Suprachiasmatic Nuclei May Regulate the Rhythm of Leptin Hormone Release in Syrian Hamsters (<i>Mesocricetus Auratus</i>)

Karakaş, Alper; Gündüz, Bülent

doi:10.1080/07420520500545821

Cited by 18 publications

(10 citation statements)

References 31 publications

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“…Leptin receptor immunoreactivity has been detected in the suprachiasmatic nuclei of the hypothalamus (SCN), the master circadian clock in mammals (6), and in the hypocretinergic neurones of the lateral hypothalamus, which are implicated in regulating and maintaining sleep/wakefulness states (7,8). Plasma leptin levels show a diurnal rhythm, with a peak around midnight in both rodents and humans (9–11), with the exception of some rodent species, such as hamsters, where peak plasma leptin occur at midday (12).…”

mentioning

confidence: 99%

Dimorphic Effects of Leptin on the Circadian and Hypocretinergic Systems of Mice

Mendoza¹,

López-López²,

Revel³

et al. 2010

Journal of Neuroendocrinology

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The hormone leptin controls food intake and body weight through its receptor in the hypothalamus, and may modulate physiological functions such as reproduction, sleep or circadian timing. In the present study, the effects of leptin on the resetting of the circadian clock, the hypothalamic suprachiasmatic nucleus (SCN) and on the activity of the hypocretinergic system were examined in vivo, with comparative analysis between male and female mice. A single leptin injection (5 mg/kg) at both the onset and offset of the activity period did not alter locomotion of mice housed under a 12 : 12 h light/dark cycle and did not shift the circadian behavioral rhythm of mice housed in constant darkness. By contrast, leptin potentiated the phase-shifting effect of a 30-min light-pulse on behavioural rhythms during the late subjective night, although only in females. This was accompanied by a higher induction of the clock genes Per1 and Per2 in the SCN. A 2-week chronic exposure to a physiological dose of leptin (100 μg/kg per day) decreased locomotor activity, expression of hypocretin receptor 1 and 2, as well as the number of hypocretin-immunoreactive neurones only in female mice, whereas the number of c-fos-positive hypocretinergic neurones was reduced in both genders. These results highlight a dimorphic effect of leptin on the hypocretinergic system and on the response of the circadian clock to light. Leptin may thus modulate the sleep/wake cycle and circadian system beside its well-established action on food intake and regulation of body weight.

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confidence: 99%

Dimorphic Effects of Leptin on the Circadian and Hypocretinergic Systems of Mice

Mendoza¹,

López-López²,

Revel³

et al. 2010

Journal of Neuroendocrinology

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“…Our animal model is a nocturnal animal, and food intake is more uniformly distributed throughout the day and night (Rowland, 1985). Differences in the phases of leptin rhythms are not due to different preferences in feeding time (Karakas and Gündüz, 2006). Although we did not estimate body fat content, the stability in body weight in response to photoperiods reflected changes in body fat stores and thereby confirmed that circulating leptin does not monitor body fat mass in male Syrian hamsters.…”

Section: Discussionmentioning

confidence: 69%

“…In the present study, which employed subcutaneous melatonin implants in pineal-intact hamsters, the marked diurnal variation in serum melatonin titers was abolished as a consequence of elevated daytime levels, but rhythmicity in serum melatonin persisted (Figure 3). It must be stressed that melatonin has receptors in the SCN (Williams et al, 1989), and it is possible that, similar to the rhythm in melatonin release, SCN control of leptin release is mainly stimulatory; thus, removal of this stimulatory SCN control results in decreased leptin levels (Karakas and Gündüz, 2006). Choi and Dallman (1999) reported that in SCN-lesion rats, increased plasma leptin levels are accompanied by obesity.…”

Section: Discussionmentioning

confidence: 99%

Serum leptin profiles, food intake, and body weight in melatonin-implanted Syrian hamsters (Mesocricetus auratus) exposed to long and short photoperiods

