Products deriving from microbial fermentation are linked to insulinaemic response in pigs fed breads prepared from whole-wheat grain and wheat and rye ingredients

The effects of wheat and rye breads made from whole-wheat grain (WWG), wheat aleurone flour (WAF) or rye aleurone flour (RAF) on net portal absorption of carbohydrate-derived nutrients (glucose, SCFA and lactate) and apparent insulin secretion were studied in a model experiment with catheterised pigs. The breads were similar in dietary fibre (DF, 120–125 g/kg DM) but differed in arabinoxylans (50–62 g/kg), β-glucans (4–9 g/kg) and content of soluble DF (13–29 g/kg). Six pigs in a repeated 3 × 3 crossover design were fitted with catheters in the portal vein and the mesenteric artery and a portal flow probe. Pigs were fed three meals daily (at 09.00, 14.00 and 19.00 hours), and blood profiles were collected repeatedly from 08.30 until 19.00 hours once weekly. Net portal absorption of glucose was similar among breads and between meals. In contrast, insulin secretion was lowest (P < 0·05) in pigs fed RAF bread (3·9 nmol/h), intermediate in pigs fed WAF bread (5·4 nmol/h) and highest in pigs fed WWG bread (5·9 nmol/h), indicating that RAF bread improved insulin economy. Portal concentrations of propionate, butyrate and valerate were high, intermediate and low (P < 0·05) when pigs were fed RAF, WAF and WWG breads, respectively. Insulin secretion was higher (P < 0·001), and portal absorption of SCFA was lower (P < 0·05) after the first daily meal than after the second daily meal (8·8v. 4·4 nmol/h). A low insulin response was associated with high portal absorption of SCFA. In conclusion, RAF bread was able to improve insulin economy compared to WWG bread.

Physical Fitness and Insulin Sensitivity in Human Subjects with a Low Insulin Response to Glucose

1. We have assessed insulin secretion, insulin sensitivity, exercise capacity and muscle fibre composition in healthy men with a low insulin response to glucose (low insulin responders and endurance-trained subjects) and in healthy men with a normally high insulin response. Low insulin responders have been considered as prediabetic subjects. 2. During glucose infusion, low insulin responders and endurance-trained subjects had acute-phase (0-10 min) insulin responses that were 26% (P < 0.001) and 31% (P < 0.001), and C-peptide responses that were 35% (P < 0.001) and 42% (P < 0.01), respectively of the responses in high insulin responders. Also, the late-phase (10-60 min) insulin and C-peptide responses were lower in low insulin responders and endurance-trained subjects. Endurance-trained subjects, compared with high and low insulin responders, had higher insulin sensitivity (blood glucose concentration during a somatostatin-insulin-glucose infusion test 3.6 ± 0.4 versus 6.3 ± 0.6 mmol/l in high insulin responders, P < 0.01, and 5.5 ± 0.4 mmol/l in low insulin responders, P < 0.01), exercise capacity (4.2 ± 0.2 versus 3.0 ± 0.2 W/kg body weight, P < 0.001, and 2.8 ± 0.1 W/kg body weight, P < 0.001) and a higher percentage of slow-twitch fibres (58.2 ± 5.2 versus 38.5 ± 3.5%, P < 0.01 and 40.9 ± 3.0%, P < 0.001). 3. In conclusion, we demonstrate that low insulin responders exhibited decreased insulin and C-peptide responses to glucose, despite normal insulin sensitivity and exercise capacity. Thus, the low insulin response in low insulin responders reflects a true impairment of insulin release and not a compensatory decrease due to increased insulin sensitivity. The insulin response to glucose in endurance-trained subjects was also decreased, probably due to increased insulin sensitivity.