Effects of growth hormone and thyroxine replacement therapy on insulin signaling in Ames dwarf mice

Impact of visceral adipose tissue on longevity and metabolic health: a comparative study of gene expression in perirenal and epididymal fat of Ames dwarf mice

Emerging research underscores the pivotal role of adipose tissue in regulating systemic aging processes, particularly when viewed through the lens of the endocrine hypotheses of aging. This study delves into the unique adipose characteristics in an important animal model of aging - the long-lived Ames dwarf (df/df) mice. Characterized by a Prop1df gene mutation, these mice exhibit a deficiency in growth hormone (GH), prolactin, and TSH, alongside extremely low circulating IGF-1 levels. Intriguingly, while surgical removal of visceral fat (VFR) enhances insulin sensitivity in normal mice, it paradoxically increases insulin resistance in Ames dwarfs. This suggests an altered profile of factors produced in visceral fat in the absence of GH, indicating a unique interplay between adipose tissue function and hormonal influences in these models. Our aim was to analyze the gene expression related to lipid and glucose metabolism, insulin pathways, inflammation, thermoregulation, mitochondrial biogenesis, and epigenetic regulation in the visceral (perirenal and epididymal) adipose tissue of Ames dwarf and normal mice. Our findings reveal an upregulation in the expression of key genes such as Lpl, Adrβ3, Rstn, Foxo1, Foxo3a, Irs1, Cfd, Aldh2, Il6, Tnfα, Pgc1α, Ucp2, and Ezh2 in perirenal and Akt1, Foxo3a, PI3k, Ir, Acly, Il6, Ring1a, and Ring 1b in epididymal fat in df/df mice. These results suggest that the longevity phenotype in Ames dwarfs, which is determined by peripubertal GH/IGF-1 levels, may also involve epigenetic reprogramming of adipose tissue influenced by hormonal changes. The increased expression of genes involved in metabolic regulation, tumor suppression, mitochondrial biogenesis, and insulin pathways in Ames dwarf mice highlights potentially beneficial aspects of this model, opening new avenues for understanding the molecular underpinnings of longevity and aging.

Growth hormone increases DNA damage in ovarian follicles and macrophage infiltration in the ovaries

Evidence points to an important role of the growth hormone (GH) in the aging process and longevity. GH-deficient mice are smaller, live longer than normal littermates, and females have an increased ovarian reserve. The aim of the study was to evaluate the role of GH in the ovarian reserve by evaluating DNA damage, macrophage infiltration, and granulosa cell number in primordial and primary follicles. Experiment 1 used GH-deficient Ames dwarf mice (df/df, n = 12) and their normal littermates (N/df, n = 12), receiving GH or saline injections. Experiment 2 included transgenic mice overexpressing bovine GH (bGH) (n = 6) and normal mice (N, n = 6). DNA damage (anti-γH2AX) and macrophage counting (anti-CD68) were evaluated by immunofluorescence. Female df/df mice had lower γH2AX foci intensity in both oocytes and granulosa cells of primordial and primary follicles (p < 0.05), indicating fewer DNA double-strand breaks (DSBs). GH treatment increased DSBs in both df/df and N/df mice. Inversely, bGH mice had a higher quantity of DSBs in both oocytes and granulosa cells of primordial and primary follicles (p < 0.05). Df/df mice showed ovarian tissue with less macrophage infiltration than N/df mice (p < 0.05) and GH treatment increased macrophage infiltration (p < 0.05). In contrast, bGH mice had ovarian tissue with more macrophage infiltration compared to normal mice (p < 0.05). The current study shows that GH increases DNA DSBs in oocytes and granulosa cells and raises macrophage infiltration in the ovaries, pointing to the role of the GH/IGF-I axis in maintenance of oocyte DNA integrity and ovarian macrophage infiltration in mice.

