Long-term ketogenic diet contributes to glycemic control but promotes lipid accumulation and hepatic steatosis in type 2 diabetic mice

Metabolic Effects of Ketogenic Diets: Exploring Whole-Body Metabolism in Connection with Adipose Tissue and Other Metabolic Organs

The ketogenic diet (KD) is characterized by minimal carbohydrate, moderate protein, and high fat intake, leading to ketosis. It is recognized for its efficiency in weight loss, metabolic health improvement, and various therapeutic interventions. The KD enhances glucose and lipid metabolism, reducing triglycerides and total cholesterol while increasing high-density lipoprotein levels and alleviating dyslipidemia. It significantly influences adipose tissue hormones, key contributors to systemic metabolism. Brown adipose tissue, essential for thermogenesis and lipid combustion, encounters modified UCP1 levels due to dietary factors, including the KD. UCP1 generates heat by uncoupling electron transport during ATP synthesis. Browning of the white adipose tissue elevates UCP1 levels in both white and brown adipose tissues, a phenomenon encouraged by the KD. Ketone oxidation depletes intermediates in the Krebs cycle, requiring anaplerotic substances, including glucose, glycogen, or amino acids, for metabolic efficiency. Methylation is essential in adipogenesis and the body's dietary responses, with DNA methylation of several genes linked to weight loss and ketosis. The KD stimulates FGF21, influencing metabolic stability via the UCP1 pathways. The KD induces a reduction in muscle mass, potentially involving anti-lipolytic effects and attenuating proteolysis in skeletal muscles. Additionally, the KD contributes to neuroprotection, possesses anti-inflammatory properties, and alters epigenetics. This review encapsulates the metabolic effects and signaling induced by the KD in adipose tissue and major metabolic organs.

The association between multiple trajectories of macronutrient intake and the risk of new-onset diabetes in Chinese adults

BACKGROUND

The association between macronutrient intake and diabetes is unclear. We used data from the China Health and Nutrition Survey to explore the association between macronutrient intake trajectories and diabetes risk in this study.

METHODS

We included 6755 participants who did not have diabetes at baseline and participated in at least three surveys. The energy supply ratio of carbohydrate, protein, and fat was further calculated from dietary data; different macronutrient trajectories were determined using multitrajectory models; and multiple Cox regression models were used to evaluate the association between these trajectories and diabetes.

RESULTS

We found three multitrajectories: decreased low carbohydrate-increased moderate protein-increased high fat (DLC-IMP-IHF), decreased high carbohydrate-moderate protein-increased low fat (DHC-MP-ILF), and balanced-macronutrients (BM). Compared to the BM trajectory, DHC-MP-ILF trajectories were significantly associated with increased risk of diabetes (hazard ratio [HR]: 3.228, 95% confidence interval [CI]: 1.571-6.632), whereas no association between DLC-IMP-IHF trajectories and diabetes was found in our study (HR: 0.699, 95% CI: 0.351-1.392).

CONCLUSIONS

The downward trend of high carbohydrate and the increasing trend of low fat increased the risk of diabetes in Chinese adults.

Ketogenic diet alleviates β-cell dedifferentiation but aggravates hepatic lipid accumulation in db/db mice

OBJECTIVE

The aim of this study was to explore the effect of the ketogenic diet (KD) on β-cell dedifferentiation and hepatic lipid accumulation in db/db mice.

METHODS

After a 3-wk habituation, male db/db mice ages 8 wk were assigned into one of three groups: normal diet (ND), KD, and 75% calorie restriction (CR) group. Free access to a standard diet, a KD, and 75% of a standard diet, respectively, were given to each group. Additionally, sex-matched 8-wk-old C57BL/6 mice were used to construct a control (C) group. After a 4-wk dietary intervention, mouse body weight, fasting blood glucose (FBG), blood lipids, fasting insulin (FINS), glucose tolerance, and β-hydroxybutyric acid level were measured. The morphologies of the islet and liver were observed by hematoxylin and eosin staining. Positive expressions of β-cell-specific transcription factors in mouse islets were determined by double immunofluorescence staining. The size and number of lipid droplets in mouse liver were examined by Oil Red O staining. Real-time quantitative reverse transcription polymerase chain reaction detected relative levels of adipogenesis-associated and lipolysis-associated genes in mouse liver. Additionally, expressions of CD36 protein in the mouse liver were determined by immunohistochemical staining and Western blot.

RESULTS

After a 4-wk dietary intervention, FBG, FINS, and glucose area under the curve in the KD group became significantly lower than in the ND group (all P < 0.05). Regular morphology of mouse islets was observed in the KD group, with an increased number of islet cells. The KD significantly reversed the decrease in β-cell number, disarrangement of β-cells, decline of β/α-cell ratio, and downregulation of β-cell-specific transcription factors in db/db mice. Serum levels of triacylglycerol, total cholesterol, and low-density lipoprotein cholesterol were comparable between the ND and KD groups. In contrast, serum triacylglycerol levels were significantly lower in the CR group than in the ND group (P < 0.05). Vacuolar degeneration and lipid accumulation in the liver were more prominent in the KD group than in the ND and CR groups. The mRNA levels of Pparα and Acox1 in the KD group were lower than those in the ND group, although no significant differences were detected. Relative levels of Cd36 and inflammatory genes in the mouse liver were significantly higher in the KD group than in the ND group (all P < 0.05).

CONCLUSION

The KD significantly reduced FBG and FINS and improved glucose tolerance in db/db mice by upregulating β-cell-specific transcription factors and reversing β-cell dedifferentiation. However, the KD also induced hepatic lipid accumulation and aggravated inflammatory response in the liver of db/db mice.

