Weight loss improves ß-cell function independently of dietary carbohydrate restriction in people with type 2 diabetes: A 6-week randomized controlled trial.

Background: Carbohydrate restriction may benefit ß-cell function and glucose metabolism in type 2 diabetes (T2D) but also leads to weight loss which in itself is beneficial. Methods: In order to determine the additional effect of carbohydrate restriction in addition to a fixed body weight loss, we randomly assigned 72 adults with T2D and obesity (mean ± SD HbA1c 7.4 ± 0.7%, BMI 33 ± 5 kg/m2) to a carbohydrate-reduced high-protein diet (CRHP; energy percent from carbohydrate/protein/fat: 30/30/40) or an isocaloric conventional diabetes diet (CD; 50/17/33) for 6 weeks. All foods were provided free of charge and total energy intake was tailored individually, so both groups lost 6% of baseline body weight. Results: Despite significantly greater reductions in HbA1c (mean [95% CI] -1.9 [-3.5, -0.3] mmol/mol) after 6 weeks, the CRHP diet neither improved glucose tolerance, ß-cell response to glucose, insulin sensitivity, during a 4-h oral glucose tolerance test, nor basal proinsulin secretion when compared to the CD diet, but increased C-peptide concentration and insulin secretion rate (area under the curve [AUC] and peak) significantly more (~10%, P ≤ 0.03 for all). Furthermore, compared with the CD diet, the CRHP diet borderline increased basal glucagon concentration (16 [-0.1, 34]%, P = 0.05), but decreased glucagon net AUC (-2.0 [-3.4, -0.6] mmol/L ×240 min, P < 0.01), decreased basal triglyceride and total AUC (~20%, P < 0.01 for both), and increased gastric inhibitory polypeptide total AUC (14%, P = 0.01). Conclusion: A moderately carbohydrate-restricted diet for 6 weeks decreased HbA1c but did not improve ß-cell function or glucose tolerance beyond the effects of weight loss when compared with a conventional diabetes diet in people with T2D. Clinical trials registration: www.Clinicaltrials.gov, Identifier: NCT02472951.

Effects of a Self-Prepared Carbohydrate-Reduced High-Protein Diet on Cardiovascular Disease Risk Markers in Patients with Type 2 Diabetes.

We previously observed beneficial effects of a carbohydrate-reduced, high-protein (CRHP) diet on cardiovascular risk markers in patients with type 2 diabetes mellitus (T2DM) in a crossover 2 × 6-week trial, when all food was provided to subjects as ready-to-eat meals. Here, we report the results from a 6-month open label extension: 28 patients with T2DM were instructed to self-prepare the CRHP diet with dietetic guidance. At weeks 0, 6, 12, and 36, fasting and postprandial (4-h meal test) blood samples were collected for measurements of total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triacylglycerol (TG), apolipoproteins A1 and B, non-esterified fatty acids (NEFA), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6. Diurnal blood pressure and heart rate were also assessed. At the end of the study (week 36), concentrations of fasting total and LDL-cholesterol, fasting and postprandial NEFA and TG, and fasting apolipoprotein-B, CRP and TNF-α concentrations were significantly lower compared with week 0 (p < 0.05). A significant decrease in diurnal heart rate was also observed. From week 12 to 36, an increase in HDL-cholesterol and apolipoprotein-A1 concentrations and a further reduction in fasting and postprandial NEFA (p < 0.05) were found. These changes were independent of minor fluctuations in body weight. We conclude that the substitution of dietary carbohydrate for protein and fat has beneficial effects on several cardiovascular risk markers in patients with T2DM, which are maintained or augmented over the next 6 months when patients select and prepare the CRHP diet on their own in a dietitian-supported setting.

Effects of carbohydrate restriction on postprandial glucose metabolism, ß-cell function, gut hormone secretion, and satiety in patients with Type 2 diabetes.

