Effect of Gelatin–Peptide Complex from Sturgeon Skin on Behavioral, Antioxidant, and Neuroprotective Functions in D-Galactose-Induced Aging Mice: Thermal Degradation vs. Enzymatic Hydrolysis

Collagen-derived products are widely applied in functional foods; however, limited information is available regarding how different preparation methods, particularly thermal degradation and enzymatic hydrolysis, affect their anti-aging efficacy and biological functions. In this study, sturgeon skin was used as raw material to prepare gelatin–peptide complexes via thermal degradation (GPC-TD) and enzymatic hydrolysis (GPC-EH), and their comparative anti-aging and biological effects were evaluated in D-galactose-induced aging mice. Female ICR mice were divided into eight groups: a blank control group (normal saline), an aging model group (D-galactose, 500 mg/kg), three GPC-TD and three GPC-EH groups (D-galactose supplemented with 100, 200, 400 mg/kg GPC-TD or GPC-EH). After eight weeks of administration, various physiological parameters were evaluated. Throughout the experiment, no statistically significant difference in body weight (BW) was observed among the groups; however, the blank and model groups consistently maintained the highest BW. The medium- and high-dose GPC-TD groups showed relatively faster weight gain, whereas the 100 mg/kg GPC-TD group and all three GPC-EH groups exhibited the slowest BW gain. Notably, the gastric indices of these latter groups were significantly lower than those of other groups (p < 0.05), which might be a key factor affecting BW gain. Behavioral tests revealed that the model group exhibited significantly reduced swimming speed and weakened nesting ability (p < 0.05), both of which were alleviated to varying degrees by treatment with GPC-TD and GPC-EH. Furthermore, both complexes markedly decreased malondialdehyde content in liver tissue (p < 0.05). Compared with the model group, high-dose GPC-TD and GPC-EH effectively increased acetylcholine content and inhibited acetylcholinesterase activity (p < 0.05). Masson staining revealed abnormal collagen fibers accumulation in certain tissues of model mice, a condition that was clearly ameliorated by GPC-TD and, to a greater extent, by GPC-EH. In addition, medium and high doses of both complexes significantly protected against D-galactose-induced loss of Nissl bodies in brain neurons; in the high-dose GPC-EH group, the density and number of Nissl bodies approached those observed in the blank group. These findings suggest that both GPC-TD and GPC-EH possess potential anti-aging effects, with GPC-EH exhibiting superior efficacy. This study provides theoretical support for consumers, the catering industry, and manufacturers in selecting appropriate processing techniques for the preparation of sturgeon skin GPC.