The Effect of Diesel Exhaust Particles on Adipose Tissue Mitochondrial Function and Inflammatory Status.

Air pollution poses a significant global health risk, with fine particulate matter (PM2.5) such as diesel exhaust particles (DEPs) being of particular concern due to their potential to drive systemic toxicities through bloodstream infiltration. The association between PM2.5 exposure and an increased prevalence of metabolic disorders, including obesity, metabolic syndrome, and type 2 diabetes mellitus (T2DM), is evident against a backdrop of rising global obesity and poor metabolic health. This paper examines the role of adipose tissue in mediating the effects of PM2.5 on metabolic health. Adipose tissue, beyond its energy storage function, is responsive to inhaled noxious stimuli, thus disrupting metabolic homeostasis and responding to particulate exposure with pro-inflammatory cytokine release, contributing to systemic inflammation. The purpose of this study was to characterize the metabolic response of adipose tissue in mice exposed to either DEPs or room air (RA), exploring both the adipokine profile and mitochondrial bioenergetics. In addition to a slight change in fat mass and a robust shift in adipocyte hypertrophy in the DEP-exposed animals, we found significant changes in adipose mitochondrial bioenergetics. Furthermore, the DEP-exposed animals had a significantly higher expression of adipose inflammatory markers compared with the adipose from RA-exposed mice. Despite the nearly exclusive focus on dietary factors in an effort to better understand metabolic health, these results highlight the novel role of environmental factors that may contribute to the growing global burden of poor metabolic health.

The Effects of a High-Carbohydrate versus a High-Fat Shake on Biomarkers of Metabolism and Glycemic Control When Used to Interrupt a 38-h Fast: A Randomized Crossover Study.

This study aimed to determine the impact of various fast-interrupting shakes on markers of glycemic control including glucose, ß-hydroxybutyrate (BHB), insulin, glucagon, GLP-1, and GIP. Twenty-seven sedentary adults (twelve female, fifteen male) with overweight or obesity completed this study. One condition consisted of a 38-h water-only fast, and the other two conditions repeated this, but the fasts were interrupted at 24 h by either a high carbohydrate/low fat (HC/LF) shake or an isovolumetric and isocaloric low carbohydrate/high fat (LC/HF) shake. The water-only fast resulted in 135.3% more BHB compared to the HC/LF condition (p < 0.01) and 69.6% more compared to the LC/HF condition (p < 0.01). The LC/HF condition exhibited a 38.8% higher BHB level than the HC/LF condition (p < 0.01). The area under the curve for glucose was 14.2% higher in the HC/LF condition than in the water condition (p < 0.01) and 6.9% higher compared to the LC/HF condition (p < 0.01), with the LC/HF condition yielding 7.8% more glucose than the water condition (p < 0.01). At the 25-h mark, insulin and glucose-dependent insulinotropic polypeptide (GIP) were significantly elevated in the HC/LF condition compared to the LC/HF condition (p < 0.01 and p = 0.02, respectively) and compared to the water condition (p < 0.01). Furthermore, insulin, GLP-1, and GIP were increased in the LC/HF condition compared to the water condition at 25 h (p < 0.01, p = 0.015, and p < 0.01, respectively). By the 38-h time point, no differences were observed among the conditions for any of the analyzed hormones. While a LC/HF shake does not mimic a fast completely, it does preserve some of the metabolic changes including elevated BHB and glucagon, and decreased glucose and insulin compared to a HC/LF shake, implying a potential for improved metabolic health.

Ceramides Mediate Insulin-Induced Impairments in Cerebral Mitochondrial Bioenergetics in ApoE4 Mice.

