Raúl Díaz-Molina

Protein Folding and Mechanisms of Proteostasis

Highly sophisticated mechanisms that modulate protein structure and function, which involve synthesis and degradation, have evolved to maintain cellular homeostasis. Perturbations in these mechanisms can lead to protein dysfunction as well as deleterious cell processes. Therefore in recent years the etiology of a great number of diseases has been attributed to failures in mechanisms that modulate protein structure. Interconnections among metabolic and cell signaling pathways are critical for homeostasis to converge on mechanisms associated with protein folding as well as for the preservation of the native structure of proteins. For instance, imbalances in secretory protein synthesis pathways lead to a condition known as endoplasmic reticulum (ER) stress which elicits the adaptive unfolded protein response (UPR). Therefore, taking this into consideration, a key part of this paper is developed around the protein folding phenomenon, and cellular mechanisms which support this pivotal condition. We provide an overview of chaperone protein function, UPR via, spatial compartmentalization of protein folding, proteasome role, autophagy, as well as the intertwining between these processes. Several diseases are known to have a molecular etiology in the malfunction of mechanisms responsible for protein folding and in the shielding of native structure, phenomena which ultimately lead to misfolded protein accumulation. This review centers on our current knowledge about pathways that modulate protein folding, and cell responses involved in protein homeostasis.

Genotype and phenotype of NAT2 and the occurrence of adverse drug reactions in Mexican individuals to an isoniazid-based prophylactic chemotherapy for tuberculosis

Isoniazid (INH) is a drug extensively used as a prophylactic and therapeutic agent for human tuberculosis (TB). INH is metabolized by the enzymatic activity of N-acetyltransferase 2 (NAT2). Human NAT2, encoded by a highly polymorphic gene, is involved in the biotransformation of xenobiotics, including drugs and certain chemical carcinogens. Numerous studies have established the correlation between the acetylator phenotype and the NAT2 genotype in several populations; however, little is known regarding Latin-American populations and the pharmacogenetics of NAT2. Here, we report the molecular genotyping of the NAT2 gene, the acetylator phenotype, and the incidence of INH-related adverse reactions in a group of 25 Mexican individuals enrolled in a prophylactic protocol for TB. Using both the NAT2 genotyping and acetylation phenotyping approach, we found a ratio of 69.2 and 30.8% of slow and fast acetylators, respectively. Concordance of the NAT2 genotype and phenotype classification was 88% in the bimodal model. Regarding INH-related adverse reactions, only 2 individuals (8%) exhibited declared gastric intolerance. In our study group, we found an association between the NAT2 genotype and acetylator phenotype (OR=7.78, 95% CI, 0.87-87.98, Fishers exact test, p<0.05), but did not find any genotype or phenotype association with the incidence of INH-related adverse reactions (Fishers exact test, p>0.05).

Thermoregulation of nutrient-restricted hair ewes subjected to heat stress during late pregnancy.

In summers with severe hot environmental temperatures, thermoregulation is expected to be critical during the last third of gestation of hair ewes, and this effect can be overstated by suboptimal feeding conditions. Twenty-four multiparous hair sheep ewes with approximately 100d of pregnancy were randomly assigned to two treatments to evaluate the effects of nutritional restriction (NR) during late gestation on some serum metabolites, physiological variables, and thyroid hormone concentrations under intense heat load (maximum temperature 42-45°C). Treatments were as follows: (1) control, ewes fed free choice wheat straw plus a concentrate at a rate of 500g/d, and (2) nutritionally-restricted (NR) ewes, which were offered wheat straw only ad libitum. Body weight of NR ewes dropped 5.1kg (P<0.05), while control ewes gained 4.7kg during the study period. Rectal temperature was not affected (P>0.05) by feeding regime either in the morning or afternoon hours. Respiration rate was greater (P<0.05) in control ewes (20 and 40breaths/min higher in the day and night, respectively) on d 130 and 145 of pregnancy compared to NR ewes. Skin temperatures during the morning and afternoon were affected (P<0.05) by feeding regime at d 130 and 145 of pregnancy. In the morning, NR ewes presented greater (P<0.05) head and rump temperature at day 145 of gestation, and lower (P<0.05) udder temperatures at d 130 and 145 than control ewes. In the afternoon, skin temperatures of NR ewes were higher (P<0.05) in head and right flank on d 130 and 145 of pregnancy, and in udder at day 145 compared to control ewes. Serum glucose was higher (P<0.05) in NR ewes than control animals at day 145 of pregnancy. Serum cholesterol, triglyceride and thyroid hormones were not affected by nutritional restriction. Overall, it was found that nutritionally restricted ewes were less affected by intense heat loads than well-fed ewes, apparently due to the lower metabolic heat produced by this underfed animals. Also, it was apparent that the lower respiration rate of NR ewes was compensated by a greater body surface temperature.

