New Insights into the PPAR γ Agonists for the Treatment of Diabetic Nephropathy

New Insights into the Role of PPARγ in Skin Physiopathology

Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor expressed in many tissues, including skin, where it is essential for maintaining skin barrier permeability, regulating cell proliferation/differentiation, and modulating antioxidant and inflammatory responses upon ligand binding. Therefore, PPARγ activation has important implications for skin homeostasis. Over the past 20 years, with increasing interest in the role of PPARs in skin physiopathology, considerable effort has been devoted to the development of PPARγ ligands as a therapeutic option for skin inflammatory disorders. In addition, PPARγ also regulates sebocyte differentiation and lipid production, making it a potential target for inflammatory sebaceous disorders such as acne. A large number of studies suggest that PPARγ also acts as a skin tumor suppressor in both melanoma and non-melanoma skin cancers, but its role in tumorigenesis remains controversial. In this review, we have summarized the current state of research into the role of PPARγ in skin health and disease and how this may provide a starting point for the development of more potent and selective PPARγ ligands with a low toxicity profile, thereby reducing unwanted side effects.

Virtual screening, pharmacokinetics & MD simulation study of active phytoconstituents of Ficus Carica Linn. against PPAR-γ in diabetes mellitus

F. carica is a small tree and commonly used as a traditional medicine against several disorders. Diabetes is currently treated with insulin and oral hypoglycemic medicines such as sulphonyl urea derivatives, bigunides, thiazolidinediones and alpha-glucosidase inhibitors. Peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists were found to be very much beneficial in the management of diabetes by inhibiting hepatic gluconeogenesis. The aim of this study is to evaluate the bioactive phytoconstituents from Ficus carica Linn. against the target PPAR-γ agonist by in silico docking approach. We investigated 68 phytoconstituents as potential inhibitors of PPAR-γ agonists and the top 24 phytoconstituents were further selected for molecular docking studies. Drug ability, side effects, and ADMET analysis were determined by using MolSoft, toxtree freeware, and ADMET SAR web server, respectively. The phytoconstituents were docked with the target PPAR-γ (PDB ID: 4Y29, 1.98 Å) receptor. Quercetin-3-o-rutinoside possessed the highest G score -14.22 kcal/mol, followed by Angelicin with a G score of -13.56 kcal/mol. All the other phytoconstituents displayed good pharmacokinetic and toxicological parameters with values within the permissible limits. The ligand-protein interaction was calculated by molecular dynamic (MD) simulation study. Subsequently, the binding free energy of the Quercetin-3-o-rutinosideand Pioglitazone complex was calculated using MMPBSA analysis. The results indicated that some of the phytoconstituents from Ficus carica have potency as an anti-diabetic agents. So, these bioactive phytoconstituents like Quercetin-3-o-glucoside, 5-O-caffeoylquinic acids may act as a good agonist for PPAR-γ.Communicated by Ramaswamy H. Sarma.

Correlation between PPARG Pro12Ala Polymorphism and Therapeutic Responses to Thiazolidinediones in Patients with Type 2 Diabetes: A Meta-Analysis

Background: Thiazolidinediones (TZDs) are a type of oral drug that are utilized for the treatment of type 2 diabetes mellitus (T2DM). They function by acting as agonists for a nuclear transcription factor known as peroxisome proliferator-activated receptor-gamma (PPAR-γ). TZDs, such as pioglitazone and rosiglitazone, help enhance the regulation of metabolism in individuals with T2DM by improving their sensitivity to insulin. Previous studies have suggested a relationship between the therapeutic efficacy of TZDs and the PPARG Pro12Ala polymorphism (C > G, rs1801282). However, the small sample sizes of these studies may limit their applicability in clinical settings. To address this limitation, we conducted a meta-analysis assessing the influence of the PPARG Pro12Ala polymorphism on the responsiveness of TZDs. Method: We registered our study protocol with PROSPERO, number CRD42022354577. We conducted a comprehensive search of the PubMed, Web of Science, and Embase databases, including studies published up to August 2022. We examined studies investigating the association between the PPARG Pro12Ala polymorphism and metabolic parameters such as hemoglobin A_1C (HbA_1C), fasting plasma glucose (FPG), triglyceride (TG), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and total cholesterol (TC). The mean difference (MD) and 95% confidence intervals (CIs) between pre- and post-drug administration were evaluated. The quality of the studies included in the meta-analysis was assessed by using the Newcastle-Ottawa Scale (NOS) tool for cohort studies. Heterogeneity across studies was assessed by using the I² value. An I² value greater than 50% indicated substantial heterogeneity, and a random-effects model was used for meta-analysis. If the I² value was below 50%, a fixed-effects model was employed instead. Both Begg's rank correlation test and Egger's regression test were performed to detect publication bias, using R Studio software. Results: Our meta-analysis incorporated 6 studies with 777 patients for blood glucose levels and 5 studies with 747 patients for lipid levels. The included studies were published between 2003 and 2016, with the majority involving Asian populations. Five of the six studies utilized pioglitazone, while the remaining study employed rosiglitazone. The quality scores, as assessed with the NOS, ranged from 8 to 9. Patients carrying the G allele exhibited a significantly greater reduction in HbA_1C (MD = -0.3; 95% CI = -0.55 to -0.05; p = 0.02) and FPG (MD = -10.91; 95% CI = -19.82 to -2.01; p = 0.02) levels compared to those with the CC genotype. Furthermore, individuals with the G allele experienced a significantly larger decrease in TG levels than those with the CC genotype (MD = -26.88; 95% CI = -41.30 to -12.46; p = 0.0003). No statistically significant differences were observed in LDL (MD = 6.69; 95% CI = -0.90 to 14.29; p = 0.08), HDL (MD = 0.31; 95% CI = -1.62 to 2.23; p = 0.75), and TC (MD = 6.4; 95% CI = -0.05 to 12.84; p = 0.05) levels. No evidence of publication bias was detected based on Begg's test and Egger's test results. Conclusions: This meta-analysis reveals that patients with the Ala12 variant in the PPARG Pro12Ala polymorphism are more likely to exhibit positive responses to TZD treatment in terms of HbA_1C, FPG, and TG levels compared to those with the Pro12/Pro12 genotype. These findings suggest that genotyping the PPARG Pro12Ala in diabetic patients may be advantageous for devising personalized treatment strategies, particularly for identifying individuals who are likely to respond favorably to TZDs.

