Changes in liver metabolic pathways demonstrate efficacy of the combined dietary and microbial therapeutic intervention in MASLD mouse model.

OBJECTIVE: Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), is the most prevalent liver disease globally, yet no therapies are approved. The effects of Escherichia coli Nissle 1917 expressing aldafermin, an engineered analog of the intestinal hormone FGF19, in combination with dietary change were investigated as a potential treatment for MASLD. METHODS: MASLD was induced in C57BL/6J male mice by American lifestyle-induced obesity syndrome diet and then switched to a standard chow diet for seven weeks. In addition to the dietary change, the intervention group received genetically engineered E. coli Nissle expressing aldafermin, while control groups received either E. coli Nissle vehicle or no treatment. MASLD-related plasma biomarkers were measured using an automated clinical chemistry analyzer. The liver steatosis was assessed by histology and bioimaging analysis using Fiji (ImageJ) software. The effects of the intervention in the liver were also evaluated by RNA sequencing and liquid-chromatography-based non-targeted metabolomics analysis. Pathway enrichment studies were conducted by integrating the differentially expressed genes from the transcriptomics findings with the metabolites from the metabolomics results using Ingenuity pathway analysis. RESULTS: After the intervention, E. coli Nissle expressing aldafermin along with dietary changes reduced body weight, liver steatosis, plasma aspartate aminotransferase, and plasma cholesterol levels compared to the two control groups. The integration of transcriptomics with non-targeted metabolomics analysis revealed the downregulation of amino acid metabolism and related receptor signaling pathways potentially implicated in the reduction of hepatic steatosis and insulin resistance. Moreover, the downregulation of pathways linked to lipid metabolism and changes in amino acid-related pathways suggested an overall reduction of oxidative stress in the liver. CONCLUSIONS: These data support the potential for using engineered microbial therapeutics in combination with dietary changes for managing MASLD.

Liraglutide demonstrates a therapeutic effect on mitochondrial dysfunction in human SGBS adipocytes in vitro.

AIMS: Liraglutide (LG), a glucagon-like peptide-1 receptor (GLP-1R) agonist, has been shown to improve white adipose tissue mitochondrial metabolism in mice but not in human adipocytes. Therefore, we explored whether LG has therapeutic efficacy in mitochondrial dysfunction in human adipocytes in vitro. METHODS: We tested the effects of short-term (ST-LG: 24 h) and long-term (LT-LG: D0-15 days) treatments in human SGBS adipocytes on mitochondrial respiration, mRNA and protein expression. GLP-1R inhibition was investigated by the co-treatment of GLP-1R inhibitor, exendin 9-39 (Ex9-39) and ST-LG treatment. We also explored the ability of ST-LG to alleviate mitochondrial dysfunction induced by tumor necrosis factor-alpha (TNFα). RESULTS: LT-LG treatment induced the formation of smaller lipid droplets and increased the expression of genes related to lipolysis. Both ST-LG and LT-LG treatments promoted mitochondrial respiration. Additionally, LT-LG treatment increased the expression of a brown adipocyte marker, uncoupling protein 1 (UCP-1), and the markers of mitochondrial biogenesis. Interestingly, ST-LG rescued TNFα-induced defects in mitochondrial energy metabolism and inflammation in SGBS adipocytes. CONCLUSION: LG stimulates mitochondrial respiration and biogenesis in human adipocytes, potentially via UCP-1-mediated adipocyte browning. Importantly, our study demonstrates for the first time that LG has a therapeutic potential on mitochondrial activity in human adipocytes.

The FADS1 genotypes modify the effect of linoleic acid-enriched diet on adipose tissue inflammation via pro-inflammatory eicosanoid metabolism.

