Design, synthesis, and evaluation of novel aryl-tetrahydropyridine PPARalpha/gamma dual agonists

Aryl-tetrahydropyridine derivatives were prepared and their PPARalpha/gamma dual agonistic activities were evaluated. Among them, compound (S)-5b was identified as a potent PPARalpha/gamma dual agonist with an EC(50) of 1.73 and 0.64 microM in hPPARalpha and gamma, respectively. In diabetic (db/db) mice, compound (S)-5b showed good glucose lowering efficacy and favorable pharmacokinetic properties.     

Trypanosoma brucei: infection in murine diabetes

The course of infection due to Trypanosoma brucei infection was observed in genetically diabetic and streptozotocin-induced diabetic mice. A strain of T. brucei, TREU 667, was used which produces a chronic infection in C57BL/6(B6) mice lasting greater than 60 days. Genetic diabetic mice (+db/+db) are obese, and have elevated blood glucose levels, normal levels of insulin, and impaired cell-mediated immunity. Their littermates (m+/m+, m+/+db) are of normal weight, and are normoglycemic and immunocompetent. The infected +db/+db mice lived significantly longer than the nondiabetic littermates. In contrast to this finding, streptozotocin-induced diabetic B6 mice developed higher parasitemia and had shorter survival times than control B6 mice. Continuous treatment with insulin of these streptozotocin-induced diabetic mice led to normalization of blood glucose and a significant reduction of parasitemia. While hyperglycemia may be associated with higher parasitemia and death in streptozotozin-induced diabetes, genetic factors may play an additional role in the genetic models.     

Design, synthesis, and pharmacological evaluation of N-bicyclo-5-chloro-1H-indole-2-carboxamide derivatives as potent glycogen phosphorylase inhibitors

As a result of the various N-bicyclo-5-chloro-1H-indole-2-carboxamide derivatives with a hydroxy moiety synthesized in an effort to discover novel glycogen phosphorylase (GP) inhibitors, 5-chloro-N-(5-hydroxy-5,6,7,8-tetrahydronaphthalen-2-yl)-1H-indole-2-carboxamide (5b) was found to have potent inhibitory activity. The introduction of fluorine atoms both at a position adjacent to the hydroxy group and in the central benzene moiety lead to the optically active derivative 5-chloro-N-[(5R)-1,3,6,6-tetrafluoro-5-hydroxy-5,6,7,8-tetrahydronaphthalen-2-yl]-1H-indole-2-carboxamide (25e(alpha), which was the most potent compound in this series (IC(50)=0.020microM). This compound inhibited glucagon-induced glucose output in cultured primary hepatocytes with an IC(50) value of 0.69microM, and showed oral hypoglycemic activity in diabetic db/db mice at 10mg/kg. Compound 25e(alpha) also had an excellent pharmacokinetic profile, with high oral bioavailability and a long plasma half-life, in male SD rats. The binding mode of 25e(alpha) to this molecule and the role of fluorine atoms in that binding were speculated in an enzyme docking study.     

Activation of insulin signal transduction pathway and anti-diabetic activity of small molecule insulin receptor activators

