Proteomic analysis of aorta and protective effects of grape seed procyanidin B2 in db/db mice reveal a critical role of milk fat globule epidermal growth factor-8 in diabetic arterial damage

Ginsenoside Rb1 combined with Lycium barbarum polysaccharide alleviate the Tripterygium wilfordii polyglycoside-induced oligoasthenozoospermia in mice by inhibiting ZnT3-mediated oxidative stress response

BACKGROUND

Oligoasthenozoospermia (OAS) is one of the main causes of male infertility. Studies have shown that ginsenoside Rb1 (GRb1) and Lycium barbarum polysaccharide (LBP) have great potential in treating OAS. This study aims to investigate the effects of combined GRb1 and LBP treatment on OAS and the underlying molecular mechanisms.

METHODS

The Tripterygium wilfordii polyglycoside (GTW)-induced mouse model and H2O2-induced cell model were intervened with GRb1 and LBP. HE staining and Johnson score were used to evaluate the degree of testicular injury. Then, sperm quality was evaluated, and the levels of sperm-related hormones were measured. The regulatory effect of GRb1 and LBP on oxidative stress in OAS mice and cells was explored. In addition, total zinc content in testicular tissues and GC-2 cells was measured, and the mRNA and protein expression levels of zinc transporter 3 (ZnT3) were detected.

RESULTS

In the OAS model of mice treated with GRb1 and LBP, the coefficient of testis and epididymis were increased, and the degree of damage and sperm quality were significantly improved. Serum levels of T, LH, and FSH were increased in mice. Moreover, inhibition of ZnT3 signaling increased total intracellular zinc content in GC-2 cells. Overexpression of ZnT3 reversed the inhibitory effects of the combination of GRb1 and LBP on oxidative stress and the therapeutic effects in OAS mice.

CONCLUSION

The combined treatment of GRb1 and LBP could inhibit oxidative stress response by down-regulating ZnT3 signaling, thereby improving OAS mice. This provided a new strategy for the drug treatment of OAS.

Omics research in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease characterized by lipid deposition within the arterial intima, as well as fibrous tissue proliferation and calcification. AS has long been recognized as one of the primary pathological foundations of cardiovascular diseases in humans. Its pathogenesis is intricate and not yet fully elucidated. Studies have shown that AS is associated with oxidative stress, inflammatory response, lipid deposition, and changes in cell phenotype. Unfortunately, there is currently no effective prevention or targeted treatment for AS. The rapid advancement of omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, has opened up novel avenues to elucidate the fundamental pathophysiology and associated mechanisms of AS. Here, we review articles published over the past decade and focus on the current status, challenges, limitations, and prospects of omics in AS research and clinical practice. Emphasizing potential targets based on omics technologies will improve our understanding of this pathological condition and assist in the development of potential therapeutic approaches for AS-related diseases.

The application of procyanidins in diabetes and its complications: a review of preclinical studies

Diabetes mellitus (DM) and its various complications, including diabetic nephropathy, retinopathy, neuropathy, cardiovascular disease, and ulcers, pose significant challenges to global health. This review investigates the potential of procyanidins (PCs), a natural polyphenolic compound, in preventing and managing diabetes and its complications. PCs, recognized for their strong antioxidant, anti-inflammatory, and anti-hyperglycemic properties, play a crucial role in reducing oxidative stress and enhancing endothelial function, which are essential for managing diabetic complications. This review elucidates the molecular mechanisms by which PCs improve insulin sensitivity and endothelial health, thereby providing protection against the various complications of diabetes. The comprehensive analysis underscores the promising therapeutic role of PCs in diabetes care, indicating the need for further clinical studies to confirm and leverage their potential in comprehensive diabetes management strategies.

Bioactive Flavonoids in Protecting Against Endothelial Dysfunction and Atherosclerosis

Atherosclerosis is a common cardiovascular disease closely associated with factors such as hyperlipidaemia and chronic inflammation. Among them, endothelial dysfunction serves as a major predisposing factor. Vascular endothelial dysfunction is manifested by impaired endothelium-dependent vasodilation, enhanced oxidative stress, chronic inflammation, leukocyte adhesion and hyperpermeability, endothelial senescence, and endothelial-mesenchymal transition (EndoMT). Flavonoids are known for their antioxidant activity, eliminating oxidative stress induced by reactive oxygen species (ROS), thereby preventing the oxidation of low-density lipoprotein (LDL) cholesterol, reducing platelet aggregation, alleviating ischemic damage, and improving vascular function. Flavonoids have also been shown to possess anti-inflammatory activity and to protect the cardiovascular system. This review focuses on the protective effects of these naturally-occuring bioactive flavonoids against the initiation and progression of atherosclerosis through their effects on endothelial cells including, but not limited to, their antioxidant, anti-inflammatory, anti-thrombotic, and lipid-lowering properties. However, more clinical evidences are still needed to determine the exact role and optimal dosage of these compounds in the treatment of atherosclerosis.

Contribution of circulating Mfge8 to human T2DM and cardiovascular disease

MFGE8 is a major exosome (EV) protein known to mediate inflammation and atherosclerosis in type 2 diabetes mellitus (T2DM) in animal studies. The pathophysiological role of this protein in obesity, T2DM, and cardiovascular disease is less investigated in humans. Earlier we reported a rare Asian Indian population-specific missense variant (rs371227978; Arg148His) in the MFGE8 gene associated with increased circulating Mfge8 and T2DM. We have further investigated the role of Mfge8 with T2DM risk in additional Asian Indians (n = 4897) and Europeans and other multiethnic cohorts from UK Biobank (UKBB) (n = 455,808) and the US (n = 1150). We also evaluated the exposure of Mfge8-enriched human EVs in zebrafish (ZF) for their impact on cardiometabolic organ system. Most individual carriers of Arg148His variant not only had high circulating Mfge8 but also revealed a positive significant correlation with glucose (r = 0.42; p = 4.9 × 10-04), while the non-carriers showed a negative correlation of Mfge8 with glucose (r = -0.38; p = 0.001) in Asian Indians. The same variant was monomorphic in non-South Asian ethnicities. Even without the variant, serum Mfge8 correlated significantly with blood glucose in other non-South Asian ethnicities (r = 0.47; p = 2.2 × 10-13). Since Mfge8 is an EV marker, we tested the exposure of Mfge8-enriched human EVs to ZF larvae as an exploratory study. The ZF larvae showed rapid effects on insulin-sensitive organs, developing fatty liver disease, heart hypertrophy and exhibiting redundant growth with poor muscular architecture with and without the high-fat diet (HFD). In contrast, the control group fishes developed fatty liver disease and heart hypertrophy only after the HFD feeding. Backed with strong support from animal studies on the role of Mfge8 in obesity, insulin resistance, and atherosclerosis, the current research suggests that circulating Mfge8 may become a potential marker for predicting the risk of T2DM and cardiovascular disease in humans.

Identification of key genes and biological pathways associated with vascular aging in diabetes based on bioinformatics and machine learning

Vascular aging exacerbates diabetes-associated vascular damage, a major cause of microvascular and macrovascular complications. This study aimed to elucidate key genes and pathways underlying vascular aging in diabetes using integrated bioinformatics and machine learning approaches. Gene expression datasets related to vascular smooth muscle cell (VSMC) senescence and diabetic vascular aging were analyzed. Differential expression analysis identified 428 genes associated with VSMC senescence. Functional enrichment revealed their involvement in cellular senescence, ECM-receptor interaction, PI3K-Akt and AGE-RAGE signaling pathways. Further analysis of diabetic vascular aging datasets revealed 52 differentially expressed genes, enriched in AMPK signaling, AGE-RAGE signaling, cellular senescence, and VEGF signaling pathways. Machine learning algorithms, including LASSO regression and SVM-RFE, pinpointed six key genes: TFB1M, FOXRED2, LY75, DALRD3, PI4K2B, and NDOR1. Immune cell infiltration analysis demonstrated correlations between diabetic vascular aging, the identified key genes, and infiltration levels of plasma cells, M1 macrophages, CD8+ T cells, eosinophils, and regulatory T cells. In conclusion, this study identified six pivotal genes (TFB1M, FOXRED2, LY75, DALRD3, PI4K2B, and NDOR1) closely associated with diabetic vascular aging through integrative bioinformatics and machine learning approaches. These genes are linked to alterations in the immune microenvironment during diabetic vascular aging. This study provides a reference and basis for molecular mechanism research, biomarker mining, and diagnosis and treatment evaluation of diabetes-related vascular aging.

