Glycerol trioctanoate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Blood D-(–)-3-Hydroxybutyrate Concentrations after Oral Administration of Trioctanoin, Trinonanoin, or Tridecanoin to Newborn Rhesus Monkeys (Macaca mulatta)

Author:

Tetrick, M.A., Greer, F.R. and Benevenga N.J.

Year:

2010

Bibliographic source:

Comperative Medicine 2010 Dec;60(6):486-90

Materials and methods

Objective of study:

absorption

Principles of method if other than guideline:

4 groups of 5 newborn monkeys were given a single dose of water or medium-chain triglycerides by nasogastric tube. The dose provided approximately 80% of the expected energy requirement. Plasma C8:0, C9:0, and C10:0 fatty acids and whole-blood D-(–)-3-hydroxybutyrate (3HB) concentrations were measured at 0, 1, and 3 h after dosing.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Glycerol trioctanoate

EC Number:

208-686-5

EC Name:

Glycerol trioctanoate

Cas Number:

538-23-8

Molecular formula:

C27H50O6

IUPAC Name:

1,3-bis(octanoyloxy)propan-2-yl octanoate

Radiolabelling:

no

Test animals

Species:

monkey

Strain:

other: Macaca mulatta

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Wisconsin National Primate Research Center
- Age at study initiation: 15 h
- Weight at study initiation: mean ca. 530 g
- Housing: the infants were held in a relatively quiet location, provided with a blanket to cling to and a heat lamp. Infants were excluded from this study if the primate center staff judged them to be at risk of maternal rejection after the 3- to 5-h separation needed for the evaluation.
- Diet: Monkey diet 5037/5038, PMI Nutrition International, St Louis, MO, USA, ad libitum, supplemented with fresh fruit 2 to 3 times per week
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 °C
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

other: nasogastric tube

Vehicle:

unchanged (no vehicle)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The dosage was calculated to provide approximately 272 kJ gross energy per kilogram or 136 kJ for a 500-g newborn rhesus monkey, based on a basal energy requirement of: (292 kJ W^(0.75)) × (0.5 kg body wt)^0.75 = 174 kJ.
The dose was estimated to provide approximately 80% (135 of 174 kJ) of the rhesus infants’ daily basal energy requirement.

Duration and frequency of treatment / exposure:

Single administration on day 0 (newborn)

Doses / concentrations

Dose / conc.:

8.1 other: mg/kg bw (actual dose received)

Remarks:

8.4 mL/kg bw; single dose

No. of animals per sex per dose / concentration:

5

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: The dose was estimated to provide approximately 80% (135 of 174 kJ) of the rhesus infants’ daily basal energy requirement. Estimation of resting energy expenditure was based on observations with newborn piglets, approximately 293 kJ/ (kg × d)17 according to expired CO2 (367 μmol/[min×kg]0.75)23 and an assumed respiratory quotient of 0.86. Use of 80% of the basal energy requirement was judged to be a sufficient amount to have an effect, based on previous work with energy metabolism in newborn piglets and their response to medium-chain triglycerides.

- Other: Treatments included also oral doses of Trinonanoin (C9:0) or water control. An additional group of 5 monkeys became available later and was treated with the Tridecanoin (C10:0).

Details on dosing and sampling:

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: blood (1 mL)
- Time and frequency of sampling: before dosing (0 h), 1 and 3 hours after administration
- From how many animals: all 5 animals, not pooled
- Method type(s) for identification: Fatty acid quantitation by HPLC, D-(–)-3-Hydroxybutyrate (3HB) analysis by dye-linked spectrophotometric
method
- Limits of detection and quantification: The 3HB detection limit in the 0.5 mL blood sample by using this assay was 3 to 5 μM.
- Other: [3-14C]3HB and [1-14C]nonanoic acid were added to sample to allow to correct for recovery

Statistics:

