The thermostability of tropomyosin

The effects of high-intensity functional training on cardiometabolic risk factors and exercise enjoyment in men and women with metabolic syndrome: study protocol for a randomized, 12-week, dose-response trial

Background

Individuals with metabolic syndrome (MetS) are at a greater risk for developing atherosclerotic cardiovascular disease (ASCVD) than those without MetS, due to underlying endothelial dysfunction, dyslipidemia, and insulin resistance. Exercise is an effective primary and secondary prevention strategy for MetS; however, less than 25% of adults meet the minimum stated public recommendations. Barriers often identified are lack of enjoyment and lack of time. High-intensity functional training (HIFT), a time-efficient modality of exercise, has shown some potential to elicit positive affectivity and elicit increased fitness and improved glucose metabolism. However, the effects of HIFT on dyslipidemia and endothelial dysfunction have not been explored nor have the effects been explored in a population with MetS. Additionally, no studies have investigated the minimal dose of HIFT per week to see clinically meaningful changes in cardiometabolic health. The purpose of this study is to (1) determine the dose-response effect of HIFT on blood lipids, insulin resistance, and endothelial function and (2) determine the dose-response effect of HIFT on body composition, fitness, and perceived enjoyment and intention to continue the exercise.

Methods/design

In this randomized, dose-response trial, participants will undergo a 12-week HIFT intervention of either 1 day/week, 2 days/week, or 3 days/week of supervised, progressive exercise. Outcomes assessed at baseline and post-intervention will be multiple cardiometabolic markers, and fitness. Additionally, the participant’s affective response will be measured after the intervention.

Discussion

The findings of this research will provide evidence on the minimal dose of HIFT per week to see clinically meaningful improvements in the risk factors of MetS, as well as whether this modality is likely to mitigate the barriers to exercise. If an effective dose of HIFT per week is determined and if this modality is perceived positively, it may provide exercise specialists and health care providers a tool to prevent and treat MetS.

Trial registration

ClinicalTrials.gov NCT05001126. August 11, 2021.

Black chokeberry Aronia melanocarpa extract reduces blood pressure, glycemia and lipid profile in patients with metabolic syndrome: a prospective controlled trial

The aim of the study was to examine the effect of 4-week supplementation of Alixir 400 PROTECT® (Standardized Aronia L. Melanocarpa Extract Extract-SAE) on clinical and biochemical parameters in patients with confirmed metabolic syndrome (MetS). This study was designed as a prospective open-label clinical case-series study with 28 days of follow-up with cases selected and followed during the period from February 1, 2018 to November 2019. The study included 143 male and female patients with MetS who were subjected to SAE. SAE supplementation significantly altered SP, BP as well as HR values. After 2 weeks, CHOL levels significantly decreased in the fMetS-DM group compared to the baseline values in this group, while the LDL levels significantly decreased in the fMetS group. Triglycerides significantly decreased only after 4 weeks of SAE treatment in diabetic groups of patients (fMetS-DM and mMetS-DM) compared to the baseline, while in non-diabetic groups this marker was not significantly altered. Increased polyphenols or SAE consumption is correlated with a positive effect on body weight, total cholesterol, low and high-density lipoproteins, blood pressure and glycemia. Increasing consumption of polyphenol-rich foods could be a promising strategy to reduce cardiovascular risk.

Significant Facility-Level Variation in Utilization of and Adherence with Secondary Prevention Therapies Among Patients with Premature Atherosclerotic Cardiovascular Disease: Insights from the VITAL (Veterans wIth premaTure AtheroscLerosis) Registry7

PURPOSE

We investigated facility-level variation in the use and adherence with antiplatelets and statins among patients with premature and extremely premature ASCVD.

METHODS

Using the 2014-2015 nationwide Veterans wIth premaTure AtheroscLerosis (VITAL) registry, we assessed patients with premature (age at first ASCVD event: males < 55 years, females < 65 years) and extremely premature ASCVD (< 40 years). We examined frequency and facility-level variation in any statin, high-intensity statin (HIS), antiplatelet use (aspirin, clopidogrel, ticagrelor, prasugrel, and ticlopidine), and statin adherence (proportion of days covered ≥ 0.8) across 130 nationwide VA healthcare facilities. Facility-level variation was computed using median rate ratios (MRR), a measure of likelihood that two random facilities differ in use of statins or antiplatelets and statin adherence.

RESULTS

Our analysis included 135,703 and 7716 patients with premature and extremely premature ASCVD, respectively. Across all facilities, the median (IQR) prescription rate of any statin therapy, HIS therapy, and antiplatelets among patients with premature ASCVD was 0.73 (0.70-0.75), 0.36 (0.32-0.41), and 0.77 (0.73-0.81), respectively. MRR (95% CI) for any statin use, HIS use, and antiplatelet use were 1.53 (1.44-1.60), 1.58 (1.49-1.66), and 1.49 (1.42-1.56), respectively, showing 53, 58, and 49% facility-level variation. The median (IQR) facility-level rate of statin adherence was 0.58 (0.55-0.62) and MRR for statin adherence was 1.13 (1.10-1.15), showing 13% facility-level variation. Similar median facility-level rates and variation were observed among patients with extremely premature ASCVD.

