The Battle Over Iron

This week in #micromeded, we will explore iron transport throughout the body and how it is affected during inflammation/infection. Iron is an essential ion in both humans and microbes, and iron transport and iron sequestration are means by which the body can prevent the growth of microbes during an infection. However, inflammation triggers the same pathway, so in cases of chronic inflammation, hepcidin can be activated to limit free iron in the body. This can lead to a state of anemia—aptly called anemia of chronic disease.

Microbes can synthesize small molecules collectively called “siderophores” which can bind iron allowing the microbe to uptake the iron and prevent sequestration by human iron binding proteins (i.e.: transferring, hepcidin, and ferritin).

Some labs that can measure the iron status of a patient:

• Ferritin: iron stores in the body

  • normally 18-300 ng/mL, low in iron deficiency anemia, can be elevated in anemia of chronic disease

• Serum Iron: iron in transit (bound to transferrin)

  • Normally 40-180 mcg/dL, low in iron deficiency anemia and anemia of chronic disease

• Total iron binding capacity (TIBC): amount of free transferrin (not bound to iron)

  • Normally 250-450 mcg/dL, elevated in iron deficiency anemia, low in anemia of chronic disease

• Transferring saturation (iron/TIBC)

  • Normally 25-35%, <15% in iron deficiency anemia, >15% in anemia of chronic disease

For more info on bacterial siderophores, check out this amazing review article.

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