Search

This study examined the influence of phytoestrogens (estrogen-like plant compounds) present in rodent diets (via soy) on brain aromatase, anxiety behavior (in the elevated plus maze), sexually dimorphic hypothalamic nuclei [sexually dimorphic nucleus of the preoptic area (SDN-POA) and anteroventral periventricular nucleus (AVPV)], visual spatial memory (VSM) and determined phytoestrogen, calbindin, and cyclooxygenase-2 levels in the rat brain. In male and female LongEvans rats fed either lifelong exposure to a high-phytoestrogen diet (Phyto-600) or a phytoestrogen-free diet (Phyto-free), there were no significant alterations in brain aromatase. In the elevated plus maze, phytoestrogens produced marked anxiolytic effects in both males and females. In a subset of rats, at age 80 d one-half were either kept on their original diet (Phyto-600 or Phyto-free) or changed to the opposite diet (Phyto-free or Phyto-600). Males fed (lifelong) or changed to a Phyto-free diet had significantly decreased SDN-POA and increased AVPV volumes compared with males fed (lifelong) or changed to the Phyto-600 diet. The opposite was found in females. Within the radial arm maze, VSM was enhanced in females fed the Phyto-600 diet, whereas in males VSM was inhibited by the same diet. Male rats fed the Phyto-600 diet had significantly higher phytoestrogen concentrations in the frontal cortex, hypothalamus and cerebellum but not in the hippocampus than did males fed the Phyto-free diet. Also, males fed the Phyto-600 diet had decreased calbindin (a neuroprotective agent) and increased cyclooxygenase-2 (an inflammatory factor prevalent in Alzheimer's disease) levels in the frontal cortex compared with males fed the Phyto-free diet. These data suggest that phytoestrogens via a soy diet do not alter brain aromatase, produce anxiolytic effects in the elevated plus-maze, significantly alter volumes of the SDNPOA and AVPV, and significantly alter VSM during adulthood. TABLE 1 Results for the three diets Control diet Glomerular filtration rate, mL * min-1 * 1.73 [m.sup.-2] 159 [+ or -] 7.7 (a) Total cholesterol, mg/dL [mmol/L] 181 [+ or -] 10.1 (a) [4.69 [+ or -] 0.26] LDL cholesterol, mg/dL [mmol/L] 115 [+ or -] 9.3a [2.98 [+ or -] 0.24] LDL oxidation, conjugated dienes,/[mu]no//L 45.1 [+ or -] 3.0 Urine sodium, mEq/h 9.20 [+ or -] 1.46 Dietary protein intake, g * kg body weight-1 * [d.sup.-1] 1.30 [+ or -] 0.12 (a) Baseline diet Glomerular filtration rate, mL * min-1 * 1.73 [m.sup.-2] 143 [+ or -] 7.4 (b) Total cholesterol, mg/dL [mmol/L] 168 [+ or -] 8.0 (b) [4.35 [+ or -] 0.21] LDL cholesterol, mg/dL [mmol/L] 105 [+ or -] 7.7 (b) [2.72 + or -] 0.20] LDL oxidation, conjugated dienes,/[mu]no//L 41.0 [+ or -] 4.7 Urine sodium, mEq/h 8.00 [+ or -] 1.61 Dietary protein intake, g * kg body weight-1 * [d.sup.-1] 1.34 [+ or -] 0.11 (a) Soy diet Glomerular filtration rate, mL * min-1 * 1.73 [m.sup.-2] 161 [+ or -] 10.0 (a) Total cholesterol, mg/dL [mmol/L] 187 [+ or -] 9.4 (a) [4.84 [+ or -] 9.4 (a) LDL cholesterol, mg/dL [mmol/L] 117 [+ or -] 8.6 (a) [3.03 [+ or -] 0.22] LDL oxidation, conjugated dienes,/[mu]no//L 43.7 [+ or -] 3.9 Urine sodium, mEq/h 7.63 [+ or -] 1.59 Dietary protein intake, g * kg body weight-1 * [d.sup.-1] 1.08 [+ or -] 0.10 (b) Means with any like superscripts are not significantly different at [alpha] = 0.05.

Background: Diabetic nephropathy is the most frequent cause of end-stage renal disease in the Western world. Dietary intake, including protein amount and type, seems to affect the progression of renal disease. This pilot study tested the hypothesis that substituting soy protein for animal protein in the diets of diabetics would help correct glomerular hyperfiltration. Methods: Twelve young adults (aged 29.9 ± 2.4 years) with type 1 diabetes mellitus (duration of diabetes 15.1 ± 2.3 years) and hyperfiltration (glomerular filtration rate, GFR > 120 mI/min/1.73 m²) completed a crossover, dietary intervention trial. After a four-week assessment of baseline characteristics and dietary habits, subjects were assigned to either a control or soy diet for eight weeks after which each subject was crossed over to the alternative diet for another eight-week period. Results: Mean GFR was significantly reduced (p < 0.02) after eight weeks on the soy diet (143 ± 7.4 ml/min/1.73 m²) compared with baseline (159 ± 7.7 mI/min/1.73 m²) and control diets (161 ± 10.0 ml/min/1.73 m²). Urinary excretion of the soy isoflavones was significantly higher (p < 0.01) at the end of the soy diet (genistein 1,014.6 ± 274.1 nmol/h, daidzein 2,645.1 ± 989.6 nmol/h) compared with baseline (genistein 53.7 ± 31.1 nmol/h, daidzein 151.1 ± 74.1 nmol/h) and control diets (genistein 41.1 ± 13.3 nmol/h, daidzein 127.5± 54.0 nmol/h). The soy diet significantly reduced total and LDL cholesterol by 7% and 9%, respectively. Conclusions: Implementation of a soy-based diet appears to reduce the GFR and total and LDL cholesterol of young adults with type 1 diabetes and glomerular hyperfiltration, thus affecting positively their clinical profile. [ABSTRACT FROM AUTHOR]