KETOSIS IN PREGNANCY.*

BY VICTOR JOHN HARDING AND KATHLEEN DREW ALLIN.

(From the Department of Pathological Chemistry, University of Toronto, and the Metabolism Ward, Burnside Maternity Wing, Toronto

General Hospital, Toronto, Canada.)

(Received for publication, April 24, 1926.)

There is a general impression that ketonuria is more easily produced in pregnancy. Porges and Novak (1) and Pritzi and Lichtmann (2) propose a test for pregnancy based on the more ready production of “acetone” when gravida are placed upon a low calory diet consisting mainly of protein. The fact that the placenta appears to be impermeable to maternal plasma lipoids (3) and the consequent supposition that the fetus manufactures its own store of fat from circulating carbohydrate is readily construed in favor of an easier production of ketonuria. The carbohydrate deficiency theories which have been proposed as an explanation of the nausea and vomiting of early pregnancy (4, 5) coupled with the facts that the ketone production (6) and urinary ammonia (7) of such patients is often extremely high, might point in the direction of a lowered threshold of ketosis, The treatment of diabetes in pregnancy also would appear to offer its own peculiar difficulties. Whether this is due to the increased metabolism as suggested by Joslin (8), or whether there is a small but definite lowering of carbohydrate assimilation as suggested by Allen (9), is not certain. A number of factors may be concerned. Geelmuyden (lo), however, seems positive in his statement that there is a special liability to acidosis and coma in pregnant diabetic women.

* The thanks of the authors are due to the Medical Research Committee of the I’niversity of Toronto for a grant which enabled them to carry out this work. Their thanks are also due to Miss F. M. Kelsey and Miss H.. Murphy for their care of the cases under observation and to Miss J. Porter and Miss M. J. Ketchem for their supervision of diets.

133

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Ketosis in Pregnancy

In order to throw light on some of these problems we have car- ried out a series of experiments to determine as precisely as pos- sible the threshold of ketonuria in normal pregnant women. The calculation of the threshold of ketosis in man has been presented in great detail during recent years. Woodyatt (11) and Shaffer (12) have been most prominent in the quantitative exposition of the antiketogenic action of glucose. The earlier work of the latter supposed one molecule of glucose to be antiketongenic to one molecule of acetoacetic acid. The supposition was based on an in vitro analogy of the oxidation of acetoacetic acid by hydrogen peroxide in the presence of glucose. The determination of the point of extinction of the ketonuria of fasting or of protein-fat diets by means of added carbohydrate, supported this analogy. Later the supposition was revised. It did not allow the predic- tion of the amounts of “total acetone” excreted on high fat diets. Diets which theoretically should have produced a high ketonuria produced only a small amount. Neither did it quantitatively predict the ketonuria of severe diabetics. It was then supposed that one molecule of glucose was ketolytic for two molecules of acetoacetic acid when the latter was produced in excess, and that the ketogenic fraction of protein had been undervalued by 50 per cent. This alteration in the values of the metabolic factors enabled Shaffer to calculate the “expected acetone” in severe diabetics and in those cases of fasting where large amounts of acetone were produced, with much greater accuracy than formerly. There were, however, still left unexplained a number of cases of ketosis, especially those occurring on low carbohydrate diets. This brief review of the general position on the quantitative as- pect of the threshold of ketonuria has been given, not with the view of disparaging able and painstaking work, but to emphasise that we find ourselves in a somewhat similar position in discussing the threshold of ketonuria in pregnancy.

Subjects.

The subjects of these experiments were all normal women at various stages of pregnancy. As far as we can tell the stage of gestation made no difference in our results. During the experi- ments the women were confined to bed. An extra 20 per cent was added to the basal metabolism to cover the specific dynamic action of protein and movements in bed.

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V. J. Harding and K. D. Allin 135

Analytical Methods.

Urines were collected in 24 hour periods. Acetone bodies were determined by the method of Van Slyke (13), all results being expressed as total acetone (acetone + acetoacetic acid + hydroxy- butyric acid). Blank determinations were made on urines showing less than 0.5 gm. of acetone in 24 hours, and a positive nitroprusside reaction confirmed the presence of abnormal amounts of acetone. Total N was determined by Kjeldahl- Gunning method.

Calculation of Results.

