Vitamin A deficiency impairs fetal islet development and causes subsequent glucose intolerance in adult rats

Association between night blindness history and risk of diabetes in the Chinese population: a multi-center, cross sectional study

AIMS

Night blindness (NB), an important manifestation of VA deficiency, may be associated with the odds of diabetes. The aim of this study was to explore the probable association between NB history and diabetes in Chinese community-dwelling adults.

METHODS

This multi-center, cross-sectional study enrolled a total of 5664 participants aged 18-82 years from eight sites in China. Information on demographics and medical history was collected using a standardized questionnaire. Diabetes was diagnosed based on the oral glucose tolerance test or a self-reported history. NB history was ascertained by a face-to-face interview with reference to the recommendation by the World Health Organization. Logistic regression analysis was used to evaluate the association between NB history and the odds of diabetes.

RESULTS

A total of 5049 participants were finally included, with 252 ascertained with NB history and 1076 with diabetes. The mean age of included participants was 52.9 years, and the percentage of participants with NB history was significantly higher in participants with diabetes than those without (7.0% vs. 4.5%). The multivariable adjusted odds ratio for diabetes was 1.41 (95% confidence interval 1.06, 1.89) in participants with NB history compared with those without. Furthermore, mediation analysis showed that obesity, as assessed by waist-height ratio, partially mediated the relationship between NB history and increased odds of diabetes.

CONCLUSIONS

The results suggest that NB history might be associated with increased odds of diabetes in Chinese community-dwelling adults.

Micronutrients in early life and offspring metabolic health programming: a promising target for preventing non-communicable diseases

Chronic non-communicable diseases are the leading cause of morbidity and mortality worldwide. Developing and implementing effective preventive strategies is the best way to ensure the overall metabolic health status of the population and to counter the global burden of non-communicable diseases. Predisposition to obesity and other non-communicable diseases is due to a combination of genetic and environmental factors throughout life, but the early environment, particularly the environment during the fetal period and the early years of life, is crucial in determining metabolic health, hence the concept of 'fetal programming'. The origins of this causal link between environmental factors and disease lie in epigenetic mechanisms. Among the environmental factors, diet plays a crucial role in this process. Substantial evidence documented the key role of macronutrients in the programming of metabolic diseases early in life. Recently, the effect of maternal micronutrient intake on offspring metabolic health in later life emerged. The purpose of this narrative review is to bring to light available evidence in the literature on the effect of maternal micronutrient status on offspring metabolic health and underlying epigenetic mechanisms that drive this link to highlight its potential role in the prevention of non-communicable diseases.

Vitamin a supplementation during pregnancy in shaping child growth outcomes: A meta-analysis

Abnormal fetal growth increases risks of childhood health complications. Vitamin A supplementation (VAS) is highly accessible, but literature inconsistency regarding effects of maternal VAS on fetal and childhood growth outcomes exists, deterring pregnant women from VAS during pregnancy. This meta-analysis aimed to analyze effects of vitamin A only or vitamin A + co-intervention during pregnancy in healthy mothers (MH) or with complications (MC, night blindness and HIV positive) on perinatal growth outcomes, also assess VAS dose impacts. The Cochrane Library, PubMed, ScienceDirect, Scopus, Embase and Web of Science databases were searched from inception to July 15, 2021. We covered subgroup analyses, including VAS in MH or MC within randomized controlled trial (RCT) or observational studies (OS). Fifty-five studies were included in this meta-analysis (426,098 pregnancies). Vitamin A decreased risk of preterm birth by 9% in MH-RCT (P < 0.001), by 62% in MH-OS (P = 0.029), by 10% in MC-RCT (P = 0.089); decreased LBW by 24% in MC-RCT (P = 0.032); increased neonatal weight in MC-RCT (SMD 0.96; P = 0.051). Besides, vitamin A + co-intervention decreased risks of preterm by 18% in MH-OS (P = 0.021); LBW by 25% in MH-OS (P < 0.001); by 32% in MC-RCT (P = 0.006); decreased neonatal defects by 33% in MH-OS (P = 0.064); decreased anemia by 25% in MH-OS (P = 0.0003); increased neonatal weight in MH-OS (SMD 0.51; P = 0.014); and increased neonatal length in MH-OS (SMD 1.83; P = 0.013). Meta-regression of VAS dose with individual outcomes was not significant, and no side effects were observed for VAS doses up to 4000 mcg (RAE/d). Regardless of maternal health conditions, VAS during pregnancy can safely and effectively improve fetal development and neonatal health even in mothers without VAD.

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

Immune Impairment Associated with Vitamin A Deficiency: Insights from Clinical Studies and Animal Model Research

Vitamin A (VA) is critical for many biological processes, including embryonic development, hormone production and function, the maintenance and modulation of immunity, and the homeostasis of epithelium and mucosa. Specifically, VA affects cell integrity, cytokine production, innate immune cell activation, antigen presentation, and lymphocyte trafficking to mucosal surfaces. VA also has been reported to influence the gut microbiota composition and diversity. Consequently, VA deficiency (VAD) results in the imbalanced production of inflammatory and immunomodulatory cytokines, intestinal inflammation, weakened mucosal barrier functions, reduced reactive oxygen species (ROS) and disruption of the gut microbiome. Although VAD is primarily known to cause xerophthalmia, its role in the impairment of anti-infectious defense mechanisms is less defined. Infectious diseases lead to temporary anorexia and lower dietary intake; furthermore, they adversely affect VA status by interfering with VA absorption, utilization and excretion. Thus, there is a tri-directional relationship between VAD, immune response and infections, as VAD affects immune response and predisposes the host to infection, and infection decreases the intestinal absorption of the VA, thereby contributing to secondary VAD development. This has been demonstrated using nutritional and clinical studies, radiotracer studies and knockout animal models. An in-depth understanding of the relationship between VAD, immune response, gut microbiota and infections is critical for optimizing vaccine efficacy and the development of effective immunization programs for countries with high prevalence of VAD. Therefore, in this review, we have comprehensively summarized the existing knowledge regarding VAD impacts on immune responses to infections and post vaccination. We have detailed pathological conditions associated with clinical and subclinical VAD, gut microbiome adaptation to VAD and VAD effects on the immune responses to infection and vaccines.

Reduced Retinoic Acid Receptor Beta (Rarβ) Affects Pancreatic β-Cell Physiology

Various studies have suggested a link between vitamin A (VA), all-trans-retinol, and type 2 diabetes (T2D). However, the functional role/expression of vitamin A receptors (Rarα, β, and γ) in pancreatic β-cells is not clear yet. Accordingly, we performed a series of bioinformatics, molecular and functional experiments in human islet and INS-1 cells to evaluate the role of Rarβ on insulin secretion and pancreatic β-cell function. Microarray and RNA-sequencing (RAN-seq) expression analysis showed that RARα, β, and γ are expressed in human pancreatic islets. RNA-seq expression of RARβ in diabetic/hyperglycemic human islets (HbA1c ≥ 6.3%) revealed a significant reduction (p = 0.004) compared to nondiabetic/normoglycemic cells (HbA1c < 6%). The expression of RARβ with INS and PDX1 showed inverse association, while positive correlations were observed with INSR and HbA1c levels. Exploration of the T2D knowledge portal (T2DKP) revealed that several genetic variants in RARβ are associated with BMI. The most associated variant is rs6804842 (p = 1.2 × 10−25). Silencing of Rarβ in INS-1 cells impaired insulin secretion without affecting cell viability or apoptosis. Interestingly, reactive oxygen species (ROS) production levels were elevated and glucose uptake was reduced in Rarβ-silenced cells. mRNA expression of Ins1, Pdx1, NeuroD1, Mafa, Snap25, Vamp2, and Gck were significantly (p < 0.05) downregulated in Rarβ-silenced cells. For protein levels, Pro/Insulin, PDX1, GLUT2, GCK, pAKT/AKT, and INSR expression were downregulated considerably (p < 0.05). The expression of NEUROD and VAMP2 were not affected. In conclusion, our results indicate that Rarβ is an important molecule for β-cell function. Hence, our data further support the potential role of VA receptors in the development of T2D.

