Expressions of mRNA and encoded proteins of mitochondrial uncoupling protein genes (UCP1, UCP2, and UCP3) in epicardial and mediastinal adipose tissue and associations with coronary artery disease

Objective

To evaluate the expression of UCP1, UCP2, and UCP3 mRNA and encoded proteins in epicardial and mediastinal adipose tissues in patients with coronary artery disease (CAD).

Subjects and methods

We studied 60 patients with CAD and 106 patients undergoing valve replacement surgery (controls). Expression levels of UCP1, UCP2, and UCP3 mRNA and encoded proteins were measured by quantitative real-time PCR and Western blot analysis, respectively.

Results

: We found increased UCP1, UCP2, and UCP3 mRNA levels in the epicardial adipose tissue in the CAD versus the control group, and higher UCP1 and UCP3 mRNA expression in the epicardial compared with the mediastinal tissue in the CAD group. There was also increased expression of UCP1 protein in the epicardial tissue and UCP2 protein in the mediastinum tissue in patients with CAD. Finally, UCP1 expression was associated with levels of fasting plasma glucose, and UCP3 expression was associated with levels of high-density lipoprotein cholesterol and low-density cholesterol in the epicardial tissue.

Conclusion

Our study supports the hypothesis that higher mRNA expression by UCP genes in the epicardial adipose tissue could be a protective mechanism against the production of reactive oxygen species and may guard the myocardium against damage. Thus, UCP levels are essential to maintain the adaptive phase of cardiac injury in the presence of metabolic disorders.

On the potential role of globins in brown adipose tissue: a novel conceptual model and studies in myoglobin knockout mice

Myoglobin (Mb) regulates O₂ bioavailability in muscle and heart as the partial pressure of O₂ (Po₂) drops with increased tissue workload. Globin proteins also modulate cellular NO pools, "scavenging" NO at higher Po₂ and converting NO₂^- to NO as Po₂ falls. Myoglobin binding of fatty acids may also signal a role in fat metabolism. Interestingly, Mb is expressed in brown adipose tissue (BAT), but its function is unknown. Herein, we present a new conceptual model that proposes links between BAT thermogenic activation, concurrently reduced Po₂, and NO pools regulated by deoxy/oxy-globin toggling and xanthine oxidoreductase (XOR). We describe the effect of Mb knockout (Mb^-/-) on BAT phenotype [lipid droplets, mitochondrial markers uncoupling protein 1 (UCP1) and cytochrome C oxidase 4 (Cox4), transcriptomics] in male and female mice fed a high-fat diet (HFD, 45% of energy, ∼13 wk), and examine Mb expression during brown adipocyte differentiation. Interscapular BAT weights did not differ by genotype, but there was a higher prevalence of mid-large sized droplets in Mb^-/-. COX4 protein expression was significantly reduced in Mb^-/- BAT, and a suite of metabolic/NO/stress/hypoxia transcripts were lower. All of these Mb^-/--associated differences were most apparent in females. The new conceptual model, and results derived from Mb^-/- mice, suggest a role for Mb in BAT metabolic regulation, in part through sexually dimorphic systems and NO signaling. This possibility requires further validation in light of significant mouse-to-mouse variability of BAT Mb mRNA and protein abundances in wild-type mice and lower expression relative to muscle and heart.NEW & NOTEWORTHY Myoglobin confers the distinct red color to muscle and heart, serving as an oxygen-binding protein in oxidative fibers. Less attention has been paid to brown fat, a thermogenic tissue that also expresses myoglobin. In a mouse knockout model lacking myoglobin, brown fat had larger fat droplets and lower markers of mitochondrial oxidative metabolism, especially in females. Gene expression patterns suggest a role for myoglobin as an oxygen/nitric oxide-sensor that regulates cellular metabolic and signaling pathways.

Ellagic Acid Affects Metabolic and Transcriptomic Profiles and Attenuates Features of Metabolic Syndrome in Adult Male Rats

