Two combinations of gluconeogenic precursors--glycerol+lactate and alanine+glutamine--were employed, the second one being dependent on liver nitrogen disposal by transamination or ureagenesis
. As these precursors enter the gluconeogenic pathway at different points, their separate infusion might reveal the sites most influenced by training and/or insulin in this model.
The elevations in the hepatic ureagenesis
could increase the losses of urine nitrogen, compromising the utilization efficiency of the dietary nitrogen compounds .
The first patient in Cohort 2 demonstrated normalization of ureagenesis
to 104% at week 24.
This patient has ornithine transcarbamylase (OTC)  deficiency, the most common disorder of ureagenesis
, with an estimated incidence of approximately 1 in 40000.
Furthermore, in patients with T2DM and fatty liver, the signal transduction for glucagon is dysfunctional in the liver leading to impaired ureagenesis
and deranged amino acid levels .
OTC deficiency is the most common inherited disease of ureagenesis
with an estimated prevalence of 1 in 62,000 to 1 in 77,000 [8, 14, 15].
In order to determine whether the AZT-induced increase in blood levels of ammonia was due to a defective liver ureagenesis
, we also measured this nitrogen by-product in the blood compartments from our experimental groups (Figures 8(e) and 8(f)).
Heymsfield, "Increased ureagenesis
and impaired nitrogen use during infusion of a synthetic amino acid formula.
In the liver, resynthesis of glutamine occurs for disposal of waste nitrogen at the expense of ureagenesis
. Since nitrogen excretion via ammonium does not utilize any bicarbonate, but nitrogen excretion via urea does, the saved bicarbonate can neutralize excess protons.
Interestingly, both studies found that protein doses greater than 20 grams resulted in an overabundance of available amino acids that subsequently resulted in an increased rate of amino acid oxidation and ureagenesis
. Additionally, a recent study (Moore et al., 2012) showed that four, 20gram doses of whey protein ingested every three hours were superior in increasing MPS than two, 40-gram doses ingested every six hours.
Relationships between ureagenesis
and gluconeogenesis in ruminants fed a high conteni of nitrogen.
The comparable increase seen in heart could have resulted from ureagenesis
within cardiomyocytes ; however, most nonhepatic tissues failed to accumulate urea during freezing.