms, such as nausea, vomiting, hypoglycemia, and liver and kidney failure. These sequelae can be prevented by a fructose-restricted diet. Recent studies in aldolase B-deficient mice and HFI patients have provided more insight into the pathogenesis of HFI, in particular the liver phenotype. Both aldolase B-deficient mice (fed a very low fructose diet) and HFI patients (treated with a fructose-restricted diet) displayed greater intrahepatic fat content when compared to controls. The liver phenotype in aldolase B-deficient mice was prevented by reduction in intrahepatic Fru 1P concentrations by crossing these mice with mice deficient for ketohexokinase, the enzyme that catalyzes the synthesis of Fru 1P. These new findings not only provide a potential novel treatment for HFI, but lend insight into the pathogenesis of fructose-induced non-alcoholic fatty liver disease (NAFLD), which has raised to epidemic proportions in Western society. This narrative review summarizes the most recent advances in the pathogenesis of HFI and discusses the implications for the understanding and treatment of fructose-induced NAFLD.

Ketohexokinase C blockade ameliorates fructose-induced metabolic dysfunction in fructose-sensitive mice.

Increasing evidence suggests a role for excessive intake of fructose in the Western diet as a contributor to the current epidemics of metabolic syndrome and obesity. Hereditary fructose intolerance (HFI) is a difficult and potentially lethal orphan disease associated with impaired fructose metabolism. In HFI, the deficiency of aldolase B results in the accumulation of intracellular phosphorylated fructose, leading to phosphate sequestration and depletion, increased adenosine triphosphate (ATP) turnover, and a plethora of conditions that lead to clinical manifestations such as fatty liver, hyperuricemia, Fanconi syndrome, and severe hypoglycemia. Unfortunately, there is currently no treatment for HFI, and avoiding sugar and fructose has become challenging in our society. In this report, through use of genetically modified mice and pharmacological inhibitors, we demonstrate that the absence or inhibition of ketohexokinase (Khk), an enzyme upstream of aldolase B, is sufficient to prevent hypoglycemia and liver and intestinal injury associated with HFI. Herein we provide evidence for the first time to our knowledge of a potential therapeutic approach for HFI. Mechanistically, our studies suggest that it is the inhibition of the Khk C isoform, not the A isoform, that protects animals from HFI.

Improving patient tolerability in immunoglobulin treatment: focus on stabilizer effects.

Various types of excipients are added to immunoglobulin preparations to stabilize the product and prevent aggregation and dimer formation. These excipients, which are also called stabilizers or additives, are not inert chemicals and may have clinical implications. This is one reason why immunoglobulin products are not interchangeable. Herein, immunoglobulin preparation, excipient types and the differences among sugar stabilizers and the amino acids, glycine and proline as excipients, are presented. Preclinical studies that unravel the complexities of dimer reduction are summarized. Details of patient considerations with respect to excipient content are outlined focusing on patients with renal insufficiency, diabetes, corn allergy, hereditary fructose intolerance, inborn errors of proline metabolism, DiGeorge Syndrome and neuropsychiatric disorders associated with hyperprolinemia. Excipients are essential components of immunoglobulin preparations and their presence should be a consideration when matching patient needs to product characteristics.

Studies with type I aldolase to understand fructose intolerance and combat parasitic disease.

A structural study of the type I aldolases has been carried out to examine the isozyme specificity of these enzymes and the potential for designing specific inhibitors. Natural mutations in these aldolase enzymes are associated with haemolytic anaemia and fructose intolerance. It has also been proposed that inhibition of the parasitic version of the enzyme may provide a new lead in the design of drugs against malaria and sleeping sickness. X-ray crystallographic data is used with molecular modelling techniques to investigate the structural properties of these enzymes.