Glucagon-like peptide-1 retards gastric emptying and small bowel transit in the rat: effect mediated through central or enteric nervous mechanisms

This study investigated effects of glucagon-like peptide-1(7-36)amide (GLP-1) on gastric emptying, small intestinal transit, and contractility of smooth muscle strips in rats. GLP-1 at doses of 10 and 20 pmol/kg/min administered intravenously dose-dependently retarded transit of the small intestine (P < 0.001), while only the higher dose of 20 pmol/kg/min retarded gastric emptying (P < 0.01). GLP-1 at concentrations up to 10(-4) M did not affect the basal tone or contractility of the gastrointestinal muscle strips that were stimulated with electric field stimulation or acetylcholine. Our results demonstrate that small intestinal transit seems more sensitive than gastric emptying to inhibition by GLP-1 at physiologic levels in plasma. Furthermore, this inhibition appears to be mediated through central mechanisms rather than through peripheral actions. Thus, GLP-1 is suggested to inhibit gastric emptying and small intestinal transit through an indirect effect via central or enteric nervous mechanisms.

Development of postoperative insulin resistance is associated with the magnitude of operation

OBJECTIVE

To study the development of insulin resistance and changes in stress hormone concentrations in patients undergoing elective operations of different magnitude.

DESIGN

Prospective open study.

SETTING

University hospital, Sweden.

SUBJECTS

12 otherwise healthy patients, undergoing elective surgery for cholecystectomy (n = 6) and inguinal hernia repair (n = 6).

INTERVENTIONS

Insulin sensitivity was measured by the normoglycaemic, hyperinsulinaemic glucose clamp technique before operation (control) and on the first postoperative day.

MAIN OUTCOME MEASURE

Relative insulin sensitivity (compared with preoperative) on the day after each operation. Changes in stress hormone concentrations in relation to the relative change in insulin sensitivity.

RESULTS

After hernia repair, mean (SEM) insulin sensitivity was reduced by 32 (4)%, p < 0.05 compared with baseline, and after open cholecystectomy by 56 (3)%, (p < 0.05). The difference between the two groups was highly significant (p < 0.01). The changes in concentrations of catecholamines, glucagon, cortisol and growth hormone after operation were only small, and did not correlate with the relative changes in insulin sensitivity.

CONCLUSIONS

Insulin resistance develops even after a minor elective operation, (inguinal hernia repair). The degree of postoperative insulin resistance was more pronounced after open cholecystectomy. The alteration in insulin sensitivity could not be related to simultaneous changes in the hormones studied.

Glucose infusion instead of preoperative fasting reduces postoperative insulin resistance

In severe catabolic states, such as burn injury, sepsis and accidental injury, a state of marked insulin resistance is encountered. Insulin resistance is also present after elective surgical treatment, more pronounced with increasingly greater magnitude of operation performed. Results of recent animal experiments have shown that even short periods of food deprivation, reducing carbohydrate reserves, alter responses to stress. This notion resulted in our questioning the rationale of carbohydrate depletion associated with overnight preoperative fasting. Twelve patients undergoing elective open cholecystectomy were randomly given no infusion (control group) or 5 milligrams per kilogram per minute of glucose infusion (glucose group) during preoperative overnight fasting. Insulin sensitivity (M value, milligram per kilogram per minute) was determined using the hyperinsulinemic normoglycemic clamp (plasma insulin level, 65 microunits per milliliter and blood glucose level, 4.5 millimoles per liter) before and the first postoperative day. Preoperative insulin sensitivity was similar in the two groups. Postoperatively, M values decreased by 55 +/- 3 percent (control group) and by 32 +/- 4 percent (glucose group) (p < 0.01). Plasma levels of insulin, c-peptide, glucagon, growth hormone, catecholamines and cortisol in connection with clamps were similar in both groups preoperatively and postoperatively. The present results indicate that active preoperative carbohydrate preservation may improve postoperative metabolism because postoperative occurrence of insulin resistance was reduced with preoperative glucose infusion.

