The meta-learning toolkit needs stronger constraints.

The implementation of meta-learning targeted by Binz et al. inherits benefits and drawbacks from its nature as a connectionist model. Drawing from historical debates around bottom-up and top-down approaches to modeling in cognitive science, we should continue to bridge levels of analysis by constraining meta-learning and meta-learned models with complementary evidence from across the cognitive and computational sciences.

Re-examining ferritin-bound iron: current and developing clinical tools.

Iron is a highly important metal ion cofactor within the human body, necessary for haemoglobin synthesis, and required by a wide range of enzymes for essential metabolic processes. Iron deficiency and overload both pose significant health concerns and are relatively common world-wide health hazards. Effective measurement of total iron stores is a primary tool for both identifying abnormal iron levels and tracking changes in clinical settings. Population based data is also essential for tracking nutritional trends. This review article provides an overview of the strengths and limitations associated with current techniques for diagnosing iron status, which sets a basis to discuss the potential of a new serum marker - ferritin-bound iron - and the improvement it could offer to iron assessment.

Nonmonotonic Superparamagnetic Behavior of the Ferritin Iron Core Revealed via Quantum Spin Relaxometry.

Ferritin is the primary storage protein in our body and is of significant interest in biochemistry, nanotechnology, and condensed matter physics. More specifically within this sphere of interest are the magnetic properties of the iron core of ferritin, which have been utilized as a contrast agent in applications such as magnetic resonance imaging. This magnetism depends on both the number of iron atoms present, L, and the nature of the magnetic ordering of their electron spins. In this work, we create a series of ferritin samples containing homogeneous iron loads and apply diamond-based quantum spin relaxometry to systematically study their room temperature magnetic properties. We observe anomalous magnetic behavior that can be explained using a theoretical model detailing a morphological change to the iron core occurring at relatively low iron loads. This model provides an L0.35±0.06 scaling of the uncompensated Fe spins, in agreement with previous theoretical predictions. The necessary inclusion of this morphological change within the model is also supported by electron microscopy studies of ferritin with low iron content. This provides evidence for a magnetic consequence of this morphological change and positions diamond-based quantum spin relaxometry as an effective, noninvasive tool for probing the magnetic properties of metalloproteins. The low detection limit (ferritin 2% loaded at a concentration of 7.5 ± 0.4 µg/mL) also makes this a promising method for precision applications where low analyte concentrations are unavoidable, such as in biological research or even clinical analysis.

Restoration of leptin responsiveness in diet-induced obese mice using an optimized leptin analog in combination with exendin-4 or FGF21.

The identification of leptin as a mediator of body weight regulation provided much initial excitement for the treatment of obesity. Unfortunately, leptin monotherapy is insufficient in reversing obesity in rodents or humans. Recent findings suggest that amylin is able to restore leptin sensitivity and when used in combination with leptin enhances body weight loss in obese rodents and humans. However, as the uniqueness of this combination therapy remains unclear, we assessed whether co-administration of leptin with other weight loss-inducing hormones equally restores leptin responsiveness in diet-induced obese (DIO) mice. Accordingly, we report here the design and characterization of a series of site-specifically enhanced leptin analogs of high potency and sustained action that, when administered in combination with exendin-4 or fibroblast growth factor 21 (FGF21), restores leptin responsiveness in DIO mice after an initial body weight loss of 30%. Using either combination, body weight loss was enhanced compared with either exendin-4 or FGF21 monotherapy, and leptin alone was sufficient to maintain the reduced body weight. In contrast, leptin monotherapy proved ineffective when identical weight loss was induced by caloric restriction alone over a comparable time. Accordingly, we find that a hypothalamic counter-regulatory response to weight loss, assessed using changes in hypothalamic agouti related peptide (AgRP) levels, is triggered by caloric restriction, but blunted by treatment with exendin-4. We conclude that leptin re-sensitization requires pharmacotherapy but does not appear to be restricted to a unique signaling pathway. Our findings provide preclinical evidence that high activity, long-acting leptin analogs are additively efficacious when used in combination with other weight-lowering agents.

Engaging with communities to foster health: the experience of inner-city children and families with learning circles.

The authors briefly introduce a clinical outreach initiative that is innovative because of the types of partnerships that have been formed within an inner-city community context. The initiative was designed to foster access to primary health care and specialized services for children and families who are vulnerable because of their social and material circumstances.Through ongoing engagement and dialogue, the clinicians and the community have developed a number of points of engagement with the children and families.The authors use the case of Learning Circles to describe ways in which Indigenous knowledge and ways of being influenced the approaches taken to working with children and families. They reflect upon the ways in which this approach influenced community engagement and consider its potential for achieving health equity.

