Natural food science based novel approach toward prevention and treatment of obesity and type 2 diabetes: recent studies on brown rice and γ-oryzanol

Effects of extracted oil of fermented Tartary buckwheat on lipid-lowering, inflammation modulation, and gut microbial regulation in mice

This study investigated the composition of Tartary buckwheat oil fermented by Monascus purpureus and extracted under supercritical CO2 conditions (FTBO) and evaluated its effects on lipid-lowering, inflammation modulation, and gut microbial regulation in mice that were fed a high-fat diet (MOD). Compared with the raw oil (TBO), the γ-oryzanol content reached 27.09 mg g-1; the monounsaturated fatty acid (MUFA) content (such as oleic acid and palmitic acid) was elevated; and the antioxidant capacities of DPPH, ABTS, and hydroxyl were improved in FTBO (p < 0.0001). Then, supplementation with FTBO had a remarkable effect on reducing the body weight and visceral obesity as well as alleviating hyperglycemia, dyslipidemia, inflammatory reactions, and liver damage. The TC, TG, and LDL-C levels in the liver and plasma were reduced, and the HDL-C levels in the liver were increased (p < 0.05). In particular, the high-dose group (FTBOH) exhibited the most significant effect on reducing the pro-inflammatory cytokines ET, TNF-α, IL-1β, and IL-6 in the liver, which were 18.85, 570.12, 50.47, and 26.22 pg mL-1, respectively (p < 0.05). Moreover, FTBO reversed intestinal disorders and increased the intestinal microbial diversity and richness. The relative abundance of beneficial bacteria, such as Bifidobacterium, Lactobacillus, Limosilactobacillus, and Lachnospiraceae_UCG-006, were increased, and the relative abundance of the harmful bacteria Staphylococcus and Lachnoclostridium were reduced. In summary, FTBO has potential applications as a dietary supplement or dietary modifier in lowering blood lipids, modulating immune activity, and reversing intestinal disorders. This study provides reference guidance for the subsequent industrialization and development of Tartary buckwheat, the extension of the industrial chain, the development of new products, and the extraction of functional components.

Strategies to fortify the nutritional values of polished rice by implanting selective traits from brown rice: A nutrigenomics-based approach

Whole-grain cereals are important components of a healthy diet. It reduces the risk of many deadly diseases like cardiovascular diseases, diabetes, cancer, etc. Brown rice is an example of whole grain food, which is highly nutritious due to the presence of various bioactive compounds (flavonoids, phenolics, vitamins, phytosterols, oils, etc.) associated with the rice bran layer of brown rice. White rice is devoid of the nutritious rice bran layer and thus lacks the bioactive compounds which are the major attractants of brown rice. Therefore, to confer health benefits to the public at large, the nutrigenomic potential of white rice may be improved by integrating the phytochemicals associated with the rice bran layer of brown rice into it via biofortification processes like conventional breeding, agronomic practices, metabolic engineering, CRISPR/Cas9 technology, and RNAi techniques. Thus, this review article focuses on improving the nutritional qualities of white/polished rice through biofortification processes, utilizing new breeding technologies (NBTs).

Involvement of intestinal flora and miRNA into the mechanism of coarse grains improving type 2 diabetes: an overview

The prevalence of type 2 diabetes has been growing at an increasing rate worldwide. Dietary therapy is probably the easiest and least expensive method to prevent and treat diabetes. Previous studies have reported that coarse grains have anti-diabetic effects. Although considerable efforts have been made on the anti-diabetic function of different grains, the mechanisms of coarse grains on type 2 diabetes have not been systematically compared and summarized so far. Intestinal flora, reported as the main 'organ' of action underlying coarse grains, is an important factor in the alleviation of type 2 diabetes by coarse grains. Furthermore, microRNA (miRNA), as a new disease marker and 'dark nutrient', plays a likely influential role in cross-border communication among coarse grains, intestinal flora, and hosts. Given this context, this article reviews several possible mechanisms for the role of coarse grains on diabetes, incorporating resistance to inflammation and oxidative stress, repair of insulin signaling and β-cell dysfunction, and highlights the regulation of intestinal flora disorders and miRNAs expression, along with some novel insights. © 2022 Society of Chemical Industry.

Whole grain rice: Updated understanding of starch digestibility and the regulation of glucose and lipid metabolism

Nowadays, resulting from disordered glucose and lipid metabolism, metabolic diseases (e.g., hyperglycemia, type 2 diabetes, and obesity) are among the most serious health issues facing humans worldwide. Increasing evidence has confirmed that dietary intervention (with healthy foods) is effective at regulating the metabolic syndrome. Whole grain rice (WGR) rich in dietary fiber and many bioactive compounds (e.g., γ-amino butyric acid, γ-oryzanol, and polyphenols) can not only inhibit starch digestion and prevent rapid increase in the blood glucose level, but also reduce oxidative stress and damage to the liver, thereby regulating glucose and lipid metabolism. The rate of starch digestion is directly related to the blood glucose level in the organism after WGR intake. Therefore, the effects of different factors (e.g., additives, cooking, germination, and physical treatments) on WGR starch digestibility are examined in this review. In addition, the mechanisms from human and animal experiments regarding the correlation between the intake of WGR or its products and the lowered blood glucose and lipid levels and the reduced incidence of diabetes and obesity are discussed. Moreover, information on developing WGR products with the health benefits is provided.

Gamma oryzanol niosomal gel for skin cancer: formulation and optimization using quality by design (QbD) approach

Skin cancer is fifth most diagnosed disease in human population due to ultraviolet radiation (UV) exposure. Gamma oryzanol (OZ) is a natural antioxidant, and it also has skin anti-aging properties. OZ is naturally found in rice bran oil. The main aim of the present work was to optimize OZ niosomal formulation using quality by design approach including one variable at a time and full factorial design. Niosomes were prepared by solvent injection method and characterized for size, polydispersity index, drug entrapment, and transmission electron microscopy. The optimized batch obtained at X1 [drug to span 60 molar ratio (1:5)], X2 [volume of hydration (75 mL)], and X3 [stirring speed (2500 rpm)] to Y1 [average vesicle size (196.6 nm)] and Y2 [entrapment efficiency (78.31%)] as dependent variables. The optimized OZ noisomes were formulated by niosomal gel to provide improved physicochemical stability upon topical application against UV. The niosomal gel was characterized using pH meter, viscometer, Draize test for skin irritancy, ex vivo permeation studies, and stability studies. Ex vivo permeation studies of OZ niosomal gel not only showed fourfold higher permeation but also exhibited better drug retention in dermal layers of skin as compared to OZ gel. Quality Target Product Profile of OZ niosomal formulation was generated. Risk analysis of optimized OZ gel suggested most critical quality attributes (CQAs) and critical process parameters (CPPs) to be characterized as low risk. Thus, γ-oryzanol niosomal gel for topical use can serve as a promising prophylactic treatment in skin cancer, and the developed prototype formulation can be further extended to future newly discovered drugs with similar characteristics.

