The effect of protease inhibitors derived from potato formulated in a minidrink on appetite, food intake and plasma cholecystokinin levels in humans

The potential of plant proteins as antifungal agents for agricultural applications

Fungal pathogens induce a variety of diseases in both plants and post-harvest food crops, resulting in significant crop losses for the agricultural industry. Although the usage of chemical-based fungicides is the most common way to control these diseases, they damage the environment, have the potential to harm human and animal life, and may lead to resistant fungal strains. Accordingly, there is an urgent need for diverse and effective agricultural fungicides that are environmentally- and eco-friendly. Plants have evolved various mechanisms in their innate immune system to defend against fungal pathogens, including soluble proteins secreted from plants with antifungal activities. These proteins can inhibit fungal growth and infection through a variety of mechanisms while exhibiting diverse functionality in addition to antifungal activity. In this mini review, we summarize and discuss the potential of using plant antifungal proteins for future agricultural applications from the perspective of bioengineering and biotechnology.

PINIR: a comprehensive information resource for Pin-II type protease inhibitors

BACKGROUND

Serine protease inhibitors belonging to the Potato type-II Inhibitor family Protease Inhibitors (Pin-II type PIs) are essential plant defense molecules. They are characterized by multiple inhibitory repeat domains, conserved disulfide bond pattern, and a tripeptide reactive center loop. These features of Pin-II type PIs make them potential molecules for protein engineering and designing inhibitors for agricultural and therapeutic applications. However, the diversity in these PIs remains unexplored due to the lack of annotated protein sequences and their functional attributes in the available databases.

RESULTS

We have developed a database, PINIR (Pin-II type PIs Information Resource), by systematic collection and manual annotation of 415 Pin-II type PI protein sequences. For each PI, the number and position for signature sequences are specified: 695 domains, 75 linkers, 63 reactive center loops, and 10 disulfide bond patterns are identified and mapped. Database analysis revealed novel subcategories of PIs, species-correlated occurrence of inhibitory domains, reactive center loops, and disulfide bond patterns. By analyzing linker regions, we predict that alternative processing at linker regions could generate PI variants in the Solanaceae family.

CONCLUSION

PINIR ( https://pinir.ncl.res.in ) provides a web interface for browsing and analyzing the protein sequences of Pin-II type PIs. Information about signature sequences, spatio-temporal expression, biochemical properties, gene sequences, and literature references are provided. Analysis of PINIR depicts conserved species-specific features of Pin-II type PI protein sequences. Diversity in the sequence of inhibitory domains and reactive loops directs potential applications to engineer Pin-II type PIs. The PINIR database will serve as a comprehensive information resource for further research into Pin-II type PIs.

Protein-enriched fiber vegan meal promote satiety and suppress food intake in rats

Dietary preferences were closely associated with the pathogenesis of numbers of metabolic disorders, in particularly, obesity. Dietary fiber was shown to be capable of preventing weight gain and excessive food intake mainly through stimulating chewing and saliva secretion, and promote satiety signals. In this study, we characterized the "Vitamin World® Vegan Meal" Formula of Feihe, a novel protein-enriched fiber dietary supplement contained potato protease inhibitor II (PI2) that developed. And we demonstrated that this particular fiber formula was effective in preventing weight gain, increasing satiety signals, and reducing food intake in rats in a dosage-dependent manner. Our study provides lines of evidence and would further bolster the use of this nutritious vegan meal in regulating satiety and food intake in clinics.

The Effect of Potato Protease Inhibitor II on Gastrointestinal Hormones and Satiety in Humans During Weight Reduction

CONTEXT

It is questioned whether the potato protein protease inhibitor II (PI2) reduces appetite and exerts effects on the satiety hormone cholecystokinin (CCK).

OBJECTIVE

To investigate PI2 impact on gastrointestinal hormones and appetite measures during weight reduction.

DESIGN

In a randomized, placebo-controlled trial over 20 weeks, fifty-two overweight/obese participants (BMI 25.2-38.0 kg/m²) received a protein-rich diet (30%) adjusted to 500 kcal below their individual daily needs. Subjects ingested a capsule containing either PI2 (150 mg) or placebo twice daily 1 hr before lunch and dinner. At week 0 and week 10 participants joined breakfast test meals to determine CCK, GLP-1, ghrelin, leptin, glucose and insulin concentrations in a time course experimental manner. Appetite sensations were measured on test meal days and in week 4, 9, 14 and 19 using visual analogue scales.

