Antidiabetic and hypolipidemic potential of DRF 2519—a dual activator of PPAR-α and PPAR-γ

Fenofibrate enhances lipid deposition via modulating PPARγ, SREBP-1c, and gut microbiota in ob/ob mice fed a high-fat diet

Obesity is characterized by lipid accumulation in distinct organs. Presently, fenofibrate is a commonly used triglyceride-lowering drug. This study is designed to investigate whether long-term fenofibrate intervention can attenuate lipid accumulation in ob/ob mouse, a typical model of obesity. Our data demonstrated that fenofibrate intervention significantly decreased plasma triglyceride level by 21.0%, increased liver index and hepatic triglyceride content by 31.7 and 52.1%, respectively, and elevated adipose index by 44.6% compared to the vehicle group. As a PPARα agonist, fenofibrate intervention significantly increased the expression of PPARα protein in the liver by 46.3% and enhanced the expression of LDLR protein by 3.7-fold. However, fenofibrate dramatically increased the expression of PPARγ and SREBP-1c proteins by ~2.1- and 0.9-fold in the liver, respectively. Fenofibrate showed no effects on the expression of genes-related to fatty acid β-oxidation. Of note, it significantly increased the gene expression of FAS and SCD-1. Furthermore, fenofibrate modulated the gut microbiota. Collectively, long-term fenofibrate induces lipid accumulation in liver and adipose tissues in ob/ob mice by enhancing the expression of adipogenesis-related proteins and gut microbiota. These data suggest that fenofibrate may have limited effects on attenuating lipid deposition in obese patients.

N-Arylation of ferrocenyl 2,4-thiazolidinedione conjugatesviaa copper-catalysed Chan–Lam cross coupling reaction with aryl boronic acids and their optoelectronic properties

Copper catalysed Chan–LamN-arylation of ferrocenyl 2,4-thiazolidinedione conjugates is described.

Thiazolidinediones and PPAR orchestra as antidiabetic agents: From past to present

Thiazolidinediones a class of drug, that provided a major breakthrough in the management of type 2 diabetes since 1990. Following the discovery of PPARs, TZDs were the first class to be reported as PPARγ modulators. This review is an attempt to summarize the chemical modifications around TZDs in past two decades to obtain a potent antidiabetic molecule. TZDs literature were initially dominated by their hypoglycemic & hypolipidemic activities, later PPARγ activity was also been incorporated. Moreover, in some cases, both benzyl and benzylidene derivatives were reported in the same manuscript for the sake of comparison. We thought of presenting the review on the basis of the variation in the linker region. Optimal linker at the time of discovery of the Ciglitazone was oxymethyl and it went on to evolve as oxyethyl (Pioglitazone) and oxyethylamino (Rosiglitazone). Few attempts were made to restrict the flexibility of the linker by introducing the cyclic structures and were summarized immediately after the respective linker class.

Triglyceride-lowering agents

This review is the first attempt at systematization of the literature data on the structures and activities of triglyceride-lowering agents which used in medical practice or are in development. The effects and mechanisms of action of statins, squalene synthase inhibitors, fibrates, PPARα and PPARα/γ agonists, nicotinic acid, omega-3 fatty acids and some other molecular targets were considered. Unfortunately, to date, harmless and effective triglyceride-lowering drug still does not exist and there is still need for development of better triglyceride-lowering agents.

In silico expressed sequence tag analysis in identification of probable diabetic genes as virtual therapeutic targets

The expressed sequence tags (ESTs) are major entities for gene discovery, molecular transcripts, and single nucleotide polymorphism (SNPs) analysis as well as functional annotation of putative gene products. In our quest for identification of novel diabetic genes as virtual targets for type II diabetes, we searched various publicly available databases and found 7 reported genes. The in silico EST analysis of these reported genes produced 6 consensus contigs which illustrated some good matches to a number of chromosomes of the human genome. Again the conceptual translation of these contigs produced 3 protein sequences. The functional and structural annotations of these proteins revealed some important features which may lead to the discovery of novel therapeutic targets for the treatment of diabetes.

