Low-amplitude pulses to the circulation through periodic acceleration induces endothelial-dependent vasodilatation

A Nonrandomized Trial of the Effects of Passive Simulated Jogging on Short-Term Heart Rate Variability in Type 2 Diabetic Subjects

Background

Diabetes mellitus has reached global epidemic proportions, with type 2 diabetes (T2DM) comprising more than 90% of all subjects with diabetes. Cardiovascular autonomic neuropathy (CAN) frequently occurs in T2DM. Heart rate variability (HRV) reflects a neural balance between the sympathetic and parasympathetic autonomic nervous systems (ANS) and a marker of CAN. Reduced HRV has been shown in T2DM and improved by physical activity and exercise. External addition of pulses to the circulation, as accomplished by a passive simulated jogging device (JD), restores HRV in nondiseased sedentary subjects after a single session. We hypothesized that application of JD for a longer period (7 days) might improve HRV in T2DM participants.

Methods

We performed a nonrandomized study on ten T2DM subjects (age range 44-73 yrs) who were recruited and asked to use a physical activity intervention, a passive simulated jogging device (JD) for 7 days. JD moves the feet in a repetitive and alternating manner; the upward movement of the pedal is followed by a downward movement of the forefoot tapping against a semirigid bumper to simulate the tapping of feet against the ground during jogging. Heart rate variability (HRV) analysis was performed using an electrocardiogram in each subject in seated posture on day 1 (baseline, BL), after seven days of JD (JD7), and seven days after discontinuation of JD (Post-JD). Time domain variables were computed, viz., standard deviation of all normal RR intervals (SDNN), standard deviation of the delta of all RR intervals (SDΔNN), and the square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD). Frequency domain measures were determined using a standard Fast Fourier spectral analysis, as well as the parameters of the Poincaré plots (SD1 and SD2).

Results

Seven days of JD significantly increased SDNN, SDΔNN, RMSSD, and both SD1 and SD2 from baseline values. The latter parameters remained increased Post-JD. JD did not modify the frequency domain measures of HRV.

Conclusion

A passive simulated jogging device increased the time domain and Poincaré variables of HRV in T2DM. This intervention provided effortless physical activity as a novel method to harness the beneficial effects of passive physical activity for improving HRV in T2DM subjects.

Non-Invasive Pulsatile Shear Stress Modifies Endothelial Activation; A Narrative Review

The monolayer of cells that line both the heart and the entire vasculature is the endothelial cell (EC). These cells respond to external and internal signals, producing a wide array of primary or secondary messengers involved in coagulation, vascular tone, inflammation, and cell-to-cell signaling. Endothelial cell activation is the process by which EC changes from a quiescent cell phenotype, which maintains cellular integrity, antithrombotic, and anti-inflammatory properties, to a phenotype that is prothrombotic, pro-inflammatory, and permeable, in addition to repair and leukocyte trafficking at the site of injury or infection. Pathological activation of EC leads to increased vascular permeability, thrombosis, and an uncontrolled inflammatory response that leads to endothelial dysfunction. This pathological activation can be observed during ischemia reperfusion injury (IRI) and sepsis. Shear stress (SS) and pulsatile shear stress (PSS) are produced by mechanical frictional forces of blood flow and contraction of the heart, respectively, and are well-known mechanical signals that affect EC function, morphology, and gene expression. PSS promotes EC homeostasis and cardiovascular health. The archetype of inducing PSS is exercise (i.e., jogging, which introduces pulsations to the body as a function of the foot striking the pavement), or mechanical devices which induce external pulsations to the body (Enhanced External Pulsation (EECP), Whole-body vibration (WBV), and Whole-body periodic acceleration (WBPA aka pGz)). The purpose of this narrative review is to focus on the aforementioned noninvasive methods to increase PSS, review how each of these modify specific diseases that have been shown to induce endothelial activation and microcirculatory dysfunction (Ischemia reperfusion injury-myocardial infarction and cardiac arrest and resuscitation), sepsis, and lipopolysaccharide-induced sepsis syndrome (LPS)), and review current evidence and insight into how each may modify endothelial activation and how these may be beneficial in the acute and chronic setting of endothelial activation and microvascular dysfunction.

