Metabolic response to glucose ingested with various amounts of protein13 Sydney
A Westphal,
ABSTRACT
Seven
fed breakfasts
C Gannon,
healthy,
of 50 g protein,
protein
plus
insulin,
C peptide,
amino
Mary
50 g glucose
nitrogen
in random
subjects
and
sequence.
measured
fatty from
were
10, 30, or 50 g Plasma
nonesterified
then
Q Nuttall
Frank
normal-weight
50 g glucose,
glucagon, were
and
glucose,
acids,
samples
and obtained
over 4 h. The postmeal net area of each response curve calculated. Ingestion of 50 g protein alone did not change serum
ingested
glucose with
concentration. 50 g glucose
a-
was the
The various amounts of protein also did not alter the serum glucose
tion
of protein
sulted
increased
larger
them
amounts
in a progressive
increase
glucagon-area responses. both the a-amino-nitrogen sponse. The null point, 50 g glucose
at which
as expected.
of protein The that there
Additions
to the
in the
glucose
of pro-
meal
a-amino-nitrogen-
would
be
sponse, was estimated to be 9 g protein and 5 g protein for glucagon. Am
no
reand
relationship was curvilinear response and the glucagon is, the protein dose ingested change
for rewith
in area
for a-amino J Clin Nutr
protocol.
bobic
response
of normal
tein,
and both
together.
re-
nitrogen 1990;52:
glucose
with
50 g glucose
amino
nitrogen,
glucagon,
protein, glycemic
diet, insulin, index,
relative
C peptide, glucose
a-
area
ies
have
been
published
that
have
quantitated
metabolic
re-
Having
demonstrated
a sensitive
relationship
between
the
doses of protein and the insulin response in subjects with NIDDM, we were interested in determining the sensitivity of the metabolic response of normal subjects to differing doses of protein. Therefore, normal subjects were studied by use of the Am J C/in Nuir
1990:52:267-72.
Printed
in USA.
© 1990 American
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
Society
same
and
unit.
Their
fat).
content
The
(Glutol,
here data
various
on the meta-
doses
50 g pro-
on the response of protein
of
given
subjects.
After
meal meat
Laboratories,
browned
until
served.
in a microwave
lean
hydrolysis
by the method was
Minneapolis).
ofcooked,
hydroxide
was determined
in a refrigerator the
mean
in the form
potassium
was determined The
three
Paddock
was given
fat content
placing
sponses on the basis ofdiffering amounts ofprotein in the meal. We (7) previously demonstrated in subjects with non-insulindependent diabetes (NIDDM), fed meals of 50 g glucose with various amounts of protein, an insulin incremental area response that was essentially linear with respect to the quantity ofprotein ingested. The increasing insulin response was associated with a decreasing plasma glucose response.
in these
males
solution
placed
It has been well established that both protein and amino acid ingestion stimulate insulin secretion and thus may affect the postprandial glucose concentration ( 1-6). However, few stud-
to
normal
traction.
Introduction
insulin
metabolic
protein
(6.5%
Dietary
We report
data
to 50 g glucose,
normal females were studied (±SD) age was 35.6 ± 7.9 y (range 27-54 y). All were within 5% of desirable body weight according to the 1959 Metropolitan Life Insurance Company tables (9). All subjects gave written, informed consent, and the study was approved by the Medical Center’s Committee on Human Subjects. All participants had ingested a diet containing 200 g carbohydrate/d with adequate food energy for 3 d before testing. After an overnight fast of 10-14 h, an indwelling catheter was inserted into an antecubital vein and was kept patent with a slow infusion ofO.45% saline. Test meals were given at 0800 and consisted of, in random order, a meal of 50 g glucose, 50 g protein, or a combination of 50 g glucose and 10, 30, or 50 g protein. Glucose (100 g/l 80 mL) was given as a standard gluin our
The
KEY WORDS
and
published
individuals
Methods
cose
267-72.
We (8) previously
serum
Four
response compared with that observed with 50 g glucose alone. Ingestion of the various amounts of protein also did not result in a further increase in insulin concentration when ingested with glucose, except with the 50-g-protein dose. This increase was modest. Ingestion of glucose resulted in a decrease in aamino nitrogen and glucagon concentrations whereas ingesgressively
same
ofZak
gravimetrically in a nonstick
Cooking oven
for
hamburger the
and
protein
Cohen
(10).
by ether frying
pan
cxand
was completed 30 s. Beef
by
protein
was selected because it is a commonly ingested form of meat protein in our society. In addition, we had used it previously in our study of the dose response to protein in diabetic subjects. The beefwas very low in fat and was considered to be less palatable than most meats eaten by Americans; however, it was not considered offensive to the volunteers. 1 From the Metabolic Research Laboratory, Section of Endocrinology, Metabolism, and Nutrition, VA Medical Center, and the Departments of Medicine and Food Science & Nutrition, University of Mmnesota, Minneapolis. 2
Supported
by VA Merit Review Funds.
Address reprint Nutrition Section,
requests to FQ Nuttall, Metabolic-Endocrine & Minneapolis VA Medical Center, One Veterans Drive, Minneapolis, MN 55417. Receivediune 13, 1989. Accepted for publication September 20, 1989. 3
for Clinical
Nutrition
267
268
WESTPHAL
ET
AL
60
.
40
50g pro/Og glu
3.00
Og pro/50g glu
2.50
0
lOg pro/5OggIu
A
3Ogpro/5OggIu
2.00
I.50 5Og pro/50g
20
glu
I
I .00
0 0)
E
0.50
E
0.00 -0.50
0
60
120
Minutes
180
after
240
‘E .
0
E E
Og
proonly
lOg
Ingestion
30g
50g
dose
FIG I . Left panel, glucose response to ingestion ofglucose, protein, or glucose plus protein. Right panel, effect of protein dose on glucose area. The incremental change in plasma glucose was determined for 4 h after ingestion of the meals (n = 7). The 0-50-g doses of protein were ingested together with 50 g glucose. Bar graphs indicate mean ± SEM. Areas are significantly different (p < 0.05) ifthey do not share a common superscript letter.
Blood
samples
1 h and then meal. Plasma
were drawn
at 30-mm glucose
method (Beckman
with a glucose Instruments,
reactive
insulin
was
Inc.
of3O K antiserum las),
and
Glucagon purchased nitrogen
a-amino
Goodwin (1 1). C peptide RIA method (12) with
with was
was kits
measured produced
baseline
the
concentration
used
rule
as a constant
we
assumed
changed.
Areas
(
I 3).
The
baseline.
that
the
below
the
by Endo-
by RIA
The mean baseline mmol/L. It reached
by use
were calculated
meals
by using
at time
were
the
zero
postmeal from
statistical
significance
(Statview
512k,
Apple
containing
value a peak
glucose,
of plasma glucose 30 mm after the
regardless
ofthe
was 4.8 ingestion
presence
± 0.1 of all
or absence
seen
with
glucose
alone.
