Effects of single and long-term administration of wheat albumin on blood glucose control: randomized controlled clinical trials

The Power of the Underutilized and Neglected Medicinal Plants and Herbs of the Middle East

The Middle east and North Africa harbour many native species with pharmaceutical and nutraceutical potential. Since the beginning of history, food and herbal medicinal plants have been an essential part of human lives and the traditional Middle Eastern healthcare system. The notable medicinal plants that have been mentioned in the Bible, which are common in West Asia and some regions of North Africa, are Aloe vera, anise, balm, cassia, cinnamon, cumin, flax, and fig. Chemical components of Aloe vera are aloin, sinapinic acid, catechin, chromone, myricetin, quercitrin and syringic acid. Anethole, safrole, and estragole are the main chemical components of anise. The chemical components of cassia are coumarin, emodin, cinnamyl alcohol, and cinnamaldehyde. The major chemical ingredients of cumin are terpinene, cuminaldehyde, sabinene, thujene, and thymoquinone. The goal of this article is to review the considerable health benefits and pharmaceutical benefits of medicinal herbs and plants that have been neglected and underutilized in the Middle East and North Africa, as well as to promote their utilization. On the basis of the results, the experimented neglected medicinal plant can offer various advantages when used together with conventional medicinal treatments for various health conditions, such as palliative care in managing the side effects of conventional treatments, access to a wider range of treatments, increased patient satisfaction, and improved emotional and mental well-being. Moreover, consuming medicinal plants may help to manage and prevent diabetes, cancer, and heart disease with notable anti-tumor, and anti-inflammatory properties.

Natural Inhibitors of Mammalian α-Amylases as Promising Drugs for the Treatment of Metabolic Diseases

α-Amylase is a generally acknowledged molecular target of a distinct class of antidiabetic drugs named α-glucosidase inhibitors. This class of medications is scarce and rather underutilized, and treatment with current commercial drugs is accompanied by unpleasant adverse effects. However, mammalian α-amylase inhibitors are abundant in nature and form an extensive pool of high-affinity ligands that are available for drug discovery. Individual compounds and natural extracts and preparations are promising therapeutic agents for conditions associated with impaired starch metabolism, e.g., diabetes mellitus, obesity, and other metabolic disorders. This review focuses on the structural diversity and action mechanisms of active natural products with inhibitory activity toward mammalian α-amylases, and emphasizes proteinaceous inhibitors as more effective compounds with significant potential for clinical use.

The impact of the soluble protein fraction and kernel hardness on wheat flour starch digestibility

Wheat is the staple crop for 35% of the world's population, providing a major source of calories, mainly in the form of starch. The digestibility of wheat starch varies between different flours and products. Wheat products that are rapidly digested elicit large post-prandial glucose peaks associated with metabolic disorders. We investigated the impact of protein on starch digestion in three commercial flours with different grain hardness. A soluble extract of wheat proteins reduced starch digestion, even following gastric proteolysis. This extract was enriched in proteinaceous α-amylase inhibitors which were partially degraded during gastric proteolysis. Starch digestion kinetic analysis was carried out for flour samples pre-treated with different pepsin activities. The rate of starch digestion was altered following pepsin pre-digestion, and the extent of starch digestion increased in response to pepsin pre-digestion. We conclude that soluble proteinaceous alpha-amylase inhibitors present in wheat can escape gastric digestion and significantly contribute to reducing starch digestion in the small intestine.

