Bovine growth hormone: human food safety evaluation

Invited Review: Somatotropin and Lactation Biology

Purpose of this review is to update the human and animal safety findings on bovine somatotropin (bST) since 1993 as well as to discuss ST action and its impacts on sustainability. Bovine somatotropin (bST) is a naturally produced hormone which is a key regulator of growth and milk production. Beginning in the 1930s and continuing until today, investigations have examined bST's impact on animal related factors such as nutrition, bioenergetics, metabolism, health, and well-being, and consumer related issues such as product safety, milk quality, and manufacturing characteristics. Overall, bST homeorhetically orchestrates (both directly and indirectly) the coordination of key physiological processes involved in lactation. Bovine somatotropin's direct effects involve adaptations in a variety tissues, and altered metabolism of all nutrient classes - water, carbohydrates, lipids, protein, and minerals. Mechanistically, this includes modifying key enzymes, intracellular signal transduction systems, tissue response to homeostatic signals and diversity of receptor subtypes. Indirect effects are mediated by the insulin-like growth factor (IGF) system. Collectively, IGF governs cellular changes within the mammary gland resulting in increased rates of milk synthesis and enhanced maintenance of secretory cells. The responses to bST are modulated by environmental and management factors, especially an animal's nutritional plane. This modulation is a principal component in allowing bST to play a key role in regulating nutrient utilization across a range of physiological states. Recombinant bST (rbST) was developed in the early 1980s and commercial rbST use in the United States began in 1994. Utilizing rbST markedly increases milk yield and improves feed efficiency and farm income; thus, it was rapidly adopted by many dairy producers. Despite reducing the environmental footprint of milk production and having no impact on cow health in well-managed dairies, milk consumption or human safety concerns, many within the processing, grocery and retailer industries began labeling and promoting "rbST-free" dairy products as a marketing strategy. The FDA was concerned this represented an implied health issue, so they required products labeled as "rbST-free" to also include the statement that "no significant difference has been shown between milk derived from rbST treated and non-rbST treated cows." Many Cooperatives had an aggressive strategy to market "rbST-free" milk to compete with "organic" milk and suggested producers would receive higher milk prices if they voluntarily stopped using rbST. The net effect was American farmers ceased using the technology. However, rbST continues to safely increase farmer revenue and to minimize the carbon footprint of dairy production in many parts of Asia, Africa, and South America. Overall, bST is a homeorhetic control which orchestrates metabolic processes affecting nutrient partitioning and animal productivity, and it is naturally higher in genetically superior animals. The intrinsic biology of endogenous bST can be harnessed with the use of exogenous rbST to safely and sustainably improve animal performance.

Genetic correlation and Mendelian randomization analyses support causal relationships between dietary habits and age at menarche

Dietary habits are essential in the mean age at menarche (AAM). However, the causal relationship between these factors remains unclear. Therefore, this study aimed to elucidate the genetic relationship between dietary habits and AAM. Genetic summary statistics for dietary habits were obtained from the UK Biobank. GWAS summary data for AAM was obtained from the ReproGen Consortium. Linkage disequilibrium score regression was used to test genetic correlations between dietary habits and AAM. The Mendelian randomization (MR) analyses used the inverse-variance weighted method. Genetic correlations with AAM were identified for 29 candi-date dietary habits, such as milk type (skimmed, semi-skimmed, full cream; coefficient = 0.2704, Pldsc = 1.13 × 10-14). MR evaluations revealed that 19 dietary habits were associated with AAM, including bread type (white vs. any other; OR 1.71, 95% CI 1.28-2.29, Pmr = 3.20 × 10-4), tablespoons of cooked vegetables (OR 0.437, 95% CI 0.29-0.67; Pmr = 1.30 × 10-4), and cups of coffee per day (OR 0.72, 95% CI 0.57-0.92, Pmr = 8.31 × 10-3). These results were observed to be stable under the sensitivity analysis. Our study provides potential insights into the genetic mechanisms underlying AAM and evidence that dietary habits are associated with AAM.

Cultured Meat Safety Research Priorities: Regulatory and Governmental Perspectives

As with every new technology, safety demonstration is a critical component of bringing products to market and gaining public acceptance for cultured meat and seafood. This manuscript develops research priorities from the findings of a series of interviews and workshops with governmental scientists and regulators from food safety agencies in fifteen jurisdictions globally. The interviews and workshops aimed to identify the key safety questions and priority areas of research. Participants raised questions about which aspects of cultured meat and seafood production are novel, and the implications of the paucity of public information on the topic. Novel parameters and targets may require the development of new analytical methods or adaptation and validation of existing ones, including for a diversity of product types and processes. Participants emphasized that data sharing of these efforts would be valuable, similar to those already developed and used in the food and pharmaceutical fields. Contributions to such databases from the private and public sectors would speed general understanding as well as efforts to make evaluations more efficient. In turn, these resources, combined with transparent risk assessment, will be critical elements of building consumer trust in cultured meat and seafood products.

Development and single laboratory validation of a targeted liquid chromatography-triple quadrupole mass spectrometry-based method for the determination of insulin like growth factor-1 in different types of milk samples

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Bovine insulin growth factor 1 (IGF-1) was estimated in different cow milk samples.

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In house validation of a LC-MS/MS IGF-1 investigation method in milks obtained by different technological treatments.

