Low Salivary Amylase Gene (AMY1) Copy Number Is Associated with Obesity and Gut Prevotella Abundance in Mexican Children and Adults

The complex web of obesity: from genetics to precision medicine

INTRODUCTION

Obesity is a growing public health concern affecting both children and adults. Since it involves both genetic and environmental components, the management of obesity requires both, an understanding of the underlying genetics and changes in lifestyle. The knowledge of obesity genetics will enable the possibility of precision medicine in anti-obesity medications.

AREAS COVERED

Here, we explore health complications and the prevalence of obesity. We discuss disruptions in energy balance as a symptom of obesity, examining evolutionary theories, its multi-factorial origins, and heritability. Additionally, we discuss monogenic and polygenic obesity, the converging biological pathways, potential pharmacogenomics applications, and existing anti-obesity medications - specifically focussing on the leptin-melanocortin and incretin pathways. Comparisons between childhood and adult obesity genetics are made, along with insights into structural variants, epigenetic changes, and environmental influences on epigenetic signatures.

EXPERT OPINION

With recent advancements in anti-obesity drugs, genetic studies pinpoint new targets and allow for repurposing existing drugs. This creates opportunities for genotype-informed treatment options. Also, lifestyle interventions can help in the prevention and treatment of obesity by altering the epigenetic signatures. The comparison of genetic architecture in adults and children revealed a significant overlap. However, more robust studies with diverse ethnic representation is required in childhood obesity.

Uncovering structural variants associated with body weight and obesity risk in labrador retrievers: a genome-wide study

Although obesity in the domestic dog (Canis lupus familiaris) is known to decrease well-being and shorten lifespan, the genetic risk variants associated with canine obesity remain largely unknown. In our study, which focused on the obesity-prone Labrador Retriever breed, we conducted a genome-wide analysis to identify structural variants linked to body weight and obesity. Obesity status was based on a 5-point body condition score (BCS) and the obese dog group included all dogs with a BCS of 5, along with dogs with the highest body weight within the BCS 4 group. Data from whole-gene sequencing of fifty dogs, including 28 obese dogs, were bioinformatically analyzed to identify potential structural variants that varied in frequency between obese and healthy dogs. The seven most promising variants were further analyzed by droplet digital PCR in a group of 110 dogs, including 63 obese. Our statistical evidence suggests that common structural mutations in or near six genes, specifically ALPL, KCTD8, SGSM1, SLC12A6, RYR3, and VPS26C, may contribute to the variability observed in body weight and body condition scores among Labrador Retriever dogs. These findings emphasize the need for additional research to validate the associations and explore the specific functions of these genes in relation to canine obesity.

Captivity restructures the gut microbiota of François' langurs (Trachypithecus francoisi)

Gut microbiota is crucial to primate survival. Data on the gut microbiota of captive and wild animals can provide a physiological and ecological basis for the conservation of rare and endangered species. To study the effect of captivity on the gut microbiota, we examine the difference in the gut microbiota composition between captive and wild Francois' langurs (Trachypithecus francoisi), using 16S rRNA sequencing technology. The results showed that the composition of the gut microbiota of captive and wild langurs was characterized by Firmicutes (51.93 ± 10.07% vs. 76.15 ± 8.37%) and Bacteroidetes (32.43 ± 10.00% vs. 4.82 ± 1.41%) at the phylum level and was characterized by Oscillospiraceae (15.80 ± 5.19% vs. 30.21 ± 4.87%) at the family level. The alpha diversity of gut microbiota in captive langurs was higher than those in wild, such as the Shannon index (4.45 ± 0.33 vs. 3.98 ± 0.19, P < 0.001) and invSimpson index (35.11 ± 15.63 vs. 19.02 ± 4.87, P < 0.001). Principal coordinates analysis (PCoA) results showed significant differences in the composition of gut microbiota between captive and wild langurs at both the phylum and family levels (weight UniFrac algorithm, phylum level: R² = 0.748, P = 0.001; family level: R² = 0.685, P = 0.001). The relative abundance of Firmicutes (51.93 ± 10.07%) in captive langurs was lower than that of wild langurs (76.15 ± 8.37%), and the relative abundance of Bacteroidetes (32.43 ± 10.00%) in captive langurs was higher than that of wild (4.82 ± 1.41%). Our study concludes that dietary composition could be a crucial determinant in shaping the gut microbiota of langurs because more fiber-rich foods used by the wild langurs could increase the abundance of Firmicutes, and more simple carbohydrate-rich foods consumed by the captive langurs increase the abundance of Bacteroidetes. We highlight the importance of captivity on the gut microbiota and the need to consider the gut microbiota in animal provision.

[From genotype to phenotype: amylase gene in childhood obesity]

Worldwide, Mexico is one of the countries with the highest rate of obesity, which is a condition considered the main risk factor for type 2 diabetes. Among the mechanisms that predispose to obesity, the interaction between food intake and genetic components has been little explored. Recently we evidenced a significant association between the copy number (CN) of AMY1A and AMY2A genes, the enzymatic activity of salivary and pancreatic amylase, and the frequency of childhood obesity in Mexico, a particular population due to the high consumption of starch in the diet and the high prevalence of obesity in children and adults. This review aims to find a better understanding of the role of amylase in obesity through a description of the evolution of the CN of its genes, the association of its enzymatic activity with obesity, and the effect of its interaction with starch intake on Mexican children. In addition, it denotes the importance of the experimental perspectives of further investigation regarding the mechanism by which amylase could regulate the abundance of oligosaccharide-fermenting bacteria and producers of short-chain fatty acids and/or branched-chain amino acids that could contribute to the alteration of the physiological processes associated with intestinal inflammation and metabolic deregulation that predispose to the development of obesity.

