高脂饮食诱导肥胖小鼠表达卵泡抑素样蛋白1与脂肪组织炎症和棕色脂肪的功能

目的 探讨卵泡抑素样蛋白1（FSTL1）在高脂饮食诱导的肥胖小鼠脂肪炎症中的作用,以及对棕色脂肪功能的影响。 方法 6周龄C57BL/6 J小鼠分为两组,每组8只,给予12周正常饮食（RD）和高脂饮食（HFD）饲养,每周称量小鼠体重,记录小鼠摄食量;12周后,进行糖耐量和胰岛素耐量的检测并取材,称量小鼠的皮下白色脂肪、肾周白色脂肪、附睾白色脂肪和棕色脂肪的重量;HE染色观察小鼠白色脂肪中的冠状结构（CLS）及小鼠棕色脂肪组织变化,RT-PCR分析小鼠附睾白色脂肪炎症因子、肿瘤坏死因子α（TNF-α)、白细胞介素6（IL-6）和白细胞介素10（IL-10）的表达,以及FSTL1的表达;Western blotting检测棕色脂肪解耦联蛋白1（UCP1）与FSTL1蛋白的表达。 结果 与RD小鼠相比,HFD组小鼠的体重增加,摄食量减少,不同部位脂肪重量显著增加,葡萄糖耐受能力显著降低,胰岛素敏感性显著下降,附睾白色脂肪观察到炎症反应CLS且附睾白色脂肪中炎症因子TNF-α、IL-6及IL-10表达显著增高, FSTL1表达亦显著增加。Western blotting结果显示,HFD小鼠的棕色脂肪组织中UCP1与FSTL1表达水平均显著性高于RD组。 结论 在高脂饮食诱导的肥胖小鼠中,FSTL1的表达可能与脂肪炎症因子的分泌增加及棕色脂肪的功能有一定相关性。     

Effects of interscapular brown adipose tissue denervation on body weight and energy metabolism in ovariectomized and estradiol-treated rats

Ovariectomy-induced increases and estradiol-induced decreased in body weight cannot be fully accounted for by changes in energy intake and appear to reflect alterations in thermogenesis. Because changes in energy expenditure have been linked to altered sympathetic nervous system (SNS) activity in brown adipose tissue (BAT), the role of estradiol in thermogenesis and body weight, as mediated by the SNS innervation of interscapular BAT (IBAT), was examined. The IBAT of ovariectomized rats was bilaterally or unilaterally surgically denervated. The chow-fed, bilaterally denervated group gained more weight than the unilaterally denervated or sham-operated group, an effect that was exaggerated by sucrose feeding. Food intake did not differ among the groups within each dietary condition. Estradiol benzoate (EB) injections decreased body weight in all groups. Bilateral, and to a lesser extent, unilateral IBAT denervation blocked the EB-induced increase in thermogenesis. Treatment with EB increased IBAT wet weight regardless of surgical treatment. Because IBAT denervation markedly decreased lipoprotein lipase activity and fatty acid synthesis/uptake, the estradiol-induced increase in denervated IBAT wet weight is most likely due to decreased lipolysis produced by the surgical sympathectomy. These results are discussed in terms of the role of the SNS and IBAT in the mediation of estradiol-induced changes in body weight and energy metabolism.     

Fat metabolism and heat production in young rabbits

1. The rates of oxygen consumption were measured in 6-8-day-old rabbits at 34 and 15 degrees C after varying periods of starvation and cold exposure. At the start of the experiment the rabbits had been fasted for 24 hr. Eight rabbits were studied immediately, six after 24 and six after 48 hr in a cold environment (20 degrees C), and twelve after a further 48 hr in a warm environment (34 degrees C). All the animals had a similar increase in oxygen consumption during the final hour of cold exposure (15 degrees C).2. The rabbits kept at 20 degrees C lost 83% of the fat stored in their brown adipose tissue within 24 hr and a further 11% in the next 24 hr. The fat content of white adipose tissue had fallen by 75% at 48 hr. In contrast rabbits kept unfed at 34 degrees C had lost 47% of the fat in brown adipose tissue and 44% of the fat in white adipose tissue after 48 hr.3. In six rabbits subcutaneous thermocouples demonstrated that local heat production continued in brown adipose tissue after 48 hr cold exposure.4. In the rabbits kept at 34 degrees C the final cold exposure caused a large increase in the serum free fatty acid and glycerol concentrations. Much lower concentrations were found in rabbits kept at 20 degrees C.5. The results show that the fat stored in the brown adipose tissue of young rabbits exposed to cold is preferentially used for heat production. When this store of fat is exhausted, brown adipose tissue still produces heat presumably by oxidizing fat and glucose taken from the circulation.     