Gündüz¹

2014

Turk J Biol

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We have shown that circadian changes in leptin concentrations are inversely linked to circulating melatonin levels in the Syrian hamster. The present study aimed to assess the effects of subcutaneous melatonin implants under different photoperiodic conditions: did the implants affect serum leptin levels, body weight, food consumption, and/or testicular weight? Male hamsters were exposed to long and short photoperiods for 10 weeks and received subcutaneous melatonin implants (1 mg in 24 mg beeswax) every 2 weeks. Blood samples were collected every week at midday (1200 hours) or midnight (0000 hours) to assess leptin and melatonin concentrations. Testes were measured to calculate weight. Body weight and food intake were determined every week. Melatonin implants blocked the testicular regression produced by short photoperiods. No differences in body weight were observed among any of the groups. Food consumption increased only with the melatonin implant in the short photoperiod. Serum leptin levels in both photoperiods remained constant. Differences were apparent between noon and night leptin profiles. Noon leptin levels were high (16-18 ng/mL) compared to night leptin levels (8-11 ng/mL) in untreated controls. On the other hand, serum leptin concentrations declined in melatoninimplanted hamsters in both photoperiods. The effects of melatonin on leptin hormone profiles are very pronounced, and melatonin seems to have both physiologically and pharmacologically suppressive effects on leptin production by direct or indirect mechanisms.

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“…In the present study, the peak of plasma leptin in hamsters exposed to long or short photoperiods takes place at night, as in other nocturnal rodents like rats and mice (Ahren, 2000 ; Kalsbeek et al, 2001 ; Cuesta et al, 2009 ). Other reports in Syrian hamsters , however, found either hardly rhythmic profile (Horton et al, 2000 ) or rhythmic leptin peaking during daytime (Karakas and Gunduz, 2006 ). The daily rhythm of leptin is thought to be controlled both by the master clock in the SCN and by the adipose clock (Kalsbeek et al, 2001 ; Karakas and Gunduz, 2006 ; Otway et al, 2009 ).…”

Section: Discussionmentioning

confidence: 87%

Pineal melatonin is a circadian time-giver for leptin rhythm in Syrian hamsters

et al. 2015

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Nocturnal secretion of melatonin from the pineal gland may affect central and peripheral timing, in addition to its well-known involvement in the control of seasonal physiology. The Syrian hamster is a photoperiodic species, which displays gonadal atrophy and increased adiposity when adapted to short (winter-like) photoperiods. Here we investigated whether pineal melatonin secreted at night can impact daily rhythmicity of metabolic hormones and glucose in that seasonal species. For that purpose, daily variations of plasma leptin, cortisol, insulin and glucose were analyzed in pinealectomized hamsters, as compared to sham-operated controls kept under very long (16 h light/08 h dark) or short photoperiods (08 h light/16 h dark). Daily rhythms of leptin under both long and short photoperiods were blunted by pinealectomy. Furthermore, the phase of cortisol rhythm under a short photoperiod was advanced by 5.6 h after pinealectomy. Neither plasma insulin, nor blood glucose displays robust daily rhythmicity, even in sham-operated hamsters. Pinealectomy, however, totally reversed the decreased levels of insulin under short days and the photoperiodic variations in mean levels of blood glucose (i.e., reduction and increase in long and short days, respectively). Together, these findings in Syrian hamsters show that circulating melatonin at night drives the daily rhythmicity of plasma leptin, participates in the phase control of cortisol rhythm and modulates glucose homeostasis according to photoperiod-dependent metabolic state.

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Suprachiasmatic Nuclei May Regulate the Rhythm of Leptin Hormone Release in Syrian Hamsters (Mesocricetus Auratus)

Cited by 18 publications

References 31 publications

Dimorphic Effects of Leptin on the Circadian and Hypocretinergic Systems of Mice

Dimorphic Effects of Leptin on the Circadian and Hypocretinergic Systems of Mice

Serum leptin profiles, food intake, and body weight in melatonin-implanted Syrian hamsters (Mesocricetus auratus) exposed to long and short photoperiods

Pineal melatonin is a circadian time-giver for leptin rhythm in Syrian hamsters

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