Amelioration of streptozotocin‑induced pancreatic β cell damage by morin: Involvement of the AMPK‑FOXO3‑catalase signaling pathway

AMPK pathway: an emerging target to control diabetes mellitus and its related complications

Purpose

In this extensive review work, the important role of AMP-activated protein kinase (AMPK) in causing of diabetes mellitus has been highlighted. Structural feature of AMPK as well its regulations and roles are described nicely, and the association of AMPK with the diabetic complications like nephropathy, neuropathy and retinopathy are also explained along with the connection between AMPK and β-cell function, insulin resistivity, mTOR, protein metabolism, autophagy and mitophagy and effect on protein and lipid metabolism.

Methods

Published journals were searched on the database like PubMed, Medline, Scopus and Web of Science by using keywords such as AMPK, diabetes mellitus, regulation of AMPK, complications of diabetes mellitus, autophagy, apoptosis etc.

Result

After extensive review, it has been found that, kinase enzyme like AMPK is having vital role in management of type II diabetes mellitus. AMPK involve in enhance the concentration of glucose transporter like GLUT 1 and GLUT 4 which result in lowering of blood glucose level in influx of blood glucose into the cells; AMPK increases the insulin sensitivity and decreases the insulin resistance and further AMPK decreases the apoptosis of β-cells which result into secretion of insulin and AMPK is also involve in declining of oxidative stress, lipotoxicity and inflammation, owing to which organ damage due to diabetes mellitus can be lowered by activation of AMPK.

Conclusion

As AMPK activation leads to overall control of diabetes mellitus, designing and developing of small molecules or peptide that can act as AMPK agonist will be highly beneficial for control or manage diabetes mellitus.

Effect of Oleanolic acid administration on hepatic AMPK, SIRT-1, IL-6 and NF-κB levels in experimental diabetes

Objectives

Diabetes mellitus (DM) is an important public health problem all over the world, considering its complications and increasing prevalence. Oleanolic acid (OA) has anti-diabetic property via modulating glucose metabolism and acting as 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) / Sirtuin-1 (SIRT-1) activator and Interleukin 6 (IL-6) / Nuclear factor kappa B (NF-κB) inhibitor. This research questioned if the OA treatment amliorates the hepatic inflammatory profile in the diabetic rats.

Methods

Twenty-eight male Sprague Dawley rats were first subjected to either no diabetes induction (healthy) or diabetes induction by i.p. injection of 50 mg/kg streptozotocin. Then rats in both groups were treated with either tap water or OA (5 mg/kg) within 1 ml tap water by oral gavage for 21 days.

Results

The diabetic rats had higher hepatic MDA (2.88x) and serum AST (2.01x), ALP (2.22x), and ALT (4.27x) levels and 50% lower hepatic SOD level than the healthy rats. The OA treatment significantly reversed these antioxidant parameters in the diabetic rats. The diabetic rats had lower AMPK (85%) and hepatic SIRT-1 (47%) levels and higher hepatic NF-κB (53%) and IL-6 (34%) levels than the healthy rats. Comparing with the health rats, the OA treatment increased hepatic SIRT-1 level, but tended to increase hepatic AMPK level and decrease hepatic NF-κB and IL-6 levels in the diabetic rats. It was also partially effective to ameliorate degenerative changes and necrosis in the diabetic rats.

Conclusion

The OA treatment can be considered to alleviate oxidative stress and reduce severity of inflammation in hepatocytes in the diabetic subjects.

