Production of thyroxine (T4) and triiodothyronine (T3) in nontoxic thyroid tumors

Summary Thyroid tissue specimens from 27 patients with thyroid tumors were examined for thyroxine (T₄) and triiodothyronine (T₃) by the peroxidase-labeled antibody method. The result revealed localization of T₄ in 12 of the 14 follicular adenomas, in all the 8 papillary carcinomas and in 1 of the 3 follicular carcinomas studied, and of T₃ in 13 of the 14 follicular adenomas, in all the 8 papillary carcinomas and in all the 3 follicular carcinomas.In the tumor tissue, the thyroid hormones were demonstrated in the colloid substance, on the luminal surface of tumor cells and in their cytoplasm. Compared with nontumorous thyroid tissue, the tumor tissue showed localization of the hormones predominantly in the cytoplasm and to a lesser extent in the colloid substance, with conspicuous variations in tissue distribution of positive areas and intensity of staining. This tendency was more marked in thyroid carcinomas.The demonstration of T₄ and T₃ in routine histological paraffin sections of formalin-fixed thyroid tissues in this investigation indicates potential usefulness of thyroid hormone detection by the peroxidase-labeled antibody technique. It is an effective diagnostic tool for evaluating the functional activity of thyroid tumors as well as for determining whether a malignant growth under examination originates from the thyroid.     

T1 and T2 temperature dependence of female human breast adipose tissue at 1.5 T: groundwork for monitoring thermal therapies in the breast

The T₁ and T₂ temperature dependence of female breast adipose tissue was investigated at 1.5 T in order to evaluate the applicability of relaxation‐based MR thermometry in fat for the monitoring of thermal therapies in the breast. Relaxation times T₁, T₂ and T_2TSE (the apparent T₂ measured using a turbo spin echo readout sequence) were measured in seven fresh adipose breast samples for temperatures from 25 to 65 °C. Spectral water suppression was used to reduce the influence of the residual water signal. The temperature dependence of the relaxation times was characterized. The expected maximum temperature measurement errors based on average calibration lines were calculated. In addition, the heating–cooling reversibility was investigated for two samples. The T₁ and T_2TSE temperature (T) dependence could be fitted well with an exponential function of 1/T. A linear relationship between T₂ and temperature was found. The temperature coefficients (mean ± inter‐sample standard deviation) of T₁ and T_2TSE increased from 25 °C (dT₁/dT = 5.35 ± 0.08 ms/°C, dT_2TSE/dT = 3.82 ± 0.06 ms/°C) to 65 °C (dT₁/dT = 9.50 ± 0.16 ms/°C, dT_2TSE/dT = 7.99 ± 0.38 ms/°C). The temperature coefficient of T₂ was 0.90 ± 0.03 ms/°C. The temperature‐induced changes in the relaxation times were found to be reversible after heating to 65 °C. Given the small inter‐sample variation of the temperature coefficients, relaxation‐based MR thermometry appears to be feasible in breast adipose tissue, and may be used as an adjunct to proton resonance frequency shift (PRFS) thermometry in aqueous tissue (glandular + tumor). Copyright © 2015 John Wiley & Sons, Ltd.     

