Association of blood lactate with type 2 diabetes: the Atherosclerosis Risk in Communities Carotid MRI Study

The reactive pyruvate metabolite dimethylglyoxal mediates neurological consequences of diabetes

Complications of diabetes are often attributed to glucose and reactive dicarbonyl metabolites derived from glycolysis or gluconeogenesis, such as methylglyoxal. However, in the CNS, neurons and endothelial cells use lactate as energy source in addition to glucose, which does not lead to the formation of methylglyoxal and has previously been considered a safer route of energy consumption than glycolysis. Nevertheless, neurons and endothelial cells are hotspots for the cellular pathology underlying neurological complications in diabetes, suggesting a cause that is distinct from other diabetes complications and independent of methylglyoxal. Here, we show that in clinical and experimental diabetes plasma concentrations of dimethylglyoxal are increased. In a mouse model of diabetes, ilvb acetolactate-synthase-like (ILVBL, HACL2) is the enzyme involved in formation of increased amounts of dimethylglyoxal from lactate-derived pyruvate. Dimethylglyoxal reacts with lysine residues, forms Nε-3-hydroxy-2-butanonelysine (HBL) as an adduct, induces oxidative stress more strongly than other dicarbonyls, causes blood-brain barrier disruption, and can mimic mild cognitive impairment in experimental diabetes. These data suggest dimethylglyoxal formation as a pathway leading to neurological complications in diabetes that is distinct from other complications. Importantly, dimethylglyoxal formation can be reduced using genetic, pharmacological and dietary interventions, offering new strategies for preventing CNS dysfunction in diabetes.

Eight Weeks of Intermittent Exercise in Hypoxia, with or without a Low-Carbohydrate Diet, Improves Bone Mass and Functional and Physiological Capacity in Older Adults with Type 2 Diabetes

In an increasingly aging and overweight population, osteoporosis and type 2 diabetes (T2DM) are major public health concerns. T2DM patients experience prejudicial effects on their bone health, affecting their physical capacity. Exercise in hypoxia (EH) and a low-carbohydrate diet (LCD) have been suggested for therapeutic benefits in T2DM, improving bone mineral content (BMC) and glycemic control. This study investigated the effects of EH combined with an LCD on body composition and functional and physiologic capacity in T2DM patients. Older T2DM patients (n = 42) were randomly assigned to the following groups: (1) control group: control diet + exercise in normoxia; (2) EH group: control diet + EH; (3) intervention group: LCD + EH. Cardiopulmonary tests (BRUCE protocol), body composition (DEXA), and functional capacity (6MWT, handgrip strength) were evaluated. Body mass index (kg/m2) and body fat (%) decreased in all groups (p < 0.001). BMC (kg) increased in all groups (p < 0.001) and was significantly higher in the EH and EH + LCD groups (p < 0.001). VO2peak improved in all groups (p < 0.001), but more so in the hypoxia groups (p = 0.019). Functional capacity was increased in all groups (p < 0.001), but more so in the EH group in 6MWT (p = 0.030). EH with and without an LCD is a therapeutic strategy for improving bone mass in T2DM, which is associated with cardiorespiratory and functional improvements.

Pump-Less, Recirculating Organ-on-Chip (rOoC) Platform to Model the Metabolic Crosstalk between Islets and Liver

Type 2 diabetes mellitus (T2DM), obesity, and metabolic dysfunction-associated steatotic liver disease (MASLD) are epidemiologically correlated disorders with a worldwide growing prevalence. While the mechanisms leading to the onset and development of these conditions are not fully understood, predictive tissue representations for studying the coordinated interactions between central organs that regulate energy metabolism, particularly the liver and pancreatic islets, are needed. Here, a dual pump-less recirculating organ-on-chip platform that combines human pluripotent stem cell (sc)-derived sc-liver and sc-islet organoids is presented. The platform reproduces key aspects of the metabolic cross-talk between both organs, including glucose levels and selected hormones, and supports the viability and functionality of both sc-islet and sc-liver organoids while preserving a reduced release of pro-inflammatory cytokines. In a model of metabolic disruption in response to treatment with high lipids and fructose, sc-liver organoids exhibit hallmarks of steatosis and insulin resistance, while sc-islets produce pro-inflammatory cytokines on-chip. Finally, the platform reproduces known effects of anti-diabetic drugs on-chip. Taken together, the platform provides a basis for functional studies of obesity, T2DM, and MASLD on-chip, as well as for testing potential therapeutic interventions.

Identification of potential serum biomarkers associated with HbA1c levels in Indian type 2 diabetic subjects using NMR-based metabolomics

BACKGROUND

The prevalence of type 2 diabetes mellitus (T2DM), a progressive metabolic disorder characterized by chronic hyperglycemia and the development of insulin resistance, has increased globally, with worrying statistics coming from children, adolescents, and young adults from developing countries like India. Here, we investigated unique circulating metabolic signatures associated with prediabetes and T2DM in an Indian cohort using NMR-based metabolomics.

MATERIALS AND METHODS

The study subjects included healthy volunteers (N = 101), prediabetic subjects (N = 75), and T2DM patients (N = 108). Serum metabolic profiling was performed using 1H NMR spectroscopy and major perturbed metabolites were identified by multivariate analysis and receiver operating characteristic (ROC) modules.

RESULTS

Of the 36 aqueous abundant metabolites, 24 showed a statistically significant difference between healthy volunteers, prediabetics, and established T2DM subjects. On performing multivariate ROC curve analysis with 5 commonly dysregulated metabolites (namely, glucose, pyroglutamate, o-phosphocholine, serine, and methionine) in prediabetes and T2DM, AUC values obtained were 0.96 (95 % confidence interval (CI) = 0.93, 0.98) for T2DM; and 0.88 (95 % CI = 0.81, 0.93) for prediabetic subjects, respectively.

CONCLUSION

We propose that the identified metabolite panel can be used in the future as a biomarker for clinical diagnosis, patient surveillance, and for predicting individuals at risk for developing diabetes.

Lactate transporter MCT1 in hepatic stellate cells promotes fibrotic collagen expression in nonalcoholic steatohepatitis

Circulating lactate is a fuel source for liver metabolism but may exacerbate metabolic diseases such as nonalcoholic steatohepatitis (NASH). Indeed, haploinsufficiency of lactate transporter monocarboxylate transporter 1 (MCT1) in mice reportedly promotes resistance to hepatic steatosis and inflammation. Here, we used adeno-associated virus (AAV) vectors to deliver thyroxin binding globulin (TBG)-Cre or lecithin-retinol acyltransferase (Lrat)-Cre to MCT1fl/fl mice on a choline-deficient, high-fat NASH diet to deplete hepatocyte or stellate cell MCT1, respectively. Stellate cell MCT1KO (AAV-Lrat-Cre) attenuated liver type 1 collagen protein expression and caused a downward trend in trichrome staining. MCT1 depletion in cultured human LX2 stellate cells also diminished collagen 1 protein expression. Tetra-ethylenglycol-cholesterol (Chol)-conjugated siRNAs, which enter all hepatic cell types, and hepatocyte-selective tri-N-acetyl galactosamine (GN)-conjugated siRNAs were then used to evaluate MCT1 function in a genetically obese NASH mouse model. MCT1 silencing by Chol-siRNA decreased liver collagen 1 levels, while hepatocyte-selective MCT1 depletion by AAV-TBG-Cre or by GN-siRNA unexpectedly increased collagen 1 and total fibrosis without effect on triglyceride accumulation. These findings demonstrate that stellate cell lactate transporter MCT1 significantly contributes to liver fibrosis through increased collagen 1 protein expression in vitro and in vivo, while hepatocyte MCT1 appears not to be an attractive therapeutic target for NASH.

Reduced graphene oxide-functionalized polymer microneedle for continuous and wide-range monitoring of lactate in interstitial fluid

Despite substantial developments in minimally invasive lactate monitoring microneedle electrodes, most such electrode developments have focused on either sensitivity or invasiveness while ignoring a wide range of detection, which is the most important factor in measuring the normal range of lactate in interstitial fluid (ISF). Herein, we present a polymer-based planar microneedle electrode fabrication using microelectromechanical and femtosecond laser technology for the continuous monitoring of lactate in ISF. The microneedle is functionalized with two-dimensional reduced graphene oxide (rGO) and electrochemically synthesized platinum nanoparticles (PtNPs). A particular quantity of Nafion (1.25 wt%) is applied on top of the lactate enzyme to create a diffusion-controlled membrane. Due to the combined effects of the planar structure of the microneedle, rGO, and membrane, the biosensor exhibited excellent linearity up to 10 mM lactate with a limit of detection of 2.04 μM, high sensitivity of 43.96 μA mM-1cm-2, a reaction time of 8 s and outstanding stability, selectivity, and repeatability. The feasibility of the microneedle is evaluated by using it to measure lactate concentrations in artificial ISF and human serum. The results demonstrate that the microneedle described here has great potential for use in real-time lactate monitoring for use in sports medicine and treatment.

