Isometric Resistance Training to Manage Hypertension: Systematic Review and Meta-analysis.

PURPOSE OF REVIEW: Hypertension is the primary risk factor for cardiovascular disease and adequate blood pressure control is often elusive. The objective of this work was to conduct a meta-analysis of trial data of isometric resistance training (IRT) studies in people with hypertension, to establish if IRT produced an anti-hypertensive effect. A database search (PubMed, CINAHL, Cochrane Central Register of Controlled Trials, and MEDLINE) identified randomised controlled and crossover trials of IRT versus a sedentary or sham control group in adults with hypertension. RECENT FINDINGS: We included 12 studies (14 intervention groups) in the meta-analyses, with an aggregate of 415 participants. IRT reduced systolic blood pressure (SBP), mean difference (MD) - 7.47 mmHg (95%CI - 10.10, - 4.84), P < 0.01; diastolic blood pressure (DBP) MD - 3.17 mmHg (95%CI - 5.29, - 1.04), P < 0.01; and mean arterial blood pressure (MAP) MD - 7.19 mmHg (95%CI - 9.06, - 5.32), P < 0.0001. Office pulse pressure and resting heart rate was not significantly reduced, neither were 24-h or day-time ambulatory blood pressures (SBP, DBP). Night-time blood pressures, however, were significantly reduced with SBP MD - 4.28 mmHg (95%CI - 7.88, - 0.67), P = 0.02, and DBP MD - 2.22 mmHg (95%CI - 3.55, - 0.88), P < 0.01. IRT does lower SBP, DBP and MAP office and night-time ambulatory SBP and DBP, but not 24-h mean ambulatory blood pressures in people with hypertension.

Effect of exercise training on liver function in adults who are overweight or exhibit fatty liver disease: a systematic review and meta-analysis.

OBJECTIVE: Exercise training has been shown to have beneficial effects on liver function in adults overweight or with fatty liver disease. To establish which exercise programme characteristics were likely to elicit optimal improvements. DESIGN: Systematic review and meta-analysis of randomised, controlled trials. DATA SOURCES: PubMed, CINAHL and Cochrane controlled trials registry searched (1966 to 2 October 2015). ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Exercise intervention, with or without dietary intervention, versus usual care in adults undertaking, exercise training, who were overweight, obese or exhibited fatty liver disease (non-alcoholic fatty liver disease or non-alcoholic steatohepatitis). RESULTS: We included 21 randomised controlled trials, totalling 1530 participants. Exercise intervention studies with total exercise programme workload >10 000 kcal produced significant improvements in intrahepatic fat, -3.46% (95% CI -5.20% to -1.73%), p<0.0001, I2=73%; effect size (standardised mean difference, SMD) -1.77 (-3.11 to -0.42), p=0.01, I2=77%. When data from only exercise studies were pooled, there was a reduction in fasting free fatty acids (FFAs) -74.15 µmol/L (95% CI -118.47 to -29.84), p=0.001, I2=67% with a large effect size (SMD) -0.94 (-1.36 to -0.52), p<0.0001, I2=0%. When data from only exercise studies were pooled, there was a significant reduction in insulin MD -1.88 UL (95% CI -3.43 to -0.34), p=0.02, I2=31%. The liver enzymes, alanine aminotransferase, aspartate aminotransferase and γ-glutamyl transpeptidase, were not significantly altered with exercise. CONCLUSIONS: Exercise training reduces intrahepatic fat and FFAs while increasing cardiorespiratory fitness. An aggregate exercise programme energy expenditure (>10 000 kcal) may be required to promote reductions in intrahepatic fat.

Repeat remote ischaemic pre-conditioning for improved cardiovascular function in humans: A systematic review.

