Diabetes and aortic dissection: unraveling the role of 3-hydroxybutyrate through mendelian randomization

BACKGROUND

In observational and experimental studies, diabetes has been reported as a protective factor for aortic dissection. 3-Hydroxybutyrate, a key constituent of ketone bodies, has been found to favor improvements in cardiovascular disease. However, whether the protective effect of diabetes on aortic dissection is mediated by 3-hydroxybutyrate is unclear. We aimed to investigate the causal effects of diabetes on the risk of aortic dissection and the mediating role of 3-hydroxybutyrate in them through two-step Mendelian randomization.

MATERIALS AND METHODS

We performed a two-step Mendelian randomization to investigate the causal connections between diabetes, 3-hydroxybutyrate, and aortic dissection and calculate the mediating effect of 3-hydroxybutyrate. Publicly accessible data for Type 1 diabetes, Type 2 diabetes, dissection of aorta and 3-hydroxybutyrate were obtained from genome-wide association studies. The association between Type 1 diabetes and dissection of aorta, the association between Type 2 diabetes and dissection of aorta, and mediation effect of 3-hydroxybutyrate were carried out separately.

RESULTS

The IVW method showed that Type 1 diabetes was negatively associated with the risk of aortic dissection (OR 0.912, 95% CI 0.836-0.995), The weighted median, simple mode and weighted mode method showed consistent results. The mediated proportion of 3-hydroxybutyrate on the relationship between Type 1 diabetes and dissection of aorta was 24.80% (95% CI 5.12-44.47%). The IVW method showed that Type 2 diabetes was negatively associated with the risk of aortic dissection (OR 0.763, 95% CI 0.607-0.960), The weighted median, simple mode and weighted mode method showed consistent results. 3-Hydroxybutyrate does not have causal mediation effect on the relationship between Type 2 diabetes and dissection of aorta.

CONCLUSION

Mendelian randomization study revealed diabetes as a protective factor for dissection of aorta. The protective effect of type 1 diabetes on aortic dissection was partially mediated by 3-hydroxybutyrate, but type 2 diabetes was not 3-hydroxybutyrate mediated.

Levels of Circulating Ketone Bodies in Patients Undergoing Cardiac Surgery on Cardiopulmonary Bypass

Ketone bodies (KBs) are energy-efficient substrates utilized by the heart depending on its metabolic demand and substrate availability. Levels of circulating KBs have been shown to be elevated in acute and chronic cardiovascular disease and are associated with severity of disease in patients with heart failure and functional outcome after myocardial infarction. To investigate whether this pattern similarly applies to patients undergoing cardiac surgery involving cardiopulmonary bypass (CPB), we analysed prospectively collected pre- and postoperative blood samples from 192 cardiac surgery patients and compared levels and perioperative changes in total KBs with Troponin T as a marker of myocardial cell injury. We explored the association of patient characteristics and comorbidities for each of the two biomarkers separately and comparatively. Median levels of KBs decreased significantly over the perioperative period and inversely correlated with changes observed for Troponin T. Associations of patient characteristics with ketone body perioperative course showed notable differences compared to Troponin T, possibly highlighting factors acting as a "driver" for the change in the respective biomarker. We found an inverse correlation between perioperative change in ketone body levels and changes in troponin, indicating a marked decrease in ketone body concentrations in patients exhibiting greater myocardial cell injury. Further investigations aimed at better understanding the role of KBs on perioperative changes are warranted.

Serum 3-Hydroxybutyrate is Expected to Serve as One of the Supportive Diagnostic Markers of Persistent Idiopathic Dentoalveolar Pain (PDAP)

Background

Persistent idiopathic dentoalveolar pain (PDAP), previously referred to as atypical odontalgia, is a chronic dental pain that occurs without signs of pathology. PDAP is considered a diagnosis of exclusion, and its definition is currently under refinement and remains ambiguous. The metabolite known as 3-hydroxybutyrate (3HB) has garnered significant interest as a potential indicator for both depression and chronic psychogenic pain. We investigated the characteristics of patients with PDAP and hypothesized that serum 3HB could support the diagnosis of PDAP.

Subjects and Methods

Forty-one patients with PDAP and 167 patients with odontogenic toothache were investigated regarding depression and anxiety scales in addition to the general dental evaluation. Blood tests including high-sensitivity CRP, HbA1c, and 3HB were performed for all patients. Associations between PDAP and patients' varying characteristics were investigated using hierarchical multivariate logistic regression analyses.

Results

There were more females, current smokers, patients with orofacial pain (such as temporomandibular joint pain, glossalgia, and headache), and people with elevated 3HB levels among patients with PDAP than among control participants. Multivariate logistic regression analyses predicting patients with PDAP identified the female sex (odds ratio [OR]: 4.16), current smoking (OR: 14.9), glossalgia (OR: 19.8) a high CES-D score (≥16) (OR: 5.98), and elevated serum 3HB (≥80 μmol/L) (OR: 18.4) factors significantly associated with PDAP.

Conclusion

Our results demonstrated that serum 3HB levels could be elevated in patients with PDAP compared to other types of odontogenic pain, although 3HB was not specific to PDAP. Based on our findings, five factors - female sex, current smoking, depressive tendencies, chronic orofacial pains, and high serum 3HB levels - could be useful for diagnosing PDAP.

Beneficial Effects of Ketone Ester in Patients With Cardiogenic Shock: A Randomized, Controlled, Double-Blind Trial

BACKGROUND

Cardiogenic shock (CS) is a life-threatening condition with sparse treatment options. The ketone body 3-hydroxybutyrate has favorable hemodynamic effects in patients with stable chronic heart failure. Yet, the hemodynamic effects of exogenous ketone ester (KE) in patients with CS remain unknown.

OBJECTIVES

The authors aimed to assess the hemodynamic effects of single-dose enteral treatment with KE in patients with CS.

METHODS

In a double-blind, crossover study, 12 patients with CS were randomized to an enteral bolus of KE and isocaloric, isovolumic placebo containing maltodextrin. Patients were assessed with pulmonary artery catheterization, arterial blood samples, echocardiography, and near-infrared spectroscopy for 3 hours following each intervention separated by a 3-hour washout period.

RESULTS

KE increased circulating 3-hydroxybutyrate (2.9 ± 0.3 mmol/L vs 0.2 ± 0.3 mmol/L, P < 0.001) and was associated with augmented cardiac output (area under the curve of relative change: 61 ± 22 L vs 1 ± 18 L, P = 0.044). Also, KE increased cardiac power output (0.07 W [95% CI: 0.01-0.14]; P = 0.037), mixed venous saturation (3 percentage points [95% CI: 1-5 percentage points]; P = 0.010), and forearm perfusion (3 percentage points [95% CI: 0-6 percentage points]; P = 0.026). Right (P = 0.048) and left (P = 0.017) ventricular filling pressures were reduced whereas heart rate and mean arterial and pulmonary arterial pressures remained similar. Left ventricular ejection fraction improved by 4 percentage points (95% CI: 2-6 percentage points; P = 0.005). Glucose levels decreased by 2.6 mmol/L (95% CI: -5.2 to 0.0; P = 0.047) whereas insulin levels remained unaltered.

