Oxidative stress in metabolic dysfunction-associated steatotic liver disease (MASLD): How does the animal model resemble human disease?

Despite decades of research, the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) is still not completely understood. Based on the evidence from preclinical models, one of the factors proposed as a main driver of disease development is oxidative stress. This study aimed to search for the resemblance between the profiles of oxidative stress and antioxidant defense in the animal model of MASLD and the group of MASLD patients. C57BL/6J mice were fed with the Western diet for up to 24 weeks and served as the animal model of MASLD. The antioxidant profile of mice hepatic tissue was determined by liquid chromatography-MS3 spectrometry (LC-MS/MS). The human cohort consisted of 20 patients, who underwent bariatric surgery, and 6 controls. Based on histological analysis, 4 bariatric patients did not have liver steatosis and as such were also classified as controls. Total antioxidant activity was measured in sera and liver biopsy samples. The hepatic levels of antioxidant enzymes and oxidative damage were determined by Western Blot. The levels of antioxidant enzymes were significantly altered in the hepatic tissue of mice with MASLD. In contrast, there were no significant changes in the antioxidant profile of hepatic tissue of MASLD patients, except for the decreased level of carbonylated proteins. Decreased protein carbonylation together with significant correlations between the thioredoxin system and parameters describing metabolic health suggest alterations in the thiol-redox signaling. Altogether, these data show that even though the phenotype of mice closely resembles human MASLD, the animal-to-human translation of cellular and molecular processes such as oxidative stress may be more challenging.

Ethyl ferulate, a lipophilic phenylpropanoid, prevents diabetes-associated renal injury in rats by amelioration of hyperglycemia-induced oxidative stress via activation of nuclear factor erythroid 2-related factor 2.

Diabetic nephropathy affects approximately 20%-40% of diabetes patients worldwide and is the leading cause of end-stage renal failure. Oxidative stress has been identified as a major causative factor in the development and progression of diabetic nephropathy; Nuclear factor erythroid 2-related factor 2 (Nrf2) activation protects the body against oxidative stress by induction of antioxidant enzymes. The renoprotective effect of ethyl ferulate was investigated in diabetes-induced renal injury. Ethyl ferulate was administered orally at three doses (50 mg/kg, 75 mg/kg, and 100 mg/kg). Metformin (500 mg/kg, p.o.) was used as a standard. Ethyl ferulate treatment decreased serum advanced glycation end products, glycosylated hemoglobin (HbA1c) levels, renal oxidative stress, tumor necrosis factor-α (TNF-α) level, and kidney hypertrophy index. It restored serum lipid profile, biomarkers of renal function, and mitigated histopathological signs of renal damage. Immunohistochemistry demonstrated higher Nrf2 protein levels in kidney sections of ethyl ferulate-treated rats. These findings suggest that ethyl ferulate ameliorated hyperglycemia-induced oxidative stress by increasing renal Nrf2 levels, thereby preventing diabetes-induced kidney injury. In conclusion, the present study endorses the usefulness of Nrf2 activators, such as ethyl ferulate, as adjuvant therapy for preventing the diabetic nephropathy. PRACTICAL APPLICATIONS: Ethyl ferulate (ethyl-3-hydroxyl-4-methoxycinnamate), a phenylpropanoid, is a naturally occurring ethyl ester of ferulic acid and is widely present in plants and especially grains, such as rice and maize. Our study has highlighted the renoprotective effect of ethyl ferulate in preventing diabetes-associated renal injury. The observed effect of ethyl ferulate is due to amelioration of diabetes-induced oxidative stress and inflammation, by activation of the Nrf2 pathway. These results indicate the potential of ethyl ferulate as a nutraceutical or adjuvant therapy in prevention of diabetic nephropathy.

Standardization of type 1 and type 2 diabetic nephropathy models in rats: Assessment and characterization of metabolic features and renal injury.

