Peritoneal dialysis in maple-syrup-urine disease: studies on branched-chain amino and keto acids

Enhanced interactions among gut mycobiomes with the deterioration of glycemic control

BACKGROUND

The gut mycobiome is closely linked to health and disease; however, its role in the progression of type 2 diabetes mellitus (T2DM) remains obscure. Here, a multi-omics approach was employed to explore the role of intestinal fungi in the deterioration of glycemic control.

METHODS

350 participants without hypoglycemic therapies were invited for a standard oral glucose tolerance test to determine their status of glycemic control. The gut mycobiome was identified through internal transcribed spacer sequencing, host genetics were determined by genotyping array, and plasma metabolites were measured with untargeted liquid chromatography mass spectrometry.

FINDINGS

The richness of fungi was higher, whereas its dissimilarity was markedly lower, in participants with T2DM. Moreover, the diversity and composition of fungi were closely associated with insulin sensitivity and pancreatic β-cell functions. With the exacerbation of glycemic control, the co-occurrence network among fungus taxa became increasingly complex, and the complexity of the interaction network was inversely associated with insulin sensitivity. Mendelian randomization analysis further demonstrated that the Archaeorhizomycetes class, Fusarium genus, and Neoascochyta genus were causally linked to impaired glucose metabolism. Furthermore, integrative analysis with metabolomics showed that increased 4-hydroxy-2-oxoglutaric acid, ketoleucine, lysophosphatidylcholine (20:3/0:0), and N-lactoyl-phenylalanine, but decreased lysophosphatidylcholine (O-18:2), functioned as key molecules linking the adverse effect of Fusarium genus on insulin sensitivity.

CONCLUSIONS

Our study uncovers a strong association between disturbance in gut fungi and the progression of T2DM and highlights the potential of targeting the gut mycobiome for the management of T2DM.

FUNDINGS

This study was supported by MOST and NSFC of China.

Emergency dialysis in neonatal metabolic crises

Metabolic crises in children with inborn errors of metabolism are caused by the accumulation of neurotoxic metabolites. Rapid elimination of these metabolites is apparently crucial to prevent irreversible neuronal damage; long-term outcome is correlated with the rate of toxin removal during the crisis. The usefulness of different blood purification techniques for removing accumulated neurotoxins is reviewed in this manuscript.

Removal of branched-chain amino acids and alpha-ketoisocaproate by haemofiltration and haemodiafiltration

Venovenous haemofiltration (VVHF) and haemodiafiltration (VVHDF) were performed with a neonatal haemo(dia)filter (Miniflow 10, Hospal) on 8 anaesthetized rabbits infused with branched-chain amino acids (leucine, isoleucine and valine) and alpha-ketoisocaproate. The branched-chain amino acids (BCAA) and alpha-ketoisocaproate blood levels were close to those previously observed in neonates with maple syrup urine disease when extracorporeal blood purification was required. VVHF and VVHDF performances were assessed with two different blood flows (Qb = 8.3 and 16.6 ml/min). VVHDF was performed with four dialysate flow rates (Qd = 0.5, 1.0, 2.0 and 3.0 L/h). Within each period, clearances of the three BCAA were strictly similar. BCAA clearances obtained by VVHF were similar to ultrafiltration rates (respectively, 0.78 +/- 0.14 and 1.79 +/- 0.28 ml/min at high and low Qb; p < 0.05). The alpha-ketoisocaproate clearances obtained by VVHF were 0.39 +/- 0.17 and 0.92 +/- 0.43 ml/min at low and high Qb (not significantly different). Whatever the Qd value, the VVHDF procedures always allowed higher BCAA and alpha-ketoisocaproate clearances as compared with the corresponding VVHF period with similar Qb. BCAA clearances obtained by VVHDF with a 0.5 L/h dialysate flow were 4.1 +/- 0.5 and 5.4 +/- 0.5 mL/min at low and high Qb, respectively. The concurrent alpha-ketoisocaproate clearances were 2.5 +/- 0.8 and 2.9 +/- 1.0 ml/min.

Organic acidurias: a review. Part 2

Laboratory findings are an essential part of the diagnostic approach to organic acidemias. In most organic acidemias, metabolism of glucose, ketone bodies, and ammonia is deranged primarily or secondarily, in addition to derangement of the acid-base balance. Hypoglycemia, lactic and/or ketoacidosis, and hyperammonemia of varying severity accompany the overt or compensated acidosis. In most instances, a definite diagnosis will be achieved by gas chromatography/mass spectrometry (GC/MS) studies of the urine. We detail the pattern of excreted organic acids in the major disorders. When the diagnosis reached by clinical and laboratory assessments is not conclusive, it must be supported by loading tests. We list the available methods of demonstrating the putative enzyme deficiency in the patient's cells and tissues. The majority of organic acidemias may be treated by limiting the source of or removing the toxic intermediary metabolite. We provide lists of available diets, supplements, and medications. In some instances, residual defective enzyme activity may be stimulated. We describe symptomatic management of the disturbed acid-base and electrolyte balance.