Regulatory T cells in human autoimmune diseases

In the most simplistic terms, immune tolerance can be envisioned as a balance with autoreactive cells that arise naturally in all individuals on one side and regulatory mechanisms designed to counter those autoreactive processes on the other. A tilt of the balance toward the autoreactive side, either by increasing the number or function of autoreactive cells or by diminishing regulatory mechanisms, is manifested as autoimmunity. In contrast, tilting of the balance toward increased regulation could conceivably cause immunodeficiency. Regulatory T cells (T_REG), and particularly the naturally arising CD4⁺CD25⁺ subset of T_REG cells, provide a substantial component of the autoimmune counterbalance. The identification of forkhead box P3 (FOXP3) as a critical determinant of CD4⁺CD25⁺ T_REG development and function has provided new opportunities and generated expanded interest in studying the delicate balance between autoimmunity and regulatory mechanisms in human autoimmune diseases. Identification of both human and mouse syndromes in which FOXP3 is mutated, and consequently CD4⁺CD25⁺ T_REG cells are absent, has led to a rapid accumulation of knowledge regarding T_REG development and function over the past 5 years. The recent development of antibody reagents to specifically identify CD4⁺CD25⁺ T_REG cells by their FOXP3 expression has provided new tools to identify these elusive cells and investigate their role in human disease. This review will focus on the current state of knowledge regarding the role of T_REG in human autoimmune diseases and on specific human immunodeficiencies that provide interesting models of autoimmunity.     

The role of regulatory T cell (Treg) subsets in gestational diabetes mellitus

Physiological changes during normal pregnancy are characterized by an inflammatory immune response and insulin resistance. Therefore, we hypothesize that gestational diabetes mellitus (GDM) may be caused by an inappropriate adaption of the maternal immune system to pregnancy. In this study we examined the role of regulatory T cell (T_reg) differentiation for the development of GDM during pregnancy. We used six-colour flow cytometric analysis to demonstrate that the total CD4⁺CD127^low+/−CD25⁺ forkhead box protein 3 (FoxP3⁺) T_reg pool consists of four different T_reg subsets: naive CD45RA⁺ T_regs, HLA-DR⁻CD45RA⁻ memory T_regs (DR⁻ T_regs) and the highly differentiated and activated HLA-DR^low+CD45RA⁻ and HLA-DR^high+CD45RA⁻ memory T_regs (DR^low+ and DR^high+ T_regs). Compared to healthy pregnancies, the percentage of CD4⁺CD127^low+/−CD25⁺FoxP3⁺ T_regs within the total CD4⁺ T helper cell pool was not different in patients affected by GDM. However, the suppressive activity of the total CD4⁺CD127^low+/−CD25⁺ T_reg pool was significantly reduced in GDM patients. The composition of the total T_reg pool changed in the way that its percentage of naive CD45RA⁺ T_regs was decreased significantly in both patients with dietary-adjusted GDM and patients with insulin-dependent GDM. In contrast, the percentage of DR⁻-memory T_regs was increased significantly in patients with dietary-adjusted GDM, while the percentage of DR^low+ and DR^high+ memory T_regs was increased significantly in patients with insulin-dependent GDM. Hence, our findings propose that alterations in homeostatic parameters related to the development and function of naive and memory T_regs may cause the reduction of the suppressive capacity of the total T_reg pool in GDM patients. However, as this is an exploratory analysis, the results are only suggestive and require further validation.     

Analogous effects of serum lipids from patients with nonthyroidal illness and normal subjects on the uptake of thyroxine and its conversion to triiodothyronine by rat hepatocytes in culture

Summary The low level of triiodothyronine (T3) in nonthyroidal illnesses (NTI) has been attributed to the decreased peripheral conversion of thyroxine (T₄) to T₃; patient's serum lipids decreased the conversion in a cell-free system. The objective of our study was to determine whether patients' serum lipids, whose content was elevated 2.5-fold above the reference serum value, and oleic acid affected the uptake of T₄ and its conversion to T₃ by rat hepatocytes in culture, thereby providing information on the cell's response to these processes. Serum ether extracts and oleic acid (0.1 mol/l) were incubated with cells followed by assessment of T₄ uptake and conversion of T₄ to T₃. The mean T4 uptake in the presence of ether extracts of NTI patients' or normals' sera were similar (112±15% and 110±24%, respectively). There was no difference in the T₄ to T₃ conversion between the patient and normal groups (90 ±14%); oleic acid also did not influence the conversion (96.7 ± 1.6%). Uptake and conversion in the absence of either extracts and oleic acid were controls. These results suggest that serum lipids from NTI patients and normal subjects exercise qualitatively and quantitatively almost similar influences on T₄ uptake and its conversion to T₃; oleic acid is not an inhibitor of T₄ uptake and T₄ to T₃ conversion in the rat hepatocyte. Since hepatocytes actively process fatty acids, their influence on intracellular conversion of T₄ is not equitable with T₄ conversion using the cell-free system. Our results do not support the hypothesis that abnormal lipid metabolism in NTI impairs hepatic T₄ to T₃ conversion.Abbreviations NTI nonthyroidal illness - T₃ triiodothyro-nine - TT₃ total T₃ - rT₃ reverse T₃ - T₄ thyroxine - TT₄ total T₄ - FT₄ free T4     

