Lactate Infusion Research Articles

Comparison of Ringer’s Lactate Versus 0.9% Normal Saline Solution in the Management of Diabetic Ketoacidosis

Background: Diabetic ketoacidosis (DKA) is a life-threatening diabetic condition characterized by metabolic and homeostatic disturbances. KDA is a common condition in people with diabetes, especially in children and adolescents Objective: To compare ringer’s lactate versus 0.9% normal saline solution in the management of diabetic ketoacidosis Methodology: The study design was randomized control trial carried out at the Medical ‘A’ ward Khyber teaching hospital (KTH) Peshawar for a period of six months after synopsis approval. Patients were divided into two groups, groups A, receive 0.9% normal saline infusion and group B receive ringers lactate infusion. 82 subjects were included in each group. SPSS software version 20 was used for analyzing data. Results: In group B subjects, the serum bicarbonates level was higher than group A subjects (p=0.091). The Anion gap and blood PH level increases non-significantly in both the groups over a period of time (p=0.061). The mean hospital stay in group A and group B was 13.11 hours and 11.5 hours respectively (p=0.0031). The fluid quantity required in group A was more than group B (p=0.0031) Conclusion: When prescribing fluid, clinicians should always be cautious since any fluid may be dangerous if dosed wrongly. The ringer’s lactate was shown to be superior to 0.9 % normal saline in terms of alleviating DKA quicker in our study. Keywords: Diabetic ketoacidosis; 0.9 % normal saline; ringer’s lactate

Modified Clavipectoral Fascial Plane Block to The Rescue: Polytrauma Patient with Brachial Plexus Injury Undergoing Awake Clavicle Surgery

Modified Clavipectoral Fascial Plane Block to The Rescue: Polytrauma Patient with Brachial Plexus Injury Undergoing Awake Clavicle Surgery

Abstract 10941: Cerebral Consumption of Lactate Increases Neurological Injury After Experimental Cardiac Arrest in Rabbits

Introduction: Neuronal consumption of lactate is known to be protective after long duration of brain ischaemia. However, its consequences on neurological function after shorter duration of ischemia like after cardiac arrest are unknown. Hypothesis: We hypothesized that cerebral lactate consumption is deleterious for neurological outcome, whereas lactate dehydrogenase inhibition by oxamate could improve recovery. Methods: Male New-Zealand rabbits were anesthetized and surgically instrumented to assess lactate, glucose and O 2 cerebral consumption by measurement of the arterio-jugular differences. After 10 min of ventricular fibrillation, animals were resuscitated and randomly received a 30-min infusion of either saline (Control, n=6), lactate (Lact, 5 mg/kg/min, n=6) or oxamate (Oxa, 37.5 mg/kg/min, n=6). They were followed during 4 h. Additional animals were submitted to the same procedure without surgical instrumentation to allow recovery and assessment of neurological function during 48 h after cardiac arrest. In both experiments, neuronal death was assessed histologically by fluorojade C staining. Results: In Control group, a strong increase of the cerebral consumption of O 2 , glucose and lactate was observed during the 4 hours following resuscitation. In Lact group, lactate consumption was increased as compared to Control, whereas it was almost abolished in Oxa group (17.13±3.59, 32.60±6.24 and 4.04±1.58 mmol/L/min in Control, Lact and Oxa, respectively). Additionally, Oxa group presented a reduced consumption of glucose and O 2 after cardiac arrest as compared to other groups. Interestingly, administration of oxamate was highly neuroprotective whereas lactate administration worsened the neurological outcome after cardiac arrest (38±4, 64±10 and 15±6 % of neurological dysfunction score at 48h in Control, Lact and Oxa, respectively). Oxamate infusion was also associated with a significant reduction in the number of degenerative neurons at 4 h and 48 h of follow-up. Conclusions: The cerebral consumption of lactate appeared to be detrimental in rabbits after cardiac arrest. Its inhibition by oxamate is potently neuroprotective.

Comparison of Sodium Lactate Infusion and Carbon Dioxide Inhalation Panic Provocation Tests: A Meta-analysis.

