Kay J. Rutherfurd-Markwick

Food proteins as a source of bioactive peptides with diverse functions.

In addition to supplying essential nutrients, some food proteins can confer additional health benefits beyond nutrition. The presence of bioactive proteins and peptides in different foods is a factor not currently taken into consideration when assessing the dietary quality of food proteins. The range of described physiological benefits attributed to bioactive proteins and peptides is diverse. Multiple factors can potentially impact on the ability of a bioactive peptide or protein to elicit an effect. Although some food proteins act directly in their intact form to elicit their effects, generally it is peptides derived from digestion, hydrolysis or fermentation that are of most interest. The levels of bioactive peptides generated must be sufficient to elicit a response, but should not be so high as to be unsafe, thus causing negative effects. In addition, some peptides cause systemic effects and therefore must be absorbed, again in sufficient amounts to elicit their action. Many studies to date have been carried out in vitro; therefore it is important that further trials are conducted in vivo to assess efficacy, dose response and safety of the peptides, particularly if health related claims are to be made. Therefore, methods must be developed and standardised that enable the measurement of health benefits and also the level of bioactive peptides which are absorbed into the bloodstream. Once standardised, such methods may provide a new perspective and an additional mechanism for analysing protein quality which is currently not encompassed by the use of the protein digestibility-corrected amino acid score (PDCAAS).

Testosterone increases urinary free felinine, N-acetylfelinine and methylbutanolglutathione excretion in cats (Felis catus)

Two days after castration, urinary free felinine plus N-acetylfelinine decreased 24% in male cats, but, by day 5, the concentration had not decreased to that routinely found in males that have been castrated for several months. In a second experiment, three groups of castrated adult male cats received different subcutaneous injections: control (carrier), testosterone, testosterone plus estradiol. A fourth group of intact adult female cats received a testosterone injection. Urine was collected and analysed for free felinine, N-acetylfelinine and 3-methylbutanolglutathione. Baseline blood testosterone and estradiol concentrations were low during the pre-period, but increased sharply after hormone injections. The concentration of all three urinary metabolites increased as a result of testosterone injections with estradiol not modulating the effect. The effect of testosterone was not gender dependent. The concentration of free felinine, N-acetylfelinine and 3-methylbutanolglutathione in the urine remained low in the placebo control group throughout the study. The relative molar contribution of free felinine to the total amount of felinine containing compounds increased due to testosterone treatment, while the contribution of 3-methylbutanolglutathione and N-acetylfelinine decreased. Testosterone increases free felinine, N-acetylfelinine and 3-methylbutanolglutathione excretion in castrated adult male and intact female cats, whereas estradiol does not modulate this effect.

The Effect of Caffeine Ingestion during Evening Exercise on Subsequent Sleep Quality in Females.

In a randomised, double-blind, placebo-controlled crossover design, 10 females taking monophasic oral contraceptives completed 90 min intermittent treadmill-running 45 min after ingestion of 6 mg∙kg(-1) body mass anhydrous caffeine or artificial sweetener (placebo). Water (3 mL∙kg(-1)) was provided every 15 min during exercise. Venous blood samples were taken before, during and after exercise, as well as after sleep (~15 h post-ingestion), and levels of caffeine, paraxanthine, theobromine and theophylline were measured using high-performance liquid chromatography. Sleep quality was assessed using the Leeds Sleep Evaluation Questionnaire. Plasma caffeine concentration peaked 100 min after ingestion. Caffeine clearance was 0.95±0.14 mL·min(-1)·kg(-1) while the elimination half-life of caffeine was 17.63±8.06 h. Paraxanthine and theophylline levels were significantly elevated at 15 h with no significant change in theobromine. Sleep latency and subsequent quality of sleep was impaired following caffeine supplementation (P<0.05); there were no differences between trials for how participants were feeling upon awakening. This is the first controlled study to examine caffeine supplementation on sleep quality in female athletes taking a low-dose monophasic oral contraceptive steroid following an intermittent-exercise running protocol. The data shows that female athletes using monophasic oral contraceptive steroids will have impaired sleep quality following evening caffeine ingestion.

