Protective action of arachidonic acid against alloxan-induced cytotoxicity and diabetes mellitus

Protective effect of preconception high dose vitamin D3 supplementation in gestational diabetes mellitus rats via modulation of placental LCPUFA metabolism, one carbon cycle components, inflammation, oxidative stress, and angiogenesis

Gestational diabetes mellitus (GDM), one of the most common pregnancy complications, adversely affects maternal and fetal health. This study investigated the impact of vitamin D3 (VD3) deficiency or supplementation on placental long chain polyunsaturated fatty acid (LCPUFA) metabolism, one-carbon cycle metabolites, inflammation, oxidative stress, angiogenesis, and birth outcomes in a GDM rat model. Wistar rats were divided into five groups: Control (1000 IU VD3/kg diet), Vitamin D Deficient (VDD, 0 IU VD3/kg diet), GDM (1000 IU VD3/kg diet + GDM), VD3 supplementation with 1500 IU (VDS-1500 +GDM), and VD3 supplementation with 10,000 IU (VDS-10,000 +GDM). GDM was induced using a high-fat, high-sugar diet and streptozotocin. Diets were provided from weaning through pregnancy. Only the VDS-10,000 +GDM group achieved sufficient serum 25(OH)D levels (>30 ng/ml). 10,000 IU/kg VD3 supplementation reduced gestational weight gain and improved fetal/placental weight ratios. It reduced the levels of FBS, fasting insulin, and HOMA-IR, while increased HOMA-IS. It regulated calcium homeostasis by decreasing parathyroid hormone and increasing phosphorous levels. It normalized one-carbon metabolites, reducing homocysteine and increasing folate levels. Both doses of VD3 supplementation mitigated oxidative stress, reducing malondialdehyde levels, which was higher in GDM and VDD groups. It restored LCPUFA profiles, increasing arachidonic acid and decreasing n-6 linoleic acid levels. High-dose VD3 reduced elevated plasma and placental TNF-α levels and downregulated IL-6 mRNA in the GDM group, while IL-6 protein levels remained comparable. The protein and mRNA levels of both VEGF and VEGF-R1 were higher in GDM group. 10,000 IU VD3 reduces VEGF levels whereas, 1500 IU VD3 reduces VEGF-R1 levels. High-dose VD3 supplementation (10,000 IU/kg) during pregnancy effectively improved vitamin D status and positively influenced placental metabolic pathways, oxidative stress, inflammation, and angiogenesis, thereby improving pregnancy outcomes in GDM.

Guava polysaccharides attenuate high fat and STZ-induced hyperglycemia by regulating gut microbiota and arachidonic acid metabolism

This study investigated the hypoglycemic mechanism of guava polysaccharides (GP) through the gut microbiota (GM) and related metabolites. Our findings demonstrated that GP significantly mitigated high-fat diet- and streptozotocin-induced hyperglycemia, insulin resistance, hyperlipidemia, elevated alanine aminotransferase, high hepatic inflammation levels, and prevented pancreatic atrophy and hepatomegaly. Interestingly, the benefits of GP were attributed to alterations in the GM. GP decreased the ratio of Firmicutes to Bacteroidetes, significantly inhibiting deleterious bacteria, including Uncultured_f_Desulfovibrionaceae, Bilophila, and Desulfovibrio, while promoting the proliferation of probiotic Bifidobacterium and Bacteroides. In addition, GP promoted the generation of short-chain fatty acids. Notably, the arachidonic acid (AA) metabolism pathway was enriched in liver metabolites. GP significantly elevated hepatic AA and 15-hydroxyeicosatetraenoic acid, while reducing prostaglandin E2 and 5- and 12-hydroxyeicosatetraenoic acid. This modulation is accompanied by the downregulation of hepatic cyclooxygenase-1, 12-lipoxygenase, P38, and c-Jun N-terminal kinase mRNA expression, and the upregulation of cytochrome P4502J5 and insulin receptor substrate 1/2 mRNA expression. However, GP antibiotic treatment did not induce significant alterations in FBG and AA levels or gene expression. Overall, our findings suggest that the hypoglycemic effect of GP may be intricately linked to alterations in AA metabolism, which depends on the GM.

Association between circulating levels of unsaturated fatty acids and risk for prediabetes in the NHANES 2003-2004 and 2011-2012

AIMS

This study aimed to investigate the association between serum levels of common and uncommon unsaturated fatty acids and prediabetes risk.

METHODS

Data were collected from the National Health and Nutrition Examination Survey for 2003-2004 and 2011-2012. Weighted proportional and multivariate logistic regression analyses were performed to assess the association of serum PUFAs and MUFAs with prediabetes risk after adjusting for potential confounders.

RESULTS

A total of 3575 individuals were enrolled in this study. Serum levels of PUFAs EPA (20:5 n3) and GLA (18:3 n6) were associated with increased prediabetes risk (EPA (20:5 n3): OR = 1.878, 95% CI: 1.177-2.996, Ptrend = 0.002; GLA (18:3 n6): 1.702, 95% CI: 1.140-2.541, Ptrend = 0.016). The MUFAs PA (16:1 n7) and EA (20:1 n9) were associated with the risk of prediabetes (OR in quintile5: PA (16:1 n7): 1.780, 95% CI: 1.056-3.001, Ptrend = 0.003; EA (20:1 n9): 0.587, 95% CI: 0.347-0.994, Ptrend = 0.010). Moreover, nonlinear analysis revealed that serum levels of EPA (20:5 n3) and EA (20:1 n-9) were nonlinearly associated with prediabetes risk.

CONCLUSION

Some serum n-3 PUFAs are positively associated with prediabetes, several serum n-6 PUFAs are inversely associated with prediabetes. Regulating individual serum USFA levels may help prevent prediabetes, thereby providing evidence for clinical and nutritional practices.

Mitigation of chronic glucotoxicity-mediated skeletal muscle atrophy by arachidonic acid

Toxicity caused by chronic hyperglycemia is a significant factor affecting skeletal muscle myogenesis, resulting in diabetic myopathy. Chronic and persistent hyperglycemia causes activation of the atrophy-related pathways in the skeletal muscles, which eventually results in inflammation and muscle degeneration. To counteract this process, various bioactive compound has been studied for their reversal or hypertrophic effect. In this study, we explored the molecular mechanisms associated with reversing glucotoxicity's effect in C2C12 cells by arachidonic acid (AA). We found a substantial increase in the pro-inflammatory cytokines and ROS production in hyperglycemic conditions, mitigated by AA supplementation. We found that AA supplementation restored protein synthesis that was downregulated under glucotoxicity conditions. AA enhanced myogenesis by suppressing high glucose induced inflammation and ROS production and enhancing protein synthesis. These results imply that AA has cytoprotective actions against hyperglycemia-induced cytotoxicity.

A review on the relationship between Arachidonic acid 15-Lipoxygenase (ALOX15) and diabetes mellitus

Arachidonic acid 15-lipoxygenase (ALOX15), as one of the lipoxygenase family, is mainly responsible for catalyzing the oxidation of various fatty acids to produce a variety of lipid components, contributing to the pathophysiological processes of various immune and inflammatory diseases. Studies have shown that ALOX15 and its related products are widely distributed in human tissues and related to multiple diseases such as liver, cardiovascular, cerebrovascular diseases, diabetes mellitus and other diseases. Diabetes mellitus (DM), the disease studied in this article, is a metabolic disease characterized by a chronic increase in blood glucose levels, which is significantly related to inflammation, oxidative stress, ferroptosis and other mechanisms, and it has a high incidence in the population, accompanied by a variety of complications. Figuring out how ALOX15 is involved in DM is critical to understanding its role in diseases. Therefore, ALOX15 inhibitors or combination therapy containing inhibitors may deliver a novel research direction for the treatment of DM and its complications. This article aims to review the biological effect and the possible function of ALOX15 in the pathogenesis of DM.

