Exploring the Intricacies of Bile Acids: Understanding Their Role in Metabolism and Intrahepatic Cholestasis of Pregnancy
Exploring the Intricacies of Bile Acids: Understanding Their Role in Metabolism and Intrahepatic Cholestasis of Pregnancy
Bile acids (BAs) are fascinating molecules that play a pivotal role in our bodies metabolic processes. From aiding in the digestion of lipids to regulating essential metabolic pathways, BAs have garnered significant interest among researchers and healthcare professionals. In this article, we will delve into the structural and functional aspects of bile acids and explore their significance in a condition called intrahepatic cholestasis of pregnancy (ICP). For additional information, we encourage you to take a look at our latest educational guide: 5th Generation Bile Acids & Intrahepatic Cholestasis of Pregnancy. So, let’s unravel the secrets of bile acids and their impact on our health!
Understanding Bile Acids
Bile acids belong to a diverse family of bile salts, characterised by their planar and amphipathic nature. They possess a hydrophilic hydroxyl and a hydrophobic methyl group, conferring their unique amphipathic properties. These properties allow bile acids to emulsify and solubilize lipids, facilitating their digestion and absorption1.
Bile acids are primarily synthesized in the liver through two pathways: the classic (neutral) pathway and the alternate (acidic) pathway. The classic pathway involves the hydroxylation of cholesterol, while the alternate pathway utilizes oxysterols as precursors. These pathways produce primary bile acids, which are further modified to generate secondary and tertiary bile acids2.
Importance of Bile Acids in Metabolism
Bile acids serve multiple functions in our bodies. Firstly, they emulsify dietary fats, breaking them down into smaller droplets that can be efficiently digested by pancreatic enzymes. Additionally, bile acids are crucial for the absorption of fat-soluble vitamins, such as vitamins A, D, E, and K. These vitamins are incorporated into micelles, facilitated by the presence of bile acids, enabling their uptake3.
Furthermore, bile acids exhibit signalling activity through various receptors, influencing metabolic responses. One key receptor associated with bile acid metabolism is the Farnesoid X receptor (FXR). Activation of FXR regulates bile acid synthesis, delivery, and clearance, maintaining their levels within a safe range. FXR also modulates lipid transport and metabolism, as well as hepatic gluconeogenesis. Another important receptor is TGR5, which influences vasodilation, gallbladder function, and exerts anti-inflammatory effects1.
Intrahepatic Cholestasis of Pregnancy
During pregnancy, the metabolic processes in the liver undergo significant adaptations to accommodate the growing foetus. One condition that can arise during pregnancy is intrahepatic cholestasis, commonly known as ICP. It is a multifactorial disorder characterised by elevated levels of bile acids in the blood, particularly chenodeoxycholic acid (CDCA) and cholic acid (CA)4.
ICP manifests in the second or third trimester and can lead to various symptoms such as pruritus (itching), abnormal liver enzyme levels, jaundice, abdominal pain, and depression. The exact mechanisms underlying ICP are not fully understood, but it is believed that elevated bile acid levels may have adverse effects on the cardiovascular system of the foetus, potentially leading to stillbirth or preterm birth5.
The detection and monitoring of ICP are essential for managing the condition and ensuring the well-being of both the mother and the foetus. Total bile acid (TBA) concentration is a commonly measured parameter to assess the severity of ICP. Monitoring TBA levels can aid in identifying potential risks and enabling timely interventions5.
Introducing the 5th Generation Total Bile Acids Assay
To facilitate the accurate quantification of total bile acids in serum and plasma, the 5th Generation Total Bile Acids Assay has emerged as a reliable and advanced diagnostic tool. This assay utilizes a highly sensitive enzymatic cycling method to measure total bile acid levels, providing precise and reproducible results. With its improved sensitivity and specificity, the 5th Generation Total Bile Acids Assay offers a valuable tool for the early detection and monitoring of intrahepatic cholestasis of pregnancy.
The assay is easy to use and can be incorporated into routine laboratory workflows. It requires a small sample volume, making it convenient for both patients and healthcare professionals. The assay provides rapid results, allowing for prompt diagnosis and timely intervention when necessary.
By accurately quantifying total bile acid levels, the 5th Generation Total Bile Acids Assay aids in assessing the severity of ICP and monitoring the response to treatment. This information is vital for guiding clinical decisions and optimizing patient care during pregnancy.
Furthermore, the assay can contribute to ongoing research on bile acids and their role in ICP. By analysing a larger population and monitoring the dynamics of bile acid levels, researchers can gain deeper insights into the mechanisms underlying this condition and explore potential therapeutic targets.
Assay Principle
Two reactions are combined in this kinetic enzyme cycling method. In the first reaction, bile acids are oxidised by 3-α hydroxysteroid dehydrogenase with the subsequent reduction of Thio-NAD to Thio-NADH. In the second reaction, the oxidised bile acids are reduced by the same enzyme with the subsequent oxidation of NADH to NAD. The rate of formation of Thio-NADH is determined by measuring the specific absorbance change at 405nm. Enzyme cycling means multiple Thio-NADH molecules are generated from each bile acid molecule giving rise to a much larger absorbance change, increasing the sensitivity of the assay.
