Hibernating black bears have blood chemistry and plasma amino acid profiles that are indicative of long-term adaptive fasting

2005 ◽  
Vol 83 (9) ◽  
pp. 1257-1263 ◽  
Author(s):  
T D Lohuis ◽  
T D.I Beck ◽  
H J Harlow
Keyword(s):  
Amino Acids ◽  
Ursus Americanus ◽  
Muscle Protein ◽  
Blood Chemistry ◽  
Black Bears ◽  
Late Winter ◽  
Amino Acid Profiles ◽  
Protein Conservation ◽  
Branched Chain

Blood samples were drawn from six black bears (Ursus americanus Pallas, 1780) active in the summer and six others in early and late hibernation. Plasma urea:creatinine ratios and concentrations of amino acids, alanine aminotransferase, and aspartate aminotransferase dropped during the winter denning season, suggesting a decreased protein breakdown. Fifteen amino acids (3 branched chain and 12 glucogenic) were lower in the early winter than in the summer, but 6 of these amino acids rose back to summer levels by the late denning season. Hydroxyproline and glycine were also elevated during late winter, suggesting an increase in collagen breakdown. This profile suggests a dynamic process of adaptive fasting and protein conservation during the winter with a mobilization of non-myofibrilar collagen and perhaps smooth muscle protein reserves to augment a potential but slight increased breakdown of skeletal muscle during the late winter.

scholarly journals Myofibrillar Protein Abundance and Anabolic Signaling in Myotubes Depleted of E1 Alpha Subunit of Branched-Chain Ketoacid Dehydrogenase Complex

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 642-642
Author(s):  
Glory Madu ◽  
Olasunkanmi Adegoke
Keyword(s):  
Skeletal Muscle ◽  
Amino Acids ◽  
Protein Content ◽  
Muscle Protein ◽  
Essential Amino Acids ◽  
Myofibrillar Protein ◽  
L6 Myotubes ◽  
Branched Chain ◽  
Ketoacid Dehydrogenase

Abstract Objectives Branched-chain amino acids (BCAAs) are essential amino acids that are crucial for skeletal muscle anabolism. Thus, alterations in their levels are associated with muscle atrophic diseases such as cancer, chronic inflammatory and neurological disorders. Others have linked impairments in BCAA metabolism to the development of insulin resistance and its sequelae. Compared to the effects of theses amino acids, much less is known on how impairment in BCAA catabolism affects skeletal muscle. BCAA catabolism starts with the reversible transamination by the mitochondrial enzyme branched-chain aminotransferase 2 (BCAT2). This is followed by the irreversible carboxylation, catalyzed by branched-chain ketoacid dehydrogenase (BCKD) complex. We have shown that BCAT2 and BCKD are essential for the differentiation of skeletal myoblasts into myotubes. Here, we investigated the effect of depletion of BCAT2 or of E1a subunit of BCKD in differentiated myotubes. Methods On day 4 of differentiation, L6 myotubes were transfected with the following siRNA oligonucleotides: scrambled (control), BCAT2, or E1a subunit of BCKD. Results Forty-eight hours after transfection, compared to control or BCAT2 siRNA group, we observed improved myotube structure in BCKD-depleted cells. BCKD depletion augmented myofibrillar protein levels: myosin heavy chain (MHC, 2-fold) and tropomyosin (4-fold), P < 0.05, n = 3. To further analyze the increase in myofibrillar protein content, we examined signaling through mTORC1 (mechanistic target of rapamycin complex 1), a vital complex necessary for skeletal muscle anabolism. BCKD depletion increased the phosphorylation of mTORC1 upstream activator AKT (52%, P < 0.05, n = 3), and of mTORC1 downstream substrates by 25%-86%, consistent with the increase in myofibrillar proteins. Finally, in myotubes treated with the catabolic cytokine (tumor necrosis factor-a), BCKD depletion tended to increase the abundance of tropomyosin (a myofibrillar protein). Conclusions We showed that depletion of BCKD enhanced myofibrillar protein content and anabolic signaling.  If these data are confirmed in vivo, development of dietary and other interventions that target BCKD abundance or functions may promote muscle protein anabolism in individuals with muscle wasting conditions. Funding Sources MHRC, NSERC York U.

Response of muscle protein and glutamine kinetics to branched-chain–enriched amino acids in intensive care patients after radical cancer surgery

Nutrition ◽  
2006 ◽  
Vol 22 (5) ◽  
pp. 475-482 ◽  
Author(s):  
Gianni Biolo ◽  
Marcello De Cicco ◽  
Viviana Dal Mas ◽  
Stefania Lorenzon ◽  
Raffaella Antonione ◽  
...  
Keyword(s):  
Amino Acids ◽  
Intensive Care ◽  
Muscle Protein ◽  
Cancer Surgery ◽  
Intensive Care Patients ◽  
Branched Chain

scholarly journals Amino acid infusion increases the sensitivity of muscle protein synthesis in vivo to insulin. Effect of branched-chain amino acids

1988 ◽  
Vol 254 (2) ◽  
pp. 579-584 ◽  
Author(s):  
P J Garlick ◽  
I Grant
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain

Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.

