Temporal dysregulation of hypothalamic integrative and metabolic nuclei in rats fed during the rest phase

ABSTRACT

Temporal coordination of organisms according to the daytime allows a better performance of physiological processes. However, modern lifestyle habits, such as food intake during the rest phase, promote internal desynchronization and compromise homeostasis and health. The hypothalamic suprachiasmatic nucleus (SCN) synchronizes body physiology and behavior with the environmental light–dark cycle by transmitting time information to several integrative hypothalamic nuclei, such as the paraventricular nucleus (PVN), dorsomedial hypothalamic nucleus (DMH) and median preoptic area (MnPO). The SCN receives metabolic information mainly via Neuropeptide Y (NPY) inputs from the intergeniculate nucleus of the thalamus (IGL). Nowadays, there is no evidence of the response of the PVN, DMH and MnPO when the animals are subjected to internal desynchronization by restricting food access to the rest phase of the day. To explore this issue, we compared the circadian activity of the SCN, PVN, DMH and MnPO. In addition, we analyzed the daily activity of the satiety centers of the brainstem, the nucleus of the tractus solitarius (NTS) and area postrema (AP), which send metabolic information to the SCN, directly or via the thalamic intergeniculate leaflet (IGL). For that, male Wistar rats were assigned to three meal protocols: fed during the rest phase (Day Fed); fed during the active phase (Night Fed); free access to food (ad libitum). After 21 d, the daily activity patterns of these nuclei were analyzed by c-Fos immunohistochemistry, as well as NPY immunohistochemistry, in the SCN. The results show that eating during the rest period produces a phase advance in the activity of the SCN, changes the daily activity pattern in the MnPO, NTS and AP and flattens the c-Fos rhythm in the PVN and DMH. Altogether, these results validate previous observations of circadian dysregulation that occurs within the central nervous system when meals are consumed during the rest phase, a behavior that is involved in the metabolic alterations described in the literature.

KEYWORDS:

• Suprachiasmatic nucleus
• dorsomedial hypothalamic nucleus
• paraventricular nucleus
• median preoptic area
• circadian asynchrony

Acknowledgements

This study was supported by Consejo Nacional de Ciencia y Tecnología, México (CONACyT grant 183078 for RSD; 243298 for NS), FAI 2020 for NS, CONACyT provided a PhD scholarship to ODRP (grant 276879). We also want to acknowledge to Dra. Carolina Escobar (Facultad de Medicina, UNAM) for the rats proportionated to realize the present work.

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Disclosure statement

No potential conflict of interest was reported by the author(s).

Data accessibility statement

All data created during this research are openly available in data repository of the Universidad Autónoma de San Luis Potosí at https://bvu.uaslp.mx; ninive.uaslp.mx/jspui/handle/i/2856.

Additional information

Funding

This work was supported by the Consejo Nacional de Ciencia y Tecnología [183078,243298,276879].