Metabolic syndrome is defined as the clustering in an individual of several metabolic abnormalities associated with insulin resistance, type 2 diabetes, and obesity, in which low-grade chronic inflammatory activity is commonly observed. Part of the European Project PlantLIBRA is concerned with methods to assess the benefits of plant food supplements (PFSs) in countering inflammatory activity and metabolic syndrome. This paper summarizes the current methods used for benefit assessment of PFS, taking into consideration only
Metabolic syndrome (MS) defines the clustering in an individual of multiple metabolic abnormalities [
A major shortcoming of current definitions of MS is the lack of inclusion of measures of a proinflammatory state and oxidative stress [
Type 2 diabetes (T2D) is considered an MS-related disease and an inflammatory disease. As with MS, patients with T2D show higher levels of circulating CRP, fibrinogen, plasminogen activator inhibitor (PAI), and proinflammatory cytokines such as interleukin-1
In the last 10 years, the link between inflammation and nutrition has become increasingly apparent [
The European Project PlantLIBRA (acronym for plant food supplements: levels of intake, benefit, and risk assessments) aims to promote the safe use of PFS or botanicals and the measurement of the risk/benefit ratio related to their consumption. Part of the project is devoted to the discovery of methods for the evaluation of the benefits of PFS and their application and validation. The first step was to review the evidence for PFS benefit in epidemiological, clinical, and intervention studies, in particular the value of PFS as anti-inflammatory agents [
The aim of the present paper was to identify the
The following databases were searched electronically to identify relevant articles published up to September 2011: PubMed/Medline, SciFinder Scholar, and Cochrane Library. Search limits were
A search strategy was developed for each electronic database using specific medical subject heading (MeSH) terms (e.g., inflammation mediators, C reactive protein CRP, and metabolic X syndrome) in addition to relevant text keywords (plant extract, plant preparation, methods, and analytical approaches).
The same MeSH terms were used in the T2D area and in the MS area to search for inflammatory biomarkers and plant extracts, and the specific terms diabetes mellitus, noninsulin-dependent OR diabetes mellitus, and type II were combined with relevant keywords (plant extract, plant preparation, methods, and analytical approaches).
Titles and abstracts of retrieved citations were first screened to identify publications reporting
The search by title and abstract retrieved 46 papers for MS and 68 for diabetes. After removal of duplicates and application of the inclusion/exclusion criteria, the total number of papers was 43. Papers were also rejected if they were not in a European language.
Neither
Table
Inflammatory parameters measured in metabolic syndrome.
Method1 | Botanical or botanical derivatives used | No. of participants and length of treatment | Parameters measured | Results | Reference |
---|---|---|---|---|---|
Double-blind randomized controlled cross-over trial | Olive oil ( |
20 (6-week washout period plus 4-h study session) | Expression of inflammatory genes (CCL3, CXCL1, CXCL3, CXCR4, IL-1 |
Expression of inflammatory genes was reduced | Camargo et al., 2010 [ |
Randomized double-blind controlled trials | ProAlgaZyme (freshwater algae infusion) |
60 (10 weeks) | hs-CRP, IL-6, and TNF- |
Significant reduction of all parameters | Oben et al., 2007 [ |
Single-blind randomized controlled trial | Plant sterol margarines (30 g/day) | 53 (5 weeks) | CRP, IL-6, CD 40 ligand (CD40L), and E-selectin | No changes | Gagliardi et al., 2010 [ |
Randomized open controlled cross-over trials | Soy nut/soy proteins | 482 (8 weeks) | Serum endothelin-1, sICAM-1, sVCAM-1, E-selectin, IL-2, IL-6, IL-18, TNF- |
Reduction of CRP for soy protein, E-selectin, TNF- |
Azadbakht et al., 2007 [ |
Randomized open controlled clinical trials | Berries and derivatives* | 61 (20 weeks) | TNF- |
No significant differences | Lehtonen et al., 2010 [ |
Open nonrandomized noncontrolled clinical trials | Freeze-dried strawberry extract | 35 (4 weeks) | Malondialdehyde (MDA), hs-CRP, and adiponectin | No significant differences | Basu et al., 2009 [ |
Cross-sectional studies | Fruit food group** |
486 (1 year) | CRP | Reduction of CRP for both groups | Esmaillzadeh et al., 2006 [ |
*Participants consumed lingonberry, bilberry, black currant, sea buckthorn as such or as derivatives (juice, oil, and powder).
**Pears, apricots, cherries, apples, raisins or grapes, bananas, cantaloupe, watermelon, oranges, grapefruit, kiwi, strawberries, peaches, nectarines, tangerines, mulberry, plums, persimmons, pomegranates, lemons, pineapples, fresh figs, and date.
***Vegetable fruit group: cabbage, cauliflower, Brussels sprouts, kale, carrots, tomatoes, spinach, lettuce, cucumber, mixed vegetables, eggplant, celery, green peas, green beans, green pepper, turnip, corn, squash, mushrooms, and onions.
1Clinical studies used to assess inflammatory parameters are listed from the best to the worst method applied.
Several publications reported in the present review used randomization in clinical trials, but in a few cases, randomization was not described in detail or incompletely applied (e.g., no randomization for age or gender). Positive aspects of randomization include the elimination of biases, balanced arms, and the capacity to form the basis for statistical tests.
A method of randomization should be considered appropriate if it allows each study participant to have the same chance of receiving the intervention [
The inflammatory parameters decreasing after PFS treatment were also reviewed. Although changes after PFS treatment depend on the plant used and on the bioavailability of the active compounds and the method conditions, parameters that change in a short period of time can be selected as useful biomarkers of the anti-inflammatory properties of PFS. In patients affected by MS (Table
On the contrary, the other four of these studies [
E-selectin levels were evaluated in four studies [
We may conclude that TNF-
Table
Method | Botanical used | Parameters measured | Results | Reference |
---|---|---|---|---|
Flow cytometry | Peanut oil ( |
Apoptosis induced by TNF- |
Reduction of apoptosis | Vassiliou et al., 2009 [ |
Luciferase assay |
|
Transcriptional activity of NF-kB induced by LPS in RAW264.7 macrophages | Reduction of transcriptional activity of NF-kB | Yin et al., 2009 [ |
Quantitative polymerase chain reaction (qRT-PCR) |
|
mRNA levels of IL-2 in human (Jurkat) T cells stimulated with anti-CD3 antibodies | Reduction of mRNA and IL-2 levels | Uemura et al., 2010 [ |
Lyophilized grape powder ( |
Gene expression of IL-6, IL-8, IL-1 |
Attenuation of all parameters measured | Chuang et al., 2011 [ | |
White grape seed extract ( |
Gene expression of CYP, PPAR |
Reduction of IL-6 and MCP-1 expressions; modulation of APM1 and LEP (adipokine) gene expressions | Kar et al., 2009 [ | |
Lyophilized grape powder ( |
Gene expression of IL-6, IL-8, IL-1 |
Reduction of IL-6, IL-8, IL-1 |
Chuang et al., 2010 [ | |
|
Expression of tristetraprolin (TTP) in mouse RAW264.7 macrophages treated with LPS | Induction of TTP | Cao et al., 2008 [ | |
|
Gene expression of iNOS and COX-2 in murine RAW264.7 macrophages treated with LPS | mRNA levels of iNOS and COX2 were inhibited by |
Li et al., 2010 [ | |
Fructus Xanthii | Protection from IL-1 |
Complete protection | Song et al., 2009 [ | |
Lyophilized grape powder ( |
Concentration of IFN- |
Reduction of IP-10 | Chuang et al., 2010 [ | |
Palmitic acid, oleic acid, or DHA | Production of TNF- |
Increase of |
Bradley et al., 2008 [ | |
Lyophilized grape powder, ( |
Activation of NF-kB factor and Ik |
Reduction of NF-kB activity and mediation of Ik |
Chuang et al., 2011 [ | |
Lyophilized grape powder, ( |
Activation of NF- |
Inhibition of NF-kB activation | Chuang et al., 2010 [ | |
|
Cytokine (TNF- |
Reduction of cytokine (TNF- |
Cao et al., 2008 [ | |
Chromogenic assay (TMPD) | Extract of rhizome of |
Enzymatic activity of COX |
Reduction of enzymatic activity |
Priya Rani et al., 2011 [ |
ELISA | Diosgenin from seeds of |
Levels of adiponectin and MCP-1 in 3T3-L1 preadipocytes | Increase of adiponectin levels and decrease of MCP-1 | Uemura et al., 2010 [ |
Caspase-3 activity luminometric assay |
|
Determination of apoptosis in rat insulinoma cell line (INS-1E) stimulated with cytokines | Inhibition of apoptosis | Menegazzi et al., 2008 [ |
White grape seed extract ( |
P65 translocation and PIKB |
Partial inhibition |
Chac |
|
No production colorimetric assay |
|
Cytotoxicity and no inhibitory activity in murine RAW 264.7 macrophages stimulated with LPS | Inhibition of cytotoxicity and no activity only by |
Li et al., 2010 [ |
Nitrite measurement colorimetric assay | Fructus Xanthii | No production in RINm5F cells treated with IL-1 |
Inhibition of no production | Song et al., 2009 [ |
NF-kB binding assay | Dietary fatty acids | Binding activity of the P65 subunit of NF-kB in nuclear extracts from 3T3-L1 murine adipocytes | Decrease of binding activity | Bradley et al., 2008 [ |
In the luciferase transfection assay only, Chuang et al. [ nuclear translocation of NF- expression of adhesion molecules (i.e., sICAM-1, sICAM-2 and sVCAM-1, and E-selectin), which are typically overexpressed in diabetes and in cardiovascular disease [ evaluation of metalloproteinase-9 (MMP-9) secretion and gene expression. MMP-9 is induced by hyperglycemia and accelerates some diabetic complications such as retinopathy [ evaluation of monocyte-macrophage chemotaxis in the endothelium. Indeed, monocytes and macrophages play a role in accelerating diabetes and in the development of atherosclerosis. They express specific receptors for advanced glycation end products (AGEs), which are proteins or lipids that become nonenzymatically glycated and oxidized after contact with aldose sugars.
