Roland

Kreis,

PhD

#{149} Brian

D. Ross,

MD,

PhD

Cerebral Metabolic Disturbances In Patients with Subacute and Chronic Diabetes Mellitus: Detection with Proton MR Spectroscopy’ Localized proton magnetic resonance (MR) spectroscopy was used to define biochemical changes in gray and white mailer of the cerebral cortex in 22 patients with diabetes mellitus (DM), including 10 episodes of diabetic with jects.

ketoacidosis

(DKA),

MR spectra Five

malities

distinct

were

compared

in 30 healthy metabolic

identified:

abnor-

Concentra-

of glucose (Gic) (P .002), ketone body or bodies, myo-inositol (P .003) (with or without glycine), and choline (Cho) metabolites were increased in both white and gray mailer, whereas a significant reof N-acetyl

metabolites

was found in the parietal cortex (P .003). Diurnal variations in the intracerebral concentration of Gic were demonstrated in a patient with DM whose condition was stable. Elevated concentrations of ketones were detected in three episodes and excess Cho in two episodes of DKA. Evidence obtained with hydrogen-i MR spectroscopy favors acetone rather than acetoacetate as the ketone present in the brain, which is a major target of biochemical change in DM. Index

terms: Brain, abnormalities, 10.599 Brain, MR, 10.12147 #{149} Diabetes mellitus, complications, 10.599 #{149} Glucose, 10.599 #{149} Magnetic resonance (MR), spectroscopy, 10.12147 Radiology

plex bohydrate, tabolism

(DM)

that

has

a variety

of coma

in hyperglycemia

glycemia, ketonemia, hyperosmolality (1).

From

the

Clinical

Magnetic

Resonance

Spec-

requests ‘.

RSNA,

to B.D.R. 1992

or

acidosis, Insulin

(2). The

less

marked

10th

and is be-

cerebral

bio-

basis

of hyperglycemic

coma

been

based

has

els (4,5).

on

to the

expected

ketone

bodies

the brain,

an increase

myo-inositol

(MI)

characteristic

in the

DM

in rats

trasts

with

(6,7). the

MI depletion

This widely

animals interest

is

observation accepted

conview

(9,10),

it has

recently

resonance noninvasive in vivo in renewed of DM.

been

has in shown

that it is possible to assay a number of relevant metabolites, including Glc (11-13), MI, and some amino acids (14), by means of hydrogen-I MR spectroscopy short echo times

with

Study

DM:

17 patients with type I DM and 10 women with a mean age of 43 years ± 3 [standard deviationj [age range, 21-79 years]), four patients with type 2 DM (three men and one woman with a mean age of 62 years ± 4) (age range, 52-70 years), and one man (seven

with

men

secondary

chronic

DM,

pancreatitis.

which

was

Eight

patients

due

to (36%)

three patients (14%) were His11 patients (50%) were white.

Glc levels,

performed with (TEs). In this article,

AA CHE

contrib(8).

While carbon-13 MR spectroscopy been used to study Glc metabolism DM

METHODS

pH, electrolyte

levels,

Abbreviations:

in peripheral

and humans has in the biochemistry

of

in

in

induced

with DM neuropathy

AND

in This

Society

in Medicine

cerebral

concentration

of chemically

of the

mod-

in GIc

and

meeting

Resonance

The group of patients in this study consisted of a consecutive series of 22 patients

Blood

animal

In addition

increases

Patients

were black, panic, and

of the

metabolic

annual

MATERIALS

chemical effects are therefore likely to be secondary to the known effects of insulin on peripheral tissues. They may nevertheless be important in the development of long-term diabetic complications in the brain and peripheral nerves (3). However, other cerebral disturbances are associated with the general vascular complications of DM (3). Most of the understanding

we report our use of localized proton MR spectroscopy of the brain to study metabolic disturbances in a general population of patients with DM. A preliminary account of some of our findings was presented at the Magnetic 1991 (15).

lieved to have no direct effect on the transport of glucose (Gbc) in the brain

The advent of magnetic (MR) techniques for the monitoring of metabolism I

of cerebral

diabetic ketoacidosis (DKA) are not completely understood but are likely to be complex interactions of hyper-

nerves of patients utes to diabetic

troscopy Laboratory, Huntington Medical Research Institutes, 660 S Fair Oaks Ave. Pasadena, CA 91 105; and California Institute of Technology, Pasadena. Received December 6, 1991; revision requested January 28, 1992; revision received February 14; accepted March 5. Supported in part by grants to the Clinical Magnetic Resonance Spectroscopy Laboratory from the L.K. Whittier Foundation and the Norris Foundation of Southern California. Address reprint

is a com-

metabolic disorder of carlipid, and amino-acid me-

biochemical effects, the most severe of which are coma and death. The mech-

that

1992; 184:123-130

mellitus

IABETES

anisms

sub-

lions

duction

D

Cho Cr CSF DKA DM Gic GIn Glu Gly GIx IDDM MI NA NAA NAAG SD TE TR

acetoacetate chronic hepatic encephalopathy choline creatine cerebrospinal fluid diabetic ketoacidosis diabetes mellitus glucose glutamine glutamate glycine sum of GIn and Glu insulin-dependent diabetes mellitus myo-inositol N-acetyl N-acetylaspartate N-acetyl-aspartyi-glutamate standard deviation echo time repetition time

123

blood gases, and plasma bicarbonate (HCO3) concentrations were measured most patients on the day of examination with lality

H-I MR spectroscopy. was estimated with

formula: ion gap

[2(Na + K) was estimated

formula:

[(Na

In patients

with

-

acute

derwent

with

examination

episodes

months

apart,

type

the start

apparently

only

whose one

patient

nation)

had

of H-i

Data quired

with

3, second

exami-

at

(1st day; n = 4), when established. The other formed on the 3rd (n day of recovery, when

cal abnormalities were minimal. underwent

in the

Table Clinical

manner

were

of Kreis

the stimulated-echo

standard

matter voxel cortex and

estiand

256

patients,

regions

of in-

in the posterogray matter

cortex, of their

typical location is shown in Figure 1. Volumes were generally between 8.0 and 16.3 cm3. . . . ..

