Pharmacoinformatics and UPLC-QTOF/ESI-MS-Based Phytochemical Screening of Combretum indicum against Oxidative Stress and Alloxan-Induced Diabetes in Long-Evans Rats

This research investigated a UPLC-QTOF/ESI-MS-based phytochemical profiling of Combretum indicum leaf extract (CILEx), and explored its in vitro antioxidant and in vivo antidiabetic effects in a Long-Evans rat model. After a one-week intervention, the animals' blood glucose, lipid profile, and pancreatic architectures were evaluated. UPLC-QTOF/ESI-MS fragmentation of CILEx and its eight docking-guided compounds were further dissected to evaluate their roles using bioinformatics-based network pharmacological tools. Results showed a very promising antioxidative effect of CILEx. Both doses of CILEx were found to significantly (p < 0.05) reduce blood glucose, low-density lipoprotein (LDL), and total cholesterol (TC), and increase high-density lipoprotein (HDL). Pancreatic tissue architectures were much improved compared to the diabetic control group. A computational approach revealed that schizonepetoside E, melianol, leucodelphinidin, and arbutin were highly suitable for further therapeutic assessment. Arbutin, in a Gene Ontology and PPI network study, evolved as the most prospective constituent for 203 target proteins of 48 KEGG pathways regulating immune modulation and insulin secretion to control diabetes. The fragmentation mechanisms of the compounds are consistent with the obtained effects for CILEx. Results show that the natural compounds from CILEx could exert potential antidiabetic effects through in vivo and computational study.

Palmitate is not an effective fuel for pancreatic islets and amplifies insulin secretion independent of calcium release from endoplasmic reticulum

The aim of the study was to determine the acute contribution of fuel oxidation in mediating the increase in insulin secretion rate (ISR) in response to fatty acids. Measures of mitochondrial metabolism, as reflected by oxygen consumption rate (OCR) and cytochrome c reduction, calcium signaling, and ISR by rat islets were used to evaluate processes stimulated by acute exposure to palmitic acid (PA). The contribution of mitochondrial oxidation of PA was determined in the presence and absence of a blocker of mitochondrial transport of fatty acids (etomoxir) at different glucose concentrations. Subsequent to increasing glucose from 3 to 20 mM, PA caused small increases in OCR and cytosolic calcium (about 20% of the effect of glucose). In contrast, the effect of PA on ISR was almost 3 times that by glucose, suggesting that the metabolism of PA is not the dominant mechanism mediating PA's effect on ISR. This was further supported by lack of inhibition of PA-stimulated OCR and ISR when blocking entry of PA into mitochondria (with etomoxir), and PA's lack of stimulation of reduced cytochrome c in the presence of high glucose. Consistent with the lack of metabolic stimulation by PA, an inhibitor of calcium release from the endoplasmic reticulum, but not a blocker of L-type calcium channels, abolished the PA-induced elevation of cytosolic calcium. Notably, ISR was unaffected by thapsigargin showing the dissociation of endoplasmic reticulum calcium release and second phase insulin secretion. In conclusion, stimulation of ISR by PA was mediated by mechanisms largely independent of the oxidation of the fuel.

Endogenous Glucose Production and Hormonal Changes in Response to Canagliflozin and Liraglutide Combination Therapy

The decrement in plasma glucose concentration with SGLT2 inhibitors (SGLT2i) is blunted by a rise in endogenous glucose production (EGP). We investigated the ability of incretin treatment to offset the EGP increase. Subjects with type 2 diabetes (n = 36) were randomized to 1) canagliflozin (CANA), 2) liraglutide (LIRA), or 3) CANA plus LIRA (CANA/LIRA). EGP was measured with [3-³H]glucose with or without drugs for 360 min. In the pretreatment studies, EGP was comparable and decreased (2.2 ± 0.1 to 1.7 ± 0.2 mg/kg ⋅ min) during a 300- to 360-min period (P < 0.01). The decrement in EGP was attenuated with CANA (2.1 ± 0.1 to 1.9 ± 0.1 mg/kg ⋅ min) and CANA/LIRA (2.2 ± 0.1 to 2.0 ± 0.1 mg/kg ⋅ min), whereas with LIRA it was the same (2.4 ± 0.2 to 1.8 ± 0.2 mg/kg ⋅ min) (all P < 0.05 vs. baseline). After CANA, the fasting plasma insulin concentration decreased (18 ± 2 to 12 ± 2 μU/mL, P < 0.05), while it remained unchanged in LIRA (18 ± 2 vs. 16 ± 2 μU/mL) and CANA/LIRA (17 ± 1 vs. 15 ± 2 μU/mL). Mean plasma glucagon did not change during the pretreatment studies from 0 to 360 min, while it increased with CANA (69 ± 3 to 78 ± 2 pg/mL, P < 0.05), decreased with LIRA (93 ± 6 to 80 ± 6 pg/mL, P < 0.05), and did not change in CANA/LIRA. LIRA prevented the insulin decline and blocked the glucagon rise observed with CANA but did not inhibit the increase in EGP. Factors other than insulin and glucagon contribute to the stimulation of EGP after CANA-induced glucosuria.

Do we know the true mechanism of action of the DPP-4 inhibitors?

The prevalence of type 2 diabetes is increasing, which is alarming because of its serious complications. Anti-diabetic treatment aims to control glucose homeostasis as tightly as possible in order to reduce these complications. Dipeptidyl peptidase-4 (DPP-4) inhibitors are a recent addition to the anti-diabetic treatment modalities, and have become widely accepted because of their good efficacy, their benign side-effect profile and their low hypoglycaemia risk. The actions of DPP-4 inhibitors are not direct, but rather are mediated indirectly through preservation of the substrates they protect from degradation. The two incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, are known substrates, but other incretin-independent mechanisms may also be involved. It seems likely therefore that the mechanisms of action of DPP-4 inhibitors are more complex than originally thought, and may involve several substrates and encompass local paracrine, systemic endocrine and neural pathways, which are discussed here.

β-Cell signalling and insulin secretagogues: A path for improved diabetes therapy

Insulin secretagogues including sulfonylureas, glinides and incretin-related drugs such as dipeptidyl peptidase 4 (DPP-4) inhibitors and glucagon-like peptide-1 receptor agonists are widely used for treatment of type 2 diabetes. In addition, glucokinase activators and G-protein-coupled receptor 40 (GPR40) agonists also have been developed, although the drugs are not clinically usable. These different drugs exert their effects on insulin secretion by different mechanisms. Recent advances in β-cell signalling studies have not only deepened our understanding of insulin secretion but also revealed novel mechanisms of insulin secretagogues. Clarification of the signalling mechanisms of the insulin secretagogues will contribute to improved drug therapy for diabetes.

Cyclocarya paliurus extract activates insulin signaling via Sirtuin1 in C2C12 myotubes and decreases blood glucose level in mice with impaired insulin secretion

Diabetes is caused by the lack of release or action of insulin. Some foods and supplements can compensate for this deficiency; thus, they can aid in the prevention or treatment of diabetes. The aim of this study was to investigate the effects of Cyclocarya paliurus extract (CPE) on insulin signaling and its capacity to correct hyperglycemia in the absence of insulin. To investigate the hypoglycemic effects of CPE, C2C12 cells were exposed to CPE (50 and 100 μg/mL). CPE promoted 2-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino)-2-Deoxyglucose (2NBDG) uptake into the cells via translocation of glucose transporter 4 (Glut4) to the plasma membrane. In addition, CPE enhanced tyrosine phosphorylation of insulin receptor substrate and activated phosphatidylinositol 3-kinase and protein kinase B (Akt) via sirtuin1 in C2C12 cells. Moreover, we found that oral administration of CPE (1 g/kg) to streptozotocin-induced hyperglycemic mice produced a progressive decrease in plasma glucose levels at 1 h after single dosing. At that point, CPE significantly increased the expression of skeletal muscle membrane Glut4 and enhanced the phosphorylation of Akt. These results suggest that CPE exerts antidiabetic effects similar to those of insulin, and may be an oral therapeutic alternative for the management of diabetes.

Preclinical characterization of 55P0251, a novel compound that amplifies glucose-stimulated insulin secretion and counteracts hyperglycaemia in rodents

AIMS

55P0251 is a novel compound with blood glucose lowering activity in mice, which has been developed from a molecular backbone structure found in herbal remedies. We here report its basic pharmacological attributes and initial progress in unmasking the mode of action.