After the binding of AGEs and intracellular processing, monocytes/macrophages synthesize and secrete growth-promoting cytokines such as TNF-
Table
Inflammatory parameters assessed in clinical trials of botanicals in diabetes.
Method1 | Botanical or botanical derivatives used | No. of participants |
Parameters measured | Results | Reference |
---|---|---|---|---|---|
Double-blind randomized controlled cross-over trial | Grape seed extract ( |
32 (4 weeks) | hs-CRP | Decreased hs-CRP | Kar et al., 2009 [ |
Double-blind randomized controlled multicenter trial | Pycnogenol (extract of bark from the French Maritime Pine, |
77 (12 weeks) | Endothelin-1 and ketoprostaglandin F1- |
Decreased endothelin-1 and increased ketoprostaglandin F1- |
Liu et al., 2004 [ |
Randomized double-blind controlled trial | Pomegranate ( |
114 (12 weeks) | Plasma MDA | Decrease of MDA |
Kutan Fenercioglu et al., 2010 [ |
Blueberry ( |
42 (4 weeks) | Serum CRP | Decreased hs- CRP | Abidov et al., 2006 [ | |
Single-blind randomized controlled trial | Coffee | 47 (1-month washout, 1 month 4 cups/day, and 1 month 8 cups/day) | CRP, IL-6, IL-1, IL-18, 8-isoprostane, MIF, adiponectin, leptin, and SSA | Decreased IL-18, 8-isoprostane and increased adiponectin and other markers unchanged | Kempf et al., 2010 [ |
Randomized controlled cross-over trial | Green tea ( |
55 (4 weeks) | hs-CRP and major cytokine mediator (IL-6) | Both mediators unchanged | Ryu et al., 2006 [ |
Randomized open controlled clinical trial | Black tea ( |
46 (4 weeks: 150 mL week 1, 300 mL week 2, 450 mL week 3, and 600 mL week 4) | Serum CRP, MDA, and fibrinogen | Decreased serum CRP after consumption of 600 mL and MDA after consumption of 300 mL; |
Neyestani et al., 2010 [ |
Open noncontrolled nonrandomized clinical trial |
|
47 (12 weeks) | Urinary metabolites of thromboxane B2 (TXB2)and prostacyclin (PGI2) | Decreased urinary TXB2and PGI2 | Kudolo et al., 2003 [ |
Prospective cohort studies | Coffee | 2040 (6 years) |
Adiponectin | Higher in drinkers of >4 cups/day | Williams et al., 2008 [ |
Macrophage migration inhibitory factor (MIF) and malondialdehyde (MDA).
1Clinical studies used to assess inflammatory parameters are listed from the best to the worst method applied.
The majority of clinical trials evaluating the effect of botanicals on inflammatory biomarkers in diabetic patients were randomized, double-blind randomized controlled trials and randomized, open and controlled studies. The lack of blinding is particularly critical when the treatment is applied versus placebo. In fact, the placebo effect is a major cause of bias due to patient or doctor awareness [
The parameters most frequently measured in clinical trials were as follows: CRP
Serum levels of malondialdehyde (MDA) were measured in three studies [
IL-6 levels were measured in three studies [
Two studies showed a significant reduction of thromboxane
The aim of the present paper was to collect and critically discuss the existing experimental approaches used
No
The writing of this paper was funded by the European Community’s Seventh Framework Programme under Grant agreement no. 245199. It has been carried out within the PlantLIBRA project (website: