Whey Protein And Prostate Health 2002[1]

Dietary whey proteins and oxidative stress in the prostate Kyle D. Kent. J. Bomser and W. J. Harper Department of Food Science and Technology The Ohio State University

The prostate • Prostate cancer is the 2nd leading cause of cancer death in men – Oxidative stress is a major contributor – Diets rich in antioxidants may prevent cancer development

Cancer development mutation

glutathione

oxidative stress

What is glutathione (GSH)? • The major cellular antioxidant

• Composed of 3 amino acids – glutamate, cysteine, glycine

• GSH synthesis is limited by cysteine availability • GSH protects against oxidant-induced cell damage

Why Whey? • Cystine-rich protein source • Whey proteins – α-lactalbumin (4 cystine per molecule) – β-lactoglobulin (2 cystine per molecule) – bovine serum albumin (17 cystine per molecule)

Hypothesis Digested whey protein isolate can elevate intracellular GSH and protect against oxidant-induced cell death in human prostate cells

The objectives of the study were: 1. To determine if digested whey protein isolate (WPI) can elevate GSH in human prostate epithelial cells 2. To determine if digested WPI protects against oxidant-induced cell death in human prostate epithelial cells

SDS-PAGE of WPI 206 kDa 91 kDa 51 kDa 35 kDa 28 kDa 20 kDa

7 kDa

A B C D E (A) undigested WPI (B) digested WPI (C) α-lactalbumin (D) β-lactoglobulin (E) bovine serum albumin

Objective #1: Can digested WPI elevate intracellular GSH in human prostate cells?

Materials • • • • •

Human prostate epithelial cells (RWPE-1) Digested whey protein isolate (d-WPI) Digested sodium caseinate (d-casein) N-acetylcysteine (NAC) Buthionine sulfoximine (BSO)

Concentration and time dependent GSH elevation 5

(A)

*

*

5 reduced glutathione (nmol/10 6 cells)

reduced glutathione (nmol/10 6 cells)

4

6

3 2 1 0

(B)

*

*

4

*

3 2 1 0

0

125

250

WPI (µ g/mL) d-WPI

500

0

12

24

time (hrs)

* significant difference from the control (p<0.05).

48

Cysteine availability and GSH concentration reduced glutathione (nmol/106 cells)

6 5 4

(A)

*

*

3 2 1 0 control d-casein d-WPI

NAC

* significant difference from the control (p<0.05).

Inhibition of GSH synthesis by BSO reduced glutathione 6 (nmol/10 cells)

5

*

4 3 2

*

1 0 control

BSO

* BSO+ d-WPI d-WPI

* significant difference from the control (p<0.05).

Objective #2: Can digested WPI protect human prostate cells against oxidantinduced cell death?

Materials • Human prostate epithelial cells (RWPE-1) • Digested whey protein isolate (d-WPI) – 500 μg/mL, 24 hrs

• Buthionine sulfoximine (BSO) – 500 μM, 24 hrs

• t-butyl hydroperoxide (TBHP) – 0-1000 μM, 24 hrs

Protection vs. TBHP-induced cell death 140 control d-WPI BSO+d-WPI

cell proliferation (% control)

120 100 80

*

60

*

40 20 0 0

20

40

60

80

100

120

TBHP (µ M)

*Significant difference from the control at each concentration of TBHP (p<0.05).

140

Conclusions • Digested WPI elevates intracellular GSH of human prostate cells • Elevation of intracellular GSH by de novo synthesis • Digested WPI also protects against oxidantinduced cell death

Acknowledgments • • • •

Joshua A. Bomser W. James Harper Institute of Food Technologists The Ohio State University Department of Food Science & Technology