Maternal high-fat diet sex-specifically alters placental morphology and transcriptome in rats: Assessment by next-generation sequencing.

INTRODUCTION: Maternal nutrition is an extremely important health issue. We evaluated the impact of maternal high fat diet (HFD) on pregnancy outcomes, elucidated how the rat placenta and fetus respond to diet manipulation based on fetal sex, and identified candidate genes and pathways. METHODS: Rats were fed a normal or HFD diet for 10 weeks before conception and during gestation. The placenta was collected on gestational day 21 and sexed. Placental histology was analyzed and placental candidate genes and pathways were identified using whole-genome RNA next-generation sequencing. RESULTS: Pup weights in both sexes from HFD dams were reduced. The weight of the placenta from the HFD group was also decreased in both sexes, but changes in placental layer distributions were only significant for female fetuses. Maternal HFD altered the placental transcriptome in a sex-specific manner. Activation of the placental renin-angiotensin system (RAS) by maternal HFD was associated with fetal growth restriction in both fetal sexes. CONCLUSIONS: The placenta reacts to maternal HFD by altering the placental layer distribution and gene expression in a sex-specific manner. The male placenta in late gestation is thought to exhibit greater plasticity relative to the female placenta; however, fetuses of both sexes exhibited similar growth restriction. Our data reveal an association between the placental RAS and HFD-induced fetal growth restriction.

Fish Oil Protects Wild Type and Uncoupling Protein 1-Deficient Mice from Obesity and Glucose Intolerance by Increasing Energy Expenditure.

SCOPE: The mechanisms and involvement of uncoupling protein 1 (UCP1) in the protection from obesity and insulin resistance induced by intake of a high-fat diet rich in omega-3 (n-3) fatty acids are investigated. METHODS AND RESULTS: C57BL/6J mice are fed either a low-fat (control group) or one of two isocaloric high-fat diets containing either lard (HFD) or fish oil (HFN3) as fat source and evaluated for body weight, adiposity, energy expenditure, glucose homeostasis, and inguinal white and interscapular brown adipose tissue (iWAT and iBAT, respectively) gene expression, lipidome, and mitochondrial bioenergetics. HFN3 intake protected from obesity, glucose and insulin intolerances, and hyperinsulinemia. This is associated with increased energy expenditure, iWAT UCP1 expression, and incorporation of n-3 eicosapentaenoic and docosahexaenoic fatty acids in iWAT and iBAT triacylglycerol. Importantly, HFN3 is equally effective in reducing body weight gain, adiposity, and glucose intolerance and increasing energy expenditure in wild-type and UCP1-deficient mice without recruiting other thermogenic processes in iWAT and iBAT, such as mitochondrial uncoupling and SERCA-mediated calcium and creatine-driven substrate cyclings. CONCLUSION: Intake of a high-fat diet rich in omega-3 fatty acids protects both wild-type and UCP1-deficient mice from obesity and insulin resistance by increasing energy expenditure through unknown mechanisms.

Loss of OcaB Prevents Age-Induced Fat Accretion and Insulin Resistance by Altering B-Lymphocyte Transition and Promoting Energy Expenditure.

The current demographic shift toward an aging population has led to a robust increase in the prevalence of age-associated metabolic disorders. Recent studies have demonstrated that the etiology of obesity-related insulin resistance that develops with aging differs from that induced by high-calorie diets. Whereas the role of adaptive immunity in changes in energy metabolism driven by nutritional challenges has recently gained attention, its impact on aging remains mostly unknown. Here we found that the number of follicular B2 lymphocytes and expression of the B-cell-specific transcriptional coactivator OcaB increase with age in spleen and in intra-abdominal epididymal white adipose tissue (eWAT), concomitantly with higher circulating levels of IgG and impaired glucose homeostasis. Reduction of B-cell maturation and Ig production-especially that of IgG2c-by ablation of OcaB prevented age-induced glucose intolerance and insulin resistance and promoted energy expenditure by stimulating fatty acid utilization in eWAT and brown adipose tissue. Transfer of wild-type bone marrow in OcaB-/- mice replenished the eWAT B2-cell population and IgG levels, which diminished glucose tolerance, insulin sensitivity, and energy expenditure while increasing body weight gain in aged mice. Thus these findings demonstrate that upon aging, modifications in B-cell-driven adaptive immunity contribute to glucose intolerance and fat accretion.