Megamitochondria plasticity: function transition from adaption to disease

As the cell's energy factory and metabolic hub, mitochondria are critical for ATP synthesis to maintain cellular function. Mitochondria are highly dynamic organelles that continuously undergo fusion and fission to alter their size, shape, and position, with mitochondrial fusion and fission being interdependent to maintain the balance of mitochondrial morphological changes. However, in response to metabolic and functional damage, mitochondria can grow in size, resulting in a form of abnormal mitochondrial morphology known as megamitochondria. Megamitochondria are characterized by their considerably larger size, pale matrix, and marginal cristae structure and have been observed in various human diseases. In energy-intensive cells like hepatocytes or cardiomyocytes, the pathological process can lead to the growth of megamitochondria, which can further cause metabolic disorders, cell damage and aggravates the progression of the disease. Nonetheless, megamitochondria can also form in response to short-term environmental stimulation as a compensatory mechanism to support cell survival. However, extended stimulation can reverse the benefits of megamitochondria leading to adverse effects. In this review, we will focus on the findings of the different roles of megamitochondria, and their link to disease development to identify promising clinical therapeutic targets.

The beneficial effects of astragaloside IV on ameliorating diabetic kidney disease

Diabetic kidney disease (DKD) has become the major cause of chronic kidney disease or end-stage renal disease. There is still a need for innovative treatment strategies for preventing, arresting, treating, and reversing DKD, and a plethora of scientific evidence has revealed that Chinese herbal monomers can attenuate DKD in multiple ways. Astragaloside IV (AS-IV) is one of the active ingredients of Astragalus membranaceus and was selected as a chemical marker in the Chinese Pharmacopeia for quality control purposes. An increasing amount of studies indicate that AS-IV is a promising novel drug for the treatment of DKD. AS-IV has been shown to improve DKD by combating oxidative stress, attenuating endoplasmic reticulum stress, regulating calcium homeostasis, alleviating inflammation, improving vascular function, improving epithelial to mesenchymal transition and so on. This review briefly summarizes the pathogenesis of DKD, systematically reviews the mechanisms by which AS-IV improves DKD, and aims to facilitate related pharmacological research and development to promote the utilization of Chinese herbal monomers in DKD.

The Activation of PPARγ by (2Z,4E,6E)-2-methoxyocta-2,4,6-trienoic Acid Counteracts the Epithelial–Mesenchymal Transition Process in Skin Carcinogenesis

Cutaneous squamous cell carcinoma (cSCC) is the most common UV-induced keratinocyte-derived cancer, and its progression is characterized by the epithelial–mesenchymal transition (EMT) process. We previously demonstrated that PPARγ activation by 2,4,6-octatrienoic acid (Octa) prevents cutaneous UV damage. We investigated the possible role of the PPARγ activators Octa and the new compound (2Z,4E,6E)-2-methoxyocta-2,4,6-trienoic acid (A02) in targeting keratinocyte-derived skin cancer. Like Octa, A02 exerted a protective effect against UVB-induced oxidative stress and DNA damage in NHKs. In the squamous cell carcinoma A431 cells, A02 inhibited cell proliferation and increased differentiation markers’ expression. Moreover, Octa and even more A02 counteracted the TGF-β1-dependent increase in mesenchymal markers, intracellular ROS, the activation of EMT-related signal transduction pathways, and cells’ migratory capacity. Both compounds, especially A02, counterbalanced the TGF-β1-induced cell membrane lipid remodeling and the release of bioactive lipids involved in EMT. In vivo experiments on a murine model useful to study cell proliferation in adult animals showed the reduction of areas characterized by active cell proliferation in response to A02 topical treatment. In conclusion, targeting PPARγ may be useful for the prevention and treatment of keratinocyte-derived skin cancer.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

Identification of copper-related biomarkers and potential molecule mechanism in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a chronic microvascular complication in patients with diabetes mellitus, which is the leading cause of end-stage renal disease. However, the role of copper-related genes (CRGs) in DN development remains unclear.

MATERIALS AND METHODS

CRGs were acquired from the GeneCards and NCBI databases. Based on the GSE96804 and GSE111154 datasets from the GEO repository, we identified hub CRGs for DN progression by taking the intersection of differentially expressed CRGs (DECRGs) and genes in the key module from Weighted Gene Co-expression Network Analysis. The Maximal Clique Centrality algorithm was used to identify the key CRGs from hub CRGs. Transcriptional factors (TFs) and microRNAs (miRNAs) targeting hub CRGs were acquired from publicly available databases. The CIBERSORT algorithm was used to perform comparative immune cell infiltration analysis between normal and DN samples.

