Margaret van Heek

Systemic pan-AMPK activator MK-8722 improves glucose homeostasis but induces cardiac hypertrophy

Hitting a dozen enzymes with one drug The adenosine monophosphate-activated protein kinase (AMPK) controls cellular energy status. AMPK is activated when energy levels fall. This stimulates adenosine triphosphate (ATP)-generating pathways that promote glucose uptake and inhibits ATP-consuming pathways associated with glucose synthesis. In principle, these effects would be beneficial in metabolic diseases, including diabetes. Pharmacological activation of AMPK has been challenging, however, because in mammals, the enzyme exists as 12 distinct complexes. Myers et al. describe an orally available compound (MK-8722) that activates all 12 complexes (see the Perspective by Hardie). In animal models, MK-8722 ameliorated diabetes, but it also caused enlargement of the heart. MK-8722 may be a useful tool compound for laboratory research on AMPK function. Science, this issue p. 507; see also p. 455 In animals, a drug activating all 12 isoforms of the energy regulator AMPK benefits metabolism but may pose heart risks. 5′-Adenosine monophosphate–activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. Despite three decades of investigation, the biological roles of AMPK and its potential as a drug target remain incompletely understood, largely because of a lack of optimized pharmacological tools. We developed MK-8722, a potent, direct, allosteric activator of all 12 mammalian AMPK complexes. In rodents and rhesus monkeys, MK-8722–mediated AMPK activation in skeletal muscle induced robust, durable, insulin-independent glucose uptake and glycogen synthesis, with resultant improvements in glycemia and no evidence of hypoglycemia. These effects translated across species, including diabetic rhesus monkeys, but manifested with concomitant cardiac hypertrophy and increased cardiac glycogen without apparent functional sequelae.

The impact of partial and complete loss-of-function mutations in endothelial lipase on high-density lipoprotein levels and functionality in humans

Background—Endothelial lipase is a phospholipase with activity against high-density lipoprotein. Although a small number of mutations in LIPG have been described, the role of LIPG in protection against atherosclerosis is unclear. Methods and Results—We identified 8 loss-of-function (LOF) mutations in LIPG in individuals with high-density lipoprotein cholesterol. Functional analysis confirmed that most rare mutations abolish lipase activity in vitro, indicating complete LOF, whereas 2 more common mutations N396S and R476W reduce activity by ≈50%, indicating partial LOF and implying ≈50% and ≈75% remaining endothelial lipase function in heterozygous complete LOF and partial LOF mutation carriers, respectively. complete LOF mutation carriers had significantly higher plasma high-density lipoprotein cholesterol levels compared with partial LOF mutation carriers. Apolipoprotein B-depleted serum from complete LOF carriers showed significantly enhanced cholesterol efflux acceptor capacity, whereas only trends were observed in partial LOF carriers. Carriers of LIPG mutations exhibited trends toward reduced coronary artery disease in 4 independent cohorts (meta-analysis odds ratio, 0.7; P=0.04). Conclusions—Our data suggest that the impact of LIPG mutations is directly related to their effect on endothelial lipase function and support that antagonism of endothelial lipase function improves cardioprotection.

Discovery of liver-targeted inhibitors of stearoyl-CoA desaturase (SCD1).

Inhibitors based on a benzo-fused spirocyclic oxazepine scaffold were discovered for stearoyl-coenzyme A (CoA) desaturase 1 (SCD1) and subsequently optimized to potent compounds with favorable pharmacokinetic profiles and in vivo efficacy in reducing the desaturation index in a mouse model. Initial optimization revealed potency preferences for the oxazepine core and benzylic positions, while substituents on the piperidine portions were more tolerant and allowed for tuning of potency and PK properties. After preparation and testing of a range of functional groups on the piperidine nitrogen, three classes of analogs were identified with single digit nanomolar potency: glycine amides, heterocycle-linked amides, and thiazoles. Responding to concerns about target localization and potential mechanism-based side effects, an initial effort was also made to improve liver concentration in an available rat PK model. An advanced compound 17m with a 5-carboxy-2-thiazole substructure appended to the spirocyclic piperidine scaffold was developed which satisfied the in vitro and in vivo requirements for more detailed studies.

Bicyclic and tricyclic heterocycle derivatives as histamine H3 receptor antagonists for the treatment of obesity.

A novel series of non-imidazole bicyclic and tricyclic histamine H3 receptor antagonists has been discovered. Compound 17 was identified as a centrally penetrant molecule with high receptor occupancy which demonstrates robust oral activity in rodent models of obesity. In addition compound 17 possesses clean CYP and hERG profiles and shows no behavioral changes in the Irwin test.

Discovery of novel quinoline carboxylic acid series as DGAT1 inhibitors

Herein we report the design and synthesis of a series of novel bicyclic DGAT1 inhibitors with a carboxylic acid moiety. The optimization of the initial lead compound 7 based on in vitro and in vivo activity led to the discovery of potent indoline and quinoline classes of DGAT1 inhibitors. The structure-activity relationship studies of these novel series of bicyclic carboxylic acid derivatives as DGAT1 inhibitors are described.