Analysis

H-i MR spectra

Type 1 DM Recovering No DKA Type2DM SecondaryDM AIIDM

treatment was well studies were per= 4) or 4th (n = 2) residual biochemi-

within

and

two

white parietal

In most

voxel in the posterior occipital across the midline. An example

MR spectroscopy.

The stability MR spectroscopy

ac-

et al (16)

technique

(17,18)

and reproducibility in the parietal

matter

voxel

Similar

evaluations

No. of Patients

No. of Patients

Diagnosis

has

been

of H-i white

established

were

(16).

performed

for

Subjects Mean Plasma Bicarbonate

Mean Blood

Receiving

Glc Concentration

Insulin

Concentration

(mmol/L)

(mmol/L)

17

17 9

10.9 10.9

± 1.2 (i3) ± 2.1 (9)

25.6

9

23.9

± ±

8

8

10.3

± 2.5 (4)

27.9

±

4

0

from DKA

1 22

Healthy

NM

7.6±0.1(2)

1.5(14) 2.6(8) 0.3(6)

26.2±0.6(2)

1

3.7(1)

18 NM

9.9±1.1(16)

25.8±1.4(17)

27.0(1)

4.0-6.0

27.0-30.0

Note.-Mean blood Glc and plasma bicarbonate levels plus or minus standard deviation (SD) are those measured dosest to examination with H-I MR spectroscopy and were, with some exceptions, obtamed within 1-2 hours before or after such examination. Details and metabolic findings in one other patient with DM, exduded from this table and subsequent tables because of coexistent hepatic encephalopathy (discussed in a previous report [13)), are presented in Figure 3. Numbers in parentheses are number of patients. NM = not measured.

proved with blood tests Two of the patients who

examination

and

with by

Total

of DKA

onset

of patients examination

we examined terest: medial

13 msec;

poor,

treatment

of the

years)

rep-

Ti-weighted

for time,

per voxel.

Table 1 Clinical Details in 22 Pail ents with DM and 30 H ealthy ________________________________________________________________

DKA,

(patient

24 hours

22-89

used:

msec = 1,500/30 estimations

7

not received

within

range,

were

(TR) msec/TE for 12-weighted

acquisitions

(Signa; GE The follow-

dur-

with

very

age

Acquisition

Localized

un-

examination. Three other patients underwent examination with H-I MR spectroscopy

age, 47

sex-matched to the group DM, underwent identical

admission examina-

was

mean

with H-i

means

parameters

time

and 3,000-9,000/30 mations); mixing

(19

known neurologic or biochemical who were approximately age-

recovery laboratory tests.

condition

subjects

ii women;

tion with H-I MR spectroscopy, are listed in Table 2. Because of the constraints of examination with H-i MR spectroscopy in patients

healthy

21 [SD];

examination

acquisition

(1,500/120

without disease,

1 DM

between and

Subjects

performed and

of DKA that occurred so that data from 10 epi-

interval of treatment)

complete.

men and years ±

sodes of DKA are reported. Details of individual patients including (ie, the

considered

Thirty

during

from DKA proved with One patient underwent ing two

ing

was

Control

(HCO3 + Cl)]. DKA, the appropri-

tests were admission

patients

ery

etition

The clinical details of all 22 patients are summarized in Table 1. Informed consent, approved by the institutional review board, was obtained from each patient. of the

by means of a 1.5-1 MR imager Medical Systems, Milwaukee).

Serum osmothe following

within 2 hours of examination MR spectroscopy.

Nine

of the onset of DKA underwent re-examination 5-7 days later, when clinical recov-

+ GIc + urea]. Anwith the following

+ K)

ate blood chemistry serially after hospital

in

24 hours

2

Findings

in

Nine

Admitted

Patients

to the

Hospital

Bioch emical

in

i/35/M 2/53/F First

Hospital Admission

3/22/M First

to DKA

At Localized H-i MR Spectroscopy

Interval between Blood Chemistry Testing and MR Spectroscopy (d)

Neurologic Finding*

Ketonuriat

pH

Gap

Glc

Bicar

pH

Gap

34.6

10.4

7.25

28

14.3

9.1

7.35

ii

6

6.9i

27

13.0 [8.8

15.8 27.7

7.34

. . .

5 12

23

10.9

30.0 22 NP

7.45

16.0 [6.6

NP NP 7.40 NA

-

-

15

1

-

-

10 9 8

4 3 3

-

-

-

-

-

-

10 10

4 3

examination

33.7

examination

Attributed

Bicar

66.1

Second

Coma

Glc

examination examination

Second

or before

(mmol/L)

Le vels

At

Patient No./ Age (y)/ Gender

Coma

. . .

. . .

. . .

.

5.6

7.1

. . .

. .

. . .

. . .

7.30

14

16.7

23.2

38.6

17.5 iO

7.29

20

20.0

30

31.7

14

7.33

24

6.0

30

35.9

20.6

7.42

17

75

25

36.4 55.5

5.0 8.2

7.1 7.16

25 27

9.2 17.8

29.4 25

4/21/F 5/32/F

50.7

6/3i/M 7/58/F 8/30/F 9/56/M

7.4

7.46 7.48 7.35 7.45

1

+

+

i

++

+

5]

-

10

3

-

NP NP

0 6J

-

-

NP +

-

-

-

-

Note-Nine patients underwent examination with H-i MR spectroscopy in 10 episodes of DKA. The intervalbetween blood chemistry testing and H-i MR spectroscopy constituted the period of recovery during full treatment for DKA. Four patients underwent examination within 24-36 hours of diagnosis; the other patients, 3 or 4 days after diagnosis. With one exception, all patients had been vigorously treated at the time of examination with H-i MR spectroscopy. Two patients subsequently underwent reexamination after “complete” clinical recovery; results of blood chemistry tests are endosed in brackets. Bicar = plasma bicarbonate, Gap = anion gap, NP = not performed. * + persistent clouded mental state, + + = severe persistent douded mental state, - = absence of mental clouding. t + = persistent ketonuria, = transitory ketonuria.

=

124

#{149} Radiology

July 1992

the second voxel in the occipital ter. The effect of diurnal alterations Glc on the cerebral H-I spectrum tested

in a single

individual

gray

mat-

follows:

in blood were

(patient

This

patient,

who

normally received insulin underwent examination 1 day. The first time was

3), as

his

usual

insulin

had

type

1 DM,

twice a day. He in five studies on at 8:00 AM, before

injection.

This

dose

insulin was withheld until his lunch at 1:30 PM, and in the meantime, two further

respectively. One examination formed at 3:00 PM, after lunch

the two voxels spectroscopy.

studied In both

by means areas, care

not to include subcutaneous of the ventricles. The parietal chosen

above

the

basal

of

of H-I MR was taken

fat or a portion volume was

ganglia.

The

tions

whole

Spectral

rime); and at 3.56 ppm

to the achieved spectrum.

This

line

width

NA and

in the

groups

in NAA,

amino-acid plus

minor

choline

droxybutyrate

(Cho)

in the

and the peak

frequency

spectra

domain,

and

peak

used for further analysis. coupled spin systems of glutamine (Gln), and Glc,

of which

overlap

and of MI were fit-

with

are

also

other

affected

by

metabolites,

a

under

and

lactate

3

2

2.

spectra

solutions

identification.

spectral were

features

recorded

To identify

in patients under

with

experimental

ppm

all major

DM, spectra conditions

peaks

seen

in healthy

of metabolites identical

to those

subjects

dissolved used

and

in aqueto record

the in vivo spectra. All solutions were adjusted to a pH of 7.1-7.2 by means of a phosphate buffer and recorded at approximately 295K. The following solution spectra are displayed in addition to the in vivo spectrum (A.), which was obtained as an average over spectra of 10 healthy individuals (parietal location): B., Glu plus glycine (Gly) (*); C., Gln plus Gly (*); D., MI; E., a mixture of N-acetylaspartate (NAA), Glu, Cr, Cho chloride, and MI to mimic the main features of the in vivo spectrum; F., D-Glc plus NAA (*); G., taurine plus acetate (*); H., ethanol plus NAA (*); I., acetoacetate (AA) plus acetate (*); J., acetone plus acetate (*) and Gly (*); K., 3-hydroxybutyrate plus acetate (*); and L., lactate plus acetate (*). All solution spectra were line broadened to approximately 4 Hz to match the in vivo conditions. Peaks marked by (*) originate from compounds added as chemical shift references. A1-A4 indicate the integration ranges used to evaluate changes in Glu and Gln (Al, A2) and GIc (A3, A4), described in “Spectral

Metabolite

Volume

184

Identification.”

#{149} Number

1

are

Some of 2. 3-hy-

easily

iden-

of AA

and

acetone

overlap

with

(13,-y)-Glx (ie, Glu plus Gln) for the CH3 peaks, and the CH2 group of AA (peak at 3.46 ppm) coincides with one half the Glc spectrum. The Glc spectrum itself also overlaps the spectra of Glx (a) and taurine. For the spectral identification of Glc and

urne

0

ppm

Metabolite

the additional

1

conditions

bodies,

difference

patients

and

spectra controls

between were

con-

(cf Results).

of peak intenas changes

metabolite

concen-

trations. Because Ti and 12 relaxation time measurements were not performed in most patients, some of the observed effects could in principle also have originated from specific changes in Ti or 12. One must also remember that the localized regions of interest are heterogeneous, especially the gray matter location across the midline; a maximum of 20% of the vol-

ethanol

4

the same

The changes in the ratios sities are primarily interpreted

+Cho+MI

1, 3,4,

tified by the doublets at 1.20 and 1.33 ppm, respectively. They both overlap with resonances from lipids. The model solution

structed

I.

my&

0

(MI; protons

obtained

jWame

1

from

and 6 [25]; Gly; Cho [CH2]; and Glc). For the identification of other metabolites possibly implicated in DM, model solutions were prepared and their spectra

in the corresponding

2

contributions

-y-amino butyrate and glutathione); at 3.21 ppm (Cho: N[CH3]3 groups in Cho, betame, and carnitine plus H5 of MI and tau-

to obtain the in vivo spectra. spectra are shown in Figure

NAA.C.L(J+Cr

ppm

N-acetyl-aspar-

[22], glycoproteins residues in peptides (Cr: CH3 of Cr and phos-

used these

A2

3

in nor-

were

Ml

4

peaks

[NAAGJ

at 3.03 ppm

[24]);

transformation

of major

standardized single peaks to Gaussian lines 4 Hz wide. The singlet-like CH3 peaks of N-acetyl (NA), creatine (Cr),

