Leptin modulates gene expression in the heart, cardiomyocytes and the adipose tissue thus mitigating LPS-induced damage.

Leptin is an adipokine of pleiotropic effects linked to energy metabolism, satiety, the immune response, and cardioprotection. We have recently shown that leptin causally conferred resistance to myocardial infarction-induced damage in transgenic αMUPA mice overexpressing leptin compared to their wild type (WT) ancestral mice FVB/N. Prompted by these findings, we have investigated here if leptin can counteract the inflammatory response triggered after LPS administration in tissues in vivo and in cardiomyocytes in culture. The results have shown that LPS upregulated in vivo and in vitro all genes examined here, both pro-inflammatory and antioxidant, as well as the leptin gene. Pretreating mice with leptin neutralizing antibodies further upregulated the expression of TNFα and IL-1ß in the adipose tissue of both mouse types, and in the αMUPA heart. The antibodies also increased the levels of serum markers for cell toxicity in both mouse types. These results indicate that under LPS, leptin actually reduced the levels of these inflammatory-related parameters. In addition, pretreatment with leptin antibodies reduced the levels of HIF-1α and VEGF mRNAs in the heart, indicating that under LPS leptin increased the levels of these mRNAs. In cardiomyocytes, pretreatment with exogenous leptin prior to LPS reduced the expression of both pro-inflammatory genes, enhanced the expression of the antioxidant genes HO-1, SOD2 and HIF-1α, and lowered ROS staining. In addition, results obtained with leptin antibodies and the SMLA leptin antagonist indicated that endogenous and exogenous leptin can inhibit leptin gene expression. Together, these findings have indicated that under LPS, leptin concomitantly downregulated pro-inflammatory genes, upregulated antioxidant genes, and lowered ROS levels. These results suggest that leptin can counteract inflammation in the heart and adipose tissue by modulating gene expression.

Leptin modulates gene expression in the heart and cardiomyocytes towards mitigating ischemia-induced damage.

Leptin, an adipocyte-derived satiety hormone, has been previously linked to cardioprotection. We have shown before that leptin conferred resistance to ischemic damage in the heart in long-lived transgenic αMUPA mice overexpressing leptin compared to the wild type (WT) FVB/N control mice. To better understand the contribution of leptin to the ischemic heart, we measured here the expression of genes encoding leptin and ischemia-related proteins in αMUPA and WT mice in the heart vs adipose tissue after MI. In addition, we investigated gene expression in neonatal rat cardiomyocytes under hypoxia in the absence and presence of exogenously added leptin or a leptin antagonist. We used real time RT-PCR and ELISA or Western blot assays to measure, respectively, mRNA and protein levels. The results have shown that circulating leptin levels and mRNA levels of leptin and heme oxygenase-1 (HO-1) in the heart were elevated in both mouse genotypes after 24 h myocardial infarction (MI), reaching higher values in αMUPA mice. In contrast, leptin gene expression in the adipose tissue was significantly increased only in WT mice, but reaching lower levels compared to the heart. Expression of the proinflammatory genes encoding TNFα and IL-1ß was also largely increased after MI in the heart in both mouse types, however reaching considerably lower levels in αMUPA mice indicating a mitigated inflammatory state. In cardiomyocytes, mRNA levels of all aforementioned genes as well as HIF-1α and SOD2 genes were elevated after hypoxia. Pretreatment with exogenous leptin largely reduced the mRNA levels of TNFα and IL-1ß after hypoxia, while enhancing expression of all other genes and reducing ROS levels. Pretreating the cells with a leptin antagonist increased solely the levels of leptin mRNA, suggesting a negative regulation of the hormone on the expression of its own gene. Overall, the results have shown that leptin affects expression of genes in cardiomyocytes under hypoxia in a manner that could mitigate inflammation and oxidative stress, suggesting a similar influence by endogenous leptin in αMUPA mice. Furthermore, leptin is likely to function in the ischemic murine heart more effectively in an autocrine compared to paracrine manner. These results suggest that leptin can reduce ischemic damage by modulating gene expression in the heart.

