# Legumes as Functional Food for Cardiovascular Disease
## 3 Legumes as Functional Food for Cardiovascular Diseases
### Cowpea (Vigna Unguiculata ([PERSON].)  
Cowpea (_Vigna unguiculata_ (L.[PERSON]) is a widely consumed legume in the world. It is rich in protein and carbohydrates while having a low fat content [314, 315, 316]. The protein content of cowpea is 2-4-fold higher than cereals and tuber crops [316, 317] although the cowpea's amino acid profile is comparable to that of cereal grains. Cowpea proteins are rich in lysine [318] but deficient in sulfur-containing amino acids such as methionine and cysteine [319]. Cowpea proteins have a low lysine:arginine ratio comparable to soybean suggesting that cowpea proteins have the potential to decrease cholesterol [320].  
Some cowpea isolates and peptides were found to be hypocholesterolemic. In hamsters, [PERSON] et al., (2008) [170] found that cowpea whole seed and protein-fed animals have significantly reduced plasma TC and non-HDL-C and promoted reductions in liver steatosis. This hypocholesteromic effect was attributed to the ability of the proteins to bind bile acids disrupting cholesterol micelles in the gastrointestinal tract as well as altering adipocyte enzyme activity and increased the transcription of lipogenic and cholesterol biosynthetic proteins which influence lipid profiles [170, 321, 322, 323, 324]. [PERSON] et al., (2008) [166] further stated that these cowpea proteins interfere with hepatic cholesterol absorption through the inhibition of the intestinal cholesterol transporter Niemann-Pick C1 Like-1 (NPC1L1) gene expression, thereby, reducing cholesterol synthesis by lowering SREBP-2 gene expression and, consequently, HMG-CoA reductase and LDL receptors. NPC1L1 is involved in the cholesterol absorption at the apical membrane of enterocytes through an unknown mechanism. The cowpea KD dipeptide and three black bean pea peptides (YAAAT, ERAF, and FATGT) were found in silico to have binding affinities to the N-terminal domain of NPC1L1 and were opined to have great potential to disrupt the interaction between NPC1L1 and membrane proteins facilitating cholesterol absorption better than Ezetimibe [325].  
Cowpea proteins are predominantly globulins (50-70%) followed by glutelins, albumins and prolamins [326, 327, 328]. The 7S globulin from cowpea (300 mg per body weight per day) was shown to significantly decrease average body weight gain, liver TC by 14%, serum non-HDL-C by 54%, hepatic TAG levels by 17% and the atherogenic index, a marker for predisposition of heart disease, while increasing serum HDL-C by 57%, lipoprotein lipase activity by 92%, and excreted total fat by 12% and total cholesterol 7% in male Wistar rats compared to the casein-fed group after feeding for 28 days. [PERSON] et al., (2015) found that rats fed with cowpea 7S globulin (300 mg/kg/day) was able to decrease TC by 32.5% compared to just 20.3% by simvastatin (50 mg/kg/day) (\(p<0.001\)) after their 28-day feeding experiment. In the same study, they found that the 7S cowpea globulin-fed mice had signifiicantly reduced serum non-HDL-C and atherogenic index by 46% and 70.6%, respectively, while simvastatin was able to significantly decrease serum non-HDL-C and the atherogenic index by 30.7% and 0.31%, respectively, compared to the hypercholesterol-fed mice (\(p<0.001\)). Supplementation of the cowpea 7S globulin also led to an significant increase of serum HDL-C by 157% when compared against a high cholesterol diet (\(p<0.001\)) outperforming simvastatin, which only contributed a non-significant increase of 18.5% As compared to the rats fed with a high cholesterol diet, hepatic TC and TAG levels were significantly reduced by 14% (\(p<0.01\)) and 17% (\(p<0.001\)), respectively, compared to the effect of simvastatin which significantly reduced TC levels by 11% (\(p<0.05\)) but not significantly reducing TAG (6%) [87].  
Bioactive peptides in cowpea are ascribed to their antihypertensive property due to ACE1 inhibition [13; 168; 169; 329]. Hydrolysis of cowpea proteins yielded peptide fractions that inhibit ACE1-activity compared to the unhydrolyzed protein [13; 168; 169].