Ionising radiation triggers fat accumulation in white adipose tissue

Purpose: To investigate changes in gonadal white adipose tissue and lipogenesis-related gene expression induced by radiation exposure. Materials and methods: Groups of two-month-old C57BL/6 mice were exposed whole-body to Cs-137 gamma-rays at a single dose (5 gray [Gy]) or fractionated doses (1 Gy x 5 times, 0.5 Gy x 10 times, or 0.2 Gy x 25 times). Six months after irradiation, gonadal white adipose tissue was isolated from mice. Two and 25-month-old mice were used as young and old study references. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to measure messenger RNA (mRNA) expression of genes related to: (i) Primary lipid metabolism (ATP-citrate lyase [ACL], malic enzyme1 [ME1] and glucose-6-phosphate dehydrogenase 2 [G6PD2]), (ii) glucose uptake (glucose transporter 4 [GLUT4]), (iii) fatty acid synthesis (sterol regulatory element binding transcription factor 1 [SREBP-1c], fatty acid synthetase [FAS] and acetylcoenzyme A carboxylase beta [ACC]), (iv) triglyceride synthesis (diacylglycerol O-acyltransferase 1 [DGAT1] and diacylglycerol O-acyltransferase 2 [DGAT2]), and (v) adipose-derived hormones (leptin [LEP]). Results: The weight of gonadal white adipose tissue in the irradiated groups tended to increase compared to the non-irradiated group though the radiation-induced increase in white adipose tissue was only significant for the 561 Gy group. The mRNA levels of SREBP-1c, ACC, FAS, ACL, GLUT4, ME1 and G6PD2 were relatively lower in gamma-irradiated groups than in non-irradiated groups. The mRNA levels of leptin and DGAT were relatively higher than non-irradiated groups. The changes in expression of these lipogenesis-related genes caused by gamma-irradiation showed a very similar pattern to changes caused by ageing. Conclusions: A physical agent such as gamma-rays can trigger biological responses resulting in fat accumulation of gonadal white adipose tissue in mice.