In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The present case suggests that obesity , hyperinsulinemia , insulin resistance , and long - term treatment with VPA may be all associated with the development of NAFLD ; this side effect is reversible after VPA withdrawal .
### Output Text:
The present case suggests that obesity , hyperinsulinemia , insulin resistance , and long - term treatment with <span class="chemical">VPA</span> may be all associated with the development of NAFLD ; this side effect is reversible after <span class="chemical">VPA</span> withdrawal . 