The fat mass and obesity-associated (FTO) gene allele rs9939609 and glucose tolerance, hepatic and total insulin sensitivity, in adults with obesity

Exploring associations between the FTO rs9939609 genotype and plasma concentrations of appetite-related hormones in adults with obesity

Associations between variants in the FTO locus and plasma concentrations of appetite related hormones are inconsistent, and might not work in a dose dependent fashion in people with obesity. Moreover, it is relevant to report meal related plasma concentrations of these hormones in persons with obesity given the growing interest in their pharmacological potential in obesity therapy. We find it clinically relevant to examine associations between the SNP rs9939609 genotypes and homeostatic appetite regulation in individuals with BMI ≥35 kg/m2. This study explored associations of the rs9939609 genotypes to plasma concentrations of acylated ghrelin, active glucagon-like peptide 1 (GLP-1), and total peptide YY (PYY), and moderating effects of fat mass (FM), in 96 adults (69% female) with BMI ≥35 kg/m2, using a cross sectional observation study designed to have 1/3 of participants each with genotypes TT, AT and AA, respectively. Participants were median (25th, 75th percentile) 42.5 (32, 50) years of age, weighed 120.9 (109.6, 142.4) kg, and had a BMI of 42.8 (39.5, 46.4) kg/m2. Acylated ghrelin, active GLP-1, and total PYY were measured in the fasted state and half-hourly for 2.5h after a standardized meal. We evaluated associations between genotype and appetite hormones in regression analysis controlling for FM and sex. Genotype did not associate with fasting or postprandial (area under curve, AUC) GLP-1 or PYY. Genotype did not associate with fasting acylated ghrelin, but in females with genotype AA, increased FM was associated with higher fasting and postprandial (AUC) acylated ghrelin concentrations relative to genotypes TT (fasting p = 0.025; AUC p = 0.004) and AT (fasting p = 0.002; AUC p < 0.001). This novel finding warrants further investigation.

RNA sequencing reveals the mechanism of FTO in inhibiting inflammation and excessive proliferation of lipopolysaccharide-induced human glomerular mesangial cells

Chronic glomerulonephritis (CGN) is a leading cause of end-stage renal disease in China; thus, there is an urgent need for effective therapeutic targets and strategies for CGN treatment. However, studies on CGN pathogenesis are limited. In this study, we found that the fat mass and obesity-associated protein (FTO) was significantly decreased in the lipopolysaccharide (LPS)-induced human glomerular mesangial cells (HGMCs) (P < 0.01) and kidney tissues of CGN patients (P < 0.05). Moreover, double-labeling immunofluorescence and flow cytometry assays demonstrated that the overexpression of FTO could inhibit inflammation and excessive proliferation of HGMCs. Furthermore, RNA-sequencing (RNA-seq) and real-time quantitative polymerase chain reaction (RT-qPCR) analyses revealed that FTO overexpression induced differential expression of 269 genes (absolute fold change ≥ 2 and P-value < 0.05), including 143 upregulated and 126 downregulated genes. Further functional analysis of these differentially expressed genes by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses suggested that FTO possibly mediates its inhibitory function by regulating the mammalian target of rapamycin (mTOR) signaling pathway and substance metabolism. Lastly, analysis of the PPI network and further identification of the top 10 hub genes (RPS15, RPS18, RPL18A, GNB2L1, RPL19, EEF1A1, RPS25, FAU, UBA52, and RPS6) indicated that FTO mediates its function by affecting the ribosomal proteins. Therefore, in this study, we elucidated the important role of FTO in the regulation of inflammation and excessive proliferation of HGMCs, suggesting FTO administration as a suitable therapeutic intervention for CGN.

NEFA Dynamics in Adults With Severe Obesity and Insulin Resistance: No Coupling to the rs9939609 FTO Risk Allele

Context

The FTO gene is highly expressed in adipose tissues; however, whether nonesterified fatty acids (NEFA) dynamics are impacted by FTO has not been rigorously tested for in a uniformly obese study population comprising both sexes.

Objective

To test for associations of the rs9939609 FTO risk allele with NEFA suppression.

Methods

We investigated 97 subjects with severe obesity but without diabetes, having genotype TT (n = 32), AT (n = 31), or AA (n = 34) in a cross-sectional observation study. NEFA suppression was assessed from a low-dose hyperinsulinemic euglycemic clamp with glucose-tracer as well as from the response to a standardized meal. Insulin sensitivity was assessed by hepatic and total insulin sensitivity measurements in the clamp and by the Matsuda index during the meal. Variables of possible importance for NEFA dynamics were primarily assessed by linear regression.

Results

No genotype associations with fasting or suppressed NEFA were found, whether in the clamp or meal situation (P > .7 for all comparisons). Independent of genotype, higher fasting concentrations of NEFA and larger NEFA suppression were found in female compared with male subjects. Fasting NEFA or degree of suppression were not associated with total fat mass or body mass index. The respiratory quotient was negatively associated with NEFA suppression.

