N-GLUCURONIDATION OF THE PLATELET-DERIVED GROWTH FACTOR RECEPTOR TYROSINE KINASE INHIBITOR 6,7-(DIMETHOXY-2,4-DIHYDROINDENO[1,2-C]PYRAZOL-3-YL)-(3-FLUORO-PHENYL)-AMINE BY HUMAN UDP-GLUCURONOSYLTRANSFERASES

The potential cancer therapeutic agent, 6,7-(dimethoxy-2, 4-dihydroindeno[1,2-c]pyrazol-3-yl)-(3-fluoro-phenyl)-amine (JNJ-10198409), formed three N-glucuronides that were positively identified by liquid chromatography-tandem mass spectrometry and NMR as N-amine-glucuronide (Glu-A), 1-N-pyrazole-glucuronide (Glu-B), and 2-N-pyrazole-glucuronide (Glu-C). All three N-glucuronides were detected in rat liver microsomes, whereas only Glu-A and -B were found in monkey and human liver microsomes. In contrast to common glucuronides, Glu-B was completely resistant to beta-glucuronidase. Kinetic analyses revealed that glucuronidation of JNJ-10198409 in human liver microsomes exhibited atypical kinetics that may be described by a two-site binding model. For the high affinity binding, K(m) values were 1.2 and 5.0 microM, and V(max) values were 2002 and 2,403 nmol min(-1) mg(-1) for Glu-A and Glu-B, respectively. Kinetic constants of low affinity binding were not determined due to low solubility of the drug. Among the human UDP-glucuronosyltransferases (UGTs) tested, UGT1A9, 1A8, 1A7, and 1A4 were the most active isozymes to produce Glu-A; for the formation of Glu-B, UGT1A9 was the most active enzyme, followed by UGT1A3, 1A7, and 1A4. Glucuronidation of JNJ-10198409 by those UGT1A enzymes followed classic Michaelis-Menten kinetics. In contrast, no glucuronides were formed by all UGT2B isozymes tested, including UGT2B4, 2B7, 2B15, and 2B17. Collectively, these results suggested that glucuronidation of JNJ-10198409 in human liver microsomes is catalyzed by multiple UGT1A enzymes. Since UGT1A enzymes are widely expressed in various tissues, it is anticipated that both hepatic and extrahepatic glucuronidation will likely contribute to the elimination of the drug in humans. Additionally, conjugation at the nitrogens of the pyrazole ring represents a new structural moiety for UGT1A-mediated reactions.

Automatic vessel segmentation and quantification of the rat aortic ring assay of angiogenesis

BACKGROUND

Pharmacologic control of angiogenesis is a promising new approach to the treatment of a variety of pathologic conditions including cancer. The recently developed in vitro rat aortic ring model provides a simple, reproducible assay for discovering angiogenic agonists and antagonists. However, quantification of results in this assay is time consuming, tedious, and subjective, because it involves visual inspection of images and manually counting the newly formed microvessels extending from the cultured aortic ring. This report describes an automated image analysis-based procedure for quantification of this assay that overcomes these difficulties.

EXPERIMENTAL DESIGN

The designed image processing algorithm segments the vessels from gray scale images. A high-pass filter is used, and the results are separated into nonvascular and vessel compartments based on object size and shape. Quantification relies on identification of vessels intersecting a closed transect set a fixed distance from the aortic ring. The number and the total area of these vessels are determined. The entire operation has been automated and packaged in an application called Vessels.

RESULTS

The correlation between computer-determined vessel area/vessel number and visual microvessel count is high (r2 = 0.91 and r2 = 0.86, respectively).

CONCLUSION

Vessels offers high-speed, fully automatic batch processing including production of a hard copy for documentation. The application runs on the Apple family of computers. On a Quadra 800, the application can process approximately 30 images/hour, which is approximately 2.5 times faster than manual quantification of this assay.

A novel series of N-(1-aminoalkylidene)carboximidamides as potential hypoglycemic agents

Nitrogen heterocyclic carboximidamides, such as linogliride, 1a, have been shown to possess significant hypoglycemic activity and have shown clinical efficacy as potential antidiabetic agents. We evaluated the biological significance of the heterocyclic ring A of general structure 1, which has always been maintained in this class of compounds, by preparing acyclic compounds of general structure 2. Preliminary in vivo biological testing, i.e., the glucose tolerance test in rats, indicates that a number of the specific acyclic carboximidamides prepared, 6a-kk, possessed significant hypoglycemic activity often comparable to, and in some cases better than, the activity noted for our model compound, 1a. These results suggest that the heterocyclic ring A of 1 is not essential for hypoglycemic activity for this class of compounds.