Ellagic acid, a natural substance found in various fruits and nuts, was previously shown to exhibit beneficial effects towards metabolic syndrome. In this study, using a genetic rat model of metabolic syndrome, we aimed to further specify metabolic and transcriptomic responses to ellagic acid treatment. Adult male rats of the SHR-Zbtb16^Lx/k.o. strain were fed a high-fat diet accompanied by daily intragastric gavage of ellagic acid (50 mg/kg body weight; high-fat diet–ellagic acid (HFD-EA) rats) or vehicle only (high-fat diet–control (HFD-CTL) rats). Morphometric and metabolic parameters, along with transcriptomic profile of liver and brown and epididymal adipose tissues, were assessed. HFD-EA rats showed higher relative weight of brown adipose tissue (BAT) and decreased weight of epididymal adipose tissue, although no change in total body weight was observed. Glucose area under the curve, serum insulin, and cholesterol levels, as well as the level of oxidative stress, were significantly lower in HFD-EA rats. The most differentially expressed transcripts reflecting the shift induced by ellagic acid were detected in BAT, showing downregulation of BAT activation markers Dio2 and Nr4a1 and upregulation of insulin-sensitizing gene Pla2g2a. Ellagic acid may provide a useful nutritional supplement to ameliorate features of metabolic syndrome, possibly by suppressing oxidative stress and its effects on brown adipose tissue.

Beige Adipose Tissue Identification and Marker Specificity-Overview

Adipose tissue (AT) is classified based on its location, physiological and functional characteristics. Although there is a clear demarcation of anatomical and molecular features specific to white (WAT) and brown adipose tissue (BAT), the factors that uniquely differentiate beige AT (BeAT) remain to be fully elaborated. The ubiquitous presence of different types of AT and the inability to differentiate brown and beige adipocytes because of similar appearance present a challenge when classifying them one way or another. Here we will provide an overview of the latest advances in BeAT, BAT, and WAT identification based on transcript markers described in the literature. The review paper will highlight some of the difficulties these markers pose and will offer new perspectives on possible transcript-specific identification of BeAT. We hope that this will advance the understanding of the biology of different ATs. In addition, concrete strategies to distinguish different types of AT may be relevant to track the efficacy and mechanisms around interventions aimed to improve metabolic health and thwart excessive weight gain.

Comprehensive proteomics and functional annotation of mouse brown adipose tissue

Knowledge about the mouse brown adipose tissue (BAT) proteome can provide a deeper understanding of the function of mammalian BAT. Herein, a comprehensive analysis of interscapular BAT from C57BL/6J female mice was conducted by 2DLC and high-resolution mass spectrometry to construct a comprehensive proteome dataset of mouse BAT proteins. A total of 4949 nonredundant proteins were identified, and 4495 were quantified using the iBAQ method. According to the iBAQ values, the BAT proteome was divided into high-, middle- and low-abundance proteins. The functions of the high-abundance proteins were mainly related to glucose and fatty acid oxidation to produce heat for thermoregulation, while the functions of the middle- and low-abundance proteins were mainly related to protein synthesis and apoptosis, respectively. Additionally, 497 proteins were predicted to have signal peptides using SignalP4 software, and 75 were confirmed in previous studies. This study, for the first time, comprehensively profiled and functionally annotated the BAT proteome. This study will be helpful for future studies focused on biomarker identification and BAT molecular mechanisms.

Near-Infrared Time-Resolved Spectroscopy for Assessing Brown Adipose Tissue Density in Humans: A Review

Brown adipose tissue (BAT) mediates adaptive thermogenesis upon food intake and cold exposure, thus potentially contributing to the prevention of lifestyle-related diseases. ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) with computed tomography (CT) (¹⁸FDG-PET/CT) is a standard method for assessing BAT activity and volume in humans. ¹⁸FDG-PET/CT has several limitations, including high device cost and ionizing radiation and acute cold exposure necessary to maximally stimulate BAT activity. In contrast, near-infrared spectroscopy (NIRS) has been used for measuring changes in O₂-dependent light absorption in the tissue in a non-invasive manner, without using radiation. Among NIRS, time-resolved NIRS (NIR_TRS) can quantify the concentrations of oxygenated and deoxygenated hemoglobin ([oxy-Hb] and [deoxy-Hb], respectively) by emitting ultrashort (100 ps) light pulses and counts photons, which are scattered and absorbed in the tissue. The basis for assessing BAT density (BAT-d) using NIR_TRS is that the vascular density in the supraclavicular region, as estimated using Hb concentration, is higher in BAT than in white adipose tissue. In contrast, relatively low-cost continuous wavelength NIRS (NIR_CWS) is employed for measuring relative changes in oxygenation in tissues. In this review, we provide evidence for the validity of NIR_TRS and NIR_CWS in estimating human BAT characteristics. The indicators (Ind_NIRS) examined were [oxy-Hb]_sup, [deoxy-Hb]_sup, total hemoglobin [total-Hb]_sup, Hb O₂ saturation (StO_2sup), and reduced scattering coefficient ( μs sup' ) in the supraclavicular region, as determined by NIR_TRS, and relative changes in corresponding parameters, as determined by NIR_CWS. The evidence comprises the relationships between the Ind_NIRS investigated and those determined by ¹⁸FDG-PET/CT; the correlation between the Ind_NIRS and cold-induced thermogenesis; the relationship of the Ind_NIRS to parameters measured by ¹⁸FDG-PET/CT, which responded to seasonal temperature fluctuations; the relationship of the Ind_NIRS and plasma lipid metabolites; the analogy of the Ind_NIRS to chronological and anthropometric data; and changes in the Ind_NIRS following thermogenic food supplementation. The [total-Hb]_sup and [oxy-Hb]_sup determined by NIR_TRS, but not parameters determined by NIR_CWS, exhibited significant correlations with cold-induced thermogenesis parameters and plasma androgens in men in winter or analogies to ¹⁸FDG-PET. We conclude that NIR_TRS can provide useful information for assessing BAT-d in a simple, rapid, non-invasive way, although further validation study is still needed.

