Glucose metabolism in bone marrow cells and granulocytes of adult mice after X-ray (5 Gy) irradiation: relationship to cell functionality

Our experiments focused on the metabolic implications of the residual haemopoietic damage in adult mice given 5 Gy X-rays. Bone marrow cells from irradiated mice exhibited an increase in protein synthesis and a decrease in ATP levels, which could be related to the enhancement of the proliferative activity of haemopoietic precursor cells. However, the kinetic parameters ( V _max and K _m) of glucose uptake, the glycolytic flux and the hexose monophospate (HMP) shunt activity were similar to those found in the control group. On the other hand, a reduction of glucose uptake ( V _max) was found in both resting and stimulated granulocytes from irradiated mice. This reduction was accompanied by a decrease in the glycolytic rate and ATP levels. However, HMP shunt activity was similar in resting granulocytes in both the control and the irradiated mice. The stimulation by PMA produced a significantly higher increase in the activity of the pathway in granulocytes from the irradiated mice and was in accordance with the enhancement of superoxide anion production that has been previously described in these cells.     

The genetic abnormality in the beta cell determines the response to an oral glucose load

Aims/hypothesis: We assessed how the role of genes genetic causation in causing maturity-onset diabetes of the young (MODY) alters the response to an oral glucose tolerance test (OGTT). Methods: We studied OGTT in 362 MODY subjects, from seven European centres; 245 had glucokinase gene mutations and 117 had Hepatocyte Nuclear Factor –1 alpha (HNF-1α) gene mutations. Results: BMI and age were similar in the genetically defined groups. Fasting plasma glucose (FPG) was less than 5.5 mmol/l in 2 % glucokinase subjects and 46 % HNF-1 α subjects (p < 0.0001). Glucokinase subjects had a higher FPG than HNF-1 α subjects ([means ± SD] 6.8 ± 0.8 vs 6.0 ± 1.9 mmol/l, p < 0.0001), a lower 2-h value (8.9 ± 2.3 vs 11.2 ± 5.2 mmol/l, p < 0.0001) and a lower OGTT increment (2-h – fasting) (2.1 ± 2.3 vs 5.2 ± 3.9 mmol/l, p < 0.0001). The relative proportions classified as diabetic depended on whether fasting (38 % vs 22 %, glucokinase vs HNF-1 α) or 2-h values (19 % vs 44 %) were used. Fasting and 2-h glucose values were not correlated in the glucokinase subjects (r = –0.047, p = 0.65) but were strongly correlated in HNF-1 α subjects (r = 0.8, p < 0.001). Insulin concentrations were higher in the glucokinase subjects throughout the OGTT. Conclusion/interpretation: The genetic cause of the beta-cell defect results in clear differences in both the fasting glucose and the response to an oral glucose load and this can help diagnostic genetic testing in MODY. OGTT results reflect not only the degree of hyperglycaemia but also the underlying cause. [Diabetologia (2002) 45: 427–435] Received: 13 September 2001 and in revised form: 26 November 2001     

Chronic Idiopathic Cough: A Discrete Clinical Entity?