Dietary carbohydrate restriction may improve the phenotype of Type 2 diabetes (T2D) patients. We aimed to investigate 6 wk of carbohydrate restriction on postprandial glucose metabolism, pancreatic α- and ß-cell function, gut hormone secretion, and satiety in T2D patients. Methods In a crossover design, 28 T2D patients (mean HbA1c: 60 mmol/mol) were randomized to 6 wk of carbohydrate-reduced high-protein (CRHP) diet and 6 wk of conventional diabetes (CD) diet (energy-percentage carbohydrate/protein/fat: 30/30/40 vs. 50/17/33). Twenty-four-hour continuous glucose monitoring (CGM) and mixed-meal tests were undertaken and fasting intact proinsulin (IP), 32,33 split proinsulin concentrations (SP), and postprandial insulin secretion rates (ISR), insulinogenic index (IGI), ß-cell sensitivity to glucose (Bup), glucagon, and gut hormones were measured. Gastric emptying was evaluated by postprandial paracetamol concentrations and satiety by visual analog scale ratings. A CRHP diet reduced postprandial glucose area under curve (net AUC) by 60% (P < 0.001), 24 h glucose by 13% (P < 0.001), fasting IP and SP concentrations (both absolute and relative to C-peptide, P < 0.05), and postprandial ISR (24%, P = 0.015), while IGI and Bup improved by 31% and 45% (both P < 0.001). The CRHP diet increased postprandial glucagon net AUC by 235% (P < 0.001), subjective satiety by 18% (P = 0.03), delayed gastric emptying by 15 min (P < 0.001), decreased gastric inhibitory polypeptide net AUC by 29% (P < 0.001), but had no significant effect on glucagon-like-peptide-1, total peptide YY, and cholecystokinin responses. A CRHP diet reduced glucose excursions and improved ß-cell function, including proinsulin processing, and increased subjective satiety in patients with T2D.

Effect of Metformin vs. Placebo in Combination with Insulin Analogues on Bone Markers P1NP and CTX in Patients with Type 2 Diabetes Mellitus.

Preclinical studies have shown a potential osteoanabolic effect of metformin but human studies of how metformin affects bone turnover are few. A post hoc sub-study analysis of an 18-month multicenter, placebo-controlled, double-blinded trial in type 2 diabetes mellitus (T2DM), randomizing participants to metformin versus placebo both in combination with different insulin analogue regimens (Metformin + Insulin vs. Placebo + Insulin). Patients were not treatment naive at baseline, 83% had received metformin, 69% had received insulin, 57.5% had received the combination of metformin and insulin before entering the study. Bone formation and resorption were assessed by measuring, N-terminal propeptide of type I procollagen (P1NP) and C-terminal telopeptide of type I collagen (CTX) at baseline and end of study. The influence of gender, age, smoking, body mass index (BMI), T2DM duration, glycosylated hemoglobin A1c (HbA1c), c-reactive protein (CRP) and insulin dosage was also included in the analyses. The levels of bone formation marker P1NP and bone resorption marker CTX increased significantly in both groups during the trial. P1NP increased less in the Metformin + Insulin compared to the placebo + insulin group (p = 0.001) (between group difference change), while the increases in CTX levels (p = 0.11) were not different. CRP was inversely associated (p = 0.012) and insulin dosage (p = 0.011) was positively related with change in P1NP levels. BMI (p = 0.002) and HbA1C (p = 0.037) were inversely associated with change in CTX levels. During 18 months of treatment with metformin or placebo, both in combination with insulin, bone turnover increased in both groups. But the pattern was different as the bone formation marker (P1NP) increased less during Metformin + Insulin treatment, while change in bone resorption (CTX) was not significantly different between the two groups.

Effects of a highly controlled carbohydrate-reduced high-protein diet on markers of oxidatively generated nucleic acid modifications and inflammation in weight stable participants with type 2 diabetes; a randomized controlled trial.