In calculating the ketogenic-antiketogenic balance the usual assumptions were made. (a) All food carbohydrate was utilised; (b) urinary N represented the catabolised protein; and (c) the remainder of the calories was derived from fat. As our object was to calculate the threshold of ketosis we utilised the first set of values given by Shaffer, assuming one molecule of glucose to be antiketogenic to one molecule acetoacetic acid.

Ketogenic (K). Antiketogenic (A).

1 gm. fat = ?z oT7 1 “ glucose = 0.00 5.56 1 “ urine N = 10.00 20.00

We have assumed the threshold of ketosis to be that point at which the amount of acetone found in the urine is 3 gm. or less. Although this seems a large amount of ketone yet it represents an amount well within the range of experimental error. The chief error in all these and similar calculations is in the determina- tion of the total metabolism. An increase of 100 calories in the total metabolism of a subject at the threshold of ketosis would cause an excretion of 2.7 gm. of acetone on the assumption that 1 gm. of fat produced its theoretical amount of acetone (0.198 gm.) and giving a value of 7.43 calories for the heat of combus- tion of 1 gm. of acetone. Allowing for the antiketogenic action of glycerol 1 gm. of fat would only produce 0.166 gm. of acetone. Under these conditions an increased combustion of fat represent- ing 100 calories of total metabolism would give slightly over 2 gm. of acetone in the urine.

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Subje

ct.

M-1

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imen

t 1.

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5 ft.

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in

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eight

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13

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23

129;

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yrs

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perim

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2.

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ft.,

4$

in.

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Jan.

7,

14

2 lb

s.

I‘ “

25,

1352

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Age

19

yrs.

S$

mos

. pr

egna

nt.

- - -

TABL

E I.

Date.

Di

et.

-I

19?8

Dec.

10

Basa

l. “

11

“

“ 12

(‘

‘I 13

“

“ 14

“

“ 15

“

“ 16

+

15 g

m.

suga

r. “

17

15

“ “

“ 18

15

“

“ “

19

15

“ “

“ 20

+

30

gm.

suga

r. (‘

21

. 30

“

‘I “

22

30

“ “

1926

Jan.

9

Basa

l. “

10

“ “

11

I‘

‘( 12

“

“ 13

“

“ 14

(‘

-

1

-

-- Urine

N.

A

K K:

A

gm.

7nM

6.22

45

7.36

58

6.99

1:

1.28

17

70

7.38

47

8.73

58

7.61

1:

1.22

17

70

7.24

47

6.16

58

7.58

1:

1.23

17

70

7.98

48

9.14

58

4.01

1:

1.19

17

60

8.77

50

3.46

58

2.99

1:

1.15

17

60

8.59

50

0.21

58

3.94

1:

1.16

17

60

6.75

54

5.09

55

4.56

1:

1.01

17

50

4.82

50

9.08

55

6.87

1:

1.09

17

50

7.24

55

4.55

55

7.40

l:l.

OO

1750

6.

65

543.

72

557.

33

1:1.

02

1750

5.

73

606.

64

534.

41

1:0.

88

1750

5.

68

605.

49

534.

26

1:0.

88

1750

6.

37

618.

21

534.

64

1:0.

86

1750

9.30

51

2.74

58

0.60

1:

1.13

17

60

9.59

51

8.77

58

4.67

1:

1.12

17

60

8.60

50

0.11

58

1.63

1:

1.16

17

60

7.29

47

6.19

58

1.91

1:

1.22

17

55

7.40

47

8.22

58

2.32

1:

1.21

17

55

8.43

49

6.43

57

8.22

1:

1.16

17

55

Calor

ies

equir

ed.

- I- Ac

etone

. E

Foun

d. gm.

0.93

1.

22

1.43

0.

67

0.69

0.

14

0.07

0.

03

0.58

0.09

0.

10

0.70

gm.

7.51

6.

31

6.46

i4

5.50

2.

4.

61

8 4.

85

G’

0.55

‘3

’ 2.

77

v 0.

02

g 0.

79

(19

-4.1

9 -4

.07

E

-4.8

5 cc

0

3.92

3.

82

4.72

6.

13

6.09

4.

74

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Jan.

15

Ba

sal.