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Development of a sample treatment for the extraction of IGF-1 from different types of cow milk.

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IGF-1 level in cow’s milk was not dependent form milk technological processing.

A simple and reliable targeted liquid chromatography-electrospray-tandem mass spectrometry (LC-MS/MS) method was developed and validated through the selection of two biomarker peptides for the identification and determination of bovine insulin like growth factor-1 (IGF-1) in milk samples. Two urea-based sample extraction procedures were tested. The validation results provided detection limits at the 1–5 ng IGF-1/mL level as a function of the milk matrix, precision ranged from 3 to 8% and the method accuracy in the different milk matrices was assured. Finally, IGF-1 was measured in milk samples obtained by treatment with eleven different technological processes: IGF-1 concentrations were spread over a wide range from 11.2 ± 0.3 ng/mL to 346 ± 8 ng/mL with a median of 57.0 ± 0.2 ng/mL. The highest amount of IGF-1 was found in fresh whole milk samples and no significant correlation was found between the total milk protein content and the IGF-1 concentration level.

Growth Factor Concentrations in Human Milk Are Associated With Infant Weight and BMI From Birth to 5 Years

Background: Human milk bioactives may play a role in infant health and development. Although the variability in their concentrations in milk is well-established, the impact of differential milk profiles on infant growth outcomes remains unclear. Thus, the aim of the present study was to investigate whether different concentrations of metabolic hormones are associated with different weight and BMI in infants beyond the first year of life. Methods: Milk samples at 2.6 (±0.4) months after birth and anthropometric measures at 13 months, 2, 3, and 5 years were collected as part of the Finnish STEPS cohort study from 501 mothers and the respective 507 infants. Leptin, adiponectin, insulin-like growth factor (IGF)-1 and cyclic glycine-proline (cGP) in milk were analyzed. Multiple regression models and a repeated measures mixed model were used to examine associations between milk hormone concentrations and weight and BMI z-scores across time, at each time-point, and weight gain from birth to each follow-up visit. All models were corrected for birth weight, infant sex, duration of exclusive and total breastfeeding, time of introduction of solid foods and maternal pre-pregnancy BMI. Results: Higher milk IGF-1 was associated with higher weight at 13 months (p = 0.004) but lower weight at 3 (p = 0.011) and 5 years of age (p = 0.049). Higher cGP was associated with lower weight across the 5 years (p = 0.019) but with higher BMI at 5 years (p = 0.021). Leptin and adiponectin did not display associations with infant growth at this time. Sex interactions were also absent. Conclusions: Our results suggest that the interplay between human milk-borne IGF-1 and cGP is similar to that reported in other mammals and may have an important role in defining infant growth trajectories beyond the first year of life. Further research should explore the determinants and origins of these milk-borne compounds and evaluate their effect on infant growth and metabolism.

Naturally occurring hormones in foods and potential health effects

Hormones and hormone-like substances, for example, phytoestrogens, are food components that can be endogenously produced by a food source or occur secondary to farming practices. The hormone content of foods has been studied for decades, and safety evaluations in the United States and Europe indicate that naturally occurring hormones found in foods are safe for human consumption. More recent studies have focused on the role of certain hormones found in specific foods (e.g. dairy or soy) and their potential health effects. However, limited summaries exist on food content of hormones and hormone-like phytoestrogens in the context of a comprehensive US diet and implications, if any, of their daily consumption for overall health. This review provides an outline of hormone biosynthesis and functions in the body; discusses the more commonly studied, naturally occurring hormones in food and their biological role within food; estimates relative dietary contribution and when available, bioavailability, of naturally occurring food hormones; and summarizes the potential health associations of their intake in food. Based on the review of the scientific literature, the hormone content of typical serving sizes of commonly consumed foods is undetectable or in quantities that fall well within safety guidelines without any evidence for adverse effects on health.

Dairy cows - an opportunity in the research field of non-genetic inheritance?

More than 1 billion cattle are raised annually for meat and milk production. Dairy cows are repeatedly impregnated and separated from their calves, usually within the first 24 h after birth. Here, I suggest that dairy cows undergo a procedure comparable to the 'Maternal separation combined with unpredictable maternal stress' paradigm (MSUS), which is used to study the non-genetic inheritance (NGI) of phenotypes in rodents. I discuss what research on dairy cows may bring to the research field of NGI. The resulting research findings are likely to have benefits to our understanding of MSUS, NGI and consumer safety.

Quantitative Risk Assessment of Antimicrobial-Resistant Foodborne Infections in Humans Due to Recombinant Bovine Somatotropin Usage in Dairy Cows