We recently described the identification of a non-peptidyl fungal metabolite (l-783,281, compound 1), which induced activation of human insulin receptor (IR) tyrosine kinase and mediated insulin-like effects in cells, as well as decreased blood glucose levels in murine models of Type 2 diabetes (Zhang, B., Salituro, G., Szalkowski, D., Li, Z., Zhang, Y., Royo, I., Vilella, D., Diez, M. T. , Pelaez, F., Ruby, C., Kendall, R. L., Mao, X., Griffin, P., Calaycay, J., Zierath, J. R., Heck, J. V., Smith, R. G. & Moller, D. E. (1999) Science 284, 974-977). Here we report the characterization of an active analog (compound 2) with enhanced IR kinase activation potency and selectivity over related receptors (insulin-like growth factor I receptor, epidermal growth factor receptor, and platelet-derived growth factor receptor). The IR activators stimulated tyrosine kinase activity of partially purified native IR and recombinant IR tyrosine kinase domain. Administration of the IR activators to mice was associated with increased IR tyrosine kinase activity in liver. In vivo oral treatment with compound 2 resulted in significant glucose lowering in several rodent models of diabetes. In db/db mice, oral administration of compound 2 elicited significant correction of hyperglycemia. In a streptozotocin-induced diabetic mouse model, compound 2 potentiated the glucose-lowering effect of insulin. In normal rats, compound 2 improved oral glucose tolerance with significant reduction in insulin release following glucose challenge. A structurally related inactive analog (compound 3) was not effective on insulin receptor activation or glucose lowering in db/db mice. Thus, small molecule IR activators exert insulin mimetic and sensitizing effects in cells and in animal models of diabetes. These results have implications for the future development of new therapies for diabetes mellitus.     

Inhibition of gluconeogenesis and glycogenolysis by 2,5-anhydro-D-mannitol

2,5-Anhydro-D-mannitol (100 to 200 mg/kg) decreased blood glucose by 17 to 58% in fasting mice, rats, streptozotocin-diabetic mice, and genetically diabetic db/db mice. Serum lactate in rats was elevated 56% by 2,5-anhydro-D-mannitol, but this could be prevented by dichloroacetate (200 mg/kg) or thiamin (200 mg/kg). In hepatocytes from fasted rats, 1 mM 2,5-anhydro-D-mannitol inhibited gluconeogenesis from a mixture of alanine, lactate, and pyruvate. It also inhibited glucose production and stimulated lactate formation from glycerol or dihydroxyacetone. Glycogenolysis in hepatocytes from fed rats was markedly inhibited by 1 mM 2,5-anhydro-D-mannitol both in the presence or absence of 1 microM glucagon. 2,5-Anhydro-D-mannitol can be phosphorylated by fructokinase or hexokinase to the 1-phosphate and then by phosphofructokinase to the 1,6-bisphosphate. Rat liver glycogen phosphorylase was inhibited by 2,5-anhydro-D-mannitol 1-phosphate (apparent Ki = 0.66 +/- 0.09 mM) but was little affected by 2,5-anhydro-D-mannitol 1,6-bisphosphate. Rat liver phosphoglucomutase was inhibited by 2,5-anhydro-D-mannitol 1-phosphate (apparent Ki = 2.8 +/- 0.2 mM), whereas 2,5-anhydro-D-mannitol 1,6-bisphosphate served as an alternative activator (apparent K alpha = 7.0 +/- 0.5 microM). Rabbit liver pyruvate kinase was activated by 2,5-anhydro-D-mannitol 1,6-bisphosphate (apparent K alpha = 9.5 +/- 0.9 microM), whereas rabbit liver fructose 1,6-bisphosphatase was inhibited by 2,5-anhydro-D-mannitol 1,6-bisphosphate (apparent Ki = 3.6 +/- 0.3 microM). The phosphate esters of 2,5-anhydro-D-mannitol would, therefore, be expected to inhibit glycogenolysis and gluconeogenesis and stimulate glycolysis in liver.     

Hepatic adrenergic receptors in the genetically diabetic C57 BL/KsJ (db/db) mouse

