1. Blood, hair and saliva biomarkers
David Lee
Manchester Metropolitan University

2. Biomarkers A biomarker is a biological characteristic that is objectively measured and evaluated as an indicator of normal biological or pathological processes, or a response to a therapeutic intervention. Examples include patterns of gene expression, levels of a particular protein in body fluids, or changes in electrical activity in the brain nature.com

3. Overview
Lipids (saturated and unsaturated fats, triglycerides and phospholipids)
Hormones (signalling molecules secreted from glands and travel through bloodstream)
Inflammatory markers (raised levels may indicate chronic underlying disease)
Biological time-varying measures

4. Lipids

5. Lipid profile Complete test called a lipid profile or lipid panel
Current guidelines typically recommend measuring lipid levels in a fasting state
Recent data suggest nonfasting lipid profiles change minimally

6. Lipid measurement Total cholesterol (TC)
High-density lipoprotein cholesterol (HDL-C)
Low-density lipoprotein cholesterol (LDL-C)
Triglycerides
Cholesterol levels are fairly constant
Triglyceride levels fluctuate considerably from day to day
Levels tends to increase with age
Premenopausal women tend to have higher HDL-C and lower LDL-C/triglycerides than men

7. Lipids levels Various guidelines exist on ‘healthy’ lipid levels
National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III)
LDL-C typically calculated from total & HDL-C and fasting triglycerides*
*Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972;18(6):

8. Biological significance
Multiple epidemiologic studies have shown that increased levels of total cholesterol and LDL-C strongly related to greater incidence of CHD
Elevated triglycerides and LDL-C are associated with the risk of atherosclerotic heart disease
High levels of HDL-C protective factor for the development of atherosclerotic heart disease - so decreased levels of HDL-C constitute a risk factor

9. Research implications
Many survey datasets will contain at least some blood lipid measurements
Can be investigated in isolation – longitudinal trends, associations with obesity etc…
Can also be used in a variety of validated algorithms to predict 10-year risk of developing CHD or experiencing a CVD event
Framingham risk score
Systemic Coronary Risk Evaluation (SCORE)

12. Endocrine function

13. Hormones Signalling molecules secreted from endocrine glands
Travel in the bloodstream to tissues or organs
Control many processes including: growth and development, metabolism, sexual function, reproduction, mood…

14. Hormone measurement Typically measured from blood (serum) sample
Can also be measured in saliva, urine and hair
Endocrine glands release more than 20 major hormones directly into the bloodstream
Assay techniques continue to evolve with improvements in sensitivity and validity
Latest analytical techniques based on mass spectrometry

15. Biological significance
Individual hormones are typically one part of a more complex hormonal axis or system
hypothalamic–pituitary–adrenal axis (HPA axis)
hypothalamic–pituitary–gonadal axis (HPG axis)
High levels of HDL-C protective factor for the development of atherosclerotic heart disease - so decreased levels of HDL-C constitute a risk factor

16. Research implications
Behavioural research has focused on both levels and changes in specific hormones
Social sciences research has also become increasingly interested in hormones
Cortisol, testosterone and DHEAS have received most attention in economics and social research
Speculated to be involved in risk aversion, work stress and persistence of poverty

17. Cortisol Typically measured from salivary samples
Glucocorticoid hormone (stress hormone)
Cortisol is the primary hormone responsible for the stress response (HPA axis)
HPA axis transduces subjective social-environmental experience into physiological changes relevant to health
Work stress, family problems, sleep deprivation can all lead to chronic elevation of cortisol
Increased cortisol levels linked to higher blood sugar, weakened immune response, depression, frailty, obesity, CVD, memory loss…

19. Testosterone (T) Primary male sex steroid and an anabolic steroid
Levels typically an order of magnitude lower in females but of vital physiological importance
T typically declines with age (particularly in men)
Declining T may influence ageing-related deteriorations in body function e.g. frailty, obesity, osteopaenia, cognitive decline, erectile failure…
Low T low testosterone associated with adverse health outcomes among men, but high T has been linked to adverse outcomes among women…

20. Keevil BG1, MacDonald P, Macdowall W, Lee DM, Wu FC; NATSAL Team
Keevil BG1, MacDonald P, Macdowall W, Lee DM, Wu FC; NATSAL Team. Salivary testosterone measurement by liquid chromatography tandem mass spectrometry in adult males and females. Ann Clin Biochem May;51(Pt 3):368-78

21. - Hair cortisol is a proxy measure of the total retrospective activity of the HPA axis over the preceding months
- Hair cortisol analysis offers an innovative approach to measuring HPA axis activity in response to chronic stressors

22. Insulin-like growth factor 1 (IGF-1)
Plays a central role in childhood growth and continues to have anabolic effects in adults
Levels of IGF-1 influenced by genetic make-up, time of day, age, sex, exercise status, stress levels, nutrition level and body mass index (BMI), disease state, ethnicity…
Mixed data that IGF-1 modulates the ageing process in humans and whether the direction of its effect is positive or negative

23. - Lower SEP was associated with lower free T among men, higher free T among women, and lower IGF-I and higher evening cortisol in both sexes
- SEP differences in endocrine function may partly underlie inequalities in health and function in later life, and may reflect variations in biological rates of ageing.

24. Glucose (+Insulin) Measured in a fasting blood sample
Aside from diagnosed diabetes, measurement of fasting glucose can pick up undiagnosed diabetes and impaired-fasting glucose (IFG)
ADA criteria: fasting plasma glucose level from 5.6 mmol/L (100 mg/dL) to 6.9 mmol/L (125 mg/dL)
Dysregulated glucose levels associated with poor health outcomes including CVD

25. Glucose and the Metabolic Syndrome
Clustering of risk factors associated with CVD risk
When 3 of 5 of the listed characteristics are present, a diagnosis of metabolic syndrome can be made.
ATP III criteria for metabolic syndrome (2004)

26. Inflammation

27. Inflammatory markers
Inflammation can result from a variety of factors including infections, trauma and malignancy
Inflammatory response initiated when inflammatory cytokines released from distressed tissue
Systemic markers of inflammation useful for indicating elevated disease risk in mid- and late-life

28. Assessing inflammation
Inflammatory markers typically measured from blood sample
Also measurable in saliva and hair
Inflammatory process is complex and not fully understood
Small number of inflammatory markers usually measured in population-based surveys

29. Biological significance
Tissue inflammation is part of the complex biological response to harmful stimuli
These stimuli are varied and can include pathogens, injury, smoking, obesity, cancer…
Inflammation can be classified as acute or chronic
Chronic inflammation is of primary interest in ageing-related research

30. Research implications
Social sciences research has become increasingly interested in inflammatory markers and SES
Research suggests that atherosclerosis is primarily an inflammatory disease
In men below 60 years of age inflammatory markers typically have a significant inverse association with socio-economic status
In older age, the SES differences in the levels of inflammatory markers may be masked by the common occurrence of longstanding diseases in all SES groups

31. C-reactive protein (CRP)
Typically measured from blood samples
Most frequently studied inflammatory marker in epidemiologic studies
Classified as an acute phase reactant, meaning its levels will rise in response to inflammation
Epidemiologic research in middle-aged samples has shown that differences in CRP, even within the “normal” range, discriminate those at high and low risk of atherosclerotic disease

32. Fibrinogen Has a critical role in both inflammation and coagulation
Acute phase reactant like CRP
Epidemiologic research has shown elevated fibrinogen is associated with disease severity of chronic pulmonary hypertension
Association between plasma fibrinogen concentration and the risk of cardiovascular disease has been demonstrated in several studies