PSVIII-5 Effect of glycemic and endocrine response to feeding time in pregnant sows

The objective of the study was to determine the glycemic and endocrine responses to feeding time in restrictively fed pregnant sows. Eighteen sows [(Landrace × Yorkshire); BW 229.17 ± 1.34 kg; parity 3.90 ± 0.12; backfat 13.60 ± 0.27 mm)] were sampled from 180 sows. Sows were blocked by parity and BW and randomly assigned to 1 of 3 treatments in a RCBD. Treatments included sows fed once at daily at 0730 h (Control, T1), 1130 h (T2), and 1530 h (T3). The daily feed quantity was kept at 1.25× maintenance energy intake (100 × (BW)0.75) kcal ME/d. On average sows received 2.27 kg corn-soybean meal-based diet which provided 6948 kcal ME/d and SID Lys:ME of 1.71 g/Mcal from d 30 to 60 of gestation. Total area under the curve (AUC) was calculated using Trapezoidal summation method. Data analysis was done using PROC MIXED and GLIMMIX procedure of SAS. Sow was the experimental unit. Adjustment for multiple comparison was by Tukey’s method. Pregnant sows fed at different times of the day had similar fasting levels of glucose, insulin, ghrelin, and PYY (P ˃ 0.10). Sows fed daily at 0730 and 1130 h had increased (P = 0.018) and propensity to increase (P = 0.088) in insulin concentration from fasting to 30 minutes post-prandial, respectively, but not in sows fed daily at 1530 h (P ˃ 0.05). Glucose, active ghrelin, and total PYY concentrations and AUC did not differ with respect to feeding time. In conclusion, plasma insulin response appears to be a function of time of the day at which calories are ingested. Feeding time to elicit maximum insulin response are 0730 and 1130 h but not at 1530 h. Therefore, feeding pregnant sows daily at or before 1130 h may elicit maximum insulin response.

The Disposition Index Does Not Reflect β-Cell Function in IGT Subjects Treated With Pioglitazone

Aims and Hypothesis: The insulin secretion/insulin resistance (IR) (disposition) index (ΔI/ΔG ÷ IR, where Δ is change from baseline, I is insulin, and G is glucose) is commonly used as a measure of β-cell function. This relationship is curvilinear and becomes linear when log transformed. ΔI is determined by 2 variables: insulin secretion rate (ISR) and metabolic clearance of insulin. We postulated that the characteristic curvilinear relationship would be lost if Δ plasma C-peptide (ΔCP) (instead of Δ plasma insulin) was plotted against insulin sensitivity. Methods: A total of 441 individuals with impaired glucose tolerance (IGT) from ACT NOW received an oral glucose tolerance test and were randomized to pioglitazone or placebo for 2.4 years. Results: Pioglitazone reduced IGT conversion to diabetes by 72% (P < .0001). ΔI/ΔG vs the Matsuda index of insulin sensitivity showed the characteristic curvilinear relationship. However, when ΔCP/ΔG or ΔISR/ΔG was plotted against the Matsuda index, the curvilinear relationship was completely lost. This discordance was explained by 2 distinct physiologic effects that altered plasma insulin response in opposite directions: 1) increased ISR and 2) augmented metabolic clearance of insulin. The net result was a decline in the plasma insulin response to hyperglycemia during the oral glucose tolerance test. These findings demonstrate a physiologic control mechanism wherein the increase in ISR ensures adequate insulin delivery into the portal circulation to suppress hepatic glucose production while delivering a reduced but sufficient amount of insulin to peripheral tissues to maintain the pioglitazone-mediated improvement in insulin sensitivity without excessive hyperinsulinemia. Conclusions: These results demonstrate the validity of the disposition index when relating the plasma insulin response to insulin sensitivity but underscore the pitfall of this index when drawing conclusions about β-cell function, because insulin secretion declined despite an increase in the plasma insulin response.

Insulin response to feeding forage with varying crude protein and amino acid content in horses at rest and after exercise

This study assessed the insulin response to forage intake with varying crude protein (CP) content in horses at rest and after exercise. Six geldings were fed three grass haylage-only diets for 7 days according to a 3×3 Latin square design. On day 7, blood samples were collected before and for 120 min after feeding 15% of the daily allowance before exercise (feeding A) and after standardised exercise (feeding B). Feed samples were collected before each feeding. Dry matter (DM) and nutrient content varied (DM: 37-58%, water-soluble carbohydrates minus fructans (WSC-f): 3-12% of DM, CP: 10-15% of DM) which resulted in a variation in nutrient intake within haylage batches. Based on individual CP and WSC-f intakes, intake groups were therefore formed (low and high CP intake; ≤ and ≯180 g CP/100 kg body weight, respectively and low and high WSC-f intake; ≤ and ≯100 g/100 kg body weight, respectively). Amino acids were analysed and intakes were generally higher in the high CP group than in the low CP group. An ANOVA model including horse, CP group and WSC-f intake explained 95% of the variation in plasma insulin response compared to 87% using a model including horse and WSC-f group alone. The plasma insulin area under curve (AUC) following feeding A tended to be higher in the high CP group than in the low CP group (P=0.08), but there was no difference after feeding B. Plasma glucose AUC was not affected by CP group (P≯0.05). The study indicates that the post-prandial plasma insulin response in horses fed a forage-only diet is increased by high WSC-f intake but may also be increased by high CP intake, at least at rest. However, due to the low number of observations further studies are needed.

The Pathophysiology of Diabetes Involves a Defective Amplification of the Late-Phase Insulin Response to Glucose by Glucose-Dependent Insulinotropic Polypeptide—Regardless of Etiology and Phenotype

The effect of the insulinotropic incretin hormone, glucagon-like peptide-1 (GLP-1), is preserved in typical middle-aged, obese, insulin-resistant type 2 diabetic patients, whereas a defective amplification of the so-called late-phase plasma insulin response (20–120 min) to glucose by the other incretin hormone, glucose-dependent insulinotropic polypeptide (GIP), is seen in these patients. The aim of the present investigation was to evaluate plasma insulin and C-peptide responses to GLP-1 and GIP in five groups of diabetic patients with etiology and phenotype distinct from the obese type 2 diabetic patients. We studied (six in each group): 1) patients with diabetes mellitus secondary to chronic pancreatitis; 2) lean type 2 diabetic patients (body mass index < 25 kg/m2); 3) patients with latent autoimmune diabetes in adults; 4) diabetic patients with mutations in the HNF-1α gene [maturity-onset diabetes of the young (MODY)3]; and 5) newly diagnosed type 1 diabetic patients. All participants underwent three hyperglycemic clamps (2 h, 15 mm) with continuous infusion of saline, 1 pmol GLP-1 (7–36)amide/kg body weight·min or 4 pmol GIP pmol/kg body weight·min. The early-phase (0–20 min) plasma insulin response tended to be enhanced by both GIP and GLP-1, compared with glucose alone, in all five groups. In contrast, the late-phase (20–120 min) plasma insulin response to GIP was attenuated, compared with the plasma insulin response to GLP-1, in all five groups. Significantly higher glucose infusion rates were required during the late phase of the GLP-1 stimulation, compared with the GIP stimulation. In conclusion, lack of GIP amplification of the late-phase plasma insulin response to glucose seems to be a consequence of diabetes mellitus, characterizing most, if not all, forms of diabetes.