Lack of O-GlcNAcylation enhances exercise-dependent glucose utilization potentially through AMP-activated protein kinase activation in skeletal muscle.

O-GlcNAcylation is a post-translational modification that is characterized by the addition of N-acetylglucosamine (GlcNAc) to proteins by O-GlcNAc transferase (Ogt). The degree of O-GlcNAcylation is thought to be associated with glucotoxicity and diabetic complications, because GlcNAc is produced by a branch of the glycolytic pathway. However, its role in skeletal muscle has not been fully elucidated. In this study, we created skeletal muscle-specific Ogt knockout (Ogt-MKO) mice and analyzed their glucose metabolism. During an intraperitoneal glucose tolerance test, blood glucose was slightly lower in Ogt-MKO mice than in control Ogt-flox mice. High fat diet-induced obesity and insulin resistance were reversed in Ogt-MKO mice. In addition, 12-month-old Ogt-MKO mice had lower adipose and body mass. A single bout of exercise significantly reduced blood glucose in Ogt-MKO mice, probably because of higher AMP-activated protein kinase α (AMPKα) protein expression. Furthermore, intraperitoneal injection of 5-aminoimidazole-4-carboxamide ribonucleotide, an AMPK activator, resulted in a more marked decrease in blood glucose levels in Ogt-MKO mice than in controls. Finally, Ogt knockdown by siRNA in C2C12 myotubes significantly increased protein expression of AMPKα, glucose uptake and oxidation. In conclusion, loss of O-GlcNAcylation facilitates glucose utilization in skeletal muscle, potentially through AMPK activation. The inhibition of O-GlcNAcylation in skeletal muscle may have an anti-diabetic effect, through an enhancement of glucose utilization during exercise.

4-Hydroxy hexenal derived from dietary n-3 polyunsaturated fatty acids induces anti-oxidative enzyme heme oxygenase-1 in multiple organs.

It has recently been reported that expression of heme oxygenase-1 (HO-1) plays a protective role against many diseases. Furthermore, n-3 polyunsaturated fatty acids (PUFAs) were shown to induce HO-1 expression in several cells in vitro, and in a few cases also in vivo. However, very few reports have demonstrated that n-3 PUFAs induce HO-1 in vivo. In this study, we examined the effect of fish-oil dietary supplementation on the distribution of fatty acids and their peroxidative metabolites and on the expression of HO-1 in multiple tissues (liver, kidney, heart, lung, spleen, intestine, skeletal muscle, white adipose, brown adipose, brain, aorta, and plasma) of C57BL/6 mice. Mice were divided into 4 groups, and fed a control, safflower-oil, and fish-oil diet for 3 weeks. One group was fed a fish-oil diet for just 1 week. The concentration of fatty acids, 4-hydroxy hexenal (4-HHE), and 4-hydroxy nonenal (4-HNE), and the expression of HO-1 mRNA were measured in the same tissues. We found that the concentration of 4-HHE (a product of n-3 PUFAs peroxidation) and expression of HO-1 mRNA were significantly increased after fish-oil treatment in most tissues. In addition, these increases were paralleled by an increase in the level of docosahexaenoic acid (DHA) but not eicosapentaenoic acid (EPA) in each tissue. These results are consistent with our previous results showing that DHA induces HO-1 expression through 4-HHE in vascular endothelial cells. In conclusion, we hypothesize that the HO-1-mediated protective effect of the fish oil diet may be through production of 4-HHE from DHA but not EPA in various tissues.

Molecular mechanisms of the inhibitory effects of bovine lactoferrin on lipopolysaccharide-mediated osteoclastogenesis.

