Table 1 Effects of vitamin D on various human cell types and tissues

Adipocytes

• Inhibits intracellular fat accumulation

• Enhances basal lipolysis without cell toxicity

• Upregulation of β-oxidation-related genes, lipolytic enzymes, and vitamin D-responsive genes

• Increased levels of nicotinamide adenine dinucleotide and sirtulin 1 expression

[105]

Cardiomyocytes

• Inhibition of cell proliferation without apoptosis

• Downregulation of expression of genes associated with cell cycle regulation

• Promotes cardiomyotube formation

• Induces cardiac differentiation

[106, 107]

Hepatocytes

• Protects against insulin resistance

• Downregulates fibrogenic TGF-β signaling

• Anti-inflammatory effects by inhibiting monocyte activation and TNF-α and IL-1 expression

[108,109,110]

Myocytes

• Modulation of calcium homeostasis and influx

• Induces cellular proliferation and differentiation

• Protects against insulin resistance

• Stimulation of arachidonic acid mobilization

[111, 112]

Nephrocytes

• Upregulation of cellular metabolic activity, IL-6, and reactive oxygen species

• Restoration of transepithelial barrier function

[113]

Neurons

• Neuroactive steroid modulating spontaneous regular firing, actin potential duration, and intrinsic excitability

• Enhances sensitivity to neurotransmitters and neurotransmitter receptors

• Upregulation of neuronal growth factors, neurotrophin 3, and glial cell line-derived neurotrophic factor

[114, 115]

T cells

• Inhibits Th1/Th17 chemokine/cytokine secretion (CXCL-10, IFN-γ, TNF-α, and IL-17)

• Enhances Th2 cytokine release (IL-4 and IL-5)

[17, 116]

B cells

• Downregulates the proliferation of memory B cells

• Inhibits plasma cell differentiation

• Reduces Ig production

[117]

Antigen-presenting cells

• Inhibits the expression of class II MHC molecules (HLA-DR)

• Inhibition of co-stimulating molecule expression (CD80, CD83, and CD86)

• Augments chemotaxis and phagocytosis of monocytes

• Downregulates the maturation of dendritic cells

• Induces tolerogenic dendritic cells capable of inducing Treg cells

• Inhibits IL-12 p70 release

• Decreases macrophage-stimulated pro-inflammatory cytokine production (IL-1, IL-1β, IL-6, IL-8, MCP-1, and RANTES)

[118,119,120,121]

NK cells

• Inhibition of NK cell development and differentiation

• Reduced INF-γ and cytotoxicity

[122]