Common polymorphisms in the first intron of FTO are associated with increased body weight in adults. Previous studies have suggested that a CUX1-regulatory element within the implicated FTO region ...controls expression of FTO and the nearby ciliary gene, RPGRIP1L. Given the role of ciliary genes in energy homeostasis, we hypothesized that mice hypomorphic for Rpgrip1l would display increased adiposity. We find that Rpgrip1l+/− mice are hyperphagic and fatter, and display diminished suppression of food intake in response to leptin administration. In the hypothalamus of Rpgrip1l+/− mice, and in human fibroblasts with hypomorphic mutations in RPGRIP1L, the number of AcIII-positive cilia is diminished, accompanied by impaired convening of the leptin receptor to the vicinity of the cilium, and diminished pStat3 in response to leptin. These findings suggest that RPGRIP1L may be partly or exclusively responsible for the obesity susceptibility signal at the FTO locus.
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•Mice heterozygous for a null Rpgrip1l allele are fatter than wild-type controls•Leptin signaling is diminished in the hypothalami of Rpgrip1l+/− mice•The localization of the leptin receptor is perturbed in Rpgrip1l+/− mice•RPGRIP1L may account for part or all of the association of the FTO locus with BMI
Common polymorphisms in the first intron of the Fat Mass and Obesity-Associated (FTO) gene are linked with increased body weight in adults. Stratigopoulos et al. show that the nearby ciliary gene, RPGRIP1L, could be responsible for the obesity susceptibility signal at the FTO locus.
The glucose response shape during an OGTT, monophasic or biphasic, can characterize physiologically distinct groups with differences in insulin secretion and sensitivity. Biphasic response (glucose ...rebound after nadir ≥ 0.025 mmol/L) has been associated with higher insulin sensitivity and β-cell function. We aimed to identify the association of the pregnancy OGTT response shape with follow-up maternal and offspring metabolic profiles.
Method: Using HAPO-FUS study data from the NIH-NIDDK repository, monophasic glucose response was defined as 2-hr glucose - 1-hr glucose < 0. Multiple linear regression assessed the relationship of glucose response shape with maternal profile at 10-year follow-up and offspring metabolic profile at 10-12 years of age. Maternal covariates include age, gestational age, field center and BMI. Child covariates include age, sex, pubertal stage, and family history of diabetes.
Results: 4,605 mothers (83.7% monophasic) and 3792 children were included. Mothers with monophasic shape were older (30.7 vs 29.8 years, p=.002), had higher BMI (26.7 vs 26.0 kg/m2, p=.003), HbA1c (4.80 vs 4.70 %, p <.001), 1-hour c-peptide level (9.60 vs 7.75 ug/dL, p <.001) and gestational diabetes (14 vs 9.5%, p <.001). At 10-year follow-up, pregnancy monophasic response was associated with higher fasting glucose level (0.06 0.01, 0.11, p =.01) and log HOMA-IR (0.06 0.02, 0.10, p=.007) in mothers at follow-up. Offspring had higher cord c-peptide (0.12 0.04, 0.21, p=.005) and body fat percent (1.35 0.50-2.21, p =.002). Offspring insulin sensitivity (-0.17 -0.04, -0.3, p=.01) and Matsuda index (-0.46 -0.15, -0.76, p=.003) were lower with monophasic response.
Conclusion: Maternal glucose response profiles during pregnancy determined by both insulin secretion and whole-body insulin resistance are associated with long-term maternal and offspring metabolic profile.
Disclosure
V. V. Thaker: None. C. A. Leduc: None. R. Salem: Other Relationship; Travere Inc.
Funding
National Institutes of Health (K23DK110539)
Understanding the developmental origins of health and disease is integral to overcome the global tide of obesity and its metabolic consequences, including atherosclerotic cardiovascular disease, type ...2 diabetes, hyperlipidemia, and nonalcoholic fatty liver disease. The rising prevalence of obesity has been attributed, in part, to environmental factors including the globalization of the western diet and unhealthy lifestyle choices. In this review we argue that
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such exposures come into play from conception significantly impact overall risk of obesity and later health outcomes. While the laws of thermodynamics dictate that obesity is caused by an imbalance between caloric intake and energy expenditure, the drivers of each of these may be laid down before the manifestation of the phenotype. We present evidence over the last half-century that suggests that the temporospatial evolution of obesity from intrauterine life and beyond is, in part, due to the conditioning of physiological processes at critical developmental periods that results in maladaptive responses to obesogenic exposures later in life. We begin the review by introducing studies that describe an association between perinatal factors and later risk of obesity. After a brief discussion of the pathogenesis of obesity, including the systemic regulation of appetite, adiposity, and basal metabolic rate, we delve into the mechanics of how intrauterine, postnatal and early childhood metabolic environments may contribute to adult obesity risk through the process of metabolic conditioning. Finally, we detail the specific epigenetic pathways identified both in preclinical and clinical studies that synergistically "program" obesity.
