Sex Differences in Thermogenesis Structure Behavior and Contact within Huddles of Infant Mice

Abstract

Brown adipose tissue (BAT) is a thermogenic effector abundant in most mammalian infants. For multiparous species such as rats and mice, the interscapular BAT deposit provides both an emergency “thermal blanket” and a target for nestmates seeking warmth, thereby increasing the cohesiveness of huddling groups. Sex differences in BAT regulation and thermogenesis have been documented in a number of species, including mice (Mus musculus)–with females generally exhibiting relative upregulation of BAT. It is nonetheless unknown whether this difference affects the behavioral dynamics occurring within huddles of infant rodents. We investigated sex differences in BAT thermogenesis and its relation to contact while huddling in eight-day-old C57BL/6 mouse pups using infrared thermography, scoring of contact, and causal modeling of the relation between interscapular temperature relative to other pups in the huddle (TIS rel) and contacts while huddling. We found that females were warmer than their male siblings during cold challenge, under conditions both in which pups were isolated and in which pups could actively huddle in groups of six (3 male, 3 female). This difference garnered females significantly more contacts from other pups than males during cold-induced huddling. Granger analyses revealed a significant negative feedback relationship between contacts with males and TIS rel for females, and positive feedback between contacts with females and TIS rel for males, indicating that male pups drained heat from female siblings while huddling. Significant sex assortment nonetheless occurred, such that females made more contacts with other females than expected by chance, apparently outcompeting males for access to each other. These results provide further evidence of enhanced BAT thermogenesis in female mice. Slight differences in BAT can significantly structure the behavioral dynamics occurring in huddles, resulting in differences in the quantity and quality of contacts obtained by the individuals therein, creating sex differences in behavioral interactions beginning in early infancy.

Individual differences in early body mass affect thermogenic performance and sibling interactions in litter huddles of the house mouse

“…These were used to test for changes across time in peripheral body temperature in response to thermal challenge, and for correlations of sibling differences in body mass with individual slopes describing the bodytemperature dynamics in response to a thermal challenge and with the pups' interactions within the huddle. We also included sex as a fixed factor, in particular as some studies in rodents indicate a higher thermogenic capacity in female pups (Harshaw et al, 2014;Valle, García-Palmer, Oliver, & Roca, 2007). We always included litter identity (n = 12 litters) and parental identity (n = 8 pairs) as random factors (random intercepts) in the analysis to take into account these two sources of same origin of F I G U R E 1 Changes in maximum peripheral body temperature in response to a thermal challenge.…”

“…Sibling differences in early body mass can lead to individual differences in the way pups behave within the litter huddle . This has been intensively studied in different species of altricial mammals and birds (Alberts, 1978;Blumberg & Sokoloff, 1998;Forbes, 2005;Gilbert, McCafferty, Giroud, Ancel, & Blanc, 2012;Hill, 1983;Rödel, Hudson, & von Holst, 2008;Sokoloff & Blumberg, 2001), including the laboratory mouse (Mus musculus: Harshaw & Alberts, 2012;Harshaw, Culligan, & Alberts, 2014;Shelton & Alberts, 2018). This has been intensively studied in different species of altricial mammals and birds (Alberts, 1978;Blumberg & Sokoloff, 1998;Forbes, 2005;Gilbert, McCafferty, Giroud, Ancel, & Blanc, 2012;Hill, 1983;Rödel, Hudson, & von Holst, 2008;Sokoloff & Blumberg, 2001), including the laboratory mouse (Mus musculus: Harshaw & Alberts, 2012;Harshaw, Culligan, & Alberts, 2014;Shelton & Alberts, 2018).…”

A Theory of Social Thermoregulation in Human Primates

“…In social psychology, such questions are typically resolved through priming methods, which is the 14 There is also growing support for gender differences in brown adipose tissue thermogenesis. This suggest that this process is enhanced in females leading to differential experiences in warmth between huddling male and female mice of 8 days old and thus possible gender differences through early interaction experiences (Harshaw et al, 2014). 15 Convergence zones were first discussed both by Barsalou (1999Barsalou ( , 2008 and Damasio (1989) as their role being "to enact formulas for the reconstitution of fragment-based momentary representations of entities or events in sensory or motor cortices" (p. 46).…”

How self-organization can guide evolution

“…For example, Haig [8] explains that the genes encoding the potential for BAT-thermogenesis (Pref1/Dlk1 and Necdin) interact with a BAT-activating gene (GNAS) either to promote thermogenesis when the maternal allele is expressed or to inhibit thermogenesis when the paternal allele is expressed, and therefore males and females have a differential genetic investment in the success of the huddle. In support, male rat pups, who generate less heat through BAT, have been described as heat sinks that drain the extra heat generated by female littermates [49]. These authors also suggest that the ratio of males to females in a litter can affect BAT-thermogenesis directly via sex hormones, hence the adaptive capacity for huddling may be affected by the sex ratio within the huddle.…”