RESULTS

Eighty-two DECRGs were identified between normal and DN samples, as were 10 hub CRGs, namely PTGS2, DUSP1, JUN, FOS, S100A8, S100A12, NAIP, CLEC4E, CXCR1, and CXCR2. Thirty-nine TFs and 165 miRNAs potentially targeted these 10 hub CRGs. PTGS2 was identified as the key CRG and FOS as the most significant gene among all of DECRGs. RELA was identified as the hub TF interacting with PTGS2 by taking the intersection of potential TFs from the ChEA and JASPAR public databases. let-7b-5p was identified as the hub miRNA targeting PTGS2 by taking the intersection of miRNAs from the miRwalk, RNA22, RNAInter, TargetMiner, miRTarBase, and ENCORI databases. Similarly, CREB1, E2F1, and RELA were revealed as hub TFs for FOS, and miR-338-3p as the hub miRNA. Finally, compared with those in healthy samples, there are more infiltrating memory B cells, M1 macrophages, M2 macrophages, and resting mast cells and fewer infiltrating activated mast cells and neutrophils in DN samples (all p< 0.05).

CONCLUSION

The 10 identified hub copper-related genes provide insight into the mechanisms of DN development. It is beneficial to examine and understand the interaction between hub CRGs and potential regulatory molecules in DN. This knowledge may provide a novel theoretical foundation for the development of diagnostic biomarkers and copper-related therapy targets in DN.

Tinospora cordifolia activates PPARγ pathway and mitigates glomerular and tubular cell injury in diabetic kidney disease

BACKGROUND

Diabetic Kidney Disease (DKD) is a common complication of diabetes and a leading cause of end-stage renal disease progression. Therefore, therapeutic strategies are desirable to mitigate the progression of disease into more severe consequences. Hypothesis/Purpose:Tinospora cordifolia is a traditionally known antidiabetic plant; however, its effect against DKD remains unexplored. Therefore, in the present study, we assessed the efficacy and mechanism of action of Tinospora cordifolia extract (TC) against DKD.

METHODS

The molecular interaction of the various phytoconstituents of TC with PPARγ were analyzed in silico. The effect of TC was studied on the viability, cell cycle, and gene expressions (PPARγ, TGFβ, and αSMA) in high glucose treated NRK-52E and SV40 MES13 cells. Further, streptozotocin-induced diabetic rats were treated with TC for eight weeks, and the effects on different biochemical, histological and molecular parameters were studied.

RESULTS

In silico analysis revealed the integration of various phytoconstituents of TC with PPARγ. It further increased PPARγ and decreased TGFβ and αSMA expressions in NRK-52E and SV40 MES13 cells. In diabetic rats, TC improved the fasting blood glucose, serum urea, and creatinine levels. It also lowered the urine microalbumin and advanced glycation end products (AGEs) levels. Histopathological studies revealed the preventive effect of TC on degenerative changes, mesangial proliferation and glomerular hypertrophy. Further, it reduced the inflammation and fibrotic changes in the kidney tissue estimated by various markers. The kidney tissue and gene expression analysis revealed the augmented levels of PPARγ after TC treatment.

CONCLUSION

In conclusion, TC exerted the protective effect against DKD by inhibiting inflammation and fibrogenesis through the activation of PPARγ dependent pathways.

Astragaloside IV protects against podocyte apoptosis by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 axis in diabetic nephropathy

AIMS

Podocyte apoptosis plays an important role in the pathogenesis of diabetic nephropathy (DN). Astragaloside IV (AS-IV) has been shown to protect against podocyte apoptosis. Here we aim to investigate the mechanism responsible for the protective effects of AS-IV.

MAIN METHODS

Diabetic db/db mice and high glucose (HG)-cultured podocytes were treated with AS-IV. Renal function and histopathological changes were measured to evaluate the therapeutic effects of AS-IV against DN. Adenovirus-mediated Klotho overexpression, Klotho siRNA, and PPARγ inhibitor were applied in vitro to investigate the potential mechanism. The expression levels of mRNA and proteins were analyzed by qRT-PCR, western blot or immunofluorescence. Intracellular ROS and mitochondrial superoxide were detected by DHE and MitoSOx Red, respectively. Cell apoptosis was evaluated by TUNEL staining and flow cytometry.

KEY FINDINGS

AS-IV improved renal function and ameliorated podocyte injury in db/db mice accompanied with enhanced Klotho expression in glomerular podocytes. In vitro, AS-IV inhibited HG-induced podocyte apoptosis and restored HG-inhibited Klotho expression, whereas Klotho knockdown abrogated the anti-apoptosis action of AS-IV. Further study showed that adenovirus-mediated Klotho overexpression enhanced Forkhead transcription factor O1 (FoxO1)-dependent antioxidant activity and attenuated HG-evoked oxidative stress and apoptosis. AS-IV prevented HG-induced FoxO1 inhibition and oxidative stress, whereas Klotho knockdown reversed these effects. Cotreatment with PPARγ inhibitor T0070907 abolished AS-IV-induced Klotho expression and anti-apoptosis action.

SIGNIFICANCE

These data suggested that AS-IV attenuated podocyte apoptosis presumably by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 signaling pathway, thereby ameliorating DN. This study provided new insights into the molecular mechanisms of AS-IV against DN.

Association between PPARγrs1801282 polymorphism with diabetic nephropathy and type-2 diabetes mellitus susceptibility in south India and a meta-analysis

BACKGROUND

Diabetic Nephropathy (DN) is a major complication of Type 2 Diabetes Mellitus (T2DM) with high morbidity rates worldwide.

OBJECTIVE

To determine the association of PPARγ rs1801282 polymorphism in T2DM and DN in south Indian population.

METHODS

We have conducted a case-control study to test the association of rs1801282 polymorphism with T2DM and DN in 424 subjects (DN=128; T2DM=148 and controls=148) belonging to the south Indian population using ARMS-PCR and Sanger sequencing method. Further, a meta-analysis was performed for rs1801282 polymorphism from the published literature retrieved from various electronic databases to determine the susceptibility among T2DM and DN across various ethnic populations under five genetic models.