Lactoferrin (LF) is an important modulator of the immune response and inflammation. It has also been implicated in the regulation of bone tissue. In our previous study we demonstrated that bovine LF (bLF) reduces LPS-induced bone resorption through a reduction of TNF-α production in vivo. However, it was not known how bLF inhibits LPS-mediated TNF-α and RANKL (receptor activator of nuclear factor κB ligand) production in osteoblasts. In this study we show that bLF impairs LPS-mediated TNF-α and RANKL production. bLF inhibited LPS-mediated osteoclastogenesis via osteoblasts in a co-culture system. Furthermore, bLF pretreatment inhibited LPS-induced NFκB DNA binding activity as well as IκBα and IKKß (IκB kinase ß) phosphorylation. MAP kinase activation was also inhibited by bLF pretreatment. However, bLF pretreatment failed to block the degradation of IRAK1 (interleukin-1 receptor-associated kinase 1), which is an essential event after its activation. Remarkably, we found that bLF pretreatment inhibited LPS-mediated Lys-63-linked polyubiquitination of TNF receptor-associated factor 6 (TRAF6). We also found that bLF is mainly endocytosed through LRP1 (lipoprotein receptor-related protein-1) and intracellular distributed bLF binds to endogenous TRAF6. In addition, bLF inhibited IL-1ß- and flagellin-induced TRAF6-dependent activation of the NFκB signaling pathway. Collectively, our findings demonstrate that bLF inhibits NFκB and MAP kinase activation, which play critical roles in chronic inflammatory disease by interfering with the TRAF6 polyubiquitination process. Thus, bLF could be a potent therapeutic agent for inflammatory diseases associated with bone destruction, such as periodontitis and rheumatoid arthritis.

Omega-3 polyunsaturated fatty acid has an anti-oxidant effect via the Nrf-2/HO-1 pathway in 3T3-L1 adipocytes.

Oxidative stress is produced in adipose tissue of obese subjects and has been associated with obesity-related disorders. Recent studies have shown that omega-3 polyunsaturated fatty acid (ω3-PUFA) has beneficial effects in preventing atherosclerotic diseases and insulin resistance in adipose tissue. However, the role of ω3-PUFA on adipocytes has not been elucidated. In this study, 3T3-L1 adipocytes were treated with ω3-PUFA and its metabolites, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), or 4-hydroxy hexenal (4-HHE). ω3-PUFA and its metabolites dose-dependently increased mRNA and protein levels of the anti-oxidative enzyme, heme oxygenase-1 (HO-1); whereas no changes in the well-known anti-oxidant molecules, superoxide dismutase, catalase, and glutathione peroxidase, were observed. Knockdown of nuclear factor erythroid 2-related factor 2 (Nrf-2) significantly reduced EPA, DHA or 4-HHE-induced HO-1 mRNA and protein expression. Also, pretreatment with ω3-PUFA prevented H(2)O(2)-induced cytotoxicity in a HO-1 dependent manner. In conclusion, treatment with EPA and DHA induced HO-1 through the activation of Nrf-2 and prevented oxidative stress in 3T3-L1 adipocytes. This anti-oxidant defense may be of high therapeutic value for clinical conditions associated with systemic oxidative stress.

Dysregulation of CXCL1 Expression and Neutrophil Recruitment in Insulin Resistance and Diabetes-Related Periodontitis in Male Mice.

Insulin resistance and hyperglycemia are risk factors for periodontitis and poor wound healing in diabetes, which have been associated with selective loss of insulin activation of the PI3K/Akt pathway in the gingiva. This study showed that insulin resistance in the mouse gingiva due to selective deletion of smooth muscle and fibroblast insulin receptor (SMIRKO mice) or systemic metabolic changes induced by a high-fat diet (HFD) in HFD-fed mice exacerbated periodontitis-induced alveolar bone loss, preceded by delayed neutrophil and monocyte recruitment and impaired bacterial clearance compared with their respective controls. The immunocytokines, CXCL1, CXCL2, MCP-1, TNFα, IL-1ß, and IL-17A, exhibited delayed maximal expression in the gingiva of male SMIRKO and HFD-fed mice compared with controls. Targeted overexpression of CXCL1 in the gingiva by adenovirus normalized neutrophil and monocyte recruitment and prevented bone loss in both mouse models of insulin resistance. Mechanistically, insulin enhanced bacterial lipopolysaccharide-induced CXCL1 production in mouse and human gingival fibroblasts (GFs), via Akt pathway and NF-κB activation, which were reduced in GFs from SMIRKO and HFD-fed mice. These results provided the first report that insulin signaling can enhance endotoxin-induced CXCL1 expression to modulate neutrophil recruitment, suggesting CXCL1 as a new therapeutic direction for periodontitis or wound healing in diabetes. ARTICLE HIGHLIGHTS: The mechanism for the increased risks for periodontitis in the gingival tissues due to insulin resistance and diabetes is unclear. We investigated how insulin action in gingival fibroblasts modulates the progression of periodontitis in resistance and diabetes. Insulin upregulated the lipopolysaccharide-induced neutrophil chemoattractant, CXCL1, production in gingival fibroblasts via insulin receptors and Akt activation. Enhancing CXCL1 expression in the gingiva normalized diabetes and insulin resistance-induced delays in neutrophils recruitment and periodontitis. Targeting dysregulation of CXCL1 in fibroblasts is potentially therapeutic for periodontitis and may also improve wound healing in insulin resistance and diabetes.

