Name: absolute quantification of a&#946;1-42 in csf using a mass spectrometric reference measurement procedure
Uploaded: 2017-03-21T14:00:00
Description: Watch this Scientific Journal Video about Absolute Quantification of AÃŽÂ²1-42 in CSF Using a Mass Spectrometric Reference Measurement Procedure at JoVE.com

This work was performed on behalf of the International Federation of Clinical Chemistry Working Group on CSF Proteins, which has the following composition: Kaj Blennow (Chair) and Henrik Zetterberg, Gothenburg University, Sweden; Les Shaw and Magdalena Korecka, University of Philadelphia, PA, USA; Ingrid Zegers, Institute for Reference Materials and Measurements, Geel, Belgium; Piotr Lewczuk, Universit&#228;tsklinikum Erlangen, Germany; and Rand Jenkins, PPD Bioanalytical Laboratory, Richmond, VA, USA; Randall Bateman, Washington University, MO, USA; and H Vanderstichele, Innogenetics NV, Ghent, Belgium. This work was also part of the Global Consortium for Biomarker Standardization CSF Reference Methods Working Group, which is led by Maria C. Carrillo, Ph.D., Senior Director, Medical &amp; Scientific Relations, Alzheimer's Association. The study was supported by The Swedish Research Council (grants #14002, #521-2011-4709, and #2013-2546); the Knut and Alice Wallenberg Foundation; Demensf&#246;rbundet; and Emil and Wera Cornell's, Aina Wallstr&#246;m and Mary-Ann Sj&#246;blom's, Gun and Bertil Stohne's, Magnus Bergvall's, and Gamla Tj&#228;narinnor's Foundations.

NOTE: This protocol requires aliquots of at least 50 &#181;L, with a concentration of 50 &#181;g/mL for each A&#946; peptide, as starting material. The A&#946; peptides should be dissolved in 20% acetonitrile (ACN) and 4% concentrated ammonia solution in deionized water (v/v) and stored at 80 &#176;C.
Caution: See Table 1 for safety information.
1. Preparation of the Solutions
<ol>
	<li>Prepare 100 mL of 20% ACN and 4% concentrated ammonia solutio...