In conclusion, understanding the intricacies of bile acids is essential for comprehending their impact on our metabolism and health. Intrahepatic cholestasis of pregnancy is a condition that warrants attention, and accurate measurement of total bile acid levels is crucial for its diagnosis and management. The 5th Generation Total Bile Acids Assay offers an advanced and reliable solution for assessing bile acid levels, enabling timely interventions, and improving patient outcomes. With ongoing research and advancements in diagnostic techniques, we can continue to unravel the complexities of bile acids and enhance our understanding of their role in health and disease.
Don’t underestimate the strength of knowledge and awareness. Empower yourself, stay informed, and prioritize your health and well-being!
If you’d like to learn more about Bile Acids and ICP we encourage you to read our new educational guide, 5th Generation Bile Acids & The Importance of Of Intrahepatic Cholestasis of Pregnancy
If you would like an additional information on our 5th Generation Total Bile Acids Assay, or anything else, don’t hesitate to reach out the marketing@randox.com. Additionally, feel free to visit our Reagent resource hub where you will find all of our brochures, support tools and a collection of educational material, to aid you in maintaining the highest possible levels of quality.
References
- McGlone ER, Bloom SR. Bile acids and the metabolic syndrome. Annals of Clinical Biochemistry. 2019;56(3):326-337. doi:https://doi.org/10.1177/0004563218817798
- Chiang JYL, Ferrell JM. Bile Acid Metabolism in Liver Pathobiology. Gene Expression. 2018;18(2):71-87. doi:https://doi.org/10.3727/105221618×15156018385515
- Chiang JYL. Bile Acid Metabolism and Signaling. Comprehensive Physiology. 2013;3(3). doi:https://doi.org/10.1002/cphy.c120023
- Di Mascio D, Quist-Nelson J, Riegel M, et al. Perinatal death by bile acid levels in intrahepatic cholestasis of pregnancy: a systematic review. The Journal of Maternal-Fetal & Neonatal Medicine. Published online November 19, 2019:1-9. doi:https://doi.org/10.1080/14767058.2019.1685965
- Piechota J, Jelski W. Intrahepatic Cholestasis in Pregnancy: Review of the Literature. Journal of Clinical Medicine. 2020;9(5):1361. doi:https://doi.org/10.3390/jcm9051361
ADLM 2024
At the Forefront of the Diagnostics Industry
With more than forty years of expertise in the medical diagnostics field, Randox is committed to improving global health outcomes. Renowned for its high-quality diagnostic solutions, Randox provides an extensive array of products and services, including Quality Control, Molecular Diagnostics, Third Party Reagents, Point of Care, and Clinical Chemistry Analysers.
Pushing Innovation to the Limits
At Randox, innovation is our cornerstone. Our recent release of Acusera SMART exemplifies our dedication to advancing medical diagnostics. This development integrates seamlessly with various test systems, streamlining the QC process by reducing human error and optimising workflow. Additionally, we’ve launched new Acusera Quality Controls, including active B12, serum indices, and ultra-low PSA, along with comprehensive panels on our MultiStat platform, now expanded to include gastrointestinal diseases, bladder cancer, and male and female hormones. These advancements ensure accurate and reliable diagnostic results, reflecting our commitment to delivering cutting-edge solutions for the evolving healthcare industry.
Learn more about the products we will be showcasing by clicking on the images to the left.
Dedicated to Improving Health Worldwide
With over four decades of experience in the medical diagnostics industry, Randox is dedicated to enhancing global health outcomes. As a provider of high-quality diagnostic solutions, Randox offers a wide range of products and services, including Quality Control, Molecular Diagnostics, Third Party Reagents, Point of Care, and Clinical Chemistry Analysers.
Acusera Quality Controls
Introducing the New Acusera True Third Party Controls. Book a meeting with a Randox QC Specialist today to learn how we can provide you with complete QC solutions for results you can trust.
Molecular Diagnostics at the Point of Care
The all in one molecular solution developed by Bosch and Randox consolidates full molecular workflow into one small benchtop platform. Randox multiplex Biochip Technology powers the Vivalytic enabling multiple results from one patient sample. Click the link below to learn more about the Vivalytic.
ACUSERA 24•7 Interlaboratory Data Management
Discover features such as; Interactive Levey-Jennings Charts, Automatic Calculation for uncertainty of Measurement as well as the Comprehensive Reports generated on demand, with a live demonstration at EuroMedLab.
RIQAS
The world’s largest External Quality Assessment Scheme with more than 55,000 laboratory participants spanning over 134 countries. Choice and flexibility are guaranteed with our 36 programme portfolio, learn more by clicking the button below!
Contract Manufacturing
At Randox, we are dedicated to helping you bring your diagnostic and life science products to market with unparalleled expertise, capacity, and commitment to quality. With over 40 years of experience and a network of over 300 global customers, our comprehensive OEM and contract manufacturing services cover the entire value chain, from concept development to full commercialisation.
