Effect of the Melanocortin 4-Receptor Ile269Asn Mutation on Weight Loss Response to Dietary, Phentermine and Bariatric Surgery Interventions.

The loss of function melanocortin 4-receptor (MC4R) Ile269Asn mutation has been proposed as one of the most important genetic contributors to obesity in the Mexican population. However, whether patients bearing this mutation respond differently to weight loss treatments is unknown. We tested the association of this mutation with obesity in 1683 Mexican adults, and compared the response of mutation carriers and non-carriers to three different weight loss interventions: dietary restriction intervention, phentermine 30 mg/day treatment, and Roux-en-Y gastric bypass (RYGB) surgery. The Ile269Asn mutation was associated with obesity [OR = 3.8, 95% CI (1.5-9.7), p = 0.005]. Regarding interventions, in the dietary restriction group only two patients were MC4R Ile269Asn mutation carriers. After 1 month of treatment, both mutation carriers lost weight: -4.0 kg (-2.9%) in patient 1, and -1.8 kg (-1.5%) in patient 2; similar to the mean weight loss observed in six non-carrier subjects (-2.9 kg; -2.8%). Phentermine treatment produced similar weight loss in six carriers (-12.7 kg; 15.5%) and 18 non-carriers (-11.3 kg; 13.6%) after 6 months of pharmacological treatment. RYGB also caused similar weight loss in seven carriers (29.9%) and 24 non-carriers (27.8%), 6 months after surgery. Our findings suggest that while the presence of a single MC4R loss of function Ile269Asn allele significantly increases obesity risk, the presence of at least one functional MC4R allele seems sufficient to allow short-term weight loss in response to dietary restriction, phentermine and RYGB. Thus, these three different interventions may be useful for the short-term treatment of obesity in MC4R Ile269Asn mutation carriers.

Genome-Wide Association Study Identifies a Functional SIDT2 Variant Associated With HDL-C (High-Density Lipoprotein Cholesterol) Levels and Premature Coronary Artery Disease.

Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.

Genetic contributors to serum uric acid levels in Mexicans and their effect on premature coronary artery disease.

BACKGROUND: Serum uric acid (SUA) is a heritable trait associated with cardiovascular risk factors and coronary artery disease (CAD). Genome wide association studies (GWAS) have identified several genes associated with SUA, mainly in European populations. However, to date there are few GWAS in Latino populations, and the role of SUA-associated single nucleotide polymorphisms (SNPs) in cardiovascular disease has not been studied in the Mexican population. METHODS: We performed genome-wide SUA association study in 2153 Mexican children and adults, evaluated whether genetic effects were modified by sex and obesity, and used a Mendelian randomization approach in an independent cohort to study the role of SUA modifying genetic variants in premature CAD. RESULTS: Only two loci were associated with SUA levels: SLC2A9 (ß = -0.47 mg/dl, P = 1.57 × 10-42 for lead SNP rs7678287) and ABCG2 (ß = 0.23 mg/dl, P = 2.42 × 10-10 for lead SNP rs2231142). No significant interaction between SLC2A9 rs7678287 and ABCG2 rs2231142 genotypes and obesity was observed. However, a significant ABCG2 rs2231142 genotype*sex interaction (P = 0.001) was observed in adults but not in children. Although SUA levels were associated with premature CAD, metabolic syndrome and decreased glomerular filtration rate (eGFR), only ABCG2 rs2231142 was associated with decreased eGFR in the premature CAD group. CONCLUSIONS: SUA elevation was independently associated with premature CAD, metabolic syndrome and decreased eGFR in the Mexican population. However, a Mendelian randomization approach using the lead SUA-associated SNPs (SLC2A9 and ABCG2) did not support a causal role of elevated SUA levels for premature CAD.

Effects of a cyclooxygenase-2 preferential inhibitor in young healthy dogs exposed to air pollution: a pilot study.

