Dysregulated 1,25-dihydroxyvitamin D levels in high-fat diet-induced obesity can be restored by changing to a lower-fat diet in mice

Vitamin D and obesity

An inverse association between vitamin D status and obesity has been reported across diverse populations and age groups in humans. In animal model of diet-induced obesity, dysregulation of vitamin D metabolism has been observed. However, the causal relationship between vitamin D status and obesity is not conclusive. Several explanations, such as volumetric dilution, sequestration of vitamin D into adipose tissue, and limited sunlight exposure, have been suggested as the underlying mechanisms linking poor vitamin D status and obesity. Vitamin D can modulate adipose tissue biology, spanning from adipocyte differentiation to adipocyte apoptosis and energy metabolism, indicating its potential impact on adiposity. In this chapter, we will review the prevalence of vitamin D deficiency and determinants of vitamin D deficiency among different populations, as well as changes in vitamin D metabolism associated with obesity. Additionally, we will review vitamin D's regulation of adipogenesis and lipogenesis at the cellular level in order to gain a deeper understanding of the underlying mechanisms linking vitamin D levels and obesity.

Effects of in vitro vitamin D treatment on function of T cells and autophagy mechanisms in high-fat diet-induced obese mice

BACKGROUND/OBJECTIVES

Obesity is associated with the impaired regulation of T cells characterized by increased numbers of Th1 and Th17 cells and the dysregulation of vitamin D metabolism. Both obesity and vitamin D have been reported to affect autophagy; however, a limited number of studies have investigated the effects of vitamin D on T cell autophagy in obese mice. Therefore, we aimed to determine whether in vitro treatment with vitamin D affects the proliferation, function, and autophagy of T cells from obese and control mice.

MATERIALS/METHODS

Five-week-old male C57BL/6 mice were fed control or high-fat diets (10% or 45% kcal fat: CON or HFDs, respectively) for 12 weeks. Purified T cells were stimulated with anti-CD3 and anti-CD28 monoclonal antibodies and cultured with either 10 nM 1,25(OH)₂D₃ or 0.1% ethanol (vehicle control). The proliferative response; expression of CD25, Foxp3, RORγt, and autophagy-related proteins (LC3A/B, SQSTM1/P62, BECLIN-1, ATG12); and the production of interferon (IFN)-γ, interleukin (IL)-4, IL-17A, and IL-10 by T cells were measured.

RESULTS

Compared with the CON group, T cell proliferation tended to be lower, and the production of IFN-γ was higher in the HFD group. IL-17A production was reduced by 1,25(OH)2D₃ treatment in both groups. The LC3 II/I ratio was higher in the HFD group than the CON group, but P62 did not differ. We observed no effect of vitamin D treatment on T cell autophagy.

CONCLUSIONS

Our findings suggest that diet-induced obesity may impair the function and inhibit autophagy of T cells, possibly leading to the dysregulation of T cell homeostasis, which may be behind the aggravation of inflammation commonly observed in obesity.

Serum 25-hydroxyvitamin D is associated with fracture risk only during periods of seasonally high levels in women with a high body mass index