Glycemic control and number of natural teeth: analysis of cross-sectional Japanese employment-based dental insurance claims and medical check-up data.

AIM: Diabetes mellitus is a well-known risk factor for onset and progression of periodontal disease. However, the continuous relationship between glycemic control and the number of natural teeth has not been well characterized in large-scale studies. We aimed to determine whether the glycated hemoglobin A1c (HbA1c) level and fasting plasma glucose (FPG) are associated with the number of natural teeth. METHODS: A cross-sectional study: A database comprising employment-based health insurance claim and medical check-up data from 706,150 participants between April 2015 and March 2016 in Japan. The exclusion criteria included missing data regarding dental receipts, number of natural teeth, HbA1c, smoking status, and age < 20 years. Ultimately, 233,567 individuals were analyzed. The participants were allocated to five groups according to their HbA1c and three groups according to their FPG, and then the number of natural teeth were compared. RESULTS: Higher HbA1c was associated with fewer teeth in participants ≥ 30 years of age (P for trend < 0.001). Higher FPG was associated with fewer teeth between 30 and 69 years of age (P for trend < 0.001). Participants with impaired fasting glucose was already at risk for fewer teeth between 40 and 69 years of age than those with normal FPG. CONCLUSIONS: Glycemic control is strongly associated with the number of natural teeth in the real-world setting. Furthermore, there are continuous relationships of HbA1c and FPG with number of natural teeth including individual with impaired fasting glucose. These data emphasize the importance of glycemic control and appropriate oral care for the protection against tooth loss. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13340-021-00533-2.

Real-world evidence of the impact of obesity on residual teeth in the Japanese population: A cross-sectional study.

BACKGROUND: Tooth loss is associated with nutritional status and significantly affects quality of life, particularly in older individuals. To date, several studies reveal that a high BMI is associated with tooth loss. However, there is a lack of large-scale studies that examined the impact of obesity on residual teeth with respect to age and tooth positions. OBJECTIVE: We assessed the impact of obesity on the number and position of residual teeth by age groups using large scale of Japanese database. METHODS: This was a cross-sectional study of 706150 subjects that were included in the database that combined the data from health insurance claims and health check-up, those lacking information about BMI, HbA1c level, smoking status, and the number of residual teeth were excluded. Thus, a total of 233517 aged 20-74 years were included. Subjects were classified into 4 categories based on BMI, and the number of teeth was compared between age-groups. The percentage of subjects with residual teeth in each position was compared between groups with obesity (BMI ≥25.0 kg/m2) and non-obesity. Logistic regression analysis was performed to clarify whether obesity predicts having <24 teeth. RESULTS: Higher BMI was associated with fewer teeth over 40s (P for trend <0.0001 when <70s). Obesity was associated with the reduction of residual teeth in the maxillary; specifically, the molars were affected over the age 30. Smoking status further affected tooth loss at positions that were not affected by obesity alone. After adjusting for age, sex, smoking status, and HbA1c ≥6.5%, obesity remained an independent predictive factor for having <24 teeth (ORs: 1.35, 95% CIs: 1.30-1.40). CONCLUSIONS: We found that an increase in BMI was associated with a decrease in the number of residual teeth from younger ages independently of smoking status and diabetes in the large scale of Japanese database.