SAR studies of C2 ethers of 2H-pyrano[2,3-d]pyrimidine-2,4,7(1H,3H)-triones as nicotinic acid receptor (NAR) agonist

Based on in house screening lead compound 1 for the NAR project, SAR studies have been focused on the modification of the C2 ethers of the pyrimidinedione core structure. In this effort, an unpredictable SAR trend was overcome in the alkyl ether and arylalkyl ether series to identify compound 24 with improved in vitro activity compared to nicotinic acid. More consistent and predictable SAR was achieved in the propargyl ether series. Lead compound 41 was identified with good in vitro and in vivo activity in rat, and much improved rat PK profile.

Engineering Glucose Responsiveness Into Insulin

Insulin has a narrow therapeutic index, reflected in a small margin between a dose that achieves good glycemic control and one that causes hypoglycemia. Once injected, the clearance of exogenous insulin is invariant regardless of blood glucose, aggravating the potential to cause hypoglycemia. We sought to create a “smart” insulin, one that can alter insulin clearance and hence insulin action in response to blood glucose, mitigating risk for hypoglycemia. The approach added saccharide units to insulin to create insulin analogs with affinity for both the insulin receptor (IR) and mannose receptor C-type 1 (MR), which functions to clear endogenous mannosylated proteins, a principle used to endow insulin analogs with glucose responsivity. Iteration of these efforts culminated in the discovery of MK-2640, and its in vitro and in vivo preclinical properties are detailed in this report. In glucose clamp experiments conducted in healthy dogs, as plasma glucose was lowered stepwise from 280 mg/dL to 80 mg/dL, progressively more MK-2640 was cleared via MR, reducing by ∼30% its availability for binding to the IR. In dose escalations studies in diabetic minipigs, a higher therapeutic index for MK-2640 (threefold) was observed versus regular insulin (1.3-fold).

Lead optimization of a pyridine-carboxamide series as DGAT-1 inhibitors.

The structure-activity relationship studies of a novel series of carboxylic acid derivatives of pyridine-carboxamides as DGAT-1 inhibitors is described. The optimization of the initial lead compound 6 based on in vitro and in vivo activity led to the discovery of key compounds 10j and 17h.

The Impact of Partial and Complete Loss of Function Mutations in Endothelial Lipase on HDL Levels and Functionality in Humans

Background—Endothelial lipase is a phospholipase with activity against high-density lipoprotein. Although a small number of mutations in LIPG have been described, the role of LIPG in protection against atherosclerosis is unclear. Methods and Results—We identified 8 loss-of-function (LOF) mutations in LIPG in individuals with high-density lipoprotein cholesterol. Functional analysis confirmed that most rare mutations abolish lipase activity in vitro, indicating complete LOF, whereas 2 more common mutations N396S and R476W reduce activity by ≈50%, indicating partial LOF and implying ≈50% and ≈75% remaining endothelial lipase function in heterozygous complete LOF and partial LOF mutation carriers, respectively. complete LOF mutation carriers had significantly higher plasma high-density lipoprotein cholesterol levels compared with partial LOF mutation carriers. Apolipoprotein B-depleted serum from complete LOF carriers showed significantly enhanced cholesterol efflux acceptor capacity, whereas only trends were observed in partial LOF carriers. Carriers of LIPG mutations exhibited trends toward reduced coronary artery disease in 4 independent cohorts (meta-analysis odds ratio, 0.7; P=0.04). Conclusions—Our data suggest that the impact of LIPG mutations is directly related to their effect on endothelial lipase function and support that antagonism of endothelial lipase function improves cardioprotection.

Phenotyping of adipose, liver, and skeletal muscle insulin resistance and response to pioglitazone in spontaneously obese rhesus monkeys

Insulin resistance and diabetes can develop spontaneously with obesity and aging in rhesus monkeys, highly similar to the natural history of obesity, insulin resistance, and progression to type 2 diabetes in humans. The current studies in obese rhesus were undertaken to assess hepatic and adipose contributions to systemic insulin resistance-currently, a gap in our knowledge-and to benchmark the responses to pioglitazone (PIO). A two-step hyperinsulinemic-euglycemic clamp, with tracer-based glucose flux estimates, was used to measure insulin resistance, and in an intervention study was repeated following 6 wk of PIO treatment (3 mg/kg). Compared with lean healthy rhesus, obese rhesus has a 60% reduction of glucose utilization during a high insulin infusion and markedly impaired suppression of lipolysis, which was evident at both low and high insulin infusion. However, obese dysmetabolic rhesus manifests only mild hepatic insulin resistance. Six-week PIO treatment significantly improved skeletal muscle and adipose insulin resistance (by ~50%). These studies strengthen the concept that insulin resistance in obese rhesus closely resembles human insulin resistance and indicate the value of obese rhesus for appraising new insulin-sensitizing therapeutics.