RESULTS

The genotyping of rs1801282 polymorphism showed significant (p-value<0.05) association with DN and T2DM compared to controls. In the meta-analysis, no significant association (p-value>0.05) was noticed for rs1801282 with DN vs. controls in homozygote, heterozygote, allelic, recessive and dominant genetic models. However, a significant association was observed between rs1801282 SNP and T2DM under heterozygote (Jj vs JJ) genetic model with OR=0.56, (95%CI [0.43-0.74]), p≤0.0001 of Asian and Caucasian populations.

CONCLUSION

Overall analysis suggests that the rs1801282 polymorphism might be associated with DN and T2DM. More case-control studies on the PPARγ gene with a larger sample size including all the confounding factors are required to corroborate the findings from this meta-analysis.

Association between PPARγrs1801282 polymorphism with diabetic nephropathy and type-2 diabetes mellitus susceptibility in south India and a meta-analysis

BACKGROUND

Diabetic Nephropathy (DN) is a major complication of Type 2 Diabetes Mellitus (T2DM) with high morbidity rates worldwide.

OBJECTIVE

To determine the association of PPARγ rs1801282 polymorphism in T2DM and DN in south Indian population.

METHODS

We have conducted a case-control study to test the association of rs1801282 polymorphism with T2DM and DN in 424 subjects (DN=128; T2DM=148 and controls=148) belonging to the south Indian population using ARMS-PCR and Sanger sequencing method. Further, a meta-analysis was performed for rs1801282 polymorphism from the published literature retrieved from various electronic databases to determine the susceptibility among T2DM and DN across various ethnic populations under five genetic models.

RESULTS

The genotyping of rs1801282 polymorphism showed significant (p-value<0.05) association with DN and T2DM compared to controls. In the meta-analysis, no significant association (p-value>0.05) was noticed for rs1801282 with DN vs. controls in homozygote, heterozygote, allelic, recessive and dominant genetic models. However, a significant association was observed between rs1801282 SNP and T2DM under heterozygote (Jj vs JJ) genetic model with OR=0.56, (95%CI [0.43-0.74]), p≤0.0001 of Asian and Caucasian populations.

CONCLUSION

Overall analysis suggests that the rs1801282 polymorphism might be associated with DN and T2DM. More case-control studies on the PPARγ gene with a larger sample size including all the confounding factors are required to corroborate the findings from this meta-analysis.

Lipotoxicity and Diabetic Nephropathy: Novel Mechanistic Insights and Therapeutic Opportunities

Lipotoxicity is characterized by the ectopic accumulation of lipids in organs different from adipose tissue. Lipotoxicity is mainly associated with dysfunctional signaling and insulin resistance response in non-adipose tissue such as myocardium, pancreas, skeletal muscle, liver, and kidney. Serum lipid abnormalities and renal ectopic lipid accumulation have been associated with the development of kidney diseases, in particular diabetic nephropathy. Chronic hyperinsulinemia, often seen in type 2 diabetes, plays a crucial role in blood and liver lipid metabolism abnormalities, thus resulting in increased non-esterified fatty acids (NEFA). Excessive lipid accumulation alters cellular homeostasis and activates lipogenic and glycogenic cell-signaling pathways. Recent evidences indicate that both quantity and quality of lipids are involved in renal damage associated to lipotoxicity by activating inflammation, oxidative stress, mitochondrial dysfunction, and cell-death. The pathological effects of lipotoxicity have been observed in renal cells, thus promoting podocyte injury, tubular damage, mesangial proliferation, endothelial activation, and formation of macrophage-derived foam cells. Therefore, this review examines the recent preclinical and clinical research about the potentially harmful effects of lipids in the kidney, metabolic markers associated with these mechanisms, major signaling pathways affected, the causes of excessive lipid accumulation, and the types of lipids involved, as well as offers a comprehensive update of therapeutic strategies targeting lipotoxicity.

Therapeutic potential of PPARγ natural agonists in liver diseases

Peroxisome proliferator‐activated receptor gamma (PPARγ) is a vital subtype of the PPAR family. The biological functions are complex and diverse. PPARγ plays a significant role in protecting the liver from inflammation, oxidation, fibrosis, fatty liver and tumours. Natural products are a promising pool for drug discovery, and enormous research effort has been invested in exploring the PPARγ‐activating potential of natural products. In this manuscript, we will review the research progress of PPARγ agonists from natural products in recent years and probe into the application potential and prospects of PPARγ natural agonists in the therapy of various liver diseases, including inflammation, hepatic fibrosis, non‐alcoholic fatty liver and liver cancer.

Effect of hyperglycemia and rosiglitazone on renal and urinary neprilysin in db/db diabetic mice

Alteration in renin-angiotensin system (RAS) has been implicated in the pathophysiology of diabetic kidney disease (DKD). The deleterious actions of angiotensin II (Ang II) could be antagonized by the formation of Ang-(1-7), generated by the actions of angiotensin-converting enzyme 2 (ACE2) and neprilysin (NEP). NEP degrades several peptides, including natriuretic peptides, bradykinin, amyloid beta, and Ang I. Although combination of Ang II receptor and NEP inhibitor treatment benefits patients with heart failure, the role of NEP in renal pathophysiology is a matter of active research. NEP pathway is a potent enzyme in Ang I to Ang-(1-7) conversion in the kidney of ACE2-deficient mice, suggesting a renoprotective role of NEP. The aim of the study is to test the hypothesis that chronic hyperglycemia downregulates renal NEP protein expression and activity in db/db diabetic mice and treatment with rosiglitazone normalizes hyperglycemia, renal NEP expression, and attenuates albuminuria. Mice received rosiglitazone (20 mg kg-1  day-1 ) for 10 weeks. Western blot analysis, immunohistochemistry, and enzyme activity revealed a significant decrease in renal and urinary NEP expression and activity in 16-wk db/db mice compared with lean control (p < .0001). Rosiglitazone also attenuated albuminuria and increased renal and urinary NEP expressions (p < .0001). In conclusion, data support the hypothesis that diabetes decreases intrarenal NEP, which could have a pivotal role in the pathogenesis of DKD. Urinary NEP may be used as an index of intrarenal NEP status. The renoprotective effects of rosiglitazone could be mediated by upregulation of renal NEP expression and activity in db/db diabetic mice.

