Distinct Adipose Depots from Mice Differentially Respond to a High-Fat, High-Salt Diet.

BACKGROUND: Dietary factors such as high-sodium or high-fat (HF) diets have been shown to induce a proinflammatory phenotype. However, there is limited information with respect to how microenvironments of distinct intra-abdominal adipose depots respond to the combination of a high-salt, HF diet. OBJECTIVE: We tested the hypothesis that HF feeding would cause changes in distinct adipose depots, which would be further amplified by the addition of high salt to the diet. METHODS: Twenty-seven male C57BL6 mice were fed an HF diet (60% of kcal from fat), an HF + high-salt diet (4% wt:wt), a control diet [low-fat (LF);10% of kcal from fat], or an LF + high-salt diet for 12 wk. The main sources of fat in the diets were corn oil and lard. Adipokines in serum and released from adipose tissue organ cultures were measured by immunoassays. QIAGEN's Ingenuity Pathway Analysis was used to perform functional analysis of the RNA-sequencing data from distinct adipose depots. RESULTS: Diet-induced obesity resulted in a classical inflammatory phenotype characterized by increased concentrations of circulating inflammatory mediators (38-56%) and reduced adiponectin concentrations (27%). However, high-salt feeding did not exacerbate the HF diet-induced changes in adipokines and cytokines. Leptin and interleukin-6 were differentially released from adipose depots and HF feeding impaired adiponectin and resistin secretion across all 3 depots (34-48% and 45-83%, respectively). The addition of high salt to the HF diet did not further modulate secretion in cultured adipose tissue experiments. Although gene expression data from RNA sequencing indicated a >4.3-fold upregulation of integrin αX (Itgax) with HF feeding in all 3 depots, markers of cellular function were differentially expressed in response to diet across depots. CONCLUSION: Collectively, these findings highlight the role of distinct adipose depots in mice in the development of obesity and emphasize the importance of selecting specific depots to study the effects of therapeutic interventions on adipose tissue function.