TSH suppression aggravates arterial inflammation - an 18F-FDG PET study in thyroid carcinoma patients.

PURPOSE: We aimed to investigate the influence of both hypothyroidism and thyroid-stimulating hormone (TSH) suppression on vascular inflammation, as assessed with 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT). METHODS: Ten thyroid carcinoma patients underwent an 18F-FDG PET/CT during post-thyroidectomy hypothyroidism and during thyrotropin (TSH) suppression after 131I (radioiodine) ablation therapy. We analysed the 18F-FDG uptake in the carotids, aortic arch, ascending, descending, and abdominal aorta to investigate the effects of thyroid hormone status on arterial inflammation. Target-to-background ratios (TBRs) corrected for blood pool activity were established for all arterial territories. Results were further compared to euthyroid historic control subjects. RESULTS: In general, there was a trend towards higher vascular TBRs during TSH suppression than during hypothyroidism (TBRmax all vessels = 1.6 and 1.8, respectively, p = 0.058), suggesting a higher degree of arterial inflammation. In concurrence with this, we found increased C-reactive protein (CRP) levels after levothyroxine treatment (CRP = 2.9 mg/l and 4.8 mg/l, p = 0.005). An exploratory comparison with euthyroid controls showed significant higher TBRs during TSH suppression for the carotids, aortic arch, thoracic descending aorta, and when all vascular territories were combined (TBRmaxp = 0.013, p = 0.016, p = 0.030 and p = 0.018 respectively). CONCLUSIONS: Arterial inflammation is increased during TSH suppression. This finding sheds new light on the underlying mechanism of the suspected increased risk of cardiovascular disease in patients with TSH suppression.

Correction: Thyroid Hormone Activates Brown Adipose Tissue and Increases Non-Shivering Thermogenesis-A Cohort Study in a Group of Thyroid Carcinoma Patients.

[This corrects the article DOI: 10.1371/journal.pone.0145049.].

Genetic Markers of Brown Adipose Tissue Identity and In Vitro Brown Adipose Tissue Activity in Humans.

OBJECTIVE: Human brown adipose tissue (BAT) activity decreases with age and obesity. In addition to uncoupling protein 1 (UCP1), several genetic markers of BAT in humans have been published. However, the link between human BAT activity and genetic markers has been inadequately explored. METHODS: White adipose tissue (WAT) and BAT biopsies were obtained from 16 patients undergoing deep neck surgery. In vitro differentiated adipocytes were used to measure norepinephrine-stimulated mitochondrial uncoupling as a measure of in vitro BAT activity. Gene expression was determined in adipose tissue biopsies. RESULTS: Norepinephrine increased in vitro BAT activity in adipocytes derived from human BAT, and this increase was abolished by propranolol. Furthermore, in vitro BAT activity showed a negative correlation to age and BMI. UCP1 messenger RNA (mRNA) expression showed a positive correlation to in vitro BAT activity, while zinc finger protein of cerebellum 1 (ZIC1) mRNA showed a negative correlation to in vitro BAT activity. In human BAT biopsies, UCP1 mRNA showed negative correlations to age and BMI, while ZIC1 mRNA showed positive correlations to age and BMI. CONCLUSIONS: Differentiated adipocytes derived from human BAT maintain intrinsic characteristics of the donor. High ZIC1 mRNA does not necessarily reflect high BAT activity.

Thyroid Hormone Activates Brown Adipose Tissue and Increases Non-Shivering Thermogenesis--A Cohort Study in a Group of Thyroid Carcinoma Patients.

BACKGROUND/OBJECTIVES: Thyroid hormone receptors are present on brown adipose tissue (BAT), indicating a role for thyroid hormone in the regulation of BAT activation. The objective of this study was to examine the effect of thyroid hormone withdrawal followed by thyroid hormone in TSH-suppressive dosages, on energy expenditure and brown adipose tissue activity. SUBJECTS/METHODS: This study was a longitudinal study in an academic center, with a follow-up period of 6 months. Ten patients with well-differentiated thyroid carcinoma eligible for surgical treatment and subsequent radioactive iodine ablation therapy were studied in a hypothyroid state after thyroidectomy and in a subclinical hyperthyroid state (TSH-suppression according to treatment protocol). Paired two-tailed t-tests and linear regression analyses were used. RESULTS: Basal metabolic rate (BMR) was significantly higher after treatment with synthetic thyroid hormone (levothyroxine) than in the hypothyroid state (BMR 3.8 ± 0.5 kJ/min versus 4.4 ± 0.6 kJ/min, P = 0.012), and non-shivering thermogenesis (NST) significantly increased from 15 ± 10% to 25 ± 6% (P = 0.009). Mean BAT activity was significantly higher in the subclinical hyperthyroid state than in the hypothyroid state (BAT standard uptake value (SUVMean) 4.0 ± 2.9 versus 2.4 ± 1.8, P = 0.039). CONCLUSIONS: Our study shows that higher levels of thyroid hormone are associated with a higher level of cold-activated BAT. TRIAL REGISTRATION: ClinicalTrials.gov NCT02499471.