MATERIALS AND METHODS

Pharmacokinetic properties of 55P0251 were portrayed in several species. First efforts to elucidate the glucose lowering mechanism in rodents included numerous experimental protocols dealing with glucose tolerance, insulin secretion from isolated pancreatic islets and comparison to established drugs.

RESULTS

A single oral dose of 55P0251 improved glucose tolerance in mice with an ED₅₀ between 1.5 and 2 mg/kg (reductions in areas under the curve, 1 mg/kg, -18%; 5 mg/kg, -30%; 27 mg/kg, -47%). Pharmacokinetic studies revealed attractive attributes, including a plasma half-life of approximately 3 hours and a bioavailability of approximately 58% in rats. 55P0251 amplified glucose stimulated insulin release from isolated mouse islets and improved glucose tolerance via increased insulin secretion in rats (increase in area under the insulin curve, +184%). Unlike sulfonylureas and glinides, 55P0251 hardly stimulated insulin release under basal conditions and did not induce hypoglycaemia in vivo, but it amplified the secretory response to glucose and other insulinotropic stimuli (KCl, glucagon-like peptide-1). Comparison to established anti-diabetic agents and examination of interaction with molecular targets (K_ATP channel, dipeptidyl peptidase-4, glucagon-like peptide-1 receptor) excluded molecular mechanisms addressed by presently marketed drugs.

CONCLUSIONS

55P0251 is a novel compound that potently counteracts hyperglycaemia in rodents via amplification of glucose-stimulated insulin release.

Beneficial effects of protein hydrolysates in exercise and sports nutrition

Protein hydrolysates (PH) are rich sources of proteins that supply the need of exercising muscles. PHs are enriched in di- and tripeptides and are better than free amino acids or intact proteins when muscle anabolic effect is considered. Digestion, absorption and muscle uptake of amino acids are faster and more efficient when PH is ingested in comparison to the respective intact protein. PHs not only enhance endurance in high intensity exercise regimen, but also help in faster post-exercise recovery of muscle by promoting glycogen synthesis, although the latter effect requires more convincing evidence. PHs have been shown to exhibit insulinotrophic effect as it enhances the secretion of insulin and the hormone, in turn, exerts muscle anabolic effect.

Prostaglandin I2 Receptor Agonism Preserves β-Cell Function and Attenuates Albuminuria Through Nephrin-Dependent Mechanisms

Discovery of common pathways that mediate both pancreatic β-cell function and end-organ function offers the opportunity to develop therapies that modulate glucose homeostasis and separately slow the development of diabetes complications. Here, we investigated the in vitro and in vivo effects of pharmacological agonism of the prostaglandin I2 (IP) receptor in pancreatic β-cells and in glomerular podocytes. The IP receptor agonist MRE-269 increased intracellular 3',5'-cyclic adenosine monophosphate (cAMP), augmented glucose-stimulated insulin secretion (GSIS), and increased viability in MIN6 β-cells. Its prodrug form, selexipag, augmented GSIS and preserved islet β-cell mass in diabetic mice. Determining that this preservation of β-cell function is mediated through cAMP/protein kinase A (PKA)/nephrin-dependent pathways, we found that PKA inhibition, nephrin knockdown, or targeted mutation of phosphorylated nephrin tyrosine residues 1176 and 1193 abrogated the actions of MRE-269 in MIN6 cells. Because nephrin is important to glomerular permselectivity, we next set out to determine whether IP receptor agonism similarly affects nephrin phosphorylation in podocytes. Expression of the IP receptor in podocytes was confirmed in cultured cells by immunoblotting and quantitative real-time PCR and in mouse kidneys by immunogold electron microscopy, and its agonism 1) increased cAMP, 2) activated PKA, 3) phosphorylated nephrin, and 4) attenuated albumin transcytosis. Finally, treatment of diabetic endothelial nitric oxide synthase knockout mice with selexipag augmented renal nephrin phosphorylation and attenuated albuminuria development independently of glucose change. Collectively, these observations describe a pharmacological strategy that posttranslationally modifies nephrin and the effects of this strategy in the pancreas and in the kidney.

GPR142 Agonists Stimulate Glucose-Dependent Insulin Secretion via Gq-Dependent Signaling

GPR142 is an islet-enriched G protein-coupled receptor that has been investigated as a novel therapeutic target for the treatment of type 2 diabetes by virtue of its insulin secretagogue activity. However, the signaling pathways downstream of GPR142 and whether its stimulation of insulin release is glucose-dependent remain poorly characterized. In this study, we show that both native and synthetic GPR142 agonists can activate Gq as well as Gi signaling when GPR142 is recombinantly expressed in HEK293 cells. However, in primary pancreatic islets, a native cellular system, the insulin secretagogue activity of GPR142 agonists only requires Gq activation. In addition, our results show that stimulation of insulin secretion by GPR142 in pancreatic islets is strictly glucose-dependent.

Cathelicidin Antimicrobial Peptide: A Novel Regulator of Islet Function, Islet Regeneration, and Selected Gut Bacteria

Cathelicidin antimicrobial peptide (CAMP) is a naturally occurring secreted peptide that is expressed in several organs with pleiotropic roles in immunomodulation, wound healing, and cell growth. We previously demonstrated that gut Camp expression is upregulated when type 1 diabetes-prone rats are protected from diabetes development. Unexpectedly, we have also identified novel CAMP expression in the pancreatic β-cells of rats, mice, and humans. CAMP was present even in sterile rat embryo islets, germ-free adult rat islets, and neogenic tubular complexes. Camp gene expression was downregulated in young BBdp rat islets before the onset of insulitis compared with control BBc rats. CAMP treatment of dispersed islets resulted in a significant increase in intracellular calcium mobilization, an effect that was both delayed and blunted in the absence of extracellular calcium. Additionally, CAMP treatment promoted insulin and glucagon secretion from isolated rat islets. Thus, CAMP is a promoter of islet paracrine signaling that enhances islet function and glucoregulation. Finally, daily treatment with the CAMP/LL-37 peptide in vivo in BBdp rats resulted in enhanced β-cell neogenesis and upregulation of potentially beneficial gut microbes. In particular, CAMP/LL-37 treatment shifted the abundance of specific bacterial populations, mitigating the gut dysbiosis observed in the BBdp rat. Taken together, these findings indicate a novel functional role for CAMP/LL-37 in islet biology and modification of gut microbiota.

Lixisenatide reduces postprandial hyperglycaemia via gastrostatic and insulinotropic effects

BACKGROUND

Lixisenatide is a once-daily, prandial, short-acting glucagon-like peptide-1 receptor agonist. Its main antidiabetic effect is to delay gastric emptying to control postprandial plasma glucose excursions. The dose-response relationship of the integrated insulinotropic and gastrostatic response to lixisenatide in healthy volunteers after a standardized liquid meal was investigated.

METHODS

Twenty healthy subjects received acetaminophen 1000 mg with a standardized liquid meal 60 min after a single subcutaneous injection of placebo or lixisenatide 2.5, 5, 10 or 20 µg in randomized order separated by a 2- to 7-day washout. Acetaminophen pharmacokinetics served as a surrogate to assess rate of gastric emptying. Postprandial plasma glucose, insulin, C-peptide and glucagon were assessed for 5 h after the meal test, and lixisenatide pharmacokinetics were determined for 6 h.

RESULTS

After lixisenatide administration and prior to the standardized meal, insulin and C-peptide transiently increased, while fasting plasma glucose decreased in a dose-dependent manner. After the meal, postprandial plasma glucose, insulin and C-peptide were dose proportionally reduced with lixisenatide versus placebo for up to 6 h. Compared with placebo, glucagon levels were transiently lower after any lixisenatide dose, with more sustained reductions after the meal and no apparent dose-related trends. Acetaminophen absorption was significantly reduced and delayed compared with placebo for lixisenatide doses ≥5 µg and demonstrated dose-dependent slowing of gastric emptying. Lixisenatide displayed near dose-proportional exposure, with gastrointestinal events increasing with dose.

CONCLUSIONS

Lixisenatide reduced fasting plasma glucose via stimulation of glucose-dependent insulin release and controlled postprandial plasma glucose by delaying gastric emptying, demonstrating it to be a valuable option for overall glycaemic control.

Effect of insulin sensitizer therapy on amino acids and their metabolites

AIMS

Prior studies have reported that elevated concentrations of several plasma amino acids (AA), particularly branched chain (BCAA) and aromatic AA predict the onset of type 2 diabetes. We sought to test the hypothesis that circulating BCAA, aromatic AA and related AA metabolites decline in response to the use of insulin sensitizing agents in overweight/obese adults with impaired fasting glucose or untreated diabetes.

