Lanza, Ian R.

Mitochondrial function declines with age but increases with caloric restriction (CR). Mitochondria and muscle fibers were prepared from young (8–11mo) and old (22–24mo) AL‐fed and old CR mice. State 3 respiration was lower in OAL vs. YAL, but preserved in OCR (). Normalizing to protein content eliminated the age‐effect in AL mice but amplified the effect of CR, indicating that CR enhances the intrinsic mito function. ROS production in isolated fibers increased with age in AL but not CR mice (). Coupling was reduced in OAL but not OCR. These results indicate that mito capacity declines with age in situ and in vitro, apparently driven largely by decreased mitochondrial protein content. CR increases mito capacity and efficiency independently of mito protein content. YAL OAL OCR Fibers (pmol/s/m g tiss) CI 54.0±4.1 38.9±1.6 50.8±3.0 CII 44.4±3.4 36.9±1.4 45.0±2.3 CI+II 63.4±5.5 51.8±2.5 67.0±3.4 Mito (pmol/s/m g tiss) CI 38.9±1.8 21.5±2.6 30.7±2.0 CII 30.6±0.9 19.6±1.2 24.7±1.4 CI+II 59.0±1.6 34.0±1.9 46.7±2.7 Mito (pmol/s/m g prot) CI 8350±635 7071±1082 10422±863 CII 6536±414 6309±506 8408±676 CI+II 12601±762 11063±1156 15949±1381 H 2 O 2 (pM/s/mg tiss) CI 10.0±1.8 30.8±3.7 15.0±2.0 CI+II 141.4±20.9 187.2±53.8 101.1±13.6 P:O State IV to III 2.94±0.03 2.71±0.02 2.92±0.05 Means±SEM. P<0.05 OAL vs YAL, P<0.05 OCR vs OAL, P<0.05 OCR vs. OAL & YAL.

Insulin has been shown to have major impact on muscle mitochondrial function. Recent data show that ceramide can decrease oxygen consumption and ATP production in isolated mitochondria. The aim of the present study was to determine whether insulin deficiency alters ceramide (CER) and its metabolites ‐ sphinganine (SPA), sphingosine (SPH) and sphingosine‐1‐phosphate (S1P) ‐ in mitochondrial (mt) and sarcoplasmic (src) fractions from quadriceps muscle of streptozotocin‐diabetic C57BL/6 male mice. We studied non‐diabetic controls (C); diabetic, insulin‐treated (D+); and diabetic, insulin‐deprived (D−). D− and D+ group received LinBit insulin implants, whereas C group received blank implants. Implants from D− group were removed 7 days prior to sacrifice. CER and its metabolites were measured in a tandem mass spectrometer connected to a UPLC system. Insulin deprivation increased CER in muscle src although decreased in mt. Insulin treatment normalized CER content in src, but further lowered CER content in mt, which was accompanied by elevation in mitochondrial SPH content. Changes in SPA and S1P levels in both the src and mt were non‐significant. In conclusion, diabetes and insulin have profound effects on CER concentrations in muscle subcellular fractions. C D− D+ src mt src mt src mt SPA Mean 0.34 nd 0.32 nd 0.34 nd SEM ±0.04 ±0.02 ±0.04 SPH Mean 0.44 1.63 0.61 2.15 0.47 2.55 SEM ±0.07 ±0.23 ±0.10 ±0.14 ±0.03 ±0.21 S1P Mean 0.32 1.14 0.27 1.06 0.23 0.91 SEM ±0.03 ±0.2 ±0.05 ±0.14 ±0.01 ±0.1 CER Mean 85.7 326.0 162.5 267.3 93.0 199.7 SEM ±17.4 ±38.4 ±19.8 ±24.0 ±4.4 ±11.2

Key points Healthy older adults exhibit lower cardiorespiratory fitness () than young in the absence of any age‐related difference in skeletal muscle mitochondrial capacity, suggesting central haemodynamics plays a larger role in age‐related declines in . Total physical activity did not differ by age, but moderate‐to‐vigorous physical activity was lower in older compared to young adults. Moderate‐to‐vigorous physical activity is associated with and muscle oxidative capacity, but physical inactivity cannot entirely explain the age‐related reduction in . AbstractDeclining fitness () is a hallmark of ageing and believed to arise from decreased oxygen delivery and reduced muscle oxidative capacity. Physical activity is a modifiable lifestyle factor that is critical when evaluating the effects of age on parameters of fitness and energy metabolism. The objective was to evaluate the effects of age and sex on , muscle mitochondrial physiology, and physical activity in young and older adults. An additional objective was to assess the contribution of skeletal muscle oxidative capacity to age‐related reductions in and determine if age‐related variation in and muscle oxidative capacity could be explained on the basis of physical activity levels. In 23 young and 52 older men and women measurements were made of , mitochondrial physiology in permeabilized muscle fibres, and free‐living physical activity by accelerometry. Regression analyses were used to evaluate associations between age and , mitochondrial function, and physical activity. Significant age‐related reductions were observed for (P < 0.001), but not muscle mitochondrial capacity. Total daily step counts did not decrease with age, but older adults showed lower moderate‐to‐vigorous physical activity, which was associated with (R2 = 0.323, P < 0.001) and muscle oxidative capacity (R2 = 0.086, P = 0.011). After adjusting for sex and physical activity, age was negatively associated with but not muscle oxidative capacity. Healthy older adults exhibit lower but preserved mitochondrial capacity compared to young. Physical activity, particularly moderate‐to‐vigorous, is a key factor in observed age‐related changes in fitness and muscle oxidative capacity, but cannot entirely explain the age‐related reduction in .

