The impact of whey protein isolate on energy balance regulation

Using C57BL/6J mice fed whey protein isolate (WPI) enriched high fat (HFD) or low-fat diets (LFD), this study tested the hypothesis that WPI directly impacts on adiposity by influencing lipid metabolism. WPI suppressed HFD-induced body fat and increased lean mass at 8 weeks of dietary challenge despite elevated plasma triacylglycerol (TAG) levels, suggesting reduced TAG storage. WPI reduced HFD-associated hypothalamic leptin and insulin receptor (IR) mRNA expression, and prevented HFD-associated reductions in adipose tissue IR and glucose transporter 4 expression. These effects were largely absent at 21 weeks of HFD feeding, however WPI increased lean mass and cause a trend towards decreased fat mass, with notable increased Lactobacillus and decreased Clostridium gut bacterial species. Increasing the protein to carbohydrate ratio enhanced the above effects, and shifted the gut microbiota composition away from the HFD group. Seven weeks of WPI intake with a LFD decreased insulin signalling gene expression in the adipose tissue in association with an increased fat accumulation. WPI reduced intestinal weight and length, suggesting a potential functional relationship between WPI, gastro-intestinal morphology and insulin related signalling in the adipose. Extending the study to 15 weeks, did not affect adipose fat weight, but decreased energy intake, weight gain and intestinal length. The functionality of protein sensing lysophosphatidic acid receptor 5 (LPA5) in 3T3-L1 pre-adipocytes was assessed. Over-expression of the receptor in 3T3-L1 pre-adipocytes provided a growth advantage to the cells and suppressed cellular differentiation into mature fat cells. In conclusion, the data demonstrates WPI impacts on adiposity by influencing lipid metabolism in a temporal manner, resulting possibly due to changes in lean mass, hypothalamic and adipose gene expression, gut microbiota and gastrointestinal morphology. The data also showed LPA5 is a novel candidate in regulating of preadipocyte growth and differentiation, and may mediate dietary protein effects on adipose tissue.

Complex coacervation with whey protein isolate and gum arabic for the microencapsulation of omega-3 rich tuna oil.

Tuna oil rich in omega-3 fatty acids was microencapsulated in whey protein isolate (WPI)-gum arabic (GA) complex coacervates, and subsequently dried using spray and freeze drying to produce solid microcapsules. The oxidative stability, oil microencapsulation efficiency, surface oil and morphology of these solid microcapsules were determined. The complex coacervation process between WPI and GA was optimised in terms of pH, and WPI-to-GA ratio, using zeta potential, turbidity, and morphology of the microcapsules. The optimum pH and WPI-to-GA ratio for complex coacervation was found to be 3.75 and 3 : 1, respectively. The spray dried solid microcapsules had better stability against oxidation, higher oil microencapsulation efficiency and lower surface oil content compared to the freeze dried microcapsules. The surface of the spray dried microcapsules did not show microscopic pores while the surface of the freeze dried microcapsules was more porous. This study suggests that solid microcapsules of omega-3 rich oils can be produced using WPI-GA complex coacervates followed by spray drying and these microcapsules can be quite stable against oxidation. These microcapsules can have many potential applications in the functional food and nutraceuticals industry.

Co-encapsulation and characterisation of omega-3 fatty acids and probiotic bacteria in whey protein isolate-gum Arabic complex coacervates

Omega-3 fatty acids and probiotic bacteria were co-encapsulated in a single whey protein isolate (WPI)-gum Arabic (GA) complex coacervate microcapsule. Tuna oil (O) and Lactobacillus casei 431 (P) were used as models of omega-3 and probiotic bacteria, respectively. The co-microcapsules (WPI-P-O-GA) and L.casei containing microcapsules (WPI-P-GA) were converted into powder by using spray and freeze drying. The viability of L.casei was significantly higher in WPI-P-O-GA co-microcapsules than in WPI-P-GA. The oxidative stability of tuna oil was significantly higher in spray dried co-capsules than in freeze dried ones.

Whey protein isolate decreases murine stomach weight and intestinal length and alters the expression of Wnt signalling-associated genes

Acknowledgements K. N. N. was supported by the Teagasc Vision Programme on Obesity (RMIS5974). L. M. was supported by the Teagasc Walsh Fellowship. J. R. S. was supported by a 1000-talents professorship from the Chinese government. The funding bodies had no input on the design of the study or in the interpretation of the data. The authors’ contributions are as follows: L. M., J. R. S., J. F. C. and K. N. N. designed the study; K. N. N. and J. F. C. obtained ethical approval for the study; L. M. performed the experiments; L. M. and J. R. S. analysed the data; L. M. generated the figures. All authors contributed to the drafting of the manuscript. All authors approved the final version for submission. The authors declare that there is no competing interest.