Analysis of fatty acids in mouse tissue via in situ transmethylation with biochar

Lipid derivatization technology-mediated fatty acid profiling studies have been suggested to dissect the contents of lipids in white fat and brown fat tissue. The focus of this study is to profile fatty acid lipidomics in brown adipose tissue and white adipose tissue of mice by derivatizing their lipids into fatty acid methyl esters via in situ transmethylation using a rice husk-derived biochar as porous media. The in situ transmethylation using biochar is advantageous in biological analysis because there was no loss of samples inevitably occurring in the loss of lipid in solvent extraction and purification steps.

Active individuals have high mitochondrial content and oxidative markers in their abdominal subcutaneous adipose tissue

OBJECTIVE

Exercise training (training) effects on white adipose tissue (WAT) thermogenic and oxidative capacities in humans are inconclusive. This study aimed to investigate whether an active lifestyle is characterized by thermogenic and/or oxidative transcriptional markers in human WAT.

METHODS

In vivo maximal muscle ATP synthetic rates (ATPmax) were measured by ³¹ P-MRS, body composition by DXA, and peak oxygen uptake (VO₂ peak) by cycle ergometry in active (n = 7) and sedentary (SED) individuals before and after 3 weeks of training (n = 9, SED only). mRNA expressions of brown adipose and β-oxidation markers, as well as mitochondrial DNA content (mtDNA), were measured by qRT-PCR and qPCR, respectively, in WAT.

RESULTS

ATPmax and VO₂ peak were higher in active versus SED individuals. Following training in SED individuals, ATPmax and VO₂ peak increased. Proliferator-activated receptor gamma coactivator-1α and carnitine palmitoyltransferase-1β gene expressions and mtDNA content were significantly higher in WAT of active versus SED individuals before training. mRNA contents of brown and beige-specific markers were not different between cohorts. Training effectively increased ATPmax and VO₂ peak but had no effect on mtDNA content or expressions of genes that regulate thermogenic and oxidative capacities in WAT.

CONCLUSIONS

Results indicate that an active lifestyle is characterized by elevated mitochondrial content and oxidative, not thermogenic, markers of WAT.

Construction of Nanodroplet/Adiposome and Artificial Lipid Droplets

The lipid droplet (LD) is a cellular organelle that consists of a neutral lipid core with a monolayer-phospholipid membrane and associated proteins. Recent LD studies demonstrate its importance in metabolic diseases and biofuel development. However, the mechanisms governing its formation and dynamics remain elusive. Therefore, we developed an in vitro system to facilitate the elucidation of these mechanisms. We generated sphere-shaped structures with a neutral lipid core and a monolayer-phospholipid membrane by mechanically mixing neutral lipids and phospholipids followed by a two-step purification. We named the nanodroplet "adiposome". We then recruited LD structure-like/resident proteins to the adiposome, including the bacterial MLDS, Caenorhabditis elegans MDT-28/PLIN-1, or mammalian perilipin-2. In addition, adipose triglyceride lipase (ATGL) and apolipoprotein A1 (apo A-I) were recruited to adiposome. We termed the functional protein-coated adiposomes, Artificial Lipid Droplets (ALDs). With this experimental system, different proteins can be recruited to build ALDs for some biological goals and potential usage in drug delivery.