Amylase Trypsin Inhibitors (ATIs) in a Selection of Ancient and Modern Wheat: Effect of Genotype and Growing Environment on Inhibitory Activities

Wheat amylase-trypsin inhibitors (ATIs) are a family of plant defense proteins with an important role in human health for their involvement in allergies, celiac disease and non-celiac wheat sensitivity. Information about the differences in ATI activities among wheat genotypes and the influence of the growing environment is scarce. Therefore, ten selected wheat accessions with different ploidy level and year of release, previously characterized for their ATI gene sequences, were grown during three consecutive crop years at two growing areas and used for in vitro ATI activities. The contributions of the genotype and the crop year were significant for both activities. The hexaploid wheat genotypes showed the highest inhibitory activities. Einkorn had a peculiar behavior showing the lowest alpha-amylase inhibitory activity, but the highest trypsin inhibitory activity. It was not possible to observe any trend in ATI activities as a function of the release year of the wheat samples. The two inhibitory activities were differently affected by the growing conditions and were negatively correlated with the protein content. This information can be important in understanding the extent of variation of ATI inhibitory properties in relation to the wheat genotype and the growing environment and the impact of ATIs, if any, on human health and nutrition.

A Treatment to Cure Diabetes Using Plant-Based Drug Discovery

The field of peptides and proteins has opened up new doors for plant-based medication development because of analytical breakthroughs. Enzymatic breakdown of plant-specific proteins yields bioactive peptides. These plant-based proteins and peptides, in addition to their in vitro and vivo outcomes for diabetes treatment, are discussed in this study. The secondary metabolites of vegetation can interfere with the extraction, separation, characterization, and commercialization of plant proteins through the pharmaceutical industry. Glucose-lowering diabetic peptides are a hot commodity. For a wide range of illnesses, bioactive peptides from flora can offer up new avenues for the development of cost-effective therapy options.

Structure, Function and Protein Engineering of Cereal-Type Inhibitors Acting on Amylolytic Enzymes

Numerous plants, including cereals, contain seed proteins able to inhibit amylolytic enzymes. Some of these inhibitors, the CM-proteins (soluble in chloroform:methanol mixtures)—also referred to as cereal-type inhibitors (CTIs)—are the topic of this review. CM-proteins were first reported 75 years ago. They are small sulfur-rich proteins of the prolamine superfamily embracing bifunctional α-amylase/trypsin inhibitors (ATIs), α-amylase inhibitors (AIs), limit dextrinase inhibitors (LDIs), and serine protease inhibitors. Phylogenetically CM-proteins are predicted across poaceae genomes and many isoforms are identified in seed proteomes. Their allergenicity and hence adverse effect on humans were recognized early on, as were their roles in plant defense. Generally, CTIs target exogenous digestive enzymes from insects and mammals. Notably, by contrast LDI regulates activity of the endogenous starch debranching enzyme, limit dextrinase, during cereal seed germination. CM-proteins are four-helix bundle proteins and form enzyme complexes adopting extraordinarily versatile binding modes involving the N-terminal and different loop regions. A number of these inhibitors have been characterized in detail and here focus will be on target enzyme specificity, molecular recognition, forces and mechanisms of binding as well as on three-dimensional structures of CM-protein–enzyme complexes. Lastly, prospects for CM-protein exploitation, rational engineering and biotechnological applications will be discussed.

Raman Fingerprints of Rice Nutritional Quality: A Comparison between Japanese Koshihikari and Internationally Renowned Cultivars

Raman spectroscopy was applied to characterize at the molecular scale the nutritional quality of the Japanese Koshihikari rice cultivar in comparison with other renowned rice cultivars including Carnaroli from Italy, Calrose from the USA, Jasmine rice from Thailand, and Basmati from both India and Pakistan. For comparison, two glutinous (mochigome) cultivars were also investigated. Calibrated and validated Raman analytical algorithms allowed quantitative determinations of: (i) amylopectin and amylose concentrations, (ii) fractions of aromatic amino acids, and (iii) protein content and secondary structure. The Raman assessments non-destructively linked the molecular composition of grains to key nutritional parameters and revealed a complex intertwine of chemical properties. The Koshihikari cultivar was rich in proteins (but with low statistical relevance as compared to other investigated cultivars) and aromatic amino acids. However, it also induced a clearly higher glycemic impact as compared to long-grain cultivars from Asian countries. Complementary to genomics and wet-chemistry analyses, Raman spectroscopy makes non-destructively available factual and data-driven information on rice nutritional characteristics, thus providing customers, dietitian nutritionists, and producers with a solid science-consolidated platform.

