Effects of consuming a high carbohydrate diet after eight weeks of exposure to a ketogenic diet

Modulation of Dyslipidemia Markers Apo B/Apo A and Triglycerides/HDL-Cholesterol Ratios by Low-Carbohydrate High-Fat Diet in a Rat Model of Metabolic Syndrome

Metabolic syndrome (MetS) risks cardiovascular diseases due to its associated Dyslipidemia. It is proposed that a low-carbohydrate, high-fat (LCHF) diet positively ameliorates the MetS and reverses insulin resistance. Therefore, we aimed to investigate the protecting effect of the LCHF diet on MetS-associated Dyslipidemia in an experimental animal model. Forty male Sprague-Dawley rats were divided into four groups (10/group): the control group, dexamethasone-induced MetS (DEX) (250 µg/kg/day), LCHF-fed MetS group (DEX + LCHF), and High-Carbohydrate-Low-Fat-fed MetS group (DEX + HCLF). At the end of the four-week experiment, fasting glucose, insulin, lipid profile (LDL-C, HDL-C, Triglyceride), oxidized-LDL, and small dense-LDL using the ELISA technique were estimated. HOMA-IR, Apo B/Apo A1 ratio, and TG/HDL were calculated. Moreover, histological examination of the liver by H & E and Sudan III stain was carried out. In the DEX group, rats showed a significant (p < 0.05) increase in the HOMA-IR, atherogenic parameters, such as s-LDL, OX-LDL, Apo B/Apo A1 ratio, and TG/HDL. The LCHF diet significantly improved the parameters of Dyslipidemia (p < 0.05) by decreasing the Apo B/Apo A1 and TG/HDL-C ratios. Decreased steatosis in LCHF-fed rats compared to HCLF was also revealed. In conclusion, the LCHF diet ameliorates MetS-associated Dyslipidemia, as noted from biochemical results and histological examination.

Isonitrogenous low-carbohydrate diet elicits specific changes in metabolic gene expression in the skeletal muscle of exercise-trained mice

With the renewed interest in low-carbohydrate diets (LCDs) in the sports field, a few animal studies have investigated their potential. However, most rodent studies have used an LCD containing low protein, which does not recapitulate a human LCD, and the muscle-specific adaptation in response to an LCD remains unclear. Therefore, we investigated the effects of two types of LCDs, both containing the same proportion of protein as a regular diet (isonitrogenous LCD; INLCD), on body composition, exercise performance, and metabolic fuel selection at the genetic level in the skeletal muscles of exercise-trained mice. Three groups of mice (n = 8 in each group), one fed a regular AIN-93G diet served as the control, and the others fed either of the two INLCDs containing 20% protein and 10% carbohydrate (INLCD-10%) or 20% protein and 1% carbohydrate (INLCD-1%) had a regular exercise load (5 times/week) for 12 weeks. Body weight and muscle mass did not decrease in either of the INLCD-fed groups, and the muscle glycogen levels and endurance capacity did not differ among the three groups. Only in the mice fed INLCD-1% did the plasma ketone concentration significantly increase, and gene expression related to glucose utilization significantly declined in the muscles. Both INLCD-1% and INLCD-10% consumption increased gene expression related to lipid utilization. These results suggest that, although INLCD treatment did not affect endurance capacity, it helped maintain muscle mass and glycogen content regardless of the glucose intake restrictions in trained mice. Moreover, an INLCD containing a low carbohydrate content might present an advantage by increasing lipid oxidation without ketosis and suppressing muscle glucose utilization.

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.

Nutritional ketosis as an intervention to relieve astrogliosis: Possible therapeutic applications in the treatment of neurodegenerative and neuroprogressive disorders