CONCLUSIONS

Treatment with KE improved cardiac output, biventricular function, tissue oxygenation, and glycemic control in patients with CS (Treatment With the Ketone Body 3-hydroxybutyrate in Patients With Cardiogenic Shock [KETO-SHOCK1]; NCT04642768).

Ketone body 3-hydroxybutyrate elevates cardiac output through peripheral vasorelaxation and enhanced cardiac contractility

The ketone body 3-hydroxybutyrate (3-OHB) increases cardiac output and myocardial perfusion without affecting blood pressure in humans, but the cardiovascular sites of action remain obscure. Here, we test the hypothesis in rats that 3-OHB acts directly on the heart to increase cardiac contractility and directly on blood vessels to lower systemic vascular resistance. We investigate effects of 3-OHB on (a) in vivo hemodynamics using echocardiography and invasive blood pressure measurements, (b) isolated perfused hearts in Langendorff systems, and (c) isolated arteries and veins in isometric myographs. We compare Na-3-OHB to equimolar NaCl added to physiological buffers or injection solutions. At plasma concentrations of 2-4 mM in vivo, 3-OHB increases cardiac output (by 28.3±7.8%), stroke volume (by 22.4±6.0%), left ventricular ejection fraction (by 13.3±4.6%), and arterial dP/dtmax (by 31.9±11.2%) and lowers systemic vascular resistance (by 30.6±11.2%) without substantially affecting heart rate or blood pressure. Applied to isolated perfused hearts at 3-10 mM, 3-OHB increases left ventricular developed pressure by up to 26.3±7.4 mmHg and coronary perfusion by up to 20.2±9.5%. Beginning at 1-3 mM, 3-OHB relaxes isolated coronary (EC50=12.4 mM), cerebral, femoral, mesenteric, and renal arteries as well as brachial, femoral, and mesenteric veins by up to 60% of pre-contraction within the pathophysiological concentration range. Of the two enantiomers that constitute racemic 3-OHB, D-3-OHB dominates endogenously; but tested separately, the enantiomers induce similar vasorelaxation. We conclude that increased cardiac contractility and generalized systemic vasorelaxation can explain the elevated cardiac output during 3-OHB administration. These actions strengthen the therapeutic rationale for 3-OHB in heart failure management.

Exploring the Therapeutic Potential of Ethyl 3-Hydroxybutyrate in Alleviating Skeletal Muscle Wasting in Cancer Cachexia

Cachexia (CAC) is a debilitating metabolic syndrome. Although dietary interventions are attractive, long-term adherence to specific diets is difficult to maintain and can lead to systemic side effects. Ethyl 3-hydroxybutyrate (EHB) is a commonly used food additive found in wine and Tribolium castaneum. In this study, we investigated the effects of EHB administration in cachectic mice. After a single intraperitoneal injection of EHB into mice, 3-hydroxybutyrate (3-HB) levels were significantly increased in the serum and gastrocnemius of mice. The administration of EHB alleviated cachexia-related symptoms, ameliorated skeletal muscle atrophy, and improved survival in cachectic mice. In addition, the supplementation of cachectic mice with 3-HB by EHB administration significantly reduced tumor weights, indicating the anti-tumor effects of 3-HB. Remarkably, the addition of 3-HB to the culture medium significantly attenuated the C2C12 myotube atrophy induced by the culture supernatant of CT26 cell lines, highlighting its potential to counteract the destructive effects of tumor-derived elements on muscle tissue. NMR-based metabolomics analysis provided insights into the underlying mechanisms and revealed that the anti-cachexia effects of 3-HB treatment can be attributed to three key mechanisms: the promotion of the TCA cycle and the attenuation of proteolysis, the promotion of protein synthesis and the improvement of metabolic homeostasis, and a reduction in inflammation and an enhancement of the antioxidant capacity. This study provided compelling evidence for the protective effects of 3-HB treatment on the cachectic gastrocnemius and highlighted the efficacy of EHB administration as a ketone supplementation approach to achieve nutritional ketosis without the need for dietary restriction.

[Research progress on medical devices of polyhydroxyalkanoate in orthopedics]

Objective

To review the research progress of natural biomaterial polyhydroxyalkanoate (PHA) in orthopedics.

Methods

The literature concerning PHA devices for bone defects, bone repair, and bone neoplasms, respectively, in recent years was extensively consulted. The three aspects of the advantages of PHA in bone repair, the preparation of PHA medical devices for bone repair and their application in orthopedics were discussed.

Results

Due to excellent biodegradability, biocompatibility, and potential osteoinduction, PHA is a kind of good bone repair material. In addition to the traditional PHA medical implants, the use of electrostatic spinning and three-dimensional printing can be designed to various functional PHA medical devices, in order to meet the orthopedic clinical demands, including the bone regeneration, minimally invasive bone tissue repair by injection, antibacterial bone repair, auxiliary establishment of three-dimensional bone tumor model, directed osteogenic differentiation of stem cells, etc.

Conclusion

At present, PHA is a hotspot of biomaterials for translational medicine in orthopedics. Although they have not completely applied in the clinic, the advantages of repair in bone defects have been gradually reflected in tissue engineering, showing an application prospect in orthopedics.

New prebiotics by ketone donation

Integrity of the microbiome is an essential element for human gut health. 3-Hydroxybutyrate (3HB) secreted into the gut lumen has gained attention as a regulator of gut physiology, including stem cell expansion. In this opinion, I propose new prebiotics leading to gut health by use of a ketone (3HB) donor. When exogenous 3HB is supplied through ketone donation, it has the potential to markedly improve gut health by altering the gut microbiome and systemic metabolic status. Poly-hydroxybutyrate (PHB) donates 3HB and primarily influences microbiota, making it an effective prebiotic for improving the gut environment. Thus, exogenous 3HB donation to the lumen of the gut may aid gut health by maintaining the integrity of microbiome.

