BCAA-nitrogen flux in brown fat controls metabolic health independent of thermogenesis.

Brown adipose tissue (BAT) is best known for thermogenesis. Rodent studies demonstrated that enhanced BAT thermogenesis is tightly associated with increased energy expenditure, reduced body weight, and improved glucose homeostasis. However, human BAT is protective against type 2 diabetes, independent of body weight. The mechanism underlying this dissociation remains unclear. Here, we report that impaired mitochondrial catabolism of branched-chain amino acids (BCAAs) in BAT, by deleting mitochondrial BCAA carriers (MBCs), caused systemic insulin resistance without affecting energy expenditure and body weight. Brown adipocytes catabolized BCAA in the mitochondria as nitrogen donors for the biosynthesis of non-essential amino acids and glutathione. Impaired mitochondrial BCAA-nitrogen flux in BAT resulted in increased oxidative stress, decreased hepatic insulin signaling, and decreased circulating BCAA-derived metabolites. A high-fat diet attenuated BCAA-nitrogen flux and metabolite synthesis in BAT, whereas cold-activated BAT enhanced the synthesis. This work uncovers a metabolite-mediated pathway through which BAT controls metabolic health beyond thermogenesis.

BCAA catabolism in brown fat controls energy homeostasis through SLC25A44.

Branched-chain amino acid (BCAA; valine, leucine and isoleucine) supplementation is often beneficial to energy expenditure; however, increased circulating levels of BCAA are linked to obesity and diabetes. The mechanisms of this paradox remain unclear. Here we report that, on cold exposure, brown adipose tissue (BAT) actively utilizes BCAA in the mitochondria for thermogenesis and promotes systemic BCAA clearance in mice and humans. In turn, a BAT-specific defect in BCAA catabolism attenuates systemic BCAA clearance, BAT fuel oxidation and thermogenesis, leading to diet-induced obesity and glucose intolerance. Mechanistically, active BCAA catabolism in BAT is mediated by SLC25A44, which transports BCAAs into mitochondria. Our results suggest that BAT serves as a key metabolic filter that controls BCAA clearance via SLC25A44, thereby contributing to the improvement of metabolic health.

Genetic evidence for involvement of ß2-adrenergic receptor in brown adipose tissue thermogenesis in humans.

BACKGROUND: Sympathetic activation of brown adipose tissue (BAT) thermogenesis can ameliorate obesity and related metabolic abnormalities. However, crucial subtypes of the ß-adrenergic receptor (AR), as well as effects of its genetic variants on functions of BAT, remains unclear in humans. We conducted association analyses of genes encoding ß-ARs and BAT activity in human adults. METHODS: Single nucleotide polymorphisms (SNPs) in ß1-, ß2-, and ß3-AR genes (ADRB1, ADRB2, and ADRB3) were tested for the association with BAT activity under mild cold exposure (19 °C, 2 h) in 399 healthy Japanese adults. BAT activity was measured using fluorodeoxyglucose-positron emission tomography and computed tomography (FDG-PET/CT). To validate the results, we assessed the effects of SNPs in the two independent populations comprising 277 healthy East Asian adults using near-infrared time-resolved spectroscopy (NIRTRS) or infrared thermography (IRT). Effects of SNPs on physiological responses to intensive cold exposure were tested in 42 healthy Japanese adult males using an artificial climate chamber. RESULTS: We found a significant association between a functional SNP (rs1042718) in ADRB2 and BAT activity assessed with FDG-PET/CT (p < 0.001). This SNP also showed an association with cold-induced thermogenesis in the population subset. Furthermore, the association was replicated in the two other independent populations; BAT activity was evaluated by NIRTRS or IRT (p < 0.05). This SNP did not show associations with oxygen consumption and cold-induced thermogenesis under intensive cold exposure, suggesting the irrelevance of shivering thermogenesis. The SNPs of ADRB1 and ADRB3 were not associated with these BAT-related traits. CONCLUSIONS: The present study supports the importance of ß2-AR in the sympathetic regulation of BAT thermogenesis in humans. The present collection of DNA samples is the largest to which information on the donor's BAT activity has been assigned and can serve as a reference for further in-depth understanding of human BAT function.

