The iconic giraffe, an ecologically important browser, has shown a substantial decline in numbers across Africa since the 1990s. In Serengeti National Park, Tanzania, giraffes reached densities of ...1.5–2.6 individuals km⁻² in the 1970s coincident with a pulse of Acacia tree recruitment. However, despite continued increases in woody cover between the 1980s and the 2000s, giraffe recruitment and survival rates have declined and density has dropped to only 0.3–0.4 giraffes km⁻². We used a decision table to investigate how four extrinsic factors may have contributed to these declines: food supply, predation, parasites, and poaching, which have all been previously shown to limit Serengeti ungulate populations. Lower recruitment likely resulted from a reduction in diet quality, owing to the replacement of preferred trees with unpalatable species, while decreased adult survival resulted from illegal harvesting, which appears to have had a greater impact on giraffe populations bordering the western and northern Serengeti. The Serengeti giraffe population will likely persist at low-to-moderate densities until palatable tree species regain their former abundance. Leslie matrix models suggest that park managers should meanwhile redouble their efforts to reduce poaching, thereby improving adult survival.
Derivation of Oocytes from Mouse Embryonic Stem Cells Hübner, Karin; Fuhrmann, Guy; Christenson, Lane K. ...
Science (American Association for the Advancement of Science),
05/2003, Letnik:
300, Številka:
5623
Journal Article
Recenzirano
Continuation of mammalian species requires the formation and development of the sexually dimorphic germ cells. Cultured embryonic stem cells are generally considered pluripotent rather than ...totipotent because of the failure to detect germline cells under differentiating conditions. Here we show that mouse embryonic stem cells in culture can develop into oogonia that enter meiosis, recruit adjacent cells to form follicle-like structures, and later develop into blastocysts. Oogenesis in culture should contribute to various areas, including nuclear transfer and manipulation of the germ line, and advance studies on fertility treatment and germ and somatic cell interaction and differentiation.
The PGC-1α/PPAR axis has been proposed as a potential therapeutic target for several metabolic disorders. The aim was to evaluate the efficacy of the pan-PPAR agonist, bezafibrate, in tafazzin ...knockdown mice (TazKD), a mouse model of Barth syndrome that exhibits age-dependent dilated cardiomyopathy with left ventricular (LV) dysfunction.
The effect of bezafibrate on cardiac function was evaluated by echocardiography in TazKD mice with or without beta-adrenergic stress. Adrenergic stress by chronic isoproterenol infusion exacerbates the cardiac phenotype in TazKD mice, significantly depressing LV systolic function by 4.5 months of age. Bezafibrate intake over 2 months substantially ameliorates the development of LV systolic dysfunction in isoproterenol-stressed TazKD mice. Without beta-adrenergic stress, TazKD mice develop dilated cardiomyopathy by 7 months of age. Prolonged treatment with suprapharmacological dose of bezafibrate (0.5% in rodent diet) over a 4-month period effectively prevented LV dilation in mice isoproterenol treatment. Bezafibrate increased mitochondrial biogenesis, however also promoted oxidative stress in cardiomyocytes. Surprisingly, improvement of systolic function in bezafibrate-treated mice was accompanied with simultaneous reduction of cardiolipin content and increase of monolysocardiolipin levels in cardiac muscle.
Thus, we demonstrate that bezafibrate has a potent therapeutic effect on preventing cardiac dysfunction in a mouse model of Barth syndrome with obvious implications for treating the human disease. Additional studies are needed to assess the potential benefits of PPAR agonists in humans with Barth syndrome.
Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin ...sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance is caused, at least in part, by the presence of high concentrations of harmful lipid metabolites, such as diacylglycerols and ceramides in muscle. Several mechanistic differences between obese sedentary individuals and their highly trained counterparts have been identified, which determine the differential capacity for IMTG synthesis and breakdown in these populations. In this review, we first describe the most up-to-date mechanisms by which a low IMTG turnover rate (both breakdown and synthesis) leads to the accumulation of lipid metabolites and results in skeletal muscle insulin resistance. We then explore current and potential exercise and nutritional strategies that target IMTG turnover in sedentary obese individuals, to improve insulin sensitivity. Overall, improving IMTG turnover should be an important component of successful interventions that aim to prevent the development of insulin resistance in the ever-expanding sedentary, overweight and obese populations.
Novelty:
A description of the most up-to-date mechanisms regulating turnover of the IMTG pool.
An exploration of current and potential exercise/nutritional strategies to target and enhance IMTG turnover in obese individuals.
