The emerging role of the mitochondrial fatty-acid synthase (mtFASII) in the regulation of energy metabolism

Malonyl-CoA synthetase (ACSF3) catalyzes the first step of the mitochondrial fatty acid biosynthesis (mtFASII). Mutations in ACSF3 cause CMAMMA a rare inborn error of metabolism. The clinical phenotype is very heterogeneous, with some patients presenting with neurologic manifestations. In some children, presenting symptoms such as coma, ketoacidosis and hypoglycemia are suggestive of an intermediary metabolic disorder. The overall pathophysiological mechanisms are not understood.In order to study the role of mtFASII in the regulation of energy metabolism we performed a comprehensive metabolic phenotyping with Seahorse technology proteomics in fibroblasts from healthy controls and ACSF3 patients. SILAC-based proteomics and lipidomic analysis were performed to investigate the effects of hypofunctional mtFASII on proteome and lipid homeostasis of complex lipids.Our data clearly confirmed an impaired mitochondrial flexibility characterized by reduced mitochondrial respiration and glycolytic flux due to a lower lipoylation degree. These findings were accompanied by the adaptational upregulation of β-oxidation and by the reduction of anaplerotic amino acids as compensatory mechanism to address the required energy need. Finally, lipidomic analysis demonstrated that the content of the bioactive lipids sphingomyelins and cardiolipins was strongly increased.Our data clearly demonstrate the role of mtFASII in metabolic regulation. Moreover, we show that mtFASII acts as mediator in the lipid-mediated signaling processes in the regulation of energy homeostasis and metabolic flexibility.     

不同胰岛素给药方式救治糖尿病酮症酸中毒临床研究

目的：比较不同胰岛素给药方式治疗糖尿病酮症酸中毒（DKA）的临床疗效。方法：82例DKA患者随机分为胰岛素泵持续皮下输液胰岛素（CSⅡ）组和微量泵持续静脉泵入胰岛素（CXqI）组各41例,分别给予胰岛素泵持续皮下输注胰岛素和小剂量胰岛素持续微量泵静脉泵入不同胰岛素给药方式,观察两组治疗后血糖变化、血糖达标时间、尿酮体变化、pH值变化、胰岛素平均日用量、平均低血糖次数及平均住院时间。结果：两组治疗后空腹血糖、餐后血糖显著下降及血糖达标时间显著缩短差异无统计学意义（P〉0．05）;CSII组尿酮体转阴时间（22．3±7．4）h短于CVII组（32．1±12．1）h（P〈0．01）;CSII组PH值恢复时间（9．4±2．5）h短于CVII组（15．7±3．5）h（P〈0．01）;CSII组平均胰岛素日用量为（47±5）U比CVII组（58＋7）U少（P〈0．01）;CSII组人均低血糖次数为（0．6±O．5）次／人。少于CVII组（1．5±0．8）次／人（P〈O．01）;CSII组住院时间（9．8±1．2）天明显比CVII组（12．5±2．0）天短（P〈0．01）。结论：CSII相较于CVII能更快更有效的纠正代谢紊乱,减少胰岛素日用量,缩短住院时间,从而提高临床疗效。具有较高的安全性及患者依从性。     

Ventilatory and treadmill endurance during acute semistarvation

Little is known about respiratory muscle function in acute undernutrition, although an inadequate caloric intake is common in numerous disease states. Twelve young-adult, healthy female volunteers performed two familiarization experiments and were then studied after 7 days of consuming 40% of normal daily caloric intake as well as after 1 wk of normal caloric intake. In each experiment subjects performed tests of resting pulmonary function, inspiratory muscle strength, and ventilatory endurance, the last of which involved two 60-s and two 6-min isocapnic maximum voluntary ventilation maneuvers. Subjects then walked to exhaustion in 8-20 min on a treadmill. The caloric restriction did not affect performance of any breathing test but did lower endurance time in severe treadmill exercise (P less than 0.05). Basal metabolic rate was lowered, resting blood levels of free fatty acids and beta-hydroxybutyrate elevated, and glucose lowered following the caloric restriction (P less than 0.05). Blood lactate levels were lower during and after exercise following caloric restriction (P less than 0.05). We conclude that ventilatory muscle strength and endurance are fully preserved in caloric restriction severe enough to cause mild ketoacidosis and hypoglycemia, lowered basal metabolic rate, and decreased endurance in severe treadmill exercise.     

