BM 17.0744: a structurally new antidiabetic compound with insulin-sensitizing and lipid-lowering activity

Bezafibrate Improves Insulin Sensitivity and Metabolic Flexibility in STZ-Induced Diabetic Mice

Bezafibrate (BEZ), a pan activator of peroxisome proliferator-activated receptors (PPARs), has been generally used to treat hyperlipidemia for decades. Clinical trials with type 2 diabetes patients indicated that BEZ also has beneficial effects on glucose metabolism, although the underlying mechanisms of these effects remain elusive. Even less is known about a potential role for BEZ in treating type 1 diabetes. Here we show that BEZ markedly improves hyperglycemia and glucose and insulin tolerance in mice with streptozotocin (STZ)-induced diabetes, an insulin-deficient mouse model of type 1 diabetes. BEZ treatment of STZ mice significantly suppressed the hepatic expression of genes that are annotated in inflammatory processes, whereas the expression of PPAR and insulin target gene transcripts was increased. Furthermore, BEZ-treated mice also exhibited improved metabolic flexibility as well as an enhanced mitochondrial mass and function in the liver. Finally, we show that the number of pancreatic islets and the area of insulin-positive cells tended to be higher in BEZ-treated mice. Our data suggest that BEZ may improve impaired glucose metabolism by augmenting hepatic mitochondrial performance, suppressing hepatic inflammatory pathways, and improving insulin sensitivity and metabolic flexibility. Thus, BEZ treatment might also be useful for patients with impaired glucose tolerance or diabetes.

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.

Effect of PPARalpha activation of macrophages on the secretion of inflammatory cytokines in cultured adipocytes

The relationship between adipocytes and infiltrated macrophages in fat tissue is important for the pathogenesis of insulin resistance through the activation of cytokines. Peroxisome proliferator-activated receptors (PPARs) play a role in the regulation of cytokine secretion in these cells. We studied the effect of the PPARalpha activation of macrophages on the modulation of the tumor necrosis factor alpha (TNFalpha) expression in adipocytes using a cell culture system. A conditioned medium of lipopolysaccharide (LPS)-stimulated RAW264.7 cells, a macrophage cell line, induced the level of TNFalpha mRNA in 3T3-L1 adipocytes. This effect was inhibited by the addition of neutralizing antibody against interleukin 6 (IL-6) in the conditioned medium or the preincubation of RAW264.7 cells with a specific PPARalpha agonist, K-111 (2,2-dichloro-12-(4-chlorophenyl)dodecanoic acid). K-111 reduced both the IL-6 production and mRNA expression in RAW264.7 cells, and its effect was stronger than that of rosiglitazone, a PPARgamma agonist. The activation of the stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) pathway and nuclear factor kappa B (NF-kappaB) subunits of p65 was significantly inhibited by K-111. The blocking of IL-6 production through the SAPK/JNK pathway or by transfection with siRNA specific for IL-6 abolished the inhibitory effect of K-111 on the TNFalpha expression in the 3T3-L1 adipocytes. As a result, the IL-6 produced by RAW264.7 cells is an inducer of TNFalpha expression in 3T3-L1 adipocytes, and the IL-6 secretion is inhibited by the activation of PPARalpha. The PPARalpha activators may suppress the pathogenetical secretion of TNFalpha in the adipocytes through the functional modulation of the infiltrated macrophages.

Continuous glucose monitoring in interstitial fluid using glucose oxidase-based sensor compared to established blood glucose measurement in rats