‘I 16

“

“ 17

+

15

gm.

suga

r. “

18

15

“ “

“ 19

15

“

I‘

“ 20

15

“

“

“ 21

+

30

gm.

suga

r. “

22

‘z&-j

“ “

‘( 23

30

“

“ “

24

30

I‘ “

- -

10.1

0 9.

96

7.70

6.

86

5.70

5.

80

5.28

4.

66

4.39

3.

92

527.

15

578.

79

1:1.

09

1755

52

5.14

58

2.88

1:

l.H

1755

55

1.03

48

5.51

1:

0.88

17

55

547.

57

554.

37

l:l.O

l 17

50

526.

25

557.

09

1:1.

05

1750

52

8.08

55

7.06

1:

1.05

17

50

598.

23

534.

37

lLO.8

9 17

50

586.

74

534.

00

1:0.

91

1750

58

1.63

53

3.01

1:

0.91

17

46

572.

97

532.

77

1:0.

93

1746

- -

- -

3.80

4.

86

2.18

0.

89

1.21

0.

73

0.94

1.

09

3.00

3.

35

-1.9

9 0.39

1.

79

1.78

c

-3.1

2 +I

-3

.06

-2.8

2 F

-2.3

4 Iz

- w.

t-ii

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138 Ketosis in Pregnancy

KetogenioAntiketogenic Ratio in Pregnancy at the Point of Extinction of Ketonuria by Cane Sugar.

(Tables I and II.)

These experiments are comparable to those of Lang (14) on the extinction of fasting ketosis in man. As it was not deemed advisable to carry out a long period of fasting in our cases a low calory diet of protein and carbohydrate was given, which, by leaving a large majority of the calories to be derived from body fat, ensured a ketonuria. The diet furnished 495 calories, con- sisted of eggs, lean beef, skim milk, vegetables, and fruit and contained protein 40.7 gm., carbohydrate 44.2 gm., fat 15.8 gm.

We have termed this the basal diet. Three experiments were performed using two subjects. The basal metabolism was de- termined at the beginning and end of each experiment by use of the Douglas bag. In all three cases the basal metabolism was found to be slightly diminished at the end of the experiment. This was allowed for in the calculation of the total metabolism, it being supposed that two-thirds of the diminution occurred in the first half of the experimental period. When N and acetone equilibrium had been established on this diet 15 gm. of cane sugar were added, and some days afterwards a further 15 gm. of cane sugar were given.

The two experiments on subject M-l-r. (Table I) are in good agreement. There is a definite but small ketosis on the basal diet which is not extinguished until 30 gm. of cane sugar have been added. We take it that the point of extinction of ketonuria in this case lies midway between these two diets, as represented by the basal diet and 15 gm. of cane sugar. The ratio K:A varies on this diet from 1.005 to 1.09 in Experiment 1, and from 1.05 to 0.88 in Experiment 2. With 30 gm. of cane sugar added to the basal diet the ratios vary from 0.86 to 0.93. The threshold of ketonuria lies somewhere around the ratio K:A: : 1: 1.

The experiment on B-l-n. (Table II) would appear to show different results. Only on 1 day (January 17) did the ratio K:A rise over 1 and yet ketonuria was constantly present until 4 days after the addition of 15 gm. of cane sugar to the basal diet. With 30 gm. addition of carbohydrate to the diet the ketonuria became vanishingly small. Also ketonuria was more quickly produced in this subject. Are we to assume that the threshold

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V. J. Harding and K. D. Allin

of ketonuria in B-l-n. was definitely lower than in M-l-r.? An additional expenditure of energy of 150 calories in the form of fat would be sufficient to make the calculations of the K: A ratio on the two subjects almost identical. Such a variation is within the error of experiment and such fluctuations in the K:A ratio should be encountered when the calculation is so dependent on a guess at the total metabolism.

