Response of brown adipose tissue to an oral glucose load in virgin and lactating rats

Objective Human brown adipose tissue (BAT) is a thermogenic tissue activated by the sympathetic nervous system in response to cold. It contributes to energy expenditure (EE) and takes up glucose and lipids from the circulation. Studies in rodents suggest that BAT contributes to the transient rise in EE after food intake, so called diet-induced thermogenesis (DIT). We investigated the relationship between human BAT activity and DIT in response to glucose intake in 17 healthy volunteers. Methods We assessed DIT, cold induced thermogenesis (CIT) and maximum BAT activity at three separate study visits within two weeks. DIT was measured by indirect calorimetry during an oral glucose tolerance-test. CIT was assessed as the difference in EE after cold exposure of two hours duration as compared to warm conditions. Maximal activity of BAT was assessed by 18F-FDG-PET/MRI after cold exposure and concomitant pharmacological stimulation with Mirabegron. Results 17 healthy men (mean age 23.4 years, mean BMI 23.2 kg/m2) participated in the study. EE increased from 1908 (±181) kcal/24 hours to 2128 (±277) kcal/24 hours (p<0.0001, +11.5%) after mild cold exposure. An oral glucose load increased EE from 1911 (±165) kcal/24 hours to 2096 (±167) kcal/24 hours at 60 minutes (p<0.0001, +9.7%). The increase in EE in response to cold was significantly associated with BAT activity (R2=0.43, p=0.004). However, DIT was not associated with BAT activity (R2=0.015, p=0.64). Conclusion DIT after an oral glucose load was not associated with stimulated 18F-FDG uptake into BAT suggesting that DIT is independent from BAT activity in humans.

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Lipogenesis in response to an oral glucose load in fed and starved rats

Bioscience Reports ◽

10.1007/bf01121580 ◽

1981 ◽

Vol 1 (6) ◽

pp. 469-476 ◽

Cited By ~ 11

Author(s):

Mary C. Sugden ◽

David L. Watts ◽

Christopher E. Marshall

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Brown Fat ◽

Oral Glucose ◽

Oral Glucose Load ◽

Glucose Load ◽

Palmitoyl Carnitine ◽

Carnitine Acyltransferase ◽

Malonyl Coa ◽

Brown Adipose

Lipogenesis in livers of fed but not of starved rats is increased after intragastric feeding with glucose. In contrast, lipogenesis in brown adipose tissue increases in both fed and starved animals. These observations suggest that lipogenesis in brown adipose tissue is regulated by mechanisms in addition to, or other than, those operating in liver. The fate of newly synthesized lipid in brown adipose tissue is not known. However, the formation of palmitoyl-carnitine from palmitoyl-CoA and carnitine by mitochondria from brown fat was inhibited by malonyl-CoA. Although inhibition was not 100%, it is implied that mitochondrial uptake of the newly synthesized fat by the carnitine acyltransferase system is restricted under conditions of increased lipogenesis.

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Multimodal Imaging for the Detection of Brown Adipose Tissue Activation in Women: A Pilot Study Using NIRS and Infrared Thermography

Journal of Healthcare Engineering ◽

10.1155/2017/5986452 ◽

2017 ◽

Vol 2017 ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

Valentina Hartwig ◽

Letizia Guiducci ◽

Martina Marinelli ◽

Laura Pistoia ◽

Tommaso Minutoli Tegrimi ◽

...

Keyword(s):

