Journal of the Neurological Sciences, 1977, 33:51-59
51
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
METABOLIC C H A N G E S D U R I N G GLUCOSE T O L E R A N C E TESTS IN MIGRAINE ATTACKS
S. W. J. SHAW, R. H. JOHNSON and H. J. KEOGH University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow (Great Britain)
(Received 18 December, 1976)
SUMMARY (1) Intravenous glucose tolerance tests have been carried out on 6 migraine sufferers on two occasions. The first study was carried out during a migraine attack and the second was performed in an attack-free period. The patients had fasted overnight and the investigations were carried out in the morning. Samples of venous blood were taken for measurement of concentrations of glucose, lactate, pyruvate, free fatty acids (FFA), glycerol, ketone-bodies, insulin and growth hormone. (2) An impaired tolerance to glucose was found during the migraine attacks compared with the control studies. Elevated ketone and FFA levels were found during the attacks and may have accounted for the glucose intolerance. The elevation of plasma F F A levels during the migraine attacks paralleled changes in blood glycerol concentrations suggesting increased lipolysis during the attacks. Growth hormone and cortisol were raised and insulin was depressed during attacks. (3) Our observations, in which the patients acted as their own controls, imply increased lipolysis during migraine attacks and are in contrast to previously reported studies. The patterns of metabolic and hormonal changes are consistent with a stress response during the attacks and the significance in relation to the causation of the attacks is discussed.
INTRODUCTION Raised plasma concentrations of certain free fatty acids (FFA) have been observed during spontaneous migraine attacks (Anthony 1973). Elevation of plasma This work was supported financially by the Migraine Trust. Address for correspondence: H. J. Keogh, University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF, Great Britain.
52 FFA has also been shown to occur in those patients who developed migraine during a glucose tolerance test after an overnight fast and patients who did not develop migraine had no elevation of plasma FFA (Hockaday, Williamson and Whitty 1971). In that investigation, however, the blood glycerol concentrations in the patients who developed migraine were similar to those found in the control study suggesting that the elevation of FFA was not dependent on an increased rate of lipolysis. In order to obtain information upon the metabolic changes occurring in spontaneous migraine we have studied patients during one of their attacks and also when free from migraine and have obtained evidence that lipolysis increased during attacks. METHODS A group of patients suffering from classical migraine, whose names were on the diagnostic list of the University Department of Neurology, Glasgow, were asked to come to the department when they had a migraine attack in the morning. The purpose and procedure of the investigation had previously been fully explained to them. The patients were chosen from those with a positive family history of migraine and who presented with features including a visual or other form of aura, unilateral throbbing headache and associated nausea or vomiting. Additional symptoms were the presence of pallor, flushing, running eyes or shivering during the headaches. A relationship between diet and migraine could not be established for any of the patients and there was no obvious link between the meals on the evening prior to the investigations and the onset of the migraine attacks. Six subjects (1 male, 5 female) with an age range of 42-57 years (mean 49 years), and a 3-42 year history of migrainous headaches (mean 19 years) were investigated, Their weights were 48-75 kg (mean 62), and their heights were 140-173 cm (mean 150 cm). They were first investigated during a migraine attack and then, in order to provide control observations, during an attack-free period, having had no attacks for at least 4 days. They were asked not to take breakfast, tea, coffee or medication and none of them was taking any prophylactic medication for migraine. On the control occasion the subjects were investigated after an overnight fast, so that the conditions of the investigations were the same on each occasion. The heart rates of 3 subjects were recorded with an electrocardiograph in both studies. On each occasion, after antecubital vein catheterisation, 2 resting blood samples were withdrawn with an interval of 15 min. A 50 ~ glucose solution (0.33 g glucose/kg body weight) was then infused over 3-5 min and subsequent blood samples were withdrawn 15, 30, 45, 75, 105, 135, 165 and 225 min after the beginning of the infusion. Throughout each investigation the catheter was kept open by flushing with physiological saline. Each blood sample (12 ml) was withdrawn without stasis and treated as follows: 4 ml blood was immediately deproteinised in ice-cold 10 ~ perchloric acid and 8 ml was gently shaken in a heparinised tube. All samples were stored in ice and centrifuged at the end of the investigation. The acid extracts were assayed for glucose (Bergmeyer and Bernt 1963), lactate and pyruvate (Hohorst, Kreutz and Biicher 1959), acetoace-
53 tate and 3-hydroxybutyrate (Williamson, Mellanby and Krebs 1962) and glycerol (Kreutz 1962). The plasma samples were assayed for free fatty acids (Itaya and Ui 1965; Dalton and Kowalski 1967) and insulin (IRI) by a charcoal radioimmunoassay (Albano, Ekins, Maritz and Turner 1972). Plasma concentrations of human growth hormone (hGH) were measured by a double-antibody method (Hunter and Ganguli 1971). Significances of difference were tested using a standard paired t-test and the results has been expressed as means -4- standard errors.