METHODS

We performed a secondary analysis of a randomized, double-blind, placebo, controlled study conducted in twenty five overweight/obese (BMI ~30kg/m(2)) adults with impaired fasting glucose or untreated diabetes. Participants were randomized to three months of pioglitazone (45mg per day) plus metformin (1000mg twice per day, N=12 participants) or placebo (N=13). We measured insulin sensitivity by the euglycemic-hyperinsulinemic clamp and fasting concentrations of AA and AA metabolites using ultra-pressure liquid chromatography tandem mass spectrometry before and after the three-month intervention.

RESULTS

Insulin sensitizer therapy that significantly enhanced insulin sensitivity reduced 9 out of 33 AA and AA metabolites measured compared to placebo treatment. Moreover, insulin sensitizer therapy significantly reduced three functionally clustered AA and metabolite pairs: i) phenylalanine/tyrosine, ii) citrulline/arginine, and iii) lysine/α-aminoadipic acid.

CONCLUSIONS

Reductions in plasma concentrations of several AA and AA metabolites in response to three months of insulin sensitizer therapy support the concept that reduced insulin sensitivity alters AA and AA metabolites.

The cholesterol-lowering agent methyl-β-cyclodextrin promotes glucose uptake via GLUT4 in adult muscle fibers and reduces insulin resistance in obese mice

Insulin stimulates glucose uptake in adult skeletal muscle by promoting the translocation of GLUT4 glucose transporters to the transverse tubule (T-tubule) membranes, which have particularly high cholesterol levels. We investigated whether T-tubule cholesterol content affects insulin-induced glucose transport. Feeding mice a high-fat diet (HFD) for 8 wk increased by 30% the T-tubule cholesterol content of triad-enriched vesicular fractions from muscle tissue compared with triads from control mice. Additionally, isolated muscle fibers (flexor digitorum brevis) from HFD-fed mice showed a 40% decrease in insulin-stimulated glucose uptake rates compared with fibers from control mice. In HFD-fed mice, four subcutaneous injections of MβCD, an agent reported to extract membrane cholesterol, improved their defective glucose tolerance test and normalized their high fasting glucose levels. The preincubation of isolated muscle fibers with relatively low concentrations of MβCD increased both basal and insulin-induced glucose uptake in fibers from controls or HFD-fed mice and decreased Akt phosphorylation without altering AMPK-mediated signaling. In fibers from HFD-fed mice, MβCD improved insulin sensitivity even after Akt or CaMK II inhibition and increased membrane GLUT4 content. Indinavir, a GLUT4 antagonist, prevented the stimulatory effects of MβCD on glucose uptake. Addition of MβCD elicited ryanodine receptor-mediated calcium signals in isolated fibers, which were essential for glucose uptake. Our findings suggest that T-tubule cholesterol content exerts a critical regulatory role on insulin-stimulated GLUT4 translocation and glucose transport and that partial cholesterol removal from muscle fibers may represent a useful strategy to counteract insulin resistance.

Fibroblast growth factor 21 improves insulin sensitivity and synergizes with insulin in human adipose stem cell-derived (hASC) adipocytes

Fibroblast growth factor 21 (FGF21) has evolved as a major metabolic regulator, the pharmacological administration of which causes weight loss, insulin sensitivity and glucose control in rodents and humans. To understand the molecular mechanisms by which FGF21 exerts its metabolic effects, we developed a human in vitro model of adipocytes to examine crosstalk between FGF21 and insulin signaling. Human adipose stem cell-derived (hASC) adipocytes were acutely treated with FGF21 alone, insulin alone, or in combination. Insulin signaling under these conditions was assessed by measuring tyrosine phosphorylation of insulin receptor (InsR), insulin receptor substrate-1 (IRS-1), and serine 473 phosphorylation of Akt, followed by a functional assay using 14C-2-deoxyglucose [¹⁴C]-2DG to measure glucose uptake in these cells. FGF21 alone caused a modest increase of glucose uptake, but treatment with FGF21 in combination with insulin had a synergistic effect on glucose uptake in these cells. The presence of FGF21 also effectively lowered the insulin concentration required to achieve the same level of glucose uptake compared to the absence of FGF21 by 10-fold. This acute effect of FGF21 on insulin signaling was not due to IR, IGF-1R, or IRS-1 activation. Moreover, we observed a substantial increase in basal S473-Akt phosphorylation by FGF21 alone, in contrast to the minimal shift in basal glucose uptake. Taken together, our data demonstrate that acute co-treatment of hASC-adipocytes with FGF21 and insulin can result in a synergistic improvement in glucose uptake. These effects were shown to occur at or downstream of Akt, or separate from the canonical insulin signaling pathway.

Identification of diarylsulfonamides as agonists of the free fatty acid receptor 4 (FFA4/GPR120)

The exploration of a diarylsulfonamide series of free fatty acid receptor 4 (FFA4/GPR120) agonists is described. This work led to the identification of selective FFA4 agonist 8 (GSK137647A) and selective FFA4 antagonist 39. The in vitro profile of compounds 8 and 39 is presented herein.

[Insulin potentiating and antidepressant effects of 3-oxypyridine and succinic acid derivatives]

The dependence of the antidepressant action of 3-oxypyridine and succinic acid derivatives (emoxipine, reamberin, and mexidol) on the insulin potentiating activity of these therapeutic agents has been studied in experiments on rats. Alpha-lipoic acid was used as a reference drug. It was established that single administration of emoxipine, reamberin, mexidol and alpha-lipoic acid in optimal doses, corresponding to the therapeutic range in humans, increased the sensitivity of animals to insulin according to the criterion of insulin coma development. Triple administration of the therapeutic agents studied in the same single dose produced an antidepressant effect according to the criterion of "desperate behavior" in Porsolt forced swimming test. Standardization of obtained data by average difference from the control and further correlation analysis demonstrated that the extent of antidepressant action of emoxipine, reamberin, mexidol and alpha-lipoic acid considerably depends on their insulin potentiating activity (r = 0.762, p = 0.004).

Comparison of independent and combined metabolic effects of chronic treatment with (pGlu-Gln)-CCK-8 and long-acting GLP-1 and GIP mimetics in high fat-fed mice

AIM

The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK) are gastrointestinal peptides with important physiological effects. However, rapid enzymatic degradation results in short-lived biological actions.

METHODS

This study has examined metabolic actions of exendin-4, GIP[mPEG] and a novel CCK-8 analogue, (pGlu-Gln)-CCK-8 as enzymatically stable forms of GLP-1, GIP and CCK, respectively.

RESULTS

All peptides significantly (p < 0.01-p < 0.001) stimulated insulin secretion from BRIN BD11 cells, and acute in vivo experiments confirmed prominent antihyperglycaemic and insulinotropic responses to GLP-1 or GIP receptor activation in normal mice. Twice daily injection of (pGlu-Gln)-CCK-8 alone and in combination with exendin-4 or GIP[mPEG] in high fat-fed mice significantly decreased accumulated food intake (p < 0.05-p < 0.01), body weight gain (p < 0.05-p < 0.01) and improved (p < 0.05) insulin sensitivity in high fat-fed mice. However, there was no evidence for superior effects compared to (pGlu-Gln)-CCK-8 alone. Combined treatment of (pGlu-Gln)-CCK-8 and exendin-4 resulted in significantly (p < 0.05) lowered circulating glucose levels and improved (p < 0.05) intraperitoneal glucose tolerance. These effects were superior to either treatment regime alone but not associated with altered insulin concentrations. A single injection of (pGlu-Gln)-CCK-8, or combined with exendin-4, significantly (p < 0.05) lowered blood glucose levels 24 h post injection in untreated high fat-fed mice.

CONCLUSION

This study highlights the potential of (pGlu-Gln)-CCK-8 alone and in combination with incretin hormones for the treatment of type 2 diabetes.

