title: Tryptophan depletion in context of the inflammatory and general nutritional status of a low-income South African HIV-infected population.
abstract: BACKGROUND
  The essential amino acid tryptophan cannot be synthesised in the body and must be acquired through dietary intake. Oxidation of tryptophan, due to immune induction of the enzyme indoleamine 2,3-dioxygenase (IDO), is considered to be the main cause of tryptophan depletion in HIV infection and AIDS. We examined plasma tryptophan levels in a low-income sub-Saharan HIV-infected population and compared it to that of developed countries. Tryptophan levels were further examined in context of the general nutritional and inflammatory status.
  
  
  METHODS
  This cross-sectional study included 105 HIV-positive patients recruited from the Kalafong Hospital in Pretoria, South Africa, and 60 HIV-negative controls.
  
  
  RESULTS
  Patient tryptophan levels were in general markedly lower than those reported for developed countries. In contrast to reports from developed countries that showed tryptophan levels on average to be 18.8 % lower than their control values, tryptophan levels in our study were 44.1 % lower than our controls (24.4 ± 4.1 vs. 43.6 ± 11.9 μmol/l; p < 0.001). Tryptophan levels correlated with both CD4 counts (r = 0.341; p = 0.004) and with pro-inflammatory activity as indicated by neopterin levels (r = -0.399; p = 0.0001). Nutritional indicators such as albumin and haemoglobin correlated positively with tryptophan and negatively with the pro-inflammatory indicators neopterin, interleukin 6 and C-reactive protein. The most probable causes of the lower tryptophan levels seen in our population are food insecurity and higher levels of inflammatory activity.
  
  
  CONCLUSIONS
  We contend that inflammation-induced tryptophan depletion forms part of a much wider effect of pro-inflammatory activity on the nutritional profile of HIV-infected patients.
authors.affiliation: Department of Physiology, School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Priyesh
authors.initials: P
authors.lastname: Bipath
authors.affiliation: Department of Internal Medicine (Kalafong Hospital), School of Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Levay
authors.affiliation: Department of Psychiatry, School of Medicine, Faculty of Health Sciences, University of Pretoria, Private Bag X323, 0007, Pretoria, South Africa. mviljoen@webafrica.org.za.
authors.forename: Margaretha
authors.initials: M
authors.lastname: Viljoen
mesh_terms: D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D015415:Biomarkers / Q000097:blood; D044383:Black People; D018791:CD4 Lymphocyte Count; D003430:Cross-Sectional Studies; D003677:Deficiency Diseases / Q000208:ethnology / Q000209:etiology* / Q000523:psychology; D004032:Diet / Q000009:adverse effects* / Q000208:ethnology / Q000523:psychology; D005260:Female; D005523:Food Supply / Q000191:economics; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy / Q000276:immunology / Q000503:physiopathology*; D006779:Hospitals, Public; D006801:Humans; D008297:Male; D008875:Middle Aged; D019798:Neopterin / Q000097:blood; D009752:Nutritional Status; D010044:Outpatient Clinics, Hospital; D011204:Poverty Areas; D013019:South Africa; D019036:Suburban Health Services; D014364:Tryptophan / Q000097:blood / Q000172:deficiency*
chemical_list: D015415:Biomarkers; D019798:Neopterin; D014364:Tryptophan