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

Differential effects of Western diet and traumatic muscle injury on skeletal muscle metabolic regulation in male and female mice

BACKGROUND

This study was designed to develop an understanding of the pathophysiology of traumatic muscle injury in the context of Western diet (WD; high fat and high sugar) and obesity. The objective was to interrogate the combination of WD and injury on skeletal muscle mass and contractile and metabolic function.

METHODS

Male and female C57BL/6J mice were randomized into four groups based on a two-factor study design: (1) injury (uninjured vs. volumetric muscle loss [VML]) and (2) diet (WD vs. normal chow [NC]). Electrophysiology was used to test muscle strength and metabolic function in cohorts of uninjured + NC, uninjured + WD, VML + NC and VML + WD at 8 weeks of intervention.

RESULTS

VML-injured male and female mice both exhibited decrements in muscle mass (-17%, P < 0.001) and muscle strength (-28%, P < 0.001); however, VML + WD females had a 28% greater muscle mass compared to VML + NC females (P = 0.034), a compensatory response not detected in males. VML-injured male and female mice both had lower carbohydrate- and fat-supported muscle mitochondrial respiration (JO2 ) and less electron conductance through the electron transport system (ETS); however, male VML-WD had 48% lower carbohydrate-supported JO2 (P = 0.014) and 47% less carbohydrate-supported electron conductance (P = 0.026) compared to male VML + NC, and this diet-injury phenotype was not present in females. ETS electron conductance starts with complex I and complex II dehydrogenase enzymes at the inner mitochondrial membrane, and male VML + WD had 31% less complex I activity (P = 0.004) and 43% less complex II activity (P = 0.005) compared to male VML + NC. This was a diet-injury phenotype not present in females. Pyruvate dehydrogenase (PDH), β-hydroxyacyl-CoA dehydrogenase, citrate synthase, α-ketoglutarate dehydrogenase and malate dehydrogenase metabolic enzyme activities were evaluated as potential drivers of impaired JO2 in the context of diet and injury. There were notable male and female differential effects in the enzyme activity and post-translational regulation of PDH. PDH enzyme activity was 24% less in VML-injured males, independent of diet (P < 0.001), but PDH enzyme activity was not influenced by injury in females. PDH enzyme activity is inhibited by phosphorylation at serine-293 by PDH kinase 4 (PDK4). In males, there was greater total PDH, phospho-PDHser293 and phospho-PDH-to-total PDH ratio in WD mice compared to NC, independent of injury (P ≤ 0.041). In females, PDK4 was 51% greater in WD compared to NC, independent of injury (P = 0.025), and was complemented by greater phospho-PDHser293 (P = 0.001).

CONCLUSIONS

Males are more susceptible to muscle metabolic dysfunction in the context of combined WD and traumatic injury compared to females, and this may be due to impaired metabolic enzyme functions.

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.

Differential effects of western versus mediterranean diets and psychosocial stress on ovarian function in female monkeys (Macaca fascicularis)

Ovarian dysfunction increases risk for chronic diseases of aging including cardiovascular disease, depression, cognitive impairment, as well as bone and muscle loss which promote frailty. Psychosocial stress can disrupt ovarian function, and recent observations suggest that consumption of a Western Diet may also. Determination of causal relationships among diet, psychosocial stress, and ovarian physiology is difficult in humans. Long-tailed (a.k.a. cynomolgus) macaques (Macaca fascicularis) are an excellent translational model for the study of diet and psychosocial effects on ovarian physiology and aging-related processes. They have 28-day menstrual cycles with hormonal fluctuations like those of women, and similar physiologic responses to alterations and/or cessation of cyclicity. We examined ovarian function in 38 middle-aged socially housed females fed either a Western or Mediterranean diet for 31 months (≈ a 9-year period for humans). During the last year, we examined cycle length and peak progesterone per cycle using blood sampling (3/week) and vaginal swabbing for menses (6/week). Repeated measures analysis revealed a circannual pattern consistent with increased menstrual cycle disturbance during the late Summer and early Fall (F(11,348)= 4.05 p < 0.001). In addition, both Western diet (F(1,34)= 3.99; p = 0.05) and the stress of low social status (F(1,34)= 3.99; p = 0.04) reduced mean progesterone levels. Thus, on average, subordinates in the Western group had the lowest average progesterone levels (10.02 ng/pl). Compared to Western diets, Mediterranean diets exhibited protective effects via menstrual cycle regularity. For dominant monkeys, consuming Mediterranean diets resulted in significantly greater likelihood of having regular menstrual cycles. Mediterranean diets also protected individuals from shorter than normal menstrual cycles. The relationships between diet and menstrual regularity were partially mediated by both adrenal reactivity and social isolation. This study demonstrates the additive negative effects of poor diet and psychosocial stress on ovarian physiology in mid-life and lays the groundwork for future investigations to uncover their impact on metabolic signatures of accelerated aging. The results also suggest that - compared to Western-style diets - a Mediterranean diet may exert a protective influence against ovarian dysfunction and its pathologic sequelae.

