Showing papers in "Clinical Science in 2000"

An Important Role for the IIIb Isoform of Fibroblast Growth Factor Receptor 2 in Mesenchymal-Epithelial Signalling during Mouse Organogenesis

Abstract: The fibroblast growth factor receptor 2 gene is differentially spliced to encode two transmembrane tyrosine kinase receptor proteins that have different ligand-binding specificities and exclusive tissue distributions. We have used Cre-mediated excision to generate mice lacking the IIIb form of fibroblast growth factor receptor 2 whilst retaining expression of the IIIc form. Fibroblast growth factor receptor 2(IIIb) null mice are viable until birth, but have severe defects of the limbs, lung and anterior pituitary gland. The development of these structures appears to initiate, but then fails with the tissues undergoing extensive apoptosis. There are also developmental abnormalities of the salivary glands, inner ear, teeth and skin, as well as minor defects in skull formation. Our findings point to a key role for fibroblast growth factor receptor 2(IIIb) in mesenchymal-epithelial signalling during early organogenesis.

Fatigue in chronic disease.

Abstract: Fatigue is an extremely common complaint among patients with chronic disease. However, because of the subjective nature of fatigue, and the lack of effective therapeutics with which to treat fatigue, this symptom is often ignored by clinicians, who instead focus on hard, objective disease end-points. Recently, the symptom of fatigue has received greater attention as part of overall health-related quality of life assessments in patients with chronic disease. Furthermore, new methods are being developed to help quantify fatigue, and are being utilized more frequently in the clinical setting. Moreover, studies in patients and using animal models of disease have provided some insight into changes within the brain which appear to be linked to the genesis of central fatigue. This review focuses on fatigue in chronic disease and outlines possible mechanisms which may give rise to central fatigue in chronic disease. Moreover, methods for measuring fatigue and an approach to the fatigued patient are discussed. Hopefully, a broader understanding of this distressing symptom will lead to the development of specific therapies for treating fatigue in these patients.

Relationship between gastro-intestinal complaints and endotoxaemia, cytokine release and the acute-phase reaction during and after a long-distance triathlon in highly trained men.

Abstract: The aim of the present study was to establish whether gastro-intestinal (GI) complaints observed during and after ultra-endurance exercise are related to gut ischaemia-associated leakage of endotoxins [lipopolysaccharide (LPS)] into the circulation and associated cytokine production. Therefore we collected blood samples from 29 athletes before, immediately after, and 1, 2 and 16 h after a long-distance triathlon for measurement of LPS, tumour necrosis factor-alpha and interleukin-6 (IL-6). As the cytokine response would trigger an acute-phase response, characteristic variables of these responses were also measured, along with creatine kinase (CK) to obtain an indicator of muscle damage. There was a high incidence (93% of all participants) of GI symptoms; 45% reported severe complaints and 7% of the participants abandoned the race because of severe GI distress. Mild endotoxaemia (5-15 pg/ml) was evident in 68% of the athletes immediately after the race, as also indicated by a reduction in IgG anti-LPS levels. In addition, we observed production of IL-6 (27-fold increase immediately after the race), leading to an acute-phase response (20-fold increase in C-reactive protein and 12% decrease in pre-albumin 16 h after the race). The extent of endotoxaemia was not correlated with the GI complaints or the IL-6 response, but did show a correlation with the elevation in C-reactive protein (r(s) 0.389; P=0.037). Creatine kinase levels were increased significantly immediately post-race, and increased further in the follow-up period. Creatine kinase levels did not correlate with those of either IL-6 or C-reactive protein. It is therefore concluded that LPS does enter the circulation after ultra-endurance exercise and may, together with muscle damage, be responsible for the increased cytokine response and hence GI complaints in these athletes.

Endothelial dysfunction as a possible link between C-reactive protein levels and cardiovascular disease.

Abstract: Low-grade chronic inflammation, characterized by elevated plasma concentrations of C-reactive protein (CRP), is associated with an increased risk of atherosclerotic cardiovascular disease. Endothelial cell activation is an early event in atherogenesis, and previous studies have reported correlations between indirect markers of endothelial cell activation and CRP concentration. Therefore, in the present study, we measured CRP concentration (and leptin concentration as an index of fat mass) in nine healthy subjects (mean age 53+/-8.1 years; body mass index 27+/-3.2 kg/m(2); mean arterial blood pressure 101+/-9.0 mmHg) undergoing measurement of basal endothelial nitric oxide (NO) synthesis using intra-brachial infusions of N(G)-monomethyl-L-arginine (L-NMMA; a substrate inhibitor of endothelial NO synthase) and noradrenaline (a non-specific control vasoconstrictor). In univariate analysis, CRP concentration was correlated with (i) the percentage decrease in forearm blood flow (FBF) during L-NMMA infusion (r=0.85, P=0.004); and (ii) the serum leptin concentration (r=0.65, P=0.05). In multivariate analysis, the relationship between CRP concentration and the FBF response to L-NMMA remained significant when age and leptin (t=2.65, P=0.045), age and BMI (t=3.69, P=0.014), or age and low-density-lipoprotein-cholesterol plus high-density-lipoprotein-cholesterol (t=3.37, P=0.044), were included in regression models. In contrast, the response of FBF to noradrenaline was not significantly related to CRP concentration. These data demonstrate for the first time a relationship between low-grade chronic inflammation and basal endothelial NO synthesis (measured using an invasive method), and support the notion that endothelial dysfunction is a critical intermediate phenotype in the relationship between inflammation and cardiovascular disease.