Effect of linogliride on hormone release from perfused rat pancreas. Fuel dependence and desensitization by tolbutamide

We examined the effect of the hypoglycemic drug linogliride on hormone release from the in vitro perfused rat pancreas. Linogliride stimulated insulin release in the absence of glucose either in the presence or absence of a physiological mixture of amino acids. In addition, linogliride inhibited amino acid-induced glucagon release. Half-maximal effects of linogliride on insulin and glucagon release were achieved at concentrations as low as 26 and 3 microM, respectively. The effects of linogliride on hormone release largely resembled those of tolbutamide. In the absence of amino acids, the stimulation of insulin release by linogliride or tolbutamide was transient. When the pancreas had been preperfused for 20 min with tolbutamide, linogliride no longer had an effect on hormone release. Likewise, tolbutamide remained without effect in pancreases preperfused with linogliride. These data suggest that linogliride and tolbutamide may have a similar mechanism of action.

Inhibition of peripheral aromatization in the male cynomolgus monkey by a novel nonsteroidal aromatase inhibitor (R 76713)

R 76713 (6-[(4-chlorophenyl)(1-H-1,2,4-trizol-1-yl)methyl]1-H benzotriazole) is a highly potent and selective inhibitor of the aromatase enzyme both in vitro and in vivo. The ability of R 76713 to inhibit peripheral aromatization of androstenedione (A) to estrone (E1) in vivo was studied in male cynomolgus monkeys (Macaca fascicularis). Peripheral aromatization was measured using a primed constant infusion of [3H] A and [14C]E1 for 3.5 h. Blood samples, collected during the final hour of infusion, were analyzed for plasma radioactivity as infused and product steroids. MCRs, conversion ratios (CR), and percent conversion of A to E1 were calculated. R 76713 (0.03-10 microgram/kg) or vehicle (10% hydroxypropyl-beta-cyclodextrin) were administered iv 90 min before beginning the infusion of radiolabeled steroids. In vehicle-treated monkeys, the aromatization of A (mean +/- SEM, 1.35 +/- 0.11%) was similar to that previously reported for cynomolgus and rhesus monkeys, baboons, and humans. Aromatization of A, measured 4-5 h after injection of R 76713, was dose-dependently decreased from the control value by 87 +/- 3%, 85 +/- 2%, 61 +/- 5%, and 33 +/- 8% (all P less than 0.05) at doses of 10.0, 3.0, 0.3, and 0.03 micrograms/kg, respectively, with an ID50 of 0.13 microgram/kg, iv (95% confidence interval, 0.06-0.21). When measured 15-16 h after iv administration of 3.0 micrograms/kg R 76713, aromatization (0.55 +/- 0.13%) was significantly inhibited by 53 +/- 11% compared to that in control monkeys (1.16 +/- 0.18%). The CRs between androgens, the CRs between estrogens, and the MCRs of A and E1 were not significantly altered by R 76713 compared to those after vehicle treatment. R 76713 potently decreased peripheral conversion of androgen to estrogen in vivo in male cynomolgus monkeys and may be a useful therapeutic agent in treating estrogen-dependent diseases, including post-menopausal breast cancer.

New non-steroidal aromatase inhibitors: focus on R76713

R76713 is a novel triazole derivative which selectively blocks the cytochrome P450-dependent aromatase. In human placental microsomes, in FSH-stimulated rat and human granulosa cells and in human adipose stromal cells, 50% inhibition of estradiol biosynthesis was obtained at drug concentrations of 2-10 nM. In PMSG-injected female rats, R76713 lowered plasma estradiol levels by 50 and 90% 2 h after single oral doses of 0.005 and 0.05 mg/kg respectively. After 1 mg/kg, estradiol levels were suppressed by 90% for 16 h. In male cynomolgus monkeys, R76713 dose-dependently (0.03-10 micrograms/kg) inhibited peripheral aromatization with an ED50 of 0.13 microgram/kg without altering metabolic clearance rates and conversion ratios. In vitro R76713 had no effect on other P450-dependent steroidogenic enzymes up to 1000 nM at least. In rats, LHRH-, ACTH- and sodium-deprived diet stimulated plasma testosterone, corticosterone and aldosterone levels were not modified 2 h after single oral administrations of R76713 (up to 20 mg/kg). Furthermore, R76713 did not show any in vitro or in vivo estrogenic or antiestrogenic property. R76713 also induced regression of DMBA-induced mammary tumors after daily oral administration of 1 mg/kg b.i.d. In male volunteers (n = 4), a single oral dose of 5 and 10 mg lowered median plasma estradiol levels from 70 pM to the detection limit of the assay (40 pM) 4, 8 and 24 h after intake whereas no changes were detected after placebo administration. In premenopausal women (n = 15), receiving a single oral dose of 20 mg, median plasma estradiol levels decreased from 389 pM (before) to 168, 133 and 147 pM, 4, 8 and 24 h after intake whereas they remained above 420 pM after placebo (n = 7).