Protein tyrosine phosphatase 1B and α-glucosidase inhibitory Phlorotannins from edible brown algae, Ecklonia stolonifera and Eisenia bicyclis

The present work investigates protein tyrosine phosphatase 1B (PTP1B) and the α-glucosidase inhibitory activities of two edible brown algae, Ecklonia stolonifera and Eisenia bicyclis, as well as in their isolated phlorotannins. Since the individual extracts and fractions showed significant inhibitory activities, column chromatography was performed to isolate six phlorotannins, phloroglucinol (1), dioxinodehydroeckol (2), eckol (3), phlorofurofucoeckol-A (4), dieckol (5), and 7-phloroeckol (6). Phlorotannins 3-6 were potent and noncompetitive PTP1B inhibitors with IC(50) values ranging from 0.56 to 2.64 µM; 4-6 exhibited the most potent α-glucosidase inhibition with IC(50) values ranging from 1.37 to 6.13 µM. Interestingly, 4 and 6 were noncompetitive, while 5 exhibited competitive inhibition in an α-glucosidase assay. E. stolonifera and E. bicyclis as well as their isolated phlorotannins therefore possessed marked PTP1B and α-glucosidase inhibitory activities; this could lead to opportunities in the development of therapeutic agents to control the postprandial blood glucose level and thereby prevent diabetic complications.

Berberine regulates peroxisome proliferator-activated receptors and positive transcription elongation factor b expression in diabetic adipocytes

Berberine has hypoglycemic and hypolipidemic effects on diabetic rats. This study investigated the relationship between hypoglycemic and hypolipidemic effects of berberine and peroxisome proliferator-activated receptors (PPARs) and positive transcription elongation factor b (P-TEFb) (including cyclin-dependent kinase 9 (CDK9) and cyclin T1) in white adipose tissue of diabetic rats and RNA interference-treated 3T3-L1 cells. Berberine promoted differentiation and inhibited lipid accumulation of 3T3-L1 cells, further decreased PPARα/δ/γ, CDK9 and cyclin T1 mRNA and protein expression and decreased tumor necrosis factor α content in supernatants of both control and RNA interference-treated 3T3-L1 cells. After a 16-week induction with 35 mg/kg streptozotocin (i.p.) and high-carbohydrate/high-fat diet, diabetic rats were treated with 75, 150 and 300 mg/kg berberine and 100 mg/kg fenofibrate or 4 mg/kg rosiglitazone for another 16 weeks. Berberine decreased white adipose tissue to body weight ratio and adipocyte size and increased adipocyte number. Berberine upregulated PPARα/δ/γ, CDK9 and cyclin T1 mRNA and protein expression in adipose tissue, decreased tumor necrosis factor α and free fatty acid content and increased lipoprotein lipase activity in serum and adipose tissue. Berberine modulated metabolic related PPARs expression and differentiation related P-TEFb expression in adipocytes, which are associated with its hypoglycemic and hypolipidemic effects.

Omega-(2-Naphthyloxy) amino alkanes as a novel class of anti-hyperglycemic and lipid lowering agents

omega-(2-Naphthyloxy) amino alkanes, obtained as major by-product during course of synthesis of carbamate esters from omega-(2-naphthyloxy) alkyl halides and amines, showed significant anti-hyperglycemic and lipid lowering activities in various test models as a novel class of compounds. Compounds were tested in rat GLM, SLM, STZ, and STZ-S models at 100mg/kg dose. Of these compound 13 was found to be the most active which caused lowering of sugar by 33.6%, 31.0%, 28.5%, and 73.8% in GLM, SLM, STZ, STZ-S, and db/db mice models, respectively. It also significantly effected lowering of LDL in rat model and also in Hamster model without reducing HDL. Most of the compounds showing anti-diabetic and lipid lowering activity have shown promising PPAR-alpha/gamma/delta-activity. Compounds 6, 13, and 19 have shown very good PPAR-alpha/gamma/delta activity.

Effect of a novel non-thiazolidinedione peroxisome proliferator-activated receptor alpha/gamma agonist on glucose uptake

AIMS/HYPOTHESIS

The effect of the benzopyran derivative T33, a novel non-thiazolidinedione agent, was studied on peroxisome proliferator-activated receptors (PPARs), insulin signalling and glucose uptake in adipocytes and skeletal muscle. We hypothesised that T33 could activate PPARgamma and exert a beneficial effect on insulin action on glucose uptake and lipid metabolism.