All-trans retinoic acid impairs glucose-stimulated insulin secretion by activating the RXR/SREBP-1c/UCP2 pathway

Diabetes is often associated with vitamin A disorders. All-trans retinoic acid (ATRA) is the main active constituent of vitamin A. We aimed to investigate whether ATRA influences diabetic progression and its mechanisms using both Goto-Kazizazi (GK) rats and INS-1 cells. Rat experiments demonstrated that ATRA treatment worsened diabetes symptoms, as evidenced by an increase in fasting blood glucose (FBG) levels and impairment of glucose homeostasis. Importantly, ATRA impaired glucose-stimulated insulin secretion (GSIS) and increased the expression of sterol regulatory element-binding protein 1c (SREBP-1c) and uncoupling protein 2 (UCP2) in the rat pancreas. Data from INS-1 cells also showed that ATRA upregulated SREBP-1c and UCP2 expression and impaired GSIS at 23 mM glucose. Srebp-1c or Ucp2 silencing attenuated GSIS impairment by reversing the ATRA-induced increase in UCP2 expression and decrease in ATP content. ATRA and the retinoid X receptor (RXR) agonists 9-cis RA and LG100268 induced the gene expression of Srebp-1c, which was almost completely abolished by the RXR antagonist HX531. RXRα-LBD luciferase reporter plasmid experiments also demonstrated that ATRA concentration-dependently activated RXRα, the EC₅₀ of which was 1.37 μM, which was lower than the ATRA concentration in the pancreas of GK rats treated with a high dose of ATRA (approximately 3 μM), inferring that ATRA can upregulate Srebp-1c expression in the pancreas by activating RXR. In conclusion, ATRA impaired GSIS partly by activating the RXR/SREBP-1c/UCP2 pathway, thus worsening diabetic symptoms. The results highlight the roles of ATRA in diabetic progression and establish new strategies for diabetes treatment.

Adapting Physiology in Functional Human Islet Organogenesis

Generation of three-dimensional (3D)-structured functional human islets is expected to be an alternative cell source for cadaveric human islet transplantation for the treatment of insulin-dependent diabetes. Human pluripotent stem cells (hPSCs), such as human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), offer infinite resources for newly synthesized human islets. Recent advancements in hPSCs technology have enabled direct differentiation to human islet-like clusters, which can sense glucose and secrete insulin, and those islet clusters can ameliorate diabetes when transplanted into rodents or non-human primates (NHPs). However, the generated hPSC-derived human islet-like clusters are functionally immature compared with primary human islets. There remains a challenge to establish a technology to create fully functional human islets in vitro, which are functionally and transcriptionally indistinguishable from cadaveric human islets. Understanding the complex differentiation and maturation pathway is necessary to generate fully functional human islets for a tremendous supply of high-quality human islets with less batch-to-batch difference for millions of patients. In this review, I summarized the current progress in the generation of 3D-structured human islets from pluripotent stem cells and discussed the importance of adapting physiology for in vitro functional human islet organogenesis and possible improvements with environmental cues.

Relationship of Vitamin A and Thyroid Function in Individuals With Obesity and After Laparoscopic Sleeve Gastrectomy

Vitamin A deficiency (VAD) occurs in obesity and may be associated with thyroid dysfunction. We aimed to investigate the association of VA with thyroid function in obesity and after laparoscopic sleeve gastrectomy (LSG). Nine hundred and seventy-six obese subjects were enrolled for this study and were divided into VAD, marginal vitamin A deficiency (MVAD), and vitamin A normal (NVA) groups. VAD was defined as VA ≤ 200 ng/ml, MVAD was defined as VA > 200 but <300 ng/ml, and NVA was defined as VA ≥ 300 ng/ml. Thyroid function was compared among groups and the relationship of VA and thyroid function was analyzed. Two hundred and forty-four of the 976 obese subjects underwent LSG, and the change in thyroid function and VA at 3, 6, and 12 months after surgery was measured. Results showed that 37% of all the subjects had subclinical hypothyroidism (SH), and the SH group had lower VA levels than the non-SH group (P = 0.008). Forty-nine percent of all the subjects had MVAD, 9% had VAD, while the MVAD or VAD group had lower FT4 than the NVA group (P = 0.005 and P = 0.001). The VAD group also had higher TSH than NVA group (P = 0.037). VA was significantly negatively associated with TSH (r = −0.151, P = 0.006) and positively associated with FT4 (r = 0.228, P < 0.001). TSH was significantly decreased at 3, 6, and 12 months (3M: from 4.43 ± 2.70 to 2.63 ± 1.46 mU/l, P < 0.001; 6M: from 4.43 ± 2.70 to 3.84 ± 2.34 mU/l, P = 0.041; 12M: from 4.43 ± 2.70 to 2.85 ± 1.68 mU/l, P = 0.024). After LSG surgery, VA levels were slightly increased, when compared to pre-surgery levels, at 3, 6, and 12 months (3M: from 262.57 ± 68.19 to 410.33 ± 76.55 ng/ml, P = 0.065; 6M: from 262.57 ± 68.19 to 281.36 ± 93.23 ng/ml, P = 0.343; 12M: from 262.57 ± 68.19 to 300.37 ± 86.03 ng/ml, P = 0.083). SH group also had lower TSH and higher VA than the non-SH group at 3 months post-surgery [TSH: −1.4(−2.3, −0.3) vs. −0.2(−0.8, −0.2) mU/l, P < 0.001; VA: 163.99 ± 32.58 vs. 121.69 ± 27.59 ng/ml, P = 0.044]. In conclusion VA, which is related to thyroid hormone production, protects against thyroid dysfunction in obese subjects. The improvement of thyroid function in subjects with SH after LSG may be related to the increased VA levels observed post-surgery.

Retinoic Acid: Sexually Dimorphic, Anti-Insulin and Concentration-Dependent Effects on Energy

This review addresses the fasting vs. re-feeding effects of retinoic acid (RA) biosynthesis and functions, and sexually dimorphic RA actions. It also discusses other understudied topics essential for understanding RA activities-especially interactions with energy-balance-regulating hormones, including insulin and glucagon, and sex hormones. This report will introduce RA homeostasis and hormesis to provide context. Essential context also will encompass RA effects on adiposity, muscle function and pancreatic islet development and maintenance. These comments provide background for explaining interactions among insulin, glucagon and cortisol with RA homeostasis and function. One aim would clarify the often apparent RA contradictions related to pancreagenesis vs. pancreas hormone functions. The discussion also will explore the adverse effects of RA on estrogen action, in contrast to the enhancing effects of estrogen on RA action, the adverse effects of androgens on RA receptors, and the RA induction of androgen biosynthesis.

