Background: We investigated whether variations in lipoprotein lipase activity, a key post-prandial enzyme involved in the removal of circulating dietary triglycerides, could contribute to the previously described nocturnal lipid intolerance. Methods: We studied lipoprotein lipase activity in 12 healthy volunteers (five women, seven men) at 11.30 h and 23.30 h on two separate occasions. Subjects consumed a high-fat mixed meal at 07.30 h for the morning study or 19.30 h for the evening study. Then, after a 4-h fast, subjects were given an intravenous bolus of 7500 U heparin. Blood samples were collected before and 15 min after heparin administration for measurement of lipoprotein lipase, hepatic lipase, triglycerides and non-esterified fatty acids concentrations. Results: Post-prandial post-heparin lipoprotein lipase activity was greater in the morning than in the evening (16.5±1.4 versus 14.4±1.0 µmol oleate/mL/h; P<0.05). Post-prandial post-heparin hepatic lipase activity was also greater in the morning than in the evening (8.7±1.5 versus 8.1±1.6 µmol oleate/mL/h; P=0.002). There were no other significant diurnal differences. Conclusion: We report a diurnal variation in post-prandial lipoprotein lipase activity. This is consistent with the notion that decreased nocturnal insulin sensitivity extends to insulin's actions on lipoprotein lipase and provides a possible explanation for nocturnal lipid intolerance.

Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.

Glucose tolerance becomes impaired towards the evening. Increased peripheral insulin resistance may be responsible, at least in part, for this effect. The mechanism for the diurnal variation in insulin sensitivity is undefined. It is, however, possible that variations in non-esterified fatty acids (NEFA) could contribute to this variation because NEFA have been implicated in the pathogenesis of insulin resistance. Therefore, we have investigated insulin sensitivity and plasma NEFA responses to insulin at 0830 h and 2030 h in nine healthy men by measuring arterialized plasma glucose and venous plasma NEFA concentrations during a short insulin tolerance test. The studies were standardized for a period of fasting, pre-test meal and exercise. Insulin sensitivity measured K ITT was greater ( P < 0·05) in the morning [(20±7) × 10 −3 mmol/L/min] than in the evening [(11·6 ± 2) × 10 −3 mmol/L/min]. Fasting NEFA levels were lower ( P < 0·01) in the morning (373 ± 84 μmol/L) than in the evening (913±122 μmol/L). Following insulin, NEFA fell more slowly ( P < 0·01) in the morning (149 ± 26 μmol/L/15 min) than in the evening (491 ± 91 μmol/L/15 min). These results confirm diurnal variations in insulin sensitivity and plasma NEFA concentrations irrespective of feeding and exercise. We speculate that the relatively elevated plasma NEFA levels in the evening are the cause rather than the consequence of increased insulin resistance at this time.

A 53-year-old woman presented to her general practitioner with a 3-month history of lethargy. She was taking lithium carbonate (900 mg daily for 9 years) and carbamezepine (400 mg daily for 3 years) for manic depressive illness, and thyroxine (50 μg daily for 4 years) for primary hypothyroidism. She smoked 20 cigarettes a day. There was no abnormality on examination. Investigations revealed hypercalcaemia (serum calcium 3.05 mmol/l). Subsequent relevant investigations are shown in the table. Chest, abdominal, hands and skull X-rays revealed no abnormality. View this table: Table Biochemical and haematological investigations 1 : What is the cause of the hypercalcaemia? 2 : What further investigations would you request? 3 : How would you manage the hypercalcaemia? ### QUESTION 1 An inappropriately elevated parathyroid hormone concentration in the presence of hypercalcaemia and normal renal function is diagnostic of primary hyperparathyroidism (HPT). Since the patient was on lithium, this raises the possibility of lithium-induced primary …