Presence of organic anion transporters 3 (OAT3) and 4 (OAT4) in human adrenocortical cells

Since the organic anion transporter-1 (OAT1) has been implicated in cortisol release from bovine and rat adrenal zona fasciculata cells, we addressed the question of whether OATs are present in human adrenal cortical cells. In the human adrenal cell line NCI-H295R, 24-h cortisol secretion increased up to 30-fold on exposure to forskolin. Incubation of forskolin-treated cells for 24 h with the OAT substrates probenecid, p-aminohippurate (PAH), glutarate or cimetidine inhibited cortisol release partly. RT-PCR did not reveal expression of human OAT1 and OAT2, but OAT3 and OAT4 mRNAs were detected in both NCI-H295R cells and human adrenal tissue. When human OAT3 (hOAT3) and hOAT4 were expressed in Xenopus laevis oocytes, only hOAT3 showed [³H]cortisol uptake in excess of that of water-injected control oocytes. Cortisol uptake via OAT3 was saturable with an apparent K_t of 2.4 µM. In NCI-H295R cells, [³H]estrone sulphate uptake was saturable, cis-inhibited by OAT substrates and trans-stimulated by preloading with glutarate or cortisol. Likewise, [³H]PAH uptake was cis-inhibited by estrone sulphate and trans-stimulated by preloading the cells with PAH, glutarate or cortisol, indicating functional expression of OATs in the plasma membrane of NCI-H295R cells.     

T follicular helper (Tfh) cells in normal immune responses and in allergic disorders

Follicular helper T cells (T_fh) are located within germinal centers of lymph nodes. Cognate interaction between T_fh, B cells, and IL‐21 drives B cells to proliferate and differentiate into plasma cells thereby leading to antibody production. T_fh cells and IL‐21 are involved in infectious and autoimmune diseases, immunodeficiencies, vaccination, and cancer. Human peripheral blood CXCR5⁺ CD4⁺ T cells comprise different subsets of T_fh‐like cells. Despite the importance of the IgE response in the pathogenesis of allergic disorders, little is known about the role of follicular and blood T_fh cells and IL‐21 in human and experimental allergic disease. Here, we review recent advances regarding the phenotypic and functional characteristics of both follicular and blood T_fh cells and of the IL‐21/IL‐21R system in the context of allergic disorders.     

BIOSENSOR FOR THE ENANTIOSELECTIVE ANALYSIS OF THE THYROID HORMONES (+)-3,3′,5-TRIIODO-L-THYRONINE (T3) AND (+)-3,3′,5,5′-TETRAIODO-L-THYRONINE (T4)

ABSTRACT

An amperometric biosensor based on L-aminoacid oxidase is proposed for enantioselective assay of (+)-3,3′,5-triiodo-L-thyronine (L-T₃) and (+)-3,3′,5,5′-tetraiodo-L-thyronine (L-T₄), due to the fact that only the L enantiomer has the hormonal activity. The construction of the amperometric biosensor is simple and reproducible. The analytical information obtained from enantioselective analysis are reliable. The RSD <1% assured by using the amperometric biosensors for L enantiomers assay as raw materials, and from tablets, demonstrated their suitability for the analysis of T₃ and T₄ at ppb concentration levels.     

