Scientific Concept of the National Cohort (status ... - Nationale Kohorte

Urine
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A.3 Study design
Urine provides useful information on exposure (e.g., diet, exposure to hazardous agents),
human metabolism, and kidney function. Many different analytic techniques can be applied
to investigate urinary samples. Biomarkers in urine have been studied for purposes of diagnosis
and monitoring of kidney or urogenital diseases (chronic kidney disease, diabetic or
obstructive nephropathy, renal transplantation, kidney, and bladder or prostate cancer), but
also for several systemic conditions (colon cancer, CVD, stem cell transplantation, etc.) 717-720 .
Collection of different types of urine has been considered: spot urine, 24-h urine, and overnight
urine. As it is more complicated to organize overnight and 24-h urine collection and
provide little additional information, sampling of spot urine directly at the study center has
been chosen as means of collection. Due to the immediate processing (centrifugation and
freezing) of the samples, no additives are necessary for urine collection.
Saliva
The possibility to characterize the oral cavity microflora is the ultimate reason for collecting
saliva. The effects of the oral microbiota on oral health and other chronic diseases can only
be studied by investigating such data 721 . Saliva also has the advantage that hormones and
some other metabolites that may be compromised in blood samples as a result of the blood
collection procedure can be measured. It is well documented that stress hormones and similarly
sensitive biomarkers can be studied in saliva samples. Notably, the proteome of saliva
is well characterized. The relationship between biomarkers in saliva and the development
of oral cancer, oral diseases (periodontitis, caries, etc.), or systemic health (e.g., celiac disease,
Sjögren’s syndrome, and nonoral cancer) is of particular interest 722-728 .
Stool
Intestinal bacteria play an important role in human health, from maturation of the immune
system to the onset and course of chronic diseases. By using fecal samples, the composition
(and activity) of microbiota in the large bowel can be analyzed.
Gut bacteria are known to be involved in several diseases of the gut (e.g., irritable bowel
syndrome; Crohn’s disease, etc.); other chronic diseases are also likely to be modulated
by the gut microflora 729-731 . For example, obesity is characterized by changes in the occurrence
of two main gut bacterial phyla, Firmicutes and Bacteroidetes. These changes can
be reversed by nutritional intervention and are associated with changes in gut bacterial
functions. Furthermore, intestinal bacteria have recently been shown to be involved in type
2 diabetes using antibiotics 732, 733 . Specific aims of future studies in this area are likely to include
measurement of the composition of the gut microbiota (phylogenetic fingerprinting and
microarray analyses) and – if a suitable collection method can be applied – analyses of both
metabolomic and physicochemical characteristics of fecal microbial cells/cell clusters 734-736 .
Although there are indications that part of the gut microbiome can be profiled in urine 737 , the
potential significance of the gut microbiota for future chronic disease research is considered
to be very high and argues for the collection of fecal samples 738 .
Nasal swabs
The anterior nares (the space distal to the turbinates) represent an easily accessible space
for sampling nasal epithelial cells, secretions, and microorganisms. It has been known for
some time that the anterior nares represents a unique microbiologic niche at the interface
between the respiratory tract, the skin, and the ambient air, which may be colonized by potentially
pathogenic microorganisms, for instance Staphylococci (including MRSA, see also
Sect. A.2.4.7) and Streptococci. Recent nucleic-based descriptive studies have shown that
A.3