Aim: The aim of this study was to investigate the hypothesis that the opioid system is involved in the development of hepatic fibrosis. Methods: The effect of naltrexone (an opioid receptor antagonist) on hepatic fibrosis in bile duct ligated (BDL) or sham rats was assessed by histology and hepatic hydroxyproline levels. Liver matrix metalloproteinase 2 (MMP-2) was measured by zymography, and α smooth muscle actin (α-SMA) and CD45 (leucocyte common antigen) by immunohistochemistry. The redox state of the liver was assessed by hepatic glutathione (GSH)/oxidised glutathione (GSSG) and S-nitrosothiol levels. Subtypes of opioid receptors in cultured hepatic stellate cells (HSCs) were characterised by reverse transcriptase-polymerase chain reaction, and the effects of selective δ opioid receptor agonists on cellular proliferation, tissue inhibitor of metalloproteinase 1 (TIMP-1), and procollagen I expression in HSCs determined. Results: Naltrexone markedly attenuated the development of hepatic fibrosis as well as MMP-2 activity (p<0.01), and decreased the number of activated HSCs in BDL rats (p<0.05). The development of biliary cirrhosis altered the redox state with a decreased hepatic GSH/GSSG ratio and increased concentrations of hepatic S-nitrosothiols, which were partially or completely normalised by treatment with naltrexone, respectively. Activated rat HSCs exhibited expression of δ1 receptors, with increased procollagen I expression, and increased TIMP-1 expression in response to δ₁ and δ₂ agonists, respectively. Conclusions: This is the first study to demonstrate that administration of an opioid antagonist prevents the development of hepatic fibrosis in cirrhosis. Opioids can influence liver fibrogenesis directly via the effect on HSCs and regulation of the redox sensitive mechanisms in the liver.

Background Oxidative stress reduces total antioxidant status (TAOS) and is implicated in atherogenesis. Mitochondrial uncoupling protein 2 (UCP2) negatively regulates reactive oxygen species generation. The UCP2 gene demonstrates a common functional promoter variant (-866G>A). Methods and results Amongst 465 diabetic men (age 61.7±13.3 years), an association of the UCP2-866A allele with significantly lower TAOS in those without CHD was even more pronounced in those with CHD (TAOS 30.1±16.1% vs. 41.6±12.4% for AA vs. GG; \(P=0.016\) ). In a sample of 20 diabetic men selected for homozygosity for the UCP2-866G>A variant, matched for baseline characteristics, plasma markers of oxidative stress in those with CHD were significantly higher in AA genotype men (TAOS 31.7±7.3% vs. 52.6±6.3%; \(P=0.001\) and F₂-isoprostanes 220.6±37.2 pg ml⁻¹ vs. 109.9±51.1 pg ml⁻¹; \(P=0.005\) for AA vs. GG). Amongst 2695 healthy men (age 56.1±3.5 years) prospectively studied for a median 10.2 years, AA homozygotes had a highly significant doubling in CHD risk after adjustment for established risk factors (HR 1.99 [1.37–2.90]; \(P=0.002\) ). Risk associated with this genotype was substantially increased by the presence of other risk factors (obesity, hypertension and diabetes). Conclusions This study provides the first in vivo evidence of a role for UCP2 in modifying oxidative stress and CHD risk in humans.

Pulse oximetry is routinely used for monitoring patients’ oxygen saturation levels with little regard to the variability of this physiological variable. There are few published studies on oxygen saturation variability (OSV), with none describing the variability and its pattern in a healthy adult population. The aim of this study was to characterise the pattern of OSV using several parameters; the regularity (sample entropy analysis), the self-similarity (detrended fluctuation analysis (DFA)) and the complexity (multiscale entropy (MSE) analysis). Secondly, to determine if there were any changes that occur with age. The study population consisted of 36 individuals. The ‘young’ population consisted of 20 individuals [Mean (±1SD) age = 21.0 (±1.36 years)] and the ‘old’ population consisted of 16 individuals [Mean (±1SD) age = 50.0 (±10.4 years)]. Through DFA analysis, OSV was shown to exhibit fractal-like patterns. The sample entropy revealed the variability to be more regular than heart rate variability and respiratory rate variability. There was also a significant inverse correlation between mean oxygen saturation and sample entropy in healthy individuals. Additionally, the MSE analysis described a complex fluctuation pattern, which was reduced with age (p<0.05). These findings suggest partial “uncoupling” of the cardio-respiratory control system that occurs with ageing. Overall, this study has characterized OSV using pre-existing tools. We have showed that entropy analysis of pulse oximetry signals carries information about body oxygenation. This may have the potential to be used in clinical practice to detect differences in diseased patient subsets.

Cardiac cycle is regulated by a complex interplay between autonomic nervous system and cardiac pacemaker cells. Decreased heart rate variability (HRV) and increased cardiac rhythm regularity are associated with poor prognosis in patients with systemic inflammation (e.g., sepsis). However, the underlying mechanism of decreased HRV in systemic inflammation is not understood. It is known that greater regularity in a complex system could indicate uncoupling of the system’s components. The present study aimed to test the hypothesis that impaired responsiveness of cardiac pacemaker to autonomic nervous system may lead to uncoupling of the cardiovascular regulatory mechanisms during systemic inflammation. Systemic inflammation was induced by intraperitoneal injection of endotoxin (lipopolysaccharide, 1 mg/kg) in rats. Cardiovascular signals were recorded in conscious animals using a telemetric system. Heart rate dynamics was analyzed using Poincaré plot, and cardiac cycle regularity was assessed by sample entropy analysis. Spontaneously beating atria were isolated, and chronotropic responsiveness to adrenergic and cholinergic stimulation was assessed using standard organ bath. Sample entropy decreased significantly 4 h after endotoxin injection in conscious rats. Vagal modulation of cardiac cycle (as assessed by Poincaré plot) also exhibited a significant reduction in endotoxemic rats. Acute endotoxin challenge was associated with a significant hyporesponsiveness of isolated spontaneously beating atria to cholinergic stimulation. The chronotropic responsiveness to adrenergic stimulation was identical in controls and endotoxin-treated rats. These data propose that systemic inflammation is linked to reduced cardiac responsiveness to cholinergic stimulation. This may lead to partial uncoupling of cardiac pacemaker cells from autonomic neural control and can explain decreased HRV during systemic inflammation.