Thyrotropic hormone (TSH) regulation of triiodothyronine (T3) concentration in immune cells

Objective:  Cells of the immune system (peritoneal lymphocytes, monocytes, granulocytes and mast cells as well as thymocytes) contain triiodothyronine (T₃). The aim of the present experiments was to study whether thyrotropic hormone (TSH) regulates or not the T₃ concentration of these cells. Methods:  Peritoneal fluid and thymus cells of adult rats were studied by immunocytochemistry, combined with flow cytometry for triiodothyronine content with or without in-vitro TSH treatment. In addition, adult female CD1 mice were treated in vivo with 10 or 40 mU TSH and after 1 hour peritoneal immune cells were studied using the above mentioned method. Results:  Both in vitro (in rat) and in vivo (in mice) TSH treatments significantly elevated the T₃ content in each cell type. In vitro TSH 0.1 mU/ml cell suspension was enough to provoke about 50 % increase in T₃ production. Conclusion:  T₃ concentration in immune cells seems to be regulated by TSH, similarly to the T₃ in the thyroid. Considering the large number of immune cells in an organism, TSH regulation of their T₃ content could have an important physiological and pathological role, both in and beyond the immune system. Received 15 April 2008; returned for revision 19 May 2008; received from final revision 20 May 2008; accepted by I. Ahnfeld-R?nne 23 June 2008     

TRH-refraktäre TSH-Werte,Trijodthyroninspiegel und T3/T4-Quotienten bei mit T3/T4-Kombinationspräparaten behandelten hypothyreoten Kindern

Zusammenfassung Bei 23 Kindern mit primärer Hypothyreose, die mit Thyroxin (T₄) und Trijodthyronin (T₃) enthaltenden Kombinationspräparaten behandelt worden waren, wurden TRH-Teste, TBI, T₃- und T₄-Bestimmungen durchgeführt. Die T₃/T₄-Quotienten wurden berechnet. 7 von 10 Patienten mit TRH-refraktären TSH-Werten und normalen T₄-Spiegeln wiesen überhöhte T₃-Werte auf. Bei 6 von diesen Patienten konnten pathologisch überhöhte T₃/T₄-Quotienten beobachtet werden. Eine TRH-refraktäre TSH-Suppression wurde nur bei hohen T₄-Werten gefunden. Nach einer Reduktion der Substitutionsdosis normalisierten sich die überhöhten T₃-Spiegel. Die Befunde zeigen, daß nicht nur die T₄-Werte sondern auch die TSH- und T₃-Spiegeln unter der Behandlung mit Schilddrüsenhormonen kontrolliert werden sollten. Die Durchführung der Substitutionstherapie der Hypothyreose mit T₃/T₄-Kombinationspräparaten im Verhältnis 1:4 sollte überdacht werden.     

Increased levels of regulatory T cells (Tregs) in human immunodeficiency virus‐infected patients after 5 years of highly active anti‐retroviral therapy may be due to increased thymic production of naive Tregs

This study determines levels of regulatory T cells (T_regs), naive T_regs, immune activation and cytokine patterns in 15 adult human immunodeficiency virus (HIV)‐infected patients receiving prolonged highly active anti‐retroviral therapy (HAART) who have known thymic output, and explores if naive T_regs may represent recent thymic emigrant T_regs. HIV‐infected patients treated with HAART with a median of 1 and 5 years were compared with healthy controls. Percentages of T_regs (CD3⁺CD4⁺CD25⁺CD127^low), naive T_regs (CD3⁺CD4⁺CD25⁺CD45RA⁺) and activation markers (CD38⁺human leucocyte antigen D‐related) were determined by flow cytometry. Forkhead box P3 mRNA expression and T cell receptor excision circles (T_REC) content in CD4⁺ cells were determined by polymerase chain reaction and cytokines analysed with Luminex technology. Levels of T_regs were significantly higher in HIV‐infected patients compared with controls, both after 1 and 5 years of HAART (P < 0·001), despite fully suppressed HIV‐RNA and normalization of both CD4 counts, immune activation and cytokine patterns. Furthermore, levels of naive T_regs were elevated significantly in HIV‐infected patients (P < 0·001) and were associated with thymic output measured as the T_REC frequency in CD4⁺ cells (P = 0·038). In summary, T_reg levels in HIV‐infected patients are elevated even after 5 years of HAART. Increased thymic production of naive T_regs may contribute to higher T_reg levels in HIV‐infection.     