Plasma fatty acid and blood 3HB concentrations from groups of newborn rhesus monkeys were analyzed by one-way ANOVA by using a General Linear Models procedure of Statistical Analysis System release 6.09 (SAS Institute, Cary, NC). The split-plot model included the main effect of oral dose, with time and time×treatment interaction as a subplot. Inferences regarding oral dose were based on nonorthogonal contrasts based on perceived biologic importance. Nonorthogonal contrasts were used to compare plasma fatty acid concentrations due to treatment: water versus 8:0, 8:0 versus 9:0, and 9:0 versus 10:0. Orthogonal contrasts were used to compare the group mean 3HB concentrations: water-treated group to MCT treatments, 8:0 versus 9:0, 8:0 versus 10:0, and 9:0 versus 10:0. Fatty acid and 3HB concentrations at 0 versus 1 h, 0 versus 3 h, and 1 versus 3 h were compared for each treatment by using orthogonal contrasts. Outlier values were defined as individual values falling outside a range of 2 SD on either side of the mean for the other animals in the group.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Plasma concentrations of free fatty acids (C8, C9, or C10) and ketone (3HB) increased with time after the dose. At 1 and 3 h, concentrations of C8 and C9 did not differ, but C9 was greater than C10. At 1 h, blood 3HB concentrations due to C8 triglyceride administration were higher than C9 or C10 (503 versus 174 and 225 μmol/L respectively). As chain length increased from C8 to C10, blood concentration of 3HB decreased.

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

C8:0 fatty acid, 3-hydroxybutyrate

Any other information on results incl. tables

Clinical observations:

Newborn monkeys dosed with MCT remained alert and active after dosage. No episodes of narcolepsy were noted.

Plasma fatty acid and whole-blood 3HB concentrations (μM , mean ± SEM):

Treatment Group	Metabolite measured	Concentration (µm) at
		0 h	1 h	3 h
water	C8:0	30 ± 8	29 ± 8^f	64 ± 28
C8	C8:0	21 ± 17^d	117 ± 28^e,g	128 ± 8^e
C9	C9:0	not detected d	154 ± 19^e,h	207 ± 60^e,f
C10^a	C10:0	4 ± 1^d	76 ± 27^e,g	83 ± 9^e,g
water	3HB^b	69 ± 36^d, f	50 ± 16^d,f	112 ± 53^d,f
C8	3HB	130 ± 25^d,g	503 ± 113^e,g	585 ± 111^e,g
C9	3HB	48 ± 12^d,f	174 ± 42^e,h	268 ± 62^e,h
C10^c	3HB	46 ± 16^d,f	225 ± 150^d,h	282 ± 177^d,h

All treatment groups contained 5 macaques, except for C10 groups, which contained 4 monkeys each due to elimination of an outlier.  

a: Concentrations (μM, mean±SEM) with outlier included were: 0 h, 13±1; 1 h, 119±47; and 3 h, 107±25.

b: Due to significant (P<0.05) treatment x time interaction, all treatment comparisons for 3HB were made within time point.

c: Concentrations (μM, mean±SEM) with outlier included were: 0 h, 163±117; 1 h, 463±265; and 3 h, 710±449.

d,e: Values that differ (P<0.05) within treatment groups (rows) are indicated by different superscript letters.

f,g,h: Values that differ (P<0.05) within time points (columns) are indicated by different superscript letters.

Applicant's summary and conclusion

Conclusions:

After single nasogastric administration of glycerol trioctanoate to monkeys at a dose of 8.1 mg/kg bw, the metabolites octanoic acid and 3-hydroxybutyrate were detectable at higher concentrations in blood, which had been sampled 1 and 3 hours after administration as compared to levels in blood sampled prior to administration. Due to the observed metabolism in monkeys, no bioaccumulation potential is expected for glycerol trioctanoate.

Executive summary:

Administration of C8 triglyceride lead to higher plasma concentrations of the respective hydrolysis products (free fatty acid) than after administration of C9 or C10 triglyceride.