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Clin. Lab. 9+10/2013 1071
Clin. Lab. 2013;59:1071-1076
©Copyright
ORIGINAL ARTICLE
Improved Glycemic Control in Patients with Advanced Type 2
Diabetes Mellitus Taking Urtica dioica Leaf Extract:
A Randomized Double-Blind Placebo-Controlled Clinical Trial
SAEED KIANBAKHT 1, FARAHNAZ KHALIGHI-SIGAROODI 2,
FATANEH HASHEM DABAGHIAN 3
1 Department of Pharmacology and Applied Medicine, Research Institute of Medicinal Plants, ACECR, Karaj, Iran
2 Department of Pharmacognosy and Pharmacy, Research Institute of Medicinal Plants, ACECR, Karaj, Iran
3 Research Institute for Islamic and Complementary Medicine, Tehran University of Medical Sciences, Tehran, Iran
SUMMARY
Background: Advanced type 2 diabetes mellitus (T2DM) needing insulin therapy is common. Most conventional
anti-hyperglycemic drugs have limited efficacies and significant side effects, so that better anti-hyperglycemic
agents are needed. Urtica dioica L. (nettle) leaves have insulin secretagogue, PPARγ agonistic, and alpha-glucosi-
dase inhibitory effects. Moreover, nettle leaves are used in traditional medicine as an anti-hyperglycemic agent to
treat diabetes mellitus. Thus, efficacy and safety of nettle in the treatment of patients with advanced type 2 diabe-
tes mellitus needing insulin were studied.
Methods: In this randomized double-blind placebo-controlled clinical trial, we evaluated the effects of taking net-
tle leaf extract (one 500 mg capsule every 8 hours for 3 months) combined with the conventional oral anti- hyper-
glycemic drugs on the blood levels of fasting glucose, postprandial glucose, glycosylated hemoglobin (HbA1c), cre-
atinine and liver enzymes SGOT and SGPT, and systolic and diastolic blood pressures in 46 patients and com-
pared with the placebo group (n = 46).
Results: At the endpoint, the extract lowered the blood levels of fasting glucose, 2 hours postprandial glucose, and
HbA1c significantly (p < 0.001, p = 0.009, and p = 0.006, respectively) without any significant effects on the other
parameters (p > 0.05) compared with placebo.
Conclusions: Nettle may safely improve glycemic control in type 2 diabetic patients needing insulin therapy.
(Clin. Lab. 2013;59:1071-1076. DOI: 10.7754/Clin.Lab.2012.121019)
KEY WORDS
Urtica dioica, type 2 diabetes, patient
INTRODUCTION
Type 2 diabetes mellitus (T2DM) is a common disease.
Most conventional anti-hyperglycemic drugs have limit-
ed efficacies and significant adverse effects [1]. Howev-
er, type 4 dipeptidyl peptidase inhibitors (vildagliptin,
sitagliptin, and linagliptin) seem to be safe and have
positive effects on renal and cardiovascular outcomes
[2]. Nevertheless, better anti-hyperglycemic agents are
required. Multiple anti-hyperglycemic drugs with differ-
ent mechanisms are often used for effective treatment of
type 2 diabetic patients [3]. T2DM is a progressive dis-
ease, characterized by a progressive decline of β-cell
function up to its exhaustion so that adequate glycemic
control with a logical combination of oral therapies can-
not be achieved which leads to the need of insulin as
sole therapy. Up to 50% of type 2 diabetic patients ini-
tially treated with oral anti-hyperglycemics ultimately
need insulin [4].
The plant kingdom is a wide field to search for natural
effective oral anti-hyperglycemic agents that have slight
or no side effects [5]. The infusion of 6 g of powdered
Urtica dioica L. (nettle) dry leaves daily in two or three
divided doses is consumed in traditional medicine as an
anti-hyperglycemic agent to treat diabetes mellitus [6].
____________________________________________
Manuscript accepted November 18, 2012
S. KIANBAKHT et al.
Clin. Lab. 9+10/2013
1072
A variety of pharmacological effects have been demon-
strated for nettle leaves including insulin secretagogue
[7], PPARγ agonistic [8], and alpha-glucosidase inhibit-
ory activities [9,10]. However, in a study, methanolic
extract of nettle aerial parts was unable to increase insu-
lin sensitivity in the culture of human muscle cells and/
or increase insulin and C-peptide secretion from the cul-
ture of rat pancreatic β cells [11]. Reports on the effects
of nettle in animal models of diabetes have been incon-
sistent [12]. Nevertheless, an infusion of a mixture con-
sisting of three herbs including nettle and also a mixture
of dry leaf extracts of four herbs including nettle had
anti-hyperglycemic effects in patients with T2DM [13,
14]. However, there is no clinical trial reporting the ef-
fects of nettle leaves as a single component herbal med-
icine in the treatment of type 2 diabetic patients. Thus,
the efficacy and safety of nettle leaf extract in the treat-
ment of type 2 diabetic patients needing insulin therapy
but declining it were evaluated and compared with pla-
cebo. Since the antioxidant potential of the Iranian net-
tle has not been studied so far, the radical scavenging
activity of the extract was evaluated, too. Further, the
extract was standardized by determining total flavonoid,
total phenolic, gallic acid, rutin, and quercetin contents.
