Dietary mung bean protein reduces high-fat diet-induced weight gain by modulating host bile acid metabolism in a gut microbiota-dependent manner.

The 8-globulin-rich mung bean protein (MPI) suppresses hepatic lipogenesis in rodent models and reduces fasting plasma glucose and insulin levels in obese adults. However, its effects on mitigating high fat diet (HFD)-induced obesity and the mechanism underlying these effects remain to be elucidated. Herein, we examined the metabolic phenotype, intestinal bile acid (BA) pool, and gut microbiota of conventionally raised (CONV-R) male C57BL/6 mice and germ-free (GF) mice that were randomized to receive either regular HFD or HFD containing mung bean protein isolate (MPI) instead of the dairy protein present in regular HFD. MPI intake significantly reduced HFD-induced weight gain and adipose tissue accumulation, and attenuated hepatic steatosis. Enhancement in the secretion of intestinal glucagon-like peptide-1 (GLP-1) and an enlarged cecal and fecal BA pool of dramatically elevated secondary/primary BA ratio were observed in mice that had consumed MPI. These effects were abolished in GF mice, indicating that the effects were dependent upon the presence of the microbiota. As revealed by 16S rRNA gene sequence analysis, MPI intake also elicited dramatic changes in the gut microbiome, such as an expansion of taxa belonging to the phylum Bacteroidetes along with a reduced abundance of the Firmicutes.

Dietary Mung Bean Protein Reduces Hepatic Steatosis, Fibrosis, and Inflammation in Male Mice with Diet-Induced, Nonalcoholic Fatty Liver Disease.

BACKGROUND: As the prevalence of nonalcoholic fatty liver disease (NAFLD), including steatosis and nonalcoholic steatohepatitis, is increasing, novel dietary approaches are required for the prevention and treatment of NAFLD. OBJECTIVE: We evaluated the potential of mung bean protein isolate (MuPI) to prevent NAFLD progression. METHODS: In Expts. 1 and 2, the hepatic triglyceride (TG) concentration was compared between 8-wk-old male mice fed a high-fat diet (61% of energy from fat) containing casein, MuPI, and soy protein isolate and an MuPI-constituent amino acid mixture as a source of amino acids (18% of energy) for 4 wk. In Expt. 3, hepatic fatty acid synthase (Fasn) expression was evaluated in 8-wk-old male Fasn-promoter-reporter mice fed a casein- or MuPI-containing high-fat diet for 20 wk. In Expt. 4, hepatic fibrosis was examined in 8-wk-old male mice fed an atherogenic diet (61% of energy from fat, containing 1.3 g cholesterol/100 g diet) containing casein or MuPI (18% of energy) as a protein source for 20 wk. RESULTS: In the high fat-diet mice, the hepatic TG concentration in the MuPI group decreased by 66% and 47% in Expt. 1 compared with the casein group (P < 0.001) and the soy protein isolate group (P = 0.001), respectively, and decreased by 56% in Expt. 2 compared with the casein group (P = 0.011). However, there was no difference between the MuPI-constituent amino acid mixture and casein groups in Expt. 2. In Expt. 3, Fasn-promoter-reporter activity and hepatic TG concentration were lower in the MuPI group than in those fed casein (P < 0.05). In Expt. 4, in mice fed an atherogenic diet, hepatic fibrosis was not induced in the MuPI group, whereas it developed overtly in the casein group. CONCLUSION: MuPI potently reduced hepatic lipid accumulation in mice and may be a potential foodstuff to prevent NAFLD onset and progression.

Soybean ß-conglycinin improves carbohydrate and lipid metabolism in Wistar rats.

The effects of dietary soybean ß-conglycinin on lipid metabolism and energy consumption were studied in Wistar adult rats. Rats were fed, a diet containing casein (control group) or ß-conglycinin (ß-conglycinin group), for 4 weeks. Carbohydrate consumption was higher and fat consumption was lower in the ß-conglycinin group than in the control group, whereas the total energy consumption was the same between the two groups. Serum adiponectin was higher in the ß-conglycinin group than in the control group. Serum triacylglycerol levels in the ß-conglycinin group were significantly lower than those in the control group. The secretion rate of triacylglycerols from the liver after the administration of tyloxapol, an inhibitor of lipolysis, was significantly lower in the ß-conglycinin group than in the control group. These results suggest the possibility that ß-conglycinin exerts hypolipidemic effects through an acceleration in carbohydrate consumption associated with an increase in adiponectin in rats.

