Whey protein, as exclusively nitrogen source, controls food intake and promotes glutathione antioxidant protection in Sprague-Dawley rats

Whey proteins inhibit food intake and tend to improve oxidative balance in obese zucker rats

BACKGROUND/AIMS

Whey proteins (WP), obtained from milk after casein precipitation, represent a heterogeneous group of proteins. WP are reported to inhibit food intake in diet-induced experimental obesity; WP have been proposed as adjuvant therapy in oxidative stress-correlated pathologies. This work evaluates the effects of WP in comparison with casein, as a source of alimentary proteins, on food intake, weight growth and some indexes of oxidative equilibrium in Zucker Rats, genetically prone to obesity.

METHODS

We monitored food intake and weight of Zucker Rats during the experiment, and some markers of oxidative equilibrium.

RESULTS

WP induced significant decrease of food intake in comparison to casein (WP 80.41 ± 1.069 ml/day; CAS: 88.95 ± 1.084 ml/day; p < 0.0005). Body weight growth was slightly reduced, and the difference was just significant (WP 128.2 ± 6.56 g/day; CAS 145.2 ± 3.29 g/day; p = 0.049), while plasma HNE level was significantly lower in WP than in CAS (WP 41.2 ± 6.3 vs CAS 69.61 ± 4.69 pmol/ml, p = 0.007). Mild amelioration of oxidative equilibrium was indicated by a slight increase of total glutathione both in the liver and in the blood and a significant decrease of plasma 4-hydroxynonenal in the group receiving WP.

CONCLUSIONS

The effect of WP on food intake and weight growth in Zucker Rats is particularly noteworthy since the nature of their predisposition to obesity is genetic; the possible parallel amelioration of the oxidative balance may constitute a further advantage of WP since oxidative stress is believed to be interwoven to obesity, metabolic syndrome and their complications.

Appetite control and gastrointestinal hormonal behavior (CCK, GLP-1, PYY 1-36) following low doses of a whey protein-rich nutraceutic

Whey proteins represent the most satiating nutrients. In particular, their effects are due to enterohormonal changes (CCK, GLP-1 and PYY 1–36) observed after their exclusive ingestion. Glucomannan has important satiety property due to volume increase following gelification. The aim of the study is the evaluation of subjective rate of hunger and enterohormone concentrations (CCK, GLP-1, PYY 1–36) following oral loading of a mixture containing WP (8 g) or casein (8 g) plus glucomannan (1 g) (Colordiet^®, Inpha DUEMILA Srl Lecco, Italy). The study was conducted as a double-blind crossover with five healthy volunteers (BMI 22–26 kg/m² aging 18–65 years) in acute and a wash-out period of 1 week between the first and the second evaluation. From the analysis of the data, we observe that the load with WP induces a significant decrease in the desire to eat after 90 min (P < 0.0446) when compared with casein. As far as plasma hormones are concerned, there was a significant increase only in GLP-1 at 90 min after WP (P < 0.00166) and 180 min after casein (T0 vs. T180 P = 0.000129). There is a significant correlation between the increase in GLP-1 and decrease of desire to eat (R = −0.93). There is a tendency to the increasing of CCK after 90 min, which is not significant (P = 0.091). These results could be due to (a) the low number of cases or (b) the low dose of protein used. The present study suggests that a mixture of WP plus glucomannan exerts a decrease in the desire to eat which is correlated to enterohormonal modification (GLP-1 increase) despite the low content of protein (8 g) and the presence of glucomannan, which could reduce the fast absorption of WP in relation to the net forming during the gelification of the gastric environment.