Crosstalk between corepressor NRIP1 and cAMP signaling on adipocyte thermogenic programming.

OBJECTIVES: Nuclear receptor interacting protein 1 (NRIP1) suppresses energy expenditure via repression of nuclear receptors, and its depletion markedly elevates uncoupled respiration in mouse and human adipocytes. We tested whether NRIP1 deficient adipocytes implanted into obese mice would enhance whole body metabolism. Since ß-adrenergic signaling through cAMP strongly promotes adipocyte thermogenesis, we tested whether the effects of NRIP1 knock-out (NRIP1KO) require the cAMP pathway. METHODS: NRIP1KO adipocytes were implanted in recipient high-fat diet (HFD) fed mice and metabolic cage studies conducted. The Nrip1 gene was disrupted by CRISPR in primary preadipocytes isolated from control vs adipose selective GsαKO (cAdGsαKO) mice prior to differentiation to adipocytes. Protein kinase A inhibitor was also used. RESULTS: Implanting NRIP1KO adipocytes into HFD fed mice enhanced whole-body glucose tolerance by increasing insulin sensitivity, reducing adiposity, and enhancing energy expenditure in the recipients. NRIP1 depletion in both control and GsαKO adipocytes was equally effective in upregulating uncoupling protein 1 (UCP1) and adipocyte beiging, while ß-adrenergic signaling by CL 316,243 was abolished in GsαKO adipocytes. Combining NRIP1KO with CL 316,243 treatment synergistically increased Ucp1 gene expression and increased the adipocyte subpopulation responsive to beiging. Estrogen-related receptor α (ERRα) was dispensable for UCP1 upregulation by NRIPKO. CONCLUSIONS: The thermogenic effect of NRIP1 depletion in adipocytes causes systemic enhancement of energy expenditure when such adipocytes are implanted into obese mice. Furthermore, NRIP1KO acts independently but cooperatively with the cAMP pathway in mediating its effect on adipocyte beiging.

Paradoxical activation of transcription factor SREBP1c and de novo lipogenesis by hepatocyte-selective ATP-citrate lyase depletion in obese mice.

Hepatic steatosis associated with high-fat diet, obesity, and type 2 diabetes is thought to be the major driver of severe liver inflammation, fibrosis, and cirrhosis. Cytosolic acetyl CoA (AcCoA), a central metabolite and substrate for de novo lipogenesis (DNL), is produced from citrate by ATP-citrate lyase (ACLY) and from acetate through AcCoA synthase short chain family member 2 (ACSS2). However, the relative contributions of these two enzymes to hepatic AcCoA pools and DNL rates in response to high-fat feeding are unknown. We report here that hepatocyte-selective depletion of either ACSS2 or ACLY caused similar 50% decreases in liver AcCoA levels in obese mice, showing that both pathways contribute to the generation of this DNL substrate. Unexpectedly however, the hepatocyte ACLY depletion in obese mice paradoxically increased total DNL flux measured by D2O incorporation into palmitate, whereas in contrast, ACSS2 depletion had no effect. The increase in liver DNL upon ACLY depletion was associated with increased expression of nuclear sterol regulatory element-binding protein 1c and of its target DNL enzymes. This upregulated DNL enzyme expression explains the increased rate of palmitate synthesis in ACLY-depleted livers. Furthermore, this increased flux through DNL may also contribute to the observed depletion of AcCoA levels because of its increased conversion to malonyl CoA and palmitate. Together, these data indicate that in fat diet-fed obese mice, hepatic DNL is not limited by its immediate substrates AcCoA or malonyl CoA but rather by activities of DNL enzymes.

Effects of dexamethasone on postoperative urinary retention after laparoscopic inguinal hernia repair.

BACKGROUND: Postoperative urinary retention (POUR) is a complication of laparoscopic inguinal hernia repair (LIHR). Previous research has identified predictive factors of POUR, such as age and history of benign prostatic hyperplasia (BPH). There is currently limited work on preventative measures. We hypothesize dexamethasone, a steroid, reduces POUR rates following LIHR due to its mechanism. METHODS: Consecutive patients (n = 979) undergoing LIHR from 2009 to 2017 at a single institution were selected from a prospectively managed database. All procedures were performed by four general surgeons. Only male patients were selected, as the majority of POUR occurs in males. Patients were retroactively chart reviewed and divided into two groups, dexamethasone use (n = 623) and no dexamethasone use (n = 356). Perioperative factors were compared between groups with Chi-square and independent samples t tests. Univariable and multivariable logistic regression analysis was used to assess whether dexamethasone use was associated with POUR. A subgroup analysis was performed on the dexamethasone group to determine any dose-dependent effects. RESULTS: We found a significant difference in POUR between the dexamethasone group and no dexamethasone group (3.7% vs. 9.8%, p = 0.0001). Patients in the dexamethasone group had a shorter length of stay, and were less likely to have BPH or a Foley placed (all p < 0.05). Age and BMI were similar between groups. Multivariable analysis showed that the use of dexamethasone was associated with a reduced risk of POUR (OR 0.52, 95% CI 0.2-0.97, p = 0.0386), while controlling for factors such as age and BPH. A subgroup analysis examined the effect of dexamethasone per unit (mg) increase. There was no significant association between dexamethasone dose and POUR rates (OR 1.07, 95% CI 0.82-1.38, p = 0.6241). CONCLUSIONS: Patients who received dexamethasone showed a lower rate of POUR regardless of dose. These results suggest dexamethasone can be administered to reduce POUR in males undergoing LIHR.