One-year high fat diet affects muscle-but not brain mitochondria

High-intensity interval training attenuates impairment in regulatory protein machinery of mitochondrial quality control in skeletal muscle of diet-induced obese mice

Mitochondrial quality control processes are essential in governing mitochondrial integrity and function. The purpose of the study was to examine the effects of 10 weeks of high-intensity interval training (HIIT) on the regulatory protein machinery of skeletal muscle mitochondrial quality control and whole-body glucose homeostasis in diet-induced obese mice. Male C57BL/6 mice were assigned to low-fat diet (LFD) or high-fat diet (HFD) group. After 10 weeks, HFD-fed mice were divided into sedentary and HIIT (HFD + HIIT) groups for another 10 weeks (n = 9/group). Graded exercise test, glucose and insulin tolerance tests, mitochondrial respiration, and protein markers of mitochondrial quality control processes were determined. HFD-fed mice exhibited lower ADP-stimulated mitochondrial respiration (p < 0.05). However, 10 weeks of HIIT prevented this impairment (p < 0.05). Importantly, the ratio of Drp1(Ser616) over Drp1(Ser637) phosphorylation, an indicator of mitochondrial fission, was significantly higher in HFD-fed mice (p < 0.05), but such increase was attenuated in HFD-HIIT compared to HFD (-35.7%, p < 0.05). Regarding autophagy, skeletal muscle p62 content was lower in the HFD group than the LFD group (-35.1%, p < 0.05); however, such reduction was disappeared in the HFD + HIIT group. In addition, LC3B II/I ratio was higher in the HFD group than the LFD group (15.5%, p < 0.05) but was ameliorated in the HFD + HIIT group (-29.9%, p < 0.05). Overall, our study demonstrated that 10 weeks of HIIT was effective in improving skeletal muscle mitochondrial respiration and the regulatory protein machinery of mitochondrial quality control in diet-induced obese mice through the alterations of mitochondrial fission protein Drp1 phosphorylations and p62/LC3B-mediated regulatory machinery of autophagy.

The interactive effects of psychosocial stress and diet composition on health in primates

Social disadvantage and diet composition independently impact myriad dimensions of health. They are closely entwined, as social disadvantage often yields poor diet quality, and may interact to fuel differential health outcomes. This paper reviews effects of psychosocial stress and diet composition on health in nonhuman primates and their implications for aging and human health. We examined the effects of social subordination stress and Mediterranean versus Western diet on multiple systems. We report that psychosocial stress and Western diet have independent and additive adverse effects on hypothalamic-pituitary-adrenal and autonomic nervous system reactivity to psychological stressors, brain structure, and ovarian function. Compared to the Mediterranean diet, the Western diet resulted in accelerated aging, nonalcoholic fatty liver disease, insulin resistance, gut microbial changes associated with increased disease risk, neuroinflammation, neuroanatomical perturbations, anxiety, and social isolation. This comprehensive, multisystem investigation lays the foundation for future investigations of the mechanistic underpinnings of psychosocial stress and diet effects on health, and advances the promise of the Mediterranean diet as a therapeutic intervention on psychosocial stress.

High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs

High-fat consumption promotes the development of obesity, which is associated with various chronic illnesses. Mitochondria are the energy factories of eukaryotic cells, maintaining self-stability through a fine-tuned quality-control network. In the present study, we evaluated high-fat diet (HFD)-induced changes in mitochondrial ultrastructure and dynamics protein expression in multiple organs. C57BL/6J male mice were fed HFD or normal diet (ND) for 24 weeks. Compared with ND-fed mice, HFD-fed mice exhibited increased body weight, cardiomyocyte enlargement, pulmonary fibrosis, hepatic steatosis, renal and splenic structural abnormalities. The cellular apoptosis of the heart, liver, and kidney increased. Cellular lipid droplet deposition and mitochondrial deformations were observed. The proteins related to mitochondrial biogenesis (TFAM), fission (DRP1), autophagy (LC3 and LC3-II: LC3-I ratio), and mitophagy (PINK1) presented different changes in different organs. The mitochondrial fusion regulators mitofusin-2 (MFN2) and optic atrophy-1 (OPA1) were consistently downregulated in multiple organs, even the spleen. TOMM20 and ATP5A protein were enhanced in the heart, skeletal muscle, and spleen, and attenuated in the kidney. These results indicated that high-fat feeding caused pathological changes in multiple organs, accompanied by mitochondrial ultrastructural damage, and MFN2 and OPA1 downregulation. The mitochondrial fusion proteins may become promising targets and/or markers for treating metabolic disease.