Intermittent fasting and Alzheimer's disease-Targeting ketone bodies as a potential strategy for brain energy rescue

Alzheimer's disease (AD) lacks effective clinical treatments. As the disease progresses, the cerebral glucose hypometabolism that appears in the preclinical phase of AD gradually worsens, leading to increasingly severe brain energy disorders. This review analyzes the brain energy deficit in AD and its etiology, brain energy rescue strategies based on ketone intervention, the effects and mechanisms of IF, the differences in efficacy between IF and ketogenic diet and the duality of IF. The evidence suggests that brain energy deficits lead to the development and progression of AD pathology. IF, which improves brain energy impairments by promoting ketone metabolism, thus has good therapeutic potential for AD.

Ketogenic Diet and Multiple Health Outcomes: An Umbrella Review of Meta-Analysis

Numerous studies have examined the effects of ketogenic diets (KD) on health-related outcomes through meta-analyses. However, the presence of biases may compromise the reliability of conclusions. Therefore, we conducted an umbrella review to collate and appraise the strength of evidence on the efficacy of KD interventions. We conducted a comprehensive search on PubMed, EMBASE, and the Cochrane Database until April 2023 to identify meta-analyses that investigated the treatment effects of KD for multiple health conditions, which yielded 23 meta-analyses for quantitative analyses. The evidence suggests that KD could increase the levels of low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C), the respiratory exchange rate (RER), and could decrease total testosterone and testosterone levels (all p-random effects: <0.05). The combination of KD and physical activity can significantly reduce body weight and increase the levels of LDL-C and cortisol. In addition, KD was associated with seizure reduction in children, which can be explained by the ketosis state as induced by the diet. Furthermore, KD demonstrated a better alleviation effect in refractory childhood epilepsy, in terms of median effective rates for seizure reduction of ≥50%, ≥90%, and seizure freedom. However, the strength of evidence supporting the aforementioned associations was generally weak, thereby challenging their credibility. Consequently, future studies should prioritize stringent research protocols to ascertain whether KD interventions with longer intervention periods hold promise as a viable treatment option for various diseases.

Low-Carbohydrate Diet Modulates Glucose-Lipid Utilization in Skeletal Muscle of Diabetic Mice

Type 2 diabetes is associated with many complications, including skeletal muscle atrophy. Ketogenic diets and low-carbohydrate diets (LCD) have recently been introduced as dietary interventions in patients with diabetes, but their effects on glucose and lipid metabolism in skeletal muscle have not been studied. In the current study, we compared the effects of LCD and ketogenic diet on glucose and lipid metabolism in skeletal muscle of diabetic mice. C57BL/6J mice with type 2 diabetes, constructed by a high-fat diet combined with streptozotocin, were fed a standard diet, a high-fat diet, an LCD, or a ketogenic diet for 14 weeks, respectively. Here, we found that the LCD, rather than the ketogenic diet, retained skeletal muscle weight and suppressed the expression of atrophy-related genes in diabetic mice. In addition, the LCD had more glycolytic/type IIb myofiber content and inhibited forkhead box O1 and pyruvate dehydrogenase kinase 4 expression, leading to improved glucose utilization. However, the ketogenic diet maintained more oxidative/type I myofibers. Moreover, compared with the ketogenic diet, the LCD decreased intramuscular triglycerides content and muscle lipolysis, suggesting improvement in lipid metabolism. Taken together, these data suggested that the LCD improved glucose utilization, and inhibited lipolysis and atrophy in skeletal muscle of diabetic mice, while the ketogenic diet showed metabolic disorders in skeletal muscle.

A low-carbohydrate diet induces hepatic insulin resistance and metabolic associated fatty liver disease in mice

OBJECTIVES

Metabolic-associated fatty liver disease (MAFLD) is the most common chronic liver disease that can range from hepatic steatosis to non-alcoholic steatohepatitis (NASH), which can lead to fibrosis and cirrhosis. Recently, ketogenic diet (KD), a low carbohydrate diet, gained popularity as a weight-loss approach, although it has been reported to induce hepatic insulin resistance and steatosis in animal model systems via an undefined mechanism. Herein, we investigated the KD metabolic benefits and its contribution to the pathogenesis of NASH.

METHODS

Using metabolic, biochemical and omics approaches, we identified the effects of a KD on NASH and investigated the mechanisms by which KD induces hepatic insulin resistance and steatosis.

RESULTS

We demonstrate that KD can induce fibrosis and NASH regardless of body weight loss compared to high-fat diet (HFD) fed mice at thermoneutrality. At ambient temperature (23 °C), KD-fed mice develop a severe hepatic injury, inflammation, and steatosis. In addition, KD increases liver cholesterol, IL-6, and p-JNK and aggravates diet induced-glucose intolerance and hepatic insulin resistance compared to HFD. Pharmacological inhibition of IL-6 and JNK reverses KD-induced glucose intolerance, and hepatic steatosis and restores insulin sensitivity.

CONCLUSIONS

Our studies uncover a new mechanism for KD-induced hepatic insulin resistance and NASH potentially via IL-6-JNK signaling and provide a new NASH mouse model.

Ketogenic Diet Combined with Moderate Aerobic Exercise Training Ameliorates White Adipose Tissue Mass, Serum Biomarkers, and Hepatic Lipid Metabolism in High-Fat Diet-Induced Obese Mice

Obesity is a serious public health issue worldwide. Growing evidence demonstrates the efficacy of the ketogenic diet (KD) for weight loss, but there may be some adverse side effects such as dyslipidemia and hepatic steatosis. Aerobic exercise is a widely recognized approach for improving these metabolic markers. Here we explored the combined impacts of KD and moderate aerobic exercise for an 8-week intervention on body weight and fat loss, serum biomarkers, and hepatic lipid metabolism in a mouse model of high-fat diet-induced obesity. Both KD and KD combined with exercise significantly reduced body weight and fat mass. No significant adverse effects of KD were observed in serum biomarkers or hepatic lipid storage, except for an increase in circulating triglyceride level. However, aerobic exercise lowered serum triglyceride levels, and further ameliorated serum parameters, and hepatic steatosis in KD-fed mice. Moreover, gene and protein expression analysis indicated that KD combined with exercise was associated with increased expression of lipolysis-related genes and protein levels, and reduced expression of lipogenic genes relative to KD without exercise. Overall, our findings for mice indicate that further work on humans might reveal that KD combined with moderate aerobic exercise could be a promising therapeutic strategy for obesity.

