Arachidonic acid stimulates glucose uptake in 3T3-L1 adipocytes by increasing GLUT1 and GLUT4 levels at the plasma membrane. Evidence for involvement of lipoxygenase metabolites and peroxisome proliferator-activated receptor gamma

Ethnic and region-specific genetic risk variants of stroke and its comorbid conditions can define the variations in the burden of stroke and its phenotypic traits

Burden of stroke differs by region, which could be attributed to differences in comorbid conditions and ethnicity. Genomewide variation acts as a proxy marker for ethnicity, and comorbid conditions. We present an integrated approach to understand this variation by considering prevalence and mortality rates of stroke and its comorbid risk for 204 countries from 2009 to 2019, and Genome-wide association studies (GWAS) risk variant for all these conditions. Global and regional trend analysis of rates using linear regression, correlation, and proportion analysis, signifies ethnogeographic differences. Interestingly, the comorbid conditions that act as risk drivers for stroke differed by regions, with more of metabolic risk in America and Europe, in contrast to high systolic blood pressure in Asian and African regions. GWAS risk loci of stroke and its comorbid conditions indicate distinct population stratification for each of these conditions, signifying for population-specific risk. Unique and shared genetic risk variants for stroke, and its comorbid and followed up with ethnic-specific variation can help in determining regional risk drivers for stroke. Unique ethnic-specific risk variants and their distinct patterns of linkage disequilibrium further uncover the drivers for phenotypic variation. Therefore, identifying population- and comorbidity-specific risk variants might help in defining the threshold for risk, and aid in developing population-specific prevention strategies for stroke.

Cladosporols and PPARγ: Same Gun, Same Bullet, More Targets

Several natural compounds have been found to act as PPARγ agonists, thus regulating numerous biological processes, including the metabolism of carbohydrates and lipids, cell proliferation and differentiation, angiogenesis, and inflammation. Recently, Cladosporols, secondary metabolites purified from the fungus Cladosporium tenuissimum, have been demonstrated to display an efficient ability to control cell proliferation in human colorectal and prostate cancer cells through a PPARγ-mediated modulation of gene expression. In addition, Cladosporols exhibited a strong anti-adipogenetic activity in 3T3-L1 murine preadipocytes, preventing their in vitro differentiation into mature adipocytes. These data interestingly point out that the interaction between Cladosporols and PPARγ, in the milieu of different cells or tissues, might generate a wide range of beneficial effects for the entire organism affected by diabetes, obesity, inflammation, and cancer. This review explores the molecular mechanisms by which the Cladosporol/PPARγ complex may simultaneously interfere with a dysregulated lipid metabolism and cancer promotion and progression, highlighting the potential therapeutic benefits of Cladosporols for human health.

Phytochemical Screening and Antidiabetic Efficacy of Balanites aegyptiaca Seed Extract and Their Silver Nanoparticles on Muscle and Pancreatic Cell Lines

Balanites aegyptiaca (L.) Delile, a member of the Zygophyllaceae family, is commonly known as the desert date. This tree is famous for yielding edible fruits and is esteemed for its nutritional richness and diverse health advantages. The primary aim of this research was to assess the potential antidiabetic and cytotoxic effects of seed extracts from B. aegyptiaca and its AgNPs for the first time on C2C12 and MIN6 cells, focusing on glucose uptake and insulin secretion, respectively. Additionally, the seed extracts underwent column chromatography through different solvent systems, resulting in the isolation of five distinct fractions with a mixture of methanol and water as an eluting solvent in different ratios. Comprehensive characterization of the aqueous seed extract was carried out using GC-MS and UPLC-MS. The study determined that the aqueous seed extract exhibited no toxicity at any tested concentration (6.25-100 μg/mL) on both cell types. The calculated IC50 values were 206.00 and 140.44 μg/mL for C2C12 and MIN6 cells, respectively, for seeds of AgNPs. Additionally, the aqueous seed extract and their AgNPs significantly increased glucose uptake by 150.45% and 156.00% of the control in C2C12 cells at a concentration of 100 μg/mL. Insulin secretion was also notably enhanced by 3.47- and 3.92-fold of the control after administering seed extracts and AgNPs, respectively, at 100 μg/mL. GC-MS and UPLC-MS analyses identified various compounds across different categories. Notably, the F2 fraction (methanol and water in ratio of 80:20 as eluting solvent) exhibited the highest glucose uptake activity (156.81% of control), while the F3 fraction (methanol and water in ratio of 70:30 as eluting solvent) fraction demonstrated the highest insulin secretion activity (3.70 folds of the control) among all fractions at 100 μg/mL. GC-MS analysis was employed to characterize both fractions, aiming to identify the compounds contributing to their antidiabetic potential. The study's findings concluded that both seed extracts and their AgNPs possess significant antidiabetic properties, with elevated activity observed in the case of AgNPs in both assays. Various compounds, including diosgenin, oleic acid, linoleic acid and palmitic acid esters were detected in the seed extracts, known for their reported antidiabetic and hypoglycemic effects.

Saturated fatty acids inhibit unsaturated fatty acid induced glucose uptake involving GLUT10 and aerobic glycolysis in bovine granulosa cells

Fatty acids have been shown to modulate glucose metabolism in vitro and in vivo. However, there is still a need for substantial evidence and mechanistic understanding in many cell types whether both saturated and unsaturated fatty acids (SFAs and UFAs) pose a similar effect and, if not, what determines the net effect of fatty acid mixes on glucose metabolism. In the present study, we asked these questions by treating granulosa cells (GCs) with the most abundant non-esterified fatty acid species in bovine follicular fluid. Results revealed that oleic and alpha-linolenic acids (UFAs) significantly increased glucose consumption compared to palmitic and stearic acids (SFAs). A significant increase in lactate production, extracellular acidification rate, and decreased mitochondrial activity indicate glucose channeling through aerobic glycolysis in UFA treated GCs. We show that insulin independent glucose transporter GLUT10 is essential for UFA driven glucose consumption, and the induction of AKT and ERK signaling pathways necessary for GLUT10 expression. To mimic the physiological conditions, we co-treated GCs with mixes of SFAs and UFAs. Interestingly, co-treatments abolished the UFA induced glucose uptake and metabolism by inhibiting AKT and ERK phosphorylation and GLUT10 expression. These data suggest that the net effect of fatty acid induced glucose uptake in GCs is determined by SFAs under physiological conditions.

Genome-wide scans identify biological and metabolic pathways regulating carcass and meat quality traits in beef cattle

Genome association studies (GWAS) provides knowledge about the genetic architecture of beef-related traits that allow linking the target phenotype to genomic information aiding breeding decision. Thus, the present study aims to uncover the genetic mechanism involved in carcass (REA: rib eye area, BF: backfat thickness, and HCW: hot carcass weight) and meat quality traits (SF: shear-force, MARB: marbling score, and IMF: intramuscular fat content) in Nellore cattle. For this, 6910 young bulls with phenotypic information and 23,859 animals genotyped with 435 k markers were used to perform the weighted single-step GBLUP (WssGBLUP) approach, considering two iterations. The top 10 genomic regions explained 8.13, 11.81, and 9.58% of the additive genetic variance, harboring a total of 119, 143, and 95 positional candidate genes for REA, BF, and HCW, respectively. For meat quality traits, the top 10 windows explained a large proportion of the total genetic variance for SF (14.95%), MARB (17.56%), and IMF (21.41%) surrounding 92, 155, and 111 candidate genes, respectively. Relevant candidate genes (CAST, PLAG1, XKR4, PLAGL2, AQP3/AQP7, MYLK2, WWOX, CARTPT, and PLA2G16) are related to physiological aspects affecting growth, carcass, meat quality, feed intake, and reproductive traits by signaling pathways controlling muscle control, key signal metabolic molecules INS / IGF-1 pathway, lipid metabolism, and adipose tissue development. The GWAS results provided insights into the genetic control of the traits studied and the genes found are potential candidates to be used in the improvement of carcass and meat quality traits.

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.