Ovine Serum Immunoglobulin Has Immunomodulatory Effects in Growing Rats Gavaged with Salmonella enteritidis

In this study, we aimed to determine whether orally administered ovine serum Ig modulate aspects of immunity and associated gut microflora in growing rats challenged with Salmonella enteritidis. The 4 groups consisted of rats fed a casein-based control diet (BD; ungavaged) and 3 groups of rats gavaged with 1 × 10(7) viable Salmonella enteritidis and fed a BD diet, a BD diet containing freeze-dried ovine Ig (FDOI), or a BD diet containing inactivated ovine Ig (IOI). The rats were randomly allocated to 1 of the 4 diets (n = 15) and consumed it for 18 d. They were orally gavaged on d 15. Phagocytic activity of peripheral blood leukocyte and lymphocyte proliferation in the presence of the concanavalin A (ConA) were greater (P < 0.05) in the ungavaged BD- and gavaged FDOI-fed rats than in the gavaged rats fed either the BD or IOI diet. ConA-stimulated Peyers patch cells and splenocytes from the gavaged rats fed the FDOI diet produced more IFNγ, IgA, and IgG than the gavaged rats fed either the BD or IOI diet (P < 0.05). The gavaged FDOI-fed rats had higher ileal and colonic digesta and plasma concentrations of anti-Salmonella secretory sIgA and secretory sIgG (P < 0.05). DNA analysis of a denatured gradient gel electrophoresis profile revealed that 6 of 10 bands had sequence similarity to probiotic strains of bacteria in the ileum and colon of the gavaged FDOI-fed rats. In conclusion, an ovine Ig fraction modulated various indices of immune function and associated gut microflora in growing rats inoculated with Salmonella.

The effects of the proportions of dietary macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs

Abstract AIM: To compare the effects of feeding diets varying in the proportions of macronutrients on the digestibility, post-prandial endocrine responses and large intestinal fermentation of carbohydrate in working dogs. METHODS: The apparent digestibility of two test diets, one comprising low-carbohydrate, high-protein dry biscuits (Diet 1), and one comprising high-carbohydrate, low-protein dry biscuits (Diet 2), fed to 12 adult Harrier Hounds (n=5 female), was determined using the indigestible-marker and total-collection methods. Serial breath samples were collected from each dog before and after feeding, and analysed for concentrations of hydrogen. Concentrations of glucose and insulin in plasma were established from serial blood samples obtained after feeding. RESULTS: The apparent dry matter, protein, fat and energy digestibility of Diet 1 were higher, but the carbohydrate digestibility was lower (p<0.05), than those of Diet 2. The apparent digestibility values determined using the total-collection method were lower (p<0.05) for carbohydrates, and tended to be lower for dry matter and energy (p<0.10) than those determined using the indigestible-marker method, but the values for protein and fat digestibility were similar using the two methods of determination. The maximum concentration (Cmax) of hydrogen detected in the breath of the dogs occurred earlier for Diet 1 than Diet 2 (p<0.01). However, the Cmax and area under the curve (AUC) for breath hydrogen were higher in the dogs fed Diet 2 than Diet 1 (p<0.01). The Cmax for glucose and insulin in plasma occurred earlier in dogs fed Diet 2 compared with those fed Diet 1 (p<0.05). However, the Cmax for glucose, and AUC for glucose and for insulin were not different between the two diets. The Cmax for insulin was greater for Diet 2 compared with Diet 1 (p<0.05). CONCLUSIONS: The low-carbohydrate, high-protein diet (Diet 1) appeared to offer certain advantages to working dogs, including higher apparent nutrient digestibility, slower release of glucose into the bloodstream, and reduced large intestinal fermentation of carbohydrate. CLINICAL RELEVANCE: A low-carbohydrate, high-protein diet may be beneficial for specific groups of dogs, including working dogs subjected to prolonged bouts of exercise requiring a sustained energy source, or those with diabetes mellitus requiring better glycaemic control.