Multifactorial control of reproductive and growth axis in male goldfish: Influences of GnRH, GnIH and thyroid hormone

Reproduction and growth are under multifactorial control of neurohormones and peripheral hormones. This study investigated seasonally related effects of GnIH, GnRH, and T3 on the reproductive and growth axis in male goldfish at three stages of gonadal recrudescence. The effects of injection treatments with GnRH, GnIH and/or T3 were examined by measuring serum LH and GH levels, as well as peripheral transcript levels, using a factorial design. As expected, GnRH elevated serum LH and GH levels in a seasonally dependant manner, with maximal elevations of LH in late stages of gonadal recrudescence (Spring) and maximal increases in GH in the regressed gonadal stage (Summer). GnIH injection increased serum LH and GH levels only in fish at the regressed stage but exerted both stimulatory and inhibitory effects on GnRH-induced LH responses depending on season. T3 treatment mainly had stimulatory effects on circulating LH levels and inhibitory effects on serum GH concentrations. In the liver and testes, we observed seasonal differences in thyroid receptors, estrogen receptors, vitellogenin, follicle-stimulating hormone receptor, aromatase and IGF-I transcript levels that were tissue- and sex-specific. Generally, there were no clear correlation between circulating LH and GH levels and peripheral transcript levels, presumably due to time-related response and possible direct interaction of GnRH and GnIH at the level of liver and testis. The results support the hypothesis that GnRH and GnIH are important components of multifactorial mechanisms that work in concert with T3 to regulate reciprocal control of reproduction and growth in goldfish.

Seasonal Related Multifactorial Control of Pituitary Gonadotropin and Growth Hormone in Female Goldfish: Influences of Neuropeptides and Thyroid Hormone

Female reproduction is under multifactorial control of brain-pituitary-peripheral origin. The present study provides information on seasonal changes in circulating LH and GH concentrations, as well as transcript levels for a number of genes involved in the regulation of reproduction and growth in female goldfish. We also provide information on the effects of treatments with GnRH and/or GnIH, and their interaction with T3, at three stages of gonadal recrudescence. Maximum basal concentration of LH was observed at late recrudescence (Spring) while no seasonal changes in basal serum GH levels was detected. Serum LH and GH levels were stimulated by GnRH as expected, depending on the season. GnIH stimulated basal GH concentrations in gonadally regressed fish. GnIH inhibitory action on GnRH-induced LH response was observed in late, but not in mid recrudescence. T3 actions on basal and GnRH- or GnIH-induced GH secretion were generally inhibitory, depending on season. Administration of T3 attenuated GnRH-induced LH responses in mid and late stages of gonadal recrudescence, and the presence of GnIH abolished inhibitory actions of T3 in fish at mid recrudescence. Our results also demonstrated seasonal patterns in basal and GnRH- and/or GnIH-induced transcript levels for ERα, ERβI, FSHR, aromatase, TRαI, TRβ, IGF-I, and Vtg in the liver and ovary. However, there were no clear correlations between changes in transcript levels and circulating levels of LH and GH. The results support the hypothesis that GnRH, GnIH, and T3 are contributing factors in complex reciprocal control of reproduction and growth in goldfish.

Blood Serum From Head and Neck Squamous Cell Carcinoma Patients Induces Altered MicroRNA and Target Gene Expression Profile in Treated Cells

The head and neck squamous cell carcinoma (HNSCC) represents one of the most common cancers in humans. Close to 600,000 new diagnoses are made every year worldwide and over half of diagnosed patients will not survive. In view of this low survival rate, the development of novel cell-based assays for HNSCC will allow more mechanistic approaches for specific diagnostics for each individual patient. The cell-based assays will provide more informative data predicting cellular processes in treated patient, which in effect would improve patient follow up. More importantly, it will increase the specificity and effectiveness of therapeutic approaches. In this study, we investigated the role of serum from HNSCC patients on the regulation of microRNA (miRNA) expression in exposed cells in vitro. Next-generation sequencing of miRNA revealed that serum from HNSCC patients induced a different miRNA expression profile than the serum from healthy individuals. Out of 377 miRNA detected, we found that 16 miRNAs were differentially expressed when comparing cells exposed to serum from HNSCC or healthy individuals. The analysis of gene ontologies and pathway analysis revealed that these miRNA target genes were involved in biological cancer-related processes, including cell cycle and apoptosis. The real-time PCR analysis revealed that serum from HNSCC patients downregulate the expression level of five genes involved in carcinogenesis and two of these genes-P53 and SLC2A1-are direct targets of detected miRNAs. These novel findings provide new insight into how cancer-associated factors in circulation regulate the expression of genes and regulatory elements in distal cells in favor of tumorigenesis. This has the potential for new therapeutic approaches and more specific diagnostics with tumor-specific cell lines or single-cell in vitro assays for personalized treatment and early detection of primary tumors or metastasis.