Background The insulinotropic hormones, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (7–36 amide) (GLP-1), regulate insulin secretion to nutrient intake and constitute the endocrine arm of the entero-insular axis. Glucagon has been implicated in the pathophysiology of conditions characterised by abnormal glucose tolerance such as obesity and diabetes mellitus although its effect on the entero-insular axis is not fully understood. Materials and methods We investigated the effect of exogenous glucagon on the entero-insular axis and its relation to gastric emptying in six healthy men aged [mean (±S.E.M.)] 23.6 (0.9) years with a body mass index of 24.0 (1.5) kg/m2. Plasma glucose, GIP, GLP-1, insulin and paracetamol concentrations were measured before and after a 100 g oral carhohydrate load containing 1.5 g of paracetamol for 6 h during intravenous infusion of either glucagon or saline. Results When compared to the saline infusion, peak and integrated insulin and glucose concentrations were higher (p<0.05) following glucagon infusion. After 60 min paracetamol concentrations were lower (p<0.05) following glucagon infusion. Integrated responses for GIP and GLP-1 were markedly reduced following glucagon infusion. Conclusions Exogenous glucagon in addition to its well-documented action of increasing glucose and insulin concentrations and delaying gastric emptying also markedly reduces GIP and GLP-1 secretion. The inhibition of GLP-1 soon after commencement of glucagon infusion supports a direct effect of glucagon on intestinal L-cells. We speculate that the marked inhibition of postprandial GLP-1 secretion by glucagon may be of importance in the pathogenesis of relative insulinopenia in Type 2 diabetes and in the development of reduced satiety in obesity and diabetes. Copyright © 1999 John Wiley & Sons, Ltd.

BackgroundCirculating non‐esterified fatty acids (NEFAs) have been causally associated with impairment of glucose metabolism, although their effect on the entero‐insular axis, either in obesity or health, is unknown.Materials and methodsGlucose, insulin, glucagon‐like peptide‐1 (7–36 amide) (GLP‐1) and glucose‐dependent insulinotropic polypeptide (GIP) responses to 100 g of carbohydrate in 400 mL water were evaluated during simultaneous modulation of circulating non‐esterified fatty acids (NEFAs). A total of 10 000 units of heparin (to increase serum NEFAs) and 500 mg of acipimox (2 h before oral carbohydrate ingestion to reduce serum NEFAs) were administered to seven obese [mean ± SEM: age 40 ± 3.7 years; body mass index (BMI) 38.9 ± 2.1 kg m−2] and seven lean (age 39.6 ± 3.6 years; BMI 22.4 ± 0.4 kg m−2) women.ResultsHigher fasting levels and post‐heparin total integrated NEFAs (P < 0.05) and glycerol (P < 0.05) responses were seen in the obese than in the lean group. Incremental integrated GLP‐1 responses to oral carbohydrate post‐heparin in lean (P < 0.01) and obese (P < 0.05) subjects were significantly lower than after acipimox. Total integrated GIP (P < 0.05) and glucose (P < 0.01) responses were higher post heparin than after acipimox in obese subjects only.ConclusionThe inverse relationship in GIP and GLP‐1 responses in the obese group after modulation of NEFAs indicates that reciprocal changes between these two hormones may exist to ensure constancy of B‐cell stimulation. Our results suggest that in obese subjects compensatory secretion of GIP was incomplete and could not prevent impairment in glucose tolerance after heparin‐induced rise in NEFAs. These results may be important in understanding the role of the insulinotropic hormones in carbohydrate metabolism characterized by high NEFA levels such as obesity and diabetes mellitus.

AIM: To investigate the contribution of proinsulin to the "hyperinsulinaemia" of hypertriglyceridaemia. METHODS: Plasma glucose, triglyceride, immunoreactive insulin, and intact proinsulin concentrations were measured before and after a mixed meal in 11 hypertriglyceridaemic men and six healthy normotriglyceridaemic male controls. RESULTS: Hypertriglyceridaemic subjects had greater fasting (101 v 50 pmol/l) and integrated (139 v 81 x 0(-3) pmol/l/h) insulin concentrations than controls. Fasting and integrated glucose and proinsulin concentrations were similar in the two groups. CONCLUSIONS: Proinsulin does not contribute to the hyperinsulinaemia observed in hypertriglyceridaemic subjects and is therefore unlikely to contribute to the increased cardiovascular risk associated with hypertriglyceridaemia.

Excess alcohol consumption is a common cause of hypertriglyceridaemia.'.2 It has, therefore, been recommended that hypertriglyceridaemic patients be screened for elevated serum y glutamyltransferase activity (yGT), a marker of ethanol intake.2,3 It has also been suggested that hypertriglyceridaemia itself may be associated with increased yGT.435 This, nevertheless, is controversial, first, because subjects often under-report their alcohol intakeh and, secondly, because of the limited sensitivity and specificity of routine laboratory markers of alcohol intake, including Y C T . ~ Measurement of carbohydrate-deficient transferrin (CDT) has provided a sensitive and specific marker of chronic elevated alcohol ingestion.h Daily intake in excess of 60g of alcohol for longer than 2 weeks results in elevated CDT levels. To assess whether elevated yGT activity in hypertriglyceridaemic patients was due to undisclosed excess ethanol ingestion, we measured CDT in hypertriglyceridaemic patients with and without raised yCT activity who reported an alcohol intake of less than 4 units (40g) per day.

