GPI-specific phospholipase D (GPI-PLD) is expressed during mouse development and is localized to the extracellular matrix of the developing mouse skeleton

Reiterative infusions of MSCs improve pediatric osteogenesis imperfecta eliciting a pro-osteogenic paracrine response: TERCELOI clinical trial

BACKGROUND

Osteogenesis imperfecta (OI) is a rare genetic disease characterized by bone fragility, with a wide range in the severity of clinical manifestations. The majority of cases are due to mutations in the COL1A1 or COL1A2 genes, which encode type I collagen. Mesenchymal stem cells (MSCs), as the progenitors of the osteoblasts, the main type I collagen secreting cell type in the bone, have been proposed and tested as an innovative therapy for OI with promising but transient outcomes.

METHODS

To overcome the short-term effect of MSCs therapy, we performed a phase I clinical trial based on reiterative infusions of histocompatible MSCs, administered in a 2.5-year period, in two pediatric patients affected by severe and moderate OI. The aim of this study was to assess the safety and effectiveness of this cell therapy in nonimmunosuppressed OI patients. The host response to MSCs was studied by analyzing the sera from OI patients, collected before, during, and after the cell therapy.

RESULTS

We first demonstrated that the sequential administration of MSCs was safe and improved the bone parameters and quality of life of OI patients along the cell treatment plus 2-year follow-up period. Moreover, the study of the mechanism of action indicated that MSCs therapy elicited a pro-osteogenic paracrine response in patients, especially noticeable in the patient affected by severe OI.

CONCLUSIONS

Our results demonstrate the feasibility and potential of reiterative MSCs infusion for two pediatric OI and highlight the paracrine response shown by patients as a consequence of MSCs treatment.

Endurance exercise training restores diabetes-induced alteration in circulating Glycosylphosphatidylinositol-specific phospholipase D levels in rats

BACKGROUND

Glycosylphosphatidylinositol-specific phospholipase D (GPLD1) is responsible for cleaving membrane-associated glycosylphosphatidylinositol (GPI) molecules, which is affected by diabetes. We aimed to examine the effect of 14 weeks treadmill running on serum GPLD1 levels and its association with glycemic indexes and serum glypican-4 (GPC-4), a novel GPI-anchored adipokine, in streptozotocin-nicotinamide-induced diabetic rats.

METHODS

Thirty-six male Wister rats were randomly divided into three groups of twelve animals each, involving sedentary control (SC), sedentary diabetic (SD), and trained diabetic (TD) groups. The diabetes was induced through intraperitoneal injection of 120 mg/kg nicotinamide 15 min prior to intraperitoneal injection of 65 mg/kg streptozotocin in SD and TD groups. The TD group was exercised on a treadmill for 60 min/days, 5 days/wk at 26 m/min, and zero grade for 14 weeks. Following the experiment period, blood samples were taken from all animals and analyzed for experimental indexes via sandwich ELISA.

RESULTS

Exercise training caused a significant decrease in the elevated blood glucose levels and a significant increase in the lowered blood insulin levels in TD rats (both p < 0.001). Glucose tolerance of TD rats significantly improved following experimental protocol, as indicated by OGTT (p < 0.001). Experimental diabetes significantly increased serum GPLD1 levels (p < 0.001), while exercise training significantly decreased its levels (p < 0.001). Serum GPLD1 levels correlated directly with glycemic indexes involving FBS, 2hOGTT, and AUC of glucose (r = 0.80, r = 0.79, r = 0.79, respectively, all p < 0.001) and inversely with serum insulin levels (r = - 0.83, p < 0.001). There were no significant differences in serum GPC-4 levels among groups, and no association with GPLD1 alteration.

CONCLUSIONS

Sedentary diabetic rats have higher circulating GPLD1 compared to controls, which can be reversed by exercise training and is associated with modifying in glycemic and insulin profile.

The effect of combined diet and exercise intervention on body weight and the serum GPIHBP1 concentration in overweight/obese middle-aged women

BACKGROUND

The relationship between the effects of diet and exercise intervention and the body weight associated with the serum lipoprotein lipase (LPL), hepatic triglyceride lipase (HTGL) and glycosylphosphatidylinositol anchored high density lipoprotein binding protein 1 (GPIHBP1) concentrations has not been elucidated.

METHODS

Sixty-six overweight/obese middle aged women were assigned to the diet and exercise intervention for 4months. They were divided into 2 groups followed by the body mass index (BMI) decreased >3% (n=41) and <3% (n=25). Serum lipids, lipoproteins and the LPL, HTGL, GPIHBP1 concentrations were determined.

RESULTS

The cases in which the BMI decreased >3% exhibited significant improvement of diagnostic markers compared with the cases with <3% decrease after the intervention. The LPL concentration did not significantly change, but GPIHBP1 increased significantly after the intervention. The increased GPIHBP1 was significantly associated with decreased body weight. Multiple regression analysis indicated a strong association between GPIHBP1 and percentage of body fat.

CONCLUSIONS

The diet and exercise intervention significantly increased the serum GPIHBP1 concentration in association with a decrease in body weight and percentage of body fat. These results suggest that GPIHBP1 is a better marker for body weight decrease than LPL.