Ovarian aging and the activation of the primordial follicle reserve in the long-lived Ames dwarf and the short-lived bGH transgenic mice

The aim of this study was to evaluate the effect of growth hormone (GH) in the maintenance of the ovarian primordial follicle reserve. Ovaries from 16 mo old GH-deficient Ames Dwarf (df/df) and Normal (N/df) mice were used. A subgroup of df/df and N mice received GH or saline injections for six weeks starting at 14 mo of age. In addition, ovaries from 12 mo old mice overexpressing bovine GH (bGH) and controls were used. df/df mice had higher number of primordial and total follicles than N/df mice (p < 0.05), while GH treatment decreased follicle counts in both genotypes (p < 0.05). In addition, bGH mice had lower number of primordial and total follicles than the controls (p < 0.05). pFoxO3a levels were higher in mice treated with GH and in bGH mice (p < 0.05) when comparing with age match controls. These results indicate that increased circulating GH is associated with a reduced ovarian primordial follicle reserve and increased pFoxO3a content in oocytes.

GH and ageing: Pitfalls and new insights

The interrelationships of growth hormone (GH) actions and aging are complex and incompletely understood. The very pronounced age-related decline in GH secretion together with benefits of GH therapy in individuals with congenital or adult GH deficiency (GHD) prompted interest in GH as an anti-aging agent. However, the benefits of treatment of normal elderly subjects with GH appear to be marginal and counterbalanced by worrisome side effects. In laboratory mice, genetic GH deficiency or resistance leads to a remarkable extension of longevity accompanied by signs of delayed and/or slower aging. Mechanisms believed to contribute to extended longevity of GH-related mutants include improved anti-oxidant defenses, enhanced insulin sensitivity and reduced insulin levels, reduced inflammation and cell senescence, major shifts in mitochondrial function and energy metabolism, and greater stress resistance. Negative association of the somatotropic signaling and GH/insulin-like growth factor 1 (IGF-1)-dependent traits with longevity has also been shown in other mammalian species. In humans, syndromes of GH resistance or deficiency have no consistent effect on longevity, but can provide striking protection from cancer, diabetes and atherosclerosis. More subtle alterations in various steps of GH and IGF-1 signaling are associated with reduced old-age mortality, particularly in women and with improved chances of attaining extremes of lifespan. Epidemiological studies raise a possibility that the relationship of IGF-1 and perhaps also GH levels with human healthy aging and longevity may be biphasic. However, the impact of somatotropic signaling on neoplastic disease is difficult to separate from its impact on aging, and IGF-1 levels exhibit opposite associations with different chronic, age-related diseases.

Healthspan and longevity can be extended by suppression of growth hormone signaling

Average and maximal lifespan are important biological characteristics of every species, but can be modified by mutations and by a variety of genetic, dietary, environmental, and pharmacological interventions. Mutations or disruption of genes required for biosynthesis or action of growth hormone (GH) produce remarkable extension of longevity in laboratory mice. Importantly, the long-lived GH-related mutants exhibit many symptoms of delayed and/or slower aging, including preservation of physical and cognitive functions and resistance to stress and age-related disease. These characteristics could be collectively described as "healthy aging" or extension of the healthspan. Extension of both the healthspan and lifespan in GH-deficient and GH-resistant mice appears to be due to multiple interrelated mechanisms. Some of these mechanisms have been linked to healthy aging and genetic predisposition to extended longevity in humans. Enhanced insulin sensitivity combined with reduced insulin levels, reduced adipose tissue, central nervous system inflammation, and increased levels of adiponectin represent such mechanisms. Further progress in elucidation of mechanisms that link reduced GH action to delayed and healthy aging should identify targets for lifestyle and pharmacological interventions that could benefit individuals as well as society.

