Metformin Reduces the Progression of Atherogenesis by Regulating the Sestrin2-mTOR Pathway in Obese and Diabetic Rats

Objective@#In previous research, we found that Sestrin2 has a strong association with plasma atherogenicity and combats the progression of atherogenesis by regulating the AMPK-mTOR pathway. Metformin, an activator of AMPK, is widely used as a first-line therapy for diabetes, but its role in preventing atherosclerosis and cardiac outcomes is unclear. Hence, we aimed to assess the effect of metformin on preventing atherosclerosis and its regulatory role in the Sestrin2-AMPK -mTOR pathway in obese/diabetic rats. @*Methods@#Animals were fed a high-fat diet to induce obesity, administered streptozotocin to induce diabetes, and then treated with metformin (150 mg/kg body weight) for 14 weeks. Aorta and heart tissues were analyzed for Sestrin2 status by western blotting and immunohistochemistry, AMPK and mTOR activities were investigated using western blotting, and atherogenicity-related events were evaluated using reverse transcription quantitative polymerase chain reaction and histology. @*Results@#Obese and diabetic rats showed significant decrease in Sestrin2 levels and AMPK activity, accompanied by increased mTOR activity in the heart and aorta tissues. Metformin treatment significantly restored Sestrin2 and AMPK levels, reduced mTOR activity, and restored the altered expression of inflammatory markers and adhesion molecules in obese and diabetic rats to normal levels. A histological analysis of samples from obese and diabetic rats showed atherosclerotic lesions both in aorta and heart tissues. The metformin-treated rats showed a decrease in atherosclerotic lesions, cardiac hypertrophy, and cardiomyocyte degeneration. @*Conclusion@#This study presents further insights into the beneficial effects of metformin and its protective role against atherosclerosis through regulation of the Sestrin2-AMPK-mTOR pathway.

Plausible diagnostic value of urinary isomeric dimethylarginine ratio for diabetic nephropathy.

Altered circulatory asymmetric and symmetric dimethylarginines have been independently reported in patients with end-stage renal failure suggesting their potential role as mediators and early biomarkers of nephropathy. These alterations can also be reflected in urine. Herein, we aimed to evaluate urinary asymmetric to symmetric dimethylarginine ratio (ASR) for early prediction of diabetic nephropathy (DN). In this cross-sectional study, individuals with impaired glucose tolerance (IGT), newly diagnosed diabetes (NDD), diabetic microalbuminuria (MIC), macroalbuminuria (MAC), and normal glucose tolerance (NGT) were recruited from Dr. Mohans' Diabetes Specialties centre, India. Urinary ASR was measured using a validated high-throughput MALDI-MS/MS method. Significantly lower ASR was observed in MIC (0.909) and MAC (0.741) in comparison to the NGT and NDD groups. On regression models, ASR was associated with MIC [OR: 0.256; 95% CI: 0.158-0.491] and MAC [OR 0.146; 95% CI: 0.071-0.292] controlled for all the available confounding factors. ROC analysis revealed ASR cut-point of 0.95 had C-statistic of 0.691 (95% CI: 0.627-0.755) to discriminate MIC from NDD with 72% sensitivity. Whereas, an ASR cut-point of 0.82 had C-statistic of 0.846 (95% CI: 0.800 - 0.893) had 91% sensitivity for identifying MAC. Our results suggest ASR as a potential early diagnostic biomarker for DN among the Asian Indians.

Role of VEGF165b/VEGFTOTAL ratio in gestational diabetes mellitus.

