Insulin receptor signaling in normal and insulin-resistant states

In the wake of the worldwide increase in type-2 diabetes, a major focus of research is understanding the signaling pathways impacting this disease. Insulin signaling regulates glucose, lipid, and energy homeostasis, predominantly via action on liver, skeletal muscle, and adipose tissue. Precise modulation of this pathway is vital for adaption as the individual moves from the fed to the fasted state. The positive and negative modulators acting on different steps of the signaling pathway, as well as the diversity of protein isoform interaction, ensure a proper and coordinated biological response to insulin in different tissues. Whereas genetic mutations are causes of rare and severe insulin resistance, obesity can lead to insulin resistance through a variety of mechanisms. Understanding these pathways is essential for development of new drugs to treat diabetes, metabolic syndrome, and their complications.

Apelin, a newly identified adipokine up-regulated by insulin and obesity

The results presented herein demonstrate that apelin is expressed and secreted by both human and mouse adipocytes. Apelin mRNA levels in isolated adipocytes are close to other cell types present in white adipose tissue or other organs known to express apelin such as kidney, heart, and to a lesser extent brown adipose tissue. Apelin expression is increased during adipocyte differentiation stage. A comparison of four different models of obesity in mice showed a large increase in both apelin expression in fat cells and apelin plasma levels in all the hyperinsulinemia-associated obesities and clearly demonstrated that obesity or high-fat feeding are not the main determinants of the rise of apelin expression. The lack of insulin in streptozotocin-treated mice is associated with a decreased expression of apelin in adipocytes. Furthermore, apelin expression in fat cells is strongly inhibited by fasting and recovered after refeeding, in a similar way to insulin. A direct regulation of apelin expression by insulin is observed in both human and mouse adipocytes and clearly associated with the stimulation of phosphatidylinositol 3-kinase, protein kinase C, and MAPK. These data provide evidence that insulin exerts a direct control on apelin gene expression in adipocytes. In obese patients, both plasma apelin and insulin levels were significantly higher, suggesting that the regulation of apelin by insulin could influence blood concentrations of apelin. The present work identifies apelin as a novel adipocyte endocrine secretion and focuses on its potential link with obesity-associated variations of insulin sensitivity status.

Apelin stimulates glucose utilization in normal and obese insulin-resistant mice

Adipose tissue (AT) secretes several adipokines that influence insulin sensitivity and potentially link obesity to insulin resistance. Apelin, a peptide present in different tissues, is also secreted by adipocytes. Apelin is upregulated in obese and hyperinsulinemic humans and mice. Although a tight relation exists between the regulation of apelin and insulin, it remains largely unknown whether apelin affects whole-body glucose utilization. Herein, we show that in chow-fed mice, acute intravenous injection of apelin has a powerful glucose-lowering effect associated with enhanced glucose utilization in skeletal muscle and AT. Through in vivo and in vitro pharmacological and genetic approaches, we demonstrate the involvement of endothelial NO synthase, AMP-activated protein kinase, and Akt in apelin-stimulated glucose uptake in soleus muscle. Remarkably, in obese and insulin-resistant mice, apelin restored glucose tolerance and increased glucose utilization. Apelin could thus represent a promising target in the management of insulin resistance.

The Canadian Neurological Scale: validation and reliability assessment

The Canadian Neurological Scale (CNS) was designed to monitor mentation and motor functions in stroke patients. We assessed its validity and reliability on a group of 157 patients with a diagnosis of acute cerebrovascular accident. We determined validity by (1) correlating scale items and total score with the standard neurologic examination; (2) exploring the scale's predictive power with different end points at 6 months--the initial CNS was a significant predictor of outcome; (3) showing that the CNS had higher correlation coefficients with the initial neurologic examination than the Glasgow Coma Scale; and (4) assessing the responsiveness of the scale to change in the neurologic status of stroke patients. Interobserver reliability, measured by kappa statistics on each scale item, was good. Accordingly, we established the validity and reliability of the CNS for its use in clinical studies and in the care of stroke patients.

Convergent neuroanatomical and behavioural evidence of an amygdala hypothesis of autism

In this study we report a convergence of behavioural and neuroanatomical evidence in support of an amygdala hypothesis of autism. We find that people with high-functioning autism (HFA) show neuropsychological profiles characteristic of the effects of amygdala damage, in particular selective impairment in the recognition of facial expressions of fear, perception of eye-gaze direction, and recognition memory for faces. Using quantitative magnetic resonance (MR) image analysis techniques, we find that the same individuals also show abnormalities of medial temporal lobe (MTL) brain structure, notably bilaterally enlarged amygdala volumes. These results combine to suggest that developmental malformation of the amygdala may underlie the social-cognitive impairments characteristic of HFA. This malformation may reflect incomplete neuronal pruning in early development.