Understanding molecular upsets in diabetic nephropathy to identify novel targets and treatment opportunities

Diabetes and related complications are becoming a global encumbrance. Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD). The available therapeutic modalities related to DN do not treat DN at the molecular level, proposing further amendments in the management of DN based on the pathogenesis of DN. This manuscript discusses the concept and applications of nanomedicine for the treatment of DN that can improve renal targeting, retention and localization. This review also highlights the current issues related to targeting DN, challenges and allied opportunities toward the development of next-generation drugs and treatments for the management of DN.

Peroxisome proliferator-activated receptor agonists and antagonists: a patent review (2014-present)

Introduction: Peroxisome proliferator-activated receptors (PPARs), PPARα, PPARδ, and PPARγ, play an important role in the regulation of various physiological processes, specifically lipid and energy metabolism and immunity. PPARα agonists (fibrates) and PPARγ agonists (thiazolidinediones) are used for the treatment of hypertriglyceridemia and type 2 diabetes, respectively. PPARδ activation enhances mitochondrial and energy metabolism but PPARδ-acting drugs are not yet available. Many synthetic ligands for PPARs have been developed to expand their therapeutic applications.Areas covered: The authors searched recent patent activity regarding PPAR ligands. Novel PPARα agonists, PPARδ agonists, PPARγ agonists, PPARα/γ dual agonists, and PPARγ antagonists have been claimed for the treatment of metabolic disease and inflammatory disease. Methods for the combination of PPAR ligands with other drugs and expanded application of PPAR agonists for bone and neurological disease have been also claimed.Expert opinion: Novel PPAR ligands and the combination of PPAR ligands with other drugs have been claimed for the treatment of mitochondrial disease, inflammatory/autoimmune disease, neurological disease, and cancer in addition to metabolic diseases including dyslipidemia and type 2 diabetes. Selective therapeutic actions of PPAR ligands should be exploited to avoid adverse effects. More basic studies are needed to elucidate the molecular mechanisms of selective actions.

Altered expression of WFS1 and NOTCH2 genes associated with diabetic nephropathy in T2DM patients

AIM

The increased incidence of type 2 diabetes mellitus (T2DM) and the importance of early identification and management of its complications, especially diabetic nephropathy (DN), have spotted the light on genetic factors that increase risk of T2DM and its related nephropathy. The present study aimed at investigating expression of (KCNJ11, ABCC8, JAZF1, WFS1, PPARG, NOTCH2 and EXOSC4) genes in peripheral blood of T2DM patients.

METHOD

The study included 30 non-complicated T2DM patients, 30 patients with DN and 40 healthy controls. Quantitative Real Time PCR Array was used to study gene expression.

RESULTS

NOTCH2 showed higher expression while KCNJ11, JAZF1, WFS1 and PPARG genes showed lower expression in DN patients compared to non-complicated patients. KCNJ11, JAZF1, WFS1, PPARG, and EXOSC4 expression showed significant negative correlation with microalbumin, while NOTCH2 expression was significantly positively correlated with microalbumin. AS regard HbA1c and studied genes expression, there was significant negative correlation between WFS1 expression and HbA1c, while NOTCH2, KCNJ11, JAZF1, PPARG, EXOSC4 expression didn't show significant correlation with HbA1c. Risk ratio of studied genes expression showed that WFS1 and NOTCH2 had highest risk ratio (30) and highest sensitivity and specificity, in relation to DN and they were the best predictors in the group of studied genes at cut off value of ≤0.861 for WFS1 and ≥0.678 for NOTCH2.

CONCLUSION

Altered expression of WFS1 and NOTCH2 genes may play a role in pathogenesis and development of DN in patients with T2DM. These results may contribute in early identification and management of DN.

Endocytosis of Albumin Induces Matrix Metalloproteinase-9 by Activating the ERK Signaling Pathway in Renal Tubule Epithelial Cells

Matrix metalloproteinase-9 (MMP-9) is dysregulated in chronic kidney diseases including diabetic nephropathy. This study was performed to examine the expression of MMP-9 in renal tubule epithelial cells (TECs) under diabetic conditions and its regulatory mechanisms. We characterized MMP-9 protein in diabetic animals and primary cultured rat TECs exposed to exogenous albumin and high glucose. We also used specific inhibitors to determine if internalization of albumin and/or extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation were required for MMP-9 secretion. Immunostaining of kidney sections revealed enhanced MMP-9 signal in the damaged proximal tubules in Zucker diabetic fatty (ZDF) rats. ZDF rats also exhibited an albuminuria-related and age-dependent increase in MMP-9 excretion, which was prevented by rosiglitazone. In primary cultured rat TECs, high glucose exposure did not increase MMP-9 secretion. In contrast, administration of rat serum albumin (RSA, 0.1–0.5 mg/mL) resulted in a dose-dependent increase in MMP-9 expression and secretion by TECs, which was abolished in the presence of an ERK1/2-specific inhibitor, U0126. Simvastatin, an inhibitor of albumin endocytosis, also prevented MMP-9 secretion. Taken together, these results demonstrate that endocytosis of albumin stimulates MMP-9 secretion by TECs through the ERK signaling pathway.

