L26/P-832 Ovarian reserve and ageing: 2 sides of the same coin? Insights from humans and gastropods

Abstract Study question Does the Klotho protein reflect the age-related decline in fertility, and can an animal model be created using gastropods? Summary answer α-Klotho levels decline with age and are higher in hormone therapy (HT), suggesting potential benefits of HT. Gastropods might serve as animal model. What is known already A decline in oocyte reserve is associated with the ageing process. The Klotho gene was first identified in 1997 as being linked to premature ageing in mice. Recently, however, its potential as a biomarker for oocyte quality and ovarian ageing has attracted considerable attention. The Klotho protein exists in three forms – α-, β- and γ-Klotho – and can be detected in organs such as the kidneys and brain, as well as in body fluids such as blood and urine. Gastropods are considered ideal animal models for research, primarily due to their anatomical characteristics and high physiological robustness. Study design, size, duration An ongoing, single-centre, cross-sectional study has been conducted since April 2024. The patients were peri- or postmenopausal and over 40 years old, healthy controls under 35 years. We analysed possible correlations between Klotho and biomarkers of ovarian reserve and ageing in patients with and without hormone therapy (HT) and the control group. Furthermore, we aimed to develop an animal model to enhance our understanding of the role of Klotho in ageing and stress regulation. Participants/materials, setting, methods So far, 180 (peri-)menopausal patients (69 with HT) and 60 control subjects were included. Secreted and soluble α-Klotho, fibroblast growth factor 23 (FGF 23), AMH, leptin, FSH, LH and inhibin B were measured. Klotho sequences derived from transcriptomes of different gastropod species were validated in vivo. Basal mRNA expression of Klotho and stress-related proteins as well as the response to Cd exposure were assessed by qRT-PCR. Statistical analyses were performed using GraphPad Prism. Main results and the role of chance The average age differed between patients (53 ± 8 years) and control subjects (30 ± 6 years). Both secreted and soluble α-Klotho were higher in control subjects than in patients with and without HT. In patients with HT, secreted α-Klotho was higher than in patients without HT, but this difference was not significant (p > 0.05). An age-related decline in Klotho concentrations was observed. Secreted Klotho levels were reduced in patients aged 40–44 years (p = 0.0089) and over 50 years (p = 0.0011) compared to those under 40 years. Soluble Klotho levels were reduced from the age of 40 onwards (p < 0.0001). Leptin, LH and FSH were higher in patients, and AMH, inhibin and oestradiol were higher in control subjects. Oestradiol levels were elevated in patients with HT compared to patients without HT (p = 0.0076).Significant correlations with AMH, LH and FSH were observed for soluble Klotho, while no significant correlations were found for secreted Klotho. Gastropods exhibit variable basal expression levels of Klotho, and the Klotho mRNA of various gastropod species examined showed a considerable degree of allelic variation at conserved positions. Individual gastropods showed different responses to environmental stress, such as exposure to cadmium (Cd). Limitations, reasons for caution The limitations include the fact that the study is not yet complete and the sample size is therefore still growing in both the patient and control groups. Differences in the respective HT composition could be more strongly reflected in a larger sample size. Wider implications of the findings α-Klotho could be a new biomarker for reproductive ageing. HT influences secreted Klotho levels, suggesting therapeutic modulation of Klotho signalling pathways and underpinning its potential clinical relevance for the assessment of menopause and personalised therapies. The Klotho protein may perform various functions in gastropods, which represent a promising animal model. Trial registration number No