Enhanced Insulin Resistance in Diet-induced Obese Rats Exposed to fine Particulate Matter

YUAN-HORNG YAN (1, 2), Jung-Yen Liu (1), Chung-Te Lee (3) , Tsun-Jen Cheng (1)

(1) National Taiwan University, Taipei, (2) Chia-Yi Christian Hospital, Chaiyi, (3) National Central University, Taoyuan, Taiwan

     Abstract Number: 47
     Last modified: October 8, 2009

Abstract
Epidemiological studies indicate that diabetes is a sub-population at risk for particulate matter (PM)-associated cardiovascular disease (CVD). A recent animal study suggested PM might impair glucose tolerance, which may lead to CVD. However, the mechanism remains unclear. This study aims to investigate further the PM effect on insulin resistance (IR) in obese and healthy rats. Male Sprague-Dawley rats were fed with either a high fat diet (HFD) or normal chow diet (NCD) for six weeks. Both groups were then further assigned to receive PM10, PM2.5 or normal saline (n=6 per group) by intratracheal instillation (IT) once per week for three weeks. Fasting glucose and insulin were measured and the homeostasis model assessment (HOMA-IR) was used to assess IR. The markers of fibrinogen and [nitrate+nitrite], an indicator of nitric oxide (NO) production, C-reactive protein (CRP) and white blood counts (WBC) in peripheral blood were also determined. Body weight, insulin and HOMA-IR of HFD rats were significantly increased compared with a NCD after six weeks. In HFD rats, PM2.5 increased HOMA-IR after first IT and further increased HOMA-IR at the end of exposure. However, this increase was not observed in NCD rats after PM exposure. In addition, this increase was not observed in HFD rats after PM10 exposure. Increased fibrinogen was also noted after chronic PM2.5 exposure in both HFD and NCD rats. However, there was no difference for NO, CRP and WBC. Exposure to PM2.5 enhanced IR in HFD rats but not in NCD rats. Exposure to PM10 did not show this effect. Obese subjects with IR may be a susceptible population to fine particulate air pollution.