Nutritional ketosis, induced via either the classical ketogenic diet or the use of emulsified medium-chain triglycerides, is an established treatment for pharmaceutical resistant epilepsy in children and more recently in adults. In addition, the use of oral ketogenic compounds, fractionated coconut oil, very low carbohydrate intake, or ketone monoester supplementation has been reported to be potentially helpful in mild cognitive impairment, Parkinson’s disease, schizophrenia, bipolar disorder, and autistic spectrum disorder. In these and other neurodegenerative and neuroprogressive disorders, there are detrimental effects of oxidative stress, mitochondrial dysfunction, and neuroinflammation on neuronal function. However, they also adversely impact on neurone–glia interactions, disrupting the role of microglia and astrocytes in central nervous system (CNS) homeostasis. Astrocytes are the main site of CNS fatty acid oxidation; the resulting ketone bodies constitute an important source of oxidative fuel for neurones in an environment of glucose restriction. Importantly, the lactate shuttle between astrocytes and neurones is dependent on glycogenolysis and glycolysis, resulting from the fact that the astrocytic filopodia responsible for lactate release are too narrow to accommodate mitochondria. The entry into the CNS of ketone bodies and fatty acids, as a result of nutritional ketosis, has effects on the astrocytic glutamate–glutamine cycle, glutamate synthase activity, and on the function of vesicular glutamate transporters, EAAT, Na⁺, K⁺-ATPase, K_ir4.1, aquaporin-4, Cx34 and K_ATP channels, as well as on astrogliosis. These mechanisms are detailed and it is suggested that they would tend to mitigate the changes seen in many neurodegenerative and neuroprogressive disorders. Hence, it is hypothesized that nutritional ketosis may have therapeutic applications in such disorders.

Benefits of resistance training on body composition and glucose clearance are inhibited by long-term low carbohydrate diet in rats

Background/Objectives

Regular exercise training is effective to altering many markers of metabolic syndrome and its effects are strongly influenced by the type of consumed diet. Nowadays, resistance training (RT) has been frequently associated with low-carbohydrate high-fat diet (LCD). After long term these diets causes body weight (BW) regain with deleterious effects on body composition and metabolic risk factors. The effects of RT associated with long-term LCD on these parameters remain unexplored. We aimed to investigate the effects of RT when associated with long-term LCD on BW, feed efficiency, body composition, glucose homeostasis, liver parameters and serum biochemical parameters during BW regain period in rats.

Subjects/Methods

Male Sprague–Dawley rats were fed with LCD (LC groups) or standard diet (STD) (ST groups). After 10 weeks-diet animals were separated into sedentary (Sed-LC and Sed-ST) and resistance-trained (RT-LC and RT-ST) groups (N = 8/group). RT groups performed an 11-week climbing program on a ladder with progressive load. Dual x-ray absorptiometry, glucose tolerance tests and insulin tolerance tests were performed at weeks 10 and 20. Liver and serum were collected at week 21.

Results

RT reduced feed efficiency, BW gain, liver fat and total and LDL cholesterol, and improved body composition and glucose clearance in animals fed on STD. In those fed with LCD, RT reduced caloric intake, BW regain, liver fat and serum triglycerides levels. However, improvement in body composition was inhibited and bone mineral density and glucose clearance was further impaired in this association.

Conclusions

The LCD nullifies the beneficial effects of RT on body composition, glucose homeostasis and impairs some health parameters. Our results do not support the association of RT with LCD in a long term period.

A prospective study on changes in blood levels of cholecystokinin-8 and leptin in patients with refractory epilepsy treated with the ketogenic diet

OBJECTIVE

To evaluate the changes in serum CCK-8 and leptin levels in patients with refractory epilepsy treated with the ketogenic diet (KD).

METHODS

In this prospective study, patients aged between one and 40 years with refractory epilepsy were included. CCK-8 and leptin were measured in serum at baseline and after three and 12 months of treatment with the KD using an enzyme-linked Immunoabsorbant Assay. Seizure frequency and responsiveness were calculated.

RESULTS

Fifty-four patients were included; 26 patients (48%) were still on the KD at 12 months. After three and 12 months, respectively, 39% and 26% were responders. CCK-8 values were statistically significantly increased at three months (p=0.005) and 12 months (p=0.012). In responders, at three months follow-up, this increase of CCK-8 was significant (p=0.020), whereas in the non-responders it was not (p=0.34). Leptin values were decreased at three and 12 months, the decrease at three months being statistically significant in post-pubertal men (p=0.028) and post-pubertal women (p=0.007).

SIGNIFICANCE

In responders to the KD, serum CCK-8 increased statistically significantly during treatment at three months. Serum leptin decreased statistically significantly at three months in men and in post-pubertal women. It is plausible that the increase of CCK-8 and the decrease of leptin contribute to the anti-convulsive effect of the KD.