Meet The Team
If you plan to attend ADLM 2024, our Product Specialists Team will be available at Booth #1413 to answer any questions you may have. To ensure the most productive use of your time, we recommend scheduling a meeting with one of our Randox representatives in advance to discuss your specific needs and book a time slot during the event.
D-3-Hydroxybutyrate & Diabetic Ketoacidosis
Diabetic Ketoacidosis is characterised by an accumulation of ketone bodies in response to insulin deficiency, most commonly occurring in T1DM patients, but is becoming increasingly prevalent among sufferers of T2DM.
Diabetic ketoacidosis is associated with symptoms such as polyuria, polydipsia, fever, vomiting, abdominal pain and fatigue with the most severe cases resulting in disastrous consequences such as cerebral oedema and death.
D-3-Hydroxybutyrate is considered to be the predominant ketone bodies associated with diabetic ketoacidosis and novel methods of detection utilise this biomarker to provide robust and accurate quantification of ketone bodies and aid in confident diagnosis of diabetic ketoacidosis.
This guide discusses the physiological and pathological processes associated with diabetic ketoacidosis and the relevant biomarkers, the complications associated with this condition and classic and novel detection methods.
To download this guide, simply click the image at the top of this post!
For more information on this assay visit https://www.randox.com/d-3-hydroxybutyrate-ranbut/
To read about some of our other superior performance reagents visit https://www.randox.com/superior-performance-and-unique-
Or, to view our wide range of diagnostic solutions visit https://www.randox.com/
Determining bilirubin concentration in paediatric facilities – Vanadate Oxidation Method
The quantification of bilirubin has a wide range of diagnostic utility. In paediatric settings, bilirubin concentrations are commonly used to identify cases of bilirubin encephalopathy or kernicterus.
Historically, bilirubin quantification has been achieved through various techniques derived from the diazo method, first described by Van der Bergh and Muller in 1918. New technologies and novel methods, like the Vanadate Oxidation method, have emerged and have been shown to display superior diagnostic power, driven by its lower sensitivity to interference caused by haemolysis and lipemia when compared with other methods.
This week, we present our educational guide, ‘Determining bilirubin concentrations in paediatric facilities’ which details the key points relating to bilirubin quantification, along with descriptions and comparisons of the methods mentioned above.
To download this guide, simply click the image at the top of this post!
For more information on our Vanadate Oxidation Bilirubin assay visit: www.randox.com/bilirubin
To view our wide range of diagnostic solutions visit: www.randox.com/
Or, if you’d like to discuss this assay, or any of our other products, please contact us at: marketing@randox.com
The Importance of Maintaining Regular Dietary Patterns to reduce CVD risk
Cardiovascular disease (CVD) is the leading cause of mortality worldwide. An estimated 17.9 million people died from some form of CVD in 2019, accounting for 32% of all-cause mortality that year1. Associations between diet and risk of cardiovascular complications have long been established, largely relating to alterations in lipid profiles.
For as long as anyone can remember, breakfast has been considered the most important meal of the day. Previous studies2 have shown an association between skipping breakfast and increased CVD risk prompting recommendations that up to 30% of one’s daily energy intake should be consumed during the first meal of the day. It has been reported that over 25% of adults skip breakfast. These individuals are often socioeconomically disadvantaged, shift workers, individuals who work particularly long hours, those who suffer from depression or those with poor health literacy2. Another study3 showed that skipping breakfast, when compared with consuming a high-energy breakfast, was associated with a 1.6x and 2.6x higher probability of non-coronary and general atherosclerosis respectively, when all other CVD risk factor had been controlled. This suggests a close relationship between eating breakfast and reducing CVD risk, however, the mechanisms and magnitude of this relationship are poorly understood.
Small, dense low-density lipoprotein cholesterol (sdLDL-C) is a smaller form of LDL-C which boasts greater propensity for uptake by arterial tissue, increased proteoglycan binding, and increased susceptibility for oxidation4. sdLDL-C concentration is strongly associated with CVD risk, yet once again, the mechanisms of this association remain enigmatic. It is thought that all of the metabolic changes associated with alterations in sdLDL-C concentration collectively contribute to the increased risk of CVD, with the main drivers being its propensity for uptake by arterial tissues and its long circulatory stability4
Skipping breakfast and sdLDL-C
A recent study investigated the relationship between skipping breakfast and the effects on lipid parameters5. In a cohort of around 28’000 people from the Japanese population, this study looked at the several markers, including sdLDL-C, to develop an understanding of the importance of regular dietary patterns for reducing the risk of CVD.
The study participants were divided into two main categories: breakfast eaters and breakfast skippers. These categories were further subdivided to differentiate men and women, over and under 55 years old, and those who eat staple products (rice, pasta, bread, etc.) and those who did not. The participants contributed blood samples which were tested for several cardiovascular biomarkers: Creatinine, Liver ALT, Total Cholesterol, Triglycerides, direct LDL-C, HDL-C and sdLDL-C.
They found that around 26% of men and 16.9% of women skipped breakfast regularly. Of these, most were considered young and had significant increases in concentration of triglycerides, LDL-C and sdLDL-C compared with those who ate breakfast almost every day.
