Drugs on the horizon for diabesity

Exploring dihydropyrimidone derivatives as modulators of carbohydrate catabolic enzyme to mitigate diabetes

Diabetes is a prevalent and serious metabolic disorder affecting millions globally, and it poses extensive health risks due to elevated blood glucose levels. One promising approach for managing diabetes is the inhibition of α-glucosidase, an enzyme that plays a crucial role in carbohydrate metabolism. Targeting α-glucosidase can help delay glucose absorption, thus controlling postprandial blood sugar spikes. Dihydropyrimidones, a core structural class present in various biologically active natural compounds, have been recognized for their diverse therapeutic potential, including anti-diabetic properties. In this study, we evaluated a library of previously synthesized 37 Dihydropyrimidone derivatives to assess their potential as α-glucosidase inhibitors. We identified 34 derivatives with significant inhibitory activity, exhibiting IC50 values in the range of 5.30-56.72 µM. Among these, compounds 2, 4-7, 9-11, 13-16, 31, 32, and 33 demonstrated high potency, with IC50 values below 20 µM; the most active compound, 5, achieved an IC50 of 5.30 µM. A detailed kinetic study on compound 5 revealed a competitive inhibition mode with a Ki value of 16.10 ± 0.0075 µM. Additionally, cytotoxicity assays confirmed that compound 5 is non-toxic to BJ cell lines, underscoring its safety for therapeutic use. The computational studies further supported the inhibitory potential by illustrating key interactions and binding affinities between the Dihydropyrimidone derivatives and the α-glucosidase, highlighting these compounds as promising candidates for diabetes management.

Ficus carica and Sizigium cumini Regulate Glucose and Lipid Parameters in High-Fat Diet and Streptozocin-Induced Rats

Obesity linked diabetes, popularly known as diabesity, has been viewed as a direct product of the modern lifestyle in both developed and developing countries, and its increased prevalence is seen as a major threat to public health globally. Ficus carica (FC) and Syzigium cumini (SC) are part of indigenous flora with traditional medicinal properties. Fresh seeds of SC fruit and fruit of FC were collected and macerated to obtain the final extract. Wistar rats were divided into seven groups fed either on a normal diet or high-fat diet (HFD) along with streptozocin (STZ) to induce diabesity. The crude extract of FC (FC.Cr.) and SC (SC.Cr.) were administered at 250 mg/kg/day and 500 mg/kg/day in induced diabesity state. Body weights, blood glucose level, complete blood count (CBC), cholesterol, triglycerides (TG), low-density lipoprotein (LDL), very-low-density lipoprotein (VLDL), and high-density lipoprotein (HDL) were recorded to analyze their effects on glucose and lipid metabolism. Further, superoxide dismutase (SOD) and malondialdehyde (MDA) were measured to examine their effects on lipid peroxidation and ant oxidative enzyme. Results showed that both FC.Cr. and SC.Cr. have the potential to control obesity-linked type 2 diabetes mellitus (T2DM) by lowering the body weights, serum glucose, cholesterol, TG, LDL, and VLDL, while increasing the protective effects of HDL dose-dependently. The crude extract of both plants showed significant activity to raise SOD and curb MDA under diabetic states. It was concluded that both FC.Cr. and SC.Cr. exhibited remarkable therapeutics potential in HFD-STZ-induced diabetic rats. However, we found that the effects of SC.Cr. are relatively more pronounced as compared to FC.Cr. in almost all parameters.

Zinc-induced activation of GPR39 regulates glucose homeostasis through glucose-dependent insulinotropic polypeptide secretion from enteroendocrine K-cells

The role of Zn²⁺-sensing receptor GPR39 on glucose homeostasis and incretin regulation was assessed in enteroendocrine L- and K-cells. Anti-hyperglycaemic, insulinotropic and incretin secreting properties of Zn²⁺ were explored in normal, diabetic and incretin receptor knockout mice. Compared to intraperitoneal injection, oral administration of Zn²⁺ (50 μmol/kg body weight) with glucose (18 mmol/kg) in lean mice reduced the glycaemic excursion by 25-34% (p < 0.05-p < 0.001) and enhanced glucose-induced insulin release by 46-48% (p < 0.05-p < 0.01). In diabetic mice, orally administered Zn²⁺ lowered glucose by 24-31% (p < 0.01) and augmented insulin release by 32% (p < 0.01). In glucagon like peptide-1 (GLP-1) receptor knockout mice, Zn²⁺ reduced glucose by 15-28% (p < 0.05-p < 0.01) and increased insulin release by 35-43% (p < 0.01). In contrast Zn²⁺ had no effect on responses of glucose-dependent insulinotropic polypeptide (GIP) receptor knockout mice. Consistent with this, Zn²⁺ had no effect on circulating total GLP-1 whereas GIP release was stimulated by 26% (p < 0.05) in lean mice. Immunocytochemistry demonstrated GPR39 expression on mouse enteroendocrine L- and K-cells, GLUTag cells and pGIP/Neo STC-1 cells. Zn²⁺ had a direct effect on GIP secretion from pGIPneo STC-1 cells, increasing GIP secretion by 1.3-fold. GPR39 is expressed on intestinal L- and K-cells, and stimulated GIP secretion plays an integral role in mediating enhanced insulin secretion and glucose tolerance following oral administration of Zn²⁺. This suggests development of potent and selective GPR39 agonists as a therapeutic approach for diabetes.