Thyroxine modifies the effects of growth hormone in Ames dwarf mice

Ames dwarf (df/df) mice lack growth hormone (GH), thyroid stimulating hormone and prolactin. Treatment of juvenile df/df mice with GH alone stimulates somatic growth, reduces insulin sensitivity and shortens lifespan. Early‐life treatment with thyroxine (T4) alone produces modest growth stimulation but does not affect longevity. In this study, we examined the effects of treatment of juvenile Ames dwarf mice with a combination of GH + T4 and compared them to the effects of GH alone. Treatment of female and male dwarfs with GH + T4 between the ages of 2 and 8 weeks rescued somatic growth yet did not reduce lifespan to match normal controls, thus contrasting with the previously reported effects of GH alone. While the male dwarf GH + T4 treatment group had no significant effect on lifespan, the female dwarfs undergoing treatment showed a decrease in maximal longevity. Expression of genes related to GH and insulin signaling in the skeletal muscle and white adipose tissue (WAT) of female dwarfs was differentially affected by treatment with GH + T4 vs. GH alone. Differences in the effects of GH + T4 vs. GH alone on insulin target tissues may contribute to the differential effects of these treatments on longevity.

The role of leptin in the sporadic form of Alzheimer's disease. Interactions with the adipokines amylin, ghrelin and the pituitary hormone prolactin

Leptin (Lep) is emerging as a pivotal molecule involved in both the early events and the terminal phases of Alzheimer's disease (AD). In the canonical pathway, Lep acts as an anorexigenic factor via its effects on hypothalamic nucleus. However, additional functions of Lep in the hippocampus and cortex have been unravelled in recent years. Early events in the sporadic form of AD likely involve cellular level alterations which can have an effect on food intake and metabolism. Thus, AD can be conceivably interpreted as a multiorgan pathology that not only results in a dramatic neuronal loss in brain areas such as the hippocampus and the cortex (ultimately leading to a significant cognitive impairment) but as a disease which also affects body-weight homeostasis. According to this view, body-weight control disruptions are to be expected in both the early- and late-stage AD, concomitant with changes in serum Lep content, alterations in Lep transport across the blood-brain barrier (BBB) and Lep receptor-related signalling abnormalities. Lep is a member of the adipokine family of molecules, while the Lep receptor belongs to the class I cytokine receptors. Since cellular response to adipokine signalling can be either potentiated or diminished as a result of specific ligand-receptor interactions, Lep interactions with other members of the adipokine family including amylin, ghrelin and hormones such as prolactin require further investigation. In this review, we provide a general perspective on the functions of Lep in the brain, with a particular focus on the sporadic AD.

Ames hypopituitary dwarf mice demonstrate imbalanced myelopoiesis between bone marrow and spleen

Ames hypopituitary dwarf mice are deficient in growth hormone, thyroid-stimulating hormone, and prolactin. The phenotype of these mice demonstrates irregularities in the immune system with skewing of the normal cytokine milieu towards a more anti-inflammatory environment. However, the hematopoietic stem and progenitor cell composition of the bone marrow (BM) and spleen in Ames dwarf mice has not been well characterized. We found that there was a significant decrease in overall cell count when comparing the BM and spleen of 4-5 month old dwarf mice to their littermate controls. Upon adjusting counts to differences in body weight between the dwarf and control mice, the number of granulocyte-macrophage progenitors, confirmed by immunophenotyping and colony-formation assay was increased in the BM. In contrast, the numbers of all myeloid progenitor populations in the spleen were greatly reduced, as confirmed by colony-formation assays. This suggests that there is a shift of myelopoiesis from the spleen to the BM of Ames dwarf mice; however, this shift does not appear to involve erythropoiesis. The reasons for this unusual shift in spleen to marrow hematopoiesis in Ames dwarf mice are yet to be determined but may relate to the decreased hormone levels in these mice.