Conclusion

In a gender-mixed adult population of obese individuals, an FTO obesity-risk allele did not affect fasting NEFA nor suppression thereof. These negative results on NEFA dynamics appear strengthened by the documentation of gender influence and associations with parameters reflective of insulin resistance.

Whole-genome sequencing study to identify candidate markers indicating susceptibility to type 2 diabetes in Bama miniature pigs

BACKGROUND

Hundreds of single-nucleotide polymorphism (SNP) sites have been found to be potential genetic markers of type 2 diabetes mellitus (T2DM). However, SNPs related to T2DM in minipigs have been less reported. This study aimed to screen the T2DM-susceptible candidate SNP loci in Bama minipigs so as to improve the success rate of the minipig T2DM model.

METHODS

The genomic DNAs of three Bama minipigs with T2DM, six sibling low-susceptibility minipigs with T2DM, and three normal control minipigs were compared by whole-genome sequencing. The T2DM Bama minipig-specific loci were obtained, and their functions were annotated. Meanwhile, the Biomart software was used to perform homology alignment with T2DM-related loci obtained from the human genome-wide association study to screen candidate SNP markers for T2DM in Bama miniature pigs.

RESULTS

Whole-genome resequencing detected 6960 specific loci in the minipigs with T2DM, and 13 loci corresponding to 9 diabetes-related genes were selected. Further, a set of 122 specific loci in 69 orthologous genes of human T2DM candidate genes were obtained in the pigs. Collectively, a batch of T2DM-susceptible candidate SNP markers in Bama minipigs, covering 16 genes and 135 loci, was established.

CONCLUSIONS

Whole-genome sequencing and comparative genomics analysis of the orthologous genes in pigs that corresponded to the human T2DM-related variant loci successfully screened out T2DM-susceptible candidate markers in Bama miniature pigs. Using these loci to predict the susceptibility of the pigs before constructing an animal model of T2DM may help to establish an ideal animal model.

Genetic architecture for skeletal muscle glycolytic potential in Chinese Erhualian pigs revealed by a genome-wide association study using 1.4M SNP array

Introduction: Muscle glycolytic potential (GP) is a key factor affecting multiple meat quality traits. It is calculated based on the contents of residual glycogen and glucose (RG), glucose-6-phosphate (G6P), and lactate (LAT) contents in muscle. However, the genetic mechanism of glycolytic metabolism in skeletal muscle of pigs remains poorly understood. With a history of more than 400 years and some unique characteristics, the Erhualian pig is called the “giant panda” (very precious) in the world’s pig species by Chinese animal husbandry.

Methods: Here, we performed a genome-wide association study (GWAS) using 1.4M single nucleotide polymorphisms (SNPs) chips for longissimus RG, G6P, LAT, and GP levels in 301 purebred Erhualian pigs.

Results: We found that the average GP value of Erhualian was unusually low (68.09 μmol/g), but the variation was large (10.4–112.7 μmol/g). The SNP-based heritability estimates for the four traits ranged from 0.16–0.32. In total, our GWAS revealed 31 quantitative trait loci (QTLs), including eight for RG, nine for G6P, nine for LAT, five for GP. Of these loci, eight were genome-wide significant (p &lt; 3.8 × 10−7), and six loci were common to two or three traits. Multiple promising candidate genes such as FTO, MINPP1, RIPOR2, SCL8A3, LIFR and SRGAP1 were identified. The genotype combinations of the five GP-associated SNPs also showed significant effect on other meat quality traits.

Discussion: These results not only provide insights into the genetic architecture of GP related traits in Erhualian, but also are useful for pig breeding programs involving this breed.

Exploring Dietary Intake in Adults with Severe Obesity and Associations with the FTO rs9939609 Genotypes

Background

Few have studied the associations between rs9939609 genotypes in the obesity candidate locus FTO and energy and nutrient intakes and meal frequencies in adults with severe obesity. We are unaware of studies that have assessed adherence to key dietary recommendations in this population, at least in Norway. Increased knowledge of genotype associations with dietary factors could improve personalized obesity therapy.

Objectives

The present study aimed to explore how the rs9939609 genotypes associate with dietary variables and adherence to key dietary recommendations in a sample of adults with severe obesity.

Methods

A cross-sectional observation study designed to have similar numbers of participants with genotypes TT, AT, and AA included 100 patients (70% women) with median (25th, 75th percentile) age 42 (32, 50) y and BMI 42.8 (39.5, 46.4) kg/m2. We assessed intakes of food groups, energy, and macro- and micronutrients from three 24-h dietary recalls and meal frequencies. Genotype associations were analyzed using regression analyses. Reported intakes were evaluated against national diet recommendations.