Differential effects of adiponectin in osteoblast-like cells

The skeleton should maintain an adequate volume, vigour and strength to carry out the role for which it is designed: to hold the whole soft tissue mass that shapes the body and to protect the vital organs. To fulfil this task a satisfactory food intake is required and regulators that are released in the feeding and fasting states, among other signals indicate how much soft mass needs to be built up. Those signals include the secretion of adipocytokines which could represent a relevant link between soft mass (adipose tissue) and skeleton. We studied the presence of adiponectin receptors (AdipoR1, AdipoR2) and its direct effects in osteosarcoma cell line Saos-2. The results indicated that adiponectin receptors were present in the osteoblastic cells with a higher expression of AdipoR1. Human recombinant globular adiponectin was able to increase viability levels and decrease cytotoxicity rates in cell cultures. Also, adiponectin significantly inhibited alkaline phosphatase activity in supernatants. Osteoprotegerin mRNA expression was significantly reduced after 72 h treatment. The FOS induction was studied and the results exhibited a significant increase caused by adiponectin. In conclusion, all these observations suggest that adiponectin influences bone metabolism decreasing the levels of bone formation. Regulators of adiponectin or its receptors could be circulating to modulate the activities of this peptide.

Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations

The present review aims to systematically and critically analyze the current knowledge on phospholipases and their role in physiological and pathological mineralization undertaken by mineralization competent cells. Cellular lipid metabolism plays an important role in biological mineralization. The physiological mechanisms of mineralization are likely to take place in tissues other than in bones and teeth under specific pathological conditions. For instance, vascular calcification in arteries of patients with renal failure, diabetes mellitus or atherosclerosis recapitulates the mechanisms of bone formation. Osteoporosis—a bone resorbing disease—and rheumatoid arthritis originating from the inflammation in the synovium are also affected by cellular lipid metabolism. The focus is on the lipid metabolism due to the effects of dietary lipids on bone health. These and other phenomena indicate that phospholipases may participate in bone remodelling as evidenced by their expression in smooth muscle cells, in bone forming osteoblasts, chondrocytes and in bone resorbing osteoclasts. Among various enzymes involved, phospholipases A₁ or A₂, phospholipase C, phospholipase D, autotaxin and sphingomyelinase are engaged in membrane lipid remodelling during early stages of mineralization and cell maturation in mineralization-competent cells. Numerous experimental evidences suggested that phospholipases exert their action at various stages of mineralization by affecting intracellular signaling and cell differentiation. The lipid metabolites—such as arachidonic acid, lysophospholipids, and sphingosine-1-phosphate are involved in cell signaling and inflammation reactions. Phospholipases are also important members of the cellular machinery engaged in matrix vesicle (MV) biogenesis and exocytosis. They may favour mineral formation inside MVs, may catalyse MV membrane breakdown necessary for the release of mineral deposits into extracellular matrix (ECM), or participate in hydrolysis of ECM. The biological functions of phospholipases are discussed from the perspective of animal and cellular knockout models, as well as disease implications, development of potent inhibitors and therapeutic interventions.

The exquisite regulation of PLD2 by a wealth of interacting proteins: S6K, Grb2, Sos, WASp and Rac2 (and a surprise discovery: PLD2 is a GEF)

Phospholipase D (PLD) catalyzes the conversion of the membrane phospholipid phosphatidylcholine to choline and phosphatidic acid (PA). PLD's mission in the cell is two-fold: phospholipid turnover with maintenance of the structural integrity of cellular/intracellular membranes and cell signaling through PA and its metabolites. Precisely, through its product of the reaction, PA, PLD has been implicated in a variety of physiological cellular functions, such as intracellular protein trafficking, cytoskeletal dynamics, chemotaxis of leukocytes and cell proliferation. The catalytic (HKD) and regulatory (PH and PX) domains were studied in detail in the PLD1 isoform, but PLD2 was traditionally studied in lesser detail and much less was known about its regulation. Our laboratory has been focusing on the study of PLD2 regulation in mammalian cells. Over the past few years, we have reported, in regards to the catalytic action of PLD, that PA is a chemoattractant agent that binds to and signals inside the cell through the ribosomal S6 kinases (S6K). Regarding the regulatory domains of PLD2, we have reported the discovery of the PLD2 interaction with Grb2 via Y169 in the PX domain, and further association to Sos, which results in an increase of de novo DNA synthesis and an interaction (also with Grb2) via the adjacent residue Y179, leading to the regulation of cell ruffling, chemotaxis and phagocytosis of leukocytes. We also present the complex regulation by tyrosine phosphorylation by epidermal growth factor receptor (EGF-R), Janus Kinase 3 (JAK3) and Src and the role of phosphatases. Recently, there is evidence supporting a new level of regulation of PLD2 at the PH domain, by the discovery of CRIB domains and a Rac2-PLD2 interaction that leads to a dual (positive and negative) effect on its enzymatic activity. Lastly, we review the surprising finding of PLD2 acting as a GEF. A phospholipase such as PLD that exists already in the cell membrane that acts directly on Rac allows a quick response of the cell without intermediary signaling molecules. This provides only the latest level of PLD2 regulation in a field that promises newer and exciting advances in the next few years.