Arginine and nutrition in renal disease

The implication of protein malnutrition on cardiovascular control systems in rats

The malnutrition in early life is associated with metabolic changes and cardiovascular impairment in adulthood. Deficient protein intake-mediated hypertension has been observed in clinical and experimental studies. In rats, protein malnutrition also increases the blood pressure and enhances heart rate and sympathetic activity. In this review, we discuss the effects of post-weaning protein malnutrition on the resting mean arterial pressure and heart rate and their variabilities, cardiovascular reflexes sensitivity, cardiac autonomic balance, sympathetic and renin-angiotensin activities and neural plasticity during adult life. These insights reveal an interesting prospect on the autonomic modulation underlying the cardiovascular imbalance and provide relevant information on preventing cardiovascular diseases.

Malnutrition enhances cardiovascular responses to chemoreflex activation in awake rats

Several studies in the literature suggest that low-protein intake is associated with increases in sympathetic efferent activity and cardiovascular disease. Among the possible mechanisms, changes in the neurotransmission of cardiovascular reflexes have been implicated. Therefore, the present study comprised the evaluation of chemoreflex responsiveness in rats subjected to a low-protein diet during the 35 days after weaning. As a result, we observed that malnourished rats presented higher levels of baseline mean arterial pressure and heart rate and exhibited a mild increase in the pressor response to chemoreflex activation. They also exhibited a massive bradycardic response to chemoreflex activation. Interestingly, bilateral ligature of the carotid body arteries further increased baseline mean arterial pressure and heart rate in malnourished animals. The data suggest severe autonomic imbalance and/or change in the central interplay between neural and cardiovascular mechanisms.

Overexpression of the disease resistance gene Pto in tomato induces gene expression changes similar to immune responses in human and fruitfly

The Pto gene encodes a serine/threonine protein kinase that confers resistance in tomato (Lycopersicon esculentum) to Pseudomonas syringae pv tomato strains that express the type III effector protein AvrPto. Constitutive overexpression of Pto in tomato, in the absence of AvrPto, activates defense responses and confers resistance to several diverse bacterial and fungal plant pathogens. We have used a series of gene discovery and expression profiling methods to examine the effect of Pto overexpression in tomato leaves. Analysis of the tomato expressed sequence tag database and suppression subtractive hybridization identified 600 genes that were potentially differentially expressed in Pto-overexpressing tomato plants compared with a sibling line lacking Pto. By using cDNA microarrays, we verified changes in expression of many of these genes at various time points after inoculation with P. syringae pv tomato (avrPto) of the resistant Pto-overexpressing line and the susceptible sibling line. The combination of these three approaches led to the identification of 223 POR (Pto overexpression responsive) genes. Strikingly, 40% of the genes induced in the Pto-overexpressing plants previously have been shown to be differentially expressed during the human (Homo sapiens) and/or fruitfly (Drosophila melanogaster) immune responses.

Effect of preoperative oral immune-enhancing nutritional supplement on patients at high risk of infection after cardiac surgery: a randomised placebo-controlled trial

BACKGROUND

Elderly patients and those with poor ventricular function have increased morbidity and mortality rates when undergoing surgery. We aimed to ascertain whether an oral immune-enhancing nutritional supplement could improve preoperative host defence, and subsequently lower postoperative infections and organ dysfunction in patients undergoing elective cardiac surgery who are at high risk of infection.

METHODS

In this prospective, randomised, double-blind, placebo-controlled study, we randomly assigned 50 patients who were scheduled to undergo coronary artery bypass to receive either an oral immune-enhancing nutritional supplement containing L-arginine, omega3 polyunsaturated fatty acids, and yeast RNA (n=25), or a control (n=25) for a minimum of 5 days. Patients were included if they were aged 70 years or older, or had an ejection fraction of less than 0.4, or were scheduled to undergo mitral valve replacement. The main outcome was preoperative host defence (delayed-type hypersensitivity response to recall antigens, expression of HLA-DR epitopes on monocytes, and concentration of interleukin 6 in plasma). Analysis was per protocol.

FINDINGS

Five patients (two in the treatment group) were excluded because they did not take the minimum dose. Preoperative expression of HLA-DR epitopes on monocytes was significantly higher in patients given the study treatment (109% [95% CI 92-128]) than those given the control (69% [58-82]) compared with baseline (100%) (p=0.02, repeated measures ANOVA). However, concentration of interleukin 6 was significantly lower in the treatment group (0.90 pg/L [0.69-1.18]) than in the control group (1.94 pg/L [1.45-2.59]) (p=0.032, repeated measures ANOVA). Additionally, delayed-type hypersensitivity response to recall antigens improved preoperatively and remained better until hospital discharge.

INTERPRETATION

Intake of an oral immune-enhancing nutritional supplement for a minimum of 5 days before surgery can improve outlook in high-risk patients who are undergoing elective cardiac surgery.

Dietary arginine alters time of symptom onset in Huntington's disease transgenic mice

Recent neuroimaging studies reported complex changes in cerebral blood flow (CBF) in early-staged Huntington's disease (HD) patients. Deckel and co-workers [Deckel and Duffy, Brain Res. (in press); Deckel and Cohen, Prog. Neuro-Psychopharmacol. Biol. Psychiatry 24 (2000) 193; Deckel et al., Neurology 51 (1998) 1576; Deckel et al., J. Nucl. Med. 41 (2000) 773] suggested that these findings might be accounted for, in part, by alterations in cerebral nitric oxide (NO) and its byproduct, peroxynitrite. The current experiment tested this hypothesis by altering NO levels via manipulations of dietary L-arginine (ARG), the dietary precursor of NO, in mice transgenic for HD. Seventy-one mice were assigned at 12 weeks of age to one of three isocaloric diets that varied in their content of ARG. These diets included: (a) 0% ARG, (b) 1.2% ARG (i.e. typical mouse chow), or (c) 5% ARG. The 5% ARG diets in HD mice accelerated the time of onset of body weight loss (P<0.05) and motor impairments (P<0.05), and increased resting CBF in HD relative to control (P<0.05). Conversely, the 0% ARG diet demonstrated no loss of body weight and had no changes in CBF relative to controls. However, the 0% ARG HD group continued to show significant deficits on motor testing (P<0. 05). The 1.2% ARG HD group showed reduced body weight loss, better motor functioning, and fewer changes in CBF compared to the 5% ARG HD group. Immunocytochemistry analysis found greater deposition of nitrotyrosine in the cortex, and vasculature, of HD+ mice, 5% and 1. 2%>0% arginine diets. When collapsed across all conditions, CBF inversely correlated (P<0.05) both with the body weight and motor changes suggesting that changes in CBF are associated with behavioral decline in HD mice. Collectively, these findings indicate that dietary consumption of the NO precursor ARG has a measurable, but complex, effect on symptom progression in HD transgenic mice, and implicates NO in the pathophysiology of HD.