Alogliptin improves survival and health of mice on a high‐fat diet

Alogliptin is a commonly prescribed drug treating patients with type 2 diabetes. Here, we show that long‐term intervention with alogliptin (0.03% w/w in diet) improves survival and health of mice on a high‐fat diet. Alogliptin intervention takes beneficial effects associated with longevity, including increased insulin sensitivity, attenuated functionality decline, decreased organ pathology, preserved mitochondrial function, and reduced oxidative stress. Autophagy activation is proposed as an underlying mechanism of these beneficial effects. We conclude that alogliptin intervention could be considered as a potential strategy for extending lifespan and healthspan in obesity and overweight.     

Postnatal expression of myostatin propeptide cDNA maintained high muscle growth and normal adipose tissue mass in transgenic mice fed a high-fat diet

Myostatin plays a robust, negative role in controlling muscle mass. A disruption of myostatin function by transgenic expression of its propeptide (the 5'region, 866 nucleotides) results in significant muscle growth (Yang et al., 2001. Mol Rep Dev 60:351-361). Studies from myostatin and the propeptide transgene mRNA indicated that myostatin mRNA was detected at day 10.5 postcoitum in fetal mice. Its level remained low, but increased by 180% during the postnatal fast-growth period (day 0-10). An early, high-level postnatal expression of the transgene was identified as being responsible for a highly muscled phenotype. High-fat diet induces adiposity in rodents. To study the effects of dietary fat on muscle growth and adipose tissue fat deposition in the transgenic mice, we challenged the mice with a high-fat diet (45% kcal fat) for 21 weeks. Transgenic mice showed 24%-50% further enhancement of growth on the high-fat diet compared to the normal-fat diet (P = 0.004) from 17 to 25 weeks of age. The total mass of the main muscles of transgenic mice showed a 27% increase on the high-fat diet compared to the normal-fat diet (P = 0.004), while the white adipose tissue mass of the transgenic mice was not significantly different from that of wild-type mice fed a normal-fat diet (P = 0.434). The high-fat diet induced wild-type mice developed 190% greater mass of white adipose tissues compared to the normal-fat diet (P = 0.008), which primarily resulted from enlarged adipocytes. These results demonstrate that disruption of myostatin function by its propeptide shifted dietary fat utilization toward muscle tissues with minimal effects on adiposity. These results suggest that enhancing muscle growth by myostatin propeptide or other means during the early developmental stage may serve as an effective means for obesity prevention.     

Biomechanical bone strength and bone mass in young male and female rats fed a fish oil diet

The study objective was to determine if male and female rats fed a diet rich in fish oil had femurs and vertebrae that were stronger and more resistant to fracture than rats not fed omega-3 long chain polyunsaturated fatty acids. Weanling rats were randomized to a control or a fish oil diet for 5 weeks. Feeding fish oil to males had no effect on biomechanical strength properties of femurs and vertebrae as measured by three point bending and compression, respectively. In contrast, females fed fish oil had reduced length growth and a lower vertebral peak load. These effects may have been partly mediated by a lower food intake but were not associated with differences in serum IGF-I, estradiol or urinary calcium. The effect of consuming a fish oil diet into later adulthood should be investigated to determine if femur strength is also affected among females.     

Hypoglycemic effect of catalpol on high-fat diet/streptozotocin-induced diabetic mice by increasing skeletal muscle mitochondrial biogenesis

Catalpol, an iridoid glycoside, exists in the root of Radix Rehmanniae. Some studies have shown that catalpol has a remarkable hypoglycemic effect in the streptozotocin- induced diabetic model, but the underlying mechanism for this effect has not been fully elucidated. Because mito- chondrial dysfunction plays a vital role in the pathology of diabetes and because improving mitochondrial function may offer a new approach for the treatment of diabetes, this study was designed. Catalpol was orally administered together with metformin to high-fat diet/streptozotocin （HFD/STZ）-induced diabetic mice daily for 4 weeks. Body weight （BW）, fasting blood glucose （FBG） level, and glucose disposal （IPGTT） were measured during or after the treatment. The results showed a dose-dependent re- duction of FBG level with no apparent changes in BW through four successive weeks of catalpol administration. Catalpol treatment substantially reduced serum total chol- esterol and triglyceride levels in the diabetic mice. In add- ition, catalpol efficiently increased mitochondrial ATP production and reversed the decrease of mitochondrial membrane potential and mtDNA copy number in skeletal muscle tissue. Furthermore, catalpol （200 mg/kg） rescued mitochondrial ultrastructure in skeletal muscle, as detected with transmission electron microscopy. The relative mRNA level of peroxisome proliferator-activated receptor gamma co-activator 1 （PGC1） α was significantly decreased in muscle tissue of diabetic mice, while this effect was reversed by catalpol. resulting in a dose-dependent up-regulation. Taken together, we found that catalpol was capable of lowering FBG level via improving mitochondrial function in skeletal musde of HFD/STZ-induced diabetic mice.     