PTP1B mediates the inhibitory effect of MFGE8 on insulin signaling through the β5 integrin

Integrins are cell adhesion receptors that dimerize to mediate cell-cell interactions and regulate processes, including proliferation, inflammation, and tissue repair. The role of integrins in regulating insulin signaling is incompletely understood. We have previously shown that binding of the integrin ligand milk fat globule epidermal growth factor like 8 (MFGE8) to the αvβ5 integrin promotes termination of insulin receptor signaling in mice. Upon ligation of MFGE8, integrin β5 complexes with the insulin receptor beta (IRβ) in skeletal muscle, resulting in dephosphorylation of IRβ and reduction of insulin-stimulated glucose uptake. Here, we investigate the mechanism by which the interaction between β5 and IRβ impacts IRβ phosphorylation status. We show in in vitro and in vivo in skeletal muscle in mice that antibody-mediated blockade of the β5 integrin inhibits and recombinant MFGE8 promotes PTP1B binding to and dephosphorylation of IRβ resulting in increased or reduced insulin-stimulated glucose uptake, respectively. The β5-PTP1B complex is recruited by MFGE8 to IRβ leading to termination of canonical insulin signaling. β5 blockade enhances insulin-stimulated glucose uptake in wildtype but not Ptp1b KO mice indicating that PTP1B functions downstream of MFGE8 in modulating insulin receptor signaling. Furthermore, in a human cohort, we report serum MFGE8 levels correlate with indices of insulin resistance. These data provide mechanistic insights into the role of MFGE8 and β5 in regulating insulin signaling.

The multiple actions of grape and its polyphenols on female reproductive processes with an emphasis on cell signalling

Grapes are an economically important fruit crop, and their polyphenols (mainly phenolic acids, flavanols, flavonols, anthocyanins, proanthocyanidins, and stilbenes) can exert a wide range of health benefits as an interesting and valuable dietary supplement for natural complementary therapy. However, their potential physiological and therapeutic actions on reproductive processes have not been sufficiently elucidated. This evidence-based study presents current knowledge of grape extracts and polyphenols, as well as their properties and therapeutical actions in relation to female reproduction in a nutshell. Grape extract, and its polyphenols such as resveratrol, proanthocyanidin B2 or delphinidin may influence female reproductive physiology and pathology, as well as regulate multiple signaling pathways related to reproductive hormones, steroid hormones receptors, intracellular regulators of oxidative stress and subsequent inflammation, apoptosis, and proliferation. Their role in the management of ovarian cancer, age-related reproductive insufficiency, ovarian ischemia, PCOS, or menopausal syndrome has been indicated. In particular, the potential involvement of grapeseed extracts and/or proanthocyanidin B2 and delphinidin on ovarian steroidogenesis, oocyte maturation, and developmental capacity has been implicated, albeit at different regulatory levels. Grape polyphenols exert a wide range of health benefits posing grape extract as an interesting and valuable dietary supplement for natural complementary therapy. This evidence-based study focuses on the actions of grapeseed extract and grape polyphenols on female reproductive processes at various regulatory levels and multiple signalling pathways by regulating reproductive hormones (GnRH, gonadotropins, prolactin, steroid hormones, IGFBP), steroid receptors, markers of proliferation and apoptosis. However, lack of knowledge of standardized dosages so far limits their clinical application despite the wide range of their biological and therapeutic potentials.

Expression and clinical association of MFG-E8 and TAM receptors in diabetic patients with different stages of microvascular complication: An experimental study

BACKGROUND

Diabetic nephropathy (DN) is a major microvascular complication of diabetes mellitus that leads to end-stage renal disease. Hyperglycemia triggers apoptosis and kidney damage. Milk fat globule-epidermal growth factor 8 (MFG-E8) and TAM receptor tyrosine kinases, Tyro3, Axl, and Mer, are phagocytic receptors that mediate the clearance of apoptotic cells. This study aimed to identify the role of MFG-E8 and TAM receptors in the development of DN.

METHODS

A total of 146 patients with type 2 diabetes mellitus (T2DM), early stage DN, clinical DN and 48 healthy controls were employed to analyze the serum levels of MFG-E8, soluble Tyro3, Axl, Mer, and RAGE by enzyme-linked immunosorbent assay. The serum levels of CREA, hsCRP, CysC, and β2-microglobulin were measured by spectrophotometric analysis using a biochemical analyzer (AU5800).

RESULTS

Our results showed that the serum levels of MFG-E8 were elevated in patients with T2DM compared with healthy controls; however, it decreased gradually in patients with DN with the severity of kidney injury, especially in the clinical DN group. Moreover, the levels of sTyro3, sAxl, and sMer were reduced in patients with T2DM and DN compared to healthy controls, particularly in patients with DN. The levels of MFG-E8, sTyro3, sAxl, and sMer were negatively correlated with UAER at 24 hours, CREA, hsCRP, CysC, β2-microglobulin, and RAGE, respectively. In addition, TAM receptors had significantly higher predictive and diagnostic values for early stage DN from T2DM than hsCRP, β2-microglobulin, and CysC, which are also predictive biomarkers of early stage DN from clinical DN.

CONCLUSIONS

Decreased MFG-E8 and TAM receptor expression is associated with an increased risk of microvascular complications in patients with T2DM, which plays a critical role in the diagnosis of diabetic patients with microvascular complications, especially early stage DN, and in monitoring the development of DN.

Procyanidin B2: A promising multi-functional food-derived pigment for human diseases

Natural edible pigments play a paramount part in the food industry. Procyanidin B2 (PB2), one of the most representative naturally occurring edible pigments, is usually isolated from the seeds, fruits, and leaves of lots of common plants, such as grapes, Hawthorn, black soybean, as well as blueberry, and functions as a food additive in daily life. Notably, PB2 has numerous bioactivities and possesses the potential to treat/prevent a wide range of human diseases, such as diabetes mellitus, diabetic complications, atherosclerosis, and non-alcoholic fatty liver disease, and the underlying mechanisms were partially elucidated, including mediating signaling pathways like NF-κB, MAPK, PI3K/Akt, apoptotic axis, and Nrf-2/HO-1. This paper presents a review of the natural sources, bioactivities, and the therapeutic/preventive potential of PB2 and the possible mechanisms, with the aim of promoting the development of PB2 as a functional food and providing references for its clinical application in the treatment of diseases.

