Several epidemiological studies have suggested that obesity complicated with insulin resistance and type 2 diabetes exerts deleterious effects on the skeleton. While obesity coexists with estrogen deficiency in postmenopausal women, their combined effects on the skeleton are poorly studied. Thus, we investigated the impact of high‐fat diet (HFD) on bone and metabolism of ovariectomized (OVX) female mice (C57BL/6J). OVX or sham operated mice were fed either HFD (60%fat) or normal diet (10%fat) for 12 weeks. HFD‐OVX group exhibited pronounced increase in body weight (~86% in HFD and ~122% in HFD‐OVX, p < 0.0005) and impaired glucose tolerance. Bone microCT‐scanning revealed a pronounced decrease in trabecular bone volume/total volume (BV/TV) (−15.6 ± 0.48% in HFD and −37.5 ± 0.235% in HFD‐OVX, p < 0.005) and expansion of bone marrow adipose tissue (BMAT; +60.7 ± 9.9% in HFD vs. +79.5 ± 5.86% in HFD‐OVX, p < 0.005). Mechanistically, HFD‐OVX treatment led to upregulation of genes markers of senescence, bone resorption, adipogenesis, inflammation, downregulation of gene markers of bone formation and bone development. Similarly, HFD‐OVX treatment resulted in significant changes in bone tissue levels of purine/pyrimidine and Glutamate metabolisms, known to play a regulatory role in bone metabolism. Obesity and estrogen deficiency exert combined deleterious effects on bone resulting in accelerated cellular senescence, expansion of BMAT and impaired bone formation leading to decreased bone mass. Our results suggest that obesity may increase bone fragility in postmenopausal women. 相似文献
White adipose tissue (WAT) is perhaps the most plastic organ in the body, capable of regeneration following surgical removal and massive expansion or contraction in response to altered energy balance. Research conducted for over 70 years has investigated adipose tissue plasticity on a cellular level, spurred on by the increasing burden that obesity and associated diseases are placing on public health globally. This work has identified committed preadipocytes in the stromal vascular fraction of adipose tissue and led to our current understanding that adipogenesis is important not only for WAT expansion, but also for maintenance of adipocyte numbers under normal metabolic states. At the turn of the millenium, studies investigating preadipocyte differentiation collided with developments in stem cell research, leading to the discovery of multipotent stem cells within WAT. Such adipose tissue-derived stem cells (ASCs) are capable of differentiating into numerous cell types of both mesodermal and nonmesodermal origin, leading to their extensive investigation from a therapeutic and tissue engineering perspective. However, the insights gained through studying ASCs have also contributed to more-recent progress in attempts to better characterize committed preadipocytes in adipose tissue. Thus, ASC research has gone back to its roots, thereby expanding our knowledge of preadipocyte commitment and adipose tissue biology. 相似文献
Bone marrow adipose tissue (BMAT) is different from fat found elsewhere in the body, and only recently have some of its functions been investigated. BMAT may regulate bone marrow stem cell niche and plays a role in energy storage and thermogenesis. BMAT may be involved also in obesity and osteoporosis onset. Given the paramount functions of BMAT, we decided to better clarify the human bone marrow adipogenesis by analyzing the role of the retinoblastoma gene family, which are key players in cell cycle regulation.
Our data provide evidence that the inactivation of RB1 or RB2/P130 in uncommitted bone marrow stromal cells (BMSC) facilitates the first steps of adipogenesis. In cultures with silenced RB1 or RB2/P130, we observed an increase of clones with adipogenic potential and a higher percentage of cells accumulating lipid droplets.
Nevertheless, the absence of RB1 or RB2/P130 impaired the terminal adipocyte differentiation and gave rise to dysregulated adipose cells, with alteration in lipid uptake and release. For the first time, we evidenced that RB2/P130 plays a role in bone marrow adipogenesis.