Although we have argued that the threshold of ketosis in these experiments lies at a point represented by the combustion of the basal diet plus 15 gm. of cane sugar, yet a small definite ketosis is still present. The addition of 15 gm. of carbohydrate in this manner to the burning mixture a priori should have shown a much greater effect on the acetone. Acting isodynamically and exclusively as a protein sparer the cane sugar would reduce the urine N by 2.4 gm. If it replaced fat isocalorically the equiva- lent of 6.61 gm. of fat should have disappeared from the urine acetone. This in simple molecular proportion of one molecule of fat to three molecules of acetone would amount to 1.3 gm., but on the theory of the antiketogenic action of carbohydrate would be 6.3 gm. (3.43 X 6.61 K + 0.57 X 6.61 A + 5.56 X 15 A = 108.73 millimols will be transferred from K to A when 6.61 gm. of fat are replaced by 15 gm. of carbohydrate: 108.73 X 0.058 = 6.3 gm. of acetone). In M-l-r. in Experiment 2 the effect was entirely confined to the protein. In M-l-r. in Experi- ment 1 there was some sparing of protein corresponding to about 1 gm. of urine N which should have left over 8 gm. of carbohydrate to act as a fat sparer and have been sufficient to abolish the keto- huria. In B-l-n. there appeared to be little effect on the N and less than 1 gm. of acetone disappeared from the urine only after 4 days.

Ketogenic-Antiketogenic Balance in Pregnancy on Diets High in Fat.

In this series of experiments diets high in fat were given to normal pregnant women. In all, eleven experiments were per- formed on five subjects. Three diets were used. Diets I and II contained ordinary articles of food given as three meals a day, whereas Diet III, consisting exclusively of milk, cream, and egg white, was given in seven portions throughout the day. The

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TABL

E 11

Subje

ct Da

te.

Diet.

Jri

ne

N.

B-l-n

. He

ight,

5 ft.

, 34

in

. W

eight

Ja

n.

11,

133;

lb

s.

“ “

30,

?25

“ 76

m

os.

preg

nant

.

------

I 19.36

Jan.

14

Ba

sal.

“ 15

“

“ 16

“

“ 17

I‘

“ 18

“

‘I 19

“

“ 20

+

15gm

. su

gar.

(‘ 21

15

“

“ “

22

15

“ ‘I

“ 23

15

‘I

<‘

6‘

24

15

‘6

u

“ 25

+

30

gm.

suga

r. “

26

30

“ “

“ 27

30

‘I

“ “

28

30

“ “

“ 29

30

“

“

gm.

10.6

0 12

.56

12.4

0 8.

35

10.4

2 9.

55

10.2

6 10

.63

10.8

0 9.

48

(11.

91:

11.5

0 9.

48

7.16

9.

15

8.39

A K

K:A

mnr

nz

db

524.

44

507.

31

560.

45

507.

70

557.

52

507.

82

482.

46

502.

98

520.

44

503.

10

504.

46

502.

98

596.

19

471.

32

603.

42

477.

42

606.

48

477.

06

581.

62

473.

12

626.

06:

(472

.39

698.

35

450.

79

660.

57

446.

37

617.

99

446.

15

653.

98

443.

08

640.

69

447.

13

1:0.

96

1.0.

90

1:0.

91

1:1.

04

1:0.

96

1:0.

99

1:0.

78

1:0.

79

1:0.

78

1:0.

81

:1:0

.75:

1:

0.64

1:

0.66

1:

0.72

1:

0.68

1:

0.69

Calor

ies

xquir

ed

-

1550

15

50

1550

15

40

1540

15

40

1530

15

30

1530

15

20

1520

15

20

1510

15

10

1510

15

10

Aceto

ne.

Foun

d.

gm.

0.02

2.

67

1.91

0.

08

0.02

0.

07

0.39

0.

13

0.19

0.

19

:o.o

5j 0.

04

0.02

0.

06

0.05

- _- (

gm.

-1.0

0 w

-3.0

4 3

-2.8

8 g E;

. 1.

19

*.

-1.0

1 -0

.09

L -6

.65

2 -7

.30

E -7

.50

93

-6.8

0 E

-8.96

) ‘c

-1

4.35

-1

2.42

-

9.96

-1

2.23

-1

1.22

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V. J. Harding and K. D. Allin 141

diets are shown in Table III. The diets were arranged to be below the calory requirements of the subjects, it being assumed that the deficiency would be made up by the combustion of body fat. Ketosis was produced in all cases. Rasal metabolism in this series was obtained by calculation according to Sandiford (15). This author has recently described a method for the calculation of the basal metabolism in pregnancy which takes into account the increased metabolism due to the surface area of the fetus.

Diet I. Diet II.

gm.

Orange ........... 60 Egg ............... 120 Butter ............ 50 Cream ............ 175 Meat .............. 55 Potatoes ........... 25 10 per cent vege-

tables .......... 20 Milk .............. 105 Macaroni ......... 32 Cheese ............ 18 Apple.. ........... 100 Sugar ............. 15

gm.

Grape fruit ....... 75 Butter ........... 40 Egg .............. 130 Cream. .......... 190 Meat ............. 55 10 per cent vege-

tables .......... 20 5 per cent vege-

tables .......... 25 Gelatin (with

saccharin). . _ . . 5 Milk ............. 20 Cheese ........... 18 Apricots or

prunes ......... 30 Sugar ............ 15 Protein ............ 45.t

Fat ............... 138.t Carbohydrate ..... 57.1 Calories .......... .1677

-

5 1 3

-

TABLE III.

Protein ........... 42. I Fat .............. 104.2 Carbohydrate .... 38.1 Calories ......... .I235

Diet III.

gm.

Cream 32 per cent 320

Milk 670 Egg white 85

Protein.. . . . . . . . . 40.6 Fat.. . . . . . . . . . . 129.0 Carbohydrate.. . 44.5 Calories.. . . . 1546

In Table IV is shown the result of this series of experiments when the acetone excretion did not exceed 3 gm. The records of the first few days of diet are omitted. In some of the experiments the intake of sodium chloride was varied greatly but without influence on the ketonuria. The K: A values vary from 1.04 to 1.47. In G-h-m. in Experiment 1 there is a good

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TABL

E IV

.

Subje

ct.

Date.

Di

et.

Urine

N.

A

K K:

A

G-h-

m.

Expe

rimen

t 1.

Se

pt.

15-2

7.

Heigh

t, 5

ft.,

4 in

. W

eight

10

7 lb

s.

Age

22

yrs.

Age

of

fetu

s, 5

mos

. Ca

lculat

ed

weigh

t, 0.

65

lbs.

To

tal

met

aboli

sm

1532

ca

lorie

s.

G-h-

m.,

Expe

rimen

t 2.

De

c. 3-

15.

Heigh

t 5

ft.,

f: in

. W

eight

11

9 Ib

s.

Age

22

yrs.

Age

of

fetu

s 71

m

os.

Calcu

lated

we

ight

2.41

lb

s.

Tota

l m

etab

olism

16

68

calo

ries.

-- 19

.94

Dec.

6 “

7 “

8 “

9 “

10

“ 11

“

12

“ 13

“

14 -

III “ “ “ “ “ “ “ III “ ‘I ‘I “ “ ‘I ‘I ‘I

om.

?nM

!Jm

.

8.34

48

3.29

49

9.74

1:

1.03

1.

45

5.76

43

6.11

49

9.11

1:

1.12

2.

00

7.75

47

2.63

49

9.44

1:

1.04

2.

81

7.39

46

6.05

49

9.61

1:

1.07

2.

46

6.34

44

6.82

49

9.43

1:

1.11

2.

17

6.75

45

4.28

49

9.70

l:l.

lO

2.23

7.

07

460.

11

499.

47

1:1.

08

1.90

6.

88

455.

02

495.

54

1:1.

08

2.07

5.44

43

8.51

54

9.36

1:

1.27

3.

69

4.74

42

5.67

54

8.92

1:

1.28

3.

64

5.50

43

9.01

54

5.53

1:

1.24

2.

42

5.30

43

5.64

54

8.97

1:

1.25

3.

33

5.05

43

1.24

54

8.88

1:

1.27

3.

49

5.04

43

1.12

54

8.82

1:

1.27

3.

17

5.00

43

0.24

54

8.38

1:

1.27

3.

87

4.53

42

1.77

54

9.18

1:

1.30

2.

19

4.13

41

4.42

54

8.96

1:

1.32

2.

55

-

Aceto

ne.

Foun

d. ( _

-

Mcula

ted.

gm.

0.95

3.

65

0.97

1.

95

8.

m

3.05

I-.

2.

63

3

2.28

w

2.35

;if

m

E

6.43

z

7.14

Q4

6.

17

6.47

6.

83

6.83

6.

85

7.29

7.

80

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G-h-

m.,

Expe

rimen

t 3.

