Zinc deficiency

Zinc function

---

• Protein structure
  • Forms bonds between cysteine and histidine
  • Forms zinc finger transcription factors
    • Zinc finger: a type of DNA-binding domain, binded by transcription factors t
      • Characteristics: zinc ion coordinated by two histidine and two cysteine residues
      • DNA binding: Several zinc finger domains are often connected as a chain and bind to an α-helix in the major groove of DNA.
• Aids in maintenance and stability of the nuclear membrane
• Essential part of many enzymes (> 100), including DNA polymerase, carbonic anhydrase, ACE, alkaline phosphatase, metallothionein, superoxide dismutase, and collagenases

Zinc deficiency

• Zinc is highly concentrated in biliary, pancreatic, and intestinal secretions
• Causes
  • Malabsorption syndromes (e.g., Crohn’s disease, Celiac disease, short bowel syndrome).
  • Inadequate dietary intake (e.g., strict vegans/vegetarians, chronic alcoholism).
  • Total parenteral nutrition (TPN) without adequate trace element supplementation. c
  • Congenital: Acrodermatitis enteropathica (AR mutation in SLC39A4 gene causing impaired intestinal zinc absorption).
  • Increased demand/loss (e.g., pregnancy, lactation, chronic diarrhea, severe burns, excessive sweating, high phytate intake which chelates zinc).
• Clinical features
  • Acrodermatitis: Erythematous, vesiculobullous, and pustular skin lesions localized to perioral, perianal, and acral (hands, feet) areas.
  • Alopecia (loss of scalp and body hair).
  • Gastrointestinal: Chronic diarrhea.
  • Sensory: Dysgeusia (taste distortion) and anosmia (loss of smell).
  • Immunological: Impaired wound healing and depressed cell-mediated immunity (recurrent bacterial/viral infections).
  • Endocrine: Hypogonadism (testicular atrophy, oligospermia, delayed puberty) and growth retardation in children.
  • Ophthalmic: Night blindness (zinc is a cofactor for retinol dehydrogenase converting retinol to retinal) and photophobia.
• Diagnosis: measurement of plasma zinc levels
• Treatment: oral zinc supplementation