Antenatal corticosteroid therapy and blood pressure at 14 years of age in preterm children

Abstract: Antenatal corticosteroid therapy substantially improves the survival rate of preterm infants, with few side effects. Higher blood pressure in adulthood has been described in several animal species after exposure to antenatal corticosteroids, but there are no similar reports in humans. The objective of the present study was to determine the relationship between exposure to antenatal corticosteroid therapy and blood pressure at 14 years of age. This was a cohort study of 210 preterm survivors with birthweights of <1501 g born in the Royal Women's Hospital, Melbourne, between 1 January 1977 and 31 March 1982. Blood pressure was measured in 177 subjects (84.3%) at 14 years of age with a standard mercury sphygmomanometer. Children exposed to antenatal corticosteroids (n=89) had higher systolic and diastolic blood pressures than those not exposed to corticosteroids (n=88) [mean difference (95% confidence interval) (mmHg): systolic, 4.1 (0.1-8.0); diastolic, 2.8 (0.05-5.6)]. However, few had blood pressure in the hypertensive range. It is concluded that antenatal corticosteroid therapy is associated with higher systolic and diastolic blood pressures in adolescence, and might lead to clinical hypertension in survivors well beyond birth.

S-Nitrosothiols: a class of nitric oxide-donor drugs

Abstract: Nitric oxide (NO) was originally described as the principal endothelium-derived relaxing factor, but it is now known to subserve a variety of functions throughout the body, both physiological and pathophysiological. NO-donor drugs decompose in the body, by a variety of mechanisms, to generate NO. Such drugs have been used for many years in cardiovascular therapeutics, in particular the organic nitrates for the prevention and treatment of angina pectoris and sodium nitroprusside for the treatment of hypertensive emergencies. However, patients taking long-term nitrates often develop tolerance, and prolonged nitroprusside administration can give rise to cyanide accumulation in the body. Newer NO-donor drugs, in particular the S-nitrosothiols, offer advantages over the existing drugs, since they do not share these drawbacks, and initial small clinical studies suggest that they may be of benefit in a variety of cardiovascular disorders. Here we briefly review the chemistry and physiology of NO, and discuss the chemistry and clinical possibilities of the S-nitrosothiols.

First clinical trial with etomoxir in patients with chronic congestive heart failure

Abstract: In the failing human myocardium, both impaired calcium homoeostasis and alterations in the levels of contractile proteins have been observed, which may be responsible for reduced contractility as well as diastolic dysfunction. In addition, levels of a key protein in calcium cycling, i.e. the sarcoplasmic reticulum Ca(2+)-ATPase, and of the alpha-myosin heavy chain have been shown to be enhanced by treatment with etomoxir, a carnitine palmitoyltransferase inhibitor, in normal and pressure-overloaded rat myocardium. We therefore studied, for the first time, the influence of long-term oral application of etomoxir on cardiac function in patients with chronic heart failure. A dose of 80 mg of etomoxir was given once daily to 10 patients suffering from heart failure (NYHA functional class II-III; mean age 55+/-4 years; one patient with ischaemic heart disease and nine patients with dilated idiopathic cardiomyopathy; all male), in addition to standard therapy. The left ventricular ejection fraction was measured echocardiographically before and after a 3-month period of treatment. Central haemodynamics at rest and exercise (supine position bicycle) were defined by means of a pulmonary artery catheter and thermodilution. All 10 patients improved clinically; no patient had to stop taking the study medication because of side effects; and no patient died during the 3-month period. Maximum cardiac output during exercise increased from 9.72+/-1.25 l/min before to 13.44+/-1.50 l/min after treatment (P<0.01); this increase was mainly due to an increased stroke volume [84+/-7 ml before and 109+/-9 ml after treatment (P<0.01)]. Resting heart rate was slightly reduced (not statistically significant). During exercise, for any given heart rate, stroke volume was significantly enhanced (P<0.05). The left ventricular ejection fraction increased significantly from 21.5+/-2.6% to 27.0+/-2.3% (P<0.01). In acute studies, etomoxir showed neither a positive inotropic effect nor vasodilatory properties. Thus, although the results of this small pilot study are not placebo-controlled, all patients seem to have benefitted from etomoxir treatment. Etomoxir, which has no acute inotropic or vasodilatory properties and is thought to increase gene expression of the sarcoplasmic reticulum Ca(2+)-ATPase and the alpha-myosin heavy chain, improved clinical status, central haemodynamics at rest and during exercise, and left ventricular ejection fraction.

Organization and reorganization of human swallowing motor cortex: Implications for recovery after stroke

Abstract: Swallowing problems can affect as many as one in three patients in the period immediately after a stroke. In some cases this can lead to serious morbidity, in particular malnutrition and pulmonary aspiration. Despite this, swallowing usually recovers to a safe level in the majority of patients within weeks. This propensity for recovery is likely to relate to how the swallowing motor cortex is organized and then reorganized after cerebral injury. In this review, we examine present knowledge on the cortical control of swallowing in humans, and examine the aspects of its organization that are important for compensating for recovery after damage. In addition, we examine approaches which may be useful in speeding up the process of recovery. Swallowing may turn out to be a useful model for studying central nervous system plasticity.

Steroid hormone receptor expression and action in bone.