Impact of Highly Saturated versus Unsaturated Fat Intake on Carbohydrate Metabolism and Vascular Reactivity in Rat

Palm olein (PO) and lard are considered harmful to health because of their highly saturated fatty acid content. On the contrary, olive oil (OO) with its high level of polyunsaturated fatty acids is considered healthier. This study aims to evaluate the effects of high consumption of these oils on carbohydrate metabolism and vascular function. Male Wistar rats were fed ad libitum for 12 weeks with different high fat diets (HFD) containing 30% of each oil. Systemic glycemia, insulinemia, and lipidemia were assessed by routine methods or by ELISA. GLUT4 muscular expression and hepatic and muscular Akt phosphorylation were analyzed by western blot. Vascular function was evaluated, ex vivo, on aortic rings and on the variations of isometric tensions. The results show that fasting blood glucose was increased with PO and OO diets and decreased with lard. Compared to control diet, this increase was significant only with PO diet. The area under the curve of IPGTT was increased in all HFD groups. Compared to control diet, this increase was significant only with PO. In contrast, stimulation of the pathway with insulin showed a significant decrease in Akt phosphorylation in all HFD compared to control diet. KCl and phenylephrine induced strong, dose-dependent vasoconstriction of rat aortas in all groups, but KCl EC₅₀ values were increased with lard and OO diets. The inhibitory effect of tempol was absent in PO and lard and attenuated in OO. Vascular insulin sensitivity was decreased in all HFD groups. This decreased sensitivity of insulin was more important with PO and lard when compared to OO diet. In conclusion, the results of this study clearly show that high consumption of palm olein, olive oil, and lard can compromise glucose tolerance and thus insulin sensitivity. Furthermore, palm olein and lard have a more deleterious effect than olive oil on the contractile function of the aorta. Excessive consumption of saturated or unsaturated fatty acids is harmful to health, regardless of their vegetable or animal origin.

Experimental models of lipid overload and their relevance in understanding skeletal muscle insulin resistance and pathological changes in mitochondrial oxidative capacity

It remains essential to decipher some of the pathological mechanisms that link obesity with deteriorating human health. Insulin resistance, due to enhanced free fatty acid substrate delivery, results in disrupted glucose homeostasis and altered mitochondrial oxidative capacity, which is a characteristic feature of an obese state. In fact, as a major site for regulating glucose homeostasis and energy production in response to insulin, the skeletal muscle has become an interesting target tissue to understand the impact of lipid overload on the development of insulin resistance and impaired mitochondrial respiratory function. In addition to systematically retrieving the discussed data, the current review brings an essential perspective in understanding the relevance of experimental models of lipid overload such as high fat diets in understanding the pathological link between insulin resistance and pathological changes in mitochondrial oxidative capacity. Importantly, inclusion of evidence from transgenic model highlights some of the unique molecular targets that are implicated in the development of insulin resistance and inefficient mitochondrial respiration processes within an obese state. Importantly, saturation with lipid products such as ceramides and diacylglycerols, especially within the skeletal muscle, appears to be instrumental in paving the path leading to worsening of metabolic complications. These metabolic consequences mostly interfere with the efficiency of the mitochondrial electron transport chain, leading to overproduction of toxic reactive oxygen species. Therefore, therapeutic agents that reverse the effects of lipid overload by improving insulin sensitivity and mitochondrial oxidative capacity are crucial for the management or even treatment of metabolic diseases.

