Time-restricted feeding counters brown adipose tissue whitening and inflammation in obese mice under chronic light...

Time-restricted feeding (TRF) is a promising dietary strategy to improve the metabolic parameters associated with obesity, but its potential benefits in obesity linked to nighttime light exposure remain largely unclear. This study examined whether chronic light exposure alone, or in combination with TRF, modulates brown adipose tissue (BAT) in lean and obese mice.

Six-week-old male C57BL/6J mice were fed a low-fat diet (LFD) or a high-fat diet (HFD) for six weeks, and were assigned to one of three experimental conditions for an additional 6 weeks: control light exposure, continuous 24-h light exposure, or 24-h light exposure combined with TRF. This yielded 6 experimental groups: LC, L24h, L24hT, HC, H24h, and H24hT.

Histological analyses showed that chronic light exposure alone induced BAT whitening, characterized by lipid droplet accumulation and structural disorganization, even in LFD-fed mice. This whitening occurred without a decrease in uncoupling protein 1 mRNA and protein levels, suggesting mechanisms independent of thermogenic suppression. Instead, lipid accumulation and elevated Lep mRNA expression were associated with increased expression of various inflammatory markers (Adgre1, Itgax, and Pycard) and F4/80-positive macrophage infiltration. Importantly, TRF intervention attenuated BAT whitening and markedly suppressed the inflammatory responses, restoring the tissue structure and reducing macrophage infiltration, particularly in HFD-fed mice.

These findings suggest that TRF may have clinical implications for obese night workers by preventing BAT from shifting toward an inflammatory and metabolically dysfunctional phenotype associated with nighttime light exposure.