There
was
little
change
in
plasma alone.
glucose concentration after ingestion of 50 g protein The calculated net area under the curve for the plasma glucose concentration increased only slightly when protein was ingested alone (Fig 1 , right panel). The plasma-glucose-area re-
areas
remained
subtracted
curve
was
unareas
above the baseline to give a net area. The analysis of variance (ANOVA) test with least significant difference was used to assess
Data
of protein. It returned to near baseline concentrations by 90 mm, decreased to a nadir at 120 mm, and then reapproached baseline by 240 mm (Fig 1, left panel). The ingestion of various amounts of protein with glucose did not significantly alter the
by a double-antibody by Immuno-Nuclear
concentration
baseline
for significance.
Results
Science Center (Dalby the method of
In calculating
fasting
Co). A p value of < 0.05 was the criterion are presented as the mean ± SEM.
electrode immuno-
kits produced
from Health was determined
for
of the oxidase
double-antibody
determined
Corp. Stillwater, MN. The areas above the fasting trapezoid
intervals
3 h after ingestion by a glucose
by a standard
method
(RIA)
Louisville.
and at 15-mm
analyzer with an oxygen Inc. Fullerton, CA). Serum
measured
radioimmunoassay tech,
before
intervals for was determined
sponse
to ingestion
of glucose
was
but was not significantly affected ofvarious amounts of protein.
Computer
much
greater,
as expected,
by the simultaneous
ingestion
800 7OO
E .
600
E 500
a. .‘
. 400 .
.(
.300
U)
C
200 1
60
proonly
after
Ingestion
Og
lOg
30g
50g
dose
FIG 2. Left panel, insulin response to ingestion ofglucose, protein, or glucose plus protein. Right protein dose on insulin area. The incremental change in plasma insulin was determined as indicated forFigure I. Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
E
0.
C
Minutes
0
panel, effect of in the legend
RESPONSE
TO
GLUCOSE-PLUS-PROTEIN
269
DOSES
.
E 0
.C
E 0.
Minutes
after
Ingestion
FIG 3. Left panel, C peptide response to ingestion of protein dose on C peptide area. The incremental legend for Figure 1.
The
initial
The
peak
then
returned
glucose
concentration
was 96 ± 7 pmol/L.
15 mm later (Fig 3, left panel). The curves
after
of 50 g glucose
for plasma
ingestion
at 180 mm
were
ingested
meal
together,
When
increase was quite (Fig 2, left panel).
modest Addition
containing
insulin-area
to the
panel). As indicated areas for the meals g glucose together.
only Thus,
The mean pmol/mL.
did
not
result was
the sum either
baseline
very
modestly
peak
at 45 mm
after
the
glucose
plus
throughout
the
meal
of protein
alone,
nitrogen out the
to
baseline,
and
was 0.69
and this
higher
increased
nitrogen
then
when
study
was
(Fig
nitrogen
concentrations
for
this
doses
remained
dose
mm
at the ofstudy.
to a
tein alone was similar (Fig 4, right panel).
it peaked
in a-amino
near
baseline.
with After
the
150-180 nitrogen For
the
glucose, glucose
this alone
to that
with
50 g protein
plus
50 g glucose
4 0
3
.C
E E
E 1
1
;
0
E E
0
z 0
-2 0
60
120
Minutes
after
180
240
pro only
Og
Ingestion
FIG 4. Left panel, a-amino
lOg
30g
50g
dose
nitrogen
effect ofprotein dose on a-amino nitrogen as indicated in the legend for Figure 1.
response
to ingestion
area. The incremental
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
3.1 mm this the
sustained throughmeals, the aremained
50 g, ingested
gluwere
was 90 near After
to a maximum at dose. The a-amino
remained
for the 240
first
increase
initially
of 30 and
the
and remained 4, left panel).
a prompt
when
with
50 g protein
over
alone
period
to those
increased
compared
30 and
decreased
there
not
ofa-amino
rapidly
rapidly increased for the lO-g protein
protein
increase
for the meal meal,
50 g glucose
were similar
was
the area was negative. It increased progressively with increasing amounts ofprotein in the meal. The area response to 50 g pro-
increased
except
with
of 50 g glucose
concentration
.06
±
area
effect in the
over the first 90 mm. This was then study. After the glucose-plus-protein
mm, except
50
and 50 g glucose additive.
meal After
ingestion
amino
protein-only 50 g protein.
mm
This
nadir
insulin
only
C peptide
increased
after
2, right
ofC peptide
glucose
It was
alone.
(Fig
concentration
with
cose
of the mean
the C peptide
for all meals
each
in an increased given
was ingested
± 0. 1 mmol/L.
the insulin for 240 ofprotein
50 g protein
concentration
insulin,
Insulin after
The
added (Fig 3, right panel). The mean initial concentration
ingestion
mm
alone,
elevated amounts
50 g protein
previously, containing
after
by 240
but it remained ofincreasing
until
insulin
50 g glucose.
was 100% that of 50 g protein these insulin responses were
Like
containing
plus
was ingested
50 g glucose
response
peak
insulin.
10 g protein
When
50 g protein
60 mm
baseline
50 g protein
the
containing
occurred
50 g protein
decreased
meals.
meal
insulin
containing
concentrations ofthe
Peak
and
(Fig 2, left panel).
at 45 mm for all but the meal
of the
the
insulin
protein
50 g glucose.
Right panel, as indicated
45 mm
to baseline
and
occurred plus
mean
occurred
ofglucose, protein, or glucose plus protein. change in plasma C peptide was determined
ofglucose, change
protein, in plasma
or glucose plus protein. a-amino
nitrogen
Right panel.
was determined
270
WESTPHAL 300
300
200
200
ET AL
E .C
E
‘)
.c
Co
C
100
100
0
‘C
.
0) C
C
j)
0
100
-100 0
60
120
Minutes
180
after
240
dose
Ingestion
FIG 5. Left panel, glucagon response to ingestion ofglucose, protein, or glucose plus protein. Right panel, effect of protein dose on glucagon area. The incremental change in plasma glucagon was determined as indicated in the legend forFigure 1.
The
mean
initial
value
ofgbucagon
was
2 1 1 ± 66 ng/L.
After
the ingestion ofglucose a nadir at 90 mm and
alone, glucagon decreased modestly to then slowly returned to baseline. After
the ingestion
ofprotein
alone
with
at 90 mm. It then (Fig 5, left panel).
a peak
mm ofstudy with
10 or 30 g protein,
mained
initially
protein
was
there
the
mean
unchanged.
ingested
with
was a considerable
increase,
remained elevated for the 240 After meals containing glucose glucagon
It decreased the glucose.
concentration
modestly
Later
re-
when
in the time
50 g
course,
a plateau
at -60
was
for all meals
lower
mm
(Fig
6, left panel).
containing
The
glucose
nadir
compared
reached with
that
resulting from ingestion of protein alone. Although the nadir reached was similar for all glucose-containing meals, the duration oftime over which the free fatty acids remained depressed varied inversely with the amount ofprotein in the meal. Mean areas under the curve of nonesterified free fatty acids were not statistically
different
containing
glucose
from plus
protein
30 g protein
alone,
except
(Fig
6, right
for
the
meal
panel).
the concentration increased after meals containing protein. The rapidity of the onset and the magnitude of the rise correbated
directly
with
the
amount
of protein
the curves were similar to those The area under the glucagon tion
of the
After
meal
all meals
containing
with
ingested.
