Leptin increases maternal investment

Abstract

The primary goal of virtually all organisms is to produce genetic offspring, thereby passing on their genes to future generations. Offspring production, however, is limited by available resources within an environment. Moreover, distributing sufficient energy among competing physiological systems is challenging and can result in trade-offs between self-maintenance and offspring investment when resources are limited. In the current study, we tested the hypothesis that the adipose hormone leptin is involved in mediating energetic trade-offs between competing physiological systems. Specifically, we tested the effects of elevated maternal leptin on investment into offspring production versus self maintenance (immune function), in the Siberian hamster (Phodopus sungorus). The current study provides the first evidence that leptin serves as a signal to mothers of available energy resulting in epigenetic effects. Therefore, elevated leptin allows females to retain more embryos to parturition, and rear more offspring to weaning via reduced maternal infanticide. Innate immune response was suppressed seemingly as a result of these enlarged litters, suggesting that the observed fitness increase is not without costs to the mother. Collectively, these findings suggest that leptin plays a critical role in allowing mothers to determine how much energy to invest in the production and care of young versus self-maintenance.

Effects of reproduction on immuno-suppression and oxidative damage, and hence support or otherwise for their roles as mechanisms underpinning life history trade-offs, are tissue and assay dependent

“…A serum bactericidal assay was performed in a sterile laminar flow cabinet to assess the functional response by the animal's innate immune system against a relevant pathogen, Escherichia coli (Tieleman et al, 2005;French et al, 2009). This assay allows characterization of a relevant immune response that involves that action of phagocytes, opsonizing proteins and natural antibodies (predominantly IgM and IgA) (Demas et al, 2011).…”

Mounting a specific immune response increases energy expenditure of the subterranean rodentCtenomys talarum(tuco-tuco): implications for intraspecific and interspecific variation in immunological traits

“…In consequence, particularly energetically costly reproductive stages can depress levels of immunocompetence (Degen, 2006;French et al, 2009). Conversely, an induced immune challenge has been shown to negatively impact reproductive behaviour (Bonneaud et al, 2003;Weil et al, 2006).…”

Exogenous insulin enhances humoural immune responses in short-day, but not long-day, Siberian hamsters (Phodopus sungorus)

“…Serum leptin concentrations were determined in day 10 serum samples (1 : 2 dilution with assay buffer) using an ELISA from a commercially prepared murine kit (EZML-82K, Millipore, St Charles, MO, USA). This assay was previously validated for use with Siberian hamsters (French et al 2009). All procedures were followed as directed by the manufacturer's instructions.…”

“…(h) Bactericidal assay As a functional assessment of an animal's ability to eliminate a bacterial infection, we used an ex vivo bactericidal assay, based on a modification (French et al 2009) of a previously published protocol (Matson et al 2006). This assay quantifies the relative number of Escherichia coli colony forming units (CFUs) that grow after incubation with serum.…”