The effects of a motorized passive simulated jogging device on descent of the arterial pulse waveform dicrotic notch: A single arm placebo-controlled cross-over trial

Whole Body Periodic Acceleration (WBPA, pGz), is a bed that moves the body headward to forward, adds pulses to the circulation inducing descent of the dicrotic notch (DN) on the pulse waveform with an increase in a/b ratio (a = the height of the pulse waveform and b = the height of the secondary wave). Since the WBPA is large, heavy, and non-portable, we engineered a portable device (Jogging Device, JD). JD simulates passive jogging and introduces pulsations to the circulation. We hypothesized that JD would increase the a/b ratio during and after its use. In Study A, a single-arm placebo-controlled cross-over trial was conducted in24 adults (53.8 ± 14.4 years) using JD or control (CONT) for 30 min. Blood pressure (BPs and BPd) and photoplethysmograph pulse (a/b) were measured at baseline (BL), during 30 min of JD or CONT, and 5 and 60 min after. In Study B (n = 20, 52.2 ± 7 years), a single-arm observational trial of 7 consecutive days of JD on BP and a/b, measured at BL, and after 7 days of JD and 48 and 72 hr after its discontinuation. In Study A, BPs, and BPd decreased during JD by 13% and 16%, respectively, while in CONT both increased by 2% and 2.5%, respectively. The a/b increased by 2-fold and remained greater than 2-fold at all-time points, with no change in a/b during CONT. In Study B, BPs and BPd decreased by 9% and remained below BL, at 72 hr after discontinuation of JD. DN descent also occurred after 7 days of JD with a/b increase of 80% and remained elevated by 60% for at least 72 h. JD improves acute and longer-term vascular hemodynamics with an increase in a/b, consistent with increased effects of nitric oxide (NO). JD may have significant clinical and public health implications.

The Effects of Passive Simulated Jogging on Parameters of Explosive Handgrip in Nondiabetics and Type 2 Diabetics: A Single Arm Study

Aims

Type 2 diabetes (T2D) is associated with sarcopenia and decreased muscle strength. Explosive and isometric voluntary handgrip strengths (EHGS and HGS) are frequently utilized methods to ascertain health status and a marker of overall muscle strength. We have previously shown that a portable, motorized device, which produces effortless, rapid stepping in place (passive simulated jogging device (JD)), improves glucose homeostasis. This study quantitatively evaluated the effects of JD in modifying parameters of the modified EHGS curve in T2D and nondiabetic (ND) subjects.

Methods

Twenty-one adult participants (11 ND and 10 T2D) (mean age: 41.3 ± 13.5 yr) performed a modified explosive handgrip strength (EHGS) test on study day 1 followed by daily use of JD (90 min per day) for 7 days. The EHGS was repeated after 3 and 7 days' use of JD (JD3 and JD7) and 3 days after completion of JD (Carryover). EHGS curves were analyzed for the following: maximal peak force value (MAX); rate of force development at 25%,75%, and 90% of maximum force; and maximum force (RFD_25%, RFD_75%, RFD_90%, and RFD_max); time to 90%, 75%, and 25% of maximal force (t₉₀, t₇₅, t₂₅) and time to maximal force (t_max); and the integrated area under the curve for force vs. time until task failure (iAUC_TF); and fatigue resistance times at 50% and 25% of maximal force (FR₅₀ and FR25) and fatigue resistance time to task failure (FR_TF).

Results

At baseline, T2D had lower MAX compared to ND. There were no differences at baseline for force development time or fatigue resistance time between T2D and ND. In both T2D and ND, 7 days of JD increased FR₂₅ and FR_TF and iAUC_TF compared to baseline.

Conclusion

JD for at least 7 days prior to EHGS increased time to task failure (fatigue resistance) and iAUC_TF of the force-time curve. JD is a reasonable intervention to decrease sedentary behavior and improve muscle fatigue resistance under various clinical and nonclinical scenarios. This trial is registered with NCT03550105 (08-06-2018).

Pulsatility damping in the microcirculation: Basic pattern and modulating factors

Blood flow pulsatility is an important determinant of macro- and microvascular physiology. Pulsatility is damped largely in the microcirculation, but the characteristics of this damping and the factors that regulate it have not been fully elucidated yet. Applying computational approaches to real microvascular network geometry, we examined the pattern of pulsatility damping and the role of potential damping factors, including pulse frequency, vascular viscous resistance, vascular compliance, viscoelastic behavior of the vessel wall, and wave propagation and reflection. To this end, three full rat mesenteric vascular networks were reconstructed from intravital microscopic recordings, a one-dimensional (1D) model was used to reproduce pulsatile properties within the network, and potential damping factors were examined by sensitivity analysis. Results demonstrate that blood flow pulsatility is predominantly damped at the arteriolar side and remains at a low level at the venular side. Damping was sensitive to pulse frequency, vascular viscous resistance and vascular compliance, whereas viscoelasticity of the vessel wall or wave propagation and reflection contributed little to pulsatility damping. The present results contribute to our understanding of mechanical forces and their regulation in the microcirculation.

