Neuropeptide Y modulates fracture healing through Y1 receptor signaling

Neuropeptide Y acting via it's Y₁ receptor represents a powerful pathway in the control of bone mass. The global or osteoblast‐specific Y₁ receptor deletion induces pronounced bone anabolic effects in mice. However, the contribution of Y₁ receptor deletion in bone repair/healing remained to be clarified. Therefore, in this study we characterized the role of Y₁ receptor deletion in fracture healing. Closed tibial fractures were generated in germline (Y₁^?/?) and osteoblastic‐specific Y₁ receptor knockout mice. The progression of tibial repair monitored from 1‐ until 6‐weeks post‐fracture demonstrated that in Y₁^?/? mice there is a delay in fracture repair, as seen by a decrease in bone callus volume and callus strength. Moreover, the histological features included elevated avascular and cartilage area and consequently delayed cartilage removal, and hence impaired union. Interestingly, this delay in bone repair was not related directly to Y₁ receptors expressed by mature osteoblasts. These findings suggest that the global absence of the Y₁ receptor delays fracture healing, through impairing the early phases of fracture repair to achieve bony union. The data acquired on the role of Y₁ receptor signaling disruption in bone regeneration is critical for the design of future therapeutic strategies. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1570–1578, 2013

     

神经肽Y在大鼠睾丸内的表达及其意义

目的 :分析神经肽Y(NPY)在大鼠睾丸中的表达 ,探讨NPY在雄激素生成和精子发生中的作用。　方法 :用RT PCR半定量法分析SD雄性大鼠睾丸中的NPYmRNA的表达 ,以β actin为内参照。用免疫组化法观察NPY在组织和细胞内的分布。　结果 :NPY基因在大鼠睾丸中有相当水平的表达 ,在PCR产物电泳图谱中见到明显的基因扩增产物条带 ;免疫组化显示 ,NPY在睾丸间质区、睾丸小血管周围及其精曲小管周围阳性表达 ,而在精曲小管内未见表达。　结论 :睾丸内表达的NPY可能直接参与了睾丸功能的调节。     

血清神经肽Y水平与绝经后妇女骨密度相关性研究

目的探讨血清神经肽Y(NPY)水平与绝经后妇女骨密度(BMD)的相关性。方法纳入在我院门诊就诊的绝经后妇女。测量血清钙、磷、白蛋白、甲状旁腺激素(parathyroid hormone,PTH)、促甲状腺激素(thyrotropin,TSH)、25-OH维生素D和NPY浓度。根据骨密度检测结果将受试者分为3组,分别为BMD值:正常(n=66)、骨量减少(n=63)和骨质疏松症(n=63)。根据血清NPY水平,受试者也被分为3组:低NPY(n=30)、正常NPY(n=126)和高NPY(n=36)。结果骨密度正常、骨质疏松、骨质疏松症患者血清NPY、PTH和年龄水平差异有显著统计学意义(P<0.05)。对于不同的NPY水平,各组腰椎、股骨总、股骨颈、转子、股骨转子间和Ward’s三角BMD值有显著差异(P<0.05)。相关性分析显示血清NPY水平与患者年龄、BMI呈现显著正相关(P<0.05),与不同部位的BMD值之间均有显著负相关性(P<0.05)。结论血清NPY水平与患者年龄、体重指数或任何部位测量的BMD值之间有相关性。     

Elevated Aromatase Expression in Osteoblasts Leads to Increased Bone Mass Without Systemic Adverse Effects