Genetic ablation of phosphatidylcholine transfer protein/StarD2 in ob/ob mice improves glucose tolerance without increasing energy expenditure.

OBJECTIVE: Phosphatidylcholine transfer protein (PC-TP; synonym StarD2) is highly expressed in liver and oxidative tissues. PC-TP promotes hepatic glucose production during fasting and aggravates glucose intolerance in high fat fed mice. However, because PC-TP also suppresses thermogenesis in brown adipose tissue (BAT), its direct contribution to obesity-associated diabetes in mice remains unclear. Here we examined the effects of genetic PC-TP ablation on glucose homeostasis in leptin-deficient ob/ob mice, which exhibit both diabetes and altered thermoregulation. ANIMALS/METHODS: Mice lacking both PC-TP and leptin (Pctp-/-;ob/ob) were prepared by crossing Pctp-/- with ob/+ mice. Glucose homeostasis was assessed by standard assays, and energy expenditure was determined by indirect calorimetry using a comprehensive laboratory animal monitoring system, which also recorded physical activity and food intake. Body composition was determined by NMR and hepatic lipids by enzymatic assays. Core body temperature was measured using a rectal thermocouple probe. RESULTS: Pctp-/-;ob/ob mice demonstrated improved glucose homeostasis, as evidenced by markedly improved glucose and pyruvate tolerance tests, without changes in insulin tolerance. However, there were no differences in EE at any ambient temperature. There were also no effects of PC-TP expression on physical activity, food intake or core body temperature. CONCLUSIONS: Improved glucose tolerance in Pctp-/-;ob/ob mice in the absence of increases in energy expenditure or core body temperature indicates a direct pathogenic role for PC-TP in diabetes in leptin deficient mice.

Metabolism and Energy Expenditure, But Not Feeding or Glucose Tolerance, Are Impaired in Young Kiss1r KO Female Mice.

Kisspeptin regulates reproduction via signaling through the receptor, Kiss1r, in GnRH neurons. However, both kisspeptin and Kiss1r are produced in several peripheral tissues, and recent studies have highlighted a role for kisspeptin signaling in metabolism and glucose homeostasis. We recently reported that Kiss1r knockout (KO) mice display a sexually dimorphic metabolic phenotype, with KO females displaying obesity, impaired metabolism, and glucose intolerance at 4-5 months of age. However, it remains unclear when this metabolic phenotype first emerges in development, or which aspects of the pleiotropic phenotype underlie the metabolic defects and which are secondary to the obesity. Here, we studied Kiss1r KO females at different ages, including several weeks before the emergence of body weight (BW) differences and later when obesity is present. We determined that at young adult ages (6 wk old), KO females already exhibit altered adiposity, leptin levels, metabolism, and energy expenditure, despite having normal BWs at this time. In contrast, food intake, water intake, and glucose tolerance are normal at young ages and only show impairments at older adult ages, suggesting that these impairments may be secondary to earlier alterations in metabolism and adiposity. We also demonstrate that, in addition to BW, all other facets of the adult metabolic phenotype persist even when gonadal sex steroids are similar between genotypes. Collectively, these data highlight the developmental emergence of a metabolic phenotype induced by disrupted kisspeptin signaling and reveal that multiple, but not all, aspects of this phenotype are already disrupted before detectable changes in BW.

Obesity resistance and increased energy expenditure by white adipose tissue browning in Oga(+/-) mice.

