Bioinformatic analysis of human ZPR1 gene pathogenic exome mutations.

Advanced sequencing technologies enable rapid detection of sequence variants, aiming to uncover the molecular foundations of human genetic disorders. The challenge lies in interpreting the influence of new exome variants that lead to diverse phenotypes. Our study introduces a detailed, multi-tiered method for assessing the impact of novel variants, particularly focusing on the zinc finger protein 1 (ZPR1) gene. Herein, we employed a combination of variant effect predictors, protein stability analyses, and the American College of Medical Genetics and Association of Molecular Pathology (ACMG/AMP) guidelines. Our structural analysis pinpoints specific amino acid residues in the ZPR1 zinc finger domains that are sensitive to changes, distinguishing between benign and disease-causing coding variants using rigorous in silico tools. We examined 223 germline ZPR1 exome variants, uncovering significant ethnic disparities in the frequency of heterozygous harmful ZPR1 variants, ranging from 0.04% in the Ashkenazi Jewish population to 0.34% in African/African Americans. Additionally, the discovery of three homozygous carriers in European and South Asian groups suggests a higher occurrence of ZPR1 variants in these demographics, meriting further exploration. This research provides insights into the prevalence and implications of amino acid substitutions in the ZPR1 protein.

Acat1/Soat1 knockout extends the mutant Npc1 mouse lifespan and ameliorates functional deficiencies in multiple organelles of mutant cells.

Multiple membrane organelles require cholesterol for proper function within cells. The Niemann-Pick type C (NPC) proteins export cholesterol from endosomes to other membrane compartments, including the endoplasmic reticulum (ER), plasma membrane (PM), trans-Golgi network (TGN), and mitochondria, to meet their cholesterol requirements. Defects in NPC cause malfunctions in multiple membrane organelles and lead to an incurable neurological disorder. Acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT1), a resident enzyme in the ER, converts cholesterol to cholesteryl esters for storage. In mutant NPC cells, cholesterol storage still occurs in an NPC-independent manner. Here we report the interesting finding that in a mutant Npc1 mouse (Npc1nmf), Acat1 gene (Soat1) knockout delayed the onset of weight loss, motor impairment, and Purkinje neuron death. It also improved hepatosplenic pathology and prolonged lifespan by 34%. In mutant NPC1 fibroblasts, ACAT1 blockade (A1B) increased cholesterol content associated with TGN-rich membranes and mitochondria, while decreased cholesterol content associated with late endosomes. A1B also restored proper localization of syntaxin 6 and golgin 97 (key proteins in membrane trafficking at TGN) and improved the levels of cathepsin D (a key protease in lysosome and requires Golgi/endosome transport for maturation) and ABCA1 (a key protein controlling cholesterol release at PM). This work supports the hypothesis that diverting cholesterol from storage can benefit multiple diseases that involve cholesterol deficiencies in cell membranes.

Signatures of natural selection and ethnic-specific prevalence of NPC1 pathogenic mutations contributing to obesity and Niemann-Pick disease type C1.

While homozygous pathogenic mutations in the NPC1 gene cause Niemann-Pick type C1 disease, heterozygous mutations cause highly-penetrant obesity. We aimed to investigate the prevalence of NPC1 mutations and their signatures of natural selection in 122,678 exome sequenced participants from six ethnic groups in the Genome Aggregation Database. Pathogenic missense coding mutations were identified by in silico tools and the ClinVar database. Signatures of natural selection were assessed by the probability of NPC1 being loss-of-function mutation intolerant and Z-scores of observed/expected synonymous and non-synonymous mutation ratios. There was no evidence of negative selection observed for synonymous, non-synonymous and loss-of-function mutations. However, there were significant ethnic differences in the prevalence of heterozygous pathogenic NPC1 mutations ranging from 0.56% in Ashkenazi Jewish to 3.26% in African/African Americans (5.8-fold difference). Four homozygous carriers of pathogenic NPC1 mutations were also identified, belonging to the South Asian population. In conclusion, NPC1 mutations are consistent with a model of balanced selection, where heterozygotes and homozygotes have higher and lower reproductive fitness, respectively. Therefore, NPC1 heterozygous mutations may account for a substantial and ethnic-dependent percentage of obesity in the general population, while NPC1 homozygous mutations may be frequent in the South Asian populations and warrants more investigation.