MATERIALS AND METHODS
Nettle
Nettle was collected from the lands of the Mazandaran
province of Iran in August and its identity was authenti-
cated by a botanist (Y. Ajanii).
A voucher specimen of the plant (number 591) was de-
posited in the Central Herbarium of the Research Insti-
tute of Medicinal Plants. The leaves were separated
from the plant, washed and dried in shade at room tem-
perature. The dry leaves were ground into powder.
Preparation of the nettle extract for patients use
The dry leaf powder (20 kg) was extracted with ethanol/
water (70/30) as the solvent in a percolator for 72 hours,
the solvent was completely removed from the extract in
a rotary evaporator, toast powder as an excipient was
added to and mixed with the concentrated extract and
the mixture was ground to a powder. The quantity of the
extract powder produced was 4.6 kg. The excipient con-
stituted 12% of the extract powder.
Preparation of the extract and placebo capsules
The extract powder as the phytomedicine and toast
powder as the placebo were filled separately into oral
gelatin capsules with identical appearance by a hand-
operated capsule-filling machine (Scientific Instruments
and Technology Corporation, USA). The nettle capsules
contained 500 mg of the extract powder.
Phytochemical studies of the extract
Following preparation of the extract for spectrophoto-
metric analyses [15], the 2,2-diphenyl-1-picrylhydrazyl
(DPPH) radical scavenging assay using DPPH from
Fluka (USA) [16] and the determination of total fla-
vonoid [17] and phenolic [18] contents were performed.
Further, gallic acid, rutin, and quercetin were quantified
in the extract by HPLC [19].
Patients
Inclusion criteria
Type 2 diabetic outpatients aged 40 to 60 years with
fasting glucose and HbA1c levels above 200 mg/dL and
8% resistant to conventional oral anti-hyperglycemic
drugs (glibenclamide, metformine, gliclazide, acarbose,
pioglitazone, and repaglinide) needing insulin therapy
but refusing it.
Exclusion criteria
Patients with cardiac, renal, hepatic or infectious dis-
eases; pregnant and breast-feeding women; women
planning pregnancy.
Protocol
One hundred and seven Iranian male and female outpa-
tients (52 patients in the nettle group and 55 patients in
the placebo group) were recruited according to the in-
clusion and exclusion criteria and randomly received
the intended treatment in the Kamkar hospital (Qom,
Iran) from 1/9/2010 to 1/8/2012. Forty six patients in
each group finished the trial which was the sample size
calculated to estimate 20 mg/dL difference of fasting
glucose between the groups, considering type I error =
0.05 and 80% power.
The CONSORT flowchart describing the progress of
the patients through the trial is shown in the Figure 1.
The demographic data of the subjects who completed
the trial are given in the Table 1.
A group of 46 patients took the nettle capsules at the
dose of one 500 mg capsule every 8 hours by the oral
route for 3 months and another, concurrently parallel,
group of 46 patients took the placebo capsules orally
every 8 hours for 3 months. The dosage of the nettle ex-
tract was based on the anti-hyperglycemic dose of nettle
leaves in the traditional medicine (6 g per day), the
yield of the extraction process used in this study
(20.24%), and the fact that the excipient (toast powder)
constituted 12% of the extract powder. Block randomi-
zation with computer generated random numbers table
and sequentially numbered containers each representing
a block consisting of two patients was used for treat-
ment allocation. Three different persons generated the
random allocation sequence, enrolled the participants,
and assigned them to interventions. These persons, care-
providers and participants, were blinded to interven-
tions. However, the person assessing the outcomes was
not blinded to interventions (it was not triple-blind).
The study was a randomized double-blind placebo-con-
trolled clinical trial. The patients took conventional oral
anti-hyperglycemic drugs during the trial as before and
without dose change. Further, the patients were recom-
mended to restrict intake of carbohydrates such as rice,
ANTI-HYPERGLYCEMIC EFFECT OF NETTLE (37 CHARACTERS WITH SPACES)
Clin. Lab. 9+10/2013 1073
Table 1. The demographic data of the trial participants.
