Download changes in biochemical parameters of carbohydrate metabolism

Volwne 7
Number 3
Medical Journal of the
Islamic: Republic of mm
Fall
1372
1993
November
CHA NGES IN BIOCHEMICAL PARAMETERS OF
CARBOHYDRATE METABOLISM FOLLOWING
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FENFLURAMINE ADMINIS TRATION IN RATS
M. ANI, M. MESSRIPOUR AND N. NAGHSHINEH
From the Dept. of Biochemistry, School of Pharmacy, Isfahan University of Medical Sciences, Isfahan,
Islamic Republic of Iran.
ABSTRACT
Fenfluramine, an anorexigenic agent, is widely used in the treatment of obesity.
Besides its anorectic effect, it may also have some effects on general metabolism with
the consequence of weight loss. In this study, the effect of fenfluramine on the
concentrations of some parameters related to carbohydrate metabolism was
investigated. It was shown that the serum insulin level was reduced by 41 %, four
hours after fenfluramine administration, which was accompanied by the elevation of
serum glucose levels by 26%. The liver glycogen content showed a transient
reduction, but reached the control level four hours post-treatment. Corticosterone
levels were elevated immediately, followed by a 20% reduction after four hours. The
short-term effects of fenfluramine on thyroid hormones were not statistically
significant.
Administration of fenfluramine for two weeks did not change the glycogen
content of the liver significantly, but 64% and 103% increases were observed after
four and six weeks of drug treatment, respectively. Insulin levels showed a gradual
increase so that by the end of six weeks, 153% increase in insulin level was observed.
No significant changes in serum glucose levels were seen during the period of
treatment. Corticosterone concentration remained unchanged up to four weeks of
treatment but a 32% reduction was seen after six weeks. The levels of T and T3
4
showed a transient increase, followed by a significant decrease after six weeks of
treatment. It is concluded that fenfluramine has some important metabolic effect that
is related to its action in decreasing food intake and weight loss.
M.lIRI, Vol. 7, No.3, 183-186, 1993.
INTRODUCTION
decreasing food intake which would be of value in tile
treatmentof obesity.' In this regard tile effect of fenflurarnine
Fenfluramine, an amphetamine derivative, was
on plasma and liver levels of lipid fractions and on plasma
introduced origimdly as an anorectic drug and it is frequently
and brain levels of tryptophan has already been investigated
used in the treaunent of obesity.' Its action is thought to
in our laboratory.'> There is also evidence that this agent
involve direct effects on serotoninergic systems at the
improves insulin action independent of its effects on food
level of hypotllalamus.' leading to anorexia and weight loss.
intake,' which in tum may affect carbohydrate metabolism.
It is also evident tlmt tllis drug may have some addition,d
The present study was undertaken to investigate changes
peripheral actions that may be unrelated to its action in
in the concentrations of some biochemical parameters
183
Carbohydrate Metabolism with Fenfluramine
Table l. The shorl-term effect of fenfluramine
nil
some biochemical parameters in rals. Each value indicates the mean
± SEM of five experiments performed in duplicate. Values in parenthesis shuw percent increase or decrease from Ihe
control level. For more details see text.
�
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T ime
GJu!.:osc
Glyt.:ogt::n
Insulin
Curticosll!ronc
T,
T,
(Illg/dl)
(Illg/g Prot.)
�IU/dl
(�g/dl)
(J-lg/dl)
(ng/dl)
ConlIol
85.4 ±5.7
20fi±21.4
37.4±4.4
37.7± 3.2
1.9±0.2
65 ± 6.8
0.5 hr
%5 ± 6.4
169.6 ± 7.6
33.4±4.7
47.2±3.0
1.6±0.2
5U.8±1.6
(13%)
(-18%)
(- JU%)
(+25%)
(-20%)
2 hr
109± 6.8
98.7±9.7
31.6±3.9
39.0±3.1
2.1±0.3
(+27%)
(-52%)
(+3%)
(+5%)
4 hr
108 ± 4.6
201± 14.5
22 ± 3.5
2lJ.9 ± 1.2
(+26%)
(-2%)
(-41%)
(-20%)
(-15%)
related to carbohydrate metabolism following fenOuramine
1.9± 0.4
--_.
