Flight of the Chinese white pine beetle (Coleoptera: Scolytidae) in relation to sex, body weight and energy reserve

The flight distance, flight time and individual flight activities of males and females of Dendroctonus armandi were recorded during 96-h flight trials using a flight mill system. The body weight, glucose, glycogen and lipid content of four treatments (naturally emerged, starved, phloem-fed and water-fed) were compared among pre-flight, post-flight and unflown controls. There was no significant difference between males and females in total flight distance and flight time in a given 24-h period. The flight distance and flight time of females showed a significant linear decline as the tethered flying continued, but the sustained flight ability of females was better than that of males. The females had higher glycogen and lipid content than the males; however, there was no significant difference between both sexes in glucose content. Water-feeding and phloem-feeding had significant effects on longevity, survival days and flight potential of D. armandi, which resulted in longer feeding days, poorer flight potential and lower energy substrate content. Our results demonstrate that flight distances in general do not differ between water-fed and starved individuals, whereas phloem-fed females and males fly better than water-fed and starved individuals.     

Maximum activities and properties of glucose 6-phosphatase in muscles from vertebrates and invertebrates.

1. The maximum catalytic activities of glucose 6-phosphatase were measured in a large number of muscles from vertebrates and invertebrates. The activities range from less than 0.1 to 8.0 mumol/min per g fresh wt. at 30 degrees C: the highest activity, observed in the flight muscle of the wasp (Vespa vulgaris), is similar to that in rat liver. The hydrolytic activity was shown to be specific towards glucose 6-phosphate. 2. The pH optimum was 6.8 and the Km was approx. 0.6 mM (flight muscle of a moth). 3. Almost all of the glucose 6-phosphatase activity from extracts of the flight muscle of a moth and the pectoral muscle of a pigeon were recovered in the cytosolic fraction (i.e. 150,000 g supernatant). 4. During development of the locust (Schistocerca gregaria), the activity of the phosphatase in the flight muscle increased during the first 3 days after the final moult. 5. The activity of glucose 6-phosphatase from insect and avian muscle was separated from that of non-specific phosphatase on a Bio-Gel P-100 column. 6. For the activities from 63 muscles, there was a strong positive correlation between those of glucose 6-phosphatase and hexokinase, but no correlation between the activities of glucose 6-phosphatase and fructose bisphosphatase. It is suggested that the role of glucose 6-phosphate in muscle is either to produce glucose from glucose 6-phosphate derived from glycogen or to provide the enzymic basis for a substrate ("futile") cycle between glucose and glucose 6-phosphatase in muscle to improve the sensitivity of the mechanism that regulates the rate of glucose phosphorylation.     

Contribution of the exercise-induced increment in glucose storage to the increased insulin sensitivity of endurance athletes

The present study was designed to evaluate the contribution of the exercise-induced increment in glucose storage to the increased insulin sensitivity characterizing endurance athletes. Plasma glucose and insulin were measured during an oral glucose tolerance test (OGTT) in six endurance athletes. Glucose storage and lipid oxidation during this test were also determined using indirect calorimetry. These measurements were compared to those obtained in five non-trained subjects who were tested before and during the three days following a 90-min cycle ergometer exercise performed at 69% of their VO2max. As expected, preexercise values of non-trained subjects revealed a much higher insulin response to glucose, and a lower glucose storage and lipid oxidation compared to results obtained in endurance trained individuals. Glucose tolerance was comparable in both groups. The morning following the exercise test, i.e. about 16 h after exercise, glucose storage was significantly increased in non-trained subjects to a level similar to that found in trained subjects. Surprisingly, this was accompanied by higher values of glucose during the OGTT without significant changes in insulinaemia. This impairment in glucose homeostasis was transitory since glucose tolerance had returned to control level on day 2 after exercise. At that time, the increase in glucose storage was less pronounced than in day 1. On day 3 after exercise, glucose and insulin responses to glucose were similar to preexercise values. These results indicate that the increase in glucose storage by acute exercise is not systematically associated with an improved glucose homeostasis, suggesting that other adaptive mechanisms also contribute to the improvement of insulin sensitivity in endurance athletes.     

Peripheral glucose metabolism in patients with insulin resistance and acanthosis nigricans.