The Effect and Potential Mechanism of Maternal Micronutrient Intake on Offspring Glucose Metabolism: An Emerging Field

Diabetes has become the most common metabolic disease around the world. In addition to genetic and environmental factors in adulthood, the early life environment is critical to the progression of diabetes in adults, especially the environment during the fetal period; this concept is called “fetal programming.” Substantial evidence has illustrated the key role of early life macronutrient in programming metabolic diseases. Recently, the effect of maternal micronutrient intake on offspring glucose metabolism during later life has become an emerging field. This review focuses on updated human and animal evidence about the effect of maternal micronutrient status on offspring glucose metabolism and the underlying mechanism.

The role of vitamin A and its pro-vitamin carotenoids in fetal and neonatal programming: gaps in knowledge and metabolic pathways

Vitamin A (VA) and its pro-vitamin carotenoids are naturally occurring lipophilic compounds involved in several cellular processes and metabolic pathways. Despite their broad spectrum of activities in the general population, dietary deficiencies of these compounds can potentially affect pregnancy outcomes. Since maternal nutritional status and diet composition during pregnancy and lactation can have long-lasting effects in offspring until adulthood, this study presents an overview of VA and the role of pro-VA carotenoids during pregnancy and lactation – the nutrition, metabolism, and biological effects in the offspring. The review aimed to discuss the pro-VA carotenoids and VA-associated pathways and summarize the results with reference to gestational disorders, and VA and pro-VA carotenoids as preventive agents. Also, considering that obesity, overweight, and metabolic diseases are major public health concerns worldwide, fetal and neonatal development is discussed, highlighting the physiological role of these molecules in obesity prevention. This review comprehensively summarizes the current data and shows the potential impact of these compounds on nutritional status in pregnancy and lactation.

How Dietary Deficiency Studies Have Illuminated the Many Roles of Vitamin A During Development and Postnatal Life

Vitamin A deficiency studies have been carried out since the early 1900s. Initially, these studies led to the identification of fat soluble A as a unique and essential component of the diet of rodents, birds, and humans. Continuing work established that vitamin A deficiency produces biochemical and physiological dysfunction in almost every vertebrate organ system from conception to death. This chapter begins with a review of representative historical and current studies that used the nutritional vitamin A deficiency research model to gain an understanding of the many roles vitamin A plays in prenatal and postnatal development and well-being. This is followed by a discussion of recent studies that show specific effects of vitamin A deficiency on prenatal development and postnatal maintenance of the olfactory epithelium, brain, and heart. Vitamin A deficiency studies have helped define the necessity of vitamin A for the health of all vertebrates, including farm animals, but the breadth of deficient states and their individual effects on health have not been fully determined. Future work is needed to develop tools to assess the complete vitamin A status of an organism and to define the levels of vitamin A that optimally support molecular and systems level processes during all ages and stages of life.

Vitamin A deficiency causes islet dysfunction by inducing islet stellate cell activation via cellular retinol binding protein 1

Background: Vitamin A (VA) plays an essential role in pancreatic homeostasis. Islet stellate cells (ISCs) are VA-storing cells in pancreatic islets. Herein, we have investigated the effect of VA on glucose homeostasis trough regulation of ISCs function in dietary VA deficiency model mice. Methods: Male C57BL/6 mice were randomly fed a VA-sufficient, a VA-deficient (VAD) or a VAD-rescued diet. Glucose metabolism was assessed by glucose tolerance tests and immunohistochemistry. ISCs activation degree was evaluated by immunofluorescence, quantitative PCR and western blotting in both, retinol-treated cultured ISCs and model mice. Changes in ISCs phenotype and their effect on islets were assessed by lentiviral transduction and enzyme-linked immunosorbent assays in a co-culture system. Results: VAD mice showed irregular shaped islet, glucose intolerance, islet size distribution excursions, and upregulated expression of α-smooth muscle actin (α-SMA, marker of ISCs activation). Reintroduction of dietary VA restored pancreatic VA levels, endocrine hormone profiles, and inhibited ISCs activation. Incubation with retinol increased the expression of VA signaling factors in ISCs, including cellular retinol binding protein 1 (CRBP1). The knockdown of CRBP1 maintained the quiescent ISCs phenotype and reduced the damage of activated ISCs on islet function. Conclusions: VA deficiency reduced islet function by activating ISCs in VAD mice. Restoring ISCs quiescence via CRBP1 inhibition could reverse the impairment of islet function caused by activated ISCs exposure.

Plasma concentrations of vitamin A and E and risk of dysglycemia in first-trimester pregnant Saudi women

BACKGROUND

Existing evidence suggest that low concentrations of vitamin A and E may have a contribution to the development of diabetes complications; however, data regarding the status of vitamin A and E among individuals with prediabetes are lacking. This study aimed to examine the association of plasma concentrations of vitamin A and E with the glycemic control status among first trimester pregnant Saudi women.

METHODS

In this cross-sectional study, 1102 first trimester pregnant Saudi women were recruited from antenatal clinics. Sociodemographic and anthropometric information were collected, and laboratory analyses of blood glycated hemoglobin (A1C) and plasma vitamins A and E were performed. Subjects were classified as normoglycemic, prediabetic, or undiagnosed diabetic. Multinomial regression models adjusted for age estimated the adjusted odds ratios (aORs) and [95% confidence intervals (CIs)].

RESULTS

Among the sample, 78.8% (n = 868) had normal glycemic control, while 19.1% (n = 211) had prediabetes and 2.1% (n = 23) had undiagnosed diabetes. Plasma concentrations of vitamin A and E of prediabetic participants were at a level midway between that of normoglycemic and diabetic participants (p < 0.01). Compared to subjects with normoglycemic status, those with higher concentrations of vitamin A and E had lower odds of being prediabetic (aOR = 0.27 [0.21-0.35] and aOR = 0.95 [0.94-0.96], respectively) or diabetic (aOR = 0.18 [0.13-0.24] and aOR = 0.93 [0.92-0.94], respectively).

CONCLUSIONS

Our findings indicate a possible contribution of vitamins A and E to the progression of prediabetes to diabetes. Future longitudinal studies are needed to elucidate the association between the antioxidant status and dysglycemia. Clinicians should monitor the glycemic and the antioxidant status closely and provide dietary guidance where needed.

Low intakes of dietary fiber and magnesium are associated with insulin resistance and hyperandrogenism in polycystic ovary syndrome: A cohort study

BACKGROUND

Women with polycystic ovary syndrome (PCOS) often have insulin resistance (IR) which may be worsened by obesity. The roles of dietary intake and activity are unclear. Our objectives were to determine whether (a) high caloric intake or inactivity explains obesity in PCOS, and (b) dietary composition is associated with PCOS phenotypes.

METHODS

Eighty-seven women with PCOS and 50 women without PCOS participated in this cohort study at a reproductive medicine center. Data collected included 3-day food and physical activity records, anthropometrics, and metabolic and hormonal assays.

RESULTS

Women with PCOS had increased body mass index (BMI) but similar caloric intake and activity to women without PCOS. There were no differences in protein, carbohydrates, fat, or glycemic load consumption, but women with PCOS consumed less fiber (medians: 19.6 vs. 24.7 g) and less magnesium (medians: 238.9 vs. 273.9 mg). In women with PCOS, those with IR consumed less fiber, less magnesium, and greater glycemic load than those without IR (medians: 18.2 vs. 22.1 g, 208.4 vs. 264.5 mg, 89.6 vs. 83.5). Fiber intake of women with PCOS was negatively correlated with IR, fasting insulin, glucose tolerance, testosterone, and dehydroepiandrosterone sulfate. Magnesium intake was negatively correlated with IR, C-reactive protein, and testosterone, but positively correlated with HDL cholesterol. Fiber intake and BMI accounted for 54.0% of the variance observed in IR.