MATERIALS AND METHODS

Using a cell-based reporter gene assay, T33 was identified as a PPARalpha/gamma dual agonist, which activated human PPARgamma and PPARalpha with EC50 values of 19 and 148 nmol/l, respectively. The effect of T33 on glucose metabolism was studied in cultured 3T3-L1 adipocytes and L6 myotubes. In vivo effects of T33 on skeletal muscle were determined in ob/ob mice treated with 8 mg/kg T33. The effect of T33 on metabolic abnormalities was observed in diet-induced obese mice.

RESULTS

Exposure of 3T3-L1 adipocytes to T33 for 4 days increased basal and insulin-stimulated glucose uptake, with no effect noted in L6 myotubes. Treatment of ob/ob mice for 20 days with T33 normalised basal and insulin-stimulated glucose uptake and increased phosphorylation of Akt and p38 mitogen-activated protein kinase in skeletal muscle. In contrast, phosphorylation of AMP-activated protein kinase was unaltered. Moreover, T33 improved insulin sensitivity and lipid metabolism in diet-induced obese mice.

CONCLUSIONS/INTERPRETATION

T33 is non-thiazolidinedione PPARalpha/gamma dual agonist which directly increases basal and insulin-stimulated glucose uptake in adipocytes and secondarily improves insulin action on insulin signalling and glucose metabolism in skeletal muscle from diabetic ob/ob mice.

International Union of Pharmacology. LXI. Peroxisome proliferator-activated receptors

The three peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors of the nuclear hormone receptor superfamily. They share a high degree of structural homology with all members of the superfamily, particularly in the DNA-binding domain and ligand- and cofactor-binding domain. Many cellular and systemic roles have been attributed to these receptors, reaching far beyond the stimulation of peroxisome proliferation in rodents after which they were initially named. PPARs exhibit broad, isotype-specific tissue expression patterns. PPARalpha is expressed at high levels in organs with significant catabolism of fatty acids. PPARbeta/delta has the broadest expression pattern, and the levels of expression in certain tissues depend on the extent of cell proliferation and differentiation. PPARgamma is expressed as two isoforms, of which PPARgamma2 is found at high levels in the adipose tissues, whereas PPARgamma1 has a broader expression pattern. Transcriptional regulation by PPARs requires heterodimerization with the retinoid X receptor (RXR). When activated by a ligand, the dimer modulates transcription via binding to a specific DNA sequence element called a peroxisome proliferator response element (PPRE) in the promoter region of target genes. A wide variety of natural or synthetic compounds was identified as PPAR ligands. Among the synthetic ligands, the lipid-lowering drugs, fibrates, and the insulin sensitizers, thiazolidinediones, are PPARalpha and PPARgamma agonists, respectively, which underscores the important role of PPARs as therapeutic targets. Transcriptional control by PPAR/RXR heterodimers also requires interaction with coregulator complexes. Thus, selective action of PPARs in vivo results from the interplay at a given time point between expression levels of each of the three PPAR and RXR isotypes, affinity for a specific promoter PPRE, and ligand and cofactor availabilities.

Increase in weight induced by muraglitazar, a dual PPARalpha/gamma agonist, in db/db mice: adipogenesis/or oedema?

BACKGROUND AND PURPOSE

Muraglitazar, a dual PPARalpha/gamma agonist, caused a robust increase in body weight in db/db mice. The purpose of the study was to see if this increase in weight was due to oedema and/or adipogenesis.

EXPERIMENTAL APPROACH

The affinity of muraglitazar at PPARalpha/gamma receptors was characterized using transactivation assays. Pre-adipocyte differentiation, expression of genes for adipogenesis (aP2), fatty acid oxidation (ACO) and sodium reabsorption (ENaCgamma and Na+, K+-ATPase); haemodilution parameters and serum electrolytes were measured to delineate the role of muraglitazar in causing weight gain vis a vis rosiglitazone.