Study of the Phytochemical Composition, Antioxidant Properties, and In Vitro Anti-Diabetic Efficacy of Gracilaria bursa-pastoris Extracts

In this study, a comparison was made of the chemical makeup of different extracts obtained from Gracilaria bursa-pastoris, a type of red seaweed that was gathered from the Nador lagoon situated in the northern part of Morocco. Additionally, their anti-diabetic and antioxidant properties were investigated. The application of GC-MS technology to analyze the fatty acid content of the samples revealed that linoleic acid and eicosenoic acid were the most abundant unsaturated fatty acids across all samples, with palmitic acid and oleic acid following in frequency. The HPLC analysis indicated that ascorbic and kojic acids were the most prevalent phenolic compounds, while apigenin was the most common flavonoid molecule. The aqueous extract exhibited significant levels of polyphenols and flavonoids, registering values of 381.31 ± 0.33 mg GAE/g and 201.80 ± 0.21 mg QE/g, respectively. Furthermore, this particular extract demonstrated a remarkable ability to scavenge DPPH radicals, as evidenced by its IC₅₀ value of 0.17 ± 0.67 mg/mL. In addition, the methanolic extract was found to possess antioxidant properties, as evidenced by its ability to prevent β-carotene discoloration, with an IC₅₀ ranging from 0.062 ± 0.02 mg/mL to 0.070 ± 0.06 mg/mL. In vitro study showed that all extracts significantly inhibited the enzymatic activity of α-amylase and α-glucosidase. Finally, molecular docking models were applied to assess the interaction between the primary phytochemicals identified in G. bursa-pastoris extracts and the human pancreatic α-amylase and α-glucosidase enzymes. The findings suggest that these extracts contain bioactive substances capable of reducing enzyme activity more effectively than the commercially available drug acarbose.

The Role of Reprogrammed Glucose Metabolism in Cancer

Cancer cells reprogram their metabolism to meet biosynthetic needs and to adapt to various microenvironments. Accelerated glycolysis offers proliferative benefits for malignant cells by generating glycolytic products that move into branched pathways to synthesize proteins, fatty acids, nucleotides, and lipids. Notably, reprogrammed glucose metabolism and its associated events support the hallmark features of cancer such as sustained cell proliferation, hijacked apoptosis, invasion, metastasis, and angiogenesis. Overproduced enzymes involved in the committed steps of glycolysis (hexokinase, phosphofructokinase-1, and pyruvate kinase) are promising pharmacological targets for cancer therapeutics. In this review, we summarize the role of reprogrammed glucose metabolism in cancer cells and how it can be manipulated for anti-cancer strategies.

Ewe early gestation supplementation with eicosapentaenoic and docosahexaenoic acids affects the liver, muscle, and adipose tissue fatty acid profile and liver mRNA expression in the offspring

Our objectives were to assess the effects of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) supplementation to pregnant ewes during the first third of gestation on their offspring's liver, adipose, and muscle tissues fatty acid (FA) profile and liver mRNA expression after a finishing period receiving diets with different FA profiles. Twenty-four post-weaning lambs, blocked by sex and body weight, were used in a 2 × 2 factorial arrangement of treatments. The first factor was dam supplementation (DS) in the first third of gestation with 1.61% of Ca salts of palm fatty acid distillate (PFAD) or Ca salts enriched with EPA-DHA. Ewes were exposed to rams with marking paint harnesses during the breeding. Ewes started DS at the day of mating, considered day 1 of conception. Twenty-eight days after mating, ultrasonography was used to confirm pregnancy, and nonpregnant ewes were removed from the groups. After weaning, the offspring lambs were supplemented (LS, second main factor) with two different FA sources (1.48% of PFAD or 1.48% of EPA-DHA) during the growing and fattening phase. Lambs were fed the LS diet for 56 d and sent to slaughter, where the liver, muscle, and adipose tissue samples were collected for FA analysis. Liver samples were collected for relative mRNA expression for genes associated with FA transport and metabolism. The data were analyzed as a mixed model in SAS (9.4). In the liver, the amount of C20:5 and C22:6 (P < 0.01) increased in lambs with LS-EPA-DHA, while some C18:1 cis FA isomers were greater in the lambs from DS-PFAD. In muscle, amounts of C22:1, C20:5, and C22:5 increased (P < 0.05) in lambs born from DS-EPA-DHA. The adipose tissue amounts of C20:5, C22:5, and C22:6 were greater (P < 0.01) in lambs from LS-EPA-DHA. Interactions (DS × LS; P < 0.05) were observed for DNMT3β, FABP-1, FABP-5, SCD, and SREBP-1; having greater mRNA expression in liver tissue of LS-EPA-DHA, DS-PFAD and LS-PFAD, DS-EPA-DHA lambs compared with the lambs in the other two treatments. Liver ELOVL2 mRNA relative expression (P < 0.03) was greater in the offspring of DS-PFAD. Relative mRNA expression (P < 0.05) of GLUT1, IGF-1, LPL, and PPARγ increased in the liver from LS-EPA-DHA lambs. Dam supplementation during early gestation using with different FA sources changed the lipid FA profile in MT, LT, and SAT during the finishing period depending on the tissue and type of FA source administered during the growing phase.

Prenylated flavonoids from Morus nigra and their insulin sensitizing activity

Six undescribed prenylated flavonoids, nigragenons H-M, and four known compounds, were isolated from Morus nigra L. Their structures were elucidated through extensive analysis of spectroscopic data, and their absolute configurations were established by time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculation. The insulin sensitizing activities of all compounds were investigated using insulin-resistant 3T3-L1 adipocytes. At a high concentration (30 μM), all compounds except nigragenon I enhanced insulin-stimulated glucose uptake in insulin-resistant 3T3-L1 adipocytes. Furthermore, nigragenons J-L and the promoted adiponectin secretion in the model cells. Among them, nigragenon L showed the most potent effect at a low concentration of 10 μM, which was comparable to that of rosiglitazone at a concentration of 1 μM. Furthermore, using the Lantha Screen™ TR-FRET assay, nigragenon L was confirmed to be the ligand of PPARγ, showing potent binding affinity toward PPARγ with an IC₅₀ value of 2.8 μM.

Insulin prevents fatty acid induced increase of adipocyte size

Metabolic disorders related to obesity are largely dependent on adipose tissue hypertrophy, which involves adipocyte hypertrophy and increased adipogenesis. Adiposize is regulated by lipid accumulation as a result of increased lipogenesis (mainly lipid uptake in mature adipocytes) and reduced lipolysis. Using realtime 2D cell culture analyses of lipid uptake, we show (1) that high glucose concentration (4.5 g/L) was required to accumulate oleic acid increasing lipid droplet size until unilocularization similar to mature adipocytes in few days, (2) oleic acid reduced Peroxisome-Proliferator Activated Receptor Gamma (PPARG) gene transcription and (3) insulin counteracted oleic acid-induced increase of lipid droplet size. Although the lipolytic activity observed in high versus low glucose (1 g/L) conditions was not altered, insulin was found to inhibit oleic acid induced gene transcription required for lipid storage such as Cell Death Inducing DFFA Like Effectors (CIDEC) and G0S2 (G0 switch gene S2), possibly through PPARA activity. Although this signalling pathway requires more detailed investigation, the results point out the differential mechanisms involved in the pro-adipogenic effect of insulin in absence versus its protective effect on adiposity in presence of oleic acid uptake.

Abbreviations: AICAR, 5-Aminoimidazole-4-carboxamide-1-D-ribofuranoside; AMPK, AMP-Activated protein kinase, ASCs, adipose stem cell; ATGL, adipose triglyceride lipase; BSA, Bovine serum albumin; CEBPA, CCAAT enhancer binding protein alpha; CIDEs, Cell Death Inducing DFFA Like Effectors; dA, differentiated adipocyte; DMEM, Dulbecco’s Modified Eagle’s Medium; FABPs, Fatty Acid Binding Proteins; FAT/CD36, Fatty acid translocase; FCS, Foetal calf serum; FN1, fibronectin 1; FFA, free fatty acid; G0S2, G0 switch gene S2; GLUTs, Glucose transporters; GPR120, G protein-coupled receptor 120; HG, high glucose; HSL, hormone sensitive lipase; INSR, insulin receptor; LG, low glucose; OA, oleic acid; PBS, Phosphate buffer saline; PPARs, Peroxisome-Proliferator Activated Receptors; PKA, Protein kinase cyclic AMP-dependent; PKG, Protein kinase cyclic GMP dependent; PTGS2, cytochrome oxidase 2; RTCA, realtime cell analysis; TG, triglyceride.