AIMS/HYPOTHESIS: O-GlcNAcylation plays a role as a metabolic sensor regulating cellular signalling, transcription and metabolism. Transcription factors and signalling pathways related to metabolism are modulated by N-acetyl-glucosamine (O-GlcNAc) modification. Aberrant regulation of O-GlcNAcylation is closely linked to insulin resistance, type 2 diabetes and obesity. Current evidence shows that increased O-GlcNAcylation negatively regulates insulin signalling, which is associated with insulin resistance and type 2 diabetes. Here, we aimed to evaluate the effects of Oga (also known as Mgea5) haploinsufficiency, which causes hyper-O-GlcNAcylation, on metabolism. METHODS: We examined whether Oga(+/-) mice developed insulin resistance. Metabolic variables were determined including body weight, glucose and insulin tolerance, metabolic rate and thermogenesis. RESULTS: Oga deficiency does not affect insulin signalling even at hyper-O-GlcNAc levels. Oga(+/-) mice are lean with reduced fat mass and improved glucose tolerance. Furthermore, Oga(+/-) mice resist high-fat diet-induced obesity with ameliorated hepatic steatosis and improved glucose metabolism. Oga haploinsufficiency potentiates energy expenditure through the enhancement of brown adipocyte differentiation from the stromal vascular fraction of subcutaneous white adipose tissue (WAT). CONCLUSIONS/INTERPRETATION: Our observations suggest that O-GlcNAcase (OGA) is essential for energy metabolism via regulation of the thermogenic WAT program.

Male mice that lack the G-protein-coupled receptor GPR41 have low energy expenditure and increased body fat content.

SCFA are produced in the gut by bacterial fermentation of undigested carbohydrates. Activation of the Gαi-protein-coupled receptor GPR41 by SCFA in ß-cells and sympathetic ganglia inhibits insulin secretion and increases sympathetic outflow, respectively. A possible role in stimulating leptin secretion by adipocytes is disputed. In the present study, we investigated energy balance and glucose homoeostasis in GPR41 knockout mice fed on a standard low-fat or a high-fat diet. When fed on the low-fat diet, body fat mass was raised and glucose tolerance was impaired in male but not female knockout mice compared to wild-type mice. Soleus muscle and heart weights were reduced in the male mice, but total body lean mass was unchanged. When fed on the high-fat diet, body fat mass was raised in male but not female GPR41 knockout mice, but by no more in the males than when they were fed on the low-fat diet. Body lean mass and energy expenditure were reduced in male mice but not in female knockout mice. These results suggest that the absence of GPR41 increases body fat content in male mice. Gut-derived SCFA may raise energy expenditure and help to protect against obesity by activating GPR41.

Genetic factors in risk assessment for the development of type 2 diabetes mellitus in a small case series.

OBJECTIVE: This study aimed to investigate the role of genetic biomarkers in assessing risk for the eventual development of type 2 diabetes mellitus (T2DM). METHODS: Three Maltese women with a history of previous severe GDM and with apparent similar clinical risk factors underwent anthropomorphic and metabolic reassessment 4-7 years post-partum. They were further genotyped for four specific genetic single nucleotide polymorphisms (SNPs) using the qPCR technique for the alleles of SLC2A2 (rs5393A/C), FTO (rs9939609A/T), PCK (rs2071023C/G) and CDKAL1 (rs10946398A/C). RESULTS: While the previous obstetric history of all the cases was similar, the biological status was characterized by an increasing degree of obesity correlating to increasing severity of current carbohydrate intolerance. Genotyping showed that all the tested SNPs were homozygous mutant in the T2DM woman and heterozygous in the impaired glucose tolerance woman. The woman with normal glucose tolerance was shown to be wild type for SLC2A2 (rs5393A/C). CONCLUSIONS: There appeared to be an interrelationship between eventual severity of carbohydrate metabolism abnormalities and the genetic allele status. It would appear that the specific allele-scoring can be used to identify further the potential risk of developing T2DM.

Adipose tissue-specific inhibition of hypoxia-inducible factor 1{alpha} induces obesity and glucose intolerance by impeding energy expenditure in mice.

