Thiazolidinediones-benefits on microvascular complications of type 2 diabetes

Computational and Pharmacological Evaluation of Carveol for Antidiabetic Potential

Background

Carveol is a natural drug product present in the essential oils of orange peel, dill, and caraway seeds. The seed oil of Carum Carvi has been reported to be antioxidant, anti-inflammatory, anti-hyperlipidemic, antidiabetic, and hepatoprotective.

Methods

The antidiabetic potential of carveol was investigated by employing in-vitro, in-vivo, and in-silico approaches. Moreover, alpha-amylase inhibitory assay and an alloxan-induced diabetes model were used for in-vitro and in-vivo analysis, respectively.

Results

Carveol showed its maximum energy values (≥ -7 Kcal/mol) against sodium-glucose co-transporter, aldose reductase, and sucrose-isomaltase intestinal, whereas it exhibited intermediate energy values (≥ -6 Kcal/mol) against C-alpha glucosidase, glycogen synthase kinases-3β, fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and other targets according to in-silico analysis. Similarly, carveol showed lower energy values (≥ 6.4 Kcal/mol) against phosphoenolpyruvate carboxykinase and glycogen synthase kinase-3β. The in-vitro assay demonstrated that carveol inhibits alpha-amylase activity concentration-dependently. Carveol attenuated the in-vivo alloxan-induced (1055.8 µMol/Kg) blood glucose level in a dose- and time-dependent manner (days 1, 3, 6, 9, and 12), compared to the diabetic control group, and further, these results are comparable with the metformin positive control group. Carveol at 394.1 µMol/Kg improved oral glucose tolerance overload in rats compared to the hyperglycemic diabetic control group. Moreover, carveol also attenuated the glycosylated hemoglobin level along with mediating anti-hyperlipidemic and hepatoprotective effects in alloxan-induced diabetic animals.

Conclusions

This study reveals that carveol exhibited binding affinity against different targets involved in diabetes and has antidiabetic, anti-hyperlipidemic, and hepatoprotective actions.

Understanding Aldose Reductase-Inhibitors interactions with free energy simulation

Aldose Reductase (AR) reduces a variety of substrates, such as aldehydes, aldoses and corticosteroids. It is the first and rate-limiting enzyme of the polyol pathway and is an important target enzyme for diabetes-associated complications, including retinopathy, neuropathy, and nephropathy. Inhibitors targeting this enzyme are structurally different and some of them have side effects. In existing publications, computational techniques are applied to investigate the binding affinities of existing inhibitors and predicting the affinities of newly designed ligands. However, these calculations only employ coarse and approximated methods such as docking and MM/PBSA. Brute force simulations are employed to study the dynamics of the system but no converged statistics is obtained. As a result, these computations provide results not consistent with experimental values and large discrepancies exist. In the current work, we employ the enhanced sampling technique of alchemical free energy simulation to calculate the binding affinities of several ligands targeting AR. The statistical error is defined with care and the correlation in the time-series data is fully considered. The statistically optimal estimators are used to extract the free energy estimates and the predicted results are in agreement with the experimental values. Less computationally demanding end-point free energy methods are also performed to compare their efficiency with the alchemical methods. As is expected, the end-point methods are of less accuracy and reliability compared with the alchemical free energy methods. The decomposition of the free energy difference in each alchemical transformation into the enthalpic and entropic components gives further insights on the thermodynamics. The enthalpy-entropy compensation is observed in this case. As the structural data obtained from experiments are only snapshots and more details are needed to understand the dynamics of the protein-ligand system, the conformational ensemble is analyzed. We identify important residues involved in the protein-ligand binding case and short-lived interactions formed due to fluctuations in the conformational ensemble. The current work shed light on the atomic detailed understanding of the dynamics of AR-inhibitors interactions.

Novel Benzylidene Thiazolidinedione Derivatives as Partial PPARγ Agonists and their Antidiabetic Effects on Type 2 Diabetes

