High-fat diet induced metabolic disruption and altered ovarian lipid profile without triggering overt inflammation in obese mice

Abstract

Objective

To investigate the effects of obesity induced by a high-fat diet on metabolic homeostasis and ovarian health in mice.

To investigate the effects of obesity induced by a high-fat diet on metabolic homeostasis and ovarian health in mice.

Methods

This study was approved by the UNICAMP Ethics Committee (#5671-1/2020 and #5300-1/2019). Six-week-old female Swiss mice (n = 5–9) were assigned to either a control normocaloric diet- CT or a high-fat diet–HF (modified AIN-93G; 35% fat derived from lard) for 16 weeks. Body weight and food intake were monitored weekly. Estrous cyclicity was evaluated by daily vaginal lavage with saline solution for 10 days at weeks 8 and 16. At the end of the experimental period, glucose tolerance and insulin sensitivity were assessed. Ovarian tissues were collected for histological evaluation, gene and protein expression analyses (RT-qPCR and Western blot), and ovarian lipid profiling by gas chromatography-mass spectrometry method. Statistical analyses were performed using Student's t-test or Mann-Whitney test (P < 0.05).

This study was approved by the UNICAMP Ethics Committee (#5671-1/2020 and #5300-1/2019). Six-week-old female Swiss mice (n = 5–9) were assigned to either a control normocaloric diet- CT or a high-fat diet–HF (modified AIN-93G; 35% fat derived from lard) for 16 weeks. Body weight and food intake were monitored weekly. Estrous cyclicity was evaluated by daily vaginal lavage with saline solution for 10 days at weeks 8 and 16. At the end of the experimental period, glucose tolerance and insulin sensitivity were assessed. Ovarian tissues were collected for histological evaluation, gene and protein expression analyses (RT-qPCR and Western blot), and ovarian lipid profiling by gas chromatography-mass spectrometry method. Statistical analyses were performed using Student's t-test or Mann-Whitney test (P < 0.05).

Results

HF-fed mice showed increased caloric intake, body weight, adiposity, and waist circumference compared to CT. Despite these changes, no differences were observed in fasting glycemia, glucose tolerance, or insulin sensitivity. However, HF-fed mice exhibited compensatory metabolic adaptation, maintaining glucose homeostasis at the expense of increased circulating insulin levels after 16 weeks. No significant differences were observed in follicle counts or estrous cyclicity; however, a subset of HF-fed mice exhibited cycle disruption, including cessation of cyclicity. Ovarian expression of inflammatory genes (Tnfα, Ccl2, Nlrp3, Il1β, Il18, Casp1, Il10) and related proteins showed no differences between groups. Notably, cleaved caspase-1 levels were increased exclusively in HF-fed mice. Additionally, HF-fed mice exhibited increased levels of specific fatty acids, including stearic (C18:0), heptadecenoic (C17:1), and eicosadienoic (C20:2), with no changes in other lipid subclasses.

HF-fed mice showed increased caloric intake, body weight, adiposity, and waist circumference compared to CT. Despite these changes, no differences were observed in fasting glycemia, glucose tolerance, or insulin sensitivity. However, HF-fed mice exhibited compensatory metabolic adaptation, maintaining glucose homeostasis at the expense of increased circulating insulin levels after 16 weeks. No significant differences were observed in follicle counts or estrous cyclicity; however, a subset of HF-fed mice exhibited cycle disruption, including cessation of cyclicity. Ovarian expression of inflammatory genes (Tnfα, Ccl2, Nlrp3, Il1β, Il18, Casp1, Il10) and related proteins showed no differences between groups. Notably, cleaved caspase-1 levels were increased exclusively in HF-fed mice. Additionally, HF-fed mice exhibited increased levels of specific fatty acids, including stearic (C18:0), heptadecenoic (C17:1), and eicosadienoic (C20:2), with no changes in other lipid subclasses.

Conclusion

Chronic high-fat diet intake induces compensatory metabolic adaptations, characterized by hyperinsulinemia despite preserved glycemic control, and promotes early ovarian lipid remodeling even in the absence of overt reproductive impairment. These alterations may represent early events preceding more severe metabolic and reproductive dysfunction.

Chronic high-fat diet intake induces compensatory metabolic adaptations, characterized by hyperinsulinemia despite preserved glycemic control, and promotes early ovarian lipid remodeling even in the absence of overt reproductive impairment. These alterations may represent early events preceding more severe metabolic and reproductive dysfunction.