Biomarkers of selenium status in dogs

Background: Inadequate dietary selenium (Se) intake in humans and animals can lead to long term health problems, such as cancer. In view of the owner's desire for healthy longevity of companion animals, the impact of dietary Se provision on long term health effects warrants investigation. Little is currently known regards biomarkers, and rate of change of such biomarkers in relation to dietary selenium intake in dogs. In this study, selected biomarkers were assessed for their suitability to detect changes in dietary Se in adult dogs within eight weeks. Results: Twenty-four dogs were fed a semi-purified diet with an adequate amount of Se (46.1 mu g/MJ) over an 8 week period. They were then divided into two groups. The first group remained on the adequate Se diet, the second were offered a semi-purified diet with a low Se concentration (6.5 mu g/MJ; 31 % of the FEDIAF minimum) for 8 weeks. Weekly urine and blood was collected and hair growth measurements were performed. The urinary Se to creatinine ratio and serum Se concentration were significantly lower in dogs consuming the low Se diet from week 1 onwards, by 84 % (adequate 25.3, low 4.1) and 7 % (adequate 257 mu g/L, low 238 mu g/L) respectively. Serum and whole blood glutathione peroxidase were also significantly lower in dogs consuming the low Se diet from weeks 6 and 8 respectively. None of the other biomarkers (mRNA expression and serum copper, creatine kinase, triiodothyronine: thyroxine ratio and hair growth) responded significantly to the low Se diet over the 8 week period. Conclusions: This study demonstrated that urinary Se to creatinine ratio, serum Se and serum and whole blood glutathione peroxidase can be used as biomarkers of selenium status in dogs. Urinary Se to creatinine ratio and serum Se concentrations responded faster to decreased dietary Se than the other parameters. This makes these biomarkers candidates for early screening of long term effects of dietary Se provision on canine health

Selenium digestibility and bioactivity in dogs : what the can can, the kibble can't

There is a growing concern for the long-term health effects of selenium (Se) over-or underfeeding. The efficiency of utilization of dietary Se is subject to many factors. Our study in dogs evaluated the effect of diet type (canned versus kibble) and dietary protein concentration on Se digestibility and bioactivity. Canned and kibble diets are commonly used formats of dog food, widely ranging in protein concentration. Twenty-four Labrador retrievers were used and four canned and four kibble diets were selected with crude protein concentrations ranging from 10.1 to 27.5 g/MJ. Crude protein concentration had no influence on the digestibility of Se in either canned or kibble diets, but a lower Se digestibility was observed in canned compared to kibble diets. However, the biological activity of Se, as measured by whole blood glutathione peroxidase, was higher in dogs fed the canned diets than in dogs fed the kibble diets and decreased with increasing crude protein intake. These results indicate that selenium recommendations in dog foods need to take diet type into account

Performance of BRCA1/2 mutation prediction models in male breast cancer patients

To establish whether existing mutation prediction models can identify which male breast cancer (MBC) patients should be offered BRCA1 and BRCA2 diagnostic DNA screening, we compared the performance of BOADICEA (Breast and Ovarian Analysis of Disease Incidence and Carrier Estimation Algorithm), BRCAPRO (BRCA probability) and the Myriad prevalence table ("Myriad"). These models were evaluated using the family data of 307 Dutch MBC probands tested for BRCA1/2, 58 (19%) of whom were carriers. We compared the numbers of observed vs predicted carriers and assessed the Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) for each model. BOADICEA predicted the total number of BRCA1/2 mutation carriers quite accurately (observed/predicted ratio: 0.94). When a cut-off of 10% and 20% prior probability was used, BRCAPRO showed a non-significant better performance (observed/predicted ratio BOADICEA: 0.81, 95% confidence interval [CI]: [0.60-1.09] and 0.79, 95% CI: [0.57-1.09], vs. BRCAPRO: 1.02, 95% CI: [0.75-1.38] and 0.94, 95% CI: [0.68-1.31], respectively). Myriad underestimated the number of carriers in up to 69% of the cases. BRCAPRO showed a non-significant, higher AUC than BOADICEA (0.798 vs 0.776). Myriad showed a significantly lower AUC (0.671). BRCAPRO and BOADICEA can efficiently identify MBC patients as BRCA1/2 mutation carriers. Besides their general applicability, these tools will be of particular value in countries with limited healthcare resources

Psychosocial impact of undergoing prostate cancer screening for men with BRCA1 or BRCA2 mutations.