Alzheimer's disease (AD) is the most common form of neurodegenerative disease worldwide. A large body of work implicates insulin resistance in the development and progression of AD. Moreover, impairment in mitochondrial function, a common symptom of insulin resistance, now represents a fundamental aspect of AD pathobiology. Ceramides are a class of bioactive sphingolipids that have been hypothesized to drive insulin resistance. Here, we describe preliminary work that tests the hypothesis that hyperinsulinemia pathologically alters cerebral mitochondrial function in AD mice via accrual of the ceramides. Homozygous male and female ApoE4 mice, an oft-used model of AD research, were given chronic injections of PBS (control), insulin, myriocin (an inhibitor of ceramide biosynthesis), or insulin and myriocin over four weeks. Cerebral ceramide content was assessed using liquid chromatography-mass spectrometry. Mitochondrial oxygen consumption rates were measured with high-resolution respirometry, and H2O2 emissions were quantified via biochemical assays on brain tissue from the cerebral cortex. Significant increases in brain ceramides and impairments in brain oxygen consumption were observed in the insulin-treated group. These hyperinsulinemia-induced impairments in mitochondrial function were reversed with the administration of myriocin. Altogether, these data demonstrate a causative role for insulin in promoting brain ceramide accrual and subsequent mitochondrial impairments that may be involved in AD expression and progression.

Yerba Maté (Ilex paraguariensis) Supplement Exerts Beneficial, Tissue-Specific Effects on Mitochondrial Efficiency and Redox Status in Healthy Adult Mice.

Yerba maté, a herbal tea derived from Ilex paraguariensis, has previously been reported to be protective against obesity-related and other cardiometabolic disorders. Using high-resolution respirometry and reverse-phase high-performance liquid chromatography, the effects of four weeks of yerba maté consumption on mitochondrial efficiency and cellular redox status in skeletal muscle, adipose, and liver, tissues highly relevant to whole-body metabolism, were explored in healthy adult mice. Yerba maté treatment increased the mitochondrial oxygen consumption in adipose but not in the other examined tissues. Yerba maté increased the ATP concentration in skeletal muscle and decreased the ATP concentration in adipose. Combined with the observed changes in oxygen consumption, these data yielded a significantly higher ATP:O2, a measure of mitochondrial efficiency, in muscle and a significantly lower ATP:O2 in adipose, which was consistent with yerba maté-induced weight loss. Yerba maté treatment also altered the hepatic glutathione (GSH)/glutathione disulfide (GSSG) redox potential to a more reduced redox state, suggesting the treatment's potential protective effects against oxidative stress and for the preservation of cellular function. Together, these data indicate the beneficial, tissue-specific effects of yerba maté supplementation on mitochondrial bioenergetics and redox states in healthy mice that are protective against obesity.

The Effects of Exercise on Appetite-Regulating Hormone Concentrations over a 36-h Fast in Healthy Young Adults: A Randomized Crossover Study.

Hunger and satiety are controlled by several physiological mechanisms, including pancreatic and gastrointestinal hormones. While the influence of exercise and fasting have been described individually, in relation to these hormones, there is a paucity of work showing the effects of the two modalities (fasting and exercise) combined. Twenty healthy adults (11 males, 9 females) completed both conditions of this study, each consisting of a 36-h water-only fast. One of the fasts began with treadmill exercise, and the differences between the conditions on various appetite hormones were measured every 12 h. The difference in the area under the curve between conditions for ghrelin was 211.8 ± 73.1 pg/mL (F = 8.40, p < 0.0105), and, for GLP-1, it was -1867.9 ± 850.4 pg/mL (F = 4.82, p < 0.0422). No significant differences were noted for areas under the curve between conditions for leptin, PP, PYY, insulin, or GIP. Initiating a fast with exercise lowers ghrelin concentrations and elevates GLP-1 concentrations. Given that ghrelin elicits feelings of hunger and GLP-1 signals feelings of satiety, adding exercise to the beginning of a fast may reduce some of the biological drive of hunger, which could make fasting more tolerable, leading to better adherence and more significant health outcomes.

A Novel Ketone-Supplemented Diet Improves Recognition Memory and Hippocampal Mitochondrial Efficiency in Healthy Adult Mice.

