KLF14, adipose dysfunction, insulin resistance and type 2 diabetes: from genetic discovery to biological mechanisms and translation.

Type 2 diabetes is a major and growing cause of illness and death across the world. However, incomplete understanding of the processes involved in the development of this condition acts as a barrier to the development of better ways for treating and preventing the disease.

In the past few years, collaborative efforts in human genetic discovery have identified over fifty positions in the human genome where individual sequence variation is associated with risk of type 2 diabetes. In principle, each of these genetic "signals" holds important clues to the mechanisms that are responsible for the maintenance of normal metabolic health. However, in most of these regions, we have yet to define the specific genetic variants responsible for the signal, or the particular genes through which the effects on diabetes-risk are mediated. As a result, the pace of biological insights has lagged behind that of genetic discovery. A key challenge for the field is to develop strategies that enable genetic signals such as these to be mined for the biological clues they can provide.

We recently demonstrated that one of these diabetes signals maps near a gene named KLF14, and that this effect on risk of diabetes is driven by a reduced ability of insulin-sensitive tissues, including muscle and liver, to respond to insulin. We have also shown that, in fat tissue, the same variants near KLF14 have widespread effects on the levels of expression of a wide range of genes, including KLF14 itself. These data are consistent with a model whereby KLF14 acts as a major regulator of events in fat tissue, with these alterations in the levels of KLF14 leading, through as yet unspecified mechanisms, to peripheral insulin resistance and type 2 diabetes.

The overall aim of this research is to define the molecular, cellular and physiological mechanisms which are responsible for the relationship between KLF14 and type 2 diabetes. To do this, we will pursue a number of complementary research strategies which include studies of human genetics and physiology and cellular studies in fat cells.

More specifically, our work aims to:
(a) define the specific sequence variants that are responsible for all of these effects, and how they influence levels of KLF14 within fat cells;
(b) characterise the suite of genes that are turned on and off by KLF14, and understand the consequences of those secondary changes on the function of fat tissue; and
(c) understand how it is that these KLF14-dependent changes in fat tissue lead to changes in the ability of remote tissues (such as muscle and liver) to respond to insulin.

We expect that, by focusing on the role of KLF14 and the ways in which it leads to an increased risk of diabetes, we will gain valuable, generic insights into the mechanisms whereby events in fat have widespread metabolic effects in other tissues. An answer to this question would help us improve our understanding of the connections between obesity and diabetes, an issue of supreme importance given that much of the increase in diabetes prevalence around the world is driven by changes in the amount, distribution and function of fat.

The research provides an opportunity to capitalise on recent discoveries in human genetics to advance understanding of disease biology. In the application, we explain how the biological information generated by this project can be exploited in directly translational studies to define novel approaches for treating, preventing, diagnosing and monitoring type 2 diabetes.

This major objective of this proposal is to define the molecular, cellular and physiological mechanisms responsible for the association between variants upstream of KLF14 and type 2 diabetes. Our recent work has demonstrated that KLF14 is a master regulator of expression in adipose tissue, and implicate this KLF14-regulated transcriptional network in the genesis of insulin resistance in remote tissues such as muscle and liver.

The research will seek to understand the causes and consequences of altered KLF14 expression using a variety of complementary approaches that include:
(a) human genetics: resequencing, fine-mapping and epigenomic analyses;
(b) integrative physiology: detailed metabolic analyses and genomic studies and their relationship to genotype; and
(c) cellular studies: cellular phenotyping and genomic studies in adipocytes following knockdown and overexpression of KLF14 and selected trans-genes.

The work has four main aims:
(a) To characterise the molecular, cellular and physiological consequences of altered KLF14 expression;
(b) To identify the trans-genes mediating the effect of KLF14 on insulin resistance and type 2 diabetes;
(c) To define the cellular and physiological mechanisms whereby altered KLF14 expression in adipose tissue leads to generalised insulin resistance and T2D;
(d) To characterise the mechanisms whereby common variants upstream of KLF14 influence KLF14 expression.

Our research will, by elucidating the mechanisms linking KLF14 sequence variation to diabetes predisposition, provide valuable, generic, insights into the consequences of adipocyte dysfunction on whole-body physiology. The research can be expected to define novel, causally-validated, targets that are substrates for therapeutic and biomarker development, and the application sets out some of the strategies that we plan to deploy to support those translational goals.

The principal beneficiaries of the research will be:
a) academics in the fields outlined in the "academic beneficiaries" section;
b) industry and biotechnology companies, in a position to exploit the improved biological understanding we seek to provide to develop novel products and services (see below);
c) the public sector (NHS, policy-makers), in the event that the research generates translational advances that provide more cost-effective means of treating and/or preventing diabetes and other insulin-resistance related diseases (e.g. hyperlipidaemias);
d) the wider public, if those translational advances provide more acceptable, more effective strategies for the treatment and prevention of those conditions.

The academic benefits will be manifest through:
a) the generation of new knowledge related to diabetes pathogenesis, which has the potential to contribute to amelioration of the social, economic and personal costs of the "epidemic" of global diabetes;
b) the development of research models and molecules of value for academic research;
c) bolstering of research in human integrative physiology (given concerns about declining expertise);
d) improved training of researchers in the specific areas of research activity, and in the development of cross-disciplinary expertise.

The broader economic and social impact will be manifest through:
a) economic benefits to pharma and biotechnology companies (including "spin-outs" with potential for attracting "inwards" investment) able to exploit actionable translational opportunities with respect to the development of novel therapeutic approaches (building on targets we validate) or clinically-useful biomarkers (building on candidates we identify). Given the scale of the global problem and the inadequacy of current therapeutic and preventative options, the opportunities for wealth creation are substantial;
b) improved effectiveness of public services if the biological insights result in better ways of treating and preventing T2D and related conditions (novel treatments, better diagnostics, improved strategies for stratifying risk and response to interventions);
c) transformation of public policy if the research leads, over time, to improved public health strategies for the prevention of T2D;
d) improved health outcomes (less diabetes-related morbidity and mortality, fewer diabetes complications) if the work leads to effective clinical translation, resulting in further personal, social and economic benefits.

It is of course important to be realistic about the timelines for effective clinical translation: too often expectations in this regard are unrealistic. In practice, the time from "new biology" to "novel treatment" involves years of biological validation, target characterisation, lead molecule optimisation, and clinical evaluation. As is well-known, substantial attrition is typical at each stage. On the positive side:
a) we have recently shown (with the validation of novel biomarkers for monogenic forms of diabetes) that it is possible to move rapidly from genetic discovery to clinical utility, at least where biomarkers are concerned;
b) the massive unmet clinical need and the scale of the global problem with respect to diabetes and insulin resistance will support investments that would not be economic for other diseases;
c) the origins of our research in genetic association data means that the benefits of modulation of the KLF14 network in man have intrinsic causal validation: they also make it possible to explore the whole body effects of such modulation (including potential "on-target" side-effects) through human genetic and physiological studies, helping thereby to minimise attrition;
d) we are well-equipped, via the Target Discovery Institute in Oxford, to initiate high-throughput screens for potential small molecule modulators of this pathway, and to do so in parallel with some of the biological validation described here, thereby expediting progress.