Carbohydrate-restricted diets are increasingly recognized as options for dietary management of type 2 diabetes mellitus (T2DM). We investigated the effects of a carbohydrate-reduced high-protein (CRHP) and a conventional diabetes (CD) diet on oxidative stress and inflammation in weight stable individuals with T2DM. We hypothesized that the CRHP diet would improve markers of oxidatively generated RNA and DNA modifications as well as inflammatory parameters. Thirty participants with T2DM were randomized to 6 weeks of CRHP or CD dietary treatment (30/50 energy percentage (E%) carbohydrate, 30/17E% protein, 40/33E% fat), followed by a cross-over to the opposite diet for a subsequent 6-week period. All meals were provided during the study and body weight was controlled. Diurnal urine samples were collected after 4 weeks on each diet and oxidatively generated RNA and DNA modifications were measured as 8-oxo-7,8-dihydroguanosine (8-oxoGuo) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), respectively. Fasting concentrations of soluble urokinase plasminogen activator receptor, high-sensitivity C-reactive protein, tumor necrosis factor alpha and interleukin-6 were measured before and after 6 weeks of interventions. Compared with the CD diet, the CRHP diet increased 24-hour urinary excretion of 8-oxoGuo by 9.3% (38.6 ± 12.6 vs. 35.3 ± 11.0 nmol/24 h, p = .03), whereas 8-oxodG did not differ between diets (24.0 ± 9.5 vs. 24.8 ± 11.1 nmol/24 h, p = .17). Changes in plasma inflammatory parameters did not differ between CRHP and CD diets, all p ≥ .2. The clinical implications of increased RNA oxidation following a CRHP diet as well as long-term effects of carbohydrate-restriction on markers of oxidatively generated nucleic acid modifications should be a field of future study.

Mechanisms of action of a carbohydrate-reduced, high-protein diet in reducing the risk of postprandial hypoglycemia after Roux-en-Y gastric bypass surgery.

BACKGROUND: Postprandial hypoglycemia is a risk after Roux-en-Y gastric bypass (RYGB). OBJECTIVES: We speculated that a carbohydrate-reduced, high-protein (CRHP) diet might reduce the risk of hypoglycemia and therefore compared the acute effects of a conventionally recommended (CR) diet and CRHP diet [55/30 energy percent (E%) carbohydrate and 15/30 E% protein, respectively] in RYGB patients. METHODS: Ten individuals (2 males, 8 females, mean ± SD age 47 ± 7 y; stable body mass index 31 ± 6 kg/m2; 6 ± 3 y post-RYGB) with recurrent postprandial hypoglycemia documented by plasma glucose (PG) ≤3.4 mmol/L were examined on 2 d with isoenergetic CRHP or CR diets comprising a breakfast and subsequent lunch meal. RESULTS: Peak PG was significantly reduced on the CRHP diet after breakfast and lunch by 11% and 31% compared with the CR diet. Nadir PG increased significantly on CRHP (by 13% and 9%). Insulin secretion was reduced, and glucagon secretion increased on the CRHP diet after both meals. Glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide secretion were lower after lunch but unaltered after breakfast on CRHP; ß-cell function and insulin clearance were unchanged. CONCLUSIONS: The CRHP diet lowered glucose excursions and reduced insulin secretion and incretin hormone responses, but enhanced glucagon responses compared with the CR diet. Taken together, the results may explain the decreased glucose variability and lower risk of postprandial hypoglycemia. This study was registered at clinicaltrials.gov as NCT02665715.

A carbohydrate-reduced high-protein diet acutely decreases postprandial and diurnal glucose excursions in type 2 diabetes patients.

The aim of the study was to assess whether a simple substitution of carbohydrate in the conventionally recommended diet with protein and fat would result in a clinically meaningful reduction in postprandial hyperglycaemia in subjects with type 2 diabetes mellitus (T2DM). In all, sixteen subjects with T2DM treated with metformin only, fourteen male, with a median age of 65 (43-70) years, HbA1c of 6·5 % (47 mmol/l) (5·5-8·3 % (37-67 mmol/l)) and a BMI of 30 (sd 4·4) kg/m2 participated in the randomised, cross-over study. A carbohydrate-reduced high-protein (CRHP) diet was compared with an iso-energetic conventional diabetes (CD) diet. Macronutrient contents of the CRHP/CD diets consisted of 31/54 % energy from carbohydrate, 29/16 % energy from protein and 40/30 % energy from fat, respectively. Each diet was consumed on 2 consecutive days in a randomised order. Postprandial glycaemia, pancreatic and gut hormones, as well as satiety, were evaluated at breakfast and lunch. Compared with the CD diet, the CRHP diet reduced postprandial AUC of glucose by 14 %, insulin by 22 % and glucose-dependent insulinotropic polypeptide by 17 % (all P<0·001), respectively. Correspondingly, glucagon AUC increased by 33 % (P<0·001), cholecystokinin by 24 % (P=0·004) and satiety scores by 7 % (P=0·035), respectively. A moderate reduction in carbohydrate with an increase in fat and protein in the diet, compared with an energy-matched CD diet, greatly reduced postprandial glucose excursions and resulted in increased satiety in patients with well-controlled T2DM.

Reduction of insulinotropic properties of GLP-1 and GIP after glucocorticoid-induced insulin resistance.

AIMS/HYPOTHESIS: We evaluated the insulinotropic properties of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) in healthy individuals at risk of developing type 2 diabetes before and after glucocorticoid-induced insulin resistance. METHODS: Nineteen healthy, glucose tolerant, first-degree relatives of type 2 diabetic patients underwent OGTT and 7 mmol/l and 15 mmol/l glucose clamps with concomitant infusions of GLP-1, GIP or NaCl and a final infusion of arginine for determination of maximum beta cell capacity before and after treatment with dexamethasone. In addition, first-phase insulin responses were determined at 7 mmol/l and 15 mmol/l and second-phase insulin responses at 7 mmol/l. RESULTS: After dexamethasone treatment, all 19 participants had increased insulin resistance (HOMA-IR and insulin sensitivity index [M/I] values) and 2 h plasma glucose concentrations, while beta cell function indices generally increased according to the increased resistance. First-phase insulin responses induced by GLP-1 and GIP at 7 mmol/l and maximal beta cell secretory capacity did not differ before and after dexamethasone, while second-phase responses to 7 mmol/l and first-phase responses to 15 mmol/l glucose were reduced equally for both hormones. CONCLUSIONS/INTERPRETATION: Glucocorticoid-induced insulin resistance in individuals at risk of type 2 diabetes leads to a reduced insulinotropic effect of the incretin hormones. This reduction was not associated with a decrease in the maximal beta cell secretory capacity, indicating that the reduced incretin effect in the developing dysglycaemia of the present experimental model is due to a specific early reduction of the insulinotropic effects of the incretin hormones. TRIAL REGISTRATION: Clinicaltrials.gov NCT02235584.

Unprecedented high insulin secretion in a healthy human subject after intravenous glucagon-like peptide-1: a case report.

BACKGROUND: The gut-derived incretin hormones, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, are released in response to ingestion of nutrients. Both hormones are highly insulinotropic in strictly glucose-dependent fashions and glucagon-like peptide-1 is often referred to as one of the most insulinotropic substances known. CASE PRESENTATION: Plasma insulin and C-peptide concentrations were measured in a healthy Caucasian male (age: 53 years; body mass index: 28.6 kg/m2; fasting plasma glucose: 5.7 mM; 2 h plasma glucose value following 75 g-oral glucose tolerance test: 3.5 mM; glycated haemoglobin A1c: 5.5%) during glucagon (1 mg) and meal (2,370 kJ) tests, and during two 2 h 15 mM-hyperglycaemic clamps with continuous intravenous infusion of glucagon-like peptide-1 (1 pmol/kg/min) and glucose-dependent insulinotropic polypeptide (4 pmol/kg/min), respectively. Normal insulin and C-peptide responses were observed during meal test (peak concentrations: 300 and 3,278 pM) and glucagon test (peak concentrations: 250 and 2,483 pM). During the hyperglycaemic clamp with continuous intravenous infusion of GLP-1 the subject exhibited plasma insulin and C-peptide concentrations of 13,770 and 22,380 pM, respectively. CONCLUSIONS: To our knowledge insulin and C-peptide concentrations of these magnitudes have never been reported. Thus, the present data support the view that glucagon-like peptide-1 is one of the most insulinotropic substances known.

Patient-reported outcomes among patients using exenatide twice daily or insulin in clinical practice in six European countries: the CHOICE prospective observational study.