Adipose Tissue ◽

Pilot Study ◽

Brown Adipose Tissue ◽

Infrared Thermography ◽

Pharmacological Intervention ◽

Oral Glucose ◽

Cold Stimulation ◽

Standard Clinical Practice ◽

Obesity And Diabetes ◽

Brown Adipose

Purpose. A clear link between obesity and brown adipose tissue (BAT) dysfunction has been recently demonstrated. The purpose of this pilot study is to determine if near-infrared spectroscopy (NIRS) 2D imaging together with infrared thermography (IRT) is capable of identifying thermal and vascular response in the supraclavicular (SCV) areas after the ingestion of an oral glucose load as a thermogenic stimulation. Method. We studied two groups of women (obese versus lean) for discerning their different responses. NIRS and IRT images were acquired on the neck in the left SCV region during a 3 h oral glucose tolerance test (OGTT) and immediately after a cold stimulation. Results. We detected a significant thermal response of BAT in SCV fossa in both groups. Both during OGTT and after cold stimulation, skin temperature was persistently higher in lean versus obese. This response was not coupled with changes in oxygen saturation of subcutaneous tissue in that area. Discussion and Conclusion. The results show that NIRS/IRT may be a novel, noninvasive, radiation-free, easy to use, and low-cost method for monitoring, during the standard clinical practice, the diet and pharmacological intervention which aims to stimulate BAT as a potential therapeutic target against obesity and diabetes.

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Effects of metformin on metabolism of white and brown adipose tissue in obese C57BL/6J mice

Diabetology & Metabolic Syndrome ◽

10.1186/s13098-019-0490-2 ◽

2019 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Tao Yuan ◽

Juan Li ◽

Wei-Gang Zhao ◽

Wei Sun ◽

Shuai-Nan Liu ◽

...

Keyword(s):

Adipose Tissue ◽

Insulin Sensitivity ◽

Glucose Tolerance ◽

Brown Adipose Tissue ◽

Tolerance Test ◽

Normal Diet ◽

The Body ◽

Oral Glucose ◽

Obese Mice ◽

Brown Adipose

Abstract Background To investigate effects of metformin on the regulation of proteins of white adipose tissue (WAT) and brown adipose tissue (BAT) in obesity and explore the underlying mechanisms on energy metabolism. Methods C57BL/6J mice were fed with normal diet (ND, n = 6) or high-fat diet (HFD, n = 12) for 22 weeks. HFD-induced obese mice were treated with metformin (MET, n = 6). After treatment for 8 weeks, oral glucose tolerance test (OGTT) and hyperinsulinemic–euglycemic clamp were performed to evaluate the improvement of glucose tolerance and insulin sensitivity. Protein expressions of WAT and BAT in mice among ND, HFD, and MET group were identified and quantified with isobaric tag for relative and absolute quantification (iTRAQ) coupled with 2D LC–MS/MS. The results were analyzed by MASCOT, Scaffold and IPA. Results The glucose infusion rate in MET group was increased significantly compared with HFD group. We identified 4388 and 3486 proteins in WAT and BAT, respectively. As compared MET to HFD, differential expressed proteins in WAT and BAT were mainly assigned to the pathways of EIF2 signaling and mitochondrial dysfunction, respectively. In the pathways, CPT1a in WAT, CPT1b and CPT2 in BAT were down-regulated by metformin significantly. Conclusions Metformin improved the body weight and insulin sensitivity of obese mice. Meanwhile, metformin might ameliorate endoplasmic reticulum stress in WAT, and affect fatty acid metabolism in WAT and BAT. CPT1 might be a potential target of metformin in WAT and BAT.

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Blood flow in skin, subcutaneous adipose tissue and skeletal muscle in the forearm of normal man during an oral glucose load

Acta Physiologica Scandinavica ◽

10.1111/j.1748-1716.1987.tb08189.x ◽

1987 ◽

Vol 130 (4) ◽

pp. 657-661 ◽

Cited By ~ 44

Author(s):

J. BULOW ◽

A. ASTRUP ◽

N. J. CHRISTENSEN ◽

J. KASTRUP

Keyword(s):

Skeletal Muscle ◽

Blood Flow ◽

Adipose Tissue ◽

Subcutaneous Adipose Tissue ◽

Oral Glucose ◽

Oral Glucose Load ◽

Glucose Load ◽

Normal Man ◽

Subcutaneous Adipose

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The Effect of Starvation and Diabetes on Glycolytic Enzymes in Human Adipose Tissue

Clinical Science ◽

10.1042/cs0410545 ◽

1971 ◽

Vol 41 (6) ◽

pp. 545-553 ◽

Cited By ~ 15

Author(s):

