Shankar Munusamy

Nephroprotective Effects of Metformin in Diabetic Nephropathy

Metformin, a well‐known anti‐diabetic agent, is very effective in lowering blood glucose in patients with type 2 diabetes with minimal side‐effects. Metformin is also being recommended in the treatment of obesity and polycystic ovary syndrome. Metformin elicits its therapeutic effects mainly via activation of AMP‐activated kinase (AMPK) pathway. Renal cells under hyperglycemic or proteinuric conditions exhibit inactivation of cell defense mechanisms such as AMPK and autophagy, and activation of pathologic pathways such as mammalian target of rapamycin (mTOR), endoplasmic reticulum (ER) stress, epithelial‐to‐mesenchymal transition (EMT), oxidative stress, and hypoxia. As these pathologic pathways are intertwined with AMPK signaling, the potential benefits of metformin therapy in patients with type 2 diabetes would extend beyond its anti‐hyperglycemic effects. However, since metformin is eliminated unchanged through the kidneys and some studies have shown the incidence of lactic acidosis with its use during severe renal dysfunction, the use of metformin was contraindicated in patients with renal disease until recently. With more studies indicating the relatively low incidence of lactic acidosis and revealing the additional benefits with metformin therapy, the US FDA has now approved metformin to be administered in patients with established renal disease based on their renal function. The purpose of this review is to highlight the various mechanisms by which metformin protects renal cells that have lost its functionality in a diabetic or non‐diabetic setting and to enlighten the advantages and therapeutic potential of metformin as a nephroprotectant for patients with diabetic nephropathy and other non‐diabetic forms of chronic kidney disease. J. Cell. Physiol. 232: 731–742, 2017.

Sestrin2 as a Novel Biomarker and Therapeutic Target for Various Diseases

Sestrin2 (SESN2), a highly conserved stress-inducible metabolic protein, is known to repress reactive oxygen species (ROS) and provide cytoprotection against various noxious stimuli including genotoxic and oxidative stress, endoplasmic reticulum (ER) stress, and hypoxia. Studies demonstrate that the upregulation of Sestrin2 under conditions of oxidative stress augments autophagy-directed degradation of Kelch-like ECH-associated protein 1 (Keap1), which targets and breaks down nuclear erythroid-related factor 2 (Nrf2), a key regulator of various antioxidant genes. Moreover, ER stress and hypoxia are shown to induce Sestrins, which ultimately reduce cellular ROS levels. Sestrin2 also plays a pivotal role in metabolic regulation through activation of the key energy sensor AMP-dependent protein kinase (AMPK) and inhibition of mammalian target of rapamycin complex 1 (mTORC1). Other downstream effects of Sestrins include autophagy activation, antiapoptotic effects in normal cells, and proapoptotic effects in cancer cells. As perturbations in the aforementioned pathways are well documented in multiple diseases, Sestrin2 might serve as a potential therapeutic target for various diseases. Thus, the aim of this review is to discuss the upstream regulators and the downstream effectors of Sestrins and to highlight the significance of Sestrin2 as a biomarker and a therapeutic target in diseases such as metabolic disorders, cardiovascular and neurodegenerative diseases, and cancer.

Metformin Attenuates Albumin-induced Alterations in Renal Tubular Cells In Vitro.

