sirolimus and Bone-Diseases--Metabolic

Chronic consumption of excessive alcohol results in reduced bone mass, impaired bone structure, and increased risk of bone fracture. However, the mechanisms underlying alcohol-induced osteoporosis are not fully understood. Here, we show that high dose chronic alcohol consumption reduces osteogenic differentiation and enhances adipogenic differentiation of bone marrow mesenchymal stem cells (BMMSCs), leading to osteopenia in a mouse model. Mechanistically, impaired osteo/adipogenic lineage differentiation of BMMSCs is due to activation of a phosphatidylinositide 3-kinase/AKT/mammalian target of rapamycin (mTOR) signaling cascade, resulting in downregulation of runt-related transcription factor 2 and upregulation of peroxisome proliferator-activated receptor gamma via activation of p70 ribosomal protein S6 kinase. Blockage of the mTOR pathway by rapamycin treatment ameliorates alcohol-induced osteopenia by rescuing impaired osteo/adipogenic lineage differentiation of BMMSCs. In this study, we identify a previously unknown mechanism by which alcohol impairs BMMSC lineage differentiation and reveal a potential rapamycin-based drug therapy for alcohol-induced osteoporosis. Stem Cells 2016;34:2157-2168.

Topics: Adipogenesis; Animals; Bone Diseases, Metabolic; Bone Marrow Cells; Cell Lineage; Ethanol; Female; Mesenchymal Stem Cells; Mice, Nude; Phenotype; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Fibrillin-1 (FBN1) deficiency-induced systemic sclerosis is attributed to elevation of interleukin-4 (IL4) and TGF-β, but the mechanism underlying FBN1 deficiency-associated osteopenia is not fully understood. We show that bone marrow mesenchymal stem cells (BMMSCs) from FBN1-deficient (Fbn1(+/-)) mice exhibit decreased osteogenic differentiation and increased adipogenic differentiation. Mechanistically, this lineage alteration is regulated by IL4/IL4Rα-mediated activation of mTOR signaling to down-regulate RUNX2 and up-regulate PPARγ2, respectively, via P70 ribosomal S6 protein kinase (P70S6K). Additionally, we reveal that activation of TGF-β/SMAD3/SP1 signaling results in enhancement of SP1 binding to the IL4Rα promoter to synergistically activate mTOR pathway in Fbn1(+/-) BMMSCs. Blockage of mTOR signaling by osteoblastic-specific knockout or rapamycin treatment rescues osteopenia phenotype in Fbn1(+/-) mice by improving osteogenic differentiation of BMMSCs. Collectively, this study identifies a previously unrecognized role of the FBN1/TGF-β/IL4Rα/mTOR cascade in BMMSC lineage selection and provides experimental evidence that rapamycin treatment may provide an anabolic therapy for osteopenia in Fbn1(+/-) mice.

Topics: Adipogenesis; Animals; Bone Diseases, Metabolic; Cell Differentiation; Cells, Cultured; Female; Fibrillin-1; Fibrillins; Flow Cytometry; Immunoblotting; Immunosuppressive Agents; Male; Mesenchymal Stem Cells; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Microfilament Proteins; Microscopy, Fluorescence; Osteogenesis; Receptors, Cell Surface; RNA Interference; Scleroderma, Systemic; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Transforming Growth Factor beta

Osteoporosis, osteopenia, and osteonecrosis are common in renal transplant recipients. In this study, we evaluated relationship between bone mineral density (BMD) and posttransplant duration; creatinine clearance; serum levels of glucose, calcium, phosphorus, alkaline phosphatase, vitamin D (vitD), parathormone, magnesium, C telopeptide, osteocalcin, lipids, and vit D therapy. Eighty five subjects included in this study had a mean age of 36.25 ± 10.5 years. At least at 6-month intervals we measured femoral neck (FN) and lumbar vertebra (LV) by DEXA and biochemical parameters. VitD was prescribed in 57 patients (vitDG). The mean duration of posttransplantation follow-up was 9.82 ± 2.72 months. T scores (TS) of FN and LV were normal in 29.4% and 21.2%; osteopenia in 56.5% and 49.4%; and osteoporosis in 12.1% and 29.4% of patients, respectively. Upon follow-up, TS improved significantly from -1.58 to -1.46 in FN and from -1.88 to -1.70 in LV (P < .05 for both). In patients receiving vitDG, TS improved significantly from -1.74 to -1.61 on FN and from -2.16 to -1.97 on LV (P < .05 for both). Osteocalcin and vitDG levels decreased in all patients (P < .05 for all). Blood urea nitrogen and serum creatinine increased (P < .05). In VitDG cohort, triglyceride levels decreased (P < .05) with unchanged blood glucose values; but among the other patients, triglycerides were unchanged but glucose levels had increased (P < .05). Bone disease including osteopenia or osteoporosis was observed among 70%. During the follow-up period, BMD increased significantly from baseline at 9.82 ± 2.72 months. VitD therapy caused more prominent improvements in BMD and decreases in serum triglycerides as well as mutigated the increase in blood glucose.

Topics: Azathioprine; Bone Density; Bone Diseases; Bone Diseases, Metabolic; Creatinine; Female; Humans; Kidney Transplantation; Lipids; Male; Methylprednisolone; Mycophenolic Acid; Osteonecrosis; Osteoporosis; Sirolimus; Vitamin D

Cyclosporine A (CsA) is associated with posttransplantation bone disease. Immunosuppressant drugs such as sirolimus (SRL), which are more potent and less deleterious than CsA, are being developed. Previous experiments have shown that SRL although immunosuppressive, is relatively bone sparing. The use of low doses of CsA and SRL in combination has displayed in vivo synergism. This study was initiated to examine the effect of low-dose CsA and SRL on bone metabolism, thereby hopefully providing a bone sparing immunosuppressive regimen for transplant recipients. One hundred and nineteen rats were divided into groups: basal, vehicle, CsA high dose, CsA low dose, SRL low dose, and combination low-dose CsA and SRL. The basal group was killed on day 0 for histomorphometry. The experimental groups were weighed and bled on days 0, 28, 56, and 84 and were killed on day 84 for histomorphometry. Serial assays for blood urea nitrogen (BUN), creatinine, and osteocalcin were performed. Osteocalcin was raised on days 28 and 56 in the high dose CsA group. Histomorphometry showed osteopenia with high-dose CsA. Low-dose CsA was relatively bone sparing, while low-dose SRL and combined low-dose CsA did not cause bone loss. In conclusion, the synergistic combination of low-dose CsA and SRL has the potential of providing both bone sparing and immunosuppressive benefits.

Topics: Animals; Blood Urea Nitrogen; Body Weight; Bone Density; Bone Diseases, Metabolic; Bone Resorption; Creatinine; Cyclosporine; Dose-Response Relationship, Drug; Drug Synergism; Immunosuppressive Agents; Male; Organ Transplantation; Osteocalcin; Rats; Rats, Sprague-Dawley; Sirolimus; Tibia