Oral administration of bovine lactoferrin suppresses the progression of rheumatoid arthritis in an SKG mouse model.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammatory bone destruction in which tumor necrosis factor alpha (TNF-α) plays a key role. Bovine lactoferrin (bLF) is a multifunctional protein with anti-inflammatory and immunomodulatory properties. This study aimed to clarify the inhibitory effects of bLF on the pathological progression of RA. The mannan-induced arthritis model in SKG mice (genetic RA model) was used. Orally applied liposomal bLF (LbLF) markedly reduced ankle joint swelling and bone destruction. Histologically, pannus formation and osteoclastic bone destruction were prevented in the LbLF-treated animals. Moreover, orally administered LbLF improved the balance between Th17 cells and regulatory T cells isolated from the spleen of mannan-treated SKG mice. In an in vitro study, the anti-inflammatory effects of bLF on TNF-α-induced TNF-α production and downstream signaling pathways were analyzed in human synovial fibroblasts from RA patients (RASFs). bLF suppressed TNF-α production from RASFs by inhibiting the nuclear factor kappa B and mitogen-activated protein kinase pathways. The intracellular accumulation of bLF in RASFs increased in an applied bLF dose-dependent manner. Knockdown of the lipoprotein receptor-related protein-1 (LRP1) siRNA gene reduced bLF expression in RASFs, indicating that exogenously applied bLF was mainly internalized through LRP-1. Immunoprecipitated proteins with anti-TNF receptor-associated factor 2 (TRAF2; an adapter protein/ubiquitin ligase) included bLF, indicating that bLF binds directly to the TRAF2-TRADD-RIP complex. This indicates that LbLF may effectively prevent the pathological progression of RA by suppressing TNF-α production by binding to the TRAF2-TRADD-RIP complex from the RASFs in the pannus. Therefore, supplemental administration of LbLF may have a beneficial effect on preventive/therapeutic reagents for RA.

Inhibitory effects of orally administrated liposomal bovine lactoferrin on the LPS-induced osteoclastogenesis.

Bovine lactoferrin (bLF) modulates the production of proinflammatory cytokines including tumor necrosis factor (TNF)-alpha, and may thus control alveolar bone destruction associated with periodontitis. In this study, the effects of bLF on mRNA expression in lipopolysaccharide (LPS)-stimulated osteoblasts (OBs) and on LPS-induced osteoclastogenesis were examined. The inhibitory effects of oral administration of liposomal-bLF (L-bLF), which improved the robustness of bLF to digestive enzymes, on alveolar bone resorption using LPS-induced periodontitis rat model are also reported. Three groups of 7-week-old male Wistar rats were treated with L-bLF (L-bLF group), bLF (bLF group), or the vehicle (control group) in drinking water (n=6 in each group). On day 7, LPS was topically applied into the gingival sulcus. Number of osteoclasts and immunoexpression of TNF-alpha were analyzed. The bLF inhibited the upregulation of TNF-alpha-mRNA- and upregulation of receptor activator of NF kappaB (RANKL)-mRNA expression and eliminated downregulation of osteoprotegerin (OPG)-mRNA expression in LPS-stimulated OBs and reduced LPS-induced osteoclastogenesis in co-culture with primary OBs and bone marrow cells. In the control group, the number of osteoclasts increased after LPS treatment. The number of osteoclasts that appeared along the alveolar bone margin was significantly reduced (P<0.01) in the L-bLF but not in the bLF group. Furthermore, L-bLF suppressed upregulation of TNF-alpha immunoexpression in periodontal tissue and TNF-alpha and interleukin (IL)-1 beta-mRNA level in gingival tissue. The results of this study indicate that oral administration of L-bLF significantly reduces alveolar bone resorption induced by LPS stimulation through inhibition of TNF-alpha production and modulation of RANKL/OPG balance in OBs. It is suggested that L-bLF could be a potent therapeutic and preventive agent for attenuating alveolar bone destruction in periodontitis patients.

Low concentration of 4-hydroxy hexenal increases heme oxygenase-1 expression through activation of Nrf2 and antioxidative activity in vascular endothelial cells.

