Glucose Dyshomeostasis Research Articles

Bisphenol A exposure under metabolic stress induces accelerated cellular senescence in vivo in a p53 independent manner

Senescence is an irreversible process that is a characteristic of age-associated disease like Type 2 diabetes (T2D). Bisphenol-A (BPA), one of the most common endocrine disruptor chemicals, received special attention in the development of insulin resistance and T2D. To understand the role played by BPA in cellular senescence under metabolic stress, zebrafish embryos were exposed to BPA in the absence and presence of hyperglycaemia. Transcriptional levels of the senescence markers p15, p53, Rb1 and β-galactosidase were increased when BPA was combined with metabolic stress. In addition, zebrafish embryos that were exposed to combination of hyperglycaemia and BPA exhibited increased levels of apoptosis. However, cellular senescence remained induced by a combination of hyperglycaemia and BPA exposure even in the absence of a translated p53 protein suggesting that senescence is primarily independent of it but dependent on the p15-Rb1 pathway under our experimental conditions. To confirm that our results hold true in adult mammalian tissues, we validated our embryonic experiments in an adult mammalian metabolic model of skeletal muscle cells. Our work reveals a novel and unique converging role of senescence and apoptosis axis contributing to glucose dyshomeostasis. Thus, we conclude that BPA exposure can exacerbate existing metabolic stress to increase cellular senescence that leads to aggravation of disease phenotype in age-associated diseases like type 2 diabetes.

Red blood cell membrane cholesterol in type 2 diabetes mellitus

Type II diabetes mellitus (T2DM) affects an estimate of 450 million individuals. Hence, there remains an urgent need to explore the use of novel biomarkers with the aim of preventing and managing cardiovascular risk among these individuals. Hallmarks of this condition are lipid and glucose dyshomeostasis which are accompanied by a prothrombotic phenotype; these pose as eminent links between T2DM and cardiovascular disease. Diabetic dyslipidemia affects not only plasma lipid profiles but extends further into the haematological system, modulating the cholesterol concentration of erythrocyte membranes. Elevations in this biomarker implicate cell biophysics and contribute to an increased cardiovascular risk. Here we investigate the variation of membrane cholesterol levels in RBCs, as well as the degree of hypercoagubility between healthy and type II diabetic subjects. Furthermore, we provide an adapted method to assess erythrocyte membrane cholesterol levels using a quantitative and qualitative approach. In conclusion, individuals with type II diabetes exhibit elevated erythrocyte membrane cholesterol levels which may act as a prominent link between the diabetic state and subsequent cardiovascular complications. Ultimately, this erythrocyte parameter exhibits applicative biomarker potential and may provide clinical utility in terms of disease monitoring and prognostics.

Chronic intake of 4-Methylimidazole induces Hyperinsulinemia and Hypoglycaemia\xa0via Pancreatic Beta Cell Hyperplasia and Glucose Dyshomeostasis

Caramel colours are the preferential food colouring agent globally, reaches wide age groups through eatables. Colas, a sweetened carbonated drink are most common caramel coloured beverage and its consumption is linked with diabetes, obesity, pancreatic cancer and other endocrine disorders. A major by-product produced during caramelization is 4-methylimidazole (4-MEI) that is detected in noteworthy concentrations in colas and other beverages. Previous studies revealed the neurotoxic and carcinogenic potential of 4-MEI in animals at higher doses but the effect of 4-MEI at theoretical maximum daily intake dose on glucose homeostasis is unexplored. Here, mice treated with 4-MEI (32 µg/kg bodyweight/day) for seven weeks exhibited severe hypoglycaemia and hyperinsulinemia mediated by hyperplasia of pancreatic beta cells and induces metabolic alterations. On combinatorial treatment, 4-MEI suppressed the glucogenic potential of non-artificial sweeteners and promotes lipogenesis. Furthermore, increased levels of C-peptide, LDL-cholesterol and triglycerides were observed in the humans with regular intake of 4-MEI containing beverages. In summary, 4-MEI induced pancreatic beta cell hyperplasia and leads to disruption of glucose and lipid homeostasis. This study suggests the need for further assessment and reconsideration of the wide usage of 4-MEI containing caramels as food additives.