Recombinant bovine somatotropin (rbST) is a production-enhancing technology that allows the dairy industry to produce milk more efficiently. Concern has been raised that cows supplemented with rbST are at an increased risk of developing clinical mastitis, which would potentially increase the use of antimicrobial agents and increase human illnesses associated with antimicrobial-resistant bacterial pathogens delivered through the dairy beef supply. The purpose of this study was to conduct a quantitative risk assessment to estimate the potential increased risk of human infection with antimicrobial-resistant bacteria and subsequent adverse health outcomes as a result of rbST usage in dairy cattle. The quantitative risk assessment included the following steps: (i) release of antimicrobial-resistant organisms from the farm, (ii) exposure of humans via consumption of contaminated beef products, and (iii) consequence of the antimicrobial-resistant infection. The model focused on ceftiofur (parenteral and intramammary) and oxytetracycline (parenteral) treatment of clinical mastitis in dairy cattle and tracked the bacteria Campylobacter spp., Salmonella enterica subsp. enterica, and Escherichia coli in the gastrointestinal tract of the cow. Parameter estimates were developed to be maximum risk to overestimate the risk to humans. The excess number of cows in the U.S. dairy herd that were predicted to carry resistant bacteria at slaughter due to rbST administration was negligible. The total number of excess human illnesses caused by resistant bacteria due to rbST administration was also predicted to be negligible with all risks considerably less than one event per 1 billion people at risk per year for all bacteria. The results indicate a high probability that the use of rbST according to label instructions presents a negligible risk for increasing the number of human illnesses and subsequent adverse outcomes associated with antimicrobial-resistant Campylobacter, Salmonella, or E. coli .

Consumer Perceptions and Attitudes towards Bovine Somatotropin

This article investigates the possible negative effects of bovine somatotropin (bST) and antibiotic use in cows on fluid-milk consumption in New York State. Based on data from a consumer survey, the potential change in milk consumption due to bST and antibiotic use is estimated. In addition, the current perceptions of consumers about bST and antibiotics are measured, and the significant socioeconomic, demographic, and attitudinal characteristics of consumers that are related to their milk-consumption response to bST are identified.

Dairy intake in relation to breast and pubertal development in Chilean girls

Background: Frequent dairy consumption in childhood has been related to higher growth-hormone concentrations that may affect mammary gland and pubertal development.Objective: We evaluated the relation of dairy intake to breast composition at Tanner stage 4 and age at menarche.Design: A total of 515 Chilean girls are included in the Growth and Obesity Cohort Study. The subjects have been followed longitudinally since they were 3-4 y old (from 2006 to the present). Starting in 2013, diet was assessed every 6 mo via a 24-h recall. The breast fibroglandular volume (FGV) was measured with the use of dual-energy X-ray absorptiometry at Tanner stage 4. The date of menarche was reported every 6 mo. Our analysis included 290 girls with data on prospective diet and breast composition and 324 girls with data on prospective diet and age at menarche.Results: The mean ± SD breast FGV and percentage of fibroglandular volume (%FGV) (i.e., FGV divided by total breast volume times 100) at Tanner stage 4 was 81.7 ± 32.2 cm³ and 42.0% ± 16.7%, respectively. Only sweetened, artificially flavored milk-based drinks were associated with the %FGV with girls who consumed >125 g/d having a %FGV that was 4.5% (95% CI: 0.9%, 8.1%) higher than that of girls who consumed none (P-trend = 0.007). Yogurt intake was associated with a lower FGV. Specifically, girls who consumed >125 g yogurt/d had -10.2 cm³ (95% CI: -20.2, -0.3 cm³) less FGV than did girls who consumed no yogurt (P-trend = 0.03). The majority (90.7%) of girls in our cohort attained menarche before the data analyses with a mean ± SD age at menarche of 11.9 ± 0.7 y. In multivariable models, low-fat dairy, low-fat milk, and yogurt intakes were associated with a later age at menarche. In particular, girls who consumed >125 g yogurt/d had menarche, on average, 4.6 mo (95% CI: 1.9, 7.4 mo) later than girls who consumed no yogurt (P-trend = 0.01).Conclusion: More-frequent consumption of sweetened, artificially-flavored milk-based drinks is associated with a higher %FGV, whereas higher yogurt intake is associated with a lower FGV and delayed age at menarche in Chilean girls.

Hormone Use in Food Animal Production: Assessing Potential Dietary Exposures and Breast Cancer Risk

In recent years, increasing attention has been paid to the role of hormones in breast cancer etiology, following reports that heightened levels of endogenous hormones and exposure to exogenous hormones and other endocrine-disrupting chemicals through food and the environment are associated with increased breast cancer risk. Seven hormone drugs (testosterone propionate, trenbolone acetate, estradiol, zeranol, progesterone, melengestrol acetate, and bovine somatotropin) are approved by the U.S. Food and Drug Administration for use in food animals. There is concern that these drugs or their biologically active metabolites may accumulate in edible tissues, potentially increasing the risk of exposure for consumers. To date, the potential for human exposure to residues of these compounds in animal products, as well as the risks that may result from this exposure, is poorly understood. In this paper, we discuss the existing scientific evidence examining the toxicological significance of exposure to hormones used in food animal production in relation to breast cancer risk. Through a discussion of U.S. federal regulatory programs and the primary literature, we interpret the state of surveillance for residues of hormone drugs in animal products and discuss trends in meat consumption in relation to the potential for hormone exposure. Given the lack of chronic bioassays of oral toxicity of the seven hormone compounds in the public literature and the limitations of existing residue surveillance programs, it is not currently possible to provide a quantitative characterization of risks that result from the use of hormonal drugs in food animal production, complicating our understanding of the role of dietary hormone exposure in the population burden of breast cancer.

Milk Consumption after Age 9 Years Does Not Predict Age at Menarche

BACKGROUND

Regular milk consumption during childhood and adolescence is recommended for bone health. However, milk consumption increases circulating insulin-like growth factor I concentrations, and may also accelerate puberty.

OBJECTIVE

We prospectively investigated the association between milk consumption and age at menarche in the Growing Up Today Study.

