Defining physiological and pathophysiological roles of the Free Fatty Acid Receptor2 by analysis of novel transgenic mouse models

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Development of new medicines is a long term ambition and challenge. Initial efforts are often based on observations and analysis of effects in rodents of either activating or blocking a specific protein or a signal transduction pathway that is believed to contribute to or influence the development of a disease in humans. Means to do this include elimination of expression of specific genes in mouse or treatment of animals with synthetic drug-like molecules with the hope that responses produced will inform or mimic those that might occur in humans. Although it is true that many important physiological process are controlled and regulated in equivalent ways between mice and humans there are also many differences that reflect the 90 million years of evolution separating the species. One common aspect of this is that there are often differences in sequence between the equivalent proteins from different species and in a number of cases this is known to markedly effect the ability of a synthetic drug to produce effects. This is the situation for the receptor FFA2 that is activated by short chain fatty acids produced by the bacteria that are present in the intestine. Antagonists of this receptor that were identified by finding ligands that block the human form simply don't work at rodent orthologues and, because of this, it has been difficult to perform preliminary studies in mice that might predict their effects in humans. To overcome this we have generated mice in which we replaced the mouse version of FFA2 with the human form, and have shown that in tissues from these animals the identified antagonists are now able to block FFA2-mediated effects. We have also taken this one step further. As there are at least two receptors in both mouse and human that are activated by short chain fatty acids we further adapted human FFA2 such that it NOT activated by short chain fatty acids but is activated instead by a set of synthetic molecules that don't activate the normal forms of FFA2. We have also generated mice in which this modified human receptor is expressed instead of the mouse form. With this underpinning knowledge we now plan to fully investigate the roles that are controlled by FFA2 in mouse. We will pay particular attention to actions in both the intestine where our preliminary studies have shown that FFA2 is a key regulator of release of a hormone called GLP-1 that after its release plays a central role in promoting insulin production from the pancreas when blood glucose levels rise after a meal. There have also been conflicting reports from other groups as to whether activating or blocking FFA2 might be an effective approach to either prevent the development of, or to treat, diseases such as ulcerative colitis that are based on inflammation of the lower intestine. We will now be able to address these questions in mouse models of this and related diseases, something that has hitherto been impossible. Another key area where there has been debate and contradictory views is whether direct activation or blockade of FFA2 would be able to enhance or limit release of insulin in humans, and specifically in type II diabetics. There are reasons to believe the control mechanisms in mouse are different from in humans and now, using both the animal models described above and detailed molecular studies on both mouse and human forms of the receptor protein we plan to assess this question. This is likely to influence thinking with the pharmaceutical industry as to the most appropriate strategy to consider as a therapeutic treatment and whether studies that have been performed in wild type mice might actually be pointing in the wrong direction for therapy in humans.