Changes in circulating iodothyronines in diabetics with various degrees of metabolic control

Plasma TSH, total and free T3 and T4, reverse T3, blood pH, HbAlc, ketonuria and glycosuria were evaluated in 8 subjects with diabetic ketoacidosis, in 54 diabetics of group 1 and group 2 without severe metabolic derangement and in 10 control women. The diabetics with ketoacidosis showed before intensive therapy low T3, total and free, and high reverse T3 concentrations as compared to controls (unpaired t-test, p less than 0.001). After one day of intensive therapy the decrease of hyperglycemia and pH increase (p less than 0.001, paired t-test), glycosuria and ketonuria are not related to significant variations of iodothyronines and TSH. The significant variations (paired t-test, p less than 0.001) in total and free T3 and in reverse T3 concentrations were found only six days after remission of ketoacidosis. In diabetics (type 1 and 2) without recent history of ketoacidosis no differences were found in mean total and free T3 and T4, in reverse T3 and in plasma concentrations although mean blood glucose and HbAlc were statistically different (t-test, p less than 0.001). The changes in serum T3 (total and free) and reverse T3 are useful indicators of total metabolic control during the management of diabetic ketoacidosis.     

Expression of Aquaporin 4 and Breakdown of the Blood-Brain Barrier after Hypoglycemia-Induced Brain Edema in Rats

Background

Hypoglycemia-induced brain edema is a severe clinical event that often results in death. The mechanisms by which hypoglycemia induces brain edema are unclear.

Methods

In a hypoglycemic injury model established in adult rats, brain edema was verified by measuring brain water content and visualizing water accumulation using hematoxylin and eosin staining. Temporal expression of aquaporin 4 (AQP4) and the integrity of the blood-brain barrier (BBB) were evaluated. We assessed the distribution and expression of AQP4 following glucose deprivation in astrocyte cultures.

Results

Brain edema was induced immediately after severe hypoglycemia but continued to progress even after recovery from hypoglycemia. Upregulation of AQP4 expression and moderate breakdown of the BBB were observed 24 h after recovery. In vitro, significant redistribution of AQP4 to the plasma membrane was induced following 6 h glucose deprivation.

Conclusion

Hypoglycemia-induced brain edema is caused by cytotoxic and vasogenic factors. Changes in AQP4 location and expression may play a protective role in edema resolution.     

Diabetic Ketoacidosis—A Review of Cases at a University Medical Center

Twenty-five cases of diabetic ketoacidosis were studied retrospectively with respect to clinical characteristics and results of therapy. In this series (as with all 88 patients admitted in the last five years with a diagnosis of diabetic ketoacidosis) there were no deaths. Infection was found to be the most common precipitating event, documented by physical findings and cultures in one-third of these cases.In about two-thirds of the cases, electrocardiograms which were read as abnormal on admission reverted to normal after therapy.In all patients serum potassium levels decreased from admission values; one patient became symptomatically hypokalemic.Low serum potassium levels on admission and early vigorous bicarbonate therapy are emphasized as major predisposing factors of symptomatic hypokalemia. None of the patients had overt hyperosmolar coma, lactic acidosis or cerebral edema during therapy.     

Cerebrolysin inhibits lipid peroxidation induced by insulin hypoglycemia in the brain and heart of mice

As a consequence of enhanced production of oxygen free radicals, lipid peroxidation leads to the degradation of membrane lipids and disturbances of membrane permeability. Lipid peroxidation increases under stress conditions such as hypoxia, ischemia or acidosis as well as in metabolic diseases, e.g. diabetes mellitus. We have shown that subcomatous doses of insulin (6.0 IU/kg) significantly increase thiobarbituric acid reactive substances (TBARs), especially malondialdehyde (MDA) - the endproduct of lipid peroxidation, in the brain and heart of mice. In our model of insulin-induced hypoglycemia, mice were treated with the neuroprotective, peptide-containing drug Cerebrolysin (100 mg/kg b.w.). Animals were sacrificed by decapitation two or three hours after the injection of tested substance and samples were taken to determine several serum parameters (glucose, total protein, triglycerides and lactic acid) and TBARs in the brain and heart. Although Cerebrolysin was not able to affect serum parameters after subcomatous insulin injection, the drug significantly influenced lipid peroxidation. A single injection of Cerebrolysin already decreased TBARs levels in the brain and heart tissue. Presuming that an increase of TBARs reflects disturbances of the cell membrane, we have documented a promising effect of Cerebrolysin on cell integrity.     

Hypothermia: a complication of diabetic ketoacidosis.

During 1969-77, 20 episodes of severe hypothermia occurred in 19 diabetic patients in Nottingham. Thirteen were associated with ketotic hyperosmolar coma, two with lactic acidosis, and one with hypoglycaemia, while in four there was no loss of diabetic control. Ketoacidosis accounted for 11.8% of all admissions for severe accidental hypothermia and was a commoner cause than hypothyroidism (8%). Patients with ketoacidosis were younger and developed hypothermia as often during the summer as during the winter. The metabolic disturbance was characteristic, with severe acidosis (mean pH 7.04), a high blood glucose concentration (mean 56.6 mmol/l; 1020 mg/100 ml), and high plasma osmolality (mean 379.7 mmol (mosmol)/kg). Eight of the 13 episodes proved fatal. Hypothermia may aggravate ketoacidosis and complicate treatment and should be sought in all patients with severe diabetic coma.     

Metabolic effects of bicarbonate in the treatment of diabetic ketoacidosis.

The effect of intravenous bicarbonate on the changes in intermediary metabolites during the initial treatment of diabetic ketoacidosis was examined in 16 patients. The results were compared with the changes seen in 16 patients receiving intravenous saline. Infusion of 150 mmol (mEq) bicarbonate significantly delayed the fall in blood lactate, lactate:pyruvate ratio, and total ketone bodies observed in the saline treated group. No difference in the rate of fall of blood glucose concentration was found. There is no metabolic indication for the use of intravenous bicarbonate in the treatment of diabetic ketoacidosis.     

Acute, same-day effects of antecedent exercise on counterregulatory responses to subsequent hypoglycemia in type 1 diabetes mellitus

Exercise-induced hypoglycemia can occur within hours after exercise in type 1 diabetes mellitus (T1DM) patients. This study tested the hypothesis that an acute exercise bout causes (within hours) blunted autonomic and metabolic responses to subsequent hypoglycemia in patients with T1DM. Twelve T1DM patients (3 W/9 M) were studied during a single-step, 2-h hyperinsulinemic (572 +/- 4 pmol/l) hypoglycemic (2.8 +/- 0.1 mmol/l) clamp 2 h after either a hyperinsulinemic euglycemic (AM EUG) or hypoglycemic clamp (AM HYPO) or after sitting in a chair with basal insulin infusion (AM CON) or 90 min of moderate-intensity exercise (50% Vo(2 max), AM EX). Both AM HYPO and AM EX significantly blunted epinephrine responses and muscle sympathetic nerve activity responses to subsequent hypoglycemia compared with both control groups. Endogenous glucose production was significantly lower and the exogenous glucose infusion rate needed to maintain the hypoglycemic level was significantly greater during subsequent hypoglycemia in AM EX vs. CON. Rate of glucose disposal (Rd) was significantly reduced following AM HYPO. In summary, within 2.5 h, both moderate-intensity AM EX and AM HYPO blunted key autonomic counterregulatory responses. Despite this, glucose Rd was reduced during afternoon hypoglycemia following morning hypoglycemia, indicating posthypoglycemic insulin resistance. After morning exercise, endogenous glucose production was blunted, but glucose Rd was maintained during afternoon hypoglycemia, thereby indicating reduced metabolic defenses against hypoglycemia. These data suggest that exercise-induced counterregulatory failure can occur very rapidly, increasing the risk for hypoglycemia in T1DM within hours.     

Effect of sex on counterregulatory responses to exercise after antecedent hypoglycemia in type 1 diabetes

A marked sexual dimorphism exists in healthy individuals in the pattern of blunted neuroendocrine and metabolic responses following antecedent stress. It is unknown whether significant sex-related counterregulatory differences occur during prolonged moderate exercise after antecedent hypoglycemia in type 1 diabetes mellitus (T1DM). Fourteen patients with T1DM (7 women and 7 men) were studied during 90 min of euglycemic exercise at 50% maximal O(2) consumption after two 2-h episodes of previous-day euglycemia (5.0 mmol/l) or hypoglycemia of 2.9 mmol/l. Men and women were matched for age, glycemic control, duration of diabetes, and exercise fitness and had no history or evidence of autonomic neuropathy. Exercise was performed during constant "basal" intravenous infusion of regular insulin (1 U/h) and a 20% dextrose infusion, as needed to maintain euglycemia. Plasma glucose and insulin levels were equivalent in men and women during all exercise and glucose clamp studies. Antecedent hypoglycemia produced a relatively greater (P < 0.05) reduction of glucagon, epinephrine, norepinephrine, growth hormone, and metabolic (glucose kinetics) responses in men compared with women during next-day exercise. After antecedent hypoglycemia, endogenous glucose production (EGP) was significantly reduced in men only, paralleling a reduction in the glucagon-to-insulin ratio and catecholamine responses. In conclusion, a marked sexual dimorphism exists in a wide spectrum of blunted counterregulatory responses to exercise in T1DM after prior hypoglycemia. Key neuroendocrine (glucagon, catecholamines) and metabolic (EGP) homeostatic responses were better preserved during exercise in T1DM women after antecedent hypoglycemia. Preserved counterregulatory responses during exercise in T1DM women may confer greater protection against hypoglycemia than in men with T1DM.     

A case of diabetic non-ketotic hyperosmolar coma with an increase with plasma 3-hydroxybutyrate.

We have seen a case of "diabetic non-ketotic hyperosmolar coma" with ketosis. An 84-year-old man was brought into the hospital in a deeply comatous and dehydrated state. The initial blood glucose level was 1252 mg/dl with plasma osmolarity of 435 mOsm/l, but no ketonuria was detected by the nitroprusside method (Ketostix). However, the plasma 3-hydroxybutyrate (3-OHBA) level was 5 mM in a newly developed bedside film test. The serum ketone bodies were later found to be 5.56 and 0.82 mmol/l for 3-OHBA and acetoacetate (AcAc), respectively. A marked increase in glucagon, cortisol and ADH with renal dysfunction (creatinine 5.0 mg/dl) were noted. An abnormal electrocardiogram, occular convergence and chorea like movement disappeared after correction of metabolic disturbances. The moderate level of IRI (14 microU/ml) on admission and a good response to glucagon 2 months after admission also indicate that the present case is a typical hyperosmolar non-ketotic coma. Because of a preferential increase in 3-OHBA, ketonuria seemed to be absent in the regular nitroprusside test. Marked dehydration is thought to cause renal dysfunction, and the increase in ADH may have helped to prevent further aggravation of ketoacidosis. We propose to change the term hyperosmolar non-ketotic coma (HNC) to diabetic hyperosmolar coma (DHC), because sometimes patients with hyperosmolar non-ketotic diabetic coma are ketotic, as seen in the present case. Determination of 3-OHBA or individual ketone bodies in blood is important and essential for the differential diagnosis of diabetic coma. The diagnosis of either ketoacidotic or hyperosmolar coma should be made depending on the major expression of ketoacidosis or hyperglycemic hyperosmolarity.     

Lactic Acidosis in Diabetes

Lactic acidosis is occasionally responsible for metabolic acidosis in diabetics. It may occur in the presence of normal blood levels of the ketone bodies, and such cases are often described as having “non-ketotic diabetic acidosis.” Lactic acid may contribute to the metabolic acidosis in patients with true diabetic ketoacidosis, but the blood lactate concentrations in these patients are not usually very high. In some patients the ketoacidosis is replaced by a lactic acidosis during treatment. This usually occurs in association with a serious underlying disorder and is associated with a poor prognosis. A transient increase in blood lactate concentration was in fact observed in most patients after the beginning of treatment, but the significance of this finding is uncertain.     

Management of diabetes mellitus in children.

In many respects the management of diabetes mellitus in children differs from the management in adults. Guidelines for the short- and long-term management of the child with diabetes mellitus, particularly as it relates to clinical presentation, treatment of ketoacidosis, long-term therapy and psychological counseling, are presented. The specific aspects of diabetes management that are unique to the child are best met by an increased understanding of the problems by the child and the family and an integrated approach by the physician and allied health personnel.     

Lactic acidosis and ketoacidosis: biochemical and clinical implications.

A case of lactic acidosis presented the opportunity for review of the association between lactic acidosis and ketoacidosis. The diagnosis of lactic acidosis or the combination of lactic acidosis and ketoacidosis is established clinically by the detection of a metabolic acidosis of the "unmeasured anion gap" type in the absence of significant renal failure, poison intake or a strongly positive clinical test for ketones. Before treatment can be planned the biochemical basis of lactic acidosis and ketoacidosis must be understood -- especially the fact that lactic acidosis is not a single disease entity but has many possible causes. Among important considerations is the relation between the blood concentrations of bicarbonate and organic acid anions. After recovery from metabolic acidosis of the unmeasured anion gap type, metabolic alkalosis is common. Decreased bicarbonate excretion plays an important role in the pathogenesis of the latter and may be the result of potassium or chloride loss, or both. The deficits, if present, should be corrected with appropriate therapy.     

Analysis of the cause of death in diabetic ketoacidosis based on 5 years of personal observation

The authors observed 53 cases of diabetic ketoacidosis treated with low doses of insulin. Mean age of the patients was 41 +/- 17 years, duration of diabetes mellitus 7.5 +/- 6.4 years. Ketoacidosis was due to: infections in 36%, other diseases in 7%, and cessation of insulin therapy in 25% of cases. Ketoacidosis was a first sign of diabetes mellitus in 19% of cases while causative factor was not detected in 13% of cases. At the admission to hospital mean blood pH was 7.02 +/- 0.15, mean bicarbonate concentration 6.17 +/- 3.45 mM/l, and glycaemia 40.6 +/- 16.8 mM/l. Therapy of ketoacidosis was complicated by hypopotassemia in 1 patient and transient hypoglycaemia in another patient. Five patients (9.6%) died. Infections, myocardial infarction, acute pancreatitis, pulmonary edema, and disseminated intravascular coagulation were the causes of deaths.     

Gene therapy for murine glycerol kinase deficiency: importance of murine ortholog

A glycerol kinase (Gyk) knock-out (KO) mouse model permits improved understanding of glycerol kinase (GK) deficiency (GKD) pathogenesis, however, early death of affected mice limits its utility. The purpose of this work was to delay death of affected males to investigate thoroughly their phenotypes. An adenoviral vector carrying the human (Adeno-XGK) or mouse (Adeno-XGyk) GK gene was injected into KO mice within 24 h of birth. Adeno-XGK did not change KO mouse survival time despite liver GK activity greater than 100% of wild type. However, Adeno-XGyk improved KO mouse survival time greater than two-fold. These investigations demonstrate that gene replacement therapy for Gyk KO mice is more efficacious using murine Gyk than human GK. These studies expand our understanding of GKD pathogenesis in the murine model, and show that while murine GKD is more severe than in humans, GKD mice have similar metabolic disturbances to affected humans with hypoglycemia and acidemia.     

