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The Use of Green Coffee Extract as a Weight Loss Supplement: A Systematic Review and Meta-Analysis of Randomised Clinical Trials

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The purpose of this paper is to assess the efficacy of green coffee extract (GCE) as a weight loss supplement, using data from human clinical trials. Electronic and nonelectronic searches were conducted to identify relevant articles, with no restrictions in time or language. Two independent reviewers extracted the data and assessed the methodological quality of included studies. Five eligible trials were identified, and three of these were included. All studies were associated with a high risk of bias. The meta-analytic result reveals a significant difference in body weight in GCE compared with placebo (mean difference: -2.47 kg; 95%CI: -4.23, -0.72). The magnitude of the effect is moderate, and there is significant heterogeneity amongst the studies. It is concluded that the results from these trials are promising, but the studies are all of poor methodological quality. More rigorous trials are needed to assess the usefulness of GCE as a weight loss tool.
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Hindawi Publishing Corporation
Gastroenterology Research and Practice
Volume 2011, Article ID 382852, 6pages
doi:10.1155/2011/382852
Review Article
The Use of Green Coffee Extract as a Weight
Loss Supplement: A Systematic Review and Meta-Analysis of
Randomised Clinical Trials
Igho Onakpoya, Rohini Terry, and Edzard Ernst
Complementary Medicine, Peninsula Medical School, University of Exeter, 25 Victoria Park Road, Exeter EX2 4NT, UK
Correspondence should be addressed to Igho Onakpoya, igho.onakpoya@pcmd.ac.uk
Received 17 June 2010; Accepted 10 August 2010
Academic Editor: Lubos Sobotka
Copyright © 2011 Igho Onakpoya et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
The purpose of this paper is to assess the ecacy of green coee extract (GCE) as a weight loss supplement, using data from human
clinical trials. Electronic and nonelectronic searches were conducted to identify relevant articles, with no restrictions in time or
language. Two independent reviewers extracted the data and assessed the methodological quality of included studies. Five eligible
trials were identified, and three of these were included. All studies were associated with a high risk of bias. The meta-analytic result
reveals a significant dierence in body weight in GCE compared with placebo (mean dierence: 2.47 kg; 95%CI: 4.23, 0.72).
The magnitude of the eect is moderate, and there is significant heterogeneity amongst the studies. It is concluded that the results
from these trials are promising, but the studies are all of poor methodological quality. More rigorous trials are needed to assess the
usefulness of GCE as a weight loss tool.
1. Introduction
Overweight and obesity have become a serious health
concern [1]. Dierent weight management strategies are
presently utilised, and a variety of weight loss supplements
sold as “slimming aids” are readily available. However,
the ecacy of some of these food supplements remains
uncertain. One such supplement is the green coee extract
(GCE).
GCE is present in green or raw coee [2]. It is also
present in roasted coee, but much of the GCE is destroyed
during the roasting process. Some GCE constituents, such
as chlorogenic acid (CGA) can also be found in a variety of
fruits and vegetables [3]. The daily intake of CGA in persons
drinking coeevariesfrom0.5to1g[4]. The traditional
method of extraction of GCE from green coee bean, Coea
canephora robusta, involves the use of alcohol as a solvent
[5]. Extracted GCE is marketed as a weight loss supplement
under a variety of brand names as a weight loss supplement
such as “Coee Slender”, and “Svetol”.
Evidence is accumulating from animal studies regarding
the use of GCE as a weight loss supplement [6,7]. In
human subjects, coee intake has been reported to be
inversely associated with weight gain [8]. Consumption of
coee has also been shown to produce changes in several
glycaemic markers in older adults [9]. Similarly, other
research has indicated that the consumption of caeinated
coee can lead to some reductions in long-term weight
gain, an eect which is likely to be due to the known
thermogenic eects of caeine intake as well as eects of
GCE and other pharmacologically active substances present
in coee [10]. GCE has also been postulated to modify
hormone secretion and glucose tolerance in humans [11].
This eect is accomplished by facilitating the absorption of
glucose from the distal, rather than the proximal part of the
gastrointestinal tract.
The objective of this paper is to analyse the results of
human clinical trials assessing the ecacy of GCE as a
weight-reducing agent.
2Gastroenterology Research and Practice
2. Methods
Electronic searches of the literature were conducted for
the following databases: MEDLINE, EMBASE, CINAHL,
AMED, and The Cochrane Library. Each database was
searched from inception up until April, 2010. Search terms
used included coee, green coee, green coee extract,
roasted coee, decaeinated coee, chlorogenic acid, caf-
feoylquinic acid, antiobesity agent, appetite suppressant,
abdominal fat, BMI, body mass index, body fat, body
weight, overweight, over weight, corpulen,obes
,weight
loss, weight decrease, weight watch, weight cycle, weight
control, weight gain, weight maintenance, weight reduc-
tion, weight change, dietary supplement, food supplement,
nutraceutical, nutrisupplement, over-the-counter OR OTC,
nonprescription drugs, randomised controlled trial, clinical
trial, and placebo. We also searched other internet databases
for relevant conference proceedings, as well as our own files.
Hand searches of the bibliography of retrieved full texts were
also conducted.
Only randomised, double-blind, and placebo-controlled
studies were included in this paper. To be considered for
inclusion, studies had to test the ecacy of GCE for weight
reduction in obese or overweight humans. Included studies
also had to report body weight and/or body mass index
(BMI) as an outcome. No age, time, or language restrictions
were imposed for inclusion of studies. Studies which involved
the use of GCE as part of a combination treatment or not
involving obese or overweight subjects were excluded from
this paper.
Two independent reviewers assessed the eligibility of
studies to be included in the paper. Data were extracted
systematically by two independent reviewers according to
the patient characteristics, interventions, and results. The
methodological quality of all included studies was assessed
by the use of a quality assessment checklist adapted from
the consolidated standard of reporting trials (CONSORT)
guidelines [12,13]. Disagreements were resolved through
discussion with the third author.
Data are presented as means with standard deviations.
Mean changes in body weight were used as common
endpoints to assess the dierences between GCE and placebo
groups. Using the standard meta-analysis software [14],
we calculated mean dierences (MD) and 95% confidence
intervals (CI). The I2statistic was used to assess for statistical
heterogeneity amongst studies.
3. Results
Our searches produced 2160 “hits”. 328 articles were
excluded because they were duplicate citations, while 767
articles were excluded because of wrong titles and abstracts.