Using Metabolomics in Diabetes Management with Traditional Chinese Medicine: A Review

The incidence of diabetes worldwide continues to rise, placing a huge economic and medical burden on human society. More than 90% of diabetic cases are type 2 diabetes (T2D). At present, the pathogenesis of T2D is not yet fully understood. Metabolomics uses high-resolution analytical techniques (typically NMR and MS) to help identify biomarkers associated with the risk of T2D and reveal potential pathogenesis. Many metabolites such as branched-chain amino acids (BCAAs), aromatic amino acids, glycine, 2-hydroxybutyric acid (2-HB), lysophosphatidylcholine (LPC) (18:2), and trehalose have proven to be biomarkers of T2D. Insulin resistance (IR) induced by BCAA in T2D mice is related to the activation of mammalian target of rapamycin (mTOR) and phosphorylation of insulin receptor substrate-1 (IRS1). Incomplete LCFA [Formula: see text]-oxidation promote acylcarnitine byproduct accumulation and stimulates proinflammatory NF[Formula: see text]B-related pathways to inhibit insulin action. Traditional Chinese Medicine (TCM) presents unique advantages in the treatment of T2D. Multiple metabolites and metabolic pathways have been identified in the treatment of TCM, providing valuable biomarkers and novel targets for drug therapy and pharmacological mechanism. Therefore, this paper reviews the modern achievements of metabolomics in T2D research and the progress of TCM management in recent years, in order to provide valuable information for related research.

The dietary arachidonic acid improved growth and immunity of honey bee (Apis mellifera ligustica)

Honeybees cannot synthesize arachidonic acid (ARA) themselves, only obtain it from food. Most pollen is deficient or contains a small amount of ARA. The necessity of supplementary ARA in bees' diet has not been studied. The objective of this study was to investigate the effects of dietary ARA levels on the growth and immunity of Apis mellifera ligustica. A total of 25 honeybee colonies were randomly assigned to five dietary groups which were fed basic diets supplemented with 0, 2, 4, 6, and 8% of ARA. The diet with 4% ARA improved the body weight of newly emerged worker bees compared with the control group. Supplement of ARA in honeybee diets changed the fatty acid composition of honeybee body. SFA and MUFA contents of bees' body declined, and PUFA content rised in the ARA group. Compared with the control group, the supplement of ARA in honeybee diets increased the contents of ARA, C22:6n-3 (DHA) and C18:3n-6 in bees' body significantly, but decreased the contents of C16:1 and C18:3n-3. The diet supplied with 4% ARA reduced the mortality rate of honeybee infected with Escherichia coli. The activity of immune enzymes (phenoloxidase, antitrypsin, and lysozyme) and the mRNA expression levels of immune genes (defensin-2, toll, myd88, and dorsal) were improved by ARA diets to varying degrees depending on the ARA levels, especially 4% ARA. These results suggested that dietary ARA could improve the growth, survival, and immune functions of honeybees. Supplement of ARA in bees' diet would be valuable for the fitness of honeybees.

Gundelia tournefortii: Fractionation, Chemical Composition and GLUT4 Translocation Enhancement in Muscle Cell Line

Type 2 diabetes (T2D) is a chronic metabolic disease, which could affect the daily life of patients and increase their risk of developing other diseases. Synthetic anti-diabetic drugs usually show severe side effects. In the last few decades, plant-derived drugs have been intensively studied, particularly because of a rapid development of the instruments used in analytical chemistry. We tested the efficacy of Gundelia tournefortii L. (GT) in increasing the translocation of glucose transporter-4 (GLUT4) to the myocyte plasma membrane (PM), as a main strategy to manage T2D. In this study, GT methanol extract was sub-fractionated into 10 samples using flash chromatography. The toxicity of the fractions on L6 muscle cells, stably expressing GLUTmyc, was evaluated using the MTT assay. The efficacy with which GLUT4 was attached to the L6 PM was evaluated at non-toxic concentrations. Fraction 6 was the most effective, as it stimulated GLUT4 translocation in the absence and presence of insulin, 3.5 and 5.2 times (at 250 μg/mL), respectively. Fraction 1 and 3 showed no significant effects on GLUT4 translocation, while other fractions increased GLUT4 translocation up to 2.0 times. Gas chromatography-mass spectrometry of silylated fractions revealed 98 distinct compounds. Among those compounds, 25 were considered anti-diabetic and glucose disposal agents. These findings suggest that GT methanol sub-fractions exert an anti-diabetic effect by modulating GLUT4 translocation in L6 muscle cells, and indicate the potential of GT extracts as novel therapeutic agents for T2D.

Alotaibi A, Al-zharani M, Ziyyat A, Mekhfi H, Legssyer A, Aziz M, Bnouham M. Opuntia dillenii (Ker Gawl.) Haw., Seeds Oil Antidiabetic Potential Using In Vivo, In Vitro, In Situ, and Ex Vivo Approaches to Reveal Its Underlying Mechanism of Action

Opuntia dillenii Ker Gawl. is one of the medicinal plants used for the prevention and treatment of diabetes mellitus (DM) in Morocco. This study aims to investigate the antihyperglycemic effect of Opuntia dillenii seed oil (ODSO), its mechanism of action, and any hypoglycemic risk and toxic effects. The antihyperglycemic effect was assessed using the OGTT test in normal and streptozotocin (STZ)-diabetic rats. The mechanisms of action were explored by studying the effect of ODSO on the intestinal absorption of d-glucose using the intestinal in situ single-pass perfusion technique. An Ussing chamber was used to explore the effects of ODSO on intestinal sodium-glucose cotransporter 1 (SGLT1). Additionally, ODSO’s effect on carbohydrate degrading enzymes, pancreatic α-amylase, and intestinal α-glucosidase was evaluated in vitro and in vivo using STZ-diabetic rats. The acute toxicity test on mice was performed, along with a single-dose hypoglycemic effect test. The results showed that ODSO significantly attenuated the postprandial hyperglycemia in normal and STZ-diabetic rats. Indeed, ODSO significantly decreased the intestinal d-glucose absorption in situ. The ex vivo test (Ussing chamber) showed that the ODSO significantly blocks the SGLT1 (IC₅₀ = 60.24 µg/mL). Moreover, ODSO indu\ced a significant inhibition of intestinal α-glucosidase (IC₅₀ = 278 ± 0.01 µg/mL) and pancreatic α-amylase (IC₅₀ = 0.81 ± 0.09 mg/mL) in vitro. A significant decrease of postprandial hyperglycemia was observed in sucrose/starch-loaded normal and STZ-diabetic ODSO-treated rats. On the other hand, ODSO had no risk of hypoglycemia on the basal glucose levels in normal rats. Therefore, no toxic effect was observed in ODSO-treated mice up to 7 mL/kg. The results of this study suggest that ODSO could be suitable as an antidiabetic functional food.

ATGL activity regulates GLUT1-mediated glucose uptake and lactate production via TXNIP stability in adipocytes

Traditionally, lipolysis has been regarded as an enzymatic activity that liberates fatty acids as metabolic fuel. However, recent work has shown that novel substrates, including a variety of lipid compounds such as fatty acids and their derivatives, release lipolysis products that act as signaling molecules and transcriptional modulators. While these studies have expanded the role of lipolysis, the mechanisms underpinning lipolysis signaling are not fully defined. Here, we uncover a new mechanism regulating glucose uptake, whereby activation of lipolysis, in response to elevated cAMP, leads to the stimulation of thioredoxin-interacting protein (TXNIP) degradation. This, in turn, selectively induces glucose transporter 1 surface localization and glucose uptake in 3T3-L1 adipocytes and increases lactate production. Interestingly, cAMP-induced glucose uptake via degradation of TXNIP is largely dependent upon adipose triglyceride lipase (ATGL) and not hormone-sensitive lipase or monoacylglycerol lipase. Pharmacological inhibition or knockdown of ATGL alone prevents cAMP-dependent TXNIP degradation and thus significantly decreases glucose uptake and lactate secretion. Conversely, overexpression of ATGL amplifies the cAMP response, yielding increased glucose uptake and lactate production. Similarly, knockdown of TXNIP elicits enhanced basal glucose uptake and lactate secretion, and increased cAMP further amplifies this phenotype. Overexpression of TXNIP reduces basal and cAMP-stimulated glucose uptake and lactate secretion. As a proof of concept, we replicated these findings in human primary adipocytes and observed TXNIP degradation and increased glucose uptake and lactate secretion upon elevated cAMP signaling. Taken together, our results suggest a crosstalk between ATGL-mediated lipolysis and glucose uptake.