Abnormal brown adipose composition and beta-adrenoceptor binding in obese Zucker rats

The composition, morphology, beta-adrenergic receptor binding, and in vitro lipolysis were examined in lean and obese, 5- to 6-mo-old male Zucker rat interscapular brown adipose tissue (IBAT). IBAT pads from obese rats were heavier (283%), had more lipid (700%), and more (75%)( and larger (83%) adipocytes than those from lean rats. Also, IBAT from obese rats had no multiloculated cells, and 50% of their IBAT adipocytes were the size of white fat cells. High affinity binding for (-)-[3H]dihydroalprenolol (KD, 15-18 nM), as well as the estimated KD values for binding and the 1/2 Vmax values for adrenergic agonist-induced lipolysis were similar in isolated IBAT cells from lean and obese rats. However, adipocytes from IBAT in obese rats had 75% fewer high affinity beta-adrenergic binding sites per cell (Bmax) compared to those in lean rats. These findings are most compatible with the infiltration of IBAT by white adipocytes. Such infiltration would be expected to reduce the overall thermogenic capacity of IBAT in obese Zucker rats and thereby contribute to the maintenance of their obesity.     

Altered sympathetic activity during development of diet-induced obesity in rat

Sprague-Dawley rats developed diet-induced obesity (DIO) after 3 mo on a high-fat, high-sucrose diet (DIO diet), with associated increases in total body and interscapular brown adipose tissue (IBAT) lipid content. After 7 days on the DIO diet, rats had increased levels of tyrosine hydroxylase (TH; 34%), norepinephrine (NE; 34%), and NE turnover (94%; estimated by alpha-methyl-p-tyrosine inhibition of TH) in their IBAT compared with chow-fed controls. After 3 mo on the DIO diet, NE levels and/or turnover were reduced by 27-50% in aortas, hearts, and pancreata in obese rats. While IBAT NE turnover was normal, TH inhibition failed to increase the lipid content of IBAT in obese rats as it did in controls, suggesting a postsynaptic defect in basal NE-stimulated lipolysis in this thermogenically active tissue. When obese rats were switched from the DIO diet to rat chow for 3 days, NE levels remained depressed in their hearts (25%) and aortas (14%) but were increased by 36-45% in IBAT, pancreata, and white adipose tissue. NE turnover rates and/or constants were increased by 37-110% in hearts, aortas, pancreata, and IBAT of these obese rats while there were increased IBAT TH (20%) and dopamine-beta-hydroxylase (87%) activities compared with chow-fed controls. Therefore, sympathetic activity varied markedly as a function of both dietary composition and relative body weight during the development of DIO.     

Brown adipose tissue response to cafeteria diet-feeding involves induction of the UCP2 gene and is impaired in female rats as compared to males