Graphical abstract

Multi-Mechanistic In Vitro Evaluation of Antihyperglycemic, Antioxidant and Antiglycation Activities of Three Phenolic-Rich Indian Red Rice Genotypes and In Silico Evaluation of Their Phenolic Metabolites

The study evaluated the antidiabetic potential of three traditional Indian red rice genotypes/RR (Kattuyanam/KA, Chennangi/CH & Karungkuruvai/KU) using a combination of in vitro, metabolomics (Quadrupole-Time of Flight-Liquid chromatography-Mass spectrometry/Q-TOF-LC-MS/MS), and in silico techniques. In terms of antihyperglycemic potential, KA exhibited the highest inhibitory activity against α-amylase; CH against α-glucosidase; and KU against DPPIV and PTP1B enzymes. KA exhibited the highest antioxidant activity (DPPH, FRAP, and ABTS) and greater inhibition of protein glycation compared to other RR indicating its potential to mitigate diabetic complications. The metabolomic analysis confirmed the presence of 99 phenolics in the sample extracts (KU-71, KA-70, CH-68). Molecular docking studies revealed seven metabolites to be good inhibitors of the four target enzymes and activators of insulin receptor substrate/IRS. The antihyperglycemic and oxidation-glycation reduction composite index revealed KA to have the highest overall antidiabetic potential. Hence, the RR could be utilized in functional foods with a multi-barrelled strategy for diabetes prevention/management.

Chlorogenic acid and β-glucan from highland barley grain ameliorate β-cell dysfunction via inhibiting apoptosis and improving cell proliferation

Recent studies have reported that highland barley as a whole grain diet has anti-hyperglycemic effects, however little information is available about the active compounds that ameliorate pancreatic β-cell dysfunction and the related mechanisms. In this study, chlorogenic acid (CA) and β-glucan (BG) were identified as the active compounds that ameliorated β-cell dysfunction. CA ameliorated β-cell dysfunction by inhibiting cell apoptosis and improving glucose-stimulated insulin secretion via targeting G protein-coupled receptor 40 (GPR40) and regulating the phospholipase C β (PLCβ) pathway. BG ameliorated β-cell dysfunction by improving cell proliferation via targeting mammalian target of rapamycin (mTOR) and regulating the protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β) pathway. Furthermore, CA and BG improved β-cell sensitivity and pancreatic insulin secretion, and inhibited β-cell apoptosis in impaired glucose tolerance (IGT) mice. Notably, CA restored homeostasis model assessment (HOMA)-β values and Ca²⁺-ATP and K⁺-ATP levels back to normal levels, and BG at 300 mg per kg BW restored β-cell insulin contents back to normal levels in IGT mice. Additionally, the combination of CA and BG had an additive effect on ameliorating β-cell dysfunction. These results help develop whole highland barley grain as a functional food for preventing type 2 diabetes by ameliorating pancreatic β-cell damage.

Biological and Pharmacological Effects of Gamma-oryzanol: An Updated Review of the Molecular Mechanisms

BACKGROUND

Gamma-oryzanol (γ-oryzanol) is one of the rice bran oil (RBO) compounds, known as a principal food source throughout the world. In recent numerous experimental studies, γ-oryzanol has been revealed to have several useful pharmacological properties, such as anti-oxidant, anti-inflammatory, anti-cancer, anti-diabetic, ameliorating unpleasant menopausal symptoms, cholesterol-lowering, improving plasma lipid pattern, etc. Methods: In this study, we reviewed the scientific literature published up until 2020, which has evaluated the biological and pharmacological activity of gamma-oryzanol. This review summarizes the published data found in PubMed, Science Direct, and Scopus.

RESULTS AND CONCLUSION

The present review attempts to summarize the most related articles about the pharmacological and therapeutic potential from recent studies on γ-oryzanol to gain insights into design further studies to achieve new evidence that confirm the observed effects.

The effect of brown rice compared to white rice on adiposity indices, lipid profile, and glycemic markers: a systematic review and meta-analysis of randomized controlled trials

A few randomized controlled trials (RCTs) have assessed the effect of brown rice consumption on metabolic parameters compared to white rice, with inconsistent findings. Therefore, the present systematic review and meta-analysis was designed to evaluate the effect of brown rice on adiposity indices, lipid profile, and glycemic markers in adult subjects compared to white rice. In this study, PubMed/Medline, Scopus, Web of Sciences, and Embase databases were comprehensively searched until March 2021. Thirteen RCTs were selected and then included in the meta-analysis. As reported, brown rice significantly reduced weight by -1.63 kg (95% CI: -2.15 to -1.11, I²=97%, n = 6), body mass index (BMI) by -0.58 kg/m² (95% CI: -0.78 to -0.37, I²=96%, n = 6), and waist circumference by -2.56 cm (95% CI: -4.86 to -0.26, I²=88%, n = 5) compared with white rice. Moreover, it had no significant effect on lipid profile and glycemic markers. Besides, pre-germinated brown rice significantly declined weight (-1.75 kg, 95% CI: -2.70 to -0.81, I²=99%, n = 4), total cholesterol (-24.22 mg/dl, 95% CI: -33.03 to -15.41, I²=78%, n = 5), triglyceride (TG) (-43.28 mg/dl, 95% CI: -74.05 to -12.50, I²=90%, n = 5), low-density lipoprotein (LDL) (-20.05 mg/dl, 95% CI: -29.57 to -10.52, I²=71%, n = 5), and fasting blood glucose (FBG) (-15.83 mg/dl, 95% CI: -25.20 to -6.46, I²=91%, n = 5). In accordance with Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, the certainly of the included evidence was low and very low. The results of the present study indicate that, brown rice has anti-obesity effects in comparison with white rice; however, it has no beneficial effects on lipid profile and glycemic markers. Contrary to brown rice, it was shown that, pre-germinated brown rice significantly decreases body weight and improves lipid profile and FBG levels compared to white rice. Accordingly, our results indicate that, pre-germinated brown rice has better functional effects on promoting lipid profile and FBG compared to brown rice.