Serum 25-hydroxyvitamin D (S-25OHD) is used to assess vitamin D status and is known to be affected by season and fat mass. Because these factors are often ignored when interpreting S-25OHD, assessment of vitamin D associations with disease outcomes may be distorted. We aimed to investigate the impact of season of blood draw and fat mass on the association of S25OHD with fracture risk. We enrolled 5000 women, mean ± SD age 68 ± 7 years, with dual-energy x-ray absorptiometry (DXA) scans and blood collection in a population-based cohort. Proportional hazards regression, stratified by season and fat mass, was used to determine hazard ratios (HRs) of fracture according to categories of S-25OHD. Our secondary exposures were serum 1,25-dihydroxycholecalciferol (1,25-(OH)₂ D₃ ), the most active vitamin D metabolite and plasma parathyroid hormone (P-PTH). During an average of 9.2 years of follow-up, 1080 women had a fracture. Women with S-25OHD <30 nmol/L drawn during sunny months (May-October) had a multivariable-adjusted fracture HR of 2.06 (95% CI, 1.27-3.35) compared with those with S-25OHD >60 nmol/L; those with S-25OHD 30-40 nmol/L had an HR of 1.59 (95% CI, 1.12-2.26). In contrast, S-25OHD drawn during November through April was unrelated to fracture risk. The increased risk with low sunny season S-25OHD was seen only among women with body mass index (BMI) ≥25 kg/m² or fat mass index (FMI) ≥9.8 kg/m² . High fat mass and low S-25OHD were independently related to lower S-1,25-dihydroxycholecalciferol, which itself predicted fracture risk with samples collected during the sunny season. Irrespective of season, P-PTH was unrelated to fracture risk. We conclude that S-25OHD is associated with fracture risk only if drawn during periods of seasonally high levels in women with a high BMI. These results have implications for the evaluation of vitamin D status and can explain the lack of effect seen with vitamin D supplementation in many fracture trials. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Molecular Interactions between Dietary Lipids and Bone Tissue during Aging

Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.

Effect of Vitamin D3 Supplements on Development of Advanced Cancer: A Secondary Analysis of the VITAL Randomized Clinical Trial

IMPORTANCE

Epidemiologic and trial data suggest that vitamin D supplementation may reduce metastatic cancer and cancer mortality, reflecting shared biological pathways.

OBJECTIVE

To follow up on the possible reduction in cancer death in the Vitamin D and Omega-3 Trial (VITAL) with an evaluation of whether vitamin D reduces the incidence of advanced (metastatic or fatal) cancer and an examination possible effect modification by body mass index.

DESIGN, SETTING, AND PARTICIPANTS

VITAL is a randomized, double-blind, placebo-controlled, 2 × 2 factorial clinical trial of vitamin D3 (cholecalciferol, 2000 IU/d) and marine omega-3 fatty acids (1 g/d). This multicenter clinical trial was conducted in the United States; participants included men aged 50 years or older and women aged 55 years or older who were free of cancer and cardiovascular disease at baseline. Randomization took place from November 2011 through March 2014, and study medication ended on December 31, 2017. Data for this secondary analysis were analyzed from November 1, 2011, to December 31, 2017.

INTERVENTIONS

Vitamin D3 (cholecalciferol, 2000 IU/d) and marine omega-3 fatty acids (1 g/d) supplements.

MAIN OUTCOMES AND MEASURES

For the present analysis, the primary outcome was a composite incidence of metastatic and fatal invasive total cancer, because the main VITAL study showed a possible reduction in fatal cancer with vitamin D supplementation and effect modification by body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) for total cancer incidence reduction for individuals with normal BMI, but not for individuals with overweight or obesity. Secondary analyses included examination of BMI (<25, 25 to < 30, and ≥30) as effect modifiers of the observed associations.

RESULTS

Among 25 871 randomized VITAL participants (51% female; mean [SD] age, 67.1 [7.1] years), 1617 were diagnosed with invasive cancer over a median intervention period of 5.3 years (range, 3.8-6.1 years). As previously reported, no significant differences for cancer incidence by treatment arm were observed. However, a significant reduction in advanced cancers (metastatic or fatal) was found for those randomized to vitamin D compared with placebo (226 of 12 927 assigned to vitamin D [1.7%] and 274 of 12 944 assigned to placebo [2.1%]; HR, 0.83 [95% CI, 0.69-0.99]; P = .04). When stratified by BMI, there was a significant reduction for the vitamin D arm in incident metastatic or fatal cancer among those with normal BMI (BMI<25: HR, 0.62 [95% CI, 0.45-0.86]) but not among those with overweight or obesity (BMI 25-<30: HR, 0.89 [95% CI, 0.68-1.17]; BMI≥30: HR, 1.05 [95% CI, 0.74-1.49]) (P = .03 for interaction by BMI).

