F. P. Alford

Do adiponectin, TNFα, leptin and CRP relate to insulin resistance in pregnancy? Studies in women with and without gestational diabetes, during and after pregnancy

The role of adiponectin, tumour necrosis factor α (TNFα), leptin and C‐reactive protein in the insulin resistance of pregnancy is not clear. We measured their levels in women with gestational diabetes (GDM) and in controls, during and after pregnancy, and related them to insulin secretion and action.

Glucagon levels in normal and diabetic subjects: use of a specific immunoabsorbent for glucagon radioimmunoassay.

SummaryNon-specific plasma effects may produce major errors in the estimation of true plasma pancreatic glucagon concentrations by radioimmunoassay. This has been circumvented by the production of glucagon-free plasma for each individual investigated, by means of glucagon antibody, coupled to sepharose beads. True fasting pancreatic glucagon levels (mean ± SEM) in 18 healthy subjects (24 ± 3 pg/ml) were significantly lower (p < 0.005) than in 10 non-ketotic non-obese diabetics (38 ± 3 pg/ml). It is suggested that, in the presence of decreased insulin-effect in the diabetic, this 55% glucagon elevation in diabetics may be of biological importance and contribute to the fasting hyperglycaemia.

Risk and mechanism of dexamethasone-induced deterioration of glucose tolerance in non-diabetic first-degree relatives of NIDDM patients.

Summary We tested the hypothesis that glucose intolerance develops in genetically prone subjects when exogenous insulin resistance is induced by dexamethasone (dex) and investigated whether the steroid-induced glucose intolerance is due to impairment of beta-cell function alone and/or insulin resistance. Oral glucose tolerance (OGTT) and intravenous glucose tolerance tests with minimal model analysis were performed before and following 5 days of dex treatment (4 mg/day) in 20 relatives of non-insulin-dependent diabetic (NIDDM) patients and in 20 matched control subjects (age: 29.6 ± 1.7 vs 29.6 ± 1.6 years, BMI: 25.1 ± 1.0 vs 25.1 ± 0.9 kg/m2). Before dex, glucose tolerance was similar in both groups (2-h plasma glucose concentration (PG): 5.5 ± 0.2 [range: 3.2–7.0] vs 5.5 ± 0.2 [3.7–7.4] mmol/l). Although insulin sensitivity (Si) was significantly lower in the relatives before dex, insulin sensitivity was reduced to a similar level during dex in both the relatives and control subjects (0.30 ± 0.04 vs 0.34 ± 0.04 10–4 min–1 per pmol/l, NS). During dex, the variation in the OGTT 2-h PG was greater in the relatives (8.5 ± 0.7 [3.9–17.0] vs 7.5 ± 0.3 [5.7–9.8] mmol/l, F-test p < 0.05) which, by inspection of the data, was caused by seven relatives with a higher PG than the maximal value seen in the control subjects (9.8 mmol/l). These “hyperglycaemic” relatives had diminished first phase insulin secretion (Ø1) both before and during dex compared with the “normal” relatives and the control subjects (pre-dex Ø1: 12.6 ± 3.6 vs 26.4 ± 4.2 and 24.6 ± 3.6 (p < 0.05), post-dex Ø1: 22.2 ± 6.6 vs 48.0 ± 7.2 and 46.2 ± 6.6 respectively (p < 0.05) pmol · l–1· min–1 per mg/dl). However, Si was similar in “hyperglycaemic” and “normal” relatives before dex (0.65 ± 0.10 vs 0.54 ± 0.10 10−4 · min–1 per pmol/l) and suppressed similarly during dex (0.30 ± 0.07 vs 0.30 ± 0.06 10−4 · min–1 per pmol/l). Multiple regression analysis confirmed the unique importance of low pre-dex beta-cell function to subsequent development of high 2-h post-dex OGTT plasma glucose levels (R2 = 0.56). In conclusion, exogenous induced insulin resistance by dex will induce impaired or diabetic glucose tolerance in those genetic relatives of NIDDM patients who have impaired beta-cell function (retrospectively) prior to dex exposure. These subjects are therefore unable to enhance their beta-cell response in order to match the dex-induced insulin resistant state. [Diabetologia (1997) 40: 1439–1448]

Morphometric documentation of abnormal intramyocellular fat storage and reduced glycogen in obese patients with Type II diabetes

