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Effect of Collagen Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Skin on UV-induced Photoaging Mice: Molecular Weight Affects Skin Repair

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  • Beijing Engineering and Technology Research Center of Food Additives

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The use of collagen hydrolysates (CHs) as a nutraceutical agent in skin aging has gained increasing attention. Here, the effects of various doses and molecular weights of CH from silver carp skin on photoaging in mice were investigated. The ingestion of CH at 50, 100 and 200 mg per kg body weight led to a dose-dependent increase in the hydroxyproline, hyaluronic acid and moisture contents of the skin, but it had no significant effect on the mice body weight, or on the spleen or thymus index. Furthermore, ingesting CH with lower (LMCH, 200-1000 Da, 65%) and higher molecular weight (HMCH, >1000 Da, 72%) significantly increased the skin components and improved the antioxidative enzyme activities in both serum and skin (p < 0.05); LMCH performed better than HMCH. By contrast, gelatin (>120 kDa) ingestion did not bring a significant change compared to model mice. These results indicated that LMCH exerted a stronger beneficial effect on the skin than did either HMCH and gelatin, which supported the feasibility of using LMCH as a dietary supplement from silver carp skin to combat photoaging.
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Food &
Function
PAPER
Cite this: Food Funct., 2017, 8, 1538
Received 24th September 2016,
Accepted 21st January 2017
DOI: 10.1039/c6fo01397j
rsc.li/food-function
The eect of collagen hydrolysates from silver
carp (Hypophthalmichthys molitrix) skin on
UV-induced photoaging in mice: molecular
weight aects skin repair
Hongdong Song,
a
Mengfei Meng,
a
Xiaofeng Cheng,
a
Bo Li*
a,c,d
and
Chengtao Wang*
b
The use of collagen hydrolysates (CHs) as a nutraceutical agent in skin aging has gained increasing atten-
tion. Here, the eects of various doses and molecular weights of CH from silver carp skin on photoaging
in mice were investigated. The ingestion of CH at 50, 100 and 200 mg per kg body weight led to a dose-
dependent increase in the hydroxyproline, hyaluronic acid and moisture contents of the skin, but it had
no signicant eect on the mice body weight, or on the spleen or thymus index. Furthermore, ingesting
CH with lower (LMCH, 2001000 Da, 65%) and higher molecular weight (HMCH, >1000 Da, 72%) signi-
cantly increased the skin components and improved the antioxidative enzyme activities in both serum
and skin (p< 0.05); LMCH performed better than HMCH. By contrast, gelatin (>120 kDa) ingestion did not
bring a signicant change compared to model mice. These results indicated that LMCH exerted a stronger
benecial eect on the skin than did either HMCH and gelatin, which supported the feasibility of using
LMCH as a dietary supplement from silver carp skin to combat photoaging.
1. Introduction
Skin aging is receiving growing attention due to the increase
in life expectancy. It is widely accepted that the aging of the
skin is induced by both intrinsic and extrinsic factors, includ-
ing aging, hormonal deficiency, malnutrition and ultraviolet
(UV) irradiation.
1
UV-exposure is a principal extrinsic factor for
skin aging, and accounts for as much as 80% of facial aging.
2
The signs of UV-induced skin aging, also called photoaging,
include deep wrinkles, loss of elasticity, increased dryness and
roughness, telangiectasia and irregular pigmentation.
3
The
UVA (320400 nm) and UVB (290320 nm) present in solar UV
irradiation are the main reasons for photoaging. The shorter
UVB only penetrates to the epidermis and particularly induces
direct damage to DNA; whereas longer UVA penetrates through
the epidermis into the dermis and causes most photoaging.
4
UV irradiation-induced reactive oxygen species (ROS) play an
important role in photoaging. In addition to directly attacking
macromolecules, such as proteins, lipids, RNA and DNA,
4
excessive ROS in the skin trigger a series of signaling transduc-
tions that down-regulate the biosynthesis of collagen, which is
a main component in skin, and up-regulate a series of matrix
metalloproteinases (MMPs), thereby causing collagen degra-
dation.
5
These changes in the skin result in the phenotype of
photoaging.
Several approaches, including photo-protection, topical
cosmetics and oral agents, have been developed to prevent and
treat photoaging. The use of diet and oral supplements to
provide appearance benefits has received increasing interest.
Many dietary supplements, such as vitamins,
6
polyphenols,
7
micronutrients,
8
and proteins,
1
have shown beneficial eects
on skin health. In recent years, food scientists have paid
substantial attention to protein hydrolysates as potential func-
tional foods. Collagen is the main constituent of animal skin,
bone and cartilage. The further enzymatic hydrolysis of
collagen results in collagen hydrolysates (CHs). The use of CH
as a dietary supplement against skin aging has received sub-
stantial attention. Many studies have demonstrated that the oral
administration of CH from Chum Salmon skin,
9
cod skin,
10
jellyfish,
11
tilapia,
12
collagen type II from chicken sternal carti-
lage
13
and porcine type I collagen
14
had beneficial eects on
skin aging in both animal experiments and clinical trials.
a
College of Food Science and Nutritional Engineering, China Agricultural University,
Beijing 100083, China. E-mail: libo@cau.edu.cn; Fax: +86 10 6273 7669;
Tel: +86 10 6273 7669
b
Beijing Laboratory for Food Quality and Safety, Beijing Technology and Business
University, Beijing 100048, China. E-mail: wangchengtao@th.btbu.edu.cn
c
Beijing Advanced Innovation Center for Food Nutrition and Human Health, College
of Food Science and Nutritional Engineering, China Agricultural University,
Beijing 100083, China
d
Key Laboratory of Functional Dairy, Ministry of Education, Beijing 100083, China
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The functional activities of protein hydrolysates are greatly
impacted by their molecular structure and weight, which are
highly aected by their processing conditions.
15
Although the
beneficial eects of CH from dierent raw materials on skin
aging have been widely reported, little work has been done to
investigate the eect of dierent CHs resulting from dierent
processing conditions on skin photoaging. Enzymatic hydro-
lysis is a valuable tool for preparing CHs with a varied mole-
cular weight range. It has been reported that CHs with
dierent molecular weights aect their ACE inhibitory activi-
ties and pre-osteoblast cell dierentiation.
16,17
Therefore, it is
essential to investigate the eects of CHs with dierent mole-
cular weights on photoaging skin.
Silver carp (Hypophthalmichthys molitrix) is one of the four
major cultured fish speciesin China, and the production of
cultured silver carp has accounted for almost 1/5 of the
production of freshwater fish.
18
With the rapid development of
the silver carp processing industry, approximately 170 000 tons
of fish skin, bones and scales are generated as by-products
annually.
19
It is therefore urgent to utilize the by-products for
an economical and environmental advantage. Because fish
skin contains a substantial amount of collagen, the combi-
nation of extracting gelatin and further preparing CHs is a
good way to utilize silver carp skin. Therefore, the objective of
the present study is to investigate whether CHs with dierent
molecular weights from silver carp skin has dierent eects
on photoaging skin. Silver carp skin was employed as a raw
material to prepare CHs with dierent molecular weights. The
appropriate administration doses of CH were first determined.
