In this study, we investigated the role of acyl-coenzyme A:diacylglycerol acyltransferase 2 (DGAT2) in glucose and lipid metabolism in obese mice by reducing its expression in liver and fat with an optimized antisense oligonucleotide (ASO). High-fat diet-induced obese (DIO) C57BL/6J mice and ob/ob mice were treated with DGAT2 ASO, control ASO, or saline. DGAT2 ASO treatment reduced DGAT2 messenger RNA (mRNA) levels by more than 75% in both liver and fat but did not change DGAT1 mRNA levels in either of these tissues, which resulted in decreased DGAT activity in liver but not in fat. DGAT2 ASO treatment did not cause significant changes in body weight, adiposity, metabolic rate, insulin sensitivity, or skin microstructure. However, DGAT2 ASO treatment caused a marked reduction in hepatic triglyceride content and improved hepatic steatosis in both models, which was consistent with a dramatic decrease in triglyceride synthesis and an increase in fatty acid oxidation observed in primary mouse hepatocytes treated with DGAT2 ASO. In addition, the treatment lowered hepatic triglyceride secretion rate and plasma triglyceride levels, and improved plasma lipoprotein profile in DIO mice. The positive effects of the DGAT2 ASO were accompanied by a reduction in the mRNA levels of several hepatic lipogenic genes, including SCD1, FAS, ACC1, ACC2, ATP-citrate lyase, glycerol kinase, and HMG-CoA reductase. In conclusion, reduction of DGAT2 expression in obese animals can reduce hepatic lipogenesis and hepatic steatosis as well as attenuate hyperlipidemia, thereby leading to an improvement in metabolic syndrome.

IntroductionAt the onset of diabetes mellitus, the kidney begins to grow and GFR increases. Some time later, structural changes can occur in the glomerulus which form the basis for progressive diabetic nephropathy. Intrarenal hemodynamic abnormalities, as manifest by glomerular hyperfiltration, are thought to be among the foremost factors responsible for the onset and progression of diabetic glomerulopathy. To account for these hemodynamic abnormalities, investigators have characterized the functional effects of diabetes on the various segments of the glomerular microvasculature (reviewed in ref. 1), and many substances have been invoked as humoral mediators of vasodilation in the diabetic glomerulus (reviewed in ref.2). However, no single cause has emerged to account for glomerular hyperfiltration in diabetes. The principal idea behind the present study is that glomerular hyperfiltration in diabetes does not develop mainly because of disordered microvascular function or from imbalanced hormones impinging directly on the glomerulus. Instead, we propose that glomerular hyperfiltration results mainly from a primary increase in proximal tubular reabsorption which causes GFR to increase through the physiologic actions of tubuloglomerular feedback (TGF). Furthermore, we propose that this primary increase in reabsorption results, in good part, from hypertrophy of the tubule. This "tubular hypothesis" of diabetic hyperfiltration reverses the order of events as typically envisioned for the diabetic kidney, in which a primary reduction in vascular resistance causes GFR to increase and the tubule then grows larger in order to accommodate the increased filtered load.If the TGF response were slow enough, one could confirm the tubular hypothesis of glomerular hyperfiltration by recording a lag time between enlargement of the kidney and the onset of hyperfiltration. However, the time required for TGF to evoke a change in GFR is on the order of several seconds (3), whereas diabetic hypertrophy proceeds continuously over days. Therefore, a TGF-mediated cause and effect relationship between kidney size and GFR will not be revealed by their temporal relationship. In fact, the most that can be said of the temporal relationship between hyperfiltration and renal hypertrophy in human type I diabetes is that they both occur early (4). Similarly, in rats with diabetes induced by streptozotocin, kidney size (5), kidney protein/DNA ratio (6), and GFR all increase within 24 hours of the onset of diabetes, the latter notwith- In early diabetes, the kidney grows and the glomerular filtration rate (GFR) increases. This growth is linked to ornithine decarboxylase (ODC). The study of hyperfiltration has focused on microvascular abnormalities, but hyperfiltration may actually result from a prior increase in capacity for proximal reabsorption which reduces the signal for tubuloglomerular feedback (TGF). Experiments were performed in Wistar rats after 1 week of streptozotocin diabetes. Kidney weight, ODC activity, and GFR were correlated in diabe...