MFGE8 inhibits insulin signaling through PTP1B

The role of integrins in regulating insulin signaling is incompletely understood. We have previously shown that binding of the integrin ligand milk fat globule epidermal growth factor like 8 (MFGE8) to the αvβ5 integrin promotes termination of insulin receptor signaling in mice. Upon ligation of MFGE8, β5 complexes with the insulin receptor beta (IRβ) in skeletal muscle resulting in dephosphorylation of IRβ and reduction of insulin-stimulated glucose uptake. Here we investigate the mechanism by which the interaction between β5 and IRβ impacts IRβ phosphorylation status. We show that β5 blockade inhibits and MFGE8 promotes PTP1B binding to and dephosphorylation of IRβ resulting in reduced or increased insulin-stimulated myotube glucose uptake respectively. The β5-PTP1B complex is recruited by MFGE8 to IRβ leading to termination of canonical insulin signaling. β5 blockade enhances insulin-stimulated glucose uptake in wild type but not Ptp1b KO mice indicating that PTP1B functions downstream of MFGE8 in modulating insulin receptor signaling. Furthermore, in a human cohort, we report serum MFGE8 levels correlate with indices of insulin resistance. These data provide mechanistic insights into the role of MFGE8 and β5 in regulating insulin signaling.

Inflammatory Role of Milk Fat Globule-Epidermal Growth Factor VIII in Age-Associated Arterial Remodeling

Background Age-associated aortic remodeling includes a marked increase in intimal medial thickness (IMT), associated with signs of inflammation. Although aortic wall milk fat globule-epidermal growth factor VIII (MFG-E8) increases with age, and is associated with aortic inflammation, it is not known whether MFG-E8 is required for the age-associated increase in aortic IMT. Here, we tested whether MFG-E8 is required for the age-associated increase in aortic IMT. Methods and Results To determine the role of MFG-E8 in the age-associated increase of IMT, we compared aortic remodeling in adult (20-week) and aged (96-week) MFG-E8 (-/-) knockout and age matched wild-type (WT) littermate mice. The average aortic IMT increased with age in the WT from 50±10 to 70±20 μm (P<0.0001) but did not significantly increase with age in MFG-E8 knockout mice. Because angiotensin II signaling is implicated as a driver of age-associated increase in IMT, we infused 30-week-old MFG-E8 knockout and age-matched littermate WT mice with angiotensin II or saline via osmotic mini-pumps to determine whether MFG-E8 is required for angiotensin II-induced aortic remodeling. (1) In WT mice, angiotensin II infusion substantially increased IMT, elastic lamina degradation, collagen deposition, and the proliferation of vascular smooth muscle cells; in contrast, these effects were significantly reduced in MFG-E8 KO mice; (2) On a molecular level, angiotensin II treatment significantly increased the activation and expression of matrix metalloproteinase type 2, transforming growth factor beta 1, and its downstream signaling molecule phosphorylated mother against decapentaplegic homolog 2, and collagen type I production in WT mice; however, in the MFG-E8 knockout mice, these molecular effects were significantly reduced; and (3) in WT mice, angiotensin II increased levels of aortic inflammatory markers phosphorylated nuclear factor-kappa beta p65, monocyte chemoattractant protein 1, tumor necrosis factor alpha, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 molecular expression, while in contrast, these inflammatory markers did not change in knockout mice. Conclusions Thus, MFG-E8 is required for both age-associated proinflammatory aortic remodeling and also for the angiotensin II-dependent induction in younger mice of an aortic inflammatory phenotype observed in advanced age. Targeting MFG-E8 would be a novel molecular approach to curb adverse arterial remodeling.

MFG-E8 promotes osteogenic transdifferentiation of smooth muscle cells and vascular calcification by regulating TGF-β1 signaling

Vascular calcification occurs in arterial aging, atherosclerosis, diabetes mellitus, and chronic kidney disease. Transforming growth factor-β1 (TGF-β1) is a key modulator driving the osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs), leading to vascular calcification. We hypothesize that milk fat globule–epidermal growth factor 8 (MFG-E8), a glycoprotein expressed in VSMCs, promotes the osteogenic transdifferentiation of VSMCs through the activation of TGF-β1-mediated signaling. We observe that the genetic deletion of MFG-E8 prevents calcium chloride-induced vascular calcification in common carotid arteries (CCAs). The exogenous application of MFG-E8 to aged CCAs promotes arterial wall calcification. MFG-E8-deficient cultured VSMCs exhibit decreased biomineralization and phenotypic transformation to osteoblast-like cells in response to osteogenic medium. MFG-E8 promotes β1 integrin–dependent MMP2 expression, causing TGF-β1 activation and subsequent VSMC osteogenic transdifferentiation and biomineralization. Thus, the established molecular link between MFG-E8 and vascular calcification suggests that MFG-E8 can be therapeutically targeted to mitigate vascular calcification.

A molecular link between the milk fat globule–epidermal growth factor 8 (MFG-E8), activation of vascular calcification driver TGF-β1 and osteogenic differentiation of vascular smooth muscle cells suggests that MFG-E8 could be a therapeutic target for vascular calcification.

Therapeutic effects of Chinese herbal medicines and their extracts on diabetes

With the improvement of people's living standards and changes in the environment, the incidence of diabetes has increased rapidly. It has gradually become one of the main diseases threatening the health and life of modern people, bringing a great burden to the society. Although the existing treatment methods can effectively control the symptoms of diabetes and delay its progression, they have not brought satisfactory improvement in the quality of life and treatment of patients. Traditional Chinese herbal medicines and their extracts combine thousands of years of experience and the scientific basis provided by modern experimental research, which is expected to bring a qualitative leap in the clinical management of diabetes. Therefore, this article systematically reviews studies on the effects of Chinese herbal medicine and its extracts on diabetes and its complications, and aims to bring new ideas and options for the clinical treatment of diabetes.

Procyanidin B2 Reduces Vascular Calcification through Inactivation of ERK1/2-RUNX2 Pathway

Vascular calcification is strongly associated with atherosclerotic plaque burden and plaque instability. The activation of extracellular signal-regulated kinase 1/2 (ERK1/2) increases runt related transcription factor 2 (RUNX2) expression to promote vascular calcification. Procyanidin B2 (PB2), a potent antioxidant, can inhibit ERK1/2 activation in human aortic smooth muscle cells (HASMCs). However, the effects and involved mechanisms of PB2 on atherosclerotic calcification remain unknown. In current study, we fed apoE-deficient (apoE^−/−) mice a high-fat diet (HFD) while treating the animals with PB2 for 18 weeks. At the end of the study, we collected blood and aorta samples to determine atherosclerosis and vascular calcification. We found PB2 treatment decreased lesions in en face aorta, thoracic, and abdominal aortas by 21.4, 24.6, and 33.5%, respectively, and reduced sinus lesions in the aortic root by 17.1%. PB2 also increased α-smooth muscle actin expression and collagen content in lesion areas. In the aortic root, PB2 reduced atherosclerotic calcification areas by 75.8%. In vitro, PB2 inhibited inorganic phosphate-induced osteogenesis in HASMCs and aortic rings. Mechanistically, the expression of bone morphogenetic protein 2 and RUNX2 were markedly downregulated by PB2 treatment. Additionally, PB2 inhibited ERK1/2 phosphorylation in the aortic root plaques of apoE^−/− mice and calcified HASMCs. Reciprocally, the activation of ERK1/2 phosphorylation by C2-MEK1-mut or epidermal growth factor can partially restore the PB2-inhibited RUNX2 expression or HASMC calcification. In conclusion, our study demonstrates that PB2 inhibits vascular calcification through the inactivation of the ERK1/2-RUNX2 pathway. Our study also suggests that PB2 can be a potential option for vascular calcification treatment.