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Time ( mini Fig. 1. Blood glucose (mmol/l) and plasma insulin (mu/l) (means ± SEMi in 6 subjects during attacks (©
©) and during an attack-free period (ml . . . . , ) . G indicates the start of the intravenous in-
fusion of glucose (0.33 g/kg body weight).
54 RESULTS Heart rates
In the 3 subjects in whom heart rates were observed no major alteration occurred during the studies and there were no significant differences between the rates measured in the two investigations.
Glucose (Fig. 1) The blood glucose concentrations were not significantly different between the two studies up to 15 min after the glucose infusion. The samples at 30, 45, 75 and 105 min, however, showed significantly different blood glucose concentrations (at 30, 45 and 75 rain P < 0.01, at 105 min P < 0.05). All subsequent blood samples showed no significant differences in glucose concentrations between the two investigations.
1'0-
tAttock S O'8O
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It~-
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.......t.y ;
0,110•
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Fig. 2. Plasma FFA (mmol/l) and blood glycvrol (mmol/i) (m©ans 4- SEM) in 6 subjects. Symbols as in Fig. I.
55
Pyruvate and lactate There were no significant differences in blood pyruvate and lactate concentrations between the two studies. Plasma FFA (Fig. 2) The differences in FFA concentrations between the attack and control studies were significantly different for all samples except those at t 50 min. In the two resting samples, comparing attacks with controls the values were significantly different (P < 0.05). After the glucose infusion, plasma FFA concentrations declined, showing a maximum depression at 75 rain in both groups with a highly significant difference between the groups (P < 0.0011. At 135, 195 and 225 min the differences between the groups were not so large though still significant (P < 0.05). In both studies plasma FFA concentrations had returned to pie-infusion values by 135 min. Glycerol (Fig. 2) The blood glycerol concentrations in the resting samples were significantly different comparing the attack and control studies (P < 0.05). During the period 30-105 min after the infusion the differences between the groups were highly significant (P < 0.01). Ketone-bodies (Fig. 3) When the 2 groups were compared the differences in concentrations of blood
/ 0 50
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I
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Time ( rain ) Fig. 3. Total bood ketone bodies (mmol/l) (means -F SEM) in 6 subjects. Symbolsas in Fig. I.
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240
Time ( rain ) Fig. 4. 3-Hydroxybutyrate:acetoaeetate ratios (means i S E M ) in 6 subjects. Symbols as in Fig. 1.
ketone bodies (acetoacetate plus 3-hydroxybutyrate) in all samples were significant. Blood ketone concentrations fell to their lowest values on both occasions at 75 min after the infusion although the difference between the groups was still significant (P < 0.05). The mean values for the 3-hydroxybutyrate:acetoacetate ratios (see Fig. 4) were all higher in the blood samples taken during attacks compared with the control studies although these were significantly different only in the resting samples.
Plasma insulin (IRI) (Fig. 1) The mean values for plasma IRI in the blood samples taken in the control studies were all higher than those taken during the migraine attacks although they were significantly different only at 45 min (P < 0.05). The maximum values occurred at 15 min. The changes in total insulin release have been examined by calculating the areas under the concentration curves of each subject from the time of the first resting sample to that of each subsequent sample. The mean values for total insulin released were significantly higher in the control investigations compared with during the attacks. In the pre-infusion period and up to 45 min the two studies showed a significantly different insulin release (P < 0.05).
Plasma human growth hormone (hGH) (Fig. 5) The mean hGH peak occurred at 105 min during the attacks and at 135 min
57 8-
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O
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¢_
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Controls
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Attacks
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0
.
