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

Physiological Basis for Using Vitamin D to Improve Health

Vitamin D is essential for life-its sufficiency improves metabolism, hormonal release, immune functions, and maintaining health. Vitamin D deficiency increases the vulnerability and severity of type 2 diabetes, metabolic syndrome, cancer, obesity, and infections. The active enzyme that generates vitamin D [calcitriol: 1,25(OH)2D], CYP27B1 (1α-hydoxylase), and its receptors (VDRs) are distributed ubiquitously in cells. Once calcitriol binds with VDRs, the complexes are translocated to the nucleus and interact with responsive elements, up- or down-regulating the expression of over 1200 genes and modulating metabolic and physiological functions. Administration of vitamin D3 or correct metabolites at proper doses and frequency for longer periods would achieve the intended benefits. While various tissues have different thresholds for 25(OH)D concentrations, levels above 50 ng/mL are necessary to mitigate conditions such as infections/sepsis, cancer, and reduce premature deaths. Cholecalciferol (D3) (not its metabolites) should be used to correct vitamin D deficiency and raise serum 25(OH)D to the target concentration. In contrast, calcifediol [25(OH)D] raises serum 25(OH)D concentrations rapidly and is the agent of choice in emergencies such as infections, for those who are in ICUs, and for insufficient hepatic 25-hydroxylase (CYP2R1) activity. In contrast, calcitriol is necessary to maintain serum-ionized calcium concentration in persons with advanced renal failure and hypoparathyroidism. Calcitriol is, however, ineffective in most other conditions, including infections, and as vitamin D replacement therapy. Considering the high costs and higher incidence of adverse effects due to narrow therapeutic margins (ED50), 1α-vitamin D analogs, such as 1α-(OH)D and 1,25(OH)2D, should not be used for other conditions. Calcifediol analogs cost 20 times more than D3-thus, they are not indicated as a routine vitamin D supplement for hypovitaminosis D, osteoporosis, or renal failure. Healthcare workers should resist accepting inappropriate promotions, such as calcifediol for chronic renal failure and calcitriol for osteoporosis or infections-there is no physiological rationale for doing so. Maintaining the population's vitamin D sufficiency (above 40 ng/mL) with vitamin D3 supplements and/or daily sun exposure is the most cost-effective way to reduce chronic diseases and sepsis, overcome viral epidemics and pandemics, and reduce healthcare costs. Furthermore, vitamin D sufficiency improves overall health (hence reducing absenteeism), reduces the severity of chronic diseases such as metabolic and cardiovascular diseases and cancer, decreases all-cause mortality, and minimizes infection-related complications such as sepsis and COVID-19-related hospitalizations and deaths. Properly using vitamin D is the most cost-effective way to reduce chronic illnesses and healthcare costs: thus, it should be a part of routine clinical care.

Vitamin D in Diabetes: Uncovering the Sunshine Hormone's Role in Glucose Metabolism and Beyond

Over the last decades, epidemiology and functional studies have started to reveal a pivotal role of vitamin D in both type 1 and type 2 diabetes pathogenesis. Acting through the vitamin D receptor (VDR), vitamin D regulates insulin secretion in pancreatic islets and insulin sensitivity in multiple peripheral metabolic organs. In vitro studies and both T1D and T2D animal models showed that vitamin D can improve glucose homeostasis by enhancing insulin secretion, reducing inflammation, reducing autoimmunity, preserving beta cell mass, and sensitizing insulin action. Conversely, vitamin D deficiency has been shown relevant in increasing T1D and T2D incidence. While clinical trials testing the hypothesis that vitamin D improves glycemia in T2D have shown conflicting results, subgroup and meta-analyses support the idea that raising serum vitamin D levels may reduce the progression from prediabetes to T2D. In this review, we summarize current knowledge on the molecular mechanisms of vitamin D in insulin secretion, insulin sensitivity, and immunity, as well as the observational and interventional human studies investigating the use of vitamin D as a treatment for diabetes.

Transcriptome and metabolome changes induced by bitter melon (Momordica charantia)- intake in a high-fat diet induced obesity model

Background and aim

Metabolic syndrome (MetS) is a complex disease of physiological imbalances interrelated to abnormal metabolic conditions, such as abdominal obesity, type II diabetes, dyslipidemia and hypertension. In the present pilot study, we investigated the nutraceutical bitter melon (Momordica charantia L) -intake induced transcriptome and metabolome changes and the converging metabolic signaling networks underpinning its inhibitory effects against MetS-associated risk factors.

Experimental procedure

Metabolic effects of lyophilized bitter melon juice (BMJ) extract (oral gavage 200 mg/kg/body weight-daily for 40 days) intake were evaluated in diet-induced obese C57BL/6J male mice [fed-high fat diet (HFD), 60 kcal% fat]. Changes in a) serum levels of biochemical parameters, b) gene expression in the hepatic transcriptome (microarray analysis using Affymetrix Mouse Exon 1.0 ST arrays), and c) metabolite abundance levels in lipid-phase plasma [liquid chromatography mass spectrometry (LC-MS)-based metabolomics] after BMJ intervention were assessed.

