Bone Mineral Is More Heterogeneously Distributed in the Femoral Heads of Osteoporotic and Diabetic Patients: A Pilot Study

Osteoporosis is associated with systemic bone loss, leading to a significant deterioration of bone microarchitecture and an increased fracture risk. Although recent studies have shown that the distribution of bone mineral becomes more heterogeneous because of estrogen deficiency in animal models of osteoporosis, it is not known whether osteoporosis alters mineral distribution in human bone. Type 2 diabetes mellitus (T2DM) can also increase bone fracture risk and is associated with impaired bone cell function, compromised collagen structure, and reduced mechanical properties. However, it is not known whether alterations in mineral distribution arise in diabetic (DB) patients’ bone. In this study, we quantify mineral content distribution and tissue microarchitecture (by μCT) and mechanical properties (by compression testing) of cancellous bone from femoral heads of osteoporotic (OP; n = 10), DB (n = 7), and osteoarthritic (OA; n = 7) patients. We report that though OP cancellous bone has significantly deteriorated compressive mechanical properties and significantly compromised microarchitecture compared with OA controls, there is also a significant increase in the mean mineral content. Moreover, the heterogeneity of the mineral content in OP bone is significantly higher than controls (+25%) and is explained by a significant increase in bone volume at high mineral levels. We propose that these mineral alterations act to exacerbate the already reduced bone quality caused by reduced cancellous bone volume during osteoporosis. We show for the first time that cancellous bone mineralization is significantly more heterogeneous (+26%) in patients presenting with T2DM compared with OA (non‐DB) controls, and that this heterogeneity is characterized by a significant increase in bone volume at low mineral levels. Despite these mineralization changes, bone microarchitecture and mechanical properties are not significantly different between OA groups with and without T2DM. Nonetheless, the observed alterations in mineral heterogeneity may play an important tissue‐level role in bone fragility associated with OP and DB bone. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Immunoneutralization of follicle stimulating hormone does not affect gonadotrophin surge-inhibiting factor/attenuating factor bioactivity during the rat ovarian cycle

The physiological role of follicle stimulating hormone (FSH) in the regulation of the release of the putative ovarian factor gonadotrophin surge-inhibiting or -attenuating factor (GnSIF/AF) was investigated. Blood FSH concentrations were immunoneutralized in female rats during different days of the ovarian cycle. FSH antiserum was injected in different protocols to neutralize the FSH surge(s) and/or basal FSH concentrations. All animals were killed on the morning of the day of pro-oestrus of the control rats. Hemi-pituitaries were incubated and gonadotrophin-releasing hormone (GnRH) stimulated and basal luteinizing hormone (LH) and FSH releases and pituitary contents were measured. The biological effectiveness of the FSH antiserum was established by monitoring the histology of vaginal smears and inhibin concentrations in trunk-blood. The predominance of small leukocytes in the smears (low oestradiol bioactivity) and the decreased (bioactive) inhibin secretion imply that anti-FSH neutralizes FSH bioactivity. Simultaneously, the results showed that all anti-FSH injections did not affect the biphasic LH response to GnRH in vitro, which shows an unaltered presence of GnSIF/AF bioactivity in the blood circulation. The results suggest that under physiological conditions GnSIF/AF bioactivity, which keeps the LH responsiveness of the pituitary gland suppressed to the action of GnRH, is not supported by inhibin and not controlled by FSH.

Purification of gonadotropin surge-inhibiting factor from Sertoli cell-enriched culture medium

Gonadotropin surge-inhibiting factor (GnSIF) is a novel biological factor in follicular fluid that inhibits the pre-ovulatory LH and FSH surges. Recent studies suggest that the biological activity of GnSIF can be attributed to inhibin. Preliminary studies showed that the Sertoli cell-conditioned medium contains GnSIF-like biological activity. Using 32 liters of primary Sertoli cell-enriched culture medium and an in vitro pituitary bioassay, GnSIF was isolated. GnSIF is a single monomeric polypeptide (Mr of 37,000) with a partial N-terminal amino acid sequence of NH2-SDXXPQL which is distinct from any existing protein sequences. The identity of the inhibin that was separated from GnSIF was confirmed by direct protein sequencing. The purified GnSIF inhibited GnRH-stimulated LH- and basal FSH-release from pituitary cells cultured in vitro dose-dependently with a half maximal effective dose of about 1.4 ng/ml and 3.5 ng/ml, respectively. The half maximal effective dose of inhibin to suppress the pituitary GnRH-stimulated LH- and basal FSH-release was 2.5 ng/ml and 0.8 ng/ml, respectively. This study demonstrates that GnSIF is a unique protein that shares some biological activities with inhibin.

Transport of desglycinamide-arginine vasopressin across the blood-brain barrier in rats as evaluated by the unit impulse response methodology

The pharmacokinetic characteristics of desglycinamide-arginine vasopressin (DGAVP) with respect to its transport across the blood-brain barrier (BBB) were studied with the use of serial CSF sampling in an individual animal and the unit impulse response methodology. Transport rate is determined as BBB clearance, the volume of plasma per unit time cleared of the peptide by BBB transport, and the extent of transport as the percentage of the administered dose transported into the central nervous system. Plasma kinetics of DGAVP were shown to be linear within the dose range studied (50-150 micrograms), plasma mean residence time (MRT) being 18 +/- 4 min (mean +/- SE; n = 9). Elimination of DGAVP from CSF after icv administration was linear, with an MRT of 10 +/- 1 min (n = 9). After iv administration of 100 micrograms DGAVP, CSF concentrations were detectable for 90 min. Transport from plasma to the central nervous system was linear. The BBB transport clearance value was 1.0 +/- 0.3 microliters/min, and 0.026 +/- 0.007% of the administered dose was transported into the central nervous system. Results demonstrate that, within the concentration range studied, DGAVP is transported across the BBB by passive diffusion, although to a very low extent.