Thyroid function and thyroid hormone metabolism in elderly people low T3-syndrome in old age?

Summary T₄-, T₃- and reverse-T₃ concentrations were measured in the sera of 365 subjects beyond the age of 65 in order to evaluate if the decrease of serum T₃ frequently observed in old age can be attributed to old age per se or to concomitant non-thyroidal disease. The results obtained from a carefully selected healthy group of elderly people show that 1) total and free T₃ levels are lower in senescence but well within the range for euthyroidism in younger healthy controls; 2) the decrease of serum T₃ is more pronounced and occurs earlier in healthy old males than in females, so that for subjects over the age of 75, the upper limit for euthyroidism has to be adjusted by 10% in women and by 20% in men; and 3) there is no low T₃ syndrome characterized by decreased serum T₃ and increased serum reverse T₃, solely due to old age.Turnover kinetics have shown the daily production of T₄ and T₃ in old age to decrease by 20 µg and 10 µg, respectively, and an increased T₃ metabolic clearance not to account for the reduction of serum T₃ concentrations. Combined stimulation tests with TSH and TRH showed that the functional reserve of the thyroid gland to produce T₃ is maintained in old age. The first step in the sequence of events may be seen in an impairment of TSH secretion leading to an adaptation of the amount of thyroid hormones to a reduced mass of metabolically active body tissue in old age.     

Regulatory T cells and chronic immune activation in human immunodeficiency virus 1 (HIV-1)-infected children

The function of CD4⁺ T cells with regulatory activity (T_regs) is the down-regulation of immune responses. This suppressive activity may limit the magnitude of effector responses, resulting in failure to control human immunodeficiency virus 1 (HIV-1) infection, but may also suppress chronic immune activation, a characteristic feature of HIV-1 disease. We evaluated the correlation between viral load, immune activation and T_regs in HIV-1-infected children. Eighty-nine HIV-1-infected children (aged 6–14 years) were included in the study and analysed for HIV-1 plasmaviraemia, HIV-1 DNA load, CD4 and CD8 cell subsets. T_reg cells [CD4⁺ CD25^highCD127^lowforkhead box P3 (FoxP3^high)] and CD8-activated T cells (CD8⁺CD38⁺) were determined by flow cytometry. Results showed that the number of activated CD8⁺CD38⁺ T cells increased in relation to HIV-1 RNA plasmaviraemia (r = 0·403, P < 0·0001). The proportion of T_regs also correlated positively with HIV-1 plasmaviraemia (r = 0·323, P = 0·002), but correlated inversely with CD4⁺ cells (r = −0·312, P = 0·004), thus suggesting a selective expansion along with increased viraemia and CD4⁺ depletion. Interestingly, a positive correlation was found between the levels of T_regs and CD8⁺CD38⁺ T cells (r = 0·305, P = 0·005), and the percentage of T_regs tended to correlate with HIV-1 DNA load (r = 0·224, P = 0·062). Overall, these findings suggest that immune activation contributes to the expansion of T_reg cells. In turn, the suppressive activity of T_regs may impair effector responses against HIV-1, but appears to be ineffective in limiting immune activation.     

