Objective To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality. Design 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory markers, anthropometry and urine metabolomics were assessed. Results 50 participants completed both periods with a whole grain intake of 179±50 g/day and 13±10 g/day in the whole grain and refined grain period, respectively. Compliance was confirmed by a difference in plasma alkylresorcinols (p<0.0001). Compared with refined grain, whole grain did not significantly alter glucose homeostasis and did not induce major changes in the faecal microbiome. Also, breath hydrogen levels, plasma short-chain fatty acids, intestinal integrity and intestinal transit time were not affected. The whole grain diet did, however, compared with the refined grain diet, decrease body weight (p<0.0001), serum inflammatory markers, interleukin (IL)-6 (p=0.009) and C-reactive protein (p=0.003). The reduction in body weight was consistent with a reduction in energy intake, and IL-6 reduction was associated with the amount of whole grain consumed, in particular with intake of rye. Conclusion Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation. Trial registration number NCT01731366; Results.

Collagen type I fragments, reflecting bone resorption, and release of gut hormones were investigated after a meal. Investigations led to a dose escalation study with glucagon like peptide‐2 (GLP‐2) in postmenopausal women. We found a dose‐dependent effect of GLP‐2 on the reduction of bone resorption. Introduction: The C‐terminal telopeptide region of type I collagen as measured in serum (s‐CTX) can be used to assess bone resorption. This marker of bone resorption has a significant circadian variation that is influenced by food intake. However, the mediator of this variation has not been identified. Materials and Methods: We studied the release of the gut hormones glucose‐dependent insulinotropic polypeptide (GIP) and glucagon‐like peptide‐2 (GLP‐2; a representative of the intestinal proglucagon‐derived peptides) after ingestion of glucose, fat, protein, and fructose, as well as their effects after parenteral administration in relation to bone turnover processes in healthy volunteers. Furthermore, we studied the effect on bone turnover of a single subcutaneous injection of GLP‐2 in four different dosages (100, 200, 400, or 800 μg GLP‐2) or placebo in 60 postmenopausal women (mean age, 61 ± 5 years). Results: All macronutrients significantly (p < 0.05) reduced bone resorption as assessed by s‐CTX (39–52% from baseline), and only the glucagon‐like peptides were secreted in parallel. Parenteral administration of GIP and GLP‐1 did not result in a reduction of the s‐CTX level, whereas GLP‐2 caused a statistically significant and dose‐dependent reduction in the s‐CTX level from baseline compared with placebo (p < 0.05). Urine DPD/creatinine, a marker of bone resorption, was significantly reduced by 25% from baseline in the 800‐μg GLP‐2 group (p < 0.01). An area under the curve (AUC_0–8h) analysis for s‐CTX after GLP‐2 injection confirmed the dose‐dependent decrease (ANOVA, p = 0.05). The s‐osteocalcin level was unaffected by the GLP‐2 treatment. Conclusion: These studies exclude both GIP and GLP‐1 as key mediators for the immediate reduction in bone resorption seen after a meal. The dose‐dependent reduction of bone resorption markers found after subcutaneous injection of GLP‐2 warrants further investigation into the mechanism and importance of GLP‐2 for the bone turnover processes.

OBJECTIVE Ingestion of probiotics can modify gut microbiota and alter insulin resistance and diabetes development in rodents. We hypothesized that daily intake of Lactobacillus reuteri increases insulin sensitivity by changing cytokine release and insulin secretion via modulation of the release of glucagon-like peptides (GLP)-1 and -2. RESEARCH DESIGN AND METHODS A prospective, double-blind, randomized trial was performed in 21 glucose tolerant humans (11 lean: age 49 ± 7 years, BMI 23.6 ± 1.7 kg/m²; 10 obese: age 51 ± 7 years, BMI 35.5 ± 4.9 kg/m²). Participants ingested 10¹⁰ b.i.d. L. reuteri or placebo over 4 weeks. Oral glucose tolerance and isoglycemic glucose infusion tests were used to assess incretin effect and GLP-1 and GLP-2 secretion, and euglycemic-hyperinsulinemic clamps with [6,6-²H₂]glucose were used to measure peripheral insulin sensitivity and endogenous glucose production. Muscle and hepatic lipid contents were assessed by ¹H-magnetic resonance spectroscopy, and immune status, cytokines, and endotoxin were measured with specific assays. RESULTS In glucose tolerant volunteers, daily administration of L. reuteri increased glucose-stimulated GLP-1 and GLP-2 release by 76% (P < 0.01) and 43% (P < 0.01), respectively, compared with placebo, along with 49% higher insulin (P < 0.05) and 55% higher C-peptide secretion (P < 0.05). However, the intervention did not alter peripheral and hepatic insulin sensitivity, body mass, ectopic fat content, or circulating cytokines. CONCLUSIONS Enrichment of gut microbiota with L. reuteri increases insulin secretion, possibly due to augmented incretin release, but does not directly affect insulin sensitivity or body fat distribution. This suggests that oral ingestion of one specific strain may serve as a novel therapeutic approach to improve glucose-dependent insulin release.

To identify factors contributing to the variation in weight loss after Roux-en-Y gastric bypass (RYGB). Cross-sectional study of patients with good (excess body mass index lost (EBL) >60%) and poor weight loss response (EBL 12 months after RYGB and a lean control group matched for age and gender. Sixteen patients with good weight loss response, 17 patients with poor weight loss response, and eight control subjects were included in the study. Participants underwent dual energy X-ray absorptiometry scan, indirect calorimetry and a 9 h multiple-meal test with measurements of glucose, insulin, total bile acids (TBA), glucagon-like peptide (GLP)-1, peptide YY_3–36 (PYY), cholecystokinin (CCK), ghrelin, neurotensin and pancreatic polypeptide (PP) as well as assessment of early dumping and appetite. Suppression of hunger was more pronounced in the good than the poor responders in response to the multiple-meal test (P=0.006). In addition, the good responders had a larger release of GLP-1 (P=0.009) and a greater suppression of ghrelin (P=0.037) during the test, whereas the postprandial secretion of CCK was highest in the poor responders (P=0.005). PYY, neurotensin, PP and TBA release did not differ between the RYGB-operated groups. Compared with control subjects, patients had exaggerated release of GLP-1 (P<0.001), PYY (P=0.008), CCK (P=0.010) and neurotensin (P<0.001). Early dumping was comparable in the good and poor responders, but more pronounced than in controlled subjects. Differences in resting energy expenditure between the three groups were entirely explained by differences in body composition. Favorable meal-induced changes in hunger and gut hormone release in patients with good compared with poor weight loss response support the role of gut hormones in the weight loss after RYGB.