Consumption of a Low Protein Diet Increases Norepinephrine Turnover in Brown Adipose Tissue of Adult Rats

Kevonian, Arlene V.; Tuig, Jerry G. Vander; Romsos, Dale R.

doi:10.1093/jn/114.3.543

Cited by 31 publications

(16 citation statements)

References 17 publications

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“…A study in adult humans has shown that isoenergetic diet with higher carbohydrates had no impact on the energy expenditure (29). The observed increase in the energy expenditure in the protein-restricted group in our study is also consistent with published data in nonpregnant rats (13)(14)(15)(16). The fetoplacental signals responsible for the change in maternal protein metabolism remain unknown.…”

Section: Discussionsupporting

confidence: 91%

“…an increase in glycine and glutamine concentration, and a decrease in branched chain amino acids and threonine concentration (11). However, these studies were not controlled for energy intake, since a low-protein diet, less than 9% protein, also caused a decrease in food intake in both pregnant and nonpregnant rats (11,12).Low protein intake in nonpregnant rats is associated with a higher rate of energy expenditure (13)(14)(15)(16). Whether protein restriction during pregnancy elicits a similar increase in energy expenditure has not been examined.…”

mentioning

confidence: 99%

“…Low protein intake in nonpregnant rats is associated with a higher rate of energy expenditure (13)(14)(15)(16). Whether protein restriction during pregnancy elicits a similar increase in energy expenditure has not been examined.…”

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confidence: 99%

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Metabolic Responses to Protein Restriction During Pregnancy in Rat and Translation Initiation Factors in the Mother and Fetus

2004

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A low-protein diet during pregnancy in the rat results in intrauterine growth restricted (IUGR) fetuses. The adaptive responses of the mother to low-protein diet and the mechanisms of IUGR in this model are not understood. In the present study, we report the maternal metabolic responses to protein restriction and their impact on growth, carcass composition, and translation initiation in the fetus. Pregnant Sprague-Dawley rats were pairfed either a 6% protein (LP, n ϭ 7) or a 24% protein (NP, n ϭ 7) diet from conception until delivery. Plasma amino acids and urea levels and rate of oxygen consumption were measured sequentially through pregnancy. Translation initiation factors eIF2␣, Ser 51 phosphorylated eIF2␣, eIF4E, phosphorylated eIF4E, and 4E-BP1 were quantified in the maternal and fetal muscle and liver. Protein restriction resulted in higher rate of oxygen consumption (p Ͻ 0.01), lower plasma branched chain amino acid (p Ͻ 0.05) in the mother, and lower plasma histidine levels (p Ͻ 0.05) in the fetus. Plasma urea nitrogen was lower in the LP group throughout gestation. The phosphorylated 4E-BP1 (␥ form) in the maternal liver was 4-fold higher in the LP group. The phosphorylated eIF2␣ was higher in the livers of IUGR fetuses. We speculate that the lower plasma branched chain amino acids in the mother during early pregnancy may be due to a lower rate of protein turnover in the LP group. The mechanism of increased energy consumption due to protein restriction remains unclear. The data on translation initiation factors suggest a higher rate of protein synthesis in the maternal liver and a lower rate in the fetal liver in response to protein restriction. Epidemiologic studies in humans have shown a significant correlation between intrauterine growth restriction (IUGR), low birth weight, and a number of morbidities in adult life (1-3). A number of studies in animals, particularly rat, have confirmed these findings (4 -7). Protein restriction during pregnancy in the rat has often been used to induce IUGR in the fetus. In the present study we have examined the adaptive responses of the mother to protein restriction during pregnancy. Specifically, we have examined the temporal changes in plasma amino acid and urea concentration, and changes in oxygen consumption in the mother.Adaptive responses to normal pregnancy in humans and animals are characterized by hypoaminoacidemia, a lower rate of urea synthesis, and a lower rate of protein turnover as compared with nonpregnant controls (8, 9). Studies in rat have shown an increase in fractional rate of protein synthesis in the liver during pregnancy. No significant effect of pregnancy on protein synthesis in skeletal muscle was observed in this study (10). Dietary restriction of protein to 9% in pregnant rat results in specific changes in plasma amino acid concentration, i.e. an increase in glycine and glutamine concentration, and a decrease in branched chain amino acids and threonine concentration (11). However, these studies were not controlled for energy intake, since ...

