Obesity is a global public health issue. It is associated with a spectrum of liver abnormalities, like nonalcoholic fatty liver disease (NAFLD). The purpose of this study was to investigate the effect of Vitamin D3 on light microscopic changes in the liver, as well as hematology and some liver enzymes in experimentally overweight albino rats. Five groups of thirty-five male albino rats were formed. For three months, Control (C) group received a standard laboratory diet. Corn oil (CO) group received normal balanced diet and given orally 20 mg/kg corn oil daily. Vitamin D (D) group received normal balanced diet and orally treated daily with 5000 IU/kg of vitamin D3. Overweight (OW) group rats received high caloric diet. Overweight/ vitamin D (OWD) group received high caloric diet and treated with oral vitamin D3 5000 IU/kg daily. Liver weights of animals were recorded, blood samples for hematology, some liver functions, catalase (CAT) and total antioxidant capacity (TAC) were collected. Liver samples were fixed in 10% formal saline then stained by H&E for histological examination. OW group had significantly higher liver weights, and liver function than CO group. Histologically, there was an increase of fatty degeneration in the OW group. However, OWD group was lower in all the measured and examined liver parameters than that of CO group in this study vitamin D3 supplement could ameliorate the abnormal changes in the hepatocytes induced by obesity.

Vitamin D deficiency is one of the major affecting factors on metabolic syndrome, cancer, cardiovascular diseases, and type 2 diabetes mellitus. So we aimed in our study to show the anti-diabetic effects of vitamin D on type 2 diabetic rats. Therefore, 45 rats were divided into three groups (15 rats per each group). The first group served as a control and fed on a standard chow diet while the other two groups served as diabetic groups as they fed on high fructose, high fat, and high sucrose diet and for 12 weeks then they injected with intraperitoneal single dose (45 mg/kg b.wt) of STZ dissolved in cold 0.01 M citrate buffer (pH 4.5) to develop type 2 diabetes mellitus. After one week of injection the third diabetic group was treated for 4 weeks with two intramuscular (20,000 IU/Kg) of vitamin D dissolved in sesame oil. The obtained results demonstrated that administration of vitamin D could improve serum glucose and insulin levels with an increase in serum calcitonin and calcium in correlation with the decrease in parathyroid hormone, phosphorus and lipids levels in the presence of significant upregulation of gene expression in liver (PPARα, GLP-1, and IGF-1) and in adipose tissue (Ptch, Smo, Gli-1, and hhip). In conclusion, vitamin D administration can improve insulin resistance by improving blood glucose and insulin levels.