Therapeutic Potentials of Microalgae and Their Bioactive Compounds on Diabetes Mellitus

Diabetes mellitus is a metabolic disorder characterized by hyperglycemia due to impaired insulin secretion, insulin resistance, or both. Oxidative stress and chronic low-grade inflammation play crucial roles in the pathophysiology of diabetes mellitus. There has been a growing interest in applying natural products to improve metabolic derangements without the side effects of anti-diabetic drugs. Microalgae biomass or extract and their bioactive compounds have been applied as nutraceuticals or additives in food products and health supplements. Several studies have demonstrated the therapeutic effects of microalgae and their bioactive compounds in improving insulin sensitivity attributed to their antioxidant, anti-inflammatory, and pancreatic β-cell protective properties. However, a review summarizing the progression in this topic is lacking despite the increasing number of studies reporting their anti-diabetic potential. In this review, we gathered the findings from in vitro, in vivo, and human studies to discuss the effects of microalgae and their bioactive compounds on diabetes mellitus and the mechanisms involved. Additionally, we discuss the limitations and future perspectives of developing microalgae-based compounds as a health supplement for diabetes mellitus. In conclusion, microalgae-based supplementation has the potential to improve diabetes mellitus and be applied in more clinical studies in the future.

Gut fungal community composition analysis of myostatin mutant cattle prepared by CRISPR/Cas9

Myostatin (MSTN) regulates muscle development and body metabolism through a variety of pathways and is a core target gene for gene editing in livestock. Gut fungi constitute a small part of the gut microbiome and are important to host health and metabolism. The influence of MSTN mutations on bovine gut fungi remains unknown. In this study, Internal Transcribed Spacer (ITS) high-throughput sequencing was conducted to explore the composition of gut fungi in the MSTN mutant (MT) and wild-type (WT) cattle, and 5,861 operational taxonomic units (OTUs) were detected and classified into 16 phyla and 802 genera. The results of the alpha diversity analysis indicated that no notable divergence was displayed between the WT and MT cattle; however, significant differences were noticed in the composition of fungal communities. Eight phyla and 18 genera were detected. According to the prediction of fungal function, saprotroph fungi were significantly more abundant in the MT group. The correlation analysis between gut fungal and bacterial communities revealed that MSTN mutations directly changed the gut fungal composition and, at the same time, influenced some fungi and bacteria by indirectly regulating the interaction between microorganisms, which affected the host metabolism further. This study analyzed the role of MSTN mutations in regulating the host metabolism of intestinal fungi and provided a theoretical basis for the relationship between MSTN and gut fungi.

Syntaxin interacts with arachidonic acid to prevent diabetes mellitus

Syntaxin regulates pancreatic β cell mass and participates in insulin secretion by regulating insulin exocytosis. In addition, syntaxin 4 reduces IFNγ and TNF-α signaling via NF-ĸB in islet β-cells that facilitates plasma glucose sensing and appropriate insulin secretion. Arachidonic acid (AA) has potent anti-inflammatory actions and prevents the cytotoxic actions of alloxan and streptozotocin (STZ) against pancreatic β cells and thus, prevents the development of type 1 diabetes mellitus (induced by alloxan and STZ) and by virtue of its anti-inflammatory actions protects against the development of type 2 diabetes mellitus (DM) induced by STZ in experimental animals that are models of type 1 and type 2 DM in humans. AA has been shown to interact with syntaxin and thus, potentiate exocytosis. AA enhances cell membrane fluidity, increases the expression of GLUT and insulin receptors, and brings about its anti-inflammatory actions at least in part by enhancing the formation of its metabolite lipoxin A4 (LXA4). Prostaglandin E2 (PGE2), the pro-inflammatory metabolite of AA, activates ventromedial hypothalamus (VMH) neurons of the hypothalamus and inhibits insulin secretion leading to reduced glucose tolerance and decreases insulin sensitivity in the skeletal muscle and liver. This adverse action of PGE2 on insulin release and action can be attributed to its (PGE2) pro-inflammatory action and inhibitory action on vagal tone (vagus nerve and its principal neurotransmitter acetylcholine has potent anti-inflammatory actions). High fat diet fed animals have hypothalamic inflammation due to chronic elevation of PGE2. Patients with type 2 DM show low plasma concentrations of AA and LXA4 and elevated levels of PGE2. Administration of AA enhances LXA4 formation without altering or reducing PGE2 levels and thus, tilts the balance more towards anti-inflammatory events. These results suggest that administration of AA is useful in the prevention and management of DM by enhancing the action of syntaxin, increasing cell membrane fluidity, and reducing VMH inflammation. Docosahexaenoic acid (DHA) has actions like AA: it increases cell membrane fluidity; has anti-inflammatory actions by enhancing the formation of its anti-inflammatory metabolites resolvins, protectins and maresins; interacts with syntaxin and enhance exocytosis in general and of insulin. But the DHA content of cell membrane is lower compared to AA and its content in brain is significant. Hence, it is likely DHA is important in neurotransmitters secretion and regulating hypothalamic inflammation. It is likely that a combination of AA and DHA can prevent DM.

Fatty acids of type 2 diabetic serum decrease the stemness properties of human adipose-derived mesenchymal stem cells

In type 2 diabetes, dyslipidemia and increased serum free fatty acids (FFAs) exacerbate the development of the disease through a negative effect on insulin secretion. Adipose-derived mesenchymal stem cells (AdMSCs) play a key role in regenerative medicine, and these cells can potentially be applied as novel therapeutic resources in the treatment of diabetes. In this study, AdMSCs were treated with diabetic or nondiabetic serum FFAs isolated from women of menopausal age. Serum FFAs were analyzed using gas-liquid chromatography. The expression level of the stemness markers CD49e and CD90 and the Wnt signaling target genes Axin-2 and c-Myc were evaluated using real-time PCR. The proliferation rate and colony formation were also assessed using a BrdU assay and crystal violet staining, respectively. The level of glutathione was assessed using cell fluorescence staining. Compared to nondiabetic serum, diabetic serum contained a higher percentage of oleate (1.5-fold, p < 0.01). In comparison with nondiabetic FFAs, diabetic FFAs demonstrated decreasing effects on the expression of CD90 (-51%, p < 0.001) and c-Myc (-48%, p < 0.05), and proliferation rate (-35%, p < 0.001), colony formation capacity (-50%, p < 0.01), and GSH levels (-62%, p < 0.05). The negative effect of the FFAs of diabetic serum on the stemness characteristics may impair the regenerative capabilities of AdMSCs.

Gamma-Linolenic Acid (GLA) Protects against Ionizing Radiation-Induced Damage: An In Vitro and In Vivo Study

Radiation is pro-inflammatory in nature in view of its ability to induce the generation of reactive oxygen species (ROS), cytokines, chemokines, and growth factors with associated inflammatory cells. Cells are efficient in repairing radiation-induced DNA damage; however, exactly how this happens is not clear. In the present study, GLA reduced DNA damage (as evidenced by micronuclei formation) and enhanced metabolic viability, which led to an increase in the number of surviving RAW 264.7 cells in vitro by reducing ROS generation, and restoring the activities of desaturases, COX-1, COX-2, and 5-LOX enzymes, TNF-α/TGF-β, NF-kB/IkB, and Bcl-2/Bax ratios, and iNOS, AIM-2, and caspases 1 and 3, to near normal. These in vitro beneficial actions were confirmed by in vivo studies, which revealed that the survival of female C57BL/6J mice exposed to lethal radiation (survival~20%) is significantly enhanced (to ~80%) by GLA treatment by restoring altered levels of duodenal HMGB1, IL-6, TNF-α, and IL-10 concentrations, as well as the expression of NF-kB, IkB, Bcl-2, Bax, delta-6-desaturase, COX-2, and 5-LOX genes, and pro- and anti-oxidant enzymes (SOD, catalase, glutathione), to near normal. These in vitro and in vivo studies suggest that GLA protects cells/tissues from lethal doses of radiation by producing appropriate changes in inflammation and its resolution in a timely fashion.

Comparative analysis of gut microbiota in healthy and diarrheic yaks

BACKGROUND

Yak (Bos grunniens) mainly inhabiting Tibet Plateau, displayed a high incidence of diarrhea due to harsh living environment and nutritional deficit. Gut microbial community has been reported to be closely related to many diseases including diabetes, obesity and inflammatory bowel disease, but information regarding diarrheic influence on gut microbiota in yaks remains scarce. Here, this study was performed to investigate the gut bacterial and fungal alternations of diarrheic yaks.

RESULTS

Results revealed that the gut bacterial and fungal communities of diarrheic yaks showed a distinct decline in alpha diversity, accompanied by significant shifts in taxonomic compositions. Specifically, diarrhea caused a distinct increase in the relative abundance of 1 phylum and 8 genera as well as a distinct decrease in 3 phyla and 30 genera. Fungal taxonomic analysis indicated that the relative richness of 1 phylum and 2 genera dramatically increased, whereas the relative richness of 2 phylum and 43 genera significantly decreased during diarrhea. Surprisingly, 2 bacterial genera and 5 fungal genera even cannot be detected in the gut microbiota of diarrheic yaks.