MFG-E8 Regulates Vascular Smooth Muscle Cell Migration Through Dose-Dependent Mediation of Actin Polymerization

Background Migration of vascular smooth muscle cells (VSMCs) is the main contributor to neointimal formation. The Arp2/3 (actin-related proteins 2 and 3) complex activates actin polymerization and is involved in lamellipodia formation during VSMC migration. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein expressed in VSMCs. We hypothesized that MFG-E8 regulates VSMC migration through modulation of Arp2/3-mediated actin polymerization. Methods and Results To determine whether MFG-E8 is essential for VSMC migration, a model of neointimal hyperplasia was induced in the common carotid artery of wild-type and MFG-E8 knockout mice, and the extent of neointimal formation was evaluated. Genetic deletion of MFG-E8 in mice attenuated injury-induced neointimal hyperplasia. Cultured VSMCs deficient in MFG-E8 exhibited decreased cell migration. Immunofluorescence and immunoblotting revealed decreased Arp2 but not Arp3 expression in the common carotid arteries and VSMCs deficient in MFG-E8. Exogenous administration of recombinant MFG-E8 biphasically and dose-dependently regulated the cultured VSMCs. At a low concentration, MFG-E8 upregulated Arp2 expression. By contrast, MFG-E8 at a high concentration reduced the Arp2 level and significantly attenuated actin assembly. Arp2 upregulation mediated by low-dose MFG-E8 was abolished by treating cultured VSMCs with β1 integrin function-blocking antibody and Rac1 inhibitors. Moreover, treatment of the artery with a high dose of recombinant MFG-E8 diminished injury-induced neointimal hyperplasia and reduced VSMC migration. Conclusions MFG-E8 plays a critical role in VSMC migration through dose-dependent regulation of Arp2-mediated actin polymerization. These findings suggest that high doses of MFG-E8 may have therapeutic potential for treating vascular occlusive diseases.

Autoregulation of insulin receptor signaling through MFGE8 and the αvβ5 integrin

The role of integrins, in particular αv integrins, in regulating insulin resistance is incompletely understood. We have previously shown that the αvβ5 integrin ligand milk fat globule epidermal growth factor like 8 (MFGE8) regulates cellular uptake of fatty acids. In this work, we evaluated the impact of MFGE8 on glucose homeostasis. We show that acute blockade of the MFGE8/β5 pathway enhances while acute augmentation dampens insulin-stimulated glucose uptake. Moreover, we find that insulin itself induces cell-surface enrichment of MFGE8 in skeletal muscle, which then promotes interaction between the αvβ5 integrin and the insulin receptor leading to dampening of skeletal-muscle insulin receptor signaling. Blockade of the MFGE8/β5 pathway also enhances hepatic insulin sensitivity. Our work identifies an autoregulatory mechanism by which insulin-stimulated signaling through its cognate receptor is terminated through up-regulation of MFGE8 and its consequent interaction with the αvβ5 integrin, thereby establishing a pathway that can potentially be targeted to improve insulin sensitivity.

Computational and In Vitro Investigation of (-)-Epicatechin and Proanthocyanidin B2 as Inhibitors of Human Matrix Metalloproteinase 1

Matrix metalloproteinases 1 (MMP-1) energetically triggers the enzymatic proteolysis of extracellular matrix collagenase (ECM), resulting in progressive skin aging. Natural flavonoids are well known for their antioxidant properties and have been evaluated for inhibition of matrix metalloproteins in human. Recently, (-)-epicatechin and proanthocyanidin B2 were reported as essential flavanols from various natural reservoirs as potential anti-inflammatory and free radical scavengers. However, their molecular interactions and inhibitory potential against MMP-1 are not yet well studied. In this study, sequential absorption, distribution, metabolism, and excretion (ADME) profiling, quantum mechanics calculations, and molecular docking simulations by extra precision Glide protocol predicted the drug-likeness of (-)-epicatechin (−7.862 kcal/mol) and proanthocyanidin B2 (−8.145 kcal/mol) with the least reactivity and substantial binding affinity in the catalytic pocket of human MMP-1 by comparison to reference bioactive compound epigallocatechin gallate (−6.488 kcal/mol). These flavanols in docked complexes with MMP-1 were further studied by 500 ns molecular dynamics simulations that revealed substantial stability and intermolecular interactions, viz. hydrogen and ionic interactions, with essential residues, i.e., His218, Glu219, His222, and His228, in the active pocket of MMP-1. In addition, binding free energy calculations using the Molecular Mechanics Generalized Born Surface Area (MM/GBSA) method suggested the significant role of Coulomb interactions and van der Waals forces in the stability of respective docked MMP-1-flavonol complexes by comparison to MMP-1-epigallocatechin gallate; these observations were further supported by MMP-1 inhibition assay using zymography. Altogether with computational and MMP-1–zymography results, our findings support (-)-epicatechin as a comparatively strong inhibitor of human MMP-1 with considerable drug-likeness against proanthocyanidin B2 in reference to epigallocatechin gallate.

Proteomic analysis of liver mitochondria of db/db mice treated with grape seed procyanidin B2

Hepatic damage has been recognized as one of the major complications in diabetes mellitus. Our previous studies have verified that grape seed procyanidin B2 (GSPB2) played a protective effect on hepatic damage of diabetes. We used isobaric tag for relative and absolute quantitation proteomics here to identify the alterant mitochondrial protein profile in diabetic liver and to seek the protective targets of GSPB2. Proteomics found that 171 proteins were upregulated or downregulated in the liver mitochondria of diabetic group compared to the control group. Of these proteins, 61 were normalized after GSPB2 treatment. These back-regulated proteins are involved in the process of fatty acid oxidation, tricarboxylic acid cycle, oxidative phosphorylation, oxidative stress, and apoptosis. Some differentially expressed proteins were confirmed by western blotting. Our study might help to better understand the mechanism of mitochondrial dysfunction in diabetic liver damage, and provide novel targets for estimating the protective effects of GSPB2. PRACTICAL APPLICATIONS: Grape seed procyanidin B2 (GSPB2), a polyphenolic component found in red wine and grapes, has beneficial effects such as antioxidative stress, antiapoptosis, and cardiovascular protection. We used proteomics here to identify the differentially expressed mitochondrial proteins in diabetic liver after GSPB2 treatment and to seek the protective targets of GSPB2. We found that the differentially expressed proteins were involved in carbon metabolism, oxidative phosphorylation, fatty acid metabolism, citrate cycle, oxidative stress, and apoptosis. These proteins may play a key role in diabetic hepatic damage as functional proteins. Targeting these proteins including apply of GSPB2 could potentially lead to an effective treatment in the diabetic hepatic disease.

A rare missense variant in the milk fat globule-EGF factor 8 (MFGE8) increases T2DM susceptibility and cardiovascular disease risk with population-specific effects

AIMS

The milk fat globule-epidermal growth factor 8 (MFGE8), also called lactadherin, is an integrin ligand and a known mediator of inflammation and atherosclerosis in T2DM in studies using animal models. However, its role in the pathophysiology of human T2DM, obesity, and cardiovascular disease has been poorly explored. Aim of this study  was to investigate the role of a missense variant (rs371227978 C/T: Arg148His) in the MFGE8 gene identified through exome sequencing for its association with T2DM and cardiometabolic traits.

METHODS

Exome-wide sequencing was performed using DNA samples from 68 Sikh individuals from multi-generation pedigrees affected with diabetes on Illumina's GAIIx using "SureSelect Human All Exon" panels. We further replicated this variant by de novo genotyping in a total of 4242 individuals of the Asian Indian Diabetic Heart Study/Sikh Diabetes Study using custom TaqMan genotyping assay. We also measured circulating concentrations of Mfge8 using frozen serum aliquots by enzyme-linked immunosorbent assay.