2-Mercapto Benzothiazole Derivatives: As Potential Leads for the Diabetic Management

BACKGROUND

Results of our previous studies on antiglycation activity, and the noncytotoxicity of 2-mercapto benzothiazoles, encouraged us to further widen our investigation towards the identification of leads against diabetes mellitus.

METHODS

33 derivatives of 2-mercapto benzothiazoles 1-33 were evaluated for in vitro α- glucosidase inhibitory activity. Mode of inhibition was deduced by kinetic studies. To predict the interactions of 2-mercapto benzothiazole derivatives 1-33 with the binding pocket of α-glucosidase enzyme, molecular docking studies were performed on the selected inhibitors.

RESULTS

Compounds 2-4, 6-7, 9-26, 28 and 30 showed many folds potent α-glucosidase inhibitory activity in the range of IC50 = 31.21-208.63 μM, as compared to the standard drug acarbose (IC50 = 875.75 ± 2.08 μM). It was important to note that except derivative 28, all other derivatives were also found previously to have antiglycating potential in the range of IC50 = 187.12-707.21 μM.

CONCLUSION

A number of compounds were identified as dual nature as antiglycating agent and α- glucosidase inhibitors. These compounds may serve as potential lead candidates for the management of diabetes mellitus.

Gluc-HET, a complementary chick embryo model for the characterization of antidiabetic compounds

Insulin resistance and β cell failure are the main causes of elevated blood glucose levels in Type 2 diabetes mellitus (T2DM), a complex and multifactorial metabolic disease. Several medications to treat or reduce the symptoms of T2DM are used, including the injection of insulin and the application of insulin sensitizing or glucose production reducing drugs. Furthermore, the use of phytochemicals has attracted increasing attention for the therapy and prevention of T2DM. In order to identify and characterize antidiabetic compounds, efficient test systems are required. Here we present a modified chick embryo model (hens egg test, HET), which has originally been developed to determine the potential irritancy of chemicals, as a versatile tool for the characterization of phytochemicals with antidiabetic properties. We termed this modified assay variation Gluc-HET. More precisely, we determined the influence of variations in the incubation time of the fertilized eggs and studied the effects of different buffer parameters, such as the temperature, composition and volume, used for drug application. In addition, we tested several putative antidiabetic plant extracts, which have been identified in an in-vitro primary screening procedure, for their effectiveness in reducing blood glucose levels in-ovo. Taken together, our Gluc-HET model has proven to be a reliable and manageable system for the characterization of antidiabetic compounds.

Design, synthesis, and biological evaluation of aryl N-methoxyamide derivatives as GPR119 agonists

A series of N-methoxyamide derivatives was identified and evaluated as GPR119 agonists. Several N-methoxyamides with thienopyrimidine and pyridine scaffolds showed potent GPR119 agonistic activities. Among them, compound 9c displayed good in vitro activity and potency. Moreover, compound 9c lowered glucose excursion in mice in an oral glucose tolerance test and increased GLP-1 secretion in intestinal cells.

GPR39 receptors and actions of trace metals on pancreatic beta cell function and glucose homoeostasis

AIMS

G-protein-coupled receptor 39 (GPR39) has been implicated in glucose homoeostasis, appetite control and gastrointestinal tract function.

METHODS

This study used clonal BRIN-BD11 cells and mouse pancreatic islets to assess the insulin-releasing actions of trace metals believed to act via GPR39, and the second messenger pathways involved in mediating their effects. Micromolar concentrations of Zn(2+), Cu(2+), Ni(2+) and Co(2+) were examined under normoglycaemic and hyperglycaemic conditions. Mechanistic studies investigated changes of intracellular Ca(2+), cAMP generation and assessment of cytotoxicity by LDH release. Cellular localisation of GPR39 was determined by double immunohistochemical staining.