Genetic factors associated with serum amylase in a Japanese population: combined analysis of copy-number and single-nucleotide variants

Amylase activity and levels in humans are heritable quantitative traits. Although many studies exist on the effects of copy-number variants (CNVs) in amylase genes (AMY) on human phenotypes, such as body mass index (BMI), the genetic factors controlling interindividual variation in amylase levels remain poorly understood. Here, we conducted a genome-wide association study (GWAS) of serum amylase levels (SAL) in 814 Japanese individuals to identify associated single-nucleotide variants (SNVs), after adjusting for non-genetic factors. Diploid copy numbers (CN) of AMY (AMY1, AMY2A, and AMY2B) were measured using droplet digital PCR to examine the association between each diploid CN and SAL. We further assessed the relative contribution of the GWAS-lead SNV and AMY CNVs to SAL. GWAS identified 14 significant SNVs (p < 5 × 10^-8) within a linkage disequilibrium block near the AMY cluster on chromosome 1. The association analyses of AMY CNVs and SAL showed a significant association between AMY1 diploid CN and SAL (p = 1.89 × 10^-19), while no significant association with SAL was found for AMY2A CN (p = 0.54) or AMY2B CN (p = 0.15). In a joint association analysis with SAL using the GWAS-lead SNV and AMY1 diploid CN, AMY1 CN remained significant (p = 5.4 ×10^-13), while the association of the lead SNV was marginal (p = 0.08). We also found no association between AMY1 diploid CN and BMI (p = 0.14). Our results indicate that AMY1 CNV is the major genetic factor for Japanese SAL, with no significant association with BMI.

Association of total and pancreatic serum amylase enzymatic activity with insulin resistance and the glucose and insulin responses to oral starch test in Mexican children

BACKGROUND/OBJECTIVES

Little is known about the effect of serum amylase enzymatic activity on glucose metabolism. We investigated the association of serum amylase enzymatic activity with fasting plasma glucose, insulin resistance (IR), and the plasma glucose and insulin response to an oral starch test (OST) in Mexican children.

METHODS

Anthropometric data, glucose and insulin levels, and the serum enzymatic activity of total (AMYt), salivary (AMY1), and pancreatic (AMY2) amylase were analysed in 764 children (N_{normal weight}  = 427/N_obesity  = 337). After categorization into low (LA) and high (HA) AMYt, an OST with commercial white bread was performed in 39 children (N_{normal weight}  = 17/N_obesity  = 22).

RESULTS

A positive association between serum enzymatic activity of AMY2 and IR was observed in children with obesity (p = 0.018). Children with normal weight had lower plasma glucose and insulin response to OST than children with obesity (P_glucose  = 4.1 × 10^-12 ; P_insulin  = 2.1 × 10^-15 ). Compared with the LA group, children with HA showed lower plasma glucose and insulin response to OST (P_glucose  ≤ 0.040; P_insulin  ≤ 0.015).

CONCLUSION

Our results suggest that AMY2 is positively associated with IR. A high level of AMYt is related to lower glucose and insulin responses to OST in Mexican children, regardless of their weight status.

Postbiotic heat-killed lactobacilli modulates on body weight associated with gut microbiota in a pig model

For decades, Lactobacillus has been extensively used as beneficial probiotics because it positively effects on the intestinal health of the host and has been studying its possible serve to treat obesity as well as various diseases. This research aimed to investigate the effects of heat-killed Ligilactobacillus salivarius strain 189 (HK LS 189) supplementation on anti-obesity and gut microbiota. A total of 48 pigs were fed either a basal diet or a diet supplemented with HK LS 189 for 4 weeks. The impact of HK LS 189 supplementation on the composition and function of the intestinal microbiota was revealed by 16 S rRNA gene sequencing. HK LS 189 supplementation significantly decreased growth performance. Moreover, HK LS 189 supplementation altered the gut microbiota of the pigs by decreasing the proportion of Prevotella and increasing the proportion of Parabacteroides. Beta-diversity analysis showed a significant difference between the two groups. The results support the potential use of HK LS 189 for its anti-obesity effect in pigs through modulation of the gut microbiota. Furthermore, we found changes in the functional pathways of the gut microbiota. The functional pathway study indicated that metabolism and lipid metabolism differed between the two groups. Our data may contribute to understanding the potential use of postbiotic supplementation with HK LS 189 for improving the anti-obesity effects.

Impact of salivary and pancreatic amylase gene copy numbers on diabetes, obesity, and functional profiles of microbiome in Northern Japanese population

Amylase genes reside in a structurally complex locus, and their copy numbers vary greatly, and several studies have reported their association with obesity. The mechanism of this effect was partially explained by changes in the oral and gut microbiome compositions; however, a detailed mechanism has been unclarified. In this study, we showed their association with diabetes in addition to obesity, and further discovered a plausible mechanism of this association based on the function of commensal bacteria. First, we confirmed that the amylase copy number in the population tends to be larger than that reported in other studies and that there is a positive association between obesity and diabetes (p = 1.89E-2 and 8.63E-3). Second, we identified that relative abundance of some genus level microbiome, Capnocytophaga, Dialister, and previously reported bacteria, were significantly associated with amylase copy numbers. Finally, through functional gene-set analysis using shotgun sequencing, we observed that the abundance of genes in the Acarbose pathway in the gut microbiome was significantly decreased with an increase in the amylase copy number (p-value = 5.80E-4). Our findings can partly explain the mechanism underlying obesity and diabetes in populations with high amylase copy numbers.