<ol>
	<li>Querfurth, H. W., LaFerla, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alzheimer's+disease.">Alzheimer's disease.</a> N Engl J Med. 362 (4), 329-344 (2010).</li><li>Braak, H., Braak, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evolution+of+the+neuropathology+of+Alzheimer's+disease.">Evolution of the neuropathology of Alzheimer's disease.</a> Acta Neurol Scand Suppl. 165, 3-12 (1996).</li><li>Blennow, K., de Leon, M. J., Zetterberg, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alzheimer's+disease.">Alzheimer's disease.</a> Lancet. 368 (9533), 387-403 (2006).</li><li>Dubois, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advancing+research+diagnostic+criteria+for+Alzheimer's+disease:+the+IWG-2+criteria.">Advancing research diagnostic criteria for Alzheimer's disease: the IWG-2 criteria.</a> Lancet Neurol. 13 (6), 614-629 (2014).</li><li>Blennow, K., Hampel, H., Weiner, M., Zetterberg, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebrospinal+fluid+and+plasma+biomarkers+in+Alzheimer+disease.">Cerebrospinal fluid and plasma biomarkers in Alzheimer disease.</a> Nat Rev Neurol. 6 (3), 131-144 (2010).</li><li>Buchhave, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebrospinal+fluid+levels+of+beta-amyloid+1-42,+but+not+of+tau,+are+fully+changed+already+5+to+10+years+before+the+onset+of+Alzheimer+dementia.">Cerebrospinal fluid levels of beta-amyloid 1-42, but not of tau, are fully changed already 5 to 10 years before the onset of Alzheimer dementia.</a> Arch Gen Psychiatry. 69 (1), 98-106 (2012).</li><li>Olsson, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CSF+and+blood+biomarkers+for+the+diagnosis+of+Alzheimer's+disease:+a+systematic+review+and+meta-analysis.">CSF and blood biomarkers for the diagnosis of Alzheimer's disease: a systematic review and meta-analysis.</a> The Lancet Neurology. 15 (7), 673-684 (2016).</li><li>Bjerke, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confounding+factors+influencing+amyloid+Beta+concentration+in+cerebrospinal+fluid.">Confounding factors influencing amyloid Beta concentration in cerebrospinal fluid.</a> Int J Alzheimers Dis. , (2010).</li><li>Dumurgier, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intersite+variability+of+CSF+Alzheimer's+disease+biomarkers+in+clinical+setting.">Intersite variability of CSF Alzheimer's disease biomarkers in clinical setting.</a> Alzheimers Dement. 9 (4), 406-413 (2013).</li><li>Mattsson, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CSF+biomarker+variability+in+the+Alzheimer's+Association+quality+control+program.">CSF biomarker variability in the Alzheimer's Association quality control program.</a> Alzheimers Dement. 9 (3), 251-261 (2013).</li><li>Kang, J. H., Korecka, M., Toledo, J. B., Trojanowski, J. Q., Shaw, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+Utility+and+Analytical+Challenges+in+Measurement+of+Cerebrospinal+Fluid+Amyloid-beta1-42+and+tau+Proteins+as+Alzheimer+Disease+Biomarkers.">Clinical Utility and Analytical Challenges in Measurement of Cerebrospinal Fluid Amyloid-beta1-42 and tau Proteins as Alzheimer Disease Biomarkers.</a> Clin Chem. 59 (6), 903-916 (2013).</li><li>Mattsson, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reference+measurement+procedures+for+Alzheimer's+disease+cerebrospinal+fluid+biomarkers:+definitions+and+approaches+with+focus+on+amyloid+beta42.">Reference measurement procedures for Alzheimer's disease cerebrospinal fluid biomarkers: definitions and approaches with focus on amyloid beta42.