Table 1. Median concentration of triglycerides, LDL-C, and sdLDL-C for breakfast skippers and eaters5
| Analyte | Breakfast Skippers (mg/dL) | Breakfast Eaters (mg/dL) |
| Triglycerides | 103 | 93 |
| LDL-C | 124 | 122 |
| sdLDL-C | 34.7 | 32 |
This investigation also revealed that in this cohort, 20% of men and 27.3% of women did not regularly consume staple foods as part of their diet and had higher median sdLDL-C concentration.
Table 2. Median concentration of sdLDL-C in men and women who eat or skip staple food products in their diet5
| Gender | Staple Skippers (mg/dL) | Staple Eaters (mg/dL) |
| Men | 34.1 | 31.6 |
| Women | 25.8 | 24.7 |
The data from this study supports the finding that individuals who skipped breakfast had higher sdLDL-C concentrations than those who ate breakfast consistently. Skipping breakfast can therefore be associated with troublesome lipid parameters in both genders and all age groups in the Japanese population. This study suggests that eating breakfast every day is crucial to maintain beneficial lipid parameters and reduce the risk of developing CVD.
The data also show that individuals who skipped staple foods in their meals presented with higher concentrations of sdLDL-C and a higher sdLDL-C/LDL-C ratio, in men and postmenopausal women, when compared with those who included staple foods in their meals. It is becoming increasingly common to remove staple foods from one’s diet due to their high carbohydrate content and the prevalence of low-carbohydrate diets. This data exhibits the importance of maintaining a nutritionally balanced diet to help reduce the risk of developing CVD.
As the first large scale study of its kind, this analysis provides clear insight into the increased risk of CVD associated with not only skipping breakfast, but failing to maintain a nutritionally balanced diet. The major limitation of this analysis is that it only includes individuals from the Japanese population and the same affects may not be seen in populations from other ethnicities. Therefore, further in-depth analysis is required to confirm these findings in other ethnicities
Randox sdLDL-C Assay
The Randox sdLDL-C assay employs the clearance method which displays good correlation with the gold standard in sdLDL-C quantification, giving laboratories increased confidence in their results first time, every time. Supplied as liquid ready-to-use reagents, this this test can be applied to a wide range of clinical chemistry analysers, producing results in as little as 10 minutes. Relevant controls and calibrators are also available from Randox as part of the Acusera range.
Randox sdLDL-C Assay Key Features
- Direct, automated test for convenience and efficiency.
- Rapid analysis results can be produced in as little as ten minutes, facilitating faster patient diagnosis and treatment plan implementation.
- Liquid ready-to-use reagents for convenience and ease of use.
- Applications available detailing instrument specific settings for a wide range of clinical chemistry analysers.
- sdLDL-C controls and calibrator available.
References
- World Health Organization. Cardiovascular Diseases. World Health Organization. Published June 11, 2021. https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases-(cvds)
- Ofori-Asenso R, Owen AJ, Liew D. Skipping Breakfast and the Risk of Cardiovascular Disease and Death: A Systematic Review of Prospective Cohort Studies in Primary Prevention Settings. Journal of Cardiovascular Development and Disease. 2019;6(3):30. doi:https://doi.org/10.3390/jcdd6030030
- Uzhova I, Fuster V, Fernández-Ortiz A, et al. The Importance of Breakfast in Atherosclerosis Disease. Journal of the American College of Cardiology. 2017;70(15):1833-1842. doi:https://doi.org/10.1016/j.jacc.2017.08.027
- Rizvi AA, Stoian AP, Janez A, Rizzo M. Lipoproteins and cardiovascular disease: An update on the clinical significance of atherogenic small, dense LDL and new therapeutical options. Biomedicines. 2021;9:1579. doi:https://doi.org/10.3390/biomedicines9111579
- Arimoto M, Yamamoto Y, Imaoka W, et al. Small dense low-density lipoprotein cholesterol levels in breakfast skippers and staple food skippers. Journal of Atherosclerosis and Thrombosis. 2023;30. doi:https://doi.org/10.5551/jat.64024
For more information on our sdLDL-C assay or any of our other products, please contact us at: marketing@randox.com
WorldlabāEuromedlab 2023
We will be exhibiting at Worldlab∙Euromedlab 2023!
We invite you to stop by RCC La Nuvola in Rome between May 21st and May 25th, 2023 for a visit.
Make sure to drop by Booth #153, where we’ll be engaging in conversations about cutting-edge diagnostic products and solutions, while also showcasing our groundbreaking technologies.
With over four decades of experience in the medical diagnostics industry, Randox is dedicated to enhancing global health outcomes. As a provider of high-quality diagnostic solutions, Randox offers a wide range of products and services, including Quality Control, Molecular Diagnostics, Third Party Reagents, Point of Care, and Clinical Chemistry Analysers.