Protective and therapeutic effects of natural products against diabetes mellitus via regenerating pancreatic β-cells and restoring their dysfunction

Diabetes mellitus is a growing public health concern and an increasing interest has been raised to search for new compounds with therapeutic effects on β-cells. There are chronic insulin resistance and loss of β-cell mass in the case of type-2 diabetes which covers about 90% of total diabetic patients. This work aims to critically review the protective and regenerative effects of various antidiabetic natural products on pancreatic β-cells. A thorough literature survey was conducted on the natural molecules and extracts having a protective, regenerative, and repairing effect on β-cells. The primary source of the literature was online scientific databases such as PubMed, Scopus, and Google Scholar. Besides, selected relevant textbooks were also consulted. Various natural molecules including berberine, curcumin, mangiferin, stevioside and capsaicin, and extracts obtained from the plants like Capsicum annum, Gymnema sylvestre, Stevia rebaudiana and Nymphaea stellate, were found to produce regenerative and anti-apoptosis effects on β-cells. These natural products were also found to increase insulin secretion by stimulating β-cells. The present review concluded that a large number of molecules and extracts, abundantly found in nature, possess antidiabetic effect via targeting β-cells. Further research is warranted to use these agents as a drug against diabetes.

Gamma oryzanol impairs alcohol-induced anxiety-like behavior in mice via upregulation of central monoamines associated with Bdnf and Il-1β signaling

Adolescent alcohol exposure may increase anxiety-like behaviors by altering central monoaminergic functions and other important neuronal pathways. The present study was designed to investigate the anxiolytic effect of 0.5% γ-oryzanol (GORZ) and its neurochemical and molecular mechanisms under chronic 10% ethanol consumption. Five-week-old ICR male mice received either control (14% casein, AIN 93 M) or GORZ (14% casein, AIN 93 M + 0.5% GORZ) diets in this study. We showed that GORZ could potentially attenuate alcohol-induced anxiety-like behaviors by significantly improving the main behavioral parameters measured by the elevated plus maze test. Moreover, GORZ treatment significantly restored the alcohol-induced downregulation of 5-hydroxytryptophan and 5-hydroxyindole acetic acid in the hippocampus and improved homovanillic acid levels in the cerebral cortex. Furthermore, a recovery increase in the level of 3-methoxy-4-hydroxyphenylglycol both in the hippocampus and cerebral cortex supported the anxiolytic effect of GORZ. The significant elevation and reduction in the hippocampus of relative mRNA levels of brain-derived neurotrophic factor and interleukin 1β, respectively, also showed the neuroprotective role of GORZ in ethanol-induced anxiety. Altogether, these results suggest that 0.5% GORZ is a promising neuroprotective drug candidate with potential anxiolytic, neurogenic, and anti-neuroinflammatory properties for treating adolescent alcohol exposure.

Gamma Oryzanol Alleviates High-Fat Diet-Induced Anxiety-Like Behaviors Through Downregulation of Dopamine and Inflammation in the Amygdala of Mice

Background

A high-fat diet (HFD) can induce obesity and metabolic disorders that are closely associated with cognitive impairments, and the progression of several psychiatric disorders such as anxiety. We have previously demonstrated the anxiolytic-like effect of Gamma oryzanol (GORZ) in chronic restraint stressed mice.

Objective

We studied the neurochemical and molecular mechanisms that underlie the preventive effect of GORZ in HFD-induced anxiety-like behaviors, monoaminergic dysfunction, and inflammation.

Methods

Eight-week-old Institute of Cancer (ICR) male mice weighing 33–34 g were divided into the following groups and free-fed for 8 weeks: control (14% casein, AIN 93M); HFD; HFD + GORZ (0.5% GORZ). Body weight gain was checked weekly. The anxiolytic-like effects of GORZ were examined via open-field test (OFT) and elevated plus maze (EPM) test. Brain levels of monoamines [5-hydroxy tryptamine (5-HT), dopamine (DA), and norepinephrine (NE)] and their metabolites [5-hydroxyindole acetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG)], proinflammatory cytokines such as tumor necrosis factor-αα (Tnf-α) mRNA levels, and interleukin 1-β (Il-1β) mRNA levels in the cerebral cortex and amygdala were examined using high-performance liquid chromatography-electrochemical detection (HPLC-ECD), and real-time reverse transcription-polymerase chain reaction (RT-PCR), respectively.

Results

Mice fed a HFD for eight weeks showed anxiety-like behaviors in association with HFD-induced body weight gain. GORZ potentially blocked HFD-induced anxiety-like behaviors via significant improvement of the primary behavioral parameters in behavioral tests, with a minor reduction in HFD-induced body weight gain. Furthermore, GORZ treatment significantly downregulated HFD-induced upregulation of dopamine levels in the brain's amygdala. Significant reduction of the relative mRNA expression of Tnf-α and Il-1 β was also observed in the amygdala of HFD + GORZ mice, compared to HFD mice.

Conclusions

Our findings strongly suggest that 0.5% GORZ exerts anxiolytic-like effects, possibly through downregulation of dopamine, and via expression of proinflammatory cytokines Tnf-α and Il-1 β in the case of chronic HFD exposure.

Effect of High β-glucan Barley on Postprandial Blood Glucose and Insulin Levels in Type 2 Diabetic Patients

The aim of our study was to investigate whether high β-glucan-containing barley (7.2 g per 100 g) improves postprandial plasma glucose levels and suppresses postprandial insulin levels during a meal tolerance test in type 2 diabetic patients. A meal tolerance test (500 kcal) was conducted using two types of test meals: a test meal with white rice (WR) alone (WR diet) and a test meal with WR mixed with 50% barley (BR diet) as staple food. The side dish was the same in the both meals. The changes in plasma glucose and serum C-peptide immunoreactivity (CPR) levels for 180 minutes after ingestion of the test meals were compared. Ten patients with type 2 diabetes (age 52.5 ± 15.1 years, and 7 males and 3 females) were included in this study. The mean HbA1c level and body mass index were 8.8 ± 1.4%, and 29.7 ± 4.5 kg/m², respectively. Plasma glucose levels after ingestion of the WR diet or BR diet peaked at 60 minutes, which showed no significant differences between the two types of test meals. However, the incremental area under the curve (IAUC) of plasma glucose levels after ingestion of BR diet was significantly lower than that of WR diet. The serum CPR levels at 180 min and their IAUC over 180 minutes after ingestion of BR diet were significantly lower than those of WR diet. Conclusion: Increase in postprandial plasma glucose and insulin levels was suppressed by mixing high-β-glucan barley with WR in type 2 diabetic patients.