CONCLUSIONS

Obesity in women with PCOS could not be explained by overeating or inactivity. Increasing dietary fiber and magnesium intakes may assist in reducing IR and hyperandrogenemia in women with PCOS.

Vitamin A and Pregnancy: A Narrative Review

Vitamin A is a crucial micronutrient for pregnant women and their fetuses. In addition to being essential for morphological and functional development and for ocular integrity, vitamin A exerts systemic effects on several fetal organs and on the fetal skeleton. Vitamin A requirements during pregnancy are therefore greater. Vitamin A deficiency (VAD) remains the leading cause of preventable blindness in the world. VAD in pregnant women is a public health issue in most developing countries. In contrast, in some developed countries, excessive vitamin A intake during pregnancy can be a concern since, when in excess, this micronutrient may exert teratogenic effects in the first 60 days following conception. Routine prenatal vitamin A supplementation for the prevention of maternal and infant morbidity and mortality is not recommended; however, in regions where VAD is a public health issue, vitamin A supplementation is recommended to prevent night blindness. Given the importance of this topic and the lack of a complete, up-to-date review on vitamin A and pregnancy, an extensive review of the literature was conducted to identify conflicting or incomplete data on the topic as well as any gaps in existing data.

Pancreatic Stellate Cells: A Rising Translational Physiology Star as a Potential Stem Cell Type for Beta Cell Neogenesis

The progressive decline and eventual loss of islet β-cell function underlies the pathophysiological mechanism of the development of both type 1 and type 2 diabetes mellitus. The recovery of functional β-cells is an important strategy for the prevention and treatment of diabetes. Based on similarities in developmental biology and anatomy, in vivo induction of differentiation of other types of pancreatic cells into β-cells is a promising avenue for future diabetes treatment. Pancreatic stellate cells (PSCs), which have attracted intense research interest due to their effects on tissue fibrosis over the last decade, express multiple stem cell markers and can differentiate into various cell types. In particular, PSCs can successfully differentiate into insulin- secreting cells in vitro and can contribute to tissue regeneration. In this article, we will brings together the main concepts of the translational physiology potential of PSCs that have emerged from work in the field and discuss possible ways to develop the future renewable source for clinical treatment of pancreatic diseases.

Nutritional Health Considerations for Persons with Spinal Cord Injury

Chronic spinal cord injury (SCI) often results in morbidity and mortality due to all-cause cardiovascular disease (CVD) and comorbid endocrine disorders. Several component risk factors for CVD, described as the cardiometabolic syndrome (CMS), are prevalent in SCI, with the individual risks of obesity and insulin resistance known to advance the disease prognosis to a greater extent than other established risks. Notably, adiposity and insulin resistance are attributed in large part to a commonly observed maladaptive dietary/nutritional profile. Although there are no evidence-based nutritional guidelines to address the CMS risk in SCI, contemporary treatment strategies advocate more comprehensive lifestyle management that includes sustained nutritional guidance as a necessary component for overall health management. This monograph describes factors in SCI that contribute to CMS risks, the current nutritional profile and its contribution to CMS risks, and effective treatment strategies including the adaptability of the Diabetes Prevention Program (DPP) to SCI. Establishing appropriate nutritional guidelines and recommendations will play an important role in addressing the CMS risks in SCI and preserving optimal long-term health.

Effects of Biotin Supplementation During the First Week Postweaning Increases Pancreatic Islet Area, Beta-Cell Proportion, Islets Number, and Beta-Cell Proliferation

During maturation, pancreatic islets achieve their full capacity to secrete insulin in response to glucose, undergo morphological changes in which alpha-cells decrease and beta-cell mass increases, and they acquire the normal alpha- and beta-cell proportion changes that are important for islet functions later in life. In rodents, the first week of postweaning is critical for islet maturation. Multiple studies have documented the detrimental effects of several conditions on pancreatic maturation; however, few studies have addressed the use of pharmacological agents to enhance islet maturation. Biotin might have a potential action on islet maturation. Pharmacological concentrations of biotin have been found to modify islet morphology and function. In a previous study, we found that mice fed a biotin-supplemented diet for 8 weeks after weaning showed an increase in basal and glucose stimulated insulin secretion, enlarged islet size, and modified islet structure. In the present study, we investigated the effect of biotin on maturation features during the first week postweaning. Female BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet for 1 week after weaning. Compared with the control, biotin-supplemented mice showed an increase in pancreatic islet number and area in addition to an augmented proportion of beta-cells in the islet. These effects were related to an increase in beta-cell proliferation. No differences were found in insulin secretion, blood glucose concentrations, or serum insulin levels. These results indicate that biotin supplementation is capable of affecting beta-cell proliferation and might be a therapeutic agent for establishing strategies for regenerative medicine.

Interleukin-33-Activated Islet-Resident Innate Lymphoid Cells Promote Insulin Secretion through Myeloid Cell Retinoic Acid Production

Pancreatic-islet inflammation contributes to the failure of β cell insulin secretion during obesity and type 2 diabetes. However, little is known about the nature and function of resident immune cells in this context or in homeostasis. Here we show that interleukin (IL)-33 was produced by islet mesenchymal cells and enhanced by a diabetes milieu (glucose, IL-1β, and palmitate). IL-33 promoted β cell function through islet-resident group 2 innate lymphoid cells (ILC2s) that elicited retinoic acid (RA)-producing capacities in macrophages and dendritic cells via the secretion of IL-13 and colony-stimulating factor 2. In turn, local RA signaled to the β cells to increase insulin secretion. This IL-33-ILC2 axis was activated after acute β cell stress but was defective during chronic obesity. Accordingly, IL-33 injections rescued islet function in obese mice. Our findings provide evidence that an immunometabolic crosstalk between islet-derived IL-33, ILC2s, and myeloid cells fosters insulin secretion.

Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate

Consistent evidence from both experimental and human studies indicates that Type 2 diabetes mellitus (T2DM) is a complex disease resulting from the interaction of genetic, epigenetic, environmental, and lifestyle factors. Nutrients and dietary patterns are important environmental factors to consider in the prevention, development and treatment of this disease. Nutritional genomics focuses on the interaction between bioactive food components and the genome and includes studies of nutrigenetics, nutrigenomics and epigenetic modifications caused by nutrients. There is evidence supporting the existence of nutrient-gene and T2DM interactions coming from animal studies and family-based intervention studies. Moreover, many case-control, cohort, cross-sectional cohort studies and clinical trials have identified relationships between individual genetic load, diet and T2DM. Some of these studies were on a large scale. In addition, studies with animal models and human observational studies, in different countries over periods of time, support a causative relationship between adverse nutritional conditions during in utero development, persistent epigenetic changes and T2DM. This review provides comprehensive information on the current state of nutrient-gene interactions and their role in T2DM pathogenesis, the relationship between individual genetic load and diet, and the importance of epigenetic factors in influencing gene expression and defining the individual risk of T2DM.

