Vitamin D insufficiency and insulin resistance in obese adolescents

The association between hepatic steatosis, vitamin D status, and insulin resistance in adolescents with obesity

Introduction

Epidemiological studies suggest an inverse relationship between circulating 25-hydroxy-vitamin D [25(OH)D] levels and insulin resistance (IR), yet interventional studies have yielded inconsistent findings. This study examined the relationship between changes in vitamin D status and markers of IR in adolescents, with a focus on the modifying effect of liver fat.

Methods

A post-hoc analysis was performed using data from 44 adolescents participating in a 6-month observational study evaluating biomarkers of hepatosteatosis. Participants were categorized into two groups based on vitamin D status at the end of the observation period: those whose vitamin D levels increased or remained sufficient (VDI, n = 22) and those whose levels decreased or remained insufficient/deficient (VDD, n = 22). Liver fat percentage was measured using magnetic resonance imaging (MRI) fat-fraction, and IR was assessed using the updated Homeostatic Model Assessment for Insulin Resistance (HOMA2-IR) and the triglyceride-to-high-density lipoprotein cholesterol ratio (TG/HDL).

Results

Across the cohort, liver fat was positively associated with HOMA2-IR (β = 0.08, p = 0.023). The association between changes in vitamin D status and HOMA2-IR trajectories was modified by liver fat but only in Hispanic adolescents (β = -0.18, p < 0.001). Among Hispanic adolescents in the VDD group, HOMA-IR worsened, particularly at higher levels of liver fat. In non-Hispanic adolescents, HOMA-IR increased in the VDD group (β = 0.65, p = 0.033) compared to the VDI group, independent of baseline liver fat. Across the cohort, changes in vitamin D status interacted with liver fat to influence TG/HDL trajectories (β = 0.20, p = 0.034).

Conclusions

The metabolic response to changes in vitamin D status in adolescents with IR may vary based on racial and ethnic differences and liver fat status. These findings underscore the importance of considering liver fat and racial/ethnic background in vitamin D and metabolic health studies. Future research with more extensive and diverse cohorts spanning the fatty liver disease spectrum is needed to clarify these relationships.

Interactions between vitamin D deficiency and inflammation on diabetes risk: data from 336,500 UK Biobank adults

OBJECTIVES

Findings regarding the effects of vitamin D supplementation on diabetes risk are inconclusive. Because inflammation and vitamin D levels are interconnected, we hypothesized that higher inflammation levels moderate the effects of vitamin D deficiency on diabetes risk.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

UK Biobank participants without pre-existing diabetes at baseline were included (N = 336,500). We first linked vitamin D and C-reactive protein (CRP; inflammation measure) levels with incident diabetes during a mean follow-up of 13.5 years (SD = 1.9). Then, we investigated the moderation effect of CRP on the associations between vitamin D deficiency (<10 ng/mL) and incident diabetes and performed subgroup analyses according to age (<60 vs. ≥60 years) and frailty status (frail; pre-frail; non-frail). Multivariate analyses were conducted using restricted cubic spline Cox proportional hazards regression models.

RESULTS

Lower vitamin D and higher CRP levels were significantly associated with an increased risk of diabetes during follow-up. There was a significant interaction between vitamin D deficiency and CRP on incident diabetes (p < 0.001). In participants with higher levels of CRP, the hazard ratio of developing diabetes comparing participants who had vitamin D deficiency to those who did not was lower than that in participants with lower levels of CRP. The moderation effect of CRP was similar between younger and older adults but was stronger in frail or pre-frail older adults than in non-frail older adults.

CONCLUSION

Our findings indicate that the effect of vitamin D deficiency on incident diabetes may be affected by inflammation. This finding may explain the inconsistent results from vitamin D supplementation trials. Vitamin D supplementation without considering the potential impact of inflammation might prove unsatisfactory.

Longitudinal analysis of vitamin D levels considering sunshine duration and suggestion for a standardised approach for vitamin D supplementation in children and adolescents with obesity

BACKGROUND

Children with obesity have low 25 hydroxy-vitamin D (25-OH-D3) levels compared to lean children. Recommendations on when to start vitamin D supplementation differ largely between countries. Longitudinal data on 25-OH-D3 levels to guide treatment decisions are scarce since they are largely influenced by solar radiation and are difficult to compare.

METHODS

We carried out a retrospective analysis of multiple 25-OH-D3 and parathyroid hormone (PTH) measurements in a cohort of 543 patients without vitamin D supplementation. All measurements were taken at the local paediatric obesity clinic as documented in the German-Austrian-Swiss APV (Prospective Documentation of Overweight Children and Adolescents) registry from 2009 to 2019. Serial 25-OH-D3 and PTH levels were adjusted for sunshine duration over the last 30 days to account for seasonal variation, as well as for sex and body mass index (BMI). We further performed an exploratory analysis of the association of sunshine duration, sex, BMI SDS (standard deviation score), abnormal lipid levels or dysglycemia with the 25-OH-D3 trend.

RESULTS

229 obese patients (mean BMI SDS: 2,58 (± 0,56), 53% females, mean age: 12 (± 3) years, range: 2-21 years) with two, 115 with three and 96 with four repeated 25-OH-D3 measurements were identified. Mean adjusted 25-OH-D3 (48.2 nmol/l) and PTH (34.9 ng/l) levels remained stable over 120 weeks. 5% of the patients had an elevated PTH > 65 ng/l. High total cholesterol ≥ 200 mg/dl and high triglycerides ≥ 130 mg/dl were associated with higher 25-OH-D3 levels.

CONCLUSION

We propose a simple method to include sunshine duration in the analysis of 25-OH-D3 levels to minimise the bias of seasonal variation. Based on our data we established the pragmatic strategy of limiting vitamin D supplementation to patients with biochemical signs of mineralisation disorders such as elevated PTH and alkaline phosphatase (AP). In children with normal PTH and AP we recommend adjustment of calcium intake and increase of outdoor activity instead.

Serum 25-Hydroxyvitamin D Levels and Youth-Onset Type 2 Diabetes: A Two-Sample Mendelian Randomization Study

Observational studies have linked vitamin D insufficiency to pediatric type 2 diabetes (T2D), but evidence from vitamin D supplementation trials is sparse. Given the rising prevalence of pediatric T2D in all ethnicities, determining the protective role of vitamin D has significant public health importance. We tested whether serum 25-hydroxyvitamin D (25OHD) levels are causally linked to youth-onset T2D risk using Mendelian randomization (MR). We selected 54 single-nucleotide polymorphisms (SNPs) associated with 25OHD in a European genome-wide association study (GWAS) on 443,734 individuals and obtained their effects on pediatric T2D from the multi-ethnic PRODIGY GWAS (3006 cases/6061 controls). We applied inverse variance weighted (IVW) MR and a series of MR methods to control for pleiotropy. We undertook sensitivity analyses in ethnic sub-cohorts of PRODIGY, using SNPs in core vitamin D genes or ancestry-informed 25OHD SNPs. Multivariable MR accounted for the mediating effects of body mass index. We found that a standard deviation increase in 25OHD in the logarithmic scale did not affect youth-onset T2D risk (IVW MR odds ratio (OR) = 1.04, 95% CI = 0.96-1.13, p = 0.35) in the multi-ethnic analysis, and sensitivity, ancestry-specific and multivariable MR analyses showed consistent results. Our study had limited power to detect small/moderate effects of 25OHD (OR of pediatric T2D < 1.39 to 2.1). In conclusion, 25OHD levels are unlikely to have significant effects on the risk of youth-onset T2D across different ethnicities.

Differences in Cardiometabolic Biomarkers between Elementary School-Age Latinx Children with Obesity versus Healthy Weight

OBJECTIVES

Low-income Latinx youth are disproportionately affected by obesity, which results in an increased risk of cardiometabolic abnormalities. Biomarker tracking may be useful for the early identification of obesity comorbidities in young Latinx children. Hence, we aimed to compare cardiometabolic biomarkers between age- and sex-matched pairs of elementary school-aged Latinx children with obesity versus healthy weight.

METHODS

This case-control study compared cardiometabolic biomarkers between 13 pairs of age- and sex-matched elementary school-age (median 6.5 years) Latinx children with obesity (body mass index for age ≥ 95th percentile) as compared with their healthy weight (between the 5th and 85th percentiles) counterparts. Anthropometric measures and a fasted venous blood sample were taken for the analysis of lipids, glycemic, inflammatory, endocrine, and hepatic markers. Group differences were tested by the Mann-Whitney U or χ² test.