50 g glucose
protein,
the area
tive and it increased progressively protein. The area under the curve
(Fig
under
After
the
ingestion from
a mean
ofall
meals,
baseline
5, right
the curve
When
ingespanel).
from
was posi-
nonesterified
that observed free
of 3 19 ± 50 mmol/L
fatty
acids
to reach
protein
meal, a significant has been reported by some investigators (6, 7, 14, 15) but not by others (16, 17). In these studies, subjects with NIDDM (14, 17) or normal subjects were used ( 1 5, 16). Spiller et al ( 1 5) and Day et ab ( 1 6) studied the effect of various amounts of protein on metabolic response in nondiabetic attenuation
with increasing amounts of resulting from ingestion of 50
g protein with 50 g glucose was not different when 50 g protein was ingested alone. decreased
Discussion
In general,
for a-amino nitrogen. curve was negative after
subjects. protein
is added
in the
Spiller together
to a carbohydrate
plasma
glucose
et al (1 5) used with
rise
breakfasts
58 g carbohydrate
containing as a mixture
200
100
‘E .C
g .;
a, .(
CO 0
-100
‘C ‘C UU-
-400
..
-200
3OO 0
60
120
Minutes
FIG 6. Left panel,
after
180
240
Ingestion
nonesterified
fatty acid response
dose
to ingestion
ofglucose,
panel, effect of protein dose on nonesterified fatty acid area. The incremental acid was determined as indicated in the legend for Figure 1 . ( 1 eq = 1 Mmol.)
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
protein, change
or glucose plus protein. in plasma
nonesterified
Right fatty
0-49 of malto-
g
RESPONSE y
-
2.57
.
0.3699*
+
.
0 01 1x’2
TO
I 380e4x’3
+
P
GLUCOSE-PLUS-PROTEIN
area
I 00
271
DOSES
under
the curve
progressively
decreased
with
an increased
amount ofprotein in the meal. In this study we found no effect on the net glucose area integrated either over 4 h (Fig 1, right panel) or when integrated over 2 h (data not shown). The
I
different
E ‘
y
.
6098
-
‘VU
.
.
Protein 17
+
Dose
(9)
04174x’2
1569+
#{149} 00047x’3
R
-
1 00
3
100
20
.
400
mmol 1
:
69.8609
-
‘
values
at 2 h had
the
could
be misleading.
erably
different
1
2
3
A
)
100 log 0
0
nAN
2
4
Area (g.hr/dI)
indicating
nitrogen
mined
fructose, by
use
a linear relation
area for the protein
and lactose.
of the
trapezoid
The area rule,
between
the glucagon
doses.
under
with
the curve,
fasting
deter-
glucose
as a
baseline, was measured for 2 h after the meal. A significant relationship was found between glucose area under the curve and the amount ofprotein in the meal. That is, the largest area under the glucose
curve
occurred
without
source
study
of the
In our
protein
protein
protein
present,
and
of untreated
protocol
response of protein
study
an
in-
with the 50-g with a dose of
was
addition
used
NIDDM
in several
not
constant.
did not have was
a
present
insulin
area
of
subjects
in this study,
increased ingested
protein
given
with
normal
and
NIDDM
more
larger
(7).
The
with
net
that
we found
linearly
a constant
the
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
subjects.
sensitive
used
that
the
respect
to
the
area
also
de-
glucose
amount The
ofglucose insulin
to protein
of protein
in NIDDM
is different
secretory
ingestion
in
response
in persons
with
ingested also has effects on the ( 18) and normal subjects (un-
published observations). As we (8) reported previously, protein ingested alone led to a rapid rise in a-amino nitrogen concentration whereas glucose ingestion resulted in a rapid fall in concentration. Also, when 50 g protein
and
50 g glucose
were
ingested
together,
there
was
little or no rise in a-amino the present study, a delay
nitrogen for the first 60 mm (8). In in the increase in a-amino nitrogen was present when 30 g protein was ingested
concentration also with the glucose but the duration
10 g protein there It was reported jects significantly is possible that
dextrins,
observed.
are consid-
by Day et al (16) differed
our results,
NIDDM. The type insulin area response
6 #{176}#{176}
FIG 7. Top and middle panels, effect of protein dose on a-amino nitrogen area and glucagon area. Each protein dose was given with 50 g glucose. The curve was generated by computer, as was the equation for the curve. The best-fitting curve for the data of each graph was a third-order polynomial, indicating a nonlinear relationship between the dose ofthe protein ingested and a-amino nitrogen or glucagon area. Bottom panel, glucagon area vs a-amino nitrogen area. Each protein dose was given with 50 g glucose. The curve was generated by computer. as was the equation for the curve. The best-fitting curve for the
data was first order,
used
the
with
meal
is much
Og 0
Thus,
results
creased in a concentration-dependent fashion with increasing doses of 10, 30, and 50 g protein. Thus, it is clear that the glucose and insulin responses to progressively larger amounts of
200
,‘_
-2
we
to baseline.
these
of protein.
quantity
§)
area and a-amino
75 g, and
the same insulin-area
300
4;
.4
Again,
.
.__#{149}#{149}
8 g, there was an increase in mean but the increase was not greater with ingestion
hril
.
from
In agreement
(9)
#{149} 49.2053*
amount of proin insulin-area
ways from that used by Spiller et al (1 5) and ours, making comparisons difficult. The test meal was given at noon and the responses were measured for just 90 mm. The meals contained various amounts offat as well as a constant amount of carbohydrate and different amounts of protein. The amount of carbohydrate also was less (25 g). The protein content ranged from
#{149}
0
et al (15) the smallest in a significant increase
results
4Q
y -
Dose
and
to be
200
40
Protein
type
insulin
3.6 .
.
to the
this remains
30g.
0
#{149}100
be due
300
/ ,
0
may
however,
crease in insulin-area response was only present dose and the C peptide area was only increased
100
.
studies
ingested;
400
)
(
two
of not the
The __+_4
of the
response when integrated over a 2-h period. With ingestion larger amounts of protein, the insulin-area response was further increased. However, as pointed out by the authors,
: 200
results
amount ofcarbohydrate determined. In the study by Spiller tein given ( 16 g) resulted
‘E
ofthis
was little change that hyperglycemia
delay
in a-amino induced
was shorter.
nitrogen. in normal
slows gastric emptying (19, 20). Therefore, the rise of plasma glucose, resulting from
With
subit
the glucose in the meal, delayed emptying ofprotein into the duodenum and thus delayed its digestion. However, because the area under the curve was negative after the glucose meal but remained near the baseline for 60 mm when protein was ingested with the glucose, it is possible that the unchanged aamino nitrogen concentration over this time resulted from a
272
WESTPHAL
rise in insulin
from
that
wasjust
the gut. This
regardless
of the
ofamino
protein
entry into (2 1 , 22). When
integrated
over
by the influx
because
dose.
acid
mented was
balanced
is unlikely the
ofamino
the results
the
from
suppression muscle
is well
a-amino-nitrogen-area
4 h, there
was
docu-
response
a curvilinear
relationship
between the amount of protein ingested and the area response (Fig 7, top panel). This was best defined by a third-degree polynomial expression. From these data it appears that the null point
(ie,
change
the
protein
in area
g, that
dose)
response
at which
would
is essentially
with
while glucose In addition,
25).
in glucagon
When
gardless
of the
a-amino
glucose
nitrogen
amino
nitrogen
was
(Fig
that
a particular
dose.