Possible Mechanisms for the Effects of Sound Vibration on Human Health

This paper presents a narrative review of research literature to “map the landscape” of the mechanisms of the effect of sound vibration on humans including the physiological, neurological, and biochemical. It begins by narrowing music to sound and sound to vibration. The focus is on low frequency sound (up to 250 Hz) including infrasound (1–16 Hz). Types of application are described and include whole body vibration, vibroacoustics, and focal applications of vibration. Literature on mechanisms of response to vibration is categorized into hemodynamic, neurological, and musculoskeletal. Basic mechanisms of hemodynamic effects including stimulation of endothelial cells and vibropercussion; of neurological effects including protein kinases activation, nerve stimulation with a specific look at vibratory analgesia, and oscillatory coherence; of musculoskeletal effects including muscle stretch reflex, bone cell progenitor fate, vibration effects on bone ossification and resorption, and anabolic effects on spine and intervertebral discs. In every category research on clinical applications are described. The conclusion points to the complexity of the field of vibrational medicine and calls for specific comparative research on type of vibration delivery, amount of body or surface being stimulated, effect of specific frequencies and intensities to specific mechanisms, and to greater interdisciplinary cooperation and focus.

Cardioprotective Effect of Whole Body Periodic Acceleration in Dystrophic Phenotype mdx Rodent

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle wasting and the development of a dilated cardiomyopathy (DCM), which is the leading cause of death in DMD patients. Despite knowing the cause of DMD, there are currently no therapies which can prevent or reverse its inevitable progression. We have used whole body periodic acceleration (WBPA) as a novel tool to enhance intracellular constitutive nitric oxide (NO) production. WBPA adds small pulses to the circulation to increase pulsatile shear stress, thereby upregulating endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) and subsequently elevating the production of NO. Myocardial cells from dystrophin-deficient 15-month old mdx mice have contractile deficiency, which is associated with elevated concentrations of diastolic Ca²⁺ ([Ca²⁺]_d), Na⁺ ([Na⁺]_d), and reactive oxygen species (ROS), increased cell injury, and decreased cell viability. Treating 12-month old mdx mice with WBPA for 3 months reduced cardiomyocyte [Ca²⁺]_d and [Na⁺]_d overload, decreased ROS production, and upregulated expression of the protein utrophin resulting in increased cell viability, reduced cardiomyocyte damage, and improved contractile function compared to untreated mdx mice.

Whole body periodic acceleration (pGz) improves endotoxin induced cardiomyocyte contractile dysfunction and attenuates the inflammatory response in mice

Sepsis-induces myocardial contractile dysfunction. We previously showed that whole body periodic acceleration (pGz), the sinusoidal motion of the supine body head-foot ward direction significantly improves survival and decreases microvascular permeability in a lethal model of sepsis. We tested the hypothesis that pGz improves LPS induced cardiomyocyte contractile dysfunction and decreases LPS pro-inflammatory cytokine response when applied pre- or post-treatment. Isolated cardiomyocytes were obtained from mice that received LPS who had been pre-treated with pGz for three days (pGz-LPS) or control. Peak shortening (PS), maximal velocity of shortening (+dL/dt), and relengthening (-dL/dt) as well as diastolic intracellular calcium concentration ([Ca⁺²]_d), sodium ([Na⁺]_d), reactive oxygen species (ROS), and cardiac troponin (cTnT) production were measured. LPS decreased PS, +dL/dt, and -dL/dt, by 37%, 41% and 35% change respectively (p < 0.01), increased [Ca⁺²]_d, [Na⁺]_d, ROS, and cTnT by 343%, 122%, 298%, and 610% change respectively (p < 0.01) compared to control. pGz pre-treatment attenuated the parameters mentioned above. In a separate cohort, the effects of a lethal dose of LPS on protein expression of nitric oxide synthases (iNOS, eNOS, nNOS), pro- and anti-inflammatory cytokines in hearts of mice was studied in pre-treated with pGz for three days prior to LPS (pGz-LPS) and post-treated with pGz 30 min after LPS (LPS-pGz) were determined. LPS increased expression of early and late iNOS and decreased expression of eNOS, phosphorylated eNOS (p-eNOS), and nNOS. Both pre- and post-treatment with pGz markedly reduced early and late pro-inflammatory surge. Therefore, pre- and post-treatment with pGz improves LPS-induced cardiomyocyte dysfunction, decreases iNOS expression, and increases cytoprotective eNOS and nNOS, with decreased pro-inflammatory response. Such results have potential for translation to benefit outcomes in human sepsis.