RESULTS

Cases had higher insulin (P = 0.003), hemoglobin A1c (P = 0.002), triglycerides (P = 0.023), and C-reactive protein (P < 0.001) and lower high-density lipoprotein (P = 0.002). Hepatic markers were similar, with alanine aminotransferase elevated among both groups.

CONCLUSIONS

The aforementioned biomarkers may be more sensitive to higher adiposity risk in this young Latinx population; however, elevated hepatic markers may indicate an ethnic/genetic predisposition to abnormal liver function. Research should be replicated in a larger group to confirm these findings.

The link between vitamin D, chemerin and metabolic profile in overweight and obese children - preliminary results

Background

Vitamin D affects adipogenesis, oxidative stress, inflammation, secretion of adipocytokines, lipid metabolism and thermogenesis. Some researchers postulate that those effects could be exerted by the influence of vitamin D on chemerin levels.

Aim of the study

We aimed to investigate if there is a link between serum 25-hydroksyvitamin D [25(OH)D], chemerin and metabolic profile in overweight and obese children before and after vitamin D supplementation.

Material and methods

The prospective study included 65 overweight and obese children aged 9.08-17.5 years and 26 peers as a control. None of the patients in the study group had received vitamin D within the last twelve months before the study.

Results

The study group had lower baseline 25(OH)D (p<0.001) and higher chemerin (p<0.001), triglycerides (TG, p<0.001), triglycerides/high density lipoprotein cholesterol (TG/HDL-C, p<0.001), C-reactive protein (CRP, p<0.05), fasting insulin (p<0.001), Homeostasis Model Assessment - Insulin Resistance (HOMA-IR, p<0.001), alanine aminotransferase (ALT, p<0.001) and uric acid (p<0.001) compared to the control group. Baseline vitamin D was related to fasting insulin (R=-0.29, p=0.021), HOMA-IR (R=-0.30, p=0.016), HDL-C (R=0.29, p=0.020) and uric acid (R=-0.28, p=0.037) in the study group. Baseline chemerin was related to insulin at 30' (R=0.27, p=0.030), 60' (R=0.27, p=0.033), 90' (R=0.26, p=0.037) and 120' (R=0.26, p=0.040) during the oral glucose tolerance test (OGTT) and ALT (R=0.25, p=0.041) in the study group. Correlation between vitamin D and chemerin (R=-0.39, p=0.046) was found only in the control group. After six months of vitamin D supplementation a decrease in CRP (p<0.01), total cholesterol (p<0.05), ALT (p<0.01), glucose at 150' OGTT (p<0.05) was observed. Moreover, we noticed a tendency for negative association between 25(OH)D and chemerin levels (p=0.085). Multivariable backward linear regression models were build using baseline vitamin D, baseline chemerin and six months chemerin as the dependent variables.

Conclusions

Our study confirmed that vitamin D has positive effect on metabolic profile in overweight and obese children. The relationship between vitamin D and chemerin is not clear, nevertheless we have observed a tendency to decrease chemerin concentrations after improving vitamin D status, even without a significant reduction in body fat mass.

Genetics, genomics, and diet interactions in obesity in the Latin American environment

Obesity is a chronic disease characterized by abnormal or excessive fat accumulation that could impact an individual's health; moreover, the World Health Organization (WHO) has declared obesity a global epidemic since 1997. In Latin America, in 2016, reports indicated that 24.2% of the adult population was obese. The environmental factor or specific behaviors like dietary intake or physical activity have a vital role in the development of a condition like obesity, but the interaction of genes could contribute to that predisposition. Hence, it is vital to understand the relationship between genes and disease. Indeed, genetics in nutrition studies the genetic variations and their effect on dietary response; while genomics in nutrition studies the role of nutrients in gene expression. The present review represents a compendium of the dietary behaviors in the Latin American environment and the interactions of genes with their single nucleotide polymorphisms (SNPs) associated with obesity, including the risk allele frequencies in the Latin American population. Additionally, a bibliographical selection of several studies has been included; these studies examined the impact that dietary patterns in Latin American environments have on the expression of numerous genes involved in obesity-associated metabolic pathways.

The correlation of vitamin D with HOMA-IR and glycated hemoglobin in type 2 diabetes mellitus patients

Background and objective: Diabetes mellitus, the most common endocrine condition, is characterised by an elevated level of plasma glucose. Vitamin D's primary functions are homeostasis of calcium and metabolism of bone, but it also has a significant role in homeostasis of plasma glucose. This study sought to examine the relationship between vitamin D and glycated haemoglobin and insulin resistance in type 2 diabetes mellitus (T2DM) subjects by analysing vitamin D, homeostasis model assessment of insulin resistance (HOMA-IR), and haemoglobin A1c (HbA1c) levels. Methods: 150 patients with newly diagnosed T2DM participated in this case-control research. Additionally, 150 controls of the same age and gender were also recruited. Serum vitamin D and fasting insulin levels were estimated by the electrochemiluminescence immunoassay (ECLIA) method. High-performance liquid chromatography (HPLC) was used to analyse HbA1c. Pearson's correlation coefficient was used to determine the relationship of vitamin D with HbA1c and HOMA-IR. Results: Around 70.7% of diabetes subjects had low vitamin D levels, compared to 31.3% in the control group. Vitamin D-deficient T2DM subjects had significantly higher HOMA-IR and HbA1c levels. Both vitamin D and HOMA-IR (r = -0.75) and vitamin D and HbA1c (r = -0.73) showed a strong inverse connection in T2DM patients. Conclusions: Vitamin D deficiency is correlated with ineffective glycemic control, and the reason might be its potential role in the secretion and sensitivity of insulin. Therefore, vitamin D screening must be incorporated as a routine check-up for T2DM patients.

Reversibility of pancreatic β-cells dysfunction after vitamin D and calcium supplementation: a pilot study in a population of obese and prepubescent North-African children

The mechanisms of diabetogenesis in children remain largely obscure. This study aimed to determine the impact of vitamin D and calcium supplementation on pancreatic β-cells function in terms of insulin secretion and sensitivity. This was a quasi-experimental study involving 30 obese and prepubescent Tunisian children (57% boys). During three months, the children received calcium and vitamin D supplementation at therapeutic doses. An oral glucose tolerance test (OGTT) was performed at the beginning and at the end of the study. The following metabolic definitions were applied: i) hyperinsulinism: insulinemia sum > 300 μ UI/ml during OGTT, ii) insulin-resistance: homeostatic model assessment of insulin-resistance > 2, iii) normal glycaemic profile: normal plasma levels during OGTT without any spike, and iv) pancreatic β-cells dysfunction reversibility: disappearance of the aforementioned disorders. The means ± standard-deviation of age and body mass index were 10.87 ± 1.9 years, and 30.17 ± 4.99 kg/m², respectively. All children were at the stage of hyperinsulinism associated with insulin-resistance. These disturbances were noted even in children having a normal glycaemic profile at OGTT. After calcium and vitamin D supplementation, glycaemic profile as well as insulin-secretion improved significantly (p < 0.0001). Hyperinsulinism and insulin-resistance decreased significantly by 56.67% (p < 0.0001) and 70.00% (p < 0.0001), respectively. Complete reversibility of these two disorders was noted in 26.6% of children. To conclude, in obese and prepubescent children, vitamin D and calcium supplementation led to the reversibility of the pancreatic β-cells dysfunction.