Then, the eects of CH with dierent molecular weights on
skin photoaging were investigated by analyzing the skin com-
ponents and antioxidative indicators.
2. Materials and methods
2.1. Materials and chemicals
Silver carp skin was supplied by Hubei Zhongke Agriculture
Co., Ltd (Jingzhou, China). Casein (from bovine milk), papain
and trypsin were purchased from Sigma-Aldrich (St Louis, MO,
USA). Casein acid hydrolysate (CAH) was purchased from
Beijing Solarbio Science and Technology Co., Ltd (Beijing,
China). Alcalase was purchased from Novozymes (Beijing,
China). Commercial kits used for determining hydroxyproline
(Hyp), hyaluronic acid (HA), superoxide dismutase (SOD), cata-
lase (CAT), and malondialdehyde (MDA) were purchased from
Jiancheng Inst. of Biotechnology (Nanjing, China). All other
chemicals used in the study were of analytical grade or better.
2.2. Collagen hydrolysate preparation
The gelatin from silver carp skin was extracted according to a
previously described method
20
with modifications. Briefly, the
thawed silver carp skin was first treated in 0.05 M NaOH
(1 : 6, w/v) for 60 min to remove the fat and non-collagenous
proteins, and it was then soaked in 0.2% H
2
SO
4
(1 : 6, w/v)
at room temperature for 60 min. After acid treatment and
thorough washing, the swollen skins were soaked in distilled
water at 45 °C for 12 h to extract gelatin. The resultant solution
was centrifuged at 4450gfor 20 min with a refrigerated centri-
fuge (TGL-185, Pingfan Co., Ltd, Changsha, China) to obtain
the upper soluble fractions. The gelatin was enzymatically
hydrolyzed by a mixture of three enzymes ( papain, trypsin and
alcalase) at pH 8.0 for 1.0 h to obtain collagen hydrolysates
(named CHs). Collagen hydrolysates with higher (HMCH) and
lower molecular weight (LMCH) were prepared with mixed
enzymes at pH 8.0 for 0.5 h and 4.0 h, respectively. HMCH and
LMCH were then dialyzed with 200 Da membranes to discard
salt and free amino acids. As the control, casein was enzymati-
cally hydrolyzed by alcalase at pH 8.0 for 4.0 h to obtain casein
peptide (CAP).
2.3. Molecular weight distribution
The molecular weight distribution was determined according
to a previously described method,
21
with slight modification,
using a Shimadzu LC-15C high performance liquid chromato-
graphy (HPLC) system (Shimadzu, Tokyo, Japan) equipped
with a TSK gel G2000 SWXL column (7.8 × 300 mm, Tosoh,
Tokyo, Japan). 10 μL samples (1 mg mL
1
) were loaded onto
the HPLC with a UV detector that monitored at 214 nm.
The determination was performed with 45% (v/v) acetonitrile
containing 0.1% (v/v) trifluoroacetic acid at a flow rate of
0.5 mL min
1
. A molecular weight calibration curve (y=
0.1881x+ 6.5867, y: log MW, x: time, R
2
= 0.9954) was
obtained from the average retention times of the following
markers: aprotinin (6512 Da), bacitracin (1423 Da), Trp-Pro-
Trp-Trp (674 Da), Asn-Cys-Ser (322 Da) and Gly-Ser (146 Da).
2.4. Amino acid composition
The samples were hydrolyzed in 6.0 M HCl at 110 °C for 24 h.
The amino acid compositions were analyzed by reversed-phase
high performance liquid chromatography (HPLC) after phenyl-
isothiocyanate (PITC) derivatization.
22
The mobile phase
consisted of phosphate buer solution with a concentration of
10 mM and pH of 6.9 (A) and acetonitrile (B). A gradient
elution program was used as follows: 05 min, 510% B;
525 min, 1017% B; 2545 min, 1735% B; 4548 min,
35100% B; 4850 min, 100% B; 5058 min, 1005% B;
and 5860 min, 5% B. The mobile phase flow rate was 1.0
mL min
1
. The detection wavelength was set at 254 nm.
The Hyp content in samples was determined using a Hyp
assay kit (Nanjing Jiancheng Bio Inst., Nanjing, China) accord-
ing to the kit instructions.
2.5. Animals
All procedures involving experimental animals were performed
in accordance with the protocols approved by the Committee
for Animal Research of Peking University and conformed to
the Guide for the Care and Use of Laboratory Animals (NIH
publication no. 86-23, revised 1996). The experiment was
approved by the Animal Experimental Welfare & Ethical
Inspection Committee, the Supervision, Inspection and
Testing Center of Genetically Modified Organisms, Ministry of
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Agriculture (Beijing, China), and it was conducted in the
Experimental Animal Center, Supervision and Testing Center
for GMOs Food Safety, Ministry of Agriculture (SPF grade,
Beijing). Five-week-old female Kunming mice (25 ± 2 g, SPF
grade) were purchased from Beijing Vital River Experiment
Animal Technology Co., Ltd (Beijing, China). All mice were
housed in cages (five mice per cage) and were allowed free
access to diet and water. The animal room was maintained at a
temperature of 22 ± 2 °C, relative humidity of 40% to 70%, and
it was artificially illuminated with a 12 h light/dark cycle.
2.6. UV-induced 6-week photoaging model
Mice were randomly divided into 6 groups (n= 12). The
normal group (N) and model group (M) were given normal
saline, whereas the other groups were given 0.4 mL CH at
doses of 50 (CH-50), 100 (CH-100) and 200 mg per kg body
weight (CH-200), respectively. The casein acid hydrolysate
(CAH) group, as the control protein hydrolysate, was given
0.4 mL of CAH with a dose of 100 mg per kg body weight
(CAH-100). Each group was preventively orally administered an
experimental diet for 1 week. Then, UV irradiation was con-
ducted and lasted for 6 weeks, except for the normal group.
Mice backs were epilated with 6% (w/w) sodium sulfide every
3 days before UV irradiation. The dorsal skin was exposed to
UV lamps, consisting of 3 UVA lamps (40 W, wavelength of
320400 nm) and 1 UVB lamp (40 W, wavelength of
290320 nm), once every two days for 6 weeks for 20 min at a
time. The distance from the lamps to the mice back was
30 cm. The irradiation intensity was measured by using a UVA-
radiometer and a UVB-radiometer (Photoelectric Instrument
Factory of Beijing Normal University, Beijing, China). The total
dose of the UVA irradiation and UVB irradiation was 14.36
Jcm
2
and 1.57 J cm
2
, respectively. During UV irradiation,
mice were fed an experimental diet daily. Mice body weight
was measured every week. After 6 weeks, the mice were sacri-
ficed and samples were collected to analyze the spleen index
(SI), thymus index (TI), and the hydroxyproline and hyaluronic
acid contents in skin.
