L9 Lipid-Soluble Vitamins

Vitamin D is synthesized in the skin when 7-dehydrocholesterol is exposed to UV light. It is then transported to the liver and hydroxylated to form 25-hydroxycholecalciferol (25-OHD3). The kidney further hydroxylates 25-OHD3 to calcitriol (1,25-dihydroxycholecalciferol), the active form of vitamin D, which plays a vital role in calcium homeostasis.

Calcitriol, the active form of vitamin D, is synthesized in the kidney, primarily under the influence of parathyroid hormone (PTH) and low calcium levels.

Low blood calcium levels (hypocalcemia) stimulate PTH secretion, which in turn activates 1α-hydroxylase in the kidney, leading to increased calcitriol production. This ultimately increases calcium absorption in the gut and releases calcium from bone.

Hypophosphatemia (low phosphate levels) also stimulates 1α-hydroxylase activity in the kidney, leading to higher calcitriol production.

Increased levels of calcitriol suppress its own synthesis through a negative feedback mechanism, ensuring that the production of this hormone is tightly controlled.

Vitamin D deficiency can lead to various consequences, including rickets in children and osteomalacia in adults, characterized by bone weakness and deformities. It can also contribute to other health issues like increased risk of fractures, cardiovascular disease, and certain types of cancer.

Excess vitamin D can be toxic, leading to hypercalcemia (high calcium levels). This can cause symptoms like nausea, vomiting, constipation, kidney stones, and even heart rhythm abnormalities in severe cases.

A condition in children characterized by insufficient calcium leading to soft bones that bend easily, affecting areas like the spine, pelvis, and tibia. This occurs due to impaired bone mineralization caused by Vitamin D deficiency, hindering the formation of hydroxyapatite.

Vitamin D deficiency leads to reduced calcium absorption from the gut, causing bones to lose their mineral content. This results in weak bones prone to fractures, characterized by normal collagen matrix but deficient mineralization. X-rays show pseudo-fractures affecting vertebral bodies and femoral necks. Occurs in adults.

The mineral component of bone, essential for bone strength and rigidity. Deficiency due to inadequate calcium intake or Vitamin D deficiency leads to soft and weak bones.

The hormone responsible for regulating calcium levels in the blood. Vitamin D deficiency triggers increased PTH release, which mobilizes calcium from bones, leading to bone weakness.

A condition characterized by insufficient Vitamin D levels, leading to impaired bone mineralization and increased risk of rickets in children and osteomalacia in adults.

Vitamin D plays a crucial role in maintaining adequate levels of calcium and phosphorus in the bloodstream, which is essential for bone health.

This refers to the process of mineral deposition in bone, where calcium and phosphorus are incorporated into the bone matrix, strengthening and supporting the skeletal structure.

Emerging research suggests that Vitamin D may have protective effects against various health conditions, including cancer, cardiovascular disease, diabetes, autoimmune disorders, and cognitive decline.

Vitamin D stimulates the production of a protein called calbindin in the gastrointestinal tract. This protein helps increase the absorption of calcium and phosphate from the intestines, making them readily available for the body to utilize.

Vitamin D acts on the kidneys, enhancing the reabsorption of calcium. This means more calcium gets returned to the bloodstream, further contributing to maintaining the overall balance of calcium levels.

Vitamin D stimulates osteoblasts, which are bone-building cells, to produce a protein called osteocalcin, which plays a critical role in calcium binding within the bone matrix. This increased activity leads to enhanced bone mineralization, strengthening the bones.

Steroid and thyroid hormones are fat-soluble and, therefore, easily penetrate cell membranes without the need for carrier proteins.

These hormones bind to specific receptor proteins located inside the cell, either in the cytoplasm or the nucleus, to initiate their biological effects.

An enzyme that helps in the formation of calcitriol, the active form of vitamin D, in the kidneys.

Low levels of calcium in the blood.

Low levels of phosphorus in the blood.

The main organic component of bone matrix, providing strength and structure.

A bone cell responsible for building new bone tissue.

A bone cell responsible for breaking down old bone tissue.

A condition where bone breakdown (resorption) exceeds bone formation, leading to decreased bone mass and density. This makes bones brittle and prone to fractures.

A group of fat-soluble compounds that are essential for vision, cell growth, and immune function. They can exist in various forms, including retinol, retinal, and retinoic acid.

A specific form of vitamin A involved in vision. It's present in rhodopsin, a protein that captures light in the eye.

