A glucose time in range of 70% attenuates the senescence-inducing and pro-inflammatory effects of hyperglycemia.

BACKGROUND: The Time In Range (TIR) represents the amount of time spent by a given individual in the range close to normoglycemia, i.e. 70-180 mg/dl. On the basis of studies demonstrating an association of TIR with the incidence of diabetes complications, guidelines recommend a target of at least 70% of TIR for most people with diabetes. However, no study has explored the effect of variable degrees of TIR on molecular mechanisms relevant for the development of diabetes complications. METHODS: We exposed endothelial cells and monocytes to increasing percentages of TIR, i.e. 50%, 70%, 85% by changing cell media twice a day as appropriate, as well as to constant normoglycemia (i.e. fixed 100 mg/dl of glucose for endothelial cells) and hyperglycemia (i.e. 500 mg/dl glucose), evaluating the development of senescence, of the associated pro-inflammatory response, and monocytes adhesion to endothelial cells as a functional assay. We then assessed the expression of a plethora of markers of senescence and inflammation at the mRNA level in peripheral blood mononuclear cells (PBMC)s derived from individuals with early (i.e. 1-year post-diagnosis) type 1 diabetes (T1D, n = 37), categorized according to the TIR (< or > 70%) observed in the previous 14 days, comparing the two groups through ANCOVA adjusted for HbA1c. As a confirmatory analysis, we also compared the expression of the same markers in people with Time Above Range (TAR), considered as the whole time above 180 mg/dl, ≥ vs < 30%. Correlations between TIR values and the expression of the same markers were tested through linear regression. RESULTS: Constant hyperglycemia promoted the development of senescence in endothelial cells and induced inflammatory responses in both endothelial cells and monocytes, promoting also monocytes adhesion to endothelial cells. A TIR of 70%, but not of 50%, suppressed these effects while a TIR of 85% did not provide additional benefit. Data from people with T1D mirrored such results, as demonstrated by the higher expression of p16, a marker of senescence, and of IL-6, MCP-1, and CXCL1, three inflammatory mediators, in PBMCs from individuals with TIR < 70% and compared with those with TIR > 70%, independently of HbA1c. Similar results were obtained when comparing people with TAR ≥ vs < 30%. When considered as a continuous variable, TIR values were correlated with p16, IL-6, and CXCL1. CONCLUSIONS: A TIR above 70% is associated with attenuated pro-senescence and pro-inflammatory effects of hyperglycemia. These molecular results support the TIR target currently recommended by guidelines, especially for people with T1D.