Adipose inflammation is proposed to be at the nexus of the systemic inflammation and metabolic derangements associated with obesity. The present study provides evidence to support adipose inflammation as a central feature of the pathophysiology of obesity. Adipose inflammation is associated with systemic and peripheral metabolic derangements, including increased systemic inflammation, reduced insulin sensitivity and reduced skeletal muscle mitochondrial respiration.

Abstract Interleukin‐6 (IL‐6) is a pleiotropic cytokine that has been shown to be produced acutely by skeletal muscle in response to exercise, yet chronically elevated with obesity and aging. The mechanisms by which IL‐6 influences skeletal muscle mitochondria acutely and chronically are unclear. To better understand the influence of extramyocellular IL‐6 on skeletal muscle mitochondrial physiology, we treated differentiated myotubes with exogenous IL‐6 to evaluate the dose‐ and duration‐dependent effects of IL‐6 on salient aspects of mitochondrial biology and the role of canonical IL‐6 signaling in muscle cells. Acute exposure of myotubes to IL‐6 increased the mitochondrial reactive oxygen species (mtROS) production and oxygen consumption rates ( J O 2 ) in a manner that was dependent on activation of the JAK/STAT pathway. Furthermore, STAT3 activation by IL‐6 was partly attenuated by MitoQ, a mitochondrial‐targeted antioxidant, suggesting that mtROS potentiates STAT3 signaling in skeletal muscle in response to IL‐6 exposure. In concert with effects on mitochondrial physiology, acute IL‐6 exposure induced several mitochondrial adaptations, consistent with the stress‐induced mitochondrial hyperfusion. Exposure of myotubes to chronically elevated IL‐6 further increased mtROS with eventual loss of respiratory capacity. These data provide new evidence supporting the interplay between cytokine signaling and mitochondrial physiology in skeletal muscle.

New Findings What is the central question of this study? How do locomotor muscle metabo‐ and mechanoreceptor expression compare in heart failure patients and controls? Do relationships exist between the protein expression and cardiopulmonary responses during exercise with locomotor muscle neural afferent feedback inhibition? What is the main finding and its importance? Heart failure patients exhibited greater protein expression of transient receptor potential vanilloid type 1 and cyclooxygenase‐2 than controls. These findings are important as they identify receptors that may underlie the augmented locomotor muscle neural afferent feedback in heart failure. AbstractHeart failure patients with reduced ejection fraction (HFrEF) exhibit abnormal locomotor group III/IV afferent feedback during exercise; however, the underlying mechanisms are unclear. Therefore, the purpose of this study was to determine (1) metabo‐ and mechanoreceptor expression in HFrEF and controls and (2) relationships between receptor expression and changes in cardiopulmonary responses with afferent inhibition. Ten controls and six HFrEF performed 5 min of cycling exercise at 65% peak workload with lumbar intrathecal fentanyl (FENT) or placebo (PLA). Arterial blood pressure and catecholamines were measured via radial artery catheter. A vastus lateralis muscle biopsy was performed to quantify cyclooxygenase‐2 (COX‐2), purinergic 2X3 (P2X3), transient receptor potential vanilloid type 1 (TRPV1), acid‐sensing ion channel 3 (ASIC3), Piezo 1 and Piezo 2 protein expression. TRPV1 and COX‐2 protein expression was greater in HFrEF than controls (both P < 0.04), while P2X3, ASIC3, and Piezo 1 and 2 were not different between groups (all P > 0.16). In all participants, COX‐2 protein expression was related to the percentage change in ventilation (r = −0.66) and mean arterial pressure (MAP) (r = −0.82) (both P < 0.01) with FENT (relative to PLA) during exercise. In controls, TRPV1 protein expression was related to the percentage change in systolic blood pressure (r = −0.77, P = 0.02) and MAP (r = −0.72, P = 0.03) with FENT (relative to PLA) during exercise. TRPV1 and COX‐2 protein levels are elevated in HFrEF compared to controls. These findings suggest that the elevated TRPV1 and COX‐2 expression may contribute to the exaggerated locomotor muscle afferent feedback during cycling exercise in HFrEF.