Long-term survival outcomes of patients with Niemann-Pick disease type C receiving miglustat treatment: A large retrospective observational study.

Miglustat has been indicated for the treatment of Niemann-Pick disease type C (NP-C) since 2009. The aim of this observational study was to assess the effect of miglustat on long-term survival of patients with NP-C. Data for 789 patients from five large national cohorts and from the NPC Registry were collected and combined. Miglustat-treated and untreated patients overall and within sub-groups according to age-at-neurological-onset, that is, early infantile-onset (<2 years), late infantile-onset (2 to <6 years), juvenile-onset (6 to <15 years), and adolescent/adult-onset (≥15 years) were analysed and compared. Survival was analysed from the time of first neurological manifestation (Neurological onset group, comprising 669 patients) and from diagnosis (Diagnosis group, comprising 590 patients) using a Cox proportional hazard model adjusted for various covariates. Overall, 384 (57.4%) patients in the Neurological onset group and 329 (55.8%) in the Diagnosis group were treated with miglustat. Miglustat treatment was associated with a significant reduction in risk of mortality in both groups (entire Neurological onset group, Hazard ratio [HR] = 0.51; entire Diagnosis group, HR = 0.44; both P < .001). The effect was observed consistently in all age-at-neurological-onset sub-groups (HRs = 0.3 to 0.7) and was statistically significant for late infantile-onset patients in both groups (Neurological onset group, HR = 0.36, P < .05; Diagnosis group, HR = 0.32, P < .01), and juvenile-onset patients in the Diagnosis group only (HR = 0.30, P < .05). Despite the limitations of the data that urge cautious interpretation, the findings are consistent with a beneficial effect of miglustat on survival in patients with NP-C.

Genetic background modifies phenotypic severity and longevity in a mouse model of Niemann-Pick disease type C1.

Niemann-Pick disease type C1 (NPC1) is a rare, fatal neurodegenerative disorder characterized by lysosomal accumulation of unesterified cholesterol and glycosphingolipids. These subcellular pathologies lead to phenotypes of hepatosplenomegaly, neurological degeneration and premature death. NPC1 is extremely heterogeneous in the timing of clinical presentation and is associated with a wide spectrum of causative NPC1 mutations. To study the genetic architecture of NPC1, we have generated a new NPC1 mouse model, Npc1em1PavNpc1em1Pav/em1Pav mutants showed notably reduced NPC1 protein compared to controls and displayed the pathological and biochemical hallmarks of NPC1. Interestingly, Npc1em1Pav/em1Pav mutants on a C57BL/6J genetic background showed more severe visceral pathology and a significantly shorter lifespan compared to Npc1em1Pav/em1Pav mutants on a BALB/cJ background, suggesting that strain-specific modifiers contribute to disease severity and survival. QTL analysis for lifespan of 202 backcross N2 mutants on a mixed C57BL/6J and BALB/cJ background detected significant linkage to markers on chromosomes 1 and 7. The discovery of these modifier regions demonstrates that mouse models are powerful tools for analyzing the genetics underlying rare human diseases, which can be used to improve understanding of the variability in NPC1 phenotypes and advance options for patient diagnosis and therapy.This article has an associated First Person interview with the first author of the paper.

111In-DANBIRT In Vivo Molecular Imaging of Inflammatory Cells in Atherosclerosis.