A single arm trial using passive simulated jogging for blunting acute hyperglycemia

Glycemic fluctuations increase oxidative stress, promote endothelial dysfunction and cardiovascular disease. Reducing glycemic fluctuations is beneficial. We previously reported that a portable motorized passive simulated jogging device, (JD) reduces 24 h glycemic indices in type 2 and non-diabetic subjects. This study evaluates effectiveness and feasibility of JD in blunting large glycemic fluctuation induced by an oral glucose tolerance test (OGTT). The study was performed in 10 adult participants mean age 41.3 ± 13.5 year using interstitial glucose monitor (IG). Each participant fasted for 8 h. followed by an OGTT (Pre-JD), thereafter JD was used for 90 min per day for 7 days, without change to diet or activities of daily living. A repeat OGTT (Post-JD) was performed after completion. The integrated area under the curve (iAUC_2h–4h) was computed for the OGTT Pre-JD and Post-JD. Seven days of JD blunted the glucose fluctuation produced by OGTT. JD decreased AUC_2h by 17 ± 4.7% and iAUC_4h by 15 ± 5.9% (p < 0.03). In healthy mostly obese participants 7 days of JD blunts the hyperglycemic response produced by an OGTT. JD may be an adjunct to current glycemic management, it can be applied in different postures for those who cannot (due to physical or cognitive limitations) or will not exercise.

Trial registration:ClinicalTrials.gov NCT03550105 (08-06-2018).

The Endothelium as a Therapeutic Target in Diabetes: A Narrative Review and Perspective

Diabetes has reached worldwide epidemic proportions, and threatens to be a significant economic burden to both patients and healthcare systems, and an important driver of cardiovascular mortality and morbidity. Improvement in lifestyle interventions (which includes increase in physical activity via exercise) can reduce diabetes and cardiovascular disease mortality and morbidity. Encouraging a population to increase physical activity and exercise is not a simple feat particularly in individuals with co-morbidities (obesity, heart disease, stroke, peripheral vascular disease, and those with cognitive and physical limitations). Translation of the physiological benefits of exercise within that vulnerable population would be an important step for improving physical activity goals and a stopgap measure to exercise. In large part many of the beneficial effects of exercise are due to the introduction of pulsatile shear stress (PSS) to the vascular endothelium. PSS is a well-known stimulus for endothelial homeostasis, and induction of a myriad of pathways which include vasoreactivity, paracrine/endocrine function, fibrinolysis, inflammation, barrier function, and vessel growth and formation. The endothelial cell mediates the balance between vasoconstriction and relaxation via the major vasodilator endothelial derived nitric oxide (eNO). eNO is critical for vasorelaxation, increasing blood flow, and an important signaling molecule that downregulates the inflammatory cascade. A salient feature of diabetes, is endothelial dysfunction which is characterized by a reduction of the bioavailability of vasodilators, particularly nitric oxide (NO). Cellular derangements in diabetes are also related to dysregulation in Ca²⁺ handling with increased intracellular Ca²⁺overload, and oxidative stress. PSS increases eNO bioavailability, reduces inflammatory phenotype, decreases intracellular Ca²⁺ overload, and increases antioxidant capacity. This narrative review and perspective will outline four methods to non-invasively increase PSS; Exercise (the prototype for increasing PSS), Enhanced External Counterpulsation (EECP), Whole Body Vibration (WBV), Passive Simulated Jogging and its predicate device Whole Body Periodic Acceleration, and will discuss current knowledge on their use in diabetes.

Endothelial pulsatile shear stress is a backstop for COVID-19

There has not been any means to inhibit replication of the SARS-CoV-2 virus responsible for the rapid, deadly spread of the COVID-19 pandemic and an effective, safe, tested across diverse populations vaccine still requires extensive investigation. This review deals with the repurpose of a wellness technology initially fabricated for combating physical inactivity by increasing muscular activity. Its action increases pulsatile shear stress (PSS) to the endothelium such that the bioavailability of nitric oxide (NO) and other mediators are increased throughout the body. In vitro evidence indicates that NO inhibits SARS-CoV-2 virus replication but there are no publications of NO delivery to the virus in vivo. It will be shown that increased PSS has potential in vivo to exert anti-viral properties of NO as well as to benefit endothelial manifestations of COVID-19 thereby serving as a safe and effective backstop.

Can Physical Activity While Sedentary Produce Health Benefits? A Single-Arm Randomized Trial

Background

Sedentary time poses a risk to health. Substituting physical activity for inactivity is obvious but this requires a behavior change. Interventions advocated to decrease uninterrupted physical inactivity (defined as Metabolic Equivalent of Task (METS) less than 1.5) are important. One such intervention is accomplished with the Gentle Jogger (GJ), a low risk motorized wellness device which produces effortless, rapid motion of the lower extremities simulating locomotion or fidgeting. GJ produces health benefits in type 2 diabetes, heart disease, and high blood pressure. The purpose of this trial was to ascertain whether GJ increases METS above 1.5 to explain its effectiveness despite sedentary behavior or whether tapping is responsible.

Methods

A randomized single-arm trial was conducted. Subjects were randomized to begin the study in either the supine or seated postures and on the same day crossed over with the starting posture reversed. Oxygen consumption was measured at rest and during GJ.