CONCLUSIONS

In summary, this study indicated that the gut bacterial and fungal compositions and diversities of yaks altered significantly during diarrhea. Moreover, these findings also contribute to understanding the gut microbial composition and diversity of yaks and developing strategies to alleviate and prevent diarrhea from gut microbial perspective.

Insights in diabetes: Molecular mechanisms-Protectin DX, an anti-inflammatory and a stimulator of inflammation resolution metabolite of docosahexaenoic acid, protects against the development of streptozotocin-induced type 1 and type 2 diabetes mellitus in male Swiss albino mice

Our previous studies revealed that certain endogenous low molecular weight lipids have potent anti-diabetic actions. Of all, arachidonic acid (AA) and its anti-inflammatory and inflammation resolving metabolite lipoxin A4 (LXA4) are the most potent anti-diabetic molecules. Similar anti-diabetic action is also shown by resolvins. In our efforts to identify other similar lipid based anti-diabetic molecules, we investigated potential anti-diabetic action of protectin DX that also has anti-inflammatory and inducer of inflammation resolution action(s) like LXA4. Protectin DX {10(S),17(S)-dihydroxy-4Z,7Z,11E,13Z,15E,19Z-docosahexaenoic acid, also called as 10(S),17(S)-DiHDoHE)} prevented the development of streptozotocin-induced type 1 and type 2 diabetes mellitus in Swiss male albino mice. Protectin DX showed potent anti-inflammatory, antioxidant and anti-apoptotic actions that could explain its anti-diabetic action. In view of these beneficial actions, efforts need to be developed to exploit PDX and other similar compounds as potential anti-diabetic molecule in humans.

Metabolic and Metabolomic Insights Regarding the Omega-3 PUFAs Intake in Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is currently considered an autoimmune disease characterized by the destruction of pancreatic β-cells, insulin deficiency, and dysglycemia. Dietary factors, including omega-3 polyunsaturated fatty acids (ω-3 PUFAs), were reported to influence T1DM. Therefore, a better understanding of the potential role of ω-3 PUFAs in the development and progression of T1DM will help to improve the clinical management of the disease. In this review, we explored the current understanding of molecular mechanisms and signaling pathways induced by ω-3 PUFAs and the beneficial effects of ω-3 PUFAs intake in the prevention and treatment of T1DM, as well as the underlying possible metabolomic (lipidomics) changes.

Sex-Specific Differences in the Associations Between Omega-6 Polyunsaturated Fatty Acids and Type 2 Diabetes in Chinese People

Background: Some evidence indicates a potential beneficial effect of omega-6 polyunsaturated fatty acids (n-6 PUFAs) on type 2 diabetes mellitus (T2DM); however, the findings to date remains inconclusive and little is known about whether sex modifies these associations. Therefore, this study aimed to investigate potential sex-specific differences in this associations among Chinese adults. Methods: We conducted a cross-sectional study in an area of Dalian city, China; Chinese men and women who attended the Department of Clinical Nutrition and Metabolism between January and December 2020 were invited to participate in this study. All participants were assessed for basic demographic characteristics, fasting blood glucose, HbA1c, and other serum biomarkers and serum phospholipid FAs. Results: In total, 575 Chinese adult participants (270 men and 305 women) were included in the analysis. Hypertension and dyslipidaemia were more common among men than women, but there were no significant differences between the sexes in fatty acid composition, except for eicosadienoic acid (EA; 20:2n-6) and total monounsaturated fatty acids (MUFA). The age-adjusted OR for having T2DM in the highest quartile of arachidonic acid (20:4n-6) level was 0.47 (95% CI, 0.22, 0.98) in men, and this association remained consistently significant in the fully adjusted multivariate models. In contrast, no significant associations between n-6 PUFAs and T2DM risk were observed in women, regardless of model adjustment. Conclusions: In conclusion, these results demonstrate a notable sex-specific differences in the associations between n-6 PUFAs and T2DM. Higher n-6 PUFA status may be protective against the risk of T2DM in men.

Resolvin D1 Decreases Severity of Streptozotocin-Induced Type 1 Diabetes Mellitus by Enhancing BDNF Levels, Reducing Oxidative Stress, and Suppressing Inflammation

Type 1 diabetes mellitus is an autoimmune disease characterized by increased production of pro-inflammatory cytokines secreted by infiltrating macrophages and T cells that destroy pancreatic β cells in a free radical-dependent manner that causes decrease or absence of insulin secretion and consequent hyperglycemia. Hence, suppression of pro-inflammatory cytokines and oxidative stress may ameliorate or decrease the severity of diabetes mellitus. To investigate the effect and mechanism(s) of action of RVD1, an anti-inflammatory metabolite derived from docosahexaenoic acid (DHA), on STZ-induced type 1 DM in male Wistar rats, type 1 diabetes was induced by single intraperitoneal (i.p) streptozotocin (STZ-65 mg/kg) injection. RVD1 (60 ng/mL, given intraperitoneally) was administered from day 1 along with STZ for five consecutive days. Plasma glucose, IL-6, TNF-α, BDNF (brain-derived neurotrophic factor that has anti-diabetic actions), LXA4 (lipoxin A4), and RVD1 levels and BDNF concentrations in the pancreas, liver, and brain tissues were measured. Apoptotic (Bcl2/Bax), inflammatory (COX-1/COX-2/Nf-κb/iNOS/PPAR-γ) genes and downstream insulin signaling proteins (Gsk-3β/Foxo1) were measured in the pancreatic tissue along with concentrations of various antioxidants and lipid peroxides. RVD1 decreased severity of STZ-induced type 1 DM by restoring altered plasma levels of TNF-α, IL-6, and BDNF (p < 0.001); expression of pancreatic COX-1/COX-2/PPAR-γ genes and downstream insulin signaling proteins (Gsk-3β/Foxo1) and the concentrations of antioxidants and lipid peroxides to near normal. RVD1 treatment restored expression of Bcl2/Pdx genes, plasma LXA4 (p < 0.001) and RVD1 levels and increased brain, pancreatic, intestine, and liver BDNF levels to near normal. The results of the present study suggest that RVD1 can prevent STZ-induced type 1 diabetes by its anti-apoptotic, anti-inflammatory, and antioxidant actions and by activating the Pdx gene that is needed for pancreatic β cell proliferation.

Bioactive Lipids in COVID-19-Further Evidence

Previously, I suggested that arachidonic acid (AA, 20:4 n-6) and similar bioactive lipids (BALs) inactivate SARS-CoV-2 and thus, may be of benefit in the prevention and treatment of COVID-19. This proposal is supported by the observation that (i) macrophages and T cells (including NK cells, cytotoxic killer cells and other immunocytes) release AA and other BALs especially in the lungs to inactivate various microbes; (ii) pro-inflammatory metabolites prostaglandin E2 (PGE2) and leukotrienes (LTs) and anti-inflammatory lipoxin A4 (LXA4) derived from AA (similarly, resolvins, protectins and maresins derived from eicosapentaenoic acid: EPA and docosahexaenoic acid: DHA) facilitate the generation of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages respectively; (iii) AA, PGE2, LXA4 and other BALs inhibit interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) synthesis; (iv) mesenchymal stem cells (MSCs) that are of benefit in COVID-19 elaborate LXA4 to bring about their beneficial actions and (v) subjects with insulin resistance, obesity, type 2 diabetes mellitus, hypertension, coronary heart disease and the elderly have significantly low plasma concentrations of AA and LXA4 that may render them more susceptible to SARS-CoV-2 infection and cytokine storm that is associated with increased mortality seen in COVID-19. Statins, colchicine, and corticosteroids that appear to be of benefit in COVID-19 can influence BALs metabolism. AA, and other BALs influence cell membrane fluidity and thus, regulate ACE-2 (angiotensin converting enzyme-2) receptors (the ligand through which SARS-CoV2 enters the cell) receptors. These observations lend support to the contention that administration of BALs especially, AA could be of significant benefit in prevention and management of COVI-19 and other enveloped viruses.