Maternal diet-induced obesity during suckling period programs offspring obese phenotype and hypothalamic leptin/insulin resistance

During the early post-natal period, offspring are vulnerable to environmental insults, such as nutritional and hormonal changes, which increase risk to develop metabolic diseases later in life. Our aim was to understand whether maternal obesity during lactation programs offspring to metabolic syndrome and obese phenotype, in addition we aimed to assess the peripheral glucose metabolism and hypothalamic leptin/insulin signaling pathways. At delivery, female Wistar rats were randomly divided in two groups: Control group (CO), mothers fed a standard rodent chow (Nuvilab); and Diet-induced obesity group (DIO), mothers who had free access to a diet performed with 33% ground standard rodent chow, 33% sweetened condensed milk (Nestlé), 7% sucrose and 27% water. Maternal treatment was performed throughout suckling period. All offspring received standard rodent chow from weaning until 91-day-old. DIO dams presented increased total body fat and insulin resistance. Consequently, the breast milk from obese dams had altered composition. At 91-day-old, DIO offspring had overweight, hyperphagia and higher adiposity. Furthermore, DIO animals had hyperinsulinemia and insulin resistance, they also showed pancreatic islet hypertrophy and increased pancreatic β-cell proliferation. Finally, DIO offspring showed low ObRb, JAK2, STAT-3, IRβ, PI3K and Akt levels, suggesting leptin and insulin hypothalamic resistance, associated with increased of hypothalamic NPY level and decreased of POMC. Maternal obesity during lactation malprograms rat offspring to develop obesity that is associated with impairment of melanocortin system. Indeed, rat offspring displayed glucose dyshomeostasis and both peripheral and central insulin resistance.

High-normal blood glucose levels may be associated with decreased spatial perception in young healthy adults.

The negative effects of high normal glucose on cognitive function were previously reported in euglycemic individuals of middle age and the elderly population. This study aimed at examining the effect of baseline blood glucose levels on spatial ability, specifically verticality perception on the computerized rod and frame test (CRFT) in young healthy adults. 63 healthy male medical students (age range from 18–23 years), of whom 30 were non-fasting outside the month of Ramadan and 33 fasting during Ramadan of the year 2016, were recruited in order to create varying degrees of glycemia during which verticality perception was carried out. Baseline blood glucose reading was obtained prior to commencing the CRFT test. Blood glucose levels at the time of testing decreased as the duration between the last meal and testing increased. A blood glucose range of 62–117 mg/dl was achieved among participants for this study. Linear regression analysis showed that blood glucose level at testing correlated positively with all alignment spatial error parameters, indicating a probable reduction of spatial perception ability with higher blood glucose levels. These results are consistent with other cognitive studies in older healthy humans and emphasize the critical impact of early glucose dys-homeostasis on cognitive function. They also indicate that elevated blood glucose may affect cognitive functioning outside of the usual complications of diabetes.

The Link between Type 2 Diabetes and Neurodegeneration: Roles for Amyloid-β, Amylin, and Tau Proteins.

A wealth of evidence indicates a strong link between type 2 diabetes (T2D) and neurodegenerative diseases such as Alzheimer's disease (AD). Although the precise mechanism remains unclear, T2D can exacerbate neurodegenerative processes. Brain atrophy, reduced cerebral glucose metabolism, and central nervous system insulin resistance are features of both AD and T2D. The T2D phenotype (glucose dyshomeostasis, insulin resistance, impaired insulin signaling) also promotes AD pathology, namely accumulation of amyloid-β (Aβ) and hyperphosphorylated tau and can induce other aspects of neuronal degeneration including inflammatory and oxidative processes. Aβ and hyperphosphorylated tau may also have roles in pancreatic β-cell dysfunction and in reducing insulin sensitivity and glucose uptake by peripheral tissues such as liver, skeletal muscle, and adipose tissue. This suggests a role for these AD-related proteins in promoting T2D. The accumulation of the islet amyloid polypeptide (IAPP, or amylin) within islet β-cells is a major pathological feature of the pancreas in patients with chronic T2D. Co-secreted with insulin, amylin accumulates over time and contributes to β-cell toxicity, ultimately leading to reduced insulin secretion and onset of overt (insulin dependent) diabetes. Recent evidence also suggests that this protein accumulates in the brain of AD patients and may interact with Aβ to exacerbate the neurodegenerative process. In this review, we highlight evidence indicating T2D in promoting Aβ and tau mediated neurodegeneration and the potential contributions of Aβ and tau in promoting a diabetic phenotype that could further exacerbate neurodegeneration. We also discuss underlying mechanisms by which amylin can contribute to the neurodegenerative processes.

