ETC-1002 regulates immune response, leukocyte homing, and adipose tissue inflammation via LKB1-dependent activation of macrophage AMPK

ETC-1002 is an investigational drug currently in Phase 2 development for treatment of dyslipidemia and other cardiometabolic risk factors. In dyslipidemic subjects, ETC-1002 not only reduces plasma LDL cholesterol but also significantly attenuates levels of hsCRP, a clinical biomarker of inflammation. Anti-inflammatory properties of ETC-1002 were further investigated in primary human monocyte-derived macrophages and in in vivo models of inflammation. In cells treated with ETC-1002, increased levels of AMP-activated protein kinase (AMPK) phosphorylation coincided with reduced activity of MAP kinases and decreased production of proinflammatory cytokines and chemokines. AMPK phosphorylation and inhibitory effects of ETC-1002 on soluble mediators of inflammation were significantly abrogated by siRNA-mediated silencing of macrophage liver kinase B1 (LKB1), indicating that ETC-1002 activates AMPK and exerts its anti-inflammatory effects via an LKB1-dependent mechanism. In vivo, ETC-1002 suppressed thioglycollate-induced homing of leukocytes into mouse peritoneal cavity. Similarly, in a mouse model of diet-induced obesity, ETC-1002 restored adipose AMPK activity, reduced JNK phosphorylation, and diminished expression of macrophage-specific marker 4F/80. These data were consistent with decreased epididymal fat-pad mass and interleukin (IL)-6 release by inflamed adipose tissue. Thus, ETC-1002 may provide further clinical benefits for patients with cardiometabolic risk factors by reducing systemic inflammation linked to insulin resistance and vascular complications of metabolic syndrome.

AMP-activated protein kinase and ATP-citrate lyase are two distinct molecular targets for ETC-1002, a novel small molecule regulator of lipid and carbohydrate metabolism

ETC-1002 (8-hydroxy-2,2,14,14-tetramethylpentadecanedioic acid) is a novel investigational drug being developed for the treatment of dyslipidemia and other cardio-metabolic risk factors. The hypolipidemic, anti-atherosclerotic, anti-obesity, and glucose-lowering properties of ETC-1002, characterized in preclinical disease models, are believed to be due to dual inhibition of sterol and fatty acid synthesis and enhanced mitochondrial long-chain fatty acid β-oxidation. However, the molecular mechanism(s) mediating these activities remained undefined. Studies described here show that ETC-1002 free acid activates AMP-activated protein kinase in a Ca(2+)/calmodulin-dependent kinase β-independent and liver kinase β 1-dependent manner, without detectable changes in adenylate energy charge. Furthermore, ETC-1002 is shown to rapidly form a CoA thioester in liver, which directly inhibits ATP-citrate lyase. These distinct molecular mechanisms are complementary in their beneficial effects on lipid and carbohydrate metabolism in vitro and in vivo. Consistent with these mechanisms, ETC-1002 treatment reduced circulating proatherogenic lipoproteins, hepatic lipids, and body weight in a hamster model of hyperlipidemia, and it reduced body weight and improved glycemic control in a mouse model of diet-induced obesity. ETC-1002 offers promise as a novel therapeutic approach to improve multiple risk factors associated with metabolic syndrome and benefit patients with cardiovascular disease.

Abstract 465: ETC-1002, a Novel Dicarboxylic Fatty Acid Analog, Inhibits Inflammatory Response in Primary Human Monocyte-Derived Macrophages as Well as in Adipose Tissue of Insulin-Resistant Mice via AMPK-Dependent Mechanisms

