Serum amino acids in weight-losing patients with cancer and tuberculosis

Glycine by enteral route does not improve major clinical outcomes in severe COVID-19: a randomized clinical pilot trial

There is a worrying scarcity of drug options for patients with severe COVID-19. Glycine possesses anti-inflammatory, cytoprotective, endothelium-protective, and platelet-antiaggregant properties, so its use in these patients seems promising. In this open label, controlled clinical trial, inpatients with severe COVID-19 requiring mechanical ventilation randomly received usual care (control group) or usual care plus 0.5 g/kg/day glycine by the enteral route (experimental group). Major outcomes included mortality, time to weaning from mechanical ventilation, total time on mechanical ventilation, and time from study recruitment to death. Secondary outcomes included laboratory tests and serum cytokines. Patients from experimental (n = 33) and control groups (n = 23) did not differ in basal characteristics. There were no differences in mortality (glycine group, 63.6% vs control group, 52.2%, p = 0.60) nor in any other major outcome. Glycine intake was associated with lower fibrinogen levels, either evaluated per week of follow-up (p < 0.05 at weeks 1, 2, and 4) or as weighted mean during the whole hospitalization (608.7 ± 17.7 mg/dl vs control 712.2 ± 25.0 mg/dl, p = 0.001), but did not modify any other laboratory test or cytokine concentration. In summary, in severe COVID-19 glycine was unable to modify major clinical outcomes, serum cytokines or most laboratory tests, but was associated with lower serum fibrinogen concentration.Registration: ClinicalTrials.gov NCT04443673, 23/06/2020.

Urinary metabolic characterization of advanced tuberculous meningitis cases in a South African paediatric population

Tuberculous meningitis (TBM) is a severe form of tuberculosis with high neuro-morbidity and mortality, especially among the paediatric population (aged ≤12 years). Little is known of the associated metabolic changes. This study aimed to identify characteristic metabolic markers that differentiate severe cases of paediatric TBM from controls, through non-invasive urine collection. Urine samples selected for this study were from two paediatric groups. Group 1: controls (n = 44): children without meningitis, no neurological symptoms and from the same geographical region as group 2. Group 2: TBM cases (n = 13): collected from paediatric patients that were admitted to Tygerberg Hospital in South Africa on the suspicion of TBM, mostly severely ill; with a later confirmation of TBM. Untargeted 1H NMR-based metabolomics data of urine were generated, followed by statistical analyses via MetaboAnalyst (v5.0), and the identification of important metabolites. Twenty nine urinary metabolites were identified as characteristic of advanced TBM and categorized in terms of six dysregulated metabolic pathways: 1) upregulated tryptophan catabolism linked to an altered vitamin B metabolism; 2) perturbation of amino acid metabolism; 3) increased energy production-metabolic burst; 4) disrupted gut microbiota metabolism; 5) ketoacidosis; 6) increased nitrogen excretion. We also provide original biological insights into this biosignature of urinary metabolites that can be used to characterize paediatric TBM patients in a South African cohort.

The impact of moderate altitude on exercise metabolism in recreational sportsmen: a nuclear magnetic resonance metabolomic approach

Although it is known that altitude impairs performance in endurance sports, there is no consensus on the involvement of energy substrates in this process. The objective of the present study was to determine whether the metabolomic pathways used during endurance exercise differ according to whether the effort is performed at sea level or at moderate altitude (at the same exercise intensity, using proton nuclear magnetic resonance, ¹H NMR). Twenty subjects performed two 60-min endurance exercise tests at sea level and at 2150 m at identical relative intensity on a cycle ergometer. Blood plasma was obtained from venous blood samples drawn before and after exercise. ¹H NMR spectral analysis was then performed on the plasma samples. A multivariate statistical technique was applied to the NMR data. The respective relative intensities of the sea level and altitude endurance tests were essentially the same when expressed as a percentage of the maximal oxygen uptake measured during the corresponding incremental maximal exercise test. Lipid use was similar at sea level and at altitude. In the plasma, levels of glucose, glutamine, alanine, and branched-chain amino acids had decreased after exercise at altitude but not after exercise at sea level. The decrease in plasma glucose and free amino acid levels observed after exercise at altitude indicated that increased involvement of the protein pathway was necessary but not sufficient for the maintenance of glycaemia. Metabolomics is a powerful means of gaining insight into the metabolic changes induced by exercise at altitude.

