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TITLE:
Bacterial products and the control of ingestive
behavior: clinical implications.
AUTHOR:
Langhans W
AUTHOR AFFILIATION:
Institute for Animal Sciences, Swiss Federal
Institute of Technology, Zurich, Switzerland.
SOURCE:
Nutrition 1996 May;12(5):303-15
NLM CIT. ID:
97029503
ABSTRACT:
Bacterial products such as lipopolysaccharides
(LPS) and muramyl peptides are delivered in the course of infections. They trigger the
host's acute phase responses to bacterial infections and are probably involved in the
accompanying hypophagia because LPS and muramyl dipeptide (MDP, the minimal
immunologically active muramyl peptide) reduce food intake after parenteral administration
in animals. LPS and MDP inhibit feeding synergistically through separate but interacting
mechanisms. The hypophagic effects of LPS and MDP are presumably mediated by the combined
actions of interleukin-1, tumor necrosis factor, and other cytokines. More work is
required to understand the interactions between these cytokines, and between bacterial
products and cytokines, before cytokine antagonists can be used for treatment of the
hypophagia during bacterial infections. As the hypophagia seems to be an early mechanism
of host defense, a treatment should be carefully considered. If an intervention is
indicated because of a patient's poor condition, inhibitors of eicosanoid synthesis and
glucocorticoids may hold more promise for therapy because such substances block LPS and
MDP hypophagia. Although LPS can reduce food intake by direct action on the brain,
presently available evidence indicates that systemic LPS acts primarily in the periphery
to generate a neural signal that is transmitted to the brain and inhibits feeding through
the vagus. The exact site where LPS acts on peripheral nerves remains to be identified.
LPS hypophagia is conditionable, but conditioning cannot solely account for LPS hypophagia
under most test conditions. Whether MDP hypophagia is also conditionable and mediated by
vagal afferents is not yet known. All in all, the putative mediators and mechanisms of LPS
and MDP hypophagia suggest some options for a treatment of the hypophagia during bacterial
infection, but present knowledge about the mechanisms and interactions of the involved
substances is still fragmentary and requires further investigation.
When my office
lease expired at the end of 2004, I decided to turn it into a
"sabbatical" from my private practice. Many years ago, in my
grandfather's 89th year of life, he told me, "John, it is important
to smell the roses while you can still smell them." His life
gave living a very good reputation. It is also true that the
pursuit of that philosophy required my grandfather to to re-open his
assay office/ore market in Wickenburg, Arizona as a 75-year-old because
he had run a little short of retirement money. Thus, if blessed with his
luck and health, I'll be back.. --jjh