Meet The Team
If you plan to attend Worldlab∙Euromedlab 23, our Product Specialists Team will be available at Booth #153 to answer any questions you may have. To ensure the most productive use of your time, we recommend scheduling a meeting with one of our Randox representatives in advance to discuss your specific needs and book a time slot during the five-day event by clicking on the button below:
Vivalytic Resource Hub
Rheumatoid Factor: The Most Remarkable Autoantibody in Rheumatoid Arthritis
Rheumatoid Factor:
The Most Remarkable Autoantibody in Rheumatoid Arthritis
Celebrating World Arthritis Day (WAD)
Rheumatoid Factor: The Most Remarkable Autoantibody in Rheumatoid Arthritis
World Arthritis Day (WAD) is celebrated on 12th October to help raise global awareness of the existence and impact of rheumatic and musculoskeletal diseases (RMDs). It is estimated that over one-hundred million people are currently undiagnosed impacting their quality of life and participation in society – including their ability to work and lead a normal life. As a result this increases dependency on state welfare, the healthcare system and the required support from their family and friends.
The European League Against Rheumatism (EULAR) launched the ‘Don’t Delay, Connect Today’ campaign focusing on the importance of early diagnosis and access to care.
Randox Reagents fully supports the importance of early diagnosis – to aid in the early implementation of effective treatment plans, aiding in improved health outcomes – it’s the ethos of our business. This blog delves deeper into rheumatoid factor (RF), the most remarkable autoantibody in rheumatoid arthritis.
Pathobiology of Rheumatoid Arthritis (RA)
The pathophysiology of RA involves various signaling pathways and immune modulators (effector cells and cytokines) as indicated in figure 1. Joint destruction is caused by the intricate interactions of immune modulators, beginning at the synovial membrane and encompassing most IA structures, with synovitis caused by both or individually, the local activation or influx of mononuclear cells, including: B cells, T cells, dendritic cells, plasma cells, mast cells and macrophages. Consequently, “the synovial lining becomes hyperplastic, and the synovial membrane expands and forms villi”. The neutrophils, chondrocytes and synoviocytes secrete enzymes that degrades the cartilage in the joint whereas the osteoclast-rich area of the synovial membrane destroys the bone 4.
Rheumatoid arthritis (RA), “the most common systemic inflammatory autoimmune disease” affecting 1% of the global population, is characterised by fatigue, synovial joint pain, stiffness, swelling and destruction, with severe symptoms resulting in disability. Whilst the exact cause of RA is unknown, it is believed that genetic and environmental factors play a role in triggering the disease 2, 3. Differences in the human leukocyte antigen (HLA)-DRB1 alleles (proteins with a critical role in the immune system) have been identified as a genetic variant for RA, observed in >80% of patients, particularly in those testing positive for RF. Moreover, those with variations in the HLA-DRB1 who smoke, increase their risk of RA. As RA is more common in women (2-fold increased risk in women compared to men), hormonal influences are an area of active research, however, an inverse correlation with breastfeeding has been identified. Women who breastfeed for >13 months aids in reducing the risk of RA compared to women who have never breastfed 3, 4.
Figure 1: Schematic view of (a) a normal joint and (b) a joint affected by RA 4
Clinical Significance of Rheumatoid Factor (RF)
Interestingly, elevated levels of RF have been observed in other autoimmune conditions such as Sjögren syndrome and systemic lupus erythematosus (SLE) as well as non-autoimmune conditions including old age and chronic infections. Despite this, RF in RA patients can be distinguished from RF in healthy individuals. RF in RA patients displays affinity maturation whereas RF in healthy individuals has low affinity and are polyreactive 2.
RF is a class of immunoglobulin (Ig) autoantibodies that are directed against the fragment crystallizable region (Fc region), the tail region of the IgG antibody. In RA, RF are produced by the B cells present in lymphoid follicles and the germinal center(GC)-like structures that mature in inflamed synovium. Most RF are IgM antibodies, but may also be IgG or IgA isoforms. IgM RF are detected in 60% to 80% of RA patients. “RF testing in RA patients has a sensitivity of 60% to 90% and a specificity of 85%” (5). RF is a highly valuable biomarker in RA 5, 2.
Key Features of the Randox Rheumatoid Factor Assay
The Randox automated latex enhanced immunoturbidimetric rheumatoid factor assay provides an accurate assessment of RF titre as the Randox rheumatoid factor calibrator is standardised against the primary WHO material, 1st British Standard 64/2. With a wide measuring range of 6.72 – 104lU/ml for the comfortable detection of clinically important results, the Randox RF assay is available in a liquid ready-to-use format for the comfortable detection of clinically important results. The Randox rheumatoid factor assay does not suffer from interference from C1q complement and is stable until expiry date. With dedicated calibrator and controls for a complete testing package, Randox offer applications, detailing instrument-specific settings for the convenient use of the Randox rheumatoid factor assay on a wide range of clinical chemistry analysers.
Related Products
Randox Reagents Homepage
Randox Reagents Resource Hub
Specific Proteins Panel
Alzheimer’s Disease: The Role of Apolipoprotein E
Alzheimer’s Disease: The Role of Apolipoprotein E
Raising awareness of Alzheimer’s Disease
Every year we celebrate Alzheimer’s Day on 21st September to help raise awareness around dementia. Dementia is the medical name attributed to a set of symptoms affecting the brain, including: difficulties with problem solving, thinking, language and memory loss. AD is the most common form of dementia accounting for 60 – 80% of cases and it is believed that half of patients with Alzheimer’s dementia (dementia due to AD) have Alzheimer’s disease 1, 2.