Plasma amino acid response after ingestion of different whey protein fractions

Background and objectives The digestion rate of proteins and subsequent absorption of amino acids can independently modulate protein metabolism. The objective of the present study was to examine the blood amino acid response to whey protein isolate (WPI), β-lactoglobulin-enriched WPI, hydrolysed WPI and a flavour-identical control.

Methods Eight healthy adults (four female, four male) were recruited (mean±standard error of the mean: age, 27.0±0.76 years; body mass index, 23.2±0.8 kg/cm2) and after an overnight fast consumed 500 ml of each drink, each containing 25g protein, in a cross-over design. Blood was taken at rest and then every 15 min for 2 h post ingestion.

Results Ingesting the β-lactoglobulin-enriched WPI drink resulted in significantly greater plasma leucine concentrations at 45-120 min and significantly greater branched-chain amino acid concentrations at 60-105 min post ingestion compared with hydrolysed WPI. No differences were observed between WPI and β-lactoglobulin-enriched WPI, and all protein drinks resulted in elevated blood amino acids compared with flavour-identical control.

Conclusions In conclusion, whole proteins resulted in a more rapid absorption of leucine and branched-chain amino acid into the blood compared with the hydrolysed molecular form of whey protein.

Whey protein ingestion activates mTOR-dependent signalling after resistance exercise in young men : a double-blinded randomized controlled trial

The effect of resistance exercise with the ingestion of supplementary protein on the activation of the mTOR cascade, in human skeletal muscle has not been fully elucidated. In this study, the impact of a single bout of resistance exercise, immediately followed by a single dose of whey protein isolate (WPI) or placebo supplement, on the activation of mTOR signalling was analyzed. Young untrained men completed a maximal single-legged knee extension exercise bout and were randomized to ingest either WPI supplement (n = 7) or the placebo (n = 7). Muscle biopsies were taken from the vastus lateralis before, and 2, 4 and 24 hr post-exercise. WPI or placebo ingestion consumed immediately post-exercise had no impact on the phosphorylation of Akt (Ser⁴⁷³). However, WPI significantly enhanced phosphorylation of mTOR (Ser²⁴⁴⁸), 4E-BP1 (Thr^37/46) and p70S6K (Thr³⁸⁹) at 2 hr post-exercise. This study demonstrates that a single dose of WPI, when consumed in modest quantities, taken immediately after resistance exercise elicits an acute and transient activation of translation initiation within the exercised skeletal muscle.

The impact of whey protein consumption and exercise on the composition and diversity of the gut microbiota: a high through-put DNA sequencing approach

Advances in culture independent technologies over the last decade have highlighted the pivotal role which the gut microbiota plays in maintaining human health. Conversely, perturbations to the composition or actions of the ‘normal/functioning’ microbiota have been frequently associated with the pathogenesis of several disease states. Therefore the selective modulation of enteric microbial communities represents a viable target for the development of novel treatments for such diseases. Notably, while bovine whey proteins and exercise have been shown to positively influence several physiological processes, such as energy balance, their effect on the composition or functionality of the gut microbiota remains largely unknown. In this thesis, a variety of ex vivo, murine and human models are used in conjunction with high-throughput DNA sequencing-based analysis to provide valuable and novel insights into the impact of both whey proteins and exercise on enteric microbial communities. Overall the results presented in this thesis highlight that the consumption both whey protein isolate (WPI), and individual component proteins of whey such as bovine serum albumin (BSA) and lactoferrin, reduce high fat diet associated body weight gain and are associated with beneficial alterations within the murine gut microbiota. Although the impact of exercise on enteric microbial communities remains less clear, it may be that longer term investigations are required for the true effect of exercise on the gut microbiota to be fully elucidated.

