Protective Effects of Swertiamarin against Methylglyoxal-Induced Epithelial-Mesenchymal Transition by Improving Oxidative Stress in Rat Kidney Epithelial (NRK-52E) Cells

Iridoids modulate inflammation in diabetic kidney disease: A review

In recent years, preclinical research on diabetic kidney disease (DKD) has surged to the forefront of scientific and clinical attention. DKD has become a pervasive complication of type 2 diabetes. Given the complexity of its etiology and pathological mechanisms, current interventions, including drugs, dietary modifications, exercise, hypoglycemic treatments and lipid-lowering methods, often fall short in achieving desired therapeutic outcomes. Iridoids, primarily derived from the potent components of traditional herbs, have been the subject of long-standing research. Preclinical data suggest that iridoids possess notable renal protective properties; however, there has been no summary of the research on their efficacy in the management and treatment of DKD. This article consolidates findings from in vivo and in vitro research on iridoids in the context of DKD and highlights their shared anti-inflammatory activities in treating this condition. Additionally, it explores how certain iridoid components modify their chemical structures through the regulation of intestinal flora, potentially bolstering their therapeutic effects. This review provides a focused examination of the mechanisms through which iridoids may prevent or treat DKD, offering valuable insights for future research endeavors. Please cite this article as: Zhou TY, Tian N, Li L, Yu R. Iridoids modulate inflammation in diabetic kidney disease: A review. J Integr Med. 2024; 22(3): 210-222.

Swertiamarin mitigates nephropathy in high-fat diet/streptozotocin-induced diabetic rats by inhibiting the formation of advanced glycation end products

CONTEXT

The molecular mechanism by which Swertiamarin (SM) prevents advanced glycation end products (AGEs) induced diabetic nephropathy (DN) has never been explored.

OBJECTIVE

To evaluate the effect of SM in preventing the progression of DN in high fat diet-streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

After 1 week of acclimatisation, the rats were divided randomly into five groups as follows: (1) Control group, which received normal chow diet; (2) High-fat diet (HFD) group which was fed diet comprising of 58.7% fat, 27.5% carbohydrate and 14.4% protein); (3) Aminoguanidine (AG) group which received HFD + 100 mg/k.b.w.AG (intraperitoneal); (4) Metformin (Met) group which received HFD + 70 mg/k.b.w. the oral dose of Met and (5) SM group which was supplemented orally with 50 mg/k.b.w.SM along with HFD. After 12 weeks all HFD fed animals were given a single 35 mg/k.b.w. dose of streptozotocin with continuous HFD feeding for additional 18 weeks. Later, various biochemical assays, urine analyses, histopathological analysis of kidneys, levels of AGEs, expression of various makers, and in-silico analysis were performed.

RESULTS

The diabetic group demonstrated oxidative stress, increased levels of AGEs, decreased renal function, fibrosis in the renal tissue, higher expression of the receptor for advanced glycation end products (RAGE), which were ameliorated in the SM treated group. In-silico analysis suggests that SM can prevent the binding of AGEs with RAGE.

CONCLUSIONS

SM ameliorated DN by inhibiting the oxidative stress induced by AGEs.HighlightsSM reduces the levels of hyperglycaemia-induced advanced glycation end products in serum and renal tissue.SM prevents renal fibrosis by inhibiting the EMT in the kidney tissue.The in-silico analysis proves that SM can inhibit the binding of various AGEs with RAGE, thereby inhibiting the AGE-RAGE axis.

Cardioprotective Role of Swertiamarin, a Plant Glycoside Against Experimentally Induced Myocardial Infarction via Antioxidant and Anti-inflammatory Functions

The study examined the protective effects of swertiamarin on rats with experimentally induced myocardial infarction. Three to six week-old male albino Wistar rats were used in this study and experimental myocardial infarction (MI) was induced using isoproterenol. Our results showed that swertiamarin restored the alteration in heart weight, body weight, and heart weight/tibia length ratio of MI-induced rats to basal levels significantly (p < 0.05). Swertiamarin significantly (p < 0.05) restored the levels of cardiac pathophysiological marker creatine kinase (CKMB), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), alanine transaminase (ALT), and cardiac troponin I (cTn-1) to near normalcy in MI-induced rats. Levels of oxidative stress markers malondialdehyde (MDA), protein carbonyls (PC), and levels of Vitamin C and Vitamin E were significantly (p < 0.05) reverted to near basal levels in MI-induced rats by swertiamarin. Levels of the antioxidant glutathione (GSH) and antioxidant enzymes which include superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-s-transferase (GST), glutathione reductase (GR), and plasma total antioxidant capacity (TAC) were (p < 0.05) brought to near normalcy in MI-induced rats by swertiamarin. Levels of sodium (Na), potassium (k), and calcium (Ca) ATPases were significantly (p < 0.05) restored to near normalcy in MI-induced rats by swertiamarin. Status of pro-inflammatory cytokines including tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and histological aberrations were also significantly (p < 0.05) restored to near normalcy in MI-induced rats by swertiamarin. Together, our results concluded that swertiamarin exerts significant cardioprotective functions in experimental MI in rats.