A brief summary of whole islet transplantation and the use of implants or Bioartificial Pancreases (BAPs) for the treatment of diabetes is presented. We have recently developed an alternative BAP design using a macro-porous carrier called Porocell (Porvair Sciences, UK) for the culture of islet cells. The three dimensional organisations of islets in Porocell closely resemble whole islets in vivo. We have demonstrated that rat islet cells are able to survive, secrete insulin and respond to glucose when cultured in Porocell.

The therapeutic effect of acarbose is generally attributed to inhibition of amylase and brush border glucosidases and consequent impaired digestion and absorption of carbohydrates. We have investigated the possibility that acarbose may also influence the rate of gastric emptying by comparing plasma glucose and gastrointestinal hormone responses to an oral sucrose load with and without acarbose in 11 healthy subjects. Gastric emptying was assessed indirectly by measuring circulating paracetamol concentrations following administration of paracetamol along with the sucrose load. Peak plasma glucose, insulin, and glucose-dependent insulinotropic polypeptide (GIP) responses were reduced when sucrose was given with acarbose. There was a significant reduction in post-sucrose paracetamol levels with acarbose suggestive of a significant delay in gastric emptying. The failure of acarbose to induce change in circulating paracetamol concentrations until after 60 min is indicative of a delay in gastric emptying rather than an osmotic malabsorption. The exaggerated and sustained release of glucagon-like peptide-1 (7-36)amide (GLP-1) seen when sucrose was given with acarbose may play a part in the inhibition of gastric emptying. This study indicates that a significant delay in gastric emptying may be an added mechanism contributing to the therapeutic effect of acarbose. (C) 1998 John Wiley & Sons, Ltd.

Ageing is one of the major risk factors for glucose intolerance including impaired glucose tolerance and Type II (non-insulin-dependent) diabetes mellitus. Reduced insulin secretion has been described as part of normal ageing although there is no information on age-related changes in the secretion of the major insulinotropic hormones, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide (7-36 amide) (GLP-1). We assessed the entero-insular axis in 6 young premenopausal and 6 older postmenopausal women following treatment with oral carbohydrate. Insulin and glucose integrated responses were similar in the younger and older groups. Total integrated responses for GIP and GLP-1 were considerably greater in the older subjects. A positive correlation between age and total integrated responses for glucose (r = 0.65; p < 0.02) as well as GLP-1 (r = 0.85; p < 0.001) was seen. We hypothesise that an age-related impairment of insulin secretion to insulinotropic hormones, GIP and GLP-1, contributes to a reduction in glucose tolerance in this age group. The pronounced compensatory increase in postprandial secretion of GIP and GLP-1 provides further evidence not only for the negative feedback relation between incretin and insulin secretion but also for the importance of the entero-insular axis in the regulation of insulin secretion.

A 56-year-old man with hypertension and a long-standing migrainous left Horner's syndrome presented with a 6-month history of lethargy and vomiting. Initial investigations were unremarkable except for hyponatraemia (plasma sodium 124 mmol/L) and a low plasma glucose of 2·6 mmol/L, Basal plasma cortisol was 54 nmol/L, which following an intravenous bolus of250 J1.g ofsynacthen (Novartis, Frimley, UK) rose suboptimally to 184 nrnol/L after 30 min (normal response > 550 nrnol/L), confirming insufficiency of the pituitary adrenal axis. Thyroid function tests were within the reference range. The patient was 'diagnosed' as having Addison's disease and commenced on hydrocortisone replacement therapy with good effect. Within 2 months he developed loss of libido, hair loss, weight gain and cold intolerance. He was therefore referred for evaluation of pituitary function. On physical examination he did not have any features of hypopituitarism, and, in particular, vision was unaffected. Luteinizing hormone releasing hormone (LHRH; Hoechst UK Ltd, Uxbridge, UK) and thyrotrophin releasing hormone (TRH; Cambridge Laboratories Ltd, Newcastle-upon-Tyne, UK) stimulation tests were diagnostic of hypogonadotrophic hypogonadism and secondary hypothyroidism (Table 1). Hydrocortisone therapy was continued and the patient was also