The present study was designed to determine forearm muscle glucose uptake and oxidation during the postabsorptive state and after an oral glucose challenge in patients with type A insulin resistance and acanthosis nigricans. Nine normal subjects and six acanthotic patients were studied after an overnight fast (12-14 h) and during 3 hours after ingestion of 75 g of glucose. Peripheral glucose metabolism was analysed by the forearm technique to estimate muscle exchange of substrate combined with indirect calorimetry in forearm. Two patients (1 and 6) with insulin resistance and acanthosis nigricans had impaired glucose tolerance. All other patients and normals revealed normal glucose tolerance during the tests. Decreased forearm muscle glucose uptake was observed in patients 1 and 6 compared to normal subjects (6.3 and 51.1 vs 127.7 +/- 10.1 mg/100 ml forearm.3 h, respectively). Decreased forearm muscle glucose oxidation was also observed in patient 1 as well as in patient 3 who showed normal glucose tolerance. Serum FFA levels were elevated in patient 1 but not in patient 3 and in the other acanthotic patients compared to the normal subjects. Serum insulin levels were significantly higher in acanthotic patients than in normals before and after glucose loading. The results of the present study revealed that two of six patients with type A insulin resistance and acanthosis nigricans who exhibited glucose intolerance also showed a decrease in peripheral muscle glucose uptake and nonoxidative glucose metabolism. Another patient (3) with normal glucose tolerance showed impaired muscle glucose oxidation but unaltered muscle glucose uptake and nonoxidative metabolism during the 3 hours of study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Continuous glucose monitoring in cystic fibrosis patients according to the glucose tolerance.

Cystic fibrosis (CF) is associated with a long preclinical state of abnormal glucose tolerance. The aim of this study was (i) to evaluate the profile of glucose tolerance in young adults with CF and (ii) to compare these results with those obtained by a continuous subcutaneous glucose monitoring (CGMS). CF subjects with fasting glycemia inferior to 126 mg/dl were included in the study. An oral glucose tolerance test (OGTT) identified the subjects either with a normal glucose tolerance (NGT), or impaired glucose tolerance (IGT), or diabetes. CGMS (Medtronic) was performed during 3 days to analyze mean glucose level, high glucose excursions, and glucose area under the curve (AUC). Forty-nine patients were included in the study. NGT (n=22), IGT (n=17), and diabetes groups (n=10) were comparable except with regard to age and BMI (p<0.001). HbA1c values in diabetes group were significantly higher (p<0.001) than in NGT and IGT groups. CGMS revealed peaks of glucose values superior to 200 mg/dl at least once after a meal in 8 patients (36%) with NGT, in 9 patients (52%) with IGT, and in all patients with diabetes (p<0.01). Mean CGMS glucose and glucose AUC values increased in patients with diabetes compared to patients with NGT and IGT (p<0.05). Peak of CGMS glucose reached 182+/-60 mg/dl in NGT group despite the normal glucose profile at OGTT. In conclusion, CGMS revealed pathological glucose excursions not only in patients with impaired glucose tolerance at OGTT but also in patients with a normal glycemic profile. CGMS could be a useful tool for the early detection of hyperglycemia in patients with CF.     

Effects of an olive oil-enriched diet on glucagon-like peptide 1 release and intestinal content, plasma insulin concentration, glucose tolerance and pancreatic insulin content in an animal model of type 2 diabetes.

In the light of a recent study conducted in normal rats, the present investigations were aimed at exploring the immediate and long-term effects of an olive oil-enriched diet (OO diet) on GLP-1 release and intestinal content, plasma insulin concentration, glucose tolerance and pancreatic insulin content in adult rats that had been injected with streptozotocin during the neonatal period (STZ rats). The OO diet, when compared to a standard diet, increased the immediate GLP-1 response in meal-trained rats, but decreased GLP-1 content in the intestinal tract after 50 days. Over 50 days, the body weight gain was lower in the rats fed the OO diet compared to standard diet. In the former, however, no improvement of glucose tolerance or insulin response during an oral glucose tolerance test was observed. Thus, a paradoxical lowering of the insulinogenic index, i. e. the paired ratio between plasma insulin and glucose concentration, was recorded during the oral glucose tolerance test in rats fed either standard or OO diet. Moreover, the insulin content of the pancreas was equally low in the STZ rats fed either standard or OO diet. These findings will be discussed in the framework of possible differences in the pathophysiology of B-cell dysfunction in most patients with type-2 diabetes and the present animal model of non-insulin-dependent diabetes.     