Carbohydrate biguanides as potential hypoglycemic agents

A series of monosaccharides containing a biguanide functionality was prepared and evaluated for hypoglycemic activity. Among the analogues prepared were those involving D-glucose substituted on the 6- or 1-position (19 and 24), D-galactose substituted on the 6-position (7), and D-arabinose (31). The target compounds were evaluated in a modified rat glucose-tolerance test (oral glucose load/oral drug, 100 mg/kg). Compounds 8 [6-biguanidino-1,2:3,5-bis-O-(1-methylethylidene)-6-deoxy-al pha-D- glucofuranose] and 23 [methyl 6-biguanidino-6-deoxy-2,3,4-O-tribenzyl-alpha-D-glucopyra nos ide] were the most active, exhibiting nearly equivalent hypoglycemic activity to that of phenformin (1) and metformin (2), as measured by the inhibition of the rise of blood glucose. Compound 31 was somewhat less active with 26% inhibition, as compared to 64% inhibition with 1 and 41% inhibition with 2.

Effect of the fatty acid oxidation inhibitor methyl palmoxirate (methyl 2-tetradecylglycidate) on recovery from insulin-induced hypoglycemia in diabetic dogs

Methyl palmoxirate, an effective hypoglycemic agent administered p.o., has been shown to decrease hepatic glucose production secondary to inhibition of mitochondrial fatty acid oxidation. Because the ability to increase hepatic glucose production is an important counter-regulatory defense against hypoglycemia, we compared the ability of streptozotocin/alloxan-induced diabetic dogs treated p.o. with vehicle or methyl palmoxirate (2.5 mg/kg/day X 7 days) to recover from insulin-induced hypoglycemia. Hepatic glucose production and glucose utilization were determined by isotope dilution before and after acute reduction of plasma glucose by i.v. insulin injection (0.10 or 0.13 U/kg). Diabetic dogs treated with methyl palmoxirate for 6 days had lower overnight fasting plasma glucose levels than vehicle-treated animals (158 +/- 7 vs. 171 +/- 11, respectively, P less than .05). Plasma glucose at 4 hr after the last dose of drug decreased to 115 +/- 5 mg/dl, whereas glucose in the vehicle-treated dogs was unchanged (172 +/- 8 mg/dl). Recovery from insulin-induced hypoglycemia (nadirs of 58 +/- 5 and 42 +/- 4 mg/dl in the vehicle- and methyl palmoxirate-treated groups, respectively) was not significantly different between the two groups of dogs. Restoration of plasma glucose was primarily due to increased hepatic glucose production in both treatment groups, as glucose utilization did not fall significantly below baseline levels. Plasma glucagon levels increased in both vehicle- and methyl palmoxirate-treated dogs in response to hypoglycemia, indicating that release of an important counter-regulatory hormone was not compromised by drug treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Aromatase inhibition by R 76713: experimental and clinical pharmacology

R 76713 is a new non-steroidal compound which inhibits aromatase in vitro and in vivo with a potency of at least 1000-fold that of aminoglutethimide. In male cynomolgus monkeys peripheral conversion of labeled androstenedione to estrone is decreased by 85%, 4-5 h after a single intravenous dose of 0.003 mg/kg of R 76713, without altering steroid metabolic clearance rates. In rats fed a sodium-depleted diet for 3 weeks, plasma levels of aldosterone and plasma renin activity remain unchanged 2 h after a single oral dose of up to 20 mg/kg of R 76713. This confirms previous data on the selectivity of R 76713 for aromatase inhibition as compared to inhibition of other enzymes involved in steroid biosynthesis. In male volunteers, a single oral dose of 5 or 10 mg of R 76713 lowers median plasma estradiol levels from 70 pM to the detection limit of the assay (30 pM) 4 and 8 h after intake, whereas no important changes are detected after placebo administration. In 15 premenopausal female volunteers receiving a single oral dose of 20 mg of R 76713, mean plasma estradiol levels decrease from 415 pM (before) to 179, 149 and 185 pM respectively 4, 8 and 24 h after intake whereas they remain above 380 pM after placebo (n = 7).