Phenolic Content and Antioxidant, Antihyperlipidemic, and Antidiabetogenic Effects of Opuntia dillenii Seed Oil

Opuntia dillenii (Ker-Gawl.) Haw. is a medicinal plant that is widely used by the Moroccan population to treat many diseases, thanks to its richness in bioactive molecules. This study aims to evaluate the total phenolic content and antioxidant, antihyperlipidemic, and antidiabetogenic activities of O. dillenii seeds oil (ODSO), in vivo. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay and the Folin–Ciocalteu method were applied in this study to determine antioxidant activity and total phenolic content of ODSO, respectively. The antihyperlipidemic effect of the ODSO (2 ml/kg) was evaluated in the high-fat diet-fed albino mice, relying on lipid profile, blood glucose, and growth performance variations. Moreover, the preventive effect of ODSO was evaluated against alloxan monohydrate-induced diabetes in albino mice. ODSO had the highest total phenolic content (518.18 ± 14.36 mg EAC/kg) and DPPH scavenging activity (IC₅₀ = 0.38 ± 0.08 mg/mL). Furthermore, ODSO showed a significant antidiabetogenic effect by reducing bodyweight loss, blood sugar level rise, and mortality rate caused by alloxan in albino mice. Then, ODSO has exhibited a significant antihyperlipidemic effect by improving the lipid profile disorder and glucose level rise in the blood, produced by the high-fat diet-fed albino mice. Results suggest that antidiabetogenic and antihyperlipidemic activities of ODSO correlate to the phenolic content and antioxidant activity of this oil. Hence, this plant could be a significant source of medically important critical compounds.

Can Bioactive Lipid Arachidonic Acid Prevent and Ameliorate COVID-19?

It is proposed that the bioactive lipid, arachidonic acid (AA, 20:4 n-6), can inactivate severe acute respiratory syndrome(SARS-CoV-2), facilitate M1 and M2 macrophage generation, suppress inflammation, prevent vascular endothelial cell damage, and regulate inflammation resolution processes based on the timely formation of prostaglandin E2 (PGE2) and lipoxin A4 (LXA4) based on the context. Thus, AA may be useful both to prevent and manage coronavrus disease-2019(COVID-19).

Bioactive Lipids as Mediators of the Beneficial Action(s) of Mesenchymal Stem Cells in COVID-19

It is proposed that the beneficial action of mesenchymal stem cells (MSCs) in COVID-19 and other inflammatory diseases could be attributed to their ability to secrete bioactive lipids (BALs) such as prostaglandin E2 (PGE2) and lipoxin A4 (LXA4) and other similar BALs. This implies that MSCs that have limited or low capacity to secrete BALs may be unable to bring about their beneficial actions. This proposal implies that pretreatment of MSCs with BALs enhance their physiological action or improve their (MSCs) anti-inflammatory and disease resolution capacity to a significant degree. Thus, the beneficial action of MSCs reported in the management of COVID-19 could be attributed to their ability to secrete BALs, especially PGE2 and LXA4. Since PGE2, LXA4 and their precursors AA (arachidonic acid), dihomo-gamma-linolenic acid (DGLA) and gamma-linolenic acid (GLA) inhibit the production of pro-inflammatory IL-6 and TNF-α, they could be employed to treat cytokine storm seen in COVID-19, immune check point inhibitory (ICI) therapy, sepsis and ARDS (acute respiratory disease). This is further supported by the observation that GLA, DGLA and AA inactivate enveloped viruses including COVID-19. Thus, infusions of appropriate amounts of GLA, DGLA, AA, PGE2 and LXA4 are of significant therapeutic benefit in COVID-19, ICI therapy and other inflammatory conditions including but not limited to sepsis. AA is the precursor of both PGE2 and LXA4 suggesting that AA is most suited for such preventive and therapeutic approach.

Resolvin D1 Ameliorates Nicotinamide-streptozotocin-induced Type 2 Diabetes Mellitus by its Anti-inflammatory Action and Modulating PI3K/Akt/mTOR Pathway in the Brain

OBJECTIVE

To study whether resolvin D1 (RvD1), a metabolite of docosahexaenoic acid (DHA), prevents NA-STZ-induced type 2 diabetes mellitus (type 2 DM) in vivo and if so, what could be the mechanism of this action.

MATERIAL AND METHODS

Single intra-peritoneal (i.p) injection of NA-STZ (175 mg/kg body weight of NA and 65 mg/kg of STZ) was injected simultaneously with RvD1 (60 ng/animal) (injected for 5 consecutive days) to Wistar rats. The effect of RvD1 on plasma glucose levels and apoptotic (Bcl2/Bax) and inflammatory (NF-κB/iNOS) protein expression, plasma lipoxin A4 and BDNF (brain-derived neurotrophic factor) were studied. Protein expressions of PI3k-Akt-mTOR pathway along with histopathological studies of brain were also evaluated.

RESULTS

NA-STZ-induced type 2 DM rats showed hyperglycemia, enhanced plasma IL-6/TNF-α (p ≤0.01), reduced plasma BDNF (p ≤0.01) and LXA4 (p ≤0.01) levels and low BDNF in pancreatic, hepatic and brain tissues (p <0.001), which were restored to near normal (p ≤0.01) in RvD1 treated group. RvD1 increased insulin sensitivity by suppressing inflammation (NF-κB/iNOS) (p ≤0.01) and decreasing apoptosis (Bcl2/Bax) and restoring BDNF and LXA4 levels to near normal. RvD1 treatment increased phosphorylation of Akt (Ser473), and subsequent activation (phosphorylation) of downstream signaling molecules of PI3K and mTOR indicating that RvD1 acts through PI3K/Akt/mTOR axis.

DISCUSSION

RvD1 is effective in preventing NA-STZ-induced type 2 DM in vivo by suppressing oxidative damage, enhancing the production of anti-inflammatory LXA4 and enhancing neuronal cell survival by augmenting the production of BDNF. Thus, RvD1 may be of benefit not only in preventing diabetes mellitus but also diabetes associated Alzheimer's disease and memory loss.

PUFAs, BDNF and lipoxin A4 inhibit chemical-induced cytotoxicity of RIN5F cells in vitro and streptozotocin-induced type 2 diabetes mellitus in vivo

Objective

To study whether minimal doses of arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and lipoxin A4 (LXA4) and brain-derived neurotrophic factor (BDNF), when used in combination can protect RIN5F cells from chemical-induced cytotoxicity. As a corollary, to know whether plasma BDNF and LXA4 are altered in STZ-induced type 2 DM animals.

Materials and methods

RIN5F cells, alloxan (AL), streptozotocin (STZ), doxorubicin (DB), and benzo(a)pyrene (BP) were used in this study. Chemical-induced apoptosis and changes in antioxidants, lipid peroxides and nitric oxide (NO) and LXA4 and BDNF levels in RIN5F cells were studied. Alterations in plasma concentrations of BDNF and LXA4 in STZ-induced type 2 diabetes animals was estimated.

Results

BDNF, LXA4 and AA, EPA and DHA protected (P < 0.001 and P < 0.01 respectively) against AL/STZ/DB/BP-induced toxicity to RIN5F cells in vitro. AL/ STZ/DB/BP inhibited BDNF and LXA4 production by RIN5F cells and were restored to normal by AA, EPA and DHA. Sub-optimal doses of BDNF, LXA4, AA and EPA when used in combination protected against cytotoxic action of AL/STZ/DB/BP on RIN5F cells in vitro by restoring LXA4/BDNF levels and altered antioxidant/lipid peroxides/NO levels (P < 0.01) to normal. STZ (65 mg/kg)-induced type 2 diabetes mellitus animals showed reduced plasma BDNF and LXA4 levels (P < 0.001).

Discussion

AL/STZ/DB/BP-induced cytotoxicity to RIN5F cells in vitro can be prevented by BDNF, LXA4 and AA. AL/STZ/DB/BP are cytotoxic, possibly, by suppressing the production of LXA4 and BDNF in RIN5F cells. STZ-induced type 2 DM animals have decreased plasma levels of LXA4 and BDNF.

Conclusion

The results of the present study suggest that BDNF, LXA4, EPA, DHA, AA, GLA and BDNF protect pancreatic β cells from the cytotoxic action of various chemicals and prevent development of diabetes mellitus. LXA4 seems to be the mediator of these cytoprotective actions of BDNF and PUFAs suggesting a close interaction exists among these molecules (BDNF, PUFAs and LXA4). Hence, methods developed to deliver a combination of PUFAs (especially AA), LXA4 and BDNF may prevent development of diabetes mellitus (both type 1 and type 2).

