What would have been the likely source of glutamine for humans in the
past? Is it basically plant foods (ie cabbage). Or is it meat?
Glutamine seems to tell the body not to store energy but instead to
burn it? Anybody know if other proteins do the same?

L-glutamine supplementation induces insulin resistance in adipose
tissue and improves insulin signalling in liver and muscle of rats
with diet-induced obesity.

AIMS/HYPOTHESIS: Diet-induced obesity (DIO) is associated with insulin
resistance in liver and muscle, but not in adipose tissue. Mice with
fat-specific disruption of the gene encoding the insulin receptor are
protected against DIO and glucose intolerance. In cell culture,
glutamine induces insulin resistance in adipocytes, but has no effect
in muscle cells. We investigated whether supplementation of a high-fat
diet with glutamine induces insulin resistance in adipose tissue in
the rat, improving insulin sensitivity in the whole animal. MATERIALS
AND METHODS: Male Wistar rats received standard rodent chow or a high-
fat diet (HF) or an HF supplemented with alanine or glutamine (HFGln)
for 2 months. Light microscopy and morphometry, oxygen consumption,
hyperinsulinaemic-euglycaemic clamp and immunoprecipitation/
immunoblotting were performed. RESULTS: HFGln rats showed reductions
in adipose mass and adipocyte size, a decrease in the activity of the
insulin-induced IRS-phosphatidylinositol 3-kinase (PI3-K)-protein
kinase B-forkhead transcription factor box 01 pathway in adipose
tissue, and an increase in adiponectin levels. These results were
associated with increases in insulin-stimulated glucose uptake in
skeletal muscle and insulin-induced suppression of hepatic glucose
output, and were accompanied by an increase in the activity of the
insulin-induced IRS-PI3-K-Akt pathway in these tissues. In parallel,
there were decreases in TNFalpha and IL-6 levels and reductions in c-
jun N-terminal kinase (JNK), IkappaB kinase subunit beta (IKKbeta) and
mammalian target of rapamycin (mTOR) activity in the liver, muscle and
adipose tissue. There was also an increase in oxygen consumption and a
decrease in the respiratory exchange rate in HFGln rats. CONCLUSIONS/
INTERPRETATION: Glutamine supplementation induces insulin resistance
in adipose tissue, and this is accompanied by an increase in the
activity of the hexosamine pathway. It also reduces adipose mass,
consequently attenuating insulin resistance and activation of JNK and
IKKbeta, while improving insulin signalling in liver and muscle. PMID:
17604977