Another 598 articles were excluded because they did not
investigate a food supplements, and 454 articles excluded due
to no report on clinical outcome. A further 13 articles were
excluded due to unsuitable study design. Thus, 5 potentially
relevant articles were identified (Figure 1). One trial was
excluded because it involved only normal weight individuals,
and did not measure weight as an outcome [15]. Another
trial was excluded because it was not randomised [16]. In
eect, 3 randomised clinical trials (RCTs) including a total
of 142 participants met our inclusion criteria, and were
included in this systematic paper [5,17,18]. Their key details
are summarized in Tables 1and 2.
Aforestplot(random-eect model) for the three trials
is shown in figure 2. The meta-analysis reveals a statistically
significant dierence in body weight between GCE and
placebo (MD: 2.47 kg; 95% CI: 4.23, 0.72). The I2
statistic of 97% suggests that there is considerable hetero-
geneity amongst the studies. A further plot of two trials
which involved CGA-enriched GCE revealed a statistically
nonsignificant dierence in body weight between GCE and
placebo (MD: 1.92 kg; 95% CI: 5.40, 1.56). Heterogeneity
was also considerable in this analysis (I2statistic of 99%).
One of the studies reported a statistically significant decrease
in the percentage of body fat in the GCE group compared
with baseline, but no significant dierence in the placebo
group [5]. There was no mention of intergroup dierences
regarding the percentage of body fat. None of the trials
reported any adverse events associated with the use of
GCE.
4. Discussion
The main purpose of this systematic paper was to assess
the ecacy of GCE as a weight loss supplement. The
overall meta-analysis revealed a significant dierence in
change in body weight between GCE and placebo. The
magnitude of this significance is moderate, and the clinical
relevance is therefore not certain. There is also considerable
heterogeneity amongst the three trials.
In animals, GCE has been reported to influence post-
prandrial glucose concentration and blood lipid concen-
tration [5]. This is thought to be via reduction in the
absorption of glucose in the intestine; a mechanism achieved
by promoting dispersal of the Na+electrochemical gra-
dient. This dispersal leads to an influx of glucose into
the enterocytes [19]. GCE is also thought to inhibit the
enzymatic activity of hepatic glucose-6-phosphatase, which
is involved in the homeostasis of glucose [20]. Reports
from animal studies have suggested that GCE mediates its
antiobesity eect possibly by suppressing the accumulation
of hepatic triglycerides [6]. Some authors have also posited
that the antiobesity eect of GCE may be mediated via
alteration of plasma adipokine level and body fat distribution
and downregulating fatty acid and cholesterol biosynthesis,
whereas upregulating fatty acid oxidation and peroxisome
proliferator-activated receptor alpha (PPARα) expression in
the liver [7].
Diets rich in polyphenols may help to prevent various
kinds of diseases associated with oxidative stress, including
coronary heart disease and some forms of cancer [21,
22]. GCE has been reported to have antioxidant activity,
demonstrated by its ability to scavenge free radicals in vitro,
and to increase the antioxidant capacity of plasma in vivo
[16,23]. There is also evidence that certain dietary phenols,
including GCE, may modify intestinal glucose uptake in a
Gastroenterology Research and Practice 3
Tab l e 1: Methodological characteristics of included studies.
Author Year
Country
Main outcome
(s)
Main
diagnoses of
study
participants
Study
design Gender M/F Randomisation
appropriate?
Allocation
concealed?
Groups
similar at
baseline?
Similar
follow-up
of groups?
Outcome
assessor
blinded?
Care
provider
blinded?
Patients
blinded?
Attrition
bias?
ITT
analysis?
Ayton
Research
2009 United
Kingdom
Body weight,
waist, bust and
hip
circumference
Healthy
overweight
subjects
Parallel Unclear ? ?++?????
Thom 2007
Norway
Body weight,
body mass
index
Slight to
moderately
overweight
subjects
Parallel 12/18 ? ?++???
−−
Dellalibera
1998 France
Body weight,
body mass
index
Overweight
volunteers Parallel Unclear ? ?++???
−−
Abbreviation: ITT (intention-to-treat); M/F: Males/Females.
Symbols: : Unpublished study, +:Yes,:No,?:Unclear.
4Gastroenterology Research and Practice
Tab l e 2: Main results of included RCTs1.
Author Year GCE
specification
No. of
participants
randomised
Age in yrs; Sex:
M/F
Body weight at
baseline
Dosage of
GCE
Treatment
duration
Main results; reported as
means with standard
deviations
Adverse
events
Control for
lifestyle
factors
Ayton Res. 2009
(unpublished)
CGA
enriched
green coee
62 Not reported
76.65 ±7.25 kg
(GCE) 77.44 ±
12.93 kg (PLA)
180 mg daily 4 weeks
Weight loss was
1.35 ±0.81 kg and
0.12 ±0.27 kg for GCE
and PLA respectively
Not reported Normal
lifestyle
Thom 2007
CGA
enriched
green coee
30 Not reported
12/18
85.2±4.5kg
(GCE)
84.3±4.3kg
(PLA)
200 mg daily 12 weeks
Mean weight loss was
5.4±0.6 kg (GCE) and
1.7±0.9 kg (PLA). Mean
fat loss was 3.6±0.3%
(GCE) and 0.7±0.4%
(PLA)
No adverse
events
Regular diet,
normal level
of exercise
Dellalibera 2007 Green coee
extract 50 Range: 19–75 Not reported 200 mg daily 12 weeks
2Mean weight loss was
4.97 ±0.32 kg and
2.45 ±0.37 kg for GCE
and PLA, respectively
Not reported Not reported
Abbreviation: PLA: placebo
1Unless otherwise specified, values are reported as means with standard deviations.
2Values reported as means with standard errors.
Gastroenterology Research and Practice 5
2 articles excluded for the following reasons:
- Only normal weight individuals: 1
3 randomised clinical
trials included
5 full texts retrieved for more
detailed evaluation of the articles
2160 references
retrieved
2155 articles excluded based on duplicate citations;
wrong title/abstract; did not investigate a food
supplement for weight loss; did not report clinical
outcome; or the study design was unsuitable
- Nonrandomised study: 1
Figure 1: Flow chart for inclusion of randomised clinical trials.