Elevated levels of salivary α- amylase activity in saliva associated with reduced odds of obesity in adult Qatari citizens: A cross-sectional study

The relationship between salivary α-amylase activity (ssAAa) and the risk of metabolic disorders remains equivocal. We aimed to assess this relationship in adults from Qatar, where obesity and type 2 diabetes are highly prevalent. We cross-sectionally quantified ssAAa in saliva and estimated AMY1 CN from whole-genome sequencing data from 1499 participants. Linear regression was used to assess the relationship between ssAAa and adiposity and glycemic markers. Logistic regression was used to examine the association between ssAAa and occurrence of obesity or diabetes. The mean and median ssAAa were significantly lower in obese individuals. There were significant inverse associations between ssAAa and BMI, and fat mass. We detected a marked effect of ssAAa on reduced odds of obesity after adjusting for age and sex, glucose, LDL, HLD, total cholesterol, and systolic and diastolic blood pressure (OR per ssAAa unit 0.998 [95% CI 0.996–0.999], p = 0.005), with ssAAa ranging between 6.8 and 422U/mL. The obesity odds were significantly lower in the upper half of the ssAAa distributional (OR 0.58 [95% CI 0.42–0.76], p<0.001) and lower in the top versus the bottom decile of the ssAAa distribution (OR 0.46 [95% CI 0.23–0.92], p = 0.03). Our findings suggest a potential beneficial relationship between high sAAa in saliva and low odds of obesity in Qatari adults.

Ethnic variability associating gut and oral microbiome with obesity in children

Obesity is a growing worldwide problem that generally starts in the early years of life and affects minorities more often than Whites. Thus, there is an urgency to determine factors that can be used as targets as indicators of obesity. In this study, we attempt to generate a profile of gut and oral microbial clades predictive of disease status in African American (AA) and European American (EA) children. 16S rDNA sequencing of the gut and saliva microbial profiles were correlated with salivary amylase, socioeconomic factors (e.g., education and family income), and obesity in both ethnic populations. Gut and oral microbial diversity between AA and EA children showed significant differences in alpha-, beta-, and taxa-level diversity. While gut microbial diversity between obese and non-obese was not evident in EA children, the abundance of gut Klebsiella and Magasphaera was associated with obesity in AA children. In contrast, an abundance of oral Aggregatibacter and Eikenella in obese EA children was observed. These observations suggest an ethnicity-specific association with gut and oral microbial profiles. Socioeconomic factors influenced microbiota in obesity, which were ethnicity dependent, suggesting that specific approaches to confront obesity are required for both populations.

High Olfactory Receptor-Rich 11q11 Copy Number in Girls and African American Children

Copy number variants (CNVs) provide numerous genetic differences between individuals, and they have been linked with multiple human diseases. Obesity is one of the highly heritable complex disorders, which is associated with copy number variance (CNV). A recent report shows that the 11q11 gene, a novel olfactory receptor, and its copy number variants are involved in the early onset of obesity. In the current study, we analyzed the 11q11 gene copy number variance (CNV) based on gender in White/European American (EA) and African American (AA) normal weight and overweight/obese children. Sixty-nine boys and fifty-eight girls between the ages of 6 and 10 years belonging to either EA or AA ethnicity were involved in this study. As per World Health Organization (WHO) guidelines, each participant’s body weight and height were recorded. DNA was extracted from saliva, and the copy number variants for the 11q11 gene were measured using digital PCR. The descriptive analysis of the 11q11 copy number showed significantly more copies in girls compared to boys; similarly, AA participants had significantly increased CNV compared to EA. The normal weight (NW) and overweight/obese (OW/OB) girls were significantly less likely to belong to the low copy number variant (LCNV) group of 11q11 compared to boys; similarly, NW and OW/OB AA children were significantly less likely to belong to the LCNV group. The AA girls in LCNV had significantly higher BMI z-scores. Our findings suggest that the 11q11 copy number in children is race and gender-specific.

Effect of AMY1 copy number variation and various doses of starch intake on glucose homeostasis: data from a cross-sectional observational study and a crossover meal study

Background

Copy number (CN) variation (CNV) of the salivary amylase gene (AMY1) influences the ability to digest starch and may influence glucose homeostasis, obesity and gut microbiota composition. Hence, the aim was to examine the association of AMY1 CNV with fasting glucose, BMI, and gut microbiota composition considering habitual starch intake and to investigate the effect of AMY1 CNV on the postprandial response after two different starch doses.

Methods

The Malmö Offspring Study (n = 1764, 18–71 years) was used to assess interaction effects between AMY1 CNV (genotyped by digital droplet polymerase chain reaction) and starch intake (assessed by 4-day food records) on fasting glucose, BMI, and 64 gut bacteria (16S rRNA sequencing). Participants with low (≤ 4 copies, n = 9) and high (≥ 10 copies, n = 10) AMY1 CN were recruited for a crossover meal study to compare postprandial glycemic and insulinemic responses to 40 g and 80 g starch from white wheat bread.