This
concentration
was began
concentration,
7, bottom
in the
meal,
did not occur
the
tegrated over 4 h showed amount ofprotein ingested The importance ofa rise the digestion of protein on the close correlation between gon
present
concentration protein
of 9
concentrain the meal a significant
for
60 mm,
time
to rise.
supcon-
re-
at which As with
glucagon-area
the the
a-
response
in-
a sigmoidal relationship with the (Fig 7, middle panel). in circulating amino acids and/or the glucagon secretion is shown by the a-amino nitrogen and gluca-
panel).
This
a-amino
the
indicating
ingestion our data
firm the observation that the circulating glucagon tion depends on the ratio ofprotein to carbohydrate rise
net
dose
ratio
are in agreement
that protein ingestion stimulates presses glucagon secretion (23-28).
(16,
no
a protein
of -5: 1. with previous studies
is, a glucose-to-protein
Our results
there
occur
linear
nitrogen
relationship
response
would
indicates be associ-
ated with a predictable glucagon response. For example, a rise in a-amino nitrogen ofO.7 mmol . h . L’ would correspond to a rise ofglucagon of-50 ng.h.L’. The amount of protein ingested with 50 g glucose that resulted in no net change in glucagon area was only 5 g. Thus, it is clear that ingested protein
potent
in stimulating
cose
a rise in glucagon
is in suppressing
protein
is 10-fold
it. Our greater
than
data that
To our knowledge the sensitivity ofprotein has not been determined.
calculated is much
concentration
suggest
that
ofglucose
of glucagon
the
to be more
than effect
on a weight
glu-
of beef basis.
to the ingestion U
References 1 . Fajans 55, Floyd JC, Knopf RF, Conn JW. Effect of amino acids and proteins on insulin secretion in men. Recent Prog Horm Res 1967:23:617-20.
2. Floyd JC, Fajans 55, Conn JW, KnopfRF, Rull J. Insulin secretion +n response to protein ingestion. J Clin Invest 1966:45:1479-86. 3. Floyd JC, Fajans 55, Knopf RF, Conn JW. Evidence that insulin release is the mechanism for experimentally induced leucine hypoglycemia in men. J Clin Invest 1963:42:1714-9. 4. Fajans 55, floyd JC, Pek 5, Knopf RF, Jacobson M, Conn JW. Effect of protein meals on plasma insulin in mildly diabetic patients. Diabetes 1969: 18:523-8. 5. Berger 5, Vongaraya N. Insulin response to ingested protein in diabetes. Diabetes 1966: 15:303-6. 6. Rabinowitz D, Merimee Ti, Maffezzoli R, Burgess iA. Patterns of hormonal release after glucose, protein, and glucose plus protein. Lancet 1966:2:454-7. 7. Nuttall FQ, Mooradian AD, Gannon MC, Billington Ci, Krezowski P. Effect of protein ingestion on the glucose and insulin re-
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
AL sponse
acid
to a standardized
oral glucose
load.
Diabetes
Care
l984;7:
465-70.
were the same
Insulin-dependent plasma
ET
8. Krezowski PA, Nuttall FQ, Gannon MC, Bartosh NH. The effect of protein ingestion on the metabolic response to oral glucose in normal individuals. Am J Clin Nutr 1986;44:847-56. 9. Metropolitan Life Insurance Company. New weight standards for men and women. Stat Bull Metropol Life InsurCo, 1959:40:1-4. 10. Zak B, Cohen J. Automatic analysis oftissue culture proteins with stable Folin reagents. Clin Chim Acts 196 1:6:665-70. 1 1 . Goodwin JF. The colorimetric estimation ofplasma amino nitrogen with DFNB. Clin Chem 1968; 14:1080-90. 12. Krause U, Von Erdmann B, Atzpodien W, Beyeri. C-peptide measurement: a simple method for the improvement of specificity. J Immunoassay 198l;2:33-44. 13. Fuller G, Parker RM. Applications 13-16. Approximate integration in analytical geometry and calculus. Princeton: Van Nostrand, 1964. 14. Estrich D, Ravnik A, SchlierfG, Fukayama G, Kinsell L. Effects ofco-ingestion of fat and protein upon carbohydrate-induced hyperglycemia. Diabetes 1976:16:232-7. 15. SpillerGA, Jensen CD, Pattison IS, Chuck CS, Whittam JH, Scala i. Effect ofprotein dose on serum glucose and insulin response to sugars. Am J Clin Nut l987;46:474-80. 16. Day IL, Johansen K, Ganda OP, Soeldner IS, Gleason RE, Midgley W. Factors governing insulin and glucagon responses during normal meals. Clin Endocrinol(Oxf) 1978;9:443-54. 17. Jenkins DJA, Wolever TMS, Jenkins AL, et al. The glycaemic index of foods tested in diabetic patients: a new basis for carbohydrate exchange favouring the use of legumes. Diabetobogia 1983; 24:257-64. 18. Gannon MC, Nuttall FQ, Neil BJ, Westphal SA. The insulin and glucose responses to meals ofglucose plus various proteins in type
II diabetic
subjects.
Metabolism
1988;37: 1081-8.
19. MacGregor IL, Gueller R, Watts HD, Meyer iH. The effect of acute hyperglycemia on gastric emptying in man. Gastroenterology 1976;70: 190-6. 20. Barnett JL, Owyang C. Serum glucose concentration as a modulator of interdigestive gastric motility. Gastroenterology 1988:94: 739-44. 2 1. Fukagawa NK, Minaker KL, Young VR, Rowe JW. Insulin dosedependent reductions in plasma amino acids in man. Am I Physiol l986;250:El 3-7. 22. Fukagawa NK, Minaker KL, Rowe JW, et al. Insulin-mediated reductions ofwhole body protein breakdown: dose-response effects on leucine metabolism in postabsorptive men. I Clin Invest 1985;76:2306-l
1.
23.
Ahmed M, Nuttall FQ, Gannon MC, Lamusga RF. Plasma glucagon and a-amino acid nitrogen response to various diets in normal humans. Am I Nutr 1980:33:1917-24. 24. Palmer JP, Benson JW, Walter RM, Ensinck JW. Arginine-stimulated acute phase ofinsulin and glucagon secretion in diabetic subjects. J Clin Invest l976;58:565-70. 25. Muller WA, Faloona GR, Unger RH, Aquilar-Parada E. Abnor-
26.
mal alpha cell function in diabetes. Response to carbohydrate and protein ingestion. N EngI I Med 1970;283: 109-15. Muller WA, Faloona GR, Unger RH. The influence of antecedent diet upon glucagon and insulin secretion. N EngI I Med 197 l;285: 1450-4.
27.
28.
Ohneda A, Aquilar-Parada E, Eisentraut AM, Unger RH. Characterization of circulating glucagon to intraduodenal and intravenous administration ofamino acids. I Clin Invest 1968;47:230522. Aquilar-Parada E, Eisentraut AM, Unger RH. Pancreatic glucagon secretion in normal and diabetic subjects. Am I Med Sci 1969;257: 4 15-9.
