Metabolic utilization and renal handling of D-lactate in men

53-years-old with mental status changes

D-lactic acidosis, a complication of short bowel syndrome, presents with a variety of neurological symptoms and metabolic acidosis. Treatment is hydration, replacement of nutritional deficiency replacement, and selective antibiotics. Prevention entails complex carbohydrate diet and vitamin and mineral supplements.

Metabolic acidosis: separation methods and biological relevance of organic acids and lactic acid enantiomers

Metabolic acidosis can result from accumulation of organic acids in the blood due to anaerobic metabolism or intestinal bacterial fermentation of undigested substrate under certain conditions. These conditions include short-bowel syndrome, grain overfeeding of ruminants and, as recently reported, severe gastroenteritis. Measuring fermentation products such as short-chain fatty acids (SCFAs) and lactic acid in various biological samples is integral to the diagnosis of bacterial overgrowth. Stereospecific measurement of D- and L-lactic acid is necessary for confirmation of the origin and nature of metabolic acidosis. In this paper, methods for the separation of SCFAs and lactic acid are reviewed. Analysis of the organic acids involved in carbohydrate metabolism has been achieved by enzymatic methods, gas chromatography, high-performance liquid chromatography and capillary electrophoresis. Sample preparation techniques developed for these analytes are also discussed.

Metabolic acidosis in the intensive care unit

Metabolic acidosis is a common occurrence in critically ill patients. Understanding the pathological mechanisms underlying the generation of protons will enable the clinician to quickly recognize these disorders and establish an acceptable treatment strategy. This article presents a logical approach to metabolic acidosis.

D-lactic acidosis 23 years after jejuno-ileal bypass

Accumulation of D-lactate after gastrointestinal surgery, particularly jejuno-ileal bypass, is an uncommon and often misdiagnosed clinical disturbance. The syndrome may be complicated by dizziness, ataxia, confusion, headache, memory loss, and aggressive behavior. Serum chemistries are often deceptive because the anion gap is frequently normal in spite of severe metabolic acidosis. Moreover, the urine anion gap may be positive, incorrectly suggesting a defect in renal net acid excretion. Indeed, the combination of a normal anion gap metabolic acidosis and positive urine anion gap may erroneously suggest a diagnosis of renal tubular acidosis. Importantly, all reported cases of D-lactic acidosis secondary to bypass surgery have been encountered within 5 to 10 years following the surgery. Here we present an unusual case of D-lactic acidosis (complicated by encephalopathy) presenting 23 years after a jejuno-ileal bypass procedure. The patient was initially diagnosed with a drug intoxication secondary to benzodiazepines. Ultimately, the diagnosis of D-lactate encephalopathy was established after challenging the patient with a carbohydrate load. Thus, administration of 40 kcal/kg over 16 hours reproduced the clinical syndrome and was accompanied by a marked increment in serum and urine D-lactate concentration. The patient had sustained resolution of her symptoms after treatment with oral vancomycin.

Assay of D-lactate in urine of infants and children with reference values taking into account data below detection limit

Accumulation of D-lactic acid produced by intestinal bacteria such as streptococci and lactobacilli has been extensively studied in ruminants [1-4]. In humans an increased production of D-lactate by intestinal bacteria under pathological conditions such as the short bowel syndrome can cause metabolic acidosis [5-8]. Since the lactate assays routinely used only measure L-lactate we developed a sensitive method of D-lactate quantification and established reference values in spot urines of infants and children (0 to 4 years of age). The enzymatic method with fluorimetric quantification of NADH is linear up to 2 mmol/l. It has a detection limit of 3.4 micromol/l. Among structurally related organic acids an interference was found only for L-lactate and DL-2-hydroxybutyrate at concentrations which are way beyond their physiological excretion. One hundred and sixty five spot urines of healthy Swiss (S), Austrian (A), German (G) and Chilean (CHI) infants aged from 0 to 4 years were analyzed. The distribution of the data is close to a lognormal one. Values below the detection limit were simulated and age groups were formed. In all populations D-lactate excretion was found highest during the first year of life; it declines with age during infancy and remains stable from 2.5 to 4 years of age. We show that D-lactate is excreted physiologically by healthy infants and children below 4 years of age and present reference values for D-lactate excretion which show some differences between the populations tested.

D-lactic acidosis: pathologic consequence of saprophytism

In this report, we describe a 50-year-old woman with a short bowel who had recurrent episodes of weakness, ataxia, slurred speech, confusion, and nausea. D-Lactic acidosis was diagnosed on the basis of a D-lactate level of 8.2 mmol/L (normal, 0 to 0.25) obtained during an episode of confusion. D-Lactic acidosis is a potentially fatal clinical condition seen in patients with a short small intestine and an intact colon. Excessive production of D-lactate by abnormal bowel flora overwhelms normal metabolism of D-lactate and leads to an accumulation of this enantiomer in the blood. This disorder provides insight into the role of intestinal flora in human metabolism and demonstrates the manner in which altered intestinal flora can produce disease in humans. Increased awareness of D-lactic acidosis is necessary for prompt and appropriate treatment. The pathophysiology and treatment of D-lactic acidosis are reviewed.

