Study of alteration in serum lipids by enalapril and ramipril in albino rabbits

1. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 7 ~
ISSN Print: 2278 - 2648 IJRPP | Vol - 3 | Issue - 1 | Jan-April-2014
ISSN Online: 2278 - 2656 Journal Home page: www.ijrpp.com
Research article Open Access
Study of Alteration in Serum Lipids by Enalapril and
Ramipril in Albino Rabbits.
Shruti chandra*1
, Singh S.P2
, Jain I.P2
, Singh S2
, Kushwaha V2
.
1
Department of pharmacology, Mahatma gandhi mission hospital and medical college,
Aurangabad, India.
2
Department of pharmacology, G S V M medical college, Kanpur, India.
* Corresponding author: Shruti Chandra.
E-mail id: dr.shruti1204@gmail.com
Abstract
Hypertension with dislipidemia is becoming a common morbidity, since ACE inhibitors are the first line of
antihypertensive drugs so present study was undertaken with the aim to evaluate the possible effects of ACE
inhibitor on lipid profile in albino rabbits. Rabbits were divided into 2 groups with 6 in each group. Rabbits of
Group I were given Enalapril in dose of 0.50 mg/kg and of group II were given Ramipril in dose of 0.25 mg/kg for
a period of 6 weeks. Lipid profile estimation (Serum Total cholesterol, serum HDL, serum LDL, serum
Triglycerides and serum VLDL) was done at day 0, 7, 21 and 45 respectively. After analysis Rabbits of group-I
(Enalapril) showed 7% decrease in serum cholesterol level at 45th day (P<.05). Serum HDL level increased by 10%
and 20% at day 21 & 45 respectively (P<.05). Serum Triglyceride level increases by 8% at day 45 (P<.05). Serum
LDL level decreases by 7.8% and 16% at day 21 and 45 respectively.(P<.05 ). There was no significant change in
Serum VLDL level. Rabbits of group- II (Ramipril) showed increase in HDL level by 7 % & 12 % at day 21 and
45.(P<.05). Total cholesterol, triglycerides and VLDL levels were not significantaly altered while serum LDL level
decreases by 6.8 % at day 45. (P<.05). From our study it was concluded that enalapril had a favourable effect on
serum lipid profile by decreasing total cholesterol, increasing serum HDL level. It may increase triglycerides,
decrease LDL. Ramipril increase serum HDL and decreases LDL, there is no significant change in cholesterol, TG
and VLDL levels.
KEY WORDS: ACE inhibitors, serum lipid profile, albino rabbits.
INTRODUCTION
Angiotensin II (AII) is an important regulator of
cardiovascular function. The ability to reduce level of
AII with orally effective ACE inhibitor represent an
important advance in treatment of hypertension. The
ACE inhibitors appear to confer a special advantage
in the treatment of patient with diabetes, slowing the
development and progression of diabetic
International Journal of Research in
Pharmacology & Pharmacotherapeutics

2. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 8 ~
glomerulopathy.1
ACE inhibitor decreases the
production of AII, increases brady kinin level, and
reduces sympathetic nervous system activity. A
number of clinical trials have evaluated the
possibility that ACE inhibitors may have particular
advantages, beyond that of blood pressure control, in
reducing cardiovascular and renal outcomes. They
decrease proteinuria and retard the rate of progression
of renal insufficiency in both diabetic and non-
diabetic renal diseases. In most patients with
hypertension and heart failure due to systolic and/or
diastolic dysfunction, ACE inhibitor is recommended
to improve survival.2
Experience from clinical trials
suggest that drugs that target the renin-angiotensin
system(RAS) may have metabolic advantage over
drugs such as beta blockers and diuretics.3
Epidemiologic studies have established a strong
correlation between elevated total cholesterol levels
in serum and morbidity and mortality from
myocardial infarction . Hyperlipidemia, in particular
hypercholesterolemia, is regarded as an independent
risk factor in the development of ischemic heart
disease. 4
One study has shown that fosinopril
therapy for 6 months resulted in a reduction of micro
albuminuria and an improvement in lipid profile and
lipoprotein(a) [Lp(a)] levels in patients with type II
diabetes.5
In the light of above facts present study had
been undertaken with the aim to observe effects of
certain ACE inhibitors on serum lipid profile in
albino rabbits.