Atherosclerosis-related morbidity and mortality remain a global concern. Atherosclerotic disease follows a slow and silent progression, and the transition from early-stage lesions to vulnerable plaques remains difficult to diagnose. Inflammation is a key component of the development of atherosclerotic plaque and consequent life-threatening complications. This study assessed 111In-DANBIRT as an in vivo, noninvasive SPECT/CT imaging probe targeting an inflammatory marker, Lymphocyte Function Associated Antigen-1 (LFA-1), in atherosclerotic plaques. Methods. Selective binding of 111In-DANBIRT was assessed using Sprague-Dawley rats exposed to filtered air and ozone (1 ppm) by inhalation for 4 hours to induce a circulating leukocytosis and neutrophilia in peripheral blood. After 24 hours, whole blood was collected and incubated with radiolabeled DANBIRT (68Ga-DANBIRT and 111In-DANBIRT). Isolated cell component smeared slides using cytospin technique were stained with Wright-Giemsa stain. Apolipoprotein E-deficient (apoE-/-) mice were fed either a normal diet or a high-fat diet (HFD) for 8 weeks. Longitudinal SPECT/CT imaging was performed 3 hours after administration at baseline, 4, and 8 weeks of HFD diet, followed by tissue harvesting for biodistribution, serum lipid analysis, and histology. 3D autoradiography was performed in both groups 24 hours after administration of 111In-DANBIRT. Results. Increased specific uptake of radiolabeled DANBIRT by neutrophils in the ozone-exposed group was evidenced by the acute immune response due to 4-hour ozone exposure. Molecular imaging performed at 3 hours using SPECT/CT imaging evidenced an exponential longitudinal increase in 111In-DANBIRT uptake in atherosclerosis lesions in HFD-fed mice compared to normal-diet-fed mice. Such results were consistent with increased immune response to vascular injury in cardiovascular and also immune tissues, correlated by 24 hours after administration of 3D autoradiography. Histologic analysis confirmed atherosclerotic disease progression with an increased vascular lesion area in HFD-fed mice compared to normal-diet-fed mice. Conclusion. 111In-DANBIRT is a promising molecular imaging probe to assess inflammation in evolving atheroma and atherosclerotic plaque.

The Extending Spectrum of NPC1-Related Human Disorders: From Niemann-Pick C1 Disease to Obesity.

The Niemann-Pick type C1 (NPC1) protein regulates the transport of cholesterol and fatty acids from late endosomes/lysosomes and has a central role in maintaining lipid homeostasis. NPC1 loss-of-function mutations in humans cause NPC1 disease, a rare autosomal-recessive lipid-storage disorder characterized by progressive and lethal neurodegeneration, as well as liver and lung failure, due to cholesterol infiltration. In humans, genome-wide association studies and post-genome-wide association studies highlight the implication of common variants in NPC1 in adult-onset obesity, body fat mass, and type 2 diabetes. Heterozygous human carriers of rare loss-of-function coding variants in NPC1 display an increased risk of morbid adult obesity. These associations have been confirmed in mice models, showing an important interaction with high-fat diet. In this review, we describe the current state of knowledge for NPC1 variants in relationship to pleiotropic effects on metabolism. We provide evidence that NPC1 gene variations may predispose to common metabolic diseases by modulating steroid hormone synthesis and/or lipid homeostasis. We also propose several important directions of research to further define the complex roles of NPC1 in metabolism. This review emphasizes the contribution of NPC1 to obesity and its metabolic complications.

Gene-nutrient interactions and susceptibility to human obesity.

A large number of genome-wide association studies, transferability studies, and candidate gene studies performed in diverse populations around the world have identified gene variants that are associated with common human obesity. The mounting evidence suggests that these obesity gene variants interact with multiple environmental factors and increase susceptibility to this complex metabolic disease. The objective of this review article is to provide concise and updated information on energy balance, heritability of body weight, origins of gene variants, and gene-nutrient interactions in relation to human obesity. It is proposed that knowledge of these related topics will provide valuable insight for future preventative lifestyle intervention using targeted nutritional and medicinal therapies.

A global evolutionary and metabolic analysis of human obesity gene risk variants.