The farnesoid X receptor (FXR) is a nuclear receptor that acts as a master regulator of bile acid metabolism and signaling. Activation of FXR inhibits bile acid synthesis and increases bile acid conjugation, transport, and excretion, thereby protecting the liver from the harmful effects of bile accumulation, leading to considerable interest in FXR as a therapeutic target for the treatment of cholestasis and nonalcoholic steatohepatitis. We identified a novel series of highly potent non-bile acid FXR agonists that introduce a bicyclic nortropine-substituted benzothiazole carboxylic acid moiety onto a trisubstituted isoxazole scaffold. Herein, we report the discovery of 1 (tropifexor, LJN452), a novel and highly potent agonist of FXR. Potent in vivo activity was demonstrated in rodent PD models by measuring the induction of FXR target genes in various tissues. Tropifexor has advanced into phase 2 human clinical trials in patients with NASH and PBC.

Nephron function is stabilized by tubuloglomerular feedback (TGF). TGF operates within the juxtaglomerular apparatus, sensing changes in tubular flow and eliciting compensatory changes in single nephron GFR (SNGFR). The mediator(s) of TGF remains unconfirmed. One theory is that ATP consumed in active transport by the macula densa leads to formation of adenosine, which causes glomerular vasoconstriction. We performed micropuncture in rats to test this hypothesis. Adenosine activity was manipulated by microperfusing nephrons with adenosine A1 receptor blocker, A1-agonist, or 5'-nucleotidase inhibitor. Effects on TGF were characterized by changes in TGF efficiency (the compensation for small perturbations in tubular flow) and by changes in the maximum range over which TGF can cause SNGFR to change. These data were further applied to generate TGF profiles [SNGFR versus late proximal flow (V(LP))]. TGF efficiency was significantly reduced by blocking A1-receptors. TGF efficiency, TGF range, and the slope of the TGF profile (DeltaSNGFR/DeltaV(LP)) were all significantly reduced by blocking 5'-nucleotidase. When adenosine activity was clamped by combining 5'-nucleotidase inhibitor with A1-agonist to determine whether TGF requires adenosine to be present or to fluctuate, the TGF slope was reduced by 83%, indicating that adenosine activity must fluctuate for normal TGF to occur and that adenosine is a mediator of TGF.

Glucocorticoids (GCs) increase hepatic gluconeogenesis and play an important role in the regulation of hepatic glucose output. Whereas systemic GC inhibition can alleviate hyperglycemia in rodents and humans, it results in adrenal insufficiency and stimulation of the hypothalamic-pituitary-adrenal axis. In the present study, we used optimized antisense oligonucleotides (ASOs) to cause selective reduction of the glucocorticoid receptor (GCCR) in liver and white adipose tissue (WAT) and evaluated the resultant changes in glucose and lipid metabolism in several rodent models of diabetes. Treatment of ob/ob mice with GCCR ASOs for 4 weeks resulted in ϳ75 and ϳ40% reduction in GCCR mRNA expression in liver and WAT, respectively. This was accompanied by ϳ65% decrease in fed and ϳ30% decrease in fasted glucose levels, a 60% decrease in plasma insulin concentration, and ϳ20 and 35% decrease in plasma resistin and tumor necrosis factor-␣ levels, respectively. Furthermore, GCCR ASO reduced hepatic glucose production and inhibited hepatic gluconeogenesis in liver slices from basal and dexamethasone-treated animals. In db/db mice, a similar reduction in GCCR expression caused ϳ40% decrease in fed and fasted glucose levels and ϳ50% reduction in plasma triglycerides. In ZDF and high-fat diet-fed streptozotocin-treated (HFD-STZ) rats, GCCR ASO treatment caused ϳ60% reduction in GCCR expression in the liver and WAT, which was accompanied by a 40 -70% decrease in fasted glucose levels and a robust reduction in plasma triglyceride, cholesterol, and free fatty acids. No change in circulating corticosterone levels was seen in any model after GCCR ASO treatment. To further demonstrate that GCCR ASO does not cause systemic GC antagonism, normal Sprague-Dawley rats were challenged with dexamethasone after treating with GCCR ASO. Dexamethasone increased the expression of GCresponsive genes such as PEPCK in the liver and decreased circulating lymphocytes. GCCR ASO treatment completely inhibited the increase in dexamethasoneinduced PEPCK expression in the liver without causing any change in the dexamethasone-induced lymphopenia. These studies demonstrate that tissue-selective GCCR antagonism with ASOs may be a viable therapeutic strategy for the treatment of the metabolic syndrome.