γ-Oryzanol suppresses cell apoptosis by inhibiting reactive oxygen species-mediated mitochondrial signaling pathway in H2O2-stimulated L02 cells

γ-Oryzanol, a mixture of ferulic acid esters of plant sterols and triterpene alcohols existed in rice bran oil, can ameliorate lipid metabolism and enhance antioxidant activity. In this study, we used hydrogen peroxide (H₂O₂)-induced injury in human hepatic L02 cells to investigate the mechanisms involved in the hepatoprotective activity of γ-oryzanol. The injuries produced by H₂O₂ in L02 cells include increased levels of malondialdehyde (MDA) and intracellular reactive oxygen species (ROS), decreased activities of superoxide dismutase (SOD) and catalase (CAT), loss of mitochondrial membrane potential (MMP), increased protein expressions of caspase-9 and caspase-3, and induced apoptosis. Pretreatment with γ-oryzanol enhanced the ROS scavenging activity of endogenous antioxidant enzymes and decreased lipid peroxidation in H₂O₂ treated cells. Moreover, pretreatment with γ-oryzanol inhibited H₂O₂-induced apoptosis by restoring MMP, upregulating the expression ratio of Bcl-2/Bax, and inhibiting the activation of caspase-9 and caspase-3. These findings show that γ-oryzanol can prevent H₂O₂-induced apoptosis by suppressing intracellular accumulation of ROS and impeding ROS-activated mitochondrial apoptotic pathway.

Whole Grain Brown Rice Extrudate Ameliorates the Symptoms of Diabetes by Activating the IRS1/PI3K/AKT Insulin Pathway in db/db Mice

The therapeutic benefits of whole grains on diabetes mellitus have been continuously confirmed by in-depth research. To date, limited studies have investigated the effect of extruded products of whole grains on the insulin signaling pathway in vivo. This study investigated the effects of oral consumption of whole grain extrudate, including 97% brown rice and 3% defatted rice bran (w/w, BRD), on glucose metabolism and the hepatic insulin signaling pathway in C57BL/KsJ-db/db mice. BRD treatment induced a remarkable reduction in blood glucose. Moreover, glucose intolerance and insulin resistance were ameliorated in the BRD-treated group compared with those in the db/db control group. BRD also increased the hepatic glycogen content by reducing the expression and increasing the phosphorylation of glycogen synthase kinase 3β (GSK3β). The activities of glucose-6-phosphatase and phosphoenolpyruvate carboxylase and their respective mRNA expression levels in the liver were simultaneously decreased in the BRD-treated group. BRD also significantly upregulated the expression of phosphatidylinositol 3-kinase (PI3K) and increased the phosphorylation of insulin receptor substrate 1 (IRS1) and protein kinase B (AKT). These results indicate that BRD exhibits antidiabetic potential by activating the IRS1/PI3K/AKT signaling pathway, further regulating the expression of the FOXO1 gene and p-GSK3β protein, thus inhibiting hepatic gluconeogenesis, increasing hepatic glycogen storage, and improving insulin resistance. Therefore, BRD could be used as a functional ingredient to alleviate the symptoms of hyperglycemia.

Cycloartenyl Ferulate and β-Sitosteryl Ferulate - Steryl Ferulates of γ-Oryzanol - Suppress Intracellular Reactive Oxygen Species in Cell-based System

γ-Oryzanol is a naturally occurring component of rice bran and consists of various steryl ferulates. The antioxidant activities of γ-oryzanol have mostly been demonstrated in cell-free systems. Therefore, we determined whether steryl ferulate of γ-oryzanol suppress spontaneous intracellular reactive oxygen species (ROS) in cell-based systems. We found that cycloartenyl ferulate and β-sitosteryl ferulate suppressed spontaneous intracellular ROS in a similar way to N-acetylcysteine and α-tocopherol.

Mangifera indica L. Leaf Extract Induces Adiponectin and Regulates Adipogenesis

Natural bioactive compounds may be used in obese patients because of their ability to impact on various key mechanisms involved in the complex pathophysiological mechanisms of such condition. The aim of this study was to investigate the effect of a Mangifera indica L. leaf extract (MLE) on adipogenic differentiation of murine preadipocyte cells. 3T3-L1 cells were treated during their differentiation with various concentrations of (Mangifera indica L.) leaves extract (MLE) (750, 380, 150, 75 and 35 μg) in order to assess their lipid content, adiponectin production, expression profile of genes involved in lipid metabolism, oxidative stress and inflammation. Our results showed that MLE was particularly enriched in polyphenols (46.30 ± 0.083 mg/g) and that pharmacological treatment of cells resulted in a significant increase of adiponectin levels and reduction of intracellular lipid content. Consistently with these results, MLE resulted in a significant decrease of the expression of genes involved in lipid metabolism (FAS, PPARG, DGAT1, DGAT2, and SCD-1). In conclusion, our results suggest that MLE may represent a possible pharmacological tool for obese or metabolic syndrome patients.

Momilactones A and B Are α-Amylase and α-Glucosidase Inhibitors

Momilactones A (MA) and B (MB) are the active phytoalexins and allelochemicals in rice. In this study, MA and MB were purified from rice husk of Oryza sativa cv. Koshihikari by column chromatography, and purification was confirmed by high-performance liquid chromatography, thin-layer chromatography, gas chromatography-mass spectrometry, liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and ¹H and ¹³C nuclear magnetic resonance analyses. By in vitro assays, both MA and MB exerted potent inhibition on α-amylase and α-glucosidase activities. The inhibitory effect of MB on these two key enzymes was greater than that of MA. Both MA and MB exerted greater α-glucosidase suppression as compared to that of the commercial diabetic inhibitor acarbose. Quantities of MA and MB in rice grain were 2.07 ± 0.01 and 1.06 ± 0.01 µg/dry weight (DW), respectively. This study was the first to confirm the presence of MA and MB in refined rice grain and reported the α-amylase and α-glucosidase inhibitory activity of the two compounds. The improved protocol of LC-ESI-MS in this research was simple and effective to detect and isolate MA and MB in rice organs.

