Association between Reduction of Muscle Mass and Faster Declines in Global Cognition among Older People: A 4-Year Prospective Cohort Study

OBJECTIVES

A few studies reported that both decrease and increase in body mass index (BMI) were associated with the development of dementia in later life. However, it is unclear what changes in body composition are associated with cognitive decline. This study investigated the longitudinal influences of changes in body composition on cognitive function among community-dwelling adults.

DESIGN, SETTING AND PARTICIPANTS

This longitudinal study included older adults aged ≥60 years without cognitive impairment who participated in National Institute for Longevity Sciences - Longitudinal Study of Aging.

MEASUREMENTS

Cognitive function was assessed using the MMSE. Body composition was measured by a dual-energy X-ray absorptiometry system. Then, BMI, fat mass index (FMI), fat-free mass index (FFMI), and muscle mass index (MMI) were calculated. The changes in body composition over 6 years (second wave to fifth wave) were calculated, and three groups were created: decreased group, decrease of >5%; stable group, change within 5%, and increased group, increase of >5%. In statistical analysis, a linear mixed model was applied by sex to investigate the influences of body composition changes on cognitive function over 4 years (fifth wave to seventh wave).

RESULTS

This study analyzed 515 participants (mean age, 67.05 years; 53.4% men). Men with decreased group in FFMI and MMI exhibited faster declines in MMSE scores than those with stable group (β [95% CI]: FFMI, -0.293 [-0.719 to -0.020]; MMI, -0.472 [-0.884 to -0.059]). In women, there was no significant association between body composition changes and cognitive functions.

CONCLUSIONS

Decrease in fat-free mass and muscle mass is associated with faster cognitive declines in men. These results suggest the importance of continuous monitoring of muscle mass to prevent cognitive decline in later life.

Elevated glucose level adversely affects infarct volume growth and neurological deterioration in non-diabetic stroke patients, but not diabetic stroke patients

BACKGROUND AND PURPOSE

Hyperglycemia is recognized as a common occurrence associated with a high risk of poor outcome in ischaemic stroke patients. However, little is known about the association between elevated glucose level, growth of infarct volume and neurological deterioration in ischaemic stroke patients without diabetes. The present study aimed to clarify this issue in acute ischaemic stroke patients with arterial occlusion.

METHODS

We studied 375 acute ischaemic stroke patients with arterial occlusion within 24 h of onset. Diabetes was diagnosed in patients with a known history of diabetes or HbA1c value ≥ 6.5%. Infarct volume was measured on admission and at follow-up within 48 h using diffusion-weighted imaging. Neurological deterioration was defined as an increase of ≥ 4 points in National Institutes of Health Stroke Scale score within 7 days of stroke onset. We examined the relationship between glucose level on admission, infarct volume growth and neurological deterioration in three categories (all patients, non-diabetes and diabetes) using multivariate modeling.

RESULTS

Diabetes was present in 104 patients (27.7%). Multivariate regression analysis showed that elevated glucose level was independently associated with infarct volume growth in all patients (P = 0.034) and non-diabetes (P = 0.002), but not in diabetes (P = 0.871). Moreover, elevated glucose level was independently associated with neurological deterioration in all patients [odds ratio (OR), 1.010; 95% confidence interval (CI), 1.004-1.017; P = 0.002] and non-diabetes (OR, 1.014; 95% CI, 1.002-1.026; P = 0.022), but not diabetes (OR, 1.006; 95% CI, 0.998-1.014; P = 0.151).

CONCLUSIONS

Glucose level appears to influence infarct volume growth and neurological deterioration, particularly in non-diabetic patients with ischaemic stroke.

Purified protein kinase C phosphorylates microtubule-associated protein 2

We have investigated actions of purified protein kinase C on microtubule- and microfilament-related proteins. Among the cytoskeletal proteins examined, microtubule-associated protein 2 (MAP2) was found to serve as a good substrate. Other cytoskeletal proteins, tubulin, fodrin, cofilin, tropomyosin, and 53,000-Da protein, were very poorly phosphorylated. The amino acid residues of MAP2 that were phosphorylated by the protein kinase C were almost exclusively serine. The peptide mapping analysis indicated that protein kinase C and cAMP-dependent protein kinase phosphorylate MAP2 differently. The ability of MAP2 to interact with actin was markedly reduced by this protein kinase C-mediated phosphorylation. These data raise the possibility that phosphorylation of MAP2 by activated protein kinase C may be involved in cell-surface signal transduction.