Results

In the observational study, no overall associations were found between AMY1 CNV and fasting glucose, BMI, or gut microbiota composition. However, interaction effects between AMY1 CNV and habitual starch intake on fasting glucose (P = 0.03) and BMI (P = 0.05) were observed, suggesting inverse associations between AMY1 CNV and fasting glucose and BMI at high starch intake levels and positive association at low starch intake levels. No associations with the gut microbiota were observed. In the meal study, increased postprandial glucose (P = 0.02) and insulin (P = 0.05) were observed in those with high AMY1 CN after consuming 40 g starch. This difference was smaller and nonsignificant after consuming 80 g starch.

Conclusions

Starch intake modified the observed association between AMY1 CNV and fasting glucose and BMI. Furthermore, depending on the starch dose, a higher postprandial glucose and insulin response was observed in individuals with high AMY1 CN than in those with low AMY1 CN.

Trial registration

ClinicalTrials.gov, NCT03974126. Registered 4 June 2019—retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-021-00701-8.

Effect of Gut Microbial Enterotypes on the Association between Habitual Dietary Fiber Intake and Insulin Resistance Markers in Mexican Children and Adults

Dietary fiber (DF) is a major substrate for the gut microbiota that contributes to metabolic health. Recent studies have shown that diet–metabolic phenotype effect might be related to individual gut microbial profiles or enterotypes. Thus, the aim of this study was to examine whether microbial enterotypes modify the association between DF intake and metabolic traits. This cross-sectional study included 204 children (6–12 years old) and 75 adults (18–60 years old). Habitual DF intake was estimated with a Food Frequency Questionnaire and biochemical, clinical and anthropometric data were obtained. Gut microbiota was assessed through 16S sequencing and participants were stratified by enterotypes. Correlations adjusting for age and sex were performed to test the associations between dietary fiber components intake and metabolic traits. In children and adults from the Prevotella enterotype, a nominal negative correlation of hemicellulose intake with insulin and HOMA-IR levels was observed (p < 0.05), while in individuals of the other enterotypes, these associations were not observed. Interestingly, the latter effect was not related to the fecal short-chain-fatty acids profile. Our results contribute to understanding the enterotype influence on the diet–phenotype interaction, which ultimate could provide evidence for their use as potential biomarkers for future precision nutrition strategies.

Dietary carbohydrates interacts with AMY1 polymorphisms to influence the incidence of type 2 diabetes in Korean adults

The relationship between AMY1 single nucleotide polymorphisms (SNPs), dietary carbohydrates, and the risk of type 2 diabetes is unclear. We aimed to evaluate this association using an ongoing large-scale prospective study, namely the Korean Genome and Epidemiology Study. We selected six genetic variants of the AMY1 gene: rs10881197, rs4244372, rs6696797, rs1566154, rs1930212, and rs1999478. Baseline dietary data were obtained using a semi-quantitative food frequency questionnaire. Type 2 diabetes was defined according to the criteria of the World Health Organization and American Diabetes Association. During an average follow-up period of 12 years (651,780 person-years), 1082 out of 4552 (23.8%) patients had type 2 diabetes. Three AMY1 SNPs were significantly associated with diabetes incidence among patients with carbohydrate intake > 65% of total energy: rs6696797, rs4244372, and rs10881197. In multivariable Cox models, Korean women with the rs6696797 AG or AA genotype had 28% higher incidence of type 2 diabetes (hazard ratio 1.28, 95% confidence interval 1.06–1.55) than Korean women with the rs6696797 GG genotype. We did not observe significant associations between AMY1 SNPs, dietary carbohydrates, and diabetes incidence in Korean men. We conclude that AMY1 genetic variants and dietary carbohydrate intake influence the incidence of type 2 diabetes in Korean women only. Korean women who are minor carriers of the AMY1 rs6696797, rs4244372, and rs10881197 genotypes may benefit from a low-carbohydrate diet to prevent the future risk of type 2 diabetes.

DNA copy number and structural variation (CNV) contributions to adult and childhood obesity

In recent years, obesity has reached epidemic proportions globally and has become a major public health concern. The development of obesity is likely caused by several behavioral, environmental, and genetic factors. Genomic variability among individuals is largely due to copy number variations (CNVs). Recent genome-wide association studies (GWAS) have successfully identified many loci containing CNV related to obesity. These obesity-related CNVs are informative to the diagnosis and treatment of genomic diseases. A more comprehensive classification of CNVs may provide the basis for determining how genomic diversity impacts the mechanisms of expression for obesity in children and adults of a variety of genders and ethnicities. In this review, we summarize current knowledge on the relationship between obesity and the CNV of several genomic regions, with an emphasis on genes at the following loci: 11q11, 1p21.1, 10q11.22, 10q26.3, 16q12.2, 16p12.3, and 4q25.

Reduced odds of diabetes associated with high plasma salivary α-amylase activity in Qatari women: a cross-sectional study

The association of salivary α-amylase activity (SAA) activity or low copy number of its coding gene AMY1 with diabetes remains controversial. We aimed to reinvestigate the association of these factors with diabetes in Qatar, where diabetes prevalence is about 16%. We obtained cross-sectional data of 929 Qataris (age > 18 years) from the Qatar Biobank. We estimated AMY1 copy number variants (CNV) from whole-genome data, and quantified the SAA activity in plasma (pSAA). We used adjusted logistic regression to examine the association between pSAA activity or AMY1 CNV and diabetes odds. We found a significant association between high pSAA activity, but not AMY1 CNV, and reduced odds of diabetes in Qatari women. The OR per pSAA activity unit was 0.95 [95% CI 0.92, 0.98] (p = 0.002) (pSAA activity range: 4.7 U/L to 65 U/L) in women. The association is driven largely by the highest levels of pSAA activity. The probability of having diabetes was significantly lower in the fifth pSAA activity quintile relative to the first (0.21 ± 0.03 (Q1) versus 0.82 ± 0.02 (Q5)), resulting in significantly reduced diabetes prevalence in Q5 in women. Our study indicates a beneficial effect of high pSAA activity, but not AMY1 CN, on diabetes odds in Qatari women, and suggests pSAA activity levels as a potential marker to predict future diabetes in Qatari women.