Integrative Proteome Analysis Revels 3-Hydroxybutyrate Exerts Neuroprotective Effect by Influencing Chromatin Bivalency

3-hydroxybutyrate (3OHB) has been proved to act as a neuroprotective molecule in multiple neurodegenerative diseases. Here, we employed a quantitative proteomics approach to assess the changes of the global protein expression pattern of neural cells upon 3OHB administration. In combination with a disease-related, protein-protein interaction network we pinpointed a hub marker, histone lysine 27 trimethylation, which is one of the key epigenetic markers in multiple neurodegenerative diseases. Integrative analysis of transcriptomic and epigenomic datasets highlighted the involvement of bivalent transcription factors in 3OHB-mediated disease protection and its alteration of neuronal development processes. Transcriptomic profiling revealed that 3OHB impaired the fate decision process of neural precursor cells by repressing differentiation and promoting proliferation. Our study provides a new mechanism of 3OHB's neuroprotective effect, in which chromatin bivalency is sensitive to 3OHB alteration and drives its neuroprotective function both in neurodegenerative diseases and in neural development processes.

The novel sustained 3-hydroxybutyrate donor poly-D-3-hydroxybutyric acid prevents inflammatory bowel disease through upregulation of regulatory T-cells

Inflammatory bowel disease (IBD) is a chronic persistent intestinal disorder, with ulcerative colitis and Crohn's disease being the most common. However, the physio-pathological development of IBD is still unknown. Therefore, research on the etiology and treatment of IBD has been conducted using a variety of approaches. Short-chain fatty acids such as 3-hydroxybutyrate (3-HB) are known to have various physiological activities. In particular, the production of 3-HB by the intestinal microflora is associated with the suppression of various inflammatory diseases. In this study, we investigated whether poly-D-3-hydroxybutyric acid (PHB), a polyester of 3-HB, is degraded by intestinal microbiota and works as a slow-release agent of 3-HB. Further, we examined whether PHB suppresses the pathogenesis of IBD models. As long as a PHB diet increased 3-HB concentrations in the feces and blood, PHB suppressed weight loss and histological inflammation in a dextran sulfate sodium-induced IBD model. Furthermore, PHB increased the accumulation of regulatory T cells in the rectum without affecting T cells in the spleen. These results indicate that PHB has potential applications in treating diseases related to the intestinal microbiota as a sustained 3-HB donor. We show for the first time that biodegradable polyester exhibits intestinal bacteria-mediated bioactivity toward IBD. The use of bioplastics, which are essential materials for sustainable social development, represents a novel approach to diseases related to dysbiosis, including IBD.

Thauera sp. Sel9, a new bacterial strain for polyhydroxyalkanoates production from volatile fatty acids

Thauera is one of the main genera involved in polyhydroxyalkanoate (PHA) production in microbial mixed cultures (MMCs) from volatile fatty acids (VFAs). However, no Thauera strains involved in PHA accumulation have been obtained in pure culture so far. This study is the first report of the isolation and characterization of a Thauera sp. strain, namely Sel9, obtained from a sequencing batch reactor (S-SBR) set up for the selection of PHA storing biomass. The 16S rRNA gene evidenced a high sequence similarity with T. butanivorans species. Genome sequencing identified all genes involved in PHA synthesis, regulation and degradation. The strain Sel9 was able to grow with an optimum of chemical oxygen demand-to-nitrogen (COD:N) ratio ranging from 4.7 to 18.9. Acetate, propionate, butyrate and valerate were used as sole carbon and energy sources: a lag phase of 72 h was observed in presence of propionate. Final production of PHAs, achieved with a COD:N ratio of 75.5, was 60.12 ± 2.60 %, 49.31 ± 0.7 %, 37.31 ± 0.43 % and 18.06 ± 3.81 % (w/w) by using butyrate, acetate, valerate and propionate as substrates, respectively. Also, the 3-hydroxybutyrate/3-hydroxyvalerate ratio reflected the type of carbon sources used: 12.30 ± 0.82 for butyrate, 3.56 ± 0.02 for acetate, 0.93 ± 0.03 for valerate and 0.76 ± 0.02 for propionate. The results allow a better elucidation of the role of Thauera in MMCs and strongly suggest a possible exploitation of Thauera sp. Sel9 for a cost-effective and environmentally friendly synthesis of PHAs using VFAs as substrate.

The Plasma Levels of 3-Hydroxybutyrate, Dityrosine, and Other Markers of Oxidative Stress and Energy Metabolism in Major Depressive Disorder

Major depressive disorder (MDD) is a serious mental disease with a pathophysiology that is not yet fully clarified. An increasing number of studies show an association of MDD with energy metabolism alteration and the presence of oxidative stress. We aimed to evaluate plasma levels of 3-hydroxybutyrate (3HB), NADH, myeloperoxidase, and dityrosine (di-Tyr) in adolescent and adult patients with MDD, compare them with healthy age-matched controls, and assess the effect of antidepressant treatment during hospitalisation on these levels. In our study, plasmatic levels of 3HB were elevated in both adolescents (by 55%; p = 0.0004) and adults (by 88%; p < 0.0001) with MDD compared to controls. Levels of dityrosine were increased in MDD adults (by 19%; p = 0.0092) but not adolescents. We have not found any significant effect of antidepressants on the selected parameters during the short observation period. Our study supports the findings suggesting altered energy metabolism in MDD and demonstrates its presence independently of the age of the patients.

Roux-En-Y Gastric Bypass (RYGB) Surgery during High Liquid Sucrose Diet Leads to Gut Microbiota-Related Systematic Alterations

Roux-en-Y gastric bypass (RYGB) surgery has been proven successful in weight loss and improvement of co-morbidities associated with obesity. Chronic complications such as malabsorption of micronutrients in up to 50% of patients underline the need for additional therapeutic approaches. We investigated systemic RYGB surgery effects in a liquid sucrose diet-induced rat obesity model. After consuming a diet supplemented with high liquid sucrose for eight weeks, rats underwent RYGB or control sham surgery. RYGB, sham pair-fed, and sham ad libitum-fed groups further continued on the diet after recovery. Notable alterations were revealed in microbiota composition, inflammatory markers, feces, liver, and plasma metabolites, as well as in brain neuronal activity post-surgery. Higher fecal 4-aminobutyrate (GABA) correlated with higher Bacteroidota and Enterococcus abundances in RYGB animals, pointing towards the altered enteric nervous system (ENS) and gut signaling. Favorable C-reactive protein (CRP), serine, glycine, and 3-hydroxybutyrate plasma profiles in RYGB rats were suggestive of reverted obesity risk. The impact of liquid sucrose diet and caloric restriction mainly manifested in fatty acid changes in the liver. Our multi-modal approach reveals complex systemic changes after RYGB surgery and points towards potential therapeutic targets in the gut-brain system to mimic the surgery mode of action.

Applications and Mechanism of 3-Hydroxybutyrate (3HB) for Prevention of Colonic Inflammation and Carcinogenesis as a Food Supplement

SCOPE

Inflammatory bowel disease and colorectal carcinogenesis (CRC) are common diseases without effective prevention approach. 3-Hydroxybutyrate (3HB) reported to have multiple functions as an oral food supplement. This study observes that 3HB prevents mouse colitis and CRC.

