Adiponectin synthesis and secretion by subcutaneous adipose tissue is impaired during obesity by endoplasmic reticulum stress.

Subcutaneous (SAT) and visceral (VAT) adipose tissues stores excess energy as triglycerides and synthesize adiponectin to prevent ectopic lipid accumulation and lipotoxicity. During obesity, an impairment in the capacity of SAT to store triglycerides and synthesize adiponectin is associated with increased free fatty acids (FFA) release, leading to VAT hypertrophy and hepatic and skeletal muscle lipotoxicity. Endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) may be involved in SAT dysfunction during obesity. The objectives of this study were to assess UPR activation and adiponectin synthesis in: 1) SAT and VAT from mice exposed to acute pharmacologic or chronic obesity-induced ER stress and in 2) cultured mice primary mature adipocytes or adipocytes differentiated in vitro from SAT and VAT exposed to tunicamycin or thapsigargin. Mice fed a high-fat diet developed obesity, increased FFA and lower circulating adiponectin in association with lower adiponectin synthesis and increased UPR markers in SAT. Mice subjected to acute ER stress by pioglitazone administration and a low-dose tunicamycin injection presented a maladaptive UPR activation in SAT along with reduced adiponectin synthesis and secretion and increased lipolysis with respect to VAT, associated with lipid accumulation in skeletal muscle and liver. Primary adipocytes and adipocytes differentiated from SAT exposed to pharmacologic ER stress also developed maladaptive UPR, along with reduced adiponectin synthesis and increased lipolysis with respect to those from VAT. Our results indicate that compared to VAT, SAT is more susceptible to ER stress, leading to increased lipolysis and reduced adiponectin synthesis and secretion.

Aguamiel concentrate from Agave salmiana and its extracted saponins attenuated obesity and hepatic steatosis and increased Akkermansia muciniphila in C57BL6 mice.

Obesity and its comorbidities are a severe public health problem worldwide. The use of bioactive compounds found in some foods has been demonstrated to ameliorate the metabolic abnormalities associated with obesity. The purpose of this study was to assess whether the bioactive compounds present in aguamiel concentrate (AC) from Agave salmiana could attenuate glucose intolerance and hepatic steatosis in mice fed a high fat (HF) diet. HPLC-ELSD analysis showed that AC contained several saponins. The consumption of an AC extract rich in saponins reduced weight gain and fat mass and lowered serum glucose, insulin and LDL-cholesterol levels in mice fed a HF diet. Additionally, mice fed the saponin extract exhibited a reduced HOMA index and hepatic lipid levels and increased expression of genes involved in fatty acid oxidation. Saponins increased white adipose tissue browning, AMPK phosphorylation, fatty acid oxidation, and mitochondrial activity in skeletal muscle and energy expenditure in mice fed the HF diet. These metabolic changes were accompanied by an increase in the abundance of Akkermansia muciniphila in the gut microbiota. Therefore, Agave salmiana saponins can be an alternative to attenuate the metabolic changes that accompany obesity.

The effect of nopal (Opuntia ficus indica) on postprandial blood glucose, incretins, and antioxidant activity in Mexican patients with type 2 diabetes after consumption of two different composition breakfasts.