Chronic high fat feeding restricts islet mRNA translation initiation independently of ER stress via DNA damage and p53 activation

Under conditions of high fat diet (HFD) consumption, glucose dyshomeostasis develops when β-cells are unable to adapt to peripheral insulin demands. Few studies have interrogated the molecular mechanisms of β-cell dysfunction at the level of mRNA translation under such conditions. We sought to address this issue through polyribosome profile analysis of islets from mice fed 16-weeks of 42% HFD. HFD-islet analysis revealed clear trends toward global reductions in mRNA translation with a significant reduction in the polyribosome/monoribosome ratio for Pdx1 mRNA. Transcriptional and translational analyses revealed endoplasmic reticulum stress was not the etiology of our findings. HFD-islets demonstrated evidence of oxidative stress and DNA damage, as well as activation of p53. Experiments in MIN-6 β-cells revealed that treatment with doxorubicin to directly induce DNA damage mimicked our observed effects in islets. Islets from animals treated with pioglitazone concurrently with HFD demonstrated a reversal of effects observed from HFD alone. Finally, HFD-islets demonstrated reduced expression of multiple ribosome biogenesis genes and the key translation initiation factor eIF4E. We propose a heretofore unappreciated effect of chronic HFD on β-cells, wherein continued DNA damage owing to persistent oxidative stress results in p53 activation and a resultant inhibition of mRNA translation.

Glucose tolerance and cardiovascular risk biomarkers in non-diabetic non-obese obstructive sleep apnea patients: Effects of long-term continuous positive airway pressure

BackgroundInsulin resistance, glucose dyshomeostasis and oxidative stress are associated to the cardiovascular consequences of obstructive sleep apnea (OSA). The effects of a long-term continuous positive airway pressure (LT-CPAP) treatment on such mechanisms still remain conflicting. ObjectiveTo investigate the effect of LT-CPAP on glucose tolerance, insulin sensitivity, oxidative stress and cardiovascular biomarkers in non-obese non-diabetic OSA patients. Patients & methodsTwenty-eight apneic, otherwise healthy, men suffering from OSA (mean age = 48.9 ± 9.4 years; apnea-hypopnea index = 41.1 ± 16.1 events/h; BMI = 26.6 ± 2.8 kg/m2; fasting glucose = 4.98 ± 0.37 mmol/L) were evaluated before and after LT-CPAP by an oral glucose tolerance test (OGTT), measuring plasma glucose, insulin and proinsulin. Glycated hemoglobin, homeostasis model assessment resistance insulin, blood lipids, oxidative stress, homocysteine and NT-pro-brain natriuretic peptide (NT-proBNP) were also measured. ResultsLT-CPAP treatment lasted 13.9 ± 6.5 months. At baseline, the time spent at SaO2<90%, minimal and mean SaO2 were associated with insulin area under the curve during OGTT (r = 0.448, P = 0.011; r = −0.382; P = 0.047 and r = −0.424; P = 0.028, respectively) and most other glucose/insulin homeostasis biomarkers, as well as with homocysteine (r = 0.531, P = 0.006; r = −0.487; P = 0.011 and r = −0.409; P = 0.034, respectively). LT-CPAP had no effect on all the OGTT-related measurements, but increased plasma total antioxidant status (+7.74%; P = 0.035) in a duration-dependent manner (r = 0.607; P < 0.001), and decreased both homocysteine (−15.2%; P = 0.002) and NT-proBNP levels (−39.3%; P = 0.002). ConclusionsIn non-obese non-diabetic OSA patients, nocturnal oxygen desaturation is strongly associated to insulin resistance. LT-CPAP does not improve glucose homeostasis nor insulin sensitivity but has a favorable effect on antioxidant capacity and cardiovascular risk biomarkers.

