Activation of renal CSE/H2S pathway by alpha-lipoic acid protects against histological and functional changes in the diabetic kidney.

INTRODUCTION: We previously reported that alpha-lipoic acid (ALA) supplementation protects against progression of diabetic kidney disease (DKD). In this study, we aim to investigate whether the mechanism of renal protection by ALA involves renal cystathionine γ-lyase/hydrogen sulfide (CSE/H2S) system in type 2 diabetes mellitus (T2DM). METHODS: Thirty-seven male Sprague-Dawley rats underwent 12 h of overnight fasting. To induce T2DM, 30 of these rats received intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). T2DM rats then received either oral administration of ALA (60 mg/kg/day) or intraperitoneal administration of 40 mg/kg/day DL-propargylglycine (PAG, a CSE inhibitor) or both for 6 weeks after which rats were sacrificed and samples collected for analysis. Untreated diabetic and non-diabetic rats served as diabetic and healthy controls respectively. RESULTS: T2DM was characterized by reduced pancreatic ß-cell function and hyperglycemia. Histologically, untreated diabetic rats showed significantly damaged pancreatic islets, glomerular and tubular injury, with elevated levels of renal function markers compared to healthy control rats (p < 0.001). These pathological changes worsened significantly following PAG administration (p < 0.05). While some renal protection was observed in ALA+PAG rats, ALA administration in untreated diabetic rats provided superior protection comparable to healthy control rats, with improved antioxidant status, lipid profile and reduced inflammation. Mechanistically, ALA significantly activated renal CSE/H2S system in diabetic rats, which was markedly suppressed in PAG-treated rats (p < 0.001). CONCLUSION: Our data suggest that ALA protects against DKD development and progression by activating renal CSE/H2S pathway. Hence, CSE/H2S pathway may represent a therapeutic target in the treatment or prevention of DKD in diabetic patients.

Combination Therapy of Alpha-Lipoic Acid, Gliclazide and Ramipril Protects Against Development of Diabetic Cardiomyopathy via Inhibition of TGF-ß/Smad Pathway.

Background: Diabetic cardiomyopathy (DCM) is a major long-term complication of diabetes mellitus, accounting for over 20% of annual mortality rate of diabetic patients globally. Although several existing anti-diabetic drugs have improved glycemic status in diabetic patients, prevalence of DCM is still high. This study investigates cardiac effect of alpha-lipoic acid (ALA) supplementation of anti-diabetic therapy in experimental DCM. Methods: Following 12 h of overnight fasting, 44 male Sprague Dawley rats were randomly assigned to two groups of healthy control (n = 7) and diabetic (n = 37) groups, and fasting blood glucose was measured. Type 2 diabetes mellitus (T2DM) was induced in diabetic group by intraperitoneal (i.p.) administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). After confirmation of T2DM on day 3, diabetic rats received monotherapies with ALA (60 mg/kg; n = 7), gliclazide (15 mg/kg; n = 7), ramipril (10 mg/kg; n = 7) or combination of the three drugs (n = 7) for 6 weeks while untreated diabetic rats received distilled water and were used as diabetic control (n = 9). Rats were then sacrificed, and blood, pancreas and heart tissues were harvested for analyses using standard methods. Results: T2DM induction caused pancreatic islet destruction, hyperglycemia, weight loss, high relative heart weight, and development of DCM, which was characterized by myocardial degeneration and vacuolation, cardiac fibrosis, elevated cardiac damage markers (plasma and cardiac creatine kinase-myocardial band, brain natriuretic peptide and cardiac troponin I). Triple combination therapy of ALA, gliclazide and ramipril preserved islet structure, maintained body weight and blood glucose level, and prevented DCM development compared to diabetic control (p < 0.001). In addition, the combination therapy markedly reduced plasma levels of inflammatory markers (IL-1ß, IL-6 and TNF-α), plasma and cardiac tissue malondialdehyde, triglycerides and total cholesterol while significantly increasing cardiac glutathione and superoxide dismutase activity and high-density lipoprotein-cholesterol compared to diabetic control (p < 0.001). Mechanistically, induction of T2DM upregulated cardiac expression of TGF-ß1, phosphorylated Smad2 and Smad3 proteins, which were downregulated following triple combination therapy (p < 0.001). Conclusion: Triple combination therapy of ALA, gliclazide and ramipril prevented DCM development by inhibiting TGF-ß1/Smad pathway. Our findings can be extrapolated to the human heart, which would provide effective additional pharmacological therapy against DCM in T2DM patients.