It is generally accepted that the selection of gene variants during human evolution optimized energy metabolism that now interacts with our obesogenic environment to increase the prevalence of obesity. The purpose of this study was to perform a global evolutionary and metabolic analysis of human obesity gene risk variants (110 human obesity genes with 127 nearest gene risk variants) identified using genome-wide association studies (GWAS) to enhance our knowledge of early and late genotypes. As a result of determining the mean frequency of these obesity gene risk variants in 13 available populations from around the world our results provide evidence for the early selection of ancestral risk variants (defined as selection before migration from Africa) and late selection of derived risk variants (defined as selection after migration from Africa). Our results also provide novel information for association of these obesity genes or encoded proteins with diverse metabolic pathways and other human diseases. The overall results indicate a significant differential evolutionary pattern for the selection of obesity gene ancestral and derived risk variants proposed to optimize energy metabolism in varying global environments and complex association with metabolic pathways and other human diseases. These results are consistent with obesity genes that encode proteins possessing a fundamental role in maintaining energy metabolism and survival during the course of human evolution.

The Niemann-Pick C1 gene interacts with a high-fat diet to promote weight gain through differential regulation of central energy metabolism pathways.

A genome-wide association study (GWAS) reported that common variation in the human Niemann-Pick C1 gene (NPC1) is associated with morbid adult obesity. This study was confirmed using our BALB/cJ Npc1 mouse model, whereby heterozygous mice (Npc1+/- ) with decreased gene dosage were susceptible to weight gain when fed a high-fat diet (HFD) compared with homozygous normal mice (Npc1+/+ ) fed the same diet. The objective for our current study was to validate this Npc1 gene-diet interaction using statistical modeling with fitted growth trajectories, conduct body weight analyses for different measures, and define the physiological basis responsible for weight gain. Metabolic phenotype analysis indicated no significant difference between Npc1+/+ and Npc1+/- mice fed a HFD for food and water intake, oxygen consumption, carbon dioxide production, locomotor activity, adaptive thermogenesis, and intestinal lipid absorption. However, the livers from Npc1+/- mice had significantly increased amounts of mature sterol regulatory element-binding protein-1 (SREBP-1) and increased expression of SREBP-1 target genes that regulate glycolysis and lipogenesis with an accumulation of triacylglycerol and cholesterol. Moreover, white adipose tissue from Npc1+/- mice had significantly decreased amounts of phosphorylated hormone-sensitive lipase with decreased triacylglycerol lipolysis. Consistent with these results, cellular energy metabolism studies indicated that Npc1+/- fibroblasts had significantly increased glycolysis and lipogenesis, in addition to significantly decreased substrate (glucose and endogenous fatty acid) oxidative metabolism with an accumulation of triacylglycerol and cholesterol. In conclusion, these studies demonstrate that the Npc1 gene interacts with a HFD to promote weight gain through differential regulation of central energy metabolism pathways.

Differential Association of Niemann-Pick C1 Gene Polymorphisms with Maternal Prepregnancy Overweight and Gestational Diabetes.

A genome-wide association study (GWAS) and subsequent replication studies in diverse ethnic groups indicate that common Niemann-Pick C1 gene (NPC1) polymorphisms are associated with morbid-adult obesity or diabetes independent of body weight. The objectives for this prospective cross-sectional study were to determine allele frequencies for NPC1 polymorphisms (644A>G, 1926C>G, 2572A>G, and 3797G>A) and association with metabolic disease phenotypes in an ethnically diverse New Mexican obstetric population. Allele frequencies for 1926C>G, 2572A>G, and 3797G>A were significantly different between race/ethnic groups (non-Hispanic white, Hispanic, and Native American). The results also indicated a significant pairwise linkage-disequilibrium between each of the four NPC1 polymorphisms in race/ethnic groups. Moreover, the derived and major allele for 1926C>G was associated (OR 2.11, 95% CI 1.10-3.96, P = 0.022) with increased risk for maternal prepregnancy overweight (BMI 25.0-29.9kg/m2) while the ancestral and major allele for 2572A>G was associated (OR 4.68, 95% CI 1.23-17.8, P = 0.024) with increased risk for gestational diabetes in non-Hispanic whites, but not Hispanics or Native Americans. In summary, this is the first transferability study to investigate common NPC1 polymorphisms in a multiethnic population and demonstrate a differential association with increased risk for maternal prepregnancy overweight and gestational diabetes.