Our data suggest that while the inactivation of retinoblastoma proteins may delay the onset of last cell division and allow more BMSC to be committed to adipocyte, it did not allow a permanent cell cycle exit, which is a prerequisite for adipocyte terminal maturation. 相似文献
The bone marrow contains mesenchymal stem cells (MSCs) that differentiate to the osteogenic and adipogenic lineages. The fact that the decrease in bone volume of age-related osteoporosis is accompanied by an increase in marrow adipose tissue implies the importance that the adipogenic process may have in bone loss. We previously observed that MSCs from control and osteoporotic women showed differences in their capacity to differentiate into the osteogenic and adipogenic pathways. In vitro studies indicate that bone marrow stromal cells are responsive to leptin, which increases their proliferation, differentiation to osteoblasts, and the number of mineralized nodules, but inhibits their differentiation to adipocytes. The aim of the present report was to study the direct effect of leptin on control and osteoporotic MSCs analyzing whether the protective effect of leptin against osteoporosis could be expressed by inhibition of adipocyte differentiation. MSCs from control, and osteoporotic donors were subjected to adipogenic conditions, in the absence or in the presence of 62.5 nM leptin. The number of adipocytes, the content of PPARgamma protein, and mRNA, and leptin mRNA were measured by flow cytometry, Western blot, and RT-PCR, respectively. Results indicate that control and osteoporotic MSCs differ in their adipogenic potential as shown by expression of active PPARgamma protein. Leptin exerted an antiadipogenic effect only on control MSCs increasing the proportion of inactive phosphorylated PPARgamma protein. Finally, results obtained during adipogenesis of osteoporotic cells suggest that this process is abnormal not only because of increased adipocyte number, but because of impaired leptin cells response. 相似文献
Objective: The goal of this study was to evaluate the impact of a 10‐month after‐school physical activity (PA) program on body composition and cardiovascular (CV) fitness in young black girls. Research Methods and Procedures: Subjects were 8‐ to 12‐year‐olds recruited from elementary schools. Body composition was measured using anthropometrics {waist circumference and BMI, DXA [percentage body fat (%BF)] and bone mineral density (BMD)}, and magnetic resonance imaging [visceral adipose tissue (VAT)]. CV fitness was measured using a graded treadmill test. The intervention consisted of 30 minutes homework/healthy snack time and 80 minutes PA (i.e., 25 minutes skills instruction, 35 minutes aerobic PA, and 20 minutes strengthening/stretching). Analyses were adjusted for age, baseline value of the dependent variable, and sexual maturation (pediatrician observation). Results: Mean attendance was 54%. Compared with the control group, the intervention group had a relative decrease in %BF (p < 0.0001), BMI (p < 0.01), and VAT (p < 0.01) and a relative increase in BMD (p < 0.0001) and CV fitness (p < 0.05). Higher attendance was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.01) and BMI (p < 0.05). Higher heart rate during PA was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.005). Discussion: An after‐school PA program can lead to beneficial changes in body composition and CV fitness in young black girls. It is noteworthy that the control and intervention groups differed in change in VAT but not waist circumference. This suggests that changes in central adiposity can occur in response to PA, even in young children, but that waist circumference may not be a good indicator of central adiposity. 相似文献
We investigated the effects of β-adrenergic activation on bone marrow adiposity and on adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). C57BL/6 mice were subjected to a control (CON), high calorie (HIGH) or low calorie (LOW) diet for 12 weeks. In each group, mice were treated with vehicle (VEH) or propranolol. The number of adipocytes per area bone marrow was increased in LOWVEH and HIGHVEH mice compared with CONVEH mice, which was attenuated by propranolol. Isoproterenol increased lipid droplet accumulation and adipogenic marker gene expression in 3T3-L1 preadipocytes and mouse BMSCs, which were blocked by propranolol. Conditioned medium obtained from MC3T3-E1 osteoblasts suppressed adipogenic differentiation of 3T3-L1 cells, which was significantly attenuated by treatment of MC3T3-E1 cells with isoproterenol. These data suggest that β-adrenergic activation enhances bone marrow adipogenesis via direct stimulation of BMSCs adipogenesis and indirect inhibition of osteoblast anti-adipogenic potential. [BMB Reports 2014; 47(10): 587-592] 相似文献
Ultrastructural localization of the leptin receptor in the rat hypothalamus was studied by immunocytochemistry. The antiserum against the leptin receptor which was used specifically recognized the carboxy terminal of the cytoplasmic domain. Intense leptin receptor immunoreactivity was detected in the arcuate, paraventricular, and ventromedial nuclei of the hypothalamus and in the lateral hypothalamic area. At the ultrastructural level, leptin receptor-like immunoreactivity appeared to be concentrated predominantly in perikarya and dendrites of these areas and strong immunolabeling for the leptin receptor was detected in the plasma membrane, rough endoplasmic reticulum, Golgi apparatus, and cytoplasmic matrix. This study provides the first detailed fine structure of leptin receptor-immunoreactive neurons in the rat hypothalamus. It may help to provide better understanding of the functions of leptin in the rat hypothalamus. 相似文献