The stimulatory effects of testosterone (T) on bone can either be through a direct activation of the androgen receptor (AR) or mediated through aromatization of T to estradiol (E2), followed by activation of estrogen receptors (ERs) in bone. Aromatase expression in osteoblasts and reproductive tissues is dependent on different promoters, which are differentially regulated. To study the effect of elevated local aromatization of T to E2 in bone, we developed a transgenic mouse model (Coll‐1α1‐Arom) that overexpresses the human aromatase gene under the control of the osteoblast specific rat type I α I procollagen promoter. The Coll‐1α1‐Arom mice expressed human aromatase mRNA specifically in bone and had unaffected serum E2 and T levels. Male Coll‐1α1‐Arom mice had clearly increased total body BMD, trabecular BMD, cortical BMD, and cortical thickness associated with elevated osteoprotegerin mRNA levels and reduced number of osteoclasts (p < 0.01). Treatment of ovariectomized mice with T increased cortical and trabecular thickness in the Coll‐1α1‐Arom mice (p < 0.001) but not in the wildtype mice. In conclusion, elevated aromatase expression specifically in osteoblasts results in stimulatory estrogenic effects in bone without increasing serum E2 levels. Because osteoblast‐specific aromatase expression results in an increased ER to AR activation ratio in bone, we propose that activation of ERs results in a more pronounced increase in bone mass than what is seen after activation of the AR. Development of osteoblast‐specific inducers of aromatase expression might identify substances with stimulatory effects on bone without systemic adverse effects.     

性激素与CD4~+CD25~+调节性T细胞的相关性及在肾移植免疫耐受中的作用研究

目的:为明确肾移植术后因供肾、受肾性别差异而排斥反应发生率不同,移植肾存活率不同而进行性激素水平的研究,明确性激素与CD4~+CD25~+调节性T细胞(CD4~+CD25~+Treg)的相关性及在肾移植免疫耐受中的作用。方法:选取正常对照组、肾移植组患者各20例,用ELISA法测定外周血性激素睾酮(T)、雌二醇(E_2)水平,用流式细胞术(FCM)测定CD4~+CD25~+Treg占CD~+T细胞比值。结果:肾移植术后女性E_2水平逐渐由高变低,男性T水平逐渐由低变高,CD~+CD25~+Treg水平也随时间相关性而逐渐升高,以单因素方差分析发现:E_2水平平稳期与正常对照组比较无显著差异(P0.05);T平稳期与正常对照组比较无显著差异(P0.05);肾移植男性受者早期2周内调节T细胞水平与正常值比较有明显差异(P0.05),门诊随访肾移植达2年患者其调节t细胞与正常对照组无明显差异(P0.05)。T与CD4~+CD25~+Treg术后均依时间相关性而逐渐上升,以直线相关性分析发现两者有明显相关性(P0.05)。结论:肾移植术后随着下丘脑-垂体-性腺轴的恢复,患者性激素水平及CD4~+CD25~+Treg水平均逐渐恢复正常。排除体重、年龄、透析时间、HLA配型、缺血时间、术后糖皮质激素、免疫抑制剂治疗方式等因素的影响,T与CD4~+CD25~+Treg有明显相关性,男性在肾移植术后不仅可以通过雄激素直接抑制效应T细胞发挥主要免疫抑制作用,还可以通过增加CD4~+CD25~+Treg水平来发挥次要免疫抑制作用。     

Genetic Variation in Sex Hormone Genes Influences Heel Ultrasound Parameters in Middle‐Aged and Elderly Men: Results From the European Male Aging Study (EMAS)

Genes involved in sex hormone pathways are candidates for influencing bone strength. Polymorphisms in these genes were tested for association with heel quantitative ultrasound (QUS) parameters in middle‐aged and elderly European men. Men 40–79 yr of age were recruited from population registers in eight European centers for the European Male Aging Study (EMAS). Polymorphisms were genotyped in AR, ESR1, ESR2, CYP19A1, CYP17A1, SHBG, SRD5A2, LHB, and LHCGR. QUS parameters broadband ultrasound attenuation (BUA) and speed of sound (SOS) were measured in the heel and used to derive BMD. The relationships between QUS parameters and polymorphisms were assessed using linear regression adjusting for age and center. A total of 2693 men, with a mean age of 60.1 ± 11.1 (SD) yr were included in the analysis. Their mean BUA was 80.0 ± 18.9 dB/Mhz, SOS was 1550.2 ± 34.1 m/s, and BMD was 0.542 ± 0.141 g/cm². Significant associations were observed between multiple SNPs in a linkage disequilibrium (LD) block within CYP19A1, peaking at the TCT indel with the deletion allele associating with reduced ultrasound BMD in heterozygotes (β =?0.016, p = ?0.005) and homozygotes (β = ?0.029, p = 0.001). The results for BUA and SOS were similar. Significant associations with QUS parameters were also observed for the CAG repeat in AR and SNPs in CYP17A1, LHCGR, and ESR1. Our data confirm evidence of association between bone QUS parameters and polymorphisms in CYP19A1, as well as modest associations with polymorphisms in CYP17A1, ESR1, LHCGR, and AR in a population sample of European men; this supports a role for genetically determined sex hormone actions in influencing male bone health.     