Comprehensive genomic evaluation of advanced and recurrent breast cancer patients for tailored precision treatments.

AIM: The aim of this study was to investigate genetic alterations within breast cancer in the setting of recurrent or de novo stage IV disease. PATIENTS AND METHODS: This study included 22 patients with recurrent breast cancer (n = 19) and inoperable de novo stage IV breast cancer (n = 3). For next generation sequencing, FoundationOneCDx (F1CDx) (Foundation Medicine Inc., Cambridge, MA, USA) was performed in 21 patients and FoundationOneLiquid CDx was performed in 1 patient. RESULTS: Median age was 62.9 years (range, 33.4-82.1). Pathological diagnoses of specimens included invasive ductal carcinoma (n = 19), invasive lobular carcinoma (n = 2), and invasive micropapillary carcinoma (n = 1). F1CDx detected a median of 4.5 variants (range, 1-11). The most commonly altered gene were PIK3CA (n = 9), followed by TP53 (n = 7), MYC (n = 4), PTEN (n = 3), and CDH1 (n = 3). For hormone receptor-positive patients with PIK3CA mutations, hormonal treatment plus a phosphoinositide 3-kinase inhibitor was recommended as the treatment of choice. Patients in the hormone receptor-negative and no human epidermal growth factor receptor 2 expression group had significantly higher tumor mutational burden than patients in the hormone receptor-positive group. A BRCA2 reversion mutation was revealed by F1CDx in a patient with a deleterious germline BRCA2 mutation during poly ADP ribose polymerase inhibitor treatment. CONCLUSION: Guidance on tailored precision therapy with consideration of genomic mutations was possible for some patients with information provided by F1CDx. Clinicians should consider using F1CDx at turning points in the course of the disease.

Evaluation of the intramammary distribution of breast lesions detected by MRI but not conventional second-look B-mode ultrasound using an MRI/ultrasound fusion technique.

The objective of this study was to evaluate the intramammary distribution of MRI-detected mass and focus lesions that were difficult to identify with conventional B-mode ultrasound (US) alone. Consecutive patients with lesions detected with MRI but not second-look conventional B-mode US were enrolled between May 2015 and June 2023. Following an additional supine MRI examination, we performed third-look US using real-time virtual sonography (RVS), an MRI/US image fusion technique. We divided the distribution of MRI-detected mammary gland lesions as follows: center of the mammary gland versus other (superficial fascia, deep fascia, and atrophic mammary gland). We were able to detect 27 (84%) of 32 MRI-detected lesions using third-look US with RVS. Of these 27 lesions, 5 (19%) were in the center of the mammary gland and 22 (81%) were located in other areas. We were able to biopsy all 27 lesions; 8 (30%) were malignant and 19 (70%) were benign. Histopathologically, three malignant lesions were invasive ductal carcinoma (IDC; luminal A), one was IDC (luminal B), and four were ductal carcinoma in situ (low-grade). Malignant lesions were found in all areas. During this study period, 132 MRI-detected lesions were identified and 43 (33%) were located in the center of the mammary gland and 87 (64%) were in other areas. Also, we were able to detect 105 of 137 MRI-detected lesions by second-look conventional-B mode US and 38 (36%) were located in the center of the mammary gland and 67 (64%) were in other areas. In this study, 81% of the lesions identified using third-look US with RVS and 64% lesions detected by second-look conventional-B mode US were located outside the center of the mammary gland. We consider that adequate attention should be paid to the whole mammary gland when we perform third-look US using MRI/US fusion technique.

Clinical performance of digital breast tomosynthesis-guided vacuum-assisted biopsy: a single-institution experience in Japan.