Brown adipose tissue triglyceride content is associated with decreased insulin sensitivity, independently of age and obesity

The aim of the present study was to determine whether single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) can non-invasively assess triglyceride content in both supraclavicular fat depots and subcutaneous white adipose tissue (WAT) to determine whether these measurements correlate to metabolic variables. A total of 25 healthy volunteers were studied using (18)F-fluorodeoxyglucose positron emission tomography (PET) and (15)O-H2O PET perfusion during cold exposure, and (1)H-MRS at ambient temperature. Image-guided biopsies were collected from nine volunteers. The supraclavicular triglyceride content determined by (1)H-MRS varied between 60 and 91% [mean ± standard deviation (s.d.) 77 ± 10%]. It correlated positively with body mass index, waist circumference, subcutaneous and visceral fat masses and 8-year diabetes risk based on the Framingham risk score and inversely with HDL cholesterol and insulin sensitivity (M-value; euglycaemic-hyperinsulinaemic clamp). Subcutaneous WAT had a significantly higher triglyceride content, 76-95% (mean ± s.d. 87 ± 5%; p = 0.0002). In conclusion, the triglyceride content in supraclavicular fat deposits measured by (1)H-MRS may be an independent marker of whole-body insulin sensitivity, independent of brown adipose tissue metabolic activation.

Human brown adipose tissue assessed by simple, noninvasive near-infrared time-resolved spectroscopy

OBJECTIVE

Human brown adipose tissue (BAT) activity has been typically evaluated by (18) F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) combined with computed tomography (CT). However, FDG-PET/CT has serious limitations (e.g., radiation and cold exposure). This study evaluated BAT density using near-infrared time-resolved spectroscopy (NIRTRS ), a simple and noninvasive method of measuring the indices of tissue hemoglobin concentration [total-Hb] and mitochondrial density (µs ').

METHODS

The NIRTRS parameters at 760, 800, and 830 nm in the supraclavicular region potentially containing BAT were evaluated. First, the NIRTRS parameters were compared at 27 °C and during a 2-h cold exposure (19 °C) in 18 men. Then, NIRTRS parameters at 27 °C were compared with mean standardized uptake values (SUVmean ) assessed by FDG-PET/CT after the 2-h cold exposure (19 °C) in 29 men.

RESULTS

There was no significant difference between the NIRTRS parameters at 27 °C and 19°C. The [total-Hb] and µs ' were significantly correlated to SUVmean (r = 0.73 and r = 0.64, respectively). A receiver operating characteristic analysis revealed that the sensitivity (75.0-82.4%), specificity (91.7-100%), and accuracy (82.8-86.2%) of the NIRTRS parameters were all good to determine the NIRTRS reliability.

CONCLUSIONS

Our novel NIRTRS method is noninvasive and simple and can reliably assess human BAT density in the supraclavicular region.

Adipose fatty acid oxidation is required for thermogenesis and potentiates oxidative stress-induced inflammation

To understand the contribution of adipose tissue fatty acid oxidation to whole-body metabolism, we generated mice with an adipose-specific knockout of carnitine palmitoyltransferase 2 (CPT2(A-/-)), an obligate step in mitochondrial long-chain fatty acid oxidation. CPT2(A-/-) mice became hypothermic after an acute cold challenge, and CPT2(A-/-) brown adipose tissue (BAT) failed to upregulate thermogenic genes in response to agonist-induced stimulation. The adipose-specific loss of CPT2 resulted in diet-dependent changes in adiposity but did not result in changes in body weight on low- or high-fat diets. Additionally, CPT2(A-/-) mice had suppressed high-fat diet-induced oxidative stress and inflammation in visceral white adipose tissue (WAT); however, high-fat diet-induced glucose intolerance was not improved. These data show that fatty acid oxidation is required for cold-induced thermogenesis in BAT and high-fat diet-induced oxidative stress and inflammation in WAT.

Miglitol protects against age-dependent weight gain in mice: A potential role of increased UCP1 content in brown adipose tissue

Miglitol is an absorbable alpha-glucosidase inhibitor that is used to control post-prandial hyperglycemia. We previously found that miglitol stimulates brown adipose tissue and prevents diet-induced obesity in mice that are fed a high-fat, high-carbohydrate diet. In this study, we examined whether miglitol can also protect against aging-dependent weight gain in mice that are fed a normal chow diet. Male C57Bl/6J mice were fed normal chow with or without miglitol (800 ppm) for 12 weeks, starting at 12 weeks of age. Food intake and body weight were monitored. After 12 weeks, adiposity, energy expenditure, and locomotor activities were measured. After sacrifice, weight of the epididymal white adipose tissue and adipocyte size were measured. Finally, Ucp1 gene expression and UCP1 protein abundance in brown adipose tissue were quantified by RT-PCR and Western analyses, respectively. Miglitol prevented age-related weight gain without affecting growth of the animals. Miglitol-treated mice showed reduced adiposity and increased oxygen consumption compared to controls, accompanied by higher UCP1 protein abundance in brown adipose tissue. Food intake and locomotor activities were not affected. These results suggest that miglitol can protect against age-dependent weight gain. Elucidating the molecular targets of miglitol in brown adipose tissue and optimizing drug delivery and efficacy may provide new strategies to combat obesity.