In silico identification of potential drug compound against Peroxisome proliferator-activated receptor-gamma by virtual screening and toxicity studies for the treatment of Diabetic Nephropathy

Diabetic Nephropathy is a serious complication of diabetes mellitus. Current therapeutic strategies of Diabetic Nephropathy are based on control of modifiable risks like hypertension, glucose levels, and dyslipidemia. Peroxisome proliferator activated receptor-gamma (PPAR-γ) is implicated in several metabolic syndromes including Diabetic Nephropathy, besides obesity, insulin insensitivity, dislipidemia, inflammation, and hypertension. In the present study, virtual screening of 617 compounds from two different public databases was done against PPAR-γ with an objective to find a possible lead compound. Two softwares, PyRx and iGEMDOCK, were used to achieve the docking accuracy in order to avoid loss of candidate compounds. Rosiglitazone (used to treat Diabetic Nephropathy) was taken as the standard compound. A total of 30 compounds with good binding affinity with PPAR-γ were selected for further filtering, on the basis of absorption, distribution, metabolism, excretion, and toxicity (ADMET). The interaction profiling of these 30 compounds, showed a minimum of one and maximum of three interactions with reference to rosiglitazone (SER-289, HIS-449, HIS-323, TYR-473). The fulfilling of ADMET analysis criteria of 30 compounds led to the selection of four compounds (ZINC ID 00181552, 00276456, 00298314, 00448009). Molecular dynamics simulation of these lead compounds in complex with PPAR-γ revealed that three of the four compounds formed a stable complex in the ligand-binding pocket of PPAR-γ during 20-ns simulation. Hence, these three (ZINC ID 00181552, 00276456, 00298314) of the four compounds are potential candidates for experimental validation of biological activity against PPAR-γ in future drug discovery studies.

Novel Anti-fibrotic Therapies

Fibrosis is a major player in cardiovascular disease, both as a contributor to the development of disease, as well as a post-injury response that drives progression. Despite the identification of many mechanisms responsible for cardiovascular fibrosis, to date no treatments have emerged that have effectively reduced the excess deposition of extracellular matrix associated with fibrotic conditions. Novel treatments have recently been identified that hold promise as potential therapeutic agents for cardiovascular diseases associated with fibrosis, as well as other fibrotic conditions. The purpose of this review is to provide an overview of emerging antifibrotic agents that have shown encouraging results in preclinical or early clinical studies, but have not yet been approved for use in human disease. One of these agents is bone morphogenetic protein-7 (BMP7), which has beneficial effects in multiple models of fibrotic disease. Another approach discussed involves altering the levels of micro-RNA (miR) species, including miR-29 and miR-101, which regulate the expression of fibrosis-related gene targets. Further, the antifibrotic potential of agonists of the peroxisome proliferator-activated receptors will be discussed. Finally, evidence will be reviewed in support of the polypeptide hormone relaxin. Relaxin is long known for its extracellular remodeling properties in pregnancy, and is rapidly emerging as an effective antifibrotic agent in a number of organ systems. Moreover, relaxin has potent vascular and renal effects that make it a particularly attractive approach for the treatment of cardiovascular diseases. In each case, the mechanism of action and the applicability to various fibrotic diseases will be discussed.

Hypolipidemic effect of XH601 on hamsters of Hyperlipidemia and its potential mechanism

BACKGROUND

The novel compound XH601 is a synthesized derivative of formononetin. The present study was to investigate the hypolipidemia effect and potential mechanism of XH601.

METHODS

Male Golden Syrian hamsters were induced by high-fat diet (HFD) for eight weeks and the hyperlipidemic model was established successfully. After XH601 treatment, serum and hepatic biochemistry parameters of hamsters were detected and the effect of XH601 on adipose tissue was also analyzed. Furthermore, 3 T3-L1 cell differentiation by Oil-Red-O staining was observed and the mRNA and protein expression of peroxisome proliferator-activated receptors (PPARs) were measured by qRT-PCR and Western-blot in mature adipocytes.

RESULTS

The in vivo results suggest that XH601 significantly decreased the adipose weight and levels of serum triglyceride (TG), total cholesterol (TC), low-density lipoprotein (LDL-C), apolipoprotein B (Apo-B), apolipoprotein E (Apo-E), while increased serum high-density lipoprotein (HDL-C). The in vitro results implied that XH601 up-regulated the mRNA and protein expression of both PPARα and PPARβ/δ in a dose-dependent manner.

CONCLUSIONS

The study suggests that XH601 exhibited strong ability to improve the dyslipidemia in hamsters fed with high-fat diet. The potential mechanism of XH601 was associated with the up-regulation of PPARα and PPARβ/δ mRNA and protein expression.

Regulatory landscape of AGE-RAGE-oxidative stress axis and its modulation by PPARγ activation in high fructose diet-induced metabolic syndrome

Background

The AGE-RAGE-oxidative stress (AROS) axis is involved in the onset and progression of metabolic syndrome induced by a high-fructose diet (HFD). PPARγ activation is known to modulate metabolic syndrome; however a systems-level investigation looking at the protective effects of PPARγ activation as related to the AROS axis has not been performed.

The aim of this work is to simultaneously characterize multiple molecular parameters within the AROS axis, using samples taken from different body fluids and tissues of a rat model of HFD-induced metabolic syndrome, in the presence or absence of a PPARγ agonist, Rosiglitazone (RGZ).

