Calbindin expression stimulated by 125OH 2D 3 inhibited by vit D def Export of

Calbindin expression stimulated by 125oh 2d 3

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§ Calbindin expression stimulated by 1,25(OH) 2 D 3 ; inhibited by vit D def - Export of Ca across the basolateral membrane by PMCA1b Maintains Ca levels with PTH 4. Parathyroid gland senses low Ca lvls in blood & signals PTH release 5. PTH stimulates kidney to o Ca reabsorption o Stimulate renal 1-hydroxylase to convert 25(OH) 2 D 3 to 1,25(OH) 2 D 3 (calcitriol) 6. blood calcitriol stimulates Ca absorption in intestine OSTEOCLAST MATURATION - 1,25(OH) 2 D 3 & PTH induce expression of RANKL causing it to mature into osteoclast elderly 600IU/d o Failure of bone to mineralize - Adults = osteomalacia o Demineralization - Impaired insulin secretion - Behavioral change - Innate immunity UL = 4000 IU/d - DBP binds 1,25(OH) 2 D 3 for transfer to tissues 1) Cholecalciferol (CCF) transported in CMR via DBP to liver 2) CCF hydroxylated at C-25 via 25-hydroxylase to produce 25(OH)D 3 , the major circulating form of vit D § 25(OH)D 3 = indicator of vit D status 3) 25(OH)D 3 transported by DBP to kidney, and taken up by megalin 4) Once inside, 25(OH)D 3 can either be § Hydroxylated to 1,25- (OH) 2 D 3 via 1- hydroxylase 1,25(OH)D 3 = metabolically active form § Hydroxylated at C-24 via 24-hydroxylase à 1,24,25(OH) 2 D 3 which is then filtered for excretion 24-hydroxylase active when circulating levels of 1,25(OH) 2 D 3 is high -
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8 Vitamin E - The term vit E describes a family of 8 fat-soluble molecules with AOX activities: four tocopherol isoforms (α-, β-, γ-, and δ- tocopherol) four tocotrienol isoforms ** α-tocopherol - The main fxn of α-TOH in humans = fat- soluble AOX; capable of terminating chain reactions among PUFAs in the membranes wherein it resides o PUFAs, an integral part of cell membranes, are vulnerable to damage through lipid peroxidation by free radicals α-TOH intercepts peroxyl radicals & thus prevents a chain reaction of lipid oxidation via donation of the phenolic H to a fatty acyl free radical (or O 2 ) to prevent the attack of that species on other PUFAs When a molecule of α-TOH neutralizes a free radical, it is oxidized & its AOX capacity is lost 15 mg/d - Def is very rare - Mutations in α-TTP à AVED (ataxia with vit E deficiency) TOXICITY High doses increase risk of bleeding via Vit K antaganoization Vitamin K - Natural sources: o Phylooquinones (PK; Vitamin K 1 ) in chloroplasts of green plants o Menaquinones (MK) in intestinal bacteria; have multiple prenyl side chains MK-4 = activated form - Synthetic form = menadione o Parent compound of MK - Contain isoprenoid side chain - Necessary for posttranslational carboxylation of specific glutamyl residues in proteins to form γ-carboxyglutmate (Gla) residues; enables the protein to bind to Ca & interact with other compounds o Carboxylations/ interactions are necessary for blood clotting (hemostasis) & bone mineralization 1. Blood clotting: for blood to clot, fibrinogen must be converted to fibrin via enzyme thrombin.
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  • Spring '14
  • Knutson,MitchellD
  • Vitamin, Vitamin B12, enterocytes

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