Influence of AMY1A copy number variations on obesity and other cardiometabolic risk factors: A review of the evidence

The rising incidence of obesity and type 2 diabetes is contributing to the escalating burden of disease globally. These metabolic disorders are closely linked with diet and in particular with carbohydrate consumption; hence, it is important to understand the underlying mechanisms that influence carbohydrate metabolism. Amylase, the enzyme responsible for the digestion of starch, is coded by the genes AMY1A, AMY1B, and AMY1C (salivary amylase) and AMY2A and AMY2B (pancreatic amylase). Previous studies demonstrate wide variations in AMY1A copy numbers, which can be attributed to several genetic, nutritional, and geographical diversities seen in populations globally. Current literature suggests that AMY1A copy number variations are important in obesity and other cardiometabolic disorders through their effects on glucose and lipid homeostasis, inflammatory markers, and the gut microbiome. This review synthesizes the available evidence to improve understanding of the role of AMY1A in obesity and related cardiometabolic risk factors and disorders including insulin resistance and type 2 diabetes, cardiovascular risk and inflammation, and the gut microbiome.

Association between Dental Caries, Obesity and Salivary Alpha Amylase in Adolescent Girls of Babol City, Iran-2017

Statement of the Problem

Adolescents are at risk of obesity and caries due to various factors such as diet and poor health habits; these factors may affect their body mass index (BMI) and salivary components. Therefore, it is necessary to assess these factors and their relationship in this age group.

Purpose

This study aimed to evaluate the association between decayed missing filled teeth index (DMFT), salivary alpha amylase (sAA) level and age-specific BMI in adolescent girls.

Materials and Method

A cross-sectional study was conducted on 81 females aged 13-15 years in 3 groups of BMI percentiles; "normal", "at risk for overweight" and "overweight" (n=27). DMFT was calculated and unstimulated saliva samples were collected. The sAA level was measured with a spectrophotometer. Data were analyzed using Kolmogorov-Smir-nov test, Kruskal- Wallis and Spearman correlation tests using SPSS (version 23) at p< 0.05.

Results

The concentration of sAA and mean DMFT were estimated 1326.56±4.73 U/L and 2.77±2.36, respectively. There was no significant difference in sAA level and mean DMFT among BMI groups. A positive and significant correlation was found between sAA and DMFT in overweight group (r 0.46, p= 0.014).

Conclusion

Within the limitation of this study, higher levels of sAA may be considered as an indicator for dental caries in overweight adolescent girls.

Ethnic-specific association of amylase gene copy number with adiposity traits in a large Middle Eastern biobank

Studies assessing the impact of amylase genes copy number (CN) on adiposity report conflicting findings in different global populations, likely reflecting the impact of ancestral and ethnic-specific environment and lifestyle on selection at the amylase loci. Here, we leverage population size and detailed adiposity measures from a large population biobank to resolve confounding effects and determine the relationship between salivary (AMY1) and pancreatic (AMY2A) amylase genes CN and adiposity in 2935 Qatari individuals who underwent whole-genome sequencing (WGS) as part of the Qatar Genome Programme. We observe a negative association between AMY1 CNs and trunk fat percentage in the Qatari population (P = 7.50 × 10^-3) and show that Qataris of Arab descent have significantly lower CN at AMY1 (P = 1.32 × 10^-10) as well as less favorable adiposity and metabolic profiles (P < 1.34 × 10^-8) than Qataris with Persian ancestry. Indeed, lower AMY1 CN was associated with increased total and trunk fat percentages in Arabs (P < 4.60 × 10^-3) but not in Persians. Notably, overweight and obese Persians reported a significant trend towards dietary restraint following weight gain compared to Arabs (P = 4.29 × 10^-5), with AMY1 CN showing negative association with dietary self-restraint (P = 3.22 × 10^-3). This study reports an association between amylase gene CN and adiposity traits in a large Middle Eastern population. Importantly, we leverage rich biobank data to demonstrate that the strength of this association varies with ethnicity, and may be influenced by population-specific behaviors that also contribute to adiposity traits.

Alpha-amylase 1A copy number variants and the association with memory performance and Alzheimer's dementia

Background

Previous studies have shown that copy number variation (CNV) in the alpha (α)-amylase gene (AMY1A) is associated with body mass index, insulin resistance, and blood glucose levels, factors also shown to increase the risk of Alzheimer’s dementia (AD). We have previously demonstrated the presence of α-amylase in healthy neuronal dendritic spines and a reduction of the same in AD patients. In the current study, we investigate the relationship between AMY1A copy number and AD, memory performance, and brain α-amylase activity.