Dietary supplementation with vitamin E and C attenuates dexamethasone-induced glucose intolerance in rats

Glucocorticoid excess induces marked insulin resistance and glucose intolerance. A recent study has shown that antioxidants prevent dexamethasone (DEX)-induced insulin resistance in cultured adipocytes. The purpose of this investigation was to examine the effects of dietary vitamin E and C (Vit E/C) supplementation on DEX-induced glucose intolerance in rats. We hypothesized that feeding rats a diet supplemented with Vit E/C would improve glucose tolerance and restore insulin signaling in skeletal muscle, adipose, and liver and prevent alterations in AMPK signaling in these tissues. Male Wistar rats received either a control or Vit E/C-supplemented diet (0.5 g/kg diet each of L-ascorbate and DL-all rac-alpha-tocopherol) for 9 days prior to, and during, 5 days of daily DEX treatment (subcutaneous injections 0.8 mg/g body wt). DEX treatment resulted in increases in the glucose and insulin area under the curve (AUC) during an intraperitoneal glucose tolerance test. The glucose, but not insulin, AUC was lowered with Vit E/C supplementation. Improvements in glucose tolerance occurred independent of a restoration of PKB phosphorylation in tissues of rats stimulated with an intraperitoneal injection of insulin but were associated with increases in AMPK signaling in muscle and reductions in AMPK signaling and the expression of fatty acid oxidation enzymes in liver. There were no differences in mitochondrial enzymes in triceps muscles between groups. This study is the first to report that dietary Vit E/C supplementation can partially prevent DEX-induced glucose intolerance in rats.     

Glucose Tolerance during Pulmonary Exacerbations in Children with Cystic Fibrosis

Background

Patients with Cystic Fibrosis (CF) are relatively insulinopenic and are at risk of diabetes, especially during times of stress. There is a paucity of data in the literature describing glucose tolerance during CF pulmonary exacerbations. We hypothesised that glucose tolerance would be worse during pulmonary exacerbations in children with CF than during clinical stability.

Methods

Patients with CF, 10 years or older, admitted with a pulmonary exacerbation underwent an OGTT within 48 hours of admission. A repeat OGTT was performed 4 to 6 weeks post discharge when the patients were well.

Results

Nine patients completed the study. Four patients were found to have normal glucose tolerance, 3 with impaired and 2 with CF related diabetes during the exacerbation. Mean change in 2-hour glucose was 1.1 mmol (SD = 0.77). At the follow up OGTT, 8 of 9 (89%) remained within their respective glucose tolerance status groupings.

Conclusion

The findings of this study show that there is little difference in glucose tolerance during CF exacerbations compared to clinical stability in the majority of patients.     

Glucose tolerance tests during gestation in the unanesthetized rat.

To establish the temporal stages at which changes in insulin/glucose interactions may appear during gestation in the rat, unanesthetized animals were subjected to oral glucose tolerance tests (2 g glucose/kg) at days 15 and 21 of gestation and were compared to virgin female controls. On day 15 glucose tolerance is enhanced in the pregnant rat whereas plasma insulin levels are like those in control animals. On day 21 glucose tolerance does not differ between the two groups although insulin is higher in the pregnant animals. Results show 2 differentiated stages of insulin/glucose relationships throughout gestation in the rat with enhanced insulin sensitivity on day 15 and enhanced insulin resistance during late gestation. It is suggested that these changes contribute to the anabolic tendencies of the mother during mid gestation and her catabolic condition during late gestation.     

Plasma hormone levels in human subject during stress loads in microgravity and at readaptation to Earth's gravity

In great part of the investigations of endocrine system functions in astronauts during space flights the plasma levels of hormones and metabolites were determined only in resting conditions, usually from one blood sample collection. Such levels reflected the psychical and physical state and new hormonal homeostasis of organism at the time of blood collection, however, the functional capacity of neuroendocrine system to respond to various stress stimuli during space flight remained unknown. The aim of present investigations was to study dynamic changes of hormone levels during the stress and metabolic loads (insulin induced hypoglycemia, physical exercise and oral glucose tolerance test) at the exposure of human subject to microgravity on the space station MIR. The responses of sympatico-adrenomedullary system to these stress and workloads were presented by Kvetnansky et al.     