30
,
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_
90
,
,
,
120
150
180
,
.
,
210
240
Time (min) Fig. 5. Plasma human growth hormone (mu/l) in 6 subjects. Symbols as in Fig. 1.
during the controls. Plasma hGH concentrations were however only significantly different at 15 min (P < 0.05). Samples taken at other times showed no significant difference probably due to the wider variation in response of the patients during the attacks. DISCUSSION
In this investigation we have found a difference in glucose tolerance between patients in migraine attacks and the same patients in an attack-free period. We have also found evidence of other metabolic differences implying increased lipolysis in attacks, both changes being in contrast to a previous report (Hockaday et al. 1971). We consider our observations to be more valid because intravenous glucose was used and the subjects acted as their own controls. The greater plasma free fatty acid concentration we observed during migraine attacks were similar to those reported by other workers (Hockaday et al. 1971 ; Anthony, 1973), and as previously shown, these were associated with a large rise in blood ketone body concentrations (Hockaday et al. 1971). The elevation of the 3-hydroxybutyrate:acetoacetate ratios during attacks may be secondary to increased free fatty acid mobilisation as ketone body production is related to the level of plasma free fatty acids (Krebs 1967; Williamson, Lund and Krebs 1967). However, our findings of significantly raised concentrations of blood
58 glycerol in attacks compared with observation in control studies is evidence for ira.creased lipolysis occurring during the migraine attacks which contrasts with a previous report (Hockaday et al. 1971). Their subjects, however, did not act as their own controis and their observation that blood glycerol concentrations did not change significantly during attacks could therefore be attributed to variability between subjects. Several causes of lipolysis may be considered. Any generalised increase in sympathetic activity during attacks would be expected to increase lipolysis by increasing circulating catecholamine concentrations. Although, in our studies, heart rates were unchanged, the significant decline in total insulin release in the attacks is in keeping with an increase in sympathetic activity (Kris, Miller, Wherry and Mason 1966; Porte and Williams 1966). Depressed insulin secretion would result in a relative decrease in plasma FFA re-esterification and greater lipolysis (Hunter, Fonseka and Passmore 1965) but this was probably not a significant contributing factor as there were no major differences in plasma hGH concentrations before glucose was given, although in the investigation of migraine attacks the patients were already experiencing severe headache and the plasma FFA concentrations were already raised. A further possibility is that the increase in lipolysis might occur as part of a generalised stress reaction to the migraine headache and may be independent of the causation of migraine. However, previous workers have reported an increase in plasma FFA concentrations prior to a migraine attack (Hockaday et al. 1971), and it remains possible that the attack is initiated by increased lipolysis. The difference we have found in the tolerance to intravenous glucose between the migraine attacks and control studies is not related to differences in absorption of glucose because in our investigations intravenous glucose was given in preference to the oral route. This eliminates the possibility of vomiting with oral glucose and potential alteration of absorption from the gut as it has been shown that a failure of absorption can occur during migraine attacks (Volans 1974). The difference in tolerance may have been due to the decrease in insulin release during the attacks. However, it is also probable that the impairment of glucose tolerance during migraine attacks may be related to the effect of increased plasma FFA and blood ketone concentrations on the peripheral utilisation of glucose. Starvation or carbohydrate deprivation in normal subjects causes elevation of plasma FFA and blood ketone levels with impairment of carbohydrate tolerance (Hales and Randle 1963; Schalch and Kipnis 1965). In addition in vitro studies have demonstrated that raised concentrations of ketone bodies or fatty acids reduce the utilisation of glucose by muscle tissue by inhibition of the enzymes hexokinase and phosphofructokinase (Randte, Newsholme and Garland 1964; Newsholme and Randle 1964; Randle, Garland, Hales, Newsholme, Denton and Pogson 1966). Our observations are at variance with those of previous workers and further investigation into the causes of lipolysis in spontaneous migraine is indicated. ACKNOWLEDGEMENTS We thank the patients for their co-operation and Professor J. A. Simpson for encouragement.