Long-Lived αMUPA Mice Show Attenuation of Cardiac Aging and Leptin-Dependent Cardioprotection.

αMUPA transgenic mice spontaneously consume less food compared with their wild type (WT) ancestors due to endogenously increased levels of the satiety hormone leptin. αMUPA mice share many benefits with mice under caloric restriction (CR) including an extended life span. To understand mechanisms linked to cardiac aging, we explored the response of αMUPA hearts to ischemic conditions at the age of 6, 18, or 24 months. Mice were subjected to myocardial infarction (MI) in vivo and to ischemia/reperfusion ex vivo. Compared to WT mice, αMUPA showed functional and histological advantages under all experimental conditions. At 24 months, none of the WT mice survived the first ischemic day while αMUPA mice demonstrated 50% survival after 7 ischemic days. Leptin, an adipokine decreasing under CR, was consistently ~60% higher in αMUPA sera at baseline. Leptin levels gradually increased in both genotypes 24h post MI but were doubled in αMUPA. Pretreatment with leptin neutralizing antibodies or with inhibitors of leptin signaling (AG-490 and Wortmannin) abrogated the αMUPA benefits. The antibodies also reduced phosphorylation of the leptin signaling components STAT3 and AKT specifically in the αMUPA myocardium. αMUPA mice did not show elevation in adiponectin, an adipokine previously implicated in CR-induced cardioprotection. WT mice treated for short-term CR exhibited cardioprotection similar to that of αMUPA, however, along with increased adiponectin at baseline. Collectively, the results demonstrate a life-long increased ischemic tolerance in αMUPA mice, indicating the attenuation of cardiac aging. αMUPA cardioprotection is mediated through endogenous leptin, suggesting a protective pathway distinct from that elicited under CR.

A superactive leptin antagonist alters metabolism and locomotion in high-leptin mice.

Transgenic alpha murine urokinase-type plasminogen activator (αMUPA) mice are resistant to obesity and their locomotor activity is altered. As these mice have high leptin levels, our objective was to test whether leptin is responsible for these characteristics. αMUPA, their genetic background control (FVB/N), and C57BL mice were injected s.c. every other day with 20  mg/kg pegylated superactive mouse leptin antagonist (PEG-SMLA) for 6 weeks. We tested the effect of PEG-SMLA on body weight, locomotion, and bone health. The antagonist led to a rapid increase in body weight and subsequent insulin resistance in all treated mice. Food intake of PEG-SMLA-injected animals increased during the initial period of the experiment but then declined to a similar level to that of the control animals. Interestingly, αMUPA mice were found to have reduced bone volume (BV) than FVB/N mice, although PEG-SMLA increased bone mass in both strains. In addition, PEG-SMLA led to disrupted locomotor activity and increased corticosterone levels in C57BL but decreased levels in αMUPA or FVB/N mice. These results suggest that leptin is responsible for the lean phenotype and reduced BV in αMUPA mice; leptin affects corticosterone levels in mice in a strain-specific manner; and leptin alters locomotor activity, a behavior determined by the central circadian clock.

Long-lived mice exhibit 24 h locomotor circadian rhythms at young and old age.

αMUPA transgenic mice exhibit spontaneously reduced eating and increased life span compared with their wild type (WT) control FVB/N mice. αMUPA mice also show high-amplitude circadian rhythms in food intake, body temperature, and hepatic clock gene expression. Here we examined young and aged WT and αMUPA mice for the period of locomotor activity (tau) under total darkness (DD). We show that tau changed in WT mice from a period <24 h at 8 months to a period >24 h at 18 months. However, the period of αMUPA mice was ~24 h at both 8 and 18 months. As deviation of tau from 24 h has been found to be inversely related to life span in a large number of rodents, our results suggest that the sustainable endogenous period of ~24 h in αMUPA mice may contribute to their prolonged life span.

