Objective: We tested the relative importance of a low-glycemic response versus a high glycemic response breakfast meal on postprandial serum glucose, insulin and free fatty acid (FFA) responses after consumption of a standardized mid-day meal in adult individuals with Type 2 diabetes mellitus (DM). Design: Following an overnight fast of 8-10 h, a randomized crossover intervention using control and test meals was conducted over a 3-week-period. A fasting baseline measurement and postprandial measurements at various time intervals after the breakfast and mid-day meal were taken. Subjects: Forty-five Type 2 DM subjects completed the requirements and were included in the study results. Interventions: Two different breakfast meals were administered during the intervention: (A) a high glycemic load breakfast meal consisting of farina (kJ 1833; carbohydrate (CHO) 78 g and psylium soluble fiber 0 g), (B) a low-glycemic load breakfast meal consisting of a fiber-loop cereal (kJ 1515; CHO 62 g and psyllium soluble fiber 6.6 g). A standardized lunch was provided approximately 4 h after breakfast. Blood plasma concentrations and area under the curve (AUC) values for glucose, insulin and FFA were measured in response to the breakfast and mid-day lunch. Statistical analyses were performed using SAS software (8.02). Comparisons between diets were based on adjusted Bonferroni t-tests. Results: In post-breakfast analyses, Breakfast B had significantly lower area under the curve (AUC) values for plasma glucose and insulin compared to Breakfast A (Po0.05) (95% confidence level). The AUC values for FFA were higher for Breakfast B than for Breakfast A (Po0.05) (95% confidence level). Post-lunch analyses indicated similar glucose responses for the two breakfast types. Insulin AUC values for Breakfasts B were significantly lower than Breakfast A (Po0.05) (95% confidence level). The AUC values for FFA were unaffected by breakfast type. Conclusions: These data indicate that ingesting a low-glycemic load meal containing psyllium soluble fiber at breakfast significantly improves the breakfast postprandial glycemic, insulinemic and FFA responses in adults with Type 2 DM. These data revealed no residual postprandial effect of the psyllium soluble fiber breakfast meal beyond the second meal consumed. Thus, there was no evidence of an improvement postprandially in the glycemic, insulinemic and FFA responses after the consumption of the lunch meal. Sponsorship: This study was supported with an unrestricted grant from Kellogg Company, Battle Creek, Michigan.

Glycogen-targeting subunits of protein phosphatase-1 facilitate interaction of the phosphatase with enzymes of glycogen metabolism. Expression of one family member, PTG, in the liver of normal rats improves glucose tolerance without affecting other plasma variables but leaves animals unable to reduce hepatic glycogen stores in response to fasting. In the current study, we have tested whether expression of other targeting subunit isoforms, such as the liver isoform G L , the muscle isoform G M /R Gl , or a truncated version of G M /R Gl termed G M ⌬C in liver ameliorates glucose intolerance in rats fed on a high fat diet (HF). HF animals overexpressing G M ⌬C, but not G L or G M /R Gl , exhibited a decline in blood glucose of 35-44 mg/dl relative to control HF animals during an oral glucose tolerance test (OGTT) such that levels were indistinguishable from those of normal rats fed on standard chow at all but one time point. Hepatic glycogen levels were 2.1-2.4-fold greater in G L -and G M ⌬C-overexpressing HF rats compared with control HF animals following OGTT. In a second set of studies on fed and 20-h fasted HF animals, G M ⌬C-overexpressing rats lowered their liver glycogen levels by 57% (from 402 ؎ 54 to 173 ؎ 27 g of glycogen/mg of protein) in the fasted versus fed states compared with only 44% in G Loverexpressing animals (from 740 ؎ 35 to 413 ؎ 141 g of glycogen/mg of protein). Since the OGTT studies were performed on 20-h fasted rats, this meant that G M ⌬C-overexpressing rats synthesized much more glycogen than G L -overexpressing HF rats during the OGTT (419 versus 117 g of glycogen/mg of protein, respectively), helping to explain why G M ⌬C preferentially enhanced glucose clearance. We conclude that G M ⌬C has a unique combination of glycogenic potency and responsiveness to glycogenolytic signals that allows it to be used to lower blood glucose levels in diabetes.

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