Proteinuria (albuminuria) plays a crucial role in the etiology of chronic kidney disease (CKD) via alteration of multiple signaling pathways and cellular process in renal cells. The objectives of this study are to investigate the effects of activation of the energy‐sensing molecule AMP‐activated kinase (AMPK) in renal cells using metformin on endoplasmic reticulum (ER) stress, AKT, mTOR, epithelial‐to‐mesenchymal transition (EMT), autophagy, and apoptosis that are thought to mediate renal cell injury during proteinuria, and to dissect the AMPK‐ and non‐AMPK mediated effects of metformin using an in vitro model of albumin‐induced renal cell injury. Rat renal proximal tubular (NRK‐52E) cells were exposed to 10 and 15 mg/ml of albumin for 72 h in the presence of 1 mM Metformin and/or 0.5 µM compound C, and assessed for alterations in the aforementioned pathways. Metformin treatment restored AMPK phosphorylation and augmented autophagy in renal cells exposed to albumin. In addition, metformin treatment attenuated the albumin‐induced phosphorylation of AKT and the downstream targets of mTOR, and prevented albumin‐mediated inductions of EMT marker (α‐SMA), pro‐apoptotic ER stress marker CHOP, and apoptotic caspases ‐12 and ‐3 in renal cells. Blockade of metformin‐induced AMPK activation with compound C blunted the ER defense response and autophagy but had no effect on the markers of EMT and apoptosis in our model. Our studies suggest that metformin protects renal cells against proteinuric cytotoxicity via suppression of AKT and mTOR activation, inhibition of EMT and apoptosis, and augmentation of autophagy and ER defense response through AMPK‐independent and AMPK‐dependent mechanisms, respectively.

Aldose Reductase as a Drug Target for Treatment of Diabetic Nephropathy: Promises and Challenges.

Diabetic nephropathy (DN) is one of the most serious microvascular complications of diabetes mellitus and the leading cause of end stage renal disease. One of the key pathways activated in DN is the polyol pathway, in which glucose is converted to sorbitol (a relatively nonmetabolizable sugar) by the enzyme aldose reductase (AR). Shunting of glucose into this pathway causes disruption to glucose metabolism and subsequently damages the tissues via increased oxidative stress, protein kinase c activation and production of advanced glycation end products (AGE) in the kidney. This review aims to provide a comprehensive overview of the AR enzyme structure, substrate specificity and topology in normal physiology; to elaborate on the deleterious effects of AR activation in DN; and to summarize the potential therapeutic benefits and major challenges associated with AR inhibition in patients with DN.

4-Phenylbutyrate protects renal proximal tubular cells from palmitic acid-induced endoplasmic reticulum stress and cell death (1063.2)

