Vitamin D, Calcium, Phosphorus, & Magnesium

Where is magnesium stored

60% in bones

Homeostasis and phposphorus

70% in blood circulates as part of phospholipids (lipoproteins, cells, platelets) Much dietary P absorbed so proper renal excretion is important Serum levels have tight control via PTH and 1,25(OH)2 cholecalciferol Protein identified- fibroblast growth factor 23 and klotho Genetic defect-> calcification of soft tissue

Where is most calcium

99% in bones and teeth 40% all minerals i body

How dietary sources move vitamin D

Absorbed from micelles in intestinal tract by passive diffusion carried by chylomicrons-> adipocytes Hylomicron remnants drop off remaining vitamin D-> liver for metabolism

How is calcium absorbed

Absorbed only in ionized form, transport through intestinal cell by diffusion or with calbindin

Absorption of CA: favoring factors

Acidic environment in upper intestinal tract Normal digestive activity and motility of intestines Dietary CA and P in equal amounts Vitamin D available Need more during pregnancy Low Ca intake Availability of PTH Presence of lactose

Metabolism of Vitamin D

Activated by enzymes in liver and kidney Liver: hydroxy group added to 25th C to make 25-OH vitamin D3 (catalyze by 25-hydroxylase reaction) Kidney: hydroxy group added to 1st C= 1,25 (OH)2 vitamin D3 1 alpha-hydroxylates catalyzes the reaction

Vitamin D is stored in

Adipocytes and circulated in blood until the active form is needed

The active form of vitamin D

Aids in calcium absorption Cholecalciferol->liver->calcifediol->kidney-> calcitriol

Hindering factors for calcium

Alkaline state in intestinal tract Increase wheat bran Excess P, Fe, An Mg in proportion to Ca Phytic acid, oxalacetate acid, unabsorbed FA Vit D deficiency Aging Menopause

Absorption of magnesium

Along small intestine, limited in colon

Functions of calcium

Bone development ad maintenance (hydroxyapatite, osteocalcin and matrix Gla protein) Bloo clot- Gla proteins bind Ca Transmission of nerve impulses to target cells Muscle contraction Cell metabolism- activates enzymes

Role of magnesium

Bone- crystal lattice development and surface o bone (Mg pool) ATP dependent reactions 300 enzyme-catalyze reactions-key in glycolysis Anti inflammatory role- decreased levels leads to asthma, arthritis, neuroinfammation PTH excretion, hydroxylation of vitamin D

Genomics of vitamin D

Calcitriol binds to VDR in nucleus- I handed or inhibits the translation of genes

Vitamin D is a prohormone from

Cholesterol

Low intake of magnesium leads to

Chronic diseases

How the sun synthesizes vitamin D

Converts 7-dehydrocholesterol-> provitamins D3 by UV-light-> Vit D3 (cholecaliferol) in skin -> blood by D binding protein

Food contains what type of vitamin D

D2 (ergosterol) which goes to the liver and kidney= 1,25 dihyroxycholecalciferol.

Deficiency and toxicity of phosphorus

Deficiency is rare Toxicity is rare but can be found in infants with high P formulas

Roles of phosphorus

Energy metabolism- P bond in ATp, GTP and creatine phosphate drives most energy reactions Glycogen production Cell signaling DNA and RNA dependent Phospholipids Essential for teeth and bone structure as part of the hydroxyapatite- calcium phosphate crystals

Increased intake of magnesium leads to

Enhances Ca, P, K excretion which leads to renal damage and insufficiency

Calcium and Bone mass

Growth, osteoblasts exceeds osteoclasts activity (make more than break) More mass in high stress areas Peak mass between age 20-30 Loss in mid-adulthood High loss at menopause

Low intake of magnesium caused by

Highly refined foods

How is calcium transported

In blood by being boun to proteins-albumin and PAB Competed w/ sulfate, phosphate, or citrate Free or ionized (50%)

Where is phosphorus absorbed

In the small intestine in its organic form- must be liberated by digestive enzymes- vitamin D stimulates absorption

Consequences of hypercalcemia

Kidney stones and calcification of tissue

2nd most abundant mineral

Phosphorus

Deficiencies of Magnesium

Rare- vomiting, diarrhea, alcohol abuse, real and endocrine disease, protein malnutrition, increased diuretics

Functions of Vitamin D

Regulate blood calcium level Kidney: PTH reabsorbs CA through calbindin D28K Intestine: absorb CA from food by calbindin D9k Bone: PTH release Ca from bone through RANKL that matures osteoclasts Overabsorption of calcium (hyperccalcemia), increase CA excretion CA deposits in kidneys, heart, blood vessels= narrow arteries and aorta, facial change, mental retardation

Deficiency of vitamin D

Rickets=Or bone mineralization in kids Osteomalacia-soft bones in adults Resistant problems with synthesis of active form/defective receptor binding

Low levels of Mg leads to

T2DM, metabolic hadron, cancer, ischemic heart disease

Where do we get vitamin d

THE SUN!!!!!....fatty fish (salmon, herring) fortified milk, fortified cereal....

Where is calcium stored

Technically in bone

What increases absorption of magnesium

Vitamin D

Causes of deficiency in the elderly (vitamin D)

Low sun exposure Impaired synthesis in skin Low dietary intake Malabsorption of dietary vitamin D Low 1,25-DiOH D3 from low 1 alpha hydroxylates activity in kidney

Regulation of blood calcium

Maintained @ Brice of bone calcium High blood calcium-PTH- retains calcium from excretion, increased calcium absorption via increased calcitriol, increased calcium release from bone Lowering blood calcium- calcitonin - decrease PTH and calcitriol

What decreased absorption of pphosphorus

Meals with high Mg or Ca Form chelates in intestinal lumen leads to decreased absorption

How to get too much vitamin D

Megadoses of supplements, NOT the sun

Deficiency of calcium

Osteoporosis-leads to fractures Osteopenia-decreased bone mass