Quantitative effects of thermal injury and insulin on the metabolism of the skeletal muscle using the perfused rat hindquarter preparation

Injury from a severe burn or trauma can propel the body into a hypermetabolic state that can lead to the significant erosion of lean muscle mass. Investigations describing this process have been somewhat limited due to the lack of adequate experimental models. Here we report the use of a perfused rat hindquarter preparation to study the consequences of a moderate burn injury (approximately 20% total body surface area), with or without the addition of exogenous insulin (12.5 mU/mL), on the fluxes of major metabolites across the isolated skeletal muscle. The metabolic flux data was further analyzed using metabolic flux analysis (MFA), which allows for the estimation of the impact of these conditions on the intracellular muscle metabolism. Results indicate that this model is able to capture the increased rate of proteolysis, glutamine formation, and the negative nitrogen balance associated with the burn-induced hypermetabolic state. The inclusion of exogenous insulin resulted in significant changes in several fluxes, including an increase in the metabolism of glucose and the flux through the pentose phosphate pathway, as well as a reduction in the metabolism of glutamine, alanine, and leucine. However, insulin administration did not affect the nitrogen balance or the rate of proteolysis in the muscle, as has been suggested using other techniques. The use of the perfused hindquarter model coupled with MFA is a physiologically relevant and experimentally flexible platform for the exploration of skeletal muscle metabolism under catabolic conditions, and it will be useful in quantifying the specific metabolic consequences of other therapeutic advances.     

An in situ collagen-HA hydrogel system promotes survival and preserves the proangiogenic secretion of hiPSC-derived vascular smooth muscle cells

Human-induced pluripotent stem cell-derived vascular smooth muscle cells (hiPSC-VSMCs) with proangiogenic properties have huge therapeutic potential. While hiPSC-VSMCs have already been utilized for wound healing using a biomimetic collagen scaffold, an in situ forming hydrogel mimicking the native environment of skin offers the promise of hiPSC-VSMC mediated repair and regeneration. Herein, the impact of a collagen type-I-hyaluronic acid (HA) in situ hydrogel cross-linked using a polyethylene glycol-based cross-linker on hiPSC-VSMCs viability and proangiogenic paracrine secretion was investigated. Our study demonstrated increases in cell viability, maintenance of phenotype and proangiogenic growth factor secretion, and proangiogenic activity in response to the conditioned medium. The optimally cross-linked and functionalized collagen type-I/HA hydrogel system developed in this study shows promise as an in situ hiPSC-VSMC carrier system for wound regeneration.     

Weekly administration of rapamycin improves survival and biomarkers in obese male mice on high‐fat diet

Recent discoveries have revealed the key role of mTOR (target of rapamycin) in aging. Furthermore, rapamycin extends lifespan in mice, especially in female mice. Here, we treated obese male mice on high‐fat diet with rapamycin given intermittently: either weekly (once a week) or alternating bi‐weekly (three injections every other week). While only marginally reducing obesity, intermittent administration of rapamycin significantly extended lifespan. Significance was achieved for weekly treated group and for the three rapamycin‐received groups combined. In weekly treatment group, 100% mice were alive by the age of 2 years, whereas 60% of mice died in untreated group by this age. The effect of weekly treatment on survival was highly significant and cannot be fully explained by partial reduction in obesity. Alternating bi‐weekly treatments seem to be less effective than weekly treatment, although effects of additional factors (see 3 ) may not be excluded. After one year of treatment, all survived mice were sacrificed 8 days after the last administration of rapamycin to avoid its direct interference with parameters examined. Fasting levels of cardiac and hepatic p‐S6, a marker of mTORC1 activity, were lower in weekly treatment group compared with control mice. In contrast, levels of p‐Akt (S473), glucose, triglycerides and insulin were unchanged, whereas leptin and IGF‐1 tended to be lower. Thus, weekly treatment with rapamycin may slow down aging in obese male mice on high‐fat diet.     