Akkermansia muciniphila is Negatively Correlated with Hemoglobin A1c in Refractory Diabetes

Patients with refractory diabetes are defined as type 2 diabetes (T2D) patients; they cannot achieve optimal glycemic control and exhibit persistent elevations of hemoglobin A1c (HbA1c) ≥8% while on appropriate therapy. Hyperglycemia can lead to severe microvascular/macrovascular complications. However, in contrast to T2D, few studies have focused specifically on the gut microbiota in refractory diabetes. To examine this issue, we recruited 79 subjects with T2D and refractory diabetes (RT2D), and all subjects received standard therapy with Metformin or other hypoglycemic agents with or without insulin for at least one year. The α-diversity displayed no significant difference, whereas the β-diversity showed a marginal significance (p = 0.054) between T2D and RT2D. The evaluation of taxonomic indices revealed reductions in both Akkermansia muciniphila and Fusobacterium and a corresponding enrichment of Bacteroides vulgatus, Veillonella denticariosi among those with RT2D. These microbial markers distinguished RT2D from T2D with an acceptable degree of discrimination (area under the curve (AUC) = 0.719, p < 0.01) and were involved in several glucose-related functional pathways. Furthermore, the relative abundance of Akkermansia muciniphila was negatively correlated with HbA1c. Our combined results reveal unique features of the gut microbiota in RT2D and suggest that the evaluation of the gut microbiota could provide insights into the mechanisms underlying glycemic control and the impact of therapeutic modalities in patients with RT2D.

Skeletal muscle expression of adipose-specific phospholipase in peripheral artery disease

Flow-limiting atherosclerotic lesions of arteries supplying the limbs are a cause of symptoms in patients with peripheral artery disease (PAD). Musculoskeletal metabolic factors also contribute to the pathophysiology of claudication, which is manifest as leg discomfort that impairs walking capacity. Accordingly, we conducted a case-control study to determine whether skeletal muscle metabolic gene expression is altered in PAD. Calf skeletal muscle gene expression of patients with PAD and healthy subjects was analyzed using microarrays. The top-ranking gene differentially expressed between PAD and controls (FDR < 0.001) was PLA2G16, which encodes adipose-specific phospholipase A2 (AdPLA) and is implicated in the maintenance of insulin sensitivity and regulation of lipid metabolism. Differential expression was confirmed by qRT-PCR; PLA2G16 was downregulated by 68% in patients with PAD (p < 0.001). Expression of Pla2g16 was then measured in control (db/+) and diabetic (db/db) mice that underwent unilateral femoral artery ligation. There was significantly reduced expression of Pla2g16 in the ischemic leg of both control and diabetic mice (by 51%), with significantly greater magnitude of reduction in the diabetic mice (by 79%). We conclude that AdPLA is downregulated in humans with PAD and in mice with hindlimb ischemia. Reduced AdPLA may contribute to impaired walking capacity in patients with PAD via its effects on skeletal muscle metabolism. Further studies are needed to fully characterize the role of AdPLA in PAD and to investigate its potential as a therapeutic target for alleviating symptoms of claudication.

Apolipoprotein D

ApoD is a 25 to 30 kDa glycosylated protein, member of the lipocalin superfamily. As a transporter of several small hydrophobic molecules, its known biological functions are mostly associated to lipid metabolism and neuroprotection. ApoD is a multi-ligand, multi-function protein that is involved lipid trafficking, food intake, inflammation, antioxidative response and development and in different types of cancers. An important aspect of ApoD's role in lipid metabolism appears to involve the transport of arachidonic acid, and the modulation of eicosanoid production and delivery in metabolic tissues. ApoD expression in metabolic tissues has been associated positively and negatively with insulin sensitivity and glucose homeostasis in a tissue dependent manner. ApoD levels rise considerably in association with aging and neuropathologies such as Alzheimer's disease, stroke, meningoencephalitis, moto-neuron disease, multiple sclerosis, schizophrenia and Parkinson's disease. ApoD is also modulated in several animal models of nervous system injury/pathology.

The Combination Effect of Aspalathin and Phenylpyruvic Acid-2-O-β-D-glucoside from Rooibos against Hyperglycemia-Induced Cardiac Damage: An In Vitro Study

Recent evidence shows that rooibos compounds, aspalathin and phenylpyruvic acid-2-O-β-d-glucoside (PPAG), can independently protect cardiomyocytes from hyperglycemia-related reactive oxygen species (ROS). While aspalathin shows more potency by enhancing intracellular antioxidant defenses, PPAG acts more as an anti-apoptotic agent. Thus, to further understand the protective capabilities of these compounds against hyperglycemia-induced cardiac damage, their combinatory effect was investigated and compared to metformin. An in vitro model of H9c2 cardiomyocytes exposed to chronic glucose concentrations was employed to study the impact of such compounds on hyperglycemia-induced damage. Here, high glucose exposure impaired myocardial substrate utilization by abnormally enhancing free fatty acid oxidation while concomitantly suppressing glucose oxidation. This was paralleled by altered expression of genes involved in energy metabolism including acetyl-CoA carboxylase (ACC), 5′ AMP-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor-alpha (PPARα). The combination treatment improved myocardial substrate metabolism, maintained mitochondrial membrane potential, and attenuated various markers for oxidative stress including nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and glutathione content. It also showed a much-improved effect by ameliorating DNA damage when compared to metformin. The current study demonstrates that rooibos compounds offer unique cardioprotective properties against hyperglycemia-induced and potentially against diabetes-induced cardiac damage. These data also support further exploration of rooibos compounds to better assess the cardioprotective effects of different bioactive compound combinations.

The Antagonist Effect of Arachidonic Acid on GLUT4 Gene Expression by Nuclear Receptor Type II Regulation

OBJECTIVES

Obesity is a complex disease that has a strong association with diet and lifestyle. Dietary factors can influence the expression of key genes connected to insulin resistance, lipid metabolism, and adipose tissue composition. In this study, our objective was to determine gene expression and fatty acid (FA) profiles in visceral adipose tissue (VAT) from lean and morbidly obese individuals. We also aimed to study the agonist effect of dietary factors on glucose metabolism.

DESIGN AND METHODS

Lean and low and high insulin resistance morbidly obese subjects (LIR-MO and HIR-MO) were included in this study. The gene expression of liver X receptor type alpha (LXR-α) and glucose transporter type 4 (GLUT4) and the FA profiles in VAT were determined. Additionally, the in vivo and in vitro agonist effects of oleic acid (OA), linoleic acid (LA), and arachidonic acid (AA) by peroxisome proliferator-activated receptor type gamma 2 (PPAR-γ2) on the activity of GLUT4 were studied.

RESULTS

Our results showed a dysregulation of GLUT4 and LXR-α in VAT of morbidly obese subjects. In addition, a specific FA profile for morbidly obese individuals was found. Finally, AA was an PPAR-γ2 agonist that activates the expression of GLUT4.

CONCLUSIONS

Our study suggests a dysregulation of LXR-α and GLUT4 expression in VAT of morbidly obese individuals. FA profiles in VAT could elucidate their possible role in lipolysis and adipogenesis. Finally, AA binds to PPAR-γ2 to activate the expression of GLUT4 in the HepG2 cell line, showing an alternative insulin-independent activation of GLUT4.

Postgenomic Properties of Natural Micronutrients

Modern medical approaches to the therapy of various diseases, including cancer, are based on the use of toxic drugs. The unfavorable side effects of traditional medicine could be counterbalanced by addition of natural bioactive substances to conventional therapy due to their mild action on cells combined with the multitargeted effects. To elucidate the real mechanisms of their biological activity, versatile approaches including a number of "omics" such as genomics, transcriptomics, proteomics, and metabolomics are used. This review highlights inclusion of bioactive natural compounds into the therapy of chronic diseases from the viewpoint of modern omics-based nutritional biochemistry. The recently accumulated data argue for necessity to employ nutrigenetic and nutrimetabolomic analyses to prevent or diminish the risk of chronic diseases.

A new method to evaluate the dose-effect relationship of a TCM formula Gegen Qinlian Decoction: "Focus" mode of integrated biomarkers

It is difficult to accurately evaluate the efficacy of traditional Chinese medicine (TCM), which leads to the uncertainty and complexity of dose-effect analysis. In this study we established the "Focus" mode of biomarkers to characterize the dose-effect relationship of Gegen Qinlian Decoction (GQD), a TCM formula for treating type 2 diabetes mellitus (2-DM). A rat model of 2-DM was established through high fat diet feeding combined with low-dose STZ injection. Rats with 2-DM were administered high, middle or low doses (6.785, 4.071, 1.357 mg·kg^-1·d^-1, respectively) of GQD extract for 60 d. Metformin (300 mg·kg^-1·d^-1) was taken as the positive control. Blood samples were collected to assess serum biochemical indexes and metabolic profiling. After "Focus" analysis, the biochemical index triglycerides (TG) and insulin sensitivity (ISI) were identified as focused integrated biomarkers (FIBs), while arachidonic acid and docosatetraenoic acid were the metabolic FIBs. Dose-effect relationship curves of GQD were built based on these types of FIBs. Furthermore, the two dose-effect relationship curves showed similar trends with the middle dosage displaying the greatest efficacy, suggesting that insulin function and arachidonic acid metabolism played important roles in 2-DM and the responses to GQD. The metabolic FIB docosatetraenoic should be further explored for understanding its involvement in the process of 2-DM occurrence and the treatment. This "Focus" mode provides a novel strategy to evaluate the dose-effect relationship of a TCM. The system and concepts established here may also be applicable for assessing the dose-effect relationships of Western medicines.