Hypoglycaemic and hypoketonaemic effects of single and repeated oral doses of methyl palmoxirate (methyl 2-tetradecylglycidate) in streptozotocin/alloxan-induced diabetic dogs

1. The hypoglycaemic and hypoketonaemic effects of orally administered methyl palmoxirate were studied in streptozotocin/alloxan-induced diabetic dogs. 2. Single oral 50 mg doses (approximately 7.5 mg kg-1) of methyl palmoxirate produced statistically significant reductions of plasma glucose (32 +/- 6% maximum reduction from baseline) and ketones (74 +/- 12% maximum reduction from baseline), with the peak effect on plasma ketones (3.5 h) preceding that for plasma glucose (6.0 h). 3. Lower doses (0.7-2.0 mg kg-1 daily) of methyl palmoxirate given repeatedly for seven days produced reductions of blood glucose and ketones equivalent to those produced with the higher single dose. Maximal reductions of plasma ketones were generally observed following the first dose of drug, whereas significant lowering of plasma glucose required several days of continuous dosing. 4. Repeated daily doses of methyl palmoxirate markedly reduced the overnight fasting ketone levels but not glucose levels of diabetic dogs. 5. In conclusion, administration of the fatty acid oxidation inhibitor methyl palmoxirate, in the absence of concomitant insulin therapy, was able to lower the plasma glucose and ketone levels of insulin-deficient streptozotocin/alloxan diabetic dogs. Only the plasma ketones were decreased to normal by this treatment.

Effect of the fatty acid oxidation inhibitor 2-tetradecylglycidic acid (TDGA) on glucose and fatty acid oxidation in isolated rat soleus muscle

1. The effect of 2-tetradecylglycidic acid (TDGA), a potent, specific inhibitor of long-chain fatty acid oxidation, on fatty acid and glucose oxidation by isolated rat soleus muscle was studied. 2. TDGA inhibited [1-14C]palmitate oxidation by soleus muscle in a concentration-dependent manner. 3. TDGA inhibited the activity of soleus muscle mitochondrial carnitine palmitoyltransferase A (CPT-A). 4. Added palmitate (0.5 mM) significantly inhibited D-[U-14C]glucose oxidation and, under conditions where TDGA inhibited palmitate oxidation, the oxidation of D-[U-14C]glucose by isolated soleus muscle was significantly stimulated. 5. TDGA stimulation of glucose oxidation was reversed by octanoate, a medium-chain fatty acid whose oxidation is not inhibited by TDGA. 6. When nondiabetic rats were treated with TDGA (10 mg/kg p.o./day x 3 days), fasting plasma glucose was significantly lowered and the ability of isolated contralateral soleus muscles to oxidize palmitate was inhibited while glucose oxidation was significantly stimulated.

Influence of the oral hypoglycemic agent linogliride (McN-3935) on insulin secretion from isolated rat islets of Langerhans

The influence of a new orally effective hypoglycemic compound, linogliride (McN-3935), on insulin release from isolated perifused rat islets was investigated. At a concentration of 100 microM, linogliride was without effect on insulin secretion in the absence of glucose. While 5.5 mM glucose alone produced a weak secretagogue effect, the secretory response was dramatically (5- to 6-fold) increased by the addition of 100 microM linogliride. This concentration of linogliride did not affect the conversion of [5-3H]glucose to 3H2O, a measure of the rate of glycolysis by the islet. Insulin secretion in response to the combination of 100 microM linogliride and 5.5 mM glucose was abolished by the omission of extracellular calcium. Mannoheptulose (10 mM), an inhibitor of glucose phosphorylation and glucose-stimulated insulin secretion, markedly attenuated the insulinotropic effect of linogliride in parallel with reduced glucose usage. Paradoxically, in the presence of another metabolic inhibitor, 2-deoxyglucose (10 mM), the insulinotropic effect of linogliride (100 microM) in the presence of 5.5 mM glucose was not diminished despite the reduced glucose usage. Linogliride significantly increased the secretory response to other secretagogues, including 2.5 mM D-glyceraldehyde, 15 mM N-acetylglucosamine, 10 mM leucine, and 100 nM of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. These data suggest that linogliride amplifies a cellular signal generated during beta-cell activation by various stimulants.

