The Leu7Pro polymorphism of preproNPY is associated with decreased insulin secretion, delayed ghrelin suppression, and increased cardiovascular responsiveness to norepinephrine during oral glucose tolerance test

Reduced Sensory-Evoked Locus Coeruleus-Norepinephrine Neural Activity in Female Rats With a History of Dietary-Induced Binge Eating

Noradrenergic pathways have been implicated in eating pathologies. These experiments sought to examine how dietary-induced binge eating influences the neuronal activity of the locus coeruleus (LC)-norepinephrine (NE) system. Young adult female Sprague Dawley rats (7-8 weeks old) were exposed to a repeated intermittent (twice weekly) cycle of 30-min access to a highly palatable sweetened fat (i.e., vegetable shortening with 10% sucrose) with or without intermittent (24 h) calorie restriction (Restrict Binge or Binge groups, respectively). Age- and weight-matched female control rats were exposed to standard chow feeding (Naive group) or intermittent chow feeding (Restrict group). The Binge and Restrict Binge groups demonstrated an escalation in sweet-fat food intake after 2.5 weeks. On week 3, in vivo single-unit LC electrophysiological activity was recorded under isoflurane anesthesia. Restrict Binge (20 cells from six rats) and Binge (27 cells from six rats) had significantly reduced (approximate 20% and 26%, respectively) evoked LC discharge rates compared with naive rats (22 cells, seven rats). Spontaneous and tonic discharge rates were not different among the groups. Signal-to-noise ratio was reduced in the groups with intermittent sweetened fat exposure. In order to investigate the neuropeptide alterations as a consequence of dietary binge eating, relative gene expression of neuropeptide Y (NPY), glucagon-like peptide 1 receptor (GLP-1r), prodynorphin, and related genes were measured in LC and hypothalamic arcuate (Arc) regions. Glp-1r, Npy2r, and Pdyn in LC region were reduced with repeated intermittent restriction. Npy1r was reduced by approximately 27% in ARC of Restrict compared with Naive group. Such data indicate that dietary-induced binge eating alters the neural response of LC neurons to sensory stimuli and dampens the neural stress response.

Association of Neuropeptide-Y (NPY) and Interleukin-1beta (IL1B), Genotype-Phenotype Correlation and Plasma Lipids with Type-II Diabetes

BACKGROUND

Neuropeptide Y (NPY) is known to play a role in the regulation of satiety, energy balance, body weight, and insulin release. Interleukin-1beta (IL1B) has been associated with loss of beta-cell mass in type-II diabetes (TIID).

OBJECTIVES

The present study attempts to investigate the association of NPY exon2 +1128 T/C (Leu7Pro; rs16139), NPY promoter -399 T/C (rs16147) and IL1B -511 C/T (rs16944) polymorphisms with TIID and their correlation with plasma lipid levels, BMI, and IL1B transcript levels.

METHODS

PCR-RFLP was used for genotyping these polymorphisms in a case-control study involving 558 TIID patients and 1085 healthy age-matched controls from Gujarat. Linkage disequilibrium and haplotype analysis of the NPY polymorphic sites were performed to assess their association with TIID. IL1B transcript levels in PBMCs were also assessed in 108 controls and 101 patients using real-time PCR.

RESULTS

Our results show significant association of both structural and promoter polymorphisms of NPY (p<0.0001 and p<0.0001 respectively) in patients with TIID. However, the IL1B C/T polymorphism did not show any association (p = 0.3797) with TIID patients. Haplotype analysis revealed more frequent association of CC and CT haplotypes (p = 3.34 x 10-5, p = 6.04 x 10-9) in diabetics compared to controls and increased the risk of diabetes by 3.02 and 2.088 respectively. Transcript levels of IL1B were significantly higher (p<0.0001) in patients as compared to controls. Genotype-phenotype correlation of IL1B polymorphism did not show any association with its higher transcript levels. In addition, NPY +1128 T/C polymorphism was found to be associated with increased plasma LDL levels (p = 0.01).

