Insulin sensitivity,insulin secretion and glucose effectiveness in diabetic and non-diabetic cirrhotic patients

Summary In cirrhotic patients with normal fasting glucose levels both insulin insensitivity and a blunted early insulin response to oral glucose are important determinants of the degree of intolerance to oral glucose. It is not known whether the ability of hyperglycaemia per se to enhance glucose disposal (glucose effectiveness) is also impaired. It is also unclear whether overt diabetes is due to (1) more marked insulin insensitivity; (2) impaired insulin secretion; (3) reduced glucose effectiveness; or (4) a combination of these mechanisms. We used the minimal model to analyse the results of a 3-h intravenous glucose tolerance test to assess glucose effectiveness, insulin sensitivity and insulin responses in 12 non-diabetic cirrhotic patients, 8 diabetic cirrhotic patients and 10 normal control subjects. Fasting blood glucose levels were 4.8±0.2, 7.5±0.6 and 4.7±0.1 mmol/l, respectively. Fasting insulin and C-peptide levels were higher in both cirrhotic patient groups compared with control subjects. The glucose clearance between 6 and 19 min after i.v. glucose was lower in both cirrhotic groups (non-diabetic, 1.56±0.14, diabetic, 0.76±0.06, control subjects, 2.49±0.16 min^–1%, both p<0.001 vs control subjects). Serum insulin peaked at 3 and 23 min in the non-diabetic cirrhotic patients and control subjects; both peaks were higher in the non-diabetic cirrhotic patients and showed a delayed return to basal levels. In the diabetic cirrhotic patients, the first phase insulin and C-peptide response to i.v. glucose was absent; their early (22–27 min) incremental insulin response to i. v. tolbutamide was however similar to that of control subjects but 43% lower than in the non-diabetic cirrhotic patients (p<0.05). Insulin sensitivity was markedly reduced in both cirrhotic groups (non-diabetic, 1.11±0.24×10^–4, diabetic, 0.33±0.53×10^–4, control subjects, 4.37±0.53×10^–4 min^–1 per mU·l^–1, both p<0.001 vs controls). Glucose effectiveness was normal in the non-diabetic cirrhotic patients but 29% lower in the diabetic group. It would appear that overt diabetes develops in those cirrhotic patients who in addition to insulin insensitivity have a marked impairment of insulin secretion. An associated reduction in glucose effectiveness may be a contributory factor.     

Salivary insulin concentrations in Type 2 (non-insulin-dependent) diabetic patients and obese non-diabetic subjects: Relationship to changes in plasma insulin levels after an oral glucose load

Summary The presence of immunoreactive insulin in saliva and its relationship to plasma immunoreactive insulin was investigated in healthy subjects, newly diagnosed non-obese Type 2 (non-insulin-dependent) diabetic patients and obese non-diabetic subjects, basally and after an oral glucose tolerance test. The mean ± SEM fasting values of plasma and salivary immunoreactive insulin were significantly higher in diabetic patients and obese non-diabetic subjects than in normal volunteers (p<0.05). During the glucose challenge, the increase of salivary insulin was related with that of plasma in the three groups of subjects, with a time lag in normal and obese subjects. In normal volunteers, plasma and salivary peak values were respectively 49.5 ± 13.4 U/ml (p<0.05 vs obese subjects) at 60 min and 12.0±3.3U/min (p<0.05 vs obese subjects) at 120 min; in diabetic patients, the values were 51.7 ± 5.6 U/ml (p<0.05 vs obese subjects) and 14.6±4.1 U/min at 120 min; in obese subjects, the peak value for plasma insulin was 111.5±40.1 U/ml at 90 min and for salivary insulin 15.6 ± 5.1 U/min at 120 min. A positive linear relationship was shown between plasma and salivary insulin during the oral glucose tolerance test. The identity of salivary insulin was assessed by reversed-phase HPLC. We conclude that salivary immunoreactive insulin can be found in Type 2 diabetic patients and in obese non-diabetic subjects, as well as normal volunteers, that plasma and salivary insulin are related after a glucose load, and that differences exist in salivary insulin secretion patterns among the three groups of subjects.     

