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Vitamin D, insulin secretion, sensitivity, and lipids: results from a case-control study and a randomized controlled trial using hyperglycemic clamp technique.

Grimnes G, Figenschau Y, Almås B, Jorde R - Diabetes (2011)

Bottom Line: A final hyperglycemic clamp was then performed.After supplementation, serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants randomized to vitamin D and 45 of 53 randomized to placebo, respectively.At the end of the study, there were no statistically significant differences in the outcome variables between the two groups.

View Article: PubMed Central - PubMed

Affiliation: Tromsø Endocrine Research Group, Department of Clinical Medicine, University of Tromsø, Tromsø, Norway. guri.grimnes@unn.no

ABSTRACT

Objective: Vitamin D deficiency is associated with an unfavorable metabolic profile in observational studies. The intention was to compare insulin sensitivity (the primary end point) and secretion and lipids in subjects with low and high serum 25(OH)D (25-hydroxyvitamin D) levels and to assess the effect of vitamin D supplementation on the same outcomes among the participants with low serum 25(OH)D levels.

Research design and methods: Participants were recruited from a population-based study (the Tromsø Study) based on their serum 25(OH)D measurements. A 3-h hyperglycemic clamp was performed, and the participants with low serum 25(OH)D levels were thereafter randomized to receive capsules of 20,000 IU vitamin D(3) or identical-looking placebo twice weekly for 6 months. A final hyperglycemic clamp was then performed.

Results: The 52 participants with high serum 25(OH)D levels (85.6 ± 13.5 nmol/L [mean ± SD]) had significantly higher insulin sensitivity index (ISI) and lower HbA(1c) and triglycerides (TGs) than the 108 participants with low serum 25(OH)D (40.3 ± 12.8 nmol/L), but the differences in ISI and TGs were not significant after adjustments. After supplementation, serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants randomized to vitamin D and 45 of 53 randomized to placebo, respectively. At the end of the study, there were no statistically significant differences in the outcome variables between the two groups.

Conclusions: Vitamin D supplementation to apparently healthy subjects with insufficient serum 25(OH)D levels does not improve insulin sensitivity or secretion or serum lipid profile.

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Related in: MedlinePlus

Flowchart showing recruitment of participants, randomization, and completion.
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Figure 1: Flowchart showing recruitment of participants, randomization, and completion.

Mentions: Subjects aged 30–75 years previously participating in the sixth Tromsø Study were invited to participate. The Tromsø Study is an ongoing longitudinal population-based study first performed in 1974 (23). The sixth survey was performed in 2008 and the following groups were invited: those who participated in the second phase of the fourth survey (1994–1995), a random 10% sample of subjects aged 30–39 years, all subjects aged 40–42 and 60–87 years, and a 40% random sample of subjects aged 43–59 years. In total, 19,762 subjects were invited and 12,984 subjects (65.7%) attended (23). Serum 25(OH)D measurements were performed in all the participants, and people with serum 25(OH)D between the 5th and 10th percentiles (low serum 25[OH]D; case subjects) or between the 80th and 95th percentiles (high serum 25[OH]D; control subjects) were invited to the current study by mail. Those who reported to be current smokers were not invited owing to a newly discovered interference between smoking and the assay used for serum 25(OH)D analyses in the sixth Tromsø Study (24). The invitation letter did not disclose the subject’s vitamin D status. A person not involved in the examinations administered the invitations to achieve a fairly equal distribution among case and control subjects regarding sex, age, and BMI. However, there was no head-to-head matching. Exclusion criteria were diabetes, acute myocardial infarction or stroke during the past 12 months, cancer during the past 5 years, steroid use, serum creatinine ≥130 μmol/L (males) or ≥110 μmol/L (females), possible primary hyperparathyroidism (plasma parathyroid hormone [PTH] >5.0 pmol/L combined with serum calcium >2.50 mmol/L), sarcoidosis, systolic blood pressure >175 mmHg or diastolic blood pressure >105 mmHg, and specifically for women, pregnancy, lactation, or fertile age and no contraception use. Participants were recruited between November 2008 and April 2010. Because there was a considerable time span between the first serum 25(OH)D measurement in the Tromsø Study and inclusion in the current study, a low or high serum 25(OH)D in the Tromsø Study had to be confirmed in a new serum sample before inclusion. The flowchart shows the recruitment of participants (Fig. 1).