Water sorption-induced crystallization, structural relaxations and strength analysis of relaxation times in amorphous lactose/whey protein systems

Water sorption-induced crystallization, α-relaxations and relaxation times of freeze-dried lactose/whey protein isolate (WPI) systems were studied using dynamic dewpoint isotherms (DDI) method and dielectric analysis (DEA), respectively. The fractional water sorption behavior of lactose/WPI mixtures shown at aw ≤ 0.44 and the critical aw for water sorption-related crystallization (aw(cr)) of lactose were strongly affected by protein content based on DDI data. DEA results showed that the α-relaxation temperatures of amorphous lactose at various relaxation times were affected by the presence of water and WPI. The α-relaxation-derived strength parameter (S) of amorphous lactose decreased with aw up to 0.44 aw but the presence of WPI increased S. The linear relationship for aw(cr) and S for lactose/WPI mixtures was also established with R2 > 0.98. Therefore, DDI offers another structural investigation of water sorption-related crystallization as governed by aw(cr), and S may be used to describe real time effects of structural relaxations in noncrystalline multicomponent solids.

Preparation, characterization and functional properties of flax seed protein isolate

Flaxseed protein isolate (FPI) was extracted from flaxseeds, and its amino acid composition and functional properties (solubility, thermal stability, emulsifying properties and electrostatic charge density, water holding and fat absorption capacities) were determined. The highest purity of FPI (90.6%) was achieved by extraction at 60°C. FPI had a low lysine to arginine ratio of 0.25, which is desired in heart-healthy foods and infant formulas. The denaturation temperature of FPI was 105°C. FPI had the highest emulsion activity index (375.51 m(2)/g), highest emulsion stability index (179.5 h) and zeta potential (-67.4 mV) when compared to those of other commonly used proteins, such as sodium caseinate (SC), whey protein isolate (WPI), gelatin (Gel) and soy protein isolate (SPI). The average emulsion droplet size of emulsions stabilized by these proteins was in the order SC

Soy protein ingestion results in less prolonged p70S6 kinase phosphorylation compared to whey protein after resistance exercise in older men

BACKGROUND: The phosphorylation of p70S6 Kinase (p70S6K) is an important step in the initiation of protein translation. p70S6K phosphorylation is enhanced with graded intakes of whey protein after resistance exercise. Soy protein ingestion results in lower muscle protein synthesis after exercise compared with whey; however, the underlying mechanisms responsible for this difference have not been reported. FINDINGS: 13 older men (60-75) completed an acute bout of lower body resistance exercise and ingested 30 g of soy protein or carbohydrate. Muscle biopsies were obtained in the rested and fasted state and 2 and 4 hours post exercise. Phosphorylation status of p70S6K was measured with western blot. Results were compared with previously reported data from the ingestion of 30 g of whey protein or placebo. p70S6K phosphorylation was increased 2, but not 4 hours post exercise with soy protein ingestion. p70S6K phosphorylation was not increased post exercise with carbohydrate ingestion. CONCLUSIONS: Ingesting 30 g of either whey or soy protein resulted in equivalent p70S6K phosphorylation at 2 hours post exercise, however, unlike whey, soy protein failed to promote prolonged phosphorylation of p70S6K to 4 hours post-exercise.

Complex coacervation between flaxseed protein isolate and flaxseed gum

Flaxseed protein isolate (FPI) and flaxseed gum (FG) were extracted, and the electrostatic complexation between these two biopolymers was studied as a function of pH and FPI-to-FG ratio using turbidimetric and electrophoretic mobility (zeta potential) tests. The zeta potential values of FPI, FG, and their mixtures at the FPI-to-FG ratios of 1:1, 3:1, 5:1, 10:1, 15:1 were measured over a pH range 8.0-1.5. The alteration of the secondary structure of FPI as a function of pH was studied using circular dichroism. The proportion of a-helical structure decreased, whereas both β-sheet structure and random coil structure increased with the lowering of pH from 8.0 to 3.0. The acidic pH affected the secondary structure of FPI and the unfolding of helix conformation facilitated the complexation of FPI with FG. The optimum FPI-to-FG ratio for complex coacervation was found to be 3:1. The critical pH values associated with the formation of soluble (pHc) and insoluble (pHΦ1) complexes at the optimum FPI-to-FG ratio were found to be 6.0 and 4.5, respectively. The optimum pH (pHopt) for the optimum complex coacervation was 3.1. The instability and dissolution of FPI-FG complex coacervates started (pHΦ2) at pH2.1. These findings contribute to the development of FPI-FG complex coacervates as delivery vehicles for unstable albeit valuable nutrients such as omega-3 fatty acids.