Feasibility of a low-fat/high-fiber diet intervention with soy supplementation in prostate cancer patients after prostatectomy.

OBJECTIVES: To evaluate the feasibility and long-term compliance with a low-fat diet supplemented with soy protein in men at increased risk for recurrence after radical prostatectomy. DESIGN: Randomized, control study. SETTING: Academic center in USA. SUBJECT: Forty men who had undergone radical prostatectomy and were at increased risk for recurrence. INTERVENTION: Low-fat (15% fat), high-fiber (18 g/1000 kcal) diet supplemented with 40 g soy protein isolate (n=26) was compared to USDA recommended diet (n=14). RESULTS: Over 4 years, subjects in the intervention group but not in the control group made and sustained significant changes in their diet as measured by the dietary assessment instruments and urinary isoflavone excretion. In the intervention group, dietary fat intake was reduced from 33.46+/-1.27% energy/day to 21.04+/-1.74% (P<0.05), fiber intake increased from 14.6+/-1.06 to 21.05+/-2.29 g/day. The insulin growth factor-1 (IGF-1) level was decreased from 260.4+/-8.6 ng/ml at baseline to 220.5+/-7.9 ng/ml at 6 months (P<0.05) in the intervention group with no significant change in the control group. An ex vivo assay demonstrated inhibition of LNCaP cell growth (-20.0+/-7.7%, P<0.05) by sera from patients in the intervention group after 6 months of dietary change compared to baseline. CONCLUSION: These data suggest that long-term low-fat dietary interventions as part of prospective randomized trials in prostate cancer survivors are feasible, and lead to reductions in circulating hormones or other growth factors stimulating prostate cancer growth ex vivo.

Glycogen turnover in the isolated working rat heart.

The isolated working rat heart was adapted for simultaneous determination of glycogen synthesis and degradation using a dual isotope technique. After prelabeling of glycogen with [U-14C]glucose, glycogenolysis was determined continuously from the washout of 14CO2 plus [14C]lactate. Glycogen synthesis was determined during the same period from incorporation of [5-3H]glucose. In the absence of added hormones, hearts were predominantly glycogenolytic (1.5 mumol/min/g, dry weight), and there was simultaneous synthesis (11% of the rate of glycogenolysis). The percentage of glucose taken up by the heart that could traverse the glycogen pool as a consequence of glycogen turnover was minor (5%). Insulin (10 milliunits/ml) predictably stimulated glycogen synthesis (3.6-fold) and nearly abolished glycogenolysis. Addition of glucagon (1 microgram/ml) increased contractile performance and initially stimulated glycogenolysis (3.8-fold) until glycogen was largely depleted. Net tritium incorporation was unaffected by glucagon. Both hormones stimulated glycolytic flux from exogenous glucose (3H2O from [5-3H]glucose) as well as total glycolytic flux (3H2O plus glycogenolysis). The initial stimulation in total glycolytic flux with glucagon was largely from glycogen, explaining the lag in stimulation from exogenous glucose. The relationship between the specific radioactivity and amount of glycogen remaining after different degrees of glycogenolysis suggests that the preference of glycogenolysis for newly synthesized glycogen is only partial.