Manganese binding proteins in human and cow's milk

Area of Science:

• Biochemistry
• Nutritional Science
• Pediatrics

Background:

• Neonatal manganese nutrition is not well understood.
• Information on manganese content and bioavailability in infant foods is limited.
• Molecular localization of manganese in food influences its bioavailability.

Purpose of the Study:

• To investigate the binding and molecular localization of manganese in human and cow's milk.
• To compare manganese distribution in human milk, cow's milk, and infant formulas.

Main Methods:

• Used an extrinsic label (54Mn) to trace manganese.
• Separated milk samples into fat, casein, and whey fractions via ultracentrifugation.
• Analyzed manganese binding within the whey fraction.

Main Results:

• Human milk: 71% manganese in whey, 11% in casein, 18% in lipids. Cow's milk: 32% in whey, 67% in casein, 1% in lipids.
• In human milk whey, manganese primarily binds to lactoferrin.
• In cow's milk whey, manganese binds to low molecular weight ligands (<200 Da).
• Manganese distribution in infant formulas more closely resembles human milk.

Conclusions:

• Significant differences exist in manganese localization between human and cow's milk.
• Manganese in human milk is largely associated with lactoferrin in the whey fraction.
• Further research is needed to assess the bioavailability of manganese bound to lactoferrin, casein, and low molecular weight complexes.