This research is a formulation of the drug as an effervescent tablet by two methods (direct compression and wet granulation). The bitter taste was masked by saccharine as sweeting agent furthermore the effervescent effect of citric acid, tartaric acid and sodium bicarbonate lead to improve the taste of the drug. Also the Guar was used as binder agent lead to hide the taste. [1] [2] The vanillin which was used as flavoring agent also enhances the palatability. [3] [4] The formulated tablets were passed all the fundamental testes in the monograph, and also microbiological sensitivity test was done against (Escherichia coli, Salmonella typhi, Salmonellapara typhi and Staphylococcus aureus ) and then the results were compared to select the suitable one. Also compression was done between two formula of wet granulation method (the binder increase concentration and die cavity when was change).This study was found that formulating the drug as effervescent tablet by wet granulation method (low binder) concentration and die cavity No thirteen or twenty is the suitable.In this study, the in vitro cytotoxicity and antioxidant properties of the ethanolic and alkaloidic extract of Delphinium Staphisagria seeds were assessed. The antioxidant activity of the plant extracts..N (NPs) are developed with an aim to improve the solubility, targetability and bioavailability of a drug. Lipid Complexed Nanocrystals (LNCs) are novel and unique nanoparticulates offering high solubility and stability both in vitro and in vivo, hence making it more sustain to body fluids (electrolytes). In vitro instability (particle aggregation) of NPs may decrease its functional behavior in vivo leading to decreased bioavailability. Development of functional NCs requires modification of its surface properties in sequence to make them clinically more acceptable. The study aim to develop Glimepiride NCs using PEG 20000 by nanonization (precipitation) and stabilize them (both in vitro and in vivo) by complexation using Phospholipon 90 G (P 90G). Particle and solid state characterization studies were performed on NCs before and after complexation using photon correlation spectroscopy (PCS) and X-ray diffraction spectrometry (PXRD), differential scanning calorimetry (DSC), scanning electron spectroscopy (SEM) and fourier transform infrared spectroscopy (FTIR). In vivo drug targeting efficacy of LNCs was studied on pancreas of Male Wistar rats using HPLC. The particle and solid state characterization results show improved stability (decreased aggregation) with no change in drug properties after complexation. In vivo results on optimized LNCs show similar drug concentration in pancreas of rat as that of pure drug. AUC was significantly higher after 1 h signifying better in vivo stability. It can be concluded that in vitro and in vivo stability of NCs could be achieved by a complexation using P90 G. The possible outcome of these studies could result in development and delivery of stable and safe nanoproducts in the treatment of diabetes.O route is generally the preferable route of administration but it has certain restrictions for those drugs which absorb from particular region of gastrointestinal tract. The bioavailability of drugs was improved by increasing their retention time in the stomach and several approaches are described which are used to increase the gastric retention time of the dosage form. Controlled released dosage forms were used to improve therapy with several essential drugs. The development processes faces several physiological problems like the failure to control and localize the system within the desired region of the gastrointestinal system. This unpredictability leads to erratic bioavailability. Inclusion of the drug in gastroretentive drug delivery systems (GRDDS) can remain in the gastric region for several hours which could considerably extend the gastric residence time of drugs and get better bioavailability, reduce drug misuse, and increase the solubility of drugs which are less soluble in high pH environment. Gastroretention would make easy local drug delivery to the stomach and proximal small intestine. Gastroretention might aid to provide greater availability of new products and consequently improve therapeutic activity thus benefiting patients. Various gastroretentive approaches designed are high density, floating, super porous hydrogels, mucoadhesive, expandable, unfoldable, and magnetic systems. GRDDS is a loom to prolong gastric residence time, targeting site-specific drug release in upper gastro intestinal tract. These systems will help in constantly releasing the drug before it reaches the absorption window, thus ensuring best possible bioavailability.D are classified based on the BCS drug classification system. Thus there are drugs that have high and low solubility and those that have high and low bioavailability. The bioavailability of Class II drugs is limited by their solubility. Thus there is a wastage of the drug that is not bioavailable. This can be minimized by improving the drug solubility which would also result in a reduction in the dose. Over the years a lot of research has been done on improving solubility of drugs and various methods (conventional and novel) have been developed. While there are theoretical aspects of improving solubility, one must also consider the practical aspect of using it and then also think of the regulatory approval process. While some strategies may appear very promising, it may not be feasible to scale them up or register such a product due to safety constraints.A are a promising class of the new generation of HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs). From thousands of reported compounds, many possess the same basic structure of an aryl substituted azole ring linked by a thioglycolamide chain with