Methods

Rats were fed with 60% HFD for the first half of the treatment duration (21 days) then continued with either HFD alone or HFD plus RGZ for the second half.

Results

Rats receiving HFD alone showed metabolic syndrome manifestations including hypertension, dyslipidemia, increased glucose levels and insulin resistance, as well as abnormal kidney and inflammatory parameters. Systolic blood pressure, plasma triglyceride and glucose levels, plasma creatinine, and albuminuria were significantly improved in the presence of RGZ. The following molecular parameters of the AROS axis were significantly upregulated in our rat model: carboxymethyl lysine (CML) in urine and liver; carboxyethyl lysine (CEL) in urine; advanced glycation end products (AGEs) in plasma; receptor for advanced glycation end products (RAGE) in liver and kidney; advanced oxidation protein products (AOPP) in plasma; and 4-hydroxynonenal (HNE) in plasma, liver, and kidney. Conversely, with RGZ administration, the upregulation of AOPP and AGEs in plasma, CML and CEL in urine, RAGE in liver as well as HNE in plasma and liver was significantly counteracted/prevented.

Conclusions

Our data demonstrate (i) the systems-level regulatory landscape of HFD-induced metabolic syndrome involving multiple molecular parameters, including HNE, AGEs and their receptor RAGE, and (ii) attenuation of metabolic syndrome by PPARγ modulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0149-z) contains supplementary material, which is available to authorized users.

Identification of dual ligands targeting angiotensin II type 1 receptor and peroxisome proliferator-activated receptor-γ by core hopping of telmisartan

It has been reported previously that some angiotensin II receptor blockers not only antagonize angiotensin II type 1 receptor (AT₁R), but also exert stimulation in peroxisome proliferator-activated receptor γ (PPARγ) partial activation, among which telmisartan displays the best. Telmisartan has been tested as a bifunctional ligand with antihypertensive and hypoglycemic activity. Aiming at more potent leads with selective AT₁R antagonism and PPARγ partial agonism, the three parts of telmisartan including the distal benzimidazole ring, the biphenyl moiety, and the carboxylic acid group experienced modification by core hopping method in our study. The central benzimidazole ring, however, remained intact considering its great affinity toward AT₁R and PPARγ. We utilized computational techniques for the sake of details on the binding interactions and conformational stability. Standard precision docking analysis and absorption, distribution, metabolism, excretion, and toxicity prediction received 10 molecules with higher Glide scores, similar interactions, and improved pharmacokinetic profiles compared to telmisartan. Comp#91 with highest scores for AT₁R (-11.92 kcal/mol) and PPARγ (-13.88 kcal/mol) exhibited excellent binding modes and pharmacokinetic parameters. Molecular dynamics trajectories on best docking pose of comp#91 confirmed the docking results and verified the conformational stability with both receptors throughout the course of 20-ns simulations. Thus, comp#91 could be identified as a promising lead in the development of dual AT₁R antagonist and PPARγ partial agonist against hypertension and type 2 diabetes.

Huangkui capsule, an extract from Abelmoschus manihot (L.) medic, improves diabetic nephropathy via activating peroxisome proliferator-activated receptor (PPAR)-α/γ and attenuating endoplasmic reticulum stress in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abelmoschus manihot (L.) medic (AM) is a natural medicinal plant used for the treatment of chronic kidney disease (CKD) in China. Huangkui capsule (HKC), an extract from AM, has been proved clinically effective in improving renal inflammation and glomerular injury in CKD. However, the mechanisms of HKC are still not fully understood.

AIM OF THE STUDY

Peroxisome proliferator-activated receptor (PPAR)-α/γ dual agonists have the potential to be used as therapeutic agents for the treatment of type 2 diabetes and diabetic nephropathy (DN). This study evaluated the function of Huangkui capsule (HKC), an extract from Abelmoschus manihot (L.) medic (AM), as a dual agonist for PPARα/γ and investigated its anti-DN effects in a DN rat model.

MATERIALS AND METHODS

ChIP and reporter gene assays were performed and the expression of PPARα/γ target genes was monitored to examine the ability of HKC to activate PPARα/γ. DN was induced in male Sprague-Dawley rats via unilateral nephrectomy and intraperitoneal injection of streptozotocin. HKC was administered to the diabetic nephropathy rats at three different doses: high dose HKC (300mg/kg/d); middle dose HKC (175mg/kg/d); and low dose HKC (75mg/kg/d). Irbesartan (4mg/kg/d body weight) was used as a positive control. Following 12 weeks' treatment, we measured general status, renal morphological appearance, proteinuria, blood biochemical parameters, and glomerular morphological changes. The expression of collagen IV, TGFβ, TNFα and IL-6 in renal tissue was evaluated. Endoplasmic reticulum (ER) stress in renal tissue was also analyzed.

RESULTS

HKC enhanced the transcriptional activity of PPARα and PPARγ in cultured cells, livers and kidneys of DN rats, and it reduced serum triglyceride and cholesterol levels and fat in livers of DN rats. Furthermore, HKC reduced the expressions of inflammatory genes in kidneys of DN rats. Strikingly, HKC reduced ER stress and c-Jun NH2-terminal kinase activation in the liver and kidney of DN rats and subsequently improved renal injury.

CONCLUSIONS

Our results show that HKC improved lipid metabolic disorders by activating PPARα/γ and attenuating ER stress. HKC could dose-dependently ameliorate renal inflammation and glomerular injury in DN rats. These results suggest that HKC has potential as an anti-DN agent for the treatment of DN in humans.