RESULTS

Weight loss at week 10 and 20 in the PI2 group was 4.3±3.1 kg and 5.6±4.1 kg, in the control group: 4.7±4.0 kg and 6.8±3.7 kg. A significant effect of PI2 on circulating CCK levels was observed at week 10. The other hormones were unaffected by PI2. At week 10, PI2 group subjects showed higher satiety and decreased desire to eat compared to placebo. During study duration, PI2 showed a significant impact on appetite ratings prior to lunch, one hour before dinner and just before dinner.

CONCLUSION

PI2 increased circulating CCK plasma levels during the diet intervention. Likewise, PI2 modulated appetite sensation from week 4 to 20. The study demonstrated that the PI2 can modulate a key satiety signal.

Effect of potatoes and other carbohydrate-containing foods on cognitive performance, glycemic response, and satiety in children

Dietary carbohydrates have been shown to influence cognitive performance and satiety in children. However, it remains unclear whether the carbohydrate source is a primary determinant of cognitive performance and satiety. The objective was to compare the effects of white potatoes and other carbohydrate-containing foods on cognitive performance, glycemic response, and satiety in children. On 6 separate mornings, in random order, children (n = 22) consumed 50 g of available carbohydrates from microwaved mashed potatoes (prepared from fresh potatoes then frozen), deep-fried potato strips (French fries), hash browns, white rice, white beans, or skipped a meal. Cognitive performance, glycemic response, and satiety were measured over 180 min. Cognitive performance was measured using a battery of tests assessing verbal declarative memory, spatial memory, short-term memory, working memory, and information processing speed. Although cognitive performance after the treatment meals did not differ from meal skipping, children recalled more words after French fries (9.1 ± 0.4 words) compared with mashed potatoes (8.2 ± 0.3 words; p = 0.001) and white rice (8.4 ± 0.3 words; p = 0.04) on the verbal declarative memory test. Blood glucose concentrations were higher after white rice compared with white beans, mashed potatoes, and hash browns (p < 0.05). Change from baseline subjective average appetite (mm/kcal) was lower after mashed potatoes compared with all other treatment meals (p < 0.05). In conclusion, verbal declarative memory was higher after French fries and subjective average appetite was lower after mashed potatoes. Future longitudinal studies are needed to confirm these short-term findings and to elucidate the mechanism of action.

Potato protease inhibitor II suppresses postprandial appetite in healthy women: a randomized double-blind placebo-controlled trial

The effect of potato protease inhibitor II (PI2) on postprandial appetite was examined in a randomized double-blind placebo-controlled cross-over trial involving 44 healthy women. In separate test sessions, participants consumed a capsule containing placebo or potato extract standardized to 15 or 30 mg PI2 after overnight fasting. One hour later, a standard 390 kcal breakfast was served. At regular time points during the three-hour period after breakfast, appetite was measured by visual analog scales, and blood samples were collected for assay of cholecystokinin, insulin, and glucose. Compared with the placebo, consumption of 15 mg or 30 mg PI2 one hour prior to a standard breakfast meal resulted in significantly lower postprandial hunger, desire to eat, and prospective consumption, as well as significantly higher postprandial fullness. Consumption of 15 mg PI2 also resulted in significantly higher postprandial plasma levels of cholecystokinin compared with the placebo. No significant main effect of treatment was found on insulin and glucose. No adverse events were reported. Results from the study revealed that consumption of potato PI2 at the examined doses was well tolerated, suppressed subjective appetite in a dose-dependent manner, and increased plasma concentrations of cholecystokinin. Future studies are needed to evaluate the long-term effect of PI2 on body weight.