Aims/hypothesis. Insulin resistance of skeletal muscle has been associated with increased lipid availability. This study aimed to estimate volume fractions of intramyocellular triglyceride droplets and glycogen granules in skeletal muscle using electron microscopy and furthermore, relate these findings to insulin sensitivity and the level of circulating lipids. Methods. We compared 11 obese patients with Type II (non-insulin-dependent) diabetes mellitus and 11 obese normoglycaemic subjects matched for age and sex. Glucose metabolism was determined using the euglycaemic hyperinsulinaemic clamp technique (40 mU · m–2· min–1) coupled with indirect calorimetry and tritiated glucose. On the second day, using an automatic procedure, a fasting muscle biopsy was carried out and processed for electron microscopy. Volume fractions of intramyocellular structures were estimated by pointcounting on photographic pictures in a blinded manner. Results. Insulin-stimulated total glucose disposal rate was lower in the Type II diabetic subjects compared with the obese normoglycaemic subjects (4.96 ± 049 vs 10.35 ± 0.89 mg · min–1· kg ffm–1, p < 0.001) as was glucose storage (2.03 ± 0.50 vs 6.59 ± 0.83, p < 0.001). The electron microscopy study revealed that the diabetic subjects had higher intramyocellular amounts of triglyceride (1.43 ± 0.21 vs 0.39 ± 0.07 %, p < 0.001) and lower amounts of glycogen (3.53 ± 0.33 vs 6.94 ± 0.54 %, p < 0.001). Mitochondrial volume was identical indicating equal aerobic capacity. The fractional intramyocellular lipid volume was found to be positively associated with fasting NEFA (r = 0.63, p = < 0.05 and r = 0.79, p = < 0.05) and triglyceride (r = 0.74, p = 0.01 and r = 0.62, p < 0.05) in the obese diabetic and normoglycaemic cohorts respectively. Intramyocellular lipid content was negatively correlated to insulin sensitivity (r = –0.71, p < 0.02) in the obese diabetic group whereas no significant association was found in the obese normoglycaemic group. Conclusion/interpretation. This study shows that fat accumulates intramyocellulary while glycogen stores are simultaneously reduced in obese subjects with Type II (non-insulin-dependent) diabetes mellitus. Quantitatively, a major component of the excessive lipid accumulation could be secondary in origin, related to the diabetic state in itself, although a contribution from the altered insulin action cascade of obesity and diabetes cannot be excluded. In both groups significant positive relations were found between circulating and intramyocellular lipid. [Diabetologia (2001) 44: 824–833]

A Simple Method for Quantitation of Insulin Sensitivity and Insulin Release from an Intravenous Glucose Tolerance Test

Both insulin secretion and insulin sensitivity are important in the development of diabetes but current methods used for their measurements are complex and cannot be used for epidemiological surveys. This study describes a simplified approach for the estimation of first phase insulin release and insulin sensitivity from a standard 40‐min intravenous glucose tolerance test (IVGTT), and compares these parameter estimations with the sophisticated minimal model analysis of a frequently sampled 3‐h IVGTT and the euglycaemic clamp technique. For the simplified IVGTT, first phase insulin release was measured as the insulin area above basal post glucose load unit−1 incremental change (i.e. peak rise) in plasma glucose over 0–10 min, and insulin sensitivity as a rate of glucose disappearance (Kg) unit−1 insulin increase above basal from 0–40 min post‐glucose load in 18 subjects who were studied twice, either basally or in a perturbed pathophysiological state (i.e. pre‐ and post‐ultramarathon race, n = 5; pre‐ and post‐20 h pulsatile hyperinsulinaemia, n = 8; pre‐ and post‐thyrotoxic state, n = 5). A further 12 subjects were compared by IVGTT, and glucose clamp. In addition, seven dogs were studied three times by IVGTT during normal saline infusion and after short‐term (1/2 hour) or long‐term (72 hour) adrenaline infusions. First phase insulin release and insulin sensitivity estimated from the simplified IVGTT as calculated by the two methods correlated closely (rs = 0.89 and rs = 0.87, respectively), although less precisely in markedly insulin‐resistant subjects and the slopes and y intercepts of the linear regression lines were similar in the basal and perturbed states. Insulin sensitivity measured by the shortened 40 min IVGTT and glucose clamp techniques were also comparable for the whole group (rs = 0.85), and for hypoinsulinaemic‐glucose intolerance subjects (rs = 0.96). It is concluded that the shortened simple IVGTT method is practical, gives reliable simultaneous estimates of glucose tolerance, first phase insulin secretion and insulin sensitivity in a diverse group of individuals with normal to moderately impaired glucose tolerance, and therefore may be useful in population surveys where prolonged, multiple blood sampling test procedures are not possible.

