Cerium dioxide

Repeated dose toxicity: other routes

Administrative data

Endpoint:

short-term repeated dose toxicity: other route

Remarks:

intra-peritoneal route

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not applicable

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: the study was insufficiently detailed in regards to toxicological endpoints allowing the assessment of nano-CeO2 hazard.

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not applicable

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: :

Remarks:

the study was considered to meet generally accepted scientific principles. However, there was no data on detection limit(s) of ICP-AES technique for cerium, on cerium levels in control animals, as well as on the exact number of animals observed for histopathology. Furthermore, results on nano-CeO2 biodistribution and histopathology analysis were too briefly described; there was no clear description on whether ICP-AES was performed on wet or dry tissues, and on the number of animals analysed for CeO2 biodistribution assessment.

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to same study

Objective of study:

distribution

other: histopathology

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Repeated administration of a suspension of nanometric cerium dioxide (nano-CeO2) by intraperitoneal (i.p.) injection to rats; sacrifice of animals at the end of 6-week exposure period
- Nano-CeO2 tissue distribution: Inductively coupled plasma-atomic emission spectrometer (ICP-AES)
- Histopathological analysis: Light microscopy

GLP compliance:

not specified

Remarks:

The GLP status was not specified in the article.

Radiolabelling:

no

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data available
- Age at study initiation: 10-week-old
- Weight at study initiation: 300 ± 25 g
- Fasting period before study: No data available
- Housing: Three animals per laboratory cage
- Individual metabolism cages: No data available
- Diet: Ad libitum (Teklad Global 18% Protein Rodent Diet, Harlan, USA)
- Water: Ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 25°C
- Humidity: 50%
- Air changes: No data available
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: No data available

Route of administration:

intraperitoneal

Vehicle:

other: sterile water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: No data available

VEHICLE
- Concentration in vehicle: 300 µg/mL
- Amount of vehicle: 500 µL
- Lot/batch no., purity: No data available

HOMOGENEITY AND STABILITY OF TEST MATERIAL: No data available

Duration and frequency of treatment / exposure:

Twice a week for 6 weeks (sacrifice at the end of exposure period)

Dose / conc.:

0 mg/kg bw (total dose)

Remarks:

(control)

Dose / conc.:

0.5 mg/kg bw (total dose)

Remarks:

basis: nominal nano-CeO2 dose

No. of animals per sex per dose / concentration:

6

Control animals:

yes

Details on study design:

- Route selection rationale: Intraperitoneal route was chosen as an optimal compromise between easiness of treatment and nanoparticles distribution. This administration route was in fact proven to provide similar biodistribution with respect to an intravenous injection (Hirst SM et al., 2011), but allowing at the same time repetitive injections without any adverse effect for the animals. Since administration of nanomaterials through the intraperitoneal route could be associated to macrophage activation and consequent cytokine release, Rocca A. et al. tested effects of acute and high-dose nano-CeO2 treatment on RAW 264.7 macrophages (50 and 100 μg/mL for 24 h), highlighting no activation of macrophages in terms of IL-6, IL-10, and TNF-α release.
- Dose selection rationale: Nano-CeO2 dose of 0.5 mg/kg was chosen based on the data of Hirst SM et al. (2011), which showed how this dose was well tolerated in vivo after 15 days of treatment.
- Rationale for animal assignment: No data available

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: visceral fat, brain, liver, kidney, spleen
- Time and frequency of sampling: After 6 weeks, rats were sacrificed in CO2 chamber. Tissues were harvested and either fixed in paraformaldehyde for histological sectioning or stored at -80° C for further analyses.
- Other:
* Nano-CeO2 distribution
Nano-CeO2 content in brain, liver, kidney, spleen was determined by using an inductively coupled plasma atomic emission spectrometer (ICP-AES). The collected tissues were weighted and placed at -80°C; thereafter, the digestion process was carried out through a treatment with a HNO3:H2O2 (4:1) solution in a microwave digestion system. The samples were finally dissolved in water, and the cerium (Ce) concentration determined at 404 nm.

