Recent Developments in Clinical Plasma Proteomics—Applied to Cardiovascular Research

The human plasma proteome mirrors the physiological state of the cardiovascular system, a fact that has been used to analyze plasma biomarkers in routine analysis for the diagnosis and monitoring of cardiovascular diseases for decades. These biomarkers address, however, only a very limited subset of cardiovascular diseases, such as acute myocardial infarct or acute deep vein thrombosis, and clinical plasma biomarkers for the diagnosis and stratification cardiovascular diseases that are growing in incidence, such as heart failure and abdominal aortic aneurysm, do not exist and are urgently needed. The discovery of novel biomarkers in plasma has been hindered by the complexity of the human plasma proteome that again transforms into an extreme analytical complexity when it comes to the discovery of novel plasma biomarkers. This complexity is, however, addressed by recent achievements in technologies for analyzing the human plasma proteome, thereby facilitating the possibility for novel biomarker discoveries. The aims of this article is to provide an overview of the recent achievements in technologies for proteomic analysis of the human plasma proteome and their applications in cardiovascular medicine.

Early Introduction of Multi-Allergen Mixture for Prevention of Food Allergy

The incidence and prevalence of food allergy (FA) are increasing. While several studies have established the safety and efficacy of early introduction of single allergens in infants for the prevention of FA, the exact dose, frequency, and number of allergens that can be safely introduced to infants particularly in those at high or low risk of atopy are still unclear. This 1-year study evaluated the safety of early introduction of single foods (milk, egg, or peanut), vs. two foods (milk/egg, egg/peanut, milk/peanut), vs. multiple foods (milk/egg/peanut/cashew/almond/shrimp/walnut/wheat/fish/soy at low, medium, or high doses) vs no early introduction in infants between 4-6 months of age. At the end of the study, they were evaluated for plasma biomarkers associated with food reactivity with standardized blood tests. Two to four years after the start of the study, participants were evaluated by standardized food challenges. The serving sizes for the single, double, and low dose mixtures were 300 mg total protein per day. The serving sizes for the medium and high dose mixture was 900 mg and 3000 mg total protein, respectively. Equal parts of each protein were used for double or mixture foods. All infants were breastfed until at least 6 months of age. Results demonstrate that infants at either high or low risk for atopy were able to tolerate early introduction of multiple allergenic foods with no increases in any safety issues, including eczema, FA, or food protein induced enterocolitis. The mixtures of foods at either low, medium, or high doses demonstrated trends for improvement in food challenge reactivity and plasma biomarkers compared to single and double food introductions. The results of this study suggest that early introduction of foods, particularly simultaneous mixtures of many allergenic foods is efficacious for preventing FA and can occur safely.

Neurodegeneration and Vascular Burden on Cognition After Midlife: A Plasma and Neuroimaging Biomarker Study

Background and Objectives: Neurodegeneration and vascular burden are the two most common causes of post-stroke cognitive impairment. However, the interrelationship between the plasma beta-amyloid (Aβ) and tau protein, cortical atrophy and brain amyloid accumulation on PET imaging in stroke patients is undetermined. We aimed to explore: (1) the relationships of cortical thickness and amyloid burden on PET with plasma Aβ40, Aβ42, tau protein and their composite scores in stroke patients; and (2) the associations of post-stroke cognitive presentations with these plasma and neuroimaging biomarkers.Methods: The prospective project recruited first-ever ischemic stroke patients around 3 months after stroke onset. The plasma Aβ40, Aβ42, and total tau protein were measured with the immunomagnetic reduction method. Cortical thickness was evaluated on MRI, and cortical amyloid plaque deposition was evaluated by 18F-florbetapir PET. Cognition was evaluated with Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS), Dementia Rating Scale-2 (DRS-2).Results: The study recruited 24 stroke patients and 13 normal controls. The plasma tau and tau*Aβ42 levels were correlated with mean cortical thickness after age adjustment. The Aβ42/Aβ40 ratio was correlated with global cortical 18F-florbetapir uptake value. The DRS-2 and GDS scores were associated with mean cortical thickness and plasma biomarkers, including Aβ42/Aβ40, tau, tau*Aβ42, tau/Aβ42, and tau/Aβ40 levels, in stroke patients.Conclusion: Plasma Aβ, tau, and their composite scores were associated with cognitive performance 3 months after stroke, and these plasma biomarkers were correlated with corresponding imaging biomarkers of neurodegeneration. Further longitudinal studies with a larger sample size are warranted to replicate the study results.