Unfamiliar face recognition in relatively able autistic children

Two experiments were carried out assessing autistic children's recognition, discrimination, and fixation of unfamiliar faces and unfamiliar buildings. The experiments showed that (i) unfamiliar face recognition is impaired relative to normal peers, non-verbal ability matched and verbal ability matched controls. Relative to verbal ability matched controls (ii) recognition of buildings is normal; (iii) there is an enhanced discrepancy between face discrimination and buildings discrimination, in favour of buildings; and (iv) fixation is normal. Analysis of the results suggests that impaired face recognition does not result from impaired attention or discrimination.

Autotaxin is released from adipocytes, catalyzes lysophosphatidic acid synthesis, and activates preadipocyte proliferation. Up-regulated expression with adipocyte differentiation and obesity

Our group has recently demonstrated (Gesta, S., Simon, M., Rey, A., Sibrac, D., Girard, A., Lafontan, M., Valet, P., and Saulnier-Blache, J. S. (2002) J. Lipid Res. 43, 904-910) the presence, in adipocyte conditioned-medium, of a soluble lysophospholipase d-activity (LPLDact) involved in synthesis of the bioactive phospholipid lysophosphatidic acid (LPA). In the present report, LPLDact was purified from 3T3F442A adipocyte-conditioned medium and identified as the type II ecto-nucleotide pyrophosphatase phosphodiesterase, autotaxin (ATX). A unique ATX cDNA was cloned from 3T3F442A adipocytes, and its recombinant expression in COS-7 cells led to extracellular release of LPLDact. ATX mRNA expression was highly up-regulated during adipocyte differentiation of 3T3F442A-preadipocytes. This up-regulation was paralleled by the ability of newly differentiated adipocytes to release LPLDact and LPA. Differentiation-dependent up-regulation of ATX expression was also observed in a primary culture of mouse preadipocytes. Treatment of 3T3F442A-preadipocytes with concentrated conditioned medium from ATX-expressing COS-7 cells led to an increase in cell number as compared with concentrated conditioned medium from ATX non-expressing COS-7 cells. The specific effect of ATX on preadipocyte proliferation was completely suppressed by co-treatment with a LPA-hydrolyzing phospholipase, phospholipase B. Finally, ATX expression was found in mature adipocytes isolated from mouse adipose tissue and was substantially increased in genetically obese-diabetic db/db mice when compared with their lean siblings. In conclusion, the present work shows that ATX is responsible for the LPLDact released by adipocytes and exerts a paracrine control on preadipocyte growth via an LPA-dependent mechanism. Up-regulations of ATX expression with adipocyte differentiation and genetic obesity suggest a possible involvement of this released protein in the development of adipose tissue and obesity-associated pathologies.

Memory deficits in early infantile autism: some similarities to the amnesic syndrome

Autistic children were compared with control children on tasks in which retention was tested by different methods. In three tests of recall, using named pictures, written words and spoken words as test stimuli, autistic children were impaired in comparison with age-matched normal children and with controls matched for verbal ability. In one test of forced-choice recognition of pictures, autistic children were impaired in comparison with ability-matched controls. In three tests of cued recall, using named pictures, written words and spoken words as test stimuli, and acoustic, graphemic and semantic cues, autistic children were not impaired in comparison with normal age-matched controls. In one test of paired-associate learning using non-related word pairs as test stimuli autistic children were not impaired in comparison with normal age-matched controls. These experimental paradigms were similar to some that have been used to investigate the amnesic syndrome in man. Thus findings on paired-associate learning differ in autistic and amnesic subjects, but findings on recall, recognition and cued recall are comparable. A possible parallel between autism and amnesia is discussed.

TNFalpha up-regulates apelin expression in human and mouse adipose tissue

We have recently identified apelin as a novel adipokine up-regulated by insulin and obesity. Since obesity and insulin resistance are associated with chronically elevated levels of both insulin and TNFalpha, the present study was performed to investigate a putative regulation of apelin expression in adipocytes by TNFalpha. Herein, we report a tight correlation between apelin and TNFalpha expression in adipose tissue of lean and obese humans. Apelin regulation by TNFalpha was further studied in cultured explants of human adipose tissue. The endogenous expression of TNFalpha in adipocytes isolated from the explants was accompanied by a 6-9 h subsequent increase of apelin expression in adipocytes. This increase was reversed by inhibiting TNFalpha expression with 100 microM isobutylmethylxanthine. In different mouse models of obesity, expression of both TNFalpha and apelin was also significantly increased in adipocytes of obese mice. Furthermore, short-term exposure to an i.p. injection of TNFalpha in C57Bl6/J mice induced an increase of apelin expression in adipose tissue as well as apelin plasma levels. Finally, a direct positive effect of TNFalpha has been shown in differentiated 3T3F442A adipocytes on apelin expression and secretion. The signaling pathways of TNFalpha for the induction of apelin were dependent of PI3-kinase, c-Jun NH2-terminal kinase (JNK), and MAPK but not PKC activation. All together, these findings suggest that apelin might be a candidate to better understand potential links between obesity and associated disorders such as inflammation and insulin resistance.