AMG 837: a novel GPR40/FFA1 agonist that enhances insulin secretion and lowers glucose levels in rodents

Agonists of GPR40 (FFA1) have been proposed as a means to treat type 2 diabetes. Through lead optimization of a high throughput screening hit, we have identified a novel GPR40 agonist called AMG 837. The objective of these studies was to understand the preclinical pharmacological properties of AMG 837. The activity of AMG 837 on GPR40 was characterized through GTPγS binding, inositol phosphate accumulation and Ca(2+) flux assays. Activity of AMG 837 on insulin release was assessed on isolated primary mouse islets. To determine the anti-diabetic activity of AMG 837 in vivo, we tested AMG 837 using a glucose tolerance test in normal Sprague-Dawley rats and obese Zucker fatty rats. AMG 837 was a potent partial agonist in the calcium flux assay on the GPR40 receptor and potentiated glucose stimulated insulin secretion in vitro and in vivo. Acute administration of AMG 837 lowered glucose excursions and increased glucose stimulated insulin secretion during glucose tolerance tests in both normal and Zucker fatty rats. The improvement in glucose excursions persisted following daily dosing of AMG 837 for 21-days in Zucker fatty rats. Preclinical studies demonstrated that AMG 837 was a potent GPR40 partial agonist which lowered post-prandial glucose levels. These studies support the potential utility of AMG 837 for the treatment of type 2 diabetes.

[Long-term evaluation of patients with type 1 diabetes mellitus treated with insulin glargine]

AIMS OF THE STUDY

To evaluate long-term effects of treatment with insulin analogue glargine in patients with type 1 diabetes mellitus and to follow up their further course of life.

PATIENT SAMPLE AND METHODOLOGY

Retrospective evaluation of 114 patients who, from September 2004, had their basal insulin changed from NPH insulin to insulin glargine. Treatment was changed again in patients in whom a year-long treatment with insulin glargine did not bring improvement in diabetes control. The original sample was divided into 3 groups and the results compared. Compensation of diabetes (HbA1c) after 1, 2 and 3 years and changes to basal and bolus daily insulin dose and body weight were evaluated.

RESULTS

The results are presented as median and 25th and 75th percentile. Group A--75 patients (65%) treated for the entire evaluation period with insulin glargine. Initial HbA1c was 7.3 (6.4-8.2)%, 6.9 (6.0-8.4)% after 1 year, 7.1 (5.9-7.9)% after 2 years and 6.6 (5.5-7.7)% after 3 years (p < 0.001). We did not identify any statistically significant changes to total, basal or bolus daily dose of insulin or statistically significant body weight increase over the evaluation period. Group B--19 patients (17%). Switch from insulin glargine to detemir twice daily. Initial HbA1c was 7.3 (6.9-8.5)%, 7.4 (6.8-8.7)% after 1 year of treatment with insulin glargine, 7.7 (7.2-8.1)% before the treatment switch and 7.8 (6.7-8.5)% (NS) after 3 years of treatment. Daily dose of total, basal and bolus insulin did not change and, similarly, no statistically significant change to patients' bodyweight was identified. Group C--17 patients (15%). Switch from insulin glargine to an insulin pump. This group had better initial compensation with HbA1c 6.7(5.7-8.6)%, HbA1c after 1 year was 6.2 (5.6-8.1)%, 7.0 (6.0-7.4)% before the treatment switch and 6.3 (5.2-7.7)% after 3 years of treatment. Total daily insulin dose: 48 (34-60)-38 (25-49) IU/day (NS). Basal daily insulin dose: 17.5 (13-28) IU/day-23 (12-32) IU/day (NS). Bolus daily dose decreased significantly: from 25.5 (21-33) to 15.5 (12-22) IU/day (p < 0.01). Body weight: 76 (71-97) kg-73 (72-99) kg (NS). Only 3% of patients went back to NPH insulin.

CONCLUSION

Insulin glargine brings improved control of diabetes. The dose of insulin glargine did not differ from NPH insulin. No statistically significant body weight increase was observed during the evaluation period.

Insulin-sensitizing activities of tanshinones, diterpene compounds of the root of Salvia miltiorrhiza Bunge

In this study, the effects of the extract and four tanshinone compounds from the dried root of Salvia miltiorrhiza Bunge (Labiatae) on the tyrosine phosphorylation of the insulin receptor (IR) beta-subunit and the downstream signaling were examined in Chinese-hamster ovary cells expressing human insulin receptors (CHO/IR cells) as well as in 3T3-L1 adipocytes. In addition the translocation of the glucose transporter 4 was investigated in 3T3-L1 adipocytes. Total extract of Danshen (1-10 microg/ml) and the four tanshinones (10 microM) did not show any activity, but the total extract and the tanshinone I, IIA and 15, 16-dihydrotanshinone I except cryptotanshinone enhanced the activity of insulin (1 nM) on the tyrosine phosphorylation of the IR as well as the activation of the downstream kinases Akt, ERK1/2, and GSK3beta. In the adipocytes the same IR-downstream signaling and the translocation of glucose transporter 4 were demonstrated by the three tanshinones in the presence of insulin. These insulin-sensitizing activities of tanshinones may be useful for developing a new class of specific IR activators as anti-diabetic agents.

[Insulin detemir in the predictive study: results in patients with type 1 diabetes in the Belgian cohort]

Insulin detemir (Levemir) is a soluble human insulin analogue acylated with a 14-carbon fatty acid, which reversibly binds to albumin, thereby providing a more prolonged metabolic effect with lower variability as compared to NPH insulin taken as reference. Thanks to this pharmacokinetic and pharmacodynamic profile, insulin detemir is essentially used within a basal-bolus regimen. We report the results obtained in 232 type 1 diabetic patients recruited in Belgium in the frame of the international observational, open, prospective PREDICTIVE study. In patients initially treated with either NPH insulin or glargine, followed for 26 weeks, the shift to insulin detemir did not change HbA1c levels, but significantly reduced both the mean and the variability of fasting blood glucose levels while diminishing the risk of hypoglycaemic episodes, especially at night. Therefore, insulin detemir was associated with significantly improved quality of life. These changes were obtained with a slight increase in daily insulin doses but without weight gain.

[Results of the PREDICTIVE project in the Czech Republic]

INTRODUCTION

The PREDICTIVE project was an international multicentric, open observation study evaluating the safety and efficiency of insulin detemir in clinical practice. 1,695 type 1 or 2 diabetes mellitus (DM) patients were enrolled in the study in the Czech Republic. The patients were treated by insulin detemir for the period of 26 weeks in accordance with the standard scheme implemented by the treating doctor. The primary objective of the study was to monitor the incidence of serious adverse events including severe hypoglycaemias. The secondary objective of the study (the number of adverse events, the incidence of all and nocturnal hypoglycaemic episodes, the variability of fasting glycaemia, the change in HbA1c at the end of the study, the change in the patients' weight) focused on the safety and efficiency of diabetes treatment.

RESULTS

Insulin detemir therapy resulted in a statistically significant decrease in all nocturnal episodes (from 26.8 to 10.4 episodes/patient/year in type 1 DM; from 9.2 to 2.6 in persons with type 2 DM), in severe nocturnal episodes (from 2.5 to 0.1 episode/patient/year in type 1 DM, and from 0.6 to 0 in type 2 DM), and also in hypoglycaemic nocturnal episodes (from 7.2 to 1.8 episode/patient/year in type 1 DM and from 1.7 to 0.3 in type 2 DM) as compared with the period preceding the therapy. In addition, detemir therapy resulted in a statistically significant improvement of diabetes compensation characterised by a decrease in the average HbAlc from 7.6% to 6.7% in type 1 DM patients, and from 7.9% to 7.0% in type 2 DM patients. Average fasting glycaemia recorded a significant decrease by 2.4 mmol/l in type 1 DM patients, and by 2.3 mmol/l in type 2 DM patients. Also the variability of fasting glycaemia recorded a significant decrease at the end of the study in both patient groups. No major change in weight was recorded in the course of the study in persons with type 1 DM, while a significant decrease in weight was recorded for type 2 DM patients.

CONCLUSION

The results of the study PREDICTIVE confirmed the data from randomised studies on the safety and efficiency of insulin detemir treatment in the conditions of standard clinical practice in the Czech Republic.

Acetylcholine exerts additive and permissive but not synergistic effects with insulin on glycogen synthesis in hepatocytes

Parasympathetic (cholinergic) innervation is implicated in the stimulation of hepatic glucose uptake by portal vein hyperglycaemia. We determined the direct effects of acetylcholine on hepatocytes. Acute exposure to acetylcholine mimicked insulin action on inactivation of phosphorylase, stimulation of glycogen synthesis and suppression of phosphoenolpyruvate carboxykinase mRNA levels but with lower efficacy and without synergy. Pre-exposure to acetylcholine had a permissive effect on insulin action similar to glucocorticoids and associated with increased glucokinase activity. It is concluded that acetylcholine has a permissive effect on insulin action but cannot fully account for the rapid stimulation of glucose uptake by the portal signal.

