Effect of the entero-pancreatic hormones, gastric inhibitory polypeptide and glucagon-like polypeptide-1(7-36) amide, on fatty acid synthesis in explants of rat adipose tissue

The effect of gastric inhibitory polypeptide (GIP), glucagon-like peptide-1(7-36) amide, (GLP-1(7-36) amide), glucagon-like peptide-2 (GLP-2), glucagon and insulin on fatty acid synthesis in explants of rat adipose tissue from various sites was investigated. GIP, GLP-1(7-36) amide and insulin stimulated fatty acid synthesis, as determined by measuring the incorporation of [14C]acetate into saponifiable fat, in a dose-dependent manner, over the concentration range 5-15 ng/ml (0.87-2.61 nmol/l) for insulin and 0.5-7.5 ng/ml for GIP (0.10-1.50 nmol/l) and GLP-1(7-36) amide (0.15-2.27 nmol/l). Insulin and GIP caused a significantly greater stimulation of [14C]acetate incorporation into fatty acids in omental adipose tissue than in either epididymal or subcutaneous adipose tissue. Both GIP and GLP-1(7-36) amide had the ability to stimulate fatty acid synthesis within the physiological range of the circulating hormones. At lower concentrations of the hormones, GLP-1(7-36) amide was a more potent stimulator of fatty acid synthesis than GIP in omental adipose tissue culture; the basal rate of fatty acid synthesis was 0.41 +/- 0.03 pmol acetate incorporated/mg wet weight tissue per 2 h; at 0.10 nmol hormone/1 1.15 +/- 0.10 and 3.40 +/- 0.12 pmol acetate incorporated/mg wet weight tissue per 2 h for GIP and GLP-1(7-36) amide respectively (P less than 0.01). GLP-2 and glucagon were without effect on fatty acid synthesis in omental adipose tissue. The study indicates that GIP and GLP-1(7-36)amide, in addition to stimulating insulin secretion, may play a direct physiological role in vivo, in common with insulin, in promoting fatty acid synthesis in adipose tissue.

Hypoglycaemia associated with anorexia nervosa

A 41 year old woman with severe emaciation due to longstanding anorexia nervosa presented with recurrent hypoglycaemia. During an episode of hypoglycaemia, serum insulin and C peptide were undetectable and plasma beta hydroxybutyrate, free fatty acids and lactate were inappropriately low. Response to intravenous glucagon was poor. Muscle enzymes were grossly elevated until she gained weight. Hypoglycaemia was abolished by weight gain.

On the reactions of superoxide with keto enols, aci-reductones and ascorbic acid derivatives

The superoxide-mediated base catalyzed autoxidation of alpha-oxo enols is initiated by the deprotonation of the labile hydroxyl group. Thus, the reaction of O2-. (generated from KO2/crown ether in aprotic media) with 3-hydroxycoumarin (1), followed by a CH3I-workup, generates products 2-4 via a deprotonation-oxidation sequence complicated by a competing saponification of the lactone linkage. The related coumarin reductone (alpha-oxo enediol) 8 is rapidly oxidized by O2-., HO- and t-butoxide to the corresponding triketone, which in turn undergoes further oxidation and rearrangement ultimately yielding (upon methyl iodide workup) products 9-14. When the O2-. mediated oxidation is carried out under argon in completely degassed solutions, large amounts (greater than 20%) of monodeprotonation product (detected as 9) accumulate. These results are discussed in light of the differing mechanisms proposed by Sawyer and Afanas'ev for the interaction of O2-. with the reductone ascorbic acid.

Hyperinsulinaemic hypoglycaemia in small for dates babies

Blood glucose concentrations were measured prospectively in 27 small for dates infants in the first 48 hours after birth: 10 infants became hypoglycaemic. Of these, five had inappropriately raised plasma insulin concentrations. Plasma free fatty acids were lower and carbohydrate intake higher in these five infants, further supporting the diagnosis of hyperinsulinism. The hypoglycaemia recurred in four of the five hyperinsulinaemic infants, but in none of those who were not hyperinsulinaemic. Hyperinsulinism is common in small for dates babies. It is important to recognise this because hypoglycaemia is likely to recur and appropriate treatment is needed to prevent long term sequelae.

Near-patient testing: implications for laboratory-based professions

The current upheaval being experienced by the National Health Service in the UK is due partly to political and partly to technological changes in the mode of delivery of health care. The two can not be separated completely, but the implications for laboratory-based health care professions of technological changes that have occurred in their specialty, mainly within the last 10 years, are considered. These have made it increasingly possible to carry out previously complicated analytical manoeuvres outside the confines of a well-founded laboratory, but in doing so have brought with them problems as well as advantages for the providers of health care, as well as for its recipients--i.e. the patients.

