Cataract development in diabetic sand rats treated with alpha-lipoic acid and its gamma-linolenic acid conjugate

Systemic administration of the antioxidant/iron chelator α-lipoic acid protects against light-induced photoreceptor degeneration in the mouse retina

PURPOSE

Oxidative stress and inflammation have key roles in the light damage (LD) model of retinal degeneration as well as in age-related macular degeneration (AMD). We sought to determine if lipoic acid (LA), an antioxidant and iron chelator, protects the retina against LD.

METHODS

Balb/c mice were treated with LA or control saline via intraperitoneal injection, and then were placed in constant cool white light-emitting diode (LED) light (10,000 lux) for 4 hours. Retinas were evaluated at several time points after LD. Photoreceptor apoptosis was assessed using the TUNEL assay. Retinal function was analyzed via electroretinography (ERG). Retinal degeneration was assessed after LD by optical coherence tomography (OCT), TUNEL analysis, and histology. The mRNAs of several oxidative stress, inflammation, and iron-related genes were quantified by quantitative PCR (qPCR).

RESULTS

The LD resulted in substantial photoreceptor-specific cell death. Dosing with LA protected photoreceptors, decreasing the numbers of TUNEL-positive photoreceptors and increasing the number of surviving photoreceptors. The retinal mRNA levels of genes indicating oxidative stress, inflammation, and iron accumulation were lower following LD in mice treated with LA than in control mice. The ERG analysis demonstrated functional protection by LA.

CONCLUSIONS

Systemic LA is protective against light-induced retinal degeneration. Since this agent already has proven protective in other retinal degeneration models, and is safe and protective against diabetic neuropathy in patients, it is worthy of consideration for a human clinical trial against retinal degeneration or AMD.

The relationship of fat soluble antioxidants with gestational diabetes in Iran: a case-control study

OBJECTIVE

The primary aim of this study was to evaluate the relationship of fat soluble antioxidants (retinol and α-tocopherol) with gestational diabetes (GDM).

METHODS

This was a case-control study in which 41 pregnant women with GDM and 41 healthy women were recruited. The inclusion criteria were gestational age ≥32 weeks, singleton foetus, nulliparous or parous women up to four pregnancies and normal fasting blood sugar in the early pregnancy. Two groups were matched regarding age, gestational age and body mass index. A 5 ml venous blood sample were drawn and analysed with the chromatograph for measuring retinol and α-tocopherol. Data were analysed through Chi-square and t test.

RESULTS

The mean serum retinol of the GDM group was 0.46 µg/dl and in the control group it was 0.59 mg/dl (p = 0.01).The mean α-tocopherol in the women with GDM was 6.21 mg/dl and in the control group it was 6.92 mg/dl (p > 0.05).

CONCLUSION

The level of retinol in the diabetic pregnant women was significantly lower than that in the control group. This reduction may be due to the reduced antioxidant defences in women with GDM.

Combating diabetes complications by 1-Fe, a corrole-based catalytic antioxidant

The potent corrole-based ROS/RNS decomposition catalyst 1-Fe was examined regarding its effect on the development of diabetes complications, in parallel with studies that addressed safety and toxicity issues that are crucial for forwarding the compound towards clinical trials. Cardiotoxicity and mutagenic potential were addressed by applying the hERG and AMES tests on 1-Fe, revealing that it is safe enough for further development. General toxicity studies in rats disclosed the appearance of mild adverse effect only at a dose of 300 mg/kg/day. In the streptozotocin-induced rat model of diabetes, 20 mg/kg/day 1-Fe prevented cataract incidents and reduced its severity, displayed a favorable effect on kidney function, and also decreased serum cholesterol and triglyceride levels. Comparisons with alpha lipoic acid, a compound with reported benefits in the same mouse model, indicate that the benefits of 1-Fe are due to the combination of its ability to disarm ROS/RNS and its positive effect on lipid profile.

Biphasic effect of linoleic acid on connexin 46 hemichannels

Connexins form hemichannels at undocked plasma membranes and gap-junction channels (GJCs) at intercellular contacting zones. Under physiological conditions, hemichannels have low open probabilities, but their activation under pathological conditions, such as ischemia, induces and/or accelerates cell death. Connexin 46 (Cx46) is a major connexin of the lens, and mutations of this connexin induce cataracts. Here, we report the effects of linoleic acid (LA) on the electrical properties of Cx46 GJCs and hemichannels expressed in Xenopus laevis oocytes. LA has a biphasic effect, increasing hemichannel current at 0.1 μM and decreasing it at concentrations of 100 μM or higher. The effects of extracellular and microinjected LA conjugated to coenzyme A (LA-CoA) suggest that the current activation site is accessible from the intracellular but not extracellular compartment, whereas the current inhibitory site is either located in a region of the hemichannel pore inaccessible to intracellular LA-CoA, or requires crossing of LA through an organelle membrane. Experiments with other fatty acids demonstrated that the block of hemichannels depends on the presence of a hydrogenated double bond at position 9 and is directly proportional to the number of double bonds. Experiments in paired oocytes expressing Cx46 showed that LA does not affect GJCs. The block by unsaturated fatty acids reported here opens the possibility that increases in the concentration of these lipids in the lens induce cataract formation by blocking Cx46 hemichannels.

The effect of dehydroepiandrosterone (DHEA) on renal function and metabolism in diabetic rats

Dehydroepiandrosterone (DHEA) is an endogenous steroid hormone involved in a number of biological actions in humans and rodents, but its effects on renal tissue have not yet been fully understood. The aim of this study is to assess the effect of DHEA treatment on diabetic rats, mainly in relation to renal function and metabolism. Diabetic rats were treated with subcutaneous injections of a 10mg/kg dose of DHEA diluted in oil. Plasma glucose and creatinine, in addition to urine creatinine, were quantified espectophotometrically. Glucose uptake and oxidation were quantified using radioactive glucose, the urinary Transforming Growth Factor β(1) (TGF-β(1)) was assessed by enzyme immunoassay, and the total glutathione in the renal tissue was also measured. The diabetic rats displayed higher levels of glycemia, and DHEA treatment reduced hyperglycemia. Plasmatic creatinine levels were higher in the diabetic rats treated with DHEA, while creatinine clearance was lower. Glucose uptake and oxidation were lower in the renal medulla of the diabetic rats treated with DHEA, and urinary TGF-β(1), as well as total gluthatione levels, were higher in the diabetic rats treated with DHEA. DHEA treatment was not beneficial to renal tissue, since it reduced the glomerular filtration rate and renal medulla metabolism, while increasing the urinary excretion of TGF-β(1) and the compensatory response by the glutathione system, probably due to a mechanism involving a pro-oxidant action or a pro-fibrotic effect of this androgen or its derivatives. In conclusion, this study reports that DHEA treatment may be harmful to renal tissue, but the mechanisms of this action have not yet been fully understood.

Efficacy of alpha-lipoic acid against diabetic cataract in rat

PURPOSE

alpha-Lipoic acid (LA) is well known as a powerful antioxidant. The efficacy of dihydrolipoate-LA for oral administration against streptozotocin (STZ)-induced diabetic cataract in rat was investigated.

METHODS

Rats were divided into three groups, control, diabetes mellitus (DM), and DM treated with LA (DM+LA). Diabetes was induced by intravenous injection of 50 mg/kg STZ. DM+LA rats were fed 30 mg/rat per day LA in their diet. Lens changes were assessed using Scheimpflug images (EAS-1000) and by measuring light-scattering intensity.

RESULTS

Increase in lens light scattering was less (P < 0.05) in DM+LA rats than in DM rats 5 weeks after induction of diabetes. DM rats had the highest and control rats the lowest blood glucose levels at every measurement point up to 111 days (P < 0.05).

CONCLUSION

LA treatment delayed development and progression of cataract in rats with streptozotocin-induced diabetes.

Increased glutathione conjugate transport: a possible compensatory protection mechanism against oxidative stress in obesity?

OBJECTIVE

To compare glutathione S-conjugate transport in obese and nonobese persons, and how glutathione S-conjugates are involved in the antioxidant status in obesity.

MATERIALS AND METHODS

The efflux of glutathione conjugates and malondialdehyde (MDA) levels were measured in erythrocytes of obese (N = 33) and nonobese (N = 28) persons at every 30 min during a 120 min incubation time in vitro. 2,4-dinitrophenyl-S-glutathione (DNP-SG) represented the glutathione S-conjugate.

