Agnes N. Pedersen

Ageing, tumour necrosis factor-alpha (TNF-alpha) and atherosclerosis

Ageing is associated with increased inflammatory activity in the blood. The purpose of this study was to investigate if age‐related increased plasma levels of TNF‐α were associated with atherosclerosis in a cohort of 130 humans aged 81 years. The elderly cohort had increased circulating levels of TNF‐α, C‐reactive protein (CRP), total cholesterol (TC), low‐density lipoproteins (LDL) and a low high‐density lipoprotein (HDL)/TC ratio compared with a young control group (n = 44). The elderly cohort was divided by tertiles into three subgroups with low, intermediate, and high levels of TNF‐α, respectively. In the group with high TNF‐α concentrations a significantly larger proportion had clinical diagnoses of atherosclerosis. Furthermore, weak correlations were found between TNF‐α on one hand and blood concentrations of triglycerides, leucocytes, CRP and a low HDL/TC ratio on the other which are known as risk factors of atherogenesis and thromboembolic complications. No correlations were found between TNF‐α, TC, LDL, or the body mass index. In conclusion, the present study shows that in a cohort of 81‐year‐old humans, high levels of TNF‐α in the blood were associated with a high prevalence of atherosclerosis.

Predicting death from tumour necrosis factor-alpha and interleukin-6 in 80-year-old people

Ageing is associated with low‐grade inflammation and markers such as IL‐6 possess prognostic value. Tumour necrosis‐alpha (TNF‐α) initiates the inflammatory cascade and has been linked to several age‐associated disorders. It remains, however, unknown if TNF‐α is associated with mortality in old populations. The aim of the present study was to investigate if serum levels of TNF‐α were associated with all‐cause mortality independently of interleukin (IL)‐6 in a prospective study of 333 relatively healthy 80‐year‐old people. A Cox regression model was used to explore effects of TNF‐α and IL‐6 on survival in the following 6 years. A total of 133 participants died during this follow‐up period. TNF‐α was associated with mortality in men, but not in women, whereas low‐grade elevations in IL‐6 were associated strongly with mortality in both sexes. TNF‐α explained only 7% of the variability in IL‐6 and effects of the two cytokines were independent of each other as well as of other traditional risk factors for death [smoking, blood pressure, physical exercise, total cholesterol, co‐morbidity, body mass index (BMI) and intake of anti‐inflammatory drugs]. These findings indicate that at least in old populations chronic elevated levels of TNF‐α and IL‐6 have different biological functions that trigger age‐associated pathology and cause mortality.

Impaired production of proinflammatory cytokines in response to lipopolysaccharide (LPS) stimulation in elderly humans

Ageing is associated with decreased resistance to bacterial infections and concomitant increased circulating levels of inflammatory cytokines. The purpose of the present study was to research age‐related changes in levels of early mediators of the acute‐phase response in whole blood supernatants following LPS stimulation, representing an ex vivo model of sepsis. Levels of tumour necrosis factor‐alpha (TNF‐α), IL‐1β and IL‐6 in whole blood supernatants were measured after in vitro LPS stimulation for 24 h in 168 elderly humans aged 81 years from the 1914 cohort in Glostrup, Denmark and in 91 young controls aged 19–31 years. Levels of TNF‐α and IL‐1β were significantly lower in elderly humans compared with young controls, whereas no difference was detected with regard to IL‐6. Elderly humans with low body mass index had the lowest levels of IL‐1β. Young women had lower levels of proinflammatory cytokines compared with young men, but this difference was blurred by ageing. No relation was found between circulating plasma levels of TNF‐α and levels after in vitro LPS stimulation. In conclusion, decreased production of TNF‐α and IL‐1β after exposure to LPS may reflect impaired host defence against infections in the elderly and be of importance in elderly humans with underlying health disorders. However, the clinical relevance is questionable in healthy elderly people because decreased levels were found compared with young men but not compared with young women.

