test3 easier

know the actions or functions of calcitriol/vitamin D in the body (multiple questions on this)

• Increases calcium absorption in intestine

• Increases phosphorus absorption in intestine

• Increases TRPV6, calbindin, PMCA1b, and NCX1 production

• Helps maintain blood calcium

• Helps bone mineralization

• Works with PTH to raise blood calcium

• Increases kidney calcium reabsorption

• Has genomic effects by binding Vitamin D Receptors (VDR)

• Acts on intestine, kidney, bone, immune system, muscle, pancreas, brain, heart, and skin

AI for water Adult women

• 2.7 L/day (91 oz)

• About 8 cups/day

AI for water Adult men

• 3.7 L/day (125 oz)

• About 12 cups/day

AI for water Other recommendations

• 25–40 mL/kg body weight/day

• 1 mL of water per kcal consumed

ANP function (atrial natriuretic peptide)

(fixes overwhelmed heart)

Released when:

• Blood volume is high

• Blood pressure is high

• Heart is stretched

Functions

• Increases sodium excretion (natriuresis)

• Increases water excretion (diuresis)

• Decreases renin release

• Decreases aldosterone release

• Dilates blood vessels

• Lowers blood pressure

• Opposes RAAS

responses to high sodium intake

• ECF osmolarity increases

• Thirst increases

• ADH increases (retain water to dilute)

• Water intake increases

• Kidneys excrete extra sodium

• ANP increases if blood volume rises (excrete sod and dilates blood vessels)

responses to low sodium intake

• RAAS is activated (a vital hormone pathway that regulates long-term blood pressure, blood volume, and fluid balance)

• Aldosterone increases (a critical for regulating blood pressure, fluid balance, and electrolyte concentrations (specifically sodium and potassium) )

• Kidneys reabsorb sodium

• Water follows sodium

• Blood volume increases

responses to high potassium levels

• Aldosterone increases

• Kidneys excrete more potassium

• Blood potassium decreases

responses to low potassium levels

• Aldosterone decreases

• Kidneys conserve potassium

• Less potassium is lost

potassium levels; where can it be stored

About 98% of potassium is inside cells, especially:

• Skeletal muscle

• Liver

Only about 2% is in extracellular fluid.

solvent drag mechanism

Water moves toward higher solute concentration.

As water moves between enterocytes, it carries small ions such as:

• Calcium

• Magnesium

This is an example of paracellular transport.

Paracellular diffusion

Movement between cells through tight junctions.

No transporter is needed.

Occurs mainly when mineral concentration in the intestinal lumen is high.

solvent drag and paracellular diffusion

Paracellular diffusion is the passive movement of solutes between adjacent cells (through the tight junctions and intercellular spaces) driven strictly by their own concentration gradient. In contrast, solvent drag is the bulk flow of solutes carried along by the physical movement of water (solvent) moving through the same spaces

movement of water in response to the colloidal pressures

Created mainly by plasma proteins (albumin).

Pulls water into capillaries.

Occurs mainly at the venous end of capillaries.

movement of water in response to the hydrostatic pressures

Pressure created by blood.

Pushes water out of capillaries into the interstitial space (area between stuff).

Occurs mainly at the arterial end of capillaries.

movement of water in response to the Osmotic pressures

Water moves toward the area with higher solute concentration.

Examples:

• High sodium

• High glucose

Water follows the solute.

A solute is the substance that is dissolved in a solution (e.g., salt or sugar),

while the solvent is the substance that does the dissolving (e.g., water)

What are the functions of phosphorus and what is it required for

Bone mineralization

Forms calcium phosphate in bone.

ATP production

Stores and transfers energy.

DNA and RNA

Forms the phosphate backbone.

Cell membranes

Part of phospholipids.

Second messenger systems

Part of:

• ATP

• cAMP

• GTP

Protein phosphorylation

Activates many enzymes.

Acid-base balance

Acts as an intracellular buffer.

Oxygen delivery

Part of 2,3-DPG, helping release oxygen from hemoglobin.

Vitamins

Needed to activate:

• Thiamin (TPP)

• Vitamin B6 (PLP)

magnesium sources

• Whole grains

• Nuts

• Legumes

• Seeds

• Seafood

• Coffee

• Tea

• Cocoa

• Green vegetables (chlorophyll)

magnesium absorption mechanisms

Absorption

Occurs mainly in the small intestine.

Two mechanisms:

Passive diffusion

Main mechanism.

Active transport

Uses TRPM6 transporter.

TRPM6 is downregulated when magnesium inside the cell is high.

functions that occur when magnesium is low

Solvent drag

Water moves from the intestinal lumen toward the blood.

Water carries magnesium between cells.