Abstract: The skeleton is a complex tissue, and hormonal control of bone remodelling is elaborate. The important role that steroid hormones play in bone cell development and in the maintenance of normal bone architecture is well established, but it is only relatively recently that it has become possible to describe their precise mechanism of action. This review focuses not only on the steroid hormones (oestrogens, corticosteroids, androgens and progesterone), but also on related hormones (vitamin D, thyroid hormone and the retinoids), all of which act via structurally homologous nuclear receptors that form part of the steroid/thyroid receptor superfamily. By examining the actions of all of these hormones in vivo and in vitro, this review gives a general overview of the current understanding of steroid hormone action in bone. In addition, a comprehensive review of steroid hormone receptor expression in bone cells is included. Finally, the role that future developments, such as steroid hormone receptor knockout mice, will play in our understanding of steroid hormone action in bone is considered.

Antihypertensive treatment in early postnatal life modulates prenatal dietary influences upon blood pressure in the rat.

Abstract: Epidemiological evidence from diverse human populations, supported by experimental evidence from animal models, suggests that maternal nutrition during pregnancy is an important fetal programming influence upon cardiovascular disease. Experiments with a low-protein-diet model of rat pregnancy suggest a role for the renin-angiotensin system in the programming mechanism, since fetal undernutrition permanently elevates pulmonary and plasma angiotensin-converting enzyme activity. Long-term beneficial effects of captopril on blood pressure in this model require further investigation in order to clarify the role of angiotensin II. Pregnant rats were fed a control diet containing 18% (w/w) casein as the protein source or a low-protein diet containing 9% (w/w) casein. Between the ages of 2 and 4 weeks postnatally, mothers and their pups were treated with losartan or nifedipine. All pups in the study had blood pressure determined at 4 and 12 weeks of age using a tail cuff. Animals exposed to the low-protein diet in utero and not subjected to drug treatment had elevated blood pressure relative to control rats (mean increase of 27 mmHg; P<0.001). Treatment of rats exposed to the control diet in utero with either nifedipine or losartan between 2 and 4 weeks of age did not alter their blood pressure. Nifedipine had no effect upon the blood pressure of low-protein-exposed pups, but losartan prevented the blood pressure elevation in these animals. Between 4 and 12 weeks of age, blood pressure increased significantly in all groups (P<0.001). The pattern of blood pressure among the groups was identical to that observed at 4 weeks, suggesting that the observed early effects of losartan would be maintained into adult life. The data are consistent with the hypothesis that angiotensin II plays a major role in the prenatal programming of hypertension. The action of angiotensin II at the AT(1) receptor between 2 and 4 weeks of age may be critically up-regulated by fetal factors, including exposure to glucocorticoids of maternal origin.

Effects of organic and inorganic selenium supplementation on selenoenzyme activity in blood lymphoctyes, granulocytes, platelets and erythrocytes

Abstract: The blood selenium (Se) concentration in the U.K. population has declined by approx. 50% between 1974 and 1991, reflecting a large decrease in dietary Se supply, with intakes only half the reference nutrient intake of 1 microg/kg body weight. Tissue levels of Se are readily influenced by dietary intake. Therefore selenoprotein activity may be sub-optimal due to low Se status, and thus compromise normal cell function. To examine the effects of changing Se intake on selenoproteins, we have determined the relative effectiveness of organic selenomethionine and inorganic sodium selenite (50 microg of Se daily for 28 days) in modulating glutathione peroxidase activities in blood cells from 45 healthy men and women, from a U.K. population. Transient and acute changes in lymphocyte, granulocyte and platelet phospholipid-hydroperoxide glutathione peroxidase (GPx4) activity occurred by day 7 or 14 of sodium selenite treatment and by day 7 in lymphocytes from selenomethionine-treated subjects compared with controls taking a placebo. In contrast, GPx4 activity in granulocytes and platelets in the selenomethionine group increased gradually over the 28 days. Cytosolic glutathione peroxidase (GPx1) activity in these blood cells from both treatment groups increased gradually over the 28 days. For each cellular selenoenzyme activity a significant inter-individual difference (P<0.001) in the extent of the response to Se supplementation was observed, but this was not related to blood Se concentrations either before or after treatments. Significant inverse correlations were evident between baseline enzyme activities and percentage change in activity after 28 days of supplementation [e.g. lymphocyte GPx4, r=-0.695 (P<0.001)], indicating that pre-treatment activity may be sub-optimal as a result of poor Se status. The different and contrasting effects that Se supplementation had on blood selenoenzyme activities may be indicative of a difference in metabolic need for Se regulated at the level of Se-dependent cell function.

Non-invasive quantification of liver perfusion with dynamic computed tomography and a dual-input one-compartmental model.

Abstract: Various liver diseases lead to significant alterations of the hepatic microcirculation. Therefore, quantification of hepatic perfusion has the potential to improve the assessment and management of liver diseases. Most methods used to quantify liver perfusion are invasive or controversial. This paper describes and validates a non-invasive method for the quantification of liver perfusion using computed tomography (CT). Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass iodinated contrast agent. Hepatic, aortic and portal-venous time-density curves were fitted with a dual-input one-compartmental model to calculate liver perfusion. Validation studies consisted of simultaneous measurements of hepatic perfusion with CT and with radiolabelled microspheres in rabbits at rest and after adenosine infusion. The feasibility and reproducibility of the CT method in humans was assessed by three observers in 10 patients without liver disease. In rabbits, significant correlations were observed between perfusion measurements obtained with CT and with microspheres (r=0.92 for total liver perfusion, r=0.81 for arterial perfusion and r=0.85 for portal perfusion). In patients, total liver plasma perfusion measured with CT was 112+/-28 ml.min(-1).100 ml(-1), arterial plasma perfusion was 18+/-12 ml.min(-1).100 ml(-1) and portal plasma perfusion was 93+/-31 ml.min(-1).100 ml(-1). The measurements obtained by the three observers were not significantly different from each other (P>0.1). Our results indicate that dynamic CT combined with a dual-input one-compartmental model provides a valid and reliable method for the non-invasive quantification of perfusion in the normal liver.

