Impaired interleukin-1beta expression by monocytes stimulated with Staphylococcus aureus in diabetes

Diabetic patients with poorly controlled blood glucose have frequent and persistent bacterial infections particularly those infecting the skin, such as Staphylococcus aureus and S. epidermidis. The function of phagocytes of diabetic patients is believed to be impaired due to hyperglycemia, leading to suboptimal immune response to clear acute infection. The present study investigated interleukin (IL)-1beta expression by diabetic patients' monocytes (n = 22) experimentally infected with S. aureus compared with that from healthy subjects (n = 30). In addition, the in vitro effect of hyperglycemia on IL-1beta expression by monocytes from normal subjects (n = 18) stimulated with S. aureus and S. epidermidis was investigated. Monocytes from diabetic patients, stimulated or not with S. aureus, express significantly lower levels of IL-1beta than those from healthy subjects. In vitro hyperglycemia did not affect IL-1beta expression by unstimulated monocytes. However, at the same levels of glucose normal monocytes stimulated with S. aureus produce significantly higher IL-1beta than those stimulated with S. epidermidis. These findings suggest that diabetic patients have abnormally lower IL-1beta expression and hyperglycemia is related to abnormal expression of IL-1beta by monocytes, which could lead to enhanced susceptibility to infection by the more virulent bacteria.