Triiodothyronine and amiodarone effects on β3-adrenoceptor density and lipolytic response to the β3-adrenergic agonist BRL 37344 in rat white adipocytes

Summary— The β-adrenergic effects of catecholamines are potentiated by thyroid hormones in adipose tissue. Amiodarone (AM) is structurally similar to thyroid hormones and was used to explore the mechanism of the triiodothyronine (T₃) effect on β-adrenergic receptors (β-ARs) in adipose tissue. AM decreases the expression of some T₃ sensitive genes in various tissues and antagonizes the effect of T₃ on its nuclear receptors. In this study, the T₃, AM and AM + T₃ effects on the β1- and β₃-AR density were assessed on rat white adipocytes by radioligand binding using [³H]CGP 12177 after characterization of these subtypes by displacement of [³H]CGP 12177 binding by isoproterenol, BRL 37344 and noradrenaline. BRL 37344 was used to study β₃-AR lipolysis. White adipocytes from hyperthyroid rats had increased responsiveness (E_max × 2) and sensitivity (+ 38%) to BRL 37344, while those given AM alone had decreased values. Moreover, AM antagonized the T₃ effect on lipolysis. The β₁-binding characteristics (receptor density [B_max]: 45 ± 4 fmol/mg of proteins; dissociation factor [K_d]: 0.96 ± 0.10 nM) were not modified by either compound. Finally, T₃ significantly increased β₃-AR density (587 ± 69 versus 363 ± 25 fmol/mg of proteins) and K_d (38 ± 2 versus 23 ± 3 nM), while AM alone had no effect and did not antagonize the T₃ effect on β₃-AR number. In conclusion, the hyperthyroid state in the rat potentiated the lipolytic response of white adipocytes to a specific β₃-agonist and increased the β₃-AR density without changing in β₁-AR number and affinity. Furthermore, the lack of antagonism between AM and T₃ on β₃-AR expression suggests that T₃ does not work directly on the β₃-AR gene. Moreover, AM induced a functional tissular hypothyroid-like effect and its antilipolytic effect probably occurred at a postreceptor level.     

Fatty Acid Composition of Adipose Cells in Red and Yellow Marrow: A Possible Determinant of Haematopoietic Potential

The fatty acid composition of whole bone marrow and that of isolated, disaggregated adipose cells from red and yellow marrow was examined by gas chromatography. Consistent and significant shifts from myristic and palmatic acids (in red marrow) to their respective monounsaturated derivatives myristoleic and palmitoleic acids (in yellow marrow) were found. These differences in the fatty acids correlate with histochemical studies and lend further support to the concept that the composition of lipid in the adipose cells of bone marrow may determine their relative stability in relation to haematopoietic requirements.     

Spontaneous mutation in Big Blue mice from fetus to old age: tissue-specific time courses of mutation frequency but similar mutation types

Transgenic mouse mutation detection systems permit rapid determination of the frequency and type of mutations allowing direct examination of mutational markers for aging, neurodegeneration, and cancer. The Big Blue transgenic mouse mutation detection system was used to determine the frequency and nature of spontaneous mutations versus age in multiple tissue types. Nuclear DNA was extracted from whole fetus at 13.5 days postcoitus (dpc) and from six tissues postbirth (cerebellum, forebrain, thymus, liver, adipose tissue, and male germline) of Big Blue transgenic mice at four ages: 10 days and at 3, 10, and 25 months postbirth. Forty million total plaque-forming units (pfu) were screened. The time course of mutation frequency with age had a significantly different shape in different tissues (P < 10(-6)). By 13.5 dpc, the whole fetus mutation frequency had already started increasing from the theoretical zero at conception to a value that was about one-half the mid-adulthood (3-10 months) average. From 10 days to 3 months, mutation frequency increased significantly in liver (P = 0.007) and showed an increasing trend in cerebellum, forebrain, and thymus. From 3 to 10 months, there was no significant change in mutation frequency in any tissue examined. From 10 to 25 months, the mutation frequency increased significantly in liver (P < 10(-6)) and adipose tissue (P = 0.002), but not in the other tissues examined (cerebellum, forebrain, and male germline). It is of interest that the mutation frequency in the male germline is consistently the lowest, remaining essentially unchanged in old age. The spectrum of mutation types was unaltered with age, tissue type and gender, although, as previously reported, tandem GG-->TT mutations are tissue specific and show significant increases with age and certain hotspots (Buettner VL et al. [1999]: Environ Mol Mutagen 33:320-324; Hill KA et al. [2003]: Mutat Res 534:173-186). The spectrum of mutation types was generally the same for all tissue types, despite the tissue-specific increases in mutation frequency with age. These data provide a useful reference for future studies of endogenous and exogenous mutagenesis.     

