Does leptin signal adiposity in the egg-laying mammal, Tachyglossus aculeatus?

Sprent, Jenny; Jones, Susan; Nicol, Stewart C.

doi:10.1016/j.ygcen.2012.06.021

Cited by 16 publications

(11 citation statements)

References 67 publications

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“…Whilst burrow boxes and heat lamps provide females with behavioural means of thermoregulation, the acquisition of fat reserves is also likely to be equally important for breeding success. Field studies have documented weight gains before the breeding season (Grigg et al 1989;Rismiller and McKelvey 2003;Nicol and Andersen 2007;Sprent et al 2012), which can be correlated with breeding success (Schmid et al 2003). Reproductively successful females in the current study did not consistently gain noticeable weight, which contrasts with the results found by Sprent et al (2012).…”

Section: Discussioncontrasting

confidence: 98%

Advances in the captive breeding and reproductive biology of the short-beaked echidna (Tachyglossus aculeatus)

et al. 2015

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Captive breeding of the short-beaked echidna (Tachyglossus aculeatus) has proven a difficult challenge; as recently as 2009, there were fewer than 10 echidnas born in captivity. We present observations of captive reproductive behaviour following video surveillance and measurements of body temperature collected from six captive female echidnas over a six-year period. In the first series of observations (2009-10) we examined the efficacy of artificial burrow boxes as possible aids for reproductive success. Females with access to burrow boxes had significantly higher levels of reproductive activity (P = 0.001), there was coincidental improvement in the production of eggs or pouch young (two eggs, one unhatched and one offspring). During 2009-10, a range of reproductive behaviours (courtship, copulation and postcopulation) were documented and analysed, as were new observations of oestrous cycle activity. Female body temperature was characteristically stable during egg incubation during this study and has the potential to be used as a tool for the assessment of reproductive status. Following initial observations, burrow boxes and infrared lamps were implemented as standard husbandry in our echidna breeding facility and the effects on reproductive success were monitored, albeit less intensively, for a further four years . Although no direct causal effect could be ascribed, the use of burrow boxes and heat lamps coincided with a total of 13 young being born to four females in the last four years . These female echidnas were found to be receptive at intervals throughout the breeding season, both before and after presumed incubation phases, suggesting that captive animals exhibit polyoestry. In 2012 and 2014, the same female showed evidence of producing two young from one breeding event.

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Section: Discussioncontrasting

confidence: 98%

Advances in the captive breeding and reproductive biology of the short-beaked echidna (Tachyglossus aculeatus)

et al. 2015

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“…Figure 3 shows a male Tasmanian echidna entering hibernation at the warmest time of the year. When they have built up sufficient fat reserves, echidnas reduce their activity (Sprent et al, 2012), and dig into the soil, and T b falls until it is with 0.5–1.0°C of substrate temperature (Nicol and Andersen, 2002; Figure 4). The factors that determine the equilibrium T b can be seen by rearranging the familiar Scholander-Irving model (Nicol et al, 2008):

\begin{matrix} T_{b} = T_{a} + \frac{\dot{V} O_{2}}{C} \end{matrix}

i.e., T b falls to a temperature dependent on ambient temperature plus an amount determined by the ratio of hibernating metabolic rate to conductance.…”

Section: Hibernationmentioning

confidence: 99%

“…Leptin binds to leptin-specific receptors in the hypothalamus, regulating the production of a range of orexigenic and anorexigenic neuropeptides, and resulting in a decrease in food intake, an increase in metabolic rate, and consequently a loss of adipose tissue (Denver et al, 2011; Florant and Healy, 2012). Although it is frequently claimed that leptin is an adipostat in mammals this been demonstrated only for eutherian mammals; it is not true for the short-beaked echidna (Sprent et al, 2012), and although pharmacological doses of leptin inhibit daily torpor in the marsupial Sminthopsis macroura (Geiser et al, 1998) the relationship between adiposity and endogenous plasma leptin has not been investigated in marsupial mammals.…”

Section: Leptin and Energeticsmentioning

confidence: 99%

“…The interaction between leptin and the leptin receptor is conserved in terrestrial vertebrates, and in mammals both leptin and its receptor are highly conserved with few variations (Prokop et al, 2012). Sprent et al (2012) hypothesized that in the echidna as in eutherian hibernators, there would be a strong relationship between adiposity and plasma leptin for most of the year which would change during pre-hibernatory fattening. Instead they found a weak negative relationship between adiposity and plasma leptin.…”

Section: Leptin and Energeticsmentioning

confidence: 99%

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Energy Homeostasis in Monotremes

Nicol

2017

Front. Neurosci.