An observational study of sequential protein-sparing, very low-calorie ketogenic diet (Oloproteic diet) and hypocaloric Mediterranean-like diet for the treatment of obesity

The impact of a rehabilitative multi-step dietary program consisting in different diets has been scantily investigated. In an open-label study, 73 obese patients underwent a two-phase weight loss (WL) program: a 3-week protein-sparing, very low-calorie, ketogenic diet (<500 kcal/day; Oloproteic(®) Diet) and a 6-week hypocaloric (25-30 kcal/kg of ideal body weight/day), low glycemic index, Mediterranean-like diet (hypo-MD). Both phases improved visceral adiposity, liver enzymes, GH levels, blood pressure and glucose and lipid metabolism. However, the hypo-MD was responsible for a re-increase in blood lipids and glucose tolerance parameters. Changes in visceral adiposity and glucose control-related variables were more consistent in patients with metabolic syndrome. However, in these patients the hypo-MD did not result in a consistent re-increase in glucose control-related variables. A dietary program consisting in a ketogenic regimen followed by a balanced MD appeared to be feasible and efficacious in reducing cardiovascular risk, particularly in patients with metabolic syndrome.

A 2-Week Course of Enteral Treatment with a Very Low-Calorie Protein-Based Formula for the Management of Severe Obesity

Background. Multiple weight loss failures among obese patients suggest the design of new therapeutic strategies. We investigated the role of 2-week course of enteral treatment with a very low-calorie protein-based formula in the management of severe obesity. Methods. We evaluated the feasibility, safety, and efficacy of 2-week continuous administration of a protein-based formula (1.2 g/kg of ideal body weight/day) by nasogastric tube in severely obese adults (body mass index (BMI) ≥ 40 kg/m(2)). Results. In total, 364 patients (59% women; BMI = 46.6 ± 7.2 kg/m(2)) were recruited. The intervention was discontinued within 48 hours in 26 patients, due to nasogastric tube intolerance. No serious adverse events occurred. During the first and the second week, 65% and 80% patients, respectively, reported no side effects. All biochemical safety parameters were affected by the intervention, particularly uric acid (+45%) and aminotransferases (+48%). In the other cases the change was negligible. We observed significant weight loss (5.7 ± 2.3%) and improvement in blood pressure and glucose and lipid metabolism parameters (P < 0.001). Conclusions. A 2-week course of enteral treatment with a very low-calorie protein-based formula appeared a feasible, likely safe, and efficacious therapeutic option to be considered for inclusion into a composite weight loss program for the management of severe obesity. This trial is registered with ClinicalTrials.gov Identifier: NCT01965990.

Neuroactive peptides as putative mediators of antiepileptic ketogenic diets

Various ketogenic diet (KD) therapies, including classic KD, medium chain triglyceride administration, low glycemic index treatment, and a modified Atkins diet, have been suggested as useful in patients affected by pharmacoresistant epilepsy. A common goal of these approaches is to achieve an adequate decrease in the plasma glucose level combined with ketogenesis, in order to mimic the metabolic state of fasting. Although several metabolic hypotheses have been advanced to explain the anticonvulsant effect of KDs, including changes in the plasma levels of ketone bodies, polyunsaturated fatty acids, and brain pH, direct modulation of neurotransmitter release, especially purinergic (i.e., adenosine) and γ-aminobutyric acidergic neurotransmission, was also postulated. Neuropeptides and peptide hormones are potent modulators of synaptic activity, and their levels are regulated by metabolic states. This is the case for neuroactive peptides such as neuropeptide Y, galanin, cholecystokinin, and peptide hormones such as leptin, adiponectin, and growth hormone-releasing peptides (GHRPs). In particular, the GHRP ghrelin and its related peptide des-acyl ghrelin are well-known controllers of energy homeostasis, food intake, and lipid metabolism. Notably, ghrelin has also been shown to regulate the neuronal excitability and epileptic activation of neuronal networks. Several lines of evidence suggest that GHRPs are upregulated in response to starvation and, particularly, in patients affected by anorexia and cachexia, all conditions in which also ketone bodies are upregulated. Moreover, starvation and anorexia nervosa are accompanied by changes in other peptide hormones such as adiponectin, which has received less attention. Adipocytokines such as adiponectin have also been involved in modulating epileptic activity. Thus, neuroactive peptides whose plasma levels and activity change in the presence of ketogenesis might be potential candidates for elucidating the neurohormonal mechanisms involved in the beneficial effects of KDs. In this review, we summarize the current evidence for altered regulation of the synthesis of neuropeptides and peripheral hormones in response to KDs, and we try to define a possible role for specific neuroactive peptides in mediating the antiepileptic properties of diet-induced ketogenesis.

