Publications

OBJECTIVES

We sought to test the hypothesis that C-reactive protein, a marker of inflammation, would correlate positively with coronary calcium, a marker of atherosclerosis, in postmenopausal women.

BACKGROUND

High sensitivity testing for C-reactive protein (hsCRP) has recently been shown in large population studies to predict cardiac events in asymptomatic postmenopausal women. Coronary calcification determined by electron beam computerized tomography (EBCT) has also been suggested to be predictive of cardiac events in women.

METHODS

We performed hsCRP testing and determined calcium scores by EBCT in 172 asymptomatic postmenopausal women (mean age: 64.5 +/- 7.9 years) at risk for cardiac disease. Risk factors were determined by history, physical, electrocardiogram, exercise testing, and lipoprotein profiles.

RESULTS

Calcium scores ranged from 0 to 2,618. For analysis, calcium scores were divided into three groups; none (0 to 10), minimal (>10 to 50), and significant (>50). Overall, there was no significant positive relationship between hsCRP level and calcium score. Specifically, the hsCRP levels (mg/dl) were 0.24 +/- 0.43, 0.33 +/- 0.47 and 0.17 +/- 0.32 (medians 0.11, 0.15, and 0.06) for women with none, minimal, and significant coronary calcification, respectively. In subgroup analysis, a similar lack of positive association was observed after stratification by smoking status and by hormone replacement therapy use, two factors known to increase hsCRP.

CONCLUSIONS

In contrast to our a priori hypothesis, we found no evidence of a positive association between hsCRP and calcium score by EBCT. These data thus raise the possibility that hsCRP and EBCT calcium score reflect different pathologic processes, an issue with implications for coronary artery disease screening.

By integrating an agonist satiety signal, provided by alpha-melanocyte-stimulating hormone (alpha-MSH), and an antagonist signal, provided by agouti-related protein (AGRP), the melanocortin-4 receptor (MC4-R) is a key element in the hypothalamic control of food intake. Inactivation of the gene encoding this G protein-coupled receptor causes obesity in mice. In humans, frameshift mutations in MC4-R cause an early-onset dominant form of obesity in two families. In this study we find a high frequency (4%) of rare heterozygous MC4-R mutations in a large population of morbidly obese patients. No such mutations were found in controls. By analyzing the phenotypes of the probands carrying these mutations, we demonstrate that these patients display a common, nonsyndromic form of obesity. Interestingly, functional analysis of the mutant receptors indicates that obesity-associated defects in MC4-R range from loss of function to constitutive activation. Transmission of these mutations in the families of the carriers indicates a variable expressivity that is not related to the functional severity of the mutations. This variable expressivity of MC4-R-associated obesity is not due to variations in genes for alpha-MSH or AGRP. Taken together, these results demonstrate that MC4-R mutations are a frequent but heterogeneous genetic cause of morbid obesity.

The integrin family (Hynes, R.O., 1992. Integrins: versatility, modulation, and signaling in cell adhesion. Cell 69, 11-25) is composed of at least 24 heterodimers formed from eight beta subunits and 18 alpha subunits. Thus far, mice expressing null mutations of seven of the eight beta subunits and 13 of the 18 known alpha subunits have been generated, With only a few exceptions, the phenotypes of each of the knockout lines are quite distinct. Studies utilizing integrin knockout mice and cells derived from these mice have provided considerable and sometimes surprising insights into unique functions of individual members of this family.