Glucose monitoring is of importance for success of complex therapeutic interventions in diabetic patients. Its impact on treatment and glycemic control is demonstrated in large clinical trials. Up to eight blood glucose measurements per day are recommended. Notwithstanding, a substantial number of diabetic patients cannot or will not monitor their blood glucose appropriately. Considerable progress in control of disturbed metabolism in diabetic patients can be expected by continuous glucose monitoring. The aim of the study was to evaluate the performance of a new amperometric glucose oxidase-based glucose sensor in vitro and in vivo after subcutaneous implantation into rats. For in vitro testing current output of sensors was measured by exposure to increasing and decreasing glucose concentrations up to 472 mg dL(-1) over a time period of 7 days. After subcutaneous implantation of sensors into interscapular region of male rats glucose in interstitial fluid was evaluated and compared to glucose in arterial blood up to 7 days. Hyper- and hypoglycaemia were induced by intravenous application of glucose and insulin, respectively. Current of each implanted sensor was converted into glucose concentration using the first blood glucose measurement only. A change of current with glucose of 0.35 nA mg(-1)dL(-1) indicates high sensitivity of the sensor in vitro. The response time (90% of steady state) was calculated by approximately 60s. Test strips for blood glucose measurement as reference for sensor readings was found as an appropriate and rapidly available method in rats by comparison with established hexokinase method in an automated lab analyzer with limits of agreement of +32.8 and -25.7 mg dL(-1) in Bland-Altman analysis. In normo- and hypoglycaemic range sensor readings in interstitial fluid correlated well with blood glucose measurements whereas hyperglycaemia was not reflected by the sensor completely when blood glucose was changing rapidly. The data given characterize a sensor with high sensitivity, long term stability and short response time. A single calibration of the sensor is required only in measurement periods up to 7 days. The findings demonstrate that the sensor is a highly promising candidate for assessment in humans.

Reduced coronary reserve in response to short-term ischaemia and vasoactive drugs in ex vivo hearts from diabetic mice

AIM

The aim of the present study was to compare the coronary flow (CF) reserve of ex vivo perfused hearts from type 2 diabetic (db/db) and non-diabetic (db/+) mice.

METHODS

The hearts were perfused in the Langendorff mode with Krebs-Henseleit bicarbonate buffer (37 degrees C, pH 7.4) containing 11 mmol L(-1) glucose as energy substrate. The coronary reserve was measured in response to three different interventions: (1) administration of nitroprusside (a nitric oxide donor), (2) administration of adenosine and (3) production of reactive hyperaemia by short-term ischaemia.

RESULTS

Basal CF was approximately 15% lower in diabetic when compared with non-diabetic hearts (2.1 +/- 0.1 vs. 2.6 +/- 0.2 mL min(-1)). The maximum increase in CF rate in response to sodium nitroprusside and adenosine was significantly lower in diabetic (0.6 +/- 0.1 and 0.9 +/- 0.1 mL min(-1) respectively) than in non-diabetic hearts (1.2 +/- 0.1 and 1.4 +/- 0.1 mL min(-1) respectively). Also, there was a clear difference in the rate of return to basal CF following short-term ischaemia between diabetic and non-diabetic hearts. Thus, basal tone was restored 1-2 min after the peak hyperaemic response in non-diabetic hearts, whereas it took approximately 5 min in diabetic hearts.

CONCLUSION

These results show that basal CF, as well as the CF reserve, is impaired in hearts from type 2 diabetic mice. As diabetic and non-diabetic hearts were exposed to the same (maximum) concentrations of NO or adenosine, it is suggested that the lower coronary reserve in type 2 diabetic hearts is, in part, because of a defect in the intracellular pathways mediating smooth muscle relaxation.

Skeletal muscle glycogen synthase subcellular localization: effects of insulin and PPAR-α agonist (K-111) administration in rhesus monkeys

Insulin covalently and allosterically regulates glycogen synthase (GS) and may also cause the translocation of GS from glycogen-poor to glycogen-rich locations. We examined the possible role of subcellular localization of GS and glycogen in insulin activation of GS in skeletal muscle of six obese monkeys and determined whether 1) insulin stimulation during a hyperinsulinemic euglycemic clamp and/or peroxisome proliferator-activated receptor (PPAR)-α agonist treatment (K-111, 3 mg·kg−1·day−1; Kowa) induced translocation of GS and 2) translocation of GS was associated with insulin activation of GS. GS and glycogen were present in all fractions obtained by differential centrifugation, except for the cytosolic fraction, under both basal and insulin-stimulated conditions. We found no evidence for translocation of GS by insulin. GS total (GST) activity was strongly associated with glycogen content ( r = 0.70, P < 0.001). Six weeks of treatment with K-111 increased GST activity in all fractions, except the cytosolic fraction, and mean GST activity, GS independent activity, and glycogen content were significantly higher in the insulin-stimulated samples compared with basal samples, effects not seen with vehicle. The increase in GST activity was strongly related to the increase in glycogen content during the hyperinsulinemic euglycemic clamp after K-111 administration ( r = 0.74, P < 0.001). Neither GS protein expression nor GS gene expression was affected by insulin or by K-111 treatment. We conclude that 1) in vivo insulin does not cause translocation of GS from a glycogen-poor to a glycogen-rich location in primate skeletal muscle and 2) the mechanism of action of K-111 to improve insulin sensitivity includes an increase in GST activity without an increase in GS gene or protein expression.