D-lactic acidosis. A review of clinical presentation, biochemical features, and pathophysiologic mechanisms

This report describes a case of d-lactic acidosis observed by the authors and then reviews all case reports of d-lactic acidosis in the literature in order to define its clinical and biochemical features and pathogenetic mechanisms. The report also reviews the literature on metabolism of d-lactic acid in humans. The clinical presentation of d-lactic acidosis is characterized by episodes of encephalopathy and metabolic acidosis. The diagnosis should be considered in a patient who presents with metabolic acidosis and high serum anion gap, normal lactate level, negative Acetest, short bowel syndrome or other forms of malabsorption, and characteristic neurologic findings. Development of the syndrome requires the following conditions 1) carbohydrate malabsorption with increased delivery of nutrients to the colon, 2) colonic bacterial flora of a type that produces d-lactic acid, 3) ingestion of large amounts of carbohydrate, 4) diminished colonic motility, allowing time for nutrients in the colon to undergo bacterial fermentation, and 5) impaired d-lactate metabolism. In contrast to the initial assumption that d-lactic acid is not metabolized by humans, analysis of published data shows a substantial rate of metabolism of d-lactate by normal humans. Estimates based on these data suggest that impaired metabolism of d-lactate is almost a prerequisite for the development of the syndrome.

Colonic lactate metabolism and D-lactic acidosis

D-Lactic acidosis is seen in patients with intestinal bypass or short bowels in whom colonic produced D-lactate accumulates. An intestinal bypassed patient with D-lactic acidosis had higher fecal D-lactate (122.4 mmol/liter) and L-lactate (90.1 mmol/liter) than described before in humans. D-Lactate fluctuated between 0.5 and 3.1 mmol/liter in plasma (normal < 0.1 mmol/liter) and between 1.1 and 52.8 mmol/liter in urine (normal < 0.7 mmol/liter) within a few hours, indicating that the human organism do metabolize and excrete D-lactate. The patient with D-lactic acidosis had a 10-fold increased DL-lactate production from glucose in fecal homogenates compared to 14 healthy controls and a patient with intestinal bypass, who did not have D-lactic acidosis. A 67% carbohydrate (starch)-enriched diet resulted in a minor elevation of fecal and plasma lactate, whereas 50 + 100 + 150 g of ingested lactose increased D-lactate in feces (84.0 mmol/liter) and plasma (2.3 mmol/liter) considerably in the patient with D-lactic acidosis. Intestinal prolongation (22 cm ileum) had a temporary effect on fecal and plasma D-lactate, but intestinal continuity was reestablished 26 months later because D-lactic acidosis recurred (plasma 8.6 mmol/liter, urine 101.3 mmol/liter). Large amounts of lactulose (160 g/day) to 12 normal individuals increased D-lactate to 13.6 +/- 3.5 mmol/liter in feces, but never increased D-lactate in plasma or urine. The in vitro fermentation of glucose in fecal homogenates increased DL-lactate, which disappeared after complete metabolization of the glucose. L-Lactate was converted to D-lactate and vice versa, and both were degraded to the short-chain fatty acids acetate, propionate, and butyrate. An infrequent, but elevated ability of the colonic flora to produce lactate may be a prerequisite for D-lactic acidosis to occur and may explain why the syndrome is so seldom seen even in patients with intestinal bypass or short bowels. The suggestion that D-lactate is not metabolized and hence accumulates is probably not valid.

Review article: practical management of the short bowel

A shortened small intestine may end at a stoma or be anastomosed to the colon. Patients with a jejunostomy, but not those with a colon, lose large amounts of sodium. The intake and absorption of sodium can be increased by sipping a sodium-glucose solution; stomal loss can be reduced by restricting water or low-sodium drinks. If a stoma is situated less than 100 cm along the jejunum, a constant negative sodium balance may necessitate parenteral saline supplements. Gastric anti-secretory drugs or a somatostatin analogue reduce jejunostomy losses in such patients but do not restore a positive sodium balance. Loperamide or codeine phosphate benefit some patients. Magnesium deficiency can usually be corrected by oral magnesium oxide supplements. An elemental or hydrolysed diet is not beneficial. Patients with a jejunostomy can maintain a normal diet without fat reduction. When the colon is present, unabsorbed carbohydrate is fermented to absorbable short chain fatty acids. Unabsorbed long chain fatty acids and bile salts cause watery diarrhoea and increased colonic oxalate absorption with hyperoxaluria. Such patients benefit from a high carbohydrate, low-fat and low-oxalate diet. Parenteral nutrition is needed only by the few patients unable to maintain health or avoid socially disabling diarrhoea despite these measures.

