Publications

The 72-kDa gelatinase A (MMP-2) is a central mediator of the response of the intrinsic glomerular mesangial cell to inflammatory stimuli and is regulated in a unique, cell-specific manner. We isolated a 6-kilobase pair genomic fragment of the rat MMP-2 gene and sequenced and characterized 1686-base pair of the 5'-flanking region. Using a series of 5' deletion constructs of the proximal 5'-flanking region, a strong MMP-2 enhancer element was identified. Gel shift and mutational analyses suggest tha the enhancer region represents the binding site for complex transcription factor demonstrating separable DNA-binding and transcriptional activating domains. The presence and activity of the enhancer element was evaluated in several cell types with varying capabilities to synthesize MMP-2 including mesangial cells, glomerular epithelial cells, and the monocytic U937 cell. Although binding activity was present in all cell types studied, enhancer activity was demonstrated only in mesangial and glomerular epithelial cells. Additional transcriptional control resided in a tissue-specific promoter, which supported transcription only in mesangial cells. These results indicate that the final control of mesangial cell-specific synthesis of MMP-2 derives from an interaction between the strong enhancer element and the tissue-specific MMP-2 promoter.

BACKGROUND

The beta 3-adrenergic receptor, located mainly in adipose tissue, is involved in the regulation of lipolysis and thermogenesis. The potential relevance of this receptor to obesity in humans led us to screen obese French patients for a recently identified mutation in the gene for the receptor.

METHODS

We used the polymerase chain reaction to amplify a region of the gene for the beta 3-adrenergic receptor encoding amino acid residues 27 to 110 in genomic DNA extracted from leukocytes from 185 patients with morbid obesity (body-mass index [the weight in kilograms divided by the square of the height in meters], > 40) and 94 normal subjects. A mutation resulting in the replacement of tryptophan by arginine at position 64 (Trp64Arg) was detected by an analysis of restriction-fragment-length polymorphisms with the use of the endonuclease BstNl, which discriminates between the normal and mutant sequences.

RESULTS

The frequency of the Trp64Arg allele was similar in the morbidly obese patients and the normal subjects (0.08 and 0.10, respectively). However, the patients with morbid obesity who were heterozygous for the Trp64Arg mutation had an increased capacity to gain weight; the mean weight in the 14 heterozygous patients was 140 kg, as compared with 126 kg in the 171 patients without the mutation (P = 0.03). There were no homozygotes in this sample. The cumulative 25-year change in weight (from the age of 20 years) was 67 kg in the Trp64Arg heterozygotes, as compared with 51 kg in those without the mutation. The maximal weight differential (the maximal lifetime weight minus the weight at 20 years of age) in the Trp64Arg heterozygotes was 74 kg, as compared with 59 kg in the patients without the mutation (P = 0.02).

CONCLUSIONS

People with the Trp64Arg mutation of the gene for the beta 3-adrenergic receptor may have an increased capacity to gain weight.