8/13/2019 CALDERON Starvation and Fasting Biochemistry Integration

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San Beda College of MedicineSection of Biochemistry

CLINICAL INTEGRATION: BIOLOGY OF FASTINGDr. Pacifico Eric E. Calderon

For the individual cell, the most immediate challenge is the safeguarding of its own energy supply.

Beyond the imperative of self-preservation, however, cells and organs must cooperate unselfishly for the

common good of the body. Together they must master the everyday challenges of overeating, fasting,

and muscular activity and the less routine challenges of infectious illnesses and environmental toxins.

These challenges require the organism-wide coordination of metabolic pathways. This coordination is

provided by nervous and hormonal signals that reach every part of the body.

 At the end of this 2-hour activity, learners are expected to:

1. To understand metabolic adaptations to environmental challenges and varying physiological

needs, specifically in starvation

2. To describe the hormonal mechanisms of metabolic regulation and some clinical conditions in

which these regulatory mechanisms are deranged

CASE

 At the end of the year, for the very first time in my life, I will be attending a wedding... not as a guest but

not as the groom, but as the best man. I counselled myself that I will go on a crash diet, will eat as

minimal as I can, probably just water and Jacob crackers most of the time until I “  lose”   weight. My goal is

to fit into a haute couture tuxedo I ordered especially for this occasion. What are will be the changes in

my body if I go on a crash diet? Will I starve? Will I still live? Help! --- Anonymous

STUDENT PREPARATION

Find the answers to the following specific learning objectives:

1. Discuss the role of glucagon in maintaining blood glucose levels

2. Discuss how energy must be provided continuously

3. Discuss the concept of basal metabolic rate and the Harris-Benedict equation and the Mifflin-St.

Joer equation

4. Discuss why adipose tissue is the most important energy depot

5. Discuss the metabolic activities of the liver in the well-fed state and in fasting

6. Discuss how the liver maintains blood glucose during fasting

7. Discuss how ketone bodies provide lipid-based energy during fasting.

Required reading:

 Anderson R.M., Weindruch R. (2010) Metabolic reprogramming, caloric restriction andaging. Trends Endocrinol Metab. 21:134-141. 

Cahill G.F. (2006) Fuel metabolism in starvation. Annu Rev Nutr . 26:1-22.

Devlin, TM (ed). (2011) Textbook of Biochemistry with Clinical Correlations, 7/e. Ch 21:Metabolic Interrelationships. US: John Wiley and Sons.