About Alzheimer’s Disease (AD)
AD is one of the most devastating and complex diseases characterised by:
- Neurodegeneration resulting in memory loss 2
- Neurofibrillary tangles composed of tau amyloid fibrils which associates with synapse loss 2
- Accumulation of β-amyloid (Aβ) plaques 2
- Other cognitive functions 2
Figure 1: Alzheimer’s Disease Demographic, 2019 3
It is believed that AD is expected to begin 20 years prior to symptom onset, as the small changes in the functioning of the brain are unnoticeable to the person affected. Overtime, the symptoms progress and begin to interfere with the patient’s ability to perform everyday tasks. The final stages of AD leaves the patient bed-bound, requiring 24/7 care. Ultimately, AD is fatal. Age has been identified as a risk factor for AD with 10% of people over the age of 65 affected. Moreover, AD has been recognised as a leading cause of morbidity and the sixth leading cause of mortality, but the fifth leading cause of death in over 65’s in the US .3
Physiological Significance of Apolipoprotein E
Apolipoprotein E (Apo E) is a lipoprotein composed of 299 amino acids with a molecular weight of 34kDa. Apo E is responsible for the regulation of homeostasis through the mediation of lipid transport from and to bodily cells and tissues. Apo E comprises of three common isoforms: apo E2, apo E3 and apo E4. The apo E isoforms differ due to differences in either the 112 and 158 amino acids, whether either arginine (ARG) or cysteine (CYS) is present 4.
Apo E3 is the parent form of apo E and is responsible for the clearance of triglyceride-rich lipoproteins. Apo E3 is associated with normal lipid plasma concentrations. Apo E2 is the rarest of the apo E isoforms and differs slightly compared to the apo E3 isoform through the substitution of a single amino acid, ARG158Cys, located near the low-density lipoprotein receptor (LDLR) recognition site.
Apo E2 displays impaired binding to the receptor, prohibiting the clearance of triglyceride-rich lipoprotein remnant particles. Apo E2 is strongly associated with type-III hyperlipoproteinemia. Apo E3 also differs from apo E4, again through the substitution of a single amino acid, Cys112Arg. The main difference between apo E3 and apo E4 is that apo E4 is unaffected by the binding of the isoform to LDLR. However, apo E4 is strongly associated with dyslipidemia 5. Fig. 2 provides a visual representation of the variations in the Apo E isoforms.
Figure 2: Variations in the Apo E Isoforms 4
Apo E is expressed in numerous bodily organs with the liver presenting with the highest expression followed by the brain. Astrocytes and, to a lesser extent, microglia are the major cells responsible for the expression of apo E in the brain. In the brain, apo E, apo J and apo A-1 are predominantly expressed on distinct high-density-like lipoprotein particles. Whilst apo A-1 is the major apolipoprotein of high-density lipoproteins (HDL), in the central nervous system (CNS), apo E is the predominant apolipoprotein of HDL-like lipoproteins. HDL-like lipoproteins are the only lipoproteins present in the CNS. It is believed that the cholesterol released from apo E supports synaptogenesis 6.
Clinical Significance of Apolipoprotein E in Alzheimer’s Disease
Whilst apo E3 is the most abundant of the three isoforms, apo E4 has been known for decades to be the most significant genetic risk factor for late-onset AD. Inheriting the one copy of the apo E4 gene increases the risk of AD 2-3-fold, whilst inheriting two copies increases the risk of AD up to 12-fold 7. Whilst the underlying mechanism of apo E’s contribution to AD risk is still unclear and debatable, apo E has been identified as promoting amyloid β (Aβ) deposition and clearance as well as neurofibrillary tangles in the brain. Interestingly, Aβ-independent pathways exist for apo E in AD, which led to the unearthing of the new roles of apo E including the most recent, iron metabolism and mitochondria dysfunction 8, 9. Captivatingly, sex-related hormones may play a role in AD in apo E4 carriers as AD has been recognised to be more pronounced in women 10. Apo E4 has also been identified as impairing lipid transport, microglial responsiveness, glucose metabolism, synaptic plasticity and integrity, and cerebrovascular function and integrity. Some of these pathogeneses are independent of Aβ pathways. Furthermore, therapeutic strategies are aiming to modulate the quantity, lipidation, structural properties, Aβ interaction and receptor expression of Apo E 11.
Key Features of the Randox Apolipoprotein E Assay
Randox are one of the only manufacturers to offer the apo E assay in an automated clinical chemistry format. Utilising the immunoturbidimetric method, the Randox apo E assay is available in a liquid ready-to-use format. Not only does the Randox apo E suffer from limited interferences from bilirubin, haemoglobin, intralipid® and triglycerides for truly accurate results, it has an excellent measuring range of 1.04 – 12.3mg/dl for the comfortable detection of clinically important results. Moreover, apolipoprotein calibrator and controls are available for a complete testing package. Applications are available detailing instrument-specific settings for the convenient use of the Randox apo E assay on a wide range of clinical chemistry analysers.
