Vaidya et al[47] showed a positive association between vitamin D

Vaidya et al.[47] showed a positive association between vitamin D concentrations and levels of adiponectin in a large cohort of 1,645 patients. Interestingly, this relationship was not modified by body mass index (BMI) and has been duplicated in other smaller studies, although those populations were notably leaner and younger.[48, 49] This could potentially be explained by the inhibitory effects of vitamin D on the RAS as previously discussed, although further study is required.

A recent study in Iranian type 2 diabetic patients showed that vitamin D therapy in the form of a fortified yogurt drink significantly improved adiponectin levels.[28] Another key adipokine is leptin, which is find more secreted by adipose tissue in response to a triglyceride-mediated expansion in adipocytes. Leptin oxidizes hepatic fatty acids (FA) by way of decreasing SREBP-1 expression[50] and prevents FA accumulation in nonadipose tissues. In addition

to promoting hepatic steatosis, leptin is thought to have proinflammatory and profibrotic effects, which are important in NASH pathogenesis.[51] Resistin is similarly produced by adipose tissue and is thought to promote the development of NASH by way of activation of c-Jun-terminal kinase (JNK) and nuclear factor kappa B (NF-κB), which leads to increased IR.[52] Tumor necrosis factor alpha (TNF-α) and IL-6 are proinflammatory cytokines secreted by adipocytes from obese and insulin-resistant patients[53] selleck chemical and weight loss has been shown to lead to a decrease in serum levels.[54] Continuous exposure to TNF-α Protein Tyrosine Kinase inhibitor and IL-6 is associated with hepatic IR, suggesting that the liver may be an important target for these adipocytokines[55] and inhibition of TNF-α activity through anti-TNF antibodies has been shown to prevent inflammation and improve NAFLD.[56] The effect of VDD on adiponectin, leptin, resistin, TNF-α, and IL-6 was recently investigated by Roth et al.[57] in a rat model where Sprague-Dawley rats were fed either a low-fat diet (LFD) or a high-fat Western diet (WD). WD/VDD mice showed increased

hepatic steatosis compared to both VDD and vitamin D replete LFD groups. Hepatic histology also correlated to VDD with increased lobular inflammation and NAFLD activity score (NAS) seen in the WD/VDD mice versus WD/vitamin D replete. Resistin and IL-6 levels were also significantly higher in the WD/VDD group compared to WD/vitamin D replete. In total, these findings suggest VDD worsens NAFLD related to up-regulation of hepatic inflammatory and oxidative stress genes. The role of the intestinal tract, nutrients, and their relationship to gut microbiota in immune response and pathogenesis of NAFLD is also intriguing and may relate to VDD. Bacterial lipopolysaccharides (LPS) play an important role in activation of the immune system and are involved in the development of both systemic inflammation and obesity.

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