Lipolysis and apoptosis of adipocytes induced by neuropeptide Y—Y5 receptor antisense oligodeoxynucleotides in obese rats

目的:探讨神经肽Y-Y5受体反义基因治疗后饮食性肥胖大鼠减肥减重效应与外周白色脂肪细胞体积、数目变化的关系。方法:建立饮食性肥胖大鼠模型,侧脑室注射Y5受体编码起始区反义、正义、错义寡脱氧核糖核酸及生理盐水,采用MPLAS-500多媒体彩色病理图文分析系统计算平均脂肪细胞面积,基因组DNA提取物凝胶电泳检测脂肪细胞凋亡,RT-PCR分析凋亡相关基因bc1-2、bax表达的改变。结果:(1)Y5受体反义基因治疗后大鼠进食量与体重显著降低,外周白色脂肪组织湿重与平均脂肪细胞面积明显减少;(2)脂肪组织基因组DNA提取物凝胶电泳出现凋亡特征性梯状条带;(3)凋亡相关基因bc1-2表达下调、bax表达上调。结论:平均脂肪细胞面积减小、脂肪细胞凋亡增加可能是Y5受体反义基因治疗减肥减重的重要原因。     

Adipocyte insulin receptor binding and lipogenesis at term in normal pregnancy

Lipogenesis in subcutaneous abdominal adipocytes during late human pregnancy was investigated by studying insulin receptor binding, 3-O-methyl-(14C-(U]-glucose flux and incorporation of (14C(U]-glucose into CO2 (oxidation) and total lipids (lipogenesis) in adipocytes from 18 health pregnant women undergoing Caesarean section at term, and 19 non-pregnant women undergoing gynaecological surgery. The cell diameter and fasting insulin were increased in the pregnant women, compared with controls (P less than 0.01 and P less than 0.05, respectively). The insulin receptor binding, 3-O-methyl-glucose flux, and basal oxidation were similar in both groups. Basal lipogenesis was higher in adipocytes from pregnant women than from controls (P less than 0.05), but the maximally stimulated increment was similar in both groups. Basal and maximally stimulated lipogenesis correlated positively with the cell diameter (P less than 0.001 and P less than 0.05, respectively). The findings indicate that lipogenesis in subcutaneous abdominal adipocytes from pregnant women is increased due to post-receptor events and that adipocytes do not contribute to the insulin resistance in late pregnancy.     

Effects of adipocytes on the proliferation and differentiation of prostate cancer cells in a 3‐D culture model

Objective: To investigate how the mechanism of adipocyte–prostate cancer cell interaction affects the proliferation and differentiation of prostate cancer cells. Methods: An androgen‐dependent cell line (LNCaP), two androgen‐independent cell lines (PC‐3, DU145), and mature adipocytes harvested from male Wistar rats were used. Cancer cells were co‐cultured with the isolated mature adipocytes in 3‐D collagen gel matrix culture. The morphology and proliferative ability of the prostate cancer cells were examined. With regard to the activation of the phosphatidylinositol 3‐kinase (PI3K) pathway, the expression of phosphatase and tensin homologue deleted on chromosome ten (PTEN), Akt and Bad were determined by immunohistochemistry. Results: LNCaP cells co‐cultured with adipocytes formed larger clusters than those of the control. PC‐3 cells co‐cultured with adipocytes did not form larger clusters, but formed spherical and spindle‐shaped cells. The phosphorylation of Akt in PC‐3 cells was greater in the co‐cultured group compared with the controls, but there were no significant differences in the phosphorylation of Akt with regard to LNCaP and DU145 cells. Conclusions: Adipocytes could modulate the proliferation and differentiation of prostate cancer cell lines. Activation of the PI3K pathway might be involved in the prostate cancer cell–adipocyte interaction.     

鬼箭羽水提液对胰淀素诱导下人脂肪细胞糖摄取的影响

目的:观察鬼箭羽水提液对人脂肪细胞糖摄取的影响。方法:分离糖尿病(n=7)及非糖尿病组(n=14)患者的脂肪细胞,在100nmol.L-1胰淀素和1.5 U/L胰岛素中培养,加入鬼箭羽水提液后观察细胞糖摄取量。结果:胰淀素使细胞糖摄取量明显降低,鬼箭羽水提液使降低的摄取量升高,但没有统计学意义。结论:胰淀素抑制人脂肪细胞糖摄取,鬼箭羽水提液对此抑制作用改善不明显。