Human circadian rhythms in temperature, trace metals, and blood variables

Area of Science:

• Physiology
• Immunology
• Chronobiology

Background:

• Circadian body temperature variations are linked to thermoregulatory set point changes.
• Understanding daily rhythms in physiological markers is crucial for health insights.

Purpose of the Study:

• To investigate the relationship between circadian body temperature rhythms and 24-hour variations in plasma iron, zinc, leukocyte counts, and interleukin-1 (IL-1) activity.
• To explore potential indirect evidence for IL-1 variations based on trace metal and leukocyte patterns.

Main Methods:

• Eight healthy men participated in two 48-hour study sessions.
• Continuous monitoring of rectal temperature, plasma iron and zinc concentrations, plasma IL-1 activity, and circulating leukocyte counts.
• Analysis of 24-hour patterns and relationships between measured variables.

Main Results:

• Demonstrated circadian rhythms in body temperature, plasma trace metals (iron, zinc), and leukocyte populations.
• Observed an approximate inverse relationship between daily changes in plasma iron and zinc concentrations and rectal temperature.
• No direct IL-1 activity was detected in plasma, but trace metal and leukocyte patterns suggested possible daily IL-1 variations.

Conclusions:

• Circadian rhythms in body temperature are inversely related to plasma iron and zinc concentrations.
• Daily fluctuations in plasma trace metals and leukocyte counts may indirectly indicate variations in interleukin-1 (IL-1) release.
• Further research is needed to confirm the direct role of IL-1 in these daily physiological rhythms.