Gluten isn't a carbohydrate, it's a protein. As a general rule the term gluten used by itself without mention of the source is referring specifically the gluten of wheat, rye, barley, or triticale which is the gluten that must be avoided by people with celiac disease, non-celiac gluten sensitivity, or anyone otherwise following a medically necessary gluten free diet. It wouldn't be overly difficult for researchers studying the effects of diet to devise a diet that swaps the gluten protein source for something else, without changing anything other aspect.

>In this study, we investigated the effect of gluten consumption on inflammation and oxidative stress in the liver of mice with NAFLD. Male ApoE−/− mice were fed a gluten-free (GF-HFD) or gluten-containing (G-HFD) high-fat diet for 10 weeks.

I imagine the two diets contained the same macronutient ratios.

The study only listed gluten and fats in the diet.