The effect of a pharmaceutical ghrelin agonist on lifespan in C57BL/6J male mice: A controlled experiment

Interventions for animal lifespan extension like caloric restriction (CR) have identified physiologic and biochemical pathways related to hunger and energy-sensing status as possible contributors, but mechanisms have not been fully elucidated. Prior studies using ghrelin agonists show greater food intake but no effect on lifespan in rodent models. This experiment in male C57BL/6J mice tested the influence of ghrelin agonism for perceived hunger, in the absence of CR, on longevity. Mice aged 4 weeks were allowed to acclimate for 2 weeks prior to being assigned (N = 60/group). Prior to lights off daily (12:12 cycle), animals were fed a ghrelin agonist pill (LY444711; Eli Lilly) or a placebo control (Ctrl) until death. Treatment (GhrAg) animals were pair-fed daily based on the group mean food intake consumed by Ctrl (ad libitum feeding) the prior week. Results indicate an increased lifespan effect (log-rank p = 0.0032) for GhrAg versus placebo Ctrl, which weighed significantly more than GhrAg (adjusted for baseline weight). Further studies are needed to determine the full scope of effects of this ghrelin agonist, either directly via increased ghrelin receptor signaling or indirectly via other hypothalamic, systemic, or tissue-specific mechanisms.     

Effect of a low-protein diet supplemented with keto-acids on autophagy and inflammation in 5/6 nephrectomized rats

Ketoacids (KA) are known to preserve muscle mass among patients with chronic kidney disease (CKD) on a low-protein diet (LPD). The present study was to compare the effects of KA supplemented diet therapy in autophagy and inflammation in CKD rats'' skeletal muscle. Rats with 5/6 nephrectomy were randomly divided into three groups and fed with either 11 g/kg/day protein [normal-protein diet (NPD)], 3 g/kg/day protein (LPD) or 3 g/kg/day protein which including 5% protein plus 1% KA (LPD + KA) for 24 weeks. Sham-operated rats with NPD intake were used as control. LPD could improve body weight, gastrocnemius muscle mass, as well as gastrocnemius muscle cross-sectional area, with the effect being more obvious in the LPD + KA group. The autophagy marker LC3 (microtubule-associated protein 1 light chain 3), p62, Parkin and PTEN induced putative kinase 1 (PINK1) were significantly attenuate in LPD + KA group than LPD group. LPD + KA group had the lower total mtDNA (mitochondiral DNA) and cytosol mtDNA, NACHT-PYD-containing protein 3 (NALP3) inflammasome than LPD group, but its reactive oxygen species (ROS), caspase-1 and apoptosis-associated speck-like protein containing a CARD (ASC) level was higher. Immunoblotting showed IL-1β (interleukin-1-beta) was lower in LPD and LPD + KA group than the NPD group, but IL-18 showed no significant difference among control and CKD group; toll-like receptor signalling-dependent IL-6 was higher in LPD + KA group than LPD group, but tumor necrosis factor-α (TNF-α) was not significantly changed between LPD + KA and LPD group. Systematic changes of the four cytokines were different from that of the tissue. Although LPD + KA could further ameliorate-activated autophagy than LPD, its effect on the activated inflammation state in CKD was not distinctly. Further study is still required to explore the method of ameliorating inflammation to provide new therapeutic approaches for CKD protein energy wasting (PEW).     