A Westphal,
ABSTRACT
Seven
fed breakfasts
C Gannon,
healthy,
of 50 g protein,
protein
plus
insulin,
C peptide,
amino
Mary
50 g glucose
nitrogen
in random
subjects
and
sequence.
measured
fatty from
were
10, 30, or 50 g Plasma
nonesterified
then
Q Nuttall
Frank
normal-weight
50 g glucose,
glucagon, were
and
glucose,
acids,
samples
and obtained
over 4 h. The postmeal net area of each response curve calculated. Ingestion of 50 g protein alone did not change serum
ingested
glucose with
concentration. 50 g glucose
a-
was the
The various amounts of protein also did not alter the serum glucose
tion
of protein
sulted
increased
larger
them
amounts
in a progressive
increase
glucagon-area responses. both the a-amino-nitrogen sponse. The null point, 50 g glucose
at which
as expected.
of protein The that there
Additions
to the
in the
glucose
of pro-
meal
a-amino-nitrogen-
would
be
sponse, was estimated to be 9 g protein and 5 g protein for glucagon. Am
no
reand
relationship was curvilinear response and the glucagon is, the protein dose ingested change
for rewith
in area
for a-amino J Clin Nutr
protocol.
bobic
response
of normal
tein,
and both
together.
re-
nitrogen 1990;52:
glucose
with
50 g glucose
amino
nitrogen,
glucagon,
protein, glycemic
diet, insulin, index,
relative
C peptide, glucose
a-
area
ies
have
been
published
that
have
quantitated
metabolic
re-
Having
demonstrated
a sensitive
relationship
between
the
doses of protein and the insulin response in subjects with NIDDM, we were interested in determining the sensitivity of the metabolic response of normal subjects to differing doses of protein. Therefore, normal subjects were studied by use of the Am J C/in Nuir
1990:52:267-72.
Printed
in USA.
© 1990 American
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
Society
same
and
unit.
Their
fat).
content
The
(Glutol,
here data
various
on the meta-
doses
50 g pro-
on the response of protein
of
given
subjects.
After
meal meat
Laboratories,
browned
until
served.
in a microwave
lean
hydrolysis
by the method was
Minneapolis).
ofcooked,
hydroxide
was determined
in a refrigerator the
mean
in the form
potassium
was determined The
three
Paddock
was given
fat content
placing
sponses on the basis ofdiffering amounts ofprotein in the meal. We (7) previously demonstrated in subjects with non-insulindependent diabetes (NIDDM), fed meals of 50 g glucose with various amounts of protein, an insulin incremental area response that was essentially linear with respect to the quantity ofprotein ingested. The increasing insulin response was associated with a decreasing plasma glucose response.
in these
males
solution
placed
It has been well established that both protein and amino acid ingestion stimulate insulin secretion and thus may affect the postprandial glucose concentration ( 1-6). However, few stud-
to
normal
traction.
Introduction
insulin
metabolic
protein
(6.5%
Dietary
We report
data
to 50 g glucose,
normal females were studied (±SD) age was 35.6 ± 7.9 y (range 27-54 y). All were within 5% of desirable body weight according to the 1959 Metropolitan Life Insurance Company tables (9). All subjects gave written, informed consent, and the study was approved by the Medical Center’s Committee on Human Subjects. All participants had ingested a diet containing 200 g carbohydrate/d with adequate food energy for 3 d before testing. After an overnight fast of 10-14 h, an indwelling catheter was inserted into an antecubital vein and was kept patent with a slow infusion ofO.45% saline. Test meals were given at 0800 and consisted of, in random order, a meal of 50 g glucose, 50 g protein, or a combination of 50 g glucose and 10, 30, or 50 g protein. Glucose (100 g/l 80 mL) was given as a standard gluin our
The
KEY WORDS
and
published
individuals
Methods
cose
267-72.
We (8) previously
serum
Four
response compared with that observed with 50 g glucose alone. Ingestion of the various amounts of protein also did not result in a further increase in insulin concentration when ingested with glucose, except with the 50-g-protein dose. This increase was modest. Ingestion of glucose resulted in a decrease in aamino nitrogen and glucagon concentrations whereas ingesgressively
same
ofZak
gravimetrically in a nonstick
Cooking oven
for
hamburger the
and
protein
Cohen
(10).
by ether frying
pan
cxand
was completed 30 s. Beef
by
protein
was selected because it is a commonly ingested form of meat protein in our society. In addition, we had used it previously in our study of the dose response to protein in diabetic subjects. The beefwas very low in fat and was considered to be less palatable than most meats eaten by Americans; however, it was not considered offensive to the volunteers. 1 From the Metabolic Research Laboratory, Section of Endocrinology, Metabolism, and Nutrition, VA Medical Center, and the Departments of Medicine and Food Science & Nutrition, University of Mmnesota, Minneapolis. 2
Supported
by VA Merit Review Funds.
Address reprint Nutrition Section,
requests to FQ Nuttall, Metabolic-Endocrine & Minneapolis VA Medical Center, One Veterans Drive, Minneapolis, MN 55417. Receivediune 13, 1989. Accepted for publication September 20, 1989. 3
for Clinical
Nutrition
267
268
WESTPHAL
ET
AL
60
.
40
50g pro/Og glu
3.00
Og pro/50g glu
2.50
0
lOg pro/5OggIu
A
3Ogpro/5OggIu
2.00
I.50 5Og pro/50g
20
glu
I
I .00
0 0)
E
0.50
E
0.00 -0.50
0
60
120
Minutes
180
after
240
‘E .
0
E E
Og
proonly
lOg
Ingestion
30g
50g
dose
FIG I . Left panel, glucose response to ingestion ofglucose, protein, or glucose plus protein. Right panel, effect of protein dose on glucose area. The incremental change in plasma glucose was determined for 4 h after ingestion of the meals (n = 7). The 0-50-g doses of protein were ingested together with 50 g glucose. Bar graphs indicate mean ± SEM. Areas are significantly different (p < 0.05) ifthey do not share a common superscript letter.
Blood
samples
1 h and then meal. Plasma
were drawn
at 30-mm glucose
method (Beckman
with a glucose Instruments,
reactive
insulin
was
Inc.
of3O K antiserum las),
and
Glucagon purchased nitrogen
a-amino
Goodwin (1 1). C peptide RIA method (12) with
with was
was kits
measured produced
baseline
the
concentration
used
rule
as a constant
we
assumed
changed.
Areas
(
I 3).
The
baseline.
that
the
below
the
by Endo-
by RIA
The mean baseline mmol/L. It reached
by use
were calculated
meals
by using
at time
were
the
zero
postmeal from
statistical
significance
(Statview
512k,
Apple
containing
value a peak
glucose,
of plasma glucose 30 mm after the
regardless
ofthe
was 4.8 ingestion
presence
± 0.1 of all
or absence
seen
with
glucose
alone.
There
was
little
change
in
plasma alone.
glucose concentration after ingestion of 50 g protein The calculated net area under the curve for the plasma glucose concentration increased only slightly when protein was ingested alone (Fig 1 , right panel). The plasma-glucose-area re-
areas
remained
subtracted
curve
was
unareas
above the baseline to give a net area. The analysis of variance (ANOVA) test with least significant difference was used to assess
Data
of protein. It returned to near baseline concentrations by 90 mm, decreased to a nadir at 120 mm, and then reapproached baseline by 240 mm (Fig 1, left panel). The ingestion of various amounts of protein with glucose did not significantly alter the
by a double-antibody by Immuno-Nuclear
concentration
baseline
for significance.
Results
Science Center (Dalby the method of
In calculating
fasting
Co). A p value of < 0.05 was the criterion are presented as the mean ± SEM.
electrode immuno-
kits produced
from Health was determined
for
of the oxidase
double-antibody
determined
Corp. Stillwater, MN. The areas above the fasting trapezoid
intervals
3 h after ingestion by a glucose
by a standard
method
(RIA)
Louisville.
and at 15-mm
analyzer with an oxygen Inc. Fullerton, CA). Serum
measured
radioimmunoassay tech,
before
intervals for was determined
sponse
to ingestion
of glucose
was
but was not significantly affected ofvarious amounts of protein.
Computer
much
greater,
as expected,
by the simultaneous
ingestion
800 7OO
E .
600
E 500
a. .‘
. 400 .
.(
.300
U)
C
200 1
60
proonly
after
Ingestion
Og
lOg
30g
50g
dose
FIG 2. Left panel, insulin response to ingestion ofglucose, protein, or glucose plus protein. Right protein dose on insulin area. The incremental change in plasma insulin was determined as indicated forFigure I. Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
E
0.
C
Minutes
0
panel, effect of in the legend
RESPONSE
TO
GLUCOSE-PLUS-PROTEIN
269
DOSES
.
E 0
.C
E 0.
Minutes
after
Ingestion
FIG 3. Left panel, C peptide response to ingestion of protein dose on C peptide area. The incremental legend for Figure 1.
The
initial
The
peak
then
returned
glucose
concentration
was 96 ± 7 pmol/L.
15 mm later (Fig 3, left panel). The curves
after
of 50 g glucose
for plasma
ingestion
at 180 mm
were
ingested
meal
together,
When
increase was quite (Fig 2, left panel).
modest Addition
containing
insulin-area
to the
panel). As indicated areas for the meals g glucose together.
only Thus,
The mean pmol/mL.
did
not
result was
the sum either
baseline
very
modestly
peak
at 45 mm
after
the
glucose
plus
throughout
the
meal
of protein
alone,
nitrogen out the
to
baseline,
and
was 0.69
and this
higher
increased
nitrogen
then
when
study
was
(Fig
nitrogen
concentrations
for
this
doses
remained
dose
mm
at the ofstudy.
to a
tein alone was similar (Fig 4, right panel).
it peaked
in a-amino
near
baseline.
with After
the
150-180 nitrogen For
the
glucose, glucose
this alone
to that
with
50 g protein
plus
50 g glucose
4 0
3
.C
E E
E 1
1
;
0
E E
0
z 0
-2 0
60
120
Minutes
after
180
240
pro only
Og
Ingestion
FIG 4. Left panel, a-amino
lOg
30g
50g
dose
nitrogen
effect ofprotein dose on a-amino nitrogen as indicated in the legend for Figure 1.
response
to ingestion
area. The incremental
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
3.1 mm this the
sustained throughmeals, the aremained
50 g, ingested
gluwere
was 90 near After
to a maximum at dose. The a-amino
remained
for the 240
first
increase
initially
of 30 and
the
and remained 4, left panel).
a prompt
when
with
50 g protein
over
alone
period
to those
increased
compared
30 and
decreased
there
not
ofa-amino
rapidly
rapidly increased for the lO-g protein
protein
increase
for the meal meal,
50 g glucose
were similar
was
the area was negative. It increased progressively with increasing amounts ofprotein in the meal. The area response to 50 g pro-
increased
except
with
of 50 g glucose
concentration
.06
±
area
effect in the
over the first 90 mm. This was then study. After the glucose-plus-protein
mm, except
50
and 50 g glucose additive.
meal After
ingestion
amino
protein-only 50 g protein.
mm
This
nadir
insulin
only
C peptide
increased
after
2, right
ofC peptide
glucose
It was
alone.
(Fig
concentration
with
cose
of the mean
the C peptide
for all meals
each
in an increased given
was ingested
± 0. 1 mmol/L.
the insulin for 240 ofprotein
50 g protein
concentration
insulin,
Insulin after
The
added (Fig 3, right panel). The mean initial concentration
ingestion
mm
alone,
elevated amounts
50 g protein
previously, containing
after
by 240
but it remained ofincreasing
until
insulin
50 g glucose.
was 100% that of 50 g protein these insulin responses were
Like
containing
plus
was ingested
50 g glucose
response
peak
insulin.
10 g protein
When
50 g protein
60 mm
baseline
50 g protein
the
containing
occurred
50 g protein
decreased
meals.
meal
insulin
containing
concentrations ofthe
Peak
and
(Fig 2, left panel).
at 45 mm for all but the meal
of the
the
insulin
protein
50 g glucose.
Right panel, as indicated
45 mm
to baseline
and
occurred plus
mean
occurred
ofglucose, protein, or glucose plus protein. change in plasma C peptide was determined
ofglucose, change
protein, in plasma
or glucose plus protein. a-amino
nitrogen
Right panel.
was determined
270
WESTPHAL 300
300
200
200
ET AL
E .C
E
‘)
.c
Co
C
100
100
0
‘C
.
0) C
C
j)
0
100
-100 0
60
120
Minutes
180
after
240
dose
Ingestion
FIG 5. Left panel, glucagon response to ingestion ofglucose, protein, or glucose plus protein. Right panel, effect of protein dose on glucagon area. The incremental change in plasma glucagon was determined as indicated in the legend forFigure 1.
The
mean
initial
value
ofgbucagon
was
2 1 1 ± 66 ng/L.
After
the ingestion ofglucose a nadir at 90 mm and
alone, glucagon decreased modestly to then slowly returned to baseline. After
the ingestion
ofprotein
alone
with
at 90 mm. It then (Fig 5, left panel).
a peak
mm ofstudy with
10 or 30 g protein,
mained
initially
protein
was
there
the
mean
unchanged.
ingested
with
was a considerable
increase,
remained elevated for the 240 After meals containing glucose glucagon
It decreased the glucose.
concentration
modestly
Later
re-
when
in the time
50 g
course,
a plateau
at -60
was
for all meals
lower
mm
(Fig
6, left panel).
containing
The
glucose
nadir
compared
reached with
that
resulting from ingestion of protein alone. Although the nadir reached was similar for all glucose-containing meals, the duration oftime over which the free fatty acids remained depressed varied inversely with the amount ofprotein in the meal. Mean areas under the curve of nonesterified free fatty acids were not statistically
different
containing
glucose
from plus
protein
30 g protein
alone,
except
(Fig
6, right
for
the
meal
panel).
the concentration increased after meals containing protein. The rapidity of the onset and the magnitude of the rise correbated
directly
with
the
amount
of protein
the curves were similar to those The area under the glucagon tion
of the
After
meal
all meals
containing
with
ingested.
