As the lipidomics field continues to advance, self-evaluation within the community is critical. Here, we performed an interlaboratory comparison exercise for lipidomics using Standard Reference Material (SRM) 1950-Metabolites in Frozen Human Plasma, a commercially available reference material. The interlaboratory study comprised 31 diverse laboratories, with each laboratory using a different lipidomics workflow. A total of 1,527 unique lipids were measured across all laboratories and consensus location estimates and associated uncertainties were determined for 339 of these lipids measured at the sum composition level by five or more participating laboratories. These evaluated lipids detected in SRM 1950 serve as community-wide benchmarks for intra- and interlaboratory quality control and method validation. These analyses were performed using nonstandardized laboratory-independent workflows. The consensus locations were also compared with a previous examination of SRM 1950 by the LIPID MAPS consortium. While the central theme of the interlaboratory study was to provide values to help harmonize lipids, lipid mediators, and precursor measurements across the community, it was also initiated to stimulate a discussion regarding areas in need of improvement.

Chronic kidney disease (CKD) patients may have high rates of bone loss and fractures, but microarchitectural and biochemical mechanisms of bone loss in CKD patients have not been fully described. In this longitudinal study of 53 patients with CKD Stages 2-5D, we used dual energy X-ray absorptiometry (DXA), high resolution peripheral quantitative computed tomography (HRpQCT) and biochemical markers of bone metabolism to elucidate effects of CKD on the skeleton. Median follow-up was 1.5 years (Range 0.9 to 4.3 years); bone changes were annualized and compared to baseline. By DXA, there were significant declines in areal bone mineral density (BMD) of the total hip and ultradistal radius: −1.3% (95% CI: −2.1 to −0.6) and −2.4% (95% CI: −4.0 to −0.9), respectively. By HRpQCT at the distal radius, there were significant declines in cortical area, density and thickness, and increases in porosity: −2.9% (95% CI −3.7 to −2.2), −1.3% (95% CI −1.6 to −0.6), −2.8% (95% CI −3.6 to −1.9), and +4.2% (95% CI 2.0 to 6.4) respectively. Radius trabecular area increased significantly: +0.4% (95% CI 0.2 to 0.6), without significant changes in trabecular density or microarchitecture. Elevated time-averaged levels of parathyroid hormone (PTH) and bone turnover markers predicted cortical deterioration. Higher levels of serum 25-hydroxyvitamin D predicted decreases in trabecular network heterogeneity. These data suggest that significant cortical loss occurs with CKD, which is mediated by hyperparathyroidism and elevated turnover. Future investigations are required to determine whether these cortical losses can be attenuated by treatments that reduce PTH levels and remodeling rates.

Summary Intact cholesterol homeostasis helps to maintain hematopoietic stem and multipotential progenitor cell (HSPC) quiescence. Mice with defects in cholesterol efflux pathways due to deficiencies of the ATP binding cassette transporters ABCA1 and ABCG1 displayed a dramatic increase in HSPC mobilization and extramedullary hematopoiesis. Increased extramedullary hematopoiesis was associated with elevated serum levels of G-CSF due to generation of IL-23 by splenic macrophages and dendritic cells. This favored hematopoietic lineage decisions towards granulocytes rather than macrophages in the bone marrow leading to impaired support for osteoblasts and decreased Cxcl12/SDF-1 production by mesenchymal progenitors. Greater HSPC mobilization and extramedullary hematopoiesis were reversed by raising HDL levels in Abca1−/−Abcg1−/− and Apoe−/− mice or in a mouse model of myeloproliferative neoplasm mediated by Flt3-ITD mutation. Our data identify a novel role of cholesterol efflux pathways in the control of HSPC mobilization. This may translate into novel therapeutic strategies for atherosclerosis and hematologic malignancies.

Bisphosphonates are a widely used class of drugs that have been proven to be extremely useful in the prevention and treatment of osteoporosis, hypercalcemia of malignancy, and bone metastases associated with multiple myeloma, breast cancer, and other solid tumors. In the past several years there have been numerous reports describing the occurrence of Osteonecrosis of the Jaws (ONJ) associated with these drugs. In the great majority of cases this condition develops after surgical manipulation of the oral tissues. The natural history and pathophysiology of ONJ however, remains unknown at the present time. Furthermore, whether the ONJ lesion initiates in the oral mucosa or derives from the underlying bone has not been determined. In this report we describe the effect of pamidronate, a second generation bisphosphonate, on oral mucosal cells. Our results show that bisphosphonate pre-treatment of oral mucosal cells inhibits proliferation and wound healing at clinically relevant doses and that this inhibition is not due to cellular apoptosis.

SUMMARY Design of small molecules that disrupt protein-protein interactions, including the interaction of RAS proteins and their effectors, have potential use as chemical probes and therapeutic agents. We describe here the synthesis and testing of potential small molecule pan-RAS ligands, which were designed to interact with adjacent sites on the surface of oncogenic KRAS. One compound, termed 3144, was found to bind to RAS proteins using microscale thermophoresis, nuclear magnetic resonance spectroscopy and isothermal titration calorimetry, and to exhibit lethality in cells partially dependent on expression of RAS proteins. This compound was metabolically stable in liver microsomes and displayed anti-tumor activity in xenograft mouse cancer models. These findings suggest that pan-RAS inhibition may be an effective therapeutic strategy for some cancers, and that structure-based design of small molecules targeting multiple adjacent sites to create multivalent inhibitors may be effective for some proteins.

Summary We compared skeletal parameters in type 2 diabetic (T2DM) and non-diabetic postmenopausal women. Bone structure by dual energy x-ray absorptiometry (DXA) and HR-pQCT was not different, although procollagen type 1 amino-terminal propeptide (P1NP) and osteocalcin levels were lower in T2DM. Introduction T2DM is associated with increased fracture risk, but, paradoxically, with higher cross-sectional bone density (BMD) as measured by DXA. We sought explanations to this puzzle by investigating detailed structural and biochemical skeletal parameters in T2DM. Methods Cross-sectional comparison of 25 postmenopausal T2DM women and 25 matched controls using DXA, high-resolution peripheral quantitative computed tomography (HR-pQCT) and biochemical bone turnover markers. Results BMD by DXA did not differ between T2DM and controls. HR-pQCT assessment also did not differ, with the exception of cortical area at the tibia, which tended to be lower in the diabetics (difference of 12±6 [mean ± SD] mm, p=0.06). P1NP and osteocalcin levels were lower in T2DM as compared to controls (P1NP, 34.3±16 vs. 57.3±28 ng/ml; p=0.005; osteocalcin, 4.5±2 vs. 6.2±2 nmol/L; p=0.001). Conclusions Postmenopausal women with T2DM had lower levels of bone formation markers as compared to controls. Aside from a possible decrease in cortical bone area at a weight-bearing site, bone structure was not altered in T2DM. Lower bone turnover may be a skeletal parameter that is present in T2DM.

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Bone remodeling consists of two phases--bone resorption and bone formation--that are normally balanced. When bone resorption exceeds bone formation, pathologic processes, such as osteoporosis, can result. Cathepsin K is a member of the papain family of cysteine proteases that is highly expressed by activated osteoclasts. Cathepsin K readily degrades type I collagen, the major component of the organic bone matrix. With such a major role in the initial process of bone resorption, cathepsin K has become a therapeutic target in osteoporosis. The antiresorptive properties of cathepsin K inhibitors have been studied in phase I and phase II clinical trials. Phase III studies are currently underway for odanacatib, a selective cathepsin K inhibitor.