2.7. UV-induced 2-week photoaging model
Mice were randomly divided into 6 groups (n= 30), including
the normal group (N), model group (M), gelatin group, HMCH
group, LMCH group and CAP group. At first, each group was
preventively fed an experimental diet for 1 week. The normal
and model groups were given normal saline. Gelatin, HMCH
and LMCH groups were administered with 0.4 mL samples at
a dose of 200 mg per kg body weight. Then, UV irradiation was
conducted and lasted for 3 days, 3 h per day, except for the
normal group. UV lamps consisted of 3 UVA lamps (40 W,
wavelength of 320400 nm) and 1 UVB lamp (40 W, wavelength
of 290320 nm). The distance from the lamps to the back of
mice was 30 cm. The irradiation intensity was measured by
using a UVA-radiometer and a UVB-radiometer (Photoelectric
Instrument Factory of Beijing Normal University, Beijing,
China). The total dose of the UVA irradiation and UVB
irradiation was 18.47 J cm
2
and 2.01 J cm
2
, respectively.
After UV irradiation, mice were continuously fed an experi-
mental diet for 2 weeks. Ten mice in each group were sacri-
ficed at weeks 0, 1, and 2 after UV-irradiation, and the samples
were collected for analysis.
2.8. Measurement of SI and TI
The spleen and thymus were excised from mice and immedi-
ately weighed. The SI and TI were calculated according to the
following equation: SI or TI (mg g
1
) = (weight of spleen or
thymus)/body weight.
11
2.9. Determination of the hydroxyproline content
Determination of the hydroxyproline content was performed
using a hydroxyproline assay kit (Nanjing Jiancheng Bio Inst.,
Nanjing, China). Briefly, 50 mg of skin tissue was hydrolyzed
by sodium hydroxide and oxidized by chloramine-T. Then, the
oxidized products reacted with dimethyl-amino-benzaldehyde
to form the end product with the maximal absorption at
550 nm. The amount of hydroxyproline in the skin was deter-
mined by comparison with the absorbance of the hydroxy-
proline standard.
2.10. Determination of hyaluronic acid content
0.8 g of skin sample was homogenized in 7.2 g pre-cooling
saline and centrifuged at 4450gfor 10 min. The supernatant
was collected to quantify the skin hyaluronic acid using an
enzyme-linked immunosorbent assay with a hyaluronic acid
measurement kit (Nanjing Jiancheng Bio Inst., Nanjing, China).
2.11. Measurement of moisture content
The moisture content of the skin sample was determined by
drying the samples in an oven at 105 °C for 4 h, as described
by GB/T5009.3-2010, China.
2.12. Histological analysis
The dorsal skins (approximately 1 cm
2
) were fixed in 4%
neutral formalin, embedded in paran and sliced. Sections
(thickness of 7 µm) were stained with haematoxylin-eosin (HE)
and Van Gieson (VG). The stained sections were analyzed
using an optical microscope.
2.13. Antioxidant indicator analysis
Skin samples were homogenized with 9 weights of pre-cooling
saline and centrifuged at 4450gfor 10 min. The blood samples
were collected from the eyeball and centrifuged to obtain
upper serum. The supernatants from the skin and blood
samples were collected to determine the SOD activity, CAT
activity and malondialdehyde MDA content (expressed as MDA
equivalents) in the skin and blood with the corresponding
diagnostic kits (Nanjing Jiancheng Bio Inst., Nanjing, China).
The protein concentration was measured using serum
albumin as standard.
2.14. Statistical analysis
All data were collected in at least triplicate. Analysis of variance
was conducted, and dierences between variables were tested
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for significance by one-way analysis of variance using a
Statistical Analysis System (SAS 16.0S, AS Institute, Cary, NC,
USA). A dierence was considered statistically significant for
p< 0.05.
3. Results and discussion
3.1. Dose eect
3.1.1. Body weight, spleen index (SI) and thymus index
(TI). The body weight and organ indices could be used to preli-
minarily determine whether a sample had obvious toxico-
logical eects on the body.
23
Therefore, a 6-week photoaging
model was employed to analyze the mice body weight, SI and
TI. As shown in Table 1, treatment with CH (50200 mg per kg
body weight) for 6 weeks did not cause obvious adverse eects
on mice growth because no statistically significant dierences
in the body weight were observed between the CH-treated mice
and normal mice.
The average values of SI and TI in the normal group were
3.41 and 2.47, respectively. The SI and TI in the model group
had no statistically significant dierences compared to the
normal group. This result indicated that UV irradiation used
in this study has no significant eect on both the SI and TI,
although a previous study has reported that UV irradiation
decreased the SI and TI.
11
One possible explanation for
this disagreement is the dierence in the intensity of UV
irradiation used. The total dose of UV irradiation in the
present study (13.68 J cm
2
of UVA and 1.4 J cm
2
of UVB) was
significantly lower than that (26.76 J cm
2
of UVA and 2.55
Jcm
2
of UVB) in the previous report. Therefore, we speculate
that the relative weak UV irradiation may not lead to observed
eects on the SI and TI. Recently, Chen et al. also reported the
eect of UV irradiation on the SI and TI.
24
They found that UV
irradiation resulted in a significant decrease in TI. However,
UV irradiation had no significant eect on SI, which agrees
with our result.
The spleen and thymus are two important immune organs.
The spleen contains many lymphocytes and macrophages, and
the thymus is where T cells dierentiate and mature. The SI
and TI could be used as indicators of immunity.
10
The data in
this study indicate that oral administration of CH (50200 mg
per kg body weight) had no observed damage on the mice
immune organs. Overall, on the basis of the results from
Table 1, doses of 50200 mg per kg body weight of CH have no
obvious toxicological eects on mice in the present study.
3.1.2. Skin components. Collagen, hyaluronic acid (HA)
and moisture in the skin are important components of the
dermis, and play an important role in the skin appearance and
function. Hydroxyproline is a peculiar amino acid, and
approximately 12.5% is found in collagen.
25
Therefore, the
hydroxyproline content is used to estimate the skin collagen
content. As shown in Table 2, UV irradiation significantly
reduced the hydroxyproline, HA and moisture content of
dorsal skin (p< 0.05 vs. the normal group). The oral adminis-
tration of CH dose-dependently increased the hydroxyproline,
HA and moisture content. CH at 100 and 200 mg per kg body
weight led to significantly increased hydroxyproline, HA and
moisture content compared to the model group (p< 0.05),
which indicated that CH ingestion significantly enhanced the
production of collagen and HA, and improved skin dehydra-
tion. These results are consistent with previous reports.
26,27
To determine whether the eect of CH ingestion is col-
lagen-specific, CAH was recruited as a control protein hydro-
lysate in this study. CAH contained all amino acids, and it was
usually used as a control.