RESULTS

The efflux of conjugate in erythrocytes from obese subjects (708 +/- 147 DNP-SG efflux nmol/ml erythrocytes/h) was significantly higher than that of control group (490 +/- 105 DNP-SG efflux nmol/ml erythrocytes/h) (P < 0.05). At all time points measured (30-120 min), there was an increase in DNP-SG efflux in obese group (P < 0.05). This is manifested by a decrease in cellular DNP-SG levels. The susceptibility of erythrocytes to in vitro 1-chloro-2,4-dinitrobenzene (CDNB)-induced oxidative stress were greater for cells of control group (P < 0.05), although hemolysis sensitivity of these cells are not different between both groups (P > 0.05). Following CDNB pretreatment, incubation of erythrocyte with vanadate, a DNP-SG transport inhibitor, resulted in an increase of MDA in both groups. However, in this case, the difference in susceptibility was not related to obesity. On the other hand, while erythrocyte glutathione level was lower in obese subjects (79% of control) than in controls (P < 0.05), the adenosine 5'-triphosphate (ATP) levels, the enzyme activities of glutathione S-transferase (GST) and the conjugation capacities of the erythrocytes were not different between groups (P>0.05).

CONCLUSION

Obesity may increase erythrocyte glutathione conjugate transport independent from ATP and GST activity that may protect against MDA formation in vitro.

The role of N-acetylcysteine treatment on anti-oxidative status in patients with type II diabetes mellitus

The development of diabetic complications has usually been attributed to the nonenzymic glycation of tissue proteins. Only recently, however, have researchers examined the possible role on free radicals in the pathogenesis of diabetes. In the present study, glutathione (GSH) and major antioxidant enzyme levels in plasma of patients with type II diabetes mellitus were assessed both before and after 3 months of N-acetylcysteine (NAC) therapy. Thirty-two diabetic patients were examined as well as fifteen healthy controls. Before treatment with NAC, glutathione peroxidase (GPx), catalase (CAT), and (GSH) levels of diabetic patients and control subjects showed no significant differences, whereas glutathione S-transferase (GST) levels were higher in type II diabetic patients. Following 3 months of Following NAC supplementation, GSH, GST, and CAT levels were found to be similar to the levels before treatment. On the other hand, GPx activity was significantly lower compared with the values before treatment. According to this finding, NAC treatment could have a positive effect on GPx values in type II diabetic patients showing abnormally high values.

Nutritionally Induced Diabetes in Desert Rodents as Models of Type 2 Diabetes: Acomys cahirinus (Spiny Mice) and Psammomys obesus (Desert Gerbil)

The dietary effects of hyperglycemia increasingly result in type 2 diabetes in humans. Two species, the spiny mice (Acomys cahirinus) and the desert gerbil (Psammomys obesus), which have different metabolic responses to such effects, are discussed. Spiny mice exemplify a pathway that leads to diabetes without marked insulin resistance due to low supply of insulin on abundant nutrition, possibly characteristic of a desert animal. They respond with obesity and glucose intolerance, beta-cell hyperplasia, and hypertrophy on a standard rodent diet supplemented with fat-rich seeds. The accompanying hyperglycemia and hyperinsulinemia are mild and intermittent but after a few months, the enlarged pancreatic islets suddenly collapse, resulting in loss of insulin and ketosis. Glucose and other secretagogues produce only limited insulin release in vivo and in vitro, pointing to the inherent disability of the beta-cells to respond with proper insulin secretion despite their ample insulin content. On a 50% sucrose diet there is marked lipogenesis with hyperlipidemia without obesity or diabetes, although beta-cell hypertrophy is evident. P.obesus is characterized by muscle insulin resistance and the inability of insulin to activate the insulin signaling on a high-energy (HE) diet. Insulin resistance imposes a vicious cycle of Hyperglycemia and compensatory hyperinsulinemia, leading to beta-cell failure and increased secretion of proinsulin. Ultrastructural studies reveal gradual disappearance of beta-cell glucokinase, GLUT 2 transporter, and insulin, followed by apoptosis of beta-cells. Studies using the non-insulin-resistant HE diet-fed animals maintained as a control group are discussed. The insulin resistance that is evident to date in the normoglycemic state on a low-energy diet indicates sparing of glucose fuel in muscles of a desert-adapted animal for the benefit of glucose obligatory tissues. Also discussed are the effect of Psammomys age on the disabetogenicity of the HE diet; the impaired function of several components of the insulin signal transduction pathway in muscles, which reduces the availability of GLUT4 transporter; the testing of several antidiabetic modalities for the prevention of nutritional diabetes in Psammomys; and various complications related to the diabetic condition.