The enteroinsular axis during hospitalization in newborn foals

The enteroinsular axis (EIA) is an energy regulatory system that modulates insulin secretion through the release of enteroendocrine factors (incretins). Despite the importance of energy homeostasis in the equine neonate, information on the EIA in hospitalized foals is lacking. The goals of this study were to measure serum insulin and plasma incretin (glucose-dependent insulinotropic polypeptide [GIP], glucagon-like peptide-1 [GLP-1] and glucagon-like peptide-2 [GLP-2]) concentrations, to determine the insulin and incretin association, as well as their link to disease severity and outcome in hospitalized foals. A total of 102 newborn foals ≤72 h old were classified into hospitalized (n = 88) and healthy groups (n = 14). Hospitalized foals included septic (n = 55) and sick non-septic (SNS; n = 33) foals based on sepsis scores. Blood samples were collected over 72 h to measure serum insulin and plasma GIP, GLP-1 and GLP-2 concentrations using immunoassays. Data were analyzed by nonparametric methods and univariate logistic regression. At admission, serum glucose and insulin and plasma GIP were significantly lower in hospitalized and septic compared to healthy foals (P < 0.01), while plasma GLP-1 and GLP-2 concentrations were higher in hospitalized and septic foals than healthy and SNS foals, and decreased over time in septic foals (P < 0.05). As a percent of admission values, GLP-1 and GLP-2 concentrations dropped faster in healthy compared to hospitalized foals. Serum insulin concentrations were lower in hospitalized and septic non-survivors than survivors at admission (P < 0.01). Hospitalized foals with serum insulin < 5.8 µIU/mL, plasma GLP-1 >68.5 pM, and plasma GLP-2 >9 ng/mL within 24 h of admission were more likely to die (OR = 4.2; 95% CI = 1.1-16.1; OR = 13.5, 95% CI = 1.4-123.7; OR = 12.5, 95% CI = 1.6-97.6, respectively; P < 0.05). Low GIP together with increased GLP-1 and GLP-2 concentrations indicates that different mechanisms may be contributing to reduced insulin secretion in critically ill foals, including impaired intestinal production (GIP, proximal intestine) and pancreatic endocrine resistance to enhanced incretin secretion (GLP-1, GLP-2; distal intestine). These imbalances could contribute to energy dysregulation in the critically ill equine neonate.

Mechanisms Linking Vitamin D Deficiency to Impaired Metabolism: An Overview

Vitamin D deficiency is a common health problem worldwide. Despite its known skeletal effects, studies have begun to explore its extra-skeletal effects, that is, in preventing metabolic diseases such as obesity, hyperlipidemia, and diabetes mellitus. The mechanisms by which vitamin D deficiency led to these unfavorable metabolic consequences have been explored. Current evidence indicates that the deficiency of vitamin D could impair the pancreatic β-cell functions, thus compromising its insulin secretion. Besides, vitamin D deficiency could also exacerbate inflammation, oxidative stress, and apoptosis in the pancreas and many organs, which leads to insulin resistance. Together, these will contribute to impairment in glucose homeostasis. This review summarizes the reported metabolic effects of vitamin D, in order to identify its potential use to prevent and overcome metabolic diseases.

Bone health in adolescence

Adolescence is a fundamental period for the formation of the skeleton, because is the stage in which bones grow more in both size and strength, laying a solid foundation for the future health of the skeleton. Any condition interfering with optimal peak bone mass accrual can increase fracture risk later in life. Up to 80% of peak bone mass is genetically determined while the remaining 20% is modulated by environmental factors that, if deleterious, may result in low bone mineral density (BMD) and an increased risk of fracture. The preferred test to assess bone health is dual-energy x-ray absorptiometry (spine or total body less head) using Z scores instead of T scores, even though in short stature or growth delay, should be used the height Z-score. The correction of risk factors is the first treatment for low BMD in children and adolescents. It's necessary having a correct lifestyle for preserving bone health: a proper nutrition, an adequate physical weight-bearing activity and avoidance of alcohol intake and tobacco smoke. Bisphosphonates could be used in children who sustained osteoporotic fractures, impairing quality of life, when spontaneous recovery is low for the persistence of osteoporosis risk factors. This clinical review discusses factors affecting bone health during childhood and adolescence and deals with diagnosis and treatment of low bone mass or osteoporosis in this age group.

The Vitamin D Decrease in Children with Obesity Is Associated with the Development of Insulin Resistance during Puberty: The PUBMEP Study

Obesity and cardiometabolic risk have been associated with vitamin D levels even in children. The objective of the present study was to evaluate the association between insulin resistance (IR), cardiometabolic risk factors, and vitamin D in children from prepubertal to pubertal stages. A total of 76 children from the PUBMEP study, aged 4–12 years at baseline, were included. Children were evaluated in prepubertal and pubertal stages. Anthropometric measurements and selected cardiometabolic risk biomarkers, such as plasma glucose, blood lipids, insulin, adiponectin, leptin, and blood pressure, and serum 25-hydroxyvitamin D (25(OH)D) were determined. Children were categorized by obesity degree and IR status combined before and after puberty. Paired t-test and multivariate linear regression analyses were conducted. During puberty, the increase in triacylglycerols, insulin, and HOMA-IR and the decrease in QUICKI were significantly associated with the reduction in 25(OH)D (B = −0.274, p = 0.032; B = −0.219, p = 0.019; B = −0.250, p = 0.013; B = 1.574, p = 0.013, respectively) after adjustment by BMI-z, sex, and pubertal stage. Otherwise, prepubertal non-IR children with overweight/obesity that became IR during puberty showed a significant decrease in 25(OH)D and HDL-c, and an increase in waist circumference and triacylglycerol concentrations (p < 0.05 for all) over time. These results suggest that changes in IR seem to be associated with an effect on 25(OH)D levels during puberty, especially in children with overweight.

Vitamin D Deficiency Is Inversely Associated with Homeostatic Model Assessment of Insulin Resistance

The study was conducted to comprehensively assess the association of the concentration of vitamin D in the blood and insulin resistance in non-diabetic subjects. The objective was to pool the results from all observational studies from the beginning of 1980 to August 2021. PubMed, Medline and Embase were systematically searched for the observational studies. Filters were used for more focused results. A total of 2248 articles were found after raw search which were narrowed down to 32 articles by the systematic selection of related articles. Homeostatic Model Assessment of Insulin Resistance (HOMAIR) was used as the measure of insulin resistance and correlation coefficient was used as a measure of the relationship between vitamin D levels and the insulin resistance. Risk of bias tables and summary plots were built using Revman software version 5.3 while Comprehensive meta-analysis version 3 was used for the construction of forest plot. The results showed an inverse association between the status of vitamin D and insulin resistance (r = -0.217; 95% CI = -0.161 to -0.272; p = 0.000). A supplement of vitamin D can help reduce the risk of insulin resistance; however further studies, like randomized controlled trials are needed to confirm the results.

The combination of omega-3 fatty acids with high doses of vitamin D3 elevate A1c levels: A randomized Clinical Trial in people with vitamin D deficiency

PURPOSE

This randomised clinical trial (RCT) was created to assess the influence of 1,25-dihydroxyvitamin D (VD₃ ), omega-3 fatty acids (n-3FA) and their combination (D+) on glycated haemoglobin (A1c) levels in Jordanian peoples with vitamin D deficiency (VDD).

PARTICIPANTS AND METHODS

This RCT was designed to examine the follow-up (2 months) effect of either 50 000 IU VD₃ , 300 mg n-3FA, or the combination of the two supplements on glycated Haemoglobin (A1c) levels in 146 Jordanian women and men with VDD, aged from 25 to 55 years. The eligible participants were randomised into four groups: Control (C); VD₃ supplementation (50 000 IU of VD₃ was taken weekly) (D₃ ); n-3FA supplementation (300 mg of omega-3FA was taken daily) (n-3FA); VD₃ and omega-3 supplementation group (D+) with the same protocol as the previous two groups.

RESULTS

The combination therapy (n-3FA plus VD3) for 8 weeks significantly increased A1c levels (5.79 ± 0.34 vs 5.41 ± 0.33, P < .001). Tukey test for post hoc comparisons of A1c at follow-up showed that the A1c mean levels were remarkably higher in the D+ study group comparing to the control group (5.78 vs 5.38).

CONCLUSION

The intervention of n-3FA alone or in combination with high doses of VD₃ may lead to negative effects on glycaemic control or accelerate the insulin resistance's development in susceptible people for diabetes mellitus (type 2).

Correlation between vitamin D deficiency and fasting blood glucose levels in obese children

BACKGROUND

This study aimed to determine the relationship between Deficiency of vitamin D and hyperglycemia in children with obesity.

METHODS

This cross-sectional study was carried out between February and April of 2020. This study's subject population consisted of high school students aged 11 to 17 who were obese. The 25 (OH) level of Vitamin D was determined using the Chemiluminescence Immune Assay method. Subjects were divided into 4 groups; vitamin D deficiency with hyperglycemia, vitamin D deficiency without hyperglycemia, normal vitamin D with hyperglycemia, and normal vitamin D without hyperglycemia.

RESULTS

The prevalence of hyperglycemia was 28 (54.9%) in the vitamin D deficiency group and 17 (378%) in the normal vitamin D group, respectively. Statistical analysis revealed no statistically significant difference between the two groups (p = 0.093). With p = 0.031, there was a significant difference in the mean value of fasting blood sugar levels between the two groups. The frequency of hyperglycemia was 54.9 percent in the vitamin D deficiency group and 37.8 percent in the normal vitamin D group. Fasting blood sugar levels were lower in obese children with vitamin D deficiency than in children with normal vitamin D.

