Investigating the Endocrine-metabolic-immunological Axis During the Female Menstrual Cycle by Functional Genomics

As there are fluctuations in the hormonal balance during the menstrual cycle, it is assumed that due to the interaction between the hormonal system and the immune system, some diseases might be worsened in the course of a cycle. This interaction is particularly important during the phases of the cycle when the corpus luteum is formed and secretes estrogens and progesterone (secretion phase, luteal phase), as well as during menstruation itself. To date, there is no comprehensive review regarding the molecular signaling pathways that are active during and influence the menstrual cycle. The menstrual cycle influences blood glucose levels. Women are subject to greater fluctuations in blood glucose levels than men according to the phases of the menstrual cycle (menstrual phase, proliferative phase, ovulation, luteal phase). Since there are contradictory results regarding the influence of the menstrual cycle on glucose metabolism, the glucose and insulin response, as well as the glucose-dependent intestinal hormone glucagon-like peptide 1(GLP-1) after food intake are determined in the study presented here using an oral glucose tolerance test.

Within the menstrual cycle there are strong hormonal fluctuations. Therefore, it is obvious that the interaction between the endocrine system and the immune system play an important role in the progression of different diseases during the course of a cycle, especially during the luteal phase and menstruation. The molecular signaling pathways that are active during the menstrual cycle and have an influence on it have not been extensively elucidated to date. Furthermore, glucose homeostasis, on which the female cycle also can have an influence, is part of the research. Study results show that when an oral glucose tolerance test (oGTT) is performed, women are subject to greater fluctuations in blood glucose levels than men. This seems to be dependent on the phases of the female menstrual cycle. It was shown that glucose metabolism was impaired in the luteal phase. Contradictory to this, in another study no significant influence on glucose metabolism by the menstrual cycle could be detected. Based on these equivocal results, in this study the postprandial glucose and insulin response, as well of the glucose-dependent gut hormone GLP-1 in the different cycle phases will be examined. For this purpose, an intervention study is set up in which blood samples are taken at five different time points and the subjects participate in an oGTT at four of these different time points in their individual menstrual cycle. Furthermore, anthropometry measures and body composition will be determined with the help of Bodpod and bioelectrical impedance analysis (BIA) measurements. A diary will also be kept during the entire study duration in order to record the habitual diet. In addition, different subgroups are studied: continuous measurement of body temperature or glucose levels using sensors, continuous collection of stool samples and documentation of daily nutrition using an app. To account for regular daily variations in immunological measurements that are not related to the menstrual cycle, a cohort of healthy, male individuals will be examined.