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Enoki, R.

Publications and source records attributed to Enoki, R..

2 recordsLinked to original sources

Body temperature regulates glucose metabolism and torpid

Glucose is a significant energy resource for maintaining physiological activities, including body temperature homeostasis, and glucose homeostasis is tightly regulated in mammals. Although ambient temperature tunes glucose metabolism to maintain euthermia, the significance of body temperature in metabolic regulation remains unclear owing to strict thermoregulation. Activation of Qrfp neurons in the preoptic area induced a harmless hypothermic state known as Q-neuron-induced hypothermia and hypometabolism (QIH), which is suitable for studying glucose metabolism under hypothermia. In this study, we first observed that QIH mice had hyperinsulinemia and insulin resistance. This glucose hypometabolic state was abolished by increasing the body temperature to euthermia. Moreover, QIH-mediated inappetence and locomotor inactivity were recovered in euthermia QIH mice. These results indicate that body temperature is considerably more powerful than ambient temperature in regulating glucose metabolism and behavior, and hypometabolism in QIH is secondary to hypothermia rather than modulated by Qrfp neurons. HighlightsO_LIQIH reorganizes glucose homeostasis which is unchanged by fasting. C_LIO_LIQIH mice exhibit glucose hypometabolism with hyperinsuliemia and insulin resistance. C_LIO_LIIncreased body temperature abolishes QIH-mediated hypometabolism and torpid behaviors. C_LIO_LIBody temperature is a strong factor in controlling metabolism and behavior. C_LIO_LIBody temperature-mediated glucose metabolism is reversible. C_LI

physiology↗

Cold-induced Suspension and Resetting of Ca2+ and Transcriptional Rhythms in the Suprachiasmatic Nucleus Neurons

Mammalian circadian rhythms are coordinated by the master clock located in the hypothalamic suprachiasmatic nucleus (SCN). Under severe environmental conditions, such as during the harsh winter season for food, certain mammalian species reduce their basal metabolism and thermogenesis, thereby undergoing torpor, a controlled state of hypothermia, which naturally returns to the normothermic state. A long-lasting debate focused on whether the SCN with a temperature-compensated clock remains functional during hypothermia. However, so far, no direct and quantitative evidence has been reported of temperature sensitivity in living SCN neurons. In this study, we performed dual-color fluorescence imaging of clock gene transcriptions and intracellular Ca2+ in mouse SCN neurons, using slices at various temperatures. We demonstrated that the Bmal1 transcription and Ca2+ circadian rhythms persisted at 22{degrees}C-28{degrees}C, although the two rhythms underwent temporal dissociation at 22 {degrees}C. Notably, Ca2+, Bmal1, and Per2 rhythms were suspended at 15{degrees}C, coupled with a significant Ca2+ increase, and all rhythms were reset by rewarming to 35{degrees}C. Upon rewarming, the Ca2+ rhythm showed stable oscillations immediately, whereas the Bmal1 and Per2 rhythms took several days to reach stable oscillations and recover their phase relationship with the Ca2+ rhythm. Taken together, we concluded that SCN neurons remain functional under moderate hypothermic conditions at approximately 22{degrees}C-28{degrees}C but stop ticking time in deep hypothermia at 15{degrees}C and that the rhythms reset after deep hypothermia. These data also indicate that the stable Ca2+ oscillation precedes clock gene transcriptional rhythms in the SCN neurons.

neuroscience↗