Brown rice-specific γ-oryzanol as a promising prophylactic avenue to protect against diabetes mellitus and obesity in humans

Chronic overconsumption of animal fats causes a variety of health problems, including diabetes mellitus and obesity. Underlying molecular mechanisms encompass leptin resistance, a decrease in rewarding effects of physical activities, xanthine oxidase-induced oxidative stress in vasculature and peripheral tissue, impaired activation of incretin signaling, deviation in food preference, and dysbiosis of gut microbiota. Based on our clinical observation that daily intake of brown rice effectively ameliorates bodyweight gain, impaired glucose tolerance/insulin resistance and dependence on fatty foods in obese, prediabetes men, a line of research on brown rice (rice bran)-derived γ-oryzanol in mice experiments, cultured cells and human clinical trials is underway in our laboratory. Our works in mice showed that γ-oryzanol, an ester mixture of ferulic acid and several kinds of phytosterols, acts as a molecular chaperone, thereby attenuating the strong preference for animal fats through suppression of endoplasmic reticulum stress in the hypothalamus. In pancreatic islets from both high-fat diet-induced and streptozotocin-induced diabetic mice, γ-oryzanol ameliorates endoplasmic reticulum stress and protects β-cells against apoptosis. Noticeably, γ-oryzanol also acts as a potent inhibitor against deoxyribonucleic acid methyltransferases in the brain reward system (striatum) in mice, thereby attenuating, at least partly, the preference for a high-fat diet through the epigenetic modulation of striatal dopamine D2 receptor. Because dopamine D2 receptor signaling in the brain reward system is considerably attenuated in obese humans and rodents, γ-oryzanol might represent a unique property to ameliorate both hedonic and metabolic dysregulation of feeding behavior, highlighting a promising prophylactic avenue to protect against metabolic derangement.

Nutraceuticals and Diet-based Phytochemicals in Type 2 Diabetes Mellitus: From Whole Food to Components with Defined Roles and Mechanisms

BACKGROUND

Over the past decades, the development and use of an array of prescription medications have considerably improved the clinical management of type 2 diabetes mellitus and the quality of life of patients. However, as our knowledge of the associated risk factors and approaches to its management increases, the increasing roles of diet and the composition of the diet in the etiology and successful management of diabetes mellitus are being illuminated. Presently, a lot of attention is being given to nutraceuticals and certain phytochemicals that are integral parts of the human diet. It is believed that a clearer understanding of their roles may be crucial to 'non-invasive' or minimallyintrusive management, with regards to daily living of patients. In this review, an overview of nutraceutical components and phytochemicals that may be of benefit, or had been known to be beneficial in diabetes mellitus is given. Also, how the roles of such dietary components are evolving in the management of this disorder is highlighted. Lastly, the obstacles that need to be overcome before nutraceuticals can be considered as options for the clinical management of diabetes mellitus areconsidered.

CONCLUSION

Despite studies that demonstrate their efficacy, no nutraceutical or food-derived compound has been formally adopted as a direct replacement for any class of antidiabetic drugs.

Hypoglycemic effect of whole grain diet in C57BL/KsJ-db/db mice by activating PI3K/Akt and AMPK pathways

Type II diabetes mellitus (T2DM), characterized by abnormal blood glucose level, is a metabolic disease caused by pancreatic β-cell dysfunction and insulin resistance. Previous studies have reported that whole grain intake alleviated various metabolic syndromes. Here, the hypoglycemic effect of whole grain diet (WGD) on type II diabetes was investigated in C57BL/KsJ-db/db mice. WGD improved the regulation of fasting and postprandial blood glucose levels and reduced weight gain and lipid accumulation. On the molecular level, WGD up-regulated the glucose transporter type 4 and stimulated the insulin receptor substrate 1/phosphoinositide 3-kinase ((PI3K)/Akt) pathway. WGD stimulated the AMP-activated protein kinase (AMPK)/p38/Acetyl-CoA carboxylate pathway related to lipid metabolism and glucose uptake, and down-regulated the pro-inflammatory cytokines, C-reactive protein, interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha. Taken together, whole grains can be employed as functional food ingredients to alleviate T2DM by enhancing the PI3K/Akt and AMPK pathways.

Innovative processing techniques for altering the physicochemical properties of wholegrain brown rice (Oryza sativa L.) - opportunities for enhancing food quality and health attributes

Rice is a globally important staple consumed by billions of people, and recently there has been considerable interest in promoting the consumption of wholegrain brown rice (WBR) due to its obvious advantages over polished rice in metabolically protective activities. This work highlights the effects of innovative processing technologies on the quality and functional properties of WBR in comparison with traditional approaches; and it is aimed at establishing a quantitative and/or qualitative link between physicochemical changes and high-efficient processing methods. Compared with thermal treatments, applications of innovative nonthermal techniques, such as high hydrostatic pressure (HHP), pulsed electric fields (PEF), ultrasound and cold plasma, are not limited to modifying physicochemical properties of WBR grains, since improvements in nutritional and functional components as well as a reduction in anti-nutritional factors can also be achieved through inducing related biochemical transformation. Much information about processing methods and parameters which influence WBR quality changes has been obtained, but simultaneously achieving the product stabilization and functionality of processed WBR grains requires a comprehensive evaluation of all the quality changes induced by different processing procedures as well as quantitative insights into the relationship between the changes and processing variables.

Phytochemical Profile of Brown Rice and Its Nutrigenomic Implications

Whole grain foods have been promoted to be included as one of the important components of a healthy diet because of the relationship between the regular consumption of whole-grain foods and reduced risk of chronic diseases. Rice is a staple food, which has been widely consumed for centuries by many Asian countries. Studies have suggested that brown rice is associated with a wide spectrum of nutrigenomic implications such as anti-diabetic, anti-cholesterol, cardioprotective and antioxidant. This is because of the presence of various phytochemicals that are mainly located in bran layers of brown rice. Therefore, this paper is a review of publications that focuses on the bioactive compounds and nutrigenomic implications of brown rice. Although current evidence supports the fact that the consumption of brown rice is beneficial for health, these studies are heterogeneous in terms of their brown rice samples used and population groups, which cause the evaluation to be difficult. Future clinical studies should focus on the screening of individual bioactive compounds in brown rice with reference to their nutrigenomic implications.

Rice bran nutraceutics: A comprehensive review

Agro-industry yields ample quantity of several byproducts with considerable importance. These byproducts are mostly under-utilized, often used as animal feed or rejected as waste; hence their true potential is not harnessed. The use of such superfluous resources is of not only economic significance but also a form of commercial recycling. Rice bran is an important byproduct of rice milling industry with a global potential of 29.3 million tons annually. It is gaining great attention of the researchers due to its nutrient-rich composition, easy availability, low cost, high antioxidant potential, and promising effects against several metabolic ailments. Bioactive components of rice bran, mainly γ-oryzanol, have been reported to possess antioxidant, anti-inflammatory, hypocholesterolemic, anti-diabetic, and anti-cancer activities. Rice bran oil contains appreciable quantities of bioactive components and has attained the status of "Heart oil" due to its cardiac-friendly chemical profile. Nutraceutics have successfully been extracted from rice bran using several extraction techniques such as solvent extraction, supercritical fluid extraction, microwave-, and ultrasonic-assisted extraction. Current paper is an attempt to highlight bioactive moieties of rice bran along with their extraction technologies and health benefits.