OBJECTIVES: To report the baseline results of a longitudinal psychosocial study that forms part of the IMPACT study, a multi-national investigation of targeted prostate cancer (PCa) screening among men with a known pathogenic germline mutation in the BRCA1 or BRCA2 genes. PARTICPANTS AND METHODS: Men enrolled in the IMPACT study were invited to complete a questionnaire at collaborating sites prior to each annual screening visit. The questionnaire included sociodemographic characteristics and the following measures: the Hospital Anxiety and Depression Scale (HADS), Impact of Event Scale (IES), 36-item short-form health survey (SF-36), Memorial Anxiety Scale for Prostate Cancer, Cancer Worry Scale-Revised, risk perception and knowledge. The results of the baseline questionnaire are presented. RESULTS: A total of 432 men completed questionnaires: 98 and 160 had mutations in BRCA1 and BRCA2 genes, respectively, and 174 were controls (familial mutation negative). Participants' perception of PCa risk was influenced by genetic status. Knowledge levels were high and unrelated to genetic status. Mean scores for the HADS and SF-36 were within reported general population norms and mean IES scores were within normal range. IES mean intrusion and avoidance scores were significantly higher in BRCA1/BRCA2 carriers than in controls and were higher in men with increased PCa risk perception. At the multivariate level, risk perception contributed more significantly to variance in IES scores than genetic status. CONCLUSION: This is the first study to report the psychosocial profile of men with BRCA1/BRCA2 mutations undergoing PCa screening. No clinically concerning levels of general or cancer-specific distress or poor quality of life were detected in the cohort as a whole. A small subset of participants reported higher levels of distress, suggesting the need for healthcare professionals offering PCa screening to identify these risk factors and offer additional information and support to men seeking PCa screening

Selenium in dog foods

Selenium is an essential trace mineral involved in many biological processes, such as anti-oxidant, thyroid and immune function. Current recommendations for selenium inclusion in dog foods lack knowledge on the requirements of adult dogs and the effect of various factors on its bioavailability (i.e. the fraction of the dietary selenium that reaches the systemic circulation) and bioactivity (i.e. the selenium that is incorporated into selenoproteins). Therefore, the objective of this PhD project was to identify factors that contribute to the biological utilisation of dietary selenium, as a first step towards correct selenium inclusion levels in dog foods to prevent long-term selenium related diseases. An in vitro study, assessing various factors of 62 pet foods, identified diet type and crude protein digestibility as most important factors to affect selenium accessibility (i.e. the amount of dietary selenium that is potentially available for absorption after in vitro digestion). A consequent in vivo study evaluated the effect of these factors on selenium bioavailability and -activity. Twenty-four dogs, four canned and four kibble diets with a range in crude protein concentration were used in a randomised cross-over study. Selenium bioavailability was higher from kibble than canned diets and was not affected by crude protein intake in both diet types. The biological activity of selenium, as measured by whole blood glutathione peroxidase activity, was higher in dogs fed the canned diets than in dogs fed the kibble diets and decreased with increasing crude protein intake. These results suggest that there were indeed differences in the bioavailability and -activity of selenium from canned and kibble diets, which can be caused either by the difference in ingredients used, by the selenium species or by the processing conditions. Another in vivo study with 24 dogs assessed selected biomarkers on their suitability to detect a decrease in dietary selenium in adult dogs within eight weeks. All dogs received a semi-purified diet with an adequate amount of selenium for eight weeks. After this, 12 of the dogs remained on this diet for another eight weeks and the other 12 dogs received a semi-purified diet with a low selenium concentration (6.5 µg/MJ; 31% of the FEDIAF minimum). Of the biomarkers measured, urinary selenium:creatinine ratio, serum selenium and serum glutathione peroxidase activity reacted most quickly and should be used in epidemiological trials, to determine their association with the occurrence of long-term selenium related diseases and could eventually be used in trials to determine the minimum selenium requirements of healthy adult dogs. In conclusion, the studies included in this PhD thesis showed that diet type was associated with selenium bioavailability and diet type and dietary crude protein concentration with selenium bioavailability and -activity. Selenium is generally more bioavailable from kibble diets, but selenium from canned diets results in an absolute higher bioactivity. Future studies may use the urinary selenium:creatinine ratio, serum selenium and serum glutathione peroxidase activity to assess the selenium requirements of healthy adult dogs

Storage of heparinised canine whole blood for the measurement of glutathione peroxidase activity

Glutathione peroxidase activity is used as a biomarker of selenium status in dogs. Freshly collected blood samples are usually measured, due to the lack of knowledge on the effect of storing the samples. This study investigated if the analysis of glutathione peroxidase activity in whole blood collected from dogs was affected by storage of between 5 and 164 days. Results indicated that glutathione peroxidase activity was more variable in the freshly analysed samples compared to the stored samples. Although the mean differences between fresh and stored samples were not always equal to zero, this is thought to be caused by the variability of reagent preparation rather than by storage, as no consistent increase or decrease in glutathione peroxidase activity was found. Therefore, it can be concluded that heparinised dog blood samples can be successfully stored up to 164 days before analysis of glutathione peroxidase activity