Occlusion cuff position is an important determinant of the time course and magnitude of human brachial artery flow-mediated dilation

Abstract: Non-invasive ultrasound techniques to assess flow-mediated vasodilation (FMD) are frequently used to assess arterial endothelial vasodilator function. However, the range of normal values varies considerably, possibly due to differences in methodological factors. We sought to determine the effect of occlusion cuff position on the time course and magnitude of brachial artery blood flow and flow-mediated dilation. Twelve healthy subjects underwent measurements of forearm blood flow using venous occlusion plethysmography (VOP) before and after 5 min of susprasystolic cuff inflation, using two randomly assigned occlusion cuff positions (upper arm and forearm). An additional 16 subjects underwent two brachial ultrasound studies, using the two cuff positions, to assess the extent and time course of changes in brachial artery diameter and blood flow. Maximum increase in blood flow (peak reactive hyperaemia), measured by VOP, occurred immediately upon each cuff deflation, but was greater after upper arm compared with forearm arterial occlusion (33.1±3.1 versus 22.8±2.2 ml/min per forearm tissue, P = 0.001). Maximal brachial artery FMD was significantly greater following upper arm occlusion (9.0±1.2%, mean±S.E.M.) compared with forearm occlusion (5.9±0.7%, P = 0.01). The time course of the change in brachial artery diameter was affected differently in response to each protocol. The time to peak dilation following upper arm occlusion was delayed by 22 s compared with forearm occlusion. Occlusion cuff position is thus a powerful determinant of peak reactive hyperaemia, volume repaid and the extent and time course of brachial artery FMD. Positioning the cuff on the upper arm produces a greater FMD. These results highlight the need for comparisons between FMD studies to be made with care.

Low paraoxonase activity in type II diabetes mellitus complicated by retinopathy.

Abstract: Human serum paraoxonase 1 (PON1) is located on high-density lipoprotein and has been implicated in the detoxification of organophosphates, and possibly in the prevention of lipid peroxidation of low-density lipoprotein. PON1 has two genetic polymorphisms, both due to amino acid substitutions: one involving glutamine (Q genotype) and arginine (R genotype) at position 192, and the other involving leucine (L genotype) and methionine (M genotype) at position 55. We investigated the effects of these polymorphisms, and of a polymorphism of the PON2 gene at position 310 (Cys/Ser; C and S genotypes respectively), on serum PON1 activity and concentration, plasma lipids and lipoproteins and glycaemic control in 93 individuals with type II diabetes with no complications and in 101 individuals with type II diabetes with retinopathy. Serum PON1 activity in the group with no complications [median 164.1 nmol.min(-1).ml(-1) (range 8.0-467.8)] was significantly higher than in the group with retinopathy [113.4 nmol. min(-1).ml(-1) (3.0-414.6)] (P LM>LL (P=0.0032), for the PON1-192 genotypes in the order RR>QR>QQ (P=0.011) and for the PON2-310 genotypes in the order CC>CS>SS (P=0.010). Low serum PON1 activity in retinopathy may be related to an increased tendency for lipid peroxidation. Our findings thus raise the possibility that, in retinopathy, the PON2 gene may influence PON1, and that an inter-relationship between the PON1 and PON2 genes may influence glycaemic control in subjects with type II diabetes complicated by retinopathy.

Induction of osteoclasts from CD14-positive human peripheral blood mononuclear cells by receptor activator of nuclear factor κB ligand (RANKL)

Abstract: Osteoclasts are bone-resorbing cells that are derived from haemopoietic precursors, including cells present in peripheral blood. The recent identification of RANKL [receptor activator of nuclear factor (NF)-kappaB ligand], a new member of the tumour necrosis factor ligand superfamily that has a key role in osteoclastogenesis, has allowed the in vitro generation of osteoclasts in the absence of cells of the stromal/osteoblast lineage. Human peripheral blood mononuclear cells (PBMC) cultured in vitro with soluble RANKL and human macrophage colony-stimulating factor form osteoclasts. However, PBMC are heterogeneous, consisting of subsets of monocytes and lymphocytes as well as other blood cells. As the CD14 marker is strongly expressed on monocytes, the putative osteoclast precursor in peripheral blood, we have selected CD14(+) cells from PBMC to examine their osteoclastogenic potential and their expression of novel members of the tumour necrosis factor superfamily involved in osteoclastogenesis. Highly purified CD14(+) cells demonstrated mRNA expression of receptor activator of NF-kappaB, but no expression of RANKL or osteoprotegerin, whereas PBMC expressed mRNAs for all three factors. CD14(+) (but not CD14(-)) cells cultured on bone slices for 21 days with human macrophage colony-stimulating factor and soluble RANKL generated osteoclasts and showed extensive bone resorption. Similar numbers of osteoclasts were generated by 10(5) CD14(+) cells and 10(6) PBMC, but there was significantly less intra-assay variability with CD14(+) cells, suggesting the absence of stimulatory/inhibitory factors from these cultures. The ability of highly purified CD14(+) cells to generate osteoclasts will facilitate further characterization of the phenotype of circulating osteoclast precursors and cell interactions in osteoclastogenesis.

Age-related changes in microvascular permeability: a significant factor in the susceptibility of children to shock?