CONCLUSION

Fasting blood sugar levels were correlated with vitamin D levels in obese children, but clinically insignificant. However, the research is ongoing, so, it is critical to conduct early screening for Vitamin D and fasting blood sugar levels in order to reduce the risk of metabolic and cardiovascular diseases.

Response to single oral dose vitamin D in obese vs non-obese vitamin D-deficient children

Obese individuals are prone to vitamin D deficiency because of sequestration of vitamin D in their body fat. We planned to evaluate the rise in serum 25(OH)D levels in vitamin D-deficient obese vs normal body mass index(BMI) children, after administration of identical single dose of vitamin D. Twenty-two obese and 22 normal BMI children with serum 25 (OH)D < 20 ng/mL were given single oral dose 150,000 IU vitamin D, and 25 (OH)D levels were measured at 1 week and 1 month post-intervention. Results show that rise in 25(OH)D level from baseline was about 2.2 times lesser in obese compared with children with normal BMI, both at 1 week and at 1 month. The rise in 25(OH)D from baseline to 1 month was inversely correlated to BMI (r = - 0.56, p = < 0.001), waist circumference (r = - 0.48, p = 0.001), total fat mass (r = - 0.58, p < 0.001), and fat mass index (r = - 0.59, p < 0.001).Conclusion: The obese children have a 2.2 times lower rise in serum vitamin D levels as compared with the normal BMI children for the same dose of vitamin D supplementation. What is Known: • The obese individuals are prone to vitamin D deficiency and may be given higher doses of vitamin D supplementation. What is New: • Our study demonstrates that obese children have 2.2 times lesser rise in serum 25(OH)D concentrations as compared with normal BMI children when administered similar oral dose vitamin D.

Micronutrient status and associated factors of adiposity in primary school children with normal and high body fat in Colombo municipal area, Sri Lanka

BACKGROUND

The prevalence of obesity and associated risk of chronic diseases are increasing among the paediatric population. The effectiveness of preventive measures and interventions are likely to improve when all factors which associate with obesity in a specific target group are considered. Currently such comprehensive data is unavailable for Sri Lankan children aged 8-9 years.

METHODS

This paper pertains to the data collected from August-2015 to November-2016 for a case-control study which included cases (high body fat) (N = 160; males-81) and controls (normal body fat) (N = 164; males-80) recruited from primary schools in the Colombo Municipal area. Anthropometry and body composition (Bioelectrical impedance analysis-BIA) were measured. Diet, physical activity and socio-demographic data were collected using validated interviewer administered questionnaires. Serum concentrations of vitamins A, D [25(OH)D], E, folate (serum and red blood cell-RBC), zinc (Zn), selenium (Se), copper (Cu), iron (Fe), magnesium (Mg), calcium (Ca), chromium (Cr), manganese (Mn), cobalt (Co), ferritin, leptin and high sensitivity C-reactive protein (hs-CRP) were assessed using fasting blood samples.

RESULTS

Cases were from higher socio-economic strata and spent significantly less time on physical activities, more time on sedentary behaviours and consumed higher energy compared to the controls. Cases from both genders had significantly lower levels of vitamin D [25 (OH)D], Fe and Mg (all p < 0.05) and higher levels of Cu and Ca (all p < 0.01) compared to controls. Higher levels of ferritin and Cr were seen among male (p < 0.001) and female (p > 0.05) cases compared to the controls. However, total serum folate levels were lower in male (p < 0.01) and female (p > 0.05) cases while the RBC folate levels were higher among male (p < 0.01) and female (p > 0.05) cases compared with controls. Vitamins A, E, Se, Mn and Co (p > 0.05) were not significantly different between groups. The inflammatory markers, both hs-CRP and leptin levels were higher among cases (p < 0.001) compared to the controls.

CONCLUSIONS

This study highlights higher socio-economic status, lower physical activity, more sedentary behaviours, higher energy intake and inconsistent distribution of micronutrients among the children with high body fat when compared with the control group. Increased levels of inflammatory markers indicate the presence of the risk of chronic inflammation in children with high body fat.

Serum Vitamin D Affected Type 2 Diabetes though Altering Lipid Profile and Modified the Effects of Testosterone on Diabetes Status

Numerous studies have investigated the associations between serum vitamin D or testosterone and diabetes; however, inconsistencies are observed. Whether there is an interaction between vitamin D and testosterone and whether the lipid profile (total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)) mediates the association between vitamin D and diabetes is unclear. To investigate the effect of vitamin D and testosterone on impaired fasting glucose (IFG) or type 2 diabetes mellitus (T2DM), 2659 participants from the Henan Rural Cohort were included in the case-control study. Generalized linear models were utilized to estimate associations of vitamin D with IFG or T2DM and interactive effects of vitamin D and testosterone on IFG or T2DM. Principal component analysis (PCA) and mediation analysis were used to estimate whether the lipid profile mediated the association of vitamin D with IFG or T2DM. Serum 25(OH)D₃, 25(OH)D₂, and total 25(OH)D levels were negatively correlated with IFG (odds ratios (ORs) (95% confidence intervals (CIs)): 0.99 (0.97, 1.00), 0.85 (0.82, 0.88), and 0.97 (0.96, 0.98), respectively). Similarity results for associations between serum 25(OH)D₂ and total 25(OH)D with T2DM (ORs (95%CIs): 0.84 (0.81, 0.88) and 0.97 (0.96, 0.99)) were observed, whereas serum 25(OH)D₃ was negatively correlated to T2DM only in the quartile 2 (Q2) and Q3 groups (both p < 0.05). The lipid profile, mainly TC and TG, partly mediated the relationship between 25(OH)D₂ or total 25(OH)D and IFG or T2DM and the proportion explained was from 2.74 to 17.46%. Furthermore, interactive effects of serum 25(OH)D₂, total 25(OH)D, and testosterone on T2DM were observed in females (both p for interactive <0.05), implying that the positive association between serum testosterone and T2DM was vanished when 25(OH)D₂ was higher than 10.04 ng/mL or total 25(OH)D was higher than 40.04 ng/mL. Therefore, ensuring adequate vitamin D levels could reduce the prevalence of IFG and T2DM, especially in females with high levels of testosterone.

Risk evaluation of vitamin D insufficiency or deficiency in children using simple scores: The Healthy Growth Study

Although identification of population groups at high risk for low vitamin D status is of public health importance,there are no risk prediction tools available for children in Southern Europe that can cover this need. The present study aimed to develop and validate 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children. A cross-sectional epidemiological study was conducted among 2280 schoolchildren (9--13-year-old) living in Greece. The total sample was randomly divided into 2 subsamples of 1524 and 756 children, used in the development and validation of the 2 scores, respectively. Multivariate logistic regression analyses were used to develop the 2 risk evaluation scores, while receiver operating characteristic curves were employed to identify the optimal "points of change" for each risk score, upon which vitamin D insufficiency and deficiency is diagnosed with the highest possible sensitivity and specificity. The components of the 2 risk evaluation scores included children's age, gender, region of residence, screen-time, body weight status, maternal education, and season. The increase in each score by 1 unit elevated the likelihood for vitamin D insufficiency and deficiency by 31% and 28%, respectively. The receiver operating characteristic curves showed that the optimal "points of change" for each risk score, upon which vitamin D insufficiency or deficiency is diagnosed with the highest possible sensitivity and specificity were 8.5 and 12.5, respectively. In conclusion, this study developed 2 simple scores that evaluate the risk for vitamin D insufficiency or deficiency in children living in Greece. However, more studies are required for these scores to be validated in other populations of children from different countries.