Plant-Derived Bioactive Peptides: A Treatment to Cure Diabetes

ABSTRACT

Recent advances in analytical techniques have opened new opportunities for plant-based drug discovery in the field of peptide and proteins. Enzymatic hydrolysis of plant parent proteins forms bioactive peptides which are explored in the treatment of various diseases. In this review, we will discuss the identified plant-based bioactive proteins and peptides and the in vitro, in vivo results for the treatment of diabetes. Extraction, isolation, characterization and commercial utilization of plant proteins is a challenge for the pharmaceutical industry as plants contain several interfering secondary metabolites. The market of peptide drugs for the treatment of diabetes is growing at a fast rate. Plant-based bioactive peptides might open up new opportunities to discover economic lead for the management of various diseases.

GRAPHIC ABSTRACT

Wheat Albumin Increases the Ratio of Fat to Carbohydrate Oxidation during the Night in Healthy Participants: A Randomized Controlled Trial

Not only are energy expenditure (EE) and the respiratory quotient (RQ) parameters of the energy nutrient utilization and energy balance, they are also related to the development of obesity. In this study, post-meal night-time energy metabolism was investigated following the oral ingestion of wheat albumin (WA) with a late evening meal. A randomly assigned, double-blind, placebo-controlled crossover trial for a single oral ingestion in healthy participants was completed. The participants ingested the placebo (PL) or WA (1.5 g) containing tablets 3 minutes before the late evening meal at 22:00 hour, and energy metabolism was measured using a whole-room indirect calorie meter until wake-up. The participants were in bed from 00:00 hour until 06:30 hour. Twenty healthy participants completed the trial and were included in the analyses. Night-time RQ and carbohydrate oxidation were significantly lower following the WA treatment as compared with the PL treatment. Although the total EE was not significantly different between treatments, postprandial fat oxidation was significantly higher following the WA treatment as compared with the PL treatment. In conclusion, WA has the potential to shift the energy balance to a higher ratio of fat to carbohydrate oxidation during the night.

Glucose Response during the Night Is Suppressed by Wheat Albumin in Healthy Participants: A Randomized Controlled Trial

Postprandial blood glucose excursions are important for achieving optimal glycemic control. In normal-weight individuals, glucose tolerance is diminished in the evening compared to glucose tolerance in the morning. Wheat albumin (WA) has the potential to suppress the postprandial glucose response with a relatively small dose, compared to the dose required when using dietary fiber. In the present study, the effect of WA on glycemic control during the night was investigated after a late evening meal. A randomly assigned crossover trial involving a single oral ingestion in healthy male participants was performed in a double-blind placebo-controlled manner. The participants ingested the placebo (PL) tablets or the WA (1.5 g)-containing tablets 3 min before an evening meal at 22:00 hour, and blood samples were drawn during the night until 07:00 hour using an intravenous cannula. The participants slept from 00:30 hour to 06:30 hour. Glucose response, as a primary outcome during the night, was suppressed significantly by the WA treatment compared to the PL treatment, but the insulin response was not. Plasma glucose-dependent insulinotropic polypeptide concentration during the night was lowered significantly by the WA treatment compared to the PL treatment. In conclusion, WA may be a useful food constituent for glycemic control during the night.

Suppressive Effect of the α-Amylase Inhibitor Albumin from Buckwheat (Fagopyrum esculentum Moench) on Postprandial Hyperglycaemia

Inhibiting starch hydrolysis into sugar could reduce postprandial blood glucose elevation and contribute to diabetes prevention. Here, both buckwheat and wheat albumin that inhibited mammalian α-amylase in vitro suppressed blood glucose level elevation after starch loading in vivo, but it had no effect after glucose loading. In contrast to the non-competitive inhibition of wheat α-amylase inhibitor, buckwheat albumin acted in a competitive manner. Although buckwheat α-amylase inhibitor was readily hydrolysed by digestive enzymes, the hydrolysate retained inhibitory activity. Together with its thermal stability, this suggests its potential use in functional foods that prevent diabetes.