Overall, highlights the importance of improving IMTG turnover to prevent the development of insulin resistance.
Celotno besedilo
Dostopno za:
DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Although lions Panthera leo are the main predators of the giraffe Giraffa camelopardalis, interactions between these species are rarely observed directly. As a consequence, little is known about the ...effects of lions on giraffe mortality and behavior. We test patterns of lion predation on Masai giraffes Giraffa camelopardalis tippelskirchi using a new methodology: lion claw marks observable on the skin of live giraffes. We studied 702 individually known giraffes in 3 non‐neighboring areas of Serengeti National Park, Tanzania between August 2008 and November 2010. Lion claw marks were observed on 13% of giraffes older than 1 year. Claw marks were most frequently detected on giraffe hindquarters and flanks, revealing that non‐lethal lion attacks occur most often from the rear. No claw marks were observed on calves (0–1 year), suggesting that calves rarely survive lion attacks. In the adult age class (>5 years), claw‐mark prevalence was significantly higher among females than males. We observed substantial variation in claw‐mark prevalence across study areas, indicating that lion predation risk may be heterogeneous within Serengeti. We find that claw marks are an important source of data on interactions between lions and giraffes.
Key points
We have recently shown that a high‐fat, high‐calorie (HFHC) diet decreases whole body glucose clearance without impairing skeletal muscle insulin signalling, in healthy lean individuals.
...These diets are also known to increase skeletal muscle IMTG stores, but the effect on lipid metabolites leading to skeletal muscle insulin resistance has not been investigated.
This study measured the effect of 7 days’ HFHC diet on (1) skeletal muscle concentration of lipid metabolites, and (2) potential changes in the perilipin (PLIN) content of the lipid droplets storing intramuscular triglyceride (IMTG).
The HFHC diet increased PLIN3 protein expression and redistributed PLIN2 to lipid droplet stores in type I fibres.
The HFHC diet increased IMTG content in type I fibres, while lipid metabolite concentrations remained the same. The data suggest that the increases in IMTG stores assists in reducing the accumulation of lipid metabolites known to contribute to skeletal muscle insulin resistance.
A high‐fat, high‐calorie (HFHC) diet reduces whole body glucose clearance without impairing skeletal muscle insulin signalling in healthy lean individuals. HFHC diets also increase skeletal muscle lipid stores. However, unlike certain lipid metabolites, intramuscular triglyceride (IMTG) stored within lipid droplets (LDs) does not directly contribute to skeletal muscle insulin resistance. Increased expression of perilipin (PLIN) proteins and colocalisation to LDs has been shown to assist in IMTG storage. We aimed to test the hypothesis that 7 days on a HFHC diet increases IMTG content while minimising accumulation of lipid metabolites known to disrupt skeletal muscle insulin signalling in sedentary and obese individuals. We also aimed to identify changes in expression and subcellular distribution of proteins involved in IMTG storage. Muscle biopsies were obtained from the m. vastus lateralis of 13 (11 males, 2 females) healthy lean individuals (age: 23 ± 2.5 years; body mass index: 24.5 ± 2.4 kg m−2), following an overnight fast, before and after consuming a high‐fat (64% energy), high‐calorie (+47% kcal) diet for 7 days. After the HFHC diet, IMTG content increased in type I fibres only (+101%; P < 0.001), whereas there was no change in the concentration of either total diacylglycerol (P = 0.123) or total ceramides (P = 0.150). Of the PLINs investigated, only PLIN3 content increased (+50%; P < 0.01) solely in type I fibres. LDs labelled with PLIN2 increased (+80%; P < 0.01), also in type I fibres only. We propose that these adaptations of LDs support IMTG storage and minimise accumulation of lipid metabolites to protect skeletal muscle insulin signalling following 7 days’ HFHC diet.
Key points
We have recently shown that a high‐fat, high‐calorie (HFHC) diet decreases whole body glucose clearance without impairing skeletal muscle insulin signalling, in healthy lean individuals.
These diets are also known to increase skeletal muscle IMTG stores, but the effect on lipid metabolites leading to skeletal muscle insulin resistance has not been investigated.
This study measured the effect of 7 days’ HFHC diet on (1) skeletal muscle concentration of lipid metabolites, and (2) potential changes in the perilipin (PLIN) content of the lipid droplets storing intramuscular triglyceride (IMTG).
The HFHC diet increased PLIN3 protein expression and redistributed PLIN2 to lipid droplet stores in type I fibres.