Mung bean peptides promote glucose uptake via Jak2 activation in L6 myotubes.

Mung beans are among the important edible legumes cultivated in Asia, Southern Europe, and Northern America. Mung beans contain 20-30% proteins with high digestibility and possess biological activities, but detailed health beneficial functions are not fully understood yet. In this study, we report the isolation and identification of active peptides from mung beans which promote glucose uptake and elucidate their mechanism in L6 myotubes. HTL, FLSSTEAQQSY, and TLVNPDGRDSY were isolated and identified as active peptides. These peptides promoted the translocation of glucose transporter 4 (GLUT4) to the plasma membrane. The tripeptide HTL promoted glucose uptake through the activation of adenosine monophosphate-activated protein kinase, while the oligopeptides FLSSTEAQQSY and TLVNPDGRDSY through the activation of the PI3K/Akt pathway. Furthermore, these peptides promoted the phosphorylation of Jak2 via interaction with the leptin receptor. Thus, mung bean is a promising functional food for the prevention of hyperglycemia and type 2 diabetes through promoting glucose uptake accompanied by JAK2 activation in the muscle cells.

Accelerating effect of soy peptides containing collagen peptides on type I and III collagen levels in rat skin.

Two weeks of feeding soy peptides containing 2% collagen peptides increased the levels of type I and III tropocollagen and their mRNAs. In contrast, the diet did not increase the mRNA levels of rat hyaluronan synthases, serine palmitoyltransferase (the rate-limiting enzyme of ceramide synthesis), and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (the key enzyme of cholesterol synthesis). These results suggest that feeding of soy peptides with collagen peptides specifically enhanced the tropocollagen level in the skin.

Soy Phospholipids Exert a Renoprotective Effect by Inhibiting the Nuclear Factor Kappa B Pathway in Macrophages.

Complications associated with chronic kidney disease (CKD), which involves kidney inflammation, are a major health problem. Soy protein isolate (SPI) reportedly inhibits CKD exacerbation; however, its detailed action mechanism remains obscure. Therefore, the role of the polar lipid component of SPI in suppressing inflammation was investigated. Zucker fatty rats were divided into three groups and fed a diet containing casein, SPI, or casein + SPI ethanol extract (SPIEE) for 16 weeks. The isoflavones and phospholipids of SPIEE were evaluated for their anti-inflammatory effects. Rats in the SPI and casein + SPIEE groups showed reduced levels of the urinary N-acetyl-ß-d-glucosaminidase and renal IL-1ß mRNA (an inflammatory marker) compared with those in the casein group. In proximal tubular cells, genistein significantly inhibited monocyte chemoattractant protein-1 (MCP-1) expression induced by an IL-1ß stimulus. In macrophages, soybean phospholipids suppressed lipopolysaccharide-induced IL-1ß gene expression by inhibiting the phosphorylation of inhibitor κB and p65. Phosphatidylinositol (PI) was found to be essential for inhibition of IL-1ß expression. SPIEE inhibited the exacerbation of kidney disease. Genistein and soybean phospholipids, especially soybean-specific phospholipids containing PI, effectively inhibited the inflammatory spiral in vitro. Hence, daily soybean intake may be effective for inhibiting chronic inflammation and slowing kidney disease progression.

Beta-conglycinin lowers very-low-density lipoprotein-triglyceride levels by increasing adiponectin and insulin sensitivity in rats.

The relationship between insulin sensitivity and the plasma triglyceride-lowering effect induced by beta-conglycinin was investigated. Male Wistar rats (19 weeks old) were fed diets containing casein, soy protein isolate, or beta-conglycinin for 4 weeks. In oral glucose administration, the beta-conglycinin-fed rats showed a significant decrease in the area under the glucose curve (0-60 min) as compared with the casein-fed rats. The hypoglycemic effect was significantly higher in the beta-conglycinin-fed rats than in the casein-fed rats at 30 min after intraperitoneal insulin injection. The liver sterol regulatory element-binding-protein-1 mRNA expression level was significantly lower and the plasma adiponectin concentration was significantly higher in the beta-conglycinin-fed rats than in the casein-fed rats. The hypotriglyceridemic effect of beta-conglycinin depended on a significant decrease in the concentration of very-low-density-lipoprotein triglycerides. These results indicate that beta-conglycinin increases adiponectin levels and improves glucose tolerance. The ability of beta-conglycinin to lower plasma lipid levels might be due to increased insulin sensitivity of the liver.