Peroxisome proliferator-activated receptor γ (PPARγ) has received significant attention as a key regulator of glucose and lipid homeostasis. In this study, we synthesized and tested a library of novel 5-benzylidene-thiazolidin-2,4-dione (BTZD) derivatives bearing a substituent on nitrogen of TZD nucleus (compounds 1a-1k, 2i-10i, 3a, 6a, and 8a-10a). Three compounds (1a, 1i, and 3a) exhibited selectivity towards PPARγ and were found to be weak to moderate partial agonists. Surface Plasmon Resonance (SPR) results demonstrated binding affinity of 1a, 1i and 3a towards PPARγ. Furthermore, docking experiments revealed that BTZDs interact with PPARγ through a distinct binding mode, forming primarily hydrophobic contacts with the ligand-binding pocket (LBD) without direct H-bonding interactions to key residues in H12 that are characteristic of full agonists. In addition, 1a, 1i and 3a significantly improved hyperglycemia and hyperlipidaemia in streptozotocin-nicotinamide (STZ-NA)-induced diabetic rats at a dose of 36 mg/kg/day administered orally for 15 days. Histopathological investigations revealed that microscopic architecture of pancreatic and hepatic cells improved in BTZDs-treated diabetic rats. These findings suggested that 1a, 1i and 3a are very promising pharmacological agents by selectively targeting PPARγ for further development in the clinical treatment of type 2 diabetes mellitus.

Does glimepiride alter the pharmacokinetics of sildenafil citrate in diabetic nephropathy animals: investigating mechanism of interaction by molecular modeling studies

The present study evaluates possible drug interactions between glimepiride (GLIM) and sildenafil citrate (SIL) in streptozotocin (STZ)-induced diabetic nephropathic (DN) animals and also postulates the possible mechanism of interaction based on molecular modeling studies. Diabetic nephropathy was induced by single dose of STZ (60 mg kg(-1), i.p.) and was confirmed by assessing blood and urine biochemical parameters 28 days after induction. Selected DN animals were used to explore the drug interaction between GLIM (0.5 mg kg(-1), p.o.) and SIL (2.5 mg kg(-1), p.o.) on the 29th and 70th day of the protocol. Possible drug interaction was assessed by evaluating the plasma drug concentration using HPLC-UV and changes in biochemical parameters in blood and urine were also determined. The mechanism of the interaction was postulated from the results of a molecular modeling study using the Maestro module of Schrodinger software. DN was confirmed as there was significant alteration in blood and urine biochemical parameters in STZ-treated groups. The concentration of SIL increased significantly (P < 0.001) in rat plasma when co-administered with GLIM on the 70th day of the protocol. Molecular modeling revealed important interactions with rat serum albumin and CYP2C9. GLIM has a strong hydrophobic interaction with binding site residues of rat serum albumin compared to SIL, whereas for CYP2C9, GLIM forms a stronger hydrogen bond than SIL with polar contacts and hydrophobic interactions. The present study concludes that bioavailability of SIL increases when co-administered chronically with GLIM in the management of DN animals, and the mechanism is supported by molecular modeling studies.

Insulin signaling: implications for podocyte biology in diabetic kidney disease

PURPOSE OF REVIEW

Several key elements of the insulin signaling cascade contribute to podocyte function and survival. While it was initially thought that the consequences of altered insulin signaling to podocyte function was strictly related to altered glucose uptake, it has become clear that upstream signaling events involved in cell survival, lipid metabolism or nutrient sensing and modulated by insulin are strong independent contributors to podocyte function.

RECENT FINDINGS

Akt2, the major isoform of Akt activated following cellular insulin stimulation, protects against the progression of renal disease in nephron-deficient mice, and podocyte-specific deletion of Akt2 results in a more rapid progression of experimental glomerular disease. In diabetes, podocyte mammalian target of rapamycin activation clearly contributes to podocyte injury and regulated autophagy. Furthermore, podocyte-specific glucose transporter type 4 (GLUT4) deficiency protects podocytes by preventing mammalian target of rapamycin signaling independently of glucose uptake. Finally, intracellular lipids have been recently recognized as major modulators of podocyte insulin signaling and as a new therapeutic target.

SUMMARY

The identification of new contributors to podocyte insulin signaling is of extreme translational value as it may lead to new drug development strategies for diabetic kidney disease, as well as for other proteinuric kidney diseases.