I Glu

Identification

a postacquisition low-frequency filter to eliminate the residual water resonance and a Lorentz-Gauss transformation

([NA]:

individual

.1

varia-

groups.

phocreatine

assignment

ketone NAA

minor

8:00 PM). To quantitate peak ratios, the spectral data were processed in the manner of Kreis et al (13,16). The processing included

severe

Mt

to

metabolites

PM, and

the

subject

and

patient

Metabolite

The

[23],

Ct,uI Cr

subjects

across

performed

of these

tyl-glutamate

c

control

changes

PM,

was perand his first

NAA

ous

major

in individual

F.

Figure

tail by Kreis et al (13), were

8.7 and 14.4 mmol/L (time course, 8.7, 9.9, 8.7, 11.0, and 14.4 mmol/L, respectively, at 8:00 uvt, 10:30 uvi, 12:20 PM, 3:00

intensities were For the strongly glutamate (Glu),

occipital

integrations, discussed in de-

tween

ted

voxel was optimized to include mostly gray matter. The Ti-weighted axial locator images were recorded with a TR of 600 msec and a TE of 20 msec.

fit is inappropriate.

mal cerebral in vivo spectra of animals and humans has been discussed extensively in the literature (11,19-21). These main resonances include the peaks at 2.02 ppm

original

Location of regions of interest. boxes indicate typical locations

peak

simple spectral in Figure 2 and

daily insulin dose. A final examination was performed before dinner and before the evening insulin dose at 8:10 PM . A total of 18 spectra was acquired in these five sessions. His blood Glc concentration, measured at each examination, varied be-

matched Figure 1. The white

Gaussian

Therefore, indicated detect

of

examinations with H-i MR spectroscopy were performed at 10:30 iuvi and 12:20

simple

in this

area

may

contain

cerebrospi-

nal fluid (CSF) (approximately 7% in a healthy subject aged 25 years) (26). Because most metabolites are present only in CSF at a concentration much smaller than that in brain tissue (27,28), this heterogeneity does not usually alter the peak ratios observed.

However,

it is estimated

that

10%-50% of the signal intensity observed for the occipital location could originate from CSF Glc (concentration of Glc in CSF, approximately

0.66

x plasma

concentra-

tion; concentration of Glc in intracellular brain matter, approximately 0.2 x plasma concentration). Allowance has been made for the effect of up to 5% blood in gray matter. This fact also has to be considered

Radiology

#{149} 125

Table 3 Effect of DM on Cerebral

Metabolites No. of Men/

Subjects

Mean

No. of Women

Age

(y)

NAA

Cho

M1

Peak Ratios Patients Healthy P valuet

with DM subjects

10/11 19/il

i.36 ± .15 1.46 ± .09 .003

47 ± 17 47 ± 21

± .08 ± .09

0.85 0.82

(vs Cr) in Parietal

0.71

± .05 0.6i ± .07 .000i

.22

A3 (Glc)t

MIt Cortex

0.69

± .05

0.61

±

.07

9/8 10/5

42 40

from

in recovery

because ported trations

“ketone

from

bodies”

acute

DKA,

observed especially

concentrations in CSF are reto lag behind the plasma concenin acute DKA (29).

Statistical

Evaluation

Two-tailed

1.28

± 14

1.32

unpaired

Student

were applied. Linear regressions F test were used for correlations.

t tests with

the

MR spectroscopy

termination tios with

malities

de-

of relative metabolite good reproducibility.

raThe

mean variations in NA and Cho, with respect to Cr, in a single subject who

(n

13).

=

PCr

and

constant study, mately

With

Cr),

examination 2% and 3%

regard

NA,

to total

Cho,

over the age with a variation 6%-11% (Table

and

Cr (ie,

MI were

range of this of approxi3). No differ-

ences between men and women were detected. Glu and Gin, as well as GIc, give strongly coupled resonances at this

examination

frequency

(Fig

I)

and were therefore measured with considerably less precision. Excess Gin had previously been identified by difference spectra in patients with chronic hepatic encephaiopathy (CHE) (14). In the spectra obtained from control subjects, whose blood Glc was within physiologic limits, the resonances

for

Gic

are

not

sufficientiy

prominent to be clearly assigned or to enable measurement of intracerebrai Glc concentration. The numeric integrations 126

A3 and

#{149} Radiology

A4,

which

.08

± .07 ± .06

0.63

±

0.58

±

.005

± .07 .Oi

Cortex .07 .05

0.i8 ± .05

0.55 ± .09

0.12

0.50

.01

± .04

.002

± .07

.04

with increasing Glc were corrected as follows: Spectra of an MI and a areas, based on the increase in A3, was subtracted from the observed

the two most prominent peaks of the Gic spectrum but were also affected by changes in taurine (for A3) and H,, of Glx and MI (for A4), varied by 33% and 12%, respectively. A major reason for the variation of A4 (and A2) from one patient to the next was the baseline uncertainties caused by the residual water peak.

Some

in the enabled

underwent repeated were, respectively,

0.66 0.59

± .09

2. test.