The Impact of Diabetes on Haemodynamic and Cardiometabolic Responses in Heart Failure With Preserved Ejection Fraction

AIMS

Heart failure with preserved ejection (HFpEF) and diabetes mellitus (DM) commonly co-exist. However, it is unclear if DM modifies the haemodynamic and cardiometabolic phenotype in patients with HFpEF. We aimed to interrogate the haemodynamic and cardiometabolic effects of DM in HFpEF.

METHODS

We compared the haemodynamic and metabolic profiles of non-DM patients and patients with DM-HFpEF at rest and during exercise using right heart catheterisation and mixed venous blood gas analysis.

RESULTS

Of 181 patients with HFpEF, 37 (20%) had DM. Patients with DM displayed a more adverse exercise haemodynamic response vs HFpEF alone (mean pulmonary arterial pressure: 47 mmHg [interquartile range {IQR} 42-55] vs 42 [38-47], p<0.001; workload indexed pulmonary capillary wedge pressure indexed: 0.80 mmHg/W [0.44-1.23] vs 0.57 [0.43-1.01], p=0.047). HFpEF-DM patients had a lower mixed venous oxygen saturation at rest (70% [IQR 66-73] vs 72 [69-75], p=0.003) and were unable to enhance O2 extraction to the same extent (Δ-28% [-33 to -15] vs -29 [-36 to -21], p=0.029), this occurred at a 22% lower median workload. Resting mixed venous lactate levels were higher in those with DM (1.5 mmol/L [IQR 1.1-1.9] vs 1 [0.9-1.3], p<0.001), and during exercise indexed to workload (0.09 mmol/L/W [0.06-0.13] vs 0.08 [0.05-0.11], p=0.018).

CONCLUSION

Concurrent diabetes and HFpEF was associated with greater metabolic responses at rest, with enhanced wedge driven pulmonary hypertension and relative lactataemia during exercise without appropriate augmentation of oxygen consumption.

Empowering mitochondrial metabolism: Exploring L-lactate supplementation as a promising therapeutic approach for metabolic syndrome

Mitochondrial dysfunction plays a critical role in the pathogenesis of metabolic syndrome (MetS), affecting various cell types and organs. In MetS animal models, mitochondria exhibit decreased quality control, characterized by abnormal morphological structure, impaired metabolic activity, reduced energy production, disrupted signaling cascades, and oxidative stress. The aberrant changes in mitochondrial function exacerbate the progression of metabolic syndrome, setting in motion a pernicious cycle. From this perspective, reversing mitochondrial dysfunction is likely to become a novel and powerful approach for treating MetS. Unfortunately, there are currently no effective drugs available in clinical practice to improve mitochondrial function. Recently, L-lactate has garnered significant attention as a valuable metabolite due to its ability to regulate mitochondrial metabolic processes and function. It is highly likely that treating MetS and its related complications can be achieved by correcting mitochondrial homeostasis disorders. In this review, we comprehensively discuss the complex relationship between mitochondrial function and MetS and the involvement of L-lactate in regulating mitochondrial metabolism and associated signaling pathways. Furthermore, it highlights recent findings on the involvement of L-lactate in common pathologies of MetS and explores its potential clinical application and further prospects, thus providing new insights into treatment possibilities for MetS.

Fasting plasma lactate as a possible early clinical marker for metabolic disease risk

BACKGROUND AND AIM

Elevated fasting plasma lactate concentrations are evident in individuals with metabolic diseases. However, it has yet to be determined if these associations exist in a young, healthy population as a possible early marker for metabolic disease risk. The purpose of this study was to determine if indices of the metabolic syndrome are related to plasma lactate concentrations in this population.

METHODS

Fifty (29 ± 7 yr) men (n = 19) and women (n = 31) classified as overweight (26.4 ± 1.8 kg/m2) participated in this observational study. Blood pressure and blood metabolites were measured after an overnight fast. Lactate was also measured before and after a three-day eucaloric high-fat (70 %) diet. The homeostatic model assessment for insulin resistance (HOMA-IR) was calculated as a measure of insulin resistance. Visceral adipose tissue mass was determined via dual X-ray absorptiometry.

RESULTS

Triglycerides (r = 0.55, p=<0.0001), HOMA-IR (r = 0.53, p=<0.0001), and systolic and diastolic (both, r = 0.36, p = 0.01) blood pressures associated with fasting plasma lactate. No differences in visceral adipose tissue existed between the sexes (p = 0.41); however, the relationship between visceral adipose tissue and lactate existed only in females (r = 0.59, p = 0.02) but not in males (p = 0.53). Fasting lactate and HOMA-IR increased in males (p = 0.01 and p = 0.02, respectively), but not females, following a three-day high-fat diet.

CONCLUSION

Indices of the metabolic syndrome associated with fasting plasma lactates in young relatively healthy individuals. Fasting lactate also increased in a sex-specific manner after a three-day high fat diet. Thus, lactate could become a clinical marker for metabolic disease risk.

Metabolomic signature between diabetic and non-diabetic obese patients: A protocol for systematic review

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a chronic and progressive condition defined by hyperglycemia caused by abnormalities in insulin production, insulin receptor sensitivity, or both. Several studies have revealed that higher body mass index (BMI) is associated with increasing risk of developing diabetes. In this study, we perform a protocol for systematic review to explore metabolite biomarkers that could be used to identify T2DM in obese subjects.

METHODS

The protocol of this review was registered in PROSPERO (CRD42023405518). Three databases, EMBASE, PubMed, and Web of Science were selected to collect potential literature from their inceptions to July December 2023. Data for collection will include title, authors, study subjects, publication date, sample size, detection and analytical platforms, participant characteristics, biological samples, confounding factors, methods of statistical analysis, the frequency and directions of changes in potential metabolic biomarkers, and major findings. Pathway analysis of differential metabolites will be performed with MetaboAnalyst 5.0 based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Human Metabolome Database.

RESULTS

The results of this systematic review will be published in a peer-reviewed journal.

CONCLUSION

This systematic review will summarize the potential biomarkers and metabolic pathways to provide a new reference for the prevention and treatment of T2DM in obese subjects.

p53 contributes to cardiovascular diseases via mitochondria dysfunction: A new paradigm

Cardiovascular diseases (CVDs) are leading causes of global mortality; however, their underlying mechanisms remain unclear. The tumor suppressor factor p53 has been extensively studied for its role in cancer and is also known to play an important role in regulating CVDs. Abnormal p53 expression levels and modifications contribute to the occurrence and development of CVDs. Additionally, mounting evidence underscores the critical involvement of mitochondrial dysfunction in CVDs. Notably, studies indicate that p53 abnormalities directly correlate with mitochondrial dysfunction and may even interact with each other. Encouragingly, small molecule inhibitors targeting p53 have exhibited remarkable effects in animal models of CVDs. Moreover, therapeutic strategies aimed at mitochondrial-related molecules and mitochondrial replacement therapy have demonstrated their advantageous potential. Therefore, targeting p53 or mitochondria holds immense promise as a pioneering therapeutic approach for combating CVDs. In this comprehensive review, we delve into the mechanisms how p53 influences mitochondrial dysfunction, including energy metabolism, mitochondrial oxidative stress, mitochondria-induced apoptosis, mitochondrial autophagy, and mitochondrial dynamics, in various CVDs. Furthermore, we summarize and discuss the potential significance of targeting p53 or mitochondria in the treatment of CVDs.

Lactate induces the development of beige adipocytes via an increase in the level of reactive oxygen species

Recent studies have indicated that lactate acts as a signaling molecule in various tissues. We previously demonstrated that intake of an amino acid mixture combined with exercise synergistically induced beige adipocyte formation in inguinal white adipose tissue (iWAT) in mice. Moreover, plasma lactate levels remained significantly elevated in the amino acid mixture + exercise group even 16 h after exercise, indicating that a lactate-mediated pathway may be involved in the induction of beige adipocyte formation. Against this background, we hypothesized that oral intake of lactate would induce beige adipocyte formation via the lactate signaling pathway without exercise. Furthermore, if oral intake of lactate can produce the same effect as exercise, lactate might be used as a food-derived exercise replacement-factor. Oral intake of lactate (100 mM in drinking water) for 4 weeks significantly induced beige adipocyte formation in iWAT in mice as well as a significant elevation of lactate transporter (monocarboxylic acid transporter 1; MCT1) and lactate dehydrogenase B levels. Administration of lactate to adipocytes significantly increased reactive oxygen species (ROS) and superoxide levels and the NADH/NAD+ ratio. The induction of lactate-mediated uncoupling protein 1 (UCP1) expression and ROS production were significantly suppressed by antioxidant treatment or inhibition of MCT1. However, UCP1 induction was not significantly affected by the inhibition of lactate receptor (hydroxycarboxylic acid receptor 1). These findings suggest that lactate-mediated ROS production induces beige adipocyte formation, and thus oral intake of lactate may confer some benefits of exercise without the need to perform exercise.

Butyrate prevents visceral adipose tissue inflammation and metabolic alterations in a Friedreich's ataxia mouse model

Friedreich's ataxia (FA) is a neurodegenerative disease resulting from a mutation in the FXN gene, leading to mitochondrial frataxin deficiency. FA patients exhibit increased visceral adiposity, inflammation, and heightened diabetes risk, negatively affecting prognosis. We investigated visceral white adipose tissue (vWAT) in a murine model (KIKO) to understand its role in FA-related metabolic complications. RNA-seq analysis revealed altered expression of inflammation, angiogenesis, and fibrosis genes. Diabetes-like traits, including larger adipocytes, immune cell infiltration, and increased lactate production, were observed in vWAT. FXN downregulation in cultured adipocytes mirrored vWAT diabetes-like features, showing metabolic shifts toward glycolysis and lactate production. Metagenomic analysis indicated a reduction in fecal butyrate-producing bacteria, known to exert antidiabetic effects. A butyrate-enriched diet restrained vWAT abnormalities and mitigated diabetes features in KIKO mice. Our work emphasizes the role of vWAT in FA-related metabolic issues and suggests butyrate as a safe and promising adjunct for FA management.

Lactate transporter MCT1 in hepatic stellate cells promotes fibrotic collagen expression in nonalcoholic steatohepatitis

Circulating lactate is a fuel source for liver metabolism but may exacerbate metabolic diseases such as nonalcoholic steatohepatitis (NASH). Indeed, haploinsufficiency of lactate transporter monocarboxylate transporter 1 (MCT1) in mice reportedly promotes resistance to hepatic steatosis and inflammation. Here, we used adeno-associated virus (AAV) vectors to deliver thyroxin binding globulin (TBG)-Cre or lecithin-retinol acyltransferase (Lrat)-Cre to MCT1fl/fl mice on a choline deficient, high fat NASH diet to deplete hepatocyte or stellate cell MCT1, respectively. Stellate cell MCT1KO (AAV-Lrat-Cre) attenuated liver type 1 collagen protein expression and caused a downward trend in trichrome staining. MCT1 depletion in cultured human LX2 stellate cells also diminished collagen 1 protein expression. Tetra-ethylenglycol-cholesterol (Chol)-conjugated siRNAs, which enter all hepatic cell types, and hepatocyte-selective tri-N-acetyl galactosamine (GN)-conjugated siRNAs were then used to evaluate MCT1 function in a genetically obese NASH mouse model. MCT1 silencing by Chol-siRNA decreased liver collagen 1 levels, while hepatocyte-selective MCT1 depletion by AAV-TBG-Cre or by GN-siRNA unexpectedly increased collagen 1 and total fibrosis without effect on triglyceride accumulation. These findings demonstrate that stellate cell lactate transporter MCT1 significantly contributes to liver fibrosis through increased collagen 1 protein expression in vitro and in vivo, while hepatocyte MCT1 appears not to be an attractive therapeutic target for NASH.

Serum branch-chained amino acids are increased in type 2 diabetes and associated with atherosclerotic cardiovascular disease

BACKGROUND AND AIM

Circulating biomarkers of metabolic and cardiovascular diseases can help in the early detection and prevention of those diseases. Using proton nuclear magnetic resonance (1H-NMR), we aimed to study the plasma levels of low-molecular-weight metabolites (LMWMs) in a cohort of 307 patients with metabolic diseases to assess their relationships with type-2 diabetes (T2D) and incident atherosclerotic cardiovascular disease (ASCVD).

METHODS

We conducted a cross-sectional and prospective study. We included 307 patients attending the Lipid Unit of our University Hospital for the treatment of the following metabolic disturbances and associated disorders: T2D (73.9%), obesity (58.7%), and hypertension (55.1%). 1H-NMR was used to study the plasma levels of 13 LMWMs. LMWM serum concentrations were evaluated in patients with and without T2D. and the correlations with several parameters and their associations with T2D were analyzed. The association between LMWM levels at baseline and the development of ASCVD in patients with T2D after 10 years of follow-up was also evaluated.

RESULTS

Among the LMWMs measured, the branched-chain amino acids (BCAAs) valine, leucine and isoleucine showed a positive association with several clinical and lipid-related biochemical parameters and inflammatory markers (p < 0.05). Likewise, these three BCAAS were associated with diabetes even after adjusting for covariates (p < 0.05). During the follow-up period of 10 years, 29 of the 185 patients with diabetes at baseline (15.68%) developed ASCVD. After adjusting for clinical covariates, baseline levels of valine and alanine were associated with the development of ASCVD (p < 0.05).

CONCLUSION

Overall, our results indicated that plasma levels of LMWMs measured by 1H-NMR could be potential biomarkers associated with T2D. Moreover, alanine and valine can help in the early detection of the cardiovascular risk associated with this metabolic disease.

Exploring a new mechanism between lactate and VSMC calcification: PARP1/POLG/UCP2 signaling pathway and imbalance of mitochondrial homeostasis

Lactate leads to the imbalance of mitochondria homeostasis, which then promotes vascular calcification. PARP1 can upregulate osteogenic genes and accelerate vascular calcification. However, the relationship among lactate, PARP1, and mitochondrial homeostasis is unclear. The present study aimed to explore the new molecular mechanism of lactate to promote VSMC calcification by evaluating PARP1 as a breakthrough molecule. A coculture model of VECs and VSMCs was established, and the model revealed that the glycolysis ability and lactate production of VECs were significantly enhanced after incubation in DOM. Osteogenic marker expression, calcium deposition, and apoptosis in VSMCs were decreased after lactate dehydrogenase A knockdown in VECs. Mechanistically, exogenous lactate increased the overall level of PARP and PARylation in VSMCs. PARP1 knockdown inhibited Drp1-mediated mitochondrial fission and partially restored PINK1/Parkin-mediated mitophagy, thereby reducing mitochondrial oxidative stress. Moreover, lactate induced the translocation of PARP1 from the nucleus to the mitochondria, which then combined with POLG and inhibited POLG-mediated mitochondrial DNA synthesis. This process led to the downregulation of mitochondria-encoded genes, disturbance of mitochondrial respiration, and inhibition of oxidative phosphorylation. The knockdown of PARP1 could partially reverse the damage of mitochondrial gene expression and function caused by lactate. Furthermore, UCP2 was upregulated by the PARP1/POLG signal, and UCP2 knockdown inhibited Drp1-mediated mitochondrial fission and partially recovered PINK1/Parkin-mediated mitophagy. Finally, UCP2 knockdown in VSMCs alleviated DOM-caused VSMC calcification in the coculture model. The study results thus suggest that upregulated PARP1 is involved in the mechanism through which lactate accelerates VSMC calcification partly via POLG/UCP2-caused unbalanced mitochondrial homeostasis.

Greater reliance on glycolysis is associated with lower mitochondrial substrate oxidation and insulin sensitivity in infant myogenic MSCs

Individuals with insulin resistance and obesity display higher skeletal muscle production of nonoxidized glycolytic products (i.e., lactate), and lower complete mitochondrial substrate oxidation to CO2. These findings have also been observed in individuals without obesity and are associated with an increased risk for metabolic disease. The purpose of this study was to determine if substrate preference is evident at the earliest stage of life (birth) and to provide a clinical blood marker (lactate) that could be indicative of a predisposition for metabolic disease later. We used radiolabeled tracers to assess substrate oxidation and insulin sensitivity of myogenically differentiated mesenchymal stem cells (MSCs), a proxy of infant skeletal muscle tissue, derived from umbilical cords of full-term infants. We found that greater production of nonoxidized glycolytic products (lactate, pyruvate, alanine) is directly proportional to lower substrate oxidation and insulin sensitivity in MSCs. In addition, we found an inverse relationship between the ratio of complete glucose oxidation to CO2 and infant blood lactate at 1 mo of age. Collectively, considering that higher lactate was associated with lower MSC glucose oxidation and has been shown to be implicated with metabolic disease, it may be an early indicator of infant skeletal muscle phenotype.NEW & NOTEWORTHY In infant myogenically differentiated mesenchymal stem cells, greater production of nonoxidized glycolytic products was directly proportional to lower substrate oxidation and insulin resistance. Glucose oxidation was inversely correlated with infant blood lactate. This suggests that innate differences in infant substrate oxidation exist at birth and could be associated with the development of metabolic disease later in life. Clinical assessment of infant blood lactate could be used as an early indicator of skeletal muscle phenotype.

Spatially Resolved Metabolites in Stable and Unstable Human Atherosclerotic Plaques Identified by Mass Spectrometry Imaging

BACKGROUND

Impairments in carbohydrate, lipid, and amino acid metabolism drive features of plaque instability. However, where these impairments occur within the atheroma remains largely unknown. Therefore, we sought to characterize the spatial distribution of metabolites within stable and unstable atherosclerosis in both the fibrous cap and necrotic core.

METHODS

Atherosclerotic tissue specimens from 9 unmatched individuals were scored based on the Stary classification scale and subdivided into stable and unstable atheromas. After performing mass spectrometry imaging on these samples, we identified over 850 metabolite-related peaks. Using MetaboScape, METASPACE, and Human Metabolome Database, we confidently annotated 170 of these metabolites and found over 60 of these were different between stable and unstable atheromas. We then integrated these results with an RNA-sequencing data set comparing stable and unstable human atherosclerosis.

RESULTS

Upon integrating our mass spectrometry imaging results with the RNA-sequencing data set, we discovered that pathways related to lipid metabolism and long-chain fatty acids were enriched in stable plaques, whereas reactive oxygen species, aromatic amino acid, and tryptophan metabolism were increased in unstable plaques. In addition, acylcarnitines and acylglycines were increased in stable plaques whereas tryptophan metabolites were enriched in unstable plaques. Evaluating spatial differences in stable plaques revealed lactic acid in the necrotic core, whereas pyruvic acid was elevated in the fibrous cap. In unstable plaques, 5-hydroxyindoleacetic acid was enriched in the fibrous cap.

CONCLUSIONS

Our work here represents the first step to defining an atlas of metabolic pathways involved in plaque destabilization in human atherosclerosis. We anticipate this will be a valuable resource and open new avenues of research in cardiovascular disease.

Gluconeogenesis Flux in Metabolic Disease

Gluconeogenesis is a critical biosynthetic process that helps maintain whole-body glucose homeostasis and becomes altered in certain medical diseases. We review gluconeogenic flux in various medical diseases, including common metabolic disorders, hormonal imbalances, specific inborn genetic errors, and cancer. We discuss how the altered gluconeogenic activity contributes to disease pathogenesis using data from experiments using isotopic tracer and spectroscopy methodologies. These in vitro, animal, and human studies provide insights into the changes in circulating levels of available gluconeogenesis substrates and the efficiency of converting those substrates to glucose by gluconeogenic organs. We highlight ongoing knowledge gaps, discuss emerging research areas, and suggest future investigations. A better understanding of altered gluconeogenesis flux may ultimately identify novel and targeted treatment strategies for such diseases.

Kidney-Related Function of Mitochondrial Protein Mitoregulin

A small protein, Mitoregulin (Mtln), localizes in mitochondria and contributes to oxidative phosphorylation and fatty acid metabolism. Mtln knockout mice develop obesity on a high-fat diet, demonstrating elevated cardiolipin damage and suboptimal creatine kinase oligomerization in muscle tissue. Kidneys heavily depend on the oxidative phosphorylation in mitochondria. Here we report kidney-related phenotypes in aged Mtln knockout mice. Similar to Mtln knockout mice muscle mitochondria, those of the kidney demonstrate a decreased respiratory complex I activity and excessive cardiolipin damage. Aged male mice carrying Mtln knockout demonstrated an increased frequency of renal proximal tubules' degeneration. At the same time, a decreased glomerular filtration rate has been more frequently detected in aged female mice devoid of Mtln. An amount of Mtln partner protein, Cyb5r3, is drastically decreased in the kidneys of Mtln knockout mice.

The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.

The association between dietary acid load and body composition in physical education students aged 18-25 years

AIM

To find the association between dietary acid load (DAL) and body composition in physical education students.

METHODS

This study was carried out on 207 students of both genders aged 18-25 years. DAL was calculated based on potential renal acid load (PRAL) and net endogenous acid production (NEAP) methods. Anthropometric indices were measured. Bioelectric impedance was used to assess body composition and other related items.

RESULTS

The mean score of NEAP and PRAL was 80.18 ± 31.30 and 33.94 ± 22.11, respectively. The mean weight and fat mass of subjects were 64.05 ± 9.72 kg and 20.28 ± 0.67 kg, respectively. Participants in the highest tertile of PRAL had a higher weight (64.56 ± 1.14 kg) in comparison with participants in the lowest tertile (61.65 ± 1.19 kg) (P = 0.027). After adjusting for confounders, a significant positive association was found between NEAP score and hip circumference (β = 0.206, P = 0.039), body mass index (β = 0.214, P = 0.031), fat mass (β = 0.218, P = 0.001) and body adiposity index (β = 0.182, P = 0.037). Furthermore, a statistically significant negative association was observed between total body water and NEAP score (β = - 0.217, P = 0.001) and the percentage of fat-free mass and NEAP (β = - 0.229, P = 0.001).

CONCLUSION

Individuals with a higher DAL score may have a higher weight, fat mass and hip circumference and a lower fat-free mass. In addition, there might be an association between DAL and obesity.

Advances in Glycolysis Metabolism of Atherosclerosis

Glycolysis is an important way for various cells such as vascular wall endothelial cells, smooth muscle cells, macrophages, and other cells to obtain energy. In pathological conditions, it can participate in the process of AS by regulating lipid deposition, calcification, angiogenesis in plaques, etc., together with its metabolite lactic acid. Recent studies have shown that lactate-related lactylation modifications are ubiquitous in the human proteome and are involved in the regulation of various inflammatory diseases. Combined with the distribution and metabolic characteristics of cells in the plaque in the process of AS, glycolysis-lactate-lactylation modification may be a new entry point for targeted intervention in atherosclerosis in the future. Therefore, this article intends to elaborate on the role and mechanism of glycolysis-lactate-lactylation modification in AS, as well as the opportunities and challenges in targeted therapy, hoping to bring some help to relevant scholars in this field. In atherosclerosis, glycolysis, lactate, and lactylation modification as a metabolic sequence affect the functions of macrophages, smooth muscle cells, endothelial cells, lymphocytes, and other cells and interfere with processes such as vascular calcification and intraplaque neovascularization to influence the progression of atherosclerosis.

Overexpressing the hydroxycarboxylic acid receptor 1 in mouse brown adipose tissue restores glucose tolerance and insulin sensitivity in diet-induced obese mice

Interscapular brown adipose tissue (BAT) plays an important role in controlling glucose homeostasis. Increased glucose entry and glycolysis in BAT result in lactate production and release. The adipose tissue expresses the lactate receptor hydrocarboxylic acid receptor 1 (HCAR1), markedly downregulated in male diet-induced obese (DIO) and ob/ob mice. In this study, we examined the role of HCAR1 in BAT in controlling glucose homeostasis in male DIO mice. We overexpressed HCAR1 in BAT by injecting adeno-associated viruses (AAVs) expressing HCAR1 into the BAT pads of male DIO C57BL/6J mice. Overexpressing HCAR1 in BAT resulted in augmented glucose uptake by BAT in response to treatment with the HCAR1 agonist. HCAR1 overexpression elevated BAT temperature associated with increased thermogenic gene expression in BAT. HCAR1 overexpression prevented body weight gain in male DIO mice. Importantly, mice overexpressing HCAR1 in BAT exhibited improved glucose tolerance and insulin sensitivity. HCAR1 overexpression upregulated the Slc2a4 gene expression and promoted GLUT4 trafficking to the plasma membrane. In addition, mice overexpressing HCAR1 displayed a decrease in hormone-sensitive lipase (HSL) phosphorylation and increased lipogenic enzyme gene expression in BAT. Unlike DIO mice, overexpressing HCAR1 in BAT of mice fed a low-fat diet did not change body weight gain and glucose homeostasis. Taken together, our results support the interpretation that HCAR1 expressed in BAT promotes glucose entry and reduces lipolysis in BAT of male DIO mice. As activation of HCAR1 in BAT restores body weight, glucose tolerance, and insulin sensitivity in male DIO mice, our study suggests that interoceptive lactate detection via HCAR1 in BAT can regulate glucose and lipid substrate utilization and/or availability to promote healthy metabolism.NEW & NOTEWORTHY HCAR1 expressed in BAT can promote glucose entry and reduce lipolysis, resulting in body weight loss and increased insulin sensitivity. Hence, targeting HCAR1 in BAT would provide an alternative way to control body weight and euglycemia in individuals with obesity.