The Treatment of Rhodiola Mimics Exercise to Resist High-Fat Diet-Induced Muscle Dysfunction via Sirtuin1-Dependent Mechanisms

Muscle dysfunction is a complication of high-fat diet (HFD)-induced obesity that could be prevented by exercise, but patients did not get enough therapeutic efficacy from exercise due to multiple reasons. To explore alternative or supplementary approaches to prevent or treat muscle dysfunction in individuals with obesity, we investigated the effects of Rhodiola on muscle dysfunction as exercise pills. SIRT1 might suppress atrogenes expression and improve mitochondrial quality control, which could be a therapeutic target stimulated by exercise and Rhodiola, but further mechanisms remain unclear. We verified the lipid metabolism disorders and skeletal muscle dysfunction in HFD feeding mice. Moreover, exercise and Rhodiola were used to intervene mice with a HFD. Our results showed that exercise and Rhodiola prevented muscle atrophy and dysfunction in obese mice and activating the SIRT1 pathway, while atrogenes were suppressed and mitochondrial quality control was improved. EX-527, SIRT1 inhibitor, was used to validate the essential role of SIRT1 in salidroside benefit. Results of cell culture experiment showed that salidroside alleviated high palmitate-induced atrophy and mitochondrial quality control impairments, but these improvements of salidroside were inhibited by EX-527 in C2C12 myotubes. Overall, Rhodiola mimics exercise that activates SIRT1 signaling leading to improvement of HFD-induced muscle dysfunction.

Impact of experimental obesity on diaphragm structure, function, and bioenergetics

Obesity is associated with bioenergetic dysfunction of peripheral muscles; however, little is known regarding the impact of obesity on the diaphragm. We hypothesized that obesity would be associated with diaphragm dysfunction attributable to mitochondrial oxygen consumption and structural and ultrastructural changes. Wistar rat litters were culled to 3 pups to induce early postnatal overfeeding and consequent obesity. Control animals were obtained from unculled litters. From postnatal day 150, diaphragm ultrasound, computed tomography, high-resolution respirometry, immunohistochemical, biomolecular, and ultrastructural histological analyses were performed. The diaphragms of obese animals, compared with those of controls, presented changes in morphology as increased thickening fraction, diaphragm excursion, and diaphragm dome height, as well as increased mitochondrial respiratory capacity coupled to ATP synthesis and maximal respiratory capacity. Fatty acid synthase gene expression was also higher in obese animals, suggesting a source of energy for the respiratory chain. Myosin heavy chain-IIA was increased, indicating shift from glycolytic toward oxidative muscle fiber profile. Diaphragm tissue also exhibited ultrastructural changes, such as compact, round, and swollen mitochondria with fainter cristae and more lysosomal bodies. Dynamin-1 expression in the diaphragm was reduced in obese rats, suggesting decreased mitochondrial fission. Furthermore, gene expressions of peroxisome γ proliferator-activated receptor coactivator-1α and superoxide dismutase-2 were lower in obese animals than in controls, which may indicate a predisposition to oxidative injury. In conclusion, in the obesity model used herein, muscle fiber phenotype was altered in a manner likely associated with increased mitochondrial respiratory capability, suggesting respiratory adaptation to increased metabolic demand.NEW & NOTEWORTHY Obesity has been associated with peripheral muscle dysfunction; however, little is known about its impact on the diaphragm. In the current study, we found high oxygen consumption in diaphragm tissue and changes in muscle fiber phenotypes toward a more oxidative profile in experimental obesity.

High-fat diet affects skeletal muscle mitochondria comparable to pressure overload-induced heart failure

In heart failure, high-fat diet (HFD) may exert beneficial effects on cardiac mitochondria and contractility. Skeletal muscle mitochondrial dysfunction in heart failure is associated with myopathy. However, it is not clear if HFD affects skeletal muscle mitochondria in heart failure as well. To induce heart failure, we used pressure overload (PO) in rats fed normal chow or HFD. Interfibrillar mitochondria (IFM) and subsarcolemmal mitochondria (SSM) from gastrocnemius were isolated and functionally characterized. With PO heart failure, maximal respiratory capacity was impaired in IFM but increased in SSM of gastrocnemius. Unexpectedly, HFD affected mitochondria comparably to PO. In combination, PO and HFD showed additive effects on mitochondrial subpopulations which were reflected by isolated complex activities. While PO impaired diastolic as well as systolic cardiac function and increased glucose tolerance, HFD did not affect cardiac function but decreased glucose tolerance. We conclude that HFD and PO heart failure have comparable effects leading to more severe impairment of IFM. Glucose tolerance seems not causally related to skeletal muscle mitochondrial dysfunction. The additive effects of HFD and PO may suggest accelerated skeletal muscle mitochondrial dysfunction when heart failure is accompanied with a diet containing high fat.

