Publications

OBJECTIVE

Peripheral fat loss and visceral fat gain have been reported in HIV infection. There are limited data on long-term change in adipose tissue in HIV-infected patients vs. controls. Therefore, we determined change in regional adipose tissue from baseline examination to 5 years later among participants in the study of Fat Redistribution and Metabolic Change in HIV Infection.

METHODS

Regional adipose tissue volume was measured using MRI at both examinations in 477 HIV-infected and 214 control men and women. Lipoatrophy was defined as leg subcutaneous adipose tissue (SAT) below the cutoff point marking the lowest decile (10%) of controls at each examination.

RESULTS

HIV-infected and control participants showed similar adipose tissue gains. In men, all SAT depots and visceral adipose tissue started lower and remained lower on average in HIV-infected vs. controls. In women, leg and arm SAT also started lower and remained lower in HIV-infected vs. controls. Mean leg SAT of HIV-infected men was 67% of control men at baseline and 65% at follow-up; for women 83% and 77%. At baseline, 48% of HIV-infected participants had lipoatrophy; on average those with baseline lipoatrophy gained 0.96L of leg SAT compared with 1.23L gain for controls in the lowest decile (P = 0.16). At follow-up, 53% of HIV-infected participants had lipoatrophy. In multivariable models, discontinuation of stavudine appeared to produce little gain in leg SAT ( approximately 1.1%/year).

CONCLUSION

HIV-infected participants did not substantially recover SAT compared with controls, although both showed average gains. HIV-associated lipoatrophy persisted after 5 years of follow-up.

CONTEXT

Inactivating mutations of the calcium-sensing receptor (CaSR) cause familial hypocalciuric hypercalcemia and neonatal severe hyperparathyroidism. Most mutations are clustered in the N-terminal and Cys-rich regions of the extracellular domain (ECD) and seven-transmembrane domain. Disease-causing mutations are uncommon in the C terminus of ECD.

OBJECTIVE

The aim of the study was to characterize the CaSR mutations causing neonatal severe hyperparathyroidism in a consanguineous family.

METHODS

Parathyroid glands from the index patient were stained for CaSR protein. The CaSR gene was sequenced, mutations were recreated in CaSR cDNA, and HEK293 cells were transfected with the CaSR mutant expression vector. Cellular CaSR targeting was detected by immunoblotting and immunocytochemistry; CaSR activity was assayed by inositol phosphate accumulation, MAPK activation, and single-cell microfluorimetry.

RESULTS

Immunocytochemistry showed reduced intracellular CaSR in patient parathyroids. An in-frame homozygous deletion/insertion mutation, c.1031 > 1034 (delACAAinsT), replaced His344-Asn345 with a single Leu in CaSR loop III. The mutant reduced cell surface expression of CaSR in transfected HEK293 cells. Inositol phosphate accumulation, MAPK activation, and single-cell microfluorimetry revealed blunted signaling responses of the mutant receptor to changes in extracellular Ca(2+) concentration.

CONCLUSION

Deletion of His344-Asn345 in the ECD loop III region affects cell surface targeting of CaSR in transfected cells and in affected parathyroid glands. Absence of conserved Asn345 may interfere with CaSR folding or glycosylation, leading to poor protein targeting to the cell membrane. This loss-of-function mutant indicates that the ECD loop III is required for CaSR activity.