BACKGROUND: Improvements in the clinical condition of patients with type 2 diabetes are often accompanied by improvements in health-related quality of life and other patient-reported outcomes (PROs), but data assessing injectable treatment initiation from the patient's perspective in routine clinical practice are lacking. We examined PROs in patients initiating injectable treatment in the CHOICE (CHanges to treatment and Outcomes in patients with type 2 diabetes initiating InjeCtablE therapy) study. METHODS: CHOICE was a 24-month, prospective observational study conducted in six European countries. Patients initiated exenatide twice daily (BID) or insulin based on a physician's clinical judgement. Clinical and PRO data were collected at baseline (injectable therapy initiation) and after approximately 3, 6, 12, 18 and 24 months. The two treatment cohorts had different baseline characteristics; therefore, no statistical comparisons of endpoints between main cohorts were conducted. RESULTS: There were 2388 patients eligible for analysis (exenatide BID cohort, n = 1114; insulin cohort, n = 1274). Mean positive changes in Impact of Weight on Quality of Life-Lite (IWQOL-Lite) total score and EuroQoL5-Dimension (EQ-5D) index and visual analogue scale (VAS) scores were observed in both cohorts with most changes observed during the first 6 months after injectable therapy initiation. Patients who experienced weight loss (≥ 1 kg) at 24 months appeared to have higher mean improvements in IWQOL-Lite total score than did patients with weight gain or no weight change. Patients who met the composite clinical endpoint of glycated haemoglobin (HbA1c) <7.0%, no weight gain (≤ 1 kg) and no hypoglycaemia generally experienced higher mean improvements in EQ-5D index and VAS scores (compared with patients who did not meet this endpoint) and Diabetes Health Profile-18 scores (versus the main cohorts). High levels of missing data were observed for all PRO measures in both cohorts compared with those for clinical outcomes. CONCLUSIONS: These data from a clinical practice study support those from clinical trials, suggesting that PROs are not adversely affected, and may be improved, by injectable therapy initiation. PRO data may aid appropriate treatment selection for individual patients. TRIAL REGISTRATION: ClinicalTrials.gov, NCT00635492.

Increased levels of YKL-40 and interleukin 6 in patients with chronic pancreatitis and secondary diabetes.

OBJECTIVES: Circulating levels of YKL-40 and interleukin 6 (IL-6) are elevated in patients with type 2 diabetes. We aimed to evaluate YKL-40 levels in patients with chronic pancreatitis (CP) with and without secondary diabetes mellitus (DM) to investigate whether elevated plasma YKL-40 could play a primary role in the pathogenesis of type 2 diabetes or rather represent a consequence of the diabetic state. METHODS: Plasma levels of YKL-40 and IL-6 were measured during an oral glucose tolerance test in 8 patients with CP and secondary DM, 8 patients with CP and normal glucose tolerance (NGT), and 8 healthy control subjects (CTRLs). RESULTS: Plasma YKL-40 and IL-6 were significantly higher in patients with CP and secondary DM (YKL-40, mean [95% confidence interval], 113 [60-215 ng/mL]; IL-6, 4.6 [2.3-9.1 pg/mL]) compared to patients with CP and NGT (YKL-40, 42 [28-63 ng/mL]; IL-6, 1.4 [0.8-2.4 pg/mL]) and healthy control subjects (YKL-40, 46 [31-69 ng/mL]; IL-6, 1.4 [0.8-2.4 pg/mL]). CONCLUSIONS: Patients with CP and secondary DM have elevated levels of YKL-40 and IL-6 compared to CP patients with NGT and healthy subjects, suggesting that YKL-40 is not a primary mediator of DM but a consequence of the diabetic state.

Glucagon-like peptide-2, but not glucose-dependent insulinotropic polypeptide, stimulates glucagon release in patients with type 1 diabetes.

This study investigated the glucagon-releasing properties of the hormones glucagon-like peptide-2 (GLP-2) and glucose-dependent insulinotropic polypeptide (GIP) in 8 patients with type 1 diabetes mellitus (T1DM) without paracrine intraislet influence of insulin (C-peptide negative following a 5 g intravenous arginine stimulation; on study days only treated with basal insulin substitution). On 3 study days, 180-minute two-step glucose clamps were performed. Plasma glucose (PG) was clamped at fasting values, with a mean of 7.4+/-0.5 mM in the first 90 min (period 1) and raised 1.5 times the fasting values to a mean of 11.1+/-0.1 mM in the last 90 min (period 2). In randomised order either GIP, GLP-2, or saline were infused intravenously during first 50 min in both periods at rates designed to mimic postprandial hormone responses. The resulting incremental area under curve values of glucagon were in period 1 -38+/-44 (GIP), 120+/-48 (GLP-2), and -16+/-61 (saline) pMx90 min (p=0.087), respectively; and in period 2 -157+/-76, 135+/-52, and -77+/-77pMx90 min (p=0.019), respectively. Post hoc analysis showed significant differences only between the GLP-2 days versus the GIP and saline days. In conclusion, GLP-2, but not GIP, was found to stimulate the release of glucagon in patients with T1DM, suggesting a role for GLP-2 in the postprandial hyperglucagonaemia characterising individuals with T1DM.

