Orale Applikation von FGF21 für eine gezielte Wirkung in der Leber
Dr. Henrik Nausch
Prof. Dr. Klaus, Susanne, DIfE
Institut: Professur Agrobiotechnologie
The endocrine acting protein fibroblast growth factor 21 (FGF21) is an important multiorgan metabolic regulator promoting health span and increasing lifespan. FGF21 was shown to improve glucose and lipid metabolism and reduce obesity in rodent models and non-human primates. The first clinical studies with FGF21 analogues confirmed the lowering of body weight, circulating lipids and insulin in humans and pointed to the liver as the most important target, particularly in patients that suffer from lipid disorders and pathological conditions, such as non-alcoholic fatty liver disease (NAFLD). However, the instability of native FGF21 makes a daily delivery necessary and the long persistence of stabilized FGF21 analogues leads to adverse effects such as reduction of bone.
Liver is not only a target but also the main source of circulating FGF21 which is thus considered a hepatokine. However, much less is known about direct hepatic effects of FGF21 than about the molecular mechanisms regulating its expression in the liver. The biology of FGF21 is quite complex and only partially understood due to its diverse metabolic functions in multiple target organs and its ability to act as an autocrine, paracrine, and endocrine factor. Despite the unequivocal beneficial metabolic effects of FGF21 there are still uncertainties and controversies concerning its physiology especially regarding the exact cellular targets and intracellular mechanisms of FGF21 signaling which is still poorly understood.
Starting from the assumption that liver is an important direct target for the beneficial metabolic actions of FGF21 we hypothesize that the targeted delivery of FGF21 to the liver through an oral administration system will lead to metabolic improvements while avoiding adverse effects. In addition oral delivery would allow an easy daily application. Accordingly, the main objectives of this project are (i) clarification of the hepatic specific molecular mechanisms of FGF21 action, and (ii) establishing the oral administration of FGF21 with the help of edible plants that express FGF21. The first objective will be addressed by investigating the effects of recombinant FGF21, transiently produced in N. benthamiana, on liver and primary hepatocytes of wildtype and FGF21 ablated mice. Using an unbiased transcriptomic approach novel molecular targets of FGF21 in hepatocytes will be identified, verified in vitro and subsequently in vivo by treating wildtype and FGF21 ablated mice with FGF21. This will also serve to establish a robust and reliable read out system for analyzing hepatic effects of orally applied FGF21. For this second objective a plant expression system will be established. For oral application, edible plants provide an excellent system since the plant cells protect intracellular compounds from degradation in the stomach and release them in the intestine when the plant material is decomposed. This is termed “in planta bioencapsulation”. The intestinal release of FGF21 will lead to a high exposure of the liver to FGF21 through the portal vein, but low concentrations in the peripheral tissue due to the short half-life of FGF21 which is subject to rapid proteolysis. To improve the protective effect of the plant cell, the FGF21 coding region, which has already been expressed in plants, , will be attached to oil or starch via fusion to an oil- or starch binding domain. For transcytosis from the intestine into the blood transferrin is used as second fusion partner. It will be cleaved off in the serum via an endogenous protease. Using transiently produced purified FGF21 variants which are added to oil or starch, the effectiveness of the strategies will be analysed in in vitro systems of a simulated gastrointestinal tract and the Ussing chamber system. The best variant will be used to stably transform edible oil-rich tobacco or starch-rich pea seeds. Thus, FGF21 expressed in plants can be directly applied after a rough concentration of the active ingredient either through binding to fatty acids (in oil rich tobacco seeds) or starch (in starch rich pea seeds). Feeding studies using FGF21 ablated and obese mice will be conducted to assess bioavailability of plant derived FGF21 and to characterize in detail the effects of FGF21 seeds with regard to amelioration of liver steatosis and metabolic improvements of obesity associated pathologies.
Dr. Henrik Nausch
Zum Projekt: Mitarbeiter,
Weitere Projekte im Forschungsteilschwerpunkt
Letzte Änderung des Projekteintrages: