|Can the guy on the right run away from the bloated macrophage coated fat cells on the left? Today's first post in the SuppVersity Exercise Science Week does hold the answer to this existential question.|
The solution I came up with is easy and in my humble opinion actually quite cool: The world's first SuppVersity Exercise Science Week! In the course of the next days, I will serve you one or two of the latest studies from the realms of exercise science per day - with the rest (if there is one) being "mashed up" in the Short News on Saturday. Cool? No? Well, bad luck, then ;-)
We will kick off the week with the modulatory effect of exercise on adipose tissue
We all know that exercise is a good way to support and control diet induced weight loss. Specifically for those of us who are already on the lean(er) side of a "divide", where obese is soon going to be the new normal (see "Obese is Going About to Become the New Normal"), it's probably even obligatory, if it's not being skinny fat that's our diet goal. That being said, a recent review of Izawa et al. provides a couple of intriguing insights and links between physical activity and the structural changes our white adipose tissue is undergoing (Izawa . 2013). In this first post of the SuppVersity Exercise Science Week I am going to summarize and expand on some of these points and point towards the implications these more or less recent, in parts pretty geeky and abstract findings have on the way we could, should, or might train:
- Training can increase lypolysis: Compared to subcutaneous fat (SAT), visceral fat (VAT) has a higher lipid turnover. Interestingly, the same high lypolytic rates which render people with high VAT so vulnerable to high levels of blood fats, are also responsible for the comparable ease with which you can shake those unhealthy VAT depots melt away, when you're working out and/or dieting. The fat around the organs is not just the easiest to store, it's also the easiest to access and liberate (Ross. 2000). That this is not a location-specific characteristic, has already been proven. What does yet still have to be elucidated, is when and due to which complex mechanisms the genetic differences between the subcutaneous and visceral fat cells are getting programmed and whether there may be a way to reverse them.
- Training will modulate the growth environment: The maturation of stem cells into SAT, VAT, or BAT (brown adipose tissue) cells appears to be highly dependent the specific milieu in which they are in. The latter, in turn, is characterized by the presence of various growth factors. The best known and allegedly most important ones belong to the transforming growth factor (TGF) family. It is their presence that will control whether a stem cell turns into a "brown" = metabollically active fat cell with thermogenic abilities or a regular white one (SAT or VAT). While BMP2- and BMP-4 are responsible for the formation of white adipocytes, BMP-7 drives brown fat cell development. Together with FGF21 another of those growth factors, these proteins determine the fate of pre-adipocytes. Unfortunately, the research on the different ways by which exercise controls these factors is yet still in its infancy. We will take a closer look at what we know already in the next paragraph.
As you know from the "CLA Destroys Body Fat" post, PPAR-γ downregulation is also the main pathway by which conjugated linolic acid strips mice of almost all their body fat (read more). The exercise induced upregulation of the so-called hypoxia-inducible factor (HIF-1α) appears to do the exact same thing: Suppress PPAR-γ and thus hit the off switch on body fat storage.
- Training improves angiogenesis in WAT: While you hear about angiogenesis, i.e. the physiological process through which new blood vessels form from pre-existing vessels, oftentimes in the context of various endothelial pathologies, its induction within the white adipose tissue is actually highly desirable. Scientists have long been speculating that the insufficient wiring of the adipose organ with blood vessels and the subsequent hypoxia are at least partly to blame for the constant inflammation in the ever-expanding fat depots of the obese (Ye. 2009). Since HIF-1α (see previous paragraph) also promotes the expression of vascular endothelial growth factors and their receptors (VEGFRs / VEGFs), its downstream activation by preferably intense physical activity should improve the endothelial wiring of the fat tissue and thus help sooth the chronic inflammation, that's at the heart of many, if not all of the key-features of the "metabolic syndrome".
- Training increases the adipocyte size depended release of adiponectin: In the past couple of months, the adipokine adiponectin turned out to do most of the good stuff (esp. improvements in glucose and fatty acid metabolism), of which scientists previously thought it was the prerogative of leptin. It is therefore important that exercise increases the rate at which a given increase in adipocyte size (obviously in response to fat storage) will increase the release of adiponectin (Miyazaki. 2010). If we use the classic notion of the adipokine as a signal the fat cells use to tell the brain and the rest of the body how much fat remains to fuel its energetic demands, you could say: Working out allows your body to see how much fat you actually got. The physiological consequences of this revelation are increases in lypolysis and fatty oxidation, as well as overall metabolic benefits.
Making HIIT a Hit! learn how in the SuppVersity Special (read more) and use it to get lean & healthy and, more importantly, stay lean and healthy!
