Prospective analyses of white adipose tissue gene expression in relation to long-term body weight changes.

BACKGROUND: Transcriptome analysis of abdominal subcutaneous white adipose tissue (sWAT) has identified important obesity-associated disturbances. However, the relation between sWAT transcriptome and long-term future changes in body weight remains elusive. OBJECTIVE: To investigate sWAT transcriptome signatures before and after long-term weight changes and assess their predictive value for body weight changes. DESIGN: A total of 56 women were followed longitudinally and subdivided into weight-stable (WS, n = 25), weight-gaining (WG, n = 14) and weight-losing (WL, n = 17) groups between baseline and follow-up (13 ± 1 years). The fasting sWAT transcriptome was analyzed by gene microarray at baseline and follow-up. Key genes associated with weight changes were validated using quantitative real-time PCR. RESULTS: In total 285 transcripts exhibited difference (FDR < 30%) in expression fold change over time between WL and WS women. WL women displayed decreased pro-inflammatory (NLRP3) but increased insulin-response gene (FASN and GLUT4) expression over time. In comparison, 461 transcripts displayed difference in expression fold change over time between WG and WS women (P < 0.05). Genes involved in autophagic processes (CDK5, SQSTM1 and FBXL2) were generally upregulated in WG women. At baseline, 307 and 302 transcripts were differentially expressed (FDR < 30%) in WL and WG women, respectively, when independently compared against WS women. Baseline expression of adipogenic and lipogenic genes (PPARG, IRS2 and HACD2) was lower, while pro-fibrotic (COL6A1) was higher, in WL than WS women; whereas protein processing genes were lower expressed in WG than in WS women. CONCLUSION: In adult women, long-term body weight change associates with altered sWAT transcriptome. Expression of genes associated with inflammation, insulin response, adipogenesis and lipogenesis are linked to weight loss. However, other pathways such as autophagy not only associate but also predict future weight gain suggesting that intrinsic factors in sWAT impact tissue expansion.

Epigenetic Programming of Adipose Tissue in the Progeny of Obese Dams.

According to the Developmental Origin of Health and Disease (DOHaD) concept, maternal obesity and the resulting accelerated growth in neonates predispose offspring to obesity and associated metabolic diseases that may persist across generations. In this context, the adipose tissue has emerged as an important player due to its involvement in metabolic health, and its high potential for plasticity and adaptation to environmental cues. Recent years have seen a growing interest in how maternal obesity induces long-lasting adipose tissue remodeling in offspring and how these modifications could be transmitted to subsequent generations in an inter- or transgenerational manner. In particular, epigenetic mechanisms are thought to be key players in the developmental programming of adipose tissue, which may partially mediate parts of the transgenerational inheritance of obesity. This review presents data supporting the role of maternal obesity in the developmental programming of adipose tissue through epigenetic mechanisms. Inter- and transgenerational effects on adipose tissue expansion are also discussed in this review.

Exome-chip association analysis reveals an Asian-specific missense variant in PAX4 associated with type 2 diabetes in Chinese individuals.

AIMS/HYPOTHESIS: Genome-wide association studies (GWASs) have identified many common type 2 diabetes-associated variants, mostly at the intronic or intergenic regions. Recent advancements of exome-array genotyping platforms have opened up a novel means for detecting the associations of low-frequency or rare coding variants with type 2 diabetes. We conducted an exomechip association analysis to identify additional type 2 diabetes susceptibility variants in the Chinese population. METHODS: An exome-chip association study was conducted by genotyping 5640 Chinese individuals from Hong Kong, using a custom designed exome array, the Asian Exomechip. Single variant association analysis was conducted on 77,468 single nucleotide polymorphisms (SNPs). Fifteen SNPs were subsequently genotyped for replication analysis in an independent Chinese cohort comprising 12,362 individuals from Guangzhou. A combined analysis involving 7189 cases and 10,813 controls was performed. RESULTS: In the discovery stage, an Asian-specific coding variant rs2233580 (p.Arg192His) in PAX4, and two variants at the known loci, CDKN2B-AS1 and KCNQ1, were significantly associated with type 2 diabetes with exome-wide significance (p discovery < 6.45 × 10-7). The risk allele (T) of PAX4 rs2233580 was associated with a younger age at diabetes diagnosis. This variant was replicated in an independent cohort and demonstrated a stronger association that reached genome-wide significance (p meta-analysis [p meta] = 3.74 × 10-15) in the combined analysis. CONCLUSIONS/INTERPRETATION: We identified the association of a PAX4 Asian-specific missense variant rs2233580 with type 2 diabetes in an exome-chip association analysis, supporting the involvement of PAX4 in the pathogenesis of type 2 diabetes. Our findings suggest PAX4 is a possible effector gene of the 7q32 locus, previously identified from GWAS in Asians.

