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Chicory extract-induced augmentation of lipogenesis in
sz95 human sebaceous gland cells.
SUMMARY
This study was to explore the lipogenic effect by ethanol extracts of chicory and possible
molecular mechanisms in sebocyte. When SZ95 sebocyte cell line was treated with the chicory
extracts, lipid droplets were accumulated in the majority of cells. Chicory extracts increased
expression of lipid droplets in the SZ95 cells. Chicory extracts augmented expression of
peroxisome proliferator-activated receptor gamma (PPAR-γ) and total cholesterol. These results
suggest that chicory extracts induces lipogenesis in SZ95 cells through PPAR-γ activations.
INTRODUCTION
Mammalian skin is composed of two primary layers, the epidermis, which is derived from
ectoderm, and the dermis, derived from mesoderm. The epidermis is composed, inter alia, of the
outermost layers of the skin. It forms a protective barrier over the body's surface, responsible for
keeping water in the body and preventing pathogens from entering, and is a stratified squamous
epithelium, composed of proliferating basal and differentiated suprabasal keratinocytes. The
epidermis also helps the skin regulate body temperature. In order to maintain healthy skin, the
stratum corneum is a constant state of moisture and lipids, amino acids, organic acids, sebum and
natural moisturizing factors have to be balanced. Dry skin, also called xerosis, is a very common
skin condition that occurs at all ages. Usually, it doesn't represent a serious problem but
sometimes it can be difficult to treat. It feels rough, scaly, sometimes painful, and itchy. Dry skin
results when lipids are depleted and there is not enough water in the stratum corneum for it to
function properly. Equally atopic dermatitis, a common dry skin condition in childhood, shows
reduced lipids levels in the stratum corneum and, consequently, an important loss of water.
Sebaceous glands secrete an oily substance called sebum that is made of fat and the debris of
dead fat-producing cells in the skin of mammals. They are found in hair-covered areas where they
are connected to hair follicles to deposit sebum on the hairs and bring it to the skin surface along
the hair shaft. In the sebaceous glands, sebum is produced within specialized cells, which are
called sebocytes, and is released as these cells burst. Sebaceous lipogenesis resulting in
accumulation of lipid droplets and subsequent sebum secretion represents a major step in the
terminal differentiation of sebocytes. Sebum excretion is associated with the functional
maintenance of the surface of skin by controlling moisture balance and providing native immunity.
Regarding sebaceous lipogenesis disorders, an excess secretion of sebum has been reported to
cause the onset of acne vulgaris and seborrhoea, which are two of the most common skin
diseases. In contrast, a decrease in sebum secretion has been associated with dry skin (xerosis),
the development of which is related to ageing and environmental conditions. Therefore,
pharmacological improvement of sebaceous gland functions is likely to result in the restoration of
skin homeostasis. Chicory is one of the popular healthy vegetables because it has useful
ingredients and abundant dietary fibers. It stimulates the immune system and alleviates intestinal
diseases and harmful bacteria. Chicory contains Vitamin A, Vitamin B2, Vitamin C, potassium, iron,
etc which is good for skin beauty and also helps digestion and blood circulation. The aim of this
study was to address whether or not chicory extracts a biological activity to modulate sebaceous
lipogenesis, which may be associated with the treatment of sebaceous disorders such as xerosis or
childhood atopic dermatitis.
MATERIAL AND METHODS
Oil Red O staining
The Oil Red O Method is a common staining technique used for demonstrating lipids in tissue. It
is performed on fresh frozen sections, as alcohol and xylene dissolves the lipids that are in the
tissue. Oil Red O has largely replaced many Sudan Dyes that were used for demonstrating lipids,
such as Sudan III and Sudan IV, because Oil Red O provides a deeper red color that is easier to
see.
Total cholesterol assay
Total cholesterol assay measure the total cholesterol within serum, plasma, cell lysate, or tissue
samples. The assays will detect total cholesterol (cholesteryl esters plus free cholesterol) in the
presence of cholesterol esterase or only free cholesterol in the absence of the esterase enzyme.
