title: Altered glucose metabolism rather than naive type 2 diabetes mellitus (T2DM) is related to vitamin D status in severe obesity.
abstract: BACKGROUND
  The last decades have provided insights into vitamin D physiology linked to glucose homeostasis. Uncertainties remain in obesity due to its intrinsic effects on vitamin D and glucose tolerance.
  
  
  OBJECTIVE
  To assess the relationship between vitamin D and glucose abnormalities in severely obese individuals previously unknown to suffer from abnormal glucose metabolism.
  
  
  METHODS
  Tertiary care centre.
  
  
  METHODS
  524 obese patients (50.3 ± 14.9 yrs; BMI, 47.7 ± 7.3 kg/m2) screened by OGTT, HbA1c and the lipid profile. Vitamin D status was assessed by 25(OH)D3, PTH and electrolyte levels. 25(OH)D3 deficiency/insufficiency were set at 20 and 30 ng/ml, respectively. All comparative and regression analyses were controlled for age, BMI and gender.
  
  
  RESULTS
  The prevalence of vitamin D deficiency/insufficiency and secondary hyperparathyroidism were 95% and 50.8%, respectively. Normal glucose tolerance (NGT), impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), and type 2 diabetes mellitus (T2DM) were found in 37.8%, 40.5% and 21.7% of cases, respectively. Large variations in metabolic parameters were seen across categories of vitamin D status, but the only significant differences were found for C-peptide, tryglicerides, LDL- and HDL-cholesterol levels (p < 0.05 for all). The prevalence of vitamin D deficiency was documented to be slightly but significantly more frequent in glucose-intolerant patients (IFG + IGT + T2DM) compared to the -normotolerant counterpart (87% vs. 80%, p < 0.05). In partial correlation analyses, there was no association between vitamin D levels and glucose-related markers but for HbA1c (r = -0.091, p < 0.05), and both basal and OGTT-stimulated insulin levels (r = 0.097 and r = 0.099; p < 0.05 for all). Vitamin D levels were also correlated to HDL-cholesterol (r = 0.13, p = 0.002). Multivariate regression analysis inclusive of vitamin D, age, BMI, gender and fat mass as independent variables, showed that vitamin D was capable of predicting HbA1c levels (β = -0.101, p < 0.05).
  
  
  CONCLUSIONS
  Given the inherent effect of obesity on vitamin D and glucose homeostasis, current data suggest a potential independent role for vitamin D in the regulation of glucose metabolism in a setting of obese patients previously unknown to harbour glucose metabolism abnormalities.
authors.forename: Mattia
authors.initials: M
authors.lastname: Bellan
authors.forename: Gabriele
authors.initials: G
authors.lastname: Guzzaloni
authors.forename: Maura
authors.initials: M
authors.lastname: Rinaldi
authors.forename: Elena
authors.initials: E
authors.lastname: Merlotti
authors.forename: Carlotta
authors.initials: C
authors.lastname: Ferrari
authors.forename: Antonella
authors.initials: A
authors.lastname: Tagliaferri
authors.forename: Mario
authors.initials: M
authors.lastname: Pirisi
authors.forename: Gianluca
authors.initials: G
authors.lastname: Aimaretti
authors.forename: Massimo
authors.initials: M
authors.lastname: Scacchi
authors.affiliation: Division of General Medicine, Ospedale S, Giuseppe, I,R,C,C,S, Istituto Auxologico Italiano, Verbania, Italy. marzullo@med.unipmn.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Marzullo
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D012720:Severity of Illness Index; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D014807:Vitamin D