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Questions and Answers
What is the primary role of Vitamin B3 in the body?
Which of the following conditions can lead to a deficiency of Vitamin B3?
What are the characteristic symptoms of Pellagra resulting from Vitamin B3 deficiency?
What dietary component is essential for the synthesis of Niacin from Tryptophan?
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What is a common side effect of excessive niacin consumption?
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Which vitamin is required for the synthesis of Vitamin B3 from Tryptophan?
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What condition can result from Malignant carcinoid syndrome related to Vitamin B3 metabolism?
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Which symptom is NOT associated with Pellagra due to Vitamin B3 deficiency?
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What treatment approach is recommended for Hartnup Disease to manage Vitamin B3 deficiency?
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What is a potential consequence of excessive niacin consumption?
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What is one of the key biochemical roles of Vitamin B3?
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Which of the following conditions is associated with reduced absorption of tryptophan?
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What symptom is NOT characteristic of Pellagra associated with Vitamin B3 deficiency?
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Which of the following statements is true regarding the excess consumption of niacin?
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What is one consequence of Isoniazid use on Vitamin B3 metabolism?
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Which condition is primarily caused by the deficiency in the transporters responsible for absorbing neutral amino acids?
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What is a symptom of excess Vitamin B3 consumption?
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What dietary approach is recommended for someone with Pellagra symptoms due to vitamin B3 deficiency?
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Which of the following options is a consequence of increased tryptophan metabolism in malignancies?
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Which vitamin deficiency can lead to decreased synthesis of Vitamin B3 from tryptophan?
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Study Notes
Vitamin B3 (Niacin, Nicotinic Acid)
- Constituent of NAD+ and NADP+, essential for redox reactions and as cofactor by dehydrogenases
- Derived from tryptophan
- B3 synthesis requires vitamins B2 (riboflavin) and B6 (biotin)
- Used to treat dyslipidemia
- Decreases VLDL levels
- Increases HDL levels
B3 Deficiency (Pellagra)
- Characterized by glossitis, dermatitis, diarrhea, and dementia
- Pellagra can be caused by Hartnup disease, a genetic disorder affecting the absorption of neutral amino acids, including tryptophan
- Hartnup disease is autosomal recessive
- Results in neutral aminoaciduria, where excess neutral amino acids are excreted in urine
- Reduced tryptophan absorption impairs niacin production
- Pellagra-like symptoms can arise due to niacin deficiency
- Treatment for Hartnup disease involves a high protein diet and nicotinic acid supplementation
- Malabsorption of tryptophan can also occur with Malignant carcinoid syndrome due to increased tryptophan metabolism and subsequent serotonin synthesis
- Isoniazid can lead to B3 deficiency by depleting vitamin B6, a crucial component in B3 synthesis
- Key symptoms of Pellagra include
- Diarrhea
- Dementia, often accompanied by hallucinations
- Dermatitis characterized by a "broad collar" rash around the neck (Casal necklace) and hyperpigmentation of sun-exposed limbs
B3 Excess
- Facial flushing is a common side-effect, mediated by prostaglandins
- Facial flushing can be prevented by taking aspirin before niacin
- Hyperglycemia and hyperuricemia can occur with high doses of niacin
Function of Vitamin B3 (Niacin)
- Vitamin B3 is a crucial component of NAD+ and NADP+ – these coenzymes are vital for redox reactions (electron transfer) and act as cofactors for various dehydrogenases.
- Body can synthesize Vitamin B3 from the amino acid tryptophan. This process requires vitamins B2 (riboflavin) and B6 (biotin).
- Vitamin B3 (Niacin) is used therapeutically to treat dyslipidemia (abnormal lipid levels in the blood).
- Specifically, it decreases VLDL (very low-density lipoprotein) and increases HDL (high-density lipoprotein).
Vitamin B3 Deficiency (Pellagra)
- Classic symptoms of pellagra are the three Ds: Dermatitis, Diarrhea, and Dementia.
- Dermatitis: Characterized by a circumferential rash in the C3/C4 dermatome, resembling a "broad collar" (Casal necklace). Sun-exposed areas of the body often show hyperpigmentation.
- Dementia: Can progress to hallucinations.
- Diarrhea: Caused by the intestinal damage that occurs due to vitamin B3 deficiency.
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Causes:
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Hartnup Disease: A rare autosomal recessive disorder involving a deficiency of transporters in the kidneys (proximal renal tubular cells) and intestines (enterocytes) responsible for absorbing neutral amino acids, including tryptophan.
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Consequences:
- Neutral aminoaciduria, resulting in excessive loss of neutral amino acids in urine.
- Reduced absorption of tryptophan, leading to niacin deficiency as tryptophan is a precursor for niacin synthesis.
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Consequences:
- Isoniazid: This medication decreases vitamin B6, which is essential for tryptophan conversion to niacin.