Expression of Reverse transcription-polymerase chain reaction (PCR)
Quantification was achieved by measuring light absorbency at 260 nm. In cases in which either
total RNA quality or quantity was not sufficient to allow further analysis, the extraction procedure
was repeated, using frozen tissue samples. The expression of PPAR-γ1 and PPAR-γ2 was assessed
by quantitative RT-PCR.
RESULTS
140
120
(% of control)
Cell viability
100
80
60
40
20
0
% of control
DMEM
100nM
Control
Linoleic Acid
100
94
25ug/ml
50ug/ml
100ug/ml
200ug/ml
Chicory extract
111
118
117
120
Figure 1. Cell viability assay of Chicory extract on sz95 human sebocytes after 48h treatment
determined by MTT assay. Positive control was sz95 treated with linoleic acid at the highest
concentrations used in the tests. The bars indicate mean ±standard deviation of three
independent experiments performed in triplicate.
160
120
(% of control)
Absorbance of Oil Red O
140
100
80
60
40
20
0
% of control
DMEM
100nM
Control
Linoleic acid
100
130
100ug/ml
200ug/ml
Chicory extract
110
133
Figure 2. Effect of Chicory extract on lipid droplet enlargement in sz95 cells. Pictographic
analysis after Oil red O staining. ⓐ The control group; ⓑ The linoleic acid treated group; ⓒ Low
dose Chicory extract (100ug/ml) group; ⓓ High dose Chicory extract (200ug/ml) group. The
contents of the lipid droplets were significantly higher in the different Chicory extract treatment
groups than in the control group. The values are shown as the means ±standard deviation and
are representative of three independent experiments. *p<0.1 compared to control; one-way
ANOVA, followed by Newman-Keuls Multiple comparison test.
200
160
140
(% of control)
PPARγ/β-Actin mRNA ratio
180
120
100
80
60
40
20
0
% of control
DMEM
100nM
Control
Linoleic Acid
100
157
100ug/ml
200ug/ml
Chicory extract
166
157
Figure 3. Effect of Chicory extract on sz95 human sebocytes mRNA expressions. Chicory
extracts significantly up-regulated mRNA expression of PPAR-γ compared with control group. The
600
500
400
(% of control)
Total cholesterol & Hyaluronan content
expression of PPAR-γ was normalized against β-Actin mRNA expression.
300
200
100
0
DMEM
100nM
100ug/ml
200ug/ml
Control
Linoleic Acid
Total cholesterol
100
442
324
333
Hyaluronan
100
123
149
300
Chicory extract
Figure 4. Effect of Chicory extract on sz95 human sebocytes about total cholesterol and
hyaluronan synthesis. Chicory extracts significantly increased total cholesterol and hyaluronan
content compared with control group.
CONCLUSION
Human sebum is mainly composed of lipids including triglycerides, free fatty acids, and wax esters.
The lipid film formed by sebum not only protects skin by providing a barrier against pathogens
and ultraviolet light, but also protects the skin surface from dehydration as well as oxidative
injuries. During the process of sebum formation, several transcription factors act as primary
regulators in the induction of lipogenic gene expression. Peroxisome proliferator-activated
receptors (PPARs) regulate lipid metabolism by binding with specific DNA sequences in the
promoter region of lipogenic genes. PPAR-α and PPAR- γ are exuberantly expressed in the human
sebaceous gland. In the present study, Chicory extracts treatment dramatically induced
accumulation of lipid droplets in SZ95 sebocytes. Theses extracts significantly induced activation
of PPAR- γ and Hyaluronic acid expression following a 48 h treatment. Through this study, we
propose a pathologic function and molecular mechanisms for extracts-induced lipogenesis and
provide valuable information for the deveolment in dry skin and childhood atopic dermatitis.
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