Proper vascular function is important for well-being of mother and growing fetus. VEGFTOTAL, and VEGF165b levels and its vascular endothelial complications in gestational diabetes mellitus (GDM) together with the association of inflammation and advanced glycation end products (AGEs) are less studied. VEGF165b/VEGFTOTAL (VEGF RATIO) in GDM pregnant women was investigated in this study. Plasma VEGFTOTAL was lower in GDM (17.68 ± 1.30 pg/mL) compared to non-GDM (25.69 ± 1.40 pg/mL). VEGF165b, ICAM-1, and AGEs were higher in GDM (9.9 ± 1.4 pg/mL, 201.04 ± 7.85 µg/mL, and 10.40 ± 0.98 µg/mL, respectively) and lower in non-GDM (6.47 ± 0.70 pg/mL, 174.1 ± 7.11 µg/mL, and 4.71 ± 0.39 µg/mL, respectively). Compared to non GDM (0.25 ± 0.02), VEGF RATIO was higher in GDM (0.45 ± 0.04) and correlated with -ICAM-1 (r = 0.375, p < .001) and AGEs (r = 0.199, p < .05). Tertile stratification of VEGF RATIO implied that frequency of GDM increases with increasing tertiles of VEGF RATIO (p for trend <.001). Association of VEGF RATIO with GDM was significant even after adjusting for AGEs (OR = 1.279, CI = 1.118-1.462, p < .0010) but it lost its significance when adjusted for ICAM-1 (OR = 1.006, CI = 0.995-1.017, p = .308). VEGF RATIO plays an important role in GDM in association with vascular inflammation.

Inflammatory markers in relation to nonalcoholic fatty liver disease in urban South Indians.

OBJECTIVE: This study assessed the association of inflammatory markers, high-sensitivity C-reactive protein (hsCRP), and total leukocyte count with nonalcoholic fatty liver disease (NAFLD) in urban South Indians. SUBJECTS AND METHODS: We randomly selected subjects with and without NAFLD (n=100 each) from the Chennai Urban Rural Epidemiology Study conducted in Chennai in south India. NAFLD was diagnosed by ultrasonography. hsCRP was measured by nephelometry, and leukocyte count was measured by flow cytometry. Insulin resistance was analyzed by homeostasis assessment model using the following expression: fasting insulin (µIU/mL)×fasting glucose (mmol/L)/22.5. RESULTS: Mean hsCRP values were significantly higher in subjects with NAFLD compared with those without (4.2±1.2 mg/L vs. 2.2±0.4 mg/L; P<0.001). Leukocyte count was also higher in subjects with NAFLD compared with those without (7.8±1.4×10(3)/µL vs 6.9±0.9×10(3)/µL, P<0.001). Both hsCRP (P<0.001) and leukocyte count (P<0.001) increased with increasing severity of NAFLD. Multiple logistic regression analysis was done using NAFLD as the dependent variable and hsCRP and leukocyte count as independent variables. Both hsCRP (odds ratio 1.293, 95% confidence interval 1.13-1.470, P<0.001) and leukocyte count (odds ratio 1.293, 95% confidence interval 1.069-1.564, P=0.008) had a significant association with NAFLD even after adjusting for waist circumference, insulin resistance, serum triglycerides, and presence of type 2 diabetes. CONCLUSIONS: hsCRP and leukocyte count are associated with NAFLD after adjusting for conventional cardiometabolic risk factors.

Transcriptional regulation of cytokines and oxidative stress by gallic acid in human THP-1 monocytes.

Increased inflammation/prooxidation has been linked not only to Type 2 diabetes but also in prediabetes state. In this study we investigated hyperglycemia-mediated proinflammatory/prooxidant effects in THP-1 monocytes and tested whether gallic acid could attenuate changes in gene expression induced by high-glucose. Cells were treated either with 5.5mM glucose or 25mM glucose in the absence and presence of gallic acid. While oxidative DNA damage was assessed by COMET assay, GSH and GSSG levels were estimated fluorimetrically. Gene expression patterns were determined by RT-PCR. Cells treated with high-glucose showed increased DNA damage and glutathione depletion and this was attenuated in the presence of gallic acid. High-glucose treated cells exhibited increased mRNA expression of TNF-alpha, IL-6, NADPH oxidase and TXNIP and gallic acid attenuated these proinflammatory and prooxidant effects. Cells treated with high-glucose revealed a deficiency in mounting SOCS-3 expression and gallic acid upregulates this feedback regulatory signal. Gallic acid attenuates DNA damage, maintains glutathione turnover, and suppresses hyperglycemia-induced activation of proinflammatory and prooxidant gene expression. Gallic acid beneficially modulate transcription of functionally diverse groups of genes and its regulation of SOCS-3 and TXNIP signals is a newly identified mechanism that has therapeutic implications.