NAFLD Susceptibility Genes and their Association with Type 2 Diabetes and Obesity in a New Mexico Population.

OBJECTIVE: Genome-wide association studies have identified single-nucleotide polymorphisms (SNPs) that increase the risk of developing non-alcoholic fatty liver disease (NAFLD). One purpose of this study was to determine the frequencies of NAFLD susceptibility SNPs in a non-Hispanic white and Hispanic population who attended a clinic in northeast Albuquerque, NM. Another goal was to determine associations with selected indicators in this New Mexican population. METHODS: This cohort study involving 168 volunteer subjects in the NM population (88 non-Hispanic whites, 63 Hispanics, 4 Native Americans, 11 Asian Americans, 2 unreported ethnicity). Eight SNPs within 6 NAFLD susceptibility genes including PNPLA3 (rs738409), LYPLAL1 (rs12137855), APOC3 (rs2854116, rs2854117), GCKR (rs780094, rs741038), FABP2 (rs1799883), PEMT (rs7946) were analyzed by genotyping using the TaqMan genotyping assay (Applied Biosystems, Foster City, CA). Statistical analyses were carried out using statistical package SAS 9.3. RESULTS: The NAFLD allele frequencies were similar in non-Hispanic whites and Hispanics except for PNPLA3 (rs738409), FABP2 (rs1799883), and PEMT (rs7946). Eight SNPs in 5 NAFLD susceptibility genes were significantly associated OR marginally associated with selected indicators for NAFLD, metabolic syndrome, overweight, obesity, insulin resistance, type 2 diabetes, hypertension, dyslipidemia. No SNPs were significantly associated with the same indicator in both the non-Hispanic white and Hispanic groups. CONCLUSIONS: In this population of non-Hispanic whites and Hispanics, there were only heterozygotes for the APOC3 derived alle le whereas for all other genes tested, both heterozygotes and homozygotes were found. Associations of alleles with indicators of chronic disease were different in non-Hispanic whites compared to Hispanics.

The Niemann-Pick C1 and caveolin-1 proteins interact to modulate efflux of low density lipoprotein-derived cholesterol from late endocytic compartments.

The Niemann-Pick C1 (NPC1) protein has a central role in regulating the efflux of lipoprotein-derived cholesterol from late endosomes/lysosomes and transport to other cellular compartments. Since the NPC1 protein has been shown to regulate the transport of cholesterol to cellular compartments enriched with the ubiquitous cholesterol-binding and transport protein caveolin-1, the present study was performed to determine whether the NPC1 and caveolin-1 proteins interact and function to modulate efflux of low density lipoprotein (LDL)-derived cholesterol from endocytic compartments. To perform these studies, normal human fibroblasts were grown in media with lipoprotein-deficient serum (LPDS) or media with LPDS supplemented with purified human LDL. The results indicated reciprocal co-immunoprecipitation and partial co-localization of the NPC1 and caveolin-1 proteins that was decreased when fibroblasts were grown in media with LDL. Consistent with interaction of the NPC1 and caveolin-1 proteins, a highly conserved caveolin-binding motif was identified within a cytoplasmic loop located adjacent to the sterol-sensing domain (SSD) of the NPC1 protein. To examine the functional relevance of this interaction, fibroblasts were transfected with caveolin-1 siRNA and found to accumulate increased amounts of LDL-derived cholesterol within late endosomes/ lysosomes. Together, this report presents novel results demonstrating that the NPC1 and caveolin-1 proteins interact to modulate efflux of LDL-derived cholesterol from late endocytic compartments.

The C57BL/6J Niemann-Pick C1 mouse model with decreased gene dosage has impaired glucose tolerance independent of body weight.