STUDY OBJECTIVES: Despite the success of specialist cough clinics, there is increasing recognition of a subgroup of chronic coughers in whom a diagnosis cannot be made even after thorough, systematic investigation. We call this condition chronic idiopathic cough (CIC). The aim of this study is to compare the clinical characteristics of CIC patients with those of coughers in whom a diagnosis has been established (non-CIC) to see if there is a recognizable clinical pattern that distinguishes CIC from non-CIC. DESIGN: Retrospective analysis of the medical records of chronic cough patients. SETTING: The Royal Brompton Hospital Chronic Cough Clinic, London. PATIENTS: One hundred patients with chronic cough referred to the Royal Brompton Hospital Cough Clinic between October 2000 and February 2004. RESULTS: Seventy-one percent of all patients were female. Median age was 57 years (range, 19 to 81 years), with a median duration of symptoms of 48 months (range, 2 to 384 months). The primary diagnoses were CIC (42%), postnasal drip syndromes (22%), gastroesophageal reflux disease (16%), asthma (7%), and others (13%). In CIC patients, the median age at referral, age at onset of cough, and proportion of females did not differ significantly from non-CIC patients. CIC patients had a longer median duration of cough (72 months vs 24 months, p = 0.002), were more likely to report an upper respiratory tract infection (URTI) as the initial trigger of their cough (48% vs 24%, p = 0.0014), and had a significantly lower cough threshold in response to capsaicin (log concentration of capsaicin required to induce five or more coughs, - 0.009 vs 0.592, p = 0.032) than non-CIC patients. CONCLUSIONS: Patients with CIC commonly describe a URTI that initiates their cough, which then lasts for many years, and they demonstrate an exquisitely sensitive cough reflex. We believe that CIC may be a distinct clinical entity with an as-yet unidentified underlying pathology.     

Myocardial fatty acid oxidation in patients with impaired glucose tolerance

Abstract Aims/hypothesis. Fatty acids are an important source of energy in the myocardium. Abnormal myocardial fatty acid metabolism could contribute to the deterioration of cardiac function frequently observed in patients with Type II (non-insulin-dependent) diabetes mellitus. In our previous study, myocardial total uptake of non-esterified fatty acid (NEFA) was measured in patients with impaired glucose tolerance and found to be normal. This study aimed to investigate the subsequent metabolic steps and β-oxidation of NEFA. Methods. A total of 6 men with impaired fasting glucose (age 50 ± 2 years, BMI 29 ± 1 kg/m², means ± SEM) and 6 healthy men (50 ± 1 years, 25 ± 1 kg/m²) were studied in the fasting state. Myocardial blood flow was measured with [¹⁵O]H₂O and positron emission tomography and myocardial NEFA metabolism with [¹¹C]palmitic acid. Results. Myocardial blood flow was normal and not different between the impaired glucose tolerance and the control group (78 ± 6 vs 73 ± 13 ml/100 g/min, NS). The [¹¹C]palmitic acid uptake indices were similar between the groups (10.4 ± 0.5 vs 11.2 ± 0.8 ml/100 g/min, respectively, NS). The clearance of [¹¹C]-palmitate from the myocardium, an index of NEFA β-oxidation, was similar between the groups (half-times of activity 17.6 ± 1.6 vs 19.5 ± 2.3 min, respectively, NS) Conclusion/interpretation. The results indicate that myocardial NEFA uptake and β-oxidation are not altered in patients with IGT. Thus, it is not likely that altered NEFA metabolism contributes to the deterioration of the cardiac function in patients with IGT or Type II diabetes. [Diabetologia (2001) 44: 184–187] Received: 9 June 2000 and in revised form: 25 September 2000     

Islet amyloid polypeptide in the islets of Langerhans: friend or foe?

Islet amyloid polypeptide (IAPP), or amylin, was originally discovered as the constituent peptide in amyloid occurring in human insulinomas and in pancreatic islets in human subjects with Type II (non-insulin-dependent) diabetes mellitus. Its normal expression in beta cells and its co-secretion with insulin in response to nutrient stimuli, suggest a metabolic function for the peptide. Specifically, IAPP has most frequently been shown to inhibit insulin secretion, implying that IAPP has a role in the regulation of islet hormone homeostasis. The physiological significance of IAPP in islets has been difficult to assess; very high IAPP concentrations are required to alter insulin secretion. Moreover, until recently, IAPP receptors have not been characterised at the molecular level, thus leaving the actual target cells for IAPP unidentified. Furthermore, in experimental diabetes in rodents, the ratio of IAPP expression to that of insulin invariably is increased. In view of the pleiotropic effects attributed to IAPP, such regulation could be both adverse and beneficial in diabetes. Metabolic characterisation of mice carrying a null mutation in the IAPP gene or which overexpress IAPP in beta cells have recently confirmed that IAPP is a physiological inhibitor of insulin secretion. Based on experiments in which IAPP-deficient mice develop a more severe form of alloxan-induced diabetes, we argue that the action of IAPP in the islets normally is beneficial for beta-cell function and survival; thus, the established up regulation of IAPP expression compared with that of insulin in experimental rodent diabetes could serve to protect islets under metabolically challenging circumstances. [Diabetologia (2000) 43: 687–695]     