METHODS

Study participants were 5583 US girls who were premenarcheal and ages 9-14 y in 1996. Girls were followed through 2001, at which time 97% of noncensored participants had reported menarche. Frequency of milk and meat consumption was calculated with the use of annual youth/adolescent food frequency questionnaires from 1996-1998. Intake of related nutrients was also measured. Age at menarche was self-reported annually through 2001.

RESULTS

During follow-up, 5227 girls attained menarche over 10,555 accrued person-years. In models adjusted for dietary and sociodemographic predictors of menarche, frequency of milk consumption did not predict age at onset of menarche (for >3 glasses of milk/d vs. 1.1-4 glasses/wk, HR: 0.93; 95% CI: 0.83, 1.04). After additional adjustment for body size, premenarcheal girls consuming >3 glasses of milk daily were 13% less likely (95% CI: -3%, -23%; P-trend: <0.01) to attain menarche in the next month relative to those consuming 1.1-4 glasses/wk. Neither total meat nor red meat consumption was associated with age at menarche.

CONCLUSIONS

Our findings suggest that regular consumption of milk in girls aged ≥9 y is unlikely to substantially affect age at onset of menarche. Studies assessing associations between diet in early childhood and pubertal timing may be more illuminating.

Milk intake and total dairy consumption: associations with early menarche in NHANES 1999-2004

BACKGROUND

Several components of dairy products have been linked to earlier menarche.

METHODS/FINDINGS

This study assessed whether positive associations exist between childhood milk consumption and age at menarche or the likelihood of early menarche (<12 yrs) in a U.S sample. Data derive from the National Health and Nutrition Examination Survey (NHANES) 1999-2004. Two samples were utilized: 2657 women age 20-49 yrs and 1008 girls age 9-12 yrs. In regression analysis, a weak negative relationship was found between frequency of milk consumption at 5-12 yrs and age at menarche (daily milk intake β = -0.32, P<0.10; "sometimes/variable milk intake" β = -0.38, P<0.06, each compared to intake rarely/never). Cox regression yielded no greater risk of early menarche among those who drank milk "sometimes/varied" or daily vs. never/rarely (HR: 1.20, P<0.42, HR: 1.25, P<0.23, respectively). Among the 9-12 yr olds, Cox regression indicated that neither total dairy kcal, calcium and protein, nor daily milk intake in the past 30 days contributed to early menarche. Girls in the middle tertile of milk intake had a marginally lower risk of early menarche than those in the highest tertile (HR: 0.6, P<0.06). Those in the lowest tertiles of dairy fat intake had a greater risk of early menarche than those in the highest (HR: 1.5, P<0.05, HR: 1.6, P<0.07, lowest and middle tertile, respectively), while those with the lowest calcium intake had a lower risk of early menarche (HR: 0.6, P<0.05) than those in the highest tertile. These relationships remained after adjusting for overweight or overweight and height percentile; both increased the risk of earlier menarche. Blacks were more likely than Whites to reach menarche early (HR: 1.7, P<0.03), but not after controlling for overweight.

CONCLUSIONS

There is some evidence that greater milk intake is associated with an increased risk of early menarche, or a lower age at menarche.

Dairy and milk consumption and child growth: Is BMI involved? An analysis of NHANES 1999-2004

Humans are unique among mammals in that many consume cow's milk or other dairy products well beyond the traditional age of weaning. Milk provides various nutrients and bioactive molecules to support growth and development, and the question arises as to whether this dietary behavior influences growth parameters. There is evidence that milk makes positive contributions to growth in height, but its associations with other aspects of body size, such as body mass index (BMI), are not well-established. National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2004 and multivariate regression analysis were used to test the hypothesis that milk (g) or total dairy product consumption (kJ) is associated with higher BMI percentile among US White, Black, and Mexican-American children of age 2-4 years (n = 1,493) and 5-10 years (n = 2,526). Younger children in the highest quartile of dairy intake had higher BMIs (beta = 7.5-8.0; P < 0.01) than those in the lowest two quartiles. Controlling for energy intake eliminated differences between QIV and QI. Among children of 5-10 years of age dairy intake had no relationship to BMI. Young children in the highest quartile of milk intake had higher BMIs than all lower quartiles (beta = 7.1-12.8; beta = 6.3-11.8 in energy-controlled models; P < 0.05). Among children of 5-10 years of age, those in QIV for milk intake had higher BMIs than those in QII (beta = 8.3; beta = 7.1 in energy-controlled model; P < 0.01). Controlling for total protein or calcium did not change the results. Milk had more consistent positive associations with BMI than did dairy products, and these were strongest among children of 2-4 years of age.

Milk consumption and circulating insulin-like growth factor-I level: a systematic literature review

Studies suggest that the circulating insulin-like growth factor I (IGF-I) level is positively associated with the prostate cancer risk. The association of milk consumption and circulating IGF-I level has been examined in epidemiological studies with inconsistent results. We conducted a systematic literature review to summarize and quantify the current evidence for milk or dairy product consumption and the circulating IGF-I level. We searched relevant papers published in English up to March 2009 in various databases. Fifteen cross-sectional studies and eight randomized controlled trials were finally identified. Ten cross-sectional studies showed statistically positive correlation between milk consumption and the circulating IGF-I level. Randomized controlled trials indicated that the circulating IGF-I level was significantly higher in the milk intervention group. After meta-analysis, the weighted mean difference of the circulating IGF-I level was 13.8 ng/ml (95% confidence interval: 6.1-21.5 ng/ml) comparing the intervention group with the control group. The current evidence suggests that milk consumption may increase the circulating IGF-I level.