Ja

n.

2-10

. He

ight

5 ft.

, $

in.

Weig

ht

1183

lb

s.

Age.

22

yrs

. Ag

e of

fe

tus

8;

mos

. Ca

lculat

ed

weigh

t 3.

34

lbs.

To

tal

met

aboli

sm

1694

ca

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TABL

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Date.

19.94

May

28

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“

30

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Ju

ne

1 Cc

2

Diet.

II “ ‘I “ “ I‘

Urine

N.

A

K

gm.

nkM

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10.80

50

6.96

58

6.78

8.

51

462.

48

568.

45

9.63

48

5.55

58

3.45

9.

73

487.

35

583.

72

10.0

3 49

2.92

58

3.99

9.

97

485

24

568.

94

- -

- -- -

K:A

1:1.

11

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22

1:1.

20

1:1.

19

1:1.

18

1:1.

17

T Ac

etone

.

- -

Foun

d.

gm.

0.45

0.

42

0.69

1.

79

1.25

0.

92

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4.62

6.

14

5.73

5.

58

5.28

4.

85

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V. J. Harding and K. D. Allin 145

agreement between the acetone excreted and calculated, but the other five experiments show much less acetone than should be expected. Such discrepancies are similar to those met with in the experiments of Hubbard and Wright (16), Hubbard (17), and of Wilder and Winter (18). If the factors for the evaluation of K and A are altered in conformity with Shaffer’s later postulates no ketonuria should be observed.

In Table V we have tabulated the remainder of our experiments where the acetone excretion rose over 5 gm. The calculations and experimental conditions were under the same control as in the cases of Table IV. Some of the subjects of this group showed high ketonuria on occasional days only, but F-b-s. showed per- sistently the highest ketonuria. We would not interpret these results to mean that the threshold of ketosis was lower in these particular subjects, but rather that we underestimated the total metabolism. Subject F-b-s. was certainly one of the most active of our cases. The diet also gave her a considerable amount of pain. Subject Le B. too was a very alert woman. How easily the total metabolism can be affected under the conditions of our experiments may be gathered from the results on M-l-r. (Table I) where for 2 days (January 15 to 16) a high acetone excretion was observed. This was due undoubtedly to a rise in total metabo- lism brought about by the presence on those 2 days of a serious case of pernicious vomiting in the same ward with consequent excitement and loss of sleep to the other patients. A similar rise in acetone excretion was observed in another subject on high fat diet at the same time. The easy production of large amounts of acetone in the cases cited in Table V led us at one time to sup- pose that pregnancy had lowered the threshold of ketosis (19).

Criticism has sometimes been directed against experimental diets such as we have used because the fat is derived mainly from milk or milk products. This would produce per gm. of fat a larger amount of ketone bodies than would be derived from the combustion of body fat. As the calculation of K: A ratios de- pends upon the use of the molecular weight of the burning fat being 874 (body fat) and as the average molecular weight of butter fat is 743 such a criticism, if valid, would cause a large alteration in the factors derived from fat. The new factors would be 1 gm. fat = K 4.02, A 0.67 millimols. We have recal-

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TABL

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Urine

N.

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A K

K:A

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.

gm.

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12

490.

99

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47

7.57

62

7.08

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55

9.51

51

6.61

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74

7.75

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2.

18

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44

7.78

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2.50

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55

7.22

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3.92

55

2.71

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86

8.24

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52

8.99

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7.63

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99

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562.

82

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22

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6.65

5

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08

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“ 17

II “ I‘ II I‘ ‘I “ ‘I ‘I ‘I I‘ III ‘I I‘ L‘

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58

1.16

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1.24

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6.90

8.

77

469.

93

581.

31

1:1.

23

5.13

6.

45

7.14

43

9.37

58

0.72

1:

1.32

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78

8.19

7.15

47

0.55

61

1.00

1:

1.29

1;

58

8.14

6.22

45

3.65

61

1.04

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55

9.11

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611.

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7.91

8.

32

492.

30

612.

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24

5.33

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96

8.18

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9.67

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2.06

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7.09

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611.

