Calcium and vitamin D in the regulation of energy balance: where do we stand?

Vitamin D status modulates mitochondrial oxidative capacities in skeletal muscle: role in sarcopenia

Skeletal muscle mitochondrial function is the biggest component of whole-body energy output. Mitochondrial energy production during exercise is impaired in vitamin D-deficient subjects. In cultured myotubes, loss of vitamin D receptor (VDR) function decreases mitochondrial respiration rate and ATP production from oxidative phosphorylation. We aimed to examine the effects of vitamin D deficiency and supplementation on whole-body energy expenditure and muscle mitochondrial function in old rats, old mice, and human subjects. To gain further insight into the mechanisms involved, we used C2C12 and human muscle cells and transgenic mice with muscle-specific VDR tamoxifen-inducible deficiency. We observed that in vivo and in vitro vitamin D fluctuations changed mitochondrial biogenesis and oxidative activity in skeletal muscle. Vitamin D supplementation initiated in older people improved muscle mass and strength. We hypothesize that vitamin D supplementation is likely to help prevent not only sarcopenia but also sarcopenic obesity in vitamin D-deficient subjects.

Maternal inappropriate calcium intake aggravates dietary-induced obesity in male offspring by affecting the differentiation potential of mesenchymal stem cells

BACKGROUND

The effects of inappropriate dietary calcium intake in early life on later obesity have not been fully elucidated.

AIM

To raise the mechanism of maternal calcium intake on the multi-differentiation potential of mesenchymal stem cells among their male offspring.

METHODS

Four-week-old female C57BL/6N mice were fed by deficient, low, normal and excessive calcium reproductive diets throughout pregnancy and lactation. Bone MSCs (BMSCs) were obtained from 7-day-old male offspring to measure the adipogenic differentiation potential by the Wnt/β-catenin signaling pathway. The other weaning male pups were fed a high-fat diet for 16 wk, along with normal-fat diet as the control. Then the serum was collected for the measurement of biochemical indicators. Meanwhile, the adipose tissues were excised to analyze the adipocyte sizes and inflammatory infiltration. And the target gene expressions on the adipogenic differentiation and Wnt/β-catenin signaling pathway in the adipose tissues and BMSCs were determined by real-time reverse transcription polymerase chain reaction.

RESULTS

Compared with the control group, maternal deficient, low and excessive calcium intake during pregnancy and lactation aggravated dietary-induced obesity, with larger adipocytes, more serious inflammatory infiltration and higher serum metabolism indicators by interfering with higher expressions of adipogenic differentiation (PPARγ, C/EBPα, Fabp4, LPL, Adiponectin, Resistin and/or Leptin) among their male offspring (P < 0.05). And there were significantly different expression of similar specific genes in the BMSCs to successfully polarize adipogenic differentiation and suppress osteogenic differentiation in vivo and in vitro, respectively (P < 0.05). Meanwhile, it was accompanied by more significant disorders on the expressions of Wnt/β-catenin signaling pathway both in BMSCs and adulthood adipose tissues among the offspring from maternal inappropriate dietary calcium intake groups.

CONCLUSION

Early-life abnormal dietary calcium intake might program the adipogenic differentiation potential of BMSCs from male offspring, with significant expressions on the Wnt/β-catenin signaling pathway to aggravate high-fat-diet-induced obesity in adulthood.

Targeting the T-type calcium channel Cav3.2 in GABAergic arcuate nucleus neurons to treat obesity

OBJECTIVE

Cav3.2, a T-type low voltage-activated calcium channel widely expressed throughout the central nervous system, plays a vital role in neuronal excitability and various physiological functions. However, the effects of Cav3.2 on energy homeostasis remain unclear. Here, we examined the role of Cav3.2 expressed by hypothalamic GABAergic neurons in the regulation of food intake and body weight in mice and explored the underlying mechanisms.

METHODS

Male congenital Cana1h (the gene coding for Cav3.2) global knockout (Cav3.2KO) mice and their wild type (WT) littermates were first used for metabolic phenotyping studies. By using the CRISPR-Cas9 technique, Cav3.2 was selectively deleted from GABAergic neurons in the arcuate nucleus of the hypothalamus (ARH) by specifically overexpressing Cas9 protein and Cav3.2-targeting sgRNAs in ARH Vgat (Vgat^ARH) neurons. These male mutants (Cav3.2KO-Vgat^ARH) were used to determine whether Cav3.2 expressed by Vgat^ARH neurons is required for the proper regulation of energy balance. Subsequently, we used an electrophysiological patch-clamp recording in ex vivo brain slices to explore the impact of Cav3.2KO on the cellular excitability of Vgat^ARH neurons.

