The association of bone mineral density and depression in an older population

OBJECTIVE

To evaluate the association between bone mineral density (BMD) and measurements of depression in an older population.

DESIGN

Population-based, cross-sectional study.

SETTING

Study subjects were participants in the Cardiovascular Health Study (CHS), a longitudinal, long-term, follow-up study, at the University of California Davis (Sacramento, California) and the University of Pittsburgh (Pittsburgh, Pennsylvania) clinical centers.

PARTICIPANTS

A random sample of 1,566 Medicare enrollees age 65 and older enrolled in the CHS.

MEASUREMENTS

Total hip BMD, measured using dual energy x-ray absorptiometry (DEXA), after adjustment for multiple covariates, was compared with depression evaluated with the Center for Epidemiological Studies 10-item Depression Scale (CES-Dm). Risk factors for osteoporosis were compared in depressed and nondepressed participants. Potential correlates were entered into a regression model. Depression scores were compared in normal, osteopenic, and osteoporotic individuals.

RESULTS

Sixteen percent of participants were clinically depressed; 9% had BMDs in the osteoporotic range. Mean BMD was 40 mg/cm2 lower in those with clinical depression. High CES-Dm scores were associated with lower BMD (P < .001) when adjusted for body mass index (BMI), age, kilocalories of activity, estrogen use, gender, race, smoking and drinking. When stratified by race, this remained true for all Caucasians (P < .01), all African Americans (P < .05), and when stratified by race and gender the association remained only for all Caucasian women (P < .001). In women and Caucasian men there was an increase in depression scores among individuals with osteoporotic-range BMDs.

CONCLUSIONS

A significant association was found between BMD and depressive symptoms after adjustment for osteoporosis risk factors. In Caucasians, depressive symptoms were associated with both osteoporotic and osteopenic levels of BMD. Causality cannot be ascribed, with only one measurement of BMD. We postulate that there may be an unmeasured third factor, such as an endogenous steroid, that is responsible for both low BMD and depression.

Effects of albumin and apolipoprotein C-II on the acyl-chain specificity of lipoprotein lipase catalysis

In this study we used monoacid triacylglycerols of various acyl-chain lengths as substrates for probing the active-site structure and substrate specificity of lipoprotein lipase (LPL). An unexpected finding was that the albumin ligand binding site is accessible not only to long-chain fatty acids for its recognized functional role as a fatty acid acceptor, but also to short- and medium-chain monoacid triacylglycerol substrates. The observed striking inhibitory effect (99%) of albumin on the LPL-catalyzed hydrolysis of trihexanoylglycerol is probably the result of the high affinity interaction of albumin with this substrate. Spectrophotometric analyses indicated that there is one high affinity binding site per albumin molecule (apparent KD = 1.8 +/- 0.9 microM) for the interaction with trihexanoylglycerol. Despite LPL acyl-chain specificity being obscured by the substrate binding effect of albumin, a systematic study of the lipolysis reaction under various assay conditions demonstrated that tributyroylglycerol represents the best substrate for LPL, and the preferential order of LPL catalysis for both the basal and apoC-II-activated activities is: C4 > C6 > C8 > C10 > C12 > C18:1. In some assay conditions, the presence of albumin affects the above-mentioned order, which can be attributed to substrate binding by albumin, rather than an alteration in the specificity of LPL. The synergistic effect of apoC-II and albumin resulted in the preferential activation of LPL for the hydrolysis of long-chain triacylglycerols. Even with optimal assay conditions for the hydrolysis of long chain triacylglycerols, there is still a preferential reactivity of LPL with short- and medium-chain triacylglycerols.