Vitamin D deficiency serves as a precursor to stunted growth and central adiposity in zebrafish

Emerging evidence demonstrates the importance of sufficient vitamin D (1α, 25-dihydroxyvitamin D3) levels during early life stage development with deficiencies associated with long-term effects into adulthood. While vitamin D has traditionally been associated with mineral ion homeostasis, accumulating evidence suggests non-calcemic roles for vitamin D including metabolic homeostasis. In this study, we examined the hypothesis that vitamin D deficiency (VDD) during early life stage development precedes metabolic disruption. Three dietary cohorts of zebrafish were placed on engineered diets including a standard laboratory control diet, a vitamin D null diet, and a vitamin D enriched diet. Zebrafish grown on a vitamin D null diet between 2-12 months post fertilization (mpf) exhibited diminished somatic growth and enhanced central adiposity associated with accumulation and enlargement of visceral and subcutaneous adipose depots indicative of both adipocyte hypertrophy and hyperplasia. VDD zebrafish exhibited elevated hepatic triglycerides, attenuated plasma free fatty acids and attenuated lipoprotein lipase activity consistent with hallmarks of dyslipidemia. VDD induced dysregulation of gene networks associated with growth hormone and insulin signaling, including induction of suppressor of cytokine signaling. These findings indicate that early developmental VDD impacts metabolic health by disrupting the balance between somatic growth and adipose accumulation.

Vitamin D status and its relation to insulin resistance in a Mexican pediatric population

Background Obesity in children and adolescents has increased alarmingly, placing them at a higher risk for impaired glucose tolerance and type 2 diabetes. The prevalence of vitamin D deficiency has increased as well. Vitamin D is critical for glucose homeostasis and insulin secretion. Studies on adults have reported an inverse association between vitamin D levels and insulin resistance (IR), but the results in children are inconsistent. The aim of our study was to determine the association between IR and serum vitamin D levels in obese Mexican children and adolescents. Methods A cross-sectional study was performed on 227 children and adolescents between 6 and 19 years of age. Obesity was diagnosed through body mass index (BMI) for age, according to the World Health Organization (WHO) criteria (2007). 25-Hydroxyvitamin D (25[OH]D) was measured using an immunoassay technique and the homeostatic model assessment of insulin resistance (HOMA-IR) was calculated using the Matthews equation. Student's t-test was carried out. Results The mean serum 25(OH)D level was 35.80 ng/mL, and 55.1% of the subjects had levels classified as sufficient, 33.5% as insufficient, and 11.5% as deficient. The mean level of HOMA-IR was 3.16, and 70% of the subjects were diagnosed with IR. Fasting insulin levels and HOMA-IR were significantly different in adolescents with hypovitaminosis, compared with adolescents in the vitamin D sufficiency group (p = 0.01 and p = 0.03, respectively). Conclusions The insulin levels and HOMA-IR were higher in adolescents with hypovitaminosis. The girls presented higher levels of insulin and HOMA-IR than the boys.

The relationship between cardiometabolic risks and vitamin D levels with the degree of obesity

Aim:

The aim of this study was to evaluate the cardiometabolic risk factors including vitamin D levels according to the degree of obesity in adolescents.

Material and Methods:

This is a retrospective cross-sectional study. A total of 363 overweight/obese adolescents aged between 11 and 18 years who were evaluated in our clinic from January 2012 to December 2015 were included in the study. The degree of obesity was calculated as the body mass index standard deviation. Hypertension, dyslipidemia, hyperinsulinemia, hyperglycemia, insulin resistance, and vitamin D deficiency were defined as cardiometabolic risk factors. Mann-Whitney U, Chi-square, Spearman and Pearson’s correlation tests, and linear regressions analyses were used for statistical analyses.

Results:

Of the 319 (n=319/363) adolescents, all of whose cardiometabolic risk factors were known, 267 (85.7%) had at least one cardiometabolic risk factor. The body mass index standard deviation had a positive correlation with the number of cardiometabolic risk factors (p<0.001). In the linear regression models in which sex and age were considered as covariates, an increase of one unit in the body mass index standard deviation led to an increase of 6.085 mm Hg in systolic blood pressure, 4.4 mm Hg in diastolic blood pressure, 1.59 points in HOMA-IR, 13% in insulin level, and a decrease of 2.16 ng/mL in vitamin D levels.

Conclusion:

In adolescents, the number of cardiometabolic risk factors increases as the degree of obesity increases. The determination of the severity of obesity can help to identify individuals at greater risk for higher blood pressure, impaired glucose metabolism, and lower serum vitamin D levels. On the other hand, the degree of obesity may not reflect the presence of abnormal lipid and glucose levels.

Effect of Vitamin D Supplementation on Faecal Microbiota: A Randomised Clinical Trial

In animal studies, vitamin D supplementation has been shown to improve gut microbiota and intestinal inflammation. However, limited evidence exists on the effect of vitamin D supplementation on the human gut microbiota. We examined the effect of vitamin D supplementation on faecal microbiota in 26 vitamin D-deficient (25-hydroxyvitamin D (25(OH)D) ≤50 nmol/L), overweight or obese (BMI ≥25 kg/m²) otherwise healthy adults. Our study was ancillary to a community based double-blind randomised clinical trial, conducted between 2014 and 2016. The participants provided stool samples at baseline and after 100,000 international units (IU) loading dose of cholecalciferol followed by 4000 IU daily or matching placebo for 16 weeks. Faecal microbiota was analysed using 16S rRNA sequencing; V6-8 region. There was no significant difference in microbiome α-diversity between vitamin D and placebo groups at baseline and follow-up (all p > 0.05). In addition, no clustering was found based on vitamin D supplementation at follow-up (p = 0.3). However, there was a significant association between community composition and vitamin D supplementation at the genus level (p = 0.04). The vitamin D group had a higher abundance of genus Lachnospira, and lower abundance of genus Blautia (linear discriminate analysis >3.0). Moreover, individuals with 25(OH)D >75 nmol/L had a higher abundance of genus Coprococcus and lower abundance of genus Ruminococcus compared to those with 25(OH)D <50 nmol/L. Our findings suggest that vitamin D supplementation has some distinct effects on faecal microbiota. Future studies need to explore whether these effects would translate into improved clinical outcomes.

Is vitamin D deficiency in obese youth a risk factor for less weight loss during a weight loss program?

BACKGROUND

Vitamin D deficiency is common in obese adolescents and a risk factor for insulin resistance. We investigated if prevailing serum 25-OH vitamin D might predict the body fat loss in a group of obese adolescents undergoing a residential weight loss program.

METHODS

In 92 (35 male) obese adolescents (aged 10.6-19 years) undergoing a residential weight loss program in Belgium, fasting serum 25-OH vitamin D (25-OH-D), insulin, glucose and lipid levels were measured and body composition was assessed by dual-energy X-ray absorptiometry (DXA).

RESULTS

Baseline median (range) serum 25-OH-D level was 17.7 µg/L (3.8-41.8). In total, 55 adolescents had a serum 25-OH-D below 20 µg/L. In 31 adolescents with a low baseline 25-OH-D level, median increase in serum 25-OH-D was 2.4 µg/L (-4.2 to 7.2) after 10 months. This resulted in normal 25-OH-D levels in seven adolescents, whereas median BMI decreased with 1.0 SDS and body fat percentage diminished with 9.9%. Obese adolescents with or without a 25-OH-D level below or above 20 µg/L at baseline had similar changes in body weight, BMI SDS, body fat percentage and body fat mass at the end of the program. The change in serum 25-OH-D did not correlate with change in serum insulin, BMI SDS or body fat percentage and body fat mass.

CONCLUSION

Vitamin D deficiency was present in 55 out of 92 obese adolescents at the start of the summer. Serum 25-OH-D concentration did not predict changes in body fat loss after a residential weight loss program.

Differential associations of ferritin and 25-hydroxyvitamin D with fasting glucose and diabetes risk in community dwelling older men

AIMS

We examined associations of ferritin and 25-hydroxyvitamin D with fasting glucose and prevalent diabetes in older men.

METHODS

Cross-sectional analysis of 4153 community-dwelling men aged 70 to 89 years in Western Australia. Plasma ferritin, 25-hydroxyvitamin D, and glucose were assayed. Diabetes was ascertained from self-report, medications, and fasting glucose.

RESULTS

There were 577 men with diabetes (13.9%). In the whole cohort, ferritin was associated with fasting glucose (0.051 mmol/L per 1 SD increase in ferritin, P = .006) and 25-hydroxyvitamin D was inversely associated (-0.085 mmol/L per 1 SD, P < .001). Ferritin was not associated with prevalent diabetes (highest vs. lowest quartile; >225 vs <66 μg/L: adjusted odds ratio [OR] 0.97, 95% confidence interval [CI], 0.74-1.27, P = .83). Higher vitamin D was associated with decreased odds of prevalent diabetes (highest vs lowest quartile; >82 nmol/L vs <53 nmol/L: OR = 0.57, 95% CI = 0.43-0.75, P < .001). There was no interaction between ferritin and vitamin D on diabetes risk.