* Histology
For tissues analysis, little fragments of visceral fat, liver, kidney and spleen were collected after animal sacrifice and immediately fixed in a 4% paraformaldehyde solution overnight at 4°C, washed in phosphate saline buffer (PBS) and finally rinsed in 70% ethanol until processing. Thereafter, the samples were dehydrated through an increasing ethanol gradient. Subsequently, the samples were clarified in xylene, rinsed in liquid paraffin at 60°C for 4 h and wax-embedded. Specimen sections 5-μm thick were obtained, mounted onto slides, stained in hematoxylin and eosin, and finally observed with a light microscope.

* Bodyweight
All the animals were weighted once a week.

Statistics:

Data were analysed with one-way ANOVA followed by Bonferroni's post-hoc test or with two-tailed unpaired t-test. In all experiments, data with p-value < 0.05 were considered statistically significant.

Preliminary studies:

No data available

Details on absorption:

No data available

Details on distribution in tissues:

Nano-CeO2 biodistribution, assessed through ICP-AES, showed that nanoparticles were mainly retained by spleen (ca. 80 to 95 µg CeO2/ g organ), while low accumulation was found in brain (ca. 70 to 80 ng/g), liver (< 1 ng/g) and kidney (ca. 500 to 800 ng/g). Overall, by considering administered doses and elemental analysis results, Rocca A et al. estimated an accumulation of about 3% of the whole injected amount of nano-CeO2 in the examined organs. Given the i.p. administration, the authors expected that a consistent amount of nano-CeO2 remained in this compartment.

Details on excretion:

No data available

Metabolites identified:

not measured

Bioaccessibility (or Bioavailability) testing results:

No data available

- BODYWEIGHT:

At the end of the six-week monitoring period, control rats showed an elevated weight gain (13.5%) since the beginning of the experiments, whereas rats treated with nano-CeO2 showed only a limited and non-statistically significant increment (2%) compared to the initial weight.

- HISTOLOGY:

Concerning the features of the adipose tissue, adipocytes maintained their large lipid droplet with the nucleus placed at the edge of the cellular cytoplasm. Kidney sections showed that nano-CeO2 did not affect tubular, glomerular and interstitial structures. In groups treated with nano-CeO2, the liver slides displayed the typical lobule architecture characterised by central vein from which hepatocytes depart, and are separated by sinusoids. Spleen histology indicated that nano-CeO2 did not cause alterations of the normal tissue architecture, composed by lymphoid aggregations and vascular sinuses.

Conclusions:

Nano-CeO2 intraperitoneally administered repeatedly at a low dose seemed to be mainly accumulated in the spleen, and to lack evidence of general toxicity and overt pathogenic side effects in treated rats.
=> Interpretation of results: bioaccumulation potential in spleen

Executive summary:

Rocca A et al. (2015) investigated the antioxidant effects of nanometric cerium oxide (nano-CeO2) as a potential pharmaceutical approach for the treatment of obesity. In this context, the authors evaluated the biodistribution of nano-CeO2 following repeated intraperitoneal (i.p.) administration to rats.

A commercial nano-CeO2 from Sigma was used in this study. The nanomaterial displayed a primary size of 5-80 nm. Moreover, the particles in suspension showed an agglomeration/aggregation tendency with a 92% peak at ~230 nm. The zeta potential was about -15 mV and the Ce3+ content of ~23%. The nanoparticles were considered to have high purity with less than 1% impurities and displayed a crystalline structure.

Male Wistar rats (6/group) were i.p. injected with nano-CeO2 at a single dose of 0 (control) or 0.5 mg/kg body weight twice a week for 6 weeks. At the end of exposure period, visceral fat, brain, liver, kidney, spleen were collected. Nano-CeO2 content was determined by using an inductively coupled plasma atomic emission spectrometer (ICP-AES). Histological analysis of visceral fat, liver, kidney and spleen was performed on tissues stained with hematoxylin and eosin and using light microscopy. In addition, all the animals were weighted once a week during the 6-week exposure period.