Fecal lactate and short bowel syndrome

In patients with short bowel syndrome (SBS), the carbohydrate overload to the colon may disturb the normal pattern of colonic fermentation with production of D-lactic acid and subsequent development of a metabolic D-lactic acidosis. We measured D-lactic acid in blood, urine, and feces, as well as the composition of fecal water and fecal reducing substances from 11 patients with SBS, comparing the results with those from normal subjects. The fecal water from patients with SBS was characterized by low pH, potassium, and volatile fatty acids, high osmotic gap, and high concentration of L- and D-lactic acid. Five of 11 had abnormal amounts of fecal reducing substances. Fecal D-lactic acid was increased in nine of 11 patients. However, none of these patients showed D-lactic acid in urine, and only one had a very low concentration in plasma. These results show that D-lactic acid was overproduced in the colon of most of the patients with SBS. However, other factors such as absorption or impaired D-lactic acid metabolism may be necessary for a plasmatic increase of D-lactic acid.

D-lactic acidosis: a treatable encephalopathy in pediatric patients

A 20-month old infant, who had short bowel syndrome following extensive surgery for a mid gut volvulus, developed hyperchloremic acidosis, with a large anion gap after enteral feeding was instituted. The organic acidosis was at least partly due to an increased concentration of D-lactic acid. This patient, as did five other pediatric patients, presented with a typical encephalopathy syndrome. Early recognition of this syndrome and treatment with an intestinal antibiotic and discontinuation of enteral feeding enabled prompt correction of the hyperchloremic acidosis and a rapid clinical recovery.

Fluorimetric assay of D-lactate

A fluorimetric assay for D-lactate in human blood samples was developed using an endpoint enzymatic assay with D-lactate dehydrogenase from Staphylococcus epidermidis. The intrabatch and interbatch coefficients of variance were 8.7% (n = 4) and 16.6% (n = 4), respectively. The limit of detection in blood was 3.73 nmol/ml. The assay suffers minor interference from S-D-lactoylglutathione, which was also present in the blood samples. The concentration of D-lactate in blood was (mean +/- SE, nmol/ml) normal healthy individuals, 11.0 +/- 1.2 (n = 7); and diabetic patients, 20.0 +/- 1.3 (n = 55) (a significant increase in diabetes mellitus; P < 0.01, Mann-Whitney U test).

Lactic acid isomers and fatty acids in sinus secretion: a longitudinal study of bacterial and leukocyte metabolism in experimental sinusitis

Concentrations of the two optic isomers of lactate (D- and L-form) as well as glucose, succinate, acetate, butyrate, isovalerate and valerate were examined in purulent sinus secretions. The samples were obtained from rabbit maxillary sinuses, experimentally infected with Streptococcus pneumoniae or Bacteroides fragilis. More soluble acids such as acetate displayed relatively low levels in the secretion, despite a high microbial production. A substantial increase in D-lactate concentration was found in secretions only the first day after induction of pneumococcal sinusitis, and not in bacteroides sinusitis. L-lactate levels were particularly high in secretions of a marked purulent character, and this isomer can be considered as indicator of anaerobic glycolysis in the leukocytes. Less diffusible fatty acids such as butyrate and isovalerate accumulated in the secretion, in spite of a relatively lower production rate, and are thus more reliable indicators of bacterial metabolism.

Effect of parenteral nutrition and enteral feeding on D-lactic acidosis in a patient with short bowel

D-Lactic acid can accumulate in blood in some patients with intestinal failure, leading to a clinical syndrome of severe acidosis and encephalopathy. The possible impact of parenteral nutrition on its clinical course has not been established. One patient with a severe short-bowel syndrome supported by long-term parenteral nutrition who suffered repeated episodes of ataxia and disorientation associated with elevated serum levels of D-lactate was studied. Results demonstrated no impact of glucose- vs lipid-based parenteral nutrition formulations on total acid production or serum D-lactic acid levels, increased serum D-lactate levels during administration of neomycin, but prompt resolution of both acidosis and clinical symptoms with discontinuation of oral intake. This study confirms the findings of other investigators that D-lactic acidosis may be a significant, heretofore unappreciated complication in patients with severe short-bowel syndrome, and that prompt resolution may be effected with abrupt discontinuation of oral intake. Furthermore, the present study suggests neither a detrimental nor a beneficial effect of parenteral nutrition on this syndrome.