Biochip Technology – Alzheimer’s Array
Utilising the Biochip Technology, Randox have developed an array to identify the risk of Alzheimer’s disease in just 3 hours with one effective test. In addition to a rapid and accurate diagnosis, this also introduces both cost and time-saving benefits. The apo E4 array is a research use only product developed for the Evidence Investigator, a semi-automated benchtop immunoassay analyser which can process up to 2376 test per hour as well as up to 44 analytes screened per biochip. The apo E4 array measures both total apo E protein levels and apo E4 protein levels directly from plasma samples as well as using a ratio, it can classify patients as negative or positive for apo E4. In turn, we can then assess their risk for the development of Alzheimer’s disease.
Related Products
Randox Reagents Homepage
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RX Series Analysers
References
[1] Alzheimer’s Society. Alzheimer’s disease. [Online] [Cited: September 2, 2019.] https://www.alzheimers.org.uk/about-dementia/types-dementia/alzheimers-disease.
[2] Gaugler, Joseph, et al. 2019 Alzheimer’s Disease Facts and Figures. s.l. : Alzheimer’s Association, 2019.
[3] 2014 Update of the Alzheimer’s Disease Neuroimaging Initiative: A review of papers published since its inception. Weiner, Michael W, et al. 6, San Francisco : Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, 2015, Vol. 11.
[4] Apolipoprotein E and Alzheimer disease: risk, mechanisms, and therapy. Liu, Chia-Chen, et al. 2, Fujian : Nature Reviews Neurology, 2013, Vol. 9.
[5] Apolipoprotein E isoforms and lipoprotein metabolism. Phillips, Michael C. 9, Philadelphia : IUBMB Journals, 2014, Vol. 66.
[6] The Role of Apolipoprotein E in Alzheimer’s Disease. Kim, Jungsu, Basak, Jacob M and Holtzman, David M. 3, St Louis : Neuron, 2009, Vol. 63.
[7] Dacks, Penny. What ApoE Means For Your Health. Cognitive Vitality. [Online] November 16, 2016. [Cited: September 11, 2019.] https://www.alzdiscovery.org/cognitive-vitality/blog/what-apoe-means-for-your-health.
[8] The Complex Role of Apolipoprotein E in Alzheimer’s Disease: an Overview and Update. Mahoney-Sanchez, Laura, et al. 3, Parkville : Journal of Molecular Neuroscience, 2016, Vol. 60.
[9] Understanding the Role of ApoE Fragments in Alzheimer’s Disease. Muñoz, SS, Gerner, B and Ooi, L. 6, Wollongong : Neurochemical Research, 2019, Vol. 44.
[10] ApoE4: an emerging therapeutic target for Alzheimer’s disease. Affieh, Mirna, Korczyn, Amos D and Michaelson, Daniel M. 64, s.l. : BMC Medicine, 2019, Vol. 17.
[11] Apolipoprotein E and Alzheimer disease: pathobiology and targeting strategies. Yamazaki, Yu, et al. 9AB, s.l. : Nature Reviews Neurology, 2019, Vol. 15.
The Importance of Diagnostic Testing in SARS-CoV-2 Adverse Outcomes
SARS-CoV-2 (COVID-19), a highly contagious disease, primarily manifests as an acute respiratory illness, however, for those with health complications, including: autoimmune diseases, asthma, heart disease and diabetes, the risk of developing serious illness and adverse outcomes is much greater. It is estimated that 1 in 6 will experience adverse outcomes that could be life-threatening 1. The spread and devastation of COVID-19 highlights the vital role laboratory diagnostics plays in the diagnosis and management of suspected and affected patients. As the COVID pandemic continues, it is imperative that fast and accurate diagnostic testing strategies are implemented for effective risk stratification and monitoring of treatment and recovery.
In this article, we will review how Randox Reagents can aid in diagnosing and managing SARS-CoV-2 adverse outcomes.
Cytokine Storms
The immune system activates a pro-inflammatory response to enhance host immunity against viruses and decrease colonisation and infection, but only if the pro-inflammatory response is controlled. Uncontrolled pro-inflammatory responses can result in a cytokine storm 2. A cytokine storm is a serious complication associated with SARS-CoV-2, which can trigger life-threatening pneumonia, acute respiratory distress syndrome (ARDS) and multiple organ failure 3, 4. Cytokine storms occur in 5% of severe COVID-19 cases, with several inflammatory cytokines observed at high levels. Due to the elevation of several pro-inflammatory and anti-inflammatory cytokines, a multiplex immunoassay approach can offer several advantages over the widely utilised single ELISA tests. The simultaneous detection of multiple cytokines from a single patient sample will provide clinicians with a comprehensive overview of cytokine markers and complete patient profile, facilitating a personalised treatment plan to be implemented 5, 6.