RESULTS

Male Cav3.2KO mice had significantly lower food intake than their WT littermate controls when fed with either a normal chow diet (NCD) or a high-fat diet (HFD). This hypophagia phenotype was associated with increased energy expenditure and decreased fat mass, lean mass, and total body weight. Selective deletion of Cav3.2 in Vgat^ARH neurons resulted in similar feeding inhibition and lean phenotype without changing energy expenditure. These data provides an intrinsic mechanism to support the previous finding on ARH non-AgRP GABA neurons in regulating diet-induced obesity. Lastly, we found that naringenin extract, a predominant flavanone found in various fruits and herbs and known to act on Cav3.2, decreased the firing activity of Vgat^ARH neurons and reduced food intake and body weight. These naringenin-induced inhibitions were fully blocked in Cav3.2KO-Vgat^ARH mice.

CONCLUSION

Our results identified Cav3.2 expressed by Vgat^ARH neurons as an essential intrinsic modulator for food intake and energy homeostasis, which is a potential therapeutic target in the treatment of obesity.

Daily intake of yogurt drink fortified either with vitamin D alone or in combination with added calcium causes a thyroid-independent increase of resting metabolic rate in adults with type 2 diabetes: a randomized double blind clinical trial

We investigated the effect of daily intake of yogurt drink fortified with either vitamin D alone or with added calcium on resting metabolic rate (RMR), thyroid hormones and homeostatic model assessment for insulin resistance (HOMA-IR) in subjects with type 2 diabetes (T2D). A total of 75 adult subjects with T2D were randomly assigned to one of the three groups to receive either D-fortified yogurt drink (DY; 1000 IU vitamin D/d), Ca-D-fortified yogurt drink (CDY; 1000 IU vitamin D plus 500 mg calcium), or plain yogurt drink (PY) for 12 weeks. All assessments were done at the baseline and after the intervention. The concentrations of anti-thyroid peroxidase antibody (anti-TPO-Ab), intact parathyroid hormone (iPTH) and thyroid stimulating hormone (TSH) had significant decline compared with baseline values only in CDY group. The mean RMR increased in both DY and CDY groups (p<0.001 for both). Also, changes of serum concentrations of 25(OH)D (B= 2.96, 95%CI= 1.3- 4.6, p=0.001) and iPTH (B= -2.41, 95%CI= -4.5- -0.31, p=0.025) remained significant predictors of RMR changes even after adjustment for changes of serum concentrations of TSH (B= -18.2, 95%CI= -61.7- 25.2, p=0.406). Daily intake of vitamin D together with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Also, vitamin D with or without added calcium causes a significant thyroid-independent increase in RMR in euthyroid subjects with T2D. Registered at clinicaltrials.gov as NCT01229891. Novelty: Daily intake of vitamin D with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Vitamin D with or without added calcium causes a thyroid-independent increase in RMR in euthyroid subjects with T2D.

Extra-skeletal effects of dietary calcium: Impact on the cardiovascular system, obesity, and cancer

Calcium is well known to be integral to bone and muscle health, with deleterious effects such as osteoporosis associated with inadequate calcium intake. Recent studies have also highlighted the significant effects of calcium in extra-musculoskeletal functioning, including the cardiovascular system, obesity, and cancer. Calcium impacts the cardiovascular system as an antagonist associated with a reduction in hypertension, increase vasodilation, and improvement in blood vessel function when obtained in the diet as an organic source, through food. However, the inorganic source of calcium, found in supplements, may be negatively associated with the cardiovascular system due to plaque deposits and atherogenesis when taken in excess. Some studies suggest that calcium intake may impact obesity by regulation of adipogenesis and reducing fat deposits with resulting weight loss. The pathogenesis of calcium for reducing obesity is thought to be related in part to its impact on gut microbiota profile, with the suggestion that calcium may have prebiotic properties. Animal and some human studies propose that calcium may also have a role in cancer prevention and/or treatment due to its function in the cell proliferation process and the impact on hormonal regulation, and thus warrants more investigations in the human population. Some prospective and small clinical studies suggest that calcium may be beneficial for colorectal cancer. Overall, emerging research in various areas continues to highlight the essentiality of dietary calcium for functioning at the molecular and biochemical level toward improvement in health and some chronic disease conditions.