Bdh1 overexpression ameliorates hepatic injury by activation of Nrf2 in a MAFLD mouse model

In 2020, a group of experts officially suggested metabolic dysfunction associated with fatty liver disease "MAFLD" as a more appropriate overarching term than NAFLD, indicating the key role of metabolism in fatty liver disease. Bdh1, as the rate-limiting enzyme of ketone metabolism, acts as an important metabolic regulator in liver. However, the role of Bdh1 in MAFLD is unclear. In this study, we used the transgenic db/db mice as a MAFLD mouse model and observed the downregulated expression of Bdh1 in fatty liver. In addition, expression of Bdh1 was also reduced by palmitic acid (PA) treatment in LO2 cells. Bdh1 knockdown led to ROS overproduction and ROS-induced inflammation and apoptosis in LO2 cells, while Bdh1 overexpression protected LO2 cells from lipotoxicity by inhibiting ROS overproduction. Mechanistically, Bdh1-mediated βOHB metabolism inhibits ROS overproduction by activation of Nrf2 through enhancement of metabolic flux composed of βOHB-AcAc-succinate-fumarate. Notably, adeno-associated virus (AAV)-mediated Bdh1 overexpression successfully reversed the hepatic function indexes, fibrosis, inflammation, and apoptosis in fatty livers from db/db mice. In conclusion, our study revealed a Bdh1-mediated molecular mechanism in pathogenesis of metabolic dysfunction related liver disease and identified Bdh1 as a novel potential therapeutic target for MAFLD.

Ketogenic diet ameliorates lipid dysregulation in type 2 diabetic mice by downregulating hepatic pescadillo 1

Background

Previous reports implied a possible link between PES1 and lipid metabolism. However, the role of PES1 in regulating T2DM related lipid metabolism and the effect of ketogenic diet (KD) on PES1 have not been reported. The aim of present study is to explore the role of PES1 in effects of KD on diabetic mice and its mediated mechanism.

Methods

Male C57BL/6J and KKA^y mice were fed with standard diet (SD) and KD, respectively. Simultaneously, McArdle 7777 cells were treated by β-hydroxybutyric acid (β-HB), Pes1 siRNA or Pes1 overexpression plasmid, respectively. Additionally, liver-conditional knockout (CKO) of Pes1 in vivo was applied.

Results

Hepatic PES1 expression in diabetic mice was markedly increased, which was suppressed by KD feeding with an accompanying reduction of hepatic and plasma triglycerides (TG). In mice with CKO of Pes1, the protein levels of p300, SREBP1c, FASN, SCD1, Caspase1, NLRP3 and GSDMD were dramatically downregulated in livers, and the plasma and hepatic TG, IL-1β and IL-18 were decreased as well. The similar outcomes were also observed in β-HB and Pes1 knockdown treated hepatocytes. By contrast, Pes1 overexpression in cultured hepatocytes showed that these levels were significantly enhanced, which were, however reduced under β-HB treatment. Mechanistically, we discovered that β-HB decreased CHOP binding to the Pes1 promoters, resulting in the downregulation of PES1, thereby reducing PES1 binding to p300 and Caspase1 promoters. The inhibition of p300 and Caspase1 expression elicited the dramatic suppression of acetylation of SREBP1c via its interaction with p300, and the decreased GSDMD levels. Besides, knockdown of Caspase1 also alleviated the TG levels in cultured hepatocytes.

Conclusion

KD may improve lipid dysregulation in type 2 diabetic mice by downregulating hepatic PES1 expression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00429-6.

Activation of G protein-coupled receptors by ketone bodies: Clinical implication of the ketogenic diet in metabolic disorders

Ketogenesis takes place in hepatocyte mitochondria where acetyl-CoA derived from fatty acid catabolism is converted to ketone bodies (KB), namely β-hydroxybutyrate (β-OHB), acetoacetate and acetone. KB represent important alternative energy sources under metabolic stress conditions. Ketogenic diets (KDs) are low-carbohydrate, fat-rich eating strategies which have been widely proposed as valid nutritional interventions in several metabolic disorders due to its substantial efficacy in weight loss achievement. Carbohydrate restriction during KD forces the use of FFA, which are subsequently transformed into KB in hepatocytes to provide energy, leading to a significant increase in ketone levels known as "nutritional ketosis". The recent discovery of KB as ligands of G protein-coupled receptors (GPCR) - cellular transducers implicated in a wide range of body functions - has aroused a great interest in understanding whether some of the clinical effects associated to KD consumption might be mediated by the ketone/GPCR axis. Specifically, anti-inflammatory effects associated to KD regimen are presumably due to GPR109A-mediated inhibition of NLRP3 inflammasome by β-OHB, whilst lipid profile amelioration by KDs could be ascribed to the actions of acetoacetate via GPR43 and of β-OHB via GPR109A on lipolysis. Thus, this review will focus on the effects of KD-induced nutritional ketosis potentially mediated by specific GPCRs in metabolic and endocrinological disorders. To discriminate the effects of ketone bodies per se, independently of weight loss, only studies comparing ketogenic vs isocaloric non-ketogenic diets will be considered as well as short-term tolerability and safety of KDs.

Dietary Interventions: A Promising Treatment for Polycystic Ovary Syndrome

BACKGROUND

Dietary interventions as a first-line treatment for patients with polycystic ovary syndrome (PCOS) have been evaluated, but the optimal diet has not been determined. Proper diet and the maintenance of adequate nutritional status are of great importance in the prevention of this disorder, and therapeutics and dietary habits play an important role in the recovery of patients with PCOS.

