The sodium pump and other mechanisms of thermogenesis in selected tissues

Kelly, John; McBride, B.W.

doi:10.1079/pns19900023

Cited by 59 publications

(37 citation statements)

References 87 publications

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“…The ATP demand of protein synthesis consumes 12-25% of total energy expenditure in mammalian muscle (Kelly and McBride, 1990;Rolfe and Brown, 1997). Reducing this energetically expensive cellular process can make an important contribution to global metabolic rate depression during hibernation and other states of hypometabolism (Frerichs et al, 1998;Storey, 2010).…”

Section: Discussionmentioning

confidence: 99%

Regulation of the mTOR signaling network in hibernating thirteen-lined ground squirrels

Storey

2012

Journal of Experimental Biology

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SUMMARYFor many small mammals, survival over the winter months is a serious challenge because of low environmental temperatures and limited food availability. The solution for many species, such as thirteen-lined ground squirrels (Ictidomys tridecemlineatus), is hibernation, an altered physiological state characterized by seasonal heterothermy and entry into long periods of torpor that are interspersed with short arousals back to euthermia. During torpor, metabolic rate is strongly reduced to achieve major energy savings, and a coordinated depression of non-essential ATP-expensive functions such as protein synthesis takes place. This study examines the mammalian target of rapamycin (mTOR) signaling pathway, a crucial component of the insulin receptor network, over six stages of the torpor-arousal cycle of hibernation. Immunoblots showed that the phosphorylation state of mTOR Ser2448 was strongly reduced in skeletal muscle (by 55%) during late torpor but increased by 200% during early arousal compared with euthermia. However, the phosphorylation state of this residue remained relatively constant in cardiac muscle during torpor but was enhanced during entrance into torpor and early arousal from torpor stages (by 2.9-and 3.2-fold, respectively). Phosphorylation states of upstream regulators of mTOR, p-Akt Thr473 and p-TSC2 Thr1462, were also suppressed in skeletal muscle by 55 and 51%, respectively, during late torpor, as were selected downstream substrates -p-4E-BP1Thr46 and p-S6 Ser235 contents dropped by 74 and 41%, respectively. Overall, the results indicate suppressed mTOR signaling in skeletal muscle, but not cardiac muscle, during torpor. By contrast, activation of mTOR and other components of the mTORC1 complex (p-PRAS40 Thr246 and GL) occurred during early arousal in both skeletal and cardiac muscle.

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Section: Discussionmentioning

confidence: 99%

Regulation of the mTOR signaling network in hibernating thirteen-lined ground squirrels

Storey

2012

Journal of Experimental Biology

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“…The coexistence of dynein and kinesin-dependent traffic for a single cargo ensures at least a proportion of oocyte mitochondria remain in the cytosol distinct from the spindle. This may be important for serving ATP supply at regions of high ATP demand such as the Na-K ATPase at the plasma membrane (Houghton et al, 2003;Kelly and McBride, 1990).…”

Section: (B-d)mentioning

confidence: 99%

Biased inheritance of mitochondria during asymmetric cell division in the mouse oocyte

Dalton

Carroll

2013

Journal of Cell Science

134

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SummaryA fundamental rule of cell division is that daughter cells inherit half the DNA complement and an appropriate proportion of cellular organelles. The highly asymmetric cell divisions of female meiosis present a different challenge because one of the daughters, the polar body, is destined to degenerate, putting at risk essential maternally inherited organelles such as mitochondria. We have therefore investigated mitochondrial inheritance during the meiotic divisions of the mouse oocyte. We find that mitochondria are aggregated around the spindle by a dynein-mediated mechanism during meiosis I, and migrate together with the spindle towards the oocyte cortex. However, at cell division they are not equally segregated and move instead towards the oocyte-directed spindle pole and are excluded from the polar body. We show that this asymmetrical inheritance in favour of the oocyte is not caused by bias in the spindle itself but is dependent on an intact actin cytoskeleton, spindle-cortex proximity, and cell cycle progression. Thus, oocyte-biased inheritance of mitochondria is a variation on rules that normally govern organelle segregation at cell division, and ensures that essential maternally inherited mitochondria are retained to provide ATP for early mammalian development.

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“…Ferrell (1988) showed that in sheep, total viscera and nervous tissue account for 58.5% of oxygen consumption although they represent only 11% of body weight. This phenomenon is attributable to two major energy requiring processes occurring in the gut: activities of the Na + , K + -ATPase enzyme and protein turnover (Lobley 1988;Kelly and McBride 1989;McBride and Kelly 1990). Kelly et al (1993) estimated Na + , K + -ATPase enzyme and protein synthesis activities to account for 15.2-41.4% and 26.5-31% as a portion of visceral oxygen consumption, respectively.…”

Section: Ii3 Metabolic Cost Associated With Endogenous N Lossesmentioning

confidence: 99%

Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review

Nyachoti¹,

Lange²,

McBride³

et al. 1997

Can. J. Anim. Sci.

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236

163

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Nyachoti, C. M., de Lange, C. F. M., McBride, B. W. and Schulze, H. 1997. Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review. Can. J. Anim. Sci. 77: 149-163. During the past two decades endogenous gut N losses (ENL) at the distal ileum in the growing pig have received considerable attention in swine nutrition research. Estimates of ENL are important for determining true ileal N and amino acid digestibilities and for identifying means to improve the efficiency of N and energy utilization in growing pigs. Endogenous secretions originate from various sources including saliva, pancreatic secretions, bile, sloughed off epithelial cells, serum albumin and mucin. It has been estimated that 70 to 80% of endogenous N secretions are digested and re-absorbed. Therefore, ENL represents only a fraction of total endogenous N secreted into the gut. Increased ENL are likely associated with elevated rates of gut protein synthesis. This is bound to increase maintenance energy and amino acid requirements of pigs. Traditionally, ENL were determined by feeding protein-free diets or by the regression method. Various alternative techniques ( 15 N-isotope dilution technique, homoarginine technique, enzymatically hydrolysed casein method) are now available to estimate the ENL in pigs fed protein-containing diets. Each of these techniques has some limitations and all require different assumptions. Results obtained with these alternative techniques indicate that the net ENL losses are much higher and more variable than previously estimated, and that they are affected both by animal and dietary factors. Recent estimates of ENL losses vary between 1.8 and 8.3 g kg -1 dry matter intake. The main factors (feed intake, body weight, content of anti-nutritional factors, fibres and [digestible] protein) that affect ENL and approaches (plant breeding and selection, ingredient processing and use of exogenous enzymes) to reduce ENL are discussed in this review. In addition, the metabolic costs associated with ENL are estimated.

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The sodium pump and other mechanisms of thermogenesis in selected tissues

Cited by 59 publications

References 87 publications

Regulation of the mTOR signaling network in hibernating thirteen-lined ground squirrels

Regulation of the mTOR signaling network in hibernating thirteen-lined ground squirrels

Biased inheritance of mitochondria during asymmetric cell division in the mouse oocyte

Significance of endogenous gut nitrogen losses in the nutrition of growing pigs: A review

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