CONCLUSION

The present study provides an evidence for a strong correlation between structural and promoter polymorphisms of NPY gene and upregulation of IL1B transcript levels with susceptibility to TIID and altering the lipid metabolism in Gujarat population.

Neuropeptide Y polymorphism increases the risk for asthma in overweight subjects; protection from atherosclerosis in asthmatic subjects--the cardiovascular risk in young Finns study

AIMS

The role of neuropeptide Y (NPY) and its gene polymorphisms in the development of atherosclerosis has become increasingly evident. In asthma, NPY has been shown to be involved as immunomodulator. In this study, we investigated the role of two functional NPY polymorphisms, NPY-Leu7Pro (rs16139) and NPY-399C/T (rs16147) and obesity for the development of asthma as well as atherosclerosis in asthmatic and non-asthmatic subjects. Also, we measured heart rate variability (HRV) and NPY in serum since these might contribute through these polymorphisms to both diseases.

METHODS AND RESULTS

Thousand hundred and seventy six Finnish young adults were genotyped and three groups (G1-G3) were formed based on the observed diplotypes. The NPY-Pro7 allele always co-existed with the NPY-399T allele indicating complete linkage disequilibrium. Here we show that overweight (BMI≥25kg/m2) was associated with 2.5-fold increased risk for asthma in subjects with the NPY-399T allele without NPY-Pro7 allele (G2, n=716). Overweight was also associated with increased atherosclerosis determined by carotid intima media thickness (cIMT), but asthma seemed to be more significant determinant than overweight in determing cIMT having a decreasing effect. NPY concentration in serum was diplotype-driven (G1=792.2(29.5), G2=849.0(18.9), G3=873.9(45.2) pg/ml) and correlated positively with cIMT in the group having NPY-Pro7 allele (G3, n=142). However, the subjects with asthma had a negative NPY-cIMT relationship. Total HRV was increased in asthma and correlated negatively with cIMT irrespective of the NPY genotype.

CONCLUSIONS

Overweight together with the NPY-399T allele without NPY-Pro7 allele was associated with increased risk for asthma. Atherosclerosis was decreased in subjects with asthma depending on the NPY genotype. The results reveal novel insights into the genetics and biology of the relationship of atherosclerosis and asthma.

Association of the leucine-7 to proline-7 variation in the signal sequence of neuropeptide Y with major depression

OBJECTIVE

There is clear evidence of a genetic component in major depression, and several studies indicate that neuropeptide Y (NPY) could play an important role in the pathophysiology of the disease. A well-known polymorphism encoding the substitution of leucine to proline in the signal peptide sequence of NPY (Leu7Pro variation) was previously found to protect against depression. Our study aimed at replicating this association in a large Danish population with major depression.

METHOD

Leu7Pro was studied in a sample of depressed patients and ethnically matched controls, as well as psychiatric disease controls with schizophrenia. Possible functional consequences of Leu7Pro were explored in vitro.

RESULTS

In contrast to previous studies, Pro7 appeared to be a risk allele for depression, being significantly more frequent in the depression sample (5.5%, n = 593; p = 0.009; odds ratio, OR: 1.46) as compared to ethnically matched controls (3.8%, n = 2912), while schizophrenia patients (4.1%, n = 503) did not differ. In vitro, the Pro7 substitution appeared to be associated with reduced levels of NPY without affecting its mRNA level.

CONCLUSION

The Leu7Pro variation may increase the risk of major depression, possibly by affecting the biosynthesis of NPY.

No association of the neuropeptide Y (Leu7Pro) and ghrelin gene (Arg51Gln, Leu72Met, Gln90Leu) single nucleotide polymorphisms with eating disorders

BACKGROUND

Genetic factors likely contribute to the biological vulnerability of eating disorders.

AIMS

Case-control association study on one neuropeptide Y gene (Leu7Pro) polymorphism and three ghrelin gene (Arg51Gln, Leu72Met and Gln90Leu) polymorphisms.