MATERIAL AND METHOD
Animals
Healthy albino rabbits of either sex 1.5-2.0 kg were
used in the study. They were housed in iron cages &
maintained under standard conditions (12 hours light
& dark cycle, at room temperature 25 ± 3°C & 35—
60% humidity). They were maintained on gram diet
& water ad libitum. The care and use of these animals
were in accordance with the guidelines of CPCSEA.
Institutional Animal Ethics Committee approved the
experimental protocols.
Drugs
Drugs used in present study included Enalapril (0.50
mg/kg) and Ramipril(0.25mg/kg)
Groups
Rabbits were divided into 2 groups with 6 rabbits in
each. Each of 6 rabbits of Group 1 received Enalapril
(0.5mg/kg/day/PO) by feeding cannula for 6 weeks.
Rabbits of group 2 were given Ramipril
(0.25mg/kg/day/PO) for 6 weeks.
Sampling
Blood samples were taken from the marginal vein of
pinna of rabbits after overnight fasting. Blood
samples were collected at day 0 (before the drugs
administration). Since day 1 drug to be studied was
given for 6 weeks . At day 7, at day 21 and at day 45
(after 7, 21 and 45 days of drugs administration),
blood samples were collected for estimation of serum
lipid profile.
Lipid profile estimation
Estimation of total serum cholesterol, Triglyceride &
HDL cholesterol were done separately by using their
respective reagent kits. Estimation of total serum
cholesterol level was done by using Cholesterol
oxidase-phenol-amino phenazone (CHOD-PAP)
method & HDL cholesterol by Polyethylene glycol
Cholesterol oxidase-phenol-amino phenazone (PEG-
CHOD-PAP) method by using a span diagnostic
reagent kit (code no. LG 052). Estimation of serum
triglyceride level was done by using glycerol
phosphate oxidase-phenol-amino phenazone (GPO-
PAP end point assay) method, by using span
diagnostic reagent kit (code no. LG 062). The
equipment used was U V Spectrophotometer.
Estimation of serum LDL & VLDL cholesterol were
done by using calculation method.
The value of serum LDL cholesterol (mg/dl) was calculated on the basis of Friedwald’s equation-
Serum LDL cholesterol(mg/dl) = Total cholesterol - (HDL+Triglyceride/5)
Serum VLDL cholesterol was calculated by the following equation-
VLDL Cholesterol(mg/dl) = Total cholesterol - (HDL + LDL)

3. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 9 ~
Stastistical analysis
The statistical analysis was carried out by using
paired t test. The values obtained at day 7, day 21 and
day 45 (after drug administration) were compared
with the day 0 (before drug administration) value in
both the groups. All values were expressed as the
mean ± SEM. Stastistical significance was set at
P<0.05.
RESULTS
Rabbits of group-I [TABLE-I] [GRAPH-I]
Mean total serum cholesterol at day ‘0’ was 220
mg% which showed 7% decrease in serum
cholesterol level at 45th day i.e. 205.6 when
compared with the level on day 0, found to be
statistically significant (P<.05). Mean serum HDL
level at Day ‘0’ was 41.8 mg% which increased by
10% and 20% at day 21 & 45 respectively (P<.05).
Mean serum Triglyceride level at day ‘0’ was
117.1mg% which increased by 8% at day 45 (P<.05).
Mean serum LDL level at day ‘0’ was 155.4 mg%,
found to be decreased by 7.8% and 16% at day 21
and 45 respectively(P<.05 ). There was no significant
change in Serum VLDL level.
Rabbits of group- II [TABLE-II] [GRAPH-II]
There was significant increase in mean serum HDL
level by 7 % & 12 % at day 21 and 45 (P<.05 ). Mean
value was 42.5 mg%. Mean Total cholesterol level at
day ‘0’ was 213.1 mg%, mean serum triglyceride at
day’0’ was 119.8 mg% and mean serum VLDL level
at day’0’ was 23.9 mg%. These values were not
significantly altered while serum LDL level
decreased significantly by 6.8 % at day 45. (P<.01 ).
