Biomarkers for cancer diagnosis: implications for nutritional research

Validation of biomarkers of food intake-critical assessment of candidate biomarkers

Biomarkers of food intake (BFIs) are a promising tool for limiting misclassification in nutrition research where more subjective dietary assessment instruments are used. They may also be used to assess compliance to dietary guidelines or to a dietary intervention. Biomarkers therefore hold promise for direct and objective measurement of food intake. However, the number of comprehensively validated biomarkers of food intake is limited to just a few. Many new candidate biomarkers emerge from metabolic profiling studies and from advances in food chemistry. Furthermore, candidate food intake biomarkers may also be identified based on extensive literature reviews such as described in the guidelines for Biomarker of Food Intake Reviews (BFIRev). To systematically and critically assess the validity of candidate biomarkers of food intake, it is necessary to outline and streamline an optimal and reproducible validation process. A consensus-based procedure was used to provide and evaluate a set of the most important criteria for systematic validation of BFIs. As a result, a validation procedure was developed including eight criteria, plausibility, dose-response, time-response, robustness, reliability, stability, analytical performance, and inter-laboratory reproducibility. The validation has a dual purpose: (1) to estimate the current level of validation of candidate biomarkers of food intake based on an objective and systematic approach and (2) to pinpoint which additional studies are needed to provide full validation of each candidate biomarker of food intake. This position paper on biomarker of food intake validation outlines the second step of the BFIRev procedure but may also be used as such for validation of new candidate biomarkers identified, e.g., in food metabolomic studies.

Biomarkers from biosimulations: Transcriptome-To-Reactome™ Technology for individualized medicine

We validated a model of the TGF-β signaling pathway using reactions from Reactome. Using a patentpending technique, gene expression profiles from individual patients are used to determine model parameters. Gene expression profiles from 45 women, normal, or benign tumor and malignant breast cancer were used as training and validating sets for assessing clinical sensitivity and specificity. Biomarkers were identified from the biosimulation results using sensitivity analyses and derivative properties from the model. A membrane signaling marker had sensitivity of 80% and specificity of 60%; while a nuclear transcription factor marker had sensitivity of 80% and specificity of 90% to predict malignancy. Use of Fagan's nomogram increased probability from 7.5% for positive mammogram to 39% with positive results of the biosimulation for the nuclear marker. Our technology will allow researchers to identify and develop biomarkers and assist clinicians in diagnostic and treatment decision making.

Associations of polyunsaturated fatty acids with residual depression or anxiety in older people with major depression

BACKGROUNDS

Depression in late life often follows a chronic course with residual depressive and anxiety symptoms. Levels of omega-3 polyunsaturated fatty acids (PUFAs) have been found to be depleted in people with major depression in the acute stage. Additionally, lower omega-3 PUFA levels have been suggested to be associated with anxiety. The aim of this study was to investigate whether PUFAs levels (omega-3 or omega-6) are correlated with residual depressive or anxiety symptoms in older people with previous depression.

METHODS

Participants aged 60 years or over with previous major depression in remission were enrolled from outpatient psychiatric services of four hospitals. Participants with residual depressive symptoms were defined as the Hamilton Depression Rating Scale (HDRS) scores>5, and those with anxiety were defined as sum of scores for the two anxiety subscale of HDRS≧2. The levels of fatty acids in erythrocyte membranes and in plasma were measured separately by gas chromatography.

RESULTS

One hundred and thirty two older people with previous major depression (mean age of 68 years, range 60-86 years) were analyzed. Erythrocyte membrane linoleic acid levels had a curvilinear association with depressive symptoms and anxiety symptoms. Plasma linoleic acid levels were found to have a negative linear relationship with depressive symptoms. No significant associations were found between any omega-3 fatty acid level and depressive or anxiety symptoms.

CONCLUSION

Linoleic acid levels may be a possible biomarker for residual depression and anxiety in older people with previous depression. Possible clinical applications need further investigation.

Advances in natural stable isotope ratio analysis of human hair to determine nutritional and metabolic status

PURPOSE OF REVIEW

We review the literature on the use of stable isotope ratios at natural abundance to reveal information about dietary habits and specific nutrient intakes in human hair protein (keratin) and amino acids. In particular, we examine whether hair isotopic compositions can be used as unbiased biomarkers to provide information about nutritional status, metabolism, and diseases.

RECENT FINDINGS

Although the majority of research on the stable isotope ratio analysis of hair has focused on bulk protein, methods have been recently employed to examine amino acid-specific isotope ratios using gas chromatography or liquid chromatography coupled to an isotope ratio mass spectrometer. The isotopic measurement of amino acids has the potential to answer research questions on amino acid nutrition, metabolism, and disease processes and can contribute to a better understanding of the variations in bulk protein isotope ratio values. First results suggest that stable isotope ratios are promising as unbiased nutritional biomarkers in epidemiological research. However, variations in stable isotope ratios of human hair are also influenced by nutrition-dependent nitrogen balance, and more controlled clinical research is needed to examine these effects in human hair.

SUMMARY

Stable isotope ratio analysis at natural abundance in human hair protein offers a noninvasive method to reveal information about long-term nutritional exposure to specific nutrients, nutritional habits, and in the diagnostics of diseases leading to nutritional stress and impaired nitrogen balance.

Responsiveness of urinary and plasma alkylresorcinol metabolites to rye intake in finnish women

Alkylresorcinols [ARs] have been proposed for use as biomarkers of whole-grain intake. The aim here was to examine the responsiveness of AR metabolites to rye intake. Sixty women were divided into three groups according to their rye consumption. We observed significant differences between groups in plasma 3-[3,5-dihydroxyphenyl]-1-propanoic acid [DHPPA] and in urinary DHPPA and 3,5-dihydroxybenzoic acid [DHBA]. In addition, these AR metabolites increased proportionally to rye fiber intake. We conclude that these ARs metabolites are accurate and useful biomarkers of rye fiber intake. Further studies are needed to confirm our results in larger and different populations.

Biomarkers of DHA status

Docosahexaenoic acid (DHA, 22:6n-3) is a long chain omega-3 fatty acid that is the primary n-3 fatty acid found in the central nervous system where it plays both a structural and functional role in cells. Because the tissues of interest are generally inaccessible for fatty acid analysis in humans and because precise DHA intake is difficult to determine, surrogate biomarkers are important for defining DHA status. Analysis of total lipid extracts or phospholipids from plasma or erythrocytes by gas chromatography meet the criteria for a useful biomarker of DHA status. Furthermore, both plasma and erythrocyte DHA levels have been correlated with brain, cardiac, and other tissue levels. Use of these biomarkers of DHA status will enable future clinical trials and observational studies to define more precisely the DHA levels required for either disease prevention or other functional benefits.

Validity of human nails as a biomarker of arsenic and selenium exposure: A review

Human nail clippings have been used in recent epidemiological studies as a routine bioindicator of arsenic and selenium exposure. To ensure sound application of this biomarker, however, it is important to consider properties and scientific knowledge pertaining to validation of this particular tool. In this review, the use of human nails to measure exposure to arsenic and selenium is discussed in the context of the biomarker validation framework. Literature related to both analytical procedures and intrinsic characteristics of the biomarker is reviewed. Specifically, the followings are addressed: sample collection and preparation methods, establishment of the exposure-biomarker relationship, intraindividual variability and reproducibility of measurements, and biomarker-disease investigations. Drawing from a rapidly growing body of literature, current knowledge of these biomarker validation steps is assessed. Therefore, this review brings attention to the important issue of biomarker validation, laying the framework for future studies measuring elemental composition of nails.