A protein found in rod cells of the retina that is essential for vision in low light conditions. It's made up of retinal and opsin, a protein.

The process of changing the shape of retinal from 11-cis to 11-trans retinal. This triggers a chain reaction that results in vision.

A molecule that helps transmit signals in the brain and nervous system. It's essential for communication between nerve cells.

The ability of the eye to adapt to different light levels. It involves changes in rhodopsin and other molecules related to vision.

The process of the eye becoming more sensitive to light after being exposed to darkness. This allows us to see better after being in a dark environment.

Retinoic acid is a potent regulator of gene expression, influencing tissue growth, development, and differentiation.

Retinoic acid binds to specific receptors within the nucleus, called retinoic acid receptors (RARs) and retinoid X receptors (RXRs), to exert its effects on gene expression.

Vitamin A deficiency can lead to night blindness, a condition where it's difficult to see in low light, due to the impairment of retinal function. Prolonged deficiency can cause irreversible loss of visual cells, leading to permanent vision impairment.

Vitamin A deficiency can impair the functions of vitamin D and thyroid hormones. This deficiency can lead to growth retardation in children due to slowed bone development and affect spermatogenesis in males.

Excess vitamin A can be teratogenic during pregnancy, meaning it can cause birth defects.

Vitamin E, particularly α-tocopherol, is a powerful antioxidant that scavenges free radicals, protecting cells from damage.

Deficiency of vitamin E can lead to hemolytic anemia, a condition where red blood cells are prematurely destroyed.

Lipid free radicals attack polyunsaturated lipids on cell membranes, initiating a chain reaction that produces lipid peroxides. These peroxides contribute significantly to cellular damage caused by reactive oxygen species (ROS).

Vitamin D3 (cholecalciferol) is formed in the skin when 7-dehydrocholesterol is exposed to UV light.

The liver converts vitamin D3 to 25-hydroxycholecalciferol (25-OHD3), a less active form.

The kidneys convert 25-OHD3 to calcitriol (1,25-dihydroxycholecalciferol), the active form of vitamin D.

Low blood calcium levels (hypocalcemia) stimulate PTH release, which activates 1-α-hydroxylase in the kidneys. This increases calcitriol production. Hypophosphatemia (low phosphate levels) also stimulates 1-α-hydroxylase.

Calcitriol increases calcium absorption in the gut and its release from bones. It also promotes phosphate reabsorption in the kidneys.

Excess vitamin D can lead to hypercalcemia (high blood calcium levels), causing symptoms like nausea, vomiting, and kidney stones.

Vitamin A is essential for vision, cell growth, and immune function.

Vitamin K is necessary for blood clotting and bone health.

Vitamin D plays a key role in the absorption of calcium in the intestines, ensuring that the body can utilize it effectively.

Vitamin D helps the kidneys conserve calcium, preventing unnecessary loss and maintaining balance.

The active form of Vitamin D binds to its specific receptor (VDR), which then teams up with another receptor (RXR), forming a powerful duo.

This complex (VDR/RXR) then attaches to specific regions on DNA called VDREs, triggering the production of proteins that support various cellular processes.

Vitamin D's active form acts as a powerful messenger, binding to its receptor and influencing gene expression, ultimately impacting a wide range of cellular processes.

The mineral component of bone that is essential for bone strength and rigidity. It is made from calcium and phosphate.

The condition in adults due to Vitamin D deficiency that causes reduced calcium absorption from the gut, leading to bones losing their mineral content. This results in weak bones prone to fractures, characterized by normal amount of collagen matrix but deficient mineralization.

The hormone that regulates calcium levels in the blood. Vitamin D deficiency triggers increased release of this hormone, which mobilizes calcium from bones, leading to bone weakness.

A condition caused by a deficiency of Vitamin D, which leads to impaired bone mineralization and an increased risk of rickets in children and osteomalacia in adults.

The mineral component of bone, essential for bone strength and rigidity.

Inadequate levels of vitamin D impair the mineralization of bones, leading to osteomalacia due to insufficient calcium and phosphate absorption.

Retinoic acid is a powerful gene regulator controlling the expression of genes involved in tissue growth, development, and differentiation.

Retinoic acid binds to specific receptors (RARs and RXRs) inside the nucleus of cells. This binding influences gene expression, ultimately affecting tissue development and growth.

Excess vitamin A during pregnancy can be harmful to the fetus, potentially causing birth defects. It's crucial to maintain a balanced intake during pregnancy.