Optimizing glycation control in diabetes: An integrated approach for inhibiting nonenzymatic glycation reactions of biological macromolecules

Diabetes is a multifactorial disorder that increases mortality and disability due to its complications. A key driver of these complications is nonenzymatic glycation, which generates advanced glycation end-products (AGEs) that impair tissue function. Therefore, effective nonenzymatic glycation prevention and control strategies are urgently needed. This review comprehensively describes the molecular mechanisms and pathological consequences of nonenzymatic glycation in diabetes and outlines various anti-glycation strategies, such as lowering plasma glucose, interfering with the glycation reaction, and degrading early and late glycation products. Diet, exercise, and hypoglycemic medications can reduce the onset of high glucose at the source. Glucose or amino acid analogs such as flavonoids, lysine and aminoguanidine competitively bind to proteins or glucose to block the initial nonenzymatic glycation reaction. In addition, deglycation enzymes such as amadoriase, fructosamine-3-kinase, parkinson's disease protein, glutamine amidotransferase-like class 1 domain-containing 3A and terminal FraB deglycase can eliminate existing nonenzymatic glycation products. These strategies involve nutritional, pharmacological, and enzymatic interventions that target different stages of nonenzymatic glycation. This review also emphasizes the therapeutic potential of anti-glycation drugs for preventing and treating diabetes complications.

Controlled Selective Formation of Amadori Compounds from α/ε Mono- or Di-glycation of Lysine with Xylose

Three Amadori rearrangement products (Xyl-α-Lys-ARP, Xyl-ε-Lys-ARP, and diXyl-α,ε-Lys-ARP) were observed in the xylose-lysine (Xyl-Lys) Maillard reaction model. They were separated and characterized by liquid chromatography with tandem mass spectrometry and NMR. The crucial roles of reaction temperature, pH, molar ratio of Xyl to Lys, and reaction time in the formation of different Xyl-Lys-ARPs were investigated. The proportion of Xyl-α-Lys-ARP among all Xyl-Lys-ARPs was increased to 48.41% (its concentration was 25.31 μmol/mL) after the reaction at pH = 5.5 and a molar ratio of 3:1 (Xyl: Lys) for 9 min, while only Xyl-ε-Lys-ARP was generated at a higher pH (7.5) and a lower molar ratio of 1:5. Moreover, the much higher activation energy (84.08 kJ/mol) of diXyl-α,ε-Lys-ARP than Xyl-α-Lys-ARP (34.19 kJ/mol) and Xyl-ε-Lys-ARP (32.32 kJ/mol) indicated a pronounced promoting effect on diXyl-α,ε-Lys-ARP formation by high temperatures. A complete conversion from Xyl-α-Lys-ARP and Xyl-ε-Lys-ARP to diXyl-α,ε-Lys-ARP was achieved through the reaction time prolongation and Xyl concentration increase at a higher temperature; the concentration of diXyl-α,ε-Lys-ARP was 39.05 μmol/mL at a molar ratio of 5:1 for 40 min. Accordingly, the selective preparation of Xyl-α-Lys-ARP, Xyl-ε-Lys-ARP, and diXyl-α,ε-Lys-ARP could be achieved through adjusting the Xyl-Lys ratio, pH, and reaction time.

A natural products solution to diabetic nephropathy therapy

Diabetic nephropathy is one of the most common complications in diabetes. It has been shown to be the leading cause of end-stage renal disease. However, due to their complex pathological mechanisms, effective therapeutic drugs other than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which have been used for 20 years, have not been developed so far. Recent studies have shown that diabetic nephropathy is characterized by multiple signalling pathways and multiple targets, including inflammation, apoptosis, pyroptosis, autophagy, oxidative stress, endoplasmic reticulum stress and their interactions. It definitely exacerbates the difficulty of therapy, but at the same time it also brings out the chance for natural products treatment. In the most recent two decades, a large number of natural products have displayed their potential in preclinical studies and a few compounds are under invetigation in clinical trials. Hence, many compounds targeting these singals have been emerged as a comprehensive blueprint for treating strategy of diabetic nephropathy. This review focuses on the cellular and molecular mechanisms of natural prouducts that alleviate this condition, including preclinical studies and clinical trials, which will provide new insights into the treatment of diabetic nephropathy and suggest novel ideas for new drug development.