There are disparate observations on central and peripheral effects of leptin, but several studies consistently support its role as a link between fat and bone. Bone marrow stroma contains mesenchymal stem cells (MSCs), which differentiate into osteoblasts and adipocytes, among others. In this study we assessed the expression of leptin receptors protein in MSCs from control and osteoporotic postmenopausal donors and their change during osteogenic and adipogenic differentiation. Also, we assessed the effects of leptin on osteogenic and adipogenic differentiation of these cells. We demonstrated high affinity leptin binding (KD = 0.36 +/- 0.02 nM) in both types of cells. Binding was very low under basal, but increased significantly (2-3 times) through osteogenic and adipogenic differentiation. Osteoporotic MSCs showed lower leptin binding capacity than control cells at an early osteogenic and adipogenic differentiation time, which could restrict cell sensitivity to the protective action of leptin. In this regard, we observed that leptin significantly inhibited adipocyte differentiation in control but not in osteoporotic MSCs, while it exerted a low stimulatory effect on calcium deposition (10%-20%) in both types of MSCs cells. In summary, we report the presence of high affinity leptin receptors on control and osteoporotic MSCs, which were modified distinctly by osteogenic and adipogenic stimulation and a direct and distinct effect of leptin on both type of cells. 相似文献
Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone that exerts insulinotropic and growth and survival effects on pancreatic β-cells. Additionally, there is increasing evidence supporting an important role for GIP in the regulation of adipocyte metabolism. In the current study we examined the molecular mechanisms involved in the regulation of GIP receptor (GIPR) expression in 3T3-L1 cells. GIP acted synergistically with insulin to increase neutral lipid accumulation during progression of 3T3-L1 preadipocytes to the adipocyte phenotype. Both GIPR protein and mRNA expression increased during 3T3-L1 cell differentiation, and this increase was associated with upregulation of nuclear levels of sterol response element binding protein 1c (SREBP-1c) and peroxisome proliferator-activated receptor γ (PPARγ), as well as acetylation of histones H3/H4. The PPARγ receptor agonists LY171883 and rosiglitazone increased GIPR expression in differentiated 3T3-L1 adipocytes, whereas the antagonist GW9662 ablated expression. Additionally, both PPARγ and acetylated histones H3/H4 were shown to bind to a region of the GIPR promoter containing the peroxisome proliferator response element (PPRE). Knockdown of PPARγ in differentiated 3T3-L1 adipocytes, using RNA interference, reduced GIPR expression, supporting a functional regulatory role. Taken together, these studies show that GIP and insulin act in a synergistic manner on 3T3-L1 cell development and that adipocyte GIPR expression is upregulated through a mechanism involving interactions between PPARγ and a GIPR promoter region containing an acetylated histone region. 相似文献
Objective: The objective of this study was to assess long‐term metabolic consequences of total body irradiation (TBI) and bone marrow transplantation. Severe obesity develops due to both hypertrophy and hyperplasia of adipocytes. We hypothesized that TBI would arrest adipose tissue growth and would affect insulin resistance (IR). Research Methods and Procedures: We exposed 2‐month‐old female ob/ob mice to 8 Grays of TBI followed by bone marrow transplantation and tested the animals for body weight (BW) gain, body composition, blood glucose, and insulin sensitivity. Results: Two months after TBI, irradiated mice stopped gaining BW, whereas non‐treated mice continued to grow. At the age of 9.5 months, body mass of irradiated mice was 60.6 ± 1.4 grams, which was only 61% of that in non‐treated ob/ob controls (99.4 ± 1.6 grams). Body composition measurements by DXA showed that decreased BW was primarily due to an impaired fat accumulation. This could not result from the production of leptin by bone marrow‐derived adipocyte progenitors because inhibition of the obese phenotype was identical in recipients of both B6 and ob/ob bone marrow. Inability of the irradiated mice to accumulate fat was associated with hepatomegaly, lower levels of monocyte chemoattractant protein‐1 expression in adipose tissue, and increased IR. Discussion: Our data argue in favor of the hypothesis that inability of adipose tissue to expand may increase IR. This mouse model may be valuable for studies of late‐onset radiation‐induced IR in humans. 相似文献
MBA-15, a marrow stromal-derived cell line, was shown to express an estrogen receptor. This finding was confirmed byin situhybridization and receptor binding assay. An exposure to estrogen (10?12–10?6m ) in a dose response manner resulted in a decrease of cell proliferation as measured by MTT assay. Cell function was measured by enzymatic activities of two osteoblastic markers, CD10/NEP and alkaline phosphatase. These enzymatic activities were elevated following the estrogen treatment. This model enabled direct evaluation of the estrogen effect on stromal osteoblast cells. 相似文献
Chronic inflammation of adipose tissue in obesity is by now an established phenomenon, but the initiating event(s) of the inflammatory cascade are still unknown. We hypothesized that neutrophil infiltration into adipose tissue may precede macrophage infiltration as in classical immune responses. Here we demonstrate that early (3 and 7 days) after initiating high-fat feeding of C57BL/6J mice, neutrophils transiently infiltrate the parenchyma of intra-abdominal adipose tissue. Mean periepdidymal fat myeloperoxidase expression (representing neutrophils) was significantly increased 3.5-fold (P < 0.01) and 2.9-fold (P < 0.03), at days 3 and 7 compared with day 0. Immunohistochemistry analysis demonstrated a physical binding between neutrophils and adipocytes, which was supported by in vitro adherence assay: mouse peritoneal neutrophils adhered to a monolayer of 3T3-L1 mouse adipocytes, in a manner dependent on their activation state, 41.9 +/- 3.7% or 29.5 +/- 2%, by PMA or the IL-8 analog CXCL1 (KC), respectively, compared with 24.8 +/- 1.5% in unstimulated neutrophils, respectively. The degree of surface exposure of CD11b (Mac-1) corresponded to the percentage of adhered neutrophils. The adherence was prevented by preincubating neutrophils or adipocytes with anti-CD11b or anti-ICAM-1 antibodies. Furthermore, immunoprecipitation of CD11b from lysates of a mixed neutrophil-adipocyte cell population resulted in coimmunoprecipitation of ICAM-1, indicating that the interaction is mediated by neutrophil CD11b and adipocyte ICAM-1. 相似文献