Urinary felinine excretion in intact male cats is increased by dietary cystine

Felinine is a branched-chain sulfur amino acid present in the urine of certain Felidae, including domestic cats. The objective of the present study was to determine if additional cystine and/or dietary N would increase felinine and N-acetylfelinine excretion by intact male cats fed a low-protein(LP) diet. Feeding five adult intact male cats an LP diet (18.8% of metabolisable energy (ME) as protein) v. a high-protein diet (38.6% of ME as protein) resulted in a trend (P=0.08) for decreased urinary felinine and no change in N-acetylfelinine excretion. In a 23 d study, when the LP diet was supplemented with L-cystine at 9.3 g/kg DM, urinary felinine:creatinine ratio showed a linear two-fold (121 %) increase (P<0.01) from 0.24 (SEM 0.05) to 0.53 (SEM 0.13) after 10 d. Subsequent feeding of the LP diet resulted in a decrease in felinine excretion to base levels. Plasma gamma-glutamyl felinylglycine concentrations were consistent with the excretion of felinine. Supplementation of the LP diet with L-cystine (9.3 g/kg DM),dispensable amino acids and arginine to a second group (n 5) also resulted in a significant (P<0.01) but smaller (+72 %) increase in the daily felinine:creatinine ratio (0.25 (SEM 0.04) to 0.43 (SEM 0.05)). The degree of felinine N-acetylation within groups was unaffected by dietary addition and withdrawal of amino acids. The results indicate that felinine synthesis is regulated by cystine availability, and that arginine may be physiologically important in decreasing felinine biosynthesis in intact male cats.

Age, breed, sex distribution and nutrition of a population of working farm dogs in New Zealand: Results of a cross-sectional study of members of the New Zealand Sheep Dog Trial Association

Abstract AIM: To establish baseline information about age, breed, sex distribution and feeding practices for a population of working farm dogs owned by members of the New Zealand Sheep Dog Trial Association (NZSDTA) throughout New Zealand. METHODS: Questionnaires were sent to members of the NZSDTA in August 2007, requesting information on the size and terrain of the farms where they worked, as well as the breed, weight, age and sex of each working dog they owned, feeding regime employed, diet fed, work levels, and general health of their dogs. RESULTS: The survey was completed by 542/676 (81%) of the eligible sample population, and provided information on 2,861 dogs, excluding those <1 year old. All of the dog owners surveyed worked on sheep and beef-cattle farms. The median farm size was 440 [Inter-quartile range (IQR) 132–1,200] ha and varied with region. The majority of farms were situated on either hill country (184/542; 34%) or a mixture of hilly and flat terrain (260/542; 48%), and had a median of six (IQR 5–8) working dogs per farm. The median age of dogs was 3.0 (IQR 2.0–6.0) years. Heading dogs were the most common type of working dog (1,510/2,861; 52.8%), followed by Huntaways (1,161/2,861; 40.6%). The gender distribution of all dogs was biased towards males (57%), but this decreased with age. There was a positive association between the number of dogs on a farm and perceived level of tiredness of dogs (p<0.001), but there were no differences in levels of tiredness between farms of different terrain. Most owners (526/542; 97%) fed their dogs once a day. The most common diet fed was a combination of dry food and homekill, which was fed by 328/542 (61%) owners during peak and 313/542 (58%) during off-peak periods of work. CONCLUSIONS and CLINICAL RELEVANCE: This study has established baseline information on the age, breed, gender and nutrition of a large population of working farm dogs in New Zealand. Current feeding practices employed by owners include offering a substantial amount of homekill to their animals. Homekill may be deficient or marginal in vitamins and minerals, therefore opportunities could exist to improve the diets and therefore the longevity and performance of these dogs.