Is ageing associated with a shift in the balance between Type 1 and Type 2 cytokines in humans

The balance between Type 1 and Type 2 cytokines is important for the outcome of several infectious diseases. As elderly humans show increased morbidity and mortality from infectious diseases, this study tests if ageing is associated with a change towards Type 2 dominance in T cells. Expression of IFN‐γ, and IL‐4 was measured in CD4+ and CD8+ T cells by flow cytometry in three groups: young controls (n = 28), 81‐year‐olds (n = 22), and centenarians (n = 25). The major findings were that the percentage of IFN‐γ+ as well as IL‐4+ T cells was increased in aged subjects. Furthermore, after adjusting for decreased lymphocyte counts in the elderly, the concentration in the blood of IFN‐γ+ and IL‐4+ CD8+ T cells was still increased in the 81‐year‐olds. In centenarians, a shift towards a relative dominance of Type 2 cytokine expression was found within CD8+ T cells. Furthermore, the percentage of T cells with cytokine expression was closely correlated to the in vivo expression of CD95 and CD45RO. In conclusion, we found some evidence for an age‐related shift towards a Type 2 cytokine profile.

Decreased natural killer cell activity is associated with atherosclerosis in elderly humans.

Well-preserved natural killer cell (NK) activity has been associated with successful aging. The aim of the present study was to perform detailed analyses of NK cell function and to investigate the clinical significance of the NK cell number and function in relationship to health in a large cohort of elderly humans. It was tested if the potential of natural cytotoxicity in the blood (evaluated as an index including cytotoxicity per NK cell and the number of circulating NK cells) was preserved in 174 81-year-old humans versus 91 young controls and if NK cell mediated immunity was associated with age-related inflammatory diseases such as atherosclerosis. Elderly people had decreased cytotoxicity per NK cell in short-term but not in long-term assays. Ca(2+) independent cytotoxicity was unaltered, and NK cells maintained their cytotoxic responses to interleukin-2 and interferon-alpha signals. The decreased cytotoxicity per NK cell was not completely counteracted by increased circulating numbers of NK cells in the blood. Elderly people with severe medical disorders had low numbers of circulating NK cells. Furthermore, elderly people with atherosclerosis had low cytotoxicity per NK cell and a high number of circulating neutrophils.

Health effects of protein intake in healthy adults: a systematic literature review

The purpose of this systematic review is to assess the evidence behind the dietary requirement of protein and to assess the health effects of varying protein intake in healthy adults. The literature search covered the years 2000–2011. Prospective cohort, case-control, and intervention studies were included. Out of a total of 5,718 abstracts, 412 full papers were identified as potentially relevant, and after careful scrutiny, 64 papers were quality graded as A (highest), B, or C. The grade of evidence was classified as convincing, probable, suggestive or inconclusive. The evidence is assessed as: probable for an estimated average requirement of 0.66 g good-quality protein/kg body weight (BW)/day based on nitrogen balance studies, suggestive for a relationship between increased all-cause mortality risk and long-term low-carbohydrate–high-protein (LCHP) diets; but inconclusive for a relationship between all-cause mortality risk and protein intake per se; suggestive for an inverse relationship between cardiovascular mortality and vegetable protein intake; inconclusive for relationships between cancer mortality and cancer diseases, respectively, and protein intake; inconclusive for a relationship between cardiovascular diseases and total protein intake; suggestive for an inverse relationship between blood pressure (BP) and vegetable protein; probable to convincing for an inverse relationship between soya protein intake and LDL cholesterol; inconclusive for a relationship between protein intake and bone health, energy intake, BW control, body composition, renal function, and risk of kidney stones, respectively; suggestive for a relationship between increased risk of type 2 diabetes (T2D) and long-term LCHP-high-fat diets; inconclusive for impact of physical training on protein requirement; and suggestive for effect of physical training on whole-body protein retention. In conclusion, the evidence is assessed as probable regarding the estimated requirement based on nitrogen balance studies, and suggestive to inconclusive for protein intake and mortality and morbidity. Vegetable protein intake was associated with decreased risk in many studies. Potentially adverse effects of a protein intake exceeding 20–23 E% remain to be investigated.

Assessment of habitual energy and macronutrient intake in adults: comparison of a seven day food record with a dietary history interview

Objective: To examine the quantitative agreement between a 7 day food record and a diet history interview when these are conducted under the same conditions and to evaluate whether the two methods assess habitual diet intake differently among subgroups of age and body mass index (BMI).Design: Cross-sectional study.Setting: Population study, Denmark.Subjects: A total of 175 men and 173 women aged 30–60 y, selected randomly from a larger population sample of Danish adults.Interventions: All subjects had habitual diet intake assessed by a diet history interview and completed a 7 day food record within 3 weeks following the interview. The diet history interview and coding of records were performed by the same trained dietician.Main outcome measure: Median between-method difference in assessment of total energy intake, absolute intake of macronutrients, and nutrient energy percentages. Difference between reported energy intake from both methods and estimated energy expenditure in different subgroups.Results: Energy and macronutrient intake was assessed slightly higher by the 7 day food record than by the diet history interview, but in absolute terms the differences were negligible. The between-method difference in assessment of total energy intake appeared to be stable over the range of age and BMI in both sexes. As compared to estimated total energy expenditure, both diet assessment methods underestimated energy intake by approximately 20%. For both methods the under-reporting increased by BMI in both sexes and by age in men.Conclusions: Energy and macronutrient intake data collected under even conditions by either a 7 day food record or a diet history interview may be collapsed and analysed independent of the underlying diet method. Both diet methods, however, appear to underestimate energy intake dependent on age and BMI.Sponsorship: Danish Medical Research Council, the FREJA programme.