Anti-obesity and anti-diabetic effects of a standardized potato extract in ob/ob mice

The potato (Solanum tuberosum) has been cultivated globally for food for millenia. Potato contains proteinase inhibitor II, which catalyzes the release of cholecystokinin (CCK), leading to delayed gastric emptying in humans. The present study investigated the anti-obesity effects of Slendesta™ Potato Extract (SLD), a standardized potato extract containing 5% proteinase inhibitor II, in the ob/ob obese mice. Three doses of SLD (50, 150 or 300 mg/kg) were orally administered to ob/ob mice once a day for 28 days, whereas control mice were administered distilled water. Four weeks after SLD treatment, the changes in body weight, food consumption, epididymal fat weight, serum chemistry, insulin, leptin and adiponectin contents, and fat histopathology were determined and compared with ob/ob mice treated with 750 mg/kg conjugate linoleic acid. As a result of SLD treatment in the obese mice, body weight, food consumption, epididymal fat, serum biochemistry, histomorphological changes of fat and pancreas were significantly and dose-dependently decreased compared with ob/ob control mice. These obesity and type 2 diabetes associated alterations were significantly inhibited after SLD treatment for 28 days. Thus, the present results indicate that SLD has potential as an alternative therapeutic agent for obesity.

Effects of various food ingredients on gall bladder emptying

Background/objectives:

The emptying of the gall bladder in response to feeding is pivotal for the digestion of fat, but the role of various food ingredients in contracting the gall bladder postprandially is not well understood. We hypothesized that different food ingredients, when consumed, will have a different effect on stimulating gall bladder emptying. To investigate this we designed two randomized, investigator-blind, cross-over studies in healthy subjects using magnetic resonance imaging (MRI) to measure gall bladder volumes serially and non-invasively.

Subjects/methods:

Study 1: exploratory study evaluating the effects of 10 different food ingredients on gall bladder emptying in eight healthy subjects. The choice of ingredients varied from common items like coffee, tea and milk to actives like curcumin and potato protease inhibitor. Study 2: mechanistic study investigating the cholecystokinin (CCK) dose response to the best performer ingredient from Study 1 in 21 healthy subjects four ways.

Results:

The largest gall bladder volume change in Study 1 was observed with fat, which therefore became the dose-response ingredient in Study 2, where the maximum % gall bladder volume change correlated well with CCK.

Conclusions:

These serial test-retest studies showed that the fasted gall bladder volume varied remarkably between individuals and that individual day-to-day variability had wide coefficients of variation. Improved knowledge of how to stimulate bile release using food ingredients will be useful to improve in vitro–in vivo correlation of bioavailability testing of hydrophobic drugs. It could improve performance of cholesterol-lowering plant stanol and sterol products and possibly aid understanding of some cholesterol gallstone disease.

White vegetables: glycemia and satiety

The objective of this review is to discuss the effect of white vegetable consumption on glycemia, satiety, and food intake. White vegetables is a term used to refer to vegetables that are white or near white in color and include potatoes, cauliflowers, turnips, onions, parsnips, white corn, kohlrabi, and mushrooms (technically fungi but generally considered a vegetable). They vary greatly in their contribution to the energy and nutrient content of the diet and glycemia and satiety. As with other foods, the glycemic effect of many white vegetables has been measured. The results illustrate that interpretation of the semiquantitative comparative ratings of white vegetables as derived by the glycemic index must be context dependent. As illustrated by using the potato as an example, the glycemic index of white vegetables can be misleading if not interpreted in the context of the overall contribution that the white vegetable makes to the carbohydrate and nutrient composition of the diet and their functionality in satiety and metabolic control within usual meals. It is concluded that application of the glycemic index in isolation to judge the role of white vegetables in the diet and, specifically in the case of potato as consumed in ad libitum meals, has led to premature and possibly counterproductive dietary guidance.

Potato extract (Potein) suppresses food intake in rats through inhibition of luminal trypsin activity and direct stimulation of cholecystokinin secretion from enteroendocrine cells

Dietary proteins and trypsin inhibitors are known to stimulate the secretion of the satiety hormone cholecystokinin (CCK). A potato extract (Potein) contains 60% carbohydrate and 20% protein including trypsin inhibitory proteins. In this study, we examined whether Potein suppresses food intake in rats and whether it directly stimulates CCK secretion in enteroendocrine cells. In fasted rats, food consumption was measured up to 6 h after the oral administration of Potein or soybean trypsin inhibitor (SBTI). CCK-releasing activities of Potein and SBTI were examined in the murine CCK-producing cell line STC-1. Potein inhibited the trypsin activity in vitro with a potency 20-fold lower than that of SBTI. Oral administration of Potein dose-dependently suppressed food intake for 1-6 h. Potein, but not the SBTI, dose-dependently induced CCK secretion in STC-1 cells. These results suggest that Potein suppresses food intake through the CCK secretion induced by direct stimulation on enteroendocrine cells and through inhibition of luminal trypsin.