1. At 30 weeks of age, homozygote diabetic C57 BL KsJ (db/db) mice were grossly obese, lethargic and displayed moderate hair loss relative to heterozygote control C 57 BL KsJ (db/+) mice. 2. In diabetic mice, compared to control, the total body weights, liver weight: body weight ratios, and blood glucose levels were increased 2.3 fold, 20% and 3.1 fold, respectively. 3. Analysis of plasma membranes isolated from control and diabetic mouse liver established that comparable purity levels were achieved since relative specific activities of the plasma membrane markers 5'-nucleotidase and gamma-glutamyltranspeptidase were similar: 10.2 and 11.4 fold with respect to 5'-nucleotidase in control and diabetic states respectively; and 8.0 and 8.3 fold with respect to gamma-glutamyltranspeptidase in control and diabetic states respectively. 4. A select effect of diabetes on gamma-glutamyltranspepetidase, however, was observed. The activity of this enzyme was found to be reduced 16% in diabetic liver compared to control liver. 5. Assessment of [3H]prazosin and [3H]dihydrolalprenolol binding to mouse liver plasma membranes indicated that although there was no difference in beta-adrenergic receptor binding in control and diabetic states, alpha 1-adrenergic receptor binding was found to be reduced 43% in diabetic mouse liver plasma membranes. 6. Scatchard analyses of kinetic studies indicate that the reduction is a reflection of decreases in alpha 1-adrenergic receptor numbers with no change in alpha 1 receptor affinity in the diabetic state: since for diabetic and control liver plasma membranes, Kd values were 3.41 +/- 0.02 nM and 3.40 +/- 0.01 nM respectively; and Bmax were 650.12 +/- 16.44 fmol mg-1 and 380.76 +/- 12.92 fmol mg-1, respectively.     

Antidiabetic effect of Cogent db,a herbal drug in alloxan-induced diabetes mellitus

Cogent db, a compound herbal drug, was investigated for its possible antidiabetic effect in alloxan-induced diabetic rats. Oral administration of 0.15, 0.30 and 0.45 g/kg body wt. of the aqueous solution of Cogent db for 40 days exhibited a significant reduction in blood glucose, glycosylated haemoglobin and increased plasma insulin, total haemoglobin along with antihyperlipidemic effects in diabetic rats. The effective dose was found to be 0.45 g/kg body wt. It also prevents body weight loss in diabetic rats. An oral glucose tolerance test (OGTT) was also performed in experimental diabetic rats in which there was a significant improvement in glucose tolerance in rats treated with Cogent db. A comparison was made between the action of Cogent db and a known antidiabetic drug — glibenclamide (600 μg/kg body wt.). The antidiabetic effect of Cogent db was more effective than that observed with glibenclamide.     

Recombinant Adiponectin Does Not Lower Plasma Glucose in Animal Models of Type 2 Diabetes

Aims/Hypothesis

Several studies have shown that adiponectin can lower blood glucose in diabetic mice. The aim of this study was to establish an effective adiponectin production process and to evaluate the anti-diabetic potential of the different adiponectin forms in diabetic mice and sand rats.

Methods

Human high molecular weight, mouse low molecular weight and mouse plus human globular adiponectin forms were expressed and purified from mammalian cells or yeast. The purified protein was administered at 10–30 mg/kg i.p. b.i.d. to diabetic db/db mice for 2 weeks. Furthermore, high molecular weight human and globular mouse adiponectin batches were administered at 5–15 mg/kg i.p. b.i.d. to diabetic sand rats for 12 days.

Results

Surprisingly, none of our batches had any effect on blood glucose, HbA1c, plasma lipids or body weight in diabetic db/db mice or sand rats. In vitro biological, biochemical and biophysical data suggest that the protein was correctly folded and biologically active.

Conclusions/Interpretation

Recombinant adiponectin is ineffective at lowering blood glucose in diabetic db/db mice or sand rats.     

Amelioration of accelerated diabetic mesangial expansion by treatment with a PKC beta inhibitor in diabetic db/db mice, a rodent model for type 2 diabetes.