59 REFERENCES Albano, J. D. M., R. P. Ekins, G. Maritz and R. C. Turner (1972) A sensitive precise radioimmunoassay of serum insulin relying on charcoal separation of bound and free hormone moieties, Acta endocr. (Kbh.), 70: 487-509. Anthony, M. (1973) Plasma free fatty acid changes in migraine, Proc. Austr. Ass. NeuroL, 10: 87-89. Bergmeyer, H. U. and E. Bernt (1963) In: H. U. Bergmeyer (Ed.), Methods of Enzymatic Analysis, Verlag Chemie, Weinheim, p. 125. Dalton, C. and C. Kowalski (1967) Automated colorimetric determination of F F A in biological fluids, Clin. Chem., 13: 744-751. Hales, C. N. and P. J. Randle (1963) Effects of low-carbohydrate diet and diabetes mellitus on plasma concentrations of glucose, non-esterified fatty acid and insulin during oral glucose tolerance tests, Lancet, 1 : 790-794. Hockaday, J. M., D. H. Williamson and C. W. M. Whitty (1971) Blood glucose levels and fatty acid metabolism in migraine related to fasting, Lancet, 2:1153-1156. Hohorst, H., F. H. Kreutz and T. B0cher (1959) l~ber Metabolitgehalte und Metabolitkonzentrationen in der Leber der Ratte, Biochem. Z., 332: 18-46. Hunter, W. M. and P. C. Ganguli (1971) The separation of antibody bound from free antigen. In: K. E. Kirkham and W. M. Hunter (Eds.), Radioimmunoassay Methods, Churchill-Livingstone, Edinburgh, pp. 243-257. Hunter, W. M., C. C. Fonseka and R. Passmore (1965) Growth hormone - - Important role in muscular exercise in adults, Science, 150: 1051-1052. Itaya, K. and M. Ui (1965) Colorimetric determination of free fatty acids in biological fluids, J. Lipid Res., 6: 16-20. Krebs, H. A. (1967) The redox state of nicotinamide adenine-dinucleotide in the cytoplasm and mitochondria of rat liver, Advanc. Enzyme Reg., No. 5, pp. 409-437. Kreutz, F. H. (1962) Enzymatic glycerin determination, Klin. Wschr., 40: 362-363. Kris, A. O., R. E. Miller, F. E. Wherry and J. W. Mason (1966) Inhibition of insulin secretion by infused epinephrine in Rhesus monkeys, Endocrinology, 78: 87-97. Newsholme, E. A. and P. J. Randle (1964) Effects of fatty acids, ketone-bodies and pyruvate, and of alloxan-diabetes, starvation, hypophysectomy and adrenalectomy on the concentrations of hexose phosphates, nucleotides and inorganic phosphate in perfused rat heart, Biochem. J., 93 : 641-651. Porte, Jr., D. and R. H. Williams (1966) Inhibition of insulin release by norepinephrine in man, Science, 152: 1248-1250. Randle, P. J., E. A. Newsholme and P. B. Garland (1964) Effects of fatty acids, ketone bodies and pyruvate, and of alloxan diabetes and starvation, on the uptake and metabolic fat of glucose in rat heart and diaphragm muscles, Biochem. J., 93: 652-665. Randle, P. J., P. B. Garland, C. N. Hales, E. A. Newsholme, R. M. Denton and C. I. Pogson (1966) Interactions of metabolism and the physiological role of insulin, Rec. Progr. Hormone Res., 22: 1-48. Schalch, D. S. and D. M. Kipnis (1965) Abnormalities in carbohydrate tolerance associated with elevated plasma nonesterified fatty acids, Clin. Invest., 14: 2010-2020. Volans, G. N. (1974) Absorption of drugs in migraine. Communication to 6th Migraine Symposium, London, September, 1974. Williamson, D. H., P. Lund and H. A. Krebs (1967) The redox state of the free nicotinamide adenine dinucleotide in the cytoplasm and mitochondria of the rat liver, Biochem. J., 103: 514-527. Williamson, D. H., J. Mellanby and H. A. Krebs, (1962) Enzymatic determination of D(--)-fl-hydroxybutyrate and acetoacetic acid in blood, Biochem. J., 82: 90-96.