1H-Nuclear magnetic resonance-based metabolomic analysis of brain in mice with nicotine treatment

Background

Nicotine is rapidly absorbed from cigarette smoke and therefore induces a number of chronic illnesses with the widespread use of tobacco products. Studies have shown a few cerebral metabolites modified by nicotine; however, endogenous metabolic profiling in brain has not been well explored.

Results

H NMR-based on metabonomics was applied to investigate the endogenous metabolic profiling of brain hippocampus, nucleus acumens (NAc), prefrontal cortex (PFC) and striatum. We found that nicotine significantly increased CPP in mice, and some specific cerebral metabolites differentially changed in nicotine-treated mice. These modified metabolites included glutamate, acetylcholine, tryptamine, glucose, lactate, creatine, 3-hydroxybutyrate and nicotinamide-adenine dinucleotide (NAD), which was closely associated with neurotransmitter and energy source. Additionally, glutathione and taurine in hippocampus and striatum, phosphocholine in PFC and glycerol in NAc were significantly modified by nicotine, implying the dysregulation of anti-oxidative stress response and membrane metabolism.

Conclusions

Nicotine induces significant metabonomic alterations in brain, which are involved in neurotransmitter disturbance, energy metabolism dysregulation, anti-oxidation and membrane function disruptions, as well as amino acid metabolism imbalance. These findings provide a new insight into rewarding effects of nicotine and the underlying mechanism.

Mechanisms of metabonomic for a gateway drug: nicotine priming enhances behavioral response to cocaine with modification in energy metabolism and neurotransmitter level

Nicotine, one of the most commonly used drugs, has become a major concern because tobacco serves as a gateway drug and is linked to illicit drug abuse, such as cocaine and marijuana. However, previous studies mainly focused on certain genes or neurotransmitters which have already been known to participate in drug addiction, lacking endogenous metabolic profiling in a global view. To further explore the mechanism by which nicotine modifies the response to cocaine, we developed two conditioned place preference (CPP) models in mice. In threshold dose model, mice were pretreated with nicotine, followed by cocaine treatment at the dose of 2 mg/kg, a threshold dose of cocaine to induce CPP in mice. In high-dose model, mice were only treated with 20 mg/kg cocaine, which induced a significant CPP. ¹H nuclear magnetic resonance based on metabonomics was used to investigate metabolic profiles of the nucleus accumbens (NAc) and striatum. We found that nicotine pretreatment dramatically increased CPP induced by 2 mg/kg cocaine, which was similar to 20 mg/kg cocaine-induced CPP. Interestingly, metabolic profiles showed considerable overlap between these two models. These overlapped metabolites mainly included neurotransmitters as well as the molecules participating in energy homeostasis and cellular metabolism. Our results show that the reinforcing effect of nicotine on behavioral response to cocaine may attribute to the modification of some specific metabolites in NAc and striatum, thus creating a favorable metabolic environment for enhancing conditioned rewarding effect of cocaine. Our findings provide an insight into the effect of cigarette smoking on cocaine dependence and the underlying mechanism.

Metabolomic analysis of the plasma of patients with high-altitude pulmonary edema (HAPE) using 1H NMR

Upon rapid ascent to a high altitude, non-acclimatized individuals, although healthy, are highly prone to contracting high-altitude pulmonary edema (HAPE). Early diagnosis is difficult and there is no reliable biomarker available. We used proton ((1)H) NMR metabolomics to profile the altered metabolic patterns of blood plasma from HAPE patients. The plasmas of ten patients with HAPE and ten individuals without HAPE were collected and compared using (1)H NMR spectroscopy. Data were evaluated with several multivariate statistical analyses, including the principal components, the orthogonal partial least-squares discriminant, and the orthogonal signal correction partial least-squares discriminant. Multivariate statistical analyses revealed a significant disparity between subjects with HAPE and those in the control group. Compared to the plasma of the controls, the HAPE patients had significant increases in valine, lysine, leucine, isoleucine, glycerol phosphoryl choline, glycine, glutamine, glutamic acid, creatinine, citrate, and methyl histidine. These were accompanied by decreases in α- and β-glucose, trimethylamine, and the metabolic products of lipids. The data demonstrate that metabolomics may be effective for the diagnosis of HAPE in the future, and can be used for further understanding HAPE pathogenesis.

