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The Relationship of Leptin and Stress Among Worksite Employees. Rachel M. Ceballos April 20, 2007. I. Background: Leptin. Hormone Released : adipocytes, ovaries, mammary glands Receptors Distributed: throughout the body (central/peripheral) Function:

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the relationship of leptin and stress among worksite employees

The Relationship of Leptin and Stress Among Worksite Employees

Rachel M. Ceballos

April 20, 2007

slide2

I. Background: Leptin

  • Hormone
    • Released: adipocytes, ovaries, mammary glands
  • Receptors
    • Distributed: throughout the body (central/peripheral)
  • Function:
    • Leptin can contribute to the regulation of…

-Metabolism

-Puberty

-Hematopoiesis

-Immune Function

-Stress Systems

i background leptin stress
I. Background: Leptin & Stress
  • What is the relevance to cancer prevention and control?

-

-

Immune

Function

Stress

Cancer

(e.g. TH1)

-

+

Leptin

slide4

I. Background: Leptin and Stress

Animal Model

  • Lower leptin levels
    • Wistar Male and Sprague-Dawley Male and Female rats
    • Immobilization Stress: 3 hrs/day for 3-10 days

or 20 min/day for 21 days

(Harris et al., 2002; Makino et al., 1999: Gomez, Houshyar, & Dallman, 2002;Ceballos et al, 2006)

  • Higher leptin levels
    • Long Evans Male and Female rats
    • Immobilization Stress: 20 min/day for 21 days

(Ceballos, Faraday & Klein, 2006)

slide5

I. Background: Leptin and Stress

  • Human Model
  • Lower leptin levels
    • Female medical students
    • Post-menopausal women exposed to acute laboratory

stressor

    • Healthy adults following physical activity

(Al-Ayadhi, et al, 2005; Ceballos,et al, in preparation;Legakis et al, 2004)

  • No difference
    • Healthy men and pre-menopausal women exposed to

acute laboratory stressor

(Ceballos, et al, in preparation)

  • High Leptin Levels
    • Male Japanese government employees (Otsuka, et al, 2006)
slide6

I. Background: Purpose

Pilot Study to examine the relationship between leptin and stress in a community based sample

ii methods
II. Methods
  • Randomized Trial: Promoting Activity and Changes In

Eating, PACE (Beresford, S.A.A., P.I.)

  • 30 Worksites in the Seattle area
    • Worksites with 40 and 350 employees
    • Pair-matched on several characteristics (e.g., size, % women,
    • baseline response rate)
    • Worksites randomly assigned to intervention or comparison

(delayed intervention) arm

    • Subgroup of individuals asked to provide blood sample and

complete additional questionnaires

ii methods1
II. Methods
  • Participants
    • 10 worksites
    • N=80
      • 33 Men, 47 Women
      • Mean Age: 41.62 (11.13)
      • Education: %

Some high School 1.10

High School Graduate/GED 9.89

Technical/Business School 17.58

Some college 23.08

College graduate 36.26

Post graduate/professional 12.09

    • Randomly selected half of the individuals from the PACE intensive subgroup
slide9

II. Methods

  • Assessment
  • Baseline assessment
  • 10-Item Perceived Stress Scale
    • Cohen, Kamarck, & Mermelstein,1983
    • “in the last week”
  • Serum leptin (ng/mL)
    • UW Northwest Lipid Research Laboratory
    • Radioimmunoassay (RIA)
ii methods2
II. Methods

Analysis

  • Mixed Analysis
    • Continuous
    • Categorical
      • Independent Variable: 4 categories of stress
      • Dependent Variable: Serum Leptin
  • Leptin data log transformed
  • Covariates:
    • Worksite (random)
    • Gender and Body Mass Index (fixed)
iii results
III. Results

Descriptives:

iii results1
III. Results
  • Stress entered as continuous predictor variable

F-value (df)p-value

Perceived Stress 0.14 (1,71) 0.71

Gender 50.09 (1,71) 0.001

Body Mass Index 118.10 (1,71) 0.001

slide13

III. Results

  • Stress entered as categorical variable

Quartile Scores:

Low (1-6) Moderate (11-15)

Low Moderate (7-10) High (16-29)

F-value (df) p-value

  • Perceived Stress 0.37 (3,69) 0.78
  • Gender 48.93 (1,69) 0.001
  • BMI 117.95 (1,69) 0.001
slide14

III. Results

  • Stress entered as categorical variable (cont.)

t-value (df)p-value

Quartile 1- Quartile 2 0.35 (69) 0.73

Quartile 1- Quartile 3 0.76 (69) 0.45

Quartile 1- Quartile 4 0.95 (69) 0.34

Quartile 2- Quartile 3 0.48 (69) 0.64

Quartile 2- Quartile 4 0.68 (69) 0.50

Quartile 3- Quartile 4 0.17 (69) 0.86

slide15

III. Results

  • Effect of Gender
slide16

III. Results

  • Stress entered as continuous predictor variable
  • F-value (df)p-value
  • Perceived Stress 0.00 (1,70) 0.949
  • Gender 22.55 (1,70) 0.001
  • Perceived Stress*Gender 1.85 (1,70) 0.178
  • Body Mass Index 122.07 (1,70) 0.001
iv conclusion
IV. Conclusion
  • No significant relationship between leptin and stress
  • Preliminary analyses conducted to determine appropriate sample size
  • Range of stress scores comparable to other studies
  • Menstrual cycle, use of medication, diet, etc. were not controlled
iv conclusion1
IV. Conclusion
  • Changes in leptin may only be evident following acute stress
  • Higher levels of stress may be required to see a change in leptin levels
  • Action of chronic stress on immune function may not be mediated by leptin
    • leptin may not contribute to changes in the

microenvironment of tumor cells

iv future directions
IV. Future Directions
  • May want to consider
    • Stress type and duration
    • Dietary intake
  • CARB Study, Glycemic Load and Obesity Effects on Cancer Biomarkers (Neuhouser, M., Lampe, J.W., PI)
  • Health SMART, Stress Management and Relaxation Training (McGregor, B.A., PI)
  • Conduct additional analyses on PACE data
acknowledgements
Acknowledgements
  • Shirley Beresford, Ph.D.
  • Dale McLerran
  • Sonia Bishop
  • Bonnie McGregor, Ph.D.