Growth hormone abolishes beneficial effects of calorie restriction in long-lived Ames dwarf mice

Disruption of the growth hormone (GH) axis promotes longevity and delays aging. In contrast, GH over-expression may lead to accelerated aging and shorter life. Calorie restriction (CR) improves insulin sensitivity and may extend lifespan. Long-lived Ames dwarf (df/df) mice have additional extension of longevity when subjected to 30% CR. The aim of the study was to assess effects of CR or GH replacement therapy separately and as a combined (CR+GH) treatment in GH-deficient df/df and normal mice, on selected metabolic parameters (e.g., insulin, glucose, cholesterol), insulin signaling components (e.g., insulin receptor [IR] β-subunit, phosphorylated form of IR [IR pY1158], protein kinase C ζ/λ [p-PKCζ/λ] and mTOR [p-mTOR]), transcription factor p-CREB, and components of the mitogen-activated protein kinase (MAPK) signaling (p-ERK1/2, p-p38), responsible for cell proliferation, differentiation and survival. CR decreased plasma levels of insulin, glucose, cholesterol and leptin, and increased hepatic IR β-subunit and IR pY1158 levels as well as IR, IRS-1 and GLUT-2 gene expression compared to ad libitum feeding, showing a significant beneficial diet intervention effect. Moreover, hepatic protein levels of p-PKCζ/λ, p-mTOR and p-p38 decreased, and p-CREB increased in CR mice. On the contrary, GH increased levels of glucose, cholesterol and leptin in plasma, and p-mTOR or p-p38 in livers, and decreased plasma adiponectin and hepatic IR β-subunit compared to saline treatment. There were no GH effects on adiponectin in N mice. Moreover, GH replacement therapy did not affect IR, IRS-1 and GLUT-2 gene expression. GH treatment abolishes the beneficial effects of CR; it may suggest an important role of GH-IGF1 axis in mediating the CR action. Suppressed somatotrophic signaling seems to predominate over GH replacement therapy in the context of the examined parameters and signaling pathways.

Insulin sensitivity in long-living Ames dwarf mice

Long-living Ames dwarf mice (df/df) characterized by growth hormone (GH) deficiency are widely used in aging research because of their 40-60 % lifespan extension compared to normal (N) littermates. Importantly, these mice not only live longer but are also protected from age-related diseases including insulin resistance. Several studies demonstrate that df/df mice have enhanced insulin signaling in different insulin-sensitive tissues and suggest that this is a mechanism for extended lifespan. However, it is unknown whether the enhanced insulin signaling in df/df mice translates to improved insulin action on hepatic glucose production and tissue glucose uptake. We performed hyperinsulinemic-euglycemic clamps to assess tissue-specific insulin action in vivo for the first time in these small long-living dwarfs. Our results demonstrate that the glucose infusion rate required to maintain euglycemia was ∼2-fold higher in df/df mice compared to N controls. Insulin-mediated glucose production was completely suppressed in dwarf mice, and stimulation of gastrocnemius and vastus muscle and adipose tissue glucose uptake was also enhanced in df/df mice (100, 86, and 65 %, respectively). These findings show that improved insulin signaling in df/df mice is associated with enhanced tissue-specific insulin action in vivo. This improved functionality of insulin action and glucose homeostasis may play a key role in promoting healthy aging and longer lifespan in df/df mice.

