Effects of yeast hydrolysate on neuropeptide Y (NPY) and tryptophan hydroxylase (TPH) immunoreactivity in rats.
Level 5 - mechanism / opinion, no new human data
Animal research
PubMed 19107837 · doi:10.1002/ptr.2668
What was done
Rats fed a normal diet were assigned to a control group or to groups receiving yeast hydrolysate fractions: low molecular weight (<10 kDa) at 0.1 g/kg (BY-1) or 1.0 g/kg (BY-2), or high molecular weight (10–30 kDa) at 0.1 g/kg (AY-1) or 1.0 g/kg (AY-2). Brain immunohistochemistry was performed to evaluate neuropeptide Y (NPY) in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA), and tryptophan hydroxylase (TPH) in the dorsal raphe (DR). Body weight gain and serum lipid levels were also assessed.
What was found
Body weight gain was significantly lower in the BY-2 group (133.0 g) than in the control group (150.1 g) (p < 0.05). BY-2 also had lower triacylglyceride, total cholesterol, and LDL-cholesterol levels than control, BY-1, and AY-2 (p < 0.05; numerical lipid values not reported). PVN NPY staining intensities were lower in BY-1 (96.1) and BY-2 (88.6) compared to control (105.6), AY-1 (110.5), and AY-2 (114.1) (p < 0.05). LHA NPY expression was lower in BY-2 (92.3) than control (98.9) (p < 0.05). Dorsal raphe TPH staining intensities were higher in BY-1 (143.9) and BY-2 (154.6) than in AY-2 (115.9) (p < 0.05).
Why it matters
This paper identifies a molecular-weight-specific effect of yeast hydrolysate on central neurochemical regulators of appetite and serotonergic signaling, providing a potential mechanism for reduced weight gain.
Limits
The study was conducted in normal diet-fed rats and findings cannot be directly applied to human appetite or obesity. The abstract does not report sample size, study duration, baseline animal characteristics, or numerical values for serum lipids.
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