28
Administration of CAH at a dose of
100 mg per kg body weight did not increase the hydroxy-
proline, HA or moisture content of the dorsal skin (p> 0.05 vs.
the model group). This implies that the eect of CH was
Table 1 Body weight, spleen index (SI) and thymus index (TI) of UV-irradiated mice after the administration of CH for 6 weeks
Group
a
Body weight (g) Spleen index
b
(mg g
1
)Thymus index
b
(mg g
1
)Week 1 Week 2 Week 3 Week 4 Week 5 Week 6
N 24.49 ± 0.98 29.06 ± 1.54 30.11 ± 1.61 31.12 ± 2.05 33.44 ± 2.52 34.06 ± 2.57 3.41 ± 0.30 2.47 ± 0.30
M 23.76 ± 1.51 28.19 ± 1.62 29.90 ± 1.92 30.96 ± 1.85 32.59 ± 2.28 33.15 ± 2.06 3.36 ± 0.45 2.45 ± 0.30
CH-50 24.26 ± 1.56 27.95 ± 1.21 29.43 ± 1.63 30.79 ± 1.74 32.53 ± 2.03 33.44 ± 2.20 3.52 ± 0.34 2.35 ± 0.27
CH-100 24.27 ± 1.15 27.72 ± 1.78 29.83 ± 1.72 31.16 ± 1.95 32.74 ± 2.06 33.41 ± 2.25 3.70 ± 0.39 2.21 ± 0.24
CH-200 24.73 ± 0.66 28.59 ± 1.18 30.31 ± 1.30 31.17 ± 1.59 32.78 ± 1.80 34.53 ± 2.03 3.59 ± 0.32 2.44 ± 0.32
CAH-100 24.31 ± 1.09 28.30 ± 2.18 29.71 ± 2.14 30.52 ± 2.49 32.46 ± 2.58 33.31 ± 2.32 3.77 ± 0.23 2.50 ± 0.17
a
N, normal group; M, model group; CH, collagen hydrolysate; and CAH, casein acid hydrolysate; 50, 100 and 200 represent administration doses
of 50, 100 and 200 mg per kg body weight, respectively. The values are shown as the mean ± SD.
b
Indicates values at week 6.
Table 2 Skin hydroxyproline, hyaluronic acid (HA) and water content of
UV-irradiated mice after administration of CH for 6 weeks
Group
a
Hydroxyproline
content (μgg
1
)HA content
(ng g
1
)Water content
(%)
N 3374.51 ± 344.58 4251.62 ± 209.50 69.72 ± 1.28
M 1864.62 ± 371.31 3215.50 ± 18.75 60.38 ± 0.43
CH-50 2024.75 ± 294.75 3311.37 ± 182.12 62.33 ± 3.12
CH-100 3005.55 ± 239.44* 3925.25 ± 556.25* 68.05 ± 1.80*
CH-200 3039.70 ± 498.48* 3947.50 ± 228.88* 69.12 ± 3.44*
CAH-100 1887.07 ± 33.45 3292.00 ± 127.87 62.64 ± 2.69
a
N, normal group; M, model group; CH, collagen hydrolysate; and
CAH, casein acid hydrolysate; 50, 100 and 200 represent administration
doses of 50, 100 and 200 mg per kg body weight, respectively. The
values are shown as the mean ± SD. Significant dierence at *p< 0.05
(vs. the model group).
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collagen-specific and did not solely depend on an increase in
the amino acid intake, which agrees with previous report.
29
The oral administration of CH increased the hydroxyproline,
HA and moisture content in a dose-dependent manner. It is
noteworthy that at doses of 100 and 200 mg per kg body
weight, the CH groups had no significant dierence compared
to the normal group (p> 0.05). However, the CH-200 group
showed the most obvious eect among the groups. Therefore,
a dose of 200 mg per kg body weight was used in subsequent
experiments.
To observe a significant eect of CHs on photoaging skin,
the experimental period that is widely reported in preclinical
studies and clinical trials usually lasts for more than
6 weeks.
13,30,31
However, in the present study, we found that
CH could result in a significant repair of photoaging skin
within approximately 2 weeks after oral administration.
Therefore, a 2-week photoaging model was established and
employed in the following experiment.
3.2. Molecular weight eect
3.2.1. Characterization of collagen hydrolysates. Gelatin
and collagen hydrolysates with higher (HMCH) and lower
molecular weight (LMCH) were used to investigate the eects
of molecular weight of collagen hydrolysates on the repair of
the photoaging skin. The molecular weight distributions and
amino acid compositions are summarized in Tables 3 and 4.
Gelatin had a main molecular weight distribution of 120 kDa
to 220 kDa (characterized by SDS-PAGE). HMCH had a broader
molecular weight distribution, and peptides in molecular
weight ranges of >1000 Da accounted for approximately
72% of the total content. LMCH mainly consisted of peptides
in molecular weight ranges of 5001000 Da, with the
2001000 Da peptides accounting for approximately 65%. CAP
mainly consisted of peptides in molecular weight ranges of
5002000 Da, and the peptides of 2001000 Da accounted for
approximately 39%.
The content of each amino acid residue was obtained by
dividing its content by the total content of the amino acid resi-
dues, and the result is shown in Table 4. Consistent with the
Gly-X-Y repeating sequence in the collagen molecule, Gly is the
most dominant amino acid in gelatin, HMCH and LMCH. As a
peculiar amino acid in collagen, Hyp accounted for approxi-
mately 6% in these three collagen hydrolysates. In addition,
gelatin, HMCH and LMCH also have high levels of Ala, Pro
and Arg. In contrast, CAP has a dierent amino acid profile
and the highest content of Glu (approximately 24%).
3.2.2. Gross appearance of the skin. The gross appearances
of the mice dorsal skin are shown in Fig. 1. The normal group
had a smooth, shiny dorsal skin, whereas a significant change
in the skin appearance was seen after UV irradiation treat-
ment. Erythema formation was the most obvious change in all
UV exposure groups at week 0. In addition, roughness and
wrinkling were also observed. Gelatin ingestion did not have a
visible significant dierence compared to the time-matched
model group throughout the experimental period. For HMCH
and LMCH groups, at week 1, obviously reduced erythema and
wrinkling and improved skin roughness were observed; the
LMCH group performed better than the HMCH group. This
positive eect was more pronounced at week 2. In particular,
there was no visible significant dierence between the LMCH
and the normal groups. In contrast, there was no significant
improvement in the skin appearance in the CAP treatment
groups compared to the time-matched model group.
Exposure to UV irradiation leads to alterations in the appear-
ance and biochemical composition of the skin. Erythema is a
Table 3 Molecular weight distributions of gelatin, HMCH and LMCH
Sample
a
Relative content (%)
200500 Da 5001000 Da 10002000 Da 20003000 Da >3000 Da
HMCH 6.86 21.31 29.31 13.23 29.61
LMCH 8.70 56.12 25.92 6.52 2.6
CAP 7.23 31.61 34.03 17.36 12.57
Gelatin About 120 kDa to 220 kDa
a
HMCH, collagen hydrolysate with higher molecular weight; LMCH, collagen hydrolysate with lower molecular weight; and CAP, casein peptide.
Table 4 Amino acid compositions of gelatin, HMCH and LMCH
Amino acid
Content (%)
Gelatin HMCH LMCH CAP
Asp 16.65 1.50 6.63 8.32
Glu 0.71 3.35 2.10 23.44
Ser 1.86 4.11 4.72 2.92
Gly 23.05 25.14 22.93 1.35
His 0.59 0.70 0.06 4.37
Thr 2.98 3.04 5.22 3.75
Ala 10.16 12.14 16.03 5.01
Pro 13.57 14.51 12.27 11.81
Arg 9.20 10.23 10.10 4.26
Tyr 1.13 0.62 0.87 7.01
Val 1.76 2.37 2.09 6.67
Met 2.30 2.86 0.09 3.67
Cys 0.13 0.05 0.14 0.13
Ile 0.13 1.75 0.14 0.13
Leu 2.74 2.95 3.04 10.65
Phe 2.73 3.18 2.95 6.10
Lys 4.25 5.54 4.48 0.06
Hyp 6.01 6.75 6.51 0.36
HMCH, collagen hydrolysate with higher molecular weight; LMCH,
collagen hydrolysate with lower molecular weight; and CAP, casein
peptide.
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common acute adverse skin reaction induced by UV
irradiation.
32
However, HMCH and LMCH were found to signifi-
cantly suppress the development of UV-induced erythema.
Wrinkle formation was related to changes in the epidermal and/
or dermal components of the skin. Loss of water and degene-
ration of dermal collagen fiber bundles increase the appearance
of wrinkles.
33,34
LMCH and HMCH significantly suppress
wrinkle formation, which indicated that the beneficial eects
may be related to the increased moisture and collagen content
of the skin (see below). Overall, according to Fig. 1, the oral
administration of LMCH and HMCH, rather than gelatin, signi-
ficantly reduced skin wrinkles and improved skin roughness.
3.2.3. Skin components. Skin weight and skin com-
ponents, including moisture, hydroxyproline and HA content
are shown in Fig. 2. In response to UV irradiation, there was a
significant increase in the mice skin weight and a decrease in
the skin moisture, hydroxyproline content and HA content in
the model group compared to the normal group (p< 0.05).
The oral administration of gelatin did not lead to a significant
change in the skin weight and skin components, which indi-
cated that gelatin had no beneficial eect on the repair of
photoaging skin. However, the oral administration of HMCH
and LMCH led to a significant decrease in the skin weight and
increased the skin moisture, hydroxyproline and HA content
(p< 0.05 vs. the model group) in weeks 1 and 2. In particular,
for LMCH, at week 0, a significant increase in skin moisture
and hydroxyproline content were observed, which indicated
that preventive oral administration of LMCH was eective
against skin photoaging. At week 2, the skin weight and skin
components in the LMCH group reached a normal level, with
no significant dierence compared to the normal group (p>
0.05). As a control, CAP ingestion did not have a significant
eect on the skin weight and skin components compared to
the model group (p> 0.05) throughout the present experi-
ments. Overall, collagen hydrolysates aected skin weight
and skin components in a molecular weight-dependent and
collagen-specific manner.
UV irradiation induced an abnormal increase in the skin
weight, and this may be explained by several factors, including
the increase in the glycosaminoglycan and epidermal thick-
ness (see below in Skin histology). Skin moisture was specu-
lated to be a critical determinant in skin aging, which may
be responsible for the wrinkling and laxity of the skin.
33
Fig. 1 Gross appearances of UV-irradiated mice skin after the adminis-
tration of gelatin, HMCH and LMCH, for 2 weeks. N, normal group;
M, model group; HMCH, collagen hydrolysate with higher molecular
weight; LMCP, collagen hydrolysate with lower molecular weight; and
CAP, casein peptide.
Fig. 2 Skin weight (a), moisture content (b), hydroxyproline content (c) and hyaluronic acid content (d) of UV-irradiated mice after the adminis-
tration of gelatin, HMCH and LMCH, for 2 weeks. N, normal group; M, model group; HMCP, collagen hydrolysate with higher molecular weight;
LMCP, collagen hydrolysate with lower molecular weight; and CAP, casein peptide. The values are shown as the mean ± SD. Signicant dierence at
*p< 0.05 (vs. the model group). No signicant dierence at
#
p> 0.05 (vs. the normal group).
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As observed in a previous study,
35
collagen hydrolysate treat-
ments significantly increased the moisture content in the skin,
thus indicating their beneficial eect against wrinkle for-
mation. HA functions as a type of large water storage, which is
essential for maintaining the skin moisture and elasticity.
36
The hydroxyproline content reflects the collagen level in mice
dorsal skin. The hydroxyproline content was significantly
increased after the oral administration of HMCH and LMCH,
and LMCH performed better than HMCH in the present
experiments. The increase in the skin components after
HMCH and LMCH ingestion, including moisture, hydroxy-
proline and HA content, may contribute to the reduced skin
wrinkles and roughness, as discussed above.
3.2.4. Skin histology. Sections of mice dorsal skin were
stained with haematoxylin and eosin (HE) and the images are
shown in Fig. 3A. UV irradiation resulted in sparse skin tissue,
a thickened epidermis and enlarged sebaceous glands com-
pared to the normal group at week 0. After UV irradiation,
the self-repair of skin tissue was observed at weeks 1 and 2.
Gelatin ingestion did not lead to a visible change compared to
the time-matched model group. The insults induced by UV
irradiation were greatly improved by the oral administration of
HMCH and LMCH at week 2. However, no significant change
was observed in the CAP groups compared to the time-
matched model group. To further determine the change in the
skin collagen morphology, sections of mice dorsal skin were
stained with Van Gieson (VG), and the results are shown in
Fig. 3B. Collagen fibres in the dermis of the model group
appeared to be more sparse, fragmented, and disorganized
than did those of the normal group. Compared with the model
group, the collagen fibres of HMCH and LMCH groups were
obviously denser at week 1 and especially at week 2. Treatment
with gelatin and CAP did not have a visible protective eect
against collagen damage.
The epidermis and dermis are the two primary layers in
skin.
37
The outermost epidermis forms a protective barrier to
retain water inside and prevent pathogens from entering.
Keratinocytes are the most abundant cells in the epidermis,
and they are involved in the creation of a highly eective physi-
cal barrier. UV irradiation could induce keratinocyte prolifer-
ation and epidermal hyperplasia by activating the epidermal
growth factor receptor, which may explain epidermis thicken-
ing.
38
A thickened epidermis could protect the skin better
from UV penetration, and this may be viewed as an adaptive
response to UV irradiation. HMCH and LMCH treatment,
rather than treatment with gelatin and CAP, significantly
decreased the epidermal thickness, although its mechanism
remains unclear. Another obvious change after UV exposure is
the enlargement of sebaceous glands. UV irradiation could
activate the function of the sebaceous gland to secrete an
increased amount of sebum on the skin surface and peroxide
in the secretions, damaging the barrier functions of the skin.
39
Ingested HMCH and LMCH could normalize the sebaceous
glands, indicating their protective eect on UV-exposed skin.
Collagen is the main fibrillar component of skin and account
for 7080% of the dry weight of the skin.
40
In contrast, the
sparse, fragmented, and disorganized collagen fibres in
dermis were significantly prevented after collagen hydrolysate
pretreatment, especially LMCH treatment. Overall, according
to Fig. 13, it was demonstrated that the oral administration of
unhydrolysed gelatin did not have a visible protective eect on
photoaging skin, whereas the ingestion of LMCH and HMCH
led to a significant beneficial eect on the repair of photo-
aging skin, and LMCH performed better than HMCH.
The above results demonstrated that gelatin, HMCH and
LMCH exhibit significantly dierent eects on mice dorsal
skin in a molecular weight-dependent manner. One possible
explanation is the dierence in their bioavailability. Previous
studies have reported that the relative and absolute bioavail-
ability of partially hydrolyzed gelatin was higher than that of
macromolecular collagen.