D. J. Galton ◽

J. P. D. Wilson

Keyword(s):

Adipose Tissue ◽

Blood Glucose ◽

Negative Correlation ◽

Marked Decrease ◽

Fasting Blood Glucose ◽

Human Adipose Tissue ◽

Oral Glucose ◽

Oral Glucose Load ◽

Glucose Load ◽

And Control

1. The activities of hexokinase (EC 2.7.1.1) and phosphofructokinase (EC 2.7.1.11) have been studied in homogenates of adipose tissue taken from human diabetics, fasting and control patients. 2. Three isoenzymes of hexokinase were observed with apparent Km values for glucose of 1.04 × 10-5 m, 2.6 × 10-4 m and 2.9 × 10-4 m, respectively. 3. No change in activity of hexokinase was found in adipose tissue of untreated diabetics (n = 22), treated diabetics (n = 13) or non-diabetic controls. However, fasting was associated with a decrease of approx. 40% in the activity of hexokinase in adipose tissue. 4. In contrast, there was a marked decrease in the activity of phosphofructokinase in adipose tissue from untreated diabetics (n = 24) which was restored to normal by either insulin therapy or treatment by hypoglycaemic drugs. 5. There was a negative correlation between the phosphofructokinase/hexokinase ratio in adipose tissue and the fasting blood glucose (P = 0.01) and the 2 h blood glucose (P = 0.03) after an oral glucose load (50 g). 6. The functional significance of the changes in enzyme activities is discussed in relation to the glucose intolerance of diabetes.

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Tissue differences in the response of the pyruvate dehydrogenase complex to a glucose load during the development of obesity in gold-thioglucose-obese mice

Biochemical Journal ◽

10.1042/bj3050811 ◽

1995 ◽

Vol 305 (3) ◽

pp. 811-816 ◽

Cited By ~ 6

Author(s):

J M Bryson ◽

G J Cooney ◽

V R Wensley ◽

J L Phuyal ◽

I D Caterson

Keyword(s):

Adipose Tissue ◽

Pyruvate Dehydrogenase ◽

Pyruvate Dehydrogenase Complex ◽

Quadriceps Muscle ◽

Oral Glucose ◽

Obese Mice ◽

Glucose Load ◽

Gold Thioglucose ◽

Brown Adipose ◽

Different Tissues

The activity of pyruvate dehydrogenase (PDHC), a key enzyme complex in the oxidative disposal of glucose, was measured after an oral glucose load in the heart, liver, quadriceps muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) of gold-thioglucose (GTG)-obese mice at different stages during the development of obesity and in age-matched controls. Significant responses to the glucose load were seen 30 min post-gavage in heart, WAT and BAT of control mice but no change was observed in quadriceps muscle. The increase in activity of the active form of PDHC (PDHCa) in response to glucose in heart was reduced 2 weeks after the induction of GTG-obesity with no response in 5 or 10 week obese mice. A 2-3-fold increase in the PDHCa response in both WAT and BAT of 2 week obese mice was absent in 5 and 10 week obese animals. Basal PDHCa activity in quadriceps muscle was increased in 2 week obese mice but subsequently returned to control levels as obesity progressed. The glucose load produced no change in the activity of PDHCa in quadriceps muscle of obese mice. These results demonstrate that changes in the capacity for oxidative glucose disposal in different tissues, as indicated by changes in PDHCa activity, may contribute to glucose-intolerance and insulin-resistance in GTG-obese mice and that the response of the PDHC to insulin during the development of obesity varies in different tissues.

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Functional characterization of human brown adipose tissue metabolism

Biochemical Journal ◽

10.1042/bcj20190464 ◽

2020 ◽

Vol 477 (7) ◽

pp. 1261-1286 ◽

Cited By ~ 3

Author(s):

Marie Anne Richard ◽

Hannah Pallubinsky ◽

Denis P. Blondin

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Functional Characterization ◽

Human Infants ◽

Positron Emission ◽

Brown Adipose ◽

Treatment Of Obesity ◽

And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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