ETC-1002, a small molecule regulator of imbalances in lipid and carbohydrate metabolism, is an investigational drug currently in Phase 2 development to treat dyslipidemia and other cardiometabolic risk factors. In hyperlipidemic LDL receptor-deficient mice, robust antiatherosclerotic activities of ETC-1002 coincided with reduced levels of inflammatory markers in mouse atheroma. To further investigate anti-inflammatory properties of ETC-1002, human monocyte-derived macrophages (MDMs) differentiated in autologous serum were stimulated with 100 ng/ml of LPS in the absence or presence of the 10 μM and 30 μM of ETC-1002. TLR4-mediated activation of downstream kinases as well as the production of pro-inflammatory mediators were assessed with phosphokinase and protein arrays. Lower levels of JNK, cJUN, p38 and ERK phosphorylation in cells treated with ETC-1002 were consistent with reduced production of pro-inflammatory cytokines (TNF-α, IL-6, IL-8 and MIP1α) and chemokines (CXCL10, CXCL1, CCL2 and CCL5). ETC-1002 at 30 mg/kg dose largely diminished thioglycolate-induced homing of neutrophils and macrophages into the mouse peritoneal cavity, supporting the inhibitory effect of ETC-1002 on leukocyte chemotactic and inflammatory activity. Furthermore, in a mouse model of diet-induced obesity and insulin resistance, epididymal fat pad mass and IL-6 release by inflamed adipose tissue were significantly attenuated (by 32% and 80% respectively) in animals treated with ETC-1002. Importantly, enhanced levels of AMPK phosphorylation, changes in intracellular energy charge coupled with reduced basal rates of sterol and fatty acid synthesis by human MDMs strongly supported AMPK-dependent anti-inflammatory effects of ETC-1002. Thus, our data suggest that ETC-1002, via stimulation of AMPK activity, may provide additional clinical benefits for patients with metabolic syndrome by reducing systemic inflammation and other cardiometabolic abnormalities linked to vascular disease.

Abstract 292: ETC-1002 Reduces Body Weight Gain and Hepatic Triglyceride Content and Improves Glycemic Control in a Mouse Model of Diet-Induced Obesity

ETC-1002 is an investigational drug currently in Phase 2 clinical development to treat dyslipidemia and other cardiometabolic risk factors. Previously, ETC-1002 prevented hyperlipidemia and atherosclerosis in rodent models; and improved hepatic triglycerides (TG) as well as fasting blood glucose and insulin in the KKA y insulin resistant mouse model via putative mechanisms including activation of AMP-activated protein kinase. In the present study we investigated the effect of ETC-1002 on body weight, hepatic TG and insulin sensitivity in a diet-induced obese (DIO) mouse model. C57BL/6 mice were fed a 60% high-fat diet beginning at 11 weeks of age. At 12 weeks of age mice were assigned to treatment groups and administered vehicle or ETC-1002 at 3, 10, or 30 mg/kg/day for 9 weeks. A separate cohort of mice was maintained on standard rodent chow diet throughout the study as a comparator. Food consumption, body weight, hepatic TG content, fasting blood glucose, fasting plasma insulin, insulin tolerance tests, and glucose tolerance tests were measured. Mice developed obesity, hyperinsulinemia, mild hyperglycemia and elevated hepatic triglycerides in response to the high-fat diet. ETC-1002 results were dose-dependent and statistically significant at doses of 10 and 30 mg/kg/day. ETC-1002 attenuated body weight gain 8% and 15% with no effect on food consumption. Body weight changes were associated with 12% and 32% decreases in epididymal fat pad mass. Hepatic TG content was also reduced with ETC-1002 by 34% and 46%; respectively. ETC-1002 treatment reduced fasting blood glucose 11% and 16%; plasma insulin 80% and 95%; and resulted in significant improvements in insulin tolerance tests (19% and 22% reduction in AUC) with modestly improved glucose tolerance (not significant). In an intervention study with a 12 week lead-in on high-fat diet, comparable effects on body weight, hepatic TG, and insulin sensitivity were observed. In summary, ETC-1002 reduced obesity and hepatic TG and improved glycemic parameters in a high-fat fed diet-induced mouse model of disease. The present data in the DIO mouse, combined with previously reported efficacy in rodent models supports ETC-1002 as a regulator of imbalances in lipid and carbohydrate metabolism.