Thioctic acid for patients with symptomatic diabetic polyneuropathy: a critical review

Diabetic neuropathy represents a major health problem, as it is responsible for substantial morbidity, increased mortality, and impaired quality of life. Near-normoglycemia is now generally accepted as the primary approach to prevention of diabetic neuropathy, but is not achievable in a considerable number of patients. A growing body of evidence suggests that oxidative stress resulting from enhanced free-radical formation and/or defects in antioxidant defense is implicated in the pathogenesis of diabetic neuropathy. Markers of oxidative stress such as superoxide anion and peroxynitrite production are increased in diabetic patients in relation to the severity of polyneuropathy. In experimental diabetic neuropathy, oxygen free-radical activity in the sciatic nerve is increased, and treatment with thioctic acid, a potent lipophilic antioxidant, results in prevention or improvement of the diabetes-induced neurovascular and metabolic abnormalities in various organ systems. Pharmacodynamic studies have shown that thioctic acid favorably influences the vascular abnormalities of diabetic polyneuropathy such as impaired microcirculation, increased indices of oxidative stress, and increased levels of markers for vascular dysfunction, such as thrombomodulin, albuminuria, and nuclear factor-kappaB. Thus far, seven controlled randomized clinical trials of thioctic acid in patients with diabetic neuropathy have been completed (Alpha-Lipoic Acid in Diabetic Neuropathy [ALADIN I-III], Deutsche Kardiale Autonome Neuropathie [DEKAN], Oral Pilot [ORPIL], Symptomatic Diabetic Neuropathy [SYDNEY], Neurological Assessment of Thioctic Acid in Neuropathy [NATHAN] II) using different study designs, durations of treatment, doses, sample sizes, and patient populations. Recently, a comprehensive analysis was undertaken of trials with comparable designs that met specific eligibility criteria for a meta-analysis to obtain a more precise estimate of the efficacy and safety of thioctic acid (600mg intravenously for 3 weeks) in diabetic patients with symptomatic polyneuropathy. This meta-analysis included the largest sample of diabetic patients (n = 1258) ever to have been treated with a single drug or class of drugs to reduce neuropathic symptoms, and confirmed the favorable effects of thioctic acid based on the highest level of evidence (Class Ia: evidence from meta-analyses of randomized, controlled trials). The following conclusions can be drawn from these trials: (i) short-term treatment for 3 weeks using intravenous thioctic acid 600 mg/day reduces the chief symptoms of diabetic polyneuropathy to a clinically meaningful degree; (ii) this effect on neuropathic symptoms is accompanied by an improvement of neuropathic deficits, suggesting potential for the drug to favorably influence underlying neuropathy; (iii) oral treatment for 4-7 months tends to reduce neuropathic deficits and improve cardiac autonomic neuropathy; and (iv) clinical and postmarketing surveillance studies have revealed a highly favorable safety profile of the drug. Based on these findings, a pivotal long-term multicenter trial of oral treatment with thioctic acid (NATHAN I) is being conducted in North America and Europe to investigate effects on progression of diabetic polyneuropathy, using a clinically meaningful and reliable primary outcome measure that combines clinical and neurophysiological assessment.

Anticataract Activity of Analogs of a Sorbitol Dehydrogenase Inhibitor

The initiation of sugar cataract formation by the aldose reductase catalyzed accumulation of sorbitol in diabetic rats, and its prevention by the administration of aldose reductase inhibitors at the onset or early stages of diabetes, has been well established. In contrast, the inhibition of sorbitol dehydrogenase by 4-[4-(N,N-dimethylsulfamoyl)piperazino]-2-hydroxymethylpyrimidine (SDI-1) has been observed to increase the onset in severity of sugar cataract formation in diabetic rats. Two analogs of SDI-1 have been synthesized, where the 4-(2-hydroxymethyl)pyrimidine ring has been replaced with either a 4-(2,6-dimethoxy)-pyrimidine ring or a 2-pyrimidine ring. Neither compound, 2-[4-(N,N-dimethylsulfamoyl)piperazino]-pyrimidine (SRA-1) or 4-[4-(N,N-dimethylsulfamoyl) piperazino]-2,6-dimethoxypyrimidine (SRA-2), demonstrated significant sorbitol dehydrogenase or aldose reductase inhibition. Oral administration of these compounds to streptozotocin diabetic rats, however, delayed cataract formation without reducing the levels of hyperglycemia or lens polyol.