Activation of protein kinase C (PKC) is implicated as an important mechanism by which diabetes causes vascular complications. We have recently shown that a PKC beta inhibitor ameliorates not only early diabetes-induced glomerular dysfunction such as glomerular hyperfiltration and albuminuria, but also overexpression of glomerular mRNA for transforming growth factor beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in streptozotocin-induced diabetic rats, a model for type 1 diabetes. In this study, we examined the long-term effects of a PKC beta inhibitor on glomerular histology as well as on biochemical and functional abnormalities in glomeruli of db/db mice, a model for type 2 diabetes. Administration of a PKC beta inhibitor reduced urinary albumin excretion rates and inhibited glomerular PKC activation in diabetic db/db mice. Administration of a PKC beta inhibitor also prevented the mesangial expansion observed in diabetic db/db mice, possibly through attenuation of glomerular expression of TGF-beta and ECM proteins such as fibronectin and type IV collagen. These findings provide the first in vivo evidence that the long-term inhibition of PKC activation in the renal glomeruli can ameliorate glomerular pathologies in diabetic state, and thus suggest that a PKC beta inhibitor might be an useful therapeutic strategy for the treatment of diabetic nephropathy.     

Synthesis of 5-chloro-N-aryl-1H-indole-2-carboxamide derivatives as inhibitors of human liver glycogen phosphorylase a

A series of 5-chloro-N-aryl-1H-indole-2-carboxamide derivatives were prepared and evaluated as inhibitors of human liver glycogen phosphorylase a (hLGPa). One compound, 5-chloro-N-[4-(1,2-dihydroxyethyl)phenyl]-1H-indole-2-carboxamide (2f), inhibited hLGPa with an IC(50) of 0.90microM. The pyridine analogue of 2f showed inhibitory activity of glucagon-induced glucose output in cultured primary hepatocytes with an IC(50) of 0.62microM and oral hypoglycemic activity in diabetic db/db mice. Crystallographic determination of the complex of 2f with hLGPa showed binding of the inhibitor in a solvent cavity at the dimer interface, with the two hydroxyl groups making favorable electrostatic interactions with hLGPa.     

Phloridzin reduces blood glucose levels and improves lipids metabolism in streptozotocin-induced diabetic rats

Phloridzin is the specific and competitive inhibition of sodium/glucose cotransporters in the intestine (SGLT1) and kidney (SGLT2). This property which could be useful in the management of postprandial hyperglycemia in diabetes and related disorders. Phloridzin is one of the dihydrochalcones typically contained in apples and in apple-derived products. The effect of phloridzin orally doses 5, 10, 20 and 40 mg/kg body weight on diabetes was tested in a streptozotocin-induced rat model of diabetes type 1. From beneficial effect of this compound is significant reduction of blood glucose levels and improve dyslipidemia in diabetic rats. As a well-known consequence of becoming diabetic, urine volume and water intake were significantly increased. Administration of phloridzin reduced urine volume and water intake in a dose-dependent manner. Phloretin decreases of food consumption, as well as a marked lowering in the weight. In conclusion, this compound could be proposed as an antihyperglycemic and antihyperlipidemic agent in diabetes and potential therapeutic in obesity.     

Protective effects of gallic acid on hepatic lipid peroxide metabolism, glycoprotein components and lipids in streptozotocin-induced type II diabetic Wistar rats

We evaluated the protective effects of gallic acid (3,4,5-trihydroxybenzoic acid) on hepatic lipid peroxidation products, antioxidants, glycoprotein components, and lipids in streptozotocin-induced type II diabetic rats. To induce type II diabetes, rats were injected with streptozotocin intraperitoneally at a single dose of 40 mg/kg. Gallic acid (10 and 20 mg/kg) treatment was given to diabetic rats orally using an intragastric tube daily for 21 days. Streptozotocin-induced diabetic rats showed a significant increase in the levels of blood glucose, hepatic lipid peroxidation products, glycoprotein components, lipids, and the activity of HMG-CoA reductase and a significant decrease in the levels of plasma insulin and liver glycogen. In addition to this, the activities/levels of hepatic antioxidants were decreased in diabetic rats. Gallic acid (10 and 20 mg/kg) treatment showed significant protective effects on all the biochemical parameters studied in diabetic rats. Thus, our study shows the antihyperglycemic, antilipid peroxidative, antioxidant, and antilipidemic effects of gallic acid in streptozotocin-induced type II diabetic rats. A diet containing gallic acid may be beneficial to type II diabetic patients.     