Noradrenaline-dependent brown adipose tissue (BAT) thermogenesis is activated by the cold and excess energy intake, largely depends on the activity of the uncoupling protein 1 (UCP1), and is mediated mainly through the beta3-adrenoceptor (beta3-AR). We investigated the expression of ucp2, a gene that encodes a putative UCP1-like uncoupling protein, along with that of ucp1 and beta3-ar, in the interscapular BAT (IBAT) of male and female rats chronically fed a cafeteria diet. After 3 months on this diet, male rats attained a 34% excess body mass and showed IBAT hypertrophy and increased IBAT thermogenic potential, in terms of both UCP1 and UCP2 mRNA expression (both by 1.6-fold), UCP1 protein expression (by 1.75-fold) and GDP binding to IBAT mitochondria (by 2.2-fold); female rats attained a larger excess body weight (50%) and their IBAT, although hypertrophied, showed no signs of increased thermogenic potential per gram of tissue. Interestingly, the IBAT of female rats was already activated compared to males. Treatment of mouse brown adipocytes in primary culture with noradrenaline also triggered a dose-dependent increase of the levels of UCP1 mRNA and UCP2 mRNA. Retroregulatory down-regulation of the beta3-AR mRNA levels was found in the two models used. The results support a physiological role for UCP2, along with UCP1, in rodent BAT thermogenesis.     

Interaction of adrenalectomy and fenfluramine treatment on body weight, food intake and brown adipose tissue

Three experiments have examined the interaction of adrenalectomy and fenfluramine on food intake, body weight and the binding of guanosine-5'-diphosphate (GDP) to interscapular brown adipose tissue (IBAT). In the first experiment, GDP-binding by IBAT mitochondria from adrenalectomized or sham-operated animals was measured for 3 hr after one of 3 doses of fenfluramine. Fenfluramine stimulated GDP-binding at lower doses in the adrenalectomized animals than in the controls. In the first chronic experiment, adrenalectomy prevented the restoration of normal food intake observed 8-10 days after the beginning of fenfluramine treatment. Adrenalectomy also increased weight loss and enhanced GDP binding to mitochondria from IBAT in rats treated with fenfluramine. In the second chronic experiment, the combination of fenfluramine and adrenalectomy led to a progressive weight loss, continuing hypophagia and stimulation of GDP-binding by IBAT, whereas rats treated with fenfluramine alone showed a recovery of food intake at a stabilized but lower body weight. These data are consistent with the hypothesis that adrenalectomy and fenfluramine disable two separate components of the food intake system and that when combined, produce a profound and persisting disturbance in energy or nutrient balance.     

Hyperactivity and obesity: The interaction of social isolation and cafeteria feeding

Rats were reared in social isolation or in social groups of 4 or 5 rats per cage from weaning and were fed either a lab chow diet or a diet of 4 palatable foods (cafeteria diet), in addition to the lab chow. The hyperactivity of isolation-reared rats appears to be a reactivity to novel environmental stimuli, since it was seen only in the 0.5 hr tests and not in the near 24 hr test. It was found that hyperactivity and increased body weight can develop within as few as 7 to 10 days in rats reared in isolation from weaning. Cafeteria feeding enhanced activity in isolation-reared rats, but suppressed it in group-reared rats. Isolation-reared rats fed a cafeteria diet had strong, stable preferences for their most preferred food over the 25 days of measurement. Rats reared in isolation had significantly different food preferences, as compared with rats reared in groups. Cafeteria fed rats had a significantly greater calorie intake and body weight than rats fed lab chow. On analysis, cafeteria fed rats had significantly greater carcass energy and an increased amount of parametrial white adipose tissue as compared with rats fed only lab chow. The interscapular brown adipose tissue (IBAT) weights of cafeteria fed rats were also greater. However, as there was no difference between the cafeteria and chow fed rats in the total amount of protein in the IBAT, it was concluded that the increased weight of the IBAT did not reflect a genuine hypertrophy of the tissue.     

Prostaglandins, brown fat and weight loss

In obesity, a situation is created in which energy intake exceeds energy expenditure. The three components of energy expenditure are resting metabolism, physical activity, and thermogenesis. Increasing attention is being paid to the role of impaired energy expenditure in obesity. Evidence indicates that impairment in activity of the sympathetic nervous system, which stimulates thermogenic processes, contributes to the etiology of obesity. In addition, insulin resistance, a well-recognized metabolic consequence of obesity, appears to interfere with feeding-related, insulin-mediated increases in thermogenesis in brown adipose tissue. This thermogenic defect results in reduced energy buffering by brown adipose tissue leading to deficient energy expenditure and an increased efficiency in weight gain. A unique weight loss program, The Princeton Metabolic Diet Program, is presented. The Program stimulates metabolism by stimulating the sympathetic nervous system and correcting insulin resistance, thereby enhancing thermogenesis in brown adipose tissue. Methods include: 1) alternating diet composition and caloric intake and, 2) the use of nutritional metabolic stimulants. This type of non-toxic therapy, directed at correcting biochemical defects, will enhance metabolic mechanisms and induce weight loss.     

