| 1. |
- Ahrén, Bo, et al.
(författare)
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Incretin hormone secretion over the day.
- 2010
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Ingår i: Vitamines and Hormones. - 0083-6729. ; 84, s. 203-220
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Tidskriftsartikel (refereegranskat)abstract
- The two incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are key factors in the regulation of islet function and glucose metabolism, and incretin-based therapy for type 2 diabetes has gained considerable interest during recent years. Regulation of incretin hormone secretion is less well characterized. The main stimulus for incretin hormone secretion is presence of nutrients in the intestinal lumen, and carbohydrate, fat as well as protein all have the capacity to stimulate GIP and GLP-1 secretion. More recently, it has been established that a diurnal regulation exists with incretin hormone secretion to an identical meal being greater when the meal is served in the morning compared to in the afternoon. Finally, whether incretin hormone secretion is altered in disease states is an area with, so far, controversial results in different studies, although some studies have demonstrated reduced incretin hormone secretion in type 2 diabetes. This review summarizes our knowledge on regulation of incretin hormone secretion and its potential changes in disease states.
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| 2. |
- Carr, Richard D., et al.
(författare)
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Incretin and islet hormonal responses to fat and protein ingestion in healthy men
- 2008
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Ingår i: American Journal of Physiology: Endocrinology and Metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 295:4, s. 779-784
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Tidskriftsartikel (refereegranskat)abstract
- Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) regulate islet function after carbohydrate ingestion. Whether incretin hormones are of importance for islet function after ingestion of noncarbohydrate macronutrients is not known. This study therefore examined integrated incretin and islet hormone responses to ingestion of pure fat (oleic acid; 0.88 g/kg) or protein (milk and egg protein; 2 g/kg) over 5 h in healthy men, aged 20-25 yr (n = 12); plain water ingestion served as control. Both intact (active) and total GLP-1 and GIP levels were determined as was plasma activity of dipeptidyl peptidase-4 (DPP-4). Following water ingestion, glucose, insulin, glucagon, GLP-1, and GIP levels and DPP-4 activity were stable during the 5-h study period. Both fat and protein ingestion increased insulin, glucagon, GIP, and GLP-1 levels without affecting glucose levels or DPP-4 activity. The GLP-1 responses were similar after protein and fat, whereas the early (30 min) GIP response was higher after protein than after fat ingestion (P < 0.001). This was associated with sevenfold higher insulin and glucagon responses compared with fat ingestion (both P < 0.001). After protein, the early GIP, but not GLP-1, responses correlated to insulin (r(2) = 0.86; P = 0.0001) but not glucagon responses. In contrast, after fat ingestion, GLP-1 and GIP did not correlate to islet hormones. We conclude that, whereas protein and fat release both incretin and islet hormones, the early GIP secretion after protein ingestion may be of primary importance to islet hormone secretion.
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| 3. |
- Carr, Richard D, et al.
(författare)
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Secretion and Dipeptidyl Peptidase-4-Mediated Metabolism of Incretin Hormones after a Mixed Meal or Glucose Ingestion in Obese Compared to Lean, Nondiabetic Men.
- 2010
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 95, s. 872-878
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Tidskriftsartikel (refereegranskat)abstract
- Context: Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are cleaved by dipeptidyl peptidase-4 (DPP-4); plasma activity of DPP-4 may be increased in obesity. The impact of this increase on incretin hormone secretion and metabolism is not known. Objective: The aim of the study was to assess incretin hormone secretion and degradation in lean and obese nondiabetic subjects. Design, Settings, and Participants: We studied the ingestion of a mixed meal (560 kcal) or oral glucose (2 g/kg) in healthy lean (n = 12; body mass index, 20-25 kg/m(2)) or obese (n = 13; body mass index, 30-35 kg/m(2)) males at a University Clinical Research Unit. Main Outcome Measures: We measured the area under the curve of plasma intact (i) and total (t) GIP and GLP-1 after meal ingestion and oral glucose. Results: Plasma DPP-4 activity was higher in the obese subjects (38.5 +/- 3.0 vs. 26.7 +/- 1.6 mmol/min . mul; P = 0.002). Although GIP secretion (AUCtGIP) was not reduced in obese subjects after meal ingestion or oral glucose, AUCiGIP was lower in obese subjects (8.5 +/- 0.6 vs. 12.7 +/- 0.9 nmol/liter x 300 min; P < 0.001) after meal ingestion. GLP-1 secretion (AUCtGLP-1) was reduced in obese subjects after both meal ingestion (7.3 +/- 0.9 vs. 10.0 +/- 0.6 nmol/liter x 300 min; P = 0.022) and oral glucose (6.6 +/- 0.8 vs. 9.6 +/- 1.1 nmol/liter x 180 min; P = 0.035). iGLP-1 was reduced in parallel to tGLP-1. Conclusions: 1) Release and degradation of the two incretin hormones show dissociated changes in obesity: GLP-1 but not GIP secretion is lower after meal ingestion and oral glucose, whereas GIP but not GLP-1 metabolism is increased after meal ingestion. 2) Increased plasma DPP-4 activity in obesity is not associated with a generalized augmented incretin hormone metabolism.