BACKGROUND: Diabetes mellitus and its complications, such as nephropathy, represent a global burden. Recent research focuses on developing drugs that specifically target the pathogenesis of diabetic nephropathy rather than merely treating hyperglycemia. Rodent models of animal disease are integral in drug discovery and represent an obligatory regulatory requirement. AIM: The aim of this study was to develop and standardize rat models of type 1 and type 2 diabetic nephropathy, resembling characteristics of human clinical condition. MATERIALS AND METHODS: Rats were administered streptozotocin (STZ) 50 mg/kg intraperitoneally (i.p.), and STZ 50 mg/kg i.p. + nicotinamide (NA) 110 mg/kg i.p., for induction of type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM), respectively. Metabolic parameters (body weight, feed and water intake, blood glucose, serum insulin, oral glucose tolerance test, intraperitoneal insulin tolerance test, and indices of insulin sensitivity) were evaluated to characterize the symptoms of T1DM and T2DM. Renal damage was confirmed by the estimation of renal function biomarkers, kidney antioxidant status, kidney hypertrophy index, and histopathology. RESULTS: STZ and STZ + NA administration increased blood glucose levels significantly. Metabolic parameters indicated that administration of STZ resulted in clinical features of human T1DM, whereas STZ + NA rats resembled human T2DM. STZ- and STZ + NA-treated rats developed diabetic nephropathy in 4 weeks, indicated by altered levels of renal function markers, increased kidney hypertrophy index, increased renal oxidative stress, and altered tissue architecture. The study proposes reproducible and cost-effective rat models for both T1DM- and T2DM-induced diabetic nephropathy characterized by stable metabolic features and typical renal lesions.

Vasant Kusmakar Ras, an ayurvedic herbo-mineral formulation prevents the development of diabetic retinopathy in rats.

BACKGROUND: Diabetic retinopathy is a slow progressing complication of diabetes mellitus with multifactorial aetiology affecting approximately 80% of diabetics worldwide. Chronic hyperglycemic milieu of Diabetes induces biochemical changes which contribute to the pathogenesis of Diabetic retinopathy. OBJECTIVE: The present study examined the protective effect of Vasant Kusumakar Ras, an Ayurvedic herbo-mineral formulation, in diabetic retinopathy. MATERIALS AND METHODS: Diabetes was induced in rats by intraperitoneal injection of streptozotocin (45 mg/kg). Rats were kept without any treatment for period of three weeks for induction of Diabetic retinopathy followed by treatment with Vasant Kusumakar Ras (11.25 mg/kg, p.o) for further 5 weeks. Fasting blood glucose levels, lipid profile and HbA1c were determined. Eye tissue homogenates were subjected to biochemical analysis to determine the levels of oxidative stress parameters (superoxide dismutase, catalase, reduced glutathione, lipid peroxidation), vascular endothelial growth factor and aldose reductase activity. Histopathological analysis of retinal tissue was conducted using Hematoxylin and Eosin staining. RESULTS: Vasant Kusumakar Ras treatment restored serum lipid profile which was altered in diabetic rats. Treatment with Vasant Kusumakar Ras significantly ameliorated the oxidative stress in eye tissue resulting in decreased lipid peroxidation and increase in endogenous antioxidant levels. Levels of aldose reductase and vascular endothelial growth factor in eye tissue were significantly decreased in Vasant Kusumakar Ras treated rats. Hematoxylin and Eosin staining indicated that the Vasant Kusumakar Ras treatment significantly restored the normal architecture of the retinal tissue. CONCLUSION: Vasant Kusumakar Ras exhibits protective effect and prevents the development of Diabetic retinopathy through its effects on multiple biochemical pathways implicated in pathogenesis of Diabetic retinopathy.

Mechanistic evaluation of Ursolic acid against rotenone induced Parkinson's disease- emphasizing the role of mitochondrial biogenesis.