Effects of propranolol on phosphatidate phosphohydrolase and mitogen-activated protein kinase activities in A7r5 vascular smooth muscle cells

High doses of propranolol inhibit phosphatidate phosphohydrolase (PAP) activity in intact cells, thus blocking metabolism of phosphatidic acid (PA), product of the phospholipase D (PLD) reaction. Vasopressin and phorbol ester activate PLD and ERK (extracellular signal-regulated protein kinase) mitogen-activated protein kinases in A7r5, a rat vascular smooth muscle cell line. Propranolol increased PA levels in intact A7r5 cells and inhibited cytosolic PAP and membrane calcium-independent phospholipase A2 but did not activate PLD or enhance agonist-induced PA accumulation. Incubation of cells with 200 microM propranolol for 10-45 min markedly elevated PA but caused only partial activation of ERKs. Propranolol and other lipophilic amines caused a time- and dose-dependent detachment of cells from their substrate. These results confirm that elevation of PA is not a strong signal for ERK activation and emphasize that caution should be exercised in using propranolol as a PAP inhibitor in intact cells.

Lysophosphatidic acid stimulates phospholipase D activity and cell proliferation in PC-3 human prostate cancer cells

Phospholipase D (PLD) is activated in mammalian cells in response to a variety of growth factors and may play a role in cell proliferation. Lysophosphatidic acid (LPA) is a bioactive metabolite potentially generated as a result of PLD activation. Two human prostate cancer cell lines, PC-3 and LNCaP, express membrane PLD activity. The effects of LPA on PLD activity and proliferation were examined in PC-3 cells, which express hPLD1a/1b. Phorbol 12-myristate 13-acetate (PMA) induced a prolonged activation of PLD, as detected in both intact cells and membranes. LPA induced a transient activation of PLD that was maximal by 10 minutes. The EC50 for LPA-induced PLD activation was approximately 1 microM. Pertussis toxin did not inhibit activation of PLD by LPA or PMA. Ro-31-8220 and bisindolylmaleimide I, inhibitors of protein kinase C, blocked activation by PLD by both PMA and LPA. PMA-induced activation of PLD did not appear to require translocation of PLDs from cytosol to membrane. LPA stimulated proliferation of PC-3 cells with an EC50 of approximately 0.2 microM; this response was not inhibited by pertussis toxin. Perillyl alcohol, an anti-cancer drug, reversibly inhibited proliferation in response to either serum or LPA but did not inhibit activation of PLD by PMA or LPA. These data establish that LPA activates PLD and stimulates proliferation via Gi-independent pathways in a human prostate cancer cell line.

Effects of phorbol ester on phospholipase D and mitogen-activated protein kinase activities in T-lymphocyte cell lines

The effects of phorbol 12-myristate 13-acetate (PMA) on the activities of phospholipase D (PLD3), mitogen-activated protein kinase (ERK), and c-Jun N-terminal kinase (JNK) were studied in Jurkat, a human T cell line, and EL4, a murine T-cell line. PMA treatment rapidly activated PLD in Jurkat, as detected either in intact or broken cells. In contrast, PMA did not stimulate PLD activity in EL4 cells. PLD activity was not detected in membranes prepared from EL4 cells. Jurkat, but not EL4, expresses a 120-kDa protein recognized by an anti-PLD antibody. In both Jurkat and EL4 cells, PMA caused activation of ERKs. Incubation of EL4 cells with bacterial PLD increased phosphatidic acid levels, but did not activate ERK. In both EL4 and Jurkat cells, co-stimulation with PMA and ionomycin stimulated JNK activity. These results show that activation of PLD is not required for activation of ERKs or JNKs by PMA in T-cell lines. Thus, while PLD activity is expressed in some T-cell lines, the role of this enzyme and its products in T-cell activation remain to be elucidated.

Effects of Ara-C on neutral sphingomyelinase and mitogen- and stress-activated protein kinases in T-lymphocyte cell lines

Neutral sphingomyelinase (SMase) can be activated by extracellular signals to produce ceramide, which may affect mitogen-activated protein kinase (MAPK) activities. Neutral SMase activity was assessed in membranes from Jurkat, a human T-cell line, and EL4, a murine T-cell line. Ara-C activated SMase with 10 minutes in both Jurkat and EL4 cells, while phorbol ester (PMA) had no effect. PMA, but not Ara-C or ceramides, activated ERK MAPKS, in Jurkat and EL4. PMA acted synergistically with ionomycin to activate JNK MAPKs in Jurkat and EL4 within 10 minutes. Ara-C activated JNKs only after prolonged incubation (90-120 minutes). Thus, ceramide is not a positive signal for ERK activation in T-cell lines. The effects of Ara-C on JNK activity may be mediated through secondary response pathways.