KEY RESULTS

Treatment with muraglitazar (10 mg kg(-1)) for 14 days significantly reduced plasma glucose and triglycerides. Reduction in plasma glucose was significantly greater than after similar treatment with rosiglitazone (10 mg kg(-1)). A marked increase in weight was also observed with muraglitazar that was significantly greater than with rosiglitazone. Muraglitazar increased aP2 mRNA and caused adipocyte differentiation in 3T3-L1 cells similar to rosiglitazone. It also caused a marked increase in ACO mRNA in the liver of the treated mice. Expression of mRNA for ENaCgamma and Na+, K+-ATPase in kidneys was up-regulated after either treatment. Increased serum electrolytes and decreased RBC count, haemoglobin and haematocrit were observed with both muraglitazar and rosiglitazone.

CONCLUSIONS AND IMPLICATIONS

Although muraglitazar has a better glucose lowering profile, it also has a greater potential for weight gain than rosiglitazone. In conclusion, muraglitazar causes both robust adipogenesis and oedema in a 14-day treatment of db/db mice as observed in humans.

Anti-hyperlipidemic properties of CM108 (a flavone derivative) in vitro and in vivo

Peroxisome proliferator-activated receptors (PPARs) and liver X receptor alpha are ligand-activated transcription factors that belong to nuclear receptors superfamily and are involved in the regulation of lipid metabolism. PPAR, especially PPAR-alpha, PPAR-gamma agonists and liver X receptor alpha agonists can regulate the expression or biosynthesis of some factors involved in the formation and function of HDL, such as apolipoprotein (apo) A-I and ATP binding cassette transporter A1 (ABCA1). It is well known that HDL plays an important role in the treatment of hyperlipidemia as the carrier of reverse cholesterol transport. In the present study, the anti-hyperlipidemic properties of CM108, a derivative of flavone, 9-Hydroxy-2-mercapto-6-phenyl-2-thioxo-1,3,5-trioxa-2lambda(5)-phospha-cyclopenta[b]naphthalen-8-one, were studied. Through the transactivation assays of in vitro study, it was discovered that CM108 could activate PPAR-alpha PPAR-gamma and liver X receptor alpha at 40-150 microg/ml, which subsequently resulted in activating ABCA1 promoter and enhancing apoA-I and apoA-II production, whereas reducing apoC-III production significantly. Furthermore, after in vivo study that the hyperlipidemic rats were treated with CM108 for 4 weeks, a significant increase was found in HDL cholesterol levels (26.7%, P<0.05) and a significant decrease was also noticed in triglyceride levels (26.3%, P<0.01) at 100 mg/kg CM108 group compared with that of control animals. Meanwhile, the atherogenicity index, represented by total cholesterol/HDL ratio, was significantly reduced (P<0.01). In conclusion, CM108 can effectively elevate HDL levels and lower triglyceride levels in hyperlipidemic rats maybe by regulating a series of genes, receptors and proteins related to HDL.

Peroxisome proliferator-activated receptor alpha-independent effects of peroxisome proliferators on cysteinyl leukotriene production in mast cells

The effects of peroxisome proliferators, the ligands of a nuclear receptor peroxisome proliferator-activated receptor (PPAR) alpha, on cysteinyl leukotriene production were investigated in rodent mast cells. Peroxisome proliferators Wy-14,643 (30 microM) and fenofibrate (100 microM) significantly inhibited the cysteinyl leukotriene production that was induced by antigen (Ag) treatment after overnight sensitization to Ag specific immunoglobulin E (IgE) in a rat basophilic leukemia (RBL)-2H3 mast cell line. Similar inhibition by these drugs was observed in IgE and Ag-treated mouse bone marrow-derived mast cells, A23187-treated RBL-2H3 and A23187-treated mouse peritoneal macrophages. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not affect the release of radioactivity from RBL-2H3 pre-incubated with [(3)H]-arachidonic acid, which is considered an index of phospholipase A(2) activity. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not directly inhibit 5-lipoxygenase activity. Troglitazone was found to directly inhibit the activity of 5-lipoxygenase. The PPARalpha mRNA level was at less than the limit of detection for the realtime polymerase chain reaction both in RBL-2H3 and bone marrow-derived mast cells. Wy-14,643 (30 microM) and fenofibrate (100 microM) did not induce acyl-CoA oxidase mRNA in RBL-2H3, which was reported to be induced by peroxisome proliferators via PPARalpha in hepatocytes. Wy-14,643 (30 microM) and fenofibrate (100 microM) inhibited the cysteinyl leukotriene production in bone marrow-derived mast cells from PPARalpha-null mice. It was concluded that the inhibitory effects of these peroxisome proliferators on cysteinyl leukotriene production are independent of PPARalpha in mast cells.