Oophorectomy promotes islet amyloid formation in a transgenic mouse model of Type II diabetes

Aims/hypothesis. In Type II (non-insulin-dependent) diabetes mellitus, amyloid depletes islet mass. We previously found that 81 % of male human islet amyloid polypeptide (IAPP) transgenic mice but only 11 % of female mice developed islet amyloid, suggesting that either testosterone promotes or ovarian products protect against amyloid deposition.¶Methods. We did a bilateral oophorectomy or sham procedure in female human IAPP transgenic mice (n = 11 and n = 8, respectively) and in female non-transgenic mice (n = 7 and n = 9, respectively) at 6–8 weeks of age. Animals were followed for 1 year on a 9 % fat (w/w) diet. Before we killed them we measured, fasting plasma human IAPP and did an intraperitoneal glucose tolerance test. Pancreatic content of IAPP and immunoreactive insulin (IRI) were estimated and pancreata were analysed for islet amyloid.¶Results. No amyloid was detected in either the sham-operated transgenic mice or, as expected, in both groups of non-transgenic mice. In strong contrast, 7 of 11 (64 %) oophorectomized mice developed islet amyloid (p < 0.05). Amyloid deposition in the oophorectomized transgenic mice was not associated with any differences in incremental body weight, fasting human IAPP concentrations or glucose tolerance between the groups. Furthermore, pancreatic content of mouse IAPP, human IAPP and immunoreactive insulin did not differ between groups.¶Conclusion/interpretation. Oophorectomy is associated with an enhancement of islet amyloid formation in the absence of changes in glucose tolerance, circulating IAPP or pancreatic content of IRI, mouse or human IAPP. Thus, the early stages of islet amyloidogenesis seem to be independent of glucose tolerance, with ovarian products having a protective role. [Diabetologia (2000) 43: 1309–1312]     

Comparison of the metabolic effects of long-term treatment with pindolol or atenolol by hypertensive patients

Summary The effects of plasma lipids, blood glucose, and serum total cholesterol, LDL-cholesterol, VLDL-cholesterol, 6-month period were studied in 18 patients with essential hypertension.There were no significant changes in the concentration of serum total cholesterol. LDL-cholesterol, VLDL-cholesterol, and triglycerides during treatment periods with pindolol or atenolol, although there was a tendency to higher triglyceride levels during atenolol treatment.The serum HDL-cholesterol levels were significantly lower after 6 months of therapy with atenolol than before treatment, but HDL-cholesterol levels increased slightly during pindolol treatment. The ratio of HDL-cholesterol to total cholesterol decreased significantly during 6 months of treatment with atenolol.Fasting blood glucose concentrations did not change significantly during 6 months of treatment with pindolol or atenolol, but during oral glucose tolerance test, blood glucose values at 60 min were raised after pindolol therapy. Serum insulin levels during oral glucose tolerance test at 120 min were decreased after pindolol therapy, but no significant changes were found in C-peptide levels during treatment periods.     