Adipose-specific inactivation of JNK alleviates atherosclerosis in apoE-deficient mice.

Both atherosclerosis and obesity, an independent atherosclerotic risk factor, are associated with enhanced systemic inflammation. Obesity is also characterized by increased adipose tissue inflammation. However, the molecular mechanism underlying the accelerated atherosclerosis in obesity remains unclear. In obesity, activation of c-Jun N-terminal kinase (JNK) contributes to adipose tissue inflammation. The present study investigated whether the suppression of fat inflammation through adipose-specific JNK inactivation could protect against atherosclerosis in mice. ApoE-/- mice were cross-bred with transgenic mice with adipose-specific expression of a dominant negative form of JNK (dnJNK) to generate apoE-/-/dnJNK (ADJ) mice. ADJ mice treated with a high-fat-high-cholesterol diet exhibited significant attenuations of visceral fat and systemic inflammation without changes in lipid or glucose metabolism, and were protected against atherosclerosis, when compared with apoE-/- mice. Lean apoE-/- mice that received transplantation of visceral fat from obese wild-type donor mice for 4 weeks showed exacerbated systemic inflammation and atherosclerotic plaque formation. Conversely, apoE-/- recipients carrying a visceral fat graft from obese dnJNK donors were protected against enhanced systemic inflammation and atherogenesis. The beneficial effects of adipose-specific JNK inactivation on atherogenesis in apoE-/- recipients were significantly compromised by continuous infusion of recombinant adipocyte-fatty acid-binding protein (A-FABP), previously shown to interact with JNK via a positive feedback loop to modulate inflammatory responses. Together these data suggested that enhanced atherosclerosis in obesity can be attributed, at least in part, to a distant cross-talk between visceral fat and the vasculature, mediated by the release of proinflammatory cytokines, such as A-FABP, from the inflamed visceral adipose tissue with JNK activation.

Fibroblastic reticular cells in lymph node potentiate white adipose tissue beiging through neuro-immune crosstalk in male mice.

Lymph nodes (LNs) are always embedded in the metabolically-active white adipose tissue (WAT), whereas their functional relationship remains obscure. Here, we identify fibroblastic reticular cells (FRCs) in inguinal LNs (iLNs) as a major source of IL-33 in mediating cold-induced beiging and thermogenesis of subcutaneous WAT (scWAT). Depletion of iLNs in male mice results in defective cold-induced beiging of scWAT. Mechanistically, cold-enhanced sympathetic outflow to iLNs activates ß1- and ß2-adrenergic receptor (AR) signaling in FRCs to facilitate IL-33 release into iLN-surrounding scWAT, where IL-33 activates type 2 immune response to potentiate biogenesis of beige adipocytes. Cold-induced beiging of scWAT is abrogated by selective ablation of IL-33 or ß1- and ß2-AR in FRCs, or sympathetic denervation of iLNs, whereas replenishment of IL-33 reverses the impaired cold-induced beiging in iLN-deficient mice. Taken together, our study uncovers an unexpected role of FRCs in iLNs in mediating neuro-immune interaction to maintain energy homeostasis.

The long noncoding RNA ADIPINT regulates human adipocyte metabolism via pyruvate carboxylase.

The pleiotropic function of long noncoding RNAs is well recognized, but their direct role in governing metabolic homeostasis is less understood. Here, we describe a human adipocyte-specific lncRNA, ADIPINT, that regulates pyruvate carboxylase, a pivotal enzyme in energy metabolism. We developed an approach, Targeted RNA-protein identification using Orthogonal Organic Phase Separation, which identifies that ADIPINT binds to pyruvate carboxylase and validated the interaction with electron microscopy. ADIPINT knockdown alters the interactome and decreases the abundance and enzymatic activity of pyruvate carboxylase in the mitochondria. Reduced ADIPINT or pyruvate carboxylase expression lowers adipocyte lipid synthesis, breakdown, and lipid content. In human white adipose tissue, ADIPINT expression is increased in obesity and linked to fat cell size, adipose insulin resistance, and pyruvate carboxylase activity. Thus, we identify ADIPINT as a regulator of lipid metabolism in human white adipocytes, which at least in part is mediated through its interaction with pyruvate carboxylase.

