A single day of high-fat diet feeding induces lipid accumulation and insulin resistance in brown adipose tissue in mice
Kuipers, Eline N. ; Held, Ntsiki M. ; Het Panhuis, Wietse In; Modder, Melanie ; Ruppert, Philip M.M. ; Kersten, Sander ; Kooijman, Sander ; Guigas, Bruno ; Houtkooper, Riekelt H. ; Rensen, Patrick C.N. ; Boon, Mariëtte R. - \ 2019
American Journal of Physiology. Endocrinology and Metabolism 317 (2019)5. - ISSN 0193-1849 - p. E820 - E830.
brown adipose tissue - high-fat diet - lipid accumulation - macrophage - mitochondrial dynamics
Brown adipose tissue (BAT) catabolizes glucose and fatty acids to produce heat and thereby contributes to energy expenditure. Long-term high-fat diet (HFD) feeding results in so-called 'whitening' of BAT characterized by increased lipid deposition, mitochondrial dysfunction, and reduced fat oxidation. The aim of the current study was to unravel the rate and related mechanisms by which HFD induces BAT whitening and insulin resistance. Wild-type mice were fed a HFD for 0, 1, 3, or 7 days. Within 1 day of HFD, BAT weight and lipid content were increased. HFD also immediately reduced insulin-stimulated glucose uptake by BAT, indicating rapid induction of insulin resistance. This was accompanied by a tendency toward a reduced uptake of triglyceride-derived fatty acids by BAT. Mitochondrial mass and Ucp1 expression were unaltered, whereas after 3 days of HFD, markers of mitochondrial dynamics suggested induction of a more fused mitochondrial network. Additionally, HFD also increased macrophage markers in BAT after 3 days of HFD. Counterintuitively, the switch to HFD was accompanied by an acute rise in core body temperature. We showed that a single day of HFD feeding is sufficient to induce the first signs of whitening and insulin resistance in BAT, which reduces the uptake of glucose and triglyceride-derived fatty acids. BAT whitening and insulin resistance are likely sustained by reduced mitochondrial oxidation due to changes in mitochondrial dynamics and macrophage infiltration, respectively. Likely, the switch to HFD swiftly induces thermogenesis in other metabolic organs, which allows attenuation of BAT thermogenesis.
Effects of macro and micronutrients on neutral lipid accumulation in oleaginous microalgae
Ghafari, Mohsen ; Rashidi, Behzad ; Haznedaroglu, Berat Zeki - \ 2018
Biofuels 9 (2018)2. - ISSN 1759-7269 - p. 147 - 156.
lipid accumulation - macronutrients - micronutrients - Oleaginous microalgae - optimization
In this study, effects of key macro and micronutrients on neutral lipid accumulation of six oleaginous microalgae species were investigated. For each nutrient, three different concentrations (0.5×, 1×, and 2×) were tested individually and compared to the most commonly utilized growth medium recipes. Neutral lipid accumulation was quantified using specific nonpolar dyes with long-wavelength absorption and fluorescence. Tested microalgae species showed different lipid accumulation responses to changes in nutrient concentrations. Optimum concentrations of nutrients were selected for each species based on either the most lipid productive case or no significant difference to the lipid contents. Selected optimal conditions were also validated where Chlorella sorokiniana, Chlorella vulgaris, Dunaliella tertiolecta, and Tetraselmis suecica showed 4, 10, 34, and 39% higher lipid productivities per unit volume, respectively. Botryococcus sudeticus and Ettlia oleoabundans did not show improved lipid productivities. Extensive optimization of macro and micronutrient concentrations offers several benefits of decreased material inputs and waste generation, improved biomass productivity, and overall cost savings.