Seasonal variability of the vitamin D effect on physical fitness in adolescents

Studies investigating the relationship between vitamin D and physical fitness in youth have provided inconsistent findings. Recent evidence indicates that the expression of receptors and vitamin D-modulated genes in young subjects has a seasonal profile. Therefore, we investigated the role of vitamin D on physical fitness across seasons in a total of 977 male adolescents. Anthropometrics, lifestyle, dietary habits, biochemical profiles and physical fitness were studied. Multiple linear regression models, including pairwise interaction terms involving total 25-OH-vitamin D, were fitted. The interacting effect of season and total 25-OH-vitamin D had a significant influence on physical fitness performance (spring and total 25-OH-vitamin D: ß 0.19, SE 0.07, p = 0.007; summer and total 25-OH-vitamin D: ß 0.10, SE 0.06, p = 0.11; autumn and total 25-OH-vitamin D: ß 0.18, SE 0.07, p = 0.01), whereas the main effect of total 25-OH-vitamin D alone was not significant (p = 0.30). Body fat percentage, recreational physical activity level, time spent per day gaming/TV-watching, smoking, and hemoglobin levels were also related to the physical fitness performance score. Future studies should further explore the role of seasonal-dependent effects of vitamin D on health.

Genetically increased circulating 25(OH)D level reduces the risk of type 2 diabetes in subjects with deficiency of vitamin D: A large-scale Mendelian randomization study

Observational studies have reported that Vitamin D deficiency and the risk type 2 diabetes are associated, but the causation is unclear. Mendelian randomization (MR) involving genetic variants as instrument variables (IVs) overcomes the reverse-casualty and unmeasured confounding. However, with limited sample size and IVs, previous MR studies showed inconsistent results. Leveraging by a largely increased sample size for both stages, we aim to provide an updated and precise estimate for the causality between Vitamin D and type 2 diabetes.A 2-sample multi-IVs MR was performed. IVs for circulating 25-hydroxyvitamin D (25(OH)D) were obtained from a genome-wide association study from UK biobank involving 329,247 subjects of European ancestry. The causal effect of 25(OH)D and type 2 diabetes was estimated using traditional inverse variance weighting and MR pleiotropy residual sum and outlier (MR-PRESSO) framework which provides a robust estimate by systematically filtering out IVs identified with potential pleiotropy effects.A higher genetically instrumented 25(OH)D was causally linked to reduced risk of type 2 diabetes risk by MR-PRESSO [odds ratio (OR) per standard deviation (SD) = 0.950, 95% confidence interval (CI) = 0.913-0.988, P = .010] after removing 13 (13/193) invalid IVs. In addition, we confirmed the causal role Vitamin D using 2 synthesis-related single-nucleotide polymorphisms (SNPs) which are consistent with previous MR studies [OR per SD = 0.894, 95% CI = 0.816-0.979, P = .016].With a largely improved sample size, our results confirmed that genetically increased 25(OH)D concentration reduced the risk of type 2 diabetes and provided a more precise estimate for the effect size. The updated result empowers the role of Vitamin D and provides nontrivial evidence for interventional studies.

Effects of Vitamin D Supplementation on Body Composition and Metabolic Risk Factors in Men: A Randomized Controlled Trial

Vitamin D might play a role in metabolic processes and obesity. We therefore examined vitamin D effects on metabolic markers and obesity in a randomized controlled trial (RCT). This is a post-hoc analysis of the Graz Vitamin D&TT-RCT, a single-center, double-blind, randomized placebo-controlled trial. We included 200 healthy men with serum 25-hydroxyvitamin D (25(OH) D) levels <75 nmol/L. Subjects received 20,000 IU of vitamin D3/week (n = 100) or placebo (n = 100) for 12 weeks. Outcome measures were metabolic markers, anthropometric measures, and body composition assessed by Dual-energy X-ray absorptiometry. One-hundred and ninety-two men completed the study. We found a significant treatment effect on fasting glucose/fasting insulin ratio (−5.3 (−10.4 to −0.2), p = 0.040), whereas we observed no significant effect on the remaining outcome parameters. In subgroup analyses of men with baseline 25(OH)D levels <50 nmol/L (n = 80), we found a significant effect on waist circumference (1.6 (0.3 to 2.9) cm, p = 0.012), waist-to-hip ratio (0.019 (0.002 to 0.036), p = 0.031), total body fat (0.029 (0.004 to 0.055) %, p = 0.026), and android fat (1.18 (0.11 to 2.26) %, p = 0.010). In middle-aged healthy men, vitamin D treatment had a negative effect on insulin sensitivity. In vitamin D deficient men, vitamin D has an unfavorable effect on central obesity and body composition.