Insulin detemir improves glycaemic control with less hypoglycaemia and no weight gain in patients with type 2 diabetes who were insulin naive or treated with NPH or insulin glargine: clinical practice experience from a German subgroup of the PREDICTIVE study

AIM

The Predictable Results and Experience in Diabetes through Intensification and Control to Target: An International Variability Evaluation (PREDICTIVE) Study is a large, multi-centre, observational study assessing the safety and efficacy of insulin detemir in everyday clinical practice.

METHODS

This subgroup analysis of the German cohort of PREDICTIVE evaluates over 3 months, patients with type 2 diabetes who were transferred to insulin detemir +/- oral antidiabetic drugs (OADs) from an OAD-only regimen (n = 1321), NPH insulin +/- OADs (n = 251) or insulin glargine +/- OADs (n = 260).

RESULTS

Among all groups, 3 months after starting treatment with insulin detemir, total, daytime and nocturnal hypoglycaemic events/patient were reduced by 84, 80 and 90%, respectively, from baseline. No major hypoglycaemic events were reported during treatment with insulin detemir. HbAlc was significantly reduced from baseline in each of the subgroups (-1.29,-0.60 and-0.59% for patients previously taking OADs only, NPH insulin +/- OADs and insulin glargine +/- OADs respectively; p < 0.0001), as was fasting blood glucose (FBG) (-58.1,-29.1 and-24.6 mg/dl; p < 0.0001) and FBG variability-8.2 mg/dl,-5.7 mg/dl; p < 0.0001 and -5.1 mg/dl; p = 0.0008). All subgroups combined lost an average of 0.9 kg of body weight (p < 0.0001) during the study. Total daily basal insulin dose increased slightly from baseline for those patients on a prior insulin regimen, and in this study 79% of patients used insulin detemir once daily.

CONCLUSIONS

These data confirm the short-term safety and efficacy of insulin detemir +/- OADs in a real-world scenario and support the findings of randomized controlled clinical trials with insulin detemir, including its limited effects on body weight.

PREDICTIVE- a global, prospective observational study to evaluate insulin detemir treatment in types 1 and 2 diabetes: baseline characteristics and predictors of hypoglycaemia from the European cohort

AIM

PREDICTIVEtrade mark (Predictable Results and Experience in Diabetes through Intensification and Control to Target: An International Variability Evaluation) is a large, multi-national, observational study assessing the safety and efficacy of insulin detemir. We report the study design, population characteristics and baseline observations, including cross-sectional analysis, from 19 911 patients with type 1 or 2 diabetes.

METHODS

Patients with type 1 or 2 diabetes requiring basal insulin are prescribed insulin detemir and followed up for 12-52 weeks. Data on demographics, haemoglobin A(1c) (HbA(1c)), fasting glucose, within-subject fasting glucose variability and weight are collected from patient records (and/or recall for hypoglycaemia). A negative binomial distribution model is used to assess the influence of predictive/confounding variables on hypoglycaemic episodes in insulin-treated patients at baseline. Multi-factorial analysis of covariance is used to evaluate the association of the variables with current body weight and within-subject fasting glucose variability.

RESULTS

Total hypoglycaemic episodes in the 4 weeks prior to study start were 47.5 per patient-year in patients with type 1 and 9.2 per patient-year in patients with type 2 diabetes. The frequency of hypoglycaemia in insulin-treated patients showed a significant, positive association with duration of diabetes, number of insulin injections and fasting glucose variability but was inversely related to HbA(1c), fasting glucose and body mass index. Weight showed a significant positive association with gender (male > female) and insulin dosage. Weight was also positively associated with fasting glucose variability in patients with type 1 diabetes, and age and number of injections in patients with type 2 diabetes.

CONCLUSIONS

These baseline data showed that, in addition to the established relationship with intensive treatment and HbA(1c), frequency of hypoglycaemia was positively associated with fasting glucose variability. Follow-up data from PREDICTIVE will provide insights on insulin detemir in diabetes management.

Albumin-bound basal insulin analogues (insulin detemir and NN344): comparable time-action profiles but less variability than insulin glargine in type 2 diabetes

AIM

This study compared the time-action profiles of the novel albumin-bound basal insulin analogue NN344 with those of insulin detemir and insulin glargine in individuals with type 2 diabetes.

METHODS

Twenty-seven insulin-treated men with type 2 diabetes [body mass index 30.8 +/- 2.6 kg/m(2) (mean +/- s.d.), haemoglobin A(1c) 7.6 +/- 1.1%] were enrolled in this randomized, double-blind trial and participated in six euglycaemic glucose clamp experiments [target blood glucose (BG) 5 mmol/l] each. Participants received NN344 in three experiments at a dose of 0.8, 1.6 and 2.8 dosing units (DU) (1 DU corresponds to 6 nmol NN344) per kilogram of body weight. In the other three experiments, the participants received 0.4, 0.8 and 1.4 U/kg of either insulin detemir or insulin glargine. The insulin preparations were characterized with regards to their effects on glucose infusion rates (GIRs) (in particular duration of action and within-subject and between-subject variabilities), BG, C-peptide, free fatty acids (FFA), endogenous glucose production (EGP) and peripheral glucose uptake (PGU) over 24 h post-dose.

RESULTS

The mean GIR profiles for all three preparations were similar in shape/flatness and showed increasing effect (area under the curve for GIR: AUC-GIR(total)) with increasing dose [low dose: 647 +/- 580, 882 +/- 634, 571 +/- 647 mg/kg (insulin detemir vs. NN344 vs. insulin glargine]; medium dose: 1203 +/- 816, 1720 +/- 1109, 1393 +/- 1203 mg/kg and high dose: 2171 +/- 1344, 3119 +/- 1549, 2952 +/- 2028 mg/kg; p = 0.48]. The duration of action increased with rising doses of all insulin preparations, without major differences between treatments. BG remained below 7 mmol/l in nearly all the experiments. Within-subject variability was lower for the albumin-bound insulin analogues, insulin detemir and NN344, than for insulin glargine (p < 0.0001). Between-subject variability did not differ between treatments, nor did the effects on BG, C-peptide, FFA, EGP or PGU.

CONCLUSIONS

In individuals with type 2 diabetes, the time-action profiles and the duration of action of the albumin-bound insulin analogues, insulin detemir and NN344, were comparable with those of insulin glargine, whereas within-subject variability in the metabolic effect was significantly lower. Therefore, insulin detemir and NN344 seem to be as well suited as insulin glargine for once-daily administration in type 2 diabetes. The better predictability may be an important characteristic of the albumin-bound analogues as insulin detemir has already been shown to improve hypoglycaemia.

Does insulin detemir have a role in reducing risk of insulin-associated weight gain?

Weight gain is often perceived as inevitable with insulin therapy, particularly as we strive for tight glycaemic control and are using increasingly proactive insulin titration regimes. The United Kingdom Prospective Diabetes Study documented that weight gain occurs most rapidly soon after insulin therapy is first initiated. The timing of this side effect is particularly undesirable, as weight gain may interfere with patients' adjustment to insulin therapy and may undermine appropriate diabetes self-management behaviours. Until recently, many patients had little alternative other than to accept unwanted weight gain if they were to achieve sufficient glycaemic control to reduce risk of chronic complications of diabetes. Insulin detemir is a novel basal insulin analogue that has consistently been shown in randomized, controlled trials to have a weight-sparing effect (i.e. weight loss or reduced weight gain compared with other insulins) in both type 1 and type 2 diabetes. Indeed, unlike neutral protamine Hagedorn (NPH) insulin, the weight-sparing effect of insulin detemir appears to be most prominent in people who are the most obese. The mechanisms behind the weight-sparing effect of insulin detemir are still being clarified. Reduced risk of hypoglycaemia with insulin detemir, coupled with a more consistent and reliable delivery of the desired dose than is available with traditional basal insulin, such as NPH, has been proposed to minimize defensive snacking by patients, and help to limit weight gain. However, even if this was proven, it would be unlikely to fully explain the weight-sparing effect of insulin detemir. Two additional theories have been put forward. One suggests that due to its novel method of prolonging action via acylation and albumin binding, insulin detemir may differentially influence hepatocytes more than peripheral tissues, thus effectively suppressing hepatic glucose output without promoting lipogenesis in the periphery. The second theory suggests that insulin detemir may be more effective than human insulin in communicating satiety signals within the central nervous system. Further clarification of these hypotheses is required.

