Brown Fat and Obesity

Obesity results from an imbalance between energy intake and expenditure.  The adipose-tissue pool in mammals is composed of at least two functionally different types of fat: white and brown. White adipose tissue is the primary site of energy storage and of release of hormones and inflammatory cytokines that modulate whole-body metabolism and insulin resistance.  Excess accumulation of white adipose tissue is the prime cause of obesity.

Brown adipose tissue, on the other hand, is important for both basal and inducible energy expenditure in the form of thermogenesis (heat generation) mediated by the expression of the tissue-specific uncoupling protein 1 (UCP1).

Brown adipose tissue affects whole-body metabolism and may alter insulin sensitivity and modify susceptibility to weight gain. Estimates suggest that as little as 50 g of maximally stimulated brown adipose tissue could account for up to 20% of daily energy expenditure in an adult human.

There is evidence that stimulating adaptive thermogenesis, defined as the facultative heat produced in response to cold and diet manipulation (like keto-adaptation), might serve as a means of preventing or treating obesity; thus, it is of interest to understand the mechanisms underlying adaptive thermogenesis.

Individual differences in energy expenditure can have large, long-term effects on body composition and weight. Several prospective studies have shown that a relatively low energy expenditure predicts a gain in body weight (often due to low basal metabolic rates). Hence, adaptive thermogenesis may be an attractive target for anti-obesity therapies.

Many studies have indicated that brown adipose tissue in rodents has profound effects on body weight, energy balance, and glucose metabolism, and the presence of brown adipose tissue has been observed in adult humans under circumstances of long-term exposure to cold or of hyper adrenergic stimulation in pheochromocytoma.  

Of great interest to me with my understanding of keto-diets and keto-adaptation, that certain dietary fuels such as fatty acids, and some drugs can alter expression of brown fat. Interestingly Beta-blockers are associated with weight gain in clinical practice possibly due to suppressed brown fat expression (through blocking adrenergic stimulation).

The depots of brown adipose tissue have similar distributions in both men and women, but the mass and activity of brown adipose tissue are greater in women than in men. Other factors appear to be associated with a higher mass of brown adipose tissue. There appears to be an interaction between brown adipose tissue and obesity with an inverse correlation between the prevalence of detectable brown adipose tissue and BMI (higher BMI correlates low brown fat); suggesting that higher levels of brown adipose tissue may protect against age-related obesity (remember to survival affect in neonates)..

 

These results are consistent with murine studies showing that strains with higher levels of intermuscular brown adipose tissue are protected from diet-induced obesity and diabetes. 

Humans, like mice, have a range of metabolic rates. Thus, methods to stimulate generation and activation of brown adipose tissue might lead to new approaches to promoting weight loss and increasing insulin sensitivity (as we see in keto-adaptation). There is recent evidence that brown adipose tissue is embryonically more closely related to skeletal muscle than to white adipose tissue. A putative shared lineage between brown adipose tissue and skeletal muscle may provide clues about the origins of stem cells that lead to the formation of brown fat and to adaptive thermogenesis. This also raises important questions as whether physical training can stimulate and activate brown adipose tissue, adding to maintaining a high metabolic rate.

I think you will agree we are a remarkably beautifully created people in the image of God.

1 Timothy 2:6

6 If you point these things out to the brothers and sisters, you will be a good minister of Christ Jesus, nourished on the truths of the faith and of the good teaching that you have followed. 7 Have nothing to do with godless myths and old wives’ tales; rather, train yourself to be godly. 8 For physical training is of some value, but godliness has value for all things, holding promise for both the present life and the life to come. 9 This is a trustworthy saying that deserves full acceptance. 10 That is why we labor and strive, because we have put our hope in the living God, who is the Savior of all people, and especially of those who believe.

Blessings

Cardiologydoc

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3 thoughts on “Brown Fat and Obesity

  1. I have been surfing online more than 3 hours today, yet I
    never found any interesting article like yours.
    It is pretty worth enough for me. Personally, if all webmasters and bloggers made good content as you
    did, the net will be much more useful than ever before.

  2. thanks for interesting article!
    will you let me know the reference (original article)of the picture of PET?

    Akiko

    • Hi Akiko

      Try: Cold-Activated Brown Adipose Tissue in Healthy Men
      Wouter D. van Marken Lichtenbelt, Ph.D., Joost W. Vanhommerig, M.S., Nanda M. Smulders, M.D., Jamie M.A.F.L. Drossaerts, B.S., Gerrit J. Kemerink, Ph.D., Nicole D. Bouvy, M.D., Ph.D., Patrick Schrauwen, Ph.D., and G.J. Jaap Teule, M.D., Ph.D.
      N Engl J Med 2009; 360:1500-1508April 9, 2009DOI: 10.1056/NEJMoa0808718

      Cardiologydoc

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