Synergistic effects of insulin and phorbol ester on mitogen-activated protein kinase in Rat-1 HIR cells

Regulation of the activity of the extracellular signal regulated kinase (ERK) mitogen-activated protein kinases was examined in Rat-1 HIR, a fibroblast cell line overexpressing the human insulin receptor. Insulin or phorbol ester induced partial activations of ERKs, while a combination of insulin and phorbol ester resulted in a synergistic activation. Preincubation with phorbol ester increased the subsequent response to insulin. Phorbol ester did not enhance tyrosine phosphorylation of the insulin receptor. Insulin did not enhance activation of phospholipase D in response to phorbol ester. Lysophosphatidic acid also acted synergistically with insulin to induce ERK activation. Lysophosphatidic acid alone had little effect on ERK, and did not activate phospholipase D. The combination of phorbol ester and insulin maintained tyrosine phosphorylation of focal adhesion kinase, while insulin alone decreased its tyrosine phosphorylation. Phorbol ester induced phosphorylation of She on serine/threonine, while insulin induced tyrosine phosphorylation of She and She-Grb2 binding. These results suggest that full activation of ERKs in fibroblasts can require the cooperation of at least two signaling pathways, one of which may result from a protein kinase C-dependent phosphorylation of effectors regulating ERK activation. In this manner, phorbol esters may enhance mitogenic signals initiated by growth factor receptors.

Activations of mitogen-activated protein kinases and phospholipase D in A7r5 vascular smooth muscle cells

Activation of mitogen-activated protein kinases (MAPKs) was examined in the A7r5 rat vascular smooth muscle cell line. Treatment of A7r5 cells with vasopressin, phorbol ester (PMA), or serum resulted in activation of two MAPKs, Erk-1 and Erk-2. Phosphatidylinositol-specific phospholipase C was activated in response to vasopressin but not to PMA. Vasopressin and PMA both caused maximal activation of PLD within 5 minutes. Application of bacterial phospholipase D (PLD) to A7r5 cells increased phosphatidic acid to levels similar to those seen with vasopressin or PMA. Acute exposure of the cells to vasopressin, PMA, or PLD increased phosphorylation of many of the same cytosolic and membrane proteins. However, bacterial PLD did not promote significant activation of Erk-1 and Erk-2. Phosphatidic acid and lysophosphatidic acid (LPA) likewise did not stimulate MAPK activity in A7r5 cells. Serum and vasopressin stimulated DNA synthesis when present for more than 30 min, while PLD, PMA, phosphatidic acid, and LPA were not mitogenic. These data suggest that activations of MAPKs and PLD are concurrent but independent responses to vasopressin in A7r5 cells. Acute activation of these enzymes is not sufficient to simulate DNA synthesis.

A fluorescent assay for agonist-activated phospholipase D in mammalian cell extracts

Phospholipase D (PLD) is activated in mammalian cells in response to a wide variety of stimuli. A rapid assay for agonist-activated PLD activity in cell extracts was developed, utilizing a fluorescent derivative of phosphatidylcholine as substrate. Utilization of the substrate was assessed following thin-layer chromatography of the reaction mixture. Hydrolysis products generated by phospholipases D, C, and A2 could be visualized in the same reaction. Phorbol ester and vasopressin increased PLD activity in intact A7r5 vascular smooth muscle cells, as measured by an isotopic labeling method. Using the in vitro fluorescent assay, enhanced PLD activity was detected in membranes prepared from A7r5 cells that had been treated with phorbol ester or vasopressin. The agonist-activated activity was independent of phosphorylation occurring during the course of the assay. PLD activity was detected, in varying amounts, in membranes prepared from a variety of different mouse tissues. These results show that a fluorescent assay can be used to rapidly assess the activity of PLD and other phosphatidylcholine-utilizing phospholipases in cell and tissue extracts. The effects of agonists on PLD activity can be retained and quantitated in a broken cell preparation, permitting characterization of the agonist-activated form of the enzyme.