Insuline is not anabolic, but maybe anti-catabolic

  1. Insuline is not anabolic, but maybe anti-catabolic


    Mechanism of Insulin's Anabolic Effect on Muscle - Measurements of Muscle Protein Synthesis and Breakdown Using Aminoacyl tRNA and Other Surrogate Measures.

    Chow LS, Albright RC, Bigelow ML, Toffolo G, Cobelli C, Nair KS.

    Division of Endocrinology, Nutrition and Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota, United States.

    Despite being an anabolic hormone in skeletal muscle, insulin's anti-catabolic mechanism in humans remains controversial with contradictory reports showing either stimulation protein synthesis (PS) or inhibition protein breakdown (PB) by insulin. Earlier measurements of muscle PS and PB in humans have relied on different surrogate measures of amino acyl tRNA and intracellular pool. We report insulin's effect on muscle protein turnover using amino acyl-tRNA as the precursor of PS and PB is calculated by mass balance of tracee amino acid (AA). We compared the results calculated from various surrogate measures. To determine the physiological role of insulin on muscle protein metabolism we infused tracers of leucine and phenylalanine into 18 healthy subjects and after a three hours, 10 subjects received a four hour femoral arterial infusion of insulin (0.125 mU/kg/min) while eight subjects continued with saline. Tracer to tracee ratios of leucine, phenylalanine and ketoisocaproate were measured in the arterial and venous plasma, muscle tissue fluid and AA-tRNA to calculate muscle PB and PS. Insulin infusion, unlike saline, significantly reduced the efflux of leucine and phenylalanine from muscle bed based on various surrogate measures which agreed with those based on leucyl-tRNA (-28%) indicating a reduction in muscle PB (P<0.02) without any significant effect on muscle PS. In conclusion, using amino-acyl tRNA as the precursor pool, it is demonstrated that in healthy humans in the postabsorptive state, insulin does not stimulate muscle protein synthesis and confirmed that insulin achieves muscle protein anabolism by inhibition of muscle protein breakdown.


  2. Quote Originally Posted by x_muscle
    Mechanism of Insulin's Anabolic Effect on Muscle - Measurements of Muscle Protein Synthesis and Breakdown Using Aminoacyl tRNA and Other Surrogate Measures.

    Chow LS, Albright RC, Bigelow ML, Toffolo G, Cobelli C, Nair KS.

    Division of Endocrinology, Nutrition and Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota, United States.

    Despite being an anabolic hormone in skeletal muscle, insulin's anti-catabolic mechanism in humans remains controversial with contradictory reports showing either stimulation protein synthesis (PS) or inhibition protein breakdown (PB) by insulin. Earlier measurements of muscle PS and PB in humans have relied on different surrogate measures of amino acyl tRNA and intracellular pool. We report insulin's effect on muscle protein turnover using amino acyl-tRNA as the precursor of PS and PB is calculated by mass balance of tracee amino acid (AA). We compared the results calculated from various surrogate measures. To determine the physiological role of insulin on muscle protein metabolism we infused tracers of leucine and phenylalanine into 18 healthy subjects and after a three hours, 10 subjects received a four hour femoral arterial infusion of insulin (0.125 mU/kg/min) while eight subjects continued with saline. Tracer to tracee ratios of leucine, phenylalanine and ketoisocaproate were measured in the arterial and venous plasma, muscle tissue fluid and AA-tRNA to calculate muscle PB and PS. Insulin infusion, unlike saline, significantly reduced the efflux of leucine and phenylalanine from muscle bed based on various surrogate measures which agreed with those based on leucyl-tRNA (-28%) indicating a reduction in muscle PB (P<0.02) without any significant effect on muscle PS. In conclusion, using amino-acyl tRNA as the precursor pool, it is demonstrated that in healthy humans in the postabsorptive state, insulin does not stimulate muscle protein synthesis and confirmed that insulin achieves muscle protein anabolism by inhibition of muscle protein breakdown.
    Nice study, that is interesting. I have seen a few similar ones as well and it seems the main anabolic property of insulin is also its nutrient loading capabilities.
    PharmD

  3. So basically the end result stays the same but the way it gets there is under scrutiny?
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  4. So would this mean it shifts a persons protein turnover rate to almost all protein synthesis since it inhibits protein breakdown.

    "Also, Postabsorbative State AKA Early Fasting State means anywhere from approx 3 to 15 hours after you've eatin a mean....In this state the synthesis of glycogen in the liver is diminished and glucose provided to the muscle comes primarly from the recycling of lactate and alanine." [Advan. Nutri. & Human Metab.]

    If im interperating this right, then the postabsorbative state is where catabolism begins. If that's true, then what happens if you give someone insulin in the fed state, within 3 hours after a meal? Or did i screw up in my analysis?

  5. that article doesnt appear to have any relevance whatsoever to the way insulin is used by BBers to gain mass. nobody is saying that it acts in a conventional anabolic manner (protein synthesis), just that it can shuttle any damn thing you eat/drink into your muscles for hours after insulin administration.

    rest assured, insulin is the most powerful "anabolic" available.

  6. Yeah it seems to be more of an argument over semantics. Insulin also facilitates glucose uptake which in turn can fuel anabolism.

  7. Quote Originally Posted by same_old
    that article doesnt appear to have any relevance whatsoever to the way insulin is used by BBers to gain mass. nobody is saying that it acts in a conventional anabolic manner (protein synthesis), just that it can shuttle any damn thing you eat/drink into your muscles for hours after insulin administration.

    rest assured, insulin is the most powerful "anabolic" available.
    Yea, this was the point I was trying to make in my post as well. I was a little confused on the study as to the way they were carrying it out. I mean I get their point but definitely not the reason why bbers use it.
    PharmD
  

  
 

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