niacin def --> carcinoid syndrome?

[MudPhud20XX]

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So FA says niacin (b3) def leads to malignant carcinoid syndrome. Not really sure if this makes sense. Can anyone explain this please?

Also, how does niacin help with hyperlipidemia?

Many thanks in advance.

 

[Dr.serotonin]

they actually want to say niacin deficiency occurs in carcinoid syndrome because tryptophan (amino acid that can synthesize both niacin and serotonin) in carcinoid syndrome becomes depletes in making bulk of serotonin and hence is not available to make niacin.
niacin inhibit VLDL synthesis in liver.
pharmacologic dose of niacin results in flushing and pruritus because it releases prostaglandins. so Asprin is advised to be takin along with niacin

 

[MudPhud20XX]

they actually want to say niacin deficiency occurs in carcinoid syndrome because tryptophan (amino acid that can synthesize both niacin and serotonin) in carcinoid syndrome becomes depletes in making bulk of serotonin and hence is not available to make niacin.
niacin inhibit VLDL synthesis in liver.
pharmacologic dose of niacin results in flushing and pruritus because it releases prostaglandins. so Asprin is advised to be takin along with niacin

thanks a lot!

Could you also explain why b2 (riboflavin) def lead to corneal neovascularization? it leads to hypoxia?

 

[Dr.serotonin]

I am not sure exactly. but riboflavin also helps in the production of Glutathione. May be its deficiency can lead to free radical injury that ultimately will release EDGF to form new vessels. but I don't know for sure

 

[aspiringmd1015]

no fad formation, no atp, no atp= bunch of bad **** waiting to happen.

 

[Keto]

Great Explanation Dr. Serotonin!

I would like to add:

• Tryptophan → Niacin → NAD+
  Cofactors: B2, B6, Iron. [1]
  
  Think about Isoniazid (B6↓) causing "Niacin deficiency" (or more precisely NAD+ deficiency) leading to pellagra (Diarrhea, Dementia, Dermatitis, Death).
  
  Think about other drugs that inhibit the Tryptophan → Niacin conversion: 5-FU, Pyrazinamide, Phenobarbital, Azathioprine (and others)
  
  
• Hartnup
  autosomal recessive defect of membrane transport system of the kidney (Reabsorption of Tryptophan↓) and gut.
  Diagnosis made by demonstrating neutral amino acids in the urine.
  Treatment is supplementing the diet with Niacin, Proteins, Amino Acids.

As an interesting side note, pellagra was endemic in the US in the beginning of the 20th century, especially in the corn eating population. pellagra was thought to be an infectious disease back then. Dr Joseph Goldberger [2] was sent to the South by the US Public Health Service to evaluate this mysterious disease. He realized, that in prisons and orphanages pellagra was more common in detainees and orphans, than in staff. After adding meat to the diet, symptoms of pellagra disappeared. Dr Goldberger hypothesized that pellagra was linked to dietary factors . The connection between Niacin and pellagra was then later made after his death.


[1] https://en.wikipedia.org/wiki/Niacin
[2] http://history.nih.gov/exhibits/Goldberger/docs/pellegra_5.htm

 

[faisal 2000]

Great Explanation Dr. Serotonin!

• 
  Think about Isoniazid (B6↓) causing "Niacin deficiency" (or more precisely NAD+ deficiency) leading to pellagra (Diarrhea, Dementia, Dermatitis, Death).

pellagra (Diarrhea, Dementia, Dermatitis, atrophic papillae, Death)