RESULTS

All trace metals (7.8-500 µmol/l) stimulated insulin release with Cu(2+) being the most potent in isolated islets, with an EC50 value of 87 μmol/l. Zn(2+) was the most selective with an EC50 value of 125 μmol/l. Enhancement of insulin secretion was also observed with Ni(2+) (179 μmol/l) and Co(2+) (190 μmol/l). These insulin-releasing effects were confirmed using clonal BRIN-BD11 cells which exhibited enhanced intracellular Ca(2+) (p < 0.05-p < 0.001) and cAMP generation (p < 0.05-p < 0.001) in response to trace metals. Oral administration of Zn(2+), Ni(2+) and Cu(2+) (50 µmol/kg together with 18 mmol/kg glucose) decreased the glycaemic excursion (p < 0.05-p < 0.01) and augmented insulin secretion (p < 0.05-p < 0.01) in NIH Swiss mice.

CONCLUSIONS

This study has demonstrated the presence of GPR39 and the insulinotropic actions of trace metals on BRIN-BD11 cells and pancreatic beta cells, together with their antihyperglycaemic actions in vivo. These data suggest that development of agonists capable of specifically activating GPR39 may be a useful new therapeutic approach for diabetes management.

Damage-associated molecular patterns and their pathological relevance in diabetes mellitus

Diabetes, a group of metabolic and age-related diseases, is a major global health problem, the incidence of which has increased dramatically in recent decades. Type 1 diabetes mellitus (T1DM) is a complex, T cell-mediated autoimmune disease characterized by immune cell infiltration and chronic inflammation in the islets of Langerhans. Type 2 diabetes mellitus (T2DM) is a complex metabolic disease characterized by hyperglycemia (high blood sugar) resulting from insulin resistance and β-cell dysfunction. The involvement of inflammatory processes, such as immune cell infiltration, and chronic inflammation in the pathogenesis of diabetes is less well understood in T2DM than in T1DM. However, studies conducted in the past decade have shown a strong link between inflammation and metabolic dysfunction. They have also shown that chronic inflammation plays a key role in the pathogenesis of both T1DM and T2DM. Two immunological factors commonly contribute to the pathogenesis of diabetes: the activation of inflammasomes and the release of proinflammatory cytokines in response to damage-associated molecular patterns (DAMPs). Inflammasomes are intracellular multiprotein molecular platforms. DAMPs act as endogenous danger signals. Here, we review current research on the function(s) of inflammasomes and DAMPs and discuss their pathological relevance and therapeutic implications in diabetes.

Prevention of cardiovascular complications of the metabolic syndrome: focus on pharmacotherapy

The metabolic syndrome increases the risk of atherothrombotic cardiovascular disease (CVD) and diabetes. In turn, diabetes promotes the development of atheroma and is regarded as a coronary heart disease risk equivalent. A multifactorial therapeutic strategy is advocated for patients with the metabolic syndrome to improve cardiovascular risk factor profiles and to reduce the chances of developing type 2 diabetes. Individual components of the syndrome must be addressed using safe, efficacious, and cost-effective measures. There is general agreement that lifestyle modifications, including control of body weight, avoidance of central adiposity, adoption of an antiatherogenic diet, and regular physical activity, are crucial. However, as the magnitude of the individual components of the metabolic syndrome increases with time, lifestyle measures are often insufficient. An individual with metabolic syndrome will often require drug treatment for hyperglycemia, atherogenic dyslipidemia, and high blood pressure, together with antiplatelet therapy. Reducing the need for polypharmacy is an increasingly important consideration for clinicians and the pharmaceutical industry; to date, no single therapy has emerged that targets the root cause(s) of the syndrome. HMG-CoA reductase inhibitors are important agents that reduce CVD morbidity and mortality, in people with impaired fasting glucose or metabolic syndrome. Selective cannabinoid receptor antagonists appear promising because they improve or attenuate several key defects of the syndrome. Thiazolidinediones and metformin are presently licensed for treatment of type 2 diabetes but may prove to have a broader role in future. Novel insulin-sensitizing drugs are under investigation. Drugs that act to prevent or reverse endothelial dysfunction may be of particular utility in preventing cardiovascular disease, especially if initiated before tissue damage has become irreversible. Insulin therapy, which has antiinflammatory and endothelial protective properties, has been shown to reduce morbidity and mortality in high-risk nondiabetic patients during critical illness. Potential synergy between different classes of drugs with metabolic and/or cardiovascular protective properties merits further investigation.

Antibodies in metabolic diseases

In the past century, incidences of chronic metabolic diseases, such as obesity and type II diabetes, have increased dramatically. Obesity and abnormal insulin level are associated with a wide variety of health problems including a markedly increased risk for type II diabetes, fatty liver, hepato-biliary and gallbladder diseases, cardiovascular pathologies, neurodegenerative disorders, asthma and a variety of cancers. The development of therapeutic antibodies has evolved over the past decades into a mainstay of therapeutic options for patients with inflammatory diseases and cancer, while other indication areas such as metabolic diseases have so far only been rarely addressed. Although therapeutic antibodies might have advantages over current type II diabetes treatments like favorable serum half-life and high specificity, their development is also likely to face obstacles. For example the technical feasibility of antibody generation against G protein coupled receptors and transporters is challenging, patient compliance for a likely needle application might be limited, bioavailability in organs involved in the pathogenesis like the brain might be suboptimal and reimbursement issues for high treatment costs have to be taken into account. The current review focuses on the pathogenesis and standard therapeutic approaches as well as antibodies in development and potential antibody targets for type II diabetes.