Treatment of rats with a self-selected hyperlipidic diet, increases the lipid content of the main adipose tissue sites in a proportion similar to that of the lipids in the rest of organs and tissues

Adipose tissue (AT) is distributed as large differentiated masses, and smaller depots covering vessels, and organs, as well as interspersed within them. The differences between types and size of cells makes AT one of the most disperse and complex organs. Lipid storage is partly shared by other tissues such as muscle and liver. We intended to obtain an approximate estimation of the size of lipid reserves stored outside the main fat depots. Both male and female rats were made overweight by 4-weeks feeding of a cafeteria diet. Total lipid content was analyzed in brain, liver, gastrocnemius muscle, four white AT sites: subcutaneous, perigonadal, retroperitoneal and mesenteric, two brown AT sites (interscapular and perirenal) and in a pool of the rest of organs and tissues (after discarding gut contents). Organ lipid content was estimated and tabulated for each individual rat. Food intake was measured daily. There was a surprisingly high proportion of lipid not accounted for by the main macroscopic AT sites, even when brain, liver and BAT main sites were discounted. Muscle contained about 8% of body lipids, liver 1–1.4%, four white AT sites lipid 28–63% of body lipid, and the rest of the body (including muscle) 38–44%. There was a good correlation between AT lipid and body lipid, but lipid in “other organs” was highly correlated too with body lipid. Brain lipid was not. Irrespective of dietary intake, accumulation of body fat was uniform both for the main lipid storage and handling organs: large masses of AT (but also liver, muscle), as well as in the ”rest” of tissues. These storage sites, in specialized (adipose) or not-specialized (liver, muscle) tissues reacted in parallel against a hyperlipidic diet challenge. We postulate that body lipid stores are handled and regulated coordinately, with a more centralized and overall mechanisms than usually assumed.

Normal Distribution of Body Weight Gain in Male Sprague-Dawley Rats Fed a High-Energy Diet

OBJECTIVE

To investigate the effect of a high-energy (HE) diet on caloric intake, body weight, and related parameters in outbred male Sprague-Dawley (SD) rats.

RESEARCH METHODS AND PROCEDURES

Twenty-eight SD rats were fed either chow (C) for 19 weeks or HE diet for 14 weeks and then C for 5 weeks. Blood hormones and metabolites were assayed, and expression of uncoupling protein-1 and hypothalamic energy-balance-related genes were determined by Northern blotting and in situ hybridization, respectively.

RESULTS

HE rats gained body weight more rapidly than C animals with a range of weight gains, but there was no evidence that weight gain was bimodally distributed. Caloric intake was transiently elevated after introduction of the HE diet. Transfer of HE rats back to C resulted in a drop in caloric intake, but a stable body weight. In terminal analysis, two of four dissected adipose tissue depots were heavier in rats that had previously been fed HE diet. Blood leptin, insulin, glucose, and nonesterified fatty acids were not different between the groups. Uncoupling protein-1 mRNA was elevated in interscapular brown adipose tissue from HE rats. There was a trend for agouti-related peptide mRNA in the hypothalamic arcuate nucleus to be higher in HE rats.

DISCUSSION

Contrary to other studies of the SD rat on HE diet, body weight and other measured parameters were normally distributed. There was no segregation into two distinct populations on the basis of susceptibility to diet-induced obesity. This characteristic may be dependent on the breeding colony from which animals were sourced.

Inhibition of soluble epoxide hydrolase reduces food intake and increases metabolic rate in obese mice

BACKGROUND AND AIMS

This study evaluated the responses to soluble epoxide hydrolase (s-EH) inhibition, an essential enzyme in the metabolism of arachidonic acid, on food intake, body weight and metabolic parameters in mice fed a high fat-high fructose diet (HFD) for 10 weeks.