Comparison and effects of natural and synthetic glucose tolerance factor in normal and genetically diabetic mice

Glucose tolerance factor (GTF) is thought to be volatile in the dry state at certain temperatures. This property allowed us to measure the stable and the volatile chromium contents of three brewer's yeast GTF preparations and to investigate the possible relationship between the volatile chromium content and its biologic activity. Two forms of chromium were found in brewer's yeast extracts by flameless atomic absorption spectroscopy using two different methods of sample preparation. Three brewer's yeast GTF preparations were found to contain total Cr concentrations ranging from 0.40 to 0.81 μg. per milligram dry weight and volatile Cr concentrations ranging from 0.02 to 0.39 μg. per milligram dry weight. The biologic response obtained with each GTF preparation was linearly related to the concentration of volatile chromium present. These observations suggest that the volatile chromium fraction in brewer's yeast is biologically important, whereas the active component of these yeast preparations is probably a precursor of GTF.

The metabolic effects of synthetic chromium-nicotinic add-ammo acid complexes and a brewer's yeast GTF preparation were compared in normal and genetically diabetic mice. The synthetic preparations mimicked the effects of brewer's yeast GTF by lowering plasma glucose and triglyceride concentrations, although at different time courses. In addition, biologically active synthetic complexes have been synthesized and may contain no volatile chromium. Synthetic complexes of chromium-nicotinic acid-amino acids lowered blood glucose by only IS to 20 per cent in normal mice as against a 36 per cent reduction with brewer's yeast GTF. Further, a synthetic product produced a significant reduction in the elevated plasma concentrations of glucose and triglycerides in genetically diabetic mice (18 and 26 per cent, respectively). This is in contrast to the 29 per cent reduction in plasma glucose and a 56 per cent reduction in plasma triglycerides produced by GTF prepared from brewer's yeast. These findings suggest that the synthetic factors are similar to, but not identical with, the active GTF fraction extracted from brewer's yeast.

Metabolic effects of the glucose tolerance factor (GTF) in normal and genetically diabetic mice

The acute metabolic effects of glucose tolerance factor (GTF), the biologically active form of trivalent chromium, were studied in normal and genetically diabetic (db/db) mice. A single intraperitoneal injection of GTF significantly reduced the nonfasting plasma glucose level in normal mice by 38 per cent, and in diabetic mice by 14 to 29 per cent. Time course studies in normal and diabetic mice showed a maximal lowering of plasma glucose at four hours after GTF treatment. Furthermore, a single injection of GTF significantly lowered the elevated plasma triglyceride and cholesterol levels by 47 and 35 per cent, respectively, four hours after injection. Genetically diabetic mice are refractory to insulin, and treatment with exogenous insulin produced a smaller decrement in plasma glucose (11-18 per cent). The combination treatment of diabetic mice with GTF and exogenous insulin was significantly more effective in reducing plasma glucose (39-51 per cent) and triglycerides (76 per cent) than either treatment alone. These findings are consistent with the suggestion that GTF and insulin act synergistically.

The influence of age on the development of hypertriglyceridaemia and hypercholesterolaemia in genetically diabetic mice

The effect of spontaneous diabetes on plasma lipids during the natural course of the disease was studied in genetically diabetic mice (C57BL/KsJ-db/db). Hyperlipidaemia developed uniformly in all mice studied and was found to be a characteristic part of the diabetic syndrome, as compared to normal littermates. The hyperlipidaemia was characterized by a marked rise in plasma triglyceride levels with age and severity of the disease increaing from 120+/-6 mg/dl at 5 weeks of age to 400+/-91 mg/dl at 19 weeks of age. In addition, db/db mice were observed to be hypercholesterolaemic as compared to age-matched normal littermates, The plasma cholesterol levels of diabetic mice were elevated early in the disease, as compared to control mice (200+/-6 vs. 130+/-7 mg/dl, respectively), and the mean level remained elevated throughout the period of observation.