The rate of substrate cycling between glucose and glucose 6-phosphate in muscle and fat-body of the hawk moth (Acherontia atropos) at rest and during flight

1. The rate of substrate cycling between glucose and glucose 6-phosphate was measured in tissues of the hawk moth (Acherontia atropos). 2. The insect was injected with [2-3H,2-14C]glucose, and after periods of time at rest or flying the animal was freeze-clamped. Separation of glucose and hexose monophosphate from the tissues was performed by paper chromatography and t.l.c., and the 3H and 14C radioactivities in these compounds were measured. 3. On the basis of the 3H/14C ratios in these compounds and the measured rate of glycolysis, the rate of cycling was calculated. The rates of cycling were 0.03, 0.10, 0.06 and 3.9 mumol/min per g for fat-body at rest and during flight and for flight muscle at rest and during flight respectively. 4. The marked increase in the cycling rate between glucose and glucose 6-phosphate upon flight contrasts with the finding of Clark, Bloxham, Holland & Lardy [(1973) Biochem. J. 134, 589-597] in the bumble-bee, in which this condition inhibited cycling. It is suggested that the increased rate of cycling increases the sensitivity of glucose phosphorylation to changes in the concentrations of effectors of hexokinase should it be necessary to increase the rate of glycolysis in muscle, for example, to increase power output of the flight muscle for increased speed of flight.     

Changes in glycosylated haemoglobin after oral glucose load.

To study the relation between hyperglycaemia and a change in the concentration of glycosylated haemoglobin (HbA1) blood glucose and HbA1 concentrations were measured during an oral glucose tolerance test and for 120 days afterwards in 20 normal subjects. These measurements showed that a minor degree of hyperglycaemia led to a significant increase in lycosylated haemoglobin concentrations. The increase appeared 10 days after the test, and values remained raised until 30 days and returned to normal 60 days after the test. If such a minor fluctuation of blood glucose can lead to a significant increase in HbA1 concentrations the test may be too sensitive as an index of long-term blood glucose control in diabetics.     

Endogenous opiate modulators of insulin secretion in the obese

The effects of endogenous opiates on insulin response to oral glucose load were studied in obese subjects and in lean healthy volunteers. None of these having a family diabetes. After 3 days on an 1,800 cal./m2, 40% carbohydrate diet all subjects underwent two standard 75 g oral glucose tolerance tests (OGTT), one of which was accompanied by an i. v. administration of 10 mg of, an antagonist of opiates, the naloxone. In one group of obese impaired oral glucose tolerance test occurred. All obese, but not the lean healthy volunteers, showed: 1) increased basal plasma insulin levels, 2) higher insulin response to OGTT, 3) a decrease in insulin response to OGTT after naloxone administration, with significant differences at 60 min (p less than 0.01) and 90 min (p less than 0.025). In none of the subjects significant differences were observed in blood glucose levels after OGTT plus naloxone administration. These data suggest that increased endogenous opiates may affect insulin response to glucose in obese with impaired or normal oral glucose tolerance test. At present there seems to be no satisfactory explanation for unchanged blood glucose levels during OGTT with and without naloxone despite a decrease in insulin secretion in the obese patients.     

Role of adrenal glands in the development of abnormal glucose and insulin homeostasis in genetically obese (ob/ob) mice

This study evaluates the role of adrenal hormones in the development of hyperinsulinaemia and impaired glucose homeostasis in genetically obese hyperglycaemic C57BL/6J ob/ob mice. Lean (+/?) and obese mice were bilaterally adrenalectomised or sham operated at 5 weeks of age, and glucose tolerance was examined after 7 and 14 days. Adrenalectomy temporarily reduced food intake and body weight gain in lean mice, and improved glucose tolerance without a significant change in plasma insulin concentrations at both intervals studied. In obese mice adrenalectomy permanently reduced body weight gain and food intake to values comparable with lean mice. Glucose tolerance was improved in adrenalectomised obese mice at both intervals studied, resulting in plasma glucose concentrations similar to adrenalectomised lean mice. Plasma insulin concentrations during the tolerance tests were reduced in adrenalectomised obese mice, but remained higher than in lean mice. Adrenalectomy did not improve the poor insulin response to parenteral glucose in obese mice. The results indicate that adrenal hormones play an important role in the development of glucose intolerance and contribute to the hyperinsulinaemia in obese (ob/ob) mice, in part by promoting hyperphagia.     

Effect of Peroral Administration of Chromium on Insulin Signaling Pathway in Skeletal Muscle Tissue of Holstein Calves

The objective of this study was to investigate the effects of peroral administration of chromium-enriched yeast on glucose tolerance in Holstein calves, assessed by insulin signaling pathway molecule determination and intravenous glucose tolerance test (IVGTT). Twenty-four Holstein calves, aged 1 month, were chosen for the study and divided into two groups: the PoCr group (n = 12) that perorally received 0.04 mg of Cr/kg of body mass daily, for 70 days, and the NCr group (n = 12) that received no chromium supplementation. Skeletal tissue samples from each calf were obtained on day 0 and day 70 of the experiment. Chromium supplementation increased protein content of the insulin β-subunit receptor, phosphorylation of insulin receptor substrate 1 at Tyrosine 632, phosphorylation of Akt at Serine 473, glucose transporter-4, and AMP-activated protein kinase in skeletal muscle tissue, while phosphorylation of insulin receptor substrate 1 at Serine 307 was not affected by chromium treatment. Results obtained during IVGTT, which was conducted on days 0, 30, 50, and 70, suggested an increased insulin sensitivity and, consequently, a better utilization of glucose in the PoCr group. Lower basal concentrations of glucose and insulin in the PoCr group on days 30 and 70 were also obtained. Our results indicate that chromium supplementation improves glucose utilization in calves by enhancing insulin intracellular signaling in the skeletal muscle tissue.     

Role of emotional stress in disorders of carbohydrate tolerance

Two series of rabbit experiments were carried out to study the influence of emotional stress on glucose tolerance. Relatively short-term (10 days) chronic emotional stress induced by prolonged (2 h daily) intermittent stimulation of negative emotiogenic zones of the hypothalamus through implanted electrodes led to decreased glucose tolerance. Repeated powerful emotional stresses induced by the clash of food and pain irritation did not pass traceless and manifested in the same glucose tolerance disturbances after a lengthy period of time (1 year).     

On the Status and Comparison of Glucose Intolerance in Female Breast Cancer Patients at Initial Diagnosis and during Chemotherapy through an Oral Glucose Tolerance Test

Aims

This study is to estimate the status and comparison of glucose intolerance in female breast cancer patients at initial diagnosis and during chemotherapy through an oral glucose tolerance test (OGTT), as well as to learn the effect of chemotherapy on the glucose metabolism of breast cancer patients.

Methods

All the 79 breast cancer patients at initial diagnosis, with the mean age of 53.2 years, and 96 breast cancer patients before the 5th or 6th cycle of chemotherapy, with the mean age of 51.5 years, participated in the study from December 2012 to October 2013. After an overnight fast, participants underwent OGTT test, and fasting and 2-hour glucose levels were measured to identify undiagnosed diabetes and prediabetes (i.e., impaired fasting glucose or impaired glucose tolerance) in them. Previously diagnosed diabetes among the female breast cancer patients was determined on the self-report and the medical record.

Results

The overall incidences of total normal glucose tolerance, prediabetes, diabetes in female breast cancer patients at initial diagnosis and during chemotherapy were 24.1% and 38.5% (p<0.05), 50.6% and 28.1% (p<0.05), and 25.3% and 33.3% (p>0.05), respectively, and the differences of normal glucose tolerance and prediabetes instead of diabetes between the two groups were statistically significant. About 84% of the total diabetes and prediabetes in the female breast cancer patients at initial diagnosis and 79.7% of those during chemotherapy need to be diagnosed with OGTT.

