Postnatal changes in lambs of two pathways for thyroxine 5'-monodeiodination in brown adipose tissue

We have recently shown that ovine fetal brown adipose tissue (BAT) contains two distinct iodothyronine 5'-monodeiodinase (5'MDI) activities, one with a high Km (type I) and another with a low Km (type II). Both activities increased to maximum levels near term (150 days gestation). BAT plays a major role in neonatal temperature regulation in lambs, and available evidence suggests that BAT 5'MDI activity is closely linked to thermogenic capacity. To better characterize the changes in 5'MDI after birth, we studied both type I and type II 5'MDI in lamb BAT from the time of birth to 30 days of postnatal age. Type I 5'MDI activity [pmol 3,5,3'-triiodothyronine (T3).mg protein-1.h-1] showed no significant changes during the first 11 days after birth [newborn (NB), 95 +/- 16; 1 day, 83 +/- 20; 3-4 days, 80 +/- 11; 10-11 days, 92 +/- 28]. Activity decreased significantly at 30 days (24 +/- 8.9, P less than 0.05). On the other hand, the type II 5'MDI activity (fmol I- released.mg protein-1.h-1) increased significantly (P less than 0.01) during the first 4 days, (NB, 348 +/- 23; 1 day, 679 +/- 37; 3-4 days, 785 +/- 199), decreased toward NB values (401 +/- 87) at 10-11 days of age, and fell to 66 +/- 31 at 30 days (P less than 0.05 vs. NB). Kinetic analysis of BAT type II thyroxine 5'MDI revealed a rise in maximum velocity from NB to 1 and 3-4 days of age without a change in the enzymatic activity Km.(ABSTRACT TRUNCATED AT 250 WORDS)

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Central stimulatory effect of leptin on T3production is mediated by brown adipose tissue type II deiodinase

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00196.2002 ◽

2002 ◽

Vol 283 (5) ◽

pp. E980-E987 ◽

Cited By ~ 31

Author(s):

Philippe Cettour-Rose ◽

Albert G. Burger ◽

Christoph A. Meier ◽

Theo J. Visser ◽

Françoise Rohner-Jeanrenaud

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Mrna Expression ◽

Uncoupling Protein ◽

Tissue Type ◽

Type I ◽

Type Ii ◽

Brown Adipose ◽

Small Doses ◽

Food Consumed

To assess whether intracerebroventricular leptin administration affects monodeiodinase type II (D2) activity in the tissues where it is expressed [cerebral cortex, hypothalamus, pituitary, and brown adipose tissue (BAT)], hepatic monodeiodinase type I (D1) activity was inhibited with propylthiouracil (PTU), and small doses of thyroxine (T4; 0.6 nmol · 100 g body wt−1 · day−1) were supplemented to compensate for the PTU-induced hypothyroidism. Two groups of rats were infused with leptin for 6 days, one of them being additionally treated with reverse triiodothyronine (rT3), an inhibitor of D2. Control rats were infused with vehicle and pair-fed the amount of food consumed by leptin-infused animals. Central leptin administration produced marked increases in D2 mRNA expression and activity in BAT, changes that were likely responsible for increased plasma T3 and decreased plasma T4 levels. Indeed, plasma T3 and T4 concentrations were unaltered by central leptin administration in the presence of rT3. The additional observation of a leptin-induced increased mRNA expression of BAT uncoupling protein-1 suggested that the effect on BAT D2 may be mediated by the sympathetic nervous system.

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Decreased liver type I 5′-deiodinase and increased brown adipose tissue type II 5′-deiodinase activity in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-treated Long-Evans rats

Toxicology ◽

10.1016/s0300-483x(96)03488-9 ◽

1996 ◽

Vol 114 (3) ◽

pp. 199-205 ◽

Cited By ~ 18

Author(s):

A Raasmaja

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Tissue Type ◽

Type I ◽

Type Ii ◽

Deiodinase Activity ◽

Brown Adipose ◽

Long Evans ◽

Tetrachlorodibenzo P Dioxin

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Mitochondria Isolated from Rat Brown Adipose Tissue and Liver

The Journal of Cell Biology ◽

10.1083/jcb.4.3.287 ◽

1958 ◽

Vol 4 (3) ◽

pp. 287-290 ◽

Cited By ~ 94

Author(s):

J. D. Lever ◽

J. B. Chappell

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Liver Mitochondria ◽

Type I ◽

Type Ii ◽

Numerous Type ◽

Mitochondrial Fractions ◽

Brown Adipose ◽

Cytoplasmic Structures ◽

Brown Fat Mitochondria

Mitochondrial fractions, relatively free from contamination by other cytoplasmic structures, have been isolated by differential centrifugation from homogenates of brown adipose tissue from starved rats. It was possible in such fractions to distinguish two types of mitochondria in this tissue. Type I mitochondria, when morphologically intact, are limited by a bilaminar membrane and show regular parallel cristae. In isolated fractions, a proportion of these mitochondria are swollen, vacuolation occurring within the cristae between their limiting membranes. Type II mitochondria are distinguished from the more numerous type I bodies by the opaque appearance of their matrix. They are limited by a membrane which is in part single, and in part double. They show a few, but crisply outlined internal membranes. Vacuolation of this type of mitochondrion has not been observed. Vacuolation comparable to that in brown fat mitochondria was also observed between the two laminae of the enclosing membrane and within the cristae of liver mitochondria.

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Cold-induced changes in brown adipose tissue thermogenic capacity of immunocompetent and immunodeficient hairless mice

Journal of Comparative Physiology B ◽

10.1007/bf00714583 ◽

1994 ◽

Vol 164 (6) ◽

pp. 459-463 ◽

Cited By ~ 4

Author(s):

J. Houštěk ◽

M. Holub

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Hairless Mice ◽

Brown Adipose ◽

Induced Changes ◽

Thermogenic Capacity

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Brown adipose tissue metabolism in ob/ob mice: effects of a high-fat diet and adrenalectomy

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1987.253.2.e149 ◽

1987 ◽

Vol 253 (2) ◽

pp. E149-E157

Author(s):

H. K. Kim ◽

D. R. Romsos

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

High Fat Diet ◽

High Fat ◽

Adipose Tissue Metabolism ◽

High Carbohydrate ◽

Bat Mitochondria ◽

Norepinephrine Turnover ◽

Brown Adipose ◽

Thermogenic Capacity

Adrenalectomy prevents development of obesity in ob/ob mice fed high-carbohydrate stock diets partly by stimulating the low thermogenic capacity of their brown adipose tissue (BAT). Adrenalectomy, however, fails to prevent development of obesity in ob/ob mice fed a high-fat diet. Effects of adrenalectomy on BAT metabolism in ob/ob mice fed a high-fat diet were thus examined. ob/ob mice fed the high-fat diet developed gross obesity despite normal BAT metabolism, as assessed by rates of norepinephrine turnover in BAT, GDP binding to BAT mitochondria, and GDP-inhibitable, chloride-induced mitochondrial swelling. Adrenalectomy failed to arrest the development of obesity or to influence BAT metabolism in ob/ob mice fed the high-fat diet. Development of obesity in ob/ob mice fed a high-fat diet is not associated with low thermogenic capacity of BAT or with adrenal secretions, as it is in ob/ob mice fed high-carbohydrate stock diets.

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