Mid-Life Vascular Risk and Rate of Physical Function Decline Among Older Adults: The Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: Physical function and its decline in older age may be connected to treatable vascular risk factors in mid-life. This study aimed to evaluate whether these factors affect the underlying rate of decline. METHODS: This prospective cohort included 5 481 older adults aged 67-91 in the Atherosclerosis Risk in Communities Study (mean [standard deviation {SD}] age = 75.8 [5.0], 58% women, 21% Black race) without a history of stroke. The main outcome was the rate of Short Physical Performance Battery (SPPB) decline over a median late-life follow-up of 4.8 years. Primary mid-life (aged 45-64) exposures were Visit 1 hypertension (>140/90 mm Hg or treatment), diabetes (>126 mg/dL or treatment), high cholesterol (>240 mg/dL or treatment), and smoking, and number of decades of vascular risk exposure across Visits 1-4. RESULTS: The average adjusted rate of SPPB decline (points per 5 years) for older adults was -0.79 (confidence interval [CI]: -0.87, 0.71) and was accelerated by mid-life hypertension (+57% decline vs normotension: additional decline of -0.47, 95% CI: -0.64, -0.30), diabetes (+73% decline vs no diabetes: additional decline of -0.67, 95% CI: -1.09, -0.24), elevated systolic blood pressure (+17% decline per SD: -0.16, 95% CI: -0.23, -0.10), and elevated fasting blood glucose (+16% decline per SD: -0.015, 95% CI: -0.24, -0.06). Each decade greater mid-life exposure to hypertension (+32% decline: -0.93, 95% CI: -1.25, -0.61) and diabetes (+35% decline: -1.03, 95% CI: -1.68, -0.38) was associated with faster SPPB decline. CONCLUSIONS: Mid-life control of blood pressure and diabetes may offset aging-related functional decline.

A small ubiquitin binding domain inhibits ubiquitin-dependent protein recruitment to DNA repair foci.

The rapid ubiquitination of chromatin surrounding DNA double-stranded breaks (DSB) drives the formation of large structures called ionizing radiation-induced foci (IRIF), comprising many DNA damage response (DDR) proteins. This process is regulated by RNF8 and RNF168 ubiquitin ligases and is thought to be necessary for DNA repair and activation of signaling pathways involved in regulating cell cycle checkpoints. Here we demonstrate that it is possible to interfere with ubiquitin-dependent recruitment of DDR factors by expressing proteins containing ubiquitin binding domains (UBDs) that bind to lysine 63-linked polyubiquitin chains. Expression of the E3 ubiquitin ligase RAD18 prevented chromatin spreading of 53BP1 at DSBs, and this phenomenon was dependent upon the integrity of the RAD18 UBD. An isolated RAD18 UBD interfered with 53BP1 chromatin spreading, as well as other important DDR mediators, including RAP80 and the BRCA1 tumor suppressor protein, consistent with the model that the RAD18 UBD is blocking access of proteins to ubiquitinated chromatin. Using the RAD18 UBD as a tool to impede localization of 53BP1 and BRCA1 to repair foci, we found that DDR signaling, DNA DSB repair, and radiosensitivity were unaffected. We did find that activated ATM (S1981P) and phosphorylated SMC1 (a specific target of ATM) were not detectable in DNA repair foci, in addition to upregulated homologous recombination repair, revealing 2 DDR responses that are dependent upon chromatin spreading of certain DDR factors at DSBs. These data demonstrate that select UBDs containing targeting motifs may be useful probes in determining the biological significance of protein-ubiquitin interactions.