Influence of acarbose on post-prandial insulin requirements in patients with Type 1 diabetes

The primary objective of this double-blind, placebo-controlled, randomised cross-over study was to investigate the influence of acarbose on insulin requirement in patients with Type 1 diabetes (T1DM) following a standardised meal. In addition, the study assessed the effects of acarbose on post-prandial triglyceride, glucagon and gastrointestinal peptide levels, gastric emptying, and oxidative glucose metabolism. Following normalisation of their blood glucose, 10 patients received a standardised meal together with acarbose (100 mg) or placebo. Each patient was evaluated twice (separated by 10+/-3 days), and the cross-over study design ensured that they received both acarbose and placebo. The insulin requirement for maintenance of normoglycaemia was assessed using a closed-loop insulin infusion system (artificial pancreas, Biostator). Acarbose produced a statistically significant reduction in mean insulin requirement over a 3-hr period following the meal compared with placebo (5171.7+/-2282.6 mU vs 8074.5+/-3045.4 mU; p=0.003). The level of blood glucose control over the same period was similar in the two groups. Gastric inhibitory polypeptide levels also showed a statistically significant decrease with acarbose treatment compared with placebo for AUC (area under the curve; p=0.006) and Cmax (maximum plasma concentration; p=0.022), but not tmax (time to reach Cmax from the start of the standardised meal; p>0.05). Analysis of the other efficacy parameters revealed no statistically significant differences between acarbose treatment and placebo (p>0.05). These results indicate that acarbose decreases insulin requirement in patients with T1DM without affecting gastric emptying.

[Treatment of type 2 diabetes. Early detection of secondary oral treatment failure is important]

As type II diabetes is caused by decreased insulin secretion and increased insulin resistance, treatment must be aimed at the correction of these abnormalities. To this end, oral hypoglycaemic agents (OHAs) are used once adverse lifestyle factors have been suitably modified. New OHAs are being developed, or have already been approved. Subsequent treatment failure, after an initially satisfactory response, occurs in 5-10 per cent of patients on OHAs, and is currently treated with a combination of an OHA for daytime use and NPH insulin (isophane insulin) for use at bedtime. This yields metabolic control at least as good as that obtained with intensive insulin treatment, and at less risk of weight gain.

Glucose uptake and binding of digoxin to skeletal muscle

Physical exercise induces increased uptake of both digoxin and glucose in exercising skeletal muscle. Glucose uptake could be a regulatory factor for the digoxin binding to skeletal muscle, since in dogs, insulin and glucose infusion have been reported to increase the uptake of digoxin in muscle. In the present study on eight healthy digitalized subjects (0.5 mg digoxin daily) the uptake of glucose in skeletal muscle was achieved by infusion of 6 mg/kg body weight/min glucose, 0.004 IE/kg body weight/min insulin and 300 micrograms/h somatostatin. Serum and skeletal muscle digoxin levels were analysed before and during the infusion. We found no changes in the digoxin levels in serum and skeletal muscle in spite of an increased uptake of glucose in the muscle. Thus, glucose uptake in skeletal muscle is probably not an important regulatory factor for the change in muscle digoxin binding induced by exercise.

[Gastrointestinal peptides among new therapeutic agents used in type 2 diabetes]

The pharmacological arsenal available today for the treatment of type II diabetes is often insufficient to allow optimal control of the disease. Each agent corrects only one or a few of the multiple defects that characterise type II diabetes. Currently, new drugs are under development that target several of the clinical abnormalities. These agents include the gastrointestinal peptides, glucagon-like polypeptide-1 (GLP-1) and amylin, and their analogues. New rapid- and long-acting insulin analogues will also constitute interesting treatment alternatives.

Association study between chromosome 10q26.11 and obesity among Swedish men

OBJECTIVE

Proximal chromosome 10q26 was recently linked to waist/hip ratio in European and African-American families. The objective was to investigate whether genomic variation in chromosome 10q26.11 reflects variation in obesity-related clinical parameters in a Swedish population.

