Circadian rhythm in serum iron levels

Area of Science:

• Biochemistry
• Chronobiology
• Human Physiology

Background:

• Circadian rhythms significantly influence physiological processes.
• Understanding diurnal variations in serum iron is crucial for accurate health assessments.
• Previous research has not fully elucidated the specific circadian pattern of serum iron in Chinese populations.

Purpose of the Study:

• To assess the circadian rhythm of endogenous serum iron concentrations in healthy Chinese male subjects.
• To establish a baseline understanding of diurnal iron level fluctuations.
• To inform the design of future iron formulation bioequivalence studies.

Main Methods:

• Recruited 19 healthy Chinese male subjects.
• Conducted a 4-day diet equilibration period.
• Collected blood samples at 8-hour intervals (0800 to 2400) on day 5.
• Quantified serum iron concentrations using inductively coupled plasma mass spectrometry (ICP-MS).

Main Results:

• Serum iron concentration exhibited a diurnal variation, decreasing from morning to afternoon.
• The maximum serum iron level was observed at 1000 and 1400 hours (2,229 μg/L and 2,278 μg/L).
• The minimum serum iron level was recorded at 2000 hours (1,987 μg/L), with an amplitude of 291 μg/L.

Conclusions:

• Serum iron levels follow a distinct circadian rhythm in healthy Chinese males.
• Simple baseline subtraction of pre-dose iron levels in bioequivalence studies may be inaccurate.
• Optimized methodologies are needed for designing robust iron formulation bioequivalence studies, accounting for diurnal variations.