Human White Adipose Tissue Displays Selective Insulin Resistance in the Obese State.

Selective hepatic insulin resistance is a feature of obesity and type 2 diabetes. Whether similar mechanisms operate in white adipose tissue (WAT) of those with obesity and to what extent these are normalized by weight loss are unknown. We determined insulin sensitivity by hyperinsulinemic euglycemic clamp and insulin response in subcutaneous WAT by RNA sequencing in 23 women with obesity before and 2 years after bariatric surgery. To control for effects of surgery, women postsurgery were matched to never-obese women. Multidimensional analyses of 138 samples allowed us to classify the effects of insulin into three distinct expression responses: a common set was present in all three groups and included genes encoding several lipid/cholesterol biosynthesis enzymes; a set of obesity-attenuated genes linked to tissue remodeling and protein translation was selectively regulated in the two nonobese states; and several postobesity-enriched genes encoding proteins involved in, for example, one-carbon metabolism were only responsive to insulin in the women who had lost weight. Altogether, human WAT displays a selective insulin response in the obese state, where most genes are normalized by weight loss. This comprehensive atlas provides insights into the transcriptional effects of insulin in WAT and may identify targets to improve insulin action.

Idiopathic central precocious puberty in a Klinefelter patient: highlights on gonadotropin levels and pathophysiology.

BACKGROUND: Idiopathic central precocious puberty (ICPP) is supposed to be non-existent in a context of testicular destruction that is typically present in Klinefelter syndrome (KS). Herein, we describe a rare case of ICPP in a Klinefelter patient (47,XXY) with 2 maternal X chromosomes. Moreover, we highlight the differences in gonadotropin levels in comparison to males with ICPP and a normal karyotype. CASE PRESENTATION: An 8 years old boy with a history of cryptorchidism was evaluated for precocious puberty (Tanner staging: P2/G3). Both testes measured 25x35mm. His hormonal profile confirmed a central origin of precocious puberty with high serum testosterone (4.3 ng/ml), luteinizing hormone [LH (3.5 UI/l)] and follicle stimulating hormone [FSH (7.7 UI/l)] levels. Luteinizing hormone-releasing hormone (LHRH) test amplified LH and FSH secretion to 24 and 14 UI/l respectively. Brain magnetic resonance imaging (MRI) was normal. No MKRN3 mutation was detected. He was treated for ICPP for two years. During puberty, he suffered from hypergonadotropic hypogonadism leading to the diagnosis of KS (47,XXY karyotype). Chromosomal analysis by fluorescent multiplex polymerase chain reaction (PCR) using X chromosome microsatellite markers identified 2 maternal X chromosomes. Analysing 8 cases of KS developing ICPP (our reported case and 7 other published cases) revealed that these KS patients with ICPP have higher LH and FSH levels during ICPP episode than in ICPP patients with a normal karyotype (ICPP with KS vs ICPP with a normal karyotype: LH levels 9.4 ± 12 vs 1.1 ± 0.6 UI/l; FSH levels 23.1 ± 38.5 vs 2.7 ± 1.5 UI/l). Furthermore, their response to gonadotropin-releasing hormone (GnRH) stimulation is characterized by excessive LH and FSH secretion (LH levels post-GnRH: 58 ± 48 vs 15.5 ± 0.8 UI/l; FSH levels post-GnRH: 49.1 ± 62.1 vs 5.7 ± 3.9 UI/l). CONCLUSIONS: ICPP in boys is extremely rare. The pathophysiology of ICPP in KS is unknown. However, maternal X supplementary chromosome and early testicular destruction may play a significant role in the initiation of ICPP, in part explaining the relative "overrepresentation of ICPP in KS. Thus, karyotype analysis could be considered for boys suffering from ICPP, especially if testicular size is smaller or gonadotropins are significantly elevated.

Possible Modifying Effect of Hemoglobin A1c on Genetic Susceptibility to Severe Diabetic Retinopathy in Patients With Type 2 Diabetes.