Association between vitamin D status during pregnancy and total gestational weight gain and postpartum weight retention: a prospective cohort

OBJECTIVES

To evaluate the association between vitamin D status during pregnancy and total gestational weight gain (GWG), GWG rates and postpartum weight retention.

METHODS

Prospective cohort of 163 women from Rio de Janeiro was followed at 5^th-13^th (baseline), 20^th-26^th, 30^th-36^th gestational weeks and at 30-62 days postpartum. Plasma 25-hydroxyvitamin D [25(OH)D] was evaluated during each trimester and was categorized as adequate (≥50 nmol/L) or inadequate (<50 nmol/L). GWG (kg) was calculated as the difference between the weight measured at baseline and 36^th-42^th gestational weeks. GWG rates (kg/week) were calculated between each visit. Postpartum weight retention (kg) was analysed as the difference between weights measured at 30-62 days postpartum and 5^th-13^th gestational weeks. Statistical analyses were performed using linear regression models that included interaction terms between vitamin D status and first trimester body mass index (BMI) (<25/≥25 kg/m²). Confounders were selected based on a directed acyclic graph.

RESULTS

The prevalence of vitamin D inadequacy was 16.6%, 9.9% and 10.6% in the first, second and third trimesters, respectively. Overweight women with vitamin D inadequacy in the first (β = 3.70; 95% CI 0.09; 7.31, p-value = 0.045) and third trimester (β = 4.59, 95% CI 0.07; 9.10, p-value = 0.047) presented higher increases in total GWG than did women with vitamin D adequacy. This association was also observed between first trimester vitamin D status and GWG rates between visits 1 and 2 (β = 0.17; 95% CI 0.13; 0.36, p-value = 0.07).

CONCLUSIONS

There was an interaction effect of first trimester BMI (≥25 kg/m²) on the association between first and third trimester vitamin D status and GWG.

Calcium Supplementation Alleviates High-Fat Diet-Induced Estrous Cycle Irregularity and Subfertility Associated with Concomitantly Enhanced Thermogenesis of Brown Adipose Tissue and Browning of White Adipose Tissue

Obesity has been demonstrated as a disruptor of female fertility. Our previous study showed the antiobesity effects of calcium on HFD-fed male mice. However, the role of calcium in alleviating reproductive dysfunction of HFD-fed female mice remains unclear. Here, we found that HFD led to estrus cycle irregularity (longer cycle duration and shorter estrus period) and subfertility (longer conception time, lower fertility index, and less implantations) in mice. However, the HFD-induced reproductive abnormality was alleviated by calcium supplementation. Additionally, calcium supplementation enhanced activation/thermogenesis of BAT and browning of WAT in HFD-fed mice. Consequently, the abnormality of energy metabolism and glucose homeostasis induced by HFD were improved by calcium supplementation, with elevated metabolic rates and core temperature. In conclusion, these data showed that calcium supplementation alleviated HFD-induced estrous cycle irregularity and subfertility associated with concomitantly enhanced BAT thermogenesis and WAT browning, suggesting the potential application of calcium in improving obesity-related reproductive disorders.

Anti-Obesity Effects of Dietary Calcium: The Evidence and Possible Mechanisms

Obesity is a serious health challenge worldwide and is associated with various comorbidities, including dyslipidemia, type 2 diabetes, and cardiovascular disease. Developing effective strategies to prevent obesity is therefore of paramount importance. One potential strategy to reduce obesity is to consume calcium, which has been implicated to be involved in reducing body weight/fat. In this review, we compile the evidence for the anti-obesity roles of calcium in cells, animals, and humans. In addition, we summarize the possible anti-obesity mechanisms of calcium, including regulation of (a) adipogenesis, (b) fat metabolism, (c) adipocyte (precursor) proliferation and apoptosis, (d) thermogenesis, (e) fat absorption and excretion, and (f) gut microbiota. Although the exact anti-obesity roles of calcium in different subjects and how calcium induces the proposed anti-obesity mechanisms need to be further investigated, the current evidence demonstrates the anti-obesity effects of calcium and suggests the potential application of dietary calcium for prevention of obesity.

