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Antihyperglycemic mechanism of M16209, an antidiabetic agent, in 3T3-L1 adipocytes.

We investigated the effect of M16209 (1-(3-bromobenzo[b]furan-2-ylsulfonyl)hydantoin) on glucose transport and the insulin signaling system in mouse-derived 3T3-L1 adipocytes. When M16209 (30 and 100 microM) was added to 3T3-L1 adipocytes and preincubated for 24 hours, the uptake of 2-deoxy-D-[3H]-glucose (2-DG) after insulin stimulation was enhanced. This effect was seen when preincubation with M16209 was performed in the presence of 6 and 20 ng/ml insulin, but M16209 did not increase the response to 600 ng/ml insulin. M16209 (100 microM) did not interfere with (125)I-insulin binding or with tyrosine phosphorylation of the insulin receptor beta-subunit and IRS-1. M16209 (100 microM) also had no effect on the level of glucose transporter (GLUT1 and GLUT4) protein, but it promoted the translocation of intracellular GLUT4 to the plasma membrane. In contrast, M16209 had no effect on the translocation of GLUT1. In summary, M16209 enhanced 2-DG uptake by 3T3-L1 adipocytes. Insulin binding to its receptor, autophosphorylation of the insulin receptor beta-subunit, and tyrosine phosphorylation of IRS-1 were unaffected by M16209. However, translocation of GLUT4 from the intracellular pool to the plasma membrane was facilitated.

3T3 Cells↗

Counteraction of retinoic acid and 1,25-dihydroxyvitamin D3 on up-regulation of adipocyte differentiation with PPARgamma ligand, an antidiabetic thiazolidinedione, in 3T3-L1 cells.

Retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (1,25 (OH)2 D3) inhibited adipocyte differentiation of 3T3-L1 preadipocytes in the presence of thiazolidinedione, a specific ligand for peroxisome proliferator-activated receptory (PPARgamma). These fat-soluble vitamins repressed the up-regulated protein expression of PPARgamma2 during the first 40 hours of initiation of 3T3-L1 preadipocyte differentiation. Compared with RA, 1,25 (OH)2 D3 inhibited PPARgamma2 expression more effectively and caused concomitantly a greater inhibition of adipocyte differentiation. These results suggest that the inhibitory action of adipocyte differentiation by RA or 1,25 (OH)2 D3 is exhibited through direct repression of the expression of PPARgamma2 protein, even in the presence of its ligand. They also raise the intriguing possibility that attenuation or amplification of the pharmacological effects of thiazolidinedione that are dependent on PPARgamma in adipose cells is caused by alteration of the levels of these fat-soluble vitamins.

3T3 Cells↗

Long-lasting antidiabetic effect of a dipeptidyl peptidase IV-resistant analog of glucagon-like peptide-1.

Glucagon-like peptide-1(7-37) (GLP-1) is the most potent insulinotropic hormone characterized thus far. Because its activity is preserved in non-insulin-dependent diabetes mellitus (NIDDM) patients, it is considered a potential new drug for the treatment of this disease. One limitation in its therapeutic use is a short half-life in vivo (5 minutes), due in part to a fast degradation by the endoprotease dipeptidylpeptidase IV (DPPIV). Recently, it was reported that GLP-1 became resistant to DPPIV when the alanine residue at position 8 was replaced by a glycine (GLP-1-Gly8). We report here that this change slightly decreased the affinity of the peptide for its receptor (IC50, 0.41 +/- 0.14 and 1.39 +/- 0.61 nmol/L for GLP-1 and GLP-1-Gly8, respectively) but did not change the efficiency to stimulate accumulation of intracellular cyclic adenosine monophosphate (cAMP) (EC50, 0.25 +/- 0.05 and 0.36 +/- 0.06 nmol/L for GLP-1 and GLP-1-Gly8, respectively). Second, we demonstrate for the first time that this mutant has an improved insulinotropic activity compared with the wild-type peptide when tested in vivo in an animal model of diabetes. A single injection of 0.1 nmol GLP-1-Gly8 in diabetic mice fed a high-fat diet can correct fasting hyperglycemia and glucose intolerance for several hours, whereas the activity of 1 nmol GLP-1 vanishes a few minutes after injection. These actions were correlated with increased insulin and decreased glucagon levels. Interestingly, normoglycemia was maintained over a period that was longer than the predicted peptide half-life, suggesting a yet undescribed long-term effect of GLP-1-Gly8. GLP-1-Gly8 thus has a markedly improved therapeutic potential compared with GLP-1, since it can be used at much lower doses and with a more flexible schedule of administration.