Metabolic Consequences of Prolonged Hyperinsulinemia in Humans: Evidence for Induction of Insulin Insensitivity

Hyperinsulinemia is frequently associated with a variety of insulin-resistant states and has been implicated causally in the development of insulin resistance. This study examines the metabolic consequences of prolonged hyperinsulinemia in humans. Basally and 1 h after cessation of a 20-h infusion of insulin (0.5 mU · kg−1 · min−1, aimed at elevating plasma insulin levels to ∼30 mU/L) or normal saline, subjects were assessed for 1) glucose turnover with 3-[3H]glucose; 2) insulin sensitivity, as measured by either the euglycemic glucose-clamp technique or the intravenous glucose tolerance test (IVGTT) minimal model method of Bergman; and 3) monocyte insulin-receptor binding. Hepatic glucose production (Ra) was suppressed by >95% during each euglycemic clamp and during the 20-h insulin infusion. After the insulin infusion, Ra and glucose utilization rate returned to the initial basal level within 1 h, as did insulin levels. At that time, insulin sensitivity was significantly decreased, as measured by the “insulin action” parameter during the 40- to 80-min phase of the clamp (0.049 ± 0.003 vs. 0.035 ± 0.007 min−1 P < .05) and during the 80- to 120-min phase (0.047 ± 0.005 vs. 0.039 ± 0.007 min−1, .05 < P < .1). The IVGTT minimal model analysis revealed a fall in the rate of glucose disposal (KGTT) (2.8 ± 0.6 vs. 1.9 ± 0.2 min−1 P < .05), which was entirely explained by a decrease in insulin sensitivity (SI, 9.4 ± 0.3 vs. 3.8 ± 0.2 min−1 · μU−1 · ml−1, P < .02); there was no change in glucose-mediated glucose disposal (SG, 0.029 ± 0.004 vs. 0.029 ± 0.004 min−1) or pancreatic Ybgr;-cell responsiveness (ø1, 2.7 ± 0.4 vs. 2.6 ± 0.5 μU · ml−1 · min mg−1 · dl−1; ø2, 7.8 ± 2.4 vs. 7.8 ± 2.4 μU · ml−1 · min−2 – mg−1 · dl−1). Monocyte insulin-receptor binding was unaffected by the prolonged hyperinsulinemia. Our studies indicate that modest sustained hyperin- sulinemia may lead to decreased insulin action in the presence of normal monocyte insulin-receptor binding and normal pancreatic insulin secretion. If the monocyte reflects insulin binding in the key insulin-sensitive tissues, this defect in insulin action probably lies at a postreceptor level.

Ketoacidosis in pancreatectomized man.

We investigated the importance of glucagon in the development of diabetic ketoacidosis by withholding insulin from six patients with juvenile-type diabetes and four totally pancreatectomized subjects. Patients were fasting and had previously been maintained on intravenous insulin for 24 hours. In diabetic patients plasma glucagon concentrations rose sharply after withdrawal of insulin, and the increases were accompanied by a rise in blood ketone concentration of 4.1+/-0.7 (S.E.M.) and blood glucose concentration of 12.5+/-1.8 mmol per liter by 12 hours. In the pancreatectomized patients, despite the absence of measurable glucagon, blood ketones rose by 1.8+/-0.8 and blood glucose by 7.7+/-1.5 mmol per liter. Thus, glucagon is not essential for the development of ketoacidosis in diabetes, as has previously been suggested, but it may accelerate the onset of ketonemia and hyperglycemia in situations of insulin deficiency.

Hormonal effects of norepinephrine on acute glucose disposal in humans: a minimal model analysis.

It is not known whether circulating norepinephrine (NE) has a direct hormonal influence on glucose disposal. This study examines whether moderate elevation of NE alters the disposal of an acute intravenous (IV) glucose load, as analysed by the minimal model of Bergman. Eight healthy normal subjects were infused with either 25 ng/kg/min NE (plasma NE 1,284 +/- 259 pg/mL) or normal saline (plasma NE 314 +/- 86 pg/mL), 30 minutes prior to and during an IV glucose tolerance test (GTT). There was a small but significant rise (P less than .05) in basal blood glucose levels during the initial 30-minute NE infusion which was accompanied by a 40% increase (0.39 +/- .02 to 0.59 +/- .07 nmol/L, P less than .01) in nonesterified fatty acid levels (NEFA). Insulin, C-peptide, and glucagon levels did not change. NE impaired the rate of acute glucose disposal (Kg 1.74 +/- 0.24 v 2.10 +/- 0.23 (min-1, P less than .05). Minimal model analysis revealed a corresponding 35% decrease in insulin sensitivity (SI 4.85 +/- 1.51 v 7.28 +/- 1.16 min-1 microU-1 mL-1 x 10(4), P less than .05) but no significant differences between glucose-mediated glucose disposal or pancreatic B-cell responsiveness. The glucose disposition index (si* phi2), a direct measure of an individuals overall insulin- mediated glucose disposal, was reduced by 70% in the NE-infussed subjects (si* phi2 69 +/-22 v 223 +/- 76 mg-1 ml-1 min-3 x 10(2), p< .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of insulin therapy on hepatic and peripheral insulin sensitivity in Type 2 (non-insulin-dependent) diabetes

SummaryHepatic glucose production and metabolic clearance rate of glucose were measured using (3-3H) glucose at steady state, basally and during two sequential 2 h insulin (25 and 40mU · kg–1 · h–1)/glucose(2 and 3mg · kg–1 · min–1) infusion periods. Eight diabetic subjects were studied before and after 1 week of twice daily insulin therapy; six control subjects matched for age, weight and degree of obesity were also studied. In the diabetic patients, pre-treatment hepatic glucose production was 20.0 ± 2.2, 9.9 ± 2.9, and 1.4 ± 0.8 μmol · kg–1 · min–1 respectively (± SEM) for each of the three periods, and fell significantly with treatment to 12.8 ± 1.7,4.0 ± 1.5 and 1.9 ± 1.0 μmol · kg–1 · min–1. Hepatic glucose production in normal subjects was 13.2 ± 0.6, 2.2 ± 0.8 and < 1 μmol · kg–1 · min–1. The pre-treatment metabolic clearance rate in all diabetic studies with insulin levels ⩾ 30 mU/l was 1.10 ± 0.14 ml · kg–1 · min–1 and remained virtually unchanged following insulin therapy; this was significantly lower than in the control subjects (6.83 ± 1.02, p < 0.001). Basal non-esterified fatty acid levels were higher (p < 0.02) in the pre-treated diabetic patients compared to post-treated diabetic patients and control subjects. Non-esterified fatty acids in each group fell to similar levels during the insulin infusions, but the rate of fall was slower in the pre-treated diabetic patients. Insulin receptor binding to erythrocytes was normal in the diabetic subjects and unchanged by treatment. Therefore, following insulin treatment of uncontrolled Type 2 (non-insulin-dependent) diabetes, the initially increased basal hepatic glucose production, and decreased hepatic sensitivity, return towards normal. However, the glucose clearance remains low, despite good diabetic control, and appears to be a major factor in the continuing glucose intolerance. As insulin receptor binding is normal, the defect of glucose clearance in Type 2 diabetes appears compatible with a post-receptor defect of glucose metabolism.

Multiple defects of both hepatic and peripheral intracellular glucose processing contribute to the hyperglycaemia of NIDDM

SummaryNon-insulin-dependent diabetic (NIDDM) patients were studied during a modified euglycaemic state when fasting hyperglycaemia was normalized by a prior (−210 to −150 min) — and later withdrawn (−150–0 min) — intravenous insulin infusion. Glucose metabolism was assessed in NIDDM patients (n=10) and matched control subjects (n=10) using tritiated glucose turnover rates, indirect calorimetry and skeletal muscle glycogen synthase activity determinations. Total and non-oxidative exogenous glycolytic flux rates were measured using appearance rates of tritiated water. A+180 min euglycaemic hyperinsulinaemic (40 mU·m−2·min−1) clamp was performed to determine the insulin responsiveness of the various metabolic pathways. Plasma glucose concentration increased spontaneously during baseline measurements in the NIDDM patients (−120 to 0 min: 4.8±0.3 to 7.0±0.3 mmol/l; p<0.01), and was primarily due to an elevated rate of hepatic glucose production (3.16±0.13 vs 2.51±0.16 mg·kg FFM−1·min−1; p<0.01). In the NIDDM subjects baseline glucose oxidation was decreased (0.92±0.17 vs 1.33±0.14 mg·kg FFM−1·min−1; p<0.01) in the presence of a normal rate of total exogenous glycolytic flux and skeletal muscle glycogen synthase activity. The simultaneous finding of an increased lipid oxidation rate (1.95±0.13 vs 1.61±0.07 mg·kg FFM−1·min−1; p=0.05) and increased plasma lactate concentrations (0.86±0.05 vs 0.66±0.03 mmol/l; p=0.01) are consistent with a role for both the glucose-fatty acid cycle and the Cori cycle in the maintenance and development of fasting hyperglycaemia in NIDDM during decompensation. Insulin resistance was demonstrated during the hyperinsulinaemic clamp in the NIDDM patients with a decrease in the major peripheral pathways of intracellular glucose metabolism (oxidation, storage and muscle glycogen synthase activity), but not in the pathway of non-oxidative glycolytic flux which was not completely suppressed during insulin infusion in the NIDDM patients (0.55±0.15 mg·kg FFM−1·min−1; p<0.05 vs 0; control subjects: 0.17±0.29; NS vs 0). Thus, these data also indicate that the defect(s) of peripheral (skeletal muscle) glucose processing in NIDDM goes beyond the site of glucose transport across the cell membrane.