Sodium lactate (NaL) infusion and carbon dioxide (CO2) inhalation are proven to provoke acute panic attacks (PAs) in patients with panic disorder (PD). A systematic literature search and meta-analysis were performed to compare the effect sizes of these methods. Odds ratios were calculated for each of the original studies and were pooled using the random-effects model. Either NaL or CO2 provocations significantly increased the rates of PAs in individuals with PD compared to those in healthy controls. However, the effect size of NaL infusion (OR=25.13, 95% CI=15.48-40.80) was significantly greater than that of CO2 inhalation (OR=10.58, 95%CI=7.88-14.21). The evidence for the efficacy of the two panic provocation tests is very strong. Yet, the results support the superiority of NaL infusion over CO2 inhalation challenge as a panic provocation test. Thus, lactate seems a much stronger stimulus than CO2 for the brain suffocation detector.

Molar Sodium Lactate Attenuates the Severity of Postcardiac Arrest Syndrome: A Preclinical Study.

To determine whether continuous IV infusion of molar sodium lactate would limit cardiac arrest-induced neurologic injury and cardiovascular failure. Randomized blinded study (animal model). University animal research facility. Twenty-four adult male "New Zealand White" rabbits. Anesthetized rabbits underwent 12.5 minutes of asphyxial cardiac arrest and were randomized to receive either normal saline (control group, n = 12) or molar sodium lactate (molar sodium lactate group, n = 12) at a rate of 5 mL/kg/hr during the whole 120-minute reperfusion period. Pupillary reactivity (primary outcome), levels of S100β protein, in vitro brain mitochondria functions, cardiovascular function, and fluid balance were assessed. Molar sodium lactate reduced brain injury, with a higher proportion of animals exhibiting pupillary reactivity to light (83% vs 25% in the CTRL group, p = 0.01) and lower S100β protein levels (189 ± 42 vs 412 ± 63 pg/mL, p < 0.01) at the end of the protocol. Molar sodium lactate significantly prevented cardiac arrest-induced decrease in oxidative phosphorylation and mitochondrial calcium-retention capacity compared with controls. At 120 minutes of reperfusion, survival did not significantly differ between the groups (10/12, 83% in the molar sodium lactate group vs nine of 12, 75% in the control group; p > 0.99), but hemodynamics were significantly improved in the molar sodium lactate group compared with the control group (higher mean arterial pressure [49 ± 2 vs 29 ± 3 mm Hg; p < 0.05], higher cardiac output [108 ± 4 vs 58 ± 9 mL/min; p < 0.05], higher left ventricle surface shortening fraction [38% ± 3% vs 19% ± 3%; p < 0.05], and lower left ventricular end-diastolic pressure [3 ± 1 vs 8 ± 2 mm Hg; p < 0.01]). While fluid intake was similar in both groups, fluid balance was higher in control animals (11 ± 1 mL/kg) than that in molar sodium lactate-treated rabbits (1 ± 3 mL/kg; p < 0.01) due to lower diuresis. Molar sodium lactate was effective in limiting the severity of the postcardiac arrest syndrome. This preclinical study opens up new perspectives for the treatment of cardiac arrest.

Lung Ultrasound Assisted Comparison of Volume Effects of Fluid Replacement Regimens in Pediatric Patients Undergoing Penile Hypospadias Repair: A Randomized Controlled Trial.

BackgroundEffective perioperative fluid therapy is a great consideration.ObjectivesUsing lung ultrasound (LUS), this study evaluated the preference of the conventional and restrictive fluid replacement regimens for their volume impact in pediatric patients undergoing a relatively long procedure with limited volume loss (hypospadias repair).MethodsEighty pediatric patients scheduled for hypospadias repair surgery were enrolled for conventional (CG) or restrictive fluid management groups (RG). The CG obtained Ringer's lactate at the conventional calculated doses, while the RG obtained infusion of Ringer's lactate at a rate of 3 mL/kg/h. B-line numbers in the LUS, recovery score, urine output, blood pressure (BP), heart rate HR, and oxygen saturation (SpO2) were recorded.ResultsAs evidenced by the LUS, RG showed a higher incidence of normal lung morphology with a mean and SD of 1.3 ± 2.2 for B-line numbers, whereas, in CG, they were 3.1 ± 2.2 with a P-value < 0.001. Urine output was 3.2 ± 0.8 and 2.9 ± 0.7 for CG and RG, respectively, with a P-value equal to 0.07. HR, BP, and SpO2 differences between groups were statistically insignificant. The recovery score was higher in RG (5.8 ± 0.4) than in CG (5.1 ± 0.8) at the first postoperative 20 minutes, with a P-value < 0.001.ConclusionsIn lengthy procedures with limited volume loss, using a moderately restrictive regimen is preferred over the conventional intraoperative fluid regimen considering both respiratory dysfunctions and recovery score.

Sevoflurane sedation and nephrogenic diabetes insipidus in patients affected with severe acute respiratory syndrome coronavirus 2.

Sevoflurane sedation and nephrogenic diabetes insipidus in patients affected with severe acute respiratory syndrome coronavirus 2.

Nutrient infusion in the dorsal vagal complex controls hepatic lipid and glucose metabolism in rats

SummaryHypothalamic regulation of lipid and glucose homeostasis is emerging, but whether the dorsal vagal complex (DVC) senses nutrients and regulates hepatic nutrient metabolism remains unclear. Here, we found in rats DVC oleic acid infusion suppressed hepatic secretion of triglyceride-rich very-low-density lipoprotein (VLDL-TG), which was disrupted by inhibiting DVC long-chain fatty acyl-CoA synthetase that in parallel disturbed lipid homeostasis during intravenous lipid infusion. DVC glucose infusion elevated local glucose levels similarly as intravenous glucose infusion and suppressed hepatic glucose production. This was independent of lactate metabolism as inhibiting lactate dehydrogenase failed to disrupt glucose sensing and neither could DVC lactate infusion recapitulate glucose effect. DVC oleic acid and glucose infusion failed to lower VLDL-TG secretion and glucose production in high-fat fed rats, while inhibiting DVC farnesoid X receptor enhanced oleic acid but not glucose sensing. Thus, an impairment of DVC nutrient sensing may lead to the disruption of lipid and glucose homeostasis in metabolic syndrome.

Does the Implementation of a Clinical Care Pathway Have an Impact on Early Intravenous Fluid Therapy of Acute Pancreatitis?: A Pilot Quality Improvement Study.

Early intravenous fluid (IVF) resuscitation is crucial in the management of acute pancreatitis; variation in IVF prescription practice had been demonstrated. This pilot study aims to assess whether the implementation of an Acute Pancreatitis Care Pathway (APCP) produces a change toward a more adequate IVF regimen in the first 24 hours. Patients with confirmed diagnosis of acute pancreatitis, from July 2015 to February 2016 (group 1) and from September 2017 to March 2018 (group 2), were considered. The APCP was developed between March 2016 and August 2017. Median IVF rate, volume, and type infused in the first 24 hours, were compared between groups. Nonparametric data were analyzed with the Mann-Whitney U test, differences in frequencies with the McNemar test; significance was set at P < 0.05. Seventy-two patients were included, 36 in each group. In the first 24 hours, the median IVF rate was 177 mL/h vs 225 mL/h (P = 0.004); Ringer lactate infusion was 30% vs 77.8% (P = 0.0003). The median total IVF volume did not differ between groups. The implementation of the APCP has the potential to lead to a successful change in early IVF resuscitation practice.