(1)H NMR-based metabolomic profiling in mice infected with Mycobacterium tuberculosis

Tuberculosis (TB) is one of three major infectious diseases, and the control of TB is becoming more difficult because of the emergence of multidrug-resistant and extensively drug-resistant strains. In this study, we explored the (1)H NMR-based metabolomics of TB using an aerobic TB infection model. Global profiling was applied to characterize the responses of C57Bl/6 mice to an aerobic infection with virulent Mycobacterium tuberculosis (MTB). The metabolic changes in organs (i.e., the lung, the target organ of TB, and the spleen and liver, remote systemic organs) and in serum from control and MTB-infected rats were investigated to clarify the host-pathogen interactions in MTB-infected host systems. Principal components analysis (PCA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) score plots showed distinct separation between control and MTB-infected rats for all tissue and serum samples. Several tissue and serum metabolites were changed in MTB-infected rats, as compared to control rats. The precursors of membrane phospholipids, phosphocholine, and phosphoethanolamine, as well as glycolysis, amino acid metabolism, nucleotide metabolism, and the antioxidative stress response were altered based on the presence of MTB infection. This study suggests that NMR-based global metabolite profiling of organ tissues and serum could provide insight into the metabolic changes in host infected aerobically with virulent Mycobacterium tuberculosis.

Perioperative GLY-GLN infusion diminishes the surgery-induced period of immunosuppression: accelerated restoration of the lipopolysaccharide-stimulated tumor necrosis factor-alpha response

OBJECTIVE

To investigate whether the administration of different glutamine-containing dipeptides, glycyl-l-glutamine (GLY-GLN) and l-alanyl-l-glutamine, has a differing impact on perioperative immunomodulation.

SUMMARY BACKGROUND DATA

Surgery leads to transitory immunosuppression, which is associated with decreased plasma glutamine (GLN) levels and increased susceptibility to infection and sepsis. A useful tool to detect immunocompetence is the ex vivo lipopolysaccharide (LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) secretion in whole blood.

METHODS

Forty-five patients undergoing major abdominal surgery were randomized prospectively to receive 0.5 g/kg/24 h GLN dipeptides administered as GLY-GLN or as ALA-GLN or isonitrogenous Vamin (a GLN-free amino acid solution; control group) as a continuous infusion over 72 hours, starting 24 hours before surgery. Blood samples were collected before infusion, at the end of surgery, and 48 hours postoperatively to determine the TNF-alpha release into whole blood stimulated with LPS. Groups were compared by analysis of variance.

RESULTS

The groups were comparable in age, gender distribution, and length of operative time. At the end of surgery a significant reduction in ex vivo LPS-stimulated TNF-alpha production was observed in all groups. In patients who received GLY-GLN, the induced TNF-alpha production was restored after 48 hours.

CONCLUSIONS

In this study perioperative infusion of GLY-GLN reduced immunosuppression. The effect of GLN-containing dipeptides seems to be different when administered in glycine or alanine form.

Acceptability and tolerance of a low tyrosine and phenylalanine diet in patients with advanced cancer -- a pilot study

BACKGROUND

Low phenylalanine (phe) and tyrosine (tyr) diets limit tumour growth in animal models and may offer a novel cancer therapy. We studied the efficacy and acceptability of a low phe and tyr diet in patients with advanced cancer.

METHODS

Patients with advanced metastatic melanoma (n=22) and metastatic breast cancer (n=15) were invited to follow a low phe and tyr diet (10 mg kg-1 phe and tyr per day) for 1 month. In those individuals who followed the diet for 1 month, we attempted to establish the effects on nutritional status (body weight, fat free mass, percentage body fat, serum albumin), immune cell function (white cell count, lymphocytes and neutrophils), plasma levels of phe-tyr and tryptophan and quality of life (Hospital Anxiety and Depression score).

