Quadancer, I think when the researchers were talking about malnourished what they really were referring to is low energy levels in the muscle cells. Once can be well fed and well nourished on a ketogenic diet, live their life perfectly normally, but if they are working out regularly, they may be in a glycogen depleted state.
Now the question is does this low glycogen state have a negative effect on muscle growth. This SEEMS to be the case. Perhaps intramuscular triglycerides, which are burned to a greater degree when lifting with low glycogen, can act as a replacement. So far this doesn't seem to be the case.
Now a very high protein, low carb diet (even with no carbs, very high protein usually prevents ketosis), might replace some of the muscle glycogen. The problem with this is that some of the research i've seen using very high protein, low carbohydrate intakes, blood glucose barely gets elevated. I haven't seen anything looking at replacing carbs with protein and muscle glycogen storage, but the excess protein of a keto/VLC diet seems to be increasing liver glycogen storage rather than muscle glycogen.
This one is in rodents, but still may be relevant as it shows low energy levels in the cell causing a rise in AMPK, a fuel sensor, will inhibit some of the anabolic signals of muscle contractions.
AMPK activation attenuates S6K1, 4E-BP1, and eEF2 signaling responses to high-frequency electrically stimulated skeletal muscle contractions
David M. Thomson, Christopher A. Fick, and Scott E. Gordon
Human Performance Laboratory, Department of Exercise and Sport Science, and Department of Physiology, East Carolina University, Greenville, North Carolina
Submitted 24 August 2007 ; accepted in final form 2 January 2008
Regulation of protein translation through Akt and the downstream mammalian target of rapamycin (mTOR) pathway is an important component of the cellular response to hypertrophic stimuli. It has been proposed that 5'-AMP-activated protein kinase (AMPK) activation during muscle contraction may limit the hypertrophic response to resistance-type exercise by inhibiting translational signaling. However, experimental manipulation of AMPK activity during such a stimulus has not been attempted. Therefore, we investigated whether AMPK activation can attenuate the downstream signaling response of the Akt/mTOR pathway to electrically stimulated lengthening muscle contractions. Extensor digitorum longus muscles (n = 8/group) were subjected to a 22-min bout of lengthening contractions by high-frequency sciatic nerve electrical stimulation (STIM) in young adult (8 mo) Fischer 344 x Brown Norway male rats. Forty minutes before electrical stimulation, rats were subcutaneously injected with saline or 5-aminoimidazole-4-carboxamide-1–4-ribofuranoside (AICAR; 1 mg/g body wt), an AMPK activator. Stimulated and contralateral resting muscles were removed at 0, 20, and 40 min post-STIM, and AMPK, acetyl CoA carboxylase (ACC), Akt, eukaryotic initiation factor 4E-binding protein (4E-BP1), 70-kDa ribosomal protein S6 kinase (S6K1), and eukaryotic elongation factor 2 (eEF2) phosphorylations were assessed by Western blot. AICAR treatment increased (P ≤ 0.05) post-STIM AMPK (Thr172) and ACC phosphorylation (Ser79/221), inhibited post-STIM S6K1 (Thr389) and 4E-BP1 (gel shift) phosphorylation, and elevated post-STIM eEF2 phosphorylation (Thr56). These findings suggest that translational signaling downstream of Akt/mTOR can be inhibited after lengthening contractions when preceded by AMPK activation and that energetic stress may be antagonistic to the hypertrophic translational signaling response to loaded muscle contractions.