Structured triacylglycerol containing behenic and oleic acids suppresses triacylglycerol absorption and prevents obesity in rats.

BACKGROUND: Dietary 1(3)-behenoyl-2,3(1)-dioleoyl-rac-glycerol (BOO) has been reported to inhibit pancreatic lipase activity in vitro and suppress postprandial hypertriacylglycerolemia in humans. In the present study, the anti-obesity activities of BOO and its inhibitory effects on lymphatic triacylglycerol (TAG) absorption were investigated in rats. METHODS: In Experiment 1, rats were fed either BOO or soybean oil (SO) diet for 6 weeks. In the BOO diet, 20% of SO was replaced with an experimental oil rich in BOO. In Experiments 2 and 3, rats cannulated in the thoracic duct were administered an emulsions containing trioleoylglycerol (OOO) or an oil mixture (OOO:BOO, 9:1). Tri[1-14C]oleoylglycerol (14C-OOO) was added to the emulsions administered in Experiment 3. RESULTS: No observable differences were detected in food intake or body weight gain between the BOO and SO groups in Experiment 1. Plasma and liver TAG concentrations and visceral fat weights were significantly lower in the BOO group than in the SO group. The apparent absorption rate of fat was significantly lower in the BOO group than in the SO group. In Experiment 2, the lymphatic recovery of oleic and behenic acids was significantly lower at 5 and 6 h after BOO administration than after OOO administration. In Experiment 3, the lymphatic recovery of 14C-OOO was significantly lower at 5 and 6 h after BOO administration than after OOO administration. CONCLUSIONS: These results suggest that BOO prevents deposition of visceral fat and hepatic TAG by lowering and delaying intestinal absorption of TAG.

Improvement of glucose and lipid metabolism via mung bean protein consumption: clinical trials of GLUCODIA™ isolated mung bean protein in the USA and Canada.

The aim of the present study was to confirm the effects of a commercially available mung bean protein isolate (GLUCODIA™) on glucose and lipid metabolism. The main component of GLUCODIA™ is 8S globulin, which constitutes 80 % of the total protein. The overall structure of this protein closely resembles soyabean ß-conglycinin, which accounts for 20 % of total soya protein (soya protein isolate; SPI). Many physiological beneficial effects of ß-conglycinin have been reported. GLUCODIA™ is expected to produce beneficial effects with fewer intakes than SPI. We conducted two independent double-blind, placebo-controlled clinical studies. In the first (preliminary dose decision trial) study, mung bean protein was shown to exert physiological beneficial effects when 3·0 g were ingested per d. In the second (main clinical trial) study, mung bean protein isolate did not lower plasma glucose levels, although the mean insulin level decreased with consumption of mung bean protein. The homeostatic model assessment of insulin resistance (HOMA-IR) values significantly decreased with mung bean protein. The mean TAG level significantly decreased with consumption of mung bean protein isolate. A significant increase in serum adiponectin levels and improvement in liver function enzymes were observed. These findings suggest that GLUCODIA™ could be useful in the prevention of insulin resistance and visceral fat accumulation, which are known to trigger the metabolic syndrome, and in the prevention of liver function decline.

Decreases in serum triacylglycerol and visceral fat mediated by dietary soybean beta-conglycinin.

Soy protein isolate (SPI) is known to reduce the risk of heart disease by lowering serum cholesterol and triacylglycerol (TG) levels. Soybean beta-conglycinin, which is a component of SPI, might be the active ingredient that prevents and/or ameliorates lifestyle-related diseases, such as hyperlipidemia and obesity. This study aimed to determine the efficacy of soybean beta-conglycinin for lowering the human serum TG level and visceral fat. Randomized double-blind placebo-controlled designs were used to test the effect of dietary beta-conglycinin, which was taken in the form of candy. [Test 1]In order to examine the serum TG level, 138 volunteers aged 26 to 69 years with TG concentrations above 1.69 mmol/L participated in the study. The subjects were divided at random into two different groups: the test group only consumed the experimental candy containing beta-conglycinin and the placebo group only consumed the placebo candy containing casein. The test period consisted of a 2-wk pre-evaluation phase to screen the participants, a 12-wk consumption period and a 4-wk post-evaluation phase. The serum TG concentrations were significantly reduced in the test group, compared with the placebo group, after consuming the experimental candy. [Test 2]In order to measure visceral fat by means of CT scanning, 102 volunteers aged 26 to 69 years with body mass indices (BMI) between 25 and 30 participated in the study. The subjects were divided at random into two different groups as for Test 1. The test period consisted of a 2-wk pre-evaluation phase to screen the participants, a 20-wk consumption period and a 4-wk post-evaluation phase. A significant reduction in visceral fat only occurred in the beta-conglycinin group. This study showed that beta-conglycinin is an effective food ingredient that will be of use to reduce high serum TG concentrations and to prevent obesity.