41,42
Oesser et al. reported that 95%
of externally applied gelatin hydrolysate, a progressive enzymo-
lysis product, could be absorbed within the first 12 h.
43
Therefore, it appears that CHs, with a lower molecular weight,
can be absorbed more easily. Indeed, it has been reported that
small peptides are more easily absorbed in the intestinal tract
than larger molecules and that oligopeptides (<1000 Da) are
more bioactive than proteins, polypeptides and free amino
acids.
44,45
LMCH had a higher oligopeptide content (2001000
Da accounting for 65%) than HMCH (2001000 Da, 28%),
which may make LMCH exert a stronger beneficial eect on
the repair of photoaging skin.
3.2.5. Antioxidant indicators in serum and skin. The
superoxide dismutase (SOD), catalase (CAT), and malondialde-
hyde (MDA) content both in serum and skin are shown in
Fig. 3 Image of dorsal skin section staining of UV-irradiated mice
after the administration of gelatin, HMCH and LMCH, for 2 weeks.
(a) Haematoxylin-eosin staining (HE, Ã200) and (b) Van Gieson staining
(VG, Ã400). N, normal group; M, model group; HMCP, collagen hydro-
lysate with higher molecular weight; LMCP, collagen hydrolysate with
lower molecular weight; and CAP, casein peptide.
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Table 5. The SOD and CAT activities in the model group were
significantly decreased in both serum and skin compared to
the normal group (p< 0.05), whereas the MDA level was sig-
nificantly increased (p< 0.05). HMCH and LMCH ingestion
could enhance the SOD and CAT activities and reduce the
MDA level of serum and skin (p< 0.05 vs. the model group). It
is noteworthy that LMCH showed much stronger eects than
HMCH, and that there was no significant dierence between
the LMCH treated group and the normal group (p> 0.05). In
contrast, orally administered gelatin and CAP did not signifi-
cantly increase the SOD and CAT activities or decrease the
MDA content in serum and skin compared to the model group
(p> 0.05). The results were consistent with those obtained for
skin components and skin histology.
UV irradiation-induced reactive oxygen species (ROS) have
been reported to be implicated in the onset of skin diseases,
mainly in the indirect signaling pathway.
5
Therefore, skin
damage could be prevented by scavenging ROS. The body has
a complex and robust network of anti-oxidant molecules to
alleviate the UV-induced oxidative stress. SOD is a major anti-
oxidant enzyme that inactivates superoxide anions, whereas
catalase detoxifies hydrogen peroxide. MDA is an aldehyde
that is usually quantified to estimate the lipid peroxidation
induced by ROS. Lipid hydroperoxide is harmful to cells,
because of its interaction with normal biomolecules. UV
irradiation significantly decreased the activities of SOD and
CAT and increased the CAT content. However, when treated
with HMCH and LMCH, the decrease in the enzyme activities
and increase in the CAT content were significantly prevented,
which is consistent with a previous report.
46
The eects of
LMCH on the enzyme activities may be due to its higher anti-
oxidative properties and bioavailability, as a previous study
reported that protein hydrolysates with low molecular weight
showed high scavenging ROS activity and could easily be taken
up in the intestine.
47
Chronic exposure of the skin to UV irradiation damages
the skin structure, leading to photoaging.
30
UV irradiation-
induced ROS play an important role in photoaging. The
present results showed that the oral administration of LMCH
and HMCH not only had a beneficial eect on the repair of
photoaging skin, but it also enhanced the bodys antioxidant
capacity. Therefore, we speculated that LMCH and HMCH
exhibited beneficial eects on photoaging skin by, at least par-
tially, enhancing the bodys antioxidant capacity. It is also
possible that LMCH and HMCH exerted bioactive eects in
other ways. Several studies have reported that Pro-Hyp is a
major constituent of Hyp-containing peptides in human
plasma after the oral ingestion of collagen hydrolysates.
48,49
Pro-Hyp has chemotactic activity for fibroblasts and signifi-
cantly increases fibroblast growth.
50,51
Therefore, it is specu-
lated that the active components from collagen hydrolysates
stimulated the fibroblasts and activated signaling for collagen
and HA synthesis. The mechanisms of collagen hydrolysates
against skin photoaging require further study.
4. Conclusion
The present study demonstrated that the molecular weight of
collagen hydrolysates from silver carp skin aected skin repair
in photoaging mice. Orally administered LMCH resulted in a
stronger beneficial eect on skin repair than did HMCH. By con-
trast, macromolecular gelatin ingestion did not have a beneficial
eect on photoaging skin. In addition, collagen hydrolysates
promoted skin repair in a collagen-specific manner compared to
casein hydrolysate, and one of the mechanisms of action may be
involved in enhancing the antioxidant properties in the body.
The results provide an alternative perspective in collagen-related
product processing, and LMCH from silver carp skin is a poten-
tial dietary supplement for use against photoaging.
Conict of interest
There is no conflict of interest to declare.
Acknowledgements
This study was supported by the earmarked fund from the
China Agriculture Research System (CARS-46), the project
from the Ministry of Science and Technology of China (no.
2011AA100803), and the fund of the Beijing Laboratory for
Table 5 SOD and CAT activities and MDA content of UV-irradiated mice after administration of gelatin, HMCH and LMCH for 2 weeks
Group
a
Serum Skin
SOD (U mL
1
) CAT (U mL
1
)MDA
(nmol mL
1
)SOD
(U per mg protein) CAT
(U per mg protein) MDA equivalents
(nmol per mg protein)
N 232.95 ± 5.10 11.24 ± 0.61 10.89 ± 0.79 170.96 ± 1.66 4.49 ± 0.19 2.68 ± 0.21
M 133.86 ± 7.46 4.30 ± 0.35 19.88 ± 0.27 99.2 ± 2.73 2.98 ± 0.22 7.27 ± 0.21
Gelatin 135.93 ± 7.21 4.37 ± 0.27 19.58 ± 0.98 99.67 ± 2.76 3.26 ± 0.16 7.16 ± 0.22
HMCH 197.20 ± 9.64* 9.03 ± 0.62* 14.11 ± 1.00* 146.98 ± 3.05* 4.05 ± 0.21* 4.20 ± 0.37*
LMCH 227.35 ± 4.51*
#
10.73 ± 0.52*
#
11.31 ± 0.79*
#
169.20 ± 0.52*
#
4.40 ± 0.16*
#
2.79 ± 0.19*
#
CAP 137.99 ± 4.98 4.49 ± 0.53 18.69 ± 0.73 102.51 ± 3.34 3.27 ± 0.34 7.01 ± 0.13
a
N, normal group; M, model group; HMCH, collagen hydrolysate with higher molecular weight; LMCH, collagen hydrolysate with lower mole-
cular weight; and CAP, casein peptide. The values are shown as the mean ± SD. Significant dierence at *p< 0.05 (vs. the model group). No sig-
nificant dierence at
#
p> 0.05 (vs. the normal group).
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Food Quality and Safety, Beijing Technology and Business
University.
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... FPH has been widely used as a supplement or fortification in several foods, especially drinks. Table 1 31,39,[42][43][44][45][46][47][48][49] reports skin health-promoting abilities of CH and GH. Recently, Benjakul et al 42 reported that HC from sea-bass skin induced the proliferation of fibroblast cells (L929 cell) dose dependently. ...