Enhanced liver but not muscle OXPHOS in diabetes and reduced glucose output by complex I inhibition

Mitochondrial function is critical in energy metabolism. To fully capture how the mitochondrial function changes in metabolic disorders, we investigated mitochondrial function in liver and muscle of animal models mimicking different types and stages of diabetes. Type 1 diabetic mice were induced by streptozotocin (STZ) injection. The db/db mice were used as type 2 diabetic model. High-fat diet-induced obese mice represented pre-diabetic stage of type 2 diabetes. Oxidative phosphorylation (OXPHOS) of isolated mitochondria was measured with Clark-type oxygen electrode. Both in early and late stages of type 1 diabetes, liver mitochondrial OXPHOS increased markedly with complex IV-dependent OXPHOS being the most prominent. However, ATP, ADP and AMP contents in the tissue did not change. In pre-diabetes and early stage of type 2 diabetes, liver mitochondrial complex I and II-dependent OXPHOS increased greatly then declined to almost normal at late stage of type 2 diabetes, among which alteration of complex I-dependent OXPHOS was the most significant. In contrast, muscle mitochondrial OXPHOS in HFD, early-stage type 1 and 2 diabetic mice, did not change. In vitro, among inhibitors to each complex, only complex I inhibitor rotenone decreased glucose output in primary hepatocytes without cytotoxicity both in the absence and presence of oleic acid (OA). Rotenone affected cellular energy state and had no effects on cellular and mitochondrial reactive oxygen species production. Taken together, the mitochondrial OXPHOS of liver but not muscle increased in obesity and diabetes, and only complex I inhibition may ameliorate hyperglycaemia via lowering hepatic glucose production.

Skeletal Muscle Mitochondrial Respiration Is Elevated in Female Cynomolgus Macaques Fed a Western Compared with a Mediterranean Diet

BACKGROUND

Western diets are associated with increased incidences of obesity, hypertension, diabetes, and hypercholesterolemia, whereas Mediterranean diets, richer in polyphenols, monounsaturated fats, fruits, vegetables, poultry, and fish, appear to have cardiometabolic health benefits. Previous work has included population-based studies with limited evidence for causation or animal studies focused on single macro- or micronutrients; therefore, primate animal models provide an opportunity to determine potential mechanisms underlying the effects of dietary patterns on health and disease.

OBJECTIVE

The aim of this study was to determine the effects of whole dietary patterns, either a Western or Mediterranean diet, on skeletal muscle mitochondrial bioenergetics in cynomolgus macaques.

METHODS

In this study, 22 adult female cynomolgus macaques (∼11-14 y by dentition) were fed either a Western or Mediterranean diet for 30 mo. The Western diet was designed to mimic the diet of a middle-aged American woman and the Mediterranean diet included key aspects of Mediterranean diets studied in humans, such as plant-based proteins and fat, complex carbohydrates, and fiber. Diets were matched on macronutrient composition (16% protein, 54% carbohydrate, and 31% fat) and cholesterol content. Skeletal muscle was collected for high-resolution respirometry, citrate synthase activity, and western blot measurements. Pearson correlation analysis between respirometry measures and measures of carbohydrate metabolism was also performed.

RESULTS

We found that consumption of a Western diet resulted in significantly higher mitochondrial respiration with fatty acid oxidation (FAO) (53%), FAO + complex I (52%), complex I + II (31%), max electron transport system (ETS) (31%), and ETS rotenone sensitive (31%) than did consumption of a Mediterranean diet. In addition, measures of respiration in response to fatty acids were significantly and positively correlated with both insulin resistance and plasma insulin concentrations.

CONCLUSIONS

This study highlights the importance of dietary composition in mitochondrial bioenergetics and that diet can influence skeletal muscle mitochondrial respiration independently of other factors such as macronutrient composition.

Diabetes and Alzheimer's Disease: A Link not as Simple as it Seems

Type 2 diabetes mellitus is associated with an increased risk to develop Alzheimer disease, however, the underlying mechanisms for this association are still unclear. In this review we will provide a critical overview of the major findings coming from clinical studies and animal models.