(-21%)
81 ±5.1
(+24%)
12.4± 1:1
(+11%)
by decapitation, their blood collected and allowed to
administmtion. The observed changes may be a secondary
coagul:ue. Theirsl!ra were then separated by cenlrifugation
effect due to the alteration in hormon,d b,d,mce of the
and used for the an,dysis. To avoid tlle probable diurnal
animal.
changes in serum honnonc levels. care was taken to
perform the sampling at the smne time each day. Livers
were rt!moved immediately for the determination of
MATERIAL
glycogen content, which was performed according to the
mcthod of Kemp. et al.1 Serum glucose was determined by
Male Wistar flUS (100 -150 gr) (obtained from Pasteur
orthotoluidine method as reported by Caraway.' The Serum
Institute, Tehran) \Vcr!! used Cor the experiments. They
cOllcentration
were kept at st�Uldard conditions in our animal labs.
corticosterone. thyroxine (T) and T) wefe determined by
or hormones
Fenfiurmnine hydrochloride (20 mg coated tablets) was
iIIIIIIunorauiOJI1L:tric tcchniq ue.
incluuing
insulin,
purchased from Loghman Pharmaceutical, Tehran.
Radioactive kits for the detennination of hormones were
RESULTS
obtained from Diagnostic Products Company, (DPC), Los
Angeles, USA. All other chemic,ds used in this study were
of reagent grade �md obtained from Sigma Chemica.l
Short term l!ffccts of fl!nfluramine on biochemical
Company.
parameters an: shown in Table I. It is shown that the
concentration of glucose is elevated following fenOuflunine
:uJministralion. which is accomprmied by a reduction in
METHODS
seruln insulin level. The liver glycogen content showed a
reduction, hut it reached the control level four hours post­
Anirn,ds were chosen in groups of five 1md kept in
lrealml!n!. The levcl of corticoslerone showed an increase
separate c;:ages. In short-tenn study. animals werc injected
(25 percenl) 0.5 hr after fcnlluraminc administration,
intraperitone,dly witil the acute dose of i"enOuflunine (100
followed by a gradual decrease in this honnone level so that
mg/kg body weight). Treated animals were killed either
20 percent reduction was observed after four hours. Changes
0.5, 2 and/or4 hours post-injection. Anim'ds used for long­
observed in the levels of thyroid honnones were not
term study received daily intr.lperitone,d doses of 10
kg fenllununine for either 1,2,4, or
109!
st;ltistic:dly significant.
6 weeks. Groups of
Long-term effects of fenOuramine were also studied,
animals werc injected with normal saline in parallel with
the results of which are shown in Table II. According to
l!<tch cxpl!riml!nt :U1d considered as controls.
results, the concentration of insulin in serum tends to
At the time of tlle experiment, the ,mim,ds were killed
increase following the continous administration of
184
1
M. Ani, et al.
Table II. The lung-term effect u f fen nu ramin c un the biochemical parameters in rats. Eal'il figur e shows the
mean ± SEM of five experiments. In parallihesis the percent increase ur decrease afC shown. For details
abuut the method uf the experiments, see text.
Week
�
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Conlmi
I
2
4
Glucose
(m!<ldl)
Insulin
Cor1iL:oslcrunc
T,
TJ
�IU""
(�g/dl)
()!g/dl)
(ngldl)
85.4±5.7
2011±21
37.4 ± 4.4
37.7±3.2
1.9 ± 0.2
65 ±6.2
73.1±:!
176.6 ±3.1
40.6±10
30.4±2.6
1.2±0.1
73.4±2.7
(·14%)
(.14%)
(+9 %)
(·19%)
(-36%)
flS.6 ±2.5
2U2 ±22
(·I�%)
(.I.R%)
84J ±3.4
338± 41
.. ..
[,
Glycogen
(mg/g Prot.)