The human Niemann-Pick C1 (NPC1) gene has been found to be associated with extreme (early-onset and morbid-adult) obesity and type 2 diabetes independent of body weight. We previously performed growth studies using BALB/cJ Npc1 normal (Npc1+/+) and Npc1 heterozygous (Npc1+/-) mice and determined that decreased Npc1 gene dosage interacts with a high-fat diet to promote weight gain and adiposity. The present study was performed using both BALB/cJ and C57BL/6J Npc1+/+ and Npc1+/- mice to determine if decreased Npc1 gene dosage predisposes to metabolic features associated with type 2 diabetes. The results indicated that C57BL/6J Npc1+/- mice, but not BALB/cJ Npc1+/- mice, have impaired glucose tolerance when fed a low-fat diet and independent of body weight. The results also suggest that an accumulation of liver free fatty acids and hepatic lipotoxicity marked by an elevation in the amount of plasma alanine aminotransferase (ALT) may be responsible for hepatic insulin resistance and impaired glucose tolerance. Finally, the peroxisome-proliferator activated receptor α (PPARα) and sterol regulatory element-binding protein-1 (SREBP-1) pathways known to have a central role in regulating free fatty acid metabolism were downregulated in the livers, but not in the adipose or muscle, of C57BL/6J Npc1+/- mice compared to C57BL/6J Npc1+/+ mice. Therefore, decreased Npc1 gene dosage among two different mouse strains interacts with undefined modifying genes to manifest disparate yet often related metabolic diseases.

A high-fat diet supplemented with fish oil improves metabolic features associated with type 2 diabetes.

OBJECTIVE: The goal of this study was to investigate the effects of a high-fat diet supplemented with fish oil or olive oil, fed to C57BL/6J mice for an extended period, on metabolic features associated with type 2 diabetes. METHODS: Mice were fed one of four diets for 30 wk: a low-fat diet, a high-fat diet supplemented with lard, a high-fat diet supplemented with fish oil, or a high-fat diet supplemented with olive oil. Phenotypic and metabolic analysis were determined at 15 and 25 to 30 wk, thereby providing comparative analysis for weight gain, energy consumption, fat distribution, glucose and insulin tolerance, and hepatic/plasma lipid analysis. RESULTS: Mice fed a high-fat diet supplemented with fish oil had improved glucose tolerance after an extended period compared with mice fed a high-fat diet supplemented with lard. Moreover, mice fed a high-fat diet supplemented with fish oil had significantly decreased concentrations of liver cholesterol, cholesteryl ester, and triacylglycerol compared with mice fed a high-fat diet supplemented with either lard or olive oil. CONCLUSION: Mice fed a high-fat diet supplemented with fish oil improved metabolic features associated with type 2 diabetes such as impaired glucose tolerance and hepatic steatosis.

The genetics of childhood obesity and interaction with dietary macronutrients.

The genes contributing to childhood obesity are categorized into three different types based on distinct genetic and phenotypic characteristics. These types of childhood obesity are represented by rare monogenic forms of syndromic or non-syndromic childhood obesity, and common polygenic childhood obesity. In some cases, genetic susceptibility to these forms of childhood obesity may result from different variations of the same gene. Although the prevalence for rare monogenic forms of childhood obesity has not increased in recent times, the prevalence of common childhood obesity has increased in the United States and developing countries throughout the world during the past few decades. A number of recent genome-wide association studies and mouse model studies have established the identification of susceptibility genes contributing to common childhood obesity. Accumulating evidence suggests that this type of childhood obesity represents a complex metabolic disease resulting from an interaction with environmental factors, including dietary macronutrients. The objective of this article is to provide a review on the origins, mechanisms, and health consequences of obesity susceptibility genes and interaction with dietary macronutrients that predispose to childhood obesity. It is proposed that increased knowledge of these obesity susceptibility genes and interaction with dietary macronutrients will provide valuable insight for individual, family, and community preventative lifestyle intervention, and eventually targeted nutritional and medicinal therapies.