Effect of BM 17.0744, a PPARα ligand, on the metabolism of perfused hearts from control and diabetic mice

Peroxisome proliferator-activated receptor-α (PPARα) regulates the expression of fatty acid (FA) oxidation genes in liver and heart. Although PPARα ligands increased FA oxidation in cultured cardiomyocytes, the cardiac effects of chronic PPARα ligand administration in vivo have not been studied. Diabetic db/db mouse hearts exhibit characteristics of a diabetic cardiomyopathy, with altered metabolism and reduced contractile function. A testable hypothesis is that chronic administration of a PPARα agonist to db/db mice will normalize cardiac metabolism and improve contractile function. Therefore, a PPARα ligand (BM 17.0744) was administered orally to control and type 2 diabetic (db/db) mice (37.9 ± 2.5 mg/(kg·d) for 8 weeks), and effects on cardiac metabolism and contractile function were assessed. BM 17.0744 reduced plasma glucose in db/db mice, but no change was observed in control mice. FA oxidation was significantly reduced in BM 17.0744 treated db/db hearts with a corresponding increase in glycolysis and glucose oxidation; glucose and FA oxidation in control hearts was unchanged by BM 17.0744. PPARα treatment did not alter expression of PPARα target genes in either control or diabetic hearts. Therefore, metabolic alterations in hearts from PPARα-treated diabetic mice most likely reflect indirect mechanisms related to improvement in diabetic status in vivo. Despite normalization of cardiac metabolism, PPARα treatment did not improve cardiac function in diabetic hearts.Key words: PPAR, cardiac metabolism and function, diabetes.

Biochemical and morphological effects of K-111, a peroxisome proliferator-activated receptor (PPAR)alpha activator, in non-human primates

K-111 has been characterized as a potent peroxisome proliferator-activated receptor (PPAR)alpha activator. Antidiabetic potency and amelioration of disturbed lipid metabolism were demonstrated in rodents, which were accompanied by elevations of peroxisomal enzymes and liver weight. To examine the possible therapeutic application of K-111 we have now assessed its efficacy in non-human primates with high transferability to humans. For this purpose obese, hypertriglyceridaemic, hyperinsulinaemic prediabetic rhesus monkeys were dosed sequentially with 0, 1, 3 and 10mg/kg per day orally over a period of 4 weeks each. In addition, the effect of K-111 on the peroxisome compartment was analyzed in cynomolgus monkeys using liver samples obtained following a 13-week oral toxicity study. In prediabetic monkeys, the reduction of hyperinsulinaemia and improvement of insulin-stimulated glucose uptake rate indicated amelioration of insulin resistance. These effects were nearly maximal at a dose of 3mg/kg per day, while triglycerides and body weight were lowered significantly in a dose-dependent manner. This reduction of body weight contrasts sharply with the adipogenic response observed with thiazolidinediones, another family of insulin-sensitizing agents. In young cynomolgus monkeys at a dosage of 5mg/kg per day and more, K-111 induced an up to three-fold increase in lipid beta-oxidation enzymes with an 1.5- to 2-fold increase in peroxisome volume density. This moderate increase in peroxisomal activity by K-111 in monkeys is consistent with its role as an PPARalpha activator and corresponds to the observations with fibrates in other low responder mammalian species. The increase in beta-oxidation may explain, at least in part, the lipid modulating effect as well as the antidiabetic potency of K-111. This pharmacological profile makes K-111 a highly promising drug candidate for clinical applications in the treatment of type 2 diabetes, dyslipidaemia, obesity and the metabolic syndrome.