I 05 ± 4
(+ 23 %)
I
45 ±10
38.9±1.7
4.0±0.5
80 ± 8
(+20%)
(+3%)
(+101%)
(±23%)
44.5 ± 9
37 ±4.5
1.9 ±0.3
(+19%)
----
89.8 ±2.8
----
(+38%)
94.8±4
25.6 ± I
1.1±0.2
48± 6.4
(+153%)
(-32%)
(-41%)
(-26%)
(+64%)
474±40
(+103%)
(+13%)
fenfluramir'le, so that after six weeks of trt.!Htmenl, the
honnone level reached 94.8 I1IU/mL compared wilh Ihe
control level of37.4 (P<O.O I). The increase in insulin level
was accomp;:mied by the accumulation of glycogen in the
liver. Thus. 103 pcrcenl increase in glycogen conleOl of lhe
liver was observed following six weeks of drug
administralion (P<O.O I). Serum glucose level did nOI c1uUlge
significantly afler four weeks of IrealmCnl. bUI Ihe
continuation of the treatment for six weeks increased serum
glucose level by 23 percen!. No signific'UlI c1uUlges were
observed in corticoslerone level afler four weeks of
fenfluramine administration,but a reduction of 32 percent.
was seen after six weeks. Thyroid honnonl!s were first
elevated due to the action of fenflununine, \VherC�L"i the
continuation oflhe treatment led to a consequent reductil)n.
Thus Ihe increase in T. level was 13,23 and38 percent
..
.I
.
following trcaUnem for one Iwo and four weeks respecuvcly.
bul levels decreased by 26 percem if Ihe treallnenl was
continued for six weeks. Serum T-Ilcvel was also increased
by aboul 100 percem afler Iwo weeks of fenflurrunine
administration, whereas a reduction of 4 1 percent was
observed after six weeks.
We have already reporled Ihat fenfluramine affecls tile
metabolism of lipids,Ihe body. The action of tilis drug on Ihe metabolism of
biomolecules may be secondary 10 its effeclon Ihe honnonal
slalUs oflhe body. In this sludy il was shown Ihal the levels
of insulin. corticoslerone and Ihyroid honnones were a1Tected
by fcnllu"unine. Ihe consequence of which are c1uUlges in
cm'bohydrate melabolism. It has ,�so been reponed that
fenlluramine treaUnenl improved glycemic control in obese
glucose-intolerant humans and in non-insulin dependent
diabeles mellilUs independenl of its effecls on food imake
and body weiglll.OI Our resulls indicale Ihal following Ihe
administration of acule doses offenfluramine, Ihe glycogen
of the liver was immedialely reduced which may be due 10
eilher increased rale of glycogenolysis or decreased rale of
glycogenesis. This reduction in liver glycogen conlent is
accomp:mied by an increasein serum glucose and adecrease
in serum insulin levels.
II is probable Ihalthe reduclion in liver glycogen level is
due to the inhibition of insulin symhesis or release from the
pancreatic cells. There are reports indicating that
fenflurrunine inhibiled IhereleHseofinsulin from the perfused
rat pancrcasy,13 Alternatively fenflurrunine may affect the
liver enzymes involved in glycogen melabolism direclly,
theconsequenceof which is the reduction in the concentration
of Ihis carbohydrale slOrage compound.
DISCUSSION
Fenfluramine. an 'Ulli-obesiIY drug,is struclu"�ly bUi
nol funclionally relaled 10 amphetmnine and is reponed 10
have some effecls on biomolecular melabolism,·' 6
hormonal balance of obese subjecls.'
The reduction in liver glycogenesis due 10 Ihe inhibition
of liver phophoglucomulase by fenfl uramine has already
been reporled." However Ihe reduclion in liver glycogen
level is transienl, so Ihat il reaches the control level four
185
Carbohydrate Metabolism with Fenfluramine
hours after fenfluramine injection. As the insulin level a t
liver levels of lipid fTactions in the rat. Ind J Pharmnc 20: 175-
this time is still below conuul, Ole increase in liver glycogen
t77,t988.
level may be mediated through some other mechanisms
5. Ani M. Boroumam.l A: Changes in plasma and brain tryptophan
involving honnones such as corticosterone and thyroid
and serotonin levels following fenfluramine administration in
honnones. It has been reported Omt the administration of
ral.lnd J Pharamoc 20, 171-t74, 1988.