Ketogenic diet increases mitochondria volume in the liver and skeletal muscle without altering oxidative stress markers in rats

Ketogenic diets (KD) consist of high fat, moderate protein and low carbohydrates. Studies have suggested that KD may influence oxidative stress by affecting mitochondrial quantity and/or quality, and perhaps lengthen lifespan. Therefore, we determined the effects of KD on multi-organ mitochondria volume and oxidative stress markers in rats. Ten month-old male Fisher 344 rats (n = 8 per group) were provided with one of two isocaloric diets: standard chow (SC) or KD. Rats were euthanized if: a) vitality scores exceeded a score of 16, b) rapid weight loss, or c) veterinarian deemed euthanasia necessary. The median lifespan of rats was higher in KD (762 days) compared to SC (624 days). Citrate synthase activity (i.e. estimate of mitochondria volume) was higher in the liver (p = 0.034) and gastrocnemius (p = 0.041) of KD compared to SC. Liver superoxide dismutase 1 and catalase antioxidant protein levels were higher in KD, albeit not significant (p = 0.094 and p = 0.062, respectively). No significant differences in protein levels of other antioxidants or markers of lipid and protein oxidative damage were observed in either the gastrocnemius, liver, or brain. In summary, KD increased mitochondria volume in liver and gastrocnemius and median lifespan in rats. Additionally, our data show that the increase in mitochondrial volume occurred without changes in oxidative damage or antioxidant protein levels in the gastrocnemius, liver, or brain.

Analysis of respiratory capacity in brain tissue preparations: high-resolution respirometry for intact hippocampal slices

The evaluation of mitochondrial function provides the basis for the study of brain bioenergetics. However, analysis of brain mitochondrial respiration has been hindered by the low yield associated with mitochondria isolation procedures. Furthermore, isolating mitochondria or cells results in loss of the inherent complexity of the central nervous system. High-resolution respirometry (HRR), is a valuable tool to study mitochondrial function and has been used in diverse biological preparations ranging from isolated mitochondria to tissue homogenates and permeabilized tissue biopsies. Here we describe a novel methodology for evaluation of mitochondrial respiration using tissue preparations from the central nervous system, namely acute hippocampal slices from rodents, with HRR. By using acute intact hippocampal slices, tissue cytoarchitecture, intercellular communication and connectivity are preserved. Mitochondrial respiration was evaluated by using an adapted substrate-uncoupler-inhibitor titration (SUIT) protocol and the expected responses were observed. This methodology can be used to detect differences in mitochondrial function at the oxidative phosphorylation level and for studies with different brain oxidative substrates in physiological and neuropathological settings, by using a system that better represents the in vivo conditions than isolated mitochondria and/or cells.

Mechanisms by Which Dietary Fatty Acids Regulate Mitochondrial Structure-Function in Health and Disease

Mitochondria are the energy-producing organelles within a cell. Furthermore, mitochondria have a role in maintaining cellular homeostasis and proper calcium concentrations, building critical components of hormones and other signaling molecules, and controlling apoptosis. Structurally, mitochondria are unique because they have 2 membranes that allow for compartmentalization. The composition and molecular organization of these membranes are crucial to the maintenance and function of mitochondria. In this review, we first present a general overview of mitochondrial membrane biochemistry and biophysics followed by the role of different dietary saturated and unsaturated fatty acids in modulating mitochondrial membrane structure-function. We focus extensively on long-chain n-3 (ω-3) polyunsaturated fatty acids and their underlying mechanisms of action. Finally, we discuss implications of understanding molecular mechanisms by which dietary n-3 fatty acids target mitochondrial structure-function in metabolic diseases such as obesity, cardiac-ischemia reperfusion injury, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and select cancers.

Your mitochondria are what you eat: a high-fat or a high-sucrose diet eliminates metabolic flexibility in isolated mitochondria from rat skeletal muscle

Extreme diets consisting of either high fat (HF) or high sucrose (HS) may lead to insulin resistance in skeletal muscle, often associated with mitochondrial dysfunction. However, it is not known if these diets alter normal interactions of pyruvate and fatty acid oxidation at the level of the mitochondria. Here, we report that rat muscle mitochondria does show the normal Randle‐type fat‐carbohydrate interaction seen in vivo. The mechanism behind this metabolic flexibility at the level of the isolated mitochondria is a regulation of the flux‐ratio: pyruvate dehydrogenase (PDH)/β‐oxidation to suit the actual substrate availability, with the PDH flux as the major point of regulation. We further report that this regulatory mechanism of carbohydrate‐fat metabolic interaction surprisingly is lost in mitochondria obtained from animals exposed for 12 weeks to a HF‐ or a HS diet as compared to rats given a normal chow diet. The mechanism seems to be a loss of the PDH flux decrease seen in controls, when fatty acid is supplied as substrate in addition to pyruvate, and vice versa for the supply of pyruvate as substrate to mitochondria oxidizing fatty acid. Finally, we report that the calculated TCA flux in the isolated mitochondria under these circumstances shows a significant reduction (~50%) after the HF diet and an even larger reduction (~75%) after the HS diet, compared with the chow group. Thus, it appears that obesogenic diets as those applied here have major influence on key metabolic performance of skeletal muscle mitochondria.