Arachidonic acid sex-dependently affects obesity through linking gut microbiota-driven inflammation to hypothalamus-adipose-liver axis

Unraveling the role of dietary lipids is beneficial to treat obesity and metabolic dysfunction. Nonetheless, how dietary lipids affect existing obesity remains unknown. Arachidonic acid (AA), a derivative of linoleic acid, is one of the crucial n-6 fatty acids. The aim of this study was to investigate whether AA affects obesity through associating microbiota-driven inflammation with hypothalamus-adipose-liver axis. Four-week old C57BL/6J mice were fed with a high-fat diet (HFD, 45% fat) for 10weeks to induce obesity, and then fed a HFD enriched with 10g/kg of AA or a continuous HFD in the following 15weeks. Systemic adiposity and inflammation, metabolic profiles, gut microbiota composition, short-chain fatty acids production, hypothalamic feeding regulators, browning process of adipocytes, hepatosteatosis, and insulin resistance in adipose were investigated. The results indicated that AA aggravates obesity for both genders whereas sex-dependently affects gut microbiota composition. Also, AA favors pro-inflammatory microbiota and reduces butyrate production and circulating serotonin, which augments global inflammation and triggers hypothalamic leptin resistance via microglia accumulation in male. AA exacerbates non-alcoholic steatohepatitis along with amplified inflammation through TLR4-NF-κB pathway and induces insulin resistance. Reversely, AA alleviates obesity-related disorders via rescuing anti-inflammatory and butyrate-producing microbiota, up-regulating GPR41 and GPR109A and controlling hypothalamic inflammation in female. Nevertheless, AA modifies adipocyte browning and promotes lipid mobilization for both genders. We show that AA affects obesity likely through a gut-hypothalamus-adipose-liver axis. Our findings formulate recommendations of n-6 fatty acids like AA from dietary intake for obese subjects preferably in a sexually dimorphic way.

Interaction of an S100A9 gene variant with saturated fat and carbohydrates to modulate insulin resistance in 3 populations of different ancestries

BACKGROUND

S100 calcium-binding protein A9 (S100A9) has previously been identified as a type 2 diabetes (T2D) gene. However, this finding requires independent validation and more in-depth analyses in other populations and ancestries.

OBJECTIVES

We aimed to replicate the associations between an S100A9 variant and insulin resistance and T2D and to initiate an investigation of potential interactions with the habitual diet in several independent populations.

DESIGN

We investigated the association of the S100A9 variant rs3014866 with insulin resistance and T2D risk and its interactions with diet in 3 diverse populations as follows: the CORDIOPREV (Coronary Diet Intervention with Olive Oil and Cardiovascular Prevention; n = 711), which consisted of Spanish white adults; the GOLDN (Genetics of Lipids Lowering Drugs and Diet Network; n = 818), which involved North American non-Hispanic white adults; and Hispanic adults who participated in the BPRHS (Boston Puerto Rican Health Study; n = 1155).

RESULTS

Meta-analysis indicated that T carriers presented a lower risk of T2D than CC carriers (pooled OR: 0.714; 95% CI: 0.584, 0.845; P = 0.002). In all 3 populations (CORDIOPREV, GOLDN, and BPRHS), we showed a significant interaction between the rs3014866 single nucleotide polymorphism and dietary SFA:carbohydrate ratio intake for the homeostasis model assessment of insulin resistance (HOMA-IR) (P = 0.028, P = 0.017, and P = 0.026, respectively). CC carriers had a significantly higher HOMA-IR only when SFA:carbohydrate intake was high (P = 0.045 for the CORDIOPREV, P = 0.033 for the GOLDN, and P = 0.046 for the BPRHS) but not when SFA:carbohydrate ratio intake was low.

CONCLUSIONS

The minor allele (T) of the S100A9 variant rs3014866 is associated with lower T2D risk in 3 populations of different ancestries. Note that individuals with the high-risk CC genotype may be more likely to benefit from a low SFA:carbohydrate ratio intake to improve insulin resistance as evaluated with the use of the HOMA-IR. These trials were registered at clinicaltrials.gov as NCT00924937 (CORDIOPREV), NCT00083369 (GOLDN), and NCT01231958 (BPRHS).

Aspalathin, a dihydrochalcone C-glucoside, protects H9c2 cardiomyocytes against high glucose induced shifts in substrate preference and apoptosis

SCOPE

Energy deprivation in the myocardium is associated with impaired heart function. This study aims to investigate if aspalathin (ASP) can ameliorate hyperglycemic-induced shift in substrate preference and protect the myocardium against cell apoptosis.

METHODS AND RESULTS

H9c2 cells were exposed to, either normal (5.5 mM) or high (33 mM) glucose concentrations for 48 h. Thereafter, cells exposed to 33 mM glucose were treated with metformin (1 μM) or ASP (1 μM), as well as a combination of metformin and ASP for 6 h. In vitro studies revealed that ASP improved glucose metabolism by decreasing fatty acid uptake and subsequent β-oxidation through the decreased expression of adenosine monophosphate-activated protein kinase threonine 172 (pAMPK (Thr172)) and carnitine palmitoyltransferase 1 (CPT1), while increasing acetyl-CoA carboxylase (ACC) and glucose transporter 4 (GLUT4) expression. ASP inhibited high glucose induced loss of membrane potential in H9c2 cells as observed by an increase in 5' ,6,6'-tetrachloro-1,1',3,3' -tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) ratio (orange\red fluorescence) and decreased apoptosis by reducing intracellular reactive oxygen species and DNA nick formation, while increasing glutathione, superoxide dismutase, uncoupling protein 2 (UCP2), and Bcl-2\Bax ratio.

CONCLUSION

Our study provides evidence that ASP increases glucose oxidation and modulates fatty acid utilization producing a favorable substrate shift in H9c2 cardiomyocytes exposed to high glucose. Such a favorable shift will be of importance in the protection of cardiomyocytes in the diabetic heart.

BmPLA2 containing conserved domain WD40 affects the metabolic functions of fat body tissue in silkworm, Bombyx mori

PLA2 enzyme hydrolyzes arachidonic acid, and other polyunsaturated fatty acids, from the sn-2 position to release free arachidonic acid and a lysophospholipid. Previous studies reported that the PLA2 in invertebrate organisms participates in lipid signaling molecules like arachidonic acid release in immune-associated tissues like hemocytes and fat bodies. In the present study, we cloned the BmPLA2 gene from fat body tissue of silkworm Bombyx mori, which has a total sequence of 1.031 kb with a 31.90 kDa protein. In silico results of BmPLA2 indicated that the protein has a putative WD40 conserved domain and its phylogeny tree clustered with Danaus plexippus species. We investigated the transcriptional expression in development stages and tissues. The highest expression of BmPLA2 was screened in fat body among the studied tissues of third day fifth instar larva, with a high expression on third day fifth instar larva followed by a depression of expression in the wandering stage of the fifth instar larva. The expression of BmPLA2 in female pupa was higher than that of male pupa. Our RNAi-mediated gene silencing results showed highest reduction of BmPLA2 expression in post-24 h followed by post-48 and post-72 h. The BmPLA2-RNAi larvae and pupa could be characterized by pharate adult lethality and underdevelopment. The phenotypic characters of fat body cells in RNAi-induced larva implied that BmPLA2 affects the metabolic functions of fat body tissue in silkworm Bombyx mori.