</a> Biomark Med. 6 (4), 409-417 (2012).</li><li>Ahmadkhaniha, R., Shafiee, A., Rastkari, N., Kobarfard, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accurate+quantification+of+endogenous+androgenic+steroids+in+cattle's+meat+by+gas+chromatography+mass+spectrometry+using+a+surrogate+analyte+approach.">Accurate quantification of endogenous androgenic steroids in cattle's meat by gas chromatography mass spectrometry using a surrogate analyte approach.</a> Anal Chim Acta. 631 (1), 80-86 (2009).</li><li>Jemal, M., Schuster, A., Whigan, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid+chromatography/tandem+mass+spectrometry+methods+for+quantitation+of+mevalonic+acid+in+human+plasma+and+urine:+method+validation,+demonstration+of+using+a+surrogate+analyte,+and+demonstration+of+unacceptable+matrix+effect+in+spite+of+use+of+a+stable+isotope+analog+internal+standard.">Liquid chromatography/tandem mass spectrometry methods for quantitation of mevalonic acid in human plasma and urine: method validation, demonstration of using a surrogate analyte, and demonstration of unacceptable matrix effect in spite of use of a stable isotope analog internal standard.</a> Rapid Commun Mass Spectrom. 17 (15), 1723-1734 (2003).</li><li>Leinenbach, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+spectrometry-based+candidate+reference+measurement+procedure+for+quantification+of+amyloid-beta+in+cerebrospinal+fluid.">Mass spectrometry-based candidate reference measurement procedure for quantification of amyloid-beta in cerebrospinal fluid.</a> Clin Chem. 60 (7), 987-994 (2014).</li><li>Li, W., Cohen, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitation+of+endogenous+analytes+in+biofluid+without+a+true+blank+matrix.">Quantitation of endogenous analytes in biofluid without a true blank matrix.</a> Anal Chem. 75 (21), 5854-5859 (2003).</li><li>Perret-Liaudet, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebrospinal+fluid+collection+tubes:+a+critical+issue+for+Alzheimer+disease+diagnosis.">Cerebrospinal fluid collection tubes: a critical issue for Alzheimer disease diagnosis.</a> Clin Chem. 58 (4), 787-789 (2012).</li><li>Lewczuk, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+sample+collection+tubes+on+cerebrospinal+fluid+concentrations+of+tau+proteins+and+amyloid+beta+peptides.">Effect of sample collection tubes on cerebrospinal fluid concentrations of tau proteins and amyloid beta peptides.</a> Clin Chem. 52 (2), 332-334 (2006).</li><li>Pannee, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reference+measurement+procedure+for+CSF+amyloid+beta+(A&#946;)1-42+and+the+CSF+A&#946;1-42+/A&#946;1-40+ratio+-+a+cross-validation+study+against+amyloid+PET.">Reference measurement procedure for CSF amyloid beta (A&#946;)1-42 and the CSF A&#946;1-42 /A&#946;1-40 ratio - a cross-validation study against amyloid PET.</a> J Neurochem. 139 (4), 651-658 (2016).</li><li>Thienpont, L. M., Van Houcke, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Traceability+to+a+common+standard+for+protein+measurements+by+immunoassay+for+in-vitro+diagnostic+purposes.">Traceability to a common standard for protein measurements by immunoassay for in-vitro diagnostic purposes.</a> Clin Chim Acta. 411 (23-24), 2058-2061 (2010).</li><li>Vesper, H. W., Thienpont, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Traceability+in+laboratory+medicine.">Traceability in laboratory medicine.</a> Clin Chem. 55 (6), 1067-1075 (2009).</li></ol>