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, supplementation with vitamin D reduced the incidence of advanced (metastatic or fatal) cancer in the overall cohort, with the strongest risk reduction seen in individuals with normal weight.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01169259.

Effects of high fat diet-induced obesity on vitamin D metabolism and tissue distribution in vitamin D deficient or supplemented mice

Background

Vitamin D deficiency has been often observed in obese persons. One of the mechanisms suggested for low vitamin D status in obesity was decreased bioavailability of vitamin D (VD) due to sequestration in adipose tissue. However, only few studies have investigated this mechanism via quantifying vitamin D levels from tissues from the obese.

Methods

Six-wk-old C57BL/6 mice were fed 10 or 45% kcal fat (CON or HFD) diets containing 50, 1000 or 25,000 IU vitamin D3/kg diet (LVd, CVd or HVd) for 13 wks. Serum 25-hydroxyvitamin D (25(OH)D) levels were determined by radioimmunoassay and liver and adipose tissue cholecalciferol (VD3) and 25-hydrocholecalciferol (25(OH)D3) levels were measured by LC-MS/MS. mRNA levels of jejunal Mttp, Cd36, Sr-b1, Npc1l1, and Abca1 and liver and adipose tissue 25-hydroxylases (Cyp2r1 and Cyp27a1) were determined by real-time PCR.

Results

Serum 25(OH)D levels were affected by dietary vitamin D content but differential effects were observed between HFD and CON groups. When vitamin D intake was at a supplementary level, the HFD-HVd group had lower serum 25(OH)D levels than the CON-HVd group, while there was no significant difference between the HFD and CON groups fed LVd or CVd. Total amount of VD3 in liver and adipose tissue were significantly higher in HFD-HVd group compared with the CON-HVd group. However, no difference in total amount of tissue VD3 was observed between the CON and HFD groups fed CVd. In jejunum, mRNA levels of Mttp and Abca1 were significantly higher in HFD groups than CON groups. There was no difference in mRNA levels of liver 25-hydroxylases by both dietary fat amount and vitamin D content.

Conclusion

A significant amount of VD3 seemed to be stored in the liver and adipose tissue when dietary vitamin D is at a supplementation level; thus excess body adiposity could contribute to relatively low serum 25(OH)D level when vitamin D was supplemented.

The functional nutritional and regulatory activities of calcium supplementation from eggshell for obesity disorders management

The present study was to investigate the effective role of renewable sources of Ca⁺² from eggshell (ES) with different doses to restrict obesity disorders. Rats were classified as follows, G₁ : normal diet for 26 weeks; G₂ : high-fat diet (HFD) for 26 weeks; G₃ , G₄ , and G₅ were supplemented with HFD for 16 weeks and treated with 7.2 g Ca⁺² ES/Kg rat chow, 18 g Ca⁺² ES/Kg rat chow, and 2% diet containing fat (DCF), respectively, for the remaining 10 weeks. Results revealed a significant effect of the low dose of Ca⁺² supplement in form of ES than high dose and 2% DCF; on basis of anthropometric parameters, lipid, leptin, adiponectin, thyroid hormones, Ca⁺² , 25-hydroxyl vitamin-D, and oxidative and inflammatory parameters were regulated. Results were confirmed with the histopathological study. Therefore, it was concluded that Ca⁺² supplementation can be used as a beneficial source for obesity management with anticholesterol actions. PRACTICAL APPLICATIONS: Obesity represented public health hazards. The eggshell is one of the waste products that contain a high percentage of Ca⁺² . The current data exposed using a low dose of ES as a new source of Ca⁺² supplement for treatment of HFD rats leads to significant enhancement of lipid profiles, liver enzymes, kidney functions, leptin, adiponectin, Ca⁺² , 25(OH)-D, TSH, fT_4, and PTH levels. Also, there was a reduction in weight gain, Bwt, BMI, BG, insulin, and HOMA-IR. Moreover, the oxidant-pro-oxidant system was improved in both hepatic and adipose tissues where NO and TBARS concentrations were diminished, and SOD specific activity was elevated. Additionally, TNF-α and ADAM17 expression were downregulated. Hence, it was concluded that there was good evidence that diets supplemented with ES were associated with the reduction of obesity complications especially regulating fat processing and storage in the body.