Ayton 2009
Dellalibera 2007
Thom 2007
1.35
4.97
5.4
0.81
1.75
0.6
30
30
15
0.12
2.45
1.7
0.27
1.66
0.9
32
20
15
34.6%
31.6%
33.8%
1.23 [1.53, 0.93]
2.52 [3.48, 1.56]
3.7 [4.25, 3.15]
10 50 510
Favours GCE Favours placebo
100%
Total (95% CI)
Test for overall eect: Z=2.76 (P=.006)
75 67
Study or subgroup Mean Mean
GCE
SD SDTotal Total Weight
Mean dierence
IV, random, 95% CI
Mean dierence
IV, random, 95% CI
2.47 [4.23, 0.72]
Placebo
Heterogeneity: τ2=2.3; χ2=61.66, df =2(P<.00001); I2=97%
Figure 2: Forest plot showing the eect of GCE on body weight.
number of ways [8,24]. This activity might provide a basis
for explaining its eects on body weight. The purported
slimming eect of GCE would have a protective eect against
diabetes mellitus, via changes in gastrointestinal hormone
secretion [10]. A few questions, however, arise from the RCTs
which involve the use of GCE as a weight loss aid.
All the RCTs involving the use of GCE which have been
conducted so far have very small sample sizes, with the largest
number of participants being 62 in one trial [17]. These
small sample sizes increase the possibility of spurious or false
positive results. Two of the RCTs were unclear about drop-
outs of participants from the trial; neither did they report
on intention-to-treat analysis [17,18]. All of the trials so far
identified have been of very short duration. This makes it
dicult to assess the ecacy and safety of GCE as a weight
reduction agent on the medium to long-term. Although
none of the RCTs identified reported any adverse events,
this does not indicate that GCE intake is “risk-free. Two
participants in a study report dropped out due to adverse
events associated with the intake of GCE [16]. These included
headache and urinary tract infection. Thus, the safety of this
weight loss aid is not established.
The eective dosage of GCE for use as a weight loss
supplement is also not established. The dosages of GCE
reported in most of the human trials identified were
estimated, as the GCE was a component of coee. While 2
of the RCTs identified enriched their GCE with CGA [5,17],
the third trial did not report that the GCE used was fortified
with CGA [18]. This warrants further investigation.
The RCTs identified from our searches were not also
clear on blinding issues. None of the RCTs reported on
how randomisation was carried out, and none provided
information regarding blinding of outcome assessors. This
casts doubt on the internal validity of these trials. Future
trials involving the use of GCE as a weight loss supplement
should be conducted in line with the CONSORT guidelines.
This will ensure the validity and applicability of study results.
Two authors in one study were aliated to a company which
marketsSvetol[18] but did not specify whether or not they
had any conflicts of interest.
6Gastroenterology Research and Practice
This systematic review has several limitations. Though
our search strategy involved both electronic and nonelec-
tronic studies, we may not have identified all the available
trials involving the use of GCE as a weight loss supplement.
Furthermore, the methodological quality of the studies
identified from our searches is poor, and all are of short
duration. These factors prevent us from drawing firm
conclusions about the eects of GCE on body weight.
5. Conclusion
The evidence from RCTs seems to indicate that the intake of
GCE can promote weight loss. However, several caveats exist.
The size of the eect is small, and the clinical relevance of this
eect is uncertain. More rigorous trials with longer duration
are needed to assess the ecacy and safety of GCE as a weight
loss supplement.
Conflict of Interests
I. Onakpoya is funded by a grant from GlaxoSmithKline. The
funder had no role in the preparation of the paper. R. Terry
and E. Ernst declare no potential conflict of interests.
References
[1] C.L.Ogden,S.Z.Yanovski,M.D.Carroll,andK.M.Flegal,
“The epidemiology of obesity,Gastroenterology, vol. 132, no.
6, pp. 2087–2102, 2007.
[2] A. Farah, M. Monteiro, C. M. Donangelo, and S. Lafay,
“Chlorogenic acids from green coee extract are highly
bioavailable in humans,Journal of Nutrition, vol. 138, no. 12,
pp. 2309–2315, 2008.
[3] C. Manach, A. Scalbert, C. Morand, C. R´
em´
esy, and L.
Jim´
enez, “Polyphenols: food sources and bioavailability,”
American Journal of Clinical Nutrition, vol. 79, no. 5, pp. 727–
747, 2004.
[4]M.N.Cliord, “Chlorogenic acids and other cinna-
mates: nature, occurrence, dietary burden, absorption and
metabolism,Journal of the Science of Food and Agriculture, vol.
80, no. 7, pp. 1033–1043, 2000.
[5] E. Thom, “The eect of chlorogenic acid enriched coee on
glucose absorption in healthy volunteers and its eect on body
mass when used long-term in overweight and obese people,
Journal of International Medical Research, vol. 35, no. 6, pp.
900–908, 2007.
[6] H. Shimoda, E. Seki, and M. Aitani, “Inhibitory eect of green
coee bean extract on fat accumulation and body weight gain
in mice,BMC Complementary and Alternative Medicine, vol.
6, article 9, 2006.
[7] A.-S. Cho, S.-M. Jeon, M.-J. Kim et al., “Chlorogenic acid
exhibits anti-obesity property and improves lipid metabolism
in high-fat diet-induced-obese mice,Food and Chemical
Tox i c o lo g y , vol. 48, no. 3, pp. 937–943, 2010.
[8] E. Lopez-Garcia, R. M. Van Dam, S. Rajpathak, W. C. Willett, J.
E. Manson, and F. B. Hu, “Changes in caeine intake and long-
term weight change in men and women,American Journal of
Clinical Nutrition, vol. 83, no. 3, pp. 674–680,2006.
[9] L. A. Hiltunen, “Are there associations between coee con-
sumption and glucose tolerance in elderly subjects?” European
Journal of Clinical Nutrition, vol. 60, no. 10, pp. 1222–1225,
2006.
[10] J. A. Greenberg, C. N. Boozer, and A. Geliebter, “Coee,
diabetes, and weight control,American Journal of Clinical
Nutrition, vol. 84, no. 4, pp. 682–693, 2006.
[11] K. L. Johnston, M. N. Cliord, and L. M. Morgan, “Coee
acutely modifies gastrointestinal hormone secretion and glu-
cose tolerance in humans: glycemic eects of chlorogenic acid
and caeine,American Journal of Clinical Nutrition, vol. 78,
no. 4, pp. 728–733, 2003.