Beneficial Effects of Vitamin D on Insulin Sensitivity, Blood Pressure, Abdominal Subcutaneous Fat Thickness, and Weight Loss in Refractory Obesity

IN BRIEF This study explored the impact of correcting vitamin D deficiency on blood pressure, metabolic status, and weight loss in patients with fatigue and obesity refractory to conventional interventions such as diet, exercise, behavioral modification, and pharmacotherapy. Correction of vitamin D deficiency in such patients was found to be significantly associated with weight reduction and improved insulin sensitivity.

CORRELATIONS OF SERUM VITAMIN D WITH METABOLIC PARAMETERS IN ADULT OUTPATIENTS WITH DIFFERENT DEGREES OF OVERWEIGHT / OBESITY COMING FROM AN URBAN COMMUNITY

OBJECTIVE

To describe the correlations between serum 25(OH) vitamin D and anthropometric and metabolic parameters in adult outpatients of both sexes with different BMI coming from an urban community.

SUBJECTS AND METHODS

264 subjects referred for obesity assessment participated - 109 men and 155 women (20-60 years). Body weight and height, waist circumference (WC), blood pressure were recorded. Body composition was assessed by bioelectrical impedance (BIA) on a Tanita BC 420 MA analyzer (Tanita Inc., Japan). Serum 25(OH)D Total, Insulin, High-sensitivity C-reactive protein, blood glucose, total, HDL-cholesterol and triglycerides were measured. The insulin resistance index was calculated (HOMA-IR). Participants with BMI>25.0 kg/m2 underwent standard 75 g OGTT. Statistical analysis was performed on an IBM SPSS Statistics 19.0 for Windows platform (Chicago, IL).

RESULTS

Normal weight was found in 27.2 % of the participants, 24.6 % had overweight, 29.2 % -class I obesity, and 18.9 % - class II or III. Vitamin D was weakly and inversely correlated to different variables in the whole group - such as weight, WC, WC/Height, % body fat and HOMA-IR index (r=-0.231, -0.283, -0.307, -0.339, -0.328 respectively, all p<0.001). Building subgroups based on BMI led to loss of significance. Backward analysis revealed Total-C/LDL-C ratio, and LDL-C/HDL-C ratio as strongest predictors of serum vitamin D (p=0.001; R2=0.204).

CONCLUSION

The association of vitamin D with blood pressure, plasma lipids, glucose and insulin is very weak on an individual level. However, several obesity indices (WC, WC/height ratio, % Body fat from BIA) might be used as a screening tool for subjects at risk for vitamin D deficiency.

Age-associated expression of vitamin D receptor and vitamin D-metabolizing enzymes in the male reproductive tract and sperm of Hu sheep

The cellular response to 1,25-dihydroxyvitamin D₃ (Vit D₃; biologically active form of Vitamin D) is complex and depends not only on Vitamin D receptor (VDR) expression but also on cellular uptake of circulating Vit D₃ and the presence and activity of Vitamin D-metabolizing enzyme. This study evaluated the expression of VDR and Vitamin D-metabolizing enzymes in the ram reproductive tract at different developmental stages and in spermatozoa. Nearly all cell types in the testes and epithelial cells of the caput, corpus, and cauda expressed VDR, CYP27B1, and CYP24A1 proteins. The mRNA and protein expression of CYP2R1, CYP27A1, and CYP27B1 in the testes and cauda increased significantly with increasing age (P < 0.05). However, epididymal VDR mRNA and protein expression showed no significant difference (P < 0.05) between adult (9- and 24-month-old) and prepubertal (3-month-old) rams. Furthermore, VDR and CYP24A1 were mainly concentrated in the mid-piece of ejaculated or cauda epididymis spermatozoa or both. Additionally, VDR and CYP27B1 mRNA and protein expression levels were significantly higher in ejaculated spermatozoa than in cauda epididymal spermatozoa (P < 0.05). Moreover, VDR and CYP24A1 expression was significantly higher in high-motility than in low-motility spermatozoa (P < 0.05). The diverse expression patterns of VDR and Vitamin D-metabolizing enzymes in the ram reproductive tract at different developmental stages and spermatozoa suggest it plays a potential role in spermatogenesis.

