Vitamin D, inflammation, and relations to insulin resistance in premenopausal women with morbid obesity

The association between obesity and vitamin D deficiency modifies the progression of kidney disease after ischemia/reperfusion injury

Acute kidney injury (AKI) alters renal hemodynamics, leading to tubular injury, activating pathways of inflammation, proliferation, and cell death. The initial damage caused to renal tissue after an ischemia/reperfusion (I/R) injury exerts an important role in the pathogenesis of the course of AKI, as well as in the predisposition to chronic kidney disease. Vitamin D deficiency has been considered a risk factor for kidney disease and it is associated with tubulointerstitial damage, contributing to the progression of kidney disease. Obesity is directly related to diabetes mellitus and hypertension, the main metabolic disorders responsible for the progression of kidney disease. Furthermore, the expansion of adipose tissue is described as an important factor for increased secretion of pro-inflammatory cytokines and their respective influence on the progression of kidney disease. We aimed to investigate the influence of vitamin D deficiency and obesity on the progression of renal disease in a murine model of renal I/R. Male Wistar rats underwent renal I/R surgery on day 45 and followed until day 90 of the protocol. We allocated the animals to four groups according to each diet received: standard (SD), vitamin D-depleted (VDD), high fat (HFD), or high fat vitamin D-depleted (HFDV). At the end of 90 days, we observed almost undetectable levels of vitamin D in the VDD and HFDV groups. In addition, HFD and HFDV groups presented alterations in the anthropometric and metabolic profile. The combination of vitamin D deficiency and obesity contributed to alterations of functional and hemodynamic parameters observed in the HFDV group. Moreover, this combination favored the exacerbation of the inflammatory process and the renal expression of extracellular matrix proteins and phenotypic alteration markers, resulting in an enlargement of the tubulointerstitial compartment. All these changes were associated with an increased renal expression of transforming growth factor β and reduced expression of the vitamin D receptor. Our results show that the synergistic effect of obesity and vitamin D deficiency exacerbated the hemodynamic and morphological changes present in the evolution of renal disease induced by I/R.

CALISTHENICS EXERCISES TO INTERVENE IN OBESITY AND DIABETES IN MIDDLE-AGED PEOPLE

ABSTRACT Introduction: There is an annual increase in type 2 diabetes (T2DM) incidence in middle-aged people. Aerobic exercise is known to influence glucose metabolic pathways positively. Few studies concerning calisthenic aerobic exercise and its influence on elderly patients with T2DM. Objective: To measure the therapeutic effect of calisthenic exercise in obese Middle-aged people with T2DM. Methods: A total of 86 patients with T2DM were selected from the physical examination of employees of the same unit. They were randomly divided into the exercise group and the control group. The exercise intervention lasted for 16 weeks, with sessions held 3-5 times per week, varying from 60 to 90 minutes per session. The markers evaluated were defined according to the literature and statistically verified. Results: After 16 weeks of calisthenic exercise intervention, compared to the control group or before the experiment, we observed significant reductions in variables VFA (visceral fat area), FPG (fasting glucose), Fins (fasting insulin), HOMA-IR (homeostasis model evaluation of insulin resistance), 2hPBG (postprandial two hours glucose) and HbAlc (hemoglobin Alc) of the exercise group were significantly reduced (P<0.01). Conclusion: Calisthenic exercise intervention can reduce the levels of VFA, FPG. FIns, HOMA-HR, 2hPBG and HbAlc in patients with T2DM. It was also found to reduce the visceral fat content of obese elderly patients with T2DM, reducing obesity risks. Level of evidence II; Therapeutic studies - investigation of treatment results.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

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.

