Confusion after antibiotics

D-Lactate: Implications for Gastrointestinal Diseases

D-lactate is produced in very low amounts in human tissues. However, certain bacteria in the human intestine produce D-lactate. In some gastrointestinal diseases, increased bacterial D-lactate production and uptake from the gut into the bloodstream take place. In its extreme, excessive accumulation of D-lactate in humans can lead to potentially life-threatening D-lactic acidosis. This metabolic phenomenon is well described in pediatric patients with short bowel syndrome. Less is known about a subclinical rise in D-lactate. We discuss in this review the pathophysiology of D-lactate in the human body. We cover D-lactic acidosis in patients with short bowel syndrome as well as subclinical elevations of D-lactate in other diseases affecting the gastrointestinal tract. Furthermore, we argue for the potential of D-lactate as a marker of intestinal barrier integrity in the context of dysbiosis. Subsequently, we conclude that there is a research need to establish D-lactate as a minimally invasive biomarker in gastrointestinal diseases.

D-lactic acidosis in humans: systematic literature review

BACKGROUND

D-lactic acidosis is an uncommon and challenging form of metabolic acidosis that may develop in short bowel syndrome. It has been documented exclusively in case reports and small case series.

METHODS

We performed a review of the literature in the National Library of Medicine and Excerpta Medica databases.

RESULTS

We identified 84 original reports published between 1977 and 2017. D-lactic acidosis was observed in 98 individuals ranging in age from 7 months to 86 years with short bowel syndrome. The clinical presentation included Kussmaul breathing, confusion, slurred speech, and gait disturbances. Furthermore, among 99 consecutive patients with short bowel syndrome, 21 reported having episodes with symptoms consistent with D-lactic acidosis. In addition, D-lactic acid might also contribute to acidosis in diabetes mellitus. Finally, abnormally high D-lactic acid was documented after administration or ingestion of large amounts of propylene glycol, as paraneoplastic phenomenon and perhaps also in a so far poorly characterized inherited inborn error of metabolism.

CONCLUSIONS

In humans with short bowel syndrome (or carbohydrate malabsorption), D-lactic acidosis is likely rather common and under-recognized. This condition should be included in the differential diagnosis of unexplained high-gap metabolic acidosis where the anion causing the acidosis is not known. Furthermore, diabetic acidosis might be caused by accumulation of both ketone bodies and D-lactic acid. Finally, there are endogenous sources of D-lactic acid in subjects with propylene glycol intoxication.

Stereoselective effects of lactate enantiomers on the enhancement of 3T3-L1 adipocyte differentiation

Lactate contains a chiral carbon and thus has two optical isomers-d-lactate and l-lactate. l-Lactate is the predominant form that is produced by the body and can be delivered to the organs. On the other hand, gut microbiota produce both isomers, which can then flow into the body. Although both d-lactate and l-lactate can contribute to energy metabolism, their potential roles in adipocyte differentiation remain to be elucidated. Here, we investigated the effects of l-lactate and d-lactate on the differentiation of 3T3-L1 preadipocytes. Both lactate enantiomers were demonstrated to enhance triglyceride accumulation by stimulating the early phase of adipocyte differentiation. Notably, d-lactate was more potent than l-lactate in inducing triglyceride accumulation. The degree of triglyceride accumulation induced by l-lactate was similar to that induced by pyruvate. d-Lactate was more potent than l-lactate in increasing the activity of glycerol-3-phosphate dehydrogenase. Both lactate enantiomers did not affect cell viability. Moreover, both enantiomers upregulated the expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, sterol regulatory element-binding protein-1c, and fatty acid synthase, with d-lactate exerting stronger effects than l-lactate. By contrast, lactate did not influence the expression of C/EBPβ and C/EBPδ. d-Lactate significantly increased and l-lactate tended to increase p38 MAPK phosphorylation, and the p38 MAPK inhibitor SB203580 inhibited the stimulation of adipocyte differentiation by d-lactate and l-lactate. These findings showed that both lactate enantiomers stimulate preadipocyte differentiation, with d-lactate showing more potent effects than l-lactate. In addition, our study demonstrated that d-lactate and l-lactate exert different effects on physiological events.