50 g glucose
protein,
the area
tive and it increased progressively protein. The area under the curve
(Fig
under
After
the
ingestion from
a mean
ofall
meals,
baseline
5, right
the curve
When
ingespanel).
from
was posi-
nonesterified
that observed free
of 3 19 ± 50 mmol/L
fatty
acids
to reach
protein
meal, a significant has been reported by some investigators (6, 7, 14, 15) but not by others (16, 17). In these studies, subjects with NIDDM (14, 17) or normal subjects were used ( 1 5, 16). Spiller et al ( 1 5) and Day et ab ( 1 6) studied the effect of various amounts of protein on metabolic response in nondiabetic attenuation
with increasing amounts of resulting from ingestion of 50
g protein with 50 g glucose was not different when 50 g protein was ingested alone. decreased
Discussion
In general,
for a-amino nitrogen. curve was negative after
subjects. protein
is added
in the
Spiller together
to a carbohydrate
plasma
glucose
et al (1 5) used with
rise
breakfasts
58 g carbohydrate
containing as a mixture
200
100
‘E .C
g .;
a, .(
CO 0
-100
‘C ‘C UU-
-400
..
-200
3OO 0
60
120
Minutes
FIG 6. Left panel,
after
180
240
Ingestion
nonesterified
fatty acid response
dose
to ingestion
ofglucose,
panel, effect of protein dose on nonesterified fatty acid area. The incremental acid was determined as indicated in the legend for Figure 1 . ( 1 eq = 1 Mmol.)
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
protein, change
or glucose plus protein. in plasma
nonesterified
Right fatty
0-49 of malto-
g
RESPONSE y
-
2.57
.
0.3699*
+
.
0 01 1x’2
TO
I 380e4x’3
+
P
GLUCOSE-PLUS-PROTEIN
area
I 00
271
DOSES
under
the curve
progressively
decreased
with
an increased
amount ofprotein in the meal. In this study we found no effect on the net glucose area integrated either over 4 h (Fig 1, right panel) or when integrated over 2 h (data not shown). The
I
different
E ‘
y
.
6098
-
‘VU
.
.
Protein 17
+
Dose
(9)
04174x’2
1569+
#{149} 00047x’3
R
-
1 00
3
100
20
.
400
mmol 1
:
69.8609
-
‘
values
at 2 h had
the
could
be misleading.
erably
different
1
2
3
A
)
100 log 0
0
nAN
2
4
Area (g.hr/dI)
indicating
nitrogen
mined
fructose, by
use
a linear relation
area for the protein
and lactose.
of the
trapezoid
The area rule,
between
the glucagon
doses.
under
with
the curve,
fasting
deter-
glucose
as a
baseline, was measured for 2 h after the meal. A significant relationship was found between glucose area under the curve and the amount ofprotein in the meal. That is, the largest area under the glucose
curve
occurred
without
source
study
of the
In our
protein
protein
protein
present,
and
of untreated
protocol
response of protein
study
an
in-
with the 50-g with a dose of
was
addition
used
NIDDM
in several
not
constant.
did not have was
a
present
insulin
area
of
subjects
in this study,
increased ingested
protein
given
with
normal
and
NIDDM
more
larger
(7).
The
with
net
that
we found
linearly
a constant
the
Downloaded from https://academic.oup.com/ajcn/article-abstract/52/2/267/4651391 by guest on 10 April 2018
subjects.
sensitive
used
that
the
respect
to
the
area
also
de-
glucose
amount The
ofglucose insulin
to protein
of protein
in NIDDM
is different
secretory
ingestion
in
response
in persons
with
ingested also has effects on the ( 18) and normal subjects (un-
published observations). As we (8) reported previously, protein ingested alone led to a rapid rise in a-amino nitrogen concentration whereas glucose ingestion resulted in a rapid fall in concentration. Also, when 50 g protein
and
50 g glucose
were
ingested
together,
there
was
little or no rise in a-amino the present study, a delay
nitrogen for the first 60 mm (8). In in the increase in a-amino nitrogen was present when 30 g protein was ingested
concentration also with the glucose but the duration
10 g protein there It was reported jects significantly is possible that
dextrins,
observed.
are consid-
by Day et al (16) differed
our results,
NIDDM. The type insulin area response
6 #{176}#{176}
FIG 7. Top and middle panels, effect of protein dose on a-amino nitrogen area and glucagon area. Each protein dose was given with 50 g glucose. The curve was generated by computer, as was the equation for the curve. The best-fitting curve for the data of each graph was a third-order polynomial, indicating a nonlinear relationship between the dose ofthe protein ingested and a-amino nitrogen or glucagon area. Bottom panel, glucagon area vs a-amino nitrogen area. Each protein dose was given with 50 g glucose. The curve was generated by computer. as was the equation for the curve. The best-fitting curve for the
data was first order,
used
the
with
meal
is much
Og 0
Thus,
results
creased in a concentration-dependent fashion with increasing doses of 10, 30, and 50 g protein. Thus, it is clear that the glucose and insulin responses to progressively larger amounts of
200
,‘_
-2
we
to baseline.
these
of protein.
quantity
§)
area and a-amino
75 g, and
the same insulin-area
300
4;
.4
Again,
.
.__#{149}#{149}
8 g, there was an increase in mean but the increase was not greater with ingestion
hril
.
from
In agreement
(9)
#{149} 49.2053*
amount of proin insulin-area
ways from that used by Spiller et al (1 5) and ours, making comparisons difficult. The test meal was given at noon and the responses were measured for just 90 mm. The meals contained various amounts offat as well as a constant amount of carbohydrate and different amounts of protein. The amount of carbohydrate also was less (25 g). The protein content ranged from
#{149}
0
et al (15) the smallest in a significant increase
results
4Q
y -
Dose
and
to be
200
40
Protein
type
insulin
3.6 .
.
to the
this remains
30g.
0
#{149}100
be due
300
/ ,
0
may
however,
crease in insulin-area response was only present dose and the C peptide area was only increased
100
.
studies
ingested;
400
)
(
two
of not the
The __+_4
of the
response when integrated over a 2-h period. With ingestion larger amounts of protein, the insulin-area response was further increased. However, as pointed out by the authors,
: 200
results
amount ofcarbohydrate determined. In the study by Spiller tein given ( 16 g) resulted
‘E
ofthis
was little change that hyperglycemia
delay
in a-amino induced
was shorter.
nitrogen. in normal
slows gastric emptying (19, 20). Therefore, the rise of plasma glucose, resulting from
With
subit
the glucose in the meal, delayed emptying ofprotein into the duodenum and thus delayed its digestion. However, because the area under the curve was negative after the glucose meal but remained near the baseline for 60 mm when protein was ingested with the glucose, it is possible that the unchanged aamino nitrogen concentration over this time resulted from a
272
WESTPHAL
rise in insulin
from
that
wasjust
the gut. This
regardless
of the
ofamino
protein
entry into (2 1 , 22). When
integrated
over
by the influx
because
dose.
acid
mented was
balanced
is unlikely the
ofamino
the results
the
from
suppression muscle
is well
a-amino-nitrogen-area
4 h, there
was
docu-
response
a curvilinear
relationship
between the amount of protein ingested and the area response (Fig 7, top panel). This was best defined by a third-degree polynomial expression. From these data it appears that the null point
(ie,
change
the
protein
in area
g, that
dose)
response
at which
would
is essentially
with
while glucose In addition,
25).
in glucagon
When
gardless
of the
a-amino
glucose
nitrogen
amino
nitrogen
was
(Fig
that
a particular
dose.
