Glucose transporters GLUT1, GLUT3, and GLUT4 have different effects on osteoblast proliferation and metabolism

Combined Effects of Cyclic Hypoxic and Mechanical Stimuli on Human Bone Marrow Mesenchymal Stem Cell Differentiation: A New Approach to the Treatment of Bone Loss

Background: The prevention and treatment of bone loss and osteoporotic fractures is a public health challenge. Combined with normobaric hypoxia, whole-body vibration has a high clinic potential in bone health and body composition. The effect of this therapy may be mediated by its action on bone marrow mesenchymal stem cells (MSCs). Objectives: Evaluate the effects of cyclic low-vibration stimuli and/or hypoxia on bone marrow-derived human MSC differentiation. Methods: MSCs were exposed four days per week, two hours/day, to hypoxia (3% O2) and/or vibration before they were induced to differentiate or during differentiation into osteoblasts or adipocytes. Gene and protein expression of osteoblastic, adipogenic, and cytoskeletal markers were studied, as well as extracellular matrix mineralization and lipid accumulation. Results: early osteoblastic markers increased in undifferentiated MSCs, pretreated in hypoxia and vibration. This pretreatment also increased mRNA levels of osteoblastic genes and beta-catenin protein in the early stages of differentiation into osteoblasts without increasing mineralization. When MSCs were exposed to vibration under hypoxia or normoxia during osteoblastic differentiation, mineralization increased with respect to cultures without vibrational stimuli. In MSCs differentiated into adipocytes, both in those pretreated as well as exposed to different conditions during differentiation, lipid formation decreased. Changes in adipogenic gene expression and increased beta-catenin protein were observed in cultures treated during differentiation. Conclusions: Exposure to cyclic hypoxia in combination with low-intensity vibratory stimuli had positive effects on osteoblastic differentiation and negative ones on adipogenesis of bone marrow-derived MSCs. These results suggest that in elderly or frail people with difficulty performing physical activity, exposure to normobaric cyclic hypoxia and low-density vibratory stimuli could improve bone metabolism and health.

Short- and long-term exposure to high glucose induces unique transcriptional changes in osteoblasts in vitro

Bone is increasingly recognized as a target for diabetic complications. In order to evaluate the direct effects of high glucose on bone, we investigated the global transcriptional changes induced by hyperglycemia in osteoblasts in vitro. Rat bone marrow-derived mesenchymal stromal cells were differentiated into osteoblasts for 10 days, and prior to analysis, they were exposed to hyperglycemia (25 mM) for the short-term (1 or 3 days) or long-term (10 days). Genes and pathways regulated by hyperglycemia were identified using mRNA sequencing and verified with qPCR. Genes upregulated by 1-day hyperglycemia were, for example, related to extracellular matrix organization, collagen synthesis and bone formation. This stimulatory effect was attenuated by 3 days. Long-term exposure impaired osteoblast viability, and downregulated, for example, extracellular matrix organization and lysosomal pathways, and increased intracellular oxidative stress. Interestingly, transcriptional changes by different exposure times were mostly unique and only 89 common genes responding to glucose were identified. In conclusion, short-term hyperglycemia had a stimulatory effect on osteoblasts and bone formation, whereas long-term hyperglycemia had a negative effect on intracellular redox balance, osteoblast viability and function.

Hyperthyroidism-driven bone loss depends on BMP receptor Bmpr1a expression in osteoblasts

Hyperthyroidism is a well-known trigger of high bone turnover that can lead to the development of secondary osteoporosis. Previously, we have shown that blocking bone morphogenetic protein (BMP) signaling systemically with BMPR1A-Fc can prevent bone loss in hyperthyroid mice. To distinguish between bone cell type-specific effects, conditional knockout mice lacking Bmpr1a in either osteoclast precursors (LysM-Cre) or osteoprogenitors (Osx-Cre) were rendered hyperthyroid and their bone microarchitecture, strength and turnover were analyzed. While hyperthyroidism in osteoclast precursor-specific Bmpr1a knockout mice accelerated bone resorption leading to bone loss just as in wildtype mice, osteoprogenitor-specific Bmpr1a deletion prevented an increase of bone resorption and thus osteoporosis with hyperthyroidism. In vitro, wildtype but not Bmpr1a-deficient osteoblasts responded to thyroid hormone (TH) treatment with increased differentiation and activity. Furthermore, we found an elevated Rankl/Opg ratio with TH excess in osteoblasts and bone tissue from wildtype mice, but not in Bmpr1a knockouts. In line, expression of osteoclast marker genes increased when osteoclasts were treated with supernatants from TH-stimulated wildtype osteoblasts, in contrast to Bmpr1a-deficient cells. In conclusion, we identified the osteoblastic BMP receptor BMPR1A as a main driver of osteoporosis in hyperthyroid mice promoting TH-induced osteoblast activity and potentially its coupling to high osteoclastic resorption.