A novel insulinotropic mechanism of whole grain‐derived γ‐oryzanol via the suppression of local dopamine D2 receptor signalling in mouse islet

γ-Oryzanol, derived from unrefined rice, attenuated the preference for dietary fat in mice, by decreasing hypothalamic endoplasmic reticulum stress. However, no peripheral mechanisms, whereby γ-oryzanol could ameliorate glucose dyshomeostasis were explored. Dopamine D2 receptor signalling locally attenuates insulin secretion in pancreatic islets, presumably via decreased levels of intracellular cAMP. We therefore hypothesized that γ-oryzanol would improve high-fat diet (HFD)-induced dysfunction of islets through the suppression of local D2 receptor signalling. Glucose metabolism and regulation of molecules involved in D2 receptor signalling in pancreatic islets were investigated in male C57BL/6J mice, fed HFD and treated with γ-oryzanol . In isolated murine islets and the beta cell line, MIN6 , the effects of γ-oryzanol on glucose-stimulated insulin secretion (GSIS) was analysed using siRNA for D2 receptors and a variety of compounds which alter D2 receptor signalling. In islets, γ-oryzanol enhanced GSIS via the activation of the cAMP/PKA pathway. Expression of molecules involved in D2 receptor signalling was increased in islets from HFD-fed mice, which were reciprocally decreased by γ-oryzanol. Experiments with siRNA for D2 receptors and D2 receptor ligands in vitro suggest that γ-oryzanol suppressed D2 receptor signalling and augmented GSIS. γ-Oryzanol exhibited unique anti-diabetic properties. The unexpected effects of γ-oryzanol on D2 receptor signalling in islets may provide a novel; natural food-based, approach to anti-diabetic therapy.

Distinct Properties of Telmisartan on Agonistic Activities for Peroxisome Proliferator-Activated Receptorγamong Clinically Used Angiotensin II Receptor Blockers: Drug-Target Interaction Analyses

A proportion of angiotensin II type 1 receptor blockers (ARBs) improves glucose dyshomeostasis and insulin resistance in a clinical setting. Of these ARBs, telmisartan has the unique property of being a partial agonist for peroxisome proliferator-activated receptor γ (PPARγ). However, the detailed mechanism of how telmisartan acts on PPARγ and exerts its insulin-sensitizing effect is poorly understood. In this context, we investigated the agonistic activity of a variety of clinically available ARBs on PPARγ using isothermal titration calorimetry (ITC) and surface plasmon resonance (SPR) system. Based on physicochemical data, we then reevaluated the metabolically beneficial effects of telmisartan in cultured murine adipocytes. ITC and SPR assays demonstrated that telmisartan exhibited the highest affinity of the ARBs tested. Distribution coefficient and parallel artificial membrane permeability assays were used to assess lipophilicity and cell permeability, for which telmisartan exhibited the highest levels of both. We next examined the effect of each ARB on insulin-mediated glucose metabolism in 3T3-L1 preadipocytes. To investigate the impact on adipogenesis, 3T3-L1 preadipocytes were differentiated with each ARB in addition to standard inducers of differentiation for adipogenesis. Telmisartan dose-dependently facilitated adipogenesis and markedly augmented the mRNA expression of adipocyte fatty acid-binding protein (aP2), accompanied by an increase in the uptake of 2-deoxyglucose and protein expression of glucose transporter 4 (GLUT4). In contrast, other ARBs showed only marginal effects in these experiments. In accordance with its highest affinity of binding for PPARγ as well as the highest cell permeability, telmisartan superbly activates PPARγ among the ARBs tested, thereby providing a fresh avenue for treating hypertensive patients with metabolic derangement.