Metabolic characteristics of long-lived mice

Genetic suppression of insulin/insulin-like growth factor signaling (IIS) can extend longevity in worms, insects, and mammals. In laboratory mice, mutations with the greatest, most consistent, and best documented positive impact on lifespan are those that disrupt growth hormone (GH) release or actions. These mutations lead to major alterations in IIS but also have a variety of effects that are not directly related to the actions of insulin or insulin-like growth factor I. Long-lived GH-resistant GHR-KO mice with targeted disruption of the GH receptor gene, as well as Ames dwarf (Prop1^df) and Snell dwarf (Pit1^dw) mice lacking GH (along with prolactin and TSH), are diminutive in size and have major alterations in body composition and metabolic parameters including increased subcutaneous adiposity, increased relative brain weight, small liver, hypoinsulinemia, mild hypoglycemia, increased adiponectin levels and insulin sensitivity, and reduced serum lipids. Body temperature is reduced in Ames, Snell, and female GHR-KO mice. Indirect calorimetry revealed that both Ames dwarf and GHR-KO mice utilize more oxygen per gram (g) of body weight than sex- and age-matched normal animals from the same strain. They also have reduced respiratory quotient, implying greater reliance on fats, as opposed to carbohydrates, as an energy source. Differences in oxygen consumption (VO₂) were seen in animals fed or fasted during the measurements as well as in animals that had been exposed to 30% calorie restriction or every-other-day feeding. However, at the thermoneutral temperature of 30°C, VO₂ did not differ between GHR-KO and normal mice. Thus, the increased metabolic rate of the GHR-KO mice, at a standard animal room temperature of 23°C, is apparently related to increased energy demands for thermoregulation in these diminutive animals. We suspect that increased oxidative metabolism combined with enhanced fatty acid oxidation contribute to the extended longevity of GHR-KO mice.

Growth hormone, inflammation and aging

Mutant animals characterized by extended longevity provide valuable tools to study the mechanisms of aging. Growth hormone and insulin-like growth factor-1 (IGF-1) constitute one of the well-established pathways involved in the regulation of aging and lifespan. Ames and Snell dwarf mice characterized by GH deficiency as well as growth hormone receptor/growth hormone binding protein knockout (GHRKO) mice characterized by GH resistance live significantly longer than genetically normal animals. During normal aging of rodents and humans there is increased insulin resistance, disruption of metabolic activities and decline of the function of the immune system. All of these age related processes promote inflammatory activity, causing long term tissue damage and systemic chronic inflammation. However, studies of long living mutants and calorie restricted animals show decreased pro-inflammatory activity with increased levels of anti-inflammatory adipokines such as adiponectin. At the same time, these animals have improved insulin signaling and carbohydrate homeostasis that relate to alterations in the secretory profile of adipose tissue including increased production and release of anti-inflammatory adipokines. This suggests that reduced inflammation promoting healthy metabolism may represent one of the major mechanisms of extended longevity in long-lived mutant mice and likely also in the human.

The emerging role of IGF-1 deficiency in cardiovascular aging: recent advances

This review focuses on cardiovascular protective effects of insulin-like growth factor (IGF)-1, provides a landscape of molecular mechanisms involved in cardiovascular alterations in patients and animal models with congenital and adult-onset IGF-1 deficiency, and explores the link between age-related IGF-1 deficiency and the molecular, cellular, and functional changes that occur in the cardiovascular system during aging. Microvascular protection conferred by endocrine and paracrine IGF-1 signaling, its implications for the pathophysiology of cardiac failure and vascular cognitive impairment, and the role of impaired cellular stress resistance in cardiovascular aging considered here are based on emerging knowledge of the effects of IGF-1 on Nrf2-driven antioxidant response.