Large-scale clinical studies have shown that n-3 polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic and docosahexaenoic acids reduce cardiovascular events without improving classical risk factors for atherosclerosis. Recent studies have proposed that direct actions of n-3 PUFAs themselves, or of their enzymatic metabolites, have antioxidative and anti-inflammatory effects on vascular cells. Although a recent study showed that plasma 4-hydroxy hexenal (4-HHE), a peroxidation product of n-3 PUFA, increased after supplementation of docosahexaenoic acid, the antiatherogenic effects of 4-HHE in vascular cells remain unclear. In the present study, we tested the hypothesis that 4-HHE induces the antioxidative enzyme heme oxygenase-1 (HO-1) through activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulatory transcriptional factor, and prevents oxidative stress-induced cytotoxicity in vascular endothelial cells. This mechanism could partly explain the cardioprotective effects of n-3 PUFAs. Human umbilical vein endothelial cells were stimulated with 1-10µM 4-HHE or 4-hydroxy nonenal (4-HNE), a peroxidation product of n-6 PUFAs. Both 4-HHE and 4-HNE dose-dependently increased HO-1 mRNA and protein expression, and intranuclear expression and DNA binding of Nrf2 at 5µM. Small interfering RNA for Nrf2 significantly reduced 4-HHE- or 4-HNE-induced HO-1 mRNA and protein expression. Furthermore, pretreatment with 4-HHE or 4-HNE prevented tert-butyl hydroperoxide-induced cytotoxicity. In conclusion, 4-HHE, a peroxidation product of n-3 PUFAs, stimulated expression of the antioxidant enzyme HO-1 through the activation of Nrf2 in vascular endothelial cells. This resulted in prevention of oxidative stress-induced cytotoxicity, and may represent a possible mechanism to partly explain the cardioprotective effects of n-3 PUFAs.

Human trial of liposomal lactoferrin supplementation for periodontal disease.

New approaches to periodontal health have been in strong demand in addition to conventional local plaque control. In this study, liposomal bovine lactoferrin (L-bLF) was orally administered to subjects with periodontal disease to investigate whether it could be a useful treatment. L-bLF composed of soy phosphatidylcholine was given as a supplement for four weeks in tablet form (180 mg bLF/d) to twelve subjects with multiple sites of more than 3 mm probing depth (PD). PD, bleeding on probing (BOP), gingival crevicular fluid (GCF) volume and the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6, and monocyte chemoattractant protein-1 (MCP-1) in GCF were evaluated for 51 sites with more than 4 mm PD in five subjects. Blood samples of all subjects were collected 0, 2 and 4 weeks after supplementation. Isolated peripheral blood mononuclear cells (PBMCs) were incubated for 24 h with or without lipopolysaccharide (LPS) (100 ng/ml) from Porphyromonas gingivalis, and TNF-α, IL-1ß, IL-6 and MCP-1 in the culture media were measured. Toll-like receptor 2 (TLR2) and TLR4 mRNA expressions of isolated PBMCs were also quantitatively analyzed using real-time reverse transcription-polymerase chain reaction (RT-PCR). The PD was significantly reduced by L-bLF supplementation, but the BOP and GCF volume were not significantly changed. The MCP-1 level in GCF was significantly reduced, while levels of other cytokines were not changed. Four-week L-bLF supplementation also showed significant decreases of LPS-induced cytokine production from PBMCs. Relative gene expressions of TLR2 and TLR4 did not change. These results suggest that L-bLF supplementation can be effective in the treatment of periodontal disease, although prospective controlled large-scale studies are required.

Bovine lactoferrin enhances osteogenesis through Smad2/3 and p38 MAPK activation.

OBJECTIVES: Lactoferrin (LF) possesses diverse biological functions. We previously reported that bovine LF (bLF) attenuates lipopolysaccharide-induced bone resorption in osteoblasts. In addition to its ability to inhibit osteoclastogenesis, bLF has been implicated in stimulating bone formation. However, the molecular mechanisms of bLF in bone cell anabolism remain unclear. Here, we tried to analyse the molecular mechanisms involved in osteogenesis in the presence of bLF. METHODS: Alkaline phosphatase activity, Runx2 activity, gene expression, and Alizarin red staining were analyzed to evaluate the osteogenic differentiation status. The expression of the Smads and mitogen-activated protein kinase (MAPK) signaling molecules was analyzed via western blotting. Ex vivo organ cultures of mouse calvariae were performed to evaluate the effect of bLF on bone regeneration. RESULTS: bLF enhanced the osteoblastic differentiation of mesenchymal stem cells through activation of Smad2/3 and p38 MAPK, which increased the transcriptional activity of Runx2. bLF treatment also enhanced osteoblastic differentiation and mineralized nodule formation of osteoblast-lineage cells, and repaired bone defects ex vivo. Moreover, inhibition of Smad2/3 or p38 MAPK signaling reduced the anabolic effects of bLF. Together, these results suggested that bLF is a potent osteogenic factor, which mediates its function via activation of the Smad2/3 and p38 MAPK signaling pathways. CONCLUSIONS: Here, we described a novel function of bLF and its signal transduction mechanisms in osseous tissue. Along with inhibiting osteoclastogenesis, bLF may limit further osteoclast formation and contribute to bone mass enlargement. Thus, bLF represents a potentially valuable therapeutic agent for bone regeneration and destructive bone diseases.