METHODS AND RESULTS

After 5 weeks of HFD, mice were divided into two groups: 1) s-EH inhibitor (AR9281, 200mg/kg/day by gavage twice daily), and 2) vehicle (0.3ml per gavage). Food intake, body weight, oxygen consumption (VO(2)), carbon dioxide production (VCO(2)), respiratory quotient (RQ), and motor activity were measured weekly for more 5 weeks. HFD increased body weight (37±1 vs. 26±1g), and plasma of glucose (316±8 vs. 188±27mg/dl), insulin (62.1±8.1 vs. 15.5±5.0μU/ml), and leptin levels (39.4±3.6 vs. 7.5±0.1ng/ml) while reducing VO(2), VCO(2) and motor activity. s-EH inhibition for 5 weeks decreased caloric intake by ~32% and increased VO(2) by ~17% (42.8±1.4 vs. 50.2±1.5ml/kg/min) leading to significant weight loss. Inhibition of s-EHi also caused significant reductions in plasma leptin levels and visceral fat content. Uncoupling protein 1 (UCP1) content in brown adipose tissue was also elevated by ~50% during s-EH inhibition compared to vehicle treatment.

CONCLUSION

These results suggest that s-EH inhibition with AR9281 promotes weight loss by reducing appetite and increasing metabolic rate, and that increased UCP1 content may contribute to the increase in energy expenditure.

A black soybean seed coat extract prevents obesity and glucose intolerance by up-regulating uncoupling proteins and down-regulating inflammatory cytokines in high-fat diet-fed mice

Black soybean seed coat extract (BE) is a polyphenol-rich food material consisting of 9.2% cyanidin 3-glucoside, 6.2% catechins, 39.8% procyanidins, and others. This study demonstrated that BE ameliorated obesity and glucose intolerance by up-regulating uncoupling proteins (UCPs) and down-regulating inflammatory cytokines in C57BL/6 mice fed a control or high-fat diet containing BE for 14 weeks. BE suppressed fat accumulation in mesenteric adipose tissue, reduced the plasma glucose level, and enhanced insulin sensitivity in the high-fat diet-fed mice. The gene and protein expression levels of UCP-1 in brown adipose tissue and UCP-2 in white adipose tissue were up-regulated by BE. Moreover, the gene expression levels of major inflammatory cytokines, tumor necrosis factor-α and monocyte chemoattractant protein-1 were remarkably decreased by BE in white adipose tissue. BE is a beneficial food material for the prevention of obesity and diabetes by enhancing energy expenditure and suppressing inflammation.

Adrenocorticotrophic hormone retarded metabolism of low‐density lipoprotein in rats

In humans, treatment with adrenocorticotrophic hormone (ACTH) has well-documented plasma cholesterol lowering and low-density lipoprotein (LDL) lowering effects. Moreover, it has recently been demonstrated that ACTH directly inhibits apolipoprotein B expression and secretion in the HepG2 cell line. The aim of the present study was to demonstrate the effects of ACTH on lipid metabolism in the rat, and particularly on LDL metabolism. Rats were treated with porcine ACTH for 3 days and plasma lipid parameters were determined. Surprisingly, the total cholesterol level and LDL-cholesterol level were increased in plasma after ACTH administration, displaying an opposite effect of ACTH in humans. Furthermore, clearance and distribution of radiolabeled human LDL in different tissues were investigated in the rat after ACTH treatment. The clearance of radiolabeled LDL was slightly decreased after ACTH treatment suggesting that ACTH can inhibit LDL catabolism in the rat. Unlike previous observations performed in human hepatic cell cultures, there was no change in apoB expression in rat liver, or in apoE and apoM expression, after treatment with ACTH. This study clearly demonstrates that ACTH has species specificity differences in humans and in the rat.

Detection of prion infectivity in fat tissues of scrapie-infected mice

Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. Transmission of prion disease from cattle to humans resulted in banning human consumption of ruminant nervous system and certain other tissues. In the present study, we surveyed tissue distribution of prion infectivity in mice with prion disease. We show for the first time detection of infectivity in white and brown fat. Since high amounts of ruminant fat are consumed by humans and also incorporated into animal feed, fat-containing tissues may pose a previously unappreciated hazard for spread of prion infection.

Prion diseases, also known as transmissible spongiform encephalopathies, are infectious progressive fatal neurodegenerative diseases which affect humans as well as wild and domestic animals. Distribution of prion infectivity in organs and tissues is important in understanding prion disease pathogenesis and designing strategies to prevent prion infection in animals and humans. We show for the first time the presence of prion infectivity in white fat and brown fat tissues of mice with prion disease. Our results suggest that fat tissues of domestic or wild animals infected with prions may pose an unappreciated hazard for spread of infection to humans or domestic animals. The presence of prion infectivity in fat suggests that additional consideration may be required to eliminate from the food chain any fat from ruminants suspected of exposure to or infection with prions. Thus, this finding has implications for public health, food safety, and prion disease prevention strategies.

