Vitamin D deficiency in the aetiology of obesity‐related insulin resistance

Abstract

The obese insulin-resistant state is often associated with low circulating concentration of vitamin D 25-hydroxyvitamin D 3 [25(OH)D 3 ]. Fat sequestration of vitamin D in the expanded obese adipose tissue mass has been pointed out as a plausible explanation for this circulating vitamin D deficiency. However, the putative mechanisms behind this hypovitaminosis D remain to be elucidated. The presence of vitamin D receptor and vitamin D-metabolizing enzymes in insulin-sensitive organs suggests that vitamin D may be involved in glucose and lipid metabolism and may be related to insulin sensitivity. Indeed, mainly in vitro studies support a role of vitamin D in regulating glucose and lipid metabolism in several insulin-sensitive tissues including adipose tissue, skeletal muscle, liver, as well as pancreatic insulin secretion. A potential role of vitamin D in gut barrier function and metabolism has also been suggested. This review summarizes recent knowledge on vitamin D deficiency in the aetiology of obesity-related insulin resistance and discusses potential underlying mechanisms. Finally, the role of vitamin D supplementation on insulin sensitivity and glycaemic control is discussed.

Mechanisms of vitamin D action in skeletal muscle

“…Specifically, OPA1 expression increased following vitamin D treatment, while mediators of mitochondrial fission (Fis1 and Drp1) were decreased (24) . Furthermore, current evidence has illustrated that treatment with 0•1 nM-1,25(OH) 2 D 3 in human primary muscle improved mitochondrial morphology (volume and structure) and altered mRNA expression of pyruvate dehydrogenase kinase 4 and carnitine palmitoyltransferase 1 (CPT1), important genes that control muscle glucose and lipid metabolism (86) . Vitamin D deficiency is known to impair muscle function and metabolism, where, in this case, skeletal muscle fibres are most likely to VDR ablation and to uptake cytoplasmic Ca 2þ released from the sarcoplasmic reticulum during twitch responses (87) .…”

Vitamin D deficiency serves as a precursor to stunted growth and central adiposity in zebrafish

“…In human population studies there is increasing evidence of a physiological role of vitamin D in glucose and lipid metabolism within insulin-sensitive tissues expressing VDR 17 . In adipose tissue (AT), vitamin D is thought to regulate markers of adipogenesis, such as adiponectin, as well as adipocyte apoptosis 18 .…”

Vitamin D Deficient Older Adults Are More Prone to Have Metabolic Syndrome, but Not to a Greater Number of Metabolic Syndrome Parameters

“…Low serum 25-hydroxyvitamin D (25(OH)D) levels are a common finding in the elderly population and are not limited to bone health risks, but also beta cell dysfunction and increased insulin resistance, leading to metabolic diseases [1][2][3]. However, a straightforward association between low serum 25(OH)D levels and cardiovascular diseases is not yet clear, especially in the elderly population which typically has more than one associated risk factor.…”