Predictive metabolic signatures for the occurrence and development of diabetic nephropathy and the intervention of Ginkgo biloba leaves extract based on gas or liquid chromatography with mass spectrometry

Diabetic nephropathy (DN) is one of the leading causes of death in diabetes mellitus (DM). Early warning and therapy has significant clinical value for DN. This research sought to find biomarkers to predict the occurrence and development of DN and the intervention of Ginkgo biloba leaves extract (GBE) by quantifying fatty acids, amino acids, and nucleosides and nucleobases in rat plasma. Samples were respectively collected at the weekend of 5-10 weeks after diabetic rats induced by streptozotocin were defined. Plasma fasting blood-glucose, kidney index, blood urea nitrogen, creatinine, urine albumin excretion and ultrastructural morphology of kidney were measured or observed. Fatty acids, amino acids and nucleosides and nucleobases in rat plasma were analyzed by gas chromatography or liquid phase chromatography and mass spectrometry, respectively. From the biochemical index and morphological change of kidney, the rats from the 5th to 7th week were in the stage of DM while from the begin of 8th week the rats were suggested in the early stage of DN. The results of quantitative metabolomics showed that 16 differential metabolites were related to the progression of DN, and oleic acid, glutamate and guanosine might be the potential biomarkers of kidney injury. 14 differential metabolites were related to GBE against the progression of DN, while oleic acid and glutamate might be the potential biomarkers of GBE against kidney injury. Those findings potentially promote the understanding of the pathogenic progression of DN and reveal the therapeutic mechanism of GBE against DN.

Erythrocyte PUFAs, circulating acylcarnitines, and metabolic syndrome risk: a prospective study in Chinese

The effects of PUFAs on metabolic syndrome (MetS) remain to be characterized, particularly in Asians. We aimed to investigate the prospective associations of PUFAs with MetS and the role of acylcarnitines in these associations in Chinese individuals. Among 1,245 Chinese men and women aged 50-70 years who completed a 6 year follow-up, baseline erythrocyte FAs and plasma acylcarnitines were profiled using gas chromatography coupled with positive chemical ionization and liquid chromatography-tandem mass spectrometry, respectively. Total n-6 PUFAs and three 22-carbon n-6 PUFAs were significantly associated with lower MetS risk comparing extreme quartiles: relative risks (RRs) (95% CIs) were 0.75 (0.57, 0.97) for total n-6 PUFAs, 0.69 (0.56, 0.85) for 22:2n-6, 0.76 (0.59, 0.99) for 22:4n-6, and 0.74 (0.58, 0.94) for 22:5n-6, while 18:3n-3 and 18:3n-6 were positively associated with MetS risk. In a network analysis, a module mostly consisting of long-chain n-6 PUFAs and very-long-chain saturated FAs was inversely associated with incident MetS (RR per SD: 0.84; 95% CI: 0.76, 0.92), and this module was more strongly associated with lower MetS risk when a short- to medium-chain acylcarnitine (C5-C10) module score was lower (P _interaction = 0.03). Our data suggested inverse associations of total n-6 and certain long-chain n-6 PUFAs with cardiometabolic disorders, and this association might be modified by certain acy-l-carnitines.

Opuntia (Cactaceae) plant compounds, biological activities and prospects - A comprehensive review

Opuntia species are utilized as local medicinal interventions for chronic diseases and as food sources mainly because they possess nutritional properties and biological activities. The Opuntia plant is distributed worldwide and has great economic potential. Differences in Opuntia species phytochemical composition exist between wild and domesticated species, and within species. Opuntia aerial and underground parts exhibit beneficial properties due to their phenolic content, other antioxidants (for example ascorbate), pigments (carotenoids, betalains), and other unidentified components. This work comprehensively reviews the phytochemical composition of the different aerial and underground plant parts of Opuntia species. The applications of Opuntia compounds and their biological activities are also discussed. Other topical aspects covered include Opuntia spp. taurine composition, Opuntia side effects, Opuntia by-products valorisation and the role of Opuntia spp. in tackling antimicrobial resistance. Although biological activities have been extensively researched, much less information is available on reaction mechanisms, herbal mixtures toxicology and commercialisation prospects - aspects which should be considered for future research in this area.

Arachidonic acid in health and disease with focus on hypertension and diabetes mellitus: A review

Arachidonic acid (AA 20:4n-6) is an essential component of cell membranes and modulates cell membrane fluidity. AA is metabolized by cyclo-oxygenase (COX), lipoxygenase (LOX) and cytochrome P450 enzymes to form several metabolites that have important biological actions. Of all the actions, role of AA in the regulation of blood pressure and its ability to prevent both type 1 and type 2 diabetes mellitus seems to be interesting. Studies showed that AA and its metabolites especially, lipoxin A4 (LXA4) and epoxyeicosatrienoic acids (EETs), potent anti-inflammatory metabolites, have a crucial role in the pathobiology of hypertension and diabetes mellitus. AA, LXA4 and EETs regulate smooth muscle function and proliferation, voltage gated ion channels, cell membrane fluidity, membrane receptors, G-coupled receptors, PPARs, free radical generation, nitric oxide formation, inflammation, and immune responses that, in turn, participate in the regulation blood pressure and pathogenesis of diabetes mellitus. In this review, role of AA and its metabolites LXA4 and EETs in the pathobiology of hypertension, pre-eclampsia and diabetes mellitus are discussed. Based on several lines of evidences, it is proposed that a combination of aspirin and AA could be of benefit in the prevention and management of hypertension, pre-eclampsia and diabetes mellitus.

Is There a Role for Bioactive Lipids in the Pathobiology of Diabetes Mellitus?

Inflammation, decreased levels of circulating endothelial nitric oxide (eNO) and brain-derived neurotrophic factor (BDNF), altered activity of hypothalamic neurotransmitters (including serotonin and vagal tone) and gut hormones, increased concentrations of free radicals, and imbalance in the levels of bioactive lipids and their pro- and anti-inflammatory metabolites have been suggested to play a role in diabetes mellitus (DM). Type 1 diabetes mellitus (type 1 DM) is due to autoimmune destruction of pancreatic β cells because of enhanced production of IL-6 and tumor necrosis factor-α (TNF-α) and other pro-inflammatory cytokines released by immunocytes infiltrating the pancreas in response to unknown exogenous and endogenous toxin(s). On the other hand, type 2 DM is due to increased peripheral insulin resistance secondary to enhanced production of IL-6 and TNF-α in response to high-fat and/or calorie-rich diet (rich in saturated and trans fats). Type 2 DM is also associated with significant alterations in the production and action of hypothalamic neurotransmitters, eNO, BDNF, free radicals, gut hormones, and vagus nerve activity. Thus, type 1 DM is because of excess production of pro-inflammatory cytokines close to β cells, whereas type 2 DM is due to excess of pro-inflammatory cytokines in the systemic circulation. Hence, methods designed to suppress excess production of pro-inflammatory cytokines may form a new approach to prevent both type 1 and type 2 DM. Roux-en-Y gastric bypass and similar surgeries ameliorate type 2 DM, partly by restoring to normal: gut hormones, hypothalamic neurotransmitters, eNO, vagal activity, gut microbiota, bioactive lipids, BDNF production in the gut and hypothalamus, concentrations of cytokines and free radicals that results in resetting glucose-stimulated insulin production by pancreatic β cells. Our recent studies suggested that bioactive lipids, such as arachidonic acid, eicosapentaneoic acid, and docosahexaenoic acid (which are unsaturated fatty acids) and their anti-inflammatory metabolites: lipoxin A4, resolvins, protectins, and maresins, may have antidiabetic actions. These bioactive lipids have anti-inflammatory actions, enhance eNO, BDNF production, restore hypothalamic dysfunction, enhance vagal tone, modulate production and action of ghrelin, leptin and adiponectin, and influence gut microbiota that may explain their antidiabetic action. These pieces of evidence suggest that methods designed to selectively deliver bioactive lipids to pancreatic β cells, gut, liver, and muscle may prevent type 1 and type 2 DM.

Arachidonic acid and lipoxin A4 attenuate alloxan-induced cytotoxicity to RIN5F cells in vitro and type 1 diabetes mellitus in vivo

OBJECTIVE

We studied whether polyunsaturated fatty acids (PUFAs) can protect rat insulinoma (RIN5F) cells against alloxan-induced apoptosis in vitro and type 1 diabetes mellitus (type 1 DM) in vivo and if so, mechanism of this beneficial action.