In vitro evaluation of anti-diabetic activity and cytotoxicity of chemically analysed Ocimum basilicum extracts

The aim of this study was to evaluate the role of glucose transporter-4 (GLUT4) in the anti-diabetic effects of methanol, hexane and dichloromethane extracts of the aerial parts of Ocimum basilicum (OB) and to analyze their phytochemical composition. Phytochemical analysis of the three extracts by GC/MS using the silylation derivatization technique revealed 53 compounds, 17 of them were found for the first time in OB. Cytotoxic and anti-diabetic properties of the extracts were evaluated using L6-GLUT4myc muscle cells stably expressing myc epitope at the exofacial loop (GLUT4). No cytotoxic effects were observed in treated cells up to 0.25 mg/ml extract as measured with MTT and LDH-leakage assays. GLUT4 translocation to the plasma membrane was elevated by 3.5 and 7 folds (-/+ insulin) after treatment with OB extracts for 20 h. Our findings suggest that the observed anti-diabetic properties of OB extracts are possibly mediated in part through one or more of the 17 new identified compound.

Aspalathin improves glucose and lipid metabolism in 3T3-L1 adipocytes exposed to palmitate

SCOPE

Saturated-free fatty acids, such as palmitate, are associated with insulin resistance. This study aimed to establish if an aspalathin-enriched green rooibos extract (GRE) and, its major flavanoid, aspalathin (ASP) could contribute significantly to the amelioration of experimentally induced insulin resistance in 3T3-L1 adipocytes.

METHODS AND RESULTS

3T3-L1 adipocytes were cultured in DMEM containing 0.75 mM palmitate for 16 h to induce insulin resistance before treatment for 3 h with GRE (10 μg/mL) or ASP (10 μM). GRE and ASP reversed the palmitate-induced insulin resistance. At a protein level GRE and ASP suppressed nuclear factor kappa beta (NF-κB), insulin receptor substrate one (serine 307) (IRS1 (Ser (307) )) and AMP-activated protein kinase phosphorylation and increased serine/threonine kinase AKT (AKT) activation, while only GRE increased glucose transporter four (Glut4) protein expression. Peroxisome proliferator-activated receptor alpha and gamma (PPARα and γ), and carnitine palmitoyltransferase one (CPT1) expression were increased by ASP alone.

CONCLUSION

Together these effects offer a plausible explanation for the ameliorative effect of GRE and ASP on insulin-resistance, an underlying cause for obesity and type 2 diabetes.

Arachidonic acid has a dominant effect to regulate lipogenic genes in 3T3-L1 adipocytes compared to omega-3 fatty acids

BACKGROUND

The effects of long-chain n-3 and n-6 polyunsaturated fatty acids (PUFA) on the regulation of adipocytes metabolism are well known. These fatty acids are generally consumed together in our diets; however, the metabolic regulation of adipocytes in the presence of these fatty acids when given together is not known.

OBJECTIVE

To investigate the effects of n-3 PUFA and arachidonic acid (AA), an n-6 PUFA, on the regulation of adipogenic and lipogenic genes in mature 3T3-L1 adipocytes.

METHODS

3T3-L1 adipocytes were incubated in the presence or absence of 100 µM of eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA; docosapentaenoic acid, DPA and AA, either alone or AA+n-3 PUFA; control cells received bovine serum albumin alone. The mRNA expression of adipogenic and lipogenic genes was measured. The fatty acid composition of adipocytes was analyzed using gas chromatography.

RESULTS

Individual n-3 PUFA or AA had no effect on the mRNA expression of peroxisome-proliferator-activated receptor-γ; however, AA+EPA and AA+DPA significantly increased (P<0.05) the expression compared to control cells (38 and 42%, respectively). AA and AA+EPA increased the mRNA expression of acetyl-CoA carboxylase 1 (P<0.05). AA treatment decreased the mRNA expression of stearoyl-CoA desaturase (SCD1) (P<0.01), while n-3 PUFA, except EPA, had no effect compared to control cells. AA+DHA and AA+DPA inhibited SCD1 gene expression (P<0.05) suggesting a dominant effect of AA. Fatty acids analysis of adipocytes revealed a higher accretion of AA compared to n-3 PUFA.

CONCLUSIONS

Our findings reveal that AA has a dominant effect on the regulation of lipogenic genes in adipocytes.

Lipid signaling in adipose tissue: Connecting inflammation & metabolism

Obesity-associated low-grade inflammation of white adipose tissue (WAT) contributes to development of insulin resistance and other disorders. Accumulation of immune cells, especially macrophages, and macrophage polarization from M2 to M1 state, affect intrinsic WAT signaling, namely anti-inflammatory and proinflammatory cytokines, fatty acids (FA), and lipid mediators derived from both n-6 and n-3 long-chain PUFA such as (i) arachidonic acid (AA)-derived eicosanoids and endocannabinoids, and (ii) specialized pro-resolving lipid mediators including resolvins derived from both eicosapentaenoic (EPA) and docosahexaenoic acid (DHA), lipoxins (AA metabolites), protectins and maresins (DHA metabolites). In this respect, potential differences in modulating adipocyte metabolism by various lipid mediators formed by inflammatory M1 macrophages typical of obese state, and non-inflammatory M2 macrophages typical of lean state remain to be established. Studies in mice suggest that (i) transient accumulation of M2 macrophages could be essential for the control of tissue FA levels during activation of lipolysis, (ii) currently unidentified M2 macrophage-borne signaling molecule(s) could inhibit lipolysis and re-esterification of lipolyzed FA back to triacylglycerols (TAG/FA cycle), and (iii) the egress of M2 macrophages from rebuilt WAT and removal of the negative feedback regulation could allow for a full unmasking of metabolic activities of adipocytes. Thus, M2 macrophages could support remodeling of WAT to a tissue containing metabolically flexible adipocytes endowed with a high capacity of both TAG/FA cycling and oxidative phosphorylation. This situation could be exemplified by a combined intervention using mild calorie restriction and dietary supplementation with EPA/DHA, which enhances the formation of "healthy" adipocytes. This article is part of a Special Issue entitled Oxygenated metabolism of PUFA: analysis and biological relevance."

Evaluation of antidiabetic properties of cactus pear seed oil in rats

CONTEXT

Cactus pear (Opuntia ficus-indica (L.) Mill. (Cactaceae)) is a medicinal plant widely used to treat diabetes.

OBJECTIVE

This work investigates the hypoglycemic and antihyperglycemic effect of cactus pear seed oil (CPSO), its mechanism of action, and any toxic effects.

MATERIALS AND METHODS

The hypoglycemic effect of CPSO was evaluated in groups of six healthy Wistar rats given 1 or 2 ml kg(-1) orally and compared with groups receiving glibenclamide (2 mg kg(-1)) or water. Glycemia was determined after 30, 60, 120, 240, and 360 min. The antihyperglycemic effect of CPSO was determined in healthy rats and in streptozotocin-induced diabetic rats (STZ); normal rats received 0.8 ml kg(-1) CPSO, while diabetic rats received 1 ml kg(-1) CPSO, their controls received water or 2 mg kg(-1) glibenclamide. For the antihyperglycemic effect evaluation, all the animals were fasted for 16 h before treatment and received glucose orally at 1 g kg(-1) 30 min after treatment; blood was taken after 30, 90, 150, and 210 min. Intestinal glucose absorption was estimated in rat jejunum perfused with a solution containing 5.55 mmol l(-1) glucose. Acute toxicity was determined in albino mice that received oral or intraperitoneal doses of 1, 3, or 5 ml kg(-1) CPSO.

RESULTS

CPSO (p.o.) decreased postprandial hyperglycemia (60 min after glucose loading), 40.33% and 16.01%, in healthy and STZ-diabetic glucose-loaded rats, respectively. CPSO, also, significantly decreased intestinal glucose absorption by 25.42%. No adverse effects were seen in mice administered CPSO at up to 5 ml kg(-1).

CONCLUSION

CPSO is antihyperglycemic. The effect can be explained partly by inhibition of intestinal glucose absorption.

Dietary combination of sucrose and linoleic acid causes skeletal muscle metabolic abnormalities in Zucker fatty rats through specific modification of fatty acid composition

A dietary combination of sucrose and linoleic acid strongly contributes to the development of metabolic disorders in Zucker fatty rats. However, the underlying mechanisms of the metabolic disorders are poorly understood. We hypothesized that the metabolic disorders were triggered at a stage earlier than the 8 weeks we had previously reported. In this study, we investigated early molecular events induced by the sucrose and linoleic acid diet in Zucker fatty rats by comparison with other combinations of carbohydrate (sucrose or palatinose) and fat (linoleic acid or oleic acid). Skeletal muscle arachidonic acid levels were significantly increased in the sucrose and linoleic acid group compared to the other dietary groups at 4 weeks, while there were no obvious differences in the metabolic phenotype between the groups. Expression of genes related to arachidonic acid synthesis was induced in skeletal muscle but not in liver and adipose tissue in sucrose and linoleic acid group rats. In addition, the sucrose and linoleic acid group exhibited a rapid induction in endoplasmic reticulum stress and abnormal lipid metabolism in skeletal muscle. We concluded that the dietary combination of sucrose and linoleic acid primarily induces metabolic disorders in skeletal muscle through increases in arachidonic acid and endoplasmic reticulum stress, in advance of systemic metabolic disorders.