BACKGROUND: The purpose of this study was to evaluate the clinical performance of Digital Breast Tomosynthesis guided vacuum-assisted biopsy (DBT-VAB) for microcalcifications in the breast. METHODS: Retrospective review of 131 mammography-guided VABs at our institution were performed. All of the targets were calcification lesion suspicious for cancer. 45 consecutive stereotactic vacuum-assisted biopsies (ST-VABs) and 86 consecutive DBT-VABs were compared. Written informed consent was obtained. Tissue sampling methods and materials were the same with both systems. Student's t-test was used to compare procedure time and the Fisher's exact test was used to compare success rate, complications, and histopathologic findings for the 2 methods. RESULTS: The tissue sampling success rate was 95.6% for ST-VAB (43/45) and 97.7% (84/86) for DBT-VAB. Time for positioning (10.6 ± 6.4 vs. 6.7 ± 5.3 min), time for biopsy (33.4 ± 13.1 vs. 22.5 ± 13.1 min), and overall procedure time (66.6 ± 16.6 min vs. 54.5 ± 13.0 min) were substantially shorter with DBT-VAB (P < 0.0001). There were no differences in the distribution of pathological findings between the 2 groups. CONCLUSION: Depth information and stable visibility of the target provided by DBT images led to quick decisions about target coordinates and improved the clinical performance of microcalcification biopsies.

Airway obstruction requiring tracheal intubation after fine-needle aspiration of the thyroid gland: a case report.

BACKGROUND: There have been no reports of tracheal intubation for airway obstruction after acute thyroid swelling following fine-needle aspiration (FNA) of the thyroid gland. CASE PRESENTATION: A 58-year-old woman with a 22 mm × 13 mm right hypervascular thyroid nodule underwent FNA once with a 22G needle under ultrasonographic guidance. Shortly after the aspiration, ultrasound revealed hypoechoic swelling with a crack-like pattern. The patient was observed under bed rest in the Fowler position and received intravenous steroids. A computed tomography (CT) scan showed swelling not only of the thyroid but also of the retropharyngeal space, and the patient complained of difficulty swallowing saliva. Laryngeal fiberscopy revealed protrusion of the posterior pharyngeal wall, edematous changes in the mucosa of the pharynx and epiglottis, and retention of saliva. The patient was intubated awake and hydrocortisone was administered every 8 h. She was extubated 3 days after FNA and discharged without any complications. CONCLUSIONS: When neck swelling is noticed after FNA, ultrasonographic findings are especially important to assess potential causes. If airway obstruction is suspected, CT findings and fiberscope observation of the pharynx provide particularly useful information.

Diurnal variations of brown fat thermogenesis and fat oxidation in humans.

BACKGROUND/OBJECTIVES: Disturbed circadian rhythm is associated with an increased risk of obesity and metabolic disorders. Brown adipose tissue (BAT) is a site of nonshivering thermogenesis (NST) and plays a role in regulating whole-body energy expenditure (EE), substrate metabolism, and body fatness. In this study, we examined diurnal variations of NST in healthy humans by focusing on their relation to BAT activity. METHODS: Forty-four healthy men underwent 18F-fluoro-2-deoxy-D-glucose positron emission tomography and were divided into Low-BAT and High-BAT groups. In STUDY 1, EE, diet-induced thermogenesis (DIT), and fat oxidation (FO) were measured using a whole-room indirect calorimeter at 27 °C. In STUDY 2, EE, FO, and skin temperature in the region close to BAT depots (Tscv) and in the control region (Tc) were measured at 27 °C and after 90 min cold exposure at 19 °C in the morning and in the evening. RESULTS: In STUDY 1, DIT and FO after breakfast was higher in the High-BAT group than in the Low-BAT group (P < 0.05), whereas those after dinner were comparable in the two groups. FO in the High-BAT group was higher after breakfast than after dinner (P < 0.01). In STUDY 2, cold-induced increases in EE (CIT), FO, and Tscv relative to Tc in the morning were higher in the High-BAT group than in the Low-BAT group (P < 0.05), whereas those after dinner were comparable in the two groups. CIT in the High-BAT group tended to be higher in the morning than in the evening (P = 0.056). CONCLUSION: BAT-associated NST and FO were evident in the morning, but not in the evening, suggesting that the activity of human BAT is higher in the morning than in the evening, and thus may be involved in the association of an eating habit of breakfast skipping with obesity and related metabolic disorders.

