Increased susceptibility to infections, particularly respiratory viral infections, is a hallmark of advancing age. The underlying mechanisms are not well understood, and there is a scarcity of information regarding the contribution of the innate immune system, which is the first line of defense against infections. In the present study, we have investigated the effect of advancing age on plasmacytoid dendritic cell (PDC) function because they are critical in generating a robust antiviral response via the secretion of interferons (IFN). Our results indicate that PDCs from the aged are impaired in their capacity to secrete IFN-I in response to influenza virus and CPG stimulation. Additionally, we observed a severe reduction in the production of IFN-III, which plays an important role in defense against viral infections at respiratory mucosal surfaces. This reduction in IFN-I and IFN-III were a result of age-associated impaired phosphorylation of transcription factor, IRF-7. Furthermore, aged PDCs were observed to be impaired in their capacity to induce perforin and granzyme in CD8 T cells. Comparison of the antigen-presenting capacity of aged PDC with young PDC revealed that PDCs from aged subjects display reduced capacity to induce proliferation and IFN-gamma secretion in CD4 and CD8 T cells as compared with PDCs from young subjects. In summary, our study demonstrates that advancing age has a profound effect on PDC function at multiple levels and may therefore, be responsible for the increased susceptibility to infections in the elderly.

Low IGFBP-2 is associated with multiple cardiovascular risk factors similarly to IGFBP-1. Such associations were not apparent for IGFBP-3. Lack of marked prandial regulation of IGFBP-2, in contradistinction to IGFBP-1, may make IGFBP-2 a more robust biomarker for identification of insulin-resistant individuals at high cardiovascular risk in epidemiological studies.

The IGF system is increasingly implicated in the development of cardiovascular disease. The effects of circulating IGFs on the vasculature are largely modulated by IGFBPs, which control their access to cell-surface IGF receptors. IGFBP-1 has been proposed as the acute regulator of IGF bioavailability because of its metabolic regulation by glucoregulatory hormones. Posttranslational phosphorylation of IGFBP-1 significantly increases its affinity for IGF-I and therefore represents a further mechanism for controlling IGF bioavailability. We have therefore examined the IGF system and IGFBP-1 phosphorylation status, using specifically developed immunoassays, in a cohort of 160 extensively characterized type 2 diabetic subjects on two occasions 12 months apart. Total IGFBP-1 (tIGFBP-1), which is predominantly highly phosphorylated, was significantly lower in subjects with known macrovascular disease triglycerides, and nonesterified fatty acids. In contrast, levels of nonphosphorylated and lesser-phosphorylated IGFBP-1 (lpIGFBP-1) were unrelated to macrovascular disease or hypertension but did correlate positively with fasting glucose concentration ( ‫؍‬ 0.350, P < 0.01). tIGFBP-1 concentrations were higher in subjects treated with insulin alone (n ‫؍‬ 29) than for any other group. This effect persisted after adjustment of tIGFBP-1 levels for BMI, C-peptide, age, and sex (F ‫؍‬ 6.5, P < 0.001, ‫؍‬ ؊0.46). Such an effect was not apparent for lpIGFBP-1. We conclude that low circulating levels of hpIGFBP-1 are closely correlated with macrovascular disease and hypertension in type 2 diabetes, whereas lpIGFBP-1 isoforms are associated with glycemic control, suggesting a dual role for IGFBP-1 in the regulation of IGF actions in type 2 diabetes. Our data suggest that high circulating concentrations of highly phosphorylated IGFBP-1 may protect against the development of hypertension and cardiovascular disease by reducing the mitogenic potential of IGFs on the vasculature.

http://radiology.rsnajnls.org/cgi/content/full/2461070030/DC1.