Pancreatic β-cell dysfunction in type 2 diabetes: Implications of inflammation and oxidative stress

Insulin resistance and pancreatic β-cell dysfunction are major pathological mechanisms implicated in the development and progression of type 2 diabetes (T2D). Beyond the detrimental effects of insulin resistance, inflammation and oxidative stress have emerged as critical features of T2D that define β-cell dysfunction. Predominant markers of inflammation such as C-reactive protein, tumor necrosis factor alpha, and interleukin-1β are consistently associated with β-cell failure in preclinical models and in people with T2D. Similarly, important markers of oxidative stress, such as increased reactive oxygen species and depleted intracellular antioxidants, are consistent with pancreatic β-cell damage in conditions of T2D. Such effects illustrate a pathological relationship between an abnormal inflammatory response and generation of oxidative stress during the progression of T2D. The current review explores preclinical and clinical research on the patho-logical implications of inflammation and oxidative stress during the development of β-cell dysfunction in T2D. Moreover, important molecular mechanisms and relevant biomarkers involved in this process are discussed to divulge a pathological link between inflammation and oxidative stress during β-cell failure in T2D. Underpinning the clinical relevance of the review, a systematic analysis of evidence from randomized controlled trials is covered, on the potential therapeutic effects of some commonly used antidiabetic agents in modulating inflammatory makers to improve β-cell function.

Acacetin antagonized lipotoxicity in pancreatic β-cells via ameliorating oxidative stress and endoplasmic reticulum stress

PURPOSE

During the pathogenesis and progression of diabetes, lipotoxicity is a major threat to the function and survival of pancreatic β-cells. To battle against the lipotoxicity induced cellular damages, the present study investigated the beneficial effects of acacetin, a natural antioxidant, on free fatty acid (FFA) stressed RINm5F cells and the potential mechanism involved.

MATERIALS AND METHODS

RINm5F cells with or without 1 h pretreatment of acacetin were treated with 0.35 mM sodium palmitate for 24 h. Cell viability, intracellular reactive oxygen species (ROS) level, antioxidant capacity, cellular apoptosis, and endoplasmic reticulum (ER) stress biomarker expression were investigated.

RESULTS

Our experiments demonstrated that acacetin treatment significantly scavenged the intracellular ROS, upregulated the endogenous antioxidant enzymes, and diminished the sub-G₁ DNA fraction in the cells exposed to FFA, suggesting its efficacy against oxidative stress. Meanwhile, acacetin treatment significantly mitigated the overload of intracellular Ca²⁺ and reduced the pro-apoptotic protein expression in the FFA stimulated cells, and thereby attenuated the ER stress-mediated cell apoptosis. Furthermore, siRNA interference results confirmed that the suppressing of C/EBP-homologous protein (CHOP) was critical to improve FFA-induced reduction in cell viability and ameliorated the ER stress caused by FFA stimulation.

CONCLUSIONS

Acacetin may antagonize lipotoxicity in pancreatic cells by attenuating the oxidative stress and ER stress.

Insulin signaling pathway assessment by enhancing antioxidant activity due to morin using in vitro rat skeletal muscle L6 myotubes cells

BACKGROUND

Plant-derived phytochemicals such as flavonoids have been explored to be powerful antioxidants that protect against oxidative stress-related diseases. In the present study, Morin, a flavonoid compound was studied for its antioxidant and antidiabetic properties in relation to oxidative stress in insulin resistant models conducted in rat skeletal muscle L6 cell line model.

METHODS

Evaluation of antioxidant property of morin was assayed using in vitro methods such as cell viability by MTT assay, estimation of SOD and CAT activity and NO scavenging activity. The anti-oxidative nature of morin on L6 cell line was conducted by the DCF-DA fluorescent activity. Glucose uptake in morin treated L6 myotubes are accessed by 2-NBDG assay in the presence or absence of IRTK and PI3K inhibitors. Further glycogen content estimation due to the morin treatment in L6 myotubes was performed. Antioxidant and insulin signaling pathway gene expression was examined over RT-PCR analysis.