Antibody Response to Pneumococcal Polysaccharide Vaccine in Systemic Sclerosis

To the Editor: Systemic sclerosis (SSc) is a connective tissue disorder characterized by cutaneous and visceral fibrosis, and obliterative vasculopathy. The lungs are frequently affected in SSc, and pulmonary disease may significantly influence morbidity and mortality1. Patients with SSc are at increased risk for microbial infections due to the immune effects of the disease itself, and the frequent use of immunosuppressive agents. Current guidelines recommend vaccination with pneumococcal polysaccharide for persons 2 to 64 years of age with chronic illness and for persons 65 years of age or older2,3. Therefore, vaccination might be useful in this infection-prone population provided that the vaccines produce a significant increase in antibody levels. To date, antibody responses to pneumococcal polysaccharide vaccine in patients with SSc are unknown. We evaluated the immunogenicity of this commercial vaccine in patients with SSc during promotional campaigns. Eighteen consecutive patients with SSc, according to the American College of Rheumatology criteria4, attending our outpatient clinic were included. Patients were grouped in subsets as defined by LeRoy, et al 5. Patients who had received pneumococcus vaccination within 5 years prior to study were excluded. There were 17 women and one man of median age 46.5 years (range 31–62) and median disease duration 7.5 years (range 1–12). Diffuse cutaneous SSc … Address reprint requests to Dr. Mercado; E-mail: ulisesmercado{at}uabc.mx

Efecto de la Hidroxicloroquina sobre la sensibilidad a la insulina y el perfil de lípidos en pacientes con artritis reumatoide

BACKGROUND Rheumatoid arthritis (RA) is associated with a decrease in insulin sensitivity (IS), which has been identified as an independent risk factor for the development of early atherosclerosis. Hydroxychloroquine (HCQ) may have beneficial effects on glucose homeostasis and lipid profile. AIM To assess the effect of HCQ on IS and lipid profile in patients with RA. MATERIAL AND METHODS An open clinical trial was performed in 15 patients aged between 35 and 56 years. During three months, patients received 400 mg/day of HCQ orally. Before and after the pharmacological intervention, demographic and anthropometric variables, serum glucose, total cholesterol (TC), triglycerides (TG), HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, insulin and uric acid were measured. IS was estimated as the rate of glucose clearance per minute obtained with the insulin tolerance test (KITT). RESULTS Baseline and final KITT values were 4.3 ± 1.2 and 4.80 ± 1.1%/min, respectively (p = 0.03). Significant reductions in serum TC (p = 0.04) and TG (p = 0.01) were also observed. No other significant differences were observed. CONCLUSIONS Oral administration of 400 mg/day of HCQ during three months in RA patients is associated with an improvement in IS, TC and TG.Background Rheumatoid arthritis (RA) is associated with a decrease in insulin sensitivity (IS), which has been identified as an independent risk factor for the development of early atherosclerosis. Hydroxychloroquine (HCQ) may have beneficial effects on glucose homeostasis and lipid profile. Aim To assess the effect of HCQ on IS and lipid profile in patients with RA. Material and methods An open clinical trial was performed in 15 patients aged between 35 and 56 years. During three months, patients received 400 mg/day of HCQ orally. Before and after the pharmacological intervention, demographic and anthropometric variables, serum glucose, total cholesterol (TC), triglycerides (TG), HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, insulin and uric acid were measured. IS was estimated as the rate of glucose clearance per minute obtained with the insulin tolerance test (KITT). Results Baseline and final KITT values were 4.3 ± 1.2 and 4.80 ± 1.1%/min, respectively (p = 0.03). Significant reductions in serum TC (p = 0.04) and TG (p = 0.01) were also observed. No other significant differences were observed. Conclusions Oral administration of 400 mg/day of HCQ during three months in RA patients is associated with an improvement in IS, TC and TG.