MATERIAL AND METHODS

In vitro study was conducted using RIN5F cells while in vivo study was performed in Wistar rats. The effect of PUFAs, cyclo-oxygenase and lipoxygenase inhibitors, various eicosanoids and PUFAs metabolites: lipoxin A4 (LXA4), resolvin D2 and protectin against alloxan-induced cytotoxicity to RIN5F cells and type 1 DM was studied. Expression of PDX1, P65 NF-kB and IKB in RIN5F cells and Nrf2, GLUT2, COX2, iNOS protein levels in the pancreatic tissue and plasma glucose, insulin and tumor necrosis factor-α and antioxidants, lipid peroxides and nitric oxide were measured.

RESULTS

Of all, arachidonic acid (AA) was found to be the most effective against alloxan-induced cytotoxicity to RIN5F cells and preventing type 1 DM. Both cyclo-oxygenase and lipoxygenase inhibitors did not block the beneficial actions of AA in vitro and in vivo. Alloxan inhibited LXA4 production by RIN5F cells and in alloxan-induced type 1 DM Wistar rats. AA-treatment restored LXA4 levels to normal both in vitro and in vivo. LXA4 protected RIN5F cells against alloxan-induced cytotoxicity and prevented type 1 DM and restored expression of Nrf2, Glut2, COX2, and iNOS genes and abnormal antioxidants to near normal.

DISCUSSION

AA seems to bring about its beneficial actions against alloxan-induced cytotoxicity and type 1 DM by enhancing the production of LXA4. © 2016 BioFactors, 43(2):251-271, 2017.

Integrated analysis of different microarray studies to identify candidate genes in type 1 diabetes

BACKGROUND

Type 1 diabetes (T1D), an autoimmune disease, occurs most commonly in children. Identifying altered gene expression in peripheral blood mononuclear cells (PBMCs) of T1D may lead to new strategies for preserving or improving β-ell function in patients with T1D.

METHODS

The Gene Expression Omnibus database was searched for microarray studies in PBMCs of T1D. Subsequently, gene expression datasets from multiple microarray studies were integrated to obtain differentially expressed genes (DEGs) between T1D and normal controls (NC). Gene function analysis was performed to determine the functions of the DEGs identified.

RESULTS

Four microarray studies were available for analysis, including 199 T1D samples and 74 NC samples. Analysis revealed 695 genes that were significantly differentially expressed in PBMCs from T1D compared with NC samples, with 450 upregulated and 245 downregulated. Signal transduction (gene ontology [GO]: 0007165; false discovery rate [FDR] = 1.54 × 10^-7 ) and protein binding (GO: 0005515; FDR = 2.93 × 10^-24 ) were significantly enriched for the GO categories of biological processes and molecular functions, respectively. The most significant pathway in the Kyoto Encyclopedia of Genes and Genomes analysis was arachidonic acid metabolism (FDR = 1.44 × 10^-3 ). Protein-protein interaction network analysis showed that the significant hub proteins contained immature colon carcinoma transcript 1 (ICT1; degree = 214; clustering coefficient [C] = 4.39 × 10^-5 ), zinc finger and BTB domain containing 16 (ZBTB16; degree = 112; C = 8.04 × 10^-4 ), and SERTA domain containing 1 (SERTAD1; degree = 38; C = 0.0014).

CONCLUSIONS

This integrated analysis will help develop improved therapies and interventions for T1D by identifying novel drug targets.

Hypoglycemic and pancreatic protective effects of Portulaca oleracea extract in alloxan induced diabetic rats

BACKGROUND

Diabetes is a major public health concern. In spite of continuous new drug development to treat diabetes, herbal remedies remain a potential adjunct therapy to maintain better glycemic control while also imparting few side-effects. Portulaca oleracea has been traditionally used to manage several diseases due to the anti-oxidant and anti-atherogenic effects it imparts. To better understand the mechanisms associated with potential protective effect of P. oleracea extract against diabetes, alloxan-induced diabetic rats were used in this study.

METHODS

Forty Wistar rats (male, 7-8-wk-old, 140-160 g) were divided into four groups (n = 10/group): Group I (control), Group II (P. oleracea-treated; gavaged with P. oleracea extract daily [at 250 mg/kg] for 4 weeks), Group III (diabetic control; daily IP injection of alloxan [at 75 mg/kg] for 5 days) and Group IV (P. oleracea-pre-treated diabetic; gavaged with P. oleracea extract daily [at 250 mg/kg] for 4 weeks and then daily IP injection of alloxan [at 75 mg/kg] for 5 days). Body weight, food consumption, blood (serum) levels of glucose, C peptide, Hb A1C, insulin, tumor necrosis factor (TNF)-α and interleukin (IL)-6 were determined for all groups.

RESULTS

The results indicated that while Hb A1C, serum levels of glucose, TNF-α and IL-6 were all significantly decreased in the P. oleracea-pre-treated diabetic rats, these hosts also had significant increases in C peptide and insulin compared to levels in the counterpart diabetic rats. These results were confirmed by the histopathological assessments which showed marked improvement of the destructive effect on pancreatic islet cells induced by alloxan.

CONCLUSION

P. oleracea extract is a general tissue protective and regeneartive agent, as evidenced by increasing β-cell mass and therefore improved the glucose metabolism. Thus, stimulation of Portulaca oleracea signaling in β- cells may be a novel therapeutic strategy for diabetes prevention.

Arachidonic acid and lipoxinA4 attenuate streptozotocin-induced cytotoxicity to RIN5 F cells in vitro and type 1 and type 2 diabetes mellitus in vivo

OBJECTIVE

The aim of this study was to observe whether polyunsaturated fatty acids (PUFAs) can protect rat insulinoma (RIN5 F) cells against streptozotocin (STZ)-induced apoptosis in vitro and type 1 diabetes mellitus (T1DM) and type 2 DM (T2DM) in vivo and if so, what would be the mechanism of this action.

METHODS

RIN5 F cells were used for the in vitro study, whereas the in vivo study was performed in Wistar rats. STZ was used to induce apoptosis of RIN5 F cells in vitro and T1- and T2DM in vivo. The effect of PUFAs: γ-linolenic acid (GLA), arachidonic acid (AA) of ω-6 series, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) of ω-3 series; cyclooxygenase (COX) and lipoxygenase (LOX) inhibitors and antiinflammatory metabolite of AA and DHA, lipoxin A4 (LXA4), and resolvin D2 and protectin, respectively against STZ-induced cytotoxicity to RIN5 F cells in vitro and LXA4 against T1- and T2DM in vivo was studied. Changes in the antioxidant content, lipid peroxides, nitric oxide, and expression of PDX1, P65, nuclear factor-κb (NF-κb), and IKB genes in STZ-treated RIN5 F cells in vitro and Nrf2, GLUT2, COX2, iNOS protein levels in the pancreatic tissue of T1- and T2DM and LPCLN2 (lipocalin 2), NF-κb, IKB I in adipose tissue of T2DM after LXA4 treatment were studied. Plasma glucose, insulin, and tumor necrosis factor (TNF)-α levels also were measured in STZ-induced T1- and T2DM Wistar rats.

RESULTS

Among all PUFAs tested, AA and EPA are the most effective against STZ-induced cytotoxicity to RIN5 F cells in vitro. Neither COX nor LOX inhibitors blocked the cytoprotective action of AA in vitro and T1- and T2DM by STZ. LXA4 production by RIN5 F cells in vitro and plasma LXA4 levels in STZ-induced T1- and T2DM animals were decreased by STZ that reverted to normal after AA treatment. AA prevented both T1- and T2DM induced by STZ. Antiinflammatory metabolite of AA and LXA4 prevented both T1- and T2DM induced by STZ. The expression of Pdx1, NF-κb, IKB genes in the pancreas and plasma TNF-α levels in T1- and T2DM; Nrf2, Glut2, COX2, and iNOS proteins in pancreatic tissue of T1DM and LPCLN2, NF-κb, IKB I in adipose tissue of T2DM reverted to normal in LXA4-treated animals.

CONCLUSION

Both AA and LXA4 prevented STZ-induced cytotoxicity to RIN5 F cells in vitro and T1- and T2DM in vivo, suggesting that these two bioactive lipids may function as antidiabetic molecules. AA is beneficial against STZ-induced cytotoxicity and T1- and T2DM by enhancing the production of LXA4.