For the described method, instead of using a surrogate matrix, we used the surrogate analyte approach13,14,15,16, which enables calibration in human CSF. The surrogate analyte approach involves two different isotopically labeled standards. One (15NA&#946;142) is used to generate the calibration curve in human CSF, while another (13CA&#946;142) is used...

Alzheimer&#39;s disease (AD) is the most common form of dementia and affects about 35 million people worldwide1. The neuropathological hallmarks of the disease widely believed to lie at the core of AD pathogenesis are intracellular neurofibrillary tangles of hyperphosphorylated tau protein2 and extracellular plaques consisting of aggregated amyloid-beta (A&#946;) peptides3. In line with this, the assessment of plaque pathology in vivo by biomarkers has recently been included in the research diagnostic criteria for AD4. For CSF measurements of A&#946;1-42, several immunoassays are available and are used in many clinical laboratories5. The concentration of A&#946;1-42 in CSF is approximately 50% lower in AD patients than in the cognitively normal elderly, reflecting the deposition of the peptide in plaques in the brain6,7.
These biomarkers are mainly analyzed using immunoassays (i.e., antibody-based techniques), but these assays may be influenced by matrix effects8. The use of immunoassays on different technology platforms and the lack of assay standardization9,10 makes the introduction of global cut-off concentrations difficult11,12. An analytically validated RMP would permit the uniform calibration of different assay platforms, ideally resulting in better comparability across analytical platforms and in better control of factors contributing to the overall measurement variability.
The absolute quantification of A&#946;1-42 using the developed LC-MS/MS method overcomes many of the issues associated with antibody-based techniques. The method, listed as an RMP by the Joint Committee for Traceability in Laboratory Medicine (JCTLM database identification number C11RMP9), will be used to determine the absolute concentration of A&#946;1-42 in a Certified Reference Material (CRM) to harmonize CSF A&#946;1-42 measurements across techniques and analytical platforms. The described workflow should be of relevance for the development of candidate reference methods for peptides and proteins within other areas of medicine.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Eppendorf Protein LoBind microcentrifuge tubes, 0.5 mL</td>
			<td>Eppendorf</td>
			<td>022431081</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Protein LoBind microcentrifuge tubes, 1.5 mL</td>
			<td>Eppendorf</td>
			<td>022431081</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Protein LoBind microcentrifuge tubes, 2 mL</td>
			<td>Eppendorf</td>
			<td>022431102</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Protein LoBind microcentrifuge tubes, 5 mL</td>
			<td>Eppendorf</td>
			<td>0030 108.310</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf Protein LoBind Deepwell Plates 96</td>
			<td>Eppendorf</td>
			<td>951032905</td>
			<td></td>
		</tr>
		<tr>
			<td>Micronic 0.75 mL polypropylene tubes, V-bottom</td>
			<td>Micronic</td>
			<td>MPW32071BC3</td>
			<td>Tubes used for collecting SPE eluate, but other collection devices can be used such as 96-well plates.</td>
		</tr>
		<tr>
			<td>Micronic Split TPE Capcluster for 96 ind. tubes</td>
			<td>Micronic</td>
			<td>MP53026</td>
			<td>Caps for Micronic tubes.</td>
		</tr>
		<tr>
			<td>Micronic Loborack-96 white w high cover bar coded</td>
			<td>Micronic</td>
			<td>MPW51015BC3</td>
			<td>Holder for Micronic tubes.</td>
		</tr>
		<tr>
			<td>Biohit Optifit tips 1.2 mL</td>
			<td>Sartorius</td>
			<td>791210</td>
			<td>Used to reach all the way to the bottom of the LoBind deepwell plates (96-well). Other narrow tips might work as well.</td>
		</tr>
		<tr>
			<td>Waters Oasis MCX 96-well &#181;Elution Plate</td>
			<td>Waters</td>
			<td>186001830BA&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Waters Plate manifold reservoir tray</td>
			<td>Waters</td>
			<td>WAT058942</td>
			<td></td>
		</tr>
		<tr>
			<td>Waters Extraction Plate Manifold for Oasis 96-Well Plates</td>
			<td>Waters</td>
			<td>186001831</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium hydroxide solution, puriss. p.a., reag. ISO, reag. Ph. Eur., ~25% NH3 basis</td>
			<td>Sigma-Aldrich</td>
			<td>30501-1L-D</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile, Far UV HPLC Gradient grade, 2.5 L</td>
			<td>Fisher Scientific</td>
			<td>A/0627/17X</td>
			<td></td>
		</tr>
		<tr>
			<td>ortho-Phosphoric acid 85%, ACS,ISO,Reag. Ph Eur</td>
			<td>Merck Millipore</td>
			<td>1005731000</td>
			<td></td>
		</tr>
		<tr>
			<td>Guanidine Hydrochloride, 500 g</td>
			<td>Thermo Scientific</td>
			<td>24110</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermo Scientific Q-exactive Hybrid Quadrupole Orbitrap Mass Spectrometer</td>
			<td>Thermo Scientific</td>
			<td>IQLAAEGAAPFALGMAZR</td>
			<td>With bundled Dionex Ultimate 3000 LC &#38; autosampler.</td>
		</tr>
		<tr>
			<td>Dionex ProSwift RP-4H Monolith Column (1.0 x 250mm)</td>
			<td>Dionex</td>
			<td>066640</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin, lyophilized powder, suitable for (for molecular biology), Non-acetylated</td>
			<td>Sigma-Aldrich</td>
			<td>B6917</td>
			<td></td>
		</tr>
		<tr>
			<td>Beta-Amyloid (1-42), Ultra Pure, TFA</td>
			<td>rPeptide</td>
			<td>A-1002-2</td>
			<td></td>
		</tr>
		<tr>
			<td>15N Beta-Amyloid (1-42), Uniformly labeled</td>
			<td>rPeptide</td>
			<td>A-1102-2</td>
			<td></td>
		</tr>
		<tr>
			<td>13C Beta-Amyloid (1-42), Uniformly labeled</td>
			<td>rPeptide</td>
			<td>A-1106-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate shakers, TiMix 2</td>
			<td>Edmund B&#252;hler</td>
			<td>6110 000</td>
			<td></td>
		</tr>
	</tbody>
</table>

absolute quantification of a&#946;1-42 in csf using a mass spectrometric reference measurement procedure

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly and accounts for 60-80% of all cases of dementia. Currently, the diagnosis of AD is based on cognitive tests and mental state exams, but the peptide amyloid-beta (A&#946;) in cerebrospinal fluid (CSF) is increasingly used in clinical trials and settings. As for most protein and peptide biomarkers, quantification is performed using antibody-based techniques, such as enzyme-linked immunosorbent assay (ELISA). However, intra- and inter-laboratory variability in these assays hamper its use as a diagnostic marker in clinical routine.
An antibody-independent Reference Measurement Procedure (RMP) was developed based on solid-phase extraction (SPE) and liquid chromatography (LC)-tandem mass spectrometry (MS/MS), where stable, isotope-labeled A&#946; peptides were used as internal standards, enabling absolute quantification. A high-resolution quadrupole-orbitrap hybrid instrument was used for the measurements. The method allows for the quantification of CSF A&#946;1-42 between 150-4,000 pg/mL.

