fructose intolerance and infertility

[Teee]

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I can't seem to find the answer anywhere. if a patient is fructose intolerant, would he be infertile since sperm need fructose? Thanks

 

[SnowTown]

no because their body can convert other things into fructose???

 

[perilou]

no because their body can convert other things into fructose???

I think he's asking because the sperm rely on fructose for energy, and if they have his geno/phenotype, they won't be able to use fructose for energy.

I don't know the answer, but it's an interesting question.

 

[scube]

sperm have aldose reductase. which turns glucose into sorbital. Sorbital can be turned into fructose for the baby makers via a enzyme called sorbital dehydrogenase. I didn't think that nugget would ever come up. thank you USMLEWORLD

 

[EBI831]

i wouldn't think so. b/c fructose intolerance, i thought was mainly a lack of the fructose kinase or aldolase B enzymes that convert fructose into intermediates for gluconeogenesis/glycolysis etc and in sperm, the main source is fructose that you get via the sorbitol/polylol pathway where the whole point is to have fructose not to convert it into some glucose form. but that's just my understanding....i guess if your fructose intolerance was due to a lack of one of the enzymes in the polyol/sorbitol pathway then maybe but overall essential fructosuria and fructose intolerance really have little to do with this sorbitol pathway and more to do with enzymes converting fructose to gluconeogenesis and glycolsyis intermediates.

 

[perilou]

sperm have aldose reductase. which turns glucose into sorbital. Sorbital can be turned into fructose for the baby makers via a hormone called sorbital dehydrogenase. I didn't think that nugget would ever come up. thank you USMLEWORLD

Maybe I am not understanding this correctly.

I don't think it's an issue of whether or not the sperm will have access to fructose. They will. Fructose will be all over the place. But, they won't be able to do anything with it. So, they'd die. Is this right?

 

[scube]

you guys make an excellent point. I have apparently gotten used to seeing a vignette and then answering a question that has little to do with the actual problem. Im not sure about the infertility. I would think that we would have evolved a better system. The fructokinase def would maybe cause a slight drop in count but could be compensated with hexokinase. the aldose b is a real bugaboo tho. Sorry about not answering the question with a answer.

 

[quietude]

you guys make an excellent point. I have apparently gotten used to seeing a vignette and then answering a question that has little to do with the actual problem. Im not sure about the infertility. I would think that we would have evolved a better system. The fructokinase def would maybe cause a slight drop in count but could be compensated with hexokinase. the aldose b is a real bugaboo tho. Sorry about not answering the question with a answer.

I think that fertility could *possibly* still be present, but the patient has much bigger issues to worry about before they get to reproductive age.

After all, like you said, hexokinase can process fructose (and does so when fructokinase is deficient). That would take it to F6P, which would bypass aldolase B (which is the conversion of F1P to DHAP and glyceraldehyde). F6P could then go through the energy cycle just fine.

Now how that patient could get fructose to go through hexokinase without simultaneously running into the problems of F1P buildup is probably a whole other issue.

 

[scube]

well. it really depends on which deficiency they have.

 

[mdorbust2018]

In the absence of fructokinase, hexokinase phosphorylates fructose for entry into glycolysis (according to UW). Maybe this just takes over preventing infertility.