Peritoneal dialysis in the treatment of metabolic crises caused by inherited disorders of organic and amino acid metabolism

Four neonates who presented with coma secondary to hyperammonaemia resulting in central respiratory failure were treated with peritoneal dialysis for between 16 and 120 hours. Underlying diseases were maple-syrup-urine disease, propionic acidaemia and citrullinaemia in two patients. Clinical improvement was observed in three patients within 16 to 72 hours after institution of peritoneal dialysis. Biochemical analysis revealed a rapid reduction in plasma concentration of leucine, isoleucine and valine as well as their alpha-keto-analogues in the infant suffering from maple-syrup-urine disease. Correction of ammonia, glycine, alanine and propionic acid concentrations was observed in the infant with propionic acidaemia 24-72 hours after institution of peritoneal dialysis. Severe hyperammonaemia (1,000-2,500mumol/l) in two infants with citrullinaemia before peritoneal dialysis was treated successfully in one infant; whereas the second infant showed no clinical improvement despite amelioration of biochemical parameters. Glucose-absorption from peritoneal dialysis solution was in the range of 216-441 mg/kg/h.

Hudson memorial lecture. Neonatal management of organic acidurias. Clinical update

Therapeutic guidelines have been obtained from a retrospective review of 41 patients affected with organic acidaemias, 16 patients with neonatal maple syrup urine disease (MSUD), 11 methylmalonic acidaemia, (MMA) seven propionic acidaemias (PA) and seven isovaleric acidaemias (IVA), and by comparing this personal series with similar reported cases. The emergency treatment of these organic acidurias in the neonate has to main goals: toxin removal and anabolism. Anabolism is always promoted by early diet therapy. The best method of toxin removal depends on the nature of the defect; peritoneal dialysis with exchange transfusions or multiple or prolonged exchange transfusions in MSUD and in PA, diuresis and exchange transfusions in MMA and glycine supplementation in IVA. Vitamin supplementation (thiamine 20 mg, biotin 10 mg, B12 2 mg and riboflavin 100 mg) should be tried in all cases although the neonatal forms of these defects are very rarely vitamin responsive. Additional treatments such as carnitine or insulin may prove to be useful.

Organic acids and branched-chain amino acids in body fluids before and after multiple exchange transfusions in maple syrup urine disease

We successfully treated a critically ill infant with the classical type of maple syrup urine disease by multiple exchange transfusions via a peripheral artery and vein and with positive calorie supplementation in the early stage of therapy. Clinical improvement was definite after the plasma leucine level fell below 1 mmol/l. There was a close linear correlation between plasma concentrations of branched-chain amino acids and their corresponding branched-chain alpha-keto acids and branched-chain alpha-hydroxy acids. alpha-Hydroxy acids were more easily excreted in the urine than alpha-keto acids and amino acids. Our studies on urinary organic acids supported the existence of minor metabolic pathways of branched-chain alpha-keto acids, although they were not thought to be important in eliminating accumulated alpha-keto acids. Urinary excretion of succinic acid and alpha-ketoglutaric acid, which are components of the citric acid cycle, increased transiently during the patient's convalescence. The cerebrospinal fluid/plasma ratios for branched-chain amino acids, alpha-keto acids, and alpha-hydroxy acids were very high before the transfusions and decreased after improvement. The cerebrospinal fluid/plasma ratios for 5-carbon acids, alpha-ketoisovaleric acid and alpha-hydroxyisovaleric acid were much higher than for other branched-chain acids not only in the patient but also in normal controls. Cerebrospinal fluid levels of alpha-ketoisocaproic acid and alpha-hydroxyisovaleric acid were as high as 1 mmol/l in our patient.

Maple syrup urine disease--therapeutic use of insulin in catabolic states

High and neurotoxic blood levels of leucine and its ketoanalogue develop in catabolic patients with maple syrup urine disease. The use of relatively high doses of insulin and additional glucose had a more pronounced effect on lowering leucine (and alpha-ketoisocaproate) blood levels than dietary elimination of leucine alone. This is demonstrated in 2 neonates after blood exchange transfusion and in one 4-months old patient suffering from febrile diarrhea.

Exchange transfusion in acute episodes of maple syrup urine disease. Studies on branched-chain amino and keto acids

Two neonates with maple syrup urine disease were treated by exchange transfusion. Within 15 h blood leucine and KICA concentrations were lowered from 2.6 mM to 1.1 mM using 570 to 620 ml blood per kg body weight. The other branched-chain amino acid/keto acid pairs fell to normal. During exchange transfusion the patient's nitrogen balance seems to be negative. Further exchange transfusion was useless. More importantly the patient should be forced into an anabolic state by high caloric supply or insulin plus glucose treatment. More KICA than leucine was eliminated, however, KICA blood levels remained slightly higher than that of leucine indicating different leucine/KICA equilibria in extravascular compartments than in blood. In a given time interval exchange transfusion was more effective than peritoneal dialysis, probably due to a lack of an additional (peritoneal) membrane. Renal excretion of branched-chain amino and keto acids was very inefficient. The allegedly most toxic metabolite, KICA, had the lowest renal clearance of the branched-chain keto acids.