Metabolomic biomarkers in liquid biopsy: accurate cancer diagnosis and prognosis monitoring

Liquid biopsy, a novel detection method, has recently become an active research area in clinical cancer owing to its unique advantages. Studies on circulating free DNA, circulating tumor cells, and exosomes obtained by liquid biopsy have shown great advances and they have entered clinical practice as new cancer biomarkers. The metabolism of the body is dynamic as cancer originates and progresses. Metabolic abnormalities caused by cancer can be detected in the blood, sputum, urine, and other biological fluids via systemic or local circulation. A considerable number of recent studies have focused on the roles of metabolic molecules in cancer. The purpose of this review is to provide an overview of metabolic markers from various biological fluids in the latest clinical studies, which may contribute to cancer screening and diagnosis, differentiation of cancer typing, grading and staging, and prediction of therapeutic response and prognosis.

Glucose Regulates Glucose Transport and Metabolism via mTOR Signaling Pathway in Bovine Placental Trophoblast Cells

It has been confirmed that improving the energy level of the diet contributed to the greater reproductive performance and birth weight of calves in periparturient dairy cows. To investigate the effect of glucose on nutrient transport during fetal development, the bovine placental trophoblast cells (BPTCs) were cultured in media with different glucose concentrations (1, 2, 4, 8, or 16 mg/mL). Subsequently, the BPTCs were cultured in media with 1, 8 mg/mL glucose and 8 mg/mL glucose plus 100 nmol/L rapamycin (the inhibitor of mTOR pathway). Compared with the 1 mg/mL glucose, the addition of 8 mg/mL glucose stimulated cell proliferation, upregulated the mRNA abundance of the glucose transporter GLUT1 and GLUT4, and increased the activity of glucose metabolism-related enzyme glucose-6-phosphate dehydrogenease (G6PD), lactate dehydrogenase (LDHA) and phosphoglycerate kinase 1 (PGK1), as well as adenosine-triphosphate (ATP) content (p < 0.05).Furthermore, compared with the treatment of 1 mg/mL glucose, adding 8 mg/mL of glucose-upregulated gene expression in the mTOR signaling pathway, including phosphatidylinositol3-kinase (PI3K), protein kinase B (Akt), mammalian target of rapamycin (mTOR) and 70 kDa ribosomal protein S6 kinase 2 (P70S6K) (p < 0.05).The supplementation of rapamycin downregulated the gene and protein expression of the mTOR signaling pathway, including mTOR, P70S6K, EIF4E-binding protein 1 (4EBP1), hypoxia-inducible factor 1-alpha (HIF-1α) and gene expression of glucose transporter upregulated by 8 mg/mL glucose (p < 0.05). Thus, these results indicated that the addition of 8 mg/mL glucose regulated the glucose transport and metabolism in BPTCs through the mTOR signaling pathway, thereby promoting the supply of nutrients to fetus.

Development of Novel Pt(IV)-Carbohydrate Derivatives as Targeted Anticancer Agents against Osteosarcoma

Despite the enormous importance of cisplatin as a chemotherapeutic agent, its application is impacted by dose-limiting side effects and lack of selectivity for cancer cells. Researchers can overcome these issues by taking advantage of the pro-drug nature of the platinum(IV) oxidation state, and by modifying the coordination sphere of the metal centre with specific vectors whose receptors are overexpressed in tumour cell membranes (e.g., carbohydrates). In this paper we report the synthesis of four novel carbohydrate-modified Pt(IV) pro-drugs, based on the cisplatin scaffold, and their biological activity against osteosarcoma (OS), a malignant tumour which is most common in adolescents and young adults. The carbohydrate-targeting vectors and Pt scaffold are linked using copper-catalysed azide-alkyne cycloaddition (CuAAC) chemistry, which is synonymous with mild and robust reaction conditions. The novel complexes are characterised using multinuclear 1D-2D NMR (¹H, ¹³C and ¹⁹⁵Pt), IR, HR-MS, Elem. Analyses, and CV. Cytotoxicity on 2D and 3D and cell morphology studies on OS cell lines, as well as non-cancerous human foetal osteoblasts (hFOBs), are discussed.