Yvonne L. J. Vissers

Measuring whole-body actin/myosin protein breakdown in mice using a primed constant stable isotope-infusion protocol

To measure actin/myosin protein breakdown, the 24 h excretion of N (tau)-methylhistidine (3MH) is used. However, in mice, this method is invalid. Therefore we have developed a liquid chromatography-MS technique to measure the tracer/tracee ratio and concentration of 3MH in plasma, enabling an in vivo primed constant infusion protocol with a deuterated stable isotope of 3MH. We tested this model by giving a primed constant infusion of L-[3-methyl-(2)H(3)]histidine, L-[phenyl-(2)H(5)]phenylalanine and L-[phenyl-(2)H(2)]tyrosine to three anaesthetized experimental groups: mice receiving saline intraperitoneally (i.p.) (CON), mice receiving saline i.p. and starved for 9 h (STA), and mice receiving lipopolysaccharide i.p. and starved for 9 h (STA+LPS). The contribution of myofibrillar to total protein breakdown was significantly lower in the STA group than the CON group (30+/-4% and 54+/-14% respectively; P <0.05), and was significantly higher in the STA+LPS group than the STA group (52+/-7% and 30+/-4% respectively; P <0.05). Whole-body myofibrillar protein breakdown, total protein breakdown, protein synthesis and net protein breakdown were not different between the groups. We conclude that this in vivo primed constant stable isotope-infusion protocol can give valuable information about the role of actin/myosin protein breakdown in mice.

Interorgan synthesis of arginine is down-regulated in tumor-bearing mice undergoing surgical trauma

Renal de novo arginine production has been suggested to be crucial for regulation of arginine production in disease. We investigated how the interorgan pathway for de novo arginine production is affected by the presence of malignant tumor and/or surgical trauma. Controls and methylcholanthrene-sarcoma-bearing mice were studied, both with and without undergoing laparotomy (n = 9-13 per group). One day after laparotomy, amino acid fluxes across the hindquarter, intestine, liver, and kidney were studied. In contrast to healthy mice, the liver of tumor-bearing mice took up citrulline (9 +/- 3 vs 1 +/- 2 nmol/[10 g min], P < .05), simultaneous with attenuated renal arginine output (4 +/- 3 vs 12 +/- 2 nmol/[10 g min], P < .05), despite increased intestinal conversion of glutamine to citrulline (15 +/- 3 vs 8 +/- 1 nmol/[10 g min], P < .05). In tumor-bearing mice undergoing surgery, intestinal citrulline output decreased (from 15 +/- 3 to 8 +/- 2 nmol/[10 g min], P < .05) and renal arginine output remained close to zero despite increased renal citrulline uptake (from 6 +/- 2 to 12 +/- 2 nmol/[10 g min], P < .05). In conclusion, the interorgan pathway for de novo arginine production was differently regulated depending on the pathophysiological situation. In methylcholanthrene-sarcoma-bearing mice, decreased de novo arginine production was accompanied by the presence of hepatic citrulline uptake, whereas tumor-bearing mice subjected to surgical trauma showed concomitant decreased intestinal citrulline output.

Metabolic and functional effects of glutamate intake in patients with chronic obstructive pulmonary disease (COPD).

BACKGROUND & AIMS Patients with chronic obstructive pulmonary disease (COPD) often suffer from skeletal muscle weakness due to muscle wasting and altered muscle metabolism. Decreased muscle glutamate concentration in COPD is consistently reported and is associated with decreased muscle glutathione concentration and early lactic acidosis. We hypothesized that an increased availability of glutamate via glutamate ingestion increases muscle glutamate concentration leading to acute improvements in skeletal muscle energy metabolism and function. METHODS Two experiments were conducted. In experiment 1, in two groups of 6 male COPD patients (FEV(1): 44.8+/-3.4%pred) and 6 healthy controls, blood samples and muscle biopsies were taken at 0 and 80 min after repeated glutamate (30 mg/kg BW) or control ingestion (1.25 ml/kg BW), and after 20 min cycling at 50% peak workload. In experiment 2, in 10 COPD patients (FEV(1): 36.1+/-2.5%pred), the effect of the two drinks was tested on cycle endurance time and contractile quadriceps fatigue measured by magnetic stimulation before and after cycling at 75% peak workload. RESULTS Glutamate ingestion increased plasma (p<0.01) but not muscle glutamate concentration. Muscle total and reduced glutathione and plasma lactate concentration were not affected by glutamate ingestion. Glutamate ingestion did not influence contractile muscle fatigue and endurance time. CONCLUSION Continuous oral glutamate ingestion for 80 min did not lead to an acute effect on skeletal muscle substrate metabolism and muscle performance in COPD patients and in age-matched healthy controls.