Survey of retail milk composition as affected by label claims regarding farm-management practices

A trend in food labeling is to make claims related to agricultural management, and this is occurring with dairy labels. A survey study was conducted to compare retail milk for quality (antibiotics and bacterial counts), nutritional value (fat, protein, and solids-not-fat), and hormonal composition (somatotropin, insulin-like growth factor-1 [IGF-1], estradiol, and progesterone) as affected by three label claims related to dairy-cow management: conventional, recombinant bovine somatotropin (rbST)-free (processor-certified not from cows supplemented with rbST), or organic (follows US Department of Agriculture organic practices). Retail milk samples (n=334) from 48 states were collected. Based on a statistical analysis that reflected the sampling schema and distributions appropriate to the various response variables, minor differences were observed for conventional, rbST-free, and organic milk labels. Conventionally labeled milk had the lowest (P<0.05) bacterial counts compared to either milk labeled rbST-free or organic; however, these differences were not biologically meaningful. In addition, conventionally labeled milk had significantly less (P<0.05) estradiol and progesterone than organic milk (4.97 vs 6.40 pg/mL and 12.0 vs 13.9 ng/mL, respectively). Milk labeled rbST-free had similar concentrations of progesterone vs conventional milk and similar concentrations of estradiol vs organic milk. Concentrations of IGF-1 in milk were similar between conventional milk and milk labeled rbST-free. Organic milk had less (P<0.05) IGF-1 than either conventional or rbST-free milk (2.73 ng/mL vs 3.12 and 3.04 ng/mL, respectively). The macronutrient profiles of the different milks were similar, except for a slight increase in protein in organic milk (about 0.1% greater for organic compared to other milks). Label claims were not related to any meaningful differences in the milk compositional variables measured. It is important for food and nutrition professionals to know that conventional, rbST-free, and organic milk are compositionally similar so they can serve as a key resource to consumers who are making milk purchase (and consumption) decisions in a marketplace where there are misleading milk label claims.

Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part I)

Through the use of the new tools of genetic engineering, genes can be introduced into the same plant or animal species or into plants or animals that are not sexually compatible-the latter is a distinction with classical breeding. This technology has led to the commercial production of genetically engineered (GE) crops on approximately 250 million acres worldwide. These crops generally are herbicide and pest tolerant, but other GE crops in the pipeline focus on other traits. For some farmers and consumers, planting and eating foods from these crops are acceptable; for others they raise issues related to safety of the foods and the environment. In Part I of this review some general and food issues raised regarding GE crops and foods will be addressed. Responses to these issues, where possible, cite peer-reviewed scientific literature. In Part II to appear in 2009, issues related to environmental and socioeconomic aspects of GE crops and foods will be covered.

Parental characteristics as predictors of birthweight

BACKGROUND

Previous studies provided conflicting results on the relevance of parental characteristics for offspring's size at birth. The objective of this study was to investigate parental predictors of birthweight.

METHODS

In this cross-sectional study, 34,063 women in the Nurses' Mother's Cohort were queried about parental characteristics during the pregnancy with and birthweight of their nurse daughter.

RESULTS

The predictive linear regression model of birthweight included 13 factors and the majority of the predictive power came from parental anthropometric factors. In the adjusted analysis, daily consumption of each additional glass of milk was associated with an increase of approximately 6 g in birthweight (P for trend = 0.01) and daily consumption of each additional cup of coffee was associated with a decrease of approximately 10 g in birthweight (P for trend < 0.0001). Drinking 1-2, 3-4 and 5+ cups of coffee daily was associated with a 28% [95% confidence interval (CI) 0.12, 0.47], 30% (95% CI 0.10, 0.55) and 63% (95% CI 0.25, 1.12) increase, respectively, in the odds of intrauterine growth restriction when compared with non-drinkers.

CONCLUSIONS

The present study confirmed several previously reported determinants of birthweight. Maternal dietary intake of milk and coffee during pregnancy may influence fetal growth.

Step-up related simultaneous confidence intervals for MCC and MCB

The derivation of compatible confidence bounds related to stepwise decision procedures is a serious issue. Especially the derivation of step-up related bounds is rather complex. In this article we consider (one-sided) multiple comparisons with a control (MCC) and multiple comparisons with the best (MCB) with the aim of establishing delta-equivalence to the best and derive step-up related confidence bounds by applying the projection method proposed in Finner and Strassburger (2006). Some examples illustrate the resulting procedures.

A rapid surface plasmon resonance (SPR) biosensor immunoassay for screening of somatotropins in injection preparations

The use of growth hormones (recombinant somatotropins (rSTs)) is approved in several countries, e.g. the USA, Brazil and Australia to enhance growth or lactating performances of livestock. Their use in the EU is banned, however, due to the widespread application, the illegal use within the EU cannot be excluded. To screen for rSTs in injection preparations, a biosensor immunoassay (BIA) using surface plasmon resonance (SPR) technology was developed. Compared to existing analysis methods for rSTs, like radio immunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), this technique provides a rapid (7 min) alternative. A direct BIA was compared to an indirect (inhibition) BIA and the performances of several antibodies against (r)STs were compared in the indirect BIA. In the final inhibition assay, using rabbit anti-bovine rST, extracts from several injection preparations were shown to contain bovine rST (rbST). The limit of detection for rbST in the assay is 0.008 microg mL(-1) which is far below the expected concentrations in injection preparations. Although the cross-reactivities for STs of other species were low, screening of injection preparations for porcine, equine and human ST was feasible through the analysis of less diluted extracts. Tryptic digestion followed by nano-electrospray liquid chromatography-ion trap tandem mass spectrometry (nano-LC-MS/MS) was used to identify STs.