51
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
METABOLIC C H A N G E S D U R I N G GLUCOSE T O L E R A N C E TESTS IN MIGRAINE ATTACKS
S. W. J. SHAW, R. H. JOHNSON and H. J. KEOGH University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow (Great Britain)
(Received 18 December, 1976)
SUMMARY (1) Intravenous glucose tolerance tests have been carried out on 6 migraine sufferers on two occasions. The first study was carried out during a migraine attack and the second was performed in an attack-free period. The patients had fasted overnight and the investigations were carried out in the morning. Samples of venous blood were taken for measurement of concentrations of glucose, lactate, pyruvate, free fatty acids (FFA), glycerol, ketone-bodies, insulin and growth hormone. (2) An impaired tolerance to glucose was found during the migraine attacks compared with the control studies. Elevated ketone and FFA levels were found during the attacks and may have accounted for the glucose intolerance. The elevation of plasma F F A levels during the migraine attacks paralleled changes in blood glycerol concentrations suggesting increased lipolysis during the attacks. Growth hormone and cortisol were raised and insulin was depressed during attacks. (3) Our observations, in which the patients acted as their own controls, imply increased lipolysis during migraine attacks and are in contrast to previously reported studies. The patterns of metabolic and hormonal changes are consistent with a stress response during the attacks and the significance in relation to the causation of the attacks is discussed.
INTRODUCTION Raised plasma concentrations of certain free fatty acids (FFA) have been observed during spontaneous migraine attacks (Anthony 1973). Elevation of plasma This work was supported financially by the Migraine Trust. Address for correspondence: H. J. Keogh, University Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, Glasgow G51 4TF, Great Britain.
52 FFA has also been shown to occur in those patients who developed migraine during a glucose tolerance test after an overnight fast and patients who did not develop migraine had no elevation of plasma FFA (Hockaday, Williamson and Whitty 1971). In that investigation, however, the blood glycerol concentrations in the patients who developed migraine were similar to those found in the control study suggesting that the elevation of FFA was not dependent on an increased rate of lipolysis. In order to obtain information upon the metabolic changes occurring in spontaneous migraine we have studied patients during one of their attacks and also when free from migraine and have obtained evidence that lipolysis increased during attacks. METHODS A group of patients suffering from classical migraine, whose names were on the diagnostic list of the University Department of Neurology, Glasgow, were asked to come to the department when they had a migraine attack in the morning. The purpose and procedure of the investigation had previously been fully explained to them. The patients were chosen from those with a positive family history of migraine and who presented with features including a visual or other form of aura, unilateral throbbing headache and associated nausea or vomiting. Additional symptoms were the presence of pallor, flushing, running eyes or shivering during the headaches. A relationship between diet and migraine could not be established for any of the patients and there was no obvious link between the meals on the evening prior to the investigations and the onset of the migraine attacks. Six subjects (1 male, 5 female) with an age range of 42-57 years (mean 49 years), and a 3-42 year history of migrainous headaches (mean 19 years) were investigated, Their weights were 48-75 kg (mean 62), and their heights were 140-173 cm (mean 150 cm). They were first investigated during a migraine attack and then, in order to provide control observations, during an attack-free period, having had no attacks for at least 4 days. They were asked not to take breakfast, tea, coffee or medication and none of them was taking any prophylactic medication for migraine. On the control occasion the subjects were investigated after an overnight fast, so that the conditions of the investigations were the same on each occasion. The heart rates of 3 subjects were recorded with an electrocardiograph in both studies. On each occasion, after antecubital vein catheterisation, 2 resting blood samples were withdrawn with an interval of 15 min. A 50 ~ glucose solution (0.33 g glucose/kg body weight) was then infused over 3-5 min and subsequent blood samples were withdrawn 15, 30, 45, 75, 105, 135, 165 and 225 min after the beginning of the infusion. Throughout each investigation the catheter was kept open by flushing with physiological saline. Each blood sample (12 ml) was withdrawn without stasis and treated as follows: 4 ml blood was immediately deproteinised in ice-cold 10 ~ perchloric acid and 8 ml was gently shaken in a heparinised tube. All samples were stored in ice and centrifuged at the end of the investigation. The acid extracts were assayed for glucose (Bergmeyer and Bernt 1963), lactate and pyruvate (Hohorst, Kreutz and Biicher 1959), acetoace-
53 tate and 3-hydroxybutyrate (Williamson, Mellanby and Krebs 1962) and glycerol (Kreutz 1962). The plasma samples were assayed for free fatty acids (Itaya and Ui 1965; Dalton and Kowalski 1967) and insulin (IRI) by a charcoal radioimmunoassay (Albano, Ekins, Maritz and Turner 1972). Plasma concentrations of human growth hormone (hGH) were measured by a double-antibody method (Hunter and Ganguli 1971). Significances of difference were tested using a standard paired t-test and the results has been expressed as means -4- standard errors.