Whole grain cereal attenuates obesity-induced muscle atrophy by activating the PI3K/Akt pathway in obese C57BL/6N mice

Whole grain comprises starchy endosperm, germ, and bran tissues, which contain fibers, minerals, vitamins, and several phytochemicals. Whole grain cereal (WGC)-based food products supply beneficial nutrients (essential for health care) and macronutrients (essential for body maintenance and support). The present study investigated the inhibitory effect of WGC on obesity-induced muscle atrophy in obese C57BL/6N mice. WGC attenuated the body weight gain, fat pad mass, adipocyte size, food efficiency ratio, serum lipid profile, and non-alcoholic fatty liver. Furthermore, WGC increased muscle mass and muscle strength by activating the phosphatidylinositol 3-kinase/protein kinase B pathway. Accordingly, WGC up-regulated the expression of factors that regulate muscle hypertrophy and myogenesis, whereas it down-regulated the atrophy-related factors. Overall, these results demonstrate that WGC effectively attenuates obesity-induced muscle atrophy as well as overall obesity, suggesting that WGC can be used as a functional food.

Marked augmentation of PLGA nanoparticle-induced metabolically beneficial impact of γ-oryzanol on fuel dyshomeostasis in genetically obese-diabetic ob/ob mice

Our previous works demonstrated that brown rice-specific bioactive substance, γ-oryzanol acts as a chaperone, attenuates exaggerated endoplasmic reticulum (ER) stress in brain hypothalamus and pancreatic islets, thereby ameliorating metabolic derangement in high fat diet (HFD)-induced obese diabetic mice. However, extremely low absorption efficiency from intestine of γ-oryzanol is a tough obstacle for the clinical application. Therefore, in this study, to overcome extremely low bioavailability of γ-oryzanol with super-high lipophilicity, we encapsulated γ-oryzanol in polymer poly (DL-lactide-co-glycolide) (PLGA) nanoparticles (Nano-Orz), and evaluated its metabolically beneficial impact in genetically obese-diabetic ob/ob mice, the best-known severest diabetic model in mice. To our surprise, Nano-Orz markedly ameliorated fuel metabolism with an unexpected magnitude (∼1000-fold lower dose) compared with regular γ-oryzanol. Furthermore, such a conspicuous impact was achievable by its administration once every 2 weeks. Besides the excellent impact on dysfunction of hypothalamus and pancreatic islets, Nano-Orz markedly decreased ER stress and inflammation in liver and adipose tissue. Collectively, nanotechnology-based developments of functional foods oriented toward γ-oryzanol shed light on the novel approach for the treatment of a variety of metabolic diseases in humans.

Impact of brown rice-specific γ-oryzanol on epigenetic modulation of dopamine D2 receptors in brain striatum in high-fat-diet-induced obesity in mice

AIMS/HYPOTHESIS

Overeating of dietary fats causes obesity in humans and rodents. Recent studies in humans and rodents have demonstrated that addiction to fats shares a common mechanism with addiction to alcohol, nicotine and narcotics in terms of a dysfunction of brain reward systems. It has been highlighted that a high-fat diet (HFD) attenuates dopamine D2 receptor (D2R) signalling in the striatum, a pivotal regulator of the brain reward system, resulting in hedonic overeating. We previously reported that the brown rice-specific bioactive constituent γ-oryzanol attenuated the preference for an HFD via hypothalamic control. We therefore explored the possibility that γ-oryzanol would modulate functioning of the brain reward system in mice.

METHODS

Male C57BL/6J mice fed an HFD were orally treated with γ-oryzanol, and striatal levels of molecules involved in D2R signalling were evaluated. The impact of γ-oryzanol on DNA methylation of the D2R promoter and subsequent changes in preferences for dietary fat was examined. In addition, the effects of 5-aza-2'-deoxycytidine, a potent inhibitor of DNA methyltransferases (DNMTs), on food preference, D2R signalling and the levels of DNMTs in the striatum were investigated. The inhibitory effects of γ-oryzanol on the activity of DNMTs were enzymatically evaluated in vitro.

RESULTS

In striatum from mice fed an HFD, the production of D2Rs was decreased via an increase in DNA methylation of the promoter region of the D2R. Oral administration of γ-oryzanol decreased the expression and activity of DNMTs, thereby restoring the level of D2Rs in the striatum. Pharmacological inhibition of DNMTs by 5-aza-2'-deoxycytidine also ameliorated the preference for dietary fat. Consistent with these findings, enzymatic in vitro assays demonstrated that γ-oryzanol inhibited the activity of DNMTs.

CONCLUSIONS/INTERPRETATION

We demonstrated that γ-oryzanol ameliorates HFD-induced DNA hypermethylation of the promoter region of D2R in the striatum of mice. Our experimental paradigm highlights γ-oryzanol as a promising antiobesity substance with the distinct property of being a novel epigenetic modulator.

Eating glutinous brown rice twice a day for 8 weeks improves glycemic control in Japanese patients with diabetes mellitus

OBJECTIVE

We recently reported that eating glutinous brown rice (GBR) for 1 day improved the whole-day glucose profile and postprandial plasma glucose level compared with eating white rice (WR) or standard brown rice. However, it was unknown whether eating GBR could maintain improvement of glycemic control for a longer period. Therefore, we evaluated the effect of GBR intake for 8 weeks on glycemic control in outpatients with diabetes mellitus.

METHODS

This was an open-label randomized crossover study in outpatients with type 2 diabetes. Among the 18 subjects registered in this study, 2 were excluded from analysis. After a 1-week observation period while eating WR twice a day, the patients were randomly assigned to two groups. One group ate GBR as a staple food twice a day for 8 weeks and then switched to WR for the next 8 weeks, while the other group ate WR first and then switched to GBR. A mixed meal tolerance test was performed at baseline and after 8 and 16 weeks of dietary intervention to evaluate plasma glucose and serum C-peptide.

RESULTS

None of the subjects failed to complete the study because of disliking the taste of GBR. Hemoglobin A1c (7.5-7.2%, P=0.014) and glycoalbumin (20.4-19.4%, P=0.029) both decreased significantly when the patients were eating GBR. Additionally, the 30-min postprandial plasma glucose level (194-172 mg dl^-1, P=0.031) and the incremental area under the concentration vs time curve of serum C-peptide (31.3-22.1 ng min ml^-1, P=0.023) during the mixed meal tolerance test were also decreased significantly by intake of GBR. In contrast, there were no changes of glycemic control during the WR period.

