Obesity-associated insulin resistance is correlated to adipose tissue vascular endothelial growth factors and metalloproteinase levels

<p>Abstract</p> <p>Background</p> <p>The expansion of adipose tissue is linked to the development of its vasculature, which appears to have the potential to regulate the onset of obesity. However, at present, there are no studies highlighting the relationship between human adipose tissue angiogenesis and obesity-associated insulin resistance (IR).</p> <p>Results</p> <p>Our aim was to analyze and compare angiogenic factor expression levels in both subcutaneous (SC) and omentum (OM) adipose tissues from morbidly obese patients (n = 26) with low (OB/L-IR) (healthy obese) and high (OB/H-IR) degrees of IR, and lean controls (n = 17). Another objective was to examine angiogenic factor correlations with obesity and IR.</p> <p>Here we found that <it>VEGF-A </it>was the isoform with higher expression in both OM and SC adipose tissues, and was up-regulated 3-fold, together with <it>MMP9 </it>in OB/L-IR as compared to leans. This up-regulation decreased by 23% in OB/-H-IR compared to OB/L-IR. On the contrary, <it>VEGF-B</it>, <it>VEGF-C </it>and <it>VEGF-D</it>, together with <it>MMP15 </it>was down-regulated in both OB/H-IR and OB/L-IR compared to lean patients. Moreover, <it>MMP9 </it>correlated positively and <it>VEGF-C</it>, <it>VEGF-D </it>and <it>MMP15 </it>correlated negatively with HOMA-IR, in both SC and OM.</p> <p>Conclusion</p> <p>We hereby propose that the alteration in <it>MMP15</it>, <it>VEGF-B</it>, <it>VEGF-C </it>and <it>VEGF-D </it>gene expression may be caused by one of the relevant adipose tissue processes related to the development of IR, and the up-regulation of <it>VEGF-A </it>in adipose tissue could have a relationship with the prevention of this pathology.</p

American Thyroid Association Guide to Investigating Thyroid Hormone Economy and Action in Rodent and Cell Models

Background: An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment ap-proaches for patients with thyroid disease. Summary: Important clinical practices in use today for the treatment of patients with hypothy-roidism, hyperthyroidism, or thyroid cancer, are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a se-ries of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings. Conclusions: It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Arachidonic acid stimulates DNA synthesis in brown preadipocytes through the activation of protein kinase C and MAPK. Biochimica et Biophysica Acta 1821:1309e1315

Abstract Arachidonic acid (AA) is a polyunsaturated fatty acid that stimulates the proliferation of many cellular types. We studied the mitogenic potential of AA in rat brown preadipocytes in culture and the signaling pathways involved. AA is a potent mitogen which induces 4-fold DNA synthesis in brown preadipocytes. The AA mitogenic effect increases by NE addition. AA also increases the mitogenic action of different growth factor combinations. Other unsaturated and saturated fatty acids do not stimulate DNA synthesis to the same extent as AA

Mechanisms of adaptation to iodine deficiency in rats: Thyroid status is tissue specific. Its relevance for man. Endocrinology 147

Many animals, man included, live in areas providing insufficient iodine (I) for optimal health. Degrees of I deficiency (ID) vary from mild-moderate to very severe, with quali-and quantitatively different negative consequences. To understand the mechanisms involved in adaptation to different grades of ID, we fed rats a low-iodine diet, plus additions resulting in a 250-fold range of I daily available to the thyroid, ranging from 5 g (adequate) down to 0.02 g I. We measured thyroid weight, total I, T 4 , T 3 , and type I 5 iodothyronine deiodinase (D1) activity, TSH, T 4 , free T 4 , and T 3 in plasma, T 4 and T 3 in 11 tissues, and two 5 deiodinase isoenzymes in four. TSHindependent thyroid autoregulation plays an important role in addition to TSH-dependent mechanisms in the adaptation to ID, avoiding a decrease of T 3 in plasma and most tissues, despite a marked decrease of plasma T 4 , whereas extrathyroidal responses of D2 mitigate T 3 deficiency in tissues in which T 3 is mostly generated from T 4 . We focused on mild and moderate ID, the least investigated experimentally, despite its current frequency in industrialized countries. The novel and important finding of our study is that thyroid status cannot be defined for the animal as a whole: at all grades of ID, T 3 is simultaneously elevated, normal, and low in different tissues. Present findings in mild-moderate ID draw attention to the importance, for man, of the resulting hypothyroxinemia that may affect mental functions and neurodevelopment of the inhabitants, even when they do not have the increased TSH or clinical hypothyroidism, often wrongly attributed to them

