The deficiency and the supplementation of vitamin D and liver: Lessons of chronic fructose-rich diet in mice

The fructose added to soft drinks and processed food, as well as frequent detection of vitamin D deficiency in the body, are two insults increasingly considered to cause lesions in target organs. We studied the liver after a chronic high-fructose diet deficient and supplemented with vitamin D. Sixty C57BL/6 mature male mice were allocated into six groups (n = 10) for ten weeks: control (C), control deficient in vitamin D (CDD), control supplemented with vitamin D (CDS), fructose (F), fructose deficient in vitamin D (FDD), and fructose supplemented with vitamin D (FDS). The gene expressions of vitamin D receptor and CYP27B1 and 25 hydroxyvitamin D plasma level ensured that the diets caused vitamin D deficiency or supplementation. Body mass did not change, but blood pressure (BP) increased in CDD, F, and FDD, whereas BP was controlled in FDS. Insulinemia, insulin tolerance and resistance were seen in both vitamin D deficiency and fructose groups but improved with vitamin D supplementation. The steatosis and fibrosis were observed in the CDD, F and FDD groups. Also, F and FDD showed activation of stellate cells (HSC). Lipogenesis and inflammation gene expressions were enhanced in the CDD, F and FDD groups, but diminished with vitamin D supplementation. In conclusion, we demonstrated the adverse effects of vitamin D deficiency on metabolism, liver steatosis and, combined with fructose intake, liver interstitial fibrosis with hepatic stellate cell activation, and alteration of the lipogenesis, beta-oxidation, and liver inflammation. All these data improved when vitamin D was supplemented in the animals.

Maternal vitamin D-restricted diet has consequences in the formation of pancreatic islet/insulin-signaling in the adult offspring of mice

The maternal deficiency of vitamin D can act on organogenesis in mice offspring, being a risk factor for chronic diseases in adulthood. This study investigates the effects of maternal deficiency of vitamin D on structural islet remodeling and insulin-signaling pathway in the offspring. We studied male C57Bl/6 offspring at 3-month old (n = 10/group) from mother fed one of the two diets: control diet (C) or vitamin D-restricted diet (VitD^-). After weaning, offspring only fed the control diet ad libitum. In the offspring, we studied insulin production, islet remodeling, and islet protein expression of the insulin-signaling pathway (Western blotting, isolated islet, n = 5/group). VitD^- offspring showed greater glycemia (P = 0.012), smaller beta-cell mass (P = 0.014), and hypoinsulinemia (P = 0.024) than C offspring. Comparing VitD^- offspring with C offspring, we observed lower protein levels in islet of insulin (P = 0.003), insulin receptor substrate-1 (P = 0.025), phosphatidylinositol-3-kinases (P = 0.045), 3-phosphoinositide-dependent protein kinase 1 (P = 0.017), protein kinase B (P = 0.028), with reduced expression of pancreas/duodenum homeobox-1 (PDX-1) (P = 0.016), glucose transporter-2 (P = 0.003), and glucokinase (P = 0.045). The maternal vitamin D-restricted diet modifies the development of the pancreas of the offspring, leading to islet remodeling and altered insulin-signaling pathway. The decrease of PDX-1 is probably significant to the changes in the beta-cell mass and insulin secretion in adulthood.