BACKGROUND: Single exposure to remote ischaemic pre-conditioning (RIPC) has been shown to be effective in reducing major adverse events during cardiac surgery. We evaluated the efficacy of repeated exposure RIPC to elicit improvements in cardiovascular function. METHODS: A systematic search was conducted up until May 1st, 2015, using the following databases: EMBASE, PubMed (Medline), Web of Science and the Cochrane Central Registry of Controlled Trials (CENTRAL). Data was extracted and synthesized from published studies of repeat RIPC. RESULTS: Data from seven studies showed evidence of improvements in vascular function and anti-hypertensive effects of systolic, diastolic and mean arterial blood pressure following repeat RIPC. Currently existing work justifies a systematic review but not data pooling of individual study data. Repeat RIPC has also produced evidence of improvements in endothelial dependent vasodilation, but not non-endothelial dependent vasodilation, cutaneous vascular conductance or cardiorespiratory fitness. CONCLUSION: Repeated RIPC exposure has produced evidence of improvements in endothelial dependent vasodilation, ulcer healing and blood pressure but no benefit in non-endothelial dependent vasodilation, cutaneous vascular conductance or cardiorespiratory fitness. The optimal delivery of RIPC remains unclear, but at least 3 or preferably 4, 5 min exposures appears to be most beneficial, at least for reducing blood pressure. Aside from those undertaking cardiac surgery, other study populations with endothelial dysfunction may benefit from repeat exposure to RIPC.

Effects of parachlorophenylalanine, quipazine and cyproheptadine on growth hormone and adrenocorticotropin secretion in steers.

Adrenergic and perhaps dopaminergic neurons provide inhibitory regulation of growth hormone (GH) secretion in ruminants. This suggests that either serotonergic or other neurons regulate the stimulatory release of GH. The nature of neurotransmitter control of adrenocorticotropin (ACTH) secretion in ruminants has not been determined. Parachlorophenylalanine (PCPA; serotonin synthesis inhibitor), quipazine (serotonin receptor agonist) and cyproheptadine (serotonin receptor antagonist) were utilized in Holstein steers to determine whether serotonin receptors mediate stimulatory actions on GH and ACTH secretion. PCPA (100 mg/kg BW) administered each day at 1900 hr for three successive days did not alter mean GH concentrations, amplitude of GH peaks, nor the number of GH peaks. Likewise, PCPA altered none of these parameters for ACTH. Quipazine injected iv at .1 or .5 mg/kg BW increased plasma GH (P less than .05) and ACTH (P less than .001) concentrations. There was a dose effect of quipazine on both GH (P less than .05) and ACTH (P less than .0001) secretion. Pretreatment of steers with cyproheptadine (.06 and .6 mg/kg BW) reduced the stimulation of GH by quipazine (P less than .0001) and decreased basal GH concentrations (P less than .0004). Cyproheptadine at .06 mg/kg BW did not alter quipazine effects on ACTH, however, the higher dose decreased the peak ACTH response (P less than .02) to quipazine. Studies with quipazine and cyproheptadine indicated that serotonergic mechanisms are likely involved in the regulation of GH and ACTH secretion in steers.

Effect of fasting and dexamethasone on binding characteristics of canine erythrocyte insulin receptors.

Insulin binding characteristics of canine erythrocyte insulin receptors were studied before and after a 72-hour fast, and one and three days following glucocorticoid (dexamethasone) administration. The 72-hour fast tended to increase maximum insulin binding, but no significant differences were found. The administration of dexamethasone resulted in an increased maximum binding of insulin to its receptors which, at day 1, was due to an increase in receptor concentration, and at day 3, to an increased insulin binding affinity of the receptor. These data suggest that the erythrocyte insulin receptor may be useful in clinical and experimental studies in the dog.

Binding characteristics of swine erythrocyte insulin receptors.

Crossbred gilts (controls; n = 7) had 8.8 +/- 1.1% (mean +/- SEM) maximum binding of [125I]insulin to insulin receptors on erythrocytes. The number of insulin-binding sites per cell was 137 +/- 19, with a binding affinity ranging from 7.4 X 10(7)M-1 to 11.2 X 10(7)M-1 and mean of 8.8 X 10(7)M-1. Pregnant sows (n = 5) had a significant increase (P less than 0.01) in maximum binding due to an increase in number of receptor sites per cell. Lactating sows fed a high-fiber diet (n = 3) and a low-fiber diet (n = 4) did not develop a significant difference in maximum binding of insulin. Sows fed the low-fiber diet had a significantly higher number of binding sites and a significantly lower binding affinity than did sows fed a high-fiber diet. Receptor-binding affinity was lower in the low-fiber diet group than in cycling gilts, whereas data from sows fed the high-fiber diet did not differ from data for cycling gilts. Data from this study indicated that insulin receptors of swine erythrocytes have binding characteristics similar to those in other species. Pregnancy and diet will alter insulin receptor binding in swine.

