Adipose tissue is more then a place for storing useless fat!

… or a more closer look on the other side of  the coin

Isn’t it amazing how science and its view on the body changes over the years, decades and centuries. Just to give you some examples: Neurones and nerve tissue were considered to be without any potential for regeneration, the muscle cell was coined as a cell without abilities to multiply and adapt, and adipose tissue still has got this negative flavor of being a burden (aesthetic view) and health hazard (medicinal view) only. Fashion on the one hand and medicine on the other hand stand for these extreme positions.
And now the breaking news: Adipose tissue is an endocrine and immunologically highly active organ. Some of you may know already that the adipocytes are producing and secreting a broad spectrum of soluble mediators that engaged in the regulation of appetite and weight. But what may be brand new to all of us who are not specifically involved in this topic of research, may be the fact that adipose tissue connects the immune system with metabolism, an interesting aspect for athletes by the way, who in many ways got a quite hysterical attitude towards fat. Fat is still seen as an inactive mass of cells that we need as energy supply in austere times only.

And now science comes in, and everything should be different? Yes, it is. More and more scientists realize, that  the body is one functional unit, and so, fat is an integral part of it. Very recent scientific data suggest that adipose tissue secretes a wide variety of hormones and proteins that regulate whole body homeostasis (balance) involving nearly all organs and cells. Scientists discovered molecular pathways that connect the adipose tissue with the immune system, and vice versa. they found out, that so many active molecules that have been assigned to the immune system only are secreted by adipocytes too. Nice to observe for me that step by step scientists who themselves erected the walls within the body are tearing them down themselves realizing that the borders they were defining are artificial, not applicable and suitable to explain the phenomenon body. Now walls have been destroyed between the nervous system and the immune system the process has expanded to the adipose tissue. Maybe fat is getting more positive attention soon.

I am not talking about obesity in this article. I want create awareness and address to those who want to be lean and perform on top level. To talk about the disease-inducing aspects of obesity is of course very important and has to do with the interdependency between body fat and immune system as well. Obesity is pushing the body into an inflammatory condition with a sincere consequence for the vessels and the body’s metabolic situation (diabetes-2 etc.). But now back to physiology, and details on pathophysiology another time.

Adipose tissue is directly connected with innate immunity, it is involved in all inflammatory and healing processes.

It expresses proinflammatory, anti-inflammatory and immunomodulating properties. Until today more than 100 molecules (peptides and proteins) have been identified. All these molecules can be seen as immunologically, metabolically and as neurologically active… all these systems are tightly intertwined. Therefore one can measure immunological alterations (CRP, TNF, IL-6) in various metabolic disturbances (Insulin resistance, important for athletes under stress; diabetes 2, obesity etc.).
The role of adipose tissue should thus been defined as a gateway connecting energy metabolism with immune function, they all influence each other.

Innate immunity is inducing adaptive immunity and is connecting us to the world, in a positive cooperative way like we live peacefully with our microbiota and negatively in the sense that invaders like viruses and bacteria are tackled. Through the pathway between adipose tissue and immune system saturated fatty acids from nutrition or endogenously degraded from triglycerol may have inflammatory potential, if a metabolic dysbalance is obvious. Here unsatured fatty acids enter the game (about these essential nutrients another time).

This was not more than a very rough approach to a complex topic that could easily cover book pages. Nevertheless, I hope I got the message across that we all have to re-instate the importance of fatty tissue. Fat makes fat, no! not true, to much food does so, fat is essential for health, energy supplies, and a proper immune function, and it is of extraordinary importance in endurance performance (about this topic in one of my next articles). To much fatty tissue induces harmful systemic inflammation harming first of all vessels and metabolism, but lack of adipose tissue leads to immunodefiecences and metabolic disturbances too. It is all about balancing our body, a real challenge for all of us to see the whole and not only the parts.

Let’s rethink our attitude towards adipose tissue, it is high time for that. We should not only demonize it.

Reference:
Schäffler A, Schölmerich J. Innate Immunity and adipose tissue biology: Trends in Immunology, 31(6), 228-235, 2010