Caffeine ingestion enhances perceptual responses during intermittent exercise in female team-game players

Abstract We examined the influence of caffeine supplementation on cognitive performance and perceptual responses in female team-game players taking low-dose monophasic oral contraceptives of the same hormonal composition. Ten females (24 ± 4 years; 59.7 ± 3.5 kg body mass; 2–6 training sessions per week) took part in a randomised, double-blind, placebo-controlled crossover-design trial. A 90-min intermittent treadmill-running protocol was completed 60 min following ingestion of a capsule containing either 6 mg • kg−1 anhydrous caffeine or artificial sweetener (placebo). Perceptual responses (ratings of perceived exertion (RPE), feeling scale (FS), felt arousal scale (FAS)), mood (profile of mood states (POMS)) and cognitive performance (Stroop test, choice reaction time (CRT)) were completed before, during and after the exercise protocol, as well as after ~12 h post exercise. Caffeine ingestion significantly enhanced the ratings of pleasure (P = 0.008) and arousal (P = 0.002) during the exercise protocol, as well as increased vigour (POMS; P = 0.007), while there was a tendency for reduced fatigue (POMS; P = 0.068). Caffeine ingestion showed a tendency to decrease RPE (P = 0.068) and improve reaction times in the Stroop (P = 0.072) and CRT (P = 0.087) tests. Caffeine supplementation showed a positive effect on perceptual parameters by increasing vigour and a tendency to decrease fatigue during intermittent running activity in female games players taking low-dose monophasic oral contraceptive steroids (OCS).

The potential for enhancement of immunity in cats by dietary supplementation.

This study was conducted to examine the potential benefits of dietary supplementation on the feline immune system. Forty three cats (8 or 9 per group) were fed a low protein control diet (22.7% DM basis), the same diet supplemented with yeast-derived nucleotides, salmon oil or l-arginine or a commercial moist high protein diet (53.0% DM basis) for a period of five weeks. The low protein diets were formulated using a commercial moist diet base with added fat and starch and fed ad libitum, along with water. Specific immune assays showed that supplementation with arginine caused a significant enhancement of lymphocyte proliferative responses to the T-cell mitogen PHA after 35 days (P=0.018), while supplementation with either nucleotides or salmon oil resulted in significant enhancement after both 14 (P=0.0048, P<0.0001 respectively) and 35 days (both P<0.0001). Dietary supplementation with arginine, nucleotides or salmon oil each led to significant increases in blood leucocyte phagocytic activity after both 14 (P=0.0003, P=0.0077, P<0.0001 respectively) and 35 days (P<0.0001). This indicates that a number of dietary ingredients have the ability to modulate the immune system of healthy cats possibly resulting in a greater ability to fight infection and disease.

Salivary Diagnostic Markers in Males and Females During Rest and Exercise

BackgroundSaliva is a useful diagnostic tool for analysis in sports, exercise and nutrition research, as collection is easy and non-invasive and it contains a large number of analytes affected by a range of physiological and pathological stressors and conditions. This study examined key salivary electrolytes and stress and immune markers in males and females at rest and during exercise.MethodsUnstimulated whole saliva from 20 healthy, recreationally active participants (8 males and 12 females) was analysed for flow rate, osmolality, sodium (Na+), potassium (K+), chloride (Cl−), secretory immunoglobulin A (SIgA), α-amylase activity and cortisol during both rest and moderate intensity (70% peak power) cycling exercise in a randomised crossover design. Each trial lasted 60 min and sampling was carried out at 15 and 45 min after the start of the trial. Saliva was collected using the gold-standard drool method; participants were required to provide at least 1 mL sample over 2 or 3-min period.ResultsFemales showed a greater response to steady-state exercise stress than males, with significant increases in osmolality (P < 0.001), α-amylase activity (P = 0.001) and secretion rate (P = 0.023) and SIgA secretion rate (P = 0.023), with trends for an increase in K+ (P = 0.053) and decrease in Cl− (P = 0.067). There were no differences between rest and exercise for any salivary analytes in males. In addition, females showed a trend for higher levels of cortisol than males at both rest (P = 0.099) and exercise (P = 0.070), as well as a higher heart rate (P < 0.001) and greater ratings of perceived exertion (P < 0.001) during the exercise trial. The coordination of the two stress response pathways (α-amylase vs cortisol) was positive in males (r = 0.799; P = 0.017) yet negative in females (r = −0.475; P = 0.036).ConclusionsMales and females show a markedly different response to steady-state exercise stress as measured in unstimulated whole saliva.