Cow's milk and linear growth in industrialized and developing countries

The strongest evidence that cow's milk stimulates linear growth comes from observational and intervention studies in developing countries that show considerable effects. Additionally, many observational studies from well-nourished populations also show an association between milk intake and growth. These results suggest that milk has a growth-stimulating effect even in situations where the nutrient intake is adequate. This effect is supported by studies that show milk intake stimulates circulating insulin-like growth factor (IGF)-I, which suggests that at least part of the growth-stimulating effects of milk occur through the stimulation of IGFs. Given that the biological purpose of milk is to support the newborn during a period of high growth velocity, such an effect seems plausible. Adding cow's milk to the diet of stunted children is likely to improve linear growth and thereby reduce morbidity. In well-nourished children, the long-term consequences of an increased consumption of cow's milk, which may lead to higher levels of IGF-I in circulation or an increase in the velocity of linear growth, are likely to be both positive and negative. Based on emerging data that suggest both growth and diet during early life program the IGF axis, the association between milk intake and later health is likely to be complex.

Diet, serum insulin-like growth factor-I and IGF-binding protein-3 in European women

OBJECTIVE

The aim of this study was to examine the relationship of diet with serum insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 in women.

DESIGN

Cross-sectional study.

SETTING AND SUBJECTS

The population are 2109 women who were control subjects in a case-control study of breast cancer nested in the European Prospective Investigation into Cancer and Nutrition. Control subjects were randomly chosen among risk sets consisting of female cohort members alive and free of cancer (except non-melanoma skin cancer) at the time of diagnosis of the index case. Matching criteria were age at enrolment, follow-up time, time of the day of blood collection and study centre. Diet was measured through validated questionnaires. Serum hormone concentrations were measured by enzyme-linked immunosorbent assays. The relationship between serum IGF-I, IGFBP-3, and intake of nutrients and foods was explored by linear regression in models adjusted for energy intake, age, body mass index, smoking, physical activity, centre and laboratory batch.

RESULTS

Serum IGF-I levels were positively related to protein intake (P(trend)<0.001), but not related to energy, fat or carbohydrate intake. Positive relationships were observed with the intake of milk (P(trend)=0.007), calcium (P(trend)<0.001), magnesium (P(trend)=0.003), phosphorus (P(trend)<0.001), potassium (P(trend)=0.002), vitamin B6 (P(trend)=0.03), vitamin B2 (P(trend)=0.001) and inverse relationships with vegetables (P(trend)=0.02) and beta-carotene (P(trend)=0.02). IGFBP-3 was not related with most of the nutrients and foods in this study.

CONCLUSIONS

In this population, circulating IGF-I is modestly related with the intake of protein and minerals, and with milk and cheese, while IGFBP-3 does not appear to be related with diet.

The effects of dairy processes and storage on insulin-like growth factor-I (IGF-I) content in milk and in model IGF-I-fortified dairy products

The effects of several dairy processes on insulin-like growth factor-I (IGF-I) concentrations in milk and the storage stability of IGF-I-fortified dairy products were examined. The IGF-I content in raw milk determined by radioimmunoassay was significantly changed by the strength of heat treatments. In commercial manufacture of whole milk dry powder, IGF-I concentration was not significantly changed. A significant reduction in IGF-I content was found as the result of fermentation with a commercial starter culture. The IGF-I content in fortified milk and dried milk powder exhibited no significant changes over the tested storage periods (12 d for milk, 4 wk for dried milk powder), but the IGF-I content in the yogurt decreased significantly during storage. The use of IGF-I was varied by lactic strains and was apparent in the viable cells. When IGF-I was encapsulated using the surface-reforming process, the remaining IGF-I content after fermentation was significantly higher compared with that of the untreated control. Therefore, enteric coating of IGF-I before fermentation might be an effective method for the prevention of IGF-I degradation during fermentation.

Dairy Product Consumption and the Risk of Breast Cancer

It has been suggested in some reports that dairy product consumption may increase the risk of breast cancer. This review gives a brief overview of the etiology of breast cancer and in particular the roles of fat, bovine growth hormone, insulin-like growth factor-1 and estrogens. Evidence from animal studies and epidemiology does not support a role for fat in the etiology of breast cancer. The daily intake of insulin-like growth factor-1 and biologically active estrogens from dairy products is minute in comparison to the daily endogenous secretion of these factors in women, whereas bovine growth hormone is biologically inactive in humans. On the other hand, milk contains rumenic acid, vaccenic acid, branched chain fatty acids, butyric acid, cysteine-rich whey proteins, calcium and vitamin D; components, which have the potential to help prevent breast cancer. Evidence from more than 40 case-control studies and 12 cohort studies does not support an association between dairy product consumption and the risk of breast cancer.