another aromatic ring. In order to find novel extensions for this basic scaffold, we explored the 5-position substitution of triazole NNRTIs using molecular docking followed by synthesis of selected compounds. We found that heterocyclic substituents in 5-position of the triazole ring are detrimental to the inhibitory activity of compounds with 4-membered thioglycolamide linker. This substitution seems to be viable only for compounds with shorter 2-membered linker such as in derivatives of 4‐benzyl‐3‐ (benzylsulfanyl) ‐5‐ (thiophen‐2‐yl)‐4H‐1,2,4‐triazole reported earlier. A new scaffold of 2‐ [(4‐benzyl‐5‐methyl‐4H‐1,2,4‐triazol‐3‐yl) sulfanyl]‐N‐phenylacetamide has been identified in this study.Obesity is implicated as a significant risk factor for chronic kidney disease (CKD). High plasma free fatty acid levels observed with obesity impairs the endoplasmic reticulum (ER) and cause ER str...T aim of this study was to design and develop Lipid drug conjugated (LDC) nanoparticles for the oral delivery of Pemetrexed as an anitfolate agent for cancer therapy. LDC was produced using cold homogenization technique and was further characterized by various parameters; Particle size, Zeta potential, TEM, DSC, FTIR, AFM and XRD. Moreover, efficacy of the LDC towards the cancer cells was studied by ex vivo gut permeation study, CLSM, and MTT assay. The particle size of the optimized LDC was found to be 121.9±0.787nm and Zeta potential of -51.6mV±1.23 indicating a stable formulation. Entrapment efficiency was found to be 81.0%±0.89. TEM images revealed spherical morphology and were in corroboration with particle size measurements. FTIR analysis of LDC proved the presence of amide bond in lipid drug conjugate powder indicating the conjugation between drug and lipid. XRD data had showed the reduced intensity of drug and lipid peaks. In vitro release kinetics indicated the sustained release behavior of the LDC with r2 value of 0.986 for first order release kinetics. Stability studies proved that the formulation was stable with shelf life of 777.134 days. Ex vivo gut permeation studies revealed a very good enhancement in permeation of drug present in the LDC as compared to plain drug solution and were confirmed by CLSM. MTT assay conformed significant % toxicity at the end of 24 hrs and 48 hrs. The pharmacokinetic data revealed that the LDC (AUC 6345.67±9.47 h/mL) significant enhancement in the oral bioavailability as compared to plain drug solution (AUC 1501.02±12.67 h/mL).D delivery systems based on food proteins hold much promise because of their high nutritional value and excellent functional properties, including emulsification, gelation, foaming and water binding capacity. Food protein networks have the ability to interact with a wide range of active compounds via functional groups on their polypeptide primary structure, thus offering a variety of possibilities for reversible binding of active molecules and for protecting them until their release at the desired site within the body. Casein, CAS, the major milk protein, possesses a number of interesting properties that make it a good candidate for conventional and novel drug delivery systems. As a natural food product, this GRAS (generally recognized as safe) protein is biocompatible and biodegradable. This article reviews are aimed to associate bioactive molecules to casein and analyze the evidence of their efficacy in modifying the release and/or improving the bioavailability of the associated molecules. The high tensile strength of casein films, favors its use as an acceptable film-coating for tablets. Naturally occurring genipin and transglutaminase, were used as crosslinkers to prepare novel casein-based hydrogels for the controlled release of bioactives. Casein floating beads were developed to increase the residence time of drugs in the stomach based on its emulsifying and bubble-forming properties. Casein-based microparticles entrapping bioactive molecules were prepared via emulsificationchemical or enzymatic crosslinking, simple coacervation and electrostatic complexation. Casein nano-formulations were also prepared to deliver nutraceuticals and synthetic drugs via enzymatic crosslinking, graft copolymerization, heat-gelation and polyelectrolyte ionic complexation. CAS nanoparticles were used to encapsulate the hydrophobic anticancer drug, flutamide, aiming at controlling its release, enhancing its anti-tumor activity and reducing its hepatotoxicity. A significantly higher antiproliferative, anti-angiogenic, and apoptotic effects was demonstrated by the nanoparticles compared to drug solution in rat prostate cancer cells. Conclusively, these novel ionically-crosslinked milk protein nanovehicles offer a promising carrier to allow controlled intravenous delivery of hydrophobic anticancer drugs.R study was aimed to evolve dual approach using synergistically active combination of paclitaxel-topotecan (Pac-Top; 20:1, w/w) using surface engineered and integrally modified liposomes. Various liposomes (size ~200 nm) viz. Liposomes (Lip), PEGylated liposomes (PL) and FR-targeted PEGylated liposomes (FPL) were developed using thin film casting technique. In vitro drug release study reflected initial burst release followed by sustained profile at physiological conditions (37±0.5°C, pH 7.4) whilst abrupt dispersal (i.e. more than 90%) within 5 min at simulated tumor conditions (41±1°C, pH 4). These liposomes were studied for shape and physical interaction (and integrity), in vitro drug release kinetics modelling, haemolytic toxicity studies, ex vivo pharmacodynamics (OVCAR-3 cell lines), florescence microscopy, and pharmacokinetics in ovarian tumorbearing mice. Potentiated anticancer activity of FPL could be attributed to multifaceted features viz. thermosenstivity, long circulatory nature and targetability.