The HFHC diet increased IMTG content in type I fibres, while lipid metabolite concentrations remained the same. The data suggest that the increases in IMTG stores assists in reducing the accumulation of lipid metabolites known to contribute to skeletal muscle insulin resistance.
Summary
Background
Although a national epidemic of childhood obesity is apparent, how community‐based programmes and policies (CPPs) affect this outcome is not well understood.
Objectives
This study ...examined the longitudinal relationship between the intensity of CPPs in 130 communities over 10 years and body mass index (BMI) of resident children. We also examined whether these relationships differ by key family or community characteristics.
Methods
Five thousand one hundred thirty‐eight children in grades K‐8 were recruited through 436 schools located within 130 diverse US communities. Measures of height, weight, nutrition, physical activity and behavioural and demographic family characteristics were obtained during in‐home visits. A subsample of families consented to medical record review; these weight and height measures were used to calculate BMI over time for 3227 children. A total of 9681 CPPs were reported during structured interviews of 1421 community key informants, and used to calculate a time series of CPP intensity scores within each community over the previous decade. Linear mixed effect models were used to assess longitudinal relationships between childhood BMI and CPP intensity.
Results
An average BMI difference of 1.4 kg/m2 (p‐value < 0.01) was observed between communities with the highest and lowest observed CPP intensity scores, after adjusting for community and child level covariates. BMI/CPP relationships differed significantly by child grade, race/ethnicity, family income and parental education; as well as community‐level race/ethnicity.
Conclusions
These results indicate that, over time, more intense CPP interventions are related to lower childhood BMI, and that there are disparities in this association by sociodemographic characteristics of families and communities.
This article is part of the upcoming supplement: The Healthy Communities Study: Examining Community Programs, Policies and Other Characteristics in Relation to Child Weight, Diet, and Physical Activity.
Summary
Background
The impact of community‐based obesity prevention efforts on child nutrition has not been adequately studied.
Objective
Examine relationships between number, type and intensity of ...community programs and policies (CPPs) and child nutrition.
Methods
An observational study of 5138 children (grades K–8) in 130 U.S. communities was conducted in 2013–2015. CPPs were identified by 10–14 key informant interviews per community. CPPs were characterized based on: count, intensity, number of different strategies used and number of different behaviours targeted. Scores for the prior 6 years were calculated separately for CPPs that addressed primarily nutrition, primarily physical activity (PA) or total combined. Child intakes were calculated from a dietary screener and dietary behaviours were based on survey responses. Multi‐level statistical models assessed associations between CPP indices and nutrition measures, adjusting for child and community‐level covariates.
Results
Implementing more types of strategies across all CPPs was related to lower intakes of total added sugar (when CPPs addressed primarily PA), sugar‐sweetened beverages (for nutrition and PA CPPs) and energy‐dense foods of minimal nutritional value (for total CPPs). Addressing more behaviours was related to higher intakes of fruit and vegetables (for nutrition and total CPPs) and fibre (total CPPs). Higher count and intensity (PA and total CPPs) were related to more consumption of lower fat compared with higher fat milk. A higher count (PA CPPs) was related to fewer energy‐dense foods and whole grains. No other relationships were significant at P < 0.05.
Conclusion
Multiple characteristics of CPPs to prevent obesity appear important to improve children's diets.
What is already known about this subject?
Multi‐component and multi‐sector community interventions are recommended to prevent child obesity.
Little is known about whether community programs and policies implemented in the U.S. are improving child nutrition; a better understanding of these efforts and their relationship to child nutrition can help inform community efforts.
What this study adds?
We conducted an observational study collecting dietary data from over 5000 children ages 4–15 years and retrospective data on community programs and policies in a diverse sample of 130 communities across the U.S.
Different features of community policies and programs were related to better child nutrition – there is likely no ‘single’ or ‘simple’ solution.
Policy and food environments that support children'’s healthy food choices in conjunction with delivering information and enhancing skills are associated with better diets.
It is important to target changes in multiple dietary behaviours – not only increasing healthy foods and beverages, but also limiting less healthy ones.
This article is part of the supplement: The Healthy Communities Study: Examining Community Programs, Policies and Other Characteristics in Relation to Child Weight, Diet, and Physical Activity
Summary
Background
Little is known about whether characteristics of communities are associated with differential implementation of community programmes and policies to promote physical activity and ...healthy eating. This study examines associations between community characteristics (e.g. region and race/ethnicity) and the intensity of community programmes and policies implemented to prevent childhood obesity. It explores whether community characteristics moderate the intensity of community efforts to prevent childhood obesity.