Parameter Nettle group Placebo group
Age (years) 52.2 ± 7.1 58.4 ± 6.7
Gender 17% male 73% female 10% male 90% female
Duration of type 2 diabetes mellitus
(years) 12.2 ± 4.7 13.3 ± 6
Body mass index
(kg/m2) 29 ± 4.4 28.8 ± 7.3
The data are given as mean ± SD.
Table 2. The blood fasting glucose, 2 hours postprandial glucose and glycosylated hemoglobin (HbA1c) levels and systolic and-
diastolic blood pressures before and after intervention and their changes during the study.
p-value
Percent
change
Mean (SD)
p-value
Decrease
(before - after)
(SD)
p-value
Mean (SD)
after
p-value
Mean (SD)
before
Parameter
< 0.001٭
34.2 (15.4) N
10.1 (20.8) P
< 0.001٭
104.9 (43.2) N
31.2 (57.8) P
< 0.001٭
146.4 (34.8) N
231.4 (37.5) P
0.33
248.08 (34.9) N
262.6 (33.4) P
Fasting
glucose
< 0.001٭
23.6 (18.1) N
-1.8 (31. 9) P
< 0.001٭
73.9 (29.3) N
-2.8 (32.1) P
0.009٭
257.4 (25.3) N
371.7 (29.4) P
0.16
331.3 (82.7) N
371.2 (21.8) P
2 hours
postprandial
glucose
< 0.001٭
18.1 (6.8) N
0.2 (10.1) P
< 0.001٭
1.54 (0.62) N
0.13 (1.9) P
0.006٭
8.2 (0.8) N
10.4 (1.5) P
0.14
9.7 (1.3) N
10.5 (0.9) P
HbA1c
0.2
-3.8 (12.4) N
-6.6 (11.8) P
0.2
-3.9 (15.9) N
-7.4 (14.4) P
0.07
130.3 (12.3) N
134.8 (11.7) P
0.6
126.3 (11.3) N
127.4 (13.6) P
Systolic
pressure
0.9
-1 (17) N
-1.2 (19.7) P
0.9
0.2 (13.1) N
0.6 (15.4) P
0.6
77.4 (9.5) N
78.3 (10.5) P
0.5
77.6 (9) N
78.9 (10.7) P
Diastolic
pressure
* - p < 0.05 = significant (MannWhitney U test). N (nettle); P (placebo); SD (standard deviation).
confectionery, pies, and cream pies from two months
before the beginning of the trial onward. All the sub-
jects recorded the names and amounts of the daily con-
sumed foods for 3 days every week. To monitor the pa-
tients' compliance with the allocated treatments, the pa-
tients returned any capsules left and were asked ques-
tions about taking the capsules on their monthly visit.
The treatment, diet, and physical activity of the patients
completing the trial remained unchanged throughout the
study. At the beginning and also the end of the study,
the blood levels of fasting (after fasting for 12 hours)
glucose, 2 hours postprandial glucose, HbA1c, create-
nine, and liver enzymes SGOT and SGPT in the nettle
and placebo groups were determined with standard en-
zymatic kits produced by the Pars Azmoon company
(Tehran, Iran) and an auto analyzer (Hitachi 902, Ja-
pan). Additionally, the systolic and diastolic blood pres-
sures were measured in both groups. The fasting glu-
cose and HbA1c levels were the primary outcome mea-
sures. The other parameters were the secondary out-
come measures. At the end of the study, the baseline ho-
mogeneity of the blood parameter means across the net-
tle and placebo groups was analyzed by the Mann-Whit-
ney U test and p-values below 0.05 were considered as
significant. Further, the data of the patients in the nettle
and placebo groups were compared by the Mann-Whit-
ney U test and p-values below 0.05 were considered as
significant. All statistical analyses were per-protocol
analyses. All participants were requested to report any
adverse effects. Written informed consent was obtained
from the patients. The medical ethics committee of the
Qom University of Medical Sciences approved the pro-
S. KIANBAKHT et al.
Clin. Lab. 9+10/2013
1074
Figure 1. The CONSORT flowchart describing the progress of the patients through the trial.
Figure 2. Glycosylated hemoglobin (HbA1c) levels before and after intervention in the nettle (N) and placebo (P) groups.
* - p = 0.006 = significant (Mann-Whitney U test) compared with the placebo group at the endpoint.
ANTI-HYPERGLYCEMIC EFFECT OF NETTLE (37 CHARACTERS WITH SPACES)
Clin. Lab. 9+10/2013 1075
tocol with full consideration to the Helsinki Declaration
of 1975 (approval number and date: 39257 and 28 Nov.