METHODS AND RESULTS

The sensitivity of wild type (WT) and GPR109a^-/- mice to colitis is compared using dextran sulfate sodium salt (DSS)-induced colitis model. Flow cytometry showed that 3HB cellular surface receptor GPR109a that can decrease the percentage of M1 macrophages from 50% of the DSS-induced acute colitis mouse group to 42% DSS+3HB group mediating the inhibitory effect on inflammation. Bone marrow transplantation experiments further demonstrated that the function of 3HB depended on bone marrow cells. Subsequently, the sensitivity of WT and GPR109a^-/- mice to CRC is compared using an azoxymethane-DSS-induced CRC mouse model. It is found that the activation of GPR109a inhibited CRC, depended on reduced myeloid-derived suppressor cells accumulation from 27% of the DSS group to 19% of the DSS+3HB group studied using flow cytometry.

CONCLUSION

It is concluded that 3HB significantly suppresses colonic inflammation and carcinogenesis, promising to benefit colon disease prevention in form of a food supplement.

Metabolic Engineering of Gas-Fermenting Clostridium ljungdahlii for Efficient Co-production of Isopropanol, 3-Hydroxybutyrate, and Ethanol

Rational design and modification of autotrophic bacteria to efficiently produce high-value chemicals and biofuels are crucial for establishing a sustainable and economically viable process for one-carbon (C1) source utilization, which, however, remains a challenge in metabolic engineering. In this study, autotrophic Clostridium ljungdahlii was metabolically engineered to efficiently co-produce three important bulk chemicals, isopropanol, 3-hydroxybutyrate (3-HB), and ethanol (together, IHE), using syngas (CO₂/CO). An artificial isopropanol-producing pathway was first constructed and optimized in C. ljungdahlii to achieve an efficient production of isopropanol and an unexpected product, 3-HB. Based on this finding, an endogenous active dehydrogenase capable of converting acetoacetate to 3-HB was identified in C. ljungdahlii, thereby revealing an efficient 3-HB-producing pathway. The engineered strain was further optimized to reassimilate acetic acid and synthesize 3-HB by introducing heterologous functional genes. Finally, the best-performing strain was able to produce 13.4, 3.0, and 28.4 g/L of isopropanol, 3-HB, and ethanol, respectively, in continuous gas fermentation. Therefore, this work represents remarkable progress in microbial production of bulk chemicals using C1 gases.

Enantiomer-specific pharmacokinetics of D,L-3-hydroxybutyrate: Implications for the treatment of multiple acyl-CoA dehydrogenase deficiency

D,L-3-hydroxybutyrate (D,L-3-HB, a ketone body) treatment has been described in several inborn errors of metabolism, including multiple acyl-CoA dehydrogenase deficiency (MADD; glutaric aciduria type II). We aimed to improve the understanding of enantiomer-specific pharmacokinetics of D,L-3-HB. Using UPLC-MS/MS, we analyzed D-3-HB and L-3-HB concentrations in blood samples from three MADD patients, and blood and tissue samples from healthy rats, upon D,L-3-HB salt administration (patients: 736-1123 mg/kg/day; rats: 1579-6317 mg/kg/day of salt-free D,L-3-HB). D,L-3-HB administration caused substantially higher L-3-HB concentrations than D-3-HB. In MADD patients, both enantiomers peaked at 30 to 60 minutes, and approached baseline after 3 hours. In rats, D,L-3-HB administration significantly increased C_max and AUC of D-3-HB in a dose-dependent manner (controls vs ascending dose groups for C_max : 0.10 vs 0.30-0.35-0.50 mmol/L, and AUC: 14 vs 58-71-106 minutes*mmol/L), whereas for L-3-HB the increases were significant compared to controls, but not dose proportional (C_max : 0.01 vs 1.88-1.92-1.98 mmol/L, and AUC: 1 vs 380-454-479 minutes*mmol/L). L-3-HB concentrations increased extensively in brain, heart, liver, and muscle, whereas the most profound rise in D-3-HB was observed in heart and liver. Our study provides important knowledge on the absorption and distribution upon oral D,L-3-HB. The enantiomer-specific pharmacokinetics implies differential metabolic fates of D-3-HB and L-3-HB.

Serum 3-Hydroxybutyrate in Patients with Psychogenic Somatoform Symptoms May Be a Predictor of the Effectiveness of Sertraline and Venlafaxine

Background

Selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs) are often used to treat outpatients with psychogenic somatoform symptoms but prove ineffective in some cases. The metabolite 3-hydroxybutyrate (3HB) is currently attracting attention as a marker of the severity of depression. We investigated whether serum 3HB levels in patients with psychogenic somatoform symptoms can predict the effectiveness of sertraline and venlafaxine.

Patients and Methods

Physical and psychiatric problems were assessed in 132 outpatients, and symptomatic response and serum 3HB concentrations were examined before and after treatment with sertraline (50 mg/day) or venlafaxine (75 mg/day).

Results

In 30.3% of patients with psychogenic symptoms, serum 3HB was above the upper limit of normal (<80 μmol/L). According to multiple logistic regression analysis, only episodes of suicidal ideation showed a significant positive association with elevated 3HB (odds ratio 10.2; 95% confidence interval (CI) 2.46–42.2). The sensitivity of 3HB for the effectiveness of sertraline or venlafaxine for psychosomatic symptoms was 44.6%, but specificity was 93.9%. Hierarchical multiple logistic regression analysis identified 3HB as a better predictor of the effectiveness of medication (odds ratio 10.0; 95% CI, 2.49–40.3) than episodes of suicidal ideation.

Conclusion

The present findings suggest that high serum 3HB levels in patients with psychogenic somatoform symptoms may be associated with suicidal ideation and the effectiveness of sertraline and venlafaxine at low to intermediate doses. The 3HB level may be a good predictor of the effectiveness of medication. Examination of serum 3HB levels may lead to earlier and more appropriate administration of sertraline and venlafaxine.

3-Hydroxybutyrate as a Metabolite and a Signal Molecule Regulating Processes of Living Organisms

3-hydroxybutyrate (3-HB) as a very important metabolite occurs in animals, bacteria and plants. It is well known that in animals, 3-HB is formed as a product of the normal metabolism of fatty acid oxidation and can therefore be used as an energy source in the absence of sufficient blood glucose. In microorganisms, 3-HB mainly serves as a substrate for the synthesis of polyhydroxybutyrate, which is a reserve material. Recent studies show that in plants, 3-HB acts as a regulatory molecule that most likely influences the expression of genes involved in DNA methylation, thereby altering DNA methylation levels. Additionally, in animals, 3-HB is not only an intermediate metabolite, but also an important regulatory molecule that can influence gene expression, lipid metabolism, neuronal function, and overall metabolic rate. Some of these effects are the direct effects of 3-HB itself, while others are indirect effects, regulated by the metabolites into which 3-HB is converted. One of the most important regulatory functions of 3-HB is the inhibition of the activity of histone deacetylases and thus the epigenetic regulation of many genes. Due to the number of functions of this compound, it also shows promising therapeutic properties.