Results

Twenty-six subjects were studied (15 women and 11 men) with a mean age of 44 ± 15 years and BMI 27.9 ± 5.0, 19 were overweight or obese, and 7 had normal BMI. GJ increased oxygen consumption and METS 15% in the seated posture and 13% in the supine posture. No individual receiving GJ achieved METS exceeding 1.5.

Conclusions

In a moderately obese population, GJ in seated or supine posture did not exceed 1.5 METS. The values are comparable to those reported for sit-stand interventions and cannot explain the health benefits of GJ.

Trial registration

ClinicalTrials.gov, NCT03602365. Registered on July 26, 2018

Whole body periodic acceleration improves survival and microvascular leak in a murine endotoxin model

Sepsis is a life threatening condition which produces multi-organ dysfunction with profound circulatory and cellular derangements. Administration of E.Coli endotoxin (LPS) produces systemic inflammatory effects of sepsis including disruption of endothelial barrier, and if severe enough death. Whole body periodic acceleration (pGz) is the headward-footward motion of the body. pGz has been shown to induce pulsatile shear stress to the endothelium, thereby releasing vascular and cardio protective mediators. The purpose of this study was to determine whether or not pGz performed as a pre-treatment or post-treatment strategy improves survival in a lethal murine endotoxin model.This study was designed as a prospective randomized controlled study in mice. pGz was performed in mice as pre-treatment (pGz-LPS, 3 days prior to LPS), post-treatment (LPS- pGz, 30 min after LPS) strategies or Control (LPS-CONT), in a lethal murine model of endotoxemia. Endotoxemia was induced with intraperitoneal injection of E.Coli LPS (40mg/kg). In a separate group of mice, a nonspecific nitric oxide synthase inhibitor (L-NAME) was provided in their drinking water and pGz-LPS and LPS-pGz performed to determine the effect of nitric oxide (NO) inhibition on survival. In another subset of mice, micro vascular leakage was determined. Behavioral scoring around the clock was performed in all mice at 30 min intervals after LPS administration, until 48 hrs. survival or death. LPS induced 100% mortality in LPS-CONT animals by 30 hrs. In contrast, survival to 48 hrs. occurred in 60% of pGz-LPS and 80% of LPS-pGz. L-NAME abolished the survival effects of pGz. Microvascular leakage was markedly reduced in both pre and post pGz treated animals and was associated with increased tyrosine kinase endothelial-enriched tunica interna endothelial cell kinase 2 (TIE2) receptor and its phosphorylation (p-TIE2). In a murine model of lethal endotoxemia, pGz performed as a pre or post treatment strategy significantly improved survival, and markedly reduced microvascular leakage. The effect was modulated, in part, by NO since a non-selective inhibitor of NO abolished the pGz survival effect.

Changes of blood pressure following initiation of physical inactivity and after external addition of pulses to circulation

PURPOSE

To determine whether an innovative, motorized, wellness device that effortlessly produces physical activity (JD) can mitigate the hypertensive effects of prolonged sitting or lying down.

METHODS

Twenty-two normotensive and hypertensive adults of both genders gave informed consent to participate in a randomized controlled crossover study of a passive simulated jogging device (JD) in both supine and seated postures. Each study participant was monitored with a continuous non-invasive arterial pressure monitoring device (CNAP) over 60 min. The initial 10 min served as baseline for each posture. The subjects were randomized to begin with either JD or SHAM control for 30 min, and monitoring was continued for an additional 10 min in one posture; three days later posture and order of JD or SHAM were changed.

RESULTS

In both seated and supine postures, SHAM was associated with a significant rise in blood pressure (BP) which was observed within 5-10 min; it continued to rise or remain elevated for over a 40-min observation period. In contrast, JD produced a significant decrease in both systolic and diastolic blood pressure in both postures. During recovery in seated posture JD decreased systolic and diastolic BP by - 8.1 and - 7.6 mmHg, respectively. In supine posture, a similar decrease in BP occurred.

CONCLUSIONS

There is rapid onset of increase in systolic and diastolic BP with physical inactivity in both supine and seated postures. Administration of JD significantly decreased BP in both postures. Further studies are needed to assess long-term effectiveness.

Are We Doing More Than We Know? Possible Mechanisms of Response to Music Therapy

Due to advances in medical knowledge the population of older adults struggling with issues of aging like Alzheimer's disease (AD), Parkinson's disease (PD), and stroke is growing. There is a need for therapeutic interventions to provide adaptive strategies to sustain quality of life, decrease neurologic impairment, and maintain or slow cognitive decline and function due to degenerative neurologic diseases. Musical interventions with adults with cognitive impairments have received increased attention over the past few years, such as the value of personalized music listening in the iPod project for AD (1); music as a tool to decrease agitation and anxiety in dementia (2); and music to aid in episodic memory (3); Rhythmic Auditory Stimulation as rehabilitation for PD (4); and recently the potential of 40 Hz sensory brain stimulation with AD and PD (5, 6). These approaches indicate the expanding scope and efficacy of music therapy and the potential mechanisms involved. This paper explicates a four-level model of mechanisms of music response (7, 8) that may help understand current music therapy approaches and treatments and help focus future research. Each level will be illustrated with research and suggestions for research directions.