Elimination of senescent osteoclast progenitors has no effect on the age‐associated loss of bone mass in mice

Both an increase in osteoclast and a decrease in osteoblast numbers contribute to skeletal aging. Markers of cellular senescence, including expression of the cyclin inhibitor p16, increase with aging in several bone cell populations. The elimination of p16‐expressing cells in old mice, using the INK‐ATTAC transgene, increases bone mass indicating that senescent cells contribute to skeletal aging. However, the identity of the senescent cells and the extent to which ablation of p16‐expressing cells may prevent skeletal aging remain unknown. Using mice expressing the p16‐3MR transgene, we examined whether elimination of p16‐expressing cells between 12 and 24 months of age could preserve bone mass; and whether elimination of these cells from 20 to 26 months of age could restore bone mass. The activation of the p16‐3MR transgene by ganciclovir (GCV) greatly diminished p16 levels in the brain, liver, and osteoclast progenitors from the bone marrow. The age‐related increase in osteoclastogenic potential of myeloid cells was also abrogated by GCV. However, GCV did not alter p16 levels in osteocytes—the most abundant cell type in bone—and had no effect on the skeletal aging of p16‐3MR mice. These findings indicate that the p16‐3MR transgene does not eliminate senescent osteocytes but it does eliminate senescent osteoclast progenitors and senescent cells in other tissues, as described previously. Elimination of senescent osteoclast progenitors, in and of itself, has no effect on the age‐related loss of bone mass. Hence, other senescent cell types, such as osteocytes, must be the seminal culprits.     

Exercise and nutritional needs of elderly people: effects on muscle and bone

Advancing age is associated with a remarkable number of changes in body composition. Reductions in lean body mass have been well characterized. This decreased lean body mass occurs primarily as a result of losses in skeletal muscle mass^{1, 2}. This age-related loss in muscle mass has been termed sarcopenial³. Loss in muscle mass accounts for the age-associated decreases in basal metabolic rate, muscle strength, and activity levels, which, in turn is the cause of the decreased energy requirements of the elderly. In sedentary individuals, the main determinant of energy expenditure is fat-free mass, which declines by about 15% between the third and eighth decade of life. It also appears that declining caloric needs are not matched by an appropriate decline in caloric intake, with the ultimate result an increased body fat content with advancing age. Increased body fatness along with increased abdominal obesity are thought to be directly linked to the greatly increased incidence of Type II diabetes among the elderly. This review will discuss the extent to which regularly performed exercise can effect nutritional needs and functional capacity in the elderly. In addition, some basic guidelines for beginning an exercise program for older men and women, and establishing community-based programs are provided.     

Reevaluation of the effect of dietary restriction on different recombinant inbred lines of male and female mice

Dietary restriction (DR) was reported to either have no effect or reduce the lifespan of the majority of the 41‐recombinant inbred (RI) lines studied by Liao et al. (Aging Cell, 2010, 9, 92). In an appropriately power longevity study (n > 30 mice/group), we measured the lifespan of the four RI lines (115‐RI, 97‐RI, 98‐RI, and 107‐RI) that were reported to have the greatest decrease in lifespan when fed 40% DR. DR increased the median lifespan of female RI‐115, 97‐RI, and 107‐RI mice and male 115‐RI mice. DR had little effect (<4%) on the median lifespan of female and male 98‐RI mice and male 97‐RI mice and reduced the lifespan of male 107‐RI mice over 20%. While our study was unable to replicate the effect of DR on the lifespan of the RI mice (except male 107‐RI mice) reported by Liao et al. (Aging Cell, 2010, 9, 92), we found that the genotype of a mouse had a major impact on the effect of DR on lifespan, with the effect of DR ranging from a 50% increase to a 22% decrease in median lifespan. No correlation was observed between the changes in either body composition or glucose tolerance induced by DR and the changes observed in lifespan of the four RI lines of male and female mice. These four RI lines of mice give the research community a unique resource where investigators for the first time can study the anti‐aging mechanism of DR by comparing mice in which DR increases lifespan to mice where DR has either no effect or reduces lifespan.     