6. Storlien LH, Thorburn A W. SmythcGA: Effectof fenflurnmine
fcnflurmnine immediately increased the serum corticosterone
on basal glucose turnover and fat-feeding-induced insulin
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levell�.[6 which is in agreement with the results obtained in
resistance in rals. Diabetes 38: 499-503,1989.
this study. Fenfluramine did not have 'my significant effect
7. Kemp A, Kits AIM: Colorimetric micromethod for the
on thyroid honnoncs in short-term, which is in agreement
determination of glycogen in tissues. Biochem J 5b: 646-648,
wiOl the report Olat this drug had no effect on TSH release."
1954.
In long-tenn however, fenflurrunine had different effects
8. Caraway WT: Methods for the determination of glucose in body
011 serum insulin and liver glycogen levels. The
fluids. In: Tietz NW. Fundamentals of Clinical Chrmistry.
administration of fenfluramine for six weeks led to 153
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!O3 percent
9. Bernini OP. Argenio GF, Corso CD, Vivaldi MS: Seroto­
increase in liver glycogen level. This is consistent with the
ninergic receptor activation by D-fenfluramine enhances the
percent increase in insulin level, followed by
blunted pituitary-adrenal responsiveness to corticotropin­
findin,gs that long term administration of fenfluramine
increased insulin secretion III a n d also inhibits
glycogenolysis.I'
releasing honnone in obese subjects. Metabolism 41 (I) 17-21.
1992.
10. Ani M. Amini SA: The effect of fenfluraminc on mitochondrial
energy metabolism. Abstructs of 9111 Int. Congress of Physiol
Our result showed that long term administration of
fenflurmnine led to a decrease in corticosterone level which
and Pharmac, Shnheed Bchcshti Universtiy. Tehran, IRAN.
may be partly responsible for the observed metabolic changes.
Administration of fenfluramine for two weeks increased
II.
the serum concentration of T, and T, which in turn may
224, May 15-18, 1989.
Verdy M, Charbonneuu L, Verdy I, Blanger R, Bolte E,
Chaissun IL: Fenfluramine in the treatment of non-insulin­
increase the rate of basaI metabolism leading to weight loss.
dependent diabetics. Int J abc, 7: 289-297, 1983.
However continuation of the treatment for up to six weeks
12. Barseghinn G, Lev-Ran A, Hwang D, Josefsberg Z. Tomkinson
led to the reduction of these honnone levels which is in good
C: Fenfluramine inhibits insulin secretion and potentiates
agreement with the well-documented tnmsient effect of Olis
glucagon release by the perfused rat pancreas. Eur J Pharmacal
96: 53-59,1983.
,tnoreclic agenl.:!o.:!J
13. Altamonte L.Zoli A. Manna R,Greco AV: Erfect offenfluramine
The reduction in thyroid honnone levels after six weeks
on insulin/growth honnoneratio in obcsesubjccts. Pharmacolog.y
of treatment may be mediated through some unknown
36: t06-III,1988.
mechanism responsible for setting up the metabolic balance
14. Macrae SM: Peripheral and metabolic effects of fennuraminc.
in Ole body.
Po,tgrad Med J (SuppJ.
The slight increase in theconccnlIation of serum glucose
I) 13-17, 1975.
15. McElroy IF, Miller 1M. Meyer JS: Fenfluramine. P­
despite Ole elevated level of insulin could be explained by
chloroamphetamine and P-fluoro.unphetamine stimulation of
the insulin resistance amI reduced glucose tolerancl:! which
pituitary-adrenocortical activity in rat. J Pharmacol Exp Ther
might have occuned in these conditions.
228(3) 593-599. 1984.
It is concluded that although the mech,mism by which
16. Van ue Kar LO. Urben JH, Richardson KD, Belthea CL:
fenflummine exerts its effects in short tenn lTIily be different
Phannacologica1 studies on the serotoninergic .and nonserotonin
from ilS long-tenn effeclS, Olis anorectic drug affects Ole
mediated stimulation of prolactin imd corticosterone secretion
by fenlluramine. Neuroencloc 41: 283-288. 1985.
honnon'� stmus of the body, the outcome of which could be
17. Coccaro EF. Siever LJ, Kouridcs IA. Adan F. Davis KL:
changes in the metabolism of fuels in the body.
Central serotoninergic stimulation by fenlluramine does not
affect plasma TSH level in man. Neuroendo. c 41.: 273-276.
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