Hypoglycemic property of soy isoflavones from hypocotyl in Goto-Kakizaki diabetic rats

The present study was carried out to investigate the hypoglycemic effect of soy isoflavones from hypocotyl in GK diabetic rats. A single administration and long-term administration tests were conducted in GK diabetic rats to test the hypoglycemic effect of soy isoflavones. At the end of long-term administration trial, blood protein, cholesterol, triglyceride, glycosylated serum protein, C-reactive protein, insulin, aminotransferase, lipid peroxide, interleukin-6, tumor necrosis factor-α were estimated. Inhibition of soy isoflavones against α-amylase and α-glucosidase, as well as on glucose uptake into brush border membrane vesicles or Caco-2 cells were determined in vitro. In single administration experiment, soy isoflavones reduced postprandial blood glucose levels in GK rats. In long-term administration, hypoglycemic effect of soy isoflavones was first observed at week 12 and maintained till week 16. A significant reduction in fasting blood glucose, C-reactive protein, and lipid peroxide was noted at week 16. However, there was no significant treatment effect on blood insulin. Furthermore, soy isoflavone administration resulted in significant decreases in glycosylated serum protein, tumor necrosis factor-α, and interleukin-6. Other biochemical parameters, such as protein, cholesterol, triglyceride and aminotransferases were not modified, however. The results in vitro showed that soy isoflavones showed a potent inhibitory effect on intestinal α-glucosidase, but not on pancreatic α-amylase. Soy isoflavones also decreased glucose transport potency into brush border membrane vesicles or Caco-2 cells. It is concluded that soy isoflavones from hypocotyl, performs hypoglycemic function in GK rats with type 2 diabetes, maybe via suppression of carbohydrate digestion and glucose uptake in small intestine.

Rice (Oryza sativa japonica) Albumin Suppresses the Elevation of Blood Glucose and Plasma Insulin Levels after Oral Glucose Loading

The suppressive effect of rice albumin (RA) of 16 kDa on elevation of blood glucose level after oral loading of starch or glucose and its possible mechanism were examined. RA suppressed the increase in blood glucose levels in both the oral starch tolerance test and the oral glucose tolerance test. The blood glucose concentrations 15 min after the oral administration of starch were 144 ± 6 mg/dL for control group and 127 ± 4 mg/dL for RA 200 mg/kg BW group, while those after the oral administration of glucose were 157 ± 7 mg/dL for control group and 137 ± 4 mg/dL for RA 200 mg/kg BW group. However, in the intraperitoneal glucose tolerance test, no significant differences in blood glucose level were observed between RA and the control groups, indicating that RA suppresses the glucose absorption from the small intestine. However, RA did not inhibit the activity of mammalian α-amylase. RA was hydrolyzed to an indigestible high-molecular-weight peptide (HMP) of 14 kDa and low-molecular-weight peptides by pepsin and pancreatin. Furthermore, RA suppressed the glucose diffusion rate through a semipermeable membrane like dietary fibers in vitro. Therefore, the indigestible HMP may adsorb glucose and suppress its absorption from the small intestine.

Antidiabetic effects of natural plant extracts via inhibition of carbohydrate hydrolysis enzymes with emphasis on pancreatic alpha amylase

INTRODUCTION

The increasing prevalence of type 2 diabetes mellitus and the negative clinical outcomes observed with the commercially available anti-diabetic drugs have led to the investigation of new therapeutic approaches focused on controlling postprandrial glucose levels. The use of carbohydrate digestive enzyme inhibitors from natural resources could be a possible strategy to block dietary carbohydrate absorption with less adverse effects than synthetic drugs.

AREAS COVERED

This review covers the latest evidence regarding in vitro and in vivo studies in relation to pancreatic alpha-amylase inhibitors of plant origin, and presents bioactive compounds of phenolic nature that exhibit anti-amylase activity.