Presence of tumour inhibits the normal post-operative response in arginine and NO production in non-cachectic mice.

We have described recently that cancer patients have low plasma arginine concentrations, even without weight loss being present, suggesting that decreased arginine availability may be a specific feature of the presence of tumour. As arginine is important in post-operative repair, we hypothesized that abnormalities in arginine metabolism in cancer lead to an aberrant post-operative response in arginine and NO metabolism. To investigate this, we studied post-operative alterations in arginine and NO production and the acute-phase response in MCA (methylcholanthrene) sarcoma-bearing mice. Controls, mice with small MCA tumours (<15% of carcass weight) and large MCA tumours (>15% of carcass weight) were studied, either with or without undergoing laparotomy. The stable isotopes L-[guanidino-(15)N(2)-(2)H(2)]arginine and L-[ureido-(15)N]citrulline were used to study whole-body arginine and NO production rates. SAP (serum amyloid P component) concentrations were measured to assess the acute-phase response. Significance was tested using Mann-Whitney U test. In healthy FVB mice, laparotomy significantly increased whole-body arginine production (from 42+/-3 to 54+/-3 nmol x 10 g(-1) of carcass weight x min(-1)), NO production (from 1.1+/-0.1 to 1.4+/-0.2 nmol x 10 g(-1) of carcass weight x min(-1)) and levels of SAP (from 4+/-1 to 115+/-23 ng/ml), whereas in all MCA tumour-bearing mice baseline values of arginine metabolism and SAP concentration were already elevated and the response to laparotomy was absent. In conclusion, MCA tumour-bearing mice had a disturbed post-operative metabolic response, as evidenced by attenuated post-operative arginine and NO production, concomitant with an attenuated acute-phase response. This indicates that altered arginine metabolism may be an important characteristic of the metabolic changes in cancer.

Pros and cons of L-arginine supplementation in disease

The amino acid arginine and one of its metabolites NO have gathered broad attention in the last decade. Although arginine is regarded as a conditionally essential amino acid in disease, L-arginine supplementation in severe illness has not found its way into clinical practice. This might be due to the invalid interpretation of results from studies with immune-enhancing diets containing L-arginine amongst other pharmaconutrients. However, not much attention is given to research using L-arginine as a monotherapy and the possibility of the alternative hypothesis: that L-arginine supplementation is beneficial in disease. The present review will discuss data from studies in healthy and diseased animals and patients with monotherapy of L-arginine to come to an objective overview of positive and negative aspects of L-arginine supplementation in disease with special emphasis on sepsis, cancer, liver failure and wound healing.

Sustainability of short stay after breast cancer surgery in early adopter hospitals

Between 2005 and 2007 a short stay programme for breast cancer surgery was successfully implemented in early adopter hospitals. The current study evaluates the sustainability of this success five years following implementation. A retrospective audit of 160 consecutive patients undergoing breast cancer surgery was performed five years following implementation of short stay. The total proportion of patients treated in short stay was 82% (hospital 1 83%, hospital 2 78%, hospital 3 87%, hospital 4 80%) after five years follow-up, which was comparable to the proportion in short stay directly after implementation (p = 0.938). Overall compliance to the key recommendations to facilitate short stay after breast cancer surgery increased from 65% directly after implementation to 78% five years after implementation. This study shows that short stay after breast cancer surgery was successfully sustained in early adopter hospitals five years following implementation.