Brain accumulation of amyloid-β (Aβ) peptides is known to be intimately associated with the physiological landscape of Alzheimer disease (AD).¹ Measures of Aβ have been used as an early marker of cognitive impairment and AD, assessed by positron emission tomography (PET) imaging or measurement in cerebrospinal fluid (CSF).¹ In a search for less expensive, minimally invasive, and fast and reliable markers, plasma measures of Aβ have recently emerged as a potential equivalent to PET imaging and CSF measurements in determining Aβ status.^2-5 Early attempts to measure Aβ in plasma presented limited utility for diagnosis or prognosis of cognitive impairment and AD due to high variability attributed to a lack of high precision methods of assessment in plasma samples.^5-7 More recently, a high-precision immunoprecipitation and liquid chromatography–mass spectrometry assay has provided reliable measures of plasma Aβ peptides,^2,3,8-11 but investigations associating this marker with clinical cognitive outcomes are scarce.

Plasma amyloid-beta (Aβ), neurofilament light chain (NfL), and progranulin (PGRN) have been related to multiple neurodegenerative conditions that might affect physical performance. The aim of this study was to explore the relationship between these plasma neurodegenerative markers and physical performance among community-dwelling older adults. Five hundred and seven older adults (aged 76 ± 5 years) previously recruited in the Multidomain Alzheimer’s Preventive Trial, and had received blood and physical performance tests, were included in this study. Plasma Aβ (Aβ ₄₂/Aβ ₄₀ ratio), NfL, and PGRN levels were measured. Physical performance was assessed by handgrip strength and the Short Physical Performance Battery (combining gait speed, chair stands, and balance tests). Physical performance measured at the same time point and after the blood tests were used. Mixed-effect linear models were performed with age, sex, allocation to Multidomain Alzheimer’s Preventive Trial group, body mass index, and Mini-Mental State Examination score as covariates. The mean values of Aβ ₄₂/Aβ ₄₀ ratio, NfL, and PGRN were 0.11, 84.06 pg/mL, and 45.43 ng/mL, respectively. At the cross-sectional level, higher plasma NfL was associated with a lower Short Physical Performance Battery score (β = −0.004, 95% CI [−0.007, −0.001]). At the longitudinal level, higher PGRN levels were associated with decreasing handgrip strength over time (β = −0.02, 95% CI [−0.04, −0.007]). All the other associations were statistically nonsignificant. Our findings suggest the possibility of using plasma NfL and PGRN as markers of physical performance in older adults.

Objectives: This study aimed to investigate the relationship between 25-hydroxyvitamin D (25(OH)D), osteocalcin, markers of glucose metabolism, and obesity-related parameters among adolescents. Methods: This was a cross-sectional study with 198 adolescents age 14–18 years. Weight, height, and waist and hip circumferences were measured, as well as the following biochemical parameters: serum 25(OH)D, parathyroid hormone (PTH), total (tOC) and undercarboxylated (ucOC) osteocalcin, adiponectin, leptin, glucose, and insulin. The homeostasis model of assessment estimate of insulin resistance (HOMA-IR) and β-cell function (HOMA-β) and quantitative insulin sensitivity check index (QUICKI) were calculated. Student's t test, analysis of variance (ANOVA), Pearson's correlation, and linear regression models were performed. Results: Overweight was observed in 42.6% of the sample. This group presented significantly higher PTH, leptin, insulin, HOMA-IR, and HOMA-β and lower 25(OH)D, adiponectin, tOC, ucOC, and QUICKI than normal-weight subjects. 25(OH)D was positively correlated with ucOC and adiponectin and negatively associated with body mass index (BMI), weight, and waist circumference (p < 0.05 for all). The association between 25(OH)D and ucOC was also observed in the multiple regression analysis, adjusted for age, BMI, and season of the year (partial r² = 0.071, p < 0.0001). 25(OH)D and ucOC were not associated with markers of glucose metabolism. However, leptin was strongly correlated with insulin, HOMA-IR, HOMA-β, and QUICKI (p < 0.0001 for all). Conclusion: The present study demonstrated that undercarboxylated osteocalcin is related to 25(OH)D and adiponectin concentrations. Both ucOC and 25(OH)D were lower in overweight and obese adolescents, reinforcing the importance of fighting obesity. Although a relationship of ucOC and 25(OH)D with markers of glucose metabolism was not observed, leptin has shown to be the hormone most related to energy homeostasis.

This study aimed to examine the associations of three operational definitions of vitality with variation in instrumental activities of daily living (IADL) and frailty over a 3-year follow-up among non-demented, community-dwelling elderly.