Elevations of local intravascular pressures release vasoactive substances in humans

Hongqu Rice Wines Ameliorate High-Fat/High-Fructose Diet-Induced Metabolic Syndrome in Rats

AIM

This study evaluated the possible protective impact of different vintages of Hongqu rice wines on metabolic syndrome (MetS) in rats induced by high-fat/high-fructose diet (HFFD).

METHODS

Rats were randomly divided into six groups and treated with (a) basal diet (13.9 kJ/g); (b) HFFD (20.0% w/w lard and 18.0% fructose, 18.9 kJ/g) and (c-f) HFFD with 3-, 5-, 8- and 15-year-aged Hongqu rice wines (9.96 ml/kg body weight), respectively, at an oral route for 20 weeks.

RESULTS

Hongqu rice wines could alleviate HFFD-induced augment of body weight gain and fat accumulation, and the release of pro-inflammatory cytokines. Glycolipid metabolic abnormalities caused by HFFD were ameliorated after Hongqu rice wines consumption by lowering levels of fasting insulin, GSP, HOMA-IR, AUC of OGTT and ITT, and lipid deposition (reduced contents of TG, TC, FFA and LDL-C, and elevated HDL-C level) in the serum and liver, probably via regulating expressions of genes involving in IRS1/PI3K/AKT pathway, LDL-C uptake, fatty acid β-oxidation, and lipolysis, export and synthesis of TG. In addition, concentrations of MDA and blood pressure markers (ANG-II and ET-1) declined, and activities of antioxidant enzymes (SOD and CAT) were improved in conditions of Hongqu rice wines compared to those in the HFFD group. Eight-year-aged Hongqu rice wine produced a more effective effect on alleviating HFFD-caused MetS among different vintages of Hongqu rice wines.

CONCLUSION

To sum up, Hongqu rice wines exhibited ameliorative effects on HFFD-induced MetS in rats based on antiobesity, antihyperlipidemic, antihyperglycemic, antioxidant, anti-inflammatory and potential antihypertensive properties.

Differential responsiveness of glabrous and nonglabrous skin to local transmural pressure elevations: impact of 5 weeks of iterative local pressure loading

We examined the in vivo pressure-flow relationship in human cutaneous vessels during acute and repeated elevations of local transmural pressure. In 10 healthy men, red blood cell flux was monitored simultaneously on the nonglabrous skin of the forearm and the glabrous skin of a finger during a vascular pressure provocation, wherein the blood vessels of an arm were exposed to a wide range of stepwise increasing distending pressures. Forearm skin blood flux was relatively stable at slight and moderate elevations of distending pressure, whereas it increased approximately three- to fourfold at the highest levels (P = 0.004). Finger blood flux, on the contrary, dropped promptly and consistently throughout the provocation (P < 0.001). Eight of the subjects repeated the provocation trial after a 5-wk pressure-training regimen, during which the vasculature in one arm was exposed intermittently (40 min, 3 times/wk) to increased transmural pressure (from +65 mmHg week 1 to +105 mmHg week 5). The training regimen diminished the pressure-induced increase in forearm blood flux by ∼34% (P = 0.02), whereas it inhibited the reduction in finger blood flux (P < 0.001) in response to slight and moderate distending pressure elevations. The present findings demonstrate that during local pressure perturbations, the cutaneous autoregulatory function is accentuated in glabrous compared with in the nonglabrous skin regions. Prolonged intermittent regional exposures to augmented intravascular pressure blunt the responsiveness of the glabrous skin but enhance arteriolar pressure resistance in the nonglabrous skin.

The Impact of Fitness Status on Vascular and Baroreceptor Function in Healthy Women and Men

BACKGROUND

Chronic endurance exercise training elicits desirable physiological adaptations in the cardiovascular system. The volume of exercise training required to generate healthy adaptations is unclear. This study assessed the effects of differing exercise training levels on arterial stiffness, compliance, and autonomic function.

METHODS

Eighty healthy adults (38.5 ± 9.7 years; 44% female) defined as endurance-trained (ET, n = 29), normally active (NA, n = 27), or inactive (IN, n = 24) participated. Cardiovascular markers, including hemodynamics, large arterial compliance and small arterial compliance (LAC and SAC), carotid-femoral pulse wave velocity (PWV), and spontaneous baroreceptor sensitivity (BRS) were assessed.

RESULTS

ET showed significantly greater LAC values (21.4 ± 6.5) than NA (16.9 ± 2.5; p = 0.002) and IN (14.7 ± 3.2 mL × mm Hg × 10; p = 0.028). Values for SAC and BRS were significantly higher in ET than IN (p < 0.001 and p = 0.028, respectively), but not NA. Compared to IN, PWV values for ET and NA were significantly lower (p < 0.003). After adjusting for covariates (age, sex, and SBP), significant associations with cardiovascular fitness status were noted for all markers but BRS.

CONCLUSION

Endurance exercise increases LAC likely due to high-volume training; however, lower volumes of physical activity may be sufficient to positively benefit vascular health overall.

Adaptation to 5 weeks of intermittent local vascular pressure increments; mechanisms to be considered in the development of primary hypertension?