[12] D. Moher, K. F. Schulz, D. G. Altman, and L. Lepage,
“The CONSORT statement: revised recommendations for
improving the quality of reports of parallel-group randomised
trials,The Lancet, vol. 357, no. 9263, pp. 1191–1194, 2001.
[13] D.G.Altman,K.F.Schulz,D.Moheretal.,“TherevisedCON-
SORT statement for reporting randomized trials: explanation
and elaboration,Annals of Internal Medicine, vol. 134, no. 8,
pp. 663–694, 2001.
[14] Review Manager (RevMan) [Computer Program], Version 5.0.
Copenhagen: The Nordic Cochrane Centre, The Cochrane
Collaboration, 2008.
[15] T. Watanabe, Y. Arai, Y. Mitsui et al., “The blood pressure-
lowering eect and safety of chlorogenic acid from green
coee bean extract in essential hypertension,Clinical and
Experimental Hypertension, vol. 28, no. 5, pp. 439–449, 2006.
[16]J.Blum,B.Lemaire,S.Lafay,etal.,“Eect of a green
decaeinated coee extract on glycemia: a pilot prospective
clinical study,Nutrafoods, vol. 6, no. 3, pp. 13–17, 2007.
[17] Ayton Global Research, “Independent market study on
the eect of coee shape on weight loss—the eect
of chlorogenic acid enriched coee (coee chape) on
weight when used in overweight people, June 2009,
http://www.coeshape.eu/independent/.
[18] O. Dellalibera, B. Lemaire, and S. Lafay, “Svetol,greencoee
extract, induces weight loss and increases the lean to fat mass
ratio in volunteers with overweight problem,Phytotherapie,
vol. 4, no. 4, pp. 194–197, 2006.
[19] C. A. Welsch, P. A. Lachance, and B. P. Wasserman, “Dietary
phenolic compounds: inhibition of Na+-dependent D-glucose
uptake in rat intestinal brush border membrane vesicles,
Journal of Nutrition, vol. 119, no. 11, pp. 1698–1704, 1989.
[20] H. Hemmerle, H.-J. Burger, P. Below et al., “Chlorogenic acid
and synthetic chlorogenic acid derivatives: novel inhibitors of
hepatic glucose-6-phosphate translocase,Journal of Medicinal
Chemistry, vol. 40, no. 2, pp. 137–145, 1997.
[21] L. B. M. Tijburg, T. Mattern, J. D. Folts, U. M. Weisgerber,
and M. B. Katan, “Tea flavonoids and cardiovascular diseases:
a review,Critical Reviews in Food Science and Nutrition, vol.
37, no. 8, pp. 771–785, 1997.
[22] H. Adlercreutz and W. Mazur, “Phyto-oestrogens and Western
diseases,Annals of Medicine, vol. 29, no. 2, pp. 95–120, 1997.
[23]M.Monteiro,A.Farah,D.Perrone,L.C.Trugo,andC.
Donangelo, “Chlorogenic acid compounds from coee are
dierentially absorbed and metabolized in humans,Journal
of Nutrition, vol. 137, no. 10, pp. 2196–2201, 2007.
[24] S. Bidel, G. Hu, J. Sundvall, J. Kaprio, and J. Tuomilehto,
“Eects of coee consumption on glucose tolerance, serum
glucose and insulin levels: a cross-sectional analysis,Hormone
and Metabolic Research, vol. 38, no. 1, pp. 38–43, 2006.
... Green coffee influence postprandrial glucose concentration and blood lipid concentration by reducing the intestinal absorption of glucose in the intestine and electrochemical gradient dispersal leading to an influx of glucose into the enterocytes [7]. Green coffee is also thought to inhibit hepatic glucose-6-phosphatase, which is involved in the homeostasis of glucose [8]. ...
... Green coffee is also thought to inhibit hepatic glucose-6-phosphatase, which is involved in the homeostasis of glucose [8]. Reports from animal studies have suggested that green coffee mediates its anti-obesity effect possibly by suppressing the accumulation of hepatic triglycerides [7]. Green coffee exhibited anti-obesity effect by altering the plasma adipokine level and body fat distribution and down-regulating fatty acid and cholesterol biosynthesis, whereas upregulating fatty acid oxidation and peroxisome proliferator-activated receptor alpha expression in the liver [9]. ...
... Certain dietary phenols, including green coffee, may modify intestinal glucose uptake that might affect the body weight. The weight loss effect of green coffee would have a protective effect against diabetes mellitus, via changes in gastrointestinal hormone secretion [7]. A few questions, however, arise which involve the use of green coffee as a weight loss aid. ...
... 1.5 ± 0.4 (9-24)* 16 ± 4** 3 ± 1 (3-9)* 35 ± 8** 3-(Phenyl)propanoic acid-4′-sulfate (DHCoA-4′-sulfate) 19 ± 5 (9-24)* 185 ± 45* 28 ± 8 (3-9)* 340 ± 66* 3-Dihydrocaffeoylquinic acid 0.22 ± 0.03 (9-24) 2.8 ± 0.4 0.16 ± 0.06 (6-24) 1.9 ± 0.5 5-Dihydrocaffeoylquinic acid 0.02 ± 0.01 (9-24) 0.2 ± 0.1 0.03 ± 0.01 (3)(4)(5)(6)(7)(8)(9)(10)(11) 0.3 ± 0.1 4-Dihydrocaffeoylquinic acid 0.033 ± 0.006 (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.40 ± 0.07 0.029 ± 0.007 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.4 ± 0.1 3-Dihydroferuloylquinic acid 0.03 ± 0.02 (6)(7)(8)(9)(10)(11)(12) 0.3 ± 0.1 0.05 ± 0.02 (0-6) 0.7 ± 0.3 5-Dihydroferuloylquinic acid 0.2 ± 0.1 (3-12) 3 ± 1 0.14 ± 0.06 (6-11) 1.9 ± 0.7 4-Dihydroferuloylquinic acid 0.05 ± 0.03 (6-24) 0.6 ± 0.3 0.04 ± 0.03 (9-24) 0.6 ± 0.4 Dihydrocoumaroylquinic acid 0.3 ± 0.1 (9-24)* 3 ± 1 0.5 ± 0.2 (3-9)* 3 ± 1 Dihydrocoumaroylquinic acid 0.14 ± 0.05 (9-24)* 1.7 ± 0.6 0.09 ± 0.03 (6-11)* 1. Values represent mean ± standard error (n = 9). ...
