A microarray analysis of sexual dimorphism of adipose tissues in high-fat-diet-induced obese mice

Abstract

Objective: A sexual dimorphism exists in body fat distribution; females deposit relatively more fat in subcutaneous/inguinal depots whereas males deposit more fat in the intra-abdominal/gonadal depot. Our objective was to systematically document depot- and sex-related differences in the accumulation of adipose tissue and gene expression, comparing differentially expressed genes in diet-induced obese mice with mice maintained on a chow diet.

Research design and methods: We used a microarray approach to determine whether there are sexual dimorphisms in gene expression in age-matched male, female or ovariectomized female (OVX) C57/BL6 mice maintained on a high-fat (HF) diet. We then compared expression of validated genes between the sexes on a chow diet.

Results: After exposure to a high fat diet for 12 weeks, females gained less weight than males. The microarray analyses indicate in intra-abdominal/gonadal adipose tissue in females 1642 genes differ by at least twofold between the depots, whereas 706 genes differ in subcutaneous/inguinal adipose tissue when compared with males. Only 138 genes are commonly regulated in both sexes and adipose tissue depots. Inflammatory genes (cytokine-cytokine receptor interactions and acute-phase protein synthesis) are upregulated in males when compared with females, and there is a partial reversal after OVX, where OVX adipose tissue gene expression is more 'male-like'. This pattern is not observed in mice maintained on chow. Histology of male gonadal white adipose tissue (GWAT) shows more crown-like structures than females, indicative of inflammation and adipose tissue remodeling. In addition, genes related to insulin signaling and lipid synthesis are higher in females than males, regardless of dietary exposure.

Conclusions: These data suggest that male and female adipose tissue differ between the sexes regardless of diet. Moreover, HF diet exposure elicits a much greater inflammatory response in males when compared with females. This data set underscores the importance of analyzing depot-, sex- and steroid-dependent regulation of adipose tissue distribution and function.

Conflict of interest statement

Conflict of interest The authors declare no conflict of interest.

Figures

Figure 1

Validation of microarray results with qPCR. (a) Differences in lipocalin 2 microarray gene expression between males, females and OVX in gonadal fat (GWAT) and inguinal fat (IWAT). (b) qPCR of lipocalin 2 mRNA in the three groups on HF diet. (c) Differences in FoxA1 microarray gene expression between males, females and OVX. (d) qPCR of FoxA1 mRNA in the three groups. (e) qPCR of GWAT lipocalin 2 mRNA in the three groups on chow (Note: S* = P<0.05 compared between the sexes; P* = P<0.05 compared between the fat pad; and I* = P<0.05 independent of the sexes).

Figure 2

qPCR validation of microarray for markers of inflammation. (a) Differences in retinol binding protein 4 (RBP4) gene expression by microarray between males, females and OVX in gonadal fat (GWAT) and inguinal fat (IWAT). (b) qPCR of RBP4 mRNA on HF diet. (c) Differences in CD68 gene expression by microarray. (d) qPCR of CD68 mRNA on HF diet. (e) Differences in SAA3 gene expression by microarray. (f) qPCR of SAA3 mRNA on HF diet. (g) Differences in CD14 gene expression by microarray. (h) qPCR of CD14 mRNA on HF diet. (i) qPCR of GWAT SAA3 mRNA on chow. (j) qPCR of GWAT CD68 on chow. (k) qPCR of GWAT CD14 mRNA on chow (Note: S* = P<0.05 compared between the sexes; P* = P<0.05 compared between the fat pad; and I* = P < 0.05 independent of the sexes).

Figure 3

qPCR validation of microarray for markers of the insulin signaling pathway. (a) Differences in insulin receptor substrate 1 (IRS1) gene expression by microarray between males, females and OVX in gonadal fat (GWAT) and inguinal fat (IWAT). (b) qPCR of IRS1 mRNA on HF diet. (c) Differences in glucose transporter 4 (Glut4) gene expression by microarray. (d) qPCR of Glut4 mRNA on HF diet. (e) Differences in phosphoenolpyruvate carboxykinase (PEPCK) gene expression by microarray. (f) qPCR of PEPCK mRNA on HF diet. (g) qPCR of GWAT IRS1 mRNA on chow. (h) qPCR of GWAT Glut4 mRNA on chow. (i) qPCR of GWAT PEPCK mRNA on chow (Note: S* = P<0.05 compared between the sexes; P* = P<0.05 compared between the fat pad; and I* = P < 0.05 independent of the sexes).

Figure 4

(a) Adipose tissue morphology. Histology (hematoxylin and eosin-stained sections) of male, female or OVX gonadal (G) or inguinal (I) showing crown-like structures (arrows, at week 12 because of numerous crown-like structures). (b) Quantification of adipocyte death determined from multiple histological sections (> 500 cells) of 6–8 mice per group per time point. Bars identified by * are significantly different (P<0.05) by Tukey′s procedure.