Effect of feeding regimens on circadian rhythms: implications for aging and longevity.

Increased longevity and improved health can be achieved in mammals by two feeding regimens, caloric restriction (CR), which limits the amount of daily calorie intake, and intermittent fasting (IF), which allows the food to be available ad libitum every other day. The precise mechanisms mediating these beneficial effects are still unresolved. Resetting the circadian clock is another intervention that can lead to increased life span and well being, while clock disruption is associated with aging and morbidity. Currently, a large body of evidence links circadian rhythms with metabolism and feeding regimens. In particular, CR, and possibly also IF, can entrain the master clock located in the suprachiasmatic nuclei (SCN) of the brain hypothalamus. These findings raise the hypothesis that the beneficial effects exerted by these feeding regimens could be mediated, at least in part, through resetting of the circadian clock, thus leading to synchrony in metabolism and physiology. This hypothesis is reinforced by a transgenic mouse model showing spontaneously reduced eating alongside robust circadian rhythms and increased life span. This review will summarize recent findings concerning the relationships between feeding regimens, circadian rhythms, and metabolism with implications for ageing attenuation and life span extension.

Cutaneous morphometric parameters of young FVB/N mice sustained in aged mice and in calorically restricted transgenic alphaMUPA mice.

Caloric restriction (CR) extends the lifespan of diverse animal species and is currently the only therapeutic intervention known to attenuate aging and increase longevity in laboratory animals. The effect of CR on intrinsic skin aging is not well understood. To study this issue, we took advantage of transgenic alphaMUPA mice that spontaneously eat less (20-30%) when fed ad libitum and live longer compared to their wild type (WT) FVB/N control mice. Herein we determined morphometric skin parameters in young (6-7 months) and aged (17-18 months) alphaMUPA and WT mice. In addition, we transplanted skin grafts excised from the aged or young alphaMUPA and WT mice into both types of young mice, to test whether the systemic environments of alphaMUPA and WT mice could affect the grafts differently. The results have shown that the mean epidermal thickness, number of hair follicles and number of dermal blood vessels were similar in all four groups regardless of age or mouse type. In addition, the post-graft specimens of all four groups exhibited increase in all parameters measured, in particular a remarkable 6-7 fold increase in epidermal thickness. However, no significant differences were detected in the post-graft samples between the four experimental groups. Our findings indicate that, at least in FVB/N mice, parameters measured in normal or grafted skin depend primarily on the intrinsic cutaneous capacity rather than on circulating factors as determined by age or reduced calories.

Effect of intermittent fasting on circadian rhythms in mice depends on feeding time.

Calorie restriction (CR) resets circadian rhythms and extends life span. Intermittent fasting (IF) also extends life span, but its affect on circadian rhythms has not been studied. To study the effect of IF alongside CR, we imposed IF in FVB/N mice or IF combined with CR using the transgenic FVB/N alphaMUPA mice that, when fed ad libitum, exhibit spontaneously reduced eating and extended life span. Our results show that when food was introduced during the light period, body temperature peak was not disrupted. In contrast, IF caused almost arrhythmicity in clock gene expression in the liver and advanced mPer2 and mClock expression. However, IF restored the amplitudes of clock gene expression under disruptive light condition regardless whether the animals were calorically restricted or not. Unlike daytime feeding, nighttime feeding yielded rhythms similar to those generated during ad libitum feeding. Taken together, our results show that IF can affect circadian rhythms differently depending on the timing of food availability, and suggest that this regimen induces a metabolic state that affects the suprachiasmatic nuclei (SCN) clock.

Relationship between calorie restriction and the biological clock: lessons from long-lived transgenic mice.