... 1.5 ± 0.4 (9-24)* 16 ± 4** 3 ± 1 (3-9)* 35 ± 8** 3-(Phenyl)propanoic acid-4′-sulfate (DHCoA-4′-sulfate) 19 ± 5 (9-24)* 185 ± 45* 28 ± 8 (3-9)* 340 ± 66* 3-Dihydrocaffeoylquinic acid 0.22 ± 0.03 (9-24) 2.8 ± 0.4 0.16 ± 0.06 (6-24) 1.9 ± 0.5 5-Dihydrocaffeoylquinic acid 0.02 ± 0.01 (9-24) 0.2 ± 0.1 0.03 ± 0.01 (3)(4)(5)(6)(7)(8)(9)(10)(11) 0.3 ± 0.1 4-Dihydrocaffeoylquinic acid 0.033 ± 0.006 (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.40 ± 0.07 0.029 ± 0.007 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.4 ± 0.1 3-Dihydroferuloylquinic acid 0.03 ± 0.02 (6)(7)(8)(9)(10)(11)(12) 0.3 ± 0.1 0.05 ± 0.02 (0-6) 0.7 ± 0.3 5-Dihydroferuloylquinic acid 0.2 ± 0.1 (3-12) 3 ± 1 0.14 ± 0.06 (6-11) 1.9 ± 0.7 4-Dihydroferuloylquinic acid 0.05 ± 0.03 (6-24) 0.6 ± 0.3 0.04 ± 0.03 (9-24) 0.6 ± 0.4 Dihydrocoumaroylquinic acid 0.3 ± 0.1 (9-24)* 3 ± 1 0.5 ± 0.2 (3-9)* 3 ± 1 Dihydrocoumaroylquinic acid 0.14 ± 0.05 (9-24)* 1.7 ± 0.6 0.09 ± 0.03 (6-11)* 1. Values represent mean ± standard error (n = 9). ...
... 1.5 ± 0.4 (9-24)* 16 ± 4** 3 ± 1 (3-9)* 35 ± 8** 3-(Phenyl)propanoic acid-4′-sulfate (DHCoA-4′-sulfate) 19 ± 5 (9-24)* 185 ± 45* 28 ± 8 (3-9)* 340 ± 66* 3-Dihydrocaffeoylquinic acid 0.22 ± 0.03 (9-24) 2.8 ± 0.4 0.16 ± 0.06 (6-24) 1.9 ± 0.5 5-Dihydrocaffeoylquinic acid 0.02 ± 0.01 (9-24) 0.2 ± 0.1 0.03 ± 0.01 (3)(4)(5)(6)(7)(8)(9)(10)(11) 0.3 ± 0.1 4-Dihydrocaffeoylquinic acid 0.033 ± 0.006 (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.40 ± 0.07 0.029 ± 0.007 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) 0.4 ± 0.1 3-Dihydroferuloylquinic acid 0.03 ± 0.02 (6)(7)(8)(9)(10)(11)(12) 0.3 ± 0.1 0.05 ± 0.02 (0-6) 0.7 ± 0.3 5-Dihydroferuloylquinic acid 0.2 ± 0.1 (3-12) 3 ± 1 0.14 ± 0.06 (6-11) 1.9 ± 0.7 4-Dihydroferuloylquinic acid 0.05 ± 0.03 (6-24) 0.6 ± 0.3 0.04 ± 0.03 (9-24) 0.6 ± 0.4 Dihydrocoumaroylquinic acid 0.3 ± 0.1 (9-24)* 3 ± 1 0.5 ± 0.2 (3-9)* 3 ± 1 Dihydrocoumaroylquinic acid 0.14 ± 0.05 (9-24)* 1.7 ± 0.6 0.09 ± 0.03 (6-11)* 1. Values represent mean ± standard error (n = 9). ...
Article
Nutraceuticals based on plant extracts rich in polyphenols, as well as dietary fibres, are new means to fight overweight/obesity and associated diseases. However, to understand the potential effects of polyphenols on health it is critical to study their bioavailability and metabolic fate. Consumption of a green coffee phenolic extract (GCPE) in combination with oat beta-glucan (BG) could affect the pharmacokinetic profile of the main polyphenols present in coffee (hydroxycinnamates). Moreover, the regular intake of the combination could also induce changes. Nine overweight men and women consumed a novel nutraceutical product containing 300 mg of green coffee hydroxycinnamic acids and 2.5 g of BG twice a day for 8 weeks. A pharmacokinetic study was carried out in blood and urine samples taken before (baseline) and at week 8 after the nutraceutical intervention, collecting samples at different times in a 0-24 h interval. Faecal samples were also obtained at 0 and 24 h after the intake of the nutraceutical at baseline and week 8. Phenolic metabolites were analysed by LC-MS-QToF. Results showed that polyphenols were differentially absorbed and extensively metabolized throughout the gastrointestinal tract. An apparent reduction in the excretion of small intestinal metabolites was accompanied by a tendency to increase colonic metabolites after sustained intake (p = 0.052). In conclusion, continued consumption of the GCPE/BG nutraceutical appears to enhance the absorption of hydroxycinnamates by increasing the colonic bioavailability of their derived metabolites compared to baseline, although the regular intake of the nutraceutical did not modify the metabolite profile in any of the biological samples.
... et al. 2009, Onakpoya et al. 2011, Ríos- Hoyo and Gutiérrez-Salmeán 2018, Tabrizi et al. 2019, Tamura, 2020 and reduce body weight of humans(Hasani-Ranjbar et al. 2009, Onakpoya et al. 2011, Tabrizi et al. 2019. A study of Sarriá et al.(2018) determined a positive effect of green and roasted coffee on metabolic indexes but not on body weight of patients.Vol. ...
... et al. 2009, Onakpoya et al. 2011, Ríos- Hoyo and Gutiérrez-Salmeán 2018, Tabrizi et al. 2019, Tamura, 2020 and reduce body weight of humans(Hasani-Ranjbar et al. 2009, Onakpoya et al. 2011, Tabrizi et al. 2019. A study of Sarriá et al.(2018) determined a positive effect of green and roasted coffee on metabolic indexes but not on body weight of patients.Vol. ...
