The following chemicals were used in the experiments: D-glucose, L-leucine, L-glutamine, pyruvate, L-lactate, IBMX, and forskolin (Sigma-Aldrich, Taufkirchen, Germany), mannoheptulose (Bujno Synthesis, Warsaw, Poland), glibenclamide (Santa Cruz Biotechnology, Dallas, USA), and Bay K 8644 (Alomone Labs, Jerusalem, Israel).
When mannoheptulose (10 mM), a specific inhibitor of glucose-induced insulin secretion, was added during the glucose (16.7 mM) stimulation period for 10 min (from min 1120), the insulin secretory rate decreased immediately (Figure 1(b)).
The specificity of the glucose-induced secretory response was documented by the inhibition with the glucokinase inhibitor mannoheptulose, the classical selective inhibitor of glucose-induced insulin secretion .
Caption: Figure 1: Kinetic profiles of insulin secretion from perifused EndoC- [beta]H1 [beta]-cell pseudoislets in response to a 30 min stimulation with glucose (16.7 mM) (a) (n = 7) and to the inhibition of glucose-induced (16.7 mM) insulin secretion by mannoheptulose (10 mM) (11-20 min) (b) (n = 4).
Of special interest is mannoheptulose, a compound which occurs naturally in avocados, though Roth says it degrades quickly once the fruit ripens.
Products based on mannoheptulose may be years away from use in man, but maybe not in man's best friend.
"We t think that a compound like mannoheptulose or a glycolytic inhibitor is going to be superior to any of the products that are out there, because of the fact that it does work somewhat similarly to true caloric restriction," Ingram says.
But mannoheptulose isn't the only natural substance that appears to mimic a state of calorie restriction.