Symbolic play in autism: a review

Experimental research into the symbolic play of autistic children is reviewed in an attempt to outline the nature of their deficit in this area. While many studies can be criticized on methodological grounds, there is good evidence for an impairment in the spontaneous symbolic play of autistic children, an impairment that appears to extend to cover spontaneous functional play also. However studies that have investigated elicited and instructed play have indicated that autistic children may have a capacity for symbolic play that they do not spontaneously exhibit. The implications of these findings for various hypotheses concerning a symbolic play deficit in autism are considered and directions for future research are outlined.

Memory impairments and communication in relatively able autistic children

Autistic people have specific memory difficulties. The effects of these difficulties on communication in relatively able autistic children and learning impaired controls were assessed in three experiments. The experiments tested the ability to: (1) carry out instructions; (2) ask questions without repetition; and (3) answer questions about past activities. When specific memory skills were required autistic children's communication was impaired relative to controls. When the need to use these skills was eliminated from the tasks the autistic children performed as well as controls. Some practical and theoretical implications of the findings are discussed.

Potential involvement of adipocyte insulin resistance in obesity-associated up-regulation of adipocyte lysophospholipase D/autotaxin expression

AIMS/HYPOTHESIS

Autotaxin is a lysophospholipase D that is secreted by adipocytes and whose expression is substantially up-regulated in obese, diabetic db/db mice. The aim of the present study was to depict the physiopathological and cellular mechanisms involved in regulation of adipocyte autotaxin expression.

METHODS

Autotaxin mRNAs were quantified in adipose tissue from db/db mice (obese and highly diabetic type 2), gold-thioglucose-treated (GTG) mice (highly obese and moderately diabetic type 2), high-fat diet-fed (HFD) mice (obese and moderately diabetic type 2), streptozotocin-treated mice (thin and diabetic type 1), and massively obese humans with glucose intolerance.

RESULTS

When compared to non-obese controls, autotaxin expression in db/db mice was significantly increased, but not in GTG, HFD, or streptozotocin-treated mice. During db/db mice development, up-regulation of autotaxin occurred only 3 weeks after the emergence of hyperinsulinaemia, and simultaneously with the emergence of hyperglycaaemia. Adipocytes from db/db mice exhibited a stronger impairment of insulin-stimulated glucose uptake than non-obese and HFD-induced obese mice. Autotaxin expression was up-regulated by treatment with TNFalpha (insulin resistance-promoting cytokine), and down-regulated by rosiglitazone treatment (insulin-sensitising compound) in 3T3F442A adipocytes. Finally, adipose tissue autotaxin expression was significantly up-regulated in patients exhibiting both insulin resistance and impaired glucose tolerance.

CONCLUSIONS/INTERPRETATION

The present work demonstrates the existence of a db/db-specific up-regulation of adipocyte autotaxin expression, which could be related to the severe type 2 diabetes phenotype and adipocyte insulin resistance, rather than excess adiposity in itself. It also showed that type 2 diabetes in humans is also associated with up-regulation of adipocyte autotaxin expression.

Memory for recent events in autistic children

An experiment is reported in which autistic children's memory for recent events was compared with that of normal age-matched and retarded age-and ability-matched controls. The autistic subjects' recall was significantly inferior to that of normal controls. Recent event memory correlated with a language measure in the autistic group and with a nonverbal measure in the retarded control group. These findings are discussed in terms of relationships between language and memory, and possible mechanisms underlying the distinctive pattern of memory ability and disability that occurs in autism.

Decreased resistin expression in mice with different sensitivities to a high-fat diet

The regulation of resistin, a new adipose-derived circulating factor, is the subject of controversy. In particular, the question of its modulation in obesity led to opposite results reported by two different groups. In the current study, we assayed adipocyte resistin mRNA using fluorescent real-time RT-PCR. We studied the expression of resistin in mice which are differently sensitive to diet-induced obesity: the FVB/n strain, which poorly responds to high-fat diet and transgenic mice that express human alpha 2A-AR in adipose tissue in the absence of beta 3-adrenergic receptor (AR) under the FVB genetic background which are highly sensitive to high-fat diet and develop hyperplastic obesity. We observed that FVB mice, which have no significant increased body weight after an 8-week high-fat diet period, exhibited no alteration of resistin expression. In contrast, the transgenic mice developing high-fat diet-induced obesity exhibited markedly downregulated adipocyte resistin mRNA. We also showed that obesity induced by gold thioglucose injection in FVB/n mice reduces the expression of resistin in isolated adipocytes. This argues for decreased expression of resistin as a hallmark of obesity. Moreover, our data show that feeding a high-fat diet is not a primary determinant of resistin regulation.