Anti-diabetic action of all-trans retinoic acid and the orphan G protein coupled receptor GPRC5C in pancreatic β-cells

Pancreatic islets express high levels of the orphan G-protein coupled receptor C5C (GPRC5C), the function of which remains to be established. Here we have examined the role of GPRC5C in the regulation of insulin secretion and β-cell survival and proliferation using human and mouse pancreatic islets. The expression of GPRC5C was analysed by RNA-sequencing, qPCR, western blotting and confocal microscopy. Insulin secretion and cell viability were determined by RIA and MTS assays, respectively. GPRC5C mRNA expression and protein level were reduced in the islets from type-2 diabetic donors. RNA sequencing in human islets revealed GPRC5C expression correlated with the expression of genes controlling apoptosis, cell survival and proliferation. A reduction in Gprc5c mRNA and protein expression was observed in islets isolated from old mice (>46 weeks of age) compared to that in islets from newborn (<3 weeks) mice. Down-regulation of Gprc5c led to both moderately reduced glucose-stimulated insulin release and also reduced cAMP content in mouse islets. Potentiation of glucose-stimulated insulin secretion concomitant with enhanced islet cAMP level by all-trans retinoic acid (ATRA) was attenuated upon Gprc5c-KD. ATRA also increased [Ca⁺²]_i in Huh7-cells. Gprc5c over expression in Huh7 cells was associated with increased ERK1/2 activity. Gprc5c-KD in clonal MIN6c4 cells reduced cell proliferation and in murine islets increased apoptosis and the sensitivity of primary islet cells to a cocktail of pro-apoptotic cytokines. Our results demonstrate that agents activating GPRC5C represent a novel modality for the treatment and/or prevention of diabetes by restoring and/or maintaining functional β-cell mass.

A retrospective analysis of a societal experiment among the Danish population suggests that exposure to extra doses of vitamin A during fetal development may lower type 2 diabetes mellitus (T2DM) risk later in life

Vitamin A deficiency has been associated with impaired fetal pancreatic development and increased risk of developing type 2 diabetes mellitus (T2DM). In 1962, mandatory margarine fortification with vitamin A was increased by 25 % in Denmark. We aimed to determine whether offspring of mothers who had been exposed to the extra vitamin A from fortification during pregnancy had a lower risk of developing T2DM in adult life, compared with offspring of mothers exposed to less vitamin A. Individuals from birth cohorts with the higher prenatal vitamin A exposure (born 1 December 1962-31 March 1964) and those with lower prenatal exposure (born 1 September 1959-31 December 1960) were followed up with regard to development of T2DM before 31 December 2012 in the Danish National Diabetes Registry and National Patient Register. Logistic and Cox regression analyses were performed to determine the risk of T2DM by vitamin A exposure level. A total of 193 803 individuals were followed up until midlife. Our results showed that individuals exposed prenatally to extra vitamin A from fortified margarine had a lower risk of developing T2DM than those exposed to lower levels: OR 0·88; 95 % CI 0·81, 0·95, P=0·001, after adjustment for sex. Fetal exposure to small, extra amounts of vitamin A from food fortification may reduce the risk of T2DM. These results may have public health relevance, as they demonstrate that one of the most costly chronic diseases may be prevented by food fortification - a simple and affordable public health nutrition intervention.

Retinol Dehydrogenase-10 Regulates Pancreas Organogenesis and Endocrine Cell Differentiation via Paracrine Retinoic Acid Signaling

Vitamin A-derived retinoic acid (RA) signals are critical for the development of several organs, including the pancreas. However, the tissue-specific control of RA synthesis in organ and cell lineage development has only poorly been addressed in vivo. Here, we show that retinol dehydrogenase-10 (Rdh10), a key enzyme in embryonic RA production, has important functions in pancreas organogenesis and endocrine cell differentiation. Rdh10 was expressed in the developing pancreas epithelium and surrounding mesenchyme. Rdh10 null mutant mouse embryos exhibited dorsal pancreas agenesis and a hypoplastic ventral pancreas with retarded tubulogenesis and branching. Conditional disruption of Rdh10 from the endoderm caused increased mortality, reduced body weight, and lowered blood glucose levels after birth. Endodermal Rdh10 deficiency led to a smaller dorsal pancreas with a reduced density of early glucagon⁺ and insulin⁺ cells. During the secondary transition, the reduction of Neurogenin3⁺ endocrine progenitors in the mutant dorsal pancreas accounted for fewer α- and β-cells. Changes in the expression of α- and β-cell-specific transcription factors indicated that Rdh10 might also participate in the terminal differentiation of endocrine cells. Together, our results highlight the importance of both mesenchymal and epithelial Rdh10 for pancreogenesis and the first wave of endocrine cell differentiation. We further propose a model in which the Rdh10-expressing exocrine tissue acts as an essential source of RA signals in the second wave of endocrine cell differentiation.

Epigenetic disruption and glucose homeostasis changes following low-dose maternal bisphenol A exposure

Developmental exposure to bisphenol A (BPA) has been linked to impaired glucose homeostasis and pancreatic function in adulthood, which has been hypothesized to result from the disruption of pancreatic β-cell development at early life. Here we evaluated whether maternal BPA exposure disrupts β-cell development and glucose tolerance and the role of epigenetic modifications of key regulator in this process. We found that maternal exposure to BPA (10 μg kg-1 d-1) reduced the pancreatic β-cell mass and the expression of pancreatic and duodenal homeobox 1 (Pdx1) at birth, as well as the expression of Pdx1 at gestational day (GD) 15.5. In parallel with the decreased expression of Pdx1, histones H3 and H4 deacetylation, along with demethylation of histone 3 lysine 4 (H3K4) and methylation of histone 3 lysine 9 (H3K9), were found at the promoter of Pdx1, while no significant changes in DNA methylation status were detected at this region. Moreover, these alterations were observed in adult life along with impaired glucose tolerance. We conclude that maternal exposure to BPA reduces pancreatic β-cell mass at birth by reducing PDX1+ progenitors during fetal development through altering the histone modifications of Pdx1, which can be propagated to later life and increase the susceptibility to glucose intolerance.

Beta Cell Function and the Nutritional State: Dietary Factors that Influence Insulin Secretion

Approximately 366 million people worldwide have been diagnosed with type-2 diabetes (T2D). Chronic insulin resistance, decreased functional β-cell mass, and elevated blood glucose are defining characteristics of T2D. Great advances have been made in understanding the pathogenesis of T2D with respect to the effects of dietary macronutrient composition and energy intake on β-cell physiology and glucose homeostasis. It has been further established that obesity is a leading pathogenic factor for developing insulin resistance. However, insulin resistance may not progress to T2D unless β-cells are unable to secret an adequate amount of insulin to compensate for decreased insulin sensitivity. Therefore, pancreatic β-cell dysfunction plays an important role in the development of overt diabetes. This paper reviews recent research findings on the effects of several micronutrients (zinc, vitamin D, iron, vitamin A), leucine, and the phytochemical, genistein on pancreatic β-cell physiology with emphasis on their effects on insulin secretion, specifically in the context of T2D.

Vitamin A: a missing link in diabetes?

Vitamin A has a critical role in embryonic development, immunity and the visual cycle. In recent years, evidence has demonstrated that vitamin A can also regulate metabolic pathways implicated in the pathogenesis of obesity and diabetes. This has increased interest in the possible antiobesity and antidiabetic properties of natural and synthetic vitamin A derivatives. However, whether vitamin A deficiency or aberrations in vitamin A metabolism contribute to the pathogenesis of diabetes is not known. This perspective article will review what is currently known and new data regarding the link between vitamin A and the clinical manifestations of common and atypical forms of diabetes.

Plasma concentrations of retinol in obese children and adolescents: relationship to metabolic syndrome components

Objective:

To evaluate obese children and adolescents' retinol plasma levels and to correlate them with metabolic syndrome components.