Lactate-induced lactylation in skeletal muscle is associated with insulin resistance in humans

Elevated circulating lactate has been associated with obesity and insulin resistance. The aim of the current study was to determine if lactate-induced lysine lactylation (kla), a post-translational modification, was present in human skeletal muscle and related to insulin resistance. Fifteen lean (Body Mass Index: 22.1 ± 0.5 kg/m2) and fourteen obese (40.6 ± 1.4 kg/m2) adults underwent a muscle biopsy and 2-h oral glucose tolerance test. Skeletal muscle lactylation was increased in obese compared to lean females (19%, p < 0.05) and associated with insulin resistance (r = 0.37, p < 0.05) in the whole group. Skeletal muscle lactylation levels were significantly associated with markers of anaerobic metabolism (plasma lactate and skeletal muscle lactate dehydrogenase [LDH], p < 0.05) and negatively associated with markers of oxidative metabolism (skeletal muscle cytochrome c oxidase subunit 4 and Complex I [pyruvate] OXPHOS capacity, p < 0.05). Treatment of primary human skeletal muscle cells (HSkMC) with sodium lactate for 24 h increased protein lactylation and IRS-1 serine 636 phosphorylation in a similar dose-dependent manner (p < 0.05). Inhibition of glycolysis (with 2-deoxy-d-glucose) or LDH-A (with sodium oxamate or LDH-A siRNA) for 24 h reduced HSkMC lactylation which paralleled reductions in culture media lactate accumulation. This study identified the existence of a lactate-derived post-translational modification in human skeletal muscle and suggests skeletal muscle lactylation could provide additional insight into the regulation of skeletal muscle metabolism, including insulin resistance.

Dietary Supplementation with Sea Buckthorn Berry Puree Alters Plasma Metabolomic Profile and Gut Microbiota Composition in Hypercholesterolemia Population

Sea buckthorn berries have been reported to have beneficial effects on plasma lipid profile and cardiovascular health. This study aimed to investigate the impact of intervention with sea buckthorn berry puree on plasma metabolomics profile and gut microbiota in hypercholesterolemic subjects. A total of 56 subjects with hypercholesterolemia consumed 90 g of sea buckthorn berry puree daily for 90 days, and plasma metabolomic profile was studied at 0 (baseline), 45, and 90 days of intervention by using proton nuclear magnetic resonance spectroscopy (¹H NMR). Gut microbiota composition was analyzed at the baseline and after 90 days of supplementation by using high-throughput sequencing. The plasma metabolic profile was significantly altered after 45 days of intervention as compared to the baseline (day 0). A clear trend of returning to the baseline metabolomic profile was observed in plasma when the intervention extended from 45 days to 90 days. Despite this, the levels of several key plasma metabolites such as glucose, lactate, and creatine were lowered at day 90 compared to the baseline levels, suggesting an improved energy metabolism in those patients. In addition, intervention with sea buckthorn puree enriched butyrate-producing bacteria and other gut microbes linked to lipid metabolisms such as Prevotella and Faecalibacterium while depleting Parasutterella associated with increased risks of cardiovascular disease. These findings indicate that sea buckthorn berries have potential in modulating energy metabolism and the gut microbiota composition in hypercholesterolemic patients.

Metabolic changes associated with two endocrine abnormalities in dogs: elevated fructosamine and low thyroxine

INTRODUCTION

Metabolomics studies in canine endocrine abnormalities are sparse and basic information on these abnormalities must be generated.

OBJECTIVES

To characterize the metabolic changes associated with elevated fructosamine, reflecting poor glycemic control, and low thyroxine, a thyroid hormone controlling metabolism.

METHODS

Leftovers of clinical serum samples; 25 controls, 79 high fructosamine, and 47 low thyroxine, were analyzed using ¹H NMR and differences were evaluated using Firth logistic regression.

RESULTS

Both high fructosamine and low thyroxine were associated with changes in concentrations of multiple metabolites, including glycoprotein acetyls and lipids.

CONCLUSION

These findings suggest promising makers for further research and clinical validation.

Influence of Maternal Exercise on Glucose and Lipid Metabolism in Offspring Stem Cells: ENHANCED by Mom

CONTEXT

Recent preclinical data suggest exercise during pregnancy can improve the metabolic phenotype not only of the mother, but of the developing offspring as well. However, investigations in human offspring are lacking.

OBJECTIVE

To characterize the effect of maternal aerobic exercise on the metabolic phenotype of the offspring's mesenchymal stem cells (MSCs).

DESIGN

Randomized controlled trial.

SETTING

Clinical research facility.

PATIENTS

Healthy female adults between 18 and 35 years of age and ≤ 16 weeks' gestation.

INTERVENTION

Mothers were randomized into 1 of 2 groups: aerobic exercise (AE, n = 10) or nonexercise control (CTRL, n = 10). The AE group completed 150 minutes of weekly moderate-intensity exercise, according to American College of Sports Medicine guidelines, during pregnancy, whereas controls attended stretching sessions.

MAIN OUTCOME MEASURES

Following delivery, MSCs were isolated from the umbilical cord of the offspring and metabolic tracer and immunoblotting experiments were completed in the undifferentiated (D0) or myogenically differentiated (D21) state.

RESULTS

AE-MSCs at D0 had an elevated fold-change over basal in insulin-stimulated glycogen synthesis and reduced nonoxidized glucose metabolite (NOGM) production (P ≤ 0.05). At D21, AE-MSCs had a significant elevation in glucose partitioning toward oxidation (oxidation/NOGM ratio) compared with CTRL (P ≤ 0.05). Immunoblot analysis revealed elevated complex I expression in the AE-MSCs at D21 (P ≤ 0.05). Basal and palmitate-stimulated lipid metabolism was similar between groups at D0 and D21.

CONCLUSIONS

These data provide evidence of a programmed metabolic phenotype in human offspring with maternal AE during pregnancy.

The membrane receptor CD44: novel insights into metabolism

CD44, a cell-surface glycoprotein, has long been studied as a cancer molecule due to its essential role in physiological activities in normal cells and pathological activities in cancer cells, such as cell proliferation, adhesion, and migration; angiogenesis; inflammation; and cytoskeleton rearrangement. Yet, recent evidence suggests a role of CD44 in metabolism, especially insulin resistance in obesity and diabetes. In line with the current concept of fibroinflammation in obesity and insulin resistance, CD44 as the main receptor of the extracellular matrix component, hyaluronan (HA), has been shown to regulate diet-induced insulin resistance in muscle and other insulin-sensitive tissues. In this review, we integrate current evidence for a role of CD44 in regulating glucose and lipid homeostasis and speculate about its involvement in the pathogenesis of chronic metabolic diseases, including obesity and diabetes. We summarize the current development of CD44-targeted therapies and discuss its potential for the use in treating metabolic diseases.

Clarifying the link between the blood lactate concentration and cardiovascular risk

The blood lactate value at rest (Lac_rest) is linked to cardiovascular outcomes. It is unclear whether this association holds true in younger, healthy subjects, especially as the pathophysiological connection between Lac_rest and cardiometabolic disease is not well understood. The aim of this study is clarifying the link between Lac_rest and cardiovascular risk, and to study explanatory factors for the variance of Lac_rest concerning metabolism and physical activity in a population of healthy patient-athletes. The distribution and intra-individual variability of Lac_rest was assessed based on 9051 samples. The 10-year cardiovascular risk was then approximated using the Framingham risk score in a group of 1315 samples from patient-athletes. Cross-validated linear regression was used to analyze explanatory variables for Lac_rest and 10-year cardiovascular risk. Lac_rest is weakly associated with the Framingham score. This association disappears when adjusting for blood lipids. Lac_rest is also linked to the predominant type of exercise with endurance athletes featuring a higher Lac_rest. Lac_rest does not independently predict the estimated cardiovascular risk but is associated with lipid parameters. Moreover, the intra-individual variability of Lac_rest is high in a relevant number of subjects, which does not point towards the feasibility to use Lac_rest as an individual risk factor.

Integrative Pathway Analysis of SNP and Metabolite Data Using a Hierarchical Structural Component Model

Integrative multi-omics analysis has become a useful tool to understand molecular mechanisms and drug discovery for treatment. Especially, the couplings of genetics to metabolomics have been performed to identify the associations between SNP and metabolite. However, while the importance of integrative pathway analysis is increasing, there are few approaches to utilize pathway information to analyze phenotypes using SNP and metabolite. We propose an integrative pathway analysis of SNP and metabolite data using a hierarchical structural component model considering the structural relationships of SNPs, metabolites, pathways, and phenotypes. The proposed method utilizes genome-wide association studies on metabolites and constructs the genetic risk scores for metabolites referred to as genetic metabolomic scores. It is based on the hierarchical model using the genetic metabolomic scores and pathways. Furthermore, this method adopts a ridge penalty to consider the correlations between genetic metabolomic scores and between pathways. We apply our method to the SNP and metabolite data from the Korean population to identify pathways associated with type 2 diabetes (T2D). Through this application, we identified well-known pathways associated with T2D, demonstrating that this method adds biological insights into disease-related pathways using genetic predispositions of metabolites.

Two untargeted metabolomics reveals yogurt-associated metabolic alterations in women with multiple metabolic disorders from a randomized controlled study

The beneficial role of yogurt on metabolic profile has been widely reported. Yet, few studies have intended to describe the integrated metabolic alterations in response to yogurt. Yogurt and milk (220 g/d) were given to 48 and 44 obese women with metabolic syndrome and nonalcoholic fatty liver disease for 24 weeks in a randomized controlled trial (registered at http://www.chictr.org.cn as ChiCTR-IPR-15006801). Fasting serum samples were collected before and after intervention for global, untargeted metabolomics based on ¹H nuclear magnetic resonance (NMR) and ultra-high-performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry (UPLC-Q-TOF-MS) (in positive and negative ion modes). Multivariable statistical analysis and pathway analysis were conducted. In both ¹H NMR and UPLC-Q-TOF-MS metabolomics, no clustering was observed between the two groups at baseline. While, a clear clustering was shown after intervention, and the yogurt group had significantly different metabolic status from the milk. The metabolites that contributed mostly to class separation were identified, and involved into pathway analysis. Pathways on amino acids metabolism, fatty acid oxidation, cholesterol catabolism and choline metabolism significantly changed after yogurt intervention. The study revealed the integrated metabolic alterations in response to yogurt via two metabolomics approaches, suggesting the potential mechanisms of yogurt against metabolic disorders. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR-IPR-15006801. Registered 20 July 2015, http://www.chictr.org.cn/ ChiCTR-IPR-15006801. SIGNIFICANCE: Both review from prospective studies and our randomized clinical trial showed the protective role of yogurt against multiple metabolic disorders. However, they were focus on targeted glucose, lipid, and other metabolic indicators, which were only part of human metabolism, failing to show an integrated metabolic feature on yogurt. Therefore, two global, untargeted metabolomics were applied in our current randomized clinical trial, trying to uncover the significant metabolic alterations characterizing the effects of yogurt on obese women with multiple metabolic disorders, and to explore the potential biological mechanisms of yogurt. The finding will shed light on a more comprehensive picture of how yogurt affects host metabolism, and provide theoretical foundation for dietary prevention of chronic diseases.

Metabolomics of Type 1 and Type 2 Diabetes: Insights into Risk Prediction and Mechanisms

PURPOSE OF REVIEW

Metabolomics enables rapid interrogation of widespread metabolic processes making it well suited for studying diabetes. Here, we review the current status of metabolomic investigation in diabetes, highlighting its applications for improving risk prediction and mechanistic understanding.

RECENT FINDINGS

Findings of metabolite associations with type 2 diabetes risk have confirmed experimental observations (e.g., branched-chain amino acids) and also pinpointed novel pathways of diabetes risk (e.g., dimethylguanidino valeric acid). In type 1 diabetes, abnormal metabolite patterns are observed prior to the development of autoantibodies and hyperglycemia. Diabetes complications display specific metabolite signatures that are distinct from the metabolic derangements of diabetes and differ across vascular beds. Lastly, metabolites respond acutely to pharmacologic treatment, providing opportunities to understand inter-individual treatment responses. Metabolomic studies have elucidated biological mechanisms underlying diabetes development, complications, and therapeutic response. While not yet ready for clinical translation, metabolomics is a powerful and promising precision medicine tool.

Machine learning models to predict in-hospital mortality in septic patients with diabetes

BACKGROUND

Sepsis is a leading cause of morbidity and mortality in hospitalized patients. Up to now, there are no well-established longitudinal networks from molecular mechanisms to clinical phenotypes in sepsis. Adding to the problem, about one of the five patients presented with diabetes. For this subgroup, management is difficult, and prognosis is difficult to evaluate.

METHODS

From the three databases, a total of 7,001 patients were enrolled on the basis of sepsis-3 standard and diabetes diagnosis. Input variable selection is based on the result of correlation analysis in a handpicking way, and 53 variables were left. A total of 5,727 records were collected from Medical Information Mart for Intensive Care database and randomly split into a training set and an internal validation set at a ratio of 7:3. Then, logistic regression with lasso regularization, Bayes logistic regression, decision tree, random forest, and XGBoost were conducted to build the predictive model by using training set. Then, the models were tested by the internal validation set. The data from eICU Collaborative Research Database (n = 815) and dtChina critical care database (n = 459) were used to test the model performance as the external validation set.

RESULTS

In the internal validation set, the accuracy values of logistic regression with lasso regularization, Bayes logistic regression, decision tree, random forest, and XGBoost were 0.878, 0.883, 0.865, 0.883, and 0.882, respectively. Likewise, in the external validation set 1, lasso regularization = 0.879, Bayes logistic regression = 0.877, decision tree = 0.865, random forest = 0.886, and XGBoost = 0.875. In the external validation set 2, lasso regularization = 0.715, Bayes logistic regression = 0.745, decision tree = 0.763, random forest = 0.760, and XGBoost = 0.699.

CONCLUSION

The top three models for internal validation set were Bayes logistic regression, random forest, and XGBoost, whereas the top three models for external validation set 1 were random forest, logistic regression, and Bayes logistic regression. In addition, the top three models for the external validation set 2 were decision tree, random forest, and Bayes logistic regression. Random forest model performed well with the training and three validation sets. The most important features are age, albumin, and lactate.

Emerging Roles of Myeloid-Derived Suppressor Cells in Diabetes

Diabetes is a syndrome characterized by hyperglycemia with or without insulin resistance. Its etiology is attributed to the combined action of genes, environment and immune cells. Myeloid-derived suppressor cell (MDSC) is a heterogeneous population of immature cells with immunosuppressive ability. In recent years, different studies have debated the quantity, activity changes and roles of MDSC in the diabetic microenvironment. However, the emerging roles of MDSC have not been fully documented with regard to their interactions with diabetes. Here, the manifestations of MDSC and their subsets are reviewed with regard to the incidence of diabetes and diabetic complications. The possible drugs targeting MDSC are discussed with regard to their potential of treating diabetes. We believe that understanding MDSC will offer opportunities to explain pathological characteristics of different diabetes. MDSC also will be used for personalized immunotherapy of diabetes.