KATP channel closure ameliorates the impaired insulinotropic effect of glucose-dependent insulinotropic polypeptide in patients with type 2 diabetes.

OBJECTIVE: The reduced incretin effect in subjects with type 2 diabetes is accompanied by a severely impaired insulinotropic effect of the incretin hormone glucose-dependent insulinotropic polypeptide (GIP). The K(ATP) channels of the beta-cell appear to be essential for the function of GIP in mice, and mutations in the gene encoding these channels have been linked to the development of type 2 diabetes. With this study we therefore aimed at clarifying the role of K(ATP) channel malfunction in the impaired function of GIP. RESEARCH DESIGN AND METHODS: We examined 12 subjects with type 2 diabetes using a 2-h (15 mM) hyperglycemic clamp on 4 separate days with concomitant infusion of one of the following: GIP; GIP + 10 mg sulfonylurea (SU, glipizide) taken orally 1 h before the clamp; saline + 10 mg SU; or saline alone. Blood was sampled to measure plasma concentrations of glucose, intact GIP, insulin, C-peptide, and glucagon. RESULTS: Compared to the results of GIP alone, SU alone, or those results added together, coadministration of GIP and SU resulted in a more-than-additive increase in the peripheral insulin (P = 0.002) and C-peptide (P = 0.028) responses and furthermore, a more-than-additive increase in total (P = 0.01), early (P = 0.02), and late-phase (P = 0.02) insulin secretion. CONCLUSION: We have demonstrated that inhibiting the K(ATP) channels of the diabetic beta-cell acutely using SU significantly increases both the peripheral insulin response to GIP and GIP-induced insulin secretion, indicating an ameliorated insulinotropic effect of GIP.

Glucagon-like peptide receptor agonists and dipeptidyl peptidase-4 inhibitors in the treatment of diabetes: a review of clinical trials.

PURPOSE OF REVIEW: To discuss the virtues and shortcomings of the glucagon-like peptide-1 receptor agonists and the dipeptidyl peptidase-4 inhibitors in the treatment of type 2 diabetes. RECENT FINDINGS: The injectable glucagon-like peptide-1 receptor agonists exenatide significantly improves glycaemic control, with average reductions in haemoglobin A1c of about 1.0%, fasting plasma glucose of about 1.4 mmol/l, and causes a weight loss of approximately 2-3 kg after 30 weeks of treatment in patients with type 2 diabetes. The adverse effects are transient nausea and vomiting. The long-acting glucagon-like peptide-1 receptor agonists liraglutide and exenatide long-acting release reduce haemoglobin A1c by about 1.0-2.0% and have fewer gastrointestinal side-effects. The orally available dipeptidyl peptidase-4 inhibitors, that is sitagliptin and vildagliptin reduce haemoglobin A1c by 0.5-1.0%, are weight neutral and without gastrointestinal side-effects. SUMMARY: The benefits and position of the glucagon-like peptide-1 analogues and the dipeptidyl peptidase-4 inhibitors in the diabetes treatment algorithm will be clarified when we have long-term trials with hard cardiovascular endpoints and data illustrating the effects on the progression of type 2 diabetes.

The insulinotropic effect of GIP is impaired in patients with chronic pancreatitis and secondary diabetes mellitus as compared to patients with chronic pancreatitis and normal glucose tolerance.