FoxO1 regulates adipose transdifferentiation and iron influx by mediating Tgfβ1 signaling pathway

Adipose plasticity is critical for metabolic homeostasis. Adipocyte transdifferentiation plays an important role in adipose plasticity, but the molecular mechanism of transdifferentiation remains incompletely understood. Here we show that the transcription factor FoxO1 regulates adipose transdifferentiation by mediating Tgfβ1 signaling pathway. Tgfβ1 treatment induced whitening phenotype in beige adipocytes, reducing UCP1 and mitochondrial capacity and enlarging lipid droplets. Deletion of adipose FoxO1 (adO1KO) dampened Tgfβ1 signaling by downregulating Tgfbr2 and Smad3 and induced browning of adipose tissue in mice, increasing UCP1 and mitochondrial content and activating metabolic pathways. Silencing FoxO1 also abolished the whitening effect of Tgfβ1 on beige adipocytes. The adO1KO mice exhibited a significantly higher energy expenditure, lower fat mass, and smaller adipocytes than the control mice. The browning phenotype in adO1KO mice was associated with an increased iron content in adipose tissue, concurrent with upregulation of proteins that facilitate iron uptake (DMT1 and TfR1) and iron import into mitochondria (Mfrn1). Analysis of hepatic and serum iron along with hepatic iron-regulatory proteins (ferritin and ferroportin) in the adO1KO mice revealed an adipose tissue-liver crosstalk that meets the increased iron requirement for adipose browning. The FoxO1-Tgfβ1 signaling cascade also underlay adipose browning induced by β3-AR agonist CL316243. Our study provides the first evidence of a FoxO1-Tgfβ1 axis in the regulation of adipose browning-whitening transdifferentiation and iron influx, which sheds light on the compromised adipose plasticity in conditions of dysregulated FoxO1 and Tgfβ1 signaling.

Impact of 4 weeks of western diet and aerobic exercise training on whole-body phenotype and skeletal muscle mitochondrial respiration in male and female mice

High dietary fat intake induces significant whole-body and skeletal muscle adaptations in mice, including increased capacity for fat oxidation and mitochondrial biogenesis. The impact of a diet that is high in fat and simple sugars (i.e., western diet [WD]), particularly on regulation of skeletal muscle mitochondrial function, is less understood. The purpose of the current study was to determine physiologic adaptations in mitochondrial respiratory capacity in skeletal muscle during short-term consumption of WD, including if adaptive responses to WD-feeding are modified by concurrent exercise training or may be sex-specific. Male and female C57BL/6J mice were randomized to consume low-fat diet (LFD) or WD for 4 weeks, with some WD-fed mice also performing concurrent treadmill training (WD + Ex). Group sizes were n = 4-7. Whole-body metabolism was measured using in-cage assessment of food intake and energy expenditure, DXA body composition analysis and insulin tolerance testing. High-resolution respirometry of mitochondria isolated from quadriceps muscle was used to determine skeletal muscle mitochondrial respiratory function. Male mice fed WD gained mass (p < 0.001), due to increased fat mass (p < 0.001), and displayed greater respiratory capacity for both lipid and non-lipid substrates compared with LFD mice (p < 0.05). There was no effect of concurrent treadmill training on maximal respiration (WD + Ex vs. WD). Female mice had non-significant changes in body mass and composition as a function of the interventions, and no differences in skeletal muscle mitochondrial oxidative capacity. These findings indicate 4 weeks of WD feeding can increase skeletal muscle mitochondrial oxidative capacity among male mice; whereas WD, with or without exercise, had minimal impact on mass gain and skeletal muscle respiratory capacity among female mice. The translational relevance is that mitochondrial adaptation to increases in dietary fat intake that model WD may be related to differences in weight gain among male and female mice.

Mitochondrial respiration in thoracic perivascular adipose tissue of diabetic mice

Introduction

Thoracic perivascular adipose tissue (tPVAT) has a phenotype resembling brown AT. Dysfunctional tPVAT appears to be linked to vascular dysfunction.