Long-term alcohol consumption and brown adipose tissue in man

Summary The purpose of the present work was to study whether long-term alcohol consumption in man affects the develeopment of brown adipose tissue. The adipose tissue around the thoracic aorta and common carotid arteries was collected at medicolegal autopsies on adults with a positive record of heavy alcohol consumption. Adults without any evident history of alcohol consumption served as controls. Histochemical reactions of the oxidative mitochondrial enzymes, cytochrome oxidase and succinate dehydrogenase were studied in samples of this adipose tissue and the activities of the enzymes were measured biochemically.There was histological evidence of some multilocular adipose tissue around the thoracic aorta and common carotid arteries of the alcohol consumers, whereas the adipose tissue from the non-drinkers was mostly unilocular resembling white adipose tissue. Histochemical evidence of brown adipose tissue was found in all alcohol consumers, but also in some of the controls. Biochemical cytochrome oxidase (CYO) and succinate dehydrogenase measurements in isolated mitochondria showed activity in 70% of the cases of drinkers and in one of the eight controls. Activity of CYO was measurable in the mitochondria from two other controls. The protein content of the samples from the alcoholics was twice that of the controls. The results suggest that chronic alcohol intake may induce a change in the white adipose tissue around the thoracic aorta and common carotid arteries of human adults into brown fat.     

Gangliosides and energy substrates in brown adipose tissue of cold-acclimated rat

Effect of cold acclimation on gangliosides as well as triglyceride and glycogen in brown adipose tissue was studied in rats. Ganglioside GM3 level per unit fresh weight and per unit fat-free-dry-matter was significantly higher in cold-acclimated rats (CA) than in warm controls, while the tissue triglyceride and glycogen levels were lower in CA. GM3 may be involved in cold-induced proliferation and differentiation of brown adipose tissue.     

Upregulation of AMPK during cold exposure occurs via distinct mechanisms in brown and white adipose tissue of the mouse

AMPK (adenosine monophosphate-activated protein kinase), a key regulator of cellular energy metabolism and whole-body energy balance, is present in brown adipose tissue but its role in regulating the acute metabolic state and chronic thermogenic potential of this metabolically unique tissue is unknown. To address this, the AMPK signalling system in brown and white adipose tissue was studied in C57Bl/6 mice under control conditions, during acute and chronic cold exposure, and during chronic adrenergic stimulation. In control mice AMPK activity in brown adipose tissue was higher than in any tissue yet reported (3-fold the level in liver) secondary to a high level of expression of the α1 isoform. During the first day of cold, a time of intense non-shivering thermogenesis, AMPK activity remained at basal levels. However, chronic (>7 days) cold caused a progressive increase in brown adipose tissue AMPK activity secondary to increased expression of the α1 isoform. To investigate the signalling pathway involved, noradrenaline (norepinephrine) and the β₃-adrenergic-specific agonist CL 316, 243 were given for 14 days. This increased uncoupling protein-1 content in brown adipose tissue, but not AMPK activity. In white adipose tissue 15 days of cold increased α1 AMPK activity 98 ± 20%, an effect reproduced by chronic noradrenaline or CL 316 243. We conclude that chronic cold not only increases AMPK activity in brown and white adipose tissue, but that it does so via distinct signalling pathways. Our data are consistent with AMPK acting primarily as a regulator of chronic thermogenic potential in brown adipose tissue, and not in the acute activation of non-shivering thermogenesis.     