Relationship between 25 Hydroxyvitamin D, Overweight/Obesity Status, Pro-Inflammatory and Oxidative Stress Markers in Patients with Type 2 Diabetes: A Simplified Empirical Path Model

Vitamin D deficiency is highly prevalent in patients with overweight/obesity and type 2 diabetes (T2DM). Herein, we investigated the relationship between vitamin D status and overweight/obesity status, insulin resistance (IR), systemic inflammation as well as oxidative stress (OS). Anthropometric and laboratory assessments of 25-hydroxyvitamin D (25(OH)D) and glycemic, pro-inflammatory and OS biomarkers were performed in a sample of 47 patients with T2DM who were divided into categories based on overweight and degree of obesity. The main findings were: the overweight/obesity status correlated negatively with the degree of serum 25(OH)D deficiency (ρ = −0.27) with a trend towards statistical significance (p = 0.069); the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly different (p = 0.024) in patients with 25(OH)D deficiency, as was total oxidant status (TOS) and oxidative stress index (OSI) in patients with severe serum 25(OH)D deficiency as compared to those with 25(OH)D over 20 ng/mL (TOS: p = 0.007, OSI: p = 0.008); and 25(OH)D had a negative indirect effect on TOS by body mass index (BMI), but BMI was not a significant mediator of the studied relationship. In a setting of overweight and increasing degree of obesity, patients with T2DM did not display decreasing values of 25(OH)D. Subjects with the lowest values of 25(OH)D presented the highest values of BMI. Patients with 25(OH)D deficiency were more insulin resistant and showed increased OS but no elevated systemic inflammation. The negative effect of 25(OH)D on TOS did not seem to involve BMI as a mediator.

Insulin Resistance Is Inversely Associated with the Status of Vitamin D in Both Diabetic and Non-Diabetic Populations

Vitamin D has been implicated in the regulation of glucose metabolism and insulin resistance. We designed this study to provide evidence that insulin resistance is dependent on the concentration of vitamin D in the body. Forty observational studies of both type 2 diabetes mellitus patients and healthy subjects were included in this meta-analysis. Related articles were searched from Embase, PubMed, and Medline through January 2021. Filters for search were used to obtain more focused results. We used Comprehensive Meta-Analysis Version 3 for the construction of forest plots. RevMan software version 5.3 was used to build the risk of bias tables and summary plots. The observational studies included in this systematic review and meta-analysis showed an inverse relationship of insulin resistance with the status of vitamin D both in non-diabetic (r = -0.188; 95% CI = -0.141 to -0.234; p = 0.000) and diabetic (r = -0.255; 95% CI = -0.392 to -0.107, p = 0.001) populations. From the meta-analysis we concluded that hypovitaminosis D is related to increased levels of insulin resistance in both type 2 diabetes patients and the healthy population all over the world.

Vitamin D Inhibits Adipokine Production and Inflammatory Signaling Through the Vitamin D Receptor in Human Adipocytes

OBJECTIVE

The purpose of this study was to investigate the effects of vitamin D on adipokine expression and inflammation in human adipose tissues and adipocytes and evaluate the molecular mechanisms involved.

METHODS

Omental and abdominal subcutaneous human adipose tissues were treated with 1,25-dihydroxyvitamin D₃ (1,25(OH)₂ D₃ ), and adipokine levels were measured. Vitamin D effects were measured with or without dexamethasone because glucocorticoids are known to affect vitamin D actions. Using RNA interference, we examined whether the vitamin D receptor (VDR) mediated vitamin D actions on adipokine expression and inflammatory signaling pathways in human adipocytes.

RESULTS

mRNA levels and secretion of leptin and IL-6 were suppressed by 1,25(OH)₂ D₃ in omental adipose tissues. Cotreatment with dexamethasone did not affect these inhibitory actions but partially blocked CYP24A1 induction. Similar results were observed in the subcutaneous depot. In addition, 1,25(OH)₂ D₃ suppressed leptin and IL-6 expression as well as nuclear factor-κB and extracellular signal-regulated kinase-1/2 phosphorylation in human adipocytes. Adipokine expression also was decreased by 25-hydroxyvitamin D₃ (25(OH)D₃ ), but not vitamin D₃ . Knockdown of VDR increased the inflammatory signaling activity in the control condition and blocked the inhibitory effects of 1,25(OH)₂ D₃ on adipokine and inflammatory signaling pathways.

