Hyperhomocysteinemia and premature vascular occlusive disease

Hyperhomocysteinemia and cardiovascular disease: The nutritional perspectives

Several members of the vitamin B-complex family are known to participate in the normal metabolism of homocysteine (Hcy). Leaving aside the genetic determinants of hyperhomocysteinemia (HHC), the deficiencies of these vitamins can also result in HHC. The situation of sustained and long standing HHC is likely to be prevalent in population groups with low/average socio-economic status, geriatric population and alcohol abusers. If not corrected by supplementation, these population groups certainly are more vulnerable to develop atherosclerosis (AS) and subsequently, cardiovascular disease (CVD). Hyperhomocysteinemia per se and/or HHC-induced oxidative stress result(s) in chronic chemical endothelial injury/dysfunction, smooth muscle proliferation, prothrombotic state and oxidation of low density lipoproteins (LDL) leading to diverse cardiovascular complications. In the first decade of the new millennium, major research efforts would be directed towards understanding the basic mechanism of HHC-induced oxidative stress and the pathophysiology of HHC-induced CVD, culminating in the evolution of hitherto unknown therapeutic strategies such as nutriceuticals and oxidant-antidotes.

Folate supplementation inhibits intimal hyperplasia induced by a high-homocysteine diet in a rat carotid endarterectomy model

OBJECTIVE

Hyperhomocysteinemia has been implicated as a causative factor in intimal hyperplasia development. The addition of dietary folate in a hyperhomocysteinemia, carotid endarterectomy rat model is postulated to decrease plasma homocysteine levels and, in turn, reduce post-carotid endarterectomy intimal hyperplasia.

METHODS

Each rat was fed one of six diets: (1) lab chow with no folate (n = 7), (2) lab chow with 10 mg/kg folate added (n = 3), (3) lab chow with 25 mg/kg folate added (n = 3), (4) a homocysteine diet with no folate (n = 7), (5) a homocysteine diet with 10 mg/kg folate added (n = 5), or (6) homocysteine diet with 25 mg/kg folate added (n = 5). Each rat then underwent an open carotid endarterectomy. In 2 weeks, intimal hyperplasia in the carotid artery was measured. Plasma homocysteine and folate levels were measured.

RESULTS

Plasma folate levels rose with folate administration. Plasma homocysteine in the lab chow group was 5.4 +/- 0.5 micromol/L and did not change with the addition of folate. In the homocysteine diet group, plasma homocysteine rose 10-fold over the lab chow group (51.9 +/- 6.5 vs 5.4 +/- 0.5, micromol/L, P <.0001). In the group fed a homocysteine diet with 10 mg/kg folate added, a significant decrease in plasma homocysteine was observed (17.5 +/- 8.5 vs 51.9 +/- 6.5, micromol/L, P =.0003). In the group fed a homocysteine diet with 25 mg/kg folate added, plasma homocysteine levels were further reduced to levels seen in the lab chow group (12.6 +/- 2.6 vs 5.4 +/- 0.5, micromol/L, P = not significant). The relationship between plasma folate and homocysteine was inverse (R = 0.39, P =.0036). Luminal stenosis due to intimal hyperplasia was minimal in lab chow groups and unaffected by folate. The homocysteine diet group demonstrated post-carotid endarterectomy luminal stenosis due to intimal hyperplasia (60.9% +/- 9.2%). In the group fed a homocysteine diet with 10 mg/kg folate added, intimal hyperplasia was reduced, compared with the homocysteine diet group (32.6% +/- 7.4% vs 60.9% +/- 9.2%, P =.009). In the group fed a homocysteine diet with 25 mg/kg folate added, intimal hyperplasia was reduced to lab chow group levels (10.8% +/- 0.8% vs 4.8% +/- 1.0%, P = not significant) and was reduced, compared with the group fed a homocysteine diet with 10 mg/kg folate added.

CONCLUSION

The use of folate in this hyperhomocysteinemia carotid endarterectomy model and the resultant attenuation of plasma homocysteine elevation and intimal hyperplasia development lend strong support to homocysteine being an independent etiologic factor in post-carotid endarterectomy intimal hyperplasia.