The aims were to study effects of iterative exposures to moderate elevations of local intravascular pressure on arterial/arteriolar stiffness and plasma levels of vasoactive substances. Pressures in the vasculature of an arm were increased by 150 mmHg in healthy men (n = 11) before and after a 5-wk regimen, during which the vasculature in one arm was exposed to fifteen 40-min sessions of moderately increased transmural pressure (+65 to +105 mmHg). This vascular pressure training and the pressure-distension determinations were conducted by exposing the subjects' arm versus remaining part of the body to differential ambient pressure. During the pressure-distension determinations, venous samples were simultaneously obtained from pressurized and unpressurized vessels. Pressure training reduced arterial pressure distension by 40 ± 23% and pressure-induced flow by 33 ± 30% (P < 0.01), but only in the pressure-trained arm, suggesting local adaptive mechanisms. The distending pressure-diameter and distending pressure-flow curves, with training-induced increments in pressure thresholds and reductions in response gains, suggest that the increased precapillary stiffness was attributable to increased contractility and structural remodeling of the walls. Acute vascular pressure provocation induced local release of angiotensin-II (ANG II) and endothelin-1 (ET-1) (P < 0.05), suggesting that these vasoconstrictors limited the pressure distension. Pressure training increased basal levels of ET-1 and induced local pressure release of matrix metalloproteinase 7 (P < 0.05), suggesting involvement of these substances in vascular remodeling. The findings are compatible with the notion that local intravascular pressure load acts as a prime mover in the development of primary hypertension.NEW & NOTEWORTHY Adaptive responses to arterial/arteriolar pressure elevation have typically been investigated in cross-sectional studies in hypertensive patients or in longitudinal studies in experimental animals. The present investigation shows that in healthy individuals, fifteen 40-min, carefully controlled, moderate transmural pressure elevations markedly increase in vivo stiffness (i.e. reduce pressure distension) in arteries and arterioles. The response is mediated via local mechanisms, and it appears that endothelin-1, angiotensin-II, and matrix metalloproteinase 7 may have key roles.

The role of fibroblast - Cardiomyocyte interaction for atrial dysfunction in HFpEF and hypertensive heart disease

AIMS

Atrial contractile dysfunction is associated with increased mortality in heart failure (HF). We have shown previously that a metabolic syndrome-based model of HFpEF and a model of hypertensive heart disease (HHD) have impaired left atrial (LA) function in vivo (rat). In this study we postulate, that left atrial cardiomyocyte (CM) and cardiac fibroblast (CF) paracrine interaction related to the inositol 1,4,5-trisphosphate signalling cascade is pivotal for the manifestation of atrial mechanical dysfunction in HF and that quantitative atrial remodeling is highly disease-dependent.

METHODS AND RESULTS

Differential remodeling was observed in HHD and HFpEF as indicated by an increase of atrial size in vivo (HFpEF), unchanged fibrosis (HHD and HFpEF) and a decrease of CM size (HHD). Baseline contractile performance of rat CM in vitro was enhanced in HFpEF. Upon treatment with conditioned medium from their respective stretched CF (CM-SF), CM (at 21 weeks) of WT showed increased Ca²⁺ transient (CaT) amplitudes related to the paracrine activity of the inotrope endothelin (ET-1) and inositol 1,4,5-trisphosphate induced Ca²⁺ release. Concentration of ET-1 was increased in CM-SF and atrial tissue from WT as compared to HHD and HFpEF. In HHD, CM-SF had no relevant effect on CaT kinetics. However, in HFpEF, CM-SF increased diastolic Ca²⁺ and slowed Ca²⁺ removal, potentially contributing to an in-vivo decompensation. During disease progression (i.e. at 27 weeks), HFpEF displayed dysfunctional excitation-contraction-coupling (ECC) due to lower sarcoplasmic-reticulum Ca²⁺ content unrelated to CF-CM interaction or ET-1, but associated with enhanced nuclear [Ca²⁺]. In human patients, tissue ET-1 was not related to the presence of arterial hypertension or obesity.

CONCLUSIONS

Atrial remodeling is a complex entity that is highly disease and stage dependent. The activity of fibrosis related to paracrine interaction (e.g. ET-1) might contribute to in vitro and in vivo atrial dysfunction. However, during later stages of disease, ECC is impaired unrelated to CF.

Pressure distension in leg vessels as influenced by prolonged bed rest and a pressure habituation regimen

Bed rest increases pressure distension in arteries, arterioles, and veins of the leg. We hypothesized that bed-rest-induced deconditioning of leg vessels is governed by the removal of the local increments in transmural pressure induced by assuming erect posture and, therefore, can be counteracted by intermittently increasing local transmural pressure during the bed rest. Ten men underwent 5 wk of horizontal bed rest. A subatmospheric pressure (−90 mmHg) was intermittently applied to one lower leg [pressure habituation (PH) leg]. Vascular pressure distension was investigated before and after the bed rest, both in the PH and control (CN) leg by increasing local distending pressure, stepwise up to +200 mmHg. Vessel diameter and blood flow were measured in the posterior tibial artery and vessel diameter in the posterior tibial vein. In the CN leg, bed rest led to 5-fold and 2.7-fold increments ( P < 0.01) in tibial artery pressure-distension and flow responses, respectively, and to a 2-fold increase in tibial vein pressure distension. In the PH leg, arterial pressure-distension and flow responses were unaffected by bed rest, whereas bed rest led to a 1.5-fold increase in venous pressure distension. It thus appears that bed-rest-induced deconditioning of leg arteries, arterioles, and veins is caused by removal of gravity-dependent local pressure loads and may be abolished or alleviated by a local pressure-habituation regimen.

Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading

Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness was determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-week period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50 %. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 weeks of sustained horizontal bedrest, induced threefold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.