Argpyrimidine bonded to RAGE regulates autophagy and cell cycle to cause periodontal destruction

Argpyrimidine (APMD), a methylglyoxal-arginine-derived product, is one of the main products of diabetes mellitus. We aimed to systematically investigate the role of APMD in regulating autophagy activity, with a specific focus on the finding of APDM binding molecule, matching amino acid residues, autophagy flux and proteins, cell cycle arrest, cell skeleton and migration, PI3K/AKT/mTOR pathways, inflammatory signals, alveolar bone destruction, and inhibition verification. In this study, binding to 59/94/121 amino acid residues of advanced glycosylation end product receptor (RAGE), APMD suppressed PI3K/AKT/mTOR pathway to attenuate cell survival of periodontal ligament cells (PDLCs). Simultaneously, autophagy proteins ATG5, Beclin1, and LC3-II/I expression ratio were upregulated while P62/SQSTM was downregulated. Cell cycle arrested at G0/G1 with enhancing Cyclin D1/CDK4 and decreasing Cyclin A/CDK2 expression. Inhibition of autophagy abrogated APMD-induced cell cycle arrest. Furthermore, the inflammation regulation network of matrix metalloproteinase (MMP)-2, MMP-9, MAPKs and NF-κB pathways were activated by APMD. Rat periodontal models confirmed that APMD induced alveolar bone resorption, increased inflammatory infiltrates, and degraded collagen fibers through RAGE and PI3K. APMD-induced autophagy, G0/G1 arrest, pro-inflammatory signals activating and periodontal destruction were reversed by RAGE knockdown while aggravated by PI3K inhibitor. This study provides the first evidence that APMD bind to RAGE to regulate autophagy and cell cycle of PDLCs through the PI3K/AKT/mTOR pathway, thereby promoting periodontal destruction.

Phenolic Compounds from Mori Cortex Ameliorate Sodium Oleate-Induced Epithelial-Mesenchymal Transition and Fibrosis in NRK-52e Cells through CD36

Lipid deposition in the kidney can cause serious damage to the kidney, and there is an obvious epithelial–mesenchymal transition (EMT) and fibrosis in the late stage. To investigate the interventional effects and mechanisms of phenolic compounds from Mori Cortex on the EMT and fibrosis induced by sodium oleate-induced lipid deposition in renal tubular epithelial cells (NRK-52e cells), and the role played by CD36 in the adjustment process, NRK-52e cells induced by 200 μmol/L sodium oleate were given 10 μmoL/L moracin-P-2″-O-β-d-glucopyranoside (Y-1), moracin-P-3′-O-β-d-glucopyranoside (Y-2), moracin-P-3′-O-α-l-arabinopyranoside (Y-3), and moracin-P-3′-O-[β-glucopyranoside-(1→2)arabinopyranoside] (Y-4), and Oil Red O staining was used to detect lipid deposition. A Western blot was used to detect lipid deposition-related protein CD36, inflammation-related protein (p-NF-κB-P65, NF-κB-P65, IL-1β), oxidative stress-related protein (NOX1, Nrf2, Keap1), EMT-related proteins (CD31, α-SMA), and fibrosis-related proteins (TGF-β, ZEB1, Snail1). A qRT-PCR test detected inflammation, EMT, and fibrosis-related gene mRNA levels. The TNF-α levels were detected by ELISA, and the colorimetric method was used to detects SOD and MDA levels. The ROS was measured by flow cytometry. A high-content imaging analysis system was applied to observe EMT and fibrosis-related proteins. At the same time, the experiment silenced CD36 and compared the difference between before and after drug treatment, then used molecular docking technology to predict the potential binding site of the active compounds with CD36. The research results show that sodium oleate can induce lipid deposition, inflammation, oxidative stress, and fibrosis in NRK-52e cells. Y-1 and Y-2 could significantly ameliorate the damage caused by sodium oleate, and Y-2 had a better ameliorating effect, while there was no significant change in Y-3 or Y-4. The amelioration effect of Y-1 and Y-2 disappeared after silencing CD36. Molecular docking technology showed that the Y-1 and Y-2 had hydrogen bonds to CD36 and that, compared with Y-1, Y-2 requires less binding energy. In summary, moracin-P-2″-O-β-d-glucopyranoside and moracin-P-3′-O-β-d-glucopyranoside from Mori Cortex ameliorated lipid deposition, EMT, and fibrosis induced by sodium oleate in NRK-52e cells through CD36.