Parkinson's disease (PD) is an age associated, progressive and a second most common neurodegenerative disease. It is caused due to degeneration of dopaminergic neurons in substantia nigra (SN). Various studies implicate mitochondrial dysfunction, oxidative stress, altered degradation of misfolded proteins in PD pathogenesis. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid, is reported to possess a number of biological activities viz. anti-oxidant, anti-inflammatory etc. The focus of our study was to assess the neuroprotective potential of UA against the rotenone induced pathophysiological alterations. In this study rats were subjected to stereotaxic bilateral injection of rotenone (12 µg/µl) in SN. Further, they were treated per-orally with UA (5 and 10 mg/kg) for 30 days. During the study, neurobehavioral tests comprising Rota-rod, Open field and Barnes maze (BMT) were conducted. At the end of 30 days, the antioxidant (Reduced glutathione, superoxide dismutase, catalase and lipid peroxidation), inflammatory (TNF-α) parameters, mitochondrial complex I, mitochondrial biogenesis (MB) and immunohistochemical analysis (TH positive neurons, Glial Fibrillary Acidic Protein (GFAP)) was performed. The results exhibited significant amelioration in the motor deficits by UA which can be attributed to the protection of TH positive neurons from degeneration. A significant improvement in the cognitive function due to UA was observed in BMT. Biochemically, the oxidative stress and inflammation triggered by rotenone was significantly diminished by UA. It also significantly obviated the complex I inhibition and promoted MB. The preliminary results thus firmly advocate the neuroprotective potential of UA to prevent rotenone induced neurotoxicity in rats.

Neuroprotective Effect of Coumarin Nasal Formulation: Kindling Model Assessment of Epilepsy.

Epilepsy is a brain disorder characterized by sudden recurrent seizures. Considering the fact that epileptogenesis is a process that affects the quality of life, our goal is to delay the process of epileptogenesis and to increase the latency of epileptic attacks, offering better quality of life to patients. Traditional system of medicines has a promise in some of the medicines, which have been used for the treatment of epilepsy. One such medicinal plant is Eclipta alba (EA). According to Ayurvedic philosophy, the juice of leaves of EA is pounded with garlic and pepper for the treatment of epilepsy. Taking clue from the Ayurvedic system of medicines, we formulated coumarin fraction of EA, namely, coumarin nasal formulation (CNF) for its nasal delivery. CNF was analyzed by using high performance liquid chromatography (HPLC) and ultraviolet absorption spectroscopy for its drug content determination. In vitro drug release studies were performed in simulated nasal electrolyte solution (SNES) maintaining constant pH of 5.5 at 37°C. Irritation by CNF was evaluated using hen's egg test chorioallantoic membrane (HET-CAM) assay. Formulation was found to be non-irritant in HET-CAM assay. CNF was further assessed in vivo by measuring the progress and attainment of pentylenetetrazole (PTZ) kindling in mice. Neuronal changes were assessed by hematoxylin and eosin (H&E) and Nissl staining technique. Glial fibrillary acidic protein (GFAP) a neuroinflammatory marker and tumor necrosis factor alpha (TNF-α) an inflammatory marker were also measured. CNF (10 mg/kg, nasal route) when given as a pretreatment lowered seizure score and delayed the progression of seizure similar to diazepam. CNF decreased the PTZ induced oxidative damage, TNF-α as well as GFAP levels in the midbrain tissue particularly in hippocampus region. The results suggest that CNF may be a promising therapeutic approach to offer protection from sudden recurrent seizures alone or in combination with current drugs in management of epilepsy.

Targeting Mitochondrial Dysfunction for the Treatment of Diabetic Complications: Pharmacological Interventions through Natural Products.