Ginseng berry reduces blood glucose and body weight in db/db mice.

In this study, we observed anti-diabetic and anti-obesity effects of Panax ginseng berry in adult C57BL/Ks db/db mice and their lean littermates. Animals received daily intraperitoneal injections of Panax ginseng berry extract at 150 mg/kg body wt. for 12 consecutive days. On Day 5, the extract-treated db/db mice had significantly lower fasting blood glucose levels as compared to vehicle-treated mice (180.5+/-10.2 mg/dl vs. 226.0+/-15.3 mg/dl, P < 0.01). On day 12, the extract-treated db/db mice were normoglycemic (134.3+/-7.3 mg/dl) as compared to vehicle-treated mice (254.8+/-24.1 mg/dl; P < 0.01). Fasting blood glucose levels of lean mice did not decrease significantly after treatment with extract. After 12 days of treatment with the extract, glucose tolerance increased significantly, and overall blood glucose exposure calculated as area under the curve (AUC) decreased 53.4% (P < 0.01) in db/db mice. Furthermore, db/db mice treated with extract (150 mg/kg body wt.) showed weight loss from 51.0+/-1.9 g on Day 0, to 46.6+/-1.7 g on Day 5, and to 45.2+/-1.4 g on Day 12 (P < 0.05 and P < 0.01 compared to Day 0, respectively). The body weight of lean littermates also decreased at the same dose of extract. These data suggest that Panax ginseng berry extract may have therapeutic value in treating diabetic and obese patients.     

A novel Steroid from Elephantopus scaber L. an Ethnomedicinal plant with antidiabetic activity

Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels in streptozotocin-induced diabetic rats significantly. Acute toxicity studies revealed the non-toxic nature of the crude extract. Fractionation of the acetone extract yielded a new steroid, 28Nor-22(R)Witha 2,6,23-trienolide. Biological testing of the compound demonstrated a significant antidiabetic activity by reducing the elevated blood glucose levels and restoring the insulin levels in streptozotocin-induced diabetic rats. This compound can be a useful candidate to treat diabetes.     

Release of beta-endorphin by caffeic acid to lower plasma glucose in streptozotocin-induced diabetic rats.

The role of alpha 1A -adrenoceptors in the regulation of opioid secretion from the adrenal glands of streptozotocin-induced diabetic rats (STZ-diabetic rats) was examined in an attempt to determine the mechanism of plasma glucose-lowering action of caffeic acid. In agreement with a previous report, we showed that caffeic acid produced a dose-dependent lowering of the plasma glucose concentration in STZ-diabetic rats along with an increase of plasma beta-endorphin-like immunoreactivity (BER). These actions of caffeic acid were abolished by pretreatment with WB 4101 or RS 17 056 at doses sufficient to block alpha 1A -adrenoceptors. In addition, naloxone and naloxonazine at doses effective for blocking opioid micro -receptors abolished the plasma glucose-lowering action of caffeic acid. Also, unlike that in wild-type diabetic mice, caffeic acid failed to produce a plasma glucose lowering effect in opioid micro -receptor knockout diabetic mice. We observed that caffeic acid could enhance BER release from isolated rat adrenal medulla in a concentration-dependent manner; inhibitors of alpha 1A -adrenoceptors such as WB 4101 and RS 1705 abolished this action. Investigations of the signal pathways further supported that activation of alpha 1A -adrenoceptor is responsible for the stimulatory effect of caffeic acid on BER secretion from the adrenal medulla. In the presence of U73312, a specific inhibitor of phospholipase C, the caffeic acid-induced increase of BER was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Chelerythrine and GF 109203X also diminished the action of caffeic acid at concentrations sufficient for inhibiting protein kinase C. Moreover, bilateral adrenalectomy in STZ-diabetic rats resulted in the loss of this plasma glucose-lowering effect of caffeic acid, and there was no increase in plasma BER with caffeic acid. Therefore, beta-endorphin release from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats induced by caffeic acid, through the activation of alpha 1A -adrenoceptors.     