Oxidation of low-density lipoprotein in NIDDM: its relationship to fatty acid composition

Summary The increased risk of atherosclerotic disease in diabetic subjects may be due to enhanced foam cell formation following an increased susceptibility of low density lipoprotein to oxidative modification. This study has compared fatty acid content and lipoprotein oxidisability in 10 non-insulin-dependent diabetic subjects with that in 10 control subjects. Both groups were normocholesterolaemic and the diabetic subjects had higher triglyceride levels (2.2±0.4 vs 1.2±0.2 mmol/l, p<0.05). The fatty acid composition was compared in low density lipoprotein following Folch extraction, separation by thin layer chromatography (for the lipid classes) and analysis by gas liquid chromatography. Low density lipoprotein oxidisability was assessed by conjugated diene and thiobarbituric acid reacting substance formation in the presence of copper ions. The esterified/free cholesterol ratio was higher in the low density lipoprotein from patients compared to control subjects (2.9±0.1 vs 1.9±0.3, p<0.05). Linoleic acid in the cholesteryl ester fraction of the lipoprotein was higher in the patients than in the control subjects (48.2±2.2% vs 42.4±3.4%, p<0.05) as was the total quantity of linoleic acid in the cholesteryl ester fraction (317.8±68.0 vs 213.2±28.0 g/mg protein, p<0.05) and in the low-density lipoprotein as a whole (443.2±70.0 vs 340.2±28.2 g/mg protein, p<0.05). Lipoprotein oxidisability was also increased in the diabetic group with increased formation of thiobarbituric acid reacting substances (35.6±7.2 vs 22.3±3.5 nmol/mg protein, p<0.05, increased total diene formation (502±60 vs 400±30 nmol/mg protein, p<0.05) and increased rate of diene formation (7.2±0.6 vs 5.1±0.9 nmol diene · mg protein^–1 · min^–1, p<0.05). This study indicates that low-density lipoprotein from diabetic subjects is more susceptible to oxidation. This could, in vivo, accelerate foam-cell formation thereby increasing atherosclerotic risk in diabetic subjects.Abbreviations BHT Butylated hydroxytoluene - EDTA ethylenediaminetetraacetic acid - TBARS thiobarbituric reacting substances - HPLC high performance liquid chromatography - MDA malondialdehyde - HbA_1c glycated haemoglobin     

The Maillard protein cross-link pentosidine in urine from diabetic patients

Summary The Maillard protein cross-link pentosidine is a fluorescent condensation product of lysine, arginine and ribose. It accumulates in human tissues with age, and the accumulation process is accelerated in the tissues of diabetic patients. Using SP-Sephadex C-25 in the pretreatment for HPLC, we examined levels of pentosidine in urine without hydrolysis (free form) and levels of pentosidine in urine after hydrolysis (total forms), from 23 diabetic patients and 21 control subjects. The mean percentages of the values of free form per total forms (±SD) were 89±15% in diabetic patients, 88±16% in control subjects and 89±15% in total populations of diabetic patients and control subjects. There was a significant correlation between the values of free form and total forms in diabetic patients (r=0.938, p=0.0001), in control subjects (r=0.820, p<0.02) and in total populations of diabetic patients and control subjects (r=0.951, p=0.0001). The mean level of pentosidine per mol creatinine (±SD) was significantly elevated in urine from diabetic patients as compared to the level in control subjects (8.8±4.3 mol/mol creatinine vs 4.2±1.4 mol/mol creatinine, p=0.0001 in free form; 10.1±5.3 mol/mol creatinine vs 4.7±1.4 mol/mol creatinine, p=0.0001 in total forms). These results demonstrate that urinary pentosidine, especially in free form, could be a useful marker for the assessment of diabetes and diabetic complications.     

Activation of Tumor Necrosis Factor-α System in Chronic Hepatitis C Virus Infection