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In 1803, the French anatomist Étienne Geoffroy Saint-Hilaire decided that the newly described echidna and platypus should be placed in a separate order, the monotremes, intermediate between reptiles and mammals. The first physiological observations showed monotremes had low body temperatures and metabolic rates, and the consensus was that they were at a stage of physiological development intermediate between “higher mammals” and “lower vertebrates.” Subsequent studies demonstrated that platypuses and echidnas are capable of close thermoregulation in the cold although less so under hot conditions. Because the short-beaked echidna Tachyglossus aculeatus, may show very large daily variations in body temperature, as well as seasonal hibernation, it has been suggested that it may provide a useful model of protoendotherm physiology. Such analysis is complicated by the very significant differences in thermal relations between echidnas from different climates. In all areas female echidnas regulate Tb within 1°C during egg incubation. The lactation period is considered to be the most energetically expensive time for most female mammals but lactating echidnas showed no measurable difference in field metabolic rate from non-lactating females, while the lactation period is more than 200 days for Kangaroo Island echidnas but only 150 days in Tasmania. In areas with mild winters echidnas show reduced activity and shallow torpor in autumn and early winter, but in areas with cold winters echidnas enter true hibernation with Tb falling as low as 4.5°C. Monotremes do not possess brown adipose tissue and maximum rates of rewarming from hibernation in echidnas were only half those of marmots of the same mass. Although echidnas show very large seasonal variations in fat stores associated with hibernation there is no relationship between plasma leptin and adiposity. Leptin levels are lowest during post-reproductive fattening, supporting suggestions that in evolutionary terms the anorectic effects of leptin preceded the adiposity signal. BMR of platypuses is twice that of echidnas although maximum metabolism is similar. High levels of thyroid hormones in platypuses may be driving metabolism limited by low body temperature. Monotremes show a mosaic of plesiomorphic and derived features but can still inform our understanding of the evolution of endothermy.

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“…U tego zwierzęcia zaobserwowano słabą ujemną korelację między poziomem leptyny w osoczu a ilością rezerw tłuszczowych (48). Najwyższe stężenie tego hormonu zanotowano u osobników o najniższej w skali sezonu masie ciała, będących w stanie hibernacji, a także u samic w okresie reprodukcji.…”

Section: Leptynooporność U Zwierzątunclassified

Physiological leptin resistance

Gogga¹,

Karbowska²,

Meissner³

et al. 2016

Medycyna Weterynaryjna

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Leptin is an adipose tissue-derived hormone whose circulating levels correlate with the amount of body fat stores. The main function of this adipokine is to regulate energy metabolism. By modulating the expression of orexigenic and anorexigenic neuropeptides in the hypothalamus, leptin reduces appetite. It also increases energy expenditure, contributing to the decrease of body fat and body weight. Mutations in the leptin receptor gene or prolonged consumption of a high-fat diet may impair leptin action, leading to leptin resistance. Resistance to leptin can also be an adaptive response that occurs in seasonal animals and in pregnant mammals. Reversible insensitivity to the satiety signal of leptin promotes hyperphagia, which is essential for animals living in dynamic environments and experiencing seasonal variation in food availability, since it allows them to forage intensely when food is abundant and accumulate fat reserves necessary to survive periods when food is scarce. Moreover, leptin resistance and subsequent hyperphagia develop during pregnancy in order to meet the energy needs of the growing fetus. Physiological leptin resistance may be due to impaired transport of leptin across the blood-brain barrier and/or to decreased sensitivity of the hypothalamus to this hormone resulting from an inhibition of leptin signalling in hypothalamic neurons. In pregnancy, an increased resistance to leptin action is also mediated by the binding of this adipokine to its placenta-derived soluble receptor. Reduced entry of leptin into the brain as well as alterations in the leptin signalling pathway in the hypothalamus leads to a transient decrease in sensitivity to this hormone preventing appetite suppression.

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Does leptin signal adiposity in the egg-laying mammal, Tachyglossus aculeatus?

Cited by 16 publications

References 67 publications

Advances in the captive breeding and reproductive biology of the short-beaked echidna (Tachyglossus aculeatus)

Advances in the captive breeding and reproductive biology of the short-beaked echidna (Tachyglossus aculeatus)

Energy Homeostasis in Monotremes

Physiological leptin resistance

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