Methods:

Cross-sectional study with 61 obese children and adolescents (body mass index Z score - ZBMI>+2). Pubertal development, arterial blood pressure, body weight and height for nutritional classification and waist circumference were obtained. A 15mL blood sample was collected (after a 12-hour fasting in a low luminosity room) for retinol determination (cut-off inadequate if <30µg/dL), lipid profile (HDL-c, LDL-c, and triglycerides), oral glucose tolerance test (fasting and 120 minutes) and for high sensitivity C-reactive protein. Spearman correlation and multiple linear regression were used in the statistical analysis.

Results:

Mean age was 10.7±2.7 years. There was a predominance of male gender 38/61 (62%) and pre-pubertal 35/61 (57%) subjects. The average plasmatic retinol was 48.5±18.6ug/dL. Retinol deficiency and severe obesity were observed in 6/61 (10%) and 36/61 (59%), respectively. Glucose level at 120 minutes was the independent and predictive variable of plasma retinol levels [β=-0.286 (95%CI -0.013 - -0.001)].

Conclusions:

An independent and inverse association between plasma retinol levels and glucose tolerance was observed, suggesting an important contribution of this vitamin in the morbidities associated to obesity in children and adolescents.

Retinoic acid receptor signaling is required to maintain glucose-stimulated insulin secretion and β-cell mass

Retinoic acid signaling is required for maintaining a range of cellular processes, including cell differentiation, proliferation, and apoptosis. We investigated the actions of all-trans-retinoic acid (atRA) signaling in pancreatic β-cells of adult mice. atRA signaling was ablated in β-cells by overexpressing a dominant-negative retinoic acid receptor (RAR)-α mutant (RARdn) using an inducible Cre-Lox system under the control of the pancreas duodenal homeobox gene promoter. Our studies establish that hypomorphism for RAR in β-cells leads to an age-dependent decrease in plasma insulin in the fed state and in response to a glucose challenge. Glucose-stimulated insulin secretion was also impaired in islets isolated from mice expressing RARdn. Among genes that are atRA responsive, Glut2 and Gck mRNA levels were decreased in isolated islets from RARdn-expressing mice. Histologic analyses of RARdn-expressing pancreata revealed a decrease in β-cell mass and insulin per β-cell 1 mo after induction of the RARdn. Our results indicate that atRA signaling mediated by RARs is required in the adult pancreas for maintaining both β-cell function and mass, and provide insights into molecular mechanisms underlying these actions.

Vitamin A deficiency causes hyperglycemia and loss of pancreatic β-cell mass

We show that vitamin A (all-trans-retinol) (VA) is required both for the maintenance of pancreatic β-cell and α-cell mass and for glucose-stimulated insulin secretion in adult mice. Dietary VA deprivation (VAD) causes greatly decreased pancreatic VA levels, hyperglycemia, and reduced insulin secretion. Adult mice fed VAD diets display remodeling of the endocrine pancreas, marked β-cell apoptosis, shifts to smaller islet size distributions, decreased β-cell mass, increased α-cell mass, and hyperglucagonemia. Importantly, although we induced VAD in the entire animal, the pancreatic β-cells are exquisitely sensitive to VAD-associated apoptosis compared with other cell types in other organs. VAD causes major reductions in levels of the VA intracellular binding protein Crbp1 and the retinoic acid-metabolizing enzyme Cyp26a1 specifically in larger islets, suggesting the use of these proteins as biomarkers for early endocrine mass abnormalities. In the VAD mice, the reductions in pancreatic islet sizes and the associated aberrant endocrine functions, which show similarities to the phenotype in advanced type 2 diabetes, result from reductions in pancreatic VA signaling. Reintroduction of dietary VA to VAD mice restores pancreatic VA levels, glycemic control, normal islet size distributions, β-cell to α-cell ratios, endocrine hormone profiles, and RARβ2 and RARγ2 transcript levels. Restoration of β-cell mass by reintroducing VA to VAD mice does not involve increased β-cell proliferation or neogenesis. Pharmacologic modulation of pancreatic VA signaling should be explored for the preservation and/or restoration of pancreatic β-cell mass and function in individuals with diabetes mellitus.

Retinoic acid receptor signaling is required to maintain glucose-stimulated insulin secretion and β-cell mass

Retinoic acid signaling is required for maintaining a range of cellular processes, including cell differentiation, proliferation, and apoptosis. We investigated the actions of all-trans-retinoic acid (atRA) signaling in pancreatic β-cells of adult mice. atRA signaling was ablated in β-cells by overexpressing a dominant-negative retinoic acid receptor (RAR)-α mutant (RARdn) using an inducible Cre-Lox system under the control of the pancreas duodenal homeobox gene promoter. Our studies establish that hypomorphism for RAR in β-cells leads to an age-dependent decrease in plasma insulin in the fed state and in response to a glucose challenge. Glucose-stimulated insulin secretion was also impaired in islets isolated from mice expressing RARdn. Among genes that are atRA responsive, Glut2 and Gck mRNA levels were decreased in isolated islets from RARdn-expressing mice. Histologic analyses of RARdn-expressing pancreata revealed a decrease in β-cell mass and insulin per β-cell 1 mo after induction of the RARdn. Our results indicate that atRA signaling mediated by RARs is required in the adult pancreas for maintaining both β-cell function and mass, and provide insights into molecular mechanisms underlying these actions.

Intrauterine nutrition: long-term consequences for vascular health

There is a growing body of evidence that improper intrauterine nutrition may negatively influence vascular health in later life. Maternal malnutrition may result in intrauterine growth retardation and, in turn, metabolic disorders such as insulin resistance, diabetes, hypertension, and dyslipidemia, and also enhanced risk of atherosclerosis and cardiovascular death in the offspring. Energy and/or protein restriction is the most critical determinant for fetal programming. However, it has also been proposed that intrauterine n-3 fatty acid deficiency may be linked to later higher blood pressure levels and reduced insulin sensitivity. Moreover, it has been shown that inadequate supply of micronutrients such as folate, vitamin B12, vitamin A, iron, magnesium, zinc, and calcium may contribute to impaired vascular health in the progeny. In addition, hypertensive disorders of pregnancy that are linked to impaired placental blood flow and suboptimal fetal nutrition may also contribute to intrauterine growth retardation and aggravated cardiovascular risk in the offspring. On the other hand, maternal overnutrition, which often contributes to obesity and/or diabetes, may result in macrosomia and enhanced cardiometabolic risk in the offspring. Progeny of obese and/or diabetic mothers are relatively more prone to develop obesity, insulin resistance, diabetes, and hypertension. It was demonstrated that they may have permanently enhanced appetites. Their atheromatous lesions are usually more pronounced. It seems that, particularly, a maternal high-fat/junk food diet may be detrimental for vascular health in the offspring. Fetal exposure to excessive levels of saturated fatty and/or n-6 fatty acids, sucrose, fructose and salt, as well as a maternal high glycemic index diet, may also contribute to later enhanced cardiometabolic risk.

Role of bioactive food components in diabetes prevention: effects on Beta-cell function and preservation

Bioactive compounds found in fruits and vegetables can have anti-oxidant, anti-inflammatory, and anti-carcinogenic effects and can be protective against various diseases and metabolic disorders. These beneficial effects make them good candidates for the development of new functional foods with potential protective and preventive properties for type 1 and type 2 diabetes. This review summarizes the most relevant results concerning the effects of various bioactive compounds such as flavonoids, vitamins, and carotenoids on several aspects of beta-cell functionality. Studies using animal models with induced diabetes and diabetic patients support the hypothesis that bioactive compounds could ameliorate diabetic phenotypes. Published data suggest that there might be direct effects of bioactive compounds on enhancing insulin secretion and preventing beta-cell apoptosis, and some compounds might modulate beta-cell proliferation. Further research is needed to establish any clinical effects of these compounds.

