Dietary Egg Protein Prevents Hyperhomocysteinemia via Upregulation of Hepatic Betaine-Homocysteine S-Methyltransferase Activity in Folate-Restricted Rats.
Study Goal
The researchers aimed to determine whether whole eggs or egg components (egg protein and choline) could regulate homocysteine balance and affect hepatic enzyme activity in a rat model of hyperhomocysteinemia.
Results Summary
Egg protein prevented elevated circulating homocysteine concentrations in folate-restricted rats, likely due to upregulated hepatic BHMT activity. The study did not report adverse effects but was limited to a rat model, leaving human applicability unclear.
Population
Male Sprague Dawley rats (6 weeks old, n=48) fed folate-restricted or folate-sufficient diets.
Effective Dosage
Diets contained 20% (wt:wt) total protein, with choline supplementation at 1.3% (wt:wt) in the C+Cho group.
Duration
8 weeks total (2 weeks baseline, 6 weeks intervention).
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
casein-based diet (folate-restricted) | increase | circulating homocysteine concentrations | rats | 53% | exhibited a 53% increase | #1 |
egg protein-based diet (folate-restricted) | no change | serum homocysteine | rats | - | did not differ | #2 |
egg protein-based diet | increase | hepatic BHMT activity | rats | 45% | increased | #3 |
whole egg-based diet | increase | hepatic BHMT activity | rats | 40% | increased | #4 |
egg protein | decrease | circulating homocysteine concentrations | rat model of hyperhomocysteinemia | - | prevented elevated | #5 |
egg protein | increase | hepatic BHMT | rat model of hyperhomocysteinemia | - | upregulation | #6 |
BACKGROUND: Hyperhomocysteinemia is associated with increased cardiovascular disease risk. Whole eggs contain several nutrients known to affect homocysteine regulation, including sulfur amino acids, choline, and B vitamins. OBJECTIVE: The aim of this study was to determine the effect of whole eggs and egg components (i.e., egg protein and choline) with respect to 1) homocysteine balance and 2) the hepatic expression and activity of betaine-homocysteine S-methyltransferase (BHMT) and cystathionine β-synthase (CBS) in a folate-restricted (FR) rat model of hyperhomocysteinemia. METHODS: Male Sprague Dawley rats (n = 48; 6 wk of age) were randomly assigned to a casein-based diet (C; n = 12), a casein-based diet supplemented with choline (C + Cho; 1.3%, wt:wt; n = 12), an egg protein-based diet (EP; n = 12), or a whole egg-based diet (WE; n = 12). At week 2, half of the rats in each of the 4 dietary groups were provided an FR (0 g folic acid/kg) diet and half continued on the folate-sufficient (FS; 0.2 g folic acid/kg) diet for an additional 6 wk. All diets contained 20% (wt:wt) total protein. Serum homocysteine was measured by HPLC and BHMT and CBS expression and activity were evaluated using real-time quantitative polymerase chain reaction, Western blot, and enzyme activity. A 2-factor ANOVA was used for statistical comparisons. RESULTS: Rats fed FR-C exhibited a 53% increase in circulating homocysteine concentrations compared with rats fed FS-C (P < 0.001). In contrast, serum homocysteine did not differ between rats fed FS-C and FR-EP (P = 0.078). Hepatic BHMT activity was increased by 45% and 40% by the EP (P < 0.001) and WE (P = 0.002) diets compared with the C diets, respectively. CONCLUSIONS: Dietary intervention with egg protein prevented elevated circulating homocysteine concentrations in a rat model of hyperhomocysteinemia, due in part to upregulation of hepatic BHMT. These data may support the inclusion of egg protein for dietary recommendations targeting hyperhomocysteinemia prevention.