Ketosis versus carbotoxicity - metabolism determines the outcome of cancer immunotherapy

Carbohydrate-rich diets have been consistently associated with detrimental effects for human health, including diabetes and obesity. Moreover, high glucose levels appear to mediate immunosuppressive effects in preclinical tumor models. Recent data from Ferrere and colleagues point to the intriguing possibility that carbotoxicity may originate from the abolition of ketosis.

Impact of Acutely Increased Endogenous- and Exogenous Ketone Bodies on FGF21 Levels in Humans

PURPOSE

Fibroblast growth factor (FGF) 21 is a circulating hormone with metabolic regulatory importance. In mice, FGF21 increases in response to a ketogenic diet and fasting. In humans, a similar increase is only observed after prolonged starvation. We aim to study the acute effects of ketone bodies on circulating FGF21 levels in humans.

METHODS

Participants from three randomized, placebo-controlled crossover studies, with increased endogenous or exogenous ketone bodies, were included. Study 1: patients with type 1 diabetes (T1D) (n = 9) were investigated after a) insulin deprivation and lipopolysaccharide (LPS) injection and b) insulin-controlled euglycemia. Study 2: patients with T1D (n = 9) were investigated after a) total insulin deprivation for 9 hours and b) insulin-controlled euglycemia. Study 3: Healthy adults (n = 9) were examined during a) 3-hydroxybutyrate (OHB) infusion and b) saline infusion. Plasma FGF21 was measured with immunoassay in serial samples.

RESULTS

Circulating OHB levels were significantly increased to 1.3, 1.5, and 5.5 mmol/l in the three studies, but no correlations with FGF21 levels were found. Also, no correlations between FGF21, insulin, or glucagon were found. Insulin deprivation and LPS injection resulted in increased plasma FGF21 levels at t = 120 min (p = .005) which normalized at t = 240 min.

CONCLUSION

We found no correlation between circulating FGF21 levels and levels of ketone bodies. This suggests that it is not ketosis per se which controls FGF21 production, but instead a rather more complex regulatory mechanism.

TRIAL REGISTRATION

clinicaltrials.gov ID number: Study 1: NCT02157155 (5/6-2014), study 2: NCT02077348 (4/3-2014), and study 3: NCT02357550 (6/2-2015).

3-Hydroxybutyrate Derived from Poly-3-Hydroxybutyrate Mobilization Alleviates Protein Aggregation in Heat-Stressed Herbaspirillum seropedicae SmR1

Under conditions of carbon starvation or thermal, osmotic, or oxidative shock, mutants affected in the synthesis or mobilization of poly-3-hydroxybutyrate (PHB) are known to survive less well. It is still unclear if the synthesis and accumulation of PHB are sufficient to protect bacteria against stress conditions or if the stored PHB has to be mobilized. Here, we demonstrated that mobilization of PHB in Herbaspirillum seropedicae SmR1 was heat-shock activated at 45°C. In situ proton (¹H) nuclear magnetic resonance spectroscopy (i.e., ¹H-nuclear magnetic resonance) showed that heat shock increased amounts of 3-hydroxybutyrate (3HB) only in H. seropedicae strains able to synthesize and mobilize PHB. H. seropedicae SmR1 mutants unable to synthesize or mobilize PHB were more susceptible to heat shock and survived less well than the parental strain. When 100 mM 3-hydroxybutyrate was added to the medium, the ΔphaC1 strain (an H. seropedicae mutant unable to synthesize PHB) and the double mutant with deletion of both phaZ1 and phaZ2 (i.e., ΔphaZ1.2) (unable to mobilize PHB) showed partial rescue of heat adaptability (from 0% survival without 3HB to 40% of the initial viable population). Addition of 200 mM 3HB before the imposition of heat shock reduced protein aggregation to 15% in the ΔphaC1 mutant and 12% in the ΔphaZ1.2 mutant. We conclude that H. seropedicae SmR1 is naturally protected by 3HB released by PHB mobilization, while mutants unable to generate large amounts of 3HB under heat shock conditions are less able to cope with heat damage.IMPORTANCE Bacteria are subject to abrupt changes in environmental conditions affecting their growth, requiring rapid adaptation. Increasing the concentration of some metabolites can protect bacteria from hostile conditions that lead to protein denaturation and precipitation, as well as damage to plasma membranes. In this work, we demonstrated that under thermal shock, the bacterium Herbaspirillum seropedicae depolymerized its intracellular stock polymer known as poly-3-hydroxybutyrate (PHB), rapidly increasing the concentration of 3-hydroxybutyrate (3HB) and decreasing protein precipitation by thermal denaturation. Mutant H. seropedicae strains unable to produce or depolymerize PHB suffered irreparable damage during thermal shock, resulting in fast death when incubated at 45°C. Our results will contribute to the development of bacteria better adapted to high temperatures found either in natural conditions or in industrial processes. In the case of H. seropedicae and other bacteria that interact beneficially with plants, the understanding of PHB metabolism can be decisive for the development of more-competitive strains and their application as biofertilizers in agriculture.

3-Hydroxybutyrate Is Active Compound in Flax That Upregulates Genes Involved in DNA Methylation

In mammalian cells, 3-hydroxybutyrate (3-HB) is not only an intermediate metabolite during the oxidation of fatty acids, but also an important signaling molecule. On the other hand, the information about the metabolism or function of this compound in plants is scarce. In our study, we show for the first time that this compound naturally occurs in flax. The expression of bacterial β-ketothiolase in flax affects expression of endogenous genes of the 3-HB biosynthesis pathway and the compound content. The increase in 3-HB content in transgenic plants or after control plants treatment with 3-HB resulted in upregulation of genes involved in chromatin remodeling. The observation that 3-HB is an endogenous activator of methyltransferase 3 (CMT3), decreased DNA methylation I (DDM1), DEMETER DNA glycosylase (DME), and an inhibitor of sirtuin 1 (SRT1) provides an example of integration of different genes in chromatin remodeling. The changes in chromatin remodeling gene expression concomitant with those involved in phenolics and the lignin biosynthesis pathway suggest potential integration of secondary metabolic status with epigenetic changes.

Cardiovascular Effects of Treatment With the Ketone Body 3-Hydroxybutyrate in Chronic Heart Failure Patients

Supplemental Digital Content is available in the text.

