Sirtuin 3 (SIRT3) is a protein deacetylase regulating beta cell function through inhibiting oxidative stress in obese and diabetic mice, but the detailed mechanism and potential effect of beta cell specific SIRT3 on metabolic homeostasis, and its potential effect on other metabolic organs are unknown. We found glucose tolerance and glucose stimulated insulin secretion (GSIS) were impaired in high fat diet (HFD)-fed beta cell selective Sirt3 knockout (Sirt3 f/f;Cre/+) mice. In addition, Sirt3 f/f;Cre/+ mice had more severe hepatic steatosis than Sirt3 f/f mice upon HFD feeding. RNA sequencing (RNA-Seq) of islets suggested that Sirt3 deficiency over-activated 5hydroxytryptamine (5-HT) synthesis as evidenced by up-regulation of tryptophan hydroxylase 1 (TPH1). 5-HT concentration was increased in both islets and serum of Sirt3 f/f;Cre/+ mice. 5-HT also facilitated the effect of palmitate to increase lipid deposition. Treatment with TPH1 inhibitor ameliorated hepatic steatosis and reduced weight gain in HFD-fed Sirt3 f/f;Cre/+ mice. These data suggested that under HFD feeding, SIRT3 deficiency in beta cells not only regulates insulin secretion but also modulates hepatic lipid metabolism via the release of 5-HT.

Aim Levels of branched‐chain amino acids (BCAAs, namely, isoleucine, leucine, and valine) are modulated by dietary intake and metabolic/genetic factors. BCAAs are associated with insulin resistance and increased risk of type 2 diabetes (T2D). Although insulin resistance predicts heart failure (HF), the relationship between BCAAs and HF in T2D remains unknown. Methods In this prospective observational study, we measured BCAAs in fasting serum samples collected at inception from 2139 T2D patients free of cardiovascular‐renal diseases. The study outcome was the first hospitalization for HF. Results During 29 103 person‐years of follow‐up, 115 primary events occurred (age: 54.8 ± 11.2 years, 48.2% men, median [interquartile range] diabetes duration: 5 years [1‐10]). Patients with incident HF had 5.6% higher serum BCAAs than those without HF (median 639.3 [561.3‐756.3] vs 605.2 [524.8‐708.7] μmol/L; P = .01). Serum BCAAs had a positive linear association with incident HF (per‐SD increase in logarithmically transformed BCAAs: hazard ratio [HR] 1.22 [95% CI 1.07‐1.39]), adjusting for age, sex, and diabetes duration. The HR remained significant after sequential adjustment of risk factors including incident coronary heart disease (1.24, 1.09‐1.41); blood pressure, low‐density lipoprotein cholesterol, and baseline use of related medications (1.31, 1.14‐1.50); HbA1c, waist circumference, triglyceride, and baseline use of related medications (1.28, 1.11‐1.48); albuminuria and estimated glomerular filtration rate (1.28, 1.11‐1.48). The competing risk of death analyses showed similar results. Conclusions Circulating levels of BCAAs are independently associated with incident HF in patients with T2D. Prospective cohort analysis and randomized trials are needed to evaluate the long‐term safety and efficacy of using different interventions to optimize BCAAs levels in these patients.

People with type 2 diabetes (T2D) have increased cancer risk. Liver cancer (LC) has a high prevalence in East Asia and is one of the leading causes of cancer death globally. Diagnosis of LC at early stage carries good prognosis. We used stored serum from patients of Hong Kong Diabetes Register before cancer diagnosis to extract RNA to screen for microRNA markers for early detection of LC in T2D. After screening with Affymetrix GeneChip microarray with serum RNA from 19 incident T2D LC (T2D-LC), 20 T2D cancer free (T2D-CF) and 20 non-T2D non-cancer patients, top signals were validated in a 3-group comparison including 1888 T2D-CF, 127 T2D-LC, and 487 T2D patients with non-liver cancer patients using qPCR. We detected 2.55-fold increase in miR-122-5p and 9.21-fold increase in miR-455-3p in the T2D-LC group. Using ROC analysis, miR-122-5p and miR-455-3p jointly predicted LC with an area under the curve of 0.770. After adjustment for confounders, each unit increase of miR-455-3p increased the odds ratio for liver cancer by 1.022. Increased serum levels of miR-122-5p and miR-455-3p were independently associated with increased risk of incident LC in T2D and may serve as potential biomarkers for early detection of LC in T2D.

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