Studies on the insulinomimetic effects of benzylamine, exogenous substrate of semicarbazide-sensitive amine oxidase enzyme in streptozotocin induced diabetic rats

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO) is believed to be a bifunctional membrane protein. It is localized extracellularly and preferentially oxidizes short chain primary amines to aldehydes, hydrogen peroxide and ammonia, but also functions as an adhesion molecule, which is involved in leukocyte migration. Serum SSAO activity is increased in diabetic patients and animals and the aldehydes formed in the enzyme reaction may contribute to vascular damage. However, administration of exogenous substrates has been shown to improve glucose tolerance and reduce hyperglycaemia in diabetic animals. Hydrogen peroxide and/or its vanadate complexes have been suggested responsible for these effects. Streptozotocin induced diabetic rats were treated with benzylamine (BZA) +/- vanadate (V) or insulin. In contrast to insulin, BZA + V treatment did not reduce HbA(1C) levels. However, it reduced the elevated serum SSAO activity, decreased the accumulation of advanced-glycation end products and increased the bioavailability of nitric oxide in diabetic animals, similarly to insulin. BZA alone did not affect any of these parameters.

Insulin detemir in the treatment of type 1 and type 2 diabetes

Insulin detemir is a soluble long-acting human insulin analogue at neutral pH with a unique mechanism of action. Following subcutaneous injection, insulin detemir binds to albumin via fatty acid chain, thereby providing slow absorption and a prolonged metabolic effect. Insulin detemir has a less variable pharmacokinetic profile than insulin suspension isophane or insulin ultralente. The use of insulin detemir can reduce the risk of hypoglycemia (especially nocturnal hypoglycemia) in type 1 and type 2 diabetic patients. However, overall glycemic control, as assessed by glycated hemoglobin, is only marginally and not significantly improved compared with usual insulin therapy. The weight gain commonly associated with insulin therapy is rather limited when insulin detemir is used. In our experience, this new insulin analogue is preferably administrated at bedtime but can be proposed twice a day (in the morning and either before the dinner or at bedtime). Detemir is a promising option for basal insulin therapy in type 1 or type 2 diabetic patients.

Antihyperglycemic effect of aporphines and their derivatives in normal and diabetic rats

The antihyperglycemic actions of some aporphines and their derivatives in normal Wistar, streptozotocin (STZ)-induced diabetic (IDDM) and nicotinamide-STZ induced diabetic (NIDDM) rats were investigated in this study. These compounds included thaliporphine, glaucine, boldine, N-methyllaurotetanine, and predicentrine and the derivatives, N-[2-(2-methoxyphenoxy)ethyl]norglaucine and diacetyl- N-allylsecoboldine. Bolus intravenous injection of these compounds decreased the plasma glucose levels in a dose-dependent manner in both normal and diabetic rats. Among them, thaliporphine was found to have the most potent antihyperglycemic effect in both NIDDM and IDDM diabetic rats. It was found that thaliporphine could stimulate the release of insulin in both normal and diabetic rats, and a dose of 1 mg per kg thaliporphine could significantly attenuate the increase of plasma glucose induced by an intravenous glucose challenge test in normal rats. Similar treatment with thaliporphine significantly increased the skeletal muscle glycogen synthesis in both normal and diabetic rats. Hence, the hypoglycemic effect of thaliporphine in diabetic rats could be attributed to the stimulation of insulin release and the increase of glucose utilization.

Pulsatile insulin secretion in elderly patients with diabetes

Insulin pulsation is impaired in type 2 diabetes. GLP-1 increases pulsatile insulin secretion in these patients. We conducted these studies with the hypothesis that GLP-1 would enhance pulsatile insulin secretion and alter glucose metabolism in elderly patients with type 2 diabetes. Experiments were conducted in nine patients (age: 72+/-5 years; BMI: 27+/-3kg/m(2); diabetes duration: 7+/-3 years; HbA(1c): 6.6+/-0.9%). Subjects underwent three glucose clamp studies. The first was a euglycemic clamp to determine individual insulin clearance. In the second, GLP-1 was infused from 0-240min (0.75pM/kg/min) and glucose was maintained at fasting levels. The third was similar except that octreotide (30ng/kg/min) was infused with GLP-1 to suppress pulsatile insulin. Insulin and glucose were given to match levels during the second study. 3-(3)H-glucose was infused to allow calculation of hepatic glucose production and glucose disposal rates. There was no significant difference in measurements of pulsatile insulin secretion or hepatic glucose production and glucose disposal rates between the studies. Because there was no difference in pulsatile insulin between experiments, we could not test the effect of pulsatile insulin on glucose metabolism. Further studies are required to determine the impact of insulin pulses on glucose metabolism.

Cost-effectiveness of basal insulin from a US health system perspective: comparative analyses of detemir, glargine, and NPH

The purpose of this study was to compare in clinical and economic terms the long-acting insulin analogue detemir with intermediate-acting Neutral Protamine Hagedorn (NPH) insulin and with long-acting insulin glargine. Investigators used the validated Center for Outcomes Research (CORE) Diabetes Model to project clinical and cost outcomes over a 35-year base case time horizon; outcome data were extracted directly from randomized, controlled trials designed to compare detemir with NPH and with insulin glargine. Modeled patient characteristics were derived from corresponding trials, and simulations incorporated published quality-of-life utilities with cost data obtained from a Medicare perspective. Detemir, when compared with NPH, increased quality-adjusted life expectancy by 0.698 quality-adjusted life-years (QALYs). Lifetime direct medical costs were increased by 10,451 dollars per patient, although indirect costs were reduced by 4688 dollars. On the basis of direct costs, the cost per QALY gained with detemir was 14,974 dollars. In comparison with glargine, detemir increased quality-adjusted life expectancy by 0.063 QALYs, reduced direct medical costs by 2072 dollars per patient, and decreased indirect costs by 3103 dollars (dominant). Reductions in diabetes-related comorbidities were also associated with detemir in both instances, most notably in the complications of retinopathy and nephropathy. Relative reductions in rates of complications were greatest in the comparison of detemir with NPH. Results were most sensitive to variation in hemoglobin A1c (HbA1c) levels. However, variation among any of the key assumptions, including HbA1c, did not alter the relative results. Detemir represents an attractive clinical and economic intervention in the US health care setting compared with both NPH insulin and insulin glargine.

What has prevented the expansion of insulin sensitisers?

The ability to improve insulin sensitivity with synthetic compounds was uncovered by empirical discoveries by Takeda in the late 1970s. The potential of a class of thiazolidinediones for the treatment of Type 2 diabetes, by decreasing glucose and triglycerides alongside lowering circulating insulin, was made public during the 1980s. As the first of the chemicals (pioglitazone, troglitazone and rosliglitazone) proceeded to clinical trials, these observations were soon extended to demonstrate a rich and complex pharmacology. The promise of this mode of action included prevention of diabetes as well as making a significant impact on the incidence and severity of the life-shortening consequences of the established disease. There are now two of these drugs on the market: pioglitazone and rosiglitazone, and they are being used to treat significant numbers of diabetic patients. However, the use of these drugs and development of future generations of successful candidates has not met the expectations that were held out in the early 1980s. This can be attributed to two major prevailing conditions. Troglitazone became the first thiazolidinedione to be approved as a result of delays in the development of pioglitazone. Unfortunately, troglitazone produced a unique idiosyncratic and sometimes fatal, hepatoxicity that necessitated its removal from the marketplace; second, there has been an incomplete understanding of the biochemical mechanism of action of these drugs that has slowed (and perhaps derailed) attempts to produce second-generation compounds. The latter issue is the subject of this editorial, which suggests that it is time to take a fresh look at the pharmacology of insulin sensitisers.

Insulin detemir: a new basal insulin analogue

Basal insulin therapy is an integral part of the intensive management of type 1 diabetes and it is also often used in type 2 diabetes. An ideal insulin regimen in patients with diabetes would mirror the 24-h insulin profile of a non-diabetic person, thereby preventing hyperglycaemia without inducing hypoglycaemia. Until recently, available insulins have pharmacokinetic disadvantages, compared to physiological insulin secretion. Insulin detemir is a new basal insulin analogue recently available for commercial use in the UK. Clinical trials have demonstrated lower fasting plasma glucose levels, lower variability in plasma glucose, predictable action profile and a reduced risk of nocturnal hypoglycaemia and weight gain, compared to conventional basal insulins. This study reviews the properties and potential use of insulin detemir.