The Bile Acid Chenodeoxycholic Acid Increases Human Brown Adipose Tissue Activity.

The interest in brown adipose tissue (BAT) as a target to combat metabolic disease has recently been renewed with the discovery of functional BAT in humans. In rodents, BAT can be activated by bile acids, which activate type 2 iodothyronine deiodinase (D2) in BAT via the G-coupled protein receptor TGR5, resulting in increased oxygen consumption and energy expenditure. Here we examined the effects of oral supplementation of the bile acid chenodeoxycholic acid (CDCA) on human BAT activity. Treatment of 12 healthy female subjects with CDCA for 2 days resulted in increased BAT activity. Whole-body energy expenditure was also increased upon CDCA treatment. In vitro treatment of primary human brown adipocytes derived with CDCA or specific TGR5 agonists increased mitochondrial uncoupling and D2 expression, an effect that was absent in human primary white adipocytes. These findings identify bile acids as a target to activate BAT in humans.

Serum FGF21 levels are associated with brown adipose tissue activity in humans.

The obesity pandemic has spurred a need for novel therapies to prevent and treat metabolic complications. The recent rediscovery of brown adipose tissue (BAT) in humans made this tissue a possible therapeutic target, due to its potentially substantial contributions to energy homeostasis. Fibroblast growth factor 21 (FGF21) has been identified as a facilitator of cold-induced thermogenesis in humans. Furthermore, pre-clinical studies revealed that FGF21 administration leads to improvement in the metabolic consequences of obesity, such as dyslipidemia and type 2 diabetes. Here we studied plasma FGF21 levels in two cohorts of human subjects, in whom BAT activity was determined using an individualized cooling protocol by [(18)F]FDG-PET/CT scan. Importantly, we found that circulating FGF21 levels correlated with BAT activity during acute cold exposure in male subjects. In addition, FGF21 levels were related to the change in core temperature upon acute cold exposure, indicating a role for FGF21 in maintaining normothermia, possibly via activation of BAT. Furthermore, cold acclimation increased BAT activity in parallel with increased FGF21 levels. In conclusion, our results demonstrate that FGF21 levels in humans are related to BAT activity, suggesting that FGF21 may represent a novel mechanism via which BAT activity in humans may be enhanced.

Verres needle desufflation as an effective treatment option for colonic perforation after colonoscopy.

BACKGROUND: This study aimed to assess the incidence of colonoscopic perforation and the efficacy of minimal invasive management by Verres needle desufflation. MATERIALS AND METHODS: All colonoscopies performed between January 2007 and January 2012, at the Maastricht University Medical Centre, were reviewed. RESULTS: During the study period, 18,449 colonoscopies were performed. Fourteen colonoscopic perforations were diagnosed. Seven patients underwent immediate surgery, whereas the remaining 7 patients were initially managed conservatively: 5 of these patients also underwent Verres needle desufflation. One of the patients who received Verres needle desufflation underwent secondary surgery because of failure of nonsurgical treatment. Conservative management of colonoscopic perforation, including treatment with Verres needle desufflation, was associated with lower complication rates and shorter hospital stays compared with immediate surgical intervention. CONCLUSIONS: Verres needle desufflation in combination with nil per os and antibiotic treatment is a safe option for managing colon perforation after colonoscopy in selected patients lacking clinical signs of peritonitis or sepsis.

Endogenous ways to stimulate brown adipose tissue in humans.

Obesity is the result of disequilibrium between energy intake and energy expenditure (EE). Successful long-term weight loss is difficult to achieve with current strategies for the correction of this caloric imbalance. Non-shivering thermogenesis (NST) in brown adipose tissue (BAT) is a possible therapeutic target for the prevention and treatment of obesity and associated metabolic diseases. In recent years, more knowledge about the function and stimulation of bat has been obtained. The sympathetic nervous system (SNS) is currently seen as the main effector for brown fat function. Also, interplay between the thyroid axis and SNS plays an important role in BAT thermogenesis. Almost daily new pathways for the induction of BAT thermogenesis and 'browning' of white adipose tissue (WAT) are identified. Especially the activation of BAT via endogenous pathways has received strong scientific attention. Here we will discuss the relevance of several pathways in activating BAT and their implications for the treatment of obesity. In this review we will focus on the discussion of the most promising endocrine and paracrine pathways to stimulate BAT, by factors and pathways that naturally occur in the human body.