Growth hormone and IGF-1 deficiency exacerbate high-fat diet-induced endothelial impairment in obese Lewis dwarf rats: implications for vascular aging

Previous studies suggest that the age-related decline in circulating growth hormone (GH) and insulin-like growth factor-1 (IGF-1) levels significantly contribute to vascular dysfunction in aging by impairing cellular oxidative stress resistance pathways. Obesity in elderly individuals is increasing at alarming rates, and there is evidence suggesting that elderly individuals are more vulnerable to the deleterious cardiovascular effects of obesity than younger individuals. However, the specific mechanisms through which aging, GH/IGF-1 deficiency, and obesity interact to promote the development of cardiovascular disease remain unclear. To test the hypothesis that low circulating GH/IGF-1 levels exacerbate the pro-oxidant and proinflammatory vascular effects of obesity, GH/IGF-1-deficient Lewis dwarf rats and heterozygous control rats were fed either a standard diet or a high-fat diet (HFD) for 7 months. Feeding an HFD resulted in similar relative weight gains and increases in body fat content in Lewis dwarf rats and control rats. HFD-fed Lewis dwarf rats exhibited a relative increase in blood glucose levels, lower insulin, and impaired glucose tolerance as compared with HFD-fed control rats. Analysis of serum cytokine expression signatures indicated that chronic GH/IGF-1 deficiency exacerbates HFD-induced inflammation. GH/IGF-1 deficiency also exacerbated HFD-induced endothelial dysfunction, oxidative stress, and expression of inflammatory markers (tumor necrosis factor-α, ICAM-1) in aortas of Lewis dwarf rats. Overall, our results are consistent with the available clinical and experimental evidence suggesting that GH/IGF-1 deficiency renders the cardiovascular system more vulnerable to the deleterious effects of obesity.

Liver-specific knockdown of IGF-1 decreases vascular oxidative stress resistance by impairing the Nrf2-dependent antioxidant response: a novel model of vascular aging

Recent studies demonstrate that age-related dysfunction of NF-E2-related factor-2 (Nrf2)-driven pathways impairs cellular redox homeostasis, exacerbating age-related cellular oxidative stress and increasing sensitivity of aged vessels to oxidative stress-induced cellular damage. Circulating levels of insulin-like growth factor (IGF)-1 decline during aging, which significantly increases the risk for cardiovascular diseases in humans. To test the hypothesis that adult-onset IGF-1 deficiency impairs Nrf2-driven pathways in the vasculature, we utilized a novel mouse model with a liver-specific adeno-associated viral knockdown of the Igf1 gene using Cre-lox technology (Igf1(f/f) + MUP-iCre-AAV8), which exhibits a significant decrease in circulating IGF-1 levels (~50%). In the aortas of IGF-1-deficient mice, there was a trend for decreased expression of Nrf2 and the Nrf2 target genes GCLC, NQO1 and HMOX1. In cultured aorta segments of IGF-1-deficient mice treated with oxidative stressors (high glucose, oxidized low-density lipoprotein, and H(2)O(2)), induction of Nrf2-driven genes was significantly attenuated as compared with control vessels, which was associated with an exacerbation of endothelial dysfunction, increased oxidative stress, and apoptosis, mimicking the aging phenotype. In conclusion, endocrine IGF-1 deficiency is associated with dysregulation of Nrf2-dependent antioxidant responses in the vasculature, which likely promotes an adverse vascular phenotype under pathophysiological conditions associated with oxidative stress (eg, diabetes mellitus, hypertension) and results in accelerated vascular impairments in aging.

Reconstitutable charged polymeric (PLGA)(2)-b-PEI micelles for gene therapeutics delivery