Oral antihyperglycemic treatment options for type 2 diabetes mellitus

Table 3 provides an overview of the oral antihyperglycemic drugs reviewed in this article. A 2011 meta-analysis by Bennett and colleagues found low or insufficient quality of evidence favoring an initial choice of metformin, SUs, glinides, TZDs, or (table see text) DPP-4 inhibitors (alpha-glucosidase inhibitors, bromocriptine mesylate, and SGLT2 inhibitors were not included in this meta-analysis) with regard to the outcomes measures of all-cause mortality, cardiovascular events and mortality, and incidence of microvascular disease (retinopathy, nephropathy, and neuropathy) in previously healthy individuals with newly diagnosed T2DM. Likewise, the Bennett and colleagues meta-analysis judged these drugs to be of roughly equal efficacy with regard to reduction of HbA1c (1%–1.6%) from the pretreatment baseline. The ADOPT clinical trial of 3 different and, at the time, popular, oral monotherapies for T2DM provides support for the consensus recommendation of metformin as first-line therapy. The ADOPT trial showed slightly superior HbA1c reduction for rosiglitazone compared with metformin, which was in turn superior to glyburide. However, significant adverse events, including edema, weight gain, and fractures, were more common in the rosiglitazone-treated patients. The implication of this trial is that the combination of low cost, low risk, minimal adverse effects, and efficacy of metformin justifies use of this agent as the cornerstone of oral drug treatment of T2DM. Judicious use of metformin in groups formerly thought to be at high risk for lactic acidosis (ie, those with CHF, chronic kidney disease [eGFR >30 mL/min/1.73 m2], and the elderly) may be associated with mortality benefit rather than increased risk. Secondary and tertiary add-on drug therapy should be individualized based on cost, personal preferences, and overall treatment goals, taking into account the wishes and priorities of the patient.

Diabetic neuropathy in older adults

Diabetic neuropathy is a heterogeneous disease with diverse pathology. Recognition of the clinical homolog of these pathologic processes is necessary in achieving appropriate intervention. Treatment should be individualized so the particular manifestation and underlying pathogenesis of each patient's clinical presentation are considered. In older adults, special care should be taken to manage pain while optimizing daily function and mobility, with the fewest adverse medication side effects. Older adults are at great risk for falling and fractures because of instability and weakness, and require strength exercises and coordination training. Ultimately agents that address large fiber dysfunction will be essential to reduce the gross impairment of quality of life and activities of daily living that neuropathy visits older people who have diabetes.

Synthesis, induced-fit docking investigations, and in vitro aldose reductase inhibitory activity of non-carboxylic acid containing 2,4-thiazolidinedione derivatives

In continuation of our studies, we here report a series of non-carboxylic acid containing 2,4-thiazolidinedione derivatives, analogues of previously synthesized carboxylic acids which we had found to be very active in vitro aldose reductase (ALR2) inhibitors. Although the replacement of the carboxylic group with the carboxamide or N-hydroxycarboxamide one decreased the in vitro ALR2 inhibitory effect, this led to the identification of mainly non-ionized derivatives with micromolar ALR2 affinity. The 5-arylidene moiety deeply influenced the activity of these 2,4-thiazolidinediones. Our induced-fit docking studies suggested that 5-(4-hydroxybenzylidene)-substituted derivatives may bind the polar recognition region of the ALR2 active site by means of the deprotonated phenol group, while their acetic chain and carbonyl group at position 2 of the thiazolidinedione ring form a tight net of hydrogen bonds with amino acid residues of the lipophilic specificity pocket of the enzyme.

Metformin/rosiglitazone combination pill (Avandamet) for the treatment of patients with Type 2 diabetes

More than 150 million people worldwide have diabetes, the prevalence of which is increasing so rapidly that the number of adults with diabetes in the world will rise to 300 million by the year 2025. In the US, approximately 21 million people have diabetes and in some areas of the country, the prevalence is as high as 50%. The pathophysiologic hallmarks consist of insulin resistance and progressive pancreatic beta-cell dysfunction. An increased metabolic demand for insulin due to increased insulin resistance usually precedes the development of hyperglycemia. At early stages, pancreatic beta cells compensate for insulin resistance by hypersecretion of insulin. However, the period of beta-cell compensation is followed by beta-cell failure, in which the pancreas fails to secrete sufficient insulin and diabetes ensues. Biguanides and thiazolidinediones (TZDs) are two unique classes of oral antidiabetic agents that are the most commonly used medications to improve insulin sensitivity. They have no direct effect on beta-cell function, although some indirect mechanisms of actions may help to preserve beta-cell function or slow beta-cell apoptosis. Their glucose-lowering effect results from improving insulin sensitivity in a complementary fashion: metformin reduces hepatic glucose production and TZDs increase skeletal muscle glucose use. The combination of metformin and rosiglitazone in a single pill (Avandamet), was approved by the FDA in October 2002 for the treatment of diabetes. As insulin resistance is a pathophysiologic cornerstone of diabetes and cardiovascular disease, the use of Avandamet represents an optimal approach to the treatment of diabetes. This manuscript reviews the pharmacology, safety and benefits of the combination pill Avandamet.