Objective
The objective of this study is to investigate associations between community characteristics and the intensity of community policies and programmes to prevent childhood obesity documented in the Healthy Communities Study that engaged a diverse sample of US communities.
Method
Programmes and policies were documented in 130 communities across the USA, reporting over 9000 different community programmes and policies to prevent obesity among children ages 4–15. We examined associations between community characteristics and the intensity of community programmes and policies implemented (i.e. their amount and reach, duration and strength of change strategy).
Conclusion
Community characteristics explain 25% of the variability in the intensity of community programmes and policies implemented in communities. Particular characteristics – urbanicity, region, being a large county and the per cent of African–Americans in a community – contributed to more (over 18% of the 25%) of the observed variability.
What is already known about this subject?
Childhood obesity is a critical public health challenge facing communities in the United States.
Community characteristics are associated with community health outcomes.
Previous community‐level interventions to reduce children's BMI have yielded modest and inconsistent outcomes.
What this study adds?
This study adds to our understanding of whether and how community characteristics are associated with differential implementation of community programmes and policies to address childhood obesity.
Measurement of the intensity of community‐level programmes and policies in a large and diverse sample of U.S. communities with different community characteristics.
This article is part of the supplement: The Healthy Communities Study: Examining Community Programs, Policies and Other Characteristics in Relation to Child Weight, Diet, and Physical Activity
Summary
Background
Rational planning of community policies and programs (CPPs) to prevent obesity requires an understanding of CPP objectives associated with dietary behaviours.
Objective
The ...objective of the study is to identify objectives of CPPs associated with healthful dietary behaviours.
Methods
An observational study identified 4026 nutrition CPPs occurring in 130 communities in the prior 6 years. Dietary intakes of fruits and vegetables, added sugar and sugar‐sweetened beverages, among others, were reported among 5138 children 4–15 years of age from the communities, using a Dietary Screener Questionnaire with children age 9 years and older (parent assisted) or parent proxies for younger children. CPPs were documented through key informant interviews and characterized by their intensity, count, and objectives including target dietary behaviour and food environment change strategy. Associations between dietary intakes and CPP objectives were assessed using hierarchical statistical models.
Results
CPPs with the highest intensity scores that targeted fast food or fat intake or provided smaller portions were associated with greater fruit and vegetable intake (0.21, 0.19, 0.23 cup equivalents/day respectively with p values <0.01, 0.04, 0.03). CPPs with the highest intensity scores that restricted the availability of less healthful foods were associated with lower child intakes of total added sugar (−1.08 tsp/day, p < 0.01) and sugar from sugar‐sweetened beverages (−1.63 tsp/day, p = 0.04). Similar associations were observed between CPP count and dietary outcomes. No other significant associations were found between CPP target behaviours or environmental strategies and dietary intakes/behaviours.
Conclusion
CPPs that targeted decreases in intakes of less healthful foods and/or aimed to modify the availability of less healthful foods and portions were associated with healthier child dietary behaviours.
What is already known about this subject:
Community programs and policies (CPPs) use a range of strategies to prevent obesity, based on ‘practice tested’ models and those with emerging evidence about their success.
Yet, understanding the relationship of types and features of CPPs that contribute to success of CPPs, including program and policy objectives in the context of the whole community effort, would inform rational planning for obesity prevention.
What this study adds:
We studied dietary intakes of 5138 children 4–15 years of age and objectives of CPPs (dietary behaviours targeted and food environment change strategies) in a diverse sample of 130 communities across the USA.
We found significant associations between CPPs that aimed to modify community food environments (by restricting availability of less healthful foods and beverages and instituting smaller portion sizes) and higher fruit and vegetable (FV) intake as well as lower sugar and sugar‐sweetened beverage intake. We also found associations between CPPs that targeted less healthful dietary behaviours (fat, fast food) with higher child FV intake. Yet, dietary intakes of interest were not generally consistent with the dietary targets reported by CPPs, e.g. those targeting FV were not associated with higher intakes of FV.
Our findings suggest potential benefits from a greater focus of CPPs on food environments. Further evaluation is recommended to identify causal relationships between objectives of CPPs and child diets, and which combinations of CPP objectives are most successful.
This article is part of the supplement: The Healthy Communities Study: Examining Community Programs, Policies and Other Characteristics in Relation to Child Weight, Diet, and Physical Activity
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