SUMMARY

A range of dietary patterns have been shown to impact weight loss and insulin resistance (IR) and improve reproductive function, including the Mediterranean diet, the ketogenic diet, Dietary Approaches to Stop Hypertension, and other dietary patterns. Key Messages: Diets that can reduce rates of obesity and IR are beneficial to women with PCOS, the status of obesity and IR should be determined at the early stage of the disease, so as to develop individualized and sustainable dietary intervention. The long-term efficacy, safety, and health benefits of diet management in patients with PCOS need to be tested by further researches.

Antidiabetic Function of Lactobacillus fermentum MF423-Fermented Rice Bran and Its Effect on Gut Microbiota Structure in Type 2 Diabetic Mice

Rice bran is an industrial byproduct that exerts several bioactivities despite its limited bioavailability. In this study, rice bran fermented with Lactobacillus fermentum MF423 (FLRB) had enhanced antidiabetic effects both in vitro and in vivo. FLRB could increase glucose consumption and decrease lipid accumulation in insulin resistant HepG2 cells. Eight weeks of FLRB treatment significantly reduced the levels of blood glucose and lipids and elevated antioxidant activity in type 2 diabetic mellitus (T2DM) mice. H&E staining revealed alleviation of overt lesions in the livers of FLRB-treated mice. Moreover, high-throughput sequencing showed notable variation in the composition of gut microbiota in FLRB-treated mice, especially for short-chain fatty acids (SCFAs)-producing bacteria such as Dubosiella and Lactobacillus. In conclusion, our results suggested that rice bran fermentation products can modulate the intestinal microbiota and improve T2DM-related biochemical abnormalities, so they can be applied as potential probiotics or dietary supplements.

Ketogenic diet impairs Mycobacterium ulcerans growth and toxin production, enhancing hosts' response to the infection in an experimental mouse model

Ketogenic diets have been used to treat diverse conditions, and there is growing evidence of their benefits for tissue repair and in inflammatory disease treatment. However, their role in infectious diseases has been little studied. Buruli ulcer (Mycobacterium ulcerans infection) is a chronic infectious disease characterized by large skin ulcerations caused by mycolactone, the major virulence factor of the bacillus. Here, we investigated the impact of ketogenic diet on this cutaneous disease in an experimental mouse model. This diet prevented ulceration, by modulating bacterial growth and host inflammatory response. β-hydroxybutyrate, the major ketone body produced during ketogenic diet and diffusing in tissues, impeded M. ulcerans growth and mycolactone production in vitro underlying its potential key role in infection. These results pave the way for the development of new patient management strategies involving shorter courses of treatment and improving wound healing, in line with the major objectives of the World Health Organization.

Ketogenic diet alleviates colitis by reduction of colonic group 3 innate lymphoid cells through altering gut microbiome

Accumulating evidence suggests that ketogenic diets (KDs) mediate the rise of circulating ketone bodies and exert a potential anti-inflammatory effect; however, the consequences of this unique diet on colitis remain unknown. We performed a series of systematic studies using a dextran sulfate sodium (DSS) animal model of inflammatory colitis. Animals were fed with a KD, low-carbohydrate diet (LCD), or normal diet (ND). Germ-free mice were utilized in validation experiments. Colon tissues were analyzed by transcriptome sequencing, RT2 profiler PCR array, histopathology, and immunofluorescence. Serum samples were analyzed by metabolic assay kit. Fecal samples were analyzed by 16S rRNA gene sequencing, liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry. We observed that KD alleviated colitis by altering the gut microbiota and metabolites in a manner distinct from LCD. Quantitative diet experiments confirmed the unique impact of KD relative to LCD with a reproducible increase in Akkermansia, whereas the opposite was observed for Escherichia/Shigella. After colitis induction, the KD protected intestinal barrier function, and reduced the production of RORγt⁺CD3⁻ group 3 innate lymphoid cells (ILC3s) and related inflammatory cytokines (IL-17α, IL-18, IL-22, Ccl4). Finally, fecal microbiota transplantation into germ-free mice revealed that the KD- mediated colitis inhibition and ILC3 regulation were dependent on the modification of gut microbiota. Taken together, our study presents a global view of microbiome-metabolomics changes that occur during KD colitis treatment, and identifies the regulation of gut microbiome and ILC3s as novel targets involving in IBD dietary therapy.

Ketogenic Diets Induced Glucose Intolerance and Lipid Accumulation in Mice with Alterations in Gut Microbiota and Metabolites

The ketogenic diet (KD), which can induce changes in gut microbiota, has shown benefits for epilepsy and several neurodegenerative diseases. However, the effects of a KD on glucose and lipid metabolism remain inconclusive. Using two formulas of ketogenic diets (KDR with 89.5% fat and KDH with 91.3% fat), which are commonly used in mouse trials, we found that KDR but not KDH induced insulin resistance and damaged glucose homeostasis, while KDH induced more fat accumulation in mice. Further study showed that KD impacted glucose metabolism, which was related to the sources of fat, while both the sources and proportions of fat affected lipid metabolism. And the KD widely used in human studies still induced insulin resistance and fat accumulation in mice. Moreover, KDs changed the gut microbiota and metabolites in mice, and the sources and proportions of fat in the diets respectively changed the abundance of specific bacteria and metabolites which were correlated with parameters related to glucose intolerance and lipid accumulation. Overall, our study demonstrated that the metabolic disorders induced by KDs are closely related to the source and proportion of fat in the diet, which may be associated with the changes of the gut microbiota and metabolites.IMPORTANCE The ketogenic diet with extremely high fat and very low carbohydrate levels is very popular in society today. Although it has beneficial effects on epilepsy and neurodegenerative diseases, how ketogenic diets impact host glucose and lipid metabolism and gut microbiota still needs further investigation. Here, we surveyed the effects of two ketogenic diets which are commonly used in mouse trials on metabolic phenotypes, gut microbiota, and metabolites in mice. We found that both ketogenic diets impaired glucose and lipid metabolism in mice, and this may be due to the sources and proportions of fat in the diets. This work highlights the potential risk of glucose and lipid metabolism disorders and the importance of evaluating the sources and proportions of fat in the diets, when using ketogenic diets for weight loss and the treatment of diseases.