Soy ß-conglycinin improves obesity-induced metabolic abnormalities in a rat model of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) has a variety of causes including calorie over-intake, an unbalanced diet, and/or genetic dysfunction of lipid metabolism. We hypothesized that NAFLD symptoms could be mitigated by specific nutritional factors. Here, we show that the potential for soy ß-conglycinin (ßCG) to improve obesity-induced metabolic abnormalities in the Otsuka Long Evans Tokushima fatty (OLETF) rat model of NAFLD. Long Evans Tokushima Otsuka (i.e., wild-type) and OLETF rats were provided a normal diet containing 20% casein for 4 weeks as a control. In a third (ßCG) group, OLETF rats were fed a diet in which half of the casein was replaced by ßCG. There was no difference in food intake between groups. Rats in the ßCG group had decreased liver weight and lipid content (triglycerides, cholesterol, and phospholipids) compared to controls. In addition, ßCG consumption decreased fatty acid synthase gene expression and enzymatic activity. These findings indicate that dietary intake of ßCG can improve obesity-induced metabolic dysfunction, possibly via suppression of de novo fatty acid synthesis.

Effects of soybean beta-conglycinin on body fat ratio and serum lipid levels in healthy volunteers of female university students.

The changes in body fat ratio and serum lipids induced by the ingestion of beta-conglycinin were examined in 41 healthy female university student volunteers. The trend of change in body fat ratio following the ingestion of beta-conglycinin differed between students with a baseline body fat ratio over 25% and those less than 25%. In the former group, the ingestion of beta-conglycinin suppressed the increase in body fat ratio. Moreover the six subjects who had a high total cholesterol level (5.72 mmol/L or higher) tended to have reduced levels of serum triglyceride, free fatty acid, total cholesterol and lipoprotein (a) after the ingestion of beta-conglycinin, although those levels did not change significantly. The number of subjects was only six, therefore it was inferred that significant changes were not observed. Thus, ingestion of soybean beta-conglycinin suppressed the increase in body fat ratio in individuals with a high baseline body fat ratio and reduced relatively high serum levels of lipids. Those results suggest that if soybean beta-conglycinin is ingested continuously (5 g daily), it will be effective in keeping body fat ratio and serum lipid levels normal and eliminating excessive lipids from the body.

Soy ß-conglycinin improves glucose uptake in skeletal muscle and ameliorates hepatic insulin resistance in Goto-Kakizaki rats.

Although the underlying mechanism is unclear, ß-conglycinin (ßCG), the major component of soy proteins, regulates blood glucose levels. Here, we hypothesized that consumption of ßCG would normalize blood glucose levels by ameliorating insulin resistance and stimulating glucose uptake in skeletal muscles. To test our hypothesis, we investigated the antidiabetic action of ßCG in spontaneously diabetic Goto-Kakizaki (GK) rats. Our results revealed that plasma adiponectin levels and adiponectin receptor 1 messenger RNA expression in skeletal muscle were higher in ßCG-fed rats than in casein-fed rats. Phosphorylation of adenosine monophosphate-activated protein kinase (AMP kinase) but not phosphatidylinositol-3 kinase was activated in ßCG-fed GK rats. Subsequently, ßCG increased translocation of glucose transporter 4 to the plasma membrane. Unlike the results in skeletal muscle, the increase in adiponectin receptor 1 did not lead to AMP kinase activation in the liver of ßCG-fed rats. The down-regulation of sterol regulatory element-binding factor 1, which is induced by low insulin levels, promoted the increase in hepatic insulin receptor substrate 2 expression. Based on these findings, we concluded that consumption of soy ßCG improves glucose uptake in skeletal muscle via AMP kinase activation and ameliorates hepatic insulin resistance and that these actions may help normalize blood glucose levels in GK rats.