scholarly journals Effect of endurance training and branched-chain amino acids on the signaling for muscle protein synthesis in CKD model rats fed a low-protein diet

2017 ◽  
Vol 313 (3) ◽  
pp. F805-F814 ◽  
Author(s):  
Takuya Yoshida ◽  
Sachika Kakizawa ◽  
Yuri Totsuka ◽  
Miho Sugimoto ◽  
Shinji Miura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Renal Function ◽  
Protein Synthesis ◽  
Sham Group ◽  
Treadmill Exercise ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Low Protein ◽  
Branched Chain

A low-protein diet (LPD) protects against the progression of renal injury in patients with chronic kidney disease (CKD). However, LPD may accelerate muscle wasting in these patients. Both exercise and branched-chain amino acids (BCAA) are known to increase muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) pathway. The aim of this study was to investigate whether endurance exercise and BCAA play a role for increasing muscle protein synthesis in LPD-fed CKD (5/6 nephrectomized) rats. Both CKD and sham rats were pair-fed on LPD or LPD fortified with a BCAA diet (BD), and approximately one-half of the animals in each group was subjected to treadmill exercise (15 m/min, 1 h/day, 5 days/wk). After 7 wk, renal function was measured, and soleus muscles were collected to evaluate muscle protein synthesis. Renal function did not differ between LPD- and BD-fed CKD rats, and the treadmill exercise did not accelerate renal damage in either group. The treadmill exercise slightly increased the phosphorylation of p70s6 kinase, a marker of mTOR activity, in the soleus muscle of LPD-fed CKD rats compared with the sham group. Furthermore, BCAA supplementation of the LPD-fed, exercise-trained CKD rats restored the phosphorylation of p70s6 kinase to the same level observed in the sham group; however, the corresponding induced increase in muscle protein synthesis and muscle mass was marginal. These results indicate that the combination of treadmill exercise and BCAA stimulates cell signaling to promote muscle protein synthesis; however, the implications of this effect for muscle growth remain to be clarified.

scholarly journals Bolus ingestion of individual branched-chain amino acids alters plasma amino acid profiles in young healthy men

SpringerPlus ◽  
2014 ◽  
Vol 3 (1) ◽  
pp. 35 ◽  
Author(s):  
Takuya Matsumoto ◽  
Koichi Nakamura ◽  
Hideki Matsumoto ◽  
Ryosei Sakai ◽  
Tomomi Kuwahara ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Branched Chain Amino Acids ◽  
Plasma Amino Acid ◽  
Healthy Men ◽  
Amino Acid Profiles ◽  
Branched Chain

Effects of branched-chain-enriched amino acids and insulin on forearm leucine kinetics

1999 ◽  
Vol 97 (4) ◽  
pp. 437-448 ◽  
Author(s):  
Michela ZANETTI ◽  
Rocco BARAZZONI ◽  
Edward KIWANUKA ◽  
Paolo TESSARI
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Aromatic Amino Acids ◽  
Leucine Kinetics ◽  
Before And After ◽  
Amino Acid Mixtures ◽  
Leucine Transport ◽  
Branched Chain ◽  
Plasma Leucine

Although amino acid mixtures enriched in branched-chain amino acids (BCAA) and deficient in aromatic amino acids (AAA) are often used together with insulin and glucose in clinical nutrition, their physiological effects on muscle protein anabolism are not known. To this aim, we studied forearm leucine kinetics in post-absorptive volunteers, before and after the systemic infusion of BCAA-enriched, AAA-deficient amino acids along with insulin and the euglycaemic clamp. The results were compared with the effects of insulin infusion alone. A compartmental leucine forearm model was employed at steady state. Hyperaminoacidaemia with hyperinsulinaemia (to ≈ 80–100 μ-units/ml) increased the leucine plasma concentration (+70%; P< 0.001), inflow into the forearm cell (+150%; P< 0.01), disposal into protein synthesis (+100%; P< 0.01), net intracellular retention (P< 0.01), net forearm balance (by ≈ 6-fold; P< 0.01) and net deamination to α-ketoisocaproate (4-methyl-2-oxopentanoate) (+9%; P< 0.05). Leucine release from forearm proteolysis and outflow from the forearm cell were unchanged. In contrast, hyperinsulinaemia alone decreased plasma leucine concentrations (-35%; P< 0.001) and leucine inflow (-20%; P< 0.05) and outflow (-30%; P< 0.01) into and out of forearm cell(s), it increased net intracellular leucine retention (P< 0.03), and it did not change leucine release from forearm proteolysis (-20%; P = 0.138), net leucine deamination to α-ketoisocaproate, leucine disposal into protein synthesis or net forearm protein balance. By considering all data together, leucine disposal into protein synthesis was directly correlated with leucine inflow into the cell (r = 0.71; P< 0.0001). These data indicate that the infusion of BCAA-enriched, AAA-deficient amino acids along with insulin is capable of stimulating forearm (i.e. muscle) protein anabolism in normal volunteers by enhancing intracellular leucine transport and protein synthesis. These effects are probably due to hyperaminoacidaemia and/or its interaction with hyperinsulinaemia, since they were not observed under conditions of hyperinsulinaemia alone.

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