CONCLUSION

Vitamin D acts through VDR to inhibit inflammatory pathways and adipokine expression in human adipocytes. Increasing vitamin D status may ameliorate obesity-associated metabolic complications by decreasing adipose tissue inflammation.

Vitamin D regulation of adipogenesis and adipose tissue functions

Vitamin D insufficiency is associated with obesity and its related metabolic diseases. Adipose tissues store and metabolize vitamin D and expression levels of vitamin D metabolizing enzymes are known to be altered in obesity. Sequestration of vitamin D in large amount of adipose tissues and low vitamin D metabolism may contribute to the vitamin D inadequacy in obesity. Vitamin D receptor is expressed in adipose tissues and vitamin D regulates multiple aspects of adipose biology including adipogenesis as well as metabolic and endocrine function of adipose tissues that can contribute to the high risk of metabolic diseases in vitamin D insufficiency. We will review current understanding of vitamin D regulation of adipose biology focusing on vitamin D modulation of adiposity and adipose tissue functions as well as the molecular mechanisms through which vitamin D regulates adipose biology. The effects of supplementation or maintenance of vitamin D on obesity and metabolic diseases are also discussed.

The impact of vitamin D supplementation on VDR gene expression and body composition in monozygotic twins: randomized controlled trial

Vitamin D supplementation is widely used. However, there is no consensus on the use and dosage of this supplement and the existing recommendations arise from studies based on the benefits that this nutrient can facilitate in bones. In addition, individual genetics can influence the response to supplementation, therefore, research involving monozygotic twins aims to reduce these differences in phenotypic responses. The objective of this randomised controlled study is to examine the effect of vitamin D supplementation on body composition and the expression of the vitamin D receptor (VDR) mRNA. An intervention was performed through supplementation with cholecalciferol at the concentration of 2000 IU in 90 healthy adult monozygotic twins (male or female pairs) for 2 months. The findings showed that serum vitamin D concentration increased by 65% and VDR gene expression sixty times (p = 0.001). Changes in body composition parameters were observed regarding body fat and lean mass. Our results indicate that an increase in serum vitamin D concentration may have potential therapeutic implications.

Effects of Vitamin D Status on Inflammatory Markers in Obese Subjects: A Systematic Review

Background:

Recent studies have demonstrated the role of micronutrients in the manifestation of comorbidities associated with obesity. Vitamin D deficiency, in particular, appears to be associated with increased levels of inflammatory markers, which may lead to chronic low-grade inflammation, elevating the risk of chronic diseases such as diabetes, metabolic syndrome, and cardiovascular disease. The objective of this study was to perform a systematic review of observational studies conducted to investigate the effect of vitamin D deficiency on inflammatory markers in obese subjects.

Methodology:

This systematic review was conducted in accordance with the “STROBE” and PRISMA recommendations. Observational studies that evaluated the effect of vitamin D status on inflammatory markers in obese subjects were selected and reviewed. Searches were conducted in the PubMed, SciVerse Scopus, and Web of Science databases from February 21 to 22, 2018.

Results:

After the selection and removal of duplicate articles, 10 eligible articles were identified. Results from eight observational studies showed an association between vitamin D deficiency or insufficiency in the body and increased concentrations of inflammatory markers in obese individuals. On the other hand, two of the studies did not demonstrate any correlation. With regard to the inflammatory markers evaluated, eight studies showed high concentrations of ultra-sensitive C-reactive protein, five studies found an increase in interleukin-6 concentrations, and two studies noted increased levels of tumor necrosis factor.

Conclusion:

The data presented in this systematic review provide evidence of the association between vitamin D deficiency and increased inflammation in obesity.

