Antidiabetic effects of glucokinase regulatory protein small-molecule disruptors

Abstract

Glucose homeostasis is a vital and complex process, and its disruption can cause hyperglycaemia and type II diabetes mellitus. Glucokinase (GK), a key enzyme that regulates glucose homeostasis, converts glucose to glucose-6-phosphate in pancreatic β-cells, liver hepatocytes, specific hypothalamic neurons, and gut enterocytes. In hepatocytes, GK regulates glucose uptake and glycogen synthesis, suppresses glucose production, and is subject to the endogenous inhibitor GK regulatory protein (GKRP). During fasting, GKRP binds, inactivates and sequesters GK in the nucleus, which removes GK from the gluconeogenic process and prevents a futile cycle of glucose phosphorylation. Compounds that directly hyperactivate GK (GK activators) lower blood glucose levels and are being evaluated clinically as potential therapeutics for the treatment of type II diabetes mellitus. However, initial reports indicate that an increased risk of hypoglycaemia is associated with some GK activators. To mitigate the risk of hypoglycaemia, we sought to increase GK activity by blocking GKRP. Here we describe the identification of two potent small-molecule GK-GKRP disruptors (AMG-1694 and AMG-3969) that normalized blood glucose levels in several rodent models of diabetes. These compounds potently reversed the inhibitory effect of GKRP on GK activity and promoted GK translocation both in vitro (isolated hepatocytes) and in vivo (liver). A co-crystal structure of full-length human GKRP in complex with AMG-1694 revealed a previously unknown binding pocket in GKRP distinct from that of the phosphofructose-binding site. Furthermore, with AMG-1694 and AMG-3969 (but not GK activators), blood glucose lowering was restricted to diabetic and not normoglycaemic animals. These findings exploit a new cellular mechanism for lowering blood glucose levels with reduced potential for hypoglycaemic risk in patients with type II diabetes mellitus.

Discovery of Small-Molecule Glucokinase Regulatory Protein Modulators That Restore Glucokinase Activity

“…Despite finding only a single GKRP hit scaffold, this provided a starting point for a chemical series with sub-µM potency against GKRP 23 and efficacy in lowering glucose in an in vivo diabetic model. 24 Also, in-house co-crystal structures with GKRP plus S6P and AMG-1694 (a smallmolecule disruptor or modulator of the GK-GKRP interaction) corroborated our intricate binding analysis. 24 The targeting of the GK-GKRP interaction serves as an example that certain PPIs can be targeted successfully with smallmolecule modulators.…”

Discrete associations of the GCKR variant with metabolic risk in a Chinese population: longitudinal change analysis

“…Such a biological mechanism might provoke new strategies in glucose-lowering drug design. Recently, two GKRP disruptors have already demonstrated great potential for glucose-lowering therapy [18]. The major strengths of our study include the prospective study design, the 5 year changes analysis in blood glucose and lipids, and a large well-defined, community-based cohort.…”

Beyond the Genetics of HDL: Why Is HDL Cholesterol Inversely Related to Cardiovascular Disease?

“…Several genetic association studies have shown that GCKR variants are associated with triglycerides, insulin resistance (Shen et al 2013), type 2 diabetes fasting plasma glucose (Li et al 2013a, b), hyperglycemia (Stancakova et al 2012), and nonalcoholic fatty liver disease (Lin et al 2014). In 2013, the crystal structure was resolved (Pautsch et al 2013) while two potent small-molecule GK-GKRP disruptors were recently reported to normalize blood glucose levels in several rodent models of diabetes (Lloyd et al 2013). …”