Comparison Of Lignocaine And Fentanyl For Attenuation Of Cardiovascular Stress Response To Laryngoscopy And Endotracheal Intubation

BACKGROUND AND AIM Intravenous Fentanyl Citrate and Lignocaine hydrochloride is being used as premedication for general anaesthesia with an intent to attenuate cardiovascular reflexes of laryngoscopy and endotracheal intubation. Present study was aimed to compare efficacy of both drugs as premedication to attenuate cardiovascular reflexes of laryngoscopy. METHODOLOGY Present study was carried out on randomly selected 50 patients of ASA Grade 1 and 2, aged 20 to 50 years with mallam pati airway assessment grade 1 scheduled for elective surgery requiring general anaesthesia with endotracheal intubation. All routine non-invasive monitors were applied and iv line secured. Glycopyrrolate 0.004 mg/kg and injection midazolam 0.02 mg/kg was given intravenously and IV infusion of ringer lactate was started. Patients were divided in two groups. Group-1: -Lignocaine hydrochloride group. Here patients received injection lignocaine hydrochloride 1.5 mg / kg IV bolus 3 minutes prior to induction. Group-2: -Fentanyl citrate group. Here patients received injection fentanyl citrate 2 µg / kg IV bolus 3 minutes prior to induction. After preoxygenation general anaesthesia with Thiopentone Sodium 5mg/kg and Succinyl choline 2mg/kg was given and endotracheal intubation was done. Heart rate, SBP, DBP, MAP and ECG were recorded in all patients pre operatively, after premedication, before study drug, after induction, after laryngoscopy and intubation and for every 1 minute up to 6 minutes after intubation during which no stimulus was given to patients. Laryngoscopy done and endotracheal intubation was done. An observation was made related to adverse effects of drugs and laryngoscopy related problems and were attended to appropriately. RESULTS In our study, injection fentanyl citrate 2 µg/kg attenuated the haemodynamic response better than Lignocaine 1.5 mg/kg. Heart rate, systolic blood pressure, diastolic blood presuure and mean arterial pressure did not rise significantly after intubation with Fentanyl compared to Lignocaine and reached basal value within study time. CONCLUSION Fentanyl citrate is safe and effective in attenuation of hemodynamic response to laryngoscopy without significant side effects as compared to lignocaine hydrochloride.

Does the implementation of a clinical care pathway have an impact on early intravenous fluid therapy of acute pancreatitis? a pilot quality improvement study

Objectives Early intravenous fluid (IVF) resuscitation is crucial in the management of acute pancreatitis; variation in IVF prescription practice had been demonstrated. This pilot study aims to assess whether the implementation of an Acute Pancreatitis Care Pathway (APCP) produces a change toward a more adequate IVF regimen in the first 24 hours. Methods Patients with confirmed diagnosis of acute pancreatitis, from July 2015 to February 2016 (group 1) and from September 2017 to March 2018 (group 2), were considered. The APCP was developed between March 2016 and August 2017. Median IVF rate, volume, and type infused in the first 24 hours, were compared between groups. Nonparametric data were analyzed with the Mann-Whitney U test, differences in frequencies with the McNemar test; significance was set at P Results Seventy-two patients were included, 36 in each group. In the first 24 hours, the median IVF rate was 177 mL/h vs 225 mL/h (P = 0.004); Ringer lactate infusion was 30% vs 77.8% (P = 0.0003). The median total IVF volume did not differ between groups. Conclusions The implementation of the APCP has the potential to lead to a successful change in early IVF resuscitation practice.

Low Microcirculatory Perfused Vessel Density and High Heterogeneity are Associated With Increased Intensity and Duration of Lactic Acidosis After Cardiac Surgery with Cardiopulmonary Bypass.

