Tier 3 — preclinical

Comparison of quantity and structures of hydroxyproline-containing peptides in human blood after oral ingestion of gelatin hydrolysates from different sources

Hiroki Ohara, Hitoshi Matsumoto, Kyoko Ito, Koji Iwai, Kenji Sato
Journal of Agricultural and Food Chemistry 2007 55(4):1532–1535

Bibliography

PubMed
PMID 17253720
DOI
10.1021/jf062834s
Funding
No external grant funding statement disclosed in the paper. Acknowledgment thanks Masahiro Nomoto and Makoto Aoki at the Pharmaceutics Research Lab of Meiji Seika Kaisha for pharmacokinetic analysis assistance.
Competing interests
No competing interests statement disclosed in the paper. Three co-authors (Hiroki Ohara, Hitoshi Matsumoto, Kyoko Ito) were employees of Meiji Seika Kaisha Ltd., Food and Health R&D Laboratories — a commercial food ingredient manufacturer whose product lines include collagen. The fish scale and porcine skin gelatin hydrolysates were gifted by Nitta Gelatin (Osaka), a commercial gelatin supplier; the fish skin hydrolysate was purchased commercially. Remaining co-authors (Iwai, Sato) were affiliated with Kyoto Prefectural University. Substantial industry involvement despite the absence of a formal declaration.

Study snapshot

DesignSingle-blind, three-arm crossover human bioavailability study with 1-week washout between arms
ModelHealthy Japanese adult males
Sample5 male volunteers, mean age 33.0 ± 5.6 years, mean weight 69.8 ± 7.4 kg
InterventionSingle oral dose of type I gelatin hydrolysate at 0.385 g per kg body weight in 20% w/v aqueous solution, after 12 h fast, from three sources tested sequentially with 1-week washouts: fish scale, fish skin, or porcine skin
DurationSingle-dose kinetics per arm; blood sampling at 0.5, 1, 2, 4, 7 and 24 h post-ingestion
EndpointsArea under the concentration–time curve (AUC0–24h) of free-form hydroxyproline in plasma; AUC0–24h of hydroxyproline-containing peptides in plasma; Identification of peptide sequences by Edman degradation; Semi-quantitative peptide composition per gelatin source

What the study showed, in plain terms

This single-blind crossover study asked whether the source of gelatin hydrolysate changes the amount and pattern of collagen-derived peptides appearing in human blood.

Five healthy men ingested type I gelatin hydrolysates from fish scale, fish skin and porcine skin on separate occasions after a 12-hour fast, with blood sampling over 24 hours.

Hydroxyproline-containing peptides represented about 30% of detected hydroxyproline. The primary report states that total peptide AUC after fish-scale hydrolysate was significantly higher than after porcine-skin hydrolysate. Fish-skin values were numerically different, but the accessible primary report does not state a separate statistically significant fish-scale-versus-fish-skin comparison, so that stronger claim should not be inferred.

Peptide profiles also differed by source. Pro-Hyp was a major constituent across sources, while several additional peptides appeared only after fish-derived hydrolysates and Ala-Hyp-Gly and Ser-Hyp-Gly were detected only after fish-scale hydrolysate.

Key findings

  • Hydroxyproline-containing peptides comprised approximately 30% of all detected hydroxyproline in plasma.
  • Total AUC for hydroxyproline-containing peptides was significantly higher after fish-scale hydrolysate than after porcine-skin hydrolysate. The primary abstract does not report a separate significant fish-scale-versus-fish-skin pairwise contrast.
  • Pro-Hyp was a major constituent of the circulating hydroxyproline-containing peptide fraction.
  • Ala-Hyp, Leu-Hyp, Ile-Hyp, Phe-Hyp and Pro-Hyp-Gly were detected only after fish-scale or fish-skin hydrolysates.
  • Ala-Hyp-Gly and Ser-Hyp-Gly were detected only after fish-scale hydrolysate.
  • The sample included only five healthy men, so source-specific differences are mechanistic and hypothesis-generating rather than population-level efficacy evidence.

What this study can and cannot tell us

  • Sample size of only five male volunteers — inadequate for population-level inference and provides no data on female-specific pharmacokinetics.
  • All subjects were Japanese. Inter-ethnic differences in peptide transporter expression could affect generalisability.
  • Single-dose kinetics only. No data on whether the source-dependent differences persist under chronic daily dosing.
  • Only three sources compared. Bovine hide, chicken and eggshell collagen — all widely marketed — were not tested.
  • No dose–response within any source. The 0.385 g/kg dose was fixed; whether higher or lower doses would preserve the same relative differences is not established.
  • Substantial commercial conflict of interest — three co-authors employed by Meiji Seika Kaisha, and gelatin hydrolysates supplied by Nitta Gelatin. No competing interests statement.
  • The paper is purely analytical. It measures what appears in blood; it does not measure any skin, joint, bone or other clinical outcome. The suggestion that source-specific peptide profiles translate to source-specific clinical effects is a hypothesis, not a finding.
  • Peptide quantification was semi-quantitative, estimated from HPLC peak areas rather than absolute quantification against stable-isotope-labelled internal standards.

Related papers in the corpus

Tier 3
Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates
Koji Iwai et al. · Journal of Agricultural and Food Chemistry · 2005

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