Conclusions

Breast cancer patients have high incidences of diabetes and prediabetes. After chemotherapy even with steroids, some breast cancer patients with abnormal glucose metabolism may even become normal. Isolated hyperglycemia 2 hours after glucose loading is common, and OGTT should be made for breast cancer patients at initial diagnosis and during chemotherapy.     

Intraportal autotransplantation of cryopreserved porcine islets of Langerhans

Mechanically prepared isolated islets of Langerhans were cryopreserved in liquid nitrogen for a period of 4 days. Intraportal autotransplantation studies were performed on two groups of six pigs rendered diabetic by total pancreatectomy (group 2) or by partial pancreatectomy combined with streptozotocin (group 4) and compared with two control groups (groups 1 and 3, respectively). The pigs were assessed for survival, weight gain, glycosuria, polyuria, systemic blood sugar and insulin, and, in selected pigs, intravenous glucose tolerance tests. Results showed that partial pancreatectomy with streptozotocin was the better tolerated experimental diabetes. Variable control of hyperglycemia was obtained over an experimental period of 3 months. Random blood glucose returned to normal in one of six pigs in the totally pancreatectomized group and three of six pigs in the partial pancreatectomy and streptozotocin group. Despite these normal circulating glucose levels, imperfect glucose homeostasis was achieved as shown by the response to glucose tolerance testing. These results report blood glucose control after cryopreserved islet autotransplants in diabetic pigs but further study is still necessary to achieve consistency.     

Metabolic Profiling of the Response to an Oral Glucose Tolerance Test Detects Subtle Metabolic Changes

Background

The prevalence of overweight is increasing globally and has become a serious health problem. Low-grade chronic inflammation in overweight subjects is thought to play an important role in disease development. Novel tools to understand these processes are needed. Metabolic profiling is one such tool that can provide novel insights into the impact of treatments on metabolism.

Methodology

To study the metabolic changes induced by a mild anti-inflammatory drug intervention, plasma metabolic profiling was applied in overweight human volunteers with elevated levels of the inflammatory plasma marker C-reactive protein. Liquid and gas chromatography mass spectrometric methods were used to detect high and low abundant plasma metabolites both in fasted conditions and during an oral glucose tolerance test. This is based on the concept that the resilience of the system can be assessed after perturbing a homeostatic situation.

Conclusions

Metabolic changes were subtle and were only detected using metabolic profiling in combination with an oral glucose tolerance test. The repeated measurements during the oral glucose tolerance test increased statistical power, but the metabolic perturbation also revealed metabolites that respond differentially to the oral glucose tolerance test. Specifically, multiple metabolic intermediates of the glutathione synthesis pathway showed time-dependent suppression in response to the glucose challenge test. The fact that this is an insulin sensitive pathway suggests that inflammatory modulation may alter insulin signaling in overweight men.     

Effects of space flight on GLUT-4 content in rat plantaris muscle

 The effects of 14 days of space flight on the glucose transporter protein (GLUT-4) were studied in the plantaris muscle of growing 9-week-old, male Sprague Dawley rats. The rats were randomly separated into five groups: pre-flight vivarium ground controls (PF-VC) sacrificed approximately 2 h after launch; flight groups sacrificed either approximately 5 h (F-R0) or 9 days (F-R9) after the return from space; and synchronous ground controls (SC-R0 and SC-R9) sacrificed at the same time as the respective flight groups. The flight groups F-R0 and F-R9 were exposed to micro-gravity for 14 days in the Spacelab module located in the cargo bay of the shuttle transport system – 58 of the manned Space Shuttle for the NASA mission named ”Spacelab Life Sciences 2”. Body weight and plantaris weight of SC-R0 and F-R0 were significantly higher than those of PF-VC. Neither body weight nor plantaris muscle weight in either group had changed 9 days after the return from space. As a result, body weight and plantaris muscle weight did not differ between the flight and synchronous control groups at any of the time points investigated. The GLUT-4 content (cpm/μg membrane protein) in the plantaris muscle did not show any significant change in response to 14 days of space flight or 9 days after return. Similarly, citrate synthase activity did not change during the course of the space flight or the recovery period. These results suggest that 14 days of space flight does not affect muscle mass or GLUT-4 content of the fast-twitch plantaris muscle in the rat. Received: 25 March 1997 / Accepted: 18 August 1997