Metabolic

in Patients

Measurements Cerebral Cortex

± .09 ± .06

0.55 0.48

± .04 ± .03 .0001

paticnt

I

b1

patient

I-normal

.

RESULTS

H-i

0.64 0.60

or minus I SD. in the MI peak area caused by overlap and the appropriate fraction of peak

Cerebral

Metabolite Normal

± .09 ± .08

.2

Note-Numbers in columns 3-9 are means plus * MI increases due to overlap with Glc. Increases GIc solution were added in the relevant proportions, Ml. t Ml corrected for overlap with GIc. tFor a definition of this GIc resonance, d Figure * P values for the two-tailed unpaired Student t

for peaks

± 17

0.21 0.13

.000i

Peak Ratios (vs Cr) in Occipital Patients with DM Healthy subjects P value1

A4 (Glc)*

covered

Abnormalities DM

with

significant were

glucose

AA

metabolic

present

abnor-

in the

brains

4

patients with DM (Table 3). NA:Cr was significantly lower in the parietal region of patients with DM compared with that in agematched control subjects. Cho was on average

unchanged,

but

showed

large

Figure 3. Identification of cerebral patients with DM by means of H-I

parietal and 9% in the occipital This excess of MI was determined

and 3.8 ppm. trum in patient

ter an appropriate correction for the observed surplus in Glc had been applied (Table 3; cf next paragraph). The concentration of GIc in the brain, estimated from the integrals A3 and A4, was significantly elevated in both locations in patients with DM. However, the average increase in brain Gic concentration was small, the mean of 9.9 mmol/L

blood (ie,

normal concentration). of solution spectra and a total Cr concentration

Glc concentwice the

On the basis assumption of of 10 mmol/L,

it is estimated that the observed increase in A3 and A4 of 0.05-0.08 arbitrary units (parietal and occipital cortices) corresponds to roughly 2 mmol

of excess brain The highest measured

Glc per liter. A3 and A4 values

in patients

recovering

were from

GIc in MR spec-

troscopy. Cerebral H-i spectra from two patients with DM are compared with a solution spectrum of o-Glc. a, Spectrum of occipital gray matter in patient I (who had insulindependent diabetes mellitus IIDDM]) ohtamed

cortex. af-

C,

“Pu,,

increases in some individuals (see below). MI was increased by 13% in the

reflecting tration

2

1

of

usual

22 hours

spectral

after

admission

features h, Parietal ii,

for DKA.

are visible

who

Un-

at 2.2, 3.4,

white matter spechad IDDM (blood

Glc level, 15.8 mmol/L; HC03 level, 24.8 mmol/L) and chronic hepatic encephalopathy (CHE). Again, abnormal spectral features exist at 3.4 and 3.8 ppm, in addition to the abnormalities at 3.2 (low choline [Cho]) and 3.6 ppm (low MI) attributed to CHE (13). C, Difference spectrum between a and the

normal average

gray matter spectrum obtained as an from 10 subjects. The abnormalities in spectrum A described herein are seen as positive

features

in the

difference

spectrum

(c). d, The peaks at 3.4 and 3.8 ppm can be clearly attributed to the main spectral features of Gic (d, dashed lines). Additional peaks

ketone

at 21-2.2

ppm

might

body; these are more 6 and 7. Furthermore,

originate

from

clearly seen the surplus

a

in in

Figures the Cho peak at 3.2 ppm could he due to his DKA, although this might also have been caused by patient motion, so that the actually localized area might not he gray matter, as defined on the locator image (Fig 2), hut more white matter. The peak at 2 02 ppm in 1 (*) is from NAA. added as a chemical shift reference

July

1992

1.4

#{149}8EPJ=3E

1.2

NA

8

r2

.5

ml

4

=.57

0

patient 1

6

normalcontrols

Cho

4

r2=.18

r201 6

8

10

plasma

12

glucose

14

16

(mM]

.4 4

6

Figure tration.

8

10

12

14

16

4. Dependency of metabolite Thirteen successive measurements

in a single

patient

of plasma

Glc

with

IDDM

concentration

levels

(patient

on blood of cerebral

Glc concenmetabolites

3) are plotted

measured

after

each

(two to four spectra each) during a period of 12 hours. intensities for NA, Cho, and MI, as well as the spectral

grals

A3 and

A4 corresponding

to cerebral

Glc

levels

for

Figure

examina-

tions peak

all 13 spec-

nations sions,

slope, and the different

Localized

H-i

the MI peak was I week apart (when

mmol/L, respectively), the average in patients parietal

white

tamed

viduals (vertical bars) and the normal range of blood Glc levels (horizontal bars). The squares of the correlation coefficients (r2) and the P values (Glc A3, P = .003; Glc A4, P .003; NA, P .14; Cho, P = .01) show that a significant correlation was found between blood GIc and cerebral GIc and between blood Glc and MI

its for the Note also

5.

spectra

featuring

high

MI peaks

in a pa-

tient with DM. This patient, who had secondary IDDM (due to pancreatitis) and liver disease, underwent examination with H-i MR spectroscopy three times within 7 months. At all three exami-

The inte-

tra from occipital gray matter, are indicated (0); normal values (A) were measured in 15 healthy subjects. The error bars for the measurements in patient 3 represent the root mean square variation of the residuals from the linear regression. The range bars for the normal values indicate the SD of the measurements within the 15 mdi-

(despite the correction for the linear correlation

0

1

ppm

as a function

of five

2

4

b beyond

a and

normal. Glc levels

On the first two occawere 14.1 and 3.7

the MI level was considerably with DM. Spectra a-c were

matter.

in 10 healthy

higher than the blood

For

comparison,

subjects

3.7 ppm

the

than from

spectrum

ob-

in d. The spectral

is shown

may

normal

higher recorded

be distorted

by artifacts.

