Soy Protein Influences the Development of the Metabolic Syndrome in Male Obese ZDFxSHHF Rats

Abstract

Previous investigations have demonstrated a marked effect of soy protein on the metabolic syndrome (MS). The purpose of this preliminary study was to identify the effects of soy-based diets on male obese ZDFxSHHF (fa/ fa-cp/?) rats. Animals were randomly assigned to one of four diets: control, casein (C); low-isoflavone (LIS) soy protein; high-isoflavone (HIS) soy protein; or casein + rosiglitazone (CR). Physiological, biochemical, and molecular parameters were determined at sacrifice. Body weight (p < 0.01) and food intake (p < 0.05) were lower in LIS-fed rodents. Rosiglitazone-treated animals had higher body weight and adiposity (p < 0.05). LIS and CR groups exhibited better glycemic control (p < 0.05), but with a limited effect in rosiglitazone-treated animals. HIS fed rats had higher glucose and triacylglyceride levels (p < 0.01), and lower plasma insulin (p < 0.01). Renal function parameters with the exception of an increase in systolic blood pressure (p < 0.05) were all suppressed in the LIS group (p < 0.01). The CR group had twofold PPARalpha and PPARgamma mRNA abundance (p < 0.01). LIS-fed animals also exhibited greater abundance of PPARgamma mRNA (p < 0.001), and nearly threefold FAS and CPT-1 mRNA levels (p < 0.05). HIS-fed rats also had higher abundance of CPT-1 mRNA, as well as a lower abundance of ACC mRNA (p < 0.05). Soy-based diets, influenced by isoflavone content and distinct from rosiglitazone, improved several metabolic parameters in obese ZDFxSHHF rats.

Effects of aglycone genistein in a rat experimental model of postmenopausal metabolic syndrome

“…Other papers showed some positive effect of soy proteins and isoflavone intake (Davis et al 2005(Davis et al , 2007 or soy-rich diets (Dyrskog et al 2005) in other animal models of metabolic syndrome; however, the exact intake of genistein has not been evaluated, since genistein is mostly present as genistin (the glycoside) the plasma levels of genistein in this studies could largely differ depending on gut absorption and microflora (which is responsible for aglycone conversion), in light of these observations it is rather difficult to compare those results with the present paper.…”

Soy Protein and Isoflavones Influence Adiposity and Development of Metabolic Syndrome in the Obese Male ZDF Rat

“…Samples were then utilized to determine total urine protein (Catalog #500-006; Bio-Rad, Hercules, Calif., USA) and urine creatinine (Catalog #8009; Quidel, San Diego, Calif., USA) according to manufacturer's instructions. Our previous studies [22,23] have validated the use of single-day urine collection as measure of average output. Blood samples were also collected from the lateral tail vein by cutting a 1-to 2-mm section from the tip of the tail with a sterile scalpel blade.…”

“…Liver composition analysis was carried out as previously described [22,23] . Briefly, total lipid extracts were obtained from 0.5 g of frozen liver tissue.…”

“…Soy is of particular interest because of its association with a multitude of health benefits including prevention of complications related to renal disease [4,[12][13][14][15] , and hypertension [16] , as well as improvement in lipid profiles [17][18][19][20][21][22][23] and maintenance of insulin sensitivity and glucose homeostasis [21][22][23] .…”

“…Alternatively, others have shown that soy protein with the isoflavone-containing fraction has little benefit over soy protein without isoflavones [19] . We have previously demonstrated a marked benefit of soy protein and isoflavone content depending on which rodent model of insulin resistance and MS was examined [20][21][22][23]25] .…”