A Dual Electrode Biosensor for Glucose and Lactate Measurement in Normal and Prolonged Obese Mice Using Single Drop of Whole Blood

Understanding the levels of glucose (G) and lactate (L) in blood can help us regulate various chronic health conditions such as obesity. In this paper, we introduced an enzyme-based electrochemical biosensor adopting glucose oxidase and lactate oxidase on two working screen-printed carbon electrodes (SPCEs) to sequentially determine glucose and lactate concentrations in a single drop (~30 µL) of whole blood. We developed a diet-induced obesity (DIO) mouse model for 28 weeks and monitored the changes in blood glucose and lactate levels. A linear calibration curve for glucose and lactate concentrations in ranges from 0.5 to 35 mM and 0.5 to 25 mM was obtained with R-values of 0.99 and 0.97, respectively. A drastic increase in blood glucose and a small but significant increase in blood lactate were seen only in prolonged obese cases. The ratio of lactate concentration to glucose concentration (L/G) was calculated as the mouse’s gained weight. The results demonstrated that an L/G value of 0.59 could be used as a criterion to differentiate between normal and obesity conditions. With L/G and weight gain, we constructed a diagnostic plot that could categorize normal and obese health conditions into four different zones. The proposed dual electrode biosensor for glucose and lactate in mouse whole blood showed good stability, selectivity, sensitivity, and efficiency. Thus, we believe that this dual electrode biosensor and the diagnostic plot could be used as a sensitive analytical tool for diagnosing glucose and lactate biomarkers in clinics and for monitoring obesity.

Basigin deficiency prevents anaplerosis and ameliorates insulin resistance and hepatosteatosis

Monocarboxylates, such as lactate and pyruvate, are precursors for biosynthetic pathways, including those for glucose, lipids, and amino acids via the tricarboxylic acid (TCA) cycle and adjacent metabolic networks. The transportation of monocarboxylates across the cellular membrane is performed primarily by monocarboxylate transporters (MCTs), the membrane localization and stabilization of which are facilitated by the transmembrane protein basigin (BSG). Here, we demonstrate that the MCT/BSG axis sits at a crucial intersection of cellular metabolism. Abolishment of MCT1 in the plasma membrane was achieved by Bsg depletion, which led to gluconeogenesis impairment via preventing the influx of lactate and pyruvate into the cell, consequently suppressing the TCA cycle. This net anaplerosis suppression was compensated in part by the increased utilization of glycogenic amino acids (e.g., alanine and glutamine) into the TCA cycle and by activated ketogenesis through fatty acid β-oxidation. Complementary to these observations, hyperglycemia and hepatic steatosis induced by a high-fat diet were ameliorated in Bsg-deficient mice. Furthermore, Bsg deficiency significantly improved insulin resistance induced by a high-fat diet. Taken together, the plasma membrane–selective modulation of lactate and pyruvate transport through BSG inhibition could potentiate metabolic flexibility to treat metabolic diseases.

Antidiabetic Effect of Noodles Containing Fermented Lettuce Extracts

The aim of the current study was to examine the antidiabetic effect of noodle containing fermented lettuce extract (FLE) on diabetic mice as a pre-clinical study. The γ-aminobutyric acid (GABA) content, antioxidant capacity, and total polyphenol content of the FLE noodles were analyzed and compared with those of standard noodles. In addition, oral glucose and sucrose tolerance, and fasting blood glucose tests were performed using a high-fat diet/streptozotocin-mediated diabetic mouse model. Serum metabolite profiling of mice feed standard or FLE noodles was performed using gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) to understand the mechanism changes induced by the FLE noodles. The GABA content, total polyphenols, and antioxidant activity were high in FLE noodles compared with those in the standard noodles. In vivo experiments also showed that mice fed FLE noodles had lower blood glucose levels and insulin resistance than those fed standard noodles. Moreover, glycolysis, purine metabolism, and amino acid metabolism were altered by FLE as determined by GC-TOF-MS-based metabolomics. These results demonstrate that FLE noodles possess significant antidiabetic activity, suggesting the applicability of fermented lettuce extract as a potential food additive for diabetic food products.

Deletion of the diabetes candidate gene Slc16a13 in mice attenuates diet-induced ectopic lipid accumulation and insulin resistance

Genome-wide association studies have identified SLC16A13 as a novel susceptibility gene for type 2 diabetes. The SLC16A13 gene encodes SLC16A13/MCT13, a member of the solute carrier 16 family of monocarboxylate transporters. Despite its potential importance to diabetes development, the physiological function of SLC16A13 is unknown. Here, we validate Slc16a13 as a lactate transporter expressed at the plasma membrane and report on the effect of Slc16a13 deletion in a mouse model. We show that Slc16a13 increases mitochondrial respiration in the liver, leading to reduced hepatic lipid accumulation and increased hepatic insulin sensitivity in high-fat diet fed Slc16a13 knockout mice. We propose a mechanism for improved hepatic insulin sensitivity in the context of Slc16a13 deficiency in which reduced intrahepatocellular lactate availability drives increased AMPK activation and increased mitochondrial respiration, while reducing hepatic lipid content. Slc16a13 deficiency thereby attenuates hepatic diacylglycerol-PKCε mediated insulin resistance in obese mice. Together, these data suggest that SLC16A13 is a potential target for the treatment of type 2 diabetes and non-alcoholic fatty liver disease.

Environmental pollution and diabetes mellitus

Diabetes mellitus (DM) is a chromic metabolic disease that affects a large segment of the population worldwide. Physical inactivity, poor nutrition, and genetic predisposition are main risk factors for disease development. In the last decade, it was clear to the scientific community that DM development is linked to a novel disease inducer that was later defined as diabetogenic factors of pollution and endocrine disrupting agents. Environmental pollution is exponentially increasing in uncontrolled manner in several countries. Environmental pollutants are of diverse nature and toxicities, including polyaromatic hydrocarbons (PAHs), pesticides, and heavy metals. In the current review, we shed light on the impact of each class of these pollutants and the underlined molecular mechanism of diabetes induction and biological toxicities. Finally, a brief overview about the connection between coronavirus disease 2019 and diabetes pandemics is presented.

Lactate accelerates vascular calcification through NR4A1-regulated mitochondrial fission and BNIP3-related mitophagy

Arterial media calcification is related to mitochondrial dysfunction. Protective mitophagy delays the progression of vascular calcification. We previously reported that lactate accelerates osteoblastic phenotype transition of VSMC through BNIP3-mediated mitophagy suppression. In this study, we investigated the specific links between lactate, mitochondrial homeostasis, and vascular calcification. Ex vivo, alizarin S red and von Kossa staining in addition to measurement of calcium content, RUNX2, and BMP-2 protein levels revealed that lactate accelerated arterial media calcification. We demonstrated that lactate induced mitochondrial fission and apoptosis in aortas, whereas mitophagy was suppressed. In VSMCs, lactate increased NR4A1 expression, leading to activation of DNA-PKcs and p53. Lactate induced Drp1 migration to the mitochondria and enhanced mitochondrial fission through NR4A1. Western blot analysis of LC3-II and p62 and mRFP-GFP-LC3 adenovirus detection showed that NR4A1 knockdown was involved in enhanced autophagy flux. Furthermore, NR4A1 inhibited BNIP3-related mitophagy, which was confirmed by TOMM20 and BNIP3 protein levels, and LC3-II co-localization with TOMM20. The excessive fission and deficient mitophagy damaged mitochondrial structure and impaired respiratory function, determined by mPTP opening rate, mitochondrial membrane potential, mitochondrial morphology under TEM, ATP production, and OCR, which was reversed by NR4A1 silencing. Mechanistically, lactate enhanced fission but halted mitophagy via activation of the NR4A1/DNA-PKcs/p53 pathway, evoking apoptosis, finally accelerating osteoblastic phenotype transition of VSMC and calcium deposition. This study suggests that the NR4A1/DNA-PKcs/p53 pathway is involved in the mechanism by which lactate accelerates vascular calcification, partly through excessive Drp-mediated mitochondrial fission and BNIP3-related mitophagy deficiency.

Vitamin D3 potentiates the nephroprotective effects of metformin in a rat model of metabolic syndrome: role of AMPK/SIRT1 activation and DPP-4 inhibition

The current study aimed to investigate the molecular mechanisms of metformin and vitamin D3-induced nephroprotection in a metabolic syndrome (MetS) rat model, evaluating the capacity of vitamin D3 to potentiate metformin action. MetS was induced by 10% fructose in drinking water and 3% salt in the diet. After 6 weeks, serum lipid profile and uric acid were measured, an oral glucose tolerance test (OGTT) was performed, and kidney function was investigated. In conjunction with the same concentrations of fructose and salt feeding, MetS rats with significant weight gain, dyslipidemia, hyperuricemia, and dysglycemia were treated orally with metformin (200 mg/kg), vitamin D3 (10 µg/kg), or both daily for 6 weeks. At the end of the study period, anthropometrical parameters were recorded, OGTT was reperformed, urine and blood samples were collected, and tissue samples were harvested at sacrifice. MetS rats showed dramatically declined renal function, enhanced intrarenal oxidative stress and inflammation, and extravagant renal histopathological damage with interstitial fibrosis. Metformin and vitamin D3 significantly reversed all the aforementioned deleterious effects in MetS rats. The study has verified the nephroprotective effects of metformin and vitamin D3 in MetS, accentuating the critical role of AMP-activated protein kinase/sirtuin-1 activation and dipeptidyl peptidase-4 inhibition. Given the synergistic effects of the combination, vitamin D3 is worth being investigated as an additional therapeutic agent for preventing MetS-induced nephropathy.