Factors involved in the development of the metabolic syndrome. We are what we eat and what we are eating

A variety of metabolic and molecular changes in brain and adipose tissue play a critical role in the pathophysiology of life style-related metabolic diseases [1-3]. Even in obese subjects with insulin resistance in skeletal muscle and liver, insulin action on adipose tissue remains intact or rather exaggerated, resulting in considerable difficulties in weight reduction. Excess in circulating insulin thus causes body fat gain as well as ectopic lipid overload in liver, skeletal and cardiac muscle, pancreas and vasculature. The adipocyte hormone, leptin controls feeding behavior, augments fatty acid b-oxidation in the skeletal muscle and enhances whole body insulin sensitivity, thereby serving as a promising therapeutic candidate for the treatment of obesity-diabetes syndrome. However, the clinical application of leptin has been hampered by the notion that leptin does not fully exert its metabolic effects in subjects with fat diet-induced obesity [4-6]. It is important to note that the future risk of cardiometabolic diseases exists for infants with low birth weight/intrauterine growth retardation (IUGR). IUGR causes a premature leptin surge in the neonatal period in mice, and conceivably, through a number of epigenetic mechanisms, it may induce hypothalamic leptin resistance in adulthood. Mechanisms of non-genomic, intergenerational transmission of metabolic diseases from parents to children have also been unveiled in an expeditious fashion. The endoplasmic reticulum (ER) is an intracellular organelle involved in protein folding and apoptosis. The accumulation of misfolded proteins in the ER, termed as ER stress, is involved in the molecular pathophysiology of type 2 diabetes and metabolic syndrome. Our recent research in mice demonstrated that high fat diet-induced ER stress in the hypothalamus plays a pivotal role in the preference for fatty foods and resultant increase in body weight. We provided the first evidence that brown rice and its major component, g-oryzanol, ameliorate glucose dyshomeostasis in mice fed high-fat diet (HFD), accompanied by reduction of hypothalamic endoplasmic reticulum (ER) stress [7]. In my talk, I try to review the update of mechanisms of metabolic syndrome, with a particular focus on the molecular food sciences.

High Fat and Highly Thermolyzed Fat Diets Promote Insulin Resistance and Increase DNA Damage in Rats

Many studies have demonstrated that DNA damage may be associated with type 2 diabetes mellitus (T2DM) and its complications. The goal of this study was to evaluate the effects of the potential relationship between fat (thermolyzed) intake, glucose dyshomeostasis and DNA injury in rats. Biochemical parameters related to glucose metabolism (i.e., blood glucose levels, insulin tolerance tests, glucose tolerance tests and fat cell glucose oxidation) and general health parameters (i.e., body weight, retroperitoneal and epididymal adipose tissue) were evaluated in rats after a 12-month treatment with either a high fat or a high thermolyzed fat diet. The high fat diet (HFD) and high fat thermolyzed diet (HFTD) showed increased body weight and impaired insulin sensitivity at the studied time-points in insulin tolerance test (ITT) and glucose tolerance test (GTT). Interestingly, only animals subjected to the HFTD diet showed decreased epididymal fat cell glucose oxidation. We show which high fat diets have the capacity to reduce glycogen synthesis by direct and indirect pathways. HFTD promoted an increase in lipid peroxidation in the liver, demonstrating significant damage in lipids in relation to other groups. Blood and hippocampus DNA damage was significantly higher in animals subjected to HFDs, and the highest damage was observed in animals from the HFTD group. Striatum DNA damage was significantly higher in animals subjected to HFDs, compared with the control group. These results show a positive correlation between high fat diet, glucose dyshomeostasis, oxidative stress and DNA damage.

