CTRP6 promotes the macrophage inflammatory response, and its deficiency attenuates LPS-induced inflammation.

Macrophages play critical roles in inflammation and tissue homeostasis, and their functions are regulated by various autocrine, paracrine, and endocrine factors. We have previously shown that CTRP6, a secreted protein of the C1q family, targets both adipocytes and macrophages to promote obesity-linked inflammation. However, the gene programs and signaling pathways directly regulated by CTRP6 in macrophages remain unknown. Here, we combine transcriptomic and phosphoproteomic analyses to show that CTRP6 activates inflammatory gene programs and signaling pathways in mouse bone marrow-derived macrophages (BMDMs). Treatment of BMDMs with CTRP6 upregulated proinflammatory, and suppressed the antiinflammatory, gene expression. We also showed that CTRP6 activates p44/42-MAPK, p38-MAPK, and NF-κB signaling pathways to promote inflammatory cytokine secretion from BMDMs, and that pharmacologic inhibition of these signaling pathways markedly attenuated the effects of CTRP6. Pretreatment of BMDMs with CTRP6 also sensitized and potentiated the BMDMs response to lipopolysaccharide (LPS)-induced inflammatory signaling and cytokine secretion. Consistent with the metabolic phenotype of proinflammatory macrophages, CTRP6 treatment induced a shift toward aerobic glycolysis and lactate production, reduced oxidative metabolism, and elevated mitochondrial reactive oxygen species production in BMDMs. Importantly, in accordance with our in vitro findings, BMDMs from CTRP6-deficient mice were less inflammatory at baseline and showed a marked suppression of LPS-induced inflammatory gene expression and cytokine secretion. Finally, loss of CTRP6 in mice also dampened LPS-induced inflammation and hypothermia. Collectively, our findings suggest that CTRP6 regulates and primes the macrophage response to inflammatory stimuli and thus may have a role in modulating tissue inflammatory tone in different physiological and disease contexts.

CTRP6 rapidly responds to acute nutritional changes, regulating adipose tissue expansion and inflammation in mice.

In chronic obesity, activated adipose tissue proinflammatory cascades are tightly linked to metabolic dysfunction. Yet, close temporal analyses of the responses to obesogenic environment such as high-fat feeding (HFF) in susceptible mouse strains question the causal relationship between inflammation and metabolic dysfunction, and/or raises the possibility that certain inflammatory cascades play adaptive/homeostatic, rather than pathogenic roles. Here, we hypothesized that CTRP6, a C1QTNF family member, may constitute an early responder to acute nutritional changes in adipose tissue, with potential physiological roles. Both 3-days high-fat feeding (3dHFF) and acute obesity reversal [2-wk switch to low-fat diet after 8-wk HFF (8wHFF)] already induced marked changes in whole body fuel utilization. Although adipose tissue expression of classical proinflammatory cytokines (Tnf-α, Ccl2, and Il1b) exhibited no, or only minor, change, C1qtnf6 uniquely increased, and decreased, in response to 3dHFF and acute obesity reversal, respectively. CTRP6 knockout (KO) mouse embryonic fibroblasts (MEFs) exhibited increased adipogenic gene expression (Pparg, Fabp4, and Adipoq) and markedly reduced inflammatory genes (Tnf-α, Ccl2, and Il6) compared with wild-type MEFs, and recombinant CTRP6 induced the opposite gene expression signature, as assessed by RNA sequencing. Consistently, 3dHFF of CTRP6-KO mice induced a greater whole body and adipose tissue weight gain compared with wild-type littermates. Collectively, we propose CTRP6 as a gene that rapidly responds to acute changes in caloric intake, acting in acute overnutrition to induce a "physiological inflammatory response" that limits adipose tissue expansion.NEW & NOTEWORTHY CTRP6 (C1qTNF6), a member of adiponectin gene family, regulates inflammation and metabolism in established obesity. Here, short-term high-fat feeding in mice is shown to increase adipose tissue expression of CTRP6 before changes in the expression of classical inflammatory genes occur. Conversely, CTRP6 expression in adipose tissue decreases early in the course of obesity reversal. Gain- and loss-of-function models suggest CTRP6 as a positive regulator of inflammatory cascades, and a negative regulator of adipogenesis and adipose tissue expansion.

Myonectin deletion promotes adipose fat storage and reduces liver steatosis.