Plasma Biomarkers of Angiogenesis Related to Small Vessel Brain Disease in SPRINT

Meta-analyses incorporating the Systolic Blood Pressure Intervention Trial (SPRINT) have shown a reduced incidence of dementia with blood pressure lowering. However, mechanistic explanations for this effect are lacking, apart from slowed progression of cerebral white matter lesions (WML). Here we examine possible biomarkers of angiogenesis related to small vessel brain disease including bFGF, FLT1, PLGF, TIE-2, VEGF, VEGF-C, and VEGF-D. The biomarkers were assayed in plasma at baseline and during follow-up (median follow-up = 3.8 years) in a subgroup of participants 60 to 89 years old from SPRINT (N=517). We modeled changes in each biomarker using robust linear mixed models accounting for treatment group, time since randomization, and kidney function. Participants were 69.8 ± 7.1 (standard deviation) years of age, 42.1% female, with a mean systolic blood pressure (SBP) of 138.2 ± 17.0 mm Hg. At baseline, none of the biomarkers were associated with WML lesion volume or total brain volumes adjusting for age (all p>0.05), while FLT1, PLGF, and TIE-2 were negatively associated with frontal gray matter cerebral blood flow (partial correlations of -0.11, -0.10, and -0.12 respectively, all p<0.05). For both intensive (target SBP<120 mm Hg) and standard (target SBP<140 m Hg) blood pressure control, mean levels for the majority of biomarkers increased during follow-up, with the exceptions of TIE-2 (decreased over follow-up) and VEGF-D (no change). We did not observe significant between-group differences for the change in these plasma biomarkers of angiogenesis comparing intensive to standard blood pressure treatment.

Urolithin A enhances muscle performance in elderly and positively impacts biomarkers linked to cellular health

Background Aging is associated with decline in mitochondrial function and reduced exercise capacity. Urolithin A (UA) is a natural gut metabolite shown to stimulate mitophagy and improve muscle function in aged animals, and induce mitochondrial gene expression in elderly. Purpose Investigate if oral administration of UA improved walking distance (6MWT), muscle fatigue resistance in hand (FDI) and leg (TA) muscles, and had an impact on plasma biomarkers. Method: We conducted a randomized, double-blind, placebo-controlled study (NCT03283462) in elderly subjects (65-90 yrs.) supplemented daily with 1000mg UA or placebo for 4 months. 128 subjects were screened and 66 randomized. 6MWT and ATPmax via MRS were assessed at baseline and at 4 months. Muscle fatigue tests and plasma analysis of biomarkers were assessed at baseline, 2 and 4 months. Results UA significantly improved muscle endurance (i.e., change in number of muscle contractions from baseline) in two different muscles (hand: PL 11.6 ±147.5, UA 95.3 ± 115.5; and leg: PL 5.7± 127.1, UA 41.4 ±65.5) compared with placebo at 2-months. Plasma levels of several acylcarnitines, ceramides and C-reactive-protein were decreased by UA at the end-of study. 6MWT distance (PL 42.5 ± 73.3 m, UA 60.8± 67.2 m) and ATPmax increased in both groups from baseline (PL 13.7±31.4%, UA19.4± 56.8%) with UA supplemented group exhibiting greater improvements, although these were not statistically different between groups. Conclusion UA supplementation improved muscle endurance, metabolic and inflammatory plasma biomarkers after 2-months, suggesting that UA can have a positive impact on muscle and cellular health in the elderly.