This study investigated the potential of creating a charged polymeric micelle-based nucleic acid delivery system that could easily be reconstituted by the addition of water. (PLGA(36kDa))(2)-b-bPEI(25kDa) (PLGA MW 36 kDa, bPEI M(w) 25 kDa, PLGA:bPEI block ratio = 2) was synthesized and used to prepare cationic micelles. The copolymer retained proton-buffering capability from the bPEI block within the endosomal pH range. Micelle/pDNA complexes retained their particle size (100-150 nm) and surface charge (30-40 mV) following reconstitution. It was found that adding a small amount of low molecular weight bPEI (1.8 kDa) completely shielded pDNA in the micelle/pDNA complexes and enhanced transfection efficiency 50-100 fold for both fresh and reconstituted complexes without affecting complex size. Transfection efficiency for "reconstituted" micelle/pDNA/bPEI(1.8kDa) (WR 1) complexes was 16-fold higher than its "fresh" counterpart. Although transfection levels achieved using "reconstituted" micelle/pDNA/bPEI(1.8kDa) complexes were 3.6-fold lower than control "fresh" bPEI(25kDa)/pDNA (N/P 5) complexes, transfection levels were 39-fold higher than "reconstituted" bPEI(25kDa)/pDNA (N/P 5) complexes. The micelle/pDNA/bPEI(1.8kDa) system showed very low cytotoxicity in MCF7 cells even with pDNA doses up to 20 μg, and transfection levels increased linearly with increasing pDNA dose. These results indicate that this PLGA-b-bPEI polymeric micelle-based system is well suited as a reconstitutable gene delivery system, and has high potential for use as a delivery system for gene therapy applications.

Smaller cardiac cell size and reduced extra-cellular collagen might be beneficial for hearts of Ames dwarf mice

PURPOSE

To test the hypothesis that cardiac morphologic differences between Ames dwarf and wild-type littermates might correlate with the increased longevity observed in the Ames dwarf mice.

METHODS

Hearts removed from young adult (5-7 mo) and old (24-28 mo) Ames dwarf and wild-type littermates underwent histological and morphometric analysis. Measurements of cell size, nuclear size, and collagen content were made using computerized color deconvolution and particle analysis methodology.

RESULTS

In the young mice at six months of age, mean cardiomyocyte area was 46% less in Ames dwarf than in wild-type mice (p<0.0001). Cardiomyocyte size increased with age by about 52% in the wild-type mice and 44% in the Ames dwarf mice (p<0.001). There was no difference in nuclear size of the cardiomyocytes between the young adult wild-type and Ames dwarf mice. There was an age-associated increase in the cardiomyocyte nuclear size by approximately 50% in both the Ames and wild-type mice (p<0.001). The older Ames dwarf mice had slightly larger cardiomyocyte nuclei compared to wild-type (2%, p<0.05). The collagen content of the hearts in young adult Ames dwarf mice was estimated to be 57% less compared to wild-type littermates (p<0.05). Although collagen content of both Ames dwarf and wild-type mouse hearts increased with age, there was no significant difference at 24 months.

CONCLUSIONS

In wild-type and Ames dwarf mice, nuclear size, cardiomyocyte size, and collagen content increased with advancing age. While cardiomyocyte size was much reduced in young and old Ames dwarf mice compared with wild-type, collagen content was reduced only in the young adult mice. Taken together, these findings suggest that Ames dwarf mice may receive some longevity benefit from the reduced cardiomyocyte cell size and a period of reduced collagen content in the heart during adulthood.

Early life growth hormone treatment shortens longevity and decreases cellular stress resistance in long-lived mutant mice

Hypopituitary Ames dwarf mice were injected either with growth hormone (GH) or thyroxine for a 6-wk period to see whether this intervention would reverse their long life span or the resistance of their cells to lethal stresses. Ames dwarf mice survived 987 ± 24 d (median), longer than nonmutant control mice (664 ± 48), but GH-injected dwarf mice did not differ from controls (707 ± 9). Fibroblast cells from Ames dwarf mice were more resistant to cadmium than cells from nonmutant controls (LD(50) values of 9.98 ± 1.7 and 3.9 ± 0.8, respectively), but GH injections into Ames dwarf mice restored the normal level of cadmium resistance (LD(50)=5.8 ± 0.9). Similar restoration of normal resistance was observed for fibroblasts exposed to paraquat, methyl methanesulfonate, and rotenone (P<0.05 in each case for contrast of GH-treated vs. untreated dwarf mice; P<0.05 for dwarf vs. nonmutant control mice.) T4 injections into Ames dwarf mice, in contrast, did not restore normal life span. We conclude that the remarkable life-span extension of Ames dwarf mice, and the stress resistance of cells from these mice, depends on low levels of GH exposure in juvenile and very young adult mice.