Pro‐inflammatory capacity of classically activated monocytes relates positively to muscle mass and strength

In mice, monocytes that exhibit a pro‐inflammatory profile enter muscle tissue after muscle injury and are crucial for clearance of necrotic tissue and stimulation of muscle progenitor cell proliferation and differentiation. The aim of this study was to test if pro‐inflammatory capacity of classically activated (M1) monocytes relates to muscle mass and strength in humans. This study included 191 male and 195 female subjects (mean age 64.2 years (SD 6.4) and 61.9 ± 6.4, respectively) of the Leiden Longevity Study. Pro‐inflammatory capacity of M1 monocytes was assessed by ex vivo stimulation of whole blood with Toll‐like receptor (TLR) 4 agonist lipopolysaccharide (LPS) and TLR‐2/1 agonist tripalmitoyl‐S‐glycerylcysteine (Pam₃Cys‐SK₄), both M1 phenotype activators. Cytokines that stimulate M1 monocyte response (IFN‐γ and GM‐CSF) as well as cytokines that are secreted by M1 monocytes (IL‐6, TNF‐α, IL‐12, and IL‐1β) were measured. Analyses were adjusted for age, height, and body fat mass. Upon stimulation with LPS, the cytokine production capacity of INF‐γ, GM‐CSF, and TNF‐α was significantly positively associated with lean body mass, appendicular lean mass and handgrip strength in men, but not in women. Upon stimulation with Pam₃Cys‐SK₄, IL‐6; TNF‐α; and Il‐1β were significantly positively associated with lean body mass and appendicular lean in women, but not in men. Taken together, this study shows that higher pro‐inflammatory capacity of M1 monocytes upon stimulation is associated with muscle characteristics and sex dependent.     

Growth characteristics of skeletal muscle tissue in Oreochromis niloticus larvae fed on a lysine supplemented diet

The effect of lysine amino acid supplementation on the growth characteristics and morphological pattern of skeletal muscle tissue in Nile tilapia Oreochromis niloticus larvae was evaluated. There were four treatments (T) with increasing levels of lysine supplement (T1 = 0·0%; T2 = 1·1%; T3 = 1·7%; T4 = 4·0%) and one treatment with a commercial diet (T5). In all treatments, morphological and histochemical muscle tissue analyses were similar. Two distinct layers were identified: a superficial red layer, more developed in the lateral line region, formed by fibres with intense to moderate NADH‐TR reaction and strong acid‐stable mATPase activity, and a deep white one, most of the muscle mass, formed by fibres with weak NADH‐TR reaction and strong alkali‐stable mATPase activity. There was an intermediate layer between these two layers with fibres exhibiting either weak acid‐stable or acid‐labile mATPase activity. Body mass increase was significantly higher in T5 than in the lysine treatments (T1–T4). There was no difference in number and diameters of muscle fibres between lysine treatments. In T5, muscle fibre diameter and number were higher. The frequency of red fibres with diameters ≤8 μm was higher in the lysine treatments, and with diameters between 16 and 24 μm, was higher in T5. Most white fibre diameters in T5 were significantly larger than 24 μm and in T1–T4 were between 8 and 16 μm. Cell proliferation was higher in the lysine treatments and muscle growth in T5 was mainly by fibre hypertrophy.     

Increases of M2a macrophages and fibrosis in aging muscle are influenced by bone marrow aging and negatively regulated by muscle‐derived nitric oxide

Muscle aging is associated with changes in myeloid cell phenotype that may influence age‐related changes in muscle structure. We tested whether preventing age‐related reductions in muscle neuronal nitric oxide synthase (nNOS) would obviate age‐related changes in myeloid cells in muscle. Our findings show that muscle aging is associated with elevations of anti‐inflammatory M2a macrophages that can increase muscle fibrosis. Expression of a muscle‐specific nNOS transgene in mice prevented age‐related increases in M2a macrophages. Transgene expression also reduced expression of collagens and decreased muscle fibrosis. The nNOS transgene prevented age‐related increases in arginase‐1 but did not influence TGFβ expression, indicating that the transgene may prevent age‐related muscle fibrosis by inhibiting the arginase‐dependent profibrotic pathway. Although aged satellite cells or fibro‐adipogenic precursor (FAPs) cells also promote fibrosis, transgene expression had no effect on the expression of key signaling molecules that regulate fibrogenic activity of those cells. Finally, we tested whether increases in M2a macrophages and the associated increase in fibrosis were attributable to aging of myeloid lineage cells. Young bone marrow cells (BMCs) were transplanted into young or old mice, and muscles were collected 8 months later. Muscles of young mice receiving young BMCs showed no effect on M2a macrophage number or collagen accumulation compared to age‐matched, nontransplanted controls. However, muscles of old mice receiving young BMCs showed fewer M2a macrophages and less accumulation of collagen. Thus, the age‐related increase in M2a macrophages in aging muscle and the associated muscle fibrosis are determined in part by the age of bone marrow cells.     