TABLE I (GROUP I)
Lipid profile at day 0 (before) , day 7, 21 &45 (after) receiving enalapril (0.50 mg/kg /day/po)
S. NO.
DAY 0 DAY 7 DAY 21 DAY45
Serum total cholesterol level
220.6±3.3 217.5±2.0 213.3±1.6* 205.6±1.6***
% DECREASE
1.4 3.3 7
Serum HDL level
41.8±2.8 43.3±3.0 46±2.6** 50±2.2**
% INCREASE
3.5 10 20
Serum triglycerides level
117.1±4.3 118.1±4.0 120.8±3.3 126.0±2.9*
% INCREASE
0.8 3.1 8
Serum LDL level
155.4±4.6 150.5±3.0* 143.1±3.4** 130.4±2.7***
% DECREASE
3.1 7.8 16
Serum VLDL level
23.4±0.8 23.6±0.8 24.1±0.6 25.2±0.5*
% INCREASE
0.8 3.1 7.6
* Significant (P<0.05) ** Highly Significant (P<0.01) *** Very Highly Significant (P<0.001)

4. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 10 ~
TABLE II (GROUP II)
Llipid profile at day 0 (before) , day 7, 21 &45 (after) receiving ramipril (0.25 mg/kg /day/po)
S. NO. DAY 0 DAY 7 DAY 21 DAY45
Serum total cholesterol level 213.1±3.3 214.0±2.6 212.0±2.3 208.6±2.5
% DECREASE 0.4 0.5 2.1
Serum HDL level 42.5±3.3 44±2.9 45.1±3.0* 47.8±3.0**
% INCREASE 3.5 6.1 12.4
Serum triglycerides level 119.8±4.7 120.8±4.7 120.5±4.4 121.5±4.4
% INCREASE 0.8 0.5 1.4
Serum LDL level 146.7±4.2 145.8±3.3 142.7±2.8 136.5±2.9**
% DECREASE 0.6 2.7 6.9
Serum VLDL level 23.9±0.9 24.1±0.9 24.1±0.8 24.3±0.8
% INCREASE 0.8 0.8 1.6
* Significant (P<0.05) ** Highly Significant (P<0.01) *** Very Highly Significant (P<0.001)
GRAPH I
Lipid Profile At Day 0 (Before) , Day 7, 21 &45 (After) Receiving Enalapril (0.50 Mg/Kg /Day/Po)
0
50
100
150
200
250
Total cho HDL TG LDL VLDL
day0
day7
day21
day45

5. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 11 ~
GRAPH II
Lipid Profile At Day 0 (Before) , Day 7, 21 &45 (After) Receiving Ramipril (0.25 Mg/Kg /Day/Po)
DISCUSSION
We had observed that administration of Enalapril
(Group-I)‘decreased’ the total serum cholesterol, the
decrease was more after long term use of drug i.e.
after 21 days (3.3%) and 45 days (7%). HDL levels
increased which were significant on long term use i.e
10% after 21 days and 20% after 45 days. Increase in
triglyceride levels were significant after 45 days
(8%). Decrease in serum LDL levels were profound
after 21 (7.8%) and 45 days (16%). Increase in
serum VLDL levels were not much after short term
use although it were found to be significant after 45
days of drug administration. Similar results were
obtained by Nandeesha H, Pavithran P et al on serum
lipid in newly diagnosed essential hypertensive men
by antihypertensive theraphy. In the enalapril group,
they found a significant reduction in Total
Cholesterol, TG, VLDL-C, non HDL-C, and TG to
HDL-C ratio after treatment.6
A randomized double
blind clinical trial done by Grimm H R, Flack M J,
Grandits A G et al showed that decreases in
triglycerides and increases in HDL cholesterol by
enalapril.7
Significant decrease was found in the
levels of very low-density lipoprotein (VLDL)
fraction at 8 and 12 weeks by enalapril as
demonstrated by Sasaki J, Arakawa K in patients
with mild essential hypertension.8
There are some
evidences that enalapril does not alter serum lipid
profile as observed by Santos L E, Souza P K et al.