CONCLUSIONS

We confirmed that GBR was well tolerated for 8 weeks and improved glycemic control in patients with type 2 diabetes.

Expanding frontiers in weight-control research explored by young investigators

At the 93rd annual meeting of the Physiological Society of Japan, a symposium entitled "Expanding frontiers in weight-control research explored by young investigators" was organized. The latest research on weight control was presented by young up-and-coming investigators. The symposium consisted of the following presentations: Gastrointestinal brush cells, immunity, and energy homeostasis; Impact of a brown rice-derived bioactive product on feeding regulation and fuel metabolism; A novel G protein-coupled receptor-regulated neuronal signaling pathway triggers sustained orexigenic effects; and NMDA receptor co-agonist D-serine regulates food preference. These four talks presented at the symposium were summarized as a series of short reviews in this review.

Anti-hyperlipidemic effect of rice bran polysaccharide and its potential mechanism in high-fat diet mice

The evaluation of the lipid-lowering effect of rice bran polysaccharides (RBP) and identification of the related genes of lipid metabolism. RBP, rice bran polysaccharide; HFD, high fat diet.

An ethnobotanical study of traditional rice landraces (Oryza sativa L.) used for medical treatment in selected local communities of the Philippines

ETHNOPHARMACOLOGICAL RELEVANCE

Rice (Oryza sativa L.) remains as one the most important staple food of the Philippines with an overabundance of varieties and gastronomic use. Despite this, no published comprehensive ethnobotanical information exists for the exclusive subject on Philippine traditional rice varieties and their ethnomedicinal value.

AIM OF THE STUDY

To identify and collect traditional rice landrace with ethnomedicinal application from local communities of the Philippines; and document the application, traditional preparation and administration of these plants.

MATERIALS AND METHODS

The ethnobotanical study was performed in nine areas distributed across four provinces: Palawan, Zamboanga del Norte, Zamboanga del Sur and North Cotabato for a period of two years (2014-2015). A total of 39 key informants were identified and interviewed using semi-structured interviews and informal discussion. Descriptive statistics was used to analyze and organize the collected information from the surveys.

RESULTS

Nineteen (19) traditional rice were identified for the native treatment and control of 22 community health concerns. Predominant use of the plants collected were for the treatment of some types of nutritional disorders (18%), digestive system disorders (18%), ill-defined symptoms (13%); viral infections (13%); and several cultural diseases and disorders (11%). Grains were the most frequently used plant part and oral administration was the most preferred mode of treatment.

CONCLUSION

This study is the first to formally confirm that certain traditional rice have a role in the healthcare system of selected local communities in the Philippines. The novel findings open a paradigm for scientists towards therapeutic investigations and development of probable high value products from the highlighted landrace.

Can We Selectively Reduce Appetite for Energy-Dense Foods? An Overview of Pharmacological Strategies for Modification of Food Preference Behavior

Excessive intake of food, especially palatable and energy-dense carbohydrates and fats, is largely responsible for the growing incidence of obesity worldwide. Although there are a number of candidate antiobesity drugs, only a few of them have been proven able to inhibit appetite for palatable foods without the concurrent reduction in regular food consumption. In this review, we discuss the interrelationships between homeostatic and hedonic food intake control mechanisms in promoting overeating with palatable foods and assess the potential usefulness of systemically administered pharmaceuticals that impinge on the endogenous cannabinoid, opioid, aminergic, cholinergic, and peptidergic systems in the modification of food preference behavior. Also, certain dietary supplements with the potency to reduce specifically palatable food intake are presented. Based on human and animal studies, we indicate the most promising therapies and agents that influence the effectiveness of appetite-modifying drugs. It should be stressed, however, that most of the data included in our review come from preclinical studies; therefore, further investigations aimed at confirming the effectiveness and safety of the aforementioned medications in the treatment of obese humans are necessary.

Antioxidant Activity of γ-Oryzanol: A Complex Network of Interactions

γ-oryzanol (Orz), a steryl ferulate extracted from rice bran layer, exerts a wide spectrum of biological activities. In addition to its antioxidant activity, Orz is often associated with cholesterol-lowering, anti-inflammatory, anti-cancer and anti-diabetic effects. In recent years, the usefulness of Orz has been studied for the treatment of metabolic diseases, as it acts to ameliorate insulin activity, cholesterol metabolism, and associated chronic inflammation. Previous studies have shown the direct action of Orz when downregulating the expression of genes that encode proteins related to adiposity (CCAAT/enhancer binding proteins (C/EBPs)), inflammatory responses (nuclear factor kappa-B (NF-κB)), and metabolic syndrome (peroxisome proliferator-activated receptors (PPARs)). It is likely that this wide range of beneficial activities results from a complex network of interactions and signals triggered, and/or inhibited by its antioxidant properties. This review focuses on the significance of Orz in metabolic disorders, which feature remarkable oxidative imbalance, such as impaired glucose metabolism, obesity, and inflammation.

A Blend of Sesame and Rice Bran Oils Lowers Hyperglycemia and Improves the Lipids

BACKGROUND

Considering the health benefits of sesame oil and rice bran oil, the study was conducted to determine the extent to which the daily use of this blend of oils controls hyperglycemia and improves the lipid profile.

METHODS

In this 8-week open-label randomized dietary intervention study, 300 type 2 diabetes mellitus patients and 100 normoglycemic subjects were grouped as 1) normoglycemic subjects (n = 100) treated with sesame oil blend Vivo (Adani Wilmar, Ahmedabad, Gujarat, India), 2) type 2 diabetes mellitus patients treated with sesame oil blend (n = 100), 3) type 2 diabetes mellitus patients treated with glibenclamide (n = 100; 5 mg/d), and 4) type 2 diabetes mellitus patients treated in combination of glibenclamide (5 mg/d) and sesame oil blend (n = 100). Twelve-hour fasting blood glucose, glycated hemoglobin (HbA1c), and lipid profile followed by postprandial blood glucose were measured at baseline. Sesame oil blend was supplied to the respective groups, who were instructed to use as cooking oil for 8 weeks. Fasting and postprandial blood glucose was measured at week 4 and week 8, while HbA1c and lipid profile were measured at week 8.

RESULTS

At week 4 and week 8, type 2 diabetes mellitus patients treated with sesame oil blend or glibenclamide or combination of glibenclamide and sesame oil blend showed significant reduction of fasting and postprandial blood glucose (P <.001). HbA1c, total cholesterol, triglycerides, low-density lipoprotein cholesterol, and non-high-density lipoprotein cholesterol were significantly reduced (P <.001), while high-density lipoprotein cholesterol was significantly increased at week 8 (P <.001) in type 2 diabetes mellitus patients treated with the sesame oil blend or combination of glibenclamide and sesame oil blend; whereas glibenclamide-alone-treated type 2 diabetes mellitus patients showed a significant reduction of HbA1c (P <.001) only.

