High‐Fat Diet Exacerbates Androgen‐Mediated Obesity and White Adipose Tissue Hypertrophy in a Mouse Model of Polycystic Ovary Syndrome
Authors: Basnet Jelina , Rezq Samar , Huffman Alexandra M. , Cardozo Licy L. Y. , Romero Damian G. 
Published: May 2022

Background

Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder in reproductive age women. PCOS is characterized by hyperandrogenemia, oligo‐ or anovulation and polycystic ovaries and is associated with obesity and white adipose tissue (WAT) dysregulation. The deleterious metabolic profile of women with PCOS is exacerbated by obesity. However, the molecular mechanisms that mediate WAT dysfunction in PCOS, as well as its modulation by the diet, are poorly understood. We aim to investigate the effect of an obesogenic diet on androgen‐mediated WAT hypertrophy by assessing the adipocyte size of the different WAT depots [mesenteric fat (MF), subcutaneous fat (SCF) and retroperitoneal fat (RPF)] using a well‐established model of PCOS in mice.

Methods

Three‐week old female mice (C57BL/6J) were implanted with Silastic tubes filled with the androgen dihydrotestosterone (DHT, 8.0 mg, S.C.) or vehicle (empty tubes). Animals were fed high‐fat diet (HFD; 60% kcal fat) or low‐fat diet (LFD; 10% kcal fat, sucrose‐matched) for 90 days. Weekly body weights and body composition (EchoMRI) were assessed. Animals were sacrificed and multiple WAT depots (MF, SCF and RPF) were harvested for histological analysis. Formalin‐fixed paraffin‐embedded tissues from the three WAT depots were sectioned (5 µm thick) and stained with hematoxylin and eosin. The stained sections were imaged at 40X magnification. Adipocyte size (cross‐sectional area) was determined using ImageJ software with the Adiposoft plugin [~2,000 adipocytes/section, 3 sections/animal, n = 6/group]. GraphPad Prism 8.4.2 was used for statistical analysis, and P‐values of 0.05 were considered statistically significant.

Results

LFD‐fed DHT‐treated mice showed significant increases in body weight (28.00 ± 0.60 vs. 23.59 ± 0.41 g, p<0.05), lean mass (21.70 ± 0.30 vs. 20.04 ± 0.23 g, p<0.05), and fat mass (6.20 ± 0.50 vs. 3.42 ± 0.33 g, p<0.05) compared to their vehicle‐treated controls. Adipocyte size analysis showed that LFD‐fed DHT‐ treated mice have significantly larger adipocytes when assessed in MF (1512.0 ± 15.55 vs. 833.3 ± 6.50 µm2, p<0.05), SCF (1907.0 ± 22.04 vs. 1395.0 ± 12.43 µm2, p<0.05) and RPF (2284.0 ± 26.20 vs. 1396.0 ± 11.61 µm2, p<0.05), compared to their vehicle‐treated controls. Notably, HFD‐fed DHT‐treated mice showed greater MF and RPF adipocyte size compared to HFD‐fed vehicle‐treated mice, which was not observed in SCF. Interestingly, HFD exacerbated DHT‐mediated increases in body weight (1.54‐fold), lean mass (1.17‐fold), and fat mass (3.03‐fold) compared to LFD‐fed DHT‐treated mice. Additionally, the increase in adipocyte size in all fat depots in response to DHT was greater in mice fed HFD by 1.50‐fold compared to those fed LFD.

Conclusion and significance

The hypertrophic effect of androgens on the WAT is modulated by the diet. Increased adipocyte size is associated with insulin resistance in women with PCOS. Our results may help explain why obesity is associated with a worsened metabolic profile in women with PCOS at the cellular level. Weight loss with a low‐fat diet may be an effective approach to ameliorate WAT dysfunction and the subsequent metabolic dysregulation in PCOS.