Tumor necrosis factor-α alters glucose metabolism in suckling rats

Tumor necrosis factor-α (TNF-α), an important mediator of endotoxic shock, induces hypoglycemia and shock in adult animals. Indomethacin ameliorates TNF-α-induced hypoglycemia in the adult. However, effects of TNF-α on glucose metabolism in the newborn have not been well documented. The present study showed that in 10-day-old rats injected with TNF-α (4.5 × 107 U/kg, intraperitoneally) the plasma glucose concentration increased from 4.1 ± 0.3 mmol/L to 6.9 ± 0.5 mmol/L (P < .05) at 2 hours and subsequently decreased to 1.4 ± 0.5 mmol/L (P < .05) at 6 hours, although plasma lactate concentration increased from 1.1 ± 0.1 mmol/L to 5.5 ± 0.3 mmol/L (P < .05) at 6 hours. Plasma insulin concentration remained unchanged throughout the experiment. TNF-α increased GLUT 1 messenger RNA (mRNA) abundance in the brain, liver, muscle, and fatty tissue (P < .05). Glucose uptake increased in association with the increase of GLUT1 mRNA abundance. TNF-α decreased mRNA abundance of GLUT 2 and phosphoenolpyruvate carboxykinase (PEPCK) in liver, suggesting decreased gluconeogenesis. Indomethacin (1.5 mg/kg 20 minutes before TNF-α, intraperitoneally) attenuated the hypoglycemia, the lactacidemia, and the increase of GLUT1 mRNA abundance and glucose uptake. Indomethacin attenuated the decrease of PEPCK mRNA abundance. We concluded that TNF-α induced hypoglycemia, increasing GLUT1 mRNA abundance and glucose uptake and decreasing PEPCK mRNA abundance in 10-day-old rats. Indomethacin attenuated the TNF-α-induced glucose dyshomeostasis.

Effect of Dexamethasone on NF-kB Activation, Tumor Necrosis Factor Formation, and Glucose Dyshomeostasis in Septic Rats

Glucocorticoids are potent anti-inflammatory and immunosuppressive therapeutic agents. The protective effect of dexamethasone (DEX) on hepatic phosphoenolpyruvate carboxykinase (PEPCK) transcript level, hepatic NF-kB (nuclear factor-kB) activation, and serum tumor necrosis factor α (TNF) formation was investigated in peritoneal sepsis induced by cecal incision in rats. For the control the rats were sham-operated with laparotomies only. Each group (N= 6) was pretreated with either normal saline (NS) or DEX before surgery (NS/Sham, NS/Sepsis, DEX/Sham, and DEX/Sepsis). At 3 hr post cecal incision, DEX treatment inhibited sepsis-induced hepatic NF-kB activation by 23%, suppressed circulating TNF by 50%, reduced serum glucose by 36%, reduced hepatic glycogen depletion by 76%, and attenuated PEPCK mRNA level. These findings suggested that DEX treatment was beneficial in attenuating glucose dyshomeostasis and significantly inhibited two sepsis-induced inflammatory mediators, NF-kB and TNF, in the early phase of peritoneal sepsis. However, in the late (6 hr) septic phase, DEX treatment inhibited serum TNF by 69%, but had no effect on NF-kB activation, glycogen depletion, and PEPCK mRNA level suggesting liver function failure injury.

Perinatal nutrition enriched with omega-3 polyunsaturated fatty acids attenuates endotoxic shock in newborn rats.

Sepsis and septic shock continue to have a high mortality and morbidity in the newborn. Eicosanoids are important mediators in Gram negative septic shock. Omega-3 polyunsaturated fatty acids (omega-3) decrease production of biologically active 2-series eicosanoids. Therefore, we hypothesized that omega-3-enriched diet could decrease 2-series eicosanoids and attenuate endotoxic shock in newborn rats. Sprague-Dawley rat dams were fed with either omega-3 polyunsaturated fatty acid-enriched diet (omega-3 PURA) or omega-6 polyunsaturated fatty acid enriched diet (omega-6PUFA; controls) from the 16th day of gestation until 10 days after parturition. In 10 day old rats, shock was induced by an intraperitoneal injection of Salmonella enteritidis lipopolysaccharide. The omega-3PUFA decreased the mortality of endotoxic shock. In omega-6PUFA, lipopolysaccharide induced hyperglycemia at 2 h and hypoglycemia thereafter without an elevation in plasma insulin concentration, omega-3PUFA attenuated the hyperglycemia and hypoglycemia. omega-3PUFA attenuated the decrease of liver phosphoenolpyruvate ca-boxykinase mRNA abundance, suggesting preserved gluconeogenesis. Therefore, perinatal feeding with omega-3PUFA was beneficial in attenuating glucose dyshomeostasis in newborn rats with endotoxic shock and may be a novel approach to the prevention of endotoxic shock in the newborn.

Efficacy of anti-tumor necrosis factor polyclonal antibody on phosphoenolpyruvate carboxykinase expression in septic and endotoxemic rats.

We studied the protective effect of anti-tumor necrosis factor-alpha (anti-TNF) polyclonal antibody on phosphoenolpyruvate carboxykinase (PEPCK) expression in lipopolysaccharide-induced endotoxemia and peritonitis sepsis induced by cecal incision. At 3 h after intraperitoneal lipopolysaccharide injection, levels of serum glucose, liver glycogen, and PEPCK expression were decreased and serum TNF was elevated. In contrast, 3 h after cecal incision, levels of serum glucose, serum TNF, and PEPCK expression were elevated. At 6 h after cecal incision (terminal sepsis), serum TNF remained elevated and levels of serum glucose, liver glycogen, and PEPCK expression were decreased. Circulating TNF was not detected in septic and endotoxemic rats pretreated with anti-TNF. Passive immunization with rat anti-TNF antibody restored PEPCK expression in early endotoxemia and sepsis (3 h), but not in terminal sepsis (6 h). Anti-TNF failed to reverse sepsis-induced hypoglycemia and hyperglycemia, suggesting that besides TNF, some other mediators are involved in glucose dyshomeostasis.

Glucose, lactate, insulin, and somatostatin responses to endotoxin in developing rats.

The purpose of this study was to examine the temporal plasma glucose, lactate, insulin, and somatostatin responses of 10-day-old (10 d) and 28-day-old (28 d) rats to the effects of an LD90 dose of endotoxin for a 4 h period. Salmonella enteritidis endotoxin was administered to 10 d and 28 d rats at .2 and 30.0 mg/kg, respectively. Hyperglycemia was the initial response to endotoxin, followed by hypoglycemia; this was similar for 10 d and 28 d rats. Lactate levels were significantly elevated in 10 d rats, but only mild hyperlactacidemia was observed in 28 d rats. Hyperinsulinemia was observed in both 10 d and 28 d rats in response to elevated glucose levels; in 10 d rats, decreased insulin levels preceded the hyperinsulinemia. Plasma somatostatin levels were elevated in both 10 d and 28 d rats in response to endotoxin, but the endotoxin-induced somatostatin levels were greater and occurred earlier in 28 d rats than in 10 d rats. The magnitude of the somatostatin response to endotoxin in the developing rats was markedly less than that previously reported in adult rats. Since previous reports indicated that somatostatin supported the glucoregulatory adaptive response to endotoxin in adult rats, the present results suggested that the diminished somatostatin response to endotoxin in developing rats may partially underlie their increased sensitivity to endotoxin and the profound glucose dyshomeostasis that results subsequently.

Decreased gluconeogenesis and increased glucose disposal without hyperinsulinemia in 10-day-old rats with endotoxic shock

Glucose dyshomeostasis is a common and life-threatening sign of endotoxic shock in the newborn. In this study, liver gluconeogenesis was evaluated in 10-day-old rats with endotoxic shock using the isolated perfused liver. Phosphoenolpyruvate car☐ykinase (PEPCK) activity and PEPCK mRNA abundance were measured to confirm altered gluconeogenesis. Glucose disposal was also evaluated by a glucose tolerance test. Twenty-four-hour-fasted rats were studied to enhance gluconeogenesis and decrease glucose disposal. Rats received an intraperitoneal (IP) injection as follows: group 1 (fed-saline), 0.2 mL saline in fed rats; group 2 (fed-LPS), 0.1 mg/kg Salmonella enteritidis lipopolysaccharide (LPS) in fed rats; group 3 (fasted-saline), 0.2 mL saline in fasted rats; and group 4 (fasted-LPS), 0.1 mg/kg LPS in fasted rats. Isolated liver perfusion, determination of liver PEPCK activity and liver PEPCK mRNA abundance, and a glucose tolerance test were performed at 4 hours in fed rats and at 6 hours in fasted rats. LPS induced hypoglycemia (1.62 ± 0.33 mmol/L, P < .05) at 6 hours in group 2 (fed-LPS), but not in group 4 (fasted-LPS). Hyperinsulinemia was not observed in either group 2 (fed-LPS) or group 4 (fasted-LPS). In group 2 (fed-LPS), liver gluconeogenesis decreased (3.0 ± 0.3 mg/g liver, P < .01). PEPCK activity decreased from 0.65 ± 0.07 (group 1) to 0.23 ± 0.02 U ( P < .01). PEPCK mRNA abundance also decreased from 100% ± 10% to 40% ± 10%. The glucose disappearance rate ( t 1/2) increased ( P < .05) in group 2 (fed-LPS) and group 4 (fasted-LPS). In group 4, gluconeogenesis, PEPCK activity, and PEPCK mRNA abundance were preserved. Thus, glucoregulation was altered without hyperinsulinemia in 10-day-old endotoxic rats. Hypoglycemia during endotoxic shock was due to decreased gluconeogenesis and increased total-body glucose disposal.