Diabetic Ketoacidosis Presenting as Neurosurgical Emergencies

Three cases of ketoacidosis in previously unsuspected diabetics are described. Each was admitted to hospital as a neurosurgical emergency. The recognition of this rare presentation is stressed since prompt treatment of the metabolic disturbance rapidly resolves the neurological abnormality.     

Adaptation of red cell enzymes and intermediates in metabolic disorders.

The metabolic activity of the red cell glycolytic pathway hexose monophosphate shunt (HMP) with dependent glutathione system was studied in patients with hyperthyroidism (n = 10), hyperlipoproteinemia (n = 16), hypoglycemia (n = 25) and hyperglycemia (n = 23). In uncontrolled diabetics and patients with hyperthyroidism the mean value of glucose phosphate isomerase (GPI), glucose-6-phosphate dehydrogenase (G-6-PD), glutathione reductase (GR) was increased, whereas these enzyme activities were reduced in patients with hypoglycemia. Apart from a few values of hexokinase (HK) which were lower than normal the results in hyperlipoproteinemia patients remained essentially unchanged, including the intermediates such as 2,3-diphosphoglycerate (2,3-DPG), adenosine triphosphate (ATP) and reduced glutathione (GSH). While increased rates of 2,3-DPG and ATP in hypoglycemia patients were obtained, these substrates were markedly reduced in diabetics.     

Hypothermia, Metabolic Stress, and NMDA-Mediated Excitotoxicity

Abstract: Isolated embryonic retinas were metabolically stressed by inhibition of glycolysis either with iodoacetate (IOA) or by glucose withdrawal plus 10 mM 2-deoxy-D-glucose, and the effects of hypothermia were examined. Incubation at 30 versus 37°C during 30 min of hypoglycemia with IOA completely reduced the rapid swelling-related GABA release [6 ± 2 vs. 68 ± 10 nmol/100 mg of protein (mean ± SEM) for 30 and 37°C, respectively]. Histology of the retina immediately following 30 min of metabolic stress at 30°C appeared normal, whereas that at 37°C showed a pattern of acute edema, characteristic of NMDA-mediated acute excitotoxicity. Coincubation with a competitive or noncompetitive NMDA antagonist, respectively, CGS-19755 (10 μM) or MK-801 (1 μM), during 30 min of hypoglycemia at 37°C completely prevented tissue swelling, whereas extracellular GABA content remained at basal levels, indicating that the cytotoxic effects of IOA treatment for 30 min at 37°C were NMDA receptor mediated. Longer periods of hypoglycemia at 37° C produced acute toxicity that was only partially NMDA receptor mediated. Hypothermia delayed the onset of NMDA-mediated toxicity by 30–60 min. At 30°C, the rate of loss of ATP was slowed during the first several minutes of hypoglycemia (82 and 58% of maximal tissue levels at 30 and 37° C, respectively, at 5 min), but by 10 min, ATP levels were comparably reduced. After a transient exposure of retina to 50 μM NMDA in Mg²⁺-free medium, hypothermia significantly attenuated acute GABA release by 30%. At 24 h of recovery, lactate dehydrogenase release was decreased by 37%. Hypothermia had no effect when the exposure was done in medium containing physiological concentrations of Mg²⁺. The above results suggest that the protective effect of hypothermia during the metabolic insult is predominately directed at the cellular events that lead up to NMDA receptor involvement. Reduction in the rate of loss of ATP, however, does not fully account for the delay in involvement of NMDA receptors during metabolic stress at 30°C. The attenuation of direct NMDA-mediated toxicity in Mg²⁺-free medium further suggests that decreased temperature may result in altered channel properties during situations when the Mg²⁺ block is lifted.