IS-
E E 10-
o
"-,I
i
~,,~,k,
I ...... ~ ...... i ...... I ............ 4 c,~t,~,
70-
60-
so.
',
E .c 30 -
~
",
_c o
20-
o
tG ~
~
~
,~o
~o
,~o
2;0
!
2~o
Time ( mini Fig. 1. Blood glucose (mmol/l) and plasma insulin (mu/l) (means ± SEMi in 6 subjects during attacks (©
©) and during an attack-free period (ml . . . . , ) . G indicates the start of the intravenous in-
fusion of glucose (0.33 g/kg body weight).
54 RESULTS Heart rates
In the 3 subjects in whom heart rates were observed no major alteration occurred during the studies and there were no significant differences between the rates measured in the two investigations.
Glucose (Fig. 1) The blood glucose concentrations were not significantly different between the two studies up to 15 min after the glucose infusion. The samples at 30, 45, 75 and 105 min, however, showed significantly different blood glucose concentrations (at 30, 45 and 75 rain P < 0.01, at 105 min P < 0.05). All subsequent blood samples showed no significant differences in glucose concentrations between the two investigations.
1'0-
tAttock S O'8O
E
It~-
0"60
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.......t.y ;
0,110•
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E "~ o,070. 0
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9;
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Time (rain)
Fig. 2. Plasma FFA (mmol/l) and blood glycvrol (mmol/i) (m©ans 4- SEM) in 6 subjects. Symbols as in Fig. I.
55
Pyruvate and lactate There were no significant differences in blood pyruvate and lactate concentrations between the two studies. Plasma FFA (Fig. 2) The differences in FFA concentrations between the attack and control studies were significantly different for all samples except those at t 50 min. In the two resting samples, comparing attacks with controls the values were significantly different (P < 0.05). After the glucose infusion, plasma FFA concentrations declined, showing a maximum depression at 75 rain in both groups with a highly significant difference between the groups (P < 0.0011. At 135, 195 and 225 min the differences between the groups were not so large though still significant (P < 0.05). In both studies plasma FFA concentrations had returned to pie-infusion values by 135 min. Glycerol (Fig. 2) The blood glycerol concentrations in the resting samples were significantly different comparing the attack and control studies (P < 0.05). During the period 30-105 min after the infusion the differences between the groups were highly significant (P < 0.01). Ketone-bodies (Fig. 3) When the 2 groups were compared the differences in concentrations of blood
/ 0 50
Attacks /
I
0/,O O
E E m o.3o. Controls OJ C 020,
0-
""
t G
y. . . . .
3'o
sb
9'o
do '~o
#o
2;0
2~o
Time ( rain ) Fig. 3. Total bood ketone bodies (mmol/l) (means -F SEM) in 6 subjects. Symbolsas in Fig. I.
56 &O-
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o
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.
120
.
.
150
II ,
180
210
,
240
Time ( rain ) Fig. 4. 3-Hydroxybutyrate:acetoaeetate ratios (means i S E M ) in 6 subjects. Symbols as in Fig. 1.
ketone bodies (acetoacetate plus 3-hydroxybutyrate) in all samples were significant. Blood ketone concentrations fell to their lowest values on both occasions at 75 min after the infusion although the difference between the groups was still significant (P < 0.05). The mean values for the 3-hydroxybutyrate:acetoacetate ratios (see Fig. 4) were all higher in the blood samples taken during attacks compared with the control studies although these were significantly different only in the resting samples.
Plasma insulin (IRI) (Fig. 1) The mean values for plasma IRI in the blood samples taken in the control studies were all higher than those taken during the migraine attacks although they were significantly different only at 45 min (P < 0.05). The maximum values occurred at 15 min. The changes in total insulin release have been examined by calculating the areas under the concentration curves of each subject from the time of the first resting sample to that of each subsequent sample. The mean values for total insulin released were significantly higher in the control investigations compared with during the attacks. In the pre-infusion period and up to 45 min the two studies showed a significantly different insulin release (P < 0.05).