The master clock located in the brain regulates circadian rhythms in mammals. Similar clocks are found in peripheral tissues. Life span has been independently increased by reset circadian rhythms and caloric restriction (CR). The mechanisms by which CR extends life span are not well understood. We found that alphaMUPA transgenic mice that exhibit reduced eating and live longer show high amplitude, appropriately reset circadian rhythms in clock gene expression, and clock-controlled output systems, such as feeding time and body temperature. As CR resets circadian rhythms, and the circadian clock controls many physiological and biochemical systems, we suggest that the biological clock could be an important mediator of longevity in calorically restricted animals.

The interrelations among feeding, circadian rhythms and ageing.

The master clock located in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus in the brain regulates circadian rhythms in mammals. Similar circadian oscillators have been found in peripheral tissues, such as the liver, intestine and retina. Life span has been previously linked independently to both circadian rhythms and caloric restriction (CR). The mechanisms by which CR attenuates ageing and extends life span are virtually unknown. It has recently been found that the alphaMUPA mice, transgenic mice that exhibit spontaneously reduced eating and live longer compared to their FVB/N wild-type control mice, show high amplitude, appropriately reset circadian rhythms. These pronounced rhythms were found both in clock gene expression in the liver and clock-controlled output systems, such as feeding time and body temperature. Furthermore, it was previously shown that CR could reset the central biological clock in the SCN. As the circadian clock in the SCN controls many physiological and biochemical systems, we suggest that appropriately reset peripheral rhythms could constitute an important mediator of longevity in calorically restricted animals. Thus, we suggest that three parameters, i.e., caloric restriction, circadian rhythms and life span, are interconnected. This surmise is novel, and we provide evidence to support it. Furthermore, we discuss other feeding regimens and their effects on circadian rhythms and/or life span.

Tumor target organs and rate of survival in long-living transgenic mice and their parental wild-type counterparts exposed to the carcinogen dimethylbenz(a)anthracene.

Two-year-old mice of the long-living transgenic mice of the alphaMUPA strain were previously found to show higher tumor resistance than the their initial wild-type (WT) strain (Tirosh, 2003). To better understand the mechanism underlying the differences in tumorigenesis rates between the two mouse lines, the rate of tumorigenesis and survival effects were studied in alphaMUPA mice and parental WT mice exposed to dimethylbenz(a)anthracene (DMBA). Each animal received three intragastric feedings of DMBA, each one week apart, at doses of 2, 1, and 1 mg dissolved in 0.2 ml corn oil; thus, the total amount of the carcinogen was 4 mg/mouse. Control mice received corn oil. The alphaMUPA mice exhibited distinctly higher survival rates in experimental chemically-induced tumorigenesis compared to their WT counterparts: 93% vs. 67%, p =2.7. The rate of tumorigenesis differed between the mouse lines (yield was 1.5 and 2.1), owing to a distinct tendency toward decreased tumor frequency in the skin and forestomach in the alphaMUPA mice. The experimental duration was also significantly higher for transgenic mice: 35.9 +/- 1.2 weeks compared to 30.5 +/- 1.3 weeks in WT mice, p <0.01. The lungs, forestomach and skin were target organs for the carcinogenic effect of DMBA. Our observations suggest that aging promotes the rate of spontaneous and induced tumorigenesis.

Long-lived alphaMUPA transgenic mice exhibit pronounced circadian rhythms.

Robust biological rhythms have been shown to affect life span. Biological clocks can be entrained by two feeding regimens, restricted feeding (RF) and caloric restriction (CR). RF restricts the time of food availability, whereas CR restricts the amount of calories with temporal food consumption. CR is known to retard aging and extend life span of animals via yet-unknown pathways. We hypothesize that resetting the biological clock could be one possible mechanism by which CR extends life span. Because it is experimentally difficult to uncouple calorie reduction from temporal food consumption, we took advantage of the murine urokinase-like plasminogen activator (alphaMUPA) transgenic mice overexpressing a serine protease implicated in brain development and plasticity; they exhibit spontaneously reduced eating and increased life span. Quantitative real-time PCR analysis revealed that alphaMUPA mice exhibit robust expression of the clock genes mPer1, mPer2, mClock, and mCry1 but not mBmal1 in the liver. We also found changes in the circadian amplitude and/or phase of clock-controlled output systems, such as feeding behavior, body temperature, and enteric cryptdin expression. A change in the light-dark regimen led to modified clock gene expression and abrogated circadian patterns of food intake in wild-type (WT) and alphaMUPA mice. Consequently, food consumption of WT mice increased, whereas that of alphaMUPA mice remained the same, indicating that reduced food intake occurs upstream and independently of the biological clock. Thus we surmise that CR could lead to pronounced and synchronized biological rhythms. Because the biological clock controls mitochondrial, hormonal, and physiological parameters, system synchronicity could lead to extended life span.