Lactic acidosis after cardiac surgery with cardiopulmonary bypass is common and associated with an increase in postoperative morbidity and mortality. A number of potential causes for an elevated lactate after cardiopulmonary bypass include cellular hypoxia, impaired tissue perfusion, ischemic-reperfusion injury, aerobic glycolysis, catecholamine infusions, and systemic inflammatory response after exposure to the artificial cardiopulmonary bypass circuit. Our goal was to examine the relationship between early abnormalities in microcirculatory convective blood flow and diffusive capacity and lactate kinetics during early resuscitation in the intensive care unit. We hypothesized that patients with impaired microcirculation after cardiac surgery would have a more severe postoperative hyperlactatemia, represented by the lactate time-integral of an arterial blood lactate concentration greater than 2.0 mmol/L. We measured sublingual microcirculation using incident darkfield video microscopy in 50 subjects on intensive care unit admission after cardiac surgery. Serial measurements of systemic hemodynamics, blood gas, lactate, and catecholamine infusions were recorded each hour for the first 6 h after surgery. Lactate area under the curve (AUC) was calculated over the first 6 h. The lactate AUC was compared between subjects with normal and low perfused vessel density (PVD < 18 mm/mm2), high microcirculatory heterogeneity index (MHI > 0.4), and low vessel-by-vessel microvascular flow index (MFIv < 2.6). Thirteen (26%) patients had a low postoperative PVD, 20 patients (40%) had a high MHI, and 26 (52%) patients had a low MFIv. Patients with low perfused vessel density had higher lactate AUC compared with subjects with a normal PVD (22.3 [9.4-31.0] vs. 2.6 [0-8.8]; P < 0.0001). Patients with high microcirculatory heterogeneity had a higher lactate AUC compared with those with a normal MHI (2.5 [0.1-8.2] vs. 13.1 [3.7-31.1]; P < 0.001). We did not find a difference in lactate AUC when comparing high and low MFIv. Low perfused vessel density and high microcirculatory heterogeneity are associated with an increased intensity and duration of lactic acidosis after cardiac surgery with cardiopulmonary bypass.

Influences of Blood Lactate Levels on Cognitive Domains and Physical Health during a Sports Stress. Brief Review

The present review aims to examine the effects of high blood lactate levels in healthy adult humans, for instance, after a period of exhaustive exercise, on the functioning of the cerebral cortex. In some of the examined studies, high blood lactate levels were obtained not only through exhaustive exercise but also with an intravenous infusion of lactate while the subject was immobile. This allowed us to exclude the possibility that the observed post-exercise effects were nonspecific (e.g., cortical changes in temperature, acidity, etc.). We observed that, in both experimental conditions, high levels of blood lactate are associated with a worsening of important cognitive domains such as attention or working memory or stress, without gender differences. Moreover, in both experimental conditions, high levels of blood lactate are associated with an improvement of the primary motor area (M1) excitability. Outside the frontal lobe, the use of visual evoked potentials and somatosensory evoked potentials allowed us to observe, in the occipital and parietal lobe respectively, that high levels of blood lactate are associated with an amplitude’s increase and a latency’s reduction of the early components of the evoked responses. In conclusion, significant increases of blood lactate levels could exercise a double-action in the central nervous system (CNS), with a protecting role on primary cortical areas (such as M1, primary visual area, or primary somatosensory cortex), while reducing the efficiency of adjacent regions, such as the supplementary motor area (SMA) or prefrontal cortex. These observations are compatible with the possibility that lactate works in the brain not only as an energy substrate or an angiogenetic factor but also as a true neuromodulator, which can protect from stress. In this review, we will discuss the mechanisms and effects of lactic acid products produced during an anaerobic exercise lactate, focusing on their action at the level of the central nervous system with particular attention to the primary motor, the somatosensory evoked potentials, and the occipital and parietal lobe.

Maintaining the firmness of minimally processed papaya using pectin methylesterase and calcium lactate

The objective of this work was to evaluate the effect of vacuum infusion of pectin methylesterase (PME) and calcium lactate (C6H10CaO6) in maintaining the firmness of minimally processed papaya, in order to maintain the quality and cellular integrity of the fruit. After minimal processing, the treatments used were: fruit without infusion (control), with H2O infusion, with PME infusion, with C6H10CaO6 infusion and with PME+C6H10CaO6 infusion. At zero times, four and eight days of storage, analyzes of total galacturonic acid, methanol, cell integrity, vitamin C, pH, acidity, soluble solids, damage, freshness and contamination were performed. Papaya treated with the PME+calcium combination showed an increase in firmness (5.8 N) on the eighth day of storage, differing from the control treatment (1.3 N), reporting the least leakage of electrolytes. On the fourth day, the fruit treated with PME+C6H10CaO6 showed the highest content of galacturonic acid and on the eighth day the highest content of methanol, indicating an effective action of the enzyme PME and calcium in this period. The PME+C6H10CaO6 treatment was effective in maintaining and improving the quality of papaya while preserving freshness, soluble solids content, acidity and pH throughout storage.