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| 4. |
- Gunnarsson, Thomas, et al.
(författare)
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Glucose-induced incretin hormone release and inactivation are differently modulated by oral fat and protein in mice.
- 2006
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Ingår i: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 147:7, s. 3173-3180
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Tidskriftsartikel (refereegranskat)abstract
- Monounsaturated fatty acids, such as oleic acid (OA), and certain milk proteins, especially whey protein (WP), have insulinotropic effects and can reduce postprandial glycemia. This effect may involve the incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). To explore this, we examined the release and inactivation of GIP and GLP-1 after administration of glucose with or without OA or WP through gastric gavage in anesthetized C57BL/6J mice. Insulin responses to glucose (75 mg) were 3-fold augmented by addition of WP (75 mg; P < 0.01), which was associated with enhanced oral glucose tolerance (P < 0.01). The insulin response to glucose was also augmented by addition of OA (34 mg; P < 0.05) although only 1.5-fold and with no associated increase in glucose elimination. The slope of the glucose-insulin curve was increased by OA (1.7-fold; P < 0.05) and by WP(4-fold; P < 0.01) compared with glucose alone, suggesting potentiation of glucose-stimulated insulin release. WP increased GLP-1 secretion (P < 0.01), whereas GIP secretion was unaffected. OA did not affect GIP or GLP-1 secretion. Nevertheless, WP increased the levels of both intact GIP and intact GLP-1 (both P < 0.01), and OA increased the levels of intact GLP-1 (P < 0.05). WP inhibited dipeptidyl peptidase IV activity in the proximal small intestine by 50% (P < 0.05), suggesting that luminal degradation of WP generates small fragments, which are substrates for dipeptidyl peptidase IV and act as competitive inhibitors. We therefore conclude that fat and protein may serve as exogenous regulators of secretion and inactivation of the incretin hormones with beneficial influences on glucose metabolism.
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| 5. |
- Lindgren, Ola, et al.
(författare)
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Differential Islet and Incretin Hormone Responses in Morning vs. Afternoon after Standardized Meal in Healthy Men.
- 2009
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 94:8, s. 2887-2892
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Tidskriftsartikel (refereegranskat)abstract
- Context: The insulin response to meal ingestion is more rapid in the morning than in the afternoon. Whether this is explained by a corresponding variation in the incretin hormones is not known. Objective: Assess islet and incretin hormones after meal ingestion in the morning versus afternoon. Design, Settings and Participants: Ingestion at 8am and at 5pm of a standardized meal (524 kcal) in healthy lean males (n=12) at a University Clinical Research Unit. Main Outcome Measures: 1)Early (30 min) area under the curve (AUC30) of plasma levels of insulin and intact (i) and total (t) glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) after meal ingestion. 2)Estimation of ss-cell function by model analysis of glucose and C-peptide. Results: Peak glucose was lower in the morning than in the afternoon (6.1+/-0.2 vs. 7.4+/-0.3 mmol/l, P=0.001). AUC30insulin (4.9+/-0.6 vs 2.8+/-0.4 nmol/l*30 min; P=0.012), AUC30tGLP-1 (300+/-40 vs. 160+/-30 pmol/l*30 min, P=0.002), AUC30iGIP (0.7+/-0.1 vs. 0.3+/-0.1 nmol/l* 30 min, P=0.002) and AUC30tGIP (1.1+/-0.1 vs. 0.6+/-0.1nmol/l*min, P=0.007) were all higher in the morning. AUC30iGLP-1 (r=0.68, P=0.021) and AUC39iGIP (r=0.78, P=0.001) both correlated to AUC30insulin. Model analysis of ss-cell function showed a higher first hour potentiation factor in the morning (P=0.009). This correlated negatively with the 60 min glucose level (r=-0.63, P<0.001). Conclusions: The early release of GLP-1 and GIP are more pronounced in the morning than in the afternoon. This may contribute to the more rapid early insulin response, more pronounced potentiation of ss-cell function and lower glucose after the morning meal.
