Publications

It is not clear whether impaired amino acid (AA) absorption occurs in adults with environmental enteropathy (EE). Therefore, we set out to determine the  association between intestinal 13C615N-allo-isoleucine absorption (reflecting  neutral AA transport) and lactulose-rhamnose ratio (LRR, reflecting permeability)  in healthy adult volunteers (aged 18-35 years; N = 6) from India, and in those  with biopsy-confirmed EE (N = 20) from Zambia. A 3-hour oral bolus protocol using  13C615N-allo-isoleucine (M), co-administered with lactulose and rhamnose sugars,  was used to estimate AA absorption (as M area under the curve [AUC]) and LRR.  Additionally, duodenal biopsies were collected from participants in Zambia. There  was no association between allo-isoleucine absorption and LRR (separately by site  or combined), but there was a significant positive correlation with crypt depth  (N = 16; Spearman's rank correlation coefficient [rs] = 0.666; P-value = 0.005)  in the Zambian participants. However, on exploratory analysis, the peak  concentration (within first hour post-dose) of allo-isoleucine was significantly  and positively correlated with the percentage of rhamnose dose recovered (%R; N =  24, participants combined; rs = 0.434; P-value = 0.034), and with crypt depth (N  = 16; rs = 0.713; P-value = 0.002). There were differences noted between the two  sites: Zambian participants had a significantly lower median [range]%R (3.0  [1.0-4.6] versus 6.1% [3.2-7.7]) and allo-isoleucine (M + [M-1] AUC, 1.62  [0.73-5.44] versus 4.41 [3.69-5.37] µM*h/L) compared with those from India. In  conclusion, allo-isoleucine absorption correlated with %R (reflecting intestinal  absorptive surface area) but not LRR.