PURPOSE: Fatty acid desaturase (FADS) variants associate with fatty acid (FA) and adipose tissue (AT) metabolism and inflammation. Thus, the role of FADS1 variants in the regulation of dietary linoleic acid (LA)-induced effects on AT inflammation was investigated. METHODS: Subjects homozygotes for the TT and CC genotypes of the FADS1-rs174550 (TT, n = 25 and CC, n = 28) or -rs174547 (TT, n = 42 and CC, n = 28), were either recruited from the METabolic Syndrome In Men cohort to participate in an intervention with LA-enriched diet (FADSDIET) or from the Kuopio Obesity Surgery (KOBS) study. GC and LC-MS for plasma FA proportions and eicosanoid concentrations and AT gene expression for AT inflammatory score (AT-InSc) was determined. RESULTS: We observed a diet-genotype interaction between LA-enriched diet and AT-InSc in the FADSDIET. In the KOBS study, interleukin (IL)1 beta mRNA expression in AT was increased in subjects with the TT genotype and highest LA proportion. In the FADSDIET, n-6/LA proportions correlated positively with AT-InSc in those with the TT genotype but not with the CC genotype after LA-enriched diet. Specifically, LA- and AA-derived pro-inflammatory eicosanoids related to CYP450/sEH-pathways correlated positively with AT-InSc in those with the TT genotype, whereas in those with the CC genotype, the negative correlations between pro-inflammatory eicosanoids and AT-InSc related to COX/LOX-pathways. CONCLUSIONS: LA-enriched diet increases inflammatory AT gene expression in subjects with the TT genotype, while CC genotype could play a protective role against LA-induced AT inflammation. Overall, the FADS1 variant could modify the dietary LA-induced effects on AT inflammation through the differential biosynthesis of AA-derived eicosanoids.

Indole-3-Propionic Acid, a Gut-Derived Tryptophan Metabolite, Associates with Hepatic Fibrosis.

BACKGROUND AND AIMS: Gut microbiota-derived metabolites play a vital role in maintenance of human health and progression of disorders, including obesity and type 2 diabetes (T2D). Indole-3-propionic acid (IPA), a gut-derived tryptophan metabolite, has been recently shown to be lower in individuals with obesity and T2D. IPA's beneficial effect on liver health has been also explored in rodent and cell models. In this study, we investigated the association of IPA with human liver histology and transcriptomics, and the potential of IPA to reduce hepatic stellate cell activation in vitro. METHODS: A total of 233 subjects (72% women; age 48.3 ± 9.3 years; BMI 43.1 ± 5.4 kg/m2) undergoing bariatric surgery with detailed liver histology were included. Circulating IPA levels were measured using LC-MS and liver transcriptomics with total RNA-sequencing. LX-2 cells were used to study hepatoprotective effect of IPA in cells activated by TGF-ß1. RESULTS: Circulating IPA levels were found to be lower in individuals with liver fibrosis compared to those without fibrosis (p = 0.039 for all participants; p = 0.013 for 153 individuals without T2D). Accordingly, levels of circulating IPA associated with expression of 278 liver transcripts (p < 0.01) that were enriched for the genes regulating hepatic stellate cells (HSCs) activation and hepatic fibrosis signaling. Our results suggest that IPA may have hepatoprotective potential because it is able to reduce cell adhesion, cell migration and mRNA gene expression of classical markers of HSCs activation in LX-2 cells (all p < 0.05). CONCLUSION: The association of circulating IPA with liver fibrosis and the ability of IPA to reduce activation of LX-2 cells suggests that IPA may have a therapeutic potential. Further molecular studies are needed to investigate the mechanisms how IPA can ameliorate hepatic fibrosis.

Differential Mitochondrial Gene Expression in Adipose Tissue Following Weight Loss Induced by Diet or Bariatric Surgery.