Hypothalamic obesity in patients with craniopharyngioma: profound changes of several weight regulatory circuits

One of the most striking examples of dysfunctional hypothalamic signaling of energy homeostasis is observed in patients with hypothalamic lesions leading to hypothalamic obesity (HO). This drastic condition is frequently seen in patients with craniopharyngioma (CP), an embryological tumor located in the hypothalamic and/or pituitary region, frequently causing not only hypopituitarism, but also leading to damage of medial hypothalamic nuclei due to the tumor and its treatment. HO syndrome in CP patients is characterized by fatigue, decreased physical activity, uncontrolled appetite, and morbid obesity, and is associated with insulin and leptin resistance. Mechanisms leading to the profoundly disturbed energy homeostasis are complex. This review summarizes different aspects of important clinical studies as well as data obtained in rodent studies. In addition a model is provided describing how medial hypothalamic lesion can interact simultaneously with several weight-regulating circuitries.

Sitagliptin augments angiotensin II-induced renal vasoconstriction in kidneys from rats with metabolic syndrome

1. Dipeptidyl peptidase (DPP) IV inhibitors enhance renovascular responses to angiotensin (Ang) II in spontaneously hypertensive rats (SHR), but not Wistar-Kyoto rats. Because DPPIV inhibitors are often used in metabolic syndrome, it is important to determine whether DPPIV inhibition in this setting enhances renovascular responses to AngII. 2. Six-week-old Lean-ZSF1 rats (harbouring SHR genes, but without metabolic syndrome; n = 11) and Obese-ZSF1 rats (harbouring SHR genes and expressing metabolic syndrome; n = 10) were provided food and water ad libitum, and metabolic parameters and renovascular responses to AngII were assessed when the animals were 7 and 8 weeks of age, respectively. 3. At 7 weeks of age, compared with Lean-ZSF1, Obese-ZSF1 demonstrated significant (P < 0.05) increases in bodyweight (262 +/- 8 vs 310 +/- 13 g), plasma glucose (112 +/- 4 vs 153 +/- 9 mg/dL), haemoglobin A1c (4.7 +/- 0.1 vs 5.8 +/- 0.4%), urinary glucose excretion (0.021 +/- 0.003 vs 6.70 +/- 1.80 g/kg bodyweight per 24 h) and urinary protein excretion (100 +/- 7 vs 313 +/- 77 mg/kg bodyweight per 24 h). Mean blood pressure was high (133 +/- 7 mmHg) in both strains. 4. At 8 weeks of age, kidneys were isolated and perfused. In Lean-ZSF1 rats, renovascular responses (i.e. changes in perfusion pressure) to physiological levels of AngII (0.1 nmol/L) were 3.4 +/- 1.3 and 18.2 +/- 5.9 mmHg in untreated (n = 5) and 1 micromol/L sitagliptin-treated (n = 6) kidneys, respectively. In Obese-ZSF1 rats, renovascular responses to AngII were 5.5 +/- 1.3 and 17.8 +/- 8.2 mmHg in untreated (n = 4) and sitagliptin-treated (n = 6) kidneys, respectively. Analysis of variance revealed a significant (P = 0.0367) effect of sitagliptin on renovascular responses to AngII that was independent of strain. 5. In conclusion, sitagliptin enhances renovascular responses to AngII in rats harbouring SHR genes and this effect persists in rats with diabetic nephropathy and metabolic syndrome.

Use of DPP-4 inhibitors in type 2 diabetes: focus on sitagliptin

Inhibition of dipeptidyl peptidase-4 (DPP-4) prevents the inactivation of glucagonlike peptide-1 (GLP-1). This increases circulating levels of active GLP-1, stimulates insulin secretion and inhibits glucagon secretion, which results in lowering of glucose levels and improvement of the glycemic control in patients with type 2 diabetes. This review summarizes experiences with DPP-4 inhibition in the treatment of type 2 diabetes, with a focus on sitagliptin. Sitagliptin has in several clinical studies been shown to improve metabolic control in type 2 diabetes, both when used as monotherapy and when used in combination with metformin, sulfonylurea, thiazolidinediones or insulin. The reduction in HbA(1c) is ≈ 0.6% to 1.0% from baseline levels of 7.5% to 8.7% over 6 to 12 months therapy. Sitagliptin has a favorable safety profile, is highly tolerable, and there is a minimal risk of hypoglycemia. Furthermore, sitagliptin is body weight neutral or induces a slight body weight reduction. Sitagliptin may be used in the early stages of type 2 diabetes in combination with metformin or other treatments in subjects with inadequate glycemic control on these treatments alone. Sitagliptin may also be used in monotherapy and, finally, sitagliptin may be used in combination with insulin in more advanced stages of the disease.

