Leptin and Metabolic Control of Reproduction

Schneider, Jill E.; Zhou, Dan; Blum, Robert M.

doi:10.1006/hbeh.2000.1590

Cited by 89 publications

(50 citation statements)

References 149 publications

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“…Ectotherms, as low-energy systems, can present a total decoupling between the phase of energy gathering and the period during which energy is invested for reproduction (Secor et al, 1994;Bonnet, Shine, Naulleau, and Vacher-Vallas, 1998b). In strong contrast to what has been documented in endotherms (Bronsson, 1998;Schneider et al, 2000), a high body condition can be sufficient to initiate and fuel reproductive effort in snakes . In addition, female snakes do not provision their neonates after parturition, males generally do not exhibit territoriality or pair fidelity, and there is no forcible insemination.…”

Section: Discussionmentioning

confidence: 97%

“…For example, several mammals are classified as typical capital breeders (Festa-Bianchet et al, 1998) but recent reviews on captive and natural populations of mammals found no support for the widely accepted "adaptationist argument that females should delay ovulation until they have sufficient energy reserves to support pregnancy and lactation" (Bronson, 1998;Schneider, Zhou, and Blum, 2000). These animals also display ability to cancel, increase, or decrease reproductive effort at a later stage long after the initiation of reproduction per se.…”

Section: Discussionmentioning

confidence: 99%

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Fat Is Sexy for Females but Not Males: The Influence of Body Reserves on Reproduction in Snakes (Vipera aspis)

Aubret

Bonnet

Shine

et al. 2002

Hormones and Behavior

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Reproduction is energetically expensive for both sexes, but the magnitude of expenditure and its relationship to reproductive success differ fundamentally between males and females. Males allocate relatively little to gamete production and, thus, can reproduce successfully with only minor energy investment. In contrast, females of many species experience high fecundity-independent costs of reproduction (such as migration to nesting sites), so they need to amass substantial energy reserves before initiating reproductive activity. Thus, we expect that the relationship between energy reserves and the intensity of reproductive behavior involves a threshold effect in females, but a gradual (or no) effect in males. We tested this prediction using captive vipers (Vipera aspis), dividing both males and females into groups of high versus low body condition. Snakes from each group were placed together and observed for reproductive behavior; sex-steroid levels were also measured. As predicted, females in below-average body condition had very low estradiol levels and did not show sexual receptivity, whereas males of all body condition indices had significant testosterone levels and displayed active courtship. Testosterone levels and courtship intensity increased gradually (i.e., no step function) with body condition in males, but high estradiol levels and sexual receptivity were seen only in females with body reserves above a critical threshold. The energetics of reproduction has been a central theme in the ecological study of life history variation (Hirshfield and Tinkle, 1975;Morris, 1987Morris, , 1992Winkler and Wallin, 1987;Stearns, 1992; Monaghan and Nager, 1997), and more recently this topic has become an important focus in behavioral endocrinology (Cherel, Mauget, Lacroix, and Gilles, 1994;Bronson, 1998). It is obvious that organisms cannot reproduce in the total absence of energy reserves (Frish, 1978;Frish and McArthur, 1974), but the relationship between the amount of energy reserves and reproductive output (or effort) is complex and varies among species. In some species there is a linear relationship between energy reserves and reproductive output. In others there appears to be no discernible relationship (e.g., if clutch and offspring sizes are fixed) or a complex nonlinear relationship between the two variables. For example, many organisms are "capital breeders" that rely on previously gathered energy stored in the form of body reserves (i.e., fat bodies, proteins) rather than on current energy intake to fuel the energetically costly process of reproduction (Drent and Daan, 1980;Jö nsson, 1997; Bonnet, Bradshaw, and Shine, 1998). In such species, life history theory predicts that a threshold level of energy reserves is necessary for a reproductive cycle to begin, rather than a linear relationship in which an increment in energy availability adds an increment in reproductive output (Schaffer, 1974;Bull and Shine, 1979;Stearns, 1992). Several empirical studies provide evidence for nonlinear relationships between...

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Fat Is Sexy for Females but Not Males: The Influence of Body Reserves on Reproduction in Snakes (Vipera aspis)

Aubret

Bonnet

Shine

et al. 2002

Hormones and Behavior

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“…Evidence suggests that the stimulus causing shutdown of the reproductive system is not actually the absolute levels of body fatness, but the immediate experience of energy imbalance and intracellular fuel oxidation status. 52,53 Famine infertility probably therefore affects obese people as much as lean people, as they are both exposed to severe negative energy imbalance. Moreover, decreases in reproductive activity will also, in part, reflect changed social conditions.…”

Section: Why This Argument Is Flawedmentioning

confidence: 99%

Thrifty genes for obesity, an attractive but flawed idea, and an alternative perspective: the ‘drifty gene’ hypothesis