Rice Bran Supplement Containing A Functional Substance, the Novel Peptide Leu-Arg-Ala, has Anti-Hypertensive Effects: A Double-Blind, Randomized, Placebo-Controlled Study.

The anti-hypertensive effect of processed rice bran (PRB) was recently reported, for which the novel peptide Leu-Arg-Ala (LRA) was identified as the functional substance. The purpose of this study was to assess the anti-hypertensive effects of a rice bran supplement containing PRB in individuals with high-normal blood pressure (systolic blood pressure (SBP): 130⁻139 mmHg and/or diastolic blood pressure (DBP): 85⁻89 mmHg) or grade 1 hypertension (SBP: 140⁻159 mmHg and/or DBP: 90⁻99 mmHg). One hundred individuals with high-normal blood pressure or grade 1 hypertension were recruited to participate in this double-blind, randomized, placebo-controlled study. Participants were randomly allocated to the placebo group (n = 50) or the test group (n = 50). Each group took four test tablets (43 µg LRA/day) or four placebo tablets daily. The decrease in blood pressure in the test group compared with the placebo group was the primary outcome. Adverse events were recorded and hematological/urinary parameters measured to determine the safety of the supplement, which was the secondary outcome. In total, 87 participants completed the study. The SBP of the test group at 12 weeks was significantly lower than that of the placebo group (p = 0.0497). No serious adverse events were observed. Daily consumption of a rice bran supplement containing PRB can safely improve mildly elevated blood pressure.

Vasorelaxant and Antihypertensive Effects That Are Dependent on the Endothelial NO System Exhibited by Rice Bran-Derived Tripeptide.

We recently identified a novel, potent antihypertensive peptide, Leu-Arg-Ala (LRA; minimum effective dose = 0.25 mg/kg), from rice bran protein. In this study, we found that LRA potently relaxed mesenteric arteries isolated from spontaneously hypertensive rats (SHRs) (EC50 = 0.1 µM). In contrast, the vasorelaxant activity of each amino acid that constitutes the LRA tripeptide was remarkably attenuated. The LRA-induced vasorelaxant activity was inhibited by N(G)-nitro-l-arginine methyl ester (L-NAME; NO synthase [NOS] inhibitor) but not by an antagonist of bradykinin B2 and Mas receptors or by a phosphoinositide 3-kinase inhibitor. The antihypertensive effect induced after the oral administration of LRA was inhibited by L-NAME. LRA also induced the phosphorylation of endothelial NOS in human umbilical vein endothelial cells. Taken together, LRA may exhibit antihypertensive effects via NO-mediated vasorelaxation. LRA is the first example of a NO-dependent vasorelaxant peptide identified from rice bran protein.

Homozygous receptors for insulin and not IGF-1 accelerate intimal hyperplasia in insulin resistance and diabetes.

Insulin and IGF-1 actions in vascular smooth muscle cells (VSMC) are associated with accelerated arterial intima hyperplasia and restenosis after angioplasty, especially in diabetes. To distinguish their relative roles, we delete insulin receptor (SMIRKO) or IGF-1 receptor (SMIGF1RKO) in VSMC and in mice. Here we report that intima hyperplasia is attenuated in SMIRKO mice, but not in SMIGF1RKO mice. In VSMC, deleting IGF1R increases homodimers of IR, enhances insulin binding, stimulates p-Akt and proliferation, but deleting IR decreases responses to insulin and IGF-1. Studies using chimeras of IR(extracellular domain)/IGF1R(intracellular-domain) or IGF1R(extracellular domain)/IR(intracellular-domain) demonstrate homodimer IRα enhances insulin binding and signaling which is inhibited by IGF1Rα. RNA-seq identifies hyaluronan synthase2 as a target of homo-IR, with its expression increases by IR activation in SMIGF1RKO mice and decreases in SMIRKO mice. Enhanced intima hyperplasia in diabetes is mainly due to insulin signaling via homo-IR, associated with increased Has2 expression.