... 47 The effects of various doses (50, 100 and 200 mg/kg body weight) and molecular weight (<1000 Da and >1000 Da) of CH from the skin of silver carp on photoaging mice were examined. 48 The ingestion of CH resulted in an increase in the hyaluronic acid, hydroxyproline, and moisture contents of the skin dose dependently, without affecting the body composition. Moreover, lower-molecular-weight CH effectively upregulated the antioxidant enzyme system in both serum and skin, and increased skin components (P < 0.05). ...
... Therefore, low-molecular-weight CH performed better than higher-molecular-weight CH and could be used as a potential dietary supplement. 48 Collagen peptide (CP) prepared from fish scales was treated with human dermal fibroblast cells at 50-500 mg/mL concentrations. The result showed an increase in the synthesis of type-I procollagen and a decrease in the matrix metalloproteinase-1 production in human dermal fibroblast cells. ...
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Ultraviolet (UV)-induced photoaging skin has become an urgent issue. The functional foods and cosmetics aiming to improve skin photoaging are developing rapidly, and the demand is gradually increasing year by year. Collagen peptides have been proven to display diverse physiological activities, such as excellent moisture retention activity, hygroscopicity, tyrosinase inhibitory activity and antioxidant activity, which indicates that they have great potential in amelioration of UV-induced photoaging. The main objective of this article is to recap the main mechanisms to improve photoaging skin by collagen peptides and their physiological activities in photo-protection. Furthermore, the extraction and structural characteristics of collagen peptides are overviewed. More importantly, some clinical trials on the beneficial effect on skin of collagen peptides are also discussed. In addition, prospects and challenges of collagen peptides are emphatically elucidated in this review. This article implies that collagen peptides have great potential as an effective ingredient in food and cosmetics industry with a wide application prospect.
... The ingestion of collagen hydrolysate led to a dose-dependent increase in the skin content of hydroxyproline, HA, and moisture. Moreover, ingesting collagen hydrolysate with lower (200-1000 Da, 65%) and higher molecular weight (>1000 Da, 72%) markedly improved the antioxidative enzyme activities in both serum and skin of Kunming mice [10]. ...
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Skin photoaging is mainly induced by ultraviolet (UV) irradiation and its manifestations include dry skin, coarse wrinkle, irregular pigmentation, and loss of skin elasticity. Dietary supplementation of nutraceuticals with therapeutic and preventive effects against skin photoaging has recently received increasing attention. This article aims to review the research progress in the cellular and molecular mechanisms of UV-induced skin photoaging. Subsequently, the beneficial effects of dietary components on skin photoaging are discussed. The photoaging process and the underlying mechanisms are complex. Matrix metalloproteinases, transforming growth factors, skin adipose tissue, inflammation, oxidative stress, nuclear and mitochondrial DNA, telomeres, microRNA, advanced glycation end products, the hypothalamic–pituitary–adrenal axis, and transient receptor potential cation channel V are key regulators that drive the photoaging-associated changes in skin. Meanwhile, mounting evidence from animal models and clinical trials suggests that various food-derived components attenuate the development and symptoms of skin photoaging. The major mechanisms of these dietary components to alleviate skin photoaging include the maintenance of skin moisture and extracellular matrix content, regulation of specific signaling pathways involved in the synthesis and degradation of the extracellular matrix, and antioxidant capacity. Taken together, the ingestion of food-derived functional components could be an attractive strategy to prevent skin photoaging damage.
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This study aimed at clarifying the mechanism by which sweet potato leaf polyphenols (SPLPs) ameliorate ultraviolet (UV) radiation damage, using the BALB/c hairless female mouse model. The moisture and hydroxyproline (HYP) contents of the model mouse skin and the thickness of the epidermis and dermis were determined by staining and histological examination. Anti-oxidative enzyme activities, malondialdehyde (MDA) content, and protein carbonyl content in skin tissue and serum were investigated. Expression of inflammatory markers and mitogen-activated protein kinase signaling pathways were evaluated. Topical caffeic acid at 30 mg kg-1 most strongly inhibited the decrease in skin moisture, HYP content, and the thickening of the epidermis. Topical SPLP at 100 mg kg-1 most significantly inhibited the dermal thickening, increased the activities of the superoxide dismutase, catalase as well as glutathione peroxidase, and decreased the content of serum MDA and protein carbonyls markedly. Furthermore, the topical SPLP suppressed the UV-induced rise in the inflammatory markers MMP-1, TNF-α, and NF-κB, and alleviated phosphorylation levels of the stress-signaling proteins JNK and p38. Thus, topical SPLP provided the best overall protection for mouse skin from UV-induced damage.
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Collagen is the most abundant extracellular matrix protein in food-producing animals. Gelatin is partially degraded collagen. Collagen peptides refer to the peptides with specific properties identified from collagen hydrolysate who produced by hydrolysis of collagen/gelatin. Due to the specific structural and bio- and physical-chemical properties, collagen and its derivatives are used in the field of food industry. In this review, the structure of the collagen molecule and its biosynthetic process in vivo are introduced, and the production methods and structures of gelatin and collagen peptides described. Then the inherent self-assembly property of collagen, the mechanical properties of collagen and gelatin gels, functional properties of collagen and gelatin, and bioactive properties of collagen peptides are reviewed. Finally, the applications of collagen and its derivatives that are correlated with their properties in food industry are summarized. The mechanisms and advantages of the applications of collagen and its derivatives in food industry are raised, and the limitations and challenges of these applications are also discussed. And possible studies to address the challenges of the applications in different areas are indicated.
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Our study aimed at investigating the effect of different molecular weight bovine collagen peptides, namely CH878, CH1370, CH2900, and CH7747 on the differentiation of MC3T3-E1 cells. Osteogenic differentiation of MC3T3-E1 cells was assessed by a series of specific assays, after culturing of cells in the presence of collagen peptides. Alkaline phosphatase activity (ALP) was evaluated by NBT/BCIP staining. Osteocalcin expression was determined by a radioimmunology method. Mineralization was quantified by Alizarin Red staining. ALP staining results demonstrated that the ALP staining of cells after culture in the presence of collagen peptides were significantly higher than the control group (P<0.05), indicating the promotion of ALP activity in MC3T3-E1 cells by these peptides. Radioimmunology results demonstrated that collagen peptides groups were all significantly higher than the control group (P<0.01). Alizarin Red staining results demonstrated that CH1370, CH2900, and CH7747 significantly promoted the formation of mineralized bone matrix. We therefore conclude that CH1370, CH2900, and CH7747 play an active role in the differentiation of MC3T3-E1 cells. Based on the above results, we provide molecular basis for further development of collagens with different molecular weight for the prevention and treatment of osteoporosis.
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We examined the effect of the daily ingestion of herb extract from Eucommia ulmoides leaves and Korean ginseng on skin damage induced by repeated UV irradiation of hairless mice. The herb extract was orally administered to mice at a dose of 1000 mg/kg/day. The hydration of mice dorsal skin decreased significantly with repeated UV irradiation, but did not decrease when the herb extract was administered for seven weeks. Transepidermal water loss (TEWL) increased with UV irradiation, but decreased with the administration of dietary herb extract. These effects were more pronounced when combined with the administration of collagen hydrolysate. Geniposidic acid from E. ulmoides leaves and ginsenoside Rg1 from Korean ginseng reduced TEWL and increased the skin moisture content of UV-damaged skin on hairless mice, respectively. We concluded that this dietary herb extract reduced the skin damage caused by UV-induced aging, with geniposidic acid and ginsenoside Rg1 detected in the blood.