The Emergence of Gender Associations in Child Language Development.

Gender associations have been a long-standing research topic in psychological and social sciences. Although it is known that children learn aspects of gender associations at a young age, it is not well understood how they might emerge through the course of development. We investigate whether gender associations, such as the association of dresses with women and bulldozers with men, are reflected in the linguistic communication of young children from ages 1-5. Drawing on recent methods from machine learning, we use word embeddings derived from large text corpora including news articles and web pages as a proxy for gender associations in society, and we compare those with the gender associations of words uttered by caretakers and children in children's linguistic environment. We quantify gender associations in childhood language through gender probability, which measures the extent to which word usage frequencies in speech to and by girls and boys are gender-skewed. By analyzing 4,875 natural conversations between children and their caretakers in North America, we find that frequency patterns in word usage of both caretakers and children correlate strongly with the gender associations captured in word embeddings through the course of development. We discover that these correlations diminish from the 1970s to the 1990s. Our work suggests that early linguistic communication and social changes may jointly contribute to the formation of gender associations in childhood.

A new glucagon and GLP-1 co-agonist eliminates obesity in rodents.

We report the efficacy of a new peptide with agonism at the glucagon and GLP-1 receptors that has potent, sustained satiation-inducing and lipolytic effects. Selective chemical modification to glucagon resulted in a loss of specificity, with minimal change to inherent activity. The structural basis for the co-agonism appears to be a combination of local positional interactions and a change in secondary structure. Two co-agonist peptides differing from each other only in their level of glucagon receptor agonism were studied in rodent obesity models. Administration of PEGylated peptides once per week normalized adiposity and glucose tolerance in diet-induced obese mice. Reduction of body weight was achieved by a loss of body fat resulting from decreased food intake and increased energy expenditure. These preclinical studies indicate that when full GLP-1 agonism is augmented with an appropriate degree of glucagon receptor activation, body fat reduction can be substantially enhanced without any overt adverse effects.

Adipocyte LDL receptor-related protein-1 expression modulates postprandial lipid transport and glucose homeostasis in mice.

Diet-induced obesity and its serious consequences such as diabetes, cardiovascular disease, and cancer are rapidly becoming a major global health threat. Therefore, understanding the cellular and molecular mechanisms by which dietary fat causes obesity and diabetes is of paramount importance in order to identify preventive and therapeutic strategies. Increased dietary fat intake results in high plasma levels of triglyceride-rich lipoproteins (TGRL). Tissue uptake of TGRL has been shown to promote glucose intolerance. We generated mice with an adipocyte-specific inactivation of the multifunctional receptor LDL receptor-related protein-1 (LRP1) to determine its role in mediating the effects of TGRL on diet-induced obesity and diabetes. Knockout mice displayed delayed postprandial lipid clearance, reduced body weight, smaller fat stores, lipid-depleted brown adipocytes, improved glucose tolerance, and elevated energy expenditure due to enhanced muscle thermogenesis. We further demonstrated that inactivation of adipocyte LRP1 resulted in resistance to dietary fat-induced obesity and glucose intolerance. These findings identify LRP1 as a critical regulator of adipocyte energy homeostasis, where functional disruption leads to reduced lipid transport, increased insulin sensitivity, and muscular energy expenditure.

Metabolic control by S6 kinases depends on dietary lipids.

Targeted deletion of S6 kinase (S6K) 1 in mice leads to higher energy expenditure and improved glucose metabolism. However, the molecular mechanisms controlling these effects remain to be fully elucidated. Here, we analyze the potential role of dietary lipids in regulating the mTORC1/S6K system. Analysis of S6K phosphorylation in vivo and in vitro showed that dietary lipids activate S6K, and this effect is not dependent upon amino acids. Comparison of male mice lacking S6K1 and 2 (S6K-dko) with wt controls showed that S6K-dko mice are protected against obesity and glucose intolerance induced by a high-fat diet. S6K-dko mice fed a high-fat diet had increased energy expenditure, improved glucose tolerance, lower fat mass gain, and changes in markers of lipid metabolism. Importantly, however, these metabolic phenotypes were dependent upon dietary lipids, with no such effects observed in S6K-dko mice fed a fat-free diet. These changes appear to be mediated via modulation of cellular metabolism in skeletal muscle, as shown by the expression of genes involved in energy metabolism. Taken together, our results suggest that the metabolic functions of S6K in vivo play a key role as a molecular interface connecting dietary lipids to the endogenous control of energy metabolism.

Ghrelin Receptor Deficiency does not Affect Diet-Induced Atherosclerosis in Low-Density Lipoprotein Receptor-Null Mice.

OBJECTIVE: Ghrelin, a stomach-derived, secreted peptide, and its receptor (growth hormone secretagogue receptor, GHSR) are known to modulate food intake and energy homeostasis. The ghrelin system is also expressed broadly in cardiovascular tissues. Since ghrelin has been associated with anti-inflammatory and anti-atherogenic properties, but is also well known to promote obesity and impair glucose metabolism, we investigated whether ghrelin has any impact on the development of atherosclerosis. The hypothesis that endogenous ghrelin signaling may be involved in atherosclerosis has not been tested previously. METHODS AND RESULTS: We crossed ghrelin receptor knockout mice (GHSr(-/-)) into a low-density lipoprotein receptor-null (Ldlr(-/-)) mouse line. In this model, atherosclerotic lesions were promoted by feeding a high-fat, high-cholesterol Western-type diet for 13 months, following a standard protocol. Body composition and glucose homeostasis were similar between Ldlr(-/-) and Ldlr/GHSR(-/-)ko mice throughout the study. Absence or presence of GHSr did not alter the apolipoprotein profile changes in response to diet exposure on an LDLRko background. Atherosclerotic plaque volume in the aortic arch and thoracic aorta were also not affected differentially in mice without ghrelin signaling due to GHSR gene disruption as compared to control LDLRko littermates. In light of the associations reported for ghrelin with cardiovascular disease in humans, the lack of a phenotype in these loss-of-function studies in mice suggests no direct role for endogenous ghrelin in either the inhibition or the promotion of diet-induced atherosclerosis. CONCLUSION: These data indicate that, surprisingly, the complex and multifaceted actions of endogenous ghrelin receptor mediated signaling on the cardiovascular system have minimal direct impact on atherosclerotic plaque progression as based on a loss-of-function mouse model of the disease.

Melanocortin signaling in the CNS directly regulates circulating cholesterol.

Cholesterol circulates in the blood in association with triglycerides and other lipids, and elevated blood low-density lipoprotein cholesterol carries a risk for metabolic and cardiovascular disorders, whereas high-density lipoprotein (HDL) cholesterol in the blood is thought to be beneficial. Circulating cholesterol is the balance among dietary cholesterol absorption, hepatic synthesis and secretion, and the metabolism of lipoproteins by various tissues. We found that the CNS is also an important regulator of cholesterol in rodents. Inhibiting the brain's melanocortin system by pharmacological, genetic or endocrine mechanisms increased circulating HDL cholesterol by reducing its uptake by the liver independent of food intake or body weight. Our data suggest that a neural circuit in the brain is directly involved in the control of cholesterol metabolism by the liver.

Defective lipid delivery modulates glucose tolerance and metabolic response to diet in apolipoprotein E-deficient mice.

OBJECTIVE: Apolipoprotein E (ApoE) regulates plasma lipid levels via modulation of lipolysis and serving as ligand for receptor-mediated clearance of triglyceride (TG)-rich lipoproteins. This study tested the impact of modulating lipid delivery to tissues on insulin responsiveness and diet-induced obesity. RESEARCH DESIGN AND METHODS: ApoE(+/+) and apoE(-/-) mice were placed on high-fat-high-sucrose diabetogenic diet or control diet for 24 weeks. Plasma TG clearance, glucose tolerance, and tissue uptake of dietary fat and glucose were assessed. RESULTS: Plasma TG clearance and lipid uptake by adipose tissue were impaired, whereas glucose tolerance was improved in control diet-fed apoE(-/-) mice compared with apoE(+/+) mice after an oral lipid load. Fat mass was reduced in apoE(-/-) mice compared with apoE(+/+) mice under both dietary conditions. The apoE(-/-) mice exhibited lower body weight and insulin levels than apoE(+/+) mice when fed the diabetogenic diet. Glucose tolerance and uptake by muscle and brown adipose tissue (BAT) was also improved in mice lacking apoE when fed the diabetogenic diet. Indirect calorimetry studies detected no difference in energy expenditure and respiratory quotient between apoE(+/+) and apoE(-/-) mice on control diet. Energy expenditure and uncoupling protein-1 expression in BAT were slightly but not significantly increased in apoE(-/-) mice on diabetogenic diet. CONCLUSIONS: These results demonstrated that decreased lipid delivery to insulin-sensitive tissues improves insulin sensitivity and ameliorates diet-induced obesity.