Increased constitutive nitric oxide production by whole body periodic acceleration ameliorates alterations in cardiomyocytes associated with utrophin/dystrophin deficiency

Duchenne Muscular Dystrophy (DMD) cardiomyopathy is a progressive lethal disease caused by the lack of the dystrophin protein in the heart. The most widely used animal model of DMD is the dystrophin-deficient mdx mouse; however, these mice exhibit a mild dystrophic phenotype with heart failure only late in life. In contrast, mice deficient for both dystrophin and utrophin (mdx/utrn^-/-, or dKO) can be used to model severe DMD cardiomyopathy where pathophysiological indicators of heart failure are detectable by 8-10weeks of age. Nitric oxide (NO) is an important signaling molecule involved in vital functions of regulating rhythm, contractility, and microcirculation of the heart, and constitutive NO production affects the function of proteins involved in excitation-contraction coupling. In this study, we explored the efficacy of enhancing NO production as a therapeutic strategy for treating DMD cardiomyopathy using the dKO mouse model of DMD. Specifically, NO production was induced via whole body periodic acceleration (pGz), a novel non-pharmacologic intervention which enhances NO synthase (NOS) activity through sinusoidal motion of the body in a headward-footward direction, introducing pulsatile shear stress to the vascular endothelium and cardiomyocyte plasma membrane. Male dKO mice were randomized at 8weeks of age to receive daily pGz (480cpm, Gz±3.0m/s², 1h/d) for 4weeks or no treatment, and a separate age-matched group of WT animals (pGz-treated and untreated) served as non-diseased controls. At the conclusion of the protocol, cardiomyocytes from untreated dKO animals had, respectively, 4.3-fold and 3.5-fold higher diastolic resting concentration of Ca²⁺ ([Ca²⁺]_d) and Na⁺ ([Na⁺]_d) compared to WT, while pGz treatment significantly reduced these levels. For dKO cardiomyocytes, pGz treatment also improved the depressed contractile function, decreased oxidative stress, blunted the elevation in calpain activity, and mitigated the abnormal increase in [Ca²⁺]_d upon mechanical stress. These improvements culminated in a significant reduction in circulating cardiac troponin T (cTnT) and an extension of the median lifespan of dKO mice from 16 to 31weeks. Treatment with L-NAME (NOS inhibitor) significantly decreased overall lifespan and abolished the cardioprotective properties elicited by pGz. Our results provide evidence that enhancement of NO synthesis by pGz can ameliorate cellular dysfunction in dKO cardiomyocytes and may represent a novel therapeutic intervention in DMD cardiomyopathy patients.

Modeling of pulsatile flow-dependent nitric oxide regulation in a realistic microvascular network

Hemodynamic pulsatility has been reported to regulate microcirculatory function. To quantitatively assess the impact of flow pulsatility on the microvasculature, a mathematical model was first developed to simulate the regulation of NO production by pulsatile flow in the microcirculation. Shear stress and pressure pulsatility were selected as regulators of endothelial NO production and NO-dependent vessel dilation as feedback to control microvascular hemodynamics. The model was then applied to a real microvascular network of the rat mesentery consisting of 546 microvessels. As compared to steady flow conditions, pulsatile flow increased the average NO concentration in arterioles from 256.8±93.1nM to 274.8±101.1nM (P<0.001), with a corresponding increase in vessel dilation by approximately 7% from 27.5±10.6% to 29.4±11.4% (P<0.001). In contrast, NO concentration and vessel size showed a far lesser increase (about 1.7%) in venules under pulsatile flow as compared to steady flow conditions. Network perfusion and flow heterogeneity were improved under pulsatile flow conditions, and vasodilation within the network was more sensitive to heart rate changes than pulse pressure amplitude. The proposed model simulates the role of flow pulsatility in the regulation of a complex microvascular network in terms of NO concentration and hemodynamics under varied physiological conditions.