Methods

We evaluated uncoupling protein 1 (UCP1) expression by Western blot, oxidative stress by measuring lipid peroxidation, the antioxidant capacity by HPLC and spectrophotometry, and mitochondrial respiration by high-resolution respirometry (HRR) in tPVAT, compared to inguinal white AT (iWAT), obtained from non-diabetic (NDM) and streptozocin-induced diabetic (STZ-DM) mice. Mitochondrial respiration was assessed by HRR using protocol 1: complex I and II oxidative phosphorylation (OXPHOS) and protocol 2: fatty acid oxidation (FAO) OXPHOS. OXPHOS capacity in tPVAT was also evaluated after UCP1 inhibition by guanosine 5'-diphosphate (GDP).

Results

UCP1 expression was higher in tPVAT when compared with iWAT in both NDM and STZ-DM mice. The malondialdehyde concentration was elevated in tPVAT from STZ-DM compared to NDM mice. Glutathione peroxidase and reductase activities, as well as reduced glutathione levels, were not different between tPVAT from NDM and STZ-DM mice but were lower compared to iWAT of STZ-DM mice. OXPHOS capacity of tPVAT was significantly decreased after UCP1 inhibition by GDP in protocol 1. While there were no differences in the OXPHOS capacity between NDM and STZ-DM mice in protocol 1, it was increased in STZ-DM compared to NDM mice in protocol 2. Moreover, complex II- and FAO-linked respiration were elevated in STZ-DM mice under UCP1 inhibition.

Conclusions

Pharmacological therapies could be targeted to modulate UCP1 activity with a significant impact in the uncoupling of mitochondrial bioenergetics in tPVAT.

Dietary magnesium intake is protective in patients with periodontitis

Background

Periodontitis is a chronic inflammatory disease of the oral cavity characterized by inflammation of the periodontal tissue and resorption of the alveolar bone, which has a high incidence and is the main cause of tooth loss in adults. In addition to its role in promoting osteogenesis, magnesium also has a role in regulating the inflammatory response, both systemically and locally. There is growing evidence that magnesium is an important factor in maintaining the normal functioning of the body's immune system. Hypomagnesaemia can lead to a variety of chronic inflammatory diseases throughout the body, including periodontitis. Two-thirds of the US population suffers from magnesium deficiency. The connection between dietary magnesium and periodontitis is unknown. As a result, we set out to investigate the link between dietary magnesium intake and periodontitis.

Methods

In this study, we collected data from the National Health and Nutrition Examination Survey (NHANES) database from 2013 to 2014. Through 24-h dietary recalls, information about food consumption was collected. We examined the association between the dietary magnesium and periodontitis using multivariable logistic regression model. Based on odds ratios (OR) and 95% confidence intervals (CIs), a strong association was detected.

Results

Multivariable logistic regression analysis showed that the OR for periodontitis comparing the highest to the lowest quintile of dietary magnesium intake was 0.69 (95% CIs = 0.52~0.92). The restricted cubic spline (RCS) analysis showed that the non-linear association between dietary magnesium and periodontitis was statistically significant and that dietary magnesium supplementation reduced the prevalence of periodontitis.

Conclusion

Dietary magnesium intake is associated with the prevalence of periodontitis. Dietary magnesium deficiency increases the prevalence of periodontitis.

Impairment of Mitochondrial Respiration in Metabolic Diseases: An Overview

Mitochondrial dysfunction has emerged as a central pathomechanism in the setting of obesity and diabetes mellitus, linking these intertwined pathologies that share insulin resistance as a common denominator. High-resolution respirometry (HRR) is a state-of-the-art research method currently used to study mitochondrial respiration and its impairment in health and disease. Tissue samples, cells or isolated mitochondria are exposed to various substrate-uncoupler-inhibitor-titration protocols, which allows the measurement and calculation of several parameters of mitochondrial respiration. In this review, we discuss the alterations of mitochondrial bioenergetics in the main dysfunctional organs that contribute to the development of the obese and diabetic phenotypes in both animal models and human subjects. Herein we review data regarding the impairment of oxidative phosphorylation as integrated mitochondrial function assessed by means of HRR. We acknowledge the critical role of this method in determining the alterations in oxidative phosphorylation occurring in the early stages of metabolic pathologies. We conclude that there is a mutual two-way relationship between mitochondrial dysfunction and insulin insensitivity that characterizes these diseases.

The Influence of Diet on Metabolism and Health Across the Lifespan in Nonhuman Primates

The macro and micronutrient composition and the overall quantity of the diet are important predictors of physical and psychological health and, as a consequence, behavior. Translational preclinical models are critical to identifying the mechanisms underlying these relationships. Nonhuman primate models are particularly instrumental to this line of research as they exhibit considerable genetic, social, and physiological similarities, as well as similarities in their developmental trajectories to humans. This review aims to discuss recent contributions to the field of diet and metabolism and health using nonhuman primate models. The influence of diet composition on health and physiology across the lifespan will be the primary focus, including recent work examining the impact of maternal diet programming of offspring physiologic and behavioral developmental outcomes.