Spirulina protects against rosiglitazone induced osteoporosis in insulin resistance rats

AIM

The study was undertaken to assess the protective effect of Spirulina fusiformis extract against Rosiglitazone induced osteoporosis and pharmacodynamic effects of Rosiglitazone with Spirulina in treating hyperglycemia and hyperlipidemia of insulin resistance rat.

METHOD

For this aim, 30 Wistar albino rats were equally divided into five groups as control (C), diabetes mellitus (DM), diabetes mellitus+Rosiglitazone (DM+R), diabetes mellitus+Spirulina (DM+S), and diabetes mellitus+Rosiglitazone+Spirulina (DM+R+S). Serum glucose, triglyceride, HDL, LDL and insulin concentrations were estimated by routine standard methods in blood samples collected on 21th day. Integrity of the bone surface was examined by scanning electronic microscopy, and bone strength was measured by micro-hardness test on 45th day.

RESULTS

A significant decrease in total bone mineral density was observed in group DM+R rats (p<0.05). The number and depth of resorptive pits on surface of the bone in Rosiglitazone treated rats improved clearly with Spirulina administration. The intactness and integrity of the bone surface as well as the bone strength improved due to the high content of calcium and phosphorous in Spirulina. Besides, chromium and gamma-linoleic acid in Spirulina helped to decrease the fasting serum glucose, HDL, LDL and triglycerides levels in insulin resistance rats.

CONCLUSION

These findings suggest that combination therapy of Rosiglitazone with Spirulina reduced the risk of osteoporosis in insulin resistance rats. Additionally, Spirulina complemented the antihyperglycemic and antilipidemic activity of Rosiglitazone.

New therapies for diabesity

Many patients with type 2 diabetes are obese (diabesity), and the two conditions together impose a particularly complex therapeutic challenge. Several differently acting agents are often required at the same time, encouraging development of more single-tablet combinations. Longer-acting (once daily and once weekly) injected agonists of glucagon-like peptide-1 are due to provide additional options to stimulate insulin secretion with weight loss and minimal risk of hypoglycemia. Further, dipeptidyl peptidase-4 inhibitors ("weight-neutral" insulinotropic agents) are also expected. Sodium-glucose cotransporter 2 inhibitors offer a new option to reduce hyperglycemia and facilitate weight loss by increasing the elimination of glucose in the urine. Selective peroxisome proliferator-activated receptor modulators are being studied to produce compounds with desired effects. Many other agents with antidiabetic and antiobesity activity are progressing in clinical development.

Islet G protein-coupled receptors as potential targets for treatment of type 2 diabetes

Islet dysfunction - characterized by a combination of defective insulin secretion, inappropriately high glucagon secretion and reduced beta-cell mass - has a central role in the pathophysiology of type 2 diabetes. Several G protein-coupled receptors (GPCRs) expressed in islet beta-cells are known to be involved in the regulation of islet function, and therefore are potential therapeutic targets. This is evident from the recent success of glucagon-like peptide 1 (GLP1) mimetics and dipeptidyl peptidase 4 (DPP4) inhibitors, which promote activation of the GLP1 receptor to stimulate insulin secretion and inhibit glucagon secretion, and also have the potential to increase beta-cell mass. Other islet beta-cell GPCRs that are involved in the regulation of islet function include the glucose-dependent insulinotropic peptide (GIP) receptor, lipid GPCRs, pleiotropic peptide GPCRs and islet biogenic amine GPCRs. This Review summarizes islet GPCR expression, signalling and function, and highlights their potential as targets for the treatment of type 2 diabetes.

Emerging dipeptidyl peptidase-4 inhibitors for the treatment of diabetes

Inhibition of dipeptidyl peptidase-4 (DPP-4) prevents the inactivation of glucagon-like peptide-1 (GLP-1). This increases circulating levels of active GLP-1, stimulates insulin secretion and inhibits glucagon secretion, resulting in lowering of glucose levels and improvement of glycemic control in patients with type 2 diabetes. Several DPP-4 inhibitors are emerging for therapeutic use. Most experience exists for sitagliptin, vildagliptin, saxagliptin and alogliptin. They all improve metabolic control in type 2 diabetes in monotherapy and in combination therapy with metformin, sulfonylurea and thiazolidinediones. Vildagliptin and alogliptin have also been shown to improve glycemic control when added to insulin therapy, and sitagliptin improves glycemic control in triple therapy with metformin plus thiazolidinedione. DPP-4 inhibition also shows a favorable safety profile, high tolerability, only a minimal risk of hypoglycemia, and body-weight neutrality. The main clinical indication for DPP-4 inhibitors will be in the early stage of type 2 diabetes, in combination with metformin or other treatments in subjects with inadequate glycemic control on these treatments alone. The durability and long-term safety of DPP-4 inhibition, as well as clinical positioning in relation to GLP-1 mimetics, remain now to be established.