2008

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Almost 50 years ago Neel proposed a hypothesis to explain the prevalence of obesity and diabetes in modern societyFthe 'thrifty gene' hypothesis. The fundamental basis of the hypothesis was that, in our early evolutionary history, genes, that promoted efficient fat deposition would have been advantageous because they allowed their holders to survive at periods of famine. In modern society, such genes are disadvantageous because they promote fat deposition in preparation for a famine that never comes, and the result is widespread obesity and diabetes. In recent years I, and others, have questioned some of the fundamental assumptions of this hypothesisFparticularly focusing on whether differential survival of lean against obese in famines provides sufficient selective pressure for the spread of so-called 'thrifty genes'. These arguments have been criticized because famines not only affect survival but also fecundity, and obese people would be expected to sustain fecundity longer in the face of food shortages. In this paper, I show that the reduced fecundity argument is flawed because famines are almost universally followed by periods of enhanced fecundity, which offsets the decline observed during the famine itself. The net effect of famines on fecundity is consequently insufficient to rescue the thrifty gene idea. Elsewhere, I have suggested an alternative scenario that subsections of the population have a genetic predisposition to obesity due to an absence of selection, combined with genetic drift. The scenario presented earlier was based on evidence from prehistory concerning the release of our ancestors from heavy predation pressure around 2 million years ago. I suggest here that this is one of a number of potential scenarios based on random genetic drift that may explain the specific aetiology of the obesity epidemic. Together, these alternatives, based on central notion that genetic drift rather than positive selection was a dominant factor, may be called the 'drifty gene' hypothesis.

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“…Conditions of food deprivation evoke an adaptive neuroendocrine response that includes increased activity of the adrenal axis and the suppression of the thyroid, gonadal, and growth axes (e.g., 4,24,131,155,197). Just as we had asked whether the brainstem in isolation of forebrain could muster a behavioral response to deprivation, it is also appropriate to consider whether these neuroendocrine responses to natural deprivation would be disrupted or degraded if the hypothalamus operated without benefit of ascending inputs from the caudal brainstem.…”

Section: Independent Processing Capabilities Of the Hypothalamusmentioning

confidence: 99%

The Neuroanatomical Axis for Control of Energy Balance

Grill

Kaplan

2002

Frontiers in Neuroendocrinology

352

219

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The hypothalamic feeding-center model, articulated in the 1950s, held that the hypothalamus contains the interoceptors sensitive to blood-borne correlates of available or stored fuels as well as the integrative substrates that process metabolic and visceral afferent signals and issue commands to brainstem mechanisms for the production of ingestive behavior. A number of findings reviewed here, however, indicate that sensory and integrative functions are distributed across a central control axis that includes critical substrates in the basal forebrain as well as in the caudal brainstem. First, the interoceptors relevant to energy balance are distributed more widely than had been previously thought, with a prominent brainstem complement of leptin and insulin receptors, glucose-sensing mechanisms, and neuropeptide mediators. The physiological relevance of this multiple representation is suggested by the demonstration that similar behavioral effects can be obtained independently by stimulation of respective forebrain and brainstem subpopulations of the same receptor types (e.g., leptin, CRH, and melanocortin). The classical hypothalamic model is also challenged by the integrative achievements of the chronically maintained, supracollicular decerebrate rat. Decerebrate and neurologically intact rats show similar discriminative responses to taste stimuli and are similarly sensitive to intake-inhibitory feedback from the gut. Thus, the caudal brainstem, in neural isolation from forebrain influence, is sufficient to mediate ingestive responses to a range of visceral afferent signals. The decerebrate rat, however, does not show a hyperphagic response to food deprivation, suggesting that interactions between forebrain and brainstem are necessary for the behavioral response to systemic/ metabolic correlates of deprivation in the neurologically intact rat. At the same time, however, there is evidence suggesting that hypothalamic-neuroendocrine responses to fasting depend on pathways ascending from brainstem. Results reviewed are consistent with a distributionist (as opposed to hierarchical) model for the control of energy balance that emphasizes: (i) control mechanisms endemic to hypothalamus and brainstem that drive their unique effector systems on the basis of local interoceptive, and in the brainstem case, visceral, afferent inputs and (ii) a set of uni-and bidirectional interactions that coordinate adaptive neuroendocrine, autonomic, and behavioral responses to changes in metabolic status. KEY WORDS: feeding behavior; leptin; glucose sensing; decerebrate; neuropeptide; hypothalamic model; caudal brainstem; energy balance.

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Leptin and Metabolic Control of Reproduction

Cited by 89 publications

References 149 publications

Fat Is Sexy for Females but Not Males: The Influence of Body Reserves on Reproduction in Snakes (Vipera aspis)

Fat Is Sexy for Females but Not Males: The Influence of Body Reserves on Reproduction in Snakes (Vipera aspis)

Thrifty genes for obesity, an attractive but flawed idea, and an alternative perspective: the ‘drifty gene’ hypothesis

The Neuroanatomical Axis for Control of Energy Balance

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