Animals↗

Subacute hepatic failure associated with a new antidiabetic agent, troglitazone: a case report with autopsy examination.

An autopsy case of fatal subacute hepatic failure after administration of troglitazone is described. The liver dysfunction developed about five months after the patient, a sixty-three-year-old woman, had been initially treated with troglitazone. The patient developed hepatic failure and died despite various hepatic auxiliary treatments such as plasmapheresis. Autopsy findings revealed focal liver cell necrosis, cholestasis and steatosis with infiltration of lymphocytes and neutrophils and lack of regenerative activity. The causative mechanism of liver dysfunction may be metabolite aberration, as a result of accumulation of hepatotoxic metabolite(s), in a category of idiosyncratic liver injury. It is proposed to monitor liver function strictly and periodically for the diabetic patients prescribed troglitazone.

Chromans↗

Novel lipid-lowering properties of Vaccinium myrtillus L. leaves, a traditional antidiabetic treatment, in several models of rat dyslipidaemia: a comparison with ciprofibrate.

Vaccinium myrtillus L. (blueberry) leaf infusions are traditionally used as a folk medicine treatment of diabetes. To further define this therapeutical action, a dried hydroalcoholic extract of the leaf was administered orally to streptozotocin-diabetic rats for 4 days. Plasma glucose levels were consistently found to drop by about 26% at two different stages of diabetes. Unexpectedly, plasma triglyceride (TG) were also decreased by 39% following treatment. Subsequent to the latter observation, possible lipid-lowering properties of the extract were investigated on other models of hyperlipidaemia and ciprofibrate, a well-established hypolipidaemic drug, was used as a reference compound. Both drug reduced TG levels of rats on hyperlipidaemic diet in a dose-dependent fashion. When administered at single doses over the same experimental period, blueberry and ciprofibrate were effective in lowering TG concentrations in ethanol-treated normolipidaemic animals and in genetically hyperlipidaemic Yoshida rats. Unlike ciprofibrate, however, blueberry failed to prevent the rise in plasma TG elicited by fructose and did not affect free fatty acid levels in any of the above experimental conditions. In rats treated with Triton WR-1339, blueberry feeding induced an hypolipidaemic activity one hour after injection but proved to be ineffective at later time points, thus suggesting that its hypolipidaemic action may reflect improved TG-rich lipoprotein catabolism. In addition, ciprofibrate and the extract were tested for antithrombotic activity using a collagen-triggered model of venous thrombosis in diabetic and Yoshida rats. Only ciprofibrate, however, significantly reduced thrombus formation in diabetics, possibly because of its effects on free fatty acid metabolism, whereas no effect was observed in Yoshida rats. In conclusion, the present findings indicate that active consituent(s) of Vaccinium myrtillus L. leaves may prove potentially useful for treatment of dyslipidaemiae associated with impaired TG-rich lipoprotein clearance.

Animals↗

Ten-year follow-up of antidiabetic drug use, nonadherence, and mortality in a defined population with type 2 diabetes mellitus.

Studies performed for drug registration provide little insight into the long-term use and effectiveness of drugs in "real world" populations and settings. To obtain such insight, we used 10 years of electronic medical-record data from Kaiser Permanente Northwest Division, a large, group-model health maintenance organization in the United States, to study drug transitions, lapses in drug therapy, and mortality among 693 persons with newly diagnosed type 2 diabetes mellitus in 1988. We also studied an equivalently defined cohort of 1071 persons with new diagnoses in 1994, for whom the availability of laboratory results via electronic data permitted additional analyses. Cumulative mortality in the 1988 cohort increased steadily to 207 of 571 patients (36%) by 1997 (year 10). In 1988, 548 of 693 patients (79%) received initial monotherapy with a sulfonylurea. Insulin use rose as the use of sulfonylureas declined. Over this period, 504 of 693 patients (73%) discontinued or added drug therapy. Eight percent to 10% of both sulfonylurea users and insulin users discontinued drug use during the study period. In the 1994 cohort, two thirds of the subjects who discontinued therapy and were tested for glycosylated hemoglobin (Hb A1c) (n = 86) maintained good-to-excellent glycemic control. However, 78 discontinuers (38%) were not tested for Hb A1c, and, among this subset, 32% failed to visit a primary care clinician. The results of this study suggest that 5% to 10% of persons with type 2 diabetes mellitus avoid contact with the medical care system. Avoidance persists for at least the first 10 years after diagnosis but is more common in the first year after diagnosis. In addition, secondary failure of sulfonylureas begins within 1 year of diagnosis and continues at a steady pace. Almost 80% of patients initially treated with sulfonylureas added or switched to metformin or insulin within 10 years of diagnosis.

