Browsing by Author "Santos Martin, José Luis"

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    Evaluación de la insulinemia post carga oral de glucosa como método diagnóstico de resistencia a la insulina
    (2014) Arancibia, Constanza; Galgani Fuentes, José; Valderas Igor, Juan Patricio; Morales, Mauricio; Santos Martin, José Luis; Pollak Cornejo, Felipe
    Background: In our country, the assessment of insulin resistance (IR) measuring serum insulin levels at 60 and 120 minutes after a 75 g oral glucose tolerance test (OGTT), is usual. However, there is no information about the distribution of serum insulin levels in the Chilean population. Aim: To assess the distribution of serum insulin levels at 60 and 120 minutes during OGTTs and suggest a statistical cut-off point to estimate the degree of IR. Material and Methods: Retrospective analysis of 1815 OGTTs performed in non-diabetic subjects aged between 18 and 75 years, at a university medical center. HOMA-IR (Homeostasis Model Assessment), insulin sensitivity index of Matsuda (ISI-Composite), and their correlation with serum insulin levels at 60 and 120 minutes were calculated. Results: The 75th percentiles for serum insulin levels at 60 and 120 minutes were 127 and 81 μU/mL, respectively. There was a high correlation between HOMA-IR and ISI-Composite (r = -089, p < 0.001). There was a weaker although significant correlation between HOMA-IR and ISI-Composite and insulin levels at 60 (r = 0.56 and -0.79 respectively, p < 0,001) and 120 minutes (r = 0.54 and -0.75 respectively, p < 0,001). Conclusions: We propose 60 and 120 min serum insulin levels of 130 and 80 μU/mL respectively, as cut-off values for normality during OGTT in Chilean normoglycemic individuals.
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    Genetics of body composition: From severe obesity to extreme leanness
    (2020) Cortes Mora, Víctor Antonio; Santos Martin, José Luis
    This chapter describes common genetic variations influencing body composition as well as rare mutations causing monogenic obesity or extreme leanness. Large population-based genome-wide association studies (GWAS) revealed more than 500 genetic loci associated with body mass index (BMI) and adiposity traits in the population. Common variations in FTO and MC4R genes are the most statistically consistent signals across studies. Although discoveries of new gene variants through GWAS are important for expanding underlying knowledge on body fat accumulation, their small effect make them insufficient for predicting obesity. Most cases of monogenic obesity are derived from rare mutations in genes belonging to the leptin-melanocortin pathway, such as LEP, LEPR, MC4R, or POMC genes. On the other extreme of BMI, the study of congenital generalized lipodystrophy syndrome has revealed mutations in AGPAT2, BSCL2, PTRF, and CAV1 genes. The evaluation of obesity and leanness as opposite phenotypes represents an interesting approach to assessing causal gene variations related to body composition.
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    Lipodistrofias primarias: presentación clínica y diagnóstico
    (2019) Cortés Mora, Víctor Antonio; Santos Martin, José Luis
    Lipodystrophies are a heterogeneous group of syndromes defined by a severe reduction of the adipose tissue. These can be congenital or acquired. Anatomically, they can be partial or generalized. The etiology of several lipodystrophies is well known. However, the cause of many others remains unknown. The commonest lipodystrophy worldwide is secondary to highly active anti-retroviral therapy in HIV-infected patients. By contrast, primary lipodystrophies (those not associated to any known disease or condition) are much less common and represent a diagnostic challenge. The major complications of lipodystrophies are metabolic, often resulting in severe insulin resistance, diabetes and dyslipidemia. No cure is available for lipodystrophies but the supplementation with recombinant leptin potently controls the metabolic abnormalities when there is a leptin deficiency. Herein, we review the clinical presentation, diagnostic process and therapeutic principles of the main primary lipodystrophy syndromes.
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    Study Designs in Genomic Epidemiology
    (ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD, 2020) Santos Martin, José Luis; Rivadeneira, Fernando
    The choice of an appropriate study design is a critical first step in any genomic epidemiology research, especially considering the current unprecedented capacity of generating massive information derived from genomics and other "-omics” disciplines. In this chapter, we will review the main types of study designs used to discover novel genes or gene variants related to human diseases, as well as to assess their quantitative impact on disease risk. Several study designs are commonly used in the field of epidemiology (for example, cohort, classical case-control, and case-cohort studies). In contrast, other study designs based on the observation of resemblance among relatives come primarily from the field of human genetics, such as family aggregation, adoption, and monozygotic-dizygotic twin studies. Finally, the massive incorporation of genetic markers and next-generation sequencing data has been used in linkage studies of nuclear or multigenerational families, genomic studies of population isolates, and genome-wide association studies.