Purpose: Glycemic control has been recognized as an important modifiable risk factor for diabetic retinopathy (DR). Whether hemoglobin A1c (HbA1c), as an indicator of glycemic control, could modify the genetic susceptibility to severe DR remains to be investigated. This study aimed to investigate whether HbA1c could modulate the genetic susceptibility to severe DR in Chinese patients with type 2 diabetes. Methods: A total of 3,093 Chinese individuals with type 2 diabetes were included in the cross-sectional case-control study: 1,051 with sight-threatening DR (STDR) and 2,042 without STDR. Sixty-nine top-ranked single nucleotide polymorphisms (SNPs) identified from previous genome-wide association studies were examined for their associations with STDR and proliferative DR as a subgroup analysis. SNPs showing suggestive associations with DR were examined in the stratified analysis by dichotomized HbA1c (<7% vs. ≥7%). An interaction analysis was performed by including an interaction term of SNP × HbA1c in the regression model. Results: Four SNPs showed suggestive associations with STDR. In the stratified analysis, patients with adequate glycemic control (HbA1c <7%) had a 42% lower risk of STDR for carrying each additional protective C allele of COL5A1 rs59126004 (P = 1.76 × 10-4; odds ratio, 0.58; 95% confidence interval, 0.44-0.77). rs59126004 demonstrated a significant interaction with dichotomized HbA1c on the risk of STDR (Pinteraction = 1.733 × 10-3). In the subgroup analysis for proliferative DR, the protective effect of rs59126004 was even more pronouncedly demonstrated (P = 8.35 × 10-5; odds ratio, 0.37; 95% confidence interval, 0.22-0.60) and it showed similar interactions with dichotomized HbA1c (Pinteraction = 1.729 × 10-3). Conclusions: Our data provided evidence for possible interactions between HbA1c and COL5A1 rs59126004 on the risk of severe DR. These findings may provide new insight into the pathophysiologic mechanism of DR.

Genetic Regulation of Pigment Epithelium-Derived Factor (PEDF): An Exome-Chip Association Analysis in Chinese Subjects With Type 2 Diabetes.

Elevated circulating levels of pigment epithelium-derived factor (PEDF) have been reported in patients with type 2 diabetes (T2D) and its associated microvascular complications. This study aimed to 1) identify the genetic determinants influencing circulating PEDF levels in a clinical setting of T2D, 2) examine the relationship between circulating PEDF and diabetes complications, and 3) explore the causal relationship between PEDF and diabetes complications. An exome-chip association study on circulating PEDF levels was conducted in 5,385 Chinese subjects with T2D. A meta-analysis of the association results of the discovery stage (n = 2,936) and replication stage (n = 2,449) was performed. The strongest association was detected at SERPINF1 (p.Met72Thr; Pcombined = 2.06 × 10-57; ß [SE] -0.33 [0.02]). Two missense variants of SMYD4 (p.Arg131Ile; Pcombined = 7.56 × 10-25; ß [SE] 0.21 [0.02]) and SERPINF2 (p.Arg33Trp; Pcombined = 8.22 × 10-10; ß [SE] -0.15 [0.02]) showed novel associations at genome-wide significance. Elevated circulating PEDF levels were associated with increased risks of diabetic nephropathy and sight-threatening diabetic retinopathy. Mendelian randomization analysis showed suggestive evidence of a protective role of PEDF on sight-threatening diabetic retinopathy (P = 0.085). Our study provided new insights into the genetic regulation of PEDF and further support for its potential application as a biomarker for diabetic nephropathy and sight-threatening diabetic retinopathy. Further studies to explore the causal relationship of PEDF with diabetes complications are warranted.

Fibroblast Growth Factor 21 Mimetics for Treating Atherosclerosis.

Fibroblast growth factor 21 (FGF21) is an atypical member of the FGF family. Acting in an endocrine fashion, it increases glucose uptake, modulates lipid metabolism, and sensitizes insulin response in metabolically active organs, including the liver and adipose tissue. Emerging evidence shows a strong correlation between circulating FGF21 levels and the incidence and severity of atherosclerosis. Animal studies have demonstrated a beneficial role of FGF21 in protecting against aberrant lipid profile, while recent development in FGF21 mimetics has provided further insight into the lipid-lowering effects of FGF21 signaling. The present review summarizes the physiological roles of FGF21, and discusses major breakthroughs and limitations of FGF21 mimetic-based therapeutic strategies for treating atherosclerosis.

An Exome-Chip Association Analysis in Chinese Subjects Reveals a Functional Missense Variant of GCKR That Regulates FGF21 Levels.