Supplementation of conventional anti-diabetic therapy with alpha-lipoic acid prevents early development and progression of diabetic nephropathy.

BACKGROUND: Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. Current pharmacological interventions only retard DN progression. Alpha-lipoic acid (ALA) is a potent antioxidant with beneficial effect in other diabetic complications. This study investigates whether ALA supplementation prevents early development and progression of DN. METHOD: Fifty-eight male Sprague-Dawley rats were randomly assigned to healthy control and diabetic groups and subjected to overnight fasting. Type 2 diabetes mellitus (T2DM) was induced in diabetic group by intraperitoneal administration of nicotinamide (110 mg/kg) and streptozotocin (55 mg/kg). On day 3 after T2DM induction, diabetic rats received oral daily administration of ALA (60 mg/kg), gliclazide (15 mg/kg), ramipril (10 mg/kg) or drug combinations for 6 weeks. Untreated diabetic rats served as diabetic control. Blood, kidneys and pancreas were harvested for biochemical and histological analyses. RESULT: Induction of T2DM resulted in hypoinsulinemia, hyperglycemia and renal pathology. ALA supplementation maintained ß-cell function, normoinsulinemia and normoglycemia in diabetic rats, and prevented renal pathology (PAS, KIM-1, plasma creatinine, total protein, blood urea nitrogen, uric acid and urine albumin/creatinine ratio) and triglycerides level compared to diabetic control (p < 0.001). Additionally, ALA supplementation significantly prevented elevated serum and tissue malondialdehyde, collagen deposition, α-SMA expression, apoptosis and serum IL-1ß and IL-6 levels while it markedly increased renal glutathione content and plasma HDL-C compared to diabetic control group (p < 0.001). CONCLUSION: ALA supplementation prevents early development and progression of DN by exerting anti-hyperglycemic, antioxidant, anti-inflammatory, anti-fibrotic and anti-apoptotic effects. Our findings provide additional option for clinical treatment of DN in T2DM patients.

In Vitro Antioxidant Potential and Effect of a Glutathione-Enhancer Dietary Supplement on Selected Rat Liver Cytochrome P450 Enzyme Activity.

BACKGROUND: There is considerable evidence that many people take dietary supplements including those of herbal origin as an alternative therapy to improve their health. One such supplement, with an amalgam of constituents, is CellGevity®. However, the effect of this dietary supplement on drug-metabolizing enzymes is poorly understood, as it has not been studied extensively. Therefore, we investigated the effect of CellGevity dietary supplement on selected rat liver microsomal cytochrome P450 (CYP) enzymes, the most common drug-metabolizing enzymes. We also determined the total antioxidant potential of this dietary supplement in vitro. METHODS: To determine the antioxidant potential of CellGevity dietary supplement, 2,2-diphenyl-2-picryl-hydrazyl (DPPH), total phenolic, and flavonoid assays were used after initial preparation of a solution form of the supplement (low dose, LD; 4 mg/kg and high dose, HD; 8 mg/kg). Rats received oral administration of these doses of the supplement for 7 days, after which the effect of the supplement on selected liver CYP enzymes was assessed using probe substrates and spectroscopic and high-performance liquid chromatographic methods. Rats which received daily administration of 80 mg/kg of phenobarbitone and distilled water served as positive and negative controls, respectively. RESULTS: The IC50 value of the supplement 0.34 ± 0.07 mg/ml compared to 0.076 ± 0.03 mg/ml of the BHT (positive control). The total phenolic content of the supplement at a concentration of 2.5 mg/ml was 34.97 g gallic acid equivalent (GAE)/100 g while its total flavonoid content at a concentration of 2.5 mg/ml was 6 g quercetin equivalent (QE)/100 g. The supplement significantly inhibited rat CYP2B1/2B2 (LDT 92.4%; HDT 100%), CYP3A4 (LDT 81.2%; HDT 71.7%), and CYP2C9 (LDT 21.7%; HDT 28.5%) while it had no significant inhibitory effect on CYPs 1A1/1A2, CYP1A2, and CYP2D6. CONCLUSION: CellGevity dietary supplement possesses moderate antioxidant activity in vitro and has an inhibitory effect on selected rat liver CYP enzymes, suggesting its potential interaction with drugs metabolized by CYP enzymes.