Tumor necrosis factor- (TNF-)plays a central role in the host's immunomodulatoryresponse to infective agents. To evaluate theTNF- system in patients with chronic hepatitis Cvirus (HCV) infection, plasma, serum, and peripheral bloodmononuclear cells (PBMC) were prospectively collectedfrom 53 patients and 33 healthy control subjects.Circulating TNF- and TNF receptors were assayed by their respective enzyme immunoassays. Inaddition, TNF- mRNA was quantitated in PBMC usinga branched DNA assay, and production of TNF- byPBMC with and without lipopolysaccharide was also assessed. Patients with chronic HCV infectionhad a higher level of circulating TNF- comparedto healthy control subjects (9.62 ± 6.01 vs 3.66± 1.23 pg/ml, P < 0.001). They also had highercirculating levels of TNF receptors compared to control(CD120a: 3323 ± 1267, pg/ml, N = 49 vs 1855± 422 pg/ml, N = 33, P < 0.001; CD120b: 1290± 650 pg/ml, N = 51, vs 863 ± 207 pg/ml,N = 33, P < 0.001). Plasma TNF- level correlated with circulatingCD120a (r = 0.52, N = 49, P < 0.001) and weakly withCD120b (r = 0.32, N = 51, P = 0.02). Plasma TNF-also correlated with markers of hepatocellular injury, including ALT (r = 0.34, N = 53, P = 0.01) and-GST (r = 0.31, N = 43, P = 0.042), but not withserum HCV RNA levels. There was no difference in theTNF- mRNA levels in PBMC between patients with chronic HCV infection (1.4 ± 1.9units/106 cells, N = 8) and healthy control subjects(2.1 ± 1.4 units/106 cells, N = 8, P = NS). Therewas also no difference in the spontaneous production ofTNF- by PBMC (1 × 10⁶ cells/ml)between patients with chronic HCV infection (14.2± 36.5 pg/ml, N = 11) and healthy subjects (11.9± 14.0 pg/ml, N = 14, P = NS). However, patientswith chronic HCV infection produced more TNF- upon stimulation withlipopolysaccharide compared to healthy control subjects(1278 ± 693 pg/ml, N = 11, vs 629 ± 689pg/ml, N = 14, P < 0.05). These data indicate thatthe TNF- system is activated in patients with chronicHCV infection.     

Consistency of pupillary abnormality in children and adolescents with diabetes

Repeat measurements on pupillary adaptation to darkness were performed in a cohort of 66 children and adolescents with insulin-dependent diabetes mellitus (IDDM) (initial age 6.9–17.0 years) after a mean interval of 3.5 years, using a portable pupillometer. While there was a close correlation between the results of the two studies (r = 0.94, p < 0.001), the pupillary dilatation, the ratio of the pupil diameter to the iris diameter % (PD%), had decreased significantly (61.5 % vs 62.9 %, p < 0.001) over these 3.5 years in children with diabetes. The same measurements were performed on 89 healthy control children in the first study and 66 in the reassessment period and PD% was not significantly different in the two control groups. Five children with diabetes identified as having abnormal pupillary dilatation in the first study were outside the normal range 3.5 years later. In addition 4 children in whom initial testing had been normal, showed abnormality at the time of the second study. None of these children had symptoms of autonomic neuropathy. These findings suggest that abnormality in pupillary adaptation in diabetic children is consistent and increases with time and may serve as an early marker of tissue damage associated with diabetes. © 1997 John Wiley & Sons, Ltd.     

The role of transient internal sphincter relaxation in faecal incontinence?

Twenty-five (18%) of 140 incontinent patients and 6 (17%) of 35 normal controls showed episodes of spontaneous internal sphincter relaxation during 30 min multiport manometric and electromyographic recording under resting conditions. The episodes lasted at least 15 s and reduced the pressure in the outermost anal channels by at least 20 cm of water. Patients exhibited more episodes of relaxation than controls (4.3±0.6 vs 2.3±0.2 per subject; mean±SEM; p<0.05) and the pressures fell to lower values (19±1 vs 42±5 cm water, p<0.01), but the duration of relaxation was not significantly different (53±4 vs 40±7 s). Episodes of spontaneous relaxation were associated with simultaneous rectal contractions in 33% of the normal subjects and 45% of incontinent patients. Unlike normal subjects, most of the episodes of transient relaxation recorded in the incontinent group were not associated with compensatory increases in the electrical activity of the external anal sphincter (77% vs 17%; p<0.05). Over 50% of the incontinent patients who showed spontaneous relaxation also showed post squeeze or post-strain IAS relaxations whereas these were seen in less than 6% of the normal subjects with spontaneous relaxation. The rectal volumes, required to elicit anal relaxation (10±0 vs 28±7 ml; p<0.05), to incude sustained relaxation (60±8 vs 82±5 ml; p<0.05), to elicit a sensation of wind (19±3 vs 27±8 ml; p<0.05) and to cause a desire to defaecate (36±4 vs 63±9 ml; p<0.05) were all lower in the incontinent patients who showed spontaneous relaxations than in the incontinent control group. In conclusion, spontaneous relaxation of the internal sphincter may be an important factor leading to faecal incontinence in patients with a sensitive rectum, especially as they tend to occur in these subjects in the absence of a compensatory increase in external sphincter activity.     