Hypoxia in adipose tissue has been postulated as a possible contributor to obesity-related chronic inflammation, insulin resistance, and metabolic dysfunction. HIF1α (hypoxia-inducible factor 1α), a master signal mediator of hypoxia response, is elevated in obese adipose tissue. However, the role of HIF1α in obesity-related pathologies remains to be determined. Here we show that transgenic mice with adipose tissue-selective expression of a dominant negative version of HIF1α developed more severe obesity and were more susceptible to high fat diet-induced glucose intolerance and insulin resistance compared with their wild type littermates. Obesity in the transgenic mice was attributed to impaired energy expenditure and reduced thermogenesis. Histological examination of interscapular brown adipose tissue (BAT) in the transgenic mice demonstrated a markedly increased size of lipid droplets and decreased mitochondrial density in adipocytes, a phenotype similar to that in white adipose tissue. These changes in BAT of the transgenic mice were accompanied by decreased mitochondrial biogenesis and reduced expression of key thermogenic genes. In the transgenic mice, angiogenesis in BAT was decreased but was little affected in white adipose tissue. These findings support an indispensable role of HIF1α in maintaining the thermogenic functions of BAT, possibly through promoting angiogenesis and mitochondrial biogenesis in this tissue.

SIRT1 mRNA expression may be associated with energy expenditure and insulin sensitivity.

OBJECTIVE: Sirtuin 1 (SIRT1) is implicated in the regulation of mitochondrial function, energy metabolism, and insulin sensitivity in rodents. No studies are available in humans to demonstrate that SIRT1 expression in insulin-sensitive tissues is associated with energy expenditure and insulin sensitivity. RESEARCH DESIGN AND METHODS: Energy expenditure (EE), insulin sensitivity, and SIRT1 mRNA adipose tissue expression (n = 81) were measured by indirect calorimetry, hyperinsulinemic-euglycemic clamp, and quantitative RT-PCR in 247 nondiabetic offspring of type 2 diabetic patients. RESULTS: High EE during the clamp (r = 0.375, P = 2.8 x 10(-9)) and high DeltaEE (EE during the clamp - EE in the fasting state) (r = 0.602, P = 2.5 x 10(-24)) were associated with high insulin sensitivity. Adipose tissue SIRT1 mRNA expression was significantly associated with EE (r = 0.289, P = 0.010) and with insulin sensitivity (r = 0.334, P = 0.002) during hyperinsulinemic-euglycemic clamp. Furthermore, SIRT1 mRNA expression correlated significantly with the expression of several genes regulating mitochondrial function and energy metabolism (e.g., peroxisome proliferator-activated receptor gamma coactivator-1beta, estrogen-related receptor alpha, nuclear respiratory factor-1, and mitochondrial transcription factor A), and with several genes of the respiratory chain (e.g., including NADH dehydrogenase [ubiquinone] 1alpha subcomplex 2, cytochrome c, cytochrome c oxidase subunit IV, and ATP synthase). CONCLUSIONS: Impaired stimulation of EE by insulin and low SIRT1 expression in insulin-sensitive tissues is likely to reflect impaired regulation of mitochondrial function associated with insulin resistance in humans.

Linkage and association analyses of type 2 diabetes/impaired glucose metabolism and adiponectin serum levels in Japanese Americans from Hawaii.

