ZINC METABOLISM HENDRA WIJAYA Esa Unggul University Zinc
ZINC METABOLISM HENDRA WIJAYA Esa Unggul University
Zinc in food
Function of zinc • • • Growth - regulation of transcription Cell replication Bone formation Skin integrity Cell-mediated immunity Generalized host defense Carbohydrate metabolism Antioxidant Stabilizes cell membranes Stabilizes proteins that regulate gene expression
Please remember. . !
Zinc-dependent enzymes • • • Carbonic anhydrase Alkaline phosphatase Alcohol dehydrogenase Carboxypeptidase Aminopeptidase Superoxide dismutase (SOD) Collagenases Phospholipase C Polyglutamate hydrolase Polymerases, kinases, nucleases, transferases, phosphorylases, transcriptases
Routes of Zn in the Body Copyright 2005 Wadsworth Group, a division of Thomson Learning
Routes of Zn in the Body
Routes of Zn in the Body
Digestion, absorption, transport, uptake, & storage – Digestion • Hydrolyzed from amino/nucleic acids in stomach & small intestine – Absorption • Carrier-mediated process – Zrt- & Irt-like protein (ZIP) 4 • Passive diffusion & paracellular absorption with high intake
Absorption, Metabolism, & Regulation of Zinc • Requires proteins to: – Transport zinc into enterocyte • Metallothionine – Bind zinc within cell • Excess excreted in feces • Genetic influences
Zinc – Intestinal cell zinc use - may be: • Used functionally • Stored • Transported across basolateral membrane into plasma for transport – Transport • Blood - bound loosely to albumin – Also transferrin, alpha-2 macroglobulin, immunoglobulin G – Histidine, cysteine
Zinc – Uptake by tissues • ZIP carriers 1, 2, 4, 6, 7, 8, 14 • Zn. T transporters – Distribution & storage • Found in all organs, especially liver, kidneys, muscle, skin, bones • Usually stored bound to thionein as metallothionein
Zinc – Factors influencing zinc absorption • Enhancers of zinc absorption – Ligands - citric acid, picolinic acid, prostaglandins, amino acids – Low zinc status • Inhibitors of zinc absorption – Phytate – Oxalate – Polyphenols – Nutrients, e. g. folate, iron, calcium, copper
Absorption
Bioavailability of Zinc • Bioavailability influenced by: – – – Phytates Iron Calcium Animal sources Acidic substances
Zinc • Interactions with other nutrients – – Vitamin A Copper Calcium Cadmium • Excretion – Mostly through GI tract – Small amount in urine & through skin exfoliation/sweat
Zinc Deficiency & Toxicity • Deficiency – – Decreases appetite Increases morbidity Decreases growth Skin irritations, diarrhea, delayed sexual maturation • Toxicity – Supplements – Poor immune function – Depressed levels of HDL – Impaired copper status – Nausea, vomiting, loss of appetite
Acrodermatitis Enteroathica • Zinc deficiency even with adequate amounts of dietary zinc • Supplementation • Infants – Growth failure – Red/scaly skin – Diarrhea • Human Genome Project
- Slides: 30