Background:

Myocardial utilization of 3-hydroxybutyrate (3-OHB) is increased in patients with heart failure and reduced ejection fraction (HFrEF). However, the cardiovascular effects of increased circulating plasma-3-OHB levels in these patients are unknown. Consequently, the authors’ aim was to modulate circulating 3-OHB levels in HFrEF patients and evaluate: (1) changes in cardiac output (CO); (2) a potential dose-response relationship between 3-OHB levels and CO; (3) the impact on myocardial external energy efficiency (MEE) and oxygen consumption (MVO₂); and (4) whether the cardiovascular response differed between HFrEF patients and age-matched volunteers.

Methods:

Study 1: 16 chronic HFrEF patients (left ventricular ejection fraction: 37±3%) were randomized in a crossover design to 3-hour of 3-OHB or placebo infusion. Patients were monitored invasively with a Swan-Ganz catheter and with echocardiography. Study 2: In a dose-response study, 8 HFrEF patients were examined at increasing 3-OHB infusion rates. Study 3 to 4: 10 HFrEF patients and 10 age-matched volunteers were randomized in a crossover design to 3-hour 3-OHB or placebo infusion. MEE and MVO₂ were evaluated using 11C-acetate positron emission tomography.

Results:

3-OHB infusion increased circulating levels of plasma 3-OHB from 0.4±0.3 to 3.3±0.4 mM (P<0.001). CO rose by 2.0±0.2 L/min (P<0.001) because of an increase in stroke volume of 20±2 mL (P<0.001) and heart rate of 7±2 beats per minute (bpm) (P<0.001). Left ventricular ejection fraction increased 8±1% (P<0.001) numerically. There was a dose-response relationship with a significant CO increase of 0.3 L/min already at plasma-3-OHB levels of 0.7 mM (P<0.001). 3-OHB increased MVO₂ without altering MEE. The response to 3-OHB infusion in terms of MEE and CO did not differ between HFrEF patents and age-matched volunteers.

Conclusions:

3-OHB has beneficial hemodynamic effects in HFrEF patients without impairing MEE. These beneficial effects are detectable in the physiological concentration range of circulating 3-OHB levels. The hemodynamic effects of 3-OHB were observed in both HFrEF patients and age-matched volunteers. 3-OHB may potentially constitute a novel treatment principle in HFrEF patients.

The use of sodium DL-3-Hydroxybutyrate in severe acute neuro-metabolic compromise in patients with inherited ketone body synthetic disorders

Background

Ketone bodies form a vital energy source for end organs in a variety of physiological circumstances. At different times, the heart, brain and skeletal muscle in particular can use ketones as a primary substrate. Failure to generate ketones in such circumstances leads to compromised energy delivery, critical end-organ dysfunction and potentially death. There are a range of inborn errors of metabolism (IEM) affecting ketone body production that can present in this way, including disorders of carnitine transport into the mitochondrion, mitochondrial fatty acid oxidation deficiencies (MFAOD) and ketone body synthesis. In situations of acute energy deficit, management of IEM typically entails circumventing the enzyme deficiency with replenishment of energy requirements. Due to profound multi-organ failure it is often difficult to provide optimal enteral therapy in such situations and rescue with sodium DL-3-hydroxybutyrate (S DL-3-OHB) has been attempted in these conditions as documented in this paper.

Results

We present 3 cases of metabolic decompensation, one with carnitine-acyl-carnitine translocase deficiency (CACTD) another with 3-hydroxyl, 3-methyl, glutaryl CoA lyase deficiency (HMGCLD) and a third with carnitine palmitoyl transferase II deficiency (CPT2D). All of these disorders are frequently associated with death in circumstance where catastrophic acute metabolic deterioration occurs. Intensive therapy with adjunctive S DL-3OHB led to rapid and sustained recovery in all. Alternative therapies are scarce in these situations.

Conclusion

S DL-3-OHB has been utilised in multiple acyl co A dehydrogenase deficiency (MADD) in cases with acute neurological and cardiac compromise with long-term data awaiting publication. The use of S DL-3-OHB is novel in non-MADD fat oxidation disorders and contribute to the argument for more widespread use.

1H NMR Based Metabolomics in Human Sepsis and Healthy Serum

Early diagnosis is essential but challenging in severe sepsis. Quantifying and comparing metabolite concentrations in serum has been suggested as a new diagnostic tool. Here we used proton nuclear magnetic resonance spectroscopy (¹H NMR) based metabolomics to analyze the possible differences in metabolite concentrations between sera taken from septic patients and healthy controls, as well as between sera of surviving and non-surviving sepsis patients. We took serum samples from 44 sepsis patients when the first sepsis induced organ dysfunction was found. Serum samples were also collected from 14 age and gender matched healthy controls. The samples were analyzed by quantitative ¹H NMR spectroscopy for non-lipid metabolites. We found that the serum levels of glucose, glycine, 3-hydroxybutyrate, creatinine and glycoprotein acetyls (mostly alpha-1-acid glycoprotein, AGP) were significantly (p < 0.05) higher in sepsis compared to healthy sera, whereas citrate and histidine were significantly (p < 0.05) lower in sepsis patients compared to healthy controls. We found statistically significantly higher serum lactate and citrate concentrations in non-survivors compared to 30-day survivors. According to our study, 3-hydroxybutyrate, citrate, glycine, histidine, and AGP are candidates for further studies to enable identification of phenotype association in the early stages of sepsis.

[Microbial production of poly (glycolate-co-lactate-co-3-hydroxybutyrate) from glucose and xylose by Escherichia coli]

Escherichia coli was metabolically engineered to produce poly(glycolate-co-lactate-co-3-hydroxybutyrate) using glucose and xylose as carbon sources. The combinatorial biosynthetic route was constructed by the overexpression of a series of enzymes including D-tagatose 3-epimerase, L-fuculokinase, L-fuculose-phosphate aldolase, aldehyde dehydrogenase, propionyl-CoA transferase, β-ketothiolase, acetoacetyl-CoA reductase, and polyhydroxyalkanoate synthase. Overexpression of polyhydroxyalkanoate granule associated protein significantly improved biopolymer synthesis, and the recombinant strain reached 3.73 g/L cell dry weight with 38.72% (W/W) biopolymer content. A co-culture engineering strategy was developed to produce biopolymer from a mixture of glucose and xylose, achieving 4.01 g/L cell dry weight containing 21.54% (W/W) biopolymer. The results of this work offer an approach for simultaneously utilizing glucose and xylose and indicate the potential for future biopolymer production from lignocellulosic biomass.