BACKGROUND: The incretin effect is reduced and the insulinotropic effect of the incretin hormone glucose-dependent insulinotropic polypeptide (GIP) is abolished in patients with type 2 diabetes mellitus (T2DM). OBJECTIVE AND DESIGN: To evaluate the causality of this deficiency we investigated 8 patients with chronic pancreatitis (CP) and normal glucose tolerance (NGT) (fasting plasma glucose (FPG): 5.5 (4.5-6.0) mM (mean (range); HbA(1c): 5.8 (5.4-6.3) %) and 8 patients with CP and secondary diabetes not requiring insulin (FPG: 7.1 (6.0-8.8) mM; HbA(1c): 7.0 (5.8-10.0) %) during three 15-mM hyperglycaemic clamps with continuous iv infusion of saline, glucagon-like peptide-1 (GLP-1) or GIP. RESULTS: The initial (0-20 min) insulin and C-peptide responses were enhanced significantly in both groups by GLP-1 and GIP, respectively, compared to saline (P<0.05). In both groups GLP-1 infusion resulted in significantly greater insulin and C-peptide responses from 20-120 min compared with saline infusion. During GIP infusion the late-phase insulin response (20-120 min) was 3.1+/-1.0 fold greater than during saline infusion in the group of patients with CP and NGT (P<0.05), whereas there was no significant differences in patients with CP and DM. CONCLUSIONS: The lack of GIP amplification of the late insulin response to iv glucose develops alongside the deterioration of glucose tolerance in patients with CP, suggesting that the same may be true for the loss of the GIP effect in patients with T2DM.

Reduced incretin effect in type 2 diabetes: cause or consequence of the diabetic state?

We aimed to investigate whether the reduced incretin effect observed in patients with type 2 diabetes is a primary event in the pathogenesis of type 2 diabetes or a consequence of the diabetic state. Eight patients with chronic pancreatitis and secondary diabetes (A1C mean [range] of 6.9% [6.2-8.0]), eight patients with chronic pancreatitis and normal glucose tolerance (NGT; 5.3 [4.9-5.7]), eight patients with type 2 diabetes (6.9 [6.2-8.0]); and eight healthy subjects (5.5 [5.1-5.8]) were studied. Blood was sampled over 4 h on 2 separate days after a 50-g oral glucose load and an isoglycemic intravenous glucose infusion, respectively. The incretin effect (100% x [beta-cell secretory response to oral glucose tolerance test - intravenous beta-cell secretory response]/beta-cell secretory response to oral glucose tolerance test) was significantly (P < 0.05) reduced (means +/- SE) in patients with chronic pancreatitis and secondary diabetes (31 +/- 4%) compared with patients with chronic pancreatitis and NGT (68 +/- 3) and healthy subjects (60 +/- 4), respectively. In the type 2 diabetes group, the incretin effect amounted to 36 +/- 6%, significantly (P < 0.05) lower than in chronic pancreatitis patients with NGT and in healthy subjects, respectively. These results suggest that the reduced incretin effect is not a primary event in the development of type 2 diabetes, but rather a consequence of the diabetic state.

Increased postprandial responses of GLP-1 and GIP in patients with chronic pancreatitis and steatorrhea following pancreatic enzyme substitution.

We aimed to investigate how assimilation of nutrients affects the postprandial responses of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) and to evaluate the effect of pancreatic enzyme substitution (PES) on insulin secretion in patients with chronic pancreatitis (CP) and pancreatic exocrine insufficiency (PEI). Eight male patients with CP and PEI were studied. Blood was sampled frequently on two separate days after ingestion of a liquid meal with and without PES, respectively. Eight healthy male subjects served as a control group. beta-Cell responsiveness was estimated as changes in insulin secretion rates in response to changes in postprandial plasma glucose (PG). There was no difference in the PG incremental area under curve (AUC) for patients with and without PES [406 +/- 100 vs. 425 +/- 80 mM.4 h (mean +/- SE), P = 0.8]. The response of total GLP-1 was higher after PES (AUC: 7.8 +/- 1.2 vs. 5.3 +/- 0.6 nM.4 h, P = 0.01), as was the response of total GIP (AUC: 32.7 +/- 7.5 vs. 21.1 +/- 8.3 nM.4 h, P = 0.01). Concurrently, both plasma insulin, plasma C-peptide, and total insulin secretion increased after PES (AUC: 17.7 +/- 4.2 vs. 13.6 +/- 2.9 nM.4 h, P = 0.02; 237 +/- 31.4 vs. 200 +/- 27.4 nM.4 h, P = 0.005; and 595 +/- 82 vs. 497 +/- 80 pmol.kg(-1).4 h, P = 0.01, respectively). beta-Cell responsiveness to glucose was not significantly different on the two study days for patients with CP. These results suggest that the secretion of GLP-1 and GIP is under influence of the digestion and absorption of nutrients in the small intestine and that PES increases insulin secretion.