We recently described myonectin (also known as erythroferrone) as a novel skeletal muscle-derived myokine with metabolic functions. Here, we use a genetic mouse model to determine myonectin's requirement for metabolic homeostasis. Female myonectin-deficient mice had larger gonadal fat pads and developed mild insulin resistance when fed a high-fat diet (HFD) and had reduced food intake during refeeding after an unfed period but were otherwise indistinguishable from wild-type littermates. Male mice lacking myonectin, however, had reduced physical activity when fed ad libitum and in the postprandial state but not during the unfed period. When stressed with an HFD, myonectin-knockout male mice had significantly elevated VLDL-triglyceride (TG) and strikingly impaired lipid clearance from circulation following an oral lipid load. Fat distribution between adipose and liver was also altered in myonectin-deficient male mice fed an HFD. Greater fat storage resulted in significantly enlarged adipocytes and was associated with increased postprandial lipoprotein lipase activity in adipose tissue. Parallel to this was a striking reduction in liver steatosis due to significantly reduced TG accumulation. Liver metabolite profiling revealed additional significant changes in bile acids and 1-carbon metabolism pathways. Combined, our data affirm the physiologic importance of myonectin in regulating local and systemic lipid metabolism.-Little, H. C., Rodriguez, S., Lei, X., Tan, S. Y., Stewart, A. N., Sahagun, A., Sarver, D. C., Wong, G. W. Myonectin deletion promotes adipose fat storage and reduces liver steatosis.

Five-year Weight Loss Maintenance With Obesity Pharmacotherapy.

CONTEXT: Long-term treatment of obesity with lifestyle changes alone is unsustainable for most individuals because of several factors including adherence and metabolic adaptation. Medical management of obesity has proven efficacy for up to 3 years in randomized controlled trials. However, there is a dearth of information regarding real-world outcomes beyond 3 years. OBJECTIVE: This work aimed to assess long-term weight loss outcomes over a 2.5- to 5.5-year period with US Food and Drug Administration (FDA)-approved and off-label antiobesity medications (AOMs). METHODS: A cohort of 428 patients with overweight or obesity were treated with AOMs at an academic weight management center with an initial visit between April 1, 2014, and April 1, 2016. Intervention included FDA-approved and off-label AOMs. The primary outcome was percentage weight loss from initial to final visit. Key secondary outcomes included weight reduction targets as well as demographic and clinical predictors of long-term weight loss. RESULTS: The average weight loss was 10.4% at a mean follow-up duration of 4.4 years. The proportions of patients who met the weight reduction targets of 5% or greater, 10% or greater, 15% or greater, and 20% or greater were 70.8%, 48.1%, 29.9%, and 17.1%, respectively. On average, 51% of maximum weight loss was regained, while 40.2% of patients maintained their weight loss. In a multivariable regression analysis, a higher number of clinic visits was associated with more weight loss. Metformin, topiramate, and bupropion were associated with increased odds of maintaining 10% or greater weight loss. CONCLUSION: Clinically significant long-term weight loss of 10% or more beyond 4 years is achievable in clinical practice settings with obesity pharmacotherapy.

The Independent Risk of Obesity and Diabetes and Their Interaction in COVID-19: A Retrospective Cohort Study.

OBJECTIVE: This study aimed to assess whether diabetes mellitus (DM) or obesity is an independent risk factor for severe coronavirus disease 2019 (COVID-19) outcomes and to explore whether the risk conferred by one condition is modified by the other. METHODS: This retrospective cohort study of inpatient adults with COVID-19 used multivariable Cox regression to determine the independent effects of DM and obesity on the composite outcome of intubation, intensive care unit admission, or in-hospital mortality. Effect modification between DM and obesity was assessed with a statistical interaction term and an exploration of stratum-specific effects. RESULTS: Out of 3,533 patients, a total of 1,134 (32%) had DM, 1,256 (36%) had obesity, and 430 (12%) had both. DM and obesity were independently associated with the composite outcome (hazard ratio [HR] 1.14 [95% CI: 1.01-1.30] and HR 1.22 [95% CI: 1.05-1.43], respectively). A statistical trend for potential interaction between DM and obesity was observed (P = 0.20). Stratified analyses showed potential increased risk with obesity compared with normal weight among patients with DM (HR 1.34 [95% CI: 1.04-1.74]) and patients without DM (HR 1.18 [95% CI: 0.96-1.43]). CONCLUSIONS: DM and obesity are independent risk factors associated with COVID-19 severity. Stratified analyses suggest that obesity may confer greater risk to patients with DM compared with patients without DM, and this relationship requires further exploration.