Influence of endocrine disease on l-lactate concentrations in blood of ponies

Background

Blood l‐lactate concentrations are higher in people with developing or established diabetes mellitus and insulin resistance.

Objectives

To investigate whether blood l‐lactate concentrations are positively correlated with measures of insulin dysregulation (ID) or increased autumnal ACTH concentrations in ponies.

Animals

Systemically healthy client‐owned ponies (n = 101).

Methods

Prospective case‐control study. Blood samples were obtained from 101 clinically healthy ponies. Breed, weight, height, and subjective and objective measures of body condition were recorded. Blood l‐lactate, glucose, triglyceride, total adiponectin, and ACTH concentrations were measured and an oral sugar test (OST) was carried out. Correlations between blood l‐lactate and variables of endocrine health were determined.

Results

Using a seasonal cutoff point of ACTH concentrations ≥47 pg/mL, 55 ponies had increased autumnal ACTH concentrations and 45 did not. Using a basal insulin concentration of >50 μiU/mL, 42 ponies were diagnosed with ID and 58 were not. Using a 60 minutes after OST cutoff point of >45 μiU/mL, 57 ponies had ID and 37 did not. Blood l‐lactate concentrations were significantly lower in obese (average body condition score ≥ 7/9) compared to nonobese ponies (0.6 mmol/L; range, 0.0‐1.9 mmol/L vs 0.8 mmol/L; range, 0.3‐2.7 mmol/L; P = .01). No other significant correlations were detected. No differences were detected between ponies with and without increased autumnal ACTH concentrations (0.7 mmol/L; range, 0.0‐2.7 mmol/L vs 0.7 mmol/L; range, 0.3‐1.8 mmol/L; P = .84) and with and without ID (0.7 mmol/L; range, 0.3‐2.7 mmol/L vs 0.8 mmol/L; range, 0.0‐1.6 mmol/L; P = .63).

Conclusions and Clinical Importance

Results do not support an effect of endocrine status on l‐lactate concentrations in blood of ponies.

Strong and Bitter Vegetables from Traditional Cultivars and Cropping Methods Improve the Health Status of Type 2 Diabetics: A Randomized Control Trial

Vegetables rich in bitter-tasting phytochemicals may exert enhanced beneficial effects against key factors associated with type two diabetes (T2D). This study investigates whether selected cultivars of bitter and strong-tasting (BST) Brassica and root vegetables exert greater health benefits on T2D patients compared to equivalent modern mild and sweet tasting (MST) vegetables. A 12-week randomized, controlled, parallel intervention study involved 92 T2D patients, who were allocated three different diets: (1) 500 g daily of bitter and strong-tasting (BST) vegetables; (2) 500 g daily of mild and sweet-tasting (MST) vegetables; (3) 120 g daily MST normal diet (control). Both vegetable diets contained root vegetables and cabbages selected based on sensory differences and content of phytochemicals. Prior to and after the study, all participants underwent an oral glucose tolerance test (OGTT), 24 h blood pressure measurements, DEXA scans, and fasted blood samples. Both diets high in vegetables significantly reduced the participants' BMI, total body fat mass, and HbA1c levels compared to control, but in the BST group, significant differences were also found regarding incremental area under the curve glucose 240 min (OGTT) and fasting glucose levels. A high daily intake of root vegetables and cabbages showed significant health improvements in both vegetable groups. BST vegetables had the greatest impact on insulin sensitivity, body fat mass, and blood pressure compared to control; moreover, they further improved glycemic control compared to MST vegetables.

Biomarker monitoring and long-acting insulin treatment in a stress model to facilitate personalized diabetic control

Diabetes is a chronic disease involving elevated blood glucose levels. Controlled insulin delivery is an ideal method to achieve glycemic control. However, glucose levels vary as a result of changes in the body's physiological conditions resulting from different daily events, such as meals, exercise and stress. It is essential to develop and to monitor appropriate biomarkers for these natural physiological perturbations in order to achieve a holistic understanding of metabolic changes in diabetic patients to facilitate optimal glucose management and make possible personalized medicine for this very debilitating disease. The novel aspects of the current research include the combination of the tail suspension stress animal model and microdialysis for stress biomarker monitoring. A tail suspension test was optimized and used as a stress inducer for different groups of model rats (normal, untreated diabetic and insulin-treated diabetic rats). The levels of multiple metabolic analytes in the subcutaneous tissue were monitored continuously using subcutaneous microdialysis analysis. Different analytes, including pH, glucose and lactate were monitored and analyzed. Another important and original aspect of the reported work is that revelation that the pH, lactate and glucose levels increased under the stress conditions and the changes tended to be more pronounced in diabetic rats (both untreated and long-acting insulin-treated) compared to normal rats. Long-acting insulin treatment was shown to shorten the duration of the pH and glucose changes in response to stress when compared to the untreated diabetic rats. An additional novel aspect of the research is that subcutaneous pH was shown to be a sensitive stress biomarker for diabetic rats as pH changes rapidly after stress initiation. This research provides insight into the importance of accurate glycemic control and diabetes management for individual patients through highlighting stress management and appropriate biomarker monitoring, especially the value of combining pH and lactate monitoring with typical glucose monitoring. This research will pave the way for individualized medicine for diabetic patients through helping to obtain a holistic understanding of the various important biomarkers, rather than solely depending on glucose monitoring to determine appropriate insulin dosing.

Ockham's razor and the metabolic syndrome

The broad effects of bariatric/metabolic surgery on virtually every tissue and organ system remain unexplained. Weight loss, although a major factor, does not fully account for the rapid, full, and durable remission of type 2 diabetes, return of islet function, reduction of the prevalence of cancers, increase in gray matter of the brain, and decrease in all-cause mortality. This review supports the thesis that the metabolic syndrome is not a group of separate diseases but rather multiple expressions of a shared defect in the utilization of carbohydrates and lipids. That error is probably caused by a dysmetabolic signal from the foregut, stimulated by food, that limits entry of 2-carbon fragments into the tricarboxylic acid cycle, the accumulation of lactate and, in turn, increases in glucose and insulin. Surgery limits that signal by reducing contact between food and foregut mucosa. Speciation of that signal(s) may offer a new pathway for drug development.

Effect of Chronic Exercise Training on Blood Lactate Metabolism Among Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

Purpose: To assess the effect of chronic exercise training on blood lactate metabolism at rest (i.e., basal lactate concentrations) and during exercise (i.e., blood lactate concentration at a fixed load, load at a fixed blood lactate concentration, and load at the individual blood lactate threshold) among patients with type 2 diabetes mellitus (T2DM). Methods: PubMed (MedLine), Embase, Web of Science, and Scopus were searched. Randomized controlled trials, non-randomized controlled trials, and case-control studies using chronic exercise training (i.e., 4 weeks) and that assessed blood lactate concentrations at rest and during exercise in T2DM patients were included. Results: Thirteen studies were eligible for the systematic review, while 12 studies with 312 participants were included into the meta-analysis. In the pre-to-post intervention meta-analysis, chronic exercise training had no significant effect on changes in basal blood lactate concentrations (standardized mean difference (SMD) = -0.20; 95% CI, -0.55 to 0.16; p = 0.28), and the results were similar when comparing the effect of intervention and control groups. Furthermore, blood lactate concentration at a fixed load significantly decreased (SMD = -0.73; 95% CI, -1.17 to -0.29; p = 0.001), while load at a fixed blood lactate concentration increased (SMD = 0.40; 95% CI, 0.07 to 0.72; p = 0.02) after chronic exercise training. No change was observed in load at the individual blood lactate threshold (SMD = 0.28; 95% CI, -0.14 to 0.71; p = 0.20). Conclusion: Chronic exercise training does not statistically affect basal blood lactate concentrations; however, it may decrease the blood lactate concentrations during exercise, indicating improvements of physical performance capacity which is beneficial for T2DM patients' health in general. Why chronic exercise training did not affect basal blood lactate concentrations needs further investigation.