Tuesday, October 21, 2014

Only Dairy, not Soy-Based Meals are Truly Anabolic: Protein Signalling Response to Complete Meals Impaired W/ Soy vs. Whey. Plus: No Response in the Obese to Either Protein

Only dairy, not soy-based lasagna will help you build muscle.
What is it that makes the latest study from the Molecular Nutrition Unit at the School of Exercise and Nutrition Sciences of the Deakin University and colleagues from the The Liggins Institute at the Faculty of Medical and Science Health of the University of Auckland different from previous studies? Actually it's more than one thing: It's the pre-packaged lasagna and fruit yogurt that was used as a test meal in a study that was designed to examine whether meals differing in amino acid composition, yet matched for total energy and macronutrient composition, result in altered mTOR signalling.

Ah, and obviously to investigate if middle aged men with MetS display a resistance of anabolic signalling to mixed meal ingestion compared with healthy control.
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The latter already tells you that the subjects of Petra Grans study were obese. Twenty 40–60 year-old men who were recruited from newspaper, poster, and flyer advertisements to participate.

The subjects were classified as having MetS based on the International Diabetes Federation criteria which means they were abdominally obese (waist circumference≥94 cm) and had two of the following health issues: raised serum triglycerides (≥1.7 mmol/l), reduced serum HDL cholesterol (<1.03 mmol/l), impaired fasting glycaemia (fasting plasma glucose≥5.6 mmol/l) or raised blood pressure (systolic blood pressure≥130 mmHg or diastolic blood pressure≥85 mmHg).

A cohort of age and height matched healthy controls, without MetS were also included and subjects from both groups were randomly assigned to consume either a breakfast meal (had to be consumed withing 15 minutes) comprised of dairy-derived protein or void of dairy-derived proteins (replaced with the same level of soy based protein).
Table 1:  Amino acid composition of the test meals (Gran. 2014)
"The interval between the two test meals was at least four weeks. To prevent possible differences between subjects at baseline from their previous meal the night prior to the study day, subjects were provided with a controlled meal for dinner. The meal consisted of a pre-packaged lasagna and fruit yogurt providing a total of 2462 kJ as 20% fat, 18% protein and 62% carbohydrates. Subjects were asked to eat only the provided food and nothing else." (Gran. 2014)
The test breakfast meals consisted of cheese, butter, and full cream milk with white bread toast (dairy breakfast) and the second meal contained soy cheese analogue, soy beverage, a soy spread, and white bread toast and contained the same amount of protein (31 g) with similar carbohydrate content.

Based on previous research you would expect that...

... switching from dairy to soy, will reduce the anabolic response to the meal. What really happened, however was that the pro-anabolic proteins mTOR (Ser448) and the ribosomal protein S6 increased only after the ingestion of the dairy, not after the consumption of the soy meal.
Figure 1: Activation of mTOR, p70S6K and S6 during the postprandial period in human skeletal muscle (Gran. 2014)
Gran et al. also found that another pro-anabolic signaling protein, i.e. p70S6K (Thr389; Figure 1 - middle), increased only in the healthy control subjects. For the guys with metabolic syndrome, on the other hand, neither the dairy nor the soy meal led to significant increases in the "protein pump" p70S6K, which is usually a good gauge for the actual protein synthetic response. As Gran et al. point out, ...
"[...] P70S6K is the primary readout used to assess the activity of the mTOR pathway (Drummond. 2009; Bodine. 2001); the lack of change in P70S6K phosphorylation after mixed-meal consumption in men with MetS is similar to the anabolic resistance induced by periods of inactivity (Glover. 2008; Breen. 2013) and is observed in older adults (Cuthbertson. 2005; Burd. 2013). Although protein synthesis was not directly measured in this study signalling deficits have been shown to underlie ageing induced anabolic resistance (Cuthbertson. 2005)." (Gran. 2014)
Now, the guys in the study at hand were not exactly old enough for age to be the determining factor, here. Rather than that, research by Villareal, et al. (2012) indicates that eating a clean, energy reduced diet - which was obviously not what the subjects consumed before the experiment in the study at hand - can restore / increase the protein anabolic response in subjects with metabolic syndrome. The non-existent increase in p70S6k in the study at hand could, as Gran et al. highlight, be evidence of this obesity / diet induced resistance to protein-induced skeletal muscle anabolism.
"Ok, being fat and gluttonous is bad, but..." the thing that's probably more interesting for most of you is the absence of increases in protein synthesis in the soy groups. As Gran et al. point out, the study at hand is one of the few studies that have looked at the effects of different proteins on muscle anabolism however - a potential explanation for the differences compared to previous soy vs. whey protein trials, 99% of which used protein shakes as test "meal", could thus be the high fat content (54g) of the test-meal in the study at hand.

Suggested: Only Whey, Not Soy Works 'Wheytloss Wonders' | more.
Yet while previous research indicates that a high fat diet leads to oversaturation of the oxidative capacity of mitochondria in muscle (Koves. 2008), the differences that were observed in the study at hand can hardly be the mere consequence of an inhibitory effect of dietary fat on protein synthesis, because the latter would have had to occur with both dairy and soy protein. We are thus - at least for the moment - left without a definitive answer to the underlying mechanism. Theoretically, it may also be possible that the increase in the soy protein trial was simply less pronounced (less leucine = lower mTOR activation) and the levels had returned to baseline, already after 2h.

It would furthermore be stupid to rely on the elevation of signaling molecules, alone. Theoretically, though, the actual protein synthesis in both trials could still have been similar. If you don't want to rely on the mere possibility that the protein synthetic response may have been similar irrespective of the absence of elevated levels of mTOR & co 2h after the meal, the study at hand does still provide another reason to prefer whey / dairy over soy proteins - in both, your post-workout shakes and regular meals.
  • Bodine, Sue C., et al. "Akt/mTOR pathway is a crucial regulator of skeletal muscle hypertrophy and can prevent muscle atrophy in vivo." Nature cell biology 3.11 (2001): 1014-1019.
  • Breen, Leigh, et al. "Two weeks of reduced activity decreases leg lean mass and induces “anabolic resistance” of myofibrillar protein synthesis in healthy elderly." The Journal of Clinical Endocrinology & Metabolism 98.6 (2013): 2604-2612. 
  • Burd, Nicholas A., Stefan H. Gorissen, and Luc JC van Loon. "Anabolic resistance of muscle protein synthesis with aging." Exercise and sport sciences reviews 41.3 (2013): 169-173.
  • Cuthbertson, Daniel, et al. "Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle." The FASEB Journal 19.3 (2005): 422-424.
  • Drummond, Micah J., et al. "Nutritional and contractile regulation of human skeletal muscle protein synthesis and mTORC1 signaling." Journal of applied physiology 106.4 (2009): 1374-1384.
  • Glover, Elisa I., et al. "Immobilization induces anabolic resistance in human myofibrillar protein synthesis with low and high dose amino acid infusion." The Journal of physiology 586.24 (2008): 6049-6061.
  • Grundy, Scott M. "Metabolic syndrome pandemic." Arteriosclerosis, thrombosis, and vascular biology 28.4 (2008): 629-636.
  • Koves, Timothy R., et al. "Mitochondrial overload and incomplete fatty acid oxidation contribute to skeletal muscle insulin resistance." Cell metabolism 7.1 (2008): 45-56.
  • Villareal, Dennis T., et al. "Effect of weight loss on the rate of muscle protein synthesis during fasted and fed conditions in obese older adults." Obesity 20.9 (2012): 1780-1786.