RESULTS

Only three of the 22 patients with metastatic melanoma and three of the 15 patients with metastatic breast cancer agreed to start the diet. All patients experienced problems and side-effects and increases in anxiety and depression. There were declines in weight, with loss of fat and fat free mass but slight increases in white cell counts and neutrophils.

CONCLUSIONS

Low phe and tyr diets do not appear to be a viable treatment option for patients with advanced cancer.

Fibrinogen synthesis is elevated in fasting cancer patients with an acute phase response

The unusual amino acid composition of acute phase proteins may be relevant to our understanding of the mechanism of tissue wasting in chronic inflammatory disease. During periods in which demand for amino acids outstrips dietary supply, skeletal muscle protein may be mobilized to meet this demand. An imbalance in the amino acid composition of these proteins may thus be detrimental to the body's nitrogen economy. To address this problem, we have measured the synthetic rate of fibrinogen (perhaps the major acute phase protein) and plasma amino acid profiles in a group of patients with adenocarcinoma of the pancreas and an ongoing inflammatory response (serum C-reactive protein >10 mg/L in the absence of any other obvious infective or inflammatory cause). These were also measured in a control group with no evidence of inflammation. Fibrinogen synthesis was measured after an overnight fast, using a flooding dose of 2H5-phenylalanine. The fractional rate of fibrinogen synthesis was significantly elevated in the cancer group compared with healthy controls [39.3 (20.0-49.9) and 21.9 (13.2-37.7) %/d, respectively; median (range), P < 0.05]. The absolute rate of fibrinogen synthesis was also elevated [84 (33-143) and 26 (15-43) mg/(kg.d), respectively; median (range), P < 0.01]. We calculated that, in cancer patients with anorexia-cachexia (i.e., documented ongoing weight loss in the absence of an obvious cause such as obstruction or malabsorption), aromatic amino acid supply (predominantly tryptophan) most limits fibrinogen synthesis from skeletal muscle reserves. Demand for the nonessential amino acids serine and glycine was elevated. Assuming that tryptophan is limiting, up to 2.6 g muscle protein ( approximately 12 g skeletal muscle tissue) may be wasted to synthesize 1 g fibrinogen. Interpretation of the observation that circulating free tryptophan concentrations were significantly reduced in the cancer patients will have to await flux measurements. The metabolic changes accompanying the inflammatory response suggest that down-regulation of this process may be beneficial.

Induction of cachexia in mice by a product isolated from the urine of cachectic cancer patients

Urine from cancer patients with weight loss showed the presence of an antigen of M(r) 24,000 detected with a monoclonal antibody formed by fusion of splenocytes from mice with cancer cachexia. The antigen was not present in the urine of normal subjects, patients with weight loss from conditions other than cancer or from cancer patients who were weight stable or with low weight loss (1 kg month(-1)). The antigen was present in the urine from subjects with carcinomas of the pancreas, breast, lung and ovary. The antigen was purified from urine using a combination of affinity chromatography with the mouse monoclonal antibody and reversed-phase high-performance liquid chromotography (HPLC). This procedure gave a 200,000-fold purification of the protein over that in the original urine extract and the material isolated was homogeneous, as determined by silver staining of gels. The N-terminal amino acid sequence showed no homology with any of the recognized cytokines. Administration of this material to mice caused a significant (P<0.005) reduction in body weight when compared with a control group receiving material purified in the same way from the urine of a normal subject. Weight loss occurred without a reduction in food and water intake and was prevented by prior administration of the mouse monoclonal antibody. Body composition analysis showed a decrease in both fat and non-fat carcass mass without a change in water content. The effects on body composition were reversed in mice treated with the monoclonal antibody. There was a decrease in protein synthesis and an increase in degradation in skeletal muscle. Protein degradation was associated with an increased prostaglandin E2 (PGE2) release. Both protein degradation and PGE2 release were significantly reduced in mice pretreated with the monoclonal antibody. These results show that the material of M(r) 24,000 present in the urine of cachectic cancer patients is capable of producing a syndrome of cachexia in mice.

