Substance P is associated with the development of obesity, chronic inflammation and type 2 diabetes mellitus.

BACKGROUND

Substance P (SP) is an important neurotransmitter and is an important pathogenic factor in obesity. However, the relationships between the inflammatory cytokines interleukin-6 (IL-6), C reactive protein (CRP) and SP with obesity and type 2 diabetes mellitus (T2DM) are poorly understood.

OBJECTIVE

We investigated the associations between SP, IL-6 and CRP with obesity and T2DM.

SUBJECTS AND METHODS

The subjects comprised patients who underwent physical examinations at the First Affiliated Hospital of Harbin Medical University between January 2006 and December 2008. Overall, 156 subjects participated in this study, including 63 obese (BMI >25 kg/m²) subjects with T2DM, and 58 obese and 35 lean subjects without T2DM. Patient characteristics were collected from a health questionnaire form. Anthropometric measurements and fasting blood samples were assessed. SP, CRP, IL-6 and HOMA-IR were converted into log values.

RESULTS

SP, IL-6, CRP and HOMA-IR were significantly higher ( P<0.05) in obese T2DM subjects compared with obese and lean subjects without T2DM. All 3 parameters were significantly associated with other risk factors for diabetes, including BMI, blood pressure, plasma glucose and high-density lipoprotein levels. After adjusting for age, SP was significantly and positively correlated with BMI and logHOMA-IR ( P≤0.05); correlation coefficients were higher in obese T2DM subjects than in lean or obese subjects without T2DM.

CONCLUSIONS

High levels of SP and IL-6 were significantly associated with obesity and risk factors for T2DM. Associations were of greatest in obese T2DM subjects. Obesity and T2DM show additive effects on the association between SP and BMI or logHOMA-IR.