Vitamin B4 (Choline) - Nutrition

What is Choline?

Choline, also referred to as vitamin B₄, is considered an essential vitamin-like substance for dogs and cats. It is soluble in water and often included with B vitamin supplement mixtures. Most animals are able to synthesise some choline endogenously during degradation of phospholipids in the liver. Free choline is released during metabolism of phosphotidylcholine and sphingomyelin, which can then be reincorporated into a new phospholipid or used as choline or the choline metabolite, betaine.

Why is it Important?

Choline is an important intermediary in reactions involving methyl donation. It is also a component of membrane phospholipids and the neurotransmitter acetylcholine.

Roles in the Body

1. Methyl Transfer: Choline contains three methyl groups (compared to one in s-adenosylmethionine or methionine), and its active metabolite betaine acts as a methyl donor in reactions such as the conversion of homocysteine to methionine. The requirement for choline is influenced by total methyl group metabolism and the intake of other methyl containing compounds, such as s-adenosylmethionine and betaine.
2. Phospholipid: Phosphotidylcholine is one of the most abundant membrane phospholipids in the body. It provides structure to cellular membranes and is required for the formation of very low-density lipoproteins (VLDL) in the liver. Phospholipids are also involved in signal transduction between cells.
3. Neurotransmitter: A small fraction of the daily choline needs are further acetylated to form acetylcholine.

Consequences of Choline Deficiency

Choline requirements are dependent on other methyl containing dietary compounds, such as methionine, Vitamin B₁₂, folate, and lecithin (phosphotidylcholine).

Dogs:

Puppies fed a choline deficient diet developed fatty accumulation within the liver; death occurred within 3 weeks of initiating feeding a choline deficient diet. Adult dogs fed choline deficient diets can develop hypocholesterolaemia, experience increased liver enzyme activities, vomiting, and fatty liver.

Cats:

Sub-optimal intake of choline results in decreased food intake and poor growth in kittens, and hepatic lipid accumulation.

Toxicity

There are no published reports of choline toxicity in cats. Early studies in excess choline intake in dogs suggest that depressed erythrocyte formation may occur.

Dietary Sources

High concentrations of choline as phosphotidylcholine are present in eggs, liver and soya. Free choline is found in vegetables, such as cauliflower and dark leafy greens. The choline metabolite betaine is found in beets, and in lecithin which is used as an industrial emulsifier in many processed foods (for pets and people).

Diagnosing Choline Deficiency

Diagnosis of choline deficiency is based on measurement of low plasma choline and phosphatidylcholine concentration. A deficiency is suspected based on the presence of compatible clinical signs and dietary analysis.

References

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