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- Anthocyanins
- Obesity
- Inflammation
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Date:
06-15-2018 | HC# 111745-594
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Re: Role of Anthocyanins in Obesity and Inflammation
Lee YM, Yoon Y, Yoon H, Park HM, Song S, Yeum
KJ. Dietary anthocyanins against obesity and inflammation. Nutrients. October 1, 2017;9(10):1089. doi: 10.3390/nu9101089.
Obesity, often accompanied by dyslipidemia,
hyperglycemia, and/or hypertension, is a major risk factor for cardiovascular (CV)
and pulmonary diseases, cancer, and diabetes mellitus (diabetes type 2).
Chronic low-grade inflammation both promotes and results from obesity, its
progression, and related diseases. Inflammation, the body's first-line defense
against harmful stimuli, reacts to excessive nutrients much as it reacts to a
wound. Cytokines and chemokines are dispatched to the damaged area and, if repeat
or prolonged harmful stimulus occurs, the immune system will also recruit antigen-presenting
cells and B- and T-lymphocytes to the site of injury. Such chronic adaptive
immunity may increase risks of obesity-related illness. Proinflammatory markers
are significantly higher in obese patients than in healthy individuals. One
possible underlying mechanism is that toll-like receptors (TLRs), especially
TLR4, connect external stimuli, including overfeeding, to transcription factors
like nuclear factor-κB, activated protein-1, and interferon regulatory factor
3. These inflammation-associated transcription factors enter cell nuclei and
bind to target genes. Preventing or ameliorating chronic proinflammatory or
meta-inflammatory conditions is a novel pathway to combat obesity. Obesity-related
mortality and morbidity are rising worldwide. Better options are needed.
Several drugs for obesity were removed from
the market after causing severe adverse events. Consuming plant compounds, like
phenolics, is associated with lower risks of obesity and associated diseases,
with low toxicity. Anthocyanins, a large class of flavonoids, occur abundantly
in flowers, fruits, seeds, and leaves. The primary structural unit of
anthocyanin is 2-phenylchromenylium; it can be further classified into six
major anthocyanins—cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and
petunidin—with varying flavylium B-rings and in some cases sugars (such as
galactose, glucose, and arabinose, etc.) on a basic 2-phenylchromenylium
structure. Anthocyanins' antimicrobial, antioxidative, anti-inflammatory, and
antimutagenic effects have been studied in relation to metabolic diseases,
cancers, eye diseases, and CV diseases. They have been assessed as regulators
of obesity and inflammation in cellular, animal, and human models. Some in
vitro and in vivo models and their strengths and limitations are described by
the authors, with in vitro assays using mouse or human stem cells. In vivo, rats
or mice are favored, divided into those that are genetically obese because of a
recessive mutation involving leptin receptors and those that become obese through
overeating. Still another model uses rats selectively bred to become obese
without high-energy feeding, but there is no discussion of its comparability to
humans. In both cell- and animal-based research, use of differing methods helps
compensate for the limitations of any single method; still, for reliable
knowledge about effects in humans, human subjects must be studied in randomized
controlled trials (RCTs).
In vitro, in vivo, and human studies report
anthocyanins effective against oxidative stress and inflammation. Overall,
mixtures of anthocyanins found in foods are reported more effective than single
compounds. Without discussing their search strategy, the authors discuss
results of 14 cell-line and animal studies that used dietary anthocyanins with well-characterized
bioactive compounds. Among them, a purple sweet potato (Ipomoea batatas, Convolvulaceae) extract had antilipogenic and
anti-inflammatory effects in mouse adipocytes. Red cabbage (Brassica oleracea var. capitata, Brassicaceae)
microgreens reduced weight gain and low-density lipoprotein (LDL),
triacylglycerol, and cholesterol levels in high-energy-fed mice. Blueberry (Vaccinium spp., Ericaceae) fruits and
juice, probably the most-studied anthocyanin-rich foods, have been reported to
reduce weight, blood glucose, liver lipid levels, and inflammatory markers, and
to improve insulin resistance. Similar and/or complementary results were found
for white mulberry (Morus alba,
Moraceae) juice, black currant (Ribes
nigrum, Grossulariaceae), "cherry" (unspecified), tart cherry (Prunus cerasus, Rosaceae), black
elderberry (Sambucus
nigra, Viburnaceae), black soy (Glycine
max, Fabaceae) bean, freeze-dried jaboticaba (Plinia cauliflora, Myrtaceae) peel, and chokeberry (Aronia spp., Rosaceae). Of three human
studies, one RCT used a soy extract with a fully-characterized anthocyanin
dose. Compared to the placebo group, subjects in the soy group at study's end had
less abdominal fat and lower cholesterol, triacylglycerol, LDL, and
inflammatory markers. In two trials of "red orange" (blood orange,
sweet orange; Citrus sinensis,
Rutaceae) juice that was not fully characterized, metabolic and inflammatory
markers were reduced.
Anthocyanins have poor bioavailability, and it
is increasingly understood that it is their metabolites, created during digestion
by gut microbiota, that impact cells, tissues, and signaling systems. Novel
delivery systems such as nanoparticles, encapsulation, liposomes, gel
emulsions, and alginate (from brown algae [class Phaeophyceae])-chitosan (from
shellfish genera) microencapsulation may all increase bioavailability of
anthocyanins.
Obesity was once seen as simply the result of
excess nutrient intake and insufficient expenditure. Awareness of chronic
inflammation's role in its progression and the potential of anthocyanins and
other plant phenolics to halt and reverse weight gain not only offers a novel pathway
to better health, but may decrease the psychological burdens of obesity. Although
not mentioned by these authors, depression and anxiety are deeply linked to
obesity in many reports. Tart cherry juice, for example, may exert antidepressant
and anxiolytic effects, in part by inhibiting monoamine oxidase A and
tyrosinase. This topic should be more deeply explored.
The study was supported by the Rural Development
Administration, Republic of Korea.
—Mariann Garner-Wizard
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