Mitochondrial dysfunction and cognitive impairment are common symptoms in many neurologic and psychiatric disorders, as well as nonpathological aging. Ketones have been suggested as therapeutic for their efficacy in epilepsy and other brain pathologies such as Alzheimer's disease and major depressive disorder. However, their effects on cognitive function in healthy individuals is less established. Here, we explored the mitochondrial and performative outcomes of a novel eight-week ketone-supplemented ketogenic (KETO) diet in healthy adult male and female mice. In a novel object recognition test, KETO mice spent more time with the novel, compared to familiar, object, indicating an improvement in recognition memory. High-resolution respirometry on permeabilized hippocampal tissue returned significant reductions in mitochondrial O2 consumption. No changes in ATP production were observed, yielding a significantly higher ATP:O2 ratio, a measure of mitochondrial efficiency. Together, these findings demonstrate the KETO diet improves hippocampal mitochondrial efficiency. They add to a growing body of evidence that suggests ketones and ketogenic diets are neuroprotective and metabolically and cognitively relevant, even in healthy adults. They also suggest that ketogenic lifestyle changes may be effective strategies for protecting against cognitive decline associated with aging and disease.

Statin therapy is not warranted for a person with high LDL-cholesterol on a low-carbohydrate diet.

PURPOSE OF REVIEW: Although there is an extensive literature on the efficacy of the low carbohydrate diet (LCD) for weight loss and in the management of type 2 diabetes, concerns have been raised that the LCD may increase cardiovascular disease (CVD) risk by increasing the level of low-density lipoprotein cholesterol (LDL-C). We have assessed the value of LDL-C as a CVD risk factor, as well as effects of the LCD on other CVD risk factors. We have also reviewed findings that provide guidance as to whether statin therapy would be beneficial for individuals with high LDL-C on an LCD. RECENT FINDINGS: Multiple longitudinal trials have demonstrated the safety and effectiveness of the LCD, while also providing evidence of improvements in the most reliable CVD risk factors. Recent findings have also confirmed how ineffective LDL-C is in predicting CVD risk. SUMMARY: Extensive research has demonstrated the efficacy of the LCD to improve the most robust CVD risk factors, such as hyperglycemia, hypertension, and atherogenic dyslipidemia. Our review of the literature indicates that statin therapy for both primary and secondary prevention of CVD is not warranted for individuals on an LCD with elevated LDL-C who have achieved a low triglyceride/HDL ratio.

A high-carbohydrate diet lowers the rate of adipose tissue mitochondrial respiration.

Adipocyte mitochondrial respiration may influence metabolic fuel partitioning into oxidation versus storage, with implications for whole-body energy expenditure. Although insulin has been shown to influence mitochondrial respiration, the effects of dietary macronutrient composition have not been well characterized. The aim of this exploratory study was to test the hypothesis that a high-carbohydrate diet lowers the oxygen flux of adipocyte mitochondria ex vivo. Among participants in a randomized-controlled weight-loss maintenance feeding trial, those consuming a high-carbohydrate diet (60% carbohydrate as a proportion of total energy, n = 10) had lower rates of maximal adipose tissue mitochondrial respiration than those consuming a moderate-carbohydrate diet (40%, n = 8, p = 0.039) or a low-carbohydrate diet (20%, n = 9, p = 0.005) after 10 to 15 weeks. This preliminary finding may provide a mechanism for postulated calorie-independent effects of dietary composition on energy expenditure and fat deposition, potentially through the actions of insulin on fuel partitioning.

The Metabolic Effects of Ketones.

The phrase "once trash, now a treasure" is an apt description of the evolving view of ketones in biomedical research [...].

The Effects of Exercise on ß-Hydroxybutyrate Concentrations over a 36-h Fast: A Randomized Crossover Study.

PURPOSE: This study assessed ß-hydroxybutyrate (BHB) concentration during a short-term fast and the degree to which an initial bout of exercise influences the rate of ketogenesis. METHODS: Twenty subjects (11 male, 9 female) completed two 36-h fasts, with one protocol requiring the subject to complete a treadmill exercise session at the beginning of the fast. BHB levels were assessed via portable meter every 2 h, along with mood and hunger ratings. Venipuncture was performed every 12 h. RESULTS: The mean (SD) areas under the curve for BHB concentration were 19.19 (2.59) mmol·L-1 (nonexercised) and 27.49 (2.59) mmol·L-1 (exercised), yielding a difference of 8.30 mmol·L-1 between conditions (95% posterior probability interval (PPI), 1.94 to 14.82 mmol·L-1; posterior probability (PP) = 0.99). The mean (SD) times to BHB concentration of 0.5 mmol·L-1 were 21.07 (2.95) h (nonexercised) and 17.5 (1.69) h (exercised), a 3.57-h difference (95% PPI, -2.11 to 10.87 h; PP = 0.89). The differences in area under the curve between conditions were 5.07 µU·mL-1 (95% PPI, -21.64 to 36.18 µU·mL-1; PP = 0.67) for insulin, 97.13 pg·mL-1 (95% PPI, 34.08 to 354.21 pg·mL-1; PP = 0.98) for glucagon, and 20.83 (95% PPI, 4.70 to 24.22; PP = 0.99) for the insulin/glucagon ratio. CONCLUSIONS: Completing aerobic exercise at the beginning of a fast accelerates the production of BHB throughout the fast without altering subjective feelings of hunger, thirst, stomach discomfort, or mood. Insulin and the insulin/glucagon ratio experience a marked reduction within the first 12 h of fasting and was not altered with exercise. Thus, exercising at the beginning of a fast may improve the metabolic outcomes of fasting.

Alzheimer's disease alters oligodendrocytic glycolytic and ketolytic gene expression.

INTRODUCTION: Sporadic Alzheimer's disease (AD) is strongly correlated with impaired brain glucose metabolism, which may affect AD onset and progression. Ketolysis has been suggested as an alternative pathway to fuel the brain. METHODS: RNA-seq profiles of post mortem AD brains were used to determine whether dysfunctional AD brain metabolism can be determined by impairments in glycolytic and ketolytic gene expression. Data were obtained from the Knight Alzheimer's Disease Research Center (62 cases; 13 controls), Mount Sinai Brain Bank (110 cases; 44 controls), and the Mayo Clinic Brain Bank (80 cases; 76 controls), and were normalized to cell type: astrocytes, microglia, neurons, oligodendrocytes. RESULTS: In oligodendrocytes, both glycolytic and ketolytic pathways were significantly impaired in AD brains. Ketolytic gene expression was not significantly altered in neurons, astrocytes, and microglia. DISCUSSION: Oligodendrocytes may contribute to brain hypometabolism observed in AD. These results are suggestive of a potential link between hypometabolism and dysmyelination in disease physiology. Additionally, ketones may be therapeutic in AD due to their ability to fuel neurons despite impaired glycolytic metabolism.

Ketones Elicit Distinct Alterations in Adipose Mitochondrial Bioenergetics.

OBJECTIVE: The rampant growth of obesity worldwide has stimulated explosive research into human metabolism. Energy expenditure has been shown to be altered by diets differing in macronutrient composition, with low-carbohydrate, ketogenic diets eliciting a significant increase over other interventions. The central aim of this study was to explore the effects of the ketone ß-hydroxybutyrate (ßHB) on mitochondrial bioenergetics in adipose tissue. METHODS: We employed three distinct systems-namely, cell, rodent, and human models. Following exposure to elevated ßHB, we obtained adipose tissue to quantify mitochondrial function. RESULTS: In every model, ßHB robustly increased mitochondrial respiration, including an increase of roughly 91% in cultured adipocytes, 113% in rodent subcutaneous adipose tissue (SAT), and 128% in human SAT. However, this occurred without a commensurate increase in adipose ATP production. Furthermore, in cultured adipocytes and rodent adipose, we quantified and observed an increase in the gene expression involved in mitochondrial biogenesis and uncoupling status following ßHB exposure. CONCLUSIONS: In conclusion, ßHB increases mitochondrial respiration, but not ATP production, in mammalian adipocytes, indicating altered mitochondrial coupling. These findings may partly explain the increased metabolic rate evident in states of elevated ketones, and may facilitate the development of novel anti-obesity interventions.

Lack of skeletal muscle liver kinase B1 alters gene expression, mitochondrial content, inflammation and oxidative stress without affecting high-fat diet-induced obesity or insulin resistance.