Inflammation
In COVID-19 patients, CRP testing has proved to perform well in discriminating disease severity and predicting adverse outcomes 7. Elevated CRP levels have been identified in 86% of patients admitted to hospital. CRP measurements are useful in diagnosis, prognosis and monitoring for clinical improvements or deterioration. Moreover, the acute phase reactant, ferritin, has been observed to increase in approximately 60% of COVID-19 patients. In the critically ill COVID-19 patients, extremely elevated ferritin concentrations were recorded, which could be attributed to a cytokine storm and secondary haemophagocytic lymphohistiocytosis (a hyper-inflammatory syndrome associated with multi-organ failure) 8.
Renal Function
Acute kidney injury (AKI) is a common complication in diabetic patients who test positive for COVID-19. Regardless, the National Institute for Health and Care Excellence (NICE) recommend AKI testing in all COVID-19 patients upon hospital admission and their condition monitored throughout their stay 9.
The most commonly utilised screening test for renal impairment is serum creatinine (SCr); however, it is important to consider the accuracy and reliability of the method. Two commercially available methods exist for SCr determination: Jaffe and enzymatic. Whilst the Jaffe method is less expensive, it is more susceptible to interferences which can lead to the misdiagnosis of patients, which isn’t ideal in the current pandemic 7. Moreover, the sensitivity of SCr, regardless of method, in the early detection of renal disease is poor, as SCr is insensitive to small changes in glomerular filtration rate (GFR). Up to 50% of renal function can potentially be lost before significant SCr levels become detectable 8, 9. In comparison, cystatin C (CysC) is a superior marker of renal function and is useful in the determination of the extent of renal damage, as well as distinguishing those with severe and mild COVID-19 10.
Hepatic Function
Abnormal liver function tests significantly increases a COVID-19 patients risk of developing severe disease and complications such as pneumonia 11. Bilirubin levels, 3 times the upper limit have been observed in COVID-19 patients 11, 12. Whilst the diazo method is commonly utilised in bilirubin testing, superior methods exist. The vanadate oxidation (VO) method offers several advantages particularly in haemolytic and lipemic samples. These advantages are particularly evident in neonatal and infant populations where haemolysis is extremely common. Moreover, the VO method offers a wider analytical measurement range for the comfortable detection of clinically important results 13.
Other liver function markers are known to be elevated in COVID-19 patients including both AST and ALT, with markers like albumin decreased.
The Importance of Lp(a) Testing
Lipoprotein(a) / Lp(a), a strong independent marker of cardiovascular disease risk has recently been identified as a key risk marker of cardiovascular complications in COVID-19 patients. Those with either baseline elevated or elevated levels of Lp(a) following COVID-19 infection may be at a significantly increased risk of developing thromboses. Consideration should be given to measurement of Lp(a) and prophylactic anticoagulation of infected patients to reduce the risk. Elevated Lp(a) levels may also cause acute destabilization of pre-existing but quiescent, atherosclerotic plaques, which could induce an acute myocardial infarction (AMI) or cerebrovascular accident (CVA) (stroke) 14.
The size heterogeneity of apo(a) isoforms represents the biggest challenge faced by laboratories in accurately measuring Lp(a). The variable numbers of repeated KIV-2 units in act as multiple epitopes, and so standardisation across calibrators is vital. Unless the calibrants have the same range of isoforms as test samples, those with higher numbers of the KIV-2 repeat, will represent with an overestimation in Lp(a) concentrations and those with smaller numbers of the KIV-2 repeat, will represent with an underestimation. The smaller isoforms are strongly associated with higher Lp(a) concentrations 15.
Lp(a) assays that are standardised to the WHO/IFCC (World Health Organization/International Federation of Clinical Chemistry) reference material, transferring values from mg/dl to nmol/l are more uniform. The assay considered the most reliable commercially available Lp(a) assay is so because: 15
1. The isoform size variations are reduced as a range of calibrators from separate pools of serum used, which covered a range of Lp(a) concentrations.
2. The isoform size and concentrations are inversely correlated, better matching calibrants with test samples.
3. Methods are calibrated in nmol/l and traceable to WHO/IFCC reference material and give acceptable bias compared with the Northwest Lipid Metabolism and Diabetes Research Laboratory (NLMDRKL) gold standard method.
Want to know more?
Contact us or visit our COVID-19 disease management webpage.
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References
[1] Complications coronavirus can cause. https://www.webmd.com/lung/coronavirus-complications#1 (accessed 22 July 2020).
[2] The powerful virus inflammatory response. https://www.mdedge.com/chestphysician/article/189513/infectious-diseases/powerful-virus-inflammatory-response (accessed 4 August 2020).
[3] George A. Cytokine storm: an overreaction of the body’s immune system. https://www.newscientist.com/term/cytokine-storm/ (accessed 22 July 2020).
[5] Del Valle DM, Kim-Schulze S, Huang HH, Beckmann M, Nirenberg S, et al. An inflammatory cytokine signature helps predict COVID-19 severity and death. The Preprint Server for Health Sciences https://www.medrxiv.org/content/10.1101/2020.05.28.20115758v1.full.pdf (accessed 24 July 2020).