Associations of Milk Consumption and Vitamin B₂ and Β12 Derived from Milk with Fitness, Anthropometric and Biochemical Indices in Children. The Healthy Growth Study

The benefits of dairy consumption seem to extend beyond its significant contribution to ensuring nutrient intake adequacy as indicated by the favourable associations with several health outcomes reported by different studies. The aims of the present study were to examine the associations of milk consumption with fitness, anthropometric and biochemical indices in children and further explore whether the observed associations are attributed to vitamins B₂ and B₁₂ derived from milk. A representative subsample of 600 children aged 9-13 years participating in the Healthy Growth Study was examined. Data were collected on children's dietary intake, using 24 h recalls, as well as on fitness, anthropometric and biochemical indices. Regression analyses were performed for investigating the research hypothesis, adjusting for potential confounders and for B-vitamin status indices (i.e., plasma riboflavin, methylmalonic acid and total homocysteine concentrations), dietary calcium intake and plasma zinc concentrations that could possibly act as effect modifiers. Milk consumption was positively associated with the number of stages performed in the endurance run test (ERT) (β = 0.10; p = 0.017) and negatively with body mass index (BMI) (β = -0.10; p = 0.014), after adjusting for several potential confounders and effect modifiers. Dietary intakes of vitamin B₂ and B₁₂ derived from milk were also positively associated with the number of ERT stages (β = 0.10; p = 0.015 and β = 0.10; p = 0.014 respectively). In conclusion, higher intake of milk as well as vitamin B₂ and B₁₂ derived from milk were independently associated with higher cardiorespiratory fitness in Greek preadolescents. The key roles of these B-vitamins in substrate oxidation, energy production, haemoglobin synthesis and erythropoiesis could provide a basis for interpreting these associations. However, further research is needed to confirm this potential interpretation.

The associations of vitamin D status and dietary calcium with the metabolic syndrome: an analysis of the Victorian Health Monitor survey

OBJECTIVE

To examine the associations between serum 25-hydroxyvitamin D (25(OH)D), dietary Ca intake and presence of the metabolic syndrome (MetS).

DESIGN

A stratified cluster sample of a population aged 18-75 years from the Victorian Health Monitor survey.

SETTING

Non-institutionalized adults living in private dwellings in Victoria, Australia.

SUBJECTS

Adults (n 3404) with complete data and without type 1 or type 2 diabetes.

RESULTS

Adjusted for sociodemographic factors, physical characteristics and dietary covariates including Ca intake, every 10 nmol/l increase in serum 25(OH)D was significantly associated with decreased odds of MetS (adjusted odds ratio (AOR)=0·85, 95 % CI 0·80, 0·89; P<0·001). Relative to the low 25(OH)D tertile (median 33 nmol/l), there was a progressive decrease in odds of MetS that reached significance with the high 25(OH)D tertile (median 77 nmol/l; AOR=0·35, 95 % CI 0·26, 0·48; P<0·001). Every 500 mg/d increase in Ca intake adjusted for 25(OH)D did not reduce odds of MetS (AOR=0·81, 95 % CI 0·66, 1·06; P=0·141) but approached significance if unadjusted for 25(OH)D in the final model (AOR=0·81, 95 % CI 0·64, 1·02; P=0·073). No significant effect was obtained for tertiles of Ca intake. However, Ca and vitamin D tertile combinations suggested a beneficial effect of high Ca (median 1233 mg/d) only at low and medium 25(OH)D. The high 25(OH)D tertile was associated with significantly decreased odds of MetS regardless of Ca intake.

CONCLUSIONS

A high vitamin D status significantly reduced the odds of MetS. A high Ca intake may have a similar favourable outcome but only at lower circulating concentrations of 25(OH)D.

Food, health, and complexity: towards a conceptual understanding to guide collaborative public health action

BACKGROUND

What we eat simultaneously impacts our exposure to pathogens, allergens, and contaminants, our nutritional status and body composition, our risks for and the progression of chronic diseases, and other outcomes. Furthermore, what we eat is influenced by a complex web of drivers, including culture, politics, economics, and our built and natural environments. To date, public health initiatives aimed at improving food-related population health outcomes have primarily been developed within 'practice silos', and the potential for complex interactions among such initiatives is not well understood. Therefore, our objective was to develop a conceptual model depicting how infectious foodborne illness, food insecurity, dietary contaminants, obesity, and food allergy can be linked via shared drivers, to illustrate potential complex interactions and support future collaboration across public health practice silos.

METHODS

We developed the conceptual model by first conducting a systematic literature search to identify review articles containing schematics that depicted relationships between drivers and the issues of interest. Next, we synthesized drivers into a common model using a modified thematic synthesis approach that combined an inductive thematic analysis and mapping to synthesize findings.

