Impact of short-term housing temperature alteration on metabolic parameters and adipose tissue in female mice

Abstract

Introduction: Ambient temperature significantly influences physiological and metabolic processes in rodents, affecting obesity and related disorders. Mice housed below thermoneutral temperatures exhibit increased energy expenditure and sympathetic-driven brown fat activation, whereas thermoneutral housing (~30°C) reduces these responses. This study aimed to determine whether short-term exposure to altered housing temperatures before and during pregnancy induces lasting changes in maternal adipose tissue. We hypothesized that even brief exposure during this critical window could cause persistent structural and molecular alterations in adipose tissue.

Methods: Female C57BL/6J mice were housed at cold (CE, 8°C), thermoneutral (TN, 30°C), or standard room temperature (RT, 22°C) conditions for one week before and throughout pregnancy. All mice were returned to RT post-delivery. Phenotypic assessments-including glucose tolerance, energy expenditure, histology, and proteomics-were performed after lactation.

Results: Temperature exposure did not significantly affect litter size or pup survival. CE-exposed mice showed increased total body weight driven by lean mass gains and reduced fat mass. Adipose tissue showed smaller adipocytes in iWAT and increased vascularity in BAT, though no persistent changes in thermogenic gene expression or glucose homeostasis were observed. Proteomic analysis of iWAT identified 38 differentially expressed proteins, with enrichment of pathways related to mitochondrial function and mTOR signaling.

Discussion: Short-term cold exposure induced lasting histological and proteomic changes in iWAT and BAT without sustained effects on energy metabolism, likely due to reversion to RT and limited sample size.

Conclusion: Brief temperature manipulation around pregnancy can durably alter maternal adipose tissue architecture and molecular signatures, underscoring ambient temperature as an important modulator of maternal metabolic adaptation.

Keywords: adipose tissue remodeling; ambient temperature; brown fat; maternal metabolism; thermal neutral zone.

Figure 1

Schematic representation of experimental design. Female mice were exposed to cold (8°C, CE), room (22°C, RT), or thermoneutral (30°C, TN) temperature for one week prior to conception and for three weeks during gestation. After four weeks of lactation, mice underwent several metabolic assays and were eventually euthanized at 21 weeks of age. All the assays were performed when mice were housed at RT.

Figure 2

Litter sizes did not differ by housing temperature. Litter sizes are plotted by treatment: room temperature (RT [20°C], n = 10 breeding pairs), thermoneutral (TN [30°C], n = 15 breeding pairs), and cold exposure (CE [8°C], n = 15 breeding pairs). No significant differences in breeding performance were found among the temperature groups.

Figure 3

Short-term exposure to cold and thermoneutral temperature altered the total body weight, body composition, and food intake. Female mice were exposed to room (22°C, RT), thermoneutral (30°C, TN), or cold (8°C, CE) temperature for a total of four weeks (one week prior to conception and three weeks during gestation). The CE group showed increased total body weight (A) with lower fat mass (B) and higher lean mass (C) when compared to the other groups. Change in total body weight was accompanied by increased food intake (D). Daily body temperature (E) and glucose tolerance (F) did not differ among groups. Sample sizes were n = 10 mice/group, except for glucose tolerance, where n = 6 mice/group. Data are presented as a box plots, with the box representing the interquartile range and a horizontal line indicating the median.

Figure 4

Short-term exposure to cold and thermoneutral temperature did not significantly alter energy expenditure in female mice. Indirect calorimetry was performed on mice at room temperature condition. Energy expenditure was measure during light and dark phases (A). There were no significant differences in energy balance (B), oxygen consumption (C), and respiratory exchange ratio (D) among the groups. RT = room temperature (22°C), TN = thermoneutral (30°C), CE = cold exposure (8°C). Sample sizes were n = 6 mice/group and data are presented as a box plots, with the box representing the interquartile range and a horizontal line indicating the median (B–D).

Figure 5

Housing of mice intermittentaly at thermoneutral and cold temperature induced changes in the adipose tissue. Female mice were exposed to room (22°C, RT), thermoneutral (30°C, TN), or cold (8°C, CE) temperature for a total of four weeks (one week prior to conception and three weeks during gestation). CE mice showed smaller sized adipocytes in iWAT and more vascularized BAT, whereas TN mice displayed lipid-laden BAT (A). An unbiased selection of images was performed by a third-party individual, blinded to the experimental conditions, from a cohort of n = 6 mice/group. In iWAT (B) and BAT (C), brown specific transcripts were unchanged. 2^−ΔΔCT method and 18S rRNA as the housekeeping gene were used for analysis. 22°C (RT) group served as the reference control for relative comparisonsSample sizes were n = 10 mice/group and data are presented as a box plots, with the box representing the interquartile range and a horizontal line indicating the median (B, C). Statistical significance was declared at p<0.05.

Figure 6

Short-term exposure to cold and thermoneutrality did not alter the thermogenic capacity of BAT and iWAT. NADH-linked (Pyr/Mal) leak respiration, NADH- and glycerophosphate-linked leak respiration (Pyr/Mal/G3p), UCP1-dependent respiration, and associated coupling control ratio for GDP in iWAT (A) and BAT (B) were measured in mice housed at room temperature conditions at 18 weeks of age in female mice. Sample sizes were n = 5 mice/group and data are presented as a box plots, with the box representing the interquartile range and a horizontal line indicating the median.

Figure 7

Previous exposure to cold temperature resulted in long-lasting changes in the proteome of iWAT. Principal co-ordinate analysis shows clustering of proteins based on temperature conditions in female mice iWAT (A). Volcano plot showing the effect of temperature on expression of iWAT proteins (B). Out of 410 proteins in iWAT, 38 were found to be differentially regulated (p<0.05, and log₂FC > 1.5fold). Heatmap reflecting differentially regulated proteins (C). Ingenuity pathway analysis of differentially expressed genes (D). Sample sizes were n = 5–6 mice/group.