Nano-CeO2, i.p. injected in Wistar rats, did not have appreciable toxic effects, but instead efficiently contributed in reducing the weight gain. Concerning organ accumulation, Rocca A et al. estimated an accumulation of about 3% of the whole injected amount of nano-CeO2 in the examined organs and nano-CeO2 was mainly accumulated in the spleen at the end of the 6-week treatment. Despite the strong accumulation in the spleen, histological analysis with hematoxylin and eosin did not reveal any impairment of the tissues. Furthermore, analysis on other organs (liver, kidney, and adipose tissue) showed the typical morphology of the tissues without difference between treated and control rats. Given the i.p. administration, the authors expected that a consistent amount of nano-CeO2 remained in this compartment. Concerning the excretion of nano-CeO2, Rocca A et al. did not perform analysis on faeces/urines.

In conclusion, after repeated i.p. injections, the tested nano-CeO2 displayed the classical behaviour of poorly soluble particles: low toxicity, distribution in reticulo-endothelial organs such as the spleen which are involved in the clearance of foreign materials. Furthermore, histological analysis did not reveal any impairment of the tissues.

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2015

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Repeated administration of a suspension of nanometric cerium dioxide (nano-CeO2) by intraperitoneal (i.p.) injection to rats; sacrifice of animals at the end of 6-week exposure period
- Body weight
- Nano-CeO2 content in brain, liver, kidney, spleen: Inductively coupled plasma atomic emission spectrometer (ICP-AES)
- Histopathology: Light microscopy
- mRNA expression of adipogenesis markers: Polymerase chain reaction (PCR)
- Metabolic changes: Glycerol-3-phosphate dehydrogenase (G3PDH) assay

GLP compliance:

not specified

Remarks:

The GLP status was not specified in the article.

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Cerium dioxide

EC Number:

215-150-4

EC Name:

Cerium dioxide

Cas Number:

1306-38-3

Molecular formula:

CeO2

IUPAC Name:

cerium dioxide

Test material form:

other: nanomaterial in suspension

Details on test material:

- Name of test material: Nanometric cerium dioxide (nano-CeO2)
- Supplier: Sigma (USA) (ref. 544841)
- Substance type: Monoconstituent substance
- Substance form: Nanoparticulate substance / crystalline nanomaterial in suspension
- Primary particle size (TEM): 5 to 80 nm
- Particle size distribution (DLS): 92% peak at a size of ca. 230 nm, with a polydispersity index of 0.290
- Stability: Agglomeration/aggregation based on the particle size distribution
- Specific surface area: No data available
- Surface charge (DLS): Zeta potential of about -15 mV
- Isoelectric point: No data available
- Shape: No data available
- Crystallinity (EDS, SEM): Crystalline nature, with a cubic face centred lattice
- Analytical purity (EDS): High purity with a chemical composition (atom content) of ca. 30% Ce, ca. 65% O, and ca. 4% Au (deriving from the sputtering procedure)
- Impurities (EDS): < 1% of atom content
- Number density of nano-CeO2 in the suspension: No data available
- Cerium content in nano-CeO2 suspension: No data available
- Solubility: No data available
- Oxidation degree (XPS, UV/Vis): Ce(III) content of ca. 23%; coexistence of Ce(III) and Ce(IV) oxidation degrees confirmed by UV/Vis
- Surface properties: No data available
- Lot/batch No.: No data available
- Expiration date of the lot/batch: No data available
- Other information: The results of the antioxidant capacity assessment demonstrated that nano-CeO2 was an efficient scavenger of reactive oxygen species (ROS); the antioxidant activity of 1 mg of nano-CeO2 corresponded to the antioxidant activity of 110 nmol of Trolox (Rocca A et al., 2015).

With the exception of the antioxidant capacity, the physico-chemical data abovementioned come from another study: Ciofani G et al (2013). Further explanations on the physico-chemical characterisation of CeO2 nanoparticles are presented below in "any other information on materials and methods incl. tables".