Electrochemical (Bio) Sensors for Environmental and Food Analyses

In recent years, great progress has been made in the development of sensors and biosensors to meet the demands of environmental and food analysis. In this Special Issue, the state of art and the future trends in the field of environmental and food analyses have been explored. A total of seven papers (three research and four review papers) are included. These are focused on the fabrication and detection of contaminates such as heavy metals, pesticides and food components, including uric acid and 3-hydroxybutyrate. Included in this Issue is a paper dedicated to the experimental determination of the electroactive area of screen-printed electrodes, an important parameter in the development of such sensors.

Enantioselective and simultaneous determination of lactate and 3-hydroxybutyrate in human plasma and urine using a narrow-bore online two-dimensional high-performance liquid chromatography system

For the enantioselective and simultaneous analysis of lactate and 3-hydroxybutyrate, a validated online two-dimensional high-performance liquid chromatography system using 4-nitro-7-piperazino-2,1,3-benzoxadiazole as a fluorescent derivatization reagent has been developed. For the reversed-phase separation in the first dimension, a Capcell Pak C18 ACR column (1.5 × 250 mm, particle size 3 μm) was used, and the target fractions were isolated by their hydrophobicity. In the second dimension, a polysaccharide-coated enantioselective column, Chiralpak AD-H (2.0 × 250 mm, 5 μm), was used. The system was validated by the calibration curve, intraday precision, interday precision, and accuracy using standards and real human samples, and satisfactory results were obtained. The present method was applied to human plasma and urine, and in the plasma, trace amounts of d-lactate (8.4 μM) and l-3-hydroxybutyrate (1.0 μM), besides high levels of l-lactate (860.9 μM) and d-3-hydroxybutyrate (59.4 μM), were successfully determined. In urine, trace levels of d-lactate (3.7 μM), d-3-hydroxybutyrate (2.3 μM), and l-3-hydroxybutyrate (3.3 μM) in addition to a relatively large amount of l-lactate (15.4 μM) were observed. The present online two-dimensional high-performance liquid chromatography system is useful for the simultaneous determination of all the lactate and 3-hydroxybutyrate enantiomers in human physiological fluids, and further clinical applications are ongoing.

An Electrochemical Enzyme Biosensor for 3-Hydroxybutyrate Detection Using Screen-Printed Electrodes Modified by Reduced Graphene Oxide and Thionine

A biosensor for 3-hydroxybutyrate (3-HB) involving immobilization of the enzyme 3-hydroxybutyrate dehydrogenase onto a screen-printed carbon electrode modified with reduced graphene oxide (GO) and thionine (THI) is reported here. After addition of 3-hydroxybutyrate or the sample in the presence of NAD⁺ cofactor, the generated NADH could be detected amperometrically at 0.0 V vs. Ag pseudo reference electrode. Under the optimized experimental conditions, a calibration plot for 3-HB was constructed showing a wide linear range between 0.010 and 0.400 mM 3-HB which covers the clinically relevant levels for diluted serum samples. In addition, a limit of detection of 1.0 µM, much lower than that reported using other biosensors, was achieved. The analytical usefulness of the developed biosensor was demonstrated via application to spiked serum samples.

Metabolic engineering of Escherichia coli for the synthesis of the quadripolymer poly(glycolate-co-lactate-co-3-hydroxybutyrate-co-4-hydroxybutyrate) from glucose

Escherichia coli was metabolically engineered to effectively produce a series of biopolymers consisted of four types of monomers including glycolate, lactate, 3-hydroxybutyrate and 4-hydroxybutyrate from glucose as the carbon source. The biosynthetic route of novel quadripolymers was achieved by the overexpression of a range of homologous and heterologous enzymes including isocitrate lyase, isocitrate dehydrogenase kinase/phosphatase, glyoxylate/hydroxypyruvate reductase, propionyl-CoA transferase, β-ketothiolase, acetoacetyl-CoA reductase, succinate semialdehyde dehydrogenase, 4-hydroxybutyrate dehydrogenase, CoA transferase and PHA synthase. In shake flask cultures using Luria-Bertani medium supplemented with glucose, the recombinant E. coli reached 7.10g/l cell dry weight with 52.60wt% biopolymer content. In bioreactor study, the final cell dry weight was 19.61g/l, containing 14.29g/l biopolymer. The structure of the produced polymer was chemically characterized by proton NMR analysis. Assessment of thermal and mechanical properties demonstrated that the quadripolymer possessed decreased crystallinity and improved toughness, in comparison to poly-3-hydroxybutyrate homopolymer. This is the first study reporting efficient microbial production of the quadripolymer poly(glycolate-co-lactate-co-3-hydroxybutyrate-co-4-hydroxybutyrate) from glucose.

GC-MS based Gestational Diabetes Mellitus longitudinal study: Identification of 2-and 3-hydroxybutyrate as potential prognostic biomarkers

Gestational Diabetes Mellitus (GDM) causes severe short- and long-term complications for the mother, fetus and neonate, including type 2-diabetes (T2DM) later in life. In this pilot study, GC-Q/MS analysis was applied for plasma metabolomics fingerprinting of 24 healthy and 24 women with GDM at different stages of gestation (second and third trimester) and postpartum (one and three months). Multivariate (unsupervised and supervised) statistical analysis was performed to investigate variance in the data, identify outliers and for unbiased assessment of data quality. Plasma fingerprints allowed for the discrimination of GDM pregnant women from controls both in the 2nd and 3rd trimesters of gestation. However, metabolic profiles tended to be similar after delivery. Follow up of these women revealed that 4 of them developed T2DM within 2 years postpartum. Multivariate PLS-DA models limited to women with GDM showed clear separation 3 months postpartum. In the 2nd trimester of gestation there was also a clear separation between GDM women that were normoglycemic after pregnancy and those with recognized postpartum T2DM. Metabolites that had the strongest discriminative power between these groups in the 2nd trimester of gestation were 2-hydroxybutyrate, 3-hydroxybutyrate, and stearic acid. We have described, that early GDM comprises metabotypes that are associated with the risk of future complications, including postpartum T2DM. In this pilot study, we provide evidence that 2-hydroxybutyrate and 3-hydroxybutyrate may be considered as future prognostic biomarkers to predict the onset of diabetic complications in women with gestational diabetes after delivery.

Biosynthesis of enantiopure (S)-3-hydroxybutyrate from glucose through the inverted fatty acid β-oxidation pathway by metabolically engineered Escherichia coli

Enantiomers of 3-hydroxybutyric acid (3-HB) can be used as the chiral precursors for the production of various optically active fine chemicals, including drugs, perfumes, and pheromones. In this study, Escherichia coli was engineered to produce (S)-3-HB from glucose through the inverted reactions of the native aerobic fatty acid β-oxidation pathway. Expression of only specific genes encoding enzymes responsible for the conversion of acetyl-CoA to acetoacetyl-CoA, reduction of acetoacetyl-CoA to 3-hydroxybutyryl-CoA and subsequent hydrolysis of 3-hydroxybutyryl-CoA to 3-HB was directly upregulated in an engineered strain. The operation of multiple turns of the inverted fatty acid β-oxidation was precluded by the deletion of gene encoding enzyme that catalyse the terminal stage of the respective cycle. While the overexpression of the C-acetyltransferase gene enabled 3-HB biosynthesis through the inverted fatty acid β-oxidation, the efficient conversion of glucose to the target product was achieved resulting from the additional overexpression of the gene encoding appropriate termination thioesterase II. The engineered strain synthesised the (S)-stereoisomer of 3-HB with an enantiomeric excess of more than 99%. Under microaerobic conditions, up to 9.58g/L of enantiopure (S)-3-HB was produced from glucose, with a yield of 66% of the theoretical maximum.

