High-fat diet causes compromised fertility and increased pro-inflammatory cytokines independent of obesity

Abstract

Female obesity is associated with ovarian dysfunction and subfertility (1). However, there are no studies to date to assess whether high-fat diet (HFD) alone (without obesity) causes reproductive dysfunction. The goal of this study was to determine if HFD impacts ovarian function, fertility, and markers of inflammation independent of obesity. Prospective animal study. 5-week old mice were fed either low fat diet containing 10% fat (control group-LF-Ln) or HFD containing 60% fat. After 10 week feeding trial HFD-fed mice were divided into three groups based on body weight (BW): group 1: BW >25 g - high fat obese (HF-Ob), group 2: BW <22 g - high fat lean (HF-Ln), and group 3: BW of 22-25 g. Approximately 1/3 of animals was included in each group. Group 3 was excluded from the study. Six animals per group were sacrificed. Ovaries were collected to assess ovarian follicle pool (primordial and growing) and to determine the degree of local inflammation (macrophage infiltration) by immunohistochemistry. Serum cytokines were measured by Milliplex Multiplex assays (Millipore EMD). The remaining 6 animals per group were kept on the same diet, and followed for breeding trials for 5 months. Statistical analysis was performed using one-way ANOVA with Bonferroni correction to account for multiple comparisons. P-value < 0.05 was considered statistically significant. 10-week exposure to HFD resulted in depleted primordial follicles irrespective of obese phenotype (Table 1). Numbers of growing follicles did not differ significantly between the three groups (p=0.15). Macrophage counts revealed significant differences between LF-Ln and both HFD groups, indicating increased tissue inflammation in the ovary with HF feeding independent of obesity (Table 1). Certain serum pro-inflammatory cytokines were increased in HF-Ln and HF-Ob in comparison to LF-Ln mice (Table 1). There were no differences in the levels of IL-6, IL-10, and interferon-gamma between the groups.Tabled 1Table 1. Primordial follicle number, macrophage counts, cytokine levels, and breeding trial outcome.LF-Ln (±SEM)HF-Ln (±SEM)HF-Ob (±SEM)Overallp-valueLF-Ln vs HF-Lnp-valueLF-Ln vs HF-Obp-valueHF-Ln vs HF-Obp-valuePrimordial follicle numbers1395 ± 229623 ± 81537±1170.0020.0070.003NSMacrophage counts12.0 ± 3.345.0 ± 3.554.0 ± 10.0<0.0010.0390.013NSSerum cytokinesLeptin (pg/mL)846.2±589.11616.6±1333.16096.3±4458.40.009NS0.0130.035IL-8 (pg/mL)51.6 ± 7.260.4 ± 10.595.9 ± 11.10.01NS0.015NSGM-CSF (pg/mL)8.9 ± 2.943.9 ± 11.837.4 ± 13.30.060.06NSNSBreeding trial resultsLittersper mouse4.7 ± 0.23.7 ± 0.41.8 ± 0.8<0.001NS0.0010.03Numberof pups per mouse31.3 ± 1.819.8 ± 4.19.8 ± 3.4<0.0010.0460.001NSNumberof pups per breeding attempt6.2 ± 0.44.1 ± 0.71.9 ±0 .80.0020.0130.002NS Open table in a new tab 10-week exposure to HFD causes significant reduction in primordial follicles, compromised fertility, higher pro-inflammatory cytokine levels, and increased ovarian macrophage infiltration, independent of obesity. In addition, obesity worsens the effects of HFD alone. The negative effects of HFD on primoridal follicles may be mediated by increased ovarian inflammation. To the best of our knowledge, this is the first time that HFD was found to be detrimental to fertility and ovarian function independent of obesity in an interventional study. Further studies are needed to elucidate the mechanisms behind these findings.