Test animals

Species:

rat

Strain:

Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: No data available
- Age at study initiation: 10-week-old
- Weight at study initiation: 300 ± 25 g
- Fasting period before study: No data available
- Housing: Three animals per laboratory cage
- Individual metabolism cages: No data available
- Diet: Ad libitum (Teklad Global 18% Protein Rodent Diet, Harlan, USA)
- Water: Ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 25°C
- Humidity: 50%
- Air changes: No data available
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: No data available

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

other: sterile water

Details on exposure:

VEHICLE
- Concentration in vehicle: 300 µg/mL
- Amount of vehicle: 500 µL

Duration of treatment / exposure:

6 weeks (sacrifice at the end of exposure period)

Frequency of treatment:

Twice a week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw (total dose)

Remarks:

(control)

Doses / concentrations 2

Dose / conc.:

0.5 mg/kg bw (total dose)

Remarks:

basis: nominal nano-CeO2 dose

No. of animals per sex per dose:

6

Control animals:

yes

Details on study design:

- Dose selection rationale: Nano-CeO2 dose of 0.5 mg/kg was chosen based on the data of Hirst SM et al. (2011), which showed how this dose was well tolerated in vivo after 15 days of treatment.
- Rationale for selecting satellite groups, post-exposure recovery period in satellite groups, section schedule rationale: No data available
- Other: Route selection rationale: intraperitoneal route was chosen as an optimal compromise between easiness of treatment and nanoparticles distribution. This administration route was in fact proven to provide similar biodistribution with respect to an intravenous injection (Hirst SM et al., 2011), but allowing at the same time repetitive injections without any adverse effect for the animals. Since administration of nanomaterials through the intraperitoneal route could be associated to macrophage activation and consequent cytokine release, Rocca A. et al. tested effects of acute and high-dose nano-CeO2 treatment on RAW 264.7 macrophages (50 and 100 μg/mL for 24 h), highlighting no activation of macrophages in terms of IL-6, IL-10, and TNF-α release.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: All the animals were weighted once a week

FOOD CONSUMPTION: No data

FOOD EFFICIENCY: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: After 6 weeks the rats were sacrificed in CO2 chamber, and blood samples collected through cardiac puncture for biochemical analysis.
- Animals fasted: No data
- How many animals: No data
- Parameters checked: Whole blood samples were centrifuged in tubes containing heparin as anti-coagulant, and isolated plasma was used for the analysis of leptin, insulin, glucose and triglycerides. The concentration of insulin and leptin were obtaining through ELISA. The circulating levels of glucose and triglycerides were determined through colorimetric kits.

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER:
- NANO-CeO2 CONTENT:
After 6 weeks the rats were sacrificed in CO2 chamber, and tissues were harvested and stored at -80° C for further analyses. Nano-CeO2 content in main organs (brain, liver, kidney, spleen) was determined through an inductively coupled plasma atomic emission spectrometer (ICP-AES). The collected tissues were weighted and placed at -80°C; thereafter, the digestion process was carried out through a treatment with a HNO3:H2O2 (4:1) solution in a microwave digestion system. The mineralized samples were finally dissolved in water, and the Ce concentration determined at 404.0 nm.

- mRNA EXPRESSIONS:
RNA isolation was performed through an automated robotic workstation. Adipose tissue (30 mg), collected through surgical excision and immediately frozen, was homogenized with an Ultra-Turrax just before the RNA extraction. The RNA quantity and purity was evaluated with analysis of absorbance at 260/280 nm. To obtain cDNA, RNA (1 μg) was reverse-transcribed. The amplification was performed using a PCR Array in order to detect the
expression profiles of 84 genes related to adipogenesis. The qPCR reaction was achieved on a thermocycler system. For the normalization, Hprt and Rplp1 were used as reference genes.