GPR119, a novel G protein-coupled receptor target for the treatment of type 2 diabetes and obesity

GPR119 is a G protein-coupled receptor expressed predominantly in the pancreas (beta-cells) and gastrointestinal tract (enteroendocrine cells) in humans. De-orphanization of GPR119 has revealed two classes of possible endogenous ligands, viz., phospholipids and fatty acid amides. Of these, oleoylethanolamide (OEA) is one of the most active ligands tested so far. This fatty acid ethanolamide is of particular interest because of its known effects of reducing food intake and body weight gain when administered to rodents. Agonists at the GPR119 receptor cause an increase in intracellular cAMP levels via G(alphas) coupling to adenylate cyclase. In vitro studies have indicated a role for GPR119 in the modulation of insulin release by pancreatic beta-cells and of GLP-1 secretion by gut enteroendocrine cells. The effects of GPR119 agonists in animal models of diabetes and obesity are reviewed, and the potential value of such compounds in future therapies for these conditions is discussed.

Small-molecule ghrelin receptor antagonists improve glucose tolerance, suppress appetite, and promote weight loss

Ghrelin, through action on its receptor, GH secretagogue receptor type 1a (GHS-R1a), exerts a variety of metabolic functions including stimulation of appetite and weight gain and suppression of insulin secretion. In the present study, we examined the effects of novel small-molecule GHS-R1a antagonists on insulin secretion, glucose tolerance, and weight loss. Ghrelin dose-dependently suppressed insulin secretion from dispersed rat islets. This effect was fully blocked by a GHS-R1a antagonist. Consistent with this observation, a single oral dose of a GHS-R1a antagonist improved glucose homeostasis in an ip glucose tolerance test in rat. Improvement in glucose tolerance was attributed to increased insulin secretion. Daily oral administration of a GHS-R1a antagonist to diet-induced obese mice led to reduced food intake and weight loss (up to 15%) due to selective loss of fat mass. Pair-feeding experiments indicated that weight loss was largely a consequence of reduced food intake. The impact of a GHS-R1a antagonist on gastric emptying was also examined. Although the GHS-R1a antagonist modestly delayed gastric emptying at the highest dose tested (10 mg/kg), delayed gastric emptying does not appear to be a requirement for weight loss because lower doses produced weight loss without an effect on gastric emptying. Consistent with the hypothesis that ghrelin regulates feeding centrally, the anorexigenic effects of potent GHS-R1a antagonists in mice appeared to correspond with their brain exposure. These observations demonstrate that GHS-R1a antagonists have the potential to improve the diabetic condition by promoting glucose-dependent insulin secretion and promoting weight loss.

Interactions between microvascular and macrovascular disease in diabetes: pathophysiology and therapeutic implications

Convention partitions the complications of diabetes into two main subtypes. First are the diabetes-specific microvascular complications of retinopathy, nephropathy and neuropathy; second are the atherothrombotic macrovascular complications that account for the majority of premature deaths. Pathological interactions between microvascular and macrovascular complications, for example, nephropathy and macrovascular disease, are common. Similar mechanisms and shared risk factors drive the development and progression of both small and large vessel disease. This concept has therapeutic implications. Mounting evidence points to the need for multifactorial strategies to prevent vascular complications in subjects with diabetes and/or the metabolic syndrome. We advocate a combined therapeutic approach that addresses small and large vessel disease. Preferential use should be made of drug regimens that (i) maximize vascular protection, (ii) reduce the risk of iatrogenic vascular damage and (iii) minimize the increasing problem of polypharmacy.

