Diet-induced weight loss in obese/diabetic mice normalizes glucose metabolism and promotes functional recovery after stroke.

BACKGROUND: Post-stroke functional recovery is severely impaired by type 2 diabetes (T2D). This is an important clinical problem since T2D is one of the most common diseases. Because weight loss-based strategies have been shown to decrease stroke risk in people with T2D, we aimed to investigate whether diet-induced weight loss can also improve post-stroke functional recovery and identify some of the underlying mechanisms. METHODS: T2D/obesity was induced by 6 months of high-fat diet (HFD). Weight loss was achieved by a short- or long-term dietary change, replacing HFD with standard diet for 2 or 4 months, respectively. Stroke was induced by middle cerebral artery occlusion and post-stroke recovery was assessed by sensorimotor tests. Mechanisms involved in neurovascular damage in the post-stroke recovery phase, i.e. neuroinflammation, impaired angiogenesis and cellular atrophy of GABAergic parvalbumin (PV)+ interneurons were assessed by immunohistochemistry/quantitative microscopy. RESULTS: Both short- and long-term dietary change led to similar weight loss. However, only the latter enhanced functional recovery after stroke. This effect was associated with pre-stroke normalization of fasting glucose and insulin resistance, and with the reduction of T2D-induced cellular atrophy of PV+ interneurons. Moreover, stroke recovery was associated with decreased T2D-induced neuroinflammation and reduced astrocyte reactivity in the contralateral striatum. CONCLUSION: The global diabetes epidemic will dramatically increase the number of people in need of post-stroke treatment and care. Our results suggest that diet-induced weight loss leading to pre-stroke normalization of glucose metabolism has great potential to reduce the sequelae of stroke in the diabetic population.

Early Motor-Behavioral Outcome of Ischemic Stroke with Ketogenic Diet Preconditioning: Interventional Animal Study.

BACKGROUND: Cerebral stroke, with ischemic stroke being its most common type, is the leading cause of chronic disability. The ketogenic diet has been used for treating seizures for centuries and has been considered to be a treatment for other neurologic diseases in recent years. The goal of this study is to evaluate the effects of ketogenic diet preconditioning on the early motor-behavior outcome of rats with induced cerebral ischemic stroke. METHODS: Twenty-four rats were surveyed in 3 groups of Main, Control, and Sham. The Main group received a ketogenic diet plus medium chain triglyceride oil starting 3 days prior to stroke induction, while the other 2 groups took a normal diet. Subsequently, Endothelin-1 was injected stereotactically near the middle cerebral artery to induce an ischemic stroke in the Main and Control group. Normal saline was injected to the members of the Sham group with the same technique. The motor-behavior functions of the rats were compared between 3 groups using adjusting step, beam, and cylinder tests. RESULTS: After stroke induction, rats on ketogenic diet were able to adjust their steps more efficiently, moved faster on the beam, and used their hands more symmetrically in the transparent cylinder in relation to the rats in the Control group. CONCLUSION: It seems that ketogenic diet preconditioning improves the early motor-behavioral outcome of ischemic stroke.

l-Homocarnosine attenuates inflammation in cerebral ischemia-reperfusion injury through inhibition of nod-like receptor protein 3 inflammasome.

We investigated the therapeutic effects of l-homocarnosine against inflammation in a rat model of cerebral ischemia-reperfusion injury. Rats were grouped into control, middle cerebral artery occlusion (MCAO), 0.5 mM l-homocarnosine + MCAO, and 1 mM l-homocarnosine + MCAO treatment groups. Superoxide dismutase (SOD), glutathione peroxidase (Gpx), catalase, lipid peroxidation, and reduced glutathione (GSH) levels were measured. Neurological scores were assessed, and histopathology, scanning electron microscopy (SEM), and fluorescence microscopy analyses were conducted. The mRNA expression levels of nod-like receptor protein 3 (NLRP3), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) and protein expression levels of NLRP3 were assessed. l-Homocarnosine supplementation substantially increased SOD, catalase, Gpx, and GSH levels, whereas it reduced the levels of lipid peroxidation relative to MCAO rats. l-Homocarnosine significantly reduced the infarct area and neurological deficit score, as well as histopathological alteration, apoptosis, and necrosis in brain tissue. The mRNA expression levels of NLRP3, TNF-α, and IL-6 were increased in MCAO rats, whereas l-homocarnosine supplementation reduced mRNA expression by >40%, and NLRP3 protein expression was reduced by >30% in 1 mM l-homocarnosine-treated MCAO rats. We propose that l-homocarnosine exerts a protective effect in cerebral ischemia-reperfusion injury-induced rats by downregulating NLRP3 expression.

Diet-Induced Ketosis Protects Against Focal Cerebral Ischemia in Mouse.

Over the past decade we have consistently shown that ketosis is neuroprotective against ischemic insults in rats. We reported that diet-induced ketotic rats had a significant reduction in infarct volume when subjected to middle cerebral artery occlusion (MCAO), and improved survival and recovery after cardiac arrest and resuscitation. The neuroprotective mechanisms of ketosis (via ketogenic diet; KG) include (i) ketones are alternate energy substrates that can restore energy balance when glucose metabolism is deficient and (ii) ketones modulate cell-signalling pathways that are cytoprotective. We investigated the effects of diet-induced ketosis following transient focal cerebral ischemia in mice. The correlation between levels of ketosis and hypoxic inducible factor-1alpha (HIF-1α), AKT (also known as protein kinase B or PKB) and 5' AMP-activated protein kinase (AMPK) were determined. Mice were fed with KG diet or standard lab-chow (STD) diet for 4 weeks. For the MCAO group, mice underwent 60 min of MCAO and total brain infarct volumes were evaluated 48 h after reperfusion. In a separate group of mice, brain tissue metabolites, levels of HIF-1α, phosphorylated AKT (pAKT), and AMPK were measured. After feeding a KG diet, levels of blood ketone bodies (beta-hydroxyburyrate, BHB) were increased. There was a proportional decrease in infarct volumes with increased blood BHB levels (KG vs STD; 4.2 ± 0.6 vs 7.8 ± 2.2 mm3, mean ± SEM). A positive correlation was also observed with HIF-1α and pAKT relative to blood BHB levels. Our results showed that chronic ketosis can be induced in mice by KG diet and was neuroprotective against focal cerebral ischemia in a concentration dependent manner. Potential mechanisms include upregulation of cytoprotective pathways such as those associated with HIF-1α, pAKT and AMPK.

Anti-oxidative nutrient-rich diet protects against acute ischemic brain damage in rats.

We evaluated the neuroprotective effects of an anti-oxidative nutrient rich enteral diet (AO diet) that contained rich polyphenols (catechins and proanthocyanidins) and many other anti-oxidative ingredients. Wistar rats were treated with either vehicle, normal AO diet (containing 100kcal/100mL, catechin 38.75mg/100mL and proanthocyanidin 19mg/100mL, 1mL/day), or high AO diet (containing 10 times the polyphenols of the normal AO diet) for 14 days, and were subjected to 90min of transient middle cerebral artery occlusion. The AO diet improved motor function, reduced cerebral infarction volume, and decreased both peroxidative markers such as 4-hydroxynonenal, advanced glycation end products, 8-hydroxy-2-deoxyguanosine and inflammatory markers such as monocyte chemotactic protein-1, ionized calcium-binding adapter molecule-1, and tumor necrosis factor-α. Our study has shown that an AO diet has neuroprotective effects through both anti-oxidative and anti-inflammatory mechanisms, indicating that nutritional control with polyphenols could be useful for patients with acute ischemic stroke.