Emerging Aspects of the Body Composition,Bone Marrow Adipose Tissue and Skeletal Phenotypes in Type 1 Diabetes Mellitus

Anthropomorphic measures among type 1 diabetic patients are changing as the obesity epidemic continues. Excess fat mass may impact bone density and ultimately fracture risk. We studied the interaction between bone and adipose tissue in type 1 diabetes subjects submitted to two different clinical managements: (I) conventional insulin therapy or (II) autologous nonmyeloablative hematopoietic stem-cell transplantation (AHST). The study comprised 3 groups matched by age, gender, height and weight: control (C = 24), type 1 diabetes (T1D = 23) and type 1 diabetes treated with AHST (T1D-AHST = 9). Bone mineral density (BMD) and trabecular bone score (TBS) were assessed by dual X-ray absorptiometry (DXA). ¹H Magnetic resonance spectroscopy was used to assess bone marrow adipose tissue (BMAT) in the L3 vertebra, and abdominal magnetic resonance imaging was used to assess intrahepatic lipids (IHL), visceral (VAT) and subcutaneous adipose tissue (SAT). Individuals conventionally treated for T1D were more likely to be overweight (C = 23.8 ± 3.7; T1D = 25.3 ± 3.4; T1D-AHST = 22.5 ± 2.2 Kg/m²; p > 0.05), but there was no excessive lipid accumulation in VAT or liver. Areal BMD of the three groups were similar at all sites; lumbar spine TBS (L3) was lower in type 1 diabetes (p < 0.05). Neither SAT nor VAT had any association with bone parameters. Bone marrow adipose tissue (BMAT) lipid profiles were similar among groups. BMAT saturated lipids were associated with cholesterol, whereas unsaturated lipids had an association with IGF1. Overweight and normal weight subjects with type 1 diabetes have normal areal bone density, but lower trabecular bone scores. Adipose distribution is normal and BMAT volume is similar to controls, irrespective of clinical treatment.     

Association Between Repeat Length of Exon 1 CAG Microsatellite in the Androgen Receptor and Bone Density in Men is Modulated by Sex Hormone Levels

In this study we examined whether the androgen receptor (AR) gene CAG repeat polymorphism and serum androgen levels are associated with bone mineral density (BMD) and changes in BMD during 2–3 years in 229 healthy men 41–76 years old. Microsatellite analysis was performed on an automated sequencer. Indices of bioavailable testosterone (free testosterone [FT] and free androgen index) were calculated. BMD was measured using both dual-energy X-ray absorptiometry and quantitative ultrasound. All participants completed a questionnaire regarding major possible osteoporosis risk factors. In linear regression analysis there was a modest positive association, which was independent of age and body mass index (BMI), between AR repeat length and BMD at all sites. Although this association was significant independent of BMI, analyses in the subgroup of obese men (BMI > 30) did not reach significance, while the effect was enhanced when analyzing only nonobese men (BMI ≤ 30). There was no association between the AR gene polymorphism and rate of bone loss, FT, and BMD or testosterone and bone loss. Interestingly, the association between AR and BMD was modified by total testosterone. The lowest age- and BMI-adjusted average femoral neck BMD was found among men in the lowest tertile for both AR repeat length and FT, whereas men within the higher categories of these variables displayed the highest BMD. In conclusion, there is a positive association between the AR CAG repeat polymorphism and BMD, which is modified by androgen levels in healthy men.