Phenylalanine: total amino acid ratio in 45 burn patients

Alterations in serum amino-acid profile in the progression of colorectal cancer: associations with systemic inflammation, tumour stage and patient survival

BACKGROUND

Cancer cachexia is a complex wasting syndrome affecting patients with advanced cancer, with systemic inflammation as a key component in pathogenesis. Protein degradation and release of amino acids (AAs) in skeletal muscle are stimulated in cachexia. Here, we define factors contributing to serum AA levels in colorectal cancer (CRC).

METHODS

Serum levels of nine AAs were characterised in 336 CRC patients and their relationships with 20 markers of systemic inflammatory reaction, clinicopathological features of cancers and patient survival were analysed.

RESULTS

Low serum glutamine and histidine levels and high phenylalanine levels associated with indicators of systemic inflammation, including high modified Glasgow Prognostic Score, high blood neutrophil/lymphocyte ratio and high serum levels of CRP, IL-6 and IL-8. Low levels of serum glutamine, histidine, alanine and high glycine levels also associated with advanced cancer stage and with poor cancer-specific survival in univariate analysis.

CONCLUSIONS

In CRC, serum AA levels are associated with systemic inflammation and disease stage. These findings may reflect muscle catabolism induced by systemic inflammation in CRC.

Immune changes and neurotransmitters: possible interactions in depression?

A disturbed metabolism of catecholamines and other neurotransmitters appears to play a major role in the pathogenesis of neurospychiatric symptoms, such as changes in mood and depression. This symptomatology is common in patients with chronic inflammatory disorders such as infections, autoimmune diseases, or cancer. The pathogenesis of these symptoms is still unclear. Pro-inflammatory stimuli interfere not only with the neural circuits and neurotransmitters of the serotonergic system but also with those of the adrenergic system. The pro-inflammatory cytokine interferon-γ stimulates the biosynthesis of 5,6,7,8-tetrahydrobiopterin (BH4), which is a co-factor for several aromatic amino acid mono-oxygenases and is rate-limiting for the biosynthesis of the neurotransmitter serotonin and the catecholamines dopamine, epinephrine (adrenaline) and norepinephrine (noradrenaline). Interferon-γ triggers the high output of reactive oxygen species in macrophages, which can destroy the oxidation-labile BH4. Recent data suggests that oxidative loss of BH4 in chronic inflammatory conditions can reduce the biosynthesis of catecholamines, which may relate to disturbed adrenergic neurotransmitter pathways in patients.

Increased blood phenylalanine to tyrosine ratio in HIV-1 infection and correction following effective antiretroviral therapy

OBJECTIVE

Higher blood levels of the essential amino acid phenylalanine (phe) have been documented in patients with HIV-1 infection. They may relate to a diminished conversion of phe to tyrosine (tyr) by the enzyme phenylalanine-hydroxylase (PAH). PAH is rate-limiting in the biosynthesis of dopamine, and impaired PAH activity is reflected by an increased phe to tyr ratio (phe/tyr).

METHODS

Plasma phe/tyr was measured in 107 patients with HIV-1 infection before and after 12 months of effective antiretroviral therapy (ART). Results were compared with CD4+ cell counts, HIV-1 RNA levels and concentrations of immune activation marker neopterin.

RESULTS

Before ART, phe/tyr was mean+/-S.D.: 0.99+/-0.57 micromol/micromol. Phe/tyr correlated significantly with plasma and urine neopterin concentrations (rs=0.434, and rs=0.392; both p<0.001) and less strongly with HIV-RNA levels (rs=0.173) and CD4+ counts (rs=-0.182, both p<0.05). After ART, phe/tyr dropped to 0.72+/-0.16 (=-27%; U=5.21, p=0.01) which was due to an average decline of -14% of phe concentrations from 73.1+/-34.0 micromol/L at baseline to 62.9+/-17.8 micromol/L after ART (U=2.51, p=0.01) and a concomitant increase of tyr concentrations (+13%, U=2.46, p=0.01). In parallel, significant reductions of plasma and urine neopterin concentrations were observed during ART.

CONCLUSIONS

Increased phe/tyr is frequent in patients with HIV-1 infection and is related to immune activation. ART was found to decrease phe/tyr and this change could indicate and influence on PAH activity. Future studies might be able to show whether the decline of phe/tyr under ART may concur with the often improved neuropsychiatric status in treated patients.