Determinants of vitamin D receptor gene expression in visceral and subcutaneous adipose tissue in non-obese, obese, and morbidly obese subjects

We aimed to illustrate determinants of VDR gene expression in visceral and subcutaneous adipose tissue among individuals without diabetes. We gathered visceral and subcutaneous adipose tissues during an elective abdominal surgery form 33 morbidly obese (BMI > 40 kg/m²), 23 obese (BMI = 30-40 kg/m²), and 35 non-obese (BMI<30 kg/m²) participants who were free of diabetes. Participants were classified according to their degree of obesity. Before the surgery, habitual dietary intake, physical activity, 25(OH)D, body mass index (BMI), waist circumference (WC), and HOMA-IR was gathered. Non-obese participants had significantly lower mean VDR gene expression in visceral adipose tissues than both the obese and morbidly obese ones and had also lower expression in subcutaneous adipose tissues than the morbidly obese participants. In multiple linear regression models, BMI and HOMA-IR were the independent positive predictors of VDR gene expression in subcutaneous fat. Among non-obese subjects, WC and 25(OH)D were the positive and negative independent predictors of visceral adipose tissue VDR gene expression, respectively. Among obese participants, 25(OH)D was negatively, and BMI and HOMA-IR were positively associated with VDR mRNA levels in visceral adipose tissue. In morbidly obese participants, the independent positive predictors of VDR gene expression in visceral fat were BMI and HOMA-IR, and negative predictors were 25(OH)D and calcium intake. Our findings suggested that 25(OH)D concentrations are the fundamental elements to determine VDR gene expression in visceral fat which by increasing fat depots, the subsequent insulin resistance became another predictor of VDR gene expression.

Vitamin D and Tissue-Specific Insulin Sensitivity in Humans With Overweight/Obesity

CONTEXT

Vitamin D deficiency in obesity has been linked to insulin resistance. However, studies that examined the association between plasma 25-hydroxyvitamin D3 [25(OH)D3] as well as plasma 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and tissue-specific insulin sensitivity are scarce. Furthermore, vitamin D receptor (VDR) and vitamin D-metabolizing enzymes [cytochrome 450 (CYP)] expression in adipose tissue (AT) might affect AT insulin sensitivity.

OBJECTIVE

To investigate the association between body mass index (BMI) and plasma 25(OH)D3 and 1,25(OH)2D3, AT VDR; between plasma 25(OH)D3, 1,25(OH)2D3, AT VDR, and tissue-specific insulin sensitivity in individuals with overweight/obesity.

DESIGN AND PATIENTS

This analysis included 92 adult individuals (BMI, >25 kg/m2). A two-step hyperinsulinemic-euglycemic clamp with a [6,6-2H2]-glucose tracer was performed to assess tissue-specific insulin sensitivity. Abdominal subcutaneous AT (SAT) mRNA expression of VDR and CYP was determined by using quantitative RT-PCR.

SETTING

University medical center.

MAIN OUTCOME MEASURES

Plasma 25(OH)D3, 1,25(OH)2D3, 1,25(OH)2D3/25(OH)D3 ratio, SAT VDR and CYPs mRNA, and tissue-specific insulin sensitivity.

RESULTS

BMI was inversely associated with plasma 25(OH)D3 (β = -0.274; P = 0.011) but not with plasma 1,25(OH)2D3. Plasma 25(OH)D3 was not related to CYPs or VDR expression in SAT. Plasma 1,25(OH)2D3 and 25(OH)D3 were not related to tissue-specific insulin sensitivity. Interestingly, SAT VDR mRNA was negatively associated with AT insulin sensitivity (β = -0.207; P = 0.025).

CONCLUSIONS

BMI was inversely associated with 25(OH)D3 concentrations, which could not be explained by alterations in SAT VDR and CYP enzymes. Plasma vitamin D metabolites were not related to tissue-specific insulin sensitivity. However, VDR expression in SAT was negatively associated with AT insulin sensitivity.