RESULTS

Morin has a negligible cytotoxic effect at doses of 20, 40, 60, 80, and 100 µM concentration according to cell viability assay. Morin revealed that the levels of the antioxidant enzymes SOD and CAT in L6 myotubes had increased. When the cells were subjected to the nitro blue tetrazolium assay, morin lowered reactive oxygen species (ROS) formation at 60 µM concentration displaying 39% ROS generation in oxidative stress condition. Lesser NO activity and a drop in green fluorescence emission in the DCFDA assay, demonstrating its anti-oxidative nature by reducing ROS formation in vitro. Glucose uptake by the L6 myotube cells using 2-NBDG, and with IRTK and PI3K inhibitors (genistein and wortmannin) showed a significant increase in glucose uptake by the cells which shows the up regulated GLUT-4 movement from intracellular pool to the plasma membrane. Morin (60 µM) significantly enhanced the expression of antioxidant genes GPx, GST and GCS as well as insulin signalling genes IRTK, IRS-1, PI3K, GLUT-4, GSK-3β and GS in L6 myotubes treated cells.

CONCLUSION

Morin has the ability to act as an anti-oxidant by lowering ROS levels and demonstrating insulin mimetic activity by reversing insulin resistance associated with oxidative stress.

Evaluation of the Antidiabetic Potential of Extracts of Urtica dioica, Apium graveolens, and Zingiber officinale in Mice, Zebrafish, and Pancreatic β-Cell

Medicinal plants are commonly used in the treatment of diabetes, particularly as they contain flavonoids and phenolic compounds. The present study aims to investigate the activities of a polyherbal formulation made from Urtica dioica, Apium graveolens, and Zingiber officinale (UAZ) against streptozotocin–nicotinamide ((STZ-NA)-induced type 2 diabetes in CD1 mice, glucose-induced type 2 diabetes (T2DM) in zebrafish, and high glucose-induced damage in RINm5F pancreatic β-cells. In fasting mice, plasma glucose, glycosylated hemoglobin (HbA1C), lipid hydroperoxides (LOOH), thiobarbituric acid reactive substances (TBARS), and lipid profiles were significantly increased, whereas insulin, enzymatic antioxidants, and carbohydrate metabolic enzymes were altered significantly in diabetic mice. Zebrafish had similar glucose levels, liver enzymes, and lipid profiles compared to mice. The study investigated the effects of the extract in enhancing cell viability, insulin secretion, and reducing lipid peroxidation and intracellular reactive oxygen species (ROS) levels in RINm5F cells damaged by high glucose. All the above biochemical parameters were enhanced in both mice and zebrafish treated; the combined extract UAZ normalized all the biochemical parameters. The medicinal plant extracts, used either separately or in combination, ameliorated the adverse effect of glucose on cell viability and functionality of beta-RINm5F cells.

Age-related expression of prominent regulatory elements in mouse brain: catastrophic decline of FOXO3a

Aging is associated with changes in regulation, particularly among diverse regulators in the brain. We assayed prominent regulatory elements in mouse brain to explore their relationship to one another, stress, and aging. Notably, unphosphorylated (activated) forkhead transcription factor 3a (uFOXO3a) expressed exponential decline congruent with increasing age-related mortality. Decline in uFOXO3a would impact homeostasis, aging rate, stress resistance, and mortality. We also examined other regulators associated with aging and FOXO3a: protein kinase B (PKB), the mechanistic target of rapamycin (mTOR), 70 kDa ribosomal S6 kinase (P70S6K), and 5' AMP-activated protein kinase (AMPK). It would require powerful regulatory distortion, conflicting tradeoffs and/or significant damage to inflict exponential decline of a transcription factor as crucial as FOXO3a. No other regulator examined expressed an exponential pattern congruent with aging. PKB was strongly associated with decreases in uFOXO3a, but the aging pattern of PKB did not support a causal linkage. Although mTOR expressed a trend for age-related increase, this was not significant. We considered that the mTOR downstream element, P70S6K, might suppress FOXO3a, but remarkably, it expressed a strong positive association. The age-related pattern of AMPK was also incompatible. Literature suggested the immunological regulator NFĸB (nuclear factor kappa-light-chain-enhancer of activated B cells) increases with age and suppresses FOXO3a. This would inhibit apoptosis, autophagy, mitophagy, proteostasis, detoxification, antioxidants, chaperones, and DNA repair, thus exacerbating aging. We conclude that a key aspect of aging involves distortion of key regulators in the brain.