Plasma dipeptidyl peptidase-IV activity in patients with type-2 diabetes mellitus correlates positively with HbAlc levels, but is not acutely affected by food intake.

OBJECTIVE: Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide are incretin hormones, secreted in response to meal ingestion. The incretin hormones stimulate insulin secretion and are essential for the maintenance of normal plasma glucose concentrations. Both incretin hormones are metabolized quickly by the enzyme dipeptidyl peptidase-IV (DPP-IV). It is well known that type-2 diabetic patients have an impaired incretin effect. Therefore, the aim of the present study was to investigate plasma DPP-IV activity in the fasting and the postprandial state in type-2 diabetic patients and control subjects. DESIGN: The study included two protocols. Protocol one involved 40 fasting type-2 diabetic patients (28 men); age 61 +/- 1.4 (mean +/- s.e.m.) years; body mass index (BMI) 31 +/- 0.6 kg/m(2); HbAlc 7.2 +/- 0.2%; and 20 matched control subjects (14 men) were studied. Protocol two involved eight type-2 diabetic patients (six men); age 63 +/- 1.2 years; BMI 33 +/- 0.5 kg/m(2); HbAlc 7.5 +/- 0.4%; eight matched control subjects were included. METHODS: In protocol one, fasting values of DPP-IV activity were evaluated and in protocol two, postprandial DPP-IV activity during a standard meal test (566 kcal) was estimated. RESULTS: Mean fasting plasma DPP-IV activity (expressed as degradation of GLP-1) was significantly higher in this patient group compared with the control subjects (67.5 +/- 1.9 vs 56.8 +/- 2.2 fmol GLP-1/h (mean +/- s.e.m.); P=0.001). In the type-2 diabetic patients, DPP-IV activity was positively correlated to FPG and HbAlc and negatively to the duration of diabetes and age of the patients. No postprandial changes were seen in plasma DPP-IV activity in any of the groups. CONCLUSIONS: Plasma DPP-IVactivity increases in the fasting state and is positively correlated to FPG and HbAlc levels, but plasma DPP-IV activity is not altered following meal ingestion and acute changes in plasma glucose.

The elimination rates of intact GIP as well as its primary metabolite, GIP 3-42, are similar in type 2 diabetic patients and healthy subjects.

UNLABELLED: The incretin hormone, glucose-dependent insulinotropic polypeptide (GIP, previously known as gastric inhibitory polypeptide), is rapidly degraded to the biologically inactive metabolite GIP (3-42) in the circulation, but little is known about the kinetics of the intact hormone and the metabolite and whether differences exist between patients with type 2 diabetes mellitus and healthy subjects. We examined eight type 2 diabetic patients (six men, two women); mean (range) age: 59 (48-69) years; BMI: 31.6 (26.0-37.7) kg/m2; HbA1C: 9.0 (8.2-13.2) %; fasting plasma glucose (FPG): 10.0 (8.3-13.2) mmol/l and 8 healthy subjects matched for age, gender and BMI. An intravenous bolus injection of GIP (7.5 nmol) was given and venous blood samples were drawn the following 45 minutes. Peak concentrations of total GIP (intact+metabolite, mean+/-SEM) and intact GIP (in brackets) were 920+/-91 (442+/-52) pmol/l in the type 2 diabetic patients and 775+/-68 (424+/-30) pmol/l in the healthy subjects (NS). GIP was eliminated rapidly with the clearance rate for intact GIP being 2.3+/-0.2 l/min in the type 2 diabetic patients and 2.4+/-0.2 l/min in the healthy subjects (NS). The volumes of distributions were similar in the two groups and ranged from 8 to 21 l per subject. The primary metabolite, GIP 3-42, generated through the action of dipeptidyl peptidase IV (DPP-IV), was eliminated with a mean half-life of 17.5 and 20.5 min in patients and healthy subjects (NS). CONCLUSION: Elimination of GIP is similar in obese type 2 diabetic patients and matched healthy subjects. Differences in elimination of GIP and its primary metabolite, therefore, do not seem to contribute to the defective insulinotropic effect of GIP in type 2 diabetes.