Characterization of periodontitis in people with type 1 diabetes of 50 years or longer duration.

BACKGROUND: Periodontitis is more common and severe in people with diabetes than the general population. We have reported in the Joslin Medalist Study that people with type 1 diabetes of ≥50 years (Medalists) may have endogenous protective factors against diabetic nephropathy and retinopathy. METHODS: In this cross-sectional study, the prevalence of periodontitis according to the Centers for Disease Control/American Academy of Periodontology classification in a subset (n = 170, mean age = 64.6 ± 6.9 years) of the Medalist cohort, and its associations to various criteria of periodontitis and diabetic complications were assessed. RESULTS: The prevalence of severe periodontitis in Medalists was only 13.5% which was lower than reported levels in diabetic patients of similar ages. Periodontal parameters, including bleeding on probing, plaque index, gingival index, and demographic traits, including male sex, chronological age, and age at diagnosis were significantly associated with severity of periodontitis, which did not associate with diabetes duration, hemoglobin A1c (HbA1c), body mass index, and lipid profiles. Random serum C-peptide levels inversely associated with severity of periodontitis (P = 0.03), lower probing depth (P = 0.0002), and clinical attachment loss (P = 0.03). Prevalence of cardiovascular diseases (CVD) and systemic inflammatory markers, plasma interleukin-6 (IL-6), and serum immunoglobulin G titer against Porphyromonas gingivalis positively associated with severity of periodontitis (P = 0.002 and 0.02, respectively). Antibody titer to P. gingivalis correlated positively and significantly with CVD, serum IL-6, and high-sensitivity C-reactive protein. CONCLUSIONS: Some Medalists could be protected from severe periodontitis even with hyperglycemia. Endogenous protective factors for periodontitis could possibly be related to residual insulin production and lower levels of chronic inflammation.

Retinol binding protein 3 is increased in the retina of patients with diabetes resistant to diabetic retinopathy.

The Joslin Medalist Study characterized people affected with type 1 diabetes for 50 years or longer. More than 35% of these individuals exhibit no to mild diabetic retinopathy (DR), independent of glycemic control, suggesting the presence of endogenous protective factors against DR in a subpopulation of patients. Proteomic analysis of retina and vitreous identified retinol binding protein 3 (RBP3), a retinol transport protein secreted mainly by the photoreceptors, as elevated in Medalist patients protected from advanced DR. Mass spectrometry and protein expression analysis identified an inverse association between vitreous RBP3 concentration and DR severity. Intravitreal injection and photoreceptor-specific overexpression of RBP3 in rodents inhibited the detrimental effects of vascular endothelial growth factor (VEGF). Mechanistically, our results showed that recombinant RBP3 exerted the therapeutic effects by binding and inhibiting VEGF receptor tyrosine phosphorylation. In addition, by binding to glucose transporter 1 (GLUT1) and decreasing glucose uptake, RBP3 blocked the detrimental effects of hyperglycemia in inducing inflammatory cytokines in retinal endothelial and Müller cells. Elevated expression of photoreceptor-secreted RBP3 may have a role in protection against the progression of DR due to hyperglycemia by inhibiting glucose uptake via GLUT1 and decreasing the expression of inflammatory cytokines and VEGF.

Co-Ingestion of Rice Bran Soymilk or Plain Soymilk with White Bread: Effects on the Glycemic and Insulinemic Response.

