S. Madsbad

Proglucagon products in plasma of noninsulin-dependent diabetics and nondiabetic controls in the fasting state and after oral glucose and intravenous arginine.

We investigated the major products of proglucagon (PG) processing in plasma in the fasting state, after intravenous arginine and after an oral glucose load in noninsulin-dependent diabetics (NIDDM) and in weight matched controls using specific radioimmunoassays and analytical gel filtration. In the fasting state the glucagonlike peptide-1 (GLP-1) immunoreactivity was significantly elevated in the NIDDM group compared with the control group. Both after intravenous arginine and after an oral glucose load a rise in the plasma concentrations of all immunoreactive moieties measured was seen. All integrated incremental responses after intravenous arginine were identical in the two groups. After oral glucose the insulin concentrations in plasma were lower and the concentrations of all proglucagon products were higher in the NIDDM group compared to the control group. The gel filtration analysis showed that arginine stimulated the secretion of pancreatic glucagon (PG 33-61), major proglucagon fragment (PG 72-158) and probably GLP-1 (PG 72-107 amide) in both groups, whereas oral glucose stimulated the secretion of glicentin (PG 1-69) and intestinal GLP-1 (PG 78-107 amide), an insulinotropic hormone. The elevated levels of immunoreactive GLP-1 in diabetics in the fasting state were mainly due to an increased concentration of major proglucagon fragment.

Acute and long-term effects of Roux-en-Y gastric bypass on glucose metabolism in subjects with Type 2 diabetes and normal glucose tolerance

Our aim was to study the potential mechanisms responsible for the improvement in glucose control in Type 2 diabetes (T2D) within days after Roux-en-Y gastric bypass (RYGB). Thirteen obese subjects with T2D and twelve matched subjects with normal glucose tolerance (NGT) were examined during a liquid meal before (Pre), 1 wk, 3 mo, and 1 yr after RYGB. Glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1), glucose-dependent-insulinotropic polypeptide (GIP), and glucagon concentrations were measured. Insulin resistance (HOMA-IR), β-cell glucose sensitivity (β-GS), and disposition index (D(β-GS): β-GS × 1/HOMA-IR) were calculated. Within the first week after RYGB, fasting glucose [T2D Pre: 8.8 ± 2.3, 1 wk: 7.0 ± 1.2 (P < 0.001)], and insulin concentrations decreased significantly in both groups. At 129 min, glucose concentrations decreased in T2D [Pre: 11.4 ± 3, 1 wk: 8.2 ± 2 (P = 0.003)] but not in NGT. HOMA-IR decreased by 50% in both groups. β-GS increased in T2D [Pre: 1.03 ± 0.49, 1 wk: 1.70 ± 1.2, (P = 0.012)] but did not change in NGT. The increase in DI(β-GS) was 3-fold in T2D and 1.5-fold in NGT. After RYGB, glucagon secretion was increased in response to the meal. GIP secretion was unchanged, while GLP-1 secretion increased more than 10-fold in both groups. The changes induced by RYGB were sustained or further enhanced 3 mo and 1 yr after surgery. Improvement in glycemic control in T2D after RYGB occurs within days after surgery and is associated with increased insulin sensitivity and improved β-cell function, the latter of which may be explained by dramatic increases in GLP-1 secretion.

Gut hormones, early dumping and resting energy expenditure in patients with good and poor weight loss response after Roux-en-Y gastric bypass

Objective:To identify factors contributing to the variation in weight loss after Roux-en-Y gastric bypass (RYGB).Design:Cross-sectional study of patients with good (excess body mass index lost (EBL) >60%) and poor weight loss response (EBL <50%) >12 months after RYGB and a lean control group matched for age and gender.Materials and methods: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 9u2009h multiple-meal test with measurements of glucose, insulin, total bile acids (TBA), glucagon-like peptide (GLP)-1, peptide YY3–36 (PYY), cholecystokinin (CCK), ghrelin, neurotensin and pancreatic polypeptide (PP) as well as assessment of early dumping and appetite.Results: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.Conclusion: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.