RESULTS

Overall, only 1.78% of 4242 individuals were carriers of this variant with MAF being 0.009. Except for the significant correlation of this variant with T2DM and triglycerides, no other quantitative risk phenotype was significant. The minor per allele-associated increased risk for T2DM showed odds ratio of 1.95 (95% CI 1.18-3.23; p = 0.008) in unadjusted model and was 1.73 (95% CI 1.02-2.93; p = 0.043) after adjusting for the age, gender, and BMI. However, there was a strong correlation between serum Mfge8 concentrations with T2DM, (r2 = 0.38; p = 0.001), fasting glucose (r2= 0.36; p = 0.002), and triglycerides (r2 = 0.33; p = 0.005). Our data revealed a significant dose-related increase in MFGE8 genotypes for affecting serum Mfge8 (p = 2.1 × 10-3) and triglyceride concentrations (p = 3.2 × 10-3). For a per risk allele-associated increase of 4.74 ng/ml ± SD of 1.62 ng/ml of the Mfge8 concentration was found to increase T2DM risk to 1.7 fold (95% CI from 1 to 3 fold).

CONCLUSIONS

Here, we report for the first time a novel population-specific rare variant in the MFGE8 gene linked with the increased Mfge8 concentrations and the risk for developing T2DM and cardiovascular risk factors in a population of Punjabi Sikhs from India. In view of a strong evidence from animal studies supporting the role of Mfge8 in obesity, insulin resistance, and the development of atherosclerosis in T2DM, our findings are important and timely. If validated in a large independent dataset, early screening of Mfge8 in blood levels may especially benefit those patients with genetically elevated Mfge8 levels to preventing or reducing the risk of T2DM and cardiovascular disease.

BMPR2 dysfunction impairs insulin signaling and glucose homeostasis in cardiomyocytes

Insulin resistance and right ventricular (RV) dysfunction are associated with lipotoxicity in heritable forms of pulmonary arterial hypertension (PAH), commonly due to mutations in bone morphogenetic protein receptor type 2 (BMPR2). How BMPR2 dysfunction in cardiomyocytes alters glucose metabolism and the response of these cells to insulin are unknown. We hypothesized that BMPR2 mutation in cardiomyocytes alters glucose-supported mitochondrial respiration and impairs cellular responses to insulin, including glucose and lipid uptake. We performed metabolic assays, immunofluorescence and Western analysis, RNA profiling, and radioactive isotope uptake studies in H9c2 cardiomyocyte cell lines with and without patient-derived BMPR2 mutations (mutant cells), with and without insulin. Unlike control cells, BMPR2 mutant cardiomyocytes have reduced metabolic plasticity as indicated by reduced mitochondrial respiration with increased mitochondrial superoxide production. These mutant cells show enhanced baseline phosphorylation of insulin-signaling protein as indicated by increased Akt, AMPK, and acetyl-CoA carboxylase phosphorylation that may negatively influence fatty acid oxidation and enhance lipid uptake, and are insulin insensitive. Furthermore, mutant cells demonstrate an increase in milk fat globule-EGF factor-8 protein (MFGE8), which influences the insulin-signaling pathway by phosphorylating AktSer473 via phosphatidylinositol 3-kinase and mammalian target of rapamycin. In conclusion, BMPR2 mutant cardiomyocytes have reduced metabolic plasticity and fail to respond to glucose. These cells have enhanced baseline insulin-signaling pattern favoring insulin resistance with failure to augment this pattern in response to insulin. BMPR2 mutation possibly blunts glucose uptake and enhances lipid uptake in these cardiomyocytes. The MFGE8-driven signaling pathway may suggest a new mechanism underlying RV lipotoxicity in PAH.

Polymorphisms of MFGE8 are associated with susceptibility and clinical manifestations through gene expression modulation in Koreans with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by impaired clearance of apoptotic cells. Milk fat globule epidermal growth factor 8 (MFGE8) is a protein that connects αvβ3 integrin on phagocytic macrophages with phosphatidylserine on apoptotic cells. We investigated whether genetic variation of the MFGE8 gene and serum MFGE8 concentration are associated with SLE. Single nucleotide polymorphisms (SNPs) were genotyped and serum concentrations were analyzed. The rs2271715 C allele and rs3743388 G allele showed higher frequency in SLE than in healthy subjects (HSs). Three haplotypes were found among 4 SNPs (rs4945, rs1878327, rs2271715, and rs3743388): AACG, CGCG, and CGTC. CGCG haplotype was significantly more common in SLE than in HSs. rs4945 was associated with the erythrocyte sedimentation rate and rs1878327 was associated with alopecia, C-reactive protein, complement 3, anti-dsDNA antibody, and high disease activity. rs2271715 and rs3743388 were associated with renal disease, cumulative glucocorticoid dose, and cyclophosphamide and mycophenolate mofetil use. Serum MFGE8 concentrations were significantly higher in SLE than in HSs. Furthermore, the levels of MFGE8 were significantly higher in SLE than HSs of the rs2271715 CC genotype. In conclusion, MFGE8 genetic polymorphisms are associated not only with susceptibility to SLE but also with disease activity through modulation of gene expression.

MFGE8 protects against CCl4 -induced liver injury by reducing apoptosis and promoting proliferation of hepatocytes

Milk fat globule-EGF factor 8 (MFGE8) has been reported to play various roles in acute injury and inflammation response. However, the role of MFGE8 in liver injury is poorly investigated. The present research was designed to clarify the expression and function of MFGE8 in carbon tetrachloride (CCl₄ )-induced liver injury. Using serum cytokine arrays, we selected a promising cytokine MFGE8 as the candidate in the process of hepatitis-fibrosis-hepatocellular carcinoma (HCC) progression, based on the elevated expression in both hepatic fibrosis and HCC models. We validated the increased expression of MFGE8 in liver tissues and serum samples of acute and chronic CCl₄ -induced mice. Immunohistochemistry staining of mouse liver tissues indicated that elevated MFGE8 expression was mainly derived from the injured hepatocytes. In addition, MFGE8 expression in the supernatant of primary hepatocytes was accumulated with prolongation of culture time, and CCl₄ treatment further increased the expression of MFGE8. Moreover, a strong correlation between serum MFGE8 expression and liver transaminase activities suggested that MFGE8 may be a novel candidate in liver injury. Intriguingly, mice pretreated with MFGE8 were protected from CCl₄ -induced liver injury through antiapoptosis role in the early stage and proproliferation role in the late stage. MFGE8 reduced apoptosis by inhibiting the activation of IRE1α/ASK1/JNK pathway and promoted proliferation by phosphorylation of ERK and AKT. Moreover, serum MFGE8 expression was increased in hepatitis patients while decreased in liver cirrhosis patients. All the results suggest MFGE8 as a novel marker and promising therapeutic agent of liver injury.

miR-96 and autophagy are involved in the beneficial effect of grape seed proanthocyanidins against high-fat-diet-induced dyslipidemia in mice

We aimed to investigate the possible signaling pathways underlying the regulation of grape seed proanthocyanidins extracts (GSPE) on lipid metabolism. One hundred male C57BL/6 mice were divided into four groups: control group (normal diet), GSPE group (normal diet + GSPE), high-fat diet group (HFD), and high-fat diet plus GSPE (200 mg/kg/day) group (HFD + GSPE). Mice received the diets for 180 days. Body weight and serum lipid levels were measured. Autophagic flux characteristics, such as accumulation of lipids, mitochondria, and autophagosomes in the liver, were detected using transmission electron microscopy. Expression profile of microRNAs (miRNAs) in the liver was determined using RNA microarray and quantitative real time polymerase chain reaction (qRt-PCR). GSPE significantly decreased the weight gain, serum levels of triglycerides, total cholesterol, and low-density lipoprotein cholesterol but increased high-density lipoprotein cholesterol in the HFD mice. Autophagic flux was significantly increased by HFD but decreased by GSPE treatment. GSPE significantly attenuated HFD-induced miR-96 upregulation, which in turn reduced the expressions of miR-96 downstream molecules, FOXO1, mTOR, p-mTOR, and LC3A/B. These results suggested that the miR-96 is involved in the protective effect of GSPE against HFD-induced dyslipidemia. Possible mechanisms might be through mTOR and FOXO1, which facilitate autophagic flux for clearance of lipid accumulation.