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3.76

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9.61

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4.66

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3.61

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8.25

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6.72

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2.62

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8.49

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-

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Ketosis in Pregnancy

culated all our figures in this series of experiments using these new factors to correct for the amount of butter fat in the diets. The same general result is seen in all the cases. The discrepancy between acetone excreted and calculated bcomes accentuated. Thus the three experiments on G-h-m. (Table IV) show an ace- tone excretion of 17.1, 28.3, and 8.1 gm. respectively for the period of observation. The calculated acetone using the ordi- nary factors is 17.8, 61.7, 34.8 gm. The calculated acetone, allowing for butter fat, is 46.2, 95.7, and 57.5 gm. Hubbard (17) discussed this question some time ago and concluded there was practically no difference in the amount of acetone excreted, whether the source of the ketone was body fat or ingested fat. Theoretically too, we should regard such a conclusion as sound. The greater part of the fat to be burned will be drawn from the fat depots of the body which remain approximately constant in composition, unless affected by prolonged feeding of a foreign fat. Only during the period of alimentary lipemia will a portion of the food fat gain direct access to the liver and thus perhaps be oxidised without mixture with body fat other than that of the lipoids of the circulating plasma.

DISCUSSION.

The problem of ketosis in pregnancy would thus appear to be similar to that in the non-pregnant condition. On the basis of one molecule of glucose being ketolytic -to one molecule of ace- toacetic acid the abnormal appearance of acetone in the urine com- mences when the ratio of antiketogenic to ketogenic molecules is 1: 1. Yet we have found that increases in the ratio up to 1: 1.47 do not significantly increase the ketonuria in pregnancy. How is this brought about? Does glucose become ketolytic as a triose instead of a hexose as was suggested first by Lusk (20), later by Wilder and Winter, and postulated by Shaffer? Such an as- sumption has not harmonised all the facts of ketogenesis in man, and to state that some experiments possess a ketogenic- antiketogenic balance expressable by the ratio 1: 1 and others by a ratio 2:l is, in our opinion only to state that there exists a mechanism not yet defined, which acts as a physi- ological check or buffer against the production of large amounts of acetone. It is probably the same mechanism, seen in a much

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V. J. Harding and K. D. Allin 149

more efficient form, which operates in animals other than man to prevent ketosis on fasting. Of laboratory animals, the dog and rat are very resistant to fasting ketosis. We ourselves, and in this we have only confirmed the experiments of many other observers, have failed to observe ketonuria either on fast- ing or on feeding diets excessively high in fat to the dog. We have even tried the experiment on a Dalmatian dog excreting uric acid, in the hope that this similarity to man might yield a positive result. Baer (21), however, reported the occurrence of ketonuria on fasting in a monkey. Levine and Smith (22) have just reported the absence of any significant ketosis in the rat on high fat diets, though Wigglesworth (23) observed a transient ketonuria lasting 1 or 2 days in these animals upon such diets.

The question too of adaptation against ketonuria on fasting or on high fat diets has never received adequate explanation. The theory of ketogenic-antiketogenic balance has made clear some apparent anomalies only to leave others. Allen (24) has made similar criticisms and has clearly defined the general problem. He has pointed out the necessity of a biological factor if we are to look at ketosis from a general standpoint. Shaffer time and time again points out the possibility of the combustion of fat without the production of acetone though he would only use such a hy- pothesis in event of failure of all other explanations. Our experi- ments on the effect of 15 gm. of cane sugar on an apparently threshold ketosis are not conclusive. The factors are too many and too uncontrolled to allow us to draw the conclusion that the difEculty of extinction of the urinary acetone was due to the re- placement of a fraction of fat burning without the production of ketone by its equivalent in carbohydrate.

Teleologically we might expect a mechanism against the keto- sis of fasting especially in animals which, in their natural state, possess an intermittent food supply. Were a few days fasting to result in a severe ketosis with the possibility of coma and death such a species would rapidly become extinct. Is the ketosis of puppies (24), and the more intense ketosis of children, an ex- pression of the non-development of the physiological regulatory mechanism until adult life?