6周有氧运动对高脂膳食的ApoE敲除小鼠骨骼肌钙调控的影响*

目的: 探讨6周有氧运动对高脂膳食的载脂蛋白E(ApoE)基因敲除小鼠骨骼肌肌浆网钙调控蛋白的影响。方法: 25只9周龄ApoE敲除小鼠(ApoE KO)随机选取5只ApoE KO小鼠进行最大跑速测试(以初始速度为4.8 m/min,坡度为0°,持续5 min后,每3 min速度增加1.2 m/min,直至力竭,最后速度为最大跑速,最大跑速的测试结果为(27.0±2.4)m/min,剩余20只ApoE KO小鼠随机分为ApoE KO小鼠高脂膳食组(KO)和ApoE KO小鼠高脂膳食+有氧运动组(KE),每组10只,同时以10只9周龄野生型C57BL/6J小鼠作为空白对照组(WT)。高脂饲料成分:脂肪含量为21%(w/w),胆固醇含量为1.5%(w/w)。KE组适应性训练1周后开始运动干预,运动方案为:40%最大跑速(10.8 m/min),运动时间40 min/d,频率每周3 d,共计6周。待末次运动后48 h,所有小鼠麻醉后经心脏穿刺处死后迅速分离双侧腓肠肌;可见光比色法检测骨骼肌Ca²⁺浓度;Western blot法检测小鼠骨骼肌肌浆网钙调控蛋白RyR、CaM、CaMKⅡ、SERCA1、SERCA2蛋白表达。结果: 与WT组相比,KO组小鼠骨骼肌Ca²⁺浓度显著降低(P＜0.01),骨骼肌肌浆网钙释放蛋白RyR、CaMKⅡ和钙回收蛋白SERCA1、SERCA2均显著降低(P＜ 0.05),但CaM蛋白无显著变化;与KO组相比,KE组小鼠骨骼肌Ca²⁺浓度和骨骼肌肌浆网钙回收蛋白SERCA1、SERCA2均显著升高(P＜0.05),但骨骼肌肌浆网钙释放蛋白RyR、CaM、CaMKⅡ蛋白表达均无显著性差异。结论: 高脂膳食可使ApoE敲除小鼠骨骼肌Ca²⁺浓度降低、肌浆网钙释放作用和钙回收作用减弱,6周有氧运动训练能够显著提高其Ca²⁺浓度、促进肌浆网钙回收作用。     

Troponin T3 expression in skeletal and smooth muscle is required for growth and postnatal survival: Characterization of Tnnt3tm2a(KOMP)Wtsi mice

The troponin complex, which consists of three regulatory proteins (troponin C, troponin I, and troponin T), is known to regulate muscle contraction in skeletal and cardiac muscle, but its role in smooth muscle remains controversial. Troponin T3 (TnnT3) is a fast skeletal muscle troponin believed to be expressed only in skeletal muscle cells. To determine the in vivo function and tissue‐specific expression of Tnnt3, we obtained the heterozygous Tnnt3+/flox/lacZ mice from Knockout Mouse Project (KOMP) Repository. Tnnt3^lacZ/+ mice are smaller than their WT littermates throughout development but do not display any gross phenotypes. Tnnt3^lacZ/lacZ embryos are smaller than heterozygotes and die shortly after birth. Histology revealed hemorrhagic tissue in Tnnt3^lacZ/lacZ liver and kidney, which was not present in Tnnt3^lacZ/+ or WT, but no other gross tissue abnormalities. X‐gal staining for Tnnt3 promoter‐driven lacZ transgene expression revealed positive staining in skeletal muscle and diaphragm and smooth muscle cells located in the aorta, bladder, and bronchus. Collectively, these findings suggest that troponins are expressed in smooth muscle and are required for normal growth and breathing for postnatal survival. Moreover, future studies with this mouse model can explore TnnT3 function in adult muscle function using the conditional‐inducible gene deletion approach genesis 51:667–675. © 2013 Wiley Periodicals, Inc.