Diabetes mellitus-associated atherosclerosis: mechanisms involved and potential for pharmacological invention

While diabetes mellitus is most often associated with hypertension, dyslipidemia, and obesity, these factors do not fully account for the increased burden of cardiovascular disease in patients with the disease. This strengthens the need for comprehensive studies investigating the underlying mechanisms mediating diabetic cardiovascular disease and, more specifically, diabetes-associated atherosclerosis. In addition to the recognized metabolic abnormalities associated with diabetes mellitus, upregulation of putative pathological pathways such as advanced glycation end products, the renin-angiotensin system, oxidative stress, and increased expression of growth factors and cytokines have been shown to play a causal role in atherosclerotic plaque formation and may explain the increased risk of macrovascular complications. This review discusses the methods used to assess the development of atherosclerosis in the clinic as well as addressing novel biomarkers of atherosclerosis, such as low-density lipoprotein receptor-1. Experimental models of diabetes-associated atherosclerosis are discussed, such as the streptozocin-induced diabetic apolipoprotein E knockout mouse. Results of major clinical trials with inhibitors of putative atherosclerotic pathways are presented. Other topics covered include the role of HMG-CoA reductase inhibitors and fibric acid derivatives with respect to their lipid-altering ability, as well as their emerging pleiotropic anti-atherogenic actions; the effect of inhibiting the renin-angiotensin system by either ACE inhibition or angiotensin II receptor antagonism; the effect of glycemic control and, in particular, the promising role of thiazolidinediones with respect to their direct anti-atherogenic actions; and newly emerging mediators of diabetes-associated atherosclerosis, such as advanced glycation end products, vascular endothelial growth factor and platelet-derived growth factor. Overall, this review aims to highlight the observation that various pathways, both independently and in concert, appear to contribute toward the pathology of diabetes-associated atherosclerosis. Furthermore, it reflects the need for combination therapy to combat this disease.

[An update on multiple insulin injection therapy in type 1 and 2 diabetes]

Achieving and maintaining glycemic control (glycated hemoglobin--HbA(1c)< or =7.0% according to American Diabetes Association and < or =6.5% according to International Diabetes Federation) is the primary goal in treating diabetes, which lowers the risk for diabetes-related complications. Insulin therapy is essential for type 1 diabetes treatment. Insulin therapy in type 2 diabetes is initiated when glycemic control is inadequate despite the combination of antihyperglycemic drugs. The type of insulin therapy is selected according to the patient's lifestyle and needs. Multiple insulin injection therapy and premixed insulin therapy are usually administered. In multiple insulin injection therapy, basal insulin is administered one or two times a day, and regular human insulin or rapid-acting insulin analog is administered with each meal. The duration of action of regular insulin is 6-8 hours; therefore, the risk for postprandial hypoglycemia is increased. The action of novel insulin analogs (rapid- and long-acting) closely mimics physiological insulin secretion. Three rapid-acting insulin analogs are currently available: insulin lispro, insulin aspart, and insulin glulisine. Insulin glulisine is the most recently approved rapid-acting insulin analog. It is safe, flexible, and effective in achieving target postprandial glycemic control. Moreover, the pharmacokinetics of insulin glulisine does not depend on the amount of subcutaneous fat. Basal insulins include intermediate-acting human insulins (neutral protamine Hagedorn) and long-acting insulin analogs (insulin glargine, insulin detemir). The latter are the optimal choice covering basal insulin requirement. Compared to neutral protamine Hagedorn insulin, long-acting insulin analogs have no pronounced concentration peak and reduce nocturnal hypoglycemia risk and weight gain.

Dehydroepiandrosterone mimics acute actions of insulin to stimulate production of both nitric oxide and endothelin 1 via distinct phosphatidylinositol 3-kinase- and mitogen-activated protein kinase-dependent pathways in vascular endothelium

Dehydroepiandrosterone (DHEA) is an adrenal steroid and nutritional supplement that may improve insulin sensitivity. Although steroid hormones classically act by regulating transcription, they may also signal through cell surface receptors to mediate nongenomic actions. Because DHEA may augment insulin sensitivity, we hypothesized that DHEA mimics vascular actions of insulin to acutely activate signaling pathways in endothelium-mediating production of nitric oxide (NO) and endothelin 1 (ET-1). Treatment of bovine aortic endothelial cells with either insulin or DHEA (100 nm, 5 min) stimulated significant increases in NO production (assessed with NO-selective fluorescent dye diaminofluorescein 2). These responses were abolished by pretreatment of cells with L-NAME (nitro-L-arginine methyl ester; NO synthase inhibitor) or wortmannin [phosphatidylinositol (PI) 3-kinase inhibitor]. Under similar conditions, insulin- or DHEA-stimulated phosphorylation of Akt (Ser473) and endothelial nitric oxide synthase (Ser1179) was inhibited by pretreatment of cells with wortmannin (but not MAPK kinase inhibitor PD98059). Acute DHEA treatment also caused phosphorylation of MAPK (Thr202/Tyr204) that was inhibitable by PD98059 (but not wortmannin). DHEA treatment of bovine aortic endothelial cells (100 nM, 5 min) stimulated a 2-fold increase in ET-1 secretion that was abolished by pretreatment of cells with PD98059 (but not wortmannin). We conclude that DHEA has acute, nongenomic actions in endothelium to stimulate production of the vasodilator NO via PI 3-kinase-dependent pathways and secretion of the vasoconstrictor ET-1 via MAPK-dependent pathways. Altering the balance between PI 3-kinase- and MAPK-dependent signaling in vascular endothelium may determine whether DHEA has beneficial or harmful effects relevant to the pathophysiology of diabetes.

[Insulin detemir (Levemir)]

Insulin detemir (Levemir) is a soluble long acting human insulin analogue acylated with a 14-carbon fatty acid. The fatty acid modification allows insulin detemir to reversibly bind to albumin, thereby providing slow absorption and a prolonged metabolic effect (up to 24 hours) with low variability. Indeed, in patients with type 1 or type 2 diabetes mellitus, insulin detemir has a more predictable, protracted and consistent effect, with less intrapatient variability in glycaemic control (particularly fasting plasma glucose levels), compared with NPH (Neutral Protamine Hagedorn) insulin. Insulin detemir, is at least as effective as NPH insulin in maintaining overall glycaemic control, with a lower risk of nocturnal hypoglycaemia. It also provides the additional benefit of less body weight gain as compared to other basal insulins. Levemir, presented in cartridges for the pen device NovoPen 3 and administered preferably at bedtime (if necessary morning and evening), is a promising new option for basal insulin therapy in diabetic patients, especially those on a basal-bolus scheme.

[Diabetes]

In 2004, a new insulin analogue was launched, Detemir insulin (Levemir). Detemir insulin is a long acting insulin and has a lower within-subject variability in comparison with other insulins. The recently published results of the CARDS study (atorvastatin treatment) also emphasize the need for a more aggressive attitude toward cardiovascular risk in diabetics even if LDL-cholesterol values are not particularly elevated. We will end this short review discussing the future of the inhibitor of GLP-1 degradation which in addition to a modest hypoglycaemic effect seems to be able to prevent apoptosis of insulin producing beta cells.

Insulin detemir and insulin aspart: a promising basal-bolus regimen for type 2 diabetes

This trial compared the efficacy and safety of basal-bolus therapy using either the soluble basal insulin analogue insulin detemir (IDet) in combination with meal-time rapid-acting analogue insulin aspart (IAsp), or NPH insulin (NPH) in combination with meal-time regular human insulin (HSI). This was a 22-week, multinational, open-labelled, symmetrically randomised, parallel group trial including 395 people with type 2 diabetes (IDet + IAsp: 195, NPH + HSI: 200). At 22 weeks, HbA1c was comparable between treatments (IDet + IAsp: 7.46%, NPH + HSI: 7.52%, P = 0.515) with decreases from baseline of 0.65% and 0.58%, respectively. Treatment with IDet + IAsp was associated with a significantly lower within-person variation in self-measured fasting plasma glucose (FPG) (SD:1.20 versus 1.54 mmol/L, p < 0.001), as well as a lower body weight gain (0.51 versus 1.13 kg, p = 0.038) than with NPH + HSI. The risk of nocturnal hypoglycaemia was 38% lower with IDet + IAsp than with NPH + HSI, but statistical significance was not attained (P = 0.14). The overall safety profile was similar between the two treatments. Basal-bolus treatment with IDet + IAsp is an effective and well tolerated insulin regimen in people with type 2 diabetes, resulting in glycaemic control comparable to that of NPH + HSI, but with the advantages of less weight gain and a lower day-to-day within-person variation in FPG.