2007). Further, the trial was registered in the Iranian
Registry of Clinical Trials with the number IRCT13880
9022288N2.
RESULTS
Phytochemical studies of the extract
The IC50 of the extract was 357.75 ± 0.05 µg/mL (mean
± SD), while the IC50 of ascorbic acid was 5.626 ±
0.001 µg/mL (mean ± SD). The total flavonoid content
as milligrams of rutin equivalents per gram of the ex-
tract was 879.06 ± 27.37 (mean ± SD). The total pheno-
lic content of the extract as milligrams of gallic acid per
gram of the extract was 621.87 ± 21.03 (mean ± SD).
Further, the amounts of gallic acid, rutin, and quercetin
in the extract were 14.95%, 17.8%, and 0%, respective-
ly.
Patients
All subjects finished the study and no adverse effects
including symptoms of hypoglycemia were reported.
The groups were matched in regard to demographic data
(age, gender, duration of diabetes, and body mass in-
dex) (Table 1) and the baseline parameters (Table 2).
At the endpoint, the extract lowered the fasting glucose,
2 hour postprandial glucose, and HbA1c levels signifi-
cantly (p < 0.001, p = 0.009, and p = 0.006, respective-
ly) without any significant effects on the other parame-
ters (p > 0.05) compared with placebo (Table 2) (Fig-
ure 2).
The percentages of endpoint reductions of the fasting
glucose, 2 hour postprandial glucose, and HbA1c levels
in the nettle group compared with baseline were 34.2%,
23.6%, and 18.1%, respectively (Table 2). The lowest
levels of fasting glucose and 2 hours postprandial glu-
cose in the nettle group at the endpoint were 106 mg/dL
and 140 mg/dL, respectively. Moreover, the parameters
of the placebo group did not change significantly com-
pared with baseline at the endpoint (p > 0.05) (Table 2).
DISCUSSION
The extract had a moderate antioxidant activity com-
pared with ascorbic acid. Since oxidative stress is con-
tributory to diabetes complications [20], the nettle anti-
oxidant effect could be useful in prevention of diabetes
complications. The extract did not affect blood pressure.
The fasting glucose, 2 hours postprandial glucose, and
HbA1c levels decreased in the nettle group at the end
point compared with the baseline. Further, the nettle
leaf extract lowered the blood levels of fasting glucose,
postprandial glucose, and HbA1c significantly com-
pared with the placebo group at the endpoint. The end
point reductions of the fasting glucose and 2 hours post-
prandial glucose were not to the extent that could cause
hypoglycemia. The lowest levels of fasting glucose and
2 hours postprandial glucose in the nettle group at the
endpoint correspond with the lack of hypoglycemia
symptoms in the patients treated with the extract. The
lack of any significant effects of the nettle extract on the
blood levels of SGOT, SGPT, and creatinine compared
with the placebo group demonstrates that nettle does not
have toxic effects on hepatic and renal functions.
Thus, nettle seems safe and may have a beneficial effect
on glycemic control in patients with advanced T2DM
needing insulin. Moreover, nettle may improve efficacy
of conventional oral anti-hyperglycemic drugs to con-
trol glycemia. It seems that anti-hyperglycemic efficacy
of nettle is more than conventional oral anti-hyperglyce-
mic drugs.
The bioactives mediating the glycemic effects of nettle
are not yet characterized. The only bioactives quantifi-
ed in the extract were total flavonoids, total phenolics,
gallic acid, rutin, and quercetin. The extract did not
contain quercetin. Further, the bioactives and mecha-
nisms involved in the anti-diabetic effects of the extract
were not examined in the present trial. Thus, consider-
ing the results of this study, further trials with a larger
number of patients assessing the efficacy and safety of
nettle in the treatment of T2DM as well as more studies
addressing the mechanisms and bioactives involved in
the anti-diabetic effects of nettle seem necessary.
Acknowledgement:
This study was funded by a grant from ACECR (Iranian
Academic Center for Education, Culture and Research).
Declaration of Interest:
No conflicts of interest.
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Correspondence:
Dr. Saeed Kianbakht
Research Institute of Medicinal Plants
Research Complex of Iranian Academic
Center for Education, Culture and Research (ACECR)
Kavosh Boulevard, Supa Boulevard
55th Kilometer of Tehran-Gazvin Freeway
Pouleh Kordan, Karaj, Iran
P.O. Box (Mehr Villa): 31375-369
Tel.: +982614764010-19
Fax: +982614764021
Email: skianbakht@yahoo.com