The Roles of Vitamin A in the Regulation of Carbohydrate, Lipid, and Protein Metabolism

Currently, two-thirds of American adults are overweight or obese. This high prevalence of overweight/obesity negatively affects the health of the population, as obese individuals tend to develop several chronic diseases, such as type 2 diabetes and cardiovascular diseases. Due to obesity's impact on health, medical costs, and longevity, the rise in the number of obese people has become a public health concern. Both genetic and environmental/dietary factors play a role in the development of metabolic diseases. Intuitively, it seems to be obvious to link over-nutrition to the development of obesity and other metabolic diseases. However, the underlying mechanisms are still unclear. Dietary nutrients not only provide energy derived from macronutrients, but also factors such as micronutrients with regulatory roles. How micronutrients, such as vitamin A (VA; retinol), regulate macronutrient homeostasis is still an ongoing research topic. As an essential micronutrient, VA plays a key role in the general health of an individual. This review summarizes recent research progress regarding VA's role in carbohydrate, lipid, and protein metabolism. Due to the large amount of information regarding VA functions, this review focusses on metabolism in metabolic active organs and tissues. Additionally, some perspectives for future studies will be provided.

The expression of Apoc3 mRNA is regulated by HNF4α and COUP-TFII, but not acute retinoid treatments, in primary rat hepatocytes and hepatoma cells

Vitamin A status regulates obesity development, hyperlipidemia, and hepatic lipogenic gene expression in Zucker fatty (ZF) rats. The development of hyperlipidemia in acne patients treated with retinoic acid (RA) has been attributed to the induction of apolipoprotein C-III expression. To understand the role of retinoids in the development of hyperlipidemia in ZF rats, the expression levels of several selected RA-responsive genes in the liver and isolated hepatocytes from Zucker lean (ZL) and ZF rats were compared using real-time PCR. The Rarb and Srebp-1c mRNA levels are higher in the liver and isolated hepatocytes from ZF than ZL rats. The Apoc3 mRNA level is only higher in the isolated hepatocytes from ZF than ZL rats. To determine whether dynamic RA production acutely regulates Apoc3 expression, its mRNA levels in response to retinoid treatments or adenovirus-mediated overexpression of hepatocyte nuclear factor 4 alpha (HNF4α) and chicken ovalbumin upstream-transcription factor II (COUP-TFII) were analyzed. Retinoid treatments for 2-6 h did not induce the expression of Apoc3 mRNA. The overexpression of HNF4α or COUP-TFII induced or inhibited Apoc3 expression, respectively. We conclude that short-term retinoid treatments could not induce Apoc3 mRNA expression, which is regulated by HNF4α and COUP-TFII in hepatocytes.

Metabolic syndrome: role of maternal undernutrition and fetal programming

Development of metabolic syndrome is attributed to genes, dietary intake, physical activity and environmental factors. Fetal programming due to maternal nutrition is also an important factor especially in developing countries where intrauterine growth retardation followed by excess nutrition postnatally is causing mismatch predisposing individuals to development of metabolic syndrome and its components. Several epidemiological and animal studies have provided evidence for the link between intrauterine growth retardation and adult metabolic diseases. Deficiency of macronutrients, protein and carbohydrates, during pregnancy and gestation results in lower infant birth weight, a surrogate marker of fetal growth and subsequently insulin resistance, glucose intolerance, hypertension and adiposity in adulthood. The role of micronutrients is less extensively studied but however gaining attention with several recent studies focusing on this aspect. Several mechanisms have been proposed to explain the developmental origin of adult diseases important among them being alteration of hypothalamic pituitary axis, epigenetic regulation of gene expression and oxidative stress. All of these mechanisms may be acting at different time during gestation and contributing to development of metabolic syndrome in adulthood.

Deletion of retinoic acid receptor β (RARβ) impairs pancreatic endocrine differentiation

All-trans retinoic acid (RA) signals via binding to retinoic acid receptors (RARs α, β, and γ). RA directly influences expression of Pdx1, a transcription factor essential for pancreatic development and beta-cell (β-cell) maturation. In this study we follow the differentiation of cultured wild-type (WT) vs. RARβ knockout (KO) embryonic stem (ES) cells into pancreatic islet cells. We found that RARβ KO ES cells show greatly reduced expression of some important endocrine markers of differentiated islet cells, such as glucagon, islet amyloid polypeptide (Iapp), and insulin 1 (Ins1) relative to WT. We conclude that RARβ activity is essential for proper differentiation of ES cells to pancreatic endocrine cells.

Evidence-based and heuristic approaches for customization of care in cardiometabolic syndrome after spinal cord injury

Component and coalesced health risks of the cardiometabolic syndrome (CMS) are commonly reported in persons with spinal cord injuries (SCIs). These CMS hazards are also co-morbid with physical deconditioning and elevated pro-atherogenic inflammatory cytokines, both of which are common after SCI and worsen the prognosis for all-cause cardiovascular disease. This article describes a systematic procedure for individualized CMS risk assessment after SCI, and emphasizes evidence-based and intuition-centered countermeasures to disease. A unified approach will propose therapeutic lifestyle intervention as a routine plan for aggressive primary prevention in this risk-susceptible population. Customization of dietary and exercise plans then follow, identifying shortfalls in diet and activity patterns, and ways in which these healthy lifestyles can be more substantially embraced by both stakeholders with SCI and their health care providers. In cases where lifestyle intervention utilizing diet and exercise is unsuccessful in countering risks, available pharmacotherapies and a preferred therapeutic agent are proposed according to authoritative standards. The over-arching purpose of the monograph is to create an operational framework in which existing evidence-based approaches or heuristic modeling becomes best practice. In this way persons with SCI can lead more active and healthy lives.

Roles of vitamin A status and retinoids in glucose and fatty acid metabolism

The rising prevalence of metabolic diseases, such as obesity and diabetes, has become a public health concern. Vitamin A (VA, retinol) is an essential micronutrient for a variety of physiological processes, such as tissue differentiation, immunity, and vision. However, its role in glucose and lipid metabolism has not been clearly defined. VA activities are mediated by the metabolite of retinol catabolism, retinoic acid, which activates the retinoic acid receptor and retinoid X receptor (RXR). Since RXR is an obligate heterodimeric partner for many nuclear receptors involved in metabolism, it is reasonable to assume that VA status and retinoids contribute to glucose and lipid homeostasis. To date, the impacts of VA and retinoids on energy metabolism in animals and humans have been demonstrated in some basic and clinical investigations. This review summarizes the effects of VA status and retinoid treatments on metabolism of the liver, adipocytes, pancreatic β-cells, and skeletal muscle. It proposes a mechanism by which the dietary and hormonal signals converge on the promoter of sterol regulatory element-binding protein 1c gene to induce its expression, and in turn, the expression of lipogenic genes in hepatocytes. Future research projects relevant to the VA's roles in metabolic diseases are also discussed.