The Mechanism of Protraction of Insulin Detemir, a Long-Acting, Acylated Analog of Human Insulin

PURPOSE

Insulin detemir has been found in clinical trials to be absorbed with very low variability. A series of experiments were performed to elucidate the underlying mechanisms.

METHODS

The disappearance from an injected subcutaneous depot and elimination studies in plasma were carried out in pigs. Size-exclusion chromatography was used to assess the self-association and albumin binding states of insulin detemir and analogs.

RESULTS

Disappearance T50% from the injection depot was 10.2+/-1.2 h for insulin detemir and 2.0+/-0.1 h for a monomeric acylated insulin analog. Self-association of acylated insulin analogs with same albumin affinity in saline correlated with disappearance rate and addition of albumin to saline showed a combination of insulin detemir self association and albumin binding. Intravenous kinetic studies showed that the clearance and volume of distribution decreased with increasing albumin binding affinity of different acylated insulin analogs.

CONCLUSIONS

The protracted action of detemir is primarily achieved through slow absorption into blood. Dihexamerization and albumin binding of hexameric and dimeric detemir prolongs residence time at the injection depot. Some further retention of detemir occurs in the circulation where albumin binding causes buffering of insulin concentration. Insulin detemir provides a novel principle of protraction, enabling increased predictability of basal insulin.

Effects of glimepiride on insulin secretion and sensitivity in patients with recently diagnosed type 2 diabetes mellitus

BACKGROUND

The exact mechanism of the efficacy of glimepiride in the achievement of glycemic control has not yet been clearly defined.

OBJECTIVE

This study was conducted to examine the influence of glimepiride on insulin secretion and sensitivity in patients with type 2 diabetes mellitus (DM) of recent onset.

METHODS

This 24-week, open-label, controlled trial was conducted at the Division of Endocrinology and Metabolism, Veterans Affairs Medical Center (Phoenix, Arizona). Study participants were aged 32 to 75 years and had recent-onset (established by a short duration of symptoms 6 weeks to 6 months prior to the study) type 2 DM, or were age-matched healthy volunteers (control group). In the diabetic patients, glimepiride tablets were administered orally, initially at 2 mg once daily in the morning, with the dosage increased by 1 mg every 2 weeks until fasting plasma glucose (FPG) decreased to 6.7 mmol/L; the dosage was then maintained for the remainder of the 24-week study period. Oral glucose tolerance tests (OGTTs) were conducted in the control group and before treatment and at 24 weeks after the achievement and maintenance of glycemic control (glycosylated hemoglobin <7.0%) in the diabetic group. For OGTT, plasma insulin and glucose levels were determined after the subjects fasted overnight and then at every 15 minutes for 2 hours after glucose challenge.

RESULTS

Fourteen diabetic men (mean [SEM] age, 50 [6] years; range, 32-75 years) and 10 male healthy controls (mean [SD] age, 48 [5] years; range, 30-68 years) were enrolled. In the DM group, FPG decreased significantly after treatment ( P<0.001); fasting plasma insulin was markedly elevated before treatment (P<0.001 vs controls) and decreased after treatment ( P<0.01) but did not normalize; first-phase insulin secretion was markedly inhibited before treatment ( P<0.001 vs controls) and normalized after treatment ( P<0.001) total insulin secretion significantly improved after treatment ( P<0.01) but did not normalize. Finally, the pretreatment insulin sensitivity index decreased significantly (P<0.01) after treatment and normalized in 6 of 14 patients (42.9%) with type 2 DM.

CONCLUSIONS

In this study, glimepiride achieved desirable glycemic control in patients with recent-onset type 2 DM through improvement in insulin secretion and sensitivity.

Insulin detemir offers improved glycemic control compared with NPH insulin in people with type 1 diabetes: a randomized clinical trial

OBJECTIVE

Insulin detemir is a soluble long-acting basal insulin analog designed to overcome the limitations of conventional basal insulin formulations. Accordingly, insulin detemir has been compared with NPH insulin with respect to glycemic control (HbA1c, prebreakfast glucose levels and variability, and hypoglycemia) and timing of administration.

RESEARCH DESIGN AND METHODS

People with type 1 diabetes (n = 408) were randomized in an open-label, parallel-group trial of 16-week treatment duration using either insulin detemir or NPH insulin. Insulin detemir was administered twice daily using two different regimens, either before breakfast and at bedtime (IDet(morn+bed)) or at a 12-h interval (IDet(12h)). NPH insulin was administered before breakfast and at bedtime. Mealtime insulin was given as the rapid-acting insulin analog insulin aspart.

RESULTS

With both insulin detemir groups, clinic fasting plasma glucose was lower than with NPH insulin (IDet(12h) vs. NPH, -1.5 mmol/l [95% CI -2.51 to -0.48], P = 0.004; IDet(morn+bed) vs. NPH, -2.3 mmol/l (-3.32 to -1.29), P < 0.001), as was self-measured prebreakfast plasma glucose (P = 0.006 and P = 0.004, respectively). The risk of minor hypoglycemia was lower in both insulin detemir groups (25%, P = 0.046; 32%, P = 0.002; respectively) compared with NPH insulin in the last 12 weeks of treatment, this being mainly attributable to a 53% reduction in nocturnal hypoglycemia in the IDet(morn+bed) group (P < 0.001). Although HbA1c for each insulin detemir group was not different from the NPH group, HbA1c for the pooled insulin detemir groups was significantly lower than for the NPH group (mean difference -0.18% [-0.34 to -0.02], P = 0.027). Within-person between-day variation in self-measured prebreakfast plasma glucose was lower for both detemir groups (both P < 0.001). The NPH group gained weight during the study, but there was no change in weight in either of the insulin detemir groups (IDet(12h) vs. NPH, -0.8 kg [-1.44 to -0.24], P = 0.006; IDet(morn+bed) vs. NPH, -0.6 kg [-1.23 to -0.03], P = 0.040).

CONCLUSIONS

Overall glycemic control with insulin detemir was improved compared with NPH insulin. The data provide a basis for tailoring the timing of administration of insulin detemir to the individual person's needs.

Effect of Hibiscus rosa sinensis Linn. ethanol flower extract on blood glucose and lipid profile in streptozotocin induced diabetes in rats

Blood glucose and total lipid levels were determined in streptozotocin induced diabetic rats after oral administration of an ethanol flower extract of Hibiscus rosa sinensis. A comparable hypoglycemic effect was evidenced from the data obtained after 7 and 21 days of oral administration of the extract and glibenclamide. Maximal diminution in blood glucose (41-46%) and insulin level (14%) was noticed after 21 days. The extract lowered the total cholesterol and serum triglycerides by 22 and 30%, respectively. The increase in HDL-cholesterol was much higher (12%) under the influence of the extract as compared to that of glibenclamide (1%). The hypoglycemic activity of this extract is comparable to that of glibenclamide but is not mediated through insulin release. Other possible mechanisms are discussed.

Species and gender differences in the formation of an active metabolite of a substituted 2,4-thiazolidinedione insulin sensitizer

1. The metabolism of a substituted 2,4-thiazolidinedione (P1) with dual PPARalpha/gamma activity was evaluated in male and female rats, dogs and monkeys. A para-hydroxylated metabolite (M1) with potent PPARgamma-selective agonist, was a major circulating drug-related component in female rats, dogs and monkeys, but not in male rats (M1-to-P1 exposure ratio of <1, 3-5, 5 and 5-11 in male rat, monkey, female rat, and dog, respectively). 2. M1 (%) formed in vitro (5, 53, 57-65, 67 and 67% in male rat, monkey, female rat, dog, and human liver microsomes, respectively), rank ordered with M1 (%) formed in vivo (24-45, 53-57, 78, 75-85%, for male rat, monkey, female rat and dog, respectively, after oral administration of P1). 3. The plasma clearance of M1 was higher in male rats (32 ml min(-1) kg(-1) compared with 6, 7 and 2 ml min(-1) kg(-1) in female rat, male monkey and male dogs, respectively). 4. The low amounts of M1 observed in male rats, with the appearance of products of the cleavage of the propyl group between the phenyl groups was probably due to the presence of the sex-specific CYP2C11, which cleaves P1 at the propyl bridge. None of the CYPs present in female rats cleaved P1 at this site and M1 was only produced by CYP2C6. In humans, only CYP2C8 and the polymorphic CYP2C19 produced M1.