Characterization of circulating leukocytes and correlation of leukocyte subsets with metabolic parameters 1 and 5 years after diabetes diagnosis.

Aims: Infiltration of pancreatic islets with different leukocyte subtypes likely contributes to deterioration of glycemia in diabetes mellitus. Different subsets of leukocytes have been previously associated with type 1 or type 2 diabetes. This study aimed at examining these subsets at different stages of diabetes progression and possible relationships with metabolic parameters.

Methods: A total of 206 patients, 76 with type 1 and 130 with type 2 diabetes, were studied within the first year of diabetes diagnosis. In addition, 31 patients with type 1 and 73 with type 2 diabetes were examined at 5 years after diagnosis. Whole body insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamps; insulin secretion by glucagon stimulation tests and white blood cells were analyzed by flow cytometry.

Results: The percentage of peripheral CD8+ cells was 15% lower in patients with type 1 diabetes at 5 years than in patients at diabetes onset and correlated positively with fasting glycemia, total cholesterol and high-sensitive C-reactive protein (hsCRP) (all r > 0.37, p < 0.05), but not with insulin secretion. Patients with type 2 diabetes had 7% higher percentages of CD4+ cells after 5 years than those at diagnosis. CD4+ cells correlated with hsCRP (r = 0.36, p < 0.05), whereas CD8+ cytotoxic T-cells did not correlate with any metabolic parameter.

Conclusion: CD8+ T-cells associate with worse glycemia, lipidemia and inflammation after 5 years of type 1 diabetes, whereas CD4+ T-cells associate with increased inflammation after 5 years upon onset of type 2 diabetes.