Inhibition of renal dipeptidyl peptidase IV enhances peptide YY1-36-induced potentiation of angiotensin II-mediated renal vasoconstriction in spontaneously hypertensive rats

Dipeptidyl peptidase IV inhibitors are a new class of antidiabetic drugs. It is urgent, therefore, to fully understand the pharmacology of these inhibitors. Although dipeptidyl peptidase IV metabolizes at least 24 endogenous substrates, the pharmacological consequences of inhibiting the metabolism of most of these substrates is unknown. Our previous results show that Y(1) receptors, but not Y(2) receptors, enhance renovascular responses to angiotensin II in kidneys from genetically susceptible animals (spontaneously hypertensive rats). Dipeptidyl peptidase IV converts peptide YY(1-36) (circulating hormone) to peptide YY(3-36), and peptide YY(1-36) is a Y(1)-receptor agonist, whereas peptide YY(3-36) is a selective Y(2)-receptor agonist. Therefore, it is conceivable that inhibition of dipeptidyl peptidase IV in genetically susceptible kidneys may increase the ability of peptide YY(1-36) to potentiate angiotensin II-induced renal vasoconstriction. Here we demonstrate that in kidneys from spontaneously hypertensive rats 1) peptide YY(1-36) potentiates renovascular responses to angiotensin II, whereas peptide YY(3-36) has little effect, 2) 3-N-[(2S,3S)-2-amino-3-methylpentanoyl]-1,3-thiazolidine (P32/98) (dipeptidyl peptidase IV inhibitor) augments the ability of peptide YY(1-36) to enhance renovascular responses to angiotensin II, 3) dipeptidyl peptidase IV is expressed in preglomerular microvessels and glomeruli, 4) kidneys metabolize arterial PYY(1-36) to PYY(3-36) via a mechanism blocked by P32/98, and 5) preglomerular microvessels and glomeruli convert peptide YY(1-36) to peptide YY(3-36), and this conversion is inhibited by P32/98. We conclude that dipeptidyl peptidase IV is expressed in the renal microcirculation and inhibition of this ecto-enzyme causes arterial PYY(1-36) to more effectively enhance angiotensin II-induced renal vasoconstriction in genetically susceptible kidneys.

Quinazolinone derivatives as orally available ghrelin receptor antagonists for the treatment of diabetes and obesity

The peptide hormone ghrelin is the endogenous ligand for the type 1a growth hormone secretagogue receptor (GHS-R1a) and the only currently known circulating appetite stimulant. GHS-R1a antagonism has therefore been proposed as a potential approach for obesity treatment. More recently, ghrelin has been recognized to also play a role in controlling glucose-induced insulin secretion, which suggests another possible benefit for a GHS-R1a antagonist, namely, the role as an insulin secretagogue with potential value for diabetes treatment. In our laboratories, piperidine-substituted quinazolinone derivatives were identified as a new class of small-molecule GHS-R1a antagonists. Starting from an agonist with poor oral bioavailability, optimization led to potent, selective, and orally bioavailable antagonists. In vivo efficacy evaluation of selected compounds revealed suppression of food intake and body weight reduction as well as glucose-lowering effects mediated by glucose-dependent insulin secretion.

Obese versus non-obese patients with type 2 diabetes: patient-reported outcomes and utility of weight change

INTRODUCTION

This study (1) used patient-reported outcome measures to assess and compare the health status of type 2 diabetes patients with and without obesity and (2) assessed the value of weight change among obese and non-obese subgroups, using standard gamble (SG) utility methodology.

METHODS

Among a sample with type 2 diabetes in the United Kingdom, individuals with obesity (BMI > or = 30 kg/m2) were identified and compared to non-obese patients. Patients completed the EQ-5D, Psychological General Well-Being Index, Appraisal of Diabetes Symptoms, and Diabetes Symptom Checklist-Revised (DSC-R). SG interviews assessed the utility of the 'basic' type 2 diabetes health state anchored to respondents' body weight, as well as health states with altered weight.

RESULTS

A total of 129 patients (74 obese; 55 non-obese) completed interviews (mean age 55.9 years; 64.3% male). Obese patients reported lower health status (EQ-5D VAS; between-group difference: p < 0.001) and greater symptom impact (several DSC-R scales, p < 0.05). Utilities of the basic health state were 0.86 (obese) and 0.91 (non-obese; p = 0.02). Hypothetical health states with higher weight received lower utilities, whereas reduced weight was associated with increased utility. There was a between-group difference in the disutility associated with 5% higher weight (obese 0.068; non-obese 0.051; p = 0.03).

DISCUSSION

Compared with non-obese patients, the obese group reported lower health status and greater symptom impact. SG interviews found an inverse relationship between weight and utility. Furthermore, obese patients with type 2 diabetes may value weight change differently than non-obese patients. Study limitations include the sample size and the use of a patient sample, rather than a sample selected from the general population. Overall, the results demonstrate that utilities can differ by patient subgroups, even among patients with the same diagnosis.

Effective surgical treatment of obesity may be mediated by ablation of the lipogenic gut hormone gastric inhibitory polypeptide (GIP): evidence and clinical opportunity for development of new obesity-diabetes drugs?

