Pharmacological modulation of RORα controls fat browning, adaptive thermogenesis, and body weight in mice.

Beiging is an attractive therapeutic strategy to fight against obesity and its side metabolic complications. The loss of function of the nuclear transcription factor RORα has been related to a lean phenotype with higher thermogenesis in sg/sg mice lacking this protein. Here we show that pharmacological modulation of RORα activity exerts reciprocal and cell-autonomous effect on UCP1 expression ex vivo, in cellulo, and in vivo.

Adipocyte Glucocorticoid Receptor Deficiency Promotes Adipose Tissue Expandability and Improves the Metabolic Profile Under Corticosterone Exposure.

Widely used for their anti-inflammatory and immunosuppressive properties, glucocorticoids are nonetheless responsible for the development of diabetes and lipodystrophy. Despite an increasing number of studies focused on the adipocyte glucocorticoid receptor (GR), its precise role in the molecular mechanisms of these complications has not been elucidated. In keeping with this goal, we generated a conditional adipocyte-specific murine model of GR invalidation (AdipoGR knockout [KO] mice).

The nuclear retinoid-related orphan receptor RORα controls circadian thermogenic programming in white fat depots.

The RORα-deficient staggerer (sg/sg) mouse is lean and resistant to diet-induced obesity. Its thermogenic activity was shown to be increased not only in brown adipose tissue (BAT), but also in subcutaneous white adipose tissue (WAT) where UCP1 content was enhanced, however, without Prdm16 coexpression. Our observation of partial multilocular lipid morphology of WAT in sg/sg mice both in the inguinal and perigonadal sites led us to focus on the phenotype of both fat depots.

Depot-Specific Response of Adipose Tissue to Diet-Induced Inflammation: The Retinoid-Related Orphan Receptor α (RORα) Involved?

Objective: Epididymal adipose tissue (EAT), a visceral fat depot, is more closely associated with metabolic dysfunction than inguinal adipose tissue (IAT), a subcutaneous depot. This study evaluated whether the nuclear receptor RORα, which controls inflammatory processes, could be implicated.

Methods: EAT and IAT were compared in a RORα loss-of-function mouse (sg/sg) and in wild-type (WT) littermates, fed a standard diet (SD) or a Western diet (WD), to evaluate the impact of RORα expression on inflammatory status and on insulin sensitivity (IS) of each fat depot according to the diet.

NOV/CCN3: A New Adipocytokine Involved in Obesity-Associated Insulin Resistance.

Identification of new adipokines that potentially link obesity to insulin resistance represents a major challenge. We recently showed that NOV/CCN3, a multifunctional matricellular protein, is synthesized and secreted by adipose tissue, with plasma levels highly correlated with BMI. NOV involvement in tissue repair, fibrotic and inflammatory diseases, and cancer has been previously reported.

The nuclear retinoid-related orphan receptor-α regulates adipose tissue glyceroneogenesis in addition to hepatic gluconeogenesis.

Circadian rhythms have an essential role in feeding behavior and metabolism. RORα is a nuclear receptor involved in the interface of the circadian system and metabolism. The adipocyte glyceroneogenesis pathway derives free fatty acids (FFA) liberated by lipolysis to reesterification into triglycerides, thus regulating FFA homeostasis and fat mass.

Plasma NOV/CCN3 levels are closely associated with obesity in patients with metabolic disorders.

Objective: Evidence points to a founder of the multifunctional CCN family, NOV/CCN3, as a circulating molecule involved in cardiac development, vascular homeostasis and inflammation. No data are available on the relationship between plasma NOV/CCN3 levels and cardiovascular risk factors in humans. This study investigated the possible relationship between plasma NOV levels and cardiovascular risk factors in humans.

Glyceroneogenesis is inhibited through HIV protease inhibitor-induced inflammation in human subcutaneous but not visceral adipose tissue.

Glyceroneogenesis, a metabolic pathway that participates during lipolysis in the recycling of free fatty acids to triglycerides into adipocytes, contributes to the lipid-buffering function of adipose tissue. We investigated whether glyceroneogenesis could be affected by human immunodeficiency virus (HIV) protease inhibitors (PIs) responsible or not for dyslipidemia in HIV-infected patients. We treated explants obtained from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots from lean individuals.

Adipose tissue as a target of HIV-1 antiretroviral drugs. Potential consequences on metabolic regulations.