Apolipoprotein(a) and cardiovascular disease in Type 2 (non-insulin-dependent) diabetic patients with and without diabetic nephropathy

Summary The relative mortality from cardiovascular disease is on average increased five-fold in Type 2 (non-insulin-dependent) diabetic patients with diabetic nephropathy compared to non-diabetic subjects. We assessed the possible contribution of dyslipidaemia in general and elevated serum apolipoprotein(a) (apo(a)) in particular. Type 2 diabetic patients with normo-, micro- and macroalbuminuria were compared with healthy subjects. Each group consisted of 37 subjects matched for age, sex and diabetes duration. Serum creatinine in the nephropathy group was 105 (54–740) mol/l. The prevalence of ischaemic heart disease (resting ECG, Minnesota, Rating Scale) was 57, 35, 19 and 2% in macro-, micro- and normoalbuminuric diabetic patients and healthy subjects, respectively. The prevalence of ischaemic heart disease was higher in all diabetic groups as compared to healthy subjects (p<0.05), and higher in macroalbuminuric as compared to normoalbuminuric diabetic patients (p<0.01). There was no significant difference between apo(a) in the four groups: 161 (10–1370), 191 (10–2080), 147 (10–942), 102 (10–1440) U/l (median (range)) in macro-, micro- and normoalbuminuric groups and healthy subjects. Serum total-cholesterol, HDL-cholesterol and LDL-cholesterol were not significantly different when comparing healthy subjects and each diabetic group. Apolipoprotein A-I was lower (p<0.05) in all diabetic groups as compared to healthy subjects (nephropathy vs healthy subjects): 1.50±0.25 vs 1.69±0.32 g/l (mean ± SD). Triglyceride was higher (p<0.05) in patients with nephropathy and microalbuminuria as compared to healthy subjects (nephropathy vs healthy subjects): 2.01 (0.66–14.7) vs 1.09 (0.41–2.75) mmol/l (median (range)). Apolipoprotein B was higher (p<0.02) in patients with nephropathy as compared to the other three groups (nephropathy vs healthy subjects): 1.54±0.47 vs 1.33±0.30 g/l. In conclusion, our case-control study has confirmed that Type 2 diabetic patients with increased urinary albumin excretion frequently suffer from dyslipidaemia and cardiovascular disease. However, our study revealed no significant elevation in serum concentration of apo(a) in patients with diabetic nephropathy, but numbers were small.     

Daily production and metabolic clearance of growth hormone in juvenile diabetes mellitus

Summary Daily production (PR) of human growth hormone (HGH) was calculated in patients with juvenile diabetes and control subjects by determining metabolic clearance rate (MCR) of¹³¹I HGH, at equilibrium, and mean endogenous HGH levels throughout a 24 h day. Half hourly sampling or a constant withdrawal pump were used to obtain an integrated mean endogenous HGH level. MCR (liters/day) was significantly reduced in all diabetic subjects both in absolute terms (96 ± 15 vs 274 ± 37) and relative to surface area (62 ± 8 vs 171 ± 21) (p < 0.01). Mean HGH levels were 8.4 ng/ml in the diabetics and 5.5 ng/ml in age matched controls. Daily HGH PR in the diabetic subjects (339 to 1365 g/day) did not exceed values in the control subjects (1005–1426 g/day). The results indicate that the elevated plasma HGH levels and increased HGH response to stimuli observed in diabetes, reflect reduced metabolic clearance, rather than increased pituitary secretion.     

Insulin resistance in Type 2 (non-insulin-dependent) diabetic patients and their relatives is not associated with a defect in the expression of the insulin-responsive glucose transporter (GLUT-4) gene in human skeletal muscle