Adaptive responses of neuronal mitochondria to bioenergetic challenges: Roles in neuroplasticity and disease resistance

An important concept in neurobiology is "neurons that fire together, wire together" which means that the formation and maintenance of synapses is promoted by activation of those synapses. Very similar to the effects of the stress of exercise on muscle cells, emerging findings suggest that neurons respond to activity by activating signaling pathways (e.g., Ca²⁺, CREB, PGC-1α, NF-κB) that stimulate mitochondrial biogenesis and cellular stress resistance. These pathways are also activated by aerobic exercise and food deprivation, two bioenergetic challenges of fundamental importance in the evolution of the brains of all mammals, including humans. The metabolic 'switch' in fuel source from liver glycogen store-derived glucose to adipose cell-derived fatty acids and their ketone metabolites during fasting and sustained exercise, appears to be a pivotal trigger of both brain-intrinsic and peripheral organ-derived signals that enhance learning and memory and underlying synaptic plasticity and neurogenesis. Brain-intrinsic extracellular signals include the excitatory neurotransmitter glutamate and the neurotrophic factor BDNF, and peripheral signals may include the liver-derived ketone 3-hydroxybutyrate and the muscle cell-derived protein irisin. Emerging findings suggest that fasting, exercise and an intellectually challenging lifestyle can protect neurons against the dysfunction and degeneration that they would otherwise suffer in acute brain injuries (stroke and head trauma) and neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's disease. Among the prominent intracellular responses of neurons to these bioenergetic challenges are up-regulation of antioxidant defenses, autophagy/mitophagy and DNA repair. A better understanding of such fundamental hormesis-based adaptive neuronal response mechanisms is expected to result in the development and implementation of novel interventions to promote optimal brain function and healthy brain aging.

Improved glucose tolerance in insulin-resistant rats after pea hull feeding is associated with changes in lipid metabolism-targeted transcriptome

Understanding of the mechanisms by which pulse grain fractions elicit beneficial effects on glucose tolerance is incomplete. An untargeted metabolomic analysis of serum from insulin-resistant rats was carried out to identify potential metabolic pathways affected by feeding rats the hull fraction of dried peas for 4 weeks. From this, we hypothesized that transcription of hepatic genes involved in lipid metabolism would be altered. cDNA was prepared from total RNA extracted from livers of rats fed a high-fat diet (HFD) or HFD + pea hulls (PH) diet. The liver lipid transcriptome of each cDNA sample was characterized using a PCR-based array of 84 genes. The activity of peroxisome-proliferator-activated receptor alpha (PPAR-α) was measured in hepatocyte nuclei. The predominant findings of the metabolomic analysis revealed a significant increase in the intermediaries of β-oxidation: C16-OH and C16:1 acylcarnitines (>50%, p < 0.05) and 3-hydroxybutyrate (100%, p < 0.05) in the PH group compared with the HFD group. mRNA of hadha, a gene involved in β-oxidation, was significantly reduced by 53% (p < 0.005) in the PH group compared with the HFD group, but no differences in PPAR-α activity were detected. 3-Hydroxybutyrate concentrations were associated with insulin sensitivity and reduced demand for insulin. The results indicate that feeding PH alters lipid metabolism in liver, which may contribute to improved glucose tolerance in insulin-resistant rats.

A spontaneous mutation in the nicotinamide nucleotide transhydrogenase gene of C57BL/6J mice results in mitochondrial redox abnormalities

NADPH is the reducing agent for mitochondrial H2O2 detoxification systems. Nicotinamide nucleotide transhydrogenase (NNT), an integral protein located in the inner mitochondrial membrane, contributes to an elevated mitochondrial NADPH/NADP(+) ratio. This enzyme catalyzes the reduction of NADP(+) at the expense of NADH oxidation and H(+) reentry to the mitochondrial matrix. A spontaneous Nnt mutation in C57BL/6J (B6J-Nnt(MUT)) mice arose nearly 3 decades ago but was only discovered in 2005. Here, we characterize the consequences of the Nnt mutation on the mitochondrial redox functions of B6J-Nnt(MUT) mice. Liver mitochondria were isolated both from an Nnt wild-type C57BL/6 substrain (B6JUnib-Nnt(W)) and from B6J-Nnt(MUT) mice. The functional evaluation of respiring mitochondria revealed major redox alterations in B6J-Nnt(MUT) mice, including an absence of transhydrogenation between NAD and NADP, higher rates of H2O2 release, the spontaneous oxidation of NADPH, the poor ability to metabolize organic peroxide, and a higher susceptibility to undergo Ca(2+)-induced mitochondrial permeability transition. In addition, the mitochondria of B6J-Nnt(MUT) mice exhibited increased oxidized/reduced glutathione ratios as compared to B6JUnib-Nnt(W) mice. Nonetheless, the maximal activity of NADP-dependent isocitrate dehydrogenase, which is a coexisting source of mitochondrial NADPH, was similar between both groups. Altogether, our data suggest that NNT functions as a high-capacity source of mitochondrial NADPH and that its functional loss due to the Nnt mutation results in mitochondrial redox abnormalities, most notably a poor ability to sustain NADP and glutathione in their reduced states. In light of these alterations, the potential drawbacks of using B6J-Nnt(MUT) mice in biomedical research should not be overlooked.

Complete genome sequence of Ilyobacter polytropus type strain (CuHbu1)

Ilyobacter polytropus Stieb and Schink 1984 is the type species of the genus Ilyobacter, which belongs to the fusobacterial family Fusobacteriaceae. The species is of interest because its members are able to ferment quite a number of sugars and organic acids. I. polytropus has a broad versatility in using various fermentation pathways. Also, its members do not degrade poly-β-hydroxybutyrate but only the monomeric 3-hydroxybutyrate. This is the first completed genome sequence of a member of the genus Ilyobacter and the second sequence from the family Fusobacteriaceae. The 3,132,314 bp long genome with its 2,934 protein-coding and 108 RNA genes consists of two chromosomes (2 and 1 Mbp long) and one plasmid, and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.