5,5-Difluoro- and 5-Fluoro-5-methyl-hexose-based C-Glucosides as potent and orally bioavailable SGLT1 and SGLT2 dual inhibitors

(2S,3R,4R,5S,6R)-2-Aryl-5,5-difluoro-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4-diols and (2S,3R,4R,5S,6R)-2-aryl-5-fluoro-5-methyl-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4-diols were discovered as dual inhibitors of sodium glucose co-transporter proteins (e.g. SGLT1 and SGLT2) through rational drug design, efficient synthesis, and in vitro and in vivo evaluation. Compound 6g demonstrated potent dual inhibitory activities (IC₅₀ = 96 nM for SGLT1 and IC₅₀ = 1.3 nM for SGLT2). It showed robust inhibition of blood glucose excursion in an oral glucose tolerance test (OGTT) in Sprague Dawley (SD) rats when dosed at both 1 mg/kg and 10 mg/kg orally. It also demonstrated postprandial glucose control in db/db mice when dosed orally at 10 mg/kg.     

Effect of Lactobacillus gasseri BNR17 on blood glucose levels and body weight in a mouse model of type 2 diabetes

Aims:  To investigate the effect of Lactobacillus gasseri BNR17 isolated from human breast milk on blood glucose and body weight in type 2 diabetic animals.
Methods and results:  db/db mice were divided into one control group and five sample groups; the sample groups received BNR17 (10⁷, 10⁸, 10⁹ and 10¹⁰ CFU) or rosiglitazone (8 mg kg⁻¹) orally twice a day for 12 weeks. BNR17 groups had a dose-dependent reduction in food, water intake and amount of excrement. Body weight loss was not seen in the BNR17 groups. Fasting and postprandial 2 h blood glucose levels were significantly lower in the BNR17 (10¹⁰ CFU) group compared with the control group. HbA1c decreased in the BNR17 group, although it was not statistically significant. During the oral glucose tolerance test, the BNR17 groups exhibited dose-dependent improvement in glucose sensitivity.
Conclusions:  Lactobacillus gasseri BNR17 has a suppressing effect on blood glucose levels and improved diabetic symptoms in db/db mice.
Significance and Impact of the Study:  Blood glucose-lowering lactic acid bacteria are expected to be useful as a therapeutic for treating type 2 diabetes in humans.     

Treatment of type 2 diabetic db/db mice with a novel PPARgamma agonist improves cardiac metabolism but not contractile function

Hearts from insulin-resistant type 2 diabetic db/db mice exhibit features of a diabetic cardiomyopathy with altered metabolism of exogenous substrates and reduced contractile performance. Therefore, the effect of chronic oral administration of 2-(2-(4-phenoxy-2-propylphenoxy)ethyl)indole-5-acetic acid (COOH), a novel ligand for peroxisome proliferator-activated receptor-gamma that produces insulin sensitization, to db/db mice (30 mg/kg for 6 wk) on cardiac function was assessed. COOH treatment reduced blood glucose from 27 mM in untreated db/db mice to a normal level of 10 mM. Insulin-stimulated glucose uptake was enhanced in cardiomyocytes from COOH-treated db/db hearts. Working perfused hearts from COOH-treated db/db mice demonstrated metabolic changes with enhanced glucose oxidation and decreased palmitate oxidation. However, COOH treatment did not improve contractile performance assessed with ex vivo perfused hearts and in vivo by echocardiography. The reduced outward K+ currents in diabetic cardiomyocytes were still attenuated after COOH. Metabolic changes in COOH-treated db/db hearts are most likely indirect, secondary to changes in supply of exogenous substrates in vivo and insulin sensitization.