Abstract
In the presence of dietary lipids, both apolipoprotein A-IV (ApoA-IV) production and brown adipose tissue (BAT) thermogenesis are increased. The effect of dietary lipid-induced AproA-IV on BAT thermogenesis and energy expenditure remains unknown. In the present study, we hypothesized that ApoA-IV knockout (ApoA-IV-KO) mice exhibited decreased BAT thermogenesis to affect energy homeostasis. To test this hypothesis, BAT thermogenesis in wildtype (WT) and ApoA-IV-KO mice fed either a standard low-fat chow diet or a high-fat diet (HFD) was investigated. When fed a chow diet, energy expenditure and food intake were comparable between WT and ApoA-IV-KO mice. After 1 week of HFD consumption, ApoA-IV-KO mice had comparable energy intake but produced lower energy expenditure relative to their WT controls in the dark phase. After an acute feeding of dietary lipids or 1-week HFD feeding, ApoA-IV-KO mice produced lower levels of uncoupling protein 1 (UCP1) and exhibited reduced expression of thermogenic genes in the BAT compared with WT controls. In response to cold exposure, however, ApoA-IV-KO mice had comparable energy expenditure and BAT temperature relative to WT mice. Thus, ApoA-IV-KO mice exhibited reduced diet-induced BAT thermogenesis and energy expenditure.
Highlights
Obesity has become a global epidemic, affecting more than 90 million people or almost 40% of adults in the U.S [1]
After 5-h fast, chow-fed WT and apolipoprotein A-IV (ApoA-IV)-KO mice exhibited comparable brown adipose tissue (BAT) temperature and body temperature (Experiment 4), and comparable levels of energy expenditure, body weight, fat mass, and plasma parameters (Experiment 1). These findings suggest that ApoA-IV-KO mice have normal energy homeostasis when they are maintained on a standard chow diet
The present study demonstrated that high-fat diet (HFD)-fed ApoA-IV-KO mice had a significant reduction in hourly energy expenditure in the dark phase
Summary
Obesity has become a global epidemic, affecting more than 90 million people or almost 40% of adults in the U.S [1]. -KO mice produced similar basal level of plasma ApoA-I protein relative to WT mice after 5-h. Expression of BAT Thermogenic Protein of Mice with Acute Feeding of Dietary Lipids. WT mice and ApoA-IV-KO mice produced similar plasma ApoA-I protein when fed the chow diet and after 1-week feeding of HFD (Figure 6A). Compared with the chow-fed WT mice, HFD-fed WT mice produced 1.5 folds of plasma ApoA-IV (Figure 6B). After 1-week HFD feeding, plasma levels of triglyceride, glucose and leptin of ApoA-IV-KO Amfitceer 1w-ewreeeckomHpFaDrafbeledtiongth, opsleaspmaaralmeveteelrssoofftrWigTlymceirciede(T, agbluleco2s).e Ianndcolnetpratisnt, opflaAspmoaAl-eIvVe-lKs Oof mice were cchoomlepstaerraobl laentdoitnhsouslienpoafrAampoeAte-IrVs-oKfOWmTicme iwcer(eTsaibglneif2ic)a. Wafetiegrhats,1c-ownetaeikneHdFsDim,iBlaAr TnuamnbdeIrWs aAndT soizfeWs oTf aadnidpoAcyptoeAs (-FIiVg-uKreO7manidceThabalde s3i)m. ilar weights, contained similar numbers and sizes of adipocytes (Figure 7 and Table 3)
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