Shared Genetic Factors Involved in Celiac Disease, Type 2 Diabetes and Anorexia Nervosa Suggest Common Molecular Pathways for Chronic Diseases

Background and Objectives

Genome-wide association studies (GWAS) have identified several genetic regions involved in immune-regulatory mechanisms to be associated with celiac disease. Previous GWAS also revealed an over-representation of genes involved in type 2 diabetes and anorexia nervosa associated with celiac disease, suggesting involvement of common metabolic pathways for development of these chronic diseases. The aim of this study was to extend these previous analyses to study the gene expression in the gut from children with active celiac disease.

Material and Methods

Thirty six target genes involved in type 2 diabetes and four genes associated with anorexia nervosa were investigated for gene expression in small intestinal biopsies from 144 children with celiac disease at median (range) age of 7.4 years (1.6–17.8) and from 154 disease controls at a median (range) age 11.4.years (1.4–18.3).

Results

A total of eleven of genes were differently expressed in celiac patients compared with disease controls of which CD36, CD38, FOXP1, SELL, PPARA, PPARG, AGT previously associated with type 2 diabetes and AKAP6, NTNG1 with anorexia nervosa remained significant after correction for multiple testing.

Conclusion

Shared genetic factors involved in celiac disease, type 2 diabetes and anorexia nervosa suggest common underlying molecular pathways for these diseases.

A central theory of biology

The history of physiologic cellular-molecular interrelationships can be traced all the way back to the unicellular state by following the pathway formed by lipids ubiquitously accommodating calcium homeostasis, and its consequent adaptive effects on oxygen uptake by cells, tissues and organs. As a result, a cohesive, mechanistically integrated view of physiology can be formulated by recognizing the continuum comprising conception, development, physiologic homeostasis and death mediated by soluble growth factor signaling. Seeing such seemingly disparate processes as embryogenesis, chronic disease and dying as the gain and subsequent loss of cell-cell signaling provides a novel perspective for physiology and medicine. It is emblematic of the self-organizing, self-referential nature of life, starting from its origins. Such organizing principles obviate the pitfalls of teleologic evolution, conversely providing a way of resolving such seeming dichotomies as holism and reductionism, genotype and phenotype, emergence and contingence, proximate and ultimate causation in evolution, cells and organisms. The proposed approach is scale-free and predictive, offering a Central Theory of Biology.

The PPARγ2 Pro12Ala variant is protective against progression of nephropathy in people with type 2 diabetes

Objective

Cross-sectional studies suggest the association between diabetic nephropathy and the PPARγ2 Pro12Ala polymorphism of the peroxisome proliferator-activated receptor γ2 (PPARγ2). Prospective data are limited to microalbuminuria and no information on renal function is available to date. The present study evaluates the association between the Pro12Ala polymorphism of PPARγ2 and the progression of albuminuria and decay in glomerular filtration rate (GFR) in type 2 diabetes.

Patients and measurements

We studied 256 patients with an average 5-year follow-up. Among others, urinary albumin excretion rate (UAER) was measured on spot sample, GFR was estimated with the CKD-EPI Equation.

Results

Baseline UAER and GFR were similar for carriers or non-carriers of the polymorphism. At follow-up no significant changes from baseline were observed for UAER or eGFR in carriers of the Pro12Ala polymorphism whereas a significant increase in UAER [17 (11.3-37.9) versus 24.5 (13.8-49.9) μg/mg, p < 0.006)] and a significant reduction in the eGFR (82.8 ± 14.5 versus 80.3 ± 17.3 ml/min/1.73, m² p = 0.02), were observed in non carriers of the Pro12Ala polymorphism. Progression of nephropathy - defined according to a combined end point of UAER and eGFR- i.e. doubling of baseline UAER to at least 100 μg/mg, or new onset microalbuminuria, or progression from micro to macroalbuminuria, or 25% reduction of eGFR, or annualized eGFR decline >3 ml/min/year - was significantly less frequent in Ala carriers than non carriers (11.4% vs 35.8%; p < 0.01); HR adjusted for baseline age, AER, eGFR, HbA1c, diabetes duration and blood pressure was 0.32 (0.12-0.80).

Conclusions

This study found that among patients with type 2 diabetes, the PPARγ2 Pro12Ala polymorphism is protective against progression of nephropathy and decay of renal function independent of major confounders.

PPAR gamma activation is neuroprotective in a Drosophila model of ALS based on TDP-43

Amyotrophic Lateral Sclerosis (ALS) is a progressive neuromuscular disease for which there is no cure. We have previously developed a Drosophila model of ALS based on TDP-43 that recapitulates several aspects of disease pathophysiology. Using this model, we designed a drug screening strategy based on the pupal lethality phenotype induced by TDP-43 when expressed in motor neurons. In screening 1200 FDA-approved compounds, we identified the PPARγ agonist pioglitazone as neuroprotective in Drosophila. Here, we show that pioglitazone can rescue TDP-43-dependent locomotor dysfunction in motor neurons and glia but not in muscles. Testing additional models of ALS, we find that pioglitazone is also neuroprotective when FUS, but not SOD1, is expressed in motor neurons. Interestingly, survival analyses of TDP or FUS models show no increase in lifespan, which is consistent with recent clinical trials. Using a pharmacogenetic approach, we show that the predicted Drosophila PPARγ homologs, E75 and E78, are in vivo targets of pioglitazone. Finally, using a global metabolomic approach, we identify a set of metabolites that pioglitazone can restore in the context of TDP-43 expression in motor neurons. Taken together, our data provide evidence that modulating PPARγ activity, although not effective at improving lifespan, provides a molecular target for mitigating locomotor dysfunction in TDP-43 and FUS but not SOD1 models of ALS in Drosophila. Furthermore, our data also identify several 'biomarkers' of the disease that may be useful in developing therapeutics and in future clinical trials.