Pharmacological characteristics of a novel nonthiazolidinedione insulin sensitizer, FK614

We evaluated antidiabetic effects of 3-(2,4-dichlorobenzyl)-2-methyl-N-(pentylsulfonyl)-3 H-benzimidazole-5-carboxamide (FK614), a benzimidazole derivative without a thiazolidinedione structure, which was obtained using C57BL/KsJ-db/db mice (db/db mice). In db/db mice, the potency of FK614 for hypoglycemic effect was comparable to that of rosiglitazone and approximately 15-fold greater than that of pioglitazone. FK614 also showed a potent attenuating effect on hypertriglyceridemia in db/db mice, as well as rosiglitazone and pioglitazone. In C57BL/6J-ob/ob mice (ob/ob mice), ED(50) values of FK614 and pioglitazone for hypoinsulinemic effect were 1.3 and 11.8 mg/kg, respectively. FK614 also improved the impaired glucose tolerance in ob/ob mice. In normal rats, FK614 did not influence plasma glucose and insulin levels but significantly decreased both plasma triglyceride and nonesterified fatty acid levels. FK614 was found to activate peroxisome proliferator-activated receptor (PPAR)gamma-mediated transcriptional activity in the reporter gene assay as well as thiazolidinedione derivatives, although its maximum effect was less than that of thiazolidinedione derivatives. In rat toxicity studies, hemodilution effects for FK614 were less than that for rosiglitazone. Overall, these studies suggest that FK614 improves insulin resistance in such animal models through activation of PPARgamma-mediated transcriptional activity and that it would be a new therapeutic candidate with potential for the treatment of type 2 diabetic patients.

Effects of a novel dual lipid synthesis inhibitor and its potential utility in treating dyslipidemia and metabolic syndrome

We have identified a novel omega-hydroxy-alkanedicarboxylic acid, ESP 55016, that favorably alters serum lipid variables in obese female Zucker (fa/fa) rats. ESP 55016 reduced serum non-HDL-cholesterol (non-HDL-C), triglyceride, and nonesterified fatty acid levels while increasing serum HDL-C and beta-hydroxybutyrate levels in a dose-dependent manner. ESP 55016 reduced fasting serum insulin and glucose levels while also suppressing weight gain. In primary rat hepatocytes, ESP 55016 increased the oxidation of [(14)C]palmitate in a dose- and carnitine palmitoyl transferase-I (CPT-I)-dependent manner. Furthermore, in primary rat hepatocytes and in vivo, ESP 55016 inhibited fatty acid and sterol synthesis. The "dual inhibitor" activity of ESP 55016 was unlikely attributable to the activation of the AMP-activated protein kinase (AMPK) pathway because AMPK and acetyl-CoA carboxylase (ACC) phosphorylation states as well as ACC activity were not altered by ESP 55016. Further studies indicated the conversion of ESP 55016 to a CoA derivative in vivo. ESP 55016-CoA markedly inhibited the activity of partially purified ACC. The activity of partially purified HMG-CoA reductase was not altered by the xenobiotic-CoA. These data suggest that ESP 55016-CoA favorably alters lipid metabolism in a model of diabetic dyslipidemia in part by initially inhibiting fatty acid and sterol synthesis plus enhancing the oxidation of fatty acids through the ACC/malonyl-CoA/CPT-I regulatory axis.

O-arylmandelic acids as highly selective human PPAR alpha/gamma agonists

A new class of O-arylmandelic acid PPAR agonists show excellent anti-hyperglycemic efficacy in a db/db mouse model of DM2. These PPARalpha-weighted agonists do not show the typical PPARgamma associated side effects of BAT proliferation and cardiac hypertrophy in a rat tolerability assay.