What foods can influence calcium absorption

Increase calcium absorption

• Foods containing vitamin D

• Milk and dairy products (lactose)

• Protein-containing foods

• Foods containing sugar alcohols

Decrease calcium absorption

Foods high in oxalic acid (oxalates):

• Spinach

• Swiss chard

• Beets

• Celery

• Eggplant

• Greens

• Okra

• Squash

• Strawberries

• Blackberries

• Blueberries

• Gooseberries

• Pecans

• Peanuts

• Tea

• Ovaltine

• Cocoa

Foods high in phytates and fiber:

• Whole-grain breads

• Wheat bran cereals

• Seeds

• Nuts

• Legumes

• Soy isolates

functions of magnesium

• ATP reactions

• Enzyme function

• DNA synthesis

• RNA synthesis

• Protein synthesis

• Muscle contraction

• Nerve transmission

• Bone formation

• Cell signaling

• GTP binding

• Second messenger systems

Hypocalcemia

= low blood calcium.

What happens during hypocalcemia

Sequence:

1. Blood calcium decreases.

2. Calcium-sensing receptors detect the drop.

3. Parathyroid glands release PTH. parathyroid hormone which signals

4. Kidney increases 1α-hydroxylase.

5. More calcitriol is made. hormonally active, synthetic form of Vitamin D.

6. Intestine absorbs more calcium.

7. Kidney reabsorbs more calcium.

8. Bone resorption increases.

9. Blood calcium returns to normal.

what does sun exposure (short) do to vitamin D in the body

• Produces Vitamin D3 from 7-dehydrocholesterol.

 what does sun exposure (long) do to vitamin D in the body?

Long sun exposure

• Extra previtamin D is converted into lumisterol and tachysterol.

• These inactive forms prevent vitamin D toxicity.

know the actions or functions of calcitriol (active vitamin D) in the body (multiple questions on this)

• Increases calcium absorption in intestine

• Increases phosphorus absorption in intestine

• Increases TRPV6, calbindin, PMCA1b, and NCX1 production

• Helps maintain blood calcium

• Helps bone mineralization

• Works with PTH to raise blood calcium

• Increases kidney calcium reabsorption

• Has genomic effects by binding Vitamin D Receptors (VDR)

• Acts on intestine, kidney, bone, immune system, muscle, pancreas, brain, heart, and skin

causes of deficiency vit D

Causes

• Little sunlight

• Poor intake

• Fat malabsorption

• Liver disease

• Kidney disease

• Older age

• Darker skin

• Breastfed infants without supplements

What enzymes can cause deficiency? vit D

Enzyme that can cause deficiencies bc lack

• 25-hydroxylase deficiency

• 1α-hydroxylase deficiency

symptoms of deficiency vit d

Symptoms

• Rickets (children)

• Osteomalacia (adults)

• Weak bones

• Bone pain

• Muscle weakness

• Fractures

blood markers and health markers during deficiency of vitamin D

Blood markers

• ↓ 25-OH Vitamin D

• ↓ Calcitriol

• ↓ Calcium

• ↑ PTH parathy ho

how is vitamin D best measured in the body

Measure:

25-OH Vitamin D (Calcidiol)

It is the best indicator because it reflects both dietary vitamin D and vitamin D made in the skin.

Normal goal:

• Above 20 ng/mL

Deficient:

• Less than 20 ng/mL

What genes are induced when Vitamin D has genomic actions with each tissue?

Vitamin D binds:

Vitamin D Receptor (VDR)

The VDR binds a:

Vitamin D Response Element (VDRE)

This changes gene transcription.

Important genes induced:

Intestine

• TRPV6

• Calbindin

• PMCA1b

• NCX1

Kidney

• TRPV5

• Calbindin

• Calcium transport proteins

Bone

• Genes involved in bone remodeling

Parathyroid

• Decreases PTH gene transcription

Vitamin D binds:

Vitamin D Receptor (VDR)

The VDR binds a:

Vitamin D Response Element (VDRE)

What genes are induced when Vitamin D has genomic actions with each tissue?

Vitamin D binds:

Vitamin D Receptor (VDR)

The VDR binds a:

Vitamin D Response Element (VDRE)

This changes gene transcription.

Important genes induced from vit D Intestine

• TRPV6

• Calbindin

• PMCA1b

• NCX1

Important genes induced from vit D Kidney

• TRPV5

• Calbindin

• Calcium transport proteins

Important genes induced from vit D Bone

• Genes involved in bone remodeling

• RANKL – stimulates osteoclast formation, leading to bone resorption and release of calcium and phosphorus.

• Osteopontin – helps regulate bone mineralization (the slide notes calcitriol increases osteopontin and inhibits bone mineralization.

Important genes induced from vit D Parathyroid

• Decreases PTH gene transcription

what are vitamin D recommendations? infants

5 μg/day (200 IU)

what are vitamin D recommendations 1-70 age

• 15 μg/day (600 IU)

what are vitamin D recommendations 70 and up

• 20 μg/day (800 IU)

what are vitamin D recommendations breastfed infants

Need supplementation

what are vitamin D recommendations practical rec

• Up to 15 minutes of sunlight/day (depending on skin type and environment).