Summary To study whether insulin resistance in Type 2 (non-insulin-dependent) diabetes mellitus is due to a defect in the expression of the insulin-responsive glucose transporter gene (GLUT-4) in human skeletal muscle, we measured the level of GLUT-4 mRNA and (in some of the subjects) its protein in muscle biopsies taken from 14 insulin-resistant patients with Type 2 diabetes, 10 first-degree relatives of the diabetic patients and 12 insulin-sensitive control subjects. Insulin sensitivity was measured with a +45 mU· ·min^–1 euglycaemic insulin clamp in combination with indirect calorimetry and infusion of [3-³H]glucose. GLUT-4 mRNA was measured using a human GLUT-4 cDNA probe and GLUT-4 protein with a polyclonal antibody specific for the 15 amino acid carboxyterminal peptide. Both Type 2 diabetic patients and their relatives showed impaired stimulation of total-body glucose disposal by insulin compared with control subjects (29.5±2.1 and 34.0±4.8 vs 57.9±3.1 mol·kg lean body mass^–1·min^–1; p<0.01). This impairment in glucose disposal was primarily accounted for by a reduction in insulin-stimulated storage of glucose as glycogen (13.0±2.4 and 15.6±3.9 vs 36.9±2.2 mol·kg lean body mass^–1·min^–1; p<0.01). The levels of GLUT-4 mRNA expressed both per g of total RNA and per g DNA, were higher in the diabetic patients compared with the control subjects (116±25 vs 53±10 pg/g RNA and 177±35 vs 112±29 pg/g DNA; p<0.05, p<0.01, respectively). The GLUT-4 mRNA levels in the relatives were not significantly different from that observed in the control subjects (90±16 pg/g RNA and 117±23 pg/g DNA; p = NS). The GLUT-4 protein levels did not significantly differ between control subjects, diabetic patients and relatives (494±85, 567±133 and 323±80 cpm/100 g protein). No correlation was observed between the level of GLUT-4 mRNA andits protein. However, the level of GLUT-4 mRNA and the rate of total-body glucose disposal correlated positively in the control group and in the relatives (both p<0.05) but not in the diabetic subjects. A positive correlation between the level of GLUT-4 protein and total-body glucose disposal was also observed in the control subjects (r = 0.759; p<0.05) and in the relatives (r = 0.794; p<0.01) but not in the diabetic subjects. We conclude that insulin resistance in Type 2 diabetes is not related to a defect in the expression of the GLUT-4 gene in skeletal muscle. Nevertheless, the levels of GLUT-4 mRNA and GLUT-4 protein are related to the rate of total-body glucose disposal in subjects with normal fasting glucose concentrations.     

Aminoguanidine inhibits the development of accelerated diabetic retinopathy in the spontaneous hypertensive rat

Summary Arterial hypertension has been identified as a major secondary risk factor for diabetic retinopathy. However, the mechanisms by which hypertension worsens retinopathy are unknown. Inhibition of advanced glycation product formation prevents the development of experimental diabetic retinopathy in normotensive diabetic rats. In this study the effect of hypertension on the rate of diabetic retinopathy development and the formation of arteriolar thrombosis was evaluated. We also evaluated the effect of aminoguanidine, an inhibitor of advanced glycation end product formation on retinal pathology of diabetic hypertensive rats. After 26 weeks of diabetes, hypertension accelerated the development of retinopathy despite a lower mean blood glucose level than in the non-hypertensive group (diabetic spontaneous hypertensive rats (SHR) 16.00±6.83 mmol/l; diabetic normotensive Wistar Kyoto rats (WKY) 34.9±3.64 mmol/l; p<0.0001). Diabetic SHR had nearly twice as many acellular capillaries as diabetic WKY (SHR diabetic: 91.9±7.5 acellular capillaries per mm² of retinal area vs WKY diabetic: 53.7±8.5 acellular capillaries per mm² of retinal area), and a 3.8-fold increase in the number of arteriolar microthromboses (SHR diabetic 23504±5523 m² vs SHR non-diabetic 6228±2707 m²). Aminoguanidine treatment of SHR diabetic rats reduced the number of acellular capillaries by 50%, and completely prevented both arteriolar deposition of PAS-positive material and abnormal microthrombus formation. These data suggest that hypertension-induced deposition of glycated proteins in the retinal vasculature plays a central role in the acceleration of diabetic retinopathy by hypertension.     

Loss of Ia-positive epidermal Langerhans cells at the onset of Type 1 (insulin-dependent) diabetes mellitus

Summary Immunocompetent antigen-presenting Langerhans cells were investigated in skin biopsies of 20 short-term Type 1 (insulin-dependent) diabetic patients and compared with 17 matched normal control subjects. Langerhans cells in epidermal sheet preparations were visualized with a monoclonal anti-HLA DR antibody using indirect immunofluorescence. A significant decrease of Langerhans cells/mm² body surface area was found in 10 patients immediately at the onset of diabetes compared to 10 patients with 6 months duration of diabetes and to normal control subjects (401±30 vs 559±43 vs 611±33, p<0.01 and p<0.002). There was no significant difference in the number of Langerhans cells between patients with 6 months duration of diabetes and control subjects. Examination of the most likely precursor of Langerhans cells, the blood monocytes, indicated an increase of monocyte counts in Type 1 diabetic patients after 6 months duration (344±37 cells/l vs 191±31 in control subjects, p<0.05) and an inverse correlation between the number of Langerhans cells in skin with the number of monocytes in peripheral blood (at onset: r=–0.73, p<0.01, after 6 months of diabetes: r=–0.61, p<0.05). In addition, a positive correlation between Langerhans cells and daily insulin dose was noted in patients after 6 months of diabetes (r=0.76, p<0.01). The data suggest a loss of Langerhans cells in skin at the onset of Type 1 diabetes and that functional alterations of these and perhaps also other antigenpresenting cells may be involved in the pathogenesis of Type 1 diabetes.     

Adipocyte insulin binding and insulin sensitivity in ‘brittle’ diabetes

Summary Adipocyte insulin binding and insulin sensitivity to stimulation of lipogenesis were assessed in a group of extremely brittle diabetic patients who were resistant to subcutaneous insulin therapy and had required frequent and prolonged hospital admission. These patients had significantly lower maximum adipocyte insulin binding (1.78±0.18%) than age-, sex- and weight-matched stable diabetic control subjects (2.57±0.36%; p<0.05). Scatchard analysis suggested that the decreased binding was secondary to reduced receptor affinity with no change in receptor number. Adipocytes from the brittle subjects displayed resistance to insulin stimulation of lipogenesis compared with those from diabetic or normal control groups (half-maximal stimulation at 34±4, 15±3 and 13±2 pmol/l respectively; p<0.01 between brittle and stable diabetic groups). In the one subject who was treated with intraperitoneal insulin, the changes in insulin binding and sensitivity were found to have reverted towards normal. The peripheral tissue abnormalities of brittle diabetes may exacerbate the clinical syndrome although the relationship of these changes to the primary cause of the syndrome is uncertain.     

Experimental streptozotocin-induced diabetes and intestinal glucose metabolism in the rat,in vivo and in vitro

The intestine has a high glycolytic activity, but its metabolic role could be altered in diabetes mellitus. The aim of the present work was to investigate in vivo the glucose retained and the lactate produced by the intestine of normal and diabetic rats and in vitro the effect of different arterial glucose concentrations on glucose utilization and lactate, alanine, and pyruvate production in normal and diabetic rats when the glucose is supplied to the intestine exclusively via the vascular route. In vivo, the normal and diabetic rats retained similar percentages of the arterially supplied glucose (14.7±3.2 and 12.6±2.4, respectively). In vitro, when the preparations were perfused under hyperglycemic conditions, the glucose consumed, as a fraction of the quantity infused, was significantly lower (P<0.05) in the diabetic (247.0±22.8 mol/mmol infused glucose) than in normal (315.0±16.3 mol/mmol infused glucose) rats. The lactate produced was significantly higher in diabetic than in normal rats whether the preparations were perfused under isoglycemic (P<0.01; 1916.4±124.0 vs 1284±67.7 mol/mmol consumed glucose) or hyperglycemic (P<0.05; 1356.4±199.7 vs 898.0±87.3 mol/mmol consumed glucose) conditions. There was significantly (P<0.05) greater alanine release from the diabetic (123.7±21.8 mol/mmol consumed glucose) than from the normal (40.7±10.3 mol/mmol consumed glucose) rat preparations perfused under isoglycemic conditions.     

In situ binding of islet hormones in the isolated perfused rat pancreas: evidence for local high concentrations of islet hormones via the islet-acinar axis

Summary Insulin and somatostatin reportedly affect pancreatic acinar cell function via specific receptor binding. Theoretically peri-insular levels depend on the islet-acinar portal system, but the actual hormone levels have never been demonstrated. Rat pancreata were perfused anterogradely or retrogradely with ¹²⁵I-insulin, -somatostatin, or -glucagon (each, 10^–11 mol/l). Tracer binding was determined from differences between influx and efflux radioactivity. Saturable binding was observed for insulin and somatostatin, but not for glucagon. Binding in the absence of unlabelled peptides was significantly higher during retrograde perfusion than during anterograde perfusion for insulin (25.9±2.6 vs 16.0±2.1%, mean±SD; each, n=4; p<0.001) and somatostatin (18.4±2.0 vs 13.6±1.2%; each, n=3; p<0.05). Non-specific binding was similar in both directions. These findings are attributable to endogenous hormones acting as unlabelled ligands competing with the tracers during anterograde perfusion. This conclusion was supported by the demonstration that endogenous insulin stimulation by d-glucose, but not by l-glucose, caused a decrease in labelled insulin binding only during anterograde perfusion. Displacement curves obtained during retrograde perfusion showed that interstitial concentrations of insulin and somatostatin were 7.5×10^–9 and 1.1×10^–9 mol/l, respectively. Thus, the exocrine pancreas is indeed exposed to locally high concentrations of islet hormones.Abbreviations SS Somatostatin - TCA trichloroacetic acid     

Insulin resistance,hypertension and microalbuminuria in patients with Type 2 (non-insulin-dependent) diabetes mellitus

Summary We examined the impact of hypertension and microalbuminuria on insulin sensitivity in patients with Type 2 (non-insulin-dependent) diabetes mellitus using the euglycaemic insulin clamp technique in 52 Type 2 diabetic patients and in 19 healthy control subjects. Twenty-five diabetic patients had hypertension and 19 had microalbuminuria. Hypertension per se was associated with a 27% reduction in the rate of total glucose metabolism and a 40% reduction in the rate of non-oxidative glucose metabolism compared with normotensive Type 2 diabetic patients (both p<0.001). Glucose metabolism was also impaired in normotensive microalbuminuric patients compared with normotensive normoalbuminuric patients (29.4±2.2 vs 40.5±2.8 mol · kg lean body mass^–1 · min^–1; p=0.012), primarily due to a reduction in non-oxidative glucose metabolism (12.7±2.9 vs 21.1±2.6 mol · kg lean body mass^–1 ·min^–1; p=0.06). In a factorial ANOVA design, however, only hypertension (p=0.008) and the combination of hypertension and microalbuminuria (p=0.030) were significantly associated with the rate of glucose metabolism. The highest triglyceride and lowest HDL cholesterol concentrations were observed in Type 2 diabetic patients with both hypertension and microalbuminuria. Of note, glucose metabolism was indistinguishable from that in control subjects in Type 2 diabetic patients without hypertension and microalbuminuria (40.5±2.8 vs 44.4±2.8 mol · kg lean body mass^–1 · min^–1). We conclude that insulin resistance in Type 2 diabetes is predominantly associated with either hypertension or microalbuminuria or with both.     

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

Summary Abnormalities of ascorbic acid metabolism have been reported in experimentally-induced diabetes and in diabetic patients. Ascorbate is a powerful antioxidant, a cofactor in collagen biosynthesis, and affects platelet activation, prostaglandin synthesis and the polyol pathway. This suggests a possible close interrelationship between ascorbic acid metabolism and pathways known to be influenced by diabetes. We determined serum ascorbic acid and its metabolite, dehydroascorbic acid, as indices of antioxidant status, and the ratio, dehydroascorbate/ascorbate, as an index of oxidative stress, in 20 matched diabetic patients with and 20 without microangiopathy and in 22 age-matched control subjects. Each study subject then took ascorbic acid, 1 g daily orally, for six weeks with repeat measurements taken at three and six weeks. At baseline, patients with microangiopathy had lower ascorbic acid concentrations than those without microangiopathy and control subjects (42.1±19.3 vs 55.6±20.0, p<0.01, vs 82.9±30.9 mol/l, p<0.001) and elevated dehydroascorbate/ascorbate ratios (0.87±0.46 vs 0.61±0.26, p<0.01, vs 0.38±0.14, p<0.001). At three weeks, ascorbate concentrations rose in all groups (p<0.0001) and was maintained in control subjects (151.5± 56.3 mol/l), but fell in both diabetic groups by six weeks (p<0.01). Dehydroascorbate/ascorbate ratios fell in all groups at three weeks (p<0.0001) but rose again in the diabetic groups by six weeks (p<0.001) and was unchanged in the control subjects. Dehydroascorbate concentrations rose significantly from baseline in all groups by six weeks of ascorbic acid supplementation (p<0.05). No significant changes were observed in fructosamine concentrations in any group during the study. Diabetes mellitus is associated with a major disturbance of ascorbic acid metabolism which is only partially corrected by ascorbate supplementation.     

Exercise as a provocative test in early renal disease in Type 1 (insulin-dependent) diabetes: albuminuric,systemic and renal haemodynamic responses

