Gender-specific expression and mechanism of regulation of estrogen sulfotransferase in adipose tissues of the mouse

Abstract

Although primarily regarded as a sex steroid, estrogen plays an important role in many other physiological processes including adipose development and disposition. Estrogen sulfotransferase (EST) regulates estrogen activity by catalyzing the sulfoconjugation and inactivation of estrogens. In the present study, we report the gender-specific expression of EST in adipose tissues of the mouse and describe contrasting mechanisms of EST regulation in the fat and liver. EST is expressed in the white adipose tissues of the male but not female mouse. Within the various fat depots of male mice, it is most abundantly expressed in the epididymal fat pad, with variable levels in other white fats and no expression in the brown fat. Fractionation of epididymal fat cells showed EST to be predominantly associated with stromal vascular cells (preadipocyte). EST expression in male mouse adipose tissues is dependent on testosterone as castration ablated, and administration of exogenous testosterone restored, EST expression. Furthermore, testosterone treatment induced abnormal EST expression in the parametrial fat of female mice. EST induction by testosterone in female mice is tissue specific because testosterone treatment had no effect on liver EST expression. Conversely, the liver X receptor agonist TO-901317 induced EST expression in female mouse liver but not in their adipose tissues. Finally, we demonstrate that male EST knockout mice developed increased epididymal fat accumulation with enlarged adipocyte size. We conclude that EST is expressed in adipose tissues in a sexually dimorphic manner, is regulated by testosterone, and plays a physiological role in regulating adipose tissue accumulation in male mice.

Figures

Figure 1

EST is expressed in adipose tissues of male mice. A, Northern blot analysis of EST mRNA in C57BL/6 male mouse tissues. Tissues were collected and pooled from two mice, and 10 μg of RNA were loaded onto the gel. EST mRNA is found in epididymal fat, epidermis, prostate, testis, and epididymis. GAPDH, Glyceraldehyde-3-phosphate dehydrogenase. B, EST mRNA is expressed in male epididymal and inguinal fat. Little or no EST mRNA is present in retroperitoneal fat or brown fat. None of the fat tissues examined in female mice expresses EST. C, Western blot analysis of EST protein in male and female adipose tissue. EST protein is found in male epididymal and inguinal adipose tissues only. D, Enzyme activity assay on WT male and female adipose tissues. EST activity is detected in male mouse epididymal and inguinal fat but not in retroperitoneal fat. E, Northern blot analysis showing EST is predominantly expressed in preadipocytes. IF, Inguinal fat; EF, epididymal fat; RF, retroperitoneal fat; PF, parametrial fat; ND, none detected; PA, preadipocytes; F, adipocytes.

Figure 2

EST expression in adipose tissues is regulated by testosterone. A, Northern blot analysis of EST mRNA in epididymal fat (EF) of castrated male mice treated with T or vehicle (olive oil). The control (con) mouse was an intact male C57BL/6 mouse. GAPDH, Glyceraldehyde-3-phosphate dehydrogenase. B, Northern blot analysis of EST mRNA in parametrial fat (PF) from female mice treated with either vehicle (olive oil) or T. C, Northern blot analysis of EST mRNA in parametrial fat and liver of female mice treated with T or vehicle (V). D, Northern blot analysis of EST mRNA in parametrial fat and liver of female mice treated with TO, an LXR agonist or vehicle (V). E, Female db/db (DB) mice had markedly induced EST expression in the liver but not in their parametrial fat. F, EST expression in the epididymal fat of db/db (DB) mice was dramatically reduced compared with normal (WT) mice, whereas EST expression was induced in their liver.

Figure 3

Increased adipogenesis in male EST-deficient mice. A, Northern blot analysis of EST expression in epididymal fat (EF) and testis (T) from WT and EST−/− male mice. B, Western blot analysis of EST expression in epididymal (EF), inguinal (IF), retroperitoneal (RF) fat, and testis of WT and EST−/− male mice. C, EST enzyme activity assay of various fat depots and testis of WT and EST−/− male mice. D, Representative epididymal fat masses collected from three WT and EST−/− male mice. KO, Knockout; M, male. E, Body weights and fat mass indices of 10-wk-old male EST WT/heterozygous (n = 23) and EST−/− mice (n = 16). Fat mass index = adipose weight/body weight × 100. Epi, Epididymal; Ing, inguinal; RP, retroperitoneal. F, Body weights and fat mass indices of 10-wk-old female EST WT/heterozygous (n = 18) and EST−/− mice (n = 7). PM, Parametrial. G, Increased epididymal fat mass in EST−/− mice was observed at all three ages examined (n = 8–12 for each group). Data presented are mean ± sem. *, P ≤ 0.05, Student’s t test.

Figure 4

Increased adipocyte size in male EST−/− mice. A, Epididymal adipocytes from EST−/− (left panel) mice are larger than those from WT (right panel). B, No difference in food intake was observed between WT and EST−/− mice over a 2-wk period (n = 3–5/group). F, Female; M, male. C, No difference in growth curve (weight gain) was observed between WT and EST−/− mice over a 12-wk period (n = 4–5/group).