Glc

approximately

features

in

for spectral overlap with Glc). The best fit (central straight line), 95% confidence limthe

true vertical

mean (curved scales. mM

lines) =

are

included.

plasma

mmol/L.

was

15

mmol/L. A spectrum from a patient with non-insulin-dependent DM excluded from the group of patients with DM because of concomitant CHE was also plotted (Fig 3). Elevated Gic peaks at 3.42 ppm and 3.80 ppm were seen in addition to the spectral changes caused by CHE. In a patient with type I DM (patient

DKA (with the highest concentration of blood Glc), but no statistically significant correlation between the measured blood Glc and brain Glc could be determined in our study. This lack of correlation was likely due mainly to the fact that plasma Gic could not

of CSF, where the Glc level is known to be higher than that in brain tissue. Relative to Cr, NA and Cho peaks were higher in white matter than in

always

of Cho in both white and gray matter characterized the small group of patients with type II DM compared with

with the changes in blood Glc levels. The values A3 and A4, which represent cerebral concentrations of Glc, and the main peak ratios were plotted

patients

as a function

be measured

ter examination troscopy, and have changed who received DKA.

As expected,

relation between Glc was observed who underwent ‘identification

Patients The was

immediately

a much

of Glc

and

better

cor-

brain Glc and blood in a single subject repeat studies (cf in the

with DM”). measured increase

smaller

af-

with H-i MR specplasma Glc content may rapidly in the patients active treatment for

less

Brains

in brain

significant

184

#{149} Number

I

matter

in healthy

differences

were

patients

with

with

differences were

of

Glc in the

subjects.

also

DM.

type

These

present

A 10%

I DM.

between

these

in the

higher

No

level

other

of Patients

of Glc with

in the

Brains

DM

A3 and

A difference spectrum between patient 1 and a group of control subjects, compared well with that of an aqueous Glc solution shown in Figure 3. The

concentration

in patient mmol/L

3), diurnal

of excess

Glc

1 was approximately when the concentration

6

changes

were

of plasma

correlated

Glc

concentra-

tion measured after each session. Although the blood plasma concentration in this patient varied only from 8 to 14 mmol/L, it was still possible to perform a linear correlation of

groups

seen.

Identification

occipital cortex than in the parietal cortex. This was rather unexpected in view of the fact that the occipital volume contained a higher contribution Volume

gray

of

A4 with

blood

Blood Glc concentrations 12 mmol/L are therefore cause clearly observable the spectral contributions in vivo brain spectrum spectroscopy.

The

tion

normal

between

poor

Glc

(Fig

4).

greater than expected to increases in of Glc to the in H-i MR discrimina-

brain

spectra

Radiology

#{149} 127

and group fore vation tion with higher

those obtained from the whole of patients with DM is thereprobably due to the modest elein the plasma Glc concentra(8-10 mmol/L). MI increased blood Glc and was generally than in control subjects. NA

was significantly slightly higher jects, but neither

post

parietal

occipital

DKA

normal

variations.

MI in the

Diabetic

Brain

The peak at 3.56 ppm, attributed mainly to MI, but which also included the singlet of Gly, was significantly elevated in the total group of patients with DM. patients

with

DM

showed

control

occipital

occipital

an

extreme increase in this peak. Parietal white matter spectra of one such patient (patient 12), a 55-year-old man with

liver

disease

and

DM

4 Figure

secondary

persistently

elevated

bodies

with that in healthy subjects. The second prominent peak of MI at 4.06 ppm was noted in these and several other spectra. Because it is very close to the water line at 4.73 ppm, it canbe used

to unequivocally

the

increase

in the

Detection Diabetic

identify

MI peak.

of Ketone Brain

Bodies

recovery

7 days,

respectively, it was attributed 2-4 mmol/L AA

sion), body,

acetone. detected. also

from

recovering

from

DKA

DKA,

ence spectrum (Fig 3) shows abnormality at 2.1-2.2 ppm, attributable to ketone bodies.

the

4

recovery.

Cerebral

noted

at 2.22

ppm

in this

spectrum,

obtained

Metabolic

Recovering

(5

differ-

a further probably The ex-

The two examination

patients earliest

their

recovery

128

#{149} Radiology

from

Changes

in

from

DKA

who underwent in the course DKA (patient

1 from

patient

3 recorded

from

an

18 cm3

volume

in the

left

22 hours after hospital admission for The representative spectrum from the parietal cortex is the sum of four (of six) spectra acquired consecutively in 64 averages (1.5 DKA.

each.

Because

of patient

motion,

the

days

later,

after

bral ketones

complete

recovery.

No

cere-

were

detected. The differences between these two examinations are displayed in c as the difference a-b. In addition to the obvious surplus in the ketone peak (K), a second spectral abnormality in the Cho peak became evident. This increase in a metabolite resonating at 3.2 ppm, which was

,

also observed in patient 1 (Fig 3), might be associated with the earliest stages of DKA

and

diabetic

coma.

showed significant elevation of the Cho peak compared with that in control subjects and to other diabetic pa22 hours after hospital patient 1 at 24 hours admission)

of 2 at

0

ppm

tients

Patients

2 spectra

2 during and examination a was re-

cess in Glc and Cho in this patient has already been discussed herein (Fig 3).