Ad libitum high-fat diet (HFD) induces obesity and skeletal muscle metabolic dysfunction. Liver kinase B1 (LKB1) regulates skeletal muscle metabolism by controlling the AMP-activated protein kinase family, but its importance in regulating muscle gene expression and glucose tolerance in obese mice has not been established. The purpose of this study was to determine how the lack of LKB1 in skeletal muscle (KO) affects gene expression and glucose tolerance in HFD-fed, obese mice. KO and littermate control wild-type (WT) mice were fed a standard diet or HFD for 14 weeks. RNA sequencing, and subsequent analysis were performed to assess mitochondrial content and respiration, inflammatory status, glucose and insulin tolerance, and muscle anabolic signaling. KO did not affect body weight gain on HFD, but heavily impacted mitochondria-, oxidative stress-, and inflammation-related gene expression. Accordingly, mitochondrial protein content and respiration were suppressed while inflammatory signaling and markers of oxidative stress were elevated in obese KO muscles. KO did not affect glucose or insulin tolerance. However, fasting serum insulin and skeletal muscle insulin signaling were higher in the KO mice. Furthermore, decreased muscle fiber size in skmLKB1-KO mice was associated with increased general protein ubiquitination and increased expression of several ubiquitin ligases, but not muscle ring finger 1 or atrogin-1. Taken together, these data suggest that the lack of LKB1 in skeletal muscle does not exacerbate obesity or insulin resistance in mice on a HFD, despite impaired mitochondrial content and function and elevated inflammatory signaling and oxidative stress.

Growth arrest-specific protein-6/AXL signaling induces preeclampsia in rats†.

Preeclampsia (PE) is a complicated obstetric complication characterized by increased blood pressure, decreased trophoblast invasion, and inflammation. The growth arrest-specific 6 (Gas6) protein is known to induce dynamic cellular responses and is elevated in PE. Gas6 binds to the AXL tyrosine kinase receptor and AXL-mediated signaling is implicated in proliferation and migration observed in several tissues. Our laboratory utilized Gas6 to induce preeclamptic-like conditions in pregnant rats. Our objective was to determine the role of Gas6/AXL signaling as a possible model of PE. Briefly, pregnant rats were divided into three groups that received daily intraperitoneal injections (from gestational day 7.5 to 17.5) of phosphate buffered saline (PBS), Gas6, or Gas6 + R428 (an AXL inhibitor administered from gestational day 13.5 to 17.5). Animals dispensed Gas6 experienced elevated blood pressure, increased proteinuria, augmented caspase-3-mediated placental apoptosis, and diminished trophoblast invasion. Gas6 also enhanced expression of several PE-related genes and a number of inflammatory mediators. Gas6 further enhanced placental oxidative stress and impaired mitochondrial respiration. Each of these PE-related characteristics was ameliorated in dams and/or their placentae when AXL inhibition by R428 occurred in tandem with Gas6 treatment. We conclude that Gas6 signaling is capable of inducing PE and that inhibition of AXL prevents disease progression in pregnant rats. These results provide insight into pathways associated with PE that could be useful in the clarification of potential therapeutic approaches.

Diesel Exhaust Particle Exposure Compromises Alveolar Macrophage Mitochondrial Bioenergetics.

Diesel exhaust particles (DEPs) are known pathogenic pollutants that constitute a significant quantity of air pollution. Given the ubiquitous presence of macrophages throughout the body, including the lungs, as well as their critical role in tissue and organismal metabolic function, we sought to determine the effect of DEP exposure on macrophage mitochondrial function. Following daily DEP exposure in mice, pulmonary macrophages were isolated for mitochondrial analyses, revealing reduced respiration rates and dramatically elevated H2O2 levels. Serum ceramides and inflammatory cytokines were increased. To determine the degree to which the changes in mitochondrial function in macrophages were not dependent on any cross-cell communication, primary pulmonary murine macrophages were used to replicate the DEP exposure in a cell culture model. We observed similar changes as seen in pulmonary macrophages, namely diminished mitochondrial respiration, but increased H2O2 production. Interestingly, when treated with myriocin to inhibit ceramide biosynthesis, these DEP-induced mitochondrial changes were mitigated. Altogether, these data suggest that DEP exposure may compromise macrophage mitochondrial and whole-body function via pathologic alterations in macrophage ceramide metabolism.

Differential placental ceramide levels during gestational diabetes mellitus (GDM).