Antioxidant Properties of Whole Body Periodic Acceleration (pGz)

The recognition that oxidative stress is a major component of several chronic diseases has engendered numerous trials of antioxidant therapies with minimal or no direct benefits. Nanomolar quantities of nitric oxide released into the circulation by pharmacologic stimulation of eNOS have antioxidant properties but physiologic stimulation as through increased pulsatile shear stress of the endothelium has not been assessed. The present study utilized a non-invasive technology, periodic acceleration (pGz) that increases pulsatile shear stress such that upregulation of cardiac eNOS occurs, We assessed its efficacy in normal mice and mouse models with high levels of oxidative stress, e.g. Diabetes type 1 and mdx (Duchene Muscular Dystrophy). pGz increased protein expression and upregulated eNOS in hearts. Application of pGz was associated with significantly increased expression of endogenous antioxidants (Glutathioneperoxidase-1(GPX-1), Catalase (CAT), Superoxide, Superoxide Dismutase 1(SOD1). This led to an increase of total cardiac antioxidant capacity along with an increase in the antioxidant response element transcription factor Nrf2 translocation to the nucleus. pGz decreased reactive oxygen species in both mice models of oxidative stress. Thus, pGz is a novel non-pharmacologic method to harness endogenous antioxidant capacity.

Non-invasive technology that improves cardiac function after experimental myocardial infarction: Whole Body Periodic Acceleration (pGz)

Myocardial infarction (MI) may produce significant inflammatory changes and adverse ventricular remodeling leading to heart failure and premature death. Pharmacologic, stem cell transplantation, and exercise have not halted the inexorable rise in the prevalence and great economic costs of heart failure despite extensive investigations of such treatments. New therapeutic modalities are needed. Whole Body Periodic Acceleration (pGz) is a non-invasive technology that increases pulsatile shear stress to the endothelium thereby producing several beneficial cardiovascular effects as demonstrated in animal models, normal humans and patients with heart disease. pGz upregulates endothelial derived nitric oxide synthase (eNOS) and its phosphorylation (p-eNOS) to improve myocardial function in models of myocardial stunning and preconditioning. Here we test whether pGz applied chronically after focal myocardial infarction in rats improves functional outcomes from MI. Focal MI was produced by left coronary artery ligation. One day after ligation animals were randomized to receive daily treatments of pGz for four weeks (MI-pGz) or serve as controls (MI-CONT), with an additional group as non-infarction controls (Sham). Echocardiograms and invasive pressure volume loop analysis were carried out. Infarct transmurality, myocardial fibrosis, and markers of inflammatory and anti-inflammatory cytokines were determined along with protein analysis of eNOS, p-eNOS and inducible nitric oxide synthase (iNOS).At four weeks, survival was 80% in MI-pGz vs 50% in MI-CONT (p< 0.01). Ejection fraction and fractional shortening and invasive pressure volume relation indices of afterload and contractility were significantly better in MI-pGz. The latter where associated with decreased infarct transmurality and decreased fibrosis along with increased eNOS, p-eNOS. Additionally, MI-pGz had significantly lower levels of iNOS, inflammatory cytokines (IL-6, TNF-α), and higher level of anti-inflammatory cytokine (IL-10). pGz improved survival and contractile performance, associated with improved myocardial remodeling. pGz may serve as a simple, safe, non-invasive therapeutic modality to improve myocardial function after MI.

A one-dimensional mathematical model for studying the pulsatile flow in microvascular networks

Techniques that model microvascular hemodynamics have been developed for decades. While the physiological significance of pressure pulsatility is acknowledged, most of the microcirculatory models use steady flow approaches. To theoretically study the extent and transmission of pulsatility in microcirculation, dynamic models need to be developed. In this paper, we present a one-dimensional model to describe the dynamic behavior of microvascular blood flow. The model is applied to a microvascular network from a rat mesentery. Intravital microscopy was used to record the morphology and flow velocities in individual vessel segments, and boundaries are defined according to the experimental data. The system of governing equations constituting the model is solved numerically using the discontinuous Galerkin method. An implicit integration scheme is adopted to increase computing efficiency. The model allows the simulation of the dynamic properties of blood flow in microcirculatory networks, including the pressure pulsatility (quantified by a pulsatility index) and pulse wave velocity (PWV). From the main input arteriole to the main output venule, the pulsatility index decreases by 66.7%. PWV obtained along arterioles declines with decreasing diameters, with mean values of 77.16, 25.31, and 8.30 cm/s for diameters of 26.84, 17.46, and 13.33 μm, respectively. These results suggest that the 1D model developed is able to simulate the characteristics of pressure pulsatility and wave propagation in complex microvascular networks.

Arterial pressure and cerebral blood flow variability: friend or foe? A review

Variability in arterial pressure and cerebral blood flow has traditionally been interpreted as a marker of cardiovascular decompensation, and has been associated with negative clinical outcomes across varying time scales, from impending orthostatic syncope to an increased risk of stroke. Emerging evidence, however, suggests that increased hemodynamic variability may, in fact, be protective in the face of acute challenges to perfusion, including significant central hypovolemia and hypotension (including hemorrhage), and during cardiac bypass surgery. This review presents the dichotomous views on the role of hemodynamic variability on clinical outcome, including the physiological mechanisms underlying these patterns, and the potential impact of increased and decreased variability on cerebral perfusion and oxygenation. We suggest that reconciliation of these two apparently discrepant views may lie in the time scale of hemodynamic variability; short time scale variability appears to be cerebroprotective, while mid to longer term fluctuations are associated with primary and secondary end-organ dysfunction.

