Metformin improves lipid metabolism disorders through reducing the expression of microsomal triglyceride transfer protein in OLETF rats

Isocitrate dehydrogenase 1 upregulation in urinary extracellular vesicles from proximal tubules of type 2 diabetic rats

Diabetic nephropathy (DN) is a major cause of chronic kidney disease. Microalbuminuria is currently the most common non-invasive biomarker for the early diagnosis of DN. However, renal structural damage may have advanced when albuminuria is detected. In this study, we sought biomarkers for early DN diagnosis through proteomic analysis of urinary extracellular vesicles (uEVs) from type 2 diabetic model rats and normal controls. Isocitrate dehydrogenase 1 (IDH1) was significantly increased in uEVs from diabetic model rats at the early stage despite minimal differences in albuminuria between the groups. Calorie restriction significantly suppressed the increase in IDH1 in uEVs and 24-hour urinary albumin excretion, suggesting that the increase in IDH1 in uEVs was associated with the progression of DN. Additionally, we investigated the origin of IDH1-containing uEVs based on their surface sugar chains. Lectin affinity enrichment and immunohistochemical staining showed that IDH1-containing uEVs were derived from proximal tubules. These findings suggest that the increase in IDH1 in uEVs reflects pathophysiological alterations in the proximal tubules and that IDH1 in uEVs may serve as a potential biomarker of DN in the proximal tubules.

Metformin induces pyroptosis in leptin receptor-defective hepatocytes via overactivation of the AMPK axis

Metformin is the biguanide of hepatic insulin sensitizer for patients with non-alcohol fatty liver disease (NAFLD). Findings regarding its efficacy in restoring blood lipids and liver histology have been contradictory. In this study, we explore metformin's preventive effects on NAFLD in leptin-insensitive individuals. We used liver tissue, serum exosomes and isolated hepatocytes from high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats and leptin receptor (Lepr) knockout rats to investigate the correlation between hepatic Lepr defective and liver damage caused by metformin. Through immunostaining, RT-PCR and glucose uptake monitoring, we showed that metformin treatment activates adenosine monophosphate (AMP)-activated protein kinase (AMPK) and its downstream cytochrome C oxidase (CCO). This leads to overactivation of glucose catabolism-related genes, excessive energy repertoire consumption, and subsequent hepatocyte pyroptosis. Single-cell RNA sequencing further confirmed the hyper-activation of glucose catabolism after metformin treatment. Altogether, we showed that functional Lepr is necessary for metformin treatment to be effective, and that long-term metformin treatment might promote NAFLD progression in leptin-insensitive individuals. This provides important insight into the clinical application of metformin.

Short-Term Metformin Treatment Enriches Bacteroides dorei in an Obese Liver Steatosis Zucker Rat Model

Obesity is the leading cause of health-related diseases in the United States and World. Previously, we reported that obesity can change gut microbiota using the Zucker rat model. Metformin is an oral anti-hyperglycemic agent approved by the FDA to treat type 2 diabetes (T2D) in adults and children older than 10 years of age. The correlation of short-term metformin treatment and specific alterations to the gut microbiota in obese models is less known. Short-term metformin has been shown to reduce liver steatosis. Here we investigate the effects of short-term metformin treatment on population of gut microbiota profile in an obese rat model. Five week old obese (n = 12) female Zucker rats after 1 week of acclimation, received AIN-93 G diet for 8 weeks and then rats were randomly assigned into two groups (6 rats/group): (1) obese without metformin (ObC), or (2) obese with metformin (ObMet). Metformin was mixed with AIN-93G diet at 1,000 mg/kg of diet. Rats were weighed twice per week. All rats were sacrificed at the end of metformin treatment at 10 weeks and fecal samples were collected and kept at -80°C. Total microbial DNA was collected directly from the fecal samples used for shotgun-metagenomics sequencing and subsequently analyzed using MetaPlAn and HUMAnN. After stringent data filtering and quality control we found significant differences (p = 0.0007) in beta diversity (Aitchison distances) between the ObC vs. ObMet groups. Supervised and unsupervised analysis of the log-ratios Bacteroides dorei and B. massiliensis vs. all other Bacteroides spp., revealed that B. dorei and B. massiliensis were enriched in the ObMet group, while the remaining Bacteroides spp. where enriched in the ObC group (p = 0.002). The contributional diversity of pathways is also significantly associated by treatment group (p = 0.008). In summary, in the obese Zucker rat model, short-term metformin treatment changes the gut microbiota profile, particularly altering the composition Bacteroides spp. between ObC and ObMet.