A stand-alone synbiotic treatment for the prevention of D-lactic acidosis in short bowel syndrome

Synbiotics are combinations of probiotics and prebiotics that have recently been used in the context of various gastrointestinal diseases, including infectious enteritis, inflammatory bowel disease, and bowel obstruction. We encountered a patient with recurrent D-lactic acidosis who was treated successfully for long periods using synbiotics. The patient was diagnosed as having short bowel syndrome and had recurrent episodes of neurologic dysfunction due to D-lactic acidosis. In addition to fasting, the patient had been treated with antibiotics to eliminate D-lactate-producing bacteria. After the failure of antibiotic treatment, a stand-alone synbiotic treatment was started, specifically Bifidobacterium breve Yakult and Lactobacillus casei Shirota as probiotics, and galacto-oligosaccharide as a prebiotic. Serum D-lactate levels declined, and the patient has been recurrence-free for 3 years without dietary restriction. Synbiotics allowed the reduction in colonic absorption of D-lactate by both prevention of D-lactate-producing bacterial overgrowth and stimulation of intestinal motility, leading to remission of D-lactate acidosis.

D-Lactic acidosis 25 years after bariatric surgery due to Salmonella enteritidis

D-Lactic acidosis is a rare complication that occurs in patients with short bowel syndrome due to surgical intestine resection for treatment of obesity. The clinical presentation is characterized by neurologic symptoms and high anion gap metabolic acidosis. The incidence of this syndrome is unknown, probably because of misdiagnosis and sometimes symptoms may be incorrectly attributed to other causes. Therapy is based on low carbohydrate diet, sodium bicarbonate intravenous, rehydratation, antiobiotics, and probiotics that only produce L-lactate. In the case we describe, D-lactic acidosis encephalopathy occurred 25 y after bypass jejunoileal, due to Salmonella enteriditis infection.

D-lactic acidosis

D-lactic acidosis, also referred to as D-lactate encephalopathy, is a rare neurologic syndrome that occurs in individuals with short bowel syndrome or following jejuno-ileal bypass surgery. Symptoms typically present after the ingestion of high-carbohydrate feedings. Neurologic symptoms include altered mental status, slurred speech, and ataxia, with patients often appearing drunk. Onset of neurologic symptoms is accompanied by metabolic acidosis and elevation of plasma D-lactate concentration. In these patients, malabsorbed carbohydrate is fermented by an abnormal bacterial flora in the colon, which produces excessive amounts of D-lactate. High amounts of D-lactate are absorbed into the circulation, resulting in an elevated concentration of D-lactate in the blood. Development of neurologic symptoms has been attributed to D-lactate, but it is unclear if this is the cause or whether other factors are responsible. This review examines the pathophysiology of the production and accumulation of D-lactate while exploring the potential factors contributing to the development of neurologic manifestations. Methods of diagnosis and treatment are reviewed. Areas requiring further investigation are identified.

D-lactate in human and ruminant metabolism

D-lactate is normally present in the blood of mammals at nanomolar concentrations due to methylglyoxal metabolism; millimolar d-lactate concentrations can arise due to excess gastrointestinal microbial production. Grain overload in ruminants, short-bowel syndrome in humans, and diarrhea in calves can all result in profound D-lactic acidemia, with remarkably similar neurological manifestations. In the past, D-lactate was thought to be excreted mainly in the urine, and metabolized slowly by the enzyme d-alpha-hydroxy acid dehydrogenase. More recent studies reported that mammals have a relatively high capacity for D-lactate metabolism and identified a putative mammalian D-lactate dehydrogenase. A growing body of literature is also emerging describing subclinical elevation of D-lactate as an indicator of sepsis and trauma. This article describes advances in the understanding of D-lactate metabolism, D-lactic acidosis in ruminants and humans, and subclinical elevation of d-lactate.

Neurologic complications of radiation therapy

Injury to the central and peripheral nervous systems is an increasingly frequent consequence of standard radiation treatment protocols for tumors involving or adjacent to nervous system structures. Characteristic temporal, clinical, radiographic, and laboratory features distinguish a number of specific radiation injury syndromes, but meticulous and repeated evaluations over time are often required to establish a diagnosis. These syndromes vary with regard to prognosis and therapeutic options, and competing diagnoses with very different natural histories and therapies often mask or mimic the signs and symptoms of radiation-related nervous system injury. The ability to efficiently negotiate this complicated differential diagnostic landscape allows for early diagnosis of tumor recurrence or an alternative etiology, prompt institution of appropriate therapy, avoidance of unnecessary diagnostic studies, and confident prognostication for patients and families. Even after the diagnosis of a radiation-related complication is made, continued vigilance for additional sites or manifestations of radiation injury is mandatory. Meanwhile, further research into treatment, prevention, and the causes of individual susceptibility to radiation injury are essential.