5. Discussion
The results of this study showed that NS oil supplementation at 1000
mg/day dosage had no significant effect on serum levels of leptin and
adiponectin. Also our finding showed Nigella sativa oil supplementation
no significant effect on systolic and diastolic blood pressure among
patients with non-alcoholic fatty liver disease. In a study by Dehkordi
et al on subjects with mild hypertension at a dose of 100 mg and 200 mg
)twice daily( were conducted, a significant reduction in systolic blood
pressure and diastolic blood pressure was shown [26]. Jarrin et al
in an animal study in rats with induced hypertension NS oil daily at a
dose of 2.5 mg / kg body weight Systolic and diastolic blood pressure
levels were significantly reduced. This effect being reduced by
stimulating nitric oxide synthesis and release from the vascular
endothelium. The hypotensive effects may also be based on the diuretic
activity [27] Also, in this study, the levels of angiotensin
converting enzyme activity in the Nigella sativa oil group were reduced
[28]. Bader et al in a study that was conducted in patients with
type 2 diabetes, NS oil supplementation significantly reduced systolic
and diastolic blood pressure in this patients[29].
Clinical trial studies on the effects of NS on adiponectin levels are
limited. Our findings are in agreement with the findings of Datau et al,
indicating that NS powder (3g/day) supplementation had no significant
effect on adiponectin serum levels in men with abdominal obesity after
12 weeks [30]. In another study by Mahdavi et al, NS oil
supplementation concurrent with a low low-calorie diet in obese women
showed a significant increase in adiponectin levels [31]. In an
animal study on rats with metabolic syndrome, the results showed that
administration of NS oil increased adiponectin levels in these rats
[32]. It has been shown that adiponectin regulate the interaction
between obesity and insulin resistance, and a reduction in weight and
body fat mass increases plasma levels of adiponectin [31]. The
current study showed that NS oil supplementation for 8 weeks do not a
significant effects on serum leptin levels, compared to the placebo
group. In animal study by Güllü et al that evaluated the effects of TQ
on leptin, a significant decrease in leptin plasma levels was observed
[33]. No significant effect of NS oil was observed on SBP and DBP.
Similar to the results of our study, Qidwai and Bin Sayeed showed that
NS seed supplementation doese not significant effect on SBP and
DBP[34, 35]. In addition, Amin et al in another study have been
shown that supplementation with Black seeds (1.5g/day) had no effect on
SBP and DBP[36].
Also In contrast with our study, there are some studies that found NS
had a significant beneficial effect on blood pressure. In clinical trial
study by Dehkordi in patients with mild hypertension, NS seed exctract
(two capsules per day containing 100 and/or 200 mg) supplementation for
8 weeks significantly lowered SBP and DBP[26]. Also, Najimi et al in
a trial study investigated the effect 500mg/days of NS Oil
supplementation on 45 patients with metabolic syndrome. They results
after 8 weeks supplementation with of NS Oil have been shown a
significant reduction in SBP and DBP[37]. There are several reasons
for the inconsistent results between our study and another previous
studies. Firstly, lack of hypertension in patients in this study.
Secondly, the dosage and duration were not the same. Perhaps a higher
dose with longer duration supplementation of NS is needed to produce an
effect on leptin, adiponectin and blood pressure in patient with NAFLD.
Further studies are needed to investigate the possible effect of black
seed on leptin and adiponectin. The feasible mechanisms involved in the
improvements in patient with NAFLD have been explained in previous
study[38]. This effects may be connected to some factors like
diuretic effect and calcium channels blocking feature of NS that are
likely related to several components of NS involved in this effect,
including TQ, and fatty acids that contain remarkable quantities of
linoleic, oleic, and arachidonic acids, nigellicine, flavonoids,
transanethole, p-Cymene, a-Pinene, limonene, carvone, and soluble
fiber[38, 39]. NS compounds are also reported to have endothelium
independent relaxation effects that may be due to suppression of Ca2+
release from the sarcoplasmic reticulum across the smooth muscle cells
membrane and decrease of Ca2+ sensitivity and influx.
This is the first clinical trial to evaluate the effect of NS oil on the
patient with NAFLD. The main limitations of our study were: short
duration of intervention and small sample size.