Factors determining insulin requirements in women with type 1 diabetes mellitus during pregnancy: a review

Most women with type 1 diabetes mellitus (T1DM) have increased insulin requirements during pregnancy. However, a minority of women have a fall in insulin requirements. When this occurs in late gestation, it often provokes concern regarding possible compromise of the feto-placental unit. In some centres, this is considered as an indication for delivery, including premature delivery. There are, however, many other factors that affect insulin requirements in pregnancy in women with type 1 diabetes mellitus and the decline in insulin requirements may represent a variant of normal pregnancy. If there is no underlying pathological process, expedited delivery in these women is not warranted and confers increased risks to the newborn. We will explore the factors affecting insulin requirements in gestation in this review. We will also discuss some novel concepts regarding beta-cell function in pregnancy.

Metabolic signatures of cultured human adipocytes from metabolically healthy versus unhealthy obese individuals

Background and Aims

Among obese subjects, metabolically healthy and unhealthy obesity (MHO/MUHO) can be differentiated: the latter is characterized by whole-body insulin resistance, hepatic steatosis, and subclinical inflammation. Aim of this study was, to identify adipocyte-specific metabolic signatures and functional biomarkers for MHO versus MUHO.

Methods

10 insulin-resistant (IR) vs. 10 insulin-sensitive (IS) non-diabetic morbidly obese (BMI >40 kg/m²) Caucasians were matched for gender, age, BMI, and percentage of body fat. From subcutaneous fat biopsies, primary preadipocytes were isolated and differentiated to adipocytes in vitro. About 280 metabolites were investigated by a targeted metabolomic approach intracellularly, extracellularly, and in plasma.

Results/Interpretation

Among others, aspartate was reduced intracellularly to one third (p = 0.0039) in IR adipocytes, pointing to a relative depletion of citric acid cycle metabolites or reduced aspartate uptake in MUHO. Other amino acids, already known to correlate with diabetes and/or obesity, were identified to differ between MUHO's and MHO's adipocytes, namely glutamine, histidine, and spermidine. Most species of phosphatidylcholines (PCs) were lower in MUHO's extracellular milieu, though simultaneously elevated intracellularly, e.g., PC aa C32∶3, pointing to increased PC synthesis and/or reduced PC release. Furthermore, altered arachidonic acid (AA) metabolism was found: 15(S)-HETE (15-hydroxy-eicosatetraenoic acid; 0 vs. 120pM; p = 0.0014), AA (1.5-fold; p = 0.0055) and docosahexaenoic acid (DHA, C22∶6; 2-fold; p = 0.0033) were higher in MUHO. This emphasizes a direct contribution of adipocytes to local adipose tissue inflammation. Elevated DHA, as an inhibitor of prostaglandin synthesis, might be a hint for counter-regulatory mechanisms in MUHO.

Conclusion/Interpretation

We identified adipocyte-inherent metabolic alterations discriminating between MHO and MUHO.

12- and 15-lipoxygenases in adipose tissue inflammation

The lipoxygenases (LOs) are principal enzymes involved in the oxidative metabolism of polyunsaturated fatty acids, including arachidonic acid. 12- and 15-LO and their lipid metabolites have been implicated in the development of insulin resistance and diabetes. Adipose tissue, and in particular visceral adipose tissue, plays a primary role in the development of the inflammation seen in these conditions. 12- and 15-LO and their lipid metabolites act as upstream regulators of many of the cytokines involved in the inflammatory response in adipose tissue. While the role that 12- and 15-LO play in chronically inflamed adipose tissue is becoming clearer, there are still many questions that remain unanswered regarding their activation, signaling pathways, and roles in healthy fat. 12- and 15-LO also generate products with anti-inflammatory properties that are under investigation. Therefore, 12- and 15-LO have the potential to be very important targets for therapeutics aimed at reducing insulin resistance and the comorbid conditions associated with obesity.

Validation of the Antidiabetic and Hypolipidemic Effects of Hawthorn by Assessment of Gluconeogenesis and Lipogenesis Related Genes and AMP-Activated Protein Kinase Phosphorylation

Since with the increased use of antidiabetic and antihyperlipidemic effect of phytonutrients for daily supplement has gained considerable attention worldwide, we examine the effect and molecular mechanism of Crataegus pinnatifida Bge. var. major N.E. Br. (hawthorn) by quantifying the expression of hepatic gluconeogenesis and lipogenesis on diabetes and dyslipidemia in high-fat (HF)-fed C57BL/6J mice. Firstly, mice were divided randomly into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was given orally hawthorn extract (including 0.2, 0.5, 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks afterward. Diabetic mice showed an increase in plasma glucose and insulin. Glucose lowering was comparable with Rosi-treated mice. This study demonstrated that hawthorn was effective in ameliorating the HF diet-induced hyperglycemia, hypertriglyceridemia and hypercholesterolaemia. Hawthorn extract significantly increases the hepatic protein contents of AMP-activated protein kinase (AMPK) phosphorylation and reduces expression of phosphenol pyruvate carboxykinase (PEPCK) and glucose production. Furthermore, hawthorn decreased in hepatic triacylglycerol and cholesterol synthesis (including sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), SREBP2). An increase in expressions of apoA-I gene and high-density lipoprotein cholesterol (HDL-C) was detected in HF-fed mice treated with high dose hawthorn. Our data suggest that hawthorn extract are capable of decreasing glucose production and triacylglycerol synthesis by inducing AMPK-phosphorylation and hawthorn is a candidate source of antidiabetic and antihyperlipidemic phytonutrients factors.

Effect of eriodictyol on glucose uptake and insulin resistance in vitro

Eriodictyol [2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-2,3-dihydrochromen-4-one] is a flavonoid with anti-inflammatory and antioxidant activities. Because inflammation and oxidative stress play critical roles in the pathogenesis of diabetes mellitus, the present study was designed to explore whether eriodictyol has therapeutic potential for the treatment of type 2 diabetes. The results show that eriodictyol increased insulin-stimulated glucose uptake in both human hepatocellular liver carcinoma cells (HepG2) and differentiated 3T3-L1 adipocytes under high-glucose conditions. Eriodictyol also up-regulated the mRNA expression of peroxisome proliferator-activated receptor γ2 (PPARγ2) and adipocyte-specific fatty acid-binding protein (aP2) as well as the protein levels of PPARγ2 in differentiated 3T3-L1 adipocytes. Furthermore, it reactivated Akt in HepG2 cells with high-glucose-induced insulin resistance. This response was strongly inhibited by pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, indicating that eriodictyol increased Akt phosphorylation by activating the PI3K/Akt pathway. These results imply that eriodictyol can increase glucose uptake and improve insulin resistance, suggesting that it may possess antidiabetic properties.

The role of dietary fatty acids in the pathology of metabolic syndrome

Dysfunctional lipid metabolism is a key component in the development of metabolic syndrome, a very frequent condition characterized by dyslipidemia, insulin resistance, abdominal obesity and hypertension, which are related to an elevated risk for type 2 diabetes mellitus. The prevalence of metabolic syndrome is strongly associated with the severity of obesity; its physiopathology is related to both genetics and food intake habits, especially the consumption of a high-caloric, high-fat and high-carbohydrate diet. With the progress of scientific knowledge in the field of nutrigenomics, it was possible to elucidate how the majority of dietary fatty acids influence plasma lipid metabolism and also the genes expression involved in lipolysis and lipogenesis within hepatocytes and adipocytes. The aim of this review is to examine the relevant mechanistic aspects of dietary fatty acids related to blood lipids, adipose tissue metabolism, hepatic fat storage and inflammatory process, all of them closely related to the genesis of metabolic syndrome.