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Section: Discussionsupporting

confidence: 91%

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Metabolic Responses to Protein Restriction During Pregnancy in Rat and Translation Initiation Factors in the Mother and Fetus

2004

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“…Indeed we have recently observed (T. Leon-Quinto, C. Magnan, unpublished data) an increase of the superior cervical ganglion firing rate in the restricted rats as compared to control rats. There are also indications in the literature for an activation of the catecholaminergic system in adult rats submitted to perinatal longlasting undernutrition or young rats fed a low-protein diet, as attested by acceleration in the norepinephrine turnover rate in brown adipose issue [26,27] or an increased turnover rate of brain dopamine and norepinephrine together with a higher tyrosine-hydroxylase activity [28].…”

Section: Discussionmentioning

confidence: 99%

Alteration of the counterregulatory hormones in the conscious rat after protein-energy restriction

León–Quinto¹,

Adnot²,

Portha

1997

Diabetologia

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“…In particular, a large increase in the activity of brown adipose tissue has been described (4)(5)(6). In keeping with this picture, one of the hormones most directly involved in energy dissipation, norepinephrine (NE), is elevated in rats fed low-protein diets (7,8). Many studies (9)(10)(11)(12)(13) have also demonstrated an increased protein deposition and an elevation in the rate of protein synthesis in skeletal muscle when either normal rats or rats fed a low-protein diet were treated with the specific ß-2 selective agonist, clenbuterol.…”

Section: Introductionmentioning

confidence: 96%

Increase in skeletal muscle protein content by the ß-2 selective adrenergic agonist clenbuterol exacerbates hypoalbuminemia in rats fed a low-protein diet

Sawaya

Lunn

1998

Braz J Med Biol Res

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This investigation examined how the nutritional status of rats fed a low-protein diet was affected when the animals were treated with the ß-2 selective agonist clenbuterol (CL). Males (4 weeks old) from an inbred, specific-pathogen-free strain of hooded rats maintained at the Dunn Nutritional Laboratory were used in the experiments (N = 6 rats per group). CL treatment (Ventipulmin, Boehringer-Ingelheim Ltd., 3.2 mg/kg diet for 2 weeks) caused an exacerbation of the symptoms associated with protein deficiency in rats. Plasma albumin concentrations, already low in rats fed a low-protein diet (group A), were further reduced in CL rats (A = 25.05 ± 0.31 vs CL = 23.64 ± 0.30 g/l, P<0.05). Total liver protein decreased below the level seen in either pair-fed animals (group P) or animals with free access to the low-protein diet (A = 736.56 ± 26 vs CL = 535.41 ± 54 mg, P<0.05), whereas gastrocnemius muscle protein was higher than the values normally described for control (C) animals (C = 210.88 ± 3.2 vs CL = 227.14 ± 1.7 mg/g, P<0.05). Clenbuterol-treated rats also showed a reduction in growth when compared to P rats (P = 3.2 ± 1.1 vs CL = -10.2 ± 1.9 g, P<0.05). This was associated with a marked decrease in fat stores (P = 5.35 ± 0.81 vs CL = 2.02 ± 0.16 g, P<0.05). Brown adipose tissue (BAT) cytochrome oxidase activity, although slightly lower than in P rats (P = 469.96 ± 16.20 vs CL = 414.48 ± 11.32 U/BAT x kg body weight, P<0.05), was still much higher than in control rats (C = 159.55 ± 11.54 vs CL = 414.48 ± 11.32 U/BAT x kg body weight, P<0.05). The present findings support the hypothesis that an increased muscle protein content due to clenbuterol stimulation worsened amino acid availability to the liver and further reduced albumin synthesis causing exacerbation of hypoalbuminemia in rats fed a low-protein diet. Correspondence

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Consumption of a Low Protein Diet Increases Norepinephrine Turnover in Brown Adipose Tissue of Adult Rats

Cited by 31 publications

References 17 publications

Metabolic Responses to Protein Restriction During Pregnancy in Rat and Translation Initiation Factors in the Mother and Fetus

Metabolic Responses to Protein Restriction During Pregnancy in Rat and Translation Initiation Factors in the Mother and Fetus

Alteration of the counterregulatory hormones in the conscious rat after protein-energy restriction

Increase in skeletal muscle protein content by the ß-2 selective adrenergic agonist clenbuterol exacerbates hypoalbuminemia in rats fed a low-protein diet

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