Article
This paper reviews provenance, chemical composition and properties of tea (Camelia sinensis L.) and coffee (Coffee arabica, L. and Coffea caniphora, L.), their general health effects, as well as the currently available knowledge concerning their action on fat storage, physiological mechanisms of their effects, as well as their safety and recommended dosage for treatment of obesity. Both tea and coffee possess the ability to promote health and to prevent, to mitigate and to treat numerous disorders. This ability can be partially due to presence of caffeine in both plants. Further physiological and medicinal effects could be explained by other molecules (theaflavins, catechins, their metabolites and polyphenols in tea and polyphenol chlorogenic acid in coffee). These plants and plant molecules can be efficient for prevention and treatment of numerous metabolic disorders including metabolic syndrome, cardiovascular diseases, type 2 diabetes and obesity. Both plants and their constituents can reduce fat storage through suppression of adipocyte functions, and support of gut microbiota. In addition, tea can prevent obesity via reduction of appetite, food consumption and food absorption in gastrointestinal system and through the changes in fat metabolism.
... When green coffee is incorporated into other products, it increases the concentration of polyphenols, antioxidants, and total phenolics [10], which reduces the loss of polyunsaturated fatty acids [16], formation of acrylamide [17], and syneresis rate [18], demonstrating excellent sensory properties [19] and high bioaccessibility and bioavailability [20]. These bioactive compounds in green coffee beans are classified as functional ingredients and can be important raw materials for making nutritious and fortified foods that can solve a worldwide challenge [20,21]. In 2019, approximately 820 million people suffered from food insecurity and with the Covid-19 pandemic, approximately 130 million people will go into extreme poverty and 265 million will be chronically hungry [22,23]. ...
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The objective of this study was the application of green coffee bean flour in gluten-free cakes with different percentages (4, 8 and 15% (w/w)), to evaluate the optimal value for fortification, and the products were characterized based on their centesimal composition and bioactive compounds (caffeine and total phenolic compounds). Significant differences (p ≤ 0.05) were observed in the content of lipids, total dietary fiber, insoluble fiber, energy values, sodium, caffeine, and total phenolics, mainly in the product in which 15% (w/w) green coffee bean flour was added. Caffeine content was only detected and quantified in products with > 8% (w/w) green coffee bean flour, whereas the total phenolic content was detected and quantified in products with > 4% (w/w) green coffee bean flour. Thus, fortification of these products with 15% green coffee bean flour promoted a higher content of total dietary fiber and lower content of lipids, calories, sodium, and increased bioactive compounds. Thus, green coffee bean flour is an excellent alternative for the production of innovative foods.
... A recent narrative review also indicates that supplements of green coffee may help to reduce blood pressure. Chlorogenic acid has also been known to show potent antioxidant properties [108]. CGA's also have other medicinal values apart from antioxidant properties, including antiviral, anti-inflammatory, hypoglycaemic, and hepatoprotective properties [109]. ...
Article
Coffee is known to be one of the popular beverages today on the globe. Due to its easy availability and preparation, it is consumed by the population of almost all countries. This wonder crop was discovered in the 6th century in Ethiopia. Since then, people have also used various brewing methods to extract hundreds of the bioactive compounds present in these aromatic seeds. No doubt, excessive consumption of the same can be harmful too. As a functional food, coffee is known to have multiple health benefits. Coffee beans contain vitamins, minerals, caffeine, chlorogenic acid, and various other biologically active ingredients. This review briefly describes the major biologically active compounds present in these seeds – caffeine, trigonelline, diterpenes, and chlorogenic acid (CGA). It also aims to describe various bioactive activities such as antioxidant, antiproliferative, antibacterial, antiviral, etc., against variable hallmarks. Thus, explaining different pharmacological effects for the welfare of the human population.
... − 0.72; P = 0.05), 2.47 kg (95%CI: − 1.75, − 0.00; P = 0.006), 1.77 kg (95%CI: − 3.33, 0.33; P = 0.10) respectively in kilograms of body weight[26][27][28]. C. fimbriata reported virtually no weight loss comparatively to the other extracts which is − 0.04 (− 1.41,1.34; ...
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Background Obesity prevalence has increased during the past few decades, causing a pandemic with an influx in other co-morbidities. Many factors influence weight gain in an obesogenic environment therefore strategies for treating obesity may vary from conventional dietary and physical activity interventions to pharamacotherapy. A shift in unconventional strategies as herbal products for treating obesity have been investigated and one such plant extract is Caralluma fimbriata ( C. fimbriata ). Further, the studies included were systematically reviewed to gather evidence on potential effects of C. fimbriata as an appetite suppressant and weight loss supplement. Methods A systematic review of clinical trials reporting the effects of C. fimbriata as appetite suppression and anti-obesity supplement was reported according to PRISMA guidelines. Data were obtained by searching three databases: PubMed®, Web of Science® and SciVerse Scopus® for studies published until 30th April 2020. Results A total of 7 articles studying C. fimbriata satisfied the inclusion and exclusion criteria and were sourced from various countries including Australia (3), Cuba (1), India (2) and Spain (1). Almost all studies recruited adults who were overweight or obese with a BMI > 25 kg/m ² ( n = 5), with the exception of two studies, one that recruited healthy adults with a BMI average of 26.5 kg/m2 and the second one utilised a population of children and adolescents with Prader-Willis Syndrome (PWS). Parameters assessing obesity, biochemical and appetite factors were analysed by carrying out a meta-analysis. Compared to placebo controlled group, C. fimbriata extract significantly reduced WC by 1.59 cm (95% CI, − 3.07 to − 0.10, p = 0.041) and WHR by 0.06 (95% CI, − 0.12 to − 0.01, p = 0.05) although no significant effects were seen on BW, BMI and HC. Biochemical and appetite parameters outcome on C. fimbriata consumption had no significant changes. Any side effects of individuals who ingested the extract were reported by few studies of which most common effects were constipation, diarrhoea, nausea and rashes. Conclusion Appetite parameters showed no significant changes and metabolic parameters did not improve with C.fimbriata supplementation therefore it is unlikely to recommend C. fimbriata as a weight loss supplement and an appetite suppressant.
... Chlorogenic acid (CA) is a common active phenolic acid found in coffee beans and citrus fruits. CA exhibits anti-oxidation capabilities, can inhibit obesity, and enable the treatment of the metabolic syndrome [21][22][23]. Zhang et al. [24] studied the non-covalent binding of CA with three kinds of whey proteins. The authors screened and obtained the most stable complex to prepare the CA-protein complex. ...
