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. 2019 Mar 12;26(11):2849-2858.e4.
doi: 10.1016/j.celrep.2019.02.039.

Mitofusin 2 in Mature Adipocytes Controls Adiposity and Body Weight

Giacomo Mancini  1 , Kevin Pirruccio  2 , Xiaoyong Yang  2 , Matthias Blüher  3 , Matthew Rodeheffer  2 , Tamas L Horvath  4
Affiliations

Mitofusin 2 in Mature Adipocytes Controls Adiposity and Body Weight

Giacomo Mancini et al. Cell Rep. .

Erratum in

Abstract

We found that exposure of adult animals to calorie-dense foods rapidly abolished expression of mitofusin 2 (Mfn2), a gene promoting mitochondrial fusion and mitochondrion-endoplasmic reticulum interactions, in white and brown fat. Mfn2 mRN was also robustly lower in obese human subjects compared with lean controls. Adipocyte-specific knockdown of Mfn2 in adult mice led to increased food intake, adiposity, and impaired glucose metabolism on standard chow as well as on a diet with high calorie content. The body weight and adiposity of mature adipocyte-specific Mfn2 knockout mice on a standard diet were similar to those of control mice on a high-fat diet. The transcriptional profile of the adipose tissue in adipocyte-specific Mfn2 knockout mice was consistent with adipocyte proliferation, increased lipogenesis at the tissue level, and decreased glucose utilization at the systemic level. These observations suggest a possible crucial role for mitochondrial dynamics in adipocytes in initiating systemic metabolic dysregulation.

Keywords: mitochondria; mitofusin; obesity; white adipocyte.