Effect of GAPDS overexpression on high glucose-induced oxidative damage

The occurrence of infertility in diabetic patients is attributed to oxidative damage of peroxidized products. High glucose-induced mitochondrial oxidative stress and glycolytic enzyme inactivation is considered to be an important mediator for sperm dysfunction. In this study, we successfully constructed TM3-GAPDS stable strain and investigated the role of sperm specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS) on high glucose-induced apoptosis in TM3 cells. High glucose decreased the protein expression of SOD2 and catalase, while the level of intracellular ROS and the apoptosis - related protein increased in TM3 cells. Furthermore, high glucose-induced oxidative stress and apoptosis were reversed by GAPDS overexpression or antioxidant treatment. In conclusion, our data suggest that GAPDS overexpression antagonize high glucose-induced apoptosis by controlling ROS accumulation in TM3 cells.

Proanthocyanidin B2 attenuates high-glucose-induced neurotoxicity of dorsal root ganglion neurons through the PI3K/Akt signaling pathway

High glucose affects primary afferent neurons in dorsal root ganglia by inhibiting neurite elongation, causing oxidative stress, and inducing neuronal apoptosis and mitochondrial dysfunction, which finally result in neuronal damage. Proanthocyanidin, a potent antioxidant, has been shown to have neuroprotective effects. Proanthocyanidin B2 is a common dimer of oligomeric proanthocyanidins. To date, no studies have reported the neuroprotective effects of proanthocyanidin B2 against high-glucose-related neurotoxicity in dorsal root ganglion neurons. In this study, 10 µg/mL proanthocyanidin B2 was used to investigate its effect on 45 mM high-glucose-cultured dorsal root ganglion neurons. We observed that challenge with high levels of glucose increased neuronal reactive oxygen species and promoted apoptosis, decreased cell viability, inhibited outgrowth of neurites, and decreased growth-associated protein 43 protein and mRNA levels. Proanthocyanidin B2 administration reversed the neurotoxic effects caused by glucose challenge. Blockage of the phosphatidylinositol 3 kinase/Akt signaling pathway with 10 µM LY294002 eliminated the protective effects of proanthocyanidin B2. Therefore, proanthocyanidin B2 might be a potential novel agent for the treatment of peripheral diabetic neuropathy.

Differential proteomic analysis of white adipose tissues from T2D KKAy mice by LC-ESI-QTOF

Type 2 diabetes (T2D) has become a worldwide increasingly social health burden for its high morbidity and heightened prevalence. As one of the main tissues involved in uptake of glucose under the stimulation of insulin, WAT plays very important role in metabolic and homeostasis regulation. We performed a differential proteomics study to investigate alterations in epididymis fat pad of high fat diet fed T2D KKAy mice compared to normal fed C57BL/6J mice, by ¹⁸ O-labeling relative quantitative technique. Among 329 confidently identified proteins, 121 proteins showed significant changes with CV ≤ 20% (fold changes of >2 or <0.5 as threshold). According to GO classification, we found that altered proteins contained members of biological processes of metabolic process, oxidative stress, ion homeostasis, apoptosis and cell division. In metabolic, proteins assigned to fatty acid biosynthesis (FAS etc.) were decreased, the key enzyme (ACOX3) in β-oxidation process was increased. Increased glycolysis enzymes (ENOB etc.) and decreased TCA cycle related enzymes (SCOT1 etc.) suggested that glucose metabolism in mitochondria of T2D mice might be impaired. Elevated oxidative stress was observed with alterations of a series of oxidordeuctase (QSOX1 etc.). Besides, alterations of ion homeostasis (AT2C1 etc.) proteins were also observed. The enhancement of cell proliferation associated proteins (ELYS etc.) and inhibition of apoptosis associated proteins (RASF6 etc.) in WAT might contributed to the fat pad and body weight gain. Overall, these changes in WAT may serve as a reference for understanding the functional mechanism of T2D.

Grape seed procyanidin B2 ameliorates hepatic lipid metabolism disorders in db/db mice

Diabetes is commonly associated with liver lipid metabolism disorders. AMP-activated protein kinase (AMPK) has a key role in regulating lipid metabolism. Grape seed procyanidin B2 (GSPB2), a natural polyphenol polymer, ameliorates mitochondrial dysfunction and inhibits oxidative stress or apoptosis via AMPK pathways. In the present study, the hypothesis that GSPB2 treatment may ameliorate liver lipid metabolic disorders by activating AMPK and downstream pathways was tested in diabetic mice. Db/m mice were used as controls, and diabetic db/db mice were randomly divided into 2 groups for treatment: Vehicle and GSPB2 (30 mg/kg/day for 10 weeks). Animals were weighed every week. Fasting blood was collected prior to sacrifice to measure fasting blood glucose (FBG), triglycerides (TG) and total cholesterol (TC). Hepatic TG and free fatty acid (FFA) levels were analyzed. Hepatic sections were examined by light microscopy following hematoxylin and eosin staining. The expression of hepatic AMPK, phosphorylated acetyl‑CoA carboxylase (ACC), carnitine palmitoyl transferase 1 (CPT1) and 4‑hydroxynonenal (4‑HNE) was measured by western blot analysis. Liver mitochondria were isolated to assess electron transport complex I (CI), complex II (CII) and complex IV by high-resolution respirometry. The results demonstrated that GSPB2 significantly decreased body weight and serum TG, TC and FFA levels, but not FBG levels in diabetic mice. GSPB2 visibly decreased lipid droplet accumulation in the liver and significantly reduced hepatic TG and FFA levels. In diabetic mice, GSPB2 restored liver AMPK and ACC phosphorylation, increased CPT1 protein expression, ameliorated lipid peroxidation damage, which was assessed by comparing 4‑HNE levels, and partially restored the damaged mitochondrial respiratory capacity of CI and CII in the liver. In conclusion, long‑term oral treatment with GSPB2 may benefit hepatic lipid metabolism disorders, potentially by decreasing hepatic lipid synthesis and increasing hepatic FFA β‑oxidation via the AMPK‑ACC pathway.

Regression of atherosclerosis with apple procyanidins by activating the ATP-binding cassette subfamily A member 1 in a rabbit model

BACKGROUND AND AIMS

Apple polyphenol contains abundant procyanidins, which have been associated with an anti-atherosclerosis and cholesterol-lowering effect. The aim of this study was to investigate whether apple procyanidins (APCs) feature therapeutic efficacy in terms of regressing atherosclerosis and whether this efficacy is due to mechanisms other than a cholesterol-lowering effect.

METHODS

After eight weeks on an atherogenic diet, rabbits were given a normal diet for another eight weeks to normalize the increased serum lipids level. The rabbits in the baseline group were sacrificed at this stage. The control group was subsequently fed a normal diet for eight weeks, while the APCs group was administrated 50 mg/kg/day of APCs in addition to the normal diet. Serum lipids and aortic intimal-medial thickness (IMT) were serially examined, and the resected aorta was examined histologically and through molecular biology.

RESULTS

Aortic IMT on ultrasonography and the lipid accumulation area examined using Sudan IV staining were significantly reduced in the APCs group as compared to the control group. Serum lipid profiles were not different between the groups. Immunohistochemistry showed significantly decreased staining of an oxidative stress marker and significantly increased staining of ATP-binding cassette subfamily A member 1 (ABCA1) in the APCs group. Western blotting and RT-PCR also showed increased expression of ABCA1 mRNA and its protein in the APCs group.

CONCLUSIONS

This study revealed that APCs administration causes a regression of atherosclerosis. APCs might hold promise as an anti-atherosclerotic agent.