Regional Anatomic Differences in Skeletal Muscle Mitochondrial Respiration in Type 2 Diabetes and Obesity

CONTEXTnPrevious studies on leg skeletal musculature have demonstrated mitochondrial dysfunction associated with type 2 diabetes mellitus (T2DM), but it is not known whether mitochondrial dysfunction is present in the upper extremities.nnnOBJECTIVEnThe aim of the study was to compare mitochondrial respiration and markers of mitochondrial content in skeletal muscle of arm and leg in patients with T2DM and obese control subjects.nnnPATIENTSnTen patients with T2DM (age, 52.3 +/- 2.7 yr; body mass index, 30.1 +/- 1.2 kg/m(2)) (mean +/- se) were studied after a 2-wk washout period of oral antihyperglycemic agents. Ten control subjects (age, 54.3 +/- 2.8 yr; body mass index, 30.4 +/- 1.2 kg/m(2)) with normal fasting and 2-h oral glucose tolerance test blood glucose levels were also included.nnnMAIN OUTCOME MEASUREnWe measured mitochondrial respiration in saponin-treated skinned muscle fibers from biopsies of m. deltoideus and m. vastus lateralis using high-resolution respirometry.nnnRESULTSnIn the arm, mitochondrial respiration and citrate synthase activity did not differ between groups, but mitochondrial respiration per milligram of muscle was significantly higher in the leg muscle of the control subjects compared to T2DM. Fiber type compositions in arm and leg muscles were not different between the T2DM and control group, and maximum rate of O(2) consumption did not differ between the groups.nnnCONCLUSIONnThe results demonstrate that reduced mitochondrial function in T2DM is only present in the leg musculature. This novel finding suggests that mitochondrial dysfunction is not a primary defect affecting all skeletal muscle but could be related to a decreased response to locomotor muscle use in T2DM.

Obesity - an indication for GLP-1 treatment? Obesity pathophysiology and GLP-1 treatment potential

Obesity is common and associated with a high rate of morbidity and mortality; therefore, treatment is of great interest. At present, bariatric surgery is the only truly successful treatment of severe obesity. Mimicking one of the effects of bariatric surgery, namely the increased secretion of glucagon‐like peptide (GLP)‐1, by artificially increasing the levels of GLP‐1 might prove successful as obesity treatment. Recent studies have shown that GLP‐1 is a physiological regulator of appetite and food intake. The effect on food intake and satiety is preserved in obese subjects and GLP‐1 may therefore have a therapeutic potential. The GLP‐1 analogues result in a moderate average weight loss, which is clinically relevant in relation to reducing the risk of type 2 diabetes and cardiovascular disease. Inspired by the hormone profile after gastric bypass, a future strategy in obesity drug development could be to combine several hormones, and thereby produce a superior appetite suppressing hormone profile that may result in a weight loss exceeding that seen in single‐agent trials. In conclusion, with the GLP‐1 analogues combining a moderate weight loss with beneficial effects on metabolic and cardiovascular risk factors, it seems that we are on the right track for future treatment of obesity.

Peptide YY and glucagon-like peptide-1 contribute to decreased food intake after Roux-en-Y gastric bypass surgery

