Soy Protein Influences Insulin Sensitivity and Cardiovascular Risk in Male Lean SHHF Rats

Abstract

Previous investigations have demonstrated a marked effect of soy protein on multiple physiological parameters associated with the metabolic syndrome (MS). This preliminary study investigated the physiological effects of soy-based diets on cardiovascular risk in a unique rodent model that reflects early stages of MS. Briefly, lean male SHHF (+/cp) rats were randomly assigned to the following treatment groups: casein (control, C); low-isoflavone (LIS) soy protein isolate; high-isoflavone (HIS) soy protein isolate; or C+ 0.01 % rosiglitazone (CR). Rats were fed for thirty-six weeks. Liver weight, heart weight, total plasma cholesterol, fasting blood glucose were lower in soy-fed animals compared to control (p < 0.01). Body weight, kidney weight, alanine aminotransferase (ALT), fasting plasma insulin, and homeostasis model assessment (HOMA) score were also lower in LIS-fed rodents (p < 0.05) compared to casein treatment. All diet groups exhibited lower urine protein (p < 0.01) and small arteriole content (p < 0.05) compared to controls. LIS feed had a slightly more profound influence on body weight, liver metabolism, and insulin sensitivity. However, both soy diets exhibited marked improvements over a casein-based diet.

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

“…0.05), however this effect was diminished by week 11. Consistent with our previous investigations [20,22,23] , total plasma cholesterol was lower in rats fed soy compared to casein-based diets at both weeks 8 ( table 3 , p ! 0.001) and 11 ( table 4 , p !…”

“…Specific antibodies used are ␣ -PPAR-␥ (1: 100) and ␣ -GLUT4 (1: 100) to identify PPAR-␥ and GLUT4 proteins, respectively. The relative intensity of the signals was quantified with NIH Image software and the values obtained for signals are expressed as fold changes compared with control, which was arbitrarily set to 1 is consistent with previous observations in SHHF rats [22] . To determine whether changes in liver lipid composition were associated with differences in adipogenesis, GPDH and FAS activity were measured.…”

“…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.…”

Identification of urinary isoflavone excretion phenotypes related to the cholesterol lowering ability of soy protein in Golden Syrian hamsters

“…Futhermore, Davis et al (2005) focused on physiological effects of soy-based diets with varying isoflavone content on pathogenesis of insulin-resistance and cardiovascular risk using a rodent model that reflects early stages of insulin resistance and MS. In this study, lean male SHHF (+/cp) rats were randomly assigned to the several treatment groups: casein (control, C); low-isoflavone (LIS) soy protein isolate; high-isoflavone (HIS) soy protein isolate; or C+ 0.01 % rosiglitazone (CR) for thirty-six weeks.…”