Hypothalamic hormones and metabolism

The ketogenic diet is an effective treatment for medically intractable epilepsy and may have antiepileptogenic, neuroprotective, and antitumor properties. While on a ketogenic diet, the body obtains most of its calories from fat rather than carbohydrates. This dramatic change in caloric composition results in a unique metabolic state. In turn, these changes in caloric composition and metabolism alter some of the neurohormones that participate in the complex neuronal network regulating energy homeostasis. Two observed changes are an increase in serum leptin and a decrease in serum insulin. These opposing changes in leptin and insulin are unique compared to other metabolic stimuli and may modify the activity of several cell signaling cascades including phosphoinositidyl-3 kinase (PI3K), adenosine monophosphate activated protein kinase (AMPK), and mammalian target of rapamycin (mTOR). These cell signaling pathways may mediate the anticonvulsant and other beneficial effects of the diet, though the neurohormonal changes induced by the ketogenic diet and the physiological consequences of these changes remain poorly characterized.

Inflammation-mediated memory dysfunction and effects of a ketogenic diet in a murine model of multiple sclerosis

A prominent clinical symptom in multiple sclerosis (MS), a progressive disorder of the central nervous system (CNS) due to heightened neuro-inflammation, is learning and memory dysfunction. Here, we investigated the effects of a ketogenic diet (KD) on memory impairment and CNS-inflammation in a murine model of experimental autoimmune encephalomyelitis (EAE), using electrophysiological, behavioral, biochemical and in vivo imaging approaches. Behavioral spatial learning deficits were associated with motor disability in EAE mice, and were observed concurrently with brain inflammation. The KD improved motor disability in the EAE model, as well as CA1 hippocampal synaptic plasticity (long-term potentiation) and spatial learning and memory (assessed with the Morris Water Maze). Moreover, hippocampal atrophy and periventricular lesions in EAE mice were reversed in KD-treated EAE mice. Finally, we found that the increased expression of inflammatory cytokines and chemokines, as well as the production of reactive oxygen species (ROS), in our EAE model were both suppressed by the KD. Collectively, our findings indicate that brain inflammation in EAE mice is associated with impaired spatial learning and memory function, and that KD treatment can exert protective effects, likely via attenuation of the robust immune response and increased oxidative stress seen in these animals.

Insulin sensitivity and glucose tolerance are altered by maintenance on a ketogenic diet

Low-carbohydrate, ketogenic diets (KD) are frequently implemented in efforts to reduce or maintain body weight, although the metabolic effects of long-term exposure to this type of diet remain controversial. This study assessed the responsivity to peripheral and central insulin, glucose tolerance, and meal-induced effects of consuming a KD in the rat. After 8 wk of consuming chow or KD, caloric intake after peripheral or central insulin and insulin and glucose levels after a glucose challenge were assessed. In a separate group of rats, glucose and insulin responses to either a low- or high-carbohydrate test meal were measured. Finally, rats maintained on KD were switched back to a chow diet, and insulin sensitivity and glucose tolerance were evaluated to determine whether the effects of KD were reversible. Maintenance on KD resulted in decreased sensitivity to peripheral insulin and impaired glucose tolerance. Furthermore, consumption of a high-carbohydrate meal in rats that habitually consumed KD induced significantly greater insulin and glucose levels for an extended period of time, as compared with chow-fed controls. Responsivity to central insulin was heightened in KD rats and associated with increased expression levels of insulin receptor mRNA. Finally, returning to a chow diet rapidly reversed the effects of KD on insulin sensitivity and glucose tolerance. These data suggest that maintenance on KD negatively affects glucose homeostasis, an effect that is rapidly reversed upon cessation of the diet.