Background/Objectives:Exaggerated postprandial secretion of glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) may explain appetite reduction and weight loss after Roux-en-Y gastric bypass (RYGB), but causality has not been established. We hypothesized that food intake decreases after surgery through combined actions from GLP-1 and PYY. GLP-1 actions can be blocked using the GLP-1 receptor antagonist Exendin 9–39 (Ex-9), whereas PYY actions can be inhibited by the administration of a dipeptidyl peptidase-4 (DPP-4) inhibitor preventing the formation of PYY3–36.Subjects/Methods:Appetite-regulating gut hormones and appetite ratings during a standard mixed-meal test and effects on subsequent ad libitum food intake were evaluated in two studies: in study 1, nine patients with type 2 diabetes were examined prospectively before and 3 months after RYGB with and without Ex-9. In study 2, 12 RYGB-operated patients were examined in a randomized, placebo-controlled, crossover design on four experimental days with: (1) placebo, (2) Ex-9, (3) the DPP-4 inhibitor, sitagliptin, to reduce formation of PYY3–36 and (4) Ex-9/sitagliptin combined.Results:In study 1, food intake decreased by 35% following RYGB compared with before surgery. Before surgery, GLP-1 receptor blockage increased food intake but no effect was seen postoperatively, whereas PYY secretion was markedly increased. In study 2, combined GLP-1 receptor blockage and DPP-4 inhibitor mediated lowering of PYY3–36 increased food intake by ~20% in RYGB patients, whereas neither GLP-1 receptor blockage nor DPP-4 inhibition alone affected food intake, perhaps because of concomitant marked increases in the unblocked hormone.Conclusions:Blockade of actions from only one of the two L-cell hormones, GLP-1 and PYY3–36, resulted in concomitant increased secretion of the other, probably explaining the absent effect on food intake on these experimental days. Combined blockade of GLP-1 and PYY actions increased food intake after RYGB, supporting that these hormones have a role in decreased food intake postoperatively.

Accelerated protein digestion and amino acid absorption after Roux-en-Y gastric bypass

BACKGROUNDnRoux-en-Y gastric bypass (RYGB) involves exclusion of major parts of the stomach and changes in admixture of gastro-pancreatic enzymes, which could have a major impact on protein digestion and amino acid absorption.nnnOBJECTIVEnWe investigated the effect of RYGB on amino acid appearance in the systemic circulation from orally ingested protein and from endogenous release.nnnDESIGNnNine obese glucose-tolerant subjects, with a mean body mass index (in kg/m(2)) of 39.2 (95% CI: 35.2, 43.3) and mean glycated hemoglobin of 5.3% (95% CI: 4.9%, 5.6%), were studied before and 3 mo after RYGB. Leucine and phenylalanine kinetics were determined under basal conditions and during 4 postprandial hours by intravenous infusions of [3,3,3-(2)H3]-leucine and [ring-(2)D5]-phenylalanine combined with ingestion of [1-(13)C]-leucine intrinsically labeled caseinate as the sole protein source of the meal. Changes in body composition were assessed by dual-energy X-ray absorptiometry.nnnRESULTSnAfter RYGB, basal plasma leucine concentration did not change, but marked changes were seen postprandially with 1.7-fold increased peak concentrations (before—mean: 217 μmol/L; 95% CI: 191, 243 μmol/L; 3 mo—mean: 377 μmol/L; 95% CI: 252, 502 μmol/L; P = 0.012) and 2-fold increased incremental AUC (before-mean: 4.1 mmol ∙ min/L; 95% CI: 2.7, 5.5 mmol ∙ min/L; 3 mo-mean: 9.5 mmol ∙ min/L; 95% CI: 4.9, 14.2 mmol ∙ min/L; P = 0.032). However, the postprandial hyperleucinemia was transient, and concentrations were below basal concentrations in the fourth postprandial hour. These concentration differences were mainly caused by changes in leucine appearance rate from orally ingested caseinate: peak rate increased nearly 3-fold [before—mean: 0.5 μmol/(kg fat-free mass ∙ min); 95% CI: 0.4, 0.5 μmol/(kg fat-free mass ∙ min); 3 mo—mean 1.4 μmol/(kg fat-free mass ∙ min); 95% CI: 0.8, 1.9 μmol/(kg fat-free mass ∙ min); P = 0.002], and time to peak was much shorter (before—mean: 173 min; 95% CI: 137, 209 min; 3 mo—mean: 65 min; 95% CI: 46, 84 min; P < 0.001). Only minor changes were seen in endogenous leucine release after RYGB.nnnCONCLUSIONSnRYGB accelerates caseinate digestion and amino acid absorption, resulting in faster and higher but more transient postprandial elevation of plasma amino acids. Changes are likely mediated by accelerated intestinal nutrient entry and clearly demonstrate that protein digestion is not impaired after RYGB. This trial was registered at clinicaltrials.gov as NCT01559792.