Urokinase-type plasminogen activator mRNA is expressed in normal developing teeth and leads to abnormal incisor enamel in alpha MUPA transgenic mice.

The urokinase-type plasminogen activator (uPA) is a secreted, inducible serine protease implicated in extracellular proteolysis and tissue remodeling. Here we detected uPA mRNA through in situ hybridization in developing molar and incisor teeth of normal mice at multiple sites of the cap and bell developmental stages. The mRNA was confined to epithelial cells, however, was undetectable in ameloblasts or their progenitor preameloblasts and the inner enamel epithelium. Furthermore, mice of five lines of previously described alphaMUPA transgenic mice, carrying a transgene consisting of the uPA cDNA linked downstream from the alphaA-crystallin promoter, overexpressed uPA mRNA in the same epithelial sites. In addition, alphaMUPA mice showed remarkably high levels of uPA mRNA in ameloblasts, however, exclusively in two specific sites late in incisor development. First, at the late secretory stage, but only on sides of the ameloblast layer. Second, in a limited zone of ameloblasts near the incisal end, coinciding with a striking morphological change of the ameloblast layer and the enamel matrix. In adult alphaMUPA mice, the incisor teeth displayed discoloration and tip fragility, and reduction of the outer enamel as determined by scanning electron microscopy. These results suggest that balanced uPA activity could play a role in normal tooth development. The alphaMUPA tooth phenotype demonstrates a remarkable sensitivity to excessive extracellular proteolysis at the incisor maturation stage of amelogenesis.

Mouse intestinal cryptdins exhibit circadian oscillation.

The innate immunity utilizes a plethora of antibacterial polypeptides, known as defensins, to combat ingested bacteria. Mouse enteric defensins (cryptdins) are produced and secreted constitutively but are overexpressed in instances of infection and/or inflammation. Our objective was to determine whether the biological clock plays a role in cryptdin expression under healthy conditions. Analysis of cryptdin 1 and cryptdin 4 expression in the ileum and jejunum of the small intestine of FVB/N mice around the circadian cycle revealed oscillation that peaked at the end of the dark phase. To eliminate the possibility that cryptdin oscillation stems from food intake, we analyzed cryptdin expression under fasting conditions and found oscillation but with a 3 h phase-shift. Comparison of cryptdin expression in two mouse strains (C57BL/6 vs. FVB/N) revealed higher levels in C57BL/6, a mouse strain that is highly susceptible to enteric infection, due, most likely, to impaired cryptdin maturation. The results of this study indicate the involvement of the biological clock in regulating cryptdin expression in the small intestine and reinforce the capacity of food to act as a zeitgeber (synchronizer). With the assumption of similar control in humans, our results may imply that defensin expression peaks during the day.

Long-lived alphaMUPA transgenic mice show reduced SOD2 expression, enhanced apoptosis and reduced susceptibility to the carcinogen dimethylhydrazine.

