Diurnal variation of the melanin-concentrating hormone level in the hypothalamus

Abstract

Melanin-concentrating hormone (MCH), the neuropeptide produced mainly in the hypothalamus, plays an operative role in regulating food intake and the sleep/wake cycle. Considering that these physiological functions pursue diurnal variations, we checked whether the total hypothalamic MCH level depends on the time of the day. The aggregated MCH peptide content of the whole MCH neuron population was significantly higher at the end of the sleeping period (lights on), than at the end of the active period (lights off). This result, together with earlier observations, indicates that in contrast to the MCH gene expression, the level of MCH peptide is object of circadian variation in the hypothalamus.

Melanin‐concentrating hormone regulates the hypercapnic chemoreflex by acting in the lateral hypothalamic area

“…Evidence suggests that there are diurnal variations in the activity of the MCHergic system, regardless of the variations throughout the sleep–wake cycle. For example, recent evidence showed that in CSF of rats (Pelluru, Konadhode & Shiromani, 2013) and in hypothalamic slices of mice (Gerics et al., 2017), MCH levels are higher in the inactive period (light phase) compared to the active period (dark phase) of rodents. In addition, a previous study showed that in slices of the frontal cortex and hippocampus of control rats, levels of MCH1‐R expression are lower in ZT0 (beginning of the light phase, at 07.00 h) compared to ZT8 (end of the light phase, at 15.00 h), suggesting that expression of MCH1‐R varies throughout the day (Dias Abdo Agamme et al., 2015).…”

“…The interaction between MCH and LHA and/or LC could, therefore, contribute to the modulation of the central chemoreflex in a sleep–wake cycle‐dependent manner. Interestingly, MCH levels in the cerebrospinal fluid (CSF) of rats (Pelluru et al., 2013) and in hypothalamic sections of mice (Gerics et al., 2017) are higher in the inactive period (light phase) compared to the active period (dark phase), but whether the mechanisms by which MCH acts in the central chemoreflex depend on the light–dark cycle is uncertain.…”

Effects of Paradoxical Sleep Deprivation on MCH and Hypocretin Systems

“…These results are in accordance with those of a previous work 29 from our group, which showed that MCH CSF levels were higher at ZT0 in relation to ZT8 in SD animals. Moreover, using immunohistochemistry, Gerics et al 30 (2017) demonstrated that hypothalamic MCH is higher at the end of the sleep period (ZT12). We can hypothesize that the higher concentration of MCH at ZT12 in the SD group is related to a higher release to the ventricular system, due to the increased sleep pressure after a long period of forced wakefulness during the natural sleep phase.…”

Crosstalk between Melanin Concentrating Hormone and Endocrine Factors: Implications for Obesity

“…MCH expression levels are increased in most models of obesity [ 37 , 38 , 39 ], suggesting that MCH may be involved in the etiology/pathogenesis of this disease. Interestingly, the MCH peptide content was significantly higher at the end of the sleeping period than at the end of the active period [ 40 ], suggesting that the level of the MCH peptide exhibits circadian variation. This result is in agreement with previous reports indicating that MCH levels in cerebrospinal fluid and neuronal MCH activity under normal or disturbed circadian rhythms patterns show a day/night difference [ 41 , 42 , 43 ].…”