High-Protein or Low Glycemic Index Diet-Which Energy-Restricted Diet Is Better to Start a Weight Loss Program?

Background: To date, no crossover studies have compared the effects of high-protein (HP) and low glycemic index (LGI) diets applied as starting energy-restricted diets. Methods: Thirty-five overweight or obese volunteers with sedentary lifestyles aged 41.4 ± 11.0 years, with body mass index (BMI) of 33.6 ± 4.2 kg/m², without diabetes, completed an 8-week randomized crossover study of an energy-restricted diet (reduction of 30%; approximately 600 kcal/day). The anthropometric parameters, body composition, 24 h blood pressure, and basic metabolic profile were measured at baseline and after completing the two 4-week diets; i.e., the HP (protein at 30% of the daily energy intake) or LGI diet, followed by the opposite diet. All subjects maintained food diaries and attended six counselling sessions with a clinical dietitian. Results: The final weight loss was not significantly different when the HP diet was used first but was associated with a greater loss of fat mass: 4.6 kg (5.8; 3.0 kg) vs. 2.2 (4.5; 0.8); p < 0.025, preserved muscle mass, and reduced LDL-cholesterol. Conclusions: A short-term HP diet applied as a jump-start diet appeared to be more beneficial than an LGI diet, as indicated by the greater fat mass loss, preservation of muscle mass, and better effects on the lipid profile.

Comparison of Ketogenic Diets with and without Ketone Salts versus a Low-Fat Diet: Liver Fat Responses in Overweight Adults

Ketogenic diets (KDs) often contain high levels of saturated fat, which may increase liver fat, but the lower carbohydrate intake may have the opposite effect. Using a controlled feeding design, we compared liver fat responses to a hypocaloric KD with a placebo (PL) versus an energy-matched low-fat diet (LFD) in overweight adults. We also examined the added effect of a ketone supplement (KS). Overweight adults were randomized to a 6-week KD (KD + PL) or a KD with KS (KD + KS); an LFD group was recruited separately. All diets were estimated to provide 75% of energy expenditure. Weight loss was similar between groups (p > 0.05). Liver fat assessed by magnetic resonance imaging decreased after 6 week (p = 0.004) with no group differences (p > 0.05). A subset with nonalcoholic fatty liver disease (NAFLD) (liver fat > 5%, n = 12) showed a greater reduction in liver fat, but no group differences. In KD participants with NAFLD, 92% of the variability in change in liver fat was explained by baseline liver fat (p < 0.001). A short-term hypocaloric KD high in saturated fat does not adversely impact liver health and is not impacted by exogenous ketones. Hypocaloric low-fat and KDs can both be used in the short-term to significantly reduce liver fat in individuals with NAFLD.

Optimization of extraction flavonoids from Exocarpium Citri Grandis and evaluation its hypoglycemic and hypolipidemic activities

ETHNOPHARMACOLOGICAL RELEVANCE

Exocarpium Citri Grandis (ECG; Huajuhong in Chinese) is a precious traditional Chinese medicine with a history of hundreds of years in China. It has been demonstrated to possess numerous pharmacological properties, including antitussive, expectorant, anti-inflammatory, hypoglycemic, and hypolipidemic. However, no in-depth report exists on the hypoglycemic and hypolipidemic properties of ECG.

AIM OF THE STUDY

This study aimed to evaluate the hypoglycemic and hypolipidemic properties of ECG flavonoids extract in vitro and in vivo so as to lay the foundation for further researches in this field.

MATERIALS AND METHODS

Total flavonoids (TF) and naringin were separately extracted from ECG, and the components of TF were identified by HPLC-MS. The antioxidant capacities of TF and naringin were determined by 2,2,1-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging tests, and digestive enzymes activity inhibition assays in vitro in order to evaluate their hypoglycemic properties. Furthermore, diabetic mice experiments were performed to assess the hypoglycemic and hypolipidemic properties of TF and naringin in vivo.

RESULTS

Five compounds were identified from TF, including naringin, rhoifolin, poncirin, bergaptol, and naringenin. The half maximal inhibitory concentration (IC₅₀) of TF and naringin to DPPH-free radicals were 0.269 and 1.946 mg/mL, respectively. TF and naringin demonstrated a certain inhibitory effect on α-glucosidase and a weaker inhibitory effect on α-amylase. The results of animal experiments showed that TF and naringin had no significant effect on the blood glucose levels, but they could lead to significant (p < 0.05 or p < 0.01) increase in the serum insulin level and high-density lipoprotein cholesterol (HDL-C) levels with concomitant reduction in the total cholesterol (TC), total triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C) levels in diabetic mice. In addition, TF and naringin could reduce the liver index of diabetic mice (p < 0.01) and reduce the kidney index at low doses (p < 0.05).

CONCLUSIONS

Our study revealed that the hypoglycemic and hypolipidemic activities of TF is mainly derived from naringin, and other active ingredients in TF also have the effects of alleviating oxidative stress, inhibiting digestive enzyme activity and reducing blood lipids. Our results thus provide a scientific basis for the application of ECG in antidiabetic treatment.