CONCLUSIONS

In older men, ferritin is associated with fasting glucose but not prevalent diabetes. Higher 25-hydroxyvitamin D concentrations are independently associated with lower fasting glucose and reduced risk of diabetes. Clinical trials are required to determine whether interventions, which raise vitamin D concentrations, would reduce incidence of diabetes in this expanding demographic group.

Obesity and hypovitaminosis D: causality or casualty?

Epidemiological studies reported that vitamin D deficiency represents an increasingly widespread phenomenon in various populations. Vitamin D deficiency is considered a clinical syndrome determined by low circulating levels of 25-hydroxyvitamin D (25(OH)D), which is the biologically-inactive intermediate and represents the predominant circulating form. Different mechanisms have been hypothesized to explain the association between hypovitaminosis D and obesity, including lower dietary intake of vitamin D, lesser skin exposure to sunlight, due to less outdoor physical activity, decreased intestinal absorption, impaired hydroxylation in adipose tissue and 25(OH)D accumulation in fat. However, several studies speculated that vitamin D deficiency itself could cause obesity or prevent weight loss. The fat-solubility of vitamin D leads to the hypothesis that a sequestration process occurs in body fat depots, resulting in a lower bioavailability in the obese state. After investigating the clinical aspects of vitamin D deficiency and the proposed mechanisms for low 25(OH)D in obesity, in this manuscript we discuss the possible role of vitamin D replacement treatment, with different formulations, to restore normal levels in individuals affected by obesity, and evaluate potential positive effects on obesity itself and its metabolic consequences. Food-based prevention strategies for enhancement of vitamin D status and, therefore, lowering skeletal and extra-skeletal diseases risk have been widely proposed in the past decades; however pharmacological supplementation, namely cholecalciferol and calcifediol, is required in the treatment of vitamin D insufficiency and its comorbidities. In individuals affected by obesity, high doses of vitamin D are required to normalize serum vitamin D levels, but the different liposolubility of different supplements should be taken into account. Although the results are inconsistent, some studies reported that vitamin D supplementation may have some beneficial effects in people with obesity.

Vitamin D insufficiency is associated with insulin resistance independently of obesity in primary schoolchildren. The healthy growth study

OBJECTIVES

To explore the associations of vitamin D status and obesity with insulin resistance (IR) in children.

METHODS

A sample of 2282 schoolchildren (9-13 years old) in Greece was examined. Sociodemographic, anthropometric (weight, height), biochemical (fasting plasma glucose, serum insulin and 25(OH)D), pubertal status and physical activity data were collected, using standard methods. The "Vitamin D Standardization Program" protocol was applied to standardize serum 25(OH)D values.

RESULTS

The prevalence of vitamin D insufficiency (serum 25(OH)D < 50 nmol/L) was higher in obese children compared to their over- and normal-weight counterparts (60.5% vs 51.6% and 51%, P = .017). Furthermore, children with IR (both obese and non-obese) had higher prevalence of vitamin D insufficiency compared to non-obese, non-insulin resistant children (66% and 59.2% vs 49.8%, P < .05), possibly indicating that IR is associated with vitamin D insufficiency, independently of obesity. In line with the above, the results from logistic regression analyses controlled for several potential confounders, showed a 1.48 (95% C.I: 1.2-1.84) higher likelihood for vitamin D insufficiency for insulin resistant children compared to the non-insulin resistant ones, while no significant association was observed with obesity.

CONCLUSIONS

The present study revealed a high prevalence of vitamin D insufficiency among schoolchildren in Greece, particularly among obese and insulin resistant ones. In addition, it highlighted that the significant association of vitamin D insufficiency with IR is possibly independent of obesity. Further clinical trials are needed to confirm this possible independent association but also explore the potential beneficial effect of vitamin D supplementation on IR and possibly on weight management too.

Higher dietary intake of vitamin D may influence total cholesterol and carbohydrate profile independent of body composition in men with Chronic Spinal Cord Injury

STUDY DESIGN

A case-control design.

OBJECTIVES

To determine the effects of dietary vitamin D intake on insulin sensitivity (Si), glucose effectiveness (Sg), and lipid profile in individuals with spinal cord injury (SCI).

METHODS

20 male, paraplegic (T3-L1) with chronic (> one year) motor complete SCI (AIS A or B) were recruited. Three-day dietary records were analyzed for dietary vitamin D (calciferol), and participants were assigned to one of two groups, a high vitamin D intake group and a low vitamin D intake group based on the mid-point of vitamin D frequency distribution. Individuals in both groups were matched based on age, weight, time since injury and level of injury. Sg, Si and lipid profiles were measured of the two groups.

RESULTS

The high vitamin D group had an average intake of 5.33 ± 4.14 mcg compared to low vitamin D group, 0.74 ± 0.24 mcg. None of the 20 participants met the recommended guidelines for daily vitamin D intake. The higher vitamin D group had a significantly lower (P = 0.035) total cholesterol (148.00 ± 14.12 mg/dl) than the lower vitamin D group (171.80 ± 36.22 mg/dl). Vitamin D adjusted to total dietary intake was positively correlated to improvement in Si and Sg (P<0.05).

CONCLUSION

The findings suggest that persons with SCI consume much less than the recommended guidelines for daily vitamin D intake. However, a higher dietary intake of vitamin D may influence total cholesterol and carbohydrate profile as demonstrated by a significant decrease in total cholesterol and improvement in glucose homeostasis independent of body composition changes after SCI.

The association of VDR polymorphisms and type 2 diabetes in older people living in community in Santiago de Chile

INTRODUCTION

Several polymorphisms have been associated with obesity and type 2 diabetes in different populations.

OBJECTIVE

To investigate the frequencies of a genetic polymorphism of vitamin D receptor (FokI and BsmI) in patients with T2D.

METHODS

The case-control study was conducted in 138 patients with T2D and 172 control subjects, men and women (60-79 years old). The genotype and allele frequency determination of VDR polymorphisms were determined in these subjects.

RESULTS

The frequency of the C allele of the FokI polymorphism was significantly higher in the T2D group than in healthy subjects (p = 0.025). The frequencies of the BsmI variant were similar in subjects with and without T2D (p = 0.747). Consistent with these data, there was an association of the C allele with T2D (OR = 1.74, 95% CI = 1.003-3.084, p = 0.036), but not the AG + GG variants for BsmI (OR = 1.02, 95% CI = 0.635-1.649, p = 0.916). We can observe a significant association between carrier of the T > C variant of FokI and type 2 diabetes, adjusted for vitamin D, age, obesity (overweight and obesity), seasonality, sex and Homa-IR. Here, we show a significant association between the FokI polymorphisms (TC + CC) and T2D with an odds ratio of 1.9001 (95% CI (1.0970-3.6838), p = 0.041).

CONCLUSION

Our study suggests that the C allele (TC + CC) of the VDR-FokI gene is a possible risk factor for T2D in older people living in a community in Santiago de Chile.

Review on Potential Vitamin D Mechanism with Type 2 Diabetes Mellitus Pathophysiology in Malaysia

Evidences on vitamin D deficiency suggest there is increasing risk of diabetes. To date, some cohort, observation, cross-sectional studies on populations and randomized controlled trials in vitamin D supplements highlighting the potential of vitamin D are essentially in modifying Type 2 Diabetes Mellitus (T2DM) pathophysiology. Relevant literature sought in a various databases focus on the discovery of vitamin D studies in Malaysia, particularly in dietary, health status and disease study. However, recent data in Malaysia, the scope of the literature focuses on the deficient vitamin D mediated insulin impairment. The development of literary findings encompasses on the etiology of diabetes which highly correlates with decreased mechanism of action of vitamin D. It is important to understand diabetes etiology before explaining more about insulin resistance mechanisms which is strongly correlated with the involvement of c-Jun N-terminal kinase (JNK) pathways in insulin signalling. Furthermore, the vitamin D works synergistically with calcium homeostasis which is believed to have interaction with insulin. The purpose of this article is to illustrate the potential of vitamin D in modulating T2DM pathophysiology. Existing evidence showing the biochemical function of vitamin D is strongly involved in the pathogenesis of T2DM which requires considerable attention.

Current Evidence on Vitamin D Deficiency and Metabolic Syndrome in Obese Children: What Does the Evidence from Saudi Arabia Tell Us?

