Serum amino acid concentrations in growing rats fed intact protein versus enzymatic protein hydrolysate-based diets

Whey protein: The “whey” forward for treatment of type 2 diabetes?

A cost-effective nutritional approach to improve postprandial glycaemia is attractive considering the rising burden of diabetes throughout the world. Whey protein, a by-product of the cheese-making process, can be used to manipulate gut function in order to slow gastric emptying and stimulate incretin hormone secretion, thereby attenuating postprandial glycaemic excursions. The function of the gastrointestinal tract plays a pivotal role in glucose homeostasis, particularly during the postprandial period, and this review will discuss the mechanisms by which whey protein slows gastric emptying and stimulates release of gut peptides, including the incretins. Whey protein is also a rich source of amino acids, and these can directly stimulate beta cells to secrete insulin, which contributes to the reduction in postprandial glycaemia. Appetite is suppressed with consumption of whey, due to its effects on the gut-brain axis and the hypothalamus. These properties of whey protein suggest its potential in the management of type 2 diabetes. However, the optimal dose and timing of whey protein ingestion are yet to be defined, and studies are required to examine the long-term benefits of whey consumption for overall glycaemic control.

Antitumor activity against murine lymphoma L5178Y model of proteins from cacao (Theobroma cacao L.) seeds in relation with in vitro antioxidant activity

Background

Recently, proteins and peptides have become an added value to foodstuffs due to new knowledge about its structural analyses as related to antioxidant and anticancer activity. Our goal was to evaluate if protein fractions from cacao seeds show antitumor activity on lymphoma murine L5178Y model. The antioxidant activity of these fractions was also evaluated with the aim of finding a correlation with the antitumor activity.

Methods

Differential extraction of proteins from unfermented and semi-fermented-dry cacao seeds was performed and characterized by SDS-PAGE and FPLC size-exclusion chromatography. Antitumor activity was evaluated against murine lymphoma L5178Y in BALB/c mice (6 × 10⁴ cells i.p.), with a treatment oral dose of 25 mg/kg/day of each protein fraction, over a period of 15 days. Antioxidant activity was evaluated by the ABTS⁺ and ORAC-FL assays.

Results

Albumin, globulin and glutelin fractions from both cacao seed type were obtained by differential solubility extraction. Glutelins were the predominant fraction. In the albumin fraction, polypeptides of 42.3 and 8.5 kDa were found in native conditions, presumably in the form of two peptide chains of 21.5 kDa each one. The globulin fraction presented polypeptides of 86 and 57 kDa in unfermented cacao seed that produced the specific-cacao aroma precursors, and after fermentation the polypeptides were of 45 and 39 kDa. The glutelin fraction presented proteins >200 kDa and globulins components <100 KDa in lesser proportion. Regarding the semifermented-dry cacao seed, it was observed that the albumin fraction showed antitumoral activity, since it caused significant decreases (p < 0.05) in the ascetic fluid volume and packed cell volume, inhibiting cell growth in 59.98 ± 13.6% at 60% of the population; while the greatest antioxidant capacity due to free radical scavenging capacity was showed by the albumin and glutelin fraction in both methods assayed.

Conclusion

This study is the first report on the biological activity of semifermented-dry cacao protein fractions with their identification, supporting the traditional use of the plant. The albumin fraction showed antitumor and free radical scavenging capacity, however both activities were not correlated. The protein fractions could be considered as source of potential antitumor peptides.

The effect of different protein hydrolysate/carbohydrate mixtures on postprandial glucagon and insulin responses in healthy subjects

OBJECTIVES

To study the effect of four protein hydrolysates from vegetable (pea, gluten, rice and soy) and two protein hydrolysates from animal origin (whey and egg) on glucagon and insulin responses.

SUBJECTS/METHODS

Eight healthy normal-weight male subjects participated in this study. The study employed a repeated-measures design with Latin square randomization and single-blind trials. Protein hydrolysates used in this study (pea, rice, soy, gluten, whey and egg protein hydrolysate) consisted of 0.2 g hydrolysate per kg body weight (bw) and 0.2 g maltodextrin per kg bw and were compared to maltodextrin alone. Postprandial plasma glucose, glucagon, insulin and amino acids were determined over 2 h.

RESULTS

All protein hydrolysates induced an enhanced insulin secretion compared to maltodextrin alone and a correspondingly low plasma glucose response. A significant difference was observed in area under the curve (AUC) for plasma glucagon between protein hydrolysates and the maltodextrin control drink (P<0.05). Gluten protein hydrolysate induced the lowest glucagon response.

CONCLUSIONS

High amino-acid-induced glucagon response does not necessarily go together with low insulin response. Protein hydrolysate source affects AUC for glucagon more profoundly than for insulin, although the protein load used in this study seemed to be at lower level for significant physiological effects.

Effect of Different Hydrolysates of Whey Protein on Hepatic Glutathione Content in Mice

This study was designed to compare the effects of diets prepared with enzymatic hydrolysate of a whey protein concentrate (WPC) by pancreatin, protamex (Novo Nordisk, Bagsvaerd, Denmark), and alcalase proteases on the hepatic glutathione content in mice. The undenatured WPC was produced in a pilot plant by membrane technology (microfiltration/diafiltration) after separation of the casein clot through a conventional process. All three hydrolysates with 20% degree of hydrolysis showed an amino acid profile similar to WPC. Male A/J mice were fed on diets containing 20% WPC or hydrolysates. Commercial casein was used as a reference protein in the biological assays. The glutathione content was determined after liver extraction through high-performance capillary electrophoresis. WPC and its pancreatin and protamex hydrolysates showed higher ability to stimulate liver glutathione synthesis than alcalase hydrolysate. This difference was probably related to an amino acid sequence in the peptides that were formed during hydrolysis of whey proteins. Commercial casein and WPC alcalase hydrolysate produced lower stimulation of liver glutathione synthesis (7.09 and 5.66 micromol/g of wet weight) compared with WPC and pancreatin and protamex hydrolysates (8.72, 8.71, and 8.45 micromol/g of wet weight, respectively). These results indicate that the hydrolysates obtained by treatment with pancreatin and protamex are good sources of peptides with activity to stimulate glutathione synthesis.

Special formulas in infant nutrition: a review

Special formulas should only be used by medical prescription and for those lactating infants with diagnosed nutritional problems. Lactose-free formulas or those based on soy are the logical choice when the exclusion of lactose from the diet is considered necessary. At present, there is no concensus on the appropriateness of soy formulas for the treatment and prevention of nutritional allergies and current opinion seems to favour hydrolyzed protein formulas. High-degree protein hydrolysate formulas are used to treat lactating infants with an allergy to cow milk proteins or with serious nutritional problems. These formulas are not without risk, as they may contain residual epitopes capable of provoking a severe allergic reaction. Before using these formulas, allergenicity tests should be performed, particularly for highly sensitive infants. The unpleasant taste and high cost of these formulas, in addition to possible nutritional problems, limit their use in the prevention of atopic disease, although their efficacy is well established. Partially protein hydrolysate formulas are only used for preventive purposes and are not suitable for lactating infants with a proven allergy to cow milk. Although these formulas can reduce the incidence or delay the appearance of certain atopic symptoms, they have not been shown to prevent IgE-mediated allergic reactions to cow's milk and so their effectiveness is open to question.