Cohort Studies↗

An orally active antidiabetic vanadyl complex, bis(1-oxy-2-pyridinethiolato)oxovanadium(IV), with VO(S2O2) coordination mode; in vitro and in vivo evaluations in rats.

According to Pearson's HSAB (hard and soft acids and bases) rule, the vanadyl ion is classified as a hard acid. However, vanadyl-cysteine methyl ester and dithiocarbamate complexes with VO(S2N2) and VO(S4) coordination modes, respectively, that contain bonds with a combination of hard acid (VO2+) and soft base (sulfur) have been found to form stable complexes and exhibit insulin-mimetic activities in in vitro and in vivo evaluations. Based on such observations, a purple bis(1-oxy-2-pyridinethiolato)oxovanadium(IV) (VO(OPT)) complex with VO(S2O2) coordination mode was prepared and found to have a strong insulin-mimetic activity in in vitro evaluation, which followed in vivo effectiveness on intraperitoneal injection and oral administration. Then, we examined the real-time ESR analysis of vanadyl species in the blood of live rats given VO(OPT) by use of the blood circulation monitoring-ESR method. The clearance of vanadyl species from the blood in terms of half-life (t(1/2)) was determined as 15 min in VO(OPT)-treated rats, while t(1/2) of VOSO4-treated rats was 5 min, indicating the long-term acting character of VO(OPT). On the basis of the results, VO(OPT) with VO(S2O2) coordination mode is proposed to be a potent orally active insulin-mimetic complex in treating insulin-dependent diabetes mellitus in experimental animals.

Adipocytes↗

Diabetic KKAy mice exhibit increased hepatic PPARgamma1 gene expression and develop hepatic steatosis upon chronic treatment with antidiabetic thiazolidinediones.

BACKGROUND/AIMS: Peroxisome proliferator-activated receptor-gamma, which is involved in the regulation of lipid homeostasis, is upregulated in the liver of obese and diabetic mice, but the biological consequences of this induction are largely unknown. This study was aimed at further characterizing this upregulation and exploring the downstream biological effects of specific activators on hepatic lipid metabolism. METHODS: Hepatic expression of peroxisome proliferator-activated receptor-gamma1 and gamma2 mRNA and protein was analyzed by real-time polymerase chain reaction and Western immunoblotting in KKAy mice and ob/ob mice. KKAy mice were treated with thiazolidinediones, and hepatic triglyceride content and lipid distribution were analyzed biochemically and by histopathology. RESULTS: KKAy mice exhibited a marked increase in hepatic peroxisome proliferator-activated receptor-gamma1 mRNA and protein levels, whereas the gamma2 isoform was upregulated in ob/ob mice. Treatment of KKAy mice with troglitazone or rosiglitazone resulted in severe microvesicular periacinar steatosis, whereas lean control mice did not develop any pathological liver changes. Hepatic triglyceride levels, however, were not altered by the treatment. CONCLUSIONS: In mice with obesity-associated upregulated hepatic peroxisome proliferator-activated receptor-gamma expression, thiazolidinediones may produce hepatic steatosis. Under pathophysiological conditions, such as non-insulin-dependent diabetes, the liver may thus become sensitized towards peroxisome proliferator-activated receptor-gamma-activating drugs.

Animals↗

Novel phthalazinone and benzoxazinone containing thiazolidinediones as antidiabetic and hypolipidemic agents.

We report here the synthesis of a series of 5-[4-[2-[substituted phthalazinones-2(or 4)yl]ethoxy]phenylmethyl]thiazolidine-2,4-diones and 5-[4-[2-[2,3-benzoxazine-4-one-2-yl]ethoxy]phenylmethyl]thiazolidine-2,4-diones and their plasma glucose and plasma triglyceride lowering activity in db/db mice. In vitro PPARgamma transactivation assay was performed in HEK 293T cells. In vitro and in vivo pharmacological studies showed that the phthalazinone analogue has better activity. PHT46 (compound 5a), the best compound in this series, showed better in vitro PPARgamma transactivation potential than troglitazone and pioglitazone. In insulin resistant db/db mice, PHT46 showed better plasma glucose and triglyceride lowering activity than the standard drugs. Pharmacokinetic study in Wistar rats showed good systemic exposure of PHT46. Subchronic toxicity study in Wistar rats did not show any treatment-related adverse effect.

Animals↗