Vitamin D, insulin secretion, sensitivity, and lipids: results from a case-control study and a randomized controlled trial using hyperglycemic clamp technique.

Grimnes G, Figenschau Y, Almås B, Jorde R - Diabetes (2011)

Flowchart showing recruitment of participants, randomization, and completion.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198082&req=5

Figure 1: Flowchart showing recruitment of participants, randomization, and completion.
Mentions: Subjects aged 30–75 years previously participating in the sixth Tromsø Study were invited to participate. The Tromsø Study is an ongoing longitudinal population-based study first performed in 1974 (23). The sixth survey was performed in 2008 and the following groups were invited: those who participated in the second phase of the fourth survey (1994–1995), a random 10% sample of subjects aged 30–39 years, all subjects aged 40–42 and 60–87 years, and a 40% random sample of subjects aged 43–59 years. In total, 19,762 subjects were invited and 12,984 subjects (65.7%) attended (23). Serum 25(OH)D measurements were performed in all the participants, and people with serum 25(OH)D between the 5th and 10th percentiles (low serum 25[OH]D; case subjects) or between the 80th and 95th percentiles (high serum 25[OH]D; control subjects) were invited to the current study by mail. Those who reported to be current smokers were not invited owing to a newly discovered interference between smoking and the assay used for serum 25(OH)D analyses in the sixth Tromsø Study (24). The invitation letter did not disclose the subject’s vitamin D status. A person not involved in the examinations administered the invitations to achieve a fairly equal distribution among case and control subjects regarding sex, age, and BMI. However, there was no head-to-head matching. Exclusion criteria were diabetes, acute myocardial infarction or stroke during the past 12 months, cancer during the past 5 years, steroid use, serum creatinine ≥130 μmol/L (males) or ≥110 μmol/L (females), possible primary hyperparathyroidism (plasma parathyroid hormone [PTH] >5.0 pmol/L combined with serum calcium >2.50 mmol/L), sarcoidosis, systolic blood pressure >175 mmHg or diastolic blood pressure >105 mmHg, and specifically for women, pregnancy, lactation, or fertile age and no contraception use. Participants were recruited between November 2008 and April 2010. Because there was a considerable time span between the first serum 25(OH)D measurement in the Tromsø Study and inclusion in the current study, a low or high serum 25(OH)D in the Tromsø Study had to be confirmed in a new serum sample before inclusion. The flowchart shows the recruitment of participants (Fig. 1).

Bottom Line: A final hyperglycemic clamp was then performed.After supplementation, serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants randomized to vitamin D and 45 of 53 randomized to placebo, respectively.At the end of the study, there were no statistically significant differences in the outcome variables between the two groups.

View Article: PubMed Central - PubMed

Affiliation: Tromsø Endocrine Research Group, Department of Clinical Medicine, University of Tromsø, Tromsø, Norway. guri.grimnes@unn.no

ABSTRACT

Objective: Vitamin D deficiency is associated with an unfavorable metabolic profile in observational studies. The intention was to compare insulin sensitivity (the primary end point) and secretion and lipids in subjects with low and high serum 25(OH)D (25-hydroxyvitamin D) levels and to assess the effect of vitamin D supplementation on the same outcomes among the participants with low serum 25(OH)D levels.

Research design and methods: Participants were recruited from a population-based study (the Tromsø Study) based on their serum 25(OH)D measurements. A 3-h hyperglycemic clamp was performed, and the participants with low serum 25(OH)D levels were thereafter randomized to receive capsules of 20,000 IU vitamin D(3) or identical-looking placebo twice weekly for 6 months. A final hyperglycemic clamp was then performed.

Results: The 52 participants with high serum 25(OH)D levels (85.6 ± 13.5 nmol/L [mean ± SD]) had significantly higher insulin sensitivity index (ISI) and lower HbA(1c) and triglycerides (TGs) than the 108 participants with low serum 25(OH)D (40.3 ± 12.8 nmol/L), but the differences in ISI and TGs were not significant after adjustments. After supplementation, serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants randomized to vitamin D and 45 of 53 randomized to placebo, respectively. At the end of the study, there were no statistically significant differences in the outcome variables between the two groups.

Conclusions: Vitamin D supplementation to apparently healthy subjects with insufficient serum 25(OH)D levels does not improve insulin sensitivity or secretion or serum lipid profile.

Show MeSH
Related in: MedlinePlus