METHODS

114 eating disorder patients (46 with anorexia nervosa, 30 with bulimia nervosa, 38 with binge eating disorder) and 164 healthy controls were genotyped.

RESULTS

No differences were detected between patients and controls for any of the four polymorphisms in allele frequency and genotype distribution (P > 0.05). Allele frequencies and genotypes had no significant influence on body mass index (P > 0.05) in eating disorder patients.

CONCLUSION

Positive findings of former case-control studies of associations between ghrelin gene polymorphisms and eating disorders could not be replicated. Neuropeptide Y gene polymorphisms have not been investigated in eating disorders before.

Transgenic mice overexpressing neuropeptide Y in noradrenergic neurons: a novel model of increased adiposity and impaired glucose tolerance

OBJECTIVE

A functional polymorphism leucine 7 proline in the human neuropeptide Y (NPY) gene leading to increased NPY release from sympathetic nerves is associated with traits of metabolic syndrome. Although hypothalamic NPY neurons play an established role in promoting positive energy balance, the role of NPY colocalized with norepinephrine in sympathetic nervous system and brain noradrenergic neurons remains obscure.

RESEARCH DESIGN AND METHODS

To clarify the role of NPY in noradrenergic neurons, we generated a transgenic mouse overexpressing NPY under dopamine-beta-hydroxylase promoter and characterized the metabolic phenotype of the OE-NPY(DbetaH) mouse.

RESULTS

NPY levels are increased by 1.3-fold in adrenal glands and 1.8-fold in the brainstem but not in the hypothalamus in OE-NPY(DbetaH) mice. They display increased white adipose tissue mass and cellularity and liver triglyceride accumulation without hyperphagia or increased body weight. Hyperinsulinemia and impaired glucose tolerance develop by the age of 6 months in the OE-NPY(DbetaH) mice. Furthermore, circulating ghrelin is significantly increased in comparison with wild-type mice.

CONCLUSIONS

The present study shows that even a moderate increase in NPY levels in noradrenergic neurons leads to disturbances in glucose and lipid metabolism. The OE-NPY(DbetaH) mouse is an interesting new model to investigate the pathophysiology of some key components of the cluster of abnormalities characterizing the metabolic syndrome.

Leu7Pro polymorphism of PreproNPY associated with an increased risk for type II diabetes in middle-aged subjects

OBJECTIVES

Neuropeptide Y (NPY) plays a central in energy homeostasis and potentially in the development of obesity-related comorbidities, like type II diabetes. As the PreproNPY Leu7Pro polymorphism probably changes the intracellular processing of the synthesized preproNPY peptide, we assessed the hypothesis that PreproNPY Leu7Pro polymorphism is a risk factor for type II diabetes, impaired glucose tolerance and hypertension.

DESIGN

Blood pressure recordings and oral glucose tolerance test were performed in the hypertensive (n=515) and control cohorts (n=525) of our well-defined Oulu Project Elucidating Risk of Atherosclerosis (OPERA) study. The prevalence of type II diabetes was 9% (n=93). The genotypes, insulin and glucose metabolism indexes and plasma ghrelin of the subjects were determined.

RESULTS

Pro7 allele frequencies were 5.9, 5.3 and 11.3% in the total cohort, in subjects without and with type II diabetes, respectively. The PreproNPY Pro7 carrier status was a significant risk factor for type II diabetes, and the effect remained significant after adjustment for age, sex, waist circumference and study group (odds ratio=3.02, confidence interval: 1.67-5.44 and P<0.001). Pro7 carriers were more insulin resistant and showed lower ghrelin levels compared to non-carriers.

CONCLUSIONS

The PreproNPY Pro7 allele is associated with an increased risk for type II diabetes. The risk seems to be associated with a higher insulin resistance among Pro7 carriers whereas low ghrelin concentrations in Pro7 carriers are possibly a consequence of high insulin levels.