Association of Sun Exposure, Skin Colour and Body Mass Index with Vitamin D Status in Individuals Who Are Morbidly Obese

Vitamin D deficiency is a common issue, particularly in obese populations, and is tested by assessing serum 25(OH)D concentrations. This study aimed to identify factors that contribute to the vitamin D status in fifty morbidly obese individuals recruited prior to bariatric surgery. Data collected included serum 25(OH)D concentrations, dietary and supplement intake of vitamin D, sun exposure measures, skin colour via spectrophotometry, and genotype analysis of several single nucleotide polymorphisms in the vitamin D metabolism pathway. Results showed a significant correlation between serum 25(OH)D concentrations and age, and serum 25(OH)D and ITAC score (natural skin colour). Natural skin colour accounted for 13.5% of variation in serum 25(OH)D, with every 10° increase in ITAC score (i.e., lighter skin) leading to a 9 nmol/L decrease in serum 25(OH)D. Multiple linear regression using age, ITAC score, and average UV index in the three months prior to testing, significantly predicted serum 25(OH)D concentrations (R² = 29.7%). Single nucleotide polymorphisms for all vitamin D genes tested, showed lower serum 25(OH)D for those with the rare genotype compared to the common genotype; this was most pronounced for fok1 and rs4588, where those with the rare genotype were insufficient (<50 nmol/L), and those with the common genotype were sufficient (≥50 nmol/L). Assessing vitamin D status in individuals with morbid obesity requires testing of 25(OH)D, but potential risk factors for this population include natural skin colour and age.

Vitamin D metabolism in human adipose tissue: could it explain low vitamin D status in obesity?

Obesity and a low vitamin D (VD) status, as well as a positive association between them, are prevalent worldwide. Additionally, a low VD status has been positively correlated with metabolic dysfunction (although not so convincingly as for obesity). The VD receptor (VDR) mediates VD biological actions in adipose tissue (AT), where VD can be activated or inactivated/degraded through specific hydroxylation steps. Additionally, AT can also store and release VD when needed. A lower VD activation/VD inactivation ratio and an impaired VDR signaling in AT could contribute to metabolic dysfunction besides the aforementioned association between obesity and VD status. However, subcutaneous (SAT) and visceral AT (VAT) are not expected to be similarly accountable as these two fat depots play differential roles in metabolic regulation/dysfunction. To our knowledge, only three articles disclose the evaluation of the expression of VDR and/or VD hydroxylating enzymes in human SAT and VAT. A clear dependence on the subcutaneous and/or the visceral fat depot is missing for the relationships of a) obesity and/or metabolic dysfunction with VD status and b) adipose VDR signaling and adipose VD activation/VD inactivation ratio with VD status, obesity and/or metabolic dysfunction. Further studies are warranted to unravel the influence of adipose VD metabolism on VD status.

Relationship of galectin-3 with obesity, IL-6, and CRP in women

PURPOSE

To evaluate the association of galectin-3 (Gal3) with obesity and inflammatory status in a cohort of metabolically healthy, predominantly African-American women with varying cardiovascular disease (CVD) risk as determined by CRP levels.

METHODS

We assessed the association between BMI and serum levels of Gal3, IL-6, CRP, and adiponectin in metabolically healthy women (N = 97) to determine the overall association between Gal3, obesity, and inflammation in groups at different CVD risk.

RESULTS

Obese women had significantly higher serum Gal3 compared to non-obese participants (P = 0.0016), although Gal3 levels were comparable among different classes of obesity. BMI (R ² = 0.1406, P = 0.0013), IL-6 (R ² = 0.0689, P = 0.035), and CRP (R ² = 0.0468, P = 0.0419), but not adiponectin, positively predicted the variance of Gal3 levels in the total study population. However, the predicting effect of BMI (R ² = 0.2923, P = 0.0125) and inflammation (R ² = 0.3138, P = 0.038) on Gal3 was only present in women at low/moderate risk of CVD (CRP ≤ 3 µg/mL).

CONCLUSIONS

Gal3 is positively correlated with obesity and inflammation in women, while the presence of elevated CVD risk may disturb the strength of Gal3 as a biomarker of inflammation.