Vitamins... A and D3...interactions...

K

kinyonga

Chameleon Queen
"the transcriptional response to RA and vitamin D depends on a complex combinatory pattern of interaction among different receptors wih DNA and coactivators"...
https://www.karger.com/Article/Abstract/53276

"Retinol does not affect vitamin D metabolism directly. Vitamin D does not affect serum retinoids directly"...
https://vitamindwiki.com/Vitamin+A+interferes+with+vitamin+D+and+may+be+the+cause+of+U+shaped+relationships+–+April+2014

http://genesdev.cshlp.org/content/9/7/769.full.pdf
 
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kinyonga said:
"the transcriptional response to RA and vitamin D depends on a complex combinatory pattern of interaction among different receptors wih DNA and coactivators"...
https://www.karger.com/Article/Abstract/53276

https://vitamindwiki.com/Vitamin+A+interferes+with+vitamin+D+and+may+be+the+cause+of+U+shaped+relationships+–+April+2014
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I’ve been reading a lot about calcium and phosphorus homeostasis lately. So most actions of 1,25 dihydroxy vitamin D3 require complex first with vitamin D receptors (VDR) and then with retinoic acid X receptors (RXR). Only then can it affect gene transcription and produce proteins/effects (increased intestinal calcium and phosphorus absorption, etc)
As noted retinoic acid receptors also use RXR receptors to affect transcription of genes.

This could definitely explain the “antagonistic” effects of Vitamin D and Vitamin A that are frequently talked about. If one or the other is not properly proportionate to the other it could outcompete the other for its normal functions (create a relative deficiency)

Awesome stuff @kinyonga
 
DocZ said:
I’ve been reading a lot about calcium and phosphorus homeostasis lately. So most actions of 1,25 dihydroxy vitamin D3 require complex first with vitamin D receptors (VDR) and then with retinoic acid X receptors (RXR). Only then can it affect gene transcription and produce proteins/effects (increased intestinal calcium and phosphorus absorption, etc)
As noted retinoic acid receptors also use RXR receptors to affect transcription of genes.

This could definitely explain the “antagonistic” effects of Vitamin D and Vitamin A that are frequently talked about. If one or the other is not properly proportionate to the other it could outcompete the other for its normal functions (create a relative deficiency)

Awesome stuff @kinyonga
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Thanks! I've been working on the connection for a long time and was so excited when I found out about the RXR connection. It's more complex than I thought though...and I'm lacking in my knowledge in the area. Should have studied science related topics more when I was in school!

Now if I could only figure out follicular stasis to my satisfaction! 😏
 
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kinyonga said:
Thanks! I've been working on the connection for a long time and was so excited when I found out about the RXR connection. It's more complex than I thought though...and I'm lacking in my knowledge in the area. Should have studied science related topics more when I was in school!
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It’s definitely pushing the limits of biochemistry knowledge 😂

It’s been a long time since college/med school
 
I don't know how we will ever get things right. Everything varies to some degree from species to species...everything is such a balancing act...give enough D3 from supplements that it's not an overdose but that we know the rest will be provided by the UVB exposure...give enough vitamin A that it balances the vitamin D3 but that the chameleon gets enough of both...give enough vitamin A that there are no eye, skin, etc issues....provide enough shade that the chameleon can chose to escape the UVB if it wants to....make sure that the vitamin A and D3 from supplements are both not overdosed but cause organ damage...etc.
 
And as you know, chameleon keeping can be done very successfully (multiple generations, keeping and breeding of species considered very difficult to keep) without any preformed A and D in the supplementation routine
 
DocZ said:
I could most certainly be wrong, but I think this ratio is found in vivo in organ storage
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However, even if this is the case, storage ratio does not necessarily reflect dietary requirements.
One could easily be avidly stored over another for a variety of reasons
 
kinyonga said:
In WC chameleons?
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No. In other animals.
kinyonga said:
One place the 10:1 ratio of A to D3...
https://www.madcham.de/en/supplementation/
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so this sites the Hoby study. I have some questions about this study. It gives data on veiled chameleon serum calcium and 25-hydroxy D3, and liver levels of 25-hydroxy D3 and vitamin A which is very cool and some of the first data of its kind

I’m unsure why groups that had A supplementation without D were included, but no groups had D supplementation without A. The addition of Calcium supplementation only and Calcium plus UV would also have been helpful. Also the UVB was supplied using 23W CFL bulbs. The UVB irradiance measured drops over 94% from 4 cm (1.57”) to 25 cm (9.8”). The Chams were in 42 cm tall cages so they could easily have very little UV exposure. Although increase in 25-hydroxy D3 was seen in all groups (that had data) that received UVB, so UV exposure showed large effects

No reasoning was given behind choosing the 10 to 1 Vitamin A to D ratio, so I don’t know where that came from exactly.
Another interesting feature was segmental calcifications of the colon seen only chameleons given A supplementation. I find these ectopic calcifications worrisome.
The Calcium and A only group had the highest liver vitamin A levels. This could highlight a lack of antagonism of Vitamin D. Otherwise the levels were similar and wasn’t noted if any statistically significant differences were found

It’s a very cool article, but i don’t think it explains the 10 to 1 ratio and I feel like there was a design flaw in not providing adequate UVB and in not examining CaD, CaDUV, Ca, and CaUV groups

https://watermark.silverchair.com/1...S9jevewXNAoq5iKwujT5Mts6KIcV-sxc8JZt7bEkVUAU8
 
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It was the only site I could find a mention of the 10:1 ratio for A to D....I'm going to look for more! Only so many hours in a day!
Also, I've never liked that study.
 
kinyonga said:
It was the only site I could find a mention of the 10:1 ratio for A:D...I'm going to look for more! Only so many hours in a day!
Also, I've never liked that study.
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I’ll be honest. I’ve been waiting to complain about that one 😂

I’ll keep digging too. I’m sure I’ve heard/seen it elsewhere
 
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