They observed effect of enalapril on body weight and
composition in young rats. The results showed that
enalapril treatment is able to reduce body fat on both
diets, without alteration in serum lipid profile.9
Administration of Ramipril (Group-II) led to
‘decrease’ in total cholesterol levels and increase in
serum HDL levels after 21(6.1%) and 45(12.5%)
days of drug administration significantly. Serum
triglycerides and serum VLDL levels were almost
unaffected. After long term administration i.e. 45
days serum LDL levels decreased significantly
(6.9%). This decrease was not much after short term
use of drug. Ramipril caused significant reduction of
C-reactive protein and oxidized low-density
lipoprotein cholesterol serum levels (p<0.001) in
patients with Type 2 Diabetes Mellitus as observed
by Koulouris S, Symeonides P, Triantafyllou K et al.
10
Similar results regarding serum HDL levels i.e.
HDL levels were increased significantly was
demonstrated by Finta M K, Fischer J M, Lee L et al
rabbits. However they found that total cholesterol
levels were elevated in the rabbits fed the atherogenic
diet containing ramipril. 11
Significantly increased levels of triglyceride as
observed in our study may be due to reduced
production of angiotensin II (AII) which in turn
decrease release of noradrenaline (NA) from the
sympathetic nerve terminals.12
NA promote
0
50
100
150
200
250
Total cho HDL TG LDL VLDL
day0
day7
day21
day45

6. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 12 ~
hydrolytic release of fatty acid and glycerol from
triglycerides in adipose tissue by activating hormone
sensitive lipase13
thus decrease in NA release by ACE
inhibitors may result in increased triglyceride
deposition. NA also causes increase in glycogen
breakdown resulting in increase in hepatic glucose
level.14
This increase in glucose production promote
insulin release from beta cells of pancreas. Insulin in
turn promotes lipogenesis.15
Thus blockage of
conversion of AI to AII may result in reduced lipid
synthesis. Drugs used in our study i.e. enalapril and
ramipril reduced levels of total cholesterol and serum
LDL levels. Insulin by favouring upregulation of the
expression of HMG CoA reductase gene may result
in increase in cholesterol synthesis.16
In our study, we
found profound reduction in total cholesterol levels
by enalapril while ramipril also decreased
cholesterol levels but to a lesser extent. This may be
due to blockade of NA release resulting in decrease
in insulin levels which in turn may result in decreased
cholesterol synthesis. There are evidences that
adipose tissue expresses components of the renin-
angiotensin system and expresses AII receptors.17
Furthermore, adipose tissue is an important
physiological target of AII. AII has been shown to
modulate adipocyte lipid metabolism, increase
inflammatory gene expression and decrease
adiponectin expression.18
In addition, adipose tissue
has been shown to secrete a number of factors that
can directly impact the vessel wall and vessel wall
cells. One of the factors highly expressed in the
adipose organ is apolipoprotein E (apoE).19
ApoE has
important effects on lipoprotein composition and
systemic lipoprotein metabolism. one study done by
Rao P, Huang Z H, and Mazzone T et al had shown
that AII treatment of adipocytes stimulate triglyceride
synthesis and suppress hydrolysis. Therefore, the
suppression of apoE expression by AII could also be
a homeostatic response to limit further triglyceride
accumulation in adipocytes.20
in our study enalapril
and ramipril increased serum triglyceride levels
significantly after 45 days of drug administration.
CONCLUSION
Thus ACE inhibitors by blocking production of
angiotensin II and its various effects, significantly
altered serum lipid profile. Reduction of total
cholesterol level, LDL, VLDL and increase in level
of HDL is beneficial for individuals having
cardiovascular risk.
REFERENCES
[1] Hoffman BB. Treatment of myocardial ischemia and Hypertension. Bruton LL, Lazo JS and Parker KL.
Goodman & Gilman The Pharmacological Basis of Therapeutics, 12th
ed : Mc Graw-Hill, 2005 : 772-778.
[2] Theodore A. hypertensive vascular disease. Braunwald E , Frauci S, Kasper DL, Hauser SL, Lango DL,
Jameson JL. Harrison’s Principles Of Internal Medicine, 17th
ed : Mc Graw-Hill, 2008 : 1559-1562.
[3] Rayner B. Selective imidazoline agonist moxonidine plus the ACE inhibitor ramipril in hypertensive patients
with impaired insulin sensitivity: partners in a successful marriage? Cur Med Res Opin. 2004 ; 20(3) : 359-67.