CONTEXT: Mitochondria are essential for cellular energy homeostasis, yet their role in subcutaneous adipose tissue (SAT) during different types of weight-loss interventions remains unknown. OBJECTIVE: To investigate how SAT mitochondria change following diet-induced and bariatric surgery-induced weight-loss interventions in 4 independent weight-loss studies. METHODS: The DiOGenes study is a European multicenter dietary intervention with an 8-week low caloric diet (LCD; 800 kcal/d; n = 261) and 6-month weight-maintenance (n = 121) period. The Kuopio Obesity Surgery study (KOBS) is a Roux-en-Y gastric bypass (RYGB) surgery study (n = 172) with a 1-year follow-up. We associated weight-loss percentage with global and 2210 mitochondria-related RNA transcripts in linear regression analysis adjusted for age and sex. We repeated these analyses in 2 studies. The Finnish CRYO study has a 6-week LCD (800-1000 kcal/d; n = 19) and a 10.5-month follow-up. The Swedish DEOSH study is a RYGB surgery study with a 2-year (n = 49) and 5-year (n = 37) follow-up. RESULTS: Diet-induced weight loss led to a significant transcriptional downregulation of oxidative phosphorylation (DiOGenes; ingenuity pathway analysis [IPA] z-scores: -8.7 following LCD, -4.4 following weight maintenance; CRYO: IPA z-score: -5.6, all P < 0.001), while upregulation followed surgery-induced weight loss (KOBS: IPA z-score: 1.8, P < 0.001; in DEOSH: IPA z-scores: 4.0 following 2 years, 0.0 following 5 years). We confirmed an upregulated oxidative phosphorylation at the proteomics level following surgery (IPA z-score: 3.2, P < 0.001). CONCLUSIONS: Differentially regulated SAT mitochondria-related gene expressions suggest qualitative alterations between weight-loss interventions, providing insights into the potential molecular mechanistic targets for weight-loss success.

Correction to: Liver DNA methylation of FADS2 associates with FADS2 genotype.

Following publication of the original article [1], the author reported the title of this article has been misspelled.

Liver DNA methylation of FADS2 associates with FADS2 genotype.

BACKGROUND: Non-alcoholic fatty liver disease has been associated with increased mRNA expression of FADS2 in the liver and estimated activity of delta-6 desaturase in serum, encoded by the FADS2 gene. Since DNA methylation in the FADS1/2/3 gene cluster has been previously linked with genetic variants and desaturase activities, we now aimed to discover factors regulating DNA methylation of the CpG sites annotated to FADS1/2 genes. METHODS: DNA methylation levels in the CpG sites annotated to FADS2 and FADS1 were analyzed from liver samples of 95 obese participants of the Kuopio Obesity Surgery Study (34 men and 61 women, age 49.5 ± 7.7 years, BMI 43.0 ± 5.7 kg/m2) using the Infinium HumanMethylation450 BeadChip (Illumina). Associations between DNA methylation levels and estimated delta-6 and delta-5 desaturase enzyme activities, liver histology, hepatic mRNA expression, FADS1/2 genotypes, and erythrocyte folate levels were analyzed. RESULTS: We found a negative correlation between DNA methylation levels of cg06781209 and cg07999042 and hepatic FADS2 mRNA expression (both p < 0.05), and with estimated delta-6 desaturase activity based on both liver and serum fatty acids (all p < 0.05). Interestingly, the methylation level of cg07999042 (p = 0.001) but not of cg06781209 (p = 0.874) was associated with FADS2 variant rs174616. CONCLUSIONS: Genetic variants of FADS2 may contribute to the pathogenesis of non-alcoholic fatty liver disease by modifying DNA methylation.

Small Intestinal Length Associates with Serum Triglycerides Before and After LRYGB.

BACKGROUND AND AIMS: Different bariatric procedures have been associated with variable weight loss and decrease in serum levels of lipids and lipoproteins. This variation could be partly related to the length of the small intestinal bypass. We evaluated the association of the small intestinal length with the non-alcoholic fatty liver disease (NAFLD) at baseline and with lipid metabolism before and after laparoscopic Roux-en-Y gastric bypass (LRYGB). METHODS: Seventy consecutive morbidly obese patients were recruited to this prospective study. A standard 60-cm biliopancreatic limb (BPL) and 120-cm alimentary limb (AL) was performed, and thereafter, the common channel (CC) length was measured during elective LRYGB. Histological analysis of liver biopsy to diagnose NAFLD was performed. The mRNA expression of genes participating in the cholesterol and fatty acid metabolism in the liver was analyzed. RESULTS: Female sex (p = 0.006), serum triglycerides (TG, p = 0.016), serum alanine aminotransferase (ALT, p = 0.007), and liver steatosis (p = 0.001) associated with the small intestinal length (BPL + AL + CC) at baseline. Association remained significant between levels of serum TG and CC length (p = 0.048) at 1-year follow-up. Liver mRNA expression of genes regulating cholesterol synthesis and bile metabolism did not associate with the baseline small intestinal length. CONCLUSIONS: Our findings support the suggestions that small intestinal length regulates TG metabolism before and after LRYGB. Therefore, modification of the length of bypassed small intestine based on measured total small intestinal length could optimize the outcomes of the elective LRYGB.