Effect of Calorie Restricted Diet on Brown Adipose Tissue in Mice

Calorie restricted diet (50% food intake of control animals) for 3 weeks decelerated weight gain in laboratory mice, reduced the weight of abdominal fat, and decreased the rate of oxygen consumption by brown adipose tissue. The relative weight of interscapular brown fat and protein content in it did not differ from the control. DNA content in brown fat in mice kept on calorie restricted diet increased by 93% compared with the control.     

TH-, NPY-, SP-, and CGRP-immunoreactive nerves in interscapular brown adipose tissue of adult rats acclimated at different temperatures: an immunohistochemical study

Interscapular brown adipose tissue (IBAT), a site of nonshivering thermogenesis in mammals, is neurally controlled. The co-existence of sympathetic and peptidergic innervation has been demonstrated in different brown adipose depots. We studied the morphological profile of IBAT innervation and tested by immunohistochemical methods whether cold and warm stimulation are accompanied by modifications in the density of parenchymal noradrenergic nerve fibers. We also studied the immunoreactivity of afferent fibers—which contain calcitonin gene-related peptide (CGRP) and substance P (SP)<197>in different functional conditions. IBAT was obtained from adult rats (6 weeks old) acclimated at different temperatures (4°, 20°, and 28°C). Tissue activity was evaluated by studying the immunolocalization of uncoupling protein (UCP-1), a specific marker of brown adipose tissue. Noradrenergic and peptidergic innervation were seen to arise from morphologically different nerves. Fibers staining for tyrosine hydroxylase (TH) were thin, unmyelinated hilar nerves, and CGRP- and SP-positive fibers were in thick nerves containing both myelinated and unmyelinated fibers. Under cold stimulation, noradrenergic neurons produce greater amounts of TH, and their axons branch, resulting in increased parenchymal nerve fibers density. Neuropeptide Y (NPY) probably co-localizes with TH in noradrenergic neurons, but only in the perivascular nerve fiber network. The parenchymal distribution of NPY to interlobular arterioles and capillaries suggests that this peptide must have other functions besides that of innervating arteriovenous anastomoses, as hypothesized by other researchers. The different distribution of CGRP and SP suggests the existence of different sensory neuronal populations. The detection of CGRP at the parenchymal level is in line with the hypothesis of a trophic action of this peptide.     

Effects of 4-hydroxyamphetamine on in vivo brown adipose tissue thermogenesis and feeding behavior in the rat

The influence of 4-hydroxyamphetamine (4-OHAM) on food and water intake and in vivo brown adipose thermogenesis was examined in two experiments. In Experiment 1, female rats were treated with 0.00, 0.25, 0.50, 1.00, or 2.00 mg/kg 4-OHAM (ip) prior to assessment of interscapular brown adipose tissue (IBAT) thermogenesis. The 4-OHAM treatment induced dose-dependent activation of IBAT thermogenesis consistent with the enhanced serum levels of norepinephrine and epinephrine observed in 4-OHAM-treated rats immediately after temperature measurement. In Experiment 2, the influence of 4-OHAM on food and water intake was assessed during 120-min test intervals in female rats fed food and water ad lib. Although there was a trend for 4-OHAM to increase water intake, there was no significant effect of 4-OHAM (0.40, 0.80, 1.00, 2.00, and 4.00 mg/kg) on either food or water intake. These data suggest that brown adipose thermogenesis does not play a role in the anorexia induced by amphetamine or in the regulation of feeding.     

Effect of nafenopin,a peroxisome proliferator,on energy metabolism in the rat as a function of acclimation temperature