Changes of α1-adrenergic receptors in human liver during intraabdominal sepsis

We studied changes in α1-adrenergic receptors in human liver plasma membranes during intraabdominal sepsis using [3H]prazosin as a radioligand. Human liver tissues were obtained from nonseptic patients undergoing elective abdominal surgery (control group) and from patients with sepsis requiring laparotomy as a therapeutic measure (septic group). Septic patients were further divided into three subgroups on the basis of septic severity scores: mild sepsis (<21), moderate sepsis (22 to 32) and severe sepsis (>33). Plasma membranes were prepared by means of sucrose gradient centrifugation and were purified fivefold on the basis of the enrichment of the activity of the marker enzyme, 5′-nucleotidase. [3H]prazosin-binding studies show that the maximal binding capacity was increased by 49.6% (p <0.01) in mild sepsis, relatively unchanged in moderate sepsis and decreased by 33.4% (p < 0.05) in severe sepsis (in femtomoles per milligram: 193.7 ± 5.7 for control [n = 6], 289.8 ± 23.4 for mild sepsis [n = 4], 192.3 ± 16.3 for moderate sepsis (n = 4), 129.1 ± 18.3 for severe sepsis [n = 5]). We found a significant inverse correlation (r = 0.85, p < 0.01) between changes in the densities of α1-adrenergic receptors and septic severity scores. These data indicate that α1-adrenergic receptors in human liver plasma membranes undergo dynamic changes during the development of sepsis — that is, the receptor number increased in mild sepsis, returned to a normal level in moderate sepsis and finally decreased in severe sepsis. Because α1-adrenergic receptor densities in human liver plasma membranes can be increased or decreased during the progression of septic shock, successful therapeutic interventions that aim to ameliorate glucose dyshomeostasis by way of α1-adrenergic receptor mediation may depend on appropriate timing of when interventions are given. These findings thus may contribute to a better remedy for hepatic glucose dyshomeostasis during sepsis. (HEPATOLOGY 1994;20:638-642).

K252a, a potent protein kinase inhibitor, improves endotoxic lethality and glucose dyshomeostasis.

To investigate whether the inhibition of protein kinases including protein kinase C can antagonize endotoxicosis, the in vivo effects of K252a, a potent inhibitor of protein kinases, on endotoxin-induced lethality and glucose dyshomeostasis were determined in conscious rats. Sprague-Dawley rats (260-340 g) were divided into the following four groups: Group DS, 2.5% dimethyl sulfoxide (DMSO), 6 ml/kg iv + 0.9% saline, 2 ml/kg iv; group KS, K252a in 2.5% DMSO, 4 mg/kg iv + 0.9% saline; group DE, 2.5% DMSO + endotoxin (E. coli), 15 mg/kg iv; and group KE, K252a in 2.5% DMSO + endotoxin. A quarter of DMSO or K252a solution was continuously infused over a 15 min period before a bolus injection of either saline or endotoxin. The remaining dose was administered over a 180 min period after saline or endotoxin. All animals in the DS and KS groups survived for 24 hrs. K252a significantly improved endotoxic lethality. It attenuated the initial hyperglycemia, and late hypoglycemia, hyperlactacidemia, and base deficit after endotoxin. However, K252a had no influence on the endotoxic alterations of blood pressure, PaCO2 or PaO2. These results suggest that the activations of protein kinases, particularly protein kinase C, are involved in the pathogenesis of lethal endotoxicosis and sepsis.