Islet Health, Hormone Secretion, and Insulin Responsivity with Low-Carbohydrate Feeding in Diabetes

Exploring new avenues to control daily fluctuations in glycemia has been a central theme for diabetes research since the Diabetes Control and Complications Trial (DCCT). Carbohydrate restriction has re-emerged as a means to control type 2 diabetes mellitus (T2DM), becoming increasingly popular and supported by national diabetes associations in Canada, Australia, the USA, and Europe. This approval comes from many positive outcomes on HbA1c in human studies; yet mechanisms underlying their success have not been fully elucidated. In this review, we discuss the preclinical and clinical studies investigating the role of carbohydrate restriction and physiological elevations in ketone bodies directly on pancreatic islet health, islet hormone secretion, and insulin sensitivity. Included studies have clearly outlined diet compositions, including a diet with 30% or less of calories from carbohydrates.

High-Intensity Interval Training Attenuates Ketogenic Diet-Induced Liver Fibrosis in Type 2 Diabetic Mice by Ameliorating TGF-β1/Smad Signaling

OBJECTIVE

Ketogenic diet (KD) and high-intensity interval training (HIIT) have preclinical benefits for type 2 diabetes (Db). However, the health risks of long-term KD use in diabetes should be ascertained and prevented. We hypothesized that KD-induced liver fibrosis in type 2 diabetic mice could be ameliorated by HIIT.

METHODS

Streptozotocin-induced type 2 diabetic mice were divided into high-fat diet (HFD) control (Db+HFD+Sed), KD control (Db+KD+Sed), HFD coupled with HIIT (Db+HFD+HIIT), and KD coupled with HIIT (Db+KD+HIIT) groups (n=6, per group). Control mice were kept in sedentary (Sed), while HIIT group mice underwent 40-minute high-intensity interval training three alternate days per week. After 8-week intervention, the indicators of body weight and insulin resistance, oxidative stress markers, hepatic fibrosis, genetic and protein expression of related pathways were tested.

RESULTS

We found that fasting blood glucose level was reduced in the Db+HFD+HIIT, Db+KD+Sed, and Db+KD+HIIT groups. Insulin sensitivity was increased in diabetic mice of these groups, whereas ROS levels were decreased in mice that underwent HIIT. The immunohistochemical staining of liver, serum index, and hepatic parameters of diabetic mice in the KD group revealed liver fibrosis, which was significantly attenuated by HIIT. Besides, these effects of HIIT were the outcome of hepatic stellate cell's inactivation, reduced protein expression of matrix metalloproteinases and tissue inhibitor of metalloproteinases, and the inhibition of TGF-β1/Smad signaling.

CONCLUSION

KD had a profound fibrotic effect on the liver of type 2 diabetic mice, whereas HIIT ameliorated this effect. KD did not show any apparent benefit as far as glucose tolerance and homeostasis were concerned. Concisely, our results demonstrated that KD should be coupled with HIIT for the prevention and preclinical mitigation of type 2 diabetes.

Beneficial effects of the ketogenic diet on nonalcoholic fatty liver disease: A comprehensive review of the literature

Nonalcoholic fatty liver disease (NAFLD) is a major cause of chronic liver disease, characterized by hepatic fat accumulation and possible development of inflammation, fibrosis, and cancer. The ketogenic diet (KD), with its drastic carbohydrate reduction, is a now popular weight loss intervention, despite safety concerns on a possible association with fatty liver. However, KDs were also reported to be beneficial on hepatic pathology, with ketone bodies recently proposed as effective modulators of inflammation and fibrosis. If the beneficial impact of weight loss on NAFLD is established, less is known on the effect of macronutrient distribution on such outcome. In a hypocaloric regimen, the latter seems not to be crucial, whereas at higher calorie intake, macronutrient ratio and, theoretically, ketosis, may become important. KDs could positively impact NAFLD for their very low carbohydrate content, and whether ketosis plays an additional role is unknown. Indeed, several mechanisms may directly link ketosis and NAFLD improvement, and elucidating these aspects would pave the way for new therapeutic strategies. We herein aimed at providing an accurate revision of current literature on KDs and NAFLD, focusing on clinical evidence, metabolic pathways involved, and strict categorization of dietary interventions.

Preclinical testing of the ketogenic diet in fragile X mice

The ketogenic diet is highly effective at attenuating seizures in refractory epilepsy, and accumulating evidence in the literature suggests that it may be beneficial in autism. To our knowledge, no one has studied the ketogenic diet in any fragile X syndrome (FXS) model. FXS is the leading known genetic cause of autism. Herein, we tested the effects of chronic ketogenic diet treatment on seizures, body weight, ketone and glucose levels, diurnal activity levels, learning and memory, and anxiety behaviors in Fmr1^KO and littermate control mice as a function of age. The ketogenic diet selectively attenuates seizures in male but not female Fmr1^KO mice and differentially affects weight gain and diurnal activity levels dependent on Fmr1 genotype, sex and age.

The effects of popular diets on type 2 diabetes management

Type 2 diabetes can be managed with the use of diabetes self-management skills. Diet and exercise are essential segments of the lifestyle changes necessary for diabetes management. However, diet recommendations can be complicated in a world full of different diets. This review aims to evaluate the evidence on the effects of three popular diets geared towards diabetes management: low-carbohydrate and ketogenic diet, vegan diet, and the Mediterranean diet. While all three diets have been shown to assist in improving glycaemic control and weight loss, patient adherence, acceptability, and long-term manageability play essential roles in the efficacy of each diet.

Fibroblast Growth Factor 21 and the Adaptive Response to Nutritional Challenges

The Fibroblast Growth Factor 21 (FGF21) is considered an attractive therapeutic target for obesity and obesity-related disorders due to its beneficial effects in lipid and carbohydrate metabolism. FGF21 response is essential under stressful conditions and its metabolic effects depend on the inducer factor or stress condition. FGF21 seems to be the key signal which communicates and coordinates the metabolic response to reverse different nutritional stresses and restores the metabolic homeostasis. This review is focused on describing individually the FGF21-dependent metabolic response activated by some of the most common nutritional challenges, the signal pathways triggering this response, and the impact of this response on global homeostasis. We consider that this is essential knowledge to identify the potential role of FGF21 in the onset and progression of some of the most prevalent metabolic pathologies and to understand the potential of FGF21 as a target for these diseases. After this review, we conclude that more research is needed to understand the mechanisms underlying the role of FGF21 in macronutrient preference and food intake behavior, but also in β-klotho regulation and the activity of the fibroblast activation protein (FAP) to uncover its therapeutic potential as a way to increase the FGF21 signaling.