Serum, liver and bile sitosterol and sitostanol in obese patients with and without NAFLD.

Background and aims: Non-alcoholic fatty liver disease (NAFLD) associates with low levels of serum plant sterols in cross-sectional studies. In addition, it has been suggested that the hepatic sterol transport mechanisms are altered in NAFLD. Therefore, we investigated the association between serum, liver and bile plant sterols and sitostanol with NAFLD.Methods: Out of the 138 individuals (age: 46.3 ± 8.9, body mass index: 43.3 ± 6.9 kg/m², 28% men and 72% women), 44 could be histologically categorized to have normal liver, and 94 to have NAFLD. Within the NAFLD group, 28 had simple steatosis and 27 had non-alcoholic steatohepatitis. Plant sterols and sitostanol were measured from serum (n=138), liver (n=38), and bile (n=41). The mRNA expression of genes regulating liver sterol metabolism and inflammation was measured (n=102).Results: Liver and bile sitostanol ratios to cholesterol were higher in those with NAFLD compared to those with histologically normal liver (all P<0.022). Furthermore, liver sitostanol to cholesterol ratio correlated positively with histological steatosis and lobular inflammation (rs > 0.407, P<0.01 for both). In contrast, liver sitosterol to cholesterol ratio correlated negatively with steatosis (rs = -0.392, P=0.015) and lobular inflammation (rs = -0.395, P=0.014). Transcriptomics analysis revealed suggestive correlations between serum plant sterol levels and mRNA expression.Conclusion: Our study showed that liver and bile sitostanol ratios to cholesterol associated positively and liver sitosterol ratio to cholesterol associated negatively with liver steatosis and inflammation in obese individuals with NAFLD..

Fatty acid uptake and blood flow in adipose tissue compartments of morbidly obese subjects with or without type 2 diabetes: effects of bariatric surgery.

Body fat accumulation, distribution, and metabolic activity are factors in the pathophysiology of obesity and type 2 diabetes (T2D). We investigated adipose blood flow, fatty acid uptake (FAU), and subcutaneous and visceral fat cellularity in obese patients with or without T2D. A total of 23 morbidly obese (mean body mass index = 42 kg/m2) patients were studied before and 6 mo after bariatric surgery; 15 nonobese subjects served as controls. Positron emission tomography was used to measure tissue FAU (with 18F-FTHA) and blood flow (with H215O); MRI was used for fat distribution and fat biopsy for adipocyte size. Obese subjects had subcutaneous hyperplasia and hypertrophy and lower blood flow; when expressed per cell, flow was similar to controls. FAU into subcutaneous and visceral depots was increased in the obese; per unit tissue mass, however, FAU was similar to controls but reduced in skeletal muscle. Fatty acid fractional extraction in subcutaneous fat and muscle was only increased in obese patients with T2D. We conclude that surgery reduces subcutaneous fat hyperplasia and hypertrophy; subcutaneous blood flow and FAU decrease in absolute terms and per cell while fractional FAU remains unchanged in T2D. In the obese, subcutaneous blood flow is a determinant of FAU and is coupled with cellularity; efficiency of FAU is enhanced in subcutaneous fat and muscle in T2D.

Interorgan cross talk between fatty acid metabolism, tissue inflammation, and FADS2 genotype in humans with obesity.