Obesity and vitamin D deficiency represent major health problems among Saudi children, and have been linked to chronic diseases. Obese children are at risk of developing vitamin D deficiency, which appears to have negative influences on energy homeostasis, impeded bone mineralisation, insulin resistance and inflammation. Evidence supporting the association between vitamin D deficiency of obese children and metabolic syndrome has not specifically been studied in early childhood. The mechanisms through which vitamin D deficiency is associated with metabolic syndrome in obese children needs further elucidation. This commentary aims to (i) summarise current knowledge of the association between vitamin D deficiency and metabolic syndrome in obese children; and (ii) discuss current evidence for the association among Saudi Arabian children.

Cardiometabolic healthy and unhealthy obesity: does vitamin D play a role?

OBJECTIVE

The aim of this observational study was to clarify the link between vitamin D status and metabolic syndrome (MetS) in people with visceral obesity.

DESIGN AND METHODS

One hundred ninety-six consecutive patients (152 women; mean age 51 ± 13 years) with visceral obesity (mean body weight 103 ± 20 kg, mean waist circumference (WC) 119 ± 13 cm) were enrolled at the Obesity Outpatient Clinic of the University of Insubria in Varese. Anthropometric measurements were recorded. Laboratory tests, including vitamin D (25(OH)D)), fasting blood glucose (FBG), lipid profile, liver and kidney function tests were assessed. Vitamin D status was defined according to the European Society of Endocrinology guidelines, MetS to the 2009 harmonized definition.

RESULTS

An inverse association emerged among 25(OH)D, body mass index (BMI) (P = 0.001) and WC (all P = 0.003). Serum 25(OH)D levels were inversely related to FBG and systolic blood pressure (SBP) (respectively, P = 0.01 and 0.02). Median serum 25(OH)D levels were 13.3 ng/mL (CI 95% 12; 15) in MetS and 16 ng/mL (CI 95% 14; 18) (P = 0.01) in non-MetS patients. Among patients with MetS, lower 25(OH)D concentrations were related to higher risk of hypertension (HT) (odds ratio (OR) 1.7, CI 95%, 0.7;4) and hyperglycemia (IFG)/type 2 diabetes (OR 5.5, CI 95% 2; 14).

CONCLUSION

Vitamin D status and MetS are inversely correlated in visceral obesity, particularly with regard to glucose homeostasis and BP. More extensive studies are required to investigate the potential for causality.

Vitamin D Status, Cardiometabolic, Liver, and Mental Health Status in Obese Youth Attending a Pediatric Weight Management Center

BACKGROUND

Vitamin D (VitD) deficiency and obesity are reaching epidemic proportions in North America, particularly in those with comorbid conditions such as diabetes or liver disease. The study objective was to determine the prevalence of suboptimal vitD status and interrelationships with anthropometric, cardiometabolic, liver, mental health, and lifestyle (sleep/screen time) parameters in an ambulatory population of children with obesity.

METHODS

Children (2-18 years) attending a pediatric weight management clinic (n = 217) were retrospectively reviewed. Variables studied included anthropometric (weight, height, body mass index, waist circumference), vitD (serum 25-hydroxyvitamin D), cardiometabolic (systolic blood pressure, diastolic blood pressure, glucose, insulin, homeostasis model assessment for insulin resistance, triglyceride, high-density lipoprotein, low-density lipoprotein, total cholesterol), liver enzymes (alanine aminotransferase, gamma-glutamyl transferase), and mental health (number, diagnosis) parameters.

RESULTS

Suboptimal vitD status (25-hydroxyvitamin D <75 nmol/L was present in 76% of children with obesity (12.0 ± 2.9 years). Blood pressure categorized as prehypertension, stage I hypertension, and stage II hypertension was present in 14%, 25%, and 7% of children, respectively. Mental health diagnoses including anxiety, attention-deficit hyperactivity disorder, mood disorders, and learning disabilities/developmental delays occurred in 18%, 17%, 10%, and 15%, of children, respectively. Waist circumferences >100 cm were associated with lower vitD levels (58 ± 18 vs 65 ± 17 nmol/L; P = 0.01). VitD status ≥50 nmol/L was associated with lower insulin (15.8 [11.7-23.1] mU/L vs 21.1 [14.3-34.2] mU/L; P < 0.01) and homeostasis model assessment for insulin resistance (3.5 [2.5-4.9] vs 4.8 [3.1-6.9]; P < 0.01) values and systolic blood pressure percentiles (73.0 ± 25.8 vs 80.6 ± 17.0; P = 0.04).

CONCLUSIONS

Children with obesity had a high prevalence of vitD deficiency, particularly those at risk for hypertension, reduced insulin sensitivity, and central obesity.

VDR Gene variation and insulin resistance related diseases

Background

Vitamin D status may influence the risk of Insulin resistance related diseases such as Type 2 diabetes (T2DM), metabolic syndrome (MetS), and polycystic ovarian syndrome (PCOS). Several studies have assessed vitamin D receptor (VDR) gene polymorphism in relationship with these diseases; however, results remain inconsistent. Our study was conducted to elucidate whether VDR Gene polymorphisms could predict insulin resistance on a large scale.

Methods

A meta-analysis using MEDLINE and EMBASE, was performed up to December 16th, 2016. Studies reporting association of vitamin D gene polymorphism with incident T2DM, MetS and PCOS outcomes were included and sub-group analysis by pigment of skin and latitude were performed.

Results

A total of 28 articles based on four gene variation, and comprising 9232 participants with 5193 Insulin resistance related diseases patients were included. No significant associations of the VDR ApaI, BsmI, FokI and TaqI variant with Insulin resistance related diseases were found. However, sub-group analysis analysis showed that PCOS in TaqI (OR = 1.47, 95% CI = 1.03–2.09, P = 0.03) for T allele and MetS for G allele (OR = 1.41, 95% CI = 1.07–1.85, P = 0.01) in BsmI was significant association with VDR gene polymorphism. Simultaneously, sub-group analysis showed VDR ApaI rs7975232(G > T)variant was associated with insulin resistance related diseases in Asians (GG/GT + TT) (OR, 1.62; 95% CI, 1.03–2.53; P = 0.04) and population who lived in middle latitude district (30–60°) (GG/GT + TT) (OR, 1.22; 95% CI, 1.04–1.43; P = 0.02), VDR BsmI rs1544410 (A > G)and VDR Taq1rs731236 (T/C) variant were associated with insulin resistance related diseases in Caucasian (dark-pigmented).

Conclusion

The results suggested that the association between insulin resistance related diseases and VDR ApaI, BsmI, FokI variant was more obvious in dark-pigmented Caucasians and Asians but not in Caucasian with white skin.

Vitamin D supplementation, the metabolic syndrome and oxidative stress in obese children

BACKGROUND

Previous studies suggest that vitamin D may play a role in cardiovascular and metabolic health. Oxidative stress has also been implicated in the development of cardiovascular disease. Evidence suggests that vitamin D deficiency may contribute to the occurrence of oxidative stress. This study aimed to determine whether treatment and correction of vitamin D deficiency in obese children led to changes in their metabolic profile, independent of changes in adiposity. In addition, we aimed to determine whether vitamin D deficiency and oxidative stress are causally related in obese children.

METHODS

In the retrospective arm, chart review identified 32 obese children who experienced normalization of vitamin D deficiency or insufficiency with vitamin D supplementation. We then correlated laboratory and anthropometric data with vitamin D levels. In the prospective arm of the study, urinary 8-isoprostane and hydrogen peroxide were measured before and after correction of vitamin D deficiency/insufficiency and correlated to vitamin D levels in seven patients.

RESULTS

In our predominantly Hispanic population of obese children in an urban setting, we demonstrated a cause-effect relationship between vitamin D deficiency and oxidative stress. In contrast, we found no association between vitamin D status, adiposity, and markers of insulin sensitivity, nor any effect of vitamin D treatment on the same parameters.

CONCLUSIONS

These discordant findings suggest a differential effect of vitamin D on cardiovascular risk factors such as oxidative stress and insulin resistance. To confirm these findings, further prospective studies with larger sample size and longer follow-up are warranted.