Interchange of amino acids between tumor and host

During the growth of a tumor, there are very relevant changes in the metabolism of the host to produce the metabolites rapidly consumed by the tumor. In this context, the exchanges of amino acids between the tumor and its host are especially important; however, they have received little attention. A rigorous study must provide data on the growth curve of the tumor, as well as on amino acid levels in tumor cells, plasma, and metabolically relevant tissues and organs from the host during the whole growth of the tumor. The main conclusions arising from a complete study in a tumor model are discussed.

Mouse liver free amino acids during the development of Ehrlich ascites tumour

Sequential amino acid concentrations were determined in the liver of mice infested with a highly malignant strain of Ehrlich ascites tumour cells. The liver concentrations of a certain group of amino acids showed changes consistent with those previously reported for plasma, ascitic liquid and tumour cells during tumour growth. Shortly after tumour transplantation a significant decrease of the essential amino acids methionine, threonine, valine, isoleucine + phenylalanine, leucine, lysine and histidine, was detected. Some non-essential amino acids, mainly the gluconeogenic substrates alanine and serine, showed a strong reduction in hepatic concentrations during the first days; these amino acids remained significantly lower than controls until animal death. Interestingly, hepatic glutamine increased at days 1 and 2 after inoculation, and proline showed a sustained increase from the seventh day onwards, reaching a value double the control at the end of animal life.

Nitrogen metabolism in tumor bearing mice

In experiments with whole animals infested with a highly malignant strain of Ehrlich ascites tumor cells, serial concentrations of amino acids were determined for host plasma, ascitic fluid, and tumor cells, throughout tumor development. Concentration gradients of glutamine, asparagine, valine, leucine, isoleucine, phenylalanine, tyrosine, histidine, tryptophan, arginine, serine, methionine, and taurine from the host plasma toward the ascitic liquid were established; while on the other hand, concentration gradients from the ascitic liquid toward the plasma were established for glutamate, aspartate, glycine, alanine, proline, and threonine. With the exception of aspartate the concentrations of these amino acids were highest inside the cells. Arginine was the only amino acid not detected in tumor cells. In vitro incubations of tumor cells in the presence of glutamine and/or glucose, as the energy and nitrogen sources, confirmed the amino acid fluxes previously deduced from the observed relative concentrations of amino acids in plasma, ascitic liquid, and tumor cells, suggesting that glutamate, alanine, aspartate, glycine, and serine can be produced by tumors. These findings support that changes in amino acid patterns occurring in the host system are related to tumor development.

Amino acid profiles in tumor-bearing and pair-fed nontumor-bearing malnourished rats

To investigate the metabolic and organ changes accompanying growth of a malignant tumor, ten male Fisher 344 rats weighing 150 to 200 g were inoculated subcutaneously with 10(6) viable MCA sarcoma cells (tumor-bearing). Ten other rats (controls) were similarly inoculated with saline. Both groups were allowed food and water ad libitum. An additional ten rats (pair-fed) were inoculated with saline and fed the same mean daily food intake as the tumor-bearing rats. Thirty-five days after inoculation the rats were killed by exsanguination. Livers, spleens, and tumors were weighed, and amino acid profiles and biochemical parameters were measured. Liver and spleen weights in tumor-bearing rats were significantly greater than control rats (P less than 0.05 and P less than 0.01, respectively). Liver weight in pair-fed rats was significantly less than control rats (P less than 0.01), but spleen weight was greater (P less than 0.01). Amino acid profiles of tumor-bearing rats and pair-fed rats were different from each other and from those of control rats. Branched-chain amino acids were lowest in tumor-bearing rats and significantly different from control and pair-fed rats. Lysine was significantly higher (P less than 0.01) and arginine significantly lower (P less than 0.05) in tumor-bearing rats compared with control rats. These different plasma amino acid profiles and changes in serum biochemistry of cachectic tumor-bearing rats compared with malnourished pair-fed rats suggest specific tumor effects on host metabolism not mediated solely by anorexia.