Pharmacological prevention of diabetic cataract

Cataract--opacification of the lens--is closely related to diabetes as one of its major late complications. This review deals with three molecular mechanisms that may be involved in the development of diabetic cataract: nonenzymatic glycation of eye lens proteins, oxidative stress, and activated polyol pathway in glucose disposition. Implications resulting from these mechanisms for possible pharmacological interventions to prevent diabetic cataract are discussed. The article reviews research on potential anticataract agents, including glycation inhibitors, antioxidants, and aldose reductase inhibitors. Information on possible benefits of putative anticataract agents comes from a variety of approaches, ranging from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients.

Diabetes, oxidative stress, and antioxidants: a review

Increasing evidence in both experimental and clinical studies suggests that oxidative stress plays a major role in the pathogenesis of both types of diabetes mellitus. Free radicals are formed disproportionately in diabetes by glucose oxidation, nonenzymatic glycation of proteins, and the subsequent oxidative degradation of glycated proteins. Abnormally high levels of free radicals and the simultaneous decline of antioxidant defense mechanisms can lead to damage of cellular organelles and enzymes, increased lipid peroxidation, and development of insulin resistance. These consequences of oxidative stress can promote the development of complications of diabetes mellitus. Changes in oxidative stress biomarkers, including superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione levels, vitamins, lipid peroxidation, nitrite concentration, nonenzymatic glycosylated proteins, and hyperglycemia in diabetes, and their consequences, are discussed in this review. In vivo studies of the effects of various conventional and alternative drugs on these biomarkers are surveyed. There is a need to continue to explore the relationship between free radicals, diabetes, and its complications, and to elucidate the mechanisms by which increased oxidative stress accelerates the development of diabetic complications, in an effort to expand treatment options.

Effects of alpha-lipoic acid on biomarkers of oxidative stress in streptozotocin-induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanisms are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. This study was designed to determine whether alpha-lipoic acid, which has been shown to have substantial antioxidant properties, when administered (10 mg/kg ip) once daily for 14 days to normal and diabetic female Sprague-Dawley rats would prevent diabetes-induced changes in biomarkers of oxidative stress in liver, kidney and heart. Serum glucose concentrations, aspartate aminotransferase activity, and glycated hemoglobin levels, which were increased in diabetes, were not significantly altered by alpha-lipoic acid treatment. Normal rats treated with a high dose of alpha-lipoic acid (50 mg/kg) survived but diabetic rats on similar treatment died during the course of the experiment. The activity of glutathione peroxidase was increased in livers of normal rats treated with alpha-lipoic acid, but decreased in diabetic rats after alpha-lipoic acid treatment. Hepatic catalase activity was decreased in both normal and diabetic rats after alpha-lipoic acid treatment. Concentrations of reduced glutathione and glutathione disulfide in liver were increased after alpha-lipoic acid treatment of normal rats, but were not altered in diabetics. In kidney, glutathione peroxidase activity was elevated in diabetic rats, and in both normal and diabetic animals after alpha-lipoic acid treatment. Superoxide dismutase activity in heart was decreased in diabetic rats but normalized after treatment with alpha-lipoic acid; other cardiac enzyme activities were not influenced by either diabetes or antioxidant treatment. These results suggest that after 14 days of treatment with an appropriate pharmacological dose, alpha-lipoic acid may reduce oxidative stress in STZ-induced diabetic rats, perhaps by modulating the thiol status of the cells.