The effects of the peroxisome proliferator, nafenopin, on body temperature, apparent gross food efficiency and activity of interscapular brown adipose tissue (IBAT) peroxisomes and mitochondria of rats acclimated at 23 degrees C or at 32 degrees C have been studied. In 23 degrees C-acclimated rats, nafenopin treatment induced an atrophy of IBAT characterized by a decrease of tissue wet weight, of amounts of mitochondrial and peroxisomal proteins and of mitochondrial total succinate dehydrogenase activity to 67%, 67%, 65% and 57%, respectively of control values. It also resulted in a 1.9-fold stimulation of peroxisome total acyl CoA oxidase activity and had no effect on apparent gross food efficiency or colonic temperature. Acclimation at 32 degrees C per se induced an atrophy of IBAT and a decrease of total catalase and acyl CoA oxidase activities to 23% and 35%, respectively of values obtained in rats acclimated at 23 degrees C. Nafenopin treatment had no effect on IBAT wet weight, on the amounts of mitochondrial and peroxisomal proteins or on total succinate dehydrogenase activity; it resulted in a 2.9- and a 3.7-fold stimulation of the catalase and acyl CoA oxidase activities, respectively with no change in IBAT oxygen consumption. Apparent gross food efficiency was decreased to 54% of control value and colonic temperature increased by 0.91 degrees C. These results may be interpreted in the following way: nafenopin may, at 23 degrees C ambient temperature, induce an extra-heat production in other tissues than IBAT. This extra-heat production is fully compensated via the thermoregulatory feedback control. This compensation cannot occur at thermoneutrality.     

Effects of ovariectomy on thermogenesis in brown adipose tissue and liver in Syrian hamsters

Weight gain in ovariectomized Syrian hamsters occurs without increased food intake, which suggests that metabolic efficiency may be enhanced through a reduction in energy expenditure. We examined the effect of ovariectomy on metabolic activity in brown adipose tissue and liver. Four groups of hamsters (n = 13, each) were killed 0, 2, 4, or 16 weeks following ovariectomy. Ovariectomized hamsters rapidly gained weight without overeating. Body weights stabilized after 8 weeks and remained 12-17% above sham-operated control weights for the duration of the experiment. Weight gain in the hamsters ovariectomized for 16 weeks was characterized by significant increases in retroperitoneal white adipose tissue weight and carcass lipid content. Similar trends were seen in 2-week and 4-week ovariectomized animals. There were no differences in interscapular brown adipose tissue weight, protein content, DNA content, or norepinephrine (NE) content among sham-operated and 2-, 4-, or 16-week ovariectomized hamsters, indicating that ovariectomy had no effect on brown adipose tissue growth. Similarly, there was no difference in either sympathetic nervous system activity (estimated by the rate of NE turnover) or mitochondrial GDP binding among the four groups of hamsters. In contrast, hepatic cytochrome P-450 activity was significantly reduced 2, 4, and 16 weeks after ovariectomy. These results suggest that reduced thermogenic activity in liver, but not in brown adipose tissue, could contribute to the weight gain in Syrian hamsters after ovariectomy.     

Increased energy expenditure and activated β3-AR-cAMP-PKA signaling pathway in the interscapular brown adipose tissue of 6-OHDA-induced Parkinson's disease model rats

To explore the possible mechanism of weight loss in Parkinson's disease (PD). Bilateral injections of 6-hydroxydopamine (6-OHDA) into substantia nigra (SN) were performed to induce the PD model rats. The rotarod test, food intake, body weight, and interscapular brown adipose tissue (IBAT) weight were recorded 6 weeks postoperation. HE staining was performed to observe the morphology of multilocular adipose cells in IBAT. Immunohistochemistry and western blot were used to determine the protein levels of tyrosine hydroxylase (TH) in the SN, and the levels of uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), phosphorylated-hormone sensitive lipase (p-HSL), HSL, TH, β3-adrenergic receptor (β3-AR), cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA) in IBAT. After treatment with 6-OHDA for 6 weeks, 6-OHDA rats exhibited decreased TH expression in SN accompanied with shortened staying time on the rotating rod. This motor impairment paralleled with no significant alteration in body mass, IBAT weight, and food intake until the end of the experimental protocol. However, the decreasing diameter of the single fat vesicle in IBAT was observed in the 6-OHDA group. Meanwhile, compared with the control group, the protein expression of UCP1, PGC-1α, p-HSL, TH, β3-AR, cAMP, and PKA in IBAT were increased significantly in the 6-OHDA group, whereas no obvious change in the expression of HSL. The present study suggested an increased energy expenditure and activation of the β3-AR-cAMP-PKA signaling pathway in the IBAT after the destruction of the dopamine system in the SN of the rat.