Roux-en-Y bypass surgery is increasingly used for treatment of gross obesity due to the general inability of lifestyle change and existing drug treatments to counter the obesity epidemic. This common form of bariatric surgery involves bypass of the small intestine with significant reduction of body of weight that is independent of malabsorption. Strikingly, obesity-related diabetes is also cured by the procedure but prior to body weight loss. This is due to rapid improvement of insulin resistance and associated pancreatic beta-cell function. Several hypotheses have been proposed to account for this phenomenon, but the most attractive concerns surgical ablation of gastric inhibitory polypetide (GIP)-secreting intestinal K-cells. Thus, circulating GIP levels are decreased after Roux-en-Y bypass surgery and GIP is known to play a key role in lipid metabolism and fat deposition. Further, both genetic and chemical ablation of GIP in animal models has been shown to protect against obesity and associated metabolic disturbances. These observations in animals and man suggest that GIP receptor antagonism may afford an alternative therapeutic option for treatment of obesity-diabetes.

Treating insulin resistance: future prospects

Insulin resistance typically reflects multiple defects of insulin receptor and post-receptor signalling that impair a diverse range of metabolic and vascular actions. Many potential intervention targets and compounds with therapeutic activity have been described. Proof of principle for a non-peptide insulin mimetic has been demonstrated by specific activation of the intracellular B-subunit of the insulin receptor. Potentiation of insulin action has been achieved with agents that enhance phosphorylation and prolong the tyrosine kinase activity of the insulin receptor and its protein substrates after activation by insulin. These include inhibitors of phosphatases and serine kinases that normally prevent or terminate tyrosine kinase signalling. Additional approaches involve increasing the activity of phosphatidylinositol 3-kinase and other downstream components of the insulin signalling pathways. Experimental interventions to remove signalling defects caused by cytokines, certain adipocyte hormones, excess fatty acids, glucotoxicity and negative feedback by distal signalling steps have also indicated therapeutic possibilities. Several hormones, metabolic enzymes, minerals, co-factors and transcription co-activators have shown insulin-sensitising potential. Since insulin resistance affects many metabolic and cardiovascular diseases, it provides an opportunity for simultaneous therapeutic attack on a broad front.

Naphthalenemethyl ester derivative of dihydroxyhydrocinnamic acid, a component of cinnamon, increases glucose disposal by enhancing translocation of glucose transporter 4

AIMS/HYPOTHESIS

Cinnamon extracts have anti-diabetic effects. Phenolic acids, including hydrocinnamic acids, were identified as major components of cinnamon extracts. Against this background we sought to develop a new anti-diabetic compound using derivatives of hydroxycinnamic acids purified from cinnamon.

METHODS

We purified hydroxycinnamic acids from cinnamon, synthesised a series of derivatives, and screened them for glucose transport activity in vitro. We then selected the compound with the highest glucose transport activity in epididymal adipocytes isolated from male Sprague-Dawley rats in vitro, tested it for glucose-lowering activity in vivo, and studied the mechanisms involved.

RESULTS

A naphthalenemethyl ester of 3,4-dihydroxyhydrocinnamic acid (DHH105) showed the highest glucose transport activity in vitro. Treatment of streptozotocin-induced diabetic C57BL/6 mice and spontaneously diabetic ob/ob mice with DHH105 decreased blood glucose levels to near normoglycaemia. Further studies revealed that DHH105 increased the maximum speed of glucose transport and the translocation of glucose transporter 4 (GLUT4, now known as solute carrier family 2 [facilitated glucose transporter], member 4 [SLC2A4]) in adipocytes, resulting in increased glucose uptake. In addition, DHH105 enhanced phosphorylation of the insulin receptor-beta subunit and insulin receptor substrate-1 in adipocytes, both in vitro and in vivo. This resulted in the activation of phosphatidylinositol 3-kinase and Akt/protein kinase B, contributing to the translocation of GLUT4 to the plasma membrane.

CONCLUSIONS/INTERPRETATION

We conclude that DHH105 lowers blood glucose levels through the enhancement of glucose transport, mediated by an increase in insulin-receptor signalling. DHH105 may be a valuable candidate for a new anti-diabetic drug.

Type 1 diabetes

Type 1 diabetes accounts for only about 5-10% of all cases of diabetes; however, its incidence continues to increase worldwide and it has serious short-term and long-term implications. The disorder has a strong genetic component, inherited mainly through the HLA complex, but the factors that trigger onset of clinical disease remain largely unknown. Management of type 1 diabetes is best undertaken in the context of a multidisciplinary health team and requires continuing attention to many aspects, including insulin administration, blood glucose monitoring, meal planning, and screening for comorbid conditions and diabetes-related complications. These complications consist of microvascular and macrovascular disease, which account for the major morbidity and mortality associated with type 1 diabetes. Newer treatment approaches have facilitated improved outcomes in terms of both glycaemic control and reduced risks for development of complications. Nonetheless, major challenges remain in the development of approaches to the prevention and management of type 1 diabetes and its complications.