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150 Ketosis in Pregnancy

The unknown and important factor of total metaboIism oc- curring in these observations prevents a satisfactory answer. It is probably neglect of this factor that has led to the conclusion that pregnant women show ketonuria more readily than non- pregnant women. Diets which would just be aketonuric in normal women, and such as were used by Porges and Novak and Pritzi and Lichtmann, would be ketonuric in pregnant women with the increased metabolic rate of the fetus. The feeding of high fat diets to diabetic pregnant women should take into account this extra metabolism of pregnancy. Then too the urinary N in pregnancy may be lower than usual, thus reducing the amount of antiketogenic material. The avidity of the fetus for N is sometimes remarkable. Thus subject G-h-m. in Experiment 2 (Table IV) on a diet containing 40 gm. of protein excreted 5 gm. or less N during the last 5 days of the experiment. On an insuffi- cient diet, and in presence of a ketosis, the subject was in a posi- tive N balance. Subject M-l-r. in Experiment 2 on a diet of only 618 calories also gained N. The combination of these two fac- tors would make it appear that the threshold of ketosis in preg- nancy is low, unless quantitative measurements are made.

SUMMARY.

The threshold of ketonuria in pregnancy is the same as in the non-pregnant condition.

Diets which theoretically should produce a large excretion of acetone may only produce a ketonuria slightly above the threshold value.

In calculating the ketogenic-antiketogenic balance in preg- nancy attention should be paid to the raised metabolism occurring in the latter half of gestation, The urinary N may be unexpect- edly low, thus reducing the antiketogenic factor.

BIBLIOGRAPHY.

1. Porges, O., and Novak, J., Bed klin. W&z., 1911, xlviii, 1757. 2. Pritei and Lichtmann, wien. klin. Woch., 1923, xxxvi, 609. 3. Slemons, J. M., and Stander, H. J., Bull. Johns Hopkins Hosp., 1923,

xxxiv, 7. Plass, E. D., and Tompkins, E. H., J. Biol. Chem., 1923, hi, 309.

4. Duncan, J. W., and Harding, J. V., Canad. Med. Assn. J., 1918, vii, 1057. Harding, V. J., Lance& 1921, ii, 327.

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V. J. Harding and K. D. Allin 151

5. Titus, P., Hoffmann, G. L., and Givens, M. H., J. Am. Med. Assn., 1920, lxxiv, 777.

6. Harding, V. J., and Potter, C. T., Brit. J. Exp. Path., 1923, iv, 105. 7. Gilliatt, W., and Kennaway, E. L., Quart. J. Med., 1913-19, xii, 61. 3. Joslin, E. P., The treatment of diabetes mellitus, Philadelphia and New

York, 2nd edition, 1917,448. 9. Allen, F. M., Am. J. Physiol., 1921, liv, 451.

10. Geelmuyden, H. C., Nor& Mug. Lzgevidensk., 1914, lxxv, abstracted in J. Am. Med. Assn., 1914, Ixiii, 1797.

11. Woodyatt, R. T., J. Am, Med. Assn., 1910, Iv, 2109; Arch. Int. Med., 1921, xxviii, 125.

12. Shaffer, P. A., J. Biol. Chem., 1921, xlvii, 433,449; 1922, liv, 399. 13. Van Slyke, D. D., J. Biol. Chem., 1917, xxxii, 455. 14. Lang, R. M., Biochem. J., 1915, ix, 456. 15. Sandiford, I., J. Biol. Chem., 1924-25, Ixii, 323. 16. Hubbard, R. S., and Wright, F. R., J. Biol. Chem., 1922,1, 361. 17. Hubbard, R. S., J. BioZ. Chem., 1923, Iv, 357. 18. Wilder, R. M., and Winter, M.D., J. BioZ. Chem., 1922, Iii, 393. 19. Harding, V. J., Allin K. D., Eagles, B. A., and Van Wyck, H. B., J. BioZ.

Chem., 1925, Ixiii, p. xlix. 20. Lusk, G., Elements of the science of nutrition, Philadelphia, 3rd edi-

tion, 1917, 271. 21. Baer, J., Arch. exp. Path. u. Pharmakol., 1906, liv, 153. 22. Smith, A. H., and Levine, H., J. Biol. Chem., 1926, lxvii, p. vi. 23. Wigglesworth, V. B., Biochem. J., 1924, xviii, 1217. 24. Allen, F. M., J. Metabol. Research, 1923, iv, 199.

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Victor John Harding and Kathleen Drew AllinKETOSIS IN PREGNANCY

1926, 69:133-151.J. Biol. Chem. 

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