Calorie restriction (CR) extends the life span of various species through mechanisms that are as yet unclear. Recently, we have reported that mitochondrion-mediated apoptosis was enhanced in alphaMUPA transgenic mice that spontaneously eat less and live longer compared with their wild-type (WT) control mice. To understand the molecular mechanisms underlying the increased apoptosis, we compared alphaMUPA and WT mice for parameters associated with SOD2 (MnSOD), a mitochondrial antioxidant enzyme that converts superoxide radicals into H(2)O(2) and is also known to inhibit apoptosis. The SOD2-related parameters included the levels of SOD2 mRNA, immunoreactivity and enzymatic activity in the liver, lipid oxidation and aconitase activity in isolated liver mitochondria, and the sensitivity of the mice to paraquat, an agent that elicits oxidative stress. In addition, we compared the mice for the levels of SOD2 mRNA after treatment with bacterial lipopolysaccharides (LPS), and for the DNA binding activity of NFkappaB as a marker for the inflammatory state. We extended SOD2 determination to the colon, where we also examined the formation of pre-neoplastic aberrant crypt foci (ACF) following treatment with dimethylhydrazine (DMH), a colonic organotypic carcinogen. Overall, alphaMUPA mice showed reduced basal levels of SOD2 gene expression and activity concomitantly with reduced lipid oxidation, increased aconitase activity and enhanced paraquat sensitivity, while maintaining the capacity to produce high levels of SOD2 in response to the inflammatory stimulus. alphaMUPA mice also showed increased resistance to DMH-induced pre-neoplasia. Collectively, these data are consistent with a model, in which an optimal fine-tuning of SOD2 throughout a long-term regimen of reduced eating could contribute to longevity, at least in the alphaMUPA mice.

Enhancement of PAI-1 mRNA in cardiovascular cells after kainate injection is mediated through the sympathetic nervous system.

Plasminogen activator inhibitor-1 (PAI-1) is a major physiological regulator of the fibrinolytic system and is thought to promote vascular diseases. Recently, we have reported that PAI-1 gene expression was markedly enhanced locally in cardiovascular cells immediately after injecting (i.p.) mice with kainate, an analog of glutamate, which is the principal excitatory neurotransmitter in the central nervous system. Here we investigated whether the induction of PAI-1 mRNA by kainate could be mediated through sympathetic versus parasympathetic efferent neurons. To this end, we used a group of drugs known to interfere with the aforementioned pathways. PAI-1 gene expression was monitored in the heart via in situ hybridization using (35)S-labeled PAI-1-specific riboprobes. We have found that the elevation of PAI-1 mRNA levels, as detected 3 h after systemic administration of kainate, was reduced by mecamylamine, guanethidine and phentolamine, but not by propranolol or atropine. In addition, the adrenergic agonists phenylephrine and adrenaline themselves, but not clonidine, induced PAI-1 with a spatial distribution similar to that of kainate (i.e. in coronary arteries throughout the heart, and in cardiocytes in the left ventricular and atrial myocardium). Collectively, these results show that kainate activated the PAI-1 gene in cardiovascular cells primarily through the sympathetic nervous system (SNS), via the alpha1-adrenergic receptor. Hence, the results suggest that PAI-1 is likely to be increased during enhanced sympathetic efferent neuronal activity, such as occurring in heart failure or cardiac hypertrophy. The results also reinforce the previously reported linkage of PAI-1 to physiological stress. Furthermore, to our knowledge, this is the first demonstration that glutamate can enhance gene expression in a peripheral tissue. Thus, these findings raise the possibility that glutamate, acting via the SNS, can affect cardiovascular homeostasis and pathology by modulating gene expression in cardiac myocytes and vascular cells.

Plasminogen activator inhibitor-1 in the aqueous humor of patients with and without glaucoma.

