Metabolisme Vitamin D

Summary

This video explains the metabolism of vitamin D in the human body, covering its two primary sources: 7-dehydrocholesterol from the skin activated by sunlight, and ergosterol from food. Sunlight triggers the activation of 7-dehydrocholesterol in the skin, converting it into vitamin D3. The absorbed vitamins are processed in the liver and kidneys, where they undergo hydroxylation to form the active form of vitamin D, calcitriol. Calcitriol then enters the bloodstream, binds with a vitamin D receptor in cells, and influences DNA transcription in the nucleus to regulate various bodily functions.

Takeaways

• 😀 Vitamin D can be obtained from two main sources: 7-dehydrocholesterol in the skin activated by sunlight and ergosterol from food.
• 🌞 UVB rays from sunlight activate 7-dehydrocholesterol in the skin, converting it into a precursor of vitamin D.
• 🍴 Vitamin D from food is absorbed in the form of vitamin B2 and vitamin B3.
• 🧑‍⚕️ Vitamin D precursors from food and the skin are transported to the liver for hydroxylation.
• 🧪 In the liver, 25-hydroxyvitamin D (calcidiol) is formed through hydroxylation by the enzyme 25-alpha-hydroxylase.
• 🩸 Calcidiol is then carried to the kidneys through the bloodstream.
• 🧬 In the kidneys, calcidiol undergoes further hydroxylation to form the active form of vitamin D, calcitriol, with the help of 1-alpha-hydroxylase.
• 💉 Calcitriol is then circulated throughout the body via the bloodstream.
• 🔬 Calcitriol enters cells by binding to the vitamin D receptor (VDR) in the cytoplasm.
• 📄 The complex between vitamin D and VDR binds with retinoic acid, which then enters the nucleus to influence DNA transcription and gene expression.

Q & A

What are the two main sources of vitamin D for the body?

The two main sources of vitamin D for the body are 7-dehydrocholesterol in the skin, which is activated by sunlight, and ergosterol, which is obtained from food.

How does sunlight contribute to vitamin D production in the body?

Sunlight contains UVB rays that, when they hit the skin, activate 7-dehydrocholesterol in the epidermis, converting it into vitamin D.

What is the process of vitamin D activation in the body?

Vitamin D from food is absorbed as vitamin D2 or D3. This vitamin is then converted into calcidiol in the liver, and further converted into calcitriol in the kidneys. Calcitriol is the active form of vitamin D that acts on cells.

What happens to vitamin D after it is absorbed into the bloodstream?

After vitamin D enters the bloodstream, it binds to a receptor called the vitamin D receptor (VDR) in the cytoplasm of cells.

How does the vitamin D receptor (VDR) play a role in the activation of vitamin D?

The vitamin D receptor (VDR) binds with vitamin D and forms a complex, which then binds with retinoic acid. This complex enters the cell nucleus, where it plays a role in DNA transcription.

What is the role of 25-alpha-hydroxylase in vitamin D metabolism?

25-alpha-hydroxylase in the liver adds an OH ion to vitamin D, converting it into calcidiol, which is then transported to the kidneys for further activation.

What enzyme is responsible for the final activation of vitamin D in the kidneys?

The enzyme responsible for the final activation of vitamin D in the kidneys is 1-alpha-hydroxylase, which converts calcidiol into calcitriol.

How is vitamin D transported after it is formed in the liver and kidneys?

After vitamin D is converted into calcidiol in the liver, it is transported to the kidneys via the bloodstream, where it undergoes further activation into calcitriol.

What is calcitriol, and why is it important?

Calcitriol, also known as 1,25-dihydroxy vitamin D, is the active form of vitamin D that is responsible for regulating various physiological processes in the body, including calcium absorption and bone health.

How does the process of DNA transcription relate to vitamin D metabolism?

Once the vitamin D-VDR complex binds with retinoic acid, it enters the cell nucleus and interacts with DNA, influencing the transcription of certain genes that regulate various bodily functions, such as calcium metabolism.