Effects of Prostaglandin E1 in Canine Subcutaneous Adipose Tissue in Situ1

The effect of PGE₁ on the uptake of glucose and the release of FFA and glycerol before and after sympathetic nerve stimulation (4 cps) was investigated in perfused canine subcutaneous adipose tissue in situ. Glucose uptake was significantly increased by PGE₁ at all concentrations used (5 times 10^-10 to 7 times 10^-7 M in blood). The effect of PGE₁ on the release of FFA and glycerol in unstimulated adipose tissue was inconsistent. Increases as well as decreases were observed. Lipolysis, as measured by glycerol release, induced by nerve stimulation was inhibited dose-dependently. A 50 per cent inhibition was produced by approximately 1.2 times 10^-7 M PGE₁. Stimulated FFA release was also inhibited but there was no clear dose-response relationship. It is concluded that PGE₁ has similar effects in canine subcutaneous adipose tissue with an intact blood supply as are known to be produced in vitro.     

Measuring renal tissue relaxation times at 7 T

As developments in RF coils and RF management strategies make performing ultra‐high‐field renal imaging feasible, understanding the relaxation times of the tissue becomes increasingly important for tissue characterization, sequence optimization and quantitative functional renal imaging, such as renal perfusion imaging using arterial spin labeling. By using a magnetization‐prepared single‐breath‐hold fast spin echo imaging method, human renal T₁ and T₂ imaging studies were successfully performed at 7 T with 11 healthy volunteers (eight males, 45 ± 17 years, and three females, 29 ± 7 years, mean ± standard deviation, S.D.) while addressing challenges of B₁⁺ inhomogeneity and short‐term specific absorption rate limits. At 7 T, measured renal T₁ values for the renal cortex and medulla (mean ± S.D.) from five healthy volunteers who participated in both 3 T and two‐session 7 T studies were 1661 ± 68 ms and 2094 ± 67 ms, and T₂ values were 108 ± 7 ms and 126 ± 6 ms. For comparison, similar measurements were made at 3 T, where renal cortex and medulla T₁ values of 1261 ± 86 ms and 1676 ± 94 ms and T₂ values of 121 ± 5 ms and 138 ± 7 ms were obtained. Measurements at 3 T and 7 T were significantly different for both T₁ and T₂ values in both renal tissues. Reproducibility studies at 7 T demonstrated that T₁ and T₂ estimations were robust, with group mean percentage differences of less than 4%. Copyright © 2014 John Wiley & Sons, Ltd.     

T(reg) cells: collection, processing, storage and clinical use

T regulatory cells are fundamental in the maintenance of immune homeostasis and self-tolerance. Experimental models suggest the existence of two functional types of T_reg cells designated naturally occurring and induced. Interest in T_reg cells increased with evidence from experimental mouse and human models demonstrating that the immunosuppressive potential of these cells can be utilized in the treatment of various pathological conditions. The existence of a subpopulation of suppressive T cells was the subject of significant controversy among immunologists for many years. T regulatory cells limit immune activation through a variety of direct and indirect interactions, many of which are yet to be determined. Fully understanding T_reg cells biology will lead us to harnessing the capacity of these cells in order to develop strategies to prevent autoimmune disorders and tolerance to transplantation. Efficient isolation, expansion and cryopreservation strategies that comply with Good Manufacturing Practice (GMP) guidelines are prerequisites for the clinical application of human CD4+ CD25+ CD127^low FOXP3+ regulatory T cells.     

Intra‐ and interindividual variability of fatty acid unsaturation in six different human adipose tissue compartments assessed by 1H‐MRS in vivo at 3 T