Inappropriately elevated plasma insulin-like growth factor II in relation to suppressed insulin-like growth factor I in the diagnosis of non-islet cell tumour hypoglycaemia

The diagnosis of non-islet cell tumour (hypoinsulinaemic) hypoglycamia has been complicated by contradictory biochemical evidence. Although insulin-like growth factor II (IGF-II) has been identified as the hypoglycaemic agent, plasma levels are often not elevated. In this study specific radioimmunoassay procedures for the measurement of IGF-I and IGF-II are described. Reference data on plasma IGF-II concentrations in relation to a wide range of IGF-I levels have been accumulated using plasma samples from acromegalic, hypopituitary and insulinoma (i.e. hyperinsulinaemic hypoglycaemia) patients as well as normal subjects from all age groups. The reference data indicate that a low plasma IGF-I value is normally associated with a relatively low plasma IGF-II level. Within a group of hypoinsulinaemic hypoglycaemia patients, a small number, invariably with evidence of a neoplasm, had low plasma IGF-I concentrations but apparently normal IGF-II levels. We propose that, in such cases, an apparently normal plasma IGF-II value is inappropriately high for the low plasma IGF-I level and, in association with non-ketotic hypoinsulinaemia and suppressed plasma growth hormone (GH), is diagnostic of a non-islet cell tumour as the cause of hypoglycaemia.

The effect of soluble- and insoluble-fibre supplementation on post-prandial glucose tolerance, insulin and gastric inhibitory polypeptide secretion in healthy subjects

Six healthy non-obese male subjects were given three test meals containing 100 g carbohydrate and 1.5 g soluble paracetamol, supplemented on one occasion with 10 g guar gum and on another with 10 g sugarbeet fiber. A further six subjects were given the same test meal supplemented on one occasion with 10 g soya-bean-cotyledon fibre and on another, 5 g glucomannan. Venous blood samples were taken before, and at intervals for 180 min following the meal, and analysed for insulin, gastric inhibitory polypeptide (GIP) and paracetamol (as an index of gastric emptying). Arterialized blood samples were taken and analysed for glucose. Meal supplementation with both guar gum and sugar-beet fibre improved glucose tolerance, but circulating glucose levels were unaffected by the addition of either soya-bean-cotyledon fibre or glucomannan to the meals. Supplementation with guar gum and glucomannan lowered post-prandial insulin levels. Insulin levels were enhanced by addition of soya-bean-cotyledon fibre to the meal and unaffected by sugar-beet fibre. Post-prandial GIP levels were lowered in the guar-gum-supplemented meal and augmented with sugar-beet fibre supplementation. Addition of glucomannan and soya-bean-cotyledon fibre did not affect circulating GIP levels. The study failed to confirm previous reports of improved glucose tolerance following glucomannan and soya-bean-cotyledon fibre supplementation. The failure of sugar-beet fibre to reduce post-prandial insulin secretion despite improved glucose tolerance may be due to the observed increased secretion of GIP. The increased insulin levels seen following soya-bean-cotyledon fibre supplementation cannot be attributed either to changes in glucose tolerance, GIP secretion or gastric emptying.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of an enzyme-linked immunosorbent assay for caffeine

A competitive enzyme-linked immunosorbent assay suitable for the measurement of caffeine in plasma and serum has been developed. Sheep immunised with an immunogen prepared by coupling 7-(5-carboxypentyl)1,3-dimethylxanthine to egg albumin produced antibodies with little crossreactivity with the metabolites of caffeine. The enzyme label was prepared by coupling 7-(5-carboxypentyl)-1,3-dimethylxanthine to peroxidase using the mixed anhydride method. The assay, which has a sensitivity of 0.01 mumol/l, permits direct measurement of caffeine in plasma and serum samples. 50 plasma samples measured by ELISA and by an established radioimmunoassay showed a correlation of r = 0.97 (P less than 0.001).