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Ultrasound technology was used to treat rice bran protein (RBP), and the structural and functional properties of ultrasonically treated RBP (URBP) and its chlorogenic acid (CA) complex were studied. When ultrasonic power of 200 W was applied for 10 min, the maximum emission peak λmax of the URBP-CA complex in the fluorescence spectrum was red-shifted by 3.6 nm compared to that of the untreated complex. The atomic force microscope (AFM) analysis indicated that the surface roughness of the complex was minimized (3.89 nm) at the ultrasonic power of 200 W and treatment time of 10 min. Under these conditions, the surface hydrophobicity (H0) was 1730, the contents of the α-helix and β-sheet in the complex were 2.97% and 6.17% lower than those in the untreated sample, respectively, the particle size decreased from 106 nm to 18.2 nm, and the absolute value of the zeta-potential increased by 11.0 mV. Therefore, ultrasonic treatment and the addition of CA changed the structural and functional properties of RBP. Moreover, when ultrasonic power of 200 W was applied for 10 min, the solubility, emulsifying activity index (EAI), and emulsion stability index (ESI) were 68%, 126 m2/g, and 37 min, respectively.
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Background This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) is intended to provide clinicians an overview of the body weight effects of concomitant medications (i.e., pharmacotherapies not specifically for the treatment of obesity) and functional foods, as well as adverse side effects of common supplements sometimes used by patients with pre-obesity/obesity. Methods The scientific information for this CPS is based upon published scientific citations, clinical perspectives of OMA authors, and peer review by the Obesity Medicine Association leadership. Results This CPS outlines clinically relevant aspects of concomitant medications, functional foods, and many of the more common supplements as they relate to pre-obesity and obesity. Topics include a discussion of medications that may be associated with weight gain or loss, functional foods as they relate to obesity, and side effects of supplements (i.e., with a focus on supplements taken for weight loss). Special attention is given to the warnings and lack of regulation surrounding weight loss supplements. Conclusions This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) on concomitant medications, functional foods, and supplements is one of a series of OMA CPSs designed to assist clinicians in the care of patients with the disease of pre-obesity/obesity. Implementation of appropriate practices in these areas may improve the health of patients, especially those with adverse fat mass and adiposopathic metabolic consequences.
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Dietary supplements (DSs) are used by 50% of Americans and 70% of United States military service members (SMs); some have adverse effects (AEs). This cross-sectional investigation examined AEs associated with specific DSs. A stratified random sample of SMs from the Air Force, Army, Marine Corps, and Navy was obtained. Volunteers completed a questionnaire reporting AEs for 96 generic and 62 specific DSs. The highest prevalence (≥1 AE) in specific DS categories was 35% prohormones, 33% weight loss supplements, 26% pre/post workout supplements, 14% herbal products, 12% multivitamin/multiminerals, 11% protein/amino acids, 9% muscle building supplements, 7% other DSs, 6% joint health products, and 5% individual vitamins/minerals. Specific DSs of concern (with proportion reporting AEs) included: Libido Max® (35%), Hydroxycut Hardcore® (33%), OxyElite® (33%), Roxylean® (31%), Growth Factor 9® (30%), Super HD® (29%), Hydroxycut Advanced® (29%), Lipo 6® (28%), The Ripper® (27%), Test Booster® (27%), Xenadrine Xtreme Thermogenic® (27%), C4 Extreme® (26%), and C4 Origional® (25%). Products marketed for weight loss, use before/after workout, and prohormones had the highest AE prevalence. DSs can contain substances with independent/additive AEs and/or interact with other ingredients or prescribed medications. Methods described here could provide a continuous surveillance system detecting dangerous DSs entering the market.
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Pour tester les effets du Svetol®, un extrait de café vert décaféiné possédant un ratio spécifique entre l’acide 5-caféyl-quinique (acide chlorogénique) et les autres isomères d’acides caféylquiniques, sur la perte de poids, 50 volontaires ayant un indice de masse corporelle (IMC) supérieur à 25 ont été sélectionnés. Ils ont été randomisés en deux groupes : l’un (n = 20) recevant le placebo, l’autre (n = 30) recevant le Svetol® en parallèle d’une alimentation légèrement hypocalorique. Chaque volontaire consomme une capsule de Svetol® ou de placebo deux fois par jour pendant 60 jours, au moment des repas principaux. Le poids, l’IMC, le ratio masse maigre/masse grasse (MM/MG) et l’auto-évaluation de l’aspect physique ont été déterminés à Jo et J60. Après 60 jours de traitement, une réduction significative du poids de 4,97 +/- 0,32 kg (5,7 %) a été observée dans le groupe Svetol® comparé au groupe contrôle (p < 0,001). Le ratio MM/MG est augmenté de façon significative dans le groupe Svetol® comparé au groupe contrôle : 4,1 +/- 0,7 %vs 1,6 +/- 0,6 % respectivement (p < 0,01). Ces résultats démontrent que le Svetol® est capable d’augmenter l’effet d’une alimentation légèrement hypocalorique chez des volontaires ayant des problèmes de surpoids. Cet effet pourrait être expliqué par une meilleure utilisation des graisses et par la prévention de leur accumulation.
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Chlorogenic acids (CGA) are cinnamic acid derivatives with biological effects mostly related to their antioxidant and antiinflammatory activities. Caffeoylquinic acids (CQA) and dicaffeoylquinic acids (diCQA) are the main CGA found in nature. Because green coffee is a major source of CGA, it has been used for production of nutraceuticals. However, data on the bioavailability of CGA from green coffee in humans are inexistent. The present study evaluated the pharmacokinetic profile and apparent bioavailability of CGA in plasma and urine of 10 healthy adults for 8 h after the consumption of a decaffeinated green coffee extract containing 170 mg of CGA. Three CQA, 3 diCQA, and caffeic, ferulic, isoferulic, and p-coumaric acids were identified in plasma by HPLC-Diode Array Detector-MS after treatment. Over 30% (33.1 +/- 23.1%) of the ingested cinnamic acid moieties were recovered in plasma, including metabolites, with peak levels from 0.5 to 8 h after treatment. CGA and metabolites identified in urine after treatment were 4-CQA, 5-CQA, and sinapic, p-hydroxybenzoic, gallic, vanillic, dihydrocaffeic, caffeic, ferulic, isoferulic, and p-coumaric acids, totaling 5.5 +/- 10.6% urinary recovery of the ingested cinnamic and quinic acid moiteties. This study shows that the major CGA compounds present in green coffee are highly absorbed and metabolized in humans.