A STUDY ON ANALGESIA PROVIDED BY ULTRASOUND GUIDED FASCIA ILIACA COMPARTMENT BLOCK WITH AND WITHOUT PARACETAMOL: EFFECT ON HEMODYNAMICS DURING INTUBATION

Introduction: Paracetamol acts by the inhibition of Cyclooxygenase (COX) mediated production of Prostaglandin unlike the non steroidal anti inflammatory agents, so it was found that tissue inflammation was not reduced. Methodology: A detailed pre-anaesthetic checkup carried out in each patient. Patient is kept nil per orally 6 hours prior to surgery, i.v line secured, pre medicated with Inj Ranitidine 50mg iv, Inj Ondansetron 4mg iv and IVF Ringer Lactate infusion at 100ml/hr 3 hours prior to surgery. Results: Among the patients undergoing spinal anaesthesia in fracture femur surgery, there was no statistically significant difference in Blood pressure, Mean arterial pressure (MAP) between the groups. Conclusion: Among the patients undergoing spinal anaesthesia in fracture femur surgery, there was no statistically significant difference in Oxygen saturation (SpO2) between the groups

Effect on cerebral metabolites of hypertonic sodium lactate infusion after resuscitation in an experimental model of cardiac arrest

Background: Among cardiac arrest (CA) survivors, hypoxic brain injury is responsible for poor outcome.1,2 In the context of traumatic brain injury, Hypertonic sodium lactate (HSL) could be beneficial as lactate is used as an alternative energetic substrate,3–6 but in the setting of global cerebral ischemia following CA, no studies have investigated the impact of HSL on cerebral metabolites.

Pharmacological modulation of the lactate fuelling of neuron by astrocytes after an experimental cardiac arrest in rabbits

Rapid induction of therapeutic hypothermia is known to prevent neurological sequelae after cardiac arrest. Its mechanism of action could involve a preservation of astrocytes function, which are known to fuel neuron with lactate in stress conditions. We investigated whether a specific stimulation of astrocyte metabolism by pyruvate administration could induce lactate release and exacerbate the neuronal death as compared to direct stimulation of neurons by lactate administration. Eighteen rabbits were anesthetized and instrumented for cerebral microdialysis and evaluation of cerebral consumption of O 2 , lactate and glucose. After 10 min of ventricular fibrillation and resuscitation, animals received an intravenous infusion of saline (control group, n = 6), sodium lactate (5 mg/kg/min, Lac group, n = 6) or pyruvate (5 mg/kg/min, Py group, n = 6). Neuronal death was quantified by fluorojade C staining after 240 min of follow-up. After cardiac arrest, cerebral concentration of lactates and glucose increased in all groups, with a concomitant decreased oxygen consumption and increased lactate and glucose consumption. In the Py group, pyruvate was reduced in lactate as suggested by a significant increase in cerebral lactate concentration in Py group vs others (8.0 ± 0.8, 3.5 ± 0.5 vs 4.4 ± 1.2 μmol/L in Py, Lac and Control groups at 30 min post-cardiac arrest, respectively). This led to a greater neuronal death (25 ± 6, 34 ± 6 vs 50 ± 6 dead neurons per field, in Control, Lac and Py groups, respectively), suggesting that astrocyte fuelling with pyruvate is worse than direct neuronal fuelling with lactate. Neuron fuelling with lactate after cardiac arrest is deleterious for neurons. Specific stimulation of astrocytes by pyruvate administration enhances lactate production and worsen the neurological death.

Pivotal Roles for pH, Lactate, and Lactate-Utilizing Bacteria in the Stability of a Human Colonic Microbial Ecosystem.