CONCLUSIONS

There is suboptimal use and significant facility-level variation in the use of statin and antiplatelet therapy among patients with premature and extremely premature ASCVD. Interventions are needed to optimize care and minimize variation among young ASCVD patients.

Brain arteriolosclerosis

Brain arteriolosclerosis (B-ASC), characterized by pathologic arteriolar wall thickening, is a common finding at autopsy in aged persons and is associated with cognitive impairment. Hypertension and diabetes are widely recognized as risk factors for B-ASC. Recent research indicates other and more complex risk factors and pathogenetic mechanisms. Here, we describe aspects of the unique architecture of brain arterioles, histomorphologic features of B-ASC, relevant neuroimaging findings, epidemiology and association with aging, established genetic risk factors, and the co-occurrence of B-ASC with other neuropathologic conditions such as Alzheimer's disease and limbic-predominant age-related TDP-43 encephalopathy (LATE). There may also be complex physiologic interactions between metabolic syndrome (e.g., hypertension and inflammation) and brain arteriolar pathology. Although there is no universally applied diagnostic methodology, several classification schemes and neuroimaging techniques are used to diagnose and categorize cerebral small vessel disease pathologies that include B-ASC, microinfarcts, microbleeds, lacunar infarcts, and cerebral amyloid angiopathy (CAA). In clinical-pathologic studies that factored in comorbid diseases, B-ASC was independently associated with impairments of global cognition, episodic memory, working memory, and perceptual speed, and has been linked to autonomic dysfunction and motor symptoms including parkinsonism. We conclude by discussing critical knowledge gaps related to B-ASC and suggest that there are probably subcategories of B-ASC that differ in pathogenesis. Observed in over 80% of autopsied individuals beyond 80 years of age, B-ASC is a complex and under-studied contributor to neurologic disability.

Stability and melting kinetics of structural domains in the myosin rod

The thermal stability and melting kinetics of the alpha-helical conformation within several regions of the rabbit myosin rod have been investigated. Cyanogen bromide cleavage of long myosin subfragment-2 produced one coiled-coil alpha-helical fragment corresponding to short subfragment-2 with molecular weight 90,000 (Mr = 45,000) and two fragments from the hinge region with molecular weights of 32,000 to 34,000 (Mr = 16,000 to 17,000) and 24,000 to 26,000 (Mr = 12,000 to 13,000). Optical rotation melting experiments and temperature-jump kinetic studies of long subfragment-2 and its cyanogen bromide fragments show that the hinge and the short subfragment-2 domains melt as quasi-independent co-operative units. The alpha-helical structure within the hinge has an appreciably lower thermal stability than the flanking short subfragment-2 and light meromyosin regions of the myosin rod. Two relaxation processes for helix-melting, one in the submillisecond range (tau f) and the other in the millisecond range (tau s), are observed in the light meromyosin and short subfragment-2 regions of the rod, but melting in the hinge domain is dominated by the fast (tau f) process. Results suggest that the hinge domain of the subfragment-2 link may be the locus of force generation in a cycling cross-bridge.

The structure and stability of trypsin-resistant segments from rabbit tropomyosin

Tropomyosin was found to undergo only limited digestion by trypsin at 0 degrees C and the two segments that accumulated amounted to two-thirds of the original protein. They are referred to as segments A and B. These segments were not resistant to trypsin digestion at 20 degrees C and at the latter temperature no large fragments remained as judged by disc gel electrophoresis. Segments A and B were separated from each other on the basis of solubility differences and were found to have molecular weights of 24600 and 21900 respectively. Each of the segments appeared to retain about 70-75% of the helical conformation as judged by circular dichroism at 20 degrees C. However, the segments did not show any of the inhibitory activity of the parent tropomyosin molecule when mixed with troponin in the Mg2+-actomyosin ATPase system. Amino acid analysis showed that the portion of tropomyosin that was digested by trypsin (EC 3.4.21.4) had a lower content of the helix stabilizing residues Glu and Leu and a higher content of the helix-destabilizing residues Arg and Lys. These differences indicate that the digested portion should be less stable in the helical conformation than the two trypsin-resistant segments. End group determinations along with the results of the amino acid analysis indicated that segment A was probably derived from the central one-third of tropomyosin and segment B from the C-terminal one-third. By the process of elimination the N-terminal third appears to have been more liable region that was digested by trypsin. The segments A and B were shown to differ in their stability to denaturation by guanidine-HCl and elevated temperature. All of these observations indicate that tropomyosin is not a uniform structure and is composed of regions of different stability.