Results and conclusion

BMJ-mediated changes showed a positive trend towards enhanced glucose homeostasis, vitamin D metabolism and suppression of glycerophospholipid metabolism. In the liver, nuclear peroxisome proliferator-activated receptor (PPAR) and circadian rhythm signaling, as well as bile acid biosynthesis and glycogen metabolism targets were modulated by BMJ (p < 0.05). Thus, our in-depth transcriptomics and metabolomics analysis suggests that BMJ-intake lowers susceptibility to the onset of high-fat diet associated MetS risk factors partly through modulation of PPAR signaling and its downstream targets in circadian rhythm processes to prevent excessive lipogenesis, maintain glucose homeostasis and modify immune responses signaling.

Vitamin D and Calcium Status Among Adolescents with Morbid Obesity Undergoing Bariatric Surgery

PURPOSE

Obesity is very prevalent among children and adolescents these days. Obese children are at increased risk of vitamin D and other micronutrient deficiencies. This risk is even higher in children and adolescents with morbid obesity who are candidates for bariatric surgery. Although multiple studies have studied the prevalence of vitamin D deficiency in adults undergoing bariatric surgery, studies are limited concerning adolescents in this regard. We aimed to study the prevalence of vitamin D deficiency and insufficiency and calcium status among morbidly obese children and adolescents.

MATERIALS AND METHODS

A number of 96 adolescents (20 years old and younger) with morbid obesity (BMI ≥ 99% percentile), who were candidates for bariatric surgery, were enrolled in this study (from 2016 to 2018), and their serum vitamin D and calcium levels were measured.

RESULTS

Sixty-four percent of the patients were vitamin D-deficient and 15.7% of them had insufficient levels of serum vitamin D. Only 20.2% of the children had sufficient serum vitamin D levels. Serum calcium levels were within the normal range among all of the patients. There was no significant relationship between age and sex with vitamin D levels.

CONCLUSION

Vitamin D deficiency is of very high prevalence among adolescents with morbid obesity.

Ultrasonographic measurements of the skin, fat and muscle in vitamin D deficiency

BACKGROUND

Vitamin D is a steroid hormone and it is essential for the musculoskeletal system health. The relationship among vitamin D levels and adiposity was shown. However, there is only one study seems to have examined the relationship between skinfold thickness and vitamin D levels.

METHODS

A total of 116 healthy subjects who had a recent vitamin D measurement were included. Skin, subcutaneous fat and muscle thicknesses were measured by ultrasound (US). Hand grip strength and usual gait speed were evaluated.

RESULTS

Subjects were classified into two groups according to 25-OH vitamin D levels. Skin thicknesses of anterior forearm in women and of anterior tibia in men, and trochanteric fat thicknesses of both genders were higher in lower 25-OH vitamin D group (both P < .05). There were no differences between the groups regarding muscle thicknesses, grip strength and gait speed (all P > .05). For identifying vitamin D deficiency (≤20 ng/mL); optimal skin thickness value was 1.25 mm in women (sensitivity: 91.3%, specificity: 54.7%), and optimal trochanteric fat thickness was 1.79 cm in men (sensitivity: 87.5%, specificity: 76.9). The specificity was increased to 79.2% if the cut-off value was taken as 1.35 mm for anterior forearm skin thickness in women.

CONCLUSION

We imply that skin thicknesses (anterior forearm and tibia) and subcutaneous fat (trochanteric region) increase in subjects with low vitamin D levels. Having also ascertained the relevant cut-off values, we underscore the possible role of these measurements as regards the assessment of vitamin D status.

Vitamin D Supplementation Improves Adipose Tissue Inflammation and Reduces Hepatic Steatosis in Obese C57BL/6J Mice

The beneficial effect of vitamin D (VD) supplementation on body weight gain limitation and inflammation has been highlighted in primary prevention mice models, but the long-term effect of VD supplementation in tertiary prevention has never been reported in obesity models. The curative effect of VD supplementation on obesity and associated disorders was evaluated in high-fat- and high-sucrose (HFS)-fed mice. Morphological, histological, and molecular phenotype were characterized. The increased body mass and adiposity caused by HFS diet as well as fat cell hypertrophy and glucose homeostasis were not improved by VD supplementation. However, VD supplementation led to a decrease of HFS-induced inflammation in inguinal adipose tissue, characterized by a decreased expression of chemokine mRNA levels. Moreover, a protective effect of VD on HFS-induced hepatic steatosis was highlighted by a decrease of lipid droplets and a reduction of triglyceride accumulation in the liver. This result was associated with a significant decrease of gene expression coding for key enzymes involved in hepatic de novo lipogenesis and fatty acid oxidation. Altogether, our results show that VD supplementation could be of interest to blunt the adipose tissue inflammation and hepatic steatosis and could represent an interesting nutritional strategy to fight obesity-associated comorbidities.