Methods and materials

The association between AMY1A copy number and development of AD was analyzed in 5422 individuals (mean age at baseline 57.5 ± 5.9, females 58.2%) from the Malmö diet and cancer study genotyped for AMY1A copy number, whereof 247 where diagnosed with AD during a mean follow-up of 20 years. Associations between AMY1A copy number and cognitive performance where analyzed in 791 individuals (mean age at baseline 54.7 ± 6.3, females 63%), who performed Montreal Cognitive Assessment (MoCA) test. Correlation analysis between α-amylase activity or α-amylase gene expression and AMY1A copy number in post-mortem hippocampal tissue from on demented controls (n = 8) and AD patients (n = 10) was also performed.

Results

Individuals with very high ( ≥10) AMY1A copy number had a significantly lower hazard ratio of AD (HR = 0.62, 95% CI 0.41–0.94) and performed significantly better on MoCA delayed word recall test, compared to the reference group with AMY1A copy number 6. A trend to lower hazard ratio of AD was also found among individuals with low AMY1A copy number (1–5) (HR = 0.74, 95% CI 0.53–1.02). A tendency towards a positive correlation between brain α-amylase activity and AMY1A copy number was found, and females showed higher brain α-amylase activity compared to males.

Conclusion

Our study suggests that the degree of α-amylase activity in the brain is affected by AMY1A copy number and gender, in addition to AD pathology. The study further suggests that very high AMY1A copy number is associated with a decreased hazard ratio of AD and we speculate that this effect is mediated via a beneficial impact of AMY1A copy number on episodic memory performance.

High plasma salivary α-amylase, but not high AMY1 copy number, associated with low obesity rate in Qatari adults: cross-sectional study

The relationship between salivary α-amylase activity (psAAa) or AMY1 copy number and the risk of obesity remains controversial. We aimed to assess this relationship in a cohort from Qatar, where obesity affects 43% of adults. The relationship was investigated cross-sectionally in 923 Qatari adults from the Qatar biobank cohort. AMY1 CN was estimated form whole genome sequencing data. The associations with obesity prevalence were assessed by linear and logistic regressions. We found no difference in AMY1 CN between obese and normal-weight individuals. However, the psAAa was significantly lower in obese individuals. Significant inverse correlations were found between adiposity markers and psAAa in both sexes, but were marginally stronger in men. A significant effect of high psAAa, but not AMY1 CN, on reduced obesity rates was identified in men (OR per psAAa unit 0.957 [95% CI 0.937–0.977], p < 0.001, with psAAa ranging between 5 to 66 U/L). A significantly higher prevalence of obesity was observed in the lowest quartile of psAAa in men (75% (Q1) vs. 36% (Q4), p < 0.001) and women (74% (Q1) vs 56% (Q4), p = 0.009). Our findings suggest that high psAAa, but not AMY1 CN, has a potential positive benefit against obesity in the Qatari population.

AMY1 diploid copy number among end-stage renal disease patients

PURPOSE

The salivary amylase gene (AMY1) copy number variation (CNV) is increased as a human adaptation to starch-enriched nutritional patterns. The purpose of this study was to evaluate the relationship between AMY1 CNV, dietary starch consumption, and anthropometric indices among a known population with elevated cardiovascular risk, being end-stage renal disease (ESRD) patients.

METHODS

A total of 43 ESRD patients were recruited based on the following inclusion criteria: being (1) adults, (2) on hemodialysis for more than 3 months, (3) able to communicate effectively, and (4) willing to participate. Anthropometric measurements were performed, dietary intake was recorded via food-frequency questionnaires, and AMY1 CNV was quantified in blood samples DNA via real-time PCR.

RESULTS

Median AMY1 CNV was 4.0 (2.0-17.0). A total of 21 patients had an even, and 22 had an odd AMY1 copy number (CN). Independent samples t tests revealed that AMY1-odd diploid CN is associated with increased body weight, waist and hip circumferences, and fat mass compared to the respective even diploid CN carrier group. No differences were observed for BMI or nutritional intake. Multiple regression analysis revealed that AMY1-odd diploid CN was positively associated with increased hip circumference (ß = 7.87, 95% CI = 0.34 to 15.39) and absolute fat mass (ß = 6.66, 95% CI = 0.98 to 12.34); however, after applying the Bonferroni correction for multiplicity, all regression analyses lost their significance.

CONCLUSIONS

AMY1-odd diploid CN appears to be associated with selected adiposity variables among hemodialysis patients. However, more research is needed to verify this finding in this population with known increased cardiovascular risk.

Starch Digestion-Related Amylase Genetic Variants, Diet, and Changes in Adiposity: Analyses in Prospective Cohort Studies and a Randomized Dietary Intervention

Salivary amylase, encoded by the AMY1 gene, is responsible for the digestion of carbohydrates. We investigated associations of AMY1 genetic variations with general and central adiposity changes considering dietary carbohydrate intake among 32,054 adults from four prospective cohort studies. A genetic risk score (GRS) was calculated based on nine AMY1 single-nucleotide polymorphisms, with higher AMY1-GRS indicating higher activity of salivary amylase. We meta-analyzed interactions between AMY1-GRS and dietary intake for changes in general and central adiposity over 5.5-10 years. We found that carbohydrate food intake significantly altered associations of AMY1-GRS with changes in BMI (P interaction = 0.001) and waist circumference (P interaction < 0.001). Results were consistent and significant in female cohorts rather than in male cohorts. Among women, higher AMY1-GRS was associated with more increases in adiposity if dietary carbohydrate food intake was high, while higher AMY1-GRS was associated with less gains in adiposity when the dietary intake was low. Also, in a 2-year randomized dietary intervention trial, associations of AMY1-GRS with changes in weight (P interaction = 0.023) and waist circumference (P interaction = 0.037) were significantly modified by carbohydrate intake. Our results suggest the importance of precision nutrition strategies considering participants' genetic adaptation to carbohydrate-rich diets in regulating general and central adiposity.