- Wnt10B response to stretching - an argument for heavy eccentrics and/or statics to revamp your body (less fat, more muscle!): The findings of Akimoto et al. point towards the existence of another rather strength-training specific contributer to the fat loss and leanness promoting effects of exercise - the stretch-induced activation of the wingless-type (WNT) MMV integration site family member WNT10b, the quasi cousin of an upstream mediator of HIF-1α (Akimoto. 2005). The activation of the WTNs does actually get down to the root of the trouble and will not just inhibit the formation of new fat cells from pre-adipocytes, it will also divert the mesenchymal and not yet specialized stem cells to turn into osteroblasts (bone) or myoblasts (muscle). In fact, research has shown that WNT signaling is a major contributer to both the recruitment of new muscle progenitor cells from the aforementioned pool of yet unspecific stem cells and skeletal muscle hypertrophy (Polesskaya. 2005; Armstrong. 2005).
You will also benefit from integrating plyometrics into your existing routine - build the Jack of All Traits Workout
- Exercise restores your body's fat gauge: If you wanted to pointedly summarize the exercise induced reductions in leptin expression, the associated restoration of leptin sensitivity in the obese, and the increased adiponectin release relative to the increase in fat cell diameter, you could actually say that exercise restores your body's fat gauge. It allows your brain and the other organs to see how much body fat you still got and have them react appropriately. Funnily this is also why you body will, clever as is is, pull the emergency break, whenever your body fat levels become too low (cf. "The Athlete Triad Series").
Did you know that 10% of the fat cells have to be renewed every year? I know this is speculative and we are not talking about ZERO adipocyte maturation here, but what do you think will happen when a fat cell is due and you just hit the off-switch on adipocyte maturation?A final word of caution: I am well aware that some of you may take this article as justification for training themselves into the ground. So please(!) keep in mind that hypoxia induced WNT10 and stretch induced WNT10b signaling, as well as most of the other fancy stuff you have learned about in the previous paragraphs are stress responses that require adequate recovery periods for the metabolic and growth responses they induce to take effect. Sleep, Eat, Train, Rest, Sleep, Eat, Train, Rest, Sleep, Eat... do you notice something? Yeah, right that's a 3/1 ratio of non-stressful occupations, namely sleeping, eating and resting to a single stressor, i.e. training. In other words, 25% of your result are "made" in the gym, 75% in bed (don't make it too stressful there ;-), in the kitchen and even, when you spend time with friends and family or simply sprawl out on the couch. Think of that, when you're designing your next training routine.
- Armstrong DD, Esser KA. Wnt/beta-catenin signaling activates growth-control genes during overload-induced skeletal muscle hypertrophy. Am J Physiol Cell Physiol. 2005 Oct;289(4):C853-9. Epub 2005 May 11.
- Akimoto T, Ushida T, Miyaki S, Akaogi H, Tsuchiya K, Yan Z, Williams RS, Tateishi T. Mechanical stretch inhibits myoblast-to-adipocyte differentiation through Wnt signal-ing. Biochem Biophys Res Commun. 2005; 329: 381-385
- Izawa T, Ogasawara J, Sakurai T, Nomura S, Kizaji T, Ohno H. Recent advances in the adaptations of adipose tissue to physical activity: Morphology and adipose tissue cellularity. J Phys Fitness Sports Med. 2013:1(3): 381-387.
- Leal ML, Lamas L, Aoki MS, Ugrinowitsch C, Ramos MS, Tricoli V, Moriscot AS. Effect of different resistance-training regimens on the WNT-signaling pathway. Eur J Appl Physiol. 2011; 111: 2535-2545
- Miyazaki S, Izawa T, Ogasawara JE, Sakurai T, Nomura S, Kizaki T, Ohno H, Komabayashi T. Effect of exercise training on adipocyte-size-dependent expression of leptin and adiponectin. Life Sci. 2010; 86: 691-698.
- Lundby C, Gassmann M, Pilegaard H. Regular endurance training reduces the exercise induced HIF-1alpha and HIF-2alpha mRNA expression in human skeletal muscle in normoxic conditions. Eur J Appl Physiol. 2006 Mar;96(4):363-9. Epub 2005 Nov 12.
- Polesskaya A, Seale P, Rudnicki MA. Wnt signaling induces the myogenic specification of resident CD45+ adult stem cells during muscle regeneration. Cell. 2003 Jun 27;113(7):841-52.
- Ross R, Dagnone D, Jones PJ, Smith H, Paddags A, Hudson R, Janssen I. Reduction in obesity and related comor-bid conditions after diet-induced weight loss or exercise-induced weight loss in men. A randomized, controlled trial. Ann Intern Med. 2000; 133: 92-103.
- Sakurai T, Endo S, Hatano D, Ogasawara J, Kizaki T, Oh-ishi S, Izawa T, Ishida H, Ohno H. Effects of exercise training on adipogenesis of stromal-vascular fraction cells in rat epididymal white adipose tissue. Acta Physiol (Oxf). 2010; 200: 325-338.
- Stallknecht B. 2004. Influence of physical training on adipose tissue metabolism -- with special focus on effects of insulin and epinephrine. Dan Med Bull. 2004; 51: 1-33.
- Ye J. Emerging role of adipose tissue hypoxia in obesity and insulin resistance. Int J Obes (Lond). 2009 Jan;33(1):54-66.