Antidiabetic effect of a novel non-thiazolidinedione PPAR gamma/alpha agonist on ob/ob mice

AIM

To study whether T33, a new synthesized non-thiazolidinedione (TZD) peroxisome proliferator-activated receptor (PPAR) gamma/alpha dual agonist has an antidiabetic effect on ob/ob mice.

METHODS

Ob/ob mice were treated with 4 mg/kg or 8 mg/kg T33 by gavage for 20 d. Blood glucose levels were measured regularly. An oral glucose tolerance test (OGTT) and an insulin tolerance test (ITT) were preformed on d 8 and d 12, respectively. The levels of insulin, triglyceride and free fatty acid (FFA) in the serum were measured at the end of administration. The intramuscular and liver triglyceride content was also determined.

RESULTS

T33 reduced the hyperglycemia, hyperinsulinemia and hyperlipidemia of the ob/ob mice. The OGTT and ITT showed that the insulin resistance state of the ob/ob mice was obviously ameliorated after T33 treatment. After 20 d treatment with 8 mg/kg T33, the triglyceride content in the gastrocnemius muscle decreased significantly. T33 did not have any effect on triglyceride content in the liver, whereas rosiglitazone significantly increased the hepatocyte lipid deposition.

CONCLUSION

The PPARgamma/alpha dual agonist T33 has antidiabetic and insulin-sensitizing effects in ob/ob mice. It has the potential to be a new therapeutic candidate for the treatment of type 2 diabetes.

Investigational PPAR-gamma agonists for the treatment of Type 2 diabetes

The tremendous increase in the global prevalence of Type 2 diabetes (T2D) and its conglomeration of metabolic disorders has dramatically intensified the search for innovative therapies to fight this emerging epidemic. Over the last decade, the family of nuclear receptors, especially the peroxisome proliferator-activated receptors (PPARs), has emerged as one of the most important drug targets aimed at combating the metabolic syndrome. Consequently, compounds that activate the PPARs have served as potential therapeutics for the treatment of T2D and the metabolic anomalies associated with this disorder. This review focuses on the currently marketed compounds and also describes the discovery and development of the next generation of PPAR ligands that are under investigation for the potential treatment of T2D and the metabolic syndrome.

Insulin resistance--a common link between type 2 diabetes and cardiovascular disease

Evidence suggests that diabetes and cardiovascular disease (CVD) may share an underlying cause(s), a theory known as the 'common soil' hypothesis. Insulin resistance is central both to the progression from normal glucose tolerance to type 2 diabetes and to a constellation of cardiovascular risk factors known as the metabolic syndrome. These risk factors include visceral obesity and dyslipidaemia characterized by low levels of high-density lipoprotein cholesterol, hypertriglyceridaemia and raised small dense low-density lipoprotein particle levels. Changes in adipose tissue mass and metabolism may link insulin resistance and visceral obesity, a condition that is common in type 2 diabetes. Furthermore, weight reduction, increased physical activity, metformin and acarbose have been shown to reduce the development of type 2 diabetes in genetically predisposed subjects and may decrease the high cardiovascular risk of patients with diabetes. Some fatty acid derivatives can affect energy metabolism by activating peroxisome proliferator-activated receptors (PPARs), nuclear receptors that play a key role in energy homeostasis. These receptors represent an ideal therapeutic target for reducing cardiovascular risk, because they are involved in the regulation of both insulin action and lipid metabolism. In addition to lifestyle changes, PPARgamma agonists such as thiazolidinediones are frequently beneficial and have been shown to ameliorate insulin resistance, while activation of PPARalpha (e.g. by fibrates) can lead to improvements in free fatty acid oxidation and lipid profile, and a reduction in cardiovascular events. The development of agents with both PPARalpha and PPARgamma activity promises added benefits with amelioration of insulin resistance, delayed progression to and of type 2 diabetes and a reduction of CVD.

