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Fasting affects thermoregulation in the cold, depending on time of the day
Author(s) -
Tokizawa Ken,
Uchida Yuki,
Nagashima Kei
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1222.3
Subject(s) - circadian rhythm , thermoregulation , endocrinology , medicine , rhythm , chemistry , zoology , biology
BACKGROUND: We have shown that circadian rhythm of body temperature (T b ) is finely regulated. However, feeding condition is a factor affecting largely the T b rhythm. During fasting, T b gradually decreases in the light (inactive) phase, whereas T b in the dark (active) phase is maintained at the free‐feeding level. The purpose of the present study was to clarify the mechanism involved in the altered T b rhythm during fasting. METHODS: Male ICR mice (2–3 mo old), used for the present study, were housed at an ambient temperature (T a ) of 27ºC in a 12:12‐h light‐dark cycle. After 48‐h fasting, T a was decreased to 20ºC at ZT1‐4 (early light phase) or ZT13‐16 (early dark phase). T b (biotelemetry) and oxygen consumption (VO 2 , indirect calorimetry) were measured. RESULTS: During a cold exposure with fasting, T b decreased by 5.5 ± 2.0ºC at ZT1‐4, and VO 2 remained unchanged. However, T b decreased by only 2.0 ± 0.5ºC at ZT13‐16, which was greater than that in the light phase (p<0.05), and VO 2 increased (p<0.05). CONCLUSION: These results indicate that fasting attenuates thermoregulatory response to the cold, and the response differs among time of the day. Factors of feeding condition and time would have influences on the mechanism regulating the T b rhythm. The possible reason will be presented, based on histological study using c‐Fos immunostaining and molecular analysis of UCP1 mRNA expression in the brown adipose tissue.