Diabetes mellitus is a chronic hyperglycemic condition with deleterious effects on microcirculation, resulting in diabetic complications. Chronic hyperglycemia induces the generation of reactive oxygen species (ROS), which are the key pathological triggers in the development of diabetic complications. ROS are responsible for the activation of various pathways involved in the genesis of diabetic complications, mitochondrial dysfunction, as well as insulin resistance. The review describes normal mitochondrial physiology and abnormal alterations, which occur in response to hyperglycemia. Mitochondrial biogenesis is a highly regulated process mediated by several transcription factors, wherein mitochondrial fusion and fission occur in harmony in a normal healthy cell. However, this harmony is disrupted in hyperglycemic condition indicated by alteration in functions of essential transcription factors. Hyperglycemia-induced mitochondrial dysfunction plays a key role in diabetic complications, pancreatic ß-cell dysfunction, as well as skeletal muscle insulin resistance as demonstrated by various in vitro, preclinical, and clinical studies. The review focuses on the various factors involved in mitochondrial biogenesis and maintenance of healthy mitochondrial function. Several phytoconstituents act through these pathways, either directly by stimulating biogenesis or indirectly by inhibiting or preventing dysfunction, and produce a beneficial effect on overall mitochondrial function. These phytoconstituents have enormous potential in amelioration of diabetic complications by restoring normal mitochondrial physiology and need detailed evaluation by preclinical and clinical studies. Such phytoconstituents can be included as nutraceuticals or adjuvant therapy to the mainstream treatment of diabetes.

Renoprotective effect of diosgenin in streptozotocin induced diabetic rats.

BACKGROUND: Diabetes mellitus is a multifactorial metabolic disorder associated with genesis of diabetes related vascular diseases. Oxidative stress along with inflammation is the major causative factor leading to diabetic complications. The present study examined the protective effect of diosgenin, a steroidal saponin, in diabetes induced early kidney injury. METHODS: Diabetes was induced by streptozotocin (45mg/kg) in rats followed by treatment for 28 days with diosgenin (5, 10 and 20mg/kg, oral). Blood glucose levels, lipid profile, serum advanced glycation end-products, biomarkers of kidney damage like urinary protein excretion, kidney hypertrophy index and creatinine in serum and urine were determined. Biochemical analysis of oxidative stress parameters such as superoxide dismutase, catalase, reduced glutathione, lipid peroxidation (LPO) and myeloperoxidase level were evaluated in kidney homogenates. Histopathological evaluation of kidney was also studied. RESULTS: Treatment with diosgenin significantly ameliorated the altered oxidative stress levels in STZ induced diabetic rats resulting in decreased LPO and increased endogenous antioxidant levels in a dose-dependent manner. Blood glucose was significantly decreased at 20mg/kg. The distorted levels of biomarkers suggestive of kidney damage were significantly normalized by diosgenin providing protection to kidneys also confirmed by histopathological studies. Decreased myeloperoxidase levels in diosgenin treatment groups revealed its anti-inflammatory activity. CONCLUSION: The above study justifies diosgenin as a promising candidate in diabetes associated complication through its antioxidant and anti-inflammatory activity.

Thymol, a monoterpene, inhibits aldose reductase and high-glucose-induced cataract on isolated goat lens.

BACKGROUND: Overactivation of aldose reductase (AR) enzyme has been implicated in the development of various diabetic complications. In the present study, the inhibitory effect of thymol was investigated on AR enzyme and its anti-cataract activity was also examined on isolated goat lens. MATERIALS AND METHODS: Various concentrations of thymol were incubated with AR enzyme prepared from isolated goat lens. Molecular docking studies were carried out using Schrodinger software to verify the binding of thymol with AR as well as to understand their binding pattern. Further, thymol was evaluated for its anti-cataract activity in high-glucose-induced cataract in isolated goat lens in vitro. Quercetin was maintained as standard (positive control) throughout the study. RESULTS: Thymol showed potent inhibitory activity against goat lens AR enzyme with an IC50 value of 0.65 µg/ml. Docking studies revealed that thymol binds with AR in similar binding pattern as that of quercetin. The high-glucose-induced cataract in isolated goat lens was also improved by thymol treatment. Thymol was also able to significantly (P < 0.001) reduce the oxidative stress associated with cataract. CONCLUSION: The results suggest that thymol may be a potential therapeutic approach in the prevention of diabetic complications through its AR inhibitory and antioxidant activities.