High intakes of skimmed milk, but not meat, increase serum IGF-I and IGFBP-3 in eight-year-old boys

OBJECTIVE

To examine whether a high protein intake (PI) from either milk or meat, at a level often seen in late infancy, could increase s-IGF-I and s-IGF-I/s-IGFBP-3 in healthy, prepubertal children. IGF-I levels are positively associated with growth velocity in children and some studies suggest that a high animal PI can stimulate growth. During protein deprivation IGF-I decrease, but it is unknown whether a high PI can increase s-IGF-I in well-nourished children.

DESIGN

In all, 24 8-y-old boys were asked to take either 1.5 l of skimmed milk (n = 12) or the same amount of protein as 250 g low fat meat (n = 12) daily for 7 days. The remaining diet they could choose freely. At baseline and after 7 days, anthropometrical variables were measured, diet was registered (3-day weighed records), and s-IGF-I and s-IGFBP-3 (RIA) were determined after fast.

RESULTS

PI increased by 61% in the milk group to 4.0 g/kg/day (P < 0.0001) and by 54% in the meat group to 3.8 g/kg/day (P = 0.001). The high milk intake increased s-IGF-I by 19% (P = 0.001) and s-IGF-I/s-IGFBP-3 by 13% (P < 0.0001). There were no increases in the meat group.

CONCLUSIONS

High intake of milk and not meat, increased concentrations of s-IGF-I and s-IGF-I/s-IGFBP-3 significantly. Compounds in milk and not a high PI as such seem to stimulate IGF-I. This might explain the positive effect of milk intake on growth seen in some studies.

Optimization of immobilized metal ion affinity chromatography for single-step purification of recombinant ovine growth hormone expressed in Escherichia coli

In the present investigation, Sepharose 6B gel with 1,4-butanediol diglycidyl ether as spacer arm, iminodiacetic acid as the ligand and Cu2+, Ni2+ as metal ions were used to prepare an immobilized metal ion affinity (IMA) gel. The binding capacities of recombinant ovine growth hormone (roGH) onto IMA gels were maximized in the packed bed column. Parameters influencing the purification efficiencies such as pH, ionic strength and flow-rate were optimized to achieve improved separation. The roGH was purified from inclusion bodies with an overall yield of 73.5% and purity of 94.3% using a Cu(2+)-iminodiacetic acid (IDA) column. However, the Ni(2+)-IDA column was more successful in purifying the roGH from crude cell lysate in a single-step with a yield of 83% and purity of 92.5%.

Comparison of a conventional immunoassay (ELISA) with a surface plasmon resonance-based biosensor for IGF-1 detection in cows' milk

Recombinant bovine somatotropin (rBST) treatment is adopted in dairy cows to augment milk yield. Previous studies showed that insulin-like growth factor-1 (IGF-1) is present in milk from cows treated with rBST. Since IGF-1 is a suspected carcinogen, its presence in milk for human consumption is potentially a health hazard. Therefore rBST use, still authorized in the United States, has been revoked in Canada and is under evaluation in the EU. The rising attention on IGF-1 presence in alimentary milk focused the necessity to develop specific, sensitive and rapid IGF-1 detection systems. We have developed a solid phase enzyme-linked immunoassay (ELISA) and also an automated surface plasmon resonance-based biosensor system (BIA-technology) for evaluating IGF-1 in fresh cow's milk. Hyperimmune polyclonal anti-IGF-1 antibodies were characterized with respect to their specific binding capacity to IGF-1. The results obtained with these two methods have been compared. This study shows the potential usefulness of the biosensor technology for biomolecular interaction analysis. The features of this technology (fully automated, measures in real time, sharpened yes/no response) offer several advantages compared to ELISA in the detection of compounds in fresh cows' milk (MURST 40%; CNR P.F. MADESS 2).

Hormones, mammary growth, and lactation: a 41-year perspective

When I was a beginning graduate student 41 yr ago it had been established that estrogen caused mammary duct growth; a combination of estrogen and progesterone was required for lobule-alveolar development of the mammary glands; and prolactin and growth hormone were essential for mammary growth. In laboratory species exogenous prolactin, glucocorticoids, and estrogen would initiate secretion of milk provided the mammary glands had a well-developed lobule-alveolar system. It was not known with certainty that progesterone inhibited the process. For some species, prolactin and thyroxine had been shown to stimulate lactation, while glucocorticoids suppressed lactation. Definitive roles for growth hormone and insulin during lactation had not been established. Studies of hormonal control of mammary growth and function in cattle were few. In vitro methods to study hormonal regulation of the mammary glands were in their infancy. Quantitative measures of changes in mammary cell numbers and specific components of milk in response to hormones were rare. The concepts for quantification of hormone concentrations, hormone receptors, growth factors, and binding proteins in blood; hormonal regulation of nutrient partitioning; and hormonally induced mechanisms of action within mammary cells were waiting to be discovered. And eventually they were. However, lest we become too enamored with our current understanding of the hormones that control mammary growth and lactation, it remains a fact that the greatest physiological stimulus for milk yield is pregnancy, not some cocktail of exogenous hormones, growth factors, receptor agonists/antagonists, or gene therapies. Viva la mom!