Fibroblast growth factor 21 (FGF21) is increasingly recognized as an important metabolic regulator of glucose homeostasis. Here, we conducted an exome-chip association analysis by genotyping 5,169 Chinese individuals from a community-based cohort and two clinic-based cohorts. A custom Asian exome-chip was used to detect genetic determinants influencing circulating FGF21 levels. Single-variant association analysis interrogating 70,444 single nucleotide polymorphisms identified a novel locus, GCKR, significantly associated with circulating FGF21 levels at genome-wide significance. In the combined analysis, the common missense variant of GCKR, rs1260326 (p.Pro446Leu), showed an association with FGF21 levels after adjustment for age and sex (P = 1.61 × 10-12; ß [SE] = 0.14 [0.02]), which remained significant on further adjustment for BMI (P = 3.01 × 10-14; ß [SE] = 0.15 [0.02]). GCKR Leu446 may influence FGF21 expression via its ability to increase glucokinase (GCK) activity. This can lead to enhanced FGF21 expression via elevated fatty acid synthesis, consequent to the inhibition of carnitine/palmitoyl-transferase by malonyl-CoA, and via increased glucose-6-phosphate-mediated activation of the carbohydrate response element binding protein, known to regulate FGF21 gene expression. Our findings shed new light on the genetic regulation of FGF21 levels. Further investigations to dissect the relationship between GCKR and FGF21, with respect to the risk of metabolic diseases, are warranted.

Heterogeneity of white adipose tissue: molecular basis and clinical implications.

Adipose tissue is a highly heterogeneous endocrine organ. The heterogeneity among different anatomical depots stems from their intrinsic differences in cellular and physiological properties, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, insulin sensitivity, hormonal control, thermogenic ability and vascularization. Additional factors that influence adipose tissue heterogeneity are genetic predisposition, environment, gender and age. Under obese condition, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. For instance, individuals with central obesity are more susceptible to developing diabetes and cardiovascular complications, whereas those with peripheral obesity are more metabolically healthy. This review summarizes the clinical and mechanistic evidence for the depot-specific differences that give rise to different metabolic consequences, and provides therapeutic insights for targeted treatment of obesity.

Impact of Genetic Loci Identified in Genome-Wide Association Studies on Diabetic Retinopathy in Chinese Patients With Type 2 Diabetes.

PURPOSE: Diabetic retinopathy (DR) is a common microvascular complication of type 2 diabetes (T2DM). Genome-wide association studies (GWAS) had identified novel DR-susceptibility genetic variants in various populations. We examined the associations of these DR-associated single nucleotide polymorphisms (SNPs) with severe DR in a Chinese T2DM cohort. METHODS: Cross-sectional case-control studies on sight-threatening DR (STDR) and proliferative DR (PDR) were performed. We genotyped 38 SNPs showing top association signals with DR in previous GWAS in 567 STDR cases, including 309 with PDR and 1490 non-DR controls. Multiple logistic regression models with adjustment for conventional risk factors, including age, sex, duration of diabetes, and presence of hypertension, were employed. RESULTS: The strongest association was found at INSR rs2115386, an intronic SNP of INSR: Padjusted = 9.13 × 10-4 (odds ratio [OR],1.28; 95% confidence interval [95%CI], 1.11-1.48) for STDR, and Padjusted= 1.12 × 10-4 (OR [95%CI],1.44 [1.20-1.74]) for PDR. rs599019 located downstream of COLEC12 (Padjusted = 0.019; OR [95%CI],1.19 [1.03-1.38]) and rs4462262 located at an intergenic region between ZWINT and MRPS35P3 (Padjusted = 0.041; OR [95%CI],1.38[1.01-1.89]) also were significantly associated with STDR, but not with PDR alone. On the other hand, MYT1L-LOC729897 rs10199521 (Padjusted = 0.022; OR [95%CI],1.25 [1.03-1.51]) and API5 rs899036 (Padjusted = 0.049; OR [95%CI],1.36 [1.00-1.85]) showed significant independent associations only with PDR. Similar results were obtained when hemoglobin A1c also was included in the adjustment models. CONCLUSIONS: We demonstrated the significant and independent associations of several GWAS-identified SNPs with DR in Chinese T2DM patients with severe DR. The findings on INSR rs2115386 are supportive of the role of insulin resistance, or the compensatory hyperinsulinemia, in the pathogenesis of DR.