Brain-Derived Neurotrophic Factor and Its Associations with Metabolism and Physical Activity in a Latino Sample.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) is associated with body weight and other health conditions but remains understudied in the Latino population. The aim of this study was to examine the associations of BDNF serum levels with body mass index (BMI), physical activity, and the rs6265 nonconservative polymorphism among 349 Latinos aged ≥18 years enrolled in the Arizona Insulin Resistance Registry. MATERIALS AND METHODS: Data on physical activity were acquired using a self-reported questionnaire. BDNF serum levels were measured utilizing a modified ELISA method, and the rs6265 polymorphism was genotyped by the Assay-by-Design service. Two sample t-tests or chi-squared tests were employed to compare demographics and outcomes between physically active and nonactive groups as well as between rs6265 CC and CT+TT groups. RESULTS: BDNF levels and rs6265 polymorphism did not differ significantly between the physically active (N = 195) and nonactive group (N = 154). Participants with the rs6265 polymorphism did not show any significant difference in BDNF levels or BMI when compared with those with the normal functional variant. Higher BDNF levels were significantly associated with higher age (r = 0.11, P = 0.04) and higher 2-hr glucose level (r = 0.11, P = 0.04). CONCLUSIONS: In this cross-sectional study, the rs6265 polymorphism was not associated with a higher risk of obesity, or lower circulating levels of BDNF. Thus, the rs6265 polymorphism may have a different impact in Latinos as compared with other previously studied populations.

Identification of Novel Changes in Human Skeletal Muscle Proteome After Roux-en-Y Gastric Bypass Surgery.

The mechanisms of metabolic improvements after Roux-en-Y gastric bypass (RYGB) surgery are not entirely clear. Therefore, the aim of our study was to investigate the role of obesity and RYGB on the human skeletal muscle proteome. Basal muscle biopsies were obtained from seven obese (BMI >40 kg/m(2)) female subjects (45.1 ± 3.6 years) pre- and 3 months post-RYGB, and euglycemic-hyperinsulinemic clamps were used to assess insulin sensitivity. Four age-matched (48.5 ± 4.7 years) lean (BMI <25 kg/m(2)) females served as control subjects. We performed quantitative mass spectrometry and microarray analyses on protein and RNA isolated from the muscle biopsies. Significant improvements in fasting plasma glucose (104.2 ± 7.8 vs. 86.7 ± 3.1 mg/dL) and BMI (42.1 ± 2.2 vs. 35.3 ± 1.8 kg/m(2)) were demonstrated in the pre- versus post-RYGB, both P < 0.05. Proteomic analysis identified 2,877 quantifiable proteins. Of these, 395 proteins were significantly altered in obesity before surgery, and 280 proteins differed significantly post-RYGB. Post-RYGB, 49 proteins were returned to normal levels after surgery. KEGG pathway analysis revealed a decreased abundance in ribosomal and oxidative phosphorylation proteins in obesity, and a normalization of ribosomal proteins post-RYGB. The transcriptomic data confirmed the normalization of the ribosomal proteins. Our results provide evidence that obesity and RYGB have a dynamic effect on the skeletal muscle proteome.

G972R IRS-1 variant impairs insulin regulation of endothelial nitric oxide synthase in cultured human endothelial cells.

BACKGROUND: Impaired insulin-mediated vasodilation might contribute to vascular damage in insulin-resistant states. Little is known about insulin regulation of nitric oxide (NO) synthesis in insulin-resistant cells. The aim of this work was to investigate insulin regulation of NO synthesis in human umbilical vein endothelial cells (HUVECs) carrying the IRS-1 gene G972R variant, known to be associated with impaired insulin activation of the PI3-kinase (PI3-K) pathway in transfected cells. METHODS AND RESULTS: HUVECs were screened for the presence of the G972R-IRS-1 (HUVEC-G972R) variant by restriction fragment length polymorphisms. After 24-hour exposure to 10(-7) mol/L insulin, endothelial NO synthase (eNOS) mRNA (reverse transcription-polymerase chain reaction), eNOS protein levels (Western blotting), and NOS activity (conversion of [(3)H]arginine into [(3)H]citrulline) were increased in wild-type HUVECs (HUVEC-WT), whereas they did not change from baseline in HUVEC-G972R. Compared with HUVEC-WT, in HUVEC-G972R after 2 and 10 minutes of insulin stimulation, IRS-1-associated PI3-K activity was reduced by 47% and 32%, respectively; Akt phosphorylation was decreased by 40% at both time points; and eNOS-Ser1177 phosphorylation was reduced by 38% and 51%, respectively. In HUVEC-WT, eNOS-Thr495 phosphorylation decreased after insulin stimulation. In contrast, in HUVEC-G972R, eNOS-Thr495 phosphorylation increased after insulin stimulation and was 40% greater than in HUVEC-WT. CONCLUSIONS: Our data demonstrate that genetic impairment of the (IRS)-1/PI3-K/PDK-1/Akt insulin signaling cascade determines impaired insulin-stimulated NO release and suggest that the G972R-IRS-1 polymorphism, through a direct impairment of Akt/eNOS activation in endothelial cells, may contribute to the genetic predisposition to develop endothelial dysfunction and cardiovascular disease.

Chronic hyperglicemia and nitric oxide bioavailability play a pivotal role in pro-atherogenic vascular modifications.

Diabetes is associated with accelerated atherosclerosis and macrovascular complications are a major cause of morbidity and mortality in this disease. Although our understanding of vascular pathology has lately greatly improved, the mechanism(s) underlying enhanced atherosclerosis in diabetes remain unclear. Endothelial cell dysfunction is emerging as a key component in the pathophysiology of cardiovascular abnormalities associated with diabetes. Although it has been established that endothelium plays a critical role in overall homeostasis of the vessels, vascular smooth muscle cells (vSMC) in the arterial intima have a relevant part in the development of atherosclerosis in diabetes. However, high glucose induced alterations in vSMC behaviour are not fully characterized. Several studies have reported that impaired nitric oxide (NO) synthesis and/or actions are often present in diabetes and endothelial dysfunction. Furthermore, although endothelial cells are by far the main site of vascular NO synthesis, vSMC do express nitric oxyde synthases (NOSs) and NO synthesis in vSMC might be important in vessel's function. Although it is known that vSMC contribute to vascular pathology in diabetes by their change from a quiescent state to an activated proliferative and migratory phenotype (termed phenotypic modulation), whether this altered phenotypic modulation might also involve alterations in the nitrergic systems is still controversial. Our recent data indicate that, in vivo, chronic hyperglycemia might induce an increased number of vSMC proliferative clones which persist in culture and are associated with increased eNOS expression and activity. However, upregulation of eNOS and increased NO synthesis occur in the presence of a marked concomitant increase of O(2-) production. Since NO bioavailabilty might not be increased in high glucose stimulated vSMC, it is tempting to hypothesize that the proliferative phenotype observed in cells from diabetic rats is associated with a redox imbalance responsible quenching and/or trapping of NO, with the consequent loss of its biological activity. This might provide new insight on the mechanisms responsible for accelerated atherosclerosis in diabetes.