- METABOLIC CHANGES:
Adipose tissue (10 mg), harvested from visceral fat, was disrupted in a buffer by Ultra-Turrax and then sonicated to perform efficient homogenisation. The collected supernatant was used for the subsequent analysis. The reaction was carried out at 37°C for 30 min, and the reading of absorbance, performed at 450 nm with a microplate reader, allowed the glycerol-3-phosphate dehydrogenase (G3PDH) content to be quantified.

Sacrifice and pathology:

GROSS PATHOLOGY: No data
HISTOPATHOLOGY: Yes
After 6 weeks the rats were sacrificed in CO2 chamber. For tissues analysis, little fragments of visceral fat, liver, kidney and spleen were collected after animal sacrifice and immediately fixed in a 4% paraformaldehyde solution overnight at 4°C, washed in phosphate saline buffer (PBS) and finally rinsed in 70% ethanol until processing. Thereafter, the samples were dehydrated through an increasing ethanol gradient. Subsequently, the samples were clarified in xylene, rinsed in liquid paraffin at 60°C for 4 h and wax-embedded. Specimen sections 5-μm thick were obtained, mounted onto slides, stained in hematoxylin and eosin, and finally observed with a light microscope.

Statistics:

Data were analysed with one-way ANOVA followed by Bonferroni's post-hoc test or with two-tailed unpaired t-test. In all experiments, data with p-value < 0.05 were considered statistically significant.

Results and discussion

Results of examinations

Clinical signs:

not specified

Mortality:

not specified

Body weight and weight changes:

no effects observed

Description (incidence and severity):

see below in "Details on results"

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not specified

Haematological findings:

not specified

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

see below in "Details on results"

Urinalysis findings:

not specified

Behaviour (functional findings):

not specified

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

see below in "Details on results"

Histopathological findings: neoplastic:

not examined

Details on results:

BODY WEIGHT AND WEIGHT GAIN
At the end of the six-week monitoring period, control rats showed an elevated weight gain (13.5%) since the beginning of the experiments, whereas rats treated with nano-CeO2 showed only a limited and non-statistically significant increment (2%) compared to the initial weight.

CLINICAL CHEMISTRY
Nano-CeO2 significantly reduced the insulin (0.4 ± 0.5 ng/mL) and the leptin concentration (8.1 ± 1.7 ng/mL) with respect to the control group (2.8 ± 1.1 ng/mL for insulin and 17 ± 4.5 ng/mL for leptin). Furthermore, the authors assured that glucose and triglycerides levels were also reduced in rats following the treatment with nano-CeO2 (0.032 ± 0.003 nmol/μL for glucose and 0.9 ± 0.1 nmol/μL for triglycerides) when compared to the control groups (0.039 ± 0.004 nmol/μL for glucose and 1.3 ± 0.1 nmol/μL for triglycerides).

HISTOPATHOLOGY: NON-NEOPLASTIC
Concerning the features of the adipose tissue, adipocytes maintained their large lipid droplet with the nucleus placed at the edge of the cellular cytoplasm. Kidney sections showed that nano-CeO2 did not affect tubular, glomerular and interstitial structures. In groups treated with nano-CeO2, the liver slides displayed the typical lobule architecture characterised by central vein from which hepatocytes depart, and are separated by sinusoids. Spleen histology indicated that nano-CeO2 did not cause alterations of the normal tissue architecture, composed by lymphoid aggregations and vascular sinuses.

NANO-CeO2 CONTENT
The nano-CeO2 biodistribution, assessed through ICP-AES, showed that nanoparticles were mainly retained by spleen, while low accumulation was found in brain, liver and kidney. The authors estimated an accumulation of about 3% of the whole injected amount of nano-CeO2 in the examined organs.

