An evolutionary trade-off between host immunity and metabolism drives fatty liver in male mice

Abstract

Adaptations to infectious and dietary pressures shape mammalian physiology and disease risk. How such adaptations affect sex-biased diseases remains insufficiently studied. In this study, we show that sex-dependent hepatic gene programs confer a robust (~300%) survival advantage for male mice during lethal bacterial infection. The transcription factor B cell lymphoma 6 (BCL6), which masculinizes hepatic gene expression at puberty, is essential for this advantage. However, protection by BCL6 protein comes at a cost during conditions of dietary excess, which result in overt fatty liver and glucose intolerance in males. Deleting hepatic BCL6 reverses these phenotypes but markedly lowers male survival during infection, thus establishing a sex-dependent trade-off between host defense and metabolic systems. Our findings offer strong evidence that some current sex-biased diseases are rooted in ancient evolutionary trade-offs between immunity and metabolism.

Figure 1.

HFD and infection elicit strong sex-dependent phenotypes in mice.(A) Schematic of housing conditions. (B to F) Body weight gain (B), fat percentage(C), liver weights (Wts) (D), hepatic lipid droplet size (E), and whole livers with corresponding hematoxylin and eosin (H&E) staining (F) after 21 weeks of SD or HFD. (G) Survival curves and body weights of C57BL/6J mice that were infected with E. coli [1 × 10⁸ colony-forming units (CFU)]. Weight curves were analyzed by two-way analysis of variance (ANOVA). (H) Bacterial CFUs of mice that were infected with E. coli (1 × 10⁷ CFU). (I) Survival curves of mice treated with LPS (2 mg/kg). All mice were housed at 30°C. Data are presented as mean ± SEM; NS, not significant; ****p < 0.0001. Scale bars, 100 mm.

Figure 2.

BCL6 maintains hepatic maleness and survival to infection but impairs metabolism. (A) In situ hybridization for Bcl6 (magenta, white arrows) in livers of mice at 22°C. Scale bar, 50 mm. (B) Immunoblot for BCL6 and LMNB1 in liver nuclear extracts of 8-week-old Bcl6^f/f and Bcl6^AlbCre mice at 22°C. (C and D) Heatmaps for top hepatic 100 (C) female- and (D) male-biased genes (filtered by fold change) with corresponding female- or male-biased H3K27ac peaks (adjusted p value for both <0.05) in mice that were housed at 22°C. Scale bars, Z-scores. (E to H) Livers (E), fat percentage (F), liver weights (G), and liver TAGs (H) from mice that were fed a HFD at 30°C. (I) Hepatic Oil Red O staining (ORO) and quantification of lipid droplet (red) size from mice that were fed a HFD for 21 weeks at 30°C. Nuclei stained with 4′,6-diamidino-2-phenylindole (DAPI) (blue). Scale bars, 100 mm. (J) Glucose concentrations and area under the curve (AUC) after an intraperitoneal (IP) glucose tolerance test (GTT) in mice that were fed a HFD for 8 weeks at 30°C. (K and L) Survival curves of mice that were fed a SD and infected with E. coli (1 × 10⁸ CFU) or treated with LPS (1.75 mg/kg) at 30°C (K) and spleen bacterial counts at 30°C (L). Data for control Bcl6^f/f mice in (F), (G), and (I) are regraphed from Fig. 1, C to E (HFD). Data are presented as mean ± SEM. LC, loading control (total protein). **p < 0.01; ****p < 0.0001.

Figure 3.

Sex-dependent hyperlipidemia is linked to host defense responses. (A and B) Plasma TAGs of (A) wild-type mice over time and (B) Bcl6^f/f and Bcl6^AlbCre mice that were infected with E. coli (1 × 10⁷ CFU) at 30°C. (C) Top 10 most abundant TAG species measured by lipidomics in infected Bcl6^f/f and Bcl6^AlbCre mice. Scale bar, Z-scores. (D) Transcript abundances of hepatic ApoB, Apoa1, and Apoc3 in Bcl6^f/f and Bcl6^AlbCre mice (RNA-seq) at 30°C. TPM, transcripts per million. (E) Genomic binding of BCL6 in Apoc3/Apoa1 locus in the male liver (ChIP-seq) at 22°C. (F) Plasma APOC3 in Bcl6^f/f and Bcl6^AlbCre mice that were housed at 30°C. (G) Plasma APOC3 and TAGs in control and LPS-treated (0.5 mg/kg) C57BL/6J female mice at 30°C. Cont., control. (H) Plasma TAGs (1 × 10⁷ CFU) and survival curves (1 × 10⁸ CFU) of female mice that were infected with E. coli at 30°C. (I) Plasma TAGs (1 × 10⁷ CFU) and survival curves (1 × 10⁸ CFU) of male mice that were infected with E. coli at 30°C. Data are presented as mean ± SEM. **p < 0.01; ***p < 0.001; ****p < 0.0001.

Figure 4.

Sex-dependent GH signaling controls BCL6 expression and survival to infection. (A and B) Heatmaps of top 100 (A) male-biased genes and (B) female-/male-biased genes at postnatal day 28 (P28) and P56 or in male mice after GH treatment at 22°C. Scale bars, Z-scores. (C) Immunoblotting and reverse transcription–quantitative polymerase chain reaction (RT-QPCR) for hepatic BCL6 protein and transcript in adult mice infused with vehicle (Veh) or recombinant mouse GH for 15 days at 22°C. (D) Bcl6 mRNA expression in primary mouse hepatocytes treated with vehicle (V), T, estradiol benzoate (E2)(n = 3), or GH (n = 6). (E) Survival curves of male mice infused with Veh or GH for 13 days and then infected with E. coli (1 × 10⁸ CFU) at 30°C. (F) STAT5 binding to Bcl6 locus in the male liver (ChIP-seq) at 22°C. Chr, chromosome. (G) Effect size correlation of all (gray) or differentially expressed (red) transcripts in livers of Bcl6^AlbCre and Ghrd3 male mice. (H) Schematic of the GH–BCL6 axis in regulating sex-dependent endpoints when challenged by diet or infection. LE, long exposure. Data are presented as mean ± SEM;*p < 0.05, ****p < 0.0001.