It is generally accepted that the amount and distribution of adipose tissue (AT) in the human body play an important role in the pathogenesis of metabolic diseases. In addition, metabolic effects of released saturated fatty acids (FAs) in blood are known to be more critical than those of unsaturated FAs. However, little is known about the variability in unsaturation of FAs in various AT compartments. The aim of this prospective study was the assessment of mono‐ and polyunsaturated FAs in various AT compartments by localized ¹H‐MRS in order to obtain insight into the intra‐ and interindividual variability. Associations of FA unsaturation with intrahepatic lipids (IHLs), insulin sensitivity and related AT volumes were analyzed. Fifty healthy Caucasians (36 male, 14 female) participated in this study. Spectroscopic examinations were performed in subcutaneous adipose tissue in the neck (SCAT_neck), abdominal deep subcutaneous adipose tissue (DSCAT), abdominal superficial subcutaneous adipose tissue (SSCAT), visceral adipose tissue (VAT), tibial bone marrow (BM) and subcutaneous adipose tissue of the lower leg (SCAT_calf) at 3 T. Unsaturated index (UI) was calculated by the ratio of olefinic and methyl resonances, polyunsaturated index (PUI) by the ratio of diallylic and methyl resonances. Volumes of AT compartments (by T₁‐weighted MRI) and IHL (single‐voxel STEAM) were assessed at 1.5 T, insulin sensitivity by an oral glucose tolerance test. UI was highest for SCAT_calf (0.622) and lowest for BM (0.527). Highest PUI was observed for SSCAT (0.108), lowest for BM (0.093). Significant intraindividual differences between UIs—but not PUIs—are present for most compartments. There is a non‐significant trend for higher UI in males but otherwise no correlation to anthropometric data (age, BMI). A significant negative correlation between UI and AT volume was observed for VAT but for none of the other compartments. Neither UIs nor PUIs show a relation with IHL; insulin sensitivity is significantly correlated to UI in BM (p < 0.01). Unsaturation indices in several distinct AT compartments are location dependent. Our cohort showed only moderate gender‐related differences, with a trend towards less unsaturated FAs (mainly PUI) in females. In BM, insulin resistant subjects are characterized by a higher UI compared with the insulin sensitive ones. Further studies in larger cohorts are necessary to gain further insight into unsaturation of AT.     

Comparison of T1 relaxation times in adipose tissue of severely obese patients and healthy lean subjects measured by 1.5 T MRI

Subcutaneous (SAT) and visceral adipose tissue (VAT) differ in composition, endocrine function and localization in the body. VAT is considered to play a role in the pathogenesis of insulin resistance, type 2 diabetes, fatty liver disease, and other obesity‐related disorders. It has been shown that the amount, distribution, and (cellular) composition of adipose tissue (AT) correlate well with metabolic conditions. In this study, T₁ relaxation times of AT were measured in severely obese subjects and compared with those of healthy lean controls. Here, we tested the hypothesis that T₁ relaxation times of AT differ between lean and obese individuals, but also between VAT and SAT as well as superficial (sSAT) and deep SAT (dSAT) in the same individual. Twenty severely obese subjects (BMI 41.4 ± 4.8 kg/m²) and ten healthy lean controls matched for age (BMI 21.5 ± 1.9 kg/m²) underwent MRI at 1.5 T using a single‐shot fast spin‐echo sequence (short‐tau inversion recovery) at six different inversion times (T_I range 100–1000 ms). T₁ relaxation times were computed for all subjects by fitting the T_I‐dependent MR signal intensities of user‐defined regions of interest in both SAT and VAT to a model function. T₁ times in sSAT and dSAT were only measured in obese patients. For both obese patients and controls, the T₁ times of SAT (275 ± 14 and 301 ± 12 ms) were significantly (p < 0.01) shorter than the respective values in VAT (294 ± 20 and 360 ± 35 ms). Obese subjects also showed significant (p < 0.01) T₁ differences between sSAT (268 ± 11 ms) and dSAT (281 ± 19 ms). More important, T₁ differences in both SAT and VAT were highly significant (p < 0.001) between obese patients and healthy subjects. The results of our pilot study suggest that T₁ relaxation times differ between severely obese patients and lean controls, and may potentially provide an additional means for the non‐invasive assessment of AT conditions and dysfunction. Copyright © 2014 John Wiley & Sons, Ltd.