RESULTS

The literature search yielded 83 relevant references containing 101 schematics. The conceptual model contained 49 shared drivers and 227 interconnections. Each of the five issues was connected to all others. Obesity and food insecurity shared the most drivers (n = 28). Obesity shared several drivers with food allergy (n = 11), infectious foodborne illness (n = 7), and dietary contamination (n = 6). Food insecurity shared several drivers with infectious foodborne illness (n = 9) and dietary contamination (n = 9). Infectious foodborne illness shared drivers with dietary contamination (n = 8). Fewer drivers were shared between food allergy and: food insecurity (n = 4); infectious foodborne illness (n = 2); and dietary contamination (n = 1).

CONCLUSIONS

Our model explicates potential interrelationships between five population health issues for which public health interventions have historically been siloed, suggesting that interventions targeted towards these issues have the potential to interact and produce unexpected consequences. Public health practitioners working in infectious foodborne illness, food insecurity, dietary contaminants, obesity, and food allergy should actively consider how their seemingly targeted public health actions may produce unintended positive or negative population health impacts.

Calcium and Vitamin D in Obesity and Related Chronic Disease

There is a pandemic of lifestyle-related diseases. In both developed and lesser developed countries of the world, an inadequacy of calcium intake and low vitamin D status is common. In this chapter, we explore a mechanistic framework that links calcium and vitamin D status to chronic conditions including obesity, systemic inflammation, endothelial dysfunction, dyslipidemia and cardiovascular disease, and type 2 diabetes mellitus. We also update the available clinical evidence, mainly from randomized controlled trials, to provide a synthesis of evidence in favor or against these hypotheses. There is consistent data to support calcium increasing whole body fat oxidation and increasing fecal fat excretion, while there is good cellular evidence for vitamin D reducing inflammation. Clinical trials support a marginal reduction in circulating lipids and some meta-analysis support an increase in insulin sensitivity following vitamin D. However, these mechanistic pathways and intermediate biomarkers of disease do not consistently transcribe into measurable health outcomes. Cementing the benefits of calcium and vitamin D for extraskeletal health needs a reexamination of the target 25(OH)D level to be achieved and the minimum duration of future trials.

A network analysis of cofactor-protein interactions for analyzing associations between human nutrition and diseases

The involvement of vitamins and other micronutrients in intermediary metabolism was elucidated in the mid 1900's at the level of individual biochemical reactions. Biochemical pathways remain the foundational knowledgebase for understanding how micronutrient adequacy modulates health in all life stages. Current daily recommended intakes were usually established on the basis of the association of a single nutrient to a single, most sensitive adverse effect and thus neglect interdependent and pleiotropic effects of micronutrients on biological systems. Hence, the understanding of the impact of overt or sub-clinical nutrient deficiencies on biological processes remains incomplete. Developing a more complete view of the role of micronutrients and their metabolic products in protein-mediated reactions is of importance. We thus integrated and represented cofactor-protein interaction data from multiple and diverse sources into a multi-layer network representation that links cofactors, cofactor-interacting proteins, biological processes, and diseases. Network representation of this information is a key feature of the present analysis and enables the integration of data from individual biochemical reactions and protein-protein interactions into a systems view, which may guide strategies for targeted nutritional interventions aimed at improving health and preventing diseases.

Calcium supplementation modulates gut microbiota in a prebiotic manner in dietary obese mice

SCOPE

Dietary calcium has been inversely associated with body fat and energy balance. The main scope of this study has been to assess the potential contribution of gut microbiota on energy regulation mediated by calcium.

METHODS AND RESULTS

Gut microbiota in C57BL/6J mice receiving calcium supplementation under a high-fat (HF) diet were analysed by PCR and their relationships with host metabolic parameters were determined. Calcium conferred a prebiotic-like effect on gut microbiota, and animals presented lower plasmatic endotoxin levels, increased expression of angiopoietin-like 4 in intestine and lower hepatic lipid content, although increased expression of stress markers in adipose tissue and of inflammation in liver was also found. To determine whether slimming effects could be transferred to obese mice, a faecal microbial transplant (FMT) was carried out, showing that host bacteria grown under a HF diet could not be superseded by those from calcium-fed animals. Therefore, FMT was not able to transfer the beneficial effects of calcium.

CONCLUSION

In conclusion, calcium modulated gut microbiota in a prebiotic manner, establishing a host cross-talk and promoting a healthier metabolic profile. However, lack of effectiveness of FMT suggests the need of further appropriate dietary factors in addition to the bacteria per se.