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The objective of this study was to investigate the effect of gelatin (SG) isolated from salmon skin and its hydrolysate (SGH) on photoaging skin, and the mechanism responsible for anti-photoaging. The average molecular weights of SG and SGH were 65 kDa and 873 Da, respectively. The amino acid compositions of SG and SGH were similar. Both of them were abundant in hydrophobic amino acids. Twenty-five peptides were identified from SGH. SG and SGH could improve UV irradiation-induced pathological changes of macroscopical tissue texture and skin morphology. Hydroxyproline content is an indicator of matrix collagen content, SG and SGH could inhibit the decrease of hydroxyproline content in photoaging skin in a dose dependent manner. In addition, SG and SGH could alleviate UV irradiation-induced oxidative damages to skin by increasing the activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), increasing the content of glutathione (GSH) and decreasing the content of malonaldehyde (MDA). Moreover, SG and SGH could enhance immune regulation system by increasing the thymus index. Thus, the anti-photoaging mechanisms of SG and SGH were by inhibiting the depletion of antioxidant defense components, involving in the synthesis of collagen and enhancing the function of immune system. Besides, SGH showed a better result in protecting skin from photoaging than SG.
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Collagen tripeptide (CTP) is a collagen-derived compound containing a high concentration of tripeptides with a Gly-X-Y sequence. In this study, the concentrations and metabolites of CTP were monitored in rat plasma after its administration. We performed a quantitative analysis using high-performance liquid chromatography tandem mass spectrometry according to the isotopic dilution method with stable isotopes. We confirmed that the tripeptides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp were transported into the plasma. Dipeptides, which are generated by degradation of the N- or C-terminus of the tripeptides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp, were also present in plasma. The plasma kinetics for peroral and intraperitoneal administration was similar. In addition, tripeptides and dipeptides were detected in no-administration rat blood. The pharmacokinetics were monitored in rats perorally administered with Gly-[(3)H]Pro-Hyp. Furthermore, CTP was incorporated into tissues including skin, bone, and joint tissue. Thus, administering collagen as tripeptides enables efficient absorption of tripeptides and dipeptides.
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A low collagen skin mice model was established and used to evaluate the effects of orally administered collagen peptide (CP) and glycine, alanine, and proline mixture (GAP) on the collagen content in the skin of mice. This model was established by feeding mice a low protein diet for 8 weeks. The oral administration of 50 mg/kg of CP led to increased collagen content in the skin, although that effect was counteracted in a dose-dependent manner. The oral administration of GAP led to a dose-dependent increase in the collagen content of the mouse skin. Prolyl-hydroxyproline led to a dose-dependent increase in the proliferation of primary cultured murine fibroblasts, and proline caused an increase in fibroblast differentiation. The results of this study demonstrated that CP and GAP influenced the collagen content of mouse skin by changing the state of fibroblasts.
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The bioavailability and bioavailable forms of collagen after oral administration to rats were investigated in this study. The relative and absolute bioavailability of collagen were 57.8% and 49.6%, respectively, which was indirectly evaluated by the bioavailability of Hyp in collagen using pharmacokinetic method. The amino acid profile of plasma showed that more than 63.4% of the collagen was absorbed from the intestine in the form of peptide and there was a good linear correlation between the absorbed amount of an amino acid and its content in collagen (R2 = 0.9225). The collagen peptides in plasma were purified by Sephadex G10 and Eclipse XDB C18 chromatography and further indentified (Ala-Asn, Ala-Hyp-Gly, Asp-Glu, Glu-Asn, Glu-Asp, Glu-Met, Gly-Pro-Hyp, Leu-Hyp, Leu-Met, Phe-Gly-Asn, Pro-Gly-Leu, Pro-Leu, Ser-Gly-Met, Ser-Hyp, Ser-Pro-Gly, Tyr-Met) with UPLC-ESI-MS. These results may help to speculate about the molecular mechanism behind the physiological effects of collagen after oral administration.
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The rate of skin aging, or that of tissue in general, is determined by a variable predominance of tissue degeneration over tissue regeneration. This review discusses the role of oxidative events of tissue degeneration and aging in general, and for the skin in particular. The mechanisms involved in intrinsic and extrinsic (photo-) aging are described. Since photoaging is recognized as an important extrinsic aging factor, we put special emphasize on the effects of UV exposure on aging, and its variable influence according to global location and skin type. We here summarise direct photochemical effects of UV on DNA, RNA, proteins and vitamin D, the factors contributing to UV-induced immunosuppression, which may delay aging, the nature and origin of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as indirect contributors for aging, and the consequences of oxidative events for extracellular matrix (ECM) degradation, such as that of collagen. We conclude that conflicting data on studies investigating the validity of the free radical damage theory of aging may reflect variations in the level of ROS induction which is difficult to quantify in vivo, and the lack of targeting of experimental ROS to the relevant cellular compartment. Also mitohormesis, an adaptive response, may arise in vivo to moderate ROS levels, further complicating interpretation of in vivo results. We here describes how skin aging is mediated both directly and indirectly by oxidative degeneration.This review indicates that skin aging events are initiated and often propagated by oxidation events, despite recently recognized adaptive responses to oxidative stress.
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A factorial design and response surface methodology were used to optimize the extraction process of tilapia skin gelatin (Oreochromis urolepis hornorum). The concentrations of NaOH (0.15%-0.35%) and H2SO4 (0.15%-0.35%), the extraction temperature (40 degrees C-60 degrees C), and the extraction time (3-15 h) were independent variables. Response variables were yield (%), viscosity (mPa.s), and gel strength (g). The NaOH (%) and H2SO4 (%) concentrations had significant influences (p<0.05) on viscosity and gel strength, while the extraction temperature (degrees C) and the extraction time (h) showed significant influences (p<0.05) on all dependent variables. Increasing the temperature and extraction time provided higher yields with a reduction in the gelatin viscosity and gel strength. Tilapia fish skin can be used as a source for production of gelatin.
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Background Gelatin has long been widely used in foods, pharmaceuticals, cosmetics, and others. However, there is little report on its bioavailability and bioavailable forms presently.ResultsThe relative and absolute bioavailability of gelatin were 74.12% and 85.97%, respectively, which was indirectly evaluated by the bioavailability of total Hyp in gelatin using pharmacokinetic method after oral administration to rats. The amino acid profile of plasma indicated that 41.91% of the digested gelatin was absorbed from the intestine in the form of peptide, and there was a good linear correlation between the absorbed amount of an amino acid and its content in gelatin (R2 = 0.9566). Moreover, 17 kinds of collagen peptides were purified by multistep chromatography and identified with UPLC-ESI-MS.Conclusion Gelatin had high oral bioavailability. Nearly half of digested gelatin was absorbed from the intestine in the form of various collagen peptides.