Summary The value of exercise as a provocative test for early renal disease in Type 1 (insulin-dependent) diabetes was reevaluated. Three carefully characterized groups of males were studied: 10 non-diabetic controls, 16 diabetic patients (group 1) with normal urinary albumin excretion (< 15 g/min) and 14 Albustix-negative diabetics (group 2) with increased urinary albumin excretion (15–122 g/min). Assignment to a study group was made on the basis of three 24-h urine collections, and the groups were well matched for age, weight, height, and serum creatinine concentration. The two diabetic groups were similar with regard to duration of disease (13±6 versus 16±3 years), metabolic control (HbA_1c: 8.4±1.4 versus 8.7±1.3%) and degree of diabetic complications (beat-to-beat variation and retinopathy). An exercise protocol of 450 and 600 kpm/min workloads was employed. In the resting state group 2 patients had elevated systolic blood pressure compared with the normal subjects (132±13 versus 119±9 mmHg), and their glomerular filtration rate was significantly reduced compared with group 1 (123±19 versus 138±15ml/min per 1.73m², p < 0.05). During exercise the urinary albumin excretion rate increased significantly in all three groups (normal subjects: 6±0.7 to 8±1.3 (g/min); group 1: 6±0.6 to 9±1 g/min and group 2: 48±10 to 113±23 g/min), the relative increase being higher in group 2 (p < 0.01). The changes in systemic haemodynamics were similar in all three groups in spite of a reduced maximum working capacity in group 2 (949±249 versus group 1:1163±200 and normal subjects 1267±264 kpm/min (p < 0.05). The renal haemodynamic changes were qualitatively similar for the three groups, but the filtration fraction during exercise increased in groups 1 and 2 to almost identical values and were significantly higher than in normal subjects (group 1 + group 2: 0.29±0.02 versus normal subjects: 0.26±0.03, p < 0.02). These findings suggest that an elevated transcapillary pressure gradient, as obtained during moderate exercise, will not cause an abnormal increase in albumin excretion per se. A functional glomerular lesion, already recognisable at rest (elevated albumin excretion) must also be present.     

Factors associated with basal metabolic rate in patients with Type 2 (non-insulin-dependent) diabetes mellitus

Summary To examine determinants of basal metabolic rate we studied 66 Type 2 (non-insulin-dependent) diabetic and 24 healthy age- and weight-matched control subjects with indirect calorimetry and infusion of [³H-3-] glucose. Eight Type 2 diabetic patients were re-studied after a period of insulin therapy. Basal metabolic rate was higher in Type 2 diabetic patients than in control subjects (102.8 ± 1.9 J · kg LBM^–1-min^–1 vs 90.7 ± 2.8 J · kg LBM^–1;min^–1; p<0.01) and decreased significantly with insulin therapy (p <0.01). The basal rate of hepatic glucose production was higher in Type 2 diabetic patients than in control subjects (1044.0 ± 29.9 vs 789.3 ± 41.7 mol/min; p <0.001) and decreased after insulin therapy (p <0.01). Hepatic glucose production correlated positively with basal metabolic rate both in Type 2 diabetic patients (r = 0.49; p <0.001) and in control subjects (r = 0.50; p<0.05). Lipid oxidation was increased in Type 2 diabetic patients compared with control subjects (1.68 ± 0.05 vs 1.37 ± 0.08 mol · kg LBM^–1 · min^–1'; p <0.01) and decreased significantly after insulin therapy (p <0.05). The rate of lipid oxidation correlated positively with basal metabolic rate both in Type 2 diabetic patients (r = 0.36; p <0.01) and in control subjects (r = 0.51; p <0.01). These data demonstrate that basal metabolic rate, rates of hepatic glucose production and lipid oxidation are interrelated in Type 2 diabetic patients. A reduction of the hepatic glucose production, however, is associated with a reduction in lipid oxidation, which in turn, may result in a reduction in basal metabolic rate.     

Urinary excretion of non-dialysable conjugates of glucose and galactose in normal people and diabetic patients

Summary Urine contains non-dialysable conjugates of glucose and galactose from which the free sugars are released by acid hydrolysis. In 14 non-diabetic subjects the 24-h outputs (mean±SEM) were 25±3 umol/24 h (glucose) and 109±15 mol/l (galactose). In collections from 23 diabetic patients output of conjugated glucose was increased to 177±96 mol/24 h but conjugated galactose was unchanged (119±10 mol/24 h). The concentration ratio of glucosyl/galactosyl allows relative 24-h outputs of conjugated glucose to be estimated on random samples. The ratio (mean±SEM) was 0.24±0.01 in 27 normal men and 0.37±0.04 in 30 normal women. The mean ratio was increased to 0.72±0.20 in 56 male and to 0.51±0.07 in 17 female diabetic patients. In individual diabetic patients, the ratio was increased significantly in 28 out of 56 men and in 5 out of 30 women. In male diabetic patients the ratio was increased in 17 out of 23 Type 1 (insulin-dependent) but in only 3 out of 15 Type 2 (non-insulin-dependent) diabetic patients. There was no correlation between the glucosyl/galactosyl ratio and patient age, known duration of diabetes, or urinary excretion of free glucose or protein. Urine samples showing increased glucosyl/galactosyl ratios did not yield bacteria on culture and were negative for Candida albicans cell-wall mannan antigen. It is concluded that 80% of male Type 1 diabetic patients show increased urinary excretion of non-dialysable conjugated glucose. In women, there is much greater variation in non-diabetic subjects which may obscure an increased excretion in diabetic patients.