[4] Weber C, Soehnlein O. ApoE controls the interface linking lipids and inflammation in atherosclerosis. J Clin
Invest. 2011 ; 121(10) : 3825–3827.
[5] Derosa G, Mugellini A, Ciccarelli L, Crescenzi G and Fogari R. Effects of fosinopril on blood pressure, lipid
profile, and lipoprotein(a) levels in normotensive patients with type II diabetes and microalbuminuria, An open-
label, uncontrolled study. Current therapeutic research 2002 ; 63(3) : 216 – 226.
[6] Nandeesha H, Pavithran P, Madanmohan T. Effect of Antihypertensive Therapy on Serum Lipids in Newly
Diagnosed Essential Hypertensive Men. Angiology 2009 ; 60(2) : 217-220.
[7] Grimm HR, Flack MJ, Grandits AG. Long-term Effects on Plasma Lipids of Diet and Drugs to Treat
Hypertension. JAMA 1996 ; 275(20) : 1549-1556.
[8] Sasaki J, Arakawa K. Effects of enalapril on serum lipoproteins in mild essential hypertension. Clin Ther. 1989
; 11(1) : 38-42.
[9] Edson L Santos, Kely De Picoli Souza et al. Effect of angiotensin converting enzyme inhibitor enalapril on
body weight and composition in young rats. International Immuno pharmacology 2008 ; 8(2) ; 247-253.

7. Shruti chandra, et al / Int. J. of Res. in Pharmacology & Pharmacotherapeutics Vol-3(1) 2014 [7-13]
www.ijrpp.com
~ 13 ~
[10]Koulouris S, Symeonides P, Triantafyllou K et al. Comparison of the Effects of Ramipril Versus Telmisartan in
Reducing Serum Levels of High-Sensitivity C-Reactive Protein and Oxidized Low-Density Lipoprotein
Cholesterol in Patients With Type 2 Diabetes Mellitus. The American Journal of Cardiology 2005 ; 95(11) :
1386-1388.
[11]Kathleen MF, Matthew JF, Linda L, David G, Bertram P et al. Ramipril prevents impaired endothelium-
dependent relaxation in arteries from rabbits fed an atherogenic diet. Atherosclerosis 1993 ; 100 ( 2) : 149-156.
[12]Rang PH, Dale MM, Ritter MJ et al. the vascular system. Rang and Dale Pharmacology, 6th
ed : Churchill
livingstone, 2007 : 304.
[13]Botham MK, Mayes AP. Lipid transport & storage. Murray KR, Granner KD, Rodwell WV. Harper’s
illustrated biochemistry, 27th
ed : Mc graw hill, 2006 : 227.
[14]Champe PC, Harvey RA, Ferrier DR.Fatty acid and triacylglycerol metabolism. Lippincott’s Illustrated
Review Biochemistry, 4th
ed : Lippincott William & Wikkin , 2008 : 190.
[15]Ganong WF. Endocrine functions of pancreas and regulation of carbohydrate metabolism. Review of medical
physiology, 22nd
ed : Mc graw hill, 2005 : 337.
[16] Champe PC, Harvey RA, Ferrier DR. Cholesterol and steroid metabolism. Lippincott’s Illustrated Review
Biochemistry, 4th
ed : Lippincott William & Wikkin, 2008 : 223.
[17]Lu H, Boustany-Kari CM, Daugherty A, Cassis LA. Angiotensin II increases adipose angiotensinogen
expression. Am J Physiol Endocrinol Metab 2007 ; 292 : E1280–E1290.
[18]Goossens GH, Blaak EE, Arner P, Saris WH, Baak MA. Angiotensin II: a hormone that affects lipid
metabolism in adipose tissue. Int J Obesity 2007 ; 31 : 382–384.
[19]Huang ZH, Reardon CA, Mazzone T. Endogenous apoE expression modulates adipocyte triglyceride content
and turnover. Diabetes 2006 ; 55 : 3394–3402.
[20]Rao P, Huang ZH, and Mazzone T et al. Angiotensin II Regulates Adipocyte Apolipoprotein E Expression. The
Journal of Clinical Endocrinology & Metabolism 2007 ; 92(11) : 4366–4372.