Correlation between long-term use of metformin and incidence of NAFLD among patients with type 2 diabetes mellitus: A real-world cohort study

BACKGROUND AND AIMS

Studies have demonstrated that the short-term use of metformin benefits liver function among patients with type 2 diabetes mellitus (T2DM). However, few studies have reported on the effects of long-term metformin treatment on liver function or liver histology. This study investigated the correlation between metformin use and the incidence of nonalcoholic fatty liver disease (NAFLD) among patients with T2DM.

METHODS

This population-based study investigated the risk of NAFLD among patients with T2DM who received metformin treatment between 2001-2018. Metformin users and metformin nonusers were enrolled and matched to compare the risk of NAFLD.

RESULTS

After 3 years, the patients who received <300 cDDD of metformin and those with metformin use intensity of <10 and 10-25 DDD/month had odds ratios (ORs) of 1.11 (95% confidence interval [CI] = 1.06-1.16), 1.08 (95% CI = 1.02-1.13), and 1.18 (95% CI = 1.11-1.26) for NAFLD, respectively. Moreover, metformin users who scored high on the Diabetes Complications and Severity Index (DCSI) were at high risk of NAFLD. Patients with comorbid hyperlipidemia, hyperuricemia, obesity, and hepatitis C were also at high risk of NAFLD.

CONCLUSION

Patients with T2DM who received metformin of <300 cDDD or used metformin at an intensity of <10 and 10-25 DDD/month were at a high risk of developing NAFLD. The results of this study also indicated that patients with T2DM receiving metformin and with high scores on the DCSI were at a high risk of developing NAFLD.

Expression pattern of perilipins in human brain during aging and in Alzheimer's disease

AIMS

Perilipins are conserved proteins that decorate intracellular lipid droplets and are essential for lipid metabolism. To date, there is limited knowledge on their expression in human brain or their involvement in brain aging and neurodegeneration. The aim of this study was to characterise the expression levels of perilipins (Plin1-Plin5) in different cerebral areas from subjects of different age, with or without signs of neurodegeneration.

METHODS

We performed real-time RT-PCR, western blotting, immunohistochemistry and confocal microscopy analyses in autoptic brain samples of frontal and temporal cortex, cerebellum and hippocampus from subjects ranging from 33 to 104 years of age, with or without histological signs of neurodegeneration. To test the possible relationship between Plins and inflammation, correlation analysis with IL-6 expression was also performed.

RESULTS

Plin2, Plin3 and Plin5, but not Plin1 and Plin4, are expressed in the considered brain areas with different intensities. Plin2 appears to be expressed more in grey matter, particularly in neurons in all the areas analysed, whereas Plin3 and Plin5 appear to be expressed more in white matter. Plin3 seems to be expressed more in astrocytes. Only Plin2 expression is higher in old subjects and patients with early tauopathy or Alzheimer's disease and is associated with IL-6 expression.

CONCLUSIONS

Perilipins are expressed in human brain but only Plin2 appears to be modulated with age and neurodegeneration and linked to an inflammatory state. We propose that the accumulation of lipid droplets decorated with Plin2 occurs during brain aging and that this accumulation may be an early marker and initial step of inflammation and neurodegeneration.