Abstract: During studies of the pathogenesis of dengue shock syndrome, a condition largely confined to childhood and characterized by a systemic increase in vascular permeability, we observed that healthy controls, age-matched to children with dengue shock syndrome, gave high values of filtration capacity (K(f)), a factor describing vascular permeability. We hypothesized that K(f) might be age dependent. Calf K(f) was studied in 89 healthy Vietnamese subjects aged 5 to 77 years. The K(f) was highest in the youngest children [7. 53 (1.96-15.46) K(f)U; median (range); where the units of K(f), K(f)U=ml.min(-1).100 ml(-1).mmHg(-1)]. Values were 3- to 4-fold lower towards the end of the second decade [4.69 (1.91-7.06) K(f)U]. Young mammals are known to have a larger microvascular surface area per unit volume of skeletal muscle than adults. During development the proportion of developing vessels is greater. Moreover, the novel microvessels are known to be more permeable to water and plasma proteins than when mature. These factors may explain why children more readily develop hypovolaemic shock than adults in dengue haemorrhagic fever and other conditions characterized by increased microvascular permeability.

Effect of inhibition of nitric oxide synthase on dynamic cerebral autoregulation in humans.

Abstract: Cerebral blood flow is maintained constant over a range of cerebral perfusion pressures by cerebral autoregulation. Impaired cerebral autoregulation may be important in the pathogenesis of cerebral ischaemia. The mechanisms mediating normal cerebral autoregulation in humans are poorly understood. We used a recently described transcranial Doppler technique, which allows non-invasive measurement of dynamic cerebral autoregulation, to test the hypothesis that nitric oxide mediates cerebral autoregulation. The rate of rise of middle cerebral artery blood flow velocity, compared with that of arterial blood pressure, was determined following a stepwise fall in arterial blood pressure, in order to calculate an autoregulatory index. The effect of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on dynamic autoregulation was compared with that of noradrenaline titrated to result in a similar rise in blood pressure. Six healthy subjects were studied in each group. The mean (S.D.) change in autoregulatory index following noradrenaline at a similar pressor dose was significantly greater than the change following the L-NMMA bolus: 1. 1 (1.2) compared with -0.8 (0.8) for the left middle cerebral artery (P=0.002), and 1.1 (0.8) compared with -0.8 (0.8) for the right middle cerebral artery (P=0.002). There was no difference in the mean (S.D.) blood pressure increase resulting from the two agents: L-NMMA, 19.7 (7.4) mmHg; noradrenaline, 15.5 (4.8) mmHg (P=0.281). These results suggest that nitric oxide mediates at least part of the dynamic phase of cerebral autoregulation in humans. Reduced nitric oxide release may play a role in the impaired cerebral autoregulation seen in patients with, or at risk of, cerebral ischaemia.

Time course of changes in serum glucose, insulin, lipids and tissue lipase activities in macrosomic offspring of rats with streptozotocin-induced diabetes

Abstract: The aim of this investigation was to determine the time course of changes in serum glucose, insulin and lipid levels, as well as lipid and protein content and lipolytic activities in insulin target organs (liver, adipose tissue and muscle), in macrosomic offspring of streptozotocin-induced mildly hyperglycaemic rats. Food intake and nutritional efficiency were also evaluated. Mild hyperglycaemia in pregnant rats was induced by intraperitoneal injection of streptozotocin (40 mg/kg body weight) on day 5 of gestation. Control pregnant rats were injected with citrate buffer. At birth, macrosomic pups (birth weight > 1.7 S.D. greater than the mean value for the control pups) had higher serum insulin, glucose and lipid levels than control pups. These macrosomic rats maintained accelerated postnatal growth combined with high adipose tissue weight up to 12 weeks of age. These rats were not hyperphagic; however, they had higher food efficiency and fat storage capacity with higher adipocyte lipoprotein lipase activity, which contributed to persisting obesity. Hepatic lipase activity was increased in macrosomic rats at all ages. Moreover, macrosomia was associated with metabolic disturbances that varied according to age and sex. After 1 month, several alterations observed at birth had disappeared. Serum glucose, insulin and lipid levels in male and female macrosomic rats became similar to those of their respective controls. At 2 months of age, hepatic and serum triacylglycerol levels were higher in macrosomic females than in controls. By 3 months, macrosomic rats (both males and females) had developed insulin resistance with hyperinsulinaemia, hyperglycaemia, and higher serum and hepatic lipids. In conclusion, macrosomia was associated with alterations in glucose and lipid metabolism through to adulthood. It should be considered as an important potential risk factor for obesity and its metabolic complications.

The gain-of-function G389R variant of the β1-adrenoceptor does not influence blood pressure or heart rate response to β-blockade in hypertensive subjects

Abstract: Original article can be found at: http://www.clinsci.org/cs/099/cs0990233.htm Copyright The Biochemical Society and the Medical Research Society [Full text of this article is not available in the UHRA]

Effects of proinsulin C-peptide on nitric oxide, microvascular blood flow and erythrocyte Na+,K+-ATPase activity in diabetes mellitus type I