miR-629 targets FOXO3 to promote cell apoptosis in gastric cancer

Gastric cancer (GC) is one of the most aggressive types of human tumor worldwide, and the 5-year survival rate is less than 25%. The transcriptional factor, forkhead box O3 (FOXO3), is regulated by various micro (mi)RNAs and has been reported to be associated with multiple regulatory signaling pathways involved in tumor development. The current study therefore assessed the impact of miR-629 and FOXO3 on gastric cancer. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to assess the expression of mRNA and protein, respectively. Additionally, the cell proliferation and apoptosis rate were determined via an MTT assay and flow cytometry, respectively. The online database TargetScan predicted that FOXO3 was a target of miR-629. A luciferase reporter assay was also performed to verify that FOXO3 was the direct target of miR-629. The results demonstrated that miR-629 and FOXO3 was upregulated and downregulated in GC tissue, respectively. Furthermore, following transfection with a miR-629 inhibitor, SGC-7901, cell proliferation and apoptosis rate were inhibited and promoted when compared with the control group, respectively. Moreover, after the treatment with SGC-7901, the expression of FOXO3, Bax, Caspase 3 was upregulated, and Bcl-2 was downregulated. Furthermore, the luciferase reporter assay revealed that FOXO3 was the target of miR-629. The results demonstrated that miR-629 and FOXO3 serve vital roles in the development of gastric cancer and may be a future therapeutic target.

Quinoa Secondary Metabolites and Their Biological Activities or Functions

Quinoa (Chenopodium quinoa Willd.) was known as the "golden grain" by the native Andean people in South America, and has been a source of valuable food over thousands of years. It can produce a variety of secondary metabolites with broad spectra of bioactivities. At least 193 secondary metabolites from quinoa have been identified in the past 40 years. They mainly include phenolic acids, flavonoids, terpenoids, steroids, and nitrogen-containing compounds. These metabolites exhibit many physiological functions, such as insecticidal, molluscicidal and antimicrobial activities, as well as various kinds of biological activities such as antioxidant, cytotoxic, anti-diabetic and anti-inflammatory properties. This review focuses on our knowledge of the structures, biological activities and functions of quinoa secondary metabolites. Biosynthesis, development and utilization of the secondary metabolites especially from quinoa bran were prospected.

Role of MAPK/NF-κB pathway in cardioprotective effect of Morin in isoproterenol induced myocardial injury in rats

Oxidative stress plays a major role in myocardial injury. Morin, a bioflavonoid has known to possess various biological activities in previous studies. Hence, this study evaluated the cardioprotective mechanism(s) of Morin against isoproterenol induced myocardial necrosis in rats. Male albino Wistar rats were divided into five groups (n = 8) i.e., I (normal), II (ISO-control), III, IV and V (morin 20, 40 and 80 mg/kg respectively). Groups III, IV and V were treated orally with daily doses of Morin accordingly for 28 days. On 26th and 27th day, a single injection of isoproterenol was injected (85 mg/kg s.c.) at 24 h interval to induce myocardial necrosis in group II, III, IV and V. On 28th day, hemodynamic parameters were evaluated, animals were euthanised and heart was excised for measurement of various parameters. In ISO-control rats, there was deterioration of hemodynamic parameters, decreased anti-oxidants levels, increased cardiac injury markers and pro-inflammatory cytokines (TNF-α and IL-6). Also, there was increased level of Bax, Caspase-3, p-JNK, p-38 and NF-κB and decreased expression of Bcl-2 and p-ERK1/2 in ISO-C group. Morin dose-dependently improved hemodynamic profile, increased anti-oxidant levels, normalized myocardial architecture and reduced inflammatory markers and apoptosis. Furthermore, immunoblot analysis of MAPK pathway proteins demonstrated the mechanism responsible for anti-apoptotic and anti-inflammatory potential of morin. Thus, this study substantiated the beneficial effect of Morin by virtue of its modulation of MAPK pathway in myocardial injury.