There are two forms of diabetes, insulin-dependent Diabetes mellitus (IDDM) and non-insulin dependent Diabetes mellitus (NIDDM). There is evidence to suggest that reactive oxygen is involved in the pathogenicity and complications arising from IDDM, but there is little to suggest a role of oxidative stress in the pathogenesis of NIDDM. In order to investigate this hypothesis further, peripheral blood samples were taken from control individuals and IDDM and NIDDM patients and examined for antioxidant capacity and in the Comet assay for DNA strand breakage. The individuals answered a questionnaire to provide information relating to lifestyle factors in case such factors might have a confounding effect. There were 20 controls, 22 IDDM patients and 23 NIDDM patients. No differences could be detected in control and diabetic patient groups in terms of creatinine levels and antioxidant capacity. DNA damage in the Comet assay was at a lower level than in the control in the IDDM patients and a slightly lower level in the NIDDM patients, which might indicate that these cells are handling more oxidative damage on a regular basis. As expected, there were differences in glycosylated haemoglobin (HbAIC) levels. The confounding factors (smoking, drinking and vitamin intakes, etc.) appeared to have no effect.

The combination of premature ovarian failure and primary hypothyroidism is rare but has been reported as part of the autoimmune pluriglandular syndromes.' We describe a 21-year-old woman with premature ovarian failure and primary hypothyroidism whose thyroid and ovarian function recovered spontaneously. The combination of transient ovarian and thyroid failure has not, to our knowledge, been reported before.

We investigated whether pancreatic beta-cell dysfunction has a role in the pathogenesis of glucose intolerance in acromegaly by comparing plasma intact proinsulin, immunoreactive insulin, C-peptide and glucose concentrations during a 75 g oral glucose load in six patients with active acromegaly and eight healthy volunteers. Only acromegalic patients with normal glucose tolerance were studied. Glucose concentrations were similar in acromegalic patients and controls. Acromegalic patients had higher fasting insulin (P < 0.005) and fasting C-peptide (P < 0.005) concentrations than controls. Although fasting proinsulin levels were higher in acromegalic patients than controls, this did not achieve statistical significance. Integrated insulin (P < 0.05), C-peptide (P < 0.05) and proinsulin (P < 0.005) concentrations were greater in acromegalic patients than control subjects. Integrated (P < 0.05) proinsulin:insulin molar ratios were higher in acromegalic patients than controls. Fasting and integrated insulin:C-peptide molar ratios were similar in acromegalic patients and controls. These results indicate that hyperproinsulinaemia contributes to the hyperinsulinaemia which characterizes active acromegaly. The disproportionate hyperproinsulinaemia in acromegaly suggests that prolonged and excessive growth hormone secretion may result in pancreatic beta-cell dysfunction which may predispose acromegalic subjects to glucose intolerance.

1. We investigated whether abnormalities of gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (7-36 amide) (GLP-1) contribute to the hypertriglyceridaemia and hyperinsulinaemia in hypertriglyceridaemic subjects. Serum triglycerides and plasma glucose GIP, GLP-1 and immunoreactive insulin (IRI) concentrations were measured before and after a mixed meal in 15 hypertriglyceridaemic patients and in eight healthy normotriglyceridaemic control subjects. 2. Integrated post-prandial GIP concentrations were greater than in controls (P < 0.05) and correlated positively with both fasting and integrated post-prandial triglyceride concentrations (P < 0.05 for both). Fasting and integrated post-prandial IRI levels were higher in hypertriglyceridaemic subjects than in controls (P < 0.02 and P < 0.05 respectively) and correlated positively with fasting triglycerides (P < 0.02 and P < 0.001 respectively) and integrated post-prandial triglycerides (P < 0.005 and P < 0.05 respectively). There was no correlation between GIP concentrations and either fasting or post-prandial IRI levels. Fasting and post-prandial concentrations of GLP-1 were similar in patients and controls. 3. Hypertriglyceridaemic subjects have post-prandial hyperGIPaemia in addition to the well-documented hyperinsulinaemia. We found no association between GIP and insulin. There is, however, clear evidence for an association between post-prandial GIP concentrations and triglyceride levels. We suggest that this association may depend on changes in lipoprotein lipase activity and that there may be a feedback loop between GIP and triglyceride lipolysis.

Increased peripheral insulin resistance and peripheral hyperinsulinaemia are characteristic features of pregnancy (6). Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (7—36) amide (GLP-l731 amide) are considered to be the major enteral hormones of the entero-insular axis (8). GIP has been reported as being normal or lower in pregnant subjects (4). GIP, therefore, does not appear tn contribute to the hyperinsulinaemia of pregnancy. The role of GLP-17.36 amide in the entero-insular axis, however, has never been studied in pregnant subjects.