Abstract: This study was conducted to evaluate the influence of proinsulin C-peptide on erythrocyte Na(+),K(+)-ATPase and endothelial nitric oxide synthase activities in patients with type I diabetes. In a randomized double-blind study design, ten patients with type I diabetes received intravenous infusions of either human C-peptide or physiological saline on two different occasions. C-peptide was infused at a rate of 3 pmol.min(-1).kg(-1) for 60 min, and thereafter at 10 pmol.min(-1).kg(-1) for 60 min. At baseline and after 60 and 120 min, laser Doppler flow (LDF) was measured following acetylcholine iontophoresis or mild thermal stimulation (44 degrees C), and venous blood samples were collected to determine plasma cGMP levels and erythrocyte membrane Na(+),K(+)-ATPase activity. The LDF response to acetylcholine increased during C-peptide infusion and decreased during saline infusion [18.6+/-19.2 and -13.2+/-9.4 arbitrary units respectively; mean+/-S.E.M.; P<0.05). No significant change in LDF was observed after thermal stimulation. The baseline plasma concentration of cGMP was 5.5+/-0.6 nmol.l(-1); this rose to 6.8+/-0.9 nmol.l(-1) during C-peptide infusion (P<0.05). Erythrocyte Na(+),K(+)-ATPase activity increased from 140+/-29 nmol of P(i).h(-1).mg(-1) in the basal state to 287+/-5 nmol of P(i). h(-1).mg(-1) during C-peptide infusion (P<0.01). There was a significant linear relationship between plasma C-peptide levels and erythrocyte Na(+),K(+)-ATPase activity during the C-peptide infusion (r=0.46, P<0.01). No significant changes in plasma cGMP levels or Na(+),K(+)-ATPase activity were observed during saline infusion. This study demonstrates an effect of human proinsulin C-peptide on microvascular function, which might be mediated by an increase in NO production and an activation of the erythrocyte Na(+),K(+)-ATPase. These mechanisms are compatible with the previous observed microvascular effects of C-peptide in patients with type I diabetes.

A guardian angel: the involvement of dipeptidyl peptidase IV in psychoneuroendocrine function, nutrition and immune defence.

Abstract: Dipeptidyl peptidase IV (DPP IV, also known as CD26; EC 3.4.14.5) is a non-integrin receptor glycoprotein with multiple functions, including cell adhesion, cellular trafficking through the extracellular matrix and co-stimulatory potential during T cell activation. By virtue of its exopeptidase activity, DPP IV plays a key regulatory role in the metabolism of peptide hormones. Based on data emerging from different biomedical specialties, it appears worthwhile to highlight the different facets of DPP IV in nutrition, immune responses and peptide hormone metabolism. The presentation of the complex regulatory circuits in which DPP IV appears to be involved may also serve as a note of caution, in view of attempts to apply selective inhibitors of DPP IV enzymic activity for the treatment of disease, e.g. Type II diabetes.

Metabolic response to feeding in weight-losing pancreatic cancer patients and its modulation by a fish-oil-enriched nutritional supplement.

Abstract: Weight-losing patients with advanced cancer often fail to gain weight with conventional nutritional support. This suboptimal response might be explained, in part, by an increased metabolic response to feeding. It has been suggested that eicosapentaenoic acid (EPA) can modify beneficially the metabolic response to cancer. The aim of the present study was to examine the metabolic response to feeding in cancer and the effects of an EPA-enriched oral food supplement on this response. A total of 16 weight-losing, non-diabetic patients with unresectable pancreatic adenocarcinoma and six healthy, weight-stable controls were studied by indirect calorimetry in the fasting and fed states. Body composition was estimated by bioimpedence analysis. Cancer patients were then given a fish-oil-enriched nutritional supplement providing 2 g of EPA and 2550 kJ daily, and underwent repeat metabolic study after 3 weeks of such supplementation. At baseline, resting energy expenditure whether expressed per kg body weight, lean body mass or body cell mass was significantly greater in the cancer patients compared with controls. Fat oxidation was significantly higher in the fasting state in cancer patients [median 1.26 g.kg(-1).min(-1) (interquartile range 0.95-1.38)] than in controls [0.76 g.kg(-1). min(-1) (0.62-0.92); P<0.05]. Over the 4 h feeding period, changes in insulin and glucose concentrations in cancer patients suggested relative glucose intolerance. In response to oral meal feeding, the percentage change in the area under the curve of energy expenditure was significantly lower in the cancer patients [median 7.9% (interquartile range 3.4-9.0)] than in controls [12.6% (9.9-15.1); P<0.01]. After 3 weeks of the EPA-enriched supplement, the body weight of the cancer patients had increased and the energy expenditure in response to feeding had risen significantly [9.6% (6. 3-12.4)], such that it was no different from baseline healthy control values. Similarly, fasting fat oxidation fell to 1.02 g. kg(-1).min(-1) (0.8-1.18), again no longer significantly different from baseline healthy control values. While weight-losing patients with advanced pancreatic cancer have an increased resting energy expenditure and increased fat oxidation, the energy cost of feeding is, in fact, reduced. Provision of a fish-oil-enriched nutritional supplement results in some normalization of the metabolic response in both the fasted and fed states, in association with an improvement in nutritional status.

Resveratrol induces vasorelaxation of mesenteric and uterine arteries from female guinea-pigs.