- Malignant carcinoid syndrome: Characterized by increased tryptophan metabolism, leading to elevated serotonin production and depletion of tryptophan for niacin synthesis.
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Hartnup Disease: A rare autosomal recessive disorder involving a deficiency of transporters in the kidneys (proximal renal tubular cells) and intestines (enterocytes) responsible for absorbing neutral amino acids, including tryptophan.
Treatment of Pellagra
- High protein diet: Supplying the body with essential amino acids like tryptophan to support niacin production.
- Nicotinic acid supplementation: Directly replacing the deficient vitamin B3.
Excess Vitamin B3 (Niacin)
- Facial flushing: A common side effect induced by prostaglandins, not histamine. Pre-treatment with aspirin can prevent this side effect.
- Hyperglycemia: Elevated blood sugar levels.
- Hyperuricemia: Increased uric acid levels in the blood.
Vitamin B3 (Niacin)
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Function:
- Constituent of NAD+ and NADP+ which are essential for redox reactions and function as cofactors for dehydrogenases.
- Derived from tryptophan.
- Niacin synthesis requires vitamin B2 (riboflavin) and B6 (biotin).
- Used to treat dyslipidemia by decreasing VLDL and increasing HDL.
Deficiency
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Presentation:
- Glossitis.
- Pellagra.
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Causes:
- Hartnup Disease (autosomal recessive)
- Deficiency in transporters responsible for absorbing neutral amino acids like tryptophan in the kidneys (proximal renal tubular cells) and intestines (enterocytes).
- Consequences:
- Neutral aminoaciduria (excess neutral amino acids excreted in the urine).
- Reduced absorption of tryptophan leading to low niacin levels.
- Pellagra-like symptoms including dermatitis, diarrhea, and dementia.
- Treatment: High protein diet and nicotinic acid.
- Malignant carcinoid syndrome (increased tryptophan metabolism into serotonin synthesis).
- Isoniazid (decreases vitamin B6).
- Hartnup Disease (autosomal recessive)
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Causes:
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Symptoms of B3 Deficiency (Pellagra):
- Diarrhea.
- Dementia (including hallucinations).
- Dermatitis (C3/C4 dermatome circumferential "broad collar" rash [Casal necklace], hyperpigmentation of sun-exposed limbs).
Excess
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Causes:
- Niacin supplementation.
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Symptoms:
- Facial flushing (induced by prostaglandins, not histamine). Taking aspirin before niacin can decrease flushing.
- Hyperglycemia.
- Hyperuricemia.
Vitamin B3 (Niacin, Nicotinic Acid)
- Niacin is used to synthesize NAD+ and NADP+, which act as cofactors for dehydrogenases and are essential for redox reactions.
- The body can synthesize niacin from the amino acid tryptophan.
- Niacin synthesis requires vitamins B2 (riboflavin) and B6 (pyridoxine).
- Niacin is used to treat dyslipidemia by decreasing very low-density lipoprotein (VLDL) levels and increasing high-density lipoprotein (HDL) levels.
Niacin Deficiency
- Deficiency results in pellagra and glossitis.
Pellagra
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Pellagra can be caused by:
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Hartnup Disease: an autosomal recessive disorder where deficient transporters in the kidneys and intestines prevent the absorption of neutral amino acids, including tryptophan, leading to:
- Neutral aminoaciduria: Excess neutral amino acids are excreted in the urine.
- Reduced tryptophan absorption: Lower tryptophan levels decrease niacin synthesis, as tryptophan is a precursor for niacin.
- Pellagra-like symptoms: Similar symptoms to pellagra, such as dermatitis, diarrhea, and dementia.
- Treatment: High protein diet and nicotinic acid supplementation.
- Malignant carcinoid syndromes: Increased tryptophan metabolism for serotonin synthesis can lead to niacin deficiency.
- Isoniazid: This medication can interfere with vitamin B6 metabolism, leading to decreased niacin synthesis and pellagra.
-
Hartnup Disease: an autosomal recessive disorder where deficient transporters in the kidneys and intestines prevent the absorption of neutral amino acids, including tryptophan, leading to:
Symptoms of Niacin Deficiency
- Diarrhea
- Dementia: This can also include hallucinations.
- Dermatitis: Presents as a circumferential rash around the neck (Casal necklace), hyperpigmentation of sun-exposed limbs (A), and affects the C3/C4 dermatomes.
Niacin Excess
- Facial flushing: Caused by prostaglandins, not histamine, and can be prevented by taking aspirin before niacin.
- Hyperglycemia
- Hyperuricemia
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Description
This quiz covers Vitamin B3 (Niacin) and its role in the body, including its synthesis and therapeutic uses, especially in treating dyslipidemia. It also discusses B3 deficiency, known as Pellagra, highlighting its symptoms, causes, and related genetic disorders like Hartnup disease. Test your knowledge on this essential vitamin and its implications on health.