Abstract
This review analyzes the published evidence regarding maternal factors that influence the developmental programming of long-term adiposity in humans and animals via the central nervous ...system (CNS). We describe the physiological outcomes of perinatal underfeeding and overfeeding and explore potential mechanisms that may mediate the impact of such exposures on the development of feeding circuits within the CNS—including the influences of metabolic hormones and epigenetic changes. The perinatal environment, reflective of maternal nutritional status, contributes to the programming of offspring adiposity. The in utero and early postnatal periods represent critically sensitive developmental windows during which the hormonal and metabolic milieu affects the maturation of the hypothalamus. Maternal hyperglycemia is associated with increased transfer of glucose to the fetus driving fetal hyperinsulinemia. Elevated fetal insulin causes increased adiposity and consequently higher fetal circulating leptin concentration. Mechanistic studies in animal models indicate important roles of leptin and insulin in central and peripheral programming of adiposity, and suggest that optimal concentrations of these hormones are critical during early life. Additionally, the environmental milieu during development may be conveyed to progeny through epigenetic marks and these can potentially be vertically transmitted to subsequent generations. Thus, nutritional and metabolic/endocrine signals during perinatal development can have lifelong (and possibly multigenerational) impacts on offspring body weight regulation.
Graphical Abstract
Graphical Abstract
Physiological insulin resistance partitions glucose for the growing fetus during the 2nd and 3rd trimester of pregnancy. The HAPO study has demonstrated that pregnancy hyperglycemia is associated ...with offspring adiposity, hyperglycemia, and glucose intolerance. Maternal insulin is a key regulator of the glucose physiology but does not cross the placenta. The goal of this study was to identify the association of pregnancy and offspring c-peptide levels, measured during oral glucose tolerance test (OGTT).
Method: Using HAPO-FUS data from the NIH-NIDDK repository, multiple linear regression assessed the association of scaled pregnancy fasting and 1-hour c-peptide with cord c-peptide (at birth), and child c-peptide from OGTT at the follow-up visit (ages 10-14 years). Maternal covariates include pregnancy gestational age, BMI, glucose level and field center. Child covariates include age, sex, tanner stage, BMI z-score and glucose level. Multiple imputation was performed using missing at random assumption.
Results: A total of 4,802 mother-child pairs were included. Pregnancy c-peptide was associated with cord c-peptide (fasting 0.02 0.01-0.03, p <.001, 1-hour 0.01 0.002-0.02, p =.006). Pregnancy fasting c-peptide was also associated with child OGTT c-peptide (fasting 0.03 0.02-0.04, p <.001; 1-hour 0.11 0.08-0.15, p <.001; 2-hour 0.01 0.007-0.02, p <.001) and pregnancy 1-hour c-peptide (fasting 0.01 0.007-0.02, p <.001; 1-hour 0.15 0.12-0.17, p <.001; 2-hour 0.11 0.09-0.14, p <.001). Similar associations were observed with child insulin levels. Pregnancy c-peptide levels were positively associated with HOMA-IR and negatively with child insulin sensitivity and Matsuda index while adjusting for child BMI z-score and pubertal stage.
Conclusion: Pregnancy insulin levels are strongly associated with the child insulin response during OGTT. This suggests a role in the offspring pancreas developmental programming.
Disclosure
H. Zheng: None. A. Rajamoorthi: None. A. Skowronski: None. R. Salem: Other Relationship; Travere Inc. C. A. Leduc: None. V. V. Thaker: None.
Funding
National Institutes of Health (K23DK110539)
The murine postnatal leptin surge occurs within the first 4 weeks of life and is critical for neuronal projection development within hypothalamic feeding circuits. Here we describe the influence of ...nutritional status on the timing and magnitude of the postnatal leptin surge in mice.
Plasma leptin concentrations were measured 1-3 times per week for the first 4 weeks of life in C57BL/6J pups reared in litters adjusted to 3 (small), 7-8 (normal), or 11-12 (large) pups per dam fed breeder chow or raised in litters of 7-8 by dams fed high-fat diet (HFD) ad libitum starting either prior to conception or at parturition.
Mice raised in small litters become fatter than pups raised in either normal or large litters. The leptin surge in small litter pups starts earlier, lasts longer, and is dramatically larger in magnitude compared to normal litter pups, even when leptin concentrations are normalized to fat mass. In mice reared in large litters, weight gain is diminished and the surge is both significantly delayed and lower in magnitude compared to control pups. Pups reared by HFD-fed dams (starting preconception or at parturition) are fatter and have augmented leptin surge magnitude compared to pups suckled by chow-fed dams. Surge timing varies depending upon nutritional status of the pup; the source of the surge is primarily subcutaneous adipose tissue. At peak leptin surge, within each group, fat mass and plasma leptin are uncorrelated; in comparison with adults, pups overproduce leptin relative to fat mass. Plasma leptin elevation persists longer than previously described; at postnatal day 27 mice continue overproducing leptin relative to fat mass.