The plate setup in Figure 1 is used for a full plate of samples. If fewer unknown samples are to be analyzed, the second calibrator, RF, and QC sets should be placed after the first half of the unknown samples.
As seen in Figure 2, the calibrators are close to the regression line, with low standard deviations. This method has a lower level of quantification of 150 pg/mL and an upper level of qua...

Watch this Scientific Journal Video about Absolute Quantification of AÃŽÂ²1-42 in CSF Using a Mass Spectrometric Reference Measurement Procedure at JoVE.com

Absolute Quantification of AÃƒÆ’Ã…Â½Ãƒâ€šÃ‚Â²1-42 in CSF Using a Mass Spectrometric Reference Measurement Procedure

A reference measurement procedure for the absolute quantification of A&#946;1-42 in human CSF based on solid-phase extraction and liquid chromatography tandem mass spectrometry is described.

Absolute Quantification of A&#946;1-42 in CSF Using a Mass Spectrometric Reference Measurement Procedure

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly and accounts for 60-80% of all cases of dementia. Currently, the ...

Research

JoVE Journal

Medicine

Magnetic Resonance Imaging Quantification of Pulmonary Perfusion using Calibrated Arterial Spin Labeling

This demonstrates a MR imaging method to measure the spatial distribution of pulmonary blood flow in healthy subjects 
during normoxia (inspired O2, ...

Segmentation and Measurement of Fat Volumes in Murine Obesity Models Using X-ray Computed Tomography

Obesity is associated with increased morbidity and mortality as well as reduced metrics in quality of life.1 Both environmental and genetic factors are ...

Epidural Intracranial Pressure Measurement in Rats Using a Fiber-optic Pressure Transducer

Elevated intracranial pressure (ICP) is a significant problem in several forms of ischemic brain injury including stroke, traumatic brain injury and ...

Quantification of Breast Cancer Cell Invasiveness Using a Three-dimensional (3D) Model

Quantification of Breast Cancer Cell Invasiveness Using a Three-dimensional 3D Model

It is now well known that the cellular and tissue microenvironment are critical regulators influencing tumor initiation and progression. Moreover, the ...

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS

The calcineurin inhibitor tacrolimus is the cornerstone of most immunosuppressive treatment protocols after solid organ transplantation in the United ...

Quantitative Mass Spectrometric Profiling of Cancer-cell Proteomes Derived From Liquid and Solid Tumors

In-depth analyses of cancer cell proteomes are needed to elucidate oncogenic pathomechanisms, as well as to identify potential drug targets and diagnostic ...

Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients

Approximately 30% of epilepsy patients are refractory to antiepileptic drugs. In these cases, surgery is the only alternative to eliminate/control ...

Spatial Quantification of Drugs in Pulmonary Tuberculosis Lesions by Laser Capture Microdissection Liquid Chromatography Mass Spectrometry (LCM-LC/MS)

Spatial Quantification of Drugs in Pulmonary Tuberculosis Lesions by Laser Capture Microdissection Liquid Chromatography Mass Spectrometry LCM-LC/MS

Tuberculosis is still a leading cause of morbidity and mortality worldwide. Improvements to existing drug regimens and the development of novel ...

An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

An In Vivo Method for Evaluating the Gut-Blood Barrier and Liver Metabolism of Microbiota Products

The gut-blood barrier (GBB) controls the passage of nutrients, bacterial metabolites and drugs from intestinal lumen to the bloodstream. The GBB integrity ...

Measurement of Carotenoids in Perifovea using the Macular Pigment Reflectometer

The macular pigment reflectometer (MPR) objectively measures the overall macular pigment optical density (MPOD) and further provides the lutein optical ...