Adipose tissue redistribution occurred at first in HIV-infected patients about 15 years ago after initiation of combination antiretroviral treatment (ART) and the responsibility of drugs was rapidly considered. This lipodystrophic syndrome can associate lipoatrophy, affecting subcutaneous adipose tissue in priority with fat hypertrophy, in particular in the upper part of the body, and metabolic alterations, dyslipidemia and altered glucose tolerance with insulin resistance. The primary role of thymidine analogue reverse transcriptase inhibitors (tNRTI) in peripheral lipoatrophy has been clearly shown in vitro and in vivo, these drugs inducing a severe mitochondrial dysfunction and an increased oxidative stress together with fat inflammation leading to fat loss.

Human lipodystrophies: genetic and acquired diseases of adipose tissue.

Human lipodystrophies represent a heterogeneous group of diseases characterized by generalized or partial fat loss, with fat hypertrophy in other depots when partial. Insulin resistance, dyslipidemia and diabetes are generally associated, leading to early complications. Genetic forms are uncommon: recessive generalized congenital lipodystrophies result in most cases from mutations in the genes encoding seipin or the 1-acyl-glycerol-3-phosphate-acyltransferase 2(AGPAT2).

Cytosolic aspartate aminotransferase, a new partner in adipocyte glyceroneogenesis and an atypical target of thiazolidinedione.

We show that cytosolic aspartate aminotransferase (cAspAT) is involved in adipocyte glyceroneogenesis, a regulated pathway that controls fatty acid homeostasis by promoting glycerol 3-phosphate formation for fatty acid re-esterification during fasting. cAspAT activity, as well as the incorporation of [(14)C]aspartate into the neutral lipid fraction of 3T3-F442A adipocytes was stimulated by the thiazolidinedione (TZD) rosiglitazone. Conversely, the ratio of fatty acid to glycerol released into the medium decreased.

Rosiglitazone controls fatty acid cycling in human adipose tissue by means of glyceroneogenesis and glycerol phosphorylation.

Control of fatty acid homeostasis is crucial to prevent insulin resistance. During fasting, the plasma fatty acid level depends on triglyceride lipolysis and fatty acid re-esterification within fat cells. In rodents, Rosiglitazone controls fatty acid homeostasis by stimulating two pathways in the adipocytes, glyceroneogenesis and glycerol phosphorylation, that provide the glycerol 3-phosphate necessary for fatty acid re-esterification.

Proposed involvement of adipocyte glyceroneogenesis and phosphoenolpyruvate carboxykinase in the metabolic syndrome.

Elevated concentration of plasma non-esterified fatty acids (NEFA) is now recognized as a key factor in the onset of insulin-resistance and type 2 diabetes mellitus. During fasting, circulating NEFAs arise from white adipose tissue (WAT) as a consequence of lipolysis from stored triacylglycerols. However, a significant part of these FAs (30-70%) is re-esterified within the adipocyte, so that a recycling occurs and net FA output is much less than << true >> lipolysis.

Disregulated glyceroneogenesis: PCK1 as a candidate diabetes and obesity gene.

Genetics and diet interact to cause type 2 diabetes mellitus and obesity. PCK1 has been implicated as one of many genes associated with type 2 diabetes mellitus. The common assumption is that mutations in PCK1 lead to excessive glucose production through hepatic gluconeogenesis.

Regulation of glyceroneogenesis and phosphoenolpyruvate carboxykinase by fatty acids, retinoic acids and thiazolidinediones: potential relevance to type 2 diabetes.

Recent studies brought adipocyte glyceroneogenesis back to the fore as an important pathway in fatty acid homeostasis and underlined the key role played by cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) in this pathway. The present review analyses the mechanisms by which a series of hormones and nutrients affect PEPCK-C gene transcription and glyceroneogenesis and describes evidence for disregulation of this pathway in type 2 diabetes.

Thiazolidinediones block fatty acid release by inducing glyceroneogenesis in fat cells.

Thiazolidinediones are used to treat type 2 diabetes mellitus because they decrease plasma glucose, insulin, triglyceride, and fatty acid levels. Thiazolidinediones are agonists for peroxisome proliferator-activated receptor gamma, a nuclear receptor that is highly expressed in fat tissue. We identify glyceroneogenesis as a target of thiazolidinediones in cultured adipocytes and fat tissues of Wistar rats.

Glyceroneogenesis comes of age.

Glyceroneogenesis is a generally ignored metabolic pathway that occurs in adipose tissues and liver of mammalian species. This short review highlights a series of recent discoveries showing that glyceroneogenesis is important in lipid homeostasis.