Residency in cities with high air pollution is associated with neuroinflammation and neurodegeneration in healthy children, young adults, and dogs. Nonsteroidal anti-inflammatory drugs may offer neuroprotection. The authors measured the plasma concentrations of 3-nitrotyrosine and the cerebro-spinal-fluid concentrations of prostaglandin E2 metabolite and the oligomeric form of amyloid derived diffusible ligand; measured the mRNA expression of cyclooxygenase-2, interleukin 1beta, CD14, and Aquaporin-4 in target brain areas; and evaluated brain MRI, cognition, and neuropathology in 8 dogs treated with a preferential cyclooxygenase-2 inhibitor (Nimesulide) versus 7 untreated litter-matched Mexico City dogs. Nimesulide significantly decreased nitrotyrosine in plasma (p < .0001), frontal gray IL1beta (p = .03), and heart IL1beta (p = .02). No effect was seen in mRNA COX2, amyloid, and PGE2 in CSF or the MRI white matter lesions. All exposed dogs exhibited olfactory bulb and frontal accumulation of Abeta(42) in neurons and blood vessels and frontal vascular subcortical pathology. White matter hyperintense MRI frontal lesions were seen in 4/6 non-treated and 6/8 treated dogs. Nonsteroidal anti-inflammatory drugs may offer limited neuroprotection in the setting of severe air pollution exposures. The search for potentially beneficial drugs useful to ameliorate the brain effects of pollution represents an enormous clinical challenge.

Comparative bioavailability of two oral formulations of omeprazole.

Omeprazole is a very widely used proton-pump inhibitor. Currently, there are several branches available in Mexico, however, limited information about their bioavailabilities is available. The purpose of this study was to compare the bioavailability of two of them, Losec and Omelcid. Twenty-eight healthy volunteers were enrolled in this study that was carried out following the recommendations of the Declaration of Helsinki. Subjects read the protocol that was approved by the institutional research and ethics committees and gave written consent for participation. After an overnight fast, volunteers received an oral dose of 20 mg omeprazole (formulation A or B) and blood samples were obtained at selected times during 8 hours. Plasma was obtained by centrifugation and stored frozen until analyzed by a validated HPLC method. Pharmacokinetic parameters were obtained by non-compartmental analysis and values (+/- s.e.m.) obtained were as follows: Cmax 354.28 +/- 51.57 and 308.95 +/- 44.42 ng/ml, t(max) 2.26 +/- 0.22 and 2.63 +/- 0.24 h and AUC(8h) 701.01 +/- 109.34 and 774.13 +/- 132.84 ngh/ml for formulations A and B respectively. Log transformed Cmax and AUC(8h) were compared by analysis of variance and 90% confidence limits of the parameters ratios (B/A) were 72.73-106.34% and 90.32-124.96%, for Cmax and AUC(8h) respectively. As confidence intervals did not exceed the 70-142.9% limits for Cmax and 80-125% for AUC(8h), it is concluded that the formulations tested are bioequivalent.

The influence of malnutrition on the oral pharmacokinetics of nimesulide in rats.

Malnutrition is a health problem in Mexico. It has been established that malnutrition may produce important changes in the pharmacological response to drugs, since changes in the pharmacodynamics and pharmacokinetics may occur. It has been described that a reduction of plasma proteins and in hepatic enzymes may occur. Due to these changes, absorption, distribution and elimination of drugs can be modified. Nimesulide is a non-steroidal anti-inflammatory agent that is widely used. This drug is importantly bound to plasma proteins and is metabolized through cytochrome P-450, two systems that are altered in malnutrition. In order to establish if malnutrition can modify the pharmacokinetics of nimesulide, a comparison of pharmacokinetic parameters obtained in control and protein-calorie malnourished rats was carried out. Two groups of 7 rats were employed in this study. At 45 days of age, group 1 received a standard balanced diet for 4 weeks, whereas, group 2 received a low protein diet for the same period. Then, rats received an oral dose of 10 mg/kg nimesulide and blood samples were drawn at selected times for 12 hr. Nimesulide whole blood levels were determined by HPLC and the pharmacokinetic parameters; Cmax 1.18 +/- 0.13 and 1.03 +/- 0.10 microg/ml, tmax 5.25 +/- 1.03 and 7.48 +/- 1.09 h and AUC12h 8.64 +/- 1.19 and 8.27 +/- 0.85 microg x h/ml were obtained. We conclude that malnutrition does not modify the oral pharmacokinetics of nimesulide.

Comparison of suspension composition on the pharmacokinetics of nimesulide in rats.