- mRNA EXPRESSIONS:
The analysis of the transcribed genes in the samples of adipose tissue demonstrated that the transcription of the Angpt2, Bmp2, Ddit3, Lep, and Twist1 in rats treated with nano-CeO2 was significantly lower with respect to the control group (Angpt2 1.6-fold, Bmp2 1.5-fold, Ddit3 1.3-fold, Lep 2.4-folds, Twist1 1.4-fold), while the transcription of Irs1 and Klf4 was significantly increased (Irs1 1.4-fold, Klf4 1.5-fold). Furthermore, Bmp4 and Ldha were down-regulated in presence of nano-CeO2 (Bmp4 2.1-folds, Ldha 2-folds), even if this decrement resulted statistically non-significant. Thus, nano-CeO2 caused a significant decrement of mRNA transcription of the main adipogenesis marker genes.

- METABOLIC CHANGES:
The measurement of G3PDH activity (which presents a key role during the triglyceride synthesis) at the end of the experiment indicated a decrease following nano-CeO2 administration, being the amount of G3PDH 11.3 ± 1.9 mU/mL for the rats treated with nano-CeO2 and 14.7 ± 0.5 for the control rats.

The authors concluded that nano-CeO2 was well tolerated in vivo after 15 days of treatment. Moreover, these data collectively confirmed as nano-CeO2 interfered with the adipogenesis due to its reactive oxygen species (ROS) scavenger ability, inhibiting both genes transcription and phenotype development typical of terminally differentiated adipocytes.

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Nano-CeO2, intraperitonally injected in Wistar rats, did not have appreciable toxic effects, but instead efficiently contributed in reducing the weight gain and in lowering the plasma levels of insulin, leptin, glucose and triglycerides.

Executive summary:

Rocca A et al. (2015) investigated the antioxidant effects of nanometric cerium dioxide (nano-CeO2) as a potential pharmaceutical approach for the treatment of obesity. In this context, the authors evaluated the impact of nano-CeO2 following repeated intraperitoneal (i.p.) administration to rats.

A commercial nano-CeO2 from Sigma was used in this study. The nanomaterial displayed a primary size of 5-80 nm. Moreover, the particles in suspension showed an agglomeration/aggregation tendency with a 92% peak at ca. 230 nm. The zeta potential was about -15 mV and the Ce(III) content of ca. 23%. The nanoparticles were considered to have high purity with less than 1% impurities and displayed a crystalline structure.

Male Wistar rats (6/group) were i.p. injected with nano-CeO2 at a single dose of 0 (control) or 0.5 mg/kg body weight twice a week for 6 weeks. Bodyweight was monitored weekly. At the end of exposure period, visceral fat, brain, liver, kidney, spleen were collected. Nano-CeO2 content was determined by using an inductively coupled plasma atomic emission spectrometer (ICP-AES). Histological analysis of visceral fat, liver, kidney and spleen was performed on tissues stained with hematoxylin and eosin and using light microscopy. In addition, isolated plasma was used for the analysis of leptin, insulin, glucose and triglycerides. mRNA expression of adipogenesis marker genes was assessed using the polymerase chain reaction (PCR) technique. Metabolic changes were evaluated by measuring the activity of glycerol-3-phosphate dehydrogenase (G3PDH) in adipose tissue.

Nano-CeO2 at 0.5 mg/kg bw did not have appreciable toxic effects in i.p. injected rats, but instead efficiently contributed in reducing the weight gain. Nano-CeO2 significantly reduced the insulin, leptin, glucose and triglycerides concentration with respect to the control group. The histopathological analysis of tissues demonstrated that adipose tissue, kidney, liver and spleen displayed no alterations of tissue architecture. The analysis of the transcribed genes in the samples of adipose tissue demonstrated that nano-CeO2 caused a significant decrement of mRNA transcription of the main adipogenesis marker genes. In addition, the measurement of G3PDH at the end of the experiment indicated a decrease following nano-CeO2 administration.

The authors concluded that nano-CeO2 was well tolerated in vivo after 15 days of treatment. Moreover, these data collectively confirmed that nano-CeO2 interfered with the adipogenesis due to its reactive oxygen species (ROS) scavenger ability, inhibiting both genes transcription and phenotype development typical of terminally differentiated adipocytes.