Vitamin D status and insulin sensitivity are novel predictors of resting metabolic rate: a cross-sectional analysis in Australian adults

PURPOSE

Resting metabolic rate (RMR) accounts for two-thirds of the total energy expenditure in sedentary individuals. After accounting for traditional factors, there still remains a considerable unexplained variance in RMR. There is a pandemic of obesity and metabolic syndrome (MetS) which coexists with a high prevalence of vitamin D insufficiency. The aim of this study was to evaluate the potential effects of vitamin D status, insulin sensitivity (IS) and the metabolic syndrome (MetS) on RMR in Australian adults.

METHODS

RMR, respiratory quotient (RQ), McAuley's insulin sensitivity index, fat mass (FM), fat-free mass (FFM) and vitamin D status were assessed in Australian adults. The presence of MetS was evaluated by current standard criteria. Predictors of RMR were examined through multiple linear regression based on stepwise and backward regression approaches with attention to multi-collinearity. All analyses were conducted on SPSS version 21.

RESULTS

One hundred and twenty-seven participants (45 men, 82 women), aged 53.4 ± 11.7 years and BMI 31.9 ± 5.2 kg/m(2), were included. Forty-one subjects were insufficient in vitamin D status (<50 nmol/L), and 75 participants had the MetS. A parsimonious regression model explained 85.8 % of RMR and was given by: RMR (kJ/d) = 1931 + 83.5 × FFM (kg) + 29.5 × FM (kg) + 5.65 × 25(OH)D (nmol/L) - 17.6 × age (years) - 57.51 × IS.

CONCLUSION

Vitamin D status and IS are novel independent predictors of RMR in adults. Future studies could validate a causal role for these factors in human energy metabolism.

A systematic review protocol examining the effect of vitamin D supplementation on endothelial function

INTRODUCTION

Vitamin D has potential benefits for extraskeletal health. These could include an anti-inflammatory effect as well as a reduction in endothelial dysfunction. We aim to provide quality evidence for the hypothesis that supplementation with vitamin D will improve endothelial function (EF), possibly through the abrogation of systemic inflammation.

METHODS AND ANALYSIS

We will conduct a systematic review of all randomised controlled trials on vitamin D supplementation and EF lasting 12 weeks or more. The search will cover the period 2000-2015 and include studies that describe direct measures of EF, markers of endothelial cell (EC) activation and if concurrently reported, indicators of systemic inflammation. Study selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and study quality will be assessed by the Jadad score in addition to an evaluation of allocation concealment and data analysis. If sufficient data are available, a meta-analysis will be conducted. The effect sizes will be generated using Hedges' g score, for both fixed and random effect models. I(2) statistics and Galbraith plots will be used to assess heterogeneity and identify their potential sources. Potential publication and small sample size bias will be assessed by visual inspections of funnel plots and also Egger's test. Meta-regression analysis (if feasible) will be conducted with restricted maximum likelihood (REML) estimation method, controlling for potential confounders (demographics, study methods, location, etc). A backward elimination process will be applied in the regression modelling procedure. Subgroup analysis, conditional on number of studies retrieved and their sample size, will be stratified on participant disease category, total dose administered, degree of 25(OH)D change and type of supplement used.

ETHICS AND DISSEMINATION

Formal ethical approval is not required as primary data will not be collected. The results will be disseminated through a peer-reviewed publication, conference presentation and the popular press.

TRIAL REGISTRATION NUMBER

International Prospective Register for Systematic Reviews (PROSPERO) number CRD42014013523.

Vitamin D & endothelial function

There is increasing interest in the extra-skeletal roles of vitamin D for health and well-being. Poor vitamin D status has been associated with obesity, cardiovascular disease, type 2 diabetes and mental health. Endothelial dysfunction may underscore insulin resistance and hence predispose to both cardiovascular disease (CVD) and type 2 diabetes. The objective of this review was to gain an appreciation of the recent causative evidence linking vitamin D and endothelial function. The PubMed database was searched from 2009 to date. Key words used were vitamin D, supplementation, systemic inflammation, endothelium, endothelial dysfunction and humans. Selected articles were restricted to the English language and to randomized control trials (RCTs) of vitamin D supplementation with direct measures of endothelial function. Final inclusion was based on a quality rating ≥ 3, based on the Jadad score. Ten RCTs met these criteria and were summarized for their outcomes. Only two studies showed an improvement in flow mediated dilatation with vitamin D. Three other studies reported decreases in C-reactive protein, platelet activation inhibitor-1, tissue plasminogen activator or B type natriuretic peptide. Recent evidence from good quality RCTs did not support a beneficial effect of vitamin D on vascular reactivity. Future intervention studies may need to target a higher vitamin D status and longer duration to determine whether the vitamin has a regulatory role in endothelial function.