Adipose-specific Vdr deletion alters body fat and enhances mammary epithelial density

Vitamin D status has been associated with obesity, metabolic syndrome and several cancers including colon and breast. Since adipocytes express VDR and obesity is a known risk factor for cancer, vitamin D actions in adipose tissue may contribute to its cancer protective effects. In the mammary gland, signaling from adipocytes to epithelial cells is necessary for breast cancer initiation, but the impact of vitamin D on this cross-talk is unclear. To examine the role of VDR in adipose tissue, particularly in the context of the mammary gland, we crossed Vdr-flox mice with Fabp4-cre mice to generate mice with adipose-specific Vdr deletion (termed CVF mice). CVF mice and Fabp4-cre control mice (termed CN1 mice) were reared on high calcium "rescue" diets (for comparison to global VDRKO mice) or on high fat diets (to stimulate adiposity). Vdr expression was significantly reduced in adipose tissue of CVF mice compared to CN1 mice. In contrast to global VDRKO mice (which exhibit adipose atrophy), female CVF mice exhibited higher growth rates and increased visceral fat pad weight compared to control mice. Expression of Ucp1 and Pparg were elevated in white adipose tissue of CVF mice supporting these genes as Vdr targets in mature adipocytes. Adipose-specific Vdr deletion did not impair glucose tolerance or alter the weight of brown adipose tissue, liver, pancreas or bone in response to high fat feeding. In contrast to the effect of adipose-specific Vdr deletion on visceral fat pads, the weight of the subcutaneous (mammary) fat pad was not increased in high fat fed CVF female mice compared to control mice. Quantitative analysis of mammary ductal development on whole mounts and H&E stained sections indicated that adipose-deletion of Vdr significantly enhanced mammary epithelial density and branching. Collectively, these data support the hypothesis that Vdr in mature adipocytes alters the metabolic response to high fat diets and exerts anti-proliferative effects on the mammary epithelium.

25-Hydroxycholecalciferol response to single oral cholecalciferol loading in the normal weight, overweight, and obese

After a single cholecalciferol load, peak serum 25-hydroxycholecalciferol (25OHD) is lower in individuals with a higher body mass index (BMI), probably due to it being distributed in a greater volume. Its subsequent disappearance from the serum is slower the higher the individual's BMI, probably due to the combination of a larger body volume and a slower release into the circulation of vitamin D stored in adipose tissue.

INTRODUCTION

The aim of the study is to examine 25-hydroxycholecalciferol (25OHD) response to a single oral load of cholecalciferol in the normal weight, overweight, and obese.

METHODS

We considered 55 healthy women aged from 25 to 67 years (mean ± SD, 50.8 ± 9.5) with a BMI ranging from 18.7 to 42 kg/m(2) (mean ± SD, 27.1 ± 6.0). The sample was divided into three groups by BMI: 20 were normal weight (BMI ≤ 25 kg/m(2)), 21 overweight (25.1 ≤ BMI ≤ 29.9 kg/ m(2)), and 14 obese (BMI ≥ 30 kg/m(2)). Each subject was given 300,000 IU of cholecalciferol orally during lunch. A fasting blood test was obtained before cholecalciferol loading and then 7, 30, and 90 days afterwards to measure serum 25OHD, 1,25 dihydroxyvitamin D [1,25 (OH)2D], parathyroid hormone (PTH), calcium (Ca), and phosphorus (P). Participants' absolute fat mass was measured using dual energy X-ray absorptiometry (DEXA).

RESULTS

The fat mass of the normal weight subjects was significantly lower than that of the overweight, which in turn was lower than that of the obese participants. Serum 25OHD levels increased significantly in all groups, peaking 1 week after the cholecalciferol load. Peak serum 25OHD levels were lower the higher the individuals' BMI. After peaking, the 25OHD levels gradually decreased, following a significantly different trend in the three groups. The slope was similar for the overweight and obese, declining significantly more slowly than in the normal weight group. In the sample as a whole, there was a weakly significant negative correlation between fat mass and baseline 25OHD level, while this correlation became strongly significant at all time points after cholecalciferol loading.

CONCLUSIONS

The lower peak 25OHD levels seen in the obese and overweight is probably due to the cholecalciferol load being distributed in a larger body volume. The longer persistence of 25OHD in their serum could be due to both their larger body volume and a slower release into the circulation of the vitamin D stored in their adipose tissue.

Prepubertal Adiposity, Vitamin D Status, and Insulin Resistance

OBJECTIVE

To evaluate the following from prepuberty to the puberty-onset: (1) changes in serum 25-hydroxyvitamin-D (25[OH]D), adiposity, and insulin resistance (IR); (2) the effect of prepubertal adiposity on serum 25(OH)D changes; and (3) the combined effect of prepubertal obesity and suboptimal-25(OH)D on IR at puberty-onset.

METHODS

A total of 426 prepubertal children (∼54% girls) were followed during pubertal-onset assessing before and after puberty-onset serum 25(OH)D, adiposity (BMI and waist circumference) and IR indicators (homeostasis-model-assessment of IR [HOMA-IR]). Associations were tested using multiple and logistic regression models adjusted by age, gender, and seasonality.

RESULTS

At puberty-onset, mean serum 25(OH)D decreased (32.2 ± 8.9 Tanner I vs 25.2 ± 8.3 ng/mL Tanner II) and total and central obesity increased (BMI-for-age-z-score ≥2 SD [%]: 16.4 vs 22.1; waist-circumference ≥75th percentile [%]: 27.2 vs 37.1, all P < .05). Children with higher adiposity before puberty onset had higher risk of suboptimal-25(OH)D (<30 ng/mL) in Tanner II (ie, odds ratio = 2.7 [1.1-6.7] for obesity and 2.7 [1.4-5.5] for central-obesity) after adjusting for relevant covariates. Children with higher adiposity and suboptimal-25(OH)D before puberty-onset had higher HOMA-IR compared with their counterparts in Tanner II (HOMA-IR: 2.8 [2.5-3.1] if central-obese and suboptimal-25[OH]D vs 2.1 [1.9-2.3] no central-obesity and optimal-25[OH]D).

CONCLUSIONS

We found that serum 25(OH)D declined with puberty-onset, likely because of adiposity increase. Moreover, children with the combined condition of central-obesity and suboptimal-25(OH)D before puberty-onset had higher pubertal IR. These results highlight the need of ensuring adequate-25(OH)D status before pubertal-onset, particularly in obese children.

The Association of Adiposity Indices and Plasma Vitamin D in Young Females in Saudi Arabia

Background. Vitamin D deficiency is a global health problem. Some evidences indicate its association with metabolic syndrome, type II diabetes, and cardiovascular diseases. In the current study we aim to study the association of vitamin D level and indicators of adiposity in young Saudi females. Subjects and Methods. 87 young healthy Saudi females were recruited from University of Dammam, Dammam, Saudi Arabia. Each subject filled vitamin D questionnaire and had exercise stress test to determine VO2 peak. Body weight, BMI, waist and hip circumference, and ratios were determined. Blood was analyzed for 25-OH vitamin D, glucose, triglycerides, total cholesterol, and differential cholesterol. Results. 25-OH vitamin D/body weight was negatively associated with waist circumference and waist/stature ratio. No significant difference was found between the groups of BMI with regard to the data of questionnaire or 25-OH vitamin D/body weight. Obese and overweight subjects had lower VO2 peak. Conclusion. In young Saudi females we found that the relative value of vitamin D to body weight is a better indicator of vitamin D status particularly in obese subjects and it is negatively associated with adiposity measures of waist circumference and waist/stature ratio.

Patients with Active Acromegaly are at High Risk of 25(OH)D Deficiency

Acromegaly is a chronic disease characterized by hypersecretion of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Electrolyte disturbances such as hypercalcemia and hyperphosphatemia are reported in patients with this disorder. There is limited data on vitamin D status in subjects with acromegaly. The aim of the study was to determine calcium, inorganic phosphate, magnesium, alkaline phosphatase, and 25(OH)D levels with regard to the activity of the disease. We also studied correlations of 25(OH)D and IGF-1, GH, body mass, body mass index, and age. A study group consisted of 55 acromegalic patients, and was divided into three subgroups: active acromegaly (AA), well-controlled acromegaly (WCA), cured acromegaly (CA). We enrolled 29 healthy subjects to a control group (CG). Vitamin D deficiency was recorded in all AA patients, 13 WCA patients (92.86%), 10 CA patients (62.5%), and 13 controls (54.17%). The highest 25(OH)D levels were found in the CG group and the lowest in the AA group (p = 0.012). The dose of octreotide did not influence serum 25(OH)D levels. A significant positive correlation between IGF-1 and 25(OH)D levels was observed in the AA group (r = 0.58, p = 0.024). Inorganic phosphate levels were the highest in the AA group. In conclusion, active acromegalic patients have lower 25(OH)D levels in comparison with the CG and are at higher risk of vitamin D deficiency.