Effect of a trans fatty acid-enriched diet on mitochondrial, inflammatory, and oxidative stress parameters in the cortex and hippocampus of Wistar rats

PURPOSE

Previously showed that dietary trans fatty acids (TFAs) may cause systemic inflammation and affect the central nervous system (CNS) in Wistar rats by increased levels of cytokines in the cerebrospinal fluid (CSF) and serum (Longhi et al. Eur J Nutr 56(3):1003-1016, 1). Here, we aimed to clarifying the impact of diets with different TFA concentrations on cerebral tissue, focusing on hippocampus and cortex and behavioral performance.

METHODS

Wistar rats were fed either a normolipidic or a hyperlipidic diet for 90 days; diets had the same ingredients except for fat compositions, concentrations, and calories. We used lard in the cis fatty acid (CFA) group and PHSO in the TFA group. The intervention groups were as follows: (1) low lard (LL), (2) high lard (HL), (3) low partially hydrogenated soybean oil (LPHSO), and (4) high partially hydrogenated soybean oil (HPHSO). Mitochondrial parameters, tumor necrosis factor alpha (TNF-α), 2'7'-dichlorofluorescein (DCFH) levels in brain tissue, and open field task were analyzed.

RESULTS

A worse brain tissue response was associated with oxidative stress in cortex and hippocampus as well as impaired inflammatory and mitochondrial parameters at both PHSO concentrations and there were alterations in the behavioral performance. In many analyses, there were no significant differences between the LPHSO and HPHSO diets.

CONCLUSIONS

Partially hydrogenated soybean oil impaired cortical mitochondrial parameters and altered inflammatory and oxidative stress responses, and the hyperlipidic treatment caused locomotor and exploratory effects, but no differences on weight gain in all treatments. These findings suggest that quality is more important than the quantity of fat consumed in terms of CFA and TFA diets.

Skeletal Muscle Nucleo-Mitochondrial Crosstalk in Obesity and Type 2 Diabetes

Skeletal muscle mitochondrial dysfunction, evidenced by incomplete beta oxidation and accumulation of fatty acid intermediates in the form of long and medium chain acylcarnitines, may contribute to ectopic lipid deposition and insulin resistance during high fat diet (HFD)-induced obesity. The present review discusses the roles of anterograde and retrograde communication in nucleo-mitochondrial crosstalk that determines skeletal muscle mitochondrial adaptations, specifically alterations in mitochondrial number and function in relation to obesity and insulin resistance. Special emphasis is placed on the effects of high fat diet (HFD) feeding on expression of nuclear-encoded mitochondrial genes (NEMGs) nuclear receptor factor 1 (NRF-1) and 2 (NRF-2) and peroxisome proliferator receptor gamma coactivator 1 alpha (PGC-1α) in the onset and progression of insulin resistance during obesity and how HFD-induced alterations in NEMG expression affect skeletal muscle mitochondrial adaptations in relation to beta oxidation of fatty acids. Finally, the potential ability of acylcarnitines or fatty acid intermediates resulting from mitochondrial beta oxidation to act as retrograde signals in nucleo-mitochondrial crosstalk is reviewed and discussed.