Nopal is a plant used in traditional Mexican medicine to treat diabetes. However, there is insufficient scientific evidence to demonstrate whether nopal can regulate postprandial glucose. The purpose for conducting this study was to evaluate the glycemic index, insulinemic index, glucose-dependent insulinotropic peptide (GIP) index, and the glucagon-like peptide 1 (GLP-1) index, and the effect of nopal on patients with type 2 diabetes after consumption of a high-carbohydrate breakfast (HCB) or high-soy-protein breakfast (HSPB) on the postprandial response of glucose, insulin, GIP, GLP-1, and antioxidant activity. In study 1, the glycemic index, insulinemic index, GIP index, and GLP-1 index were calculated for seven healthy participants who consumed 50 g of available carbohydrates from glucose or dehydrated nopal. In study 2, 14 patients with type 2 diabetes consumed nopal in HCB or HSPB with or without 300 g steamed nopal. The glycemic index of nopal was 32.5±4, insulinemic index was 36.1±6, GIP index was 6.5±3.0, and GLP-1 index was 25.9±18. For those patients with type 2 diabetes who consumed the HCB+nopal, there was significantly lower area under the curve for glucose (287±30) than for those who consumed the HCB only (443±49), and lower incremental area under the curve for insulin (5,952±833 vs 7,313±1,090), and those patients with type 2 diabetes who consumed the HSPB avoided postprandial blood glucose peaks. Consumption of the HSPB+nopal significantly reduced the postprandial peaks of GIP concentration at 30 and 45 minutes and increased the antioxidant activity after 2 hours measured by the 2,2-diphenyl-1-picrilhidracyl method. These findings suggest that nopal could reduce postprandial blood glucose, serum insulin, and plasma GIP peaks, as well as increase antioxidant activity in healthy people and patients with type 2 diabetes.

Opuntia ficus indica (nopal) attenuates hepatic steatosis and oxidative stress in obese Zucker (fa/fa) rats.

Nonalcoholic fatty liver disease (NAFLD) is associated with multiple factors such as obesity, insulin resistance, and oxidative stress. Nopal, a cactus plant widely consumed in the Mexican diet, is considered a functional food because of its antioxidant activity and ability to improve biomarkers of metabolic syndrome. The aim of this study was to assess the effect of nopal consumption on the development of hepatic steatosis and hepatic oxidative stress and on the regulation of genes involved in hepatic lipid metabolism. Obese Zucker (fa/fa) rats were fed a control diet or a diet containing 4% nopal for 7 wk. Rats fed the nopal-containing diet had ∼50% lower hepatic TG than the control group as well as a reduction in hepatomegaly and biomarkers of hepatocyte injury such as alanine and aspartate aminotransferases. Attenuation of hepatic steatosis by nopal consumption was accompanied by a higher serum concentration of adiponectin and a greater abundance of mRNA for genes involved in lipid oxidation and lipid export and production of carnitine palmitoyltransferase-1 and microsomal TG transfer proteins in liver. Hepatic reactive oxygen species and lipid peroxidation biomarkers were significantly lower in rats fed nopal compared with the control rats. Furthermore, rats fed the nopal diet had a lower postprandial serum insulin concentration and a greater liver phosphorylated protein kinase B (pAKT):AKT ratio in the postprandial state. This study suggests that nopal consumption attenuates hepatic steatosis by increasing fatty acid oxidation and VLDL synthesis, decreasing oxidative stress, and improving liver insulin signaling in obese Zucker (fa/fa) rats.

A dietary pattern including nopal, chia seed, soy protein, and oat reduces serum triglycerides and glucose intolerance in patients with metabolic syndrome.

Metabolic syndrome (MetS) is a health problem throughout the world and is associated with cardiovascular disease and diabetes. Thus, the purpose of the present work was to evaluate the effects of a dietary pattern (DP; soy protein, nopal, chia seed, and oat) on the biochemical variables of MetS, the AUC for glucose and insulin, glucose intolerance (GI), the relationship of the presence of certain polymorphisms related to MetS, and the response to the DP. In this randomized trial, the participants consumed their habitual diet but reduced by 500 kcal for 2 wk. They were then assigned to the placebo (P; n = 35) or DP (n = 32) group and consumed the reduced energy diet plus the P or DP beverage (235 kcal) minus the energy provided by these for 2 mo. All participants had decreases in body weight (BW), BMI, and waist circumference during the 2-mo treatment (P < 0.0001); however, only the DP group had decreases in serum TG, C-reactive protein (CRP), and AUC for insulin and GI after a glucose tolerance test. Interestingly, participants in the DP group with MetS and the ABCA1 R230C variant had a greater decrease in BW and an increase in serum adiponectin concentration after 2 mo of dietary treatment than those with the ABCA1 R230R variant. The results from this study suggest that lifestyle interventions involving specific DP for the treatment of MetS could be more effective if local foods and genetic variations of the population are considered.