MAPLE SYRUP URINE DISEASE

BLOCKED PATHWAY OF BCAA CATABOLISM

Its being proposed that therapy with phenyl butyrate in MSUD patients has been associated with a selective reduction in branched-chain amino acids (BCAA) in spite of adequate dietary protein intake.

Hypothesis

RATS (Rattus norvegicus)

Age (10-30 days old) The physiology is easier to

monitor in the rat The physiology is more

like the corresponding human condition

The distance effects of drug administration to specific anatomical areas

Over time, a volume of data has developed that will take years to be replicated in the mouse .

RESEARCH SUBJECTS

RESEARCH SUBJECTS

RESEARCH SUBJECTS

BCAA Catabolism

E1: 2-oxoisovalerate dehydrogenase, composed itself of two polypeptide chains:

E1-alpha (probably the catalytic subunit) and E1-beta; E1 IS THE MOST COMMON SITE OF

MUTATIONS. E2: dihydrolipoamide acyltransferase. E3: dihydrolipoamide dehydrogenase.

BCKDH

Specific Aim: To increase the proportion of active BCKDH.In order to see how phenyl butyrate increases the activity of BCKDH enzyme, the following procedure will be followed;

In vitro testing with fibroblast cells from rat In vivo testing with rats In vivo testing with human subjects

RESEARCH DESIGN

In vitro Test (Fibroblast)

Four Rats : 2 healthy control , 2 MSUD patients

2 induced with MSUD via BCAA IV administration

Fibroblast cells are collected from subjects 2mm phenyl

butyrate CIC

Based on the success of the in vitro test, a similar test is carried out in humans and the serum levels of BCAA and BCKA data before and after administration of phenyl butyrate generates charts for comparison.

In vivo testing with Human Subjects

ResultsIn vivo with Human Subjects

PROPOSED MECHANISM

α –keto isovalerate+ CIC + BKD+ Phenyl butyrate +NAD+ + TPP RCOCoA+CO2+NADH+

+ + BKD + + +

+ CO2 +

Team A rats are orally given a saline solution for three days

Team B rats are orally given phenyl butyrate for three days .

After 3 days they are sacrificed, livers harvested and analysed using western blot

In vivo with Rats

Results

It contains Na+ hence, patients on salt diet cannot use

It can cause drowsiness It contains inactive ingredients that may

cause allergic reactions

Side Effects of Phenyl butyrate

INNOVATION: Lactating Porcine Mammary Tissue Catabolizes

Branched-Chain Amino Acids for Glutamine and Aspartate Synthesis

Future Directions

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2675817/

http://ars.els-cdn.com/content/image/1-s2.0-S0014299901014893-gr6.jpg

http://wildpro.twycrosszoo.org/S/0MRodenti/muridae/rattus/Rattus_norvegicus/Rattus_norvegicus.htm

Sources