Nimesulide is a non-steroidal anti-inflammatory agent that is widely used in the treatment of inflammatory pain. The drug belongs to the class II of Biopharmaceutical Classification System (low solubility, high permeability) and therefore, absorption of this drug is limited by its dissolution. It has been established that complex formation of insoluble substances with cyclodextrins may increase their oral bioavailability since solubility is improved. In order to provide test this hypothesis, a comparison on the oral pharmacokinetics of two suspensions of nimesulide in rats was carried out. Two groups of 7 rats were employed. One group received an oral dose of 10 mg/kg of a suspension prepared with 0.5% carboxymethylcellulose solution in water, whereas the other group received a commercially available formulation containing the complex of nimesulde-beta cyclodextrins (Eskaflam). Blood samples were obtained at selected times for a period of 12 hours and analyzed by an HPLC method. Pharmacokinetic parameters obtained were as follows: Cmax 1.18 +/- 0.16 and 1.93 +/- 0.12 microg/ml, tmax 5.25 +/- 1.03 and 3.21 +/- 0.91 h and AUC 8.65 +/- 1.19 and 13.74 +/- 0.70 microg hr/ml for carboxy-methylcellulose and Eskaflam, respectively. Values for Cmax and AUC12hr were increased and a reduction of tmax was observed indicating improved absorption of nimesulide in the formulation containing beta-cyclodextrins.

Comparison of the oral pharmacokinetics of fluconazole and itraconazole in Mexicans.

Fluconazole and itraconazole are antimycotics widely used in Mexico. However, limited information about their pharmacokinetics is available. It has been reported that physicochemical characteristics of these compounds are disparate, leading to different pharmacokinetic profiles. Moreover, it has been suggested that pharmacokinetics of some drugs may vary in Mexicans when compared with Caucasians due to reduced metabolism by CYP3A4. Based on these distinctions, it is important to carry out local studies in order to establish dosage regimens according the characteristics of each population. The purpose of this study was to compare the oral pharmacokinetics of fluconazole and itraconazole in Mexicans and to compare our results with those reported in other populations. Two groups of 16 subjects volunteered for this study that was approved by the Institutional Research and Ethics Committees. All subjects gave written informed consent for participation. After an overnight fast, volunteers received an oral dose of 100 mg fluconazole or itraconazole and blood samples were obtained at selected times over 96 hr. Plasma was obtained and analyzed by HPLC and pharmacokinetic parameters were obtained. As expected, fluconazole plasma levels were higher than itraconazole due to a lower volume of distribution. Additionally, less variability was observed for fluconazole. When data obtained in Mexicans was compared with those obtained in other populations, no differences were observed, suggesting that there are not interethnic differences in the pharmacokinetics of fluconazole and itraconazole.

Gender differences in the oral pharmacokinetics of fluconazole.

BACKGROUND AND OBJECTIVE: Fluconazole is a triazole derivative widely used for the treatment of mycoses. It has been established that several factors are able to modify its pharmacokinetics, including the bodyweight of the patient; however, there is controversy about the influence of gender on the pharmacokinetics of fluconazole. In order to clarify this controversy we decided to evaluate the pharmacokinetics of fluconazole in males and females. METHODS: Fifty-nine subjects (26 males and 33 females) were enrolled in this study. Volunteers received an oral dose of fluconazole 100mg under fasting conditions and blood samples were collected at selected times over a period of 96 hours. Plasma was obtained and analysed by a high-performance liquid chromatography method. RESULTS: The plasma fluconazole concentrations obtained in women were higher than those obtained in men. This was reflected in differences in most pharmacokinetic parameters. However, when parameters were normalised according to the bodyweight of subjects, differences were reduced, indicating that this factor plays a role in the differences observed. Notwithstanding, differences in other parameters, such as normalised maximum plasma concentration, time to reach maximum plasma concentration, volume of distribution and half-life, remained. CONCLUSION: Fluconazole pharmacokinetics are influenced by both bodyweight and gender, most likely because of differences in total body water between males and females. Although the clinical impact on efficacy and safety of the pharmacokinetic differences observed in this study was not established, it is desirable that fluconazole dosage regimens take into account both the gender and the bodyweight of the patient.