Elevated serum milk fat globule-epidermal growth factor 8 levels in type 2 diabetic patients are suppressed by overweight or obese status

Inflammation is the most important link between obesity and type 2 diabetes (T2D). Although milk fat globule-epidermal growth factor 8 (MFG-E8) is a key mediator in anti-inflammatory responses, its role in obesity and diabetes is not yet completely understood. We aimed to measure MFG-E8 serum levels and to explore the role of MFG-E8 in obesity and T2D. Fasting serum MFG-E8 levels were quantified by enzyme-linked immunosorbent assay for 168 individuals, whose oral glucose tolerance test was conducted, and levels of inflammatory factors, including tumor necrosis factor-α (TNF-α) and C-reactive protein, were measured. The participants were subdivided into 66 newly diagnosed T2D individuals, 44 impaired glucose tolerance (IGT) subjects and 58 healthy controls. Their characteristics were further classified as lean or nonlean for investigation. MFG-E8 levels were significantly higher in T2D subjects than in healthy controls (P = 0.028). Decreased levels of MFG-E8 were found in overweight or obese individuals, compared to those in lean subjects, in both the T2D and IGT groups (P < 0.001). Interestingly, MFG-E8 levels showed a negative correlation with body mass index (BMI) and TNF-α levels in the total population and the T2D subgroup. Further, BMI and TNF-α concentrations were found to be independent predictors of MFG-E8 levels in all subjects. MFG-E8 levels are elevated in T2D but suppressed by increased adipose tissues, thereby allowing inflammatory factors to rise to high levels. MFG-E8 may serve as a potential biomarker for obesity and T2D in the clinical setting. © 2017 IUBMB Life, 69(2):63-71, 2017.

Investigation of the Effects and Mechanisms of Mai Tong Formula on Lower Limb Macroangiopathy in a Spontaneous Diabetic Rat Model

A new Chinese herbal formula called Mai Tong Formulae (MTF) has recently been used to treat lower limb macroangiopathy in type 2 diabetes mellitus (T2DM) patients. In this study, we investigated the effect of MTF on lower limb macroangiopathy in a spontaneous diabetic rat model (GK rats). We found that MTF treatment significantly reduced serum fasting blood glucose (FBG), triglycerides (TG), total cholesterol (TC), IL6, and VEGF and increased serum insulin in this model. Histological and ultrastructural observations showed that MTF treatment significantly reduced vascular endothelial cell shedding and improved endothelium injuries. We further detect proteome alteration following MTF treatment. 25 differential proteins (DPs) abnormally expressed in GK rats were normalized by MTF treatment. These DPs significantly are enriched in biological processes and pathways that regulate muscle contraction and cGMP-PKG signaling pathway and so on. Additional protein-protein interaction (PPI) network analyses of the DPs showed that Fasn and Prkar2a are involved in the AMPK signaling pathway, and Gnas, Myh11, and Myh6 are involved in vascular smooth muscle contraction; these 5 DPs were validated by Western blotting. These results indicate that MTF treatment effectively treats lower limb macroangiopathy by regulating key proteins involved in AMPK signaling pathway and vascular smooth muscle contraction.

Mfge8 regulates enterocyte lipid storage by promoting enterocyte triglyceride hydrolase activity

The small intestine has an underappreciated role as a lipid storage organ. Under conditions of high dietary fat intake, enterocytes can minimize the extent of postprandial lipemia by storing newly absorbed dietary fat in cytoplasmic lipid droplets. Lipid droplets can be subsequently mobilized for the production of chylomicrons. The mechanisms that regulate this process are poorly understood. We report here that the milk protein Mfge8 regulates hydrolysis of cytoplasmic lipid droplets in enterocytes after interacting with the αvβ3 and αvβ5 integrins. Mice deficient in Mfge8 or the αvβ3 and αvβ5 integrins accumulate excess cytoplasmic lipid droplets after a fat challenge. Mechanistically, interruption of the Mfge8-integrin axis leads to impaired enterocyte intracellular triglyceride hydrolase activity in vitro and in vivo. Furthermore, Mfge8 increases triglyceride hydrolase activity through a PI3 kinase/mTORC2-dependent signaling pathway. These data identify a key role for Mfge8 and the αvβ3 and αvβ5 integrins in regulating enterocyte lipid processing.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Anti-inflammatory effects of grape seed procyanidin B2 on a diabetic pancreas

The prevalence of type 2 diabetes mellitus (T2DM) has increased considerably in recent years, highlighting the importance of developing new therapeutic strategies. Insulin-resistance and gradual dysfunction of pancreatic islets are the mainstay in the progression of T2DM. Therefore, preserving the function of the pancreas may lead to new prospective approaches. Our previous studies suggested that grape seed procyanidin B2 (GSPB2), a natural polyphenol product, exhibited protective effects on diabetic vasculopathy. However, effects of GSPB2 on a diabetic pancreas remain unknown. In this study, we provided strong evidence that GSPB2 exerted protective effects on a diabetic pancreas. GSPB2 attenuated the elevated body weights, food intake and advanced glycation end-product (AGE) levels in db/db mice (p < 0.05), though it had no significant effect on glucose levels. The increased islet sizes, insulin levels, as well as HOMA-IR were also improved by GSPB2 treatment in db/db mice (p < 0.05). Milk fat globule epidermal growth factor-8 (MFG-E8), an estimated target of GSPB2 in our previous studies, was up-regulated in pancreatic tissues whereas GSPB2 treatment down-regulated the protein level (p < 0.05). Since MFG-E8 is highly involved in inflammation, we further investigate pro-inflammatory cytokines interleukin-1β (IL-1β) and NLRP3 levels. We found that levels of IL-1β and NLRP3 increased in a diabetic pancreas while GSPB2 treatment notably attenuated these alterations (p < 0.05). In conclusion, our results suggest that inflammation is involved in the damage of a diabetic pancreas and GSPB2 provides protective effects at least in part through anti-inflammation.

Critical Role of FoxO1 in Granulosa Cell Apoptosis Caused by Oxidative Stress and Protective Effects of Grape Seed Procyanidin B2

Reactive oxygen species (ROS) are closely related to the follicular granulosa cell apoptosis. Grape seed procyanidin B2 (GSPB2) has been reported to possess potent antioxidant activity. However, the GSPB2-mediated protective effects and the underlying molecular mechanisms in granulosa cell apoptosis process remain unknown. In this study, we showed for the first time that GSPB2 treatment decreased FoxO1 protein level, improved granulosa cell viability, upregulated LC3-II protein level, and reduced granulosa cell apoptosis rate. Under a condition of oxidative stress, GSPB2 reversed FoxO1 nuclear localization and increased its level in cytoplasm. In addition, FoxO1 knockdown inhibited the protective effects of GSPB2 induced. Our findings suggest that FoxO1 plays a pivotal role in regulating autophagy in granulosa cells, GSPB2 exerts a potent and beneficial role in reducing granulosa cell apoptosis and inducing autophagy process, and targeting FoxO1 could be significant in fighting against oxidative stress-reduced female reproductive system diseases.