Obesity and efficacy of vitamin D3 supplementation in healthy black adults

PURPOSE

Results from recent clinical trials suggest that vitamin D efficacy against cancer may be influenced by body mass index. As suppression of parathyroid hormone (PTH) is one indicator of vitamin D efficacy, we examined to what extent doses of vitamin D₃ supplementation suppress PTH levels in individuals with and without obesity.

METHODS

A total of 328 healthy African Americans were randomized into the following four groups and treated for 3 months: placebo, 1,000, 2,000, or 4,000 IU/day of vitamin D₃ supplementation.

RESULTS

Among the participants, 250 individuals with PTH measurements were included in the analysis. Obese individuals (n = 141) experienced a steep reduction of 3-month PTH from placebo to 1,000 IU/day of vitamin D₃ supplementation, but no further reduction at 2,000 or 4,000 IU/day. For non-obese individuals (n = 109), the reduction of 3-month PTH was approximately linear for increasing vitamin D₃ doses. At supplementation of 2,000 to 4,000 IU/day, 3-month 25(OH)vitamin D levels were high in both non-obese and obese individuals, but the 3-month PTH levels remained about 10 pg/mL higher in individuals with obesity.

CONCLUSION

Our findings suggest that excess adiposity confers resistance to vitamin D efficacy in suppressing PTH levels, even when given at high doses.

Effects of 1,25-dihydroxyvitamin D3 on the Inflammatory Responses of Stromal Vascular Cells and Adipocytes from Lean and Obese Mice

Vitamin D status has been implicated in obesity and adipose tissue inflammation. In the present study, we explored the effects of dietary vitamin D supplementation on adipose tissue inflammation and immune cell population, and the effects of in vitro 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) treatment on pro-inflammatory cytokine production by stromal vascular cells (SVCs) and adipocytes in lean and high-fat diet-induced obese mice. The results show that epididymal fat Mcp-1 and Rantes mRNA levels, which were higher in obese mice compared with lean mice, were significantly down-regulated by vitamin D supplementation. While obese mice had higher numbers of macrophages and natural killer (NK) cells within adipose tissue, these remained unaltered by vitamin D supplementation. In accordance with these in vivo findings, the in vitro 1,25(OH)2D3 treatment decreased IL-6, MCP-1, and IL-1β production by SVCs from obese mice, but not by adipocytes. In addition, 1,25(OH)2D3 treatment significantly decreased Tlr2 expression and increased mRNA levels of Iκba and Dusp1 in SVCs. These findings suggest that vitamin D supplementation attenuates inflammatory response in adipose tissue, especially in SVCs, possibly through inhibiting NF-κB and MAPK signaling pathways in SVCs but not by the inhibition of macrophage infiltration.

The Impact of Obesity on the Association between Vitamin D Deficiency and Cardiovascular Disease

The aim of this article is to review the literature regarding the relationship between vitamin D deficiency and cardiovascular disease (CVD) and its modification in the presence of obesity. Despite the strong association between vitamin D status and cardiovascular outcomes, vitamin D supplementation trials in the general population have failed to decrease the incidence of cardiovascular events and mortality. A comprehensive study of the published literature and a comparison with experimental data lead to the conclusion that obesity, due to its high prevalence and strong association with both vitamin D deficiency and CVD, may act as a critical confounder, which is responsible for the different results on this association. Adoption of a vitamin D preventive supplementation strategy for CVD is unlikely to yield any benefit to the general population. However, it might be particularly useful in obese adults with increased risk for CVD.