para-aminobenzoic acid used as a marker for completeness of 24 hour urine : assessment of control limits for a specific HPLC method

Objective and design: The study comprised three protocols. Protocol 1 compared a HPLC method with the commonly employed colorimetric diazocoupling method. Protocol 2 examined, if the last dosage of p-aminobenzoic acid (PABA) could be advanced in the old to allow for a delayed age-dependent urinary excretion of PABA. Protocol 3 established limits for recovery of PABA in 24 h urine applying the HPLC method. Subjects and setting: A total of 151 healthy volunteers participated in the study of which 140 were accepted. In protocol 1: 37 subjects aged 20–78 y were included. All subjects took PABA as recommended (80 mg orally at 08.00, 12.00 and 18.00 h). Protocol 2: compared urinary PABA excretion in two groups of 80 y old subjects who had their last PABA dosage administered at 15.00 h (n=16) and at 18.00 h (n=31), respectively. Protocol 3: comprised 56 subjects aged 20–80 y. In the younger age group (20–59 y; n=34) PABA was taken as recommended, whereas in the older age group (60–80 y; n=22) the last PABA dosage was advanced three hours. Results: Protocol 1: HPLC gave significantly lower PABA recovery results compared to colorimetry, the difference between methods being 23.9±8.5 mg/24 h (P<0.001). Protocol 2: higher PABA recoveries were demonstrated with the advanced dosage schedule compared to the recommended schedule (208±14 mg/24 h vs 181±22 mg/24 h; P<0.001). Protocol 3: PABA recovery with HPLC was 211±12 mg/24 h, and the lower limit comprising 95% of subjects was 187 mg/24 h. Similar PABA recoveries were demonstrated in the younger subjects and the older subjects (211±11 mg/24 h vs 211±13 mg/24 h; NS). Conclusion: An advanced dosage schedule for PABA in the aged is recommended. Because of lower recoveries with HPLC, the low limit for recovered PABA in a complete 24 h urine differs from the limit based on colorimetry. This study found a limit of 187 mg/24 h corresponding to the lower 95% confidence limit for a single subject. Sponsorship: Supported by the National Food Agency, the Velux Foundation of 1981, and the Health Insurance Foundation.

Brain‐Derived Neurotrophic Factor Predicts Mortality Risk in Older Women

OBJECTIVES: To test the hypothesis that low circulating brain‐derived neurotrophic factor (BDNF), a secretory member of the neurotrophin family that has a protective role in neurodegeneration and stress responses and a regulatory role in metabolism, predicts risk of all‐cause mortality in 85‐year‐old men and women.

The IL-6 −174G>C polymorphism is associated with cardiovascular diseases and mortality in 80-year-old humans

Chronic low-grade elevations in circulating levels of interleukin (IL)-6 act as a marker of subclinical cardiovascular diseases (CVD) and provide an independent predictor of increased mortality in elderly populations. The purpose of the present study was to test the hypothesis that the IL-6 -174G>C promoter polymorphism was associated with a high prevalence of CVD and acted as an independent predictor of mortality in a longitudinal study of 324 relatively healthy 80-year-old people with a history of CVD in 18% of the cases. The C allele was associated with elevated serum levels of IL-6 at baseline and the CC genotype had a high prevalence of CVD. A Cox regression model was used to explore the effect of the polymorphism on survival in the following six years. A significant interaction was found between smoking status and the polymorphism. Thus, C allele carrier status was associated with increased all-cause mortality risk in non-smokers independently of sex, body mass index, co-morbidity, and low-grade elevations in serum levels of IL-6. This effect was not detected among smokers. We conclude that the IL-6 -174G>C polymorphism was an independent predictor of all-cause mortality in octogenarians but the effect was complex and interacted with the smoking status.