@article {1368, title = {Chronic kidney disease, insulin resistance, and incident diabetes in older adults.}, journal = {Clin J Am Soc Nephrol}, volume = {7}, year = {2012}, month = {2012 Apr}, pages = {588-94}, abstract = {

BACKGROUND AND OBJECTIVES: Insulin resistance is a complication of advanced CKD. Insulin resistance is less well characterized in earlier stages of CKD. The response of the pancreatic β cell, effects on glucose tolerance, and risk of diabetes are not clear.

DESIGN, SETTING, PARTICIPANTS, \& MEASUREMENTS: The Cardiovascular Health Study included 4680 adults without baseline diabetes. The Chronic Kidney Disease Epidemiology Collaboration creatinine equation was used to obtain the estimated GFR (eGFR). Insulin resistance was evaluated as fasting insulin concentration. The insulin sensitivity index, β cell function, and glucose tolerance were assessed by oral glucose tolerance testing. Incident diabetes was defined as fasting glucose >=126 mg/dl, nonfasting glucose >=200 mg/dl, or use of glucose-lowering medications.

RESULTS: Mean age was 72.5 years (range, 65-98 years). Mean eGFR was 72.2 (SD 17.1) ml/min per 1.73 m(2). After adjustment, each 10 ml/min per 1.73 m(2) lower eGFR was associated with a 2.2\% higher fasting insulin concentration (95\% confidence interval [CI], 1.4\%, 2.9\%; P<0.001) and a 1.1\% lower insulin sensitivity index (95\% CI, 0.03\%, 2.2\%; P=0.04). Surprisingly, eGFR was associated with an augmented β cell function index (P<0.001), lower 2-hour glucose concentration (P=0.002), and decreased risk of glucose intolerance (P=0.006). Over a median 12 years{\textquoteright} follow-up, 437 participants (9.3\%) developed diabetes. eGFR was not associated with the risk of incident diabetes.

CONCLUSIONS: Among older adults, lower eGFR was associated with insulin resistance. However, with lower eGFR, β cell function was appropriately augmented and risks of impaired glucose tolerance and incident diabetes were not increased.

}, keywords = {Age Factors, Aged, Aged, 80 and over, Biomarkers, Chronic Disease, Creatinine, Diabetes Mellitus, Female, Glomerular Filtration Rate, Glucose Tolerance Test, Health Surveys, Humans, Hypoglycemic Agents, Incidence, Insulin, Insulin Resistance, Insulin-Secreting Cells, Kidney, Kidney Diseases, Linear Models, Male, Proportional Hazards Models, Risk Assessment, Risk Factors, United States}, issn = {1555-905X}, doi = {10.2215/CJN.11861111}, author = {Pham, Hien and Robinson-Cohen, Cassianne and Biggs, Mary L and Ix, Joachim H and Mukamal, Kenneth J and Fried, Linda F and Kestenbaum, Bryan and Siscovick, David S and de Boer, Ian H} } @article {1554, title = {Genetic variants and associations of 25-hydroxyvitamin D concentrations with major clinical outcomes.}, journal = {JAMA}, volume = {308}, year = {2012}, month = {2012 Nov 14}, pages = {1898-905}, abstract = {

CONTEXT: Lower serum 25-hydroxyvitamin D concentrations are associated with greater risks of many chronic diseases across large, prospective community-based studies. Substrate 25-hydroxyvitamin D must be converted to 1,25-dihydroxyvitamin D for full biological activity, and complex metabolic pathways suggest that interindividual variability in vitamin D metabolism may alter the clinical consequences of measured serum 25-hydroxyvitamin D.

OBJECTIVE: To investigate whether common variation within genes encoding the vitamin D-binding protein, megalin, cubilin, CYP27B1, CYP24A1, and the vitamin D receptor (VDR) modify associations of low 25-hydroxyvitamin D with major clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS: Examination of 141 single-nucleotide polymorphisms in a discovery cohort of 1514 white participants (who were recruited from 4 US regions) from the community-based Cardiovascular Health Study. Participants had serum 25-hydroxyvitamin D measurements in 1992-1993 and were followed up for a median of 11 years (through 2006). Replication meta-analyses were conducted across the independent, community-based US Health, Aging, and Body Composition (n = 922; follow-up: 1998-1999 through 2005), Italian Invecchiare in Chianti (n = 835; follow-up: 1998-2000 through 2006), and Swedish Uppsala Longitudinal Study of Adult Men (n = 970; follow-up: 1991-1995 through 2008) cohort studies.

MAIN OUTCOME MEASURE: Composite outcome of incident hip facture, myocardial infarction, cancer, and mortality over long-term follow-up.

RESULTS: Interactions between 5 single-nucleotide polymorphisms and low 25-hydroxyvitamin D concentration were identified in the discovery phase and 1 involving a variant in the VDR gene replicated in independent meta-analysis. Among Cardiovascular Health Study participants, low 25-hydroxyvitamin D concentration was associated with hazard ratios for risk of the composite outcome of 1.40 (95\% CI, 1.12-1.74) for those who had 1 minor allele at rs7968585 and 1.82 (95\% CI, 1.31-2.54) for those with 2 minor alleles at rs7968585. In contrast, there was no evidence of an association (estimated hazard ratio, 0.93 [95\% CI, 0.70-1.24]) among participants who had 0 minor alleles at this single-nucleotide polymorphism.

CONCLUSION: Known associations of low 25-hydroxyvitamin D with major health outcomes may vary according to common genetic differences in the vitamin D receptor.

}, keywords = {25-Hydroxyvitamin D3 1-alpha-Hydroxylase, Aged, Chronic Disease, Cohort Studies, Female, Genetic Variation, Genotype, Hip Fractures, Humans, Low Density Lipoprotein Receptor-Related Protein-2, Male, Meta-Analysis as Topic, Myocardial Infarction, Neoplasms, Polymorphism, Single Nucleotide, Receptors, Calcitriol, Receptors, Cell Surface, Risk, Steroid Hydroxylases, Vitamin D, Vitamin D3 24-Hydroxylase}, issn = {1538-3598}, doi = {10.1001/jama.2012.17304}, author = {Levin, Gregory P and Robinson-Cohen, Cassianne and de Boer, Ian H and Houston, Denise K and Lohman, Kurt and Liu, Yongmei and Kritchevsky, Stephen B and Cauley, Jane A and Tanaka, Toshiko and Ferrucci, Luigi and Bandinelli, Stefania and Patel, Kushang V and Hagstr{\"o}m, Emil and Micha{\"e}lsson, Karl and Melhus, H{\r a}kan and Wang, Thomas and Wolf, Myles and Psaty, Bruce M and Siscovick, David and Kestenbaum, Bryan} }