TY - JOUR

T1 - Protein ingestion induces muscle insulin resistance independent of leucine-mediated mTOR activation

AU - Smith, Gordon I

AU - Yoshino, Jun

AU - Stromsdorfer, Kelly L

AU - Klein, Seth J

AU - Magkos, Faidon

AU - Reeds, Dominic N

AU - Klein, Samuel

AU - Mittendorfer, Bettina

N1 - © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

PY - 2015

Y1 - 2015

N2 - Increased plasma branched-chain amino acid concentrations are associated with insulin resistance, and intravenous amino acid infusion blunts insulin-mediated glucose disposal. We tested the hypothesis that protein ingestion impairs insulin-mediated glucose disposal by leucine-mediated mTOR signaling, which can inhibit AKT. We measured glucose disposal and muscle p-mTORSer2448, p-AKTSer473, and p-AKTThr308 in 22 women during a hyperinsulinemic-euglycemic clamp procedure with and without concomitant ingestion of whey protein (0.6 g/kg fat-free mass; n = 11) or leucine that matched the amount given with whey protein (n = 11). Both whey protein and leucine ingestion raised plasma leucine concentration by approximately twofold and muscle p-mTORSer2448 by ∼30% above the values observed in the control (no amino acid ingestion) studies; p-AKTSer473 and p-AKTThr308 were not affected by whey protein or leucine ingestion. Whey protein ingestion decreased insulin-mediated glucose disposal (median 38.8 [quartiles 30.8, 61.8] vs. 51.9 [41.0, 77.3] µmol glucose/µU insulin · mL-1 · min-1; P < 0.01), whereas ingestion of leucine did not (52.3 [43.3, 65.4] vs. 52.3 [43.9, 73.2]). These results indicate that 1) protein ingestion causes insulin resistance and could be an important regulator of postprandial glucose homeostasis and 2) the insulin-desensitizing effect of protein ingestion is not due to inhibition of AKT by leucine-mediated mTOR signaling.

AB - Increased plasma branched-chain amino acid concentrations are associated with insulin resistance, and intravenous amino acid infusion blunts insulin-mediated glucose disposal. We tested the hypothesis that protein ingestion impairs insulin-mediated glucose disposal by leucine-mediated mTOR signaling, which can inhibit AKT. We measured glucose disposal and muscle p-mTORSer2448, p-AKTSer473, and p-AKTThr308 in 22 women during a hyperinsulinemic-euglycemic clamp procedure with and without concomitant ingestion of whey protein (0.6 g/kg fat-free mass; n = 11) or leucine that matched the amount given with whey protein (n = 11). Both whey protein and leucine ingestion raised plasma leucine concentration by approximately twofold and muscle p-mTORSer2448 by ∼30% above the values observed in the control (no amino acid ingestion) studies; p-AKTSer473 and p-AKTThr308 were not affected by whey protein or leucine ingestion. Whey protein ingestion decreased insulin-mediated glucose disposal (median 38.8 [quartiles 30.8, 61.8] vs. 51.9 [41.0, 77.3] µmol glucose/µU insulin · mL-1 · min-1; P < 0.01), whereas ingestion of leucine did not (52.3 [43.3, 65.4] vs. 52.3 [43.9, 73.2]). These results indicate that 1) protein ingestion causes insulin resistance and could be an important regulator of postprandial glucose homeostasis and 2) the insulin-desensitizing effect of protein ingestion is not due to inhibition of AKT by leucine-mediated mTOR signaling.

KW - Aged

KW - Amino Acids/blood

KW - Blood Glucose

KW - Dietary Proteins/administration & dosage

KW - Female

KW - Glucose Clamp Technique

KW - Humans

KW - Insulin/blood

KW - Insulin Resistance/physiology

KW - Leucine/metabolism

KW - Middle Aged

KW - Milk Proteins/pharmacology

KW - Muscle, Skeletal/physiology

KW - Signal Transduction

KW - TOR Serine-Threonine Kinases/genetics

KW - Whey Proteins

U2 - 10.2337/db14-1279

DO - 10.2337/db14-1279

M3 - Journal article

C2 - 25475435

VL - 64

SP - 1555

EP - 1563

JO - Diabetes

JF - Diabetes

SN - 0012-1797

IS - 5

ER -