Effect of the codon following the ATG start site on the expression of ovine growth hormone in Escherichia coli

For expression of ovine growth hormone (OGH) in inclusion bodies without an affinity histidine tag at either end of the protein, three clones, differing only in the second codon following the ATG start site, were constructed. Their expression was studied by SDS-PAGE followed by immunoblotting. Clone Ala.OGH (clone 1), beginning with Met.Ala.Phe.Pro ellipsis, did not show any expression. Clone Phe.OGH (clone 3), beginning with Met.Phe.Pro ellipsis, gave very high levels of OGH expression following IPTG induction. However, in clone Gly.OGH (clone 2), in which the Ala codon was replaced with a Gly codon at the second position after the start site, a lower level of expression was obtained. Northern hybridization analysis showed that upon IPTG induction, OGH mRNA was transcribed from all three clones. These results therefore, imply that lack of expression in clone 1 and a lower level of expression in clone 2 are not due to a failure of transcription; however, they may be due to inefficient initiation of translation. The secondary structure analysis of mRNA predicts inaccessibility of different elements of the RBS in the case of Ala.OGH (clone 1). The present study highly underscores the importance of mRNA secondary structure at the start site in regulation of expression of a cloned gene in Escherichia coli, a prokaryotic expression system.

Somatotropin delivery to farmed animals

Bovine somatotropin (bST) is marketed worldwide for increased milk production in cows while porcine somatotropin (pST) is approved in one country for increasing growth in swine. Somatotropin physicochemical properties, animal production method limitations and the need for cost effectiveness each contribute to the type of formulation developed. Various somatotropin physicochemical properties made formulation design difficult: heat and enzyme lability, tendency to aggregate, pH dependent solubility and stability, complicated degradation pathways and rapid in vivo clearance. The main problem of improving chemical and physical stability has been partially solved using certain excipients and vehicles. Formulations design to prolong somatotropin release include implants (matrix, osmotic), oleaginous suspensions and microparticles. This article presents the current status of somatotropin delivery in farmed animals, reviews the challenges encountered with formulation development, summarizes formulation approaches and discusses future somatotropin uses.

Biology of somatotropin in growth and lactation of domestic animals

Impressive progress has been made during the past 15 years in our understanding of the biology of somatotropin (ST) in domestic animals. In part, this progress was sparked by advances in biotechnology that made feasible the production of large quantities of recombinant bovine ST (bST) and porcine ST (pST). The availability of recombinant bST and pST resulted in an exponential increase in investigations that explored their role in growth and lactation biology, as well as evaluated their potential for commercial use. Collectively, these studies established that administration of bST to lactating dairy cows increased milk yield, and treatment of growing pigs with pST markedly stimulated muscle growth and reduced fat deposition. In addition to these "efficacy" studies, a substantial number of investigations examined the mechanisms by which ST affects lactation and growth of domestic animals. This review summarizes the diverse physiological effects ST has on growth and lactation and discusses the underlying mechanisms that mediate these effects in domestic animals.

High-level expression of ovine growth hormone in Escherichia coli: single-step purification and characterization

The gene for ovine growth hormone (oGH) was expressed without signal sequences in Escherichia coli. A recombinant plasmid expression vector has been constructed which directs the synthesis of a fusion protein containing a stretch of six histidine residues (His6) at the amino-terminus under the control of a T5 promoter. Upon induction with isopropyl-beta-D-thiogalactopyranoside, the recombinant protein was synthesized and accumulated in the cytoplasm in the form of inclusion bodies, at levels of approximately 18% of the total cellular protein. The recombinant ovine growth hormone containing His tag was recovered and purified to >95% homogeneity in a single step by immobilized metal-ion chromatography with a special affinity Ni2+.NTA resin that has selectivity for proteins with neighboring histidine residues. Characterization by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting and amino terminal analysis demonstrated the authenticity of the fusion protein. The purified RoGH after refolding was found to be functionally active in terms of its receptor binding and antigenicity as analyzed by radio receptor assay and radio immuno assay. Yields of the purified expressed protein were found to be 32 microg/ml at a shake-flask level. Thus, results indicate that a combination of E. coli expression and affinity purification by Ni2+.NTA chromatography promises to be a rapid method to produce oGH for use in structure-function studies.

Assessment of the nutritional effects of olestra

Olestra is a mixture of polyesters formed from sucrose and fatty acids derived from edible fats and oils. It is not absorbed or digested and can serve as a zero-calorie replacement for dietary fat. Because olestra is lipophilic and not absorbed, it has the potential to interfere with the absorption of other dietary components, especially lipophilic ones, when it is in the digestive tract with those components. A series of studies were conducted in the domestic pig and in healthy adult humans to define the nature and extent of olestra's effect on fat-soluble vitamins, selected water-soluble micronutrients, and macronutrients, and to demonstrate that the effects of olestra on the absorption of fat-soluble vitamins can be offset by adding extra amounts of the affected vitamins to olestra foods. Before conducting the human and pig studies, the intake of olestra from the consumption of snack foods made with olestra was estimated for various subgroups. The potential for olestra to affect the absorption of nonessential but potentially beneficial dietary phytochemicals was also assessed. In addition, an assessment of how consumption patterns influence the effect of olestra on the absorption of the highly lipophilic carotenoids was made. Finally, the results from the pig and human studies were used to assess the potential for olestra to affect the nutritional status of subgroups of the population who have particularly high nutrient needs or unique dietary patterns that may lead to large olestra-to-nutrient intake ratios.