Opposite effects of pioglitazone and rosiglitazone on mitochondrial respiration in skeletal muscle of patients with type 2 diabetes.

Aim: Skeletal muscle insulin resistance has been linked to mitochondrial dysfunction. We examined how improvements in muscular insulin sensitivity following rosiglitazone (ROSI) or pioglitazone (PIO) treatment would affect muscle mitochondrial function in patients with type 2 diabetes mellitus (T2DM).

Improved glycaemic control decreases inner mitochondrial membrane leak in type 2 diabetes

Aim:u2002 Several mechanisms have been targeted as culprits of weight gain during antihyperglycaemic treatment in type 2 diabetes (T2DM). These include reductions in glucosuria, increased food intake from fear of hypoglycaemia, the anabolic effect of insulin, decreased metabolic rate and increased efficiency in fuel usage. The purpose of the study was to test the hypothesis that mitochondrial efficiency increases as a result of insulin treatment in patients with type 2 diabetes.

Homozygous carriers of the G allele of rs4664447 of the glucagon gene (GCG) are characterised by decreased fasting and stimulated levels of insulin, glucagon and glucagon-like peptide (GLP)-1

Aims/hypothesisThe glucagon gene (GCG) encodes several hormones important for energy metabolism: glucagon, oxyntomodulin and glucagon-like peptide (GLP)-1 and -2. Variants in GCG may associate with type 2 diabetes, obesity and/or related metabolic traits.MethodsGCG was re-sequenced as a candidate gene in 865 European individuals. Twenty-nine variants were identified. Four variants that were considered to have a likelihood for altered functionality: rs4664447, rs7581952, Ile158Val and Trp169Ter, were genotyped in 17,584 Danes.ResultsWhen examined in 5,760 treatment-naive individuals, homozygous carriers of the low frequency (minor allele frequency 2.3%) G allele of rs4664447, predicted to disrupt an essential splice enhancer binding site, had lower levels of fasting plasma glucose (meanu2009±u2009SD, 4.8u2009±u20091.2 vs 5.5u2009±u20090.8xa0mmol/l, pu2009=u20090.004); fasting serum insulin (22u2009±u200914 vs 42u2009±u200927xa0pmol/l, pu2009=u20090.04); glucose-stimulated serum insulin (159u2009±u200983 vs 290u2009±u2009183xa0pmol/l, pu2009=u20090.01) and adult height (165u2009±u200910 vs 172u2009±u20099xa0cm, pu2009=u20090.0009) compared with A allele carriers. During oral glucose tolerance and hyperglycaemic arginine stimulation tests, the plasma AUC for GLP-1 (730u2009±u200969 vs 1,334u2009±u2009288xa0pmol/lu2009×u2009min, pu2009=u20090.0002) and basal and stimulated levels of serum insulin and plasma glucagon were ∼50% decreased (pu2009<u20090.001) among three homozygous carriers compared with nine matched wild-type carriers. rs7581952, Ile158Val and Trp169Ter (where ‘Ter’ indicates ‘termination’) variants of GCG did not significantly associate or co-segregate with the metabolic traits examined.Conclusions/interpretationRe-sequencing of GCG revealed a low frequency intronic variant, rs4664447, and follow-up physiological studies suggest that this variant in homozygous form may cause decreased fasting and stimulated levels of insulin, glucagon and GLP-1. Overall, our findings suggest that variation in GCG has no major impact on carbohydrate metabolism in the study populations examined.