Adipocyte expression of PU.1 transcription factor causes insulin resistance through upregulation of inflammatory cytokine gene expression and ROS production

We have reported previously that ETS family transcription factor PU.1 is expressed in mature adipocytes of white adipose tissue. PU.1 expression is increased greatly in mouse models of genetic or diet-induced obesity. Here, we show that PU.1 expression is increased only in visceral but not subcutaneous adipose tissues of obese mice, and the adipocytes are responsible for this increase in PU.1 expression. To further address PU.1's physiological function in mature adipocytes, PU.1 was knocked down in 3T3-L1 cells using retroviral-mediated expression of PU.1-targeting shRNA. Consistent with previous findings that PU.1 regulates its target genes, such as NADPH oxidase subunits and proinflammatory cytokines in myeloid cells, the mRNA levels of proinflammatory cytokines (TNFα, IL-1β, and IL-6) and cytosolic components of NADPH oxidase (p47phox and p40phox) were downregulated significantly in PU.1-silenced adipocytes. NADPH oxidase is a main source for reactive oxygen species (ROS) generation. Indeed, silencing PU.1 suppressed NADPH oxidase activity and attenuated ROS in basal or hydrogen peroxide-treated adipocytes. Silencing PU.1 in adipocytes suppressed JNK1 activation and IRS-1 phosphorylation at Ser(307). Consequently, PU.1 knockdown improved insulin signaling and increased glucose uptake in basal and insulin-stimulated conditions. Furthermore, knocking down PU.1 suppressed basal lipolysis but activated stimulated lipolysis. Collectively, these findings indicate that obesity induces PU.1 expression in adipocytes to upregulate the production of ROS and proinflammatory cytokines, both of which lead to JNK1 activation, insulin resistance, and dysregulation of lipolysis. Therefore, PU.1 might be a mediator for obesity-induced adipose inflammation and insulin resistance.

Lipid peroxidation of poly-unsaturated fatty acids in normal and obese adipose tissues

Adipose tissues function as the primary storage compartment of fatty acids and as an endocrine organ that affects peripheral tissues. Many of adipose tissue-derived factors, often termed adipokines, have been discovered in recent years. The synthesis and secretion of these factors vary in different depots of adipose tissues. Excessive lipid accumulation in adipocytes induces inflammatory processes by up-regulating the expression and release of pro-inflammatory cytokines. In addition, activated macrophages in the obese adipose tissue release inflammatory cytokines. Adipose tissue inflammation has also been linked to an enhanced metabolism of polyunsaturated fatty acids (PUFAs). The non-enzymatic peroxidation of PUFAs and of their 12/15-lipoxygenase-derived hydroperoxy metabolites leads to the generation of the reactive aldehyde species 4-hydroxyalkenals. This review shows that 4-hydroxyalkenals, in particular 4-hydroxynonenal, play a key role in lipid storage homeostasis in normal adipocytes. Nonetheless, in the obese adipose tissue an increased production of 4-hydroxyalkenals contributes to the inflamed phenotype.

Palmitic acid acutely stimulates glucose uptake via activation of Akt and ERK1/2 in skeletal muscle cells

Chronic exposure to saturated fatty acids can cause insulin resistance. However, the acute effects of fatty acids are not clear and need to be elucidated because plasma fatty acid concentrations fluctuate postprandially. Here, we present the acute effects of palmitate (PA) on skeletal muscle cells and their underlying molecular mechanisms. Immuno-fluorescence results showed that PA rapidly induced GLUT4 translocation and stimulated glucose uptake in rat skeletal muscle cell line L6. Phosphorylation of AMP-activated protein kinase (AMPK), Akt, and extracellular signal-related kinase1/2 (ERK1/2) was enhanced by PA in a time-dependent manner. Cell surface-bound PA was sufficient to stimulate Akt phosphorylation. The inhibitors of PI3 kinase (PI3K), AMPK, Akt, and ERK1/2 could decrease PA-induced glucose uptake, and PI3K inhibitor decreased AMPK, Akt, and ERK1/2 phosphorylation. Weakening AMPK activity reduced phosphorylation of Akt but not ERK1/2, and Akt inhibitor could not affect ERK1/2 activation either. Meanwhile, ERK1/2 inhibitors had no effect on Akt phosphorylation. Taken together, our data suggest that PA-mediated glucose uptake in skeletal muscle cells may be stimulated by the binding of PA to cell surface and followed by PI3K/AMPK/Akt and PI3K/ERK1/2 pathways independently.

Functional and pathological roles of the 12- and 15-lipoxygenases

The 12/15-lipoxygenase enzymes react with fatty acids producing active lipid metabolites that are involved in a number of significant disease states. The latter include type 1 and type 2 diabetes (and associated complications), cardiovascular disease, hypertension, renal disease, and the neurological conditions Alzheimer's disease and Parkinson's disease. A number of elegant studies over the last thirty years have contributed to unraveling the role that lipoxygenases play in chronic inflammation. The development of animal models with targeted gene deletions has led to a better understanding of the role that lipoxygenases play in various conditions. Selective inhibitors of the different lipoxygenase isoforms are an active area of investigation, and will be both an important research tool and a promising therapeutic target for treating a wide spectrum of human diseases.

Role of caveolin-3 and glucose transporter-4 in isoflurane-induced delayed cardiac protection

BACKGROUND

Caveolae are small, flask-like invaginations of the plasma membrane. Caveolins are structural proteins found in caveolae that have scaffolding properties to allow organization of signaling. The authors tested the hypothesis that delayed cardiac protection induced by volatile anesthetics is caveolae or caveolin dependent.

METHODS

An in vivo mouse model of ischemia-reperfusion injury with delayed anesthetic preconditioning (APC) was tested in wild-type, caveolin-1 knockout, and caveolin-3 knockout mice. Mice were exposed to 30 min of oxygen or isoflurane and allowed to recover for 24 h. After 24 h recovery, mice underwent 30-min coronary artery occlusion followed by 2 h of reperfusion at which time infarct size was determined. Biochemical assays were also performed in excised hearts.

RESULTS

Infarct size as a percent of the area at risk was reduced by isoflurane in wild-type (24.0 +/- 8.8% vs. 45.1 +/- 10.1%) and caveolin-1 knockout mice (27.2 +/- 12.5%). Caveolin-3 knockout mice did not show delayed APC (41.5 +/- 5.0%). Microscopically distinct caveolae were observed in wild-type and caveolin-1 knockout mice but not in caveolin-3 knockout mice. Delayed APC increased the amount of caveolin-3 protein but not caveolin-1 protein in discontinuous sucrose-gradient buoyant fractions. In addition, glucose transporter-4 was increased in buoyant fractions, and caveolin-3/glucose transporter-4 colocalization was observed in wild-type and caveolin-1 knockout mice after APC.

CONCLUSIONS

These results show that delayed APC involves translocation of caveolin-3 and glucose transporter-4 to caveolae, resulting in delayed protection in the myocardium.

Momordica charantia extract on insulin resistance and the skeletal muscle GLUT4 protein in fructose-fed rats

AIM OF THE STUDY

We investigated the preventive effect of Momordica charantia Linn. (Cucurbitaceae) fruit, commonly known as bitter melon, on hyperglycemia and insulin resistance in rats fed with a fructose-enriched diet.

MATERIALS AND METHODS

First, rats were divided randomly into two groups: the control group was fed with control diet, whereas the experimental group was fed with a 60% high-fructose diet for 8 weeks. After the first 6 weeks, the fructose-treated rats were further subdivided into six groups and were orally fed with or without Momordica charantia L. or rosiglitazone (ROS) for 2 weeks while rats were still on fructose diet.

RESULTS

We demonstrated that bitter melon was effective in ameliorating the fructose diet-induced hyperglycemia, hyperleptinemia, hyperinsulinemia, and hypertriglyceridemia as well as in decreasing the levels of free fatty acid (FFA) (P<0.001, P<0.05, P<0.05, P<0.05, P<0.05, respectively). Bitter melon reversed fructose diet-induced hypoadiponectinemia (P<0.05), which provides a therapeutic advantage to insulin resistance in improving insulin sensitivity. Additionally, bitter melon decreased the weights of epididymal (P<0.05) and retroperitoneal white adipose tissue (WAT) (P<0.05). Bitter melon increased the expression of peroxisome proliferator-activated receptor gamma (PPAR gamma) in white adipose tissue (WAT). Conversely, bitter melon decreased the expression of leptin in WAT. Furthermore, we demonstrate that bitter melon significantly increases the mRNA expression and protein of glucose transporter 4 (GLUT4) in skeletal muscle.

CONCLUSIONS

This study demonstrates, for the first time, the beneficial effects of two different extracts of bitter melon on insulin resistance in rats fed a high-fructose diet thereby producing evidence of the role of changes in expression of PPAR gamma and GLUT4.