DESIGN

Genetic association study of single-nucleotide polymorphisms (SNPs) in chromosome 10q26.11 and obesity-related clinical parameters was performed. Obesity was defined as body mass index (BMI) > or = 30 kg/m2.

SUBJECTS

Swedish Caucasians comprising 276 obese and 480 nonobese men, 313 obese and 494 nonobese women, 177 obese and 163 nonobese patients with type 2 diabetes mellitus (T2DM), and 106 obese and 201 nonobese subjects with impaired glucose tolerance (IGT) patients.

MEASUREMENTS

Genotypes of 11 SNPs at chromosome 10q26.11, and various obesity-related clinical parameters.

RESULTS

Homozygosity of a common haplotype constructed by three SNPs, rs2185937, rs1797 and hCV1402327, covering an interval of 2.7 kb, was suggested to confer an increased risk for obesity of 1.5 among men (P = 0.043). The C allele frequency and homozygous genotype frequency of the rs1797 tended to be higher among obese compared to among nonobese men (P = 0.017 and 0.020, respectively). The distribution of BMI and diastolic blood pressure was higher among those with the C/C genotype (P = 0.022 and 0.0061, respectively). The obese and the nonobese groups were homogeneous over BMI subgroups with regard to rs1797 risk genotype distribution. There was no tendency for association between rs1797 and obesity among neither women nor T2DM nor IGT patients.

CONCLUSION

We show support for association between proximal chromosome 10q26.11 and obesity among Swedish men but not women through the analysis of a haplotype encompassing 2.7 kb.

Glucose intolerance in uremic patients: the relative contributions of impaired beta-cell function and insulin resistance

Glucose tolerance and tissue sensitivity to insulin were examined in 19 renal failure patients on chronic regular hemodialysis (group U) and in 6 matched control subjects with normal renal function (group A). Based on glucose tolerance as assessed by an oral glucose tolerance test (OGTT), glucose tolerance was normal in 5 (group U:N), borderline in 5 (group U:BL) and decreased in 9 uremic subjects (group U:D). Compared with group A the uremics demonstrated significantly (p less than 0.01) impaired insulin sensitivity as assessed by a continuous mixed infusion of somatostatin, insulin and glucose (SIGIT). In addition 19 non-diabetic subjects with normal fasting blood glucose and normal renal function, matching the uremic patients with respect to glucose tolerance as assessed by OGTT, were studied (group B). In group B impairments in both insulin secretion and insulin sensitivity tended to be more pronounced in subjects with decreased OGTT as compared with those with borderline OGTT. In contrast, insulin resistance was present to a similar degree in uremic subjects of group U:N, U:BL and U:D. During SIGIT endogenous insulin, glucagon and growth hormone (GH) were suppressed in both uremic and control subjects. This implies that insulin resistance in uremia is most likely not due to hyperglucagonemia or abnormal GH metabolism. During OGTT subjects of group U:N had significantly higher insulin response than subjects of group U:BL (p less than 0.02) and group U:D (p less than 0.01). Insulinogenic index was significantly higher in group U:N than in group U:BL (p less than 0.02) and group U:D (p = 0.01) and was higher in group U:BL than in group U:D (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Indications that branched chain amino acids, in addition to glucagon, affect the glomerular filtration rate after a high protein diet in insulin-dependent diabetes