In mice, small litter size and maternal HFD feeding during the perinatal period augment the plasma leptin surge whereas large litter size is associated with a delayed surge of reduced magnitude.
The clinical use of the hormone leptin, a key regulator of food intake, to treat the most common instances of obesity has so far failed. In this issue, Zhao et al. (2019) report that, paradoxically, ...reducing leptin levels in obese mice increases their sensitivity to the concentrations that remain, and leads to reductions in weight gain, thus suggesting why these earlier trials may have failed and possibly a new approach to treating obesity.
Noncoding polymorphisms in the fat mass and obesity-associated (FTO) gene represent common alleles that are strongly associated with effects on food intake and adiposity in humans. Previous studies ...have suggested that the obesity-risk allele rs8050136 in the first intron of FTO alters a regulatory element recognized by the transcription factor CUX1, thereby leading to decreased expression of FTO and retinitis pigmentosa GTPase regulator-interacting protein-1 like (RPGRIP1L). Here, we evaluated the effects of rs8050136 and another potential CUX1 element in rs1421085 on expression of nearby genes in human induced pluripotent stem cell-derived (iPSC-derived) neurons. There were allele-dosage effects on FTO, RPGRIP1L, and AKT-interacting protein (AKTIP) expression, but expression of other vicinal genes, including IRX3, IRX5, and RBL2, which have been implicated in mediating functional effects, was not altered. In vivo manipulation of CUX1, Fto, and/or Rpgrip1l expression in mice affected adiposity in a manner that was consistent with CUX1 influence on adiposity via remote effects on Fto and Rpgrip1l expression. In support of a mechanism, mice hypomorphic for Rpgrip1l exhibited hyperphagic obesity, as the result of diminished leptin sensitivity in Leprb-expressing neurons. Together, the results of this study indicate that the effects of FTO-associated SNPs on energy homeostasis are due in part to the effects of these genetic variations on hypothalamic FTO, RPGRIP1L, and possibly other genes.
Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein-9 (Cas9) has become the tool of choice for genome editing. Despite the fact that it has evolved as a ...highly efficient means to edit/replace coding sequence, CRISPR/Cas9 efficiency for "clean" editing of non-coding DNA remains low. We set out to introduce a single base-pair substitution in two intronic SNPs at the FTO locus without altering nearby non-coding sequence. Substitution efficiency increased up to 10-fold by treatment of human embryonic stem cells (ESC) with non-toxic levels of DMSO (1%) before CRISPR/Cas9 delivery. Treatment with DMSO did not result in CRISPR/Cas9 off-target effects or compromise the chromosomal stability of the ESC. Twenty-four hour treatment of human ESC with DMSO before CRISPR/Cas9 delivery may prove a simple means to increase editing efficiency of non-coding DNA without incorporation of undesirable mutations.
The first intron of FTO contains common single nucleotide polymorphisms associated with body weight and adiposity in humans. In an effort to identify the molecular basis for this association, we ...discovered that FTO and RPGRIP1L (a ciliary gene located in close proximity to the transcriptional start site of FTO) are regulated by isoforms P200 and P110 of the transcription factor, CUX1. This regulation occurs via a single AATAAATA regulatory site (conserved in the mouse) within the FTO intronic region associated with adiposity in humans. Single nucleotide polymorphism rs8050136 (located in this regulatory site) affects binding affinities of P200 and P110. Promoter-probe analysis revealed that binding of P200 to this site represses FTO, whereas binding of P110 increases transcriptional activity from the FTO as well as RPGRIP1L minimal promoters. Reduced expression of Fto or Rpgrip1l affects leptin receptor isoform b trafficking and leptin signaling in N41 mouse hypothalamic or N2a neuroblastoma cells in vitro. Leptin receptor clusters in the vicinity of the cilium of arcuate hypothalamic neurons in C57BL/6J mice treated with leptin, but not in fasted mice, suggesting a potentially important role of the cilium in leptin signaling that is, in part, regulated by FTO and RPGRIP1L. Decreased Fto/Rpgrip1l expression in the arcuate hypothalamus coincides with decreased nuclear enzymatic activity of a protease (cathepsin L) that has been shown to cleave full-length CUX1 (P200) to P110. P200 disrupts (whereas P110 promotes) leptin receptor isoform b clustering in the vicinity of the cilium in vitro. Clustering of the receptor coincides with increased leptin signaling as reflected in protein levels of phosphorylated Stat3 (p-Stat3). Association of the FTO locus with adiposity in humans may reflect functional consequences of A/C alleles at rs8050136. The obesity-risk (A) allele shows reduced affinity for the FTO and RPGRIP1L transcriptional activator P110, leading to the following: 1) decreased FTO and RPGRIP1L mRNA levels; 2) reduced LEPR trafficking to the cilium; and, as a consequence, 3) a diminished cellular response to leptin.
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