Visualization of intracellular lipid metabolism in brown adipocytes by time-lapse ultra-multiplex CARS microspectroscopy with an onstage incubator.

We visualized a dynamic process of fatty acid uptake of brown adipocytes using a time-lapse ultra-broadband multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopic imaging system with an onstage incubator. Combined with the deuterium labeling technique, the intracellular uptake of saturated fatty acids was traced up to 9 h, a substantial advance over the initial multiplex CARS system, with an analysis time of 80 min. Characteristic metabolic activities of brown adipocytes, such as resistance to lipid saturation, were elucidated, supporting the utility of the newly developed system.

Interfacial Energy Measurement on the Reconstructive Polymer Surface: Dynamic Polymer Brush by Segregation of Amphiphilic Block Copolymers.

Herein, the interfacial energy of a reconstructive polymer surface formed by segregation is analyzed by measuring the change in the size of elastomer thin films floating on water. When a system in which amphiphilic diblock copolymers are mixed with the hydrophobic elastomer is in contact with water, surface reconstruction is triggered by the segregation of copolymers with a gain in the hydration energy of the hydrophilic blocks. The hydrophilic brush layer spontaneously formed at the elastomer-water interface is named the dynamic polymer brush. Although it is anticipated that the interfacial energy will significantly decrease in the dynamic polymer brush system, a direct measurement of the interfacial energy of the reconstructive interface is a challenge. We propose a novel method to measure the interfacial energy of a reconstructive polymer surface by measuring the deformation of elastomer thin films floating on water and apply it to the dynamic polymer brush system. The interfacial energy of the dynamic polymer brush formed by the segregation of amphiphilic diblock copolymers with longer hydrophilic chains drastically decreased to zero due to the high hydration energy of hydrophilic chains. Based on the neutron reflectometry results, the graft density and thickness of the dynamic polymer brush system floating on water were found to be lower than those of the system fixed onto solid substrates. This indicates that the floating system can respond to an external environment with a high degree of freedom (graft density, brush thickness, and interface area).

Multiorgan contribution to non-shivering and shivering thermogenesis and vascular responses during gradual cold exposure in humans.

PURPOSE: Human brown adipose tissue (BAT) is known to be a significant thermoeffector in non-shivering thermogenesis (NST), albeit with individual variations in the BAT activity. We hypothesized that humans with less BAT would have more contribution from the skeletal muscle (SM) to NST or earlier shivering onset and greater vasoconstriction to compensate for less BAT-mediated thermogenesis. METHODS: Eighteen males participated in this study. Their BAT activity and detectable volume were investigated. A gradual cold exposure was conducted for inducing NST at 18.6 °C and initiating shivering at 11.6 °C. The energy expenditure, electromyograph of the pectoralis major, skin blood flow, and rectal (Tre) and skin temperatures were evaluated. RESULTS: BAT volume significantly correlated with the change in metabolic heat production during mild cold phase relative to baseline (NST; r = 0.562, P < 0.05), but not with shivering initiation phase (NST+ ST). SM mass correlated with baseline metabolic heat production (Mbase; r = 0.839, P < 0.01) but not with NST or NST + ST. A positive correlation was noted between BAT volume and Tre at the end of the 18.6 °C exposure period (r = 0.586, P < 0.05), which positively correlated with shivering onset time (r = 0.553, P < 0.05). The skin blood flow, mean skin temperature, and forearm and finger skin temperature difference at the end of the 18.6 °C exposure period did not correlate with NST or BAT volume. CONCLUSION: BAT volume positively correlated with NST. Notably, lower Tre in individuals with less BAT volume induced earlier shivering onset for offsetting the less NST. Whereas, no correlation between metabolic and vasomotor responses was observed.