Modulation of Amyloidogenesis Controlled by the C-Terminal Domain of Islet Amyloid Polypeptide Shows New Functions on Hepatocyte Cholesterol Metabolism

The islet amyloid polypeptide (IAPP) or amylin maintains a key role in metabolism. This 37-residues-peptide could form pancreatic amyloids, which are a characteristic feature of diabetes mellitus type 2. However, some species do not form amyloid fibril structures. By employing a biomimetic approach, we generated an extensive panel of optimized sequences of IAPP, which could drastically reduce aggregation propensity. A structural and cellular characterization analysis was performed on the C-terminal domain with the highest aggregation propensity. This allowed the observation of an aggregative phenomenon dependent of the lipid environment. Evaluation of the new F23R variant demonstrated inhibition of β-sheet structure and, therefore, amyloid formation on the native C-terminal, phenomenon that was associated with functional optimization in calcium and cholesterol management coupled with the optimization of insulin secretion by beta cells. When F23R variant was evaluated in microglia cells, a model of amyloidosis, cytotoxic conditions were not registered. In addition, it was found that C-terminal sequences of IAPP could modulate cholesterol metabolism in hepatocytes through regulation of SREBP-2, apoA-1, ABCA1, and LDLR, mechanism that may represent a new function of IAPP on the metabolism of cholesterol, increasing the LDL endocytosis in hepatocytes. Optimized sequences with only one residue modification in the C-terminal core aggregation could diminish β-sheet formation and represent a novel strategy adaptable to other pharmacological targets. Our data suggest a new IAPP function associated with rearrangements on metabolism of cholesterol in hepatocytes.

Efecto de época del año (verano vs. invierno) en variables fisiológicas, producción de leche y capacidad antioxidante de vacas Holstein en una zona árida del noroeste de México

El estres por calor (EC) induce la produccion de radicales libres derivados del oxigeno que se asocian con efectos negativos en la fisiologia, patologia y productividad de vacas lecheras. Con el proposito de medir y comparar variables fisiologicas y productivas de vacas Holstein en verano e invierno en una zona arida, se seleccionaron aleatoriamente 40 vacas lactantes (100 a 150 d en leche) en un mes representativo de cada epoca del ano (n = 20/ epoca). Los datos fueron analizados en un ANOVA bajo un diseno experimental completamente al azar, con epoca del ano como factor de interes (verano vs. invierno), y un nivel de significacion del 5%. Las temperaturas de la piel en costado derecho, nalga, ubre y cabeza, asi como de la leche, fueron 10 oC mas altas (P < 0,05) en verano. La tasa respiratoria fue dos veces mayor (106,87 ± 0,05 vs. 47,74 ± 0,06; P < 0,05) en verano, mientras que la temperatura rectal alcanzo 1,6 oC mas (P < 0,05) en verano. Las concentraciones de colesterol y TAS fueron menores (P < 0,05) en verano, mientras que la glucosa, TOS and IEO fueron mayores (P < 0,05) en la misma epoca. La produccion de leche se redujo en mas del 50% (P < 0,05) en verano, observandose reducciones de 42,6% en la produccion de energia en leche y de 48,4% en la produccion de leche ajustada a 3,5% de grasa. Se concluye que el efecto del EC es evidente y tiene un efecto perjudicial en la fisiologia y productividad de vacas Holstein en produccion, lo que hace necesario utilizar innovaciones ambientales para reducir este impacto negativo de las altas temperaturas

Cervicouterine cancer screening – TruScreen™ vs. conventional cytology: Pilot study

Introduction: Cervicouterine cancer (CC) is a health problem worldwide and is the fourth most common cancer in women, with a greater proportion of individuals affected by advanced stages of the disease in developing countries. Objective: To determine the sensitivity and specificity of the TruScreen™ opto-electronic device vs. conventional cytology in CC screenings. Methodology: This is a prospective observational study that included individuals who presented for the first time at the Dysplasia Clinic of the Instituto Nacional de Cancerología from March 1 through April 30, 2016, and those referred due to abnormal conventional cytology. The patients were evaluated with the TruScreen™ device, conventional cytology, colposcopy and, if necessary, cervical biopsy. The results were analyzed by descriptive statistics as well as the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the TruScreen™, using conventional cytology as the standard. Results: Thirty-two patients were included who met the inclusion criteria. The average age of the patients was 40 years (range, 23–61 years). For the diagnosis of high-grade intraepithelial lesions, the TruScreen™ device showed a 43% sensitivity, a 92% specificity, a PPV of 60%, and a NPV of 85%, whereas evaluation via cervical biopsy exhibited a 33% sensitivity, an 86% specificity, a 33% PPV, and an 86% NPV. The Kappa agreement index of the TruScreen™ with the colposcopies was 0.70. Conclusions: TruScreen™ demonstrated low sensitivity and high specificity compared with conventional cytology, which had a high NPV.

Cinética de la inmunoglobulina-A salival (IgAs) en adultos jóvenes con capacidad aeróbica promedio o excelente antes y después de una prueba de esfuerzo máximo

BACKGROUND Aim: To compare the concentration of secretory immunoglobulin-A (sIgA) in young adults with average or excellent aerobic capacity before and after a cardiopulmonary graded exercise test. METHODS Participants were nine apparently healthy physically active males (Mean age = 21.3 ± 2.1 yr.), randomly allocated in two groups based on their VO2max: a) average aerobic capacity (AEC, n = 5) or b) excellent aerobic capacity (EAC, n = 4). Participants performed the Bruce protocol to determine their aerobic capacity. The sIgA was measured before the test, immediately after the test and 60-, 120-, 240-, and 1440-min after the test. RESULTS Mixed factorial 2 x 6 ANOVA indicated no significant interactions between groups and measurements (p = 0.956), and main effect groups on sIgA (AEC = 85.4 ± 19.3 μg/mL vs. EAC = 79.2 ± 21.5 μg/mL, p = 0.836). Tukeys post hoc analysis revealed significant differences measurement obtained immediately after the test and between the initial measurement (p = 0.020), 60-min (p = 0.030), 240-min (p = 0.016), and 1440-min (p = 0.028) following the test. CONCLUSION There is no change in sIgA kinetics depending on the aerobic capacity of the participants following an aerobic capacity cardiopulmonary graded exercise test.

Effect of time of progesterone supplementation on serum progesterone and the conception rate of cooled Holstein heifers during the summer.

To investigate the effects of progesterone supplementation at two different times on serum progesterone (P4 ) concentration, conception rate and resynchronization of cooled Holstein heifers in summer, 90 heifers were randomly assigned to two groups: (i) heifers subjected to TAI (timed artificial insemination) and progesterone supplementation from days 4 to 14 after TAI (S1; n = 45); and (ii) heifers under the same TAI protocol as S1 and progesterone supplementation from days 17 to 22 after TAI (S2 ; n = 45). The groups S1 and S2 were cooled 10 days before and 21 days after TAI. Respiratory rate, body surface temperature, vaginal temperature and rectal temperature recorded during the experiment were not different (P > 0.05) between S1 and S2 groups. Progesterone concentration was not different (P > 0.05) in S1 compared to S2 . The conception rates on days 30 and 55 were similar between groups (P > 0.05). Progesterone supplementation did not increase either conception rate or concentrations of P4 in heifers during the summer. Heifers not pregnant to first service in the group S2 were resynchronized (77.7%) for a second breeding.