Comparative expression analysis of the renin-angiotensin system components between white and brown perivascular adipose tissue

Recent studies have demonstrated that the rat adipose tissue expresses some of the components necessary for the production of angiotensin II (Ang II) and the receptors mediating its actions. The aim of this work is to characterize the expression of the renin-angiotensin system (RAS) components in perivascular adipose tissue and to assess differences in the expression pattern depending on the vascular bed and type of adipose tissue. We analyzed Ang I and Ang II levels as well as mRNA levels of RAS components by a quantitative RT-PCR method in periaortic (PAT) and mesenteric adipose tissue (MAT) of 3-month-old male Wistar-Kyoto rats. PAT was identified as brown adipose tissue expressing uncoupling protein-1 (UCP-1). It had smaller adipocytes than those from MAT, which was identified as white adipose tissue. All RAS components, except renin, were detected in both PAT and MAT. Levels of expression of angiotensinogen, Ang-converting enzyme (ACE), and ACE2 were similar between PAT and MAT. Renin receptor expression was five times higher, whereas expression of chymase, AT(1a), and AT(2) receptors were significantly lower in PAT compared with MAT respectively. In addition, three isoforms of the AT(1a) receptor were found in perivascular adipose tissue. The AT(1b) receptor was found at very a low expression level. Ang II levels were higher in MAT with no differences between tissues in Ang I. The results show that the RAS is differentially expressed in white and brown perivascular adipose tissues implicating a different role for the system depending on the vascular bed and the type of adipose tissue.

Expression of deoxynucleoside kinases and 5'-nucleotidases in mouse tissues: implications for mitochondrial toxicity

Anti-HIV nucleoside therapy can result in mitochondrial toxicity affecting muscles, peripheral nerves, pancreas and adipose tissue. The cytosolic deoxycytidine kinase (dCK; EC 2.7.1.74) and thymidine kinase (TK1; EC 2.7.1.21), the mitochondrial thymidine kinase (TK2) and deoxyguanosine kinase (dGK; EC 2.7.1.113) as well as 5'-deoxynucleotidases (5'-dNT; EC 3.1.3.5) are enzymes that control rate-limiting steps in formation of intracellular and intra-mitochondrial nucleotides. The mRNA levels and activities of these enzymes were determined in mouse tissues, using real-time PCR and selective enzyme assays. The expression of mRNA for all these enzymes and the mitochondrial deoxynucleotide carrier was detected in all tissues with a 5-10-fold variation. TK1 activities were only clearly detected in spleen and testis, while TK2, dGK and dCK activities were found in all tissues. dGK activities were higher than any other dNK in all tissues, except spleen and testis. In skeletal muscle dGK activity was 5-fold lower, TK2 and dCK levels were 10-fold lower as compared with other tissues. The variation in 5'-dNT activities was about eight-fold with the highest levels in brain and lowest in brown fat. Thus, the salvage of deoxynucleosides in muscles is 5-10-fold lower as compared to other non-proliferating tissues and 100-fold lower compared to spleen. These results may help to explain tissue specific toxicity observed with nucleoside analogs used in HIV treatment as well as symptoms in inherited mitochondrial TK2 deficiencies.

Adrenomedullin and its receptor components in adipose tissues: Differences between white and brown fats and the effects of adrenergic stimulation

Male Sprague-Dawley rats were subcutaneously injected with 2.5mg/kg phenylephrine or 2.5mg/kg isoproterenol or both (2.5mg/kg for each drug) for 4 days, twice a day. Samples of scapular brown adipose tissue (BAT) and epididymal white adipose tissue (WAT) were collected for the measurement of adrenomedullin (AM) levels and the gene expression of preproAM, calcitonin receptor like receptor (CRLR) and its activity modifying proteins (RAMPs) by radioimmunoassay and RT-PCR. These values were compared with those in the rats that received 0.9% saline. The gene expression of AM and AM receptor components in BAT are much less than that in epididymal WAT. In BAT there were an increase in AM peptide level after a combined treatment of alpha(1) and beta adrenoceptor agonists and increases in preproAM mRNA levels for rats treated with alpha(1) and beta receptor agonists alone or in combination. Both CRLR and RAMP2 mRNA levels of alphabeta group were increased significantly. In WAT, AM peptide level, RAMP1 and RAMP2 mRNA expression levels were augmented in the alpha group while CRLR mRNA level was enhanced in the beta group. The levels of AM, its receptor and RAMPs are much less in BAT than in WAT but adrenergic stimulation has a greater effect on the AM and its receptor components in BAT than those in WAT. AM stimulates lipolysis and increases the level of uncoupling protein-1 (UCP-1) in BAT. It may therefore enhance thermogenesis by increasing the availability of free fatty acids substrate as well as the UCP-1 level on the mitochondrial membrane.