Ketogenic diet in endocrine disorders: Current perspectives

Ketogenic diet (KD) is a high-fat, adequate-protein, and low-carbohydrate diet that leads to nutritional ketosis, long known for antiepileptic effects and has been used therapeutically to treat refractory epilepsy. This review attempts to summarize the evidence and clinical application of KD in diabetes, obesity, and other endocrine disorders. KD is usually animal protein based. An empiric vegetarian Indian variant of KD has been provided keeping in mind the Indian food habits. KD has beneficial effects on cardiac ischemic preconditioning, improves oxygenation in patients with respiratory failure, improves glycemic control in diabetics, is associated with significant weight loss, and has a beneficial impact on polycystic ovarian syndrome. Multivitamin supplementations are recommended with KD. Recently, ketones are being proposed as super-metabolic fuel; and KD is currently regarded as apt dietary therapy for "diabesity."

Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets

New dietary strategies have been created to treat overweight and obesity and have become popular and widely adopted. Nonetheless, they are mainly based on personal impressions and reports published in books and magazines, rather than on scientific evidence. Animal models and human clinical trials have been employed to study changes in body composition and metabolic outcomes to determine the most effective diet. However, the studies present many limitations and should be carefully analyzed. The aim of this review was to discuss the scientific evidence of three categories of diets for weight loss. There is no one most effective diet to promote weight loss. In the short term, high-protein, low-carbohydrate diets and intermittent fasting are suggested to promote greater weight loss and could be adopted as a jumpstart. However, owing to adverse effects, caution is required. In the long term, current evidence indicates that different diets promoted similar weight loss and adherence to diets will predict their success. Finally, it is fundamental to adopt a diet that creates a negative energy balance and focuses on good food quality to promote health.

An 8-Week, Low Carbohydrate, High Fat, Ketogenic Diet Enhanced Exhaustive Exercise Capacity in Mice Part 2: Effect on Fatigue Recovery, Post-Exercise Biomarkers and Anti-Oxidation Capacity

A low-carbohydrate, high-fat ketogenic diet (KD) is a nutritional approach ensuring that the body utilizes lipids. In our previous study, we found that an eight-week ketogenic high-fat, low-carbohydrate diet increased the capacity of endurance exercise in mice without aggravated muscle injury, despite the decrease of absolute muscle volume. The potential mechanism is most possibly to be enhanced capacity to mobilize and utilize fat. In the present study, we investigated whether a ketogenic diet influences post-exercise recovery by measuring blood biomarkers, muscle and liver oxidative state as well as fatigue recovery 24 h post exercise by employing an open-field locomotion test. Several biochemistry markers indicating exercise-induced injury after exhaustive exercise were improved by KD, followed by a 24-h rest with free feed access, including lactate. No aggravated hepatic oxidative damage was observed, whereas muscular oxidative stress was increased by KD. Accelerated recovery induced by exhaustive exercise was also observed from blood biomarkers of injury. For fatigue recovery, lactate concentration, a marker often employed as exhaustion index was lowered by KD, whereas an open field test showed that KD application contributed to increased locomotion after exhaustive exercise, followed by a 24-h rest. These results suggest that KD has the potential to be used as a fatigue-preventing and/or recovery-promoting diet approach in endurance athletes.

Very low-carbohydrate, high-fat, weight reduction diet decreases hepatic gene response to glucose in obese rats

Background

Very low carbohydrate (VLC) diets are used to promote weight loss and improve insulin resistance (IR) in obesity. Since the high fat content of VLC diets may predispose to hepatic steatosis and hepatic insulin resistance, we investigated the effect of a VLC weight-reduction diet on measures of hepatic and whole body insulin resistance in obese rats.

Methods

In Phase 1, adult male Sprague-Dawley rats were made obese by ad libitum consumption of a high-fat (HF1, 60% of energy) diet; control rats ate a lower-fat (LF, 15%) diet for 10 weeks. In Phase 2, obese rats were fed energy-restricted amounts of a VLC (5%C, 65%F), LC (19%C, 55%F) or HC (55%C, 15%F) diet for 8 weeks while HF2 rats continued the HF diet ad libitum. In Phase 3, VLC rats were switched to the HC diet for 1 week. At the end of each phase, measurements of body composition and metabolic parameters were obtained. Hepatic insulin resistance was assessed by comparing expression of insulin-regulated genes following an oral glucose load,that increased plasma insulin levels, with the expression observed in the feed-deprived state.

Results

At the end of Phase 1, body weight, percent body fat, and hepatic lipid levels were greater in HF1 than LF rats (p < 0.05). At the end of Phase 2, percent body fat and intramuscular triglyceride decreased in LC and HC (p < 0.05), but not VLC rats, despite similar weight loss. VLC and HF2 rats had higher HOMA-IR and higher insulin at similar glucose levels following an ip glucose load than HC rats (p < 0.05). HC, but not VLC or HF2 rats, showed changes in Srebf1, Scd1, and Cpt1a expression (p < 0.05) in response to an oral glucose load. At the end of Phase 3, switching from the VLC to the HC diet mitigated differences in hepatic gene expression.

Conclusion

When compared with a high-carbohydrate, low-fat diet that produced similar weight loss, a commonly used VLC diet failed to improve whole body insulin resistance; it also reduced insulin’s effect on hepatic gene expression, which may reflect the development of hepatic insulin resistance.