Relation between glucose levels, high-sensitivity C-reactive protein (hs-CRP), body mass index (BMI) and serum and dietary retinol in elderly in population-based study

The aim of this study was to evaluate the relationships between fasting glucose levels, hs-CRP, BMI and serum retinol and diet in elderly people. For this study, a cross-sectional, epidemiological, population-based format was adopted. One hundred and sixty-three individuals between 60 and 90 years of age participated; the participants were from different socioeconomic and health backgrounds, except for the individuals diagnosed with diabetes. Most subjects had serum concentrations in the reference ranges for all variables. There was not a significant relationship between fasting glucose and serum retinol or diet. There was a significant correlation between hs-CRP and BMI (r=0.22, p=0.0082) and hs-CRP and total calorie intake (p=0.0091), which reinforces the notion that an increased intake of calories results in being overweight and/or obese. Considering the importance of vitamin A in various physiological processes, more studies on these relationships are necessary to establish a recommendation of vitamin A for the treatment and prevention of changes in fasting glucose and obesity in the elderly population.

The Roles of PPARs in the Fetal Origins of Metabolic Health and Disease

Beyond the short-term effects on fertility, there is increasing evidence that obesity or the consumption of an inappropriate diet by the mother during pregnancy adversely affects the long-term health of her offspring. PPAR and RXR isotypes are widely expressed in reproductive tissues and in the developing fetus. Through their interactions with fatty acids, they may mediate adaptive responses to the changes in the maternal diet. In the maturing follicle, PPAR-γ has an important role in the granulosa cells that surround the maturing oocyte. After fertilisation, PPAR-γ and PPAR-β/δ are essential regulators of placentation and the subsequent development of key metabolic tissues such as skeletal muscle and adipose cells. Activation of PPAR-γ and PPAR-β/δ during fetal development has the potential to modify the growth and development of these tissues. PPAR-α is expressed at low levels in the fetal liver, however, this expression may be important, as changes in the methylation of DNA in its promoter region are reported to take place during this period of development. This epigenetic modification then programmes subsequent expression. These findings suggest that two separate PPAR-dependent mechanisms may be involved in the fetal adaptations to the maternal diet, one, mediated by PPAR-γ and PPAR-β/δ, regulating cell growth and differentiation; and another adapting long-term lipid metabolism via epigenetic changes in PPAR-α to optimise postnatal survival.

Identification of 9-cis-retinoic acid as a pancreas-specific autacoid that attenuates glucose-stimulated insulin secretion

The all-trans-retinoic acid (atRA) isomer, 9-cis-retinoic acid (9cRA), activates retinoic acid receptors (RARs) and retinoid X receptors (RXRs) in vitro. RARs control multiple genes, whereas RXRs serve as partners for RARs and other nuclear receptors that regulate metabolism. Physiological function has not been determined for 9cRA, because it has not been detected in serum or multiple tissues with analytically validated assays. Here, we identify 9cRA in mouse pancreas by liquid chromatography/tandem mass spectrometry (LC/MS/MS), and show that 9cRA decreases with feeding and after glucose dosing and varies inversely with serum insulin. 9cRA reduces glucose-stimulated insulin secretion (GSIS) in mouse islets and in the rat β-cell line 832/13 within 15 min by reducing glucose transporter type 2 (Glut2) and glucokinase (GK) activities. 9cRA also reduces Pdx-1 and HNF4α mRNA expression, ∼8- and 80-fold, respectively: defects in Pdx-1 or HNF4α cause maturity onset diabetes of the young (MODY4 and 1, respectively), as does a defective GK gene (MODY2). Pancreas β-cells generate 9cRA, and mouse models of reduced β-cell number, heterozygous Akita mice, and streptozotocin-treated mice have reduced 9cRA. 9cRA is abnormally high in glucose-intolerant mice, which have β-cell hypertropy, including mice with diet-induced obesity (DIO) and ob/ob and db/db mice. These data establish 9cRA as a pancreas-specific autacoid with multiple mechanisms of action and provide unique insight into GSIS.

Effects of combination of zinc and vitamin A supplementation on serum fasting blood sugar, insulin, apoprotein B and apoprotein A-I in patients with type I diabetes

BACKGROUND AND AIM

There is accumulating evidence that shows the metabolism of zinc and vitamin A are altered in diabetes mellitus type I (DMTI), thus the present study was conducted to evaluate the effects of combination of zinc and vitamin A supplementation on serum fasting blood sugar (FBS), insulin, apoprotein B and apoprotein A-I in patients with DMTI.

DESIGN

Forty-eight, 7-year-old to 20-year-old patients with at least 2 years of DMTI history, without any metabolic condition or medicine intake with insulin treatment, participated in a randomized double-blind clinical trial for 12 weeks. They were divided into zinc and vitamin A (VAZ)-supplemented (10 mg elemental zinc per day and one-half of a 25,000 IU vitamin A tablet every other day) and/or placebo groups after matching for sex, age and DMTI duration. Nutrient intake was estimated using 24 h recall and was analyzed by food processor program. Serum apoproteins B and A-I, FBS and insulin levels were determined at the beginning and end of the trial.

RESULTS

There was significant increase in apoprotein A-I (P < 0.0001) and a significant decrease in apoprotein B (P < 0.0001) and apoprotein B/apoprotein A-I ratio (P < 0.0001) at the end of the study compared with baseline values in the VAZ group but apoprotein A-I had a significant increase (P < 0.0001) and the apoprotein B/apoprotein A-I ratio had a significant decrease (P = 0.02) at the end of study in the VAZ group compared with the control group

CONCLUSION

It seems that combined zinc and vitamin A supplementation can improve serum apoprotein A-I, apoprotein B and the apoprotein B/apoprotein A-I ratio in patients with DMTI.

Maternal micronutrient deficiency, fetal development, and the risk of chronic disease

Early life nutritional exposures, combined with changes in lifestyle in adult life, can result in increased risk of chronic diseases. Although much of the focus on the developmental origins of disease has been on birth size and growth in postnatal life and the availability of energy and protein during these critical developmental periods, micronutrient deficiencies may also play an important role in fetal growth and development. Micronutrient status in fetal and early life may alter metabolism, vasculature, and organ growth and function, leading to increased risk of cardiometabolic disorders, adiposity, altered kidney function, and, ultimately, to type 2 diabetes and cardiovascular diseases. This review elucidates pathways through which micronutrient deficiencies lead to developmental impairment and describes the research to date on the evidence that micronutrient deficiencies in utero influence the development of chronic disease risk. Animal studies, observational human studies examining maternal diet or micronutrient status, and limited data from intervention studies are reviewed. Where data are lacking, plausible mechanisms and pathways of action have been derived from the existing animal and in vitro models. This review fills a critical gap in the literature related to the seminal role of micronutrients in early life and extends the discussion on the developmental origins of health and disease beyond birth size and energy and protein deficiency.

High-dose dietary supplementation of vitamin A induces brain-derived neurotrophic factor and nerve growth factor production in mice with simultaneous deficiency of vitamin A and zinc

Marginal vitamin A and zinc (Zn) deficiency often co-exist in many populations. Vitamin A plays a trophic role in brain and is important for its development. We investigated effects of dietary supplementation of vitamin A on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) production in mice depleted for vitamin A and Zn. After 3 months' feeding with a low vitamin A and Zn (LVA-LZ) diet, mice were divided into two groups and replenished with either normal or high vitamin A with low Zn diet for an additional 2 months. Levels of BDNF and NGF were measured from extracts of hippocampus, cortex and cerebellum at the end of the third and fifth months. The LVA-LZ group tended to show decreased amounts of the BDNF and NGF, while animals supplemented with high vitamin A along with Zn deficiency had high BDNF and NGF concentrations. From these results, we conclude that vitamin A may increase BDNF and NGF levels.