Age-dependent changes in metabolism, contractile function, and ischemic sensitivity in hearts from db/db mice

Glucose and palmitate metabolism and contractile function were measured with ex vivo perfused working hearts from control (db/+) and diabetic (db/db) female mice at 6, 10-12, and 16-18 weeks of age. Palmitate oxidation was increased by 2.2-fold in 6-week-old db/db hearts and remained elevated in 10- to 12- and 16- to 18-week-old hearts. Carbohydrate oxidation was normal at 6 weeks but was reduced to 27 and 23% of control at 10-12 and 16-18 weeks, respectively. At 6 weeks, db/db hearts exhibited a slight reduction in mechanical function, whereas marked signs of dysfunction were evident at 10-12 and 16-18 weeks. Mechanical function after ischemia-reperfusion was examined in hearts from male mice; at 6 weeks, db/db hearts showed normal recovery, whereas at 12 weeks it was markedly reduced. Fatty acid oxidation was the predominant substrate used after reperfusion. Thus, diabetic db/db hearts exhibit signs of a progressive cardiomyopathy; increased fatty acid oxidation preceded reductions in carbohydrate oxidation. Postischemic recovery of function was reduced in db/db hearts, in parallel with age-dependent changes in normoxic contractile performance. Finally, peroxisome proliferator-activated receptor-alpha treatment (3 weeks) did not affect sensitivity to ischemia-reperfusion, even though carbohydrate oxidation was increased and palmitate oxidation was decreased.

Cardiac function and metabolism in Type 2 diabetic mice after treatment with BM 17.0744, a novel PPAR-alpha activator

Hearts from diabetic db/db mice, a model of Type 2 diabetes, exhibit left ventricular failure and altered metabolism of exogenous substrates. Peroxisome proliferator-activated receptor-alpha (PPAR-alpha) ligands reduce plasma lipid and glucose concentrations and improve insulin sensitivity in db/db mice. Consequently, the effect of 4- to 5-wk treatment of db/db mice with a novel PPAR-alpha ligand (BM 17.0744; 25-38 mg x kg(-1) x day(-1)), commencing at 8 wk of age, on ex vivo cardiac function and metabolism was determined. Elevated plasma concentrations of glucose, fatty acids, and triacylglycerol (34.0 +/- 3.6, 2.0 +/- 0.4, and 0.9 +/- 0.1 mM, respectively) were reduced to normal after treatment with BM 17.0744 (10.8 +/- 0.6, 1.1 +/- 0.1, and 0.6 +/- 0.1 mM). Plasma insulin was also reduced significantly in treated compared with untreated db/db mice. Chronic treatment of db/db mice with the PPAR-alpha agonist resulted in a 50% reduction in rates of fatty acid oxidation, with a concomitant increase in glycolysis (1.7-fold) and glucose oxidation (2.3- fold). Correction of the diabetes-induced abnormalities in systemic and cardiac metabolism after BM 17.0744 treatment did not, however, improve left ventricular contractile function.

Peroxisome proliferator-activated receptor-alpha ligands inhibit cardiac lipoprotein lipase activity

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that regulate gene expression of lipoprotein lipase (LPL) in liver and adipose tissue. We examined the direct effect of PPAR-alpha ligands on LPL catalytic activity in cultured cardiomyocytes from adult rat heart. After overnight culture (16 h), 1 microM Wy-14643 and 10 microM BM-17.0744 decreased total cellular LPL activity to approximately 50% of control with no change in enzyme synthesis or mass; as a consequence, PPAR-alpha activation produced a significant decrease in LPL specific activity (mU/ng LPL protein). Wy-14643 and BM-17.0744 also reduced heparin-releasable LPL activity and mass in the culture medium. Inhibition of LPL activity by Wy-14643 did not reduce the ability of insulin plus dexamethasone to stimulate cellular and heparin-releasable LPL activities. A similar inhibitory effect on cellular and heparin-releasable LPL activity was observed when cardiomyocytes were cultured with 60 microM linoleic acid. In conclusion, two different PPAR-alpha ligands (Wy-14643 and BM-17.0744) inhibited cellular LPL activity in cultured cardiomyocytes by a posttranscriptional and posttranslational mechanism.

Thiazolidinediones: an update

Thiazolidinediones, which are being developed for the treatment of insulin resistance and type 2 diabetes mellitus, bind and activate peroxisome proliferator-activated receptor gamma, a nuclear receptor that regulates the expression of several genes involved in metabolism. This receptor controls adipocyte differentation, lipid storage, and insulin sensitisation. Besides metabolic activities, thiazolidinediones have effects as diverse as the control of host defence, cell proliferation, and tumorigenesis.