OBJECTIVE: Fatty acid (FA) composition affects obesity-associated low-grade inflammation. It has been shown that the fatty acid desaturase (FADS) 2 gene polymorphism associates with FA metabolism and adipose tissue (AT) inflammation. This study aimed to investigate the relationship between FA metabolism and inflammation in different tissues and the possible interorgan cross talk. METHODS: Cross-sectional baseline data from 155 individuals with obesity (both male and female) participating in the Roux-en-Y gastric bypass operation in the ongoing Kuopio Obesity Surgery Study were used. Gas chromatograph for FA composition, liver histology, and targeted RNA expression for gene expression profile were performed. RESULTS: It was demonstrated that the saturated fatty acid (SFA) proportion in AT correlated positively with inflammation in subcutaneous AT (SAT) and visceral AT (VAT) but not in the liver, while the monounsaturated fatty acid (MUFA) proportion in SAT and VAT correlated negatively with AT inflammation. Notably, there was a positive correlation between AT n-6 polyunsaturated fatty acids (PUFAs), but not AT SFAs or MUFAs, and liver inflammation. This correlation was modified by the FADS2 genotype. CONCLUSIONS: The AT FA profile relates with AT inflammation. Additionally, there seems to be a complex interaction, partly regulated by the FADS2 genotype, regulating the interaction between FAs in AT and liver inflammation.

Serum Plant Sterols Associate with Gallstone Disease Independent of Weight Loss and Non-Alcoholic Fatty Liver Disease.

BACKGROUND: Gallstone disease (GD) has been associated with low serum levels of plant sterols. We evaluated the impact of laparoscopic Roux-en-Y gastric bypass (LRYGB) and non-alcoholic fatty liver disease (NAFLD) on the association of GD with low levels of serum plant sterols. METHODS: Two hundred forty-two consecutive morbidly obese patients were recruited to this prospective study. Histological analysis of liver biopsy to diagnose NAFLD was performed. Bile sample was taken during the LRYGB. Associations of GD with serum non-cholesterol sterol to cholesterol ratios, measured using gas liquid chromatography and with mRNA expression of genes participating in the cholesterol, bile, and fatty acid metabolism in the liver, were analyzed. RESULTS: Out of the 242 participants, 95 had GD. Lower weight (p = 0.002) and female sex (p = 0.0006) were associated with GD. Serum plant sterols, campesterol (p = 0.003), sitosterol (p = 0.002), and avenasterol (p = 0.015), were lower in patients with GD compared to those without GD. This association remained significant after adjustment for NAFLD, use of statin medication, and previous laparoscopic cholecystectomy (LCC). Levels of sitosterol (p = 0.001) and campesterol (p = 0.001) remained lower in obese individuals with GD also after obesity surgery. Liver mRNA expression of genes regulating cholesterol synthesis and bile metabolism was increased in individuals with GD. CONCLUSIONS: Serum plant sterols were lower in patients with GD independent of NAFLD, history of LCC, use of statin medication, and weight loss after LRYGB. Low serum plant sterols in patients with GD suggest potentially inherited alterations in sterol absorption and biliary transport in subjects susceptible for GD.

Fatty acid metabolism is altered in non-alcoholic steatohepatitis independent of obesity.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is associated with changes in fatty acid (FA) metabolism. However, specific changes in metabolism and hepatic mRNA expression related to NASH independent of simple steatosis, obesity and diet are unknown. METHODS: Liver histology, serum and liver FA composition and estimated enzyme activities based on the FA ratios in cholesteryl esters and triglycerides were assessed in 92 obese participants of the Kuopio Obesity Surgery Study (KOBS) divided to those with normal liver, steatosis or NASH (30 men and 62 women, age 46.8±9.5years (mean±SD), BMI 44.2±6.2kg/m(2)). Plasma FA composition was also investigated in the Metabolic Syndrome in Men (METSIM) Study (n=769), in which serum alanine aminotransferase (ALT) was used as a marker of liver disease. RESULTS: Obese individuals with NASH had higher activity of estimated activities of delta-6 desaturase (D6D, p<0.002) and stearoyl-CoA desaturase 1 (SCD1, p<0.002) and lower activity of delta-5 desaturase (D5D, p<0.002) when compared to individuals with normal liver. Estimated activities of D5D, D6D and SCD1 correlated positively between liver and serum indicating that serum estimates reflected liver metabolism. Accordingly, NASH was associated with higher hepatic mRNA expression of corresponding genes FADS1, FADS2 and SCD. Finally, differences in FA metabolism that associated with NASH in obese individuals were also associated with high ALT in the METSIM Study. CONCLUSIONS: We demonstrated alterations in FA metabolism and endogenous desaturase activities that associate with NASH, independent of obesity and diet. This suggests that changes in endogenous FA metabolism are related to NASH and that they may contribute to the progression of the disease.