OBJECTIVE: To determine the levels of plasminogen activator inhibitor-1 (PAI-1) and total protein in the aqueous humor of patients with glaucoma vs those without glaucoma. METHODS: A total of 125 aqueous humor samples (50-150 microL each) were collected at 3 institutions from patients with glaucoma and a control group of patients with cataract. Fifteen samples were excluded, and the levels of PAI-1 antigen were determined by enzyme-linked immunosorbent assay in 110 samples (36 glaucoma and 74 control). Total protein levels were determined by the Bradford method in 81 samples (28 glaucoma and 53 control), in which the aqueous humor collected was sufficient. Statistical analysis of the results was conducted using the Mann-Whitney U test. The correlation between PAI-1 and protein levels was calculated using the Spearman rank correlation coefficient. RESULTS: The mean +/- SD PAI-1 levels detected in aqueous humor samples of the control and glaucoma groups were 0.44 +/- 0.61 and 1.45 +/- 1.91 ng/mL, respectively. The mean +/- SD levels of total protein were 64.91 +/- 89.75 and 86.64 +/- 44.16 microg/mL, respectively. For both parameters, the difference between the 2 groups was significant (P< .001). The correlation between PAI-1 and total protein levels was moderate in the glaucoma group (r = 0.43; P = .01) and low in the control group (r = 0.23; P = .04). CONCLUSIONS: The glaucoma group showed in the aqueous humor a 3.3-fold increase in the mean level of PAI-1 compared with the control group, whereas the increase in total protein level was only 1.3-fold. These data are consistent with the possibility that intraocularly produced PAI-1 may contribute to glaucoma pathogenesis. CLINICAL RELEVANCE: Reducing the production or activity of PAI-1 in the eye could constitute a new target for the design of drugs to treat glaucoma.

AlphaMUPA mice: a transgenic model for longevity induced by caloric restriction.

Caloric restriction (CR) is currently the only therapeutic intervention known to attenuate aging in mammals, but the underlying mechanisms of this phenomenon are still poorly understood. To get more insight into these mechanisms, we took advantage of the alphaMUPA transgenic mice that previously were reported to spontaneously eat less and live longer compared with their wild-type control mice. Currently, two transgenic lines that eat less are available, thus implicating the transgenic enzyme, i.e. the urokinase-type plasminogen activator (uPA), in causing the reduced appetite. This phenotypic change could have resulted from the ectopic transgenic expression that we detected in the adult alphaMUPA brain, or alternatively, from a transgenic interference in brain development. Here, we have summarized similarities and differences so far found between alphaMUPA and calorically restricted mice. Recently, we noted several changes in the alphaMUPA liver, at the mitochondrial and cellular level, which consistently pointed to an enhanced capacity to induce apoptosis. In addition, alphaMUPA mice showed a reduced level of serum IGF-1 and a reduced incidence of spontaneously occurring or carcinogen-induced tumors in several tissues. In contrast, alphaMUPA did not differ from wild type mice in the levels of low molecular weight antioxidants when compared in several tissues at a young or an old age. Overall, the alphaMUPA model suggests that fine-tuning of the threshold for apoptosis, possibly linked in part to modulation of serum IGF-1 and mitochondrial functions, could play a role in the attenuation of aging in calorically restricted mice.

Long-lived alpha MUPA transgenic mice exhibit increased mitochondrion-mediated apoptotic capacity.

Caloric restriction (CR) is currently the only therapeutic intervention known to attenuate aging in mammals, but the mechanisms underlying this phenomenon are still poorly understood. To study this issue, the transgenic model of alpha MUPA mice, which previously were reported to spontaneously eat less and live longer compared with their wild-type (WT) control mice, were used. Currently, two transgenic lines that eat less are available, thus implicating the transgenic enzyme, that is, the urokinase-type plasminogen activator (uPA), in causing the reduced appetite. Recently, several changes in the alpha MUPA liver were noted, at the mitochondrial and cellular level, which consistently pointed to an enhanced capacity to induce apoptosis. In addition, alpha MUPA mice showed a reduced level of serum IGF-1 and a reduced incidence of spontaneously occurring or carcinogen-induced tumors in several tissues. Overall, the alpha MUPA model suggests that long-lasting, moderately increased apoptotic capacity, possibly linked in part to modulation of serum IGF-1 and mitochondrial functions, could play a role in the attenuation of aging in calorically restricted mice.