A Ketogenic Diet in Rodents Elicits Improved Mitochondrial Adaptations in Response to Resistance Exercise Training Compared to an Isocaloric Western Diet

Purpose: Ketogenic diets (KD) can facilitate weight loss, but their effects on skeletal muscle remain equivocal. In this experiment we investigated the effects of two diets on skeletal muscle mitochondrial coupling, mitochondrial complex activity, markers of oxidative stress, and gene expression in sedentary and resistance exercised rats. Methods: Male Sprague-Dawley rats (9-10 weeks of age, 300-325 g) were fed isocaloric amounts of either a KD (17 g/day, 5.2 kcal/g, 20.2% protein, 10.3% CHO, 69.5% fat, n = 16) or a Western diet (WD) (20 g/day, 4.5 kcal/g, 15.2% protein, 42.7% CHO, 42.0% fat, n = 16) for 6 weeks. During these 6 weeks animals were either sedentary (SED, n = 8 per diet group) or voluntarily exercised using resistance-loaded running wheels (EXE, n = 8 per diet group). Gastrocnemius was excised and used for mitochondrial isolation and biochemical analyses. Results: In the presence of a complex II substrate, the respiratory control ratio (RCR) of isolated gastrocnemius mitochondria was higher (p < 0.05) in animals fed the KD compared to animals fed the WD. Complex I and IV enzyme activity was higher (p < 0.05) in EXE animals regardless of diet. SOD2 protein levels and GLUT4 and PGC1α mRNA expression were higher (p < 0.05) in EXE animals regardless of diet. Conclusion: Our data indicate that skeletal muscle mitochondrial coupling of complex II substrates is more efficient in chronically resistance trained rodents fed a KD. These findings may provide merit for further investigation, perhaps on humans.

Translating Mouse Models

Mice and humans branched from a common ancestor approximately 80 million years ago. Despite this, mice are routinely utilized as animal models of human disease and in drug development because they are inexpensive, easy to handle, and relatively straightforward to genetically manipulate. While this has led to breakthroughs in the understanding of genotype-phenotype relationships and in the identification of therapeutic targets, translation of beneficial responses to therapeutics from mice to humans has not always been successful. In a large part, these differences may be attributed to variations in the alignment of protein expression and signaling in the immune systems between mice and humans. Well-established inbred strains of "The Laboratory Mouse" vary in their immune response patterns as a result of genetic mutations and polymorphisms arising from intentional selection for research relevant traits, and even closely related substrains vary in their immune response patterns as a result of genetic mutations and polymorphisms arising from genetic drift. This article reviews some of the differences between the mouse and human immune system and between inbred mouse strains and shares examples of how these differences can impact the usefulness of mouse models of disease.

Reduction in cardiolipin decreases mitochondrial spare respiratory capacity and increases glucose transport into and across human brain cerebral microvascular endothelial cells

Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. Cardiolipin is a mitochondrial phospholipid required for function of the electron transport chain and ATP generation. We examined the role of cardiolipin in maintaining mitochondrial function necessary to support barrier properties of brain microvessel endothelial cells. Knockdown of the terminal enzyme of cardiolipin synthesis, cardiolipin synthase, in hCMEC/D3 cells resulted in decreased cellular cardiolipin levels compared to controls. The reduction in cardiolipin resulted in decreased mitochondrial spare respiratory capacity, increased pyruvate kinase activity, and increased 2-deoxy-[(3) H]glucose uptake and glucose transporter-1 expression and localization to membranes in hCMEC/D3 cells compared to controls. The mechanism for the increase in glucose uptake was an increase in adenosine-5'-monophosphate kinase and protein kinase B activity and decreased glycogen synthase kinase 3 beta activity. Knockdown of cardiolipin synthase did not affect permeability of fluorescent dextran across confluent hCMEC/D3 monolayers grown on Transwell(®) inserts. In contrast, knockdown of cardiolipin synthase resulted in an increase in 2-deoxy-[(3) H]glucose transport across these monolayers compared to controls. The data indicate that in hCMEC/D3 cells, spare respiratory capacity is dependent on cardiolipin. In addition, reduction in cardiolipin in these cells alters their cellular energy status and this results in increased glucose transport into and across hCMEC/D3 monolayers. Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. In human adult brain endothelial cell hCMEC/D3 monolayers cultured on Transwell(®) plates, knockdown of cardiolipin synthase results in decrease in mitochondrial cardiolipin and decreased mitochondrial spare respiratory capacity. The reduced cardiolipin results in an increased activity of adenosine monophosphate kinase (pAMPK) and protein kinase B (pAKT) and decreased activity of glycogen synthase kinase 3 beta (pGSK3β) which results in elevated glucose transporter-1 (GLUT-1) expression and association with membranes. This in turn increases 2-dexoyglucose uptake from the apical medium into the cells with a resultant 2-deoxyglucose movement into the basolateral medium.