FADS2 genotype regulates delta-6 desaturase activity and inflammation in human adipose tissue.

Obesity is associated with disturbed lipid metabolism and low-grade inflammation in tissues. The aim of this study was to investigate the association between FA metabolism and adipose tissue (AT) inflammation in the Kuopio Obesity Surgery study. We investigated the association of surgery-induced weight loss and FA desaturase (FADS)1/2 genotypes with serum and AT FA profile and with AT inflammation, measured as interleukin (IL)-1ß and NFκB pathway gene expression, in order to find potential gene-environment interactions. We demonstrated an association between serum levels of saturated and polyunsaturated n-6 FAs, and estimated enzyme activities of FADS1/2 genes with IL-1ß expression in AT both at baseline and at follow-up. Variation in the FADS1/2 genes associated with IL-1ß and NFκB pathway gene expression in SAT after weight reduction, but not at baseline. In addition, the FA composition in subcutaneous and visceral fat correlated with serum FAs, and the associations between serum PUFAs and estimated D6D enzyme activity with AT inflammation were also replicated with corresponding AT FAs and AT inflammation. We conclude that the polymorphism in FADS1/2 genes associates with FA metabolism and AT inflammation, leading to an interaction between weight loss and FADS1/2 genes in the regulation of AT inflammation.

Gene-diet interaction of a common FADS1 variant with marine polyunsaturated fatty acids for fatty acid composition in plasma and erythrocytes among men.

SCOPE: Limited information exists on how the relationship between dietary intake of fat and fatty acids in erythrocytes and plasma is modulated by polymorphisms in the FADS gene cluster. We examined gene-diet interaction of total marine PUFA intake with a known gene encoding Δ-5 desaturase enzyme (FADS1) variant (rs174550) for fatty acids in erythrocyte membranes and plasma phospholipids (PL), cholesteryl esters (CE), and triglycerides (TG). METHODS AND RESULTS: In this cross-sectional study, fatty acid compositions were measured using GC, and total intake of polyunsaturated fat from fish and fish oil was estimated using a food frequency questionnaire in a subsample (n = 962) of the Metabolic Syndrome in Men Study. We found nominally significant gene-diet interactions for eicosapentaenoic acid (EPA, 20:5n-3) in erythrocytes (pinteraction = 0.032) and for EPA in plasma PL (pinteraction = 0.062), CE (pinteraction = 0.035), and TG (pinteraction = 0.035), as well as for docosapentaenoic acid (22:5n-3) in PL (pinteraction = 0.007). After excluding omega-3 supplement users, we found a significant gene-diet interaction for EPA in erythrocytes (pinteraction < 0.003). In a separate cohort of the Kuopio Obesity Surgery Study, the same locus was strongly associated with hepatic mRNA expression of FADS1 (p = 1.5 × 10(-10) ). CONCLUSION: FADS1 variants may modulate the relationship between marine fatty acid intake and circulating levels of long-chain omega-3 fatty acids.

MFAP5 is related to obesity-associated adipose tissue and extracellular matrix remodeling and inflammation.

OBJECTIVE: Low-grade inflammation is involved in adipose tissue (AT) and extracellular matrix (ECM) remodeling and induces deposition of ECM proteins in AT. We have previously shown that MFAP5 (microfibrillar-associated protein 5) expression decreases in AT after weight loss. The aim of this study was to investigate MFAP5 localization in human AT and gene expression in adipocytes and the role of MFAP5 in adipocyte metabolism and inflammation. METHODS: MFAP5 protein localization and gene expression were studied with immunohistochemistry and quantitative reverse transcriptase PCR (RT-qPCR) in human subcutaneous AT and cultured Simpson-Golabi-Behmel syndrome (SGBS) adipocytes, respectively. The effect of MFAP5 knock-down by siRNA on gene expression and insulin action was examined with RT-qPCR, western blot, and insulin-stimulated glucose uptake. The effect of different cytokines on MFAP5 gene and protein expression was investigated in cultured human SGBS preadipocytes. RESULTS: MFAP5 protein was highly expressed in AT, and gene expression decreased during adipocyte differentiation in SGBS cells. Treatment of preadipocytes with TNFα and TGFß1 increased MFAP5 gene and protein expression. Furthermore, MFAP5 knock-down decreased the expression of genes involved in inflammation. CONCLUSIONS: Our results demonstrate that factors involving low-grade inflammation modulate MFAP5 expression and that the modified expression of MFAP5 may further regulate AT inflammation.