This
concentration
was began
concentration,
7, bottom
in the
meal,
did not occur
the
tegrated over 4 h showed amount ofprotein ingested The importance ofa rise the digestion of protein on the close correlation between gon
present
concentration protein
of 9
concentrain the meal a significant
for
60 mm,
time
to rise.
supcon-
re-
at which As with
glucagon-area
the the
a-
response
in-
a sigmoidal relationship with the (Fig 7, middle panel). in circulating amino acids and/or the glucagon secretion is shown by the a-amino nitrogen and gluca-
panel).
This
a-amino
the
indicating
ingestion our data
firm the observation that the circulating glucagon tion depends on the ratio ofprotein to carbohydrate rise
net
dose
ratio
are in agreement
that protein ingestion stimulates presses glucagon secretion (23-28).
(16,
no
a protein
of -5: 1. with previous studies
is, a glucose-to-protein
Our results
there
occur
linear
nitrogen
relationship
response
would
indicates be associ-
ated with a predictable glucagon response. For example, a rise in a-amino nitrogen ofO.7 mmol . h . L’ would correspond to a rise ofglucagon of-50 ng.h.L’. The amount of protein ingested with 50 g glucose that resulted in no net change in glucagon area was only 5 g. Thus, it is clear that ingested protein
potent
in stimulating
cose
a rise in glucagon
is in suppressing
protein
is 10-fold
it. Our greater
than
data that
To our knowledge the sensitivity ofprotein has not been determined.
calculated is much
concentration
suggest
that
ofglucose
of glucagon
the
to be more
than effect
on a weight
glu-
of beef basis.
to the ingestion U
References 1 . Fajans 55, Floyd JC, Knopf RF, Conn JW. Effect of amino acids and proteins on insulin secretion in men. Recent Prog Horm Res 1967:23:617-20.
2. Floyd JC, Fajans 55, Conn JW, KnopfRF, Rull J. Insulin secretion +n response to protein ingestion. J Clin Invest 1966:45:1479-86. 3. Floyd JC, Fajans 55, Knopf RF, Conn JW. Evidence that insulin release is the mechanism for experimentally induced leucine hypoglycemia in men. J Clin Invest 1963:42:1714-9. 4. Fajans 55, floyd JC, Pek 5, Knopf RF, Jacobson M, Conn JW. Effect of protein meals on plasma insulin in mildly diabetic patients. Diabetes 1969: 18:523-8. 5. Berger 5, Vongaraya N. Insulin response to ingested protein in diabetes. Diabetes 1966: 15:303-6. 6. Rabinowitz D, Merimee Ti, Maffezzoli R, Burgess iA. Patterns of hormonal release after glucose, protein, and glucose plus protein. Lancet 1966:2:454-7. 7. Nuttall FQ, Mooradian AD, Gannon MC, Billington Ci, Krezowski P. Effect of protein ingestion on the glucose and insulin re-
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AL sponse
acid
to a standardized
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Diabetes
Care
l984;7:
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ET
8. Krezowski PA, Nuttall FQ, Gannon MC, Bartosh NH. The effect of protein ingestion on the metabolic response to oral glucose in normal individuals. Am J Clin Nutr 1986;44:847-56. 9. Metropolitan Life Insurance Company. New weight standards for men and women. Stat Bull Metropol Life InsurCo, 1959:40:1-4. 10. Zak B, Cohen J. Automatic analysis oftissue culture proteins with stable Folin reagents. Clin Chim Acts 196 1:6:665-70. 1 1 . Goodwin JF. The colorimetric estimation ofplasma amino nitrogen with DFNB. Clin Chem 1968; 14:1080-90. 12. Krause U, Von Erdmann B, Atzpodien W, Beyeri. C-peptide measurement: a simple method for the improvement of specificity. J Immunoassay 198l;2:33-44. 13. Fuller G, Parker RM. Applications 13-16. Approximate integration in analytical geometry and calculus. Princeton: Van Nostrand, 1964. 14. Estrich D, Ravnik A, SchlierfG, Fukayama G, Kinsell L. Effects ofco-ingestion of fat and protein upon carbohydrate-induced hyperglycemia. Diabetes 1976:16:232-7. 15. SpillerGA, Jensen CD, Pattison IS, Chuck CS, Whittam JH, Scala i. Effect ofprotein dose on serum glucose and insulin response to sugars. Am J Clin Nut l987;46:474-80. 16. Day IL, Johansen K, Ganda OP, Soeldner IS, Gleason RE, Midgley W. Factors governing insulin and glucagon responses during normal meals. Clin Endocrinol(Oxf) 1978;9:443-54. 17. Jenkins DJA, Wolever TMS, Jenkins AL, et al. The glycaemic index of foods tested in diabetic patients: a new basis for carbohydrate exchange favouring the use of legumes. Diabetobogia 1983; 24:257-64. 18. Gannon MC, Nuttall FQ, Neil BJ, Westphal SA. The insulin and glucose responses to meals ofglucose plus various proteins in type
II diabetic
subjects.
Metabolism
1988;37: 1081-8.
19. MacGregor IL, Gueller R, Watts HD, Meyer iH. The effect of acute hyperglycemia on gastric emptying in man. Gastroenterology 1976;70: 190-6. 20. Barnett JL, Owyang C. Serum glucose concentration as a modulator of interdigestive gastric motility. Gastroenterology 1988:94: 739-44. 2 1. Fukagawa NK, Minaker KL, Young VR, Rowe JW. Insulin dosedependent reductions in plasma amino acids in man. Am I Physiol l986;250:El 3-7. 22. Fukagawa NK, Minaker KL, Rowe JW, et al. Insulin-mediated reductions ofwhole body protein breakdown: dose-response effects on leucine metabolism in postabsorptive men. I Clin Invest 1985;76:2306-l
1.
23.
Ahmed M, Nuttall FQ, Gannon MC, Lamusga RF. Plasma glucagon and a-amino acid nitrogen response to various diets in normal humans. Am I Nutr 1980:33:1917-24. 24. Palmer JP, Benson JW, Walter RM, Ensinck JW. Arginine-stimulated acute phase ofinsulin and glucagon secretion in diabetic subjects. J Clin Invest l976;58:565-70. 25. Muller WA, Faloona GR, Unger RH, Aquilar-Parada E. Abnor-
26.
mal alpha cell function in diabetes. Response to carbohydrate and protein ingestion. N EngI I Med 1970;283: 109-15. Muller WA, Faloona GR, Unger RH. The influence of antecedent diet upon glucagon and insulin secretion. N EngI I Med 197 l;285: 1450-4.
27.
28.
Ohneda A, Aquilar-Parada E, Eisentraut AM, Unger RH. Characterization of circulating glucagon to intraduodenal and intravenous administration ofamino acids. I Clin Invest 1968;47:230522. Aquilar-Parada E, Eisentraut AM, Unger RH. Pancreatic glucagon secretion in normal and diabetic subjects. Am I Med Sci 1969;257: 4 15-9.