Association of AMY1A/AMY2A copy numbers and AMY1/AMY2 serum enzymatic activity with obesity in Mexican children

BACKGROUND

Mexican children are characterized by a high-starch intake diet and high prevalence of obesity.

OBJECTIVES

To investigate the association of AMY1A/AMY2A copy numbers (CNs) and AMY1/AMY2 serum enzymatic activity with childhood obesity in up to 427 and 337 Mexican cases and controls.

METHODS

Anthropometric and dietary starch intake data were collected. CN of AMY1A/AMY2A and AMY1/AMY2 serum enzymatic activity were determined using droplet digital PCR (ddPCR) and enzymatic colorimetry, respectively. An individual participant level data meta-analysis of association between AMY1A CNVs and obesity was also performed.

RESULTS

A positive association between AMY1A/AMY2A CNs and their corresponding AMY1/AMY2 serum enzyme activity was observed in children with normal weight and obesity. The serum enzyme activity of AMY1 and AMY2 was negatively associated with childhood obesity risk, and the association was restricted to kids eating medium/high amount of starch (P_interaction = .004). While no association between AMY1A and AMY2A CNs and childhood obesity was observed in our sample, we confirmed a significant association between AMY1A CN and obesity in a meta-analysis of 3100 Mexican children.

CONCLUSIONS

Our data suggest that genetically determined salivary and pancreatic amylase activity can increase/decrease the risk of obesity in Mexican children, this effect being blunted by a low-starch diet.

Sex-Specific Associations between Gut Prevotellaceae and Host Genetics on Adiposity

The gut microbiome has been recognized as a tool for understanding adiposity accumulation and for providing personalized nutrition advice for the management of obesity and accompanying metabolic complications. The genetic background is also involved in human energy homeostasis. In order to increase the value of nutrigenetic dietary advice, the interplay between genetics and microbiota must be investigated. The purpose of the present study was to evaluate interactive associations between gut microbiota composition and 95 obesity-related single nucleotide polymorphisms (SNPs) searched in the literature. Oral mucosa and fecal samples from 360 normal weight, overweight and obese subjects were collected. Next generation genotyping of these 95 SNPs and fecal 16S rRNA sequencing were performed. A genetic risk score (GRS) was constructed with 10 SNPs statistically or marginally associated with body mass index (BMI). Several microbiome statistical analyses at family taxonomic level were applied (LEfSe, Canonical Correspondence Analysis, MetagenomeSeq and Random Forest), and Prevotellaceae family was found in all of them as one of the most important bacterial families associated with BMI and GRS. Thus, in this family it was further analyzed the interactive association between BMI and GRS with linear regression models. Interestingly, women with higher abundance of Prevotellaceae and higher GRS were more obese, compared to women with higher GRS and lower abundance of Prevotellaceae. These findings suggest relevant interrelationships between Prevotellaceae and the genetic background that may determine interindividual BMI differences in women, which opens the way to new precision nutrition-based treatments for obesity.

Low AMY1 Copy Number Is Cross-Sectionally Associated to an Inflammation-Related Lipidomics Signature in Overweight and Obese Individuals

SCOPE

Reduced amylase 1 (AMY1) copy numbers are associated with obesity, insulin resistance, and inflammation. Although mechanisms linking AMY1 copy number with metabolic disorders are poorly understood, recent findings suggest that lipids play a key role.

METHODS AND RESULTS

Plasma lipidomic signatures associated with AMY1 copy number are explored in 57 non-diabetic overweight/obese subjects aged 18-60. Serum amylase and inflammatory cytokines levels are also measured. AMY1 copy number is strongly associated with the serum amylase concentration. Participants are divided into low-(≤4) and high-(>4) AMY1 carriers based on the median. Low-AMY1 carriers have higher BMI and fat mass. They also have higher levels of dihexosylceramides (R = -0.27, p = 0.044), cholesterol esters (CE) (R = -0.32, p = 0.020), alkylphosphatidylcholines [PC(O)] (R = -0.33, p = 0.014), and sphingomyelins (SM) (R = -0.38, p = 0.005). From 459 lipid species, 28 differ between low- and high-AMY1 carriers. These include CE species with long-chain PUFA; PC(O) and PC plasmalogens containing arachidonic acid; and PC, mono-, di-, and tri-hexosylceramides, and SM containing saturated fatty acids (mainly C16:0 and C20:0). This lipidomic signature is strongly associated with inflammatory cytokines, which are also negatively associated with the AMY1 copy number.

CONCLUSION

A lipidomics signature associated with low AMY1 copy numbers is revealed, which is linked to obesity and chronic low-grade inflammation.

Pretreatment Prevotella-to-Bacteroides ratio and salivary amylase gene copy number as prognostic markers for dietary weight loss

BACKGROUND

The inconsistent link observed between salivary amylase gene copy number (AMY1 CN) and weight management is likely modified by diet and microbiome.

OBJECTIVE

Based on analysis of a previously published study, we investigated the hypothesis that interaction between diet, Prevotella-to-Bacteriodes ratio (P/B ratio), and AMY1 CN influence weight change.

