Accumulation of catechins in bone and liver of mice fed green tea while under physical stress

Abstract

Epidemiological evidence has linked increased habitual consumption of catechin rich tea to reduced risk of fractures and improved bone mineral density. The objective of this study was to determine the extent to which dietary tea catechins accumulate in bone and if induced osteopenia impacts catechin levels in bone. Male NIH Swiss mice were treated for 16 d in a 2x2 design: control diet (AIN 93G basal diet) or control diet supplemented with green tea water extract (30 g/kg), and with or without hindlimb suspension for 9 d. Following treatment, mice were euthanized and liver, muscle, femur, and tibia were harvested. Catechins were extracted by homogenization of tissue in organic solvent, followed by enzymatic deconjugation. HPLC-ECD analysis detected major tea catechins including epigallocatechin gallate (EGCG), epicatechin gallate (ECG), epigallocatechin (EGC), and epicatechin (EC) only in tissues of mice fed tea. Bone content (μmol/g, in the order of EGC, EC, EGCG, ECG, and total) was: 3.3±1.1, 1.8±0.6, 48.6±17.6, 8.2±3.5, and 61.9±21.9 for suspended mice; and 7.3±1.8, 2.2±0.9, 76.4±21.9, 8.6±3.2, and 94.4±26.3 in unsuspended mice. Liver content was: 1.8±1.1, 0, 0, 1.1±1.1, and 2.8±1.9 in suspended mice; and 4.0±2.5, 3.2±1.2, 28.7±11.8, 3.9±2.5, and 39.9±14.9 in unsuspended mice. Concentrations in bone were not significantly different between suspension treatments, while EC, EGCG, and total catechins in liver were significantly lower in suspended mice (p<0.05). These data confirm that dietary green tea catechins accumulate in bone tissue and that atrophy appears to impact tissue accumulation of these phytochemicals.