EXPERT OPINION

Pancreatic alpha-amylase inhibitors from traditional plant extracts are a promising tool for diabetes treatment. Many studies have confirmed the alpha-amylase inhibitory activity of plants and their bioactive compounds in vitro, but few studies corroborate these findings in rodents and very few in humans. Thus, despite some encouraging results, more research is required for developing a valuable anti-diabetic therapy using pancreatic alpha-amylase inhibitors of plant origin.

Fundamental studies on the inhibitory action of Acanthopanax senticosus Harms on glucose absorption

AIM OF THE STUDY

Acanthopanax senticosus Harms extract (ASE) is used as an ingredient of over-the-counter drugs and functional foods, such as health supplements, in Japan. ASE exhibits a hypoglycemic effect; however, the mechanism of the hypoglycemic effect is not clear. In the present study, we investigated whether ASE has a glucose absorption inhibitory action.

MATERIALS AND METHODS

We examined the effects of ASE on α-amylase and α-glucosidase activities, and on glucose uptake in Caco-2 cells. We also examined the effects of ASE oral administration on glucose tolerance in type 2 diabetes mellitus model db/db mice.

RESULTS

The addition of ASE inhibited α-glucosidase activity but not α-amylase activity. The α-glucosidase inhibitory activity of ASE was approximately 1/13 of that of acarbose. The addition of ASE inhibited 2'-deoxy-D-glucose (DG) uptake in human intestinal Caco-2 cells, and the inhibitory activity of ASE was approximately 1/40 of that of phloretin. Kinetic analysis of glucose uptake indicated that ASE has no effects on DG uptake through passive diffusion, but that ASE inhibits intracellular DG uptake chiefly by inhibiting transport via a glucose transporter. In the glucose tolerance study, db/db mice orally administered ASE for 3 days showed significantly lower plasma glucose level than the control group 30 min after sucrose loading, without affecting plasma insulin levels. In addition, ASE oral administration significantly inhibited α-glucosidase activity in the small intestine mucosa extirpated from the mice.

CONCLUSION

These findings indicate that ASE may be useful as an ingredient of functional foods to improve postprandial hyperglycemia and prevent type II diabetes mellitus.

The corn protein, zein hydrolysate, administered into the ileum attenuates hyperglycemia via its dual action on glucagon-like peptide-1 secretion and dipeptidyl peptidase-IV activity in rats

We previously showed that a hydrolysate prepared from corn zein [zein hydrolysate (ZeinH)] strongly stimulates glucagons-like peptide-1 (GLP-1) secretion from the murine GLP-1-producing enteroendocrine cell line and in the rat small intestine, especially in the ileum. Here, we investigated whether ZeinH administered into the ileum affects glucose tolerance via stimulating GLP-1 secretion. To observe the effect of luminal ZeinH itself on GLP-1 secretion and glycemia, ip glucose tolerance tests were performed in conscious rats with ileal and jugular catheters, and plasma glucose, insulin, and GLP-1 (total and active) were measured. In addition, plasma dipeptidyl peptidase-IV activities in the ileal vein were measured after the administration of ZeinH into the ileal-ligated loop in anesthetized rats. The ileal administration of ZeinH attenuated the glucose-induced hyperglycemia accompanied by the enhancement of insulin secretion, whereas meat hydrolysate (MHY) neither induced insulin secretion nor attenuated hyperglycemia. The antihyperglycemic effect was also demonstrated by the oral administration of ZeinH. From these results, it was predicted that the GLP-1-releasing potency of ZeinH was higher than that of MHY. However, both peptides induced a similar increase in total GLP-1 concentration after the ileal administration. In contrast, active GLP-1 concentration was increased only in ZeinH-treated rats. In anesthetized rats, ileal administration of ZeinH, but not MHY, decreased plasma dipeptidyl peptidase-IV activity in the ileal vein. These results indicate that the ileal administration of a dietary peptide, ZeinH, has the dual functions of inducing GLP-1 secretion and inhibiting GLP-1 degradation, resulting in the enhancement of insulin secretion and the prevention of hyperglycemia in rats.