Amino Acid Metabolism in Man

Felig, Philip

doi:10.1146/annurev.bi.44.070175.004441

Cited by 745 publications

(332 citation statements)

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“…Also in the liver, we saw a decreased hepatic conversion of pyruvate to alanine, potentially indicating an increased supply of alanine from outside the liver due to insulin resistance. [21][22][23] The data could be representative of a change in the relative flux through the exchange reaction mediated by ALT, decreasing the incorporation of the 13 C label from pyruvate into the hepatic pool of alanine.…”

Section: Diabetic Studymentioning

confidence: 97%

Simultaneous in vivo assessment of cardiac and hepatic metabolism in the diabetic rat using hyperpolarized MRS

Page

Ball

et al. 2016

NMR in Biomedicine

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Understanding and assessing diabetic metabolism is vital for monitoring disease progression and improving treatment of patients. In vivo assessments, using MRI and MRS, provide non-invasive and accurate measurements, and the development of hyperpolarized 13 C spectroscopy in particular has been demonstrated to provide valuable metabolic data in real time. Until now, studies have focussed on individual organs. However, diabetes is a systemic disease affecting multiple tissues in the body. Therefore, we have developed a technique to simultaneously measure metabolism in both the heart and liver during a single acquisition.A hyperpolarized 13 C MRS protocol was developed to allow acquisition of metabolic data from the heart and liver during a single scan. This protocol was subsequently used to assess metabolism in the heart and liver of seven control male Wistar rats and seven diabetic rats (diabetes was induced by three weeks of high-fat feeding and a 30 mg/kg injection of streptozotocin).Using our new acquisition, we observed decreased cardiac and hepatic pyruvate dehydrogenase flux in our diabetic rat model. These diabetic rats also had increased blood glucose levels, decreased insulin, and increased hepatic triglycerides. Decreased production of hepatic [1-13 C]alanine was observed in the diabetic group, but this change was not present in the hearts of the same diabetic animals.We have demonstrated the ability to measure cardiac and hepatic metabolism simultaneously, with sufficient sensitivity to detect metabolic alterations in both organs. Further, we have noninvasively observed the different reactions of the heart and liver to the metabolic challenge of diabetes.

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Section: Diabetic Studymentioning

confidence: 97%

Simultaneous in vivo assessment of cardiac and hepatic metabolism in the diabetic rat using hyperpolarized MRS

Page

Ball

et al. 2016

NMR in Biomedicine

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“…Protein synthesis requires the availability, in all cells, of all amino acids in the adequate proportions, a complex task partially accomplished by transport through the bloodstream. A decrease in energy availability results in the growing utilization of a larger share of dietary Ð and body Ð protein for gluconeogenesis and energy (Felig, 1975), increasing the pace of the urea cycle and other amino acid catabolic pathways (Felig et al, 1969) and slowing of protein turnover (Li et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

Short-term effects of a hypocaloric diet on nitrogen excretion in morbid obese women

et al. 2001

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Objective: To determine whether the daily pattern of urine excretion of N wastes is affected by obesity and very low-calorie diets (VLCD). Design: The plasma amino acid, urea and other energy parameters, as well as the urinary excretion of total nitrogen, urea and creatinine were studied in obese and normal-weight women. The obese women's data were obtained under hospital basal controlled conditions (8.1 MJaday) and after 3 days of VLCD diet (1.9 MJaday) controls were studied only once (5.8 MJaday). The hourly excretion patterns of total N, urea and creatinine were determined from the composition of each bladder voiding. Subjects: Twenty morbidly obese and 10 age-matched normal-weight control women. Results: Plasma amino acid levels were higher in obese women, which showed a limited ability to metabolize amino acid hydrocarbon skeletons. Neither differences in the patterns between groups nor total 24 h values for urine volume were found. Total N and urea excretion diminished under VLCD diet. Hourly creatinine excretion showed a¯at pattern and was higher in obese women than in the controls, VLCD diet diminished the amount of creatinine excreted in 24 h. Conclusions: The early change in energy availability that the creatinine excretion ®gures re¯ect may result from the energy conservation mechanisms induced in response to energy restriction. The early onset of this effect (3 days, and the extent of decrease ( $ 19%) also suggest that the impact of VLCD on the muscle energy budget of the obese is more marked than usually assumed. Sponsorship: Grants FIS-94a0034, BIO98-0316 and 2FD97-0233 of the Government of Spain.

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“…In mammals, alanine can also act as a carbon carrier for inter-organ carbon transport (Felig, 1975). When delivered to the heart, for example, it can be converted to pyruvate for further oxidation.…”

mentioning

confidence: 99%

“…When delivered to the heart, for example, it can be converted to pyruvate for further oxidation. In liver, it can act as a glucose precursor in gluconeogenesis (Felig, 1975). Thus, alanine is an important alternative energy source to glycogen, which can then be spared for utilization in the future.…”

mentioning

confidence: 99%

Dogmas and controversies in the handling of nitrogenous wastes: Ammonia tolerance in the oriental weatherloachMisgurnus anguillicaudatus

Tsui

Randall

Hanson

et al. 2004

Journal of Experimental Biology

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SUMMARYThe oriental weatherloach Misgurnus anguillicaudatus is an extremely ammonia-tolerant fish. Many ammonia-protection mechanisms have been reported in this fish. Six strategies used by this fish to deal with the problem of excess ammonia are described. The fish can (1) reduce ammonia production through reduction in protein and/or amino acid catabolism; (2)reduce ammonia production and obtain energy through partial amino acid catabolism leading to alanine formation; (3) detoxify ammonia to glutamine;(4) tolerate very high ammonia levels in its tissues; (5) get rid of ammonia as NH3 gas and, probably, (6) possesses background K+channels that are impermeable to NH4+. The effects of extracellular ammonia on the contraction performance of the heart from this fish were found to be the same as in rainbow trout, an ammonia-sensitive fish. It suggests that the hearts of most, if not all, fish species are protected against ammonia. MK-801, an NMDA receptor blocker, was found to have a protective effect against ammonia intoxication in the oriental weatherloach,which suggests that the NMDA receptor, as in mammals, is involved in ammonia toxicity.

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Amino Acid Metabolism in Man

Cited by 745 publications

References 1 publication

Simultaneous in vivo assessment of cardiac and hepatic metabolism in the diabetic rat using hyperpolarized MRS

Simultaneous in vivo assessment of cardiac and hepatic metabolism in the diabetic rat using hyperpolarized MRS

Short-term effects of a hypocaloric diet on nitrogen excretion in morbid obese women

Dogmas and controversies in the handling of nitrogenous wastes: Ammonia tolerance in the oriental weatherloachMisgurnus anguillicaudatus

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