Relationships between symbolic play, functional play, verbal and non-verbal ability in young children

It is well established that certain aspects of play in young children are related to their emerging linguistic skills. The present study examined the relationships between functional play, symbolic play, non-verbal ability, and expressive and receptive language in normally developing children aged between 1 and 6 years using standardized assessment procedures, including a recently developed Test of Pretend Play (ToPP). When effects of chronological age were partialled out, symbolic play remained significantly correlated with both expressive and receptive language, but not with functional play or non-verbal ability; and functional play was only correlated significantly with expressive language. It is concluded that ToPP will provide practitioners with a useful way of assessing symbolic ability in children between the ages of 1 and 6 years, and will contribute to the assessment and diagnosis of a number of communication difficulties, and have implications for intervention.

Source monitoring by children with autism

The term "source monitoring" refers to the ability to distinguish the origins of memories. One type of source monitoring is reality monitoring-which means distinguishing internally and externally generated memories. This experiment examined reality monitoring by children with autism (with a mean mental age of 7 years 8 months). The children said several words and listened to another person say similar words. The children were then given a surprise memory test and asked to identify which words they had said and which the other person had said. The children with autism were compared to matched groups of normal children and children with mental retardation. There were no differences between the groups and, at least for this task, there was no evidence that children with autism have a deficit in their reality monitoring abilities.

Hand preference in autistic children and their parents

Hand preference was tested in groups of between 40 and 50 autistic children and in sex-, age-, and ability-matched controls. Results were also compared with existing findings on normal children. Small differences occurred between the groups in the directions which would be predicted on the assumption that mental subnormality is associated with delayed development of normal patterns of handedness, and on the hypothesis that autistic children as a group will show a persistent slightly increased tendency to use the left hand. Parents of the autistic group were also assessed for handedness. Contrary to the prediction of slightly increased sinistrality in this group of subjects, some indication of increased dextrality occurred. Results were discussed in relation to possible genetic factors in the etiology of autism.

Articulation in early childhood autism

Using a standardized articulation test, comparisons were made between the articulation of autistic children and (1) a group of predominantly subnormal language matched controls; (2) developmental receptive dysphasic controls. The autistic children's articulation was significantly superior to that of both control groups. The findings are discussed in relation to differences in the pattern of language impairment in the three groups.

Word fluency in high-functioning autistic children

The performance of a group of seven high-functioning autistic children on tests of word fluency was compared with that of controls of similar age and vocabulary level. The two groups performed equally well when generating words in response to familiar category cues. However, autistic children performed significantly less well than controls when generating miscellaneous words. Results are discussed in relation to semantic organization and memory in autism.

Immediate free recall in early childhood autism: another point of behavioural similarity with the amnesic syndrome

Autistic children were compared with age and ability matched controls on a test of immediate recall of word lists. Overall performance in the two groups was very similar. However, the overall recall scores were achieved differently by the two groups, the autistic subjects recalled significantly fewer earlier presented items and more later presented items than did controls. This finding is discussed in relation to the memory disabilities of adults suffering from the amnesic syndrome.

Generativity in the play of young people with autism

Examines the ability of young people with autism to generate ideas for play. Young people with autism, children with learning difficulties, and younger normal children were asked to generate 12 different actions and follow 12 instructions with a car and a doll. The young people with autism were impaired, relative to the controls, at generating original actions with the car, but were as able as the controls to follow the instructions. However, the young people with autism were not impaired at generating original actions with the doll. All three groups produced similar amounts of symbolic play. Possible explanations for the difference in results for the two toys are discussed.

Metamemory in children with autism

Five experiments are reported comparing metamemory abilities in children with autism, age- and language-matched mentally retarded children, and language-matched young normal controls. The mean language age of the participants in Experiment 1 was approximately 6 years, in Experiments 2, 3, and 4 approximately 8 years, and in Experiment 5 approximately 9 years. All the children were given one or more false belief tests. Experiment 1 assessed the children's understanding that a task variable (list length) and a person variable (age) will affect their own and others' performances on an immediate auditory-verbal recall task. Experiment 2 assessed the ability to utilize category cues in a picture recall task. Experiments 3 and 4 assessed the ability to verbalize strategies used in a memory span test and in one retrospective and two prospective memory situations. Experiment 5 assessed the children's knowledge and understanding of another person's memory. On the basis of available evidence and theory, we predicted that the children with autism would be impaired on all the metamemory tasks and that impairment would be associated with failure on tests of false belief. Our predictions were not supported. The children with autism were not impaired on any of the metamemory tasks, although they were less likely than controls to make spontaneous use of memory strategies involving other people. Unexpectedly few of the children failed the false belief tasks. These results are discussed in relation to theories concerning primary psychological deficits underlying autism.