The cytosolic adaptor AP-1A is essential for the trafficking and function of Niemann-Pick type C proteins.

Niemann-Pick type C (NPC) disease is a fatal neurodegenerative disorder characterized by over-accumulation of low-density lipoprotein-derived cholesterol and glycosphingolipids in late endosomes/lysosomes (LE/L) throughout the body. Human mutations in either NPC1 or NPC2 genes have been directly associated with impaired cholesterol efflux from LE/L. Independent from its role in cholesterol homeostasis and its NPC2 partner, NPC1 was unexpectedly identified as a critical player controlling intracellular entry of filoviruses such as Ebola. In this study, a yeast three-hybrid system revealed that the NPC1 cytoplasmic tail directly interacts with the clathrin adaptor protein AP-1 via its acidic/di-leucine motif. Consequently, a nonfunctional AP-1A cytosolic complex resulted in a typical NPC-like phenotype mainly due to a direct impairment of NPC1 trafficking to LE/L and a partial secretion of NPC2. Furthermore, the mislocalization of NPC1 was not due to cholesterol accumulation in LE/L, as it was not rescued upon treatment with Mß-cyclodextrin, which almost completely eliminated intracellular free cholesterol. Our cumulative data demonstrate that the cytosolic clathrin adaptor AP-1A is essential for the lysosomal targeting and function of NPC1 and NPC2.

The Niemann-Pick C1 gene is downregulated in livers of C57BL/6J mice by dietary fatty acids, but not dietary cholesterol, through feedback inhibition of the SREBP pathway.

The Niemann-Pick C1 (NPC1) gene is associated with human obesity. Mouse models with decreased Npc1 gene dosage are susceptible to weight gain when fed a high-fat diet, but not a low-fat diet, consistent with an Npc1 gene-diet interaction. The objectives of this study were to define regulation of the Npc1 gene and to investigate the Npc1 gene-diet interaction responsible for weight gain. The experimental design involved feeding C57BL/6J male mice a low-fat diet (with 0.00, 0.10, or 1.00% cholesterol) or a high-fat diet (with 0.02% cholesterol) until 30 wk to determine regulation of the Npc1 gene in liver. The key results showed that the Npc1 gene was downregulated by dietary fatty acids (54%, P = 0.022), but not by dietary cholesterol, through feedback inhibition of the sterol regulatory element-binding protein (SREBP) pathway. However, the dietary fatty acids secondarily increased liver cholesterol, which also inhibits the SREBP pathway. Similarly, the Npc1 gene was downregulated in peritoneal fibroblasts isolated from C57BL/6J weanling male mice not exposed to the experimental diets and incubated in media supplemented with purified oleic acid (37%, P = 0.038) but not in media supplemented with purified cholesterol. These results are important because they suggest a novel mechanism for the interaction of fatty acids with the Npc1 gene to influence energy balance and to promote weight gain. Moreover, the responsiveness of the Npc1 gene to fatty acids is consistent with studies that suggest that the encoded NPC1 protein has a physiologic role in regulating both cholesterol and fatty acid metabolism.

Gene-diet interactions in childhood obesity.

Childhood overweight and obesity have reached epidemic proportions worldwide, and the increase in weight-associated co-morbidities including premature type 2 diabetes mellitus (T2DM) and atherosclerotic cardiovascular disease will soon become major healthcare and economic problems. A number of studies now indicate that the childhood obesity epidemic which has emerged during the past 30 years is a complex multi-factorial disease resulting from interaction of susceptibility genes with an obesogenic environment. This review will focus on gene-diet interactions suspected of having a prominent role in promoting childhood obesity. In particular, the specific genes that will be presented (FTO, MC4R, and NPC1) have recently been associated with childhood obesity through a genome-wide association study (GWAS) and were shown to interact with nutritional components to increase weight gain. Although a fourth gene (APOA2) has not yet been associated with childhood obesity, this review will also present information on what now represents the best characterized gene-diet interaction in promoting weight gain.