Possible mechanism of bamboo shoots (Bambusa balcooa) induced thyroid disruption - An in vitro study.

Endemic goitre and associated iodine deficiency disorders (IDDs) are a major concern in public health even in the period of post salt iodization in many regions. Among others the consumption of cyanogenic plants found responsible for the persistence of such diseases. Bamboo shoots (BS) is one such cyanogenic plant food that caused disruption of certain thyroid hormone synthesizing regulatory element as has already been reported in our earlier study. In this investigation the possible mechanism of thyrocytes disruption along with interruption of thyroid hormone biosynthesis by BS has been worked out. Commonly consumed BS, Bambusa Balcooa Roxb (BBR) water extract was analysed by GC MS; three doses below IC50 were administered to thyrocytes in culture with and without iodine. Expressions of thyroglobulin (Tg), pendrin (PDS) and monocarboxylate transporter 8 (MCT8) were evaluated in thyrocytes with cell cycle analysis, reactive oxygen species (ROS) generation, DNA oxidation and apoptotic regulation through Bax, Bcl-2 and p53. Phytochemical analysis of BBR extract revealed the presence of precursors and metabolic end products of cyanogenic glycosides. Dose dependent decrease in expression of Tg and PDS with concomitant decrease in gene expression of these with MCT8 were observed. Increased ROS, DNA oxidation and associated imbalance were found through increased Bax and p53 with decreased Bcl-2 that perturbed thyrocytes cell cycle. Cyanogenic constituents of BBR generates ROS associated oxidative changes in thyrocytes with DNA damage and oxidation and cell cycle disruption followed by inhibition of thyroid hormone synthesizing regulatory elements; addition of extra iodine showed partial prevention.

Dietary supplies of iodine & thiocyanate in the aetiology of endemic goitre in Imphal East district of Manipur, north east India.

BACKGROUND & OBJECTIVE: The present investigation was undertaken to study the iodine nutritional status of school children of Imphal east district in Manipur where endemic goitre persists during post-salt iodization phase along with the investigation of the factors responsible for the occurrence of goitre endemicity. METHODS: A total of 1,286 children (6-12 yr) were clinically examined for goitre from study areas of Imphal east district. A total of 160 urine samples were collected and analyzed to measure urinary iodine and thiocyanate levels. Iodine content was measured in 140 salt samples and 16 drinking water samples. RESULTS: Overall goitre prevalence was about 30 per cent (grade 1-24.7%; grade 2-5.3%) and median urinary iodine level was 17.25 microg/dl. The mean urinary thiocyanate level was 1.073 +/- 0.39 mg/dl. Iodine/thiocyanate ratio (microg/mg) was in the ranges from 15.65 to 22.34. The mean iodine content in drinking water samples was 2.92 +/- 1.75 microg/l and 97.8 per cent of edible salts had iodine level above 15 ppm at the consumption point. INTERPRETATION & CONCLUSION: Our findings showed that in spite of no biochemical iodine deficiency, iodine deficiency disorders (IDD) is a serious public health problem in Imphal east district of Manipur. The consumption pattern of certain plant foods containing thiocyanate (or its precursors) was relatively high that interfere with thyroid hormone synthesis resulting in the excretion of more iodine. Thus, the existing dietary supplies of thiocyanate in relation to iodine may be a possible aetiological factor for the persistence of endemic goitre in the study region during post salt iodization period.