Alpha lipoic acid changes iron uptake and storage in lens epithelial cells

Alpha lipoic acid (LA) is a cofactor in mitochondrial dehydrogenase complexes. Previous studies have shown that when administered exogenously LA has antioxidant properties, which include free radical scavenging, metal chelation and regeneration of other antioxidants. The cells convert LA into dihydroplipoic acid (DHLA), which in the presence of iron can act as a prooxidant. In vitro DHLA reduces Fe(+3) to Fe(+2) and removes iron from ferritin, increasing the risk of Fe catalyzed free radical formation. In the present study we examined the in vivo effects of lipoic acid treatment on Fe metabolism in cultured lens epithelial cells, and found that LA decreases Fe uptake from transferrin, increases Fe deposition into ferritin and increases the concentration of this protein. When administered together with ascorbic acid, lipoic acid changes the characteristic heavy to light chain ratio of ferritin makeup. The decreased Fe uptake and increased storage diminishes the size of the cytosolic highly reactive Fe pool (LIP). These changes are associated with increased cell resistance to H(2)O(2) challenge. Therefore, LA may reduce the risk of Fe induced oxidative damage and also might be useful as a treatment of Fe overload.

Early oxidative stress in the diabetic kidney: effect of DL-alpha-lipoic acid

Oxidative stress is implicated in the pathogenesis of diabetic nephropathy. The attempts to identify early markers of diabetes-induced renal oxidative injury resulted in contradictory findings. We characterized early oxidative stress in renal cortex of diabetic rats, and evaluated whether it can be prevented by the potent antioxidant, DL-alpha-lipoic acid. The experiments were performed on control rats and streptozotocin-diabetic rats treated with/without DL-alpha-lipoic acid (100 mg/kg i.p., for 3 weeks from induction of diabetes). Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats vs. controls (p <.01) and this increase was partially prevented by DL-alpha-lipoic acid. F(2) isoprostane concentrations (measured by GCMS) expressed per either mg protein or arachidonic acid content were not different in control and diabetic rats but were decreased several-fold with DL-alpha-lipoic acid treatment. Both GSH and ascorbate (AA) levels were decreased and GSSG/GSH and dehydroascorbate/AA ratios increased in diabetic rats vs. controls (p <.01 for all comparisons), and these changes were completely or partially (AA) prevented by DL-alpha-lipoic acid. Superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione transferase, and NADH oxidase, but not catalase, were upregulated in diabetic rats vs. controls, and these activities, except glutathione peroxidase, were decreased by DL-alpha-lipoic acid. In conclusion, enhanced oxidative stress is present in rat renal cortex in early diabetes, and is prevented by DL-alpha-lipoic acid.

Alpha-lipoic acid ameliorates myocardial toxicity induced by doxorubicin

The effect of alpha-lipoic acid (LA) on the cardiotoxicity induced by doxorubicin (DOX) was investigated. A single dose of DOX (15 mg kg(-1), i.p) induced cardiotoxicity manifested biochemically by a significant elevation of serum creatine phosphokinase (CK; EC: 2.7.3.2) and lactate dehydrogenase (LDH; EC: 1.1.1.27) 48 h later. Moreover, cardiotoxicity was further confirmed by the significant increase in lipid peroxides measured as malondialdehyde (MDA), and significant decrease in protein thiols (Protein-SH) content in heart tissues. Administration of LA (100 mg kg(-1)) orally for 5 days before and 2 days after DOX injection produced a significant protection against cardiotoxicity induced by DOX. The amelioration of cardiotoxicity was evident by significant reductions in serum CK and LDH. Moreover, LA prevented the rise of MDA as well as the significant reduction of Protein-SH. These results may suggest that LA has a protective effect against cardiotoxicity induced by DOX and it may, therefore, improve the therapeutic index of DOX.

The Harderian gland in diabetic sand rats (Psammomys obesus) a light microscopic study

The purpose of this study was to examine the long-term effects of synthetic diet on the sand rat Harderian gland. From the third month, animals showed a diabetic syndrome characterized histologically by Harderian gland necrotic changes. Some gland tubules and melanocytes were disintegrated and numerous mast cells were densely populated in the connective capsule of the gland. Moreover, luminal porphyrin accretions and cellular debris were often associated with alcian blue positive materials. If the synthetic diet lasted more than 6 months, the gland was strongly damaged and numerous plasma cells, macrophages, and lymphocytes infiltrated the gland. These results clearly demonstrate that the sand rat Harderian gland is affected by the diabetic syndrome induced by the synthetic diet.