Consumption of a structured triacylglycerol containing behenic and oleic acids increases fecal fat excretion in humans.

We examined the fecal fat excretion of mildly hypertriacylglycerolemic subjects who ingested soft cookies containing 1(3)-behenoyl-2,3(1)-dioleoyl-rac-glycerol (BOO) for 7 days. The subjects included 14 healthy men (average age; 44.9 ± 1.7) whose fasting plasma triacylglycerol level ranged from 150 to 250 mg/dL. Every day for 7 days, the subjects ate 5 soft cookies containing margarine with the BOO-rich experimental oil (BOO intake, 2.46 g/day). The placebo group ate soft cookies containing margarine without BOO. This study was a randomized double-blind, placebo-controlled, crossover study. Feces were collected for 3 days prior to the end of the treatment period, and fecal fat and fatty acid composition were determined. The fecal wet weight was significantly increased in BOO group compared with that in the placebo group. Moreover, fecal fat and fatty acid level were significantly higher in the BOO group than in the placebo group. There were no significant differences in the fecal fatty acid composition of the BOO and placebo groups. These results suggest that dietary BOO increases fecal excretion of dietary fat in humans. However, BOO does not increase the excretion of specific fatty acids; it increases the excretion of all fatty acids of dietary origin, which may lead to lower and delay intestinal absorption of dietary fat.

Effects of soy protein isolate feeding on severe kidney damage in DOCA salt-treated obese Zucker rats.

This study assessed the effects of soy protein isolate (SPI) on severe kidney damage in deoxycorticosterone acetate (DOCA) salt-treated obese Zucker rats. These rats underwent heminephrectomy and were fed either casein or SPI diet for 12 weeks. From weeks 8 to 10 of the experiment, kidney damage was induced by biweekly injection of 25 mg/kg DOCA and administration of 0.5% NaCl (w/v) ad libitum. Urinary protein and N-acetyl-ß-d-glucosaminidase excretions of SPI rats were much lower than those of casein rats at weeks 1 (p < 0.01) and 2 (p < 0.05) after DOCA treatment. Abnormal mineral excretions induced by DOCA treatment in casein rats were hardly detected in SPI rats. Severe atrophy of tubular epithelium and some flattened/detached renal tubules were also observed in casein rats, but not in SPI rats. These results indicate that consecutive treatment of SPI protects against renal dysfunction, particularly tubulointerstitial nephritis, in DOCA salt-treated obese Zucker rats.

Changes in lipid metabolism by soy beta-conglycinin-derived peptides in HepG2 cells.

In this study, HepG2 cells were treated with short peptides (7S-peptides) derived from highly purified soybean beta-conglycinin (7S), which was free from lipophilic protein, and the effect of the peptide treatment on lipid metabolism was determined. 7S-peptide treatment suppressed the secretion of apolipoprotein B-100 from HepG2 cells into the medium. The 7S-peptides also suppressed the incorporation of (3)H-glycerol and (14)C-acetate into triacylglyceride but not into major phospholipids, such as phosphatidylcholine and phosphatidylethanolamine. Additionally, the synthesis of cholesterol esters was dramatically decreased for 2 h after the addition of the 7S-peptides, whereas the synthesis of cholesterol remained unchanged by 4 h and increased by 8 h after the addition of the 7S-peptides. The cleaved nuclear form of SREBP-2 increased 8 h after the addition of the 7S peptides, suggesting a decrease in intracellular cholesterol levels. Analysis of changes in mRNA expression after 7S-peptide treatment suggested that the 7S-peptides lower the level of cholesterol in the endoplasmic reticulum, increase the mRNA of genes related to beta-oxidation of fatty acids, and increase the synthesis of cholesterol. From these results, it may be concluded that the peptides derived from 7S altered the lipid metabolism to decrease secretion of apolipoprotein B-100-containing lipoprotein from HepG2 cells.

Effects of soybean beta-conglycinin on hepatic lipid metabolism and fecal lipid excretion in normal adult rats.

beta-Conglycinin decreased blood triacylglycerol (TAG) levels in male Wistar adult rats. Liver mitochondrial carnitine palmitoyltransferase activity in the beta-conglycinin-fed group significantly increased as against the casein-fed group. Hepatic fatty acid synthase activity in the beta-conglycinin group significantly decreased as against that of the casein-fed group. Fecal fatty acid excretion in the beta-conglycinin group was significantly higher than in the casein group.