The regular consumption of soy products is associated with inverse incidence of type 2 diabetes, and there has been an increasing interest in the glycemia reducing potential of rice bran and its components. In this study, we investigated whether consuming soymilk with the addition of rice bran (fiber) can reduce the glycemic response of a carbohydrate meal. Seventeen healthy Asian men (BMI: 18.5-29 kg/m²) participated in this randomized crossover trial. On four occasions, they consumed white bread (two times) and white bread with two different soymilks differing in protein and rice bran content. Blood samples were taken to measure glucose and insulin response over a period of 3 hours. Taking the glycemic index (GI) value of white bread as a reference value of 100, the GI of white bread when co-ingested with rice bran soymilk (RBS) was 83.1 (±7.7) and sugar-free soymilk (SFS) was 77.5 (±10.1), both were lower than white bread (p < 0.05). The insulin response of both soymilk treatments was similar to white bread (p > 0.05). The glucose/insulin ratio of RBS and SFS were respectively 43.1 (± 6.1) and 60.0 (± 17.0) and were lower (p < 0.05) than white bread (123.5 ± 21.1) during the first 30 min. In conclusion, co-ingestion of low amounts of soy protein with a carbohydrate meal stimulated early-phase insulin secretion and thereby increased blood glucose clearance effectiveness. Furthermore, rice bran-fortified soymilk reduced the glycemic response similarly to soymilk with a greater dose of soy protein. Rice bran and its components offer therapeutic potential for glycemic and insulinemic control.

A Novel Antihypertensive Peptide Identified in Thermolysin-Digested Rice Bran.

SCOPE: Hypertension is a risk factor for arteriosclerosis. In this study, we investigate the antihypertensive effect of protease-digested rice bran in a spontaneously hypertension rat (SHR) model. We also purify a novel antihypertensive peptide from the digest. METHODS AND RESULTS: Thermolysin-digested rice bran (TRB) is administered to SHRs for 4 weeks, and systolic blood pressure (SBP) was measured weekly using the tail-cuff method. TRB shows an antihypertensive effect in a dose-dependent manner. TRB also reduces angiotensin I-converting enzyme (ACE) activity in lung tissue and serum troponin I levels. TRB is fractionated by HPLC and ACE-inhibitory activity in the HPLC fractions is measured. Peptides LRA and YY are identified from the two fractions with the strongest ACE-inhibitory activity. Amino acid sequence of these peptides are found in a vicilin-like seed storage protein, and identified in rice bran protein using the peptide mass fingerprint method. We confirm that LRA and YY are cleaved by thermolysin digestion of a model synthetic peptide. Orally administered LRA (0.25 mg kg-1 ) or YY (0.5 mg kg-1 ) lowers the SBP of SHRs at 4 h after administration. CONCLUSION: We identify a novel, orally active antihypertensive peptide, LRA from the digest of rice bran protein.

Fiber-rich diet with brown rice improves endothelial function in type 2 diabetes mellitus: A randomized controlled trial.

BACKGROUND & AIMS: A fiber-rich diet has a cardioprotective effect, but the mechanism for this remains unclear. We hypothesized that a fiber-rich diet with brown rice improves endothelial function in patients with type 2 diabetes mellitus. METHODS: Twenty-eight patients with type 2 diabetes mellitus at a single general hospital in Japan were randomly assigned to a brown rice (n = 14) or white rice (n = 14) diet and were followed for 8 weeks. The primary outcome was changes in endothelial function determined from flow debt repayment by reactive hyperemia using strain-gauge plethysmography in the fasting state. Secondary outcomes were changes in HbA1c, postprandial glucose excursions, and markers of oxidative stress and inflammation. The area under the curve for glucose after ingesting 250 kcal of assigned rice was compared between baseline (T0) and at the end of the intervention (T1) to estimate glucose excursions in each group. RESULTS: Improvement in endothelial function, assessed by fasting flow debt repayment (20.4% vs. -5.8%, p = 0.004), was significantly greater in the brown rice diet group than the white rice diet group, although the between-group difference in change of fiber intake was small (5.6 g/day vs. -1.2 g/day, p<0.0001). Changes in total, HDL-, and LDL-cholesterol, and urine 8-isoprostane levels did not differ between the two groups. The high-sensitivity C-reactive protein level tended to improve in the brown rice diet group compared with the white rice diet group (0.01 µg/L vs. -0.04 µg/L, p = 0.063). The area under the curve for glucose was subtly but consistently lower in the brown rice diet group (T0: 21.4 mmol/L*h vs. 24.0 mmol/L*h, p = 0.043, T1: 20.4 mmol/L*h vs. 23.3 mmol/L*h, p = 0.046) without changes in HbA1c. CONCLUSIONS: Intervention with a fiber-rich diet with brown rice effectively improved endothelial function, without changes in HbA1c levels, possibly through reducing glucose excursions.