METHODS

Sixty-two people with increased waist circumference were randomly assigned to receive an ad libitum New Nordic Diet (NND) high in dietary fiber, whole grain, intrinsic sugars, and starch or an Average Danish (Western) Diet (ADD) for 26 weeks. All foods were provided free of charge. Before subjects were randomly assigned to receive the NND or ADD diet, blood and fecal samples were collected, from which AMY1 CN and P/B ratio, respectively, were determined. Body weight change was described by using linear mixed models, including biomarker [log10(P/B ratio) and/or AMY1 CN] diet-group interactions.

RESULTS

Baseline means ± SDs of log10(P/B ratio) and AMY1 CN were -2.1 ± 1.8 and 6.6 ± 2.4, respectively. Baseline P/B ratio predicted a 0.99-kg/unit (95% CI: 0.40, 1.57; n = 54; P < 0.001) higher weight loss for those subjects on the NND compared with those on the ADD diet, whereas AMY1 CN was not found to predict weight loss differences between the NND and ADD groups [0.05 kg/CN (95% CI: -0.40, 0.51; n = 54; P = 0.83)]. However, among subjects with low AMY1 CN (<6.5 copies), baseline P/B ratio predicted a 2.12-kg/unit (95% CI: 1.37, 2.88; n = 30; P < 0.001) higher weight loss for the NND group than the ADD group. No such differences in weight loss were found among subjects in both groups with high AMY1 CN [-0.17 kg/unit (95% CI: -1.01, 0.66; n = 24; P = 0.68)].

CONCLUSIONS

The combined use of low AMY1 CN and pretreatment P/B ratio for weight loss prediction led to highly individualized weight loss results with the introduction of more fiber, whole grain, intrinsic sugars, and starch in the diet. These preliminary observations suggest that more undigested starch reaches the colon in individuals with low AMY1 CN, and that the fate of this starch depends on the gut microbiota composition. This trial was registered at clinicaltrials.gov as NCT01195610.

Copy Number Variation of the Salivary Amylase Gene and Glucose Metabolism in Healthy Young Japanese Women

Background

Many studies have shown that low copy number variation (CNV) of the salivary amylase gene (AMY1) and low serum amylase concentration are associated with impaired glucose metabolism and obesity. We aimed to clarify the conflicting results of previous studies by examining AMY1 expression and metabolic indices in a homogenous group of healthy participants.

Methods

Sixty healthy non-obese young Japanese women aged 20 - 39 years were examined for AMY1 CNV, salivary amylase, body mass index (BMI) and serum parameters including glycated hemoglobin (HbA1c), ketones, and total, salivary and pancreatic amylase. Respiratory quotient at rest and changes in blood glucose after starch loading were also examined.

Results

AMY1 CNV (range, 4 - 14) and the level of serum salivary amylase were correlated inversely with HbA1c (r = -0.36, P = 0.003 and r = -0.30, P = 0.02, respectively), whereas the percentage of serum salivary amylase in total serum amylase was positively correlated with blood glucose at 30 and 45 min after starch loading (r = 0.38, P = 0.004 and r = 0.27, P = 0.04, respectively). The level of serum total amylase, but not AMY1 CNV, was correlated inversely with BMI (r = -0.29, P = 0.02). Logistic regression analysis showed that low AMY1 CNV (4 - 7) was significantly associated with an HbA1c of ≥ 5.4% (34 mmol/mol) even after adjustment for age, BMI and energy consumption, compared with high AMY1 CNV (8 - 14).

Conclusions

Although a higher percentage of serum salivary amylase was associated with higher levels of blood glucose at the early stage after starch loading, low AMY1 CNV was associated with chronic unfavorable glucose metabolism in healthy non-obese young women in Japan.

Salivary Amylase Gene Copy Number Is Associated with the Obesity and Inflammatory Markers in Children

BACKGROUND

We have recently shown that the copy number of salivary amylase (AMY1) gene was significantly decreased, and the obesity-related salivary biomarkers resistin, MCP-1, TNF-α, IL-6, and CRP were significantly increased in overweight/obese children compared to normal weight. This study aimed to evaluate the association of AMY1 copy number variant (CNV) with obesity and inflammatory markers. Seventy-six participants aged between 6 and 10 years have participated, and the saliva samples were collected along with the anthropometric measurements.

METHODS

AMY1 copy number was analyzed by 3D digital PCR, and obesity-related biomarkers were performed with a Bioplex multiplex analyzer.

RESULTS

The mean AMY1 copy number was higher in normal weight (7.90 ± 0.38) compared to the overweight/obese group (6.20 ± 0.29). The association of AMY1 CNV with obesity and inflammatory markers showed significant negative correlation [CRP, β = -0.238 (p < 0.05); resistin, β = -0.25 (p < 0.05); MCP-1, β = -0.304 (p < 0.01)] except for complement factor D, TNF α and IL-6. The anti-inflammatory cytokine, IL-10 reported a positive correlation with AMY1 copy number with a β = 0.268 (p < 0.05). The multivariable model adjusted with age and gender depicted a similar correlation with obesity markers.

CONCLUSION

Our results report that AMY1 CNV is associated with obesity and inflammatory biomarkers in children's saliva sample.

Host Genetics, Diet, and Microbiome: The Role of AMY1

Host gene variants selected by diet adaptation have been associated with the microbiome. Poole et al. (Cell Host Microbe 2019;25;553-564.E7) reported that AMY1 copy number, associated with obesity, also impacts microbiome composition and function. Complex genetics-diet-microbiome interactions and their effect on obesity could eventually translate into personalized nutrition.