The Effect of Vegan Protein-Based Diets on Metabolic Parameters, Expressions of Adiponectin and Its Receptors in Wistar Rats

Abstract

Vegan protein-based diet has attracted increasing interest in the prevention of metabolic syndrome (MetS). Meanwhile, adiponectin has become a highly potential molecular target in the prevention of MetS. Our study will identify a potential vegan protein diet for the prevention of MetS using rat models. Thirty-six Wistar rats were randomly assigned into three groups and given diets containing one of the following proteins for 12 weeks: casein (CAS, control diet), soy protein (SOY), and gluten-soy mixed protein (GSM). Changes in metabolic parameters as well as the expressions of adiponectin and its receptors were identified. Compared to CAS diet, both SOY and GSM diets led to decreases in blood total cholesterol and triglycerides, but only GSM diet led to an increase in HDL-cholesterol; no marked difference was observed in blood glucose in all three groups; HOMA-IR was found lower only in SOY group. Among groups, the order of serum adiponectin level was found as GSM > SOY > CAS. Similar order pattern was also observed in expression of adiponectin in adipose tissue and AdipoR1 mRNA in skeletal muscle. Our results suggested for the first time that, besides SOY diet, GSM diet could also be a possible substitute of animal protein to prevent MetS.

Keywords: adiponectin; dietary intervention; metabolic syndromes; rats; vegan protein.

Figure 1

Weekly average feed intakes of three groups over the 12-week feeding period. Average feed intake of rats across all groups at the end of the study was statistically analyzed by one-way ANOVA followed by LSD-test and no significant difference was shown.

Figure 2

Change of body weights of rats from three groups over the 12-week feeding period. Body weights of rats at the end of the study were statistically analyzed by one-way ANOVA followed by LSD-test; * p < 0.05 versus CAS and GSM group.

Figure 3

The effect of different dietary proteins on serum adiponectin. Serum adiponectin showed no significant difference among all three groups at the beginning of the study. During the 12-week period, serum adiponectin in the CAS group decreased significantly whereas that in SOY and GSM group increased significantly as compared to their respective baseline levels. Among groups, SOY and GSM groups demonstrated higher levels of serum adiponectin than that of CAS group at the end of the study. One-way ANOVA followed by an LSD-test was used to detect significant differences of the means, ** p < 0.001 versus CAS group; ^# p < 0.05 versus baseline; ^## p < 0.001 versus baseline.

Figure 4

The effect of different dietary proteins on the expressions of adiponectin in adipose tissue, AdipoR1 in skeletal muscle and AdipoR2 in liver tissue. (A–C) demonstrate the expression levels (absorbance) of mRNA of adiponectin—AdipoR1 and AdipoR2—that were normalized against those of β-actin (served as a loading control). One-way ANOVA followed by LSD-test was used to detect significant differences of the means, * p < 0.05.

Figure 5

The effect of different dietary proteins on the expression of adiponectin protein in epididymal adipose tissue. Protein levels of adiponectin were normalized against that of β-actin (served as a loading control). One-way ANOVA followed by LSD-test was used to detect significant differences of the means, * p < 0.05.