Further

3 H-i

lines were somewhat broader, but the ketone characteristic peak at 2.22 ppm (K) was still easily identifiable. Spectrum b was recorded 5

was was

who

was

minutes)

after admisto a ketone or 1-2 mmol/L

No 3-hydroxybutyrate In a third patient,

1 and

corded

2

nance at 2.22 ppm (Figs 6, 7). Because this peak was absent in both patients

complete

2 of DKA

episodes

Figure 7 Spectra from patient after DKA. Patient 2 underwent twice within 5 days. Spectrum

in the

Of nine patients in the early stages of recovery from DKA, two (patients and 3, who underwent examination during three separate episodes of DKA) showed an unexpected reso-

after and

3

Two

parietal lobe. The patient relapsed into DKA 2 days later. The spectrum on the lower left was acquired 5 months later, during a second episode of DKA. In addition to the same well-resolved ketone peak at 2.22 ppm (K), resonance peaks for GIc (G ) were seen. This spectrum was obtained from an occipital gray matter location (10.3 cm3). The spectra on the right are control spectra. The one on the top is from the same subject 6 days later, when no more ketone bodies were detected in the urine. The spectrum on the lower right was obtained from the occipital cortex of an age- and sex-matched healthy subject. None of the control spectra displayed the ketone peak or contributions from GIc. All four spectra are shown before the usual Lorentz-Gauss transformation. An exponential line broadening of 0.5 Hz was applied.

compared

not

6.

during (left, top and bottom) and after (right, top) episodes of DKA. The top left spectrum was acquired 3 days after admission for DKA, at a time when the patient had supposedly totally recovered and was ready to be discharged. A peak characteristic for the presence of ketone

to pancreatitis, repeated within 1 week and then 5 months later, are displayed in Figure 5. The Ml peak was

DKA

lower and Cho was than in control subwas affected by Glc

or diurnal

Some

DKA

changes clearing clinical herein.

had

admission after hospital

persistent

and

mental

consistent with incomplete of their diabetic coma. The details have been given Difference spectra (Figs 3, 7)

without

DKA.

When

patient

2

underwent reexamination 5 days later, mental and biochemical recovery were virtually complete. At that time cerebral Cho had returned to normal (Fig 7). This finding points to the existence of additional cerebral metabolic abnormalities in patients July 1992

patient

1

durlngDKA

.

0

ppm

Figure

8.

In vivo

peak. Three from

characterization H-i spectra location in patient

a panetal

ketosis.

The

of ketone obtained 3 during

cerebral

acquisition

parameters

had

been

varied

to estimate relaxation times Ti and T2: for Ti, a change in TR from 3,000 msec (a) to 1,500 msec (b), and for T2, two acquisitions with a TE of 30 msec (b) and 120 msec (c). The ketone body peak (arrows) displayed Ti relaxation similar to that of the other compounds, whereas the T2 relaxation seemed faster than for the other singlet peaks, a difference that indicated either restricted motion or chemical exchange. x 1.53, x 2.09 = the factor by which this spectrum is magnifled in comparison with a.

Cho

have

been

Biochemical Identity of Ketone Bodies in H-i MR Spectra The most likely candidate for the ketone body that accumulates in the human brain during DKA is -hydroxybutyrate (4,5). This was not found. The peak at 2.22 ppm agrees with

the

solution

acetone. AA, which found in the brain 3-hydroxybutyrate, shift

in aqueous

solution

were ation peak glet

of the

peaks

in vivo

in the

spectrum,

pointing

seconds.

A compari-

of the two spectra acquired with of 30 and 120 msec showed that peak diminished more quickly

with longer approximately that indicates tion

peak

ppm

T2 mea-

made (patient 3, Fig 8). Ti relaxaffected the intensity of the at 2.22 ppm similarly to the sin-

to a Ti of 1.3-1.5 son TEs this

ketone

TE (an apparent T2 of 100 msec), a finding effects of restricted mo-

or chemical

Volumel84

exchange.

#{149} Number

1

a, obtained from the occipital tient 3 during ketosis (0.5-Hz 0.5-Hz

Gaussian

line

cortex of paLorentzian and

broadening),

spectra

from in vitro solutions of suspected metabolites were acquired. The chemical shift of peak K is very similar to the one obtained from acetone in aqueous solution (d) but does not coincide with the methyl resonance of AA in aqueous solution (c). Furthermore, the methylene resonance of AA at 3.46 ppm is not

detectable

underneath

the

appropriate

Glc peak

in a. However, a change in the medium from a purely aqueous to a 10% bovine albumin solution caused the spectrum of AA to change drastically. The methyl resonance broadened and shifted slightly, whereas the methylene resonance disappeared altogether. These effects were observed more

found

of pure AA in a solution of 10% bovine serum albumin, fraction V dissolved in Krebs-Henseleit saline at pH 7.2 and at approximately 5#{176}C, markedly altered the AA spectrum. The peak at 3.46 ppm was broadened beyond visibility, and the methyl peak originally at 2.26 ppm shifted to 2.24 and broadened (Fig 9). These spectral changes could be caused by chemical binding, a shift in the tautomeric equilibrium of AA (from the keto to the enol form) as the result of solvent effects, or chemical transformation of AA to acetone. DISCUSSION Several the brain

metabolic of patients

observed

in this

study.