Vitamin E, particularly α-tocopherol, serves as a strong antioxidant, protecting cells from damage caused by free radicals.

Vitamin E is an antioxidant that protects cell membranes from damage caused by free radicals, which are highly reactive molecules that can damage cells. It works by breaking the chain reaction of free radical damage, preventing further damage and promoting cell health.

Vitamin K is essential for blood clotting. It acts as a coenzyme for an enzyme called glutamate carboxylase, which adds a carboxyl group to glutamate residues in clotting factors. This modification allows the clotting factors to bind calcium, which is necessary for blood clotting.

A lack of Vitamin K can lead to a deficiency in the production of functional clotting factors, which are proteins that help stop bleeding. This can result in excessive bleeding, which is called hemorrhagic disease. This deficiency can also be caused by a lack of intestinal bacteria, which produce the active form of vitamin K.

Vitamin K antagonists, such as warfarin and dicumarol, are medications used to reduce the risk of blood clots. They work by blocking the action of Vitamin K, preventing the activation of clotting factors. They are often prescribed to individuals at high risk of developing blood clots, like those with atrial fibrillation or a history of blood clots.

Lipid peroxides are unstable molecules formed by the breakdown of fatty acids. They are damaging to cells and are associated with various health problems like oxidative stress and inflammation. To protect against this, Vitamin E works by breaking the chain reaction that leads to the formation of lipid peroxides.

Vitamin K is essential for bone health. It plays a role in the activation of proteins that help regulate calcium levels in the blood and bone formation. By impacting bone density, it indirectly supports overall bone health and strength.

Vitamin E helps reduce the risk of cancer, heart disease, and age-related diseases. It does this by neutralizing free radicals and preventing oxidative damage to cells. These free radicals can damage DNA and contribute to the development of these diseases.

Retinoic acid is a potent gene regulator, meaning it controls the activity of genes involved in tissue growth, development, and differentiation.

Lipid peroxides are highly reactive molecules that contribute to cell damage. They are formed when free radicals attack polyunsaturated lipids, initiating a chain reaction. Vitamin E helps prevent the formation of lipid peroxides by breaking this damaging chain reaction.

Vitamin K antagonists are medications, like warfarin, that block the action of Vitamin K. This prevents the activation of clotting factors, making blood less likely to clot. They are used to prevent blood clots in people with conditions like atrial fibrillation.

Vitamin D plays a major role in bone mineralization by promoting the deposition of calcium and phosphorus into the bone matrix, making bones stronger.

Beyond bones, Vitamin D is linked to protecting against various health issues like cancer, cardiovascular disease, diabetes, autoimmune disorders, and cognitive decline.

Vitamin D, or calcitriol, binds to its receptor (VDR) forming a complex that attaches to specific regions on DNA called VDREs, triggering the production of proteins that support various cellular processes.

Vitamin D deficiency can lead to impaired bone mineralization causing osteomalacia, characterized by weak, brittle bones prone to fracture.

Osteoporosis is a condition where bone resorption (breakdown) exceeds bone formation, leading to decreased bone mass and density. This makes bones weak and prone to fracture.

A decrease in both bone mineral and bone matrix, resulting in a reduced bone density, though the composition remains normal.

Parathyroid hormone (PTH), vitamin D, estrogen, and calcium are all essential for maintaining bone health. But with osteoporosis, calcium and bone mineral content are lost with resorption.

Vitamin A is crucial for vision, especially in low-light conditions. It helps form rhodopsin, a light-sensitive protein in the eyes.

Retinal, a form of vitamin A, is part of rhodopsin, which is essential for sight in low light.

The absorption of light by rhodopsin (in the eye) causes isomerization (change in shape) of retinal. This triggers a cascade of events that leads to signaling to the brain.

Vitamin A plays a role in growth and development, immune function, and overall health. It's a vital micronutrient.

A deficiency in Vitamin K can lead to a shortage of functional clotting factors, which are proteins that help stop bleeding. This can cause excessive bleeding, a condition known as hemorrhagic disease.

The dietary form of Vitamin K, known as phytomenadione or K1, is found in leafy vegetables. The active form, menaquinones or K2, is produced by bacteria in the intestinal flora.

Low blood calcium levels (hypocalcemia) stimulate PTH secretion, which in turn activates 1α-hydroxylase in the kidneys, leading to increased calcitriol production. This ultimately increases calcium absorption in the gut and releases calcium from bone.

Retinoic acid is a powerful regulator of gene expression, influencing tissue growth, development, and differentiation.