BACKGROUND: Gestational diabetes mellitus (GDM) is associated with important factors that influence fetal development. Sphingolipids are known to be associated with the development of diabetes. Our objective was to examine ceramide, a key sphingolipid, hyperosmolarity, and apoptosis in placentas from GDM patients treated with insulin or diet. METHODS: Ceramide levels were assessed in placental tissues using immunohistochemistry. Immunoblot was performed to quantify serine palmitoyltransferase (SPT), the rate-limiting enzyme in ceramide biosynthesis, NFAT5, SMIT, AR, caspase 3 and the X-linked inhibitor of apoptosis. Trophoblast cells were treated with insulin or ceramide and assessments for mitochondrial respiration, caspase 3 and XIAP were also performed. RESULTS: Immunohistochemistry showed increased ceramides in the placental villous trophoblasts of the insulin-treated GDM patients. Nuclear SPT was upregulated only in the insulin-treated GDM placenta when compared to controls. Nuclear NFAT5 was also increased in the GDM placenta. Active caspase 3 was elevated in placentas from both insulin- and diet-treated GDM patients. Mitochondrial respiration was decreased in trophoblasts treated with ceramide. Active caspase was not changed while XIAP protein was increased in trophoblasts treated with ceramide. CONCLUSIONS: Our findings confirm the presence of ceramide in the human placenta of control and GDM patients. Furthermore, we conclude that ceramide is increased in the placental trophoblast during insulin treatment and that its upregulation correlates with elevated NFAT5, SMIT, increased apoptosis and decreased trophoblast mitochondrial respiration.

Improvement in Glycemic and Lipid Profiles in Type 2 Diabetics with a 90-Day Ketogenic Diet.

Because low-carbohydrate diets are effective strategies to improve insulin resistance, the hallmark of type 2 diabetes, the purpose of reporting these clinical cases was to reveal the meaningful changes observed in 90 days of low-carbohydrate (LC) ketogenic dietary intervention in female type 2 diabetics aged 18-45. Eleven women (BMI 36.3 kg/m2) who were recently diagnosed with type 2 diabetes based on HbA1c over 6.5% (8.9%) volunteered to participate in an intensive dietary intervention to limit dietary carbohydrates to under 30 grams daily for 90 days. The main outcome was to determine the degree of change in HbA1c, while secondary outcomes included body weight, blood pressure, and blood lipids. The volunteers lost significant weight (85.7 ± 3.2 kg to 76.7 ± 2.8 kg) and lowered systolic (134.0 ± 1.6 to 123.3 ± 1.1 mmHg) and diastolic (89.9 ± 1.3 to 82.6 ± 1.0 mmHg) blood pressure. HbA1c dropped to 5.6%. Most blood lipids were significantly altered, including HDL cholesterol (43.1 ± 4.4 to 52.3 ± 3.3 mg/dl), triglycerides (177.0 ± 19.8 to 92.1 ± 8.7 mg/dl), and the TG : HDL ratio (4.7 ± 0.8 to 1.9 ± 0.2). LDL cholesterol was not significantly different. AST and ALT, plasma markers of liver health, were reported for eight patients and revealed no significant changes. These findings indicate that a short-term intervention emphasizing protein and fat at the expense of dietary carbohydrate functionally reversed the diabetes diagnosis, as defined by HbA1c. Furthermore, the intervention lowered body weight and blood pressure, while eliciting favorable changes in blood lipids.

Resistance mechanisms and cross-resistance for a pyridine-pyrimidine amide inhibitor of microtubule polymerization.

Despite their clinical importance, drug resistance remains problematic for microtubule targeting drugs. D4-9-31, a novel microtubule destabilizing agent, has pharmacology that suggests it can overcome common resistance mechanisms and has been shown to remain efficacious in cell and animal models with acquired taxane resistance. To better understand resistance mechanisms and the breadth of cross-resistance with D4-9-31, this study examines the A2780 ovarian cancer cell line as it develops acquired resistance with continuous exposure to D4-9-31. Analyzing cellular responses to D4-9-31 reveals that D4-9-31 resistance is associated with increased mitochondrial respiration, but no cross-resistance to other microtubule targeting agents is observed. Sequencing of transcripts of parental cells and resistant counterparts reveals mutations and altered expression of microtubule-associated genes, but not in genes commonly associated with resistance to microtubule targeting drugs. Additionally, our findings suggest distinct mechanisms drive short- and long-term drug resistance.