Crayfish abdominal muscle adenylate cyclase. Studies on the stimulation by a Ca2+-binding protein.

A plasma-membrane preparation of crayfish muscle showed an adenylate cyclase activity which is inhibited to about 80% of its original activity by 100 microM-EGTA. Measurements of the enzyme activity in the presence of 100 microM-EGTA and various concentrations of Ca2+ revealed an increase in enzyme activity of about 400%, indicating an adenylate cyclase which is dependent on Ca2+ for activity. Fluphenazine (1 mM), a blocker of the Ca2+-binding protein calmodulin, decreased enzyme activity to zero. The enzyme can be re-activated by the addition of certain concentrations of calmodulin to the assay medium. This suggests that crayfish muscle adenylate cyclase is dependent on Ca2+ and calmodulin for activity.

Modulation of growth hormone-releasing factor stimulated growth hormone secretion by plasma glucose and free fatty acid concentrations in sheep.

Effects of plasma glucose and free fatty acid (FFA) concentrations on bovine growth hormone-releasing factor (bGRF)-induced release of growth hormone (GH) were examined in ovariohysterectomized sheep. In experiment 1, the effects of an infusion of insulin (0.025 U/kg BW.h-1), glucose (40 mg/kg BW.h-1), insulin plus glucose or saline on the subsequent effects of bGRF on plasma GH concentrations were determined. Insulin-induced hypoglycemia inhibited GRF effects on plasma GH concentrations while glucose infusion enhanced bGRF actions. Infusing a higher glucose dose (120 mg/kg BW.h-1) had no effect on GRF actions. Subsequently, infusion of FFA (0.25 g/kg/.h-1), nicotinic acid (50 mg/kg BW) or saline for 1 h prior to bGRF injection demonstrated that FFA inhibited GRF actions but FFA depletion by nicotinic acid infusion had no effect on GRF actions. Nicotinic acid (40 mg/kg BW.h-1) infused for 2 h prior to bGRF injection significantly enhanced bGRF-stimulated GH secretion. Finally, to determine whether central nervous system glucopenia produced similar effects to insulin-induced hypoglycemia, 2-deoxyglucose (500 mg) was injected into the lateral ventricle followed in 1 by the i.v. injection of bGRF. The central glucopenia produced by 2-DG inhibited GRF-stimulated GH release. These data demonstrate that decreased peripheral or central nervous system glucose availability and exogenous administration of FFA antagonized GRF-induced release of GH. And, pharmacologic depletion of circulating FFA for at least 2 h facilitated GRF-induced release of GH.

Effects of acute insulin deficiency on catecholamine and indoleamine content and catecholamine turnover in microdissected hypothalamic nuclei in streptozotocin-diabetic rats.

The effects of streptozotocin-induced diabetes on catecholamine and indoleamine concentrations and catecholamine turnover rates in individual microdissected hypothalamic nuclei known, or believed, to be involved in the control of neuroendocrine function, were examined in control, insulin-treated diabetic and acutely insulin-withdrawn diabetic female rats. Streptozotocin-induced diabetes and acute insulin deficiency were demonstrated to result in increased concentrations of epinephrine in the suprachiasmatic nucleus, decreased turnover of epinephrine in the arcuate nucleus and decreased turnover of dopamine in the ventromedial nucleus was found to be increased in the insulin-treated diabetic animals. These data indicate that experimental diabetes and acute insulin deficiency result in the rapid onset of detectable alterations in epinephrine and dopamine activity in specific hypothalamic nuclei. These diabetes-induced changes may cause, or contribute to, the development of secondary neuroendocrine abnormalities known to occur in the diabetic condition.