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Figures

Figure 1.
Figure 1.. Effect of a High-Fat Diet on the Gene Expression of Factors Mediating Mitochondrial Dynamics
(A)Body weight of wild-type (WT) mice receiving a standard diet (SD) or high-fat diet (HFD) for a total treatment time of 12 weeks. Mice receiving the SD, n = 10; mice on the HFD, n = 10. (B)Inverse relationship between mitofusin 2 gene expression in epididymal fat and body weight gain in mice exposed to the HFD. (C)Relative mitofusin 2 mRNA levels in epididymal fat (EF) at different time points during diet treatment. SD, n = 5–6; HFD, n = 4–6. Values were normalized to the SD. (D)Gene expression analysis of different genes involved in the regulation of mitochondrial dynamics in white adipose tissue from the mice shown in (C) at the end of the 12 weeks of HFD treatment. Mfn1, mitofusin 1; opa, optic atrophy 1; drp1, pro-fission dynamin-related protein-1. Values were normalized to the SD. (E and F) Relative mitofusin 2 mRNA levels in subcutaneous (E) and visceral (F) fat from lean (n = 17) and obese (n = 295) human subjects. Data are mean ± SEM. Statistics: Student’s t test; *p < 0.05, **p < 0.01, ***p < 0.001 versus control. See also Figure S1.
Figure 2.
Figure 2.. Body Weight, Adipose Tissue Proliferation, and Glucose Homeostasis Are Affected by Adipocyte Deletion of Mitofusin 2
(A and B) Body weight analysis of Ati-mfn2-CT and Ati-mfn2-KO mice on the SD (A; controls, n = 16; KO, n = 12) and HFD (B; controls, n = 19; KO, n = 15) at 3, 7, and 12 weeks on the respective diets. (C) Data from (A) and (B) presented as body weight gain (as a percentage) over the 12 weeks of diet treatment. (D and E) MRI of Ati-mfn2-CT and Ati-mfn2-KO mice on SD (D) and HFD (E) correlated the increased body weight of the Ati-mfn2-KO compared with controls because of increased adiposity (the mice from A and B were used for evaluation of body composition by MRI). (F–K) Plasma profile of adiponectin (F), leptin (G), and glucose (H) on standard diet, and adiponectin (I), leptin (J), and glucose (K) on high-fat diet of Ati-mfn2-CT (n = 5–6) and Ati-mfn2-KO (n = 6–7) mice. (L–O) Glucose tolerance test (L and M) and insulin tolerance test (N and O) on Ati-mfn2-CT and Ati-mfn2-KO mice on the SD (controls, n = 5–6; KO, n = 6–8) and HFD (controls, n = 5–6; KO, n = 5–8). Data are mean ± SEM. Statistics: (A), (B), and (D)–(K), Student’s t test; (E), one-way ANOVA; (L)–(O), cumulative quantification of blood glucose in mice during the respective experiments, derived as area under the curve (AUC) and statistically compared by Student’s t test. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figures S2–S5.
Figure 3.
Figure 3.. Energy Homeostasis in Adipocyte-Specific Mitofusin 2 Knockout Mice
Energy expenditure analysis (A–D) and respiratory exchange ratio (RER) (E–H) measured over 48 h in Ati-mfn2-CT (n = 8) and Ati-mfn2-KO (n = 8) mice on SD and HFD treatments. Data are mean ± SEM. Statistics: Student’s t test. *p < 0.05, **p < 0.01 versus controls. See also Figure S6.
Figure 4.
Figure 4.. MFN2 Gene Inactivation in Adipose Tissue Leads to Modifications of Mitochondrial Morphology and Overall Adipose Tissue Histology
(A) Electron microscopy presentation of epididymal fat from Ati-mfn2-KO mice and controls littermates (Ati-mfn2-CT) both on the SD and HFD. Scale bar, 1 μm. (B–F) Quantification of mitochondria area (in square nanometers; B) and mitochondrial coverage (C) in adipocytes on SD and the same parameters on HFD (D and E) of Ati-mfn2-KO mice and their controls littermates (Ati-mfn2-KO and controls receiving both the SD and HFD, n = 3). (F)Relative change of mitochondrial area on HFD compared to SD values (100%) between Ati-mfn2-CT and Ati-mfn2-KO mice (n = 3 in all groups). (G)Representative H&E staining of epididymal fat from SD- and HFD-fed Ati-mfn2-KO mice and controls. Scale bar, 30 üm. (H and I) Adipocyte cell population distribution according to their cell area SD (H) and HFD (I) of Ati-mfn2-CT and Ati-mfn2-KO mice (n = 3 in all groups). (J) Schematic depicting the time points for BrdU treatment and analysis of adipocyte nuclei by immunofluorescence. (K and L) Quantification of BrdU-positive nuclei in epididymal fat from Ati-mfn2-KO mice and controls receiving either the SD (K) or HFD (L). (M) Quantification of peroxisome proliferator-activated receptor γ (PPAR-γ) mRNA levels in epididymal fat from HFD-treated mice. Data are mean ± SEM. In (F), data from (B)–(D) are presented as variation to control mice receiving the SD. In (K) and (L), data are expressed as percentage variation versus the control group. n = 3 mice for each group, 300–500 cells/group. Statistics: (B)–(E) and (K)–(M), Student’sttest; (F), one-way ANOVA; *p < 0.05, **p < 0.01, ***p < 0.001 versus controls. See also Figure S7.
Figure 5.
Figure 5.. Pharmacological Blocking of PPAR-γ during HFD Feeding Increases Mitofusin 2 Protein Expression in Epididymal Fat and Prevents Its Pathological Expansion
(A) Schematic depicting the time points and diet of BL6/N mice receiving vehicle (n = 4) or 5 mg/kg GW9662 (n = 7). (B and C) Representative western blot (B) of mitofusin 2 and protein expression quantification (C) in epididymal fat from BL6/N mice receiving vehicle or GW9662, respectively. (D and E) Body weight analysis (D) and quantification of epididymal fat weight (E) from mice receiving vehicle or GW9662. Data are mean ± SEM. In (B), shown is whole epididymal fat lysate from BL6/N mice receiving vehicle or 5 mg/kg GW9662 treatment, respectively. In (D), mitofusin 2 protein quantification of samples shown in (B) is presented as variation to controls (vehicle-treated mice). Student’s t test, **p < 0.01 versus controls.
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