Hormonal changes and whole blood free amino acid levels and their relation to renal function were measured in 12 insulin-dependent diabetic patients after two 10-day periods with a diet consisting of 10% and 20% respectively of the energy as protein. The patients were 15-21 years old and mean duration of diabetes was 12 (5-20) years. Glomerular filtration rate, renal plasma flow, and albumin excretion rate were measured together with plasma concentrations of glucagon, growth hormone, insulin-like growth factor 1 (IGF-1), somatostatin, serum insulin and free amino acids in blood. Glomerular filtration rate was 123 +/- 3 ml/min/1.73 m2 on high protein diet and 113 +/- 3 ml/min/1.73 m2 on low protein diet (p = 0.02). Renal plasma flow was unchanged. Glucagon, IGF-1, branch chained amino acids (BCAA), tyrosine, phenylalanine, lysine, and methionine were increased after the high protein diet. Growth hormone, somatostatin, insulin, and other amino acids remained unchanged. The increase in glomerular filtration rate was significantly correlated to the increase in glucagon, isoleucine, and valine (glucagon r = 0.71, p = 0.01, isoleucine r = 0.59, p = 0.04, valine r = 0.62, p = 0.03). In a multiple regression model the increase in glomerular filtration correlated most strongly to the increase in isoleucine, followed by valine and glucagon. Together these variables explained 88% of the total variance of the change in glomerular filtration rate (r2 = 0.88, p = 0.001). Albumin excretion rate was correlated to IGF-1 (r = 0.86, p less than 0.001) on the high protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Can somatostatin prevent injection pancreatitis after ERCP?

In a double-blind randomized study, 30 patients received somatostatin infusion during ERCP and 30 patients placebo with the aim of evaluating whether somatostatin can reduce the incidence of injection pancreatitis. S-amylase, U-amylase and S-lipase were evaluated before, during and after (up to 48 hours) ERCP. C-peptide was also determined as a marker of the function of the endocrine pancreas. While no statistically significant effect of somatostatin in terms of amylase and lipase was to be found, somatostatin did significantly decrease c-peptide levels in plasma, indicating that the peptide inhibited beta-cell secretion. About 40% of patients in the somatostatin group and about 50% in the placebo group showed signs of injection pancreatitis (elevated levels of enzymes) and in both groups there are patients with clinically apparent pancreatitis.

Molecular cloning of PEC-60 and expression of its mRNA and peptide in the gastrointestinal tract and immune system

The peptide PEC-60, structurally related to the pancreatic secretory trypsin inhibitor, inhibits glucose-induced insulin secretion. Here we report on the structure of a cDNA clone from pig duodenum encoding PEC-60. The cDNA encodes a 86-amino acid long precursor protein containing a 26-amino acid signal sequence, implying that the mature PEC-60 peptide is secreted from cells. Analysis of porcine duodenum demonstrated a high expression of a 0.6-kilobase long PEC-60 mRNA in this tissue, as well as the presence of strong PEC-60-like immunoreactivity in the cytoplasm of the majority of the goblet cells of the epithelium. High levels of PEC-60 mRNA were also found in the bone marrow and the peripheral blood and moderate levels in the spleen. A strong PEC-60-like immunoreactivity was localized in the monocytes of peripheral blood. Radioimmunoassay revealed high levels of pig PEC-60-like immunoreactivity in pig plasma suggesting that the PEC-60 peptide is efficiently released from cells. These findings imply that the gastrointestinal peptide PEC-60 is formed, stored, and secreted from monocytes present within the bone marrow and in the peripheral blood, indicating a role of the PEC-60 peptide in the immune system in addition to its function as a gastrointestinal peptide.

Insulin release in type 2 diabetes mellitus

Impaired insulin response is a characteristic feature of Type 2 diabetes. Overt diabetes develops when beta-cells fail to release enough insulin to compensate for decreased insulin sensitivity. However, a subgroup of normal weight patients demonstrates a pronounced beta-cell secretory defect and a normal insulin sensitivity. The molecular basis behind the impaired insulin response in Type 2 diabetes is not clear. Our studies in two animal models of this disease (GK rat and ob/ob mouse) suggest that an impaired glucose metabolism may be a primary defect in the stimulus-secretion coupling in the beta-cells in Type 2 diabetes. In the GK rat, three major alterations in the islet metabolism of glucose have been demonstrated: 1) increased glucose utilization but unchanged glucose oxidation; 2) increased glucose cycling and 3) decreased activity of the glycerol phosphate shuttle. In ob/ob animals we have found an increased rate of glucose cycling. These derangements might result in an incomplete closure of ATP-sensitive K(+)-channels with a decreased insulin response as a consequence.