Diabetic macular edema, retinopathy and age-related macular degeneration as inflammatory conditions

Diabetic macular edema (DME) and diabetic retinopathy (DR) are complications affecting about 25% of all patients with long-standing type 1 and type 2 diabetes mellitus and are a major cause of significant decrease in vision and quality of life. Age-related macular degeneration (AMD) is not uncommon, and diabetes mellitus affects the incidence and progression of AMD through altering hemodynamics, increasing oxidative stress, accumulating advanced glycation end products, etc. Recent studies suggest that DME, DR and AMD are inflammatory conditions characterized by a breakdown of the blood-retinal barrier, inflammatory processes and an increase in vascular permeability. Key factors that seem to have a dominant role in DME, DR and AMD are angiotensin II, prostaglandins and the vascular endothelial growth factor and a deficiency of anti-inflammatory bioactive lipids. The imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DME, DR and AMD. This implies that bioactive lipids that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DME, DR and AMD.

BDNF protects pancreatic β cells (RIN5F) against cytotoxic action of alloxan, streptozotocin, doxorubicin and benzo(a)pyrene in vitro

OBJECTIVE

The study was conducted to observe whether brain-derived neurotrophic factor (BDNF) has cytoprotective actions against alloxan (AL), streptozotocin (STZ), doxorubicin (DB) and benzo(a)pyrene (BP) compounds in vitro that may account for its beneficial action in diabetes mellitus.

MATERIALS AND METHODS

This in vitro study was performed using rat insulinoma (RIN5F) cells. Possible cytoprotective action of BDNF (using pre-treatment, simultaneous and post-treatment schedules of RIN5F cells with BDNF) against the four chemicals tested was evaluated using MTT and apoptosis assays. Possible mechanism of cytoprotective action of BDNF was assessed by measuring BCl2/IKB-β/Pdx mRNA transcripts and anti-oxidant levels in RIN5F cells. Effect of alloxan, STZ, doxorubicin and BP on the production of BDNF by RIN5F cells was also studied.

RESULTS

Results of the present study revealed that BDNF in the doses (100ng>50ng>10ng/ml) has significant cytoprotection (P<0.001, P<0.01) on cytotoxic action of AL, STZ, DB and BP against rat insulinoma RIN5F (5×10(4) cells/100μl) cells in vitro. It was observed that AL, STZ, DB and BP inhibited BDNF production significantly (P<0.001) in a dose-dependent manner by RIN5F cells (0.5×10(6) cells/500μl) in vitro, while BDNF not only prevented apoptosis induced by these four chemicals but also significantly increased (P<0.001) BCl2/IKB-β/Pdx mRNA transcripts and restored anti-oxidant levels (P<0.01) in RIN5F cells to normal.

DISCUSSION

These results suggest that BDNF has potent cytoprotective actions, restores anti-oxidant defenses to normal and thus, prevents apoptosis and preserves insulin secreting capacity of β cells. In addition, BDNF enhanced viability of RIN 5F in vitro. Thus, BDNF not only has anti-diabetic actions but also preserves pancreatic β cells integrity and enhances their viability. These results imply that BDNF functions as an endogenous cytoprotective molecule that may explain its beneficial actions in some neurological conditions as well.

Serum n-6 polyunsaturated fatty acids, Δ5- and Δ6-desaturase activities, and risk of incident type 2 diabetes in men: the Kuopio Ischaemic Heart Disease Risk Factor Study

BACKGROUND

The role of n-6 (ω-6) polyunsaturated fatty acids (PUFAs) in type 2 diabetes (T2D) is inconclusive. In addition, little is known about how factors involved in PUFA metabolism, such as zinc, may affect the associations.

OBJECTIVES

We investigated the associations of serum n-6 PUFAs and activities of enzymes involved in PUFA metabolism, Δ5 desaturase (D5D) and Δ6 desaturase (D6D), with T2D risk to determine whether serum zinc concentrations could modify these associations.

DESIGN

The study included 2189 men from the prospective Kuopio Ischaemic Heart Disease Risk Factor Study, aged 42-60 y and free of T2D at baseline in 1984-1989. T2D was assessed by self-administered questionnaires, by fasting and 2-h oral-glucose-tolerance test blood glucose measurement at re-examination rounds 4, 11, and 20 y after baseline, and by record linkage to the hospital discharge registry and the reimbursement register on diabetes medication expenses. Multivariate-adjusted Cox proportional hazards regression models were used to analyze associations.

RESULTS

During the average follow-up of 19.3 y, 417 men developed T2D. Those with higher estimated D5D activity (extreme-quartile HR: 0.55; 95% CI: 0.41, 0.74; P-trend < 0.001) and higher concentrations of total n-6 PUFAs (HR: 0.54; 95% CI: 0.41, 0.73; P-trend < 0.001), linoleic acid (LA; HR: 0.52; 95% CI: 0.39, 0.70; P-trend < 0.001), and arachidonic acid (AA; HR: 0.62; 95% CI: 0.46, 0.85; P-trend = 0.007) had a lower risk and those with higher concentrations of γ-linolenic acid (GLA; HR: 1.28; 95% CI: 0.98, 1.68; P = 0.021) and dihomo-γ-linolenic acid (DGLA; HR: 1.38; 95% CI: 1.04, 1.84; P-trend = 0.005) and higher D6D activity had a higher (HR: 1.50; 95% CI: 1.14, 1.97; P-trend < 0.001) multivariate-adjusted risk of T2D. Zinc mainly modified the association with GLA on T2D risk, with a higher risk observed among those with serum zinc concentrations above the median (P-interaction = 0.04).

CONCLUSIONS

Higher serum total n-6 PUFA, LA, and AA concentrations and estimated D5D activity were associated with a lower risk of incident T2D, and higher GLA and DGLA concentrations and estimated D6D activity were associated with a higher risk. In addition, a higher serum zinc concentration modified the association of GLA on the risk of T2D.

Increased Dietary Intake of Saturated Fatty Acid Heptadecanoic Acid (C17:0) Associated with Decreasing Ferritin and Alleviated Metabolic Syndrome in Dolphins

Similar to humans, bottlenose dolphins (Tursiops truncatus) can develop metabolic syndrome and associated high ferritin. While fish and fish-based fatty acids may protect against metabolic syndrome in humans, findings have been inconsistent. To assess potential protective factors against metabolic syndrome related to fish diets, fatty acids were compared between two dolphin populations with higher (n = 30, Group A) and lower (n = 19, Group B) mean insulin (11 ± 12 and 2 ± 5 μIU/ml, respectively; P < 0.0001) and their dietary fish. In addition to higher insulin, triglycerides, and ferritin, Group A had lower percent serum heptadecanoic acid (C17:0) compared to Group B (0.3 ± 0.1 and 1.3 ± 0.4%, respectively; P < 0.0001). Using multivariate stepwise regression, higher percent serum C17:0, a saturated fat found in dairy fat, rye, and some fish, was an independent predictor of lower insulin in dolphins. Capelin, a common dietary fish for Group A, had no detectable C17:0, while pinfish and mullet, common in Group B's diet, had C17:0 (41 and 67 mg/100g, respectively). When a modified diet adding 25% pinfish and/or mullet was fed to six Group A dolphins over 24 weeks (increasing the average daily dietary C17:0 intake from 400 to 1700 mg), C17:0 serum levels increased, high ferritin decreased, and blood-based metabolic syndrome indices normalized toward reference levels. These effects were not found in four reference dolphins. Further, higher total serum C17:0 was an independent and linear predictor of lower ferritin in dolphins in Group B dolphins. Among off the shelf dairy products tested, butter had the highest C17:0 (423mg/100g); nonfat dairy products had no detectable C17:0. We hypothesize that humans' movement away from diets with potentially beneficial saturated fatty acid C17:0, including whole fat dairy products, could be a contributor to widespread low C17:0 levels, higher ferritin, and metabolic syndrome.

Evaluation of protective effect of cactus pear seed oil (Opuntia ficus-indica L. MILL.) against alloxan-induced diabetes in mice

OBJECTIVE

To evaluate the in vitro antioxidant power of cactus pear seed oil [Opuntia ficus-indica L. MILL. (CPSO)] and its protective effect against chemically induced diabetes mellitus in mice.

METHODS

The in vitro antioxidant effect of CPSO was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay. The preventive effect was conducted on Swiss albino mice treated with CPSO (2 mL/kg, per os), before and after a single intraperitoneal alloxan administration (100 mg/kg). Survival rate, body weight and fasting blood glucose were measured and histopathological analysis of pancreas was performed to evaluate alloxan-induced tissue injuries.