Type 2 diabetes is a common disorder associated with obesity. Lower plasma levels of adiponectin were associated with type 2 diabetes. Candidate regions on chromosomes 1 ( approximately 70 cM) and 14 ( approximately 30 cM) were evaluated for replication of suggestive linkage results for type 2 diabetes/impaired glucose homeostasis in an independent sample of Japanese Americans. Replication of independent linkage evidence for serum levels of adiponectin on chromosome 14 was also evaluated. We investigated 529 subjects from 175 sibships who were originally part of the Honolulu Heart Program. Analyses included nonparametric linkage and association using SAGE (Statistical Analysis for Genetic Epidemiology) and FBAT (family-based test of association) programs and Monte Carlo simulation of Fisher's exact test in SAS. For type 2 diabetes/impaired glucose metabolism, nominal linkage evidence (P < 0.02) followed-up by genotypic association (P = 0.016) was found with marker D14S297 at 31.8 cM; linkage analyses using only diabetes phenotype were also nominally significant at this marker (P < 0.02). Nominal evidence for genotypic association to adiponectin serum level phenotype (P = 0.04) was found with the marker D14S1032 at 23.2 cM. The present study was limited by relatively small sample size. Nevertheless, these results corroborate earlier studies, suggesting that further research is warranted in the candidate region approximately 30 cM on chromosome 14.

Estimation of resting energy expenditure considering effects of race and diabetes status.

OBJECTIVE: To evaluate the impact of diabetes status and race, in addition to other covariables, on the estimation of resting energy expenditure (REE). RESEARCH DESIGN AND METHODS: Demographic, anthropometric, and clinical parameters were assessed in 166 adults of varying weights. Subjects were categorized by race (white versus black) and into three subgroups based on glucose tolerance (normoglycemia, impaired glucose tolerance, and type 2 diabetes), termed the diabetes status index (DSI). REE was measured by indirect calorimetry. A multiple regression model was established for optimal prediction of REE based on covariables. RESULTS: An average decrease in REE of 135 kcal/day independent of all other variables was observed in blacks (P < 0.001). DSI was found to be a significant covariable (P = 0.002) in predicting REE, which was observed to be higher in diabetic women. Therefore, race and DSI entered the multiple regression equation to predict REE as significant independent variables, together with lean body mass (LBM) and age x BMI interaction (P < 0.001). Overall, REE prediction resulted in an R(2) of 0.79 and a root mean square error of 136 kcal/day. These values indicate that the resultant equations could offer advantages over other key published prediction equations. The equations are: 1) REE(female) = 803.8 + 0.3505 x age x (BMI - 34.524) - 135.0 x race + 15.866 x LBM + 50.90 x DSI; and 2) REE(male) = 909.4 + 0.3505 x age x (BMI -34.524) -135.0 x race + 15.866 x LBM -9.10 x DSI. The predictive value of the equations did not diminish substantially when fat-free mass estimated by skinfold calipers was substituted for dual-energy X-ray absorptiometry scan measurements of LBM. CONCLUSIONS: Race and diabetes status are important when predicting REE, coupled with LBM, age, BMI, and sex. Race and DSI have not been considered in equations commonly used to predict REE. Their inclusion could improve individualization of dietary prescriptions for type 2 diabetic subjects and heterogeneous populations.

Minimal model-based insulin sensitivity has greater heritability and a different genetic basis than homeostasis model assessment or fasting insulin.

Insulin resistance is an important risk factor for development of type 2 diabetes as well as other chronic conditions, including hypertension, cardiovascular disease, and colon cancer. To find genes for insulin resistance it is necessary to assess insulin action in large populations. We have previously measured insulin action in a large cohort of subjects (Insulin Resistance and Atherosclerosis Study [IRAS] Family Study) using the minimal model approach. In this study, we compare sensitivity from the minimal model (insulin sensitivity index [S(I)]) with the measure of insulin resistance emanating from the homeostasis model assessment (HOMA) approach. The former measure emerges from the glycemic response to endogenous and exogenous insulin; the latter is based solely on fasting measures of glucose and insulin. A total of 112 pedigrees were represented, including 1,362 individuals with full phenotypic assessment. Heritability of S(I) was significantly greater than that for HOMA (0.310 vs. 0.163) and for fasting insulin (0.171), adjusted for age, sex, ethnicity, and BMI. In addition, correlation between S(I) and either HOMA or fasting insulin was only approximately 50% accounted for by genetic factors, with the remainder accounted for by environment. Thus S(I), a direct measure of insulin sensitivity, is determined more by genetic factors rather than measures such as HOMA, which reflect fasting insulin.