The relationship weight change, protein turnover
between dietary nitrogen balance, in man1’ 2
M. Golden,3 B.Sc., M.B., B.Ch., B.A.O., J. C. Waterlow,4 M.D., Sc.D., F.R.C.P., and D. Picou,5 M.B., B.S., Ph.D.
ABSTRACT sis,
and
who
We have
protein
were
tabolism
recovering
level
of dietary
tions
between
balance, protein
and
in protein
breakdown, breakdown
and Over
protein the
5-fold.
breakdown not
1345-1348,
contribute
metabolism.
range
of
dietary
changes
being
least
to changes
turnover, nitrogen
protein balance
the
were
intake, in dietary
60
on an inadequate in nitrogen
dietary
to 270
intake
intake.
urea.
correla-
intake,
nitrogen
per
in small Changes
or body
meThe
significant cal/kg
resulted
balance
Protein
of urinary
highly
ad libitum
synthein children
.
the enrichment There
and
Large
and
protein-energy-malnutrition
measuring
synthesis
protein
change,
severe and
protein
between
weight
from
[“'N]glycine affect
with did
intake,
recovered
flux
increased
the relationships
dietary
not
change.
rate
of protein
J. Clin. Nutr. 30:
did
protein
weight
synthesis
had
by giving
protein both
and
and
was measured
M.R.C.P.,
examined
breakdown
intake, and
weight.
day,
the
changes in the
rate Am.
1977.
Both infection and trauma usually result in a negative nitrogen balance Because there is increased catabolism of amino acids from the amino acid pool, it has long been assumed that there is an increase in the rate of breakdown of body proteins; however, this is not necessarily the case The availability of amino acids for catabolism can be increased by either an increase in the breakdown rate or a decrease in the synthesis rate of whole body protein In infection the magnitude of this imbalance between synthesis and breakdown depends upon the severity of the illness, the amount of fever, the nutritional status, the immunological and hormonal responses, and the presence of anorexia (1). The infection results in loss of weight or cessation of growth. .
whether the long-assumed increase in the protein breakdown rate with an inadequate diet was the cause of the excessive nitrogen loss. Methods
.
.
In order to examine these determinants of the “catabolic response” individually, we have measured protein synthesis, breakdown, and flux in children recovering from protein-energy-malnutrition and related them to the ad libitum food intake (appetite), the nitrogen balance, and the rate of weight change. We wished to determine whether the rates of synthesis or breakdown were sensitive to dietary change and The American
Journal of Clinical Nutrition
30:
AUGUST
Downloaded from https://academic.oup.com/ajcn/article-abstract/30/8/1345/4650116 by University of Minnesota Law Library user on 27 May 2018
Variation
in protein
intake
Seventeen children who had recovered from severe malnutrition were studied. The diets of the high-pro(em and five of the low-protein group have been described previously (2). The other five in the low-protein group received 107 cal-and 1 .2 g of protein/kg per day. The very low-protein group received 0.6 g of protein and 95 cal/kg per day. Protein turnover was measured as previously described (2) with a [“'Njglycine constant infusion.
‘ From the Tropical Metabolism Research Unit, University of the West Indies, Mona, Kingston 7, Jamaica. 2 Address reprint requests to: Dr. D. Picou, Tropical Metabolism Research Unit, University of the West Indies, Mona, Kingston 7, Jamaica. Visiting Lecturer and Wellcome Trust Research Fellow, Tropical Metabolism Research Unit. Professor of Human Nutrition, Department of Human Nutrition, London School of Hygiene and Tropical Medicine, London, England. “Professor of Experimental Medicine and Director, Tropical Metabolism Research Unit.
1977,
pp.
1345-1348.
Printed
in U.S.A.
1345
1346
GOLDEN
Variation
in dietary
ET AL.
intake
Ii
:OO4Ox.19 r:093 pc000l
12
Five children were studied four or five times during and after recovery from severe malnutrition. Two children received a soybean-based formula and three received a cow’s milk-based formula.6 The diet supplied 3 1 g of protein/liter and 1 ,350 cal/liter. The children were all fed the diets ad libitum. Protein synthesis, breakdown, and flux were measured with a single dose o [“'Nglycine and determining the amount excreted in the urine (3). The proportion of the dose excreted is then equal to the proportion of the flux which is excreted. This technique gives values that are not significantly different from the constant infusion method (3).
10 PROTEIN FLUX gm kgday
8 6
12
y =0031x .1.9 r=0.87
10
p