Treatment of Diabetic Mice with a Combination of Ketogenic Diet and Aerobic Exercise via Modulations of PPARs Gene Programs

Type 2 diabetes is a prevalent chronic disease arising as a serious public health problem worldwide. Diet intervention is considered to be a critical strategy in glycemic control of diabetic patients. Recently, the low-carbohydrate ketogenic diet is shown to be effective in glycemic control and weight loss. However, hepatic lipid accumulation could be observed in mice treated with ketogenic diet. On the other hand, exercise is a well-known approach for treating nonalcoholic fatty liver disease. We thus hypothesize that the combination of ketogenic diet and exercise could improve insulin sensitivity, while minimizing adverse effect of hepatic steatosis. In order to test this hypothesis, we established diabetic mice model with streptozotocin (STZ) and divided them into control group, ketogenic diet group, and ketogenic diet with aerobic exercise group. We found that after six weeks of intervention, mice treated with ketogenic diet and ketogenic diet combined with exercise both have lower body weights, HbAlc level, HOMA index, and improvements in insulin sensitivity, compared with diabetes group. In addition, mice in ketogenic diet intervention exhibited hepatic steatosis shown by serum and hepatic parameters, as well as histochemistry staining in the liver, which could be largely relieved by exercise. Furthermore, gene analysis revealed that ketogenic diet in combination with exercise reduced PPARγ and lipid synthetic genes, as well as enhancing PPARα and lipid β-oxidation gene program in the liver compared to those in ketogenic diet without exercise. Overall, the present study demonstrated that the combination of ketogenic diet and a moderate-intensity aerobic exercise intervention improved insulin sensitivity in diabetic mice, while avoiding hepatic steatosis, which provided a novel strategy in the combat of diabetes.

Efficacy of a ketogenic diet with concomitant intranasal perillyl alcohol as a novel strategy for the therapy of recurrent glioblastoma

It has been hypothesized that persistent ketotic hypoglycemia represents a potential therapeutic strategy against high-grade gliomas. Perillyl alcohol (POH) is a non-toxic, naturally-occurring, hydroxylated monoterpene that exhibits cytotoxicity against temozolomide-resistant glioma cells, regardless of O6-methylguanine-methyltransferase promoter methylation status. The present study aimed to evaluate the toxicity and therapeutic efficacy of intranasal POH when administered in combination with a ketogenic diet (KD) program for the treatment of patients with recurrent glioblastoma. The 32 enrolled patients were divided into two groups, KD or standard diet, with intranasal POH treatment (n=17 and n=15, respectively). The nutritional status and anthropometric parameters of the patients were measured. Patients that adhered to the KD maintained a strict dietary regimen, in addition to receiving 55 mg POH four times daily, in an uninterrupted administration schedule for three months. Neurological examination and magnetic resonance imaging analysis were used to monitor disease progression. A total of 9/17 patients in the KD group survived and maintained compliance with the KD. After three months of well-tolerated treatment, a partial response (PR) was observed for 77.8% (7/9) of the patients, stable disease (SD) in 11.1% (1/9) and 11.1% (1/9) presented with progressive disease (PD). Among the patients assigned to the standard diet group, the PR rate was 25% (2/8 patients), SD 25% (2/8) and PD 50% (4/8 patients). The patients assigned to the KD group presented with reduced serum lipid levels and decreased low-density lipoprotein cholesterol levels. These results are encouraging and suggest that KD associated with intranasal POH may represent a viable option as an adjunct therapy for recurrent GBM.

Muscle PGC-1α is required for long-term systemic and local adaptations to a ketogenic diet in mice

Low-carbohydrate/high-fat (LCHF) diets are increasingly popular dietary interventions for body weight control and as treatment for different pathological conditions. However, the mechanisms of action are still poorly understood, in particular, in long-term administration. Besides liver, brain, and heart, skeletal muscle is one of the major organs involved in the regulation of physiological and pathophysiological ketosis. We assessed the role of the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in skeletal muscle of male wild-type control and PGC-1α muscle-specific knockout mice upon 12 wk of LCHF diet feeding. Interestingly, LCHF diet administration increased oxygen consumption in a muscle PGC-1α-dependent manner, concomitant with a blunted transcriptional induction of genes involved in fatty acid oxidation and impairment in exercise performance. These data reveal a new role for muscle PGC-1α in regulating the physiological adaptation to long-term LCHF diet administration.

Ketogenic diet improves the spatial memory impairment caused by exposure to hypobaric hypoxia through increased acetylation of histones in rats

Exposure to hypobaric hypoxia causes neuron cell damage, resulting in impaired cognitive function. Effective interventions to antagonize hypobaric hypoxia-induced memory impairment are in urgent need. Ketogenic diet (KD) has been successfully used to treat drug-resistant epilepsy and improves cognitive behaviors in epilepsy patients and other pathophysiological animal models. In the present study, we aimed to explore the potential beneficial effects of a KD on memory impairment caused by hypobaric hypoxia and the underlying possible mechanisms. We showed that the KD recipe used was ketogenic and increased plasma levels of ketone bodies, especially β-hydroxybutyrate. The results of the behavior tests showed that the KD did not affect general locomotor activity but obviously promoted spatial learning. Moreover, the KD significantly improved the spatial memory impairment caused by hypobaric hypoxia (simulated altitude of 6000 m, 24 h). In addition, the improving-effect of KD was mimicked by intraperitoneal injection of BHB. The western blot and immunohistochemistry results showed that KD treatment not only increased the acetylated levels of histone H3 and histone H4 compared to that of the control group but also antagonized the decrease in the acetylated histone H3 and H4 when exposed to hypobaric hypoxia. Furthermore, KD-hypoxia treatment also promoted PKA/CREB activation and BDNF protein expression compared to the effects of hypoxia alone. These results demonstrated that KD is a promising strategy to improve spatial memory impairment caused by hypobaric hypoxia, in which increased modification of histone acetylation plays an important role.