Isolation and characterization of the UGT2B28 cDNA encoding a novel human steroid conjugating UDP-glucuronosyltransferase

UDP-glucuronosyltransferase (UGT) enzymes belonging to the UGT2B subfamily catalyze the transfer of glucuronic acid to a large number of endogenous compounds, particularly steroids, to facilitate their elimination from target cells. A novel human UGT2B cDNA of 1666 bp was isolated and encodes a 529-amino acid protein named UGT2B28 type I. Glucuronidation assays demonstrated that UGT2B28 type I catalyzes the conjugation of endogenous and exogenous compounds. The tissue distribution of UGT2B28 revealed the expression of the type I transcript in the liver, breast, and LNCaP cells. Two other UGT2B cDNAs were isolated, and sequence analysis led to the identification of two truncated UGT2B28 species. UGT2B28 type II differs from type I by a deletion of 308 bp in the cofactor binding domain, whereas UGT2B28 type III lacks 351 bp in the putative substrate binding domain. All UGT2B28 isoforms are encoded by a single UGT2B28 gene which has a genomic organization similar to that of the other UGT2B genes characterized thus far. Although no substrates could be identified for the shorter isoforms, the three subtypes were shown to be located in the endoplasmic reticulum and the perinuclear membrane, demonstrating that the missing domains are not required for the subcellular localization of these UGT2B proteins. However, all the domains remain necessary for observing glucuronidation activity. The expression of UGT2B28 type I in the breast and liver suggests a role of this enzyme in the androgen and estrogen metabolism in these tissues.

Effect of a long-term percutaneous adrenal steroid treatment on rat adipose tissue metabolism

OBJECTIVE

To examine some cellular mechanisms which regulate adipose cell metabolism in ovariectomized (OVX) and intact rats subjected or not to dehydroepiandrosterone (DHEA).

DESIGN

Rats were assigned to one of four treatment groups for 27 weeks. The main effects tested were castration (-or+) and DHEA treatment (-or+) which consisted of a single daily percutaneous application of DHEA cream (30 mg/ml in 50% ethanol-50% propyleneglycol).

SUBJECTS

Forty female Sprague- Dawley rats (sixteen-month old).

MEASUREMENTS

Body weight and fat mass (by dual-energy X-ray absorptiometry), retroperitoneal (RP) fat pad weight; plasma insulin and triglyceride levels, and HDL-cholesterol (C) concentrations; lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activities.

RESULTS

No difference in body composition and RP fat pad weight was observed between the intact and intact-DHEA groups. LPL and HSL activities were also similar in both groups. The increased weight of OVX rats was paralleled by a higher adiposity and greater RP adipose tissue mass, which was associated with both a marked rise in LPL activity and a slight diminution in HSL activity in this depot, compared to intact animals. OVX-DHEA rats displayed a reduced adiposity and a lighter RP fat depot, which was associated with a decrease in LPL and an increase in HSL activities, compared to untreated OVX animals. Fasting plasma insulin and TG levels were also decreased whereas plasma HDL-C concentrations were increased in intact-DHEA and OVX-DHEA rats.

CONCLUSION

These results show that the antiobesity effects of DHEA are dependent upon the ovarian status of the animal. These effects may involve changes in the lipid storage and the mobilization capacity of adipose tissue.