Translational Aspects of Brown Fat Activation by Food-Derived Stimulants.

Since the rediscovery of brown adipose tissue (BAT) in humans, its energy-dissipating ability has been well-recognized. The negative correlations of BAT activity with adiposity and insulin sensitivity provided an obvious rationale for discerning reliable and practical strategies for stimulating BAT. Though cold exposure or use of pharmacological adrenomimetics can activate BAT, they may have adverse effects. Therefore, determining alternative stimulants of BAT with lower risks such as commonly used food ingredients is highly desirable. Recent observations revealed that chemical activation of temperature-sensitive transient receptor potential (TRP) channels by food ingredients can recruit BAT in humans. Furthermore, animal studies have identified several food-derived stimulants of BAT acting through multiple mechanisms distinct from a TRP-mediated process. Dietary compounds acting as an activator of Sirtuin 1, a critical regulator of mitochondrial biogenesis and brown adipocyte differentiation, are one such class of promising food-derived BAT activators in humans. While the individual effects of various dietary factors are increasingly established in a laboratory setting, the potential synergistic effects of multiple stimulants on BAT remain to be tested in a clinical environment. These investigations may support the development of efficient, flexible dietary regimens capable of boosting BAT thermogenesis.

Interaction of Nerve Growth Factor ß with Adiponectin and SPARC Oppositely Modulates its Biological Activity.

Both adiponectin and secreted protein, acidic and rich in cysteine (SPARC) inhibit platelet-derived growth factor-BB (PDGF-BB)-induced and basic fibroblast growth factor (FGF2)-induced angiogenic activities through direct and indirect interactions. Although SPARC enhances nerve growth factor (NGF)-dependent neurogenesis, the physical interaction of NGFß with adiponectin and SPARC remains obscure. Therefore, we first examined their intermolecular interaction by surface plasmon resonance method. NGFß bound to immobilized SPARC with the binding constant of 59.4 nM, comparable with that of PDGF-BB (24.5 nM) but far less than that of FGF2 (14.4 µM). NGFß bound to immobilized full length adiponectin with the binding constant of 103 nM, slightly higher than those of PDGF-BB (24.3 nM) and FGF2 (80.2 nM), respectively. Treatment of PC12 cells with SPARC did not cause mitogen-activated protein kinase (MAPK) activation and neurite outgrowth. However, simultaneous addition of SPARC with NGFß enhanced NGFß-induced MAPK phosphorylation and neurite outgrowth. Treatment of the cells with adiponectin increased AMP-activated protein kinase (AMPK) phosphorylation but failed to induce neurite outgrowth. Simultaneous treatment with NGFß and adiponectin significantly reduced cell size and the number of cells with neurite, even after silencing the adiponectin receptors by their siRNA. These results indicate that NGFß directly interacts with adiponectin and SPARC, whereas these interactions oppositely regulate NGFß functions.

Applicability of Supraclavicular Oxygenated and Total Hemoglobin Evaluated by Near-Infrared Time-Resolved Spectroscopy as Indicators of Brown Adipose Tissue Density in Humans.

Brown adipose tissue (BAT) may potentially be used in strategies for preventing lifestyle-related diseases. We examine evidence that near-infrared time-resolved spectroscopy (NIRTRS) is capable of estimating human BAT density (BAT-d). The parameters examined in this study are total hemoglobin [total-Hb]sup, oxygenated Hb [oxy-Hb]sup, deoxygenated Hb [deoxy-Hb]sup, Hb O2 saturation (StO2sup), and the reduced scattering coefficient in the supraclavicular region (µs'sup), where BAT deposits can be located; corresponding parameters in the control deltoid region are obtained as controls. Among the NIRTRS parameters, [total-Hb]sup and [oxy-Hb]sup show region-specific increases in winter, compared to summer. Further, [total-Hb]sup and [oxy-Hb]sup are correlated with cold-induced thermogenesis in the supraclavicular region. We conclude that NIRTRS-determined [total-Hb]sup and [oxy-Hb]sup are useful parameters for evaluating BAT-d in a simple, rapid, non-invasive manner.