The effect of synthetic very low calorie diets on the GH-IGF-1 axis in obese subjects

IGF-1 concentrations were measured in plasma from 20 obese patients and 20 age- and sex-matched control subjects all of whom were fasting. Plasma IGF-1 concentrations were lower (p less than 0.05) in the obese individuals than in the controls. Plasma GH and insulin responses to stimulation with oral glucose were measured in 7 healthy normal weight individuals and both before and after energy restriction in 7 obese individuals. Before treatment the obese individuals were hyperinsulinaemic (fasting and integrated stimulated concentrations p less than 0.05) and showed attenuation of the plasma GH response to stimulation (peak and integrated stimulated values p less than 0.05 and less than 0.005, respectively) following oral glucose when compared to normal weight controls. Plasma insulin levels fell (both fasting and integrated concentrations p less than 0.05 and less than 0.005, respectively) and stimulated plasma GH responses increased (both peak and integrated values p less than 0.01 and less than 0.05, respectively) in the obese individuals following 3 wk treatment with a synthetic very low energy diet. Plasma IGF-1 concentrations remained unchanged during energy restriction. These results fail to support an endocrine IGF-1 mediated feedback inhibition on the hypothalamic-pituitary axis as the cause of the attenuated release of GH in obesity.

Insulin-like growth factor 1 in patients with hypoglycaemia

Plasma insulin-like growth factor 1 (IGF-1) concentrations were measured in a group of patients with hypoglycaemia due to endogenous hyperinsulinism, and compared with those in a group of patients matched for age and sex with hypoglycaemia and appropriately suppressed insulin levels. Insulin-like growth factor 1 concentrations were significantly higher in the hyperinsulinaemic hypoglycaemic group than in either the hypoinsulinaemic hypoglycaemia group or a group of euglycaemic control subjects. These data provide further evidence that insulin promotes IGF-1 production and release from the liver.

Circulating and secretory antibodies to specific food proteins in adults

Indirect enzyme-linked immunosorbent assays (ELISA) for the detection of antibodies to gliadin, beta-lactoglobulin and ovalbumin have been developed. Specific antibody immunoglobulin levels were quantified. Serum and saliva samples were collected from twenty normal subjects and measured for the presence of specific antibodies. For each subject food intake was calculated from a 7-d weighed food inventory record. The total IgG level was 14.2 +/- 4.3 mg/ml (mean +/- s.d.). Levels of beta-lactoglobulin IgG were significantly lower than ovalbumin IgG levels (130 +/- 130 micrograms/ml versus 637 +/- 703 micrograms/ml, P less than 0.01). Gliadin IgG levels were also significantly lower than ovalbumin IgG levels (262 +/- 398 micrograms/ml versus 637 +/- 703 micrograms/ml, P less than 0.05). However, no significant difference was observed between gliadin and ovalbumin IgA levels in the subjects (29 +/- 39 per cent versus 56 +/- 122 per cent). A significant correlation was observed between ovalbumin IgG levels in serum and dietary intake of egg protein (r = 0.46, P less than 0.05). No other significant correlations were observed.

Stimulatory effects of glucagon-like peptides on human insulinoma cells and insulin-releasing clonal RINm5F cells

Insulin-releasing effects of glucagon-like peptides, glucagon and various nutrients were examined using tumour cells from a freshly resected human insulinoma and RINm5F cells. Insulin release by human insulinoma cells or RINm5F cells was not affected by 16.7 mM glucose. Both cell types exhibited secretory responses to 20 mM alanine, 25 mM K+ and 7.6 mM Ca2+. Insulin release by human insulinoma cells was enhanced at 2 x 10(-7) M by glucagon, GLP-1[1-37], GLP-1[7-36] and its N- and C-terminal fragments GLP-1[7-14] and GLP-1[31-37]. The intact peptides (2 x 10(-6)-2 x 10(-12) M) also stimulated insulin release by RINm5F cells, but neither of the fragments enhanced secretion. The cyclic AMP content of human insulinoma cells and RINm5F cells was increased by glucagon. GLP-1[7-36] (2 x 10(-8)-2 x 10(-10) M) increased cyclic AMP in RINm5F cells, but no additional effects were noted in these or human insulinoma cells. These results suggest that GLP-1[7-36] stimulates insulin release by a direct action on human and rat B-cells, partly involving modulation of intracellular cyclic AMP.

The extraction and purification of a peptide from rat insulinoma tissue

A peptide was extracted and purified from rat insulinoma tissue which, although similar, was not identical to normal rat C peptides. The purity of the peptide, called rat insulinoma peptide (RIP), was investigated using polyacrylamide gel electrophoresis, isoelectric focusing and high-performance liquid chromatography. It appears to contain two peptides similar to each other but differing in their isoelectric points. The peptides as assessed by fast atom bombardment mass spectrometry have molecular masses in the region of 1982 Da, given a chain length of approx. 22 amino-acid residues. Evidence obtained using an established rat C peptides radioimmunoassay suggests that RIP shares a common C-terminus with rat C peptides. The antiserum produced to RIP was used to develop a radioimmunoassay using a tracer prepared by iodinating purified tyrosylated RIP.