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Overwhelming evidence now indicates that the quality of reporting of randomized, controlled trials (RCTs) is less than optimal. Recent methodologic analyses indicate that inadequate reporting and design are associated with biased estimates of treatment effects. Such systematic error is seriously damaging to RCTs, which boast the elimination of systematic error as their primary hallmark. Systematic error in RCTs reflects poor science, and poor science threatens proper ethical standards. A group of scientists and editors developed the CONSORT (Consolidated Standards of Reporting Trials) statement to improve the quality of reporting of RCTs. The statement consists of a checklist and flow diagram that authors can use for reporting an RCT. Many leading medical journals and major international editorial groups have adopted the CONSORT statement. The CONSORT statement facilitates critical appraisal and interpretation of RCTs by providing guidance to authors about how to improve the reporting of their trials. This explanatory and elaboration document is intended to enhance the use, understanding, and dissemination of the CONSORT statement. The meaning and rationale for each checklist item are presented. For most items, at least one published example of good reporting and, where possible, references to relevant empirical studies are provided. Several examples of flow diagrams are included. The CONSORT statement, this explanatory and elaboration document, and the associated Web site (http://www.consort -statement.org) should be helpful resources to improve reporting of randomized trials.
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This paper summarises the occurrence in foods and beverages of the cinnamic acids, their associated conjugates and transformation products. Quantitative data are lacking for some commodities known to contain them, but it is clear that for many people coffee will be the major source. The daily dietary intake of total cinnamates may vary substantially from almost zero to perhaps close to 1 g. The data relating to their absorption and metabolism are presented along with a consideration of their possible in vivo effects. Data for true bioavailability are incomplete: in particular it is not clear whether availability differs markedly with the form of the conjugate, and whether as a consequence some dietary sources may be superior to others.© 2000 Society of Chemical Industry
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In the United States, obesity among adults and overweight among children and adolescents have increased markedly since 1980. Among adults, obesity is defined as a body mass index of 30 or greater. Among children and adolescents, overweight is defined as a body mass index for age at or above the 95th percentile of a specified reference population. In 2003-2004, 32.9% of adults 20-74 years old were obese and more than 17% of teenagers (age, 12-19 y) were overweight. Obesity varies by age and sex, and by race-ethnic group among adult women. A higher body weight is associated with an increased incidence of a number of conditions, including diabetes mellitus, cardiovascular disease, and nonalcoholic fatty liver disease, and with an increased risk of disability. Obesity is associated with a modestly increased risk of all-cause mortality. However, the net effect of overweight and obesity on morbidity and mortality is difficult to quantify. It is likely that a gene-environment interaction, in which genetically susceptible individuals respond to an environment with increased availability of palatable energy-dense foods and reduced opportunities for energy expenditure, contributes to the current high prevalence of obesity. Evidence suggests that even without reaching an ideal weight, a moderate amount of weight loss can be beneficial in terms of reducing levels of some risk factors, such as blood pressure. Many studies of dietary and behavioral treatments, however, have shown that maintenance of weight loss is difficult. The social and economic costs of obesity and of attempts to prevent or to treat obesity are high
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This paper summarises the occurrence in foods and beverages of the cinnamic acids, their associated conjugates and transformation products. Quantitative data are lacking for some commodities known to contain them, but it is clear that for many people coffee will be the major source. The daily dietary intake of total cinnamates may vary substantially from almost zero to perhaps close to 1 g. The data relating to their absorption and metabolism are presented along with a consideration of their possible in vivo effects. Data for true bioavailability are incomplete: in particular it is not clear whether availability differs markedly with the form of the conjugate, and whether as a consequence some dietary sources may be superior to others.
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This study investigated the efficacy of chlorogenic acid on altering body fat in high-fat diet (37% calories from fat) induced-obese mice compared to caffeic acid. Caffeic acid or chlorogenic acid was supplemented with high-fat diet at 0.02% (wt/wt) dose. Both caffeic acid and chlorogenic acid significantly lowered body weight, visceral fat mass and plasma leptin and insulin levels compared to the high-fat control group. They also lowered triglyceride (in plasma, liver and heart) and cholesterol (in plasma, adipose tissue and heart) concentrations. Triglyceride content in adipose tissue was significantly lowered, whereas the plasma adiponectin level was elevated by chlorogenic acid supplementation compared to the high-fat control group. Body weight was significantly correlated with plasma leptin (r=0.894, p<0.01) and insulin (r=0.496, p<0.01) levels, respectively. Caffeic acid and chlorogenic acid significantly inhibited fatty acid synthase, 3-hydroxy-3-methylglutaryl CoA reductase and acyl-CoA:cholesterol acyltransferase activities, while they increased fatty acid beta-oxidation activity and peroxisome proliferator-activated receptors alpha expression in the liver compared to the high-fat group. These results suggest that caffeic acid and chlorogenic acid improve body weight, lipid metabolism and obesity-related hormones levels in high-fat fed mice. Chlorogenic acid seemed to be more potent for body weight reduction and regulation of lipid metabolism than caffeic acid.
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The enzyme system glucose-6-phosphatase (EC 3.1.3.9) plays a major role in the homeostatic regulation of blood glucose. It is responsible for the formation of endogenous glucose originating from gluconeogenesis and glycogenolysis. Recently, chlorogenic acid was identified as a specific inhibitor of the glucose-6-phosphate translocase component (Gl-6-P translocase) of this enzyme system in microsomes of rat liver. Glucose 6-phosphate hydrolysis was determined in the presence of chlorogenic acid or of new synthesized derivatives in intact rat liver microsomes in order to assess the inhibitory potency of the compounds on the translocase component. Variation in the 3-position of chlorogenic acid had only poor effects on inhibitory potency. Introduction of lipophilic side chain in the 1-position led to 100-fold more potent inhibitors. Functional assays on isolated perfused rat liver with compound 29i, a representative of the more potent derivatives, showed a dose-dependent inhibition of gluconeogenesis and glycogenolyosis, suggesting glucose-6-phosphatase as the locus of interference of the compound for inhibition of hepatic glucose production also in the isolated organ model. Gl-6-P translocase inhibitors may be useful for the reduction of inappropriately high rates of hepatic glucose output often found in non-insulin-dependent diabetes.