Results

Using a significance level of 0.01, we found no genotype associations with energy intake, energy density, adherence to recommendations, or meal frequency but tendencies of associations with energy adjusted protein intake (AA > AT, P = 0.037; AT > TT, P = 0.064), food groups milk and cream (AT > TT, P = 0.029), and Mixed dishes (AA > TT, P = 0.039). Few participants complied with recommendations for intakes of whole grains (21%), fruits and vegetables (11%), and fish (37%); however, 67% followed the recommendation to limit added sugar. Less than 20% had recommended intakes of vitamin D and folate.

Conclusions

In our patients with severe obesity, we found tendencies of associations between the FTO rs9939609 genotypes and diet but no significant associations at the 0.01 level and below. Few met key food-based diet recommendations, suggesting that the food habits in this population pose an increased risk of nutrient deficiencies. Curr Dev Nutr 2023;xx:xx.

Linking Mitochondrial Function to Insulin Resistance: Focusing on Comparing the Old and the Young

Long-term intake of high-energy diet can lead to decreased insulin sensitivity and even insulin resistance, eventually leading to diabetes. Diabetes often occurs in middle-aged and elderly people. However, there is growing evidence that the incidence rate of young body is increasing over the years. This means that insulin resistance can be caused by excessive energy intake in both young and old people. In this study, high-fat diet (HFD) and normal diet were fed to rats of elderly experimental group (EE), elderly control group (EC), young experimental group (YE), and young control group (YC), respectively, for 8 weeks, by which insulin resistance model was obtained. Insulin sensitivity was measured, histopathology changes in liver and skeletal muscle tissues were observed, and mitochondrial fusion and division and cell senescence were detected in four groups of rats. The results showed that both young and elderly rats developed significant insulin resistance, fat deposition, decline of mitochondrial function and mitochondrial biosynthesis in liver and skeletal muscle, and cell aging after HFD feeding. In addition, the degree of mitochondrial dysfunction and aging in young rats was similar to that of aged rats fed a normal diet after HFD. This experiment provides a reference for an in-depth study of the regulatory mechanisms of cellular energy metabolism in this state.

Obesity Management and Chronic Kidney Disease

Obesity is one of the risk factors for the development and progression of chronic kidney disease (CKD). Several studies have shown the association between increased body mass index and kidney function decline. Obesity leads to CKD directly by acting as an independent risk factor and indirectly through increasing risks for diabetes, hypertension, and atherosclerosis, a group of well-established independent risk factors for CKD. Alterations in renal hemodynamics, inflammation, and in hormones and growth factors results in hyperfiltration injury and focal segmental glomerulosclerosis. In recent years, many studies have shown that the gut microbiome may play a role in the pathogenesis of obesity. Dysbiosis has been noted in obese subjects in both human and animal studies. Changes in the gut microbiome in obese patients promote weight gain by effectively extracting energy from diet, and induction of low-grade inflammation. Evidence also points to the role of inflammation within the adipose tissue in obesity as a key factor in the pathogenesis of obesity-related complications. Thus, obesity is the net result of complex interactions between behavioral, genetic, and environmental factors. In terms of management, conservative approaches are often the first option, but they often are unsuccessful in achieving and/or maintaining weight loss, particularly in severe obesity. Consequently, nonmedical management with bariatric surgery is the most effective treatment option for morbid obesity and has shown mitigation of multiple risk factors for the progression of CKD. The most frequently performed interventions are vertical sleeve gastrectomy and Roux-en-Y gastric bypass. Studies have shown that bariatric surgery is associated with beneficial effects on CKD by mitigating its risk factors by weight loss, reducing insulin resistance, hemoglobin A1c, and proteinuria, in addition to positive long-term outcomes. Because of the epidemic of obesity, the prevalence of obesity in kidney transplant recipients also is increasing. The maximal body mass index (BMI) threshold for kidney transplantation is not clear. The Organ Procurement Transplant Network/Scientific Registry of Transplant Recipients 2019 annual data report showed that the proportion of kidney transplant recipient candidates with a BMI of 30 kg/m² or greater is increasing steadily. Morbid obesity is linked to adverse graft outcomes including delayed graft function, primary nonfunction, and decreased graft survival. Obesity is also an independent risk factor for cardiovascular death in kidney transplant recipients, suggesting that these patients should not be excluded from transplantation based on their BMI because transplantation is associated with lower mortality compared with dialysis. However, many centers exclude obese patients (with different BMI cut-off values) from transplantation to avoid postoperative complications. To minimize the surgical complications of kidney transplantation in obese patients, our center has adopted the robot-assisted kidney transplantation procedure. Our data show that this approach is comparable with historical nonobese controls in the United Network for Organ Sharing database in terms of patient and graft survival. Another surgical option for this group of patients at our center is a combined robotic sleeve gastrectomy and robotic-assisted kidney transplant. In a recent study, this approach showed promising results in terms of weight loss, patient survival, and graft survival, and might become more common in the future.