Plasma human growth hormone (hGH) (Fig. 5) The mean hGH peak occurred at 105 min during the attacks and at 135 min
57 8-
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O
-1-
¢_
{.9
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Controls
O
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Attacks
o E (/)
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0
.
30
,
60
,
_
90
,
,
,
120
150
180
,
.
,
210
240
Time (min) Fig. 5. Plasma human growth hormone (mu/l) in 6 subjects. Symbols as in Fig. 1.
during the controls. Plasma hGH concentrations were however only significantly different at 15 min (P < 0.05). Samples taken at other times showed no significant difference probably due to the wider variation in response of the patients during the attacks. DISCUSSION
In this investigation we have found a difference in glucose tolerance between patients in migraine attacks and the same patients in an attack-free period. We have also found evidence of other metabolic differences implying increased lipolysis in attacks, both changes being in contrast to a previous report (Hockaday et al. 1971). We consider our observations to be more valid because intravenous glucose was used and the subjects acted as their own controls. The greater plasma free fatty acid concentration we observed during migraine attacks were similar to those reported by other workers (Hockaday et al. 1971 ; Anthony, 1973), and as previously shown, these were associated with a large rise in blood ketone body concentrations (Hockaday et al. 1971). The elevation of the 3-hydroxybutyrate:acetoacetate ratios during attacks may be secondary to increased free fatty acid mobilisation as ketone body production is related to the level of plasma free fatty acids (Krebs 1967; Williamson, Lund and Krebs 1967). However, our findings of significantly raised concentrations of blood
58 glycerol in attacks compared with observation in control studies is evidence for ira.creased lipolysis occurring during the migraine attacks which contrasts with a previous report (Hockaday et al. 1971). Their subjects, however, did not act as their own controis and their observation that blood glycerol concentrations did not change significantly during attacks could therefore be attributed to variability between subjects. Several causes of lipolysis may be considered. Any generalised increase in sympathetic activity during attacks would be expected to increase lipolysis by increasing circulating catecholamine concentrations. Although, in our studies, heart rates were unchanged, the significant decline in total insulin release in the attacks is in keeping with an increase in sympathetic activity (Kris, Miller, Wherry and Mason 1966; Porte and Williams 1966). Depressed insulin secretion would result in a relative decrease in plasma FFA re-esterification and greater lipolysis (Hunter, Fonseka and Passmore 1965) but this was probably not a significant contributing factor as there were no major differences in plasma hGH concentrations before glucose was given, although in the investigation of migraine attacks the patients were already experiencing severe headache and the plasma FFA concentrations were already raised. A further possibility is that the increase in lipolysis might occur as part of a generalised stress reaction to the migraine headache and may be independent of the causation of migraine. However, previous workers have reported an increase in plasma FFA concentrations prior to a migraine attack (Hockaday et al. 1971), and it remains possible that the attack is initiated by increased lipolysis. The difference we have found in the tolerance to intravenous glucose between the migraine attacks and control studies is not related to differences in absorption of glucose because in our investigations intravenous glucose was given in preference to the oral route. This eliminates the possibility of vomiting with oral glucose and potential alteration of absorption from the gut as it has been shown that a failure of absorption can occur during migraine attacks (Volans 1974). The difference in tolerance may have been due to the decrease in insulin release during the attacks. However, it is also probable that the impairment of glucose tolerance during migraine attacks may be related to the effect of increased plasma FFA and blood ketone concentrations on the peripheral utilisation of glucose. Starvation or carbohydrate deprivation in normal subjects causes elevation of plasma FFA and blood ketone levels with impairment of carbohydrate tolerance (Hales and Randle 1963; Schalch and Kipnis 1965). In addition in vitro studies have demonstrated that raised concentrations of ketone bodies or fatty acids reduce the utilisation of glucose by muscle tissue by inhibition of the enzymes hexokinase and phosphofructokinase (Randte, Newsholme and Garland 1964; Newsholme and Randle 1964; Randle, Garland, Hales, Newsholme, Denton and Pogson 1966). Our observations are at variance with those of previous workers and further investigation into the causes of lipolysis in spontaneous migraine is indicated. ACKNOWLEDGEMENTS We thank the patients for their co-operation and Professor J. A. Simpson for encouragement.
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