Cell death-inducing DNA fragmentation factor A-like effector A and fat-specific protein 27ß coordinately control lipid droplet size in brown adipocytes.

Adipose tissue stores neutral lipids and is a major metabolic organ involved in regulating whole-body energy homeostasis. Triacylglycerol is stored as unilocular large lipid droplets (LDs) in white adipocytes and as multilocular small LDs in brown adipocytes. Proteins of the cell death-inducing DNA fragmentation factor A-like effector (Cide) family include CideA, CideB, and fat-specific protein of 27 (FSP27). Of these, FSP27 has been shown to play a crucial role in the formation of unilocular large LDs in white adipocytes. However, the mechanisms by which brown adipocytes store small and multilocular LDs remain unclear. An FSP27 isoform, FSP27ß, was recently identified. We herein report that CideA and FSP27ß are mainly expressed in brown adipose tissue and that FSP27ß overexpression inhibits CideA-induced LD enlargements in a dose-dependent manner in COS cells. Furthermore, RNAi-mediated FSP27ß depletion resulted in enlarged LDs in HB2 adipocytes, which possess the characteristics of brown adipocytes. Brown adipocytes in FSP27-knock-out mice that express CideA, but not FSP27ß, had larger and fewer LDs. Moreover, we confirmed that FSP27ß and CideA form a complex in brown adipose tissue. Our results suggest that FSP27ß negatively regulates CideA-promoted enlargement of LD size in brown adipocytes. FSP27ß appears to be responsible for the formation of small and multilocular LDs in brown adipose tissue, a morphology facilitating free fatty acid transport to mitochondria adjacent to LDs for oxidation in brown adipocytes.

Enhancement of Warfarin Anticoagulant Reaction in Patients with Repeated Oral Tolvaptan Administration.

The pharmacokinetics and pharmacodynamics of warfarin remained unaffected by tolvaptan during clinical trials. However, tolvaptan prolonged the prothrombin time-international normalized ratio (PT-INR) level of patients with cardiovascular disease taking warfarin. Tolvaptan was prescribed to 576 patients from December 2010 to December 2015. Of these patients, 37 underwent anticoagulant therapy. We investigated PT-INR fluctuation immediately before tolvaptan therapy was initiated. PT-INR remained unchanged in the control group and in groups administered with less than 7.5 mg/d tolvaptan, whereas it was significantly increased (p=0.03) in the group administered with more than 7.5 mg/d tolvaptan. This result indicates the possibility that tolvaptan affects the pharmacodynamics of warfarin in vivo. However, further research is necessary to clarify the mechanism of this phenomenon.

A new era in brown adipose tissue biology: molecular control of brown fat development and energy homeostasis.

Brown adipose tissue (BAT) is specialized to dissipate chemical energy in the form of heat as a defense against cold and excessive feeding. Interest in the field of BAT biology has exploded in the past few years because of the therapeutic potential of BAT to counteract obesity and obesity-related diseases, including insulin resistance. Much progress has been made, particularly in the areas of BAT physiology in adult humans, developmental lineages of brown adipose cell fate, and hormonal control of BAT thermogenesis. As we enter into a new era of brown fat biology, the next challenge will be to develop strategies for activating BAT thermogenesis in adult humans to increase whole-body energy expenditure. This article reviews the recent major advances in this field and discusses emerging questions.

Progesterone dose-dependently modulates hepatocyte growth factor production in 3T3-L1 mouse preadipocytes.