Abstract: Naturally occurring hydroxystilbenes have been shown to induce vasorelaxation. Here, we studied the mechanism of resveratrol-induced vasorelaxation in dierent types of blood vessels, namely mesenteric (resistance) and main uterine (conductance) arteries, from female guinea-pigs on day 7 and day 15 of the oestrous cycle. Resveratrol (5‐70 lmol/l) induced concentrationdependent relaxation of both mesenteric and uterine arteries preconstricted with either noradrenaline (NA; 10 lmol/l) or KCl (125 mmol/l). Resveratrol was 2-fold more potent in inducing relaxation of mesenteric arteries than of uterine arteries. Its eects on uterine arteries from both day-7 and day-15 guinea-pigs were similar, irrespective of the constrictor used, but it was significantly (P ! 0.01) more potent in inducing relaxation of mesenteric arteries contracted with NA compared with those constricted with KCl. In day-7 arteries precontracted with NA, N G -nitro-L-arginine methyl ester (L-NAME; 10 lmol/l) had no eects on the time course of resveratrol-induced vasorelaxation in either mesenteric or uterine arteries. However, indomethacin (50 lmol/l) significantly (P ! 0.05) potentiated resveratrol’s eect on mesenteric, but not uterine, arteries. Indomethacin had no eect on resveratrol-induced vasorelaxation of arteries contracted with KCl, whereas L-NAME significantly (P ! 0.05) reduced the eects of resveratrol on uterine, but not on mesenteric, arteries. In day-15 arteries, L-NAME significantly (P ! 0.01) attenuated the eects of resveratrol on mesenteric arteries contracted with NA. Indomethacin had no eect on resveratrol activity. This study indicates that: (a) the eect of resveratrol on resistance arteries is greater than that on conductance arteries; (b) the eects of resveratrol are not mediated via prostanoids, but NO may play a role; and (c) the stage of the oestrous cycle has no influence on resveratrol-induced vasorelaxation.

Conjugated linoleic acid induces lipid peroxidation in men with abdominal obesity.

Abstract: Conjugated linoleic acid (CLA) has been shown in experimental studies to have chemoprotective properties, and may decrease the deposition of body fat. CLA is prone to oxidation, and it has been suggested that increased lipid oxidation may contribute to the anti-tumorigenic effects of this agent. The present study investigates the urinary levels of 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)), a major isoprostane, and of 15-oxo-dihydro-PGF(2alpha), a major metabolite of PGF(2alpha), as indicators of non-enzymic and enzymic arachidonic acid oxidation respectively after dietary supplementation with CLA in middle-aged men (mean age 53 years) with abdominal obesity for 1 month in a randomized controlled trial. Significant increases in the levels of both 8-iso-PGF(2alpha) and 15-oxo-dihydro-PGF(2alpha) in urine (P<0. 0001 and P=0.0013 respectively) were observed after 1 month of daily CLA intake (4.2 g/day) as compared with the control group. The lipid peroxidation parameters had returned to their basal levels at 2 weeks after the cessation of CLA intake, and remained at the same levels for a further 2 weeks until the end of the study. CLA had no effect on serum alpha-tocopherol and gamma-tocopherol levels, or on the urinary levels of 2,3-dinor-thromboxane B(2). Thus CLA may induce both non-enzymic and enzymic lipid peroxidation in vivo in middle-aged men with abdominal obesity, without any side effects. The consequences of the increased lipid peroxidation after CLA supplementation are unknown.

Relationship between the clinical features of neurological decompression illness and its causes.

Abstract: There is dispute as to whether paradoxical gas embolism is an important aetiological factor in neurological decompression illness, particularly when the spinal cord is aected. We performed a blind case-controlled study to determine the relationship between manifestations of neurological decompression illness and causes in 100 consecutive divers with neurological decompression illness and 123 unaected historical control divers. The clinical eects of neurological decompression illness (including the sites of lesions and latency of onset) were correlated with the presence of right-to-left shunts, lung disease and a provocative dive profile. The prevalence and size of shunts determined by contrast echocardiography were compared in aected divers and controls. Right-to-left shunts, particularly those which were large and present without a Valsalva manoeuvre, were significantly more common in divers who had neurological decompression illness than in controls (P ! 0.001). Shunts graded as large or medium in size were present in 52% of aected divers and 12.2% of controls (P ! 0.001). Spinal decompression illness occurred in 26 out of 52 divers with large or medium shunts and in 12 out of 48 without (P ! 0.02). The distribution of latencies of symptoms diered markedly in the 52 divers with a large or medium shunt and in the 30 divers who had lung disease or a provocative dive profile. In most cases of neurological decompression illness the cause can be determined by taking a history of the dive profile and latency of onset, and by performing investigations to detect a right-to-left shunt and lung disease. Using this information it is possible to advise divers on the risk of returning to diving and on ways of reducing the risk if diving is resumed. Most cases of spinal decompression illness are associated with a right-to-left shunt.

Increased gene expression of adrenomedullin and adrenomedullin-receptor complexes, receptor-activity modifying protein (RAMP)2 and calcitonin-receptor-like receptor (CRLR) in the hearts of rats with congestive heart failure

Abstract: Adrenomedullin is a vasodilator peptide produced in various organs, including heart and kidney. A novel adrenomedullin receptor complex has recently been identified, namely the calcitonin receptor-like receptor (CRLR) and receptor-activity modifying protein (RAMP) 2. In the present study, we have examined gene expression of RAMP2, CRLR and adrenomedullin in hearts and kidneys of rats with congestive heart failure caused by coronary artery ligation. Partial cloning was performed to determine the rat RAMP2 nucleotide sequence. Messenger RNA levels were then determined using competitive, quantitative reverse transcription-PCR techniques. Significantly increased expression levels (means±S.E.) of RAMP2, CRLR and adrenomedullin mRNA were found in the atrium (1.8±0.2-fold, 1.8±0.2-fold and 2.1±0.1-fold, respectively, compared with sham operated rats) and in the ventricle (1.4±0.1-fold, 1.3±0.03-fold and 3.0±0.5-fold respectively). On the other hand, expression levels of RAMP2, CRLR and adrenomedullin mRNAs were not significantly changed in the kidney. These findings suggest potential roles of locally-produced and locally-acting adrenomedullin in the failing heart.

Deleterious effects of chronic clenbuterol treatment on endurance and sprint exercise performance in rats.

