AKAP1 Deficiency Attenuates Diet‐Induced Obesity and Insulin Resistance by Promoting Fatty Acid Oxidation and Thermogenesis in Brown Adipocytes

Abstract Altering the balance between energy intake and expenditure is a major strategy for treating obesity. Nonetheless, despite the progression in antiobesity drugs on appetite suppression, therapies aimed at increasing energy expenditure are limited. Here, knockout ofAKAP1, a signaling hub on outer mitochondrial membrane, renders mice resistant to diet‐induced obesity.AKAP1 knockout significantly enhances energy expenditure and thermogenesis in brown adipose tissues (BATs) of obese mice. Restoring AKAP1 expression in BAT clearly reverses the beneficial antiobesity effect in AKAP1−/− mice. Mechanistically, AKAP1 remarkably decreases fatty acid β‐oxidation (FAO) by phosphorylating ACSL1 to inhibit its activity in a protein‐kinase‐A‐dependent manner and thus inhibits thermogenesis in brown adipocytes. Importantly, AKAP1 peptide inhibitor effectively alleviates diet‐induced obesity and insulin resistance. Altogether, the findings demonstrate that AKAP1 functions as a brake of FAO to promote diet‐induced obesity, which may be used as a potential therapeutic target for obesity.

Data were expressed as mean ± SEM. Student's t test was used in c and d. Two-way ANOVA with Bonferroni's post hoc test was used in b. *p < 0.05, **p < 0.01. b) and c) Blood glucose and plasma insulin level of WT and AKAP1 -/mice on HFD (n = 6 mice per group). d) and e) Raw data of glucose tolerance test (GTT, n = 6 mice per group) and insulin tolerance test (ITT, n = 7-9 mice per group) of WT and AKAP1 -/-ND mice by the age of 28 weeks (left).
Blood glucose during GTT or ITT was expressed as a percentage of basal (Right). The area under the curve (AUC) was calculated for each mouse from both groups. f) Western blotting analysis of Ins Rec β, p-Akt (S473), Akt, p-S6K (T389) and S6K expression in liver, muscle and eWAT from WT and AKAP1 -/mice on ND for 24 weeks which were sacrificed 15 min after i.p. injection of insulin (5 U kg -1 ). n = 3 mice per group.
β-actin was used as a loading control.
Data were expressed as mean ± SEM. Student's t test was used in a, d (AUC), e (AUC) and f. Two-way ANOVA with Bonferroni's post hoc test was used for analysis of the data in b, c, d (raw data of GTT) and e (raw data of ITT). *p < 0.05, **p < 0.01. Figure S4. AKAP deficiency has no impact on energy expenditure in mice fed with a normal diet. a) Cumulative food intake of WT and AKAP1 -/-ND mice was measured every 3 days from 15 to 19 weeks of age (n = 5-6 mice per group). b) 24 h Food intake and c) physical activity of WT and AKAP1 -/-HFD mice (n = 4 mice per group). d) and (e) Oxygen consumption (VO 2 ) and carbon dioxide expiration (VCO 2 ) during light and dark phases were determined by metabolic cages in WT and AKAP1 -/-ND mice (n = 4 mice per group). f) Energy expenditure (EE) was estimated by the amount of O 2 consumption and CO 2 production in WT and AKAP1 -/-ND mice (n = 4 mice per group). g) Rectal core temperature of WT and AKAP1 -/-ND mice exposed to 4℃ for 6 hours (n = 8 -12 mice per group). h) Representative infrared thermography of WT and AKAP1 -/-ND mice exposed to 4°C for 6 hours (left). Surface temperature was quantified in the interscapular BAT area indicated by circle (right). n = 7 mice per group.
i) FCCP titration analyses for isolated BAT mitochondria from WT mice by seahorse analyzer.
Mitochondria (5 μg  Data were expressed as mean ± SEM. Student's t test was used in c and d.  Data were expressed as mean ± SEM. Student's t test was used in d (GSE92405, GSE77962).
One-way ANOVA with Bonferroni's post hoc test was used in a (GSE59034). Correlations between measured variables were tested using Pearson correlation analysis in c. *p < 0.05, **p < 0.01. c) Representative H&E-staining images of kidney, heart and muscle from HFD mice with treatment as indicated. Scale bar, 40 μm.
Data were expressed as mean ± SEM. Two-way ANOVA with Bonferroni's post hoc test was used in a. One-way ANOVA with Bonferroni's post hoc test was used in d and e. *p < 0.05, **p < 0.01