Long-term recovery from unawareness,deficient counterregulation and lack of cognitive dysfunction during hypoglycaemia,following institution of rational,intensive insulin therapy in IDDM

Summary Hypoglycaemia unawareness, is a major risk factor for severe hypoglycaemia and a contraindication to the therapeutic goal of near-normoglycaemia in IDDM. We tested two hypotheses, first, that hypoglycaemia unawareness is reversible as long as hypoglycaemia is meticulously prevented by careful intensive insulin therapy in patients with short and long IDDM duration, and that such a result can be maintained long-term. Second, that intensive insulin therapy which strictly prevents hypoglycaemia, can maintain long-term near-normoglycaemia. We studied 21 IDDM patients with hypoglycaemia unawareness and frequent mild/severe hypoglycaemia episodes while on conventional insulin therapy, and 20 nondiabetic control subjects. Neuroendocrine and symptom responses, and deterioration in cognitive function were assessed in a stepped hypoglycaemia clamp before, and again after 2 weeks, 3 months and 1 year of either intensive insulin therapy which meticulously prevented hypoglycaemia (based on physiologic insulin replacement and continuous education, experimental group, EXP, n=16), or maintenance of the original conventional therapy (control group, CON, n=5). At entry to the study, all 21 IDDM-patients had subnormal neuroendocrine and symptom responses, and less deterioration of cognitive function during hypoglycaemia. After intensive insulin therapy in EXP, the frequency of hypoglycaemia decreased from 0.5±0.05 to 0.045±0.02 episodes/patient-day; HbA_1C increased from 5.83±0.18 to 6.94±0.13% (range in non-diabetic subjects 3.8–5.5%) over a 1-year period; all counterregulatory hormone and symptom responses to hypoglycaemia improved between 2 weeks and 3 months, with the exception of glucagon which improved at 1 year; and cognitive function deteriorated further as early as 2 weeks (p<0.05). The improvement in responses was maintained at 1 year. The improvement in plasma adrenaline and symptom responses inversely correlated with IDDM duration. In contrast, in CON, neither frequency of hypoglycaemia, nor neuroendocrine responses to hypoglycaemia improved. Thus, meticulous prevention of hypoglycaemia by intensive insulin therapy reverses hypoglycaemia unawareness even in patients with long-term IDDM, and is compatible with long-term near-normoglycaemia. Because carefully conducted intensive insulin therapy reduces, not increases the frequency of moderate/severe hypoglycaemia, intensive insulin therapy should be extended to the majority of IDDM patients in whom it is desirable to prevent/delay the onset/progression of microvascular complications.Abbreviations IDDM Insulin-dependent diabetes mellitus - IIT intensive insulin therapy - HU hypoglycaemia unawareness - EXP experimental patient group - CON control group     

Elevated GLUT 1 level in crude muscle membranes from diabetic Zucker rats despite a normal GLUT 1 level in perineurial sheaths

Summary Recently, we demonstrated that approximately 60 % of GLUT 1 in a crude membrane fraction of rat skeletal muscle originates from perineurial sheaths. To study the in vivo regulation of GLUT 1 expression in different tissues in muscles, we measured the level of GLUT 1 in crude muscle membranes and in perineurial sheaths in diabetic (fa/fa) Zucker rats and lean controls, with and without metformin treatment. The GLUT 1 concentration in perineurial sheaths was identical in all four groups of rats, both when measured by quantitative immunofluorescence and by immunoblotting and densitometry. In a fraction of crude membranes of soleus muscles GLUT 1 expression was more than two-fold higher in (fa/fa) rats than in lean controls (p<0.005). Metformin treatment significantly elevated GLUT 1 in control rats (p<0.05) and tended to decrease GLUT 1 in diabetic rats (p<0.075). The expressions of GLUT 1 and GLUT 4 in crude muscle membranes were inversely correlated (p<0.01), and GLUT 1 expression correlated positively with fasting glucose (p<0.05). In conclusion, GLUT 1 expression in perineurial sheaths is unaffected by alterations in glucose homeostasis and by the genes responsible for obesity and diabetes in the Zucker rat. GLUT 1 expression in a crude membrane fraction of soleus muscle is increased in the diabetic animals, likely due to an increased expression in muscle cells proper. [Diabetologia (1994) 37: 443–448] Received: 17 June 1993 and in revised form: 19 November 1993