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That uncoupling protein 1 (UCP1) is the sole mediator of adipocyte thermogenesis is a conventional viewpoint that has primarily been inferred from the attenuation of the thermogenic output of mice genetically lacking Ucp1 from birth (germline Ucp1 −/−). However, germline Ucp1 −/− mice harbor secondary changes within brown adipose tissue. To mitigate these potentially confounding ancillary changes, we constructed mice with inducible adipocyte-selective Ucp1 disruption. We find that, although germline Ucp1 −/− mice succumb to cold-induced hypothermia with complete penetrance, most mice with the inducible deletion of Ucp1 maintain homeothermy in the cold. However, inducible adipocyte-selective co-deletion of Ucp1 and creatine kinase b (Ckb , an effector of UCP1-independent thermogenesis) exacerbates cold intolerance. Following UCP1 deletion or UCP1/CKB co-deletion from mature adipocytes, moderate cold exposure triggers the regeneration of mature brown adipocytes that coordinately restore UCP1 and CKB expression. Our findings suggest that thermogenic adipocytes utilize non-paralogous protein redundancy—through UCP1 and CKB—to promote cold-induced energy dissipation. [Display omitted] • Inducible adipocyte-specific Ucp1 deletion evades secondary changes beyond UCP1 • Individually, UCP1 and CKB are dispensable for cold-stimulated thermogenesis • UCP1 and CKB co-deletion causes hypothermia with near-full penetrance • Quantitative contribution of UCP1-independent adipocyte thermogenesis is defined Rahbani and Bunk et al. reveal that thermogenic adipocytes utilize UCP1 and CKB in parallel to support whole-body thermogenic demand in response to acute cold exposure. [ABSTRACT FROM AUTHOR]

In eukaryotes, cellular respiration is driven by mitochondrial cytochrome c oxidase (CcO), an enzyme complex that requires copper cofactors for its catalytic activity. Insertion of copper into its catalytically active subunits, including COX2, is a complex process that requires metallochaperones and redox proteins including SCO1, SCO2, and COA6, a recently discovered protein whose molecular function is unknown. To uncover the molecular mechanism by which COA6 and SCO proteins mediate copper delivery to COX2, we have solved the solution structure of COA6, which reveals a coiled-coil-helix-coiled-coil-helix domain typical of redox-active proteins found in the mitochondrial inter-membrane space. Accordingly, we demonstrate that COA6 can reduce the copper-coordinating disulfides of its client proteins, SCO1 and COX2, allowing for copper binding. Finally, our determination of the interaction surfaces and reduction potentials of COA6 and its client proteins provides a mechanism of how metallochaperone and disulfide reductase activities are coordinated to deliver copper to CcO. • COA6 is a coiled-coil-helix-coiled-coil-helix domain containing protein • COA6 preferentially interacts with SCO1 over SCO2 • COA6 acts as a disulfide reductase of SCO1 and COX2 • COA6 function can be bypassed under hypoxic conditions Soma et al. reports the solution structure of cytochrome c oxidase assembly factor COA6 and establishes that it functions as a thiol-disulfide oxidoreductase in a relay system that delivers copper to COX2, a copper-containing subunit of the mitochondrial cytochrome c oxidase. [ABSTRACT FROM AUTHOR]

• Depression severity is associated with blunted CAR irrespective of comorbid status. • Attachment avoidance is associated with higher CAR. • T1 attachment anxiety and depression severity predict future T2 depression severity. Early life experiences shape individual attachment, creating a template for regulating emotions in interpersonal situations, likely to persist across the lifespan. Research has shown that individual attachment creates vulnerability for depression, and also impacts the Hypothalamic-Pituitary-Adrenal (HPA) axis. Still, the relationship between attachment and the HPA axis in depressed individuals is unclear. Cortisol awakening response (CAR) has been recently investigated as a possibly useful physiological marker related to attachment insecurity and depression risk. However, research exploring the relationship between the CAR and attachment in individuals with chronic depression in either the presence or the absence of comorbid anxiety is lacking. The purpose of the current study was to fill this gap, by comparing the CAR in individuals with chronic depression with/without comorbid anxieties and controls. In addition, we also wanted to explore the relationship between attachment and the CAR in this group and to explore their predictive role for later depression severity. Individuals experiencing a current depressive episode at least six months in length (cMDD; n = 63) and healthy controls (HC; n = 57) were enrolled in the study (total n = 120). Participants completed a structured clinical diagnostic interview (SCID-I) as well as measures of depression severity (Beck Depression Inventory-II (BDI-II) and Hamilton Rating Scale for Depression) and attachment dimensions (Experiences in Close Relationships scale; ECR) at baseline. In addition, participants provided salivary samples at four time points (i.e. 0 (S1), 30, 45 and 60 min) following awakening on two consecutive days. S1 cortisol, the area under the curve with respect to ground (AUCg) and increase (AUCi) were calculated based on the average values across both days. The HC and cMDD groups were compared on all measures. The CAR for individuals with cMDD alone (n = 14) and individuals with cMDD with two or more comorbid anxiety disorders (cMDD ≥ 2Anx; n = 30) were also compared. A subset of participants (n = 59) agreed to return for follow up one year later. Participants returning for follow up repeated the BDI-II and ECR. No salivary samples were collected at follow-up. The cMDD group had significantly lower S1 cortisol and AUCg compared to the HC group (both p ≤ 0.02). cMDD and cMDD ≥ 2Anx groups did not differ in their CAR. Regression analyses revealed that depression severity and the attachment interaction term was associated with lower S1 and AUCg cortisol (p < 0.01). Greater attachment avoidance was positively associated with S1 cortisol (p = 0.02), while mean awakening time on sample days was negatively associated with S1 cortisol. We also found a significant interaction between the attachment dimensions such that at low levels of attachment anxiety, attachment avoidance had a positive relationship with S1 cortisol and AUCg. The opposite relationship existed when attachment anxiety was high. Higher baseline BDI-II score and higher baseline attachment anxiety were predictive of higher scores on the BDI-II one-year later (both p < 0.05). The current findings bring evidence that depression severity is associated with blunting of the CAR irrespective of the comorbid status with anxiety disorders. In addition, attachment avoidance may protect against the CAR blunting in individuals with low attachment anxiety. However, individuals with high attachment anxiety and avoidance might have additional CAR blunting. Attachment anxiety might be a good predictor of future depression severity. [ABSTRACT FROM AUTHOR]