Abstract: The beta(2)-adrenergic agonist, clenbuterol, has powerful muscle anabolic and lipolytic effects and is used by athletes to improve exercise performance; however, its use in conjunction with different forms of exercise training has received limited attention. Since previous studies have reported that chronic use of other beta(2)-adrenergic agonists has deleterious effects on cardiac muscle structure and function, the aim of the present study was to determine whether chronic clenbuterol administration would reduce the exercise capabilities of rats subjected to long-term treadmill sprint running, endurance swimming or voluntary wheel running training. The effect of clenbuterol treatment on exercise performance in rats was evaluated in three separate studies. Different groups of male rats were assigned to an endurance swimming (2 h/day, 5/7 days, 18 weeks) group, a treadmill sprint running (8x1 min bouts, 1.05 m/s, 20 weeks) group, or a voluntary wheel running (16 weeks) group. In each study, rats were allocated into either a treated group that received clenbuterol (2 mg.kg(-1).day(-1)) in their drinking water or an untreated control group. In each of the three studies, treated rats exhibited a reduction in exercise performance compared with untreated rats. Treated rats ran approximately 57% less total distance than untreated rats in the voluntary running programme and were unable to complete the swimming and sprinting protocols performed by the untreated rats. In each of the studies, the treated rats exhibited cardiac hypertrophy, with absolute heart mass increased by approximately 19% and heart mass relative to body mass increased by approximately 20%. The hearts of sedentary rats treated with clenbuterol exhibited extensive collagen infiltration surrounding blood vessels and in the wall of the left ventricle. The results indicate strongly that chronic clenbuterol administration deleteriously affects exercise performance in rats, potentially due to alterations in cardiac muscle structure and function.

Differential timing for programming of glucose homoeostasis, sensitivity to insulin and blood pressure by in utero exposure to dexamethasone in sheep.

Abstract: Numerous epidemiological studies have related an increased risk of adult-onset cardiovascular and metabolic disease to an adverse intra-uterine environment at critical periods. We have shown that fetal sheep exposed to dexamethasone for only 2 days at 27 days of gestation (term E 150 days) became hypertensive adults, whereas those exposed at 64 days of gestation remained normotensive, as did controls. In the same sheep, now nearly 5 years old, we performed glucose tolerance tests and hyperinsulinaemic euglycaemic clamps to study the insulin sensitivity of glucose, amino acid and non-esterified fatty acid metabolism. Glucose tolerance, calculated as the area under the curve, after intravenous administration of bolus glucose and insulin secretion in response to a glucose challenge were not altered in any group. There were no significant dierences in the insulin sensitivity of net whole-body glucose or amino acid uptake. However, suppression of lipolysis by insulin, measured as the proportional decrease in the circulating concentration of non-esterified fatty acids during the hyperinsulinaemic clamp, was 69‡1.2% at steady-state plasma insulin levels (E 1000 m-units/l) in the group exposed to dexamethasone at 27 days of gestation, but only 50.8‡6.5% in the controls (P ! 0.05). In the group exposed to dexamethasone at 64 days of gestation, the decrease was 66.4‡5.1%, which did not reach significance compared with the controls (P fl 0.10). Thus brief dexamethasone exposure during early gestation programmed hypertension independently of insulin resistance of glucose or amino acid metabolism; however, it did lead to increased insulin sensitivity of the inhibition of lipolysis, which may increase susceptibility to the development of obesity postnatally.

Insulin sensitivity of glucose and fat metabolism in severe sepsis.

Abstract: In order to quantify the changes in insulin sensitivity, particularly of endogenous glucose production and fat metabolism, in patients with severe sepsis, a prospective study was conducted in five normal subjects and in five patients with severe sepsis hospitalized in an intensive care unit. The responses of endogenous glucose production, glucose utilization, plasma fatty acids and ketone body concentrations to progressive increase in plasma insulin levels (exogenous insulin infusion rates of 0, 0.5, 1 and 2 m-units x min(-1) x kg(-1)) were measured using the isoglycaemic clamp technique. Total glucose turnover was determined with D-[6,6-(2)H(2)]glucose. In each group, plasma glucose was maintained at basal levels (control subjects, 4.32+/-0.22 mmol x l(-1); patients with sepsis, 7.10+/-2.29 mmol x l(-1); P<0.05). Plasma insulin concentrations were comparable in the two groups at an insulin infusion rate of 0.4 m-unit x min(-1) x kg(-1) for controls and 0.5 m-unit x min(-1) x kg(-1) for patients with sepsis, but differed following infusion at 2 m-unit x min(-1) x kg(-1) (control subjects, 102+/-13.4 m-units x l(-1); patients with sepsis, 124.8+/-19.7 m-units x l(-1); P<0.05). Endogenous glucose production was completely suppressed in control subjects by the first insulin infusion (0.4 m-unit x min(-1) x kg(-1)), but was only suppressed during infusion at 1 m-unit x min(-1) x kg(-1) insulin in patients with sepsis. The glucose utilization rate increased significantly with exogenous insulin infusion in control subjects, but did not increase in patients with sepsis. Plasma non-esterified (free) fatty acid and ketone body levels were significantly decreased in both groups by the infusion of exogenous insulin, but the sensitivity of lipolysis was impaired in patients with sepsis. In conclusion, sepsis impaired to a varying extent the action of insulin on endogenous glucose production, glucose utilization, lipolysis and ketogenesis. Whole-body glucose uptake was the most affected, with a total lack of response to the elevated insulin levels obtained in this study. Suppression of endogenous glucose production and lipolysis could only be achieved with higher doses of insulin than those required in normal subjects.