Metformin Preserves β-Cell Compensation in Insulin Secretion and Mass Expansion in Prediabetic Nile Rats

Prediabetes is a high-risk condition for type 2 diabetes (T2D). Pancreatic β-cells adapt to impaired glucose regulation in prediabetes by increasing insulin secretion and β-cell mass expansion. In people with prediabetes, metformin has been shown to prevent prediabetes conversion to diabetes. However, emerging evidence indicates that metformin has negative effects on β-cell function and survival. Our previous study established the Nile rat (NR) as a model for prediabetes, recapitulating characteristics of human β-cell compensation in function and mass expansion. In this study, we investigated the action of metformin on β-cells in vivo and in vitro. A 7-week metformin treatment improved glucose tolerance by reducing hepatic glucose output and enhancing insulin secretion. Although high-dose metformin inhibited β-cell glucose-stimulated insulin secretion in vitro, stimulation of β-cell insulin secretion was preserved in metformin-treated NRs via an indirect mechanism. Moreover, β-cells in NRs receiving metformin exhibited increased endoplasmic reticulum (ER) chaperones and alleviated apoptotic unfold protein response (UPR) without changes in the expression of cell identity genes. Additionally, metformin did not suppress β-cell mass compensation or proliferation. Taken together, despite the conflicting role indicated by in vitro studies, administration of metformin does not exert a negative effect on β-cell function or cell mass and, instead, early metformin treatment may help protect β-cells from exhaustion and decompensation.

Metformin ameliorates acetaminophen-induced sub-acute toxicity via antioxidant property

Acetaminophen or N-acetyl-p-amino-phenol (APAP) is a drug which is available over-the-counter for fever and pain. Its overdosing causes oxidative stress and subsequent acute liver damage. In the present study, we scrutinized the protective effect of metformin co-treatment in APAP induced blood and liver sub-acute toxicity. This is a pre-clinical study in which male Wistar Rats (BW: 300 ± 20 g) were orally co-treated with APAP (1 g/kg/day) and metformin (300 mg/kg/day) for 28-days. Pro- and anti-oxidant markers viz reactive oxygen species, protein carbonyl, malondialdehyde (MDA), the ferric reducing ability of plasma (FRAP), plasma membrane redox system(PMRS) and reduced glutathione (GSH) were evaluated in blood. Additionally, in liver tissue, catalase (CAT), superoxide dismutase (SOD), MDA and GST level were also evaluated. Histological study and estimation of alanine aminotransferase (ALT), and aspartate aminotransferase (AST) level in serum were performed. APAP induces pro-oxidant markers as well as reduces anti-oxidant markers in blood and liver. Hepatic tissues degeneration and vacuolization of hepatocytes were evident after APAP treatment. Metformin treatment reduces pro-oxidant markers as well as increases anti-oxidant markers in both tissues. It also improves liver tissue architecture after treatment. The outcome of this study suggests that metformin has protective capability against APAP-induced blood and liver toxicity. Thus, metformin co-treatment with APAP attenuates oxidative stress and its consequences.

Long-term treatment with metformin in the prevention of fatty liver in Zucker diabetic fatty rats

BACKGROUND

Treatment with metformin, the biguanide of hepatic insulin sensitizer, in patients with non-alcoholic fatty liver disease (NAFLD) has been reported with contradictory findings regarding the effectiveness on blood lipids and liver histology. In this study, we aimed to explore the preventive effects of metformin on NAFLD in Zucker diabetic fatty (ZDF) rats.

METHODS

Male ZDF rats and Zucker lean rats aged 4-8 weeks were subjected to vehicle or metformin treatment for 6 months. Liver cDNA microarray assay, and protein semiquantitative and histological examinations were performed.

RESULTS

Data demonstrated that ZDF rats developed hyperglycemia, hyperlipidemia, liver deficiency and hepatocyte degeneration. The metformin treatment significantly reduced post-load blood glucose levels, but not blood lipid profiles or liver enzyme levels. Hepatocyte degeneration was not attenuated after the treatment. The metformin-treated ZDF rats showed activation of AMP-activated protein kinase by Western blot and overexpression of cytochrome c oxidase by immunofluorescent microscopy. Gene expression microarray assay demonstrated that a panel of genes participating in glucose and lipid metabolisms were changed in the ZDF rats, and most of the altered genes involved in glucose and cholesterol metabolisms, but not those in fatty acid metabolisms, were corrected by the metformin treatment. No genes associated with inflammation, apoptosis, fibrosis, or cell death were overexpressed in the metformin-treated ZDF rats.

CONCLUSIONS

These results suggest that long-term metformin treatment presents no preventive effect for NAFLD in ZDF rats.