AQP7 is localized in capillaries of adipose tissue, cardiac and striated muscle: implications in glycerol metabolism

Aquaporin (AQP7) is expressed in proximal tubules and is involved in glycerol uptake. The cellular expression and physiological function in other organs remain largely undefined. AQP7 knockout (KO) mice were generated and used for immunohistochemical analyses to define the organ and cellular expression of AQP7. AQP7 labeling was found in kidney proximal tubule, heart, skeletal muscle, testis, epididymis, as well as in white and brown adipose tissue (WAT and BAT) of wild-type mice. Importantly, immunoreactivity was completely absent from these tissues in AQP7 KO mice. At the cellular level, the capillary endothelium WAT and BAT displayed prominent staining, whereas AQP7 labeling in adipocyte membranes was undetectable. Double-labeling confocal microscopy revealed coexpression of AQP7 with capillary AQP1 but not with adipocyte GLUT4. Moreover, immunoelectron microscopy and RT-PCR of isolated microvessels confirmed the vascular AQP7 expression. Distinct immunolabeling of the capillary endothelium was also observed in both skeletal and heart muscle with no apparent staining of skeletal or cardiac myocytes. As previously reported, specific immunolabeling was confined to brush border in segment 3 renal proximal tubules and to spermatids and spermatozoa in male reproductive tract. The expression of AQP7 was induced up to 2.2-fold in WAT of mice with streptozotocin-induced diabetes mellitus (S-DM) compared with controls and fasting for 72 h (but not 24 h) induced significant increase in AQP7 expression. In conclusion, AQP7 is expressed in capillary endothelia of adipose tissue (and cardiac and striated muscle) and is upregulated in WAT in response to S-DM supporting its role in glycerol metabolism.

Ectopic brown adipose tissue in muscle provides a mechanism for differences in risk of metabolic syndrome in mice

C57BL/6 (B6) mice subjected to a high-fat diet develop metabolic syndrome with obesity, hyperglycemia, and insulin resistance, whereas 129S6/SvEvTac (129) mice are relatively protected from this disorder because of differences in higher basal energy expenditure in 129 mice, leading to lower weight gain. At a molecular level, this difference correlates with a marked higher expression of uncoupling protein 1 (UCP1) and a higher degree of uncoupling in vitro in mitochondria isolated from muscle of 129 versus B6 mice. Detailed histological examination, however, reveals that this UCP1 is in mitochondria of brown adipocytes interspersed between muscle bundles. Indeed, the number of UCP1-positive brown fat cells in intermuscular fat in 129 mice is >700-fold higher than in B6 mice. These brown fat cells are subject to further up-regulation of UCP1 after stimulation with a beta3-adrenergic receptor agonist. Thus, ectopic deposits of brown adipose tissue in intermuscular depots with regulatable expression of UCP1 provide a genetically based mechanism of protection from weight gain and metabolic syndrome between strains of mice.

Sex Differences in Brown Adipose Tissue Thermogenic Features During Caloric Restriction

Caloric restriction (CR) studies have shown that females rats conserve energy more efficiently, showing a higher resistance to weight loss and higher protection of vital organs mass than male rats. Gender-dependent inactivation of thermogenesis in brown adipose tissue (BAT) has been proposed as one of these possible energy conserving mechanisms. To study the changes underlying this inactivation in rats, a three month study with 40% CR was undertaken to unravel the effects on BAT recruitment. Under ad libitum conditions female rats had greater BAT recruitment and greater oxygen consumption than their male counterparts. Total and mitochondrial protein, as well as triglyceride and DNA content were more reduced in restricted female rats than in restricted males. Similarly, the levels of key BAT functional proteins (UCP1, LPL, HSL, TFAM) were more reduced in restricted females, whereas no changes were found in mitochondrial DNA levels (mtDNA) and OXPHOS activities in males and females. Furthermore, alpha (2A)/beta (3) adrenergic receptor ratio remained constant in male rats whereas in female rats CR increased 60%. In conclusion, our results suggest that female rats, whose BAT thermogenic activity is higher in ad libitum conditions, is depressed during CR. This inactivation involves the mitochondrial differentiation process and lipolytic system and could be due, at least in part, to the unfavourable adrenergic receptor balance for thermogenic activation.