The Targeted Inactivation of TRβ Gene in Thyroid Follicular Cells Suggests a New Mechanism of Regulation of Thyroid Hormone Production

International audienceThyroid epithelial cells, or thyrocytes, express functional thyroid hormone receptors but no precise role has yet been assigned to either TRα or TRβ in the thyroid gland. In this study, we analyzed the impact of inactivating the TRβ gene in the thyroid of mice. First, we generated a mouse line named Thyr-Cre, expressing the Cre recombinase under the control of the thyroglobulin gene promoter, which led to a complete recombination of floxed genes in thyrocytes. Thyr-Cre mice were then crossed with TRβ floxed mice (TRβflox/flox) to obtain a thyrocyte-selective deletion of TRβ. Thyr-TRβ−/− mice were characterized by a decrease in the size and functional activity of the thyroid gland. These alterations were associated with a decrease in plasma TSH concentration. Surprisingly, Thyr-TRβ−/− displayed elevated serum T4 and rT3 concentrations with no significant change in serum T3 levels. Their intrathyroidal free T4 and rT3 contents were also elevated, whereas the ratio of serum T4 to thyroid free T4 was decreased by comparison with wild-type littermates. Also, within the thyroid, deiodinases D1 and D2 were reduced as well as the expression levels of genes encoding monocarboxylate transporters (Mct8 and Mct10). Such a decrease in intrathyroidal deiodination of T4 and in the expression of genes encoding thyroid hormone transporters may contribute to the primary overproduction of T4 observed in Thyr-TRβ−/− mice. In conclusion, these data show that the control of thyroid hormone production involves not only TRβ-dependent mechanisms acting at the level of hypothalamus and pituitary but also TRβ-dependent mechanisms acting at the thyroid level

Cerebral Cortex Hyperthyroidism of Newborn Mct8-Deficient Mice Transiently Suppressed by Lat2 Inactivation

Thyroid hormone entry into cells is facilitated by transmembrane transporters. Mutations of the specific thyroid hormone transporter, MCT8 (Monocarboxylate Transporter 8, SLC16A2) cause an X-linked syndrome of profound neurological impairment and altered thyroid function known as the Allan-Herndon-Dudley syndrome. MCT8 deficiency presumably results in failure of thyroid hormone to reach the neural target cells in adequate amounts to sustain normal brain development. However during the perinatal period the absence of Mct8 in mice induces a state of cerebral cortex hyperthyroidism, indicating increased brain access and/or retention of thyroid hormone. The contribution of other transporters to thyroid hormone metabolism and action, especially in the context of MCT8 deficiency is not clear. We have analyzed the role of the heterodimeric aminoacid transporter Lat2 (Slc7a8), in the presence or absence of Mct8, on thyroid hormone concentrations and on expression of thyroid hormone-dependent cerebral cortex genes. To this end we generated Lat2-/-, and Mct8-/yLat2-/- mice, to compare with wild type and Mct8-/y mice during postnatal development. As described previously the single Mct8 KO neonates had a transient increase of 3,5,3′-triiodothyronine concentration and expression of thyroid hormone target genes in the cerebral cortex. Strikingly the absence of Lat2 in the double Mct8Lat2 KO prevented the effect of Mct8 inactivation in newborns. The Lat2 effect was not observed from postnatal day 5 onwards. On postnatal day 21 the Mct8 KO displayed the typical pattern of thyroid hormone concentrations in plasma, decreased cortex 3,5,3′-triiodothyronine concentration and Hr expression, and concomitant Lat2 inactivation produced little to no modifications. As Lat2 is expressed in neurons and in the choroid plexus, the results support a role for Lat2 in the supply of thyroid hormone to the cerebral cortex during early postnatal development.</p