Abstract Abstract SCI-3 The processes that lead to the susceptibility of post-mitotic tissues to diseases of aging are poorly understood, but mitochondria are considered a key regulator. SIRT3 is mitochondrial sirtuin, a member a family of NAD+-dependent deacetylases. We have previously shown that increased levels of NAD+ in mitochondria promote cell survival in a SIRT3-dependent manner, but how this protection is mediated is unknown. Here we show that mitochondrial NAD+ levels decline dramatically with age and that SIRT3 is a critical component and regulator of the mitochondrial transition pore (MTP). Mice lacking SIRT3 exhibit hyperacetylation of the MTP with age, and as a result, develop multiple defects in post-mitotic tissues as they age, including mitochondrial defects, susceptibility to cardiac failure, and learning and memory deficits. In a mouse model of Alzheimer's disease (AD), SIRT3 knockout mice show striking phenotypes including small size, kyphosis, and a markedly reduced lifespan. Similar to mice, human brain samples show that acetylation of the MTP increases with age and with AD. These findings indicate that declining NAD levels with age lead to memory deficits and accelerate age-related diseases in post-mitotic tissues due to a decline in SIRT3 activity and unscheduled opening of the MTP. Disclosures: Sinclair: GlaxoSmithKline: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Omega-3 polyunsaturated fatty acids ( n-3 PUFAs) exert numerous beneficial biological effects and attenuate diet-induced insulin resistance in rodent models. In the present study, the independent, tissue-specific effects of two nutritionally relevant n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were characterized in the context of a high-fat diet (HFD). EPA and DHA supplementation (3.2% of total fat) in 6-mo-old male C57BL/6 mice fed an HFD (60% fat) partially mitigated reductions in insulin sensitivity. At 5 wk, the area above the curve below baseline glucose following an intraperitoneal insulin tolerance test was 54.5% lower in HFD than control, whereas HFD + EPA and HFD + DHA showed 27.6% and 17.1% reductions, respectively. At 10 wk, HFD increased mitochondrial oxidative capacity supported by lipid and carbohydrate-based substrates in both liver and skeletal muscle ( P < 0.05), with little effect of EPA or DHA supplementation. Whole genome transcriptomic analyses revealed HFD-induced transcriptional changes indicative of inflammation and fibrosis in both liver and muscle. Gene set enrichment analyses indicated a downregulation of transcripts associated with extracellular matrix in muscle (family-wise error rate P < 0.01) and liver ( P = 0.04) and in transcripts associated with inflammation in muscle ( P = 0.03) in HFD + DHA compared with HFD alone. In contrast, EPA appeared to potentiate some proinflammatory effects of the HFD. In the skeletal muscle, DHA increased the expression of stress-responsive genes, whereas EPA upregulated the expression of transcripts related to cell cycle. Therefore, although both EPA and DHA supplementation during HFD partially preserve insulin signaling, they modulate distinct processes, highlighting their unique biological effects in the context of obesity.

AbstractOmega-3 polyunsaturated fatty acids (n3-PUFA) are well recognized for their potent triglyceride-lowering effects, but the potential influence of these bioactive lipids on other biological processes, particularly in the context of healthy aging, remains unknown. With the goal of gaining new insight into some less well-characterized biological effects of n3-PUFAs in healthy older adults, we performed metabolomics of fasting peripheral blood plasma collected from 12 young adults and 12 older adults before and after an open-label intervention of n3-PUFA (3.9 g/day, 2.7 g eicosapentaenoic [EPA], 1.2 g docosahexaenoic [DHA]). Proton nuclear magnetic resonance (1H-NMR) based lipoprotein subclass analysis revealed the expected reduction in total triglyceride (TG), but also demonstrated that n3-PUFA supplementation reduced very low-density lipoprotein (VLDL) particle number, modestly increased high-density lipoprotein (HDL) cholesterol, and shifted the composition of HDL subclasses. Further metabolite profiling by 1H-NMR and mass spectrometry revealed pronounced changes in phospholipids, cholesterol esters, diglycerides, and triglycerides following n3-PUFA supplementation. Furthermore, significant changes in hydroxyproline, kynurenine, and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF) following n3-PUFA supplementation provide further insight into some less well-recognized biological effects of n3-PUFA supplementation, including possible effects on protein metabolism, the kynurenine pathway, and glucose metabolism.