Raw vegetable food containing high cyclo (his-pro) improved insulin sensitivity and body weight control

Cyclo (his-pro), controlled-energy diet, soy protein hydrolysate (SPH), and raw vegetable food (RVF) are known to improve insulin sensitivity and body weight (BW) control. Enhancement of high cyclo (his-pro) content in SPH (HCS) was performed by refluxing SPH with 1 N KH(2)CO(3) dissolved in 70% ethanol for 2 weeks at room temperature. Using this material, we examined the effects of HCS plus RVF on glucose metabolism and BW control in genetically diabetic Goto-Kakizaki (G-K) and insulin-resistant aged overweight Sprague-Dawley (S-D) rats. Thirty 7-week-old G-K rats and 18 16- to 18-month-old S-D rats were divided into 3 groups and treated with normal chow (NC), RVF diet, or HCS diet for 8 weeks. Raw vegetable food diet was made of 1:3 RVF and 2:3 NC; HCS diet was made of 1:27 portion HCS, 8:27 RVF, and 2:3 NC. Oral glucose tolerance significantly improved in both RVF- (P<.01) and HCS-treated (P<.001) G-K rats and worsened in NC-fed rats compared with the baseline values. Similarly, oral glucose tolerance also improved in aged overweight S-D rats when treated with RVF (P<.05) and with HCS (P<.01), compared with the baseline values. Although HCS diet treatment very significantly lowered fed plasma insulin levels compared with NC diet treatment in G-K rats (P<.01), RVF diet treatment alone did not decrease plasma insulin levels. In contrast, there was no change of insulin levels in overweight aged S-D rats after either RVF or HCS diet treatment. Postfeeding glucose levels in G-K rats fed RVF or HCS significantly fell, compared with the rats fed NC (P<.05). Interestingly, fasting blood glucose levels in RVF- or HCS-fed rats were very significantly lower than in NC-fed rats (P<.001). There was no change of blood glucose levels in S-D rats due to treatments with different diet. In G-K rats, food intake did not decrease during the first 3 weeks but fell very significantly from the fifth to eighth weeks with RVF (P<.01) and HCS (P<.001) treatments in G-K rats. However, food intake reduction in aged S-D rats was shown only for the HCS-treated rat group (P<.05). Water intake slightly decreased in G-K rats with either RVF or HCS treatment (P<.05) but very significantly decreased in S-D rats with HCS treatment (P<.01). Body weight gain in young G-K rats and BW in aged S-D rats significantly decreased only when rats were treated with HCS diet (P<.05). These data suggest that regular consumption of HCS diet helps to control blood glucose metabolism in diabetic G-K rats and BW control in aged obese S-D rats.

Design, synthesis and evaluation of carbazole derivatives as PPAR alpha/gamma dual agonists and antioxidants

A series of hydroxycarbazole derivatives were synthesized and evaluated for PPAR alpha/gamma dual agonist as well as antioxidant activities. While most compounds showed good antioxidant activity, some compounds were identified as potential PPAR alpha/gamma dual agonists as well. Compounds 10a and 16 were found to be active in animal studies.

Rosiglitazone protects against cyclosporine-induced pancreatic and renal injury in rats

Rosiglitazone (RGTZ) has protective effect against various types of injury. This study was performed to evaluate the effect of RGTZ on pancreatic and renal injury caused by cyclosporine (CsA). CsA (15 mg/kg) and RGTZ (3 mg/kg) were administered alone and together to the rats for 28 days. The effect of RGTZ on CsA-induced pancreatic injury was evaluated by intraperitoneal glucose tolerance test (IPGTT), plasma insulin concentrations and pancreatic beta-cell morphology. The effect of RGTZ on CsA-induced renal injury was evaluated by assessing renal function and pathology; mediators of inflammation and fibrosis such as angiotensin II (AngII), osteopontin (OPN) and transforming growth factor-beta1 (TGF-beta1) and apoptotic cell death. Four weeks of CsA treatment caused diabetes, renal dysfunction, typical pathologic lesions (arteriolopathy, interstitial fibrosis and inflammatory cells infiltration) and apoptotic cell death. RGTZ treatment decreased blood glucose concentration, increased plasma insulin concentration and preserved pancreatic beta islet mass. RGTZ treatment improved renal function and histopathology. Pro-inflammatory and pro-fibrotic molecules such as AngII, OPN and TGF-beta1, and apoptotic cell death also decreased with RGTZ treatment. These data suggest that RGTZ has a protective effect against CsA-induced pancreatic and renal injury.