Preliminary observations of passive exercise using whole body periodic acceleration on coronary microcirculation and glucose tolerance in patients with type 2 diabetes

BACKGROUND

The whole body periodic acceleration (WBPA) system was recently developed as a passive exercise device by providing increased pulsatile shear stress for improvement of endothelial function. This study aimed to investigate the acute effects of WBPA on coronary microcirculation and glucose tolerance in patients with type 2 diabetes (T2D).

METHODS

The study subjects were 8 patients with T2D who underwent transthoracic Doppler echocardiography for the assessment of coronary flow reserve (CFR) before and immediately after a 45-min session of WBPA. The flow velocity in the distal portion of the left anterior descending coronary artery was measured at baseline and during adenosine infusion. The CFR represented the ratio of hyperemic to basal mean diastolic flow velocity.

RESULTS

WBPA increased CFR from 2.3±0.3 to 2.6±0.4 (p=0.02). WBPA decreased serum insulin level from 26±19μIU/ml to 19±15μIU/ml (p=0.01) and increased total adiponectin from 11.6±7.3μg/ml to 12.5±8.0μg/ml (p=0.02) and high molecular weight adiponectin from 4.9±3.6μg/ml to 5.3±3.9μg/ml (p=0.03), whereas the serum glucose level was stable from 207±66mg/dl to 203±56mg/dl (p=0.8).

CONCLUSIONS

This study demonstrates that a single session of WBPA treatment simultaneously improved coronary microcirculation and glucose tolerance in patients with T2D.

Whole body periodic acceleration (pGz) improves survival and allows for resuscitation in a model of severe hemorrhagic shock in pigs

BACKGROUND

Whole body periodic acceleration (pGz), the repetitive, head-foot sinusoidal motion of the body, increases pulsatile shear stress on the vascular endothelium producing increased release of endothelial derived nitric oxide (eNO) into circulation. Based upon prior CPR investigations, we hypothesized that pGz instituted prior to and during hemorrhagic shock (HS) should improve survival.

MATERIALS AND METHODS

Sixteen anesthetized male pigs, 23 ± 5 kg, were randomized to receive 1 h pGz or no pGz (CONT) prior to and during severe controlled graded HS up to 2-1/2 h. HS was induced by removing blood at 10 mL/kg increments from the circulation at 30-min intervals up to a maximum blood loss of 50 mL/kg. Thirty minutes after maximum blood loss, shed blood and lactated Ringers solution was infused intravenously.

RESULTS

All animals survived up to 30 mL/kg blood loss. Survival and return to normal blood pressure to 120 min was achieved in 50% of animals receiving pGz compared with none in CONT. Cardiac output, blood pressure, and oxygen delivery decreased equally in both groups but oxygen consumption was significantly lower with pGz than CONT during all hemorrhage time points. Regional blood flow (RBF) was preserved in brain, heart, kidneys, ileum, and stomach in both groups up to 40 mL/kg of blood loss. After 40 mL/kg blood loss, RBF was much better preserved in pGz than CONT.

CONCLUSIONS

pGz applied 1 h prior to and during severe graded hemorrhagic shock delays onset of irreversible shock, enabling potential restoration of blood loss and survival.

"Passive exercise" using whole body periodic acceleration: effects on coronary microcirculation

BACKGROUND

The whole body periodic acceleration (WBPA) system has recently been developed as a "passive exercise" device by providing increased pulsatile shear stress for improvement of endothelial function. This study aimed to investigate the short-term effect of WBPA on coronary flow reserve (CFR) through transthoracic Doppler echocardiography (TTDE) in healthy subjects and patients with coronary artery disease (CAD).

METHODS

This study consisted of 15 healthy subjects and 20 patients with CAD who underwent CFR examination before and immediately after WBPA. The flow velocity in the distal portion of the left anterior descending coronary artery (LAD) was measured with TTDE at baseline and during adenosine infusion. Coronary flow reserve was calculated as the ratio of hyperemic to basal mean diastolic flow velocity.

RESULTS

The WBPA treatment was completed in all 35 subjects without complications. There were no significant differences in heart rate and systolic blood pressure before and after WBPA. Whole body periodic acceleration increased CFR from 3.3 +/- 1.0 to 3.7 +/- 1.1 in the 35 subjects (P < .001). Coronary angiography showed significant LAD narrowing in 8 of the 20 CAD patients, but WBPA increased CFR from 2.4 +/- 0.4 to 2.7 +/- 0.5 in them as well (P < .01).

CONCLUSIONS

This study demonstrates that WBPA improves CFR in healthy subjects and patients with CAD.