Postmenopausal estrogen and the metabolism of plasma lipoproteins

Thematic review series: Patient-Oriented Research. Design and analysis of lipoprotein tracer kinetics studies in humans

Lipoprotein tracer kinetics studies have for many years provided new and important knowledge of the metabolism of lipoproteins. Our understanding of kinetics defects in lipoprotein metabolism has resulted from the use of tracer kinetics studies and mathematical modeling. This review discusses all aspects of the performance of kinetics studies, including the development of hypotheses, experimental design, statistical considerations, tracer administration and sampling schedule, and the development of compartmental models for the interpretation of tracer data. In addition to providing insight into new metabolic pathways, such models provide quantitative information on the effect of interventions on lipoprotein metabolism. Compartment models are useful tools to describe experimental data but can also be used to aid in experimental design and hypothesis generation. The SAAM II program provides an easy-to-use interface with which to develop and test compartmental models against experimental models. The development of a model requires that certain checks be performed to ensure that the model describes the experimental data and that the model parameters can be estimated with precision. In addition to methodologic aspects, several compartment models of apoprotein and lipid metabolism are reviewed.

Apolipoprotein B metabolism: tracer kinetics, models, and metabolic studies

The study of apolipoprotein (apo) B metabolism is central to our understanding of lipoprotein metabolism. However, the assembly and secretion of apoB-containing lipoproteins is a complex process. Specialized techniques, developed and applied to in vitro and in vivo studies of apoB metabolism, have provided insights into the mechanisms involved in the regulation of this process. Moreover, these studies have important implications for understanding both the pathophysiology as well as the therapeutic options for the dyslipidemias. The purpose of this review is to examine the role of apoB in lipoprotein metabolism and to explore the applications of kinetic analysis and multicompartmental modeling to the study of apoB metabolism. New developments and significant advances over the last decade are discussed.

Functional studies of subcutaneous ovarian transplants in non-human primates: steroidogenesis, endometrial development, ovulation, menstrual patterns and gamete morphology

BACKGROUND

The study objective was to determine if ovarian function would be restored following fresh and cryopreserved extrapelvic autologous ovarian transplantation and if vascular endothelial growth factor (VEGF) administration would augment the success rate.

METHODS

Sixteen regularly cycling female cynomolgus monkeys underwent bilateral oophorectomy and were randomly assigned to one of three treatment groups: (i) sham transplant group (n = 5) underwent transplantation of pieces of adipose tissue; (ii) fresh autologous ovarian transplantation without VEGF administration (n = 6) and (iii) fresh autologous ovarian transplantation with 1 microg of VEGF (n = 5) administered at the transplantation site daily for 14 days after transplantation. The ovarian tissue from the sham transplanted group was cryopreserved. This material was later thawed and transplanted in four out of five of the sham operated group.

RESULTS

Five out of six (83%) of the primates in our transplantation group without VEGF had functioning ovarian transplants while two of five (40%) primates in our transplantation group with VEGF administration had functioning ovarian transplants. The cryopreserved group had two of four primates (50%) with functioning transplants. Ovarian stimulation yielded multiple follicles and one metaphase II oocyte from the fresh and one metaphase II oocyte from the cryopreserved group.

CONCLUSIONS

The success of ovarian transplantation in these non-human primates with menstrual cycles bodes well for the development of ovarian transplantation protocols for women at risk of ovarian failure.