RESULTS

CPSO exhibited an antioxidant effect in DPPH scavenging assay. Moreover, the administration of CPSO (2 mL/kg) significantly attenuated alloxan-induced death and hyperglycemia (P < 0.001) in treated mice. Morphometric study of pancreas revealed that CPSO significantly protected islets of langerhans against alloxan induced-tissue alterations.

CONCLUSIONS

Based on theses results, CPSO can prevente alloxan-induced-diabetes by quenching free radicals produced by alloxan and inhibiting tissue injuries in pancreatic β-cells.

Effect of polyunsaturated fatty acids and their metabolites on bleomycin-induced cytotoxic action on human neuroblastoma cells in vitro

In the present study, we noted that bleomycin induced growth inhibitory action was augmented by all the polyunsaturated fatty acids (PUFAs) tested on human neuroblastoma IMR-32 (0.5 × 10(4) cells/100 µl of IMR) cells (EPA > DHA > ALA = GLA = AA > DGLA = LA: ∼ 60, 40, 30, 10-20% respectively) at the maximum doses used. Of all the prostaglandins (PGE1, PGE2, PGF2α, and PGI2) and leukotrienes (LTD4 and LTE4) tested; PGE1, PGE2 and LTD4 inhibited the growth of IMR-32 cells to a significant degree at the highest doses used. Lipoxin A4 (LXA4), 19,20-dihydroxydocosapentaenoate (19, 20 DiHDPA) and 10(S),17(S)-dihydroxy-4Z,7Z,11E,13Z,15E,19Z-docosahexaenoic acid (protectin: 10(S),17(S)DiHDoHE), metabolites of DHA, significantly inhibited the growth of IMR-32 cells. Pre-treatment with AA, GLA, DGLA and EPA and simultaneous treatment with all PUFAs used in the study augmented growth inhibitory action of bleomycin. Surprisingly, both indomethacin and nordihydroguaiaretic acid (NDGA) at 60 and 20 µg/ml respectively enhanced the growth of IMR-32 cells even in the presence of bleomycin. AA enhanced oxidant stress in IMR-32 cells as evidenced by an increase in lipid peroxides, superoxide dismutase levels and glutathione peroxidase activity. These results suggest that PUFAs suppress growth of human neuroblastoma cells, augment growth inhibitory action of bleomycin by enhancing formation of lipid peroxides and altering the status of anti-oxidants and, in all probability, increase the formation of lipoxins, resolvins and protectins from their respective precursors that possess growth inhibitory actions.

Potential role of polyunsaturated fatty acids in diabetic retinopathy

Diabetic retinopathy (DR) is a serious complication of long-standing diabetes mellitus. It affects about 25% of all patients with diabetes mellitus and causes a significant decrease in the quality of life. Despite many years of research, the exact pathway that leads to the development and progression of DR is not clear. Recent studies suggest that polyunsaturated fatty acids (PUFAs) and their metabolites could play a significant role in DR. There is evidence to suggest that an imbalance between pro- and anti-inflammatory eicosanoids and enhanced production of pro-angiogenic factors may initiate the onset and progression of DR. This implies that PUFAs and their metabolites that possess anti-inflammatory actions and suppress the production of angiogenic factors could be employed in the prevention and management of DR.

Chronic intraocular pressure elevation impairs autoregulatory capacity in streptozotocin-induced diabetic rat retina

PURPOSE

To assess ocular blood flow responses to acute IOP stress following 4 weeks of chronic IOP elevation in streptozotocin (STZ)-induced diabetic and control rats. We hypothesise that chronic IOP elevation for 4 weeks will further impair blood flow regulation in STZ-induced diabetic rats eyes.

METHODS

Two weeks following citrate buffer or STZ-injections chronic IOP elevation was induced in Long Evans rats via fortnightly intracameral injections of microspheres (15 μm) suspended in 5% polyethylene glycol. IOP was monitored daily. Electroretinography (ERG, -6.79-2.07 log cd s m(-2) ) was undertaken at Week 4 to compare photoreceptor (RmPIII ), ON-bipolar cell (Vmax ) and ganglion cell dominant ERG [scotopic threshold response (STR)] components. 4 weeks post-chronic IOP induction, ocular blood flow (laser Doppler flowmetry) was measured in response to acute IOP challenge (10-100 mmHg, in 5 mmHg steps, each 3 min).

RESULTS

Four weeks of chronic IOP (mean ± S.E.M., citrate: 24.0 ± 0.3 to 30.7 ± 1.3 and STZ-diabetes: 24.2 ± 0.2 to 31.1 ± 1.2 mmHg) was associated with reduced photoreceptor amplitude in both groups (-25.3 ± 2.2% and -17.2 ± 3.0%, respectively). STZ-diabetic eyes showed reduced photoreceptor sensitivity (citrate: 0.5 ± 1.8%, STZ-diabetic: -8.1 ± 2.4%). Paradoxically ON-bipolar cell sensitivity was increased, particularly in citrate control eyes (citrate: 166.8 ± 25.9%, STZ-diabetic: 64.8 ± 18.7%). The ganglion cell dominant STR was not significantly reduced in STZ-diabetic rats. Using acute IOP elevation to probe autoregulation, we show that STZ-diabetes impaired autoregulation compared with citrate control animals. The combination of STZ-diabetes and chronic IOP elevation further impaired autoregulation.

CONCLUSIONS

STZ-diabetes and chronic IOP elevation appear to be additive risk factors for impairment of ocular blood flow autoregulation.

Evaluation of the insulin-releasing and glucose-lowering effects of GPR120 activation in pancreatic β-cells

AIMS

To assess the potency and selectivity of various GPR120 agonists and to determine the cellular localization of GPR120 in clonal β-cells and pancreatic islets.

METHODS

Insulin secretion and alterations in intracellular Ca(2+) and cAMP response to glucose and GPR120 agonists, including endogenous agonists α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and a synthetic analogue (GW-9508), were examined using clonal pancreatic BRIN-BD11 cells, mouse pancreatic islets and in vivo studies using NIH Swiss mice. Cytotoxicity was assessed by lactate dehydrogenase release. Cellular localization of GPR120 was explored by double-staining immunohistochemistry.

RESULTS

The most potent and selective GPR120 agonist tested was ALA (half maximum effective concentration 1.2 × 10(-8) mol/l) with a maximum stimulation of insulin secretion of 53% at 10(-4) mol/l (p < 0.001) in BRIN-BD11 cells. Stimulation of insulin secretion was also observed with GW-9508 (6.4 × 10(-8) mol/l; 47%), EPA (7.9 × 10(-8) mol/l; 36%) and DHA (1.0 × 10(-7) mol/l; 50%). Results were corroborated by islet studies, with no evidence of cytotoxic effects. Dose-dependent insulin secretion by GPR120 agonists was glucose-sensitive and accompanied by significant elevations of intracellular Ca(2+) and cAMP. Immunocytochemistry showed GPR120 expression on BRIN-BD11 cells and was confined to islet β-cells with no distribution on α-cells. Administration of GPR120 agonists (0.1 µmol/kg body weight) in glucose tolerance studies significantly reduced plasma glucose and augmented insulin release in mice.

CONCLUSIONS

These results indicate that GPR120 is expressed on pancreatic β-cells and that agonists at this receptor are potent insulin secretagogues with therapeutic potential for type 2 diabetes.

Linoleic and alpha linolenic acids ameliorate streptozotocin-induced diabetes in mice

Streptozotocin (STZ)-induced diabetes in mice progresses with decreased desaturase activities and alterations in the metabolism of essential fatty acids (EFA).

OBJECTIVES

Based on our previous studies with soybean oil that ameliorated the STZ damage in mice, we tested here the accountability of its main EFA components, i.e. linoleic acid (LA) and alpha linolenic acid (ALA), in the prevention of pancreas damage and Δ6 desaturase decrease.

MATERIALS AND METHODS

Seven days after injection with STZ and EFA gavage, ICR mice were sacrificed. Plasma glucose and insulin levels, pancreas histology and liver fatty acid desaturases were analysed.

RESULTS

EFA reduced pancreas damage, insulin and glucose plasma levels and restored Δ6 desaturase activity and mRNA expression levels.

DISCUSSION

By reducing pancreas damage, EFA ameliorated insulin levels, Δ6 desaturase and fatty acid metabolism. LA further enhanced Fads2 promoter activity.

CONCLUSION

EFA ameliorate STZ induced diabetes in mice.