CONCLUSIONS

A novel blend of 20% cold-pressed unrefined sesame oil and 80% physically refined rice bran oil as cooking oil, lowered hyperglycemia and improved the lipid profile in type 2 diabetes mellitus patients.

Conventional steaming retains tocols and γ-oryzanol better than boiling and frying in the jasmine rice variety Khao dok mali 105

The aim of this study was to determine the effect of various cooking methods on the white rice (WR), brown rice (BR) and parboiled geminated brown rice (PGBR) of the same variety, focusing on γ-oryzanol and tocols. The methods used for analysis of γ-oryzanol and tocols included solvent extraction and HPLC. The results indicated that PGBR had a higher content of γ-oryzanol and tocols compared to BR and WR, when different cooking methods (raw, steamed, boiled and fried) were used. Steaming method retained the higher γ-oryzanol content (53.6-62.2mg/100g) in both PGBR and BR, in comparison with boiling (53.0-60.6mg/100g) and frying (23.4-31.5mg/100g) methods. Frying reduced the γ-oryzanol content significantly regardless of the rice type. Regarding tocols, a similar trend was noticed in all the methods studied. Tocotrienol was the most abundant tocol found in PGBR and BR. Therefore, steaming is the best cooking method to preserved most of the bioactive compounds; however, a slight increase in total tocols was observed after frying.

A novel insulinotropic mechanism of whole grain-derived γ-oryzanol via the suppression of local dopamine D2 receptor signalling in mouse islet

BACKGROUND AND PURPOSE

γ-Oryzanol, derived from unrefined rice, attenuated the preference for dietary fat in mice, by decreasing hypothalamic endoplasmic reticulum stress. However, no peripheral mechanisms, whereby γ-oryzanol could ameliorate glucose dyshomeostasis were explored. Dopamine D₂ receptor signalling locally attenuates insulin secretion in pancreatic islets, presumably via decreased levels of intracellular cAMP. We therefore hypothesized that γ-oryzanol would improve high-fat diet (HFD)-induced dysfunction of islets through the suppression of local D₂ receptor signalling.

EXPERIMENTAL APPROACH

Glucose metabolism and regulation of molecules involved in D₂ receptor signalling in pancreatic islets were investigated in male C57BL/6J mice, fed HFD and treated with γ-oryzanol . In isolated murine islets and the beta cell line, MIN6 , the effects of γ-oryzanol on glucose-stimulated insulin secretion (GSIS) was analysed using siRNA for D₂ receptors and a variety of compounds which alter D₂ receptor signalling.

KEY RESULTS

In islets, γ-oryzanol enhanced GSIS via the activation of the cAMP/PKA pathway. Expression of molecules involved in D₂ receptor signalling was increased in islets from HFD-fed mice, which were reciprocally decreased by γ-oryzanol. Experiments with siRNA for D₂ receptors and D₂ receptor ligands in vitro suggest that γ-oryzanol suppressed D₂ receptor signalling and augmented GSIS.

CONCLUSIONS AND IMPLICATIONS

γ-Oryzanol exhibited unique anti-diabetic properties. The unexpected effects of γ-oryzanol on D₂ receptor signalling in islets may provide a novel; natural food-based, approach to anti-diabetic therapy.

Rice Bran Protein Hydrolysates Improve Insulin Resistance and Decrease Pro-inflammatory Cytokine Gene Expression in Rats Fed a High Carbohydrate-High Fat Diet

A high carbohydrate-high fat (HCHF) diet causes insulin resistance (IR) and metabolic syndrome (MS). Rice bran has been demonstrated to have anti-dyslipidemic and anti-atherogenic properties in an obese mouse model. In the present study, we investigated the beneficial effects of rice bran protein hydrolysates (RBP) in HCHF-induced MS rats. After 12 weeks on this diet, the HCHF-fed group was divided into four subgroups, which were orally administered RBP 100 or 500 mg/kg, pioglitazone 10 mg/kg, or tap water for a further 6 weeks. Compared with normal diet control group, the MS rats had elevated levels of blood glucose, lipid, insulin, and HOMA-IR. Treatment with RBP significantly alleviated all those changes and restored insulin sensitivity. Additionally, RBP treatment increased adiponectin and suppressed leptin levels. Expression of Ppar-γ mRNA in adipose tissues was significantly increased whereas expression of lipogenic genes Srebf1 and Fasn was significantly decreased. Levels of mRNA of proinflammatory cytokines, Il-6, Tnf-α, Nos-2 and Mcp-1 were significantly decreased. In conclusion, the present findings support the consumption of RBP as a functional food to improve insulin resistance and to prevent the development of metabolic syndrome.

Rice protein hydrolysates stimulate GLP-1 secretion, reduce GLP-1 degradation, and lower the glycemic response in rats

Rice has historically been consumed in Asia as a major source of carbohydrates, however, little is known regarding the functional roles of rice proteins as dietary factors. In the present study, we investigated whether peptides derived from rice proteins could stimulate GLP-1 secretion, which results in reducing glycemia via the incretin effect in normal rats. Hydrolysates were prepared from the protein fraction of rice endosperm or rice bran, and the effects of these hydrolysates on GLP-1 secretion were examined in a murine enteroendocrine cell line GLUTag. Plasma was collected after oral administration of the rice protein hydrolysates, under anesthesia, or during glucose tolerance tests in rats. In anesthetized rats, plasma dipeptidyl peptidase-IV (DPP-IV) activity was measured after ileal administration of the rice protein hydrolysates. GLP-1 secretion from GLUTag cells was potently stimulated by the rice protein hydrolysates, especially by the peptic digest of rice endosperm protein (REPH) and that of rice bran protein (RBPH). Oral administration of REPH or RBPH elevated plasma GLP-1 concentrations, which resulted in the reduction of glycemia under the intraperitoneal glucose tolerance test. In addition, the plasma DPP-IV activity was attenuated after ileal administration of REPH or RBPH, which resulted in a higher ratio of intact (active) GLP-1 to total GLP-1 in the plasma. These results demonstrate that rice proteins exert potent stimulatory effects on GLP-1 secretion, which could contribute to the reduction of postprandial glycemia. The inhibitory effect of these peptides on the plasma DPP-IV activity may potentiate the incretin effect of GLP-1.