It is well documented that estrogen is predominant inducer of hepatocyte growth factor (HGF) in a variety of cell types. However, the effect of progesterone (P) remains to be elusive. Thus, in the present study, we examined the effect of P and combined effect of P and 17ß-estradiol (E2) on HGF expression and production in 3T3-L1 fibroblastic preadipocytes and mature adipocytes, as a model of stromal cells. Northern blot analysis showed that hgf mRNA expressed in preadipocytes was notably higher than that of mature adipocytes, and increased by treatment of preadipocytes with E2 or 10 nM P, but not with 1,000 nM P. The E2-induced hgf mRNA expression was enhanced by 10 nM P, but suppressed by 1,000 nM P. Western blot analysis revealed that biological active forms of HGF protein was found in the preadipocyte culture medium, while the lesser amount of HGF precursor protein was detected in the mature adipocyte culture medium. The amounts of HGF were changed dependently on the hgf mRNA expression levels. These results indicate that HGF production is intricately regulated by E2 and P at the transcriptional levels in 3T3-L1 cells, and may explain the changes in the HGF production during the mammary gland development, especially decrease in HGF expression during pregnancy when P concentration is high.

Brown adipose tissue is involved in the seasonal variation of cold-induced thermogenesis in humans.

Brown adipose tissue (BAT) contributes to whole-body energy expenditure (EE), especially cold-induced thermogenesis (CIT), in humans. Although it is known that EE and CIT vary seasonally, their relationship with BAT has not been investigated. In the present study, we examined the impact of BAT on seasonal variations of EE/CIT and thermal responses to cold exposure in a randomized crossover design. Forty-five healthy male volunteers participated, and their BAT was assessed by positron emission tomography and computed tomography. CIT, the difference of EE at 27ºC and after 2-h cold exposure at 19ºC, significantly increased in winter compared to summer, being greater in subjects with metabolically active BAT (High BAT, 185.6 kcal/d, 18.3 kcal/d, P<0.001) than those without (Low BAT, 90.6 kcal/d, -46.5 kcal/d, P<0.05). Multivariate regression analysis revealed a significant interaction effect between season and BAT on CIT (P<0.001). The cold-induced drop of tympanic temperature (Tty) and skin temperature (Tskin) in the forehead region and in the supraclavicular region close to BAT deposits were smaller in the High BAT group than in the Low BAT group in winter but not in summer. In contrast, the drop of Tskinin the subclavicular and peripheral regions distant from BAT was similar in the two groups in both seasons. In conclusion, CIT increased from summer to winter in a BAT-dependent manner, paralleling cold-induced changes in Tty/Tskin, indicating a role of BAT in seasonal changes in the thermogenic and thermal responses to cold exposure in humans.

Evaluation of Brown Adipose Tissue Using Near-Infrared Time-Resolved Spectroscopy.

Human brown adipose tissue (BAT) activity (SUVmax) has been typically evaluated by 18F-fluorodeoxy glucose (FDG)-positron emission tomography (PET) combined with computed tomography (CT). In this study, the objective was to detect human BAT by near-infrared time-resolved spectroscopy (NIRTRS), a noninvasive and simple method for measuring total hemoglobin concentration [total-Hb] and reduced scattering coefficient (µs') in the tissue. The [total-Hb] in the supraclavicular region of the BAT (+) (SUVmax≥2.0) group was 95.0±28.2 µM (mean+/-SD), which was significantly higher than that of the BAT (-) (SUVmax<2.0) group (52.0±14.8 µM), but not in other regions apart from the BAT deposits. The µs' in the supraclavicular region of the BAT (+) group was 8.4±1.7 cm(-1), which was significantly higher than that of BAT (-) group (4.3±1.0 cm(-1)), but not in other regions. The area under the receiver operating characteristic curve closest to (0, 1) for [total-Hb] and µs' to discriminate BAT (+) from BAT (-) was 72.5 µM and 6.3 cm(-1), respectively. The sensitivity, specificity, and accuracy for both parameters were 87.5, 100, and 93.3%, respectively. Our novel NIRTRS method is noninvasive, simple, and inexpensive compared with FDG-PET/CT, and is reliable for detecting human BAT.