abnormalities in with DM were We

have

ob-

in the

brain

within

24-36

hours

of treatment of DKA. We were surprised to find that the chemical shift of the ketone body observed in the brain in these conditions was more consistent with the presence of acetone than of AA. Biochemical arguments also support the conclusion that acetone rather than AA is the ketone detected here. In rats with severe DKA, the reported concentrations of AA were consistently less than 0.1 mmol/L (An estimated accumulation of up to 5 mmol/L AA is necessary to explain

the

peak

intensity

in these

patients.) and were always accompanied by the appropriate accumulation of 3-hydroxybutyrate at approximately fourfold higher concentration (4,5).

of

of 2.26

Ti and

9. Chemical identification of observed cerebral ketone body. To identify the metabolite giving rise to peak K in spectrum

Preparation

is less likely to be in the absence of has a chemical

(Fig 2). Approximate surements

spectrum

Figure

tion of the ketone peak is therefore still equivocal, these spectra demonstrate the importance of the proper solution medium for phantom spectra, especially for compounds with known binding affinities or in tautomeric equilibrium, like AA. The peaks marked with an asterisk (*) were caused by compounds added as chemical shift references (acetate, Cr, and Gly) or the solution medium.

seen in response to severe hyperosmolality in rat brain extracts (30).

closely

TT

#{149} ‘

readily at a lower solution temperature (approximately 5#{176}C in b). While the identifica-

earlier in the course of recovery from DKA. Serum osmolality was increased in both patients. Similar changes in (glycerophosphoryl)

m

,

served the following in different patients: elevated cerebral concentrations of Glc, ketone bodies, MI (or Gly) and choline-like metabolites in both white and gray matter, and a small but significant reduction in the concentration of NA (on the assumplion that Cr is constant) in white matter only. It was possible to correlate the plasma Glc concentration with cerebral Glc content in a single patient with DM who underwent repeat examination, and demonstrate elevated cerebral Glc in most patients with DM. H-i MR spectroscopy could not be used to accurately measure normal intracerebral GIc, which is close to i mmol/L (4,5), and we have insuffident information to define the intracellular Glc content because all measurements must take account of the CSF included in the volume of interest, the (unknown) blood content, and the poorly defined extracellular fluid compartment. Ketone bodies were consistently

3-hydroxybutyrate

is readily

defined with H-i MR spectroscopy by means of its isolated doublet at 1.2 ppm (Fig 1) but was not observed in any of the patients with DM in our study. Sulway and Malins (31) demonstrated up to i2.9 mmol/L acetone in plasma in DKA; Reichard et al (32) reviewed other supportive evidence for significant acetone production and metabolism in patients with DM. The distinction between AA and acetone, which appears to depend on exact definition of the intracellular environment in the brain compartment that contains ketones, has yet to be explored. It is intriguing that, by clinical standards, one of the patients had fully recovered from DKA when H-i MR spectroscopy demonstrated persistent ketones in the brain. This patient reRadiology

#{149} 129

lapsed into DKA 2 days after the examination. Because there is a wellrecognized

lag

in clearance

of ketones

from CSF in patients with DKA (29), acetone may possibly be cleared less rapidly from brain cells because of its known lipid solubility. A rather unexpected finding in our group of patients with DM was the small but significant elevation of the peak attributed to cerebral MI. However, it has been known for many years

that

cerebral

MI

content

is in-

creased in rats made diabetic by means of treatment with either streptozocin or alloxan. The degree of elevation was greatest in the most severely diabetic rats (6). The finding of elevated cerebral MI in a group of patients with DM under relatively good control is therefore surprising. A simple hypothesis is the development of persistent hyperglycemia in cerebral capillaries, with formation of excess glucose-6-phosphate. Glucose-6-phosphate is the principal precursor of inositol-i-phosphate, which in turn may be the substrate for MI formation in the brain. One patient with hyperglycemia due to secondary DM had particularly high MI levels, which persisted over 5 months. It is interesting to speculate that a genetically determined abnormality of MI biosynthesis may also exist. The acute effects of DKA include the expected changes of intracerebral Glc and ketones, but neither of these metabolites nor intracellular pH is considered entirely responsible for hyperglycemic coma in patients with DKA (33-35). Two patients were examined at a time when the clouding of consciousness associated with DKA had not completely abated. Excess cerebral Cho in both patients may indicate the more profound biochemical changes that cause diabetic coma. H-i MR spectroscopy provides new insights into brain biochemistry in chronic as well as acute DM. Until now, physicians have had little incentive to perform cerebral examinations with MR imaging or MR spectroscopy in their patients during acute diabetic crises. We believe that the early findings

of a plethora

of biochemical

ab-

normalities in the diabetic brain that are described herein should encourage wider use of image-guided H-i MR spectroscopy to explore the

mechanisms of diabetic coma and record events in the very earliest phase of treatment for DKA. The crucial report by Ohman et al (29) defined “treated” DKA as the period 4-9 hours after introduction of treatment. This

#{149} Radiology

scale

provides

for future

studies

the

with

16.

best

H-i

MR

17.

spectroscopy. 18. Acknowledgments: Pinto, PhD, for clinical Bellinger for preparation

We are grateful to R. chemistry and to Jennifer of the manuscript. Pa-

tients were referred by J. Ma, MD, D. Johnson, MD, P. Thomas, MD, and M. Tong, MD, as well as by K. Sullivan and members of the medical staff

of Huntington

Memorial

Hospital,

Memorial

tington

Hospital

for help

19.

20.

Pasa-

dena, Calif. We are grateful in particular to the staff of the medical intensive care unit of Hunwith

21.

these

studies. References 1. 2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

130

time

guide

15.

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July

1992