TY - GEN A1 - Omari, Mohamed A1 - Lange, Alexander A1 - Plöntzke, Julia A1 - Röblitz, Susanna T1 - A Mathematical Model for the Influence of Glucose-Insulin Dynamics on the Estrous Cycle in Dairy Cows N2 - Nutrition plays a crucial role in regulating reproductive hormones and follicular development in cattle. This is visible particularly during the time of negative energy balance at the onset of milk production after calving. Here, elongated periods of anovulation have been observed, resulting from alterations in luteiniz- ing hormone concentrations, likely caused by lower glucose and insulin concen- trations in the blood. The mechanisms that result in a reduced fertility are not completely understood, although a close relationship to the glucose-insulin metabolism is widely supported. Following this idea, a mathematical model of the hormonal network combining reproductive hormones and hormones that are coupled to the glucose compartments within the body of the cow was developed. The model is built on ordinary differential equations and relies on previously introduced models on the bovine estrous cycle and the glucose-insulin dynam- ics. Necessary modifications and coupling mechanisms are thoroughly discussed. Depending on the composition and the amount of food, in particular the glu- cose content in the dry matter, the model quantifies reproductive hormones and follicular development over time. Simulation results for different nutritional regimes in lactating and non-lactating dairy cows are examined and compared with experimental studies. Regarding its applicability, this work is an early attempt towards developing in silico feeding strategies and may eventually help refining and reducing animal experiments. T3 - ZIB-Report - 19-22 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-73475 SN - 1438-0064 ER - TY - GEN A1 - Omari, Mohamed A1 - Plöntzke, Julia A1 - Röblitz, Susanna T1 - A pharmacokinetic-pharmacodynamic model for single dose administration of Dexamethasone in dairy cows N2 - We present a mechanistic pharmacokinetic-pharmacodynamic model to simulate the effect of dexamethasone on the glucose metabolism in dairy cows. The coupling of the pharmacokinetic model to the pharmacodynamic model is based on mechanisms underlying homeostasis regulation by dexamethasone. In particular, the coupling takes into account the predominant role of dexamethasone in stimulating glucagon secretion, glycogenolysis and lipolysis and in impairing the sensitivity of cells to insulin. Simulating the effect of a single dose of dexamethasone on the physiological behaviour of the system shows that the adopted mechanisms are able to induce a temporary hyperglycemia and hyperinsulinemia, which captures the observed data in non-lactating cows. In lactating cows, the model simulations show that a single dose of dexamethasone reduces the lipolytic effect, owing to the reduction of glucose uptake by the mammary gland. T3 - ZIB-Report - 19-53 KW - systems biology; modelling; differential equations; metabolism; nutrition; bovine; fertility; reproduction; hormones; follicles; Dexamethasone; PK-PD Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:0297-zib-75043 SN - 1438-0064 ER - TY - JOUR A1 - Omari, Mohamed A1 - Lange, Alexander A1 - Plöntzke, Julia A1 - Röblitz, Susanna T1 - Model-based exploration of the impact of glucose metabolism on the estrous cycle dynamics in dairy cows JF - Biology Direct Y1 - 2019 U6 - https://doi.org/10.1186/s13062-019-0256-7 VL - 15 ER - TY - GEN A1 - Omari, Mohamed A1 - Plöntzke, Julia A1 - Berg, Mascha A1 - Röblitz, Susanna T1 - Modelling of glucose-insulin metabolism and its effect on the estrous cycle in bovine T2 - Annual Meeting of the Population Approach Group in Europe Y1 - 2016 ER -