Predictive equations of selenium accessibility of dry pet foods

The trace element selenium is essential to both dogs and cats. Dry diets are formulated with a large range of ingredients, which may vary in selenium concentration and accessibility. This paper reports equations to predict the average invitro selenium accessibility from dry pet foods based on essential dietary nutrient concentrations, including crude protein, amino acids and crude fat. Predictive equations were made using stepwise linear regression for extruded and pelleted diets. The equations can be used to aid diet formulation to optimize selenium accessibility within the diet and to prevent selenium deficiency or toxicity

Preliminary data on biomarkers for selenium status in dogs

Introduction: The current European recommended allowance for selenium (Se) in adult dogs is largely based on extrapolated data from a study in puppies. There is currently no literature on specific and sensitive biomarkers for Se adequacy in dogs and therefore the minimum Se requirement may not be accurate. In the current study, several biomarkers were assessed for their suitability to detect Se adequacy in adult dogs. These markers may then be used in future long-term trials to determine the minimum requirement of Se in adult dogs. Material and methods: Two groups of dogs were fed a semi-purified pre-feed with an adequate amount of Se (46.1 µg/MJ ME) over an 8 week period. They were then divided into two groups and fed either the same adequate Se diet or a semi-purified diet with a low Se content (6.5 µg/MJ ME, 33% of Fediaf min. rec.) for 8 weeks. Weekly urine, blood and hair growth samples were collected. The difference between the diets was measured based on the urinary Se:creatinine (CT) ratio, whole blood glutathione peroxidase (GPx), hair growth, mRNA expression of 10 Se related genes, and serum GPx, Se, triiodothyronine to thyroxine (T3:T4) ratio, creatine kinase (CK), and copper (Cu). Data were analysed using linear mixed effects models to investigate the effects of diet, week and their interaction. A significance level of p<0.025 was used for the primary parameters whole blood GPx and urinary Se:CT and p<0.05 for all other parameters. Results and discussion: Urinary Se:CT ratio and serum Se concentration were lower in the low Se diet from week 1 onwards (adequate 32.8, low 6.1, p<0.001 and adequate 271.0, low 252.0 µg/L, p=0.030, respectively). It can be argued that urinary Se only gives an indication on the intake, but if corrected for Se intake, it shows a tendency towards a higher relative urinary Se excretion in the low Se diet in the first week (p=0.083), where after it equalizes with the excretion of the adequate diet (week 2, adequate 96.5, low 154.3, p=0.208). This may indicate a higher relative endogenous loss of Se in the first week of feeding the low Se diet. Whole blood GPx only became significantly lower in the low than in the adequate Se diet after 8 weeks (p=0.016). However, serum GPx reacted more quickly to changes in Se intake. After 6 weeks the serum GPx activity in the low Se diet was lower than in the adequate Se diet (p=0.012). The difference between whole blood and serum GPx may be due to the higher GPx activity and its variation in whole blood. Modelling the kinetics may bring further insights in the response of all parameters to changes in Se intake, but with the present statistical evaluation, T3:T4 ratio, CK, Cu, mRNA expression and hair growth data did not show significant differences between the diet types. Conclusion: Based on the linear mixed model approach, urinary Se excretion and serum Se were the most sensitive biomarkers for Se intake. Serum GPx reacted more quickly than whole blood GPx, but still much slower than serum Se

Selenium absorption and bioactivity in dogs are affected by dietary format

Introduction: The main function of the essential trace mineral selenium (Se) is the protective effect against oxidative stress. Raw materials of dog foods vary greatly in their Se concentration and availability and canned diets are formulated with different raw materials than kibble diets. These dietary formats (canned and kibble) also undergo a different type of processing. However, the current recommendation on Se in dog foods is not format specific. Our previous in vitro study already identified dietary format (canned vs. kibble) and protein digestibility as the main determinants of in vitro Se accessibility in dog foods. The present study was designed to evaluate if these findings are reflected in in vivo Se absorption, i.e. the fraction of dietary Se that reaches the systemic circulation, and Se bioactivity, i.e. the amount of Se that can be used for incorporation into enzymes. Material and methods: Twenty-four Labrador retrievers were randomized to four balanced groups in an incomplete cross-over design in which they were fed 4 of 8 diets during 6 transition days and 29-43 experimental days. The 8 diets were commercially available and varied in format (canned or kibble) and crude protein (CP) concentration. For every format, diets with an intended concentration of 9.6, 14.3, 19.1 and 23.9 g CP/MJ ME were selected. At the end of every feeding period, blood, urine and faecal samples were collected. Blood was analysed for whole blood glutathione peroxidase (GPx) and serum Se. Urine samples were analysed for total Se and creatinine (CT) and faeces for Se. Apparent Se absorption was calculated as the percentage of Se intake that was not found in the faeces. Data were analysed using linear mixed effects models to investigate the effects of actual CP intake, format and their interaction. Results and discussion: The average dietary Se content of the canned and kibble diets was 40.6 and 22.3 µg/MJ ME, respectively. Canned diets also had a higher dietary Se content in our in vitro study; 34.8 µg/MJ ME in canned (n=20) vs. 22.5 µg/MJ ME in kibble diets (n=23). This indicates that a higher dietary Se content is inherent to canned diets. Both apparent Se absorption (as % of Se intake) and urinary Se excretion corrected for the absolute amount of absorbed Se were lower in canned compared to kibble diets (p<0.001 and p<0.001, resp.). The former is in accordance with our in vitro Se accessibility findings(3). In contrast to the in vitro study, CP did not have a significant impact on Se absorption (p=0.753). The potential bioactivity was higher in canned than in kibble diets and decreased with increasing CP intake as measured by GPx (p<0.001 and p<0.001, resp.). This may be partly attributed to the higher amount of dietary Se in canned diets. Conclusion: This study demonstrated that kibble diets result in a higher percentage of apparent Se absorption, but that feeding canned diets causes a higher absolute amount of biologically active Se (in this study measured as GPx). Therefore, recommended allowances for Se should take dietary format into account