Grape Seed Proanthocyanidin Extract Ameliorates Diabetic Bladder Dysfunction via the Activation of the Nrf2 Pathway

Diabetes Mellitus (DM)-induced bladder dysfunction is predominantly due to the long-term oxidative stress caused by hyperglycemia. Grape seed proanthocyanidin extract (GSPE) has been reported to possess a broad spectrum of pharmacological and therapeutic properties against oxidative stress. However, its protective effects against diabetic bladder dysfunction have not been clarified. This study focuses on the effects of GSPE on bladder dysfunction in diabetic rats induced by streptozotocin. After 8 weeks of GSPE administration, the bladder function of the diabetic rats was improved significantly, as indicated by both urodynamics analysis and histopathological manifestation. Moreover, the disordered activities of antioxidant enzymes (SOD and GSH-Px) and abnormal oxidative stress levels were partly reversed by treatment with GSPE. Furthermore, the level of apoptosis in the bladder caused by DM was decreased following the administration of GSPE according to the Terminal Deoxynucleotidyl Transferase (TdT)-mediated dUTP Nick-End Labeling (TUNEL) assay. Additionally, GSPE affected the expression of apoptosis-related proteins such as Bax, Bcl-2 and cleaved caspase-3. Furthermore, GSPE showed neuroprotective effects on the bladder of diabetic rats, as shown by the increased expression of nerve growth factor (NGF) and decreased expression of the precursor of nerve growth factor (proNGF). GSPE also activated nuclear erythroid2-related factor2 (Nrf2), which is a key antioxidative transcription factor, with the concomitant elevation of downstream hemeoxygenase-1 (HO-1). These findings suggested that GSPE could ameliorate diabetic bladder dysfunction and decrease the apoptosis of the bladder in diabetic rats, a finding that may be associated with its antioxidant activity and ability to activate the Nrf2 defense pathway.

Quantitative proteomics study of protective effects of grape seed procyanidin B2 on diabetic cardiomyopathy in db/db mice

Diabetic cardiomyopathy is one of the major complications of diabetes mellitus. Oxidative stress appears to play a substantial role in cardiomyopathy. Grape seed procyanidin B2 (GSPB2) has been known as an anti-oxidant in treating diabetes mellitus; however, little is known about its effects and underlying mechanisms on diabetic cardiomyopathy. The present study is to explore the molecular targets of GSPB2 responsible for the anti-oxidative effects in db/db mice by quantitative proteomics. GSPB2 (30 mg/kg body weight/day) were intragastric administrated to db/db mice for 10 weeks. Proteomics of the heart tissue extracts by isobaric tags for relative and absolute quantification analysis was obtained from db/db mice. Our study provides important evidence that GSPB2 protect against cardiomyopathy in diabetes mellitus, which are believed to result from regulating the expression of key proteins involving cardiac fibrosis and proliferation. GSPB2 could be expected to become novel clinical application in fighting against diabetic cardiomyopathy.

Beneficial effects of phlorizin on diabetic nephropathy in diabetic db/db mice

AIMS

This study observes the effects of phlorizin on diabetic nephrology in db/db diabetic mice and explores possible underlying mechanisms.

METHODS

Sixteen diabetic db/db mice and eight age-matched db/m mice were divided into three groups: vehicle-treated diabetic group (DM group), diabetic group treated with phlorizin (DMT group) and normal control group (CC group). Phlorizin was given in normal saline solution by intragastric administration for 10 weeks. Differentially expressed proteins in three groups were identified using iTRAQ quantitative proteomics and the data were further analyzed with ingenuity pathway analysis.

RESULTS

The body weight and serum concentrations of fasting blood glucose (FBG), advanced glycation end products (AGEs), total cholesterol, triglycerides, blood urea nitrogen, creatinine and 24-h urine albumin were increased in the DM group compared to those of the CC group (P<0.05), and they were decreased by treatment with phlorizin (P<0.05). Morphologic observations showed phlorizin markedly attenuated renal injury. Phlorizin prevented diabetic nephropathy by regulating the expression of a series of proteins involved in renal and urological disease, molecular transport, free radical scavenging, and lipid metabolism.

CONCLUSIONS

Phlorizin protects mice from diabetic nephrology and thus may be a novel therapeutic approach for the treatment of diabetic nephrology.

Mfge8 promotes obesity by mediating the uptake of dietary fats and serum fatty acids

Fatty acids are integral mediators of energy storage, membrane formation and cell signaling. The pathways that orchestrate uptake of fatty acids remain incompletely understood. Expression of the integrin ligand Mfge8 is increased in human obesity and in mice on a high-fat diet, but its role in obesity is unknown. We show here that Mfge8 promotes the absorption of dietary triglycerides and the cellular uptake of fatty acid and that Mfge8-deficient (Mfge8(-/-)) mice are protected from diet-induced obesity, steatohepatitis and insulin resistance. Mechanistically, we found that Mfge8 coordinates fatty acid uptake through αvβ3 integrin- and αvβ5 integrin-dependent phosphorylation of Akt by phosphatidylinositide-3 kinase and mTOR complex 2, leading to translocation of Cd36 and Fatp1 from cytoplasmic vesicles to the cell surface. Collectively, our results imply a role for Mfge8 in regulating the absorption and storage of dietary fats, as well as in the development of obesity and its complications.

Identification of MFG-E8 as a novel therapeutic target for diseases

INTRODUCTION

Milk fat globule-epidermal growth factor-factor 8 (MFG-E8), a peripheral membrane glycoprotein has been widely studied in recent years due to its omnipresent locations, express and multiple functions. Traditionally, MFG-E8 was identified as an outstanding factor for phagocytosis of apoptotic cells and a significant factor in immune systems. Recent studies with some new findings have shed an interesting light on the old peripheral membrane glycoprotein in various diseases.

AREAS COVERED

In inflammatory and the systemic lupus erythematosus-type autoimmune disease, age-related diseases and tumors, MFG-E8 plays a multifunctional role in attenuating inflammation and improving prognosis, healing wound and remodeling arterial and enhancing tumorigenicity and cancer metastasis. This review provides a comprehensive view on the latest advances in the field. The summarized knowledge will help to explore the potential therapeutic roles of MFG-E8 and to design MFG-E8-based strategies for the treatment of these diseases.

EXPERT OPINION

Though the exact roles of MFG-E8 have not been fully elucidated in diseases. MFG-E8 may serve as a promising therapeutic strategy.

PIMT prevents the apoptosis of endothelial cells in response to glycated low density lipoproteins and protective effects of grape seed procyanidin B2

Background

The development of diabetic angiopathy is associated with profound vascular endothelial cells (VEC) dysfunction and apoptosis. Glycated low density lipoproteins (gly-LDL) continuously produced in the setting of diabetic patients play an important role in causing VEC dysfunction and apoptosis. However, the underlying molecular mechanism remains largely elusive. Protein L-isoaspartyl methyltransferase (PIMT) is a widely expressed protein repair enzyme by multiple cell types of arterial wall including VEC. Our previous proteomic studies showed that the expression of PIMT was significantly decreased in the aorta of diabetic rats as compared with control rats and treatment with grape seed procyanidin extracts significantly increased the PIMT expression in diabetic rats. We hypothesized that PIMT plays a critical role in gly-LDL induced VEC apoptosis; grape seed procyanidin B2 (GSPB2) protect against gly-LDL induced VEC apoptosis through PIMT regulation.

Methods and Results

HUVEC transfected negative control and PIMT siRNA were treated with or without GSPB2 (10 µmol/L) for 48 h. Moreover, HUVEC of PIMT overexpression were stimulated by gly-LDL (50 µg/ml) in the presence or absence of GSPB2 (10 µmol/L) for 48 h. Our results showed that gly-LDL downregulated PIMT expression and PIMT overexpression or GSPB2 significantly attenuated gly-LDL induced VEC apoptosis. PIMT siRNA increased VEC apoptosis with up-regulation of p53, cytochrome c release, caspase-9 and caspase-3 activation. Mechanistically, overexpression of PIMT or GSPB2 increased the phosphorylation of ERK1/2 and GSK3β in the gly-LDL induced VEC.

Conclusion

In summary, our study identified PIMT as a key player responsible for gly-LDL induced VEC apoptosis and GSPB2 protect against gly-LDL induced VEC apoptosis by PIMT up-regulation. Targeting PIMT including use of GSPB2 could be turned into clinical application in the fighting against diabetic vascular complications.