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| 6. |
- Lindgren, Ola, et al.
(författare)
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Incretin Effect after Oral Amino Acid Ingestion in Humans.
- 2015
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 100:3, s. 1172-1176
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Tidskriftsartikel (refereegranskat)abstract
- Context: The incretin effect is the augmented insulin secretion by oral versus intravenous glucose at matching glucose levels. We previously demonstrated an augmented insulin secretion when fat is given orally rather than intravenously, suggesting an incretin effect also after fat. However, whether there is an incretin effect is also present after amino acid ingestion is not known. Objective: To explore insulin secretion and islet hormones after oral and intravenous amino acid administration at matched total amino acid concentrations in healthy subjects. Design: Amino acid mixture (Vaminolac(R)) was administered orally or intravenously at a rate resulting in matching total amino acid concentrations to twelve male volunteers with age 22.5±1.4 yr and BMI 22.4±1.4 kg/m(2), who had no history of diabetes. Main outcome measures: Area under the 120 min curve (AUC) for insulin, C-peptide, glucagon, intact and total glucagon like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and insulin secretory rate and insulin clearance. Results: Insulin, C-peptide and glucagon levels increased after both oral and intravenous administration, but insulin secretion was 25% higher after oral than after intravenous amino acid challenges (P=0.006), whereas there was no significant difference in the glucagon response. Intact and total GIP rose after oral but not after intravenous amino acid administration, whereas intact and total GLP-1 levels did not change significantly in either test. Conclusion: Oral amino acid mixture ingestion elicits a stronger insulin secretory response than intravenous amino acid at matching amino acid levels and that this is associated with increased GIP level, suggesting that an incretin effect exists also after oral amino acids, possibly mediated by GIP.
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| 7. |
- Lindgren, Ola, et al.
(författare)
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Incretin Hormone and Insulin Responses to Oral Versus Intravenous Lipid Administration in Humans.
- 2011
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Ingår i: The Journal of clinical endocrinology and metabolism. - : The Endocrine Society. - 1945-7197 .- 0021-972X. ; 96, s. 2519-2524
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Tidskriftsartikel (refereegranskat)abstract
- Context: The incretin effect is responsible for the higher insulin response to oral glucose than to iv glucose at matching glucose levels. It is not known whether this effect is restricted to glucose only. Objective: The aim of the study was to examine whether insulin and incretin hormone responses are higher after oral vs. iv challenge of a lipid emulsion with matching triglyceride levels in humans. Design, Settings, and Participants: A lipid emulsion (Intralipid) was administered orally (3 ml/kg) or iv (variable infusion rates to match triglyceride levels after oral ingestion) in healthy lean males (n = 12) at a University Clinical Research Unit. Samples were collected during 300 min. Main Outcome Measures: We measured the suprabasal area under the curve for insulin, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and the insulin secretory rate based on C-peptide levels by deconvolution. Results: Triglyceride levels increased similarly after oral and iv lipid; also, glucose and free fatty acid levels were similar in the two tests. Oral lipid elicited a clear insulin and C-peptide response, whereas no insulin or C-peptide responses were observed during iv lipid. Total and intact GIP and GLP-1 levels both increased after oral lipid administration but were not significantly altered after iv lipid. Conclusions: At matching triglyceride levels and with no difference in glucose and free fatty acid levels, oral lipid ingestion but not iv lipid infusion elicits a clear insulin response in association with increased GIP and GLP-1 concentrations. This may suggest that the incretin hormones also contribute to the islet response to noncarbohydrate nutrients.
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