Lactate can be produced by many gut bacteria, but in adults its accumulation in the colon is often an indicator of microbiota perturbation. Using continuous culture anaerobic fermentor systems, we found that lactate concentrations remained low in communities of human colonic bacteria maintained at pH 6.5, even when dl-lactate was infused at 10 or 20 mM. In contrast, lower pH (5.5) led to periodic lactate accumulation following lactate infusion in three fecal microbial communities examined. Lactate accumulation was concomitant with greatly reduced butyrate and propionate production and major shifts in microbiota composition, with Bacteroidetes and anaerobic Firmicutes being replaced by Actinobacteria, lactobacilli, and Proteobacteria Pure-culture experiments confirmed that Bacteroides and Firmicutes isolates were susceptible to growth inhibition by relevant concentrations of lactate and acetate, whereas the lactate-producer Bifidobacterium adolescentis was resistant. To investigate system behavior further, we used a mathematical model (microPop) based on 10 microbial functional groups. By incorporating differential growth inhibition, our model reproduced the chaotic behavior of the system, including the potential for lactate infusion both to promote and to rescue the perturbed system. The modeling revealed that system behavior is critically dependent on the proportion of the community able to convert lactate into butyrate or propionate. Communities with low numbers of lactate-utilizing bacteria are inherently less stable and more prone to lactate-induced perturbations. These findings can help us to understand the consequences of interindividual microbiota variation for dietary responses and microbiota changes associated with disease states.IMPORTANCE Lactate is formed by many species of colonic bacteria, and can accumulate to high levels in the colons of inflammatory bowel disease subjects. Conversely, in healthy colons lactate is metabolized by lactate-utilizing species to the short-chain fatty acids butyrate and propionate, which are beneficial for the host. Here, we investigated the impact of continuous lactate infusions (up to 20 mM) at two pH values (6.5 and 5.5) on human colonic microbiota responsiveness and metabolic outputs. At pH 5.5 in particular, lactate tended to accumulate in tandem with decreases in butyrate and propionate and with corresponding changes in microbial composition. Moreover, microbial communities with low numbers of lactate-utilizing bacteria were inherently less stable and therefore more prone to lactate-induced perturbations. These investigations provide clear evidence of the important role these lactate utilizers may play in health maintenance. These should therefore be considered as potential new therapeutic probiotics to combat microbiota perturbations.

A Freshening Breath of Insight

A Freshening Breath of Insight

Elevated plasma lactate levels via exogenous lactate infusion do not alter resistance exercise-induced signaling or protein synthesis in human skeletal muscle.

Lactate has been implicated as a potential signaling molecule. In myotubes, lactate incubation increases mechanistic target of rapamycin complex 1 (mTORC1)- and ERK-signaling and induces hypertrophy, indicating that lactate could be a mediator of muscle adaptations to resistance exercise. However, the potential signaling properties of lactate, at rest or with exercise, have not been explored in human tissue. In a crossover design study, 8 men and 8 women performed one-legged resistance exercise while receiving venous infusion of saline or sodium lactate. Blood was sampled repeatedly, and muscle biopsies were collected at rest and at 0, 90, and 180 min and 24 h after exercise. The primary outcomes examined were intracellular signaling, fractional protein synthesis rate (FSR), and blood/muscle levels of lactate and pH. Postexercise blood lactate concentrations were 130% higher in the Lactate trial (3.0 vs. 7.0 mmol/L, P < 0.001), whereas muscle levels were only marginally higher (27 vs. 32 mmol/kg dry wt, P = 0.003) compared with the Saline trial. Postexercise blood pH was higher in the Lactate trial (7.34 vs. 7.44, P < 0.001), with no differences in intramuscular pH. Exercise increased the phosphorylation of mTORS2448 (∼40%), S6K1T389 (∼3-fold), and p44T202/T204 (∼80%) during recovery, without any differences between trials. FSR over the 24-h recovery period did not differ between the Saline (0.067%/h) and Lactate (0.062%/h) trials. This study does not support the hypothesis that blood lactate levels can modulate anabolic signaling in contracted human muscle. Further in vivo research investigating the impact of exercised versus rested muscle and the role of intramuscular lactate is needed to elucidate its potential signaling properties.