Downregulation of CPPED1 expression improves glucose metabolism in vitro in adipocytes.

We have previously demonstrated that the expression of calcineurin-like phosphoesterase domain containing 1 (CPPED1) decreases in adipose tissue (AT) after weight reduction. However, the function of CPPED1 in AT is unknown. Therefore, we investigated whether the change in CPPED1 expression is connected to changes in adipocyte glucose metabolism. First, we confirmed that the expression of CPPED1 decreased after weight loss in subcutaneous AT. Second, the expression of CPPED1 did not change during adipocyte differentiation. Third, CPPED1 knockdown with small interfering RNA increased expression of genes involved in glucose metabolism (adiponectin, adiponectin receptor 1, and GLUT4) and improved insulin-stimulated glucose uptake. To conclude, CPPED1 is a novel molecule involved in AT biology, and CPPED1 is involved in glucose uptake in adipocytes.

Adipose tissue TCF7L2 splicing is regulated by weight loss and associates with glucose and fatty acid metabolism.

We investigated the effects of obesity surgery-induced weight loss on transcription factor 7-like 2 gene (TCF7L2) alternative splicing in adipose tissue and liver. Furthermore, we determined the association of TCF7L2 splicing with the levels of plasma glucose and serum free fatty acids (FFAs) in three independent studies (n = 216). Expression of the short mRNA variant, lacking exons 12, 13, and 13a, decreased after weight loss in subcutaneous fat (n = 46) and liver (n = 11) and was more common in subcutaneous fat of subjects with type 2 diabetes than in subjects with normal glucose tolerance in obese individuals (n = 54) and a population-based sample (n = 49). Additionally, there was a positive correlation between this variant and the level of fasting glucose in nondiabetic individuals (n = 113). This association between TCF7L2 splicing and plasma glucose was independent of the TCF7L2 genotype. Finally, this variant was associated with high levels of serum FFAs during hyperinsulinemia, suggesting impaired insulin action in adipose tissue, whereas no association with insulin secretion or insulin-stimulated whole-body glucose uptake was observed. Our study shows that the short TCF7L2 mRNA variant in subcutaneous fat is regulated by weight loss and is associated with hyperglycemia and impaired insulin action in adipose tissue.

Gene expression of FTO in human subcutaneous adipose tissue, peripheral blood mononuclear cells and adipocyte cell line.

BACKGROUND/AIMS: The common polymorphism rs9939609 of the fat mass and obesity-associated gene (FTO) is strongly associated with obesity, but the biological function is still unknown. We compared the FTO gene expression in subcutaneous adipose tissue and peripheral blood mononuclear cells (PBMCs) between overweight and normal weight individuals. We also investigated if mRNA levels of FTO in adipose tissue correlated with the adiposity or inflammatory markers and mRNA levels of genes involved in the response to hypoxia (HIF-1a) and cell death(HMGB1). RESULTS: The mRNA expression of FTO in adipose tissue was greater in obese than normal weight individuals (p < 0.001), but there was no difference in FTO expression in PBMCs. FTO mRNA levels did not correlate with adiposity or inflammatory markers and FTO expression was not influenced by the FTO rs9939609 genotype. FTO mRNA level correlated positively with gene expression levels of HIF-1a and HMGB1 in subcutaneous adipose tissue (r = 0.59, p < 0.001; r = 0.69, p < 0.001, respectively; adjusted for BMI and adipocyte cell size). CONCLUSIONS: Altogether, FTO expression appeared not to have a well-defined impact on clinical or biochemical parameters comprising the metabolic syndrome. The correlations with the genes related to hypoxia and cell death suggest novel biological activities for FTO.