Brain region-specific disruption of mitochondrial bioenergetics in cynomolgus macaques fed a Western versus a Mediterranean diet

Mitochondrial dysfunction is evident in diseases affecting cognition and metabolism such as Alzheimer's disease and type 2 diabetes. Human studies of brain mitochondrial function are limited to postmortem tissue, preventing the assessment of bioenergetics by respirometry. Here, we investigated the effect of two diets on mitochondrial bioenergetics in three brain regions: the prefrontal cortex (PFC), the entorhinal cortex (ERC), and the cerebellum (CB), using middle-aged nonhuman primates. Eighteen female cynomolgus macaques aged 12.3 ± 0.7 yr were fed either a Mediterranean diet that is associated with healthy outcomes or a Western diet that is associated with poor cognitive and metabolic outcomes. Average bioenergetic capacity within each brain region did not differ between diets. Distinct brain regions have different metabolic requirements related to their function and disease susceptibility. Therefore, we also examined differences in bioenergetic capacity between brain regions. Mitochondria isolated from animals fed a Mediterranean diet maintained distinct differences in mitochondrial bioenergetics between brain regions, whereas animals fed the Western diet had diminished distinction in bioenergetics between brain regions. Notably, fatty acid β-oxidation was not affected between regions in animals fed a Western diet. In addition, bioenergetics in animals fed a Western diet had positive associations with fasting blood glucose and insulin levels in PFC and ERC mitochondria but not in CB mitochondria. Altogether, these data indicate that a Western diet disrupts bioenergetic patterns across brain regions and that circulating blood glucose and insulin levels in Western-diet fed animals influence bioenergetics in brain regions susceptible to Alzheimer's disease and type 2 diabetes.NEW & NOTEWORTHY We show that compared with cynomolgus macaques fed a Mediterranean diet, a Western diet resulted in diminished bioenergetic pattern between brain regions related to blood glucose and insulin levels, specifically in brain regions susceptible to neurodegeneration and diabetes. In addition, fatty acid metabolism not directly linked to the TCA cycle and glucose metabolism did not show differences in bioenergetics due to diet.

Heterochronic Parabiosis: Old Blood Induces Changes in Mitochondrial Structure and Function of Young Mice

Heterochronic parabiosis models have been utilized to demonstrate the role of blood-borne circulating factors in systemic effects of aging. In previous studies, heterochronic parabiosis has shown positive effects across multiple tissues in old mice. More recently, a study demonstrated old blood had a more profound negative effect on muscle performance and neurogenesis of young mice. In this study, we used heterochronic parabiosis to test the hypothesis that circulating factors mediate mitochondrial bioenergetic decline, a well-established biological hallmark of aging. We examined mitochondrial morphology, expression of mitochondrial complexes, and mitochondrial respiration from skeletal muscle of mice connected as heterochronic pairs, as well as young and old isochronic controls. Our results indicate that young heterochronic mice had significantly lower total mitochondrial content and on average had significantly smaller mitochondria compared to young isochronic controls. Expression of complex IV followed a similar pattern: young heterochronic mice had a trend for lower expression compared to young isochronic controls. Additionally, respirometric analyses indicate that young heterochronic mice had significantly lower complex I, complex I + II, and maximal mitochondrial respiration and a trend for lower complex II-driven respiration compared to young isochronic controls. Interestingly, we did not observe significant improvements in old heterochronic mice compared to old isochronic controls, demonstrating the profound deleterious effects of circulating factors from old mice on mitochondrial structure and function. We also found no significant differences between the young and old heterochronic mice, demonstrating that circulating factors can be a driver of age-related differences in mitochondrial structure and function.

Are Alterations in Skeletal Muscle Mitochondria a Cause or Consequence of Insulin Resistance?

As a major site of glucose uptake following a meal, skeletal muscle has an important role in whole-body glucose metabolism. Evidence in humans and animal models of insulin resistance and type 2 diabetes suggests that alterations in mitochondrial characteristics accompany the development of skeletal muscle insulin resistance. However, it is unclear whether changes in mitochondrial content, respiratory function, or substrate oxidation are central to the development of insulin resistance or occur in response to insulin resistance. Thus, this review will aim to evaluate the apparent conflicting information placing mitochondria as a key organelle in the development of insulin resistance in skeletal muscle.

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.

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.