Dietary format affects selenium absorption and bioactivity in dogs

Selenium (Se) is an essential trace element with antioxidant properties that protects the body against oxidative stress. A dietary safety margin is needed to avoid loss of this protection at low concentrations and development of Se toxicity at high concentrations. The current recommended allowance for Se in dog foods is not format specific, but it is known that canned and kibble diets differ in the raw materials that are used and the way the diets are processed. Raw materials vary greatly in their Se concentration and availability. However, little is known about which dietary factors affect Se absorption, i.e. the fraction of dietary Se that reaches the systemic circulation, and Se bioactivity, i.e. the amount of Se that can be used for the incorporation into enzymes, in dog foods. Our previous work has identified diet format and apparent crude protein (CP) digestibility as factors that affect in vitro Se accessibility. Based on the in vitro results, it was hypothesized that canned diets have a lower Se absorption than kibble diets and that CP concentration is positively associated with Se absorption in kibble diets and negatively in canned diets in vivo. Twenty-four Labrador retrievers were divided into four treatment groups of 6 dogs. The study consisted of four feeding periods, each starting with six days to wean the dogs to their new diets, followed by periods of between 29-43 days for every diet. Eight commercially available diets were selected that varied in format (canned or kibble) and CP concentration. For every format, diets with an intended concentration of 9.6, 14.3, 19.1 and 23.9 g CP/MJ ME (40, 60, 80 and 100 g CP/1000 kcal ME, resp.) were selected. Diets with different CP concentrations were selected, hence leading to a range in digestible CP intakes. During the trial each dog was fed four of the eight experimental diets in a randomised incomplete cross-over design. During the final 6 days of each feeding period, titanium dioxide (TiO2) was added as an inert digestibility marker. Blood, urine and faecal samples were collected at the end of every feeding period. Blood was analysed for whole blood glutathione peroxidase (GPx), serum Se, and general haematology and biochemistry parameters in plasma. Urine samples were analysed for total Se and creatinine (CT) and faeces for TiO2, dry matter (DM), ash, CP (N×6.25) and Se. Apparent Se absorption was calculated as the percentage of Se intake that was not found in the faeces. Data were analysed using linear mixed effects models to investigate the effects of actual CP intake, format and their interaction. Apparent Se absorption (as % of Se intake) was lower in canned compared to kibble diets (p<0.001), which is in accordance with our in vitro Se accessibility findings. Unlike in vitro, no effect of CP intake on apparent Se absorption was found (p=0.753). Urinary Se excretion relative to Se intake was lower in canned than kibble diets (p<0.001) and tended to decrease with increasing CP intake (p=0.059). Even when urinary Se:CT ratio was corrected for the absolute amount of absorbed Se, the excretion was lower in canned diets (p=0.001) and decreased with increasing CP intake (p=0.017). The potential bioactivity was higher in canned than in kibble diets as measured by GPx (p<0.001) and this also decreased with increasing CP intake (p<0.001). This may be partly attributed to the higher amount of Se in canned diets. The average dietary Se content of the canned and kibble diets in this study was 40.6 and 22.3 µg/MJ ME, respectively. A higher dietary Se content is inherent to canned diets, as was also shown in our in vitro study, where analysis of the diets (20 canned and 23 kibble diets) showed an average dietary Se content of 34.8 vs. 22.5 µg/MJ ME, respectively. Other factors that differ between canned and kibble diets (e.g. type of ingredients) may also have influenced the results. In conclusion, this study demonstrated that despite the lower percentage of apparent Se absorption in canned diets, the absolute amount of biologically active Se (in this study measured as GPx) was higher. Therefore, recommended allowances for Se should take dietary format into account