Role of Proteins in Insulin Secretion and Glycemic Control - Advances in Food and Nutrition Research - page 13

( Sener & Malaisse, 2002 ). However, these differences may be due to the use
of different cell lines all of rat origin. Although the literature more heavily
suggests that alanine is proinsulinogenic, this is based on a very limited num-
ber of studies. Data from more studies are required.
Arginine has been shown to stimulate insulin secretion from b -cells
through derived nitrogen oxides ( Schmidt, Warner, Ishii, Sheng, &
Murad, 1992 ). Dupre, Curtis,Waddell, and Beck (1968) infused healthy par-
ticipants with 15 g of arginine intraduodenally and intravenously over 40 min
and found that insulin increased in both instances. Similarly, Floyd et al.
(1966b) infused 172 mMof arginine to healthy subjects and observed an insu-
lin increase (maximal increase of 81 m U/ml). Interestingly, in both studies,
intravenous infusion also resulted in increased blood glucose, suggesting that
argininemay be glucogenic. However, intraduodenal infusion had no impact
on glucose possibly due to plasma arginine concentrations being less. More
recent work looking at the effects of oral arginine on insulin secretion found
no effects. Gannon, Nuttall, and Nuttall (2002b) fed nine healthy subjects
1 mM/kg body weight of arginine andmeasured insulin, plasma amino acids,
and glucagon for the subsequent 2 h. They found that arginine did not
increase insulin secretion although it did increase glucagon. These results sug-
gest that arginine at levels usually found inmeals is not insulinogenic although
it may be at higher levels (as observed by Dupre and colleagues). In vitro
work carried out using rat pancreatic cells show that arginine stimulates insu-
lin secretion through cationic amino acid transportation into the islet cells
resulting in membrane depolarization ( Herchuelz, Lebrun, Boschero, &
Malaisse, 1984 ) . These effects were seen when the cells were exposed to
an arginine concentration of 10 mM. Gerich, Charles, and Grodsky (1974)
observed a nonphasic insulin release in perfused rat pancreas when it was
exposed to 6 mM of arginine. Therefore, the literature on arginine's effect
on insulin secretion is equivocal. In vitro studies show that arginine stimulates
insulin secretion from pancreatic cells which suggests that exposure of b -cells
to higher arginine concentrations stimulates insulin. More data from whole
body studies are required to ascertain if arginine levels typically found in
dietary proteins have a significant effect on insulin secretion.
Glycine is an amino acid found in large quantities in gelatin (approxi-
mately 30% of total amino acids; Gannon &Nuttall, 2010 ) . Beef protein also
contains a relatively higher amount compared to other proteins ( Table 1.1 ) .
Previous work showed that gelatin induced a significantly large insulin
response ( Gannon et al., 1988 ) and this was attributed to the presence of